TW201502186A - Rubber composition and vulcanized molding article thereof - Google Patents

Abstract

The present invention provides a chloroprene-based rubber composition and a vulcanized molding article thereof even without the use of a styrene-butadiene block copolymer as a compatibilizer, but can obtain a vulcanized molding article that maintains the original mechanical strength of the chloroprene rubber and also has excellent low-temperature characteristics. The rubber composition of the present invention comprises, with respect to 100 parts by mass of the rubber constituent comprising 10-90 mass% of a chloroprene rubber, and 10-90 mass% of a natural rubber or a isoprene rubber, 3-30 parts by mass of adipic acid-based plasticizers represented by the structure of the following chemical formula (I), (in the chemical formula (I), R1,R2 represents an alkyl having a carbon number of 1-20, or a ether which may have an alkyl having a carbon number of 1-20 and having one or more ether linkage).

Description

Rubber composition and vulcanized molded body thereof

The present invention relates to a rubber composition and a vulcanized molded body obtained by vulcanization molding the rubber composition. More specifically, the present invention relates to a mixed rubber composition in which a natural rubber or an isoprene rubber is blended in a chloroprene rubber and a vulcanized formed body thereof.

Chloroprene rubber is excellent in heat resistance, weather resistance, ozone resistance, chemical resistance, and the like, and is used in a wide range of fields such as general industrial rubber products, automobile parts, and adhesives. On the other hand, in some applications, chloroprene rubber has insufficient rubber properties in a low temperature environment. Therefore, in order to improve the low-temperature characteristics, a technique of mixing a natural rubber having a relatively low-temperature property in a chloroprene rubber has been continuously studied (see Patent Documents 1 to 3).

For example, Patent Document 1 proposes a rubber composition in which a sulfur-based vulcanizing agent and a thiuram-based compound are added to a mixed rubber containing a chloroprene rubber and a natural rubber, thereby not only improving the low temperature. Rubber properties also improve storage stability and process safety. Further, Patent Document 2 discloses a rubber composition comprising natural rubber, chloroprene rubber, sulfur, zinc white, and a vulcanization accelerator, wherein the vulcanization promotion The agent vulcanizes the natural rubber but does not vulcanize the chloroprene rubber. The rubber composition described in Patent Document 2 achieves improved attenuation characteristics and low temperature by using a usual vulcanization accelerator together with a vulcanization accelerator which is effective for natural rubber but less effective for chloroprene rubber. Balance of characteristics.

Further, Patent Document 3 proposes a chloroprene rubber composition which is prepared by blending a specific amount of styrene and butyl in a mixed rubber of chloroprene rubber and natural rubber in order to improve the mechanical strength of the vulcanized molded body. Copolymer of alkene. In the chloroprene rubber composition of Patent Document 3, the block copolymer of styrene and butadiene becomes a compatibilizer of chloroprene rubber and natural rubber, and can be finely dispersed in chloroprene rubber in natural rubber. In the state in which the co-vulcanization is carried out, a sulfide having excellent compression and permanent strain over a wide temperature range and excellent mechanical strength is obtained.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 11-172046

[Patent Document 2] Japanese Patent Laid-Open No. Hei 11-153169

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2012-111899

However, the rubber composition described in the above-mentioned Patent Document 3 has a problem that if the mixing ratio of the chloroprene rubber to the natural rubber deviates by 60:40 to 95:5 by mass ratio, styrene and The block copolymer of butadiene does not sufficiently function as a compatibilizer. Therefore, a rubber composition is not used which does not use a block copolymer of styrene and butadiene. As the compatibilizer, the mixing ratio of the chloroprene rubber and the natural rubber can be arbitrarily set, and a vulcanized molded body excellent in mechanical strength and low-temperature characteristics can be obtained.

Accordingly, it is a primary object of the present invention to provide a rubber composition and a vulcanization former which can maintain a chloroprene rubber even without using a block copolymer of styrene and butadiene as a compatibilizer. A vulcanized body which is excellent in mechanical strength and excellent in low-temperature characteristics.

The rubber composition of the present invention contains the following chemical formula (I) with respect to 100 parts by mass of the rubber component containing 10 to 90% by mass of the chloroprene rubber and 10 to 90% by mass of the natural rubber or the isoprene rubber. The adipic acid plasticizer having the structure shown is 3 to 30 parts by mass.

