Acrylic rubber composition and acrylic rubber molded product

Abstract

Provided is an acrylic rubber composition providing a rubber crosslinked product with reduced compression set. The acrylic rubber composition according to one embodiment of the present invention comprises component A: acrylic rubber, and component B: a biomass-derived filler. The content of component B is 5-100 parts by weight based on 100 parts by weight of the content of component A.

Description

Acrylic rubber composition and acrylic rubber molded product

[0001] The present invention relates to an acrylic rubber composition and an acrylic rubber molded article.

[0002] Acrylic rubber is a rubber whose main component is a unit derived from an acrylic ester. Acrylic rubber has excellent heat resistance and oil resistance, and is used in automobile parts, etc. Patent Document 1 is an example of a document disclosing an invention related to acrylic rubber. This document discloses an acrylic rubber composition containing acrylic rubber, silica obtained by calcining wet-process silica, and a crosslinking agent.

[0003] JP 2004-168885 A

[0004] There is still room for further reduction in compression set in the rubber molded articles obtained from the acrylic rubber compositions disclosed in the above-mentioned prior art documents.

[0005] An object of one aspect of the present invention is to provide an acrylic rubber composition that gives a cross-linked rubber product with reduced compression set.

[0006] In order to solve the above problems, an acrylic rubber composition according to one aspect of the present invention comprises the following components A and B: component A: acrylic rubber; component B: biomass-derived filler; the content of component B is 5 to 100 parts by weight, assuming that the content of component A is 100 parts by weight.

[0007] According to one aspect of the present invention, there is provided an acrylic rubber composition that gives a cross-linked rubber product with reduced compression set.

[0008] However, the present invention is not limited to the following embodiments and various modifications may be made within the scope of the claims. Embodiments that combine technical means described in different embodiments are also included in the technical scope of the present invention.

[0009] Unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0010] As used herein, "biomass" refers to renewable biological resources (excluding fossil resources). Biomass is typically organic material, but can also be inorganic, such as eggshells and seashells. As used herein, "biomass content" refers to the weight of biomass-derived materials relative to the dry weight.

[0011] [1. Components Contained in Acrylic Rubber Composition] The acrylic rubber composition according to one embodiment of the present invention contains Component A: acrylic rubber and Component B: biomass-derived filler. The acrylic rubber composition may further contain, as an optional component, one or more selected from the group consisting of Component C: biomass-derived plasticizer, Component D: coupling agent, and Component E: pigment. The acrylic rubber composition may further contain components other than the above-mentioned Components A to E. Each of these components may contain only one type, or two or more types. Each component will be described in detail below.

[0012] Component A: Acrylic Rubber Component A is an acrylic rubber. Acrylic rubber is a rubber containing an acrylic ester as a main monomer. In one embodiment, the acrylic rubber is ACM and / or AEM.

[0013] ACM is an acrylic rubber obtained by copolymerizing an acrylic ester and a crosslinkable monomer. The acrylic ester is one or more selected from methyl acrylate, ethyl acrylate, butyl acrylate, and methoxyethyl acrylate. Examples of the crosslinkable monomer include a carboxyl group-containing monomer, an epoxy group-containing monomer, and an active chlorine-containing monomer. Among these, a carboxyl group-containing monomer is preferred from the viewpoint of heat resistance.

[0014] Examples of carboxy group-containing monomers include α,β-ethylenically unsaturated monocarboxylic acids having 3 to 12 carbon atoms, α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms, and monoesters of α,β-ethylenically unsaturated dicarboxylic acids having 3 to 11 carbon atoms with alkanols having 1 to 8 carbon atoms. Examples of α,β-ethylenically unsaturated monocarboxylic acids having 3 to 12 carbon atoms include acrylic acid, methacrylic acid, ethylacrylic acid, crotonic acid, and cinnamic acid. Examples of α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms include butenedioic acid (fumaric acid, maleic acid, etc.), itaconic acid, citraconic acid, and chloromaleic acid. Examples of monoesters of α,β-ethylenically unsaturated dicarboxylic acids having 3 to 11 carbon atoms and alkanols having 1 to 8 carbon atoms include chain alkyl butenedioates (monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monomethyl maleate, monoethyl maleate, monobutyl maleate, etc.), butenedioate monoesters having an alicyclic structure (monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclohexenyl fumarate, monocyclopentyl maleate, monocyclohexyl maleate, monocyclohexenyl maleate, etc.), itaconic acid monoesters (monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, etc.), and mono-2-hydroxyethyl fumarate. Among these, one or more selected from the group consisting of monobutyl fumarate, monobutyl maleate, monocyclohexyl fumarate, and monocyclohexyl maleate are preferred.

