JPS6255522B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyvinyl butyral, and more specifically, when an interlayer film for laminated glass is produced by adding a plasticizer, the adhesion of the interlayer films to each other at room temperature (hereinafter referred to as self-adhesion of the interlayer film) is greatly improved. The present invention relates to a method for producing polyvinyl butyral that yields a polyvinyl butyral interlayer film for laminated glass. The methods for producing polyvinyl butyral that are widely used industrially today are broadly divided into precipitation methods and dissolution methods. In this internal precipitation method, for example, butyraldehyde is added to an aqueous solution of polyvinyl alcohol in the presence of an acid catalyst, a butyralization reaction is carried out at a relatively low temperature of 20°C or less to produce fine precipitates of polyvinyl butyral, and then the precipitation is continued for a long time. This method involves stirring and heating. The dissolution method is, for example, a method in which polyvinyl alcohol is dispersed in an organic solvent such as isopropyl alcohol, and butyraldehyde is added in the presence of an acid catalyst, and the mixture is heated and reacted for a long time. However, interlayer films for laminated glass obtained by adding plasticizers to polyvinyl butyral produced by these conventional methods have strong adhesion on the film surface, so the films tend to stick to each other during winding after film formation. In order to prevent such adhesion, methods include spraying an anti-adhesive agent such as sodium bicarbonate on the film surface or cooling the interlayer film to a temperature of 10° C. or less. However, the method of spraying an anti-adhesive agent has the disadvantage that it requires a washing process and a drying process to remove the anti-adhesive agent before bonding the polyvinyl butyral film and glass. The problem is that a refrigeration device is required for the production, packaging, transportation, storage, and use of the interlayer film, which is expensive, and the emergence of an interlayer film that is substantially free of self-adhesion at room temperature has been awaited. In view of the above-mentioned current state of the method for producing polyvinyl butyral, the present invention provides an interlayer film for laminated glass with greatly improved self-adhesion by adding a plasticizer to the obtained polyvinyl butyral to produce an interlayer film for laminated glass. The purpose of the present invention is to provide a method for producing polyvinyl butyral obtained by condensing polyvinyl alcohol and butyraldehyde in an aqueous phase in the presence of an acid catalyst. , a precipitate is precipitated in the presence of at least one water-soluble salt of each of hydrobromic acid and nitric acid, and then the reaction system is maintained at a temperature of 30°C or higher in a strongly acidic region to ripen. The present invention relates to a method for producing polyvinyl butyral. As for the acid catalyst used in the present invention, acids known to have the effect of condensing polyvinyl alcohol and butyraldehyde can be appropriately used, such as inorganic acids such as sulfuric acid, nitric acid, and hydrochloric acid, and para-toluenesulfonic acid. Examples include organic acids. The amount of acid catalyst used is preferably such that the concentration at the end of the reaction is 0.5 to 5% by weight. The required amount of the catalyst may be added at once, but in order to precipitate fine polyvinyl butyral, it is preferable to add the catalyst in portions at an appropriate number of times. For example, in the case of hydrochloric acid, it is preferable to add 1/20 to 1/3 of the total required weight before precipitation, and add the rest after precipitation. The average degree of polymerization of the polyvinyl alcohol used in the present invention is preferably 800 to 3000, and the degree of saponification is preferably 95 mol% or more, particularly preferably 98 mol%, in order to obtain polyvinyl butyral with good transparency. That's all. The concentration of the aqueous solution of polyvinyl alcohol is not particularly limited as long as it can carry out the acetalization reaction, but it is usually 3 to 3.
It is said to be 20% by weight. In the present invention, the amount of butyraldehyde to be condensed with polyvinyl alcohol is appropriately determined depending on the degree of butyralization of the target polyvinyl alcohol, but when polyvinyl butyral is used for an interlayer film for laminated glass, the degree of butyralization is 60%.
It is desirable that the content is from 49 to 75 mol%, and for that purpose, 49 to 74 parts by weight per 100 parts by weight of polyvinyl alcohol.
