JP2007177091A - Latex for dip molding and dip molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a latex for dip molding, a dip molding composition containing the latex and a dip molded article, wherein smell and itch due to sulfur etc., are not caused and durability and resistances to organic solvents are excellent. <P>SOLUTION: The dip molded article is produced by immersing a dip molding die into a dip molding composition comprising an acid-modified nitrile rubber latex wherein an insoluble content in methyl ethyl ketone of a dried film is 50-90 wt.% and a swelling ratio of the insoluble content in methyl ethyl ketone is 3-15, and taking out the resultant, followed by heating. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a dip-molding latex, a dip-molding composition containing the latex, and a dip-molded product. More specifically, the dip-molded product has no odor or itching caused by sulfur or the like and has excellent organic solvent resistance. Relates to a dip-forming latex, a dip-forming composition comprising the same, and a dip-formed product.

Rubber gloves are used in a wide range of applications such as housework, food-related industry, precision industry, and medical care. Among these, as a rubber glove having high tensile strength and excellent oil resistance, a composition comprising a latex of a carboxy-modified acrylonitrile-butadiene copolymer (nitrile rubber) and sulfur and a vulcanization accelerator was used. Molded products by dip molding are frequently used. However, this dip-molded product has an odor due to sulfur, and it may cause itchiness and rash caused by sulfur, a vulcanization accelerator, etc. on the skin when working with rubber gloves for a long time.
With respect to these problems, Patent Document 1 dip-molds a dip-molding composition in which dicumyl peroxide, di-t-butyl peroxide, etc. are blended with natural rubber or synthetic rubber latex, and then chemically. It discloses that a dip-molded article is obtained by crosslinking reaction in an inert high-temperature molten salt bath. However, rubber gloves produced by this method have a good texture and sufficient tensile strength, but they are exposed to high temperatures during cross-linking, and have a resistance to bending that causes microcracks in the crotch area when worn for 2 to 3 hours. It had the problem which is inferior to fatigue.

International Patent No. 0177210

  The present invention is made in view of such a situation, and does not generate odor or itching due to sulfur or the like, and also provides a dip-molded product excellent in organic solvent resistance, and a dip-molded latex comprising the dip-molded latex An object is to provide a composition and a dip-formed product.

As a result of diligent research to achieve the above object, the present inventor uses an acid-modified nitrile rubber latex in which a dry film exhibits a specific gel content and solvent swelling degree, and dip-molds without a vulcanizing agent. It has been found that the above object can be achieved, and the present invention has been completed based on this finding.
Thus, according to the first aspect of the present invention, the film obtained by drying has a methylethylketone insoluble content of 50 to 90% by weight, and the insoluble matter has a methylethylketone swelling degree of 3 to 15 for dip molding. An acid-modified nitrile rubber latex and a dip-forming composition comprising the same are provided.
According to the second aspect of the present invention, there is provided a dip-molded product obtained by immersing a dip-molding die in the above-described dip-molding composition and then heating it. Preferably, the dip-formed product is a rubber glove.

  According to the present invention, there is provided a dip-forming latex that gives a dip-molded product that is free of odor and itching due to sulfur and the like and has excellent organic solvent resistance, a dip-molding composition comprising the same, and a dip-molded product Is done.

  The first dip molding latex of the present invention is an acid-modified nitrile having a methylethylketone insoluble content of a film obtained by drying of 50 to 90% by weight and a methylethylketone swelling degree of 3 to 15 Rubber latex.

  The acid-modified nitrile rubber latex of the present invention is not particularly limited as long as it is a latex of a synthetic rubber containing an acidic group as a copolymer of an ethylenically unsaturated nitrile monomer and a conjugated diene monomer. As the synthetic rubber latex, an ethylenically unsaturated nitrile monomer, a conjugated diene monomer, an ethylenically unsaturated acid monomer and, if necessary, other monomers copolymerizable therewith are emulsion-polymerized. Thus obtained latex is preferred.

