JP3498840B2 - Chloroprene rubber composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chloroprene rubber composition, and more specifically, it has excellent vulcanization adhesiveness and the like, and the vulcanized product has a high static shear modulus and elongation at break. The present invention relates to a chloroprene rubber composition.

[0002]

2. Description of the Related Art A laminated rubber bearing is installed between the foundation of a structure such as a bridge or a building and its superstructure, and mainly extends the natural period of the vibration system of the entire structure to prevent earthquake motion. Used to reduce the response of structures. The structure is made by laminating several layers of rubber sheets and steel plates alternately, and requires high rigidity and high proof strength in the vertical direction and low rigidity and large deformability in the horizontal direction.

The properties of rubber materials are high static shear modulus (denoted by GS) and high elongation at break (denoted by EB).
Is required. Natural rubber or chloroprene rubber is used for this rubber material. As a required property, in the case of chloroprene rubber, GS is 10 ± 1 in the “Road Bridge Support Handbook” (published in July 1991, edited by Japan Road Association).
The standard value of kgf / cm ² and EB is 440% or more.

On the other hand, with the recent increase in the size of bridges and buildings, the demand for higher GS and higher EB of laminated rubber bearing rubber materials is increasing.

As a measure for increasing the GS of chloroprene rubber in general applications, on the polymer side, the sulfur copolymerization ratio is increased, the number of crosslinking points is increased by adjusting the polymerization temperature, and on the compounding / prescribing side. Increase the amount or type of reinforcing filler such as carbon black,
Reinforcing resins such as phenol resins have been blended, and the amount of vulcanization accelerator has been increased or the type has been changed.

[0006]

However, these methods have the disadvantages such as low temperature resistance, scorch resistance, heat aging resistance, and deterioration of compression set. Furthermore, high G
When S is added, EB generally tends to decrease, so that a high balance between GS and EB as a supporting rubber is maintained, and a chloroprene rubber composition that satisfies various requirements, for example, static shear elasticity of a vulcanized product. Rate 13.5 kgf / cm
High E with a breaking elongation of 600% or more when a high GS of ² is used.
B chloroprene-based rubber composition, while EB is 800
% Or more, the static shear modulus is 8 kgf / cm ²
It has been difficult to obtain a chloroprene-based rubber composition that gives a vulcanized product having a high balance such as

The object of the present invention is to solve the above-mentioned problems, to simultaneously satisfy a high GS and a high EB of a vulcanized product, and to have a good balance of other mechanical properties, a good low temperature resistance, and a vulcanized adhesive property. It is to provide a chloroprene-based rubber composition having excellent properties and suitable for bearing a laminated rubber.

[0008]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the above problems, and found that the combination of a specific chloroprene rubber and carbon black can achieve this. Completed the invention.

That is, the present invention is characterized in that it contains chloroprene rubber and carbon black and that the vulcanized product has a static shear modulus B and an elongation at break A satisfying the following formula (1). Is a chloroprene-based rubber composition. A ≧ −36.4 × B + 1090 (1) where A is elongation at break (%) and B is static shear modulus (k
gf / cm ² ).

In the above formula, B is preferably 4 or more and 20 or less, more preferably 6 or more and 18 or less, and particularly preferably 8 or more and 16 or less.

The present invention further comprises a chloroprene rubber composition containing a xanthogen-modified chloroprene rubber and carbon black other than acetylene black, or a chloroprene rubber other than the xanthogen-modified chloroprene rubber and acetylene black. A chloroprene rubber composition, or a chloroprene rubber composition for bearings, which is a chloroprene rubber composition containing xanthogen-modified chloroprene rubber and acetylene black, preferably a xanthogen-modified chloroprene rubber and acetylene. A chloroprene rubber composition containing black, which is a chloroprene rubber composition suitable for bearings.

The present invention will be described in more detail below. The rubber component in the chloroprene rubber composition of the present invention is mainly composed of chloroprene rubber,
In addition to chloroprene rubber, natural rubber, butyl rubber, BR, NBR, EPDM, etc. can be contained, if necessary. The content of these is preferably 0 to 50 phr.

