JPWO2007015450A1 - Dip molded product - Google Patents

Abstract

A dip-molded product obtained by dip-molding a dip-molding composition containing a rubber latex, wherein the dip-molded product contains an aromatic acid compound, and the dip-molded product is converted into ASTM-D135. A dip-molded product having an extraction amount of the aromatic acid compound measured in compliance with methanol in a condition of 10 minutes for 10 minutes or less with respect to the entire dip-molded product. According to the present invention, it is possible to provide a dip-molded article that is excellent in tensile strength and elongation at break, has a reduced amount of impurities near the surface of the molded article, and has a low surface electrical resistance.

Description

  The present invention relates to a dip-molded product obtained by dip-molding a dip-molding composition containing a rubber latex, and more specifically, a dip having a reduced surface electrical resistance with a reduced amount of impurities near the surface of the molded product. It relates to molded products.

  The molded product obtained by dip molding a composition for dip molding consisting of natural rubber latex or acrylonitrile-butadiene copolymer latex is flexible and has sufficient mechanical strength. Used in various fields.

  Such a rubber glove (dip-molded product) is obtained by attaching a coagulant such as calcium chloride to the surface of a mold having a shape such as a hand or a finger, and applying the mold to a latex composition for dip molding containing rubber latex. Then, the film is pulled up to form a coating film (dip-molded layer) on the surface of the mold, and then the dip-molded layer is vulcanized (crosslinked) by heating.

  It is important that gloves for manufacturing electronic parts and semiconductor parts have sufficiently high tensile strength and elongation at break, are attached close to the hand, and do not easily loosen or sag even after a long time. is there. Such properties are realized to some extent by rubber gloves using natural rubber latex. However, natural rubber products have poor resistance to organic solvents and contain proteins, so that there is a problem that it causes allergic reactions although there are differences among individuals, causing itching, rashes, respiratory disorders, and the like.

  Attempts have been made to use synthetic rubber latex in order to improve the above disadvantages of such natural rubber latex. For example, Patent Document 1 discloses a carboxy-modified acrylonitrile-butadiene copolymer latex. The dip-molded body obtained by dip-molding the latex described in this document is widely used because it has better oil resistance than rubber gloves obtained from natural rubber latex.

  On the other hand, in gloves for manufacturing precision electronic parts and semiconductor parts, it is demanded to reduce impurities such as fine particles on the surface and metal ions in the gloves, and in recent years, the demand has become increasingly severe. Furthermore, these electronic components are electrically very fragile, and in order to avoid the risk of contamination due to discharge due to charging of the glove, adsorption of fine particles, etc., reduction in surface electrical resistance is also required.

Although the polymer constituting the carboxy-modified acrylonitrile-butadiene copolymer latex as described above has a relatively low electrical insulating property, static electricity may be generated during the operation.
US Pat. No. 2,880,189

  The present invention has been made in view of such a situation, and has an object to provide a dip-molded product that is excellent in tensile strength and elongation at break, has a reduced amount of impurities near the surface of the molded product, and has a low surface electrical resistance. And

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have incorporated an aromatic acid compound in a dip-molded product obtained by dip-molding a dip-molding composition containing a rubber latex. The inventors have found that the above object can be achieved by controlling the amount of the free aromatic acid compound present in the vicinity of the surface of the molded product and extracted with methanol within a predetermined range, and the present invention has been completed.

That is, the dip molded product according to the present invention is
A dip molding product obtained by dip molding a dip molding composition containing rubber latex,
The dip-molded product contains an aromatic acid compound,
When the dip-molded product is measured according to ASTM-D135 and immersed in methanol for 10 minutes, the extraction amount of the aromatic acid compound is 10 ppm or less with respect to the entire dip-molded product. It is.

Preferably, when the dip molded article is immersed in methyl ethyl ketone at a temperature of 23 ° C. for 24 hours, the extraction amount of the aromatic acid compound is 20 to 10,000 ppm with respect to the entire dip molded article. It is a range.
Preferably, the surface electrical resistivity measured according to ASTM D257-93 under conditions of a temperature of 23 ° C., a relative humidity of 50%, and a measurement voltage of 250 V is 10 ¹⁰ Ω / square or less.
The aromatic acid compound is preferably an aromatic carboxylic acid compound, more preferably an aromatic monocarboxylic acid and / or an alkali metal salt thereof, and particularly preferably benzoic acid.

