Acrylic rubber with excellent rollability, strength characteristics, and water resistance.

Abstract

Provided is an acrylic rubber having excellent roll processability, strength properties and water resistance. An acrylic rubber according to the present invention contains a (meth)acrylic acid ester as a main component; the weight-average molecular weight (Mw) of the acrylic rubber, based on the absolute molecular weight and the absolute molecular weight distribution measured by the GPC-MALS method using a dimethylformamide solvent as a developing solvent, is 1,000,000 or more, and the ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) is 3.4 or more; and the acrylic rubber has an ash content of 0.4 weight% or less, and in addition, the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash content is 80 weight% or more.

Description

Technical Field

[0001] The present invention relates to an acrylic rubber, a method for producing the same, a rubber composition, and a rubber crosslinked product. More specifically, the present invention relates to an acrylic rubber having excellent roll processing properties, and excellent strength characteristics and water resistance of the crosslinked product, a method for producing the same, a rubber composition containing the acrylic rubber, and a rubber crosslinked product obtained by crosslinking the same.

Background Art

[0002] Acrylic rubber is a polymer mainly composed of an acrylate ester, and is generally known as a rubber having excellent heat resistance, oil resistance, and ozone resistance, and is widely used in fields related to automobiles.

[0003] For example, Patent Document 1 (International Publication No. 2019 / 188709 pamphlet) discloses a method for producing an acrylic rubber by charging a monomer component composed of ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and monobutyl fumarate, water, and sodium lauryl sulfate, repeating vacuum degassing and nitrogen substitution, and then adding sodium aldehyde sulfoxylate and cumene hydroperoxide which is an organic radical generator to initiate emulsion polymerization at normal pressure and normal temperature, performing emulsion polymerization until the polymerization conversion rate reaches 95% by weight, coagulating with an aqueous calcium chloride solution, filtering with a wire mesh, and dehydrating and drying with an extrusion dryer having a screw. However, the acrylic rubber obtained by such a method has problems of extremely poor roll processing properties and Banbury processing properties, and also poor storage stability and water resistance.

[0004] Patent Document 2 (Japanese Patent Publication No. 2019-119772) describes a process in which monomer components consisting of ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and monobutyl maleate are combined with pure water and emulsifiers sodium lauryl sulfate and polyoxyethylene dodecyl ether to form a monomer emulsion. A portion of the monomer emulsion is then placed in a polymerization reactor and cooled to 12°C under a nitrogen atmosphere. The remaining monomer emulsion, ferrous sulfate, sodium ascorbate, and potassium persulfate as an inorganic radical generator are then added. A method has been disclosed in which an aqueous solution is continuously added dropwise over 3 hours, followed by emulsion polymerization at 23°C for 1 hour until the polymerization conversion rate reaches 97% by weight, at which point the temperature is raised to 85°C, and sodium sulfate is continuously added to coagulate and filter out the mixture to obtain a hydrated crumb. This hydrated crumb is then washed four times with water, once with acid, and once with pure water, and then acrylic rubber is continuously produced in sheet form using an extruder with a screw. The resulting sheet of acrylic rubber is then crosslinked with an aliphatic polyhydric amine compound such as hexamethylenediamine carbamate. However, the sheet-like acrylic rubber obtained by this method has problems with poor rollability and poor water resistance of the crosslinked product.

[0005] Patent Document 3 (Japanese Patent Publication No. 1-135811) discloses a method for producing acrylic rubber by emulsifying 1 / 4 of a monomer mixture consisting of monomer components comprising ethyl acrylate, caprolactone-added acrylic acid ester, cyanoethyl acrylate, and vinyl chloroacetate, and n-dodecyl mercaptan as a chain transfer agent, with sodium lauryl sulfate, polyethylene glycol nonylphenyl ether, and distilled water, adding sodium sulfite and ammonium persulfate as an inorganic radical generator to start polymerization, adding the remaining monomer mixture and a 2% aqueous solution of ammonium persulfate dropwise for 2 hours while maintaining the temperature at 60°C, and continuing polymerization for another 2 hours after the dropwise addition to produce a latex with a polymerization conversion rate of 96-99%, which is then placed in an aqueous sodium chloride solution at 80°C to solidify, and after thorough washing with water and drying, crosslinking with sulfur. However, the acrylic rubber obtained by this method has problems with poor roll processability and storage stability, as well as poor strength properties and water resistance of the crosslinked product.

[0006] Patent Document 4 (Japanese Patent Publication No. 2018-168343) discloses a method for producing acrylic rubber by preparing a monomer emulsion consisting of monomer components comprising ethyl acrylate, butyl acrylate, and monobutyl fumarate, pure water, sodium lauryl sulfate, polyethylene glycol monostearate, and n-dodecyl mercaptan as a chain transfer agent; then, adding a portion of the monomer emulsion and pure water to a polymerization reactor and cooling to 12°C, and then continuously adding the remaining monomer emulsion, ferrous sulfate, sodium ascorbate, and potassium persulfate as an inorganic radical generator dropwise over 2.5 hours; after that, maintaining the temperature at 23°C and continuing the reaction for 1 hour, industrial water is added and the temperature is raised to 85°C, and then sodium sulfate is continuously added at 85°C to coagulate and obtain a hydrated crumb, which is then washed three times with pure water and dried in a hot air dryer to produce acrylic rubber, which is then crosslinked with 2,2-bis[4-(4-aminophenoxy)phenyl]propane. However, while the acrylic rubber obtained by this method has excellent stress relaxation properties and extrusion processability, it suffers from insufficient roll processability and storage stability, as well as inferior strength characteristics and water resistance of the crosslinked material.

[0007] Patent Document 5 (Japanese Patent Publication No. 9-143229) discloses a method for producing acrylic rubber by adding a monomer mixture consisting of ethyl acrylate, special acrylate, and vinyl monochloroacetate, sodium lauryl sulfate as an emulsifier, n-octyl mercaptan as a chain transfer agent, and water to a reaction vessel, purging with nitrogen, and then adding ammonium bisulfite and sodium persulfate as an inorganic radical generator to initiate a polymerization reaction, copolymerizing at 55°C for 3 hours with a conversion rate of 93-96%, and then crosslinking with sulfur. However, the acrylic rubber obtained by this method has problems with poor storage stability and poor strength properties and water resistance of the crosslinked product.

[0008] Patent Document 6 (Japanese Unexamined Patent Publication No. 62-64809) discloses an acrylic rubber having a monomer composition comprising 50 to 99.9% by weight of at least one compound selected from alkyl acrylates and alkoxyalkyl acrylates, 0.1 to 20% by weight of a dihydrodicyclopentenyl group-containing ester of an unsaturated carboxylic acid having a radical-reactive group, and 0 to 20% by weight of at least one other monovinyl, monovinylidene, and monovinylene unsaturated compound, characterized in that its number average molecular weight (Mn) on a polystyrene basis with tetrahydrofuran as the developing solvent is 200,000 to 1,200,000, and the ratio of weight-average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) is 10 or less, exhibiting excellent processability, compression set, and tensile strength, and capable of sulfur vulcanization. Furthermore, regarding the number-average molecular weight (Mn), it is stated that it is between 200,000 and 1,000,000, preferably between 200,000 and 1,000,000, and that if Mn is less than 200,000, the physical properties and processability of the vulcanized product are inferior, and if it exceeds 1,200,000, the processability is also inferior. Regarding the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn), it is stated that if it exceeds 10, the compression set becomes large and is undesirable. As a specific example, a manufacturing method is disclosed in which monomer components including ethyl acrylate and radically crosslinkable dihydrodicyclopentenyl acrylate, sodium lauryl sulfate as an emulsifier, potassium persulfate as an inorganic radical generator, and octyl thioglycolate or t-dodecyl mercaptan as molecular weight modifiers are added in variable amounts to polymerize acrylic rubber having a number average molecular weight (Mn) of 530,000 to 1,150,000, a weight average molecular weight (Mw) of 3,540,000 to 6,260,000, and a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) of 4.7 to 8, and after coagulation in an aqueous calcium chloride solution, it is thoroughly washed with water and directly dried. The examples and comparative examples show that when the amount of chain transfer agent is small, the number-average molecular weight (Mw) of the resulting acrylic rubber is large at 5 million, and the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) is narrow at 1.4, while when the amount of chain transfer agent is large, the number-average molecular weight (Mn) is small at 200,000, and the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) is extremely wide at 17.However, the acrylic rubber obtained by this method has poor compression set resistance and storage stability, and because it contains radical-reactive groups, even if an appropriate molecular weight distribution (Mw / Mn) is obtained in the polymerization reaction using a radical generator, the molecular weight (Mw, Mn) becomes too large and complex, resulting in problems with insufficient roll processability and Banbury processability. In addition, in the crosslinking reaction of the acrylic rubber obtained by this method, sulfur as a crosslinking agent and a vulcanization accelerator are added and kneaded with a roll, then processed at 100 kg / cm. 2 The process required a long crosslinking time, 15 minutes at 170°C in a vulcanizing press, followed by 4 hours at 175°C in a gear oven. Furthermore, the resulting crosslinked material exhibited inferior compression set resistance, water resistance, and strength properties, as well as poor resistance to changes in physical properties after thermal degradation. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] International Publication No. 2019 / 188709 Pamphlet [Patent Document 2] Japanese Patent Publication No. 2019-119772 [Patent Document 3] Japanese Patent Application Publication No. 1-135811 [Patent Document 4] Japanese Patent Publication No. 2018-168343 [Patent Document 5] Japanese Patent Application Publication No. 9-143229 [Patent Document 6] Japanese Patent Application Publication No. 62-64809 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] This invention has been made in view of the actual state of the prior art, and aims to provide an acrylic rubber that has excellent roll processability and highly excellent strength characteristics and water resistance of the crosslinked product, a method for producing the same, a rubber composition containing the acrylic rubber, and a rubber crosslinked product obtained by crosslinking the same. [Means for solving the problem]

[0011] In view of the above problems, the inventors have conducted diligent research and have found that acrylic rubber, when mainly composed of (meth)acrylic acid ester, has a specific absolute molecular weight and weight-average molecular weight (Mw) and the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) as measured by the GPC-MALS method, and also has a specific ash content and specific component content in the ash, exhibits excellent roll processability and highly superior strength properties and water resistance of the crosslinked material.

[0012] The inventors have found that the roll processability of acrylic rubber is greatly related to the number-average molecular weight (Mn) measured by the GPC-MALS method and the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn), and that when these are within a specific range, the roll processability can be dramatically improved without impairing the strength properties. In particular, the larger the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn), the better the roll processability. However, it has been difficult to manufacture acrylic rubber with a specific number-average molecular weight (Mn) and a wide range of weight-average molecular weight (Mw) to number-average molecular weight (Mn) ratio (Mw / Mn). The inventors have found that this can be achieved by adding the chain transfer agent batch-wise during polymerization, rather than adding it initially. The inventors have also found that by drying the water-containing crumb produced by the solidification reaction at a high shear using a screw-type twin-screw extruder, the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) is greatly increased without impairing the number-average molecular weight (Mn), thereby further improving roll processability.

[0013] The inventors have also found that the amount and composition of ash in acrylic rubber greatly influences its water resistance. While it is difficult to reduce the amount of ash in acrylic rubber, which uses large amounts of emulsifiers and coagulants in emulsion polymerization, the inventors have found that water-containing crumb produced by solidification using a specific method exhibits significantly improved washing efficiency with hot water and ash removal efficiency during dewatering, resulting in a significant improvement in the water resistance of the acrylic rubber. In particular, the inventors have found that by increasing the proportion of water-containing crumb of a specific particle size produced in the solidification process and performing washing, dewatering, and drying, the water resistance of the resulting acrylic rubber can be significantly improved without impairing properties such as roll processability, strength characteristics, and compression set resistance. Furthermore, the inventors have found that using a specific emulsifier in the emulsion polymerization of acrylic rubber, or using a specific coagulant when solidifying the emulsion polymerization liquid, results in excellent water resistance of acrylic rubber and significantly improves its release properties from molds, etc.

[0014] The inventors have also found that acrylic rubber possessing ionic reactive groups or specific reactive groups further enhances its rollability, strength properties, and water resistance, as well as its short-time crosslinking properties and compression set resistance.

[0015] The inventors have found that in GPC measurements of acrylic rubber, particularly acrylic rubber having the above-mentioned reactive group, tetrahydrofuran, which is used in the GPC measurements of radical-reactive acrylic rubber copolymerized with ethyl acrylate or dihydrodicyclopentenyl acrylate in the prior art, does not dissolve sufficiently, and therefore the molecular weight and molecular weight distribution cannot be measured cleanly and reproducibly. However, by using a specific solvent with a higher SP value than tetrahydrofuran as the developing solvent, clean dissolution and reproducible measurements can be achieved. Furthermore, by specifying each characteristic value, it is possible to achieve a high level of balance between the roll processability of the acrylic rubber and the water resistance, strength properties, and compression set resistance properties of the crosslinked material.

[0016] The inventors have also found that by specifying the amount of methyl ethyl ketone-insoluble content in acrylic rubber, excellent roll processability, strength properties, and water resistance are achieved, as well as excellent Banbury processability. The amount of methyl ethyl ketone-insoluble content in acrylic rubber is generated during the polymerization reaction, and in particular, it increases rapidly when the polymerization conversion rate is increased to improve strength properties, making it difficult to control. However, they found that it can be suppressed to some extent by emulsion polymerization in the presence of a chain transfer agent in the latter half of the polymerization reaction, and that the rapidly increasing amount of methyl ethyl ketone-insoluble content disappears when the acrylic rubber is melt-kneaded and extruded in a screw-type twin-screw extruder dryer in a substantially water-free state (water content less than 1% by weight), thereby dramatically improving Banbury processability without impairing roll processability.

[0017] The inventors have also found that by specifying the specific gravity of acrylic rubber, excellent roll processability, strength properties, and water resistance are achieved, as well as excellent storage stability. Acrylic rubber, especially acrylic rubber having ionic reactive groups or reactive groups that react with crosslinking agents such as carboxyl groups, epoxy groups, or chlorine atoms, is sticky and air does not easily escape. Clam-type acrylic rubber, which is made by directly drying water-containing crumbs, contains a large amount of air (lowering the specific gravity) and worsening storage stability. However, by compressing the clam-type acrylic rubber at high pressure with a bailer or the like to form a bale, some air can be removed and storage stability can be improved. Preferably, the water-containing crumbs are extruded and dried under reduced pressure using a screw-type twin-screw extruder to extrude them into an air-free sheet, or, if necessary, the extruded sheet-type acrylic rubber is laminated to produce a bale-type acrylic rubber that contains almost no air, has a high specific gravity, and significantly improved storage stability. The inventors also found that the specific gravity, taking into account the air content, can be measured in accordance with Method A of JIS K6268 Crosslinked Rubber - Density Measurement, which utilizes the difference in buoyancy. Furthermore, they found that the storage stability of acrylic rubber can be further improved by specifying the pH.

[0018] The present inventors have also found that by increasing the cooling rate of the dried acrylic rubber, the scorch stability of the rubber composition can be remarkably improved without impairing properties such as roll processability, water resistance, strength characteristics, and compression set resistance characteristics.

[0019] The present inventors have also found that by specifying the monomer composition of the acrylic rubber, the ratio of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw), the complex viscosity ([η]60°C) at 60°C, the complex viscosity ([η]100°C) at 100°C, the ratio of the complex viscosity ([η]100°C) at 100°C to the complex viscosity ([η]60°C) at 60°C ([η]100°C / [η]60°C), and the shape, roll processability, strength characteristics, and water resistance can be further highly improved, and that by using a polyvalent organic compound as a crosslinking agent, the crosslinkability in a short time and each property of the obtained rubber crosslinked product can be greatly improved.

[0020] The present inventors have also found that after emulsifying a specific monomer component with water and an emulsifier, emulsion polymerization is initiated in the presence of a redox catalyst composed of an inorganic radical generator such as potassium persulfate and a reducing agent, and the chain transfer agent is added batchwise during the polymerization without adding it initially to conduct emulsion polymerization, coagulating the obtained emulsion polymerization under specific conditions, washing the water-containing clam produced by the coagulation reaction with warm water, and drying the water-containing clam after washing and dehydration, whereby the high molecular weight component and the low molecular weight component of the acrylic rubber can coexist to have a broad molecular weight distribution and a specific component ash content, and the roll processability, strength characteristics, and water resistance of the acrylic rubber are highly balanced.

[0021] The present inventors have also found that by melt-kneading and drying acrylic rubber under high-shear conditions using a specific extrusion dryer, an acrylic rubber with further improved roll processability, strength characteristics, and water resistance can be produced. Furthermore, by post-adding a reducing agent and specifying the polymerization temperature, an acrylic rubber with more balanced roll processability, strength characteristics, and water resistance can be produced.

[0022] The present inventors have further found that in a rubber composition comprising the acrylic rubber, filler, and crosslinking agent of the present invention, by incorporating carbon black or silica as the filler, the composition exhibits excellent roll processability, Banbury processability, and short-time crosslinking, and also exhibits highly superior water resistance, strength properties, and compression set resistance properties of the crosslinked product. The present inventors have also found that the crosslinking agent is preferably an organic compound, a polyvalent compound, or an ionic crosslinking compound, and for example, a polyvalent ionic organic compound having multiple ionic reactive groups that react with ionic reactive groups of acrylic rubber such as amine groups, epoxy groups, carboxyl groups, or thiol groups exhibits excellent roll processability, Banbury processability, and short-time crosslinking, and also exhibits highly superior water resistance, strength properties, and compression set resistance properties of the crosslinked product.

[0023] Based on these findings, the inventors have completed the present invention.

[0024] Thus, the present invention provides an acrylic rubber having (meth)acrylic acid ester as the main component, with an absolute molecular weight and weight-average molecular weight (Mw) of 1 million or more as measured by the GPC-MALS method using a dimethylformamide solvent as the developing solvent, a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) of 3.4 or more, an ash content of 0.4% by weight or less, and a total amount of sodium, magnesium, calcium, phosphorus, and sulfur in the ash of 80% by weight or more.

[0025] In the acrylic rubber of the present invention, it is preferable that the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) is 3.5 or higher. In the acrylic rubber of the present invention, the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) is preferably in the range of 3.7 to 6.5.

[0026] In the acrylic rubber of the present invention, it is preferable that it has a reactive group. In the acrylic rubber of the present invention, it is preferable that the reactive group is an ionic reactive group. In the acrylic rubber of the present invention, it is preferable that the reactive group is at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group, and a chlorine atom.

[0027] In the acrylic rubber of the present invention, it is preferable that the acrylic rubber consists of at least one bond unit derived from a (meth)acrylic acid ester selected from the group consisting of alkyl (meth)acrylate esters and alkoxyalkyl (meth)acrylate esters, a bond unit derived from a reactive group-containing monomer, and a bond unit derived from other monomers. In the acrylic rubber of the present invention, the ratio of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) is preferably in the range of 1.3 to 3.

[0028] In the acrylic rubber of the present invention, it is preferable that the amount of methyl ethyl ketone insoluble is 50% by weight or less. It is also preferable that the complex viscosity ([η]60°C) at 60°C is 15,000 [Pa·s] or less. In the acrylic rubber of the present invention, it is preferable that the values ​​obtained when measuring the methyl ethyl ketone insoluble content at 20 points all fall within the range of (average value ± 5) weight%. In the acrylic rubber of the present invention, it is preferable that the ratio of the complex viscosity at 100°C ([η]100°C) to the complex viscosity at 60°C ([η]60°C) ([η]100°C / [η]60°C) is 0.8 or higher.

[0029] In the acrylic rubber of the present invention, it is preferable that the specific gravity is 0.8 or higher. In the acrylic rubber of the present invention, it is preferable that it be in the form of a sheet or a veil.

[0030] Furthermore, the acrylic rubber of the present invention is preferably produced by emulsion polymerization using a phosphate ester salt or a sulfate ester salt as an emulsifier, and is preferably solidified by using an alkali metal salt or a Group 2 metal salt of the periodic table as a coagulant, and then dried. Furthermore, the acrylic rubber of the present invention is preferably melt-kneaded and dried after solidification, and it is preferable that the melt-kneading and drying are carried out in a substantially moisture-free state, and that the melt-kneading and drying are carried out under reduced pressure. Moreover, it is preferable that the acrylic rubber of the present invention is cooled at a cooling rate of 40°C / hr or higher after the melt-kneading and drying.

[0031] In the acrylic rubber of the present invention, it is preferable that the water-containing crumb, in which the proportion of particles with a particle size in the range of 710 μm to 6.7 mm is 50% by weight or more, is washed, dehydrated, and dried.

[0032] The present invention also provides a method for producing acrylic rubber, comprising: an emulsion step of emulsifying an acrylic rubber monomer component mainly composed of (meth)acrylic acid ester with water and an emulsifier; an emulsion polymerization step of starting polymerization in the presence of a redox catalyst containing an inorganic radical generator and a reducing agent, and continuing polymerization by batch-adding a chain transfer agent during polymerization to obtain an emulsion polymerization liquid; a coagulation step of adding the obtained emulsion polymerization liquid to a stirred coagulation liquid and coagulating to produce a water-containing crumb; a washing step of washing the produced water-containing crumb with hot water; a dehydration step of dehydrating the washed water-containing crumb; and a drying step of drying the dehydrated water-containing crumb to less than 1% by weight.

[0033] The present invention's method for producing acrylic rubber is preferable for producing the above-mentioned acrylic rubber. In the method for producing acrylic rubber of the present invention, it is preferable to use a phosphate ester salt or a sulfate ester salt as an emulsifier and carry out emulsion polymerization. In the method for producing acrylic rubber of the present invention, it is preferable to solidify the polymerization solution produced in the emulsion polymerization step by using an alkali metal salt or a Group 2 metal salt of the periodic table as a coagulant and then dry it. In the method for producing acrylic rubber of the present invention, it is preferable to solidify the polymerization solution produced in the emulsion polymerization step by adding it to an aqueous solution containing a coagulant containing an alkali metal salt or a Group 2 metal salt of the periodic table and stirring.

[0034] In the method for producing acrylic rubber of the present invention, it is preferable to contact the polymerization solution produced in the emulsion polymerization step with a coagulant to solidify it, and then melt-knead and dry it. In the method for producing acrylic rubber according to the present invention, it is preferable that the melting and kneading and drying are carried out in a state that is substantially free of moisture. In the method for producing acrylic rubber according to the present invention, it is preferable that the melting and kneading and drying are carried out under reduced pressure. In the method for producing acrylic rubber according to the present invention, it is preferable that the melting and kneading and drying are carried out in a screw-type twin-screw extruder. In the method for producing acrylic rubber according to the present invention, it is preferable that the maximum torque of the screw-type twin-screw extruder during melt mixing and drying is 20 N·m or more. In the method for producing acrylic rubber of the present invention, it is preferable to cool the acrylic rubber after melt-mixing and drying at a cooling rate of 40°C / hr or higher.

[0035] In the method for producing acrylic rubber according to the present invention, it is preferable that the coagulant concentration of the coagulation solution is 1% by weight or more. In the method for producing acrylic rubber according to the present invention, it is preferable that the stirring speed of the coagulation liquid being stirred is 100 rpm or more.

[0036] In the method for producing acrylic rubber according to the present invention, it is preferable that the peripheral speed of the stirring coagulation liquid is 1 m / s or more. In the method for producing acrylic rubber according to the present invention, it is preferable to add a reducing agent after the emulsion polymerization step.

[0037] In the method for producing acrylic rubber of the present invention, it is preferable to wash, dehydrate, and dry a water-containing crumb in which the proportion of particles with a particle size in the range of 710 μm to 6.7 mm is 50% by weight or more.

[0038] The present invention also provides a rubber composition comprising a rubber component including the above-mentioned acrylic rubber, a filler, and a crosslinking agent.

[0039] In the rubber composition of the present invention, it is preferable that the filler is a reinforcing filler. Furthermore, in the rubber composition of the present invention, it is preferable that the filler is carbon black. Furthermore, in the rubber composition of the present invention, it is preferable that the filler is silica.

[0040] In the rubber composition of the present invention, it is preferable that the crosslinking agent is an organic crosslinking agent. Furthermore, in the rubber composition of the present invention, it is preferable that the crosslinking agent is a polyvalent compound. Furthermore, in the rubber composition of the present invention, it is preferable that the crosslinking agent is an ionic crosslinkable compound. Furthermore, in the rubber composition of the present invention, it is preferable that the crosslinking agent is an ionic crosslinkable organic compound. Furthermore, in the rubber composition of the present invention, it is preferable that the crosslinking agent is a polyvalent ionic organic compound.

[0041] In the rubber composition of the present invention, it is preferable that the ion of the ion-crosslinkable compound, ion-crosslinkable organic compound, or polyvalent ion organic compound used as the crosslinking agent is at least one ion-reactive group selected from the group consisting of an amino group, an epoxy group, a carboxyl group, and a thiol group.

[0042] In the rubber composition of the present invention, it is preferable that the crosslinking agent is at least one polyvalent ion compound selected from the group consisting of polyvalent amine compounds, polyvalent epoxy compounds, polyvalent carboxylic acid compounds, and polyvalent thiol compounds.

