Rubber composition for hoses, automotive transmission oil pipes, and method for manufacturing the same

Abstract

To provide a rubber composition for a hose capable of being made into a cured object comprising excellent hardness and elongation in cutting, by only primary cross linking.SOLUTION: A rubber composition for a hose contains: a ternary copolymer including respective constitutional units formed of, ethylene, (meth) acrylic ester, and a carboxyl group-containing monomer with a carboxyl group, and including the carboxyl group; hexamethylene diamine carbamate; diazabicycloundecene; carbon black; and a plasticizer. A content of the carbon black is 77-87 pts.mass with respect to 100 pts.mass of the ternary copolymer. There are also provided a transmission oil piping for a vehicle formed by using the rubber composition for a hose, and a production method of the transmission oil piping for a vehicle.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for hoses, an automotive transmission oil pipe, and a method for manufacturing the same.

Background Art

[0002] Conventionally, a Transmission Oil Cooler hose (TOC hose) has been used as a pipe for circulating automotive transmission oil. The TOC hose is required to have heat resistance, oil resistance, cold resistance, caulking sealability when joined to a metal pipe (specifically, as rubber performance, it has high hardness and high elongation to obtain flexibility), and the like. In order to satisfy the above heat resistance, oil resistance, and cold resistance, a rubber composition containing an AEM polymer (a terpolymer of ethylene, an acrylic ester, and a crosslinking point monomer having a carboxyl group) and a crosslinking agent such as hexamethylenediamine is used for the TOC hose. Also, conventionally, in order to develop the characteristics of the AEM polymer and the like, the rubber composition containing the AEM polymer and the like is generally crosslinked up to secondary crosslinking, that is, the crosslinking process is performed in two steps to cure the rubber composition.

[0003] Regarding the two-stage crosslinking of the AEM polymer, for example, the case where a rubber composition containing an AEM polymer represented by the following formula (I) and hexamethylenediamine as a crosslinking agent is used and the rubber composition is crosslinked in two stages (the crosslinking process is performed in two steps) will be taken up and explained using the following reaction formula (schematic diagram). In the formula (I) representing the AEM polymer, [CH2CH2] represents a repeating unit by ethylene, [CR1(CO2R2)CH2] represents a repeating unit by (meth)acrylate, [X(COOH)] represents a repeating unit by a carboxyl group-containing monomer having a carboxyl group, R1 represents hydrogen or a methyl group, R2 represents an ester residue, and o, p, q each independently represent 1 or more. [X(COOH)] is not particularly limited as long as it is a repeating unit formed from a monomer having a carboxyl group and a group copolymerizable with ethylene and (meth)acrylate. In the following reaction formula, first, in the primary crosslinking of the rubber composition (the first crosslinking step in the two-step crosslinking), two amino groups of hexamethylenediamine react with the carboxyl groups of the AEM polymer represented by the formula (I) intermolecularly or intramolecularly to form two amide bonds and water, and the AEM polymer can be crosslinked via the residue of hexamethylenediamine by amide-type crosslinking. Note that the AEM polymer crosslinked by amide-type crosslinking is shown with the parts other than the amide-type crosslinking omitted. Next, in the secondary crosslinking (the second crosslinking step in the two-step crosslinking), the two amide bonds further react with another carboxyl group in the AEM polymer to form two imide bonds and water, and the AEM polymer can be crosslinked by imide-type crosslinking.

[0004]

Chemical formula

[0005] When crosslinking the rubber composition containing the AEM polymer etc. by two-step crosslinking, actually, the primary crosslinking is carried out under conditions around 180 °C for about 5 to 15 minutes. After taking out the cured product from the primary crosslinking step, the secondary crosslinking is carried out under conditions around 170 to 180 °C for about 2 to 4 hours.

[0006] Thus, when using a rubber composition containing an AEM polymer or the like, it is recommended to crosslink the above composition by two-stage crosslinking in order to manufacture a hose or the like having the properties of the AEM polymer (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, for the above two-stage crosslinking, usually, a temperature bath facility of about 180°C and a secondary crosslinking process are required, and the cost and man-hours become problems. Under such circumstances, the present inventor prepared a rubber composition containing an AEM polymer or the like with reference to Patent Documents 1 and 2, crosslinked this only by primary crosslinking (that is, crosslinked by one-stage crosslinking), and evaluated the obtained cured product. As a result, it became clear that such a cured product may have a hardness (type A durometer hardness) not within an appropriate range and / or a low elongation at break (Comparative Examples 1 to 3, 5). As described above, the fact that the hardness (type A durometer hardness) of the cured product of the rubber composition is not within an appropriate range and / or the elongation at break is low is considered to lead to a decrease in the caulking sealability when joining a hose formed using the above rubber composition and a metal pipe.

[0009] Therefore, an object of the present invention is to provide a rubber composition for a hose that can obtain a cured product having excellent hardness and elongation at break by only primary crosslinking. Another object of the present invention is to provide an automotive transmission oil pipe and a method for manufacturing the same.

Means for Solving the Problems

[0010] As a result of intensive studies to solve the above problems, the present inventor has found that a rubber composition for a hose has constituent units derived from ethylene, (meth)acrylate, and a carboxyl group-containing monomer having a carboxyl group, and a ternary copolymer having a carboxyl group derived from the carboxyl group-containing monomer, hexamethylenediamine carbamate, diazabicycloundecene, carbon black, and a plasticizer, and that a desired effect can be obtained by the content of the carbon black being 77 to 87 parts by mass with respect to 100 parts by mass of the ternary copolymer, thereby arriving at the present invention. The present invention is based on the above findings and the like, and specifically solves the above problems by the following configuration.

