Chloroprene latex composition

Abstract

In immersion molding, a chloroprene latex composition with good mechanical properties is provided by smoothing the surface of the film. [Solution] A chloroprene latex composition comprising a chloroprene polymer and an emulsifier is used, wherein, in the ¹H-MAS-NMR spectrum of a sample obtained by drying the latex, the ratio of the peak derived from 2,3-dichloro-1,3-butadiene to the peak derived from chloroprene, calculated using formula (I), is within the range shown by formula (II), where X is the ratio of the peak derived from 2,3-dichloro-1,3-butadiene to the peak derived from 2,3-dichloro-1,3-butadiene, and Y is the sodium content (ppm) of the latex, and the potassium content is 3000 ppm or less, and the toluene-insoluble portion is in the range of 89 to 95% by weight.

Description

[[Technical Field]]

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

[0002] In glove applications, allergies caused to medical workers and patients by proteins contained in conventionally used natural rubber latex have become a problem, and replacement with synthetic rubber gloves is underway (see, for example, Patent Document 1).

[0003] Among these, chloroprene rubber has a good balance of mechanical strength, weather resistance, oil resistance, heat resistance, flame retardancy, adhesiveness and the like, and further, various physical properties such as film flexibility and texture are close to those of natural rubber, so replacement of natural rubber gloves is being promoted.

[0004] In the production of rubber gloves, a so-called dip molding method is widely used, in which after a coagulating liquid is adhered to a former and dried, the former is immersed in a composition obtained by mixing a latex with a compound such as a vulcanization accelerator to form a rubber film and obtain a product. It has been known that the compounded vulcanization accelerator also causes allergies, and attempts have been made to produce gloves without using it. However, since unvulcanized rubber generally has inferior mechanical properties, it has been necessary to obtain good film properties without using a vulcanization accelerator.

[0005] Further, in a film obtained by dip molding, if there is thickness unevenness or flow marks (poor processability where dripping marks remain) on the film surface, there is a problem that the physical properties of the film decrease, and good surface smoothness has been required to improve the physical properties. [[Prior Art Literature]] [[Patent Literature]]

[0006] [[Patent Document 1]] Japanese Unexamined Patent Application Publication No. 2017-214593 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0007] The present invention has been made in view of the above problems, and its objective is to provide a chloroprene latex composition and a rubber composition suitable for producing immersion products such as gloves, which improve the surface smoothness of the coating and have excellent mechanical properties such as tensile strength without the use of vulcanization accelerators. [Means for solving the problem]

[0008] Under these circumstances, the inventors diligently investigated the problem and found that, in the ¹H-MAS-NMR spectrum of a sample obtained by drying latex, when the ratio of the peak derived from 2,3-dichloro-1,3-butadiene to the peak derived from chloroprene, calculated using the following formula (I), is X%, and the sodium content of the latex (ppm) is Y, the composition falls within the range shown by the following formula (II), and the potassium content is 3000 ppm or less, and the toluene-insoluble portion is in the range of 89-95% by weight, the surface smoothness of the immersion molded body is excellent and the tensile strength is good, even in a formulation without the use of a vulcanization accelerator.

[0009] In other words, the various embodiments of the present invention are as follows [1] to [6].

[0010] [1] A chloroprene latex composition comprising a chloroprene polymer and an emulsifier, wherein, in the ¹H-MAS-NMR spectrum of a sample obtained by drying the latex, the ratio of the peak derived from 2,3-dichloro-1,3-butadiene to the peak derived from chloroprene, calculated by the following formula (I), is within the range shown by the following formula (II), where X is the ratio of the peak derived from 2,3-dichloro-1,3-butadiene to the peak derived from chloroprene, and Y is the sodium content (ppm) of the latex, and the potassium content is 3000 ppm or less, and the toluene-insoluble portion is in the range of 89 to 95% by weight.

[0011] [Formula I] Formula for finding X when the areas of each peak in the 1H-MAS-NMR spectrum are (A) to (E). X(%)=(2A-B-8C+14D+9E)×100 / (2A+3B+6D+5E) (A): Peak area of ​​2.0-3.3 ppm (B): Peak area at 5.0-5.3 ppm (C): Peak area of ​​5.3-5.7 ppm (D): Peak area of ​​5.7-5.8 ppm (E): Peak area of ​​5.8-6.0 ppm [Equation II] Y ≥ -100X + 2550 (However, the ranges of X and Y are 7 ≤ X ≤ 20 and Y ≤ 3000.) [2] The chloroprene latex composition described in [1], wherein the pH is 11.0 to 13.5.

[0012] [3] The chloroprene latex composition according to [1] or [2], which does not contain a vulcanization accelerator. [4] A chloroprene latex composition according to any one of [1] to [3], further comprising zinc oxide.

