JP2007297613A - Polyvinyl acetal-based resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyvinyl acetal-based resin having a high elastic modulus, excellent dissolvability in alcohol-based solvents and giving an alcoholic solution high in transparency. <P>SOLUTION: This polyvinyl acetal-based resin (A) is obtained by acetalizing a polyvinyl alcohol-based resin having 0.1-1.5 mol% of 1,2-diol structural unit expressed by general formula (1), and having ≥98.5 mol% of saponification degree, wherein the formula, R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>each independently denote a hydrogen atom or an organic group; X denotes a single bond or a bonding chain; and R<SP>4</SP>, R<SP>5</SP>and R<SP>6</SP>each independently denotes a hydrogen atom or an organic group. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polyvinyl acetal resin, and more particularly, to a polyvinyl acetal resin having a high elastic modulus, excellent solubility in an alcohol solvent alone, and a highly transparent alcohol solution.

  A polyvinyl acetal resin is generally obtained by acetalizing a polyvinyl alcohol resin obtained by saponifying a polyvinyl ester resin (hereinafter, polyvinyl alcohol is abbreviated as PVA). It is a polymer having a structural unit obtained by acetalizing a vinyl alcohol structural unit with an aldehyde compound, an unreacted vinyl alcohol structural unit, and a vinyl acetate structural unit that is an unsaponified portion of a PVA resin. Such polyvinyl acetal resins have excellent toughness, dispersibility of inorganic and organic powders, adhesion to various materials, transparency, and are soluble in many organic solvents. Paints such as metal paints, printing inks such as flexo inks and gravure inks, printed circuit boards, varnishes for coil wires, adhesives, binders such as ceramic binders and magnetic tapes, coating materials such as inkjet media and textile printing, glass interlayers It is used for various purposes.

  Such a polyvinyl acetal resin is often used as an organic solvent solution. However, in recent years, a reduction in the amount of the organic solvent is required from the viewpoint of environmental protection, and a polyvinyl acetal resin is also required to be used in a higher concentration solution. It has been. Therefore, a polyvinyl acetal resin having a low solution viscosity when made into a high concentration solution is desired. For example, a polyvinyl acetal resin obtained by acetalizing a PVA resin having ethylene as a structural unit in the main chain has been proposed ( For example, see Patent Document 1.)

Moreover, as an organic solvent when using a polyvinyl acetal resin as a solution, a mixed solvent of an aromatic solvent such as toluene and xylene and an alcohol solvent is obtained because a solution having a low viscosity and a small viscosity change during storage is obtained. However, since aromatic solvents have a large impact on the environment and have a great impact on health, their use tends to be limited, and polyvinyl acetal resin solutions are also desired to be based on alcohol-based single solvents. ing.
However, ordinary polyvinyl acetal resins do not have sufficient solubility in a single solvent of alcohol. For example, polyvinyl acetal resins described in Patent Document 1 also have good solubility in an aromatic / alcohol mixed solvent solution. However, the solubility in a solvent alone is insufficient.

On the other hand, the hydroxyl group in the unreacted vinyl alcohol structural unit derived from the PVA resin as the raw material has a great influence on the properties of the polyvinyl acetal resin. A polyvinyl acetal resin excellent in elastic modulus and toughness can be obtained. Therefore, for applications that require high elastic modulus and toughness, such as films, coatings, and glass interlayers, polyvinyl obtained by using PVA-based resins with a high degree of saponification, that is, a large amount of hydroxyl groups. An acetal resin is used.
However, the polyvinyl acetal resin based on such a high saponification degree PVA resin may not have sufficient solubility in a single alcohol solvent, and even if dissolved, only a solution with low transparency can be obtained. Therefore, it was difficult to apply to films and the like.
JP 2003-183325 A

  The present applicant has already proposed a polyvinyl acetal resin obtained by acetalizing a PVA resin having a 1,2-diol structure in the side chain as a polyvinyl acetal resin excellent in solubility in alcohol alone (a patent application). 2004-292098). However, another purpose of the novel polyvinyl acetal resin is to improve flexibility, and the polyvinyl acetal resins evaluated in the study are all low in elastic modulus and suitable for applications such as films and glass interlayers. It was not a thing. Further, it has been found that such a novel polyvinyl acetal resin still has room for improvement in terms of transparency when it is used as a solvent solution of alcohol alone.

  That is, an object of the present invention is to provide a polyvinyl acetal resin having a high elastic modulus, excellent solubility in an alcohol-based single solvent, and an alcohol solution excellent in transparency.

なお、式中のＲ¹、Ｒ²、及びＲ³はそれぞれ独立して水素原子または有機基を示し、Ｘは単結合、すなわちビニル構造部分の炭素と１，２−ジオール構造部分の炭素が直接結合したもの、または結合鎖を示し、Ｒ⁴、Ｒ⁵、及びＲ⁶はそれぞれ独立して水素原子または有機基を示す。 As a result of intensive studies in view of the above circumstances, the present inventor has 0.1 to 1.5 mol% of a 1,2-diol structural unit represented by the general formula (1) and has a saponification degree of 95 mol. It was found that the object of the present invention was achieved by a polyvinyl acetal-based resin obtained by acetalizing a PVA-based resin that is at least%, and the present invention was completed.

In the formula, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic group, and X is a single bond, that is, a carbon of a vinyl structure portion and a carbon of a 1,2-diol structure portion are directly R ⁴ , R ⁵ , and R ⁶ each independently represent a hydrogen atom or an organic group.