[0011] [1] A rubber composition for a hose, comprising a ternary copolymer having constituent units derived from ethylene, (meth)acrylate, and a carboxyl group-containing monomer having a carboxyl group, hexamethylenediamine carbamate, diazabicycloundecene, carbon black, and a plasticizer, wherein the content of the carbon black is 77 to 87 parts by mass with respect to 100 parts by mass of the ternary copolymer. [2] Crosslinking is carried out only by primary crosslinking, and the elongation at break of the cured product after the primary crosslinking is 220% or more, and the type A durometer hardness of the cured product after the primary crosslinking is 75 or more and 85 or less. The rubber composition for a hose according to [1]. [3] The carbon black contains carbon black C1 having a nitrogen adsorption specific surface area of 38 m 2 / g or more and 45 m 2 / g or less, and a DBP oil absorption amount of 100 ml / 100 g or more and 130 ml / 100 g or less. The rubber composition for a hose according to [1] or [2]. [4] The plasticizer contains an ester-based plasticizer. The rubber composition for a hose according to any one of [1] to [3]. [5] The rubber composition for a hose according to any one of [1] to [4], wherein the content of the plasticizer is 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the terpolymer. [6] The rubber composition for a hose according to any one of [1] to [5], wherein the content of the hexamethylenediamine carbamate is 1 part by mass or more and 1.6 parts by mass or less with respect to 100 parts by mass of the terpolymer. [7] The rubber composition for a hose according to any one of [1] to [6], which is used to form an automobile transmission oil pipe. [8] An automobile transmission oil pipe formed by using the rubber composition for a hose according to any one of [1] to [6]. [9] The automobile transmission oil pipe according to [8], which has an inner pipe and an outer pipe, and the inner pipe and the outer pipe are each independently formed by using the rubber composition for a hose.

[10] A method for manufacturing an automobile transmission oil pipe, which manufactures the automobile transmission oil pipe by performing only primary crosslinking using the rubber composition for a hose according to any one of [1] to [6].

[11] The method for manufacturing an automobile transmission oil pipe according to

[10] , wherein the elongation at break of the cured product of the rubber composition for a hose after the primary crosslinking is 220% or more, and the type A durometer hardness of the cured product of the rubber composition for a hose after the primary crosslinking is 75 or more and 85 or less.

[12] The method for manufacturing an automobile transmission oil pipe according to

[10] or

[11] , which independently uses the rubber composition for a hose as the inner pipe rubber composition and the outer pipe rubber composition, arranges the outer pipe rubber composition on the inner pipe rubber composition, and performs only the primary crosslinking.

[13] The method for manufacturing an automobile transmission oil pipe according to

[12] , wherein a reinforcing layer is further arranged between the inner pipe rubber composition and the outer pipe rubber composition. [Effects of the Invention]

[0012] The rubber composition for a hose of the present invention can become a cured product having excellent hardness and elongation at break with only primary crosslinking. The transmission oil pipe for an automobile of the present invention can have excellent hardness and elongation at break with only primary crosslinking. According to the method for manufacturing a transmission oil pipe for an automobile of the present invention, a transmission oil pipe for an automobile having excellent hardness and elongation at break can be manufactured with only primary crosslinking of the rubber composition for a hose of the present invention. [Embodiments for Carrying Out the Invention]

[0013] The present invention will be described in detail below. In this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In this specification, unless otherwise specified, each component can be used alone or in combination of two or more of the substances corresponding to the component. When the component contains two or more substances, the content of the component means the total content of the two or more substances. In this specification, unless otherwise specified, each component is not limited with respect to its production method. For example, conventionally known methods can be mentioned. In this specification, (meth)acrylic represents acrylic or methacrylic. In this specification, in some cases, the effect of the present invention is considered to be more excellent when at least one of the hardness (type A durometer hardness) and elongation at break of the cured product obtained with only primary crosslinking is more excellent.

[0014] [Rubber Composition for Hose] The rubber composition for a hose of the present invention (the composition of the present invention) has each structural unit composed of ethylene, (meth)acrylate, and a carboxyl group-containing monomer having a carboxyl group, and contains a terpolymer having the above carboxyl group, hexamethylenediamine carbamate, diazabicycloundecene, carbon black, and a plasticizer. It is a rubber composition for a hose in which the content of the carbon black is 77 to 87 parts by mass with respect to 100 parts by mass of the above-mentioned terpolymer. Hereinafter, each component contained in the composition of the present invention will be described in detail.

[0015] <Terpolymer> The terpolymer contained in the composition of the present invention has respective structural units derived from ethylene, (meth)acrylate, and a carboxyl group-containing monomer having a carboxyl group (-COOH), and is a terpolymer having the above-mentioned carboxyl group. By containing the above-mentioned terpolymer in the composition of the present invention, the heat resistance, oil resistance, and cold resistance of the obtained cured product are excellent. The carboxyl group possessed by the above-mentioned terpolymer can function as a crosslinking point that reacts with hexamethylenediamine carbamate described later. The carboxyl group possessed by the above-mentioned terpolymer is derived from a carboxyl group-containing monomer having a carboxyl group. The form of the above-mentioned terpolymer is not particularly limited. For example, a random copolymer and a block copolymer can be mentioned.

[0016] <Ethylene> The terpolymer has a structural unit derived from ethylene. Ethylene as a monomer forming the structural unit of the terpolymer is not particularly limited. The content of the structural unit derived from ethylene in the terpolymer can be an amount obtained by subtracting the total of the content of the structural unit derived from (meth)acrylate and the content of the structural unit derived from the carboxyl group-containing monomer, which will be described later, from the whole terpolymer (the total amount of the structural units constituting the terpolymer).

[0017] <(Meth)acrylate> The terpolymer has a structural unit derived from (meth)acrylate. The (meth)acrylate ester as a monomer forming the constitutional unit of the terpolymer is not particularly limited. For example, esters of (meth)acrylic acid and alkanols (compounds in which a hydroxy group is bonded to an aliphatic hydrocarbon group which is linear, branched, cyclic or a combination thereof) can be mentioned. The (meth)acrylate ester is preferably an ester of an alkanol having 1 to 8 carbon atoms (for example, a monoalkanol having one hydroxy group) and (meth)acrylic acid. Specific examples of the (meth)acrylate ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Among them, from the viewpoint of being particularly excellent in the effects of the present invention, methyl (meth)acrylate is preferred.

