JPH05155915A - Production of poly(vinyl acetal) resin - Google Patents

Abstract

PURPOSE:To continuously and efficiently produce a poly(vinyl acetal) resin which has low contents of too fine particles and too coarse particles, and does not coagulates thereof, has good heat stability, and shows little fluctuation in quality. CONSTITUTION:Poly(vinyl alcohol) is reacted with n-butyraldehyde in the presence of hydrochloric acid as a catalyst. The resulting slurry is pre-dehydrated on a pre- dehydrator 10 and then introduced into a neutralization tank 20. Water is added to the pre-dried reactional product to disperse it to form a slurry, which is then neutralized with sodium bicarbonate and regulated to have a concentration of 8-14wt.%. This concentration regulation is accomplished by determining, with a slurry concentration meter 23 and a flowmeter 24, the concentration and flow rate of the slurry which is being introduced into an auxiliary neutralization tank 40, and by controlling the degree of opening of a control valve 12 according to instructions from a computer 30 to automatically control the amount of the water to be introduced into the tank 20. The slurry in the tank 20 is successively introduced into the tank 40 and other auxiliary neutralization tanks 41 to 44 at 60 deg.C, 65 deg.C, 70 deg.C, 65 deg.C, and 35 deg.C, respectively, thereby accelerating the neutralization. The slurry is then washed with water, dehydrated, and dried on a dryer 60 to obtain the desired resin powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously and efficiently producing a polyvinyl acetal resin having stable quality.

[0002]

2. Description of the Related Art Polyvinyl acetal resins such as polyvinyl butyral are widely used in interlayer films for laminated glass, paints, adhesives, binders and the like.

As a method for producing this kind of polyvinyl acetal resin, polyvinyl alcohol and aldehyde are reacted in the presence of an acid catalyst to preliminarily dehydrate a slurry of resin particles produced, and the dehydrated cake is introduced into a neutralization tank and water is poured. Then, it is dispersed in a slurry form and neutralized with an alkali, and this slurry is sequentially introduced into a plurality of auxiliary neutralization tanks to promote neutralization, and then washed with water, dehydrated and dried to obtain a powdery resin. The method has been adopted.

In this case, the preliminary dehydration is carried out in order to separate the resin particles and the mother liquor and to mainly remove water-soluble components (acid, aldehyde, etc.) in the slurry. Further, the promotion of neutralization in a plurality of auxiliary neutralization tanks sufficiently neutralizes mainly the acid remaining in the voids and the surface of the resin particles, and at the same time, dissolves the water-soluble components (acid, alkali, neutralization) in the slurry. It is carried out to elute (salts, aldehydes, etc.), and it is carried out continuously at a temperature (about 40 to 80 ° C.) at which the resin particles swell for several hours.

[0005]

In such a method for producing a polyvinyl acetal resin, a predetermined fixed amount of washing water is poured into the neutralization tank, but the slurry concentration in the neutralization tank is not constant. Without changing, the slurry concentration in the auxiliary neutralization tank also changes accordingly. The reason is considered that, when the slurry of resin particles is preliminarily dehydrated by the preliminary dehydrator, the dehydration rate changes due to changes in the slurry temperature, the particle size of the resin particles, the dehydration rate, and the like.

As described above, when the slurry temperature in the auxiliary neutralization tank is maintained at a temperature at which the resin particles swell to promote the neutralization, the slurry concentration changes, and when the slurry concentration becomes low, fine particles increase, which causes dehydration. When this happens, it may flow out into the drainage or be scattered from the dryer. Further, when the slurry concentration is low and the slurry flows into the slurry in the auxiliary neutralization tank at a relatively high temperature, coalescence of resin particles occurs to cause agglomeration of coarse particles (for example, a diameter of about 5 cm or more). Generated, this lump accumulates in the auxiliary neutralization tank and interferes with long-term continuous operation, and the water-soluble components remaining on the voids and the surface of the resin particles are not sufficiently removed, resulting in thermal stability of the resin. Is reduced.

On the contrary, as the slurry concentration increases, the agglomerates of coarse particles decrease, but the larger coarse particles having a comparatively smaller particle size (for example, the diameter is about 0.5 to 2 cm) increase, which is the final auxiliary neutralization tank. The strainer attached to the extraction pipe will be clogged, and the number of coarse particle sieve-on products that cannot be made into products will increase, resulting in poor productivity and product efficiency.

