JP2014031487A - Modified polyvinyl acetate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modified polyvinyl acetate having excellent alkali resistance and a narrow particle diameter distribution.SOLUTION: A modified polyvinyl acetate is obtained by copolymerizing 99 to 50 mol% of vinyl acetate with 1 to 50 mol% of a fatty acid vinyl ester in the presence of a modified polyvinyl alcohol having a bond unit represented by formula I (in the formula I, X1 and X2 represent a lower alkyl group having 1 to 12 carbon atoms, a hydrogen atom, or metal salt; g represents an integer of 0 to 3; h represents an integer of 0 to 12; and Y1 represents a carboxylic acid, carboxylic acid ester, a metal carboxylate or a hydrogen atom.).

Description

The present invention relates to modified polyvinyl acetate. In particular, it relates to a modified polyvinyl acetate having excellent alkali resistance and a narrow particle size distribution.

Conventional polyvinyl acetate is widely used as a raw material for paints, adhesives and coating agents, denture stabilizers, chewing gum bases, FRP shrinkage inhibitors, vibration damping materials and the like.

As a coating material using polyvinyl acetate, one made of a resin composition containing a silicone resin in polyvinyl acetate (for example, see Patent Document 1) is known.
Examples of the adhesive and coating agent include polyvinyl acetate containing an aqueous silicon dioxide dispersion having a specific average particle size (see, for example, Patent Document 2), polyvinyl acetate, epoxy group-containing compound, and acidic. A compound, a non-asbestos filler, a surfactant (for example, see Patent Document 3), and the like are known.
Known denture stabilizers are those containing vinyl acetate resin containing petrolatum, ethanol and water (see, for example, Patent Document 4).

Thus, products using polyvinyl acetate are used in a wide range of fields. However, these polyvinyl acetates are produced by a solution polymerization method or an emulsion polymerization method, the production process is complicated, and the resulting polyvinyl acetate has a wide particle size distribution. When the particle size distribution of the obtained polyvinyl acetate is wide, the filter may be clogged or the particles may be scattered in the filtration step or drying step after polymerization, which may make handling difficult. In addition, since polyvinyl acetate has low alkali resistance, when used in a place exposed to an alkaline environment, the coating may be damaged or deteriorated.

JP 2005-146070 A JP 2007-314786 A JP 2001-207153 A JP 2011-063538 A

An object of the present invention is to provide modified polyvinyl acetate having excellent alkali resistance and a narrow particle size distribution.

The above problems can be solved by modified polyvinyl acetate obtained by copolymerizing vinyl acetate and a fatty acid vinyl ester by a suspension polymerization method using a specific modified polyvinyl alcohol (hereinafter referred to as modified PVA) as a dispersant.

That is, the present invention is represented by formula I (in formula I, X1 and X2 represent a lower alkyl group having 1 to 12 carbon atoms, a hydrogen atom or a metal salt. G represents an integer of 0 to 3. h represents 0. Y1 represents a carboxylic acid, a carboxylic acid ester, a carboxylic acid metal salt, or a hydrogen atom.) In the presence of a modified PVA containing a bonding unit represented by 99 to 50 mol of vinyl acetate. % And 1 to 50 mol% of a fatty acid vinyl ester are modified polyvinyl acetate obtained by copolymerization by a suspension polymerization method.
The modified polyvinyl acetate is at least one selected from the group consisting of vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cinnamate, and vinyl neodecanoate. It is preferable that the average degree of polymerization is 1000 to 9000.

According to the present invention, modified polyvinyl acetate having excellent alkali resistance and a narrow particle size distribution can be obtained.

The modified polyvinyl acetate of the present invention is obtained by copolymerizing vinyl acetate and a fatty acid vinyl ester by a suspension polymerization method in the presence of a modified PVA containing a binding unit having a specific structure.

<Modified PVA>
Modified PVA is used to uniformly disperse vinyl acetate and fatty acid vinyl ester forming modified polyvinyl acetate in a polymerization liquid for suspension polymerization.
The modified PVA has a dispersion unit (protective colloid property) at the time of suspension polymerization by having a bond unit having a specific structure in the molecule. Since the protective colloid properties are high, the polymerization reaction of vinyl acetate and fatty acid vinyl ester can be carried out uniformly, and the particle size distribution of the resulting modified polyvinyl acetate can be narrowed.

Modified PVA can be obtained by saponifying a copolymer obtained by copolymerizing vinyl acetate and a dicarboxylic acid ester.

The copolymerization amount of the dicarboxylic acid ester in the modified PVA is preferably 0.1 to 10 mol%. When the copolymerization amount of the dicarboxylic acid ester is less than 0.1 mol%, the specific bonding units contained in the resulting modified PVA are insufficient, and the protective colloid properties cannot be improved. For this reason, the distribution of the particle diameter of the obtained modified polyvinyl acetate may become wide. In addition, when the copolymerization amount of the dicarboxylic acid ester exceeds 10 mol%, when the resulting modified polyvinyl acetate is used as an adhesive or a paint, the adhesiveness or the coating film strength is reduced. There is.