The chloroprene rubber used in the present invention is obtained by polymerizing a homopolymer of chloroprene or a mixture of chloroprene and at least one other copolymerizable monomer (hereinafter referred to as chloroprene-based monomer). It is a copolymer obtained.

Examples of the monomer copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene,
1-chloro-1,3-butadiene, sulfur, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, acrylic acid, methacrylic acid and their esters, and the like, which can be used within a range satisfying the object of the present invention. .

The polymerization method for obtaining the chloroprene rubber used in the present invention is not particularly limited, and an ordinary polymerization method can be used. The chloroprene-based monomer is usually used in the presence of a polymerization initiator generally used for the polymerization of chloroprene. It can be obtained by emulsion polymerization according to the method used.

The emulsifier for carrying out this emulsion polymerization is not particularly limited, and is generally an emulsifier used for emulsion polymerization of chloroprene, such as an alkali metal salt of a saturated or unsaturated fatty acid having 6 to 22 carbon atoms, or rosin acid. Alternatively, an alkali metal salt of disproportionated rosin acid, an alkali metal salt of a formalin condensate of β-naphthalenesulfonic acid, and the like are used.

Chloroprene rubber is a polymer of chloroprene and is produced by emulsion polymerization. It is classified into sulfur-modified chloroprene rubber, mercaptan-modified chloroprene rubber, and xanthogen-modified chloroprene rubber depending on the type of molecular weight modifier. It The sulfur-modified chloroprene rubber is obtained by plasticizing a polymer obtained by copolymerizing sulfur and chloroprene with thiuram disulfide to adjust the Mooney viscosity to a predetermined value. The mercaptan-modified chloroprene rubber uses alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan and octyl mercaptan as a molecular weight modifier. The xanthogen-modified chloroprene rubber uses an alkylxanthogen compound as a molecular weight modifier.

As the chloroprene rubber of the present invention, chloroprene rubber modified by any method can be used, but it has an excellent balance of high GS and high EB and other mechanical properties such as tensile strength and modulus. Good balance, low temperature resistance, scorch resistance, heat aging resistance, compression set,
In addition, a xanthogen-modified chloroprene rubber is most preferable because a product having further excellent processability and vulcanization adhesiveness can be obtained.

Specific examples of the alkylxanthogen compound include dimethylxanthogen disulfide, diethylxanthogen disulfide, diisopropylxanthogen disulfide and diisobutylxanthogen disulfide.

The amount of alkylxanthogen compound used is
It is selected so that the molecular weight of the chloroprene polymer (or the Mooney viscosity of the chloroprene rubber obtained by isolating the polymer) is appropriate. Depending on the structure of the alkyl group and the target molecular weight, it is generally 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the chloroprene-based monomer,
It is preferably used in the range of 0.3 to 1.0 part by weight.

As the polymerization initiator, known organic peroxides such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide and t-butyl hydroperoxide which are generally used for emulsion polymerization of chloroprene are used. .

In the present invention, the polymerization temperature and the final conversion rate of the monomer are not particularly limited, but the polymerization temperature is 0 to 50.
The temperature is preferably 0 ° C, and more preferably 20 to 50 ° C. Further, it is preferable to carry out so that the monomer conversion rate falls within the range of 60 to 90%, and when this conversion rate is reached, a small amount of a polymerization inhibitor is added to terminate the polymerization.

Examples of the polymerization inhibitor include thiodiphenylamine, 4-tert-butylcatechol, 2,
A commonly used inhibitor such as 2-methylenebis-4-methyl-6-tert-butylphenol is used.

Unreacted monomers are removed by, for example, steam stripping, and then the latex p
The polymer can be isolated by adjusting H and subjecting it to conventional freeze-coagulation, washing with water, drying with hot air, and the like.

As the carbon black blended in the chloroprene rubber composition of the present invention, either thermal black or acetylene black by a thermal decomposition method, or furnace black or channel black by an incomplete combustion method can be used. Furnace black and acetylene black have a large reinforcing effect and are advantageous. Among these carbon blacks, those having a DBP oil absorption of 50 ml / 100 g or more are preferable, and further 10
0-400ml / 100g, especially 150-350ml /
100 g is preferable.