The present invention is intended to solve the above problems, and an object thereof is to prevent generation of fine particles and coarse particles or agglomerates of coarse particles, and to provide a polyvinyl acetal resin having good thermal stability and stable quality. It is to provide a method for continuously and efficiently manufacturing

[0009]

In order to achieve the above-mentioned object, the present invention comprises reacting polyvinyl alcohol and an aldehyde in the presence of an acid catalyst, preliminarily dehydrating a slurry of resin particles produced, and subjecting this slurry to dehydration. The cake is introduced into a neutralization tank and water is poured to disperse it into a slurry, which is neutralized with an alkali, and the slurry is sequentially introduced into a plurality of auxiliary neutralization tanks to promote neutralization, and then washed and dehydrated. In the method for producing a polyvinyl acetal resin by drying, the concentration of the slurry introduced into the first auxiliary neutralization tank is detected, and the concentration of the slurry is kept in the range of 8 to 14% by weight and almost constant. The amount of water injection is automatically adjusted.

In the present invention, as the polyvinyl alcohol, polyvinyl alcohol having an average polymerization degree of 200 to 2600 and a saponification degree of 90% or more is generally used.
Then, it is generally a solution of 5 to 12% by weight of water or alcohol. At this time, a conventional acid catalyst is added.

As the acid catalyst, hydrochloric acid, phosphoric acid, sulfuric acid, paratoluenesulfonic acid, etc. may be used alone or in a mixture of two or more kinds. These acid catalysts are generally used in the reaction solution.
An appropriate amount is added so that H becomes 0.2 to 2.

As the aldehyde, formaldehyde,
Aliphatic aldehydes such as acetaldehyde, propionaldehyde, butyraldehyde and the like may be used alone or as a mixture of two or more kinds. When manufacturing a resin for a laminated glass interlayer film, n-butyraldehyde is generally used.

As the reactor, a tank reactor equipped with a stirrer or a reactor in which a loop reactor and a tank reactor equipped with a stirrer are connected is generally used. These reactors are well known.

The reaction is carried out by a precipitation method using an aqueous medium or a solution method using an alcohol solvent. In the precipitation method, resin particles are precipitated and obtained as a slurry. In the solution method, the resin is obtained in the form of a solution, but then water is added to precipitate the resin particles and the resin is converted into a slurry. Usually, a precipitation method using an industrially advantageous aqueous medium is adopted.

A polyvinyl alcohol solution and an aldehyde are supplied to a reactor, and an acetalization reaction is carried out in the presence of an acid catalyst. After that, aging is performed as necessary.
The amount of aldehyde charged (feed amount) is generally supplied in excess of 2 to 10% by weight of the theoretical amount required to obtain the desired degree of acetalization.

The reaction temperature is generally set in the range of 0 to 95 ° C. The reaction and aging time is generally 1 to 4 hours. The degree of acetalization of the resin varies depending on the use, but is generally 56 to 75 mol%, preferably 60 to 70 mol% in terms of average acetalization degree.

The slurry of resin particles produced by the acetalization reaction is acidified by an acid catalyst, and this slurry is neutralized with alkali. This neutralization is performed by the following method.

That is, as shown in FIG. 1, the slurry of resin particles is introduced into the preliminary dehydrator 10 and preliminarily dehydrated.
By this preliminary dehydration, the resin particles and the mother liquor are separated, and mainly water-soluble components (acid, aldehyde, etc.) in the slurry are newly removed. After that, the dehydrated cake is introduced into the neutralization tank 20, and washing water is poured into the dehydrated cake from the water injection pipe 11 and is stirred in the neutralization tank 20 to be dispersed in a slurry state. From 25, an alkali such as caustic soda or baking soda is added with stirring to perform neutralization. These alkalis generally have a pH of the slurry liquid.
Is added to be 7-8.

A preliminary neutralization tank is installed in front of the preliminary dehydrator 10, and a slurry of resin particles obtained by the acetalization reaction is introduced into this preliminary neutralization tank, and an alkali is added to this to prepare a slurry liquid. The pH may be pre-neutralized to about 5 to stop the reaction, and this may be introduced into the pre-dehydrator 10. Such neutralization stabilizes the slurry.

