Chloroprene latex composition

Abstract

To provide a chloroprene latex composition, a coating film of which has good surface smoothness during immersion molding.SOLUTION: A chloroprene latex composition contains a chloroprene polymer and an emulsifying agent. The emulsifying agent is composed of an alkali metal carboxylate and a nonionic emulsifying agent having a HLB of 18.1 to 20.0. The chloroprene latex composition contains 3.0 to 6.0 pts.wt. of the alkali metal carboxylate and 0.15 to 0.9 pt.wt. of the nonionic emulsifying agent relative to 100 pts.wt. of the chloroprene polymer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a chloroprene latex composition. [Background technology]

[0002] In glove applications, the proteins contained in the natural rubber latex that has been used conventionally have caused allergies among medical workers and patients, and so replacement with synthetic rubber gloves is underway (see, for example, Patent Document 1).

[0003] Among them, chloroprene rubber has a good balance of mechanical strength, weather resistance, oil resistance, heat resistance, flame retardancy, and adhesiveness, and furthermore, various physical properties such as the flexibility and feel of the coating are close to those of natural rubber, so it is being increasingly used as a replacement for natural rubber gloves.

[0004] In the manufacture of rubber gloves, a so-called dip molding method is often used in which a coagulating liquid is applied to a former, which is then dried, and then the former is immersed in a latex composition to form a rubber coating, thereby obtaining a product. However, when the immersed former is pulled out of the latex composition, there is a problem that the smoothness of the surface is impaired due to dripping or the like.

[0005] Since impairing the surface smoothness leads to holes, cracks, breaks, etc. in the coating, various methods for improving the surface smoothness have been proposed (see, for example, Patent Documents 2 and 3). However, these methods are limited in the types of polymers and glass transition points that can be used. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-214593 A [Patent Document 2] JP 2021-116389 A [Patent Document 3] JP 2016-055542 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a chloroprene latex composition and a rubber composition which are suitable for producing dipped products such as gloves by improving the surface smoothness of a dip-molded coating film obtained by dip molding of a chloroprene latex composition, thereby preventing holes and cracks and maintaining excellent mechanical properties such as breaking strength. [Means for solving the problem]

[0008] Under such a background, the present inventors have conducted intensive studies to solve the above-mentioned problems, and have found that the surface smoothness of the dip-molded coating can be improved by using a chloroprene latex composition containing an alkali metal carboxylate and a nonionic emulsifier having an HLB of 18.1 to 20.0 as an emulsifier.

[0009] That is, the respective aspects of the present invention are as follows [1] to [6].

[0010] [1] A chloroprene latex composition comprising a chloroprene polymer and an emulsifier, the emulsifier being an alkali metal carboxylate and a nonionic emulsifier having an HLB of 18.1 to 20.0, the chloroprene latex composition comprising 3.0 to 6.0 parts by weight of the alkali metal carboxylate and 0.15 to 0.9 parts by weight of the nonionic emulsifier per 100 parts by weight of the chloroprene polymer.

[0011] [2] The chloroprene latex composition according to [1], wherein the nonionic emulsifier is a nonionic emulsifier represented by the following general formula (1):

[0012] RO(CH 2 CXHO) n H (1) (In the formula, R represents a lipophilic group consisting of an alkyl chain having 9 to 16 carbon atoms, X represents hydrogen or an alkyl chain having 1 to 2 carbon atoms, and n represents an integer in the range that gives the nonionic emulsifier an HLB value of 18.1 to 20.0.) [3] The chloroprene latex composition according to [1] or [2], which has a pH of 11.0 to 13.5.

[0013] [4] The chloroprene latex composition according to any one of [1] to [3], further comprising zinc oxide. [5] A chloroprene latex composition for dip molding, comprising the chloroprene latex composition according to any one of [1] to [4].

[0014] [6] A rubber composition comprising the chloroprene latex composition for dip molding according to [5]. Effect of the Invention

[0015] The chloroprene latex composition of the present invention improves the surface smoothness of dip-cast coatings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described in detail below.

[0017] The chloroprene latex composition according to one embodiment of the present invention contains a chloroprene polymer and, as an emulsifier, an alkali metal salt of a carboxylic acid and a nonionic emulsifier having an HLB of 18.1 to 20.0.

