JP2012188552A - Polychloroprene latex - Google Patents

Abstract

【Task】
It is an object of the present invention to provide a polychloroprene latex excellent in storage stability and mechanical stability.
[Means for Solving the Problems]
That is, in the present invention, chloroprene alone or a monomer copolymerizable with chloroprene and chloroprene is emulsion-polymerized in the presence of 1.0 to 10 parts by mass of polyvinyl alcohol, and free polyvinyl alcohol is 70% of the total polyvinyl alcohol. It is the following polychloroprene latex. The solid content of the polychloroprene latex is preferably 40 to 65% by mass. The saponification degree of polyvinyl alcohol is preferably 80 to 93 mol%, and the monomer copolymerizable with chloroprene is preferably an ethylenically unsaturated carboxylic acid. Polychloroprene latex can be used as a raw material for the adhesive.
[Selection figure] None

Description

  The present invention relates to a polychloroprene latex and a water-based adhesive using the same.

Polychloroprene latex is used in civil engineering and construction, plywood, furniture, shoes, wet suits, water-based adhesives, labor gloves, laboratory gloves, medical gloves, rubber threads, balloons and other immersion moldings, civil engineering, and construction. It is used in various fields such as waterproof coatings. In particular, polychloroprene latex produced using polyvinyl alcohol as an emulsifier is often used as an aqueous adhesive because it is excellent in blending stability and tackiness. However, compared to latex using an emulsifier other than polyvinyl alcohol, the mechanical stability tends to be low, and when the product is vibrated during transportation or mechanical shearing force is applied by a stirrer or pump, May be generated. In addition, since polyvinyl alcohol is water-soluble, adhesives using polychloroprene latex obtained by emulsion polymerization using this may have insufficient water resistance in places exposed to rain and moisture. . In order to solve such problems, several improvements have been studied.
For example, Patent Document 1 invents the production of polychloroprene latex having excellent water resistance by copolymerizing chloroprene and ethylenically unsaturated carboxylic acid in the presence of polyvinyl alcohol and glycol diether.
In Patent Literature 2, chloroprene alone or a monomer copolymerizable with chloroprene and chloroprene is emulsion-polymerized in the presence of a polyoxyethylene alkyl ether having an HLB value of 14 to 19 and polyvinyl alcohol to lower the viscosity. Inventing that a polychloroprene latex composition having excellent handling properties and water resistance can be obtained.

JP 2004-076015 A JP 2005-008859 A

  The polychloroprene latex produced by the techniques of Patent Documents 1 and 2 has no problem in normal use, but depending on the storage environment of the product, aggregates may be generated in the latex or component sedimentation may occur. It was. Further, when an extreme mechanical shear force is applied, a solidified product may be generated. In addition, although these known technologies have an effect of improving a certain level of water resistance, the water resistance is further improved for use in an application that is completely immersed in water, such as an adhesive for shoes and wet suits. Was necessary.

This invention makes it a subject to provide the polychloroprene latex excellent in these storage stability and mechanical stability.

  That is, in the present invention, chloroprene alone or a monomer copolymerizable with chloroprene and chloroprene is emulsion-polymerized in the presence of 1.0 to 10 parts by mass of polyvinyl alcohol with respect to a total of 100 parts by mass of all monomers. And the polychloroprene latex whose free polyvinyl alcohol is 70 mass% or less in the total polyvinyl alcohol. The solid content of the polychloroprene latex is preferably 40 to 65% by mass. The saponification degree of polyvinyl alcohol is preferably 80 mol% or more, and the monomer copolymerizable with chloroprene is preferably an ethylenically unsaturated carboxylic acid. Polychloroprene latex can be used as a raw material for the adhesive.

According to the present invention, a polychloroprene latex excellent in storage stability and mechanical stability can be obtained.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

  The polychloroprene latex is a latex (emulsion) obtained by dispersing polychloroprene in water. Polychloroprene is a homopolymer of 2-chloro-1,3-butadiene (hereinafter referred to as chloroprene), or a copolymer of chloroprene and a monomer copolymerizable with chloroprene.

  Examples of the monomer copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, sulfur, butadiene, isoprene, styrene, methacrylic acid and esters thereof. There are acrylic acid and esters thereof, and two or more kinds may be used as necessary. In the present invention, the chloroprene polymer is preferably a copolymer of chloroprene and an ethylenically unsaturated carboxylic acid. As the ethylenically unsaturated carboxylic acid, methacrylic acid is most preferable, and the charging amount is preferably 0.01 to 5 parts by mass of the carboxyl group-containing vinyl monomer out of a total of 100 parts by mass of the monomers. When a carboxyl group-containing vinyl monomer is copolymerized, when a metal oxide such as zinc oxide or magnesium oxide is added to the adhesive, cross-linking of divalent metal ions and carboxyl groups occurs, resulting in adhesion such as heat resistance and solvent resistance. This is because the performance can be improved.

