JP5496215B2 - Thickener containing vinyl alcohol polymer - Google Patents

Description

  The present invention relates to a thickener containing a polyoxyalkylene-modified vinyl alcohol polymer. More specifically, by containing a polyoxyalkylene-modified vinyl alcohol polymer, the thickener has high solubility in water or a water-containing solvent, is highly viscous, and has little decrease in viscosity due to temperature increase. About.

  Vinyl alcohol polymers (hereinafter sometimes abbreviated as PVA) have excellent interface and strength properties as one of the few crystalline water-soluble polymers, so various binders, paper processing, fiber processing, emulsions, etc. In addition, it occupies an important position as a raw material for PVA films and PVA fibers. On the other hand, the pursuit of high functionality in which specific performance is improved by controlling crystallinity or introducing a functional group has been performed, and various so-called modified PVAs have been developed.

  It is known that a hydrophobic group-modified PVA into which a long-chain alkyl group is introduced exhibits a markedly thickening action due to the association of hydrophobic groups due to hydrophobic group interaction in an aqueous solvent, thereby giving a high viscosity solution. For example, Patent Document 1 discloses a thickener using a high-viscosity solution of PVA modified with a long-chain alkyl group which is a hydrophobic group, and is used as a thickener for vinyl acetate emulsions. . The alkyl-modified PVA has a higher solution viscosity as the alkyl group content in the PVA increases. However, when the content exceeds a certain content, the water solubility of the PVA decreases. Therefore, it has been difficult to obtain a high viscosity solution using alkyl-modified PVA.

  In addition, the alkyl-modified PVA solution gives a high-viscosity solution in a temperature range below room temperature, but the viscosity decreases as the solution temperature increases, and when the temperature such as summer increases, the performance as a thickener does not appear. was there. Therefore, a PVA-based thickener that is not affected by surrounding temperature changes has been desired.

JP-A-8-60137

  The present invention has been made in order to solve the above-mentioned problems, and has a high solubility in water or a water-containing solvent, and has a high viscosity and a PVA-containing thickener that has a low viscosity decrease due to a change in solution temperature. I will provide a.

  The above-described problem is a thickener containing a polyoxyalkylene-modified vinyl alcohol polymer (hereinafter sometimes abbreviated as POA-modified PVA), and the modified PVA is represented by the following general formula (I). A polyoxyalkylene group (hereinafter sometimes abbreviated as POA group) is contained in the side chain, the viscosity average polymerization degree P is 200 to 5000, the saponification degree is 20 to 99.99 mol%, This can be solved by providing a thickener characterized by an alkylene group modification amount S of 0.1 to 10 mol%.

(In the formula, R1 represents a hydrogen atom or a methyl group, R2 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. M and n represent the number of repeating units of each oxyalkylene unit, 1 ≦ m ≦ 10, (3 ≦ n ≦ 20)

  In the above case, it is preferable that the thickener further contains water or a water-containing solvent.

  The present invention further includes a thickener-containing composition containing the above thickener, water and oil, and containing 0.1 to 50 parts by weight of the POA-modified PVA with respect to 100 parts by weight of the oil. .

  The thickener containing the POA-modified PVA of the present invention can provide a large thickening effect when used in a small amount, and there is almost no decrease in viscosity due to temperature increase.

  The POA-modified PVA contained in the thickener of the present invention has a POA group represented by the following general formula (I) in the side chain.

  In the formula, R1 represents a hydrogen atom or a methyl group, and R2 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. m and n represent the number of repeating units of each oxyalkylene unit, and 1 ≦ m ≦ 10 and 3 ≦ n ≦ 20. Here, a unit having the number of repeating units m is referred to as unit 1, and a unit having the number of repeating units n is referred to as unit 2. The arrangement of the unit 1 and the unit 2 may be random or block.

