JPH1143516A - Chloroprene rubber for chloroprene rubber composition having excellent dynamic fatigue resistance, chloroprene rubber composition and boots made thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject chloroprene rubber for chloroprene rubber composition having excellent dynamic fatigue resistance without deteriorating the scorch time of unvulcanized compound or the mechanical properties of vulcanized product by polymerizing chloroprene in such a manner as to get an elastic stress fall-ing within a prescribed range. SOLUTION: The objective chloroprene rubber is produced by carrying out emulsion polymerization of 2-chloro-1,3-butadiene and <=50 wt.% of a comonomer copolymerizable therewith such as 2,3-dichloro-1,3-butadiene at a palymerization temperature of 5-50 deg.C while controlling the Mooney viscosity using ndodecyl- mercaptan as a molecular weight controlling agent and suppressing the formation of branched structure in the presence of an emulsifier such as rosic acid potassium salt under a condition to get an elastic stress Y satisfying the formula Y>=0.023X+5.28 (X is Mooney viscosity; 55<=X<=85). The chloroprene rubber is useful e.g. for a uniform velocity joint boot of automobile.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a chloroprene rubber for a chloroprene rubber composition and a chloroprene rubber composition having excellent dynamic fatigue resistance. More specifically, the present invention relates to a chloroprene rubber for a chloroprene rubber composition having better dynamic fatigue resistance than a conventional chloroprene rubber composition, and a chloroprene rubber composition using the same.

[0002]

2. Description of the Related Art Chloroprene rubber is well-balanced in workability, mechanical strength, weather resistance, oil resistance, flame retardancy, adhesiveness, etc., and is widely used as a material for automobile parts and other industrial parts. Used. However, in recent years, quality requirements of rubber materials for automobiles are particularly severe, and there is a demand for improvement in reliability of automobile performance. BACKGROUND ART Constant velocity joint boots (hereinafter referred to as CVJ boots), which are one type of automobile boots, are important components that are subjected to the most severe stress, and various improvements have been made to improve performance and life.

There are various factors regarding the destruction of CVJ boots, such as destruction due to fatigue, destruction due to low-temperature curing, deformation due to negative pressure, or ozone deterioration. Taking fatigue fracture as an example, the cause is the presence of fracture nuclei, especially the presence of fracture nuclei due to poor dispersion of carbon black. It is widely known that poor dispersion of carbon black significantly impairs the performance of rubber products, particularly dynamic fatigue resistance, and various attempts have been made to improve the dynamic fatigue resistance by improving the dispersibility of carbon black. It has been done. However, if kneading is carried out sufficiently so as not to cause carbon black dispersion failure, the heat generated during kneading increases, causing a short scorch time of the unvulcanized compound, that is, so-called burning, which hinders the molding of the product. Even if molding vulcanization is performed, mechanical properties and dynamic fatigue resistance are inferior. Addition of a vulcanization retarder for the purpose of further preventing burning after kneading sufficiently improves the dynamic fatigue resistance, but has the problem that the mechanical properties of the vulcanizate are reduced. No chloroprene rubber composition having excellent dynamic fatigue resistance without impairing the rubber composition has not been provided.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object has been to achieve the scorch time and vulcanization of an unvulcanized compound which could not be achieved by the conventional chloroprene rubber composition. An object of the present invention is to provide a chloroprene rubber and a chloroprene rubber composition for a chloroprene rubber composition having excellent dynamic fatigue resistance without impairing the mechanical properties of the sulphate.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a chloroprene rubber composition using chloroprene rubber having an elastic stress Y of a chloroprene raw rubber within a specific range. The product was found to have excellent dynamic fatigue resistance, which led to the present invention. That is, the present invention is a chloroprene rubber for a chloroprene rubber composition having excellent dynamic fatigue resistance in which the elastic stress Y of the chloroprene raw rubber is in the range represented by the following formula (1).

