JP2018145321A - Chloroprene rubber composition and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chloroprene rubber composition excellent in extrudability and mechanical properties, and a production method thereof. SOLUTION: Toluene-soluble chloroprene polymer A and chloroprene rubber having an alkylpolythiocarbonate group at the molecular end, monomer conversion of 80% or more and Mooney viscosity of 150 or more A chloroprene rubber composition obtained by blending polymer B having a toluene-insoluble gel content of 70% by weight or more, and a method for producing the same. [Selection figure] None

Description

  The present invention relates to chloroprene rubber and a method for producing the same, and more particularly to a chloroprene rubber composition having excellent mechanical properties and extrusion processability and a method for producing the same.

  Chloroprene rubber has good processability, mechanical strength, oil resistance, flame retardancy, adhesiveness and the like, and is used in a wide range of applications. Among these, chloroprene rubber excellent in extrusion processability is required for applications requiring extrusion molding in order to cope with the shape of the product. In order to solve the problem, a method of blending chloroprene gel polymer with chloroprene rubber has been proposed (see, for example, Patent Document 1). However, in the conventional method, when chloroprene gel polymer is contained, the extrudability is improved while the mechanical properties of the vulcanizate are impaired. For this reason, it is difficult to improve both the extrudability and mechanical properties, and a chloroprene rubber composition having excellent mechanical properties and extrudability has not been realized yet.

JP-A-9-176386

  In the prior art, it is difficult to improve both extrudability and mechanical properties, and a chloroprene rubber composition having excellent mechanical properties and extrudability has not been realized yet.

  This invention is made | formed in view of said subject, and it aims at providing the chloroprene rubber composition excellent in extrusion processability and a mechanical characteristic, its manufacturing method, and a vulcanizate.

  As a result of intensive studies in order to solve the above problems, the present inventors have arrived at the present invention. That is, the present invention is a polymer of a trifunctional monomer having toluene-soluble chloroprene polymer A and 2-chloro-1,3-butadiene and three ethylenically unsaturated bonds in the molecule, A chloroprene rubber composition excellent in extrudability and mechanical properties, obtained by blending a chloroprene polymer B having an alkylpolythiocarbonate group at the molecular end with a toluene-insoluble gel content of 70% by weight or more and its It is a manufacturing method.

  Hereinafter, the present invention will be described in more detail.

  The present invention is a chloroprene rubber composition comprising the following chloroprene polymer A and the following chloroprene polymer B having an alkylpolythiocarbonate group at the molecular end.

  A: A chloroprene polymer soluble in toluene and having a Mooney viscosity of 10 to 120.

  B: 2-chloro-1,3-butadiene and a trifunctional monomer polymer having three ethylenically unsaturated bonds in the molecule, and a chloroprene copolymer having a toluene-insoluble gel content of 70% by weight or more Coalescence.

  The chloroprene polymer B has a sulfur content in the range of 0.1 to 2.0% by weight, more preferably in the range of 0.4 to 1.6% by weight, as long as the mechanical properties of the vulcanized product of the chloroprene rubber composition are not impaired. Preferably there is. The sulfur content of the chloroprene polymer A is not particularly limited.

  The chloroprene polymer A is obtained by emulsion polymerization of chloroprene. Further, a mixture of chloroprene and a copolymerizable monomer may be subjected to emulsion polymerization.

  The chloroprene polymer B is obtained by emulsion polymerization of chloroprene and a trifunctional monomer having three ethylenically unsaturated bonds in the molecule. Further, a mixture of chloroprene and a copolymerizable monomer may be subjected to emulsion polymerization.