Examples of these dicarboxylic acid esters include monomethyl maleate, dimethyl maleate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monoethyl fumarate, and diethyl fumarate.

In order to copolymerize vinyl acetate and dicarboxylic acid ester, known polymerization methods such as solution polymerization, emulsion polymerization, and suspension polymerization can be arbitrarily used. In solution polymerization, as a method for charging vinyl acetate, any means such as divided charging or batch charging may be used. The polymerization reaction is performed using a known radical polymerization catalyst such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, or lauroyl peroxide. The reaction temperature is selected from the range of 50 ° C. to the boiling point of the reaction mixture.

The obtained vinyl acetate-dicarboxylic acid ester copolymer is dissolved in alcohol and saponified in the presence of an alkali catalyst or an acid catalyst. Examples of the alcohol include methanol, ethanol, butanol and the like. The concentration of the vinyl acetate-dicarboxylic acid ester copolymer in the alcohol is preferably set in the range of 20 to 50% by weight. Alkali catalysts such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate and other alkali metal hydroxides and alcoholates can be used as the alkali catalyst, and acid catalysts such as hydrochloric acid, An inorganic acid aqueous solution such as sulfuric acid and an organic acid such as p-toluenesulfonic acid can be used. The amount of these catalysts used must be 1 to 100 millimolar equivalents relative to vinyl acetate. The saponification temperature is not particularly limited, but is usually selected from the range of 10 to 70 ° C, preferably 30 to 50 ° C. The reaction is usually carried out for 1 to 3 hours.

The degree of saponification of the modified PVA is preferably adjusted to a range of 65 to 75 mol%. By using a modified PVA having a saponification degree within this range, the resulting modified polyvinyl acetate has a narrow particle size distribution, and when used as an adhesive or paint, its adhesion or coating strength is reduced. Can be maintained.

The number average molecular weight of the modified PVA is not particularly limited. However, when the number average molecular weight is 3800 to 28500, the balance between the solubility in the polymerization solution during suspension polymerization and the protective colloid properties of vinyl acetate and fatty acid vinyl ester is used. Is preferable because it is good.

When the concentration of the modified PVA in the polymerization liquid for suspension polymerization is 0.05 to 0.5%, the viscosity of the polymerization liquid at the time of suspension polymerization becomes appropriate while maintaining the protective colloid properties, and polymerization is performed. This is preferable because the reaction is carried out efficiently.

<Modified polyvinyl acetate>
The modified polyvinyl acetate according to the present invention is obtained by copolymerizing 99 to 50 mol% of vinyl acetate and 1 to 50 mol% of a fatty acid vinyl ester by suspension polymerization in the presence of the above-described modified PVA. is there.
Since modified polyvinyl acetate has a fatty acid vinyl ester bond unit in its molecule, it is superior in alkali resistance to conventional polyvinyl acetate.

Vinyl acetate is used for copolymerization with a fatty acid vinyl ester to form a modified polyvinyl acetate skeleton. The copolymerization amount of vinyl acetate is in the range of 99 to 50 mol%. If the amount of copolymerization is less than 50 mol%, when the resulting modified polyvinyl acetate is used as an adhesive or paint, its adhesiveness and coating film strength are reduced. Moreover, when the copolymerization amount exceeds 99 mol%, the effect of improving the alkali resistance of the resulting modified polyvinyl acetate cannot be obtained. The copolymerization amount of vinyl acetate is preferably 95 to 70 mol%, more preferably 90 to 75 mol%.

The fatty acid vinyl ester is copolymerized in the modified polyvinyl acetate in order to improve the alkali resistance of the resulting modified polyvinyl acetate. The copolymerization amount of the fatty acid vinyl ester is in the range of 1 to 50 mol%. If the copolymerization amount is less than 1 mol%, the effect of improving the alkali resistance of the resulting modified polyvinyl acetate cannot be obtained. Moreover, when the copolymerization amount of fatty acid vinyl ester exceeds 50 mol%, when the modified polyvinyl acetate obtained is used as an adhesive or a paint, its adhesiveness or coating film strength is lowered.
The copolymerization amount of the fatty acid vinyl ester is preferably 5 to 30 mol%, more preferably 10 to 25 mol%.

The fatty acid vinyl ester is preferably a fatty acid vinyl ester having 5 to 20 carbon atoms. When a fatty acid ester having less than 5 carbon atoms is used, the alkali resistance of the resulting modified polyvinyl acetate may not be improved. Moreover, the water resistance may also decrease.
When a fatty acid ester having more than 20 carbon atoms is used, the alkali resistance of the resulting modified polyvinyl acetate may be inferior.
When the fatty acid vinyl ester used preferably has 8 to 16 carbon atoms, more preferably 12 to 14 carbon atoms, the alkali resistance and adhesion or film strength of the resulting modified polyvinyl acetate is improved. This is desirable.

The compound having a fatty acid vinyl ester unit having 5 to 20 carbon atoms is not particularly limited, but vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, cinnamic acid. Vinyl, vinyl neodecanoate, etc.