[0043] In the rubber composition of the present invention, it is preferable that the content of the crosslinking agent is in the range of 0.001 to 20 parts by weight per 100 parts by weight of the rubber component.

[0044] The rubber composition of the present invention preferably further contains an anti-aging agent. In the rubber composition of the present invention, it is preferable that the anti-aging agent is an amine-based anti-aging agent.

[0045] The present invention also provides a method for producing a rubber composition, which involves mixing the above-mentioned acrylic rubber component, a filler, and an optional antioxidant, and then mixing in a crosslinking agent.

[0046] The present invention further provides a crosslinked rubber product obtained by crosslinking the above-mentioned rubber composition. In the crosslinked rubber product of the present invention, it is preferable that the crosslinking of the rubber composition is performed after molding. Furthermore, in the crosslinked rubber product of the present invention, it is preferable that the crosslinking of the rubber composition involves primary crosslinking and secondary crosslinking. [Effects of the Invention]

[0047] The present invention provides an acrylic rubber with excellent roll-processability and highly superior strength characteristics and water resistance of the crosslinked product, an efficient method for producing the same, a high-quality rubber composition containing the acrylic rubber, and a crosslinked rubber product obtained by crosslinking the same. [Brief explanation of the drawing]

[0048] [Figure 1] This figure schematically shows an example of an acrylic rubber manufacturing system used in the production of acrylic rubber according to one embodiment of the present invention. [Figure 2] This diagram shows the configuration of a screw-type extruder. [Figure 3] This figure shows the configuration of the transport-type cooling device used as the cooling device in Figure 1. [Modes for carrying out the invention]

[0049] The acrylic rubber of the present invention is characterized in that it mainly consists of (meth)acrylic acid ester, has a weight-average molecular weight (Mw) of 1 million or more as measured by the GPC-MALS method using a dimethylformamide solvent as the developing solvent, a weight-average molecular weight (Mw) of 1 million or more as measured by the GPC-MALS method, a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) of 3.4 or more, and an ash content of 0.4% by weight or less, with the total amount of sodium, magnesium, calcium, phosphorus, and sulfur in the ash being 80% by weight or more. Here, "GPC-MALS method" refers to the following: GPC (gel permeation chromatography) is a type of liquid chromatography that separates based on differences in molecular size. This method incorporates a multi-angle laser light scattering photometer (MALS) and a differential refractometer (RI) into the apparatus, and by measuring the light scattering intensity and refractive index difference of the molecular chain solution separated by size in the GPC apparatus over time, the molecular weight and content of the solute are sequentially calculated, and finally the absolute molecular weight distribution and absolute average molecular weight value of the polymer substance are determined.

[0050] <Monomer components> The acrylic rubber of the present invention is characterized by having (meth)acrylic acid ester as its main component, where "main component" means that the content in the acrylic rubber is usually 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more. In this invention, "(meth)acrylic acid ester" is used as a general term for esters of acrylic acid and / or methacrylic acid.

[0051] The acrylic rubber of the present invention is also preferable if it has a reactive group, preferably an ionic reactive group, or at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups, and chlorine atoms, as these exhibit excellent crosslinkability and compression set resistance. There are no particular limitations on the ionic reactive group as long as it is a functional group that reacts ionically, but preferably at least one functional group selected from the group consisting of carboxyl groups, epoxy groups, and chlorine atoms, more preferably epoxy groups, carboxyl groups, and particularly preferably carboxyl groups. The acrylic rubber having such a reactive group may be obtained by introducing the reactive group into acrylic rubber by a post-reaction, but preferably an acrylic rubber copolymerized with a reactive group-containing monomer is preferred.

[0052] The preferred monomer components of the acrylic rubber of the present invention consist of at least one (meth)acrylic acid ester selected from the group consisting of alkyl (meth)acrylate esters and alkoxyalkyl (meth)acrylate esters, a reactive group-containing monomer, and other monomers that can be copolymerized as needed.

[0053] The alkyl (meth)acrylate is not particularly limited, but typically an alkyl (meth)acrylate having an alkyl group with 1 to 12 carbon atoms is used, preferably an alkyl (meth)acrylate having an alkyl group with 1 to 8 carbon atoms, and more preferably an alkyl (meth)acrylate having an alkyl group with 2 to 6 carbon atoms.

[0054] Specific examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Among these, ethyl (meth)acrylate and n-butyl (meth)acrylate are preferred, and ethyl acrylate and n-butyl acrylate are more preferred.

[0055] The (meth)acrylate alkoxyalkyl ester is not particularly limited, but usually an (meth)acrylate alkoxyalkyl ester having 2 to 12 alkoxyalkyl groups is used, preferably an (meth)acrylate alkoxyalkyl ester having 2 to 8 alkoxyalkyl groups, and more preferably an (meth)acrylate alkoxyalkyl ester having 2 to 6 C16 alkoxyalkyl groups.

[0056] Specific examples of (meth)acrylate alkoxyalkyl esters include methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate. Among these, methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate are preferred, and methoxyethyl acrylate and ethoxyethyl acrylate are more preferred.

[0057] At least one (meth)acrylic acid ester selected from the group consisting of alkyl (meth)acrylic acid esters and alkoxyalkyl (meth)acrylic acid esters is used individually or in combination of two or more types. The proportion of these esters in the total monomer components is usually in the range of 50 to 99.99% by weight, preferably 62 to 99.95% by weight, more preferably 74 to 99.9% by weight, particularly preferably 80 to 99.5% by weight, and most preferably 87 to 99% by weight. This range provides excellent weather resistance, heat resistance, and oil resistance for the acrylic rubber.

[0058] There are no particular limitations on the reactive group-containing monomer as long as it is a monomer having a functional group that is involved in the reaction with the crosslinking agent, etc., and it can be appropriately selected according to the purpose of use. However, it is preferable to use a monomer having an ionic reactive group that is involved in ionic reactions, or a monomer having at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups, and chlorine atoms, more preferably a monomer having a carboxyl group or an epoxy group, and even more preferably a monomer having a carboxyl group, as this can greatly improve the short-term crosslinking properties and the compression set resistance and water resistance of the crosslinked product.

[0059] There are no particular limitations on the monomer having a carboxyl group, but ethylenically unsaturated carboxylic acids can be suitably used. Examples of ethylenically unsaturated carboxylic acids include ethylenically unsaturated monocarboxylic acids, ethylenically unsaturated dicarboxylic acids, and ethylenically unsaturated dicarboxylic acid monoesters. Among these, ethylenically unsaturated dicarboxylic acid monoesters are particularly preferred because they can further improve the compression set resistance when acrylic rubber is used as a rubber crosslinked product.

[0060] There are no particular limitations on the ethylenically unsaturated monocarboxylic acid, but ethylenically unsaturated monocarboxylic acids having 3 to 12 carbon atoms are preferred, such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and cinnamic acid.

[0061] While there are no particular limitations on the ethylenically unsaturated dicarboxylic acid, ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms are preferred. Examples include fumaric acid, butendionic acid such as maleic acid, itaconic acid, and citraconic acid. It should be noted that ethylenically unsaturated dicarboxylic acids also exist as anhydrides.

[0062] The above-mentioned ethylenically unsaturated dicarboxylic acid monoesters are not particularly limited, but typically include ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms and alkyl monoesters having 1 to 12 carbon atoms, preferably ethylenically unsaturated dicarboxylic acids having 4 to 6 carbon atoms and alkyl monoesters having 2 to 8 carbon atoms, and more preferably alkyl monoesters having 2 to 6 carbon atoms of butendionic acid having 4 carbon atoms.

[0063] Specific examples of ethylenically unsaturated dicarboxylic acid monoesters include monoalkyl butendionates such as monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate, monomethyl maleate, monoethyl maleate, mono-n-butyl maleate, monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclohexenyl fumarate, monocyclopentyl maleate, and monocyclohexyl maleate; and monoalkyl itaconic acid esters such as monomethyl itaconic acid, monoethyl itaconic acid, mono-n-butyl itaconic acid, and monocyclohexyl itaconic acid. Among these, mono-n-butyl fumarate and mono-n-butyl maleate are preferred, and mono-n-butyl fumarate is particularly preferred.

[0064] Examples of monomers containing epoxy groups include epoxy group-containing (meth)acrylic acid esters such as glycidyl (meth)acrylate; epoxy group-containing vinyl ethers such as allyl glycidyl ether and vinyl glycidyl ether; and the like.

[0065] Monomers containing a chlorine atom are not particularly limited, but examples include unsaturated alcohol esters of chlorine-containing saturated carboxylic acids, chloroalkyl esters of (meth)acrylates, chloroacyloxyalkyl esters of (meth)acrylates, (chloroacetylcarbamoyloxy)alkyl esters of (meth)acrylates, unsaturated ethers containing a chlorine atom, unsaturated ketones containing a chlorine atom, aromatic vinyl compounds containing a chloromethyl group, unsaturated amides containing a chlorine atom, and unsaturated monomers containing a chloroacetyl group.

[0066] Specific examples of unsaturated alcohol esters of chlorine atom-containing saturated carboxylic acids include vinyl chloroacetate, vinyl 2-chloropropionate, and allyl chloroacetate. Specific examples of chloroalkyl esters of (meth)acrylate include chloromethyl (meth)acrylate, 1-chloroethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 1,2-dichloroethyl (meth)acrylate, 2-chloropropyl (meth)acrylate, 3-chloropropyl (meth)acrylate, and 2,3-dichloropropyl (meth)acrylate. Specific examples of chloroacyloxyalkyl esters of (meth)acrylate include 2-(chloroacetoxy)ethyl (meth)acrylate, 2-(chloroacetoxy)propyl (meth)acrylate, 3-(chloroacetoxy)propyl (meth)acrylate, and 3-(hydroxychloroacetoxy)propyl (meth)acrylate. Examples of (meth)acrylic acid (chloroacetylcarbamoyloxy) alkyl esters include 2-(chloroacetylcarbamoyloxy)ethyl (meth)acrylic acid and 3-(chloroacetylcarbamoyloxy)propyl (meth)acrylic acid. Specific examples of chlorine atom-containing unsaturated ethers include chloromethyl vinyl ether, 2-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, 2-chloroethyl allyl ether, and 3-chloropropyl allyl ether. Specific examples of chlorine atom-containing unsaturated ketones include 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, and 2-chloroethyl allyl ketone. Specific examples of chloromethyl group-containing aromatic vinyl compounds include p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, and p-chloromethyl-α-methylstyrene. Specific examples of chlorine atom-containing unsaturated amides include N-chloromethyl(meth)acrylamide. Specific examples of chloroacetyl group-containing unsaturated monomers include 3-(hydroxychloroacetoxy)propyl allyl ether and p-vinylbenzylchloroacetic acid.

[0067] These reactive group-containing monomers are used individually or in combination of two or more, and their proportion in the total monomer components is usually in the range of 0.01 to 10% by weight, preferably 0.05 to 8% by weight, more preferably 0.1 to 6% by weight, particularly preferably 0.5 to 5% by weight, and most preferably 1 to 3% by weight.

[0068] Other monomers (hereinafter referred to as "other monomers" in this invention) that can be used together with each of the above monomers as needed are not particularly limited as long as they can copolymerize with the above monomers, and include, for example, aromatic vinyls such as styrene, α-methylstyrene, and divinylbenzene; ethylenically unsaturated nitriles such as acrylonitrile and methacrylonitrile; acrylamide monomers such as acrylamide and methacrylamide; and olefin monomers such as ethylene, propylene, vinyl acetate, ethyl vinyl ether, and butyl vinyl ether.

[0069] These other monomers are used individually or in combination of two or more, and their proportion in the total monomer components is usually kept within the range of 0 to 40% by weight, preferably 0 to 30% by weight, more preferably 0 to 20% by weight, particularly preferably 0 to 15% by weight, and most preferably 0 to 10% by weight.

[0070] <Acrylic rubber> The acrylic rubber of the present invention mainly consists of (meth)acrylic acid esters, preferably at least one (meth)acrylic acid ester selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters, a reactive group-containing monomer, and other monomers as needed, with the proportion of each in the acrylic rubber being typically 50 to 99.99% by weight of the bonding units derived from at least one (meth)acrylic acid ester selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters. The monomer composition is preferably in the range of 62-99.95% by weight, more preferably 74-99.9% by weight, particularly preferably 80-99.5% by weight, and most preferably 87-99% by weight. The bonding units derived from reactive group-containing monomers are usually in the range of 0.01-10% by weight, preferably 0.05-8% by weight, more preferably 0.1-6% by weight, particularly preferably 0.5-5% by weight, and most preferably 1-3% by weight. The bonding units derived from other monomers are usually in the range of 0-40% by weight, preferably 0-30% by weight, more preferably 0-20% by weight, particularly preferably 0-15% by weight, and most preferably 0-10% by weight. When the monomer composition of acrylic rubber is within this range, properties such as short-term crosslinkability, compression set resistance, weather resistance, heat resistance, and oil resistance are well balanced and preferable.

[0071] The reactive group content of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected according to the intended use. However, when the weight percentage of the reactive groups themselves is in the range of 0.001 to 5% by weight, preferably 0.01 to 3% by weight, more preferably 0.05 to 1% by weight, and especially preferably 0.1 to 0.5% by weight, the processability, crosslinkability, and properties such as strength, compression set resistance, oil resistance, cold resistance, and water resistance of the crosslinked material are well balanced, making it preferable.

[0072] The weight-average molecular weight (Mw) of the acrylic rubber of the present invention is the absolute molecular weight measured by the GPC-MALS method using dimethylformamide as the developing solvent, and is 1 million or more, preferably 1.2 million or more, and more preferably 1.5 million or more. If the weight-average molecular weight (Mw) of the acrylic rubber of the present invention is excessively low, it is undesirable as it will result in inferior strength properties and compression set resistance properties. The weight-average molecular weight (Mw) of the acrylic rubber of the present invention is also suitable when it is in the range of typically 1 million to 3.5 million, preferably 1.2 million to 3 million, more preferably 1.3 million to 3 million, particularly preferably 1.5 million to 2.5 million, and most preferably 1.9 million to 2.1 million, as this provides a high balance of roll processability, strength properties, and compression set resistance properties of the acrylic rubber.

[0073] The number-average molecular weight (Mn) of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected depending on the intended use. However, the absolute molecular weight measured by the GPC-MALS method using a dimethylformamide-based solvent as the developing solvent is typically in the range of 100,000 to 500,000, preferably 200,000 to 480,000, more preferably 250,000 to 450,000, particularly preferably 300,000 to 400,000, and most preferably 350,000 to 400,000, when the roll processability, strength characteristics, and compression set resistance characteristics of the acrylic rubber are well balanced and suitable.

[0074] The z-average molecular weight (Mz) of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected according to the intended use. However, the absolute molecular weight, which emphasizes the high molecular weight range measured by the GPC-MALS method using a dimethylformamide-based solvent as the developing solvent, is typically in the range of 1.5 million to 6 million, preferably 2 million to 5 million, more preferably 2.5 million to 4.5 million, and particularly preferably 3 million to 4 million. In such a range, the roll processability, strength characteristics, and compression set resistance characteristics of the acrylic rubber are well-balanced and therefore preferable.

[0075] The ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the acrylic rubber of the present invention is 3.4 or higher, preferably 3.5 or higher, more preferably 3.6 or higher, and particularly preferably 3.7 or higher, as measured by the GPC-MALS method using a dimethylformamide-based solvent as the developing solvent. If the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the acrylic rubber of the present invention is excessively low, it is undesirable as it results in poor roll processability. The ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the acrylic rubber of the present invention is also suitable when it is usually in the range of 3.7 to 6.5, preferably 3.8 to 6.2, more preferably 4 to 6, particularly preferably 4, 5 to 5.7, and most preferably 4.7 to 5.5, as it allows for a high balance between roll processability, strength characteristics when crosslinked, and compression set resistance characteristics.

[0076] The ratio of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected according to the intended use. However, when the absolute molecular weight distribution, which emphasizes the high molecular weight region and is measured by the GPC-MALS method using a dimethylformamide-based solvent as the developing solvent, is in the range of 1.3 to 3, preferably 1.4 to 2.7, more preferably 1.5 to 2.5, particularly preferably 1.8 to 2, and most preferably 1.8 to 1.95, the processability and strength characteristics of the acrylic rubber are highly balanced, and changes in physical properties during storage are mitigated, making it suitable.

[0077] The dimethylformamide-based solvent used as the measurement solvent in the GPC-MALS method is not particularly limited as long as it has dimethylformamide as its main component. For example, a solvent containing 100% dimethylformamide or a solvent in which dimethylformamide is present at a concentration of 90% by weight, preferably 95% by weight, and more preferably 97% by weight or more is used. There are no particular limitations on the compound added to dimethylformamide, but in the present invention, a solution in which lithium chloride is added to dimethylformamide at a concentration of 0.05 mol / L and 37% concentrated hydrochloric acid at a concentration of 0.01% is particularly preferred.

[0078] The ash content of the acrylic rubber of the present invention is 0.4% by weight or less, preferably 0.3% by weight or less, more preferably 0.2% by weight or less, even more preferably 0.18% by weight or less, particularly preferably 0.15% by weight or less, and most preferably 0.13% by weight or less. When the ash content is within this range, the water resistance, strength properties, and processability of the acrylic rubber are well balanced and therefore preferable.

[0079] The lower limit of the ash content of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected depending on the intended use, but it is generally preferable when the ash content is 0.0001% by weight or more, preferably 0.0005% by weight or more, more preferably 0.001% by weight or more, even more preferably 0.003% by weight or more, particularly preferably 0.005% by weight or more, and most preferably 0.01% by weight or more, as this reduces the metal adhesion of the rubber and improves workability.

[0080] When the acrylic rubber of the present invention achieves a high balance of water resistance, strength characteristics, processability, and workability, the ash content is typically in the range of 0.0001 to 0.4% by weight, preferably 0.0005 to 0.3% by weight, more preferably 0.001 to 0.2% by weight, even more preferably 0.003 to 0.18% by weight, particularly preferably 0.005 to 0.15% by weight, and most preferably 0.01 to 0.13% by weight.

[0081] The water resistance of the acrylic rubber is highly improved and preferable when the total amount of sodium, magnesium, calcium, phosphorus, and sulfur in the ash content of the acrylic rubber of the present invention is 80% by weight or more, preferably 83% by weight or more, more preferably 85% by weight or more, particularly preferably 87% by weight or more, and most preferably 90% by weight or more. Furthermore, when the total amount of sodium, magnesium, calcium, phosphorus, and sulfur in the ash content of the acrylic rubber of the present invention is within this range, metal adhesion is reduced, resulting in excellent workability and making it preferable.

[0082] The total amount of magnesium and phosphorus in the ash content of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected according to the intended use, but it is generally preferable when the amount is 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more, as this provides a high balance of water resistance, strength properties, and processability of the acrylic rubber. Furthermore, when the total amount of magnesium and phosphorus in the ash content of the acrylic rubber of the present invention is within this range, metal adhesion is reduced, resulting in excellent workability, which is preferable.

[0083] The amount of magnesium in the ash of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected depending on the intended use, but is usually in the range of 10% by weight or more, preferably 15-60% by weight, more preferably 20-50% by weight, particularly preferably 25-45% by weight, and most preferably 30-40% by weight.

[0084] The amount of phosphorus in the ash of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected depending on the intended use, but is usually in the range of 10% by weight or more, preferably 20-90% by weight, more preferably 30-80% by weight, particularly preferably 40-70% by weight, and most preferably 50-60% by weight.

[0085] The ratio of magnesium to phosphorus ([Mg] / [P]) in the ash content of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected depending on the intended use. However, a ratio of 0.4 to 2.5 by weight is usually preferred, preferably 0.45 to 1.2, more preferably 0.45 to 1, particularly preferably 0.5 to 0.8, and most preferably 0.55 to 0.7, which provides a good balance of water resistance, strength properties, and processability of the acrylic rubber.

[0086] Here, the ash content in acrylic rubber mainly originates from the emulsifier used when emulsifying monomer components and emulsion polymerization, and the coagulant used when solidifying the emulsion polymerization solution. However, the total ash content and the magnesium and phosphorus content in the ash are affected not only by the conditions of the emulsion polymerization and solidification processes, but also by the conditions of each subsequent process.

[0087] The acrylic rubber of the present invention is preferable when an anionic emulsifier, cationic emulsifier, or nonionic emulsifier, preferably an anionic emulsifier, more preferably a phosphate ester salt or sulfate ester salt is used as the emulsifier during emulsion polymerization as described later, as this allows for a high degree of improvement in water resistance, strength properties, mold release properties, and processability. The water resistance of acrylic rubber is uniquely correlated with the amount of ash in the acrylic rubber and the total amount of sodium, magnesium, calcium, phosphorus, and sulfur in the ash, but using the above-mentioned emulsifiers allows for an even higher degree of balance between the water resistance, strength properties, mold release properties, and processability of the acrylic rubber, making it preferable.

[0088] The acrylic rubber of the present invention is preferable when a metal salt, preferably an alkali metal salt or a Group 2 metal salt of the periodic table, is used as a coagulant as described later, as this allows for a significant improvement in not only water resistance and strength properties but also mold release properties and processability. The water resistance of acrylic rubber is uniquely correlated with the amount of ash in the acrylic rubber and the total amount of sodium, magnesium, calcium, phosphorus, and sulfur in the ash. However, when the above-mentioned coagulant is used, the water resistance, strength properties, mold release properties, and processability of the acrylic rubber are further balanced, making it preferable.

[0089] The glass transition temperature (Tg) of the acrylic rubber of the present invention can be appropriately selected depending on the intended use of the acrylic rubber, but is generally 20°C or lower, preferably 10°C or lower, and more preferably 0°C or lower, as this provides excellent processability and cold resistance. The lower limit of the glass transition temperature (Tg) of the acrylic rubber is not particularly limited, but is generally -80°C or higher, preferably -60°C or higher, and more preferably -40°C or higher. Setting the glass transition temperature above the lower limit provides superior oil resistance and heat resistance, while setting it below the upper limit provides superior processability, crosslinkability, and cold resistance.

[0090] The complex viscosity ([η]60°C) of the acrylic rubber of the present invention at 60°C is not particularly limited and can be appropriately selected according to the intended use. However, it is generally preferable that the viscosity is in the range of 15,000 [Pa·s] or less, preferably 1,000 to 10,000 [Pa·s], more preferably 2,000 to 5,000 [Pa·s], particularly preferably 2,500 to 4,000 [Pa·s], and most preferably 2,500 to 3,000 [Pa·s], as this provides excellent processability, oil resistance, and shape retention.

[0091] The complex viscosity ([η]100°C) of the acrylic rubber of the present invention at 100°C is not particularly limited and can be appropriately selected according to the intended use. However, it is generally suitable when it is in the range of 1,500 to 6,000 [Pa·s], preferably 2,000 to 5,000 [Pa·s], more preferably 2,300 to 4,000 [Pa·s], particularly preferably 2,500 to 3,500 [Pa·s], and most preferably 2,500 to 3,000 [Pa·s], as this provides excellent processability, oil resistance, and shape retention.

[0092] The ratio of the complex viscosity of the acrylic rubber of the present invention at 100°C ([η]100°C) to the complex viscosity at 60°C ([η]60°C) ([η]100°C / [η]60°C) is not particularly limited and can be appropriately selected according to the intended use, but is usually 0.5 or higher, preferably 0.6 or higher, more preferably 0.7 or higher, particularly preferably 0.8 or higher, and most preferably 0.83 or higher. The ratio of the complex viscosity of the acrylic rubber of the present invention at 100°C ([η]100°C) to the complex viscosity at 60°C ([η]60°C) ([η]100°C / [η]60°C) is also preferable when it is in the range of 0.5 to 0.99, preferably 0.6 to 0.98, more preferably 0.7 to 0.97, particularly preferably 0.8 to 0.96, and most preferably 0.85 to 0.95, as this provides a high balance of processability, oil resistance, and shape retention.

[0093] The amount of methyl ethyl ketone insoluble in the acrylic rubber of the present invention is not particularly limited and can be appropriately selected depending on the intended use, but it is generally preferable when it is 50% by weight or less, preferably 30% by weight or less, more preferably 15% by weight or less, particularly preferably 10% by weight or less, and most preferably 5% by weight or less, as this greatly improves the processability during kneading, such as in Banbury.

[0094] The values ​​(variation) of the methyl ethyl ketone insoluble content of the acrylic rubber of the present invention, when measured at 20 arbitrary points, are not particularly limited, but it is preferable that all 20 points fall within the range of (average ± 5) weight%, preferably within the range of (average ± 3) weight%, as this results in no variation in processability and stabilizes the various physical properties of the rubber composition and rubber crosslinked product. Note that when the values ​​of the methyl ethyl ketone insoluble content of the acrylic rubber, when measured at 20 arbitrary points, fall within the range of average ± 5, it means that all 20 measured values ​​of methyl ethyl ketone insoluble content fall within the range of (average - 5) to (average + 5) weight%. For example, if the average value of the measured methyl ethyl ketone insoluble content is 20 weight%, it means that all 20 measured values ​​fall within the range of 15 to 25 weight%.

