Acrylic rubber excellent in Banbury processability, storage stability, and water resistance

Abstract

To provide acryl rubber excellent in Banbury mixer processability, storage stability, and water proofness.SOLUTION: The acryl rubber pertaining to the present invention comprises acryl rubber having a reactive group, and a reactive group content of 0.001-5 wt.%, where the gel amount of a methyl ethyl ketone-insoluble content is 50 wt.% or less, pH is 6 or less, the ash content is 0.4 wt.% or less, the total amount of magnesium, phosphorous, calcium, sodium, and sulfur is 50 wt.% or more, and the specific gravity is 0.8 or more.SELECTED DRAWING: None

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 excellent in Banbury processability, storage stability, and water resistance, a method for producing the same, a crosslinkable rubber composition containing the acrylic rubber, and a rubber crosslinked product obtained by crosslinking the rubber composition.

Background Art

[0002] Acrylic rubber is a polymer mainly composed of acrylic acid esters, and is generally known as a rubber excellent in heat resistance, oil resistance, and ozone resistance, and is widely used in fields related to automobiles and the like.

[0003] For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 11-12427) discloses 100 parts of a monomer component containing ethyl acrylate, butyl acrylate, methoxyethyl acrylate, acrylonitrile, and a monomer having a carbon-carbon double bond introduced into the side chain such as allyl methacrylate or cyclopentenyl oxyethyl acrylate, 4 parts of sodium lauryl sulfate, 0.25 part of p-menthane hydroperoxide as an organic radical generator, 0.01 part of ferrous sulfate, 0.025 part of sodium ethylenediaminetetraacetate, 0.04 part of sodium formaldehyde sulfoxylate, and 0.01 to 0.05 part of t-dodecyl mercaptan as a chain transfer agent, charged into an autoclave replaced with nitrogen, reacted at a reaction temperature of 30° C. until the conversion rate of the monomer mixture reaches 100%, the obtained latex is added to a 0.25% aqueous calcium chloride solution to be coagulated, the coagulated product is sufficiently washed with water, dried at about 90° C. for 3 hours, and crosslinked with an organic peroxide such as 1,3-bis(t-butylperoxyisopropyl)benzene. An acrylic rubber and a crosslinked composition excellent in extrusion processability and scorch characteristics are disclosed. However, the acrylic rubber obtained by this method has problems in that the Banbury processability and roll processability are not sufficient, and the storage stability, compression set resistance characteristics, water resistance, and strength characteristics are inferior.

[0004] Further, Patent Document 2 (Japanese Patent Application Laid-Open No. 5-86137) discloses a method for producing an acrylic rubber in which polymerization is initiated with an organic radical generator and a chain transfer agent is continuously added to a monomer emulsion. Specifically, one-fifth of a mixture of a monomer mixture containing crosslinkable monomers such as 2-(-cyanoethoxy)ethyl acrylate, ethyl acrylate, n-butyl acrylate, and vinyl chloroacetate and allyl glycidyl ether and an appropriate amount of n-dodecyl mercaptan is mixed and stirred with one-half of 1 part by weight of polyoxyethylene lauryl ether, 4 parts by weight of sodium lauryl sulfate, 0.7 part by weight of disodium hydrogen phosphate, and 0.3 part by weight of sodium dihydrogen phosphate to form an emulsion. After adjusting the temperature to 15°C, 0.005 part by weight of iron(II) sodium ethylenediaminetetraacetate, 0.02 part by weight of tetrasodium ethylenediaminetetraacetate, 0.02 part by weight of Rongalit, and 0.02 part by weight of sodium hydrosulfite are added. Polymerization is initiated by dropping a 0.2% by weight aqueous solution of tert-butyl hydroperoxide, which is an organic radical generator, at a rate of 1.5 parts per hour while maintaining the temperature at 15°C. While maintaining the temperature at 15°C, an emulsion composed of the remaining monomer and n-dodecyl mercaptan mixture and an aqueous emulsifier solution is dropped over 3 hours to carry out a polymerization reaction until the monomer conversion rate reaches 96 to 99%. Further, the obtained copolymer latex is poured into an aqueous calcium chloride solution at 85°C to isolate the copolymer, thoroughly washed, and then dried to obtain the target copolymer rubber, which is described as being sulfur-crosslinked. However, the acrylic rubber obtained by this method has problems in that its Banbury processability and roll processability are not sufficient, and its storage stability, water resistance, and strength characteristics are inferior.

[0005] Further, Patent Document 3 (International Publication No. WO2019 / 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 under normal pressure and normal temperature, carrying out emulsion polymerization until the polymerization conversion rate reaches 95% by weight, coagulating with an aqueous calcium chloride solution, and dehydrating and drying with an extrusion dryer having a screw. However, the acrylic rubber obtained by such a method has problems of poor Banbury processability, roll processability, storage stability, and water resistance.

[0006] Furthermore, Patent Document 4 (International Publication No. WO2018 / 117037 pamphlet) discloses a method for producing an acrylic rubber by charging a monomer component composed of ethyl acrylate and monobutyl fumarate, water and sodium dodecyl sulfate, performing vacuum degassing and nitrogen substitution three times to sufficiently remove oxygen, and then adding azobis(isobutyronitrile) which is an organic radical generator and ethyl-2-methyl-2-phenylteranylpropionate to initiate a polymerization reaction at 50 degrees under normal pressure, carrying out polymerization until the polymerization conversion rate reaches 89%, coagulating with a calcium chloride solution, washing with water, and drying. However, the acrylic rubber obtained by such a method has problems of poor Banbury processability, roll processability, storage stability, and water resistance.

[0007] On the other hand, as a method for producing an acrylic rubber using an inorganic radical generator, for example, in Patent Document 5 (Japanese Patent Application Laid-Open No. 2019-119772), a monomer component composed of ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and monobutyl maleate is made into a monomer emulsion using pure water and emulsifiers such as sodium lauryl sulfate and polyoxyethylene dodecyl ether. After that, a part of the monomer emulsion is put into a polymerization reaction tank and cooled to 12°C under a nitrogen stream. Then, the remaining monomer emulsion, ferrous sulfate, sodium ascorbate, and an aqueous solution of potassium persulfate as an inorganic radical generator are continuously dropped over 3 hours. After that, the temperature is maintained at 23°C and emulsion polymerization is continued for 1 hour. After the polymerization conversion rate reaches 97% by weight, the temperature is raised to 85°C, and then sodium sulfate is continuously added to perform coagulation filtration to obtain a water-containing crumb. The water-containing crumb is washed with water 4 times, acid-washed once, and washed with pure water once, and then an acrylic rubber is continuously produced in a sheet form using an extrusion dryer having a screw and crosslinked with an aliphatic polyvalent amine compound such as hexamethylenediamine carbamate. However, the sheet-like acrylic rubber obtained by this method has problems of inferior storage stability and water resistance of the crosslinked product.

[0008] In Patent Document 6 (Japanese Patent Application Laid-Open No. 1-135811), 1 / 4 of a monomer mixture composed of a monomer component consisting of ethyl acrylate, a caprolactone-added acrylate, cyanoethyl acrylate, and vinyl chloroacetate and n-dodecyl mercaptan as a chain transfer agent is emulsified with sodium lauryl sulfate, polyethylene glycol nonylphenyl ether, and distilled water. Sodium sulfite and ammonium persulfate as an inorganic radical generator are added to initiate polymerization. While maintaining the temperature at 60°C, the remaining monomer mixture and a 2% aqueous solution of ammonium persulfate are dropped over 2 hours. After the dropping, polymerization is continued for another 2 hours. A latex with a polymerization conversion rate of 96 to 99% is poured into an aqueous sodium chloride solution at 80°C to be coagulated, and then thoroughly washed with water and dried to produce an acrylic rubber and crosslinked with sulfur. However, the acrylic rubber obtained by this method has problems of insufficient Banbury processability, inferior storage stability, and water resistance.

[0009] Patent Document 7 (Japanese Unexamined Patent Publication No. 62-64809) discloses an acrylic rubber capable of sulfur vulcanization, which is a copolymer having a monomer composition consisting of 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, and 0 to 20% by weight of at least one selected from other monovinyl, monovinylidene, and monovinylene unsaturated compounds. The number average molecular weight (Mn) in terms of polystyrene, with tetrahydrofuran as the developing solvent, is 200,000 to 1,200,000, and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 10 or less. As specific examples thereof, 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 a molecular weight regulator are added in variable amounts, and an acrylic rubber with 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 (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 4.7 to 8 is disclosed. And it is shown in the examples and comparative examples that when the amount of the chain transfer agent is small, the number average molecular weight (Mw) is as large as 5,000,000 and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is as narrow as 1.4, and when the amount of the chain transfer agent is large, the number average molecular weight (Mn) is as small as 200,000 and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is extremely wide at 17. However, the acrylic rubber obtained by this method has insufficient Banbury processability and roll processability. In the crosslinking reaction, sulfur as a crosslinking agent and a vulcanization accelerator are added, and after kneading on a roll, there is a problem that crosslinking at 170 °C for 15 minutes in a vulcanization press of 100 kg / cm 2 In the vulcanization press, crosslinking at 170 °C for 15 minutes and further in a gear oven at 175 °C for 4 hours is required for a long time. Also, the obtained crosslinked product has problems such as inferior water resistance, compression set resistance characteristics, and strength characteristics, and also inferior physical property changes after thermal degradation.

Prior Art Documents

Patent Document

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been made in view of the actual state of such prior art, and an object thereof is to provide an acrylic rubber excellent in Banbury processability, storage stability, and water resistance, a method for producing the same, a crosslinkable rubber composition containing the acrylic rubber, and a rubber crosslinked product obtained by crosslinking the same.

Means for Solving the Problems

[0012] As a result of intensive studies in view of the above problems, the present inventors have found that an acrylic rubber containing a specific amount of a reactive group that reacts with a crosslinking agent or the like and having a specific gel amount, pH, ash content, ash component amount, and specific gravity of a specific solvent-insoluble component is highly balanced and excellent in Banbury processability, storage stability, and water resistance.

[0013] The present inventors have also found that, with respect to Banbury processability, the gel content of the acrylic rubber, particularly the gel content of the insoluble matter in a specific solvent, has a great influence. Further, the insoluble matter content (gel content) of the specific solvent of the acrylic rubber is generated during the emulsion polymerization of the acrylic rubber. In particular, as the polymerization conversion rate increases in an attempt to enhance the strength characteristics, it rapidly increases, making it difficult to control during the polymerization. However, the presence of a chain transfer agent at the end stage of the emulsion polymerization can improve it to some extent. And, by melt-kneading and drying the water-containing crumb produced by coagulation in a screw-type twin-screw extruder dryer in a substantially water-free state (water content less than 1% by weight), the rapidly increasing gel content of the insoluble matter in the specific solvent disappears, and it has been found that an acrylic rubber with extremely excellent Banbury processability can be produced.

[0014] The present inventors have also found that, with respect to storage stability, it is greatly affected by the specific gravity of the acrylic rubber. Although the specific gravity of the acrylic rubber itself is large, air is entrained during production. In particular, acrylic rubbers having reactive groups such as carboxyl groups, epoxy groups, or chlorine atoms are sticky and have a high affinity for air, and once air is entrained, it is difficult to remove. However, by belling with a high-pressure beller, the specific gravity can be slightly increased and the storage stability can be improved. And, by extruding a sheet-like acrylic rubber containing no air with a screw-type twin-screw extruder dryer under reduced pressure, it has been found that an acrylic rubber with almost no air content, a higher specific gravity, and extremely excellent storage stability can be produced. The present inventors have also found that the storage stability of the acrylic rubber is also greatly affected by the pH of the acrylic rubber, and the storage stability can be improved by lowering the pH.

[0015] The present inventors have also found that, with respect to water resistance, the ash content and ash components in the acrylic rubber have a great influence. The ash content of the acrylic rubber is difficult to reduce from a production method that uses a large amount of emulsifier and coagulant. However, the water-containing crumb produced by a specific coagulation method has extremely high washing efficiency with warm water and ash removal rate during dehydration, and it has been found that the ash content in the acrylic rubber can be significantly reduced and the water resistance can be extremely improved.

[0016] The inventors have also found that when the reactive group is a carboxyl group, an epoxy group or a chlorine atom that reacts with a crosslinking agent or the like, or an ionic reactive group, and particularly when the content of the reactive group in the acrylic rubber is within a specific range, the acrylic rubber is excellent in Banbury processability, storage stability and water resistance, and is also highly excellent in compression set resistance characteristics and strength characteristics, and is suitable.

[0017] The inventors have also found that the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is related to the roll processability of acrylic rubber. In particular, when the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is within a specific range, it is excellent in Banbury processability, storage stability and water resistance, and is also excellent in roll processability and is suitable. The inventors have also found that an acrylic rubber having a specific ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) and excellent in roll processability, Banbury processability, storage stability and water resistance can be obtained by emulsifying a specific monomer component with water and an emulsifier, and then initiating emulsion polymerization in the presence of a redox catalyst composed of an inorganic radical generator such as potassium persulfate and a reducing agent, adding a chain transfer agent batchwise during the polymerization without adding it initially, 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, so that the high molecular weight component and the low molecular weight component of the acrylic rubber coexist to form a broad molecular weight distribution and the ash content of the specific component can be achieved.

[0018] Also, by melt-kneading and drying acrylic rubber under high-shear conditions using a specific extruder dryer, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) can be widened without decreasing the weight average molecular weight (Mw), and the roll processability and strength characteristics of the acrylic rubber can be highly balanced.

[0019] The inventors of the present invention have also found that an acrylic rubber having an acrylate ester and a methacrylate ester is excellent in Banbury processability, storage stability, water resistance, and heat resistance. In particular, it has been found that the effect of heat resistance is highly enhanced by including a methacrylate ester having a specific number of carbon atoms.

[0020] Based on these findings, the inventors of the present invention have completed the present invention.

[0021] Thus, according to the present invention, there is provided an acrylic rubber comprising an acrylic rubber having a reactive group and a reactive group content of 0.001 to 5% by weight, wherein the gel amount of the methyl ethyl ketone-insoluble matter is 50% by weight or less, the pH is 6 or less, the ash content is 0.4% by weight or less, the total amount of magnesium, phosphorus, calcium, sodium, and sulfur in the ash is 50% by weight or more, and the specific gravity is 0.8 or more.

[0022] In the acrylic rubber of the present invention, the ash content is preferably 0.15% by weight or less.

[0023] In the acrylic rubber of the present invention, the lower limit value of the ash content is preferably 0.0001% by weight or more.

[0024] In the acrylic rubber of the present invention, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber is preferably in the range of 1.1 to 8.

[0025] In the acrylic rubber of the present invention, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber is preferably 3.4 or more.

[0026] In the acrylic rubber of the present invention, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber is preferably in the range of 3.7 to 6.5.

[0027] In the acrylic rubber of the present invention, the weight average molecular weight (Mw) of the acrylic rubber is preferably 1,000,000 or more.

[0028] In the acrylic rubber of the present invention, it is preferable that the acrylic rubber is composed of a bonding unit (A) derived from a (meth)acrylic acid ester, a bonding unit (B) derived from a reactive group-containing monomer, and, if necessary, a bonding unit (C) derived from other monomers.

[0029] In the acrylic rubber of the present invention, the bonding unit (A) derived from a (meth)acrylic acid ester is preferably at least one selected from the group consisting of an alkyl (meth)acrylate and an alkoxyalkyl (meth)acrylate.

[0030] In the acrylic rubber of the present invention, the bonding unit (A) derived from a (meth)acrylic acid ester preferably consists of a bonding unit (A1) derived from an acrylate ester and a bonding unit (A2) derived from a methacrylate ester.

[0031] In the acrylic rubber of the present invention, the reactive group is preferably an ionic reactive group.

[0032] In the acrylic rubber of the present invention, the reactive group is preferably at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group, and a chlorine atom.

[0033] In the acrylic rubber of the present invention, it is preferably in a sheet form or a veil form.

[0034] In the present invention, further, an emulsion polymerization step of emulsifying an acrylic rubber monomer component containing a reactive group-containing monomer with water and an emulsifier and then initiating polymerization in the presence of a redox catalyst composed of a radical generator and a reducing agent to obtain an emulsion polymerization liquid; A coagulation step of adding the obtained emulsion polymerization liquid to a coagulation liquid having a coagulant concentration of 1% by weight or more while stirring to coagulate and produce a water-containing clam; A washing step of washing the produced water-containing clam with warm water; A dehydration step of dehydrating the washed water-containing crumb to a water content of 1 to 40% by weight, A drying step of drying the dehydrated water-containing crumb to less than 1% by weight, A method for producing an acrylic rubber containing the same is provided.

[0035] In the method for producing an acrylic rubber of the present invention, it is preferable to bale the dried rubber.

[0036] In the method for producing an acrylic rubber of the present invention, the radical generator is preferably an inorganic radical generator.

[0037] In the method for producing an acrylic rubber of the present invention, it is preferable that a chain transfer agent is added batchwise during emulsion polymerization.

[0038] In the method for producing an acrylic rubber of the present invention, it is preferable that the drying of the water-containing crumb is carried out using a screw-type twin-screw extrusion dryer.

[0039] In the method for producing an acrylic rubber of the present invention, the dehydration and drying steps are carried out by dehydrating the water-containing crumb after washing to a water content of 1 to 40% by weight in a dehydration barrel having a dehydration slit, then drying to less than 1% by weight in a drying barrel under reduced pressure using a screw-type twin-screw extrusion dryer having a die at the tip, and extruding a sheet-like dried rubber from the die.

[0040] In the method for producing an acrylic rubber of the present invention, it is preferable to laminate and bale the extruded sheet-like dried rubber.

[0041] In the method for producing an acrylic rubber of the present invention, the acrylic rubber monomer component preferably contains an acrylate ester and a methacrylate ester.

[0042] In the present invention, a rubber composition comprising the above acrylic rubber, a filler, and a crosslinking agent is also provided.

[0043] In the present invention, there is also provided a method for producing a rubber composition in which a crosslinking agent is mixed after mixing the acrylic rubber and the filler.

[0044] In the present invention, there is also provided a rubber crosslinked product obtained by crosslinking the above rubber composition.

Advantages of the Invention

[0045] According to the present invention, there are provided an acrylic rubber excellent in Banbury processability, storage stability and water resistance, an efficient production method thereof, a rubber composition containing the acrylic rubber, and a rubber crosslinked product obtained by crosslinking the same.

Brief Description of the Drawings

[0046]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0047] The acrylic rubber of the present invention is composed of an acrylic rubber having a reactive group and a reactive group content of 0.001 to 5% by weight, and has a gel amount of methyl ethyl ketone insoluble matter of 50% by weight or less, a pH of 6 or less, an ash content of 0.4% by weight or less, and a total amount of magnesium, phosphorus, calcium, sodium and sulfur in the ash of 50% by weight or more, and a specific gravity of 0.8 or more.

[0048] <Reactive group> The acrylic rubber of the present invention is characterized by having a reactive group. There is no particular limitation on the reactive group as long as it is a reactive group that reacts with a crosslinking agent or the like. For example, it is at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group, and a chlorine atom, or when it is an ionic reactive group involved in an ionic reaction, preferably an epoxy group, a carboxyl group, and particularly preferably a carboxyl group, it can highly improve the crosslinkability in a short time and the compression set resistance and water resistance of the crosslinked product, which is suitable.

[0049] The content of the reactive group in the acrylic rubber of the present invention 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 particularly preferably 0.1 to 0.5% by weight in terms of the weight ratio of the reactive group itself. At this time, the processability, crosslinkability, and properties such as strength characteristics, compression set resistance, oil resistance, cold resistance, and water resistance of the crosslinked product are highly balanced, which is suitable.

[0050] The acrylic rubber having a reactive group of the present invention may be obtained by introducing a reactive group, preferably at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group, and a chlorine atom or an ionic reactive group, into the acrylic rubber by a post-reaction. Preferably, an acrylic rubber copolymerized with a reactive group-containing monomer is suitable.

[0051] <Monomer component> The monomer component of the acrylic rubber of the present invention is not particularly limited as long as it is a monomer having the above reactive group and constituting a normal acrylic rubber. Preferably, it is an acrylic rubber monomer component containing a reactive group-containing monomer, more preferably a monomer component consisting of (meth)acrylate (a), a reactive group-containing monomer (b), and other copolymerizable monomers (c) as required. In the present invention, the term "(meth)acrylate" is used as a general term for esters of acrylic acid and / or methacrylic acid.

[0052] When at least one (meth)acrylic acid ester (a) is selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters, the weather resistance, heat resistance, and oil resistance of the acrylic rubber are highly balanced, which is preferable.

[0053] The (meth)acrylic acid alkyl ester is not particularly limited, but usually a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 12 carbon atoms, preferably a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 8 carbon atoms, more preferably a (meth)acrylic acid alkyl ester having an alkyl group with 2 to 6 carbon atoms is used.

[0054] Specific examples of the (meth)acrylic acid alkyl ester 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, cyclohexyl (meth)acrylate, etc. Among these, ethyl (meth)acrylate and n-butyl (meth)acrylate are preferable, and ethyl acrylate and n-butyl acrylate are more preferable.

[0055] The (meth)acrylic acid alkoxyalkyl ester is not particularly limited, but usually a (meth)acrylic acid alkoxyalkyl ester having an alkoxyalkyl group with 2 to 12 carbon atoms, preferably a (meth)acrylic acid alkoxyalkyl ester having an alkoxyalkyl group with 2 to 8 carbon atoms, more preferably a (meth)acrylic acid alkoxyester having an alkoxyalkyl group with 2 to 6 carbon atoms is used.

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

[0057] At least one (meth)acrylic acid ester selected from the group consisting of these (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters is used alone or in combination of two or more, and the proportion of these 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, 80 to 99.5% by weight, 87 to 99% by weight, and in this case, the weather resistance, heat resistance, and oil resistance of the acrylic rubber are highly excellent and suitable.

[0058] When the (meth)acrylic acid ester (a) consists of an acrylic acid ester (a1) and a methacrylic acid ester (a2), the heat resistance of the acrylic rubber is remarkably excellent and suitable.

[0059] The acrylic acid alkyl ester (a1) is not particularly limited, and examples thereof include acrylic acid alkyl esters having an alkyl group with 1 to 12 carbon atoms, preferably acrylic acid alkyl esters having an alkyl group with 1 to 8 carbon atoms, more preferably acrylic acid alkyl esters having an alkyl group with 2 to 6 carbon atoms.

[0060] Specific examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, etc. Among them, methyl acrylate, ethyl acrylate, isopropyl acrylate, and n-butyl acrylate are preferred, and ethyl acrylate and n-butyl acrylate are more preferred.

