JPS608043B2 - Method for producing polyvinyl acetal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyvinyl acetal, particularly polyvinyl acetal with improved heat resistance.

Polyvinyl acetal is used as an interlayer film for safety laminated glass because of its good adhesiveness and physical strength, but on the other hand, it is soluble in many organic solvents, and it is also soluble in phenolic resins, etc. It is highly compatible with thermosetting resins such as epoxy resins, and has excellent adhesion and adhesion to metals, making it suitable for structural adhesives such as metal paints such as wash primers and metal adhesives. It is widely used as a main raw material indispensable for the production of pharmaceuticals.

When polyvinyl acetal is used as the metal adhesive, a solution in which only the polyvinyl acetal is dissolved in an organic solvent such as an alcohol, a ketone, or an aromatic hydrocarbon, alone or in a mixture, may be used. Polyvinyl acetal and phenolic resin are used when an adhesive that does not cause a large change in adhesive strength even under a wide range of environmental temperatures from low to high temperatures is required. Alternatively, a thermosetting resin such as an epoxy resin dissolved in an organic solvent is generally used.

However, even in the conventional metal adhesives made from polyvinyl acetal and thermosetting resins as described above, the temperature dependence of the adhesive strength cannot be said to have been sufficiently improved.

The present invention was accomplished by conducting various studies aimed at improving the above-mentioned drawbacks, and by discovering a method for producing polypynylacetal having particularly excellent heat resistance.

That is, the gist of the present invention is that an unsaturated carboxylic acid compound in an amount smaller than the equivalent amount of the polyvinyl alcohol is added to an aqueous polyvinyl alcohol solution to carry out an esterification reaction, and then an aldehyde compound is added to carry out an acetalization reaction. The present invention relates to a method for producing voripinyl acetal.

In the present invention, an aqueous solution of polyvinyl alcohol is used, and the polyvinyl alcohol used has an average degree of polymerization of 200 to 3,00, and its saponification degree is within a range that exhibits the properties as polyvinyl alcohol. If so, there are no particular restrictions.

Further, the unsaturated carboxylic acid compound used in the present invention refers to an unsaturated carboxylic acid, an unsaturated dicarboxylic acid, a monoalkali metal salt of an unsaturated dicarboxylic acid, or a monoalkyl ester of the dicarboxylic acid. Preferred are unsaturated carboxylic acid compounds such as maleic acid, maleic anhydride, fumaric acid, acrylic acid, and methacrylic acid, with maleic acid being particularly preferred.

Further, the aldehyde compounds used in the present invention include formaldehyde, acetaldehyde, propionaldehyde,
It refers to compounds having an aldehyde group such as butyraldehyde and hebutyraldehyde, and paraformalin which changes into formaldehyde during the reaction, and butyraldehyde is particularly preferably used.

-Aldehyde compounds may be used alone or in a mixture of two or more. To produce polyvinyl acetal by the method of the present invention, first, the polyvinyl acetal is dissolved in water to prepare an aqueous solution of polypinyl alcohol, and the unsaturated carboxylic acid compound is added to this to perform an esterification reaction.

It is necessary that the amount of the unsaturated carboxylic acid compound used at this time is less than the equivalent amount of the polyvinyl alcohol used, but if the amount used is too small, the effects of the present invention cannot be achieved, and If the amount is too large, the favorable effects of using a large amount of the unsaturated carboxylic acid compound will not improve much, so it is not favorable from a profitability standpoint.In addition, the polypynylacetal obtained will have strong water-soluble properties, and the reaction system will become weak during the acetalization reaction. Since there is a possibility that the stability of the polyvinyl alcohol may decrease, it is preferable that the amount corresponds to 5 to 50 mol % of the polyvinyl alcohol used, and it is particularly preferable that the amount corresponds to 10 to 40 mol %. Appeal: The conditions for the esterification reaction are not particularly limited, and may be carried out according to a conventional method, for example, preferably at a temperature of about 85 to 100 qo.

