JPH0160485B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for emulsion polymerization of styrene in the presence of a specific modified polyvinyl alcohol (hereinafter polyvinyl alcohol will be abbreviated as PVA) having a hydrophobic group and a hydrophilic group.

Conventionally, when emulsion polymerizing styrene,
It is known to use low-molecular surfactants such as alkylbenzene sulfonates, alkylnaphthalene sulfonates, higher fatty acid salts, and disproportionated rosin salts alone or in mixtures as emulsion polymerization stabilizers.
However, when the emulsion obtained by such a method using a low-molecular-weight surfactant is used as a paint, adhesive, paper processing agent, etc., coarse particles are generated when urea resin, pigment, etc. are added. It has drawbacks such as poor mechanical stability and the tendency for cohesive failure of the emulsion to occur during transfer using a pump or coating using a spreader roll, so extreme care must be taken when handling it. When used as an adhesive, the low-molecular surfactant tends to migrate to the surface of the film, resulting in poor adhesion. In order to overcome these difficulties, it has been proposed to use water-soluble polymers such as PVA. PVA is useful as an emulsion polymerization stabilizer for vinyl acetate ester. Vinyl acetate polymer emulsions obtained using PVA as an emulsion polymerization stabilizer can be used as a variety of stabilizers for mechanical stability, freeze-thaw stability, etc. in adhesives and paints. It is often used as such.

However, even when emulsion polymerization of styrene is attempted using PVA as a stabilizer, the polymerization progresses extremely slowly, and smooth polymerization cannot be achieved as coarse particles are generated during polymerization or the entire polymer gels. Although emulsion polymerization using a low-molecular-weight surfactant and PVA in combination is possible, it has not been possible to overcome the problems such as poor adhesion due to the migration of the low-molecular-weight surfactant to the film surface.

However, the present inventors conducted extensive research with the aim of eliminating the above-mentioned difficulties by emulsion polymerization using a specific modified PVA alone, and found that (A) vinyl esters of fatty acids having 5 or more carbon atoms; , at least one monomer selected from the group consisting of vinyl ethers of alkyl groups having 4 or more carbon atoms and α-olefins having 6 or more carbon atoms, (B) ethylenically unsaturated carboxylic acids or lower alkyl esters thereof, or At least one acid anhydride and
(C) A saponified copolymer obtained by copolymerizing three essential components of vinyl acetate, emulsifying styrene in the presence of a specific modified PVA that satisfies the following formula (). The inventors have completed the present invention by discovering that the polymerization proceeds quickly and that emulsion polymers can be obtained without problems such as generation of coarse particles or gelation.

0.2D10...() D=nA+(1-△)C/27.5/lB However, A is the copolymerization ratio (molar basis) of component (A) and is 0.0005 or more in mole fraction, and B is component (B) The copolymerization ratio (molar basis) is 0.001 or more in mole fraction,
C is the copolymerization ratio (molar basis) of component (C), which is a mole fraction of 0.5 or more, and n is an integer of 4 or more, but when component (A) is a vinyl ester of a fatty acid, n = number of carbon atoms in the fatty acid. 1. When component (A) is an alkyl vinyl ether, n-number of carbon atoms in the alkyl group, when component (A) is α-olefin, n = number of carbon atoms in α-olefin - 2, l is (B)
The number of carboxyl groups in the component, △ is the saponification ratio (molar basis) of component (C), △=
Saponified component (C)/component (C) is shown respectively.

