JPS6056723B2 - Method for producing particulate polyvinyl butyral - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an industrially advantageous method for producing finely divided polyvinyl butyral having excellent transparency and solubility.

Polyvinyl butyral is used in a wide range of applications such as paints, safety glass interlayers, and adhesives.

These products are produced by using polyvinyl alcohol as a raw material and converting it into butyral, and known methods include a dissolution method and a precipitation method. Since this internal precipitation method can obtain a powdered product from an aqueous solution in a single step, the process is simpler and production costs are lower than with the dissolution method, which requires precipitating and separating polyvinyl butyral from the solution after the reaction. This method is cheap and suitable for industrial production.
In general, in the precipitation method, when the reaction temperature is high, the time required for precipitation is shortened, but the obtained polyvinyl butyral particles become coarser, and in some cases, the precipitated particles coagulate. Adding butyraldehyde to an aqueous polyvinyl alcohol solution at a relatively low temperature, such as below 0.degree. C., produced a fine powdery precipitate.

However, in some cases, the method of keeping an aqueous polyvinyl alcohol solution at a low temperature may cause gelation of the aqueous solution, which may have an adverse effect on the physical properties of the polyvinyl butyral obtained. There were disadvantages such as the need for cooling equipment to maintain it.

Improvements to this precipitation method include a method in which the presence of a surfactant improves the hydrophilicity of the precipitate interface and allows the reaction to proceed, thereby improving solubility and transparency;
A known method is to improve solubility by adding a water-soluble polymeric substance such as methyl cellulose or polyethylene oxide, and then adding and reacting an aldehyde at a relatively high temperature.

However, in these methods, it is necessary to completely remove the above additives that are not involved in the polyvinyl butyral production reaction system from the final product, and the resin must not be cloudy, especially when used as an interlayer film for safety glass. The processing process to prevent these additives from being included in the final product becomes complicated, and if the above-mentioned surfactants are included in the reaction waste liquid, the waste water treatment process is also complicated as it further increases the water quality burden of the waste liquid. Furthermore, there was a problem that the stability of the obtained product quality was adversely affected.

The purpose of the present invention is to eliminate the drawbacks of these conventional methods and to stably precipitate fine particulate polyvinyl butyral of good quality from an aqueous polyvinyl alcohol solution at a relatively high temperature without increasing the load in wastewater. The gist is that when polyvinyl butyral is produced by condensing polyvinyl alcohol and butyraldehyde in an aqueous phase in the presence of an acid catalyst, the condensation reaction is carried out by keeping the reaction system at a temperature of 2 CfC or higher. and from just before to immediately after the precipitation of polyvinyl butyral,
A method for producing particulate polyvinyl butyral characterized by further adding an aqueous solution containing polyvinyl alcohol in an amount of 0.5 to 20% by weight based on the total amount of polyvinyl alcohol used.

In the present invention, the degree of polymerization of the polyvinyl alcohol that is first added to the reaction tank and the polyvinyl alcohol that is further added from immediately before to immediately after the precipitation described below is not specified;
Generally, a suitable range is 500 to 3,000, and there is no problem even if residual acetyl groups are contained. The concentration of the aqueous solution may be as long as it can carry out the acetalization reaction, but it is generally 3 to 15% by weight.
are used. Normally, when the concentration of polyvinyl alcohol exceeds 15% by weight, the viscosity is too high, which often interferes with the acetalization reaction and subsequent processing.
This is because if it is less than % by weight, too little polyvinyl butyral will precipitate, resulting in many industrial disadvantages in the purification process.

In the present invention, butyraldehyde to be combined with polyvinyl alcohol may be added to the reaction system in the desired amount at once, or may be added in appropriate amounts in multiple amounts, such as before and after the precipitation of polyvinyl butyral. It may be added several times.

Further, as the acid catalyst used in the present invention, any acidic substance known to have the effect of condensing polyvinyl alcohol and aldehyde can be appropriately used, such as inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, etc. Examples include organic acids such as balatoluenesulfonic acid. The amount of acid catalyst used is usually 0.5 to 5% by weight in the final system, but it is not limited to this amount. In the present invention, if the concentration of the acid catalyst during precipitation of polyvinyl butyral is too high, the precipitated particles will become coarse and the dispersion state will become unstable, and in some cases, the particles may aggregate, etc.
Fine particles cannot be obtained.

