JP2003165870A - Composition for dip-molding, dip-molded product and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for dip-molding suitable as a raw material for a dip-molded product having few pinholes, and further having excellent persistence of feeling and stuck state, and to provide the dip-molded product and a method for efficiently producing the molded product. <P>SOLUTION: This composition for the dip-molding contains a conjugate dienic rubber latex obtained by copolymerizing an ethylenically unsaturated acid monomer. The content of methyl ethyl ketone-insoluble components in the copolymer constituting the conjugate dienic rubber latex at latex pH 10 is ≥50 wt.%, and the pH of the composition for the dip-molding is ≥8.5. The composition for the dip-molding is substantially free from a sulfur-containing vulcanizing agent, a vulcanization accelerator for the vulcanizing agent, and zinc oxide. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition for dip molding, a dip molded article and a method for producing the same, and more specifically, as a raw material for a dip molded article having very few pinholes and excellent in texture and adhesion. The present invention relates to a suitable dip-molding composition, a dip-molded article, and a production method for efficiently producing the molded article.

[0002]

2. Description of the Related Art Rubber gloves are widely used for various purposes such as household chores, food industry and electronic parts manufacturing, and medical (especially surgery). Rubber gloves do not have pinholes, the gloves are easy to stretch with a small force according to the movement of the fingers (feeling good) so that the hand does not get tired even if it is worn for a long time. In addition, even if the gloves are deformed, there is little slack or wrinkling, and it is required that the close contact state be maintained (the close contact state is good). BACKGROUND ART Conventionally, rubber gloves obtained by dip-molding natural rubber latex have been widely used. However, a glove made of natural rubber latex may cause an allergy depending on the user due to a protein present in a small amount in the rubber component, and therefore a synthetic rubber latex without such a concern, for example, acrylonitrile-butadiene copolymer, is used. Gloves made of coalesced latex have been proposed.

For example, in US Pat. No. 5,014,362, a carboxy-modified nitrile-butadiene rubber, a small amount of zinc oxide, sulfur and a vulcanization accelerator are dip-molded and stretched 100% immediately after stretching. Disclosed is a glove having a characteristic that the ratio of stress (stress retention rate) immediately after stretching 6 minutes after the stretching is almost zero. However, although such gloves are excellent in texture, they are inferior in the durability of the adhered state.

Further, International Publication WO97 / 48765 discloses a glove which does not contain zinc oxide and is dip-molded from a carboxy-modified acrylonitrile-butadiene copolymer latex, ammonium casein, sulfur and a vulcanization accelerator. ing. Such gloves do not have sufficient durability in terms of texture and close contact.

Further, in International Publication WO 00/21451, dip molding is carried out from an acrylonitrile-butadiene copolymer latex containing a specific amount of a carboxyl group, a very small amount of zinc oxide, sulfur and a vulcanization accelerator,
A glove in which the stress retention of the dip-molded product is in the range of 50 to 70% is disclosed. Such gloves have excellent durability in a close contact state, but may have poor texture.

Further, in any of the above gloves,
Since pinholes are likely to occur, there is a problem that many defective products must be discarded.

On the other hand, in the manufacture of dip molded products,
Usually, in order to dip-mold a dip-molding composition containing sulfur and to vulcanize the dip-molding layer formed on the surface of the dip-molding die with sulfur, the dip-molding layer is added in an amount of 100 to 1: 1.
A vulcanization step of heat-treating at a temperature of 30 ° C. for 30 minutes to 1 hour is performed. Since a large amount of heat energy is required to perform such heat treatment, a more energy efficient manufacturing method is required.

[0008]

In view of the above circumstances, an object of the present invention is to provide a dip-molding composition suitable for use as a raw material for a dip-molded product, which has extremely few pinholes and is excellent in texture and durability of the adhered state, and a dip. It is to provide a molded product and a manufacturing method for efficiently manufacturing the molded product.

[0009]

[Means for Solving the Problems] As a result of intensive investigations aimed at achieving the above object, the inventors of the present invention have found that the copolymerization of a conjugated diene rubber latex obtained by copolymerizing an ethylenically unsaturated acid monomer By increasing the methyl ethyl ketone insoluble content of the coalescence and further controlling the pH of the dip molding composition containing it, it is possible to perform high-temperature heat treatment without adding normally used sulfur or vulcanization accelerators. However, the inventors have found that a dip-molded article exhibiting sufficient performance can be obtained, and based on this finding, the present invention has been completed.

Thus, according to the present invention, there is provided a dip molding composition containing a conjugated diene rubber latex obtained by copolymerizing an ethylenically unsaturated acid monomer, wherein the latex pH is
The copolymer constituting the conjugated diene rubber latex in 10 has a methyl ethyl ketone insoluble content of 50% by weight or more, and the pH of the dip molding composition is 8.5 or more,
Further, there is provided a dip molding composition, which is substantially free of a sulfur-containing vulcanizing agent, a vulcanization accelerator for the vulcanizing agent, and zinc oxide.

