JP7207095B2 - Chloroprene-based polymer latex and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a chloroprene-based polymer latex used for vulcanized composition products such as gloves obtained by dip molding, and a method for producing the same. More specifically, the present invention relates to a chloroprene polymer latex capable of shortening the processing time of a vulcanized composition obtained by dip molding, and a method for producing the same.

Chloroprene-based polymer latex has a good balance of mechanical properties, mechanical strength, weather resistance, oil resistance, heat resistance, flame retardancy, and adhesiveness. Widely used as adhesives and surface treatment agents. In particular, natural rubber latex has been used for gloves obtained by dip molding, but synthetic rubber gloves have been recommended because the proteins contained in natural rubber cause allergies for medical staff and patients. (See Patent Document 1, for example). Among various types of synthetic rubber latex, chloroprene rubber has similar properties to natural rubber, such as flexibility and texture, so it is being replaced by natural rubber gloves. processing time and temperature are inferior. In general, in order to manufacture dip-molded products using synthetic rubber latex, a latex composition in which additives such as metal oxides, sulfur, vulcanization accelerators, fillers and antioxidants are dispersed in synthetic rubber latex. A rubber film is formed by immersing a mold to which a coagulant is attached, and the mold is heated together to dry and vulcanize. Here, it is necessary to set the optimum heating temperature and time for each synthetic rubber in order to obtain a molded product with excellent mechanical properties. The higher the temperature and the longer the drying and vulcanizing conditions, the higher the production cost and the lower the productivity. Compared to other synthetic rubber gloves (e.g. nitrile rubber), chloroprene rubber gloves tend to require a higher heating temperature in the vulcanization process and require a longer vulcanization time, resulting in poor productivity. (See Patent Documents 2 and 3, for example).

JP 2017-214593 A JP-A-11-61527 JP 2011-122141 A

The present invention has been made in view of the above problems, and its object is to provide a chloroprene-based polymer latex that can give a vulcanized rubber product by dip molding, and maintains mechanical properties such as breaking strength and is cured. An object of the present invention is to provide a chloroprene-based polymer latex capable of shortening the vulcanization time in the vulcanization step.

The present inventor has completed the present invention as a result of intensive studies to solve the above problems. That is, in the present invention, the composition of the copolymer is 80 to 99% by weight of a structure derived from 2-chloro-1,3-butadiene, and a structure derived from a monomer having the following compositions (A), (B), and (C) A chloroprene-based polymer latex characterized by containing 1 to 20% by weight of a chloroprene-based polymer.
(A): 2,3-dichloro-1,3-butadiene 90.0 to 95.0% by weight
(B): 2.5-5.0% by weight of 1,2-dichloro-1,3-butadiene
(C): 2.5 to 5.0% by weight of 1,3-dichloro-1,3-butadiene
The present invention will be described in detail below.

The chloroprene-based polymer contained in the chloroprene-based polymer latex of the present invention contains 80 to 99% by weight of a structure derived from 2-chloro-1,3-butadiene, the following (A), (B), Consists of 1 to 20% by weight of structures derived from monomers having the composition (C).
(A): 2,3-dichloro-1,3-butadiene 90.0 to 95.0% by weight
(B): 2.5-5.0% by weight of 1,2-dichloro-1,3-butadiene
(C): 2.5 to 5.0% by weight of 1,3-dichloro-1,3-butadiene
If the structure derived from 2-chloro-1,3-butadiene is less than 80% by weight, the properties of the chloroprene rubber will be impaired due to poor breaking strength, etc., and if it exceeds 99% by weight, the crystallization rate will increase and hardening will occur at a low temperature. This is not preferable because it makes it easier.

The monomer-derived structure having the compositions (A), (B), and (C) is preferably 1 to 20% by weight so long as the properties of the vulcanized rubber obtained by dip molding are not impaired.

The composition of components (A), (B) and (C) is as follows: component (A) 90.0 to 95.0% by weight; component (B) 2.5 to 5.0% by weight; 5 to 5.0% by weight. Preferably, component (A) is 92.0 to 95.0% by weight, component (B) is 2.5 to 4.0% by weight, and component (C) is 2.5 to 4.0% by weight.

When the composition of the monomer mixture of monomers having the composition of (A), (B), and (C) is less than 90% by weight or more than 95% by weight, the flexibility of the resulting vulcanized rubber is impaired, and the color tone of the dip-molded product is impaired.

If either component (B) or (C) is less than 2.5% by weight or more than 5% by weight, the flexibility is similarly impaired and the color tone of the dip-molded product is also impaired, which is undesirable.