Examples of the copolymerizable monomer include 2,3-dichloro-1,3-butadiene, 2-cyano-1,3-butadiene, 1-chloro-1,3-butadiene, 1,3-butadiene, Styrene, acrylonitrile, methyl methacrylate, methacrylic acid, acrylic acid and the like can be mentioned, and among these, alone or in combination of two or more. The comonomer content in the chloroprene polymers A and B is preferably 50% by weight or less, and more preferably 30% by weight or less as long as the properties of the chloroprene rubber are not impaired.
The trifunctional monomer is not particularly limited as long as it is a trifunctional monomer having three ethylenically unsaturated bonds in its molecule. For example, trimethylol ethane trimethacrylate, trimethylol ethane triacrylate , Trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, triallylamine, triallyl isocyanurate and the like, and can be used alone or in combination of two or more. Of these, trimethylolpropane trimethacrylate and trimethylolpropane triacrylate are particularly preferred. The content of the component derived from the trifunctional monomer in the chloroprene polymer B is 0.5 to 10% by weight, and the extrusion process of the chloroprene rubber composition obtained from the present invention is less than 0.5% by weight. When the content exceeds 10% by weight, the mechanical properties of the vulcanized product of the chloroprene rubber composition are impaired. Of these, the amount is particularly preferably 0.8 to 3.0 parts by weight.

  Emulsion polymerization is performed by adding an emulsion aqueous solution containing an emulsifier to chloroprene (or a mixture of chloroprene and a monomer copolymerizable therewith), and adding a chain transfer agent and a polymerization catalyst.

  The emulsifier is not particularly limited as long as it is of sulfonic acid type or sulfate ester salt type. For example, rosin acid metal salt, alkylsulfonic acid alkali metal salt, alkylsulfonic acid amine salt, alkylsulfone Ammonium salt of acid, alkali metal salt of alkyl sulfate ester, ammonium metal salt of alkyl sulfate ester, amine metal salt of alkyl sulfate ester, alkali metal salt of alkyl aryl sulfonic acid, ammonium salt of alkyl aryl sulfonic acid, alkyl aryl sulfonic acid An amine salt of an alkylaryl sulfate, an ammonium salt of an alkylaryl sulfate, an amine metal of an alkylaryl sulfate, an alkali metal of a polyoxyethylene alkylphenyl ether sulfate, Ammonium salt of reoxyethylene alkylaryl ether sulfate, amine salt of polyoxyethylene alkylaryl ether sulfate, alkali metal salt of polyoxyethylene alkyl ether sulfate, ammonium salt of polyoxyethylene alkyl ether sulfate, polyoxyethylene Examples include amine salts of alkyl ether sulfates. Among these, it can use individually or in combination of 2 or more types.

  As the polymerization catalyst, for example, potassium persulfate, ammonium persulfate, hydrogen peroxide, t-butyl hydroperoxide and the like are used. These may be used alone or in a redox system with a reducing substance such as hydrosulfite, thiosulfate, thiosulfite, ascorbic acid and the like.

  The chain transfer agent used when polymerizing the chloroprene polymer A is not particularly limited. For example, alkyl mercaptan, halogenated hydrocarbon, dialkyl xanthogen disulfide, dialkyl xanthogen polysulfide, tetraalkyl thiuram disulfide, α-methylstyrene dimer. 1,1-diphenylethylene, sulfur and the like. The amount used is preferably 0.1 to 3 parts by weight, more preferably 0.3 to 1 part by weight.

  Dialkylxanthogen polysulfide is used as the chain transfer agent used when the chloroprene polymer B is polymerized. Examples of the dialkyl xanthogen polysulfide include dimethyl xanthogen polysulfide, diethyl xanthogen polysulfide, diisopropyl xanthogen polysulfide, dibutyl xanthogen polysulfide, and the like. Among these, it can use individually or in combination of 2 or more types.

  The amount of dialkylxanthogen polysulfide is preferably 0.1 to 3 parts by weight in order to obtain chloroprene polymer B having a sulfur content in the range of 0.1 to 2.0 parts by weight, More preferred is ~ 3 parts by weight.

  The polymerization is desirably performed at a temperature of 10 to 60 ° C. while mixing and stirring, and the pH of the emulsion is preferably 10 to 13. As the pH adjuster, for example, among basic compounds such as sodium hydroxide, sodium phosphate, potassium phosphate, triethylamine, diethylamine and the like can be used alone or in combination of two or more.

  Polymerization is carried out to the desired polymerization conversion rate, and then a small amount of a polymerization terminator containing a polymerization inhibitor is added to terminate the polymerization. The polymerization terminator may contain an emulsifier and chloroprene.

  Examples of the polymerization inhibitor include thiodiphenylamine, 4-t-butylcatechol, 2,2′-methylenebis (4-ethyl-6-t-butylphenol), hydroquinone, N, N-diethylhydroxylamine, and the like. Among these, it can use individually or in combination of 2 or more types.

