Neoprene latex composition

Abstract

The present invention provides a chlorobutadiene latex composition having good surface smoothness of a film formed by dip molding. The chlorobutadiene latex composition is a chlorobutadiene latex composition comprising a chlorobutadiene polymer and an emulsifier, wherein the emulsifier is a carboxylic acid alkali metal salt and a nonionic emulsifier having an HLB of 18.1 to 20.0, and contains, relative to 100 parts by weight of the chlorobutadiene polymer, 3.0 to 6.0 parts by weight of the carboxylic acid alkali metal salt and 0.15 to 0.9 parts by weight of the nonionic emulsifier.

Description

Technical Field

[0001] This invention relates to chloroprene latex compositions. Background Technology

[0002] In the application of gloves, allergies caused by proteins and other substances contained in the natural rubber latex used in the past have become a problem for medical staff and patients, and there is a push to replace them with synthetic rubber gloves (for example, see Patent Document 1).

[0003] Among them, chloroprene rubber has a good balance of mechanical strength, weather resistance, oil resistance, heat resistance, flame retardancy, and adhesion. Moreover, the softness, feel and other physical properties of the coating are close to those of natural rubber. Therefore, it is gradually replacing natural rubber gloves.

[0004] In the manufacture of rubber gloves, the so-called dip molding method is mostly used. This method is to form a rubber film by dipping a mold in a latex composition after the coagulated liquid is attached to the mold and dried. However, when the mold is lifted out of the latex composition after dipping, problems such as liquid dripping can damage the smoothness of the surface.

[0005] If the surface smoothness is compromised, it can lead to openings, cracks, and fractures in the film. Therefore, various improvement methods have been proposed (for example, see Patent Documents 2 and 3). However, the types of polymers used and the glass transition temperature are limited in these methods.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2017-214593

[0009] Patent Document 2: Japanese Patent Application Publication No. 2021-116389

[0010] Patent Document 3: Japanese Patent Application Publication No. 2016-055542

[0011] Content of the invention

[0012] The problem that the invention aims to solve

[0013] The present invention was made in view of this problem, and its object is to provide a chloroprene latex composition and rubber composition suitable for making immersion products such as gloves by improving the surface smoothness of the chloroprene latex composition for obtaining coated products by dip molding, thereby preventing pores and cracks and maintaining excellent tensile strength.

[0014] Problem Solving Methods

[0015] Against this backdrop, the inventors conducted in-depth research to solve the aforementioned problems and discovered that by using a chloroprene latex composition containing a carboxylic acid alkali metal salt and a nonionic emulsifier of HLB 18.1~20.0 as an emulsifier, the surface smoothness of its impregnated film can be improved.

[0016] That is, the various embodiments of the present invention are as follows [1] to [6].

[0017] [1] A chloroprene latex composition comprising a chloroprene polymer and an emulsifier, wherein,

[0018] The emulsifier is an alkali metal salt of carboxylic acid and a nonionic emulsifier of HLB 18.1~20.0. Relative to 100 parts by weight of chloroprene polymer, the chloroprene latex composition contains 3.0~6.0 parts by weight of alkali metal salt of carboxylic acid and 0.15~0.9 parts by weight of nonionic emulsifier.

[0019] [2] According to the chloroprene latex composition described in [1], wherein,

[0020] The above-mentioned nonionic emulsifier is a nonionic emulsifier represented by the following general formula (1).

[0021] RO(CH2CXHO) n H (1)

[0022] (In the formula, R represents a lipophilic group formed by an alkyl chain with 9 to 16 carbon atoms, X represents hydrogen or an alkyl chain with 1 to 2 carbon atoms, and n represents an integer that makes the HLB of the nonionic emulsifier range from 18.1 to 20.0.)

[0023] [3] The chloroprene latex composition according to [1] or [2] has a pH of 11.0 to 13.5.

[0024] [4] The chloroprene latex composition according to any one of [1] to [3] further comprises zinc oxide.

[0025] [5] A chloroprene latex composition for impregnation molding, comprising any one of the chloroprene latex compositions described in [1] to [4].

[0026] [6] A rubber composition comprising the chloroprene latex composition for impregnation molding described in [5].