In addition, a catalyst for esterification such as sodium acetate, zinc chloride, or hydrochloric acid may also be used during the esterification. In the present invention, the aldehyde compound is then added to the aqueous system of polyvinyl alcohol esterified as described above to carry out an acetalization reaction.

The acetalization reaction may be carried out according to a conventional method, and for example, a catalyst known to condense polyvinyl alcohol and an aldehyde, such as an acid catalyst such as hydrochloric acid, sulfuric acid, or nitric acid, can be used. The amount is preferably 1 to 5% by weight of the reaction system. The acid catalyst may be added to the reaction system in the required amount at once, or may be added in divided portions at an appropriate number of times. In addition, if the temperature during the reaction is too high in the acetalization reaction, the particle size of the polyvinyl acetal that is generated and precipitated will become coarse, or the acetalization reaction will become uneven, which will adversely affect the meltability and transparency of the product. Furthermore, since the reaction rate slows down even if the temperature is too low, it is usually preferable to carry out the reaction at a temperature in the range of 0 to 50 qC.

Therefore, in the present invention, when the esterification reaction is carried out at a higher temperature, it is preferable to cool the reaction system and lower the temperature to 0 to 50 qC to carry out the acetalization reaction. Further, the aldehyde compound added to the reaction system for the acetalization reaction may be one type or two or more types, and may not be added all at once but in appropriate amounts. It is possible. In this way, the acetalization reaction takes place, and when polyvinyl acetal is produced, it becomes water-insoluble and precipitates, so after the reaction is complete, it is filtered in a furnace,
The product can be obtained by washing with water and drying.

Since the polyvinyl acetal thus obtained has an unsaturated bond introduced into the molecule, a crosslinked structure is formed by heating, etc., and the polyvinyl acetal has excellent heat resistance.

The polyvinyl acetal obtained by the method of the present invention can be used in applications such as paints and adhesives, and is particularly suitable for applications that require heat resistance, such as self-fusing wire coatings.

When imparting heat resistance to the polyvinyl acetal obtained by the method of the present invention, 0.5 to 5% by weight, more preferably 1 to 3% by weight, based on the polyvinyl acetal.
For example, it is preferable to blend an organic peroxide such as penzoyl peroxide, and after dissolving the polyvinylacetal blend in an appropriate solvent or using it as a paint or adhesive without dissolving it, Heating for a minute causes crosslinking and significantly improves heat resistance. Since the method of the present invention is as described above, polyvinyl acetal with excellent heat resistance can be easily produced.

Examples of the present invention will be described below.

Production of Example Resin A-1 Polyvinyl alcohol with a degree of polymerization of 1,750 and a degree of saponification of 99.5 mol% was poured into 3,000 quarts of water and left at 90 quarts for 2 hours to dissolve the polyvinyl alcohol. Add 119% of acid (equivalent to 20 mol% of polyvinyl alcohol); 2. The solution was cooled to 5,000 ℃ after being left for an hour, and 200 mol of hydrochloric acid with a concentration of 35% was added, then cooled to 100 C, and then 15 M of n-butyraldehyde was added. When reacted at this temperature, a white powder was formed. The resin precipitated out.

After the reaction was completed, the resin solution was neutralized, passed through a water washing oven, and the resulting resin was dried. The degree of atamolization of the resin is approximately 65 mol%
Met. Production of Resin A-2 was carried out in the same manner as in the production of Resin A-1, except that the amount of maleic acid was changed to 30% (5 hol% based on OH groups).

Production of Resin A-3 was carried out in the same manner as in the production of Resin A-1, except that the amount of maleic acid was changed to 297 units (5 ol % based on OH groups).

Production of Resin B (Comparative Example) Production was carried out in the same manner as Resin A-1 except that maleic acid was not added.

Production of Resin C Production was carried out in the same manner as for Resin A-1, except that polyvinyl alcohol with a degree of polymerization of 800 and a degree of saponification of 99.0 mol% was used.

Production of Resin D (Comparative Example) The same machine as that used for the production of Resin A-1 was used, except that polyvinyl alcohol with a degree of polymerization of 80 and a degree of saponification of 99.0 mol % was used, and maleic acid was not added.

