JP2009197149A - Copolymer latex for dip forming, composition for dip forming, and dip-formed product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copolymer latex for dip forming having high polymerization stability, to provide a composition for dip forming having high mechanical stability and salt solidifying property, and to provide a dip-formed product excellent in physical properties such as texture, tensile strength and elongation. <P>SOLUTION: The copolymer latex for dip forming is obtained by emulsion polymerization of monomers comprising 30 to 80 wt.% of 1,3-butadiene, 15 to 50 wt.% of acrylonitrile, 0.1 to 10 wt.% of ethylenically unsaturated carboxylic acid-based monomers and 0 to 54.9 wt.% of other ethylenically unsaturated monomers copolymerizable with the above monomers, and satisfies 0.05≤B/A≤0.5, wherein A (meq/g) represents an amount of acids bonded to particles and B (meq/g) represents an amount of acids not bonded to particles. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dip-forming copolymer latex, a dip-forming composition, and a dip-formed product. More specifically, the copolymer latex for dip molding having high polymerization stability, the dip molding composition having a good balance between mechanical stability and salt coagulation property with respect to the coagulation liquid, and physical properties such as texture, tensile strength and elongation. It relates to an excellent dip-molded product.

In recent years, rubber gloves have been widely used in various fields such as medical treatment (nosocomial infection, prevention of SARS infection, etc.), food processing field (O-157 problem) 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, an anode adhesion dipping method in which a mold made of wood, glass, ceramics, metal or plastic is previously immersed in a coagulant solution and then immersed in a natural rubber latex composition or a synthetic rubber latex composition. In addition, there is known a Tigue 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.
As typical dip molding latex, natural rubber latex or synthetic rubber latex such as acrylonitrile butadiene rubber (NBR rubber) is known. 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-copolymer latex) not containing the latter protein has attracted attention. The amount used is also increasing.
Further, with the increase in the amount of use, high productivity and high quality are being promoted for the dip-molding copolymer latex. For high productivity, a good machine to avoid agglomerates when using dip molding compositions and to reduce the occurrence of agglomerates that induce pinholes that are a significant defect in dip moldings. Stability and good salt coagulation with respect to the coagulating liquid are required. For quality improvement, physical properties at a high level such as texture, tensile strength and elongation of the dip-molded product obtained from the dip-molding composition are required.
For example, Japanese Patent Laid-Open No. 6-182788 (Patent Document 1) discloses that a dip-molded product having a uniform film thickness and a soft texture is obtained by adjusting the methylethylketone insoluble content and polystyrene equivalent weight average molecular weight of NBR latex. ing.
In the re-published patent international publication WO2002 / 036665 (Patent Document 2), a dip-molded product having few pinholes, good texture and sufficient strength by crosslinking with a water-soluble polyvalent metal salt. Is disclosed.
Furthermore, in Japanese Patent Application Laid-Open No. 7-60766 (Patent Document 3), a calcium salt / methanol solution having a calcium salt concentration of 65 to 90% and a thixotropy value of 0.6 to 2.0 is used as the coagulating liquid. Discloses a method of producing a rubber molded article having a relatively thick film thickness and good film thickness uniformity.
However, the performance required for the dip-molded product is further increased, and the conventional technology alone cannot meet the demand.
JP-A-6-182788 Republished Patent International Publication No. WO2002 / 036665 Japanese Patent Laid-Open No. 7-60766 JP 2007-126613 A

  The object of the present invention is to provide a copolymer latex for dip molding having high polymerization stability, a dip molding composition having good mechanical stability and salt coagulation properties, and a dip having excellent physical properties such as texture, tensile strength and elongation. It is to provide a molded article.

  As a result of intensive studies in view of the above-mentioned circumstances, the present inventors have a high polymerization stability in the copolymer latex for dip molding obtained as a specific ratio of the amount of particle-bound acid and the amount of particle-unbound acid, The resulting dip-molding composition has good mechanical stability and salt coagulation properties, and the dip-molded product obtained has an excellent balance of physical properties such as texture, tensile strength, and elongation. The invention has been completed.

