阅读说明：本技术 一种聚乙烯醇缩丁醛的制备方法 (Preparation method of polyvinyl butyral ) 是由 不公告发明人 于 2021-08-26 设计创作，主要内容包括：本发明涉及高分子材料制备技术领域,具体涉及一种聚乙烯醇缩丁醛的制备方法,所述制备方法包括如下步骤：(1)聚乙烯醇加入水中,升温至溶解,得到聚乙烯醇溶液；(2)在聚乙烯醇溶液中加入正丁醛,得到混合物A；(3)将催化剂分两次加入混合物A中,反应后得到PVB粗品；(4)将PVB粗品水洗至中性,加入碱,再进行二次水洗,离心、干燥后即得。本发明具有粘度低、粒径小、附着力高的优点。(The invention relates to the technical field of preparation of high polymer materials, in particular to a preparation method of polyvinyl butyral, which comprises the following steps: (1) adding polyvinyl alcohol into water, and heating to dissolve the polyvinyl alcohol to obtain a polyvinyl alcohol solution; (2) adding n-butyraldehyde into a polyvinyl alcohol solution to obtain a mixture A; (3) adding a catalyst into the mixture A twice, and reacting to obtain a PVB crude product; (4) and (3) washing the PVB crude product to be neutral, adding alkali, washing for the second time, centrifuging and drying to obtain the PVB. The invention has the advantages of low viscosity, small particle size and high adhesive force.)

1. A preparation method of polyvinyl butyral is characterized by comprising the following steps:

(1) adding polyvinyl alcohol into water, and heating to dissolve the polyvinyl alcohol to obtain a polyvinyl alcohol solution;

(2) adding n-butyraldehyde into a polyvinyl alcohol solution to obtain a mixture A;

(3) adding a catalyst into the mixture A twice, and reacting to obtain a PVB crude product;

(4) and (3) washing the PVB crude product to be neutral, adding alkali, washing for the second time, centrifuging and drying to obtain the PVB.

2. The preparation method according to claim 1, wherein in the step (1), the polyvinyl alcohol is added into water and soaked for more than 0.5h, the temperature is raised to 90-98 ℃, the polyvinyl alcohol is dissolved for 1.5-2h, and the temperature is kept for 1.5-2h after the polyvinyl alcohol is dissolved, so that 8-11% polyvinyl alcohol solution is prepared.

3. The preparation method according to claim 1, wherein the n-butyraldehyde is added to the polyvinyl alcohol solution in the step (2) when the temperature of the polyvinyl alcohol solution is reduced to 7-10 ℃, and the addition time is 5-10min, so as to obtain the mixture A.

4. The preparation method according to claim 1, wherein in the step (3), the temperature of the mixture A is reduced to 3-6 ℃, part of the catalyst is added within 2-6min, and after the temperature is kept for 25-40min, the rest of the catalyst is added.

5. The process according to claim 4, wherein the catalyst in the range of 1/4 to 1/3 is added for the first time and the remaining catalyst is added for the second time in the step (3); the catalyst is an acid catalyst, preferably at least one of hydrochloric acid, sulfuric acid and maleic acid.

6. The preparation method according to claim 1, wherein the catalyst is added in step (3), and then the low-temperature heat preservation and the high-temperature heat preservation are sequentially carried out, so as to obtain a PVB crude product after the reaction; the low temperature is 8-12 ℃, and the high temperature is not more than 35 ℃.

7. The preparation method according to claim 6, characterized in that, the temperature is kept for 1-1.5h after the catalyst is added in the step (3), and then the temperature is raised to 8-12 ℃ within 1-1.5h, and the temperature is kept for 1-1.5 h; and raising the temperature to 32-35 ℃ within 1-1.5h, preserving the heat for 1-1.5h, and reacting to obtain a PVB crude product.

