JPH0693019A - Production of polyvinyl acetal resin - Google Patents

Abstract

PURPOSE:To produce a polyvinyl acetal resin having high degree of acetalization in acetalizating a polyvinyl alcohol with an aldehyde in the presence of an acid catalyst in an aqueous solvent. CONSTITUTION:In acetalizating a polyvinyl alcohol having preferably 200-10,000 average degree of polymerization (0.1-50wt.% concentration based on a solvent) with an aldehyde (preferably 1-10C aldehyde) in the presence of an acid catalyst (0.02-10wt.% based on the solvent) by using water alone or a mixed system of water and an alcohol [<=20wt.% alcohol concentration in the mixed system], a phase transfer catalyst (preferably quaternary ammonium salt or quaternary phosphonium salt) is added to the reaction system, the reaction is carried out preferably at 0-80 deg.C to give a polyvinyl acetal resin having >80mol% degree of acetalization. In an aqueous reaction having a low reaction rate, catalytic activity between solid and liquid is improved by the use of the phase transfer catalyst to promote acetalization.

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 a polyvinyl acetal, and more specifically, a polyvinyl acetal resin having a high degree of acetalization of about 80 mol% or more, which has been considered difficult to produce with an aqueous solvent. Manufacturing method.

[0002]

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 polyvinyl acetal resin is used for these applications is
It has excellent adhesion to metal and glass. And this excellent adhesiveness is due to the fact that the polyvinyl acetal resin has essentially many hydroxyl groups.

[0003]

However, with the conventional method for producing polyvinyl butyral, it is difficult to produce a polyvinyl acetal resin having a high degree of acetalization,
In particular, when the reaction solvent is water or a mixed system mainly composed of water, as described in, for example, JP-A-56-92142, the degree of acetalization is about 75 mol% and the degree of acetalization is limited. No industrial method has hitherto been known for obtaining highly acetalized polyvinyl butyral exceeding about 80 mol%.

On the other hand, phase transfer catalysts are usually radical polymerized
Although it is used for polymer synthesis such as ionic polymerization, it is rarely used for reactions in which the polymer substance itself is used as a reactant. Examples of applications to such polymer reactions include chloromethylation and bromination of polythretin, but no examples have been used for the acetalization reaction.

The present invention has been made in view of the above points, and an object thereof is a specific reaction in a condensation reaction of polyvinyl alcohol and an aldehyde in an aqueous solvent which has been conventionally carried out industrially. It is to provide a method for obtaining a polyvinyl acetal resin having a high degree of acetalization exceeding 80 mol% by setting the conditions.

[0006]

The method for producing a polyvinyl acetal resin according to the present invention has been devised to solve the above-mentioned problems, and is used as a reaction solvent for acetalizing polyvinyl alcohol with an aldehyde in the presence of an acid catalyst. It is characterized by using water alone or a mixed system of water and alcohol, and adding a phase transfer catalyst to the reaction system.

The degree of polymerization of polyvinyl alcohol, which is one of the raw materials, 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 50% by weight, which is usually applied. If this concentration is less than 0.1% by weight, it may be economically disadvantageous. Moreover, this concentration is 50% by weight.
If it exceeds, the reversible reactivity may decrease due to the interaction of the hydroxyl groups with each other due to the high concentration of the polyvinyl acetal resin. 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 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, n-nonylaldehyde, n-decylaldehyde, cinnamaldehyde. Are exemplified. These may be used alone or in combination of two or more.
Examples of more suitable aldehydes include acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, valeraldehyde, 2-ethylbutyraldehyde, n-hexylaldehyde and the like.

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

As the acid catalyst, an inorganic acid such as hydrochloric acid, sulfuric acid, trifluoroacetic acid or paratoluenesulfonic acid, or an organic acid such as acetic acid is appropriately used. 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. If the concentration of the acid catalyst is less than 0.02% by weight,
The effect of donating protons as a catalyst is poor, and even if it exceeds 10% by weight, there is no additional effect in terms of catalyst efficiency and it is uneconomical. However, this concentration range does not limit the method of the present invention.

The phase transfer catalyst used is, for example, a quaternary ammonium salt such as tetrabutylammonium iodide, tetrabutylammonium chloride, tetramethylammonium chloride, tetramethylammonium bromide or tetrabutylammonium bromide.
Quaternary phosphonium salts such as tetrabutylphosphonium iodide, tetrabutylphosphonium chloride, tetrabutylphosphonium bromide, tetramethylphosphonium iodide, tetramethylphosphonium chloride, tetramethylphosphonium bromide; potassium oxalate,
Potassium dicarboxylates such as potassium malonate, potassium succinate, potassium glutarate, potassium adipate, potassium maleate, potassium fumarate, potassium phthalate, potassium isophthalate and potassium terephthalate; sodium disulfinate benzoyl dichloride;
Sodium disulfinate benzoyl dibromide, sodium disulfinate-p-toluene dichloride, sodium disulfinate-p-toluene dibromide, etc. sodium disulfinate aromatic dihalide; xylylene bromide 4- (α-bromo-p-tolyl) butanoic acid Examples thereof include salts. More preferably, the above quaternary ammonium salts or quaternary phosphonium salts are used alone or in combination.

