JP2005187544A - Copolymer latex for use in dip molding, composition for use in dip molding, and dip-molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copolymer latex for use in dip molding, high in a degree of whiteness and excellent in touch feeling, tensile strength, elongation, and oil resistance and to provide a dip-molded product. <P>SOLUTION: The copolymer latex for use in dip molding is one obtained by polymerizing in an emulsion a monomer mixture comprising 50 to 80 wt.% 1,3-butadiene, 15 to 50 wt.% acrylonitrile, 0 to 10 wt.% ethylenically unsaturated carboxylic acid monomer, and 0 to 35 wt.% ethylenically unsaturated monomer copolymerizable therewith, wherein the concentration of 4-cyanocyclohexene remaining in the copolymer latex is not higher than 500 ppm based on the solid content of the copolymer latex. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a dip-molding copolymer latex, a dip-molding composition, and a dip-molded product. More specifically, the present invention relates to a dip-molding copolymer latex, a dip-molding composition, and a dip-molded product having high whiteness and excellent texture, tensile strength, elongation, and oil resistance.

In recent years, rubber gloves have been widely used in various fields such as medical treatment, food processing field and electronic component manufacturing field due to increasing interest in safety and health. One method for producing these rubber gloves is the dip molding method. As the dip molding method, anode coagulation dipping is performed in which a mold made of wood, glass, ceramics, metal or plastic is dipped in a coagulant solution in advance and then dipped in a natural rubber latex composition or a synthetic rubber latex composition. There are known methods such as the Teg adhesion dipping method in which a mold is dipped in a latex composition and then dipped in a coagulating liquid, and a molded product obtained by these dip molding methods is a dip molded product. In these dip-molded products, the influence on the texture, tensile strength, elongation, and oil resistance is largely due to factors of the latex composition and the coagulation liquid composition. Conventionally, latex used in the dip molding method is typically natural rubber latex or synthetic rubber latex of acrylonitrile butadiene rubber (NBR rubber) having resistance to organic solvents and oils and fats. Recently, the former natural rubber latex may cause an allergic reaction depending on the amount of protein contained in some users. Synthetic rubber latex (NBR rubber) that does not contain the latter protein has attracted attention, and its use amount is also large. It has become to.
NBR rubber gloves are required to have a high degree of whiteness, particularly when used in the medical / food field where cleanliness is required. However, if the whiteness of the copolymer latex, which is the raw material, is low, the product will be yellowish in the case of white non-colored gloves, and its commercial value will be impaired, and even in the case of colored gloves, color adjustment is difficult. It may become. For this reason, whiteness is required for the copolymer latex, but the examination is not sufficient and no drastic solution has been proposed yet. In addition, improvement in texture (softness when wearing gloves) is required as a basic physical property of gloves. For this purpose, for example, a method for defining the molecular weight of copolymer latex and the insoluble part of methyl ethyl ketone (JP-A-5-247266: Patent Document) 1, JP-A-6-182788: Patent Document 2) has been proposed, and JP-A 2003-165814 (Patent Document 3) has different glass transition temperatures by adjusting the composition of the copolymer. It has been proposed to use a latex composed of two copolymers.
However, texture and other characteristics tend to conflict with each other, and it has been very difficult to satisfy all the characteristic balances simultaneously. For example, when the amount of a conjugated diene compound such as butadiene having a low glass transition temperature is increased for the purpose of improving the texture, the texture is improved but the oil resistance and chemical resistance are poor.
JP-A-5-247266 JP-A-6-182788 JP 2003-165814 A

An object of the present invention is to provide a copolymer latex for dip molding in which the whiteness of a dip product is high and the texture, tensile strength, elongation and oil resistance are excellent.

As a result of intensive studies in view of the above-described circumstances, the present inventors limit 4-cyanocyclohexene, which is a reaction product of 1,3-butadiene and acrylonitrile, which is by-produced in the polymerization step, to a specific amount or less. As a result, it was found that a dip-molded copolymer latex having high whiteness of the dip product and excellent in texture, tensile strength, elongation and oil resistance was obtained, and the present invention was completed.

