Plasticizer for rubber, rubber composition, and molded article

Abstract

The present invention provides a plasticizer for rubber capable of exhibiting sufficient plasticizing effect on rubber while improving compatibility with rubber. Specifically, the plasticizer for rubber comprises a diester obtained from a polyoxyalkylene glycol and a monocarboxylic acid as reaction raw materials, wherein the monocarboxylic acid is a fatty acid having 12 to 24 carbon atoms and includes a polyunsaturated fatty acid having 12 to 24 carbon atoms.

Description

Plasticizer for rubber, rubber composition, molded article

[0001] The present invention relates to a plasticizer for rubber, a rubber composition, and a molded article.

[0002] Rubber has a problem of poor flexibility at low temperatures. For example, in rubber parts for automobiles, in applications where oil resistance and cold resistance are important, plasticizers such as dioctyl phthalate, dioctyl adipate, and dibutyl diglycol adipate are blended and used. The need to improve the flexibility of rubber is strong, and various plasticizers have been proposed for further improving the flexibility of rubber (for example, Patent Documents 1-2).

[0003] Japanese Patent Application Laid-Open No. 2019-178229, Japanese Patent Application Laid-Open No. 2008-201933

[0004] All of the above plasticizers have a problem that their compatibility with rubber is not sufficient. There are problems such that the plasticizer bleeds on the surface of rubber products in a high-temperature environment, or a sufficient plasticizing effect cannot be exhibited in a low-temperature environment. Also, when the physical properties of the plasticizer are structured with priority given to compatibility with rubber, for example, in products such as rubber parts for automobiles that have many opportunities to come into contact with oil, there is also a problem that the plasticizer migrates into the oil and the plasticizing effect is lost.

[0005] The problem to be solved by the present invention is to provide a plasticizer for rubber that can improve compatibility with rubber and exhibit a sufficient plasticizing effect on rubber.

[0006] As a result of intensive studies to solve the above problems, the inventors have found that a diester having a specific structure can exhibit high compatibility with rubber and a sufficient plasticizing effect, and have completed the present invention.

[0007] In other words, the present invention relates to the following rubber plasticizers, etc. 1. A rubber plasticizer which is a diester made from polyoxyalkylene glycol and a monocarboxylic acid as reaction raw materials, wherein the monocarboxylic acid is a fatty acid having 12 to 24 carbon atoms, and contains a polyunsaturated fatty acid having 12 to 24 carbon atoms. 2. The rubber plasticizer according to 1, wherein the polyunsaturated fatty acid is a polyunsaturated fatty acid having 12 to 22 carbon atoms. 3. The rubber plasticizer according to 1 or 2, wherein the content of the polyunsaturated fatty acid in the monocarboxylic acid is 30 mol% or more. 4. The rubber plasticizer according to any one of 1 to 3, wherein the monocarboxylic acid is one or more selected from the group consisting of soybean oil fatty acid, tall oil fatty acid, corn oil fatty acid, coconut oil fatty acid, safflower oil fatty acid, linseed oil fatty acid, palm kernel oil fatty acid, palm oil fatty acid, olive oil fatty acid, castor oil fatty acid, and rapeseed oil fatty acid. 5. 1. A rubber plasticizer according to any one of 1 to 4, wherein the monocarboxylic acid does not contain monocarboxylic acids having an unsaturated alicyclic structure or aromatic monocarboxylic acids. 6. A rubber plasticizer according to any one of 1 to 5, wherein the polyoxyalkylene glycol is one or more selected from polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene ether glycol and polyneopentyl glycol. 7. A rubber plasticizer according to any one of 1 to 6, wherein the number average molecular weight of the polyoxyalkylene glycol is in the range of 200 to 1,500. 8. A rubber plasticizer according to any one of 1 to 7, wherein the iodine value of the diester is in the range of 20 to 200. 9. A rubber composition containing rubber and a rubber plasticizer according to any one of 1 to 8. 10. The rubber composition according to 9, wherein the rubber is a diene-based rubber. 11. The rubber composition according to 9 or 10, containing the rubber plasticizer in an amount of 10 to 100 parts by mass per 100 parts by mass of the rubber. 12. A molded article of the rubber composition according to any one of 9 to 11.

[0008] The present invention provides a plasticizer for rubber that can improve compatibility with rubber while exhibiting a sufficient plasticizing effect on rubber.

[0009] One embodiment of the present invention will be described below. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications without impairing the effects of the present invention. The compounds used herein may be derived from fossil resources or from biological resources.

