JP5380839B2 - DIP MOLDING COMPOSITION AND DIP MOLDED ARTICLE - Google Patents

Description

  The present invention relates to a dip-molding composition and a dip-molded product. More specifically, the present invention has good release properties from a mold, sufficient tensile strength and elongation at break, and excellent ethanol resistance. The present invention relates to a dip-molding composition that can provide a dip-molded product, and a dip-molded product obtained by dip-molding the dip-molding composition.

  A molded product obtained by dip molding a composition for dip molding composed of natural rubber latex or synthetic rubber latex is flexible and has sufficient mechanical strength. It is widely used for various industries such as the food industry and electronic component manufacturing industry, and also for medical use.

  Such a rubber glove (dip-molded product) is particularly required to be hard to tear during wearing (a sufficient tensile strength and elongation at break) in order to protect the hand safely. At the same time, many disposable rubber gloves are required to be resistant to ethanol (ethanol resistance) because they are used after first being worn on the hand and then disinfected with ethanol.

  The dip-formed product used for such rubber gloves is usually manufactured by the following method. That is, first, a coagulant such as calcium chloride is attached to the surface of a mold such as a hand or a finger, and the above-described mold is dipped in a dip molding composition containing rubber latex. Subsequently, after raising this and forming the coating film (dip molding layer) on the surface of a shaping | molding die, it shape | molds by vulcanizing (bridge | crosslinking) a dip molding layer by heating. However, rubber gloves (dip-molded products) produced in this way are highly tacky and easily adhere to the mold, so that it is often difficult to remove (release) the mold from the mold. For this reason, it is also required that the mold is easily detached from the mold (having good releasability), that is, it is not in close contact with the mold (low adhesion).

  Conventionally, as such rubber gloves, those obtained by dip molding natural rubber latex have been frequently used. However, gloves made of natural rubber latex may cause allergies depending on the user due to a protein component present in a trace amount in the rubber component. Therefore, synthetic rubber latex gloves that do not have such concerns have been proposed.

  For example, Patent Document 1 discloses a carboxy-modified conjugated diene rubber latex having a glass transition temperature of −50 ° C. or lower, and a glove obtained by dip molding this latex. While the glove described in this document is excellent in flexibility and elongation at break, it has a problem that it is inferior in tensile strength and easily adheres to a mold.

  Patent Document 2 discloses a copolymer latex obtained by emulsion copolymerization of an aromatic vinyl monomer, a conjugated diene monomer and an unsaturated acid monomer, and having a gel content (indicating the level of internal crosslinking) of a specific value or less. , And gloves obtained by dip molding this latex. The purpose of this document is to obtain a glove with excellent tensile strength, but the tensile strength is still insufficient, and there is a problem of poor ethanol resistance and releasability from the mold. .

Furthermore, Patent Document 3 discloses a latex glove characterized by being formed from a carboxylated open chain aliphatic diene / acrylonitrile / (meth) acrylic acid ester terpolymer, and having improved releasability and wearability. It is disclosed. This document aims to improve the slipperiness between the glove surfaces, but on the other hand, there is a problem that the elongation at break is insufficient and the ethanol resistance is inferior.
US Pat. No. 5,910,533 US Pat. No. 6,627,325 Japanese Patent Publication No. 6-70143

  The present invention has been made in view of such a situation, and provides a dip-molded product that has good release properties from a mold, has sufficient tensile strength and elongation at break, and is excellent in ethanol resistance. An object of the present invention is to provide a dip molding composition that can be used. Another object of the present invention is to provide a dip-molded product obtained by dip-molding such a dip-molding composition and having the above characteristics.

  As a result of intensive studies to achieve the above object, the present inventors have found a monomer mixture containing a conjugated diene monomer, an aromatic vinyl monomer, and an ethylenically unsaturated acid monomer. In the dip molding composition having a copolymer latex obtained by copolymerizing the above, the ratio of these monomers is within a predetermined range, and the copolymer constituting the copolymer latex is toluene under predetermined conditions. The inventors have found that the above-described object can be achieved by controlling the toluene insoluble content in the case of being immersed in a specific value or more, and have completed the present invention.

That, dip-forming composition according to the present invention is a conjugated diene monomer from 37 to 55 parts by weight, the aromatic vinyl monomer 42 to 60 parts by weight, ethylenically unsaturated acid monomer 10 parts by weight A dip molding composition having a copolymer latex obtained by copolymerizing 100 parts by weight of a monomer mixture containing
When the copolymer constituting the copolymer latex is immersed in toluene at a temperature of 20 ° C. for 24 hours, the insoluble content of toluene in the copolymer is 100% by weight based on the whole copolymer. 30% by weight or more.