Y ≧ 0.023X + 5.28 (1) (where X is the Mooney viscosity of chloroprene raw material rubber, Y
Indicates the elastic stress of chloroprene raw rubber. However, 5
5 ≦ X ≦ 85. Hereinafter, the present invention will be described in detail.

The chloroprene rubber of the present invention is a chloroprene rubber in which the elastic stress Y of the chloroprene raw rubber is in the range represented by the above formula (1).

The Mooney viscosity of chloroprene rubber raw material rubber is a value of ML (1 + 4) at a measuring temperature of 100 ° C. using a square groove die in accordance with JIS K6388 method B (1996 edition). The Mooney viscosity of the chloroprene rubber raw material rubber of the present invention is 55 to 85. If the Mooney viscosity exceeds 85, poor dispersion of carbon black occurs during kneading and satisfactory dynamic fatigue resistance cannot be obtained. On the other hand, if the Mooney viscosity is less than 55, the tensile stress of the vulcanized material is reduced, and satisfactory dynamic fatigue resistance cannot be obtained. Among them, the Mooney viscosity is preferably from 60 to 80.

The chloroprene rubber composition of the present invention comprising chloroprene rubber is superior in dynamic fatigue resistance to a conventional chloroprene rubber composition under the same compounding and kneading conditions. Specific examples include, for example, 4 parts by weight of magnesium oxide, 0.5 parts by weight of stearic acid, 1 part by weight of paraffin wax, 4,4'-bis (α, α-dimethylbenzyl) based on 100 parts by weight of chloroprene raw rubber. 3 parts by weight of diphenylamine, N-
1 part by weight of (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, FEF carbon black 6
0 parts by weight, di- (2-ethylhexyl) sebacate 30
Parts by weight, in an OOC type 3.6 l Banbury, the clearance between the casing and the rotor is 2.50 mm, the rotation number of the rotor is 55 to 63 rpm, and the ram pressure is 3.0 kg /.
cm ² , the temperature of the casing before kneading is set to 25 ° C., and kneading is performed by an upside-down method at a filling rate of 60%. The kneading process has two stages. First, as a first step, only the above compounded chemicals are charged into the Banbury, and after stirring for 60 seconds, chloroprene raw rubber is charged. Then, the mixture is kneaded for 150 seconds, dumped at a temperature of 120 ° C. or lower, and the unvulcanized chloroprene rubber is taken out. As a second step, the accelerator is charged on a 12 inch roll. The setting conditions include a front roll rotation speed of 15 rpm and a rear roll rotation speed of 16.5 rpm.
m, nip thickness 4 mm, guide width 500 mm, roll temperature 40 to 50 ° C. The unvulcanized chloroprene rubber after the Banbury dump is wound around a roll, and 5 parts by weight of zinc oxide, 1 part by weight of ethylenethiourea, and 0.5 part by weight of tetramethylthiuram disulfide are added. After the addition,
Sheets are cut out three times with a nip thickness of 1 mm and three times with a nip thickness of 2 mm to obtain a chloroprene rubber composition. Further, the obtained chloroprene rubber composition was
By performing press vulcanization at 60 ° C. for 20 minutes, a vulcanized rubber can be obtained. By doing so, the chloroprene rubber composition of the present invention can be obtained. The dynamic fatigue resistance was evaluated, for example, in a constant elongation fatigue test of 100% elongation of the vulcanized chloroprene rubber by measuring the number of times until the test piece fractured using a dematcher type fatigue tester. A chloroprene rubber composition having excellent fatigue properties was obtained. That is, for example, in a constant elongation fatigue test, the average life (MTBF) is 70,000 times or more, and m
A composition having a value (a parameter indicating the degree of variation in the number of breaks) of 1.0 or more could be obtained.

