JPH05140216A - Production of polyvinyl acetal resin - Google Patents

Abstract

PURPOSE:To obtain a polyvinyl acetal resin having a color improved to such an extent that any problem of quality does not arise by forming a part of the reactor which comes into contact with the reaction solution from a material having a specified rate of corrosion. CONSTITUTION:A process for producing a polyvinyl acetal resin comprising reacting PVA with an aldehyde in the presence of an acid catalyst, neutralizing the slurried produce with an alkali, washing the produce with water and drying it, wherein a part of the reactor which comes into contact with the reaction solution is formed from a material of a rate of corrosion of 0.1mm/year or below. The rate of corrosion is a value obtained by measuring the corrosion loss according to JIS G 4303 and erpressing it in mm/year. The testing solution is a 5wt.% aqueous hydrochloric acid solution, and the testing temperature is 90 deg.C. As the above material, a glass-lined material is desirable from the viewpoint of equipment cost. According to the above process, a polyvinyl acetal resin having a color improved to such an extent that any problem of quality does not arise can be produced, and this resin is desirable as a starting resin for an interlayer of a laminated glass, a coating material, an adhesive, a binder or the like.

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 resin whose color is improved to the extent that quality problems do not occur.

[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.

This type of polyvinyl acetal resin is produced by reacting polyvinyl alcohol with an aldehyde in the presence of an acid catalyst, neutralizing the slurry of the reaction product with an alkali, washing with water and drying. And as a reactor,
A stainless steel reactor is commonly used.

When using a stainless steel reactor,
Mainly, iron ions and chromium ions are eluted from the reactor into the reaction solution, and the resulting polyvinyl acetal resin is slightly yellowed. Generally, p of the reaction solution
When H is 5 or less, elution of iron ions and chromium ions from the reactor becomes a serious problem.

The reason is considered as follows. That is,
The eluted iron ions become water-soluble iron chloride or iron sulfate by an acid catalyst such as hydrochloric acid or sulfuric acid, which becomes water-insoluble and yellowish brown iron hydroxide upon subsequent neutralization with alkali. It is considered that this iron hydroxide remains in the resin without being removed even by washing with water. The same applies to chromium ions.

Although iron ions and chromium ions may remain in the raw materials such as polyvinyl butyral, the residual amount thereof is a trace amount and is not a problem. An intermediate film for laminated glass is produced using the resin obtained by such a method, and when it is used particularly in a thick film, it appears to be colored yellow, which is a defect in the appearance of the laminated glass. Further, even when the intermediate film is colored, the color tone changes, which causes inconvenience. Further, in the case of paints, adhesives, binders, etc., there are drawbacks similar to the above.

In order to prevent such coloring of the polyvinyl acetal resin, Japanese Patent Publication No. 38-25040 adds a chelating agent which forms a complex compound with a metal ion, for example, tetrasodium salt of ethylenediaminetetraacetic acid. It is described that the reaction is carried out.

[0008]

However, the complex compound formed by the above chelating agent and iron ion or chromium ion is generally colored yellow or the like,
In addition, the solubility in water is not sufficient, and even if it is washed with water, it is not completely removed and a part thereof remains in the resin. Therefore, the obtained polyvinyl acetal resin still has coloring,
There are still quality issues.

[0009] The present invention is to provide a method for producing a polyvinyl acetal resin in which coloring is improved to the extent that quality problems do not occur.

[0010]

In order to achieve the above object, the present invention comprises reacting polyvinyl alcohol with an aldehyde in the presence of an acid catalyst, neutralizing the slurry of the reaction product with an alkali, washing with water and drying. In the method for producing a polyvinyl acetal resin by performing the above, the liquid contact part of the reactor is formed of a material having a corrosion rate of 0.1 mm / year or less.

Here, the corrosion rate is JIS G 430
The value obtained by measuring the corrosion weight loss according to No. 3 and converting this to mm / year. However, the test liquid is a 0.5 wt% hydrochloric acid aqueous solution, and the test temperature is 90 ° C.

In the present invention, polyvinyl alcohol having an average degree of polymerization of 200 to 2600 and a saponification degree of 90% or more is generally used as the polyvinyl alcohol.
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 as 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 producing a resin for a laminated glass interlayer film, butyraldehyde is generally used.