Preferably, the rubber latex is 30 to 89.5 wt% of conjugated diene monomer units, 10 to 50 wt% of ethylenically unsaturated nitrile monomer units, based on 100 wt% of all monomer units, This is a rubber latex containing 0.5 to 20% by weight of ethylenically unsaturated carboxylic acid monomer units.
In the present invention, the conjugated diene monomer unit is a 1,3-butadiene unit, the ethylenically unsaturated nitrile monomer unit is an acrylonitrile unit, and the ethylenically unsaturated carboxylic acid monomer unit is methacrylic acid. Preferably it is a unit.

According to the present invention, since the aromatic acid compound is contained in the dip-molded product, the insulation effect of the dip-molded product can be lowered by the effect of addition of the aromatic acid compound, and the dip molding with low surface electric resistance is achieved. Goods can be obtained.
Moreover, in the present invention, the content of the aromatic acid compound in the vicinity of the surface of the molded product is controlled within a predetermined range. Therefore, for example, even when the dip-formed product of the present invention is a glove for manufacturing a precision electronic component / semiconductor component, it is possible to effectively prevent the occurrence of contamination due to adsorption of impurities and fine particles.

  The dip-molded product of the present invention is obtained by dip-molding a dip-molding composition. First, before describing the dip-molded product of the present invention, the dip-molding composition used to obtain the dip-molded product of the present invention will be described.

Dip molding composition The dip molding composition used in the present invention contains at least a rubber latex, a crosslinking agent for crosslinking the rubber latex, and an aromatic acid compound added as necessary. .

Examples of the rubber latex constituting the rubber latex dip molding composition include natural rubber latex and synthetic conjugated diene rubber latex. Among these, a synthetic conjugated diene rubber latex can be preferably used because various properties of the molded product after dip molding can be arbitrarily adjusted.

  As a synthetic conjugated diene rubber latex, a monomer mixture consisting of a conjugated diene monomer and another monomer copolymerizable with the conjugated diene monomer added as necessary is emulsion-polymerized. Can be obtained.

  Although it does not specifically limit as a conjugated diene monomer, The C4-C12 compound containing a conjugated diene is preferable. Examples of such conjugated diene monomers include halogen-substituted butadienes such as chloroprene, 1,3-butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and the like can be mentioned. These conjugated diene monomers can be used alone or in combination of two or more. Of these, 1,3-butadiene can be preferably used. The content of the conjugated diene monomer unit in the resultant synthetic rubber latex is preferably 30 to 89.5% by weight, more preferably 45 to 79% by weight with respect to 100% by weight of the total monomer units. It is.

  Other monomers that can be copolymerized with the conjugated diene monomer are not particularly limited, and examples thereof include ethylenically unsaturated nitrile monomers, aromatic vinyl monomers, and ethylenically unsaturated carboxylic acid monomers. And ethylenically unsaturated carboxylic acid ester monomers and ethylenically unsaturated carboxylic acid amide monomers. Among these, an ethylenically unsaturated nitrile monomer, an aromatic vinyl monomer, and an ethylenically unsaturated carboxylic acid monomer are preferable. In particular, an ethylenically unsaturated nitrile monomer and an ethylenically unsaturated carboxylic acid monomer are preferable. The body is more preferably used.

Examples of the ethylenically unsaturated nitrile monomer include acrylonitrile and methacrylonitrile. Of these, acrylonitrile can be preferably used.
Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, monochlorostyrene, vinyltoluene and the like.
Examples of the ethylenically unsaturated carboxylic acid monomer include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid and cinnamic acid; itaconic acid, fumaric acid, maleic acid, butenetricarboxylic acid and the like. And ethylenically unsaturated polyvalent carboxylic acids; partial esters of ethylenically unsaturated polyvalent carboxylic acids such as itaconic acid monoethyl ester, fumaric acid monobutyl ester and maleic acid monobutyl ester; Among these, ethylenically unsaturated monocarboxylic acid is preferable, and methacrylic acid can be more preferably used.
Examples of the ethylenically unsaturated carboxylic acid ester monomer include methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, β-hydroxyethyl acrylate, β-hydroxypropyl acrylate, and β-hydroxy methacrylate. Examples include ethyl, glycidyl acrylate, glycidyl methacrylate, and N, N-dimethylaminoethyl (meth) acrylate.
Examples of the ethylenically unsaturated carboxylic acid amide monomer include (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N-methylol (meth) acrylamide and the like.