The washing water injection pipe 11 is provided in the middle of the pipe connecting the preliminary dehydrator 10 and the neutralization tank 20. The water injection pipe 11 is provided with a control valve 12, and the opening of the control valve 12 is automatically adjusted based on an instruction from the control computer 30.

The slurry of the resin particles stabilized by the neutralization is supplied to a plurality of auxiliary neutralization tanks 40, 41, 42, 4 connected in series by a feed pump 22 provided in a pipe 21.
Introduced sequentially in 3, 44. The number of auxiliary neutralization tanks is appropriately determined in consideration of the residence time and the like, and the temperature of each tank is generally 40 to 40 due to an outer jacket or the like in order to promote neutralization.
It is heated and maintained at 80 ° C. Particularly, 50 ° C. or higher is preferable, but in the prior art, such a temperature causes the above-mentioned problems.

The pipe 21 is provided with a slurry concentration meter 23 for detecting the slurry concentration. The slurry densitometer 23 is an in-line type that can output a signal with current or voltage, and for example, an optical detection type slurry densitometer such as an infrared transmission type or a laser light reflection type is preferable. In addition, a vibration type or ultrasonic type slurry concentration meter can also be used. Further, the pipe 21 is provided with a flow meter 24 for detecting the flow rate of the slurry. The instruction of the slurry concentration meter may change depending on the flow rate, and the flow meter 24 is provided to correct this, but depending on the slurry concentration meter, the flow meter does not necessarily have to be provided.

The slurry concentration meter 23 and the flow meter 24 detect the concentration and flow rate of the slurry introduced into the first auxiliary neutralization tank 40, and the detection result is detected by the computer 3.
It is fed back to 0. And computer 3
With an instruction of 0, the opening degree of the control valve 12 is automatically adjusted according to the slurry concentration and flow rate, whereby the slurry concentration is 8 to 14% by weight, preferably 9 to 12% by weight.
The water injection amount is automatically adjusted so as to be in the range of and substantially constant.

If the slurry concentration is lower than 8% by weight, fine particles increase, which may flow out into the drainage during dehydration,
Splash from dryer. Further, when the slurry concentration becomes low, agglomerates of coarse particles increase, and these accumulate in the auxiliary neutralization tank, and the thermal stability of the resin also decreases. Conversely, the slurry concentration is 14
When it is higher than the weight%, coarse particles having a relatively large particle size increase, and this causes clogging of the extract strainer or the number of sieve-on products that cannot be made into products.

The slurry thus adjusted in concentration is stirred in a plurality of auxiliary neutralization tanks to promote neutralization, and the acid remaining mainly in the voids and the surface of the resin particles is sufficiently neutralized. In addition, the water-soluble components (acid, alkali, neutralized salt, aldehyde, etc.) are eluted into the slurry, and the water-soluble components remaining on the voids and the surface of the resin particles are sufficiently removed. After that, the extraction strainer 45 removes coarse particles having a relatively large diameter.

Subsequently, washing, dehydration and drying are carried out by known methods and other methods. For example, as shown in FIG. 1, the continuous washing tank 60 and the continuous dehydrator 70 perform washing and dehydration through the preliminary dehydrator 50, and the continuous washing tank 80 and the continuous dehydrator 90 repeat washing and dehydration, and thereafter, Drying is performed by the dryer 100 through the feeder 91. In this case, in the continuous water washing tank 60 and the continuous water washing tank 80,
Wash water is supplied from water supply pipes 51 and 71, respectively. In this way, a powdery polyvinyl acetal resin is manufactured.

[0027]

In this way, when the alkali-neutralized slurry is sequentially introduced into a plurality of auxiliary neutralization tanks to promote neutralization, the concentration of the slurry introduced into the first auxiliary neutralization tank is detected. Therefore, if the amount of water injection is automatically adjusted so that the slurry concentration in the auxiliary neutralization tank is in the range of 8 to 14% by weight and is substantially constant, the generation of fine particles and coarse particles and their lumps can be suppressed to a small level. Further, the water-soluble components remaining on the voids and the surface of the resin particles are sufficiently removed.