[0010] [Rubber Plasticizer] The rubber plasticizer of the present invention is a diester reacted with polyoxyalkylene glycol and a monocarboxylic acid as reaction raw materials, wherein the monocarboxylic acid is a fatty acid having 12 to 24 carbon atoms and includes a polyunsaturated fatty acid having 12 to 24 carbon atoms. It is presumed that because the rubber plasticizer has carbon-carbon unsaturated bonds derived from the polyunsaturated fatty acid, during the vulcanization of the rubber composition, the carbon-carbon unsaturated bond portion of the plasticizer also reacts to form a thioether bond, thereby increasing the compatibility between the plasticizer and rubber and improving the plasticizing effect. Since the rubber plasticizer of the present invention can form a thioether bond with rubber, it can solve the problem of the plasticizer migrating to oil components other than rubber, for example, and losing its plasticizing effect on rubber. The reaction raw materials of the rubber plasticizer of the present invention (hereinafter sometimes referred to as "the diester of the present invention") will be described below.

[0011] (Polyoxyalkylene glycol) The reaction raw material, polyoxyalkylene glycol, is a compound represented by the following general formula (POAG-1), for example.

[0012] (In the above formula (POAG-1), R １１ R is an alkylene group having 1 to 6 carbon atoms. x is the number of repetitions, and x is, for example, an integer of 4 or more, preferably an integer of 5 or more, and more preferably an integer of 8 or more. The upper limit of x is, for example, 60. Multiple R １１ They may be the same or they may be different.

[0013] The polyoxyalkylene glycol is preferably one or more selected from polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene ether glycol, and polyneopentyl glycol.

[0014] The number-average molecular weight of polyoxyalkylene glycol is, for example, in the range of 100 to 3,000, preferably in the range of 100 to 2,000, and more preferably in the range of 200 to 1,500. The number-average molecular weight of polyoxyalkylene glycol is confirmed by the method described in the examples.

[0015] The polyoxyalkylene glycol used may be a single type or two or more types may be used in combination.

[0016] (Monocarboxylic acid) The monocarboxylic acid used as a reaction raw material is a fatty acid having 12 to 24 carbon atoms, and the fatty acid includes a polyunsaturated fatty acid having 12 to 24 carbon atoms. In this application, "polyunsaturated fatty acid" means a fatty acid having two or more carbon-carbon unsaturated bonds, and the number of carbon atoms in the polyunsaturated fatty acid is in the range of 12 to 24, preferably in the range of 12 to 22.

[0017] Specific examples of polyunsaturated fatty acids include diunsaturated fatty acids such as linoleic acid, eicosadienoic acid, and docosadienoic acid; triunsaturated fatty acids such as linolenic acid, pinolenic acid, eleostearic acid, meadic acid, and eicosatrienoic acid; and tetraunsaturated fatty acids such as stearic acid, arachidonic acid, eicosatetraenoic acid, and adrenaline.

[0018] The polyunsaturated fatty acids used may be a single type or two or more types may be used in combination.

[0019] The reaction raw material, monocarboxylic acid, is a fatty acid having 12 to 24 carbon atoms, including a polyunsaturated fatty acid having 12 to 24 carbon atoms, and may further contain a saturated fatty acid having 12 to 24 carbon atoms and / or a monounsaturated fatty acid having 12 to 24 carbon atoms.

[0020] Examples of saturated fatty acids having 12 to 24 carbon atoms include lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, and arachidic acid. The saturated fatty acids having 12 to 24 carbon atoms may have secondary hydroxyl groups and / or tertiary hydroxyl groups in their fatty acid chains, and may also include 12-hydroxystearic acid residues.

[0021] Examples of monounsaturated fatty acids having 12 to 24 carbon atoms include oleic acid, myristoleic acid, palmitrenic acid, elaidic acid, gadoleic acid, eicosenoic acid, and erucic acid.

[0022] The saturated fatty acids used may be one type alone or two or more types in combination. The monounsaturated fatty acids used may be one type alone or two or more types in combination.

[0023] When a monocarboxylic acid contains a polyunsaturated fatty acid having 12 to 24 carbon atoms and a saturated fatty acid and / or a monounsaturated fatty acid having 12 to 24 carbon atoms, the proportion of polyunsaturated fatty acids in the monocarboxylic acid is preferably 30 mol% or more, more preferably 40 mol% or more, and more preferably 50 mol% or more. There is no particular upper limit to the proportion of polyunsaturated fatty acids in the monocarboxylic acid, but it is, for example, 100 mol% or less, 90 mol% or less, 80 mol% or less, or 70 mol% or less.

