Foam layer-producing composition, method for producing foam layer, and foamed rubber roller

Abstract

To provide a foam layer-producing composition for producing a foam layer of a foamed rubber roller, a method for producing the foam layer, and a foamed rubber roller comprising the foam layer.SOLUTION: A foam layer-producing composition of the present invention comprises a silicone rubber, water, a water-absorbing polymer, a surfactant, and an alkaline agent, and is characterized in that a weight ratio (X wt.%) of the water-absorbing polymer and a weight ratio (Y wt.%) of the surfactant with respect to 100 pts.wt. of the silicone rubber satisfy [0<X≤1.75], [0<Y≤0.5], and [0.625<X+3Y<3.0]. A method for producing a foam layer of the present invention comprises the steps of: applying alkaline treatment to a polymer dispersion; preparing a foam layer-producing composition; molding a cured silicone rubber; and producing the foam layer. A foamed rubber roller of the present invention is characterized in that the foam layer comprises the silicone rubber, the water-absorbing polymer having undergone the alkaline treatment, and the surfactant.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a foam layer manufacturing composition for manufacturing a foam layer of a foam rubber roller, a method for manufacturing a foam layer, and a foam rubber roller provided with a foam layer. [Background technology]

[0002] 2. Description of the Related Art In electrophotographic image forming apparatuses such as copying machines and laser beam printers, a thermal fixing method is generally used to fix an unfixed toner image onto a sheet of paper. In the thermal fixing method, a fixing roller that performs fixing and heating, and a pressure roller that comes into pressure contact with the fixing roller, are used, each of which has a rubber layer on the outer periphery of a core material such as aluminum or iron, and a release layer of fluororesin or the like on the surface of the rubber layer. In particular, in recent years, foam rubber rollers whose rubber layer is made of foam rubber with open cells have become popular in order to suppress changes in the surface hardness and outer diameter of the rubber layer.

[0003] Generally, methods for producing foamed rubber include (1) a method using a heated foaming agent, (2) a method using resin microballoons, and (3) an elution method. Of these, (1) the method using a heated foaming agent forms bubbles in the rubber by foaming the foaming agent during crosslinking. (2) The method using resin microballoons forms bubbles by dispersing resin microballoons in the rubber. (3) The elution method forms bubbles by dispersing a water-soluble powder in a rubber composition, curing the rubber, and then eluting the water-soluble powder. Patent Document 1 discloses (3) a method for manufacturing a rubber roller for thermal fixing using an elution method, in which sugar powder such as glucose or lactose is dispersed in a silicone rubber composition to cause primary curing, and after curing, the mold is immersed in water to cause the sugar powder to elute into the water, and after elution, the silicone rubber together with the core material is pulled out of the mold and subjected to secondary curing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-8990

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the elution method using sugar powder, sugar precipitates from water after elution and needs to be treated as industrial waste, resulting in increased disposal costs. Furthermore, since a step of immersing the foamed rubber roller in water to elute sugar is required between primary vulcanization and secondary vulcanization, the number of steps is large, the processing cost is high, and there is room for improvement in terms of manufacturing efficiency and manufacturing cost.

[0006] An object of the present invention is to provide a composition for manufacturing a foamed layer, a method for manufacturing the foamed layer, and a foamed rubber roller provided with the foamed layer manufactured using the composition for foaming, in order to solve the above problems.

Means for Solving the Problems

[0007] The composition for manufacturing a foamed layer of the present invention is a composition for manufacturing a foamed layer in a foamed rubber roller including a core material and a foamed layer provided on the outer periphery of the core material, and includes silicone rubber, water, a water-absorbing polymer, a surfactant, and an alkaline agent. The weight ratio (Xwt%) of the water-absorbing polymer and the weight ratio (Ywt%) of the surfactant with respect to 100 parts by weight of silicone rubber satisfy the following formulas (1) to (3). 0 < X ≦ 1.75 ·· Formula (1) 0 < Y ≦ 0.5 ·· Formula (2) 0.625 < X + 3Y < 3.0 ·· Formula (3)

[0008] The method for manufacturing the foam layer of the present invention is a method for manufacturing a foam layer in a foam rubber roller including a core material and a foam layer provided on the outer periphery of the core material, the method comprising: a step of alkali-treating a polymer dispersion containing water and a water-absorbing polymer; a step of preparing a composition for manufacturing a foam layer by mixing the polymer dispersion with a liquid silicone rubber to which a surfactant is added; a step of primary vulcanizing the composition for manufacturing a foam layer in a mold to form a silicone rubber cured body; and a step of demolding the silicone rubber cured body and performing secondary vulcanization to manufacture a foam layer. In the composition for manufacturing a foam layer, the weight ratio (Xwt%) of the water-absorbing polymer and the weight ratio (Ywt%) of the surfactant with respect to 100 parts by weight of the silicone rubber satisfy the following formulas (1) to (3). 0 < X ≤ 1.75 ··· Formula (1) 0 < Y ≤ 0.5 ··· Formula (2) 0.625 < X + 3Y < 3.0 ··· Formula (3)

