JP5549856B2 - Method for producing highly elastic sulfur-modified chloroprene rubber - Google Patents

Description

  The present invention relates to a sulfur-modified chloroprene rubber and a method for producing the same, and particularly relates to a sulfur-modified chloroprene rubber that does not include a gel part and has high elastic stress, and can also be used for calender roll processing molding. It is.

  Chloroprene rubber is used in a wide range of applications because of a good balance of physical properties among various synthetic rubbers. For example, sulfur-modified chloroprene rubber is widely used in belt applications because of its excellent adhesion to fibers, tensile strength, dynamic characteristics, and the like.

  Among them, those that require high loads and high performance, such as automobile and agricultural machinery belts, have a high lateral modulus that can withstand lateral pressure from the pulley, a small-diameter pulley, and a circumferential flexibility that supports reverse bending. In order to achieve this, short fibers such as polyester, nylon, and cotton are blended, and the short fibers are oriented perpendicular to the belt circumferential direction. Therefore, in the belt molding, a step of molding the compound into a thin sheet by a calendar roll is provided, and the short fibers are oriented in a certain direction. At that time, as the sheet becomes thinner, the degree of orientation of the short fibers improves, so it is indispensable to reduce the thickness of the calendar sheet in order to improve the performance of the belt. Adhesion was a problem.

  On the other hand, the use of sulfur-modified chloroprene rubber containing a gel part can improve the adhesion of the compound to the calender roll. There was a limit to reducing the thickness of the sheet by roll molding.

  Therefore, there has been a demand for sulfur-modified chloroprene rubber that does not contain a gel portion that has a good roll releasability and can give a compound with low mill shrinkage.

  The present invention has been made in view of the above-mentioned problems, and its purpose is to have a high elastic sulfur modification that does not contain a gel part that has a good roll releasability and can give a compound with a small mill shrinkage. The present invention provides a chloroprene rubber, a highly elastic sulfur-modified chloroprene rubber for calender roll processing molding, and a method for producing the same.

  As a result of intensive studies in order to solve the above-mentioned problems, the present inventors copolymerized an appropriate amount of sulfur in the polymerization of sulfur-modified chloroprene rubber, and a high polymerization conversion rate in a range not including a gel part, It has been found that by selecting a method for increasing rubber elasticity such as increasing the Mooney viscosity, a compound with improved roll adhesion can be obtained without impairing mill shrinkage.

  That is, the present invention provides at least one kind of copolymerizable with 2-chloro-1,3-butadiene 80 to 99.7% by weight, sulfur 0.3 to 2% by weight, and 2-chloro-1,3-butadiene. A sulfur-modified chloroprene rubber composed of 0 to 19.7% by weight of a comonomer having a pore size of 0.5 μm in a 0.1% by weight tetrahydrofuran solution and containing no gel part having a transmittance of 97% or more. Then, 250 g of the rubber was wound around an 8-inch open roll and masticated for 3 minutes under the conditions of 30 ° C., a gap of 1 mm, and a guide width of 20 cm, and then viscoelasticity measuring device RPA-2000 (manufactured by Alpha Technologies) was used. The elastic stress measured under conditions of 60 ° C. (preheating 2 minutes), vibration frequency 10 cpm, vibration width 60 deg is 10 dNm or more. High elasticity sulfur-modified chloroprene rubber and high modulus sulfur-modified chloroprene rubber calender roll processing molding without the gel portion containing no gel portion, wherein the door, and to a manufacturing method thereof.

  Hereinafter, the present invention will be described in detail.

  The amount of 2-chloro-1,3-butadiene in the highly elastic sulfur-modified chloroprene rubber not containing the gel portion of the present invention is 80 to 99.7% by weight. When the amount of 2-chloro-1,3-butadiene is less than 80% by weight, the resulting polymer is not preferable because the properties of the chloroprene rubber are impaired. When the amount exceeds 99.7% by weight, the amount of copolymerized sulfur is small and the sulfur modification The characteristics as chloroprene rubber are impaired, which is not preferable. Among these, 90 to 99.6% by weight is particularly preferable.