Examples of the ethylenically unsaturated nitrile monomer include (meth) acrylonitrile (meaning acrylonitrile and methacrylonitrile), 2-chloropropenenitrile, 2-butenenitrile and the like. Of these, acrylonitrile is preferred. These ethylenically unsaturated nitrile monomers can be used alone or in combination of two or more.
The amount of the ethylenically unsaturated nitrile monomer used is preferably 9.5 to 50% by weight, more preferably 15 to 45% by weight, particularly preferably 17 to 43% by weight based on the total monomers. . If this amount is too small, the dip-molded product may be inferior in organic solvent resistance, and conversely if too large, the texture may be inferior.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and chloroprene. Of these, 1,3-butadiene and isoprene are preferable, and 1,3-butadiene is more preferable. These conjugated diene monomers can be used alone or in combination of two or more.
The amount of the conjugated diene monomer used is preferably 30 to 90% by weight, more preferably 50 to 84% by weight, and particularly preferably 55 to 81% by weight with respect to the total monomers. If this amount is too small, the dip-formed product may be inferior in texture, while if it is too large, the tensile strength may be inferior.

Examples of the ethylenically unsaturated acid monomer include a carboxyl group-containing ethylenically unsaturated monomer, a sulfonic acid group-containing ethylenically unsaturated monomer, and a phosphoric acid group-containing ethylenically unsaturated monomer.
As the carboxyl group-containing ethylenically unsaturated monomer, (meth) acrylic acid (meaning acrylic acid and methacrylic acid), ethylenically unsaturated monocarboxylic acid such as crotonic acid; fumaric acid, maleic acid, itaconic acid, Examples thereof include ethylenically unsaturated polyvalent carboxylic acids such as maleic anhydride and itaconic anhydride and anhydrides thereof; partially esterified products of ethylenically unsaturated polyvalent carboxylic acids such as methyl maleate and methyl itaconic acid.

  Examples of the sulfonic acid group-containing ethylenically unsaturated monomer include vinyl sulfonic acid, methyl vinyl sulfonic acid, styrene sulfonic acid, (meth) allyl sulfonic acid (meaning allyl sulfonic acid and methallyl sulfonic acid), ( And (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-hydroxypropane sulfonic acid, and the like.

Examples of phosphoric acid group-containing ethylenically unsaturated monomers include (meth) acrylic acid-3-chloro-2-phosphate, (meth) acrylic acid-2-ethyl phosphate, 3-allyloxy-2-hydroxypropane Examples thereof include phosphoric acid.
These ethylenically unsaturated acid monomers can also be used as an alkali metal salt or an ammonium salt, and can be used alone or in combination of two or more.

Among the above ethylenically unsaturated acid monomers, carboxyl group-containing ethylenically unsaturated monomers are preferable, ethylenically unsaturated monocarboxylic acids are more preferable, and methacrylic acid is particularly preferably used.
The amount of the ethylenically unsaturated acid monomer used is preferably 0.5 to 10% by weight, more preferably 1 to 9% by weight, and particularly preferably 2 to 8% by weight based on the total monomers. . If this amount is too small, the dip-formed product tends to be inferior in tensile strength, and conversely if it is too much, the texture tends to be inferior.

  The ethylenically unsaturated nitrile monomer, conjugated diene monomer, and other monomers copolymerizable with the ethylenically unsaturated acid monomer are not particularly limited, but styrene, α-methylstyrene, monochlorostyrene. , Aromatic vinyl monomers such as dichlorostyrene, trichlorostyrene, monomethylstyrene, dimethylstyrene, trimethylstyrene, and hydroxymethylstyrene; ethylenic polymers such as (meth) acrylamide, N, N-dimethylacrylamide, and N-methylolacrylamide Saturated carboxylic acid amide monomer; ethylenically unsaturated carboxylic acid alkyl ester monomer such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate Vinyl acetate, vinyl propionate, versatile Carboxylic acid vinyl ester monomers such as vinyl acid; Vinyl halide monomers such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; Olefin monomers such as ethylene, propylene, 1-butene and isobutene; Vinyl ether monomers such as methyl vinyl ether, n-propyl vinyl ether, isobutyl vinyl ether and dodecyl vinyl ether; (meth) allyl compounds such as (meth) allyl acetate and (meth) allyl chloride; vinylsilyl compounds such as vinyltrimethoxysilane; divinylbenzene , Polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate and other crosslinkable monomers Vinyl pyridine, N-vinyl pyrrolidone and the like. These can be used alone or in combination of two or more.

Among these other monomers, aromatic vinyl monomers and ethylenically unsaturated carboxylic acid alkyl ester monomers can be preferably used. An aromatic vinyl monomer can be preferably used in that a dip-molded product having more excellent tensile strength can be obtained.
The amount of the other monomer used is preferably 0 to 60% by weight, more preferably 7 to 34% by weight, and particularly preferably 11 to 26% by weight with respect to the total monomers. If it is this usage-amount range, the tensile strength, organic-solvent resistance, and texture of a dip molded product can be maintained favorable.