The elastic stress Y of the chloroprene raw material rubber in the present invention was set using a moving die rheometer (MDR-2000) manufactured by Monsanto Co., Ltd. under the following conditions: die torsion frequency 1.66 Hz, amplitude angle ± 1 degree, measurement temperature 60.
It is a torque value (dNm) 5 minutes after the start of measurement under the measurement conditions of ° C. and no preheating. The elastic stress Y of the chloroprene raw material rubber in the present invention is 0.023X + 5.28 or more. When Y is less than 0.023X + 5.28, the dispersion of carbon black during kneading is small because the ratio of the elasticity term of the raw rubber is small. Poor, satisfactory dynamic fatigue resistance cannot be obtained.

Further, the chloroprene rubber of the present invention is a rubber obtained by polymerization of 2-chloro-1,3-butadiene containing 50% by weight or less of a comonomer copolymerizable with chloroprene. The comonomer referred to here is
The monomer is not particularly limited as long as it is a monomer copolymerizable with 2-chloro-1,3-butadiene. Examples thereof include monovinyl compounds such as acrylonitrile, methacrylonitrile, and vinylidene chloride, acrylates, and methacrylates. , Aromatic vinyl compounds such as styrene and α-methylstyrene, 1,3-butadiene, 1-chloro-1,
Examples thereof include conjugated diene compounds such as 3-butadiene and 2,3-dichloro-1,3-butadiene, and sulfur, and these can be used alone or in combination of two or more. Of these, 1-chloro-1,3-butadiene and 2,3-dichloro-1,3-butadiene are particularly preferred.

Further, the chloroprene rubber of the present invention is produced by a polymerization method in which the formation of a branched structure is suppressed, and examples thereof include methods such as emulsion polymerization, solution polymerization, and bulk polymerization. Among them, emulsion polymerization, as a method of suppressing the formation of a branched structure, a method of lowering the polymerization conversion rate, a method of lowering the polymerization rate, a method of lowering the polymerization temperature, a method of dividing and adding a molecular weight regulator during the polymerization, There is a method using chloroform, iodoform or the like as a chain transfer agent.

In the present invention, the emulsifier used for the polymerization is not particularly restricted but includes, for example, alkali metal abietic acid, disproportionated alkali metal abietic acid,
Alkali metal salts of alkyl sulfates, alkali metal salts of alkyl benzene sulfonic acid, alkali metal salts of polyoxyethylene alkyl phenyl ether sulfate, alkali metal salts of higher fatty acids, alkali metal salts of naphthalene sulfonic acid formalin condensates, alkali metal salts of higher fatty acid sulfonates, etc. Any anionic surfactant or a nonionic surfactant such as polyoxyethylene alkyl ether and polyoxyethylene alkyl phenyl ether can be used.

In the present invention, the polymerization initiator is not particularly limited, and examples thereof include inorganic or organic initiators such as potassium persulfate, ammonium persulfate, paramenthane hydroperoxide, cumene hydroperoxide and tert-butyl hydroperoxide. Or a redox system using the above peroxide in combination with a reducing agent such as ferrous sulfate, sodium hydrosulfite, and sodium formaldehyde sulfoxylate.

In the present invention, the terminator used for the polymerization is not particularly limited. For example, phenothiazine, 2,2-methylenebis- (4-methyl-6-ter
t-butylphenol), 2,2-methylenebis- (4
-Ethyl-6-tert-butylphenol), 2,6
Radical inhibitors such as -di-tert-butyl-4-methylphenol, hydroquinone, 4-methoxyphenol, N, N-diethylhydroxylamine are used.

In the present invention, the temperature of polymerization is not particularly limited, but is preferably from 0 to 60 ° C, more preferably from 5 to 50 ° C. When the heat generation during the polymerization is so large that it is difficult to control the temperature, the polymerization can be carried out while the monomer mixture is added little by little or continuously to the aqueous emulsifier solution. After terminating the polymerization, the unreacted monomers in the latex are removed by a method such as steam stripping under reduced pressure, and then the polymer is isolated by neutralization, freeze coagulation or salting out, etc., washed with water and dried to obtain a polymer.