  That is, the present invention relates to 1,3-butadiene 30 to 80% by weight, acrylonitrile 15 to 50% by weight, ethylenically unsaturated carboxylic acid monomer 0.1 to 10% by weight and other ethylene copolymerizable therewith. Copolymer latex obtained by emulsion polymerization of 100 parts by weight of a monomer (total) consisting of 0 to 54.9% by weight of the unsaturated monomer, wherein the amount of particle-bound acid is A (meq / g ), When the particle non-binding acid amount is B (meq / g), 0.05 ≦ B / A ≦ 0.5, a dip-forming copolymer latex, a dip-forming composition, The present invention also provides a dip-molded product obtained by dipping the dip-molding composition.

  According to the present invention, copolymer latex for dip molding having high polymerization stability, dip molding composition having good mechanical stability and salt coagulation property, and dip molding having excellent balance of physical properties such as texture, tensile strength and elongation. It is possible to obtain a product, and rubber gloves and the like widely used in various fields such as medical treatment, food processing field and electronic component manufacturing field can be obtained, which is extremely useful.

The present invention is described in detail below.
The monomer composition of the copolymer latex in the present invention is 30 to 80% by weight of 1,3-butadiene, 15 to 50% by weight of acrylonitrile, 0.1 to 10% by weight of ethylenically unsaturated carboxylic acid monomer, and Consists of 0 to 54.9% by weight of other ethylenically unsaturated monomers copolymerizable therewith.

  1,3-butadiene needs to be used in the range of 30 to 80% by weight in the total monomers. If the amount of 1,3-butadiene is less than 30% 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 50 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 20 to 45 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 0.1 to 10% by weight in all monomers. When the ethylenically unsaturated carboxylic acid monomer is less than 0.1% by weight, the mechanical stability of the dip molding composition is lowered, and when it exceeds 10% by weight, the viscosity of the copolymer latex becomes too high. This is not preferable because the possibility of handling problems increases in all applications.

  Examples of other ethylenically unsaturated monomers copolymerizable with the monomers used in the present invention include 2-methyl-1,3-butadiene and 2,3-dimethyl-1,3-butadiene. Aliphatic conjugated diene compounds such as 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, for example, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, and the like Vinyl chloride compounds such as aromatic vinyl compounds such as styrene and α-methylstyrene, such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, 2-hydroxyethyl methacrylate , Unsaturated carboxylic acid alkyl ester compounds such as glycidyl methacrylate, , Acrylamide, methacryloamide, N, N-dimethylacrylamide, N-methylolacrylamide and other ethylenically unsaturated carboxylic acid amide compounds, for example, carboxylic acid vinyl esters such as vinyl acetate, for example, methylaminoethyl (meth) acrylate And ethylenically unsaturated amine compounds such as dimethylaminoethyl (meth) acrylate and 2-vinylpyridine can be used, and one or more can be used. Other ethylenically unsaturated monomers capable of copolymerization need to be used in the range of 0 to 54.9% by weight in the total monomers. Preferably it is 0-29.9 weight%.

The copolymer latex obtained by the present invention has a particle bound acid amount of A (meq / g) and a particle non-bonded acid amount of B (meq / g), 0.05 ≦ B / A ≦ 0.5. It is necessary to be. If B / A is less than 0.05, the salt coagulation property with respect to the coagulating liquid is lowered, and it is difficult to obtain a dip-molded product having the desired thickness. If it exceeds 0.5, copolymer latex and dip-molding composition The mechanical stability of the product is lowered, and the tensile strength of the dip-formed product is lowered. Preferably 0.1 ≦ B / A ≦ 0.45, and more preferably 0.15 ≦ B / A ≦ 0.4.
In the present invention, the carboxylic acid bonded to the copolymer latex particles is a particle-bound acid, and the carboxylic acid not bonded to the copolymer latex particles is a particle-unbound acid. Is measured by the titration method described in the following Examples.
The above B / A values are the polymerization temperature at the time of copolymerization, the polymerization rate, the amount and timing of addition of each monomer (especially ethylenically unsaturated carboxylic acid monomer), and the carboxylic acid weight. Adjustment is possible by adding a coalescence (eg, sodium polyacrylate, ammonium polyacrylate, etc.).