Therefore, when adding an acid catalyst to a reaction system, if the catalyst concentration is dilute, the required amount may be added at once, but it is usually preferable to add the acid catalyst in divided portions. That is, it is preferable to precipitate fine particles by adding the total amount of an acid catalyst of 1B or less used up to the precipitation of polyvinyl butyral, and then to reach a predetermined degree of butyralization by adding the remaining acid catalyst. . In the present invention, the acid catalyst is added to the aqueous polyvinyl alcohol solution, and butyraldehyde is added to the aqueous polyvinyl alcohol solution, usually with stirring at a temperature of 2 or more generations, to precipitate polyvinyl butyral. The term "from just before precipitation to immediately after precipitation" refers to the time period from about 2 minutes before the moment when the precipitate is considered to be precipitated to about 2 days after precipitation. Therefore, when adopting a method of adding an aqueous polyvinyl alcohol solution immediately before the precipitation of polyvinyl butyral, a preliminary experiment is conducted in advance under substantially the same conditions as the method of the present invention, except that an aqueous polyvinyl alcohol solution is not added. It is preferable to predict the time point of precipitation by measuring the time required from the start of butyral production to the precipitation, or by measuring the change in viscosity of the reaction system at the time of precipitation.

To measure changes in viscosity, for example, if a stirring tool is provided to stir the reaction system at a constant speed, consider the change in load applied to the motor driving the stirring tool as a change in viscosity. Specifically, it is convenient to read the current value, etc., which indicates the motor load. Further, the aqueous polyvinyl alcohol solution may be added immediately before or immediately after the polyvinyl butyral precipitate is precipitated, or may be added to both. Further, a predetermined amount may be added all at once, or may be added continuously or intermittently in portions within the time period immediately before or after the precipitation. Further, the degree of polymerization of the polyvinyl alcohol to be added is not particularly specified, and there is no problem even if the polyvinyl alcohol contains residual acetyl groups. Furthermore, there is no particular restriction on the concentration of the polyvinyl alcohol aqueous solution to be added, but industrially it is preferably 3 to 15% by weight. However, the amount of polyvinyl alcohol added is 0.5 to 2% of the total amount of polyvinyl alcohol used.
It is said that If the amount added is less than 0.5% by weight, agglomeration of polyvinyl butyral particles will occur, and if it exceeds 2% by weight, the distribution of the degree of butyralization in the final product will be widened, and various physical properties, especially transparency, will decrease. It is. Furthermore, it is thought that the polyvinyl alcohol that is further added is adsorbed to the precipitated polyvinyl butyral as described below, but as the reaction progresses thereafter, it is converted to butyral, and eventually the polyvinyl butyral that forms the precipitate is It is thought that the same degree of butyralization will be achieved.

Next, in the present invention, preferably after adding the remaining aldehyde, the remaining acid catalyst is added, and the reaction system is aged at a temperature of two or more generations at the time of precipitation, or is aged by raising the temperature as appropriate. After that, it is neutralized by a conventional method, and the precipitate is then filtered, washed with water, and dried to obtain the final product. If polyvinyl alcohol and butyraldehyde are condensed while the temperature of polyvinyl is maintained at 20°C or higher, and if polyvinyl alcohol is not further added from immediately before to immediately after the precipitation of polyvinyl butyral, the precipitated particles will become coarse and the dispersion system will deteriorate. In some cases, particles become unstable and aggregate together, but according to the present invention, such a phenomenon is not observed at all.Fine powdery particles are precipitated and then an acid catalyst is added or Even if the temperature of the reaction system is increased, the dispersion state of the precipitate remains stable.

And although the reason is not always clear,
It is estimated as follows.