Preferably, the conjugated diene monomer is 1,3-butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene. , 1,3-pentadiene and chloroprene, more preferably 1,3-butadiene and / or isoprene, and still more preferably 1,3-butadiene.
Preferably, the aromatic vinyl monomer is selected from the group consisting of styrene, α-methylstyrene, p-methylstyrene, p-phenylstyrene, p-methoxystyrene, chloromethylstyrene, m-fluorostyrene and vinylnaphthalene. More preferably, styrene.
Preferably, the ethylenically unsaturated acid monomer is an ethylenically unsaturated monocarboxylic acid monomer, ethylenically unsaturated polyvalent carboxylic acid monomer, ethylenically unsaturated polyvalent carboxylic acid anhydride, ethylenic It is at least one selected from the group consisting of unsaturated polycarboxylic acid partial ester monomers and ethylenically unsaturated sulfonic acid monomers, more preferably ethylenically unsaturated monocarboxylic acids, and even more preferably methacrylic acid It is.

The dip molding composition of the present invention preferably further contains a crosslinking agent. The cross-linking agent is more preferably at least one selected from the group consisting of sulfur, organic peroxides, and polyamines, and more preferably sulfur. Moreover, it is preferable that the compounding quantity of the said crosslinking agent is 0.1-3 weight part with respect to 100 weight part of solid content in the composition for dip molding.
The dip molding composition of the present invention preferably further contains a crosslinking accelerator. The amount of the crosslinking accelerator is preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the solid content in the dip molding composition.
The dip molding composition of the present invention preferably further contains zinc oxide. It is preferable that the compounding quantity of the said zinc oxide is 0.3-3 weight part with respect to 100 weight part of solid content in the composition for dip molding.
The dip molding composition of the present invention preferably has a pH of 8.5-12.

  In the dip molding composition of the present invention, preferably, when the dip molding film is formed on the metal plate by immersing the metal plate in the dip molding composition, 180 ° of the dip molding film. The value of the peel test is 4.9 (N / 25 mm) or less.

The dip-molded product according to the present invention is a dip-molded product obtained by dip-molding any of the above dip-molding compositions.
The dip-formed product of the present invention preferably has a tensile strength measured in accordance with ASTM D-412 of 20 MPa or more and a breaking elongation of 600% or more.
The dip-molded product of the present invention preferably has a tensile strength of 16 MPa or more measured at a tensile speed of 500 mm / min after being immersed in ethanol at a temperature of 20 ° C. for 1 hour.

  According to the present invention, the copolymer latex to be contained in the dip molding composition contains a conjugated diene monomer, an aromatic vinyl monomer, and an ethylenically unsaturated acid monomer within the above-described range. The monomer mixture containing the copolymer is copolymerized, and the toluene-insoluble content of the copolymer constituting the copolymer latex is set to the predetermined range. Therefore, it is possible to obtain a dip-molded product that has good releasability from the mold during production, has sufficient tensile strength and elongation at break, and is excellent in ethanol resistance. In particular, it is possible to improve productivity by making the mold release from the mold good. Further, by improving the ethanol resistance, for example, even when a dip-molded product is used for rubber gloves and sterilized with ethanol, tearing of the gloves during use can be effectively prevented.

  Hereinafter, the dip molding composition of the present invention and the dip molded product obtained by crosslinking the dip molding composition of the present invention will be described in detail.

Dip Molding Composition The dip molding composition of the present invention is obtained by copolymerizing a monomer mixture containing a conjugated diene monomer, an aromatic vinyl monomer, and an ethylenically unsaturated acid monomer. The copolymer latex obtained in this way is at least included.

Copolymer latex
Although it does not specifically limit as a conjugated diene monomer A conjugated diene monomer, The C4-C12 compound containing a conjugated diene is preferable. Examples of such a conjugated diene monomer include 1,3-butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-ethyl-1,3. -Butadiene, 1,3-pentadiene, chloroprene and the like. 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 34 to 60 parts by weight, preferably 38 to 55 parts by weight, and more preferably 40 to 52 parts by weight with respect to 100 parts by weight of the total monomers. If the amount is too small, the elongation at break is inferior. On the other hand, if the amount is too large, the releasability from the mold and the tensile strength are inferior.

Examples of aromatic vinyl monomers include styrene, α-methyl styrene, p-methyl styrene, p-phenyl styrene, p-methoxy styrene, chloromethyl styrene, m-fluoro styrene, vinyl naphthalene. Etc. Of these, styrene is particularly preferable. These aromatic vinyl monomers can be used alone or in combination of two or more.
The usage-amount of an aromatic vinyl monomer is 39-65 weight part with respect to 100 weight part of all monomers, Preferably it is 42-60 weight part, More preferably, it is 45-58 weight part. If the amount of the aromatic vinyl monomer is too small, the release property from the mold and the ethanol resistance are inferior, and conversely if too large, the elongation at break is inferior.