As the reaction solvent, water alone or a mixed system of water and alcohol is used. The alcohol concentration in the mixed system is preferably 20% by weight or less. The alcohol used in the mixed system is methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, or the like, and may be a mixture of two or more thereof.

The reaction temperature is not particularly limited, but is preferably 0 to 80 ° C. The reaction temperature is mainly determined by the solvent used, the raw material aldehyde, the catalyst and the like, but when the reaction temperature exceeds the boiling points of these substances, the reaction system is pressurized to allow the reaction to proceed. In the reaction process, a purposeful additive such as a dispersant for preventing particle coalescence, a surfactant, and an antioxidant for preventing oxidation during the reaction may be appropriately added. 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 an appropriate solvent such as water or methanol. 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 hydrogencarbonate, sodium carbonate or the like 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 procedure such as vacuum drying,
Further, a white polyvinyl acetal resin is obtained through drying.

[0015]

In the method of the present invention, the use of a phase transfer catalyst allows the acetal reaction in a solid-liquid state to proceed, and as a result, the acetalization can be achieved with a high degree of acetalization. It is possible to manufacture a polyvinyl acetal resin having a high degree of acetalization of about 80 mol% or more, which is considered to be difficult to manufacture.

The technical reason therefor is that, in an aqueous reaction having a very slow reaction rate, the use of a phase transfer catalyst improves the solid-liquid catalytic activity of a solid-liquid heterogeneous system, and thereby the acetalization reactivity. In order to continue and progress to a higher degree of acetalization. In other words,
By adding a phase transfer catalyst, the reactivity of acetalization can be improved, and the hydroxyl groups that have become extremely small as the reaction progresses can be included in the reaction as much as possible, and the acetalization reaction can be continued and proceeded.

Thus, a polyvinyl acetal resin having a high degree of acetalization can be produced.

[0018]

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

The degree of butyralization 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% heavy water-benzene solution of polyvinyl butyral resin was prepared, and a small amount of tetramethylsilane [(CH ₃ ) ₄ Si] was added as a standard substance.
The spectrum was measured at 3 ° 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 is the proton (hydrogen).
Corresponding to the amount of. 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.

[0022]

[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 facilitate the dissolution in butyl alcohol, a heating / refluxing operation was also used in combination, and after dissolution, the above JIS operation was followed.

<Example 1> A polymerization degree of 1 was added to 2900 g of pure water.
700 and 193 g of polyvinyl alcohol having a saponification degree of 99.2 mol% were added and dissolved by heating. The temperature of the reaction system was adjusted to 30 ° C., 200 g of 35 wt% hydrochloric acid, 30 g of tetrabutylammonium iodide as a phase transfer catalyst and 300 g of n-butyraldehyde 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 drying was performed to obtain a white powder of polyvinyl butyral resin.

The degree of butyralization of this polyvinyl butyral resin was 85.0 mol% as measured by the proton NMR method and 85.2 mol% as measured by the titration method.

<Examples 2 to 13> Polyvinyl butyral resin was obtained in the same manner as in Example 1 except that the phase transfer catalyst shown in Table 2 was used.

Comparative Example 1 A polyvinyl butyral resin was obtained in the same manner as in Example 1 except that the phase transfer catalyst was not used.

<Comparative Example 2> The reaction condition after charging was set to a temperature of 60.
A polyvinyl butyral resin was obtained by performing the same operation as in Comparative Example 1 except that the temperature was 3 hours and the temperature was 3 hours.

<Comparative Example 3> The reaction conditions after charging were set to a temperature of 60.
A polyvinyl butyral resin was obtained in the same manner as in Comparative Example 1 except that the temperature was 6 hours and the temperature was 6 hours.

Measurement of degree of butyralization The measured values of degree of butyralization by the proton NMR method and the titration method measured for each polyvinyl butyral resin obtained in Examples and Comparative Examples are shown in Table 2.

[0031]

[Table 2] As is apparent from Table 2, it is recognized that the use of the phase transfer catalyst makes it possible to produce a polyvinyl acetal resin having a high degree of acetalization of about 80 mol% or more in an aqueous solvent.

[0032]

In the method of the present invention, since the phase transfer catalyst is added to the reaction system of the aqueous reaction solvent, it is possible to obtain a high acetalization degree of about 80 mol% or more, which has been considered difficult to produce with the aqueous solvent. The polyvinyl acetal resin which has can be manufactured.

Claims (2)

[Claims] 1. When acetalizing polyvinyl alcohol with an aldehyde in the presence of an acid catalyst, water alone or a mixed system of water and alcohol is used as a reaction solvent, and a phase transfer catalyst is added to the reaction system. Method for producing polyvinyl acetal resin. 2. The method for producing a polyvinyl acetal resin according to claim 1, wherein a quaternary ammonium salt or a quaternary phosphonium salt is used as the phase transfer catalyst.