Further, according to the present invention, there is provided a dip molded article molded from a conjugated diene rubber latex obtained by copolymerizing an ethylenically unsaturated acid monomer, wherein the dip molded article is a water-soluble polyvalent metal salt. Is cross-linked with a sulfur-containing vulcanizing agent, a vulcanization accelerator for the vulcanizing agent, and zinc oxide, and the stress retention rate is 45%.
There is provided a dip-molded product characterized by being at least%.

Further, according to the present invention, after a latex coagulant comprising a water-soluble polyvalent metal salt is adhered to the dip molding die, the die is immersed in the dip molding composition described above to form a mold surface. There is provided a method for producing a dip-molded article, which comprises forming a dip-molded layer on the substrate, then drying the dip-molded layer and then detaching from the mold.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The conjugated diene rubber latex used in the present invention is obtained by copolymerizing an ethylenically unsaturated acid monomer, and the methyl ethyl ketone insoluble component (of the copolymer constituting the conjugated diene rubber latex at latex pH 10 ( Hereinafter, it may be abbreviated as "MEK insoluble matter") is 50% by weight or more.

The conjugated diene rubber latex is a copolymer latex obtained by polymerizing a monomer mixture containing a conjugated diene and an ethylenically unsaturated acid monomer as essential components, preferably a conjugated diene monomer. From 30 to 90% by weight, from 0.1 to 20% by weight of ethylenically unsaturated acid monomer and from 0 to 69.9% by weight of other ethylenically unsaturated monomer copolymerizable with these monomers It is a copolymer latex obtained by polymerizing the following monomer mixture. (Hereinafter, it may be simply referred to as "copolymer latex".)

The conjugated diene monomer is not particularly limited and, for example, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3. -Pentadiene, chloroprene, etc. can be mentioned. These conjugated diene monomers can be used alone or in combination of two or more, and 1,3-butadiene or isoprene is preferably used. The amount of the conjugated diene monomer used is preferably 30 to 90% by weight, more preferably 40 to 85% by weight, based on the monomer mixture.
%, Particularly preferably 50-80% by weight. If this amount is too small, the texture tends to be poor, and conversely, if it is too large, the shape retention as a glove cannot be obtained and the tensile strength tends to decrease.

The ethylenically unsaturated acid monomer 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, and examples thereof include acrylic acid. Ethylenically unsaturated monocarboxylic acid monomers such as methacrylic acid; Ethylenically unsaturated polycarboxylic acid monomers such as itaconic acid, maleic acid and fumaric acid; Ethylenically unsaturated monocarboxylic acid monomers such as maleic anhydride and citraconic acid Saturated polycarboxylic acid anhydrides; Ethylenically unsaturated sulfonic acid monomers such as styrene sulfonic acid; Ethylenically unsaturated polycarboxylic acid moieties such as monobutyl fumarate, monobutyl maleate, mono-2-hydroxypropyl maleate Ester monomers; 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. Of these ethylenically unsaturated acid monomers,
Ethylenically unsaturated carboxylic acids are preferable, ethylenically unsaturated monocarboxylic acids are more preferable, and methacrylic acid is particularly preferable.

The amount of the ethylenically unsaturated acid monomer used is preferably 0.1 to 20% by weight, more preferably 1 to 15% by weight, particularly preferably 2 based on the monomer mixture.
~ 6% by weight. If this amount is too small, the tensile strength is too low to obtain a satisfactory dip-molded product, and if it is too large, the texture tends to be poor.

Examples of the other ethylenically unsaturated monomer copolymerizable with the conjugated diene monomer and the ethylenically unsaturated acid monomer include acrylonitrile, methacrylonitrile, fumaronitrile, α-chloroacrylonitrile, α An ethylenically unsaturated nitrile monomer such as cyanoethylacrylonitrile; styrene, alkylstyrene,
Vinyl aromatic monomers such as vinylnaphthalene; fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether; (meth) acrylamide, N-methylol (meth)
Ethylenically unsaturated amide monomers such as acrylamide, N, N-dimethylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide; methyl (meth) acrylate, (meth) Ethyl acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, dibutyl maleate,
Dibutyl fumarate, diethyl maleate, methoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, methoxyethoxyethyl (meth) acrylate,
Cyanomethyl (meth) acrylate, 2-cyanoethyl (meth) acrylate, 1-cyanopropyl (meth) acrylate, 2-ethyl-6-cyanohexyl (meth) acrylate, (meth) acrylic acid-3 Ethylenically unsaturated carboxylic acid ester monomers such as cyanopropyl, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate; divinylbenzene, polyethylene Examples thereof include crosslinkable monomers such as glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and pentaerythritol (meth) acrylate. Among these, ethylenically unsaturated nitrile monomer is preferable, and acrylonitrile is more preferably used. These ethylenically unsaturated monomers may be used alone or in combination of two or more.

The amount of the ethylenically unsaturated monomer used is preferably 0 to 69.9% by weight, more preferably 0 to 59% by weight, particularly preferably 1 based on the monomer mixture.
It is 4 to 48% by weight. If this amount is too large, the texture tends to be poor.