[0027] The effects of the invention

[0028] The chloroprene latex composition of the present invention can improve the surface smoothness of impregnated films. Detailed Implementation

[0029] The present invention will now be described in detail.

[0030] One embodiment of the present invention comprises a chloroprene latex composition containing a chloroprene polymer, and as an emulsifier, comprises an alkali metal salt of a carboxylic acid and a nonionic emulsifier of HLB 18.1 to 20.0.

[0031] Chloroprene polymers can be polymers of 2-chloro-1,3-butadiene, i.e., chloroprene, or copolymers obtained by polymerizing chloroprene monomers and one or more monomers that can copolymerize with chloroprene.

[0032] Examples of monomers that can copolymerize 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, etc. Examples of monomers include substances obtained by using them at 20 parts by weight or less relative to 100 parts by weight of chloroprene monomer.

[0033] Emulsifiers containing alkali metal salts of carboxylic acids refer to emulsifiers containing both lipophilic and hydrophilic groups, with the hydrophilic group being a carboxylic acid. Examples of emulsifiers containing alkali metal salts of carboxylic acids include: alkali metal salts of rosin acid, alkali metal salts of fatty acids, alkali metal salts of alkenyl succinic acid, and polymers containing alkali metal salts of polycarboxylic acids. Examples of alkali metal salts include: lithium, sodium, potassium, and cesium. They may contain one or more of these. From the viewpoint of polymerization stability and adhesive properties, alkali metal salts of rosin acid are preferred, and potassium salts of rosin acid are more preferred. The content of this emulsifier is not particularly limited, but considering the balance between stability and adhesive properties when compounded with latex, it is 3.0 to 6.0 parts by weight relative to 100 parts by weight of the chloroprene polymer.

[0034] The chloroprene latex of the present invention contains a nonionic emulsifier with an HLB value of 18.1 to 20.0. HLB represents the balance between lipophilicity and hydrophilicity, and is obtained by dividing the molecular weight of the hydrophilic portion by the molecular weight of the emulsifier and then multiplying by 20. When the HLB value is below 18.0, the surface smoothness of the impregnated film of the obtained chloroprene latex composition is poor.

[0035] As a nonionic emulsifier, there are ester type, ether type, etc., without particular limitation, preferably ether type, more preferably a nonionic emulsifier of the ether type represented by the following general formula (1).

[0036] RO(CH2CXHO) n H (1)

[0037] (In the formula, R represents a lipophilic group formed by an alkyl chain with 9 to 16 carbon atoms, X represents hydrogen or an alkyl chain with 1 to 2 carbon atoms, and n represents an integer that makes the HLB of the nonionic emulsifier range from 18.1 to 20.0.)

[0038] Considering the balance between the surface smoothness and physical properties of the impregnated film, the amount of nonionic emulsifier relative to 100 parts by weight of chloroprene polymer is 0.15 parts by weight or more and 0.9 parts by weight or less, preferably 0.2 parts by weight or more and 0.7 parts by weight or less.

[0039] The pH of the chloroprene latex composition of the present invention is preferably 11.0 to 13.5. This improves impregnation and molding properties. Within this pH range, the liquid exhibits good stability, and the rubber does not precipitate during storage or use. For pH adjustment, common acids or bases can be used without particular limitation; typically, hydrochloric acid, sodium hydroxide, potassium hydroxide, etc., are added after dilution with water in a manner that prevents rubber precipitation.

[0040] The chloroprene latex composition of the present invention preferably contains zinc oxide. By including zinc oxide, the storage stability of the chloroprene latex composition is improved, and the mechanical properties of the rubber composition as an impregnating molding film are also improved. The amount of zinc oxide is not limited, but is preferably 1.0 part by weight or more and 10.0 parts by weight or less relative to 100 parts by weight of the chloroprene polymer.

[0041] Alternatively, fillers, reinforcing agents, antioxidants, plasticizers, lubricants, vulcanization accelerators, sulfur, etc., or a dispersion of these substances in water, can be added to the chloroprene latex composition for impregnation molding.

[0042] The chloroprene latex composition of the present invention can be synthesized using chloroprene monomers, or chloroprene monomers and monomers capable of copolymerizing with chloroprene, an emulsifier of an alkali metal salt having a carboxylic acid, and a nonionic emulsifier with an HLB of 18.1 to 20.0. The nonionic emulsifier with an HLB of 18.1 to 20.0 can be added during or after polymerization. Alternatively, two or more latexes can be mixed to prepare a chloroprene latex composition.