It is preferred to add parts by weight of butyraldehyde. Preferred examples of water-soluble salts of hydrochloric acid, hydrobromic acid and nitric acid in the present invention include magnesium, calcium, zinc,
Examples include those having a valence of two or more, such as aluminum, iron, and titanium. These salts are used alone or in appropriate combinations, and the amount used is usually 2 to 100 parts by weight, preferably 7 to 50 parts by weight, per 100 parts by weight of the polyvinyl alcohol used.
Parts by weight. In the present invention, the strongly acidic region refers to a pH of 2 or lower, preferably a pH of 1 or lower, although it depends on the temperature of the polyvinyl butyral dispersion. Furthermore, although there is no particular upper limit to the temperature for ripening polyvinyl butyral, it is generally set at 90°C or lower to prevent excessive evaporation of aldehyde, and the aging time at which the temperature is maintained at 30°C or higher depends on the temperature rise and fall of the dispersion liquid. Usually, the duration is 1 to 20 hours, including the time for . To produce polyvinyl butyral by the method of the present invention, an acid catalyst is usually added to an aqueous polyvinyl alcohol solution at a temperature of over 20°C, then at least one of the above water-soluble salts is added, and then the reaction system is cooled. , butyraldehyde is added and a condensation reaction is carried out to precipitate polyvinyl butyral at a low temperature such as 20° C. or lower. In this way, the temperature of the reaction system is kept low during precipitation in order to obtain the precipitate in the form of fine particles or powder, and the lower limit of the temperature is not particularly limited as long as it does not freeze the reaction system. Although it is not always necessary, a temperature of -6°C or higher is usually employed. Next, after precipitation of polyvinyl butyral, the reaction system was heated in the presence of the above-mentioned water-soluble salt and kept at a temperature of 30°C or higher to further advance the reaction for ripening, and then the acid catalyst was neutralized with a base. The reaction product is extracted and washed and purified using conventional methods. In this way, a precipitate of polyvinyl butyral is precipitated in the aqueous phase in the presence of at least one water-soluble salt of hydrochloric acid, hydrobromic acid, and nitric acid, and then the temperature of the reaction system is set in a strongly acidic region. If an interlayer film for laminated glass is manufactured by adding a plasticizer by aging it by keeping it at 30℃ or higher, an interlayer film that has virtually no self-adhesion at room temperature can be obtained, and the reason for this is still not fully understood. Although it is not clear, it is assumed as follows. Since the butyralization reaction is an equilibrium reaction, the degree of butyralization becomes approximately constant in an equilibrium state where the reaction has progressed to a certain extent. In conventional production methods, the reaction was generally stopped before the degree of butyralization reached a certain level, and the remaining hydroxyl groups in the polyvinyl butyral at this time are thought to be randomly arranged. If this polyvinyl butyral is precipitated in the aqueous phase in the presence of the above-mentioned water-soluble salt and then aged in a strongly acidic region while maintaining the temperature of the reaction system at 30°C or higher, the reverse butyralization reaction occurs during the ripening. The hydroxyl groups produced by this process tend to exhibit association by hydrogen bonding, while the butyralization reaction tends to occur selectively to hydroxyl groups that do not have a strong tendency to associate rather than to hydroxyl groups that have a strong tendency to associate. Therefore, as the final equilibrium state approaches, the tendency for hydroxyl groups to remain in chains in the molecule increases, which increases the rigidity of the obtained polyvinyl butyral, which contributes to a decrease in the self-adhesion of the interlayer film. It is considered that The present inventors have found that by aging polyvinyl butyral precipitated even in the absence of the above-mentioned water-soluble salt at a relatively high temperature for a long time, adding a plasticizer to the resulting polyvinyl butyral results in an intermediate product with improved self-adhesion. Although it has already been found that a film can be obtained, the use of the water-soluble salt in the present invention allows the above-mentioned aging time to be significantly shortened and allows aging to be performed at a lower temperature. In addition, the above-mentioned water-soluble salt has a tendency to accelerate the butyralization reaction in the presence of an acid catalyst, and when the butyralization reaction is carried out in the presence of an acid catalyst, polyvinyl butyral is precipitated compared to the case in its absence. It also shortens the time it takes. In addition, if fine particles of polyvinyl butyral are precipitated in the absence of the above-mentioned water-soluble salt and then heated and aged