The monomer mixture for producing the conjugated diene rubber latex is particularly preferably composed of 1,3-butadiene, acrylonitrile and methacrylic acid, and the composition thereof is 40 to 79% by weight, respectively. Two
It is preferably in the range of 0 to 45% by weight and 1 to 15% by weight, and more preferably in the range of 54 to 73% by weight, 25 to 40% by weight and 2 to 6% by weight.

The content of the methyl ethyl ketone insoluble matter in the copolymer constituting the conjugated diene rubber latex at latex pH 10 is 50% by weight or more, preferably 65-9.
It is 5% by weight, more preferably 75 to 90% by weight. M
If the EK insoluble content is too small, the durability of the adhered state will be poor.

The degree of swelling of methyl ethyl ketone (hereinafter sometimes abbreviated as MEK swelling degree) of the copolymer constituting the conjugated diene rubber latex at latex pH 10 is preferably 5 to 30, more preferably 10.
The range is 25. When the MEK swelling degree is in this range,
Excellent balance between texture and durability of close contact.

The MEK swelling degree is measured as follows.
A 1 mm-thick dry film of a copolymer latex adjusted to have a latex pH of 10 is prepared. A test piece cut out into a disk shape with a diameter of 2 cm (R1) of this dry film was prepared.
After soaking in 100 ml of methyl ethyl ketone for 48 hours,
The diameter (R2) of the swollen film was measured. R2 to R
The value calculated by squaring the value divided by 1 is the MEK swelling degree.

The conjugated diene rubber latex used in the present invention is usually produced by an emulsion polymerization method.

Examples of the emulsifier include nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester; myristic acid, palmitic acid, oleic acid, and linolene. Anionic emulsifiers such as salts of fatty acids such as acids, alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, higher alcohol sulfate ester salts, alkyl sulfosuccinates; cations such as alkyl trimethyl ammonium chloride, dialkyl ammonium chloride, benzyl ammonium chloride Emulsifier; α, β-unsaturated carboxylic acid sulfoester, α, β-unsaturated carboxylic acid sulfate ester, sulfoalkyl , And the like copolymerizable emulsifiers such as reel ether. Among them, anionic emulsifiers are preferably used. These emulsifiers can be used alone or in combination of two or more kinds. The amount of the emulsifier used is about 1 to 10 parts by weight, and more preferably 2 to 6 parts by weight, based on 100 parts by weight of the monomer mixture.

Examples of the polymerization initiator include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate and hydrogen peroxide; diisopropylbenzene hydroperoxide, cumene hydroperoxide and t-. Butyl hydroperoxide,
1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, di-α-cumyl peroxide, acetyl peroxide Examples thereof include organic peroxides such as isobutyryl peroxide and benzoyl peroxide; and azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile and methyl azobisisobutyrate. Among them, the use of an inorganic peroxide is preferable because the latex can be stably produced. These polymerization initiators can be used alone or in combination of two or more kinds. The amount of the polymerization initiator used varies slightly depending on the type, but the monomer mixture 1
It is about 0.1 to 1 part by weight with respect to 00 parts by weight.

Further, the peroxide can be used as a redox type polymerization initiator in combination with a reducing agent. Examples of the reducing agent 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; an amine compound such as dimethylaniline; Can be mentioned. These reducing agents can be used alone or in combination of two or more. The amount of the reducing agent used varies slightly depending on the kind of the reducing agent, but is about 0.03 to 10 parts by weight with respect to 1 part by weight of the peroxide.

In carrying out emulsion polymerization, a molecular weight modifier may be used in order to adjust the methyl ethyl ketone insoluble content of the copolymer. Examples of the molecular weight modifier include n
Examples thereof include mercaptans such as -butyl mercaptan and t-dodecyl mercaptan, sulfides such as tetraethyl thiuram sulfide, dibentamethylene thiuram hexasulfide, α-methylstyrene dimer, and carbon tetrachloride. Among them, mercaptans are preferable, and t-dodecyl mercaptan is more preferable. These can be used alone or in combination of two or more.
The amount of the molecular weight modifier used may be appropriately determined so that the methyl ethyl ketone insoluble content of the copolymer falls within a desired range, but is preferably 0.5 parts by weight or less relative to 100 parts by weight of the monomer mixture, It is more preferably 0.1 to 0.4 parts by weight.

The amount of water used for emulsion polymerization is about 80 to 600 parts by weight, preferably 100 to 200 parts by weight, based on 100 parts by weight of the monomer mixture.

Further, if necessary, a polymerization auxiliary material such as a particle size adjusting agent, a chelating agent and an oxygen scavenger can be used.

The method of adding the monomer mixture is not particularly limited, and a method of charging the monomer mixture into the polymerization reactor all at once,
Any one of a method of continuously supplying the monomer mixture to the polymerization reactor, a method of charging a part of the monomer mixture to the polymerization reactor and continuously supplying the remaining monomer to the polymerization reactor, etc. May be adopted.

