JPWO2019044654A1 - Manufacturing method of dip molded product - Google Patents

Abstract

A method for producing a dip molded product by dip molding a dip molding composition containing a polymer latex, in which nitrate is used as a coagulating salt and the amount of nitrite ions in the dip molding composition. Provided is a method for producing a dip molded article, which comprises performing dip molding under the condition of controlling the amount to 10 wt ppm or less.

Description

The present invention relates to a method for producing a dip molded product, and more particularly to a method for producing a dip molded product in which the occurrence of coloring such as yellowing is effectively prevented.

A technique is known for obtaining a dip-molded product such as a nipple, a balloon, a glove, a balloon, a sack, etc. by dip-molding a dip-molding composition containing a polymer latex.

For example, Patent Document 1 discloses a technique for producing a dip molded product by dip molding a composition for dip molding containing a carboxylic acid-modified nitrile copolymer latex using nitrate as a coagulating salt. There is. According to this Patent Document 1, a dip molded product used for surgical gloves, inspection gloves, condoms, catheters, industrial gloves, household gloves, health care products, etc. is obtained, but on the other hand, this patent The dip molded product obtained in the technique of Document 1 has a problem of yellowing due to heating at the time of crosslinking or the like, and it has been desired to suppress such yellowing from the viewpoint of improving the product value.

Japanese Unexamined Patent Publication No. 2016-532743

The present invention has been made in view of such an actual situation, and an object of the present invention is to provide a method for producing a dip molded product in which the occurrence of coloring such as yellowing is effectively prevented.

As a result of diligent studies to achieve the above object, the present inventors have conducted dip molding when dip molding a composition for dip molding containing a polymer latex using nitrate as a coagulating salt. We have found that the above object can be achieved by performing dip molding under the condition that the amount of nitrite ion contained in the composition is controlled to 10 wt ppm or less, and have completed the present invention.

That is, according to the present invention, it is a method of producing a dip molded product by dip molding a composition for dip molding containing a polymer latex, in which nitrate is used as a coagulating salt and the composition for dip molding is described. Provided is a method for producing a dip molded article, which comprises performing dip molding under a condition in which the amount of nitrite ions in a product is controlled to 10 wt ppm or less.

In the production method of the present invention, it is preferable to perform dip molding under the condition that the amount of nitrate ions in the dip molding composition is controlled to 10 ppm by weight or less.
In the production method of the present invention, it is preferable to perform dip-molded by the amount of denitrifying bacteria in the dip-forming composition in ^{1.0 × 10 5 (CFU / ml} ) The following controlled conditions.
Further, in the production method of the present invention, the storage temperature at the time of storing the dip molding composition is preferably in the range of 0 to 18 ° C.
In the production method of the present invention, as the dip molding composition, a dip molding composition having a history of being used for dip molding using nitrate as a coagulating salt can be used.
In the production method of the present invention, the solid content concentration of the dip molding composition is preferably 3.0 to 50% by weight.
In the production method of the present invention, the polymer constituting the polymer latex is preferably nitrile rubber.

According to the present invention, it is possible to provide a method for producing a dip molded product in which the occurrence of coloring such as yellowing is effectively prevented.

The method for producing a dip molded product of the present invention is a method for producing a dip molded product by dip molding a composition for dip molding containing a polymer latex, in which nitrate is used as a coagulating salt and the dip is described. Dip molding is performed under the condition that the amount of nitrite ion in the molding composition is controlled to 10 wt ppm or less.

<Polymer latex>
First, the polymer latex used in the production method of the present invention will be described.
The polymer constituting the polymer latex used in the production method of the present invention is not particularly limited in the type of the polymer, and is formed by polymerizing a natural rubber; a monomer containing a conjugated diene such as butadiene or isoprene. Conjugated diene rubber; etc. Among these, conjugated diene rubber is preferable. Examples of the conjugated diene rubber include so-called nitrile rubber, isoprene rubber, styrene-butadiene rubber, and chloroprene rubber obtained by copolymerizing a nitrile group-containing monomer, and among these, nitrile rubber is particularly preferable.

The nitrile rubber is not particularly limited, but is obtained by copolymerizing an α, β-ethylenic unsaturated nitrile monomer, a conjugated diene monomer, and other copolymerizable monomers used as necessary. Can be used.

The α, β-ethylenically unsaturated nitrile monomer is not particularly limited, but an ethylenically unsaturated compound having a nitrile group and preferably having 3 to 18 carbon atoms can be used. Examples of such α, β-ethylenically unsaturated nitrile monomers include acrylonitrile, methacrylonitrile, and halogen-substituted acrylonitrile, and among these, acrylonitrile is particularly preferable. It should be noted that these α, β-ethylenically unsaturated nitrile monomers may be used alone or in combination of two or more.

The content ratio of the α, β-ethylenically unsaturated nitrile monomer unit in the nitrile rubber is preferably 10 to 50% by weight, more preferably 15 to 45% by weight, still more preferably 15% by weight, based on all the monomer units. 20-40% by weight. By setting the content ratio of the α, β-ethylenically unsaturated nitrile monomer unit in the above range, the obtained dip molded product can be made excellent in tensile strength and texture.

As the conjugated diene monomer, a conjugated diene monomer having 4 to 6 carbon atoms such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and chloroprene is preferable. , 1,3-butadiene and isoprene are more preferred, and 1,3-butadiene is particularly preferred. In addition, these conjugated diene monomers may be used individually by 1 type, and may be used in combination of 2 or more type.

The content ratio of the conjugated diene monomer unit in the nitrile rubber is preferably 30 to 89% by weight, more preferably 40 to 84% by weight, still more preferably 50 to 50% by weight, based on all the monomer units constituting the nitrile rubber. It is 78% by weight. By setting the content ratio of the conjugated diene monomer unit in the above range, the obtained dip molded product can be made excellent in tensile strength and texture.

Further, the nitrile rubber may be obtained by copolymerizing an ethylenically unsaturated acid monomer in addition to the α, β-ethylenically unsaturated nitrile monomer and the conjugated diene monomer.

The ethylenically unsaturated acid monomer is not particularly limited, and for example, a carboxyl group-containing ethylenically unsaturated monomer, a sulfonic acid group-containing ethylenically unsaturated monomer, and a phosphoric acid group-containing ethylenically unsaturated monopoly. Examples include quantities.

The carboxyl group-containing ethylenically unsaturated monomer is not particularly limited, but is an ethylenically unsaturated monocarboxylic acid such as acrylic acid, methacrylic acid, and crotonic acid; fumaric acid, maleic acid, itaconic acid, maleic anhydride, and anhydrous. Examples thereof include ethylenically unsaturated polyvalent carboxylic acid such as itaconic acid and its anhydride; a partial esterified product of ethylenically unsaturated polyvalent carboxylic acid such as methyl maleate and methyl itaconic acid.

