JPS6359403B2 - - 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, and a butyralization reaction is carried out at a relatively low temperature of 20°C or less to produce fine precipitates of polyvinyl butyral. This method involves stirring and heating for a period of time. 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 surface of the film or cooling the interlayer film to a temperature of 20° C. or lower. 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 acetalizing polyvinyl alcohol. 30℃ in sexual area
The present invention provides a method for producing polyvinyl butyral with improved self-adhesiveness, which is characterized by maintaining the temperature at a temperature above. The polyvinyl butyral used in the present invention may be polyvinyl acetate as a starting material as long as it is obtained by acetalizing polyvinyl alcohol. Widely used. However, since it is dispersed in the aqueous phase, it is preferred to use polyvinyl butyral which is also produced in the aqueous phase.
In this case, it is particularly preferred industrially to react polyvinyl alcohol and butyraldehyde in the presence of an acid catalyst to precipitate polyvinyl butyral in the aqueous phase, without separating the resin from the reaction system. This means post-treatment in the same aqueous phase. However, it is of course possible to use dried polyvinyl butyral powder obtained by conventionally known methods such as the above-mentioned precipitation method or dissolution method. As for the polyvinyl butyral used in the present invention, when polyvinyl butyral obtained by keeping the temperature at 30°C or higher is used as an interlayer film for laminated glass, it is desirable that the degree of butyralization is 60 to 75 mol%. The degree of oxidation is 95 mol% or more, and
It is preferable that the resin be made from polyvinyl alcohol containing 98 mol% or more, since a resin with good transparency can be obtained in the end. In addition, if the average degree of polymerization of polyvinyl alcohol at this time is too low, the effect of improving self-adhesion when forming an interlayer film by adding a plasticizer is poor, and if it is too high, the viscosity is high, which is inconvenient for industrial acetalization. Therefore, it is usually 800~
3000 are used. The thiocyanate-based compound in the present invention means thiocyanate and its salts, and preferred examples of thiocyanate include sodium thiocyanate,
Examples include alkali metal salts such as potassium thiocyanate, and alkaline earth metal salts such as calcium thiocyanate and magnesium thiocyanate. These thiocyanate compounds may be used alone or in combination, and the amount used is usually such that the concentration in the final polyvinyl butyral dispersion is 0.2 to 10% by weight, but within this range. It is not limited to. In order to prevent the polyvinyl butyral particles from becoming coarse, it is preferable to add the thiocyanate-based compound to the polyvinyl butyral dispersion before a too long period of time has elapsed at a high temperature after polyvinyl alcohol is acetalized. In the present invention, in order to obtain a polyvinyl butyral dispersion in a strongly acidic region, conventionally known hydrochloric acid, sulfuric acid,
Dry polyvinyl butyral may be added to a strongly acidic aqueous phase obtained using an inorganic acid such as nitric acid or an organic acid such as para-toluenesulfonic acid, and after dispersing the polyvinyl butyral in the aqueous phase, An acid may be added or the polyvinyl butyral may be precipitated in a strongly acidic aqueous phase. The strongly acidic region in the present invention is usually PH2 or less, preferably PH1 or less, although it depends on the temperature of the polyvinyl butyral dispersion. Furthermore, when it is necessary to increase the degree of butyralization of polyvinyl butyral, the degree of butyralization can be increased by making a predetermined amount of butyraldehyde exist in the dispersion. In addition, the upper limit of the temperature for ripening polyvinyl butyral is not particularly set, but it is generally set at 90°C or lower, and 30°C or lower.
The time for maintaining the temperature at or above .degree. C. is usually 1 to 20 hours, including the time for raising and lowering the temperature of the dispersion. To produce polyvinyl butyral by the method of the present invention, usually an acid catalyst is added to an aqueous polyvinyl alcohol solution at a temperature exceeding 20°C, the reaction system is then cooled, and butyraldehyde is added to cause a condensation reaction to precipitate polyvinyl butyral. Polyvinyl butyral is prepared by precipitating it at a low temperature such as 20°C or lower and dispersing it in an aqueous phase. 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, a thiocyanic acid compound is added while the pH of the reaction system is 2 or less, the temperature of the reaction system is raised, and the reaction is kept at a temperature of 30°C or higher to further advance the reaction.The catalyst is neutralized with a base and the reaction is generated. The material is extracted and washed and purified using conventional methods. In this way, polyvinyl butyral obtained by acetalization of polyvinyl alcohol is dispersed in an aqueous phase, and the temperature of the dispersion is maintained at 30°C or higher in a strongly acidic region in the presence of a thiocyanate-based compound, thereby making it plastic. When an interlayer film for laminated glass is manufactured by adding a chemical agent, an interlayer film with virtually no self-adhesion at room temperature is obtained, and the reason why polyvinyl butyral with improved self-adhesion is produced is still unknown. Although it is not completely 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. However, when this polyvinyl butyral is dispersed in an aqueous phase and the temperature of the dispersion is maintained at 30°C or higher in a strongly acidic region in the presence of a thiocyanate-based compound, the polyvinyl butyral is formed by a reverse butyralization reaction that occurs in a strongly acidic region. Hydroxyl groups that tend to associate with each other tend to exhibit hydrogen bond association, while the butyralization reaction is more likely to occur selectively on hydrogen groups that do not have a strong tendency to associate than on hydroxyl groups that have a strong tendency to associate. Therefore, as the final equilibrium state approaches, the tendency for hydroxyl groups to remain in a chain within the molecule increases, which increases the rigidity of the resulting polyvinyl butyral, which leads to self-adhesion when used as an interlayer film. It is thought that this contributes to the reduction, or improvement, of sexual performance. The present inventors have found that when a dispersion of polyvinyl butyral is maintained at a relatively high temperature in a strongly acidic region for a long period of time even in the absence of the above-mentioned thiocyanate-based compound, when a plasticizer is added to the polyvinyl butyral, self-adhesion is improved. Although it has already been found that a film can be obtained, the use of the thiocyanate-based compound in the present invention significantly relaxes the above-mentioned temperature and time conditions, which is advantageous in terms of the process. In addition, for example, if fine particles of polyvinyl butyral are precipitated by a precipitation method and then kept at high temperature for a long time in the absence of the thiocyanate-based compound, the precipitated particles tend to become coarse due to agglomeration, etc. The acid catalyst and the base used to neutralize it tend to remain in it, reducing transparency and thermal stability, but the thiocyanate compound has the ability to prevent the coarsening of fine particles. There is almost no reduction in transparency 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 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 preferred. 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 polyvinyl butyral obtained can be produced at industrially advantageous temperatures and temperatures compared to when the above thiocyanate compound is not used.
It can be obtained under the condition of time. Furthermore, when fine polyvinyl butyral particles are used in the present invention, it is possible to obtain polyvinyl butyral with 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 Particle size distribution 100g of polyvinyl butyral is 4, 16, 28, 48,
The resin was classified using sieves with mesh numbers of 60, 80, and 100, and the weight of the resin remaining on each sieve was measured. 2 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. 3. 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, and when this test is performed, polyvinyl butyral is colored yellow. 4 Self-adhesiveness Add 42 parts by weight of the specified plasticizer to 100 parts by weight of polyvinyl butyral, mix for 15 minutes using a Raikai machine, knead for 3 minutes at 120°C using a roll, and then mix at 150°C for 40 minutes.
Press for 3 minutes at Kg/cm ² , smooth surface thickness 0.76mm
A uniform film was created. This film is 3
It was cut into a rectangular shape of cm x 10 cm, and two sheets were stacked together and left in a desiccator kept at a temperature of 20° C. under a load of 6 kg for 48 hours. One end of the sample obtained in this way was peeled off from each other,
After bending the peeled film in the direction of 90℃ to make the entire T-shape, grab both ends of the peeled film with a tensile tester and measure the T-shaped peel strength at 20℃ and a tensile speed of 500mm/min. did. 5 Impact resistance Add and knead 42 parts by weight of plasticizer to 100 parts by weight of polyvinyl butyral, and extrude to a thickness of 0.76 mm.
A 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, place it horizontally on a square iron frame with an outer frame of 31 cm x 31 cm, an inner frame of 26 cm x 26 cm, and a height of 20 cm. A ball was dropped from a specified height onto the center of the laminated glass. 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. 6. Adhesion to glass 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. The degree of exposure of the film after the glass was peeled off was determined using limit samples graded in advance, and the results were expressed as pummel values according to Table 1.