In addition to the above monomers, vinyl acetate, vinyl pyrrolidone, and the like can be used.
These monomers can be used alone or in combination of two or more.

  The conjugated diene rubber latex used in the present invention is a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, and an ethylenically-unsaturated monomer in that a dip-molded product having excellent flexibility and oil resistance and mechanical strength can be obtained. Those obtained by polymerizing a monomer mixture comprising a saturated carboxylic acid monomer can be preferably used. That is, in the present invention, a conjugated diene rubber obtained by polymerizing these monomers and containing a conjugated diene monomer unit, an ethylenically unsaturated nitrile monomer unit, and an ethylenically unsaturated carboxylic acid monomer unit. Latex is preferred.

  In this case, the content of each monomer unit in the resulting conjugated diene rubber latex is preferably in the following range.

  That is, the content of the conjugated diene monomer unit is preferably 30 to 89.5% by weight and more preferably 45 to 79% by weight with respect to 100% by weight of the total monomer units. The content of the ethylenically unsaturated nitrile monomer unit is preferably 10 to 50% by weight and more preferably 20 to 40% by weight with respect to 100% by weight of the total monomer units. The content of the ethylenically unsaturated carboxylic acid monomer unit is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight with respect to 100% by weight of the total monomer units.

Next, the manufacturing method of the conjugated diene rubber latex used by this invention is demonstrated.
The conjugated diene rubber 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 and polymerization initiators can be used.

  The emulsifier is not particularly limited, and examples thereof include an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant. Among these, anionic surfactants such as alkylbenzene sulfonates, aliphatic sulfonates, higher alcohol sulfates, α-olefin sulfonates, and alkyl ether sulfates can be preferably used. The amount of the emulsifier used is preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight with respect to 100 parts by weight of the total monomers.

  Although it does not specifically limit as a polymerization initiator, A radical initiator can be used preferably. Examples of such radical initiators include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; t-butyl peroxide, cumene hydroperoxide, p- Menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide , Organic peroxides such as t-butylperoxyisobutyrate; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate; Door can be. These polymerization initiators can be used alone or in combination of two or more. Among these radical initiators, inorganic or organic peroxides are preferable, inorganic peroxides are more preferable, and persulfates are particularly preferable. The amount of the polymerization initiator used is preferably 0.01 to 2 parts by weight, more preferably 0.05 to 1.5 parts by weight with respect to 100 parts by weight of the total monomers.

  In the present invention, polymerization auxiliary materials other than those described above may be used as necessary. Examples of such a polymerization auxiliary material include a molecular weight adjusting agent, a chelating agent, a dispersing agent, a pH adjusting agent, an oxygen scavenger, a particle diameter adjusting agent, and the like, and the type and amount used are not particularly limited.

  Emulsion polymerization is usually carried out in water using the monomers and polymerization auxiliary materials. The polymerization temperature is not particularly limited, but is usually 0 to 95 ° C, preferably 5 to 70 ° C. After stopping the polymerization reaction, a conjugated diene rubber latex can be obtained by removing unreacted monomers and adjusting the solid concentration and pH, if desired.

Crosslinking agent The dip molding composition used in the present invention further contains a crosslinking agent in order to crosslink the rubber latex described above.
Although it does not specifically limit as a crosslinking agent, Organic peroxide; Sulfur, such as powder sulfur, sulfur white, precipitation sulfur, colloidal sulfur, surface treatment sulfur, insoluble sulfur; Hexamethylenediamine, triethylenetetramine, tetraethylenepentamine, etc. Of polyamines; and the like. Of these, organic peroxides or sulfur are preferable.

  The content of the crosslinking agent is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 4 parts by weight, particularly preferably 0.1 to 100 parts by weight of the solid content in the dip molding composition. ~ 2 parts by weight. If the content of the cross-linking agent is too small, the molding tends to be insufficient, and if too much, the texture and tensile strength tend to be inferior.