The sulfonic acid group-containing ethylenically unsaturated monomer is not particularly limited, but is limited to vinyl sulfonic acid, methyl vinyl sulfonic acid, styrene sulfonic acid, (meth) allyl sulfonic acid, and ethyl (meth) acrylic acid-2-sulfonate. , 2-acrylamide-2-hydroxypropanesulfonic acid and the like.

The phosphoric acid group-containing ethylenically unsaturated monomer is not particularly limited, but is limited to propyl (meth) acrylic acid-3-chloro-2-phosphate, ethyl (meth) -2-phosphate, and 3-allyloxy. -2-Hydroxypropane phosphoric acid and the like can be mentioned.

These ethylenically unsaturated acid monomers can be used as alkali metal salts or ammonium salts, or may be used alone or in combination of two or more. Among the above ethylenically unsaturated acid monomers, a carboxyl group-containing ethylenically unsaturated monomer is preferable, an ethylenically unsaturated monocarboxylic acid is more preferable, methacrylic acid or acrylic acid is preferable, and methacrylic acid is particularly preferable. preferable.

The content ratio of the ethylenically unsaturated acid monomer unit in the nitrile rubber is preferably 1 to 20% by weight, more preferably 1 to 15% by weight, still more preferably 1 to 15% by weight, based on all the monomer units constituting the nitrile rubber. Is 2 to 10% by weight. By setting the content ratio of the ethylenically unsaturated acid monomer unit in the above range, the tensile strength of the obtained dip molded product can be further increased.

Further, as the nitrile rubber, in addition to the α, β-ethylenically unsaturated nitrile monomer, the conjugated diene monomer, and the ethylenically unsaturated acid monomer contained as necessary, a single amount of these. It may be a copolymer of another monomer copolymerizable with the body.

Other copolymerizable monomers include vinyl aromatic monomers such as styrene, alkylstyrene and vinylnaphthalene; fluoroalkylvinyl ethers such as fluoroethylvinyl ether; (meth) acrylamide, N-methylol (meth) acrylamide, etc. Ethylene unsaturated amide monomers such as N, N-dimethylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide; methyl (meth) acrylic acid, (meth) acrylic acid Ethyl, butyl (meth) acrylate, -2-ethylhexyl (meth) acrylate, trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, dibutyl maleate, dibutyl fumarate, diethyl maleate, ( Methoxymethyl acrylate, ethoxyethyl (meth) acrylate, methoxyethoxyethyl (meth) acrylate, cyanomethyl (meth) acrylate, -2-cyanoethyl (meth) acrylate, -1-cyano (meth) acrylate Propyl, -2-ethyl-6-cyanohexyl (meth) acrylate, -3-cyanopropyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, Ethylene unsaturated carboxylic acid ester monomer such as dimethylaminoethyl (meth) acrylate; divinylbenzene, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylpropantri (meth) acrylate, pentaerythritol Crosslinkable monomers such as (meth) acrylate; and the like. These other copolymerizable monomers can be used alone or in combination of two or more.

The content ratio of the units of other copolymerizable monomers in the nitrile rubber is preferably 20% by weight or less, preferably 15% by weight or less, more preferably 15% by weight or less, based on all the monomer units constituting the nitrile rubber. It is 10% by weight or less.

When the polymer latex used in the present invention is a conjugated diene rubber such as nitrile rubber, the polymer latex used in the present invention is, for example, emulsion-polymerized with a monomer mixture containing the above-mentioned monomer. Can be obtained by In emulsion polymerization, commonly used polymerization auxiliary materials such as emulsifiers, polymerization initiators, and molecular weight modifiers can be used. The method of adding these polymerization auxiliary materials is not particularly limited, and any method such as an initial batch addition method, a split addition method, or a continuous addition method may be used.

The emulsifier is not particularly limited, and is, for example, a nonionic emulsifier such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester; potassium dodecylbenzenesulfonate, dodecylbenzene. Anionic emulsifiers such as alkylbenzene sulfonates such as sodium sulfonate, higher alcohol sulfates, alkyl sulfosuccinates; cationic emulsifiers such as alkyltrimethylammonium chloride, dialkylammonium chloride, benzylammonium chloride; α, β-unsaturated Examples thereof include sulfoesters of carboxylic acids, sulfate esters of α, β-unsaturated carboxylic acids, and copolymerizable emulsifiers such as sulfoalkylaryl ethers. Among them, an anionic emulsifier is preferable, alkylbenzene sulfonate is more preferable, and potassium dodecylbenzene sulfonate and sodium dodecylbenzene sulfonate are particularly preferable. 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 with respect to 100 parts by weight of the monomer mixture.

The polymerization initiator is not particularly limited, and for example, inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; diisopropylbenzene hydroperoxide, cumene hydroperoxide, etc. t-Butylhydroperoxide, 1,1,3,3-tetramethylbutylhydroperoxide, 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; etc. Can be mentioned. These polymerization initiators can be used alone or in combination of two or more.
The peroxide initiator is preferably used because a polymer latex can be stably produced, and a dip molded product having high mechanical strength and a soft texture can be obtained. The amount of the polymerization initiator used is preferably 0.01 to 10 parts by weight, more preferably 0.01 to 2 parts by weight, based on 100 parts by weight of the monomer mixture.

In addition, the peroxide initiator can be used as a redox-based polymerization initiator in combination with a reducing agent. The reducing agent is not particularly limited, but is a compound containing a metal ion in a reduced state such as ferrous sulfate and ferrous naphthenate; a sulfonic acid compound such as sodium methanesulfonate; an amine compound such as dimethylaniline. ; Carboxylic acid compounds such as ethylenediamine tetraacetate; and the like. These reducing agents can be used alone or in combination of two or more. The amount of the reducing agent used is preferably 3 to 1000 parts by weight with respect to 100 parts by weight of the peroxide.

The amount of water used in the emulsion polymerization is preferably 80 to 600 parts by weight, particularly preferably 100 to 200 parts by weight, based on 100 parts by weight of all the monomers used.

Examples of the method for adding the monomer include a method of collectively adding the monomers used in the reaction vessel, a method of adding the monomers continuously or intermittently as the polymerization progresses, and a method of adding a part of the monomers. Then, the reaction is carried out to a specific conversion rate, and then the remaining monomer is continuously or intermittently added to polymerize, and any of these methods may be adopted. When the monomers are mixed and added continuously or intermittently, the composition of the mixture may be constant or varied. Further, each monomer may be added to the reaction vessel after mixing various monomers to be used in advance, or may be added to the reaction vessel separately.

