JPH0160484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses specific modified polyvinyl alcohol (hereinafter referred to as PVA) to stabilize hydrophobic groups and hydrophilic groups, such as acrylic esters and methacrylic esters ( The present invention relates to a method for emulsion polymerization of (meth)acrylic acid esters (hereinafter collectively referred to as (meth)acrylic acid esters).

In emulsion polymerization of (meth)acrylic acid esters, stabilizers have conventionally been used with low molecules such as alkylbenzenesulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, polyoxyethyl ether, and sodium alkylsulfosuccinates. It is known that surfactants are used. However, emulsions obtained by methods using such low-molecular-weight surfactants are not mechanically stable when used as paints, adhesives, paper processing agents, etc., and coarse particles are generated when urea resins, pigments, etc. are added. When used as an adhesive, low-molecular surfactant The problem is that the agent migrates to the surface of the film and tends to cause 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, when emulsion polymerization of (meth)acrylic acid esters is attempted using PVA as a stabilizer, a good emulsion cannot be obtained, as coarse particles are generated during polymerization, or in extreme cases, the entire gelation occurs. be. Low molecular surfactant and
Although emulsion polymerization using 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 product of a copolymer obtained by copolymerizing a tertiary product of vinyl acetate as an essential component (meth) in the presence of a specific modified PVA that satisfies the following formula (). When emulsion polymerizing acrylic acid esters, it was discovered that emulsion polymers can be obtained without problems such as generation of coarse particles or gelation, and the present invention was completed.

0.05D4...() D=nA+(1-△)C/27.5/lB However, A is the copolymerization ratio (molar basis) of component (A), which 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 this way, a hydrocarbon group of a specific size introduced as component (A), a carboxyl group introduced as component (B), and vinyl acetate and/or its saponified component introduced as component (C) are essential. Toshikatsu
It is surprising that emulsion polymerization can be carried out stably only when the components (A), (B), and (C) satisfy a specific relationship. This is unimaginable from the combination with C).

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 to obtain an emulsion polymer with good stability. 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 obtain an emulsion polymer with good stability. In addition, as an α-olefin with a carbon number of 6 or more, heptene-
Preferred examples include 1, octene-1, and dodecene-1. If the number of carbon atoms is less than 5, it is difficult for emulsion polymerization to proceed stably. 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.

Further, 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, and maleic anhydride are preferably used, but the stability of the emulsion polymer is improved when maleic acid, maleic anhydride, maleic acid monomethyl ester, and itaconic acid are used. Larger and more suitable. The reason for this is not clear, but it is thought that the polymerizability with components (C) and (A), the mutual positional relationship of the introduced carboxyl groups, etc. influence 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 three components (A), (B), and (C) described above as essential components. The copolymerization ratio of the three components and the saponification ratio of the acetyl group of component (C) are selected from within the range of the following formula ().

0.05D4...() D=nA+(1-△)C/27.5/lB However, A: Copolymerization ratio of component (on a molar basis), which is 0.0005 or more in mole fraction B: Copolymerization ratio of component (B) (on a molar basis) and a mole fraction of 0.001 or more C: Copolymerization ratio of component (C) (on a molar basis) a mole fraction of 0.5 or more n: A number of 4 or more and when the component (A) is a vinyl ester of fatty acid n=
Number of carbon atoms in fatty acid - 1 (A) When component is alkyl vinyl ether, n =
Number of carbon atoms in alkyl group (A) When component (A) is α-olefin, n = number of carbon atoms in α-olefin - 2 l; Number of carboxyl groups in component (B) △; Saponification ratio of component (C) (on a molar basis) △ = Saponified component (C) / component (C) If modified PVA exceeding the range of the above formula () is used, emulsion polymerization may not proceed smoothly, or even if the polymerization is somehow unsuccessful. Even so, the obtained emulsion polymer has some drawbacks such as poor stability, and does not satisfy the object of the present invention. The reason is mainly due to modified PVA.
This is thought to be because the balance between the hydrophobicity based on component (A) and unsaponified component (C) and the hydrophilicity mainly based on component (B) is lost, and emulsion dispersion stability can no longer be maintained.

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 materials 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, in addition to the three components (A), (B), and (C), a saponified copolymer copolymerized as a copolymer.