In the present invention, the number of carbon atoms used as component (A) is 5.
Examples of vinyl esters of the above fatty acids include vinyl valerate, vinyl caprate, vinyl myristate, vinyl stearate, and vinyl pivalate, vinyl 1,1,3,3-tetramethylbutyrate, etc. Ester or average carbon number
Fatty acid vinyl esters having a branched alkyl group, such as a saturated branched fatty acid vinyl ester of 10, are preferred. If the number of carbon atoms is 4 or less, it is difficult for emulsion polymerization to proceed smoothly. Examples of alkyl vinyl ethers having 4 or more carbon atoms include butyl vinyl ether, octyl vinyl ether, lauryl vinyl ether, and the like. However, vinyl ethers having a branched alkyl group such as isoamyl vinyl ether are preferred. When the number of carbon atoms is 3 or less, it is difficult to carry out smooth emulsion polymerization. Further, as the α-olefin having 6 or more carbon atoms, heptene-1, octene-1, dodecene-1, etc. are preferable. If the number of carbon atoms is 5 or less, smooth emulsion polymerization cannot be carried out and it cannot be applied. As the alkyl group having 4 or more carbon atoms, a branched alkyl group is more preferably used since a good emulsion polymer can be obtained. The reason for this is not clear, but it is due to the fact that the ratio of methyl, methylene, and methine groups in the alkyl group is different between branched and straight-chain alkyl groups, and differences in crystallinity, orientation, association, etc. It is thought that they may do so.

Furthermore, as the ethylenically unsaturated carboxylic acid or its lower alkyl ester or acid anhydride used as component (B), acrylic acid, methacrylic acid,
Crotonic acid, maleic acid, itaconic acid, ethyl acrylate, methyl methacrylate, methyl crotonic acid, citraconic acid,
Citraconic acid diethyl ester, maleic acid, maleic acid monomethyl ester, maleic acid diethyl ester, itaconic acid dimethyl ester, maleic anhydride, aconitic acid, etc. are used.
Citraconic acid, maleic acid, itaconic acid, maleic acid monomethyl ester, maleic anhydride are preferably used, but maleic acid, maleic anhydride,
It is more preferable to use maleic acid monomethyl ester or itaconic acid because the stability of the emulsion polymer is greater. The reason for this is not clear, but (C) and (A)
It is thought that the polymerizability with the components and the mutual positional relationship of the introduced carboxyl groups may affect the performance of modified PVA.

The modified PVA used in the present invention contains (A), (B), and (C) contained in the copolymer obtained by copolymerization with the above-mentioned three components (A), (B), and (C) as essential components. The ratio of copolymerization of the three components and saponification of the acetyl group of component (C) is selected from within the range of formula () below.

0.2D10...() D=nA+(1-△)C/27.5/lB However, A: Copolymerization ratio (molar basis) of component (A), which is 0.0005 or more in mole fraction B: Copolymerization ratio of component (B) Polymerization ratio (on a molar basis) of 0.001 or more in terms of mole fraction C: Copolymerization ratio of component (C) (on a molar basis) of 0.5 or more in terms of mole fraction n: A number of 4 or more, and (A) component is fatty acid vinyl time of ester n
= Number of carbon atoms in fatty acid - 1 (A) When component is alkibinyl ether n =
Number of carbon atoms in alkyl group (A) When component (A) is α-olefin, n = α-
Number of carbon atoms in olefin - 2 l: Number of carboxyl groups in component (B) △: Saponification ratio of component (C) (molar basis) △ = Saponified component (C) / component (C) Above If modified PVA that exceeds the range of formula () is used, the emulsion polymerization of styrene will not proceed smoothly, or even if polymerization is possible, the stability of the resulting emulsion polymer will be poor. It has the following. This does not satisfy the purpose of the present invention. The reason for this is that in modified PVA, the balance between hydrophobicity, which is mainly based on component (A) and unsaponified component (C), and hydrophilicity, which is mainly based on component (B), is lost, and emulsion dispersion stability can no longer be maintained. This is thought to be due to the

Furthermore, in the present invention, emulsion polymerization can be effectively carried out only by using modified PVA that satisfies the above-mentioned formula (), and when the entire modified PVA is 1 on a molar basis, (A If it is less than 0.0005 for component () and less than 0.001 for component (B), it is no longer possible to achieve smooth emulsion polymerization or stable emulsion polymerization. Furthermore, if the content of component (C) is 0.5 or less, the modified PVA will no longer have the film-forming properties inherent to PVA, and the resulting emulsion polymer may suffer from a decline in practical physical properties such as adhesive performance. This will happen. The modified PVA used in the present invention is a saponified copolymer containing the three components (A), (B), and (C) described above as essential components, but other components may be used as long as the purpose of the present invention is not impaired. Copolymerization components such as methacrylamide, N-substituted methacrylamide, acrylamide, N-substituted acrylamide, N-vinylpyrrolidone, vinyl ethers of alkyl groups with 3 or less carbon atoms, olefins with 5 or less carbon atoms, etc. There is no problem in using a saponified copolymer obtained by copolymerizing in addition to the three components (A), (B), and (C) mentioned above.