Further, if necessary, polymerization auxiliary materials such as a chelating agent, a dispersant, a pH adjusting agent, an oxygen scavenger, and a particle size adjusting agent can be used, and these are not particularly limited in type and amount.

The polymerization temperature at the time of carrying out emulsion polymerization is not particularly limited, but is usually 5 to 95 ° C, preferably 30 to 70 ° C. The polymerization time is about 5 to 40 hours.

As described above, the monomer mixture is emulsion-polymerized, and when a predetermined polymerization conversion rate is reached, the polymerization system is cooled or a polymerization inhibitor is added to terminate the polymerization reaction. The polymerization conversion rate when the polymerization reaction is stopped is preferably 90% by weight or more, more preferably 93% by weight or more.

The polymerization terminator is not particularly limited, but for example, hydroxylamine, hydroxyamine sulfate, diethylhydroxylamine, hydroxyamine sulfonic acid and its alkali metal salt, sodium dimethyldithiocarbamate, hydroquinone derivative, catechol derivative, and hydroxydimethyl. Examples thereof include aromatic hydroxydithiocarboxylic acids such as benzenethiocarboxylic acid, hydroxydiethylbenzenedithiocarboxylic acid, and hydroxydibutylbenzenedithiocarboxylic acid, and alkali metal salts thereof. The amount of the polymerization inhibitor used is preferably 0.05 to 2 parts by weight with respect to 100 parts by weight of the monomer mixture.

After stopping the polymerization reaction, if desired, the unreacted monomer is removed and the solid content concentration and pH are adjusted to obtain a polymer latex.

<Composition for dip molding>
The composition for dip molding used in the production method of the present invention contains at least the above-mentioned polymer latex, and preferably contains a cross-linking agent in addition to the above-mentioned polymer latex.

As the cross-linking agent, those usually used in dip molding can be used, for example, sulfur such as powdered sulfur, sulfur flower, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur; sulfur chloride, sulfur dichloride, morpholini disulfide. , Sulfur-containing compounds such as alkylphenol disulfide, dibenzothiazyl disulfide, caprolactam disulfide, phosphorus-containing polysulfide, high molecular weight polysulfide; tetramethylthium disulfide, selenium dimethyldithiocarbamate, 2- (4'-morpholinodithio) benzothiazole, etc. Sulfur-donating compounds; polyamines such as hexamethylenediamine, triethylenetetramine, tetraethylenepentamine; and the like. These cross-linking agents may be used alone or in combination of two or more.

The blending amount of the cross-linking agent is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymer contained in the polymer latex.

When sulfur is used as the cross-linking agent, it is preferable to use a cross-linking accelerator (vulcanization accelerator) or zinc oxide in combination.
The cross-linking accelerator (vulcanization accelerator) is not particularly limited, and for example, dithiocarbamines such as diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, and dibenzyldithiocarbamic acid. Acids and their zinc salts; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazolin, dibenzothiadyl disulfide, 2- (2,4-dinitrophenylthio) benzothiazole, 2- (N, N-diethylthiocarbaylthio) benzothiazole, 2- (2,6-dimethyl-4-morpholinothio) benzothiazole, 2- (4'-morpholino dithio) benzothiazole, 4-morpholinyl-2-benzothiazole disulfide, 1 , 3-Bis (2-benzothiadyl mercaptomethyl) urea and the like, and among these, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, 2-mercaptobenzothiazole and 2-mercaptobenzothiazole zinc are preferable. These cross-linking accelerators may be used alone or in combination of two or more.

Further, the composition for dip molding used in the production method of the present invention includes, if desired, a cross-linking aid, a filler, a pH adjuster, a thickener, an antiaging agent, a dispersant, a pigment, a filler, a softening agent and the like. May be blended.

The solid content concentration of the dip molding composition used in the production method of the present invention is preferably 3.0 to 50% by weight, more preferably 5.0 to 40% by weight. More preferably, it is 7.0 to 40% by weight. The pH of the dip molding composition used in the production method of the present invention is preferably 8.5 to 12, more preferably 9 to 11.

<Manufacturing method of dip molded product>
Next, a method for producing the dip molded product of the present invention will be described.
The method for producing a dip molded product of the present invention is a method for producing a dip molded product by dip molding the above-mentioned composition for dip molding containing the polymer latex using nitrate as a coagulating salt. At this time, the dip molding is performed under the condition that the amount of nitrite ion in the dip molding composition is controlled to 10 wt ppm or less and the amount of nitrite ion is controlled to 10 wt ppm or less. is there.

In the production method of the present invention, dip molding can be performed by, for example, the following method. That is, the dip molding mold is immersed in an aqueous solution of nitrate as a coagulating salt to adhere the nitrate to the surface of the dip molding mold, and then immersed in the dip molding composition to immerse the dip molding mold surface. This can be done by forming a dip molding layer on the surface.

Examples of the nitrate as a coagulating salt include barium nitrate, calcium nitrate, zinc nitrate and the like. In the production method of the present invention, a nitrate is used as the coagulating salt, and by using such a nitrate, the coagulation property at the time of dip molding and the mechanical properties of the obtained dip molded product are good. Can be. The nitrate as a coagulating salt is usually used in the form of an aqueous solution, but the aqueous solution of nitrate may further contain a water-soluble organic solvent such as methanol or ethanol or a nonionic surfactant. The concentration of nitrate in the aqueous solution of nitrate is usually 5 to 70% by weight, preferably 10 to 50% by weight.

In the production method of the present invention, nitrate is used as the coagulating salt from the viewpoint of improving the coagulation property at the time of dip molding and the mechanical properties of the obtained dip molded product, but on the other hand, the coagulating salt. When dip molding is performed using nitrate, there is a problem that the obtained dip molded product is colored such as yellowing, especially by heating during cross-linking, etc., and in particular, the product value is From the viewpoint of improvement, it is desirable to suppress the occurrence of such coloring.

On the other hand, as a result of diligent studies by the present inventors, such yellowing and the like can be caused by controlling the amount of nitrite ion in the dip molding composition used for dip molding to 10 wt ppm or less. It has been found that the occurrence of coloring can be effectively prevented, and the present invention has been completed.

That is, in the manufacturing method of the present invention, used in dip molding, nitrite ions in the composition for dip molding (NO 2 ^_-) the amount of what controls below 10 ppm by weight, preferably not more than 8 ppm by weight , More preferably, it is controlled to 6 wt ppm or less. By controlling the amount of nitrite ion to 10 ppm by weight or less, the occurrence of coloring such as yellowing of the obtained dip molded product can be effectively suppressed, while when the amount of nitrite ion exceeds 10 ppm by weight, Coloring such as yellowing occurs in the obtained dip molded product.

