阅读说明：本技术 一种聚乙烯醇缩丁醛树脂的制备方法 (Preparation method of polyvinyl butyral resin ) 是由 田宗杰 陈建旭 王平林 朱宝华 徐红波 戴伟 沈瑞 于 2020-07-28 设计创作，主要内容包括：本发明公开了一种聚乙烯醇缩丁醛树脂的制备方法,其原料除包括聚乙烯醇、丁醛、酸性催化剂和水外,还包含聚乙烯醇缩丁醛。本发明使用高缩醛率的原料聚乙烯醇缩丁醛颗粒作为凝聚核心,替代初生的PVB,可显著提升成品PVB的缩醛率,又因为反应体系中有原料聚乙烯醇缩丁醛颗粒的存在,有利于聚乙烯醇分子链的舒展,提高缩醛反应的稳定性,一定程度上改善产品缩醛基的分布。(The invention discloses a preparation method of polyvinyl butyral resin, which comprises the following raw materials of polyvinyl alcohol, butyraldehyde, an acid catalyst and water, and also comprises the polyvinyl butyral. The invention uses the raw material polyvinyl butyral particles with high acetalization rate as the condensation core to replace nascent PVB, can obviously improve the acetalization rate of finished PVB, is favorable for the extension of polyvinyl alcohol molecular chains due to the existence of the raw material polyvinyl butyral particles in a reaction system, improves the stability of acetalization reaction, and improves the distribution of acetal groups of the product to a certain extent.)

1. A preparation method of polyvinyl butyral resin comprises the following raw materials of polyvinyl alcohol, butyraldehyde, acid catalyst and water, and is characterized in that: the raw materials also comprise polyvinyl butyral.

2. The method for producing a polyvinyl butyral resin as claimed in claim 1, wherein the raw materials comprise, in parts by mass: 1-6 parts of polyvinyl butyral; 100 parts of polyvinyl alcohol; 40-80 parts of butyraldehyde; 10-40 parts of an acid catalyst; 400 to 1900 parts of water.

3. The method for producing a polyvinyl butyral resin as claimed in claim 1 or 2, characterized in that: the polyvinyl butyral has an average particle size of 20-50 μm and an acetalization rate of not less than 50%.

4. The method for producing a polyvinyl butyral resin as claimed in claim 1 or 2, characterized in that: the acid catalyst is hydrochloric acid with the mass fraction of 10-20%.

5. The method of producing a polyvinyl butyral resin as claimed in claim 1 or 2, characterized by comprising three main steps of dissolution, condensation, and post-treatment.

6. The method for producing a polyvinyl butyral resin as claimed in claim 5, characterized in that: the dissolving step is to completely dissolve polyvinyl alcohol in hot water with the temperature of more than 85 ℃ by stirring and uniformly mix the polyvinyl alcohol and the hot water to form a polyvinyl alcohol aqueous solution; filtering the polyvinyl alcohol aqueous solution, cooling to 65-75 ℃, adding polyvinyl butyral, and fully stirring to uniformly disperse raw material polyvinyl butyral particles in the polyvinyl alcohol aqueous solution to form a mixed solution; and continuously cooling to 45-55 ℃, adding butyraldehyde, and fully stirring to uniformly disperse butyraldehyde in the mixed solution to form a reaction solution.

7. The method for producing a polyvinyl butyral resin as claimed in claim 5, characterized in that: the condensation process is to cool the reaction liquid obtained in the dissolution process to 5-15 ℃, dropwise add an acid catalyst, and keep the temperature for reaction for 0.5-1.5 h; then the temperature of the reaction system is raised to 20-30 ℃ within 1-1.5 h, and the reaction is carried out for 1-2 h under the condition of heat preservation; then the temperature of the reaction system is raised to 40-50 ℃ within 1-1.5 h, and the reaction is carried out for 1-2 h under the condition of heat preservation; then the temperature of the reaction system is raised to 65-75 ℃ within 1-2 h, and the reaction is carried out for 1.5-2.5 h under the condition of heat preservation; after the reaction is finished, reaction mother liquor containing granular PVB semi-finished products is formed.