As the reactor, a tank type reactor equipped with a stirrer or a reactor in which a loop type reactor and a tank type reactor equipped with a stirrer are connected is generally used. Reactors of this type are well known.

According to the present invention, in the known type of reactor as described above, the wetted part has a corrosion rate of 0.1 mm / ye.
It is necessary to form the material with ar or less. If the corrosion rate exceeds 0.1 mm / year, the amount of elution of substances that cause coloring such as iron ions and chromium ions increases, and coloring of the resin cannot be sufficiently prevented. This is what the present inventor has found by experiments in consideration of the volume and contact area of the reactor, the resin concentration of the reaction system, the reaction temperature and the time.

Here, the corrosion rate is JIS G430
It is a value obtained by measuring the corrosion weight loss (g / m ² · hr) in accordance with No. 3 and considering the density of the material, and converting this to the unit of mm / year. However, the test liquid is a 0.5 wt% hydrochloric acid aqueous solution, and the test temperature is 90 ° C.

Examples of materials having a corrosion rate of 0.1 mm / year or less include corrosion-resistant inorganic materials such as glass, titanium alloys, Hastelloy, and zirconium alloys. Among them, the glass lining material is preferable from the viewpoint of equipment cost.
In addition, the corrosion rate of the corrosion resistant organic material such as plastic or rubber is 0.1mm / year or less,
Moreover, a material that is heat resistant and does not deteriorate by aldehyde, such as a fluorine resin, can be used.

Not only in the reactor, but also in the auxiliary equipment of this reactor, the portion which comes into contact with the liquid whose pH is 5 or less by the acid catalyst used has a corrosion rate of 0.1 mm /
It is preferable to use a material of year or less.

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,
The resin particles are deposited and the reaction product is obtained as a slurry. In the solution method, the reaction product is obtained in the form of a solution, but then water is added to precipitate the resin particles and the reaction product 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 composed of the above materials, and an acetalization reaction is carried out in the presence of an acid catalyst. The amount of aldehyde charged (supply amount) is generally supplied in excess of 2 to 10 times the theoretical amount necessary 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 the reaction product of polyvinyl alcohol and an aldehyde thus formed exhibits acidity by an acid catalyst, and in order to neutralize this, an alkali such as caustic soda or baking soda is added with stirring to the reaction product slurry. And mixed.

In order to prevent the aldol condensation, these alkalis are generally added in an appropriate amount so that the pH of the slurry liquid becomes 7 to 10 after removing the excess aldehyde. After the reaction for a certain period of time, the reaction is stopped by adding an alkali so that the pH of the slurry liquid becomes about 5, and then the excess aldehyde is removed, and then the pH of the slurry liquid becomes 7 to 10. You may add a suitable amount so that it may become. In this way the slurry is stabilized.

If the alkali concentration of the slurry liquid is too high,
Aldol condensation occurs due to residual aldehyde, which causes deterioration of the resin. In addition, alkali remains in the resin, and when the resin is dissolved in a solvent, insoluble matter remains, which causes a problem.

The slurry of the reaction product stabilized by neutralization is dehydrated by a conventional method, and washed and dried by a conventional method. In this way, a polyvinyl acetal resin having improved coloring to the extent that quality problems do not occur is produced.

[0027]

[Function] When polyvinyl alcohol and aldehyde are reacted in the presence of an acid catalyst, if the wetted part of the reactor is made of a material having a corrosion rate of 0.1 mm / year or less, the acid catalyst elutes from the reactor. The amount of the substance (a substance that causes coloring such as iron ions and chromium ions) is reduced, and the amount of the substance remaining in the polyvinyl acetal resin is reduced. As a result, the coloring of the resin is improved to the extent that quality problems do not occur.

[0028]

EXAMPLES Examples and comparative examples of the present invention will be shown below. Example 1 (1) Description of Reaction Device The reaction device shown in FIG.
A butyraldehyde tank 3, a first loop reactor 11, a second loop reactor 12, an auxiliary reactor 20 provided in the middle of the second loop reactor 12, and a tank reactor 2. It has and. All of these devices are made of glass lining (iron content 0.12% by weight, chromium content 0), and the corrosion rate is 0.02 mm / year.