The ethylenically unsaturated acid monomer is not particularly limited as long as it is an ethylenically unsaturated monomer containing an acidic group. Examples of the acidic group include a carboxyl group, a sulfonic acid group, and an acid anhydride group.
Specifically, ethylenically unsaturated monocarboxylic acid monomers such as acrylic acid and methacrylic acid; ethylenically unsaturated polycarboxylic acid monomers such as itaconic acid, maleic acid, and fumaric acid; maleic anhydride, anhydrous Ethylenically unsaturated polyvalent carboxylic acid anhydrides such as citraconic acid; ethylenically unsaturated polyvalent carboxylic acid partial ester monomers such as monobutyl fumarate, monobutyl maleate and mono-2-hydroxypropyl maleate; styrene sulfonic acid And the like, and the like. Of these, ethylenically unsaturated carboxylic acid is preferable, ethylenically unsaturated monocarboxylic acid is more preferable, and methacrylic acid is particularly preferable. These ethylenically unsaturated acid monomers can also be used as alkali metal salts or ammonium salts. These ethylenically unsaturated acid monomers can be used alone or in combination of two or more.
The amount of the ethylenically unsaturated acid monomer used is 1 to 10 parts by weight, preferably 1.5 to 8 parts by weight, more preferably 2 to 7 parts by weight, based on 100 parts by weight of the total monomers. . When the amount of the ethylenically unsaturated acid monomer is too small, the tensile strength is inferior. On the other hand, when the amount is too large, the elongation at break is inferior.

Other monomers In addition to the above monomers, the copolymer latex contained in the dip molding composition of the present invention may contain other monomers copolymerizable with these as necessary. Can be used.
Examples of other monomers include fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether; (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethylol (meth) acrylamide, and N-methoxymethyl (meth) acrylamide. Ethylenically unsaturated amide monomers such as N-propoxymethyl (meth) acrylamide; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylate-2-ethylhexyl , Trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, dibutyl maleate, dibutyl fumarate, diethyl maleate, methoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, (meth) Metoki acrylate Ethoxyethyl, (meth) acrylic acid cyanomethyl, (meth) acrylic acid-2-cyanoethyl, (meth) acrylic acid-1-cyanopropyl, (meth) acrylic acid-2-ethyl-6-cyanohexyl, (meth) acrylic Ethylenically unsaturated carboxylic acid ester monomers such as acid-3-cyanopropyl, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate; Ethylenically unsaturated nitrile monomers such as (meth) acrylonitrile; divinylbenzene, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol (meth) acrylate Crosslinkable monomer rate and the like; and the like. These monomers can be used alone or in combination of two or more.
The amount used in the case of using these other monomers is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and further preferably 10 parts by weight or less with respect to 100 parts by weight of the total monomers. . If the amount of the other monomer is too large, the effects of the present invention described above tend to be difficult to obtain.

Method for Producing Copolymer Latex Next, a method for producing the copolymer latex used in the present invention will be described.
The copolymer latex used in the present invention can be produced by emulsion polymerization of a mixture of the above monomers. As the emulsion polymerization method, a conventionally known emulsion polymerization method may be employed. In emulsion polymerization, commonly used polymerization auxiliary materials such as emulsifiers, polymerization initiators, chain transfer agents and the like can be used.

  Although it does not specifically limit as an emulsifier, For example, nonionic emulsifiers, such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester; myristic acid, palmitic acid, oleic acid A salt of a fatty acid such as linolenic acid, an alkylbenzene sulfonate such as sodium dodecylbenzenesulfonate, an anionic emulsifier such as a higher alcohol sulfate, an alkylsulfosuccinate; a sulfoester of α, β-unsaturated carboxylic acid, α , Β-unsaturated carboxylic acid sulfate esters, sulfoalkyl aryl ethers and other copolymerizable emulsifiers. Of these, anionic emulsifiers are preferably used. These emulsifiers can be used alone or in combination of two or more. The amount of the emulsifier used is preferably 0.1 to 10 parts by weight, more preferably 2 to 6 parts by weight with respect to 100 parts by weight of the total monomers.

  The polymerization initiator is not particularly limited, and examples thereof include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, di-α- Organic peroxides such as cumyl peroxide, acetyl peroxide, isobutyryl peroxide, benzoyl peroxide; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, methyl azobisisobutyrate; Can be mentioned. Among these, when an inorganic peroxide is used, a copolymer latex can be stably produced, and a dip-molded product excellent in tensile strength and elongation at break can be obtained. These polymerization initiators can be used alone or in combination of two or more. The usage-amount of a polymerization initiator is 0.01-1 weight part normally with respect to 100 weight part of all the monomers.

