A kind of polyvinyl butyral resin and preparation method thereof

Abstract

The invention discloses a polyvinyl butyral resin and a preparation method thereof, belonging to the technical field of polymer materials. The polyvinyl butyral resin in the invention is configured to be dissolved in a 10.0wt% ethanol solution within 30 minutes; the viscosity change rate of the polyvinyl butyral resin configured to be a 10.0wt% ethanol solution after being placed for 24 hours is less than 1.5; the particle size distribution of the polyvinyl butyral resin is in the range of 1.20 to 2.00; the viscosity change is small under high solid content, the polyvinyl butyral resin is configured to be a 10wt% or 20wt% ethanol solution, and the rotation viscosity is tested, V 20wt％ / V 10wt％ <20. In the preparation method provided by the present invention, a hydrogen bond disruptor is added to the polyvinyl alcohol-water system to effectively reduce the hydrogen bond force, and the ceramic slurry has good dispersibility and solubility when prepared, and has good market competitiveness.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a polyvinyl butyral resin and a preparation method thereof. Background Art

[0002] Polyvinyl butyral (PVB) is commonly used for bonding and assembling electronic instrument components, bonding metals to porous materials, and in electronic ceramics due to its excellent bonding properties. The PVB molecular chain contains vinyl alcohol groups (VA units), vinyl butyral (VB units), and vinyl acetate (VAc units). The distribution of these groups within the molecular chain influences the solubility and bonding properties of the PVB resin. In electronic ceramic applications, PVB resin is generally used as a binder to increase the strength of the ceramic after bonding. First, the PVB polymer is dissolved in an organic solvent to form a solution with a certain degree of adhesion. Ceramic powder is then added to this solution and stirred continuously to ensure that the ceramic powder is evenly dispersed in the organic solvent and adheres to each other. Finally, drying forms a tape-cast green body with a certain strength and plasticity. The dissolution rate of the PVB resin in the organic solvent is crucial. A fast dissolution rate and minimal viscosity change facilitate the preparation of slurry compositions and improve production efficiency.

[0003] In the engineering production of PVB resin adhesives for electronic ceramics, to ensure the stability of the reaction system and prevent problems such as agglomeration during resin synthesis, a long, stable reaction at low temperatures of 0-5.0°C is required. However, this results in slow acetalization reaction speed, high energy consumption, and low production efficiency, hindering efficient engineering production. Furthermore, at relatively low condensation reaction temperatures, hydrogen bonding forces are strong in the conventional polyvinyl alcohol-water system, which easily forms strong interchain interactions. Due to the strong hydrogen bonding between and within the polyvinyl alcohol-water molecular chains, intermolecular crosslinking is likely to occur during the acetalization reaction. As the reaction proceeds, crosslinking intensifies, making it difficult for butyraldehyde to react with the encapsulated PVA chains, resulting in uneven acetalization. Ultimately, the resulting PVB resin exhibits low solubility in solution, or even insolubility. If the PVB resin cannot be dissolved evenly and quickly in the alcohol solvent, the ceramic powder cannot be fully dispersed when mixed with the ceramic powder. Ultimately, during the preparation of the ceramic green body, uneven surfaces will appear on the green body, seriously affecting product quality.

[0004] The key to improving the solubility of PVB resin products lies in controlling the uniformity of the acetalization reaction of PVB resin and reducing the degree of cross-linking between PVB molecules. The key to controlling the uniformity of the acetalization reaction of PVB resin is to reduce the hydrogen bond interaction in the reaction system.

[0005] Furthermore, it is necessary to regulate the size of the resin particles, ensuring a wide particle size distribution, good dispersibility in the solvent, and the ability to penetrate the solvent to the particle size, further accelerating the dissolution rate. Some patents report methods for regulating hydrogen bond interactions. For example, patent application publication number CN115677886A discloses the use of inorganic salts to inhibit interchain crosslinking reactions. By introducing ions that can disrupt strong hydrogen bond interactions into the PVA stock solution, crosslinking reactions can be prevented to a certain extent. However, the use of large amounts of inorganic salts makes water washing difficult, and residual trace ions can adversely affect the product's weather resistance and aging resistance. Alternatively, patent application publication number CN103124748A discloses the use of modified polyvinyl alcohol to improve solubility and surface activity in water by changing the polarity of the molecular ends, thereby producing a polyvinyl acetal resin with excellent solubility properties. However, this process is complex and requires high production processes for the PVA raw materials. Moreover, the changes in the molecular end groups require confirmation by nuclear magnetic resonance, which is not conducive to industrial production. Summary of the Invention