[0095] The acrylic rubber of the present invention is preferable because it exhibits a high balance of Banbury processability and strength characteristics when the water-containing crumb produced by the solidification reaction is melt-kneaded and dried in a screw-type twin-screw extruder with almost all the water removed (water content less than 1% by weight).

[0096] The water content of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected depending on the intended use, but is generally less than 1% by weight, preferably 0.8% by weight or less, and more preferably 0.6% by weight or less. In such cases, the vulcanization characteristics of the acrylic rubber are optimized, and properties such as heat resistance and strand water resistance are greatly improved, making it preferable.

[0097] The pH of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected depending on the intended use, but it is generally preferable when the pH is in the range of 6 or less, preferably 2 to 6, more preferably 2.5 to 5.5, and most preferably 3 to 5, as this greatly improves the storage stability of the acrylic rubber.

[0098] The Mooney viscosity (ML1 + 4, 100°C) of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected depending on the intended use. However, a range of 10 to 150, preferably 20 to 100, and more preferably 25 to 70 is preferable, as it provides a high balance of processability and strength characteristics for the acrylic rubber.

[0099] The specific gravity of the acrylic rubber of the present invention is not particularly limited, but it is generally preferable when it is 0.7 or higher, preferably 0.8 or higher, more preferably 0.9 or higher, particularly preferably 0.95 or higher, and most preferably 1 or higher, as it contains almost no air and has excellent storage stability. The specific gravity of the acrylic rubber of the present invention is also preferable when it is in the range of 0.7 to 1.6, preferably 0.8 to 1.5, more preferably 0.9 to 1.4, particularly preferably 0.95 to 1.3, and most preferably 1.0 to 1.2, as this provides a high balance of productivity, storage stability, and the stability of the crosslinking properties of the crosslinked product. When the specific gravity of the acrylic rubber is excessively low, it indicates a large amount of air in the acrylic rubber, which greatly affects storage stability, including oxidative degradation, and is therefore undesirable. The specific gravity of the acrylic rubber of this invention is calculated by dividing the mass by the volume including voids, that is, by dividing the mass measured in air by the buoyancy, and is usually measured in accordance with Method A of JIS K6268 Crosslinked Rubber - Density Measurement.

[0100] The acrylic rubber of the present invention is also preferable when the water-containing crumb produced by the solidification reaction is dried under reduced pressure using a screw-type twin-screw extruder, or when it is melt-kneaded and dried under reduced pressure, because it exhibits particularly excellent and highly balanced storage stability, injection moldability, and strength characteristics.

[0101] The shape of the acrylic rubber of the present invention is not particularly limited and can be appropriately selected according to the intended use. For example, it may be in powder form, crumb form, strand form, sheet form, bale form, etc., but it is preferable when it is in sheet form or bale form as it offers excellent workability and storage stability.

[0102] The thickness of the acrylic rubber of the present invention, when in sheet form, is not particularly limited and can be appropriately selected according to the intended use, but is generally suitable when it is in the range of 1 to 40 mm, preferably 2 to 35 mm, more preferably 3 to 30 mm, and most preferably 5 to 25 mm, as this provides a high balance of workability, storage stability, and productivity. The width of the sheet-shaped acrylic rubber of the present invention is not particularly limited and can be appropriately selected according to the intended use, but is generally suitable when it is in the range of 300 to 1200 mm, preferably 400 to 1000 mm, and more preferably 500 to 800 mm, as this provides particularly excellent handling. The length of the sheet-shaped acrylic rubber of the present invention is not particularly limited, but is generally suitable when it is in the range of 300 to 1200 mm, preferably 400 to 1000 mm, and more preferably 500 to 800 mm, as this provides particularly excellent handling.

[0103] The size of the acrylic rubber of the present invention when it is in veil form is not particularly limited and can be appropriately selected according to the intended use, but it is appropriate for the width to be in the range of 100 to 800 mm, preferably 200 to 500 mm, more preferably 250 to 450 mm, the length to be in the range of 300 to 1,200 mm, preferably 400 to 1,000 mm, more preferably 500 to 800 mm, and the height (thickness) to be in the range of 50 to 500 mm, preferably 100 to 300 mm, more preferably 150 to 250 mm. Furthermore, the shape of the veil-shaped acrylic rubber of the present invention is not limited and can be appropriately selected according to the intended use of the acrylic rubber veil, but in many cases a rectangular parallelepiped is preferred.

[0104] <How to manufacture acrylic rubber> The above-mentioned method for producing acrylic rubber is not particularly limited, but for example, it can be easily produced by a method that includes: an emulsion polymerization step in which an acrylic rubber monomer component mainly composed of (meth)acrylic acid ester is emulsified with water and an emulsifier, polymerization is started in the presence of a redox catalyst consisting of an inorganic radical generator and a reducing agent, and a chain transfer agent is added batch by batch during polymerization to continue polymerization and obtain an emulsion polymerization liquid; a coagulation step in which the obtained emulsion polymerization liquid is added to a stirred coagulation liquid and coagulated to produce a water-containing crumb; a washing step in which the produced water-containing crumb is washed with hot water; a dehydration step in which the washed water-containing crumb is dehydrated; and a drying step in which the dehydrated water-containing crumb is dried to less than 1% by weight.

[0105] (monomer components) The monomer components mainly composed of (meth)acrylic acid esters used in the present invention are the same as the examples and preferred ranges of monomer components described above. The amount of monomer components used is also as described above, and in emulsion polymerization, each monomer can be appropriately selected to achieve the above composition of the acrylic rubber of the present invention.

[0106] (emulsifier) There are no particular limitations on the emulsifier used in the present invention, but examples include anionic emulsifiers, cationic emulsifiers, and nonionic emulsifiers, with anionic emulsifiers being preferred.

[0107] There are no particular limitations on the anionic emulsifiers, and examples include salts of fatty acids such as myristic acid, palmitic acid, oleic acid, and linolenic acid; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; sulfate esters such as sodium lauryl sulfate; phosphate esters such as polyoxyalkylene alkyl ether phosphate esters; and alkyl sulfosuccinates. Among these anionic emulsifiers, phosphate esters and sulfate esters are preferred, phosphate esters are particularly preferred, and divalent phosphate esters are most preferred, as they allow for a high balance of the water resistance, strength properties, mold release properties, and processability of the resulting acrylic rubber. Furthermore, when these phosphate esters and sulfate esters are preferably alkali metal salts of phosphate esters or sulfate esters, and more preferably sodium salts of phosphate esters or sulfate esters, they allow for a high balance of the water resistance, strength properties, mold release properties, and processability of the resulting acrylic rubber, which is preferable.

[0108] The divalent phosphate ester salt is not particularly limited as long as it can be used as an emulsifier in emulsion polymerization reactions, but examples include alkyloxypolyoxyalkylene phosphate ester salts and alkylphenyloxypolyoxyalkylene phosphate ester salts, among which the metal salts of these are preferred, the alkali metal salts of these are more preferred, and the sodium salts of these are most preferred.

[0109] Examples of the alkyloxypolyoxyalkylene phosphate salts mentioned above include alkyloxypolyoxyethylene phosphate salts and alkyloxypolyoxypropylene phosphate salts, and among these, alkyloxypolyoxyethylene phosphate salts are preferred.

[0110] Specific examples of alkyloxypolyoxyethylene phosphate salts include octyloxydioxyethylene phosphate, octyloxytrioxyethylene phosphate, octyloxytetraoxyethylene phosphate, decyloxytetraoxyethylene phosphate, dodecyloxytetraoxyethylene phosphate, tridecyloxytetraoxyethylene phosphate, tetradecyloxytetraoxyethylene phosphate, hexadecyloxytetraoxyethylene phosphate, octadecyloxytetraoxyethylene phosphate, octyloxypentaoxyethylene phosphate, decyloxypentaoxyethylene phosphate, dodecyloxypentaoxyethylene phosphate, tridecyloxypentaoxyethylene phosphate, tetradecyloxypentaoxyethylene phosphate, hexadecyloxypentaoxyethylene phosphate, and octadecyloxypentaoxyethylene phosphate. Examples of metal salts include octoxyhexaoxyethylene phosphate, octyloxyhexaoxyethylene phosphate, decyloxyhexaoxyethylene phosphate, dodecyloxyhexaoxyethylene phosphate, tridecyloxyhexaoxyethylene phosphate, tetradecyloxyhexaoxyethylene phosphate, hexadecyloxyhexaoxyethylene phosphate, octadecyloxyhexaoxyethylene phosphate, octyloxyoctaoxyethylene phosphate, decyloxyoctaoxyethylene phosphate, dodecyloxyoctaoxyethylene phosphate, tridecyloxyoctaoxyethylene phosphate, tetradecyloxyoctaoxyethylene phosphate, hexadecyloxyoctaoxyethylene phosphate, and octadecyloxyoctaoxyethylene phosphate. Among these, alkali metal salts, particularly sodium salts, are preferred.

[0111] Specific examples of alkyloxypolyoxypropylene phosphate salts include octyloxydioxypropylene phosphate, octyloxytrioxypropylene phosphate, octyloxytetraoxypropylene phosphate, decyloxytetraoxypropylene phosphate, dodecyloxytetraoxypropylene phosphate, tridecyloxytetraoxypropylene phosphate, tetradecyloxytetraoxypropylene phosphate, hexadecyloxytetraoxypropylene phosphate, octadecyloxytetraoxypropylene phosphate, octyloxypentaoxypropylene phosphate, decyloxypentaoxypropylene phosphate, dodecyloxypentaoxypropylene phosphate, tridecyloxypentaoxypropylene phosphate, tetradecyloxypentaoxypropylene phosphate, hexadecyloxypentaoxypropylene phosphate, and octadecyloxypentaoxypropylene phosphate. Examples include octyloxyhexaoxypropylene phosphate, decyloxyhexaoxypropylene phosphate, dodecyloxyhexaoxypropylene phosphate, tridecyloxyhexaoxypropylene phosphate, tetradecyloxyhexaoxypropylene phosphate, hexadecyloxyhexaoxypropylene phosphate, octadecyloxyhexaoxypropylene phosphate, octyloxyoctaoxypropylene phosphate, decyloxyoctaoxypropylene phosphate, dodecyloxyoctaoxypropylene phosphate, tridecyloxyoctaoxyethylene phosphate, tetradecyloxyoctaoxypropylene phosphate, hexadecyloxyoctaoxypropylene phosphate, octadecyloxyoctaoxypropylene phosphate, and their metal salts, among which alkali metal salts, particularly sodium salts, are preferred.

[0112] Specific examples of alkylphenyloxypolyoxyalkylene phosphate salts include alkylphenyloxypolyoxyethylene phosphate salts and alkylphenyloxypolyoxypropylene phosphate salts, and among these, alkylphenyloxypolyoxyethylene phosphate salts are preferred.

[0113] Specific examples of alkylphenyloxypolyoxyethylene phosphate salts include methyloxytetraoxyethylene phosphate, ethylphenyloxytetraoxyethylene phosphate, butylphenyloxytetraoxyethylene phosphate, hexylphenyloxytetraoxyethylene phosphate, nonylphenyloxytetraoxyethylene phosphate, dodecylphenyloxytetraoxyethylene phosphate, octadecyloxytetraoxyethylene phosphate, methylphenyloxypentaoxyethylene phosphate, ethylphenyloxypentaoxyethylene phosphate, butylphenyloxypentaoxyethylene phosphate, hexylphenyloxypentaoxyethylene phosphate, nonylphenyloxypentaoxyethylene phosphate, and dodecylphenyloxypentaoxyethylene phosphate. Examples of metal salts include phosphate esters, methylphenyloxyhexaoxyethylene phosphate ester, ethylphenyloxyhexaoxyethylene phosphate ester, butylphenyloxyhexaoxyethylene phosphate ester, hexylphenyloxyhexaoxyethylene phosphate ester, nonylphenyloxyhexaoxyethylene phosphate ester, dodecylphenyloxyhexaoxyethylene phosphate ester, methylphenyloxyhexaoxyethylene phosphate ester, ethylphenyloxyoctaoxyethylene phosphate ester, butylphenyloxyoctaoxyethylene phosphate ester, hexylphenyloxyoctaoxyethylene phosphate ester, nonylphenyloxyoctaoxyethylene phosphate ester, and dodecylphenyloxyoctaoxyethylene phosphate ester. Among these, alkali metal salts, particularly sodium salts, are preferred.

[0114] Specific examples of alkylphenyloxypolyoxypropylene phosphate salts include methylphenyloxytetraoxypropylene phosphate, ethylphenyloxytetraoxypropylene phosphate, butylphenyloxytetraoxypropylene phosphate, hexylphenyloxytetraoxypropylene phosphate, nonylphenyloxytetraoxypropylene phosphate, dodecylphenyloxytetraoxypropylene phosphate, methylphenyloxypentaoxypropylene phosphate, ethylphenyloxypentaoxypropylene phosphate, butylphenyloxypentaoxypropylene phosphate, hexylphenyloxypentaoxypropylene phosphate, nonylphenyloxypentaoxypropylene phosphate, dodecylphenyloxypentaoxypropylene phosphate, methyl Examples of metal salts include phenyloxyhexaoxypropylene phosphate, ethylphenyloxyhexaoxypropylene phosphate, butylphenyloxyhexaoxypropylene phosphate, hexylphenyloxyhexaoxypropylene phosphate, nonylphenyloxyhexaoxypropylene phosphate, dodecylphenyloxyhexaoxypropylene phosphate, methylphenyloxyoctaoxypropylene phosphate, ethylphenyloxyoctaoxypropylene phosphate, butylphenyloxyoctaoxypropylene phosphate, hexylphenyloxyoctaoxyethylene phosphate, nonylphenyloxyoctaoxypropylene phosphate, and dodecylphenyloxyoctaoxypropylene phosphate. Among these, alkali metal salts, particularly sodium salts, are preferred.

[0115] As the phosphate ester salt, monovalent phosphate ester salts such as di(alkyloxypolyoxyalkylene) phosphate sodium salt can be used alone or in combination with divalent phosphate ester salts. Examples of sulfate ester salts include sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, sodium myristyl sulfate, sodium polyoxyethylene alkyl sulfate, and sodium polyoxyethylene alkylaryl sulfate, with sodium lauryl sulfate being preferred.

[0116] Examples of cationic emulsifiers include alkyltrimethylammonium chloride, dialkylammonium chloride, and benzylammonium chloride.

[0117] Examples of nonionic emulsifiers include polyoxyalkylene fatty acid esters such as polyoxyethylene stearate; polyoxyalkylene alkyl ethers such as polyoxyethylene dodecyl ether; polyoxyalkylene alkylphenol ethers such as polyoxyethylene nonylphenyl ether; and polyoxyethylene sorbitan alkyl ester. Polyoxyalkylene alkyl ethers and polyoxyalkylene alkylphenol ethers are preferred, and polyoxyethylene alkyl ethers and polyoxyethylene alkylphenol ethers are more preferred.

[0118] These emulsifiers can be used individually or in combination of two or more, and the amount used is usually in the range of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 1 to 3 parts by weight, per 100 parts by weight of the monomer component.

[0119] The method of mixing the monomer component, water, and emulsifier (mixing method) can be any conventional method, for example, by stirring the monomer, emulsifier, and water using a stirrer such as a homogenizer or a disk turbine. The amount of water used is usually in the range of 1 to 1000 parts by weight, preferably 5 to 500 parts by weight, more preferably 4 to 300 parts by weight, particularly preferably 3 to 150 parts by weight, and most preferably 20 to 80 parts by weight, per 100 parts by weight of the monomer component.

[0120] (Inorganic radical generator) The polymerization catalyst used in this invention is characterized by the use of a redox catalyst consisting of an inorganic radical generator and a reducing agent. In particular, the use of an inorganic radical generator is preferable because it can greatly improve the processability of acrylic rubber rolls and the like produced.

[0121] As for the inorganic radical generating agent, there are no particular limitations as long as it is one that is commonly used in emulsion polymerization. Examples include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, and hydrogen peroxide. Among these, persulfates are preferred, potassium persulfate and ammonium persulfate are more preferred, and potassium persulfate is particularly preferred.

[0122] These inorganic radical generators can be used individually or in combination of two or more types, and the amount used is typically in the range of 0.0001 to 5 parts by weight, preferably 0.0005 to 1 part by weight, more preferably 0.001 to 0.25 parts by weight, particularly preferably 0.01 to 0.21 parts by weight, and most preferably 0.1 to 0.2 parts by weight, per 100 parts by weight of monomer component.

[0123] (Reducing agent) The reducing agent used in this invention is not particularly limited as long as it is one that is normally used in emulsion polymerization, but preferably at least two types of reducing agents are used, and a combination of a metal ion compound in a reduced state and another reducing agent is preferable as it allows for an even higher balance of the Banbury processability, roll processability and strength characteristics of the resulting acrylic rubber.

[0124] The metal ion compounds in the reduced state are not particularly limited, but examples include ferrous sulfate, sodium ferric hexamethylenediaminetetraacetate, and cuprous naphthenate, with ferrous sulfate being preferred among these. These metal ion compounds in the reduced state can be used individually or in combination of two or more, and the amount used is usually in the range of 0.000001 to 0.01 parts by weight, preferably 0.00001 to 0.001 parts by weight, and more preferably 0.00005 to 0.0005 parts by weight, per 100 parts by weight of monomer components.

[0125] The reducing agents used in the present invention, other than metal ion compounds in a reduced state, are not particularly limited, but include, for example, ascorbic acid or its salts, such as ascorbic acid, sodium ascorbate, potassium ascorbate; erythorbic acid or its salts, such as erythorbic acid, sodium erythorbate, potassium erythorbate; sulfinates such as sodium hydroxymethanesulfinate; sulfites of sodium sulfite, potassium sulfite, sodium bisulfite, sodium aldehyde bisulfite, potassium bisulfite; pyrosulfites such as sodium pyrosulfite, potassium pyrosulfite, sodium pyrosulfite, potassium pyrosulfite; thiosulfates such as sodium thiosulfate, potassium thiosulfate; phosphorous acid or its salts, such as phosphorous acid, sodium phosphite, potassium phosphite, sodium bisulfite, potassium bisulfite; pyrosulfites or their salts, such as pyrosulfite, sodium pyrosulfite, potassium pyrosulfite, sodium pyrosulfite, potassium pyrosulfite; and sodium formaldehyde sulfoxylate. Among these, ascorbic acid or its salts, sodium formaldehyde sulfoxylate, and others are preferred, with ascorbic acid or its salts being particularly preferred.

[0126] These reducing agents, other than metal ion compounds in the reduced state, can be used individually or in combination of two or more. The amount used is typically 0.001 to 1 part by weight, preferably 0.005 to 0.5 parts by weight, and more preferably 0.01 to 0.1 parts by weight, per 100 parts by weight of monomer components.

[0127] A preferred combination of a metal ion compound in a reduced state and another reducing agent is ferrous sulfate and ascorbic acid or its salt and / or sodium formaldehyde sulfoxylate, more preferably ferrous sulfate and ascorbic acid or its salt. The amount of ferrous sulfate used is usually in the range of 0.000001 to 0.01 parts by weight, preferably 0.00001 to 0.001 parts by weight, and more preferably 0.00005 to 0.0005 parts by weight, per 100 parts by weight of the monomer component, and the amount of ascorbic acid or its salt and / or sodium formaldehyde sulfoxylate used is usually in the range of 0.001 to 1 part by weight, preferably 0.005 to 0.5 parts by weight, and more preferably 0.01 to 0.1 parts by weight, per 100 parts by weight of both components.

[0128] The amount of water used in the emulsion polymerization reaction may be the same as the amount used during the emulsion formation of the monomer components, but it is usually adjusted to be in the range of 10 to 1000 parts by weight, preferably 50 to 500 parts by weight, more preferably 80 to 400 parts by weight, and most preferably 100 to 300 parts by weight, per 100 parts by weight of the monomer components used for polymerization.

[0129] The emulsion polymerization reaction can be carried out according to conventional methods, and may be batch, semi-batch, or continuous. The polymerization temperature and polymerization time are not particularly limited and can be appropriately selected depending on the type of polymerization initiator used. The polymerization time is usually 0.5 to 100 hours, preferably 1 to 10 hours.

[0130] Emulsion polymerization is an exothermic reaction, and if left uncontrolled, the temperature can rise and shorten the polymerization reaction. However, in the present invention, controlling the emulsion polymerization reaction temperature to 35°C or lower, preferably 0-35°C, more preferably 5-30°C, and particularly preferably 10-25°C is preferable as it provides a high balance between the strength characteristics of the produced acrylic rubber and the processability during kneading, such as for Banbury.

[0131] (Addition of chain transfer agent afterwards) The present invention is characterized by adding the chain transfer agent in batches during polymerization rather than adding it initially. This allows for the production of acrylic rubber in which high molecular weight and low molecular weight components are separated, and the strength characteristics of the produced acrylic rubber and its processability during kneading, such as with rolls, are well-balanced, making it highly suitable.

[0132] The chain transfer agent used is not particularly limited as long as it is one that is commonly used in emulsion polymerization; for example, mercaptan compounds can be suitably used. As the mercaptan compound, alkyl mercaptan compounds having 2 to 20 carbon atoms are usually used, preferably alkyl mercaptan compounds having 5 to 15 carbon atoms, and more preferably alkyl mercaptan compounds having 6 to 14 carbon atoms.

[0133] The alkyl mercaptan compound can be any of n-alkyl mercaptan compounds, sec-alkyl mercaptan compounds, or t-alkyl mercaptan compounds, but preferably n-alkyl mercaptan compounds or t-alkyl mercaptan compounds, and more preferably n-alkyl mercaptan compounds, as this allows the chain transfer agent to be stably exerted and greatly improves the processability of the acrylic rubber rolls and the like produced.

[0134] Specific examples of alkyl mercaptan compounds include n-pentyl mercaptan, n-hexyl mercaptan, n-heptyl mercaptan, n-octyl mercaptan, n-decyl mercaptan, n-dodecyl mercaptan, n-tridecane mercaptan, n-tetradecyl mercaptan, n-hexadecyl mercaptan, n-octadecyl mercaptan, sec-pentyl mercaptan, sec-hexyl mercaptan, sec-heptyl mercaptan, sec-octyl mercaptan, sec-decyl mercaptan, sec-dodecyl mercaptan, sec-tridecane mercaptan, sec-tetradecyl mercaptan. Examples include decyl mercaptan, sec-hexadecyl mercaptan, sec-octadecyl mercaptan, t-pentyl mercaptan, t-hexyl mercaptan, t-heptyl mercaptan, t-octyl mercaptan, t-decyl mercaptan, t-dodecyl mercaptan, n-tridecane mercaptan, t-tetradecyl mercaptan, t-hexadecyl mercaptan, t-octadecyl mercaptan, and the like, with n-octyl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan being preferred, and n-octyl mercaptan and n-dodecyl mercaptan being more preferred.

[0135] These chain transfer agents can be used individually or in combination of two or more. The amount of chain transfer agent used is not particularly limited, but the strength characteristics and roll processability of the acrylic rubber produced are well balanced and preferable when the amount is in the range of 0.0001 to 1 part by weight, preferably 0.0005 to 0.5 parts by weight, more preferably 0.001 to 0.5 parts by weight, particularly preferably 0.005 to 0.1 parts by weight, and most preferably 0.01 to 0.06 parts by weight per 100 parts by weight of monomer component.

[0136] In the present invention, the chain transfer agent is not added in the initial stages of polymerization but added batch-wise during polymerization, which is preferable because it produces high molecular weight and low molecular weight components in the acrylic rubber and allows for a high degree of balance between strength characteristics and processability for rolls, etc., by setting the molecular weight distribution within a specific range.

[0137] There are no particular limitations on the number of batches of post-addition of the chain transfer agent, and it can be appropriately selected depending on the intended use. However, it is usually preferable to add it 1 to 5 times, preferably 2 to 4 times, more preferably 2 to 3 times, and especially preferably 2 times, as this allows for a high balance between the strength characteristics of the acrylic rubber produced and the processability of rolls and the like.

[0138] There are no particular limitations on the timing of the batch-based addition of the chain transfer agent, and it can be appropriately selected depending on the intended use. However, it is preferable to start the addition 20 minutes or more after the start of polymerization, preferably 30 minutes or more after the start of polymerization, more preferably 30 to 200 minutes after the start of polymerization, particularly preferably 35 to 150 minutes after the start of polymerization, and most preferably 40 to 120 minutes after the start of polymerization, as this allows for a high balance between the strength characteristics and processability of the acrylic rubber produced.

[0139] The amount of chain transfer agent added per batch during batch post-addition is not particularly limited and can be appropriately selected according to the intended use. However, when the amount is typically in the range of 0.00005 to 0.5 parts by weight, preferably 0.0001 to 0.1 parts by weight, more preferably 0.0005 to 0.05 parts by weight, particularly preferably 0.001 to 0.03 parts by weight, and most preferably 0.002 to 0.02 parts by weight per 100 parts by weight of monomer component, it is preferable to manufacture acrylic rubber in a way that allows for a high balance between strength characteristics and roll processability.