[0009] The foam rubber roller of the present invention is a foam rubber roller including a core material and a foam layer provided on the outer periphery of the core material, wherein the foam layer contains silicone rubber, a water-absorbing polymer that has been alkali-treated, and a surfactant, and the weight ratio (Xwt%) of the water-absorbing polymer and the weight ratio (Ywt%) of the surfactant with respect to 100 parts by weight of the silicone rubber satisfy the following formulas (1) to (3). 0 < X ≤ 1.75 ··· Formula (1) 0 < Y ≤ 0.5 ··· Formula (2) 0.625 < X + 3Y < 3.0 ··· Formula (3)

Effects of the Invention

[0010] In the composition for manufacturing a foam layer of the present invention, by using a water-absorbing polymer as a material for continuous cell forming, moisture volatilizes simultaneously with secondary vulcanization during the process of manufacturing the foam layer, so there is no disposal cost as industrial waste such as sugar powder. Furthermore, an elution step of immersing the foam rubber roller in water is unnecessary, and the foam layer can be manufactured in two steps of primary vulcanization and secondary vulcanization, so the manufacturing efficiency is high and the manufacturing cost is relatively low. Furthermore, by increasing the dispersibility of the water-absorbent polymer in the silicone rubber through alkali treatment and specifying the range of the weight ratio of the water-absorbent polymer to the silicone rubber and the surfactant, the compression set and open cell ratio of the foamed layer can be optimized, and a high-quality foamed rubber roller for an image-forming device can be obtained. [Brief explanation of the drawings]

[0011] [Figure 1] Foam rubber roller illustration [Figure 2] Enlarged cross-section of foam layer DETAILED DESCRIPTION OF THE INVENTION

[0012] The foam layer manufacturing composition, the foam layer manufacturing method, and the foam rubber roller of the present invention will be described in detail below with reference to the drawings.

[0013] <1> Foam rubber roller Foam rubber roller A is a roller used in electrophotographic copiers, and is used as a fixing roller, pressure roller, transport roller, etc. Here, the "fixing roller" is a roller that applies heat to paper onto which toner has been transferred, fixing the toner to the paper. The "pressure roller" is a roller that pairs with the fixing roller and presses the paper against the fixing roller to adhere the toner to the paper. The "transport roller" is a roller that moves the paper within the device. The foam rubber roller A comprises a core material A1 made of aluminum alloy, iron, stainless steel, etc., a foam layer A2 provided on the outer periphery of the core material A1, and a release layer A3 covering the outer periphery of the foam layer A2 (Figure 1). The thickness of each layer varies depending on the use and specifications of the foam rubber roller A, but typically the foam layer A2 has a thickness of about 1 to 10 mm, and the release layer A3 has a thickness of about 10 to 100 μm. When the foam rubber roller A is a transport roller, the release layer A3 is not an essential component.

[0014] <1.1> Compression set and open cell ratio The fuser roller and pressure roller work as a pair, sandwiching the paper between them and transporting it at high speed. Therefore, if the compression set of the foam layer A2 is large, the contact width (nip width) between the fuser roller and pressure roller will fluctuate, which could result in uneven fusing and affect print quality. Furthermore, if the compression set of the foam layer of the transport roller is large, the contact resistance when the paper comes into contact with it will be different from that of other parts, causing uneven transport and possibly resulting in uneven printing. Therefore, the smaller the compression set of the foam layer A2, the better, and it is desirable for it to be 30% or less. Furthermore, the foam layer A2 contains numerous cells (voids) within it, but if the cell continuity (open cell ratio) is low, isolated cells that do not communicate with the outside will be formed within the foam layer A2. If the isolated cells burst within the foam layer A2 during use of a fixing roller or the like, this can cause a decrease in hardness and may degrade print quality. Therefore, the higher the open cell ratio of the foam layer A2, the better. If the water absorption rate is used as a measure of the open cell ratio, a water absorption rate of 20% or more is desirable.