There are no particular difficulties in producing the modified PVA used in the present invention, and conventionally known polymerization methods and saponification methods can be applied. In other words, the polymerization method involves adding components (A), (B), and (C) to a polymerization system all at once, in portions, or continuously, depending on their respective copolymerization reactivity ratios, and then adding them to the polymerization system without a solvent or in an aqueous medium. Alternatively, in the coexistence of lower alcohols such as methyl alcohol and ethyl alcohol, 2,2′-
A method of polymerization using a radical polymerization catalyst such as azobisisobutyronitrile or benzoyl peroxide can be applied. (A), (B) and
As a method for saponifying the copolymer containing component (C), many known methods used for saponifying polyvinyl acetate copolymers can be applied, but usually, in an alcohol solvent or a hydroalcoholic solvent, A saponification method using an alkali such as sodium alcoholate, caustic soda, or caustic potash is applicable. As alcohol, methyl alcohol,
Lower alcohols such as ethyl alcohol are particularly preferred. Further, these alcohol solvents may contain 40% by weight or less of a low dielectric constant solvent such as acetone, methyl acetate, ethyl acetate, or benzene.

The degree of polymerization of the modified PVA used in the present invention should be appropriately selected depending on its intended use, but is usually within the range of 100 to 3,000.

Using the modified PVA obtained above alone as a stabilizer, emulsion polymerization of styrene is carried out in the presence of an initiator in an aqueous phase by a known method to obtain a good emulsion polymer. In emulsion polymerization, it is also possible to copolymerize dienes, acrylic esters, methacrylic esters, vinyl chloride acrylic acid, acrylamide, itaconic acid, etc. as minor components.

In this invention, the use of a low-molecular surfactant in combination is not an essential condition, but it may be used in combination as an auxiliary means for adjusting the particle size, for example. In addition, optionally other protective colloids, such as unmodified PVA, polyacrylic acid, polymethacrylic acid and their salts, polyvinyl alkyl ethers, copolymers of vinyl acetate with acrylic acid or methacrylic acid, or vinyl acetate with anhydrous Copolymers with maleic acid and saponified products thereof, lower alkyl vinyl ether-maleic anhydride copolymers, cellulose derivatives such as alkyl cellulose, hydroxyalkyl cellulose, alkyl hydroxyalkyl cellulose, carboxymethyl cellulose, alkyl starch, carboxymethyl starch , oxidized starch, gum arabic, gum tragacanth, polyalkylene glycols, etc. can also be used during the polymerization or added to the degree of polymerization. In addition, liquid regulators used in ordinary emulsion polymerization, monohydric or polyhydric alcohols, plasticizers, inorganic salts such as sodium chloride, sodium iodide, sodium phosphate, and sodium sulfate, ammonia, and sodium hydroxide. There is no problem in using auxiliary agents such as PH regulators, such as hydrochloric acid, and antifoaming agents during or after polymerization.

The modified PVA used in the present invention is used in an amount of 0.5 to 40% by weight, particularly 2 to 25% by weight, based on the styrene monomer.

The polymerization initiator used in this invention is a water-soluble initiator system used in ordinary emulsion polymerization, such as hydrogen peroxide alone or hydrogen peroxide and oxycarboxylic acids such as tartaric acid, citric acid, and ascorbic acid, oxalic acid, and sulfinic acid. and combinations thereof with salts thereof, oxyaldehydes, water-soluble iron salts, etc., persulfates, percarbonates, perborates, peroxides, etc. can be applied.

Further, the object of the present invention can be fully achieved by using the above-mentioned modified PVA until the emulsion polymerization is completed.

The emulsion polymerization emulsion obtained in this way exhibits excellent stability and moderate viscosity, and is effective in adhesives, pressure-sensitive adhesives, fiber processing agents, paper processing agents, and even cement mixtures. The value of industrial use is truly great.

