Polyvinyl acetal resin for electronic ceramics and preparation method of polyvinyl acetal resin

Abstract

The invention discloses polyvinyl acetal resin for electronic ceramics and a preparation method of the polyvinyl acetal resin, and belongs to the technical field of high polymer materials. The method comprises the following steps: adding a first part of butyraldehyde and aldehyde A into an aqueous solution of polyvinyl alcohol, uniformly mixing, then adding an acid catalyst, and carrying out primary aldolization reaction to obtain a mixture 1; and adding a second part of butyraldehyde and aldehyde B into the mixture 1, uniformly mixing, carrying out secondary aldolization reaction, and adding an alkali solution to adjust the pH value, thereby obtaining the polyvinyl butyral resin. In a step-by-step aldehyde feeding manner, the reaction degree and the reaction rate are controlled by using an alkyl branched chain or aldehyde A containing a benzene ring branched chain, so that the viscosity of the system is slowly increased; and long-chain aldehyde B is utilized to increase the intermolecular distance and reduce cross-linking, and meanwhile, the glass-transition temperature of PVB can be further reduced, so that the long-chain aldehyde B can interact with a plasticizer and a solvent more easily in the pulping process, the compatibility of the long-chain aldehyde B is improved, and uniform preparation of PVB is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a polyvinyl acetal resin for electronic ceramics and a preparation method thereof. Background Art

[0002] With the rapid development of today's information age, electronic components are indispensable. Among them, chip multilayer ceramic capacitors (MLCCs), as the most widely used basic electronic components, account for 93% of the global ceramic capacitor market size. They are known as "industrial rice" and are widely used in consumer electronics, 5G communications, industrial control, automotive electronics, aerospace and military industries. The main preparation process of MLCC devices includes mixing ceramic powder with adhesives and solvents through ball milling, casting to form a ceramic dielectric diaphragm, printing electrodes on it and stacking them in a dislocated manner, and then sintering them at a high temperature once to form a ceramic chip, and then sealing the metal layer (external electrode) at both ends of the chip. Throughout the entire process, polyvinyl butyral (PVB) resin adhesive mainly plays the role of bonding and dispersing ceramic dielectric materials. Whether the slurry is well prepared determines the uniformity and density of the dielectric layer, and determines the yield and performance of the device.

[0003] At present, the main production process of PVB is a one-step precipitation method, that is, PVA is dissolved in water, and at low temperature, a certain amount of hydrochloric acid is directly added in one step to react with n-butyraldehyde to produce a condensation reaction, and then the temperature is raised to a certain temperature for a period of time, and finally the PVB resin is obtained by washing and drying. Under the one-step process, the system viscosity is extremely large when the phase change is precipitated, and materials are still added before and after the phase change, which is easy to produce uneven acetalization during the phase change, and cross-linking reaction is prone to occur, resulting in the occurrence of agglomerates and uneven particle size. Patent document CN117645679A provides a method for preparing polyvinyl alcohol acetal resin, in which aldehyde is defined as any one of formaldehyde, acetaldehyde, butyraldehyde, valeraldehyde, isovaleraldehyde, hexanal, heptaldehyde, octanal, nonanal, decanal, benzaldehyde, and phenylacetaldehyde, and the problem of PVB particle size being large and easy to agglomerate is avoided by adding in steps. However, the aldehyde defined in the method has both a long-chain aldehyde with a high boiling point and a branched-chain aldehyde with a low boiling point, and the influence of temperature and by-products on the reaction rate during the reaction of different aldehydes with PVA is not considered.

[0004] The ceramic diaphragm is prepared by first preparing polyvinyl acetal and solvent into an adhesive solution, then mixing with ceramic powder to prepare a slurry, and finally casting into a film. The structural uniformity of polyvinyl acetal has a very important influence on the mixing uniformity of the ceramic slurry and the density of the film. For example, when the uneven reaction of polyvinyl acetal causes uneven acetalization degree, or uneven cross-linking degree, under the action of the solvent, the difference in interaction with the plasticizer solvent will form an uneven concentration distribution, resulting in defects and pinholes in the ceramic film casting manufacturing. Therefore, optimizing the phase change stage process in the preparation of the adhesive PVB is crucial to whether a ceramic diaphragm with uniform casting thickness and good density can be obtained.