[0140] After adding the chain transfer agent, there are no particular limitations, but the polymerization reaction can usually be continued for 30 minutes or more, preferably 45 minutes or more, and more preferably 1 hour or more before being terminated.

[0141] (Reducing agent added afterwards) In the present invention, the reducing agent of the redox catalyst can be added later during polymerization, which allows for a high degree of balance between the strength characteristics and processability of the acrylic rubber produced, such as for rolls, making it preferable.

[0142] The examples and preferred ranges of reducing agents to be added during polymerization are the same as those described above. In the present invention, ascorbic acid or a salt thereof is preferred as the reducing agent to be added later.

[0143] The amount of reducing agent added during polymerization is not particularly limited and can be appropriately selected according to the purpose of use. However, when the amount is in the range of 0.0001 to 1 part by weight, preferably 0.0005 to 0.5 parts by weight, more preferably 0.001 to 0.5 parts by weight, particularly preferably 0.005 to 0.1 parts by weight, and most preferably 0.01 to 0.05 parts by weight per 100 parts by weight of monomer components, it is preferable to have excellent productivity in acrylic rubber production and to have a high balance between the strength characteristics and processability of the produced acrylic rubber.

[0144] The reducing agent added during polymerization may be added continuously or batch-wise, but batch-wise is preferred. There are no particular limitations on the number of batch-wise additions of the reducing agent during polymerization, but it is usually 1 to 5 times, preferably 1 to 3 times, and more preferably 1 to 2 times.

[0145] When the reducing agent added during and after polymerization is ascorbic acid or a salt thereof, the ratio of the amount of ascorbic acid or a salt added initially to the amount of ascorbic acid or a salt added later is not particularly limited. However, when the weight ratio of "initially added ascorbic acid or a salt thereof" / "batch-added ascorbic acid or a salt thereof" is in the range of 1 / 9 to 8 / 2, preferably 2 / 8 to 6 / 4, and more preferably 3 / 7 to 5 / 5, it is preferable to have excellent productivity in acrylic rubber production and to achieve a high balance between the strength characteristics and processability of the produced acrylic rubber.

[0146] There are no particular limitations on the timing of post-addition of the reducing agent, and it can be appropriately selected according to the intended use. However, it is preferable to add the reducing agent at least 1 hour after the start of polymerization, preferably 1 to 3 hours after the start of polymerization, and more preferably 1.5 to 2.5 hours later, as this allows for excellent productivity in acrylic rubber production and a high balance between the strength characteristics of the produced acrylic rubber and the processability of rolls, etc.

[0147] The amount of reducing agent added in batches is not particularly limited and can be appropriately selected according to the intended use. However, when the amount is typically in the range of 0.00005 to 0.5 parts by weight, preferably 0.0001 to 0.1 parts by weight, more preferably 0.0005 to 0.05 parts by weight, and particularly preferably 0.001 to 0.03 parts by weight per 100 parts by weight of monomer component, it is preferable to have a high balance between the strength characteristics of the acrylic rubber produced and the processability of rolls, etc.

[0148] There are no particular limitations on the operation after adding the reducing agent, but the polymerization reaction can usually be continued for 30 minutes or more, preferably 45 minutes or more, and more preferably 1 hour or more before being terminated.

[0149] The polymerization conversion rate in the emulsion polymerization reaction is not particularly limited, but is usually 90% by weight or more, preferably 95% by weight or more. The acrylic rubber produced at this time is suitable because it has excellent strength properties and is free of monomer odor. A polymerization inhibitor may be used to stop the polymerization.

[0150] (solidification process) The solidification step after emulsion polymerization is characterized by adding the emulsion polymerization solution obtained in the above emulsion polymerization to a stirring solidification solution and allowing it to solidify to produce a water-containing acrylic rubber crumb.

[0151] The solid content concentration of the emulsion polymerization solution used in this coagulation reaction is not particularly limited, but is usually adjusted to a range of 5 to 50% by weight, preferably 10 to 45% by weight, and more preferably 20 to 40% by weight.

[0152] The coagulant used in the coagulation solution is not particularly limited, but metal salts are usually used. Examples of metal salts include alkali metals, Group 2 metal salts of the periodic table, and other metal salts. Preferably, alkali metal salts, Group 2 metal salts of the periodic table, more preferably Group 2 metal salts of the periodic table, and especially preferably magnesium salts are used, as this allows for a high balance of water resistance, strength properties, mold release properties, and processability of the resulting acrylic rubber.

[0153] Examples of alkali metal salts include sodium salts such as sodium chloride, sodium nitrate, and sodium sulfate; potassium salts such as potassium chloride, potassium nitrate, and potassium sulfate; and lithium salts such as lithium chloride, lithium nitrate, and lithium sulfate. Among these, sodium salts are preferred, and sodium chloride and sodium sulfate are particularly preferred.

[0154] Examples of Group 2 metal salts of the periodic table include magnesium chloride, calcium chloride, magnesium nitrate, calcium nitrate, magnesium sulfate, and calcium sulfate, with calcium chloride and magnesium sulfate being preferred.

[0155] Other metal salts include, for example, zinc chloride, titanium chloride, manganese chloride, iron chloride, cobalt chloride, nickel chloride, aluminum chloride, tin chloride, zinc nitrate, titanium nitrate, manganese nitrate, iron nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate, tin nitrate, zinc sulfate, titanium sulfate, manganese sulfate, iron sulfate, cobalt sulfate, nickel sulfate, aluminum sulfate, and tin sulfate.

[0156] These coagulants can be used individually or in combination of two or more types. The amount used is typically 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weight, and more preferably 1 to 30 parts by weight, per 100 parts by weight of the monomer component. When the coagulant is within this range, it is preferable because it allows for sufficient solidification of the acrylic rubber while significantly improving the compression set resistance and water resistance when the acrylic rubber is crosslinked.

[0157] In the solidification process of the present invention, the washing efficiency and ash removal efficiency during dewatering are significantly improved by concentrating the particle size of the generated water-containing crumbs in a specific region, which is preferable. There are no particular limitations on the proportion of the generated water-containing crumbs in the range of 710 μm to 6.7 mm (those that do not pass through 710 μm but pass through 6.7 mm), but it is preferable that the water resistance of the acrylic rubber is significantly improved when it is usually 30% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more, particularly preferably 70% by weight or more, and most preferably 80% by weight or more, relative to the total generated water-containing crumbs. Furthermore, while there are no particular limitations on the proportion of the generated water-containing crumbs in the range of 710 μm to 4.75 mm (those that do not pass through 710 μm but pass through 4.75 mm), it is preferable that the water resistance of the acrylic rubber is significantly improved when it is typically 30% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more, particularly preferably 70% by weight or more, and most preferably 80% by weight or more, relative to the total generated water-containing crumbs. In addition, while there are no particular limitations on the proportion of the generated water-containing crumbs in the range of 710 μm to 3.35 mm (those that do not pass through 710 μm but pass through 3.35 mm), it is preferable that the water resistance of the acrylic rubber is significantly improved when it is typically 20% by weight or more, preferably 30% by weight or more, more preferably 40% by weight or more, particularly preferably 50% by weight or more, and most preferably 60% by weight or more, relative to the total generated water-containing crumbs.

[0158] There are no particular limitations on the means for generating the particle size of the water-containing crumb within the above range. For example, the method of contact between the emulsion polymerization solution and the coagulant can be achieved by adding the coagulant to the coagulation solution (aqueous solution of coagulant) while stirring the emulsion polymerization solution, or by specifying the coagulant concentration of the coagulation solution, the number of stirs of the coagulation solution being stirred, and the peripheral speed.

[0159] The coagulation solution used is usually an aqueous solution, and while there are no particular limitations on the concentration of the coagulant in the aqueous solution, it is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more, and particularly preferably 1.5% by weight or more. The coagulant concentration of the coagulation solution is also suitable when it is usually in the range of 0.1 to 20% by weight, preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight, and particularly preferably 1.5 to 5% by weight, as it allows the particle size of the resulting water-containing crumbs to be concentrated uniformly within a specific region.

[0160] While there are no particular limitations on the temperature of the coagulation solution, it is generally preferable to have a temperature of 40°C or higher, preferably 40-90°C, and more preferably 50-80°C, in which a uniform water-containing crumb is produced.

[0161] The stirring speed (rotation speed) of the coagulated liquid being stirred is, in other words, the rotation speed of the stirring blades of the stirring device. There are no particular limitations, but it is usually in the range of 100 rpm or more, preferably 200 rpm or more, more preferably 200 to 1000 rpm, particularly preferably 300 to 900 rpm, and most preferably 400 to 800 rpm.

[0162] A rotation speed that allows for fairly vigorous stirring is preferable, as it enables the formation of smaller and more uniform water-containing crumb particles. Setting the rotation speed above the lower limit suppresses the formation of excessively large and small crumb particles, while setting it below the upper limit makes it easier to control the coagulation reaction.

[0163] The peripheral speed of the agitated solidifying liquid, that is, the speed of the outer circumference of the agitator's impeller, is not particularly limited, but it is preferable to a certain degree of vigorous agitation to make the generated water-containing crumb particle size smaller and more uniform, and is usually 0.5 m / s or more, preferably 1 m / s or more, more preferably 1.5 m / s or more, particularly preferably 2 m / s or more, and most preferably 2.5 m / s or more. On the other hand, the upper limit of the peripheral speed is not particularly limited, but it is usually 50 m / s or less, preferably 30 m / s or less, more preferably 25 m / s or less, and most preferably 20 m / s or less, as this facilitates control of the solidification reaction and is therefore preferable.

[0164] By setting the above conditions for the coagulation reaction (addition method, solid content concentration of emulsion polymerization solution, concentration and temperature of coagulation solution, rotation speed and peripheral speed during stirring of coagulation solution, etc.) within a specific range, the shape and diameter of the resulting water-containing crumbs become uniform and concentrated, the removal of emulsifiers and coagulants during washing and dewatering is significantly improved, and as a result, the water resistance and storage stability of the manufactured acrylic rubber can be greatly improved, making this method preferable.

[0165] (Washing process) The washing step in the method for producing acrylic rubber of the present invention is characterized by washing the water-containing crumb produced by the above-mentioned coagulation reaction with hot water.

[0166] There are no particular limitations on the washing method; for example, the generated hydrated crumb can be mixed with a large amount of hot water.

[0167] The amount of hot water added for washing is not particularly limited, but it is preferable that the amount of water added per wash is usually 50 parts by weight or more, preferably 50 to 15,000 parts by weight, more preferably 100 to 10,000 parts by weight, and even more preferably 500 to 5,000 parts by weight per 100 parts by weight of monomer component, as this effectively reduces the amount of ash in the acrylic rubber.

[0168] The temperature of the hot water used is not particularly limited, but is usually 40°C or higher, preferably 40-100°C, and more preferably 50-90°C. In particular, a temperature of 60-80°C is optimal as it can significantly increase cleaning efficiency. By using water at a temperature above the lower limit mentioned above, emulsifiers and coagulants are released from the water-containing crumb, further improving cleaning efficiency.

[0169] There are no particular limitations on the washing time, but it is usually in the range of 1 to 120 minutes, preferably 2 to 60 minutes, and more preferably 3 to 30 minutes.

[0170] The number of washes (rinses with water) is not particularly limited, and is usually 1 to 10 times, preferably 1 to 5 times, and more preferably 2 to 3 times. From the viewpoint of reducing the amount of residual coagulant in the final acrylic rubber, a higher number of washes is desirable, but as described above, the number of washes can be significantly reduced by setting the shape and diameter of the water-containing crumbs to a specific range and / or setting the washing temperature to the above range.

[0171] (Dehydration process) The dehydration step in the method for producing acrylic rubber of the present invention is a step of dehydrating the washed water-containing crumb.

[0172] There are no particular limitations on the method for dewatering the water-containing crumb, as long as it can squeeze out the water from the crumb, and it can usually be done using a dewatering machine. This is preferable because it reduces the amount of emulsifier and coagulant ash contained in the water-containing crumb that could not be removed in the washing process, and significantly improves the water resistance of the acrylic rubber.

[0173] The dewatering machine is not particularly limited; for example, a centrifugal separator, squeezer, or screw extruder can be used. However, a screw extruder is particularly preferable because it can significantly reduce the water content of the water-containing crumb. With adhesive acrylic rubber, centrifugal separators and the like can only dewater it to about 45-55% by weight because the acrylic rubber adheres to the walls and between the slits. In contrast, a screw extruder is preferable because it has a mechanism that forcibly squeezes out the water.

[0174] The water content of the dehydrated crumb is not limited, but is usually in the range of 1 to 50% by weight, preferably 1 to 40% by weight, more preferably 10 to 40% by weight, and more preferably 15 to 35% by weight. By keeping the water content after dehydration above the lower limit, the dehydration time can be shortened and deterioration of the acrylic rubber can be suppressed, while keeping it below the upper limit can sufficiently reduce the amount of ash.

[0175] (drying process) The drying step in the method for producing acrylic rubber of the present invention is a step of drying the dehydrated water-containing crumb to less than 1% by weight.

[0176] There are no particular limitations on the method for drying the dehydrated crumb, but for example, the dehydrated crumb may be dried by a direct drying method, although it is preferable to use a screw-type twin-screw extruder. There are no particular limitations on the screw-type twin-screw extruder used as long as it is an extruder with two screws, but in the present invention, it is particularly preferable to use a screw-type twin-screw extruder with two screws to dry the crumb under high shear conditions, as this allows for a high balance of roll processability, Banbury processability, and strength characteristics of the acrylic rubber obtained.

[0177] In this invention, acrylic rubber can be obtained by melting and extruding hydrated crumb in a screw-type twin-screw extruder. The drying temperature (set temperature) of the screw-type twin-screw extruder can be selected as appropriate, but it is generally suitable when it is in the range of 100 to 250°C, preferably 110 to 200°C, and more preferably 120 to 180°C, as this allows for efficient drying without burning or deterioration of the acrylic rubber.

[0178] In the present invention, when the water-containing crumb is melted under reduced pressure and extruded dry in a screw-type twin-screw extruder, the storage stability of the acrylic rubber can be greatly enhanced without impairing its rollability or strength characteristics, which is preferable. The degree of reduced pressure in the screw-type twin-screw extruder, which is suitable for removing the air contained in the acrylic rubber at this stage and enhancing storage stability, can be appropriately selected, but is usually in the range of 1 to 50 kPa, preferably 2 to 30 kPa, and more preferably 3 to 20 kPa.

[0179] In the present invention, it is preferable that the Banbury processability of the acrylic rubber be greatly enhanced without impairing its roll processability or strength characteristics when the water-containing crumb is melt-kneaded and dried in a screw-type twin-screw extruder with almost all the water removed. The state in which almost all the water is removed to greatly enhance Banbury processability can be appropriately selected, but the water content of the acrylic rubber is usually less than 1% by weight, preferably 0.8% by weight or less, and more preferably 0.6% by weight or less. In the present invention, "melt kneading" or "melt kneading and drying" means that the acrylic rubber is kneaded (mixed) in a molten state or extruded in a molten state in a screw-type twin-screw extruder and dried at that stage, or that the acrylic rubber is kneaded in a molten (plasticized) state in a screw-type twin-screw extruder, extruded and dried.

[0180] The maximum torque of the screw-type twin-screw extruder used in the present invention is not particularly limited, but is usually 20 N·m or more, preferably 25 N·m or more, more preferably 30 N·m or more, particularly preferably 35 N·m or more, and most preferably 40 N·m or more. The maximum torque of the screw-type twin-screw extruder used in the present invention is also suitable when it is in the range of 25 to 125 N·m, preferably 30 to 100 N·m, more preferably 35 to 75 N·m, and particularly preferably 40 to 60 N·m, as this allows for a high balance of roll processability, Banbury processability, and strength characteristics of the manufactured acrylic rubber.

[0181] While there are no particular limitations on the specific power of the screw-type twin-screw extruder used in the present invention, it is generally preferable that the roll processability, Banbury processability, and strength characteristics of the acrylic rubber obtained are well balanced when the specific power is in the range of 0.1 to 0.25 [kW·h / kg] or higher, preferably 0.13 to 0.23 [kW·h / kg], and more preferably 0.15 to 0.2 [kW·h / kg].

[0182] While there are no particular limitations on the specific power of the screw-type twin-screw extruder used in the present invention, it is generally preferable that the roll processability, Banbury processability, and strength characteristics of the acrylic rubber obtained are highly balanced when the specific power is in the range of 0.2 to 0.6 [A·h / kg] or higher, preferably 0.25 to 0.55 [A·h / kg], and more preferably 0.35 to 0.5 [A·h / kg].

[0183] While there are no particular limitations on the shear speed of the screw-type twin-screw extruder used in the present invention, it is generally preferable that the acrylic rubber obtained is in the range of 40 to 150 [1 / s] or higher, preferably 45 to 125 [1 / s], and more preferably 50 to 100 [1 / s], as this provides a high balance of storage stability, roll processability, Banbury processability, and strength characteristics.

[0184] While there are no particular limitations on the shear viscosity of the acrylic rubber in the screw-type twin-screw extruder used in the present invention, it is generally preferable that the storage stability, roll processability, Banbury processability, and strength characteristics of the obtained acrylic rubber are well-balanced when it is in the range of 4000 to 8000 [Pa·s] or less, preferably 4500 to 7500 [Pa·s], and more preferably 5000 to 7000 [Pa·s].

[0185] The acrylic rubber of the present invention is cooled after melt-mixing and drying. There are no particular limitations on the cooling rate, but it is preferable that the acrylic rubber is cooled at 40°C / hr or higher, preferably 50°C / hr or higher, more preferably 100°C / hr or higher, and especially preferably 150°C / hr or higher, as this provides excellent storage stability, roll processability, Banbury processability, strength properties, water resistance, and compression set resistance, as well as significantly improved scorch stability.

[0186] The acrylic rubber obtained in this way is excellent in roll processability, strength characteristics, and water resistance, and can be used for various applications. There are no particular limitations on the shape of the acrylic rubber of this invention, and it can be selected according to the purpose of use. For example, it can be in powder form, crumb form, strand form, sheet form, bale form, etc., but sheet form and bale form are preferable because they offer excellent workability and storage stability.

[0187] (Method for manufacturing sheet-like or bale-like acrylic rubber) The method for producing sheet-like or bale-like acrylic rubber according to the present invention is not particularly limited, but sheet-like acrylic rubber can be easily produced by dewatering the washed water-containing crumb in a dewatering barrel having a dewatering slit, a drying barrel under reduced pressure, and a screw-type twin-screw extruder with a die at the tip, to a water content of 1 to 40% by weight in the dewatering barrel, then drying it to less than 1% by weight in the drying barrel, and extruding the sheet-like dried rubber from the die. Alternatively, bale-like acrylic rubber can be easily produced by laminating the extruded sheet-like dried rubber to form a bale.

[0188] In the present invention, it is preferable that the water-containing crumb supplied to the screw-type twin-screw extruder dryer is one from which free water has been removed (drained) after washing.

[0189] (Draining process) In the present invention, it is preferable to include a dewatering step in which free water is separated from the water-containing crumb after washing using a dewatering machine in order to improve the dewatering efficiency.

[0190] Any known draining device can be used without any particular limitations, such as wire mesh, screens, or electric sieving machines, with wire mesh or screens being preferred.

[0191] While there are no particular limitations on the mesh size of the drainer, it is generally preferable when it is in the range of 0.01 to 5 mm, preferably 0.1 to 1 mm, and more preferably 0.2 to 0.6 mm, as this minimizes water crumb loss and allows for efficient draining.

[0192] The water content of the crumb after draining, that is, the water content of the crumb that is put into the dehydration and drying process, is not particularly limited, but is usually in the range of 50 to 80% by weight, preferably 50 to 70% by weight, and more preferably 50 to 60% by weight.

[0193] The temperature of the water-containing crumb after draining, that is, the temperature of the water-containing crumb introduced into the dewatering and drying process, is not particularly limited, but is usually 40°C or higher, preferably 40-100°C, more preferably 50-90°C, especially preferably 55-85°C, and most preferably 60-80°C. This is suitable because it allows for efficient dewatering and drying of water-containing crumb, such as the acrylic rubber of the present invention, which has a high specific heat of 1.5-2.5 kJ / kg·K and is difficult to raise in temperature, using a screw-type twin-screw extruder dryer.

[0194] (Dehydration of water-containing crumb in the dehydration barrel) Dewatering of the water-containing crumb is performed in a dewatering barrel in a screw-type twin-screw extruder dryer equipped with dewatering slits. The opening of the dewatering slits can be appropriately selected according to the operating conditions, but it is generally preferable to have an opening of 0.01 to 5 mm, preferably 0.1 to 1 mm, and more preferably 0.2 to 0.6 mm, as this minimizes water-containing crumb loss and allows for efficient dewatering.

[0195] The number of dewatering barrels in a screw-type twin-screw extruder dryer is not particularly limited, but it is usually preferable to have several, preferably 2 to 10, and more preferably 3 to 6, when efficiently dewatering sticky acrylic rubber.

[0196] In a dewatering barrel, there are two methods for removing water from water-containing crumb: removing it as a liquid through a dewatering slit (wastewater) and removing it as a vapor (exhaust steam). In this invention, wastewater is defined as dewatering, and exhaust steam is defined as pre-drying, and these two methods are distinguished.

[0197] In the dewatering of water-containing crumb, the water discharged from the dewatering slit can be in either liquid (wastewater) or vapor (exhaust steam) form. However, when using a screw-type twin-screw extruder dryer equipped with multiple dewatering barrels, combining wastewater and exhaust steam is preferable for efficient dewatering of adhesive acrylic rubber. The choice between wastewater-type and exhaust steam-type dewatering barrels in a screw-type twin-screw extruder dryer equipped with three or more dewatering barrels can be made appropriately depending on the intended use. Generally, to reduce the ash content in sheet-type or bale-type acrylic rubber manufactured, more wastewater-type barrels are used, while to reduce the water content, more exhaust steam-type barrels are used.

[0198] The set temperature of the dewatering barrel is appropriately selected depending on the monomer composition of the acrylic rubber, ash content, water content, and operating conditions, but is usually in the range of 60 to 150°C, preferably 70 to 140°C, and more preferably 80 to 130°C. The set temperature of the dewatering barrel when dewatering in a drainage state is usually 60 to 120°C, preferably 70 to 110°C, and more preferably 80 to 100°C. The set temperature of the dewatering barrel when dewatering in a drainage steam state is usually in the range of 100 to 150°C, preferably 105 to 140°C, and more preferably 110 to 130°C.

[0199] While there are no particular limitations on the water content after dewatering in drainage-type dewatering, which squeezes water out of water-containing crumb, it is generally preferable that productivity and ash removal efficiency are well balanced when the water content is typically 1 to 40% by weight, preferably 5 to 40% by weight, more preferably 5 to 35% by weight, and especially preferably 10 to 35% by weight.

[0200] When dewatering sticky acrylic rubber containing reactive groups using a centrifuge or the like, the acrylic rubber adheres to the dewatering slits, making dewatering almost impossible (water content reduced to about 45-55% by weight). However, in this invention, by using a screw-type twin-screw extruder dryer that has dewatering slits and forcibly squeezes with a screw, the water content can be reduced to this extent.

[0201] When a drain-type dewatering barrel and an exhaust-steam type dewatering barrel are provided, the dewatering of the water-containing crumb is such that the water content after draining in the drain-type dewatering barrel is typically 5 to 40% by weight, preferably 10 to 40% by weight, more preferably 15 to 35% by weight, and the water content after pre-drying in the exhaust-steam type dewatering barrel is typically 1 to 30% by weight, preferably 3 to 20% by weight, more preferably 5 to 15% by weight.

[0202] By keeping the water content after dewatering above the lower limit, the dewatering time can be shortened and deterioration of the acrylic rubber can be suppressed. By keeping it below the upper limit, the amount of ash can be sufficiently reduced.

[0203] (Drying of moist crumb in the drying barrel section) The drying of the dehydrated crumb is preferably carried out under reduced pressure in a screw-type twin-screw extruder equipped with a drying barrel. Drying the acrylic rubber under reduced pressure increases the production efficiency of the drying process, and removes the air contained within the acrylic rubber, resulting in the production of sheet-like or bale-like acrylic rubber with a high specific gravity and excellent storage stability, which is preferable. In this invention, the storage stability can also be greatly enhanced by melting the acrylic rubber under reduced pressure and extruding it. The storage stability of acrylic rubber can be largely controlled in correlation with its specific gravity, but when controlling high storage stability with a high specific gravity, it can be controlled by the degree of reduced pressure during extrusion drying.

[0204] The degree of vacuum in the drying barrel can be selected as appropriate, but it is generally preferable to set it to 1-50 kPa, preferably 2-30 kPa, and more preferably 3-20 kPa, as this allows for efficient drying of the water-containing crumb and removes air from the acrylic rubber, significantly improving the storage stability of the sheet-like or bale-like acrylic rubber.