for a long time at high temperature, coarsening due to agglomeration of the precipitated particles is likely to occur, and in the coarsened particles. However, the water-soluble salts mentioned above have the effect of preventing the coarsening of fine particles and are transparent. There is almost no decrease in properties or thermal stability. As the plasticizer used for the polyvinyl butyral obtained by the method of the present invention, any of those conventionally used as a plasticizer for polyvinyl butyral can be used, such as triethylene glycol di2-ethyl butyrate, triethylene glycol Examples include general-purpose plasticizers such as di-2-ethylhexoate. Furthermore, dibutoxydiethylene glycol adipate and the like are preferably used. The amount of plasticizer added is preferably 30 to 60 parts by weight per 100 parts by weight of polyvinyl butyral. If the plasticizer content is less than 30 parts by weight, the penetration resistance will decrease when used as an interlayer film for laminated glass, and if the plasticizer content exceeds 60 parts by weight, a so-called bleed phenomenon will occur in which the plasticizer seeps onto the film surface, resulting in poor performance of laminated glass. This is because it has an adverse effect on transparency and adhesion when used as an interlayer film. The method of the present invention is configured as described above, and according to the present invention, when an interlayer film for laminated glass is manufactured by adding a plasticizer, an interlayer film for laminated glass with significantly improved self-adhesion at room temperature can be obtained. The resulting polyvinyl butyral can be obtained under industrially advantageous temperature and time conditions as described above, compared to when none of the water-soluble salts of hydrochloric acid, hydrobromic acid, and nitric acid are used. It is. Further, in the present invention, when fine polyvinyl butyral particles are precipitated, it is possible to obtain polyvinyl butyral having good transparency and thermal stability with almost no remaining coarse particles. Examples of the present invention are shown below. % simply means weight %. In addition, each physical property value in Examples was based on the following measuring method. 1 Transparency A sample obtained by sandwiching polyvinyl butyral between two glass plates was placed in a heated oven to melt the polyvinyl butyral, and then allowed to cool at room temperature. The obtained sample was observed under white light, and those without bluishness, turbidity, etc. were evaluated as good. 2. Thermal stability A test tube containing polyvinyl butyral was immersed in a heated oil bath, and the thermal stability was determined to be good if the polyvinyl butyral did not change color even after a predetermined period of time at 120°C. Generally, when neutralization or water washing is incomplete, catalysts such as hydrochloric acid remain in polyvinyl butyral.
When this test is performed, polyvinyl butyral is colored yellow. 3 Self-adhesiveness Add 42 parts by weight of a specified plasticizer to 100 parts by weight of polyvinyl butyral, mix in a Laikai machine, knead using heated rolls, and press to create a uniform film with a smooth surface and a thickness of 0.76 mm. did.
Cut this film into a rectangular shape of 3cm x 10cm, stack the two pieces together and apply a load of 6kg.
It was left for 48 hours in a desiccator kept at a temperature of 20°C. One end of the sample obtained in this way was peeled off from each other, and the peeled film was bent in a 90° direction to form a T-shape. Then, both ends of the peeled film were held in a tensile tester and heated at 20°C. The T-peel strength was measured at a tensile speed of 500 mm/min. 4 Impact resistance 100 parts by weight of polyvinyl butyral and 42 parts by weight of plasticizer
Add and knead parts by weight, and use an extruder to measure the thickness.
0.76 mm of plasticized polyvinyl butyral was obtained.
This film was sandwiched between two glass plates of 3.0 mm thickness and 30 cm x 30 cm, and heated and pressed under conventionally known conditions to obtain a laminated glass. After storing this laminated glass at the specified temperature for more than 8 hours, the outer frame
A steel ball weighing 2.268 kg (5 pounds) was dropped from the specified height onto the center of the laminated glass, which was placed horizontally on a square steel frame with a size of 31 cm x 31 cm, an inner frame of 26 cm x 26 cm, and a height of 20 cm. The height at which 50% of the steel balls penetrate the laminated glass is defined as the penetration resistance. The laminated glass sample used was one in which the pummel value, which will be described later, was set to 6, which is within the range normally used as a product, by using a plasticizer mixed with an appropriate amount of metal soap. Adhesion to 5 laths The laminated glass was adjusted by leaving it at a temperature of -18°C ± 0.6°C for 16 hours, and was crushed by hitting it with a hammer with a head weighing 0.45 kg until the particle size of the glass became 6 mm or less. After the glass has peeled off, the degree of exposure of the film is determined using pre-graded limit samples.