  Moreover, the above-mentioned inorganic peroxide initiator and organic peroxide initiator can be used as a redox polymerization initiator in combination with a reducing agent. Such a reducing agent is not particularly limited, but includes compounds containing metal ions in a reduced state such as ferrous sulfate and cuprous naphthenate; sulfonic acid compounds such as sodium methanesulfonate; dimethylaniline and the like. Amine compounds; and the like.

When carrying out emulsion polymerization, it is preferable to use a chain transfer agent. By using a chain transfer agent, it is possible to adjust the toluene insoluble content of the copolymer constituting the copolymer latex.
Examples of chain transfer agents include mercaptans such as n-butyl mercaptan and t-dodecyl mercaptan; sulfides such as tetraethylthiuram sulfide and dipentamethylenethiuram hexasulfide; α-methylstyrene dimer; carbon tetrachloride; Is mentioned. Among these, 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 chain transfer agent used is preferably 0.1 to 1 part by weight, more preferably 0.2 to 0.5 part by weight, based on 100 parts by weight of all monomers.

  The amount of water used for emulsion polymerization is usually about 80 to 600 parts by weight, preferably 100 to 300 parts by weight, based on 100 parts by weight of the total monomers.

  The method of adding each monomer described above is not particularly limited, and a method of mixing each monomer into a monomer mixture and charging this monomer mixture into a polymerization reactor all together, a monomer mixture A method of continuously adding a monomer to a polymerization reactor, a method of charging a part of a monomer into a polymerization reactor, and adding a remaining monomer continuously or divided into a polymerization reactor, etc. It may be adopted.

  In the emulsion polymerization, polymerization auxiliary materials such as a particle size adjusting agent, a chelating agent, an oxygen scavenger, and a dispersing agent can be used as necessary.

  Emulsion polymerization is usually carried out in water using the monomers and polymerization auxiliary materials. Although polymerization temperature is not specifically limited, Preferably it is 5-60 degreeC, More preferably, it is 30-50 degreeC. The polymerization time is about 5 to 30 hours.

  Emulsion polymerization is performed under the above conditions, and when a predetermined polymerization conversion rate is reached, the polymerization reaction is stopped by a method of cooling the polymerization system or a method of adding a polymerization terminator. The polymerization conversion rate when stopping the polymerization reaction is preferably 90% by weight or more, more preferably 94% by weight or more. And after stopping a polymerization reaction, a copolymer latex can be obtained by removing an unreacted monomer as needed and adjusting solid content concentration and pH.

In the present invention, each monomer constituting the copolymer latex to be contained in the dip molding composition is set to the above predetermined amount, and further, toluene of the copolymer constituting the copolymer latex. The insoluble content is set to the following specific range. By adopting such a configuration, it is possible to improve mold release properties and ethanol resistance while maintaining tensile strength and elongation at break.
That is, the toluene insoluble content is 30% by weight or more, preferably 40 to 95% by weight, more preferably 50 to 90% by weight, based on 100% by weight of the entire copolymer constituting the copolymer latex. Range. For example, the insoluble content of toluene is obtained by placing a dry film made of a copolymer latex in a wire mesh cage and immersing it in toluene at a temperature of 20 ° C. for 24 hours, then lifting the basket and drying it. The weight can be measured and calculated from the ratio. The toluene insoluble matter depends on various factors such as polymerization temperature, reaction time, type and amount of polymerization initiator, type and amount of crosslinkable monomer, and type and amount of chain transfer agent. It can select and adjust suitably.

  The number average particle diameter of the copolymer latex is a number average particle diameter measured with a transmission electron microscope, and is preferably 60 to 300 nm, more preferably 80 to 150 nm. In addition, this particle diameter can be adjusted to a desired value by a method of adjusting the usage-amount of an emulsifier and a polymerization initiator.

  If desired, the copolymer latex may further contain auxiliary materials such as an anti-aging agent, an ultraviolet absorber, a preservative, and an antibacterial agent.

Crosslinking agent The dip molding composition of the present invention preferably further contains a crosslinking agent in order to crosslink the copolymer latex.
Although it does not specifically limit as a crosslinking agent, Sulfur, an organic peroxide, a polyamine, etc. are mentioned. Of these, sulfur is preferable.

Examples of sulfur include powdered sulfur, sulfur white, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.
Examples of the organic peroxide include dibenzoyl peroxide, benzoyl (3-methylbenzoyl) peroxide, di (4-methylbenzoyl) peroxide, dilauroyl peroxide, distearoyl peroxide, and di-α-cumyl peroxide. Examples thereof include oxide, 1,1-bis (t-butylperoxy) cyclododecane, succinic acid peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate, and t-butylperoxymaleic acid.
Examples of the polyamine include hexamethylenediamine, triethylenetetramine, and tetraethylenepentamine.