[0061] There is no particular limitation on the alkoxyalkyl acrylate, and examples thereof include alkoxyalkyl acrylates having an alkoxyalkyl group with 2 to 12 carbon atoms. Preferably, it is an alkoxyalkyl acrylate having an alkoxyalkyl group with 2 to 8 carbon atoms, and more preferably, it is an alkoxyalkyl acrylate having an alkoxyalkyl group with 2 to 6 carbon atoms.

[0062] Specific examples of the alkoxyalkyl acrylate include methoxymethyl acrylate, methoxyethyl acrylate, methoxypropyl acrylate, methoxybutyl acrylate, ethoxymethyl acrylate, ethoxyethyl acrylate, propoxyethyl acrylate, butoxyethyl acrylate, etc. Among these, methoxyethyl acrylate, ethoxyethyl acrylate, ethoxymethyl acrylate, methoxymethyl acrylate, etc. are preferred, and methoxyethyl acrylate and ethoxyethyl acrylate are more preferred.

[0063] The bonding units (A1) derived from these acrylic esters (a1) can be used alone or in combination of two or more. The bonding amount of the bonding unit (A1) in the acrylic rubber is usually in the range of 10 to 98.9% by weight, preferably 32 to 97.7% by weight, more preferably 50 to 96.5% by weight, and particularly preferably 62 to 94% by weight. If the amount of the bonding unit (A1) in the acrylic rubber is excessively small, the weather resistance, heat resistance, and oil resistance may decrease. If it is excessively large, the strength characteristics and compression set resistance characteristics may decrease, which is not preferable.

[0064] There is no particular limitation on the methacrylic acid ester (a2). For example, at least one methacrylic acid ester selected from the group consisting of alkyl methacrylic acid esters and alkyl methacrylic acid esters is a preferred example, and alkyl methacrylic acid esters are particularly preferred.

[0065] Examples of the alkyl methacrylic acid ester include alkyl methacrylic acid esters having an alkyl group with 1 to 14 carbon atoms, preferably alkyl methacrylic acid esters having an alkyl group with 2 to 8 carbon atoms, and more preferably alkyl methacrylic acid esters having an alkyl group with 2 to 6 carbon atoms.

[0066] Specific examples of the alkyl methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, octyl methacrylate, dodecyl methacrylate, isotridecyl methacrylate, etc. Preferably, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, octyl methacrylate, and more preferably ethyl methacrylate and n-butyl methacrylate.

[0067] Examples of the alkoxyalkyl methacrylic acid ester include alkoxyalkyl methacrylic acid esters having an alkoxyalkyl group with 2 to 14 carbon atoms, preferably alkoxyalkyl methacrylic acid esters having an alkoxyalkyl group with 2 to 8 carbon atoms, and more preferably alkoxyalkyl methacrylic acid esters having an alkoxyalkyl group with 2 to 6 carbon atoms.

[0068] Specific examples of the alkoxyalkyl methacrylate include methoxymethyl methacrylate, methoxyethyl methacrylate, methoxypropyl methacrylate, methoxybutyl methacrylate, ethoxymethyl methacrylate, ethoxyethyl methacrylate, propoxyethyl methacrylate, butoxyethyl methacrylate, and the like. Among these, methoxyethyl methacrylate, ethoxyethyl methacrylate, ethoxymethyl methacrylate, ethoxyethyl methacrylate, etc. are preferred, and methoxyethyl methacrylate and ethoxyethyl methacrylate are more preferred.

[0069] These bonding units (A2) derived from these methacrylic esters (a2) can be used alone or in combination of two or more. The bonding amount in the acrylic rubber is usually in the range of 1 to 50% by weight, preferably 2 to 40% by weight, more preferably 3 to 30% by weight, and particularly preferably 5 to 25% by weight.

[0070] These (meth)acrylic esters (a) can be used alone or in combination of two or more. When their proportion 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, 80 to 99.5% by weight, and 87 to 99% by weight, the acrylic rubber has highly excellent weather resistance, heat resistance, and oil resistance and is suitable.

[0071] The reactive group-containing monomer (b) is not particularly limited. Examples include monomers having at least one functional group selected from the group consisting of a carboxyl group, an epoxy group, and a halogen group. Monomers having an ionic reactive group are preferred, and monomers having a carboxyl group, an epoxy group, and a chlorine atom are more preferred. Monomers having a carboxyl group and an epoxy group are particularly preferred.

[0072] As the monomer having a carboxyl group, there is no particular limitation, but ethylenically unsaturated carboxylic acids can be preferably used. Examples of the ethylenically unsaturated carboxylic acids include ethylenically unsaturated monocarboxylic acids, ethylenically unsaturated dicarboxylic acids, ethylenically unsaturated dicarboxylic acid monoesters, etc. Among these, ethylenically unsaturated dicarboxylic acid monoesters are preferable because they can further enhance the compression set resistance characteristics of the resulting acrylic rubber.

[0073] As the ethylenically unsaturated monocarboxylic acid, there is no particular limitation, but ethylenically unsaturated monocarboxylic acids having 3 to 12 carbon atoms are preferable, and examples thereof include acrylic acid, methacrylic acid, ethylacrylic acid, crotonic acid, cinnamic acid, etc.

[0074] As the ethylenically unsaturated dicarboxylic acid, there is no particular limitation, but ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms are preferable, and examples thereof include butenedioic acids such as fumaric acid and maleic acid, itaconic acid, citraconic acid, etc. The ethylenically unsaturated dicarboxylic acids also include those existing as anhydrides.

[0075] As the ethylenically unsaturated dicarboxylic acid monoesters, there is no particular limitation, but usually, they are monoesters of ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms and alkyl monoesters having 1 to 12 carbon atoms, preferably monoesters of ethylenically unsaturated dicarboxylic acids having 4 to 6 carbon atoms and alkyl monoesters having 2 to 8 carbon atoms, more preferably alkyl monoesters of butenedioic acid having 4 carbon atoms and having 2 to 6 carbon atoms.

[0076] Specific examples of the ethylenically unsaturated dicarboxylic acid monoester include monoalkyl maleates 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; monoalkyl itaconates such as monomethyl itaconate, monoethyl itaconate, mono-n-butyl itaconate, and monocyclohexyl itaconate; etc. Among them, mono-n-butyl fumarate and mono-n-butyl maleate are preferred, and mono-n-butyl fumarate is particularly preferred.

[0077] Examples of the monomer having an epoxy group 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; etc. Here, the "(meth)acrylic acid" is used as a generic term for acrylic acid and / or methacrylic acid, and the same applies hereinafter.

[0078] Examples of the monomer having a halogen group include unsaturated alcohol esters of halogen-containing saturated carboxylic acids, (meth)acrylic acid haloalkyl esters, (meth)acrylic acid haloacyloxyalkyl esters, (meth)acrylic acid (haloacetylcarbamoyloxy)alkyl esters, halogen-containing unsaturated ethers, halogen-containing unsaturated ketones, halomethyl group-containing aromatic vinyl compounds, halogen-containing unsaturated amides, haloacetyl group-containing unsaturated monomers, etc. Among them, those containing chlorine atoms are particularly preferred.

[0079] Examples of unsaturated alcohol esters of halogen-containing saturated carboxylic acids include vinyl chloroacetate, vinyl 2-chloropropionate, allyl chloroacetate, etc. Examples of (meth)acrylic acid haloalkyl esters 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, 2,3-dichloropropyl (meth)acrylate, etc. Examples of (meth)acrylic acid haloacyloxyalkyl esters include 2-(chloroacetoxy)ethyl (meth)acrylate, 2-(chloroacetoxy)propyl (meth)acrylate, 3-(chloroacetoxy)propyl (meth)acrylate, 3-(hydroxychloroacetoxy)propyl (meth)acrylate, etc. Examples of (meth)acrylic acid (haloacetylcarbamoyloxy)alkyl esters include 2-(chloroacetylcarbamoyloxy)ethyl (meth)acrylate, 3-(chloroacetylcarbamoyloxy)propyl (meth)acrylate, etc. Examples of halogen-containing unsaturated ethers include chloromethyl vinyl ether, 2-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, 2-chloroethyl allyl ether, 3-chloropropyl allyl ether, etc. Examples of halogen-containing unsaturated ketones include 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, 2-chloroethyl allyl ketone, etc. Examples of aromatic vinyl compounds containing a halomethyl group include p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, p-chloromethyl-α-methylstyrene, etc. Examples of halogen-containing unsaturated amides include N-chloromethyl (meth)acrylamide, etc. Examples of unsaturated monomers containing a haloacetyl group include 3-(hydroxychloroacetoxy)propyl allyl ether, p-vinylbenzyl chloroacetate, etc.

[0080] These reactive group-containing monomers (b) are each used alone or in combination of two or more, and their proportions in all monomer components are usually in the range of 0.1 to 10% by weight, preferably 0.3 to 8% by weight, more preferably 0.5 to 5% by weight, and particularly preferably 1 to 3% by weight.

[0081] As the other monomers (c), there are no particular limitations as long as they are other than the above monomers (a) and (b) and are copolymerizable therewith. Examples include aromatic vinyls, ethylenically unsaturated nitriles, acrylamide-based monomers, and other olefin-based monomers. Examples of aromatic vinyls include styrene, α-methylstyrene, divinylbenzene, etc. Examples of ethylenically unsaturated nitriles include acrylonitrile, methacrylonitrile, etc. Examples of acrylamide-based monomers include acrylamide, methacrylamide, etc. Examples of other olefin-based monomers include ethylene, propylene, vinyl acetate, ethyl vinyl ether, butyl vinyl ether, etc.

[0082] These other monomers (c) are each used alone or in combination of two or more, and their proportions in all monomer components are usually in the range of 0 to 30% by weight, preferably 0 to 20% by weight, more preferably 0 to 15% by weight, and particularly preferably 0 to 10% by weight.

[0083] <Acrylic rubber> The acrylic rubber of the present invention is not particularly limited as long as it has a reactive group, but preferably comprises a bonding unit (A) derived from the above (meth)acrylic acid ester (a), a bonding unit (B) derived from a reactive group-containing monomer (b), and, if necessary, a bonding unit (C) derived from other monomer (c). The proportions of each are such that the bonding unit (A) is usually in the range of 10 to 98.9% by weight, preferably 32 to 97.7% by weight, more preferably 50 to 96.5% by weight, particularly preferably 62 to 94% by weight; the bonding unit (B) is usually in the range of 1 to 50% by weight, preferably 2 to 40% by weight, more preferably 3 to 30% by weight, particularly preferably 5 to 25% by weight; and the bonding unit (C) is usually in the range of 0.1 to 10% by weight, preferably 0.3 to 8% by weight, more preferably 0.5 to 5% by weight, particularly preferably 1 to 3% by weight. That is, the acrylic rubber of the present invention is a copolymer containing the above respective bonding units in the specific weight ratios described above and containing them so that the total of each bonding unit is 100% by weight. When each monomer bonding unit in the acrylic rubber is within this range and it is made into a crosslinked product of the acrylic rubber, it is suitable because the heat resistance, water resistance, and compression set resistance characteristics can be highly balanced. In the present invention, when the bonding unit (A) and the bonding unit (A1) derived from the acrylic acid ester (a1) are usually in the range of 10 to 98.9% by weight, preferably 32 to 97.7% by weight, more preferably 50 to 96.5% by weight, particularly preferably 62 to 94% by weight; the bonding unit (A2) derived from the methacrylic acid ester (a2) is usually in the range of 1 to 50% by weight, preferably 2 to 40% by weight, more preferably 3 to 30% by weight, particularly preferably 5 to 25% by weight; and the bonding unit (B) is usually in the range of 0.1 to 10% by weight, preferably 0.3 to 8% by weight, more preferably 0.5 to 5% by weight, particularly preferably 1 to 3% by weight, it is a process in which the heat resistance of the acrylic rubber can be highly improved.

[0084] The weight average molecular weight (Mw) of the acrylic rubber of the present invention is not particularly limited and may be appropriately selected according to the intended use. Usually, it is 1 million or more, preferably 1.1 million or more, more preferably 1.2 million or more, particularly preferably 1.5 million or more, and most preferably 1.6 million or more. If the weight average molecular weight (Mw) of the acrylic rubber of the present invention is excessively small, it is inferior in strength characteristics and compression set resistance characteristics, which is not preferable. The weight average molecular weight (Mw) of the acrylic rubber of the present invention is also usually in the range of 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. At this time, the roll processability, strength characteristics, and compression set resistance characteristics of the acrylic rubber are highly balanced, which is preferable.

[0085] The weight average molecular weight (Mw) of the acrylic rubber of the present invention is also preferably in the range of 1,000,000 to 5,000,000 (1 million to 5 million), more preferably 1,100,000 to 4,000,000 (1.1 million to 4 million), still more preferably 1,150,000 to 3,000,000 (1.15 million to 3 million), and most preferably 1,200,000 to 2,500,000 (1.2 million to 2.5 million). At this time, the processability, strength characteristics, and compression set resistance characteristics of the acrylic rubber during mixing are highly balanced, which is preferable.

[0086] The number average molecular weight (Mn) of the acrylic rubber of the present invention is not particularly limited and may be appropriately selected according to the intended use. Usually, it is 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. At this time, the roll processability, strength characteristics, and compression set resistance characteristics of the acrylic rubber are highly balanced, which is preferable.

[0087] The z-average molecular weight (Mz) of the acrylic rubber of the present invention may be appropriately selected according to the intended use without any particular limitation, but is usually 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. When it is in this range, the roll processability, strength characteristics, and compression set resistance characteristics of the acrylic rubber are highly balanced and suitable.

[0088] The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the acrylic rubber of the present invention is not particularly limited, but when it is usually in the range of 1.1 to 8, preferably 1.2 to 7, and more preferably 1.4 to 6, the processability, strength characteristics, and compression set resistance characteristics of the acrylic rubber are highly balanced, so it is suitable.

[0089] The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the acrylic rubber of the present invention is not particularly limited, but is usually 3.4 or more, preferably 3.5 or more, more preferably 3.6 or more, and particularly preferably 3.7 or more. If the ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the acrylic rubber of the present invention is excessively small, the roll processability is poor. The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the acrylic rubber of the present invention is also 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. When it is in this range, the roll processability, strength characteristics when crosslinked, and compression set resistance characteristics can be highly balanced, which is suitable.

[0090] The ratio (Mz / Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of the acrylic rubber of the present invention may be appropriately selected according to the intended use without any particular limitation, but is usually 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. When it is in this range, the processability and strength characteristics of the acrylic rubber are highly balanced, and the change in physical properties during storage can be alleviated, which is suitable.

[0091] The molecular weights (Mn, Mw, Mz) and molecular weight distribution (Mw / Mn, Mz / Mw) of the acrylic rubber constituting the acrylic rubber bale of the present invention are not particularly limited, but when they are the absolute molecular weights (Mn, Mw, Mz) and absolute molecular weight distribution (Mw / Mn, Mz / Mw) by the GPC-MALS method, each characteristic can be accurately determined and is suitable.

[0092] The measurement solvent of the GPC-MALS method for measuring the molecular weights (Mn, Mw, Mz) and molecular weight distribution (Mw / Mn, Mz / Mw) of the acrylic rubber constituting the acrylic rubber bale of the present invention is not particularly limited as long as the acrylic rubber bale of the present invention can be dissolved and measured, but a dimethylformamide-based solvent is preferred. As the dimethylformamide-based solvent to be used, there is no particular limitation as long as it is mainly composed of dimethylformamide, but 100% dimethylformamide or a polar substance can be added to dimethylformamide for use. The proportion of dimethylformamide in the dimethylformamide-based solvent is 90% by weight or more, preferably 95% by weight or more, more preferably 97% by weight or more. The compound added to dimethylformamide is not particularly limited, but in the present invention, in particular, a solution in which lithium chloride is added to dimethylformamide at a concentration of 0.05 mol / L and 37% concentrated hydrochloric acid is added at a concentration of 0.01% is preferred.

[0093] When the gel amount of the methyl ethyl ketone-insoluble matter of the acrylic rubber of the present invention 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, the processability during kneading such as in a Banbury mixer is highly improved and is suitable.

[0094] The pH of the acrylic rubber of the present invention is not particularly limited and may be appropriately selected according to the purpose of use. Usually, when it 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, the storage stability of the acrylic rubber is highly improved and is suitable.

[0095] 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, still 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 it is within this range, the water resistance, strength characteristics, and processability as an acrylic rubber are highly balanced and suitable.

[0096] There is no particular limitation on the lower limit value of the ash content of the acrylic rubber of the present invention, and it may be appropriately selected according to the intended use. Usually, it is 0.0001% by weight or more, preferably 0.0005% by weight or more, more preferably 0.001% by weight or more, still 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. When it is in this range, the metal adhesion of the rubber is reduced and the workability is excellent, which is suitable.

[0097] When the ash content of the acrylic rubber of the present invention is highly balanced in terms of water resistance, strength characteristics, processability, and workability, it is usually 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, still 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.

[0098] When the total amount of sodium, magnesium, calcium, phosphorus, and sulfur in the ash of the acrylic rubber of the present invention is 50% by weight or more, preferably 60% 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, the water resistance of the acrylic rubber is highly improved, the metal adhesion is reduced, and the workability is excellent, which is suitable.

[0099] The total amount of magnesium and phosphorus in the ash of the acrylic rubber of the present invention may be appropriately selected according to the intended use without any particular limitation, but is usually 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. When it is in this range, the water resistance, strength characteristics, and processability of the acrylic rubber are highly balanced, and the metal adhesion is reduced, making it excellent in workability and suitable.

[0100] The amount of magnesium in the ash of the acrylic rubber of the present invention may be appropriately selected according to the intended use without any particular limitation, but is usually 10% by weight or more, preferably 15 to 60% by weight, more preferably 20 to 50% by weight, particularly preferably 25 to 45% by weight, and most preferably in the range of 30 to 40% by weight.

[0101] The amount of phosphorus in the ash of the acrylic rubber of the present invention may be appropriately selected according to the intended use without any particular limitation, but is usually 10% by weight or more, preferably 20 to 90% by weight, more preferably 30 to 80% by weight, particularly preferably 40 to 70% by weight, and most preferably in the range of 50 to 60% by weight.

[0102] The ratio ([Mg] / [P]) of magnesium to phosphorus in the ash of the acrylic rubber of the present invention may be appropriately selected according to the intended use without any particular limitation, but in terms of weight ratio, it is usually 0.4 to 2.5, 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. When it is in this range, the water resistance, strength characteristics, and processability of the acrylic rubber are highly balanced and suitable.

[0103] Here, the ash in the acrylic rubber mainly comes from the emulsifier used when emulsifying the monomer components for emulsion polymerization and the coagulant used when coagulating the emulsion polymerization liquid. However, the total ash content and the contents of magnesium and phosphorus in the ash vary not only depending on the conditions of the emulsion polymerization process and the coagulation process but also on the various conditions of each subsequent process.

[0104] The specific gravity of the acrylic rubber of the present invention is not particularly limited, but when it is usually 0.7 or more, preferably 0.8 or more, more preferably 0.9 or more, particularly preferably 0.95 or more, and most preferably 1 or more, it hardly contains air and has excellent storage stability and is suitable. The specific gravity of the acrylic rubber of the present invention is also usually 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, when productivity, storage stability, crosslinking property stability of the crosslinked product, etc. are highly balanced and suitable.

[0105] The glass transition temperature (Tg) of the acrylic rubber of the present invention may be appropriately selected according to the purpose of use of the acrylic rubber, but when it is usually 20°C or lower, preferably 10°C or lower, more preferably 0°C or lower, it is excellent in processability and cold resistance and is suitable. The lower limit value of the glass transition temperature (Tg) of the acrylic rubber is not particularly limited, but it is usually -80°C or higher, preferably -60°C or higher, more preferably -40°C or higher. By setting the glass transition temperature above the lower limit, the oil resistance and heat resistance can be made more excellent, and by setting it below the above upper limit, the processability, crosslinkability and cold resistance can be made more excellent.

[0106] The complex viscosity ([η]60°C) of the acrylic rubber of the present invention has no particular limitation and may be appropriately selected according to the purpose of use, but when it is usually 15,000 [Pa·s] or lower, 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], it is excellent in processability, oil resistance and shape retention and is suitable.

[0107] The complex viscosity ([η]100°C) of the acrylic rubber of the present invention at 100°C may be appropriately selected according to the purpose of use without particular limitation, but is usually 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]. When it is in this range, it is excellent in processability, oil resistance, and shape retention and is suitable.

[0108] The ratio ([η]100°C / [η]60°C) of the complex viscosity ([η]100°C) of the acrylic rubber of the present invention at 100°C to the complex viscosity ([η]60°C) at 60°C may be appropriately selected according to the purpose of use without particular limitation, but is usually 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, particularly preferably 0.8 or more, and most preferably 0.83 or more. The ratio ([η]100°C / [η]60°C) of the complex viscosity ([η]100°C) of the acrylic rubber of the present invention at 100°C to the complex viscosity ([η]60°C) at 60°C is also usually 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. When it is in this range, the processability, oil resistance, and shape retention are highly balanced and suitable.

[0109] The water content of the acrylic rubber of the present invention may be appropriately selected according to the purpose of use without particular limitation, but when it is usually less than 1% by weight, preferably 0.8% by weight or less, more preferably 0.6% by weight or less, the vulcanization characteristics of the acrylic rubber are optimized and characteristics such as heat resistance and strand-like water resistance are highly improved and suitable.

[0110] The Mooney viscosity (ML1+4,100°C) of the acrylic rubber of the present invention may be appropriately selected according to the purpose of use without particular limitation, but when it is usually in the range of 10 to 150, preferably 20 to 100, more preferably 25 to 70, the processability and strength characteristics of the acrylic rubber are highly balanced and suitable.

[0111] The shape of the acrylic rubber of the present invention is not particularly limited and may be appropriately selected according to the intended use. For example, it may be in the form of powder, crumb, strand, sheet, veil, etc. However, when it is preferably in the form of a sheet or a veil, it is excellent in workability and storage stability and is suitable.

[0112] When the acrylic rubber of the present invention is in the form of a sheet, its thickness is not particularly limited and may be appropriately selected according to the intended use. However, when it is usually 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, workability, storage stability and productivity are highly balanced and it is suitable. The width of the sheet-shaped acrylic rubber of the present invention is appropriately selected according to the intended use. However, when it is usually in the range of 300 to 1200 mm, preferably 400 to 1000 mm, and more preferably 500 to 800 mm, it is particularly excellent in handleability and is suitable. The length of the sheet-shaped acrylic rubber of the present invention is not particularly limited, but when it is usually in the range of 300 to 1200 mm, preferably 400 to 1000 mm, and more preferably 500 to 800 mm, it is particularly excellent in handleability and is suitable.

