JPH07316211A - Copolymer latex composition and its production - Google Patents

Abstract

PURPOSE:To obtain a copolymer latex which is excellent in resistances to oil and chemicals, has a soft hand, and is suitable for a dip-molded article, etc. CONSTITUTION:A vinyl cyanide monomer (e.g. acrylonitrile) and a conjugated diene (e.g. butadiene) are subjected to emulsion polymn. in the presence of a polyhydroxy compd. An ethylenically unsatd. carboxylic acid [e.g. (meth) acrylic acid] may be added to the polymn. system to stabilize the resulting copolymer latex.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a latex, and more particularly to a method for producing a copolymer latex capable of obtaining a latex film having excellent oil resistance and chemical resistance and having a soft texture. . More specifically, it relates to latex that can be used for dip-molded articles such as gloves.

[0002]

BACKGROUND OF THE INVENTION Nitrile-butadiene copolymer latex (hereinafter abbreviated as NBR) is a dip for gloves, finger cots, etc. because it is a rubber that has excellent tensile strength and elongation characteristics, as well as oil resistance and chemical resistance. Widely used in products. However, NBR containing a large amount of a vinyl cyanide compound such as acrylonitrile is generally excellent in oil resistance and chemical resistance, but its glass transition temperature (Tg) becomes high, so that a soft texture cannot be obtained.
On the other hand, there are methods of increasing the content of a conjugated diene compound such as butadiene in NBR in order to improve the texture of NBR, or blending NBR and natural rubber, or laminating them. Become less sexual. Therefore,
As a method for obtaining an NBR latex film having excellent oil resistance and chemical resistance and having a soft texture, for example, a method of defining the molecular weight of the copolymer and the insoluble content of methyl ethyl ketone (JP-A-5-247266) and the like have been proposed. However, it cannot be said that the texture is still sufficient, and the texture tends to be poor especially at low temperatures. Therefore, there is a demand for a method of obtaining an NBR latex film having excellent oil resistance and chemical resistance and having a soft texture.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made in order to meet such a demand, and is an NBR latex capable of obtaining a film having excellent oil resistance and chemical resistance and having a soft texture. And its manufacturing method. That is, the present invention is: (1) Production of a copolymer latex characterized by emulsion-polymerizing a vinyl cyanide-based monomer and a conjugated diene-based monomer as monomer components in the presence of a polyhydroxy compound. Method. (2) The method for producing a copolymer latex according to (1), wherein the polyhydroxy compound is a glycol. (3) The method for producing a copolymer latex according to (1), wherein the polyhydroxy compound is propylene glycol. (4) The method for producing a copolymer latex according to (1), wherein the polyhydroxy compound is present in the range of 1 to 10 parts by weight per 100 parts by weight of the monomer mixture. (5) The method for producing a copolymer latex according to (1), wherein the vinyl cyanide-based monomer is acrylonitrile. (6) The method for producing a copolymer latex according to (1), wherein the conjugated diene monomer is butadiene. (7) The vinyl cyanide-based monomer is 20 to 45 parts by weight per 100 parts by weight of the monomer mixture, and the conjugated diene-based monomer is 5 parts by weight.
The method for producing the copolymer latex according to (1), wherein the amount is 5 to 80 parts by weight. (8) The method for producing a copolymer latex as described in (1), which further uses an ethylenically unsaturated carboxylic acid as a monomer component. (9) The method for producing a copolymer latex as described in (8), wherein the ethylenically unsaturated carboxylic acid is (meth) acrylic acid. (10) Monomer mixture 1 of ethylenically unsaturated carboxylic acid
The method for producing a copolymer latex according to (8), wherein the amount is 0.1 to 20 parts by weight per 00 parts by weight. (11) The method for producing a copolymer latex as described in (1), wherein the polyhydroxy compound is added at the start of emulsion polymerization. (12) The method for producing a copolymer latex according to (1), wherein the polyhydroxy compound is added during the emulsion polymerization. (13) A copolymer latex obtained by emulsion-polymerizing a vinyl cyanide-based monomer and a conjugated diene-based monomer as monomer components in the presence of a polyhydroxy compound. (14) The copolymer latex according to (13), which is for dip molding. Is.