That is, the present invention relates to 1,3-butadiene 50 to 80% by weight, acrylonitrile 15 to 50% by weight, ethylenically unsaturated carboxylic acid monomer 0 to 10% by weight, and ethylenically unsaturated copolymerizable therewith. A copolymer latex obtained by emulsion polymerization of a monomer consisting of 0 to 35% by weight of a monomer, wherein 4-cyanocyclohexene remaining in the copolymer latex is a copolymer latex. Copolymer latex for dip molding characterized by being 500 ppm or less with respect to the solid content, a dip molding composition containing this dip molding latex, and a dip molded product obtained by dipping this dip molding composition Is to provide.

By using the dip molding latex of the present invention, a dip molded product having high whiteness and excellent texture, tensile strength, elongation and oil resistance can be obtained. Rubber gloves and the like widely used in various fields such as the parts manufacturing field can be obtained and are extremely useful.

The present invention is described in detail below.
The monomer composition of the copolymer latex in the present invention is 1,3-butadiene 50-80% by weight, acrylonitrile 15-50% by weight, ethylenically unsaturated carboxylic acid monomer 0-10% by weight, and these It is constituted by 0 to 35% by weight of an ethylenically unsaturated monomer copolymerizable with.

1,3-butadiene needs to be used in the range of 50 to 80% by weight in the total monomers. If the amount of 1,3-butadiene is less than 50% by weight, the latex polymer after drying does not exhibit properties as an NBR rubber, which is not preferable. When 1,3-butadiene exceeds 80% by weight, the oil resistance decreases. Preferably it is 55 to 75% by weight.

Acrylonitrile needs to be used in the range of 15 to 50% by weight in all monomers. If acrylonitrile is less than 15% by weight, the oil resistance decreases, and if it exceeds 50% by weight, the latex polymer after drying does not exhibit properties as an NBR rubber, which is not preferable. Preferably it is 25 to 45% by weight.

Examples of the ethylenically unsaturated carboxylic acid monomer used in the present invention include acrylic acid, methacrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid and the like. Can do. In particular, methacrylic acid is preferred.
The ethylenically unsaturated carboxylic acid-based monomer needs to be used in the range of 0 to 10% by weight in all monomers. If the ethylenically unsaturated carboxylic acid monomer exceeds 10% by weight, the viscosity of the copolymer latex becomes too high, and there is a high possibility that handling problems will occur in all applications.

  Examples of the ethylenically unsaturated monomer copolymerizable with these include 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, Aliphatic conjugated diene compounds such as substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, for example, vinyl cyanide compounds such as methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, such as styrene, α-methyl Aromatic vinyl compounds such as styrene, for example, unsaturated carboxylic acid alkyl such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate Ester compounds such as acrylamide, Ethylenically unsaturated carboxylic acid amide compounds such as rhoamide, N, N-dimethylacrylamide and N-methylolacrylamide, for example, carboxylic acid vinyl esters such as vinyl acetate, such as methylaminoethyl (meth) acrylate, dimethylaminoethyl ( Examples thereof include ethylenically unsaturated amine compounds such as (meth) acrylate and 2-vinylpyridine, and one or more of them can be used.

The amount of 4-cyanocyclohexene remaining in the copolymer latex of the present invention needs to be 500 ppm or less based on the solid content of the latex. If the residual amount of 4-cyanocyclohexene exceeds 500 ppm or more, the texture is inferior and the whiteness is remarkably lowered. Preferably it is 300 ppm or less, More preferably, it is 250 ppm or less.
The method for reducing the amount of residual 4-cyanocyclohexene can be appropriately adjusted depending on the monomer composition of the copolymer latex, the addition method thereof, the polymerization temperature, the polymerization time, and the like. Furthermore, it can be adjusted as appropriate depending on the conditions of steam distillation after the polymerization step, the conditions of reduced pressure treatment under heating, and the like.

Although there is no restriction | limiting in particular about the gel content of the copolymer latex in this invention, A preferable gel content is 20 to 80 weight% especially from a viewpoint, such as a balance of texture, tensile strength, elongation, and oil resistance.

The particle diameter of the copolymer latex is not particularly limited, but the preferable particle diameter of the copolymer latex is 0.2 μm or less. More preferably, it is 0.18 μm or less, and the most preferable particle diameter of the copolymer latex is 0.05 to 0.15 μm.