[0113] When the acrylic rubber of the present invention is in the form of a veil, its size is not particularly limited and may be appropriately selected according to the intended use. However, the width is usually in the range of 100 to 800 mm, preferably 200 to 500 mm, and more preferably 250 to 450 mm, the length is usually in the range of 300 to 1,200 mm, preferably 400 to 1,000 mm, and more preferably 500 to 800 mm, and the height (thickness) is usually in the range of 50 to 500 mm, preferably 100 to 300 mm, and more preferably 150 to 250 mm, which is appropriate. Also, the shape of the veil-shaped acrylic rubber of the present invention is not limited and is appropriately selected according to the intended use of the acrylic rubber veil. However, in many cases, a rectangular parallelepiped is suitable.

[0114] <Manufacturing method of acrylic rubber> The method for producing the above acrylic rubber is not particularly limited. For example, after emulsifying an acrylic rubber monomer component containing a reactive group-containing monomer with water and an emulsifier, polymerization is initiated in the presence of a redox catalyst composed of a radical generator and a reducing agent to obtain an emulsion polymerization liquid in an emulsion polymerization step, The obtained emulsion polymerization liquid is added to a coagulating liquid with a coagulant concentration of 1% by weight or more while stirring to cause coagulation to produce a water-containing crumb, in a coagulation step, A washing step of washing the produced water-containing crumb with warm water, A dehydration step of dehydrating the washed water-containing crumb to a water content of 1 to 40% by weight, A drying step of drying the dehydrated water-containing crumb to less than 1% by weight, It can be easily produced by a method for producing an acrylic rubber including

[0115] The acrylic rubber monomer component containing a reactive group-containing monomer used in the present invention is the same as the exemplified and preferred ranges of the monomer components described above. Regarding the usage amount of the monomer component, it is also as described above. In emulsion polymerization, each monomer may be appropriately selected so that the acrylic rubber of the present invention has the above composition.

[0116] (Emulsifier) The emulsifier used in the present invention is not particularly limited. For example, anionic emulsifiers, cationic emulsifiers, nonionic emulsifiers, etc. can be mentioned, and preferably an anionic emulsifier.

[0117] There is no particular limitation on the anionic emulsifier. For example, salts of fatty acids such as myristic acid, palmitic acid, oleic acid, linolenic acid; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; sulfate esters such as sodium lauryl sulfate, phosphate esters such as polyoxyalkylene alkyl ether phosphate ester salts; alkyl sulfosuccinates, etc. can be mentioned. Among these anionic emulsifiers, phosphate ester salts and sulfate ester salts are preferred, phosphate ester salts are particularly preferred, and divalent phosphate ester salts are most preferred.

[0118] The divalent phosphate salts are not particularly limited as long as they can be used as emulsifiers in the emulsion polymerization reaction, and examples thereof include alkyloxy polyoxyalkylene phosphate salts and alkylphenyloxy polyoxyalkylene phosphate salts. Among these, their metal salts are preferred, their alkali metal salts are more preferred, and their sodium salts are most preferred.

[0119] Examples of the alkyloxy polyoxyalkylene phosphate salts include alkyloxy polyoxyethylene phosphate salts and alkyloxy polyoxypropylene phosphate salts. Among these, alkyloxy polyoxyethylene phosphate salts are preferred.

[0120] Specific examples of the alkyl polyoxyethylene phosphate ester salts include metal salts such as octyloxy diethylene phosphate, octyloxy triethylene phosphate, octyloxy tetraethylene phosphate, decyloxy tetraethylene phosphate, dodecyloxy tetraethylene phosphate, tridecyloxy tetraethylene phosphate, tetradecyloxy tetraethylene phosphate, hexadecyloxy tetraethylene phosphate, octadecyloxy tetraethylene phosphate, octyloxy pentaethylene phosphate, decyloxy pentaethylene phosphate, dodecyloxy pentaethylene phosphate, tridecyloxy pentaethylene phosphate, tetradecyloxy pentaethylene phosphate, hexadecyloxy pentaethylene phosphate, octadecyloxy pentaethylene phosphate, octyloxy hexaethylene phosphate, decyloxy hexaethylene phosphate, dodecyloxy hexaethylene phosphate, tridecyloxy hexaethylene phosphate, tetradecyloxy hexaethylene phosphate, hexadecyloxy hexaethylene phosphate, octadecyloxy hexaethylene phosphate, octyloxy octaethylene phosphate, decyloxy octaethylene phosphate, dodecyloxy octaethylene phosphate, tridecyloxy octaethylene phosphate, tetradecyloxy octaethylene phosphate, hexadecyloxy octaethylene phosphate, and octadecyloxy octaethylene phosphate. Among these, their alkali metal salts, especially sodium salts, are preferred.

[0121] Specific examples of the 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, octadecyloxypentaoxypropylene phosphate, 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 these, their alkali metal salts, particularly sodium salts, are preferred.

[0122] Specific examples of the alkylphenyloxy polyoxyalkylene phosphate ester salts include alkylphenyloxy polyoxyethylene phosphate ester salts, alkylphenyloxy polyoxypropylene phosphate ester salts, etc. Among these, alkylphenyloxy polyoxyethylene phosphate ester salts are preferred.

[0123] Specific examples of the alkylphenyloxy polyoxyethylene phosphate ester salts include metal salts such as methyloxypolyoxyethylene phosphate ester, ethylphenyloxypolyoxyethylene phosphate ester, butylphenyloxypolyoxyethylene phosphate ester, hexylphenyloxypolyoxyethylene phosphate ester, nonylphenyloxypolyoxyethylene phosphate ester, dodecylphenyloxypolyoxyethylene phosphate ester, octadecylphenyloxypolyoxyethylene phosphate ester, methylphenyloxypentaoxyethylene phosphate ester, ethylphenyloxypentaoxyethylene phosphate ester, butylphenyloxypentaoxyethylene phosphate ester, hexylphenyloxypentaoxyethylene phosphate ester, nonylphenyloxypentaoxyethylene phosphate ester, dodecylphenyloxypentaoxyethylene phosphate ester, 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, dodecylphenyloxyoctaoxyethylene phosphate ester. Among these, their alkali metal salts, particularly sodium salts, are preferred.

[0124] Specific examples of the alkylphenyl polyoxypropylene phosphate ester salts include metal salts such as methylphenyltetraoxypropylene phosphate ester, ethylphenyltetraoxypropylene phosphate ester, butylphenyltetraoxypropylene phosphate ester, hexylphenyltetraoxypropylene phosphate ester, nonylphenyltetraoxypropylene phosphate ester, dodecylphenyltetraoxypropylene phosphate ester, methylphenylpentaoxypropylene phosphate ester, ethylphenylpentaoxypropylene phosphate ester, butylphenylpentaoxypropylene phosphate ester, hexylphenylpentaoxypropylene phosphate ester, nonylphenylpentaoxypropylene phosphate ester, dodecylphenylpentaoxypropylene phosphate ester, methylphenylhexaoxypropylene phosphate ester, ethylphenylhexaoxypropylene phosphate ester, butylphenylhexaoxypropylene phosphate ester, hexylphenylhexaoxypropylene phosphate ester, nonylphenylhexaoxypropylene phosphate ester, dodecylphenylhexaoxypropylene phosphate ester, methylphenyloctaoxypropylene phosphate ester, ethylphenyloctaoxypropylene phosphate ester, butylphenyloctaoxypropylene phosphate ester, hexylphenyloctaoxyethylene phosphate ester, nonylphenyloctaoxypropylene phosphate ester, dodecylphenyloctaoxypropylene phosphate ester, etc. Among these, their alkali metal salts, especially sodium salts, are preferred.

[0125] As the phosphate ester salts, monovalent phosphate ester salts such as sodium di(alkyloxypolyoxyalkylene) phosphate ester can be used alone or in combination with divalent phosphate ester salts. Examples of the sulfate salt include sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, sodium myristyl sulfate, sodium polyoxyethylene alkyl sulfate, sodium polyoxyethylene alkylaryl sulfate, etc., and sodium lauryl sulfate is preferred.

[0126] Examples of the cationic emulsifier include alkyltrimethylammonium chloride, dialkylammonium chloride, benzylammonium chloride, etc.

[0127] Examples of the nonionic emulsifier 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; polyoxyethylene sorbitan alkyl esters, etc. Polyoxyalkylene alkyl ethers and polyoxyalkylene alkylphenol ethers are preferred, and polyoxyethylene alkyl ethers and polyoxyethylene alkylphenol ethers are more preferred.

[0128] These emulsifiers can be used alone or in combination of two or more. The usage amount is usually in the range of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of the monomer component.

[0129] The mixing method (mixing mode) of the monomer component, water, and emulsifier may follow a conventional method. For example, a method of stirring the monomer, emulsifier, and water using a stirrer such as a homogenizer or a disk turbine can be mentioned. The usage amount of water 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, based on 100 parts by weight of the monomer component.

[0130] (Radical initiator) As the polymerization catalyst used in the present invention, a redox catalyst composed of a radical generator and a reducing agent is used. There is no particular limitation on the radical generator, and an organic radical generator, an inorganic radical generator, etc. are selected according to the purpose of use. In particular, by using an inorganic radical generator, the processability in rolls of acrylic rubber produced can be highly improved, which is preferable.

[0131] There is no particular limitation on the organic radical generator as long as it is usually used in emulsion polymerization. For example, organic peroxides, azo compounds, etc. can be mentioned.

[0132] As the organic peroxide, there is no particular limitation as long as it is a known one used in emulsion polymerization. For example, 2,2 - bis(4,4 - di - (t - butylperoxy)cyclohexyl)propane, 1,1 - di - (t - hexylperoxy)cyclohexane, 1,1 - di - (t - butylperoxy)cyclohexane, n - butyl 4,4 - di - (t - butylperoxy)valerate, 2,2 - di - (t - butylperoxy)butane, t - butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramethane hydroperoxide, benzoyl peroxide, 1,1,3,3 - tetraethylbutyl hydroperoxide, t - butyl cumyl peroxide, di - t - butyl peroxide, di - t - hexyl peroxide, di(2 - t - butylperoxyisopropyl)benzene, dicumyl peroxide, diisobutyryl peroxide, di(3,5,5 - trimethylhexanoyl)peroxide, dilauroyl peroxide, disuccinic peroxide, dibenzoyl peroxide, di(3 - methylbenzoyl)peroxide, benzoyl(3 - methylbenzoyl)peroxide, diisobutyryl peroxydicarbonate, di - n - propyl peroxydicarbonate, di(2 - ethylhexyl)peroxydicarbonate, di - sec - butyl peroxydicarbonate, 1,1,3,3 - tetramethylbutyl peroxyneodecanoate, t - hexyl peroxypivalate, t - butyl peroxyneodecanoate, t - hexyl peroxypivalate, t - butyl peroxypivalate, 2,5 - dimethyl - 2,5 - bis(2 - ethylhexanoylperoxy)hexane, 1,1,3,3 - tetramethylbutyl peroxy - 2 - ethylhexanoate, t - hexyl peroxy - 2 - ethylhexanoate, t - butyl peroxy - 3,5,5 - trimethylhexanoate, t - hexyl peroxyisopropyl monocarbonate, t - butyl peroxyisopropyl monocarbonate, t - butyl peroxy - 2 - ethylhexyl monocarbonate, 2,5 - dimethyl - 2,5 - bis(benzoylperoxy)hexane, t - butyl peroxyacetate, t - hexyl peroxybenzoate, t - butyl peroxybenzoate, 2,5 - dimethyl - 2,Examples include 5 - di(t - butylperoxy)hexane, and among these, diisopropylbenzene hydroperoxide, cumene hydroperoxide, paramethane hydroperoxide, benzoyl peroxide, etc. are preferred.,

[0133] Examples of azo compounds include azobisisobutyronitrile, 4,4'-azobis(4 - cyanovaleric acid), 2,2'-azobis[2-(2 - imidazolin - 2 - yl)propane, 2,2'-azobis(propane - 2 - carboxamidine), 2,2'-azobis[N-(2 - carboxyethyl)-2 - methylpropanamide], 2,2'-azobis{2-[1-(2 - hydroxyethyl)-2 - imidazolin - 2 - yl]propane}, 2,2'-azobis(1 - imino - 1 - pyrrolidin - 2 - methylpropane), and 2,2'-azobis{2 - methyl - N-[1,1 - bis(hydroxymethyl)-2 - hydroxyethyl]propanamide}, etc.

[0134] There is no particular limitation on the inorganic radical generator as long as it is commonly used in emulsion polymerization. Examples include persulfates such as sodium persulfate, potassium persulfate, ammonium persulfate, and hydrogen peroxide. Among these, persulfates are preferred, potassium persulfate and ammonium persulfate are more preferred, and potassium persulfate is particularly preferred.

[0135] These radical generators can be used alone or in combination of two or more. The amount used is usually 0.0001 - 5 parts by weight, preferably 0.0005 - 1 part by weight, more preferably 0.001 - 0.25 part by weight, particularly preferably 0.01 - 0.21 part by weight, and most preferably 0.1 - 0.2 part by weight, based on 100 parts by weight of the monomer component.

[0136] (Reducing agent) There is no particular limitation on the reducing agent used in the present invention as long as it is commonly used in emulsion polymerization. Preferably, at least two reducing agents are used, and a combination of a metal ion compound in a reduced state and other reducing agents is preferred.

[0137] Although the metal ion compound in a reduced state is not particularly limited, examples thereof include ferrous sulfate, sodium iron(III) hexamethylenediaminetetraacetate, cuprous naphthenate, etc. Among these, ferrous sulfate is preferable. These metal ion compounds in a reduced state can be used alone or in combination of two or more thereof. 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, more preferably 0.00005 to 0.0005 parts by weight with respect to 100 parts by weight of the monomer component.

[0138] Although the reducing agent other than those metal ion compounds in a reduced state is not particularly limited, examples thereof include 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 such as sodium sulfite, potassium sulfite, sodium bisulfite, sodium aldehyde bisulfite, potassium bisulfite; pyrosulfites such as sodium pyrosulfite, potassium pyrosulfite, sodium bisulfite pyrosulfite, potassium bisulfite pyrosulfite; thiosulfates such as sodium thiosulfate, potassium thiosulfate; phosphorous acid or its salts such as phosphorous acid, sodium phosphite, potassium phosphite, disodium hydrogen phosphite, dipotassium hydrogen phosphite; pyrophosphorous acid or its salts such as pyrophosphorous acid, sodium pyrophosphite, potassium pyrophosphite, disodium hydrogen pyrophosphite, dipotassium hydrogen pyrophosphite; sodium formaldehyde sulfoxylate, etc. Among these, ascorbic acid or its salts, sodium formaldehyde sulfoxylate, etc. are preferable, and ascorbic acid or its salts are particularly preferable.

[0139] Reducing agents other than these metal ion compounds in a reduced state can be used alone or in combination of two or more thereof, and the amount used is usually in the range of 0.001 to 1 part by weight, preferably 0.005 to 0.5 part by weight, more preferably 0.01 to 0.1 part by weight, based on 100 parts by weight of the monomer component.

[0140] A preferred combination of the metal ion compound in a reduced state and other reducing agents is a combination of ferrous sulfate and ascorbic acid or its salt and / or sodium formaldehyde sulfoxylate, more preferably a combination of ferrous sulfate and ascorbate and / or sodium formaldehyde sulfoxylate, and most preferably a combination of ferrous sulfate and ascorbate. At this time, the amount of ferrous sulfate used is usually in the range of 0.000001 to 0.01 part by weight, preferably 0.00001 to 0.001 part by weight, more preferably 0.00005 to 0.0005 part by weight, based on 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 part by weight, more preferably 0.01 to 0.1 part by weight, based on 100 parts by weight of both components.

[0141] The amount of water used in the emulsion polymerization reaction may be only the amount used at the time of emulsifying the monomer component, but is adjusted to be usually 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, based on 100 parts by weight of the monomer component used for polymerization.

[0142] The method of the emulsion polymerization reaction may follow a conventional method, and any of a batch method, a semi-batch method, and a continuous method may be used. The polymerization temperature and the polymerization time are not particularly limited and can be appropriately selected from the type of polymerization initiator used, etc. The polymerization time is usually 0.5 to 100 hours, preferably 1 to 10 hours.

[0143] The emulsion polymerization reaction is an exothermic reaction. If not controlled, the temperature will rise and the polymerization reaction can be shortened. However, in the present invention, it is preferable to control the emulsion polymerization reaction temperature to usually 35°C or lower, preferably 0 to 35°C, more preferably 5 to 30°C, and particularly preferably 10 to 25°C. This is because the strength characteristics of the acrylic rubber to be produced and the processability during kneading such as in a Banbury mixer are highly balanced and suitable.

[0144] (Post-addition of chain transfer agent) In the present invention, it is characterized in that the chain transfer agent is not added initially but is added batchwise during the polymerization. By doing so, an acrylic rubber in which high molecular weight components and low molecular weight components are separated can be produced, and the strength characteristics of the acrylic rubber to be produced and the processability during kneading such as on a roll are highly balanced and suitable.

[0145] The chain transfer agent to be used is not particularly limited as long as it is commonly used in emulsion polymerization. For example, mercaptan compounds can be preferably used. As the mercaptan compound, an alkyl mercaptan compound having 2 to 20 carbon atoms, preferably an alkyl mercaptan compound having 5 to 15 carbon atoms, and more preferably an alkyl mercaptan compound having 6 to 14 carbon atoms can be used.

[0146] As the alkyl mercaptan compound, any of n-alkyl mercaptan compounds, sec-alkyl mercaptan compounds, and t-alkyl mercaptan compounds may be used. However, preferably n-alkyl mercaptan compounds and t-alkyl mercaptan compounds, and more preferably n-alkyl mercaptan compounds. When it is an n-alkyl mercaptan compound, the effect of the chain transfer agent can be stably exerted, and the processability of the acrylic rubber to be produced such as on a roll can be highly improved, which is suitable.

[0147] Specific examples of the alkyl mercaptan compound 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, 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, etc. Preferably, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, more preferably n-octyl mercaptan, n-dodecyl mercaptan.

[0148] These chain transfer agents can be used alone or in combination of two or more. The amount of the chain transfer agent used is not particularly limited, but is usually 0.0001 to 1 part by weight, preferably 0.0005 to 0.5 part by weight, more preferably 0.001 to 0.5 part by weight, particularly preferably 0.005 to 0.1 part by weight, most preferably 0.01 to 0.06 part by weight, based on 100 parts by weight of the monomer component. When in this range, the strength characteristics and roll processability of the acrylic rubber produced are highly balanced and suitable.

[0149] In the present invention, it is characterized in that the above chain transfer agent is not added at the initial stage of polymerization but is added batchwise during the polymerization process, and the high molecular weight component and low molecular weight component of the acrylic rubber produced are produced and the molecular weight distribution is within a specific range, so that the strength characteristics and processability such as roll can be highly balanced and suitable.

[0150] The number of batchwise post-additions of the chain transfer agent is not particularly limited and is appropriately selected according to the purpose of use. Usually, it is 1 to 5 times, preferably 2 to 4 times, more preferably 2 to 3 times, and particularly preferably 2 times. When it is 2 times, the strength characteristics of the acrylic rubber produced and the processability such as roll can be highly balanced, which is suitable.

[0151] The timing of batchwise post-addition of the chain transfer agent is not particularly limited and is appropriately selected according to the purpose of use. However, it is usually after 20 minutes from the start of polymerization, preferably after 30 minutes from 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. When it is within this range, the strength characteristics of the acrylic rubber produced and the processability such as roll can be highly balanced, which is suitable.

[0152] The amount of a single batchwise addition of the chain transfer agent is not particularly limited and is appropriately selected according to the purpose of use. However, with respect to 100 parts by weight of the monomer component, it is usually 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. When it is within this range, the strength characteristics of the acrylic rubber produced and the roll processability can be highly balanced, which is suitable.

[0153] After the addition of the chain transfer agent, there is no particular limitation, but usually, the polymerization reaction can be continued for 30 minutes or more, preferably 45 minutes or more, more preferably 1 hour or more and then terminated.

[0154] (Post-addition of reducing agent) In the present invention, the reducing agent of the redox catalyst can be post-added during the polymerization, and by doing so, the strength characteristics of the acrylic rubber produced and the processability such as roll can be highly balanced, which is suitable.

[0155] As the reducing agent to be added later during the polymerization, the exemplified and preferred ranges of the above-mentioned reducing agents are the same. In the present invention, as the reducing agent to be added later, ascorbic acid or its salt is preferable.

[0156] The amount of the reducing agent to be added later during the polymerization is not particularly limited and may be appropriately selected according to the purpose of use. However, based on 100 parts by weight of the monomer component, it is usually 0.0001 to 1 part by weight, preferably 0.0005 to 0.5 part by weight, more preferably 0.001 to 0.5 part by weight, particularly preferably 0.005 to 0.1 part by weight, and most preferably 0.01 to 0.05 part by weight. When in this range, it is excellent in the productivity of acrylic rubber production and can highly balance the strength characteristics and processability of the produced acrylic rubber, which is preferable.

[0157] The reducing agent to be added later during the polymerization may be either continuous or batchwise, but preferably batchwise. The number of times of batchwise addition of the reducing agent during the polymerization is not particularly limited, but is usually 1 to 5 times, preferably 1 to 3 times, and more preferably 1 to 2 times.

[0158] When the reducing agent added initially and the reducing agent added later during the polymerization are ascorbic acid or its salt, the ratio of the amount of ascorbic acid or its salt added initially to the amount of ascorbic acid or its salt added later is not particularly limited. However, in terms of the weight ratio of "ascorbic acid or its salt added initially" / "ascorbic acid or its salt added batchwise later", when it is usually 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 excellent in the productivity of acrylic rubber production and can highly balance the strength characteristics and processability of the produced acrylic rubber, which is preferable.

[0159] The timing of adding the reducing agent later is not particularly limited and may be appropriately selected according to the purpose of use. However, usually after 1 hour from the start of polymerization, preferably within the range of 1 to 3 hours after the start of polymerization, and more preferably 1.5 to 2.5 hours. When in this range, it is excellent in the productivity of acrylic rubber production and can highly balance the strength characteristics of the produced acrylic rubber and the processability such as rolling, which is preferable.

[0160] The batch addition amount of the reducing agent is not particularly limited and is appropriately selected according to the intended use. However, it is usually 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 with respect to 100 parts by weight of the monomer component. When it is in this range, the strength characteristics of the acrylic rubber produced and the processability such as rolls can be highly balanced, which is preferable.

[0161] After adding the reducing agent, there is no particular limitation, but usually the polymerization reaction can be continued for 30 minutes or more, preferably 45 minutes or more, more preferably 1 hour or more and then terminated.

[0162] The polymerization conversion rate of the emulsion polymerization reaction is not particularly limited, but is usually 90% by weight or more, preferably 95% by weight or more. At this time, the acrylic rubber produced is excellent in strength characteristics and has no monomer odor, which is preferable. When terminating the polymerization, a polymerization terminator may be used.

[0163] (Coagulation step) The coagulation method after emulsion polymerization is characterized in that the emulsion polymerization liquid obtained by the above emulsion polymerization is added to a coagulation liquid with a coagulant concentration of 1% by weight or more while stirring to cause coagulation to produce a water-containing crumb.