In the above formula (I), R ₁ and R _{2 each} represent an alkyl group having a total carbon number of 1 to 20, or an alkyl group bonded by one or more ether bonds, and the total number of carbon atoms is an integer of 1 or more and 20 or less. ether.

As the chloroprene rubber, at least one chloroprene rubber selected from the group consisting of thiol-modified chloroprene rubber, xanthogen-modified chloroprene rubber, and sulfur can be used. Denatured neoprene rubber.

Further, as the adipic acid plasticizer, at least one compound selected from the group consisting of dimethyl adipate and diethyl adipate can be used. Dipropyl adipate, dibutyl adipate, diisopropyl adipate, diisobutyl adipate, diisononyl adipate, diisononyl adipate, adipic acid (2-Ethylhexyl) ester, bis(2-butoxyethyl) adipate and bis[2-(2-butoxyethoxy)ethyl] adipate.

On the other hand, the chloroprene rubber of the present invention may further contain 0.1 to 10 parts by mass of the glycol ether-based plasticizer having the structure represented by the following chemical formula (II) per 100 parts by mass of the rubber component.

[Chemical 2] R ₃ -(OCH ₂ CH ₂ ) ₂ OH···(II)

In the above chemical formula (II), R ₃ represents an alkyl group having a total number of carbon atoms of 1 to 20, or an alkyl group having an alkyl group bonded by one or more ether bonds and having a total carbon number of 1 to 20 in total.

As the glycol ether-based plasticizer, at least one compound selected from the group consisting of diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and diethylene glycol can be used. Monohexyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monophenyl ether and diethylene glycol mono(2-ethylhexyl) ether.

The vulcanization molding system of the present invention is obtained by vulcanization molding the aforementioned rubber composition.

According to the present invention, even if a block copolymer of styrene and butadiene is not used as the compatibilizer, a vulcanized molded article excellent in rubber properties at low temperature and excellent in mechanical strength can be obtained.

Hereinafter, the form for carrying out the invention will be described in detail. Furthermore, the present invention is not limited to the embodiments described below.

(First embodiment)

First, the rubber composition of the first embodiment of the present invention will be described. The rubber composition of the present embodiment contains a specific structure of 100 parts by mass of the rubber component containing 10 to 90% by mass of the chloroprene rubber and 10 to 90% by mass of the natural rubber or the isoprene rubber. The acid plasticizer is 3 to 30 parts by mass.

[chloroprene rubber]

The chloroprene rubber is obtained by polymerizing a raw material monomer containing 2-chloro-1,3-butadiene while adjusting the molecular weight. The chloroprene rubber used in the rubber composition of the present embodiment may be obtained by separately polymerizing 2-chloro-1,3-butadiene, or may be 2-chloro-1,3- Butadiene is copolymerized with one or more other monomers copolymerizable therewith.

Examples of the monomer copolymerizable with chloroprene include esters of acrylic acid such as methyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; or methyl methacrylate or butyl methacrylate; An ester of methacrylic acid such as 2-ethylhexyl methacrylate; or 2-hydroxyethyl (meth)acrylate, 2-hydroxymethyl (meth)acrylate, or (meth)acrylic acid- Hydroxy (meth) acrylate such as 2-hydroxypropyl ester; or 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, acrylonitrile, and the like.

In the rubber composition of the present embodiment, it is particularly preferred to use 2-chloro a chloroprene rubber obtained by copolymerizing 1,3-butadiene with 2,3-dichloro-1,3-butadiene, more preferably 5 to 20% by mass of 2,3-dichlorobutyl A chloroprene rubber of a diene unit. When such a chloroprene rubber is used, a vulcanized molded article having excellent rubber properties and excellent in rubber properties in a wide temperature range from a low temperature region to a high temperature region can be obtained.

On the other hand, chloroprene rubber can be classified into a type in which the crystallization rate is slow, a type in which the crystallization rate is not fast or slow, and a type in which the crystallization rate is fast, depending on the crystallization rate. The rubber composition of the present embodiment may be any of the above-described types of chloroprene rubber, and may be appropriately selected and used depending on the use and the like.