[0005] Compared with conventional film-grade PVB resin, the casting thickness of electronic ceramic diaphragms is extremely thin, only a few microns, which puts higher requirements on the multi-scale uniformity of PVB resin. How to prepare PVB resin powder with uniform acetal degree and uniform macroscopic particles is crucial for the production of electronic ceramic diaphragms and MLCC capacitors. Summary of the invention

[0006] The object of the present invention is to provide a polyvinyl acetal resin for electronic ceramics and a preparation method thereof, so as to solve the problem of uneven reaction rate of PVB in the prior art.

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

[0008] A method for preparing polyvinyl acetal resin for electronic ceramics comprises the following steps:

[0009] Add the first portion of butyraldehyde and aldehyde A to the aqueous solution of polyvinyl alcohol, mix well, then add an acidic catalyst to perform an acetalization reaction to obtain a mixture 1;

[0010] Add the second portion of butyraldehyde and aldehyde B to the mixture 1, mix them evenly for secondary acetalization, and then add an alkaline solution to adjust the pH to 3-4; wash with water, filter, and air-dry to obtain a polyvinyl butyral resin;

[0011] The aldehyde A is selected from the chemical structural formula I: Formula II: Any of the compounds;

[0012] Wherein, x is any integer > 0, at least one of R1, R2, R3, and R4 is -CH3 or -Ph, and the rest are -H;

[0013] y is any integer ≥ 0, and R5 and R6 can be selected from any one of -H, -CH3, and -Ph.

[0014] In one embodiment, aldehydes A include, but are not limited to:

[0015]

[0016] The chemical structural formula of the aldehyde B is Formula III: Wherein z is any integer ≥3, such as 3, 4, 5, 6, 7, 8, etc.

[0017] Furthermore, the polyvinyl alcohol is at least one of polyvinyl alcohols of 0499, 0899, 1599, 1799 or 2699.

[0018] Furthermore, the amounts of the first butyraldehyde and the second butyraldehyde are 15%-25% and 30%-40% of the amount of polyvinyl alcohol, respectively.

[0019] Furthermore, the dosage of aldehyde A is 0.5%-5% of the dosage of polyvinyl alcohol; the dosage of aldehyde B is 1%-4% of the dosage of polyvinyl alcohol.

[0020] Further, the acidic catalyst includes at least one of concentrated hydrochloric acid, concentrated sulfuric acid or concentrated nitric acid;

[0021] And / or, the amount of the acidic catalyst used is 14%-35% of the amount of the polyvinyl alcohol used. Preferably, the amount of the acidic catalyst used is 20%-30% of the amount of the polyvinyl alcohol used.

[0022] Further, the alkaline solution includes at least one of sodium hydroxide and potassium hydroxide solution;

[0023] And / or, after the alkaline solution is added, the reaction system is kept warm for 30-60 minutes.

[0024] Furthermore, the primary acetalization reaction adopts a constant temperature insulation reaction, specifically: the reaction temperature is 0-30°C, and the reaction time is 30-180min.

[0025] Furthermore, the secondary acetalization reaction adopts a gradient heating and insulation reaction, specifically: the temperature is kept at 30-180°C under the temperature condition of 5-20°C, and then the temperature is increased to 40-50°C at a heating rate of 10-30°C / h, and the insulation reaction is carried out for 1-3h.