[0013] A chloroprene latex composition for immersion molding, characterized by comprising the chloroprene latex composition described in any of [5] [1] to [4].

[0014] A rubber composition comprising the chloroprene latex composition for immersion molding described in [6] [5]. [Effects of the Invention]

[0015] The chloroprene latex composition of the present invention reduces the amount of precipitate in the compounding solution, and the immersion molded product produced using a formulation without a vulcanization accelerator has good mechanical properties. [Modes for carrying out the invention]

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

[0017] A 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 nonionic emulsifier.

[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 at least one monomer copolymerizable with chloroprene.

[0019] 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, and methyl methacrylate, and examples thereof include those obtained by using the above in an amount of 20 parts by weight or less based on 100 parts by weight of the chloroprene monomer.

[0020] An emulsifier having an alkali metal salt of a carboxylic acid has a lipophilic group and a hydrophilic group, wherein 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 alkali metal salts of rosin acid, alkali metal salts of fatty acids, alkali metal salts of alkenyl succinic acid, and high molecular compounds of alkali metal salts of polycarboxylic acids. Examples of the alkali metal salt include lithium, sodium, potassium, cesium and the like. These may be included alone or in combination of two or more. From the viewpoints of polymerization stability and adhesion performance, an alkali metal salt of rosin acid is preferred, and a potassium salt of rosin acid is more preferred. The content of this emulsifier is not particularly limited, but from the balance between stability in latex blending and adhesive physical properties, it is preferably 3.0 to 6.0 parts by weight based on 100 parts by weight of the chloroprene polymer.

[0021] For nonionic emulsifiers, the index of the balance between lipophilicity and hydrophilicity is indicated by HLB, which 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. When the HLB is 18.0 or less, the obtained chloroprene latex composition has inferior surface smoothness of the dip-molded film.

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

[0023] R-O(CH2CXHO) n nH (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 a range that makes the HLB of the nonionic emulsifier 18.1 to 20.0.) The content of the nonionic emulsifier is preferably 0.15 parts by weight or more and 0.9 parts by weight or less, more preferably 0.2 parts by weight or more and 0.7 parts by weight or less, relative to 100 parts by weight of the chloroprene polymer, in view of the balance between the surface smoothness and physical properties of the dipped film.

[0024] 1H-MAS-NMR spectroscopy is a common method for structural analysis of organic compounds. This method enables analysis of the microstructure of a polymer, and the molar ratio of each microstructure corresponds to the area of each peak in the 1H-MAS-NMR spectrum. The microstructure of a chloroprene polymer consists of 1,4-linkages, 1,2-linkages, and 3,4-linkages, and the microstructure of a 2,3-dichloro-1,3-butadiene polymer consists of 1,4-linkages and 1,2-linkages. In the 1H-MAS-NMR spectrum of a sample obtained by drying the chloroprene latex composition, the formula for calculating the ratio X% of peaks derived from 2,3-dichloro-1,3-butadiene among the total peaks derived from chloroprene and peaks derived from 2,3-dichloro-1,3-butadiene is represented by the following mathematical formula (I). [Mathematical Formula I] X(%)=(2A-B-8C+14D+9E)×100 / (2A+3B+6D+5E) (A): Peak area of ​​2.0-3.3 ppm (B): Peak area at 5.0-5.3 ppm (C): Peak area of ​​5.3-5.7 ppm (D): Peak area of ​​5.7-5.8 ppm (E): Peak area of ​​5.8-6.0 ppm The peak area of ​​2.0-3.3 ppm in (A) includes signals originating from the hydrogen of -CH2- in the 1,4-bond in chloroprene polymer, signals from the hydrogen of -CH- in the 3,4-bond, signals originating from the hydrogen of -CH2- in the 1,4-bond in 2,3-dichloro-1,3-butadiene polymer, and signals originating from one of the two hydrogens of -CH2- in the 1,2-bond.

[0025] The peak area of ​​5.0–5.3 ppm in (B) includes signals originating from one of the two hydrogen atoms of =CH2 in the 1,2-bond in the chloroprene polymer and signals originating from the hydrogen of =CH2 in the 3,4-bond.

[0026] The peak area of ​​5.3-5.7 ppm in (C) includes signals originating from the hydrogen of =CH- in the 1,4-bond in chloroprene polymer, signals originating from one of the two hydrogens of =CH2 in the 1,2-bond, and signals originating from one of the two hydrogens of =CH2 in the 1,2-bond in 2,3-dichloro-1,3-butadiene polymer.

[0027] The peak area of ​​5.7–5.8 ppm in (D) contains a signal originating from one of the two hydrogen atoms of the =CH2 group in the 1,2-bond in the 2,3-dichloro-1,3-butadiene polymer.