The polymerization temperature for emulsion polymerization is usually from 0 to
95 ° C. In particular, the first half of the polymerization reaction (polymerization conversion rate 0 to 5
0% by weight) at 30 to 50 ° C. and the latter half of the polymerization reaction (polymerization conversion rate exceeds 70% by weight until the polymerization reaction is stopped) at 60 to 9
Polymerization at a temperature of 0 ° C. to adjust the methyl ethyl ketone insoluble content of the copolymer to a predetermined amount is preferable from the viewpoint of obtaining a dip-molded product having an excellent balance of texture and durability of the adhered state. The polymerization time is about 5 to 40 hours, and the polymerization conversion rate is preferably 90% by weight or more, more preferably 95% by weight or more.

The particle size of the copolymer latex obtained by emulsion polymerization is preferably 60 to 300 nm, more preferably 80, as the number average particle size measured by a transmission electron microscope.
~ 150 nm. The particle size can be adjusted to a desired value by adjusting the amounts of the emulsifier and the polymerization initiator used.

The copolymer latex is emulsion-polymerized to a predetermined polymerization conversion rate, and if desired, a polymerization terminator is added to stop the reaction, and further the remaining monomer is removed if desired to obtain a predetermined solid content concentration. And the latex pH.

The dip molding composition of the present invention contains the above conjugated diene rubber latex, and the pH of the dip molding composition is 8.5 or more, preferably 9.5 to 13, and more preferably 10.5. It is characterized in that it is substantially up to 12 and contains substantially no sulfur-containing vulcanizing agent, vulcanization accelerator for the vulcanizing agent, or zinc oxide. If the pH of the dip-forming composition is less than 8.5, the strength will be too low to obtain a satisfactory dip-formed product, and it will be considerably difficult to adjust the pH to more than 13.

In order to adjust the pH of the dip molding composition of the present invention, a basic substance is usually added. Examples of the basic substance include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal hydroxides such as sodium hydrogen carbonate. Hydrogen carbonate; ammonia; organic amine compounds such as trimethylammonium and triethanolamine. Among them, alkali metal hydroxides and / or ammonia are preferable, alkali metal hydroxides are more preferable, and potassium hydroxide is particularly preferable. These basic substances are usually added in the form of a solution having a concentration of 1 to 40% by weight, preferably 2 to 15% by weight, preferably an aqueous solution, in order to prevent generation of aggregates during addition.

As a method for adjusting the pH of the dip molding composition, the pH of the conjugated diene rubber latex is adjusted in advance, or the pH is adjusted after mixing the conjugated diene rubber latex with other compounding agents as desired. However, the method is not particularly limited as long as the pH of the dip-forming composition finally falls within a desired range.

In the present invention, the sulfur-containing vulcanizing agent is a substance capable of cross-linking the polymer chains of the conjugated diene rubber in a network form, and sulfur is a representative thereof. Sulfur-containing vulcanizing agents are roughly classified into inorganic vulcanizing agents and organic vulcanizing agents. Specific examples of the former include sulfur (powdered sulfur, sulfur white, deoxidized sulfur, precipitated sulfur, colloidal sulfur, high Molecular sulfur, insoluble sulfur) and sulfur monochloride, and specific examples of the latter include organic vulcanizing agents capable of releasing active sulfur by thermal dissociation of morpholine disulfide, alkylphenol disulfide and the like. Specific examples of other organic sulfur-containing vulcanizing agents include
"Rubber Industry Handbook 4th Edition" edited by Japan Rubber Association
(Published by Japan Rubber Association, January 1994) III Compounding chemicals
1. It is described in Vulcanizing agent.

The presence of the sulfur-containing vulcanizing agent increases the number of pinholes in the dip-molded product. It is particularly preferable that the sulfur-containing vulcanizing agent is “substantially free”, but it is particularly preferable that the sulfur-containing vulcanizing agent is not included at all, for example, with respect to 100 parts by weight of the solid content of the conjugated diene rubber latex. It is preferably 0.4 parts by weight or less, more preferably 0.2 parts by weight or less, still more preferably 0.1 parts by weight or less.

In the present invention, the vulcanization accelerator means to accelerate the vulcanization reaction in the presence of a sulfur-containing vulcanizing agent to shorten the vulcanization time, lower the vulcanization temperature, or to perform the sulfur-containing vulcanization. A substance that has the effect of reducing the amount of the drug. Specific examples of vulcanization accelerators include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole zinc, thiourea vulcanization accelerators such as diphenylthiourea, guanidine vulcanization accelerators such as diphenylguanidine, hexamethylenetetramine, etc. And aldehyde / ammonia and aldehyde / amine vulcanization accelerators. Specific examples of other vulcanization accelerators are described in “Rubber Industry Handbook 4th Edition” edited by Japan Rubber Association (1994).
Published by The Japan Rubber Association in January, 2013) III Chemicals blended 3. It is described in Vulcanization accelerator.