In particular, as a result of studies by the present inventors, when dip molding is performed using nitrate as the coagulating salt, nitrate as the coagulating salt is contained in the composition for dip molding as nitrate ion (NO ₃ ⁻ ). the causes mixed in the form, by contaminating nitrate ions are reduced, nitrite (NO 2 ^_-), and the such nitrite ions, the dip molded product obtained generating a colored, such as yellowing It turned out to be the cause of causing. In particular, the influence of mixing nitrate into the dip molding composition is as follows: (1) When the dip molding composition is repeatedly used to repeatedly produce the dip molded body, that is, the dip molding composition. In addition, when a plurality of dip molded bodies are manufactured by repeatedly immersing the dip molding die, or (2) the dip molding composition is used to manufacture the dip molded body, and then the dip. This is remarkable when the molding composition is stored once and the stored dip molding composition is used again to produce a dip molded product.

On the other hand, according to the present invention, by controlling the amount of nitrite ion in the dip molding composition to 10 wt ppm or less, it can be obtained even in the above cases (1) and (2). It is possible to effectively suppress the occurrence of coloring such as yellowing in the dip molded product.

That is, for example, when the dip molding composition is repeatedly used to repeatedly manufacture the dip molded body as in (1) above, that is, the operation of immersing the dip molding mold in the dip molding composition is performed. When a plurality of dip molded articles are produced by repeating the process, the amount of nitrite ion in the dip molding composition is continuously controlled to 10 wt ppm or less during the repeated production, thereby repeating the process. It is possible to effectively suppress the occurrence of coloring such as yellowing in the manufactured dip molded product.

In this case, the method for controlling the amount of nitrite ion in the dip molding composition to 10 wt ppm or less is not particularly limited, but for example, the amount of nitrate ion in the dip molding composition. The method for controlling the amount of denitrifying bacteria is preferably 10% by weight or less, more preferably 8% by weight or less, still more preferably 6% by weight or less, and the amount of denitrifying bacteria in the dip molding composition is preferably 1.0 × 10. Examples thereof include a method of controlling to ⁵ (CFU / ml) or less, more preferably 1.0 × 10 ⁴ (CFU / ml) or less, still more preferably 1.0 × 10 ³ (CFU / ml) or less. By setting at least one of the amount of nitrate ion and the amount of denitrifying bacteria in the above range, the amount of nitrite ion in the dip molding composition can be controlled to 10 wt ppm or less.

For example, when a dip molded product is repeatedly produced by repeatedly using the dip molding composition to obtain a plurality of dip molded products, the dip molding is repeated and the product is derived from nitrate as a coagulating salt. While the amount of nitrate ions increases, or denitrifying bacteria are inevitably taken up from the outside air during storage or dip molding after preparation of the dip molding composition, the amount of these nitrate ions and By controlling the amount of denitrifying bacteria within the above range, the amount of nitrite ion in the dip molding composition can be controlled within the above-mentioned predetermined range. In particular, as a result of studies by the present inventors, the involvement of denitrifying bacteria is mainly the cause of the reduction of nitrate ion derived from nitrate as a coagulating salt to nitrite in the composition for dip molding. Considerably, by setting at least one of the amount of nitrate ion and the amount of denitrifying bacteria in the above range, the amount of nitrite ion in the dip molding composition can be controlled to 10 wt ppm or less. It is a thing. For example, even when the amount of nitrate ion is larger than the above range, if the amount of denitrifying bacteria is within the above range, the production of nitrite ion can be effectively suppressed, and thereby the amount of nitrite ion. Can be controlled to 10 wt ppm or less, and similarly, even when the amount of denitrifying bacteria is larger than the above range, if the amount of nitrate ion is within the above range, the production of nitrite ion is generated. It can be effectively suppressed and the amount of nitrite ion can be controlled to 10 wt ppm or less.

Denitrifying bacteria is a general term for a wide variety of microorganisms that undergo a reaction to reduce nitrate ions, and includes fungi as well as bacteria. Examples of the denitrifying bacterium include bacteria belonging to the genus Pseudomonas such as Pseudomonas airginosa, Pseudomonas denitrificans, and Pseudomonas stazzeri, as well as bacteria belonging to the genus Micrococcus and Paracoccus.

The method for controlling the amount of nitrate ions in the dip molding composition is not particularly limited, but after immersing the dip molding mold to which nitrate is attached in the dip molding composition, A method for controlling the nitrate-containing liquid, which is dropped from the dip molding mold when the dip molding mold having a dip molding layer formed on the surface thereof, is not mixed in the dip molding composition, or in dip molding. Examples thereof include a method of shortening the immersion time of the dip molding mold to 2 to 5 seconds. Specifically, when the dip molding mold is pulled up, a method of covering the dip tank containing the dip molding composition and the like can be mentioned. However, the method is not particularly limited to such a method, and any method can be used as long as the amount of nitrate ion can be controlled within the above range.

Further, the method for setting the amount of denitrifying bacteria in the dip molding composition within the above range is not particularly limited, but the environment when the dip molding composition is prepared and then stored is not exposed to the outside air. Such an environment (for example, a method of reducing the area of the liquid surface per unit volume of the dip molding composition), a method of minimizing the contact area with the outside air, and a method of repeatedly performing dip molding. The environment (outside air environment) in the above is a method in which the amount of denitrifying bacteria is controlled, and a method in which the contact area of the dip molding composition with the outside air is as small as possible. Be done.

Further, as described in (2) above, after the dip molding composition is produced using the dip molding composition, the dip molding composition is once stored, and the stored dip molding composition is reused. In the production of the dip molded product, the amount of nitrite ion in the composition for dip molding during storage, after storage, and when used again is controlled to 10 wt ppm or less. It is possible to effectively suppress the occurrence of coloring such as yellowing in a dip molded product produced by using the composition for dip molding after storage.

In this case, the method for controlling the amount of nitrite ion in the dip molding composition to 10 wt ppm or less is not particularly limited, but as in the case of (1) above, for example, dip molding. The amount of nitrite ion in the dip molding composition during storage after dip molding using the composition for dip molding, after storage, and when used again is preferably 10 wt ppm or less. more preferably 8 ppm by weight or less, more preferably a method of controlling below 6 ppm by weight, the amount of denitrifying bacteria in the dip-forming composition, preferably ^{1.0 × 10 5 (CFU / ml} ) or less, more A method of controlling to 1.0 × 10 ⁴ (CFU / ml) or less, more preferably 1.0 × 10 ³ (CFU / ml) or less can be mentioned.

