JPH05247266A - Latex for dip forming and product of dip forming - Google Patents

Abstract

(57) [Summary] [Purpose] Dip moldings with excellent oil resistance, high mechanical strength such as tensile strength and tear strength, and soft texture, and dip moldings for obtaining the dip moldings with high productivity. Provide latex. [Structure] 1,3-butadiene 53.5 parts, acrylonitrile 38 parts, methacrylic acid 5.5 parts and butyl acrylate 3.0 parts by emulsion polymerization,
The polystyrene-converted weight average molecular weight of the copolymer is 120,
And the content of the copolymer insoluble in methyl ethyl ketone is 2% by weight to obtain a dip molding latex. A glove mold with a coagulant attached is immersed in this latex-based compounded liquid, pulled up, dried, and heat treated, and finally the solid film obtained on the mold surface is peeled from the mold to form a glove-shaped dip Get things.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dip-molded product and a dip-molded latex, and more particularly to a dip-molded product having excellent oil resistance, high mechanical strength, and soft texture, and a dip-molded product produced from the same. The present invention relates to a latex for dip molding for obtaining good properties.

[0002]

2. Description of the Related Art Various properties are required for dip-molded articles such as gloves and finger cots used in workplaces using organic solvents, such as automobile factories, but especially excellent oil resistance and mechanical strength. It is important that it is high and has a soft texture. A carboxylic acid-modified nitrile copolymer latex such as an acrylic acid-acrylonitrile-butadiene copolymer latex has hitherto been used as a method for meeting this demand. However, the dip-molded product obtained by dip-molding only a single carboxylic acid-modified nitrile copolymer latex has a drawback that the texture is hard. Therefore, as a method for softening the texture of the dip-molded product, a method of dip-molding the natural rubber latex and the carboxylic acid-modified nitrile copolymer latex alternately, and the carboxylic acid-modified nitrile copolymer latex, It was necessary to adopt a method of dip-molding a mixed latex (JP-A-53-101036) mixed with a carboxylic acid-modified synthetic cis-1,4-polyisoprene rubber latex. However, these methods have a problem that the process is complicated and the productivity is low. Therefore, it has excellent oil resistance, high mechanical strength,
A method for easily obtaining a dip-molded product having a soft texture is desired.

[0003]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a dip-molded article which is excellent in oil resistance, has high mechanical strength such as tensile strength and tear strength, and has a soft texture, and high productivity of the dip-molded article. It is to provide a dip-forming latex for obtaining. As a result of intensive studies to achieve this object, the present inventors have found that this object can be achieved by using a latex in which the polystyrene-equivalent weight average molecular weight and the methyl ethyl ketone insoluble content of the copolymer are specified in a specific range. Based on this finding, the present invention has been completed.

[0004]

Thus, according to the present invention, 30 to 90% by weight of conjugated diene monomer, 9 to 50% by weight of ethylenically unsaturated nitrile monomer, and 0 to ethylenically unsaturated acid monomer. 1 to 20% by weight and 0 to 20% by weight of another ethylenically unsaturated monomer copolymerizable with these monomers, which is a latex of a copolymer obtained by polymerizing a monomer mixture. And (b) the polystyrene-converted weight average molecular weight of the copolymer is 50,000 to 500,000, and (b) the methyl ethyl ketone insoluble component is 5
A dip-forming latex having a content of 0% by weight or less and a dip-formed product obtained by dip-forming the same are provided.

The present invention will be described in detail below. The dip molding latex of the present invention comprises a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, an ethylenically unsaturated acid monomer and other ethylenically unsaturated monomers copolymerizable therewith. It is a latex of a copolymer obtained by polymerizing a monomer mixture.

The conjugated diene monomer used in the present invention is
It is not particularly limited, and examples thereof include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, and chloroprene. .. Particularly, 1,3-butadiene or isoprene is preferably used. These conjugated diene monomers can be used alone or in combination of two or more. The amount of the conjugated diene monomer used is 30 to 90% by weight, preferably 35 to 80% by weight of the monomer mixture. If it is less than 30% by weight, the texture of the dip molded product becomes hard, and conversely if it is more than 90% by weight, the oil resistance of the dip molded product becomes poor and the tensile strength and tear strength are deteriorated, which is not preferable.