  The monomer conversion rate when polymerizing the chloroprene polymer A is not particularly limited. Chloroprene polymer A is soluble in toluene, and Mooney viscosity of chloroprene polymer A is in the range of 10-120. When the Mooney viscosity is less than 10, the mechanical properties of the vulcanized product of the chloroprene rubber composition are impaired, and when it exceeds 120, the extrusion processability is impaired. Furthermore, the Mooney viscosity is preferably 30-80.

  In addition, toluene soluble means that a chloroprene polymer is dissolved in toluene so as to have a concentration of 1.0% in terms of weight, and if the gel content insoluble in toluene is less than 1% by weight, it is determined that toluene is soluble. .

  The chloroprene polymer B has a toluene-insoluble gel content of 70% by weight or more, or the chloroprene polymer B has a Mooney viscosity of 150 or more. When the Mooney viscosity is less than 150 or the gel content that does not require toluene is less than 70% by weight, the extrudability of the chloroprene rubber composition is impaired.

  The chloroprene polymer B is obtained by setting the monomer conversion rate when the chloroprene polymer B is polymerized to 80% or more, and preferably 85 to 95%.

  After termination of the polymerization, unreacted monomers in the chloroprene polymer latex are removed by a reduced pressure steam stripping method, followed by freeze solidification, separation of rubber and dehydration drying to obtain a polymer.

  The chloroprene rubber composition of the present invention can be obtained by blending the polymerized chloroprene polymers A and B in either a latex state or an isolated polymer state. The mixing ratio of the chloroprene polymers A and B is preferably A: 30 to 95 parts by weight and B: 5 to 70 parts by weight (the total of A and B is 100 parts by weight). When the weight mixing ratio of the chloroprene polymer A is 30 or more, the mechanical properties of the vulcanized product of the chloroprene rubber composition of the present invention are excellent, and when it is 95 parts by weight or less, the extrudability of the chloroprene rubber composition is excellent. Furthermore, it is preferable that A: 60 to 90 parts by weight and B: 10 to 40 parts by weight (the total of A and B is 100 parts by weight).

  The obtained chloroprene rubber composition is kneaded with various compounding agents and vulcanized by a conventional method to give a chloroprene rubber vulcanizate. Examples of the compounding agent include a vulcanizing agent, a vulcanization accelerator, a filler, a plasticizer, and an antiaging agent.

  The chloroprene rubber composition of the present invention is obtained by improving the tensile strength of the vulcanizate while maintaining the conventional extrudability.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these.

Example 1
First, the chloroprene polymer A was polymerized by the following procedure. Monomer mixture of chloroprene polymer A shown in Table 1, 4 parts by weight of potassium salt of rosin acid, 0.5 part by weight of sodium salt of formalin naphthalene sulfonate formalin, 0.2 part by weight of sodium hydroxide, 100 parts by weight of distilled water Were stirred and emulsified. A polymerization catalyst of 0.1 part by weight of potassium persulfate and 20 parts by weight of water was added thereto at a constant rate by a pump, and emulsion polymerization was carried out at 40 ° C. Emulsion polymerization is carried out by adding a polymerization catalyst until the polymerization conversion becomes 70%, and then 0.01 parts by weight of 4-t-butylcatechol, 0.02 parts by weight of sodium dodecylbenzenesulfonate, 0.5 parts by weight of chloroprene. Then, a polymerization terminator containing 0.5 part by weight of water was added to stop the emulsion polymerization, and unreacted chloroprene was removed and recovered by steam stripping under reduced pressure to obtain a latex of chloroprene polymer A. A part of the latex was adjusted to pH 6.1 with acetic acid, freeze-coagulated by a conventional method to separate a rubber component, and then dried to obtain a chloroprene polymer A. The measurement results of Mooney viscosity of chloroprene polymer A are shown in Table 1.

  Subsequently, a latex of chloroprene polymer B was obtained in the same manner as the previous chloroprene polymer A except that the monomer mixture of chloroprene polymer B shown in Table 1 was used and the conversion rate was 90%. A part of the latex was adjusted to pH 6.1 with acetic acid, freeze-coagulated by a conventional method to separate a rubber component, and then dried to obtain a chloroprene polymer B. The measurement results of Mooney viscosity of chloroprene polymer B are shown in Table 1.

