JP4611157B2 - Modified polyvinyl alcohol and method for producing the same - Google Patents

Description

The present invention relates to a modified polyvinyl alcohol having a double bond derived from a specific monomer in the main chain and a method for producing the same.

As the polyvinyl alcohol having a reactive unsaturated double bond introduced into the molecule, polyvinyl alcohol or modified polyvinyl alcohol can be modified by post-modification with a reactive molecule containing a polymerizable double bond. After obtaining a product obtained by introducing an unsaturated double bond into an alcohol side chain (for example, see Patent Document 1) or a polyvinyl ester copolymer having a protected ethylenically unsaturated double bond. Those obtained by removing the protection (for example, see Patent Document 2), those obtained by introducing an unsaturated double bond at the end of the polyvinyl alcohol molecule using an aldehyde as a chain transfer agent (for example, see Patent Document 3), etc. It has been known.
JP 04-283749 A JP 2001-072720 A JP 2004-250695 A

This invention makes it a subject to provide the modified polyvinyl alcohol which has the unsaturated double bond derived from a specific monomer in the principal chain in a molecule | numerator, and its manufacturing method.

The above-mentioned problems can be solved by modified polyvinyl alcohol obtained by polymerizing a specific monomer to cause a saponification reaction.

（式中、Ｘ１とＸ２は、炭素数１〜１２の低級アルキル基、水素原子または金属塩を表す。ｇは、０〜３の整数を表す。ｈは、０〜１２の整数を表す。Ｙ１は、カルボン酸、カルボン酸エステル、カルボン酸金属塩または水素原子を表す。） That is, the present invention is a modified polyvinyl alcohol containing a binding unit represented by the general formula (Formula 9) and a binding unit having an anionic group in the molecular main chain. In this case, the absorbance at 270 nm according to the ultraviolet absorption spectrum of 0.2% by mass of an aqueous solution, methanol solution, or aqueous methanol mixed solution is preferably 0.05 or more.

(In formula, X1 and X2 represent a C1-C12 lower alkyl group, a hydrogen atom, or a metal salt. G represents the integer of 0-3. H represents the integer of 0-12. Y1. Represents a carboxylic acid, a carboxylic acid ester, a carboxylic acid metal salt or a hydrogen atom.)

A modified polyvinyl alcohol having an unsaturated double bond derived from a specific monomer and an anionic group in the main chain in the molecule is obtained.

The modified polyvinyl alcohol is obtained by copolymerizing a monomer having an ethylenically unsaturated double bond and a monomer having a vinyl ester unit, followed by saponification to obtain a carbonyl group-containing polyvinyl alcohol, washing and drying. In this case, an unsaturated double bond starting from a carboxyl group is randomly introduced into the main chain.

（式中、Ｘ３とＸ４は、炭素数１〜１２の低級アルキル基または水素原子を表す。ｉは、０〜１２の整数を表す。Ｙ２は、カルボン酸、カルボン酸エステル、カルボン酸金属塩または水素原子を表す。）
これらモノマーとしては、例えば、マレイン酸ジメチル、マレイン酸ジエチル等がある。 As the monomer having an ethylenically unsaturated double bond, those represented by the general formula (Formula 10) can be suitably used.

(Wherein X3 and X4 represent a lower alkyl group having 1 to 12 carbon atoms or a hydrogen atom. I represents an integer of 0 to 12. Y2 represents a carboxylic acid, a carboxylic acid ester, a carboxylic acid metal salt, or Represents a hydrogen atom.)
Examples of these monomers include dimethyl maleate and diethyl maleate.

（式中、Ｘ５とＸ６は、炭素数１〜１２の低級アルキル基または水素原子を表す。ｊは、０〜１２の整数を表す。Ｙ３は、カルボン酸、カルボン酸エステル、カルボン酸金属塩または水素原子を表す。）
これらモノマーとしては、例えば、フマル酸ジメチル、フマル酸モノエチル、フマル酸ジエチル、シトラコン酸ジメチル等がある。 Moreover, the monomer represented by the general formula (Chemical Formula 11) can also be suitably used.

(In the formula, X5 and X6 represent a lower alkyl group having 1 to 12 carbon atoms or a hydrogen atom. J represents an integer of 0 to 12. Y3 represents a carboxylic acid, a carboxylic acid ester, a carboxylic acid metal salt, or Represents a hydrogen atom.)
Examples of these monomers include dimethyl fumarate, monoethyl fumarate, diethyl fumarate, and dimethyl citraconic acid.