  The sulfur in the highly elastic sulfur-modified chloroprene rubber not containing the gel part of the present invention is 0.3 to 2% by weight. When the amount of sulfur is less than 0.3% by weight, the resulting polymer is not preferred because it impairs the properties of the sulfur-modified chloroprene rubber. When the amount exceeds 2% by weight, the elastic stress after masticating the raw rubber with a roll is remarkably high. Since it falls, it is not preferable. Of these, 0.4 to 1% by weight is particularly preferred.

  The at least one comonomer copolymerizable with 2-chloro-1,3-butadiene in the highly elastic sulfur-modified chloroprene rubber not including the gel portion of the present invention is 0 to 19.7% by weight. The copolymerizable comonomer here is not particularly limited, and examples thereof include monovinyl compounds such as acrylonitrile, methacrylonitrile, vinylidene chloride, aromatic vinyl compounds such as styrene and α-methylstyrene, acrylic acid, methacrylic acid, and the like. Unsaturated group-containing carboxylic acid, acrylic acid ester, methacrylic acid ester and the like unsaturated group-containing carboxylic acid ester, isoprene, 1,3-butadiene, 1-chloro-1,3-butadiene, 2,3-dichloro- Examples thereof include conjugated diene compounds such as 1,3-butadiene, 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 preferable. When the comonomer copolymerizable with 2-chloro-1,3-butadiene exceeds 19.7% by weight, the copolymer obtained is unfavorable because the characteristics of the sulfur-modified chloroprene rubber are impaired. Of these, 0 to 9.6% by weight is particularly preferable.

  In the present invention, the sulfur-modified chloroprene rubber not containing a gel portion allows a 0.1 wt% tetrahydrofuran solution of the rubber to pass through a 0.5 μm pore size filter, and the permeate is introduced into a gel permeation chromatograph (GPC). The filter transmittance of the pore diameter 0.5 μm calculated from the obtained peak area is 97% or more. A compound obtained from a sulfur-modified chloroprene rubber having a pore size of 0.5 μm with a filter transmittance of less than 97% and containing a gel portion has a large mill shrinkage. For example, it is difficult to mold a thin sheet in calendar roll molding. It becomes.

  The elastic stress in the present invention is a viscoelasticity measurement using a sample obtained by winding 250 g of chloroprene rubber around an 8-inch open roll and masticating for 3 minutes at 30 ° C., a gap of 1 mm and a guide width of 20 cm. It was evaluated by. The viscoelasticity measurement was performed using an alpha technology viscoelasticity measuring device RPA-2000, and the elastic stress was measured under the conditions of 60 ° C. (preheating 2 minutes), vibration frequency 10 cpm, and vibration width 60 deg. When the value is 10 dNm or more, the elastic stress of the present invention is satisfied, and when it is less than 10 dNm, the elasticity of the chloroprene rubber is low. For example, in the calendar roll molding of the compound, the adhesion to the roll surface becomes strong, and a thin sheet Is difficult to mold.

  In addition, mill shrinkage refers to shrinkage after sheet molding with a roll or the like, and when a compound with large mill shrinkage is molded into a thin sheet with a roll or the like, the sheet deforms while standing still, The length direction shrinks, and the width direction and thickness direction increase. Therefore, it is difficult to form such a compound into a thin sheet with a roll or the like.

  A method for producing the sulfur-modified chloroprene rubber of the present invention will be described below.

  The sulfur-modified chloroprene rubber of the present invention is produced by radical polymerization, and there are methods such as emulsion polymerization, solution polymerization, and bulk polymerization. Among these methods, radical emulsion polymerization is exemplified by the following method.