In particular, during storage of the dip forming composition, nitrate ions derived from nitrate as a coagulating salt do not newly increase, but due to the dip forming performed before storage, the dip forming composition can be contained. coagulation nitrate ions derived from nitrate are introduced in the form of a salt, thereby, the amount of nitrate ions has a higher amount than the above range, and the amount of denitrifying bacteria 1.0 × 10 5 ^(CFU If it exceeds / ml), nitrite ions will be generated during storage depending on the storage environment. Therefore, in the case of (2) above, in addition to the case of performing dip molding again using the composition for dip molding after storage, the amount of nitrate ions and the amount of denitrifying bacteria even during such storage. It is preferable to control at least one of them within the above range, and it is desirable to suppress the production of nitrite ions during storage. In this case, the method for setting the amount of nitrate ions and the amount of denitrifying bacteria within the above ranges may be the same as in the case of (1) above. Further, when dip molding is performed again using the composition for dip molding after storage, at least one of the amount of nitrate ions and the amount of denitrifying bacteria is within the above range, as in the case of (1) above. It is preferable to control to.

On the other hand, even when both the amount of nitrate ions and the amount of denitrifying bacteria in the dip molding composition are larger than the above range, the temperature during storage is preferably in the range of 0 to 18 ° C. Since the denitrifying bacteria can be inactivated by preferably setting the temperature in the range of 0 to 15 ° C., it is also preferable to adopt a method in which the temperature during storage is set in such a range. In particular, in this case, even if both the amount of nitrate ions and the amount of denitrifying bacteria in the dip molding composition before storage are larger than the above range, the temperature during storage is set within the above range. , by inactivating the denitrifying bacteria can reduce the denitrifying bacteria (e.g., can be a ^{1.0 × 10 5 (CFU / ml} ) or less), thereby, the amount of nitrite ion It is possible to control the weight to 10 ppm by weight or less.

Further, in the production method of the present invention, before dip molding is performed using the dip molding composition, the dip molding composition is aged (also referred to as pre-vulcanization) and aged. May be good.
The aging time is not particularly limited and depends on the aging temperature, but is preferably 1 to 14 days, more preferably 1 to 7 days. The aging temperature is preferably 5 to 40 ° C, more preferably 20 to 40 ° C. From the viewpoint of suppressing the contamination of denitrifying bacteria even during aging, we adopted a method of making the environment during aging so that it does not come into contact with the outside air, and a method of minimizing the contact area with the outside air. It is preferable to do so.

The temperature at the time of dip molding, that is, the temperature of the composition for dip molding at the time of dip molding is preferably in the range of 20 to 40 ° C, more preferably in the range of 22 to 38 ° C. If the temperature of the dip molding composition during dip molding is too low or too high, dip molding becomes difficult or the thickness of the dip molding layer formed on the surface of the dip molding mold is non-uniform. May be.

The dip-molded layer obtained by dip molding is usually heat-treated and crosslinked. Before the heat treatment, water-soluble impurities (for example, excess emulsifier, coagulant, etc.) may be removed by immersing in water, preferably warm water at 30 to 70 ° C. for about 1 to 60 minutes. The operation for removing water-soluble impurities may be performed after the dip molding layer has been heat-treated, but it is preferably performed before the heat treatment because the water-soluble impurities can be removed more efficiently.

Crosslinking of the dip molded layer is usually carried out by subjecting the dip molded layer to a heat treatment at a temperature of 100 to 150 ° C., preferably 10 to 120 minutes. As a heating method, a method of external heating by infrared rays or heated air or internal heating by high frequency can be adopted. Of these, external heating with heated air is preferable.

Then, by removing the crosslinked dip molding layer from the dip molding mold, a dip molded body is obtained. As a method for removing it, a method of manually peeling it from the molding mold or a method of peeling it by water pressure or compressed air pressure can be adopted. After removing from the dip molding mold, heat treatment may be further performed at a temperature of 60 to 120 ° C. for 10 to 120 minutes.

The dip molded product obtained by the production method of the present invention is one in which the occurrence of discoloration such as yellowing is effectively suppressed, and is suitable for glove applications, especially for thin surgical gloves, or gloves. In addition, medical supplies such as baby bottle nipples, droppers, tubes, water pillows, balloon sack, catheters, condoms; toys such as balloons, dolls, balls; industrial supplies such as pressure molding bags and gas storage bags. It can also be used for finger cots and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In the following, unless otherwise specified, "parts" are based on weight. The test or evaluation method for physical properties and properties is as follows.

<Amount of nitrate ion, amount of nitrite ion>
The dip molding composition was diluted 1000-fold with ion-exchanged water. The diluted liquid was centrifuged at 110,000 rpm for 2 hours to separate into a solid layer and a liquid phase. Next, a liquid phase was collected from the sample after centrifugation, and a transparent liquid was obtained by passing this through a 0.2 μm filter, and the obtained transparent liquid was measured by anion chromatography. The amount of nitrate ion and the amount of nitrite ion in the composition for dip molding were measured.

<Amount of denitrifying bacteria>
Bacterial detection medium (product name "Easicult (R) TTC", manufactured by Orion) is immersed in a carboxyl group-containing nitrile rubber latex and a dip molding composition, and the bacteria are cultured at 29 ° C. for 48 hours, and then the bacteria are detected. By observing the number of colonies formed in the medium, the number of colonies per 1 mL of the carboxyl group-containing nitrile rubber latex or the dip molding composition was counted to determine the amount of denitrifying bacteria (unit: CFU / ml). It was.

<Yellowness measurement>
The film-shaped molded product obtained by dip molding was placed in an oven and vulcanized at 120 ° C. for 20 minutes. Then, the yellowness (YI) of the vulcanized film-shaped molded product was measured using a color meter. Yellowness (YI) was evaluated according to the following criteria.
A: Yellowness (YI) is less than 5 B: Yellowness (YI) is 5 or more and less than 10 C: Yellowness (YI) is 10 or more

<Manufacturing example 1>
In a pressure-resistant polymerization reactor substituted with nitrogen, 13.5 parts of acrylonitrile, 33.75 parts of 1,3-butadiene and 2.75 parts of methacrylate were used as the initial polymerization monomer, and t-dodecyl mercaptan (tDM) was used as the molecular weight modifier. 0.5 part, 95 parts of deionized water, 1.0 part of sodium dodecylbenzenesulfonate (DBS) as an emulsifier, 0.2 part of potassium persulfate as a polymerization initiator, and sodium ethylenediaminetetraacetate (EDTA) as a reducing agent. 0.1 part was charged, the temperature in the polymerization system was raised to 35 ° C., and the polymerization reaction was started. Then, when the polymerization conversion rate reached 50%, 1.0 part of sodium dodecylbenzenesulfonate was collectively added in the form of a 10% aqueous solution as an additional emulsifier. Then, as the residual monomer, a monomer mixture consisting of 13.5 parts of acrylonitrile, 33.75 parts of 1,3-butadiene and 2.75 parts of methacrylic acid, and 0.4 part of t-dodecyl mercaptan were removed. The emulsion obtained by emulsifying with 15.0 parts of ionized water and 0.5 parts of sodium dodecylbenzenesulfonate was continuously added to the polymerization system for 270 minutes. The polymerization conversion rate at the end of this continuous addition was 60%. Then, the polymerization was continued until the polymerization conversion rate of all the monomers became 97%, and then the polymerization reaction was stopped by adding 0.1 part of diethylhydroxylamine as a polymerization terminator.
Then, after distilling off the unreacted monomer from the obtained latex, the solid content concentration and pH were adjusted to obtain a latex of a carboxyl group-containing nitrile rubber having a solid content concentration of 45% and a pH of 8.3. ..