[0006] The object of the present invention is to provide a polyvinyl butyral resin and a preparation method thereof, so as to solve the problem of poor solubility of the polyvinyl butyral resin.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A polyvinyl butyral resin, wherein the polyvinyl butyral resin is dissolved in a 10.0 wt% ethanol solution within 30 minutes;

[0009] The viscosity of the polyvinyl butyral resin prepared into a 10.0 wt% ethanol solution is placed for 24 hours and the viscosity change rate is less than 1.5, that is, V 10wt％，24h / V 10wt％ <1.5;

[0010] The particle size distribution of the polyvinyl butyral resin is in the range of 1.20 to 2.00;

[0011] The polyvinyl butyral resin was prepared into 10wt% and 20wt% ethanol solutions, and the rotational viscosity was tested. The ratio between the two (viscosity change rate) was less than 20, that is, V 20wt％ / V 10wt％ <20.

[0012] Furthermore, the polyvinyl butyral resin is used as an adhesive for ink, an adhesive for coating, or an adhesive for ceramic molding.

[0013] A method for preparing polyvinyl butyral resin comprises adding a hydrogen bond breaker in the process of preparing a polyvinyl alcohol solution, wherein the hydrogen bond breaker is a diol.

[0014] Furthermore, the amount of the hydrogen bond disruptor added is 5%-10% of the mass of the polyvinyl alcohol;

[0015] The diol is one of propylene glycol and butylene glycol.

[0016] Butanediol is one of 1,2-butanediol, 1,3-butanediol and 1,4-butanediol;

[0017] Propylene glycol is one of 1,2-propylene glycol and 1,3-propylene glycol.

[0018] Preferably, the butanediol is 1,4-butanediol, and the propylene glycol is 1,3-propylene glycol.

[0019] A method for preparing polyvinyl butyral resin comprises the following steps:

[0020] Step a, dissolving polyvinyl alcohol in water, and then adding a hydrogen bond breaker to obtain a polyvinyl alcohol solution;

[0021] Step b, controlling the temperature of the reaction system to 20-60°C, adding part of butyraldehyde and part of the acidic catalyst to the mixed solution and mixing them evenly, and controlling the temperature of the system to 30-50°C and keeping warm;

[0022] Step c, controlling the system temperature to 20-30°C, and adding the remaining butyraldehyde and the remaining acidic catalyst dropwise; in the present invention, by reacting at 20-30°C, the hydrogen bonding effect is further reduced, and at this temperature, the amount of butyraldehyde and hydrochloric acid added and the time used for adding the materials form a certain degree of acetalization.

[0023] Step d: After the remaining butyraldehyde and the remaining acidic catalyst are added dropwise, the system temperature is controlled to 20-30°C, the reaction is continued by stirring at low temperature, and then the system temperature is controlled to rise gradually to 40-60°C and kept warm for aging;

[0024] Step e: cooling the matured system to below 60° C., adding alkali solution to the system, stirring, and filtering, and washing and drying the solid resin product obtained after filtration to obtain polyvinyl butyral resin.

[0025] Furthermore, the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 5%-15%;

[0026] The degree of polymerization of the polyvinyl alcohol is 200-2500.

[0027] Furthermore, the acidic catalyst is one of hydrochloric acid, sulfuric acid and phosphoric acid.

[0028] Furthermore, the total amount of butyraldehyde is 50%-60% of the mass of polyvinyl alcohol;

[0029] The mass fraction of the acidic catalyst is 31%, and the total amount of the acidic catalyst is 30%-50% of the mass of the polyvinyl alcohol;

[0030] In step b, the portion of butyraldehyde is 5% to 60% of the total amount of butyraldehyde;

[0031] In step b, the portion of the acidic catalyst is 50%-100% of the total amount of the acidic catalyst.

[0032] Furthermore, the holding time in step b is 0.5-2h;

[0033] The reaction time during the low temperature stirring in step d is 30-120 min;

[0034] The gradient heating time in step d is 60-240 min;

[0035] The heat preservation and aging time in step d is 60-240 minutes;

[0036] The time for adding the alkali solution and stirring in step e is 5-30 minutes.