[0024] The reaction raw material, monocarboxylic acid, is preferably a vegetable oil fatty acid, and more preferably one or more selected from the group consisting of soybean oil fatty acid, tall oil fatty acid, corn oil fatty acid, coconut oil fatty acid, safflower oil fatty acid, linseed oil fatty acid, palm kernel oil fatty acid, palm oil fatty acid, olive oil fatty acid, castor oil fatty acid, and rapeseed oil fatty acid. The above vegetable oil fatty acids are fatty acids extracted from soybeans, pine, corn, coconut, safflower, flax, palm kernel, palm, olive, castor, and rapeseed, and are all mixtures of two or more fatty acids having 12 to 24 carbon atoms, and include polyunsaturated fatty acids.

[0025] The reaction raw material monocarboxylic acid is a fatty acid having 12 to 24 carbon atoms, but it may also contain monocarboxylic acids other than fatty acids having 12 to 24 carbon atoms, as long as it does not impair the effects of the present invention. The reaction raw material monocarboxylic acid may be, for example, a fatty acid having 12 to 24 carbon atoms in an amount of 90 mol% or more, 95 mol% or more, 98 mol% or more, 99 mol% or more, or 100 mol%.

[0026] The monocarboxylic acid used as a reaction raw material preferably substantially does not contain monocarboxylic acids having an unsaturated alicyclic structure or aromatic monocarboxylic acids. If the monocarboxylic acid contains monocarboxylic acids having an unsaturated alicyclic structure such as abietic acid, neoabietic acid, palastic acid, pimaric acid, or isopimaric acid, the resulting diester may not have sufficient thioether bonds formed during vulcanization. Furthermore, if the monocarboxylic acid contains aromatic monocarboxylic acids such as benzoic acid or dehydroabietic acid, the aromatic ring structure may not adequately ensure compatibility with rubber. "Substantially does not contain" means that the total content of monocarboxylic acids having an unsaturated alicyclic structure and aromatic monocarboxylic acids in the monocarboxylic acid is 5 mol% or less, 3 mol% or less, 1 mol% or less, less than 1 mol%, or 0 mol%.

[0027] The monocarboxylic acid preferably consists substantially of a polyunsaturated fatty acid having 12 to 24 carbon atoms, a saturated fatty acid having 12 to 24 carbon atoms, and / or a monounsaturated fatty acid having 12 to 24 carbon atoms. Here, "substantially" means that in the monocarboxylic acid, the total content of the polyunsaturated fatty acid having 12 to 24 carbon atoms, the saturated fatty acid having 12 to 24 carbon atoms, and the monounsaturated fatty acid having 12 to 24 carbon atoms is 90 mol% or more, 95 mol% or more, 98 mol% or more, 99 mol% or more, or 100 mol%.

[0028] (Diester) The iodine value of the diester of the present invention may be in the range of 20 to 200, preferably in the range of 30 to 130, and more preferably in the range of 50 to 100. The iodine value of the diester is confirmed by the method described in the examples.

[0029] The acid value of the diester of the present invention may be in the range of 0.01 to 6.0, preferably in the range of 0.05 to 5.0, and more preferably in the range of 0.1 to 3.0. The acid value of the diester is confirmed by the method described in the examples.

[0030] [Method for producing diesters] The diesters of the present invention can be produced, for example, by reacting a polyoxyalkylene glycol and a monocarboxylic acid containing a polyunsaturated fatty acid in a known manner, and it is preferable to use an excess amount of monocarboxylic acid.

[0031] In the production of the diester of the present invention, the reaction of the reaction raw materials may be carried out in the presence of an esterification catalyst as needed, for example, at a temperature range of 180 to 250°C for 10 to 25 hours. The temperature, time, and other conditions of the esterification reaction are not particularly limited and may be set as appropriate.

[0032] Examples of the esterification catalysts include titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate; tin-based catalysts such as dibutyltin oxide; and organic sulfonic acid-based catalysts such as p-toluenesulfonic acid.

[0033] The amount of esterification catalyst used can be set as appropriate, but it is usually used in the range of 0.001 to 0.1 parts by mass per 100 parts by mass of the total amount of reaction raw materials.

[0034] [Rubber Composition] The rubber composition of the present invention contains the rubber plasticizer and rubber of the present invention. The rubber contained in the rubber composition of the present invention is not particularly limited as long as it is a rubber that is used after vulcanization (rubber having carbon-carbon unsaturated bonds, so-called "diene rubber"), and examples include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), ethylene-propylene-diene copolymer rubber (EPDM), isoprene-butadiene rubber (IBR), nitrile rubber, hydrogenated nitrile rubber, etc.