The number average particle size of the copolymer latex in the present invention is not particularly limited, but is preferably 200 nm or less, more preferably 180 nm or less, and the most preferable number average particle size of the copolymer latex is 50 to 150 nm. It is.
The gel content of the copolymer latex in the present invention is not particularly limited, but is preferably 90% by weight or less, more preferably 85% by weight or less.

  In the emulsion polymerization of the copolymer latex of the present invention, conventional emulsifiers, polymerization initiators, reducing agents, chain transfer agents, redox catalysts, electrolytes, polymerization accelerators, chelating agents, and the like can be used.

  Examples of emulsifiers that can be used in the production of the copolymer latex of the present invention include higher alcohol sulfates, alkylbenzene sulfonates, alkyl diphenyl ether disulfonates, 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 disulfonate 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, it is preferable to use a water-soluble polymerization initiator of potassium persulfate, sodium persulfate, or ammonium persulfate.

  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 saccharides such as dextrose and saccharose, and amines such as dimethylaniline, ethylenediaminetetraacetate and triethanolamine.

  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 to make the coagulant adhere 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, and 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, a rubber latex such as natural rubber latex and isoprene rubber latex, a pH adjuster such as potassium hydroxide, sodium hydroxide, and aqueous ammonia, colloidal sulfur, and thiuram disulfide. Vulcanization accelerators such as dialkyldithiocarbamate and xanthate, vulcanization accelerators such as zinc white, lisage (PbO), red lead (Pb3O4), magnesium oxide, phthalic anhydride, benzoic acid A filler such as acid, salicylic acid, and magnesium carbonate, an anti-aging agent such as styrenated phenol, imidazole, and paraphenylenediamine, and a colorant such as first yellow, phthalocyanine blue, and ultramarine blue may be appropriately blended.

[Example]
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 number average number average particle size particle size measurement of the copolymer latex was measured by dynamic light scattering method. In the measurement, FPAR-1000 manufactured by Otsuka Electronics Co., Ltd. was used.

Measurement of gel content of copolymer latex Drying is carried out in a room temperature atmosphere for 24 hours to prepare a film of 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 bound acid amount and unbound acid amount of copolymer latex 50 g of 0.1N sodium hydroxide aqueous solution and 3 g of carbon tetrachloride were added to copolymer latex diluted to 5% by weight and stirred for 1 hour. Thereafter, the latex particles were centrifugally settled by a centrifugal separator to separate the supernatant layer and the latex particle layer. Each of the obtained two layers was diluted with pure water, and an excess amount of 0.1N hydrochloric acid was added, followed by back titration with a 0.1N aqueous sodium hydroxide solution. (A (meq / g)) and the amount of unbound acid (B (meq / g)) were determined as milliequivalent (meq) per gram of latex solids.

Measurement of polymerization stability of copolymer latex The polymerization stability in the copolymer latex was evaluated by the following method.
The latex after completion of the polymerization is filtered through a 300-mesh wire mesh, and the aggregates captured by the wire mesh are weighed. The results are shown in Tables 1 and 2.
○: Captured aggregate is 0.05 g or less / latex 100 g
Δ: Captured aggregate exceeds 0.05 g, 0.10 g or less / latex 100 g
X: Captured aggregate exceeds 0.10 g / latex 100 g

Measurement of mechanical stability of dip-forming composition The mechanical stability of the dip-forming composition was evaluated by the following method. Using a Maron mechanical stability tester manufactured by Kumagai Riki Kogyo Co., Ltd., 50 g (solid content concentration: 33%) of a dip-molding composition filtered in advance with 300 mesh, a rotor rotation speed of 1000 rpm, a rotor load of 30 kg, and a rotation time After applying mechanical shear for 15 minutes, the sample was filtered through 300 mesh. After the captured solidified product was washed with water and dried, the ratio of the solidified product to the original solid content was determined by weight%. The results are shown in Tables 1 and 2.
◯: The ratio of the generated coagulum is 0.01% by weight or less. Δ: The ratio of the generated coagulum exceeds 0.01% by weight and is 0.05% or less. Exceed