[0037] Beneficial effects of the present invention:

[0038] 1. The present invention changes the polyvinyl alcohol-water system to a polyvinyl alcohol-diol-water ternary system. By adding a hydrogen bond breaker, the hydrogen bonding forces between the polyvinyl alcohol molecular chains are weakened, reducing the degree of intermolecular crosslinking. By introducing a hydrogen bond breaker that disrupts hydrogen bonding interactions into the reaction system and controlling the thermodynamic conditions of the acetalization reaction, the crosslinking reaction during the PVB resin synthesis process is controlled, and the uniformity of the acetalization reaction is regulated, thereby achieving the purpose of regulating the solubility of the product.

[0039] 2. Because PVA molecules contain a large number of hydroxyl groups, strong hydrogen bonding interactions are easily formed between and within the molecules, which increases the degree of crosslinking between PVA molecules. The subsequent acetalization reaction with an acidic catalyst and aldehyde through a temperature-increasing reaction forms PVB with a high degree of intramolecular crosslinking, which is not conducive to dissolution in solvents. The present invention introduces a hydrogen bond breaker into the PVA system. When heated, the hydrogen bonds in the polyvinyl alcohol aqueous solution are reorganized. The previous hydrogen bonding between PVA molecular chains is replaced by hydrogen bonding between PVA molecular chains and aqueous solvents and co-solvents, weakening the hydrogen bonding force and reducing the degree of crosslinking between PVA molecules in the homogeneous phase. In addition, by regulating the synthesis process, the degree of crosslinking between PVB molecular chains is reduced, thereby achieving the purpose of improving the solubility of PVB resin. The hydrogen bonding force can be weakened by increasing the reaction temperature and dilution concentration, that is, by reducing the solid content, thereby reducing intermolecular crosslinking. Adding some butyraldehyde and hydrochloric acid makes it easier to form a certain degree of acetalization within the system, but not to the extent that PVB can precipitate. At the same time, at high temperatures, a small amount of PVB molecular chains crosslink and the degree of stretch between the chains is high, which is more conducive to the further reaction of butyraldehyde with the internally encapsulated PVB with a lower degree of acetalization, promoting the acetalization reaction and making the acetalization more uniform throughout the system. When the reaction temperature is lowered to a low temperature, since a certain degree of acetalization has already been formed in the system at high temperature, the addition of the remaining butyraldehyde and hydrochloric acid at this time will cause the PVB resin to precipitate faster and the particle size to be more uniform.

[0040] 3. In the preparation method of the present invention, when the phase transition critical point is reached, the feed is stopped. The acetalization degree is further increased by holding the mixture at high temperature for a period of time. A small amount of crystals precipitate in the system, resulting in turbidity in the macroscopic appearance. At this point, the remaining butyraldehyde and acid are simultaneously added to further acetalize the precipitated crystals, forming a PVB resin with a wide particle size distribution. A PVB resin with a wide particle size distribution is better dispersed in the solvent, improving solubility.

[0041] 4. The process of the present invention is simple and low-cost. Compared with existing production processes, the present invention does not require the addition of other catalysts or emulsifiers that may affect product performance. The added hydrogen bond breaker does not participate in the reaction and can be washed away by water after the reaction is completed without leaving any residue. At the same time, the process conditions of the present invention are simple, and the solubility of the resin can be controlled without modifying existing production equipment, so that it has better dispersibility, solubility and adhesion when making ceramic slurry, and has good market competitiveness.

[0042] 5. According to the present invention, a polyvinyl acetal resin can be provided. When the resin of the present invention is used as an ink or coating binder, it has good dispersibility in the ink when used at a high concentration.

[0043] 6. According to the present invention, a polyvinyl acetal resin can be provided. When the resin of the present invention is used as an electronic ceramic adhesive, it dissolves quickly in an organic solvent and has no undissolved micelles. It has good adhesion to inorganic materials when preparing ceramic slurry, and the composite system has good uniformity and stability. It can greatly optimize cracking and other phenomena during high-temperature sintering, and can produce highly reliable stacked ceramic capacitors, which greatly improves production efficiency. DETAILED DESCRIPTION

[0044] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a polyvinyl butyral resin, which is prepared by the following steps:

[0047] Step a, dissolving 100 g of polyvinyl alcohol with an average degree of polymerization of 500 (alcoholysis degree of 99.05 wt%) in 1150.0 g of pure water and stirring at 95° C. for 3 h to fully dissolve it to obtain a polyvinyl alcohol stock solution with a solid content of 8.0 wt%; adding 10.0 g of butanediol to the prepared stock solution to obtain a polyvinyl alcohol solution;

[0048] Step b: Cool the polyvinyl alcohol solution prepared above to 30° C., add 6.05 g of butyraldehyde to the system, mix thoroughly, then add 23.59 g of hydrochloric acid with a mass concentration of 36% to 38% to the system at a uniform rate within 30 minutes, and keep warm for 0.5 hours.

