Modified polymer and method for producing the same

Abstract

To provide a modified polymer having superior kneading processability.SOLUTION: A modified polymer is an ethylene-α-olefin elastomer modified with a compound having a mercapto group.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a modified polymer and a method for producing the same.

Background Art

[0002] It is known to use a modified polymer as a rubber component of a crosslinked rubber composition for forming a rubber product. For example, Patent Document 1 discloses using a modified polymer obtained by modifying polybutadiene rubber with mercaptoacetic acid as a rubber component of a crosslinked rubber composition for forming the core of a golf ball.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, for example, an ethylene-propylene-diene monomer modified with a carboxylic acid has an increased viscosity due to the introduction of a carboxyl group. Therefore, when producing an uncrosslinked rubber composition using this as a rubber component, there is a problem that the kneading processability is poor when compounding and kneading rubber compounding agents.

[0005] An object of the present invention is to provide a modified polymer having excellent kneading processability.

Means for Solving the Problems

[0006] The present invention is a modified polymer obtained by modifying an ethylene-α-olefin elastomer with a compound having a mercapto group.

[0007] The present invention relates to a method for producing a modified polymer by reacting an ethylene-α-olefin elastomer, a compound having a mercapto group, and a reaction initiator while kneading to modify the ethylene-α-olefin elastomer with the compound having a mercapto group.

Advantages of the Invention

[0008] According to the present invention, an ethylene-α-olefin elastomer modified with a compound having a mercapto group can provide excellent kneading processability.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described in detail.

[0010] The modified polymer according to the embodiment is obtained by modifying an ethylene-α-olefin elastomer with a compound having a mercapto group (hereinafter referred to as "Compound A").

[0011] According to the modified polymer according to this embodiment, since it is an ethylene-α-olefin elastomer modified with Compound A, excellent kneading processability can be obtained. As a result, for example, when fillers such as carbon black and short fibers are blended, their excellent dispersibility can be obtained.

[0012] Here, examples of the ethylene-α-olefin elastomer include ethylene-propylene copolymer (EPR), ethylene-propylene-diene monomer (hereinafter referred to as "EPDM"), ethylene-octene copolymer, ethylene-butene copolymer, ethylene-butene-diene monomer (hereinafter referred to as "EBDM"), and the like. The ethylene-α-olefin elastomer preferably contains one or more of these, and from the viewpoint of obtaining excellent kneading processability, it is more preferable to contain an ethylene-α-olefin elastomer having a diene component, and even more preferable to contain EPDM.

[0013] From the perspective of obtaining excellent kneading processability, the ethylene content of the ethylene-α-olefin elastomer is preferably 40% by mass or more and 70% by mass or less, more preferably 50% by mass or more and 60% by mass or less, and still more preferably 51% by mass or more and 53% by mass or less.

[0014] When the ethylene-α-olefin elastomer contains EPDM, examples of the diene component include ethylidene norbornene (ENB), dicyclopentadiene, 1,4-hexadiene, etc. From the perspective of obtaining excellent kneading processability, ethylidene norbornene (ENB) among these is preferable as the diene component. In this case, from the same perspective as above, the diene content (ENB content) is preferably 4% by mass or more and 12% by mass or less, more preferably 5% by mass or more and 10% by mass or less, and still more preferably 7% by mass or more and 9% by mass or less.

