JPS6358843B2 - - 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 between the interlayer films at room temperature (hereinafter referred to as self-adhesion of the interlayer film) is reduced. The present invention relates to a method for producing porvinyl butyral from which an interlayer film for glass can be obtained. Polyvinyl butyral is widely used as a raw material for interlayer films for laminated glass, adhesives, paints, etc., but when used as interlayer films for laminated glass, properties such as high transparency and heat resistance stability are particularly required. be done. In addition, interlayer films for laminated glass obtained by adding a plasticizer to polyvinyl butyral produced by conventional precipitation or dissolution methods have strong adhesion on the surface of the film, so the films may stick together during winding after film formation. In order to prevent such adhesion, methods such as spraying an anti-tack agent such as sodium bicarbonate on the surface of the film or cooling the interlayer film to a temperature of 10° C. or lower have been carried out. However, since all of these methods have various drawbacks, the emergence of an interlayer film that is substantially free of self-adhesion at room temperature has been awaited. For example, the present inventors precipitated fine precipitates of polyvinyl butyral at a relatively low temperature using a precipitation method, and then raised the temperature of the reaction system and aged the resulting polyvinyl butyral at a high temperature for a long period of time. We have already obtained the knowledge that an interlayer film with reduced self-adhesion can be obtained by adding an agent, but in this case, depending on the aging temperature or time conditions, the precipitated particles may become coarse due to agglomeration, etc. As a result, transparency and heat resistance stability sometimes deteriorated. On the other hand, JP-A No. 54-22489 discloses that polyvinyl butyral is treated at high temperature in an aqueous medium in the presence of 0.01 to 0.5% by weight of an organic sulfonic acid based on the polyvinyl butyral to obtain highly transparent polyvinyl butyral. It is disclosed that a polyvinyl butyral sheet with reduced tackiness can be obtained. However, in this method, it is thought that this is due to the difficulty in sufficiently removing the above amount of organic sulfonic acid from the resin by washing, but the obtained polyvinyl butyral has good transparency and heat resistance stability. was insufficient and could not be used practically as an interlayer film. In view of the above-mentioned current state of the method for producing polyvinyl butyral, the present invention aims to obtain polyvinyl butyral with good transparency and heat resistance under industrially advantageous conditions, and to combine the obtained polyvinyl butyral with a plasticizer. The purpose of the present invention is to provide a method for producing polyvinyl butyral that produces an interlayer film for laminated glass with reduced self-adhesion when producing an interlayer film for glass. In the method of producing polyvinyl butyral by condensing polyvinyl alcohol and butyraldehyde in a medium, a precipitate is precipitated in the presence of a nonionic surfactant, and then the reaction system is heated to a temperature of 30°C or higher in a strongly acidic region. The present invention relates to a method for producing polyvinyl butyral, which is characterized by raising the temperature and aging while maintaining the temperature at 30°C or higher. 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 valatoluenesulfonic 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 15% 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 butyral, but when polyvinyl butyral is used for an interlayer film for laminated glass, the degree of butyralization is 60 to 60. The content is desirably 75 mol %, and for that purpose it is preferable to add 49 to 74 parts by weight of butyraldehyde to 100 parts by weight of polyvinyl alcohol. Examples of nonionic surfactants used in the present invention include polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether (typical example polyoxyethylene alkyl phenyl ether), polyoxyethylene alkyl ester, and polyoxyethylene sorbitan. Examples include polyoxyethylene activators such as fatty acid esters, polyoxyethylene-polyoxypropylene glycol, and polyhydric alcohol activators such as sorbitan fatty acid esters. More specific examples include the general formula RO-(CH ₂ CH ₂ O-) _o H (R is an alkyl group having 4 to 30 carbon atoms, an alkylaryl group having 1 to 30 carbon atoms in the alkyl group, aryl group) or alkyl has 4 to 30 carbon atoms
represents an acyl group, and n represents an integer of 1 to 15. ) are preferably used, and among these, active agents having an HLB (hydrophilic-lipophilic balance) of 14 or less are particularly preferably used. The surfactant represented by the above general formula has excellent compatibility with polyvinyl butyral resin and the plasticizer described below, so even if it remains in the resin without being sufficiently removed in the washing process after the reaction, it becomes transparent. In addition, those with an HLB of 14 or less have particularly good heat resistance stability, so they do not stain the interlayer film or laminated glass. These nonionic surfactants are used alone or in combination, and the amount used is usually determined by the concentration in the final system of the polyvinyl butyral dispersion.