The chloroprene rubber can be classified, for example, as a sulfur-denatured chloroprene rubber and a non-sulfur-modified chloroprene rubber. The sulfur-denatured chloroprene rubber is obtained by copolymerizing a raw material monomer having 2-chloro-1,3-butadiene as a main component with sulfur, and the obtained copolymer is subjected to disulfide autumn. Lamb is plasticized and adjusted to a specific Mooney viscosity.

Further, as the non-sulfur-modified chloroprene rubber, a thiol-modified chloroprene rubber and a xanthogen-based modified chloroprene rubber are generally known. Here, the thiol-modified chloroprene rubber is obtained by polymerizing an alkyl thiol such as n-dodecyl mercaptan, t-dodecyl mercaptan or octyl mercaptan as a molecular weight modifier, and a xanthogen group. The denatured chloroprene rubber is obtained by polymerizing an alkylxanthogen group-based compound as a molecular weight modifier.

The rubber composition of the present embodiment is not restricted by the above classification, and any type of chloroprene can be used. Further, the chloroprene rubber may be used alone or in combination of different types of chloroprene rubber. The mixing ratio at this time is not particularly limited and may be appropriately set depending on the purpose or use.

[Natural rubber or isoprene rubber]

A known natural rubber or isoprene rubber can be used for the rubber composition of the present embodiment, and the origin, type and structure thereof are not particularly limited. In addition, one type of natural rubber and isoprene rubber may be used, and a plurality of kinds of natural rubber or isoprene rubber having different origins or structures may be mixed and used at an arbitrary ratio depending on the purpose or use.

[mixing ratio of chloroprene rubber to natural rubber or isoprene rubber]

The rubber component of the rubber composition of the present embodiment is a chloroprene rubber, a natural rubber or an isoprene rubber. When the content of the chloroprene content of the rubber component is less than 10% by mass, that is, if the content of the natural rubber or the isoprene rubber is more than 90% by mass, the heat resistance and weather resistance of the vulcanized molded article are insufficient. On the other hand, when the natural rubber or the isoprene rubber is mixed with the chloroprene rubber, the low-temperature characteristics of the vulcanized molded body can be improved, and when the chloroprene content of the rubber component exceeds 90% by mass, that is, When the content of the natural rubber or the isoprene rubber is less than 10% by mass, the low-temperature characteristics of the vulcanized molded article are insufficient.

Therefore, the chloroprene content of the rubber component is set to 10 to 90% by mass. Further, the content of the natural rubber or isoprene rubber of the rubber component is 10 to 90% by mass, and the mixing ratio of the chloroprene rubber to the natural rubber or the isoprene rubber is chloroprene in terms of mass ratio. Rubber: natural rubber or isoprene rubber = 10:90~90:10. Further, in view of the aforementioned improvement of the characteristics of the vulcanized molded body, the mixing of the chloroprene rubber with the natural rubber or the isoprene rubber is preferably a mass ratio of the chloroprene rubber: However, rubber or isoprene rubber = 35:65~85:15, more preferably chloroprene rubber: natural rubber or isoprene rubber = 60:40~80:20.

[Adipic acid plasticizer]

The adipic acid plasticizer used in the rubber composition of the present embodiment has a chemical structure represented by the following chemical formula (I). In the following chemical formula (I), R ₁ and R _{2 each} represent an alkyl group having a total carbon number of 1 to 20, or an alkyl group bonded by one or more ether bonds, and the total carbon number is 1 or more and 20 or more. The following integer ethers.

In the rubber composition of the present embodiment, the adipic acid plasticizer represented by the above chemical formula (I) is contained in an amount of 3 to 30 parts by mass based on 100 parts by mass of the rubber component. When the amount of the adipic acid plasticizer is less than 3 parts by mass per 100 parts by mass of the rubber component, the natural rubber and the isoprene rubber cannot be stably dispersed in the chloroprene rubber. The microdispersed state becomes unstable, and the mechanical strength of the vulcanized molded body is lowered. In addition, when the amount of the adipic acid plasticizer is more than 30 parts by mass per 100 parts by mass of the rubber component, the amount of the plasticizer is excessive, which causes a poor appearance due to bleeding out.

The blending amount of the adipic acid plasticizer represented by the above formula (I) is preferably relative to the rubber from the viewpoint of improving the mechanical strength of the vulcanized molded body. The rubber component is preferably 5 parts by mass or more per 100 parts by mass, and is preferably 20 parts by mass or less per 100 parts by mass of the rubber component from the viewpoint of suppressing bleeding of the plasticizer.