Further, acetylene black is a carbon black obtained by thermally decomposing acetylene gas, and crystallization progresses, a structure develops, and oil absorption is large.
A chloroprene-based rubber composition using acetylene black as a reinforcing agent is most preferable because it gives a vulcanized product with high GS and high EB.

The amount of carbon black added is preferably 20 to 80 parts by weight, more preferably 30 to 60 parts by weight, based on 100 parts by weight of chloroprene rubber. If the addition amount exceeds 80 parts by weight, the workability is deteriorated, scorch is likely to occur, and the brittle temperature of the vulcanized product is increased. Addition amount is 2
If the amount is less than 0 parts by weight, the tensile strength and the modulus decrease.

The chloroprene rubber composition of the present invention is required to satisfy the above formula (1), but a chloroprene rubber composition in which furnace black is blended with a xanthogen-modified chloroprene rubber is more preferable. Is a chloroprene rubber composition containing acetylene black as carbon black, particularly preferably a chloroprene rubber composition containing acetylene black as carbon black in a xanthogen-modified chloroprene rubber, and a vulcanized rubber vulcanizate thereof. Has a high static shear modulus and elongation at break, has a good balance of other mechanical properties, etc., and has excellent vulcanization adhesion, and has extremely excellent properties as a rubber composition for bearings. Therefore, it is particularly preferable.

The vulcanizing agent used for vulcanizing the chloroprene rubber composition of the present invention is not particularly limited, but metal oxides are preferable, and specifically, zinc oxide, magnesium oxide, lead oxide, and tetraoxide are used. Examples include trilead oxide, iron trioxide, titanium dioxide, calcium oxide and the like. These may be used in combination of two or more. Further, the vulcanization can be performed more effectively by using the following vulcanization accelerator together. The addition amount of these vulcanizing agents is chloroprene rubber 1
3 to 15 parts by weight is preferable with respect to 00 parts by weight.

As the vulcanization accelerator, there are thiourea type and guanidine type, which are generally used for vulcanizing chloroprene rubber.
Although thiuram-based and thiazole-based vulcanization accelerators can be used, thiourea-based ones are preferable. Examples of the thiourea-based vulcanization accelerator include ethylenethiourea, diethylthiourea, trimethylthiourea, trimethylthiourea, N, N′-diphenylthiourea, and the like.
Trimeryl thiourea is particularly preferable. The vulcanization accelerators may be used in combination of two or more of the above. The addition amount of these vulcanization accelerators is 1
0.5 to 5 parts by weight is preferable with respect to 00 parts by weight.

If desired, various additives such as a softening agent, a processing aid, an antiaging agent, a lubricant, a filler and the like can be added to the chloroprene rubber composition of the present invention.

Since the chloroprene rubber composition of the present invention has good processability, it is mixed by a kneader such as a kneader, Banbury or roll in the same manner as a normal chloroprene rubber, and the shape according to the purpose is obtained. A molded vulcanizate can be obtained by molding. Specifically, each component is kneaded at a temperature not higher than the vulcanization temperature, and then the kneaded product is molded into various shapes and vulcanized. The temperature during vulcanization and the vulcanization time can be appropriately set. The vulcanization temperature is preferably 140 to 180 ° C, more preferably 150 to 180 ° C.

Using the chloroprene-based rubber composition of the present invention, as described in "Road Bridge Support Handbook" (published in July 1991, Japan Road Association), pages 26 and 200, A bearing can be obtained by forming the obtained rubber composition into a sheet shape, alternately laminating it with a metal plate, and then performing vulcanization adhesion.

The chloroprene rubber composition of the present invention is excellent in processability and vulcanization adhesiveness, and the vulcanized product has a high static shear modulus and a high elongation at break, and is also excellent in other mechanical properties. It is extremely useful as a rubber material for bearings.

[0035]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

Examples 1 to 9 and Comparative Examples 1 to 5 were compounded according to the compounding recipes shown in Tables 1, 2 and 3 to evaluate the workability and vulcanization adhesiveness, and the vulcanizates were tested for physical properties. The results are shown in Tables 1, 2 and 3.