In emulsion polymerization of the copolymer latex of the present invention, a conventional emulsifier, polymerization initiator, reducing agent, chain transfer agent, redox catalyst, hydrocarbon solvent, electrolyte, polymerization accelerator, chelating agent, etc. are used. be able to.

Examples of emulsifiers that can be used in the production of the copolymer latex of the present invention include sulfate esters of higher alcohols, alkylbenzene sulfonates, alkyl diphenyl ether sulfonates, aliphatic sulfonates, aliphatic carboxylates, and nonionic surfactants. Nonionic surfactants such as anionic surfactants such as sulfuric acid ester salts of polyethylene or alkyl ester type, alkyl phenyl ether type, alkyl ether type of polyethylene glycol, and the like, and one or more of these should be used Can do. In particular, alkylbenzene sulfonate and alkyl diphenyl ether sulfonate are preferable.

As the polymerization initiator, water-soluble polymerization initiators such as potassium persulfate, sodium persulfate, ammonium persulfate, cumene hydroperoxide, benzoyl peroxide, t-butyl hydroperoxide, acetyl peroxide, diisopropylbenzene hydroperoxide, An oil-soluble polymerization initiator such as 1,1,3,3-tetramethylbutyl hydroperoxide can be appropriately used. In particular, water-soluble polymerization initiators such as potassium persulfate, sodium persulfate and ammonium persulfate and oil-soluble polymerization initiators of cumene hydroperoxide are preferred.

Specific examples of the reducing agent preferably used in the present invention include sulfite, bisulfite, pyrosulfite, nitrite, nithionate, thiosulfate, formaldehyde sulfonate, benzaldehyde sulfonate, Examples thereof include carboxylic acids such as L-ascorbic acid, tartaric acid and citric acid, further reducing sugars such as dextrose and saccharose, and amines such as dimethylaniline and triethanolamine. L-ascorbic acid is particularly preferable.

Examples of the chain transfer agent that can be used for the production of the copolymer latex of the present invention include alkyls such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan. Xanthogen compounds such as mercaptan, dimethylxanthogen disulfide, diisopropylxanthogen disulfide, terpinolene, thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide, 2,6-di-t-butyl-4 -Halogenation of phenolic compounds such as methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, dichloromethane, dibromomethane, carbon tetrabromide, etc. Hydrogenated compounds, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglyco A rate etc. are mentioned, These can be used 1 type or 2 or more types. In particular, n-octyl mercaptan and t-dodecyl mercaptan are preferable. The amount of these chain transfer agents is not particularly limited, but is usually 0 to 5 parts by weight with respect to 100 parts by weight of the monomer.

In the present invention, α-methylstyrene dimer can also be used as a chain transfer agent. α-Methylstyrene dimer includes 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-methyl-2-pentene and 1,1,3-trimethyl-3-phenyl as isomers. Although there is indane, the α-methylstyrene dimer used in the present invention has a content of 2,4-diphenyl-4-methyl-1-pentene of 60% by weight or more, particularly 80% by weight or more. preferable. Since α-methylstyrene dimer has a high boiling point and remains in the latex particles even after the production of the copolymer latex, the amount used is 100 parts by weight of the monomer due to environmental problems different from the object of the present invention. The amount is preferably less than 2 parts by weight.

In the polymerization, unsaturated hydrocarbons such as pentene, hexene, heptene, cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, and 1-methylcyclohexene may be used. In particular, cyclohexene, which has a moderately low boiling point and can be easily recovered and reused after the completion of polymerization by steam distillation or the like, is preferable from the viewpoint of environmental problems although it differs from the object of the present invention.

  Furthermore, anti-aging agents, preservatives, dispersants, thickeners and the like can be appropriately added to the copolymer latex as necessary.

As the polymerization method in the present invention, any one of single-stage polymerization, two-stage polymerization, multi-stage polymerization, seed polymerization, power feed polymerization and the like may be adopted. Further, the addition method of various components in the polymerization method of the present invention is not particularly limited, and any of a batch addition method, a divided addition method, and a continuous addition method can be employed.