  The number m of repeating units 1 of the POA group unit 1 represented by the general formula (I) needs to satisfy 1 ≦ m ≦ 10, more preferably 1 ≦ m ≦ 5, and particularly preferably 1 ≦ m ≦ 2. When m is 0, the hydrophobicity of the POA group increases and the water solubility of the POA-modified PVA decreases. Further, the number n of repeating units of unit 2 needs to satisfy 3 ≦ n ≦ 20, preferably 5 ≦ n ≦ 18, and particularly preferably 8 ≦ n ≦ 15. When n is less than 3, the interaction between POA groups does not appear, and the viscosity of the POA-modified PVA aqueous solution is low. On the other hand, when n exceeds 20, the hydrophobicity of the POA group increases and the water solubility of the POA-modified PVA decreases.

  The POA-modified PVA contained in the thickener of the present invention is only required to contain the POA group represented by the general formula (I) in the side chain, and the method for producing the POA-modified PVA is not particularly limited. A method of copolymerizing an unsaturated monomer having a POA group represented by the general formula (I) and a vinyl ester monomer and saponifying the obtained POA-modified vinyl ester copolymer is preferable. Here, the above copolymerization is preferably performed in an alcohol solvent or without a solvent.

  The unsaturated monomer having a POA group represented by the general formula (I) is preferably an unsaturated monomer represented by the following general formula (II).

In the formula, R1, R2, m, and n are the same as those in the general formula (I). R3 represents a hydrogen atom or a -COOM group, where M represents a hydrogen atom, an alkali metal or an ammonium group. R4 represents a hydrogen atom, a methyl group or a —CH ₂ —COOM group, where M is as defined above. X represents —O—, —CH ₂ —O—, —CO—, — (CH ₂ ) _k —, —CO—O— or —CO—NR 5 —. Here, R5 represents a hydrogen atom or a saturated alkyl group having 1 to 4 carbon atoms, k represents the number of repeating units of a methylene unit, and 1 ≦ k ≦ 15.

  R2 of the unsaturated monomer represented by the general formula (II) is preferably a hydrogen atom, a methyl group or a butyl group, more preferably a hydrogen atom or a methyl group. Furthermore, it is particularly preferable that R1 of the unsaturated monomer represented by the general formula (II) is a hydrogen atom or a methyl group, R2 is a hydrogen atom or a methyl group, and R3 is a hydrogen atom.

  For example, when R1 in the general formula (II) is a hydrogen atom or a methyl group, R2 is a hydrogen atom, and R3 is a hydrogen atom, the unsaturated monomer represented by the general formula (II) is specifically polyoxyethylene. Polyoxybutylene monoacrylate, polyoxyethylene polyoxybutylene monomethacrylate, polyoxyethylene polyoxybutylene monoacrylic amide, polyoxyethylene polyoxybutylene monomethacrylamide, polyoxyethylene polyoxybutylene monoallyl ether, polyoxyethylene Polyoxybutylene monomethallyl ether, polyoxyethylene polyoxybutylene monovinyl ether, polyoxypropylene polyoxybutylene monoacrylate, polyoxypropylene polyoxybutylene monomethacrylate, polyoxypropylene Lopylene polyoxybutylene monoacrylamide, polyoxypropylene polyoxybutylene monomethacrylamide, polyoxypropylene polyoxybutylene monoallyl ether, polyoxypropylene polyoxybutylene monomethallyl ether, polyoxypropylene polyoxybutylene monovinyl ether, etc. Is mentioned. Among them, polyoxyethylene polyoxybutylene monoacrylic acid amide, polyoxyethylene polyoxybutylene monomethacrylic acid amide, polyoxyethylene polyoxybutylene monovinyl ether are preferably used, polyoxyethylene polyoxybutylene monomethacrylic acid amide, Polyoxyethylene polyoxybutylene monovinyl ether is particularly preferably used.

  When R2 in the general formula (II) is an alkyl group having 1 to 8 carbon atoms, specifically, as the unsaturated monomer represented by the general formula (II), R2 in the general formula (II) is a hydrogen atom. In the case of the above, there may be mentioned those obtained by substituting the terminal OH group of the unsaturated monomer with an alkoxy group having 1 to 8 carbon atoms. Of these, unsaturated monomers in which the OH group at the terminal of polyoxyethylene polyoxybutylene monomethacrylamide or polyoxyethylene polyoxybutylene monovinyl ether is substituted with a methoxy group are preferably used. An unsaturated monomer in which the OH group at the terminal of butylene monomethacrylamide is substituted with a methoxy group is particularly preferably used.