[0015] AEM is an acrylic rubber obtained by copolymerizing methyl acrylate, ethylene, and a crosslinkable monomer. Examples of the crosslinkable monomer include a carboxyl group-containing monomer. Examples and preferred examples of the carboxyl group-containing monomer are as described above.

[0016] Commercially available ACM and / or AEM may be used as component A. Examples of commercially available ACM include Nipol (Zeon Corporation) and NOXTITE (Unimatec Corporation). Examples of commercially available AEM include VAMAC (Celanese).

[0017] The acrylic rubber composition may contain a rubber component other than component A. Examples of rubbers other than component A include fluororubber (FKM), natural rubber (NR), styrene-butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), urethane rubber (U), and silicone rubber (Q).

[0018] The rubber component in the acrylic rubber composition is preferably mainly composed of component A. In one embodiment, the weight proportion of component A among all rubber components contained in the acrylic rubber composition is 70% by weight or more, 80% by weight or more, or 90% by weight or more. In one embodiment, the acrylic rubber composition does not contain any rubber component other than component A.

[0019] [1.2. Component B: Biomass-derived Filler] Component B is a biomass-derived filler. Component B may be a substance obtained by processing biomass, such as by pulverizing it. Component B may be a substance synthesized using biomass as a starting material. Component B may be a composite substance of a biomass-derived material and a material not derived from biomass. The biomass content of component B may be 10% or more.

[0020] Examples of component B include biomass-derived silica, cellulose fiber, ground eggshells, and ground seashells. In one embodiment, component B is biomass-derived silica. Examples of biomass-derived silica include vegetable silica (such as rice husk silica).

[0021] In one embodiment, Component B is a white filler. By using Component B as a white filler, the acrylic rubber composition is less likely to be discolored due to Component B. Therefore, color development is improved when Component E (pigment) is blended. Examples of Component B as a white filler include biomass-derived silica and cellulose fiber.

[0022] [1.3. Component C: Biomass-derived plasticizer] Component C is a biomass-derived plasticizer. Component C may be a substance extracted from biomass. Component C may be a substance synthesized using biomass as a starting material. Component C may be obtained by synthesizing a biomass-derived raw material and a non-biomass-derived raw material. The biomass content of component C may be 10% or more.

[0023] Examples of component C include fatty oils (castor oil, linseed oil, rapeseed oil, soybean oil, coconut oil, etc.) and waxes (beeswax, carnauba wax, etc.).

[0024] Commercially available products may be used as component C. Examples of commercially available products include Biocizer (Riken Vitamin Co., Ltd.); Polycizer W-1810-BIO (DIC Corporation); Adeka CycloAid PNB-205 (ADEKA Corporation); Vinicizer 105 and 124N (all from Kao Corporation); Trimex N-08A (Kao Corporation); Rika Vinyl C and S60 (all from New Japan Chemical Co., Ltd.); Sanso Cizer E-2000H and E-PO (all from New Japan Chemical Co., Ltd.); and Green Cizer BZ-100, BZ-200, BZ-300, and BZ-400 (all from New Japan Chemical Co., Ltd.).

[0025] [1.4. Component D: Coupling Agent] Component D is a coupling agent. Examples of component D include a silane coupling agent and a titanium coupling agent. Preferably, component D is a silane coupling agent. Component D bonds the inorganic component and the polymer to improve the physical properties of the cross-linked acrylic rubber.

[0026] Silane coupling agents are compounds containing silicon atoms that are used to modify the surface of materials. Silane coupling agents generally have a hydrolyzable group (such as an alkoxy group) and a reactive functional group (such as a vinyl group, (meth)acryloyl group, epoxy group, or amino group) linked to the silicon atom.

[0027] Examples of silane coupling agents include alkoxysilanes having a vinyl group (such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris(2-methoxyethoxy)silane); and alkoxysilanes having a (meth)acryloyl group (such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-acryloxypropyltrimethoxysilane). The silane coupling agent may be an oligomer of these alkoxysilanes.

[0028] [1.5. Component E: Pigment] Component E is a pigment. The pigment colors the acrylic rubber composition and the acrylic rubber molded product to a desired color. Examples of pigments include organic pigments, inorganic pigments, and fluorescent pigments. Examples of pigment hues include black, red, blue, yellow, green, brown, and white. Two or more types of pigments may be blended in an appropriate ratio to produce a desired hue.