  The amount of the crosslinking agent is preferably 0.1 to 3 parts by weight, more preferably 0.3 to 2.5 parts by weight, based on 100 parts by weight of the solid content (latex solid content) in the dip molding composition. More preferably, it is 0.5 to 2 parts by weight. If the amount of the crosslinking agent is too small, the tensile strength is inferior, and conversely if too large, the elongation at break is inferior.

  When sulfur is used as the crosslinking agent, it is preferable to blend a crosslinking accelerator (vulcanization accelerator) or zinc oxide.

As the crosslinking accelerator (vulcanization accelerator), those usually used in dip molding can be used. For example, diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, diphenyldithiocarbamic acid Dithiocarbamic acids such as benzyldithiocarbamic acid and zinc salts thereof; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2- (2,4-dinitrophenylthio) benzothiazole 2- (N, N-diethylthio-carbylthio) benzothiazole, 2- (2,6-dimethyl-4-morpholinothio) benzothiazole, 2- (4′-morpholino-dithio ) Benzothiazole, 4-morpholinyl-2-benzothiazyl disulfide, 1,3-bis (2-benzothiazyl mercaptomethyl) urea and the like. These can be used alone or in combination of two or more.
The blending amount of the crosslinking accelerator (vulcanization accelerator) is preferably 0.1 to 2 parts by weight, more preferably 0.2 to 1.5 parts by weight, and still more preferably 100 parts by weight of the latex solid content. 0.25 to 1 part by weight. If this amount is too small, the tensile strength decreases, and conversely if too large, the elongation at break is inferior.

  The blending amount of zinc oxide is preferably 0.3 to 3 parts by weight, more preferably 0.5 to 2 parts by weight, and further preferably 1 to 1.5 parts by weight with respect to 100 parts by weight of the latex solid content. . If the amount is too small, the tensile strength is inferior. Conversely, if the amount is too large, the elongation at break is inferior.

  The dip molding composition of the present invention may further contain a pH adjuster, a thickener, an anti-aging agent, a dispersant, a pigment, a filler, a softening agent and the like as necessary.

  The solid content concentration of the dip molding composition of the present invention is preferably 10 to 60% by weight, more preferably 20 to 45% by weight. Moreover, the pH of the dip molding composition of this invention becomes like this. Preferably it is 8.5-12, More preferably, it is 9-11.

  The dip-forming composition of the present invention has a value of 180 ° peel test of 4.9 (N when the dip-formed film is formed on the metal plate by immersing the metal plate. / 25 mm) or less, and preferably 3.4 (N / 25 mm) or less. When the value of the peel test is low, release from the mold becomes easy at the time of dip molding. Therefore, the value of the peel test is preferably low. The peel test value is determined by, for example, forming a dip-molded layer made of a dip-molding composition on a metal plate, then heating to crosslink the copolymer latex, and then peeling the molded film. It can be measured by determining the tensile load required. In addition, as a metal plate used in this case, a metal plate generally used for an adhesion test may be used, and is not particularly limited, but a stainless steel plate, an aluminum and aluminum alloy plate, a chromium plate, or the like can be used. Among these, a stainless steel plate can be preferably used.

Dip-molded product The dip-molded product of the present invention is obtained by dip-molding the dip-molding composition of the present invention described above. As the dip-molding method, a conventionally known 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 in that it is easy to obtain a dip-formed product having a uniform thickness. Hereinafter, a dip molding method using an anode adhesion dipping method as one embodiment will be described.

  First, the dip mold is immersed in a coagulant solution, and the coagulant is attached to the surface of the dip mold. Various materials such as porcelain, glass, metal, and plastic can be used as the dip mold. The shape of the mold may be adapted to the shape of the dip molded product that is the final product.

  The coagulant solution is a solution in which a coagulant such as a salting-out agent is dissolved in water, alcohol, or a mixture thereof. Metal halides such as barium chloride, calcium chloride, magnesium chloride, zinc chloride and aluminum chloride; nitrates such as barium nitrate, calcium nitrate and zinc nitrate; acetates such as barium acetate, calcium acetate and zinc acetate; calcium sulfate and magnesium sulfate And sulfates such as aluminum sulfate. The concentration of the coagulant in the coagulant solution is preferably 5 to 70% by weight, more preferably 15 to 50% by weight.

  Next, the dip molding die to which the coagulant is adhered is immersed in the dip molding composition of the present invention described above, and then the dip molding die is pulled up to form a dip molding layer on the dip molding die.

  Next, the dip molding layer formed on the dip molding die is heated to crosslink the copolymer latex. The heating temperature is preferably 100 to 150 ° C. If the temperature is too low, the cross-linking reaction takes a long time, which may reduce productivity. On the other hand, if it is too high, the oxidative deterioration of the copolymer latex is accelerated, and the physical properties of the molded product may be lowered. The heat treatment time may be appropriately selected depending on the heat treatment temperature, but is usually 10 to 120 minutes. The heating method is not particularly limited. For example, 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.