  That is, the present invention uses a modified PVA having a 1,2-diol structural unit represented by the general formula (1) in the side chain as a PVA-based resin that is a raw material of the polyvinyl acetal-based resin. The most characteristic feature is that the content of the diol structural unit is relatively low and that has a high degree of saponification, thereby providing a high elastic modulus and excellent solubility in alcohol solvents. The effect peculiar to the present invention is obtained.

Usually, when a polyvinyl acetal resin having a high elastic modulus is obtained, the raw material PVA resin is preferably one having a high saponification degree, but a low saponification degree is desirable for alcohol solubility. Therefore, in the present invention, by introducing a 1,2-diol structure capable of remarkably improving the alcohol solubility even in a small amount into the side chain, a high elastic modulus by using a high saponification degree PVA resin, and a modified group It is presumed that the excellent alcohol solubility by can be made compatible.
Polyvinyl acetal resins are usually produced by acetalizing a PVA resin in an aqueous solution at a low temperature. However, in the case of a highly saponified PVA resin, microcrystals are easily generated in the aqueous solution, which is uniform. Although the PVA resin (A) used in the present invention has a high degree of saponification, it is difficult to form microcrystals in a low-temperature aqueous solution, and the acetalization is uniform. By proceeding, it is presumed that a polyvinyl acetal resin having the characteristics of the present invention was obtained.

  Since the polyvinyl acetal resin of the present invention has a high elastic modulus, excellent solubility in an alcohol-based single solvent, and an alcohol solution excellent in transparency, a film, a coating film, and a glass interlayer film are obtained. It is extremely suitable for applications that require a high elastic modulus and toughness, and applications that form a transparent film by casting and drying a solvent solution.

The effect of the present invention is obtained by using a PVA resin (A) having a 1,2-diol structure in the side chain as a raw material.
On the other hand, the 1,3-glycol bond, which is the main bonding mode of the PVA main chain, increases the ratio of head-to-head or tail-to-tail bonding by making the polymerization temperature of polyvinyl acetate higher than usual. There is known a PVA resin in which the amount of main chain 1,2-glycol bonds obtained is larger than a normal value (about 1.6 mol%) (for example, JP-A No. 2001-355175). However, unlike the side chain 1,2-diol structure of the PVA resin (A) used in the present invention, such a main chain 1,2-glycol bond has little effect of lowering the crystallinity, and the main chain 1,2-glycol bond has a slight effect in a low temperature aqueous solution. The effect of suppressing crystal formation cannot be expected so much. Further, the hydroxyl group due to the main chain 1,2-glycol bond is a secondary hydroxyl group similar to a normal PVA resin, and a strong hydrogen bond like the primary hydroxyl group in the side chain 1,2-diol structure of the present invention. The high elastic modulus resulting from intermolecular cohesive force cannot be expected.

  Further, PVA resins having a monohydroxyalkyl group in the side chain obtained by copolymerizing an α-olefin having a hydroxyl group at the terminal are also known (for example, JP-A-7-179707). In many cases, it is difficult to obtain a PVA resin having a high degree of polymerization with the monomer used, and it is insufficient for use as a raw material for a polyvinyl acetal resin that requires film strength.

The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and is not limited to these contents.
Hereinafter, the present invention will be described in detail.

［式中、Ｒ¹、Ｒ²及びＲ³はそれぞれ独立して水素原子または有機基を示し、Ｘは単結合または結合鎖を示し、Ｒ⁴、Ｒ⁵、及びＲ⁶はそれぞれ独立して水素原子または有機基を示す。］
すなわち、本発明のポリビニルアセタール系樹脂は、ＰＶＡ系樹脂（Ａ）の連続するビニルアルコール構造単位がアルデヒド化合物によってアセタール化された構造単位と、一般式（１）で表される構造単位中の１，２−ジオール部分がアセタール化された構造単位、未反応のビニルアルコール構造単位、未反応の一般式（１）で表される構造単位、およびＰＶＡ系樹脂の未ケン化部分である酢酸ビニル構造単位を有する高分子である。 The polyvinyl acetal resin of the present invention is obtained by acetalizing a PVA resin (A) having a 1,2-diol structural unit represented by the following general formula (1).

[Wherein R ¹ , R ² and R ³ each independently represents a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent hydrogen. Indicates an atom or an organic group. ]
That is, the polyvinyl acetal resin of the present invention includes a structural unit obtained by acetalizing a continuous vinyl alcohol structural unit of the PVA resin (A) with an aldehyde compound, and 1 in the structural unit represented by the general formula (1). , 2-diol part acetalized structural unit, unreacted vinyl alcohol structural unit, unreacted structural unit represented by general formula (1), and vinyl acetate structure which is an unsaponified part of PVA resin It is a polymer having units.

Hereinafter, the PVA resin (A) used as a raw material for the polyvinyl acetal resin of the present invention will be described in detail.
The PVA resin (A) used in the present invention is a PVA resin having a 1,2-diol structural unit represented by the following general formula (1). In the general formula (1), R ¹ , R ² , And R ³ each independently represents a hydrogen atom or an organic group, X represents a single bond, that is, a direct bond of carbon of a vinyl structure part and carbon of a 1,2-diol structure part, or a bond chain; ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom or an organic group.