[0205] The drying barrel temperature can be selected as appropriate, but it is generally suitable when it is in the range of 100 to 250°C, preferably 110 to 200°C, and more preferably 120 to 180°C, as this allows for efficient drying without burning or deterioration of the acrylic rubber and reduces the amount of methyl ethyl ketone insoluble in the sheet-like or veil-like acrylic rubber.

[0206] The number of drying barrels in a screw-type twin-screw extruder dryer is not particularly limited, but is usually several, preferably 2 to 10, and more preferably 3 to 8. When there are multiple drying barrels, the degree of reduced pressure may be similar for all drying barrels, or it may be varied. When there are multiple drying barrels, the set temperature may be similar for all drying barrels, or it may be varied, but it is preferable to set the temperature at the discharge section (closer to the die) higher than the temperature at the inlet section (closer to the dewatering barrel) to improve drying efficiency.

[0207] The water content of the dried rubber after drying is usually less than 1% by weight, preferably 0.8% by weight or less, and more preferably 0.6% by weight or less. In the present invention, it is particularly preferable to melt-extrude the dried rubber in a screw-type twin-screw extruder to this water content (a state in which almost all water has been removed) in order to reduce the amount of methyl ethyl ketone insoluble in the sheet-type or bale-type acrylic rubber. In the present invention, acrylic rubber that has been melt-mixed or melt-mixed and dried in a screw-type twin-screw extruder is preferable because it has a high balance of both strength characteristics and Banbury processability characteristics. In the present invention, "melt-mixing" or "melt-mixing and drying" means that the acrylic rubber is mixed (combined) in a molten state or extruded in a molten state in a screw-type twin-screw extruder and dried at that stage, or that the acrylic rubber is mixed in a molten (plasticized) state in a screw-type twin-screw extruder, extruded, and dried.

[0208] In the present invention, the shear rate in the drying barrel of a screw-type twin-screw extruder, when the acrylic rubber is substantially free of water, is not particularly limited, but is usually in the range of 10 [1 / s] or more, preferably 10 to 400 [1 / s], and more preferably 50 to 250 [1 / s]. When this range is used, the storage stability, roll processability, Banbury processability, strength characteristics, and compression set resistance characteristics of the sheet-like or bale-like acrylic rubber obtained are well-balanced and preferable.

[0209] In the screw-type twin-screw extruder used in the present invention, particularly in the drying barrel, the shear viscosity of the acrylic rubber is not particularly limited, but is usually 12,000 [Pa·s] or less, preferably 1,000 to 12,000 [Pa·s], more preferably 2,000 to 10,000 [Pa·s], particularly preferably 3,000 to 7,000 [Pa·s], and most preferably 4,000 to 6,000 [Pa·s]. When this range is obtained, the storage stability, roll processability, Banbury processability, and strength characteristics of the resulting sheet-like or bale-like acrylic rubber are well-balanced and preferable.

[0210] (Extrusion of dried rubber from the die section) The dried rubber, dewatered and dried in the screw section of the dewatering barrel and drying barrel described above, is sent to a die section without a screw for straightening the flow, and is extruded from the die section into the desired shape. A breaker plate or wire mesh may or may not be provided between the screw section and the die section.

[0211] The extruded dried rubber is preferably produced in a sheet form with a roughly rectangular die shape, resulting in a dried rubber with less air entrapment, a higher specific gravity, and excellent storage stability.

[0212] The resin pressure in the die section is not particularly limited, but it is generally preferable to set it in the range of 0.1 to 10 MPa, preferably 0.5 to 5 MPa, and more preferably 1 to 3 MPa, as this minimizes air entrapment in the sheet-like or bale-like acrylic rubber (resulting in high specific gravity) and excellent productivity.

[0213] Screw-type twin-screw extruder dryer and operating conditions The screw length (L) of the screw-type twin-screw extruder dryer used can be appropriately selected according to the intended use, but is typically in the range of 3,000 to 15,000 mm, preferably 4,000 to 10,000 mm, and more preferably 4,500 to 8,000 mm.

[0214] The screw diameter (D) of the screw-type twin-screw extruder dryer used can be appropriately selected depending on the intended use, but is typically in the range of 50 to 250 mm, preferably 100 to 200 mm, and more preferably 120 to 160 mm.

[0215] The ratio (L / D) of the screw length (L) to the screw diameter (D) of the screw-type twin-screw extruder dryer used is not particularly limited, but is usually in the range of 10 to 100, preferably 20 to 80, and more preferably 30 to 60, as this allows the water content to be reduced to less than 1% by weight without causing a decrease in molecular weight or burning of the dried rubber.

[0216] The rotational speed (N) of the screw-type twin-screw extruder used can be appropriately selected according to various conditions, but it is generally suitable when it is 10 to 1000 rpm, preferably 50 to 750 rpm, more preferably 100 to 500 rpm, and most preferably 120 to 300 rpm, as this efficiently reduces the water content and methyl ethyl ketone insoluble content of the sheet-like or bale-like acrylic rubber.

[0217] The extrusion rate (Q) of the screw-type twin-screw extruder dryer used is not particularly limited, but is usually in the range of 100 to 1,500 kg / hr, preferably 300 to 1,200 kg / hr, more preferably 400 to 1,000 kg / hr, and most preferably 500 to 800 kg / hr.

[0218] The ratio (Q / N) of the extrusion rate (Q) to the rotational speed (N) of the screw-type twin-screw extruder dryer used is not particularly limited, but is usually in the range of 2 to 10, preferably 3 to 8, and more preferably 4 to 6.

[0219] The maximum torque of the screw-type twin-screw extruder used is not particularly limited, but is usually 30 N·m or more, preferably 35 N·m or more, and more preferably 40 N·m or more. The maximum torque of the screw-type twin-screw extruder used in the present invention is also suitable when it is usually in the range of 30 to 100 N·m, preferably 35 to 75 N·m, and more preferably 40 to 60 N·m, as this allows for a high balance of roll processability, Banbury processability, and strength characteristics of the sheet-like or bale-like acrylic rubber produced.

[0220] While there are no particular limitations on the specific power of the screw-type twin-screw extruder used, it is generally preferable that the roll processability, Banbury processability, and strength characteristics of the resulting sheet-like or bale-like acrylic rubber are well-balanced when it is in the range of 0.1 to 0.25 [kW·h / kg] or higher, preferably 0.13 to 0.23 [kW·h / kg], and more preferably 0.15 to 0.2 [kW·h / kg].

[0221] While there are no particular limitations on the specific power of the screw-type twin-screw extruder used, it is generally preferable that the roll processability, Banbury processability, and strength characteristics of the resulting sheet-like or bale-like acrylic rubber are well-balanced when it is in the range of 0.2 to 0.6 [A·h / kg] or higher, preferably 0.25 to 0.55 [A·h / kg], and more preferably 0.35 to 0.5 [A·h / kg].

[0222] While there are no particular limitations on the shear speed of the screw-type twin-screw extruder used, it is generally preferable that the storage stability, roll processability, Banbury processability, and strength characteristics of the resulting sheet-like or bale-like acrylic rubber are well-balanced when the shear speed is in the range of 40 to 150 [1 / s] or higher, preferably 45 to 125 [1 / s], and more preferably 50 to 100 [1 / s].

[0223] While there are no particular limitations on the shear viscosity of the acrylic rubber in the screw-type twin-screw extruder used, it is generally preferable that the storage stability, roll processability, Banbury processability, and strength characteristics of the resulting sheet-like or bale-like acrylic rubber are well-balanced when it is in the range of 4000 to 8000 [Pa·s] or less, preferably 4500 to 7500 [Pa·s], and more preferably 5000 to 7000 [Pa·s].

[0224] Thus, in the present invention, using an extrusion dryer having twin screws makes it possible to dehydrate, dry, and mold under high-shear conditions, which is preferable.

[0225] (Sheet-shaped dry rubber) The dried rubber extruded from a screw-type twin-screw extruder is in the form of a sheet. This process avoids the entrainment of air, increasing the specific gravity and significantly improving storage stability, making it highly suitable. The sheet-shaped dried rubber extruded from the screw-type twin-screw extruder is typically cooled and cut for use as sheet-shaped acrylic rubber.

[0226] While there are no particular limitations on the thickness of the sheet-like dried rubber extruded from a screw-type twin-screw extruder, it is generally preferable for workability and productivity when the thickness is in the range of 1 to 40 mm, preferably 2 to 35 mm, more preferably 3 to 30 mm, and most preferably 5 to 25 mm. In particular, when the thermal conductivity of the sheet-like dried rubber is low at 0.15 to 0.35 W / mK and cooling efficiency is increased to significantly improve productivity, the thickness of the sheet-like dried rubber is generally in the range of 1 to 30 mm, preferably 2 to 25 mm, more preferably 3 to 15 mm, and especially preferably 4 to 12 mm.

[0227] The width of the sheet-like dried rubber extruded from the screw-type twin-screw extruder is appropriately selected depending on the intended use, but is usually in the range of 300 to 1200 mm, preferably 400 to 1000 mm, and more preferably 500 to 800 mm.

[0228] The temperature of the dried rubber extruded from the screw-type twin-screw extruder is not particularly limited, but is usually in the range of 100 to 200°C, preferably 110 to 180°C, and more preferably 120 to 160°C.

[0229] The water content of the dried rubber extruded from the screw-type twin-screw extruder is not particularly limited, but is usually less than 1% by weight, preferably 0.8% by weight or less, and more preferably 0.6% by weight or less.

[0230] The complex viscosity ([η]100°C) of sheet-shaped dried rubber extruded from a screw-type twin-screw extruder is not particularly limited, but is generally suitable when it is in the range of 1500 to 6000 [Pa·s], preferably 2000 to 5000 [Pa·s], more preferably 2500 to 4000 [Pa·s], and most preferably 2500 to 3500 [Pa·s], as this provides a high balance between extrudeability and shape retention as a sheet. In other words, setting it above the lower limit improves extrudeability, while setting it below the upper limit suppresses deformation and breakage of the sheet-shaped dried rubber.

[0231] The sheet-like dried rubber extruded from the screw-type twin-screw extruder can be used as is after folding, but it is usually cut before use.

[0232] While there are no particular limitations on how the sheet-shaped dried rubber is cut, because the acrylic rubber of the present invention is highly adhesive, it is preferable to cool the sheet-shaped dried rubber before cutting in order to cut it continuously without trapping air.

[0233] While there are no particular limitations on the cutting temperature of sheet-shaped dried rubber, it is generally preferable to have a cutting temperature of 60°C or lower, preferably 55°C or lower, and more preferably 50°C or lower, as this provides a good balance between cutability and productivity.

[0234] The complex viscosity ([η]60°C) of sheet-shaped dry rubber at 60°C is not particularly limited, but is usually 15,000 [Pa·s] or less, preferably 2,000 to 10,000 [Pa·s], more preferably 2,500 to 7,000 [Pa·s], and most preferably in the range of 2,700 to 5,500 [Pa·s], when it is possible to cut continuously without entrapping air, which is preferable.

[0235] The ratio of the complex viscosity of sheet-shaped dry rubber at 100°C ([η]100°C) to the complex viscosity at 60°C ([η]60°C) ([η]100°C / [η]60°C) is not particularly limited and can be appropriately selected according to the intended use, but is usually 0.5 or higher, preferably 0.6 or higher, more preferably 0.7 or higher, particularly preferably 0.8 or higher, and most preferably 0.85 or higher. When the upper limit is usually 0.98 or lower, preferably 0.97 or lower, more preferably 0.96 or lower, particularly preferably 0.95 or lower, and most preferably 0.93 or lower, air entrapment is low and cutting and productivity are well balanced, making it preferable.

[0236] There are no particular limitations on the method of cooling sheet-shaped dried rubber; it may be left at room temperature. However, because the thermal conductivity of sheet-shaped dried rubber is very low (0.15-0.35 W / mK), forced cooling methods such as air cooling with a fan or under air conditioning, water spraying, or immersion in water are preferable to increase productivity, and air cooling with a fan or under air conditioning is particularly preferable.

[0237] In the air-cooling method for sheet-shaped dried rubber, for example, the sheet-shaped dried rubber can be extruded from a screw-type extruder onto a conveyor such as a belt conveyor, and then conveyed and cooled while blowing cold air onto it. The temperature of the cold air is not particularly limited, but is usually in the range of 0 to 25°C, preferably 5 to 25°C, and more preferably 10 to 20°C. The length to be cooled is not particularly limited, but is usually in the range of 5 to 500 m, preferably 10 to 200 m, and more preferably 20 to 100 m. The cooling rate of the sheet-shaped dried rubber is not particularly limited, but is usually 40°C / hr or higher, preferably 50°C / hr or higher, more preferably 100°C / hr or higher, and particularly preferably 150°C / hr or higher, as this makes cutting easier, prevents air from being trapped, and allows for good storage stability. In the present invention, the scorch stability of the acrylic rubber composition is significantly superior and preferable when the cooling rate of the sheet-like dried rubber is typically 40°C / hr or higher, preferably 50°C / hr or higher, more preferably 100°C / hr or higher, and particularly preferably 150°C / hr or higher.

[0238] The cutting length of the sheet-shaped dried rubber is not particularly limited and can be appropriately selected depending on the intended use, but is usually in the range of 100 to 800 mm, preferably 200 to 500 mm, and more preferably 250 to 450 mm.

[0239] The resulting sheet-like acrylic rubber offers superior handling compared to clam-like acrylic rubber, as well as excellent roll-processability, crosslinking properties, strength characteristics, and compression set resistance. It also boasts superior storage stability, Banbury processability, and water resistance, and can be used as is or laminated into bales.

[0240] (Lamination process) The method for producing the veil-like acrylic rubber of the present invention is not particularly limited, but it is preferable to laminate the above-mentioned sheet-like acrylic rubber to obtain a veil-like acrylic rubber with excellent storage stability and minimal air entrapment.

[0241] The lamination temperature of the sheet-shaped acrylic rubber is not particularly limited, but it is generally preferable to have a temperature of 30°C or higher, preferably 35°C or higher, and more preferably 40°C or higher, as this allows air trapped during lamination to escape. The number of layers can be appropriately selected according to the size or weight of the bale-shaped acrylic rubber. The bale-shaped acrylic rubber of the present invention is integrated by the weight of the laminated sheet-shaped acrylic rubber.

[0242] The bale-shaped acrylic rubber obtained in this way is superior to clam-shaped acrylic rubber in terms of operability, roll processability, crosslinkability, strength characteristics, and compression set resistance, as well as superior storage stability, Banbury processability, and water resistance. The bale-shaped acrylic rubber can be used as is, or cut to the required amount and fed into a mixer such as a Banbury or roll.

[0243] <Rubber composition> The rubber composition of the present invention is characterized by comprising a rubber component including the acrylic rubber, a filler, and a crosslinking agent.

[0244] The main rubber component of the rubber composition of the present invention may be the acrylic rubber of the present invention alone, or, if necessary, the acrylic rubber of the present invention may be used in combination with other rubber components. The content of the acrylic rubber of the present invention in the rubber components may be selected according to the intended use, for example, usually 30% by weight or more, preferably 50% by weight or more, and more preferably 70% by weight or more.

[0245] Other rubber components to be combined with the acrylic rubber of the present invention are not particularly limited, and examples include natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, fluororubber, olefin-based elastomers, styrene-based elastomers, vinyl chloride-based elastomers, polyester-based elastomers, polyamide-based elastomers, polyurethane-based elastomers, and polysiloxane-based elastomers.

[0246] These other rubber components can be used individually or in combination of two or more. The form of these other rubber components may be clam-like, strand-like, bale-like, sheet-like, powder-like, or any other form. The content of these other rubber components in the total rubber components is appropriately selected within a range that does not impair the effects of the present invention, for example, usually 70% by weight or less, preferably 50% by weight or less, and more preferably 30% by weight or less.

[0247] There are no particular limitations on the fillers included in the rubber composition, but examples include reinforcing fillers and non-reinforcing fillers. Preferably, when a reinforcing filler is used, the rubber composition exhibits excellent roll processability, Banbury processability, and short-time crosslinking properties, and the crosslinked material exhibits extremely excellent water resistance, strength properties, and compression set resistance properties, making it preferable.

[0248] Examples of reinforcing fillers include carbon blacks such as furnace black, acetylene black, thermal black, channel black, and graphite; and silicas such as wet silica, dry silica, and colloidal silica. Examples of non-reinforcing fillers include quartz powder, diatomaceous earth, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, aluminum sulfate, calcium sulfate, and barium sulfate.

[0249] These fillers can be used individually or in combination of two or more types, and their blending amounts are appropriately selected within a range that does not impair the effects of the present invention, and are typically in the range of 1 to 200 parts by weight, preferably 10 to 150 parts by weight, and more preferably 20 to 100 parts by weight, per 100 parts by weight of the rubber component.

[0250] There are no particular limitations on the crosslinking agent used in the rubber composition; conventionally known crosslinking agents can be selected according to the intended use. Examples include inorganic crosslinking agents such as sulfur compounds and organic crosslinking agents, with organic crosslinking agents being preferred. The crosslinking agent may also be a polyvalent compound or a monovalent compound, but a polyvalent compound with two or more reactive atoms is preferred. The crosslinking agent may also be an ionic crosslinking compound or a radical crosslinking compound, but an ionic crosslinking compound is preferred.

[0251] There are no particular limitations on the organic crosslinking agent, but ionic crosslinkable organic compounds are preferred, and polyvalent ionic organic compounds are particularly preferred. When the crosslinking agent is a polyvalent ionic organic compound (polyvalent ionic crosslinkable compound), the rubber composition exhibits excellent roll processability, Banbury processability, and short-time crosslinking, and the crosslinked material has extremely excellent strength properties and compression set resistance, as well as excellent water resistance, making it particularly preferable. The "ion" in ionic crosslinking or polyvalent ion refers to an ionically reactive ion, and there are no particular limitations as long as it reacts ionically with the ionically reactive groups of the ionically reactive group-containing monomer of the acrylic rubber, for example, but preferably, ionic crosslinkable organic compounds having ionic reactivity such as amine groups, epoxy groups, carboxyl groups, and thiol groups are mentioned.

[0252] Specific examples of polyvalent ionic organic compounds include polyvalent amine compounds, polyvalent epoxy compounds, polyvalent carboxylic acid compounds, and polyvalent thiol compounds, with polyvalent amine compounds and polyvalent thiol compounds being preferred, and polyvalent amine compounds being more preferred.

[0253] Examples of polyhydric amine compounds include aliphatic polyhydric amine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, and N,N'-disinnamyridene-1,6-hexanediamine; and aromatic polyhydric amine compounds such as 4,4'-methylenedianiline, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-(m-phenylenediisopropylidene)dianiline, 4,4'-(p-phenylenediisopropylidene)dianiline, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminobenzanilide, 4,4'-bis(4-aminophenoxy)biphenyl, m-xylylenediamine, p-xylylenediamine, and 1,3,5-benzenetriamine. Among these, hexamethylenediamine carbamate and 2,2'-bis[4-(4-aminophenoxy)phenyl]propane are preferred. As polyhydric amine compounds, their carbonates can also be suitably used. These polyhydric amine compounds are particularly suitably used in combination with carboxyl group-containing acrylic rubber or epoxy group-containing acrylic rubber.

[0254] Preferably, triazine thiol compounds are used as polyvalent thiol compounds, such as 6-trimercapto-s-triazine, 2-anilino-4,6-dithiol-s-triazine, 1-dibutylamino-3,5-dimercaptotriazine, 2-dibutylamino-4,6-dithiol-s-triazine, 1-phenylamino-3,5-dimercaptotriazine, 2,4,6-trimercapto-1,3,5-triazine, and 1-hexylamino-3,5-dimercaptotriazine. These triazine thiol compounds are particularly preferably used in combination with chlorine atom-containing acrylic rubber.

[0255] Other polyvalent organic compounds include polyvalent carboxylic acid compounds such as tetradecanedioic acid, and metal salts of dithiocarbamates such as zinc dimethyldithiocarbamate. These other polyvalent organic compounds are particularly suitable for use in combination with epoxy group-containing acrylic rubber.

[0256] These crosslinking agents can be used individually or in combination of two or more, and their blending amount is usually 0.001 to 20 parts by weight, preferably 0.1 to 10 parts by weight, and more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the rubber component. By blending the crosslinking agents within this range, it is possible to achieve sufficient rubber elasticity while also providing excellent mechanical strength as a crosslinked rubber product, which is preferable.

[0257] The rubber composition of the present invention may optionally contain an anti-aging agent. The type of anti-aging agent is not particularly limited, but examples include 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butylphenol, butylhydroxyanisole, 2,6-di-t-butyl-α-dimethylamino-p-cresol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, styrene phenol, 2,2'-methylene-bis(6-α-methylbenzyl-p-cresol), and 4,4'-methylene Other examples include bis(2,6-di-t-butylphenol), 2,2'-methylene-bis(4-methyl-6-t-butylphenol), 2,4-bis[(octylthio)methyl]-6-methylphenol, 2,2'-thiobis-(4-methyl-6-t-butylphenol), 4,4'-thiobis-(6-t-butyl-o-cresol), 2,6-di-t-butyl-4-(4,6-bis(octylthio)-1,3,5-triazine-2-ylamino)phenol, and others. Phenolic antioxidants; Phosphite ester antioxidants such as tris(nonylphenyl) phosphite, diphenylisodecyl phosphite, tetraphenyldipropylene glycol diphosphite; Sulfur ester antioxidants such as dilauryl thiodipropionate; Phenyl-α-naphthylamine, phenyl-β-naphthylamine, p-(p-toluenesulfonylamide)-diphenylamine, 4,4'-(α,α-dimethylbenzyl)diphenylamine Examples include amine-based antioxidants such as amine, N,N-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, and butyraldehyde-aniline condensate; imidazole-based antioxidants such as 2-mercaptobenzimidazole; quinoline-based antioxidants such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; and hydroquinone-based antioxidants such as 2,5-di-(t-amyl)hydroquinone. Among these, amine-based antioxidants are particularly preferred.

[0258] These anti-aging agents can be used individually or in combination of two or more, and the amount added is in the range of 0.01 to 15 parts by weight, preferably 0.1 to 10 parts by weight, and more preferably 1 to 5 parts by weight, per 100 parts by weight of the rubber component.

[0259] The rubber composition of the present invention contains the above-mentioned acrylic rubber component, filler, and crosslinking agent as essential components, and optionally includes an antioxidant. Furthermore, other additives commonly used in the art, such as crosslinking aids, crosslinking accelerators, crosslinking retarders, silane coupling agents, plasticizers, processing aids, lubricants, pigments, colorants, antistatic agents, and foaming agents, may be optionally added. These other additives can be used individually or in combination of two or more, and their amounts are appropriately selected within a range that does not impair the effects of the present invention.

[0260] A method for producing the rubber composition of the present invention includes mixing rubber components including the acrylic rubber of the present invention, fillers, crosslinking agents, and optionally included antioxidants and other compounding agents. Any conventional means used in the field of rubber processing, such as open rolls, Banbury mixers, and various kneaders, can be used for mixing. The mixing procedure for each component can be carried out using the usual procedures used in the field of rubber processing. For example, it is preferable to thoroughly mix components that are not easily reacted or decomposed by heat, and then quickly mix components that are easily reacted or decomposed by heat, such as crosslinking agents, at a temperature at which no reaction or decomposition occurs.

[0261] <Rubber Crosslinked Products> The rubber crosslinked product of the present invention is obtained by crosslinking the above-mentioned rubber composition.

[0262] The crosslinked rubber product of the present invention can be manufactured by using the rubber composition of the present invention, molding it using a molding machine corresponding to the desired shape, such as an extruder, injection molding machine, compressor, or roll, and then heating it to perform a crosslinking reaction and fix the shape as a crosslinked rubber product. In this case, crosslinking may be performed either after molding or simultaneously with molding. The molding temperature is usually 10 to 200°C, preferably 25 to 150°C. The crosslinking temperature is usually 100 to 250°C, preferably 130 to 220°C, more preferably 150 to 200°C, and the crosslinking time is usually 0.1 minutes to 10 hours, preferably 1 minute to 5 hours. As for the heating method, any method used for crosslinking rubber, such as press heating, steam heating, oven heating, and hot air heating, may be appropriately selected.

[0263] Depending on the shape and size of the rubber crosslinked material of the present invention, further heating and secondary crosslinking may be performed. The duration of secondary crosslinking varies depending on the heating method, crosslinking temperature, and shape, but is preferably 1 to 48 hours. The heating method and heating temperature can be selected as appropriate.

[0264] The crosslinked rubber material of the present invention maintains basic rubber properties such as tensile strength, elongation, and hardness, while possessing excellent compression set resistance and water resistance.

[0265] The crosslinked rubber material of the present invention, taking advantage of the above properties, is suitably used as a sealing material such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, wellhead seals, seals for electrical and electronic equipment, and seals for air compressor equipment; various gaskets such as rocker cover gaskets fitted to the connection between the cylinder block and the cylinder head, oil pan gaskets fitted to the connection between the oil pan and the cylinder head or transmission case, fuel cell separator gaskets fitted between a pair of housings that sandwich a unit cell equipped with a positive electrode, electrolyte plate, and negative electrode, and gaskets for the top cover of a hard disk drive; cushioning material, vibration damping material; wire insulation material; industrial belts; tubes and hoses; sheets; and the like.