[0049] Step c: Cool the system to 20.0°C, and add the remaining 54.45g of butyraldehyde and 23.59g of hydrochloric acid dropwise at a uniform rate over 60min.

[0050] Step d: After all the butyraldehyde and hydrochloric acid were added, the reaction was continued to stir at the same temperature for 30 minutes; then the reaction system was heated to 40° C. at a rate of 5° C. / h and stirred at the same temperature for 2 hours.

[0051] Step e: After stirring at 40° C. for 2 h, 80 mL of 15 wt % sodium hydroxide was added to the reaction solution, and the mixture was stirred for 30 min. The mixture was centrifuged for dehydration and dried to obtain a solid product.

[0052] Example 2

[0053] This example was prepared using the same method and conditions as in Example 1, with the only difference being that propylene glycol was replaced with butanediol in step a.

[0054] Example 3

[0055] This example was prepared using the same method and conditions as Example 1, except that the content of butanediol in step a was changed from 10.0 g to 5.0 g.

[0056] Example 4

[0057] This example was prepared using the same method and conditions as in Example 1, with the only difference being that the butanediol was added after phase change and precipitation in step c instead of in step a.

[0058] Example 5

[0059] This example was prepared according to the same method and conditions as Example 1, except that the mass ratio of polyvinyl alcohol to pure water in step a was 1:12; the amount of butyraldehyde added in the first step in step b was changed from 6.05 g to 12.10 g, and the amount of butyraldehyde added in the second step in step c was changed from 54.45 g to 48.40 g.

[0060] Example 6

[0061] This example was prepared according to the same method and conditions as Example 1, except that the mass ratio of polyvinyl alcohol to pure water in step a was 1:14; the amount of butyraldehyde added in the first step in step b was changed from 6.05 g to 18.15 g, and the amount of acid added in the first step was changed from 47.17 g to 33.02 g; the amount of butyraldehyde added in the second step in step c was changed from 54.45 g to 42.35 g; and the amount of acid added in the second step was changed from 0 g to 14.15 g.

[0062] Example 7

[0063] This example was prepared using the same method and conditions as in Example 1, except that: in step a, the PVA with an average degree of polymerization of 500 was replaced with PVA with an average degree of polymerization of 800;

[0064] Example 8

[0065] This example was prepared using the same method and conditions as in Example 1, except that: in step a, the PVA with an average degree of polymerization of 500 was replaced with PVA with an average degree of polymerization of 1700;

[0066] Comparative Example 1

[0067] This example was prepared using the same method and conditions as in Example 1, except that the amount of butanediol added in step a was changed from 10.0 g to 0 g.

[0068] Comparative Example 2

[0069] This example was prepared using the same method and conditions as in Example 1, except that the amount of butanediol added in step a was changed from 10.0 g to 20.0 g.

[0070] Comparative Example 3

[0071] This example was prepared using the same method and conditions as in Example 1, with the only difference being that the addition of butanediol in step a was changed to step d;

[0072] Comparative Example 4

[0073] This example was prepared by the same method and conditions as in Example 1, with the only difference being that the temperature in steps b and c was lowered from 30.0°C and 20°C to 5.0°C instead.

[0074] Comparative Example 5

[0075] This example was prepared using the same method and conditions as in Example 1, with the only differences being that in step a, PVA with an average degree of polymerization of 500 was replaced with PVA with an average degree of polymerization of 800; and the amount of butanediol added was changed from 10.0 g to 0 g.

[0076] Comparative Example 6

[0077] This comparative example was prepared by the same method and conditions as in Example 1, except that butanediol in step a was replaced with methanol.

[0078] Comparative Example 7

[0079] This example was prepared using the same method and conditions as in Example 1, with the only difference being that in step a, PVA with an average degree of polymerization of 500 was replaced with PVA with an average degree of polymerization of 1700; and the amount of butanediol added was changed from 10.0 g to 0 g.

[0080] <Evaluation method>:

[0081] 1. High solid viscosity ratio: PVB resin was dissolved in ethanol to prepare 10.0wt% and 20wt% solutions. The rotational viscosity was tested at 20.0℃ and the different solid viscosity ratios were calculated.