[0164] The solid content concentration of the emulsion polymerization liquid used in the coagulation reaction is not particularly limited, but is usually adjusted to the range of 5 to 50% by weight, preferably 10 to 45% by weight, more preferably 20 to 40% by weight.

[0165] The coagulant used for the coagulation liquid is not particularly limited, but usually a metal salt is used. Examples of the metal salt include alkali metals, Group 2 metal salts of the periodic table, and other metal salts. Preferably, they are alkali metal salts and Group 2 metal salts of the periodic table. More preferably, they are Group 2 metal salts of the periodic table, and particularly preferably magnesium salts.

[0166] Examples of the 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; 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.

[0167] Examples of the Group 2 metal salts of the periodic table include magnesium chloride, calcium chloride, magnesium nitrate, calcium nitrate, magnesium sulfate, and calcium sulfate. Calcium chloride and magnesium sulfate are preferred.

[0168] Examples of the other metal salts include 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.

[0169] These coagulants can be used alone or in combination of two or more. The amount used is usually in the range of 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the monomer component. When the coagulant is within this range, it is suitable because it can make the coagulation of the acrylic rubber sufficient and highly improve the compression set resistance characteristics and water resistance when the acrylic rubber is crosslinked.

[0170] There is no particular limitation on the coagulant concentration of the coagulating liquid used, but 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 coagulating liquid is also preferably 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, because the particle size of the water-containing clam generated can be focused in a specific region and uniformly.

[0171] The temperature of the coagulating liquid is not particularly limited, but when it is usually 40°C or higher, preferably in the range of 40 to 90°C, more preferably 50 to 80°C, a uniform water-containing clam is generated, which is suitable.

[0172] The stirring speed (rotation speed) of the stirred coagulating liquid, that is, the rotation speed of the stirring blade of the stirring device, is not particularly limited, but is usually 100 rpm or higher, preferably 200 rpm or higher, more preferably in the range of 200 to 1000 rpm, particularly preferably 300 to 900 rpm, and most preferably 400 to 800 rpm.

[0173] A rotation speed at which the coagulating liquid is stirred more vigorously to some extent is more suitable for making the particle size of the generated water-containing clam small and uniform. By setting it above the lower limit, it is possible to suppress the generation of clams with excessively large and small particle sizes. By setting it below the upper limit, the control of the coagulation reaction can be made easier.

[0174] The peripheral speed of the stirred coagulating liquid, that is, the speed of the outer periphery of the stirring blade of the stirring device, is not particularly limited, but it is more suitable for making the particle size of the generated water-containing clam small and uniform when it is stirred more vigorously to a certain extent. Usually, it is 0.5 m / s or higher, preferably 1 m / s or higher, more preferably 1.5 m / s or higher, particularly preferably 2 m / s or higher, and most preferably 2.5 m / s or higher. On the other hand, the upper limit value of the peripheral speed is not particularly limited, but when it is usually 50 m / s or lower, preferably 30 m / s or lower, more preferably 25 m / s or lower, and most preferably 20 m / s or lower, it is suitable for facilitating the control of the coagulation reaction.

[0175] By setting the above conditions of the coagulation reaction (such as the addition method, the solid content concentration of the emulsion polymerization liquid, the concentration and temperature of the coagulating liquid, the rotation speed and peripheral speed during the stirring of the coagulating liquid, etc.) within a specific range, the shape and clam diameter of the generated water-containing clam are uniform and aggregated, and the removal of the emulsifier and coagulant during washing and dehydration is significantly improved. As a result, the water resistance and storage stability of the produced acrylic rubber can be highly improved, which is suitable.

[0176] (Washing step) The washing step in the method for producing the acrylic rubber of the present invention is characterized in that the water-containing crumb produced by the above coagulation reaction is washed with warm water.

[0177] The washing method is not particularly limited. For example, the produced water-containing crumb can be mixed with a large amount of warm water for washing.

[0178] The amount of warm water added for washing is not particularly limited. However, when the amount per washing with water 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 still more preferably 500 to 5,000 parts by weight with respect to 100 parts by weight of the monomer component, the ash content in the acrylic rubber can be effectively reduced, which is preferable.

[0179] The temperature of the warm water used is not particularly limited. However, it is usually 40°C or higher, preferably 40 to 100°C, more preferably 50 to 90°C, and particularly 60 to 80°C is optimal because the washing efficiency can be significantly improved. By setting the temperature of the water used to be equal to or higher than the above lower limit, the emulsifier and coagulant are released from the water-containing crumb, and the washing efficiency is further improved.

[0180] The washing time is not particularly limited, but it is usually in the range of 1 to 120 minutes, preferably 2 to 60 minutes, more preferably 3 to 30 minutes.

[0181] The number of times of washing (washing with water) is not particularly limited either. Usually, it is 1 to 10 times, preferably 1 to 5 times, more preferably 2 to 3 times. From the viewpoint of reducing the residual amount of the coagulant in the finally obtained acrylic rubber, it is desirable to have a larger number of water washing times. However, by setting the shape and diameter of the water-containing crumb within a specific range as described above, and / or setting the washing temperature within the above range, the number of water washing times can be significantly reduced.

[0182] (Dehydration step) The dehydration step in the method for producing the acrylic rubber of the present invention is a step of dehydrating the above-washed water-containing crumb.

[0183] As a method for dehydrating the water-containing crumb, there is no particular limitation as long as it is a method capable of squeezing out moisture from the water-containing crumb, and it can usually be carried out using a dehydrator or the like. By this, the ash content of the emulsifier and coagulant inherent in the water-containing crumb that could not be removed in the washing step can be reduced, and the water resistance of the acrylic rubber can be remarkably improved, which is preferable.

[0184] The dehydrator is not particularly limited, and for example, a centrifuge, a squeezer, a screw-type extruder, etc. can be used. In particular, the screw-type extruder is preferable because it can highly reduce the water content of the water-containing crumb. For the sticky acrylic rubber, in a centrifuge or the like, the acrylic rubber adheres to the wall surface and between the slits, and it can only be dehydrated to about 45 to 55% by weight at most. On the other hand, the screw-type extruder has a mechanism for forcibly squeezing out moisture, which is preferable.

[0185] The water content of the water-containing crumb after dehydration is not limited, but it 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 still more preferably 15 to 35% by weight. By setting the water content after dehydration to be not less than the above lower limit, the dehydration time can be shortened and the deterioration of the acrylic rubber can be suppressed. On the other hand, by setting it to be not more than the above upper limit, the ash content can be sufficiently reduced.

[0186] (Drying step) The drying step in the method for producing the acrylic rubber of the present invention is a step of drying the above dehydrated water-containing crumb to less than 1% by weight.

[0187] The method for drying the water-containing clam after dehydration is not particularly limited. For example, the water-containing clam after dehydration can be directly dried by drying or the like, but preferably, it can be carried out using a screw-type twin-screw extrusion dryer. The screw-type twin-screw extrusion dryer to be used is not particularly limited as long as it is an extrusion dryer having two screws. In the present invention, particularly, by drying the water-containing clam under high-shear conditions using a screw-type twin-screw extrusion dryer having two screws, it is possible to highly balance the roll processability, Banbury processability, and strength characteristics of the acrylic rubber, which is preferable.

[0188] The maximum torque of the screw-type twin-screw extrusion dryer used in the present invention is not particularly limited, but there is no particular limitation. Usually, it is 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 extrusion dryer used in the present invention is also usually 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. At this time, it is possible to highly balance the roll processability, Banbury processability, and strength characteristics of the acrylic rubber produced, which is preferable.

[0189] The specific power of the screw-type twin-screw extrusion dryer used in the present invention is not particularly limited, but usually, when it is 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], the roll processability, Banbury processability, and strength characteristics of the acrylic rubber obtained are highly balanced, which is preferable.

[0190] The specific electric power of the screw-type twin-screw extrusion dryer used in the present invention is not particularly limited, but usually, when it is 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 / ], the roll processability, Banbury processability, and strength characteristics of the acrylic rubber obtained are highly balanced, which is preferable.

[0191] Although there is no particular limitation on the shear rate of the screw-type twin-screw extrusion dryer used in the present invention, when it is usually 40 to 150 [1 / s] or more, preferably 45 to 125 [1 / s], more preferably 50 to 100 [1 / s], the storage stability, roll processability, Banbury processability, and strength characteristics of the acrylic rubber obtained are highly balanced and suitable.

[0192] Although there is no particular limitation on the shear viscosity of the acrylic rubber in the screw-type twin-screw extrusion dryer used in the present invention, when it is usually 4000 to 8000 [Pa·s] or less, preferably 4500 to 7500 [Pa·s], more preferably 5000 to 7000 [Pa·s], the storage stability, roll processability, Banbury processability, and strength characteristics of the acrylic rubber obtained are highly balanced and suitable.

[0193] The obtained dried rubber can be baled. The baling of the dried rubber may be carried out according to a conventional method. For example, the dried rubber can be put into a baler and compressed for production. The pressure for compression is appropriately selected according to the purpose of use, but it is usually in the range of 0.1 to 15 MPa, preferably 0.5 to 10 MPa, more preferably 1 to 5 MPa. The compression time is not particularly limited, but it is usually in the range of 1 to 60 seconds, preferably 5 to 30 seconds, more preferably 10 to 20 seconds.

[0194] The acrylic rubber of the present invention thus obtained is excellent in roll processability, strength characteristics, and water resistance and can be used for various applications. The shape of the acrylic rubber of the present invention is not particularly limited and is selected according to the purpose of use. Examples include powder form, crumb form, strand form, sheet form, bale form, etc. Among them, sheet form and bale form are excellent in workability and storage stability and are suitable. (Method for producing sheet-shaped or bale-shaped acrylic rubber)

[0195] The method for producing the sheet-like or veil-like acrylic rubber of the present invention is not particularly limited. After washing, the water-containing clam is dehydrated to a water content of 1 to 40% by weight in a dehydration barrel using a screw-type twin-screw extrusion dryer having a dehydration slit, a drying barrel under reduced pressure, and a die at the tip, and then dried to less than 1% by weight in the drying barrel, and the sheet-like dry rubber is extruded from the die, whereby the sheet-like acrylic rubber can be easily produced. Further, the veil-like acrylic rubber can be easily produced by laminating the extruded sheet-like dry rubber to form a veil.

[0196] In the present invention, it is preferable that the water-containing clam supplied to the screw-type twin-screw extrusion dryer is one from which free water has been removed (drained) after washing.

[0197] Draining step In the present invention, it is preferable to provide a draining step of separating free water from the water-containing clam after washing using a draining machine in order to improve the dehydration efficiency.

[0198] As the draining machine, known ones can be used without particular limitation, and examples thereof include a wire mesh, a screen, an electric sieve machine, etc., and preferably a wire mesh and a screen.

[0199] The mesh size of the draining machine is not particularly limited, but when it is usually in the range of 0.01 to 5 mm, preferably 0.1 to 1 mm, more preferably 0.2 to 0.6 mm, the loss of the water-containing clam is small and draining can be efficiently performed, which is preferable.

[0200] The water content of the water-containing clam after draining, that is, the water content of the water-containing clam input into the dehydration and drying step, is not particularly limited, but is usually in the range of 50 to 80% by weight, preferably 50 to 70% by weight, more preferably 50 to 60% by weight.

[0201] The temperature of the water-containing clam after water drainage, that is, the temperature of the water-containing clam input into the dehydration and drying process, is not particularly limited, but is usually 40°C or higher, preferably 40 to 100°C, more preferably 50 to 90°C, particularly preferably 55 to 85°C, and most preferably 60 to 80°C. When in this range, for a water-containing clam with a specific heat as high as 1.5 to 2.5 KJ / kg·K like the acrylic rubber of the present invention and difficult to increase the temperature, it is suitable to efficiently dehydrate and dry it using a screw-type twin-screw extruder dryer.

[0202] Dehydration of the water-containing clam (dehydration barrel part) The dehydration of the water-containing clam is carried out in a dehydration barrel having a dehydration slit. The opening of the dehydration slit may be appropriately selected according to the use conditions, but when it is usually in the range of 0.01 to 5 mm, preferably 0.1 to 1 mm, more preferably 0.2 to 0.6 mm, it is suitable because there is less loss of the water-containing clam and the dehydration of the water-containing clam can be carried out efficiently.

[0203] The number of dehydration barrels in the screw-type twin-screw extruder dryer is not particularly limited, but when it is usually a plurality, preferably 2 to 10, more preferably 3 to 6, it is suitable for efficiently dehydrating the sticky acrylic rubber.

[0204] There are two ways to remove water from the water-containing clam in the dehydration barrel, one is to remove it in a liquid state (drainage) from the dehydration slit, and the other is to remove it in a vapor state (exhaust steam). In the present invention, drainage is defined as dehydration and exhaust steam is defined as preliminary drying and distinguished.

[0205] In the dehydration of the water-containing crumb, the water discharged from the dehydration slit may be in either a liquid state (drain water) or a vapor state (exhaust vapor). However, when performing dehydration using a screw-type twin-shaft dryer equipped with a plurality of dehydration barrels, it is preferable to combine drain water and exhaust vapor to efficiently dehydrate the adhesive acrylic rubber. The selection of whether to use a drain-type dehydration barrel or an exhaust-vapor-type dehydration barrel in a screw-type twin-screw extrusion dryer equipped with three or more dehydration barrels may be appropriately made according to the purpose of use. Generally, when reducing the ash content in the acrylic rubber produced, more drain-type barrels are used, and when reducing the water content, more exhaust-vapor-type barrels are used.

[0206] The set temperature of the dehydration barrel is appropriately selected according to the monomer composition, ash content, water content, and operating conditions of the acrylic rubber, etc. Usually, it is in the range of 60 to 150°C, preferably 70 to 140°C, more preferably 80 to 130°C. The set temperature of the dehydration barrel for dehydration in a drain state is usually 60 to 120°C, preferably 70 to 110°C, more preferably 80 to 100°C. The set temperature of the dehydration barrel for dehydration in an exhaust-vapor state is usually in the range of 100 to 150°C, preferably 105 to 140°C, more preferably 110 to 130°C.

[0207] There is no particular limitation on the water content after dehydration in the drain-type dehydration for squeezing out water from the water-containing crumb. However, when it is usually 1 to 40% by weight, preferably 5 to 40% by weight, more preferably 5 to 35% by weight, and particularly preferably 10 to 35% by weight, the productivity and the ash removal efficiency are highly balanced and suitable.

[0208] When dehydrating an adhesive acrylic rubber having a reactive group using a centrifuge or the like, the acrylic rubber adheres to the dehydration slit portion and hardly any dehydration can be performed (the water content is about 45 to 55% by weight). However, in the present invention, by using a screw-type twin-screw extrusion dryer having a dehydration slit and being forcibly squeezed by a screw, the water content can be reduced to this extent.

[0209] When dehydrating the water-containing crumb with a drainage-type dehydration barrel and a steam-draining type dehydration barrel, the water content after drainage in the drainage-type dehydration barrel part is usually 5 to 40% by weight, preferably 10 to 40% by weight, more preferably 15 to 35% by weight, and the water content after preliminary drying in the steam-draining type dehydration barrel part is usually 1 to 30% by weight, preferably 3 to 20% by weight, more preferably 5 to 15% by weight.

[0210] By setting the water content after dehydration to be not less than the lower limit, the dehydration time can be shortened and the deterioration of the acrylic rubber can be suppressed. By setting it to be not more than the upper limit, the ash content can be sufficiently reduced.

[0211] Drying of the water-containing crumb (drying barrel part) The drying of the water-containing crumb after the above dehydration is characterized by being carried out in a drying barrel part under reduced pressure. By drying the acrylic rubber under reduced pressure, the drying efficiency of the adhesive acrylic rubber having reactive groups can be increased, and the air inherent in the acrylic rubber can be removed, so that an acrylic rubber having a high specific gravity and excellent storage stability can be produced, which is preferable.

[0212] The degree of reduced pressure of the drying barrel may be appropriately selected, but it is usually 1 to 50 kPa, preferably 2 to 30 kPa, more preferably 3 to 20 kPa, at which time the water-containing crumb can be efficiently dried, which is preferable. By setting the degree of reduced pressure of the drying barrel within this range, the acrylic rubber has excellent drying properties and the air inherent in the dried rubber is removed, resulting in an increase in the specific gravity of the produced acrylic rubber and a remarkable improvement in storage stability, which is preferable.

[0213] The set temperature of the drying barrel may be appropriately selected, but it is usually in the range of 100 to 250 °C, preferably 110 to 200 °C, more preferably 120 to 180 °C, at which time there is no burning or deterioration of the acrylic rubber, drying can be efficiently carried out, and the methyl ethyl ketone-insoluble component (gel amount of methyl ethyl ketone-insoluble matter) in the sheet-like or veiled acrylic rubber can be reduced, which is preferable.

[0214] The number of drying barrels in the screw-type twin-screw extrusion dryer is not particularly limited, but usually there are a plurality of them, preferably 2 to 10, more preferably 3 to 8. When there are a plurality of drying barrels, the degree of vacuum can be approximated for all drying barrels or can be varied. When there are a plurality of drying barrels, the set temperature can be approximated for all drying barrels or can be varied, but it is preferable to make the temperature of the discharge part (the part closer to the die) higher than the temperature of the introduction part (the part closer to the dehydration barrel) in order to increase the drying efficiency.

[0215] The water content of the dried rubber after drying is usually less than 1% by weight, preferably 0.8% by weight or less, more preferably 0.6% by weight or less. In the present invention, in particular, when the water content of the dried rubber in the screw-type twin-screw extrusion dryer is at this value (a state where almost all water has been removed) and melt-extruded, it is suitable for reducing the methyl ethyl ketone-insoluble component of the sheet-like or veil-like acrylic rubber.

[0216] In the present invention, the shear rate at which the above acrylic rubber is substantially water-free in the drying barrel of the screw-type twin-screw extrusion dryer is not particularly limited, but usually, when it is in the range of 10 [1 / s] or more, preferably 10 to 400 [1 / s], more preferably 50 to 250 [1 / s], the storage stability, roll processability, Banbury processability, strength characteristics, and compression set resistance characteristics of the sheet-like or veil-like acrylic rubber obtained are highly balanced and suitable.

[0217] The shear viscosity of the acrylic rubber in the screw-type twin-screw extrusion dryer used in the present invention, particularly in the drying barrel, is not particularly limited, but usually when it is in the range of 12000 [Pa·s] or less, preferably 1000 to 12000 [Pa·s], more preferably 2000 to 10000 [Pa·s], particularly preferably 3000 to 7000 [Pa·s], and most preferably 4000 to 6000 [Pa·s], the storage stability, roll processability, Banbury processability, and strength characteristics of the sheet-like or veil-like acrylic rubber obtained are highly balanced and suitable.

[0218] Dried rubber (die section) The dried rubber dehydrated and dried in the screw sections of the dehydration barrel and the drying barrel is sent to a rectifying die section without a screw. A breaker plate or a wire mesh may or may not be provided between the screw section and the die section.

[0219] The dried rubber to be extruded is preferably in a substantially rectangular die shape and extruded into a sheet shape, so that a dried rubber with less air entrapment, high specific gravity, and excellent storage stability can be obtained.

[0220] The resin pressure in the die section is not particularly limited, but when it is usually in the range of 0.1 to 10 MPa, preferably 0.5 to 5 MPa, more preferably 1 to 3 MPa, the air entrapment of the sheet-shaped or veil-shaped acrylic rubber is small (high specific gravity) and the productivity is excellent, which is suitable.

[0221] Screw-type twin-screw extrusion dryer and operating conditions The screw length (L) of the screw-type twin-screw extrusion dryer used may be appropriately selected according to the purpose of use, but it is usually in the range of 3000 to 15000 mm, preferably 4000 to 10000 mm, more preferably 4500 to 8000 mm.

[0222] The screw diameter (D) of the screw-type twin-screw extrusion dryer used may be appropriately selected according to the purpose of use, but it is usually in the range of 50 to 250 mm, preferably 100 to 200 mm, more preferably 120 to 160 mm.

[0223] The ratio (L / D) of the screw length (L) to the screw diameter (D) of the screw-type twin-screw extrusion dryer used is not particularly limited, but when it is usually in the range of 10 to 100, preferably 20 to 80, more preferably 30 to 60, the water content can be reduced to less than 1% by weight without causing a decrease in the molecular weight or burning of the dried rubber, which is suitable.

[0224] The rotational speed (N) of the screw-type twin-screw extrusion dryer to be used may be appropriately selected according to various conditions, but is usually 10 to 1000 rpm, preferably 50 to 750 rpm, more preferably 100 to 500 rpm, and most preferably 120 to 300 rpm. When it is in this range, the water content and the methyl ethyl ketone insoluble content of the sheet-like or veil-like acrylic rubber can be efficiently reduced, which is suitable.

[0225] The extrusion amount (Q) of the screw-type twin-screw extrusion dryer to be used is not particularly limited, but is usually in the range of 100 to 1,500 kg / hr, preferably 300 to 1200 kg / hr, more preferably 400 to 1000 kg / hr, and most preferably 500 to 800 kg / hr.

[0226] The ratio (Q / N) of the extrusion amount (Q) to the rotational speed (N) of the screw-type twin-screw extrusion dryer to be 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.

[0227] The maximum torque of the screw-type twin-screw extrusion dryer to be used is not particularly limited, but 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 extrusion dryer used in the present invention is also usually in the range of 30 to 100 N·m, preferably 35 to 75 N·m, and more preferably 40 to 60 N·m. When it is in this range, the roll processability, Banbury processability, and strength characteristics of the produced sheet-like or veil-like acrylic rubber can be highly balanced, which is suitable. In the present invention, by using an extrusion dryer having twin screws, dehydration, drying, and molding under high-shear conditions are possible, which is suitable.

[0228] The specific power of the screw-type twin-screw extrusion dryer used is not particularly limited, but usually when it is in the range of 0.1 to 0.25 [kW·h / kg] or more, preferably 0.13 to 0.23 [kW·h / kg], more preferably 0.15 to 0.2 [kW·h / kg], the roll processability, Banbury processability, and strength characteristics of the sheet-like or veil-like acrylic rubber obtained are highly balanced and suitable.

[0229] The specific power of the screw-type twin-screw extrusion dryer used is not particularly limited, but usually when it is in the range of 0.2 to 0.6 [A·h / kg / ] or more, preferably 0.25 to 0.55 [A·h / kg / ], more preferably 0.35 to 0.5 [A·h / kg / ], the roll processability, Banbury processability, and strength characteristics of the sheet-like or veil-like acrylic rubber obtained are highly balanced and suitable.

[0230] The shear rate of the screw-type twin-screw extrusion dryer used is not particularly limited, but usually when it is in the range of 40 to 150 [1 / s] or more, preferably 45 to 125 [1 / s], more preferably 50 to 100 [1 / s], the storage stability, roll processability, Banbury processability, and strength characteristics of the sheet-like or veil-like acrylic rubber obtained are highly balanced and suitable.