Representative examples of the emulsion polymerization method of the present invention in which the formation of a branched structure of the chloroprene rubber is suppressed, which is a method of lowering the polymerization conversion rate and lowering the polymerization rate, will be described in detail. At a polymerization temperature of 30 ° C. to 50 ° C., a mixture of a monomer component of the chloroprene polymer and n-dodecyl mercaptan, a molecular weight regulator in such an amount as to obtain a predetermined Mooney viscosity, is used. And then emulsified by mixing with the chloroprene polymer by weight. An aqueous solution of potassium persulfate was continuously added to this emulsion from the start of polymerization, and polymerization was carried out so that the rate of polymerization conversion per hour became 9.0% or less.
The polymerization is terminated by adding 0.02% by weight (% by weight based on the monomer of the chloroprene polymer) of N, N-diethylhydroxylamine as a terminator at a polymerization conversion rate of not more than%.
After terminating the polymerization, unreacted monomers in the latex are removed by a steam stripping method under reduced pressure, neutralized with dilute acetic acid, and the polymer is isolated by freeze-coagulation, washed with water and dried with hot air to obtain a polymer. The method of polymerizing the chloroprene rubber of the present invention is not particularly limited as long as the chloroprene rubber described in claim 1 can be obtained.

The compounding agent for rubber in the chloroprene rubber composition of the present invention includes, as fillers, carbon black, clay, talc, diatomaceous earth, calcium carbonate, magnesium carbonate, silicic acid and silicate compounds, white carbon and the like. Of these, carbon black is preferred. The type of carbon black is not particularly limited. For example, SRF, FEF, MAF, HAF,
FT, MT, etc. can be used. As the addition amount,
In order to maintain mechanical properties such as elongation at break or tensile stress, the amount is preferably 15 to 70 parts by weight, and particularly preferably 30 to 65 parts by weight of carbon black.

The type of the plasticizer and / or the rubber softener used in the present invention is not particularly limited. For example, rapeseed oil as vegetable oil, linseed oil, soybean oil, and diester as ester plasticizer. -(2-ethylhexyl) adipate, di- (2-ethylhexyl) sebacate, di- (2-ethylhexyl) phthalate, di- (2
-Ethylhexyl) azelate, a process oil as a mineral oil-based softener, and the like can be used. The addition amount is preferably 5 to 40 parts by weight, particularly preferably 10 to 30 parts by weight of a plasticizer and / or a rubber softener in order to maintain tensile stress and elongation at break.

Further, other additives such as an antioxidant, a processing aid, a lubricant, a flame retardant, a vulcanizing agent, a vulcanization accelerator, and a vulcanization retarder can be used as required.

The chloroprene rubber composition of the present invention is mixed with a kneading machine such as a roll or a Banbury in the same manner as a commonly known chloroprene rubber, and molded into a desired shape to obtain a molded vulcanizate. be able to.

Since the obtained chloroprene rubber molded vulcanizate has excellent mechanical properties and excellent dynamic fatigue resistance, it can be widely used for various applications including dynamic applications such as various belts, air springs and boots. It is possible. The boots here include CVJ boots for automobiles, steering boots, dust boots, and the like.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

