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 polyoxyethylene derivative having surface tension of 39.0 to 55.0 mN / m at 25°C in a 0.1% aqueous solution, and the chloroprene latex composition contains 3.0 to 6.0 pts.wt. of the alkali metal carboxylate and 0.3 to 1.3 pts.wt. of the polyoxyethylene derivative 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, as an emulsifier, a chloroprene latex composition containing an alkali metal carboxylate and a polyoxyethylene derivative having a surface tension of 39 to 55 mN / m in a 0.1% aqueous solution at 25°C.

[0009] That is, the respective aspects of the present invention are as follows [1] to [6]. [1] A chloroprene latex composition comprising a chloroprene polymer and an emulsifier, the emulsifier being an alkali metal carboxylate and a polyoxyethylene derivative having a surface tension of 39.0-55.0 mN / m in a 0.1% aqueous solution at 25°C, the chloroprene latex composition comprising 3.0-6.0 parts by weight of the alkali metal carboxylate and 0.3-1.3 parts by weight of the polyoxyethylene derivative per 100 parts by weight of the chloroprene polymer. [2] The chloroprene latex composition according to [1], having a pH of 11.0 to 13.5. [3] The chloroprene latex composition according to [1] or [2], further comprising zinc oxide. [4] A chloroprene latex composition for dip molding, comprising the chloroprene latex composition according to any one of [1] to [3]. [5] A rubber composition comprising the chloroprene latex composition for dip molding according to [4].

Advantages of the Invention

[0010] The chloroprene latex composition of the present invention improves the surface smoothness of the dip-molded film.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail.

[0012] The chloroprene latex composition which is one embodiment of the present invention contains a chloroprene polymer, an alkali metal salt of a carboxylic acid as an emulsifier, and a polyoxyethylene derivative having a surface tension of 39 to 55 mN / m in a 0.1% aqueous solution at 25°C.

[0013] The chloroprene polymer may be a polymer of chloroprene which is 2-chloro-1,3-butadiene, or a copolymer polymerized using the monomer of chloroprene and one or more monomers copolymerizable with chloroprene.

[0014] Examples of the monomer 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, etc. Among them, those obtained by using these, for example, in an amount of 20 parts by weight or less based on 100 parts by weight of the chloroprene monomer can be mentioned.

[0015] 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.

[0016] The chloroprene latex of the present invention contains a polyoxyethylene derivative having a surface tension of 39.0 to 55.0 mN / m in a 0.1% aqueous solution at 25° C. The amount of the polyoxyethylene derivative used is not particularly limited, but is 0.3 to 1.3 parts by weight, preferably 0.3 to 1.0 parts by weight, based on 100 parts by weight of the chloroprene polymer, in view of the balance between the surface smoothness and physical properties of the dip coating.

[0017] 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.

[0018] 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.

[0019] 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 prepared by synthesizing the composition using a chloroprene monomer or a chloroprene monomer and a monomer copolymerizable with chloroprene, and an emulsifier having an alkali metal salt of a carboxylic acid, and mixing the composition with a polyoxyethylene derivative having a surface tension of 39 to 55 mN / m in a 0.1% aqueous solution at 25°C. The polyoxyethylene derivative may be added before or during polymerization. Two or more types of latexes may also be mixed to form a chloroprene latex composition.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The polymerization temperature is not particularly limited, but is preferably in the range of 10 to 50°C.

[0024] 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.

[0025] 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.

[0026] 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

[0027] 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.

[0028] <ph> It was measured with a pH meter (manufactured by Horiba, Ltd.).

[0029] <Surface tension> Pure water was added to the polyoxyethylene derivative and adjusted to 0.1% by weight, and the measurement was carried out by the Wilhelmy method.

[0030] <Surface smoothness> The ceramic former was preheated at 70 °C for 30 minutes, immersed in the coagulating solution (25% aqueous calcium nitrate solution) for 10 seconds, dried at 70 °C for 10 minutes, then the dried former was immersed in the chloroprene latex composition for 10 seconds, pulled out, and air-dried at room temperature for 30 minutes, and the surface was observed visually.

[0031] ○: The surface is smooth.

[0032] ×: There is liquid dripping or unevenness on the surface Example 1 5 kg of chloroprene monomer, 0.05 part by weight of n-dodecyl mercaptan, 4.5 parts by weight of potassium rosinate (trade name: Ronzis K-25, Arakawa Chemical Industries, Ltd.) (4.8 parts by weight based on 100 parts by weight of the chloroprene polymer), 0.3 part by weight of the condensate of sodium naphthalenesulfonate and formaldehyde (trade name: Demol N, Kao Corporation), 0.45 part by weight of sodium hydroxide, 0.01 part by weight of sodium hydrosulfite, and 90 parts by weight of pure water were used to carry out polymerization in a 10 L autoclave equipped with a stirrer at 40 °C to prepare a chloroprene latex. The polymerization was carried out by continuously dropping a 0.35% by weight aqueous solution of potassium persulfate under a nitrogen atmosphere. When the polymerization conversion rate reached 93%, 0.05 part by weight of 2,6-tert-butyl-4-methylphenol was added as a polymerization terminator to stop the polymerization. Then, the solid content of the latex was adjusted to 50% by removing unreacted monomers and moisture under reduced pressure to obtain chloroprene latex A.