[0231] The shear viscosity of the acrylic rubber in the screw-type twin-screw extrusion dryer used is not particularly limited, but usually when it is in the range of 4000 to 8000 [Pa·s] or less, preferably 4500 to 7500 [Pa·s], more preferably 5000 to 7000 [Pa·s], the storage stability, roll processability, Banbury processability, and strength characteristics of the sheet-like or veil-like acrylic rubber obtained are highly balanced and suitable.

[0232] Sheet-like dried rubber The shape of the dried rubber extruded from the screw-type twin-screw extrusion dryer is sheet-like. At this time, air is not entrained and the specific gravity can be increased, and the storage stability is highly improved and suitable. The sheet-like dried rubber extruded from the screw-type twin-screw extrusion dryer is usually cooled and cut and used as sheet-like acrylic rubber.

[0233] The thickness of the sheet-like dried rubber extruded from the screw-type twin-screw extrusion dryer is not particularly limited, but is usually 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, and it is excellent in workability and productivity and suitable. In particular, since the thermal conductivity of the sheet-like dried rubber is as low as 0.15 to 0.35 W / mK, the thickness of the sheet-like dried rubber in the case of improving the cooling efficiency and significantly improving the productivity is usually in the range of 1 to 30 mm, preferably 2 to 25 mm, more preferably 3 to 15 mm, and particularly preferably 4 to 12 mm.

[0234] The width of the sheet-like dried rubber extruded from the screw-type twin-screw extrusion dryer is appropriately selected according to the purpose of use, but is usually in the range of 300 to 1200 mm, preferably 400 to 1000 mm, and more preferably 500 to 800 mm.

[0235] The temperature of the dried rubber extruded from the screw-type twin-screw extrusion dryer 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.

[0236] The water content of the dried rubber extruded from the screw-type twin-screw extrusion dryer 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.

[0237] The complex viscosity ([η]100 °C) of the sheet-like dried rubber extruded from the screw-type twin-screw extrusion dryer at 100 °C is not particularly limited, but is usually 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], and when it is in this range, the extrudability and shape retention as a sheet are highly balanced and suitable. That is, by setting it above the lower limit, the extrudability can be made more excellent, and by setting it below the upper limit, the collapse and breakage of the shape of the sheet-like dried rubber can be suppressed.

[0238] The sheet-like dried rubber extruded from a screw-type two-axis extrusion dryer may be used as it is folded, but usually it can be cut and used.

[0239] There is no particular limitation on the cutting of the sheet-like dried rubber. However, since the acrylic rubber of the present invention has strong adhesiveness, it is preferable to cool the sheet-like dried rubber before cutting it continuously without entraining air.

[0240] There is no particular limitation on the cutting temperature of the sheet-like dried rubber. However, when it is usually 60°C or lower, preferably 55°C or lower, more preferably 50°C or lower, the cuttability and productivity are highly balanced and suitable.

[0241] The complex viscosity ([η]60°C) of the sheet-like dried rubber at 60°C is not particularly limited, but is usually 15,000 [Pa·s] or less, preferably 2000 - 10,000 [Pa·s], more preferably 2500 - 7000 [Pa·s], and most preferably 2700 - 5500 [Pa·s]. When it is in this range, it can be cut continuously without entraining air and is suitable.

[0242] The ratio ([η]100°C / [η]60°C) of the complex viscosity ([η]100°C) of the sheet-like dried rubber at 100°C to the complex viscosity ([η]60°C) at 60°C is not particularly limited and may be appropriately selected according to the purpose of use. However, it is usually 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, particularly preferably 0.8 or more, and most preferably 0.85 or more. The upper limit value is usually 0.98 or less, preferably 0.97 or less, more preferably 0.96 or less, particularly preferably 0.95 or less, and most preferably 0.93 or less. When it is in this range, the air entrainment property is small, and the cutting and productivity are highly balanced and suitable.

[0243] As a method for cooling the sheet-shaped dried rubber, there is no particular limitation, and it may be left at room temperature. However, since the thermal conductivity of the sheet-shaped dried rubber is very low, at 0.15 to 0.35 W / mK, forced cooling such as an air-cooling method under blowing or refrigeration, a watering method of spraying water, or an immersion method of immersing in water is preferable to increase productivity. In particular, the air-cooling method under blowing or refrigeration is suitable.

[0244] In the air-cooling method of the 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 conveyed and cooled while blowing cold air. 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, 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, more preferably 20 to 100 m. The cooling rate of the sheet-shaped dried rubber is not particularly limited, but when it is usually 50°C / hr or more, more preferably 100°C / hr or more, and still more preferably 150°C / hr or more, cutting becomes particularly easy and is suitable.

[0245] The cutting length of the sheet-shaped dried rubber is not particularly limited and is appropriately selected according to the intended use, but is usually in the range of 100 to 800 mm, preferably 200 to 500 mm, more preferably 250 to 450 mm.

[0246] The sheet-shaped acrylic rubber thus obtained is excellent in operability compared to the clam-shaped acrylic rubber, and is also excellent in roll processability, crosslinkability, strength characteristics, and compression set resistance characteristics, as well as storage stability, Banbury processability, and water resistance, and can be used as it is or laminated and veiled. Laminating process The method for producing the veiled acrylic rubber of the present invention is not particularly limited, but it is suitable to laminate the above sheet-shaped acrylic rubber to obtain a veiled acrylic rubber excellent in storage stability with less air entrapment.

[0247] The lamination temperature of the sheet-like acrylic rubber is not particularly limited, but it is preferably 30°C or higher, more preferably 35°C or higher, and even more preferably 40°C or higher, so that air trapped during lamination can be released, which is suitable. The number of laminated sheets may be appropriately selected according to the size or weight of the veil-like acrylic rubber. The veil-like acrylic rubber of the present invention is integrated by the self-weight of the laminated sheet-like acrylic rubber.

[0248] The veil-like acrylic rubber of the present invention thus obtained is excellent in operability compared to the clam-like acrylic rubber, and is also excellent in roll processability, crosslinkability, strength characteristics, and compression set resistance characteristics, as well as storage stability, Banbury processability, and water resistance. The veil-like acrylic rubber can be used as it is, or a necessary amount can be cut and put into a mixer such as a Banbury or a roll for use.

[0249] <Rubber composition> The rubber composition of the present invention is characterized by containing a rubber component containing the acrylic rubber, a filler, and a crosslinking agent.

[0250] As the rubber component that is the main component of the rubber composition of the present invention, the acrylic rubber of the present invention may be used alone, or, if necessary, the acrylic rubber of the present invention and other rubber components may be used in combination. The content of the acrylic rubber of the present invention in the rubber component may be selected according to the purpose of use. For example, it is usually 30% by weight or more, preferably 50% by weight or more, and more preferably 70% by weight or more.

[0251] There are no particular limitations on the other rubber components to be combined with the acrylic rubber of the present invention, and examples thereof include natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, fluororubber, olefin-based elastomer, styrene-based elastomer, vinyl chloride-based elastomer, polyester-based elastomer, polyamide-based elastomer, polyurethane-based elastomer, polysiloxane-based elastomer, and the like.

[0252] These other rubber components can be used individually or in combination of two or more. The shape of these other rubber components can be any of claw shape, strand shape, veil shape, sheet shape, powder shape, etc. The content of the other rubber components in the whole rubber components is appropriately selected within a range not impairing the effects of the present invention. For example, it is usually 70% by weight or less, preferably 50% by weight or less, more preferably 30% by weight or less.

[0253] There is no particular limitation on the filler contained in the rubber composition. For example, reinforcing fillers, non-reinforcing fillers, etc. can be mentioned, and a reinforcing filler is preferred.

[0254] Examples of the reinforcing filler include carbon blacks such as furnace black, acetylene black, thermal black, channel black and graphite; silicas such as wet silica, dry silica, colloidal silica; etc. Examples of the non-reinforcing filler include quartz powder, diatomaceous earth, zinc white, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, aluminum sulfate, calcium sulfate, barium sulfate, etc.

[0255] These fillers can be used individually or in combination of two or more, and the blending amount is appropriately selected within a range not impairing the effects of the present invention. With respect to 100 parts by weight of the rubber component, it is usually in the range of 1 to 200 parts by weight, preferably 10 to 150 parts by weight, more preferably 20 to 100 parts by weight.

[0256] There is no particular limitation on the crosslinking agent used in the rubber composition, and a conventionally known crosslinking agent is selected according to the use purpose. For example, inorganic crosslinking agents such as sulfur compounds and organic crosslinking agents can be mentioned, and an organic crosslinking agent is preferred.

[0257] As the organic crosslinking agent, there is no particular limitation, but an ion-crosslinkable organic compound is preferred, and a polyvalent ion organic compound is particularly preferred. As the "ion" of the ion-crosslinkable or polyvalent ion, there is no particular limitation as long as it can ion-react with the ion-reactive group of the ion-reactive group-containing monomer of the acrylic rubber. Examples include an amine group, an epoxy group, a carboxyl group, a thiol group, etc.

[0258] Specific examples of the polyvalent ion organic compound include a polyvalent amine compound, a polyvalent epoxy compound, a polyvalent carboxylic acid compound, a polyvalent thiol compound, etc. Preferred are a polyvalent amine compound and a polyvalent thiol compound, and more preferred is a polyvalent amine compound.

[0259] Examples of the polyvalent amine compound include aliphatic polyvalent amine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, N,N'-dicyclohexylidene-1,6-hexanediamine; aromatic polyvalent 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, 1,3,5-benzenetriamine; etc. Among these, hexamethylenediamine carbamate, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, etc. are preferred. As the polyvalent amine compound, carbonates thereof can also be suitably used. These polyvalent amine compounds are particularly preferably used in combination with a carboxyl group-containing acrylic rubber or an epoxy group-containing acrylic rubber.

[0260] As the polyvalent thiol compound, a triazine thiol compound is preferably used. For example, 6-trimercapto-s-triazine, 2-anilino-4,6-dimercapto-s-triazine, 1-dibutylamino-3,5-dimercaptotriazine, 2-dibutylamino-4,6-dimercapto-s-triazine, 1-phenylamino-3,5-dimercaptotriazine, 2,4,6-trimercapto-1,3,5-triazine, 1-hexylamino-3,5-dimercaptotriazine and the like can be mentioned. These triazine thiol compounds are particularly preferably used in combination with a chlorine atom-containing acrylic rubber.

[0261] As other polyvalent organic compounds, polyvalent carboxylic acid compounds such as tetradecanedioic acid, metal dithiocarbamates such as zinc dimethyldithiocarbamate and the like can be mentioned. These other polyvalent organic compounds are particularly preferably used in combination with an epoxy group-containing acrylic rubber.

[0262] These crosslinking agents can be used alone or in combination of two or more. The compounding amount is usually 0.001 to 20 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the rubber component. By setting the compounding amount of the crosslinking agent within this range, while making the rubber elasticity sufficient, the mechanical strength of the rubber crosslinked product can be made excellent, which is preferable.

[0263] The rubber composition of the present invention can be compounded with an anti-aging agent as needed. The type of the anti-aging agent is not particularly limited. For example, other phenolic anti-aging agents such as 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, styrenated phenol, 2,2'-methylene-bis(6-α-methyl-benzyl-p-cresol), 4,4'-methylenebis(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-triazin-2-ylamino)phenol; phosphite-based anti-aging agents such as tris(nonylphenyl)phosphite, diphenylisodecylphosphite, tetraphenyldipropylene glycol diphosphite; sulfur ester-based anti-aging agents such as dilauryl thiodipropionate; amine-based anti-aging agents such as phenyl-α-naphthylamine, phenyl-β-naphthylamine, p-(p-toluenesulfonylamide)-diphenylamine, 4,4'-(α,α-dimethylbenzyl)diphenylamine, N,N-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, butyraldehyde-aniline condensate; imidazole-based anti-aging agents such as 2-mercaptobenzimidazole; quinoline-based anti-aging agents such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; hydroquinone-based anti-aging agents such as 2,5-di-(t-amyl)hydroquinone; etc. Among these, amine-based anti-aging agents are particularly preferred.

[0264] These anti-aging agents can be used individually or in combination of two or more. The compounding amount is in the range of 0.01 to 15 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, based on 100 parts by weight of the rubber component.

[0265] The rubber composition of the present invention contains, as essential components, a rubber component containing the acrylic rubber of the present invention, a filler, and a crosslinking agent, and optionally contains an anti-aging agent. Further, 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, foaming agents, etc., can be arbitrarily compounded. These other compounding agents can be used individually or in combination of two or more, and the compounding amount is appropriately selected within a range that does not impair the effects of the present invention.

[0266] Examples of the method for producing the rubber composition of the present invention include a method of mixing a rubber component containing the acrylic rubber of the present invention, a filler, a crosslinking agent, and optionally an anti-aging agent and other compounding agents that can be contained. For mixing, any means used in the conventional rubber processing field, such as an open roll, a Banbury mixer, various kneaders, etc., can be used. The mixing procedure of each component may be carried out according to the normal procedure in the field of rubber processing. For example, after sufficiently mixing the components that are difficult to react or decompose by heat, it is preferable to mix crosslinking agents and the like, which are components that are easy to react or decompose by heat, at a temperature at which reaction or decomposition does not occur for a short time.

[0267] <Rubber crosslinked product> The rubber crosslinked product of the present invention is obtained by crosslinking the above rubber composition.

[0268] The rubber crosslinked product of the present invention can be produced by using the rubber composition of the present invention, performing molding with a molding machine corresponding to a desired shape, such as an extruder, an injection molding machine, a compressor, or a roll, and then performing a crosslinking reaction by heating to fix the shape as a rubber crosslinked product. In this case, crosslinking may be performed after pre-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 minute to 10 hours, preferably 1 minute to 5 hours. As the heating method, a method used for crosslinking rubber, such as press heating, steam heating, oven heating, and hot air heating, may be appropriately selected.

[0269] Depending on the shape, size, etc. of the rubber crosslinked product of the present invention, further heating may be performed to carry out secondary crosslinking. The secondary crosslinking varies depending on the heating method, crosslinking temperature, shape, etc., but is preferably performed for 1 to 48 hours. The heating method and heating temperature may be appropriately selected.

[0270] The rubber crosslinked product of the present invention has excellent compression set resistance characteristics and water resistance while maintaining basic rubber properties such as tensile strength, elongation, and hardness.

[0271] Taking advantage of the above characteristics, the rubber crosslinked product of the present invention is suitably used, for example, as sealing materials such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, wellhead seals, seals for electric and electronic devices, and seals for pneumatic equipment; various gaskets such as rocker cover gaskets mounted at the connecting part between the cylinder block and the cylinder head, oil pan gaskets mounted at the connecting part between the oil pan and the cylinder head or the transmission case, fuel cell separator gaskets mounted between a pair of housings sandwiching a unit cell provided with a positive electrode, an electrolyte plate, and a negative electrode, and top cover gaskets for hard disk drives; cushioning materials, vibration damping materials; wire coating materials; industrial belts; tubes and hoses; sheets; etc.

[0272] The rubber crosslinked product of the present invention is also suitable for use as extrusion molded products and mold crosslinked products used in automotive applications, such as fuel hoses for fuel tanks such as fuel hoses, filler neck hoses, vent hoses, paper hoses, oil hoses, etc., air hoses such as turbo air hoses, transmission control hoses, and various hoses such as radiator hoses, heater hoses, brake hoses, and air conditioner hoses.

[0273] <Apparatus configuration used in the production of acrylic rubber> Next, the apparatus configuration used in the production of acrylic rubber according to an embodiment of the present invention will be described. FIG. 1 is a diagram schematically showing an example of an acrylic rubber production system having an apparatus configuration used in the production of acrylic rubber according to an embodiment of the present invention. For the production of acrylic rubber according to the present invention, for example, the acrylic rubber production system 1 shown in FIG. 1 can be used.

[0274] The acrylic rubber production system 1 shown in FIG. 1 is composed of an emulsion polymerization reactor (not shown), a coagulation device 3, a washing device 4, a draining machine 43, and a screw type twin-screw extrusion dryer.

[0275] The emulsion polymerization reactor is configured to perform the processes related to the above-described emulsion polymerization step. Although not shown in FIG. 1, this emulsion polymerization reactor has, for example, a polymerization reaction tank, a temperature control unit for controlling the reaction temperature, and a stirring device including a motor and stirring blades. In the emulsion polymerization reactor, water and an emulsifier are mixed with the monomer components for forming acrylic rubber, and while appropriately stirring with a stirrer, it is emulsified, and an emulsion polymerization reaction is started in the presence of a redox catalyst composed of an inorganic radical generator and a reducing agent. A chain transfer agent can be added batchwise during the polymerization to obtain an emulsion polymerization liquid. The emulsion polymerization reactor may be any of a batch type, a semi-batch type, and a continuous type, and may be any of a tank type reactor and a tube type reactor.

[0276] 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, a water-containing clam can be produced by bringing the emulsion polymerization liquid obtained in the emulsion polymerization reactor into contact with the coagulation liquid to cause coagulation.

[0277] 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 a water-containing clam.

[0278] 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 controlling the heating operation of the heating unit 31 while monitoring the temperature inside the stirring tank 30 measured by a thermometer. 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, more preferably in the range of 50 - 80°C.

[0279] 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.

[0280] 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 so as to set the rotational speed and rotational velocity 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 such that the stirring speed of the solidifying liquid is, for example, usually 100 rpm or more, preferably 200 to 1000 rpm, more preferably 300 to 900 rpm, and particularly preferably 400 to 800 rpm. The rotation of the stirring blades 33 is controlled by the drive control unit such that the peripheral velocity of the solidifying liquid 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. Further, the rotation of the stirring blades 33 is controlled by the drive control unit such that the upper limit value of the peripheral velocity of the solidifying 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.

[0281] The cleaning device 4 shown in FIG. 1 is configured to perform the processes related to the above-described cleaning step. As schematically illustrated in FIG. 1, the cleaning device 4 includes, for example, a cleaning tank 40, a heating unit 41 that heats the inside of the cleaning tank 40, and a temperature control unit (not shown) that controls the temperature inside the cleaning tank 40. In the cleaning device 4, by mixing the water-containing clam produced by the solidification device 3 with a large amount of water and cleaning it, the ash content in the finally obtained acrylic rubber can be effectively reduced.

[0282] The heating unit 41 of the cleaning device 4 is configured to heat the inside of the cleaning tank 40. Further, the temperature control unit of the cleaning device 4 is configured to control the temperature inside the cleaning tank 40 by monitoring the temperature inside the cleaning tank 40 measured by a thermometer and controlling the heating operation by the heating unit 41. As described above, the temperature of the cleaning water inside the cleaning tank 40 is controlled to be usually 40°C or more, preferably 40 to 100°C, more preferably 50 to 90°C, and most preferably 60 to 80°C.

[0283] The water-containing clam washed by the washing device 4 is supplied to a screw-type twin-screw extrusion dryer 5 that performs a dehydration process and a drying process. At this time, it is preferable that the water-containing clam after washing is supplied to the screw-type twin-screw extrusion dryer 5 through a water draining machine 43 capable of separating free water. For the water draining machine 43, for example, a wire mesh, a screen, an electric sieve machine, etc. can be used.

[0284] Also, when the water-containing clam after washing is supplied to the screw-type twin-screw extrusion dryer 5, the temperature of the water-containing clam is preferably 40°C or higher, and more preferably 60°C or higher. For example, by setting the temperature of the water used for water washing in the washing device 4 to 60°C or higher (for example, 70°C), the temperature of the water-containing clam when supplied to the screw-type twin-screw extrusion dryer 5 can be maintained at 60°C or higher, or it may be heated so that the temperature of the water-containing clam is 40°C or higher, preferably 60°C or higher when being transported from the washing device 4 to the screw-type twin-screw extrusion dryer 5. Thereby, it becomes possible to effectively perform the subsequent dehydration process and drying process, and it becomes possible to significantly reduce the water content rate of the finally obtained dried rubber.

[0285] The screw-type twin-screw extrusion dryer 5 shown in FIG. 1 is configured to perform the processes related to the above-described dehydration process and drying process. Although the screw-type twin-screw extrusion dryer 5 is shown in FIG. 1 as a preferred example, a centrifuge or a squeezer, etc. may be used as a dehydrator that performs the process related to the dehydration process, and a hot air dryer, a vacuum dryer, an expander dryer, a kneader-type dryer, etc. may be used as a dryer that performs the process related to the drying process.

[0286] The screw-type twin-screw extrusion dryer 5 is configured to form the dried rubber obtained through the dehydration process and the drying process into a predetermined shape and discharge it. Specifically, the screw-type twin-screw extrusion dryer 5 includes a dehydration barrel portion 53 having a function as a dehydrator for dehydrating the water-containing clam washed by the washing device 4, a drying barrel portion 54 having a function as a dryer for drying the water-containing clam, and further includes a die 59 having a forming function for forming the water-containing clam on the downstream side of the screw-type twin-screw extrusion dryer 5.

[0287] Hereinafter, with reference to FIG. 2, the configuration of the screw type twin-screw extrusion dryer 5 will be described. FIG. 2 shows the configuration of a specific example suitable as the screw type twin-screw extrusion dryer 5 shown in FIG. 1. With this screw type twin-screw extrusion dryer 5, the above-described dehydration and drying processes can be suitably performed.

[0288] The screw type twin-screw extrusion dryer 5 shown in FIG. 2 is a twin-screw type extrusion dryer provided with a pair of screws (not shown) in a barrel unit 51. The screw type twin-screw extrusion dryer 5 has a drive unit 50 that rotationally drives the pair of screws in the barrel unit 51. With this configuration, high shear can be applied to the acrylic rubber for drying, which is suitable. The drive unit 50 is attached to the upstream end (the left end in FIG. 2) of the barrel unit 51. Further, the screw type twin-screw extrusion dryer 5 has a die 59 at the downstream end (the right end in FIG. 2) of the barrel unit 51.

[0289] The barrel unit 51 has a supply barrel portion 52, a dehydration barrel portion 53, and a drying barrel portion 54 extending from the upstream side to the downstream side (from the left side to the right side in FIG. 2).

[0290] The supply barrel portion 52 is composed of two supply barrels, that is, a first supply barrel 52a and a second supply barrel 52b.

[0291] Further, the dehydration barrel portion 53 is composed of three dehydration barrels, that is, a first dehydration barrel 53a, a second dehydration barrel 53b, and a third dehydration barrel 53c.

[0292] Further, the drying barrel portion 54 is composed of eight drying barrels, that is, 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.

[0293] In this way, the barrel unit 51 is configured by connecting the 13 divided barrels 52a to 52b, 53a to 53c, and 54a to 54h from the upstream side to the downstream side.