The Mooney viscosity of chloroprene raw rubber is J
Evaluation was performed using a square groove die according to the IS K6388 B method (1996 version). The mechanical properties of vulcanized rubber
According to JIS K6251 (1996 version), a dumbbell-shaped No. 3 test piece was used, and the tensile speed was 500 mm / min.
Was evaluated. The Mooney scorch time of the chloroprene rubber composition was evaluated using a square groove die in accordance with JIS K6300 (1996). Evaluation of dynamic fatigue resistance is performed by using a dematcher-type bending fatigue tester in a constant elongation fatigue test of 100% elongation of the chloroprene rubber vulcanizate, and adjusting the elongation ratio to 100% with respect to the wire spacing. The test was performed by repeatedly stretching a dumbbell-shaped No. 3 test piece under the conditions of 23 ° C. and 300 rpm, and measuring the number of times the test piece was broken. The measurements were each n = 2
The average life (MTBF) and the slope m of the straight line were determined on the assumption that the number of breaks followed the Weibull distribution. The m value is a parameter that expresses the degree of variation in the number of breaks. When m is less than 1, an initial failure, when m is greater than 1, a wear failure, and when m is 1, a random failure is represented. Become. The elastic stress of the chloroprene raw rubber is determined by a moving die rheometer (MDR-200 manufactured by Monsanto Co.).
0), the set condition was changed to die torsional frequency 1.66H.
The torque value (dNm) 5 minutes after the start of the measurement under the measurement conditions of z, an amplitude angle of ± 1 degree, a measurement temperature of 60 ° C., and no preheating was used as a measurement value.

In the following description, parts by weight means raw rubber 1
Represents the weight ratio to 00 parts by weight. Examples 1 to 3 According to the polymerization formula A in Table 1, 10 l of an autoclave equipped with a stirrer was charged and sufficiently replaced with nitrogen to emulsify. Then 5
The temperature was kept at 0 ° C., and after about 5 hours from the start of polymerization, the polymerization conversion was about 4 hours.
An aqueous solution of potassium persulfate was continuously added dropwise while controlling the amount so as to be 0%, and polymerization was carried out. When the polymerization conversion reached about 40%, a terminator was added to terminate the polymerization.

[0026]

[Table 1]

Next, the remaining unreacted monomers were removed by a reduced pressure steam stripping method to obtain a latex.
Then, it freeze-coagulated, washed with water, and dried with hot air to obtain the desired chloroprene rubber. Table 3 shows the Mooney viscosity of the raw rubber and the elastic stress of the raw rubber.

Next, kneading was carried out in an upside-down system with a 3.6 L Banbury, OOC type manufactured by Kobe Steel. Banbury is 55-65 rpm, clearance between casing and rotor is 2.50 mm, ram pressure is 3.0 kg
/ Cm ² and set the casing temperature before kneading to 2
The filling rate was 5 ° C. and the filling rate was 60%. In Formula A shown in Table 2, the compounding chemicals except zinc oxide, ethylene thiourea, and tetramethylthiuram disulfide were introduced into Banbury.
After stirring for 60 seconds, the chloroprene raw rubber was charged, and
The mixture was kneaded for 2 seconds, dumped at a temperature of 120 ° C. or lower, and an unvulcanized chloroprene rubber was taken out. Next, the accelerator was charged with a 12-inch roll manufactured by Nishimura Koki. First, the front roll rotation speed is 15 rpm, the rear roll is 16.5 rpm, the nip thickness is 4 mm, the guide width is 500 mm, and the roll temperature is 40 to 50.
The roll conditions were set to ° C., the unvulcanized chloroprene rubber after kneading the Banbury was wound around a roll, and zinc oxide, ethylenethiourea, and tetramethylthiuram disulfide were added. After the addition was completed, the sheet was cut out three times, cut through a round three times with a nip thickness of 1 mm and three times with a nip thickness of 2 mm to obtain a chloroprene rubber composition.

[0029]

[Table 2]

Table 3 shows the scorch time of the obtained chloroprene rubber composition. Further, the composition is heated to 160 ° C.
A vulcanized rubber was prepared by performing press vulcanization for 20 minutes, and the mechanical properties and the constant elongation fatigue properties (average life MTBF value and m value) were measured. The results are shown in Table 3. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

[0031]

[Table 3]

Examples 4 to 6 According to the polymerization recipe B in Table 1, 10 liters of an autoclave equipped with a stirrer were charged and sufficiently purged with nitrogen and emulsified. Then 4
The temperature was kept at 0 ° C., and about 10 hours after the start of the polymerization, the aqueous solution of potassium persulfate was continuously added dropwise and controlled so as to have a polymerization conversion of about 60%. When the polymerization conversion reached about 55%, a terminator was added to terminate the polymerization. Table 3 shows the polymerization results. Thereafter, the Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) of the raw rubber were measured in the same manner as in Example 1, and the results were tabulated. 3 is shown. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