  The temperature employed when copolymerizing the unsaturated monomer having a POA group represented by the general formula (I) and the vinyl ester monomer is preferably 0 to 200 ° C, more preferably 30 to 140 ° C. preferable. When the copolymerization temperature is lower than 0 ° C., it is difficult to obtain a sufficient polymerization rate. Moreover, when the temperature which superposes | polymerizes is higher than 200 degreeC, it is difficult to obtain POA modified PVA which has the POA group modification amount prescribed | regulated by this invention. As a method for controlling the temperature employed in the copolymerization to 0 to 200 ° C., for example, by controlling the polymerization rate, the heat generated by the polymerization is balanced with the heat released from the surface of the reactor. Examples thereof include a method and a method of controlling by an external jacket using an appropriate heating medium, but the latter method is preferable from the viewpoint of safety.

  Polymerization methods used for copolymerization of unsaturated monomers having a POA group represented by the general formula (I) and vinyl ester monomers include batch polymerization, semi-batch polymerization, continuous polymerization, Any of continuous polymerization may be used. As the polymerization method, any known method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method can be used. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without a solvent or an alcohol solvent is suitably employed, and an emulsion polymerization method is employed for the purpose of producing a copolymer having a high degree of polymerization. Examples of the alcohol solvent include methyl alcohol, ethyl alcohol, propyl alcohol, and the like, but are not limited thereto. These solvents can be used in combination of two or more.

  As the initiator used for copolymerization, conventionally known azo initiators, peroxide initiators, redox initiators and the like are appropriately selected according to the polymerization method. As the azo initiator, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4- Dimethyl valeronitrile) and the like, and peroxide initiators include perisopropyl compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate; t-butyl Perester compounds such as peroxyneodecanate, α-cumylperoxyneodecanate, and t-butylperoxydecanate; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, etc. Is mentioned. Furthermore, the initiator can be combined with potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like to form an initiator. Moreover, as a redox-type initiator, what combined said peroxide and reducing agents, such as sodium hydrogen sulfite, sodium hydrogencarbonate, tartaric acid, L-ascorbic acid, Rongalite, is mentioned.

  In addition, when copolymerization of the unsaturated monomer having a POA group represented by the general formula (I) and the vinyl ester monomer is carried out at a high temperature, PVA resulting from the decomposition of the vinyl ester monomer In this case, for the purpose of preventing coloring, an antioxidant such as tartaric acid is added to the polymerization system in an amount of about 1 to 100 ppm (relative to the vinyl ester monomer). There is no problem.

  Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, Examples include vinyl stearate, vinyl oleate, vinyl benzoate, etc. Among them, vinyl acetate is most preferable.

  When the unsaturated monomer having a POA group represented by the general formula (I) and the vinyl ester monomer are copolymerized, other monomers may be copolymerized within a range not to impair the gist of the present invention. There is no problem. Examples of monomers that can be used include α-olefins such as ethylene, propylene, n-butene, and isobutylene; acrylic acid and its salts; methyl acrylate, ethyl acrylate, n-propyl acrylate, and i-propyl acrylate. Acrylic acid esters such as n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate and octadecyl acrylate; methacrylic acid and salts thereof; methyl methacrylate, methacryl Methacrylic acid such as ethyl acetate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate Esters; N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid and its salt, acrylamide propyl dimethylamine and its salt or its quaternary salt, N-methylol acrylamide and its Acrylamide derivatives such as derivatives; methacrylamide; N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts or quaternary salts thereof, N-methylolmethacrylamide and Methacrylamide derivatives such as derivatives thereof; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether , N-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, vinyl ethers such as 2,3-diacetoxy-1-vinyloxypropane; nitriles such as acrylonitrile and methacrylonitrile; Vinyl halides such as vinyl and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane and allyl chloride; maleic acid, Examples thereof include unsaturated dicarboxylic acids such as itaconic acid and fumaric acid and salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like.