  As the organic peroxide, those having a solid property at normal pressure and 30 ° C. and having a 10-hour half-life temperature of 150 ° C. or less are preferred, more preferably 130 ° C. or less, particularly 40 ° C. or more, and 120 ° C. or less Are preferred. The 10-hour half-life temperature means a temperature at which the amount of the organic peroxide that retains activity becomes half when the organic peroxide is heated at that temperature for 10 hours. That is, for example, an organic peroxide having a 10-hour half-life temperature of 100 ° C. has a property that the amount of the organic peroxide retaining activity is halved when heated at 100 ° C. for 10 hours. Have

  Examples of the organic peroxide include dibenzoyl peroxide, benzoyl (3-methylbenzoyl) peroxide, di (4-methylbenzoyl) peroxide, dilauroyl peroxide, distearoyl peroxide, and di-α-cumi. Examples include ruperoxide, 1,1-bis (t-butylperoxy) cyclododecane, succinic acid peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate, t-butylperoxymaleic acid, and the like. . These can be used alone or in combination of two or more.

  Of the above organic peroxides, dibenzoyl peroxide, benzoyl (3-methylbenzoyl) peroxide, di (4-methylbenzoyl) peroxide, and di-α-cumyl peroxide have acted as crosslinking agents. , At least a part of which becomes an aromatic acid compound. Therefore, when an aromatic acid compound is contained in a dip-molded product, which will be described later, a method of incorporating these organic peroxides as a crosslinking agent may be employed. Of these organic peroxides, dibenzoyl peroxide can be preferably used.

  Moreover, when using sulfur as a crosslinking agent, it is preferable to mix | blend a crosslinking accelerator (vulcanization accelerator) and a zinc oxide. As the crosslinking accelerator, those usually used in dip molding can be used. The usage-amount of a crosslinking accelerator is 0.1-10 weight part with respect to 100 weight part of solid content in the latex for dip molding, Preferably it is 0.2-4 weight part. The amount of zinc oxide used is 5 parts by weight or less, preferably 2 parts by weight or less, based on 100 parts by weight of the solid content in the dip molding latex.

Aromatic acid compound The dip molding composition used in the present invention preferably further contains an aromatic acid compound. By including an aromatic acid compound in the dip-molding composition, the insulation of the resulting dip-molded product can be lowered, and the surface electrical resistivity can be lowered. However, when the above-mentioned specific organic peroxide is used as the crosslinking agent, these organic peroxides, after acting as a crosslinking agent, at least part of them become an aromatic acid compound, Further, it is not necessary to contain an aromatic acid compound.

  As such an aromatic acid compound, a conventionally known aromatic acid compound can be used, and examples thereof include an aromatic carboxylic acid compound, an aromatic sulfonic acid compound, and the like. It is preferable to use a group carboxylic acid compound.

  Examples of the aromatic carboxylic acid compound include aromatic monocarboxylic acids such as benzoic acid, toluic acid, chlorobenzoic acid, and salicylic acid; aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, trimellitic acid, trimesic acid, and pyromellitic acid; And ester compounds such as methyl benzoate, ethyl benzoate, and propyl benzoate; and aromatic amide compounds such as benzoic acid methylamide, benzoic acid ethylamide, and benzoic acid propylamide; Moreover, the compound which has a carboxyl group can also be used as salts of alkali metals, such as potassium and sodium. These aromatic carboxylic acid compounds can be used alone or in combination of two or more. Of these, aromatic monocarboxylic acids and / or alkali metal salts thereof are preferred, and benzoic acid is particularly preferred from the viewpoint that the effect of lowering the insulating properties of the resulting dip-molded product is great.

The addition amount in the case of containing an aromatic acid compound in the dip molding composition is preferably 0.1 to 5.0 parts by weight, more preferably 100 parts by weight of the solid content in the dip molding composition. Is 0.2 to 4.0 parts by weight. By adjusting the addition amount of the aromatic acid compound, the content of the free aromatic acid compound in the obtained molded article can be controlled. If the amount of the aromatic acid compound added is too small, the effect of reducing the surface electrical resistivity of the resulting molded product tends to be lost. On the other hand, when the addition amount is too large, characteristics such as tensile strength and elongation at break of the obtained molded product tend to deteriorate.
Even when the above-mentioned specific organic peroxide is contained instead of the aromatic acid compound, it should be added so that the amount of the aromatic acid compound generated after acting as a crosslinking agent is within the above range. Is preferred.