Examples 7 and 8 According to the polymerization formula C shown in Table 1, 10 liters of an autoclave equipped with a stirrer were charged and sufficiently replaced with nitrogen to emulsify. Then 3
At 0 ° C., about 8 hours after the start of the polymerization, the polymerization conversion was about 5 hours.
An aqueous solution of potassium persulfate was continuously added dropwise while controlling the amount so as to be 0%, and polymerization was carried out. When the polymerization conversion reached about 50%, a terminator was added to terminate the polymerization. Table 3 shows the polymerization results. Thereafter, the Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) of the raw rubber were measured in the same manner as in Example 1, and the results were tabulated. 3 is shown. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

Example 9 After chloroprene rubber was obtained in the same manner as in Example 7, Mooney viscosity of the raw rubber, elastic stress of the raw rubber, scorch time, mechanical properties and constant elongation fatigue (average) were obtained in the same manner. Life MTBF value and m value) were measured, and the results are shown in Table 4. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

[0035]

[Table 4]

Example 10 The same procedure as in Example 2 was repeated except that the chloroprene rubber obtained in Example 2 was used and the amount of carbon black was changed to 10 parts by weight in accordance with Formulation B shown in Table 2. Mooney viscosity and elastic stress of raw rubber, scorch time,
Mechanical properties and constant elongation fatigue (average life MTBF value and m
) Were measured and the results are shown in Table 4. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

Example 11 The same procedure as in Example 2 was repeated except that the chloroprene rubber obtained in Example 2 was used and the amount of carbon black was changed to 40 parts by weight in accordance with the composition C shown in Table 2. Mooney viscosity and elastic stress of raw rubber, scorch time,
Mechanical properties and constant elongation fatigue (average life MTBF value and m
) Were measured and the results are shown in Table 4. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

Example 12 The same procedure as in Example 2 was repeated except that the chloroprene rubber obtained in Example 2 was used and the amount of carbon black was changed to 90 parts by weight in accordance with Formulation D shown in Table 2. Mooney viscosity and elastic stress of raw rubber, scorch time,
Mechanical properties and constant elongation fatigue (average life MTBF value and m
) Were measured and the results are shown in Table 4. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

Example 13 The same procedure as in Example 2 was carried out except that the amount of di- (2-ethylhexyl) sebacate was changed to 3 parts by weight in accordance with Formulation E shown in Table 2 using the chloroprene rubber obtained in Example 2. The Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue property (average life MTBF value and m value) of the raw rubber were measured by the method. The results are shown in Table 4. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

Example 14 The same procedure as in Example 2 was carried out except that the amount of di- (2-ethylhexyl) sebacate was changed to 15 parts by weight in accordance with the composition F shown in Table 2 using the chloroprene rubber obtained in Example 2. The Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue property (average life MTBF value and m value) of the raw rubber were measured by the method. The results are shown in Table 4. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

Example 15 The same procedure as in Example 2 was carried out except that the amount of di- (2-ethylhexyl) sebacate was changed to 50 parts by weight according to the formulation G shown in Table 2 using the chloroprene rubber obtained in Example 2. The Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue properties (average life MTBF value and m value) of the raw rubber were measured by the method. The results are shown in Table 4. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

Example 16 Using the chloroprene rubber obtained in Example 2, the amount of carbon black was adjusted to 10 parts by weight, and
Except that the amount of (2-ethylhexyl) sebacate was changed to 3 parts by weight, Mooney viscosity of raw rubber and elastic stress of raw rubber, scorch time, mechanical properties and constant elongation fatigue property (average life) in the same manner as in Example 2. MTBF value and m
) Were measured and the results are shown in Table 4. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

Example 17 Using the chloroprene rubber obtained in Example 2, according to Formulation I shown in Table 2, the amount of carbon black was 90 parts by weight, and
Except that the amount of (2-ethylhexyl) sebacate was changed to 50 parts by weight, the Mooney viscosity of the raw rubber, the elastic stress of the raw rubber, scorch time, mechanical properties and constant elongation fatigue (average life MTBF) were the same as in Example 2. Value and m
Values) were measured and the results are shown in Table 5. As a result, a chloroprene rubber composition having good mechanical properties and excellent dynamic fatigue resistance was obtained.