  In addition, for the purpose of adjusting the degree of polymerization of the copolymer obtained in the copolymerization of the unsaturated monomer having a POA group represented by the general formula (I) and the vinyl ester monomer, the present invention is used. Copolymerization may be carried out in the presence of a chain transfer agent as long as the gist of the invention is not impaired. Chain transfer agents include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; halogenated hydrocarbons such as trichloroethylene and perchloroethylene; sodium phosphinate 1 Examples thereof include phosphinic acid salts such as hydrates, among which aldehydes and ketones are preferably used. The addition amount of the chain transfer agent is determined according to the chain transfer constant of the chain transfer agent to be added and the degree of polymerization of the target vinyl ester polymer, but is generally 0.1% relative to the vinyl ester monomer. -10 wt% is desirable.

  In the saponification reaction of the POA-modified vinyl ester copolymer, an alcoholysis reaction using a conventionally known basic catalyst such as sodium hydroxide, potassium hydroxide or sodium methoxide or an acidic catalyst such as P-toluenesulfonic acid. Alternatively, a hydrolysis reaction can be applied. Examples of the solvent that can be used in this reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene and toluene; These can be used alone or in combination of two or more. Among them, it is convenient and preferable to perform the saponification reaction using methanol or a methanol / methyl acetate mixed solution as a solvent and sodium hydroxide as a catalyst.

  The POA-modified PVA contained in the thickener of the present invention needs to have a POA group modification amount S of 0.1 to 10 mol%. When the POA group modification amount S exceeds 10 mol%, the proportion of hydrophobic groups contained in one molecule of POA-modified PVA increases, and the solubility of the PVA in a water-containing solvent may decrease. On the other hand, when the POA group modification amount S is less than 0.1 mol%, the water solubility of the POA-modified PVA is excellent, but the number of POA units contained in the PVA is small, and physical properties based on the POA modification are not expressed. There is a case.

  The POA group modification amount S is represented by the molar fraction of the POA group with respect to the main chain methylene group of PVA. The lower limit of the POA group modification amount S is preferably 0.2 mol% or more. The upper limit of the POA group modification amount S is preferably less than 2 mol%, more preferably 1.5 mol% or less.

The POA group modification amount S of the POA-modified PVA can be determined from proton NMR of the POA-modified vinyl ester copolymer that is a precursor of the POA-modified PVA. Specifically, after reprecipitation and purification of the POA-modified vinyl ester copolymer with n-hexane / acetone three times or more sufficiently, drying at 50 ° C. under reduced pressure for 2 days is performed, and POA-modified for analysis is performed. A sample of vinyl ester copolymer is prepared. The sample is dissolved in CDCl ₃ and measured at room temperature using 500 MHz proton NMR (JEOL GX-500). From the peak α (4.7 to 5.2 ppm) derived from the main chain methine of the vinyl ester copolymer and the peak β (0.8 to 1.0 ppm) derived from the terminal methyl group of the unit 2, the following formula is used. The POA group modification amount S is calculated. In the formula, n represents the number of repeating units of unit 2.
S (mol%) = {(number of protons of β / 3n) / (number of protons of α + (number of protons of β / 3n))} × 100

The viscosity average polymerization degree P of the POA-modified PVA is measured according to JIS-K6726. That is, after re-saponifying and purifying the PVA, it is obtained by the following equation from the intrinsic viscosity [η] measured in water at 30 ° C. The viscosity average degree of polymerization may be simply referred to as the degree of polymerization.
P = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

  The polymerization degree of the POA-modified PVA contained in the thickener of the present invention is 200 to 5000. When the degree of polymerization exceeds 5000, the productivity of the POA-modified PVA is lowered, which is not practical. On the other hand, when the degree of polymerization is less than 200, the thickening effect of the POA-modified PVA-containing thickener is lowered and may not be practically used.

  The saponification degree of the POA-modified PVA needs to be 20 to 99.99 mol%, and preferably 40 to 99.9 mol%. When the saponification degree is less than 20 mol%, the thickening effect expressed by the hydrophobic group interaction of the POA-modified PVA decreases, and when the saponification degree exceeds 99.99 mol%, it is difficult to produce POA-modified PVA. So it is not practical. The saponification degree of the POA-modified PVA is a value that can be measured according to JIS-K6726.