  An arbitrary amount of 2-chloro-1,3-butadiene, sulfur, and a mixture of at least one comonomer copolymerizable with 2-chloro-1,3-butadiene are introduced into a polymerization vessel and heated at 30 to 50 ° C. for 1 hour. By stirring above, sulfur is completely dissolved in the monomer. Thereafter, an aqueous emulsifier solution is mixed with the mixture, followed by stirring to emulsify. Polymerization is carried out by adding a polymerization initiator to this emulsion, and when an arbitrary conversion rate is reached, a polymerization terminator is added to terminate the polymerization. The emulsifier / dispersant used here is not particularly limited, and anion type emulsifiers such as carboxylate type, sulfonate type and sulfate type, and nonionic type emulsifiers are used. Alkali metal salt of leveled rosin acid, alkali metal salt of rosin acid, higher fatty acid alkali metal salt, alkyl sulfonate, alkyl aryl sulfonate, alkyl sulfate, alkyl aryl sulfate, sodium naphthalene sulfonate and formaldehyde Examples include condensates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, sorbitan fatty acid esters, polyoxyethylene acyl esters, and the like, which can be used alone or in combination of two or more. Although the optimum range of the amount of each emulsifying / dispersing agent varies depending on the type, it is particularly preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of all charged monomers as a range in which emulsion polymerization can be carried out stably. The polymerization initiator is not particularly limited, and a known free radical-generating substance can be used. For example, persulfate such as potassium persulfate and ammonium persulfate, hydrogen peroxide, paramentane hydroperoxide, t-butyl Examples thereof include inorganic or organic peroxides such as hydroperoxide and cumene hydroperoxide. These alone or the above compounds and ferrous sulfate, sodium hydrosulfite, sodium formaldehyde sulfoxylate, thiosulfate, thiosulfite A redox system in combination with a reducing substance such as an organic amine is used. The terminator is not particularly limited, and examples thereof include phenothiazine, 2,2′-methylenebis- (4-methyl-6-tert-butylphenol), 2,2′-methylenebis- (4-ethyl-6-t). -Butylphenol), 2,6-di-t-butyl-4-methylphenol, hydroquinone, 4-methoxyhydroquinone, radical inhibitors such as N, N-diethylhydroxylamine, etc., may be used alone or in combination of two or more. The

  The polymerization temperature can be carried out in the range of 0 to 60 ° C, preferably 5 to 50 ° C, more preferably 35 to 40 ° C.

  The polymerization termination conversion is preferably 50 to 95%. When the polymerization termination conversion is less than 50%, the amount of sulfur-modified chloroprene rubber obtained is small and the productivity is poor, and when it exceeds 95%, it is difficult to obtain a sulfur-modified chloroprene rubber containing no gel part. Among these, 70 to 90% is particularly preferable, and 80 to 86% is more preferable.

  Subsequently, a peptizer and a peptizer are added to the polymerization-terminated latex, and peptization is performed until an appropriate Mooney viscosity is obtained. Examples of peptizers include thiuram compounds such as tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetraoctylthiuram disulfide, etc. In order to stably add to latex, use the above-mentioned emulsifier etc. after dissolving in toluene. There is a method of adding in an emulsified state. Examples of the peptizing aid include thiocarbamic acid compounds such as sodium dibutyldithiocarbamate and ammonium dimethyldithiocarbamate.

  The peptization temperature can be performed in the range of 0 to 60 ° C, and preferably in the range of 5 to 50 ° C. Generally, the higher the peptization temperature, the faster the peptization reaction.

  The Mooney viscosity for terminating the peptization reaction is not particularly limited as long as it satisfies the high elastic stress of the present invention, but is preferably 20 to 80 in view of kneading workability.

  After the peptization reaction is completed, the unreacted monomer in the latex is removed with a monomer strip or the like. Thereafter, the polymer is isolated from the latex by a method such as freeze coagulation or salting out, and washed with water and dried to obtain sulfur-modified chloroprene rubber.