[0026] A polyvinyl alcohol acetal resin for electronic ceramics is prepared by the above preparation method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention provides a polyvinyl alcohol acetal resin for electronic ceramics and a preparation method thereof, wherein a PVA stock solution is first subjected to a one-step phase change reaction with part of butyraldehyde and aldehyde A under the action of a catalyst, and under the action of controlling the amount of butyraldehyde added, an aldehyde A with an alkyl side chain or a benzene ring side chain is used to control the reaction degree and reaction rate, so that the viscosity of the system rises slowly, and the viscosity surge under the one-step aldehyde process is avoided, which causes uneven material mixing and uneven reaction. The reaction degree and speed are controlled in the early stage of the reaction to avoid drastic phase change and sudden increase in viscosity. Through step-by-step control, as the reaction proceeds, a weak phase change first occurs, so that the viscosity does not surge, but the reaction is mixed and reacted as evenly as possible. During the first weak phase change, other materials will not be added to cause uneven phase change and uneven reaction. After the system is stable, the remaining butyraldehyde and long-chain aldehyde B are slowly added, and the long-chain aldehyde is used to increase the distance between molecules, reduce crosslinking, and further reduce the glass transition temperature of PVB, so that it is easier to interact with plasticizers and solvents during pulping, and increase its compatibility. The pinhole problem caused by local uneven concentration during the pulping, casting and film making process is avoided, thereby further improving the degree of acetal reaction, extending the homogeneous reaction time, and making the viscosity slowly increase during the reaction to reach a certain value and maintain stability. The secondary phase change with a gentle phase change rate keeps the viscosity of the system below 6000cp.

[0029] 2. In the homogeneous reaction stage, the present invention uses the method of adjusting the amount of aldehyde added in steps, so that the viscosity in the initial stage of the condensation reaction will not suddenly rise (the highest critical value exceeds 10000cp) as in other one-step precipitation processes, resulting in the phenomenon of adhesion, agglomeration, and wall hanging in the condensation kettle, resulting in a lot of waste and increased labor costs. The method of the present invention also shortens the viscosity time of the precipitated resin in the heterogeneous stage, avoids the phenomenon of uneven reaction caused by uneven material mixing due to excessive viscosity, and can also ensure the stable production of materials, so that the obtained PVB resin powder is a fine powder with uniform particle size and good dispersibility, thereby preparing a ceramic slurry with uniform distribution of components and no large particle agglomeration, which is beneficial to the casting of the film and significantly improves the quality of the product.

[0030] 3. The present invention does not add any emulsifier or other surfactant, has a simple process, safe operation, is suitable for industrial production, has strong practicability, and the prepared product has good dispersibility and practicability. It can be used to prepare ceramic slurry that is uniformly distributed in electronic ceramics and has no large particle agglomeration, and effectively solves the problem of pinholes and bubbles generated when preparing multi-layer electronic ceramic cast ceramic films. The synthesized ceramic slurry has a lower surface tension, which avoids the growth of agglomerates between ultrafine powders; at the same time, it also improves the bonding force between the diaphragms and improves the reliability of the final chip-type multilayer ceramic capacitor product. DETAILED DESCRIPTION

[0031] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing polyvinyl acetal resin for electronic ceramics comprises the following steps:

[0034] Add 800 kg of polyvinyl alcohol and 7000 kg of deionized water into a dissolving kettle at the same time, heat to 95°C, stir thoroughly to completely dissolve into polyvinyl alcohol solution, and filter to obtain a uniform polyvinyl alcohol aqueous solution;

[0035] Place it in a condensation kettle and cool it to 10°C, add 120kg butyraldehyde (first portion) and 4kg After uniform mixing, 113 kg of 30% concentrated hydrochloric acid was added to carry out an acetal reaction for 30 min to obtain a mixture 1;

[0036] Add 320 kg of butyraldehyde (second portion) and 8 kg of After the feeding is completed and the reaction is carried out at 10°C for 1 hour, the temperature is gradually increased from 10°C to 45°C at a heating rate of 15°C / h and kept warm for 3 hours. After the secondary acetal reaction is completed, sodium hydroxide solution is added to adjust the pH to 3.5, and the temperature is kept warm for 40 minutes. Then, after washing, filtering, and air drying steps, white fine powder polyvinyl alcohol butyral resin is obtained.

[0037] Embodiment 2-8

[0038] A method for preparing polyvinyl acetal resin for electronic ceramics is different from Example 1 in that aldehyde A with a different structure is used (the specific structure is shown in Table 1), and the other steps and parameters remain the same.

[0039] Embodiment 9-10

[0040] A method for preparing polyvinyl acetal resin for electronic ceramics is different from Example 1 in that an aldehyde B with a different structure (specific structure is shown in Table 1) is used, and the other steps and parameters remain the same.

[0041] Embodiment 11

[0042] A method for preparing polyvinyl acetal resin for electronic ceramics, which differs from Example 1 in that the amount of the first portion of butyraldehyde is replaced by 160 kg, the amount of the second portion of butyraldehyde is replaced by 280 kg, and the other steps and parameters remain the same.