[0294] Further, the screw-type twin-screw extrusion dryer 5 has heating means (not shown) for individually heating the above-described barrels 52a to 52b, 53a to 53c, and 54a to 54h to heat the water-containing clams in the respective barrels 52a to 52b, 53a to 53c, and 54a to 54h to a predetermined temperature. The heating means has a number corresponding to each of the barrels 52a to 52b, 53a to 53c, and 54a to 54h. As such heating means, for example, 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 to 52b, 53a to 53c, and 54a to 54h is adopted, but it is not limited thereto. Further, the screw-type twin-screw extrusion dryer 5 has temperature control means (not shown) for controlling the set temperature of each heating means corresponding to each of the barrels 52a to 52b, 53a to 53c, and 54a to 54h.

[0295] Note that the number of supply barrels, dehydration barrels, and drying barrels that respectively constitute each of the barrel portions 52, 53, and 54 in the barrel unit 51 is not limited to the mode shown in FIG. 2, and can be set to a number according to, for example, the water content of the water-containing clams of the acrylic rubber to be dried.

[0296] For example, the number of supply barrels provided in the supply barrel portion 52 is, for example, 1 to 3. Further, the number of dehydration barrels provided in the dehydration barrel portion 53 is preferably, for example, 2 to 10, and more preferably 3 to 6 because the dehydration of the water-containing clams of the sticky acrylic rubber can be efficiently performed. Further, the number of drying barrels provided in the drying barrel portion 54 is preferably, for example, 2 to 10, and more preferably 3 to 8.

[0297] 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 downstream 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.

[0298] Also, the rotational directions of the pair of screws may be the same or different, but in terms of self-cleaning performance, a type that rotates in the same direction is preferred. The screw shape of the pair of screws is not particularly limited, and it may be any shape required in each barrel portion 52, 53, 54, and is not particularly limited.

[0299] The supply barrel portion 52 is an area 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.

[0300] The dehydration barrel portion 53 is an area for separating and discharging a liquid (ceramic water) containing a coagulant or the like from the water-containing clam.

[0301] 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.

[0302] 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 viewpoints 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.

[0303] In each of the dehydration barrels 53a to 53c of the dehydration barrel section 53, there are two ways to remove moisture from the water-containing clams, namely, removing it in a liquid state from the respective dehydration slits 56a, 56b, 56c and removing it in a vapor state. In the dehydration barrel section 53 of the present embodiment, the case of removing moisture in a liquid state is defined as drainage, and the case of removing it in a vapor state is defined as exhaust steam and distinguished.

[0304] In the dehydration barrel section 53, it is preferable to combine drainage and exhaust steam because the moisture content of the pressure-sensitive acrylic rubber can be efficiently reduced. In the dehydration barrel section 53, among the first to third dehydration barrels 53a to 53c, which dehydration barrel performs drainage or exhaust steam can be appropriately set according to the purpose of use. However, when reducing the ash content in the acrylic rubber produced normally, it is advisable to increase the number of dehydration barrels that perform drainage. In that case, for example, as shown in FIG. 2, drainage is performed in the upstream first and second dehydration barrels 53a and 53b, and exhaust steam is performed in the downstream third dehydration barrel 53c. Also, for example, when the dehydration barrel section 53 has four dehydration barrels, a mode such as performing drainage in the three upstream dehydration barrels and performing exhaust steam in the one downstream dehydration barrel can be considered. On the other hand, when reducing the water content, it is advisable to increase the number of dehydration barrels that perform exhaust steam.

[0305] The set temperature of the dehydration barrel section 53 is usually in the range of 60 to 150°C, preferably 70 to 140°C, more preferably 80 to 130°C, as described in the above dehydration and drying process. The set temperature of the dehydration barrel that dehydrates in a drainage state is usually 60 to 120°C, preferably 70 to 110°C, more preferably 80 to 100°C, and the set temperature of the dehydration barrel that dehydrates in an exhaust steam state is usually in the range of 100 to 150°C, preferably 105 to 140°C, more preferably 110 to 130°C.

[0306] The drying barrel section 54 is a region for drying the water-containing clam after dehydration under reduced pressure. Among the first to eighth drying barrels 54a to 54h constituting 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 pipes (not shown) are respectively connected to the vent ports 58a, 58b, 58c, and 58d.

[0307] At the end of each vent pipe, a vacuum pump (not shown) is respectively connected. By the operation of these vacuum pumps, the inside of the drying barrel section 54 is reduced in pressure to a predetermined pressure. The screw extruder 5 has pressure control means (not shown) for controlling the degree of vacuum inside the drying barrel section 54 by controlling the operation of these vacuum pumps.

[0308] The degree of vacuum in the drying barrel section 54 may be appropriately selected. As described above, it is usually set to 1 to 50 kPa, preferably 2 to 30 kPa, and more preferably 3 to 20 kPa.

[0309] Also, the set temperature inside the drying barrel section 54 may be appropriately selected. As described above, it is usually set to 100 to 250 °C, preferably 110 to 200 °C, and more preferably 120 to 180 °C.

[0310] In each of the drying barrels 54a to 54h constituting the drying barrel section 54, the set temperatures inside all the drying barrels 54a to 54h may be approximated or may be made different. However, if the temperature on the downstream side (die 59 side) is set higher than the temperature on the upstream side (dehydration barrel section 53 side), the drying efficiency is improved, which is preferable.

[0311] The die 59 is a mold disposed at the downstream end of the barrel unit 51 and has a discharge port with a predetermined nozzle shape. The acrylic rubber dried in the drying barrel portion 54 is extruded into a shape corresponding to the predetermined nozzle shape by passing through the discharge port of the die 59. The acrylic rubber passing through the die 59 can be formed into various shapes such as granular, columnar, round bar-shaped, sheet-shaped, etc. according to the nozzle shape of the die 59, but in the present invention, it is formed into a sheet shape. A breaker plate or a wire mesh may or may not be provided between the screw and the die 59.

[0312] The water-containing clam of the acrylic rubber obtained through the cleaning process is supplied from the feed port 55 to the supply barrel portion 52. The water-containing clam supplied to the supply barrel portion 52 is sent from the supply barrel portion 52 to the dehydration barrel portion 53 by the rotation of a pair of screws in the barrel unit 51. In the dehydration barrel portion 53, as described above, drainage and exhaust steam of the moisture contained in the water-containing clam are performed from the dehydration slits 56a, 56b, 56c provided in the first to third dehydration barrels 53a to 53c respectively, and the water-containing clam is dehydrated.

[0313] The water-containing clam dehydrated in the dehydration barrel portion 53 is sent to the drying barrel portion 54 by the rotation of a pair of screws in the barrel unit 51. The water-containing clam sent to the drying barrel portion 54 is plastically mixed to become a melt, and is carried downstream while generating heat and raising the temperature. Then, the moisture contained in the melt of this acrylic rubber vaporizes, and the moisture (steam) is discharged to the outside through vent pipes (not shown) respectively connected to the vent ports 58a, 58b, 58c, 58d.

[0314] As described above, by passing through the drying barrel portion 54, the water-containing clam is dried to become a melt of acrylic rubber, and the acrylic rubber is supplied to the die 59 and extruded from the die 59 by the rotation of a pair of screws in the barrel unit 51.

[0315] Here, an example of the operating conditions of the screw-type twin-screw extrusion dryer 5 according to this embodiment is given.

[0316] The rotational speed (N) of the pair of screws in the barrel unit 51 may be appropriately selected according to various conditions, and is usually 10 to 1000 rpm. From the viewpoint of efficiently reducing the water content and methyl ethyl ketone insoluble content of the acrylic rubber, it is preferably 50 to 750 rpm, more preferably 100 to 500 rpm, and most preferably 120 to 300 rpm.

[0317] Also, 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.

[0318] The ratio (Q / N) of the extrusion rate (Q) of the acrylic rubber to the rotational speed (N) of the screw 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.

[0319] The maximum torque in the barrel unit 51 is not particularly limited, but 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.

[0320] The specific power in the barrel unit 51 is not particularly limited, but is usually 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].

[0321] The specific electricity in the barrel unit 51 is not particularly limited, but is usually 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].

[0322] The shear rate in the barrel unit 51 is not particularly limited, but is usually 40 to 150 [1 / s] or more, preferably 45 to 125 [1 / s], and more preferably 50 to 100 [1 / s].

[0323] The shear viscosity of the acrylic rubber in the barrel unit 51 is not particularly limited, but is usually 4000 to 8000 [Pa·s] or less, preferably 4500 to 7500 [Pa·s], and more preferably 5000 to 7000 [Pa·s].

[0324] The cooling device 6 shown in FIG. 1 is configured to cool the dried rubber obtained through the dehydration process by a dehydrator and the drying process by a dryer. As the cooling method by the cooling device 6, various methods including a blowing method, an air-cooling method under air conditioning, a watering method of spraying water, an immersion method of immersing in water, etc. can be adopted. Also, the dried rubber may be cooled by leaving it at room temperature.

[0325] As described above, depending on the nozzle shape of the die 59, the dried rubber discharged from the screw extruder 5 is extrusion-molded into various shapes such as granular, columnar, round bar-shaped, sheet-shaped, etc., but in the present invention, it is molded into a sheet shape. Hereinafter, as an example of the cooling device 6, a conveyor-type cooling device 60 for cooling the sheet-shaped dried rubber 10 molded into a sheet shape will be described with reference to FIG. 3.

[0326] FIG. 3 shows the configuration of a conveyor-type cooling device 60 suitable as the cooling device 6 shown in FIG. 1. The conveyor-type cooling device 60 shown in FIG. 3 is configured to cool the sheet-shaped dried rubber 10 discharged from the discharge port of the die 59 of the screw extruder 5 by an air-cooling method while conveying it. By using this conveyor-type cooling device 60, the sheet-shaped dried rubber discharged from the screw extruder 5 can be suitably cooled.

[0327] The conveyor-type cooling device 60 shown in FIG. 3 is, for example, directly connected to the die 59 of the screw extruder 5 shown in FIG. 2 or installed in the vicinity of the die 59 for use.

[0328] The conveyor-type cooling device 60 has a conveyor 61 that conveys the sheet-shaped dried rubber 10 discharged from the die 59 of the screw extruder 5 in the direction of arrow A in Fig. 3, and a cooling means 65 that blows cold air onto the sheet-shaped dried rubber 10 on the conveyor 61.

[0329] The conveyor 61 has rollers 62, 63 and a conveyor belt 64 wound around these rollers 62, 63, on which the sheet-shaped dried rubber 10 is placed. The conveyor 61 is configured to continuously convey the sheet-shaped dried rubber 10 discharged from the die 59 of the screw extruder 5 downstream (to the right in Fig. 3) on the conveyor belt 64.

[0330] The cooling means 65 is not particularly limited, and examples include those having a configuration capable of blowing the cooling air sent from a cooling air generating means (not shown) onto the surface of the sheet-shaped dried rubber 10 on the conveyor belt 64.

[0331] The length L1 of the conveyor 61 and the cooling means 65 of the conveyor-type cooling device 60 (the length of the portion where cooling air can be blown) is not particularly limited, but is, for example, 10 to 100 m, preferably 20 to 50 m. Also, the conveying speed of the sheet-shaped dried rubber 10 in the conveyor-type cooling device 60 may be appropriately adjusted according to the length L1 of the conveyor 61 and the cooling means 65, the discharge speed of the sheet-shaped dried rubber 10 discharged from the die 59 of the screw extruder 5, the target cooling speed, the cooling time, etc., but is, for example, 10 to 100 m / hr, more preferably 15 to 70 m / hr.

[0332] According to the conveyor-type cooling device 60 shown in Fig. 3, while the sheet-shaped dried rubber 10 discharged from the die 59 of the screw extruder 5 is conveyed by the conveyor 61, the sheet-shaped dried rubber 10 is cooled by blowing cooling air from the cooling means 65.

[0333] Note that the conveyor-type cooling device 60 is not particularly limited to a configuration including one conveyor 61 and one cooling means 65 as shown in FIG. 3, and may 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 cooling means 65 may be within the above range.

[0334] The bailing device 7 shown in FIG. 1 is configured to process the dried rubber extruded from the screw extruder 5 and further cooled by the cooling device 6 to produce a bale, which is a single block. As described above, the screw extruder 5 can extrude the dried rubber into various shapes such as granular, columnar, round bar-shaped, sheet-shaped, etc., and the bailing device 7 is configured to bale the dried rubber thus formed into various shapes. The weight, shape, etc. of the bale-shaped acrylic rubber produced by the bailing device 7 are not particularly limited. For example, a bale-shaped acrylic rubber having a substantially rectangular parallelepiped shape and weighing about 20 kg is produced.

[0335] The bailing device 7 may be provided with, for example, a bailer and produce the bale-shaped acrylic rubber by compressing the cooled dried rubber with the bailer.

[0336] Also, when the sheet-shaped dried rubber 10 is produced by the screw extruder 5, a bale-shaped acrylic rubber obtained by laminating the sheet-shaped dried rubbers 10 may be produced. For example, a cutting mechanism for cutting the sheet-shaped dried rubber 10 may be provided in the bailing device 7 disposed on the downstream side of the conveyor-type cooling device 60 shown in FIG. 3. Specifically, the cutting mechanism of the bailing device 7 is configured to continuously cut the cooled sheet-shaped dried rubber 10 at a predetermined interval to process it into a cut sheet-shaped dried rubber 16 having a predetermined size. By laminating a plurality of cut sheet-shaped dried rubbers 16 cut to a predetermined size by the cutting mechanism, a bale-shaped acrylic rubber obtained by laminating the cut sheet-shaped dried rubbers 16 can be produced.

[0337] When manufacturing a veil-shaped acrylic rubber laminated with cut-sheet-shaped dry rubber 16, it is preferable to laminate the cut-sheet-shaped dry rubber 16 at 40 °C or higher, for example. By laminating the cut-sheet-shaped dry rubber 16 at 40 °C or higher, good air venting is achieved by further cooling and compression due to its own weight.

Example

[0338] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In each example, "parts", "%", and "ratio" are based on weight unless otherwise specified. In addition, various physical properties and the like were evaluated according to the following methods.

[0339] [Monomer composition] Regarding the monomer composition in the acrylic rubber, the monomer constitution of each monomer unit in the acrylic rubber was 1 confirmed by 1H-NMR, and it was confirmed by the following method that the activity of the reactive groups remained in the acrylic rubber and the content of each reactive group. In addition, the content ratio of each monomer unit in the acrylic rubber was calculated from the usage amount of each monomer used in the polymerization reaction and the polymerization conversion rate. Specifically, the polymerization reaction was an emulsion polymerization reaction, and since the polymerization conversion rate was approximately 100% where no unreacted monomer could be confirmed, the content ratio of each monomer unit in the rubber was made the same as the usage amount of each monomer.

[0340] [Reactive group content] The content of the reactive groups in the 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 a 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 thereto 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 in water, and titrating with silver nitrate.

[0341] [Ash content] The ash content (%) contained in the acrylic rubber was measured according to JIS K6228 Method A.

[0342] [Ash component amount] For each component amount (ppm) in the acrylic rubber ash, the ash collected during the above ash content measurement was pressed onto a Φ20 mm titration filter paper and subjected to XRF measurement using ZSX Primus (manufactured by Rigaku).

[0343] [Molecular weight and molecular weight distribution] The molecular weight (Mw, Mn, Mz) and molecular weight distribution (Mw / Mn and Mz / Mw) of the acrylic rubber are the absolute molecular weight and absolute molecular weight distribution measured by the GPC-MALS method using a solution in which lithium chloride is added to dimethylformamide as a solvent at a concentration of 0.05 mol / L and 37% concentrated hydrochloric acid is added at a concentration of 0.01%.

[0344] The configuration of the gel permeation chromatography multi-angle light scattering photometer, which is this device, consists of a pump (LC-20ADOpt manufactured by Shimadzu Corporation), a differential refractive index meter (Optilab rEX manufactured by Wyatt Technology) as a detector, 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 refractive index meter (RI) are incorporated into a GPC (Gel Permeation Chromatography) device, and the light scattering intensity and refractive index difference of the molecular chain solution size-fractionated by the GPC device are measured following the elution time, thereby sequentially calculating and obtaining the molecular weight of the solute and its content rate. The measurement conditions and measurement method by the GPC layer device are as follows.

[0345] Columns: 2 TSKgel α-M (φ7.8 mm × 30 cm, manufactured by Tosoh Corporation) Column temperature: 40 °C Flow rate: 0.8 ml / mm Sample preparation: 5 ml of solvent was added to 10 mg of the sample (acrylic rubber) and gently stirred at room temperature (dissolution was visually confirmed). Then, filtration was performed using a 0.5 μm filter.

[0346] [Glass transition temperature (Tg)] The glass transition temperature (Tg) of the acrylic rubber was measured using a differential scanning calorimeter (DSC, product name "X-DSC7000", manufactured by Hitachi High-Technologies Corporation).

[0347] [Methyl ethyl ketone insoluble content (gel content)] The methyl ethyl ketone insoluble content (%) of the acrylic rubber is the amount of insoluble matter (gel) in methyl ethyl ketone and was determined by the following method.

[0348] Weighed approximately 0.2 g of acrylic rubber (X g), immersed it in 100 ml of methyl ethyl ketone, left it at room temperature for 24 hours, and then filtered off the insoluble matter in methyl ethyl ketone using an 80-mesh wire mesh. The filtrate, that is, the filtrate in which only the rubber component soluble in methyl ethyl ketone was dissolved, was evaporated to dryness and solidified, and the dry solid content (Y g) was weighed and calculated by the following formula. Methyl ethyl ketone insoluble content (%) = 100×(X - Y) / X [Specific gravity] The specific gravity of the acrylic rubber was measured in accordance with JIS K6268 (1998): Method A for Measuring the Density of Crosslinked Rubber.

[0349] [Water content] The water content (%) was measured in accordance with JIS K6238-1: Method A (Measurement of Volatile Matter) in an oven.

[0350] [pH] The pH was measured with 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.

[0351] [Complex viscosity] The complex viscosity η was measured using a dynamic viscoelasticity measuring device "RPA-2000 Rubber Process Analyzer" (manufactured by Alpha Technology Co., Ltd.) at a strain of 473% and 1 Hz with temperature dispersion (40 to 120 °C) to obtain the complex viscosity η at each temperature. Here, among the above-mentioned dynamic viscoelasticities, the dynamic viscoelasticity at 60 °C was taken as the complex viscosity η(60 °C), and the dynamic viscoelasticity at 100 °C was taken as the complex viscosity η(100 °C), and the value of the ratio η(100 °C) / η(60 °C) was calculated.

[0352] [Mooney viscosity (ML1+4, 100 °C)] The Mooney viscosity (ML1+4, 100 °C) was measured according to the unvulcanized rubber physical test method of JIS K6300.

[0353] [Vulcanizability] The vulcanizability of the rubber sample was judged according to the following criteria by calculating the change rate of the breaking strength of the rubber crosslinked product after secondary crosslinking for 2 hours and the breaking strength of the rubber crosslinked product after 4 hours ((breaking strength of 4-hour crosslinked rubber crosslinked product / breaking strength of 2-hour crosslinked rubber crosslinked product) × 100). ◎: Those with a breaking strength change rate of less than 10% ×: Those with a breaking strength change rate of 10% or more

[0354] [Roll processability] The roll processability of the rubber sample was evaluated according to the following criteria by observing the roll winding property and the state of the rubber when the rubber sample was kneaded on a roll. ◎: Those for which kneading is easy, which are easy to wind around the roll, show no separation from the roll, and the surface of the rubber composition after kneading is smooth 〇: Those for which kneading is easy, which are easy to wind around the roll, show no separation from the roll, and have slight unevenness on a part of the surface of the rubber composition after kneading □: Those for which kneading is easy, which have excellent roll winding property, and the surface of the rubber composition after kneading is somewhat uneven △: Those for which kneading is easy, which are somewhat inferior in roll winding property, and the surface of the rubber composition after kneading is somewhat rough ×: Those for which kneading is difficult and the roll winding property is also poor

[0355] [Banbury Processability 1] The Banbury processability 1 of the rubber sample was measured by putting the rubber sample into a Banbury mixer heated to 50 °C, kneading it for 1 minute, then adding compounding agent A in the rubber composition formulation shown in Table 1 until the first-stage rubber mixture was integrated and showed the maximum torque value, that is, the time of BIT (Black Incorporation Time). It was evaluated with an index with Comparative Example 1 as 100 (the smaller the index, the better the processability). [Banbury Processability 2] The Banbury processability 2 of the rubber sample was measured by putting the rubber sample into a Banbury mixer heated to 50 °C, kneading it for 1 minute, then adding compounding agent A in the rubber composition formulation shown in Table 1 until the first-stage rubber mixture was integrated and showed the maximum torque value, that is, the time of BIT (Black Incorporation Time). It was evaluated with an index with Comparative Example 2 as 100 (the smaller the index, the better the processability).

[0356] [Storage Stability Evaluation 1] The storage stability 1 of the rubber sample was evaluated by putting the rubber mixture of the rubber sample into a constant temperature and humidity chamber at 45 °C × 80% RH for 7 days. Before and after the test, the rubber sample was used as a rubber composition to conduct a cross-linking test at 180 °C for 10 minutes using a rubber vulcanization tester (Moving Die Rheometer MDR; manufactured by Alpha Technology). The change rate of the cross-linking density, which is the difference between the maximum torque (MH) and the minimum torque (ML) (MH - ML), was calculated and evaluated with an index with Comparative Example 1 as 100 (the smaller the index, the better the storage stability). [Storage Stability Evaluation 2] The storage stability 2 of the rubber sample was evaluated by putting the rubber sample into a constant temperature and humidity chamber (SH-222 manufactured by ESPEC) at 45 °C × 80% RH, calculating the change rate of the water content before and after 7 days, and evaluating it with an index with Comparative Example 2 as 100 (the smaller the index, the better the storage stability).

[0357] [Water Resistance Evaluation 1] The water resistance 1 of the rubber sample was evaluated by conducting an immersion test in which the crosslinked product of the rubber sample was immersed 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 using an index with Comparative Example 1 as 100 (the smaller the index, the better the water resistance). Volume change rate before and after immersion (%) = ((Volume of the test piece after immersion - Volume of the test piece before immersion) / Volume of the test piece before immersion) × 100 [Water resistance evaluation 2] The water resistance 2 of the rubber sample was evaluated by conducting a wetting test and calculating the volume change rate before and after wetting in the same manner as above, and using an index with Comparative Example 2 as 100 (the smaller the index, the better the water resistance).

