JP3484504B2 - Method for producing melt-modified polyvinyl alcohol - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polyvinyl alcohol having water solubility and having a carboxyl group introduced by carboxylic acid anhydride.

[0002]

2. Description of the Related Art Polyvinyl alcohol (hereinafter abbreviated as PVA) has high water solubility, adhesiveness and chemical stability.
It is widely used in applications such as resin plate materials for printing, cosmetics, adhesives, warp sizing agents, fibers, fiber resin finishing agents, paper finishing agents, paints, emulsifiers, protective colloid agents and films. Especially P
When VA is used as a printing resin plate material, PV is often used.
Attempts have been made to improve the photosensitivity by introducing a functional group into A.

A carboxyl group is mentioned as a functional group effective when introduced into PVA. For example, US Pat. No. 2,8
In JP 08,348, a carboxylic acid is introduced into PVA by copolymerizing maleic anhydride with vinyl acetate and then saponifying it. JP-A-39-24,708 and US Pat. No. 2,850,471 disclose a method of saponifying a copolymer of vinyl acetate and crotonic acid to introduce a carboxylic acid into PVA. In addition, JP-A-4-
283749 and Chemical Abstracts 86
(10): 55883W (1976) describes a method of dissolving or swelling PVA in a solvent and then reacting with carboxylic acid anhydride to give a carboxyl group.

However, US Pat. No. 2,808,3
No. 48, JP-A-39-24,708, US Pat. No. 2,850,471, etc., a method using a copolymer reacts with monomers having different reactivity in the polymerization stage. Therefore, there is a problem that the reaction is difficult to control, extreme block copolymerization is likely to occur, and the degree of polymerization is difficult to increase.

JP-A-4-283749 and Chemical Abstracts 86 (10): 55883W (197).
In the method described in 6), the reaction is easy to control because the carboxylic acid is introduced after PVA polymerization, but it requires the use of a large amount of an organic solvent as a solvent and the step of separating and purifying the polymer from the solvent. Therefore, there is a problem that the manufacturing cost becomes very high because the process becomes complicated. Also, in terms of polymer quality, it is impossible to completely remove impurities such as solvents, and it is very difficult to control the water present in the polymer and solvent, so acid anhydrides easily react with water. There are also problems that the esterification rate becomes low, and when swollen in a solvent, crystallization progresses due to solvent-induced crystallization and the water solubility of the polymer powder decreases.

[0006]

DISCLOSURE OF THE INVENTION The present invention is based on the previously known P
It is an object of the present invention to overcome the various drawbacks of the VA modification method and to develop a modification method for easily producing a highly pure carboxylic acid anhydride-modified PVA at low cost.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventor has conducted a carboxylic acid anhydride modification of PVA, which was conventionally considered to be an essential condition, to use a solvent.
It has been found that this can be achieved by reacting in the molten state. PVA modified with carboxylic acid anhydride in the molten state
Has a very high degree of esterification, a high degree of purity, and is highly soluble in water because it is obtained in an amorphous state, and has completed the present invention.

That is, according to the present invention, PVA100 having a saponification degree of 60 to 99 mol% and a number average degree of polymerization of 300 to 2,000 is used.
Melt-modified PVA produced by reacting 0.001 to 5 parts by weight of carboxylic acid anhydride with respect to parts by weight, and a saponification degree of 60 to 99 mol% and a number average degree of polymerization of 300 to 2,000. 0.001 to 10 parts by weight of carboxylic anhydride with respect to 100 parts by weight of PVA in the presence of a solvent in a molten state at a temperature of 100 to 400 ° C. It provides a manufacturing method.

As the PVA used in the present invention, polyvinyl acetate having a number average degree of polymerization of 300 to 2,000 is 60 to
It is a vinyl resin obtained by saponification of 99 mol%. P
When the degree of saponification of VA is lower than 60 mol%, the water solubility is significantly reduced, which is not preferable. Number average degree of polymerization is 300
If it is lower, the mechanical strength of the polymer produced is significantly lowered, which is not preferable, and the number average degree of polymerization is 2,000.
If it is higher, the water solubility of the modified PVA decreases, which is not preferable.

In the PVA used in the present invention, another olefinically unsaturated compound may be copolymerized in the range of 0 to 5 mol%. Specific olefinically unsaturated compounds include ethyl acrylate, n-butyl acrylate, crotonic acid, ethylene, maleic acid, methyl methacrylate, vinyl chloride and the like.

The carboxylic acid anhydride used in the present invention is not particularly limited as long as it is a general carboxylic acid anhydride, but a carboxylic acid anhydride having two or more carboxyl groups in the molecule is preferable, and two carboxylic acid anhydrides in the molecule are preferable. The carboxylic acid anhydride having the above-mentioned carboxyl group and containing no olefinic unsaturated bond is more preferable. Specific examples thereof include succinic anhydride, maleic anhydride, acetic anhydride, trimellitic anhydride, phthalic anhydride, pyromellitic anhydride, glutaric anhydride, hydrogenated phthalic anhydride, and naphthalene dicarboxylic acid anhydride. Among these, succinic anhydride, maleic anhydride,
Trimellitic anhydride, phthalic anhydride, pyromellitic anhydride, glutaric anhydride, hydrogenated phthalic anhydride, naphthalene dicarboxylic acid anhydride are preferable, and succinic anhydride, phthalic anhydride, hydrogenated phthalic anhydride are more preferable. Particularly preferred is succinic anhydride. The present invention also includes the use of one or more of these carboxylic acid anhydrides.