8. The preparation method according to claim 1, wherein in the step (4), the PVB crude product is washed to be neutral by water, alkali is added to adjust the pH value to 11-13, secondary washing is carried out after the stabilization for 5-8h until the pH value is 8-10, and the PVB crude product is obtained after centrifugation and drying.

9. The production method according to claim 1, wherein the catalyst is added in three times in the step (3).

10. The polyvinyl butyral obtained by the production method as described in any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of preparation of high polymer materials, and particularly relates to a preparation method of polyvinyl butyral.

Background

Polyvinyl Butyral (PVB) is a product of condensation of Polyvinyl alcohol and butyraldehyde under acid catalysis. The PVB molecule contains longer branched chain, so that the PVB has good flexibility, low glass transition temperature and high tensile strength and impact strength. PVB has excellent transparency, good solubility, good light resistance, water resistance, heat resistance, cold resistance and film forming property. The functional group contained in the copolymer can perform various reactions such as saponification of phthalidyl, acetification and sulfonation of hydroxyl, and has high adhesion to materials such as glass and metal (especially aluminum). Therefore, the resin is widely applied to the fields of manufacturing laminated safety glass, printing ink, adhesive, ceramic stained paper, aluminum foil paper, electrical equipment materials, glass fiber reinforced plastic products, fabric treating agents and the like, and becomes an indispensable synthetic resin material.

The ink vehicle, an important component of the printing ink, is the fluid portion of the ink. The rheology, viscosity, drying, film formation and printing properties of the printing inks depend mainly on the binder. The solid components in the ink can be ground in the manufacturing process by the wetting action of the binder, the transfer in the printing process is completed by the viscosity of the binder, and the pigment is protected by drying and film-forming property of the binder on a printed matter to form an ink film with gloss fastness on a print.

Therefore, the binder is the main component of the ink, is the key and core of the ink, and is used as a carrier of the pigment and filler to disperse and support the pigment, so that the pigment and filler and other ink auxiliary agents are fused and connected to form uniform and stable paste ink, and the ink is endowed with proper viscosity, fluidity and transfer performance.

The oily binder prepared from the drying oil alone has the advantages of small molecular weight, low fixation speed and poor gloss, and is easy to emulsify with fountain solution, so that the resin is introduced into the binder of the ink, and various performances of the binder are greatly improved. The vast majority of inks in the prior art are not resin-independent.

In the prior art, the common polyurethane binder has poor surface adhesion to low-polarity substrates, but the problem of low adhesion fastness of the ink to some surface substrates can be effectively solved by using PVB as the binder. Because PVB has a certain amount of hydroxyl, the PVB has excellent adhesive force on the surfaces of ceramics, wood, metal, plastics, fiber products and the like, and can ensure that the ink can be well adhered to a printing stock. Meanwhile, the PVB resin has low transparency and small color number, has small influence on the color display of the printing ink, can obviously improve the glossiness of the printing ink, enables the base material to display brighter color and improves the glossiness of the product.

PVB resins also have a low freezing point, and the addition of inks as a vehicle makes the inks difficult to freeze during use, during winter storage, expands the range of applications for the inks, and also has flow, leveling, and good printing requirements at low temperatures. The good water resistance, excellent anti-blocking property, high fluidity and excellent pigment wettability make the PVB resin series very suitable for being used as a binder of printing ink, and the PVB resin is also an environment-friendly resin, is odorless and tasteless and has wide application range.

However, the PVB resin for ink is required to have a finer and more uniform appearance and particle size, a lower viscosity, good fluidity and a proper amount of hydroxyl groups to ensure the adhesion strength of the ink. The conventional process for producing PVB is generally to directly add hydrochloric acid at one time, the temperature for starting low-temperature reaction is generally above 10 ℃, and the temperature rise reaction is completed in one step, so that the produced PVB is difficult to meet the use requirement of printing ink, which is also a main problem for limiting the application of PVB in the field of printing ink. Therefore, the PVB resin with small particle size, low viscosity and proper hydroxyl ratio has important development and research significance.