  The copolymer latex in the present invention is used as a copolymer latex for dip molding. In order to obtain a dip-molded product, for example, a conventionally known dip-molding method such as a direct dipping method, an anode adhesion dipping method, or a teag dipping method is applied.

  Hereinafter, the anode adhesion dipping method will be briefly described. First, the mold is dipped in a coagulating liquid, and then pulled up and dried so that a coagulant is attached to the mold surface. The coagulation liquid is obtained by dissolving a calcium salt such as calcium chloride, calcium nitrate, or calcium acetate in water or a hydrophilic organic solvent such as alcohol or ketone. The calcium concentration in the coagulation liquid is usually 5 to 50% by weight, preferably 10 to 30% by weight. If necessary, the coagulation liquid may contain a surfactant such as nonionic or anionic surfactant, or a filler such as calcium carbonate, talc, or silica gel. Next, the mold to which the coagulant is attached is dipped in the copolymer latex composition for dip molding and pulled up. At this time, the coagulant and the copolymer latex react to form a rubbery film on the mold. The obtained film is washed with water, dried, and then peeled off from the mold to form a dip-molded product.

The latex composition for dip molding of the present invention includes, as necessary, rubber latex such as natural rubber latex and isoprene rubber latex, vulcanizing agents such as colloidal sulfur and thiuram disulfide, dialkyldithiocarbamate and xanthate. Vulcanization accelerator, vulcanization accelerator such as zinc white, lisage (PbO), red lead (Pb ₃ O ₄ ), magnesium oxide, filler such as phthalic anhydride, benzoic acid, salicylic acid, magnesium carbonate, styrenation You may mix | blend suitably coloring agents, such as anti-aging agents, such as phenol, imidazoles, and paraphenylenediamine, and fast yellow, phthalocyanine blue, and ultramarine blue.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded. In the examples, parts and percentages indicating percentages are based on weight unless otherwise specified. In addition, various physical properties in the examples were evaluated by the following methods.

The particle size number measured average particle size of the copolymer latex was measured by dynamic light scattering method. In the measurement, LPA-3000 / 3100 manufactured by Otsuka Electronics was used.

Measurement of the gel content of the copolymer latex The film is dried at room temperature for 24 hours to prepare a film of the copolymer latex. About 1 g of the film is weighed and placed in 400 cc of methyl ethyl ketone and expanded and dissolved for 48 hours. Thereafter, this was filtered through a 300-mesh wire mesh, the methyl ethyl ketone insoluble part captured by the wire mesh was dried and weighed, and the ratio of this weight to the initial film weight was calculated as a gel content in wt%.

Measurement of Residual 4-Cyanocyclohexene Content in Copolymer Latex 4-Cyanocyclohexene in the copolymer latex was measured by the following method using a gas chromatograph GC-14A manufactured by Shimadzu Corporation.
1 g of copolymer latex (solid content: 40 to 50% by weight) was weighed, dissolved in 25 ml of DMF (dimethylformamide), allowed to stand for 24 HR in a sealed container, and used as a measurement sample. Using a calibration curve prepared using a known concentration of 4-cyanocyclohexene, the amount of 4-cyanocyclohexene remaining (ppm) relative to the copolymer latex solid content was determined from the obtained gas chromatograph.

Each physical property of the dip-formed product was evaluated as follows, and the results are shown in Tables 1 and 2.
Evaluation of Whiteness of Dip Molded Product The whiteness of the dip molded product sample was determined with the naked eye as follows.
○: Yellow is not felt and white.
Δ: Slightly yellowish.
X: Obviously yellowish.
Evaluation of the texture of the dip-molded product The evaluation of the texture was performed by measuring the tensile stress when the glove-shaped dip-molded product reached a 300% elongation at a tensile rate of 300 mm / min. A smaller value indicates a better texture.
Evaluation of tensile strength of dip-molded product In tensile strength evaluation , a glove-shaped dip-formed product was pulled at a pulling speed of 300 mm / min, and the tensile strength immediately before breaking was measured.
Elongation Evaluation of Dip Molded Product For the evaluation of elongation, a glove-shaped dip molded product was pulled at a pulling speed of 300 mm / min, and the elongation immediately before breaking was measured.
Evaluation of oil resistance of dip-molded product The oil resistance evaluation was performed by immersing the obtained dip-molded product in kerosene for 24 HR, and then evaluating the degree of swelling obtained from the following formula. The smaller this value, the better the oil resistance.
Swelling degree (%) = A / B * 100
A: Film weight after immersion 24HR
B: The film weight evaluation before immersion was performed in the following three stages according to the degree of swelling.
○: Swelling degree = 125% or less Δ: Swelling degree = 125% to 175%
X: Swelling degree = 175% or more