[0018] · Content of the constitutional unit by the (meth)acrylate ester The content of the constitutional unit by the (meth)acrylate ester in the terpolymer is not particularly limited, but from the viewpoint of the effects of the present invention being more excellent and the weather resistance, heat resistance, and oil resistance of the obtained cured product being improved, 30 to 99% by mass in the terpolymer is preferred.

[0019] <Carboxyl group-containing monomer> The terpolymer has a constitutional unit by a carboxyl group-containing monomer having a carboxyl group. The carboxyl group-containing monomer as a monomer forming the constitutional unit of the terpolymer has a carboxyl group and a reactive group (excluding the carboxyl group) copolymerizable with ethylene and (meth)acrylate ester. Examples of the above reactive group include α,β-ethylenically unsaturated bonds.

[0020] Examples of the carboxyl group-containing monomer include α,β-ethylenically unsaturated monocarboxylic acid monomers having 3 to 12 carbon atoms, α,β-ethylenically unsaturated dicarboxylic acid monomers having 4 to 12 carbon atoms, and monoester monomers of α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms and alkanols having 1 to 8 carbon atoms.

[0021] Specific examples of the α,β-ethylenically unsaturated monocarboxylic acid monomers having 3 to 12 carbon atoms include, for example, acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and cinnamic acid. Specific examples of the α,β-ethylenically unsaturated dicarboxylic acid monomers having 4 to 12 carbon atoms include, for example, butenedioic acids such as fumaric acid and maleic acid; itaconic acid; citraconic acid; chloromaleic acid.

[0022] Specific examples of the monoester monomers of α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms and alkanols having 1 to 8 carbon atoms include, for example, monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate, monomethyl maleate, monoethyl maleate, mono-n-butyl maleate and other monochain alkyl esters of butenedioic acid; monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclohexenyl fumarate, monocyclopentyl maleate, monocyclohexyl maleate, monocyclohexenyl maleate and other monoesters of butenedioic acid having an alicyclic structure; monomethyl itaconate, monoethyl itaconate, mono-n-butyl itaconate, monocyclohexyl itaconate and other monoesters of itaconic acid.

[0023] · Content of the structural unit derived from the carboxyl group-containing monomer From the viewpoint that the effects of the present invention can be more excellent, the content of the structural unit derived from the carboxyl group-containing monomer in the terpolymer is preferably 0.5 to 10% by mass in the terpolymer.

[0024] The composition of the present invention contains the above ternary copolymer as a rubber component. From the viewpoint that the effects of the composition of the present invention are more excellent, it is preferable that the rubber component contained in the composition of the present invention is only the above ternary copolymer. When the composition of the present invention further contains a rubber component other than the above ternary copolymer as a rubber component, the content of the above ternary copolymer is preferably 90% by mass or more in the above rubber component. Examples of the rubber component other than the above ternary copolymer include a binary copolymer having each structural unit of ethylene and (meth)acrylate.

[0025] <Hexamethylenediamine carbamate> The hexamethylenediamine carbamate (HMDAC) contained in the composition of the present invention is a compound represented by the following structural formula.

Chemical formula

[0026] Hexamethylenediamine carbamate can react with the carboxyl group of the ternary copolymer. Hexamethylenediamine carbamate can generate hexamethylenediamine by, for example, decarboxylation (de-CO2). If the two amino groups of the above hexamethylenediamine react with the above carboxyl group respectively, the ternary copolymer can be crosslinked. In the invention, only by primary crosslinking (only one-stage crosslinking), the above hexamethylenediamine can react with the carboxyl group of the ternary copolymer to form an amide-type crosslink.

[0027] (Content of hexamethylenediamine carbamate) From the viewpoint that the effects of the present invention are more excellent, the content of hexamethylenediamine carbamate is preferably 1 part by mass or more and 1.6 parts by mass or less, more preferably 1.4 to 1.6 parts by mass, based on 100 parts by mass of the above ternary copolymer.

[0028] <Diazabicycloundecene> The 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) contained in the composition of the present invention can promote the above reaction between the terpolymer and hexamethylenediamine carbamate.

[0029] (Content of 1,8-diazabicyclo[5.4.0]undec-7-ene) From the viewpoint of excellent effects of the present invention, the content of 1,8-diazabicyclo[5.4.0]undec-7-ene is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the above terpolymer.

[0030] <Carbon black> The carbon black contained in the composition of the present invention is not particularly limited. Examples of the carbon black include carbon blacks such as FEF (Fast Extruding Furnace) grade, GPF (General Purpose Furnace) grade, and SRF (Semi-Reinforcing Furnace) grade.

[0031] · Carbon black C1 From the viewpoint of excellent effects of the present invention, the carbon black preferably includes carbon black C1 having a nitrogen adsorption specific surface area of 38 m 2 / g or more and 45 m 2 / g or less, and a DBP (dibutyl phthalate) oil absorption amount of 100 ml / 100 g or more and 130 ml / 100 g or less. The fact that the carbon black contains carbon black C1 means that part or all of the carbon black is carbon black C1. From the viewpoint of excellent effects of the present invention, it is preferable that all of the carbon black is carbon black C1. The nitrogen adsorption specific surface area of the carbon black can be measured according to JIS K6217-2:2017. The DBP oil absorption amount of the carbon black can be measured according to JIS K6217-4:2017. Examples of the carbon black C1 include FEF (Fast Extruding Furnace) grade carbon black. From the viewpoint of being excellent due to the effects of the present invention, the carbon black C1 is preferably FEF grade carbon black.

[0032] <Carbon black content> In the present invention, the content of carbon black is 77 to 87 parts by mass with respect to 100 parts by mass of the above-mentioned terpolymer. When the content of carbon black is within the above range, the elongation at break and hardness (type A durometer hardness) of the obtained cured product can be balanced at an excellent level. From the viewpoint of being excellent due to the effects of the present invention, the content of carbon black is preferably 82 to 85 parts by mass with respect to 100 parts by mass of the above-mentioned terpolymer.