The adipic acid plasticizer to be used in the rubber composition of the present embodiment is not particularly limited as long as it is a structure represented by the above chemical formula (I). Among the various adipic acid plasticizers, from the viewpoint of the balance between the tensile strength and the elongation at break in the case of forming a vulcanized molded body, preferred are: dimethyl adipate, diethyl adipate, and Dipropyl diacrylate, dibutyl adipate, diisopropyl adipate, diisobutyl adipate, diisononyl adipate, diisononyl adipate, adipic acid bis ( 2-ethylhexyl)ester, bis(2-butoxyethyl) adipate, bis[2-(2-butoxyethoxy)ethyl] adipate. These adipic acid plasticizers may be used singly or in combination of plural kinds.

[Glycol ether plasticizer]

In the rubber composition of the present embodiment, in addition to the above respective components, a glycol ether-based plasticizer having a structure represented by the following chemical formula (II) may be further prepared. In the following chemical formula (II), R ₃ represents an alkyl group having a total carbon number of 1 to 20, or an alkyl group is bonded by one or more ether bonds, and the total carbon number is an integer of 1 to 20. ether.

R ₃ -(OCH ₂ CH ₂ ) ₂ OH···(II)

In the case of arranging the glycol ether-based plasticizer having the structure represented by the above formula (II), it is preferably added in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the rubber component. Thereby, the machine for vulcanizing the molded body can be further improved strength. In addition, when the amount of the glycol ether-based plasticizer is less than 0.1 part by mass or more than 10 parts by mass per 100 parts by mass of the rubber component, the effect of improving the mechanical strength of the vulcanized molded article is insufficient.

The glycol ether-based plasticizer to be blended in the rubber composition of the present embodiment is not particularly limited as long as it is a structure represented by the above chemical formula (II). Among the various glycol ether-based plasticizers, from the viewpoint of improving the mechanical strength at the time of forming a vulcanized molded body, it is preferably diethylene glycol monomethyl ether, diethylene glycol monoethyl ether or diethylene glycol monobutylene. Ether, diethylene glycol monohexyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monophenyl ether and diethylene glycol mono(2-ethylhexyl) ether. These glycol ether-based plasticizers may be used singly or in combination of plural kinds.

[Vulcanizing agent]

A vulcanizing agent may be added to the rubber composition of the embodiment. Examples of the vulcanizing agent which can be added to the rubber composition of the present embodiment include sulfur, bismuth, magnesium, zinc, calcium, strontium, barium, titanium, tin, zirconium, hafnium, vanadium, niobium, molybdenum, tungsten, rhenium, a metal monomer such as selenium, iron, nickel, cobalt or ruthenium, or an oxide or hydroxide of the metal. Among these vulcanizing agents, sulfur, calcium oxide, zinc oxide, cerium oxide, antimony trioxide, and magnesium oxide are preferred in terms of particularly high vulcanization effect. Further, the vulcanizing agent may be used singly or in combination of two or more.

[Other auxiliary materials]

In the rubber composition of the present embodiment, in addition to the above-described respective components, various auxiliary materials which are usually used in the production of a rubber product may be added: a vulcanization accelerator, a filler or a reinforcing agent, a plasticizer, a processing aid or Lubricants, anti-aging agents, decane coupling agents, and the like.

<vulcanization accelerator>

The vulcanization accelerator to be blended in the rubber composition of the present embodiment is not particularly limited, and examples thereof include a thiourea vulcanization accelerator, a thiazole vulcanization accelerator, a thiuram vulcanization accelerator, and an oxime vulcanization accelerator. . These vulcanization accelerators may be used singly or in combination of two or more.

<filler or enhancer>

The filler or the reinforcing agent is added to adjust the hardness of the rubber or to increase the mechanical strength, and the type thereof and the like are not particularly limited, and examples thereof include carbon black, cerium oxide, clay, talc, and calcium carbonate. In addition, the amount of the filler and the reinforcing agent to be added is not particularly limited, and can be appropriately set depending on the physical properties required for the rubber composition or the vulcanized molded article.