  In order to obtain a polychloroprene latex, chloroprene alone or a monomer copolymerizable with chloroprene and chloroprene is emulsion-polymerized using a polymerization initiator and a chain transfer agent in the presence of polyvinyl alcohol, and a predetermined polymerization is performed. When the rate is reached, a polymerization terminator may be added to terminate the polymerization.

  In the present invention, polyvinyl alcohol is used as an emulsifier used for emulsion polymerization of chloroprene. Polyvinyl alcohol is a polymer obtained by saponifying a homopolymer of a vinyl ester monomer or a copolymer of a vinyl ester monomer and a monomer copolymerizable therewith.

The vinyl ester monomer is not particularly limited, but vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and Examples include vinyl versatate. Among these, it is desirable to use vinyl acetate that is excellent in stability during polymerization.
When producing polyvinyl alcohol, if necessary, other monomers copolymerizable with the above-described monomers may be copolymerized. In this case, the copolymerizable monomer is not particularly limited, and examples thereof include olefins such as ethylene, propylene, 1-butene and isobutene, acrylic acid, methacrylic acid, crotonic acid, phthalic acid, maleic acid. Acids, unsaturated acids such as itaconic acid, or salts thereof, acrylamide, N-alkyl acrylamide having 1 to 18 carbon atoms, N, N-dialkyl acrylamide, diacetone acrylamide, 2-acrylamidopropanesulfonic acid and salts thereof, acrylamidopropyl Acrylamides such as dimethylamine and salts thereof or quaternary salts thereof, methacrylamide, N-alkyl methacrylamide having 1 to 18 carbon atoms, N, N-dialkyl methacrylamide, diacetone methacrylamide, 2-methacrylamide propane sulfonic acid And its salt 3,4-diacetoxy-1-butene, glycerin monoallyl ether, methacrylamide such as methacrylamide propyl dimethylamine and its salt or quaternary salt thereof, alkyl vinyl ether having alkyl chain length of 1 to 18 carbon atoms, hydroxyalkyl Vinyl ethers such as vinyl ether and alkoxyalkyl vinyl ether, N-vinyl amides such as N-vinyl pyrrolidone, N-vinyl formamide and N-vinyl acetamide, vinyl cyanides such as acrylonitrile and methacrylonitrile, vinyl chloride, vinylidene chloride, fluorine Vinyl halides such as vinyl chloride, vinylidene fluoride, vinyl bromide, vinylidene bromide, vinyl silanes such as trimethoxyvinyl silane, allyl acetate, allyl chloride, allyl alcohol, dimethyl Allyl compounds such as Lil alcohol and vinyl silyl compounds, and isopropenyl acetate such as vinyl trimethoxy silane.
In addition, although the usage-amount of these other copolymerizable monomers is not specifically limited, It is preferable that it is 0.001 mol% or more and less than 20 mol% with respect to the monomer whole quantity.

  The polymerization method of these monomers is not particularly limited, and a known radical polymerization method can be employed. Generally, it is produced by solution polymerization using alcohol such as methanol, ethanol and isopropyl alcohol as a solvent, but may be produced by bulk polymerization, emulsion polymerization, suspension polymerization or the like. Moreover, when performing bulk polymerization or solution polymerization, continuous polymerization or batch polymerization may be used. Furthermore, the monomers may be charged all at once, may be charged separately, or may be added continuously or intermittently.

  The polymerization initiator used in radical polymerization is not particularly limited, but azobisisobutyronitrile, azobis-2,4-dimethylpareronitrile, azobis (4-methoxy-2,4-dimethylpareronitrile). ), Etc., peroxides such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, diisopropylpropyloxy Percarbonate compounds such as dicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, t-butylperoxyneodecanate, α-cumylperoxyneodecanate, t-butylperoxy Perester compounds such as Odekaneto, azobisdimethylvaleronitrile can be used a known radical polymerization initiator such as azo-bis-methoxy valeronitrile. In addition, the polymerization reaction temperature is not particularly limited, but can usually be set in a range of about 30 to 90 ° C.