[0358] [Compression set resistance characteristics] The compression set resistance characteristics of the rubber sample were evaluated according to the following criteria by measuring the compression set rate after placing the crosslinked rubber product of the rubber sample at 175°C for 90 hours in a state of being compressed by 25% in accordance with JIS K6262. ◎: Compression set rate is less than 15% ×: Compression set rate is 15% or more

[0359] [Heat resistance evaluation] The heat resistance evaluation of the rubber sample was conducted by performing a heating test in which the crosslinked product of the rubber sample was allowed to stand at 175°C for 250 hours. The tensile strength of the crosslinked rubber product before and after the test was measured in accordance with JIS K6251, and the hardness was measured in accordance with JIS K6253. The changes in elongation at break and hardness were evaluated according to the following criteria. Regarding the change in elongation at break, it was evaluated as "◎" when the elongation at break change rate was 20% or less, and as "×" when the elongation at break change rate exceeded 20%. Regarding the change in hardness, it was evaluated as "◎" when the hardness change rate was 20 points or less, and as "×" when the hardness change rate exceeded 20 points.

[0360] [Normal physical property evaluation] The normal physical properties of the rubber sample were evaluated according to the following criteria by measuring the breaking strength, 100% tensile stress, and elongation at break of the crosslinked rubber product of the rubber sample in accordance with JIS K6251. (1) The breaking strength was evaluated as "◎" when it was 10 MPa or more and as "×" when it was less than 10 MPa. (2) The 100% tensile stress was evaluated as ◎ when it was 5 MPa or more and × when it was less than 5 MPa. (3) The elongation at break was evaluated as ◎ when it was 150% or more and × when it was less than 150%.

[0361] [Example 1] Into a mixing vessel equipped with a homomixer, 46 parts of pure water, 63.25 parts of ethyl acrylate, 17 parts of n-butyl acrylate, 7 parts of methoxyethyl acrylate, 11 parts of butyl methacrylate, and 1.75 parts of monoethyl fumarate as monomer components, and 1.8 parts of sodium octyloxydioxyethylene phosphate as an emulsifier were charged and stirred to obtain a monomer emulsion.

[0362] Into a polymerization reaction tank equipped with a thermometer and a stirring device, 170 parts of pure water and 3 parts of the monomer emulsion obtained above were charged and cooled to 12 °C under a nitrogen stream. Next, the remainder of the monomer emulsion, 0.00033 part of ferrous sulfate, 0.264 part of sodium ascorbate, and 0.22 part of potassium persulfate were continuously dropped into the polymerization reaction tank over 3 hours. Then, the reaction was continued while maintaining the temperature in the polymerization reaction tank at 23 °C. When it was confirmed that the polymerization conversion rate reached approximately 100%, hydroquinone as a polymerization terminator was added to stop the polymerization reaction, and an emulsion polymerization liquid was obtained.

[0363] Next, in a coagulation tank equipped with a thermometer and a stirring device, the emulsion polymerization liquid obtained above was heated to 80 °C and continuously added to 350 parts of a 2% magnesium sulfate aqueous solution (a coagulation liquid using magnesium sulfate as a coagulant) heated to 80 °C and vigorously stirred at a stirring blade rotation speed of 600 rotations (peripheral speed 3.1 m / s) of the stirring device to coagulate the polymer, and a coagulation slurry containing crumbs of acrylic rubber and water as a coagulated product was obtained. While filtering off the crumbs from the obtained slurry, water was discharged from the coagulation layer to obtain hydrated crumbs.

[0364] 194 parts of warm water (70 °C) was added to the remaining coagulation tank of the filtered water-containing clam, and it was stirred for 15 minutes to wash the water-containing clam. Then, the water was discharged. Again, 194 parts of warm water (70 °C) was added and stirred for 15 minutes to wash the water-containing clam (the total number of washing times was 2). The washed water-containing clam (clam temperature 65 °C) was supplied to a screw extruder, dehydrated, dried, and formed to extrude a sheet-like dried rubber (sheet-like acrylic rubber molded body) with a width of 300 mm and a thickness of 10 mm. Next, using a conveyor cooling device provided directly connected to the screw extruder, the sheet-like dried rubber was cooled at a cooling temperature of 200 °C / hr.

[0365] Note that the screw extruder used in this Example 1 is composed of one supply barrel, three dehydration barrels (the first to third dehydration barrels), and five drying barrels (the first to fifth drying barrels). The first dehydration barrel discharges water, and the second and third dehydration barrels discharge steam. The operating conditions of the screw extruder were as follows.

[0366] Water content · Water content of the water-containing clam after draining in the first dehydration barrel: 20% · Water content of the water-containing clam after discharging steam in the third dehydration barrel: 10% · Water content of the water-containing clam after drying in the fifth drying barrel: 0.4% Rubber temperature · Temperature of the water-containing clam supplied to the supply barrel: 65 °C · Temperature of the rubber discharged from the screw extruder: 140 °C Set temperature of each barrel: · The first dehydration barrel: 100 °C · The second dehydration barrel: 120 °C · The third dehydration barrel: 120 °C · The first drying barrel: 120 °C · The second drying barrel: 130 °C · The third drying barrel: 140 °C · The fourth drying barrel: 160 °C · The fifth drying barrel: 180 °C Operating conditions: · Diameter (D) of the screw: 132 mm · Overall length (L) of the screw: 4620 mm · L / D: 35 · Rotation speed of the screw: 135 rpm · Degree of vacuum in the drying barrel: 10 kPa · Extrusion rate of rubber from the die: 700 kg / hr · Resin pressure at the die: 2 MPa

[0367] The sheet-like dried rubber extruded from the screw-type extruder was cooled to 50°C and then cut with a cutter to obtain sheet-like dried rubber.

[0368] Next, before the temperature of the sheet-like dried rubber dropped below 40°C, a plurality of cut sheet-like dried rubbers were laminated to a total of 20 parts (20 kg) to obtain bale-like acrylic rubber (A). The content of reactive groups, gel content, specific gravity, ash content, glass transition temperature (Tg), pH, water content, weight average molecular weight, and Mooney viscosity (ML1+4, 100°C) of the obtained acrylic rubber (A) were measured, and the results are shown in Table 2.

[0369] Next, 100 parts of acrylic rubber (A) and compounding agent A of "Formulation 1" described in Table 1 were put into a Banbury mixer and mixed at 50°C for 5 minutes (first-stage mixing). The BIT at this time was measured to evaluate the Banbury processability 1 of acrylic rubber (A), and the results are shown in Table 2.

[0370] Furthermore, each of the mixtures obtained in the first-stage mixing was transferred to a 50°C roll, and compounding agent B of "Formulation 1" was compounded and mixed (second-stage mixing) to obtain a rubber composition. A cross-linking test of the rubber composition using acrylic rubber (A) before and after the storage stability test was conducted to measure the change in cross-linking density (MH-ML), and the results (storage stability 1) are shown in Table 2.

[0371]

Table 1

[0372] The rubber composition thus obtained was placed in a mold measuring 15 cm in length, 15 cm in width, and 0.2 cm in depth, and was press-cured at 180 °C for 10 minutes while applying a press pressure of 10 MPa for primary crosslinking. The obtained primary crosslinked product was further heated in a gear-type oven under the conditions of 180 °C for 2 hours for secondary crosslinking to obtain a sheet-like rubber crosslinked product. Then, a test piece measuring 3 cm × 2 cm × 0.2 cm was cut from the obtained sheet-like rubber crosslinked product, and water resistance evaluation 1, heat resistance evaluation, and normal state physical property evaluation were performed, and the results are shown in Table 2.

[0373] [Example 2] The monomer components were changed to 4.5 parts of ethyl acrylate, 53.5 parts of n-butyl acrylate, 29.5 parts of methoxyethyl acrylate, 11 parts of hexyl methacrylate, and 1.5 parts of monoethyl fumarate, and the procedure was carried out in the same manner as in Example 1 to obtain acrylic rubber (B), and each property (the compounding agent was changed to "compounding 2") was evaluated. The results are shown in Table 2.

[0374] [Example 3] The monomer components were changed to 48.6 parts of ethyl acrylate, 39 parts of n-butyl acrylate, 11 parts of butyl methacrylate, and 1.4 parts of monoethyl fumarate, and the procedure was carried out in the same manner as in Example 2 to obtain acrylic rubber (C), and each property was evaluated. The results are shown in Table 2.

[0375] [Example 4] The monomer components were changed to 42.3 parts of ethyl acrylate, 45.3 parts of n-butyl acrylate, 11 parts of butyl methacrylate, and 1.4 parts of monoethyl fumarate, and the procedure was carried out in the same manner as in Example 2 to obtain acrylic rubber (D), and each property was evaluated. The results are shown in Table 2.

[0376] [Example 5] The procedure was carried out in the same manner as in Example 4 except that the water content of the water-containing clam after dehydration in a screw-type extruder (the water content of the water-containing clam after drainage until before preliminary drying for discharging steam) was set to 30% to obtain acrylic rubber (E), and each property was evaluated. The results are shown in Table 2.

[0377] [Comparative Example 1] Into a polymerization reaction tank equipped with a thermometer and a stirring device, under a nitrogen stream, 200 parts of pure water, 42.3 parts of ethyl acrylate, 45.3 parts of n-butyl acrylate, 11 parts of butyl methacrylate, and 1.4 parts of monoethyl fumarate as monomer components, 2.5 parts of octyloxydioxyethylene phosphate and 0.5 part of polyoxyethylene dodecyl ether as emulsifiers were charged, 0.1 part of potassium persulfate and 0.1 part of sodium ascorbate were charged, and then 0.1 part of potassium persulfate and 0.1 part of sodium ascorbate were added to initiate the reaction. The reaction was continued at room temperature, and when it was confirmed that the polymerization conversion rate reached approximately 100%, hydroquinone as a polymerization terminator was added to stop the polymerization reaction, and an emulsion polymerization liquid was obtained.

[0378] Next, an aqueous sodium sulfate solution (a coagulating liquid using sodium sulfate as a coagulant) of 0.4% was added to the emulsion polymerization liquid being stirred at a stirring blade rotation speed of 100 revolutions (peripheral speed 0.5 m / s) of the stirring device to coagulate the polymer, and a coagulated slurry containing crumbs of acrylic rubber as a coagulated product and water was obtained. While filtering off the crumbs from the obtained slurry, moisture was discharged from the coagulated layer to obtain water-containing crumbs.

[0379] 194 parts of water at 25 °C was added to the remaining coagulation tank of the filtered water-containing crumbs, and the mixture was stirred for 15 minutes to wash the water-containing crumbs, and then the moisture was discharged to wash the water-containing crumbs (the number of washing times was 1 time). The washed water-containing crumbs were dried with a hot air dryer to obtain crumb-shaped acrylic rubber (F) having a water content of 0.4% by weight. Regarding this acrylic rubber (F), the reactive group content, gel content, specific gravity, ash content, glass transition temperature (Tg), pH, water content, weight average molecular weight, and Mooney viscosity (ML1+4, 100 °C) were measured, and the results are shown in Table 2.

[0380] Next, 100 parts of acrylic rubber (F) and compounding agent A of "Formulation 2" described in Table 1 were charged into a Banbury mixer and mixed at 50°C for 5 minutes (first-stage mixing). At this time, BIT was measured to evaluate the Banbury processability 1 of acrylic rubber (F), and the results are shown in Table 2. Further, each of the mixtures obtained in the first-stage mixing was transferred to a roll at 50°C, and compounding agent B of "Formulation 2" was compounded and mixed (second-stage mixing) to obtain a rubber composition. A cross-linking test of the rubber composition using acrylic rubber (F) before and after the storage stability test was conducted, and the change in cross-linking density (MH-ML) was measured, and the results (storage stability 1) are shown in Table 2.

[0381] The obtained rubber composition was put into a mold with a length of 15 cm, a width of 15 cm, and a depth of 0.2 cm, and was press-molded at 180°C for 10 minutes while applying a press pressure of 10 MPa for primary cross-linking. The obtained primary cross-linked product was further heated in a gear-type oven at 180°C for 2 hours for secondary cross-linking to obtain a sheet-like rubber cross-linked product. Then, a test piece of 3 cm × 2 cm × 0.2 cm was cut out from the obtained sheet-like rubber cross-linked product, and water resistance evaluation 1, heat resistance evaluation, and normal physical property evaluation were performed, and the results are shown in Table 2.

[0382]

Table 2

[0383] From Table 2, it can be seen that acrylic rubbers (A) to (E) having a reactive group of the present invention and a reactive group content of 0.001 to 5% by weight, with a gel amount of methyl ethyl ketone-insoluble matter of 50% by weight or less, a pH of 6 or less, an ash content of 0.4% by weight or less, and a total amount of magnesium, phosphorus, calcium, sodium, and sulfur in the ash of 50% by weight or more, and a specific gravity of 0.8 or more are excellent in Banbury processability, water resistance, and storage stability, and also excellent in normal physical properties including heat resistance and strength characteristics (Examples 1 to 5).

[0384] From Table 2, it can be seen that the acrylic rubbers (A) to (F) of the examples and comparative examples have a carboxyl group and a relatively large weight-average molecular weight (Mw), and contain a bonding unit (A1) derived from an acrylate ester, a bonding unit (A2) derived from a methacrylate ester, and a bonding unit (B) derived from a monomer containing a reactive group. Thus, it can be understood that their normal physical properties including heat resistance and strength characteristics are extremely excellent (Examples 1 to 5 and Comparative Example 1). However, it can be seen that the acrylic rubber (F) is inferior in Banbury processability, water resistance, and storage stability (Comparative Example 1).

[0385] From Table 2, it can be seen that the processability (BIT) of the acrylic rubber in a Banbury mixer correlates with the gel amount of the methyl ethyl ketone-insoluble matter in the acrylic rubber. In order to reduce the gel amount, it is important to melt and rotate the acrylic rubber in a state substantially free of moisture (water content less than 1% by weight) in the fifth drying barrel section. On the other hand, retaining the acrylic rubber in the screw-type extruder for a long time is not preferable because molecular scission, burning, etc. occur, deteriorating properties such as the normal physical properties including the strength characteristics of the acrylic rubber, heat resistance, and storage stability. As can be seen from Table 2, in order to quickly bring it to a state substantially free of moisture in the drying barrel section, the issue is how to efficiently perform dehydration in the dehydration barrel section. In this case, it has been solved by adjusting the temperature and degree of vacuum in each barrel section. Also, in order to prevent deterioration of the acrylic rubber melted and rotated in a state substantially free of moisture in the drying barrel section and to reduce the water content and gel amount of the acrylic rubber, it was important to keep the extrusion amount Q or the ratio (Q / N) of the extrusion amount Q to the rotation speed N of the screw-type extruder within a specific range.

[0386] From Table 2, it can also be seen that the acrylic rubbers (A) to (E) of the present invention are extremely excellent in water resistance (comparison between Examples 1 to 5 and Comparative Example 1). Also, from Table 2, it can be seen that the water resistance is extremely improved by adding to a thick coagulation liquid while vigorously stirring the emulsion polymerization liquid to carry out the coagulation reaction, using warm water for washing, and performing dehydration (squeezing out moisture from the water-containing crumb) (comparison between Examples 1 to 5 and Comparative Example 1). In particular, although not shown in Table 2, by adding the emulsion polymerization liquid to a vigorously stirred thick coagulation liquid to carry out the coagulation reaction, it is possible to generate a water-containing crumb in which the particle size is concentrated in a relatively small range of 710 μm to 4.75 mm. The washing efficiency with warm water and the removal efficiency during dehydration are extremely improved, the ash content in the acrylic rubber is extremely reduced, and the water resistance is improved (comparison between Examples 1 to 5 and Comparative Example 1).

[0387] From Table 2, it can further be seen that the acrylic rubbers (A) to (E) of the present invention have highly improved strength characteristics, processability, and storage stability because they are acrylic rubber molded articles with a large specific gravity and no air (comparison between Examples 1 to 5 and Comparative Example 1). Acrylic rubber (F) is obtained by directly drying the generated water-containing crumb after washing. Although acrylic rubber having a reactive group such as a carboxyl group has adhesiveness and is difficult to remove air and has a small specific gravity, the acrylic rubbers (A) to (E) of the present invention are dried under reduced pressure using a screw-type twin-screw extruder dryer, and the resin pressure at the die part is adjusted to extrude a sheet-like dried rubber containing almost no air. Also, by cutting and laminating the extruded sheet-like dried rubber at a specific temperature, air entrainment is excluded and air can easily escape, and it is obtained in a state containing almost no air (with a large specific gravity), so it can be seen that the storage stability is extremely excellent (Examples 1 to 5 and Comparative Example 1).

[0388] [Example 6] As shown in Table 4-1, 46 parts of pure water, 4.5 parts of ethyl acrylate as a monomer component, 64.5 parts of n-butyl acrylate, 29.5 parts of methoxyethyl acrylate, 1.5 parts of mono-n-butyl fumarate, and 1.8 parts of sodium octyloxydioxyethylene phosphate as an emulsifier were charged into a mixing vessel equipped with a homomixer and stirred to obtain a monomer emulsion.

[0389] 170 parts of pure water and 3 parts of the monomer emulsion obtained above were charged into a polymerization reaction tank equipped with a thermometer and a stirring device, cooled to 12°C under a nitrogen stream, and then 0.00033 parts of ferrous sulfate, 0.02 parts of sodium ascorbate, and 0.2 parts of potassium persulfate as an inorganic radical initiator were charged to initiate the polymerization reaction. The temperature in the polymerization reaction tank was maintained at 23°C, and the remainder of the monomer emulsion was continuously added dropwise over 3 hours. 0.0072 parts of n-dodecyl mercaptan were added 50 minutes after the start of the reaction, 0.0036 parts of n-dodecyl mercaptan were added 100 minutes after the start of the reaction, and 0.4 parts of sodium L-ascorbate were added 120 minutes after the start of the reaction to continue the polymerization reaction. When the polymerization conversion rate reached approximately 100%, hydroquinone as a polymerization terminator was added to stop the polymerization reaction, and an emulsion polymerization solution was obtained.

[0390] Next, in a coagulation tank equipped with a thermometer and a stirring device, it was heated to 80°C and vigorously stirred at a stirring blade rotation speed of 600 revolutions (peripheral speed 3.1 m / s) of the stirring device. The emulsion polymerization solution obtained above was heated to 80°C and continuously added to 350 parts of a 2% magnesium sulfate aqueous solution (a coagulation solution using magnesium sulfate as a coagulant) to coagulate the polymer, and a coagulation slurry containing crumbs of acrylic rubber as a coagulated product and water was obtained. While filtering the crumbs from the obtained slurry, water was discharged from the coagulation layer to obtain hydrated crumbs.

[0391] 194 parts of warm water (70 °C) was added to the remaining coagulation tank of the filtered water-containing clam, and it was stirred for 15 minutes to wash the water-containing clam. After that, the water was drained, and 194 parts of warm water (70 °C) was added again and stirred for 15 minutes to wash the water-containing clam (the total number of washing times was 2 times). The washed water-containing clam (water-containing clam temperature 65 °C) was supplied to the screw-type twin-screw extrusion dryer 15, dehydrated and dried to extrude a sheet-shaped dried rubber with a width of 300 mm and a thickness of 10 mm. Next, using a conveyor-type cooling device provided directly connected to the screw-type twin-screw extrusion dryer 15, the sheet-shaped dried rubber was cooled at a cooling rate of 200 °C / hr.

[0392] Note that the screw-type twin-screw extrusion dryer used in Example 1 is composed of one supply barrel, three dehydration barrels (the first to third dehydration barrels), and five drying barrels (the first to fifth drying barrels). The first dehydration barrel drains water, and the second and third dehydration barrels discharge steam. The operating conditions of the screw-type twin-screw extrusion dryer were as follows.

[0393] Water content: · Water content of the water-containing clam after draining in the first dehydration barrel: 20% · Water content of the water-containing clam after discharging steam in the third dehydration barrel: 10% · Water content of the water-containing clam after drying in the fifth drying barrel: 0.4% Rubber temperature: · Temperature of the water-containing clam supplied to the supply barrel: 65 °C · Temperature of the rubber discharged from the screw-type twin-screw extrusion dryer: 140 °C Set temperature of each barrel: · The first dehydration barrel: 100 °C · The second dehydration barrel: 120 °C · The third dehydration barrel: 120 °C · The first drying barrel: 120 °C · The second drying barrel: 130 °C · The third drying barrel: 140 °C · The fourth drying barrel: 160 °C · The fifth drying barrel: 180 °C Operating conditions: · Diameter (D) of the screw: 132 mm · Overall length (L) of the screw: 4620 mm · L / D: 35 · Rotation speed of the screw: 135 rpm · Degree of vacuum reduction of the drying barrel: 10 kPa · Extrusion amount of rubber from the die: 700 kg / hr · Resin pressure at the die: 2 MPa · Maximum torque in the screw-type twin-screw extrusion dryer: 15 N·m

[0394] The extruded sheet-like dried rubber was cooled to 50 °C and then cut with a cutter, and stacked into 20 parts (20 kg) within the time when the temperature did not drop below 40 °C to obtain bale-shaped acrylic rubber (G). The reactive group content, ash content, ash component amount, methyl ethyl ketone insoluble component (gel amount), 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 (G) were measured and shown in Table 4-2. In addition, Storage Stability Test 2 of acrylic rubber (G) was carried out to obtain the water content change rate, and the results were shown in Table 4-2.

[0395] Next, using a Banbury mixer, 100 parts of acrylic rubber (G) and compounding agent A of "Formulation 3" described in Table 3 were charged and mixed at 50 °C for 5 minutes (first-stage mixing). The BIT at this time was measured to evaluate the Banbury processability 2 of the acrylic rubber, and the results were shown in Table 4-2. Next, the obtained mixture was transferred to a roll at 50 °C, and compounding agent B of "Formulation 3" was compounded and mixed (second-stage mixing) to obtain a rubber composition. The roll processability at this time was evaluated, and the results were shown in Table 4-2.

[0396]

Table 3

[0397] The obtained rubber composition was put into a mold with a length of 15 cm, a width of 15 cm, and a depth of 0.2 cm, and was press-cured at 180 °C for 10 minutes while applying a pressing pressure of 10 MPa for primary crosslinking. The obtained primary crosslinked product was further heated in a gear-type oven at 180 °C for 2 hours for secondary crosslinking to obtain a sheet-shaped rubber crosslinked product. Then, a test piece of 3 cm × 2 cm × 0.2 cm was cut from the obtained sheet-shaped rubber crosslinked product, and the water resistance 2, compression set resistance characteristics, and normal physical properties were evaluated. In addition, the normal physical properties of the sheet-shaped rubber crosslinked product subjected to secondary crosslinking for an additional 2 hours were measured to evaluate the crosslinkability. The results are shown in Table 4-2.

[0398] [Example 7] The same procedure as in Example 6 was carried out except that the emulsifier was changed to 1.8 parts of sodium nonylphenylhexaoxyethylene phosphate, the amount of potassium persulfate as an inorganic radical generator was changed to 0.21 part, and the post-addition of the chain transfer agent n-dodecyl mercaptan was changed to 0.017 part after 50 minutes, 0.017 part after 100 minutes, and 0.017 part after 120 minutes. Acrylic rubber (H) was obtained and its various properties were evaluated. The results are shown in Table 4-2.