Example 1
Preparation of copolymer latex 1 (example of the present invention)
In a pressure-resistant polymerization reactor, 140 parts of pure water in a nitrogen atmosphere, 2.0 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer shown in Table 1 and 0.5 part of t-dodecyl mercaptan, L-ascorbine After adding 1.0 part of acid and stirring sufficiently, 0.5 part of cumene hydroperoxide was charged and polymerization was started at 35 ° C. After the polymerization conversion reached 60%, 0.4 part of t-dodecyl mercaptan, 0.1 part of n-octyl mercaptan, 0.5 part of sodium dodecylbenzenesulfonate, 0.5 part of potassium persulfate, pure water 20 The reaction was continued by raising the reaction temperature to 45 ° C. 25 hours after the start of the polymerization, 0.05 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with a caustic potash aqueous solution, steam distillation was performed at 90 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Further, the pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 1 having the particle size, gel content, and residual 4-cyanocyclohexene amount shown in Table 1.

Example 2
Preparation of copolymer latex 2 (example of the present invention)
In a pressure-resistant polymerization reactor, 125 parts of pure water under a nitrogen atmosphere, 2.5 parts of sodium alkyldiphenyl ether disulfonate as an emulsifier, each monomer in the first stage shown in Table 1, and 0.7 part of t-dodecyl mercaptan After adding 1.0 part of cyclohexene and stirring sufficiently, 0.7 part of potassium persulfate was charged and polymerization was started at 40 ° C. After the polymerization conversion reached 65%, each monomer in the second stage shown in Table 1 and 0.4 part of t-dodecyl mercaptan, cumene hydroperoxide 0.7 part, L-ascorbic acid 1.2 part Then, 0.5 part of sodium dodecylbenzenesulfonate and 20 parts of pure water were added, the reaction temperature was raised to 50 ° C., and the reaction was further continued. 25 hours after the start of polymerization, 0.15 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with a caustic potash aqueous solution, steam distillation was performed at 90 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Further, the pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 2 having the particle size, gel content, and residual 4-cyanocyclohexene amount shown in Table 1.

Example 3
Preparation of copolymer latex 3 (example of the present invention)
In a pressure-resistant polymerization reactor, 120 parts of pure water in a nitrogen atmosphere, 1.5 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer in the first stage shown in Table 1, and α-methylstyrene dimer 0.1 Part, t-dodecyl mercaptan 0.4 part, L-ascorbic acid 0.2 part was added and sufficiently stirred, then potassium persulfate 0.2 part and cumene hydroperoxide 0.2 part were charged and polymerized at 40 ° C. Started. After the polymerization conversion reached 65%, each second-stage monomer shown in Table 1 and t-dodecyl mercaptan 0.2 part, n-octyl mercaptan 0.2 part, cyclohexene 1.0 part, cumene hydro 0.7 parts of peroxide, 1.2 parts of L-ascorbic acid, 1.5 parts of sodium dodecylbenzenesulfonate and 20 parts of pure water were added, the reaction temperature was raised to 50 ° C., and the reaction was further continued. 30 hours after the start of the polymerization, 0.1 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with a caustic potash aqueous solution, steam distillation was performed at 80 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Furthermore, pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 3 having the particle size, gel content, and residual 4-cyanocyclohexene amount shown in Table 1.