[0082] 2. Uniformity: PVB resin was dissolved in ethanol at 60° C. to prepare a 10.0 wt % solution. The transmittance of the solution at a wavelength of 660 nm was measured using an ultraviolet spectrophotometer.

[0083] 3. Solubility:

[0084] (1) Dissolution time: PVB resin was dissolved in ethanol solvent to prepare a 10.0 wt% solution, placed in a 20.0°C water bath and stirred at 500 r / min. The time until complete dissolution was recorded.

[0085] (2) Viscosity change after standing: PVB resin was dissolved in ethanol to prepare a 10.0 wt% solution and then left for 24 hours to measure the viscosity change:

[0086] Excellent solubility: V 10wt％，24h / V 10wt％ <1.5;

[0087] General solubility: 1.5 <V 10wt％，24h / V 10wt％ <1.7

[0088] Poor solubility: V 10wt％，24h / V 10wt％ >1.7;

[0089] (3) Dissolution state after 30 minutes.

[0090] 4. Particle size distribution (discreteness): Use a laser particle size analyzer to test and obtain the particle size and discreteness.

[0091] The test results corresponding to Examples 1 to 7 and Comparative Examples 1 to 6 are shown in Tables 1 and 2 below:

[0092] Table 1

[0093]

[0094] Table 2

[0095]

[0096] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0097] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a polyvinyl butyral resin, characterized in that: Adding a hydrogen bond breaker in the process of preparing the polyvinyl alcohol solution, wherein the hydrogen bond breaker is a diol; The preparation method comprises the following steps: Step a, dissolving polyvinyl alcohol in water, and then adding a hydrogen bond breaker to obtain a polyvinyl alcohol solution; Step b, controlling the temperature of the reaction system to 20-60° C., adding part of butyraldehyde and part of the acid catalyst to the mixed solution and mixing them evenly, and controlling the temperature of the system to 30-50° C. for insulation; Step c, controlling the system temperature to 20-30° C., and adding the remaining butyraldehyde and the remaining acid catalyst dropwise; Step d, after the remaining butyraldehyde and the remaining acid catalyst are added dropwise, the system temperature is controlled to 20-30° C., the reaction is continued with low temperature stirring, and then the system temperature is controlled to 40-60° C., and the temperature is kept for aging; Step e, cooling the matured system to below 60° C., adding alkali solution to the system, stirring, filtering, and washing and drying the solid resin product obtained after filtering to obtain polyvinyl butyral resin; The amount of the hydrogen bond destroyer added is 5%-10% of the mass of the polyvinyl alcohol; The total amount of butyraldehyde is 50%-60% of the mass of polyvinyl alcohol; The mass fraction of the acidic catalyst is 31%, and the total amount of the acidic catalyst is 30%-50% of the mass of the polyvinyl alcohol; In step b, the portion of butyraldehyde is 5% to 60% of the total amount of butyraldehyde; In step b, part of the acidic catalyst is 50%-100% of the total amount of the acidic catalyst; The insulation time in step b is 0.5-2h; The time of low temperature stirring reaction in step d is 30-120min; The heat preservation and aging time in step d is 60-240 minutes; The stirring time of adding the alkali solution in step e is 5-30 minutes.

2. The method for preparing a polyvinyl butyral resin according to claim 1, characterized in that: The diol is one of propylene glycol and butylene glycol.

3. The method for preparing a polyvinyl butyral resin according to claim 1, characterized in that: The mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 5%-15%; The degree of polymerization of the polyvinyl alcohol is 200-2500.

4. The method for preparing a polyvinyl butyral resin according to claim 1, characterized in that: The acidic catalyst is one of hydrochloric acid, sulfuric acid and phosphoric acid.

5. A polyvinyl butyral resin, characterized in that Prepared by the preparation method according to any one of claims 1 to 4: The polyvinyl butyral resin is configured to be dissolved in a 10.0 wt % ethanol solution within 30 minutes; The viscosity of the polyvinyl butyral resin in a 10.0 wt% ethanol solution is set aside for 24 hours and the viscosity change rate is less than 1.5; The particle size distribution of the polyvinyl butyral resin is in the range of 1.20 to 2.00; Polyvinyl butyral resin was prepared into 10wt%, 20wt% ethanol solution, and the rotational viscosity and viscosity change rate V were tested. 20wt% / V 10wt% <20.

6. The polyvinyl butyral resin according to claim 5, characterized in that The polyvinyl butyral resin is used as an adhesive for ink, an adhesive for coating or an adhesive for ceramic molding.

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