[0035] The rubber composition of the present invention may also contain non-diene rubbers such as silicone rubber, acrylic rubber (ACM, ANM), and urethane rubber (AU, EU).

[0036] The rubber composition may contain one type of rubber alone, or two or more types of rubber in combination.

[0037] The content of the plasticizer of the present invention in the rubber composition of the present invention is, for example, in the range of 1 to 200 parts by mass, preferably in the range of 5 to 150 parts by mass, and more preferably in the range of 10 to 100 parts by mass, per 100 parts by mass of rubber.

[0038] The rubber composition of the present invention may contain the rubber plasticizer and rubber of the present invention, but may also contain other components. Examples of other components contained in the rubber composition include reinforcing agents, silane coupling agents, vulcanization agents, vulcanization accelerators, co-crosslinking agents, vulcanization aids, processing aids, anti-aging agents, plasticizers other than the rubber plasticizer of the present invention, etc.

[0039] Reinforcement agents are added to rubber composition molded bodies to improve their mechanical properties and include oxide-based fillers such as silica, alumina, magnesium oxide, barium oxide, calcium oxide, and talc; hydroxide-based fillers such as aluminum hydroxide and magnesium hydroxide; sedimentary rock-based fillers such as diatomaceous earth and limestone; clay mineral-based fillers such as kaolinite and montmorillonite; magnetic-based fillers such as ferrite, iron, and cobalt; conductive fillers such as silver, gold, copper, and alloys; and carbon black and calcium carbonate.

[0040] When using carbon black as a reinforcing material, the grade of the carbon black may be any of the following: SAF, ISAF, HAF, EPC, XCF, FEF, GPF, HMF, SRF, FT, MT, etc.

[0041] The reinforcing agent contained in the rubber composition may be a single type or two or more types may be used in combination.

[0042] If the rubber composition of the present invention contains a reinforcing agent, the amount of the reinforcing agent is, for example, in the range of 1 to 100 parts by mass, preferably in the range of 1 to 50 parts by mass, per 100 parts by mass of rubber.

[0043] Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, vinyltrichlorosilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N,N'-bis(3-(trimethoxysilyl)propyl)ethylenediamine, polyoxyethylene propyltrialkoxysilane, polyethoxydimethylsiloxane, p-styryltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, and the like.

[0044] The silane coupling agent contained in the rubber composition may be used alone or in combination of two or more.

[0045] When the rubber composition of the present invention contains a silane coupling agent, the content of the silane coupling agent is, for example, in the range of 0.2 to 10 parts by mass, preferably in the range of 0.5 to 9 parts by mass, and more preferably in the range of 1 to 8 parts by mass with respect to 100 parts by mass of the rubber.

[0046] The vulcanizing agent can be classified into two types: sulfur-based vulcanizing agents and peroxide-based vulcanizing agents. Examples of sulfur-based vulcanizing agents include sulfur, sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, selenium dithiocarbamate, etc. Examples of peroxide-based vulcanizing agents include peroxyketals such as 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)octane, 1,1-bis(t-butylperoxy)cyclododecane; dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, t-butylperoxy-2-ethylhexanoate, t-butylperoxy-3,5,5-trimethylhexanoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, etc.

[0047] The vulcanizing agent contained in the rubber composition may be used alone or in combination of two or more.

[0048] When the rubber composition of the present invention contains a vulcanizing agent, the content of the vulcanizing agent is, for example, in the range of 0.2 to 15 parts by mass, preferably in the range of 0.3 to 10 parts by mass, and more preferably in the range of 1 to 7 parts by mass with respect to 100 parts by mass of the rubber.

[0049] Examples of vulcanization accelerators include thiazole compounds such as N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, N,N'-diisopropyl-2-benzothiazole sulfenamide, N-(tert-butyl)-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole, 2-(4-morpholinodithio)benzothiazole, 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, and dibenzothiadyl disulfide; and guanidine compounds such as diphenylguanidine, triphenylguanidine, and diorthotrylguanidine. Examples include aldehyde amine compounds such as acetaldehyde-aniline condensate and butyraldehyde-aniline condensate; imidazoline compounds such as 2-mercaptoimidazoline; thiourea compounds such as diethylthiourea and dibutylthiourea; thiram compounds such as tetramethylthiuram monosulfide, dibenzothiazyl disulfide, and tetramethylthiuram disulfide; dithioate compounds such as zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and tellurium diethyldithiocarbamate; thiourea compounds such as ethylenethiourea and N,N'-diethylthiourea; xantate compounds such as zinc dibutylxatonate; and zinc oxide.