Example 4
Preparation of copolymer latex 4 (example of the present invention)
In a pressure-resistant polymerization reactor, in a nitrogen atmosphere, 130 parts of pure water, 1.8 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer in the first stage shown in Table 1, and α-methylstyrene dimer 0.1 Part, 0.4 part of t-dodecyl mercaptan and 1.0 part of L-ascorbic acid were added and stirred sufficiently, and then 0.8 part of cumene hydroperoxide was charged and polymerization was started at 25 ° C. After the polymerization conversion reached 65%, each second-stage monomer shown in Table 1 and t-dodecyl mercaptan 0.2 part, n-octyl mercaptan 0.20 part, cyclohexene 1.0 part, cumene hydro 0.5 parts of peroxide, 0.2 parts of L-ascorbic acid, 0.7 parts of sodium alkyldiphenyl ether disulfonate and 20 parts of pure water were charged, the reaction temperature was raised to 45 ° C., and the reaction was further continued. 30 hours after the start of polymerization, 0.2 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with a caustic potash aqueous solution, steam distillation was performed at 90 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Furthermore, pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 4 having the particle size, gel content, and residual 4-cyanocyclohexene amount shown in Table 1.

Example 5
Preparation of copolymer latex 5 (example of the present invention)
In a pressure-resistant polymerization reactor, in a nitrogen atmosphere, 130 parts of pure water, 1.8 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer in the first stage shown in Table 1, and α-methylstyrene dimer 0.1 Part, 0.4 part of t-dodecyl mercaptan and 1.0 part of L-ascorbic acid were added and stirred sufficiently, and then 0.8 part of cumene hydroperoxide was charged and polymerization was started at 25 ° C. After the polymerization conversion reached 65%, each second-stage monomer shown in Table 1 and t-dodecyl mercaptan 0.2 part, n-octyl mercaptan 0.2 part, cyclohexene 1.0 part, cumene hydro 0.5 parts of peroxide, 0.2 parts of L-ascorbic acid, 0.7 parts of sodium alkyldiphenyl ether disulfonate and 20 parts of pure water were charged, the reaction temperature was raised to 45 ° C., and the reaction was further continued. 30 hours after the start of polymerization, 0.2 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, the pH of the copolymer latex was adjusted to about 8 with an aqueous caustic potash solution, and 2.0 parts of a dispersion of styrenated phenol was added, followed by steam distillation at 90 ° C. for 12 hours. Other low boiling compounds were removed. Furthermore, pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 5 having the particle diameter, gel content, and residual 4-cyanocyclohexene amount shown in Table 1.

Example 6
Preparation of copolymer latex 6 (example of the present invention)
In a pressure-resistant polymerization reactor, 140 parts of pure water in a nitrogen atmosphere, 2.0 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer in the first stage shown in Table 1, and 0.5 part of t-dodecyl mercaptan After adding 1.0 part of L-ascorbic acid and stirring sufficiently, 0.8 part of cumene hydroperoxide was charged, and polymerization was started at 35 ° C. After the polymerization conversion reached 65%, each monomer in the second stage shown in Table 1 and 0.3 part of t-dodecyl mercaptan, 0.5 part of cumene hydroperoxide, 0.2 part of L-ascorbic acid Then, 0.5 part of sodium dodecylbenzenesulfonate and 20 parts of pure water were added, the reaction temperature was raised to 45 ° C., and the reaction was further continued. 25 hours after the start of polymerization, 0.2 part of sodium dimethyldithiocarbamate was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with a caustic potash aqueous solution, steam distillation was performed at 90 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Furthermore, pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 6 having the particle size, gel content, and residual 4-cyanocyclohexene amount shown in Table 1.

Example 7
Preparation of copolymer latex 7 (example of the present invention)
In a pressure-resistant polymerization reactor, 130 parts of pure water in a nitrogen atmosphere, 1.8 parts of sodium dodecylbenzenesulfonate as an emulsifier, 0.5 part of sodium alkyldiphenyl ether disulfonate, and each unit of the first stage shown in Table 1 And 0.6 parts of t-dodecyl mercaptan and 0.3 part of L-ascorbic acid were added and stirred sufficiently, and then 0.1 part of potassium persulfate and 0.3 part of cumene hydroperoxide were added and polymerized at 15 ° C. Started. After the polymerization conversion reached 65%, each of the second stage monomers shown in Table 1 and 0.3 part of t-dodecyl mercaptan, cumene hydroperoxide 0.3 part, L-ascorbic acid 0.3 part Then, 0.7 part of sodium dodecylbenzenesulfonate and 20 parts of pure water were charged, the reaction temperature was raised to 30 ° C., and the reaction was further continued. 25 hours after the start of polymerization, 0.15 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with a caustic potash aqueous solution, steam distillation was performed at 90 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Furthermore, pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 7 having the particle size, gel content, and residual 4-cyanocyclohexene amount shown in Table 1.

