JPH0336842B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polybutadiene-based vulcanized rubber. More specifically, the present invention relates to polybutadiene-based vulcanized rubber that exhibits high resistance to gas and fuel oil permeation. There are currently many types of rubber materials known, but among them, butyl rubber (IIR) has the unique property of being almost impervious to gas. For this reason, butyl rubber is used in a variety of applications, including tire inner tubes. In recent years, air pollution due to leakage of vaporized gasoline from automobile fuel tanks, fuel hoses, and other sealing parts has become a problem, and therefore, it has become necessary to use high resistance to permeation of hydrocarbons. The demand for rubber materials shown is increasing. Furthermore, recently there has been a partial trend to use alcohol-containing gasoline (gasohol) instead of gasoline as a fuel for automobiles, and rubber materials used in automobile fuel systems are becoming more and more similar to gasohol. In addition to durability against heavy fuel oils, resistance to their permeation is also becoming an issue. As mentioned above, butyl rubber has high resistance to gas permeation, but because butyl rubber shows high resistance to vulcanization, vulcanization takes a long time or requires special vulcanizing agents. There are disadvantages such as the need to use Butyl rubber also has drawbacks such as poor roll processability, poor compatibility with other diene rubbers, and poor adhesion to metals and other rubbers. Furthermore, butyl rubber has the disadvantage of being susceptible to deterioration upon contact with oily liquids such as fuel oil, so its use in automobile fuel systems is problematic. For this reason, attempts have been made to modify butyl rubber into chlorinated butyl rubber, but this has not yielded fully satisfactory results, and rubbers such as chloroprene, which have excellent oil resistance, do not have sufficient resistance to gas permeation. On the other hand, butadiene rubber has excellent vulcanizability, processability, compatibility with other rubbers, and durability as a general-purpose rubber, but it has extremely low resistance to permeation of gases and fuel oil. However, there are problems with its use in tire inner tubes and automobile fuel systems. The main object of the present invention is to provide a rubber material with high resistance to permeation of gases, fuel oil, etc., which is obtained by vulcanizing a polymer with excellent processability and various other properties. A particular object of the present invention is to provide a polybutadiene-based vulcanized rubber that exhibits high resistance to gas and fuel oil permeation and is also excellent in other properties. Another object of the present invention is to provide a vulcanized rubber that exhibits high resistance to permeation, particularly of alcohol-containing gasoline. The object of the present invention as described above is to
Achieved by the present invention, which is made of a polybutadiene-based vulcanized rubber obtained by vulcanizing dihalocyclopropanated polybutadiene in which 5-75% of the total double bonds of polybutadiene have been converted to dihalocyclopropane groups with sulfur or a sulfur compound. can do. Next, the present invention will be explained in detail. The polymer used as a raw material for the polybutadiene-based vulcanized rubber of the present invention is dihalocyclopropanated polybutadiene in which 5 to 75% of the total double bonds of cis-1,4-polybutadiene have been converted to dihalocyclopropane groups. be. Dihalocyclopropanated polybutadiene in which most of the double bonds of cis-1,4-polybutadiene are converted to dihalocyclopropane groups is already known, as disclosed in, for example, U.S. Pat. No. 3,369,012. . This US Patent No. 3369012
In the specification, all double bonds are removed by reacting cis-1,4-polybutadiene with a carbene prepared from ethyl trichloroacetate and sodium methoxide under anhydrous, nitrogen atmosphere, and low temperature reaction conditions. It is disclosed that dihalocyclopropanated polybutadiene in which around 90% of the polybutadiene is converted to dihalocyclopropane groups can be obtained,
The description states that the resulting dihalocyclopropanated polybutadiene is a tough, flame-retardant, rubbery polymer. Therefore, based on the above method, cis-1,4-
The modification rate of polybutadiene, that is, the ratio of double bonds converted to dihalocyclopropane groups to the total number of double bonds contained in the raw material cis-1,4-polybutadiene, is 5% to 75%. The polybutadiene-based vulcanized rubber of the present invention can be produced by producing cyclopropanated polybutadiene and vulcanizing it. However, the above method of producing carbene and reacting it with cis-1,4-polybutadiene uses unstable raw materials that easily react with moisture, such as sodium methoxide.