The chloroprene-based polymer latex of the present invention preferably contains 20 to 90% by weight of 1% by weight toluene-insoluble matter in the chloroprene-based polymer. When the 1 wt% toluene insoluble content is 20 wt% or more, the polymer crosslink density in the latex particles is high, and the vulcanized rubber obtained by dip molding has a high crosslink density and excellent vulcanized physical properties such as breaking strength. When the amount is 90% by weight or less, the latex particles contain a large amount of components having a low polymer crosslink density, and the vulcanized rubber obtained by dip molding has a low modulus at low elongation, resulting in excellent flexibility. The method for producing the chloroprene-based polymer latex of the present invention is described below.

The chloroprene-based polymer latex of the present invention is produced by adding a chain transfer agent to a mixture of chloroprene and a monomer copolymerizable therewith and mixing and suspending an aqueous emulsifier solution to carry out a polymerization reaction.

The chloroprene-based polymer contained in the chloroprene-based polymer latex is 80 to 99% by weight of 2-chloro-1,3-butadiene, and 1 to 20% by weight of a monomer mixture having the following compositions (A), (B), and (C). It is obtained by copolymerizing %.
(A): 2,3-dichloro-1,3-butadiene 90.0 to 95.0% by weight
(B): 2.5-5.0% by weight of 1,2-dichloro-1,3-butadiene
(C): 2.5 to 5.0% by weight of 1,3-dichloro-1,3-butadiene
Other copolymerizable monomers such as 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, etc., and these may be used alone or in combination of two or more. Although the content of these monomers is not particularly limited, it is preferably 0 to 20% by weight so long as the properties of the vulcanized rubber obtained by dip molding are not impaired.

Chain transfer agents include, for example, alkylmercaptans, halogenated hydrocarbons, alkylxanthogen disulfides, alkylxanthogen polysulfides, and molecular weight modifiers such as sulfur. Disulfides are preferred. The amount of the chain transfer agent is not particularly limited as long as it is an amount used in general radical polymerization for adjusting the molecular weight. For the flexibility and good mechanical properties of the vulcanized rubber obtained by molding, it is preferably 0.01 to 1.0% by weight with respect to 100% by weight of the monomer mixture other than the chain transfer agent.

Examples of emulsifiers include anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers and amphoteric emulsifiers. Examples of anionic emulsifiers include higher fatty acid salts, alkenyl succinates, rosinates, sodium alkyl sulfates, sodium higher alcohol sulfates, alkylbenzene sulfonates, alkyldiphenyl ether disulfonates, sulfonates of higher fatty acid amides, Examples of nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene sorbitan fatty acid ester, and higher fatty acid alkanol. Examples of cationic emulsifiers include alkylamine salts, quaternary ammonium salts, and alkyl ether type quaternary ammonium salts. Examples of amphoteric emulsifiers include alkylbetaine, alkylsulfo Examples include betaine and alkylamine oxide. Any one or more of the emulsifiers listed above may be used singly or in combination.

The polymerization is desirably carried out at a temperature of 10 to 60° C. with mixing and stirring and by adding the catalyst solution at a pH of 7 to 13 in the polymerization system. As the pH adjuster, for example, one or more of basic compounds such as sodium hydroxide, potassium hydroxide, sodium phosphate, potassium phosphate, triethylamine, diethylamine, triethanolamine, diethanolamine, ethanolamine, and ammonia. Used alone or in combination.

As a catalyst (polymerization initiator) for initiating polymerization, for example, potassium persulfate, ammonium persulfate, hydrogen peroxide, t-butyl hydroperoxide and the like are used.

The polymerization is carried out until the polymerization conversion rate is about 40 to 99%, and then terminated by adding a small amount of a polymerization inhibitor.

Examples of polymerization inhibitors include thiodiphenylamine, 4-t-butylcatechol, 2,6-di-t-butyl-4-methylphenol, 2,2′-methylenebis(4-ethyl-6-t-butylphenol). , 4,4′-thiobis(3-methyl-6-t-butylphenol), 2,2′-methylenebis(4-methyl-6-t-butylphenol), hydroquinone, N,N-diethylhydroxylamine and the like. , one or more of these may be used singly or in combination.

In order to produce a vulcanized composition by dip molding using the chloroprene-based polymer latex of the present invention and to produce a rubber product, an ordinary dip molding technique can be used.