[0029] [1.6. Other Components] The acrylic rubber composition may contain components that can be used in the rubber industry in addition to Components A to E. Examples of such components include plasticizers / softeners other than Component C, antioxidants / stabilizers, processing aids, crosslinking agents, co-crosslinking agents, crosslinking accelerators, crosslinking accelerator assistants, and crosslinking retarders.

[0030] (Plasticizer / Softener) Examples of plasticizers other than component C include coal tar, higher fatty acids or salts or esters thereof, naphthenic acid, pine oil, rosin or derivatives thereof, synthetic polymers (terpene resins, petroleum resins, coumarone-indene resins, etc.), ester-based plasticizers (dioctyl phthalate, dioctyl adipate, etc.), microcrystalline wax, poly-α-olefins (liquid polybutadiene, modified liquid polybutadiene, etc.), hydrocarbon-based synthetic lubricating oils, tall oil, and sub(factice).

[0031] Examples of higher fatty acids constituting higher fatty acids or their salts or esters include oleic acid, palmitic acid, stearic acid, lauric acid, linoleic acid, abietic acid, erucic acid, myristic acid, arachic acid, lignoceric acid, and ricinoleic acid. The higher fatty acids may be saturated or unsaturated, and preferably contain unsaturated fatty acids. The salts of higher fatty acids are usually metal salts, preferably alkali metal salts or alkaline earth metal salts. Examples of metal salts include lithium salts, potassium salts, sodium salts, barium salts, calcium salts, magnesium salts, aluminum salts, iron salts, and zinc salts. Specific examples of higher fatty acids or their salts include ricinoleic acid, palmitic acid, stearic acid, lauric acid, barium stearate, zinc stearate, and calcium stearate.

[0032] (Antiaging Agent / Stabilizer) Examples of the antiaging agent include amine-based antiaging agents, phenol-based antiaging agents, and sulfur-based antiaging agents.

[0033] Specific examples of amine-based antioxidants include aromatic amines (such as phenylbutylamine and N,N-di-2-naphthyl-p-phenylenediamine) and amine-ketones. Specific examples of phenol-based antioxidants include monophenols (such as dibutylhydroxytoluene), bisphenols, and polyphenols (such as tetrakis[methylene(3,5-di-t-butyl-4-hydroxy)hydrocinnamate]methane). Specific examples of sulfur-based antioxidants include thioethers (such as bis[2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl]sulfide), dithiocarbamates (such as nickel dibutyldithiocarbamate), thiourea, 2-mercaptobenzoylimidazole, 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, dilauryl thiodipropionate, and distearyl thiodipropionate.

[0034] (Processing aid) Examples of processing aids include the higher fatty acids or salts or esters thereof listed in the section on plasticizers and softeners. Further examples of processing aids include higher fatty acid amides (e.g., oleic acid amide).

[0035] (Crosslinking Agent) Examples of crosslinking agents include polyamine compounds. Polyamine compounds include compounds having two or more amino groups and compounds that become equipped with two or more amino groups in an environment where a crosslinking reaction proceeds. Examples of suitable polyamine compounds include compounds in which multiple hydrogen atoms in an aliphatic hydrocarbon or aromatic hydrocarbon are converted into amino groups or hydrazide groups (-CONHNH ２ ) substituted compounds. Specific examples of the polyamine compound include aliphatic polyamine compounds (hexamethylenediamine, hexamethylenediamine carbamate, tetramethylenepentamine, hexamethylenediamine-cinnamaldehyde adduct, hexamethylenediamine-dibenzoate salt, etc.); aromatic polyamine compounds (2,2-bis{4-(4-aminophenoxy)phenyl}propane, 4,4'-methylenedianiline, m-phenylenediamine, p-phenylenediamine, 4,4'-methylenebis(o-chloroaniline), etc.); and compounds having two or more hydrazide structures (isophthalic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, etc.). Among these, aliphatic polyamine compounds are preferred, and hexamethylenediamine carbamate is particularly preferred.