Comparative Example 8
Preparation of copolymer latex 8 (comparative example)
In a pressure-resistant polymerization reactor, 135 parts of pure water under a nitrogen atmosphere, 2.7 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer shown in Table 2 and 0.5 part of n-octyl mercaptan, L-ascorbine After adding 0.3 part of acid and sufficiently stirring, 0.15 part of potassium persulfate and 0.15 part of cumene hydroperoxide were charged, and polymerization was started at 40 ° C. After the polymerization conversion reached 60%, 0.4 part of n-octyl mercaptan, 0.1 part of potassium persulfate, 0.5 part of sodium dodecylbenzenesulfonate and 15 parts of pure water were charged, and the reaction temperature was 45 ° C. The reaction was continued further. 25 hours after the start of polymerization, 0.2 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with an aqueous caustic potash solution, steam distillation was performed at 70 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Furthermore, pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 8 having the particle size, gel content, and residual 4-cyanocyclohexene amount shown in Table 2.

Comparative Example 9
Preparation of copolymer latex 9 (comparative example)
In a pressure-resistant polymerization reactor, 140 parts of pure water in a nitrogen atmosphere, 2.0 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer in the first stage shown in Table 2, and 0.5 part of t-dodecyl mercaptan After adding 0.6 parts of L-ascorbic acid and stirring sufficiently, 0.65 part of potassium persulfate was charged and polymerization was started at 45 ° C. After the polymerization conversion reached 65%, each monomer in the second stage shown in Table 2 and 0.2 part of α-methylstyrene dimer, 0.4 part of t-dodecyl mercaptan, n-octyl mercaptan 0.1 Part, 0.1 part of potassium persulfate, 1.0 part of sodium alkyldiphenyl ether disulfonate and 20 parts of pure water were added, the reaction temperature was raised to 55 ° C., and the reaction was further continued. 25 hours after the start of polymerization, 0.08 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with a caustic potash aqueous solution, steam distillation was performed at 80 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Further, the pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 9 having the particle diameter, gel content, and residual 4-cyanocyclohexene amount shown in Table 2.

Comparative Example 10
Preparation of copolymer latex 10 (comparative example)
In a pressure-resistant polymerization reactor, 140 parts of pure water in a nitrogen atmosphere, 2.2 parts of sodium alkyldiphenyl ether disulfonate as an emulsifier, each monomer in the first stage shown in Table 2, and 0.5 part of t-dodecyl mercaptan After adding 0.3 part of L-ascorbic acid and stirring sufficiently, 0.15 part of potassium persulfate and 0.15 part of cumene hydroperoxide were charged, and polymerization was started at 40 ° C. After the polymerization conversion reached 60%, each monomer in the second stage shown in Table 2 and 0.3 part of t-dodecyl mercaptan, 0.1 part of potassium persulfate, 0.5 part of sodium dodecylbenzenesulfonate Then, 15 parts of pure water was charged, the reaction temperature was raised to 55 ° C., and the reaction was further continued. 25 hours after the start of the polymerization, 0.1 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with an aqueous caustic potash solution, steam distillation was performed at 70 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Further, the pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 10 having the particle size, gel content, and residual 4-cyanocyclohexene amount shown in Table 2.