  In the present invention, before the heat treatment of the dip-molded layer, the dip-molded layer is immersed in warm water of 20 to 80 ° C. for about 0.5 to 60 minutes, and water-soluble impurities (emulsifier, water-soluble polymer, It is preferable to remove a coagulant and the like.

Next, the dip-molded layer crosslinked by heat treatment is removed from the dip-molding die to obtain a dip-molded product. As a demolding method, a method of peeling from a mold by hand, a method of peeling by water pressure or compressed air pressure, and the like can be adopted.
The dip-molded article of the present invention is obtained by dip-molding the above-described dip-molding composition of the present invention (preferably a composition having a 180 ° peel test value of 4.9 (N / 25 mm) or less). Therefore, it is excellent in releasability from the mold. Therefore, adhesion to the mold is effectively prevented, and as a result, the mold can be removed easily and easily.

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

  In addition, when the dip-formed product is a glove, inorganic or organic fine particles such as talc, calcium carbonate, starch particles, etc. are used in order to prevent the dip-formed products from sticking to each other at the contact surface and to improve slippage during attachment / detachment. May be dispersed on the surface of the glove, an elastomer layer containing these fine particles may be formed on the surface of the glove, or the surface layer of the glove may be chlorinated.

The dip-molded product of the present invention thus obtained has a good tensile strength of 20 MPa or more and an elongation at break of 600% or more, and has ethanol resistance that can sufficiently withstand normal use conditions. That is, the tensile strength at break after immersion in ethanol is preferably 16 MPa or more, more preferably 20 MPa or more, and further preferably 25 MPa or more, and has excellent ethanol resistance. The tensile strength at break after immersion in ethanol can be measured by immersing the dip-molded product in ethanol at a temperature of 20 ° C. for 1 hour, and then performing a tensile test on the immersed molded product.
Conventionally, in such dip-molded products, the tensile strength at break after immersion in ethanol was insufficient, so for example, when dip-molded products are used for rubber gloves and ethanol disinfection is used, There was a problem that gloves were easily broken.
On the other hand, according to the dip-molded product of the present invention, since the dip-molding composition of the present invention described above is formed by dip molding, such a problem can be effectively solved.

  Such a dip-formed product of the present invention can have a thickness of about 0.1 to about 3 mm, particularly 0.1 to 0.3 mm, and is therefore suitable for a thin product having such a thickness. Can be used. Specifically, medical supplies such as baby bottle nipples, syringes, conduits, and water pillows; toys and exercise equipment such as balloons, dolls, and balls; industrial articles such as pressure forming bags and gas storage bags; It can be used for household, agricultural, fishery and industrial gloves; finger sack, etc., and is particularly suitable for thin medical gloves. When the molded product is a glove, it may be a support type or an unsupport type.

  The present invention will be specifically described below with reference to examples and comparative examples. [Part] and [%] in these examples are based on weight unless otherwise specified. However, the present invention is not limited only to these examples. Evaluation of the copolymer latex, the dip-molding composition, and the dip-molded product was performed by the following method.

Toluene-insoluble fraction of copolymer latex First, the copolymer latex was cast on a framed glass plate, and then allowed to stand for 120 hours under conditions of a temperature of 20 ° C. and a relative humidity of 65%. A dry film was obtained. Next, about 0.2 g of this dried film was precisely weighed (weight W ₀ ), placed in an 80 mesh wire netting basket, and immersed in 100 ml of toluene at a temperature of 20 ° C. for 24 hours. Then, the immersed basket was pulled up, dried at a temperature of 105 ° C., toluene was removed, and the amount of film remaining in the basket without being dissolved in toluene was precisely weighed (weight W ₁ ). Finally, from the weights W ₀ and W ₁ obtained, a toluene insoluble matter was determined according to the following formula (1).
Toluene insoluble matter (% by weight) = (W ₁ / W ₀ ) × 100 (1)