  The highly elastic sulfur-modified chloroprene rubber of the present invention that does not contain a gel portion according to the example of this polymerization method is, for example, a method of copolymerizing an appropriate amount of sulfur and increasing the conversion rate and viscosity in a range not including the gel portion. Can be obtained by selecting.

  The highly elastic sulfur-modified chloroprene rubber that does not contain the gel portion of the present invention can be molded and vulcanized in the same manner as a conventionally known sulfur-modified chloroprene rubber. For example, a vulcanizing agent, a vulcanization accelerator, a reinforcing agent, a filler, a plasticizer, an anti-aging agent, etc. are mixed with chloroprene rubber by a kneader such as a roll, kneader or Banbury, and molded into a shape according to the purpose, There is a way to vulcanize. The highly elastic sulfur-modified chloroprene rubber that does not contain the gel portion of the present invention is a compound with excellent processability that does not impair mill shrinkage and improves roll adhesion in this molding process, particularly in the formation of a thin sheet using a calender roll. give.

  As explained above, since the sulfur-modified chloroprene rubber obtained by the production method of the present invention does not contain a gel part and has high elastic stress, mill shrinkage is not impaired and roll releasability is improved. It is clear that a formulation can be given.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples.

  The Mooney viscosity, 0.5 μm filter transmittance, elastic stress, mill shrinkage, roll releasability and vulcanizate properties were measured and evaluated by the following methods.

<Mooney viscosity>
The Mooney viscosity of the sulfur-modified chloroprene rubber was measured and evaluated according to JIS K6388 (1995 edition).

<0.5 μm filter transmittance>
The pore permeability of the sulfur-modified chloroprene rubber having a pore size of 0.5 μm was obtained by allowing a 0.1 wt% tetrahydrofuran solution to pass through a pore size of 0.5 μm filter and introducing the permeate into a gel permeation chromatograph (GPC). Calculated from the peak area.

<Elastic stress>
The elastic stress of the raw rubber is viscoelasticity manufactured by Alpha Technologies Co., Ltd. using a sample obtained by winding 250 g of chloropre-rubber around an 8-inch open roll and masticating for 3 minutes under the conditions of 30 ° C., 1 mm gap and 20 cm guide width. Measurement and evaluation were performed with a measuring device RPA-2000. The viscoelasticity measurement conditions are 60 ° C. (preheating 2 minutes), vibration frequency 10 cpm, and vibration width 60 deg.

<Mill shrinkage>
Mill shrinkage in the characteristics of the compound was obtained when 750 g of a sulfur-modified chloroprene rubber compound obtained according to the compounding described below was wound around an 8-inch open roll adjusted to a guide width of 20 cm and 40 ° C., and the gap became 2 mm. The change in sheet length before and after standing at 23 ° C. for 3 hours was measured and evaluated by shrinkage.

<Roll releasability>
The roll releasability was evaluated sensuously by the ease of peeling from the roll when the blend was molded into a 0.5 mm sheet with an 8-inch calendar roll adjusted to 90 ° C. Those having excellent releasability were indicated by ○, and those having inferiority were indicated by ×.

<Vulcanized properties>
Vulcanizate properties were measured and evaluated at a pulling speed of 500 mm / min using dumbbell-shaped No. 3 type test pieces in accordance with JIS K6251 (1993 edition).

  In the following description, “part by weight” means a weight ratio based on 100 parts by weight of the total monomer mixture.

Example 1
Production of sulfur-modified chloroprene rubber was carried out by the following procedure.

  The monomers shown in Table 1 were charged into a 2 liter autoclave equipped with a stirrer and stirred at 30 ° C. for 1 hour to completely dissolve sulfur. Emulsification comprising 4 parts by weight of potassium rosinate, 0.7 parts by weight of a condensate of sodium naphthalenesulfonate and formaldehyde, 0.7 parts by weight of trisodium phosphate, 0.05 parts by weight of sodium hydroxide and 120 parts by weight of distilled water The solution was added to it and thoroughly purged with nitrogen, then stirred and emulsified. Polymerization was carried out by dropping a 3 wt% aqueous potassium persulfate solution while controlling the jacket temperature so that the inside of the polymerization vessel was kept constant at 40 ° C. When the conversion reached 86%, 0.05 part by weight of N, N-diethylhydroxylamine was added to complete the polymerization.