That is, in the precipitation method, when polyvinyl butyral is precipitated by keeping the reaction system at a relatively high temperature of 2 CfC or higher, agglomeration of the precipitated particles is particularly likely to occur. Immediately thereafter, polyvinyl alcohol that is further added adsorbs onto the surface of the precipitated particles of polyvinyl butyral and takes in the surrounding water to form a hydration layer, thereby reducing the rate at which the remaining hydroxyl groups in the polyvinyl butyral associate with each other. (In other words, the added polyvinyl alcohol acts like a protective colloid), so it is thought that stable microparticles of polyvinyl butyral are precipitated. As mentioned above, in the method of the present invention, when polyvinyl butyral is produced by condensing polyvinyl alcohol and butyraldehyde in an aqueous phase in the presence of an acid catalyst, the condensation reaction is carried out by keeping the reaction system at a temperature of two or more generations. A predetermined amount of polyvinyl alcohol aqueous solution is further added from immediately before to immediately after the polyvinyl butyral precipitates. This allows the polyvinyl butyral to proceed stably and precipitates fine particles, resulting in excellent transparency and solubility. A homogeneous polyvinyl butyral is obtained.

In addition, since there is no need to add additives such as surfactants that increase the wastewater load, there is no need for complex removal and treatment processes.
Furthermore, since the reaction proceeds at a relatively high temperature of 20'C or higher, no special cooling equipment is required, making this production method industrially extremely advantageous compared to conventional methods.

In particular, when an interlayer film for safety glass is produced by adding a plasticizer to the particulate polyvinyl butyl obtained according to the present invention, an interlayer film with excellent transparency can be obtained.

Examples of the present invention will be described below. Example 1 5V of concentrated hydrochloric acid (concentration 35% by weight) was added to 950y of a 1 rut volume% aqueous solution of polyvinyl alcohol with a degree of saponification of 99 mol% and a degree of polymerization of 1800, and the reaction system was maintained at n°C while stirring.
-30 minutes after adding 57.0f of butyraldehyde, saponification degree of 99 mol%, polymerization degree of 1800, 1(2)I
% polyvinyl alcohol aqueous solution was added, and 5 minutes later, white fine particles of polyvinyl butyral were precipitated.

After precipitation, 91 powders were added to concentrated hydrochloric acid (concentration 35% by weight) 55
After 5 minutes of adding y, the temperature was raised to 60C at a heating rate of 15°C/hour, maintained at that temperature for 2 hours, and then cooled to 2nd generation after 3 powders. The obtained resin is neutralized, filtered, and
A white powder was obtained by washing with water and drying. The average particle size of the obtained polyvinyl butyral powder was 96 μm, and the degree of butyralization was mol %. 40 fI of triethylene glycol di-2-ethyl butyrate as a plasticizer was added to 100 f of this resin, mixed for 5 minutes using a Raikai machine, kneaded for 5 minutes at 120°C using a 6-inch roll, and then pressed at 120°C for 5 minutes. A transparent film with a thickness of about 2.3 m and a smooth surface was obtained. The light transmittance of the film was measured using a Hitachi Recording Spectrophotometer EPS3T. 300n1 when using tungsten light source
The total light transmittance in the wavelength range of μ to 700 mμ (visible light range) was 95%. Comparative Example 1 An experiment was carried out in exactly the same manner as in Example 1, except that the initial polyvinyl alcohol aqueous solution was 1000' and no polyvinyl alcohol aqueous solution was added before or after precipitation.

When 55y of concentrated hydrochloric acid (concentration 35% by weight) was added after the first phase of precipitation, the precipitated particles, which had been dispersed almost uniformly until then, strongly coalesced together and formed coarse lumps, making it impossible to continue stirring. However, fine polyvinyl butyral particles were not obtained. Example 2 Polyvinyl butyral was produced in exactly the same manner as in Example 1, except that the degree of polymerization of the initially charged polyvinyl alcohol and the polyvinyl alcohol added immediately before precipitation was changed to 600.

The degree of butyralization of the obtained polyvinyl butyral is 67
The mol% and average particle size were 152μ, and the plasticizer was easily kneaded to obtain a transparent soft film. ．． The total light transmittance of the film was %%, and the film showed no cloudiness or blue haze. Comparative Example 2 In Example 2,
The initial polyvinyl alcohol aqueous solution was set to 1000 fI, and polyvinyl alcohol was added before and after precipitation. The experiment was conducted in exactly the same manner as in Example 2, except that the alcohol aqueous solution was not added.

When 55f of concentrated hydrochloric acid (concentration 31% by weight) was added after one step of precipitation, the particles strongly adhered to each other and became coarse lumps, so stirring could not be continued and fine polyvinyl butyral particles could not be obtained. Nakatsuta. Example 3 Same as Example 1 except that the temperature maintained during precipitation was 31°C.
Polyvinyl butyral was produced in exactly the same manner.