Dip-molded article The dip-molded article of the present invention is obtained by dip-molding the above-described dip-molding composition, and contains at least a rubber latex and an aromatic acid compound.

  By including an aromatic acid compound in the dip molded product, the insulation of the dip molded product can be reduced, and as a result, the surface electrical resistivity can be lowered.

  Moreover, in the dip molded product of the present invention, the amount of the free aromatic acid compound in the vicinity of the surface of the dip molded product is controlled to a specific amount or less. Specifically, the dip-formed product of the present invention has an extraction amount of the aromatic acid compound measured in accordance with ASTM D-135 when immersed in methanol for 10 minutes. It is 10 ppm or less, preferably 5 ppm or less, based on the weight of the entire product. In this way, while containing an aromatic acid compound in the dip molded product, and by controlling the content in the vicinity of the surface to a specific amount or less, dip molding is performed while reducing impurities in the vicinity of the molded product surface. The insulation of the product can be reduced. The free aromatic acid compound extracted with methanol is mainly a free aromatic acid compound present in the vicinity of the surface of the dip-molded product.

  Furthermore, in the dip-molded product of the present invention, it is preferable that the amount of free aromatic acid compound in the entire dip-molded product is also controlled within a specific range. Specifically, when the dip molded product of the present invention is immersed in methyl ethyl ketone (MEK) at a temperature of 23 ° C. for 24 hours, the extraction amount of the aromatic acid compound is based on the total weight of the dip molded product. Thus, the range is preferably 20 to 10,000 ppm, more preferably 500 to 5000 ppm. By setting the amount of the free aromatic acid compound in the vicinity of the surface of the dip-molded product to the specified amount or less, and the amount of the free aromatic acid compound in the entire dip-molded product within the specified range, the aromatic acid The effect of reducing the surface electrical resistivity due to the inclusion of the compound can be effectively exhibited. The free aromatic acid compound extracted with methyl ethyl ketone is mainly a free aromatic acid compound present in the entire dip-molded product including the inside of the dip-molded layer.

In addition, since the dip-formed product of the present invention has the above-described configuration, the surface electrical resistivity measured in accordance with ASTM D257-93 under the conditions of a temperature of 23 ° C., a relative humidity of 50%, and a measurement voltage of 250 V. , Preferably 1 × 10 ¹⁰ Ω / square or less, more preferably 1 × 10 ⁹ Ω / square or less.

  In addition, as a method of including an aromatic acid compound in a dip-molded product, (1) the above-mentioned specific organic peroxide is contained as a crosslinking agent in the dip-molding composition, and acts as a crosslinking agent (reaction). And (2) a method of directly adding the above-mentioned aromatic acid compound into the dip-forming composition, and the like. The method and the method (2) may be used in combination.

Subsequently, the manufacturing method of the dip molded product of this invention is demonstrated.
The dip-molded product of the present invention is obtained by dip-molding the above-described dip-molding composition. 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. For example, when the dip-formed product is a glove, the shape of the dip-molding die may be various shapes such as a shape from the wrist to the fingertip and a shape from the elbow to the fingertip. The surface of the dip mold may be subjected to surface processing such as gloss processing, semi-gloss processing, non-gloss processing, and weave pattern processing on the entire surface or a part thereof.

  The coagulant solution is a solution in which a coagulant capable of coagulating latex particles is dissolved in water, alcohol or a mixture thereof. Examples of the coagulant include metal halides, nitrates, sulfates and the like.

  Next, the dip molding die to which the coagulant is adhered is immersed in the above dip molding latex composition, 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 in the dip molding die is heated to crosslink the rubber (polymer composition after coagulating latex) constituting the dip molding layer.
The heating temperature for crosslinking is preferably 60 to 160 ° C, more preferably 80 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 the temperature is too high, the oxidative degradation of the rubber is promoted and the physical properties of the molded product may be lowered. The heat treatment time may be appropriately selected according to the heat treatment temperature, but is usually 5 to 120 minutes.