  In addition, content of the 1, 2-diol structural unit represented by General formula (1) of this PVA-type resin (A) is 0.1-1.5 mol%, and PVA-type resin (A) remains. The portion includes a vinyl alcohol structural unit and a slight amount of vinyl acetate structural unit, as in a normal PVA resin.

All of R ^{1 to} R ³ and R ^{4 to} R ⁶ in the 1,2-diol structural unit represented by the general formula (1) are preferably hydrogen atoms, but the resin properties are not significantly impaired. It may be an organic group as long as it is in an amount. Although it does not specifically limit as the organic group, For example, a C1-C4 alkyl group, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, is preferable, Moreover, the C1-C4 alkyl group may have substituents, such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, and a sulfonic acid group, as needed.

X in the 1,2-diol structural unit represented by the general formula (1) is preferably a single bond, that is, a carbon in the vinyl structure portion and a carbon in the 1,2-diol structure portion directly bonded. However, a bond chain may be used as long as it does not inhibit the effect of the present invention, and the bond chain is not particularly limited, but hydrocarbons such as alkylene, alkenylene, alkynylene, phenylene, naphthylene (these hydrocarbons are fluorine, chlorine, may be substituted with halogen such as bromine, etc.) _{other, -O -, - (CH 2} O) m -, - (OCH 2) m -, - (CH 2 O) m CH 2 -, - CO -, - COCO -, - CO (CH 2) m CO -, - CO (C 6 H 4) CO -, - S -, - CS -, - SO -, - SO 2 -, - NR -, -CONR-, -NRCO-, -CSNR-, NRCS -, - NRNR -, - HPO 4 -, - Si (OR) 2 -, - OSi (OR) 2 -, - OSi (OR) 2 O -, - Ti (OR) 2 -, - OTi (OR) _2- , -OTi (OR) ₂ O-, -Al (OR)-, -OAl (OR)-, -OAl (OR) O-, and the like. There, a hydrogen atom, an alkyl group preferably, and m is a natural number), an alkylene group having 6 or less carbon atoms or -CH ₂ OCH _2, in terms of stability during production or use among them - are preferred.

［式中、Ｒ¹、Ｒ²、及びＲ³、はそれぞれ独立して水素または有機基を示し、Ｘは単結合または結合鎖を示し、Ｒ⁴、Ｒ⁵、及びＲ⁶はそれぞれ独立して水素原子または有機基を示し、Ｒ⁷及びＲ⁸はそれぞれ独立して水素原子またはＲ⁹−ＣＯ−（式中、Ｒ⁹はアルキル基である）を示す］ The production method of the PVA resin (A) used in the present invention is not particularly limited, but (i) a method of saponifying a copolymer of a vinyl ester monomer and a compound represented by the following general formula (2) Preferably used.

[Wherein, R ¹ , R ² , and R ³ each independently represent hydrogen or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ , and R ⁶ each independently represent A hydrogen atom or an organic group, R ⁷ and R ⁸ each independently represent a hydrogen atom or R ⁹ —CO— (wherein R ⁹ is an alkyl group)]

［式中、Ｒ¹、Ｒ²及びＲ³はそれぞれ独立して水素原子または有機基を示し、Ｘは単結合または結合鎖を示し、Ｒ⁴、Ｒ⁵、及びＲ⁶はそれぞれ独立して水素原子または有機基を示す。］
（ｉｉｉ）ビニルエステル系モノマーと下記一般式（４）で示される化合物との共重合体をケン化及び脱ケタール化する方法を用いてもよい。

［式中、Ｒ¹、Ｒ²及びＲ³はそれぞれ独立して水素原子または有機基を示し、Ｘは単結合または結合鎖を示し、Ｒ⁴、Ｒ⁵、及びＲ⁶はそれぞれ独立して水素原子または有機基を示し、Ｒ¹⁰及びＲ¹¹はそれぞれ独立して水素原子または有機基を示す。］ Moreover, as a manufacturing method other than (i),
(Ii) a method of saponifying and decarboxylating a copolymer of a vinyl ester monomer and a compound represented by the following general formula (3),

[Wherein R ¹ , R ² and R ³ each independently represents a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent hydrogen. Indicates an atom or an organic group. ]
(Iii) A method of saponifying and deketalizing a copolymer of a vinyl ester monomer and a compound represented by the following general formula (4) may be used.

[Wherein R ¹ , R ² and R ³ each independently represents a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent hydrogen. An atom or an organic group is shown, and R ¹⁰ and R ¹¹ each independently represent a hydrogen atom or an organic group. ]

The vinyl ester monomers used in the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate. , Vinyl benzoate, vinyl versatate, and the like, among which vinyl acetate is preferably used from an economical viewpoint.
Hereinafter, the methods (i), (ii), and (iii) will be described.

[Method (i)]
In the method (i), a vinyl ester monomer and a compound represented by the general formula (2) are copolymerized and then saponified to have a 1,2-diol structural unit represented by the general formula (1). This is a method for producing a PVA-based resin.
In the compound represented by the general formula (2), R ^{1 to} R ³ , R ^{4 to} R ⁶ and X are the same as those in the general formula (1), and R ⁷ and R ⁸ are each independently A hydrogen atom or R ⁹ —CO— (wherein R ⁹ is an alkyl group, preferably a methyl group, a propyl group, a butyl group, a hexyl group or an octyl group; It may have a substituent such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group as long as it does not adversely affect the subsequent steps.