The ethylenically unsaturated nitrile monomer used in the present invention is not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, fumaronitrile, α-chloroacrylonitrile and α-cyanoethylacrylonitrile. These ethylenically unsaturated nitrile monomers can be used alone or in combination of two or more kinds. The amount of the ethylenically unsaturated nitrile monomer used is 9 to 50% by weight of the monomer mixture, preferably 20 to
It is 45% by weight. If it is less than 9% by weight, the oil resistance of the dip-molded product becomes poor, and conversely if it exceeds 50% by weight, the texture of the dip-molded product becomes hard.

The ethylenically unsaturated acid monomer used in the present invention is not particularly limited as long as it is an ethylenically unsaturated monomer containing an acidic group such as a carboxyl group, a sulfonic acid group and an acid anhydride group. For example, ethylenically unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid; polycarboxylic acid anhydrides such as maleic anhydride and citraconic anhydride; ethylene such as styrene sulfonic acid Unsaturated sulfonic acid monomer; ethylenically unsaturated polycarboxylic acid monoester monomer such as monobutyl fumarate, monobutyl maleate, mono-2-hydroxypropyl maleate; and the like. These ethylenically unsaturated acid monomers can also be used as alkali metal salts or ammonium salts. These ethylenically unsaturated acid monomers may be used alone or in combination of two or more. The amount of the ethylenically unsaturated acid monomer used is 0.1 to 20% by weight of the monomer mixture, preferably 1 to 1
It is 5% by weight, more preferably 2 to 10% by weight.
If it is less than 0.1% by weight, the tensile strength of the dip-molded product will be lowered, and conversely if it is more than 20% by weight, the tear strength of the dip-molded product will be low and the texture will be hard.

Other ethylenically unsaturated monomers copolymerizable with the ethylenically unsaturated nitrile monomer and the ethylenically unsaturated acid monomer include, for example, styrene, alkylstyrene, vinyl naphthalene, and other vinyl fragrances. Group monomer;
Fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether; (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, etc. Ethylenically unsaturated amide monomer of; vinyl pyridine; vinyl norbornene; dicyclopentadiene, 1,
Non-conjugated diene monomer such as 4-hexadiene; methyl (meth) acrylate, ethyl (meth) acrylate, (meth)
Butyl acrylate, 2-ethylhexyl (meth) acrylate, trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, dibutyl maleate, dibutyl fumarate, diethyl maleate, methoxy (meth) acrylate Methyl, ethoxyethyl (meth) acrylate, methoxyethoxyethyl (meth) acrylate, cyanomethyl (meth) acrylate, 2-cyanoethyl (meth) acrylate, 1-cyanopropyl (meth) acrylate, (meth) acrylic acid 2-ethyl-6-cyanohexyl, 3-cyanopropyl (meth) acrylate,
Examples thereof include ethylenically unsaturated carboxylic acid ester monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, and dimethylaminoethyl (meth) acrylate. These ethylenically unsaturated monomers may be used alone or in combination of two or more. The amount of the ethylenically unsaturated monomer used is 20% by weight or less of the monomer mixture.

In the dip-molding latex of the present invention, the copolymer has a polystyrene reduced weight average molecular weight (hereinafter, simply referred to as "molecular weight") of 50,000 to 50.
It is important that it is 50,000, preferably 80,
It is 000 to 200,000. If it is less than 50,000, the tensile strength of the dip molded product will be low
If it is more than 20,000, the texture of the dip molded product becomes hard.

In the latex for dip molding of the present invention, the methyl ethyl ketone insoluble matter of the copolymer (hereinafter,
It is called "MEK insoluble matter". Is 50% by weight or less, preferably 25% by weight or less, and more preferably 10% by weight or less. If it exceeds 50% by weight, the texture of the dip-molded product becomes hard, which is not preferable. The MEK-insoluble content is the proportion of the copolymer that is not soluble in methyl ethyl ketone in the copolymer.