Mechanical properties such as tensile strength, modulus and static shear modulus were determined according to JIS K6301. The embrittlement temperature was measured by a low temperature impact embrittlement test according to JIS K6301. For roll workability, an 8-inch roll is used, roll temperature is 50 ° C., roll interval is 1.14
The workability when the unvulcanized material was cut back for 3 minutes was evaluated.

The vulcanization adhesiveness is based on a 90 ° peel test of a metal piece and rubber of JIS K-6256 (adhesion test method of vulcanized rubber), and Chemlock 205 and 220 manufactured by Road Corporation are used as vulcanization adhesives. Iron pieces were used as metal pieces.

[0039]

[Table 1]

The materials used in Table 1, Table 2 and Table 3 are as follows. 1) Denki Kagaku Kogyo Co., Ltd., xanthogen-modified chloroprene rubber 2) Denki Kagaku Kogyo Co., Ltd., xanthogen-modified chloroprene rubber 3) Denki Kagaku Kogyo Co., Ltd., mercaptan modified chloroprene rubber 4) Denki Kagaku Kogyo Co., Ltd., mercaptan modified Chloroprene rubber 5) Denki Kagaku Kogyo Co., Ltd., mercaptan modified chloroprene rubber 6) Denki Kagaku Kogyo Co., Ltd., sulfur modified chloroprene rubber 7) Denki Kagaku Kogyo Co., Ltd., mercaptan modified chloroprene rubber 8) Denki Kagaku Kogyo Co., Ltd., Granular product (DBP oil absorption 1
60 ml / 100 g) 9) Tokai Carbon Co., Ltd., Seast 116 10) Asahi Carbon Co., Ltd., # 50 11) Sumitomo Dures Co., Ltd., PR-12686

[0041]

[Table 2]

[0042]

[Table 3]

Reference Example 1 Using the chloroprene rubber composition obtained in Example 8, 31
After 8 layers of 0 mm × 310 mm × 7.5 mm (thickness) rubber and 7 sheets of 300 mm × 300 mm × 2.3 mm (thickness) steel plates (SS400) were alternately laminated, a temperature of 155 was obtained.
A bearing was prepared by vulcanizing at a temperature of ℃ for 120 minutes.

Bearing stress 80 kgf / cm ² was applied, and the amount of shear deformation was ± 70%, ± 150%, ± 175%, ± 25.
0% was applied three times each, and the shear spring constant was calculated from the third deformation curve. Furthermore, the static shear elastic modulus was obtained from the shear spring constant. In addition, after measuring 250% shear spring constant, shear deformation was continuously performed until shear failure, and the amount of deformation at shear failure was obtained. The results are shown in Table 4.

Comparative Reference Example 1 Using the chloroprene rubber composition obtained in Comparative Example 5, bearings were prepared and measured in the same manner as in Reference Example 1, and the results are shown in Table 4.
It was shown to.

[0046]

[Table 4]

[0047]

As shown in Tables 1 and 2, in the chloroprene rubber composition of the present invention, the vulcanized product thereof has both high static shear modulus (GS) and elongation at break (EB), In addition, it has a good balance of other mechanical properties, good low temperature resistance, and excellent vulcanization adhesiveness, and has extremely excellent properties as a rubber composition. In particular, as shown in Table 4, the bearing using the chloroprene rubber composition of the present invention has excellent performance.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-262918 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 11/00

Claims (5)

(57) [Claims] 1. A chloroprene containing chloroprene rubber and carbon black, wherein the vulcanized product at vulcanization has elongation at break A and static shear modulus B satisfying the following formula (1). Rubber composition. A ≧ −36.4 × B + 1090 (1) where A is elongation at break (%) and B is static shear modulus (k
gf / cm ² ). 2. The chloroprene rubber composition according to claim 1, wherein B is 4 or more and 20 or less. 3. The chloroprene rubber composition according to claim 1, wherein the carbon black is acetylene black. 4. The chloroprene rubber is a xanthogen-modified chloroprene rubber.
The chloroprene rubber composition described. 5. The chloroprene rubber composition according to claim 1, wherein the chloroprene rubber is a xanthogen-modified chloroprene rubber and the carbon black is acetylene black.