  On the other hand, the saponification conditions for producing the modified polyvinyl alcohol are not particularly limited, and the polymer obtained by the above-described method may be saponified by a known method. Generally, it can carry out by hydrolyzing the ester part in a molecule | numerator in presence of an alkali catalyst or an acid catalyst. At this time, although the density | concentration of the copolymer in alcohol which is a polymerization solvent is not specifically limited, It is desirable that it is 10-80 mass%.

  Examples of the alkali catalyst used in this case include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate, alcoholates, and the like. As the acid catalyst, for example, an inorganic acid aqueous solution such as hydrochloric acid and sulfuric acid, or an organic acid such as p-toluenesulfonic acid can be used, and sodium hydroxide is particularly preferable.

  Further, the temperature of the saponification reaction is not particularly limited, but is preferably in the range of 10 to 70 ° C, more preferably 30 to 40 ° C. Although reaction time is not specifically limited, It is desirable to carry out in 30 minutes-3 hours.

  In the present invention, from the viewpoint of stably performing the emulsion polymerization operation of the chloroprene monomer, the saponification degree of polyvinyl alcohol is preferably 80 mol% or more, more preferably 85 to 99 mol%. The degree of polymerization is desirably 200 to 3000, and more desirably 200 to 700. The degree of saponification and the degree of polymerization described here are values measured by the method defined in JIS K 6726.

  The addition amount of polyvinyl alcohol is preferably 1.0 to 10 parts by mass with respect to 100 parts by mass in total of all monomers to be polymerized. If the amount is less than 1.0 part by mass, the protective colloid at the time of emulsion polymerization will be insufficient, and the polymerization stability tends to be poor. If the amount exceeds 10 parts by mass, the viscosity of the polymerization reaction system will increase and be uniform. Stirring becomes difficult.

  As the emulsifier used in the emulsion polymerization of the chloroprene monomer, polyvinyl alcohol is essential, but other nonionic emulsifiers can be used in combination as required. By using other nonionic emulsifiers together, it is possible to suppress the thickening during the polymerization and reduce the fine coagulum that becomes a clog during filtration. Specific examples of the nonionic emulsifier include, for example, polyoxyethylene derivatives such as polyoxyalkylene alkyl ether, polyoxyalkylene alkyl allyl ether, polyoxyalkylene sorbitan ether, polyoxyethylene castor oil ether, sorbitan monostearate, sorbitan monolaurate. Rate, sorbitan fatty acid esters such as sorbitan monopalmitate, glycerol fatty acid esters such as glycerol monostearate and glycerol monooleate, aliphatic alkanolamines, polyoxyethylene distyryl phenyl ether, polyoxyethylene tristyryl phenyl Examples include ether, polyoxyethylene naphthyl ether, polyoxyethylene hydroxy naphthyl ether, and the like.

  The polymerization temperature during the emulsion polymerization of the chloroprene monomer is preferably 5 to 45 ° C. in order to make the amount of free polyvinyl alcohol 70% or less. In particular, it is preferable to set the polymerization temperature to 30 to 40 ° C. because generation of chloroprene dimer as a by-product can be reduced.

  The polymerization initiator used in the emulsion polymerization of the chloroprene monomer is not particularly limited. For example, inorganic peroxides such as potassium persulfate, ketone peroxides, peroxyketals, hydroperoxides, There are organic peroxides such as dialkyl peroxides and diacyl peroxides. Of these, potassium persulfate is preferably used for stable polymerization.

  It is also possible to enhance the activity of the polymerization initiator during emulsion polymerization by using a redox initiator in combination with the above polymerization initiator. Specific examples of the reducing agent include sodium sulfite, ferrous sulfate, sodium anthraquinone-β-sulfonate, formamidine sulfonic acid, L-ascorbic acid and the like. The addition amount of the reducing agent is preferably 0.6 parts by mass or less.

  The type of chain transfer agent used in emulsion polymerization of chloroprene monomer is not particularly limited, and those usually used in emulsion polymerization of chloroprene can be used. For example, long chain such as n-dodecyl mercaptan and tert-dodecyl mercaptan Known chain transfer agents such as alkyl mercaptans, dialkylxanthogen disulfides such as diisopropylxanthogen disulfide and diethylxanthogen disulfide, and iodoform can be used.

  The polymerization terminator (polymerization inhibitor) is not particularly limited. For example, thiodiphenylamine, diethylhydroxylamine, hydroquinone, phenothiazine, pt-butylcatechol, 1,3,5-trihydroxybenzene, hydroquinone methyl ether, 2,6-di-t-butyl-4-methylphenol, 2,2-methylenebis (6-t-4-methylphenol), 4,4-butylenebis (6-t-butyl-3-methylphenol), ethylene Bis (oxyethylene) bis [3- (5-t-butyl-4-hydroxy-m-tolyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, penta Erythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphen Le) propionate], hydroxylamine or the like can be used.