  The content of the POA group represented by the general formula (I) is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and particularly preferably 15 parts by weight or less. When the content of the POA group exceeds 50 parts by weight, the hydrophobicity of the PVA increases, and the solubility in a water-containing solvent may decrease. The lower limit of the content is preferably 2.5 parts by weight or more.

  Here, the content of the POA group represented by the general formula (I) is expressed by the weight part (weight fraction) of the POA group represented by the general formula (I) with respect to 100 parts by weight of the main chain of PVA, and the POA group This is a value calculated using the amount of modification S, the number m of repeating units of unit 1, the number of repeating units n of unit 2, and the saponification degree of POA-modified PVA. Even if the above-mentioned POA group modification amount S is equivalent, the POA group content in the POA-modified PVA increases as the degree of saponification increases or as m or n increases.

When the viscosity of a 4% by weight aqueous solution of POA-modified PVA contained in the thickener of the present invention was measured with a BL-type viscometer under the condition of a rotor rotation speed of 6 rpm, viscosity η _{1 at} 20 ° C. and viscosity η at 40 ° C. it is preferred ratios eta ₂ / eta ₁ and ₂ is 0.8 or more. The viscosity ratio η ₂ / η ₁ is more preferably 1.0 or more, further preferably 1.5 or more, and particularly preferably 2.0 or more. When the viscosity ratio η ₂ / η ₁ is less than 0.8, the interaction between POA groups is small, and physical properties associated with POA modification may not be exhibited.

The POA-modified PVA contained in the thickener of the present invention has a viscosity of 4% by weight of an unmodified PVA having a similar polymerization degree measured at 20 ° C. and a rotor rotation speed of 6 rpm as η ₃ . The viscosity ratio η ₁ / η ₃ is preferably greater than 1.2, more preferably greater than 1.5, even more preferably greater than 2.0, and particularly preferably greater than 5.0. Here, unmodified PVA having a similar degree of polymerization refers to unmodified PVA having a degree of polymerization in the range of 0.95 to 1.05 times the degree of polymerization of POA-modified PVA.

  The thickener of the present invention contains the above POA-modified PVA. The thickener of the present invention can be used as it is in the form of a resin powder, or can be mixed with water or a water-containing solvent and used as a liquid thickener. Here, the water-containing solvent is composed of water and a solvent other than water. Liquid thickeners are suitable for use in aqueous emulsions such as paints and adhesives.

  When used as a liquid thickener, the solvent other than water contained in the water-containing solvent includes alcohol solvents such as methanol and ethanol; ester solvents such as methyl acetate and ethyl acetate; diethyl ether, 1,4- Ether solvents such as dioxane, methyl cellosolve, cellosolve, butyl cellosolve, MTBE (methyl tertiary butyl ether) and butyl carbitol; ketone solvents such as acetone and diethyl ketone; glycols such as ethylene glycol, propylene glycol, diethylene glycol and triethylene glycol Solvents: Glycol ethers such as diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol Medium, ethylene glycol monomethyl ether acetate, PMA (propylene glycol monomethyl ether acetate), diethylene glycol monobutyl ether acetate, but glycol ester solvents such as diethylene glycol monoethyl ether acetate, but is not limited thereto.

  When used as a liquid thickener, the amount of the POA-modified PVA is preferably 10 to 70 parts by weight, more preferably 10 to 40 parts by weight with respect to 100 parts by weight of the solvent. The liquid thickener is produced by adding the POA-modified PVA to water or a water-containing solvent and mixing them by heating.

  In preparing the liquid thickener, various plasticizers, various surfactants, various antifoaming agents, ultraviolet absorbers and the like may be blended within a range that does not impair the effects of the present invention.

  Similarly, other various water-soluble polymers such as various PVA, starch, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose and the like may be blended within a range not impairing the effects of the present invention. The blending amount of such other water-soluble polymer is preferably 50 parts by weight or less with respect to 100 parts by weight of the above POA-modified PVA.

  The thickener-containing composition which is another embodiment of the present invention can be obtained by mixing the above-described thickener of the present invention, water and oil by a conventional method. Examples of the thickener-containing composition include an aqueous polyacrylate dispersion, an aqueous dispersion of an olefinically unsaturated monomer or copolymer, an aqueous polyvinyl acetate dispersion, an aqueous polyurethane dispersion, an aqueous Examples thereof include aqueous dispersions such as polyester dispersions. The content of the POA-modified PVA in the composition is preferably 0.1 to 50 parts by weight, more preferably 0.3 to 5.0 parts by weight with respect to 100 parts by weight of oil.