Chinese patent application CN110343198A discloses a PVB resin material and a preparation method and application thereof, wherein the preparation method comprises the steps of adding water into PVA, heating to 90-100 ℃ until the PVA is completely dissolved; cooling to 45-55 ℃, adding butyraldehyde, then cooling to 8-15 ℃, adding hydrochloric acid, and keeping the temperature for 0.4-0.8 hours; heating to 70-80 ℃, preserving heat for 1.8-2.2 hours, and then cooling to below 30 ℃; adding water, stirring, draining, adding water, soaking, repeating the operation for multiple times until no acid or chlorine radical is detected, heating to 45-55 ℃, adding sodium hydroxide to adjust the pH value to 8-9, stabilizing for 4-6 hours, cooling, and washing with water until no acid or chlorine radical is detected. The preparation method can obviously improve the performance of the PVB resin material, and the finally prepared PVB film with super-white and bulletproof performance has high transparency, good mechanical performance and good practical application value. However, the PVB resin prepared by the patent application has large particle size, high viscosity and nonuniform particle size, and is not suitable for being used in ink.

Therefore, it is necessary to develop a method for preparing polyvinyl butyral which can solve the above-mentioned technical problems.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a preparation method of polyvinyl butyral with low viscosity, small particle size and high adhesive force, wherein the temperature control adopts gradient heating reaction to ensure that a reaction system gradually reacts at different temperature gradients; the catalyst is added for multiple times, so that the resin is prevented from being too violent and crosslinked in the condensation process, and the particles of the resin are prevented from being coarse and uneven in particle size; the ink has good leveling property when being applied in the ink.

The invention is realized by the following technical scheme:

a preparation method of polyvinyl butyral comprises the following steps:

(1) adding polyvinyl alcohol into water, and heating to dissolve the polyvinyl alcohol to obtain a polyvinyl alcohol solution;

(2) adding n-butyraldehyde into a polyvinyl alcohol solution to obtain a mixture A;

(3) adding a catalyst into the mixture A twice, and reacting to obtain a PVB crude product;

(4) and (3) washing the PVB crude product to be neutral, adding alkali, washing for the second time, centrifuging and drying to obtain the PVB.

The catalyst is added for multiple times, and the reaction rate can be controlled by adding a small amount of catalyst for multiple times, so that the phenomenon that the reaction is too fast to cause the coarsening of resin particles is prevented.

Preferably, the polyvinyl butyral comprises the following raw materials in parts by weight: 30-35 parts of polyvinyl alcohol, 17-20 parts of n-butyl aldehyde and 25-28 parts of catalyst.

Preferably, the polymerization degree of the polyvinyl alcohol is 500 or less, and the alcoholysis degree is 99% or more.

More preferably, the catalyst is an acid catalyst.

More preferably, the acid catalyst is at least one of hydrochloric acid, sulfuric acid, and maleic acid.

More preferably, the mass concentration of the hydrochloric acid is 16-20%.

Preferably, in the step (1), the polyvinyl alcohol is added into water to be soaked for more than 0.5h, the temperature is raised to 90-98 ℃, the polyvinyl alcohol is dissolved for 1.5-2h, and the temperature is kept for 1.5-2h after the polyvinyl alcohol is dissolved, so that 8-11% polyvinyl alcohol solution is prepared.

Preferably, when the polyvinyl alcohol solution in the step (2) is cooled to 7-10 ℃, n-butyraldehyde is added for 5-10min (i.e. the n-butyraldehyde is added within 5-10 min), so as to obtain the mixture A.

Preferably, in the step (3), the temperature of the mixture A is reduced to 3-6 ℃, part of the catalyst is added within 2-6min, and the rest catalyst is added after the temperature is kept for 25-40 min.

More preferably, the total amount of catalyst 1/4-1/3 is added a first time and the remaining catalyst is added a second time in step (3).