The results were expressed as pummel values according to Table 1.

【table】

[Table] Example 1 Concentrated hydrochloric acid (concentration 35
%) and 15.3 kg of a 16% aqueous solution of calcium bromide were added (the amount of calcium bromide was 19 parts by weight per 100 parts by weight of polyvinyl alcohol charged) for 30 minutes at 13°C with stirring. When 6.7 kg of butyraldehyde was added dropwise, fine white particles of polyvinyl butyral were precipitated. moreover
After adding 7 kg of 35% concentrated hydrochloric acid to bring the pH of the reaction system below 0.5, the temperature was raised to 40°C at a rate of 20°C/hour, and the temperature was maintained for an additional 6 hours for ripening, followed by hydroxylation. Add sodium to neutralize the reaction system and lower the pH.
It was set at 9.6. The time of ripening at a temperature above 30℃ is 6.8
It was time. The obtained resin was washed with water and dried according to a conventional method to obtain a white fine powder. The degree of butyralization of this polyvinyl butyral was 66.4 mol%. Polyvinyl butyral obtained in this way,
Triethylene glycol di-2-ethyl butyrate 42 as a plasticizer to 100 kg of the polyvinyl butyral.
The physical properties of the interlayer film obtained by adding Kg and the laminated glass obtained from the interlayer film were as shown in Table 2. Example 2 Polyvinyl butyral powder was obtained in the same manner as in Example 1 except that aluminum chloride was used instead of calcium bromide. Its physical properties were as shown in Table 2. Example 3 Polyvinyl butyral powder was obtained in the same manner as in Example 1 except that ferric chloride was used instead of calcium bromide. Its physical properties were as shown in Table 2. Example 4 Everything was the same as in Example 1, except that magnesium bromide was used instead of calcium bromide in Example 1, and the reaction system was heated at a rate of 20°C/hour and then kept at an aging temperature of 60°C for 3 hours. A polyvinyl butyral powder was obtained. Its physical properties were as shown in Table 2. Example 5 Everything was the same as in Example 1 except that zinc bromide was used instead of calcium bromide and the reaction system was heated at a rate of 20°C/hour and then kept at an aging temperature of 38°C for 6 hours. A polyvinyl butyral powder was obtained. Its physical properties were as shown in Table 2. Example 6 Polyvinyl butyral powder was obtained in the same manner as in Example 1 except that zinc nitrate was used instead of calcium bromide. Its physical properties were as shown in Table 2. Comparative Example 1 Polyvinyl butyral powder was obtained in the same manner as in Example 1 except that calcium bromide was not added. Its physical properties were as shown in Table 2. Comparative Example 2 Polyvinyl butyral powder was obtained in the same manner as in Example 4 except that magnesium bromide was not added. Its physical properties were as shown in Table 2.

【table】

Claims (1)

[Claims] 1. A method for producing polyvinyl butyral by condensing polyvinyl alcohol and butyraldehyde in an aqueous phase in the presence of an acid catalyst, comprising: 1. A method for producing polyvinyl butyral, which comprises precipitating a precipitate in the presence of one type of polyvinyl butyral, and then aging the reaction system in a strongly acidic region while maintaining a temperature of 30°C or higher. 2. The manufacturing method according to item 1, wherein the amount of the water-soluble salt is 2 parts by weight or more based on 100 parts by weight of the polyvinyl alcohol used. 3. The manufacturing method according to item 1 or 2, wherein the positive component of the water-soluble salt is at least one of magnesium, calcium, zinc, aluminum, iron, and titanium. 4 Items 1 to 3 where the aging time is 1 to 20 hours
1. The manufacturing method according to any one of the above.