The presence of the vulcanization accelerator for the vulcanizing agent increases the number of pinholes in the dip-molded article. It is particularly preferable that the vulcanization accelerator for the vulcanizing agent is "substantially free", but it is preferable that the vulcanization accelerator is not contained at all, but the range does not impair the object of the present invention, for example, the solid content of the conjugated diene rubber latex is 100.
It is preferably 0.4 parts by weight or less, more preferably 0.2 parts by weight or less, still more preferably 0.1 parts by weight or less, based on parts by weight.

The presence of zinc oxide increases the number of pinholes in the dip molded product. The phrase "substantially free of zinc oxide" is particularly preferred to include no zinc oxide at all, but is preferably 0 per 100 parts by weight of the solid content of the conjugated diene rubber latex, as long as the object of the present invention is not impaired. 0.7 parts by weight or less, more preferably 0.3 parts by weight or less,
More preferably, it is 0.1 part by weight or less.

The total solid content concentration in the dip-forming composition of the present invention is usually 5 to 50% by weight, preferably 10
˜45% by weight, more preferably 20 to 40% by weight. If this concentration is too low, it becomes difficult to obtain a dip-molded article having a desired thickness, and if it is too high, the viscosity of the dip-molding composition becomes high and handling becomes difficult, and Thickness unevenness is likely to occur.

The dip-molding composition of the present invention contains a commonly used anti-aging agent, dispersant, thickener, pigment, filler, softening agent, etc. within a range not impairing the object of the present invention. May be. Further, other latex such as natural rubber latex and isoprene rubber latex can be used in combination as long as the object of the present invention is not impaired.

The dip molding composition of the present invention does not need to undergo the aging step which is usually carried out in the conventional dip molding composition. Even if this aging is not performed, a dip-molded product having sufficient strength can be obtained, so that the production of the dip-molded product is simple.

The dip-molded article of the present invention is formed by forming a dip-molding layer on the surface of the dip-molding die with a latex coagulant comprising a water-soluble polyvalent metal salt, then drying the dip-molding layer, and then detaching from the die. Obtained. The dip molding layer is prepared by immersing the dip molding die in a latex coagulant liquid consisting of a water-soluble polyvalent metal salt to adhere the latex coagulant to the surface of the die, and then applying the die to the dip molding composition of the present invention. Anode coagulation dipping method of immersing in a product or dipping mold is dipped in the dip molding composition of the present invention to form a dip molding composition film on the mold surface, and then a water-soluble polyvalent metal salt is used. It can be formed by a Teague coagulation dipping method in which it is dipped in a latex coagulant liquid. Both methods can be repeated or alternately repeated to form a dip molding layer having a large film thickness. The anode coagulation dipping method is preferable in that a dip-molded product with less thickness unevenness can be obtained.

The water-soluble polyvalent metal salt used in the present invention is a salt of a metal of Groups 2, 12 and 13 of the Periodic Table,
The solubility in 100 parts by weight of water at 25 ° C. is 5 parts by weight or more, preferably 20 parts by weight or more. This water-soluble polyvalent metal salt has a function of reducing the stability of the latex particles dispersed in the aqueous phase and coagulating the latex particles, and thus is also referred to as a latex coagulant.

Specific examples of the water-soluble polyvalent metal salt include halides such as barium chloride, calcium chloride, magnesium chloride, zinc chloride and aluminum chloride; nitrates such as barium nitrate, calcium nitrate and zinc nitrate; barium acetate and acetic acid. Examples thereof include acetates such as calcium and zinc acetate; sulfates such as calcium sulfate, magnesium sulfate and aluminum sulfate. Of these, calcium chloride and calcium nitrate are preferable. These water-soluble polyvalent metal salts are preferably used in the state of an aqueous solution. The concentration in the case of an aqueous solution varies depending on the kind of the water-soluble polyvalent metal salt, but is usually 5 to 70% by weight, preferably 20 to 5%.
It is 0% by weight. The temperature of the aqueous solution used is usually 0
~ 90 ° C, preferably 30-70 ° C.

The temperature of the dip molding die and the temperature of the dip molding composition during dip molding are usually room temperature to 90 ° C., preferably 40 to 80 ° C. In the anode coagulation dipping method, the time for immersing the dip molding die in the latex coagulant liquid and the time for immersing the dip molding die having the latex coagulant adhered in the dip molding composition are the dip molding layer having a desired thickness. It may be adjusted appropriately so that

Before being dried, the obtained dip-molded layer is immersed in water, preferably warm water at 40 to 70 ° C., for about 2 to 60 minutes to dissolve water-soluble impurities (for example, excess emulsifier and water-soluble polyvalent metal). Salt etc.) may be removed. This operation may be performed after drying the dip molding layer, but it is preferable to perform this operation before drying because the water-soluble impurities can be removed more efficiently. By performing this operation, the tensile strength of the dip-molded product is improved.

The dip-molded layer thus obtained has a high water content and must be dried. Drying
The water content of the dip molding layer is preferably 5% by weight or less, more preferably 2% by weight or less. As a method of drying, a method of external heating with infrared rays or hot air or internal heating with high frequency can be adopted. Of these, drying with hot air is preferable. The drying temperature is usually
The temperature is 60 to 95 ° C., preferably 70 to 85 ° C., and the drying time is usually about 10 to 120 minutes.