  After the latexes of the chloroprene polymers A and B obtained as described above were mixed so as to have a mixing ratio of the chloroprene rubber composition shown in Table 1, the pH was adjusted to 6.1 using acetic acid and frozen by a conventional method. The rubber component was solidified to separate and then dried to obtain the intended chloroprene rubber composition.

In order to evaluate the rubber properties of the vulcanized product of the obtained chloroprene rubber composition, chemicals other than the vulcanization accelerator were kneaded with a kneader according to the formulation shown in Table 2. A vulcanization accelerator was added to the obtained rubber composition and kneaded with an open roll to obtain an unvulcanized rubber. The obtained unvulcanized rubber was press vulcanized at 160 ° C. for 20 minutes to obtain a vulcanized product. The following tests were conducted on the obtained rubber composition and its vulcanizate. The results are shown in Table 1.
<Mooney viscosity measurement>
About the obtained chloroprene rubber, the Mooney viscosity was measured according to JISK6300-1.
<Die Swell>
Continuously using a processability tester (manufactured by Monsanto) under the conditions of a die inner diameter of 1.5 mm, L / D = 1, a cylinder temperature of 70 ° C., a die temperature of 70 ° C., and S / R = 300 (1 / sec) The expansion ratio of the extrudate diameter relative to the inner diameter of the die during extrusion was measured as a die swell, and the extrudability of the chloroprene rubber composition was evaluated. The smaller the die swell, the better the extrudability.
<Rubber hardness>
The hardness (HS) of the vulcanized rubber composition was measured using a JIS-A hardness meter.
<Tensile test>
In accordance with JIS K6251, a tensile test was performed using a No. 3 dumbbell-shaped test piece made of a vulcanizate, and the tensile strength TB (MPa) and elongation at break EB (%) of the test piece were measured.

  Because the die swell was small and the tensile strength was excellent, it was possible to achieve both excellent extrudability and excellent mechanical properties of the vulcanizate.

<Sulfur content analysis>
After the combustion absorption treatment by the oxygen flask combustion method, ion chromatography measurement was performed to quantify the sulfur content of the chloroprene rubber composition.

<Analysis of gel content>
The chloroprene polymer is dissolved in toluene to a concentration of 1.0% in terms of weight, mixed and dissolved for 16 hours, the resulting solution is filtered with a 200 mesh wire mesh, washed with toluene, and the residue is removed. After drying at 170 ° C. for 10 minutes, the ratio of the weight to the weight of the dissolved rubber was taken as the gel content.

Examples 2-5
A latex of chloroprene polymer A was obtained in the same manner as in Example 1 using the monomer mixture of chloroprene polymer A shown in Table 1. Subsequently, a latex of chloroprene polymer B was obtained in the same manner as in Example 1 using the monomer mixture of chloroprene polymer B shown in Table 1. Table 1 shows the Mooney viscosities of the polymers A and B measured in the same procedure as in Example 1.

  After the obtained latexes of chloroprene polymers A and B were mixed so as to have a mixing amount of the chloroprene rubber composition shown in Table 1, a chloroprene rubber composition was obtained in the same manner as in Example 1. Table 1 shows the mechanical properties of the die swell and vulcanizate evaluated by the same method as in Example 1 in order to evaluate the rubber properties of the vulcanized product of the obtained chloroprene rubber composition. Because the die swell was small and the tensile strength was excellent, both excellent extrudability and excellent mechanical properties of the vulcanizate could be achieved.

Comparative Example 1
Using the monomer mixture of chloroprene polymer A shown in Table 3, latex of chloroprene polymer A was obtained in the same manner as in Example 1. Subsequently, a latex of chloroprene polymer B was obtained in the same manner as in Example 1 except that the chain transfer agent of polymer B shown in Table 1 was changed. Table 1 shows the Mooney viscosities of the polymers A and B measured in the same procedure as in Example 1.