（式中、ｋは、０〜１２の整数を表す。Ｙ４は、カルボン酸、カルボン酸エステル、カルボン酸金属塩または水素原子を表す。）
これらモノマーとしては、例えば、無水マレイン酸、無水シトラコン酸等がある。 Moreover, the monomer represented by the general formula (Chemical Formula 12) can also be suitably used.

(In the formula, k represents an integer of 0 to 12. Y4 represents a carboxylic acid, a carboxylic acid ester, a carboxylic acid metal salt, or a hydrogen atom.)
Examples of these monomers include maleic anhydride and citraconic anhydride.

The content (copolymerization amount) of these monomers is not particularly limited, but is preferably 0.1 to 50 mol% from the viewpoint of ensuring the amount of unsaturated double bonds in the molecule and water solubility, 1-10 mol% is more preferable.

The monomer having a vinyl ester unit is not particularly limited, but vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate In addition, vinyl acetate is preferable from the viewpoint of stable polymerization.

In order to introduce a bond unit having an anionic group into the molecule, there is no particular limitation. However, when the modified polyvinyl alcohol is polymerized, a monomer having an anionic group is copolymerized, or a hydroxyl group in the polyvinyl alcohol is combined. There is a method of post-modification using the reactivity of From the viewpoint of ensuring the dispersibility of the modified polyvinyl alcohol itself, the content of the anionic group in the molecule is preferably 0.05 to 10 mol%, more preferably 0.1 to 3 mol%.
The monomer having an anionic group is not particularly limited, and examples thereof include a carboxylic acid group-containing vinyl monomer and a sulfonic acid group-containing vinyl monomer. It is preferable to use a monomer.
Examples of the carboxylic acid group-containing vinyl monomer include polymerizable monocarboxylic acids such as (meth) acrylic acid, crotonic acid and isocrotonic acid and esters thereof, polymerizable dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, There are polymerizable dicarboxylic acid anhydrides such as maleic anhydride, aliphatic vinyl esters and the like, and itaconic acid is preferably used from the viewpoint of improving the dispersibility of the resulting modified polyvinyl alcohol.
Examples of the sulfonic acid group-containing vinyl monomer include olefin sulfonic acids such as ethylene sulfonic acid and allyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-1-methylsulfonic acid, and 2-methacrylic acid. Amido-2-methylpropanesulfonic acid and the like.

Moreover, you may copolymerize the monomer which can be copolymerized with these monomers as needed. Although it does not specifically limit as a monomer which can be copolymerized, For example, olefins, such as ethylene, propylene, 1-butene, and isobutene, acrylate, methacrylate, crotonic acid salt, phthalate, maleic acid Salts of unsaturated acids such as salts, monoalkyl esters or dialkyl esters having 1 to 18 carbon atoms, acrylamide, N-alkyl acrylamide, N, N-dialkyl acrylamide, diacetone acrylamide, acrylamide propyl having 1 to 18 carbon atoms Acrylamides such as dimethylamine and its salts or quaternary salts thereof, methacrylamide, N-alkyl methacrylamide having 1 to 18 carbon atoms, N, N-dialkyl methacrylamide, diacetone methacrylamide, methacrylamide propyl dimethylamine and Or quaternary salts thereof, vinyl ethers such as alkyl vinyl ethers having an alkyl chain length of 1 to 18 carbon atoms, hydroxyalkyl vinyl ethers, alkoxyalkyl vinyl ethers, N-vinylpyrrolidone, N-vinylformamide, N -N-vinylamides such as vinylacetamide, vinyl cyanides such as acrylonitrile and methacrylonitrile, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl bromide, vinylidene bromide, Examples include vinylsilanes such as trimethoxyvinylsilane, allyl compounds such as allyl acetate, allyl chloride, allyl alcohol, and dimethylallyl alcohol, vinylsilyl compounds such as vinyltrimethoxysilane, and isopropenyl acetate. Although the usage-amount of these copolymerizable monomers is not specifically limited, 0.001-20 mol% is preferable with respect to all the monomers to be used.

The number average molecular weight (hereinafter abbreviated as Mn) of the modified polyvinyl alcohol is not particularly limited, but is generally in the range of 1900 to 66500 which is generally used, and the viewpoint of improving the balance between water solubility and protective colloid properties. To 3800-28500 is more preferable.