<Reference example 1>
The latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 was adjusted to a solid content concentration of 25% by weight, and then the vulcanizing agent dispersion was applied to 100 parts of the solid content in the latex whose solid content concentration was adjusted. (Dispersion consisting of 1 part of sulfur, 1.5 parts of zinc oxide, 0.5 part of zinc diethylcarbamate, 0.03 part of potassium hydroxide and 5.63 parts of water) After mixing 8.66 parts, an appropriate amount. A 5 wt% potassium hydroxide aqueous solution and deionized water were added to obtain a dip molding composition having a solid content concentration of 25 wt% and a pH of 10.0. Separately from the above, an aqueous coagulant solution was prepared by mixing 13 parts of calcium nitrate, 0.05 parts of polyoxyethylene octylphenyl ether as a nonionic emulsifier, and 87 parts of water.

Then, dip molding was performed using the dip molding composition and the coagulant aqueous solution obtained above. Specifically, the ceramic mold was immersed in an aqueous solution of a coagulant for 1 minute, pulled up, and then dried at 70 ° C. for 30 minutes to allow the coagulant to adhere to the ceramic mold. Next, the ceramic mold to which the coagulant was attached was immersed in a dip molding composition at a temperature of 30 ° C. for 2 seconds and pulled up. In this example, when the ceramic mold is pulled up from the dip molding composition, the dip molding layer formed on the surface of the ceramic mold is formed by covering the dip tank containing the dip molding composition. Measures were taken to prevent the nitrate ion-containing liquid (show liquid) dripping from the dip molding composition from being mixed in the dip molding composition (show liquid cut). Then, in this example, such dip molding was performed 50 times.

When the amount of nitrate ions in the dip molding composition after performing the dip molding 50 times was measured, the amount of nitrate ions contained in the dip molding composition was 0 ppm by weight.

<Reference example 2>
The latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 was adjusted to a solid content concentration of 17% by weight, and then the vulcanizing agent dispersion was applied to 100 parts of the solid content in the latex whose solid content concentration was adjusted. (Dispersion consisting of 1 part of sulfur, 1.5 parts of zinc oxide, 0.5 part of zinc diethylcarbamate, 0.03 part of potassium hydroxide and 5.63 parts of water) After mixing 8.66 parts, an appropriate amount. A 5 wt% potassium hydroxide aqueous solution and deionized water were added to obtain a dip molding composition having a solid content concentration of 17 wt% and a pH of 10.0.

Then, dip molding was performed using the dip molding composition obtained above and the coagulant aqueous solution prepared in the same manner as in Reference Example 1. Specifically, the dip molding was performed 50 times in the same manner as in Reference Example 1 except that the immersion time of the ceramic mold in the dip molding composition was changed from 2 seconds to 10 seconds.

When the amount of nitrate ion in the dip molding composition after performing the dip molding 50 times was measured, the amount of nitrate ion contained in the dip molding composition was 15 wt ppm.

<Reference example 3>
The latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 was adjusted to a solid content concentration of 9% by weight, and then the vulcanizing agent dispersion was applied to 100 parts of the solid content in the latex whose solid content concentration was adjusted. (Dispersion consisting of 1 part of sulfur, 1.5 parts of zinc oxide, 0.5 part of zinc diethylcarbamate, 0.03 part of potassium hydroxide and 5.63 parts of water) After mixing 8.66 parts, an appropriate amount. A 5 wt% potassium hydroxide aqueous solution and deionized water were added to obtain a dip molding composition having a solid content concentration of 9 wt% and a pH of 10.0.

Then, dip molding was performed using the dip molding composition obtained above and the coagulant aqueous solution prepared in the same manner as in Reference Example 1. Specifically, the immersion time of the ceramic mold in the dip molding composition is changed from 2 seconds to 30 seconds, and a liquid containing nitrate ions (show liquid) is prevented from being mixed in the dip molding composition. Dip molding was performed 50 times in the same manner as in Reference Example 1 except that no countermeasure (show liquid cut) was taken.

When the amount of nitrate ion in the dip molding composition after performing the dip molding 50 times was measured, the amount of nitrate ion contained in the dip molding composition was 780 ppm by weight.

<Example 1>
The denitrifying bacteria were propagated in the latex by immersing the culture medium in which the denitrifying bacteria were cultured in the latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 and storing the culture medium at room temperature for one day. When the denitrifying bacteria count was measured by the above method, it was ^{1.0 × 10 6 (CFU / ml} ) or more. Next, the latex in which the denitrifying bacteria were propagated was adjusted to a solid content concentration of 25% by weight, and then, with respect to 100 parts of the solid content in the latex whose solid content concentration was adjusted, a vulcanizing agent dispersion (1 part of sulfur, After mixing 8.66 parts of a dispersion consisting of 1.5 parts of zinc oxide, 0.5 parts of zinc diethylcarbamate, 0.03 parts of potassium hydroxide and 5.63 parts of water), an appropriate amount of 5% by weight hydroxide is added. An aqueous potassium solution and deionized water were added to obtain a dip molding composition having a solid content concentration of 25% by weight and a pH of 10.0. Then, the obtained dip molding composition is placed in a container so that the amount is 1/2 or more of the volume of the container, and the lid is put on the container to create an environment in which there is no contact with the outside air. It was aged at ° C for 1 day.

Then, the dip molding was performed 50 times in the same manner as in Reference Example 1 except that the dip molding composition thus obtained was used. The amount of nitrate ions in the dip molding composition after 50 times of dip molding is considered to be about the same as in Reference Example 1.