[0028]

EXAMPLES Examples and comparative examples of the present invention will be shown below. Example 1 In a tank reactor, 10 parts by weight of polyvinyl alcohol (polyvinyl alcohol having a degree of polymerization of 1700 and a degree of saponification of 99.0 mol%) was added to 90 parts by weight of pure water to disperse the mixture. After the temperature was raised to 0 and the polyvinyl alcohol was dissolved with stirring, the mixture was cooled to 30 ° C. To this polyvinyl alcohol aqueous solution, 0.6 part by weight of hydrochloric acid having a concentration of 35% by weight as an acid catalyst was added, and then 1.2 parts by weight of n-butyraldehyde was added.

The solution was cooled, and when the temperature reached 10 ° C., 4.2 parts by weight of n-butyraldehyde was added and the reaction was allowed to proceed with stirring to precipitate resin particles. % While adding 5.1 parts by weight hydrochloric acid
The temperature was raised to 0 ° C. Further, while stirring, an aging reaction was carried out at 50 ° C. for 3 hours. Then, the slurry was cooled to 30 ° C. and pre-neutralized to pH 5 with caustic soda.

This pre-neutralized slurry is introduced into the centrifugal separation type dehydrator 10 shown in FIG. 1 for preliminary dehydration, and this dehydrated cake is continuously introduced into the neutralization tank 20 and the dehydrated cake is also added. Wash water at 30 ° C. was continuously poured into the mixture, and sodium bicarbonate was added to neutralize the pH to 8, and the slurry concentration was adjusted to 9 to 10% by weight. At this time, the slurry concentration and flow rate were detected by the infrared type slurry concentration meter 23 and the flow meter 24, and the opening of the control valve 12 was adjusted according to the instruction of the computer 30 to automatically adjust the water injection amount.

The slurry in the neutralization tank 20 was stirred, and subsequently the slurry was continuously introduced into the five auxiliary neutralization tanks 40 to 44 successively by the feed pump 22 and stirred to promote neutralization. The temperatures of the five auxiliary neutralization tanks 40 to 44 are 60 ° C., 65 ° C., 70 ° C., 65 ° C. in order from the beginning in the outer jacket.
It was set such that the total of residence times of the four auxiliary neutralization tanks before heating and cooling at 50 ° C or 35 ° C and holding at 50 ° C or more was 4 hours.

The slurry discharged from the final auxiliary neutralization tank 44 is withdrawn and passed through a strainer 45 to remove coarse particles having a relatively large particle diameter (diameter of about 0.5 cm or more), and then through a preliminary dehydrator 50. The continuous washing tank 60 and the centrifugal continuous dehydrator 70, and the continuous washing tank 80 and the centrifugal continuous dehydrator 90 were repeatedly washed with water and dehydrated twice, and then dried by the airflow dryer 100. Thus, a powdery polyvinyl butyral resin was produced.

In this case, the fine particles scattered from the exhaust pipe of the airflow dryer accounted for 0.03% by weight of the total production amount, and the 28 mesh sieve-on product, which is not a product, accounted for 0.1% by weight. Furthermore, after continuous operation for 2 months, the total amount of coarse particles having a diameter of 5 cm or more and retained in the auxiliary neutralization tank was about 200 kg. The heat stability of the obtained resin was 1.5.

The thermal stability of the resin is evaluated by visually observing the degree of deterioration of the resin after putting 2 g of the resin in a test tube and heating it in an oil bath at 170 ° C. for 1 hour using a five-step sample ratio. The smaller the value, the better the thermal stability.

Example 2 In Example 1, the slurry concentration was adjusted to 12 to 13% by weight. Other than that, it went in the same way.

In this case, the fine particles scattered from the exhaust pipe of the airflow dryer were 0.01% by weight of the total production, and the 28 mesh sieve-on product which was not a product was 0.3% by weight. Furthermore, after continuous operation for 2 months, the total amount of coarse particles having a diameter of 5 cm or more retained in the auxiliary neutralization tank was about 100 kg. The heat stability of the obtained resin was 1.5.

Example 3 In Example 1, the slurry concentration was adjusted to 9 to 12% by weight. Other than that, it went in the same way.

In this case, the fine particles scattered from the exhaust pipe of the airflow dryer accounted for 0.03% by weight of the total production, and the 28-mesh sieve-on product, which is not a product, accounted for 0.5% by weight. Furthermore, after continuous operation for two months, the total amount of coarse particles having a diameter of 5 cm or more retained in the auxiliary neutralization tank was about 250 kg. The heat stability of the obtained resin was 1.5.