[0036] [2. Composition of Acrylic Rubber Composition] In the acrylic rubber composition, the lower limit of the content of Component B is 5 parts by weight or more, based on 100 parts by weight of the content of Component A. In one embodiment, the lower limit of the content of Component B may be 7 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, or 40 parts by weight or more, based on 100 parts by weight of the content of Component A. In one embodiment, the upper limit of the content of Component B is 100 parts by weight or less, based on 100 parts by weight of the content of Component A. In one embodiment, the lower limit of the content of Component B may be 95 parts by weight or less, 90 parts by weight or less, 85 parts by weight or less, 80 parts by weight or less, 75 parts by weight or less, 70 parts by weight or less, 65 parts by weight or less, 60 parts by weight or less, 55 parts by weight or less, or 50 parts by weight or less, based on 100 parts by weight of the content of Component A.

[0037] In the acrylic rubber composition, the lower limit of the content of Component C may be 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 2 parts by weight or more, or 3 parts by weight or more, based on 100 parts by weight of the content of Component A. In the acrylic rubber composition, the upper limit of the content of Component C may be 20 parts by weight or less, 19 parts by weight or less, or 18 parts by weight or less, based on 100 parts by weight of the content of Component A.

[0038] In the acrylic rubber composition, the lower limit of the content of Component D may be 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.1 parts by weight or more, relative to 100 parts by weight of the content of Component A. In the acrylic rubber composition, the upper limit of the content of Component D may be 10 parts by weight or less, 8 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, or 1 part by weight or less, relative to 100 parts by weight of the content of Component A.

[0039] In the acrylic rubber composition, the lower limit of the content of Component E may be 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight or more, relative to 100 parts by weight of the content of Component A. In the acrylic rubber composition, the upper limit of the content of Component E may be 10 parts by weight or less, 8 parts by weight or less, or 5 parts by weight or less, relative to 100 parts by weight of the content of Component A.

[0040] In one embodiment, the biomass degree of the acrylic rubber composition is 5% or more. The biomass degree of the acrylic rubber composition may be 10% or more, 15% or more, 20% or more, 25% or more, or 30% or more. The upper limit of the biomass degree of the acrylic rubber composition may be 80% or less, 70% or less, or 60% or less. It can be said that an acrylic rubber composition having a biomass degree within the above range has a higher biomass degree and a smaller environmental impact than conventional products. In this respect, the present invention can also contribute to achieving Goal 13 of the Sustainable Development Goals (SDGs) advocated by the United Nations, "Take urgent action to combat climate change."

[0041] In order to improve the biomass content of the acrylic rubber composition, a biomass-derived component may be used or the amount of the biomass-derived component may be increased. As described above, at least a portion of Components B and C is a biomass-derived component. Furthermore, if the monomer constituting Component A is a biomass-derived monomer, at least a portion of Component A is also a biomass-derived component. Examples of such monomers include ethyl acrylate, butyl acrylate, and ethylene. In one embodiment, Component A is a biomass-derived monomer and contains one or more monomers selected from the group consisting of ethyl acrylate, butyl acrylate, and ethylene as structural units.

[0042] [3. Cross-linked acrylic rubber product and acrylic rubber molded article] The cross-linked acrylic rubber product according to one embodiment of the present invention is obtained by cross-linking the acrylic rubber composition according to one embodiment of the present invention. For example, an acrylic rubber composition can be produced by kneading the components described in section [1]. A kneader can be used to knead the components. Examples of kneaders include an open roll, a kneader, a planetarium mixer, a Banbury mixer, an internal mixer, and an extruder. The kneading temperature may be 25 to 200°C. The kneading time may be 1 minute to 1 hour.

[0043] A cross-linked acrylic rubber product can be produced by curing the acrylic rubber composition. The curing temperature may be 120 to 200°C. The curing time may be 10 seconds to 120 minutes. The cured molded product may be further subjected to secondary curing. The secondary curing temperature may be 120 to 250°C. The secondary curing time may be 30 minutes to 4 hours.

[0044] An acrylic rubber molded article according to one embodiment of the present invention includes the cross-linked acrylic rubber according to one embodiment of the present invention. The acrylic rubber molded article can be produced by molding and cross-linking the acrylic rubber composition. Examples of molding methods include injection molding, transfer molding, compression molding, press processing, and extrusion molding.

[0045] In one embodiment, the acrylic rubber molded article is a seal or gasket material. In this specification, a seal refers to a material that is fitted between moving members to form a seal. In this specification, a gasket refers to a material that is fitted between stationary members to form a seal.

[0046] [3.1. Physical Properties of Crosslinked Acrylic Rubber] The upper limit of the compression set of the crosslinked acrylic rubber is preferably 80% or less, more preferably 70% or less, even more preferably 60% or less, particularly preferably 50% or less, and even more preferably 40% or less. In this specification, the compression set is measured by a method in accordance with JIS K6262 (see Examples for details).