8. The method for producing a polyvinyl butyral resin as claimed in claim 5, characterized in that: and the post-treatment process is to carry out solid-liquid separation on the reaction mother liquor obtained in the condensation process to obtain a PVB semi-finished product, and then the PVB semi-finished product is washed by deionized water and dried to obtain a finished product PVB.

Technical Field

The invention belongs to the technical field of chemical production, and particularly relates to a preparation method of polyvinyl butyral resin.

Background

Polyvinyl butyral (PVB) resin is a high polymer material generated by condensation reaction of polyvinyl alcohol (PVA) and butyraldehyde under an acidic condition, has superior performances of high transparency, cold resistance, impact resistance, ultraviolet resistance and the like, and has good adhesive force with products such as metal, glass, wood, ceramic, fiber and the like. The film made of PVB resin can be used as an interlayer material of safety glass, and the prepared safety glass has good transparency, high impact strength and high safety, and can be widely used in the fields of aviation, automobiles and buildings. PVB can be used for preparing anticorrosive coatings in the coating industry, and has strong antirust capacity; PVB can also be used for preparing metal primer coating and cold-proof paint with good adhesive force and water resistance. In addition, PVB is widely used in the industrial fields of ceramics, resins, adhesives, textiles, food, paper and the like.

The condensation reaction mechanism for producing PVB is as follows: in the presence of a catalyst [ H⁺]Under the action of (C) < H >⁺]Attack carbonyl in butyraldehyde molecules to generate active groups with positive electricity, carbon with positive electricity in the active groups attacks hydroxyl in PVA, the generated product unstably removes a molecule of water, the positive electricity is transferred to carbon atoms after dehydration, then another adjacent hydroxyl is attacked, PVB with a stable six-membered ring structure is generated, and [ H ] is released at the same time⁺]。

The preparation method of PVB is mainly divided into three methods according to the change of a reaction system in the reaction process: 1. a precipitation method, wherein homogeneous PVA aqueous solution reacts with butyraldehyde, generated PVB is slowly separated out to form precipitate, and the system is changed from homogeneous phase to heterogeneous phase; 2. homogeneous phase process, homogeneous PVA solution reacts with butyraldehyde in a suitable solvent, and the resulting PVB dissolves in the solvent; 3. in the one-step process, polyvinyl acetate hydrolysis and acetalization of PVA are carried out simultaneously. The three reaction processes have advantages and disadvantages: 1. in the production process of the precipitation method, PVB is easy to recover and wash, but the reaction temperature and time of each stage need to be accurately controlled, or intermolecular crosslinking and agglomeration are easy to occur, and the acetal group of the finished PVB is not uniformly distributed and has low acetal rate; 2. in the production process of the homogeneous phase method, a large amount of organic solvent is needed, the cost is high, the industrial implementation is not facilitated, the separation and purification of the resin and the solvent are difficult, the resin is easy to color, and the thermal stability is poor; 3. although PVB with high acetalization rate can be obtained in the one-step method, the PVB is easy to wrap a catalyst and wash off, acetal groups are distributed unevenly, the product performance is unstable, the requirement on equipment is high, and the reaction condition is harsh.

From the viewpoint of easy industrialization, the U.S. DuPont company and most of domestic manufacturers generally produce the polyvinyl butyral resin by a precipitation method. The production process comprises the following steps: dissolving PVA in water, carrying out aldol condensation reaction with butyraldehyde under an acidic condition to generate PVB precipitate, adding alkali for neutralization, washing with water and drying to obtain a finished product PVB, namely, carrying out five main procedures of dissolution, condensation, neutralization, washing with water, drying and the like.