Comparative Example 1 In Example 1, the slurry concentration was adjusted to 6 to 7% by weight. Other than that, it went in the same way.

In this case, the fine particles scattered from the exhaust pipe of the airflow dryer were 0.2% by weight of the total production, and the 28 mesh sieving-on product which was not a product was 0.5% by weight. Furthermore, after continuous operation for 2 months, the total amount of coarse particles having a diameter of 5 cm or more retained in the auxiliary neutralization tank was about 500 kg. The heat stability of the obtained resin was 2.5.

Comparative Example 2 In Example 1, the slurry concentration was adjusted to 15 to 16% by weight. Other than that, it went in the same way.

In this case, the fine particles scattered from the exhaust pipe of the airflow dryer accounted for 0.01% by weight of the total production, and the 28-mesh sieve-on product, which was not a product, accounted for 5% by weight.
Furthermore, after continuous operation for 2 months, the total amount of coarse particles with a diameter of 5 cm or more that are retained in the auxiliary neutralization tank is about 100 k.
It was g. The heat stability of the obtained resin was 1.5.

Comparative Example 3 In Example 1, when the slurry concentration was not controlled at all, the slurry concentration varied from 5 to 17% by weight.
Other than that, it went in the same way.

In this case, the fine particles scattered from the exhaust pipe of the airflow dryer accounted for 0.5% by weight of the total production amount, and the 28 mesh sieve-on product which was not a product accounted for 0.7% by weight. Furthermore, after continuous operation for 2 months, the amount of coarse particles with a diameter of 5 cm or more retained in the auxiliary neutralization tank is about 800.
It was kg. The thermal stability of the obtained resin is 1 to
Varies up to 3.5.

[0045]

As described above, according to the present invention, polyvinyl alcohol and aldehyde are reacted in the presence of an acid catalyst,
Preliminarily dewater the slurry of resin particles produced, introduce this dehydrated cake into a neutralization tank, pour water to disperse it into a slurry, neutralize this with an alkali, and successively introduce this slurry into multiple auxiliary neutralization tanks. In order to accelerate the neutralization, and then to wash and dehydrate and dry the polyvinyl acetal resin by performing dehydration and drying, the concentration of the slurry introduced into the first auxiliary neutralization tank is detected, and the slurry concentration is detected. Is 8 to 1
The amount of water injection is automatically adjusted so as to be substantially constant within the range of 4% by weight, whereby generation of fine particles and coarse particles and agglomerates thereof can be suppressed.

Therefore, the continuous operation period becomes long, the outflow of the resin particles into the drainage and the scattering from the dryer are reduced, and the clogging of the strainer and the sieve-on product are reduced.
Productivity and product efficiency are improved. Further, the water-soluble components remaining on the voids and the surface of the resin particles are sufficiently removed, and the thermal stability is also improved.

Therefore, the polyvinyl acetal resin obtained by the method of the present invention is suitable as a raw material resin for interlayer films for laminated glass, paints, adhesives, binders and the like.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of the present invention.

[Explanation of symbols]

 10 Preliminary dehydrator 11 Water supply pipe 12 Control valve 20 Neutralization tank 22 Feed pump 23 Slurry concentration meter 24 Flowmeter 25 Alkali addition pipe 30 Computer 40 Auxiliary neutralization tank 41 Auxiliary neutralization tank 42 Auxiliary neutralization tank 43 Auxiliary neutralization Tank 44 Auxiliary neutralization tank 45 Strainer 50 Preliminary dehydrator 60 Continuous water washer 70 Continuous dehydrator 80 Continuous water washer 90 Continuous dehydrator 100 Dryer

Claims (1)

[Claims] 1. A polyvinyl alcohol and an aldehyde are reacted in the presence of an acid catalyst to preliminarily dehydrate the resulting slurry of resin particles, and the dehydrated cake is introduced into a neutralization tank and water is poured to disperse it in a slurry state. Is neutralized with an alkali, and the slurry is sequentially introduced into a plurality of auxiliary neutralization tanks to promote neutralization, followed by washing with water, dehydration and drying to produce a polyvinyl acetal resin. A polyvinyl acetal resin characterized by detecting the concentration of a slurry introduced into a Japanese tank and automatically adjusting the water injection amount so that the slurry concentration is in the range of 8 to 14% by weight and substantially constant. Production method.