[0015] <2> Composition for producing foam layer The foam layer producing composition 1 is a composition for producing the foam layer A2. The foam layer manufacturing composition 1 comprises at least silicone rubber 10, water 20, water-absorbing polymer 30, surfactant 40, and alkaline agent 50, and is liquid at room temperature. The foam layer-producing composition 1 is cured by vulcanization according to a predetermined procedure to form the foam layer A2 of the foam rubber roller A.

[0016] <2.1> Water-absorbent polymer The water-absorbing polymer 30 is a material that thickens the water 20, disperses the water component in the silicone rubber 10, and forms cells in the foam layer A2. The higher the weight ratio of the water-absorbent polymer 30 to the silicone rubber 10, the more cells there are in the foam layer A2. However, if the weight ratio of the water-absorbent polymer 30 is too high, the water-absorbent polymer 30 remains in the foam layer A2 after vulcanization, causing the compression set to worsen (increase). By treating the water-absorbing polymer 30 with alkali, the thickening performance is improved, the dispersibility of the cells in the silicone rubber 10 is improved, and the cells become dense and uniform.

[0017] <2.2> Surfactants The surfactant 40 is a material that uniformly emulsifies the water 20 in the composition of the silicone rubber 10 and makes the foam layer A2 porous. The higher the weight ratio of surfactant 40 to silicone rubber 10, the higher the open cell ratio of the cells in silicone rubber 10. However, if the weight ratio is too high, surfactant 40 remains in foam layer A2 after vulcanization, worsening the compression set. Furthermore, if the weight ratio of surfactant 40 is too small, the open cells will be reduced, and the moisture remaining in the cells of silicone rubber 10 will burst during vulcanization, resulting in a deterioration in the compression set of foam layer A2.

[0018] <2.3> Blending of the composition for manufacturing the foam layer From the above <2.1> and <2.2>, in order to produce a foamed layer A2 having a small compression set and a high open cell ratio, it is necessary to set upper and lower limits for the weight ratio of the water-absorbent polymer 30, the weight ratio of the surfactant 40, and the weight ratio of the total amount of the water-absorbent polymer 30 and the surfactant 40 to the silicone rubber 10 in the composition for producing a foamed layer 1. In the present invention, the formulation of the foam layer manufacturing composition 1 satisfies the following formulas (1) to (3) in terms of the weight ratio (X wt%) of the water-absorbing polymer 30 to the silicone rubber 10 and the weight ratio (Y wt%) of the surfactant 40 to the silicone rubber 10, respectively.

[0019]

number

[0020] <2.4> Examples of materials for the composition for manufacturing the foam layer Examples of the silicone rubber 10 that can be used include an addition reaction type liquid silicone rubber that hardens through an addition reaction of a platinum catalyst, a condensation reaction type liquid silicone rubber that hardens through a condensation reaction, and an organic peroxide type liquid silicone rubber that hardens through a peroxidation reaction. The silicone rubber 10 may also contain a reinforcing filler such as carbon black, silica, or calcium carbonate as a reinforcing material. The water 20 may be ion-exchanged water, distilled water, tap water, well water, or the like. As the water-absorbent polymer 30, for example, alginic acid, sodium alginate, polyvinyl alcohol, carboxyvinyl polymer, or sodium salt of carboxyvinyl polymer can be used. The surfactant 40 can be selected from anionic, cationic, amphoteric, or nonionic surfactants, and examples thereof include sorbitan monooleate and sorbitan trioleate in sorbitan fatty acid esters, and various monooleates, dioleates, or trioleates in glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, or polyoxysorbitol fatty acid esters. As the alkaline agent 50, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate, ammonia, methylamine, ethylamine, or an aqueous solution thereof can be used.

[0021] <3> mold release layer The release layer A3 is a layer for improving the releasability from the toner, and may be configured as a tube structure that covers the outer periphery of the foam layer A2. The release layer A3 may be made of, for example, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVdF), etc. Also, instead of fluororesin, polyimide resin, polyamide-imide resin, etc. may be used. It is desirable to previously roughen the inner surface of the tube of the release layer A3 by etching.

[0022] <4> Manufacturing method of foam rubber roller When the foamed rubber roller A is a fixing roller, the foamed rubber roller A is manufactured by, for example, the following method.

[0023] <4.1> Alkali treatment A water-absorbing polymer 30 is mixed into water 20 to produce a polymer dispersion 30a, and the polymer dispersion 30a is then subjected to an alkali treatment. In this example, an aqueous sodium hydroxide solution is used as the alkaline agent 50, and the aqueous sodium hydroxide solution is mixed into the polymer dispersion 30a. The aqueous sodium hydroxide solution neutralizes the polymer dispersion 30a, thickening it and turning it into a gel.