[0047] The lower limit of the Shore A hardness of the acrylic rubber crosslinked product is preferably 10 or more, and more preferably 20 or more. The upper limit of the Shore A hardness of the acrylic rubber crosslinked product is preferably 80 or less. If the Shore A hardness is within the above range, it can be said to have softness suitable for use as a gasket. In this specification, the Shore A hardness is measured using a Type A durometer based on JIS K6253. For more specific examples of the measurement method, see the examples of this application.

[0048] [4. Summary] The present invention includes the following aspects. <1> An acrylic rubber composition comprising the following components A and B: Component A: acrylic rubber; Component B: biomass-derived filler; the content of Component B is 5 to 100 parts by weight, relative to 100 parts by weight of the content of Component A. <2> The acrylic rubber composition according to <1>, in which Component A contains a unit derived from a biomass-derived monomer. <3> The acrylic rubber composition according to <1> or <2>, further comprising the following component C: Component C: biomass-derived plasticizer. <4> The acrylic rubber composition according to any one of <1> to <3>, further comprising the following component D: Component D: coupling agent. <5> The acrylic rubber composition according to any one of <1> to <4>, further comprising the following component E: Component E: pigment. <6> The acrylic rubber composition according to any one of <1> to <5>, having a biomass degree of 5% or more. <7> An acrylic rubber molded article obtained by crosslinking and molding the acrylic rubber composition according to any one of <1> to <6>. <8> The acrylic rubber molded article according to <7>, which is a sealing material or a gasket material.

[0049] Hereinafter, one embodiment of the present invention will be described in detail with reference to examples, although the present invention is not limited to these examples.

[0050] [Materials used] ●Component A ・Acrylic rubber (ACM, Nipol AR12, Zeon Corporation) ●Component B ・Biomass silica (derived from rice husks) ●Component B' (filler that is not component B) ・Mineral silica (derived from silica sand, Ultrasil VN2, Evonik) ●Component D ・Coupling agent (3-(2-aminoethylamino)propyltrimethoxysilane, KBM-603, Shin-Etsu Chemical Co., Ltd.) ●Component E ・Pigment 1 (carbon black (black pigment), SEAST G116, Tokai Carbon Co., Ltd.) ・Pigment 2 (ferric oxide (red pigment), TODA COLOR 120ED, Toda Kogyo Co., Ltd.) ●Others ・Plasticizer (polyester compound, Polycizer W-320, DIC Corporation) ・Stearic acid ・Anti-aging agent (4,4'-bis(α,α-dimethylbenzyl)diphenylamine, Nocrac CD, Ouchi Shinko Chemical Industry Co., Ltd.) ・Wax (hydrocarbon, PARAFFIN WAX-135, Nippon Seiro Co., Ltd.) Crosslinking agent (hexamethylenediamine carbamate, VC-1A, Chemours Inc.) Crosslinking accelerator (1,3-di-o-tolylguanidine, Noccela DT, Ouchi Shinko Chemical Industry Co., Ltd.)

[0051] Examples 1 to 4, Comparative Examples 1 to 3 Crosslinked rubber sheets were prepared according to the following procedure. The crosslinked rubber sheets served as the material for preparing test specimens in the tests described below. 1. The components listed in Table 1, excluding the crosslinking agent, were kneaded in a kneader. The temperature during kneading was 130°C. The kneading time was 10 minutes. 2. The crosslinking agent was added and kneaded in an open roll. The temperature during kneading was 30 to 40°C. The kneading time was 10 minutes. 3. An uncrosslinked rubber sheet was prepared from the resulting kneaded product. 4. The uncrosslinked rubber sheet was press-crosslinked at 170°C for 20 minutes. 5. Secondary crosslinking was further performed at 170°C for 4 minutes. In this manner, a crosslinked rubber sheet with a thickness of 2 mm and an O-ring with a wire diameter of 2.4 mm were obtained.