[0004]

The copolymer latex in the present invention is obtained by emulsion polymerization of vinyl cyanide type monomers and conjugated diene type monomers as monomer components in the presence of a polyhydroxy compound. To be Examples of the vinyl cyanide-based monomer include acrylonitrile, methacrylonitrile, α-ethylacrylonitrile and the like. Of these, acrylonitrile is preferred. Vinyl cyanide monomer is 2 per 100 parts by weight of the monomer mixture.
It contains 0 to 45 parts by weight, preferably 30 to 45 parts by weight. When the amount of vinyl cyanide-based monomer is less than 20 parts by weight, the oil resistance and chemical resistance of the obtained NBR may be insufficient. On the other hand, when it exceeds 45 parts by weight, the vinyl cyanide-based monomer may be insufficient. The copolymerization reaction is difficult to proceed from the viewpoint of the copolymerization ratio between the polymer and the conjugated diene monomer, and a homopolymer of vinyl cyanide monomer may be produced. As the conjugated diene-based monomer, butadiene, isoprene, chloroprene, etc. are used, and butadiene or isoprene is particularly preferably used. The conjugated diene-based monomer is a monomer mixture 1
55 to 80 parts by weight per 100 parts by weight, preferably 5
Including 5 to 70 parts by weight.

In the present invention, an ethylenically unsaturated carboxylic acid can be further used as a monomer component in order to improve the stability of the latex. Examples of the ethylenically unsaturated carboxylic acid monomer include monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, and dicarboxylic acids (anhydrides) such as maleic acid, fumaric acid and itaconic acid. These may be used alone or in combination of two or more. Of these, acrylic acid and methacrylic acid are particularly preferably used. When an ethylenically unsaturated carboxylic acid monomer is used, the amount used is 0.1 to 20 parts by weight, preferably 1 to 15 parts by weight, more preferably 3 to 7 parts by weight, based on 100 parts by weight of the monomer mixture. The range is appropriate.

In the present invention, a polyhydroxy compound is contained in the copolymer latex in order to improve the flexibility of NBR. The polyhydroxy compound is preferably added at the start of the copolymer latex polymerization or during the polymerization. When added during the polymerization, the higher the conversion of the monomer is, the lower the effect of softening is. Therefore, the conversion is preferably up to 70%, more preferably 50.
It is suitable to add up to%. When the polyhydroxy compound is added after polymerization, it is very difficult to obtain a soft texture. Such a polyhydroxy compound has a molecular weight of 10
A polyhydroxy compound of 00 or less is preferable, for example, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, capryl alcohol, nonyl alcohol, decyl alcohol, cyclopentanol, monohydric alcohols such as benzyl alcohol, ethylene glycol, propylene glycol, Three glycols such as dipropylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, pinacol, glycerin, trimethylolpropane and the like. Polyhydric alcohols, erythritol, pentaerythritol, tetrahydric alcohols such as traits, hexahydric alcohols such as sorbit, sucrose, other, polyether polyols, polyester Polyols and the like can be mentioned. Of these, glycols are particularly preferable, and propylene glycol is further preferable. The amount of the polyhydroxy compound used is 1 to 100 parts by weight of the monomer mixture.
The range of 10 parts by weight is preferable, and the range of 1 to 4 parts by weight is more preferable.

The copolymer latex used in the present invention can be obtained by emulsion polymerization. Emulsion polymerization is carried out by adding a monomer mixture, an emulsifier, a polymerization initiator, a molecular weight modifier and the like to an aqueous medium such as water according to a conventional method.
Sodium dodecylbenzene sulfonate as an emulsifier,
Sodium lauryl sulfate, sodium diphenyl ether disulfonate, formalin condensate of naphthalene sulfonate, anionic emulsifier such as sodium succinate dialkyl ester sulfonate, cationic emulsifier such as trimethylammonium chloride, dialkylammonium chloride, polyoxyethylene alkyl ether, polyoxy Nonionic emulsifiers such as ethylene alkylphenol ether and polyoxyethylene alkyl ester may be used alone or in combination of two or more kinds. The emulsifier is used in an amount of 0.1 per 100 parts by weight of the monomer mixture.
1 to 10 parts by weight is suitable.

The polymerization initiator is not particularly limited, and examples thereof include persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, and organic compounds such as cumene hydroperoxide, benzoyl peroxide and isopropylbenzene hydroperoxide. Azo initiators such as peroxides and azobisisobutyronitrile are used. These may be used alone or in combination of two or more. In the present invention, the above-mentioned polymerization initiator can also be used as a redox polymerization initiator in combination with a reducing agent such as sodium bisulfite and ferrous sulfate. In the present invention, a redox type polymerization initiator is preferable. In the present invention, the amount of the polymerization initiator used is suitably 0.01 to 2 parts by weight per 100 parts by weight of the monomer mixture.