  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.

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

Next, it is preferable to subject the inner surface and / or outer surface of the dip-formed product to a surface treatment by a method of chlorination treatment or a method of washing with ultrapure water. In the present invention, by performing such a surface treatment, the amount of free aromatic acid compound contained in the dip-molded product, particularly the amount of free aromatic acid compound in the vicinity of the surface of the dip-molded product is described above. It becomes possible to control to a specific amount.
Although it does not specifically limit as said chlorination process, For example, the method of immersing the obtained dip molding goods in the aqueous solution of chlorine concentration 100-5000ppm for about 1 second-about 10 minutes, and washing and drying after that is mentioned. . Examples of the cleaning with ultrapure water include a method in which ultrapure water having a specific resistance at 25 ° C. of 16 MΩcm or more is used for cleaning multiple times and then dried.
The above-described methods may be performed in combination. For example, a method of cleaning with ultrapure water after performing chlorination treatment may be employed.

The dip-molded product of the present invention has excellent tensile strength and elongation at break, has reduced impurities near the surface of the molded product, and has low surface electrical resistance.
In particular, the dip molded product of the present invention employs a configuration in which the amount of free aromatic acid compound in the vicinity of its surface is kept low, while the molded product contains a predetermined amount of aromatic acid compound. Yes. Therefore, while reducing the amount of impurities (free aromatic acid compound) in the vicinity of the surface, the effect of reducing the surface electrical resistance due to the effect of the aromatic acid compound contained inside the molded product. have.
Such dip-molded articles of the present invention include, for example, medical supplies such as nipples for baby bottles, syringes, conduits, and water pillows; toys and exercise tools such as balloons, dolls, balls, etc .; pressure forming bags, gas storage bags It can be suitably used for industrial articles such as; surgical gloves, household gloves, agricultural gloves, fishery gloves and industrial gloves; In particular, the dip-molded product of the present invention can be suitably used for gloves for manufacturing precision electronic parts and semiconductor parts, taking advantage of the above characteristics. 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. The dip molded product was evaluated by the following method.

Methanol extraction amount The methanol extraction amount of the obtained rubber gloves (dip-molded product) was determined according to ASTM-D135. That is, first, the inside of the obtained rubber gloves was filled with 250 ml of methanol, and then immersed in a beaker (with an internal volume of 1 L) containing 400 ml of methanol for 10 minutes, and then the rubber was put into the beaker from inside the beaker. The gloves were removed. Subsequently, the methanol in the beaker was evaporated to dryness, and the total amount of the extract was determined. Then, by correcting the total amount of the extract with the area of the blank and the sample, the actual weight of the extract is obtained, and by calculating the ratio of the actual weight of the extract to the total weight of the rubber gloves, the amount of methanol extracted Asked.
In this example, most (90% or more) of the extracted impurities were benzoic acid and benzoic acid derivatives.

Extraction amount of methyl ethyl ketone First, the palm part of the obtained rubber glove (dip molded product) was cut out and cut into about 5 mm square (about 1 g) to obtain a test piece. Next, this test piece was precisely weighed and immersed in 100 ml of methyl ethyl ketone at a temperature of 23 ° C. for 24 hours. Thereafter, the test piece was separated by filtration, and the amount of benzoic acid in the filtrate was quantified by high performance liquid chromatography. . And the methyl ethyl ketone extraction amount was calculated | required by calculating the ratio of the weight of a benzoic acid with respect to the weight of the test piece before immersion.

A 10 cm square test piece was cut out from the palm portion of a rubber glove (dip-molded product) from which the surface electrical resistivity was obtained. The test piece was then left in a constant temperature / humidity chamber at 23 ° C. and a relative humidity of 50% for 12 hours, and under the same atmosphere, in accordance with ASTM D257-93, at a measurement voltage of 250 V, the surface electricity of the test piece was measured. The resistivity was measured. The upper limit in this measurement was 3.8 × 10 ¹² Ω / square.

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 at a tensile speed of 500 mm / min, and the tensile strength at break (MPa) and the elongation at break (%) were measured.