In addition, the blending amount of the filler or the reinforcing agent is usually 15 to 200 parts by mass per 100 parts by mass of the rubber component from the viewpoint of the balance between the workability and the mechanical strength of the vulcanized molded body. When the amount of the filler or the reinforcing agent is less than 15 parts by mass per 100 parts by mass of the rubber component, the strength of the vulcanized molded article may be insufficient. In addition, when more than 200 parts by mass of the filler or the reinforcing agent is blended per 100 parts by mass of the rubber component, the workability is rapidly deteriorated.

<Other plasticizers>

In the rubber composition of the present embodiment, a plasticizer other than the adipic acid plasticizer and the glycol ether plasticizer may be blended. The other plasticizer to be added to the rubber composition of the present embodiment is not particularly limited as long as it has compatibility with the chloroprene rubber, and examples thereof include rapeseed oil and flaxseed. Vegetable oil such as seed oil, castor oil, coconut oil, phthalate plasticizer, DUP (di-undecyl phthalate), DOS (dioctyl sebacate), DOA Dioctyl acid ester, ester plasticizer, ether ester plasticizer, thioether plasticizer, aromatic hydrocarbon oil, naphthenic oil, lubricating oil, process oil, paraffin, liquid paraffin, petroleum jelly, petroleum asphalt, etc. Plasticizer.

These plasticizers can be used singly or in combination of two or more. In addition, the amount of the other plasticizer can be appropriately set according to the physical properties required for the rubber composition or the vulcanized molded article, and from the viewpoint of further improving the workability, it is preferably 5 parts per 100 parts by mass of the rubber component. ~50 parts by mass.

<Processing Aids, Lubricants>

The processing aid or the lubricant is added for the purpose of kneading or vulcanizing the rubber composition, and it is easy to peel off from a roll, a molding die, a screw of an extruder, or the like, thereby improving processing characteristics and surface lubricity. Specific examples of the processing aid or the lubricant include a fatty acid-based processing aid such as stearic acid, a paraffin-based processing aid such as polyethylene, and a fatty acid decylamine.

<anti-aging agent>

In the rubber composition of the present embodiment, an anti-aging agent can be formulated for the purpose of improving heat resistance. The anti-aging agent used in the usual rubber composition has a primary anti-aging agent for capturing free radicals and preventing auto-oxidation, and a secondary anti-aging agent for detoxifying the hydroperoxide. The rubber composition of the present embodiment can be used therein. Any one.

Here, specific examples of the primary anti-aging agent include a phenol-based anti-aging agent, an amine-based anti-aging agent, an acrylate-based anti-aging agent, and an imidazole-based anti-aging agent. An aging agent, a metal amide, a wax, and the like. Further, specific examples of the secondary anti-aging agent include a phosphorus-based anti-aging agent, a sulfur-based anti-aging agent, and an imidazole-based anti-aging agent. These anti-aging agents may be used singly or in combination of two or more.

<decane coupling agent>

In the rubber composition of the present embodiment, in order to improve the adhesion between the chloroprene rubber and the natural rubber and the filler or the reinforcing agent, and to increase the mechanical strength of the vulcanized product, a decane couple may be added together with the filler or the reinforcing agent. mixture. The decane coupling agent may be added at the time of kneading the rubber composition, or may be in the form of a surface treatment of a filler or a reinforcing agent with a decane coupling agent in advance, and when the filler or the reinforcing agent is added as an auxiliary material, it is added together In the rubber composition.

[Production method]

When the rubber composition of the present embodiment is produced, a usual method for producing a rubber composition can be applied. Specifically, the rubber composition of the present embodiment can be produced by molding a chloroprene rubber, a natural rubber or an isoprene rubber, an adipic acid plasticizer, or a glycol ether as desired. The agent, vulcanizing agent, and other auxiliary materials are metered in a specific amount and mixed. The mixing method at this time is not particularly limited, and for example, kneading may be carried out at a temperature equal to or lower than the vulcanization temperature by using a known kneading device such as a kneader, an open roll, a Banbury mixer, and an extruder.

Since the rubber composition of the present embodiment is a mixed rubber of a chloroprene rubber and a natural rubber or an isoprene rubber, a specific amount of adipic acid plasticizer having a specific structure is added, so that the rubber property at a low temperature is obtained. Excellent, Further, the mechanical strength is also excellent, and various vulcanized molded bodies which are industrially useful can be obtained.