Each physical property of the dip-formed product was evaluated as follows, and the results are shown in Tables 1 and 2.
Measurement of thickness of dip-molded product The thickness of four points was measured from the palm portion of the dip-molded product (gloves) and averaged. The thin glove thickness indicates that the salt coagulation property with respect to the coagulating liquid is low, it is difficult to obtain a desired thickness, and defects such as thickness unevenness are likely to occur.
Evaluation of the texture of the dip molded article The evaluation of the texture was performed by pulling a glove-shaped dip molded article at a pulling speed of 500 mm / min and measuring the tensile stress when reaching 300% elongation. 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 500 mm / min, and the tensile strength immediately before breakage 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 500 mm / min, and the elongation immediately before breakage was measured.

Example 1
Preparation of copolymer latex 1 (example of the present invention)
In a pressure-resistant polymerization reactor, under a nitrogen atmosphere, 0.6 part of sodium bicarbonate, each monomer shown in addition 1 in Table 1, n-octyl mercaptan, α-methylstyrene dimer, cyclohexene, sodium dodecylbenzenesulfonate, After adding pure water and raising the temperature to 25 ° C., cumene hydroperoxide and sodium formaldehyde sulfoxylate were added to initiate polymerization. Five hours after the start of polymerization, each monomer, cumene hydroperoxide, sodium formaldehyde sulfoxylate, sodium dodecylbenzenesulfonate and pure water shown in addition 2 in Table 1 were added, and polymerization was continued. 23 hours after the start of polymerization, the pH is adjusted to 8 with an aqueous caustic potash solution, and diethylhydroxylamine shown in Table 1 is added as a polymerization terminator. Thereafter, 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 an aqueous caustic potash solution to obtain a copolymer latex 1 having a number average particle size, a gel content, and a non-binding acid amount / binding acid amount shown in Table 1.

Example 2
Preparation of copolymer latex 2 (example of the present invention)
To a pressure-resistant polymerization reactor, under a nitrogen atmosphere, 0.6 parts of sodium bicarbonate, each monomer shown in addition 1 of Table 1, t-dodecyl mercaptan, sodium dodecylbenzenesulfonate, and pure water were added to 35 ° C. After raising the temperature, cumene hydroperoxide and L-ascorbic acid were added to initiate polymerization. Three hours after the start of polymerization, each monomer, t-dodecyl mercaptan, cumene hydroperoxide, L-ascorbic acid, sodium dodecylbenzenesulfonate, and pure water shown in addition 2 in Table 1 were added, and polymerization was continued. 17 hours after the start of the polymerization, the pH is adjusted to 8 with an aqueous caustic potash solution, and diethylhydroxylamine shown in Table 1 is added as a polymerization terminator. Thereafter, 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 an aqueous caustic potash solution to obtain a copolymer latex 2 having a number average particle size, a gel content, and a non-binding acid amount / binding acid amount shown in Table 1.

Example 3
Preparation of copolymer latex 3 (example of the present invention)
In a pressure-resistant polymerization reactor, under a nitrogen atmosphere, 0.6 part of sodium bicarbonate, each monomer shown in addition 1 of Table 1, t-dodecyl mercaptan, sodium dodecylbenzenesulfonate, sodium alkyldiphenyl ether disulfonate, pure water Then, the temperature was raised to 40 ° C., and cumene hydroperoxide and L-ascorbic acid were added to initiate polymerization. Three hours after the start of polymerization, each monomer shown in addition 2 in Table 1, t-dodecyl mercaptan, sodium dodecylbenzenesulfonate, sodium alkyldiphenyl ether disulfonate, and pure water were added, and polymerization was continued. 15 hours after the start of polymerization, the pH is adjusted to 8 with a caustic potash aqueous solution, and diethylhydroxylamine shown in Table 1 is added as a polymerization terminator. Further, sodium polyacrylate (T-50 manufactured by Toagosei Co., Ltd.) shown in Table 1 was added. Thereafter, 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 an aqueous caustic potash solution to obtain a copolymer latex 3 having a number average particle size, a gel content, and a non-binding acid amount / binding acid amount shown in Table 1.