[0018] The chloroprene polymer may be a polymer of chloroprene, which is 2-chloro-1,3-butadiene, or a copolymer obtained by polymerizing a chloroprene monomer and one or more types of monomers copolymerizable with chloroprene.

[0019] Examples of monomers copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, butadiene, isoprene, styrene, acrylonitrile, methyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, methyl methacrylate, and the like. Examples of monomers copolymerizable with chloroprene include those obtained by using these in an amount of, for example, 20 parts by weight or less per 100 parts by weight of chloroprene monomer.

[0020] The emulsifier having an alkali metal salt of a carboxylic acid has a lipophilic group and a hydrophilic group, and the hydrophilic group is an alkali metal salt of a carboxylic acid. Examples of the emulsifier having an alkali metal salt of a carboxylic acid include an alkali metal salt of a rosin acid, an alkali metal salt of a fatty acid, an alkali metal salt of an alkenyl succinic acid, and a polymer compound of an alkali metal salt of a polycarboxylic acid. Examples of the alkali metal salt include lithium, sodium, potassium, and cesium. These may be one type or may contain two or more types. From the viewpoint of polymerization stability and adhesive performance, an alkali metal salt of a rosin acid is preferred, and a potassium salt of a rosin acid is more preferred. The content of this emulsifier is not particularly limited, but is 3.0 to 6.0 parts by weight per 100 parts by weight of the chloroprene polymer from the viewpoint of the balance between stability in the blending of the latex and adhesive properties.

[0021] The chloroprene latex of the present invention contains a nonionic emulsifier having an HLB of 18.1 to 20.0. The HLB indicates the balance between lipophilicity and hydrophilicity, and is a value obtained by dividing the molecular weight of the hydrophilic part by the molecular weight of the emulsifier and multiplying the result by 20. If the HLB is 18.0 or less, the surface smoothness of the dip-molded coating of the obtained chloroprene latex composition is poor.

[0022] Nonionic emulsifiers include ester type and ether type, and are not particularly limited. However, ether type is preferred, and more preferred is an ether type nonionic emulsifier represented by the following general formula (1).

[0023] RO(CH 2 CXHO) n H (1) (In the formula, R represents a lipophilic group consisting of an alkyl chain having 9 to 16 carbon atoms, X represents hydrogen or an alkyl chain having 1 to 2 carbon atoms, and n represents an integer in the range that gives the nonionic emulsifier an HLB value of 18.1 to 20.0.) The amount of the nonionic emulsifier used is from 0.15 to 0.9 parts by weight, preferably from 0.2 to 0.7 parts by weight, per 100 parts by weight of the chloroprene polymer, in view of the balance between the surface smoothness and physical properties of the dip coating.

[0024] The pH of the chloroprene latex composition of the present invention is preferably 11.0 to 13.5. This improves the immersion moldability. Within this pH range, the liquid has good stability and does not precipitate rubber during storage or use. For pH adjustment, a general acid or alkali can be used, and although there is no particular limitation, hydrochloric acid, sodium hydroxide, potassium hydroxide, etc. are generally added after diluting with water to prevent rubber from precipitating.

[0025] The chloroprene latex composition of the present invention preferably contains zinc oxide. By containing zinc oxide, the storage stability of the chloroprene latex composition is improved, and the mechanical properties of the rubber composition, which is a dip-molded coating, are improved. The amount of zinc oxide used is not limited, but is preferably 1.0 part by weight or more and 10.0 parts by weight or less per 100 parts by weight of the chloroprene polymer.

[0026] If necessary, a filler, a reinforcing agent, an antioxidant, a plasticizer, a lubricant, a vulcanization accelerator, sulfur, or the like, or a dispersion thereof in water may be added to the chloroprene latex composition and dip molding may be performed. The chloroprene latex composition of the present invention can be synthesized using a chloroprene monomer or a monomer copolymerizable with a chloroprene monomer and chloroprene, an emulsifier having an alkali metal salt of a carboxylic acid, and a nonionic emulsifier having an HLB of 18.1 to 20.0, and the nonionic emulsifier having an HLB of 18.1 to 20.0 may be added during or after the polymerization. Also, two or more types of latexes can be mixed to form the chloroprene latex composition.

