JPH05230129A - Production of polyvinyl acetal resin - Google Patents

Abstract

PURPOSE:To provide a polyvinyl acetal resin having a high degree of acetalization exceeding the Flory's maximum degree of acetalization (81.6mol%). CONSTITUTION:In acetalizing polyvinyl alcohol with acetaldehyde in the presence of an acid catalyst, a mixed solvent containing >=30wt.% of dimethylsufoxide is used as the reaction solvent and the reaction temperature is set at 55-90 deg.C during the entire reaction process, at least at a point when the degree of acetalization exceeds 50mol%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a polyvinyl acetal resin having a high degree of acetalization.

This polyvinyl acetal resin having a high degree of acetalization has a high sound wave transmission loss coefficient of the resin sheet and is excellent in moisture resistance, so that it is used as a material for an interlayer film of a sound insulating laminated glass or a print. It is particularly useful as a material for adhesives of substrates.

[0003]

2. Description of the Related Art Polyvinyl acetal resins typified by polyvinyl butyral have long been excellent in transparency, adhesion to glass, metal, etc., mechanical strength, etc. It is used as a resin for printed circuit board adhesives. One of the reasons why the polyvinyl acetal resin is used for these applications is its excellent adhesion to metals and glass. And this excellent adhesiveness is due to the fact that the polyvinyl acetal resin has essentially many hydroxyl groups.

On the other hand, however, such a hydroxyl group causes excessive moisture absorption under high humidity, resulting in deterioration of mechanical strength and deterioration of weather resistance due to water swelling of the resin. As a countermeasure against this, the occurrence of such problems is usually suppressed by structural measures such that moisture does not enter from the outside when using a resin, and by adding and compounding other deterioration inhibitors, but when the process is complicated or When measures cannot be taken, resins other than polyvinyl acetal resins have been used, and polyvinyl acetal resins have been limited or partially used.

Therefore, there is a demand for a polyvinyl acetal resin which retains the above excellent adhesiveness and does not have excessive hygroscopicity. To obtain this, it is necessary to leave a proper amount of hydroxyl groups in the resin. In addition, it is important to increase the degree of acetalization to the required value.

Regarding the degree of acetalization of polyvinyl acetal resin, it was reported in 1939 that J. P. Flory concludes that the degree of acetalization is up to 81.6 mol%. This conclusion was obtained by adding statistical consideration under the assumption that the acetalization reaction is an irreversible reaction. Since the publication of the paper, many researchers have attempted to synthesize polyvinyl acetal resins that exceed the maximum acetalization degree proposed by Flory. In 1961, S. G. Matsoyan has succeeded in synthesizing a polyvinyl acetal resin that exceeds the maximum degree of flory acetalization by polymerizing divinyl acetal.

[0007]

However, the S.
G. Industrial implementation of Matsoyan's method envisions the synthesis of special monomers and stringent reaction conditions, which require years of technical completion. Furthermore, this method is not practical in terms of cost.

The present invention has been made in view of the above points, and an object thereof is to set specific reaction conditions in a condensation reaction between polyvinyl alcohol and an aldehyde which has been conventionally carried out industrially. Accordingly, it is to provide a method for obtaining a polyvinyl acetal resin having a high degree of acetalization exceeding the maximum degree of flory acetalization (81.6 mol%).

[0009]

The present invention has been devised to solve the above-mentioned problems, and the above-mentioned object is achieved by using a specific reaction solvent and setting the reaction temperature to a specific value. It was completed after obtaining knowledge.

That is, in the method for producing a polyvinyl acetal resin according to the present invention, when polyvinyl alcohol is acetalized with an aldehyde in the presence of an acid catalyst, at least at a stage where the degree of acetalization exceeds 50 mol% in all reaction stages. As a reaction solvent, a mixed solvent containing dimethyl sulfoxide (hereinafter abbreviated as DMSO) in an amount of 30% by weight or more based on the total amount of the solvent is used, and the reaction temperature is 55 to 90 ° C.

The degree of polymerization of polyvinyl alcohol, which is one of the starting materials for the method of the present invention, is not particularly limited, but one having an average degree of polymerization of 200 to 10,000, which is usually used for producing a polyvinyl acetal resin, is suitable. ..

The concentration of polyvinyl alcohol with respect to the solvent is appropriately determined within the range of 0.1 to 20% by weight, which is usually applied. If this concentration is less than 0.1% by weight, it is economically disadvantageous. If this concentration exceeds 20% by weight, the concentration of the polyvinyl acetal resin is high,
In some cases, the effect of preventing the interaction between hydroxyl groups by DMSO, which will be described later in the "Action" section, is not sufficiently exerted. However, this concentration range does not limit the method of the present invention.