[0050] The vulcanization accelerator contained in the rubber composition may be a single type or two or more types may be used in combination.

[0051] When the rubber composition of the present invention contains a vulcanization accelerator, the amount of the vulcanization accelerator is, for example, in the range of 0.1 to 15 parts by mass, preferably in the range of 0.5 to 10 parts by mass, per 100 parts by mass of rubber.

[0052] When using a peroxide-based crosslinking agent as the above crosslinking agent, the rubber composition may further contain a co-crosslinking agent for purposes such as improving the vulcanization rate of the rubber composition or the physical properties of the resulting molded article.

[0053] Examples of cocrosslinking agents include polyethylene glycol dimethacrylate, diallyl phthalate, triallyl isocyanurate, triallyl cyanurate, tetrahydrofurfuryl methacrylate, ethylene dimethacrylate, 1,3-butylene dimethacrylate, and trimethylolpropane trimethacrylate.

[0054] The cocrosslinking agent contained in the rubber composition may be a single type or two or more types may be used in combination.

[0055] If the rubber composition of the present invention contains a co-crosslinking agent, the amount of the co-crosslinking agent is, for example, in the range of 1 to 10 parts by mass per 100 parts by mass of rubber.

[0056] Examples of vulcanization aids include magnesium oxide and zinc oxide.

[0057] The vulcanization aid contained in the rubber composition may be a single type or two or more types may be used in combination.

[0058] If the rubber composition of the present invention contains a vulcanization aid, the amount of the vulcanization aid is, for example, in the range of 1 to 20 parts by mass per 100 parts by mass of rubber.

[0059] Examples of processing aids include higher fatty acids such as ricinoleic acid, stearic acid, palmitic acid, and lauric acid; salts of higher fatty acids such as barium stearate, zinc stearate, and calcium stearate; and esters of higher fatty acids such as ricinoleic acid, stearic acid, palmitic acid, and lauric acid.

[0060] The processing aid contained in the rubber composition may be a single type or two or more types may be used in combination.

[0061] If the rubber composition of the present invention contains a processing aid, the amount of the processing aid is, for example, in the range of 0.1 to 10 parts by mass, preferably in the range of 0.1 to 5 parts by mass, per 100 parts by mass of rubber.

[0062] Anti-aging agents are added to prevent the deterioration of molded articles obtained from rubber compositions over time. Examples include aromatic secondary amine-based anti-aging agents such as phenylbutylamine, N,N-di-2-naphthyl-p-phenylenediamine, and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine; dibutylhydroxytoluene and tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Examples include phenolic antioxidants such as bis[2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl] sulfide; dithiocarbamate antioxidants such as dibutyldithiocarbamate nickel; and sulfur-based antioxidants such as 2-mercaptobenzoylimidazole, zinc salt of 2-mercaptobenzoylimidazole, dilaurylthiodipropionate, and distearylthiodipropionate.

[0063] The rubber composition may contain one type of antioxidant, or two or more types may be used in combination.

[0064] If the rubber composition of the present invention contains an anti-aging agent, the amount of the anti-aging agent is, for example, in the range of 0.3 to 10 parts by mass, preferably in the range of 0.5 to 7 parts by mass, and more preferably in the range of 0.7 to 5 parts by mass, per 100 parts by mass of rubber.

[0065] [Method for preparing the rubber composition] The rubber composition of the present invention can be prepared by known methods. For example, methods include mixing each component contained in the rubber composition using a kneading machine such as a mixer, kneader, or roll, or preparing a solution in which each component contained in the rubber composition is dissolved or dispersed, and then removing the solvent from the solution.

[0066] [Molded Article] The molded article of the present invention is obtained by vulcanizing (crosslinking) the rubber composition of the present invention. Known methods can be used as methods for vulcanizing the rubber composition of the present invention. Specific methods for vulcanizing the rubber composition include: (1) a method of pre-molding a rubber composition containing a vulcanizing agent into a desired shape by extrusion molding, press molding, injection molding, roll processing, etc., and heating the obtained pre-molded article; (2) a method of molding a rubber composition containing a vulcanizing agent into a desired shape by extrusion molding, press molding, injection molding, roll processing, etc., and heating it at the same time; and (3) a method of pre-molding a rubber composition containing a vulcanizing agent into a desired shape by extrusion molding, press molding, injection molding, roll processing, etc., and heating it at the same time (primary vulcanization), and further heating the pre-molded article (secondary vulcanization).