The polymerization method of the monomer is not particularly limited, and a known polymerization method is used, and solution polymerization is usually performed using an alcohol such as methanol, ethanol or isopropyl alcohol as a solvent. Bulk polymerization, emulsion polymerization, and suspension polymerization can also be performed. Such solution polymerization may be continuous polymerization or batch polymerization, and the monomer may be charged in a divided manner, may be charged all at once, or any means such as adding continuously or intermittently may be used.

The polymerization initiator used in the solution polymerization is not particularly limited, but azobisisobutyronitrile, azobis-2,4-dimethylpareronitrile, azobis (4-methoxy-2,4-dimethylpareronitrile). ) And other azo compounds, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, peroxides such as 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, and diisopropylpropyl Percarbonate compounds such as dicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, t-butylperoxyneodecanate, α-cumylperoxyneodecane, t-butylperoxyneo Decanate The perester compound, azobisdimethylvaleronitrile can be used a known radical polymerization initiator such as azo-bis-methoxy valeronitrile. The polymerization reaction temperature is usually selected from the range of about 30 ° C to 90 ° C.

In saponification, a copolymer obtained by copolymerizing monomers is dissolved in alcohol, and an ester in the molecule is hydrolyzed 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 copolymer in the alcohol is not particularly limited, but is selected from a range of 10 to 80% by weight. As the alkali catalyst, for example, alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate can be used. For example, an inorganic acid aqueous solution such as hydrochloric acid or sulfuric acid, or an organic acid such as p-toluenesulfonic acid can be used. The amount of these catalysts used is preferably 1 to 100 mmol equivalents relative to the copolymer. The saponification temperature is not particularly limited, but is in the range of 10 to 70 ° C, preferably 30 to 40 ° C. Although reaction time is not specifically limited, It is performed over 30 minutes-3 hours.

The absorbance of the modified polyvinyl alcohol is not particularly limited, but it is preferable that the absorbance at 270 nm according to the ultraviolet absorption spectrum of 0.2% by mass of an aqueous solution, a methanol solution or a water-methanol mixed solution is 0.05 or more. This absorbance can be adjusted to any value by changing the amount of catalyst used in the saponification step, the saponification time, and the saponification temperature.

Here, regarding the attribution of the ultraviolet absorption spectrum, in JP-A-2004-250695, etc., the absorption at 215 nm is attributed to the structure of —CO—CH═CH— in polyvinyl alcohol, and the absorption at 280 nm is − There is a description that the absorption at 320 nm is related to the structure of —CO— (CH═CH) ₃ — in polyvinyl alcohol, belonging to the structure of CO— (CH═CH) ₂ —.

The UV absorption spectrum derived from the double-chain structure (—CO— (CH═CH) ₂ —) of an unsaturated double bond of polyvinyl alcohol using a general aldehyde as a chain transfer agent has a peak top in the vicinity of 280 nm. Is derived from the structure of the general formula (Chemical Formula 13) in the modified polyvinyl alcohol of the present invention and has a peak included in the range of 265 to 275 nm at the center of 270 nm.

The saponification degree of the modified polyvinyl alcohol is not particularly limited, but is preferably 30 mol% to 99.9 mol% from the viewpoint of generating sufficient unsaturated double bonds.

The dispersant of the present invention is suitably used, for example, when polymerizing an ethylenically unsaturated monomer. The ethylenically unsaturated monomer here means, for example, a monomer having an ethylenically unsaturated double bond, a monomer having a vinyl ester unit, a styrene monomer, a butadiene monomer, and a (meth) acrylic acid monomer, and these monomers. There are polymerizable monomers and the like, and these may be polymerized alone or a plurality of monomers may be copolymerized.
Examples of the polymerization method include suspension polymerization and emulsion polymerization.

Hereinafter, the present invention will be described in more detail with reference to examples.
Unless otherwise specified, “parts” and “%” mean “parts by mass” and “mass%”.

Example 1
<Production of modified polyvinyl alcohol>
17 parts of vinyl acetate, 14 parts of methanol, 0.023 part of dimethyl maleate, 0.257 part of itaconic acid and 0.10% azobisisobutyronitrile with respect to vinyl acetate were charged into the polymerization vessel, and heated after purging with nitrogen. 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 in hot air at 90 ° C. for 90 minutes, and the molecular weight (Mn) was 11000, the saponification degree was 88.0 mol%, dimethyl maleate 0.6 mol%, itaconic acid 1.0 mol%, and the wavelength of 0.2% aqueous solution A modified polyvinyl alcohol having an absorbance at 270 nm of 1.0 and an unmodified polyvinyl alcohol amount of 12% was obtained.