Preferably, after the catalyst is added in the step (3), sequentially performing low-temperature heat preservation and high-temperature heat preservation, and obtaining a PVB crude product after reaction; the low temperature is 8-12 deg.C, and the high temperature is no more than 35 deg.C, preferably 32-35 deg.C.

More preferably, after the catalyst is added in the step (3), the temperature is kept for 1 to 1.5 hours, then the temperature is raised to 8 to 12 ℃ within 1 to 1.5 hours, and the temperature is kept for 1 to 1.5 hours; and raising the temperature to 32-35 ℃ within 1-1.5h, preserving the heat for 1-1.5h, and reacting to obtain a PVB crude product.

According to the invention, by controlling the reaction temperature in different stages, the reaction is uniformly and slowly carried out, and the obtained resin is uniform and fine. And the highest reaction temperature of the resin does not exceed 35 ℃, thereby preventing the resin from caking.

Preferably, the PVB crude product is washed with water to be neutral, added with alkali to adjust the pH to 11-13, stabilized for 5-8h, washed with water again to pH 8-10, centrifuged, and dried to obtain the PVB product.

More preferably, the preparation method comprises the following steps:

(1) adding polyvinyl alcohol into water, soaking for more than 0.5h, heating to 90-98 deg.C, dissolving for 1.5-2h, and maintaining the temperature for 1.5-2h to obtain 8-11% polyvinyl alcohol solution;

(2) cooling the polyvinyl alcohol solution to 7-10 ℃, adding n-butyl aldehyde for 5-10min (namely adding n-butyl aldehyde within 5-10 min) to obtain a mixture A;

(3) continuously cooling the mixture A to 3-6 ℃, adding catalyst 1/4-1/3 in total amount within 2-6min, keeping the temperature for 25-40min, adding the rest catalyst, keeping the temperature for 1-1.5h, heating to 8-12 ℃ within 1-1.5h, and keeping the temperature for 1-1.5 h; heating to 32-35 ℃ within 1-1.5h again, preserving the heat for 1-1.5h, and reacting to obtain a PVB crude product;

(4) and (3) washing the PVB crude product to be neutral, adding alkali to adjust the pH value to 11-13, stabilizing for 5-8h, washing for the second time until the pH value is 8-10, centrifuging and drying to obtain the PVB.

Preferably, the catalyst is added in three portions in step (3).

More preferably, the specific process of adding the catalyst in three portions is as follows: and continuously cooling the mixture A to 3-DEG C, adding 1/4-1/3 of total catalyst within 2-6min, keeping the temperature for 25-40min, then adding 1/4-1/3 of total catalyst, and continuously keeping the temperature for 25-40min, and then adding the rest catalyst.

The invention also relates to the polyvinyl butyral prepared by the preparation method.

The invention has the beneficial effects that:

(1) the PVB resin for the printing ink has the characteristics of small particle size and uniform particles, the prepared resin can completely pass through a 40-mesh sieve, the dissolving rate is high when the PVB resin is used in the printing ink, the re-dissolving property is strong, and the plate blocking accident is not easily caused; the PVB resin has good transparency and strong tinting strength in the production of printing ink.

(2) The PVB resin for the printing ink, prepared by the invention, has the characteristics of low viscosity and good fluidity, and the produced printing ink is stable in storage, moderate in viscosity, not easy to precipitate after being stored for a long time, and free from obvious layering phenomena of thickening and thinning.

(3) The PVB resin for the printing ink, prepared by the invention, also has a proper amount of hydroxyl groups, and the higher the hydroxyl group content is, the better the adhesive force is. The PVB resin prepared by the method has high hydroxyl content, so that good adhesive force is generated between the printing ink and a printing stock, and agglomeration cannot be formed between the PVB resins.

Detailed Description

The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. These examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.

Example 1

The method comprises the following specific steps:

(1) dissolving PVA: 30kg of 0599 PVA (0599 represents the polymerization degree of 500 and the alcoholysis degree of 99%) is soaked in pure water for 30min, then heated to 85 ℃ to be dissolved for 1.5h, and then kept warm for 2h after being dissolved, thus preparing 11% PVA solution.