Specific examples of the compound represented by the formula (2) include 3,4-dihydroxy-1-butene, 3,4-diacyloxy-1-butene, and 3-acyloxy-4-hydroxy-1- wherein X is a single bond. Butene, 4-acyloxy-3-hydroxy-1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4,5-dihydroxy-1-pentene, wherein X is an alkylene group, 4,5-diacyloxy- 1-pentene, 4,5-dihydroxy-3-methyl-1-pentene, 4,5-diacyloxy-3-methyl-1-pentene, 5,6-dihydroxy-1-hexene, 5,6-diacyloxy-1- hexene, X is -CH ₂ OCH ₂ - or -OCH ₂ - in which glycerol monoallyl ether, 2,3-diacetoxy-1-allyloxypropane, 2-acetoxy -1 Allyloxy-3-hydroxypropane, 3-acetoxy-1-allyloxy-2-hydroxypropane, glycerin monovinyl ether, glycerin monomethyl isopropenyl ether, and the like.

Among them, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are hydrogen, X is a single bond, R ⁷ and R ⁸ are R in that they are excellent in copolymerization reactivity and industrial handling. 3,4-Diacyl-1-butene, which is ^9- CO- and R ⁹ is an alkyl group, is preferred, and 3,4-diacetoxy-1-butene in which R ⁹ is a methyl group is particularly preferred.
It should be noted that when vinyl acetate is used as the vinyl ester monomer and this is copolymerized with 3,4-diacetoxy-1-butene, the reactivity ratio of each monomer is r (vinyl acetate) = 0.710, r ( 3,4-diacetoxy-1butene) = 0.701, which is compared with r (vinyl acetate) = 0.85 and r (vinyl ethylene carbonate) = 5.4 in the case of vinyl ethylene carbonate described later. Thus, 3,4-diacetoxy-1-butene is excellent in copolymerization reactivity with vinyl acetate.
The chain transfer constant Cx of 3,4-diacetoxy-1-butene is 0.003 (65 ° C.), and Cx = 0.005 (65 ° C.) of vinyl ethylene carbonate or 2,2-dimethyl-4- This is a small value compared to Cx = 0.223 (65 ° C.) of vinyl-1,3-dioxolane, which is obtained when 3,4-diacetoxy-1-butene is used as a comonomer of a vinyl ester monomer. This indicates that it is difficult to inhibit the increase in the degree of polymerization as compared with other monomers. Also, 3,4-diacetoxy-1-butene is superior to the above-mentioned other monomers in terms of polymerization rate.
Further, the 3,4-diacetoxy-1-butene is an acetic acid derivative similar to a vinyl acetate structural unit in which a by-product generated when the copolymer is saponified is frequently used as a main structural unit, The fact that there is no need to provide a special device or process for the subsequent treatment is also a great industrial advantage.

  As for 3,4-diacetoxy-1-butene, products from Eastman Chemical Company for industrial production and Acros Company at the reagent level can be obtained from the market. Further, 3,4-diacetoxy-1-butene obtained as a by-product during the production process of 1,4-butanediol can be purified and used. Further, 1,4-diacetoxy-2-butene can be converted to 3,4-diacetoxy-1-butene by a known isomerization reaction using a palladium chloride catalyst or the like.

The copolymerization of the vinyl ester monomer and the compound represented by the general formula (2) is not particularly limited, and is a known method such as bulk polymerization, solution polymerization, suspension polymerization, dispersion polymerization, or emulsion polymerization. In general, solution polymerization is performed.
The method for charging the monomer component at the time of copolymerization is not particularly limited, and any method such as batch charging, split charging, continuous charging, etc. is adopted, but 1,2-derived from the compound represented by the general formula (2) Drop polymerization is preferred from the viewpoint that the diol structural unit is uniformly distributed in the molecular chain of the polyvinyl ester polymer, and the polymerization method based on the HANNA method using the reactivity ratio with vinyl acetate is particularly preferred.

Examples of the solvent used in such copolymerization include usually lower alcohols such as methanol, ethanol, isopropyl alcohol, n-propanol and butanol, and ketones such as acetone and methyl ethyl ketone, and industrially preferred is methanol. used.
The amount of the solvent used may be appropriately selected in consideration of the chain transfer constant of the solvent in accordance with the degree of polymerization of the target copolymer. For example, when the solvent is methanol, S (solvent) / M ( Monomer) = 0.01 to 10 (weight ratio), preferably 0.05 to 3 (weight ratio).

For the copolymerization, a polymerization catalyst is used. Examples of the polymerization catalyst include known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, lauryl peroxide, azobisdimethylvaleronitrile, azo Examples include low-temperature active radical polymerization catalysts such as bismethoxydimethylvaleronitrile, and the amount of polymerization catalyst used varies depending on the type of comonomer and the type of catalyst and cannot be determined unconditionally, but is arbitrarily selected according to the polymerization rate. The For example, when azoisobutyronitrile or acetyl peroxide is used, 0.01 to 0.7 mol% is preferable with respect to the vinyl ester monomer, and 0.02 to 0.5 mol% is particularly preferable.
Moreover, the reaction temperature of a copolymerization reaction is performed at about 30 degreeC-a boiling point by the solvent and pressure to be used, More specifically, it is 35-150 degreeC, Preferably it is carried out in 40-75 degreeC.