  The polymerization rate of the chloroprene (co) polymer is not particularly limited, but can be arbitrarily adjusted to 80 to 100%. Removal of the unreacted monomer (demonomer) is performed by a known method such as heating under reduced pressure.

  In the polychloroprene latex in the present invention, the toluene insoluble content of the chloroprene (co) polymer is preferably 20 to 99%. If it is this range, the adhesive agent with the outstanding balance of adhesive force can be made.

The solid content concentration of the polychloroprene latex after removing the unreacted monomer and concentrating is preferably in the range of 40 to 65% by mass. When solid content concentration is less than 40 mass%, the adhesive strength of the adhesive agent obtained may fall, and when it exceeds 65 mass%, mechanical stability may fall.
The solid content concentration of the polychloroprene latex can be measured by the following method.
<Concentration of solid content>
Let X (g) be the mass of the aluminum dish alone. Let Y (g) be the mass of an aluminum dish containing 2 ml of latex sample. Let Z (g) be the mass after the aluminum dish containing the latex sample is dried at 125 ° C. for 1 hour. Solid content concentration (%) is calculated by the following formula.
Solid content concentration (%) = {(Z−X) / (Y−X)} × 100

The free polyvinyl alcohol contained in the polychloroprene latex is preferably 70% by mass or less in the total polyvinyl alcohol. When the amount of free polyvinyl alcohol exceeds 70% by mass, storage stability and mechanical stability are lowered. The amount of free polyvinyl alcohol is more preferably 20 to 50% by mass. Free polyvinyl alcohol can be calculated by the following method.
<Free polyvinyl alcohol>
A polychloroprene latex was coated on a PET film using an applicator for 100 μm, left to stand in a dark place at 23 ° C. and 50% RH for 3 days, further vacuum dried at room temperature, and then dried at 125 ° C. for 1 hour. To create a film. The film contains polyvinyl alcohol and water-soluble auxiliary agents other than polyvinyl alcohol. The film is weighed 1 (g) in a 100 ml beaker, 50 g of pure water at 30 ° C. is added, the film is immersed for 48 hours, and water-soluble components present in the film are extracted. After removing the film by wire mesh filtration, the extract is dried and solidified at 125 ° C. until there is no mass change, and the mass A (g) of the solid content is measured. This solid content includes free polyvinyl alcohol B (g) and water-soluble auxiliary agents other than polyvinyl alcohol.
The mass C (g) of the total polyvinyl alcohol and the mass D (g) of the water-soluble auxiliary other than polyvinyl alcohol contained in the coating 1 (g) are determined based on the preparation conditions for obtaining the polychloroprene latex. Is 100 parts by mass, the polymerization rate is E (%), the amount of polyvinyl alcohol charged is F (mass part), the amount of water-soluble auxiliary agent other than polyvinyl alcohol is G (mass part), The total of the charged substances is calculated as H (parts by mass) by the following formula.
C (g) = F / (E + F + G + H)
D (g) = G / (E + F + G + H)
Free polyvinyl alcohol B (g) is calculated by the following formula.
B (g) = AD
The ratio I of the free polyvinyl alcohol with respect to the total polyvinyl alcohol mass is calculated by the following formula.
I = B / C

  The amount of free polyvinyl alcohol can be controlled by the amount of reducing agent, chain transfer agent, comonomer and polymerization temperature. 0.5 parts by mass or less of the reducing agent, 0.1 to 1.0 parts by mass of the chain transfer agent, and 5.0 parts by mass of the comonomer monomer with respect to chloroprene and the monomer copolymerizable with chloroprene. The amount of free polyvinyl alcohol can be made 70% or less by setting the polymerization temperature in the range of 5 to 45 ° C. or less.

The solid content concentration of the polychloroprene latex is preferably in the range of 40 to 65% by mass. When solid content concentration is less than 40 mass%, the adhesive strength of the adhesive agent obtained may fall, and when it exceeds 65 mass%, mechanical stability may fall.
The solid content concentration of the polychloroprene latex can be calculated by the following method.
<Concentration of solid content>
Let X (g) be the mass of the aluminum dish alone. Let Y (g) be the mass of an aluminum dish containing 2 ml of latex sample. Let Z (g) be the mass after the aluminum dish containing the latex sample is dried at 125 ° C. for 1 hour. Solid content concentration (%) is calculated by the following formula.
Solid content concentration (%) = {(Z−X) / (Y−X)} × 100

Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention.