[0015] Examples of Compound A include mercaptoacetic acid and its esters, 2-mercaptopropionic acid and its esters, 3-mercaptopropionic acid and its esters, mercaptosuccinic acid and its esters, thiosalicylic acid and its esters, thiocyanuric acid and its esters, mercaptobenzoxazole, mercaptobenzothiazole, mercaptobenzimidazole, ethanethiol, benzenethiol, mercaptophenol, mercaptotoluene, 2-mercaptoethylamine, mercaptoethyl alcohol, mercaptoxylene, thioxylenol, 2-mercaptoquinoline, mercaptocyclohexane, α-mercaptodiphenylmethane, C-mercaptotetrazole, mercaptonaphthalene, mercaptonaphthol, 4-mercaptobiphenyl, mercaptohypoxanthine, mercaptopyridine, 2-mercaptopyrimidine, mercaptopurine, thiocumazone, thiocumothiazone, butane-2,3-dithiol, 2,4,6-trimercapto-s-triazine, 2-dibutylamino-4,6-dimercapto-s-triazine, 2-anilino-4,6-dimercapto-s-triazine, and the like. Examples of mercaptoacetic acid esters include methyl mercaptoacetate, ethyl mercaptoacetate, 2-ethylhexyl mercaptoacetate, and the like. Examples of 2-mercaptopropionic acid esters include methyl 2-mercaptopropionate, ethyl 2-mercaptopropionate, 2-ethylhexyl 2-mercaptopropionate, and the like. Examples of 3-mercaptopropionic acid esters include methyl 3-mercaptopropionate, ethyl 3-mercaptopropionate, 2-ethylhexyl 3-mercaptopropionate, and the like. Compound A preferably contains one or more of these. From the viewpoint of obtaining excellent kneading processability, it preferably contains an organic acid and / or its ester, more preferably contains a carboxylic acid and / or its ester, still more preferably contains a monocarboxylic acid and / or its ester, and even more preferably contains one or more of mercaptoacetic acid and its esters, 2-mercaptopropionic acid and its esters, and 3-mercaptopropionic acid and its esters.

[0016] The modified polymer according to the embodiment can be produced by subjecting an ethylene-α-olefin elastomer, Compound A, and a reaction initiator to a thiol-ene reaction while kneading to modify the ethylene-α-olefin elastomer with Compound A.

[0017] At this time, from the viewpoint of obtaining excellent kneading processability, the compounding amount of Compound A with respect to 100 parts by mass of the ethylene-α-olefin elastomer is preferably 0.5 part by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 7 parts by mass or less, and still more preferably 2 parts by mass or more and 6 parts by mass or less.

[0018] The reaction initiator is a substance that forms radicals at the reaction points where Compound A grafts onto the polymer of the ethylene-α-olefin elastomer. The reaction initiator is not particularly limited as long as it is such a substance, but preferably contains an organic peroxide.

[0019] Examples of the organic peroxide as the reaction initiator include peroxyesters, ketone peroxides, diacyl peroxides, dialkyl peroxides, peroxyketals, alkyl peresters, and the like. Examples of peroxyesters include di(4-t-butylcyclohexyl) peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, diisopropyl peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, di(3-methyl-3-methoxybutyl) peroxydicarbonate, and the like. Examples of ketone peroxides include methyl ethyl ketone peroxide, acetylacetone peroxide, and the like. Examples of diacyl peroxides include benzoyl peroxide, and the like. Examples of dialkyl peroxides include dicumyl peroxide, 1,3-bis-(t-butylperoxyisopropyl)-benzene, and the like. Examples of peroxyketals include t-butyl peroxybenzoate, 1,1-di-t-butylperoxycyclohexane, and the like. Examples of alkyl peresters include α-cumyl peroxyneodecanoate, t-butyl peroxyneodecanoate, and the like. The organic peroxide as the reaction initiator preferably contains one or more of these. From the viewpoint of obtaining excellent kneading processability, it is more preferable to contain peroxyesters, and even more preferable to contain di(4-t-butylcyclohexyl) peroxydicarbonate.

[0020] From the viewpoint of appropriately modifying the ethylene-α-olefin elastomer, the compounding amount of the organic peroxide as the reaction initiator with respect to 100 parts by mass of the ethylene-α-olefin elastomer is preferably 0.05 part by mass or more and 1 part by mass or less, more preferably 0.1 part by mass or more and 0.8 part by mass or less, and even more preferably 0.2 part by mass or more and 0.6 part by mass or less.