[0044]

[Table 5]

Comparative Example 1 A chloroprene rubber was obtained in the same manner as in Example 1. However, the Mooney viscosity was changed. Next, in the same manner as in Example 1, the Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) of the raw rubber were measured. The results are shown in Table 5. As a result, the elastic stress Y of the raw rubber becomes 0.
Although it was 023X + 5.28 or more, the tensile properties and dynamic fatigue resistance were inferior.

Comparative Example 2 A chloroprene rubber was obtained in the same manner as in Example 1. However, the Mooney viscosity was changed. Next, in the same manner as in Example 1, the Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) of the raw rubber were measured. The results are shown in Table 5. As a result, the elastic stress Y of the raw rubber becomes 0.
Although it was 023X + 5.28 or more, the dynamic fatigue resistance was inferior.

Comparative Examples 3 to 5 In accordance with the polymerization recipe A in Table 1, 10 liters of an autoclave equipped with a stirrer were charged and sufficiently replaced with nitrogen to emulsify. Then 5
At 0 ° C., about 5 hours after the start of the polymerization, the polymerization conversion was about 7 hours.
An aqueous solution of potassium persulfate was continuously added dropwise while controlling the amount so as to be 0%, and polymerization was carried out. When the polymerization conversion reached about 70%, a terminator was added to terminate the polymerization. The results of the polymerization are shown in Table 5. Thereafter, the Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) of the raw rubber were measured in the same manner as in Example 1, and the results were tabulated. 5 is shown. As a result, the elastic stress Y of the raw rubber
Was less than 0.023X + 5.28, resulting in inferior tensile properties and dynamic fatigue resistance.

Comparative Example 6 A chloroprene rubber was obtained in the same manner as in Example 4. However, the Mooney viscosity was changed. Next, in the same manner as in Example 4, the Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) of the raw rubber were measured. The results are shown in Table 5. As a result, the elastic stress Y of the raw rubber becomes 0.
Although it was 023X + 5.28 or more, the tensile properties and dynamic fatigue resistance were inferior.

Comparative Example 7 A chloroprene rubber was obtained in the same manner as in Example 4. However, the Mooney viscosity was changed. Next, in the same manner as in Example 4, the Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) of the raw rubber were measured. The results are shown in Table 5. As a result, the elastic stress Y of the raw rubber becomes 0.
Although it was 023X + 5.28 or more, the dynamic fatigue resistance was inferior.

Comparative Example 8 A chloroprene rubber was obtained in the same manner as in Example 7. However, the Mooney viscosity was changed. Next, in the same manner as in Example 7, the Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) of the raw rubber were measured. The results are shown in Table 6. As a result, the elastic stress Y of the raw rubber becomes 0.
Although it was 023X + 5.28 or more, the tensile properties and dynamic fatigue resistance were inferior.

[0051]

[Table 6]

Comparative Example 9 A chloroprene rubber was obtained in the same manner as in Example 7. However, the Mooney viscosity was changed. Next, in the same manner as in Example 7, the Mooney viscosity of the raw rubber and the elastic stress, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) of the raw rubber were measured. The results are shown in Table 6. As a result, the elastic stress Y of the raw rubber becomes 0.
Although it was 023X + 5.28 or more, the dynamic fatigue resistance was inferior.