  After mixing the latexes of the chloroprene polymers A and B obtained as described above so as to have a mixing amount of the chloroprene rubber composition shown in Table 1, chloroprene rubber compositions were obtained in the same manner as in Example 1. Table 1 shows the mechanical properties of the die swell and vulcanizate evaluated in the same manner as in Example 1. As a result, since the tensile strength was inferior, it was not possible to achieve both excellent extrudability and excellent mechanical properties of the vulcanizate.

Comparative Examples 2-3
Using the monomer mixture of chloroprene polymer A shown in Table 3, latex of chloroprene polymer A was obtained in the same manner as in Example 1. Subsequently, a latex of chloroprene polymer B was obtained in the same manner as in Example 1 using the monomer mixture of chloroprene polymer B shown in Table 1. Table 1 shows the Mooney viscosities of the polymers A and B measured in the same procedure as in Example 1.

  After mixing the latexes of the chloroprene polymers A and B obtained as described above so as to have a mixing amount of the chloroprene rubber composition shown in Table 3, chloroprene rubber compositions were obtained in the same manner as in Example 1. Table 1 shows the mechanical properties of the die swell and vulcanizate evaluated in the same manner as in Example 1. As a result, since the tensile strength was inferior, it was not possible to achieve both excellent extrudability and excellent mechanical properties of the vulcanizate.

Comparative Examples 4-5
A latex of chloroprene polymer A was obtained in the same manner as in Example 1 using the monomer mixture of chloroprene polymer A shown in Table 1. Subsequently, a latex of chloroprene polymer B was obtained in the same manner as in Example 1 using the monomer mixture of chloroprene polymer B shown in Table 3. Table 1 shows the Mooney viscosities of the polymers A and B measured in the same procedure as in Example 1.

  After mixing the latexes of the chloroprene polymers A and B obtained as described above so as to have a mixing amount of the chloroprene rubber composition shown in Table 1, chloroprene rubber compositions were obtained in the same manner as in Example 1. Table 1 shows the mechanical properties of the die swell and vulcanizate evaluated in the same manner as in Example 1. As a result, due to the large die swell, it was not possible to achieve both excellent extrudability and excellent vulcanizate mechanical properties.

  The chloroprene rubber composition obtained by the present invention can be used in applications requiring extrusion molding and requiring excellent mechanical properties of vulcanizates.

Claims (5)

A chloroprene rubber composition comprising the following chloroprene polymer A and the following chloroprene polymer B having an alkylpolythiocarbonate group at the molecular end of chloroprene.
A: A chloroprene polymer soluble in toluene and having a Mooney viscosity of 10 to 120.
B: a trifunctional monomer polymer having 2-chloro-1,3-butadiene and three ethylenically unsaturated bonds in the molecule, and having a Mooney viscosity of 150 or higher or a toluene-insoluble gel content of 70 A chloroprene copolymer of not less than wt%. The chloroprene rubber composition according to claim 1, wherein the chloroprene polymer B has a sulfur content in the range of 0.1 to 2.0% by weight. The weight mixing ratio of chloroprene polymer A and chloroprene polymer B is in the range of A: 30 to 95 parts by weight, B: 5 to 70 parts by weight (the total of A and B is 100 parts by weight) The chloroprene rubber composition according to claim 1 or 2. A vulcanized product of a chloroprene rubber composition comprising the chloroprene rubber composition according to any one of claims 1 to 3 and a compounding agent. By polymerizing a monomer mixture consisting of 50 to 100 parts by weight of 2-chloro-1,3-butadiene and 0 to 50 parts by weight of a comonomer copolymerizable therewith (100 parts by weight in total), chloroprene heavy A step of obtaining coalescence A, 47 to 99.5 parts by weight of 2-chloro-1,3-butadiene, 0.5 to 10 parts by weight of a trifunctional monomer having three ethylenically unsaturated bonds in the molecule, and A monomer mixture composed of 0 to 50 parts by weight of a comonomer copolymerizable therewith (the total of these being 100 parts by weight) is polymerized to a monomer conversion rate of 80% or more in the presence of a chain transfer agent, whereby chloroprene weight is increased. The chloroprene rubber assembly according to any one of claims 1 to 3, comprising a step of obtaining a coalescence B and a step of blending the chloroprene polymer A and the chloroprene copolymer B. Method of manufacturing a thing.