Example 4
Preparation of copolymer latex 4 (example of the present invention)
In a pressure resistant polymerization reactor, under a nitrogen atmosphere, 0.6 part of sodium bicarbonate, each monomer shown in addition 1 of Table 1, potassium persulfate, t-dodecyl mercaptan, sodium dodecylbenzenesulfonate, and pure water were added. Then, cumene hydroperoxide and L-ascorbic acid were added to initiate polymerization. After 14 hours from the start of polymerization, the pH is adjusted to 8 with an aqueous caustic potash solution, and diethylhydroxylamine shown in Table 1 is added as a polymerization terminator. Further, sodium polyacrylate (T-50 manufactured by Toagosei Co., Ltd.) shown in Table 1 was added. Thereafter, 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 an aqueous caustic potash solution to obtain a copolymer latex 4 having a number average particle size, a gel content, and a non-binding acid amount / binding acid amount shown in Table 1.

Comparative Example 5
Preparation of copolymer latex 5 (comparative example)
In a pressure-resistant polymerization reactor, under a nitrogen atmosphere, 0.6 parts of sodium bicarbonate, each monomer shown in addition 1 of Table 2, t-dodecyl mercaptan, α-methylstyrene dimer, sodium dodecylbenzenesulfonate, pure water Then, the temperature was raised to 45 ° C., and cumene hydroperoxide and sodium formaldehyde sulfoxylate were added to initiate polymerization. After 4 hours from the start of polymerization, each monomer, t-dodecyl mercaptan, cumene hydroperoxide, sodium formaldehyde sulfoxylate, sodium dodecylbenzenesulfonate and pure water shown in addition 2 in Table 1 were added, and polymerization was continued. . 14 hours after the start of the polymerization, the pH is adjusted to 8 with a caustic potash aqueous solution, and diethylhydroxylamine shown in Table 2 is added as a polymerization terminator. Thereafter, 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 an aqueous caustic potash solution to obtain a copolymer latex 5 having a number average particle size, a gel content, and a non-binding acid amount / binding acid amount shown in Table 2.

Comparative Example 6
Preparation of copolymer latex 6 (comparative example)
In a pressure-resistant polymerization reactor, under a nitrogen atmosphere, 0.6 part of sodium bicarbonate, each monomer shown in addition 1 of Table 2, t-dodecyl mercaptan, potassium persulfate, sodium dodecylbenzenesulfonate, alkyldiphenyl ether disulfonate Sodium and pure water were added and the temperature was raised to 65 ° C. to initiate polymerization. Three hours after the start of the polymerization, each monomer shown in addition 2 in Table 2, t-dodecyl mercaptan, potassium persulfate, sodium dodecylbenzenesulfonate, sodium alkyldiphenyl ether disulfonate, and pure water were added to continue the polymerization. 12 hours after the start of polymerization, the pH is adjusted to 8 with an aqueous caustic potash solution, and diethylhydroxylamine shown in Table 2 is added as a polymerization terminator. Further, sodium polyacrylate (T-50 manufactured by Toagosei Co., Ltd.) shown in Table 2 was added. Thereafter, 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 an aqueous caustic potash solution to obtain a copolymer latex 6 having a number average particle size, a gel content, and a non-binding acid amount / binding acid amount shown in Table 2.