In the present invention, the carboxylic acid anhydride is used in an amount of 0.001 to 5 parts by weight based on 100 parts by weight of PVA. If the amount of the carboxylic acid anhydride is less than 0.001 part by weight, a satisfactory modification effect will not be exhibited, and if it is more than 5 parts by weight, side reactions such as a crosslinking reaction in a molten state become severe, which is not preferable.

The melting reaction temperature in the present invention is 100 to 4
The temperature is 00 ° C, preferably 150 to 300 ° C, more preferably 180 to 280 ° C, and the reaction is carried out in the substantial absence of a solvent. The present invention also includes a method of lowering the melt softening temperature by adding a plasticizer or the like to PVA. Examples of the plasticizer for PVA include glycols such as ethylene glycol, diethylene glycol, triethylene glycol and polyethylene glycol, water and the like. These plasticizers may be optionally added and reacted as long as they do not significantly impair the carboxylic anhydride modification of PVA.

The method for melt-modifying PVA with carboxylic acid anhydride is not particularly limited. For example, if necessary, PVA and acid anhydride may be added with a ribbon blender, a Henschel mixer, a V
Examples of the method include dry blending with a blender and the like, followed by melt kneading with a Banbury mixer, mixin roll, single-screw or twin-screw extruder, and kneader. Of these, a typical method is melt kneading using a single-screw or twin-screw extruder having a sufficient kneading force.

[0015]

The present invention will be described in more detail with reference to the following examples.

The esterification rate, heating residue, and insoluble content described in Examples and Comparative Examples were evaluated and measured according to the following methods.

Esterification ratio: The carboxyl groups introduced into the reprecipitated and purified modified PVA were neutralized and titrated with 0.1N potassium hydroxide, and the end point was detected with a Hiranuma titrator. Next, the esterification rate was evaluated from the titration amount and the addition amount of carboxylic acid anhydride.

Heating residue: TG / manufactured by Seiko Denshi Kogyo
Using DTA-200, the weight loss was evaluated as a percentage by holding at 200 ° C. for 30 minutes in a nitrogen atmosphere.

Insoluble matter: 0.5 with respect to water at 80 ° C.
Polymer was added at a concentration of g / mL and dissolved for 1 hour. Next, high-purity filter paper No. 5 A was used for filtration, and the amount of insoluble matter remaining on the filter paper was evaluated by the weight percentage.

The PVA bulk powders used in the examples and comparative examples are PVA-1: KL-05 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., PVA-2: NH-18 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., It was used after being vacuum dried at 60 ° C. for 8 hours.

Example 1 PVA-1 (1,000 g) and 30 g of succinic anhydride were dry-blended, melt-kneaded by a single-screw extruder set to a temperature condition of 210 ° C., and then cooled by a cooling belt. I pelletized with a cutter. The obtained pellets were light yellow, transparent and in an amorphous state, and easily dissolved in water. The esterification rate after reprecipitation purification with water / ethanol was 99.6%. The heating residue at 200 ° C. was 100% and the insoluble content was 0%.

Example 2 PVA-2 (1,000 g) and succinic anhydride (30 g) were dry-blended, melt-kneaded by a single-screw extruder set to a temperature condition of 210 ° C., and then cooled by a cooling belt. I pelletized with a cutter. The obtained pellets were light yellow, transparent and in an amorphous state, and easily dissolved in water. The esterification rate after reprecipitation purification with water / ethanol was 99.8%. The heating residue at 200 ° C. was 100% and the insoluble content was 0%.

Example 3 PVA-1 (1,000 g) and hydrogenated phthalic anhydride (50 g) were added.
g was dry-blended, melt-kneaded with a twin-screw extruder set to a temperature condition of 210 ° C., cooled with a cooling belt, and pelletized with a cutter.
The obtained pellets were yellow-brown, transparent and in an amorphous state, and dissolved in water. The esterification rate after reprecipitation purification with water / ethanol was 99.2%. The heating residue at 200 ° C. was 99.8%, and the rate was 53%. The heating residue at 200 ° C. was 93%, and the insoluble content was 0%. It is clear that the reaction time is very long as compared with Example 1, and the process is complicated because a solvent is used. Further, as compared with Example 1, it is clear that impurities such as a solvent are contained in the polymer due to the low esterification rate of the obtained polymer and the large heat loss.

[0024]

INDUSTRIAL APPLICABILITY The present invention overcomes various drawbacks of the conventionally known PVA modification method and can easily produce a high-purity carboxylic acid anhydride-modified PVA at low cost.

Claims (5)

(57) [Claims] 1. A method of reacting 0.001 to 5 parts by weight of carboxylic acid anhydride in a molten state with respect to 100 parts by weight of polyvinyl alcohol having a saponification degree of 60 to 99 mol% and a number average degree of polymerization of 300 to 2,000. A method for producing a melt-modified polyvinyl alcohol characterized by the above. 2. 100 to 400 in the substantial absence of a solvent.
The method for producing a melt-modified polyvinyl alcohol according to claim 1, wherein the reaction is carried out in a molten state at a temperature of ° C. 3. The method for producing a melt-modified polyvinyl alcohol according to claim 1, wherein the carboxylic acid anhydride is a carboxylic acid anhydride having two or more carboxyl groups in the molecule. 4. The method for producing a melt-modified polyvinyl alcohol according to claim 1, wherein the carboxylic acid anhydride is a carboxylic acid anhydride having two or more carboxyl groups in the molecule and containing no olefinic unsaturated bond. 5. The method for producing a melt-modified polyvinyl alcohol according to claim 1, wherein the carboxylic acid anhydride is succinic anhydride.