Example 1
Acrylonitrile-butadiene-methacrylic acid copolymer latex (manufactured by Nippon Zeon Co., Ltd., LX550L, pH: 8.3, solid content concentration: 45%, acrylonitrile unit: 27% by weight): 222.2 parts, sulfur as a crosslinking agent : 1.0 part, zinc dibutyldithiocarbamate as a vulcanization accelerator: 0.8 part, and zinc oxide: 1.0 part, respectively, and then adding a 3% aqueous solution of KOH to pH : 9.5, the solid content concentration was adjusted to 30% to obtain a latex. Next, 0.5 part of benzoic acid was added to 100 parts of the solid content in the latex, and the mixture was stirred for 12 hours to prepare a dip molding composition.

Next, rubber gloves (dip-molded products) were produced by the following method using the dip-molding composition prepared above.
That is, first, an aqueous coagulant solution was prepared by mixing 20 parts of calcium nitrate, 0.05 parts of polyethylene glycol octylphenyl ether, which is a nonionic emulsifier, and 80 parts of water. Next, a ceramic glove mold preliminarily heated to 60 ° C. is immersed in this aqueous coagulant solution for 5 seconds, pulled up, and then dried at a temperature of 50 ° C. for 10 minutes to allow the coagulant to adhere to the glove mold. It was. The glove mold to which the coagulant is attached is dipped in the dip molding composition obtained above for 6 seconds, pulled up, dried at a temperature of 50 ° C. for 10 minutes, and then heated to 40 ° C. It was immersed in warm water for 3 minutes to elute water-soluble impurities and form a dip-molded layer on the glove mold.

  Next, the glove mold on which the dip-formed layer was formed was dried under conditions of a temperature of 70 ° C. for 10 minutes, and subsequently heat-treated at a temperature of 120 ° C. for 30 minutes to cross-link the dip-formed layer. The dip-molded layer was peeled from the glove mold to obtain a rubber glove (dip-molded product) having a thickness of 0.1 mm.

  Next, the obtained rubber gloves were chlorinated. Specifically, first, the obtained rubber gloves were immersed in an aqueous solution having a chlorine concentration of 1000 ppm for 2 minutes, subsequently washed with running water for 5 minutes, and then dried at a temperature of 70 ° C. for 1 hour. The rubber gloves after the chlorination treatment were each evaluated for methanol extraction amount, methyl ethyl ketone extraction amount, surface electrical resistivity, tensile strength, and elongation at break by the above methods. The results are shown in Table 1.

Example 2
A rubber glove was produced in the same manner as in Example 1 except that the obtained rubber glove (dip-molded product) was subjected to chlorination treatment and further washed with ultrapure water. Evaluation was performed in the same manner as above. That is, in Example 2, the rubber gloves before the surface treatment were first immersed in an aqueous solution with a chlorine concentration of 1000 ppm for 2 minutes, then washed with running water for 5 minutes, and then the specific resistance at 25 ° C. was more than 15 MΩcm. It was washed with pure water three times, and after washing, dried at a temperature of 70 ° C. for 1 hour. The results are shown in Table 1.

Example 3
About the obtained rubber glove (dip molded product), a rubber glove was produced in the same manner as in Example 1 except that cleaning with ultrapure water was performed instead of chlorination treatment. Evaluation was performed. That is, first, in Example 3, talc was beaten on the rubber gloves before the surface treatment to reduce the surface tackiness. Next, it was washed three times with ultrapure water having a specific resistance at 25 ° C. of 15 MΩcm or more, and then dried at a temperature of 70 ° C. for 1 hour. The results are shown in Table 1.

Example 4
A rubber glove (dip-molded product) was produced in the same manner as in Example 1 except that the amount of benzoic acid added was changed to 2 parts by weight, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 5
Except for using sulfur as a crosslinking agent, zinc dibutyldithiocarbamate as a vulcanization accelerator, and dibenzoyl peroxide (BPO) as a crosslinking agent in place of zinc oxide, and not using benzoic acid In the same manner as in Example 1, rubber gloves (dip-molded products) were produced and evaluated in the same manner as in Example 1. The amount of dibenzoyl peroxide (BPO) added was 0.5 parts with respect to 100 parts of the solid content in the latex. The results are shown in Table 1.