  The above thickening agent containing POA-modified PVA has a large thickening effect at a low use amount, and also has a small viscosity drop accompanying a rise in temperature, so that the thickening performance is stable even when the temperature rises in summer. Demonstrate. Therefore, it can be suitably used as a thickener for use in aqueous solutions and aqueous emulsions such as paints, paints, cement, concrete, paper coatings, binders, adhesives, and cosmetics.

  Hereinafter, the present invention will be described in detail by way of examples and comparative examples. In the following Examples and Comparative Examples, “parts” and “%” mean weight basis unless otherwise specified.

  The PVA obtained by the following production examples was evaluated according to the following method.

[Saponification degree of PVA]
The degree of saponification of PVA was determined by the method described in JIS-K6726.

[Solubility of PVA]
4 g of POA-modified PVA was added to 96 g of distilled water at room temperature and stirred for 30 minutes. The obtained aqueous solution of POA-modified PVA was heated to 90 ° C., stirred as it was for 1 hour, cooled to room temperature, and filtered using a 105 mmφ wire mesh. After filtration, the wire mesh was dried at 105 ° C. for 3 hours, cooled to room temperature in a desiccator, and then weighed to determine the weight of the wire mesh increased before and after filtration. The weight of the wire mesh increased after filtration was defined as a (g), and the insoluble content was calculated according to the following formula. In the formula used to calculate the insoluble content, the pure content (%) is a value obtained using the following formula.
Pure content (%) = [weight of POA-modified PVA dried at 105 ° C. for 3 hours (g) / weight of POA-modified PVA before drying (g)] × 100
Insoluble content (%) = a (g) / 4 (g) × 100 / pure content (%) × 100
The insoluble matter calculated according to the above formula was determined according to the following criteria.
A: Insoluble content less than 0.01% B: Insoluble content 0.01% to less than 0.1% C: Insoluble content 0.1% to less than 0.5% D: Insoluble content 0.5% or more Less than 1.0% E: Insoluble matter 1.0% or more

[Viscosity of PVA aqueous solution]
A PVA aqueous solution having a concentration of 4% was prepared, and the viscosity at a temperature of 20 ° C. or 40 ° C. was measured at a rotor rotation speed of 6 rpm using a BL type viscometer.

[Thickening test of ethylene-vinyl acetate copolymer emulsion]
100 parts of an ethylene-vinyl acetate copolymer emulsion (OM-4200NT manufactured by Kuraray Co., Ltd., concentration 55%) and 20.6 parts of a PVA aqueous solution having a concentration of 4% (the solid content of PVA is 1. 5 parts) and 2.4 parts of water were added to prepare a mixed solution of PVA and emulsion having a concentration of 45%, and the viscosity at a temperature of 20 ° C. was measured at a rotor rotation speed of 6 rpm using a BL type viscometer.

[Storage stability test of ethylene-vinyl acetate copolymer emulsion]
The solution used for the thickening test was stored in a dryer at 50 ° C., the number of days on which the emulsion layer and the aqueous layer were separated was observed, and judged according to the following criteria.
A: 30 days or more B: 15 to 30 days C: 7 to 15 days D: 3 to 7 days E: to 3 days