Comparative Example 7
Preparation of copolymer latex 7 (comparative example)
To a pressure-resistant polymerization reactor, under a nitrogen atmosphere, 0.6 parts of sodium bicarbonate, each monomer shown in addition 1 of Table 2, t-dodecyl mercaptan, sodium dodecylbenzenesulfonate, and pure water were added to 35 ° C. After raising the temperature, cumene hydroperoxide and L-ascorbic acid were added to initiate polymerization. Six hours after the start of polymerization, each monomer, t-dodecyl mercaptan, cumene hydroperoxide, L-ascorbic acid, sodium dodecylbenzenesulfonate, and pure water shown in addition 2 in Table 2 were added, and polymerization was continued. 16 hours after the start of polymerization, the pH is adjusted to 8 with a caustic potash aqueous solution, and diethylhydroxylamine shown in Table 2 is added as a polymerization terminator. Thereafter, 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 an aqueous caustic potash solution to obtain a copolymer latex 7 having a number average particle size, a gel content, and a non-binding acid amount / binding acid amount shown in Table 2.

Comparative Example 8
Preparation of copolymer latex 8 (comparative example)
In a nitrogen-resistant atmosphere, 0.6 parts of sodium bicarbonate, each monomer shown in addition 1 of Table 2, t-dodecyl mercaptan, sodium dodecylbenzenesulfonate, and pure water were added to a pressure-resistant polymerization reactor at 25 ° C. After raising the temperature, cumene hydroperoxide and L-ascorbic acid were added to initiate polymerization. Three hours after the start of the polymerization, each monomer, t-dodecyl mercaptan, sodium dodecylbenzenesulfonate, cumene hydroperoxide, L-ascorbic acid and pure water shown in addition 2 in Table 2 were added, and polymerization was continued. 25 hours after the start of the polymerization, the pH is adjusted to 8 with an aqueous caustic potash solution, and diethylhydroxylamine shown in Table 2 is added as a polymerization terminator. Further, sodium polyacrylate (T-50 manufactured by Toagosei Co., Ltd.) shown in Table 2 was added. Thereafter, 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 an aqueous caustic potash solution to obtain a copolymer latex 8 having a number average particle size, a gel content, and a non-binding acid amount / binding acid amount shown in Table 2.

Preparation of Dip Molding Latex Composition The following compounding ingredients are added to the dip molding copolymer latexes 1-8 obtained in Examples 1 to 4 and Comparative Examples 5 to 8 to obtain a dip molding composition. It was.
<Latex composition for dip molding>
Latex for dip molding (solid content) 100.0 parts Potassium hydroxide 0.4 parts Zinc oxide 1.5 parts Colloidal sulfur 1.0 parts Zinc di-ethyldithiocarbamate 0.5 parts Titanium dioxide 1.5 parts (solid content Density 33%)

A 15% strength aqueous solution of calcium nitrate was prepared as a coagulating solution for each dip-molded product, and a glove mold pre-dried at 80 ° C. was immersed for 5 seconds, pulled up, leveled and dried under rotation (80 ° C x 2 minutes). Subsequently, the glove mold was immersed in the dip-forming composition for 5 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 2 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.

  Number average particle diameter, gel content, particle-bound acid amount (A), particle-unbound acid amount (B) of each copolymer latex, B / A determined from these, polymerization stability, dip molding composition Tables 1 and 2 summarize the evaluation results of mechanical stability, dip-formed product thickness, texture, tensile strength, and elongation at break.

  As described above, the dip molding latex of the present invention has high polymerization stability. By using this latex, the composition for dip molding having good mechanical stability and salt coagulation property, and texture, tensile strength, elongation, etc. A dip-molded product having excellent physical properties can be obtained, and rubber gloves and the like widely used in various fields such as medical treatment, food processing field and electronic component manufacturing field can be obtained.

Claims (3)

1,3-butadiene 30 to 80% by weight, acrylonitrile 15 to 50% by weight, ethylenically unsaturated carboxylic acid monomer 0.1 to 10% by weight and other ethylenically unsaturated monomers copolymerizable therewith A copolymer latex obtained by emulsion polymerization of a monomer comprising 0 to 54.9% by weight of a body having a particle-bound acid amount of A (meq / g) and a particle non-bound acid amount of B (meq / g). In the case of g), a dip-forming copolymer latex characterized by satisfying 0.05 ≦ B / A ≦ 0.5. A dip-forming composition comprising the dip-forming copolymer latex according to claim 1. A dip-molded product obtained by dip-molding the dip-molding composition according to claim 2.