Example 6
A rubber glove was produced in the same manner as in Example 5 except that the obtained rubber glove (dip-molded product) was subjected to chlorination treatment and further washed with ultrapure water. Evaluation was performed in the same manner as above. The chlorination treatment and cleaning with ultrapure water were performed under the same conditions as in Example 2. The results are shown in Table 1.

Comparative Example 1
About the obtained rubber glove (dip molded article), a rubber glove was produced in the same manner as in Example 1 except that chlorination treatment was not performed, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2
About the obtained rubber glove (dip molded product), a rubber glove was produced in the same manner as in Example 5 except that chlorination treatment was not performed, and evaluation was performed in the same manner as in Example 5. The results are shown in Table 1.

Comparative Example 3
A rubber glove (dip-formed product) was produced in the same manner as in Example 1 except that benzoic acid was not used, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

From Table 1, the following can be confirmed.
In Examples 1 to 6 containing a predetermined amount of benzoic acid, and the amount of free benzoic acid (impurity amount) in the vicinity of the rubber glove surface by methanol extraction was not more than a specific amount, the amount of free benzoic acid in the vicinity of the rubber glove surface It can be confirmed that the surface electrical resistivity can be lowered to 1 × 10 ¹⁰ Ω / square or less while realizing the reduction of the above. Furthermore, in Examples 1-6, the tensile strength and the elongation at break are also kept good. In particular, in Examples 1 to 6, when benzoic acid was directly added to rubber gloves (dip molded products), benzoic acid was directly added (Examples 1 to 4) and dibenzoyl peroxide (BPO). Good results could be obtained by any of the methods when added (Examples 5 and 6).

On the other hand, from Comparative Examples 1 and 2, in the case where the surface treatment of the rubber glove (dip molded product) was not performed, the surface electrical resistivity could be lowered, but in the vicinity of the rubber glove surface by methanol extraction. As a result, the amount of benzoic acid (amount of impurities) increases and there is a risk of contamination.
Further, from Comparative Example 3, when benzoic acid was not contained, the surface electrical resistivity was increased. In Comparative Example 3, both the methanol extraction amount and the methyl ethyl ketone extraction amount were very small and were below the detection limit value.

Claims (10)

A dip molding product obtained by dip molding a dip molding composition containing rubber latex,
The dip-molded product contains an aromatic acid compound,
When the dip-molded product is measured according to ASTM-D135 and immersed in methanol for 10 minutes, the extraction amount of the aromatic acid compound is 10 ppm or less with respect to the entire dip-molded product. Dip molded product.   When the dip-molded product is immersed in methyl ethyl ketone at a temperature of 23 ° C. for 24 hours, the extraction amount of the aromatic acid compound is in the range of 20 to 10,000 ppm with respect to the entire dip-molded product. The dip-formed product according to claim 1. 3. The dip molding according to claim 1, wherein the surface electrical resistivity measured in accordance with ASTM D257-93 under conditions of a temperature of 23 ° C., a relative humidity of 50%, and a measurement voltage of 250 V is 10 ¹⁰ Ω / square or less. Goods.   The dip-molded product according to any one of claims 1 to 3, wherein the aromatic acid compound is an aromatic carboxylic acid compound.   The dip-molded article according to claim 4, wherein the aromatic carboxylic acid compound is an aromatic monocarboxylic acid and / or an alkali metal salt thereof.   The dip-molded article according to claim 4 or 5, wherein the aromatic carboxylic acid compound is benzoic acid.   The rubber latex is 30 to 89.5% by weight of conjugated diene monomer unit, 10 to 50% by weight of ethylenically unsaturated nitrile monomer unit, The dip-molded article according to any one of claims 1 to 6, which is a latex of rubber containing 0.5 to 20% by weight of a saturated carboxylic acid monomer unit.   The dip-molded article according to claim 7, wherein the conjugated diene monomer unit is a 1,3-butadiene unit.   The dip-molded product according to claim 7 or 8, wherein the ethylenically unsaturated nitrile monomer unit is an acrylonitrile unit. The dip-molded product according to any one of claims 7 to 9, wherein the ethylenically unsaturated carboxylic acid monomer unit is a methacrylic acid unit.