[0052] [Test Method] [1. Compression Set] The compression set of the cross-linked acrylic rubber was measured using a method in accordance with JIS K6262. The specific procedure is as follows: 1. The O-rings obtained in step 5 of the Examples and Comparative Examples were used as test specimens. 2. Using a spacer with a thickness of 1.8 mm, the test specimen was compressed by 25% and held in a constant temperature bath at 150°C for a predetermined time. The predetermined time was 72 hours or 168 hours. 3. The test specimen was removed from the constant temperature bath and quickly released from the spacer. 4. The test specimen was placed on a wooden stand and left at the standard temperature of the test room (23°C) for 30 minutes. 5. The thickness of the test specimen was measured and the compression set was calculated. The calculation formula is as follows: Compression set (%) = (thickness of test specimen before test (mm) - thickness of test specimen after test (mm)) ÷ (thickness of test flame before test (mm) - thickness of spacer (mm)) x 100

[0053] [2. Shore A Hardness] Shore A hardness was measured using a method in accordance with JIS K6253. The specific procedure is as follows. 1. Three crosslinked rubber sheets obtained in step 5 of the Examples and Comparative Examples were stacked to prepare a measurement sample having a thickness of 6 mm. 2. Measurement was performed using a Type A durometer, and the peak value was taken as the Shore A hardness. The measurement environment was a temperature of 23°C and a relative humidity of 50%.

[0054] [3. Heat Aging Test] A heat aging test was performed in accordance with JIS K6257. The test specimen was left standing in air at 150°C for 72 hours. The increase or decrease in Shore A hardness before and after the heat aging test (hardness before the test - hardness after the test) was calculated. The method for measuring Shore A hardness was as described above.

[0055] [4. Oil Immersion Test] An oil immersion test was performed in accordance with JIS K6268. Specifically, the test specimen was left in lubricating oil (IRM903) at 150°C for 72 hours. The increase or decrease in Shore A hardness before and after the oil immersion test (hardness after test - hardness before test) was calculated. The method for measuring Shore A hardness was as described above. In addition, the rate of change in volume before and after the oil immersion test ((volume after test - volume before test) ÷ volume before test × 100) was measured. The volume measurement method was in accordance with JIS K6268.

[0056] [Results] The results are shown in Table 1.

[0057] As can be seen from Table 1, the difference between Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 was whether or not the type of filler used was derived from biomass. In these Examples and Comparative Examples, when the cross-linked acrylic rubber products of the Examples were compared with the cross-linked acrylic rubber products of the Comparative Examples, the former tended to have a smaller compression set. These results suggest that the acrylic rubber composition according to one embodiment of the present invention can produce a cross-linked acrylic rubber product that has a small compression set and high recovery force even after long-term compression. In particular, in an acrylic rubber composition in which the amount of Component B was approximately 50 parts by weight per 100 parts by weight of Component A, the effect of reducing compression set in the resulting cross-linked acrylic rubber product was remarkable.

[0058] Furthermore, looking at the results of the Examples and Comparative Examples, there were no significant differences in Shore A hardness, density, heat aging test results, and oil immersion test results, depending on whether the filler type was biomass-derived or not. In other words, this suggests that with regard to these physical properties, the acrylic rubber composition according to one embodiment of the present invention can produce a cross-linked acrylic rubber product with performance equal to or better than that of conventional techniques.

[0059] As can be seen from Example 4, even when the type of component E was changed, a crosslinked acrylic rubber product was successfully obtained.

[0060] The present invention can be used for sealing materials, gasket materials, etc.

[0061] This international application claims priority based on Japanese Patent Application No. 2024-052107, filed on March 27, 2024, the entire contents of which are incorporated herein by reference.

[0062] The above descriptions of specific embodiments of the present invention have been presented for purposes of illustration. They are not intended to be exhaustive or to limit the invention to the precise forms described. Numerous modifications and variations will be apparent to those skilled in the art in light of the above description.

Claims

1. An acrylic rubber composition comprising the following components A and B: component A: acrylic rubber; component B: biomass-derived filler; and the content of component B is 5 to 100 parts by weight, relative to 100 parts by weight of the content of component A.

2. The acrylic rubber composition according to claim 1, wherein said component A contains a unit derived from a biomass-derived monomer.

3. The acrylic rubber composition according to claim 1, further comprising the following component C: Component C: a biomass-derived plasticizer.

4. The acrylic rubber composition according to claim 1, further comprising the following component D: Component D: a coupling agent.

5. The acrylic rubber composition according to claim 1, further comprising the following component E: Component E: pigment.

6. The acrylic rubber composition according to claim 1, having a biomass content of 5% or more.

7. An acrylic rubber molded product obtained by crosslinking and molding the acrylic rubber composition according to any one of claims 1 to 6.

8. The acrylic rubber molded product according to claim 7, which is a sealing material or gasket material.

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