(2) Cooling and adding aldehyde: when the PVA solution system is cooled to 10 ℃, 17kg of n-butyl aldehyde is added, and the aldehyde adding time is 5 minutes.

(3) Adding acid for the first time: the temperature is continuously reduced, and when the temperature is reduced to 6.0 ℃, 9.3kg of hydrochloric acid with the concentration of 16 percent is added within 2 minutes.

(4) And (3) adding acid for the second time: after 25 minutes of incubation, 18.7kg of 16% strength hydrochloric acid were added within 4 minutes.

(5) First temperature rise: after the acid is added, the temperature is kept for 1 hour, then the temperature is raised to 10 ℃ for 1 hour, and the temperature is kept for 1 hour.

(6) And (3) second temperature rise: and raising the temperature again, raising the temperature to 35 ℃ for 1 hour, and preserving the heat for 1 hour to obtain a PVB crude product.

(7) Washing with water: the PVB crude product is washed to be neutral by pure water, the pH is adjusted to 11 by adding 40% sodium hydroxide solution, and after stabilization for 8 hours, the PVB crude product is washed to be pH 8.

(8) Centrifugally drying and drying to obtain the finished product PVB resin.

EXAMPLE 2 catalyst addition in three portions

The method comprises the following specific steps:

(1) dissolving PVA: 30kg of 0599 PVA is soaked in pure water for 30min, heated to 85 ℃, dissolved for 1.5 hours, and then kept warm for 2 hours to prepare 11% PVA solution.

(2) Cooling and adding aldehyde: when the PVA solution system is cooled to 10 ℃, 17kg of n-butyl aldehyde is added, and the aldehyde adding time is 5 minutes.

(3) Adding acid for the first time: the temperature is continuously reduced, and when the temperature is reduced to 6.0 ℃, 9.3kg of hydrochloric acid with the concentration of 16 percent is added within 2 minutes.

(4) And (3) adding acid for the second time: 9.3kg of 16% strength hydrochloric acid are added within 2 minutes after 25 minutes of incubation.

(5) Adding acid for the third time: after the incubation for 25 minutes, 9.3kg of 16% strength hydrochloric acid was added within 2 minutes.

(5) Low-temperature heat preservation: after the acid is added, the temperature is kept for 1 hour, then the temperature is raised to 10 ℃ within 1 hour, and the temperature is kept for 1 hour.

(6) High-temperature heat preservation: and raising the temperature again, raising the temperature to 35 ℃ for 1 hour, and preserving the heat for 1 hour to obtain a PVB crude product.

(7) Washing with water: the PVB crude product is washed to be neutral by pure water, the pH is adjusted to 11 by adding 40% sodium hydroxide solution, and after stabilization for 8 hours, the PVB crude product is washed to be pH 8.

(8) Centrifugally drying and drying to obtain the finished product PVB resin.

Example 3

The method comprises the following specific steps:

(1) dissolving PVA: 30kg of 0599 PVA (0599 represents the polymerization degree of 500 and the alcoholysis degree of 99%) is soaked in pure water for 30min, then heated to 85 ℃ to be dissolved for 1.5h, and then kept warm for 2h after being dissolved, thus preparing 11% PVA solution.

(2) Cooling and adding aldehyde: when the PVA solution system is cooled to 10 ℃, 17kg of n-butyl aldehyde is added, and the aldehyde adding time is 5 minutes.

(3) Adding acid for the first time: the temperature is continuously reduced, and when the temperature is reduced to 6.0 ℃, 7kg of sulfuric acid with the concentration of 16 percent is added within 2 minutes.

(4) And (3) adding acid for the second time: after 25 minutes of incubation, 21kg of 16% strength sulfuric acid were added within 4 minutes.