For example, the chloroprene-based polymer latex of the present invention may optionally contain an acid acceptor, a filler, a reinforcing agent, an anti-aging agent, a plasticizer, a lubricant, zinc oxide, a vulcanization accelerator, sulfur, etc., or they may be added to water. A latex composition is prepared by adding an emulsifier, a viscosity adjuster, and a pH adjuster as necessary to the dispersed liquid, and impregnating it with a coagulant such as calcium nitrate to produce the desired vulcanized rubber molding. Immerse the mold to form a rubber film on the mold. Further, there is a technique of immersing the rubber film together with the mold in water, washing away excess emulsifier and the like with water, heating the rubber film together with the mold in an oven or the like, and drying and vulcanizing the rubber film.

The latex composition contains 0.1 to 10 parts by weight of a metal oxide, 0.1 to 3 parts by weight of sulfur, and 0.1 to 0.1 parts by weight of a vulcanization accelerator with respect to 100 parts by weight of the chloroprene polymer component in the chloroprene polymer latex. It preferably contains 5 parts by weight. When the metal oxide content is 0.1 parts by weight or more, a sufficient vulcanization effect can be obtained, and when it is 10 parts by weight or less, a good vulcanization rate can be obtained. Similarly, when the sulfur content is 0.1 parts by weight or more, a sufficient vulcanization effect can be obtained, and when it is 3 parts by weight or less, a good vulcanization rate can be obtained. When the content of the vulcanization accelerator is 0.1 parts by weight or more, a sufficient vulcanization acceleration effect can be obtained, resulting in excellent physical properties such as breaking strength. When it is 5 parts by weight or less, a suitable vulcanization density can be obtained and physical properties such as elongation at break and flexibility are excellent.

Examples of metal oxides include zinc oxide, magnesium oxide, and calcium oxide. As the vulcanization accelerator, those generally used for vulcanization of chloroprene-based polymer latex can be used. thiourea accelerators such as diethylthiourea, trimethylthiourea and N,N'-diphenylthiourea; guanidine accelerators such as diphenylguanidine; thiazole accelerators such as 2-mercaptobenzothiazole and 2-mercaptobenzothiazole; and thiuram accelerators such as tetrabutyl thiuram disulfide. Any one or more of the vulcanization accelerators listed above may be used singly or in combination.

The chloroprene-based polymer latex of the present invention is a chloroprene-based polymer latex that can give a vulcanized rubber product by dip molding, and is intended to shorten the vulcanization time in the vulcanization process while maintaining mechanical properties such as breaking strength. can be done.

The present invention is specifically described by the following examples. However, the present invention is not limited to these.

<1 wt% toluene insoluble content>
The 1% by weight toluene insoluble content in the polymer is obtained by adding acetic acid to the chloroprene-based polymer latex to adjust the pH to 6.0, spreading it on a petri dish, freezing it, and freeze-drying it with a vacuum dryer. was dissolved in toluene at a concentration of , stirred for 20 hours, and filtered through a 200-mesh wire mesh.

<Normal physical properties>
The normal physical properties of the vulcanizate were measured by using a dumbbell-shaped C-type test piece according to ASTM D-412 from the obtained dip-molded product, tensile strength at break under the conditions of a tensile speed of 500 mm / min and 23 ° C. Elongation at break, 300% elongation stress (modulus) and 500% elongation stress were measured.

Example 1
Chloroprene monomer, a monomer mixture having the composition shown in Table 1 (2,3-dichloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 1,3-dichloro-1,3-butadiene ), n-dodecyl mercaptan, potassium rosinate, condensate of sodium naphthalenesulfonate and formaldehyde, sodium hydroxide, sodium hydrosulfite, and pure water in the proportions shown in Table 1 were charged in a 10 L autoclave equipped with a stirrer and heated at 40°C. Polymerization was carried out at Polymerization was carried out by continuously dropping a 0.35% by weight aqueous solution of potassium persulfate under a nitrogen atmosphere, and the polymerization conversion rate was 90%. 05% by weight was added to stop the polymerization. Thereafter, unreacted monomers were removed under reduced pressure to obtain the desired chloroprene-based polymer latex.

On the other hand, zinc oxide, sulfur, vulcanization accelerator DPTU (N,N'-diphenylthiourea), vulcanization accelerator DPG (1,3-diphenylguanidine), 100 parts by weight each, ammonium casein 3 parts by weight, naphthalene 3 parts by weight of formalin condensate of sodium sulfonate and 100 parts by weight of distilled water were mixed and stirred for one day in a ball mill to prepare a stable dispersion of each compounding agent.