[0043] As a method for synthesizing chloroprene latex, for example, the following method can be used: in addition to the monomers and emulsifiers containing alkali metal salts of carboxylic acids mentioned above, polymerization initiators, chain transfer agents, other stabilizers, etc. are used to carry out polymerization at a given temperature, and polymerization terminators are added to stop polymerization at a given polymerization conversion rate.

[0044] As polymerization initiators, known free radical substances such as peroxides like potassium persulfate and ammonium persulfate, and inorganic or organic peroxides such as hydrogen peroxide and tert-butyl hydroperoxide can be used. Furthermore, these can be used alone or in combination with reducing substances such as thiosulfates, thiosulfites, dithionites, and organic amines in redox systems.

[0045] Examples of chain transfer agents include alkyl thiols, halogenated hydrocarbons, disulfide alkyl xanthates, and sulfur, among which n-dodecyl thiols are preferred from the perspective of unpleasant odor and operability.

[0046] There is no particular limitation on the polymerization temperature, but it is preferably in the range of 10~50℃.

[0047] There is no particular limitation on the termination time of polymerization, but from a productive point of view, it is preferable to continue polymerization until the monomer conversion rate is above 70%.

[0048] As a polymerization terminator, any commonly used terminator can be used without special limitations. For example, phenothiazine, 2,6-tert-butyl-4-methylphenol, hydroxylamine, etc. can be used.

[0049] The chloroprene latex composition of the present invention can be mixed with antioxidants, pigments for coloring, and other common fillers such as calcium carbonate as needed for dip molding applications. Rubber compositions containing the chloroprene latex composition for dip molding are suitable for use in rubber gloves.

[0050] Example

[0051] The present invention will now be specifically described through examples, but the present invention is not limited to these examples. pH and surface smoothness were measured by the following methods.

[0052] <ph>

[0053] The pH was measured using a pH meter (manufactured by Horiba Corporation).

[0054] <Surface Smoothness>

[0055] The ceramic mold was preheated at 70°C for 30 minutes, immersed in a coagulating liquid (25% calcium nitrate aqueous solution) for 10 seconds, dried at 70°C for 10 minutes, and then immersed in a chloroprene latex composition for 10 seconds. After being lifted out, it was air-dried at room temperature for more than 30 minutes, and the surface was observed with the naked eye.

[0056] ○: Smooth surface.

[0057] ×: Liquid dripping or unevenness on the surface.

[0058] Example 1

[0059] Chloroprene latex was prepared by polymerization at 40°C in a 10L autoclave equipped with a stirrer using 5 kg of chloroprene monomer and 0.07 parts by weight of n-dodecyl mercaptan, 4 parts by weight of potassium rosinate (trade name: RONDIS K-25, Arakawa Chemical Industry Co., Ltd.) (4.2 parts by weight relative to 100 parts by weight of chloroprene polymer), 0.3 parts by weight of the 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 dithionite, and 90 parts by weight of pure water. Polymerization was then carried out by continuously adding 0.35% by weight of potassium persulfate aqueous solution under a nitrogen atmosphere. The polymerization was stopped by adding 0.05 parts by weight of 2,6-tert-butyl-4-methylphenol as a polymerization terminator when the polymerization conversion reached 95%. Then, by removing unreacted monomers and water under reduced pressure, the solid content of the latex was adjusted to 50%, thus obtaining chloroprene latex A.

[0060] To 100 parts by weight of the synthesized chloroprene latex A, 0.5 parts by weight of a nonionic emulsifier A (polyoxyethylene decyl ether; product name NOIGEN XL-400D: manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) with an HLB of 18.4 was added, resulting in a chloroprene latex composition. The pH was 12.5. Surface smoothness was evaluated using this composition. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is good.

[0061]

[0062] Example 2

[0063] The amount of nonionic emulsifier A mixed in latex A was changed to 0.4 parts by weight relative to 100 parts by weight of chloroprene polymer. Otherwise, a chloroprene latex composition was obtained in the same manner as in Example 1, and its surface smoothness was evaluated. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is good.