(5) First temperature rise: after the acid is added, the temperature is kept for 1 hour, then the temperature is raised to 10 ℃ for 1 hour, and the temperature is kept for 1 hour.

(6) And (3) second temperature rise: and raising the temperature again, raising the temperature to 35 ℃ for 1 hour, and preserving the heat for 1 hour to obtain a PVB crude product.

(7) Washing with water: the PVB crude product is washed to be neutral by pure water, the pH is adjusted to 11 by adding 40% sodium hydroxide solution, and after stabilization for 8 hours, the PVB crude product is washed to be pH 8.

(8) Centrifugally drying and drying to obtain the finished product PVB resin.

Comparative example 1 the low temperature reaction temperature was 15 deg.C

(1) Dissolving PVA: 30kg of 0599 PVA is soaked in pure water for 30min, heated to 85 ℃, dissolved for 1.5 hours, and then kept warm for 2 hours to prepare 11% PVA solution.

(2) Cooling and adding aldehyde: when the PVA solution system is cooled to 10 ℃, 17kg of n-butyl aldehyde is added, and the aldehyde adding time is 5 minutes.

(3) Adding acid for the first time: the temperature is continuously reduced, and when the temperature is reduced to 6.0 ℃, 9.3kg of hydrochloric acid with the concentration of 16 percent is added within 2 minutes.

(4) And (3) adding acid for the second time: after 25 minutes of incubation, 18.7kg of 16% strength hydrochloric acid were added within 4 minutes.

(5) Low-temperature heat preservation: after the acid addition was completed, the temperature was close to 15 ℃, the temperature was raised to 15 ℃, and the temperature was maintained for 3 hours.

(6) High-temperature heat preservation: and raising the temperature again, raising the temperature to 35 ℃ for 1 hour, and continuously preserving the heat for 1 hour to obtain a PVB crude product.

(7) Washing with water: the PVB crude product is washed to be neutral by pure water, the pH is adjusted to 11 by adding 40% sodium hydroxide solution, and after stabilization for 8 hours, the PVB crude product is washed to be pH 8.

(8) Centrifugally drying and drying to obtain the finished product PVB resin.

Comparative example 2 high temperature reaction temperature 40 deg.C

The method comprises the following steps:

(1) dissolving PVA, namely soaking 30kg of 0599 PVA in pure water for 30min, heating to 85 ℃, dissolving for 1.5 hours, and preserving heat for 2 hours after dissolving to prepare 11% PVA solution.

(2) Cooling and adding aldehyde: when the PVA solution system is cooled to 10 ℃, 17kg of n-butyl aldehyde is added, and the aldehyde adding time is 5 minutes.

(3) Adding acid for the first time: the temperature is continuously reduced, and when the temperature is reduced to 6.0 ℃, 9.3kg of hydrochloric acid with the concentration of 16 percent is added within 2 minutes.

(4) And adding acid for the second time, namely adding 18.7kg of hydrochloric acid with the concentration of 16% within 4 minutes after the temperature is kept for 25 minutes.

(5) First temperature rise: after the acid is added, the temperature is kept for 1 hour, then the temperature is raised to 10 ℃ for 1 hour, and the temperature is kept for 1 hour.

(6) And (3) second temperature rise: and raising the temperature again, raising the temperature to 40 ℃ for 1 hour, and preserving the heat for 1 hour to obtain a PVB crude product.

(7) Washing with water: the PVB crude product is washed to be neutral by pure water, the pH is adjusted to 11 by adding 40% sodium hydroxide solution, and after stabilization for 8 hours, the PVB crude product is washed to be pH 8.

(8) Centrifugally drying and drying to obtain the finished product PVB resin.

Comparative example 3 catalyst addition in one portion

(1) Dissolving PVA, namely soaking 30kg of 0599 PVA in pure water for 30min, heating to 85 ℃, dissolving for 1.5 hours, and preserving heat for 2 hours after dissolving to prepare 11% PVA solution.