(Second embodiment)

Next, a vulcanized molded body according to a second embodiment of the present invention will be described. In the vulcanized molded article of the first embodiment, the rubber composition of the first embodiment is vulcanized into a shape conforming to the target. The vulcanization molding method at this time is not particularly limited, and may be, for example, press vulcanization, injection vulcanization, direct pot vulcanization, indirect pot vulcanization, direct steam continuous vulcanization, continuous vulcanization at atmospheric pressure, or after molding of the rubber composition. The vulcanization may be carried out by a known method such as continuous vulcanization pressurization.

The vulcanization temperature is not particularly limited, and can be appropriately set depending on the composition of the rubber composition or the type of the vulcanizing agent. Generally, the vulcanization temperature is preferably from 140 to 190 ° C, more preferably from 150 to 180 ° C, from the viewpoint of productivity and process safety. Here, the "processing safety" is a processing characteristic obtained based on the evaluation of the coking time, and the "processing safety" greatly affects the rate of occurrence of defects. Specifically, when the coking time is short, the frequency of the unvulcanized rubber component is vulcanized and the molding failure occurs during the molding process at a high temperature.

[Examples]

Hereinafter, the effects of the present invention will be specifically described by exemplifying the examples and comparative examples of the present invention. In the present embodiment, the rubber compositions of the examples and the comparative examples were produced by changing the component compositions, and the properties at the time of forming the vulcanized molded articles were evaluated.

[Production of rubber composition]

A chloroprene rubber, a natural rubber, and an adipic acid plasticizer, and a part of the examples, a glycol ether plasticizer, and a carbon black as a reinforcing agent, a stearic acid as a processing aid, and an anti-aging agent The mixture was blended at a specific ratio and kneaded using a pressure kneading tester. In the kneaded product obtained in the kneading tester, sulfur, zinc oxide, magnesium oxide as a vulcanizing agent and excipient thiourea as a vulcanization accelerator are further added at a specific ratio, and two open rolls having a diameter of 8 Å are used. The mixture was kneaded at 40 ° C to prepare a rubber composition sheet having a thickness of 2.3 mm.

At this time, the chloroprene rubber is a thiol-modified chloroprene rubber, a xanthogen-based modified chloroprene rubber, and a sulfur-denatured chloroprene rubber. In addition, natural rubber is used in standard Malaysian rubber, and isoprene rubber is commercially available. Further, commercially available products are used as the adipic acid plasticizer and the glycol ether plasticizer. Sulfur, zinc oxide and magnesium oxide are used as the vulcanizing agent, and ethylene sulfide urea is used as the vulcanization accelerator. N-762 is used for carbon black and stearic acid is used as a processing aid. As the anti-aging agent, N-phenyl-1-naphthylamine and 4,4'-bis(α,α-dimethylbenzyl)diphenylamine were used.

[Evaluation]

Each of the rubber composition sheets of the examples and the comparative examples produced by the above method was press-vulcanized under the conditions of a temperature of 160 ° C, 5 minutes, and a pressure of 0.8 MPa to prepare a vulcanized molded body sheet having a thickness of 2.0 mm. The test piece was cut out from the molded body sheet, and tensile strength, elongation at break, duometer hardness, and embrittlement temperature were measured by the methods described below.

<tensile strength, elongation at break>

Tensile strength and elongation at break are values of mechanical strength, and are measured in accordance with JIS K6251. Specifically, the self-vulcanized molded body sheet is cut A dumbbell-shaped No. 3 test piece was cut out, and the measurement was carried out under the conditions of a temperature of 23 ° C and a tensile speed of 500 mm/min using a fully automatic rubber tensile tester (AGS-H manufactured by Shimadzu Corporation). The results showed that the tensile strength was 15 MPa or more and the elongation at break was 450% or more.

<hardness tester hardness>

The hardness of the durometer was measured in a state in which three sheets of the vulcanized molded body sheets were stacked under the temperature conditions of 23 ° C according to JIS K6253-3. A durometer (Asker rubber hardness meter type A) was used for the measurement. When the hardness of the resulting durometer was 40 to 70 minutes, it was evaluated as qualified.