[0033] To the synthesized chloroprene latex A, 0.5 parts by weight of polyoxyethylene derivative A (polyoxyethylene polyoxypropylene polymer: Epane 785: surface tension 46.8 mN / m: manufactured by Daiichi Kogyo Seiyaku) was added per 100 parts by weight of chloroprene polymer to obtain a chloroprene latex composition. The pH was 13.0. 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.

[0034] [Table 1]

[0035] Example 2 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the amount of polyoxyethylene derivative A mixed with latex A was changed to 0.4 parts by weight based on 100 parts by weight of the chloroprene polymer, and the surface smoothness was evaluated using this composition. The results are shown in Table 1. The results in Table 1 show that the surface smoothness was good.

[0036] Example 3 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the amount of polyoxyethylene derivative A mixed with latex A was changed to 1.0 part by weight based on 100 parts by weight of the chloroprene polymer, and the surface smoothness was evaluated using this composition. The results are shown in Table 1. The results in Table 1 show that the surface smoothness was good.

[0037] Example 4 Chloroprene latex B was obtained in the same manner as in Example 1, except that the monomers used were 4.75 kg of chloroprene monomer and 0.25 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 polyoxyethylene derivative A based on 100 parts by weight of the chloroprene copolymer was added to chloroprene latex B, 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.

[0038] Example 5 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the polyoxyethylene derivative mixed with latex A was changed to polyoxyethylene derivative B (polyoxyethylene polyoxypropylene polymer: Epane 485: surface tension 53.3 mN / m: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the surface smoothness was evaluated using this composition. The results are shown in Table 1. The results in Table 1 show that the surface smoothness was good.

[0039] Example 6 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the polyoxyethylene derivative mixed with latex A was changed to polyoxyethylene derivative C (polyoxyethylene polyoxypropylene polymer: Epane 750: surface tension 41.4 mN / m: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the surface smoothness was evaluated using the obtained composition. The results are shown in Table 1. The results in Table 1 show that the surface smoothness was good.

[0040] Example 7 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the polyoxyethylene derivative mixed with latex A was changed to polyoxyethylene derivative D (polyoxyethylene tridecyl ether: Noigen TDS-500F: surface tension 45.7 mN / m: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the surface smoothness was evaluated using the obtained composition. The results are shown in Table 1. The results in Table 1 show that the surface smoothness was good.

[0041] Example 8 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the polyoxyethylene derivative mixed with latex A was changed to polyoxyethylene derivative E (polyoxyethylene lauryl ether: Noigen NL-600F: surface tension 45.8 mN / m: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the surface smoothness was evaluated using this composition. The results are shown in Table 1. The results in Table 1 show that the surface smoothness was good.

[0042] Comparative Example 1 A chloroprene latex composition was obtained in the same manner as in Example 1 except that no polyoxyethylene derivative was used, and the surface smoothness was evaluated using this composition. The results are shown in Table 2. The results in Table 2 show that the surface smoothness was poor.

[0043] [Table 2]

[0044] Comparative Example 2 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the amount of polyoxyethylene derivative A used was changed to 0.2 parts by weight based on 100 parts by weight of the chloroprene polymer, and the surface smoothness was evaluated using this composition. The results are shown in Table 2. As shown in Table 2, the surface smoothness was poor.

[0045] Comparative Example 3 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the amount of polyoxyethylene derivative A used was changed to 1.5 parts by weight based on 100 parts by weight of the chloroprene polymer, and the surface smoothness was evaluated using this composition. The results are shown in Table 2. As shown in Table 2, the surface smoothness was poor.

[0046] Comparative Example 4 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the polyoxyethylene derivative mixed with latex A was changed to polyoxyethylene derivative F (polyoxyethylene polyoxypropylene polymer: Epane 720: surface tension 37.9 mN / m: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the surface smoothness was evaluated using the obtained composition. The results are shown in Table 2. The results in Table 2 show that the surface smoothness was poor.

[0047] Comparative Example 5 A chloroprene latex composition was obtained in the same manner as in Example 1, except that the polyoxyethylene derivative mixed with latex A was changed to polyoxyethylene derivative G (polyoxyethylene decyl ether: Noigen XL-100: surface tension 27.5 mN / m: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the surface smoothness was evaluated using the obtained composition. The results are shown in Table 2. As shown in Table 2, the surface smoothness was poor. [Industrial Applicability]

[0048] 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. A chloroprene latex composition comprising a chloroprene polymer and an emulsifier, the emulsifier being an alkali metal carboxylate and a polyoxyethylene derivative having a surface tension of 39.0 to 55.0 mN / m in a 0.1% aqueous solution at 25°C, the chloroprene latex composition comprising 3.0 to 6.0 parts by weight of the alkali metal carboxylate and 0.3 to 1.3 parts by weight of the polyoxyethylene derivative per 100 parts by weight of the chloroprene polymer.

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

5.

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

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

5. A rubber composition comprising the chloroprene latex composition for dip molding according to claim 4.

Images