Harsh reaction conditions such as anhydrous, nitrogen atmosphere, and low temperature reaction conditions are required. Therefore, such a method is not suitable as an industrial production method for obtaining dihalocyclopropanated polybutadiene in which the double bonds of cis-1,4-polybutadiene are partially converted into dihalocyclopropane groups. It cannot be said that it is advantageous. For the above reasons, dihalocyclopropanated polybutadiene in which 5 to 75% of all double bonds in cis-1,4-polybutadiene are converted to dihalocyclopropane groups is produced by converting haloform into cis-1,4-polybutadiene. , a phase transfer catalyst and an alkali metal hydroxide aqueous solution. In the above method for producing dihalocyclopropanated polybutadiene, the cis-1,4-polybutadiene generally uses a solid polymer having a cis-1,4 structure content of 90% or more. Further, haloform is a compound also called trihalomethane, and specific examples thereof include chloroform, bromoform, bromodichloromethane, chlorodibromomethane, bromodifluoromethane, and chlorodifluoromethane. For example, when chloroform is used as a raw material, a dichlorocyclopropane group is introduced into the polybutadiene, and when bromoform is used, a dibromocyclopropane group is introduced into the polybutadiene. This haloform is usually used in a proportion of 0.3 to 30 moles per 100 g of cis-1,4-polybutadiene. Examples of phase transfer catalysts include quaternary ammonium salts such as triethylbenzylammonium chloride, tributylbenzylammonium chloride, diethyldodecylbenzylammonium chloride, and tetrabutylammonium chloride; tetraphenylphosphonium chloride, tetrabutylphosphonium chloride, etc. Quaternary phosphonium salts; dibenzo-18-crown-6, dicyclohexyl-18-crown-6,
Crown ethers such as 18-crown-6; and cryptands such as [2.2.2.]-cryptate may be mentioned. This phase transfer catalyst is
It is usually used in a proportion of 0.01 to 1.0 g per 100 g of cis-1,4-polybutadiene. As an aqueous alkali metal hydroxide solution, sodium hydroxide or potassium hydroxide is generally used.
A 65% by weight aqueous solution is used. Further, the aqueous alkali metal hydroxide solution is added in an amount such that the amount of alkali metal hydroxide contained therein is 0.3 to 40 moles per 100 g of cis-1,4-polybutadiene. The above method for producing dihalocyclopropanated polybutadiene usually involves preparing a solution in which cis-1,4-polybutadiene is dissolved in an organic solvent such as toluene or xylene, and adding a phase transfer catalyst and an alkali metal hydroxide solution to the solution. aqueous solution, then gradually add haloform to this mixture, and
It is carried out by stirring at a temperature of 80°C for 10 minutes or more. This reaction proceeds in an emulsified state consisting of an aqueous phase and an organic phase. In order to take out the reaction product after the above reaction is completed, a method that is the same as, or similar to, a method for recovering the product of a normal emulsion polymerization reaction can be used. In the above reaction, the ratio of the number of double bonds converted to dihalocyclopropane groups (modification rate) to the total number of double bonds contained in the raw material cis-1,4-polybutadiene is Type of polymer (cis-1,4-polybutadiene), type and amount of haloform added, type and amount of alkali metal hydroxide added, and concentration of its aqueous solution, type and amount of catalyst added, type of reaction solvent, reaction It changes depending on the selection of polymer concentration in the liquid, reaction temperature, reaction time, etc. Therefore, by arbitrarily changing each of these conditions, it is possible to easily obtain dihalocyclopropanated polybutadiene with a modification rate of 5 to 75%, which is used as a raw material for the vulcanized rubber of the present invention. The dihalocyclopropanated polybutadiene used in the present invention has a modification rate of 5 to 75%, as described above. Dihalocyclopropanated polybutadiene with a modification rate of less than 5% has almost no difference in properties from unmodified cis-1,4-polybutadiene, and its properties after vulcanization are also similar to those of ordinary cis-1,4-polybutadiene.
Since it is not much different from the vulcanizate of polybutadiene, the improvement in gas and hydrocarbon permeability is not significant. Furthermore, dihalocyclopropanated polybutadiene with a modification rate exceeding 75% is not preferred in practice because it becomes difficult to vulcanize. For vulcanization to obtain the polybutadiene-based vulcanized rubber of the present invention from the above-mentioned dihalocyclopropanated polybutadiene, a vulcanization method using sulfur or a sulfur compound used for the vulcanization of ordinary diene-based polymers is used. Ru. In addition to the vulcanizing agent, the dihalocyclopropanated polybutadiene described above can also be used with compounding ingredients commonly used when vulcanizing natural rubber and synthetic rubber, such as vulcanization accelerators and vulcanization accelerators. , reinforcing agents, inorganic or organic fillers, anti-aging agents,