The dip molding latex of the present invention is usually produced by an emulsion polymerization method. The polymerization temperature at the time of emulsion polymerization is not particularly limited, but it is particularly preferable to carry out the polymerization at 40 ° C. or lower because a latex can be stably produced, and a dip-molded product having high mechanical strength and soft texture can be obtained.

In the production of the dip molding latex of the present invention, the method of adding the monomer mixture is not particularly limited,
A method of charging the monomer mixture into the polymerization reactor all at once, a method of continuously supplying the monomer mixture to the polymerization reactor, a part of the monomer mixture is charged into the polymerization reactor, and the remaining unit amount Any method such as continuously supplying the body to the polymerization reactor may be adopted.

The polymerization initiator used for producing the dip molding latex of the present invention is not particularly limited, but a redox type polymerization initiator is preferable.

As the peroxide, it is preferable to use a peroxide having a temperature of 100 ° C. or higher for obtaining a half-life of 10 hours. Specific examples thereof include diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1, 1, 3,
3-tetramethylbutyl hydroperoxide, 2,
Hydroperoxides such as 5-dimethylhexane-2,5-dihydroperoxide can be mentioned. In particular, a peroxide having a temperature of 130 ° C. or higher for obtaining a half-life of 10 hours, such as 1,1,3,3-tetramethylbutyl hydroperoxide, can stably produce a latex, and It is preferably used since a dip-formed product having high mechanical strength and soft texture can be obtained. Although the amount of the peroxide used varies slightly depending on the peroxide, it is preferably 0.01 to 0.6% by weight based on the monomer mixture.

The reducing agent is not particularly limited, and specific examples thereof include a compound containing a metal ion in a reduced state such as ferrous sulfate and cuprous naphthenate; a sulfonic acid compound such as sodium methanesulfonate; Amine compounds such as dimethylaniline; and the like. These reducing agents may be used alone or in combination of two or more. The amount of reducing agent used varies slightly depending on the reducing agent, but the amount of peroxide 1
It is preferably 0.03 to 10 parts by weight with respect to parts by weight.

The emulsifier used in the dip-forming latex of the present invention is not particularly limited, and examples thereof include nonionics such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, and polyoxyethylene sorbitan alkyl ester. Emulsifier; myristic acid, palmitic acid,
Fatty acids and salts thereof such as oleic acid and linolenic acid, anionic emulsifiers such as higher alcohol sulfate and alkylsulfosuccinic acid; ammonium chloride such as trimethylammonium chloride and dialkylammonium chloride, benzylammonium salt and the like, and
Examples thereof include cationic emulsifiers such as primary ammonium salts; sulfoesters of α, β-unsaturated carboxylic acids, sulfate esters of α, β-unsaturated carboxylic acids, and copolymerizable emulsifiers such as sulfoalkylaryl ethers. In particular, an anionic emulsifier or a nonionic emulsifier is preferably used. These emulsifiers can be used alone or in combination of two or more kinds. The amount of the emulsifier used is not particularly limited, but is 0.1-9.
It is preferably 0% by weight.

When the latex for dip molding of the present invention is polymerized, a polymerization auxiliary material such as a molecular weight adjusting agent, a particle size adjusting agent, an antiaging agent, a chelating agent, an oxygen scavenger may be used, if necessary. it can.

The dip-molded product of the present invention is a dip-molded product obtained by dip-molding the latex for dip-molding of the present invention. Usually, dip molding involves immersing the mold in the dip molding compounding liquid, depositing latex on the surface of the mold, then pulling up the mold with the latex deposited from the dip molding compounding liquid, and drying if necessary. By As a specific example of the dip molding method, a direct dipping method,
Examples include an anode coagulation dipping method and a Teague coagulation dipping method.