[0266] The rubber crosslinked material of the present invention is also suitably used as extruded molded products and mold crosslinked products for automotive applications, such as fuel oil system hoses such as fuel tanks, fuel hoses, filler neck hoses, vent hoses, paper hoses, and oil hoses; air system hoses such as turbo air hoses and transmission control hoses; and various types of hoses such as radiator hoses, heater hoses, brake hoses, and air conditioning hoses.

[0267] <Equipment configuration used in the manufacture of acrylic rubber> Next, the apparatus configuration used for manufacturing acrylic rubber according to one embodiment of the present invention will be described. Figure 1 is a schematic diagram showing an example of an acrylic rubber manufacturing system having the apparatus configuration used for manufacturing acrylic rubber according to one embodiment of the present invention. For example, the acrylic rubber manufacturing system 1 shown in Figure 1 can be used for manufacturing acrylic rubber according to the present invention.

[0268] The acrylic rubber manufacturing system 1 shown in Figure 1 consists of an emulsion polymerization reactor (not shown), a coagulation device 3, a washing device 4, a dewatering machine 43, and a screw-type twin-screw extruder dryer.

[0269] The emulsion polymerization reactor is configured to perform the emulsion polymerization process described above. Although not shown in Figure 1, this emulsion polymerization reactor includes, for example, a polymerization reactor, a temperature control unit for controlling the reaction temperature, a motor, and a stirring device equipped with stirring blades. In the emulsion polymerization reactor, monomer components for forming acrylic rubber are mixed with water and an emulsifier and emulsified while being appropriately stirred with a stirrer. The emulsion polymerization reaction is then started in the presence of a redox catalyst consisting of an inorganic radical generator and a reducing agent, and a chain transfer agent is added batch-wise during polymerization to obtain an emulsion polymerization solution. The emulsion polymerization reactor may be batch type, semi-batch type, or continuous type, and may be a tank reactor or a tubular reactor.

[0270] The coagulation device 3 shown in Fig. 1 is configured to perform the processes related to the coagulation process described above. As schematically illustrated in Fig. 1, the coagulation device 3 includes, for example, a stirring tank 30, a heating unit 31 for heating the inside of the stirring tank 30, a temperature control unit (not shown) for controlling the temperature inside the stirring tank 30, a stirring device 34 including a motor 32 and a stirring blade 33, and a drive control unit (not shown) for controlling the rotation speed and rotational velocity of the stirring blade 33. In the coagulation device 3, an aqueous clam can be produced by bringing the emulsion polymerization liquid obtained in the emulsion polymerization reactor into contact with a coagulation liquid to cause coagulation.

[0271] In the coagulation device 3, for example, the contact between the emulsion polymerization liquid and the coagulation liquid is achieved by a method of adding the emulsion polymerization liquid into the coagulation liquid being stirred. That is, the stirring tank 30 of the coagulation device 3 is filled with the coagulation liquid, and the emulsion polymerization liquid is added to and brought into contact with this coagulation liquid to coagulate the emulsion polymerization liquid, thereby producing an aqueous clam.

[0272] The heating unit 31 of the coagulation device 3 is configured to heat the coagulation liquid filled in the stirring tank 30. Also, the temperature control unit of the coagulation device 3 is configured to control the temperature inside the stirring tank 30 by monitoring the temperature inside the stirring tank 30 measured by a thermometer and controlling the heating operation by the heating unit 31. The temperature of the coagulation liquid inside the stirring tank 30 is controlled by the temperature control unit to be usually 40°C or higher, preferably in the range of 40 - 90°C, and more preferably in the range of 50 - 80°C.

[0273] The stirring device 34 of the coagulation device 3 is configured to stir the coagulation liquid filled in the stirring tank 30. Specifically, the stirring device 34 includes a motor 32 that generates rotational power and a stirring blade 33 that extends in a direction perpendicular to the rotation axis of the motor 32. The stirring blade 33 can cause the coagulation liquid to flow by rotating around the rotation axis by the rotational power of the motor 32 inside the coagulation liquid filled in the stirring tank 30. The shape, size, number of installations, etc. of the stirring blade 33 are not particularly limited.

[0274] The drive control unit of the solidification device 3 is configured to control the rotational drive of the motor 32 of the stirring device 34 and set the rotational speed and rotational number of the stirring blades 33 of the stirring device 34 to predetermined values. The rotation of the stirring blades 33 is controlled by the drive control unit so that the stirring speed of the solidified liquid is, for example, usually 100 rpm or more, preferably 200 to 1000 rpm, more preferably 300 to 900 rpm, and most preferably 400 to 800 rpm. The rotation of the stirring blades 33 is controlled by the drive control unit so that the peripheral speed of the solidified liquid is usually 0.5 m / s or more, preferably 1 m / s or more, more preferably 1.5 m / s or more, most preferably 2 m / s or more, and most preferably 2.5 m / s or more. Furthermore, the rotation of the stirring blades 33 is controlled by the drive control unit so that the upper limit of the peripheral speed of the solidified liquid is usually 50 m / s or less, preferably 30 m / s or less, more preferably 25 m / s or less, and most preferably 20 m / s or less.

[0275] The cleaning apparatus 4 shown in Figure 1 is configured to perform the cleaning process described above. As schematically illustrated in Figure 1, the cleaning apparatus 4 includes, for example, a cleaning tank 40, a heating unit 41 for heating the inside of the cleaning tank 40, and a temperature control unit (not shown) for controlling the temperature inside the cleaning tank 40. The cleaning apparatus 4 effectively reduces the amount of ash in the acrylic rubber obtained by washing the water-containing crumb produced in the solidification apparatus 3 with a large amount of water.

[0276] The heating unit 41 of the cleaning device 4 is configured to heat the inside of the cleaning tank 40. The temperature control unit of the cleaning device 4 is configured to control the temperature inside the cleaning tank 40 by controlling the heating operation of the heating unit 41 while monitoring the temperature inside the cleaning tank 40 measured by a thermometer. As described above, the temperature of the cleaning water inside the cleaning tank 40 is normally controlled to be in the range of 40°C or higher, preferably 40 to 100°C, more preferably 50 to 90°C, and most preferably 60 to 80°C.

[0277] The water-containing crumb washed in the washing device 4 is supplied to the screw-type twin-screw extruder dryer 5, which performs the dewatering and drying processes. At this time, it is preferable that the water-containing crumb after washing is supplied to the screw-type twin-screw extruder dryer 5 through a dewatering machine 43 capable of separating free water. For example, a wire mesh, a screen, or an electric sieving machine can be used for the dewatering machine 43.

[0278] Furthermore, when the washed water-containing crumb is supplied to the screw-type twin-screw extruder dryer 5, it is preferable that the temperature of the water-containing crumb be 40°C or higher, and more preferably 60°C or higher. For example, the temperature of the water used for washing in the washing device 4 may be set to 60°C or higher (e.g., 70°C) to maintain the temperature of the water-containing crumb at 60°C or higher when supplied to the screw-type twin-screw extruder dryer 5. Alternatively, the water-containing crumb may be heated to 40°C or higher, preferably 60°C or higher, when it is transported from the washing device 4 to the screw-type twin-screw extruder dryer 5. This makes it possible to effectively carry out the subsequent dewatering and drying processes, and to significantly reduce the moisture content of the final dried rubber.

[0279] The screw-type twin-screw extruder dryer 5 shown in Figure 1 is configured to perform the dewatering and drying processes described above. Although Figure 1 shows the screw-type twin-screw extruder dryer 5 as a preferred example, a centrifugal separator or squeezer may be used as the dewatering machine for the dewatering process, and a hot air dryer, vacuum dryer, expander dryer, kneader dryer, etc. may be used as the dryer for the drying process.

[0280] The screw-type twin-screw extruder dryer 5 is configured to mold the dried rubber obtained through the dewatering and drying processes into a predetermined shape and discharge it. Specifically, the screw-type twin-screw extruder dryer 5 is equipped with a dewatering barrel section 53 that functions as a dewatering machine for dewatering the water-containing crumb washed by the washing device 4, and a drying barrel section 54 that functions as a dryer for drying the water-containing crumb. Furthermore, a die 59 with a molding function for molding the water-containing crumb is provided downstream of the screw-type twin-screw extruder dryer 5.

[0281] The configuration of the screw-type twin-screw extruder dryer 5 will be described below with reference to Figure 2. Figure 2 shows a suitable example configuration of the screw-type twin-screw extruder dryer 5 shown in Figure 1. This screw-type twin-screw extruder dryer 5 can suitably perform the dewatering and drying process described above.

[0282] The screw-type twin-screw extruder dryer 5 shown in Figure 2 is a twin-screw extruder dryer equipped with a pair of screws (not shown) inside a barrel unit 51. The screw-type twin-screw extruder dryer 5 has a drive unit 50 that rotates the pair of screws inside the barrel unit 51. This configuration is suitable for drying acrylic rubber with high shear. The drive unit 50 is attached to the upstream end (left end in Figure 2) of the barrel unit 51. The screw-type twin-screw extruder dryer 5 also has a die 59 at the downstream end (right end in Figure 2) of the barrel unit 51.

[0283] The barrel unit 51 has a supply barrel section 52, a dewatering barrel section 53, and a drying barrel section 54, extending from the upstream side to the downstream side (from left to right in Figure 2).

[0284] The supply barrel section 52 is composed of two supply barrels, namely a first supply barrel 52a and a second supply barrel 52b.

[0285] Furthermore, the dewatering barrel section 53 is composed of three dewatering barrels, namely, a first dewatering barrel 53a, a second dewatering barrel 53b, and a third dewatering barrel 53c.

[0286] Furthermore, the drying barrel section 54 is composed of eight drying barrels, namely, a first drying barrel 54a, a second drying barrel 54b, a third drying barrel 54c, a fourth drying barrel 54d, a fifth drying barrel 54e, a sixth drying barrel 54f, a seventh drying barrel 54g, and an eighth drying barrel 54h.

[0287] Thus, the barrel unit 51 is constructed by connecting 13 divided barrels 52a-52b, 53a-53c, and 54a-54h from the upstream side to the downstream side.

[0288] Furthermore, the screw-type twin-screw extruder dryer 5 has heating means (not shown) that individually heat each of the barrels 52a-52b, 53a-53c, and 54a-54h to heat the water-containing crumb in each barrel 52a-52b, 53a-53c, and 54a-54h to a predetermined temperature. The heating means is provided in a number corresponding to each of the barrels 52a-52b, 53a-53c, and 54a-54h. Such heating means may, but are not limited to, a configuration in which high-temperature steam is supplied from a steam supply means to a steam flow jacket formed in each of the barrels 52a-52b, 53a-53c, and 54a-54h. The screw-type twin-screw extruder dryer 5 also has temperature control means (not shown) that control the set temperature of each heating means corresponding to each of the barrels 52a-52b, 53a-53c, and 54a-54h.

[0289] Furthermore, the number of supply barrels, dewatering barrels, and drying barrels that constitute each barrel section 52, 53, and 54 in the barrel unit 51 is not limited to the configuration shown in Figure 2, and can be set to a number that corresponds to the water content of the water-containing crumb of acrylic rubber to be dried.

[0290] For example, the number of supply barrels in the supply barrel section 52 is, for example, 1 to 3. The number of dewatering barrels in the dewatering barrel section 53 is preferably, for example, 2 to 10, and more preferably 3 to 6, as this allows for efficient dewatering of the water-containing crumb of sticky acrylic rubber. The number of drying barrels in the drying barrel section 54 is preferably, for example, 2 to 10, and more preferably 3 to 8.

[0291] The pair of screws within the barrel unit 51 are rotationally driven by drive means such as a motor stored in the drive unit 50. The pair of screws extend from the upstream side to the downstream side within the barrel unit 51, and by being rotationally driven, they can convey the water-containing clam supplied to the supply barrel portion 52 to the downstream side while mixing it. As the pair of screws, a two-axis meshing type in which the ridges and valleys mesh with each other is preferably adopted, and thereby, the dehydration efficiency and drying efficiency of the water-containing clam can be enhanced.

[0292] Also, the rotational directions of the pair of screws may be the same or different, but in terms of the self-cleaning performance, a type that rotates in the same direction is preferably adopted. The screw shape of the pair of screws is not particularly limited, and it may be any shape required in each of the barrel portions 52, 53, 54, and is not particularly limited.

[0293] The supply barrel portion 52 is a region for supplying the water-containing clam into the barrel unit 51. The first supply barrel 52a of the supply barrel portion 52 has a feed port 55 for supplying the water-containing clam into the barrel unit 51.

[0294] The dehydration barrel portion 53 is a region for separating and discharging a liquid (ceramic water) containing a coagulant or the like from the water-containing clam.

[0295] The first to third dehydration barrels 53a to 53c constituting the dehydration barrel portion 53 each have dehydration slits 56a, 56b, 56c for discharging the moisture of the water-containing clam to the outside. A plurality of each of the dehydration slits 56a, 56b, 56c are formed in each of the dehydration barrels 53a to 53c.

[0296] The slit width, that is, the mesh size, of each of the dehydration slits 56a, 56b, 56c may be appropriately selected according to the usage conditions, and is usually 0.01 to 5 mm. From the viewpoint of less loss of the water-containing clam and efficient dehydration of the water-containing clam, it is preferably 0.1 to 1 mm, and more preferably 0.2 to 0.6 mm.

[0297] In the dewatering barrel section 53, there are two ways to remove moisture from the water-containing crumb in each dewatering barrel 53a to 53c: by removing it in liquid form through the respective dewatering slits 56a, 56b, and 56c, and by removing it in vapor form. In the dewatering barrel section 53 of this embodiment, the removal of moisture in liquid form is defined as drainage, and the removal of moisture in vapor form is defined as exhaust steam.

[0298] In the dewatering barrel section 53, combining drainage and exhaust steam is preferable because it efficiently reduces the moisture content of the adhesive acrylic rubber. In the dewatering barrel section 53, the choice of which of the first to third dewatering barrels 53a to 53c is used for drainage or exhaust steam can be appropriately set according to the intended use. However, to reduce the ash content in the acrylic rubber that is typically manufactured, it is preferable to use more dewatering barrels for drainage. In that case, for example, as shown in Figure 2, drainage is performed in the upstream first and second dewatering barrels 53a and 53b, and exhaust steam is performed in the downstream third dewatering barrel 53c. Also, for example, if the dewatering barrel section 53 has four dewatering barrels, it is conceivable that drainage is performed in the three upstream dewatering barrels and exhaust steam in the downstream one dewatering barrel. On the other hand, to reduce the moisture content, it is preferable to use more dewatering barrels for exhaust steam.

[0299] The set temperature of the dewatering barrel section 53 is typically in the range of 60 to 150°C, preferably 70 to 140°C, and more preferably 80 to 130°C, as described in the dewatering and drying process above. The set temperature of the dewatering barrel used for dewatering in a drainage state is typically in the range of 60 to 120°C, preferably 70 to 110°C, and more preferably 80 to 100°C. The set temperature of the dewatering barrel used for dewatering in a steam exhaust state is typically in the range of 100 to 150°C, preferably 105 to 140°C, and more preferably 110 to 130°C.

[0300] The drying barrel section 54 is a region where the dehydrated crumb is dried under reduced pressure. Of the first to eighth drying barrels 54a to 54h that make up the drying barrel section 54, the second drying barrel 54b, the fourth drying barrel 54d, the sixth drying barrel 54f, and the eighth drying barrel 54h each have vent ports 58a, 58b, 58c, and 58d for degassing. Vent piping (not shown) is connected to each of the vent ports 58a, 58b, 58c, and 58d.

[0301] Each vent pipe is connected to a vacuum pump (not shown), and the operation of these vacuum pumps reduces the pressure inside the drying barrel section 54 to a predetermined level. The screw-type extruder 5 has a pressure control means (not shown) that controls the operation of these vacuum pumps to control the degree of pressure reduction inside the drying barrel section 54.

[0302] The degree of reduced pressure in the drying barrel section 54 can be selected as appropriate, but as mentioned above, it is usually set to 1 to 50 kPa, preferably 2 to 30 kPa, and more preferably 3 to 20 kPa.

[0303] Furthermore, the set temperature inside the drying barrel section 54 can be selected as appropriate, but as mentioned above, it is usually set to 100-250°C, preferably 110-200°C, and more preferably 120-180°C.

[0304] In each of the drying barrels 54a to 54h that make up the drying barrel section 54, the set temperatures within all of the drying barrels 54a to 54h may be approximate or different. However, it is preferable to set the temperature on the downstream side (die 59 side) to be higher than the temperature on the upstream side (dewatering barrel section 53 side) because this improves drying efficiency.

[0305] The die 59 is a mold positioned at the downstream end of the barrel unit 51 and has an outlet with a predetermined nozzle shape. The acrylic rubber dried in the drying barrel section 54 passes through the outlet of the die 59 and is extruded into a shape corresponding to the predetermined nozzle shape. The acrylic rubber passing through the die 59 can be molded into various shapes such as granular, columnar, round rod, or sheet, depending on the nozzle shape of the die 59, but in this invention it is molded into a sheet. A breaker plate or wire mesh may or may not be provided between the screw and the die 59.

[0306] The water-containing acrylic rubber crumb obtained through the washing process is supplied from the feed port 55 to the supply barrel section 52. The water-containing crumb supplied to the supply barrel section 52 is sent from the supply barrel section 52 to the dewatering barrel section 53 by the rotation of a pair of screws in the barrel unit 51. In the dewatering barrel section 53, as described above, the water contained in the water-containing crumb is drained or exhausted steam is removed through dewatering slits 56a, 56b, and 56c provided in the first to third dewatering barrels 53a to 53c, respectively, and the water-containing crumb is dewatered.

[0307] The water-containing crumb, dewatered in the dewatering barrel section 53, is sent to the drying barrel section 54 by the rotation of a pair of screws in the barrel unit 51. The water-containing crumb sent to the drying barrel section 54 is plasticized and mixed to become a molten material, which is then carried downstream while generating heat and increasing in temperature. The water contained in this molten acrylic rubber then vaporizes, and this water (steam) is discharged to the outside through vent pipes (not shown) connected to the respective vent ports 58a, 58b, 58c, and 58d.

[0308] As described above, the water-containing crumb is dried by passing through the drying barrel section 54 and becomes a molten acrylic rubber. This acrylic rubber is then supplied to the die 59 by the rotation of a pair of screws in the barrel unit 51 and extruded from the die 59.

[0309] Here is an example of the operating conditions for the screw-type twin-screw extruder dryer 5 according to this embodiment.

[0310] The rotational speed (N) of the pair of screws in the barrel unit 51 can be appropriately selected according to various conditions, and is usually 10 to 1000 rpm. Preferably, it is 50 to 750 rpm, more preferably 100 to 500 rpm, and most preferably 120 to 300 rpm, as it can efficiently reduce the water content of the acrylic rubber and the amount of methyl ethyl ketone insoluble.

[0311] Furthermore, the extrusion rate (Q) of the acrylic rubber is not particularly limited, but is usually 100 to 1500 kg / hr, preferably 300 to 1200 kg / hr, more preferably 400 to 1000 kg / hr, and most preferably 500 to 800 kg / hr.

[0312] The ratio (Q / N) of the amount of acrylic rubber extruded (Q) to the number of screw rotations (N) is not particularly limited, but is usually 1 to 20, preferably 2 to 10, more preferably 3 to 8, and particularly preferably 4 to 6.

[0313] The maximum torque within the barrel unit 51 is not particularly limited, but is typically in the range of 30 to 100 N·m, preferably 35 to 75 N·m, and more preferably 40 to 60 N·m.

[0314] The specific power within the barrel unit 51 is not particularly limited, but is usually in the range of 0.1 to 0.25 [kW·h / kg] or more, preferably 0.13 to 0.23 [kW·h / kg], and more preferably 0.15 to 0.2 [kW·h / kg].

[0315] The specific power within the barrel unit 51 is not particularly limited, but is usually in the range of 0.2 to 0.6 [A·h / kg] or more, preferably 0.25 to 0.55 [A·h / kg], and more preferably 0.35 to 0.5 [A·h / kg].

[0316] The shear rate within the barrel unit 51 is not particularly limited, but is usually in the range of 40 to 150 [1 / s] or more, preferably 45 to 125 [1 / s], and more preferably 50 to 100 [1 / s].

[0317] The shear viscosity of the acrylic rubber in the barrel unit 51 is not particularly limited, but is usually in the range of 4000 to 8000 [Pa·s] or less, preferably 4500 to 7500 [Pa·s], and more preferably 5000 to 7000 [Pa·s].

[0318] The cooling device 6 shown in Figure 1 is configured to cool the dried rubber obtained through the dewatering process using a dewatering machine and the drying process using a dryer. Various cooling methods can be employed by the cooling device 6, including air cooling using a fan or air conditioner, water spraying, and immersion. Alternatively, the dried rubber may be cooled by leaving it at room temperature.

[0319] As described above, depending on the nozzle shape of the die 59, the dried rubber discharged from the screw-type extruder 5 is extruded into various shapes such as granules, columnar, round rods, and sheets, but in the present invention, it is molded into a sheet. Hereinafter, with reference to Figure 3, a conveying-type cooling device 60 for cooling the sheet-shaped dried rubber 10 will be described as an example of a cooling device 6.

[0320] Figure 3 shows the configuration of a transport-type cooling device 60 suitable as the cooling device 6 shown in Figure 1. The transport-type cooling device 60 shown in Figure 3 is configured to cool the sheet-shaped dried rubber 10 discharged from the discharge port of the die 59 of the screw-type extruder 5 by air cooling while transporting it. By using this transport-type cooling device 60, the sheet-shaped dried rubber discharged from the screw-type extruder 5 can be effectively cooled.

[0321] The transport-type cooling device 60 shown in Figure 3 is used, for example, by being directly connected to the die 59 of the screw-type extruder 5 shown in Figure 2, or by being installed near the die 59.

[0322] The conveyor-type cooling device 60 includes a conveyor 61 that transports the sheet-shaped dried rubber 10 discharged from the die 59 of the screw-type extruder 5 in the direction of arrow A in Figure 3, and a cooling means 65 that blows cold air onto the sheet-shaped dried rubber 10 on the conveyor 61.

[0323] The conveyor 61 has rollers 62 and 63, and a conveyor belt 64 that is wound around these rollers 62 and 63 and on which the sheet-shaped dried rubber 10 is placed. The conveyor 61 is configured to continuously transport the sheet-shaped dried rubber 10 discharged from the die 59 of the screw-type extruder 5 downstream (to the right in Figure 3) on the conveyor belt 64.

[0324] The cooling means 65 is not particularly limited, but examples include having a configuration that allows cooling air sent from a cooling air generating means (not shown) to be blown onto the surface of the sheet-like dry rubber 10 on the conveyor belt 64.

[0325] The length L1 of the conveyor 61 and cooling means 65 of the conveyor-type cooling device 60 (the length of the portion to which cooling air can be blown) is not particularly limited, but is for example 10 to 100 m, preferably 20 to 50 m. The conveying speed of the sheet-shaped dried rubber 10 in the conveyor-type cooling device 60 can be appropriately adjusted according to the length L1 of the conveyor 61 and cooling means 65, the discharge speed of the sheet-shaped dried rubber 10 discharged from the die 59 of the screw-type extruder 5, the target cooling speed and cooling time, etc., but is for example 10 to 100 m / hr, more preferably 15 to 70 m / hr.

[0326] According to the conveying type cooling device 60 shown in Figure 3, the sheet-shaped dried rubber 10 discharged from the die 59 of the screw-type extruder 5 is conveyed by the conveyor 61, and the sheet-shaped dried rubber 10 is cooled by blowing cooling air onto it from the cooling means 65.

[0327] The conveying-type cooling device 60 is not particularly limited to the configuration shown in Figure 3, which comprises one conveyor 61 and one cooling means 65. It may also be configured to include two or more conveyors 61 and two or more corresponding cooling means 65. In that case, the total length of each of the two or more conveyors 61 and the cooling means 65 should be within the above range.

[0328] The baling apparatus 7 shown in Figure 1 is configured to process dried rubber, which is extruded from a screw-type extruder 5 and then cooled by a cooling device 6, to produce a bale, which is a single block. As described above, the screw-type extruder 5 is capable of extruding dried rubber into various shapes such as granules, columns, rods, and sheets, and the baling apparatus 7 is configured to bale dried rubber that has been molded into various shapes in this way. The weight and shape of the bale-shaped acrylic rubber produced by the baling apparatus 7 are not particularly limited, but for example, a roughly rectangular bale-shaped acrylic rubber weighing about 20 kg is produced.

[0329] The baling apparatus 7 may, for example, include a baler, and bale-shaped acrylic rubber may be produced by compressing cooled, dried rubber with the baler.