[0399] [Example 8] The monomer components were changed to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate, and 1.75 parts of mono-n-butyl fumarate, and the emulsifier was changed to 1.8 parts of sodium tridecylhexaoxyethylene phosphate. Further, after the washed water-containing clam was dried using a hot air dryer at 160 °C to a water content of 0.4% to obtain a clam-shaped acrylic rubber, it was filled into a beaker of 300 × 650 × 300 mm and pressed firmly at a pressure of 3 MPa for 25 seconds to obtain a beaker-shaped acrylic rubber. The same procedure as in Example 6 was carried out except for the above to obtain acrylic rubber (I). The various properties of acrylic rubber (I) were evaluated (the compounding agent was changed to "Compounding 4"), and the results are shown in Table 4-2.

[0400] [Example 9] The monomer components were changed to 28 parts of ethyl acrylate, 38 parts of n-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile, and 2 parts of allyl glycidyl ether, and the procedure was carried out in the same manner as in Example 8 to obtain an acrylic rubber (J), and each property (the compounding agent was changed to "Compounding 5") was evaluated. The results are shown in Table 4-2.

[0401] [Example 10] The monomer components were changed to 42.2 parts of ethyl acrylate, 35 parts of n-butyl acrylate, 20 parts of methoxyethyl acrylate, 1.5 parts of acrylonitrile, and 1.3 parts of vinyl chloroacetate, and the procedure was carried out in the same manner as in Example 8 to obtain an acrylic rubber (K), and each property (the compounding agent was changed to "Compounding 5") was evaluated. The results are shown in Table 4-2.

[0402] [Example 11] The monomer components were changed to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate, and 1.75 parts of mono-n-butyl fumarate, the emulsifier was changed to 1.8 parts of sodium tridecyl oxyhexaoxyethylene phosphate ester, and further, after the water-containing clam after washing was dried to a water content of 0.4% using a hot air dryer at 160 °C to obtain a clam-shaped acrylic rubber, it was filled into a beiler of 300×650×300 mm and pressed firmly at a pressure of 3 MPa for 25 seconds to obtain a beiler-shaped acrylic rubber, and the procedure was carried out in the same manner as in Example 7 to obtain an acrylic rubber (L). Each property of the acrylic rubber (L) was evaluated (the compounding agent was changed to "Compounding 4"), and the results are shown in Table 4-2.

[0403] [Example 12] The monomer components were changed to 28 parts of ethyl acrylate, 38 parts of n-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile, and 2 parts of allyl glycidyl ether, and the procedure was carried out in the same manner as in Example 11 to obtain an acrylic rubber (M), and each property (the compounding agent was changed to "Compounding 5") was evaluated. The results are shown in Table 4-2.

[0404] [Example 13] The monomer components were changed to 42.2 parts of ethyl acrylate, 35 parts of n-butyl acrylate, 20 parts of methoxyethyl acrylate, 1.5 parts of acrylonitrile, and 1.3 parts of vinyl chloroacetate, and the procedure was carried out in the same manner as in Example 12 to obtain an acrylic rubber (N), and each property (the compounding agent was changed to "Compounding 6") was evaluated. The results are shown in Table 4-2.

[0405] [Example 14] The amount of potassium persulfate as the inorganic radical generator was changed to 0.22 part, and except that 0.025 part of n-dodecyl mercaptan as the chain transfer agent was continuously added to the monomer emulsion and not added later, the procedure was carried out in the same manner as in Example 13 to obtain an acrylic rubber (O), and each property was evaluated. The results are shown in Table 4-2.

[0406] [Comparative Example 2] Without adding a chain transfer agent, the coagulation reaction was carried out by adding an aqueous solution of 0.7% magnesium sulfate to the emulsified polymerization solution being stirred after emulsion polymerization (stirring speed 100 rpm, peripheral speed 0.5 m / s), and a clam-shaped acrylic rubber was obtained without veiling by a beiler. Except for this, the procedure was carried out in the same manner as in Example 14 to obtain an acrylic rubber (P), and each property was evaluated. The results are shown in Table 4-2.

[0407] [Comparative Example 3] The emulsifier was changed to 0.709 part of sodium lauryl sulfate and 1.82 parts of polyoxyethylene dodecyl ether. The coagulation reaction was carried out by adding sodium sulfate to the emulsified polymerization solution being stirred after emulsion polymerization (stirring speed 100 rpm, peripheral speed 0.5 m / s). For washing the water-containing clam, 194 parts of industrial water was added, and after stirring at 25 °C for 5 minutes in the coagulation tank, the operation of discharging water from the coagulation tank was carried out twice, and a clam-shaped acrylic rubber was obtained without veiling by a beiler. Except for this, the procedure was carried out in the same manner as in Example 14 to obtain an acrylic rubber (Q), and each property was evaluated. The results are shown in Table 4-2.

[0408]

Table 4-1

[0409] [Table 4-2]

[0410] From Tables 4-1 and 4-2, it can be seen that the acrylic rubbers (G) to (O) having the reactive groups of the present invention and a reactive group content of 0.001 to 5% by weight, with a gel amount of methyl ethyl ketone insoluble matter of 50% by weight or less, a pH of 6 or less, an ash content of 0.4% by weight or less, and a total amount of magnesium, phosphorus, calcium, sodium and sulfur in the ash of 50% by weight or more, and a specific gravity of 0.8 or more, are excellent in Banbury processability, storage stability and water resistance. Furthermore, it can be seen that they are also extremely excellent in normal physical properties including roll processability, crosslinkability, compression set resistance characteristics and strength characteristics (Examples 6 to 14).

[0411] From Table 4-2, it can also be seen that the acrylic rubbers (G) to (Q) produced under the conditions of the examples and comparative examples of the present application have either an ionic reactive group or a reactive group such as a carboxyl group, an epoxy group or a chlorine atom, and are excellent in normal physical properties including crosslinkability, compression set resistance characteristics and strength characteristics because of their large weight average molecular weight (Mw) (Examples 6 to 14 and Comparative Examples 2 to 3). However, the acrylic rubbers (P) to (Q) are inferior in roll processability, Banbury processability, water resistance and storage stability (Comparative Example 2), and are also inferior in water resistance and storage stability (Comparative Example 3).

[0412] From Table 4-2, it can be seen that the Banbury processability of the acrylic rubber correlates with the gel amount of the methyl ethyl ketone-insoluble component, and it is understood that the lower the methyl ethyl ketone-insoluble component, the better the Banbury processability (comparison between Examples 6 to 14 and Comparative Example 2). The amount of methyl ethyl ketone-insoluble component of the acrylic rubber can be decreased by emulsion polymerization in the presence of a chain transfer agent (Examples 8 to 13 and Comparative Example 3). In particular, since the amount of methyl ethyl ketone-insoluble component rapidly increases at the end of the polymerization reaction to increase the polymerization conversion rate in order to enhance the strength characteristics, it can be seen that the generation of methyl ethyl ketone-insoluble component can be suppressed in Examples 8 to 13 where the chain transfer agent is added later at the end of the polymerization reaction. The amount of methyl ethyl ketone-insoluble component of the acrylic rubber is further significantly decreased by drying the aqueous clam with a screw-type twin-screw extrusion dryer, greatly improving the Banbury processability of the produced acrylic rubber (comparison between Examples 6 to 7 and Examples 8 to 13). In the present invention, although not shown in this example, it has been confirmed that the amount of methyl ethyl ketone-insoluble component that rapidly increases by emulsion polymerization without adding a chain transfer agent (Comparative Example 2) disappears by melt-kneading in a state substantially free of moisture (water content less than 1% by weight) in a screw-type twin-screw extrusion dryer, and the Banbury processability of the acrylic rubber can be greatly improved.

[0413] From Table 4-2, also, the storage stability of the acrylic rubber is greatly related to the specific gravity of the acrylic rubber, and it can be seen that when the specific gravity is large, the acrylic rubber does not entrap air and has excellent storage stability (comparison between Examples 6 to 7, Examples 8 to 14 and Comparative Examples 2 to 3). The acrylic rubber with a large specific gravity can be obtained by compressing the clam-shaped acrylic rubber with a beller to form a bale (Examples 8 to 14), and more preferably by extruding and laminating it into a sheet shape containing almost no air with a screw-type twin-screw extrusion dryer to form a bale (Examples 6 to 7). The storage stability of the acrylic rubber is also preferably such that the ash content is less (Examples 6 to 14). Also, the storage stability of the acrylic rubber is also contributed by the pH being 6 or less.

[0414] From Table 4-2, it can be seen that with respect to water resistance, the acrylic rubbers (G) to (O) of the present invention are overwhelmingly excellent (comparison between Examples 6 to 14 and Comparative Examples 2 to 3). From Table 4-2, it can also be seen that for the acrylic rubbers (G) to (O) with such significantly excellent water resistance, in the coagulation step of the emulsion polymerization liquid obtained by emulsion polymerization with a chain transfer agent added continuously or batchwise using an inorganic radical generator, instead of adding the coagulation liquid to the emulsion polymerization liquid, the coagulation reaction is carried out by adding it to the stirring coagulation liquid, and more preferably by vigorously stirring the coagulation liquid (stirring speed 600 rpm / peripheral speed 3.1 m / s) and increasing the coagulant concentration of the stirring coagulation liquid (comparison between Examples 6 to 14 and Comparative Example 2). Although not shown in the data of the examples of the present application, it can be seen that by this coagulation reaction, water-containing clams focused on a clam diameter in the range of 710 μm to 4.75 mm are generated, and the removal efficiency of the emulsifier and coagulant in the washing and dehydration steps with warm water is overwhelmingly improved, and the ash content in the acrylic rubber can be reduced and the water resistance can be significantly improved.

[0415] From Table 4-2, it can also be seen that with respect to water resistance, among the reactive groups, when they are carboxyl groups or epoxy groups, they are superior to chlorine atoms (comparison between Examples 8 to 9 and Examples 11 to 12 and Examples 10 and 13).

[0416] From Table 4-2, it can be seen that with respect to water resistance, furthermore, the acrylic rubbers (G) to (H) dehydrated (water squeezed out) before drying the water-containing clams have a significantly reduced ash content and improved water resistance (comparison between Examples 6 to 7 and Examples 8 to 14). Also, looking at the component amounts in the ash of the acrylic rubbers (G) to (H), most are phosphorus (P) and magnesium (Mg). It is presumed that the sodium phosphate salt of the emulsifier is salt-exchanged with magnesium sulfate of the coagulant and exists in the water-containing clams as magnesium phosphate, and although it cannot be sufficiently removed in the washing step, it can be reduced by dehydration (squeezing). It can also be seen that the components in the ash of the acrylic rubber with a large amount of phosphorus and magnesium do not deteriorate the water resistance (comparison between Examples 6 to 14 and Comparative Example 2 and Comparative Example 3).

[0417] From Table 4-2, regarding roll processability, it is closely related to the molecular weight distribution of the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn). It can be seen that the wider the molecular weight distribution, the better the roll processability (comparison between Examples 6 to 14 and Comparative Example 3 and Comparative Example 2). Also, in order to highly balance the strength characteristics and roll processability, it was important that the weight average molecular weight (Mw) was high and the molecular weight distribution focused on the high molecular weight region (the ratio (Mz / Mw) of the z average molecular weight (Mz) to the weight average molecular weight (Mw) was high).

[0418] From Tables 4-1 and 4-2, it can be seen that an acrylic rubber having excellent strength characteristics and excellent roll processability, with a large weight average molecular weight (Mw) and a wide Mw / Mn, can be produced by using a specific amount of an inorganic radical generator and a chain transfer agent, particularly n-dodecyl mercaptan (Examples 6 to 14). From Table 4-2, it can also be seen that, compared to continuously adding n-dodecyl mercaptan (Example 14), by reducing the amount of the inorganic radical generator used and adding n-dodecyl mercaptan batchwise after the initial addition without adding it initially, the roll processability can be further improved without sacrificing the strength characteristics (Examples 6 to 13). This is because by reducing the amount of the inorganic radical generator and not adding the chain transfer agent initially, the length of a single polymer chain is extended. Although it does not form distinct bimodality in the GPC chart, by producing a well-balanced high molecular weight component and low molecular weight component to increase Mw and widen Mw / Mn, the strength characteristics and roll processability are highly balanced. Also, in order to efficiently widen Mw / Mn, the number of batchwise post-additions of the chain transfer agent has a greater influence than the difference in the added amount of the batchwise post-addition. When the number of batchwise post-additions is 2 times rather than 3 times, Mw / Mn becomes wider (comparison between Examples 8 to 10 and Examples 11 to 13), but the continuous addition of the chain transfer agent limits the broadening of Mw / Mn to a certain extent (Example 14). Also, although not shown in Table 4-2, in the examples of the present application, sodium ascorbate as a reducing agent is added 120 minutes after the start of polymerization. By doing so, the generation of the high molecular weight component of the acrylic rubber becomes easier and the effect of widening Mw / Mn by the post-addition of the chain transfer agent is increased. On the other hand, although not shown in Table 4-1, when polymerizing using an organic radical generator, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) does not widen and the roll processability is inferior, which is not preferable.

[0419] [Example 15] As shown in Table 5-1, except that the monomer components were changed to 74.5 parts of ethyl acrylate, 17 parts of n-butyl acrylate, 7 parts of methoxyethyl acrylate, 1.5 parts of mono-n-butyl fumarate, and the emulsifier was changed to 1.8 parts of sodium tridecyl oxyhexaoxyethylene phosphate, the procedure was carried out in the same manner as in Example 7 to obtain an acrylic rubber (R), and each property was evaluated. The results are shown in Table 5-2. Table 5-1 also shows the water content, maximum torque, specific power, specific dynamic power, shear rate, and shear viscosity after dehydration (drainage) of the screw-type twin-screw extrusion dryer.

[0420] [Example 16] Except that the monomer components were changed to 74.5 parts of ethyl acrylate, 17 parts of n-butyl acrylate, 7 parts of methoxyethyl acrylate, 1.5 parts of mono-n-butyl fumarate, and the emulsifier was changed to sodium tridecyl oxyhexaoxyethylene phosphate, the procedure was carried out in the same manner as in Example 6 to obtain an acrylic rubber (S), and each property was evaluated. The results are shown in Table 5-2. Table 5-1 also shows the water content, maximum torque, specific power, specific dynamic power, shear rate, and shear viscosity after dehydration (drainage) of the screw-type twin-screw extrusion dryer.

[0421] [Example 17] Except that the monomer components were changed to 28 parts of ethyl acrylate, 38 parts of n-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile, and 2 parts of allyl glycidyl ether, and the operating conditions of the screw-type twin-screw extrusion dryer were changed to a high share (maximum torque of 45 N·m), the procedure was carried out in the same manner as in Example 15 to obtain an acrylic rubber (T), and each property (the compounding agent was changed to "Compounding 5") was evaluated. The results are shown in Table 5-2. Table 5-1 also shows the water content, maximum torque, specific power, specific dynamic power, shear rate, and shear viscosity after dehydration (drainage) of the screw-type twin-screw extrusion dryer.

[0422] [Example 18] The monomer components were changed to 48.5 parts of ethyl acrylate, 50 parts of n-butyl acrylate, and 1.5 parts of mono-n-butyl fumarate, and the procedure was carried out in the same manner as in Example 17 to obtain an acrylic rubber (U). Each property (the compounding agent was changed to "Compounding 3") was evaluated, and the results are shown in Table 5-2. Table 5-1 also shows the water content, maximum torque, specific power, specific power consumption, shear rate, and shear viscosity after dehydration (drainage) of the screw-type twin-screw extrusion dryer.

[0423] [Example 19] The monomer components were changed to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate, and 1.75 parts of mono-n-butyl fumarate, and the procedure was carried out in the same manner as in Example 17 to obtain an acrylic rubber (V). Each property (the compounding agent was changed to "Compounding 4") was evaluated, and the results are shown in Table 5-2. Table 5-1 also shows the water content, maximum torque, specific power, specific power consumption, shear rate, and shear viscosity after dehydration (drainage) of the screw-type twin-screw extrusion dryer.

[0424] [Example 20] The monomer components were changed to 28 parts of ethyl acrylate, 38 parts of n-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile, and 2 parts of allyl glycidyl ether, and the operating conditions of the screw-type twin-screw extrusion dryer were changed to a high share (maximum torque 45 N·m). The procedure was carried out in the same manner as in Example 16 to obtain an acrylic rubber (X). Each property (the compounding agent was changed to "Compounding 5") was evaluated, and the results are shown in Table 5-2. Table 5-1 also shows the water content, maximum torque, specific power, specific power consumption, shear rate, and shear viscosity after dehydration (drainage) of the screw-type twin-screw extrusion dryer.

[0425] [Example 21] The monomer components were changed to 48.5 parts of ethyl acrylate, 50 parts of n-butyl acrylate, and 1.5 parts of mono-n-butyl fumarate, and the procedure was carried out in the same manner as in Example 20 to obtain an acrylic rubber (Y). Each property (the compounding agent was changed to "Compounding 3") was evaluated, and the results are shown in Table 5-2. Table 5-1 also shows the water content, maximum torque, specific power, specific power consumption, shear rate, and shear viscosity after dehydration (drainage) of the screw-type twin-screw extrusion dryer.

[0426] [Example 22] The monomer components were changed to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate, and 1.75 parts of monobutyl fumarate, and the procedure was carried out in the same manner as in Example 20 to obtain an acrylic rubber (Z). Each property (the compounding agent was changed to "Compounding 4") was evaluated, and the results are shown in Table 5-2. Table 5-1 shows the water content after dehydration (drainage) of the screw-type twin-screw extrusion dryer, the maximum torque, the specific power, the specific power consumption, the shear rate, and the shear viscosity.

[0427]

Table 5-1

[0428]

Table 5-2

[0429] From Table 5-2, it can be seen that the acrylic rubbers (T) to (Z) of the present invention are excellent in normal physical properties including Banbury processability, water resistance, storage stability, crosslinkability, compression set resistance characteristics, and strength characteristics, and the roll processability is remarkably improved (comparison between Examples 17 to 22 and Examples 15 to 16). This is because the acrylic rubber composed of a high molecular weight component and a low molecular weight component obtained by post-adding a chain transfer agent and emulsion polymerization is dried at a high shear using a screw-type twin-screw extrusion dryer, resulting in an acrylic rubber with a more balanced molecular weight and molecular weight distribution, and the roll processability can be remarkably improved.

Explanation of Symbols

[0430] 1 Acrylic rubber production system 3 Coagulation device 4 Cleaning device 5 Screw-type extruder 6 Cooling device 7 Bale-forming device

Claims

1. An acrylic rubber having at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group, and a chlorine atom, or an ionic reactive group exhibiting ionic reactivity as a reactive group, and having a reactive group content of 0.001 to 5% by weight. The gel amount of the methyl ethyl ketone-insoluble matter is 30% by weight or less, the pH is 2 to 6, the ash content is 0.09 to 0.4% by weight, and the total amount of magnesium, phosphorus, calcium, sodium, and sulfur in the ash is 50% by weight or more. And an acrylic rubber having a specific gravity of 0.8 or more measured by Method A for measuring the density of crosslinked rubber in JIS K6268, which is composed of 10 to 98.9% by weight of a bonding unit (A) derived from (meth)acrylate, 0.1 to 10% by weight of a bonding unit (B) derived from a reactive group-containing monomer, and 0 to 30% by weight of a bonding unit (C) derived from other monomers.

2. The acrylic rubber according to claim 1, wherein the ash content is 0.15% by weight or less.

3. The acrylic rubber according to claim 1 or 2, wherein the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber is in the range of 1.1 to 8.

4. The acrylic rubber according to any one of claims 1 to 3, wherein the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber is 3.4 or more.

5. The acrylic rubber according to any one of claims 1 to 4, wherein the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber is in the range of 3.7 to 6.

5.

6. The acrylic rubber according to any one of claims 1 to 5, wherein the weight average molecular weight (Mw) of the acrylic rubber is 1,000,000 or more.

7. The acrylic rubber according to claim 1, wherein the bonding unit (A) derived from (meth)acrylate is at least one selected from the group consisting of (meth)acrylate alkyl esters and (meth)acrylate alkoxyalkyl esters.

8. The acrylic rubber according to claim 1, wherein the bonding unit (A) derived from (meth)acrylate is composed of a bonding unit (A1) derived from acrylate and a bonding unit (A2) derived from methacrylate.

9. The acrylic rubber according to any one of claims 1 to 8, which is in the form of a sheet or a veil.

10. An emulsion polymerization step of obtaining an emulsion polymerization liquid by emulsifying an acrylic rubber monomer component containing a reactive group-containing monomer with water and an emulsifier and then initiating polymerization in the presence of a redox catalyst composed of a radical generator and a reducing agent; A coagulation step of adding the obtained emulsion polymerization liquid to a coagulation liquid having a coagulant concentration of 1% by weight or more while stirring to coagulate and produce a water-containing crumb; A washing step of washing the produced water-containing crumb with warm water at 60°C or higher; A dehydration step of dehydrating the washed water-containing crumb to a water content of 1 to 40% by weight; A drying step of drying the dehydrated water-containing crumb to a water content of less than 1% by weight; The method for producing an acrylic rubber according to any one of claims 1 to 9, comprising:

11. The method for producing an acrylic rubber according to claim 10, wherein the dried rubber is veiled.

12. The method for producing an acrylic rubber according to claim 10 or 11, wherein the radical generator is an inorganic radical generator.

13. The method for producing an acrylic rubber according to any one of claims 10 to 12, wherein a chain transfer agent is added batchwise during the emulsion polymerization.

14. The method for producing an acrylic rubber according to any one of claims 10 to 13, wherein the drying of the water-containing crumb is performed using a screw-type twin-screw extrusion dryer.

15. The dehydration and drying steps are performed by using a screw-type twin-screw extrusion dryer having a dehydration barrel with a dehydration slit, a drying barrel under reduced pressure, and a die at the tip. The washed water-containing crumb is dehydrated in the dehydration barrel to a water content of 1 to 40% by weight and then dried in the drying barrel to a water content of less than 1% by weight, and a sheet-like dried rubber is extruded from the die. The method for producing an acrylic rubber according to any one of claims 10 to 14.

16. The method for producing an acrylic rubber according to claim 15, wherein the extruded sheet-like dried rubber is laminated and veiled.

17. The method for producing an acrylic rubber according to any one of claims 10 to 16, wherein the acrylic rubber monomer component contains an acrylate ester and a methacrylate ester.

18. A rubber composition comprising a rubber component containing the acrylic rubber according to any one of claims 1 to 9, a filler, and a crosslinking agent.

19. A method for producing a rubber composition, comprising mixing the acrylic rubber according to any one of claims 1 to 9 and a filler and then mixing a crosslinking agent.

20. A rubber crosslinked product obtained by crosslinking the rubber composition according to claim 18.

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