Since the dip-molded layer has sufficient strength by drying, the dip-molded article can be obtained by detaching it from the dip-molding die.
As the desorption method, a method of peeling by hand from the molding die or peeling by water pressure or compressed air pressure is adopted.

Before desorption, a heat treatment may be further carried out at a temperature of 100 to 150 ° C. for 10 to 120 minutes, but the dip molding composition of the present invention has sufficient strength only by the above-mentioned drying. A dip molded product is obtained. After desorption, if desired, at a temperature of 60 to 120 ° C., 1
You may heat-process for 0 to 120 minutes.

The dip-molded article of the present invention is a dip-molded article molded from a conjugated diene rubber latex obtained by copolymerizing an ethylenically unsaturated acid monomer, and the dip-molded article is a water-soluble polyvalent metal salt. Is cross-linked, and is molded without substantially using any of the sulfur-containing vulcanizing agent, the vulcanization accelerator for the vulcanizing agent, and zinc oxide, and the stress retention is 45% or more.

The stress retention rate is measured as follows.
The tensile stress (Md0) immediately after the elongation rate was set to 100% and the tensile stress (Md6) after the elongation rate was kept at 100% for 6 minutes were measured using a Tensilon universal tester, and
The stress retention was determined by dividing d6 by Md0.

The stress retention of the dip-molded product of the present invention is
It is 45% or more, preferably 55 to 80%, more preferably 60 to 75%. If the stress retention rate is too low, the durability of the adhered state will be poor.

The tensile stress of the dip-molded product at 300% elongation is preferably less than 3.5 MPa, more preferably less than 3.0 MPa, particularly preferably less than 2.5 MPa. If this stress is too high, the texture will be poor.

The tensile strength of the dip-molded product is preferably 10 MPa or more, more preferably 15 MPa or more, particularly preferably 20 MPa or more.

The dip-molded article of the present invention may be provided with a surface treatment layer on the inner and / or outer surface thereof for the purpose of improving the slipperiness of the hand when wearing gloves.

The dip-molded product of the present invention has a thickness of about 0.
1 to about 3 mm can be manufactured, especially the thickness is about 0.1
It can be suitably used for thin things of about 0.3 mm. Specifically, medical supplies such as baby bottle nipples, droppers, conduits, water pillows; toys and exercise equipment such as balloons, dolls and balls; industrial products such as pressure molding bags and gas storage bags; surgery, Household, agricultural, fishing and industrial gloves; such as finger cots. In particular, it is suitable for thin surgical gloves.

[0061]

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

[Physical property evaluation method] (p of copolymer latex and dip molding composition)
H) It measured at 25 degreeC using the pH meter (M12: HORIBA make). (Methyl ethyl ketone insoluble matter of copolymer:%) 5% potassium hydroxide aqueous solution to pH 10 and solid content concentration 30%
The copolymer latex prepared as described above was cast on a glass plate with a frame and allowed to stand at a temperature of 23 ° C. and a relative humidity of 50% for 48 hours to obtain a dry film having a thickness of 1 mm. This dry film 0.
3 g was put into a wire mesh of 80 mesh and immersed in 100 ml of methyl ethyl ketone at 20 ° C. for 48 hours. Next, the film remaining in the cage of the wire net was dried under reduced pressure at 100 ° C., and the residual rate was calculated to obtain the methyl ethyl ketone insoluble matter. (Methyl ethyl ketone swelling degree of copolymer) The above-mentioned dried film was cut out into a disc shape having a diameter of 2 cm (R1). This test piece was immersed in 100 ml of methyl ethyl ketone for 48 hours, and then the diameter (R2) of the swollen film was measured. The value calculated by squaring the value obtained by dividing R2 by R1 was defined as the degree of swelling of methyl ethyl ketone.

(Preparation of Test Piece for Evaluation of Physical Properties of Dip Molded Article) A rubber glove-shaped dip molded article was punched with a dumbbell (Die-C) according to ASTM D412 to obtain a test piece. (Stress at 300% elongation: MPa) The test piece was pulled with a Tensilon universal testing machine (RTC-1225A: manufactured by Orientec Co., Ltd.) at a pulling speed of 500 mm / min, and the tensile stress at an elongation of 300% was measured. It was measured. The smaller this value, the better the texture. (Tensile strength: MPa) The test piece was pulled with a Tensilon universal testing machine at a pulling speed of 500 mm / min, and the tensile strength immediately before breaking was measured. (Elongation at break:%) The test piece was pulled by a Tensilon universal testing machine at a pulling speed of 500 mm / min, and the elongation immediately before breaking was measured.

(Stress retention rate:%) Tensileon universal testing machine was used for tensile stress (Md0) immediately after the elongation rate was set to 100% and tensile stress (Md6) after the elongation rate was kept at 100% for 6 minutes. ) Was measured and Md6 was divided by Md0 to obtain the stress retention rate. The higher the stress retention rate, the better the durability of the adhered state.