[Table] Example 1 Concentrated hydrochloric acid (concentration 35
%) was added thereto, and 6.4 kg of butyraldehyde was added dropwise over 30 minutes while stirring at 13°C, resulting in the precipitation of white fine particles of polyvinyl butyral. Furthermore, 7 kg of 35% concentrated hydrochloric acid was added and stirred to bring the pH of the reaction system to 0.5 or less, and the calcium thiocyanate was
Add 5.6 kg of 43% aqueous solution and heat at a rate of 20°C/hour.
The temperature was raised to 40°C and the temperature was maintained for an additional 12 hours for ripening, and then sodium hydroxide was added to neutralize the reaction system and the pH was adjusted to 9.6. The time that the temperature was maintained at 30°C or higher was 12.5 hours. 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 63.6%. Polyvinyl butyral obtained in this way,
Triethylene glycol = di-2-ethyl butyrate 4.2 as a plasticizer to 10 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 In the same manner as in Example 1 except that the amount of butyraldehyde was changed to 6.7 kg, white fine particles of polyvinyl butyral were precipitated in the reaction system. Furthermore, a white powder was obtained in the same manner as in Example 1, except that 2.0 kg of a 40% aqueous solution of potassium thiocyanate was added instead of the 43% aqueous solution of calcium thiocyanate, and the temperature was raised to 70°C and maintained for 3 hours. The time that the temperature was maintained at 30°C or higher was 5 hours. The polyvinyl butyral thus obtained had a degree of butyralization of 67.8 mol%, and its physical properties were as shown in Table 2. Example 3 Concentrated hydrochloric acid (concentration 35
%) and 6.7 kg of butyraldehyde was added over a period of 30 minutes while stirring at 13°C, resulting in the precipitation of white fine particles of polyvinyl butyral.
Furthermore, 7 kg of concentrated hydrochloric acid was added and the reaction system was heated to 20°C while stirring.
The temperature was raised to 40°C at a temperature increase rate of 1 hour and kept at that temperature for 3 hours, and then neutralized and washed with water using a conventional method to obtain dried polyvinyl butyral with a degree of butyralization of 65.8 mol% and an average particle size of 170μ. Obtained. 6 kg of 35% hydrochloric acid was added to 84 kg of a 12% aqueous solution of calcium thiocyanate to disperse 10 kg of the above dry polyvinyl butyral (PH of the dispersion was 0.5 or less), and the dispersion was kept at 48°C for 5 hours. After
The mixture was neutralized with sodium hydroxide to bring the pH to 8.6, and the same procedure as in Example 1 was carried out to obtain polyvinyl butyral powder. Its physical properties were as shown in Table 2.