The polyvinyl alcohol dissolving tank 1 and the first loop type reactor 11 are connected by a supply pipe 24, and the first loop type reactor 11 and the second roux type reactor 12 are connected by a transfer pipe 26. The second loop reactor 12 and the tank reactor 2 are connected by a transfer pipe 27. Reference numeral 17 is an extraction valve. The butyraldehyde tank 3 and the first loop reactor 11 are connected by a supply pipe 25.

The first loop reactor 11 and the second loop reactor 12 are provided with a circulation pump 7, a pressure gauge 8 and a flowmeter 9, and the supply pipes 24 and 25 are provided with a supply pump 14. Are provided respectively. The polyvinyl alcohol dissolution tank 1 has a volume of 100 liters, and the butyraldehyde tank has a volume of 10 liters.

The diameter of the first loop reactor 11 is 40
It is formed of mm tubing and its volume is 1 liter. The second loop reactor 12 is formed by a pipe having a diameter of 25 mm, and the auxiliary reactor 20 having a volume of 3.5 liters is provided in the middle of the pipe line, and the total volume is 5 liters.
The volume of the tank reactor 2 is 100 liters. The tank reactor 2 is provided with a reflux condenser (not shown) in order to prevent butyraldehyde from flowing out of the system.

(2) Production of polyvinyl butyral resin Using the reaction apparatus shown in FIG. 1, a polyvinyl butyral resin was produced by the following method.

Polyvinyl alcohol having an average degree of polymerization of 1500 and a degree of saponification of 99.5 mol% was dispersed in pure water to a concentration of 10% by weight in a polyvinyl alcohol dissolution tank 1 and then heated to 90 ° C. After melting, the mixture was cooled to 75 ° C. Furthermore, this polyvinyl alcohol aqueous solution 10
3.1 parts by weight of an aqueous solution of hydrochloric acid having a concentration of 10% by weight was mixed with 0 parts by weight. Further, 5.5 parts by weight of butyraldehyde was prepared in the butyraldehyde tank 3.

Further, the first loop type reactor 11 and the second loop type reactor 12 were filled with pure water at 75 ° C., and the circulating pump 7 was operated to circulate the pure water. Further, the tank reactor 2 was charged with pure water at 85 ° C. and an aqueous solution of hydrochloric acid at a hydrochloric acid concentration of 0.1.
The amount was adjusted so as to be 5% by weight, and the amount of stirring was added.

The above-mentioned aqueous solution of polyvinyl alcohol containing an acid catalyst and butyraldehyde are mixed at a constant ratio so that the total amount of them disappears in 60 minutes.
1 was supplied. Both are mixed through the confluence, and the mixed liquid is circulated in the first loop reactor 11 by the circulation pump 7. The flow rate in the first loop reactor 11 is adjusted to 6 m / sec to prevent the particles generated by the reaction from coalescing.

An amount of slurry liquid commensurate with the supply of the polyvinyl alcohol aqueous solution and butyraldehyde is transferred into the second loop reactor 12 and circulated in the second loop reactor 20 by the circulation pump 7. The flow rate in the second loop reactor 12 was adjusted to 3 m / sec, and the extraction valve 17 was adjusted so that the pressure became 2 kg / cm ² , and the reaction proceeded while preventing the coalescence of particles. .. The first loop reactor 1
When the slurry liquid was sampled from the outlet of No. 1 and the butyralization degree of the resin particles was measured, the butyralization degree was 40.0 mol%.

Further, the slurry liquid circulating in the second loop reactor 12 is transferred into the tank reactor 2, and the tank reactor 2
Rotation speed of the stirring blade of 250 rpm, peripheral speed of the stirring blade 2 m /
The reaction and aging were carried out at 85 ° C. for 3 hours with stirring while setting the use efficiency to 10 w / liter for 2 seconds. The second
When the slurry liquid was sampled from the outlet of the loop reactor 12 and the butyralization degree of the resin particles was measured, the butyralization degree was 55.0 mol%.

Thereafter, sodium bicarbonate was added to stop the reaction, the pH was adjusted to about 5, and the mixture was cooled to 40 ° C. The cooled slurry liquid was extracted into a filter cloth bag, washed with pure water for 30 minutes, and then separately prepared from 100 liters made of stainless steel (SUS316) (iron content 62 to 69% by weight, chromium content 16 to 18). (Wt%), the pH was adjusted to about 8 with baking soda, neutralized at 70 ° C. for 3 hours, washed with pure water for 30 minutes, and dried. Thus
A white granular polyvinyl butyral resin was produced.