[0021] The ratio of the compounding amount of compound A to the compounding amount of the organic peroxide as the reaction initiator in the ethylene-α-olefin elastomer (compounding amount of compound A / compounding amount of organic peroxide) is preferably 5 or more and 15 or less, more preferably 8 or more and 12 or less, from the viewpoint of moderately modifying the ethylene-α-olefin elastomer.

[0022] For kneading the ethylene-α-olefin elastomer, compound A and the reaction initiator, a closed kneader such as a kneader or a Banbury mixer can be used, for example. The kneading temperature is preferably ±5°C of the 1-minute half-life temperature of the organic peroxide of the reaction initiator, from the viewpoint of moderately modifying the ethylene-α-olefin elastomer and suppressing the crosslinking of the ethylene-α-olefin elastomer by the reaction initiator. In the case of a typical reaction initiator, specifically, it is preferably 140°C or higher and 160°C or lower, more preferably 145°C or higher and 155°C or lower. The kneading time is preferably 2 minutes or more and 10 minutes or less, more preferably 3 minutes or more and 7 minutes or less, from the same viewpoint as above.

[0023] The modified polymer according to the embodiment can be used as part or all of the rubber component of the crosslinked rubber composition forming the rubber product.

Example

[0024] (Modified polymer) The modified polymers of the following Examples 1 to 6 and Comparative Examples were prepared. Each configuration is also shown in Table 1.

[0025] <Example 1> EPDM(1) (manufactured by ENEOS MATERIALS Co., Ltd., EP T7241, ethylene content: 52% by mass, diene content (ENB content): 7.7% by mass) was charged into a closed kneader and kneaded, and 3 parts by mass of 3-mercaptopropionic acid and 0.3 parts by mass of an organic peroxide (Perkadox 16, manufactured by Akzo Chemicals, di(4-t-butylcyclohexyl) peroxydicarbonate) as a reaction initiator were added thereto with respect to 100 parts by mass of EPDM(1), and they were kneaded at a temperature of 100°C for 10 minutes to prepare a modified polymer. This modified polymer was designated as Example 1.

[0026] <Example 2> A modified polymer prepared in the same manner as in Example 1, except that methyl 3-mercaptopropionate was used instead of 3-mercaptopropionic acid, and the blending amounts of methyl 3-mercaptopropionate and the organic peroxide as the reaction initiator were 5 parts by mass and 0.5 parts by mass, respectively, per 100 parts by mass of EPDM(1), was designated as Example 2.

[0027] <Example 3> A modified polymer prepared in the same manner as in Example 1, except that 2-ethylhexyl mercaptoacetate was used instead of 3-mercaptopropionic acid, and the blending amounts of 2-ethylhexyl mercaptoacetate and the organic peroxide as the reaction initiator were 5 parts by mass and 0.5 parts by mass, respectively, per 100 parts by mass of EPDM(1), was designated as Example 3.

[0028] <Example 4> A modified polymer prepared in the same manner as in Example 3, except that EPDM(2) (manufactured by ENEOS MATERIALS, EP 57F / C, ethylene content: 67% by mass, diene content (ENB content): 4.5% by mass) was used instead of EPDM(1), was designated as Example 4.

[0029] <Example 5> A modified polymer prepared in the same manner as in Example 3, except that EPDM(3) (manufactured by Mitsui Chemicals, EPT8030M, ethylene content: 47% by mass, diene content (ENB content): 9.5% by mass) was used instead of EPDM(1), was designated as Example 5.

[0030] <Example 6> A modified polymer prepared in the same manner as in Example 3, except that EBDM (manufactured by Mitsui Chemicals, K-9330M, ethylene content: 50% by mass, diene content (ENB content): 7.1% by mass) was used instead of EPDM(1), was designated as Example 6.