[0067] The molded articles of the present invention include sealing materials such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, well head seals, shock absorber seals, gas sealing seals for air conditioning systems, and valve seats; gaskets such as intake manifold gaskets, cylinder head gaskets, rocker cover gaskets, oil pan gaskets, and battery separator gaskets; rolls such as printing rolls, steelmaking rolls, papermaking rolls, industrial rolls, and office machine rolls; belts such as flat belts, V-belts, V-ribbed belts, timing belts, toothed belts, and conveyor belts; fuel hoses, turbos It can be used in a wide range of applications, including hoses such as air hoses, oil hoses, radiator hoses, heater hoses, water hoses, vacuum brake hoses, control hoses, air conditioning hoses, brake hoses, power steering hoses, marine hoses, etc.; boots such as propeller shaft boots, constant velocity joint boots, rack and pinion boots, etc.; damping rubber parts such as cushioning materials, dynamic dampers, rubber couplings, air springs, vibration dampers, clutch facings, etc.; cooling piping, dust covers, automotive interior components, friction materials, tires, coated cables, shoe soles, electromagnetic shielding, etc.

[0068] The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0069] In the embodiments of this invention, the acid value and viscosity values ​​were evaluated by the following methods. <Method for measuring acid value> Measured according to the method in accordance with JIS K0070-1992. <Method for measuring viscosity> Measured according to the method in accordance with JIS K6901-1986.

[0070] In the present invention, the number-average molecular weight of polyalkylene glycol is a value converted to polystyrene based on GPC measurement, and the measurement conditions are as follows: [GPC Measurement Conditions] Measurement device: Tosoh Corporation high-speed GPC device "HLC-8420GPC" Column: Tosoh Corporation "TSKgel SuperMultiporeHZ-N" x 4 Detector: RI (differential refractometer) Data processing: Tosoh Corporation "EcoSEC Data Analysis Version 1.07" Column temperature: 40°C Developing solvent: Tetrahydrofuran Flow rate: 0.35 mL / min Sample: 20 mg of the sample was dissolved in 10 ml of tetrahydrofuran, and the resulting solution was filtered through a microfilter to be used as the sample. Sample injection volume: 20 μl Standard substance: Tosoh Corporation "PStQuick MP-N"

[0071] (Synthesis Example 1: Synthesis of Plasticizer A) 379 g of polyethylene glycol (number average molecular weight 300, 1.3 mol), 768 g of soybean oil fatty acid (2.8 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The mixture was heated in stages to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer A (acid value 0.2, viscosity 60 mPa·s (25°C)). Soybean oil fatty acid is a monocarboxylic acid substantially composed of palmitic acid (saturated fatty acid), stearic acid (saturated fatty acid), oleic acid (monounsaturated fatty acid), linoleic acid (polyounsaturated fatty acid), and α-linolenic acid (polyounsaturated fatty acid), and is a monocarboxylic acid containing 30 mol% or more of polyounsaturated fatty acids (linoleic acid and αounsaturated fatty acid).

[0072] (Synthesis Example 2: Synthesis of Plasticizer B) 554 g of polyethylene glycol (number average molecular weight 600, 0.9 mol), 561 g of soybean oil fatty acid (2.0 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The mixture was heated in stages to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer B (acid value 0.4, viscosity 100 mPa·s (25°C)).

[0073] (Synthesis Example 3: Synthesis of Plasticizer C) 385 g of polyethylene glycol (number average molecular weight 300, 1.3 mol), 762 g of tall oil fatty acid (2.8 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The mixture was heated in stages to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer C (acid value 1.0, viscosity 80 mPa·s (25°C)). Tall oil fatty acid is a monocarboxylic acid substantially composed of oleic acid (monounsaturated fatty acid) and linoleic acid (polyounsaturated fatty acid), and is a monocarboxylic acid containing 30 mol% or more of polyounsaturated fatty acid (linoleic acid).

[0074] (Synthesis Example 4: Synthesis of Plasticizer D) 560 g of polyethylene glycol (number average molecular weight 600, 0.9 mol), 555 g of tall oil fatty acid (2.1 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The mixture was heated in stages to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer D (acid value 0.8, viscosity 140 mPa·s (25°C)).

[0075] (Synthesis Comparative Example 1: Synthesis of Plasticizer A') 560 g of polyethylene glycol (number average molecular weight 300, 1.9 mol), 592 g of 2-ethylhexanoic acid (4.1 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The mixture was heated in stages to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer A' (acid value 0.1, viscosity 30 mPa·s (25°C)).