[0033] <Plasticizer> The plasticizer contained in the composition of the present invention may be any substance that can plasticize or soften the above-mentioned terpolymer. Note that the plasticizer does not include the processing aids described later.

[0034] (Ester-based plasticizer) From the viewpoint of being excellent due to the effects of the present invention, the plasticizer preferably contains an ester-based plasticizer. The ester-based plasticizer may be any compound having an ester bond derived from a carboxylic acid. Examples of the ester-based plasticizer include ester compounds of aromatic hydrocarbon polycarboxylic acids such as trimellitic acid-based plasticizers, pyromellitic acid-based plasticizers, and phthalic acid-based plasticizers; ester compounds of aliphatic hydrocarbon polycarboxylic acids such as adipic acid ester-based plasticizers and sebacic acid ester-based plasticizers; and polyester polymers.

[0035] Ester plasticizers can further have an ether bond in addition to the ester bond derived from carboxylic acid. A plasticizer having an ether bond in addition to the ester bond derived from carboxylic acid may be referred to as an "ether ester plasticizer".

[0036] From the viewpoint of excellent effects of the present invention, the plasticizer preferably contains an ether ester plasticizer. The ether ester plasticizer has at least one ether bond and at least one ester bond respectively. The ether ester plasticizer can have a plurality of ether bonds and ester bonds respectively. Examples of the ether ester plasticizer include polyesters of polyoxyalkylene polyol and monocarboxylic acid such as polyethylene glycol di(butanoic acid) ester, polyethylene glycol di(isobutanoic acid) ester, polyethylene glycol di(2-ethylbutanoic acid) ester, polyethylene glycol di(2-ethylhexanoic acid) ester, polyethylene glycol di(decanoic acid) ester, etc.; Polyesters of polycarboxylic acid and a monool having an ether bond such as di(butoxyethanol) adipate, di(butyl diglycol) adipate (also known as di(2-(2-butoxyethoxy)ethanol) adipate), di(butyl polyglycol) adipate (also known as di(polyethylene glycol monobutyl ether) adipate), di(2-ethylhexyloxyethanol) adipate, di(2-ethylhexyl diglycol) adipate, di(2-ethylhexyl polyglycol) adipate, dioctoxyethanol adipate, di(octyl diglycol) adipate, di(octyl polyglycol) adipate, etc.

[0037] (Content of plasticizer) From the viewpoint of excellent effects of the present invention, the content of the plasticizer is preferably 5 to 15 parts by mass, more preferably 8 to 12 parts by mass, based on 100 parts by mass of the above ternary copolymer.

[0038] (Additive) The composition of the present invention can further contain additives, provided that the effects of the present invention are not impaired. Examples of the additives include polymers other than the above ternary copolymer, processing aids, antioxidants, fillers other than carbon black, and the like.

[0039] · Processing aids Examples of the processing aids include stearic acid; polyoxyethylene alcohol ethers such as polyoxyethylene lauryl ether and polyoxyethylene oleyl ether; polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; polypropylene glycol ethylene oxide adducts; phosphoric acid esters such as alkyl phosphate esters and polyoxyethylene alkyl ether phosphate esters; alkylamines such as octadecylamine.

[0040] From the viewpoint of being more excellent in the effects of the present invention, it is preferable to use stearic acid, polyoxyethylene alkyl ether phosphate ester, and octadecylamine in combination as the processing aids.

[0041] · Content of processing aids The content of the processing aids (when two or more processing aids are used in combination, the total amount thereof) is preferably 1 to 5 parts by mass with respect to 100 parts by mass of the above ternary copolymer.

[0042] · Method for producing the composition of the present invention The method for producing the composition of the present invention is not particularly limited. Usually, components other than hexamethylenediamine carbamate and diazabicycloundecene are mixed with a mixer such as a Banbury mixer, an intermix, or a kneader, and then transferred to a roll or the like, and hexamethylenediamine carbamate and diazabicycloundecene are added and mixed to produce the composition of the present invention. In the above production method, the mixing is preferably carried out under conditions where the above terpolymer and hexamethylenediamine carbamate do not undergo a crosslinking reaction. In the above production method, the mixing conditions when the above terpolymer and hexamethylenediamine carbamate coexist are preferably, for example, 120°C or lower for 5 minutes or less.

[0043] (Crosslinking of the composition of the present invention) · Primary crosslinking The composition of the present invention can be crosslinked only by primary crosslinking (crosslinking only once. Single-stage crosslinking). According to the composition of the present invention, even if the crosslinking is only primary crosslinking, the elongation at break and hardness (type A durometer hardness) of the obtained cured product are excellent. The crosslinking (crosslinking step) of the composition of the present invention is preferably carried out only by primary crosslinking (only the single-stage crosslinking step) from the viewpoint of maintaining the elongation at break and / or hardness (type A durometer hardness) of the obtained cured product. It is preferable to heat the composition of the present invention in primary crosslinking.

[0044] · Heating method In the present invention, examples of the heating method for primary crosslinking of the composition of the present invention include press heating, steam heating, oven heating, etc.

[0045] · Heating temperature In the present invention, as the crosslinking conditions for primary crosslinking of the composition of the present invention, from the viewpoint of being excellent due to the effects of the present invention, the heating temperature is preferably 140 to 160°C. In the present invention, when crosslinking the composition of the present invention only by primary crosslinking, in the reaction of the above terpolymer and hexamethylenediamine carbamate, from the viewpoint of suppressing the formation of imide bonds from amide-type crosslinking and maintaining excellent levels of hardness and elongation at break, the heating temperature preferably does not exceed 160°C. When the heating method is steam heating, since the heating temperature is usually 160°C or lower, adopting steam heating as the heating method is cited as one of the preferred embodiments from the viewpoint that the heating temperature does not exceed 160°C as described above. When the heating method is a method other than steam heating, the heating temperature can be set in each of the above methods. Therefore, when a method other than steam heating is adopted as the heating method, the heating temperature may be set to, for example, 160 °C or lower.

[0046] ·Crosslinking time In the present invention, from the viewpoint of excellent effects and productivity of the present invention, the crosslinking time of the primary crosslinking of the composition of the present invention is preferably, for example, 45 to 120 minutes.