(2) Cooling and adding aldehyde: when the PVA solution system is cooled to 10 ℃, 17kg of n-butyl aldehyde is added, and the aldehyde adding time is 5 minutes.

(3) Adding acid: the temperature is continuously reduced, and when the temperature is reduced to 6.0 ℃, 28kg of hydrochloric acid with the concentration of 16 percent is added within 6 minutes.

(4) First temperature rise: after the acid is added, the temperature is kept for 1.5 hours, then the temperature is raised to 10 ℃ for 1 hour, and the temperature is kept for 1 hour.

(5) And (3) second temperature rise: and raising the temperature again, raising the temperature to 35 ℃ for 1 hour, and preserving the heat for 1 hour to obtain a PVB crude product.

(6) Washing with water: the PVB crude product is washed to be neutral by pure water, the pH is adjusted to 11 by adding 40% sodium hydroxide solution, and after stabilization for 8 hours, the PVB crude product is washed to be pH 8.

(7) Centrifugally drying and drying to obtain the finished product PVB resin.

Comparative example 4 direct temperature reaction

The method comprises the following steps:

(1) dissolving PVA, namely soaking 30kg of 0599 PVA in pure water for 30min, heating to 85 ℃, dissolving for 1.5 hours, and preserving heat for 2 hours after dissolving to prepare 11% PVA solution.

(2) Cooling and adding aldehyde: when the PVA solution system is cooled to 10 ℃, 17kg of n-butyl aldehyde is added, and the aldehyde adding time is 5 minutes.

(3) Adding acid for the first time: the temperature is continuously reduced, and when the temperature is reduced to 6.0 ℃, 9.3kg of hydrochloric acid with the concentration of 16 percent is added within 2 minutes.

(4) And adding acid for the second time, namely adding 18.7kg of hydrochloric acid with the concentration of 16% within 4 minutes after the temperature is kept for 25 minutes.

(5) Heating and preserving heat: after the acid is added, the temperature is kept for 3 hours, then the temperature is raised to 35 ℃ within 1 hour, and the temperature is kept for 1 hour to obtain a PVB crude product.

(6) Washing with water: the PVB crude product is washed to be neutral by pure water, the pH is adjusted to 11 by adding 40% sodium hydroxide solution, and after stabilization for 8 hours, the PVB crude product is washed to be pH 8.

(7) Centrifugally drying and drying to obtain the finished product PVB resin.

Test example

The PVB resins prepared in examples 1-3 and comparative examples 1-4 were subjected to the following performance tests:

(1) viscosity test method

A detection instrument: VT-04 rotary viscometer

A20 g sample was weighed, dissolved in a 50 ℃ water bath using 180g absolute ethanol, and after complete dissolution, the resin viscosity was measured at 23 ℃ using a VT-04 rotational viscometer.

(2) Method for detecting hydroxyl content

Acetic anhydride reacts with hydroxyl groups to obtain acetic acid, and the mass percent of the hydroxyl groups of the polyvinyl acetal resin is determined by an acetoxylation method.

Detection reagent

Pyridine (AR); acetic Anhydride (AR); 1, 2-dichloroethane (AR); phenolphthalein indicator; sodium hydroxide standard solution (0.5 mol/L).

Detection instrument

An electronic balance: the induction is 0.1 mg; grinding the conical flask: 250 mL; an alkali burette: 50 mL; a spherical condenser pipe: 300 mm; a water bath kettle; a pipette: 10mL and 5 mL; a measuring cylinder: 25 mL.

Analytical procedure

1. A sample of polyvinyl acetal (1 g; 0.1 mg; accurate) was weighed out accurately and placed in a 250mL ground flask.

2. A mixture of 90mL pyridine and 10mL acetic anhydride was prepared in a fume hood.

3. To a sample of polyvinyl acetal was added exactly 10mL of the mixture of step 2.

4. The conical bottle was loaded on a condenser tube and heated to 95. + -. 2 ℃ under reflux for 3 hours until the sample was completely dissolved.