<Example 1>
Using a reactor with an internal volume of 3 liters, under a nitrogen stream, 100 parts by mass of water, polyvinyl alcohol [Nichigo G Polymer (registered trademark) OKS-8041 (degree of saponification 89 mol%) manufactured by Nippon Synthetic Chemical Industry Co., Ltd.]] 3 .5 parts by mass, 3.0 parts by mass of methacrylic acid, and 0.1 parts by mass of sodium sulfite were charged. After dissolution, 97 parts by mass of chloroprene and 0.3 parts by mass of n-octyl mercaptan were added with stirring. Polymerization was carried out at 40 ° C. in a nitrogen atmosphere using potassium persulfate as an initiator. When the polymerization rate reached 95%, an emulsion of phenothiazine was added to terminate the polymerization. After the unreacted monomer was removed under reduced pressure, the water was further evaporated under reduced pressure to perform concentration to obtain a polychloroprene latex having a solid content concentration of 50%.

<Example 2 to Example 16>
Polymerization was carried out under the conditions shown in Table 1 and Table 2, and polychloroprene latex was obtained under the same conditions as in Example 1 under other conditions.

<Comparative Examples 1 to 7>
Polymerization was carried out under the conditions shown in Table 3, and polychloroprene latex was obtained under the same conditions as in Example 1 for the other conditions.

<Storage stability>
Eight 235 g polychloroprene latex having a body diameter of 19.5 cm and sealed in a 225 ml glass container is prepared. All of them are stored at 40 ° C., one of them is taken out every week, and the polychloroprene latex therein is filtered through a 100-mesh wire mesh. The thickness of the latex remaining at the bottom of the glass container is 2 mm or more, or the coagulum obtained by drying the coagulum remaining on the wire mesh at 110 ° C. for 3 hours is 0.005% or more with respect to the solid content of the polychloroprene latex. Record the period until.

<Mechanical stability>
Based on JISK6828, the amount of coagulum generated when a 10 kg load and a shearing force of 1000 rpm were applied for 10 minutes to 50 g of polychloroprene latex using a Marlon test device was evaluated. The value is obtained by dry weighing the produced coagulated product and calculated by the following formula. The smaller the value, the more stable the shearing force is.
Mechanical stability (%) = dry weight g of coagulum / latex amount 50 g x 100

Formulation of 100 parts by mass of the polychloroprene latex thus obtained (in terms of solid content), 50 parts by mass of a tackifier resin (Tamanol E-100 manufactured by Arakawa Chemical Industries), and 1 part by mass of zinc oxide (AZ-SW manufactured by Osaki Kogyo Co., Ltd.) The mixture was stirred using a three-one motor at a ratio to prepare an adhesive. About the obtained adhesive, the sample was produced as follows and adhesive strength was evaluated. The results are shown in Table 1.

<Preparation of sample>
Apply 300 g (solid content) / m ² of adhesive composition to each of the two canvases (25 x 150 mm) with a brush, dry for 9 minutes at 80 ° C, leave it for 1 minute at room temperature, and then apply the coated surfaces together. Crimped with a roller. About this, the following adhesive strength evaluation test was done.
"Initial peel strength"
Ten minutes after roller pressing, the 180 ° peel strength was measured using a tensile tester at a pulling rate of 200 mm / min.
"Normal peel strength"
Seven days after pressing, 180 ° peel strength was measured using a tensile tester at a pulling rate of 200 mm / min.
"Water resistance"
Seven days after pressing, it was immersed in water for 2 days, and a 180 ° peel strength was measured at a pulling rate of 200 mm / min using a tensile tester.

Claims (5)

Produced by emulsion polymerization of chloroprene alone or a monomer copolymerizable with chloroprene and chloroprene in the presence of 1.0 to 10 parts by mass of polyvinyl alcohol with respect to a total of 100 parts by mass of all monomers, And the free polyvinyl alcohol is 70 mass% or less with respect to all the polyvinyl alcohol, The polychloroprene latex characterized by the above-mentioned. The polychloroprene latex according to claim 1, wherein the solid content concentration is 40 to 65 mass%. The polychloroprene latex according to claim 1 or 2, wherein the saponification degree of polyvinyl alcohol is 80 mol% or more. The polychloroprene latex according to any one of claims 1 to 3, wherein the chloroprene polymer is a copolymer of chloroprene and an ethylenically unsaturated carboxylic acid. The adhesive agent using the polychloroprene latex as described in any one of Claims 1-4.