[0047] ·Heating temperature and crosslinking time From the viewpoint of excellent effects and productivity of the present invention, the combination of the heating temperature and the crosslinking time of the primary crosslinking of the composition of the present invention is preferably 45 to 120 minutes under the condition of 140 to 160 °C. Conventionally, when curing a rubber composition containing an AEM polymer by two-stage crosslinking, in order to form an imide-type crosslinking in the secondary crosslinking, it was necessary to crosslink under the condition of 170 °C or higher, otherwise the crosslinking time would be extremely long. In this regard, in the present invention, the crosslinking process can be only the primary crosslinking, and an amide-type crosslinking can be formed by the primary crosslinking. In addition, when the primary crosslinking is carried out at a temperature lower than the conventional one, even if the primary crosslinking is carried out for a longer time than the conventional one, the amide-type crosslinking formed in the primary crosslinking can be suppressed from reacting with another carboxy group to generate an imide bond or an imide-type crosslinking.

[0048] In the present invention, in the terpolymer after the primary crosslinking, it is presumed that the crosslinking between (or within) the terpolymers is mainly an amide-type crosslinking. The above matters are considered to be proved from the fact that the cured product after the primary crosslinking in this example has an excellent balance between hardness and elongation at break. In addition, in the terpolymer after the primary crosslinking, the terpolymer may have a side chain formed by bonding only one amino group in hexamethylenediamine to the terpolymer in addition to the above amide-type crosslinking. Furthermore, the terpolymer after the primary crosslinking may further have an imide bond or an imide-type crosslinking generated from the amide-type crosslinking in addition to the above amide-type crosslinking. It is technically impossible to prove by analysis or the like the extent to which the crosslinking between the terpolymers after the primary crosslinking is mainly amide-type crosslinking, or the extent to which the terpolymers after the primary crosslinking have the above-mentioned side chains, imide bonds or imide-type crosslinking in addition to the amide-type crosslinking. For this reason, when the composition of the present invention or the pipe of the present invention described later defines "crosslinking", the applicant believes that it falls under the "impossible or unrealistic circumstances" of the examination handbook 2205.

[0049] ·Pressurization In the primary crosslinking, pressurization may be applied. When pressure is applied during the primary crosslinking, the pressure can be 2 to 4 MPa.

[0050] ·Coating material (mold) When the composition of the present invention is primarily crosslinked, in order to prevent foaming, it is preferable to cover part or all of the composition of the present invention with a coating material (mold), and it is more preferable to cover all of it with a coating material (mold). The above matters are the same when the pipe of the present invention described later is primarily crosslinked. Examples of the coating material (mold) include polymethylpentene (trade name TPX, Mitsui Chemicals). After crosslinking, the above coating material (mold) may be peeled off from the cured product (hose, etc.). When the primary crosslinking of the composition of the present invention is carried out under pressure (for example, press heating), foaming can be prevented by pressurization (press), so it is not necessary to use a coating material (mold).

[0051] In the present invention, the primary crosslinking does not include the crosslinking between the above terpolymer and hexamethylenediamine carbamate at the stage of manufacturing the composition of the present invention.

[0052] Also, for the composition of the present invention, performing crosslinking only by primary crosslinking (the crosslinking process is only carried out once. One-step crosslinking) means crosslinking the composition of the present invention after production with only one crosslinking process. When the crosslinking of the composition of the present invention is only primary crosslinking, the above "only primary crosslinking" does not include two-step crosslinking. Two-step crosslinking means performing secondary crosslinking after primary crosslinking. Usually, primary crosslinking and secondary crosslinking differ in the mode of heating method (for example, primary crosslinking is press heating and secondary crosslinking is oven heating), temperature conditions, and crosslinking time. Also, in two-step crosslinking, usually, after primary crosslinking, the temperature of the crosslinked product decreases and is reheated in secondary crosslinking.

[0053] Also, in the present invention, primary crosslinking does not include changing the heating temperature in two stages during one crosslinking process. For example, during one crosslinking process, maintaining the heating temperature below 100°C and then changing it to 140 - 160°C is excluded from primary crosslinking in the present invention. In the present invention, during primary crosslinking (one crosslinking process), the heating temperature is preferably constant, for example, within the above range of heating temperature. When the crosslinking time is 90 minutes and the heating temperature is 157°C during primary crosslinking (one crosslinking process), the heating temperature is preferably kept constant at approximately 157°C for 90 minutes of crosslinking time.

[0054] In the present invention, for the evaluation of "(physical properties of the cured product)" described later, the composition of the present invention was press crosslinked at 157°C and a surface pressure of 3.0 MPa for 90 minutes, and the cured product (2 mm thick) obtained after the above crosslinking (primary crosslinking) was used.

[0055] (Physical properties of the cured product) The elongation at break of the cured product obtained after primary crosslinking the composition of the present invention is 220% or more, and preferably, the Shore A durometer hardness of the cured product is 75 or more and 85 or less. ·Elongation at break From the viewpoint that the above elongation at break is excellent due to the effect of the present invention, 230 - 320% is preferable. In the present invention, the elongation at break was measured by performing a tensile test in accordance with JIS K6251:2017 under the conditions of 23°C ± 2°C and a tensile speed of 500 mm / min.

[0056] · Hardness (Type A durometer hardness) From the viewpoint that the Type A durometer hardness is excellent due to the effects of the present invention, it is preferably 76 or more and 83 or less, more preferably 80 to 83. In the present invention, the appropriate range of the hardness (Type A durometer hardness) of the cured product after primary crosslinking can be 76 or more and 83 or less. In the present invention, the hardness (Type A durometer hardness) was measured using a Type A durometer under the condition of 23°C in accordance with JIS K 6253-3:2012. In addition, when evaluating the above hardness, three cured products (thickness 2 mm) obtained as described above were stacked and used.

[0057] The cured product obtained by the above primary crosslinking can be used as it is, without subsequent secondary crosslinking, as a rubber product (for example, a hose, etc.).