As the other raw material, an aldehyde, which is usually used for acetalization of polyvinyl alcohol, is used. From the viewpoint of solubility in a solvent, an aliphatic or aromatic aldehyde having 1 to 10 carbon atoms is particularly preferable. For example, formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, 2-ethylbutyraldehyde, n-hexylaldehyde, n-octylaldehyde, 2-ethylhexylaldehyde, benzaldehyde, phenylacetaldehyde, n-nonylaldehyde, n- Examples include decyl aldehyde and cinnamaldehyde. These may be used alone or in combination of two or more. More preferable aldehydes include acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, valeraldehyde, 2
-Ethyl butyraldehyde, n-hexyl aldehyde, etc. are exemplified.

The amount of aldehyde charged is determined according to the desired degree of final acetalization.

As the acid catalyst, inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid are appropriately used. Particularly preferred acids are hydrochloric acid and sulfuric acid. The concentration of the acid catalyst can be set within a wide range of 0.02 to 10% by weight with respect to the solvent.
When the concentration of the acid catalyst is less than 0.02% by weight, the proton donating effect as a catalyst is poor, and when it exceeds 10% by weight, it is uneconomical because there is no additional effect in terms of catalyst efficiency. However, this concentration range does not limit the method of the present invention.

One of the characteristic parts of the present invention is that DMSO is used as a reaction solvent in at least the stage where the degree of acetalization exceeds 50 mol% in all the reaction stages, and 30% by weight of the total amount of the solvent is used.
The reaction temperature is set to 55 to 90 ° C. by using the mixed solvent containing the above.

Solvents to be used in combination with DMSO include
Solubility parameter (Hildebrand's formula: "Oil resistance of rubber and its idea" by Morichikazu Maeda [Rubber Society of Japan] Vol. 58 No. 3 (1985), page 122), referring to carbon tetrachloride ( δ = 8.6) to DMSO (δ = 1
Among the solvents having a δ value up to 2.8), those which are not affected by the acid catalyst used for the acetalization reaction and which do not react with the aldehyde can be selected. For example, toluene, xylene, carbon tetrachloride, acetylacetone, acetonitrile, aniline, ethylbenzene, methylene chloride, capronitrile, chloroform, amyl acetate, isobutyl acetate, isopropyl acetate, ethyl acetate, cyclohexanone, cyclopentane, butyl bromide, dioxane,
1,2-dichloropropane, 1,1,2-trichloroethane, nitroethane, nitrobenzene, nitropropane, nitromethane, tetrahydrofuran, benzene, tetrachloroethylene, acetone, dichloromethane, chlorobenzene, anisole, 1,2-dichloroethane, methyl iodide, bromobenzene , Carbon disulfide, benzonitrile, nitromethane, nitrobenzene, phenol and the like. These may be used alone or in combination of two or more. Further, the reaction solvent may contain water, methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-butyl alcohol in a ratio of 10% by weight or less based on the total amount of the solvent. These inclusions may be used alone or in combination of two or more. DMSO
Particularly suitable solvents to be used together with are toluene, xylene, carbon tetrachloride and the like.

In the method of the present invention, DMS in the reaction solvent is used.
The reason why the content of O is limited to 30% by weight or more of the whole solvent is that when the content is less than 30% by weight, the effect of preventing the interaction between hydroxyl groups by DMSO, which will be described later in the "Action" section, is sufficiently exerted. It is not done. DM
A particularly preferable range of the SO content is 40 to 85% by weight or more.

Another important point of the present invention is to maintain the reaction temperature at 55 to 90 ° C.

Although the experiment for confirming the maximum degree of acetalization has already been conducted by Mr. Noma et al. (See Kyoto Institute of Polymer Chemistry, June 30, 1949, theoretical theory), the reaction temperature was the highest in this experiment. Was 40 ° C. But,
At the reaction temperature of 40 ° C., it is clear from the data in the article that the attachment / detachment reaction of the acetal ring necessary for replacement of the acetal ring is not substantially carried out, and thus the high degree of acetalization is not achieved.

In the method of the present invention, the deacetalization reaction proceeds to such a large extent that it can be industrially utilized as a reversible reaction only by setting the reaction temperature within the range of 55 to 90 ° C. under the condition that the solvent is specified. To do. Reaction temperature is 55
If the temperature is lower than 0 ° C, a polyvinyl acetal resin having a desired degree of acetalization cannot be obtained. When the reaction temperature exceeds 90 ° C., it is difficult to control the reaction.