[0024] <4.2> Adjustment of mixture composition The polymer dispersion 30a is added to and mixed with the liquid silicone rubber 10 to which the surfactant 40 has been added, to prepare the foam layer manufacturing composition 1.

[0025] <4.3> Setting the mold A cylindrical mold is set upright, the bottom of which is sealed with a bottom plate having an injection hole, a fluororesin tube that will form the release layer A3 is inserted into the mold, and the core material A1 is set upright and fixed in the center of the fluororesin tube. It is desirable to coat the outer surface of the core material A1 and the inner surface of the fluororesin tube with a primer.

[0026] <4.4> Primary vulcanization The foam layer manufacturing composition 1 is injected into the space between the fluororesin tube and the core material A1 in the mold through the injection hole in the bottom plate, and the top of the mold is sealed with a lid to carry out primary vulcanization. The vulcanization temperature is preferably 80°C to 90°C, and the vulcanization time is preferably about 20 to 100 minutes. By primary vulcanization, the foam layer manufacturing composition 1 is thermally cured, and a silicone rubber cured body 1a is formed between the core material A1 and the release layer A3, with the water-retaining water-absorbent polymer 30 dispersed therein.

[0027] <4.5> Post-vulcanization The silicone rubber cured body 1a and the release layer A3 are removed from the mold together with the core A1, and then secondary vulcanization is carried out. The vulcanization temperature is preferably 160°C to 230°C, and the vulcanization time is preferably about 4 to 6 hours. The secondary vulcanization stabilizes the physical properties of the silicone rubber cured body 1a, and simultaneously volatilizes the moisture in the water-absorbent polymer 30, generating fine interconnected cells within the silicone rubber cured body 1a to form a foam layer A2. Through the above steps, a three-layer foamed rubber roller A can be obtained, in which a silicone rubber foam layer A2 and a fluororesin release layer A3 are laminated in this order on a core A1. If the foamed rubber roller A is a conveying roller without the release layer A3, the same manufacturing steps are carried out except for the fluororesin tube.

[0028] <5> Comparison Test In order to produce a foamed rubber roller suitable for use as a fixing roller for an image forming apparatus, test pieces of foamed layers were produced using foamed layer production compositions of various blends, and comparative tests were carried out on the physical properties of the test pieces. [Silicone Rubber] Addition reaction type liquid silicone rubber [Water-absorbent polymer 1] Cross-linked acrylic acid-based water-soluble polymer ("AQUPEC (registered trademark) HV-505E" manufactured by Sumitomo Seika Chemicals Co., Ltd.) [Water-absorbent polymer 2] Cross-linked acrylic acid-based water-soluble polymer (Sumitomo Seika Chemicals Co., Ltd. "AQUPEC HV-501E") [Water] Ion-exchanged water [Surfactant] Sorbitan monooleate (Kao Corporation, "Rheodor (registered trademark) SP-O10V") [Alkaline agent] Sodium hydroxide solution [Primary vulcanization] Vulcanization temperature: 90°C Vulcanization time: 25 minutes [Secondary vulcanization] Vulcanization temperature: 230°C Vulcanization time: 5 hours [Physical properties] Water absorption (%), compression set (%) [Test piece] Cylinder (diameter 29.0±0.5mm, height 12.5±0.5mm) [Evaluation method (water absorption)] Original method (described below) [Evaluation method (compression set)] JIS k 6249

[0029] <5.1> Water absorption test The water absorption test was carried out in the following manner. (1) Cut out a test piece and measure its dry weight (W0). (2) Submerge the test piece in a container of water, using a wire mesh or similar to hold the top of the test piece underwater so that the entire test piece is submerged. (3) The pressure in the container is reduced to approximately 65 mgHg. The reduced pressure is maintained for 3 minutes, and the air in the open-cell cells is replaced with water. (4) Release the vacuum and return to normal pressure. (5) Remove the test piece, wipe off any water droplets on the surface, and measure the weight (W1) after decompression, taking care not to wipe off the water inside the cell. (6) Calculate the water absorption rate. Water absorption rate=(W1-W0) / W0×100(%)

[0030] <6> Required performance of foam rubber rollers As mentioned above in <1.1>, the compression set of the foam layer of the foam rubber roller must be 30% or less. Also, the more open cells there are, the greater the water absorption rate. Therefore, the water absorption rate is used as a measure of the open cell rate, and the water absorption rate must be 20% or more.

[0031] <7> Test results The test results of the comparison test are shown in Tables 1 to 5 below.