180 ° Peel Test First, a stainless steel plate (SUS304) having a length of 200 mm × width 25 mm × thickness 1.5 mm conforming to JIS K6854 is vertically raised in a 20% aqueous solution of calcium nitrate and 175 mm from the bottom end of the plate. It was immersed in the position, then pulled up and dried at 60 ° C. for 10 minutes. Next, the dried plate is dipped in the dip-forming composition in the same manner as described above to a position of 170 mm from the bottom end of the plate, and then pulled up to form a dip-molded layer before crosslinking on both sides of the plate. did. The plate on which the dip-formed layer was formed was washed with distilled water at 40 ° C. for 5 minutes, pre-dried at 20 ° C. for 5 minutes, and then dried at 60 ° C. for 10 minutes, and then at 120 ° C. for 30 minutes. Crosslinking was performed under conditions to obtain a dip-formed film, and a test piece for a peel test was obtained.
Next, in accordance with JIS K6854, one end of the dip-formed film was peeled in advance in the vertical direction by 95 mm using one side of the test piece prepared above. Then, the upper end portion of the stainless steel plate where the dip-formed film is not formed is attached to the upper grip of the Tensilon universal testing machine, and one end of the dip-formed film previously peeled off is attached to the lower grip of the Tensilon universal testing machine. Attached to. Thereafter, a 180 ° peel test was performed by pulling at a pulling speed of 200 mm / min. As a result of the peel test, the maximum value of the tensile load (peel resistance value, unit: N / 25 mm) when the dip-formed film (length 75 mm × width 25 mm) was peeled from the stainless steel plate was measured. This peeling test was performed three times, and the average value was defined as the peeling resistance value. When the peel resistance value is low, it is easy to release from the mold during dip molding. Therefore, it is preferable that the peel resistance value is low.

Releasability from glove mold (molding mold) Evaluation of ease of peeling (releasing properties) when peeling the crosslinked dip-formed film formed on the surface of the glove mold (molding mold) from the glove mold according to the following criteria did.
A: The dip-formed film is not in close contact with the glove mold and can be easily detached.
B: The dip-molded film is partially adhered to the glove mold, and is somewhat difficult to detach.
C: The dip-molded layer is in close contact with the glove mold and is difficult to detach.

A dumbbell-shaped test piece was produced from a rubber glove (dip-formed product) obtained with tensile strength and breaking elongation using a dumbbell (Die-C) according to ASTM D-412. Subsequently, this test piece was pulled with a Tensilon universal testing machine at a tensile speed of 500 mm / min, and the tensile strength (MPa) at break and the elongation (%) at break were measured.

Tensile strength after ethanol immersion (ethanol resistance)
First, a test piece similar to the test piece used for measurement of tensile strength and elongation at break was immersed in ethanol (special grade reagent) at a temperature of 20 ° C. for 1 hour. And the test piece after immersion was pulled at a tensile speed of 500 mm / min with a Tensilon universal tester, and the tensile strength at break (tensile strength after ethanol immersion) was measured.

Example 1
Production of copolymer latex First, 47 parts of styrene, 3 parts of methacrylic acid, 50 parts of 1,3-butadiene, 0.3 part of t-dodecyl mercaptan as a chain transfer agent, 150 parts of deionized water, After charging 2.5 parts of sodium dodecylbenzenesulfonate, 0.3 part of potassium persulfate and 0.1 part of sodium ethylenediaminetetraacetate, the temperature in the system was changed to 45 ° C. to initiate the polymerization reaction. The polymerization reaction was continued until the polymerization conversion reached 95%, and then 0.1 part of diethylhydroxylamine was added to stop the polymerization reaction. And after removing the unreacted monomer, solid content concentration and pH were adjusted, and copolymer latex of solid content concentration 45% and pH 8.5 was obtained. A pH meter (M12: manufactured by HORIBA) was used for pH measurement.

Preparation of Dip Molding Composition First, 1.0 part of sulfur, 0.5 part of zinc diethyldithiocarbamate, 1.0 part of zinc oxide, 1.5 parts of titanium oxide, 0.03 part of potassium hydroxide and 5.63 water. By mixing the parts, a vulcanizing agent (crosslinking agent) dispersion was obtained. Then, 9.16 parts of this vulcanizing agent dispersion was added to and mixed with 222.2 parts of the copolymer latex produced above (100 parts as the solid content). Thereafter, an appropriate amount of deionized water was added to adjust the solid content concentration to 30% and pH 9.0, and further aged for 1 day to obtain a dip molding composition.

Rubber gloves (dip molded products)
Next, using the dip molding composition obtained above, a rubber glove (dip molded product) was produced by the following method.
First, a coagulant aqueous solution was prepared by mixing 20 parts of calcium nitrate, 0.05 part of polyethylene glycol octylphenyl ether as a nonionic emulsifier and 80 parts of water. Next, a glove mold heated to 60 ° C. was immersed in this aqueous coagulant solution for 10 seconds, pulled up, and then dried at a temperature of 60 ° C. for 10 minutes to attach the coagulant to the glove mold. Next, the glove mold to which the coagulant was adhered was dipped in the dip molding composition obtained above for 15 seconds and pulled up to form a dip molding layer on the surface of the glove mold. The formed dip-formed layer is immersed in distilled water at 40 ° C. for 5 minutes to remove water-soluble impurities, preliminarily dried at 20 ° C. for 5 minutes, further dried at 60 ° C. for 10 minutes, and then at 120 ° C. for 30 minutes. Vulcanization was performed under conditions. Finally, the dip-molded layer after vulcanization was peeled from the glove mold to obtain a rubber glove (dip-molded product) having a thickness of 0.1 mm.