  At the end of the polymerization, a known polymerization inhibitor used in radical polymerization is preferably added to the reaction system. Examples of such polymerization inhibitors include m-dinitrobenzene, ascorbic acid, benzoquinone, and α-methylstyrene. Examples thereof include a monomer and p-methoxyphenol.

  The obtained copolymer is then saponified. In the saponification, the copolymer obtained as described above is dissolved in a solvent such as alcohol, and the reaction is carried out using an alkali catalyst or an acid catalyst. Typical solvents include methanol, ethanol, propanol, tert-butanol and the like, and methanol is particularly preferably used. The concentration of the copolymer in the alcohol is appropriately selected depending on the viscosity of the system, but is usually selected from the range of 10 to 60% by weight. Catalysts used for saponification include alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate, lithium methylate, etc., sulfuric acid, Examples include acid catalysts such as hydrochloric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resin.

The amount of the saponification catalyst used is appropriately selected depending on the saponification method, the target degree of saponification, and the like. When an alkali catalyst is used, the vinyl ester monomer and the compound represented by the formula (2) are usually used. A ratio of 0.1 to 30 mmol, preferably 2 to 17 mmol, is appropriate with respect to 1 mol of the total amount of 1,2-diol structural units derived from.
Moreover, although the reaction temperature of saponification reaction is not specifically limited, 10-60 degreeC is preferable, More preferably, it is 20-50 degreeC.

As the compound represented by the formula (2), glycerin monoallyl ether in which X is —CH ₂ OCH ₂ — and R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are hydrogen is also preferable. Although it is a monomer, compared with the above-mentioned 3,4-diacetoxy-1-butene, it is difficult to obtain a PVA resin having a high polymerization degree, and it is somewhat unsuitable as a raw material for a polyvinyl acetal resin that requires film strength. is there.

[Method (ii)]
In the method (ii), a vinyl ester monomer and a compound represented by the above general formula (3) are copolymerized, then saponified and decarboxylated, and then 1,2-diol represented by the above general formula (1). This is a method for producing a PVA-based resin having a structural unit.
In the compound represented by the general formula (3) used in the present invention, R ^{1 to} R ³ , R ^{4 to} R ⁶ and X are the same as those in the general formula (1). Among them, vinyl ethylene carbonate in which R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ are hydrogen and X is a single bond is preferably used because it is easily available and has good copolymerizability. It is done.

Copolymerization and saponification of the vinyl ester monomer and the compound represented by the general formula (3) are carried out in the same manner as in the above method (i).
In addition, about decarboxylation, without performing a special process, decarboxylation is performed with saponification, and it transform | converts into a 1, 2- diol structure by opening an ethylene carbonate ring.
It is also possible to perform decarboxylation without saponifying the vinyl ester moiety under a constant pressure (normal pressure to 1 × 10 ⁷ Pa) and at a high temperature (50 to 200 ° C.). The saponification can also be performed after carbonation.

  In addition, when vinyl ethylene carbonate is used, when saponifying the copolymer with the vinyl ester monomer, dimethyl carbonate, a harmful substance, is by-produced. It is necessary to pay attention to remaining in

[Method (iii)]
In the method (iii), a vinyl ester monomer and a compound represented by the above general formula (4) are copolymerized and then saponified and deketalized to obtain a 1,2-diol represented by the above general formula (1). This is a method for producing a PVA-based resin having a structural unit.
In the compound represented by the general formula (4) used in the present invention, R ^{1 to} R ³ , R ^{4 to} R ⁶ and X are the same as those in the general formula (1), and R ¹⁰ , R ¹¹ Are each independently hydrogen or an alkyl group, and the alkyl group is not particularly limited, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. The C1-C4 alkyl group of these is preferable. Such an alkyl group may have a substituent such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group as long as the copolymerization reactivity and the like are not impaired. Among them, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ are hydrogen and R ¹⁰ , R ¹¹ are methyl groups in terms of easy availability and good copolymerizability -Dimethyl-4-vinyl-1,3-dioxolane is preferred.

The copolymerization and saponification of the vinyl ester monomer and the compound represented by the general formula (4) is performed in the same manner as in the method (i).
As for deketalization, when the saponification reaction is carried out using an alkali catalyst, an aqueous solvent (lower alcohol mixed solvent such as water, water / acetone, water / methanol, etc.) is used after further saponification using an acid catalyst. Etc.) is deketalized and converted to a 1,2-diol structure. In this case, examples of the acid catalyst include acetic acid, hydrochloric acid, sulfuric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resin.
Moreover, when a saponification reaction is performed using an acid catalyst, deketalization is performed with saponification, without performing a special process, and is converted into a 1,2-diol structure.

  As described above, since 2,2-dimethyl-4-vinyl-1,3-dioxolane has a larger chain transfer constant than 3,4-diacetoxy-1-butene and the like, it has a high polymerization degree. It is not suitable as a raw material for polyvinyl acetal resins that are difficult to remove and require high film strength.

Moreover, the PVA-type resin (A) used for this invention can use what copolymerized various unsaturated monomers in the range which does not inhibit the objective of this invention. The introduction amount of the unsaturated monomer cannot be generally specified, but if the introduction amount is too large, the water solubility may be impaired or the gas barrier property may be deteriorated.
Examples of the unsaturated monomer include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, 3-buten-1-ol, 4-penten-1-ol, and 5-hexene- Hydroxyl group-containing α-olefins such as 1-ol, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, salts, monoesters, dialkyl esters, acrylonitrile, meta Nitriles such as acrylonitrile, amides such as diacetone acrylamide, acrylamide and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or salts thereof, alkyl vinyl ethers, dimethylallyl vinyl ketone, -Vinyl compounds such as vinylpyrrolidone and vinyl chloride, substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate, vinylidene chloride, 1,4-diacetoxy-2-butene, vinylene carbonate, acetoacetyl group-containing monomers, etc. Can be mentioned.