The dip molding compound liquid used for the dip molding is a compound liquid containing the dip molding latex of the present invention as a main component. The dip-forming latex of the present invention used in this dip-forming compounded liquid can be used alone or in combination of two or more kinds. Further, other latex such as natural rubber latex and isoprene rubber latex may be used in combination as long as the object of the present invention is not impaired. If necessary, a vulcanizing agent, a vulcanization accelerator, an antiaging agent, a filler, a thickener, etc. can be mixed with the dip molding compounding liquid. The mixing method is not particularly limited, and for example, a method of mixing and kneading the latex with a vulcanizing agent, a filler, a thickener, etc. using a general disperser such as a kneader or a disperser can be used.

In the dip molding, a coagulant may be used if necessary before the mold is immersed in the compounding liquid or after the mold is pulled out of the compounding liquid. Specific examples of the method of use include a method of immersing a mold before immersion in a solution of a coagulant so that the mold adheres to the mold, and a method of sprinkling the solution of the coagulant on a mold in which latex is deposited.

In dip molding, hot water treatment or heat treatment can be carried out, if necessary, after withdrawing from the dip molding compound liquid. By performing hot water treatment or heat treatment, surplus monomers and compounding aids are removed, and the crosslinking reaction of the copolymer is promoted. The method of hot water treatment or heat treatment is not particularly limited, for example, a method of immersing a latex-deposited mold in warm water, a method of blowing hot air in the latex-deposited mold in an oven, a latex is deposited. Examples include a method of irradiating the mold with infrared rays.

[0023]

Thus, according to the present invention, a dip-molded product having excellent oil resistance, high mechanical strength and soft texture, and a dip-molding latex for obtaining the dip-molded product with high productivity are obtained. You can

[0024]

EXAMPLES The present invention will now be described in more detail by way of examples. The parts and% in the examples are by weight unless otherwise specified.

[Evaluation method of latex] (Molecular weight) Latex is dissolved in tetrahydrofuran,
The solution was determined by gel permeation chromatography (carrier liquid: tetrahydrofuran) based on the calibration curve determined for standard polystyrene.

(MEK insoluble matter) Latex is cast on a glass plate with a frame and left standing at 25 ° C. for 4 days to form a film. A certain amount of it is weighed accurately (weight W ₀ ), put in a basket of 80 mesh wire mesh, and put in methyl ethyl ketone at 20 ° C.
After soaking for 8 hours, the basket is pulled up, vacuum dried at 25 ° C. for 2 days, and the copolymer remaining in the basket without being dissolved is precisely weighed (weight W ₁ ). The MEK insoluble matter was expressed as a percentage of W ₁ with respect to W ₀ .

(Mechanical stability) Based on the mechanical stability of JIS-K 6392, a load of 10 kg, 10 minutes, 100
It was measured under the condition of mesh.

[Evaluation Method of Dip Molded Product] (Evaluation of Texture) A test piece of a dip molded product punched out with dumbbell deformation No. 2 (small size) was pulled at a tensile speed of 200 mm / min and stretched at an elongation of 300%. The strength was measured. The smaller the value, the softer the texture.

(Tensile Strength Test) A test piece of a dip molded product punched with dumbbell deformation No. 2 (small size) was pulled at a pulling speed of 2
Tensile strength (Tb) immediately before breaking by pulling at 00 mm / min
And the elongation rate (Tl) were measured.

(Tear strength test) A test piece of a dip-molded product punched out with a dumbbell JIS B type was used to tear a test piece at a tear speed of 500 m.
It was torn at m / min, and the tear strength immediately before breaking was measured.

(Oil resistance test) A test piece of a dip-molded product having a diameter of 20 mm punched out was dipped in a predetermined test oil for 48 hours, the area of the test piece was measured, and before and after dipping in the test oil. The value (area swelling ratio) obtained by dividing the change in the area by the area before immersion was used as an index of oil resistance.