  The acid-modified nitrile rubber latex of the present invention has a methylethylketone (hereinafter sometimes referred to as “MEK”) insoluble content in a film obtained by drying of 50 to 90% by weight, preferably 55 to 88% by weight, More preferably 60 to 85% by weight and emulsion polymerization using the above monomers so that the MEK swelling degree of the insoluble matter is 3 to 15, preferably 4 to 12, more preferably 5 to 10. Can be prepared.

The MEK insoluble content is the weight ratio of MEK insoluble content in a film obtained by natural drying of rubber latex. The MEK swelling degree is a weight ratio between the MEK absorption state and the non-absorption state of the insoluble matter.
The rubber latex film was obtained by allowing the latex to stand at 23 ° C. and 50% relative humidity for 5 days and drying. The thickness of the obtained film was 0.2 to 0.3 mm. This film is subdivided into a size of 5 mm in length and 5 mm in width to prepare a sample. About 0.2 g of the sample (A) was weighed accurately, immersed in a beaker containing 80 ml of MEK in a 80 mesh stainless steel wire cage, placed at 23 ° C. for 24 hours, taken out, and placed in the cage. The weight (B) of the MEK absorption state of the insoluble matter is measured. Next, the insoluble matter in the MEK absorption state is placed in a room at 23 ° C. for 1 hour and then heated at 105 ° C. for 1 hour, and the weight (C) of the insoluble matter in the dry state is measured. The MEK insoluble content and the MEK swelling degree of the insoluble content are determined by the following formula.
MEK insoluble content = (C / A) × 100 (% by weight)
MEK swelling degree = B / C (weight ratio)

Examples of a method for increasing the MEK insoluble content in emulsion polymerization include, for example, a method in which a polymerization temperature selected usually in the range of 0 to 50 ° C. is set to 55 to 95 ° C., and the crosslinkable monomer And a method of setting the final polymerization conversion rate higher.
Further, as a method of reducing the MEK swelling degree, a method of increasing the polymerization temperature in the latter half of the polymerization (in which the polymerization conversion rate is increased), a so-called prop polymerization in which a monomer is added to the reaction system during the polymerization reaction. Method, etc.

  Monomer addition methods include batch addition of monomers used in the reaction vessel, continuous or intermittent addition according to the progress of polymerization, and addition of a part of the monomer. And a method of polymerizing by continuously or intermittently adding the remaining monomers, and any method may be employed. When the monomers are mixed and added continuously or dividedly, the composition of the mixture may be constant or may be changed. In particular, it is preferable to employ a system in which a monomer mixture having a constant composition is supplied to the reactor at a constant rate throughout the reaction so that solvent-insoluble components are not unevenly distributed in the resulting copolymer.

  Moreover, the weight average molecular weight (Mw) of the tetrahydrofuran (hereinafter sometimes referred to as THF) of the copolymer in the acid-modified nitrile rubber latex used in the present invention is preferably 10,000 to 100,000. More preferably, it is 20,000-80,000, Most preferably, it is 30,000-70,000. If Mw is in this range, the tensile strength, organic solvent resistance and texture of the dip-formed product can be maintained well.

  In emulsion polymerization, commonly used polymerization auxiliary materials such as emulsifiers, polymerization initiators, molecular weight regulators and the like can be used. The addition method of these polymerization auxiliary materials is not particularly limited, and any method such as an initial batch addition method, a divided addition method, or a continuous addition method can be employed.

The emulsifier is not particularly limited, but the following is preferably used. That is, sodium salt such as dodecylbenzene sulfonate, aliphatic sulfonate, α-olefin sulfonate, β-naphthalene sulfonate formalin condensate, lauryl alcohol sulfate, alkyl ether sulfate, potassium salt, etc. Anionic surfactant comprising: Nonionic surfactant such as polyethylene glycol alkyl ether, polyethylene glycol alkyl ester, polyethylene glycol alkyl phenyl ether; Cationic surfactant such as alkyl diamine salt and tetraalkyl ammonium salt; Carboxylic acid salts, sulfuric acid ester salts, sulfonic acid salts, phosphoric acid salts, phosphoric acid ester salts and the like, and amphoteric surfactants having an amine salt or a quaternary ammonium salt as the cation moiety. . Among these, an anionic surfactant can be preferably used.
The amount of the emulsifier used is preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight with respect to 100 parts by weight of the total monomers.