Comparative Example 10 The scorch time, mechanical properties and constant elongation fatigue (average) were determined in the same manner as in Comparative Example 4 except that the kneading time in the Banbury was 10 minutes using the chloroprene rubber obtained in Comparative Example 4. Life MTBF value and m value) were measured, and these results are shown in Table 6. As a result, the elastic stress Y of the raw rubber is
0.023X + less than 5.28, scorch time,
Tensile strength and dynamic fatigue resistance were inferior.

Comparative Example 11 Using the chloroprene rubber obtained in Comparative Example 4, according to Formulation J shown in Table 2, the scorch time and mechanical properties were the same as in Comparative Example 4 except that the kneading time in Banbury was 10 minutes. Physical properties and constant elongation fatigue (average life MTBF value and m value)
Was measured, and these results are shown in Table 6. As a result, the elastic stress Y of the raw rubber was less than 0.023X + 5.28, and the tensile strength was poor.

Comparative Example 12 Using the chloroprene rubber obtained in Comparative Example 4, according to Formulation F shown in Table 2, scorch time, mechanical properties and constant elongation fatigue properties (average life MTBF value and m value) were measured and the results are shown in Table 6. As a result, the elastic stress Y of the raw rubber is 0.023X + 5.2.
It was less than 8, and elongation at break and dynamic fatigue resistance were inferior.

Comparative Example 13 Using the chloroprene rubber obtained in Comparative Example 4, according to Formulation C shown in Table 2, in the same manner as in Comparative Example 4, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) were measured and the results are shown in Table 6. As a result, the elastic stress Y of the raw rubber is 0.023X + 5.2.
It was less than 8, resulting in inferior tensile stress and dynamic fatigue resistance.

Comparative Example 14 Using the chloroprene rubber obtained in Comparative Example 4, according to the formulation H shown in Table 2, in the same manner as in Comparative Example 4, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) were measured and the results are shown in Table 6. As a result, the elastic stress Y of the raw rubber is 0.023X + 5.2.
It was less than 8, resulting in inferior tensile stress and dynamic fatigue resistance.

Comparative Example 15 Using the chloroprene rubber obtained in Comparative Example 4, according to Formulation I shown in Table 2, scorch time, mechanical properties and constant elongation fatigue (average life MTBF value and m value) were measured and the results are shown in Table 6. As a result, the elastic stress Y of the raw rubber is 0.023X + 5.2.
It was less than 8, resulting in inferior tensile stress and dynamic fatigue resistance.

[0059]

From the above results, the chloroprene rubber for the chloroprene rubber composition and the chloroprene rubber composition obtained by the present invention do not impair the mechanical properties of scorch time and vulcanizate, and are superior to the conventional chloroprene rubber composition. It is clear that it has dynamic fatigue resistance, and is useful for CVJ boots, steering boots, dust boots and the like for automobiles.

Claims (5)

[Claims] 1. A chloroprene rubber for a chloroprene rubber composition having excellent dynamic fatigue resistance, wherein the elastic stress Y of the chloroprene raw rubber is in the range represented by the following formula (1). Y ≧ 0.023X + 5.28 (1) (where X is Mooney viscosity of chloroprene raw rubber, Y
Indicates the elastic stress of chloroprene raw rubber. However, 5
5 ≦ X ≦ 85. ) 2. A chloroprene rubber composition having excellent dynamic fatigue resistance, comprising the chloroprene rubber according to claim 1 and a compounding agent for rubber. 3. The chloroprene rubber composition having excellent dynamic fatigue resistance according to claim 2, wherein the compounding chemical for rubber is carbon black and a plasticizer and / or a rubber softener. 4. The chloroprene rubber 100 according to claim 1,
The chloroprene rubber composition having excellent dynamic fatigue resistance according to claim 3, comprising 15 to 70 parts by weight of carbon black and 5 to 40 parts by weight of a plasticizer and / or a rubber softener with respect to parts by weight. . 5. A boot using the chloroprene rubber composition excellent in dynamic fatigue resistance according to any one of claims 2 to 4.