Furthermore, polyoxyethylene (meth) allyl ether, polyoxyethylene (meth) acrylamide, polyoxypropylene (meth) acrylamide, polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, polyoxyethylene (1- ( Poly) alkylene groups such as (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine Containing monomer, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylic Amidopropyltrimethylammonium chloride, 2-acryloxyethyltrimethylammonium chloride, 2-methacryloxyethyltrimethylammonium chloride, 2-hydroxy-3-methacryloyloxypropyltrimethylammonium chloride, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, 3- Examples also include cation group-containing monomers such as butenetrimethylammonium chloride, dimethyldiallylammonium chloride, and diethyldiallylammonium chloride.
In addition, by setting the polymerization temperature to 100 ° C. or higher, it is possible to use a PVA main chain having 1,2-diol bonds of about 1.6 to 3.5 mol%, which are heterogeneous bonds. .

The content of the 1,2-diol structural unit represented by the general formula (1) in the PVA resin (A) thus obtained is 0.1 to 1.5 mol%, and further 0.2 to 1. 2 mol%, especially 0.3-1 mol% is preferable. If the content of the 1,2-diol structural unit is too small, the transparency of the alcohol solution may be insufficient, or the viscosity stability during long-term storage may decrease. Conversely, if the content is too large, polyvinyl acetal This is not preferable because the elastic modulus of the resin may be too low. This is because, in the manufacturing process, when the raw material PVA resin is used as an aqueous solution, a microjunction due to molecular association may be formed at the molecular level even in an apparently uniform aqueous solution. It is presumed that the acetalization reaction is caused by non-uniform acetalization degree between molecules or within a molecule.
On the other hand, when the content of the 1,2-diol structural unit is too large, the elastic modulus of the obtained polyvinyl acetal resin becomes small, making it difficult to apply to applications that require high rigidity, toughness, etc. This is not preferable.

  The degree of saponification of the PVA resin (A) is 95 mol% or more, preferably 96 to 99.9 mol%, more preferably 97 to 99.8 mol%, and particularly 99.0 to 99.5 mol. %. If the degree of saponification is too low, the resulting polyvinyl acetal resin may have insufficient elasticity, which is not preferable.

  The average degree of polymerization (measured in accordance with JIS K6726) of the PVA resin (A) is usually 100 to 4000, more preferably 200 to 3500, and particularly preferably 250 to 3000. If it is too small, the strength of the obtained polyvinyl acetal resin is not sufficient. Conversely, if it is too large, the viscosity of the polyvinyl acetal resin solution becomes too high and the workability is lowered or it is difficult to make a high concentration solution. This is not preferable.

  In addition, the PVA resin (A) used in the present invention may be a mixture with other different PVA resins, and as such other PVA resins, 1, represented by the general formula (1) Examples thereof include those having different contents of 2-diol structural units, those having different saponification degrees, those having different polymerization degrees, and those having different other copolymerization components.

Next, a method for producing the polyvinyl acetal resin of the present invention will be described.
The method for producing the polyvinyl acetal resin of the present invention is not particularly limited, and a known method can be used. Among them, a method of acetalizing the PVA resin (A) with an aldehyde compound in a solvent in the presence of an acid catalyst is preferably used. The method is roughly classified into a precipitation method and a dissolution method. In the former case (precipitation method), a PVA resin (A) is used as an aqueous solution, and an acetalization reaction is performed at a low temperature in a solvent mainly composed of water. After the acetal resin is deposited, a method of raising the temperature of the system and causing an aging reaction (completion of the acetalization reaction and rearrangement of the acetalization part) is preferably used. In the case of the latter (dissolution method), an acetalization reaction is performed at a high temperature using an alcohol solvent such as isopropyl alcohol or a mixed solvent in which water is used in combination with this, and then water is added to the system to add polyvinyl. It is carried out by precipitating the acetal resin.

  The aldehyde compound used in the acetalization reaction is not particularly limited. For example, formaldehyde (including trimer and multimeric paraformaldehyde), acetaldehyde (including trimeric paraacetaldehyde), propionaldehyde, Butyraldehyde, isobutyraldehyde, pentyl aldehyde, isopentyl aldehyde, hexyl aldehyde, aliphatic aldehyde such as 2-ethylhexyl aldehyde, cyclohexyl aldehyde, aliphatic dialdehyde such as glyoxal, succindialdehyde, glutardialdehyde, benzaldehyde, o-tolu Aromatic aldehydes such as aldehyde, p-tolualdehyde, m-tolualdehyde, p-hydroxybenzaldehyde, salicylaldehyde, furfural What heterocyclic aldehyde and the like. Of these, acetaldehyde and butyraldehyde are preferably used, and butyraldehyde is particularly preferably used. Moreover, these aldehydes may be used independently and may mix and use 2 or more types of aldehydes.