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, in the presence of an initiator in the aqueous phase, acrylic esters such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, methacrylic acid, etc. Good emulsion polymers can be obtained by emulsion polymerization of methacrylic acid esters such as ethyl, butyl methacrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate. As a small component in emulsion polymerization,
It is also possible to copolymerize vinyl acetate, styrene, acrylic acid, acrylamide, itaconic acid, and the like.

In this invention, the use of a low-molecular-weight surfactant in combination is not an essential condition, but it may be used in combination as an auxiliary means, for example, for adjusting the particle size. 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 hydroxide. There is no problem in using auxiliary agents such as pH regulators such as sodium and hydrochloric acid and antifoaming agents during or after polymerization.

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

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.

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 97.8 mol% of the vinyl acetate component of a polyvinyl acetate copolymer containing 0.3 mol% lauryl vinyl ether as component (A) and 3.7 mol% crotonic acid as component (B) was saponified and
10 parts of modified PVA with D=0.99 and 1.0 part of disodium phosphate having a 4% aqueous solution viscosity of 37 centipoise at 20°C are dissolved in 225 parts of water and kept at 65°C. _N2
Under an atmosphere, 16 parts of butyl acrylate and 10 parts of a 5% aqueous solution of ammonium persulfate were added to initiate polymerization. Butyl acrylate for 2 hours after 15 minutes
Polymerization was carried out by continuously adding 150 parts. After the addition was completed, the internal temperature was continued to be maintained at 65°C for 30 minutes, and then cooled and taken out. It was a clean emulsion with no coarse particles, and it remained stable even after being left for 3 months.
The viscosity of the emulsion at 30° C. measured using a B-type viscometer at 10 revolutions/minute was 1920 centipoise. Also, the thickness of the emulsion is 0.5
The film cast to a thickness of mm was slightly cloudy.

Comparative Example 1 The vinyl acetate component of a polyvinyl acetate copolymer containing 0.3 mol% lauryl vinyl ether as component (A) and no component (B).
Emulsion polymerization of butyl acrylate was attempted in the same manner as in Example 1, except for using modified PVA in which 98.1 mol% of the butyl acrylate was saponified and the viscosity of a 4% aqueous solution at 20°C was 185 centipoise.
At the time of addition of 50%, the entire product turned into a muddy gelatinous substance, and smooth emulsion polymerization could not be carried out.

Comparative Example 2 Contains 3.7 mol% of crotonic acid as component (B) and (A)
Same as Example 1 except that modified PVA in which 97.9 mol% of the vinyl acetate component of the polyvinyl acetate ester component containing no component was saponified and the viscosity of a 4% aqueous solution at 20°C was 10 centipoise was used. An attempt was made to emulsion polymerize butyl acrylate, but when 25 parts of butyl acrylate was added, the entire product turned into a muddy gel, and smooth emulsion polymerization could not be carried out.

Comparative Example 3 Unmodified PVA whose 4% aqueous solution at 20°C is 28 centipoise and saponification degree is 98.5 mol%
Emulsion polymerization of butyl acrylate was attempted in the same manner as in Example 1 except that PVA-117 (manufactured by Kuraray Co., Ltd.) was used, but when 35 parts of butyl acrylate was added, the entire product turned into a muddy gel and smooth emulsion was not achieved. Polymerization could not be carried out.

Example 2 Polyacetate vinyl ester system containing 0.5 mol% of branched fatty acid vinyl ester (VeoVa-10 manufactured by Ciel) with an average carbon number of 10 as the (A) component and 0.3 mol% of itaconic acid as the (B) component 96.5 mol% of the vinyl acetate component of the copolymer was saponified and
Emulsion polymerization of butyl acrylate was carried out in the same manner as in Example 1, except that modified PVA with D = 0.60 and a 4% aqueous solution viscosity of 10 centipoise at 20°C was used, and a clean emulsion without coarse particles was obtained. , remained stable even after being left for 6 months. The B type viscosity of the emulsion at 30°C and 10 revolutions/min is 2340.
centipoise, and the thickness of the emulsion
The film cast to a thickness of 0.5 mm had good transparency.