[0027] As a method for synthesizing the chloroprene latex, for example, polymerization is carried out at a predetermined temperature using the above-mentioned monomer, the emulsifier having an alkali metal salt of carboxylic acid, a polymerization initiator, a chain transfer agent, other stabilizers, etc., and a polymerization terminator is added at a predetermined polymerization conversion rate to terminate the polymerization.

[0028] As the polymerization initiator, known free radical substances can be used, for example, peroxides such as potassium persulfate and ammonium persulfate, hydrogen peroxide, inorganic or organic peroxides such as tertiary butyl hydroperoxide, etc. These can be used alone or in combination with reducing substances such as thiosulfates, thiosulfites, hydrosulfites, organic amines, etc. in a redox system.

[0029] Examples of the chain transfer agent include alkyl mercaptans, halogenated hydrocarbons, alkyl xanthogen disulfides, molecular weight regulators such as sulfur, and the like. Among these, n-dodecyl mercaptan is preferred from the standpoint of odor and workability.

[0030] The polymerization temperature is not particularly limited, but is preferably in the range of 10 to 50°C.

[0031] The time when the polymerization is to be completed is not particularly limited, but from the viewpoint of productivity, it is preferable to carry out the polymerization until the monomer conversion rate reaches 70% or more.

[0032] The polymerization terminator is not particularly limited as long as it is a commonly used terminator, and examples thereof include phenothiazine, 2,6-t-butyl-4-methylphenol, and hydroxylamine.

[0033] The chloroprene latex composition of the present invention is mixed with an antioxidant, a pigment for coloring, and other general fillers such as calcium carbonate, as necessary, and is used for dip molding. The rubber composition containing the chloroprene latex composition for dip molding is suitably used for rubber gloves. EXAMPLES

[0034] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The pH and surface smoothness were measured by the following methods.

[0035] <ph> The pH was measured using a pH meter (manufactured by Horiba, Ltd.).

[0036] <Surface smoothness> A ceramic former was preheated at 70°C for 30 minutes, immersed in a coagulating liquid (aqueous solution of 25% calcium nitrate) for 10 seconds, and then dried at 70°C for 10 minutes. The dried former was then immersed in a chloroprene latex composition for 10 seconds, and then pulled out and air-dried at room temperature for 30 minutes or more. The surface was then visually observed.

[0037] A: The surface is smooth.

[0038] ×: Dripping or uneven surface Example 1 5 kg of chloroprene monomer, 0.07 parts by weight of n-dodecyl mercaptan, 4 parts by weight of potassium rosinate (trade name: Longis K-25, Arakawa Chemical Industries Co., Ltd.) (4.2 parts by weight per 100 parts by weight of chloroprene polymer), 0.3 parts by weight of a condensate of sodium naphthalenesulfonate and formaldehyde (trade name: Demol N, Kao Corporation), 0.4 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 90 parts by weight of pure water were used to polymerize at 40°C in a 10 L autoclave equipped with a stirrer to produce a chloroprene latex. The polymerization was carried out under a nitrogen atmosphere by continuously dropping a 0.35% by weight aqueous solution of potassium persulfate, and at a polymerization conversion rate of 95%, 0.05 parts by weight of 2,6-tertiary butyl-4-methylphenol was added as a polymerization terminator to terminate the polymerization. Thereafter, the unreacted monomers and water were removed under reduced pressure to adjust the solid content of the latex to 50%. Thus, chloroprene latex A was obtained.

[0039] A nonionic emulsifier A (polyoxyethylene decyl ether; product name Noigen XL-400D: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) having an HLB of 18.4 was added to the synthesized chloroprene latex A in an amount of 0.5 parts by weight per 100 parts by weight of the chloroprene polymer to obtain a chloroprene latex composition. The pH was 12.5. The surface smoothness was evaluated using this. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good.

[0040] [Table 1]

[0041] Example 2 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the amount of nonionic emulsifier A mixed with latex A was changed to 0.4 parts by weight per 100 parts by weight of the chloroprene polymer, and the surface smoothness was evaluated using this composition. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good.