[0076] (Synthesis Comparative Example 2: Synthesis of Plasticizer B') 726 g of polyethylene glycol (number average molecular weight 600, 1.2 mol), 384 g of 2-ethylhexanoic acid (2.7 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The temperature was gradually increased to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer B' (acid value 0.1, viscosity 80 mPa·s (25°C)).

[0077] (Synthesis Comparative Example 3: Synthesis of Plasticizer C') 466 g of polyethylene glycol (number average molecular weight 300, 1.6 mol), 683 g of lauric acid (3.4 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The temperature was gradually increased to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer C' (acid value 0.8, viscosity 50 mPa·s (25°C)).

[0078] (Synthesis Comparative Example 4: Synthesis of Plasticizer D') 642 g of polyethylene glycol (number average molecular weight 600, 1.1 mol), 471 g of lauric acid (2.4 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The mixture was heated in stages to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer D' (acid value 0.9, viscosity 100 mPa·s (25°C)).

[0079] (Synthesis Comparative Example 5: Synthesis of Plasticizer E') 459 g of polyethylene glycol (number average molecular weight 300, 1.5 mol), 690 g of hydrogenated coconut oil fatty acid (3.4 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The temperature was gradually increased to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer E' (acid value 1.3, viscosity 60 mPa·s (25°C)). Hydrogenated coconut oil fatty acid is a vegetable oil fatty acid obtained by hydrogenating coconut oil fatty acid to convert all unsaturated fatty acids in coconut oil fatty acid into saturated fatty acids.

[0080] (Synthesis Comparative Example 5: Synthesis of Plasticizer F') 635 g of polyethylene glycol (number average molecular weight 600, 1.1 mol), 477 g of hydrogenated coconut oil fatty acid (2.3 mol), and 0.34 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2-liter four-necked flask equipped with a thermometer, stirrer, and reflux condenser. The mixture was heated in stages to 230°C while stirring under a nitrogen atmosphere, and heating was continued at 230°C, with the generated water being continuously removed to obtain plasticizer F' (acid value 1.1, viscosity 110 mPa·s (25°C)).

[0081] (Examples 1-4 and Comparative Examples 1-6: Evaluation of Plasticizers and Molded Articles Using Plasticizers) The plasticizers produced in the synthesis examples and comparative examples were evaluated as follows. The results are shown in Tables 1 and 2.

[0082] (Iodine Value) The iodine value of the plasticizers prepared in the synthesis examples and comparative examples was evaluated based on section 2.3.4 of the 2013 edition of the Japan Oil Chemists' Society's Standard Test Methods for Analysis of Fats and Oils. The results are shown in Table 1.

[0083] (Preparation of rubber composition and production and evaluation of molded articles) 100 parts by mass of nitrile rubber ("Nipol 1042" manufactured by Nippon Zeon Co., Ltd., acrylonitrile content: 33% by mass), 30 parts by mass of a plasticizer shown in Table 1 or 2, 60 parts by mass of carbon black (grade: SRF), 5.0 parts by mass of zinc oxide, 1.5 parts by mass of tetramethylthiuram disulfide, 1.5 parts by mass of N-cyclohexyl-2-benzothiazole sulfenamide, 1.0 part by weight of stearic acid, and 0.5 parts by mass of sulfur were kneaded in a Banbury mixer and roll to prepare an unvulcanized rubber composition.

[0084] (Compatibility) The obtained unvulcanized rubber composition was primary vulcanized by pressing at 170°C for 20 minutes, and then secondary vulcanized by further heating in an oven at 170°C for 240 minutes to produce a test vulcanized rubber sheet (thickness 2.0 mm). From this sheet, 2.0 mm thick sheets measuring 5 cm x 5 cm were prepared. The prepared sheets were exposed to a 120°C environment for 70 hours. After that, the surface condition of the sheets was evaluated according to the following evaluation criteria. The results are shown in Tables 1 and 2. ○: When the surface of the sheet is visually inspected, no foreign matter such as powder or viscosity (bleed) is observed, and when the surface of the sheet is touched with a finger, no bleeding is observed. ×: When the surface of the sheet is visually inspected, bleeding is observed, or when the surface of the sheet is touched with a finger, bleeding is observed.