(Number of Pinholes Generated) The rubber gloves were filled with water, and after 30 minutes, one pinhole was defined as the location where the internal water leaked to the outer surface of the glove, and the number of pinholes generated was measured. . In addition, 1 rubber glove for 1 sample
00 sheets were prepared and the total number of pinholes generated in all rubber gloves was measured.

(Manufacturing Example 1)
28 parts of acrylonitrile, 68 parts of 1,3-butadiene,
Methacrylic acid 4 parts, t-dodecyl mercaptan (TD
M) 0.2 part, soft water 132 parts, sodium dodecylbenzenesulfonate 3.0 parts, β-naphthalenesulfonic acid formalin condensate sodium salt 0.5 part, potassium persulfate 0.3 part and ethylenediaminetetraacetic acid sodium salt 0 ．
The polymerization temperature was maintained at 37 ° C. to start polymerization. When the polymerization conversion rate reached 80%, the polymerization temperature was raised to 70 ° C., and then the reaction was continued while maintaining 70 ° C. until the polymerization conversion rate reached 97%. Then, 0.1 part of sodium dimethyldithiocarbamate was added as a polymerization terminator to stop the polymerization reaction. After removing unreacted monomers from the obtained copolymer latex, the pH and the solid content concentration of the copolymer latex were adjusted to obtain a copolymer latex A having a solid content concentration of 40% and a pH of 8. A part of the copolymer latex A was taken out, and the methyl ethyl ketone insoluble content and the methyl ethyl ketone swelling degree of the copolymer were measured. The results are shown in Table 1.

(Production Examples 2 to 4) A copolymer latex was produced in the same manner as in Production Example 1 except that the monomer composition and TDM amount shown in Table 1 were changed.
~ D was obtained. Table 1 shows the methyl ethyl ketone insoluble content and the methyl ethyl ketone swelling degree of each copolymer.

(Preparation Example 5) A copolymer latex was prepared in the same manner as in Preparation Example 1 except that the TDM amount shown in Table 1 was changed and the polymerization was conducted at a polymerization conversion rate of 80% without raising the temperature to 70 ° C. A copolymer latex E was obtained by the production. Table 1 shows the methyl ethyl ketone insoluble matter and the methyl ethyl ketone swelling degree of this copolymer.

[0069]

[Table 1]

Example 1 Copolymer latex A was added at 5%
Adjust the pH to 10 with aqueous potassium hydroxide and adjust the solids concentration to 30.
% To prepare a dip molding composition. 20 parts of calcium nitrate as a water-soluble polyvalent metal salt, a nonionic emulsifier (Emulgen-810: product of Kao Corporation) 0.0
The latex coagulant aqueous solution obtained by mixing 5 parts and 80 parts of water was dipped in a glove mold for dip molding heated at 60 ° C for 10 seconds, then pulled up and dried at 60 ° C for 10 minutes to be water-soluble. A polyvalent metal salt was attached to the mold surface. Next, the glove mold to which the coagulant was attached was dipped in the above dip molding composition for 15 seconds and then pulled up to form a dip molding layer on the surface of the glove mold. Add this to distilled water at 40 ℃ 5
After dipping for a minute to remove water-soluble impurities, preliminary drying was carried out at 20 ° C. for 5 minutes and further drying at 80 ° C. for 20 minutes to obtain a solid film on the surface of the glove mold. Finally, the solid film product was peeled off from the glove mold to obtain a glove-shaped dip-molded product having a thickness of 0.1 to 0.2 mm (the same applies to the following). Table 2 shows the evaluation results of this dip-formed product.

(Example 2) pH of dip molding composition
Was carried out in the same manner as in Example 1 except that pH was adjusted to 11 with a 5% aqueous potassium hydroxide solution. The results are shown in Table 2.

(Examples 3 to 5) The same procedure as in Example 2 was carried out except that copolymer latexes B to D were used instead of copolymer latex A, respectively. The results are shown in Table 2.

Comparative Example 1 Zinc dibutylcarbamate 1
Parts, 1 part of sulfur, 1.5 parts of zinc oxide, 0.5 part of 40% sodium salt aqueous solution of β-naphthalenesulfonic acid-formalin condensate, and 4 parts of water are mixed with a ball mill to give a vulcanizing agent dispersion. Obtained. After mixing 8 parts of this vulcanizing agent dispersion with 250 parts of conjugated diene rubber latex E (corresponding to 100 parts of solid content), pH was adjusted with a 5% aqueous potassium hydroxide solution.
What was adjusted to 10.0 and the solid content concentration to 30% was 1
It was aged for days and used as a dip molding composition. Using this dip-forming composition, except that heat vulcanization is performed at 120 ° C. for 25 minutes instead of drying at 80 ° C. for 20 minutes.
The same procedure as in Example 1 was performed. The results are shown in Table 2.