5. The mixture of step 4 was cooled to room temperature and then 25mL of 1, 2-dichloroethane was added from the top of the condenser.

6. The condenser tube was removed, the stopper was closed and shaken gently.

7. 5mL of distilled water was added to wash the stopper and the wall of the flask, the mixture was shaken gently and left for 1 hour.

8. Remove 25mL of distilled water with a pipette and rinse along the wall of the flask.

9. Add phenolphthalein indicator 2 mL.

10. Titration was performed with 0.5mol/L sodium hydroxide standard solution.

Presentation of analysis results

1. The reaction product acetic acid was detected using 0.5mol/L NaOH standard solution, and Vs represents the volume of NaOH solution used for neutralizing acetic acid, and the mass of the neutralized polyvinyl acetal sample was E.

2. Let Vb denote the volume of the blank consuming the NaOH standard solution, i.e.the volume of acetic anhydride completely converted to acetic acid in the blank, 1mol of acetic acid corresponding to 1mol of polyvinyl alcohol (44 g).

3. The hydroxyl group content was calculated as follows

In the formula: x-hydroxy content,%;

V_b-titration of the blank consumes mL of the sodium hydroxide standard solution volume;

V_s-titration of sample consumption of sodium hydroxide standard solution volume, mL;

c-actual concentration of sodium hydroxide standard solution, mol/L;

sample mass of E-polyvinylacetal, g;

h-sample volatile content,%.

Two parallel tests are needed, the arithmetic mean value is taken as the test result, and the effective numerical value is regulated to two decimal points according to the GB/T8170.

Tolerance error: the difference between the two values of the parallel test results is not more than 0.3%.

The volatile content of the H sample is detected as follows:

the instrument comprises the following steps: an electronic balance: the induction is 0.1 mg; moisture content tester: the temperature control precision is +/-1 DEG C

The method comprises the following steps: before the moisture meter is used, the power supply is switched on. The temperature was set at 90 ℃ and the detection time was 5 minutes. The tray for placing the powder is placed in the apparatus and returned to zero. Putting a layer of tin-platinum paper on a tray, weighing 5-8 g (plus or minus 0.1g) of a sample, putting the sample in the tray, and pressing a start/stop key to start detection. After the detection is finished, the instrument can make an alarm sound, and the data is read by pressing a start/stop key. Reading the data to obtain the volatile matter of the sample to be measured. Two parallel tests should be performed, and the arithmetic mean value is taken as the test result.

(3) Yield after sieving with a 40-mesh sieve

The weight of the resin powder after passing through a 40-mesh sieve and the specific gravity of the total weight were weighed, and the yield of the PVB resin after passing through a 40-mesh sieve was calculated.

Specific detection results are shown in table 1:

TABLE 1

As shown in table 1, the resin yield was high under the low-temperature reaction conditions, and the resin powder was fine. Since PVA is condensed with butyraldehyde at a high temperature and is likely to undergo intermolecular crosslinking entanglement to increase the viscosity of PVB to be produced and to increase the size of particles, the reaction conditions of the ink resin at a low temperature are preferably controlled to 6 ℃ or lower to make the reaction relatively smooth and uniform. The adding mode of the catalyst can also influence the reaction rate, the catalyst needs to be added in several times, the catalyst is continuously added after partial butyraldehyde is condensed to accelerate the reaction rate, the catalyst cannot be added at one time, the reaction is too fast, the generated resin powder is thicker, and the yield is reduced. Because the polymerization degree of PVA is low, the temperature of high-temperature reaction cannot be too high, and the yield is reduced and the resin quality is influenced because of the easy intermolecular entanglement crosslinking caused by the too high reaction temperature.

The above detailed description is specific to one possible embodiment of the present invention, and the embodiment is not intended to limit the scope of the present invention, and all equivalent implementations or modifications without departing from the scope of the present invention should be included in the technical scope of the present invention.