The average degree of polymerization of the modified polyvinyl acetate is preferably 1000 to 9000. By limiting the average degree of polymerization of the modified polyvinyl acetate within this range, when the modified polyvinyl acetate is used as an adhesive or a paint, the solution viscosity becomes appropriate and workability can be improved.

The average degree of polymerization of the modified polyvinyl acetate can be arbitrarily adjusted by appropriately adjusting the polymerization temperature, polymerization time, concentration in the polymerization solution during suspension polymerization of vinyl acetate and fatty acid vinyl ester, and the amount of polymerization initiator added Can be adjusted.

Example 1
<Creation of modified PVA>
17 parts of vinyl acetate, 14 parts of methanol, 0.023 parts of dimethyl maleate, 0.257 parts of itaconic acid and 0.10% azobisisobutyronitrile with respect to vinyl acetate were charged into the polymerization vessel, and heated after nitrogen substitution. The mixture was heated to the boiling point, and a mixture of 6 parts of vinyl acetate, 5 parts of methanol and 0.207 parts of dimethyl maleate was continuously added and polymerized until the polymerization rate reached 75%, and the polymerization rate was 90%. The polymerization was stopped when the value reached. Subsequently, unpolymerized vinyl acetate was removed by a conventional method, and the resulting polymer was saponified with sodium hydroxide by a conventional method. Thereafter, it was dried with hot air at 90 ° C. for 90 minutes, dimethyl maleate 0.6 mol%, saponification degree 88.0 mol%, molecular weight (Mn) 11000, absorbance of 0.2% aqueous solution at a wavelength of 270 nm of 1.0, A modified PVA having a modified PVA content of 12% was obtained. The content of dimethyl maleate is measured by NMR. The degree of saponification of the modified PVA was measured according to JIS K6276 “3.5 degree of saponification”. And Mn was calculated in terms of standard polyethylene glycol.

<Creation of modified polyvinyl acetate>
To a glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet, 270 parts of ion exchange water was added, 0.1 part of the modified PVA obtained above was added, and the mixture was heated and stirred to dissolve.
Thereafter, the temperature in the polymerization vessel was set to 58 ° C., 0.08 part of lauroyl peroxide, 100 parts of vinyl acetate and 20 parts of neodecanoic acid vinyl ester were added as polymerization initiators and polymerized for 6 hours to obtain modified polyvinyl acetate. . The physical properties of the obtained modified polyvinyl acetate were measured according to the following method.

<Average polymerization degree>
It was measured according to “3.2 Average degree of polymerization” in JIS K6725-1977 “Testing method for polyvinyl acetate”.
<Residual vinyl acetate monomer amount>
Measured according to the 7th edition “vinyl acetate resin” purity test of the Food Additives Authority.
<Alkali resistance>
3 g of modified polyvinyl acetate is dissolved in 97 g of acetone, poured onto a film made of polytetrafluoroethylene, and dried for 3 days in an environment of room temperature 23 ± 2 ° C. and humidity 50 ± 5% RH to obtain a casting film having a thickness of 100 μm. It was. The surface state when the obtained casting film was immersed in a 5% aqueous sodium hydroxide solution at 70 ° C. for 24 hours was visually determined according to the following criteria.
A: No abnormality is observed.
A: The surface is slightly white and cloudy. X: Abnormalities such as whitening are observed.
<Particle size distribution>
The particle size distribution was determined by using a laser diffraction particle size measuring device SALD-3000S (manufactured by Shimadzu Corporation) and an average particle size (d50) based on volume and a standard deviation (σ50) based on d50. Was measured and a CV value (σ50 / d50 × 100) was calculated and evaluated according to the following criteria (the smaller the CV value, the more uniform the particle diameter).
○: CV value is 0.8 or less ×: CV value exceeds 0.8

Examples 2-12, Comparative Examples 1-3
The type of modified PVA used in the suspension polymerization of the modified polyvinyl acetate, the type and copolymerization amount (content) of the fatty acid vinyl ester when polymerizing the modified polyvinyl acetate, the average degree of polymerization of the modified polyvinyl acetate, A modified polyvinyl acetate was prepared in the same manner as in Example 1 except that the conditions were changed as described in Tables 1 to 3 and evaluated in the same manner as in Example 1.

It can be seen that the modified polyvinyl acetate of the present invention is excellent in alkali resistance and has a narrow particle size distribution.

Claims (3)

Formula I (In Formula I, X1 and X2 represent a lower alkyl group having 1 to 12 carbon atoms, a hydrogen atom, or a metal salt. G represents an integer of 0 to 3. h represents an integer of 0 to 12. Y1 represents carboxylic acid, carboxylic acid ester, carboxylic acid metal salt, or hydrogen atom.) In the presence of a modified polyvinyl alcohol containing a bond unit represented by: Modified polyvinyl acetate obtained by copolymerizing 1 to 50 mol% of ester by suspension polymerization.
The fatty acid vinyl ester is at least one selected from vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cinnamate, and vinyl neodecanoate. 1. Modified polyvinyl acetate according to 1. The modified polyvinyl acetate according to claim 1 or 2, wherein the average degree of polymerization is 1000 to 9000.