[0330] Furthermore, if sheet-shaped dried rubber 10 is manufactured using a screw-type extruder 5, bale-shaped acrylic rubber may be manufactured by laminating the sheet-shaped dried rubber 10. For example, a cutting mechanism for cutting the sheet-shaped dried rubber 10 may be provided in the bale-forming device 7 located downstream of the conveying-type cooling device 60 shown in Figure 3. Specifically, the cutting mechanism of the bale-forming device 7 is configured, for example, to continuously cut the cooled sheet-shaped dried rubber 10 at predetermined intervals to process it into cut sheet-shaped dried rubber 16 of a predetermined size. By laminating multiple cut sheet-shaped dried rubber 16 cut to a predetermined size by the cutting mechanism, bale-shaped acrylic rubber made of laminated cut sheet-shaped dried rubber 16 can be manufactured.

[0331] When manufacturing a bale-shaped acrylic rubber by laminating cut sheet-shaped dried rubber 16, it is preferable to laminate cut sheet-shaped dried rubber 16 at a temperature of 40°C or higher. By laminating cut sheet-shaped dried rubber 16 at a temperature of 40°C or higher, good air release is achieved through further cooling and compression due to its own weight. [Examples]

[0332] The present invention will be described in more detail below with reference to examples and comparative examples. Unless otherwise specified, "parts," "%," and "ratio" in each example are based on weight. Various physical properties were evaluated according to the following methods.

[0333] [Monomer composition] Regarding the monomer composition in acrylic rubber, the monomer composition of each monomer unit in acrylic rubber is 1 The activity of reactive groups remained in the acrylic rubber, and the content of each reactive group was confirmed by 1H-NMR using the method described below. The content ratio of each monomer unit in the acrylic rubber was calculated from the amount used in the polymerization reaction of each monomer and the polymerization conversion rate. Specifically, the polymerization reaction was an emulsion polymerization reaction, and the polymerization conversion rate was approximately 100%, with no unreacted monomers detected. Therefore, the content ratio of each monomer unit in the rubber was assumed to be the same as the amount of each monomer used.

[0334] [Reactive group content] The content of reactive groups in acrylic rubber was measured by the following method. (1) The amount of carboxyl groups was calculated by dissolving the sample (acrylic rubber) in acetone and performing potentiometric titration with potassium hydroxide solution. (2) The amount of epoxy groups was calculated by dissolving the sample in methyl ethyl ketone, adding a specified amount of hydrochloric acid to react with the epoxy groups, and titrating the remaining amount of hydrochloric acid with potassium hydroxide. (3) The amount of chlorine was calculated by completely burning the sample in a combustion flask, absorbing the generated chlorine into water, and titrating with silver nitrate.

[0335] [Ash content] The ash content (%) in the acrylic rubber was measured according to JIS K6228 Method A.

[0336] [Ash content] The amount of each component (ppm) in the acrylic rubber ash was determined by pressing the ash sample collected during the above ash content measurement onto a Φ20 mm titration filter paper and performing XRF measurement using a ZSX Primus (manufactured by Rigaku).

[0337] [Molecular weight and molecular weight distribution] The weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn and Mz / Mw) of acrylic rubber are measured by the GPC-MALS method using a solution prepared by adding 0.05 mol / L lithium chloride and 0.01% 37% concentrated hydrochloric acid to dimethylformamide as solvents. The absolute molecular weight and absolute molecular weight distribution, with a focus on the high molecular weight range, are measured by this method.

[0338] The configuration of this device, a gel permeation chromatography multi-angle light scattering photometer, consists of a pump (LC-20ADOpt, manufactured by Shimadzu Corporation), a differential refractometer (Optilab rEX, manufactured by Wyatt Technology), and a multi-angle light scattering detector (DAWN HELEOS, manufactured by Wyatt Technology). Specifically, a multi-angle laser light scattering photometer (MALS) and a differential refractometer (RI) were incorporated into a GPC (Gel Permeation Chromatography) instrument. The light scattering intensity and refractive index difference of the molecular chain solution, separated by size by the GPC instrument, were measured over time to sequentially calculate and determine the molecular weight and content of the solute. The measurement conditions and methods using the GPC instrument are as follows.

[0339] Column: TSKgel α-M, 2 pieces (φ7.8mm x 30cm, manufactured by Tosoh Corporation) Column temperature: 40℃ Flow rate: 0.8ml / mm Sample preparation: 10 mg of the sample (acrylic rubber) was added to 5 ml of solvent and gently stirred at room temperature (dissolution was visually confirmed). Then, the mixture was filtered using a 0.5 μm filter.

[0340] [Glass transition temperature (Tg)] The glass transition temperature (Tg) of acrylic rubber was measured using a differential scanning calorimeter (DSC, product name "X-DSC7000", manufactured by Hitachi High-Tech Science Corporation).

[0341] [Amount of methyl ethyl ketone insoluble] The percentage of methyl ethyl ketone insoluble material in acrylic rubber is the amount of material that is insoluble in methyl ethyl ketone, and was determined by the following method.

[0342] Approximately 0.2 g of acrylic rubber was weighed (X g), immersed in 100 ml of methyl ethyl ketone, and left at room temperature for 24 hours. The filtrate, which contained only the rubber components soluble in methyl ethyl ketone, was filtered out using an 80-mesh wire mesh. The dried solid content (Y g) was then weighed and calculated using the following formula. Methyl ethyl ketone insoluble portion (%) = 100 × (XY) / X

[0343] [specific gravity] The specific gravity of the acrylic rubber was measured according to Method A of JIS K6268 Crosslinked Rubber - Density Measurement. The measurement obtained by the following measurement method is density, but the density of water is 1 Mg / m³. 3 The specific gravity is used as the specific gravity. Specifically, the specific gravity of a rubber sample obtained according to Method A of JIS K6268 Crosslinked Rubber - Density Measurement is obtained by dividing the mass by the volume including the voids of the rubber sample, and is obtained by dividing the density of the rubber sample, measured according to Method A of JIS K6268 Crosslinked Rubber - Density Measurement, by the density of water (dividing the density of the rubber sample by the density of water results in the same numerical value but eliminates the units). In detail, the specific gravity of the rubber sample is determined according to the following procedure. (1) Cut a 2.5 g test piece from a rubber sample that has been left to stand at a standard temperature (23°C ± 2°C) for at least 3 hours. Suspend the test piece from a hook on a chemical balance with an accuracy of 1 mg using a thin nylon thread with a mass of less than 0.010 g so that the bottom of the test piece is 25 mm above the sorting pan of the chemical balance. Measure the mass (m1) of the test piece twice in air to the nearest mg. (2) Next, a 250 cm² weighing scale is placed on a weighing pan for a chemical balance. 3 Fill a beaker of the specified capacity with distilled water that has been boiled and cooled to standard temperature. Immerse the test specimen in the water, remove any air bubbles adhering to the surface of the specimen, observe the movement of the balance needle for several seconds, and confirm that the needle gradually stops moving due to convection. Then, measure the mass (m²) of the test specimen in water in mg twice. (3) Also, the density of the test specimen is 1 Mg / m³ 3 If the value is less than (when the test specimen floats in water), attach a weight to the test specimen and measure the mass of the weight in water (m3) and the mass of the test specimen and the weight together (m4) in mg twice. (4) The specific gravity of the rubber sample is calculated using the average values ​​of m1, m2, m3, and m4 measured above, based on the following formula: density (Mg / m³ 3 Calculate the density and use the calculated density as the density of water (1.00 Mg / m³). 3 Divide by ) to find the answer. (Density of rubber sample without using weights) Density=m1 / (m1-m2) (Density of rubber sample when weight is used) Density=m1 / (m1+m3-m4)

[0344] [Water content] The moisture content (%) was measured in accordance with JIS K6238-1: Oven A (Volatile content measurement) method.

[0345] [pH] pH was measured using a pH electrode after dissolving 6 g (±0.05 g) of acrylic rubber in 100 g of tetrahydrofuran, adding 2.0 ml of distilled water, and confirming complete dissolution.

[0346] [Complex viscosity] The complex viscosity η was determined by measuring the temperature dispersion (40-120°C) at a strain of 473% and 1 Hz using the dynamic viscoelasticity measuring device "Rubber Process Analyzer RPA-2000" (manufactured by Alpha Technology Co., Ltd.), and calculating the complex viscosity η at each temperature. Here, the dynamic viscoelasticity at 60°C was defined as the complex viscosity η(60°C), and the dynamic viscoelasticity at 100°C was defined as the complex viscosity η(100°C), and the ratio η(100°C) / η(60°C) was calculated.

[0347] [Mooney viscosity (ML1+4, 100℃)] Mooney viscosity (ML1+4, 100℃) was measured according to the physical testing method for uncrosslinked rubber specified in JIS K6300.

[0348] [Crosslinkability] The crosslinking properties of the rubber samples were determined by calculating the rate of change between the tensile strength of the crosslinked rubber after 2 hours of secondary crosslinking and the tensile strength of the crosslinked rubber after 4 hours ((tensile strength of the crosslinked rubber after 4 hours / tensile strength of the crosslinked rubber after 2 hours) × 100), and judging according to the following criteria. ◎: Products with a fracture strength change rate of less than 10% ×: Items with a fracture strength change rate of 10% or more.

[0349] [Rolling properties] The roll processability of the rubber sample was evaluated by observing the roll winding properties and the state of the rubber when the rubber sample was kneaded on a roll, according to the following criteria. ◎: Easy to knead, easily wraps around a roll without detaching from the roll, and the surface of the kneaded rubber composition is smooth. ○: Easy to knead, easily wraps around the rolls and does not detach from the rolls, and the surface of the kneaded rubber composition shows slight irregularities. □: Easy to knead, excellent roll-wrapping properties, and the surface of the kneaded rubber composition is slightly uneven. △: Easy to mix, slightly inferior in roll-wrapping properties, and the surface of the rubber composition after mixing is slightly rough. ×: This product puts a strain on the mixing process and has poor roll-wrapping properties.

[0350] [Banbury workability] The Banbury processability of the rubber samples was evaluated by placing the rubber samples in a Banbury mixer heated to 50°C, kneading for 1 minute, adding compounding agent A of the rubber mixture formulations listed in Table 1, and measuring the time until the first stage of the rubber mixture became integrated and showed the maximum torque value, i.e., the BIT (Black Incorporation Time), and evaluating it on an index with Comparative Example 1 set to 100 (a smaller index indicates better processability).

[0351] [Storage stability evaluation] The storage stability of the rubber samples was evaluated by placing them in a constant temperature and humidity chamber (ESPEC SH-222) at 45°C and 80%RH, and calculating the percentage change in moisture content before and after the 7-day test. This was then evaluated using an index with Comparative Example 1 set to 100 (a smaller index indicates better storage stability).

[0352] [Water resistance evaluation] The water resistance of the rubber samples was evaluated by immersion testing in distilled water at 85°C for 100 hours, in accordance with JIS K6258. The volume change rate before and after immersion was calculated according to the following formula and evaluated on an index with Comparative Example 1 set to 100 (a smaller index indicates better water resistance). Volume change rate before and after immersion (%) = ((Volume of specimen after immersion - Volume of specimen before immersion) / Volume of specimen before immersion) × 100

[0353] [Compression set resistance characteristics] The compression set resistance characteristics of the rubber samples were evaluated according to the following criteria by measuring the compression set rate after the rubber crosslinked material of the rubber sample was compressed to 25% in accordance with JIS K6262 and left at 175°C for 90 hours. ◎: Compression set is less than 15% ×: The compression set is 15% or more.

[0354] [Evaluation of physical properties under normal conditions] The normal physical properties of the rubber samples were evaluated according to JIS K6251 by measuring the breaking strength, 100% tensile stress, and elongation at break of the crosslinked rubber samples, and using the following criteria. (1) Breaking strength was evaluated as follows: ◎ for 10 MPa or more, and × for less than 10 MPa. (2) 100% tensile stress was evaluated as ◎ for 5 MPa or more and × for less than 5 MPa. (3) Elongation at break was evaluated as ◎ for 150% or more and × for less than 150%.

[0355] [Evaluation of variability in the amount of methyl ethyl ketone insoluble] The variability in the amount of methyl ethyl ketone insoluble material in rubber samples was evaluated by measuring the amount of methyl ethyl ketone insoluble material in 20 points randomly selected from 20 rubber samples (20 kg), and evaluating it based on the following criteria. ◎: The average value of the methyl ethyl ketone insoluble content of the 20 measured points was calculated, and all 20 measured points fell within the range of ±3 of the average value. ○: The average value of the methyl ethyl ketone insoluble content of the 20 measured points was calculated, and all 20 measured points fell within the range of ±5 of the average value (a range of ±3 of the average value would mean that at least one of the 20 measured points would be outside this range, but a range of ±5 of the average value would mean that all 20 points fall within this range). ×: The average value of the methyl ethyl ketone insoluble content of the 20 measured points was calculated, and any point that fell outside the range of ±5 of the average value was considered a failure.

[0356] [Evaluation of processing stability by suppressing Mooney scorch] The cooling rate of sheet-like acrylic rubber extruded from a screw-type twin-screw extruder dryer described in Japanese Patent Publication No. 6683189 and the Mooney scorch stability of the acrylic rubber composition were evaluated.

[0357] [Example 1] As shown in Table 2-1, 46 parts of pure water, 4.5 parts of ethyl acrylate, 64.5 parts of n-butyl acrylate, 29.5 parts of methoxyethyl acrylate, and 1.5 parts of mono-n-butyl fumarate as monomer components, and 1.8 parts of octyloxydioxyethylene phosphate sodium salt as an emulsifier were charged into a mixing vessel equipped with a homomixer and stirred to obtain a monomer emulsion.

[0358] In a polymerization reactor equipped with a thermometer and a stirring device, 170 parts of pure water and 3 parts of the monomer emulsion obtained above were added and cooled to 12°C under a nitrogen stream. Then, 0.00033 parts of ferrous sulfate, 0.02 parts of sodium ascorbate, and 0.2 parts of potassium persulfate, an inorganic radical generator, were added to start the polymerization reaction. Maintaining the temperature in the polymerization reactor at 23°C, the remaining monomer emulsion was continuously added dropwise over 3 hours. 50 minutes after the start of the reaction, 0.0072 parts of n-dodecyl mercaptan were added, 0.0036 parts of n-dodecyl mercaptan were added after 100 minutes, and 0.4 parts of sodium L-ascorbate were added after 120 minutes to continue the polymerization reaction. When the polymerization conversion rate reached approximately 100%, hydroquinone was added as a polymerization stopper to stop the polymerization reaction and obtain an emulsion polymerization solution.

[0359] Next, in a solidification tank equipped with a thermometer and a stirring device, 350 parts of a 2% magnesium sulfate aqueous solution (a solidification solution using magnesium sulfate as a solidifying agent) were heated to 80°C and vigorously stirred at a stirring blade speed of 600 rpm (circumferential speed of 3.1 m / s). The emulsion polymerization solution obtained above was then heated to 80°C and continuously added to the aqueous solution to solidify the polymer, obtaining a solidification slurry containing acrylic rubber crumbs and water. The crumbs were filtered from the obtained slurry, and water was drained from the solidification layer to obtain hydrated crumbs.

[0360] 194 parts of hot water (70°C) were added to the solidification tank containing the filtered water-containing crumb, and the mixture was stirred for 15 minutes to wash the water-containing crumb. After draining the water, another 194 parts of hot water (70°C) were added and stirred for 15 minutes to wash the water-containing crumb again (total of 2 washes). The washed water-containing crumb (water-containing crumb temperature 65°C) was supplied to a screw-type twin-screw extruder dryer 15, where it was dewatered and dried to extrude a sheet of dried rubber with a width of 300 mm and a thickness of 10 mm. Next, the sheet of dried rubber was cooled at a cooling rate of 200°C / hr using a conveyor-type cooling device directly connected to the screw-type twin-screw extruder dryer 15.

[0361] The screw-type twin-screw extruder dryer used in this embodiment 1 consists of one feed barrel, three dewatering barrels (the first to third dewatering barrels), and five drying barrels (the first to fifth drying barrels). The first dewatering barrel is used for draining water, while the second and third dewatering barrels are used for exhausting steam. The operating conditions for the screw-type twin-screw extruder dryer were as follows.

[0362] Water content: • Moisture content of the crumb after draining in the first dewatering barrel: 20% • Moisture content of the crumb after steam extraction in the third dewatering barrel: 10% • Moisture content of the crumb after drying in the fifth drying barrel: 0.4% Rubber temperature: • Temperature of the moist crumb supplied to the supply barrel: 65°C • Temperature of rubber discharged from a screw-type twin-screw extruder: 140°C Temperature settings for each barrel: • First dehydration barrel: 100℃ • Second dehydration barrel: 120℃ • Third dehydration barrel: 120℃ • First drying barrel: 120℃ • Second drying barrel: 130℃ • Third drying barrel: 140℃ • Fourth drying barrel: 160℃ • Fifth drying barrel: 180℃ Driving conditions: • Screw diameter (D): 132mm • Screw length (L): 4620mm L / D: 35 • Screw rotation speed: 135 rpm • Depressurization degree of the drying barrel: 10kPa • Rubber extrusion rate from the die: 700 kg / hr • Resin pressure in the die: 2 MPa • Maximum torque inside a screw-type twin-screw extruder dryer: 15 N·m

[0363] The extruded sheet-like dried rubber was cooled to 50°C, cut with a cutter, and then laminated to 20 parts (20 kg) before the temperature dropped below 40°C to obtain bale-like acrylic rubber (A). The reactive group content, ash content, ash component content, methyl ethyl ketone insoluble content, pH, specific gravity, glass transition temperature (Tg), water content, molecular weight, molecular weight distribution, and complex viscosity at 100°C and 60°C of the obtained acrylic rubber (A) were measured and are shown in Table 2-2. In addition, a storage stability test was performed on acrylic rubber (A) to determine the rate of change in water content, and the results are shown in Table 2-2.

[0364] Next, using a Banbury mixer, 100 parts of acrylic rubber (A) and compounding agent A of "Formulation 1" as described in Table 1 were added and mixed at 50°C for 5 minutes (first stage mixing). The BIT at this time was measured to evaluate the Banbury processability of the acrylic rubber, and the results are shown in Table 2-2. Next, the obtained mixture was transferred to a roll at 50°C, and compounding agent B from "Formulation 1" was added and mixed (second stage mixing) to obtain a rubber composition. The roll processability at this stage was evaluated, and the results are shown in Table 2-2.

[0365] [Table 1]

[0366] The obtained rubber composition was placed in a mold measuring 15 cm in length, 15 cm in width, and 0.2 cm in depth, and primary crosslinking was performed by pressing it at 180°C for 10 minutes under a press pressure of 10 MPa. The resulting primary crosslinked material was then further heated in a gear oven at 180°C for 2 hours to perform secondary crosslinking, thereby obtaining a sheet-like crosslinked rubber material. A 3 cm × 2 cm × 0.2 cm test piece was then cut from the obtained sheet-like crosslinked rubber material, and its water resistance, compression set resistance, and normal physical properties were evaluated. Furthermore, the normal physical properties of the sheet-like crosslinked rubber material after a further 2 hours of secondary crosslinking were measured to evaluate its crosslinking ability. The results are shown in Table 2-2.

[0367] [Example 2] The procedure was carried out in the same manner as in Example 1, except that the emulsifier was changed to 1.8 parts of sodium nonylphenyloxyhexaoxyethylene phosphate, the amount of potassium persulfate (inorganic radical generator) to 0.21 parts, and the amount of n-dodecyl mercaptan (chain transfer agent) added after 50 minutes to 0.017 parts, after 100 minutes to 0.017 parts, and after 120 minutes to 0.017 parts. Acrylic rubber (B) was obtained and its properties were evaluated. The results are shown in Table 2-2.

[0368] [Example 3] Acrylic rubber (C) was obtained in the same manner as in Example 1, except that the monomer components were changed to 48.25 parts ethyl acrylate, 50 parts n-butyl acrylate, and 1.75 parts mono-n-butyl fumarate, and the emulsifier was changed to 1.8 parts tridecyloxyhexaoxyethylene sodium phosphate. Furthermore, the washed, water-containing crumb was dried to a water content of 0.4% using a hot air dryer at 160°C to obtain crumb-like acrylic rubber, which was then filled into a 300 × 650 × 300 mm bailer and compacted at a pressure of 3 MPa for 25 seconds to obtain bale-like acrylic rubber. The properties of acrylic rubber (C) were evaluated (the compounding agents were changed to "Compound 2"), and the results are shown in Table 2-2.

[0369] [Example 4] The procedure was carried out in the same manner as in Example 3, except that the monomer components were changed to 28 parts ethyl acrylate, 38 parts n-butyl acrylate, 27 parts methoxyethyl acrylate, 5 parts acrylonitrile, and 2 parts allyl glycidyl ether. Acrylic rubber (D) was obtained and its properties (the compounding agents were changed to those of "Compound 3") were evaluated. The results are shown in Table 2-2.

[0370] [Example 5] The procedure was carried out in the same manner as in Example 3, except that the monomer components were changed to 42.2 parts ethyl acrylate, 35 parts n-butyl acrylate, 20 parts methoxyethyl acrylate, 1.5 parts acrylonitrile, and 1.3 parts vinyl chloroacetate. Acrylic rubber (E) was obtained, and its properties (the compounding agent was changed to "Compound 4") were evaluated. The results are shown in Table 2-2.

[0371] [Example 6] Acrylic rubber (F) was obtained in the same manner as in Example 2, except that the monomer components were changed to 48.25 parts ethyl acrylate, 50 parts n-butyl acrylate, and 1.75 parts mono-n-butyl fumarate, and the emulsifier was changed to 1.8 parts tridecyloxyhexaoxyethylene sodium phosphate. Furthermore, the washed, water-containing crumb was dried to a water content of 0.4% using a hot air dryer at 160°C to obtain crumb-like acrylic rubber, which was then filled into a 300 × 650 × 300 mm bailer and compacted at a pressure of 3 MPa for 25 seconds to obtain bale-like acrylic rubber. The properties of acrylic rubber (F) were evaluated (the compounding agents were changed to "Compound 2"), and the results are shown in Table 2-2.

[0372] [Example 7] The procedure was carried out in the same manner as in Example 6, except that the monomer components were changed to 28 parts ethyl acrylate, 38 parts n-butyl acrylate, 27 parts methoxyethyl acrylate, 5 parts acrylonitrile, and 2 parts allyl glycidyl ether. Acrylic rubber (G) was obtained and its properties (the compounding agent was changed to "Compound 3") were evaluated. The results are shown in Table 2-2.

[0373] [Example 8] The procedure was carried out in the same manner as in Example 7, except that the monomer components were changed to 42.2 parts ethyl acrylate, 35 parts n-butyl acrylate, 20 parts methoxyethyl acrylate, 1.5 parts acrylonitrile, and 1.3 parts vinyl chloroacetate. Acrylic rubber (H) was obtained and its properties (the compounding agent was changed to "Compound 4") were evaluated. The results are shown in Table 2-2.

[0374] [Example 9] Except for changing the amount of potassium persulfate, an inorganic radical generator, to 0.22 parts, and continuously adding 0.025 parts of n-dodecyl mercaptan, a chain transfer agent, to the monomer emulsion and then not adding it again, the procedure was carried out in the same manner as in Example 8 to obtain acrylic rubber (I) and evaluate its various properties. The results are shown in Table 2-2.

[0375] [Comparative Example 1] Except for not adding a chain transfer agent and performing the coagulation reaction by adding a 0.7% magnesium sulfate aqueous solution to the emulsion polymerization solution (stirring speed 100 rpm, peripheral speed 0.5 m / s) that was being stirred after emulsion polymerization, and obtaining crumb-shaped acrylic rubber without baling using a bailer, the procedure was carried out in the same manner as in Example 9, and acrylic rubber (J) was obtained and its properties were evaluated. The results are shown in Table 2-2.

[0376] [Comparative Example 2] The emulsifier was changed to 0.709 parts of sodium lauryl sulfate and 1.82 parts of polyoxyethylene dodecyl ether. The coagulation reaction was carried out by adding sodium sulfate to the emulsion polymerization solution (stirring speed 100 rpm, peripheral speed 0.5 m / s) that was being stirred after emulsion polymerization. In the washing step, 194 parts of industrial water were added to wash the water-containing crumb, which was stirred in the coagulation tank at 25°C for 5 minutes, and the water was drained from the coagulation tank. This operation was performed only twice, and baling was not performed using a bailer to obtain crumb-shaped acrylic rubber. Except for these changes, the procedure was the same as in Example 9, and acrylic rubber (K) was obtained and its properties were evaluated. The results are shown in Table 2-2.

[0377] [Table 2-1]

[0378] [Table 2-2]

[0379] From Tables 2-1 and 2-2, it can be seen that the acrylic rubbers (A) to (I) of the present invention, which mainly consist of the (meth)acrylic acid ester of the present invention, have an absolute molecular weight and absolute molecular weight distribution measured by the GPC-MALS method using a dimethylformamide-based solvent as the developing solvent, with a weight-average molecular weight (Mw) of 1 million or more, a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) of 3.4 or more, an ash content of 0.4% by weight or less, and a total amount of sodium, magnesium, calcium, phosphorus, and sulfur in the ash of 80% by weight or more, exhibit excellent normal physical properties including roll processability, water resistance, and strength characteristics, and are also remarkably superior in Banbury processability, storage stability, crosslinkability, and compression set resistance (Examples 1 to 9).