[0042] Example 3 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the amount of nonionic emulsifier A mixed with latex A was changed to 0.3 parts by weight per 100 parts by weight of the chloroprene polymer, and the surface smoothness was evaluated using this composition. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good.

[0043] Example 4 Chloroprene latex B was obtained in the same manner as in Example 1, except that the monomers used were 4.5 kg of chloroprene monomer and 0.5 kg of 2,3-dichloro-1,3-butadiene, and other additives were weighed based on a total of 100 parts by weight of the chloroprene monomer and 2,3-dichloro-1,3-butadiene. Then, 0.5 parts by weight of nonionic emulsifier A was added to chloroprene latex B based on 100 parts by weight of the chloroprene copolymer, and a chloroprene latex composition was obtained in the same manner as in Example 1, and the surface smoothness was evaluated using this. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good.

[0044] Comparative Example 1 A chloroprene latex composition was obtained in the same manner as in Example 1 except that the nonionic emulsifier A was not used, and the surface smoothness was evaluated using the obtained composition. The results are shown in Table 1. As shown in Table 1, the surface smoothness was poor.

[0045] Comparative Example 2 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the amount of nonionic emulsifier A used was changed to 0.1 parts by weight per 100 parts by weight of the chloroprene polymer, and the surface smoothness was evaluated using this composition. The results are shown in Table 1. As shown in Table 1, the surface smoothness was poor.

[0046] Comparative Example 3 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the amount of nonionic emulsifier A used was changed to 1.0 part by weight per 100 parts by weight of the chloroprene polymer, and the surface smoothness was evaluated using this composition. The results are shown in Table 1. As shown in Table 1, the surface smoothness was poor.

[0047] Comparative Example 4 A chloroprene latex composition was obtained in the same manner as in Example 1, except that nonionic emulsifier B (Noigen XL-140: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used instead of nonionic emulsifier A, and the surface smoothness was evaluated using the obtained composition. The results are shown in Table 1. As shown in Table 1, the surface smoothness was poor.

[0048] Comparative Example 5 A chloroprene latex composition was obtained in the same manner as in Example 1, except that nonionic emulsifier C (Noigen XL-80: manufactured by Daiichi Kogyo Seiyaku) was used instead of nonionic emulsifier A, and the surface smoothness was evaluated using the obtained composition. The results are shown in Table 1. As shown in Table 1, the surface smoothness was poor.

[0049] Comparative Example 6 A chloroprene latex composition was obtained in the same manner as in Example 1, except that nonionic emulsifier D (Noigen TDS-100: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used instead of nonionic emulsifier A, and the surface smoothness was evaluated using the obtained composition. The results are shown in Table 1. As shown in Table 1, the surface smoothness was poor. [Industrial Applicability]

[0050] The chloroprene latex composition of the present invention is used for dip-molded products and is widely used in the field of rubber products.< / ph>

Claims

1. The chloroprene latex composition contains a chloroprene polymer and an emulsifier, the emulsifier being an alkali metal carboxylate and a nonionic emulsifier having an HLB of 18.1 to 20.0, and the chloroprene latex composition contains 3.0 to 6.0 parts by weight of the alkali metal carboxylate and 0.15 to 0.9 parts by weight of the nonionic emulsifier per 100 parts by weight of the chloroprene polymer.

2. The chloroprene latex composition according to claim 1, wherein the nonionic emulsifier is a nonionic emulsifier represented by the following general formula (1): R-O(CH ２ CXHO) ｎ H (1) (In the formula, R represents a lipophilic group consisting of an alkyl chain having 9 to 16 carbon atoms, X represents hydrogen or an alkyl chain having 1 to 2 carbon atoms, and n represents an integer in the range that results in an HLB of the nonionic emulsifier of 18.1 to 20.0.)

3. 2. The chloroprene latex composition according to claim 1, having a pH of 11.0 to 13.

5.

4. The chloroprene latex composition of claim 1, further comprising zinc oxide.

5. A chloroprene latex composition for dip molding, comprising the chloroprene latex composition according to claim 1 or 2.

6. A rubber composition comprising the chloroprene latex composition for dip molding according to claim 5 .

Images