Assuming that the solid content in the obtained chloroprene-based polymer latex is 100% by weight, zinc oxide is 5% by weight, sulfur is 1% by weight, vulcanization accelerator DPTU is 3% by weight, and vulcanization accelerator DPG is 2% by weight. A suspension of each compounding agent was added to a chloroprene-based polymer latex, and stirred for 24 hours to prepare a latex composition.

A flat plate mold was immersed in a 25% calcium nitrate aqueous solution and then dried, and then immersed in the chloroprene-based polymer latex composition to aggregate and form a rubber film on the flat plate. Next, the mold was immersed in warm water at 60°C to elute water-soluble impurities, and then dried and vulcanized (Table 3) by heating in a hot air dryer at 120°C for 25 minutes. The rubber was peeled off from the mold to obtain a vulcanized rubber sheet with a thickness of about 0.20 mm.

Next, the normal properties of the vulcanized rubber sheet obtained were measured. Vulcanizate properties are shown in Table 1. A vulcanized rubber excellent in strength and flexibility with high breaking strength and low modulus was obtained.

Examples 2-5
Polymerization was carried out in the same manner as in Example 1 with the compositions shown in Table 1 to obtain the intended chloroprene latex polymer. Next, a latex composition was prepared in the same manner as in Example 1 and dipped to obtain a vulcanized rubber sheet. Vulcanized rubber excellent in strength and flexibility with high breaking strength and low modulus was obtained.

Comparative example 1
Polymerization was carried out in the same manner as in Example 1 with the composition shown in Table 2 to obtain the target chloroprene latex polymer. Next, a latex composition was prepared in the same manner as in Example 1, dipped, and vulcanized under the conditions shown in Table 3 to obtain a vulcanized rubber sheet. Compared with Example 1, the vulcanization was insufficient and the breaking strength was inferior.

Comparative example 2
Polymerization was carried out in the same manner as in Example 1 with the composition shown in Table 2 to obtain the target chloroprene latex polymer. Next, a latex composition was prepared in the same manner as in Example 1, dipped, and vulcanized under the conditions shown in Table 3 to obtain a vulcanized rubber sheet. Vulcanization was sufficient as in Example 1, but the vulcanization time was lengthened.

Comparative example 3
Polymerization was carried out in the same manner as in Example 1 with the composition shown in Table 2 to obtain the target chloroprene latex polymer. Next, a latex composition was prepared in the same manner as in Example 1, dipped, and vulcanized under the conditions shown in Table 3 to obtain a vulcanized rubber sheet. Poor elongation at break.

Comparative example 4
Polymerization was carried out in the same manner as in Example 1 with the composition shown in Table 2 to obtain the target chloroprene latex polymer. Next, a latex composition was prepared in the same manner as in Example 1, dipped, and vulcanized under the conditions shown in Table 3 to obtain a vulcanized rubber sheet. Poor breaking strength.

The chloroprene-based polymer latex of the present invention can be easily dip-molded, and is used for applications requiring high breaking strength, excellent flexibility, and mechanical properties of the dip-vulcanized film, such as examination gloves and medical gloves. can be used as such, and the processing time can be shortened.

Claims (5)

The composition of the copolymer is 80 to 99% by weight of a structure derived from 2-chloro-1,3-butadiene, and 1 to 20% by weight of a structure derived from a monomer having the following composition (A), (B), and (C). A chloroprene-based polymer latex characterized by containing a chloroprene-based polymer.
(A): 2,3-dichloro-1,3-butadiene 90.0 to 95.0% by weight
(B): 2.5-5.0% by weight of 1,2-dichloro-1,3-butadiene
(C): 2.5 to 5.0% by weight of 1,3-dichloro-1,3-butadiene 2. The chloroprene-based polymer latex according to claim 1, wherein the 1% by weight toluene-insoluble content in the chloroprene-based polymer is 20 to 90% by weight. 2-chloro-1,3-butadiene and a monomer mixture comprising (A), (B) and (C) below are subjected to emulsion polymerization at a temperature of 10 to 50° C. or 2. The method for producing a chloroprene-based polymer latex according to 2.
(A): 2,3-dichloro-1,3-butadiene 90.0 to 95.0% by weight
(B): 2.5-5.0% by weight of 1,2-dichloro-1,3-butadiene
(C): 2.5 to 5.0% by weight of 1,3-dichloro-1,3-butadiene 0.1 to 10 parts by weight of metal oxide, 0.1 to 3 parts by weight of sulfur, and a vulcanization accelerator per 100 parts by weight of the chloroprene polymer component in the chloroprene polymer latex according to claim 1 or 2 A latex composition characterized by containing 0.1 to 5 parts by weight. A vulcanized composition obtained from the latex composition of claim 4.