[0028] The peak area of ​​5.8–6.0 ppm in (E) contains signals originating from the hydrogen atoms of the -CH= group in the 1,2-bonds in the chloroprene polymer.

[0029] In other words, by performing CED, the 1,2-bonded components in the 2,3-dichloro-1,3-butadiene polymer contained in C are eliminated by D, and the 1,2-bonded components in the chloroprene polymer are eliminated by E, which is also derived from 1,2-bonds and present in the same amount. Therefore, the relative amount of 1,4-bonds in the chloroprene polymer can be represented.

[0030] Furthermore, E can represent the relative amount of 1,2-bonds in the chloroprene polymer.

[0031] Furthermore, by performing (BE) / 2, the 1,2-bonded components in the chloroprene polymer contained in B can be eliminated by E, which is also derived from 1,2-bonds and present in the same amount, thus representing the relative amount of 3,4-bonds in the chloroprene polymer.

[0032] Therefore, the relative amount of chloroprene polymer can be expressed as (B + 2C - 2D - E) / 2, which is the sum of the relative amounts of each microstructure.

[0033] Similarly, the relative amount of 1,4-bonds in 2,3-dichloro-1,3-butadiene polymer can be expressed by (A-(CED)×4-(BE) / 2-D) / 4.

[0034] Furthermore, D can represent the relative amount of 1,2-bonds in the 2,3-dichloro-1,3-butadiene polymer.

[0035] Therefore, the relative amount of 2,3-dichloro-1,3-butadiene polymer can be expressed as (2A-B-8C+14D+9E) / 8, which is the sum of the individual microstructures.

[0036] From the above, the proportion X% derived from 2,3-dichloro-1,3-butadiene in the sample obtained by drying the chloroprene latex composition is calculated by (relative amount of 2,3-dichloro-1,3-butadiene polymer) × 100 / (relative amount of chloroprene polymer and 2,3-dichloro-1,3-butadiene polymer), and is shown by formula (I).

[0037] Regarding the relationship between the 2,3-dichloro-1,3-butadiene content ratio in the chloroprene polymer and the sodium content in the chloroprene latex composition, in the ¹H-MAS-NMR spectrum of a sample obtained by drying the latex, if the ratio of the peak derived from 2,3-dichloro-1,3-butadiene to the peak derived from chloroprene calculated by formula (I) is X%, and the sodium content of the latex (ppm) is Y, then when X and Y are within the range shown by formula (II), and the potassium content is 3000 ppm or less, the immersion molded body exhibits a stable rate of film deposition, yielding a film with good surface smoothness. By adjusting the 2,3-dichloro-1,3-butadiene ratio, it is possible to obtain an immersion molded body with good tensile strength while maintaining elongation and modulus.

[0038] The toluene-insoluble portion of the chloroprene latex composition is in the range of 89 to 95% by weight. If it is less than 89% by weight, the tensile strength of the immersion-molded film is poor due to insufficient crosslinking of molecular chains, and if it is more than 95% by weight, the tensile properties are poor due to excessive crosslinking of molecular chains.

[0039] The pH of the chloroprene latex composition is preferably 11.0 to 13.5. This improves the immersion moldability. Within this pH range, the liquid has good stability, and rubber does not precipitate during storage or use. For pH adjustment, any common acid or alkali can be used, and there are no particular limitations, but it is common to add hydrochloric acid, sodium hydroxide, potassium hydroxide, etc., diluted with water to prevent rubber precipitation.

[0040] The chloroprene latex composition preferably contains zinc oxide. The inclusion of zinc oxide improves the storage stability of the chloroprene latex composition and also improves the mechanical properties of the rubber composition, which is a dipping-molded film. The amount of zinc oxide used is not limited, but it is preferably 1.0 part by weight to 10.0 parts by weight, and more preferably 2 to 7 parts by weight, per 100 parts by weight of chloroprene polymer.

[0041] Furthermore, if necessary, fillers, reinforcing agents, antioxidants, plasticizers, lubricants, vulcanization accelerators, sulfur, etc., or dispersions thereof in water, may be added to the chloroprene latex composition and then immersion molding may be performed. Chloroprene latex compositions can be synthesized using a monomer of chloroprene or a monomer copolymerizable with a monomer of chloroprene and chloroprene, an emulsifier having an alkali metal salt of 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 may be added during or after polymerization. Chloroprene latex compositions can also be obtained by mixing two or more types of latex.

[0042] For example, a method for synthesizing chloroprene latex involves using the monomers and emulsifiers containing alkali metal salts of carboxylic acids as described above, along with polymerization initiators, chain transfer agents, and other stabilizers, to carry out polymerization at a predetermined temperature, and then adding a polymerization termination agent at a predetermined polymerization conversion rate to stop the polymerization.