The acid catalyst used in the acetalization reaction is not particularly limited, and examples thereof include organic acids such as acetic acid and p-toluenesulfonic acid, and inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and hydrochloric acid and sulfuric acid are preferably used. .
In addition, after the acetalization reaction is completed, as a reaction terminator, alkaline compounds such as sodium hydroxide, potassium hydroxide, ammonia, sodium acetate, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, and alkylene oxides such as ethylene oxide can be used. It is also possible to add glycidyl ethers such as ethylene glycol diglycidyl ether.

The degree of acetalization of the polyvinyl acetal resin of the present invention is not particularly limited, but is preferably 40 to 80 mol%, particularly 50 to 80 mol%, more preferably 60 to 75 mol%. If the degree of acetalization is too small, it becomes water-soluble, so that it is difficult to take out the polyvinyl acetal resin from the reaction system in both the precipitation method and the dissolution method, and the hydrophilic property of the polyvinyl acetal resin is low. It is not preferable because the water resistance becomes insufficient, and if it is too large, the residual hydroxyl group decreases, so the toughness of the polyvinyl acetal resin becomes insufficient, or the solubility in an alcohol-based single solvent is low. Since it may become poor, it is not preferable.
In the polyvinyl acetal resin of the present invention, both the hydroxyl group in the main chain of the PVA resin (A) and the hydroxyl group in the 1,2-diol structure in the side chain may be acetalized. The degree of conversion is represented by the amount of acetalized hydroxyl groups relative to the total amount of hydroxyl groups before acetalization.

The polyvinyl acetal resin of the present invention thus obtained has an unreacted 1,2-diol structural unit in the molecular chain since the raw material is a PVA resin having a 1,2-diol structure in the side chain. The effect shows high elasticity and excellent solubility in alcohol solvents.
Furthermore, since the polyvinyl acetal resin of the present invention produces a small amount of crystallites of the PVA resin during the acetalization reaction of the PVA resin in low-temperature water, a uniform acetalized product can be obtained, and the intermolecular or intramolecular It is estimated that the acetalization distribution is uniform. As a result, when used as a binder for paints, ceramics, heat-developable photosensitive materials, etc., good adhesion is obtained, and when used as a glass interlayer, pressurization / heating adhesion with an autoclave, or In any case of the adhesion by the vacuum bag method, it is estimated that it is difficult to cause poor melt adhesion.

Hereinafter, the present invention will be described with reference to examples. However, the present invention is not limited to the description of the examples unless it exceeds the gist.
In the examples, “parts” and “%” mean weight basis unless otherwise specified.

Example 1
[Production of PVA resin (A)]
A reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 1200 g of vinyl acetate, 240 g of methanol, and 12 g of 3,4-diacetoxy-1-butene (0.5 mol% with respect to vinyl acetate). Isobutyronitrile was added in an amount of 0.017 mol% (vs. vinyl acetate charged), and the temperature was raised in a nitrogen stream while stirring and polymerization was performed while refluxing.
When the polymerization rate of vinyl acetate reached 74.5%, 0.3 g of m-dinitrobenzene was added to complete the polymerization, and then unreacted vinyl acetate monomer was removed from the system by blowing methanol vapor. To obtain a methanol solution of the copolymer.
The solution was then diluted with methanol to a concentration of 35% and charged into a kneader. While maintaining the solution temperature at 40 ° C., a 2% methanol solution of sodium hydroxide was added to the vinyl acetate structural units and 3 in the copolymer. The saponification was carried out at a ratio of 8 mmol per 1 mol of the total amount of 1,4-diacetoxy-1-butene structural units. When saponification progressed and saponified product was precipitated and became particulate, it was separated by filtration, washed well with methanol and dried in a hot air dryer to obtain PVA resin (A1).

The saponification degree of the obtained PVA-based resin (A1) was 99.3 mol% when analyzed by the alkali consumption required for hydrolysis of residual vinyl acetate and 3,4-diacetoxy-1-butene, When the average degree of polymerization was analyzed according to JIS K6726, it was 1850. The content of the 1,2-diol structure was 0.4 mol% when calculated by measurement with ¹ H-NMR. In addition, “AVANCE DPX400” manufactured by Nippon Bruker Co., Ltd. was used for NMR measurement.

[Production of polyvinyl acetal]
18 g of PVA resin (A1) was put in a beaker containing 284 g of water, stirred and dispersed, then heated to 90 ° C. and dissolved over 1.5 hours.
The obtained aqueous solution of PVA resin (A1) was prepared to a concentration of 5%, 250 g of the solution was cooled to 10 ° C., and 1.3 g of hydrochloric acid having a concentration of 35% and 7.45 g of n-butyraldehyde were added thereto, The liquid temperature was maintained at 10 ° C. to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the liquid temperature was maintained at 25 ° C. for 30 minutes and further at 40 ° C. for 5 hours to complete the reaction, and neutralized, washed with water and dried by a conventional method to obtain a polyvinyl acetal resin. The degree of acetalization of the polyvinyl acetal resin by ¹ H-NMR was 69.8 mol%.

[Transparency of alcohol solution]
The obtained polyvinyl acetal resin is made into a 4% solution of methanol and ethanol, and light transmittance (%) at 430 nm at 25 ° C. using a spectrophotometer (manufactured by JASCO Corporation, UV-visible spectrophotometer V-560). Asked.