[0031] <Comparative Example> A modified polymer was prepared in the same manner as in Example 1, except that maleic anhydride was used instead of 3-mercaptopropionic acid, and the blending amounts of maleic anhydride and the organic peroxide as the reaction initiator were 0.5 parts by mass and 0.05 parts by mass, respectively, based on 100 parts by mass of EPDM(1). This modified polymer was used as a comparative example.

[0032]

Table 1

[0033] (Test evaluation methods and results) The following test evaluations were performed on Examples 1 to 6 and the comparative example.

[0034] <Gel fraction> For each of Examples 1 to 6 and the comparative example, the gel fraction was determined by the toluene swelling method. Specifically, strip-shaped test pieces with a length of 20 mm, a width of 10 mm, and a thickness of 2 mm were immersed in toluene at room temperature for 72 hours to swell, and then dried to remove toluene. Then, from the mass (W0) before toluene immersion and the mass (W1) of the insoluble matter after toluene immersion dried, the gel fraction gw = (W1 / W0) × 100 was calculated. The gel fraction is an index of kneading processability, and it can be evaluated that the higher this value is, the poorer the kneading processability. The results are shown in Table 1.

[0035] <Payne effect index> An uncrosslinked rubber composition P was prepared by blending and kneading para-aramid short fibers (Kevlar (registered trademark), manufactured by Toray DuPont Co., fiber length: 3 mm) into the modified polymer of Example 1. The blending amount of the para-aramid short fibers was 28 parts by mass based on 100 parts by mass of the EPDM before modification of the modified polymer of Example 1. Similarly, an uncrosslinked rubber composition Q was prepared by blending and kneading para-aramid short fibers into unmodified EPDM.

[0036] For each of the unvulcanized rubber composition P and the unvulcanized rubber composition Q, using a rubber analyzer (manufactured by Alpha Technologies, RPA2000), at a measurement temperature of 40°C, a shear strain was applied with a small strain amount of 0.28% and a frequency of 10 Hz to measure the complex elastic modulus G * (0.28%). Similarly, with a strain amount of 60%, the complex elastic modulus G * (60%) was measured. And, as a Payne effect index, the complex elastic modulus G * (60%) / G * (0.28%) was calculated.

[0037] As a result of the measurement, the Payne effect index of the unvulcanized rubber composition P was closer to 1 than that of the unvulcanized rubber composition Q. That is, the modified polymer in which EPDM was modified with 3-mercaptopropionic acid had a lower Payne effect suppressed than the unmodified EPDM. Therefore, it means that the dispersibility of the para-aramid short fibers is excellent. Also, this means that the former has better kneading processability than the latter.

Industrial Applicability

[0038] The present invention is useful in the technical field of modified polymers and their production methods.

Claims

1. A modified polymer in which an ethylene-α-olefin elastomer is modified with a compound having a mercapto group.

2. The modified polymer according to Claim 1, wherein the ethylene content of the ethylene-α-olefin elastomer is 40% by mass or more and 70% by mass or less.

3. The modified polymer according to Claim 1, wherein the ethylene-α-olefin elastomer contains an ethylene-propylene-diene monomer.

4. The modified polymer according to Claim 3, wherein the diene component of the ethylene-propylene-diene monomer is ethylidene norbornene, and the diene content of the ethylene-propylene-diene monomer is 4% by mass or more and 12% by mass or less.

5. The modified polymer according to Claim 1, wherein the compound having a mercapto group contains one or more of 3-mercaptopropionic acid and its esters and mercaptoacetic acid and its esters.

6. A method for producing a modified polymer, which comprises reacting an ethylene-α-olefin elastomer with a compound having a mercapto group while kneading an ethylene-α-olefin elastomer, a compound having a mercapto group, and a reaction initiator to modify the ethylene-α-olefin elastomer with the compound having a mercapto group.

7. The method for producing a modified polymer according to Claim 6, wherein the reaction initiator is a peroxydicarbonate of an organic peroxide.

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