The polymerization initiator is not particularly limited as long as it is a radical initiator, but inorganic peroxides such as potassium persulfate, sodium persulfate, ammonium persulfate, potassium perphosphate, hydrogen peroxide; t-butyl peroxide, cumene Hydroperoxide, p-menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3, 5, 5 Organic peroxides such as trimethylhexanoyl peroxide and t-butylperoxyisobutyrate; azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, etc. Azotization Mention may be made of things like. These polymerization initiators can be used alone or in combination of two or more. The peroxide can be used as a redox polymerization initiator in combination with a reducing agent such as sodium bisulfite or ferrous sulfate. As the polymerization initiator, an inorganic or organic peroxide is preferable, an inorganic peroxide is more preferable, and a persulfate can be particularly preferably used.
The amount of the polymerization initiator used is preferably 0.01 to 2 parts by weight, more preferably 0.05 to 1.5 parts by weight with respect to 100 parts by weight of the total monomers.

The molecular weight modifier is not particularly limited, but mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, octyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, methylene bromide; α-methylstyrene dimer; And sulfur-containing compounds such as tetraethylthiuram disulfide, dipentamethylene thiuram disulfide, and diisopropylxanthogen disulfide. These can be used alone or in combination of two or more. Among these, mercaptans are preferable, and t-dodecyl mercaptan can be more preferably used.
The amount of the molecular weight modifier used varies depending on the type, but is preferably 0.1 to 0.8 parts by weight, more preferably 0.2 to 0.7 parts by weight with respect to 100 parts by weight of all monomers. It is a range.

  Emulsion polymerization is usually performed in water. The amount of water used is preferably 80 to 500 parts by weight, more preferably 100 to 200 parts by weight with respect to 100 parts by weight of the total monomers.

  Furthermore, polymerization auxiliary materials such as a chelating agent, a dispersant, a pH adjuster, a deoxidizing agent, and a particle size adjuster can be used as necessary, and these are not particularly limited in terms of type and amount used.

  The composition for dip molding of the present invention comprises the above-mentioned acid-modified nitrile rubber latex, and an antioxidant, preservative, antibacterial agent, ultraviolet absorber, pH adjuster, etc. are appropriately added as necessary.

  The dip molding composition of the present invention may not contain a vulcanizing agent. Therefore, basically it does not contain sulfur and vulcanization accelerators, so the resulting dip-molded product does not give off a sulfur odor, and itching and irritation of the skin caused by sulfur and vulcanization accelerators. Don't make it happen.

In the dip molding composition of the present invention, if necessary, an ionic crosslinking agent that ionically crosslinks between acidic groups of the acid-modified nitrile rubber can be blended. Examples of the ion crosslinking agent include compounds that generate divalent cations such as zinc, calcium, magnesium, and strontium ions; trivalent cations such as aluminum ions, and preferably compounds that generate divalent cations. Particularly preferred is zinc oxide.
The compounding amount of the ionic crosslinking agent is preferably 5 parts by weight or less, more preferably 1.0 part by weight or less, and particularly preferably 0.5 part by weight or less per 100 parts by weight of the acid-modified nitrile rubber.

  When it is desired to contain sulfur in the dip molding composition for the purpose of adjusting the properties of the dip molded article, the amount is preferably 0.3 parts by weight or less, more preferably 0.1 parts by weight per 100 parts by weight of the acid-modified nitrile rubber. The following shall be suppressed.

The solid content concentration of the dip molding composition of the present invention is preferably 20 to 40% by weight, more preferably 25 to 35% by weight.
The pH range of the dip molding composition is preferably 8.5 or more,
It is more preferable to set it as 9-11.
By using a dip molding composition having a solid content concentration and pH in the above ranges, a dip molded product having a uniform film thickness can be easily obtained.

  The dip-molded article of the present invention can be obtained by immersing a dip-molding die in the dip-molding composition and then heating it.

  Various materials such as porcelain, glass, metal, and plastic can be used as the dip mold. What is necessary is just to use what match | combined the shape of the type | mold with the shape of the dip molded product. When the dip-molded product is a glove, the shape of the dip-molding die may be various shapes such as a shape from the wrist to the fingertip and a shape from the elbow to the fingertip. The surface of the dip molding die may be subjected to surface processing such as gloss processing, semi-gloss processing, non-gloss processing, and weave pattern processing, for example, on the entire mold surface or partially.