[0058] In addition, if the cured product obtained by the above primary crosslinking can maintain a balanced state of the excellent elongation at break (specifically, 220% or more) and the appropriate range of hardness (75 to 85 in terms of Type A durometer hardness) that the cured product has, it may be subsequently subjected to secondary crosslinking. From the viewpoint that the cured product obtained by the above primary crosslinking can easily maintain a balanced state of the excellent elongation at break and the appropriate range of hardness (Type A durometer hardness) that the cured product has, and has excellent productivity due to fewer processes, it is preferable not to subject the cured product obtained by the above primary crosslinking to secondary crosslinking. In addition, in this specification, when secondary crosslinking is performed, the conditions for secondary crosslinking are not particularly limited. As described above, it is preferable that after secondary crosslinking, the excellent elongation at break and the appropriate range of hardness (Type A durometer hardness) that the cured product after the above primary crosslinking has can be maintained in a balanced state. In addition, in this specification, when evaluating the elongation at break and hardness after secondary crosslinking, the condition for secondary crosslinking means leaving the cured product at 180°C for 240 minutes after primary crosslinking.

[0059] <Rubber composition for hose> Using the composition of the present invention, a hose can be formed. Examples of the hose include, as a preferred embodiment, an automotive transmission oil pipe and the like. An automotive transmission oil pipe is a pipe for circulating oil to a transmission mounted on an automobile.

[0060] [Automotive transmission oil pipe] The automotive transmission oil pipe of the present invention (the pipe of the present invention) is An automotive transmission oil pipe formed using the rubber composition for hose of the present invention.

[0061] The rubber composition for hose used in the pipe of the present invention is not particularly limited as long as it is the rubber composition for hose of the present invention.

[0062] (Inner tube and outer tube) Examples of the pipe of the present invention include an embodiment having an inner tube and an outer tube. When the pipe of the present invention has an inner tube and an outer tube, it is preferable to form the inner tube and / or the outer tube using the rubber composition for hose, and it is more preferable that the inner tube and the outer tube are each independently formed using the rubber composition for hose. When the inner tube and the outer tube are each independently formed using the rubber composition for hose, the rubber composition for hose used for the inner tube (rubber composition for inner tube) and the rubber composition for hose used for the outer tube (rubber composition for outer tube) may both be the rubber composition for hose of the present invention, and they may be the same or different from each other.

[0063] In the pipe of the present invention, the portion formed using the composition of the present invention and having the composition once crosslinked preferably has an elongation at break of 220% or more and a Type A durometer hardness of 75 or more and 85 or less. When the inner tube is a cured product obtained after the primary crosslinking of the composition of the present invention, the inner tube (the cured product obtained after the primary crosslinking of the composition of the present invention) preferably has an elongation at break of 220% or more and a Type A durometer hardness of 75 or more and 85 or less. Also, when the outer tube is a cured product obtained after the primary crosslinking of the composition of the present invention, the outer tube (the cured product obtained after the primary crosslinking of the composition of the present invention) preferably has an elongation at break of 220% or more and a Type A durometer hardness of 75 or more and 85 or less.

[0064] The thickness of the inner tube can usually be 0.5 to 3 mm. The thickness of the outer tube can usually be 0.5 to 3 mm. The inner diameter of the pipe of the present invention can usually be 8 to 20 mm. The length of the pipe of the present invention can usually be 0.1 to 200 m.

[0065] (Reinforcing layer) In addition to the layer (or tube) formed of the rubber composition for hoses of the present invention, the pipe of the present invention may further have, for example, a reinforcing layer. The pipe of the present invention may further have, for example, a reinforcing layer between the inner tube and the outer tube. Examples of the material of the reinforcing layer include metals and fiber materials (such as polyamide and polyester). The reinforcing layer may be surface-treated. Examples of the form of the reinforcing layer include those braided in a spiral structure and / or a blade structure.

[0066] The pipe of the present invention can be manufactured, for example, by the method for manufacturing an automotive transmission oil pipe of the present invention described later.

[0067] [Method for manufacturing an automotive transmission oil pipe] The method for manufacturing an automotive transmission oil pipe of the present invention (the manufacturing method of the present invention) is A method for manufacturing an automotive transmission oil pipe, which uses the rubber composition for hoses of the present invention and performs only primary crosslinking to manufacture the automotive transmission oil pipe.

[0068] The rubber composition for hoses used in the manufacturing method of the present invention is not particularly limited as long as it is the rubber composition for hoses of the present invention.

[0069] It is preferable that the elongation at break of the cured product (for example, the inner tube or the outer tube) of the rubber composition for hoses after the above primary crosslinking is 220% or more, and the Shore A durometer hardness of the cured product is 75 or more and 85 or less.

[0070] As the manufacturing method of the present invention, for example, using the rubber composition for hoses as the rubber composition for the inner tube and / or the rubber composition for the outer tube, laminating the rubber composition for the outer tube on the rubber composition for the inner tube (at least one or both of the rubber composition for the inner tube and the rubber composition for the outer tube are the compositions of the present invention), and performing only primary crosslinking on the obtained laminate to manufacture an automotive transmission oil pipe having an inner tube and an outer tube. The rubber composition for the inner tube may be first placed on a mandrel, for example (the same applies hereinafter). When the pipe further has a reinforcing layer (specifically, for example, when a reinforcing layer is further disposed between the rubber composition for the inner tube and the rubber composition for the outer tube), for example, a reinforcing layer is disposed on the rubber composition for the inner tube, and the rubber composition for the outer tube is disposed on the reinforcing layer, and only primary crosslinking is performed to manufacture an automotive transmission oil pipe having an inner tube, a reinforcing layer, and an outer tube. The placement of the rubber composition for the inner tube on the mandrel may be, for example, extrusion molding. The placement of the rubber composition for the outer tube is the same as above. When using a coating material (mold), the coating material (mold) can be disposed on the rubber composition for the outer tube by extrusion molding, for example. Examples of the coating material (mold) include the same as those described above.