[0043] As polymerization initiators, known free radical substances, such as peroxides like potassium persulfate and ammonium persulfate, and inorganic or organic peroxides like hydrogen peroxide and tertiary butyl hydroperoxide, can be used. These may also be used alone or in combination with reducing substances, such as thiosulfates, thiosulfites, hydrosulfites, and organic amines, in a redox system.

[0044] Examples of chain transfer agents include alkyl mercaptans, halogenated hydrocarbons, alkyl xanthogen disulfides, sulfur, and other molecular weight modifiers. Of these, n-dodecyl mercaptan is preferred in terms of odor and workability.

[0045] The polymerization temperature is not particularly limited, but it is preferably in the range of 10 to 40°C, and more preferably in the range of 15 to 35°C.

[0046] While there is no particular limit to the time when polymerization is completed, from a productivity standpoint, it is preferable to carry out polymerization until the monomer conversion rate reaches 70% or more, and more preferably 85% or more.

[0047] The polymerization inhibitor is not particularly limited as long as it is a commonly used inhibitor; for example, phenothiazine, 2,6-t-butyl-4-methylphenol, hydroxylamine, etc., can be used.

[0048] Chloroprene latex compositions are mixed with anti-aging agents, pigments for coloring, and other common fillers such as calcium carbonate, as needed, and used for dipping molding. Rubber compositions containing chloroprene latex compositions for dipping molding are suitably used for rubber gloves. [Examples]

[0049] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. pH and surface smoothness were measured by the following method.

[0050] <1H-MAS-NMR measurement> As a pre-measurement preparation, 5g of chloroprene polymer latex is weighed onto a petri dish, air-dried in a fume hood for one day, and then dried under reduced pressure at 50°C for 2 hours. 2g of the dried sample is placed in a beaker containing 50mL of ethanol and left to stand for 48 hours. After that, the sample is removed, washed with ethanol, and then dried under reduced pressure at 50°C for 48 hours to complete the pre-measurement preparation. The prepared sample is punched out in a circular shape and packed into the sample tube to be used for measurement. For the spectrum after measurement, the peak top in the 2.0-3.3ppm region of the chloroprene polymer is set to 2.4ppm, and the peak area in the region (A)-(E) of equation (I) is analyzed.

[0051] <Measurement conditions for 1H-MAS-NMR measurement> ¹H-MAS-NMR was performed under the following measurement conditions.

[0052] ·Measurement frequency: 700MHz • Measured nuclide: 1H Pulse width: 3.0 μs • Total number of times: 1024 • Rotation frequency: 24kHz <Potassium and sodium content> The samples were wet-decomposed with sulfuric acid and nitric acid, and then quantified by ICP-AES.

[0053] <ph> The pH was measured using a pH meter (manufactured by Horiba, Ltd.).

[0054] <Toluene-insoluble portion> The amount of toluene-insoluble portion in the chloroprene polymer was calculated by adjusting the pH of the chloroprene polymer latex to 6.0 with acetic acid, freeze-drying it, washing it with water to remove water-soluble components such as emulsifiers, and then heat-drying the resulting polymer. The polymer was weighed, immersed in toluene with stirring for more than 20 hours to a concentration of 1%, filtered through a 200-mesh wire mesh, weighed the insoluble portion, and the ratio was calculated.

[0055] <Surface smoothness> A ceramic former was preheated at 70°C for 30 minutes, immersed in a coagulation solution (30% calcium nitrate aqueous solution) for 10 seconds, and then dried at 70°C for 10 minutes. After that, the dried former was immersed in a chloroprene latex composition for immersion molding for 20 seconds, removed, and air-dried at room temperature for at least 30 minutes, and the surface was visually inspected.

[0056] ○: The surface is smooth.

[0057] ×: Dripping or uneven surface <Dip molding> A ceramic former was preheated at 70°C for 30 minutes, immersed in a coagulation solution (30% calcium nitrate aqueous solution) for 10 seconds, and then dried at 70°C for 10 minutes. After that, the dried former was immersed in a chloroprene latex composition for immersion molding for 20 seconds, removed, air-dried at room temperature for 30 minutes or more, and then heated at 130°C for 40 minutes to produce a coating.

[0058] <Normal physical properties> The coating obtained by the immersion molding operation was peeled off the former to form a sheet, and a dumbbell-shaped C-type test specimen was prepared in accordance with ASTM D-412. The tensile strength at fracture was measured under conditions of a tensile speed of 500 mm / min and 23°C.