It is preferable to immerse the coagulant in advance on the surface of the dip molding die and then immerse it in the dip molding composition because a dip molded product having a uniform thickness can be easily obtained.
The coagulant is not limited as long as it is an inorganic salt having a salting-out effect. For example, metal halide salts such as barium chloride, calcium chloride, magnesium chloride, zinc chloride, aluminum chloride; barium nitrate, calcium nitrate, zinc nitrate Nitrates such as barium acetate, calcium acetate, and zinc acetate; sulfates such as calcium sulfate, magnesium sulfate, and aluminum sulfate; and the like. Of these, metal halide salts and nitrates are preferable, and calcium chloride and calcium nitrate are more preferable. The coagulant is usually used as a solution or dispersion of water, alcohol or a mixture thereof (hereinafter, both forms are collectively referred to as “coagulant liquid”). The coagulant concentration is preferably 5 to 70% by weight, more preferably 10 to 50% by weight.

  In order to adhere the coagulant liquid to the surface of the dip mold, a method of dipping the mold in the coagulant liquid and pulling it up and drying is usually employed. In order to prevent the coagulant solution from being repelled from the mold and causing the concentration of the adhering coagulant to become non-uniform, the nonionic surfactant is preferably added to the coagulant liquid in an amount of 0.001 to 1.0% by weight, more preferably. Is effective when added to a concentration of 0.01 to 0.5% by weight.

  As the dip-molding method, a conventionally known dip-molding method can be adopted, and examples thereof include a direct dipping method, an anode adhesion dipping method, and a teag adhesion dipping method. Among these, the anode coagulation dipping method is preferable because a dip-molded product having a uniform thickness can be easily obtained.

  Before heat-treating the dip-molded layer formed on the mold, the mold is immersed in water, preferably warm water at 30 to 70 ° C. for about 1 to 60 minutes to dissolve water-soluble impurities (for example, excess emulsifier). Or a coagulant is preferably removed. Although this removal operation may be performed after heat-treating the dip-formed layer, it is preferably performed before the heat treatment from the viewpoint that water-soluble impurities can be more efficiently removed.

  Moreover, when the dip-molding layer contains a large amount of moisture, a drying step at 40 to 100 ° C. for 1 to 60 minutes can be performed before heating.

The heat treatment of the dip-formed layer is preferably 100 to 150 ° C., more preferably 110 to 140 ° C., preferably 1 to 120 minutes, more preferably 5 to 60 minutes. A uniform film is formed by this heat treatment, and a tough film is produced.
As the heat treatment method, an external heating method using infrared rays or hot air or an internal heating method using high frequency can be employed. Of these, heating with hot air is preferred.

  A dip-molded product is obtained by removing the crosslinked dip-molded layer from the dip-mold. As a demolding method, a method of peeling from a molding die by hand or a method of peeling by water pressure or air pressure can be employed.

  After demolding, a heat treatment (post-heating step) for 10 to 120 minutes may be performed at a temperature of 60 to 120 ° C.

  The dip-molded product may further have a non-adhesive surface layer formed by coating polyurethane, acrylic polymer, or the like on the inner and / or outer surfaces, or by chlorinating the surface.

The dip-formed product of the present invention has a thickness of about 0.05 to 3 mm, preferably 0.1 to 0.3 mm, and is uniform.
Applications of the dip-molded product of the present invention include medical supplies such as nipples for baby bottles, syringes, conduits and water pillows; toys and exercise tools such as balloons, dolls and balls; bags for pressure molding, bags for gas storage, etc. Examples include industrial articles; surgical, household, agricultural, fishery and industrial rubber gloves; finger sack, and the like. Among these, since it has no odor and is strong against organic solvents, it is particularly suitable for thin rubber gloves for surgery, rubber gloves for inspection, and industrial rubber gloves.

Hereinafter, the present invention will be described more specifically with reference to production examples, examples, and comparative examples, but the present invention is not limited to these examples. Further, “parts” in these examples are based on weight unless otherwise specified.
The test and evaluation of each characteristic were performed by the following method.