The degree of butyralization of the obtained polyvinyl butyral is 67
The mol% and average particle size were 174μ, the plasticizer was easily kneaded, and a transparent soft film was obtained. The total light transmittance of the obtained film was 1%, and the film had cloudiness and
No blue cloudiness was observed. Comparative Example 3 The experiment was conducted in exactly the same manner as in Example 3, except that the initial polyvinyl alcohol aqueous solution was 1000' and no polyvinyl alcohol aqueous solution was added before or after precipitation. However, since the precipitated particles strongly adhered to each other and separated into a solid phase and a liquid phase, stirring could not be continued and fine polyvinyl butyral particles could not be obtained.

3 after precipitation of polyvinyl butyral in Example 1
After beating, saponification degree is 99 mol%, polymerization degree is 1800
Polyvinyl butyral was produced in exactly the same manner as in Example 1, except that 50 y of a polyvinyl alcohol aqueous solution having a weight of s1% was added. The degree of butyralization of the obtained polyvinyl butyral was 68.2 mol%, and the average particle size was 124.
It was μ. The resin was easily kneaded with a plasticizer and a transparent soft film was obtained. The total light transmittance of the obtained film was %, and the film showed no cloudiness or blue haze. Comparative Example 4 The same procedure as in Example 1 was carried out except that the temperature until the precipitation of polyvinyl butyral was kept at 1TC, the initial aqueous solution of polyvinyl alcohol was set at 1000f, and no aqueous polyvinyl alcohol solution was added before or after precipitation. Polyvinyl butyral was produced in exactly the same manner as in Example 1.

Immediately after the precipitation, 55y of concentrated hydrochloric acid (35% by weight) was added, and an enlargement of the precipitated particles was observed. The degree of butyralization of the obtained polyvinyl butyral was approximately mol%, and the average particle size was 40%.
0 μ, it is not easily plasticized even if a plasticizer is added and kneaded, and it is clear that unplasticized polyvinyl butyral particles are present in the soft material obtained by kneading with a roll and press. Ta.

Further, the total light transmittance of this film was 72%, and cloudiness was observed in the film. Comparative Example 5 In Example 1, 10% polyvinyl alcohol aqueous solution 1
An experiment was conducted in exactly the same manner as in Example 1, except that 1.5 f of sodium laurylbenzenesulfonic acid was added as a surfactant to 000y, and no aqueous polyvinyl alcohol solution was added before or after precipitation.

The degree of butyralization of the obtained polyvinyl butyral was 68.
．． The content was 4 mol %, and the average particle size was 102 μm. This resin 10
When 0y was kneaded with plasticizer 40f, a soft film was obtained. Although the total light transmittance of this film was 84%, the film had a significant blue haze and could not be used, for example, as an interlayer film for safety glass. Comparative Example 6 In Comparative Example 5, polyethylene oxide (molecular weight 1500
) 10f to 10% aqueous solution of polyvinyl alcohol
The experiment was conducted in exactly the same manner as in Comparative Example 5, including neutralization, water washing, drying, etc., except that the experiment was conducted after sufficiently dissolving at 0V.

The degree of polyvinyl butyralation obtained was 68.1 mol%,
The average particle size was 126μ.

Claims (1)

[Claims] 1. When polyvinyl butyral is produced by condensing polyvinyl alcohol and butyraldehyde in an aqueous phase in the presence of an acid catalyst, the condensation reaction is carried out while maintaining the reaction system at a temperature of 20°C or higher, and polyvinyl A method for producing particulate polyvinyl butyral, which comprises further adding an aqueous solution containing polyvinyl alcohol in an amount of 0.5 to 20% by weight based on the total amount of polyvinyl alcohol used, immediately before and after the precipitation of butyral. 2. The method for producing polyvinyl butyral according to item 1, wherein the concentration of the polyvinyl alcohol aqueous solution added is 3 to 15% by weight. 3. The method for producing polyvinyl butyral according to item 1 or 2, wherein the weight of the catalyst added to the reaction system before precipitation of polyvinyl butyral is 1/3 or less of the total amount of catalyst used.