In the reaction process, additives such as a dispersant for preventing particle coalescence, a surfactant, and an antioxidant for preventing oxidation at the time of reaction may be appropriately added.

In the initial stage of the reaction, that is, until the degree of acetalization reaches 50 mol%, known conditions for the acetalization reaction can be adopted. That is,
The acetalization reaction can be promoted using water, an alcohol solvent, or a water-alcohol mixed solvent as a reaction solvent. As the alcohol solvent, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-
Butyl alcohol and the like are exemplified. As the reaction solvent, a solvent that selectively dissolves polyvinyl alcohol, which is a starting material, and a solvent that selectively dissolves a polyvinyl acetal resin, which is a reaction product, are preferable. Further, the reaction temperature may be less than 55 ° C. and is set appropriately.

When the known conditions of the acetalization reaction are adopted, the solvent used in the initial stage is replaced with the solvent used in the initial stage after the degree of acetalization is increased to 50 mol% in the initial stage of the reaction. For example, when the reaction is carried out using water as a solvent in the initial stage of the reaction, the solvent and the resin are separated under conditions that precipitate the resin, and the solvent of the method of the present invention is added to the resin. In this case, the process according to the invention can be carried out continuously after the initial stage of the reaction.

After completion of the reaction in the initial stage of the reaction, the obtained resin is once isolated as a dried resin through the steps of neutralization, washing and drying, and then the method of the present invention can be applied thereto.

Also in the initial stage of the reaction, a mixed solvent containing DMSO in an amount of 30% by weight or more of the total solvent amount may be used as the reaction solvent according to the reaction conditions of the present invention, and the reaction temperature may be 55 to 90 ° C. Absent. In this case, the reaction can be continuously carried out in one step at the above reaction temperature using the above DMSO mixed solvent from the initial stage of the reaction to obtaining the desired polyvinyl acetal resin having a high degree of acetalization.

Considering shortening of the reaction time and the like, it is preferable to change the reaction solvent to the DMSO mixed solvent at a stage where the degree of acetalization exceeds 50 mol% and to set the reaction temperature to 55 to 90 ° C.

Further, a higher acetalization degree (approximately 100)
To obtain a polyvinyl acetal resin having a mol%), the reaction solvent is changed to the DMSO mixed solvent at a stage where the degree of acetalization exceeds 80 mol%, and the reaction temperature is 55 to 55%.
The temperature may be 90 ° C.

The polyvinyl acetal resin having a high degree of acetalization obtained by the method of the present invention is purified by the following operation. That is, the obtained polyvinyl acetal resin is reprecipitated by introducing it into a suitable solvent such as water. Then, in order to remove the unreacted aldehyde and acid catalyst, a solvent that dissolves the resin is selected and dissolved, and the resin is precipitated again. Repeat this operation. Thereafter, a neutralizing agent such as potassium hydroxide, sodium hydroxide, sodium hydrogen carbonate, sodium carbonate, etc. is appropriately added to the system to neutralize the residual acid. Then, the above-mentioned reprecipitation operation is repeated to remove the produced salt. Finally, the solvent is removed by an appropriate treatment such as vacuum drying, and further dried to obtain a white polyvinyl acetal resin.

[0030]

In the method of the present invention, by using a mixed solvent containing DMSO in an amount of 30% by weight or more based on the total amount of solvent, it is possible to achieve acetalization with a high degree of acetalization. It is possible to produce a polyvinyl acetal resin having a degree of acetalization.

The technical reason is that the acetalization reaction in which polyvinyl alcohol is acetalized with an aldehyde is essentially a reversible reaction. Due to this reversible reaction, the acetalization essentially goes beyond the limit of 81.6 mol%. Since DMSO used as at least a part of the reaction solvent has a strong polarity, it is possible to prevent interaction due to hydrogen bond between hydroxyl groups, which is likely to occur during the reversible reaction.
As a result, this reversible reaction can be continued and proceeded, and a polyvinyl acetal resin having a high degree of acetalization can be produced.

[0032]

EXAMPLES The present invention will be specifically described with reference to some examples of the present invention.

The butyralization degree of the obtained polyvinyl butyral resin was measured by the following NMR method and titration method.

NMR Method The proton nuclear magnetic resonance spectrum of the product was measured by the following method.

A 2 wt% deuterated chloroform solution of polyvinyl butyral resin was prepared, a small amount of tetramethylsilane [(CH ₃ ) ₄ Si] was added as a standard substance, and spectrum measurement was performed at a temperature of 23 ° C. One example is shown in FIG. The horizontal axis of FIG. 1 is the chemical shift (ppm) based on the resonance frequency of the standard substance tetramethylsilane used, and the vertical axis is the resonance absorption intensity, which corresponds to the amount of protons (hydrogen). .. From this measurement chart, the attribution and integral intensity of each absorption peak as described in Table 1, fitted value of the integral intensity (I _A and I _B) in the formula below, was calculated butyral degree.