(1) MEK Insoluble Content 40 g of latex with a solid content concentration of 30%, adjusted to pH 8 with an aqueous ammonia solution, was cast on a framed glass plate (16 cm × 23 cm), and 5% at 23 ° C. and 50% relative humidity. The film was allowed to stand for a day to obtain a film having a thickness of 0.2 to 0.3 mm. This film is subdivided into a size of 5 mm in length and 5 mm in width to prepare a sample. About 0.2 g of the sample (A) was weighed accurately, immersed in a beaker containing 80 ml of MEK in a 80 mesh stainless steel wire cage, placed at 23 ° C. for 24 hours, taken out, and placed in the cage. The weight (B) of the MEK absorption state of the insoluble matter is measured. Subsequently, the insoluble matter in the MEK absorption state is placed in a room at 23 ° C. for 1 hour and then heated at 105 ° C. for 1 hour, and the weight (C) of the insoluble matter in the dry state is measured. The MEK insoluble content and the MEK swelling degree of the insoluble content are determined by the following formula.
MEK insoluble content = (C / A) × 100 (% by weight)
MEK swelling degree = B / C (weight ratio)

(2) Weight average molecular weight (Mw) of THF soluble matter
A polymer latex film 0.5 g prepared in the same manner as in (1) above was placed in an 80-mesh wire mesh cage, immersed in 100 ml of THF at 20 ° C. for 24 hours, and then the weight average of the polymer dissolved in tetrahydrofuran. Measure the molecular weight. The molecular weight is determined in terms of polystyrene by high performance liquid chromatography (GPC) using THF as a carrier. Specifically, the measurement is performed using an HLC8220 manufactured by Tosoh Corporation. The molecular weight calibration is performed with 12 points of standard polystyrene (500 to 3 million) manufactured by Polymer Laboratories.

(3) Tensile strength, tensile stress and elongation A dumbbell-shaped test piece was produced from a rubber glove (dip-molded product) obtained by dip molding using a dumbbell (Die-C) according to ASTM D-412. Subsequently, this test piece was pulled at a tensile speed of 500 mm / min, and the tensile stress (MPa) when the elongation rate was 300%, the tensile strength (MPa) at break, and the elongation (%) at break were measured.

(4) Durability Ten test subjects wore the obtained rubber gloves and performed light work.
Every time 1 hour passed after wearing rubber gloves, the crotch part of the fingers of the rubber gloves was observed to confirm the occurrence of microcracks.
After measuring the time until a microcrack occurs in each subject's rubber glove, the time is shown as a simple average time excluding the shortest and longest time. This wearing test was conducted for a maximum of 6 hours. It shows that it is excellent in durability, so that the said time is long.
(5) Organic solvent resistance A disk having a diameter of 2.0 cm was prepared from a rubber glove (dip molded product) obtained by dip molding. Next, the disk was immersed in 15 ml of cyclohexanone, and the diameter of the disk after 1 hour was measured. The area before immersion was A, the area of the disk after immersion was B, and the swelling rate was [(B−A) / A]. It was calculated as x100 and used as an index of organic solvent resistance. The lower the swelling rate, the better the organic solvent resistance.

(Production Example 1)
A polymerization reactor equipped with a stirrer was charged with 13.2 parts of ion-exchanged water, 0.3 part of sodium dodecylbenzenesulfonate and 0.05 part of β-naphthalenesulfonate sodium formalin condensate and heated to a temperature of 60 ° C. I made it. To this, 132 parts of ion-exchanged water, 27 parts of acrylonitrile, 67.5 parts of 1,3-butadiene, 5.5 parts of methacrylic acid, 0.3 part of t-dodecyl mercaptan, 3 parts of sodium dodecylbenzenesulfonate, β-naphthalene sulfone An emulsion comprising 0.5 part of sodium formalin condensate, 0.3 part of potassium persulfate and 0.05 part of sodium ethylenediaminetetraacetate was added at a constant rate over 5 hours. Meanwhile, the liquid temperature was kept at 60 ° C. After the addition of the emulsion, the temperature of the solution was raised to 80 ° C. and stirred for 5 hours until the polymerization conversion reached 95%. Thereafter, 0.1 part of a polymerization terminator sodium dimethyldithiocarbamate was added to terminate the polymerization reaction. After removing unreacted monomers from the obtained copolymer latex, the pH and solid content concentration were adjusted to obtain a carboxy-modified nitrile rubber latex A having a pH of 8 and a solid content concentration of 40% by weight. The Mw of the THF-soluble component of the latex A copolymer by GPC was 40,000.