[0059] Example 1 Chloroprene latex was prepared by polymerizing 4.6 kg of chloroprene monomer and 0.4 kg of 2,3-dichloro-1,3-butadiene in a 10 L autoclave with a stirrer at 20°C using 100 parts by weight of the total of chloroprene monomer and 2,3-dichloro-1,3-butadiene, with 0.04 parts by weight of n-dodecyl mercaptan, 4 parts by weight of potassium rosinate (product name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.4 parts by weight of a condensate of sodium naphthalene sulfonate and formaldehyde (product name: Demol® N, Kao Corporation), 0.2 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 80 parts by weight of pure water. Polymerization was carried out by continuously adding a 0.35 wt% aqueous potassium persulfate solution dropwise under a nitrogen atmosphere. Polymerization was stopped at a polymerization conversion rate of 90% by adding 0.05 wt parts of 2,6-tert-butyl-4-methylphenol as a polymerization stopper. This was designated as latex A. Subsequently, 0.3 wt parts of sodium hydroxide, 1 wt part of potassium rosinate, 0.7 wt parts of a condensate of sodium naphthalene sulfonate and formaldehyde, and 0.5 wt parts of a nonionic emulsifier (polyoxyethylene decyl ether; product name Neugen XL-400D: manufactured by Daiichi Kogyo Seiyaku) were added, and the solid content of the latex was adjusted to 50 wt% by removing unreacted monomers and water under reduced pressure. The pH was 12.8, and the toluene-insoluble portion was 89 wt%. Furthermore, a zinc oxide emulsion (product name AZ-SW, manufactured by Osaki Industries Co., Ltd.) was mixed with 100 parts by weight of chloroprene polymer so that the zinc oxide content was 5 parts by weight on a pure content basis, thereby obtaining a chloroprene latex composition for immersion molding. Immersion molded bodies were prepared using this composition, and the surface smoothness and normal physical properties were evaluated. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good, and the normal physical properties were also good.

[0060] [Table 1]

[0061] Example 2 Chloroprene latex was prepared by polymerizing 4.4 kg of chloroprene monomer and 0.6 kg of 2,3-dichloro-1,3-butadiene in a 10 L autoclave with a stirrer at 25°C. To a total of 100 parts by weight of chloroprene monomer and 2,3-dichloro-1,3-butadiene, 0.04 parts by weight of n-dodecyl mercaptan, 5 parts by weight of potassium rosinate (trade name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.3 parts by weight of a copolymer of sodium styrenesulfonate and methacrylic acid, 0.5 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 80 parts by weight of pure water. Polymerization was carried out under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate dropwise. Polymerization was stopped at a polymerization conversion rate of 90% by adding 0.05 parts by weight of 2,6-tertiary butyl-4-methylphenol as a polymerization stopper. Subsequently, 0.4 parts by weight of a nonionic emulsifier (polyoxyethylene decyl ether; product name Neugen XL-400D: manufactured by Daiichi Kogyo Seiyaku) was added, and the solid content of the latex was adjusted to 50% by weight by removing unreacted monomers and water under reduced pressure. The pH was 12.8, and the toluene-insoluble portion was 89% by weight. In addition, zinc oxide emulsion (product name AZ-SW, manufactured by Osaki Kogyo Co., Ltd.) was mixed with 100 parts by weight of chloroprene polymer so that the zinc oxide content was 5 parts by weight on a pure content basis, to obtain a chloroprene latex composition for immersion molding. Immersion molded bodies were prepared using this composition, and the surface smoothness and normal physical properties were evaluated. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good, and the normal physical properties were also good.

[0062] Example 3 Surface smoothness and normal physical properties were evaluated in the same manner as in Example 2, except that n-dodecyl mercaptan was changed to 0.02 parts by weight. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good and the normal physical properties were also good.

[0063] Example 4 Chloroprene latex was prepared by polymerizing 4.1 kg of chloroprene monomer and 0.9 kg of 2,3-dichloro-1,3-butadiene in a 10 L autoclave with a stirrer at 25°C. To a total of 100 parts by weight of chloroprene monomer and 2,3-dichloro-1,3-butadiene, 0.04 parts by weight of n-dodecyl mercaptan, 5 parts by weight of potassium rosinate (trade name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.3 parts by weight of a copolymer of sodium styrenesulfonate and methacrylic acid, 0.5 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 80 parts by weight of pure water. Polymerization was carried out under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate dropwise. Polymerization was stopped at a polymerization conversion rate of 90% by adding 0.05 parts by weight of 2,6-tert-butyl-4-methylphenol as a polymerization stopper. Subsequently, 0.4 parts by weight of a nonionic emulsifier (polyoxyethylene decyl ether; product name Neugen XL-400D: manufactured by Daiichi Kogyo Seiyaku) was added, and the solid content of the latex was adjusted to 50% by weight by removing unreacted monomers and water under reduced pressure. The toluene-insoluble portion was 89% by weight. In addition, zinc oxide emulsion (product name AZ-SW, manufactured by Osaki Kogyo Co., Ltd.) was mixed with 100 parts by weight of chloroprene polymer so that the zinc oxide content was 5 parts by weight on a pure content basis, to obtain a chloroprene latex composition for immersion molding. Immersion molded bodies were prepared using this composition, and the surface smoothness and normal physical properties were evaluated. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good, and the normal physical properties were also good.