In the earlier stage of the condensation reaction, the reactant PVA has good water solubility and can be completely dissolved in solvent water, and the reaction of the PVA and the butyraldehyde is carried out in a homogeneous phase. When the reaction is carried out to a certain degree, the number of hydroxyl groups on PVA macromolecules is less than a critical value, namely the reaction is carried out until the acetal group content on a PVA molecular chain reaches about 40 percent, the polarity of the generated primary PVB is reduced, the intersolubility with water is reduced (similar compatibility principle), the primary PVB is separated out to form granular solids, and the reaction is changed from homogeneous reaction to heterogeneous reaction. At this time, butyraldehyde cannot enter the inside of the precipitated particles to perform acetalization reaction with hydroxyl groups, and only proceeds on the surface of the solid particles, resulting in a low acetalization ratio of the finished PVB product and an uneven distribution of acetal groups.

Disclosure of Invention

Based on the above-mentioned disadvantages and drawbacks of the prior art, an object of the present invention is to provide a method for producing a polyvinyl butyral resin having a controlled acetal ratio and a uniform distribution of acetal groups.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of polyvinyl butyral resin comprises the following steps of preparing polyvinyl butyral resin;

furthermore, the raw materials comprise the following components in addition to the polyvinyl butyral: polyvinyl alcohol, butyraldehyde, an acid catalyst and water.

In the prior art, the polarity of primary PVB generated by a precipitation method is reduced, the intersolubility of the primary PVB with water is reduced, solid particles are formed and separated out from a system, and according to the similarity principle, when polyvinyl butyral exists in a reaction system, nascent PVB can gather by taking the polyvinyl butyral as a center. Along with the increase of the usage amount and the reduction of the particle size of the raw material polyvinyl butyral, the specific surface area of the raw material polyvinyl butyral in a reaction system is increased, the thickness of primary PVB accumulated on the surface of raw material polyvinyl butyral particles is reduced, butyraldehyde can perform acetalization reaction with unreacted hydroxyl without entering the interior of the reaction particles, the acetalization rate of the finished product polyvinyl butyral resin can be effectively improved, and the distribution of acetal groups is more uniform. However, in actual use, the larger the amount of polyvinyl butyral used as a raw material and the smaller the particle size, the poorer the dispersibility thereof in the reaction system, and from the viewpoint of reducing the production cost, improving the production efficiency and the production stability, the amount of polyvinyl butyral added as the raw material is from 1 to 6 parts; the average grain diameter is 20-50 μm; the acetalization rate is not less than 50%.

PVB is generally a linear condensation polymer whose molecular weight is largely dependent on the degree of polymerization of the PVA starting material, with greater degrees of polymerization of PVA producing greater molecular weights of PVB. PVB has wide application, and the PVB with the polymerization degree of 300 to 3000 can be used for the production of PVB by selecting the raw material PVA with different polymerization degrees according to different applications. In the present invention, the amount of the polyvinyl alcohol as the raw material is 100 parts.

Theoretically, when polyvinyl alcohol and butyraldehyde are subjected to complete acetalization, the mass ratio of butyraldehyde to polyvinyl alcohol is 0.818. Because of the limitation of the production process, in the process of producing PVB by a precipitation method, the consumption of butyraldehyde is less than a theoretical value, the difficulty and the cost of post-treatment are increased by excessive butyraldehyde, the utilization rate of the butyraldehyde and the acetal rate of a PVB product are comprehensively considered, and the addition amount of the butyraldehyde in the raw materials is 40-80 parts;