  Subsequently, a solution obtained by emulsifying a toluene solution of 2 parts by weight of tetraethylthiuram disulfide with potassium rosinate and 0.3 parts by weight of sodium dibutyldithiocarbamate were added thereto, and peptization was performed at 40 ° C. until the Mooney viscosity reached 60. went.

  After the peptization was completed, the remaining unreacted monomer was removed by a reduced pressure steam stripping method, a polymer was precipitated from the obtained latex by freezing and coagulation, washed with water, and dried with hot air to obtain a sulfur-modified chloroprene rubber.

  The resulting sulfur-modified chloroprene rubber was measured for Mooney viscosity, 0.5 μm filter permeability and elastic stress, and the results are shown in Table 1.

  This sulfur-modified chloroprene rubber was kneaded with a 1 l kneader in accordance with the formulation shown in Table 2, and mill shrinkage and roll releasability of the formulation were measured. The results are shown in Table 1.

  A vulcanized rubber sheet was prepared by press vulcanizing the blend at 150 ° C. for 30 minutes, and its vulcanizate characteristics were measured. The results are shown in Table 1.

  From these results, it is clear that a sulfur-modified chloroprene rubber containing no gel part and having a high elastic stress was obtained, and a blend using the same had a small mill shrinkage and an excellent roll releasability.

実施例２〜実施例４
表１に示したモノマー組成において、重合温度、重合停止転化率、ムーニー粘度を変更した以外は実施例１と同様の方法で重合、解膠を行い、硫黄変性クロロプレンゴムを得た。

Example 2 to Example 4
In the monomer composition shown in Table 1, polymerization and peptization were performed in the same manner as in Example 1 except that the polymerization temperature, the polymerization termination conversion rate, and the Mooney viscosity were changed to obtain a sulfur-modified chloroprene rubber.

  In the same manner as in Example 1, Mooney viscosity, 0.5 μm filter permeability, elastic stress, mill shrinkage, roll releasability, and vulcanizate properties were measured, and the results are shown in Table 1.

  From these results, it is clear that a sulfur-modified chloroprene rubber containing no gel part and having a high elastic stress was obtained, and a blend using the same had a small mill shrinkage and an excellent roll releasability.

Example 5
In the monomer composition shown in Table 3, polymerization and peptization were performed in the same manner as in Example 1 except that the polymerization temperature, the polymerization termination conversion rate, and the Mooney viscosity were changed to obtain a sulfur-modified chloroprene rubber.

  As in Example 1, Mooney viscosity, 0.5 μm filter permeability, elastic stress, mill shrinkage, roll releasability, and vulcanizate properties were measured, and the results are shown in Table 3.

  From these results, it is clear that a sulfur-modified chloroprene rubber containing no gel part and having a high elastic stress was obtained, and a blend using the same had a small mill shrinkage and an excellent roll releasability.

比較例１〜比較例３
表３に示したモノマー組成において、重合温度、重合停止転化率、ムーニー粘度を変更した以外は実施例１と同様の方法で重合、解膠を行い、硫黄変性クロロプレンゴムを得た。

Comparative Examples 1 to 3
In the monomer composition shown in Table 3, polymerization and peptization were performed in the same manner as in Example 1 except that the polymerization temperature, the polymerization termination conversion rate, and the Mooney viscosity were changed to obtain a sulfur-modified chloroprene rubber.

  As in Example 1, Mooney viscosity, 0.5 μm filter permeability, elastic stress, mill shrinkage, roll releasability, and vulcanizate properties were measured, and the results are shown in Table 3.

  From these results, a sulfur-modified chloroprene rubber containing no gel part was obtained, and although the mill shrinkage of the compound obtained therefrom was small, the roll release property of the compound was low because the elastic stress was lower than the range of the present invention. inferior.