Next, the composition for dip molding after 50 times of dip molding is covered in the same container in an amount of 1/2 or more of the container volume, so that there is no contact with the outside air. An evaluation dip molded product was obtained by storing the product at 30 ° C. for one day in an environment and then performing dip molding again under the same conditions using the stored dip molding composition. Then, according to the above method, the amount of nitrite ions, the number of denitrifying bacteria, and the yellowness of the evaluation dip molded product in the dip molding composition after obtaining the evaluation dip molded product were measured. The results are shown in Table 2.

<Example 2>
By measuring the number of denitrifying bacteria in the latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 by the above method, it was confirmed that the number of denitrifying bacteria was 1.0 × 10 ³ (CFU / ml) or less. After that, the latex was adjusted to a solid content concentration of 9% by weight, and then, with respect to 100 parts of the solid content in the latex whose solid content concentration was adjusted, a vulcanizer dispersion (1 part of sulfur, zinc oxide 1. 8.66 parts of a dispersion consisting of 5 parts, 0.5 parts of zinc diethylcarbamate, 0.03 parts of potassium hydroxide and 5.63 parts of water) was mixed, and then an appropriate amount of 5 wt% potassium hydroxide aqueous solution was removed. Ionized water was added to obtain a dip molding composition having a solid content concentration of 9% by weight and a pH of 10.0. Then, the obtained dip molding composition is placed in a container so that the amount is 1/2 or more of the volume of the container, and the lid is put on the container to create an environment in which there is no contact with the outside air. It was aged at ° C for 1 day.

Then, the dip molding was performed 50 times in the same manner as in Reference Example 3 except that the dip molding composition thus obtained was used. The amount of nitrate ions in the dip molding composition after 50 times of dip molding is considered to be about the same as in Reference Example 3.

Next, the composition for dip molding after 50 times of dip molding is covered in the same container in an amount of 1/2 or more of the container volume, so that there is no contact with the outside air. In an environment, it is stored at 30 ° C. for one day, and the dip molding composition after storage is used to perform dip molding again under the same conditions to obtain an evaluation dip molded product, which is the same as in Example 1. Each measurement was performed. The results are shown in Table 2.

<Example 3>
By measuring the number of denitrifying bacteria in the latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 by the above method, it was confirmed that the number of denitrifying bacteria was 1.0 × 10 ³ (CFU / ml) or less. After that, the latex was adjusted to a solid content concentration of 17% by weight, and then, with respect to 100 parts of the solid content in the latex whose solid content concentration was adjusted, a vulcanizing agent dispersion (1 part of sulfur, zinc oxide 1. 8.66 parts of a dispersion consisting of 5 parts, 0.5 parts of zinc diethylcarbamate, 0.03 parts of potassium hydroxide and 5.63 parts of water) was mixed, and then an appropriate amount of 5 wt% potassium hydroxide aqueous solution was removed. Ionized water was added to obtain a dip molding composition having a solid content concentration of 17% by weight and a pH of 10.0. Then, the obtained dip molding composition is placed in a container so that the amount is less than 1/2 of the volume of the container, and the lid is not closed to create an environment in which there is contact with the outside air. , 30 ° C. for 1 day.

Then, the dip molding was performed 50 times in the same manner as in Reference Example 2 except that the dip molding composition thus obtained was used. The amount of nitrate ions in the dip molding composition after 50 times of dip molding is considered to be about the same as in Reference Example 2.

Next, the dip molding composition after 50 times of dip molding is brought into contact with the outside air in the same container in an amount less than 1/2 of the container volume and without a lid. In an environment where there is a problem, the product is stored at 30 ° C. for one day, and the dip molding composition after storage is used to perform dip molding again under the same conditions to obtain an evaluation dip molded product. Each measurement was performed in the same manner as above. The results are shown in Table 2.

<Example 4>
The denitrifying bacteria were propagated in the latex by immersing the culture medium in which the denitrifying bacteria were cultured in the latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 and storing the culture medium at room temperature for one day. When the denitrifying bacteria count was measured by the above method, it was ^{1.0 × 10 6 (CFU / ml} ) or more. Next, the latex in which the denitrifying bacteria were propagated was adjusted to a solid content concentration of 9% by weight, and then the vulcanizer dispersion (1 part of sulfur, After mixing 8.66 parts of a dispersion consisting of 1.5 parts of zinc oxide, 0.5 parts of zinc diethylcarbamate, 0.03 parts of potassium hydroxide and 5.63 parts of water), an appropriate amount of 5% by weight hydroxide is added. An aqueous potassium solution and deionized water were added to obtain a dip molding composition having a solid content concentration of 9% by weight and a pH of 10.0. Then, the obtained dip molding composition is placed in a container so that the amount is less than 1/2 of the volume of the container, and the lid is not closed to create an environment in which there is contact with the outside air. It was aged at 5 ° C. for 1 day.

Then, the dip molding was performed 50 times in the same manner as in Reference Example 3 except that the dip molding composition thus obtained was used. The amount of nitrate ions in the dip molding composition after 50 times of dip molding is considered to be about the same as in Reference Example 3.

Next, the dip molding composition after 50 times of dip molding is brought into contact with the outside air in the same container in an amount less than 1/2 of the container volume and without a lid. In an environment where there is a problem, the product is stored at 5 ° C. for one day, and the dip molding composition after storage is used to perform dip molding again under the same conditions to obtain an evaluation dip molded product. Each measurement was performed in the same manner as above. The results are shown in Table 2.

<Example 5>
The denitrifying bacteria were propagated in the latex by immersing the culture medium in which the denitrifying bacteria were cultured in the latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 and storing the culture medium at room temperature for one day. When the denitrifying bacteria count was measured by the above method, it was ^{1.0 × 10 6 (CFU / ml} ) or more. Next, the latex in which the denitrifying bacteria were propagated was adjusted to a solid content concentration of 25% by weight, and then the vulcanizing agent dispersion (1 part of sulfur, After mixing 8.66 parts of a dispersion consisting of 1.5 parts of zinc oxide, 0.5 parts of zinc diethylcarbamate, 0.03 parts of potassium hydroxide and 5.63 parts of water), an appropriate amount of 5% by weight hydroxide is added. An aqueous potassium solution and deionized water were added to obtain a dip molding composition having a solid content concentration of 25% by weight and a pH of 10.0. Then, the obtained dip molding composition is placed in a container so that the amount is less than 1/2 of the volume of the container, and the lid is not closed to create an environment in which there is contact with the outside air. , 30 ° C. for 1 day.

Then, the dip molding was performed 50 times in the same manner as in Reference Example 1 except that the dip molding composition thus obtained was used. The amount of nitrate ions in the dip molding composition after 50 times of dip molding is considered to be about the same as in Reference Example 1.