Next, the present invention will be explained in more detail with reference to Examples. In the examples, "parts" and "%" are based on weight unless otherwise specified.

Example 1 A polyvinyl acetate copolymer containing 0.9 mol% of lauryl vinyl ether as component (A) and 2.4 mol% of crotonic acid as component (B), 98.5 mol% of the vinyl acetate component of the copolymer was 10 parts of modified PVA that has been saponified and has a viscosity of 4% aqueous solution at 20°C of 49 centipoise, 1.0 part of disodium phosphate, 3 parts of concentrated aqueous ammonia, and 260 parts of water are dissolved in an atmosphere of chitso gas and kept at 60°C. Styrene 150
After stirring for 5 minutes, 5 parts of a 2% aqueous solution of ammonium persulfate was added to initiate polymerization.
After 1.5 hours, I cooled it down and took out the contents.
A clean emulsion with an average particle size of 0.2μ and no coarse particles could not be obtained. The polymerization rate of styrene was 98%. This product remained stable even after being left unused for three months. The modified PVA used in this example is D=
It is 4.25.

Comparative Example 1 Modified PVA with D=0.036 containing 0.04 mol% lauryl vinyl ether as component (A) and 15 mol% crotonic acid as component (B), with 98.2 mol% of the vinyl acetate component saponified. Emulsion polymerization of styrene was attempted in the same manner as in Example 1 except for the use of the following. The polymerization rate of styrene was 9.0%, and the polymerization rate was extremely slow and smooth polymerization did not proceed.

The viscosity of a 4% aqueous solution of modified PVA at 20°C was 43 centipoise.

Comparative Example 2 Normal propyl ether, which is a vinyl ether of an alkyl group with 3 carbon atoms, was used as component (B).
D = 5.52 when 90.1 mol% of the vinyl acetate ester moiety of the vinyl acetate copolymer containing 4.3 mol% and 1.2 mol% of maleic anhydride as component (B) was saponified, and D = 5.52 and 4 at 20°C. Emulsion polymerization was attempted in the same manner as in Example 1 except that modified PVA with a viscosity of 19 centipoise aqueous solution was used.
After 1.5 hours, the styrene polymerization rate reached 89.2%, but coarse particles were generated and emulsion polymerization was not good.

Example 2 Saturated branched fatty acid vinyl ester with an average carbon number of 10 as component (A) (VeoVa-10, manufactured by Ciel)
When 97.5 mol% of the vinyl acetate ester portion of the vinyl acetate copolymer containing 1.2 mol% and 3.0 mol% of itaconic acid as component (B) is saponified, D = 1.42 and at 20 ° C. Emulsion polymerization of styrene was carried out in the same manner as in Example 1, except that modified PVA having a viscosity of 8 centipoise in a 4% aqueous solution was used. The resulting emulsion polymer had a styrene polymerization rate of 98.8%, an average particle size of 0.15μ, and no aggregated particles. This product remained stable even after being left unused for 6 months.

Comparative Example 3 A vinyl acetate copolymer containing 1.2 mol% of saturated branched fatty acid vinyl ester (VeoVa-10) with an average carbon number of 10 as component (A), but no component (B). A modified product in which 82 mol% of the vinyl acetate portion of the copolymer has been saponified.
An attempt was made to use PVA as an emulsion polymerization stabilizer, but the modified PVA did not dissolve well in either cold or hot water, so it could not be used as the desired stabilizer for emulsion polymerization of styrene.

Comparative Example 4 A vinyl acetate copolymer containing no component (A) and 3.2 mol% of maleic anhydride as component (B), in which the vinyl acetate ester portion of the copolymer was
4 at 20°C, where 88.2 mol% was saponified.
Example 1 except that modified PVA with an aqueous solution viscosity of 15.2 centipoise was used as the emulsion polymerization stabilizer.
When emulsion polymerization of styrene was carried out in the same manner as above, the polymerization rate of styrene after 1.5 hours was 2.0%, indicating that almost no polymerization had occurred.