Comparative Example 4
In the monomer composition shown in Table 4, polymerization and peptization were performed in the same manner as in Example 1 except that the polymerization temperature, the polymerization termination conversion rate, and the Mooney viscosity were changed to obtain a sulfur-modified chloroprene rubber.

  As in Example 1, Mooney viscosity, 0.5 μm filter permeability, elastic stress, mill shrinkage, roll releasability, and vulcanizate properties were measured, and the results are shown in Table 4.

  From these results, a sulfur-modified chloroprene rubber containing no gel part was obtained, and although the mill shrinkage of the compound obtained from the rubber was small, the elastic stress was lower than the range of the present invention, so that the roll releasability of the compound was low. inferior.

比較例５
表４に示したモノマー組成において、重合温度、重合停止転化率、ムーニー粘度を変更した以外は実施例１と同様の方法で重合、解膠を行い、硫黄変性クロロプレンゴムを得た。

Comparative Example 5
In the monomer composition shown in Table 4, polymerization and peptization were performed in the same manner as in Example 1 except that the polymerization temperature, the polymerization termination conversion rate, and the Mooney viscosity were changed to obtain a sulfur-modified chloroprene rubber.

  As in Example 1, Mooney viscosity, 0.5 μm filter permeability, elastic stress, mill shrinkage, roll releasability, and vulcanizate properties were measured, and the results are shown in Table 4.

  Since the sulfur-modified chloroprene rubber obtained from these results contained a slight gel part, the mill shrinkage of the resulting blend was large. Moreover, since the elastic stress was lower than the range of this invention, the roll release property of the compound was inferior.

Comparative Example 6
In the monomer composition shown in Table 4, polymerization was carried out in the same manner as in Example 1 except that both A and B were changed in polymerization temperature and polymerization termination conversion. After mixing the latex so that A: B = 2: 8, peptization was performed in the same manner as in Example 1 until the Mooney viscosity shown in Table 4 to obtain a sulfur-modified chloroprene rubber.

  As in Example 1, Mooney viscosity, 0.5 μm filter permeability, elastic stress, mill shrinkage, roll releasability, and vulcanizate properties were measured, and the results are shown in Table 4.

  The sulfur-modified chloroprene rubber obtained from these results contained a gel portion derived from A. Since the elastic stress was sufficiently high and within the range of the present invention, the roll release property of the blend was excellent, but since the gel part was contained, the mill shrinkage of the blend was greatly inferior.

Claims (1)

80-99.7 parts by weight of 2-chloro-1,3-butadiene, 0.3-2 parts by weight of sulfur, and at least one comonomer copolymerizable with 2-chloro-1,3-butadiene 0-19. Using 7 parts by weight, the polymerization is carried out at a polymerization temperature of 35 to 40 ° C., the polymerization is terminated when the conversion rate becomes 70 to 90%, tetraethyl thiuram disulfide or tetrabutyl thiuram disulfide is added, and the Mooney viscosity is wherein the peptization until 56-67, 2-chloro-1,3-butadiene 80 to 99.7 wt%, sulfur 0.3 to 2 wt%, and 2-chloro-1,3 Permeation of 0.5 μm pore size filter in 0.1 wt% tetrahydrofuran solution consisting of 0 to 19.7 wt% of at least one comonomer copolymerizable with butadiene and thiuram compound Is 97% or more, does not contain a gel part, and 250 g of the rubber is wound around an 8-inch open roll and masticated for 3 minutes under the conditions of 30 ° C., a gap of 1 mm, and a guide width of 20 cm. Highly elastic sulfur-modified chloroprene rubber that does not contain a gel part with an elastic stress of 10 dNm or more measured using RPA-2000 (manufactured by Alpha Technologies) at 60 ° C. (preheating 2 minutes), vibration frequency 10 cpm, vibration width 60 deg. Manufacturing method.