[0085] (Oil Resistance Evaluation) The obtained unvulcanized rubber composition was primary vulcanized by pressing at 170°C for 20 minutes, and then secondary vulcanized by further heating in an oven at 170°C for 240 minutes to prepare a vulcanized rubber sheet (thickness 2.0 mm) for testing. The obtained vulcanized rubber sheet was punched out with a JIS No. 3 dumbbell to make test specimens, and the tensile strength of these specimens was measured in an environment of 120°C according to JIS K6251:2017. Separately prepared test specimens were immersed in JIS No. 2 oil at 120°C for 70 hours, and the tensile strength of the oil-immersed specimens was measured in the same manner as above. The rate of change in tensile strength was calculated using the tensile strength of the oil-immersed specimens and the tensile strength of the unimmersed specimens (tensile strength of oil-immersed specimen / tensile strength of unimmersed specimen × 100 - 100). The results are shown in Tables 1 and 2. A smaller value indicates better oil resistance of the plasticizer.

[0086] During the oil resistance evaluation described above, the weights of test specimens immersed in oil and those not immersed in oil were measured, and the weight change rate was also calculated (weight of oil-immersed test specimen / weight of non-oil-immersed test specimen × 100 - 100). The results are shown in Tables 1 and 2. A smaller absolute value of this formula indicates that the plasticizer has superior oil resistance.

[0087] (Cold resistance evaluation) The obtained unvulcanized rubber composition was primary vulcanized by pressing at 170°C for 20 minutes, and then secondary vulcanized by further heating in an oven at 170°C for 240 minutes to produce a vulcanized rubber sheet (thickness 2.0 mm) for testing. The obtained vulcanized rubber sheet was punched out into strips measuring 40.0 mm × 6.0 mm × 2.0 mm, and the low-temperature impact embrittlement temperature of these test pieces was measured according to JIS K6261-2:2017. The results are shown in Tables 1 and 2. A larger absolute value indicates that the plasticizer has superior cold resistance.

[0088]

[0089]

[0090] The results in Tables 1 and 2 show that the rubber plasticizer of the present invention exhibits excellent compatibility with rubber and provides a high plasticizing effect. This is presumed to be because the plasticizer has unsaturated bonds derived from polyunsaturated fatty acids, and during vulcanization, the plasticizer reacts with the rubber to form thioether bonds, thereby suppressing bleeding. On the other hand, in Comparative Examples 1 and 2, 2-ethylhexanoic acid was used as the monocarboxylic acid, which is the reaction raw material for the plasticizer. While this improved compatibility with rubber, it is presumed that because it is a short-chain fatty acid, the plasticizer easily migrated to the oil, thus impairing the plasticizing effect. Furthermore, in Comparative Examples 3-6, since they do not contain unsaturated bonds derived from polyunsaturated fatty acids, the aforementioned bleeding suppression effect was not obtained, and the plasticizing effect was presumed to be impaired.

Claims

1. A rubber plasticizer which is a diester reacted with polyoxyalkylene glycol and a monocarboxylic acid, wherein the monocarboxylic acid is a fatty acid having 12 to 24 carbon atoms, and the rubber plasticizer contains a polyunsaturated fatty acid having 12 to 24 carbon atoms.

2. The plasticizer for rubber according to claim 1, wherein the polyunsaturated fatty acid is a polyunsaturated fatty acid having 12 to 22 carbon atoms.

3. The plasticizer for rubber according to claim 1, wherein the content of the polyunsaturated fatty acid in the monocarboxylic acid is 30 mol% or more.

4. The rubber plasticizer according to claim 1, wherein the monocarboxylic acid is one or more selected from the group consisting of soybean oil fatty acid, tall oil fatty acid, corn oil fatty acid, coconut oil fatty acid, safflower oil fatty acid, linseed oil fatty acid, palm kernel oil fatty acid, palm oil fatty acid, olive oil fatty acid, castor oil fatty acid, and rapeseed oil fatty acid.

5. The rubber plasticizer according to claim 1, wherein the monocarboxylic acid does not contain monocarboxylic acids having an unsaturated alicyclic structure or aromatic monocarboxylic acids.

6. The rubber plasticizer according to claim 1, wherein the polyoxyalkylene glycol is one or more selected from polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene ether glycol, and polyneopentyl glycol.

7. The rubber plasticizer according to claim 1, wherein the number-average molecular weight of the polyoxyalkylene glycol is in the range of 200 to 1,500.

8. The rubber plasticizer according to claim 1, wherein the iodine value of the diester is in the range of 20 to 200.

9. A rubber composition containing rubber and a rubber plasticizer according to any one of claims 1 to 8.

10. The rubber composition according to claim 9, wherein the rubber is a diene-based rubber.

11. The rubber composition according to claim 9, wherein the rubber plasticizer is contained in an amount of 10 to 100 parts by mass per 100 parts by mass of the rubber.

12. A molded article of the rubber composition according to claim 9.

Images