(Production Example 2)
A latex of carboxy-modified nitrile rubber having a pH of 8 and a solid content concentration of 40% by weight was carried out in the same manner as in Production Example 1 except that acrylonitrile was changed to 37 parts and 1,3-butadiene was changed to 57.5 parts. B was obtained. The Mw of the THF soluble part by GPC of the copolymer of Latex B was 37,000.

(Production Example 3)
Carboxy-modified nitrile having a pH of 8 and a solid content concentration of 40% by weight was the same as in Production Example 1 except that acrylonitrile was changed to 22 parts, 1,3-butadiene was changed to 74 parts, and methacrylic acid was 4 parts. Rubber latex C was obtained. The Mw of the THF soluble part by GPC of the copolymer of Latex C was 35,000.

(Production Example 4)
In a polymerization reactor equipped with a stirrer, 132 parts of ion-exchanged water, 3 parts of sodium dodecylbenzenesulfonate, 0.5 parts of β-naphthalenesulfonate sodium formalin condensate, 27 parts of acrylonitrile, 67.5 parts of 1,3-butadiene, methacrylic acid 5.5 parts, 0.3 part of t-dodecyl mercaptan, 0.3 part of potassium persulfate and 0.05 part of ethylenediaminetetraacetic acid sodium salt were charged and the temperature was maintained at 37 ° C. to initiate the polymerization reaction. When the polymerization conversion reached 60%, 0.15 part of t-dodecyl mercaptan was added, and the polymerization temperature was raised to 40 ° C., and the reaction was continued until the polymerization conversion reached 94%. Thereafter, 0.1 part of a polymerization terminator sodium dimethyldithiocarbamate was added to terminate the polymerization reaction.
After removing unreacted monomers from the obtained copolymer latex, the pH and solid content concentration of the copolymer latex were adjusted to obtain latex D having a pH of 8 and a solid content concentration of 40%. The Mw of the THF soluble part by GPC of the copolymer of latex D was 120,000.

Example 1
To latex A, a 5% potassium hydroxide aqueous solution and ion-exchanged water were added to obtain a dip molding composition having a solid content concentration of 30% and a pH of 10.
A glove mold is dipped in a coagulant aqueous solution in which 20 parts of calcium nitrate, 0.05 part of nonionic surfactant polyoxyethylene octylphenyl ether and 80 parts of water are mixed for 5 seconds, and then pulled up at 50 ° C. for 10 minutes. Dry and allow the coagulant to adhere to the glove mold. Next, the glove mold with the coagulant attached is dipped in the above dip molding composition for 6 seconds and pulled up, and the glove mold with the dip molding layer formed is dried at 50 ° C. for 10 minutes, and then 40 ° C. Was immersed in warm water for 3 minutes to elute water-soluble impurities. Next, the glove mold was dried at 70 ° C. for 10 minutes, and subsequently heated at 120 ° C. for 20 minutes to obtain a dip-molded layer. Finally, the dip molding layer was peeled off from the glove mold to obtain a rubber glove having a thickness of 0.1 mm. Table 1 shows the results of testing and evaluating the MEK insoluble content of the acid-modified nitrile rubber in latex and the MEK swelling degree; the tensile strength, elongation, 300% tensile stress and durability of rubber gloves.

(Examples 2 and 3 and Comparative Example 1)
A rubber glove was obtained in the same manner as in Example 1 except that latex A was changed to latex B, latex C, or latex D, respectively. Table 1 shows the results of tests and evaluations as in Example 1.

As shown in Table 1, the MEK insoluble content of the film obtained by drying, and the amount of MEK swelling degree of the insoluble content are made of latex A, B or C within the scope of the claims of the present application. The dip-formed product by the composition had sufficient mechanical strength, excellent durability, and organic solvent resistance (Examples 1 to 3).
On the other hand, the dip-molded product by the dip-molding composition composed of latex D that gives a dry film that is out of the scope of the present application in terms of both MEK insoluble content and MEK swell degree does not show a decrease in mechanical strength, but is durable. And the organic solvent resistance was significantly inferior (Comparative Example 1).

Claims (4)

  An acid-modified nitrile rubber latex for dip molding, wherein the film obtained by drying has a methylethylketone insoluble content of 50 to 90% by weight and a methylethylketone swelling degree of 3 to 15 of the insoluble matter.   A dip-molding composition comprising the acid-modified nitrile rubber latex according to claim 1.   A dip-molded product obtained by immersing a dip-molding die in the dip-molding composition according to claim 2 and then heating. The dip-molded product according to claim 4, which is a rubber glove.