[0064] Example 5 Chloroprene latex was prepared by polymerizing 4.4 kg of chloroprene monomer and 0.6 kg of 2,3-dichloro-1,3-butadiene in a 10 L autoclave with a stirrer at 25°C with 100 parts by weight of the total of chloroprene monomer and 2,3-dichloro-1,3-butadiene, along with 0.04 parts by weight of n-dodecyl mercaptan, 4 parts by weight of potassium rosinate (product name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.4 parts by weight of a condensate of sodium naphthalene sulfonate and formaldehyde (product name: Demol® N, Kao Corporation), 0.2 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 80 parts by weight of pure water. Polymerization was carried out by continuously adding a 0.35 wt% aqueous potassium persulfate solution dropwise under a nitrogen atmosphere. Polymerization was stopped at a polymerization conversion rate of 90% by adding 0.05 wt parts of 2,6-tert-butyl-4-methylphenol as a polymerization stopper. Subsequently, 0.3 wt parts of sodium hydroxide, 1 wt part of potassium rosinate, 0.7 wt parts of a condensate of sodium naphthalene sulfonate and formaldehyde, and 0.4 wt parts of a nonionic emulsifier (polyoxyethylene decyl ether; product name Neugen XL-400D: manufactured by Daiichi Kogyo Seiyaku) were added, and the solid content of the latex was adjusted to 50 wt% by removing unreacted monomers and water under reduced pressure. The pH was 12.8, and the toluene-insoluble portion was 89 wt%. Furthermore, a zinc oxide emulsion (product name AZ-SW, manufactured by Osaki Industries Co., Ltd.) was mixed with 100 parts by weight of chloroprene polymer so that the zinc oxide content was 5 parts by weight on a pure content basis, thereby obtaining a chloroprene latex composition for immersion molding. Immersion molded bodies were prepared using this composition, and the surface smoothness and normal physical properties were evaluated. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good, and the normal physical properties were also good.

[0065] Example 6 Chloroprene latex was prepared by polymerizing 4.1 kg of chloroprene monomer and 0.9 kg of 2,3-dichloro-1,3-butadiene in a 10 L autoclave with a stirrer at 25°C with 100 parts by weight of the total of chloroprene monomer and 2,3-dichloro-1,3-butadiene, along with 0.04 parts by weight of n-dodecyl mercaptan, 4 parts by weight of potassium rosinate (product name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.4 parts by weight of a condensate of sodium naphthalene sulfonate and formaldehyde (product name: Demol® N, Kao Corporation), 0.2 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 80 parts by weight of pure water. Polymerization was carried out by continuously adding a 0.35 wt% aqueous potassium persulfate solution dropwise under a nitrogen atmosphere. Polymerization was stopped at a polymerization conversion rate of 90% by adding 0.05 wt parts of 2,6-tert-butyl-4-methylphenol as a polymerization stopper. Subsequently, 0.3 wt parts of sodium hydroxide, 1 wt part of potassium rosinate, 0.7 wt parts of a condensate of sodium naphthalene sulfonate and formaldehyde, and 0.4 wt parts of a nonionic emulsifier (polyoxyethylene decyl ether; product name Neugen XL-400D: manufactured by Daiichi Kogyo Seiyaku) were added, and the solid content of the latex was adjusted to 50 wt% by removing unreacted monomers and water under reduced pressure. The pH was 12.8, and the toluene-insoluble portion was 89 wt%. Furthermore, a zinc oxide emulsion (product name AZ-SW, manufactured by Osaki Industries Co., Ltd.) was mixed with 100 parts by weight of chloroprene polymer so that the zinc oxide content was 5 parts by weight on a pure content basis, thereby obtaining a chloroprene latex composition for immersion molding. Immersion molded bodies were prepared using this composition, and the surface smoothness and normal physical properties were evaluated. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good, and the normal physical properties were also good.