Comparative Example 11
Preparation of copolymer latex 11 (comparative example)
In a pressure-resistant polymerization reactor, 135 parts of pure water under a nitrogen atmosphere, 2.2 parts of sodium alkyldiphenyl ether disulfonate as an emulsifier, each monomer in the first stage shown in Table 2, and 0.5 part of t-dodecyl mercaptan After adding 0.3 part of L-ascorbic acid and stirring sufficiently, 0.15 part of potassium persulfate and 0.15 part of cumene hydroperoxide were charged, and polymerization was started at 40 ° C. After the polymerization conversion reached 65%, each monomer in the second stage shown in Table 2 and 0.3 part of t-dodecyl mercaptan, 0.1 part of potassium persulfate, 0.5 part of sodium dodecylbenzenesulfonate Then, 15 parts of pure water was charged, the reaction temperature was raised to 55 ° C., and the reaction was further continued. 25 hours after the start of polymerization, 0.07 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with an aqueous caustic potash solution, steam distillation was performed at 70 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds. Furthermore, pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 11 having the particle size, gel content, and residual 4-cyanocyclohexene amount shown in Table 2.

Comparative Example 12
Preparation of copolymer latex 12 (comparative example)
In a pressure-resistant polymerization reactor, 140 parts of pure water in a nitrogen atmosphere, 2.0 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer shown in Table 1 and 0.5 part of t-dodecyl mercaptan, L-ascorbine After adding 1.0 part of acid and stirring sufficiently, 0.5 part of cumene hydroperoxide was charged and polymerization was started at 35 ° C. After the polymerization conversion reached 60%, 0.4 part of t-dodecyl mercaptan, 0.1 part of n-octyl mercaptan, 0.5 part of sodium dodecylbenzenesulfonate, 0.5 part of potassium persulfate, pure water 20 The reaction was continued by raising the reaction temperature to 45 ° C. 25 hours after the start of polymerization, 0.05 part of diethylhydroxylamine was added as a polymerization terminator to complete the polymerization. Next, after adjusting the pH of the copolymer latex to about 8 with a caustic potash aqueous solution, steam distillation was performed at 90 ° C. for 6 hours to remove unreacted monomers and other low-boiling compounds. Further, the pH was adjusted to about 9 with aqueous ammonia to obtain a copolymer latex 12 having the particle diameter, gel content, and residual 4-cyanocyclohexene amount shown in Table 2.

Preparation of latex composition for dip molding The following compounding agents were added to the copolymer latexes 1 to 12 obtained in Examples 1 to 7 and Comparative Examples 8 to 12 for dip molding. A composition was obtained.
<Dip molding latex composition>
Latex for dip molding (solid content) 100.0 parts Zinc oxide 1.5 parts Colloidal sulfur 1.0 parts Zinc di-n-butyldithiocarbamate 0.5 parts Titanium dioxide 1.5 parts (solid content concentration 33%)

Manufacture of dip-molded product Separately, a 15% strength aqueous solution of calcium nitrate was prepared as a coagulation solution, dipped in a glove mold pre-dried at 80 ° C for 2 seconds, pulled up, leveled and rotated And dried (80 ° C. × 2 minutes). Subsequently, the mold for gloves was immersed in the dip molding composition for 2 seconds, pulled up, and then leveled and dried under rotation (80 ° C. × 2 minutes). Next, the mold for gloves was immersed in warm water at 40 ° C. for 3 minutes, washed, and then heated at 120 ° C. for 20 minutes to obtain a solid film on the surface of the mold for gloves. Finally, the solid coating was removed from the glove mold to obtain a glove-shaped dip molding.

Tables 1 and 2 summarize the composition, particle size, gel content, 4-cyanocyclohexene content, whiteness, texture, tensile strength, elongation, and oil resistance evaluation results of each copolymer latex.

As described above, by using the dip molding latex of the present invention, a dip molded product having high whiteness and excellent texture, tensile strength, elongation, and oil resistance can be obtained. Rubber gloves and the like widely used in various fields such as the processing field and the electronic component manufacturing field can be obtained.

Claims (3)

1,3-butadiene 50 to 80% by weight, acrylonitrile 15 to 50% by weight, ethylenically unsaturated carboxylic acid monomer 0 to 10% by weight, and ethylenically unsaturated monomer 0 to copolymerizable therewith A copolymer latex obtained by emulsion polymerization of a monomer comprising 35% by weight, wherein the concentration of 4-cyanocyclohexene remaining in the copolymer latex is based on the solid content of the copolymer latex. A copolymer latex for dip molding characterized by being 500 ppm or less. A composition for dip molding comprising the latex for dip molding according to claim 1. A dip-molded product obtained by dip-molding the dip-molding composition according to claim 2.