[Storage modulus]
A 10% ethanol solution of the polyvinyl acetal resin was cast on a glass plate and dried to produce a film having a thickness of 10 μm. The viscoelasticity of the film was measured using a humidity-controlled viscoelasticity measuring device (DVA-225Rheometer manufactured by IT Measurement Control Co., Ltd.) with a relative humidity of 40% RH, a frequency of 10 Hz, and a temperature of 30 to 90 ° C. The storage elastic modulus at 45 ° C. was determined from the obtained data.

Example 2
In the production process of the polyvinyl acetal resin of Example 1, the polyvinyl acetal resin is obtained in the same manner as in Example 1 except that the dissolution condition of the PVA resin is increased to 80 to 85 ° C. and 1.5 hours. (Acetalization degree 66.7 mol%) was prepared, and the transparency of the alcohol solution was similarly evaluated. The results are shown in Table 1.

Example 3
In the production process of the polyvinyl acetal resin of Example 1, except that the dissolution condition of the PVA resin was raised to 90 ° C. for 1.5 hours, and further raised to 120 ° C. by an autoclave for 1 hour. In the same manner as in Example 1, a polyvinyl acetal resin (the degree of acetalization was 62.4 mol%) was prepared, and the transparency of the alcohol solution was similarly evaluated. The results are shown in Table 1.

Comparative Example 1
In Example 1, polyvinyl alcohol was used in the same manner as in Example 1 except that PVA was composed of only a vinyl alcohol structural unit and a vinyl acetate structural unit, and PVA having a saponification degree of 99.0 mol% and an average polymerization degree of 1750 was used. An acetal resin (degree of acetalization 67.4 mol%) was prepared and evaluated in the same manner. The evaluation results are shown in Table 1.

Comparative Example 2
In Comparative Example 1, the polyvinyl acetal resin (degree of acetalization 65.2 mol) was the same as Comparative Example 1 except that the dissolution condition of the PVA resin was raised to 80 to 85 ° C. to 1.5 hours. %) And the transparency of the alcohol solution was similarly evaluated. The results are shown in Table 1.

Comparative Example 3
In Comparative Example 1, polyvinyl alcohol was dissolved in the same manner as in Comparative Example 1 except that the dissolution condition of the PVA resin was raised to 90 ° C. and 1.5 hours, and further raised to 120 ° C. by an autoclave to 1 hour. An acetal resin (degree of acetalization 65.8 mol%) was prepared, and the transparency of the alcohol solution was similarly evaluated. The results are shown in Table 1.

Comparative Example 4
A PVA resin (content of 1,2-diol structure 6.1 mol%, saponification degree 99 mol%, average polymerization degree 860) prepared according to the production process of the PVA resin (A) of Example 1 In the same manner as in Example 1, polyvinyl acetal (degree of acetalization 69 mol%) was prepared and evaluated in the same manner. The results are shown in Table 1.

Comparative Example 5
In Example 1, ethylene-modified PVA having an ethylene content of 6%, a saponification degree of 98 mol% and an average polymerization degree of 1700 obtained by saponifying a copolymer of ethylene and vinyl acetate was used as the PVA resin. Produced a polyvinyl acetal resin (degree of acetalization 64 mol%) in the same manner as in Example 1 and evaluated in the same manner. The evaluation results are shown in Table 1.

[Table 1]

As is apparent from Table 1, the polyvinyl acetal resins (Examples 1 to 3) of the present invention are methanol and ethanol compared to the polyvinyl acetal resins (Comparative Examples 1 to 3) using unmodified PVA as a raw material. An alcohol solution having excellent solubility in water and transparency was obtained. In particular, it can be seen that the polyvinyl acetal resin of the present invention provides good alcohol solubility and transparency even when PVA is dissolved at the time of production.
In addition, the polyvinyl acetal resin of the present invention has a higher elastic modulus than that using a PVA resin having a large 1,2-diol structure content (Comparative Example 4), and is transparent when used as an alcohol solution. High nature.

  Since the polyvinyl acetal resin of the present invention has a high elastic modulus, excellent solubility in alcohol solvents, and a transparent alcohol solution is obtained, it has a high elastic modulus such as a film, a coating film, and a glass interlayer film. It is extremely suitable for applications that require toughness and applications that form a transparent film by casting and drying a solvent solution.

Claims (5)

The polyvinyl alcohol resin (A) having 0.1 to 1.5 mol% of 1,2-diol structural unit represented by the following general formula (1) and having a saponification degree of 95 mol% or more is acetalized. A polyvinyl acetal resin characterized by comprising:

[Wherein R ¹ , R ² and R ³ each independently represents a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent hydrogen. Indicates an atom or an organic group. ] In the 1,2-diol structural unit represented by the general formula (1), R ¹ , R ² , and R ³ are all hydrogen, X is a single bond, and R ⁴ , R ⁵ , and R ⁶ are any The polyvinyl acetal resin according to claim 1, which is also hydrogen. The polyvinyl alcohol resin (A) is obtained by saponifying a copolymer of a vinyl ester monomer and a compound represented by the general formula (2). Polyvinyl acetal resin.

[Wherein, R ¹ , R ² and R ³ each independently represent hydrogen or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represent hydrogen. An atom or an organic group, R ⁷ and R ⁸ each independently represent a hydrogen atom or R ⁹ —CO— (wherein R ⁹ is an alkyl group)] The polyvinyl acetal resin according to any one of claims 1 to 3, wherein the degree of acetalization is 40 to 80 mol%. The polyvinyl acetal resin according to claim 1, which is acetalized with butyraldehyde.