(Comparative Example 2) Zinc dibutylcarbamate 1
Part, 1 part of sulfur, 0.5 part of a 40% β-naphthalenesulfonic acid-formalin condensate sodium salt aqueous solution, and 2.5 parts of water were mixed by a ball mill to obtain a vulcanizing agent dispersion liquid. After mixing 5 parts of this vulcanizing agent dispersion and 250 parts of conjugated diene rubber latex E (corresponding to 100 parts of solid content), the pH was adjusted to 10.0 with a 5% aqueous potassium hydroxide solution.
The thing which adjusted solid content concentration to 30% was aged for 1 day, and this was made into the composition for dip molding. The same procedure as in Comparative Example 1 was carried out except that this dip molding composition was used. The results are shown in Table 2.

Comparative Example 3 1.5 parts of zinc oxide, 0.5 part of a 40% sodium salt aqueous solution of β-naphthalenesulfonic acid-formalin condensate, and 2 parts of water were mixed in a ball mill to prepare a zinc oxide dispersion liquid. Got After mixing 4 parts of this dispersion and 250 parts of conjugated diene rubber latex E (corresponding to 100 parts of solid content), the pH was adjusted to 10.0 and the solid content concentration to 30% with a 5% aqueous potassium hydroxide solution. The composition was aged for 1 day to obtain a dip molding composition.
Comparative Example 1 except that this dip molding composition was used.
I went the same way. The results are shown in Table 2.

Comparative Example 4 Copolymer latex E was added to 5
% Potassium hydroxide aqueous solution to pH 11 and solid content concentration 3
The composition was adjusted to 0% to obtain a dip molding composition. The same procedure as in Example 1 was carried out except that this dip molding composition was used. The results are shown in Table 2.

(Comparative Example 5) Copolymer latex A was prepared to a solid content concentration of 30%, which was used as a dip molding composition. The same procedure as in Example 1 was carried out except that this dip molding composition was used. The results are shown in Table 2. However, when peeling the glove-shaped dip molded product from the glove mold,
Since the dip-molded product extends or breaks, a dip-molded product having a satisfactory glove shape cannot be obtained.

[0078]

[Table 2]

The following can be seen from Table 2. The dip-molded article of Comparative Example 1 containing sulfur, a vulcanization accelerator and zinc oxide was inferior in texture and stress retention and had a large number of pinholes. The dip-molded article of Comparative Example 2 containing sulfur and a vulcanization accelerator has relatively good texture and stress retention, but has a large number of pinholes. The dip-molded article of Comparative Example 3 containing zinc oxide was inferior in texture and stress retention and had a large number of pinholes.

The dip-molded article of Comparative Example 4 obtained by using the copolymer latex E having a methylethylketone-insoluble content lower than the value specified in the present invention has a small number of pinholes and is excellent in texture, but has stress retention. Inferior in rate. The dip-molded product of Comparative Example 5 in which the pH of the dip-molding composition is lower than the value specified in the present invention has a good texture, but the tensile strength is too low to obtain a satisfactory dip-molded product.

In contrast to these comparative examples, all of the dip-molded products of Examples 1 to 5, which are within the range specified by the present invention, have extremely few pinholes and are excellent in texture and stress retention. Further, the dip molding composition of the present invention need not be aged. Furthermore, in the production of a dip-molded product, it is possible to obtain a dip-molded product having sufficient properties only by drying, without adding heat for vulcanization, which has been conventionally required.

[0082]

INDUSTRIAL APPLICABILITY According to the present invention, a dip-molding composition suitable for use as a raw material for a dip-molded product which has extremely few pinholes and is excellent in the texture and the durability of the adhered state, the dip-molded product and the molded product efficiently. A manufacturing method for manufacturing is provided.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F205 AA46J AB03 AB16 AC05                       AH70 GA08 GB01 GC01 GE02                       GE24 GF02 GN30                 4J002 AC021 AC071 AC081 AC091                       GC00 HA07

Claims (3)

[Claims] 1. A dip molding composition comprising a conjugated diene rubber latex obtained by copolymerizing an ethylenically unsaturated acid monomer, wherein methyl ethyl ketone is a copolymer constituting the conjugated diene rubber latex at a latex pH of 10. The insoluble content is 50% by weight or more, the pH of the dip-forming composition is 8.5 or more, and the sulfur-containing vulcanizing agent, the vulcanization accelerator for the vulcanizing agent, and zinc oxide are all substantially A dip molding composition, characterized in that it does not contain 2. A dip-molded article molded from a conjugated diene rubber latex obtained by copolymerizing an ethylenically unsaturated acid monomer, wherein the dip-molded article is crosslinked with a water-soluble polyvalent metal salt, A dip-molded article characterized by being molded substantially without using any of a sulfur-containing vulcanizing agent, a vulcanization accelerator for the vulcanizing agent and zinc oxide, and having a stress retention rate of 45% or more. . 3. A dip molding die having a latex coagulant made of a water-soluble polyvalent metal salt adhered to the dip molding die and then dipped in the dip molding composition according to claim 1 to dip on the surface of the die. A method for producing a dip-molded article, which comprises forming a molding layer, drying the dip-molding layer, and then detaching from the mold.