The slurry liquid can be neutralized in the tank reactor 2 without using a separately prepared 100-liter stirring container. In this case, after removing excess butyraldehyde, baking soda is charged into the tank reactor 2 to adjust the pH to about 8.

(3) Quality of polyvinyl butyral resin Regarding the obtained polyvinyl butyral resin, JIS
When the degree of butyralization was measured by K 6728,
The degree of butyralization was 64.7 mol%. Further, a transparent plate having a thickness of 3 mm was formed using this polyvinyl butyral resin, and the yellowness (YI) of this transparent plate was measured according to JIS K 7103.
Was 0.7. For reference, iron and chromium in this polyvinyl butyral resin were quantified, and iron was 0.15 ppm and chromium was 0.05 ppm or less.

The present inventor has confirmed through experiments that the polyvinyl butyral resin having improved coloring to the extent that quality problems do not occur has a yellowness index (YI) of 1.0 or less as measured by the above-mentioned measurement method. ing. In addition, when iron or chromium is contained in the resin, the present inventor has confirmed by experiments that the iron content should be 0.3 ppm or less and the chromium content should be 0.1 ppm or less. Therefore, it is understood that the polyvinyl butyral resin obtained in Example 1 has a good quality without coloring.

Example 2 In Example 1, all the reactors were made of titanium (iron content 0.5% by weight, chromium content 0). Its corrosion rate is 0.08 mm / year. Other than that was performed like Example 1.

The yellowness (YI) of the transparent plate is 0.9,
The polyvinyl butyral resin obtained in this Example 2 is
It can be seen that it has good quality without coloring. In addition,
Iron in resin is 0.22ppm, chromium is 0.05ppm
It was below.

Comparative Example 1 In Example 1, all reactors were made of stainless steel (SUS316) (iron content 62 to 69% by weight, chromium content 16 to 18% by weight). Its corrosion rate is 9.
It is 7 mm / year. Other than that was performed like Example 1.

In this case, the yellowness (YI) of the transparent plate is 4.
It has a defect in appearance because it is colored yellow. Iron in the resin is 2.5 ppm and chromium is 0.2
It was 5 ppm.

Comparative Example 2 In Comparative Example 1, an aqueous polyvinyl alcohol solution 100 was used.
0.022 parts by weight of a tetrasodium salt of ethylenediaminetetraacetic acid was mixed as a chelating agent with respect to parts by weight.
Other than that was performed like the comparative example 1.

In this case, the yellowness (YI) of the transparent plate is 4.
It is 5 and has a defect in appearance by being colored yellow. In addition, iron in the resin is 1.6 ppm, and chromium is 0.3
It was ppm.

[0048]

As described above, according to the present invention, polyvinyl alcohol and aldehyde are reacted in the presence of an acid catalyst,
In a method for producing a polyvinyl acetal resin by neutralizing a slurry of a reaction product with an alkali, washing with water and drying, a wetted part of a reactor is formed of a material having a corrosion rate of 0.1 mm / year or less. As a result, it is possible to produce a polyvinyl acetal resin whose color is improved to the extent that quality problems do not occur.

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

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an example of a reaction apparatus used in the present invention.

[Explanation of symbols]

 1 polyvinyl alcohol dissolution tank 2 tank type reactor 3 butyraldehyde tank 7 circulation pump 11 first loop type reactor 12 second loop type reactor 14 supply pump 17 extraction valve 20 auxiliary reactor 24 supply pipe 25 supply pipe 26 transfer pipe 27 Transfer pipe

Claims (1)

[Claims] 1. A method for producing a polyvinyl acetal resin by reacting polyvinyl alcohol with an aldehyde in the presence of an acid catalyst, neutralizing the slurry of the reaction product with an alkali, and washing and drying the mixture to prepare a polyvinyl acetal resin. A method for producing a polyvinyl acetal resin, characterized in that the liquid portion is formed of a material having a corrosion rate of 0.1 mm / year or less. Here, the corrosion rate is a value obtained by measuring the corrosion weight loss according to JIS G 4303 and converting this to mm / year. However, the test solution is a 0.5 wt% hydrochloric acid aqueous solution, and the test temperature is 90 ° C.
And