<embrittlement temperature>

The embrittlement temperature is a value of an index of low-temperature characteristics and is measured in accordance with JIS K6261. Specifically, the embrittlement temperature is applied to a cantilever-type short strip test piece placed in a test tank at a certain temperature, and a specific impact is applied, and the number of damages is measured at each temperature, and the obtained value is substituted into a specific calculation. Calculated in the formula. When the result embrittlement temperature was -40 ° C or less, it was evaluated as qualified.

The compositions of the rubber compositions of the examples and the comparative examples and the evaluation results thereof are summarized in Tables 1 to 6 below.

As shown in the above Table 1, the rubber composition of Comparative Example 1 had a small amount of addition of the adipic acid plasticizer, and thus the mechanical strength of the vulcanized molded article was inferior to those of the rubber compositions of Examples 1 to 4. Further, in Comparative Example 2, since the amount of the adipic acid plasticizer added was large, appearance defects due to bleeding occurred. Further, as shown in the above Tables 2 and 3, the rubber compositions of Comparative Examples 3 to 6 were inferior to Example 2 because the plasticizer was not the adipic acid plasticizer having the structure represented by the above formula (I). 5~14 rubber composition, The vulcanized molded body has poor mechanical strength.

As shown in Table 4 above, the rubber component is only a chloroprene rubber, and the rubber composition of Comparative Examples 8 to 10 which is not mixed with natural rubber or isoprene rubber is chloroprene rubber and rubber component. The rubber compositions of Examples 2 and 15 to 19 of the mixed rubber of natural rubber have poor low-temperature characteristics (embrittlement temperature). Further, the rubber component was only a natural rubber, and the rubber composition of Comparative Example 7 in which the chloroprene rubber was not mixed was inferior to the rubber composition of Examples 2 and 15 to 19 in mechanical strength (tensile strength).

On the other hand, as shown in the above Tables 5 and 6, the rubber composition of Examples 20 to 31 in which the adipic acid plasticizer of a specific structure was used in combination with the glycol ether plasticizer was compared with the addition of only adipic acid. The rubber composition of Example 2 which is a plasticizer has an improved elongation at break when the vulcanized molded body is formed.

Based on the above results, it was confirmed that a specific amount of a specific adipic acid plasticizer can be vulcanized by blending a mixture of chloroprene rubber and natural rubber or isoprene rubber to obtain excellent mechanical strength and low temperature characteristics. The vulcanized molded body.

Claims (6)

A rubber composition containing 100 parts by mass of a rubber component containing 10 to 90% by mass of chloroprene rubber and 10 to 90% by mass of natural rubber or isoprene rubber, and containing the following chemical formula (I) The structure of the adipic acid plasticizer is 3 to 30 parts by mass, (In the above formula (I), R ₁ and R _{2 each} represent an alkyl group having a total carbon number of 1 to 20, or an alkyl group bonded by one or more ether bonds, and the total number of carbon atoms is an integer of 1 or more and 20 or less. Ether). The rubber composition according to claim 1, wherein the chloroprene rubber is at least one chloroprene rubber selected from the group consisting of thiol-modified chloroprene rubber and xanthogen-based denatured chloroprene Diene rubber and sulfur-modified chloroprene rubber. The rubber composition according to claim 1 or 2, wherein the adipic acid plasticizer is at least one compound selected from the group consisting of dimethyl adipate, diethyl adipate, and adipic acid. Dipropyl ester, dibutyl adipate, diisopropyl adipate, diisobutyl adipate, diisononyl adipate, diisononyl adipate, adipic acid bis (2- Ethylhexyl)ester, bis(2-butoxyethyl) adipate and bis[2-(2-butoxyethoxy)ethyl] adipate. The rubber composition according to any one of claims 1 to 3, further comprising a glycol ether-based plasticizer having a structure represented by the following chemical formula (II) per 100 parts by mass of the rubber component: 0.1 to 10 R ₃ -(OCH ₂ CH ₂ ) ₂ OH···(II) (In the above chemical formula (II), R ₃ represents an alkyl group having a total carbon number of 1 to 20, or an alkyl group; The above ether bond is bonded, and the total carbon number is an integer of 1 to 20). The rubber composition according to claim 4, wherein the glycol ether-based plasticizer is at least one compound selected from the group consisting of diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol. Monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monophenyl ether and diethylene glycol mono(2-ethylhexyl) ether. A vulcanized molded article obtained by vulcanization molding the rubber composition according to any one of claims 1 to 5.