[0032] [Table 1]

[0033] [Table 2]

[0034] [Table 3]

[0035] [Table 4]

[0036]

Table 5

[0037] <7.1> Examples 1 - 17 (Tables 1 - 3) In Examples 1 - 17, in the weight ratio (Xwt%) of the water-absorbing polymer to 100 parts by weight of the silicone rubber in the composition for producing the foam layer, [0 < X ≤ 1.75], in the weight ratio (Ywt%) of the surfactant to 100 parts by weight of the silicone rubber, [0 < Y ≤ 0.5], and in the weight ratio of the water-absorbing polymer and the surfactant to 100 parts by weight of the silicone rubber, [0.625 < X + 3Y < 3.0] is satisfied. With the above formulations, all of Examples 1 - 17 achieved a compression set of 30% or less and a water absorption rate of 20% or more. Therefore, Examples 1 - 17 meet the performance requirements as the foam layer of the foamed rubber roller for electrophotographic copiers.

[0038] <7.2> Comparative Examples 1 - 12 (Tables 4, 5) In Comparative Examples 1 - 4, the water-absorbing polymer was not alkali-treated. As a result, in Comparative Example 1, the water absorption rate was below the standard, and in Comparative Examples 2 - 4 where the surfactant was increased, in exchange for the improvement of the water absorption rate, the compression set increased and exceeded the standard. In Comparative Examples 5 and 6, since they do not contain a surfactant, the water absorption rate is below the standard. Especially in Comparative Example 5, the amount of the water-absorbing polymer is too large and the compression set also exceeds the standard. In Comparative Example 7, since the total amount of the water-absorbing polymer and the surfactant is small, the water absorption rate is below the standard. In Comparative Examples 8 - 12, since the amount of the surfactant or the total amount of the surfactant and the silicone rubber is too large, the compression set of all of them exceeds the standard. From the above, none of Comparative Examples 1 - 12 meet the quality level of the foam layer for the foamed rubber roller of the present invention.

[0039] <8> Comparison of Cross Sections (Figure 2) Figure 2 shows a magnified cross-sectional photograph (50 times) of the foam layer. In Example 8, countless tiny cells are uniformly distributed within the silicone rubber. In Comparative Example 2, the cells were not uniformly dispersed and there was a large variation in cell size. This is thought to be because the water-absorbent polymer was not alkali-treated, resulting in insufficient dispersion of the cells within the silicone rubber. [Explanation of symbols]

[0040] 1. Composition for manufacturing foam layer 1a Silicone rubber hardened body 10 Silicone rubber 20 water 30 Water-absorbent polymer 30a Polymer Dispersion 40 Surfactants 50 Alkaline Agent A Foam rubber roller A1 Core material A2 foam layer A3 release layer

Claims

1. A composition for producing a foam layer in a foam rubber roller having a core material and a foam layer provided on the outer periphery of the core material, comprising: The composition comprises silicone rubber, water, a water-absorbing polymer, a surfactant, and an alkaline agent; The weight ratio (X wt%) of the water-absorbing polymer and the weight ratio (Y wt%) of the surfactant relative to 100 parts by weight of the silicone rubber satisfy the following formulas (1) to (3): composition. 0<X≦1.75...Formula (1) 0<Y≦0.5...Formula (2) 0.625<X+3Y<3.0...Formula (3)

2. A method for manufacturing a foam layer in a foam rubber roller having a core material and a foam layer provided on the outer periphery of the core material, comprising: A step of alkali treating a polymer dispersion containing water and a water-absorbing polymer; a step of mixing the polymer dispersion with liquid silicone rubber containing a surfactant to prepare a composition for producing a foam layer; a step of subjecting the foam layer-producing composition to primary vulcanization in a mold to form a silicone rubber cured body; and a step of demolding the cured silicone rubber and subjecting it to secondary vulcanization to produce a foam layer, In the composition for manufacturing a foam layer, the weight ratio (X wt%) of the water-absorbing polymer and the weight ratio (Y wt%) of the surfactant relative to 100 parts by weight of the silicone rubber satisfy the following formulas (1) to (3): Manufacturing method. 0<X≦1.75...Formula (1) 0<Y≦0.5...Formula (2) 0.625<X+3Y<3.0...Formula (3)

3. A foam rubber roller comprising a core material and a foam layer provided on the outer periphery of the core material, the foam layer contains silicone rubber, an alkali-treated water-absorbing polymer, and a surfactant; The weight ratio (X wt%) of the water-absorbing polymer and the weight ratio (Y wt%) of the surfactant relative to 100 parts by weight of the silicone rubber satisfy the following formulas (1) to (3): Foam rubber roller. 0<X≦1.75...Formula (1) 0<Y≦0.5...Formula (2) 0.625<X+3Y<3.0...Formula (3)

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