in the acetalization reaction of polyvinyl alcohol and butyraldehyde, the presence of an acidic catalyst is crucial, and the acidic catalyst not only influences the reaction rate in the initial stage of the reaction, but also influences the particle size of PVB generated in the middle and later stages, and also has a certain influence on the adhesion degree among PVB particles, thereby influencing the acetalization rate of a final PVB product. When the addition amount of the acidic catalyst is small, the pH value of the reaction system is high, the acetalization reaction cannot be carried out or the reaction rate is slow; when the amount of the acidic catalyst to be added is too large, the initial acetalization reaction is severe, the primary PVB coagulates too quickly, the acetalization reaction tends to be nonuniform, the acetalization ratio of the product decreases, the particle size increases, and the corrosion of the reaction equipment becomes severe. In the production of PVB, the acidic catalyst can be inorganic acid such as hydrochloric acid, sulfuric acid and the like, and can also be organic acid such as methyl benzene sulfonic acid, acetic acid and the like. The production cost and the easy operability are comprehensively considered, the local acidic catalyst concentration of the reaction system is prevented from being too high, the acidic catalyst used in the invention is hydrochloric acid with the mass fraction of 10-20%, and the addition amount of the acidic catalyst is 10-40 parts.

The water is used as solvent, and its main function is to dissolve polyvinyl alcohol at a certain temp. to prepare the aqueous solution of polyvinyl alcohol with a certain concentration, in the invention, the water consumption is 400-1900 portions.

The preparation method of the polyvinyl butyral resin needs three main processes of dissolution, condensation and post-treatment. The method comprises the following specific steps:

a dissolving process: completely dissolving polyvinyl alcohol in hot water with the temperature of more than 85 ℃ by stirring and uniformly mixing to form a polyvinyl alcohol aqueous solution; filtering the polyvinyl alcohol aqueous solution, cooling to 65-75 ℃, adding polyvinyl butyral, and fully stirring to uniformly disperse raw material polyvinyl butyral particles in the polyvinyl alcohol aqueous solution to form a mixed solution; and continuously cooling to 45-55 ℃, adding butyraldehyde, and fully stirring to uniformly disperse butyraldehyde in the mixed solution to form a reaction solution.

A condensation process: cooling the reaction liquid to 5-15 ℃, dropwise adding an acid catalyst, and reacting for 0.5-1.5 h under heat preservation; then the temperature of the reaction system is raised to 20-30 ℃ within 1-1.5 h, and the reaction is carried out for 1-2 h under the condition of heat preservation; then the temperature of the reaction system is raised to 40-50 ℃ within 1-1.5 h, and the reaction is carried out for 1-2 h under the condition of heat preservation; then the temperature of the reaction system is raised to 65-75 ℃ within 1-2 h, and the reaction is carried out for 1.5-2.5 h under the condition of heat preservation; after the reaction is finished, reaction mother liquor containing granular PVB semi-finished products is formed.

And a post-treatment process: and carrying out solid-liquid separation on the reaction mother liquor to obtain a PVB semi-finished product, and washing and drying the PVB semi-finished product by deionized water for multiple times to obtain a finished product PVB.

Compared with the prior art, the invention has the beneficial effects that:

1. the raw material polyvinyl butyral particles with high acetalization rate are used as a condensation core to replace nascent PVB, so that the acetalization rate of finished PVB can be obviously improved, and because the raw material polyvinyl butyral particles exist in a reaction system, the extension of polyvinyl alcohol molecular chains is facilitated, the stability of acetalization reaction is improved, and the distribution of acetal groups of the product is improved to a certain extent.

2. The starting polyvinyl butyral can be produced by a solution method, in which case the distribution of acetal groups is uniform in the starting polyvinyl butyral as a core of condensation. In the reaction process of the invention, the nascent PVB is condensed by taking the nascent PVB as a center, and the butyraldehyde can carry out an acetal reaction with hydroxyl in the polyvinyl alcohol without entering the interior of a product, so that the distribution of acetal groups in the finished PVB can be obviously improved, and the utilization rate of the butyraldehyde is higher.

3. The technical scheme of the invention can be used for producing various polyvinyl butyral resins with low viscosity, high viscosity and the like. The raw materials in the system are simple, and the application range is wide.

Detailed Description

The process for producing a polyvinyl butyral resin of the present invention is further illustrated by the following specific embodiments, which are described herein for the purpose of illustration and explanation only and are not intended to limit the present invention. All other embodiments, which can be obtained by a skilled person without making creative efforts based on the embodiments of the present invention, belong to the protection scope of the present invention.