[0036]

[Table 1] <Formula> butyralization degree _{= {2I A / (3I B} -4I A)} × 1
00 (mol%) Titration method JIS "Polyvinyl butyral test method" (K-672
The degree of butyralization was measured by the hydroxylamine hydrochloride method in accordance with the test method of "vinyl butyral" in the section of composition analysis in 8-877).

In order to smoothly dissolve in butyl alcohol, a heating / refluxing operation was also used in combination, and after dissolution, the above JIS operation was followed.

<Example 1> Step i) Pure water 2900, polymerization degree 1740, saponification degree 9
198 g of 9.2 mol% polyvinyl alcohol was added and dissolved by heating. Temperature of the reaction system was adjusted to 9 ° C, 35% by weight
196 g of hydrochloric acid (1.99 wt% relative to the total system) and 152 g of butyraldehyde (97.2 mol% relative to polyvinyl alcohol) were added to precipitate polyvinyl butyral.
Then, the reaction system was kept at a temperature of 50 ° C. for 3 hours to complete the reaction. Unreacted aldehyde was washed away by washing with excess water, the hydrochloric acid catalyst was neutralized, salts were removed, and the product was dried to obtain a white powder of polyvinyl butyral resin.

The degree of butyralization of this polyvinyl butyral resin was 74.8 mol% as measured by the proton NMR method.

Step ii) Next, 60 g of this polyvinyl butyral resin (3% by weight relative to the total system) was added to 968 g of DM.
In a mixed solvent consisting of SO and 800 g of xylene, at 25 ° C
Dissolved in. Then, 115 g of 35 wt% hydrochloric acid solution
(1.97% by weight relative to the total system), n-butyraldehyde 9
4.8 g (200 mol% relative to polyvinyl alcohol)
Was added as follows. First, n-butyraldehyde was added all at once to the solution, and then thoroughly mixed by stirring for about 5 minutes, and then hydrochloric acid was added by a dropping funnel over about 15 minutes and mixed. About 30 minutes after mixing these,
About 60 for the whole system at a rate of 0.5-0.6 ° C / min up to 60 ° C
The temperature was raised in minutes. Then, the reaction system was kept at 60 ° C. for 3 hours to complete the reaction.

After completion of the reaction, a large excess of water was added to the reaction mixture to separate the catalyst and DMSO. After that, 10% by weight of water (weight ratio to solid resin content) was added, and 6% by weight of baking soda (weight ratio to solid resin content) was added, and then 6
Neutralize the liquid at 5 ° C for 4 hours, transfer it to a separating funnel,
A large excess of water was added to remove the salt. The post-treatment operation after completion of this reaction was repeated.

Finally, the residual xylene was volatilized and dried to obtain a white powder of polyvinyl butyral resin having a high degree of butyralization shown in Table 2.

Example 2 A polyvinyl butyral resin was prepared in the same manner as in step i) of Example 1. The butyralization degree of the polyvinyl butyral resin measured by the proton NMR method was also 74.8 mol%.

Next, this polyvinyl butyral resin 70 is used.
g (5% by weight relative to the total system) with 720 g of DMSO and 68
It was dissolved in a mixed solution of 0 g of toluene at 25 ° C. Thereafter, 80 g of a 35 wt% hydrochloric acid solution (compared to the whole system, 2.
0% by weight) and 117 g of n-butyraldehyde (200 mol% relative to polyvinyl alcohol) were added as follows. That is, first, n-butyraldehyde was divided into 4 equal parts, and while each part was sequentially added to the solution, they were mixed by stirring for about 5 minutes for a total of 20 minutes, and then hydrochloric acid was added by a dropping funnel over about 15 minutes. And mixed. About 30 minutes after mixing these, the whole system was heated to 60 ° C. at a rate of 0.5 to 0.6 ° C./minute in about 60 minutes. Then, the reaction system was kept at 60 ° C. for 10 hours to complete the reaction.

Operation after completion of the reaction, that is, neutralization of the resin,
Washing, purification and drying were carried out in the same manner as in step ii) of Example 1.

Thus, a white powder of polyvinyl butyral resin having a high degree of butyralization shown in Table 2 was obtained.

Example 3 A polyvinyl butyral resin was prepared in the same manner as in step i) of Example 1. The butyralization degree of the polyvinyl butyral resin measured by the proton NMR method was also 74.8 mol%.