<Method for producing PVA>
Production Example 1 (Production of PVA1)
In a 3 L reactor equipped with a stirrer, reflux condenser, nitrogen inlet, comonomer dropping port and initiator addition port, 750 g of vinyl acetate, 250 g of methanol, unsaturated monomer having POA group (monomer A ) 3.3 g was charged, and the system was purged with nitrogen for 30 minutes while bubbling nitrogen. Further, a comonomer solution having a concentration of 20% was prepared by dissolving an unsaturated monomer having a POA group (monomer A) in methanol as a delay solution, and nitrogen substitution was performed by bubbling nitrogen gas. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.25 g of 2,2′-azobisisobutyronitrile (AIBN) was added to initiate polymerization. While the delay solution was added dropwise so that the monomer composition (ratio of vinyl acetate and monomer A) in the polymerization solution was constant, polymerization was performed at 60 ° C. for 3 hours and then cooled to stop the polymerization. The total amount of comonomer solution added until the polymerization was stopped was 75 ml. The solid content concentration when the polymerization was stopped was 24.4%. Subsequently, unreacted vinyl acetate monomer was removed while occasionally adding methanol under reduced pressure at 30 ° C. to obtain a methanol solution (concentration 35%) of POA-modified polyvinyl acetate (POA-modified PVAc). Furthermore, 55.6 g of an alkali solution (10% methanol solution of sodium hydroxide) was added to 453.4 g of POA-modified PVAc methanol solution prepared by adding methanol to this (100.0 g of POA-modified PVAc in the solution). Saponification was carried out (POA-modified PVAc concentration of saponified solution 20%, molar ratio of sodium hydroxide to vinyl acetate unit in POA-modified PVAc 0.1 mol%). A gel-like product was formed in about 1 minute after the addition of the alkaline solution. This was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to proceed with saponification. Neutralized. After confirming that the neutralization was completed using a phenolphthalein indicator, a white solid was obtained by filtration, 2000 g of methanol was added thereto, and the mixture was allowed to stand and washed at room temperature for 3 hours. After the above washing operation was repeated three times, the white solid obtained by centrifugal drainage was left in a dryer at 65 ° C. for 2 days to obtain POA-modified PVA (PVA1). The polymerization degree of PVA1 was 1760, the saponification degree was 98.7 mol%, and the POA group modification amount was 0.4 mol%.

Production Examples 2 to 28 (Production of PVA 2 to 28)
Charge amount of vinyl acetate and methanol, type of unsaturated monomer having POA group used during polymerization (Table 2), polymerization conditions such as addition amount, concentration of POA-modified PVAc during saponification, hydroxylation to vinyl acetate unit Various POA-modified PVA (PVA 2 to 28) were produced in the same manner as in Production Example 1 except that the saponification conditions such as the molar ratio of sodium were changed as shown in Tables 1 and 2.

Production Example 29 (Production of PVA29)
700 g of vinyl acetate and 300 g of methanol were charged into a 3 L reactor equipped with a stirrer, a reflux condenser, a nitrogen inlet, and an initiator addition port, and the system was purged with nitrogen for 30 minutes while bubbling nitrogen. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.25 g of 2,2′-azobisisobutyronitrile (AIBN) was added to start polymerization, and polymerization was performed at 60 ° C. for 3 hours. After cooling, the polymerization was stopped. The solid content concentration when the polymerization was stopped was 17.0%. Subsequently, unreacted vinyl acetate monomer was removed while sometimes adding methanol under reduced pressure at 30 ° C. to obtain a methanol solution (concentration 30%) of polyvinyl acetate (PVAc). Furthermore, saponification was performed by adding 55.8 g of an alkaline solution (sodium hydroxide in 10% methanol) to 544.1 g of PVAc methanol solution prepared by adding methanol thereto (120.0 g of PVAc in the solution). (PVAc concentration of saponification solution 20%, molar ratio of sodium hydroxide to vinyl acetate unit in PVAc 0.1 mol%). A gel-like product was formed in about 1 minute after the addition of the alkaline solution. This was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to proceed with saponification. Neutralized. After confirming that the neutralization was completed using a phenolphthalein indicator, a white solid was obtained by filtration, 2000 g of methanol was added thereto, and the mixture was allowed to stand and washed at room temperature for 3 hours. After repeating the above washing operation three times, the white solid obtained by centrifugal drainage was left in a dryer at 65 ° C. for 2 days to obtain unmodified PVA (PVA29). The polymerization degree of PVA29 was 1700, and the saponification degree was 98.5 mol%.

Production Examples 30 to 34 (Production of PVA 30 to 34)
Various methods were used in the same manner as in Production Example 29, except that the saponification conditions such as the amount of vinyl acetate and methanol, the concentration of PVAc during saponification, and the molar ratio of sodium hydroxide to vinyl acetate unit were changed as shown in Table 1. Of unmodified PVA (PVA 30-34).