Example 3 The vinyl acetate component of a polyvinyl acetate copolymer containing 0.2 mol% of a branched fatty acid vinyl ester with an average carbon number of 10 as the (A) component and 7.0 mol% of crotonic acid as the (B) component. Emulsion polymerization was carried out in the same manner as in Example 1, except that 97.1 mol% of the modified PVA was saponified and the viscosity of a 4% aqueous solution at 20°C was 12 centipoise, D = 0.27, and 2-ethylhexyl acrylate was used as the emulsion polymerization monomer. When this was carried out, a clean emulsion with no coarse particles was obtained and remained stable even after being left for 6 months.

The B-type viscosity of the emulsion at 30 DEG C. and 10 revolutions per minute was 620 centipoise, and the film obtained by casting the emulsion to a thickness of 0.5 mm had good transparency.

Comparative Example 4 96.8 mol% of the vinyl acetate component of a polyvinyl acetate copolymer containing 0.06 mol% of butyl vinyl ether as the (A) component and 9.8 mol% of itaconic acid as the (B) component was saponified and 20
Emulsion polymerization of 2-ethylhexyl acrylate was attempted in the same manner as in Example 3, except that modified PVA with D = 0.018 and a 4% aqueous solution viscosity of 19 centipoise at °C was used, but 80 parts of 2-ethylhexyl acrylate was added. However, the entire emulsion turned into a gel and a good emulsion could not be obtained.

Comparative Example 5 0.9 mol% of normal propyl vinyl ether having an alkyl group having 3 carbon atoms as component (A),
(B) 97.0 mol% of the vinyl acetate component of the polyvinyl acetate copolymer containing 2.8 mol% of crotonic acid as the component is saponified, and the viscosity of a 4% aqueous solution at 20°C is 16 centipoise D
An attempt was made to emulsion polymerize 2-ethylhexyl acrylate in the same manner as in Example 3, except that modified PVA with a concentration of 1.00 was used, but when 40 parts of 2-ethylhexyl acrylate was added, the emulsion turned into a muddy gel and no good emulsion was obtained. I couldn't get it.

Comparative Example 6 4 branched fatty acid vinyl esters (VeoVa-10 manufactured by Ciel Chemical Co., Ltd.) with an average carbon number of 10 were used as component (A).
mol%, 1 mol% maleic anhydride as component (B)
The viscosity of a 4% aqueous solution at 20°C where 96 mol% of the vinyl acetate component of the polyvinyl acetate copolymer contained was saponified was 25 centipoise, and modified PVA with D = 14.0 was used. Emulsion polymerization was attempted in the same manner as in Example 3, but when 90 parts of 2-ethylhexyl acrylate was added, the entire mixture turned into a muddy gel, and a good emulsion could not be obtained.

Example 4 Emulsion polymerization was carried out in the same manner as in Example 3 except that methyl methacrylate was used as the emulsion polymerization monomer, and a clean emulsion without coarse particles was obtained.
It remained stable even after being left for several months.

The emulsion had a Type B viscosity of 1720 centipoise at 30°C and 10 revolutions/minute.

Example 5 Example 3 except that a 70:30 mixture of butyl acrylate and vinyl acetate was used as the emulsion polymerization monomer.
Emulsion polymerization was carried out in the same manner as above, and a clean emulsion without coarse particles was obtained, which remained stable even after being left for 6 months.

The B-type viscosity of the emulsion at 30 DEG C. and 10 revolutions per minute was 1940 centipoise, and the film obtained by casting the emulsion to a thickness of 5 mm had good transparency.

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 saponified product of a copolymer containing a tertiary product of vinyl acetate ester as an essential copolymerization component, which emulsifies (meth)acrylic esters in the presence of modified polyvinyl alcohol that satisfies the following formula (). How to polymerize. 0.05D4...() D=nA+(1-△)C/27.5/lB However, A is the copolymerization ratio (molar 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 carbon atoms in the alkyl group, when component (A) is α-olefin, n = number of carbon atoms in α-olefin – 2, l is
The number of carboxyl groups in component (B), △ is the saponification ratio (molar basis) of component (C) in the copolymer, △=
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 the (meth)acrylic acid ester according to claim 1, which is an acid anhydride. 3 Claim 2 in which component (B) is itaconic acid
A method of emulsion polymerization of (meth)acrylic esters described in .