[0064] Example 3

[0065] The amount of nonionic emulsifier A mixed in latex A was changed to 0.3 parts by weight relative to 100 parts by weight of chloroprene polymer. Otherwise, a chloroprene latex composition was obtained in the same manner as in Example 1, and its surface smoothness was evaluated. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is good.

[0066] Example 4

[0067] The monomers used were set as follows: 4.5 kg of chloroprene monomer and 0.5 kg of 2,3-dichloro-1,3-butadiene. Other additives were measured relative to a total of 100 parts by weight of the chloroprene monomer and 2,3-dichloro-1,3-butadiene. Chloroprene latex B was obtained in the same manner as in Example 1. Then, 0.5 parts by weight of nonionic emulsifier A relative to 100 parts by weight of the chloroprene copolymer were added to chloroprene latex B, resulting in a chloroprene latex composition similar to that in Example 1. The surface smoothness of this composition was evaluated. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is good.

[0068] Comparative Example 1

[0069] Nonionic emulsifier A was not used. Otherwise, a chloroprene latex composition was obtained in the same manner as in Example 1, and its surface smoothness was evaluated. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is poor.

[0070] Comparative Example 2

[0071] The amount of nonionic emulsifier A used was changed to 0.1 parts by weight relative to 100 parts by weight of the chloroprene polymer. Otherwise, a chloroprene latex composition was obtained in the same manner as in Example 1, and its surface smoothness was evaluated. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is poor.

[0072] Comparative Example 3

[0073] The amount of nonionic emulsifier A used was changed to 1.0 part by weight relative to 100 parts by weight of the chloroprene polymer. Otherwise, a chloroprene latex composition was obtained in the same manner as in Example 1, and its surface smoothness was evaluated. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is poor.

[0074] Comparative Example 4

[0075] Nonionic emulsifier B (NOIGEN XL-140: manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) was used instead of nonionic emulsifier A. Otherwise, a chloroprene latex composition was obtained in the same manner as in Example 1, and its surface smoothness was evaluated. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is poor.

[0076] Comparative Example 5

[0077] Nonionic emulsifier C (NOIGEN XL-80: manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) was used instead of nonionic emulsifier A. Otherwise, a chloroprene latex composition was obtained in the same manner as in Example 1, and its surface smoothness was evaluated. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is poor.

[0078] Comparative Example 6

[0079] Nonionic emulsifier D (NOIGEN TDS-100: manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) was used instead of nonionic emulsifier A. Otherwise, a chloroprene latex composition was obtained in the same manner as in Example 1, and its surface smoothness was evaluated. The results are shown in Table 1. According to the results in Table 1, the surface smoothness is poor.

[0080] Industrial applicability

[0081] The chloroprene latex composition of the present invention can be used for impregnation molding and is widely used in the field of rubber products.

[0082] The present invention has been described in detail with reference to specific embodiments. It will be obvious to those skilled in the art that various modifications and variations can be made without departing from the essence and scope of the present invention.

[0083] It should be noted that the entire contents of the specification, claims and abstract of Japanese Patent Application No. 2023-192746, filed on November 13, 2023, are incorporated herein by reference and are included as part of the disclosure of this invention.< / ph>

Claims

1. A chloroprene latex composition, comprising a chloroprene polymer and an emulsifier, wherein, The emulsifier is an alkali metal salt of carboxylic acid and a nonionic emulsifier of HLB 18.1~20.

0. Relative to 100 parts by weight of chloroprene polymer, the chloroprene latex composition contains 3.0~6.0 parts by weight of alkali metal salt of carboxylic acid and 0.15~0.9 parts by weight of nonionic emulsifier.

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(CH2CXHO) n H (1) In the formula, R represents a lipophilic group formed by an alkyl chain with 9 to 16 carbon atoms, X represents hydrogen or an alkyl chain with 1 to 2 carbon atoms, and n represents an integer in the range of 18.1 to 20.0 that makes the HLB of the nonionic emulsifier range from 18.1 to 20.

0.

3. The chloroprene latex composition according to claim 1, wherein the pH is 11.0~13.

5.

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

5. A chloroprene latex composition for impregnation molding, comprising the chloroprene latex composition of claim 1 or 2.

6. A rubber composition comprising the chloroprene latex composition for impregnation molding as described in claim 5.

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