[0066] Example 7 Chloroprene latex was prepared by polymerizing 3.9 kg of chloroprene monomer and 1.1 kg of 2,3-dichloro-1,3-butadiene in a 10 L autoclave with a stirrer at 25°C with 100 parts by weight of the total of chloroprene monomer and 2,3-dichloro-1,3-butadiene, along with 0.04 parts by weight of n-dodecyl mercaptan, 4 parts by weight of potassium rosinate (product name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.4 parts by weight of a condensate of sodium naphthalene sulfonate and formaldehyde (product name: Demol® N, Kao Corporation), 0.2 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 80 parts by weight of pure water. Polymerization was carried out by continuously adding a 0.35 wt% aqueous potassium persulfate solution dropwise under a nitrogen atmosphere. Polymerization was stopped at a polymerization conversion rate of 90% by adding 0.05 wt parts of 2,6-tert-butyl-4-methylphenol as a polymerization stopper. Subsequently, 1 wt part of potassium rosinate, 0.7 wt parts of a condensate of sodium naphthalene sulfonate and formaldehyde, and 0.4 wt parts of a nonionic emulsifier (polyoxyethylene decyl ether; product name Neugen XL-400D: manufactured by Daiichi Kogyo Seiyaku) were added, and the solid content of the latex was adjusted to 50 wt% by removing unreacted monomers and water under reduced pressure. The toluene-insoluble portion was 89 wt%. In addition, zinc oxide emulsion (product name AZ-SW, manufactured by Osaki Kogyo Co., Ltd.) was mixed with 100 wt parts of chloroprene polymer so that the zinc oxide content was 5 wt parts on a pure basis to obtain a chloroprene latex composition for immersion molding. Using this, immersion-molded bodies were produced, and their surface smoothness and normal physical properties were evaluated. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good, and the normal physical properties were also good.

[0067] Example 8 Chloroprene latex was prepared by polymerizing 3.9 kg of chloroprene monomer and 1.1 kg of 2,3-dichloro-1,3-butadiene in a 10 L autoclave with a stirrer at 25°C. To a total of 100 parts by weight of chloroprene monomer and 2,3-dichloro-1,3-butadiene, 0.04 parts by weight of n-dodecyl mercaptan, 4 parts by weight of potassium rosinate (trade name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.3 parts by weight of a copolymer of sodium styrenesulfonate and methacrylic acid, 0.5 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 80 parts by weight of pure water. Polymerization was carried out under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate dropwise. Polymerization was stopped at a polymerization conversion rate of 90% by adding 0.05 parts by weight of 2,6-tert-butyl-4-methylphenol as a polymerization stopper. Subsequently, 0.4 parts by weight of a nonionic emulsifier (polyoxyethylene decyl ether; product name Neugen XL-400D: manufactured by Daiichi Kogyo Seiyaku) was added, and the solid content of the latex was adjusted to 50% by weight by removing unreacted monomers and water under reduced pressure. The toluene-insoluble portion was 89% by weight. In addition, zinc oxide emulsion (product name AZ-SW, manufactured by Osaki Kogyo Co., Ltd.) was mixed with 100 parts by weight of chloroprene polymer so that the zinc oxide content was 5 parts by weight on a pure content basis, to obtain a chloroprene latex composition for immersion molding. Immersion molded bodies were prepared using this composition, and the surface smoothness and normal physical properties were evaluated. The results are shown in Table 1. From the results in Table 1, the surface smoothness was good, and the normal physical properties were also good.

[0068] Comparative Example 1 Surface smoothness and normal physical properties were evaluated in the same manner as in Example 1, except that the amount of sodium hydroxide added to latex A as described in Example 1 was changed to 0 parts by weight. The results are shown in Table 2. From the results in Table 2, the surface smoothness was poor and the tensile strength of the film was low.

[0069] [Table 2]

[0070] Comparative Example 2 Surface smoothness and normal physical properties were evaluated in the same manner as in Example 1, except that the amount of sodium hydroxide added to latex A as described in Example 1 was changed to 0.1 parts by weight. The results are shown in Table 2. From the results in Table 2, the surface smoothness was poor and the tensile strength of the film was low.

[0071] Comparative Example 3 Surface smoothness and normal physical properties were evaluated in the same manner as in Example 1, except that the amount of sodium hydroxide added to latex A as described in Example 1 was changed to 0.2 parts by weight. The results are shown in Table 2. From the results in Table 2, the tensile strength of the film was good, but the surface smoothness was poor.

[0072] Comparative Example 4 Chloroprene latex was prepared by polymerizing 4.6 kg of chloroprene monomer and 0.4 kg of 2,3-dichloro-1,3-butadiene in a 10 L autoclave with a stirrer at 25°C. To a total of 100 parts by weight of chloroprene monomer and 2,3-dichloro-1,3-butadiene, 0.04 parts by weight of n-dodecyl mercaptan, 5 parts by weight of potassium rosinate (trade name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.3 parts by weight of a copolymer of sodium styrenesulfonate and methacrylic acid, 0.5 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 80 parts by weight of pure water. Polymerization was carried out under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate dropwise. Polymerization was stopped at a polymerization conversion rate of 90% by adding 0.05 parts by weight of 2,6-tert-butyl-4-methylphenol as a polymerization stopper. Subsequently, 0.4 parts by weight of a nonionic emulsifier (polyoxyethylene decyl ether; product name Neugen XL-400D: manufactured by Daiichi Kogyo Seiyaku) was added, and the solid content of the latex was adjusted to 50% by weight by removing unreacted monomers and water under reduced pressure. The toluene-insoluble portion was 89% by weight. In addition, zinc oxide emulsion (product name AZ-SW, manufactured by Osaki Kogyo Co., Ltd.) was mixed with 100 parts by weight of chloroprene polymer so that the zinc oxide content was 5 parts by weight on a pure content basis, to obtain a chloroprene latex composition for immersion molding. Immersion molded bodies were prepared using this composition, and the surface smoothness and normal physical properties were evaluated. The results are shown in Table 2. From the results in Table 2, the surface smoothness was good, but the normal physical properties were poor.