[0071] (Crosslinking) In the production method of the present invention, crosslinking can be only primary crosslinking (crosslinking only once). According to the production method of the present invention, even if the crosslinking is only primary crosslinking, the obtained cured product is excellent in elongation at break and hardness (Type A durometer hardness).

[0072] Regarding the crosslinking conditions of the production method of the transmission oil pipe for automobiles of the present invention, they can be the same as the description from "(Crosslinking of the composition of the present invention)" to before "(Physical properties of the cured product)" described above.

[0073] According to the production method of the present invention, by using the composition of the present invention, a transmission oil pipe for automobiles having excellent heat resistance, oil resistance, cold resistance, excellent elongation at break without performing secondary crosslinking, and a hardness (Type A durometer hardness) within an appropriate range can be manufactured. As described above, since the elongation at break is excellent and the hardness (Type A durometer hardness) is within an appropriate range, it is presumed that the caulking sealability at the time of joining with a metal pipe is improved for the transmission oil pipe for automobiles manufactured by the production method of the present invention.

[0074] The pipe of the present invention or the pipe manufactured by the production method of the present invention can be used as it is as a pipe without performing secondary crosslinking. In addition, if the pipe obtained by the above primary crosslinking can maintain the excellent elongation at break (specifically, 220% or more) and the hardness within an appropriate range (75 to 85 in terms of Type A durometer hardness) possessed by the pipe in a balanced state, secondary crosslinking may be performed thereafter. From the viewpoint that the pipe of the present invention or the production method of the present invention can easily maintain a balanced state of excellent elongation at break and hardness within an appropriate range (Type A durometer hardness), and has few processes and thus excellent productivity, it is preferable not to perform secondary crosslinking.

Examples

[0075] Examples are shown below to specifically explain the present invention. However, the present invention is not limited thereto.

[0076] <Manufacture of Composition> Using each component in Table 1 below in the composition (parts by mass) shown in the same table, components other than hexamethylenediamine carbamate (Diak #1), diazabicycloundecene (ACT 55) and the comparative crosslinking accelerator were mixed in a Banbury mixer under the conditions of 30 to 150 °C, and then the mixture was transferred to a roll. To the above mixture, hexamethylenediamine carbamate and diazabicycloundecene or the comparative crosslinking accelerator were added and they were mixed under the conditions of 100 °C for 5 minutes to produce each composition.

[0077] <Crosslinking> Each composition produced as described above was press-crosslinked with a press molding machine at 157 °C for 90 minutes (surface pressure 3.0 MPa) to obtain a crosslinked sheet (thickness 2 mm) as a cured product. The above crosslinking is primary crosslinking and secondary crosslinking is not performed. Since the primary crosslinking was performed under pressure as described above, each composition was not covered with a coating material.

[0078] <<Evaluation>> ·Tensile Physical Properties From each crosslinked sheet obtained as described above, JIS No. 3 dumbbell-shaped test pieces were punched out, and the tensile physical properties were evaluated using each of the obtained test pieces. The results are shown in Table 1.

[0079] ··Tensile Test Using each of the test pieces obtained as described above, a tensile test was performed in accordance with JIS K6251:2017 under the conditions of 23 °C ± 2 °C and a tensile speed of 500 mm / min, and the tensile strength (Tb) [unit: MPa], elongation at break (Eb) [unit: %], and 100% modulus (M100) [unit: MPa] were measured.

[0080] ··Evaluation Criteria for Elongation at Break (Eb) In the present invention, when the elongation at break was 220% or more, it was evaluated that the elongation at break of the cured product was excellent, and this was indicated as "〇" (in the "Eb determination" column). The larger the elongation at break is than 220%, the more excellent the elongation at break of the cured product is. On the other hand, when the elongation at break was less than 220%, the elongation at break of the cured product was evaluated as poor and marked with "×" in the "Eb Judgment" column.

[0081] ··Evaluation criteria for tensile strength From the perspective of product strength, it is preferable that the above-mentioned tensile strength is 12 MPa or more. ··Evaluation criteria for M100 From the perspective of the caulking sealability during joining with a metal pipe, it is preferable that the above is 6.0 MPa or more.

[0082] ·Hardness (Type A durometer hardness. HS) Three sheets of each crosslinked sheet obtained as described above were stacked, and in accordance with JIS K 6253-3:2012, a hardness measurement test was conducted using a Type A durometer under the condition of 23°C, and the hardness (HS) of each test piece was measured.

[0083] ··Evaluation criteria for hardness (Type A durometer hardness) (HS) In the present invention, when the above-mentioned hardness (Type A durometer hardness) was 75 to 85, the hardness (Type A durometer hardness) of the cured product was evaluated as excellent and marked with "〇" in the "HS Judgment" column. On the other hand, when the above-mentioned hardness (Type A durometer hardness) was less than 75 or exceeded 85, the hardness (Type A durometer hardness) of the cured product was evaluated as poor and marked with "×" in the "HS Judgment" column.

[0084] It is considered that excellent elongation at break and hardness (Type A durometer hardness) of the cured product lead to an improvement in the caulking sealability when joining a hose formed using a rubber composition and a metal pipe. In the present invention, the caulking sealability when joining a hose and a metal pipe was mainly considered based on the results of the elongation at break and hardness (Type A durometer hardness) of the cured product. Regarding the evaluation of the caulking sealability when joining with a metal pipe, the evaluation of M100 shall be treated supplementarily.

[0085]

Table 1

[0086] The details of each component shown in Table 1 are as follows. (Terpolymer) · Vamac Ultra IP (terpolymer AEM): "Vamac® Ultra IP", manufactured by Dupont (a terpolymer of ethylene - acrylate ester - carboxyl group - containing monomer, having a carboxyl group as a cross - linking point).

[0087] (Carbon black) FEF C.B: FEF carbon black. N550. Trade name Nitron #10N, manufactured by Nippon Steel Carbon Co., Ltd. N2SA: 41m 2 / g, DBP oil absorption: 120 ml / 100 g. Note that carbon black C1 has a nitrogen adsorption specific surface area of 38 m 2 / g or more and 45 m 2 / g or less, and a DBP oil absorption of 100 ml / 100 g or more and 130 ml / 100 g or less, so it corresponds to carbon black C1.