Of course, it is also possible to prepare a vulcanizing compound by blending and kneading pigments, process oils, scorch inhibitors, etc., mold this, and then vulcanize it. Alternatively, an oil-extended rubber product can also be produced by kneading oil for oil extension into dihalocyclopropanated polybutadiene during vulcanization. Note that the vulcanizate of dihalocyclopropanated polybutadiene of the present invention does not necessarily have to be a vulcanizate of the above-mentioned dihalocyclopropanated polybutadiene alone, but rather a vulcanizate of the above-mentioned dihalocyclopropanated polybutadiene and natural rubber and/or Alternatively, it may be a vulcanized product obtained by vulcanizing a mixture with other synthetic rubbers by a similar method. However, when vulcanizing such a mixture, the mixture contains 50% by weight of the above dihalocyclopropanated polybutadiene.
It is desirable that the above items are included. The polybutadiene-based vulcanized rubber of the present invention produced from dihalocyclopropanated polybutadiene by the method described above has various properties such as modulus, elongation, strength, and durability compared to ordinary unmodified cis-1,4. - It has properties almost equal to or better than vulcanized rubber obtained by vulcanizing polybutadiene, while resistance to permeation of gases, fuel oil, etc. is dramatically improved. For example, its resistance to gas permeation is comparable to that of butyl rubber and chlorinated butyl rubber, which are known as gas-impermeable rubber materials. It exhibits excellent properties that are difficult to predict from the gas permeability of the vulcanized rubber obtained by vulcanizing 4-polybutadiene. Furthermore, the polybutadiene vulcanized rubber of the present invention exhibits high resistance to permeation of vapors from alcohol-containing gasoline. For the reasons mentioned above, the polybutadiene-based vulcanized rubber of the present invention is used for applications such as inner tubes of tires, and has many other uses, including being particularly useful as a rubber material for various parts of the fuel system of automobiles. It is a rubber material. Next, Examples and Comparative Examples of the present invention will be shown. The production method, vulcanization method, and evaluation method for various properties of the dihalocyclopropanated polybutadiene used in the following examples are as follows. [Method for producing dihalocyclopropanated polybutadiene] In a reaction vessel, 1600 ml of toluene, 108.2 g of cis-1,4-polybutadiene (cis-1,4 structure content: about 97.5%, [η]: 2.2), and 1.08g of 2,
6-di-tert-butyl-para-cresol (stabilizer) is introduced and the mixture is stirred into solution at 45°C. To this solution, 1.0 g of tetrabutylammonium bromide (catalyst) is added, and then a 50% by weight aqueous solution containing 200 g of sodium hydroxide is added under stirring, and stirring is continued for 20 minutes to form an emulsion. Next, continue stirring this emulsion and lower its temperature.
Add 340 ml of chloroform dropwise over 20 minutes while maintaining the temperature at 45°C. After completion of the dropwise addition, stirring was continued for another 2 hours while maintaining the temperature of the reaction solution at 45°C. Thereafter, 2 parts of water and 1.5 parts of toluene (for viscosity adjustment) are added to the reaction solution to substantially stop the reaction. After the reaction solution was left overnight, the lower aqueous layer was removed. To the organic layer, water 2 and a small amount of dilute hydrochloric acid are further added while stirring to neutralize the organic layer. After this is left to stand and the aqueous layer is separated, the organic layer is finally washed with water. Approximately 3 ml of methanol is added dropwise to the organic layer of the cleaning agent to precipitate the reaction product. After removing the solvent by filtration, about 1 part of methanol is further added to the reaction product, which is the filtered product, and the reaction product is thoroughly washed, and the mixture is left overnight. Then, after removing methanol by filtration, the reaction product is manually cut into pieces and dried under vacuum at room temperature for 48 hours or more. The chlorine content of the dihalocyclopropanated polybutadiene obtained by the above method was 35.90%, and the modification rate calculated from this chlorine content was 47.2.