Production of resin E Polymerization degree 1750, saponification degree 99.5 mol%
Polyvinyl alcohol 225% was added to 3000% water and left at 90oC for 2 hours to dissolve the polyvinyl alcohol, then maleic acid 119% was added at the same 90qC and left for 2.5 hours to dissolve the solution. Cool to 5,000 ml, add 200 ml of hydrochloric acid with a concentration of 35%, and cool until 30:00 pm.

Next, 58 quarts of valaldehyde (99% purity) was added and the temperature was maintained at 30 to 25 quarts for 3 hours, and then cooled to 15 quarts. Then, 78 qo of n-butyraldehyde was added to the 150 qo reaction system, and a white powdery resin was precipitated. After the reaction was completed, the resin solution was neutralized, washed with water, and the resulting resin was dried.

The acetalization reaction of the solution was about 65 mol%. Production of Resin F (Comparative Example) Production was carried out in the same manner as Resin E except that maleic acid was not added.

Each of the resins A (A-1 to A-3) to F obtained above was dissolved in a 1:1 mixed solvent of methanol and methyl ethyl ketone to form a solution with a resin content of 15% by weight.
2 parts by weight of penzoyl peroxide were added to 100 parts by weight of 1 to 3) to F and mixed to obtain an adhesive.

After using the above adhesive and polishing the adhesive surface with sandpaper, we placed two iron plates with a thickness of 2 ribs, a medium thickness of 25 ribs, and a length of 11 meters, which had been cleaned with Triclean. A sample piece for measuring adhesive strength was prepared by gluing the pieces together and leaving them for 3 minutes at a temperature of 180 oo and under a pressure of 20 k9/base.

The above sample piece was subjected to a tensile tester at a tensile rate of IQ/min and at a temperature of 150 oo to measure the adhesive strength. The results are shown in Table 1. Table 1 Also, the resins A (A-1 to A-3) to F obtained above were dissolved in a 1:1 mixed solvent of ethanol and toluene to form a solution with a resin content of 1% by weight, and each was divided into two parts. , ■.

2 parts of penzoyl peroxide was added to each 100 parts by weight of resins A (A-1 to A-3) to F and mixed.

The solutions (1) and (2) were each applied onto a polyester film and air-dried to obtain a film with a thickness of about 100 mm.

After heating this film in a gear oven at 150 pm for 30 minutes, it was cut into 3 x 3 arc pieces and soaked in a beaker containing a 1:1 mixed solvent of ethanol and toluene for 30 minutes. It was filtered through a 60-mesh wire gauze and the residual rate was determined. The results were as seen in Table 2. The numbers in Table 2 indicate the survival rate after solvent soaking.

As shown in Tables 1 and 2, the resin obtained by the method for producing polyvinyl acetal according to the method of the present invention has unsaturated bonds, and by using an organic peroxide, it becomes a cross-linked structure, which is different from the conventional method. Shows superior heat resistance compared to polyvinyl acetal.

Claims (1)

[Claims] 1. A method characterized by adding an unsaturated carboxylic acid compound in an amount smaller than the equivalent amount of the polyvinyl alcohol to an aqueous polyvinyl alcohol solution to carry out an esterification reaction, and then adding an aldehyde compound to carry out an acetalization reaction. A method for producing polyvinyl acetal. 2. The manufacturing method according to item 1, wherein the amount of the unsaturated carboxylic acid compound added is equivalent to 5 to 50 mol% of the polyvinyl alcohol. 3. The first unsaturated carboxylic acid compound is water-soluble.
Manufacturing method described in section. 4. The manufacturing method according to item 1, wherein the unsaturated carboxylic acid compound is maleic acid. 5 The temperature of the reaction system during the esterification reaction is 85 to 100°C
The manufacturing method according to item 1. 6. The manufacturing method according to item 1 or 5, wherein the temperature of the reaction system during the acetalization reaction is 0 to 50°C.