[0088] · Nocrack CD (anti - aging agent): Diphenylamine. Trade name Nocrack CD, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti - aging agent · Stearic acid (processing aid): "Stearic acid 50S" (manufactured by Nisshin Rikagaku Co., Ltd.) · RL210 (processing aid): Polyoxyethylene stearyl ether phosphate. Trade name Phosphanol RL - 210, manufactured by Toho Chemical Industry Co., Ltd. · Armeen18D (processing aid): Octadecylamine. Trade name Armeen18D, manufactured by Akzo Nobel Co., Ltd.

[0089] (Plasticizer) · TP 759 (plasticizer): Ether - ester - based plasticizer. Trade name TP759, manufactured by HallStar Co., Ltd.

[0090] (Hexamethylenediamine carbamate) · Diak #1 (HMDAC) crosslinking agent: hexamethylene diamine carbamate. Trade name Diak #1, manufactured by DuPont.

[0091] (Diazabicycloundecene) · ACT 55 crosslinking accelerator: diazabicycloundecene. Trade name ACT 55, manufactured by SAFIC ALCAN.

[0092] · Comparative crosslinking accelerator: 1,3-diphenylguanidine. Trade name Sunseller D, manufactured by Sanshin Chemical Industry Co., Ltd.

[0093] As is clear from the results shown in Table 1, in Comparative Example 1 where the carbon black content was more than the predetermined content, the elongation at break and hardness (Type A durometer hardness) after the primary crosslinking were poor. In Comparative Examples 2 and 3 where the carbon black content was less than the predetermined content, the hardness (Type A durometer hardness) after the primary crosslinking was poor. In Comparative Example 4 which did not contain a plasticizer, the elongation at break after the primary crosslinking was poor. In Comparative Example 5 where the carbon black content was less than the predetermined range, did not contain a plasticizer, and contained a crosslinking accelerator (guanidine-based compound) other than diazabicycloundecene, the hardness (Type A durometer hardness) after the primary crosslinking was poor.

[0094] In contrast, the composition of the present invention could be a cured product having excellent hardness (Type A durometer hardness) and elongation at break with only primary crosslinking.

[0095] In addition, the cured products after the primary crosslinking obtained in Examples 1 to 6 were subjected to secondary crosslinking by placing them at 180°C for 240 minutes. For the cured products after the secondary crosslinking of Examples 1 to 6, the elongation at break and hardness (Type A durometer hardness) were measured in the same manner as above. As a result, the elongation at break of the cured products after the secondary crosslinking of Examples 2 to 4 was less than 220%, and the hardness (Type A durometer hardness) exceeded 85, and it was not possible to maintain excellent elongation at break and an appropriate range of hardness (Type A durometer hardness). The elongation at break of the cured product after the secondary crosslinking of Example 5 was less than 220%, and it was not possible to maintain excellent elongation at break. The cured products after the secondary crosslinking of Examples 1 and 6 could well balance and maintain excellent elongation at break and an appropriate range of hardness (Type A durometer hardness).

Claims

1. It has constituent units of ethylene, (meth)acrylate ester, and a carboxyl group-containing monomer having a carboxyl group, and contains a terpolymer having the carboxyl group, hexamethylenediamine carbamate, diazabicycloundecene, FEF grade carbon black, and a plasticizer. The content of the FEF grade carbon black is 77 to 87 parts by mass with respect to 100 parts by mass of the terpolymer. A rubber composition for a hose, wherein the rubber component is only the terpolymer.

2. Crosslinking is carried out only by primary crosslinking. The elongation at break of the cured product after the primary crosslinking is 220% or more, and the type A durometer hardness of the cured product after the primary crosslinking is 75 or more and 85 or less. The rubber composition for a hose according to Claim 1.

3. The rubber composition for a hose according to Claim 1 or 2, wherein the plasticizer includes an ester-based plasticizer.

4. The content of the plasticizer is 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the terpolymer. The rubber composition for a hose according to any one of Claims 1 to 3.

5. The content of the hexamethylenediamine carbamate is 1 part by mass or more and 1.6 parts by mass or less with respect to 100 parts by mass of the terpolymer. The rubber composition for a hose according to any one of Claims 1 to 4.

6. The rubber composition for a hose according to any one of Claims 1 to 5, which is used to form an automobile transmission oil pipe.

7. An automobile transmission oil pipe formed by using the rubber composition for a hose according to any one of Claims 1 to 5.

8. The automobile transmission oil pipe according to Claim 7, which has an inner pipe and an outer pipe, and the inner pipe and the outer pipe are each independently formed by using the rubber composition for a hose.

9. It has constituent units of ethylene, (meth)acrylate ester, and a carboxyl group-containing monomer having a carboxyl group, and contains a terpolymer having the carboxyl group, hexamethylenediamine carbamate, diazabicycloundecene, FEF grade carbon black, and a plasticizer. A method for manufacturing an automotive transmission oil pipe, which uses a rubber composition for a hose, wherein the content of the FEF grade carbon black is 77 to 87 parts by mass with respect to 100 parts by mass of the terpolymer, and only primary crosslinking is performed.

10. The method for manufacturing an automotive transmission oil pipe according to claim 9, wherein the elongation at break of the cured product of the rubber composition for the hose after the primary crosslinking is 220% or more, and the type A durometer hardness of the cured product of the rubber composition for the hose after the primary crosslinking is 75 or more and 85 or less.

11. The method for manufacturing an automotive transmission oil pipe according to claim 9 or 10, wherein the rubber composition for the hose is independently used as the inner tube rubber composition and the outer tube rubber composition, the outer tube rubber composition is disposed on the inner tube rubber composition, and only the primary crosslinking is performed.

12. The method for manufacturing an automotive transmission oil pipe according to claim 11, wherein a reinforcing layer is further disposed between the inner tube rubber composition and the outer tube rubber composition.

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