Next, the dip molding composition after 50 times of dip molding is brought into contact with the outside air in the same container in an amount less than 1/2 of the container volume and without a lid. In an environment where there is a problem, the product is stored at 30 ° C. for one day, and the dip molding composition after storage is used to perform dip molding again under the same conditions to obtain an evaluation dip molded product. Each measurement was performed in the same manner as above. The results are shown in Table 2.

<Comparative example 1>
The denitrifying bacteria were propagated in the latex by immersing the culture medium in which the denitrifying bacteria were cultured in the latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 and storing the culture medium at room temperature for one day. When the denitrifying bacteria count was measured by the above method, it was ^{1.0 × 10 6 (CFU / ml} ) or more. Next, the latex in which the denitrifying bacteria were propagated was adjusted to a solid content concentration of 9% by weight, and then the vulcanizer dispersion (1 part of sulfur, After mixing 8.66 parts of a dispersion consisting of 1.5 parts of zinc oxide, 0.5 parts of zinc diethylcarbamate, 0.03 parts of potassium hydroxide and 5.63 parts of water), an appropriate amount of 5% by weight hydroxide is added. An aqueous potassium solution and deionized water were added to obtain a dip molding composition having a solid content concentration of 9% by weight and a pH of 10.0. Then, the obtained dip molding composition is placed in a container so that the amount is less than 1/2 of the volume of the container, and the lid is not closed to create an environment in which there is contact with the outside air. , 30 ° C. for 1 day.

Then, the dip molding was performed 50 times in the same manner as in Reference Example 3 except that the dip molding composition thus obtained was used. The amount of nitrate ions in the dip molding composition after 50 times of dip molding is considered to be about the same as in Reference Example 3.

Next, the dip molding composition after 50 times of dip molding is brought into contact with the outside air in the same container in an amount less than 1/2 of the container volume and without a lid. In an environment where there is a problem, the product is stored at 30 ° C. for one day, and the dip molding composition after storage is used to perform dip molding again under the same conditions to obtain an evaluation dip molded product. Each measurement was performed in the same manner as above. The results are shown in Table 2.

<Comparative example 2>
The denitrifying bacteria were propagated in the latex by immersing the culture medium in which the denitrifying bacteria were cultured in the latex of the carboxyl group-containing nitrile rubber obtained in Production Example 1 and storing the culture medium at room temperature for one day. When the denitrifying bacteria count was measured by the above method, it was ^{1.0 × 10 6 (CFU / ml} ) or more. Next, the latex in which the denitrifying bacteria were propagated was adjusted to a solid content concentration of 9% by weight, and then the vulcanizer dispersion (1 part of sulfur, After mixing 8.66 parts of a dispersion consisting of 1.5 parts of zinc oxide, 0.5 parts of zinc diethylcarbamate, 0.03 parts of potassium hydroxide and 5.63 parts of water), an appropriate amount of 5% by weight hydroxide is added. An aqueous potassium solution and deionized water were added to obtain a dip molding composition having a solid content concentration of 9% by weight and a pH of 10.0. Then, the obtained dip molding composition is placed in a container so that the amount is 1/2 or more of the volume of the container, and the lid is put on the container to create an environment in which there is no contact with the outside air. It was aged at ° C for 1 day.

Then, the dip molding was performed 50 times in the same manner as in Reference Example 3 except that the dip molding composition thus obtained was used. The amount of nitrate ions in the dip molding composition after 50 times of dip molding is considered to be about the same as in Reference Example 3.

Next, the composition for dip molding after 50 times of dip molding is covered in the same container in an amount of 1/2 or more of the container volume, so that there is no contact with the outside air. In an environment, it is stored at 30 ° C. for one day, and the dip molding composition after storage is used to perform dip molding again under the same conditions to obtain an evaluation dip molded product, which is the same as in Example 1. Each measurement was performed. The results are shown in Table 2.

Table 1 shows the dip molding conditions and measurement results of Reference Examples 1 to 3, and Table 2 shows the dip molding conditions, storage conditions, and measurement results of Examples 1 to 5 and Comparative Examples 1 and 2, respectively.

As shown in Table 2, the amount of nitrate (50 times the amount of nitrate ions in after the dip molding) 10 ppm by weight or less, or the amount of 1.0 × denitrifying bacteria after storage 10 ⁵ ( In Examples 1 to 5 in which CFU / ml) or less, the amount of nitrite ion (the amount of nitrite ion after storage) can be controlled to 10 wt ppm or less, and the yellowness (yellowness) of the obtained dip molded product (CFU / ml) or less can be controlled. YI) was kept low and yellowing was properly prevented.

On the other hand, the amount of nitrate ions (the amount of nitrate ions in after 50 times of dip molding) is greater than 10 wt ppm, and denitrifying bacteria after preservation is ^{1.0 × 10 5 (CFU / ml} ) than In Comparative Examples 1 and 2, the amount of nitrite ion was more than 10 wt ppm, and the yellowness (YI) of the obtained dip molded product became high, resulting in yellowing.

In this example and the comparative example, as described in (2) above, after the dip molding composition was produced using the dip molding composition, the dip molding composition was once stored and stored. The evaluation was performed when the dip molding composition was used again to produce a dip molded product. However, by repeating the dip molding in the storage environment of Examples 1 to 3 and 5, a plurality of dip molded products were evaluated. Since it can be considered that the same results as in Examples 1 to 3 and 5 can be obtained even when the above is obtained, a plurality of dips are repeatedly used as described in (1) above. It can be said that the same result can be obtained even when the molded product is repeatedly manufactured.

Claims (7)

A method for producing a dip molded product by dip molding a dip molding composition containing a polymer latex.
Nitrate is used as the coagulation salt and
A method for producing a dip molded product, which comprises performing dip molding under the condition that the amount of nitrite ion in the dip molding composition is controlled to 10 wt ppm or less. The method for producing a dip molded product according to claim 1, wherein the dip molding is performed under the condition that the amount of nitrate ions in the dip molding composition is controlled to 10 wt ppm or less. Method for producing a dip molding according to claim 1 or 2 perform dip molding by the amount of denitrifying bacteria in the dip-forming composition in ^{1.0 × 10 5 (CFU / ml} ) The following controlled conditions. The method for producing a dip molded product according to any one of claims 1 to 3, wherein the storage temperature at the time of storing the dip molding composition is in the range of 0 to 18 ° C. The method for producing a dip molded product according to any one of claims 1 to 4, wherein a dip molding composition having a history of being used for dip molding using nitrate as a coagulating salt is used. The method for producing a dip molded product according to any one of claims 1 to 5, wherein the solid content concentration of the dip molding composition is 3.0 to 50% by weight. The method for producing a dip molded product according to any one of claims 1 to 6, wherein the polymer constituting the polymer latex is nitrile rubber.