It was %. Note that dihalocyclopropanated polybutadienes having different modification rates were produced by a method similar to the above method. [Vulcanization method] Compounding example Sulfur vulcanization Rubber (dihalocyclopropanated polybutadiene, etc.) 100 parts (parts by weight, the same applies hereinafter), 2 parts zinc oxide, 1 part stearic acid, antiaging agent (D: phenyl-β) -naphthylamine), 0.1 part of tetramethylthiuram disulfide (TT), 1 part of diphenylguanidine, and 1.2 parts of sulfur. Compounding example Thiuram/thiazole vulcanized rubber (dihalocyclopropanated polybutadiene, etc.) 100 parts (parts by weight, the same applies below), 1 part zinc oxide, 1 part stearic acid, anti-aging agent (D: phenyl-β-naphthylamine) 1 part tetramethylthiuram disulfide (TT), 2 parts thiazole (dibenzothiazyl disulfide). The above formulation example or a formulation blended according to the above formulation is kneaded using a Brabender and/or a roll, and the optimum vulcanization time for this formulation is determined using a JSR culastometer. The above compound was introduced into a heat press machine, and by using a spacer and applying a pressure of 210 Kg/cm ² and a temperature of 150°C for the optimum vulcanization time of the compound, a film-form,
Create a test piece in the form of a sheet, etc. [Method for evaluating properties of vulcanized rubber] Gas permeability test Nitrogen gas and oxygen gas were measured through a vulcanized rubber sheet using a gas permeability measurement device GTR-30 (manufactured by Yanagimoto Seisakusho Co., Ltd.) using a reduced pressure gas chromatography method. (Diameter: 6cm, thickness 0.2-0.3mm) Find the speed of transmission. The gas permeability coefficient (PC) was calculated using the following formula. PC = Permeated gas amount [cm ³ ] x Film thickness [cm] / Area [cm ² ] x Time [seconds] x Pressure [cmHg] Fuel oil permeability test Ordinary unleaded gasoline ( After filling the cup with 25 ml of gasoline (abbreviated as NO-Pb) and sealing the opening of this cup with a vulcanized rubber sheet, place it upside down on a balance, and measure the decrease in the weight of gasoline every few minutes. the speed of,
That is, the permeation rate is determined, and the weight loss rate of gasoline at the time when the permeation rate is maximum is calculated. The permeability coefficient (FPC) was calculated using the following formula. FPC = weight loss [g] x film thickness [cm] /
Permeation area [cm ² ] x time [minutes] Alcohol-containing gasoline permeability test Add 20% by volume of methanol to fuel oil B (gasoline: abbreviated as SF-B) specified in JIS K-6301.
Alcohol-containing gasoline prepared by mixing (SF
The permeability coefficient (FPC) was determined by the same method as the above fuel oil permeability test, except that the test oil was (abbreviated as -BM). Further, for comparison, the permeability coefficient (FPC) was similarly determined for SF-B alone. The SF-B above is 30% toluene and isooctane.
70%, SF-BM is 24% toluene,
Consists of 56% isooctane and 20% methanol (both volume %). Moisture Permeability Measurement Test The test was conducted in accordance with the moisture permeability test method for moisture-proof packaging materials (Cup method) specified in JIS Z0208. Place 5 g of anhydrous calcium chloride in a moisture-permeable cup, seal the opening with a vulcanized rubber sheet, and place it in a desiccator with distilled water in the bottom.
The weight of the cup is measured every 24 hours, and this measurement is continued until the weight increase is constant within 5% for two consecutive measurements (provided that the weight increase is 5% or less).
mg or more). The moisture permeability was calculated using the following formula. Moisture permeability = 240 x weight increase [mg] / absorption time [
time] x moisture permeable area [cm ² ] In addition, the film thickness of the sample sheet [mm] is added to the moisture permeability above.
The water vapor permeability of 1mm thickness was determined by multiplying by . Example 1 Dichlorocyclopropanated polybutadiene (rubber: Tg = -35°C) with a modification rate of 47% was produced using cis-1,4-polybutadiene as a raw material, and Compounds 1 and 2 were prepared from this rubber according to the compounding example and the following. The mixture was prepared and vulcanized at a pressure of 210 kg/m ² and a temperature of 150° C. for 16 minutes for compound 1 and 50 minutes for compound 2 to obtain a vulcanized rubber sheet with a thickness of 0.2 to 0.3 mm. Using this vulcanized rubber sheet, gas permeability tests (measured at temperatures of 25°C and 50°C), gasoline and alcohol-containing gasoline permeability tests, and moisture permeability tests were conducted. A tensile test was also conducted in accordance with JIS K6301 (vulcanized rubber physical testing method).
The respective results are shown in Tables 1 to 4.