Next, this polyvinyl butyral resin 70 is used.
g (2% by weight relative to the total system) with 1420 g of DMSO and 8
It was dissolved at 25 ° C. in a mixed solution of 00 g of toluene and 963 g of carbon tetrachloride. Thereafter, 200 g of a 35 wt% hydrochloric acid solution (2.0 wt% relative to the total system) and 117 g of n-butyraldehyde (200 mol% relative to polyvinyl alcohol) were added as follows. That is, first, n-
After adding butyraldehyde to the solution all at once, the mixture was thoroughly mixed by stirring for about 5 minutes, and then hydrochloric acid was added by a dropping funnel over about 15 minutes and mixed. About 30 minutes after mixing these, the whole system was heated to 60 ° C. at a rate of 0.5 to 0.6 ° C./minute in about 60 minutes. Then, the reaction system was kept at 60 ° C. for 5 hours to complete the reaction.

Operation after completion of the reaction, that is, neutralization of the resin,
Washing, purification and drying were carried out in the same manner as in step ii) of Example 1. In this way, white powders of polyvinyl butyral resin having a high degree of butyralization shown in Table 2 were obtained.

Comparative Example 1 In this reaction, the reaction temperature was about 45 ° C. and the aging time was 48 hours.

Step i) A polyvinyl butyral resin was prepared in the same manner as in step i) of Example 1. The butyralization degree of the polyvinyl butyral resin measured by the proton NMR method was also 74.8 mol%.

Step ii) Next, n-butyraldehyde and hydrochloric acid were added to and mixed with this polyvinyl butyral resin by the same operation as in Step ii) of Example 1.

Approximately 30 minutes after mixing, the entire system was adjusted to 0.5-0.
The temperature was raised to 45 ° C at a rate of 6 ° C / min in about 30 minutes. Then, this was kept at a constant temperature of 45 ° C. for 48 hours to complete the reaction.

Operation after completion of the reaction, that is, neutralization of the resin,
Washing, purification and drying were carried out in the same manner as in step ii) of Example 1.

Thus, a white powder of polyvinyl butyral resin having a butyralization degree shown in Table 2 was obtained.

Comparative Example 2 In this reaction, a reaction solvent containing water / methyl alcohol as a main component was used.

Step i) A polyvinyl butyral resin was prepared by the same procedure as in step i) of Example 1. The butyralization degree of the polyvinyl butyral resin measured by the proton NMR method was also 74.8 mol%.

Step ii) Next, 60 g of this polyvinyl butyral resin (3% by weight relative to the total system) was dissolved at 40 ° C. in a mixed solvent consisting of 1195 g of methanol and 595 g of water.

Then, 115 g of 35% by weight hydrochloric acid solution (1.97% by weight relative to the total system) and n-butyraldehyde 94.
8 g (200 mol% relative to polyvinyl alcohol) were added as follows. That is, first, n-butyraldehyde was added all at once, and then thoroughly mixed by stirring for about 5 minutes. Then, hydrochloric acid was added by a dropping funnel over about 15 minutes and mixed. Approximately 30 minutes after mixing, 0.5-
The temperature was raised to 60 ° C. in about 60 minutes at a rate of 0.6 ° C./min. Then, this was kept at a constant temperature of 60 ° C. for 3 hours to complete the reaction.

Operation after the reaction, that is, neutralization of the resin,
Washing, purification and drying were carried out in the same manner as in step ii) of Example 1.

Thus, a white powder of polyvinyl butyral resin having a butyralization degree shown in Table 2 was obtained.

[0062]

[Table 2]

[0063]

EFFECTS OF THE INVENTION According to the method of the present invention, at least in all the reaction steps, the degree of acetalization of which exceeds 50 mol%,
As a reaction solvent, dimethyl sulfoxide was used in a total amount of 3
A mixed solvent containing 0% by weight or more is used, and the reaction temperature is 55-55.
Since the temperature is 90 ° C., acetalization can be achieved with a high degree of acetalization, and in particular, a polyvinyl acetal resin having a high degree of acetalization of 81.6 mol% or more can be produced.

[Brief description of drawings]

FIG. 1 is an NMR spectrum of polyvinyl butyral resin.

Claims (1)

[Claims] 1. When acetalizing polyvinyl alcohol with an aldehyde in the presence of an acid catalyst, dimethyl sulfoxide is used as a reaction solvent at least in all reaction steps when the degree of acetalization exceeds 50 mol%. 30% by weight or more of the mixed solvent is used, and the reaction temperature is 55 to 90 ° C., the method for producing a polyvinyl acetal resin.