As the molecular weight modifier, dodecyl mercaptan, octyl mercaptan, decyl mercaptan, hexyl mercaptan, triglycol dimercaptan, 2
-Alkyl mercaptans such as ethylhexyl thioglycolate, dimethylxanthogen disulfide,
Xanthogen disulfides such as diisopropylxanthogen disulfide, thiuram disulfides such as tetraethylthiuram disulfide and tetrabutylthiuram disulfide, halogen compounds such as carbon tetrachloride and carbon tetrabromide, acrolein, terpinolene, dipentene and the like are used. These may be used alone or in combination of two or more. The amount of the molecular weight modifier used is appropriately in the range of 0.01 to 10 parts by weight per 100 parts by weight of the monomer.

The emulsion polymerization in the present invention is usually 0 to 100.
It is carried out at a temperature of [deg.] C. until the conversion of the monomer reaches 95 to 98%. In the polymerization of the copolymer latex of the present invention, if necessary, antiaging agents such as styrenated phenols and hindered phenols, silicone-based,
Defoaming agents such as higher alcohols, as well as additives such as reaction terminators and dispersants may be used. The emulsion polymerization may be carried out by a seed polymerization method in which a small amount of a vinyl compound is emulsion-polymerized beforehand to form a seed in order to make the particle size of the latex obtained uniform. In addition to the batch charging method in which the monomer components are batch-added to the polymerization system, the monomer split charging polymerization method or the monomer continuous addition batch polymerization method in which the monomer components are split and added to the polymerization system can also be used. The copolymer latex of the present invention can be used in a wide range of fields such as dip molding processed products and molding materials such as foam rubber,
It can be suitably used for dip-formed products. Dip-molded products are made by immersing the mold in a dip-molding compounding liquid containing sulfur, vulcanization accelerator, vulcanizing agent such as zinc or anti-aging agent, filler, thickener, etc. After the latex is deposited, a rubber film is formed and, if necessary, it is obtained by heat treatment such as drying.

[0011]

As described above, the copolymer latex according to the present invention is obtained by emulsion-polymerizing a vinyl cyanide monomer and a conjugated diene monomer as a monomer component in the presence of a polyhydroxy compound. A method for producing a copolymer latex characterized by: forming an NBR film having excellent oil resistance and chemical resistance and having a soft texture, which is used for dip products such as gloves and finger cots. be able to.

[0012]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples. The parts by weight in the examples are based on 100 parts by weight of the monomer mixture unless otherwise specified.

[0013]

Examples 1 to 9 In an autoclave equipped with a thermometer and a stirrer, 3 parts by weight of sodium dodecylbenzene sulfonate, 0.8 parts by weight of naphthalene sulfonic acid formalin condensate, 2 parts by weight of seed polymer, [Table 1] were carried out. A predetermined amount of the polyhydroxy compound shown in Examples 1 to 9 is charged together with 100 parts by weight of deionized water and dissolved with stirring. 5 parts by weight of methacrylic acid or acrylic acid (however, [Table 1]
8 parts by weight in Example 6), [Table 1] a predetermined amount of acrylonitrile and butadiene shown in Examples 1 to 9, and t-
0.3 parts by weight of dodecyl mercaptan was added, and 0.1 part by weight of cumene hydroperoxide was added and reacted at a temperature of 10 ° C. in the presence of a ferrous sulfate-based reducing agent to obtain a copolymer latex. . After the reaction was completed, the copolymer latex was concentrated to adjust the solid content to 40%.

[0014]

[Comparative Examples 1 and 2] As a comparative example, a copolymer latex (Comparative Example 1) in which no polyhydroxy compound was used in the method for producing copolymer latex described in Examples, and 2 parts by weight of propylene glycol were used after completion of polymerization. The copolymer latex (Comparative Example 2) added under stirring was shown. [Table 1] shows the monomer composition of the copolymer latex, the polyhydroxy compound used, the polymerization rate of the monomer, the average particle size, and the amount of aggregate formation. The average particle diameter was determined by a light scattering method using a Coulter counter at a temperature of 25 ° C. After the polymerization was completed, 100 g of the obtained copolymer latex (WET) was filtered through a 100-mesh wire net to measure the amount of the aggregate that remained on the wire net.