Production Example 35 (Production of PVA35)
A 6 L reactor equipped with a stirrer, reflux condenser, nitrogen inlet, comonomer dropping port and initiator addition port was charged with 2400 g of vinyl acetate, 600 g of methanol, and 16.6 g of 1-hexadecene, while bubbling nitrogen. The system was purged with nitrogen for 30 minutes. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 2.8 g of 2,2′-azobisisobutyronitrile (AIBN) was added to initiate polymerization. After polymerization at 60 ° C. for 2 hours, the polymerization was stopped by cooling. The solid content concentration when the polymerization was stopped was 32.5%. Subsequently, unreacted vinyl acetate monomer was removed while occasionally adding methanol under reduced pressure at 30 ° C. to obtain a methanol solution (concentration 35%) of alkyl-modified polyvinyl acetate (alkyl-modified PVAc). Furthermore, 55.6 g of an alkaline solution (10% methanol solution of sodium hydroxide) was added to 453.4 g of an alkyl-modified PVAc methanol solution prepared by adding methanol thereto (100.0 g of the alkyl-modified PVAc in the solution). Saponification was performed (concentration of alkyl-modified PVAc in the saponification solution was 20%, molar ratio of sodium hydroxide to vinyl acetate unit in the alkyl-modified PVAc was 0.1 mol%). A gel-like product was formed in about 1 minute after the addition of the alkaline solution. This was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to proceed with saponification. Neutralized. After confirming that the neutralization was completed using a phenolphthalein indicator, a white solid was obtained by filtration, 2000 g of methanol was added thereto, and the mixture was allowed to stand and washed at room temperature for 3 hours. After repeating the above washing operation three times, the white solid obtained by centrifugal drainage was left in a dryer at 65 ° C. for 2 days to obtain alkyl-modified PVA (PVA35). The polymerization degree of PVA35 was 1720, the saponification degree was 98.6 mol%, and the amount of alkyl modification was 0.3 mol%.

  The production conditions for PVA 1 to 35 are shown in Tables 1 and 2.

Examples 1-19 and Comparative Examples 1-16
Tables 3 and 4 show the results of the above evaluation for PVA 1 to 35.

  The POA-modified PVA contained in the thickener of the present invention is excellent in solubility, and has a higher viscosity than non-modified PVA having an equivalent degree of polymerization. Moreover, it has the feature that aqueous solution viscosity at 40 degreeC is high compared with aqueous solution viscosity at 20 degreeC. Therefore, it has very excellent performance in the thickening effect and storage stability of the emulsion. Furthermore, it has a remarkably high thickening effect compared with polyethylene oxide modified PVA (Comparative Example 7) and polypropylene oxide modified PVA (Comparative Example 8). However, when m = 0, even when the value of n is within the range of 3 ≦ n ≦ 20, the obtained POA-modified PVA has low water solubility, and insoluble matter was confirmed in the aqueous solution (Comparative Example 9 ). Moreover, although the alkyl-modified PVA produced using 1-hexadecene has a certain thickening effect, the storage stability is low, and separation of the aqueous solution was confirmed (Comparative Example 16).

As shown in Examples, the thickener of the present invention can impart high viscosity and high storage stability by using POA-modified PVA. Therefore, it is suitably used as a thickener for various emulsions and paints.

Claims (3)

A thickener containing a polyoxyalkylene-modified vinyl alcohol polymer, wherein the modified vinyl alcohol polymer contains a polyoxyalkylene group represented by the following general formula (I) in the side chain, and has a viscosity average A thickener having a polymerization degree P of 200 to 5000, a saponification degree of 20 to 99.99 mol%, and a polyoxyalkylene group modification amount S of 0.1 to 10 mol%.

(In the formula, R1 represents a hydrogen atom or a methyl group, R2 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. M and n represent the number of repeating units of each oxyalkylene unit, 1 ≦ m ≦ 10, (3 ≦ n ≦ 20) Furthermore, the thickener of Claim 1 containing water or a water-containing solvent. A thickener-containing composition comprising the thickener according to claim 1, water and an oil, and containing 0.1 to 50 parts by weight of the polyoxyalkylene-modified vinyl alcohol polymer with respect to 100 parts by weight of the oil. .