The amount should preferably be 0.03 to 1.0% by weight, but
It is not limited to this range. 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. It is usually 1 to 15 hours, including the time for . When the main purpose is to reduce the self-adhesion of polyvinyl butyral, it is preferable to set the aging temperature to 40° C. or higher or the aging time to 3 hours or longer. 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 exceeding 20°C, then the nonionic surfactant is added, and the reaction system is cooled to produce butyraldehyde. is added to cause a condensation reaction 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 should be a temperature that does not freeze the reaction system, and there are no particular restrictions. Although it is not something that will be done,
Usually a temperature of -6°C or higher is employed. Next, after precipitation of polyvinyl butyral, the reaction system is heated and kept at a temperature of 30°C or higher to further advance the reaction, usually in the presence of a nonionic surfactant, and after ripening, an acid catalyst is used. The reaction product is neutralized with a base, and the reaction product is extracted and washed and purified using conventional methods. When producing polyvinyl butyral with reduced self-adhesiveness, after precipitating fine particles of polyvinyl butyral in the absence of the above-mentioned nonionic surfactant, the reaction system is heated to a temperature exceeding, for example, 40°C. When aged at a low temperature, for example, the precipitated particles tend to become coarse due to agglomeration, resulting in a decrease in transparency and thermal stability.On the other hand, when aged at a low temperature of, for example, around 30°C, coarsening of the particles is less likely to occur. The disadvantage was that it required an extremely long time to ripen. On the other hand, when the nonionic surfactant of the present invention is used, even when aged at temperatures exceeding 40°C,
It is assumed that this is because the nonionic surfactant has the effect of suppressing the coarsening of fine particles, and a resin with good transparency and thermal stability can be obtained. The ripening time is greatly reduced. 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 In addition to general-purpose plasticizers such as di-2-ethylhexoate, dibutoxydiethylene glycol adipate and the like are preferably used. The amount of plasticizer added is 30 to 100 parts by weight of polyvinyl butyral.
60 parts by weight is desirable. 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, the particles are fine and have good transparency and thermal stability, and when an interlayer film for laminated glass is produced by adding a plasticizer, Polyvinyl butyral, which provides an interlayer film for laminated glass with reduced self-adhesion, can be obtained under industrially advantageous temperature and time conditions as described above, compared to when the nonionic surfactant is not used. It is possible. 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 Particle size distribution 100g of polyvinyl butyral is 4, 16, 28,
Classify with sieves with mesh numbers of 48, 60, 80, and 100,
The weight of the resin remaining on each sieve was determined. 2 Degree of butyralization After extracting each stage of ripening and immediately adjusting the pH to 8.6 with a weak alkali, the resulting resin was purified and dried and measured in accordance with JISK67285.52. 3 Thermal Stability Thermal stability was determined to be good if the test tube containing polyvinyl butyral was immersed in a heated oil bath and the polyvinyl butyral did not change color even after a predetermined period of time at 120°C. 4 Transparency of interlayer film 100g of polyvinyl butyral as a plasticizer,
After adding 42 g of triethylene glycol (di2-ethyl butyral) and kneading with a roll, a plasticized polyvinyl butyral interlayer film with a smooth surface and a thickness of 10 mm was obtained using a hot press. The total light transmittance in the visible region of this interlayer film was measured, and a case where the light transmittance was 85% or more was considered to be a pass. 5 Self-adhesiveness of interlayer film Add 42 parts by weight of a specified plasticizer to 100 parts by weight of polyvinyl butyral, mix for 15 minutes in a Raikai machine, and knead for 3 minutes at 120°C using a roll.
A uniform film with a smooth surface and a thickness of 0.76 mm was prepared by pressing at 150° C. and 40 kg/cm ² for 3 minutes.
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. Example 1 15 kg of polyvinyl alcohol with a degree of saponification of 99.4 mol% and a degree of polymerization of 1700 was dispersed in 85 kg of water and heated while stirring to obtain a 15% aqueous solution of polyvinyl alcohol. Add 1.0 kg of hydrochloric acid with a concentration of 35% to this aqueous solution,
As a nonionic surfactant