Example 3 A vinyl acetate-based copolymer containing 1.0 mol% of saturated branched fatty acid vinyl ester (VeoVa-10) with an average carbon number of 10 as the (A) component and 3.1 mol% of itaconic acid as the (B) component. 10 parts of modified PVA in which 99.0 mol% of the vinyl acetate portion of the polymer was saponified, D = 1.47, and the viscosity of a 4% aqueous solution at 20% °C was 11 centipoise, was dissolved by heating in 200 parts of water and then cooled. Then, add and dissolve 1.5 parts of potassium persulfate and 0.1 part of ethylenediaminetetraacetic acid (EDTA). Thereafter, 90 parts of styrene and 60 parts of butadiene were added, and the mixture was kept at 60°C for 12 hours with stirring, then cooled and the contents were taken out.

The reaction rate was 98.5%, and the latex was clean with no agglomeration and had an average particle size of 0.2μ. This product remained stable without aggregation or thickening even when left at room temperature for 6 months. This latex was measured using a B-type viscometer.
The viscosity measured at 10 rpm at 30°C was 8900 centipoise and gave a clear film.

Example 4 98.8 mol% of the vinyl acetate ester moiety of a vinyl acetate copolymer containing 1.3 mol% lauryl vinyl ether as component (A) and 3.0 mol% itaconic acid as component (B) was saponified. Yes, D
=2.61 and the viscosity of a 4% aqueous solution at 20℃ is 13
A latex was obtained by carrying out emulsion polymerization of styrene-butadiene in the same manner as in Example 3, except that Centipoise's modified PVA was used as a stabilizer for emulsion polymerization. This product remained stable without aggregation or thickening even when left at room temperature for 6 months.

The viscosity of this latex was measured using a B-type viscometer at 30° C. and 10 rpm, and the viscosity was 3200 centipoise, and a slightly cloudy film was obtained.

Comparative Example 5 90% of the vinyl acetate ester moiety of a vinyl acetate copolymer containing 20 mol% heptene as component (A) and 4 mol% crotonic acid as component (B)
Modification of D = 25.0 where mol% was saponified
Emulsion polymerization of styrene-butadiene was attempted in the same manner as in Example 3 except that PVA was used as an emulsion polymerization stabilizer, but coarse particles were generated and smooth emulsion polymerization could not be carried out.

Claims (1)

[Scope of Claims] 1 (A) A monomer selected from the group consisting of vinyl esters of fatty acids having 5 or more carbon atoms, vinyl ethers of alkyl groups having 4 or more carbon atoms, and α-olefins having 6 or more carbon atoms. (B) at least one ethylenically unsaturated carboxylic acid or its lower alkyl ester or acid anhydride;
(C) A method of emulsion polymerizing styrene in the presence of a modified polyvinyl alcohol which is a saponified product of a copolymer containing three components of vinyl acetate as essential copolymerization components and which satisfies the following formula (). 0.2D10...() D=nA+(1-△)C/27.5/lB However, A is the copolymerization ratio (mole basis) of component (A), which is 0.0005 or more in mole fraction, and B is component (B). The copolymerization ratio (mole basis) is 0.001 or more in mole fraction,
C is the copolymerization ratio (molar basis) of component (C), which is a mole fraction of 0.5 or more, and n is an integer of 4 or more, but when component (A) is a vinyl ester of a fatty acid, n = number of carbon atoms in the fatty acid. -1, when component (A) is an alkyl vinyl ether, n = number of alkyl groups, when component (A) is α-olefin, n = number of carbon atoms in α-olefin – 2, l is carboxyl group in component (B) number, △ is (C) in the copolymer
Saponification ratio of components (molar basis), △=
Saponified component (C)/component (C) is shown respectively. 2 Component (A) is a branched fatty acid vinyl ester in which the carboxyl group is present at the α-position relative to the tertiary or quaternary carbon atom, and component (B) is an ethylenically unsaturated dicarboxylic acid or its lower alkyl ester or A method for emulsion polymerization of styrene according to claim 1, which is an acid anhydride. 3 Claim 2 in which component (B) is itaconic acid
A method for emulsion polymerization of styrene as described in .