Example 1 A reactor purged with nitrogen was charged with a monomer, a molecular weight modifier (TDM: t-dodecyl mercaptan), a polymerization initiator, soft water and an emulsifier (warolate) according to the formulation shown in Tables 1 and 2. u: Toshin Chemical Co., Ltd.)
The temperature was maintained at 50 ° C. and stirring was continued for 50 hours to obtain a latex. The evaluation results of these latexes are shown in Table 1 and Table 2.
Shown in.

Example 2 Solid content concentration 50 prepared by mixing 0.5 part of sulfur, 5.0 parts of zinc oxide, 3.0 parts of titanium oxide, 0.2 part of 10% ammonia casein and 8.3 parts of water. % Of the vulcanizing agent solution was mixed with 220 parts of the latex having a solid content concentration of 45% obtained in Example 1 to obtain a dip molding compound liquid. On the other hand, the glove mold was immersed for 1 minute in a coagulant solution having a solid content concentration of 66% prepared by mixing 65 parts of calcium nitrate, 1 part of a nonionic emulsifier (Emulgen-810: Kao Co. product) and 34 parts of water. After pulling up, it was dried at 20 ° C. for 3 minutes and the coagulant was attached to the glove mold. Next, the glove mold to which the coagulant was attached was dipped in the dip molding compound solution for 6 minutes, pulled up, and dried at 20 ° C. for 3 minutes. Then, the glove mold was immersed in warm water at 35 ° C. for 6 minutes, pulled up, and then heat-treated at 80 ° C. for 20 minutes and subsequently at 130 ° C. for 20 minutes to obtain a solid film on the surface of the glove mold. Finally, the solid film was peeled from the glove mold to obtain a glove-shaped dip-molded product. The evaluation results of these dip-formed products are shown in Tables 1 and 2.

[0034]

[Table 1]

[0035]

[Table 2]

From Tables 1 and 2, the dip-molded product obtained from the latex (Experiment No. 6) in which the amount of the ethylenically unsaturated nitrile monomer used was less than 9% by weight of the monomer mixture had an oil resistance. Poor, the tensile strength and tear strength were low, and conversely, the dip-molded product obtained from the latex (Experiment No. 5) exceeding 50% by weight of the monomer mixture had a hard hand. The dip-molded product obtained from the latex (Experiment No. 8) in which the amount of the ethylenically unsaturated acid monomer used is less than 0.1% by weight of the monomer mixture has low tensile strength, and conversely the monomer is used. It can be seen that the dip-molded product obtained from the latex (Experiment No. 7) which exceeds 20% by weight of the mixture has a hard texture and a low tear strength. MEK
Latex whose insoluble content exceeds 50% by weight (Experiment No. 1
It can be seen that the dip-formed product obtained from 9) has a hard texture. Molecular weight is 500,000
The dip-molded product obtained from the latex above (Experiment No. 18) has a hard texture of the dip-molded product, and conversely the dip-molded product obtained from the latex below 50,000 (Experiment No. 17) is the dip-molded product. It can be seen that the tensile strength of is low. Also, conventional natural rubber latex (Experiment No. 9) or vinyl chloride sol (Experiment No. 10)
It can be seen that the dip-molded product obtained from above has poor oil resistance and low tensile strength.

On the other hand, it can be seen that the dip-molded product obtained by dip-molding the latex of the present invention has excellent oil resistance, high mechanical strength such as tensile strength and tear strength, and soft texture.

Claims (2)

[Claims] 1. A conjugated diene monomer of 30 to 90% by weight, an ethylenically unsaturated nitrile monomer of 9 to 50% by weight, an ethylenically unsaturated acid monomer of 0.1 to 20% by weight, and a single amount thereof. Other ethylenically unsaturated monomers copolymerizable with the body 0
A latex of a copolymer obtained by polymerizing a monomer mixture of 20 to 20% by weight, wherein the polystyrene-reduced weight average molecular weight of the copolymer (a) is 50,000 to 500,
And the content of the (b) copolymer insoluble in methyl ethyl ketone is 50% by weight or less, a latex for dip molding. 2. A dip-molded product obtained by dip-molding the latex for dip-molding according to claim 1.