[Formula] (HLB is 8) Add 700g dissolved in 3Kg of water,
(The surfactant concentration was 0.58% in the final system) When 8.0 kg of butyraldehyde was added dropwise over 30 minutes while stirring at 13°C, white fine particles of polyvinyl butyral were precipitated. Further, 7.6 kg of 35% concentrated hydrochloric acid was added to bring the pH of the reaction system to below 0.5, and the temperature was then raised to 45° C. at a rate of 25° C./hour, and the temperature was maintained at this temperature for an additional 4 hours for ripening. Sodium hydroxide was added to neutralize the reaction system and the pH was adjusted to 8.5. The aging time in a strongly acidic region at a temperature above 30°C was 5 hours. The resulting resin was washed with water and dried in a conventional manner to obtain a fine white powder. The degree of butyralization of polyvinyl butyral at this time was 65.1 mol%. On the other hand, the degree of butyralization of the resin obtained after aging for 0 hours, 2 hours, and 6 hours was measured. The degree of butyralization, resin particle size distribution, thermal stability, transparency and self-adhesion of the plasticized polyvinyl butyral interlayer film at each reaction stage were as shown in Table 1. Note that triethylene glycol di-2-ethyl butyrate was used as the plasticizer. Example 2 In Example 1,

Instead of [formula], C ₁₂ H ₂₅ -O- (CH ₂ CH ₂ -O-) ₂ H (HLB is 5)
A white powder was obtained in the same manner as in Example 1 except that . The degree of butyralization of the obtained resin is
The content was 65.1 mol%, and its physical properties were as shown in Table 1. Example 3 In Example 1, Daiichi Kogyo Seiyaku Co., Ltd.'s nonionic surfactant "Neugen EA50" was used as the surfactant.
A white powder was obtained in the same manner as in Example 1 except that (HLB was 5). The physical properties of the obtained resin were as shown in Table 1. Example 4 As a surfactant in Example 1
A white powder was obtained in the same manner as in Example 1 except that C ₁₁ H ₂₃ COO-(CH ₂ CH ₂ O-) ₄ H (HLB was 6) was used. The physical properties of the obtained polyvinyl butyral were as shown in Table 1. Comparative Example 1 Polyvinyl butyral powder was obtained in the same manner as in Example 1 except that no surfactant was used. Its physical properties were as shown in Table 1. The degree of butyralization was measured after 0 hours, 4 hours, 10 hours, and 12 hours of ripening. Comparative Example 2 In Example 1

75g of dodecylbenzenesulfonic acid (relative to resin) in place of [Formula]
Polyvinyl butyral powder was obtained in the same manner as in Example 1 except that 0.33%) was dissolved in 3 kg of water. Its physical properties were as shown in Table 1. Comparative Example 3 White fine particulate polyvinyl butyral was precipitated in the same manner as in Example 1 except that no surfactant was used. Furthermore, 7.6 kg of 35% concentrated hydrochloric acid was added to bring the pH of the reaction system to 0.5 or less, and then the reaction was carried out at 25°C/hour.
The temperature was raised to 25°C and kept at this temperature for 20 hours. The degree of butyralization of polyvinyl butyral obtained in the same manner as in Example 1 was 64.8 mol%.
Its physical properties were as shown in Table 1. The degree of butyralization was measured after 0 hours, 8 hours, 16 hours, and 20 hours of ripening.

【table】

【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, in which a precipitate is precipitated in the presence of a nonionic surfactant. A method for producing polyvinyl butyral, which is characterized in that the reaction system is then heated to a temperature of 30°C or higher in a strongly acidic region, and then aged by maintaining the temperature at 30°C or higher. 2 The nonionic surfactant has the general formula R—O—(CH ₂ CH ₂ O—) _o H (R is an alkyl group having 4 to 30 carbon atoms, an alkylaryl group in which the alkyl group has a prime number of 1 to 30, or Represents an acyl group whose alkyl group has 4 to 30 carbon atoms, n
represents an integer from 1 to 15. ) The manufacturing method according to item 1, which is a compound represented by: 3. The manufacturing method according to item 1 or 2, wherein the nonionic surfactant has an HLB of 14 or less. 4. The manufacturing method according to any one of Items 1 to 3, wherein the concentration of the nonionic surfactant in the final reaction system is 0.03 to 1.0%. 5. The manufacturing method according to any one of Items 1 to 4, wherein the time for maintaining the temperature at 30°C or higher is 1 to 15 hours.