  The copolymer latex obtained above was dissolved in toluene, the dip molding composition was subjected to a 180 ° peel test, and the dip molded product was peeled from the mold, tensile strength, elongation at break and ethanol immersion. Each evaluation of the later tensile strength was performed by the said method, respectively. The results are shown in Table 1.

Examples 2-4, Comparative Examples 1-5
Example 1 except that the monomer composition in producing the copolymer latex was changed as shown in Table 1 and the toluene insoluble content of the copolymer constituting the copolymer latex was changed. In the same manner as above, a copolymer latex, a dip-molding composition, and a dip-molded product were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  In Examples 2 to 4 and Comparative Examples 1 to 5, the copolymer latex to be contained in the dip molding composition is constituted by changing the conditions of the addition amount of the chain transfer agent and the addition method. The toluene insoluble content of the copolymer was adjusted. Specifically, in Examples 2 and 4, t-dodecyl mercaptan in the amount shown in Table 1 was added at the start of polymerization. In Example 3, the amount of t-dodecyl mercaptan added at the start of polymerization was 0.2 part, and 0.1 part of t-dodecyl mercaptan was added when the polymerization conversion reached 60%. Similarly, in Comparative Examples 1 to 3, the amount of t-dodecyl mercaptan at the start of polymerization was set to the amount shown in Table 1 (in Table 1, “at the start of polymerization”), and the polymerization conversion rate was 60%. An amount of t-dodecyl mercaptan shown in Table 1 was additionally added (in Table 1, “post-addition”).

From Table 1, the following can be confirmed.
When styrene as the aromatic vinyl monomer was not contained, the releasability from the mold was poor, the tensile strength after ethanol immersion was low, and the ethanol resistance was insufficient (Comparative Examples 1 and 5). ). In addition, this comparative example 1 is corresponded to synthetic | combination NBR for gloves generally marketed.
When the toluene insoluble content of the copolymer constituting the copolymer latex was too low, the releasability from the mold was poor and the ethanol resistance was insufficient (Comparative Example 2).

When the content of 1,3-butadiene as the conjugated diene monomer and the content of styrene as the aromatic vinyl monomer are outside the scope of the present invention, and the toluene-insoluble content is too low The mold release property from the mold was poor, and the tensile strength was insufficient (Comparative Example 3).
When the content of 1,3-butadiene as the conjugated diene monomer and the content of styrene as the aromatic vinyl monomer are outside the scope of the present invention, the toluene insoluble matter is determined as the present invention. Even in the case of within the range, ethanol resistance was insufficient (Comparative Example 4).

For these comparative examples, the rubber gloves obtained by using the dip molding composition according to the present invention (dip molded products) all have good releasability from the mold, tensile strength and The elongation at break was sufficient, and the tensile strength after immersion in ethanol was high, resulting in excellent ethanol resistance (Examples 1 to 4). That is, according to these Examples 1 to 4, since the adhesion to the mold is low, it is possible to remove from the mold satisfactorily, and it is suitable for glove use that is used after being disinfected with ethanol. Can be used.

Claims (10)

And a conjugated diene monomer from 37 to 55 parts by weight, the aromatic vinyl monomer 42 to 60 parts by weight, an ethylenically unsaturated acid monomer 10 parts by weight, the monomer mixture 100 parts by weight comprising , A dip molding composition having a copolymer latex obtained by copolymerization,
When the copolymer constituting the copolymer latex is immersed in toluene at a temperature of 20 ° C. for 24 hours, the insoluble content of toluene in the copolymer is 100% by weight based on the whole copolymer. The composition for dip molding which is 30 weight% or more.   The dip-molding composition according to claim 1, wherein the toluene-insoluble content of the copolymer is 40 to 95% by weight with respect to 100% by weight of the whole copolymer. Furthermore, the composition for dip shaping | molding of Claim 1 or 2 containing the crosslinking agent. The composition for dip molding according to claim 3 , wherein the amount of the crosslinking agent is 0.1 to 3 parts by weight with respect to 100 parts by weight of the solid content in the dip molding composition. Furthermore, the composition for dip shaping | molding of Claim 3 or 4 containing the crosslinking accelerator. The composition for dip molding according to claim 5 , wherein a blending amount of the crosslinking accelerator is 0.1 to 2 parts by weight with respect to 100 parts by weight of a solid content in the dip molding composition. Furthermore, the composition for dip molding of any one of Claims 3-6 containing the zinc oxide. The composition for dip molding according to claim 7 , wherein the compounding amount of the zinc oxide is 0.3 to 3 parts by weight with respect to 100 parts by weight of the solid content in the dip molding composition. pH is 8.5 to 12, dip-forming composition according to any one of claims 1-8. Claim 1 of the dip-forming composition according to any one of 9, a dip molded article obtained by dip-forming.