<Analysis method>
The contents of dimethyl maleate and itaconic acid were measured by NMR. The degree of saponification of the modified polyvinyl alcohol is measured according to JIS K 6276 “3.5 degree of saponification”. The molecular weight of the modified polyvinyl alcohol is GPC and the sample concentration is 0.25 w / v% aqueous solution. Is measured at 40 ° C., and Mn is calculated in terms of standard polyethylene glycol. The content of the unmodified polyvinyl alcohol was determined by completely saponifying the modified polyvinyl alcohol with an alkali catalyst in methanol, adjusting the Soxhlet-extracted sample to a 0.01 w / v% aqueous solution, using ion exclusion HPLC, IR It is calculated by the area ratio of the detector. The absorbance at 270 nm is obtained by adjusting the absorbance of ultraviolet rays at 270 nm by adjusting the modified polyvinyl alcohol to a 0.2% by mass aqueous solution.

<Suspension polymerization of vinyl acetate>
270 parts of ion-exchanged water was added to a glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet, 0.010 parts of polyvinyl alcohol 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 and 100 parts of vinyl acetate monomer were added as polymerization initiators, and polymerization was performed for 6 hours. The physical property of the obtained vinyl acetate resin was measured according to the following method.

<Average particle size>
From the particle size distribution measured using a roller tap type vibrating sieve, the median diameter (50% weight diameter) was determined and used as the average particle size.

Examples 2-6, Comparative Examples 1-2
Except for changing the degree of saponification, molecular weight (Mn), the type of monomer having an ethylenically unsaturated double bond, the amount of modification, and the amount of polyvinyl alcohol added during suspension polymerization of vinyl acetate as shown in Table 1, respectively. A modified polyvinyl alcohol was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1.
When the modified polyvinyl alcohol of the present invention is used as a dispersant for suspension polymerization of an ethylenically unsaturated polymer, it can be seen that the resulting polymer particles are excellent in dispersibility because the average particle size of the polymer particles is small.

Modified polyvinyl alcohol can be easily cured with energy rays such as ultraviolet rays and electron beams by combining with a photoinitiator, a polymerizable monomer, etc., if necessary. Effectively used for plates, etching resists, solder resists, dispersants during suspension polymerization, protective colloids during vinyl acetate emulsion polymerization, protective colloids during acrylic emulsion polymerization, protective colloids during styrene emulsion polymerization, etc. it can.

Claims (6)

A modified polyvinyl alcohol obtained by saponifying a copolymer obtained by continuously adding vinyl acetate and dimethyl maleate or vinyl acetate and maleic anhydride to a polymerization vessel, In the main chain, a linking unit represented by the general formula (formula 1) derived from dimethyl maleate or maleic anhydride and a linking unit having an anionic group derived from itaconic acid, maleic acid or monomethyl maleate is contained. A dispersant for suspension polymerization of an ethylenically unsaturated monomer comprising a modified polyvinyl alcohol.

(In the formula, 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. Y1 represents Represents a hydrogen atom.) 0.2 wt%, aqueous solution, the absorbance of 270nm by UV absorption spectrum of a methanol solution or water methanol mixed solution, ethylenically unsaturated consists modified polyvinyl alcohol according to claim 1, wherein a is 0.05 or more Dispersant for suspension polymerization of saturated monomers . From the modified polyvinyl alcohol according to claim 1 or 2, wherein the peak top of the ultraviolet absorption spectrum derived from the unsaturated double bond represented by the general formula (Chemical Formula 2) is between 265 and 275 nm. A dispersant for suspension polymerization of an ethylenically unsaturated monomer .

The saponification degree is 71.0-88.0 mol%, The dispersing agent for suspension polymerization of the ethylenically unsaturated monomer which consists of the modified polyvinyl alcohol as described in any one of Claims 1-3 characterized by the above-mentioned. A dispersant for suspension polymerization of an ethylenically unsaturated monomer , comprising 75% by mass or more of the modified polyvinyl alcohol according to any one of claims 1 to 4. The dispersant for suspension polymerization according to claim 1 , wherein the ethylenically unsaturated monomer is a vinyl acetate monomer .