[0380] From Tables 2-1 and 2-2, it can be seen that the acrylic rubbers (A) to (K) produced under the conditions of the examples and comparative examples of this application have an ionic reactive group or at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group, and a chlorine atom, and have excellent normal physical properties including crosslinkability, compression set resistance, and strength properties due to their large weight-average molecular weight (Mw) (Examples 1 to 9 and Comparative Examples 1 to 2). However, the acrylic rubbers (J) to (K) are inferior in roll processability, Banbury processability, water resistance, and storage stability (Comparative Example 1), and also inferior in water resistance and storage stability (Comparative Example 2).

[0381] Table 2-2 shows that the molecular weight distribution, specifically the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn), is significantly related to roll processability, and that a broader molecular weight distribution is essential for good roll processability (Examples 1-9 and Comparison of Comparative Example 2 with Comparative Example 1). Furthermore, to achieve a high balance between strength characteristics and roll processability, it was important to have a relatively high weight-average molecular weight (Mw) and a molecular weight distribution that emphasizes the high molecular weight region (i.e., a high ratio of z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw)).

[0382] Tables 2-1 and 2-2 show that acrylic rubber with excellent strength characteristics and roll processability, having a high weight-average molecular weight (Mw) and a wide Mw / Mn ratio, can be produced by using specific amounts of inorganic radical generators and chain transfer agents, particularly n-dodecyl mercaptan (Examples 1-9). Table 2-2 also shows that, compared to continuously adding n-dodecyl mercaptan (Example 9), reducing the amount of inorganic radical generator and adding n-dodecyl mercaptan in batches rather than initially can further improve roll processability without impairing strength characteristics (Examples 1-8). This is because reducing the amount of inorganic radical generator and not adding the chain transfer agent initially extends the length of a single polymerization chain, and although the GPC chart does not show a clear bimodal curve, it produces a well-balanced mixture of high and low molecular weight components, resulting in a high Mw and wide Mw / Mn ratio, thus achieving a high balance between strength characteristics and roll processability. Furthermore, to efficiently broaden the Mw / Mn ratio, the number of batches of post-addition of the chain transfer agent has a greater influence than the difference in the amount of post-addition of the chain transfer agent. Two batches of post-addition broaden the Mw / Mn ratio more than three batches (comparison between Examples 3-5 and Examples 6-8), but continuous addition of the chain transfer agent limits the broadening of the Mw / Mn ratio to some extent (Example 9). Although not shown in Table 2-2, in the present examples, sodium ascorbate, a reducing agent, was added 120 minutes after the start of polymerization. This facilitates the generation of high molecular weight components in acrylic rubber and increases the effect of broadening the Mw / Mn ratio with post-addition of the chain transfer agent. On the other hand, although not shown in the present examples, it has been confirmed that polymerization using an organic radical generator does not broaden the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn), resulting in poor roll processability.

[0383] Table 2-2 shows that the acrylic rubbers (A) to (I) of the present invention are overwhelmingly superior in terms of water resistance (comparison of Examples 1 to 9 and Comparative Examples 1 to 2). Table 2-2 also shows that such acrylic rubbers (A) to (I), which are excellent in roll processability and strength characteristics and have significantly superior water resistance, can be produced by adding the coagulation agent to the stirring coagulation solution rather than adding the coagulation solution to the emulsion polymerization solution, which is emulsion polymerization obtained by adding a chain transfer agent continuously or batch by an inorganic radical generator, and more preferably by vigorously stirring the coagulation solution (stirring speed 600 rpm / peripheral speed 3.1 m / s) and increasing the coagulation agent concentration of the stirring coagulation solution (comparison of Examples 1 to 9 and Comparative Example 1). As will be shown in the data later, this coagulation reaction generates water-containing crumbs with a crumb diameter in the range of 710 μm to 4.75 mm, dramatically improving the efficiency of removing emulsifiers and coagulants in the washing and dewatering processes, reducing the ash content in the acrylic rubber, and significantly improving water resistance.

[0384] Table 2-2 shows that, regarding water resistance, carboxyl groups and epoxy groups are superior to chlorine atoms among ionic reactive groups (comparison between Examples 3-4 and 6-7 and Examples 5 and 8).

[0385] Table 2-2 shows that the total amount of phosphorus, magnesium, sodium, calcium, and sulfur in the ash of the acrylic rubbers (A) to (I) of the present invention and the acrylic rubbers (J) to (K) of the comparative examples all exceed 90% by weight. This indicates that the acrylic rubbers have excellent properties such as water resistance and mold release properties. Furthermore, it can be seen that the higher the proportion of phosphorus and magnesium in the ash, the better the water resistance (the ash content of Comparative Example 1 is more than twice that of Comparative Example 2, but the water resistance evaluation was similar).

[0386] Table 2-2 shows that, regarding water resistance, acrylic rubber (A) to (B) in which the water-containing crumb was dehydrated (water squeezed out) before drying had a significantly reduced ash content and improved water resistance (comparison between Examples 1-2 and Examples 3-9). Furthermore, looking at the component amounts in the ash of acrylic rubber (A) to (B), five elements—phosphorus (P), magnesium (Mg), sodium (Na), calcium (Ca), and sulfur (S)—account for a large proportion, but as the ash removal process progresses, it becomes clear that it is almost entirely phosphorus (P) and magnesium (Mg). This suggests that the emulsifier sodium phosphate salt is exchanged with the coagulant magnesium sulfate and is present in the water-containing crumb as magnesium phosphate, which cannot be sufficiently removed in the washing process, but can be reduced by dehydration (squeezing). In addition, it can be seen that acrylic rubber with high phosphorus and magnesium content in the ash does not have a worsened water resistance (comparison between Examples 1-9 and Comparative Example 1 to Comparative Example 2).

[0387] Table 2-2 shows that the acrylic rubbers (A) to (I) of the present invention are excellent in roll processability, water resistance and strength properties, as well as Banbury processability, demonstrating excellent processability in both roll processability and Banbury processability (Examples 1 to 9). The Banbury processability of acrylic rubber correlates with the amount of methyl ethyl ketone insoluble content, and it can be seen that the lower the amount of methyl ethyl ketone insoluble content, the better the Banbury processability (comparison of Examples 1 to 9 and Comparative Example 1). The amount of methyl ethyl ketone insoluble content in acrylic rubber can be reduced by emulsion polymerization in the presence of a chain transfer agent (Examples 3 to 8 and Comparative Example 2). In particular, the amount of methyl ethyl ketone insoluble content increases rapidly when the polymerization conversion rate is increased to improve strength properties, so it can be seen that the generation of methyl ethyl ketone insoluble content can be suppressed even in Examples 3 to 8 where the chain transfer agent is added afterwards. The amount of methyl ethyl ketone insoluble in acrylic rubber is further significantly reduced by drying the water-containing crumb in a screw-type twin-screw extruder, greatly improving the Banbury processability of the manufactured acrylic rubber (comparison of Examples 1-2 and Examples 3-8). In the present invention, although not shown in these examples, it has been confirmed that the amount of methyl ethyl ketone insoluble, which increased rapidly during emulsion polymerization without the addition of a chain transfer agent (Comparative Example 1), disappears when melt-kneaded in a screw-type twin-screw extruder in a substantially water-free state (water content less than 1% by weight), thereby greatly improving the Banbury processability without impairing the roll processability of the acrylic rubber.

[0388] Table 2-2 shows that the acrylic rubbers (A) to (I) of the present invention are excellent in roll processability, water resistance and strength characteristics, as well as significantly superior storage stability (Examples 1 to 9). The storage stability of acrylic rubber is largely related to its specific gravity, and it can be seen that a higher specific gravity means that less air is trapped in the acrylic rubber, resulting in superior storage stability (comparison with Examples 1 to 2, Examples 3 to 9 and Comparative Examples 1 to 2). Acrylic rubber with a high specific gravity can be obtained by compressing clam-shaped acrylic rubber with a bailer to form a bale (Examples 3 to 9), and more preferably by extruding it into a sheet using a screw-type twin-screw extruder and laminating it to form a bale (Examples 1 to 2). In the present invention, in particular, it can be seen that bale-shaped acrylic rubber obtained by laminating sheet-shaped acrylic rubber melt-kneaded and dried under reduced pressure has significantly improved storage stability without impairing normal physical properties including short-time crosslinkability, roll processability, compression set resistance, strength characteristics, and water resistance (Examples 1 to 2). The storage stability of acrylic rubber is also found to be preferable when the ash content is low or when the pH is specific (Examples 1-9).

[0389] Table 2-2 further shows that the acrylic rubbers (A) to (K) of the present invention's examples and comparative examples exhibit excellent crosslinking properties and compression set resistance due to the presence of ionic reactive groups such as carboxyl groups, epoxy groups, or chlorine atoms.

[0390] [Regarding the particle size of the generated hydrated crumbs] For the water-containing crumbs generated during the coagulation process in Examples 1-9 and Comparative Example 1, the proportion of the total water-containing crumb amount for the following sizes was measured using a JIS sieve: (1) 710 μm to 6.7 mm (passed through 6.7 mm but not 710 μm), (2) 710 μm to 4.75 mm (passed through 4.75 mm but not 710 μm), and (3) 710 μm to 3.35 mm (passed through 3.35 mm but not 710 μm). The results are shown below.

[0391] Example 1: (1) 90% by weight, (2) 90% by weight, (3) 87% by weight Example 2: (1) 92% by weight, (2) 91% by weight, (3) 89% by weight Example 3: (1) 89% by weight, (2) 87% by weight, (3) 83% by weight Example 4: (1) 91% by weight, (2) 90% by weight, (3) 83% by weight Example 5: (1) 93% by weight, (2) 91% by weight, (3) 89% by weight Example 6: (1) 95% by weight, (2) 89% by weight, (3) 80% by weight Example 7: (1) 92% by weight, (2) 92% by weight, (3) 88% by weight Example 8: (1) 94% by weight, (2) 93% by weight, (3) 87% by weight Example 9: (1) 90% by weight, (2) 89% by weight, (3) 88% by weight Comparative example 1: (1) 15% by weight, (2) 1% by weight, (3) 0% by weight

[0392] These results show that even with the same washing process, the amount of ash remaining in the acrylic rubber differs depending on the size of the water-containing crumbs generated in the solidification process. It can be seen that materials with a higher proportion of the specific percentages (1) to (3) have higher washing efficiency, reduced ash content, and superior water resistance (comparison of Examples 3 to 9 and Comparative Example 1 in Table 2-2). Furthermore, materials with a higher proportion of the specific percentages (1) to (3) also show a higher ash removal rate during 20% ​​weight dehydration, further reducing ash content and significantly improving the water resistance of the acrylic rubber (comparison of Examples 1 to 2 and Examples 3 to 9).

[0393] For reference, the same procedure as in Comparative Example 1 was followed except that the emulsion polymerization solution was added to the solidification solution during the solidification process (Reference Example 1), and the same procedure as in Comparative Example 1 was followed except that the emulsion polymerization solution was added to the solidification solution and the coagulant concentration of the solidification solution was changed from 0.7% by weight to 2% by weight (Reference Example 2). The particle size ratio of the resulting water-containing crumbs and the amount of ash in the acrylic rubber were then measured.

[0394] Reference example 1: (1) 90% by weight, (2) 55% by weight, (3) 22% by weight, ash content 0.55% by weight Reference example 2: (1) 91% by weight, (2) 70% by weight, (3) 40% by weight, ash content 0.41% by weight

[0395] These results show that the ash content in acrylic rubber can be reduced by increasing the coagulation solution concentration (2%), changing the method of adding the emulsion polymerization solution to the coagulation solution while stirring (Lx↓), and increasing the stirring of the coagulation solution (stirring speed 600 rpm / peripheral speed 3.1 m / s). This allows the crumb diameter of the generated water-containing crumbs to be concentrated within a specific range of 710 μm to 4.75 mm, significantly improving the efficiency of washing with hot water and the efficiency of removing emulsifiers and coagulants during dewatering. This reduces the ash content of the acrylic rubber and significantly improves water resistance without impairing the properties of the acrylic rubber, including its crosslinkability, roll processability, compression set resistance, and strength characteristics (Examples 1-2). It was also confirmed that the presence or absence of the chain transfer agent has almost no effect on the particle size of the generated water-containing crumbs.

[0396] [Example 10] As shown in Table 3-1, the procedure was carried out in the same manner as in Example 2, except that the monomer components were changed to 74.5 parts ethyl acrylate, 17 parts n-butyl acrylate, 7 parts methoxyethyl acrylate, and 1.5 parts mono-n-butyl fumarate, and the emulsifier was changed to 1.8 parts tridecyloxyhexaoxyethylene sodium phosphate. Acrylic rubber (L) was obtained and its properties were evaluated, and the results are shown in Table 3-2. Table 3-1 also shows the water content after dewatering (wastewater) of a screw-type twin-screw extruder dryer, maximum torque, specific power, specific force, shear rate, and shear viscosity.

[0397] [Example 11] The procedure was carried out in the same manner as in Example 1, except that the monomer components were changed to 74.5 parts ethyl acrylate, 17 parts n-butyl acrylate, 7 parts methoxyethyl acrylate, 1.5 parts mono-n-butyl fumarate, and the emulsifier to 1.8 parts tridecyloxyhexaoxyethylene sodium phosphate. Acrylic rubber (M) was obtained, and its properties were evaluated. The results are shown in Table 3-2. Table 3-1 shows the water content after dewatering (wastewater) of a screw-type twin-screw extruder dryer, maximum torque, specific power, specific force, shear rate, and shear viscosity.

[0398] [Example 12] Except for changing the monomer components to 28 parts ethyl acrylate, 38 parts n-butyl acrylate, 27 parts methoxyethyl acrylate, 5 parts acrylonitrile, and 2 parts allyl glycidyl ether, and changing the operating conditions of the screw-type twin-screw extruder to high shear (maximum torque 45 N·m), the same procedure as in Example 10 was followed to obtain acrylic rubber (N), and its various properties (the compounding agent was changed to "Compound 3") were evaluated. The results are shown in Table 3-2. Table 3-1 shows the water content after dewatering (wastewater) of the screw-type twin-screw extruder, maximum torque, specific power, specific force, shear rate, and shear viscosity.

[0399] [Example 13] The procedure was carried out in the same manner as in Example 12, except that the monomer components were changed to 48.5 parts ethyl acrylate, 50 parts n-butyl acrylate, and 1.5 parts mono-n-butyl fumarate. Acrylic rubber (O) was obtained, and its properties (the compounding agent was changed to "Compound 1") were evaluated, and the results are shown in Table 3-2. In addition, Table 3-1 shows the water content after dewatering (wastewater) of a screw-type twin-screw extruder dryer, maximum torque, specific power, specific force, shear rate, and shear viscosity.

[0400] [Example 14] The procedure was carried out in the same manner as in Example 12, except that the monomer components were changed to 48.25 parts ethyl acrylate, 50 parts n-butyl acrylate, and 1.75 parts n-butyl fumamonate. Acrylic rubber (P) was obtained, and its properties (the compounding agent was changed to "Compound 2") were evaluated, and the results are shown in Table 3-2. In addition, Table 3-1 shows the water content after dewatering (wastewater) of a screw-type twin-screw extruder dryer, maximum torque, specific power, specific force, shear rate, and shear viscosity.

[0401] [Example 15] Except for changing the monomer components to 28 parts ethyl acrylate, 38 parts n-butyl acrylate, 27 parts methoxyethyl acrylate, 5 parts acrylonitrile, and 2 parts allyl glycidyl ether, and changing the operating conditions of the screw-type twin-screw extruder to high shear (maximum torque 45 N·m), the same procedure as in Example 11 was followed to obtain acrylic rubber (Q), and each property (the compounding agent was changed to "Compound 3") was evaluated, and the results are shown in Table 3-2. In addition, Table 3-1 shows the water content after dewatering (wastewater) of the screw-type twin-screw extruder, maximum torque, specific power, specific force, shear rate, and shear viscosity.

[0402] [Example 16] The procedure was carried out in the same manner as in Example 15, except that the monomer components were changed to 48.5 parts ethyl acrylate, 50 parts n-butyl acrylate, and 1.5 parts mono-n-butyl fumarate. Acrylic rubber (R) was obtained, and its properties (the compounding agent was changed to "Formulation 1") were evaluated, and the results are shown in Table 3-2. In addition, Table 3-1 shows the water content after dewatering (wastewater) of a screw-type twin-screw extruder dryer, maximum torque, specific power, specific force, shear rate, and shear viscosity.

[0403] [Example 17] The procedure was carried out in the same manner as in Example 15, except that the monomer components were changed to 48.25 parts ethyl acrylate, 50 parts n-butyl acrylate, and 1.75 parts mono-n-butyl fumarate. Acrylic rubber (S) was obtained, and its properties (the compounding agent was changed to "Compound 2") were evaluated, and the results are shown in Table 3-2. In addition, Table 3-1 shows the water content after dewatering (wastewater) of a screw-type twin-screw extruder dryer, maximum torque, specific power, specific force, shear rate, and shear viscosity.

[0404] [Table 3-1]

[0405] [Table 3-2]

[0406] Table 3-2 shows that the acrylic rubbers (N) to (S) of the present invention exhibit excellent normal physical properties, including Banbury processability, water resistance, storage stability, crosslinkability, compression set resistance, and strength, and that roll processability is significantly improved (comparison between Examples 12-17 and Examples 10-11). This is because acrylic rubber composed of high molecular weight and low molecular weight components, which is emulsion polymerized by adding a chain transfer agent afterwards, is dried at high shear using a screw-type twin-screw extruder, resulting in acrylic rubber with a more balanced molecular weight and molecular weight distribution, which dramatically improves roll processability.

[0407] Furthermore, the variability of the methyl ethyl ketone insoluble content in each rubber sample was evaluated using the method described above. Specifically, the variability of the methyl ethyl ketone insoluble content in the rubber samples was evaluated by measuring the methyl ethyl ketone insoluble content at 20 points arbitrarily selected from 20 rubber samples (20 kg) and evaluating it based on the criteria described above.

[0408] When the variability of methyl ethyl ketone insoluble content was evaluated using the acrylic rubbers (L) to (S) obtained in Examples 10 to 17 and the acrylic rubber (J) obtained in Comparative Example 1 as rubber samples, the results for the acrylic rubbers (L) to (S) of Examples 10 to 17 according to the present invention were all "◎", but the result for the acrylic rubber (J) of Comparative Example 1 was "×".

[0409] It is presumed that this is because acrylic rubber (L) to (S) is melt-mixed in a screw-type twin-screw extruder and dried in a state with virtually no moisture (moisture content less than 1% by weight), which almost completely eliminates the amount of methyl ethyl ketone insoluble material and also virtually eliminates variations in the amount of methyl ethyl ketone insoluble material. As a result, the Banbury processability is significantly improved without impairing the normal physical properties, including crosslinkability, roll processability, compression set resistance, and strength properties.

[0410] On the other hand, the amount of methyl ethyl ketone insoluble matter and the variation in the amount of methyl ethyl ketone insoluble matter measured for the acrylic rubber obtained by carrying out emulsion polymerization and coagulation washing under the same conditions as for the acrylic rubber (J) of Comparative Example 1, and then feeding the resulting hydrated crumb into a screw-type twin-screw extruder and extruding it under the same conditions as for Example 10, were found to be almost the same as for acrylic rubber (L), indicating that Banbury processability had also improved. However, the roll processability remained rated as "×".

[0411] For the acrylic rubber compositions containing acrylic rubbers (L) to (S) of Examples 10 to 17, the Mooney scorch time t5 (minutes) at a temperature of 125°C was measured according to JIS K 6300 using the method described above for evaluating processing stability by suppressing Mooney scorch, and the Mooney scorch storage stability was evaluated according to the following criteria. As a result, all results were excellent, rated "◎". ◎: Mooneys coach time t5 exceeds 2.0 minutes ○: Mooney Scorch with a time t5 of 1.5 to 2.0 minutes. ×: Mooneys coach time t5 is less than 1.5 minutes Furthermore, for these acrylic rubbers (L) to (S), the cooling rate of the sheet-like dried rubber extruded from the screw-type twin-screw extruder is fast, approximately 200°C / hr, similar to Example 1, and is 40°C / hr or higher in all cases.

[0412] [Release properties from molds] The acrylic rubber compositions (L) to (S) obtained in Examples 10 to 17 were injected under pressure into a 10 mmφ × 200 mm mold, and the crosslinked rubber products were removed after crosslinking at a mold temperature of 165°C for 2 minutes. When the mold release properties were evaluated according to the following criteria, all of the acrylic rubbers (L) to (S) received a good rating of "◎". ◎: Easy to release from the mold with no mold residue. ○: It can be easily released from the mold, but a very small amount of mold residue is observed. △: Easily released from the mold, but a small amount of mold residue remains. ×: Difficult to remove from the mold [Explanation of Symbols]

[0413] 1. Acrylic rubber manufacturing system 3 Coagulation device 4. Washing device 5. Screw-type extruder 6 Cooling device 7. Baling device

Claims

1. Emulsion process in which an acrylic rubber monomer component, mainly composed of (meth)acrylic acid ester, is emulsified with water and an emulsifier. An emulsion polymerization step in which polymerization is initiated in the presence of a redox catalyst containing an inorganic radical generator and a reducing agent, and a chain transfer agent is added batch-wise during polymerization to continue polymerization and obtain an emulsion polymerization solution, The obtained emulsion polymerization solution is solidified using an alkali metal salt or a Group 2 metal salt of the periodic table as a coagulant, and then added to a stirred solidified solution to solidify and produce a hydrated crumb; A washing process in which the generated water-containing crumb is washed with hot water, A dehydration process to dehydrate the washed, water-containing crumb, A drying process in which the dehydrated crumb is dried to a moisture content of less than 1% by weight, A method for manufacturing acrylic rubber containing [a specific component].

2. A method for producing acrylic rubber according to claim 1, wherein the acrylic rubber is mainly composed of (meth)acrylic acid ester, has an absolute molecular weight and a weight-average molecular weight (Mw) of 1 million or more as measured by the GPC-MALS method using a dimethylformamide solvent as the developing solvent, and has a weight-average molecular weight (Mw) of 1 million or more as measured by the GPC-MALS method, and a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) of 3.4 or more, and is formed by solidifying the polymerized liquid produced by continuing polymerization using a chain transfer agent using an alkali metal salt or a Group 2 metal salt of the periodic table as a coagulant, and drying, and has an ash content of 0.4% by weight or less and a total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash of 80% by weight or more.

3. A method for producing acrylic rubber according to claim 1 or 2, wherein emulsion polymerization is carried out using a phosphate ester salt or a sulfate ester salt as an emulsifier.

4. A method for producing acrylic rubber according to claim 1, wherein the polymerization solution produced in the emulsion polymerization step is added to an aqueous solution containing a coagulant containing an alkali metal salt or a Group 2 metal salt of the periodic table and stirred to solidify it.

5. A method for producing acrylic rubber according to claims 1 to 4, wherein the polymerization solution produced in the emulsion polymerization step is brought into contact with a coagulant to solidify, and then melt-kneaded and dried.

6. The method for producing acrylic rubber according to claim 5, wherein the melting and kneading and drying are carried out in a substantially moisture-free state.

7. The method for producing acrylic rubber according to claim 5 or 6, wherein the melting and kneading and drying are carried out under reduced pressure.

8. The method for producing acrylic rubber according to any one of claims 5 to 7, wherein the melting and kneading and drying are performed in a screw-type twin-screw extruder.

9. The method for producing acrylic rubber according to claim 8, wherein the maximum torque of the screw-type twin-screw extruder dryer during melt mixing and drying is 20 N·m or more.

10. A method for producing acrylic rubber according to any one of claims 5 to 9, wherein the acrylic rubber after melt-mixing and drying is cooled at a cooling rate of 40°C / hr or higher.

11. A method for producing acrylic rubber according to any one of claims 1 to 10, wherein the coagulant concentration of the coagulation solution is 1% by weight or more.

12. A method for producing acrylic rubber according to any one of claims 1 to 11, wherein the stirring speed of the coagulating liquid being stirred is 100 rpm or more.

13. A method for producing acrylic rubber according to any one of claims 1 to 12, wherein the peripheral speed of the coagulating liquid being stirred is 1 m / s or more.

14. A method for producing acrylic rubber according to any one of claims 1 to 13, wherein a reducing agent is added after the emulsion polymerization step.

15. A method for producing acrylic rubber according to any one of claims 1 to 14, comprising washing, dewatering, and drying a water-containing crumb in which the proportion of particles with a diameter in the range of 710 μm to 6.7 mm is 50% by weight or more.

16. A method for producing a rubber composition comprising mixing a rubber component containing acrylic rubber, a filler, and an antioxidant as needed, after mixing the rubber component, a filler, and an antioxidant as needed, and then mixing in a crosslinking agent.

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