[0015]

[Table 1]

The amount of aggregates produced after polymerization was an index of polymerization stability, and was extremely small in any of Examples 1 to 9 and Comparative Examples 1 and 2. Therefore, it can be seen that the use of the polyhydroxy compound does not reduce the polymerization stability.

[0017]

[Test Example] Next, each of the copolymer latexes thus obtained was blended in the following parts by weight ratio to prepare a film, which was heat-treated at 120 ° C for 30 minutes to obtain oil resistance, chemical resistance and texture. The tensile strength (300% modulus) test, which serves as an index for, was tested. Here, the smaller the value of 300% modulus, the softer the feel of the film. Rubber latex (DRY) 100.0 parts ZnO 3.0 parts S 1.0 parts BZ 0.25 parts (BZ; ZnBDC; zinc n-butyldithiocarbamate)

The oil resistance test was evaluated by immersing the film heat-treated by the above method in kerosene and gasoline for 40 hours, and then evaluating the area swelling ratio obtained by the following formula. Further, the chemical resistance test, after immersing the film subjected to the heat treatment by the above method in 20% NaOH and 20% H ₂ SO ₄ for 40 hours, the area swelling ratio obtained by the following formula is the same as the oil resistance test. Evaluated. Here, it is shown that the smaller the numerical value of the area swelling rate is, the better the oil resistance and the chemical resistance are. Area swelling ratio (%) = (A−A ₀ ) / A ₀ × 100 A ₀ ; Area of film before immersion, A; Area of film after 40 hours of immersion Oil resistance, chemical resistance test and tensile strength (300 % Modulus)
The test results are shown in [Table 2].

[0019]

[Table 2]

It can be seen that Comparative Example 1 is excellent in oil resistance and chemical resistance, but the texture becomes hard because no polyhydroxy compound is used. Comparative Example 2 is a copolymer latex in which propylene glycol was added with stirring after the completion of the polymerization, and it was found that the texture was harder than when the polyhydroxy compound was added at the start of the polymerization or during the polymerization. On the other hand, it is understood that the latex of the present invention is excellent in oil resistance and chemical resistance and has a soft texture.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area C08L 9/04 LAY

Claims (14)

[Claims] 1. A method for producing a copolymer latex, comprising emulsion-polymerizing a vinyl cyanide monomer and a conjugated diene monomer as monomer components in the presence of a polyhydroxy compound. 2. The method for producing a copolymer latex according to claim 1, wherein the polyhydroxy compound is a glycol. 3. The method for producing a copolymer latex according to claim 1, wherein the polyhydroxy compound is propylene glycol. 4. A monomer mixture 10 containing a polyhydroxy compound.
The method for producing a copolymer latex according to claim 1, wherein the amount is 1 to 10 parts by weight per 0 parts by weight. 5. The method for producing a copolymer latex according to claim 1, wherein the vinyl cyanide-based monomer is acrylonitrile. 6. The method for producing a copolymer latex according to claim 1, wherein the conjugated diene monomer is butadiene. 7. A vinyl cyanide based monomer mixture 1
The method for producing a copolymer latex according to claim 1, wherein the conjugated diene-based monomer is 55 to 80 parts by weight per 20 parts by weight of 00. 8. The method for producing a copolymer latex according to claim 1, wherein an ethylenically unsaturated carboxylic acid is further used as a monomer component. 9. The method for producing a copolymer latex according to claim 8, wherein the ethylenically unsaturated carboxylic acid is (meth) acrylic acid. 10. The method for producing a copolymer latex according to claim 8, wherein the ethylenically unsaturated carboxylic acid is 0.1 to 20 parts by weight per 100 parts by weight of the monomer mixture. 11. The method for producing a copolymer latex according to claim 1, wherein the polyhydroxy compound is added at the start of emulsion polymerization. 12. The method for producing a copolymer latex according to claim 1, wherein the polyhydroxy compound is added during the emulsion polymerization. 13. A copolymer latex obtained by emulsion-polymerizing a vinyl cyanide monomer and a conjugated diene monomer as monomer components in the presence of a polyhydroxy compound. 14. The method according to claim 13, which is for dip molding.
The copolymer latex according to the item.