[0073] Comparative Example 5 Chloroprene latex was prepared by polymerizing 4.1 kg of chloroprene monomer and 0.9 kg of 2,3-dichloro-1,3-butadiene in a 10 L autoclave with a stirrer at 25°C with 100 parts by weight of the total of chloroprene monomer and 2,3-dichloro-1,3-butadiene, along with 0.04 parts by weight of n-dodecyl mercaptan, 4 parts by weight of potassium rosinate (product name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.4 parts by weight of a condensate of sodium naphthalene sulfonate and formaldehyde (product name: Demol® N, Kao Corporation), 0.2 parts by weight of sodium hydroxide, 0.01 parts by weight of sodium hydrosulfite, and 80 parts by weight of pure water. Polymerization was carried out by continuously adding a 0.35 wt% aqueous potassium persulfate solution dropwise under a nitrogen atmosphere. Polymerization was stopped at a polymerization conversion rate of 90% by adding 0.05 wt parts of 2,6-tert-butyl-4-methylphenol as a polymerization stopper. Subsequently, 1 wt part of potassium rosinate (trade name: Rondis® K-25, Arakawa Chemical Industries, Ltd.), 0.7 wt parts of a condensate of sodium naphthalene sulfonate and formaldehyde (trade name: Demol® N, Kao Corporation), and 0.4 wt parts of a nonionic emulsifier (polyoxyethylene decyl ether; product name: Neugen XL-400D, Daiichi Kogyo Seiyaku Co., Ltd.) were added, and the solid content of the latex was adjusted to 50 wt% by removing unreacted monomers and water under reduced pressure. The toluene-insoluble portion was 89 wt%. Furthermore, a zinc oxide emulsion (product name AZ-SW, manufactured by Osaki Industries Co., Ltd.) was mixed with 100 parts by weight of chloroprene polymer so that the zinc oxide content was 5 parts by weight on a pure content basis, thereby obtaining a chloroprene latex composition for immersion molding. Immersion molded bodies were prepared using this composition, and the surface smoothness and normal physical properties were evaluated. The results are shown in Table 2. From the results in Table 2, the normal physical properties were good, but the surface smoothness was poor.

[0074] Comparative Example 6 Surface smoothness and normal physical properties were evaluated in the same manner as in Example 1, except that n-dodecyl mercaptan was changed to 0.07 parts by weight. The results are shown in Table 2. From the results in Table 2, surface smoothness was good, but normal physical properties were poor. [Industrial applicability]

[0075] The chloroprene latex composition of the present invention is used in dipping molded products and is widely used in the rubber products field.< / ph>

Claims

1. A chloroprene latex composition comprising a chloroprene polymer and an emulsifier, wherein, in the 1H-MAS-NMR spectrum of a sample obtained by drying the latex, the ratio of the peak derived from 2,3-dichloro-1,3-butadiene to the peak derived from 2,3-dichloro-1,3-butadiene, calculated using the following formula (I), is X%, and the sodium content of the latex (ppm) is Y, such that X and Y are within the range shown by the following formula (II), the potassium content is 3000 ppm or less, and the toluene-insoluble portion is in the range of 89 to 95% by weight. [Formula I] Formula for finding X when the areas of each peak in the 1H-MAS-NMR spectrum are (A) to (E). X (%) = (2A-B-8C+14D+9E) x 100 / (2A+3B+6D+5E) (A): Peak area of ​​2.0–3.3 ppm (B): Peak area of ​​5.0–5.3 ppm (C): Peak area of ​​5.3–5.7 ppm (D): Peak area of ​​5.7–5.8 ppm (E): Peak area of ​​5.8–6.0 ppm [Equation II] Y ≥ -100X + 2550 (However, the ranges of X and Y are 7 ≤ X ≤ 20 and Y ≤ 3000.)

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

5.

3. The chloroprene latex composition according to claim 1, which does not contain a vulcanization accelerator.

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

5. A chloroprene latex composition for immersion molding, characterized by comprising the chloroprene latex composition described in any one of claims 1 to 4.

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

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