[Table] The numerical values in the above table represent gas permeability coefficients (PC), and the unit is [cm ² /sec·cmHg]×10 ^-10 .

[Table] The numbers in the table above represent the permeability coefficient (FPC) of fuel oil, etc., and the unit is [g・cm/cm ²・min]. NO-Pb: Unleaded gasoline SF-B: Gasoline SF-BM: Alcohol-containing gasoline

【table】

[Table] Comparative Example 1 For cis-1,4-polybutadiene (Tg=-104°C), which was used as a raw material for the dichlorocyclopropanated polybutadiene used in Example 1, formulations 3 and 4 were prepared according to the formulation example and pressure
13 for formulation 3 at 210Kg/m ² and temperature 150℃
Vulcanization was carried out for 80 minutes in the case of compound 4 to obtain a vulcanized rubber sheet with a thickness of 0.2 to 0.3 mm. Using this vulcanized rubber sheet, gas permeability tests (measured at temperatures of 25°C and 50°C), gasoline and alcohol-containing gasoline permeability tests, and moisture permeability tests were conducted. A tensile test was also conducted in accordance with JIS K6301 (vulcanized rubber physical testing method).
The respective results are shown in Tables 5-8.

[Table] The numerical values in the above table represent gas permeability coefficients (PC), and the unit is [cm ² /sec·cmHg]×10 ^-10 .

[Table] The numbers in the table above represent the permeability coefficient (FPC) of fuel oil, etc., and the unit is [g・cm/cm ²・min].

【table】

[Table] Comparative example 2 Chlorinated butyl rubber (Mooney viscosity: ML1+8
(212〓) = 55, unsaturation: 1.4 mol%, chlorine content: 1.2% by weight), compound 5 was prepared according to the following formulation example (standard formulation for chlorinated butyl rubber vulcanization), and this formulation Pressure 210Kg/for item 5
cm ² and vulcanization for 17 minutes at a temperature of 150°C.
A vulcanized rubber sheet with a thickness of ~0.3 mm was obtained. Compounding example: 100 parts of chlorinated butyl rubber (parts by weight, same below),
5 parts zinc oxide, 1 part stearic acid, 1 part anti-aging agent (D: phenyl-β-naphthylamine), 1 part magnesia, 1 part tetramethylthiuram disulfide (TT), thiazole (dibenzothiazyl disulfide) Part 2. Using this vulcanized rubber sheet, a gas permeability test (measured at temperatures of 25°C and 50°C) and a moisture permeability test were conducted. A tensile test was also conducted in accordance with JIS K6301 (vulcanized rubber physical testing method). The respective results are shown in Tables 9-11. Comparative example 3 Chloroprene rubber (Mooney viscosity: ML1+4
(100°C) = 50, Tg = -45°C), a formulation 6 was prepared according to the formulation example below (standard formulation for chloroprene rubber vulcanization), and a pressure of 210Kg/cm ² and a temperature of 150℃ were prepared for this formulation 6. Vulcanization was performed at ℃ for 15 minutes to obtain a vulcanized rubber sheet with a thickness of 0.2 to 0.3 mm. Compounding example: 100 parts of chloroprene rubber (parts by weight, same below),
5 parts of zinc oxide, anti-aging agent (D: phenyl-β-
naphthylamine) 2 parts, magnesia 2 parts. A gas permeability test (measured at temperatures of 25°C and 50°C) was conducted using this vulcanized rubber sheet. Also
A tensile test was also conducted in accordance with JIS K6301 (vulcanized rubber physical testing method). The respective results are shown in Tables 9 to 11 along with the results of Comparative Example 2.

[Table] The numerical values in the above table represent gas permeability coefficients (PC), and the unit is [cm ² /sec·cmHg]×10 ^-10 .