[Table] * Glass containing metallic soap in the interlayer film and having a pummel value of 6 was used as a sample. (The same applies to the following examples and comparative examples.)
Comparative Example 1 Polyvinyl butyral powder was obtained in the same manner as in Example 1 except that calcium thiocyanate was not added. Its physical properties are the third
It was as shown in the table. Comparative Example 2 Polyvinyl butyral powder was obtained in the same manner as in Example 2 except that potassium thiocyanate was not added. Its physical properties were as shown in Table 3. Comparative Example 3 A polyvinyl butyral powder was obtained in the same manner as in Example 5 except that calcium thiocyanate was not used in Example 3. Its physical properties were as shown in Table 3.

【table】

Claims (1)

[Claims] 1. Polyvinyl butyral obtained by acetalization of polyvinyl alcohol is dispersed in an aqueous phase and maintained at a temperature of 30°C or higher in a strongly acidic region in the presence of a thiocyanic acid compound. A method for producing polyvinyl butyral with improved self-adhesion. 2 The thiocyanate-based compound is at least one of thiocyanic acid, an alkali metal salt of thiocyanic acid, and an alkaline earth metal salt of thiocyanic acid.
Manufacturing method described in section. 3. The manufacturing method according to item 1 or 2, wherein the time for maintaining the temperature at 35°C or higher is 1 to 20 hours. 4. The manufacturing method according to any one of Items 1 to 3, wherein the pH in the strongly acidic region is 2 or less. 5. The production method according to any one of Items 1 to 4, wherein the polyvinyl butyral obtained by acetalization is aged in the same aqueous phase without being separated from the reaction system.