【table】

[Table] Example 2 Dichlorocyclopropanated polybutadiene (rubber: Tg = -12°C) with a modification rate of 67% was produced using cis-1,4-polybutadiene as a raw material, and Compound 7 was prepared from this rubber according to the compounding example. 37 at a pressure of 210 Kg/cm ² and a temperature of 150°C for formulation 7.
Vulcanization was carried out for 1 minute to obtain a vulcanized rubber sheet with a thickness of 0.2 to 0.3 mm. A gas permeability test (measured at temperatures of 25°C and 50°C) was conducted using this vulcanized rubber sheet. The results are shown in Table 12. Example 3 Dichlorocyclopropanated polybutadiene (rubber: Tg = -74°C) with a modification rate of 23% was produced using cis-1,4-polybutadiene as a raw material, and Compound 8 was prepared from this rubber according to the blending example, For formulation 8 at a pressure of 210 Kg/m ² and a temperature of 150°C, 11
Vulcanization was carried out for 1 minute to obtain a vulcanized rubber sheet with a thickness of 0.2 to 0.3 mm. Using this vulcanized rubber sheet, gas permeability tests (measured at temperatures of 25°C and 50°C), gasoline and alcohol-containing gasoline permeability tests, and moisture permeability tests were conducted. Each result is shown in the 12th to 14th results along with the results of Example 2.
Shown in the table.

[Table] The numerical values in the above table represent gas permeability coefficients (PC), and the unit is [cm ² /sec·cmHg]×10 ^-10 .

[Table] The numbers in the table above represent the permeability coefficient (FPC) of fuel oil, etc., and the unit is [g・cm/cm ²・min].

[Table] Example 4 Dichlorocyclopropanated polybutadiene (rubber: Tg = -52°C) with a modification rate of 35% was produced using cis-1,4-polybutadiene as a raw material, and Compound 9 was prepared from this rubber according to the compounding example. 15 at a pressure of 210 Kg/m ² and a temperature of 150°C for formulation 9.
Vulcanization was carried out for 1 minute to obtain a vulcanized rubber sheet with a thickness of 0.2 to 0.3 mm. A gas permeability test (measured at temperatures of 25°C and 50°C) was conducted using this vulcanized rubber sheet. Also
A tensile test was also conducted in accordance with JIS K6301 (vulcanized rubber physical testing method). The respective results are shown in Tables 15 and 16. Example 5 Dichlorocyclopropanated polybutadiene (rubber: Tg = -84°C) with a modification rate of 15% was produced using cis-1,4-polybutadiene as a raw material, and Compound 10 was prepared from this rubber according to the Compounding Example, and compounded. Product 10 was vulcanized at a pressure of 210 kg/m ² and a temperature of 150° C. for 15 minutes to obtain a vulcanized rubber sheet with a thickness of 0.2 to 0.3 mm. A gas permeability test (measured at temperatures of 25°C and 50°C) was conducted using this vulcanized rubber sheet. A tensile test was also conducted in accordance with JIS K6301 (vulcanized rubber physical testing method). The respective results are shown in Tables 15 and 16 along with the results of Example 4.

[Table] The numerical values in the above table represent gas permeability coefficients (PC), and the unit is [cm ² /sec·cmHg]×10 ^-10 .

[Table] Example 6 Dibromocyclopropanated polybutadiene (rubber: Tg = -84°C) with a modification rate of 14% was produced using cis-1,4-polybutadiene as a raw material, and compound 11 was prepared using the following formulation example for this rubber. was prepared and for this formulation 11 the pressure was 210Kg/cm ² and the temperature
Vulcanization was performed at 200°C for 15 minutes to obtain a vulcanized rubber sheet with a thickness of 0.2 to 0.3 mm. Formulation example Dibromocyclopropanated polybutadiene 100
parts by weight, 1 part of sulfur, 1 part of anti-aging agent (D: phenyl-β-naphthylamine), 1 part of tetramethylthiuram disulfide (TT),
Thiazole (dibenzothiazyl disulfide) 1
part, 1 part diphenylguanidine. Using this vulcanized rubber sheet, we conducted a gas permeability test (at a temperature of 25°C and 50°C).
(measured at °C). The results are shown in Table 17.

[Table] The numerical values in the above table represent gas permeability coefficients (PC), and the unit is [cm ² /sec·cmHg]×10 ^-10 .

Claims (1)

[Claims] 1 Polybutadiene vulcanization obtained by sulfur or sulfur compound vulcanization of dihalocyclopropanated polybutadiene in which 5 to 75% of all double bonds in cis-1,4-polybutadiene have been converted to dihalocyclopropane groups. rubber.