[0043] Example 12

[0044] A method for preparing polyvinyl acetal resin for electronic ceramics, which differs from Example 1 in that the amount of the first portion of butyraldehyde is replaced by 176 kg, the amount of the second portion of butyraldehyde is replaced by 264 kg, and the remaining steps and parameters remain the same.

[0045] Embodiment 13

[0046] A method for preparing polyvinyl acetal resin for electronic ceramics, which differs from Example 1 in that the amount of the first portion of butyraldehyde is replaced by 200 kg, the amount of the second portion of butyraldehyde is replaced by 240 kg, and the other steps and parameters remain the same.

[0047] Embodiment 14

[0048] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of aldehyde A is replaced by 16 kg, and the other steps and parameters remain the same.

[0049] Embodiment 15

[0050] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of aldehyde A is replaced by 24 kg, and the other steps and parameters remain the same.

[0051] Example 16

[0052] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of aldehyde B is replaced by 16 kg, and the other steps and parameters remain the same.

[0053] Embodiment 17

[0054] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of aldehyde B is replaced by 32 kg, and the other steps and parameters remain the same.

[0055] Embodiment 18

[0056] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of hydrochloric acid is replaced by 160 kg, and the other steps and parameters remain the same.

[0057] Comparative Example 1

[0058] A method for preparing polyvinyl acetal resin for electronic ceramics, which differs from Example 1 in that the amount of the first portion of butyraldehyde is replaced by 440 kg, the amount of the second portion of butyraldehyde is replaced by 0 kg, and the other steps and parameters remain the same.

[0059] Comparative Example 2

[0060] A method for preparing polyvinyl acetal resin for electronic ceramics, which differs from Example 1 in that the amount of the first portion of butyraldehyde is replaced by 320 kg, the amount of the second portion of butyraldehyde is replaced by 120 kg, and the other steps and parameters remain the same.

[0061] Comparative Example 3

[0062] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of aldehyde A is replaced by 0 kg, and the other steps and parameters remain the same.

[0063] Comparative Example 4

[0064] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of aldehyde A is replaced by 48 kg, and the other steps and parameters remain the same.

[0065] Comparative Example 5

[0066] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of aldehyde B is replaced by 0 kg, and the other steps and parameters remain the same.

[0067] Comparative Example 6

[0068] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of aldehyde B is replaced by 64 kg, and the other steps and parameters remain the same.

[0069] Comparative Example 7

[0070] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of aldehyde A is replaced by 0 kg, the amount of aldehyde B is replaced by 0 kg, and the other steps and parameters remain the same.

[0071] Comparative Example 8

[0072] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of the first portion of butyraldehyde is replaced by 440 kg, and the amount of the second portion of butyraldehyde is replaced by 0 kg;

[0073] The amount of aldehyde A was replaced with 0 kg, the amount of aldehyde B was replaced with 0 kg, and the other steps and parameters remained the same.

[0074] Comparative Example 9

[0075] A method for preparing polyvinyl acetal resin for electronic ceramics, which is different from Example 1 in that the amount of hydrochloric acid is replaced by 320 kg, and the other steps and parameters remain the same.

[0076] The relevant dosage parameters and aldehyde structures of Examples 1-18 and Comparative Examples 1-9 are shown in Table 1.

[0077] Table 1

[0078]

[0079]

[0080]

[0081] Comparative Example 10

[0082] A method for preparing polyvinyl alcohol acetal resin for electronic ceramics is different from that of Example 1 in that the feeding is completed and the reaction is carried out at 20° C. for 4.5 hours to complete the secondary acetal reaction; the other steps and parameters remain the same.

[0083] The performance of the polyvinyl acetal resins obtained in Examples 1-18 and Comparative Examples 1-10 was tested, and the test results are shown in Table 2;

[0084] Table 2

[0085]

[0086]

[0087] It can be seen from the test results in Table 2 that the present invention adopts a method of adjusting the step-by-step aldehyde addition in the homogeneous reaction stage, wherein the first portion of butyraldehyde and the branched aldehyde A are added at the initial stage of the reaction and are uniformly mixed to carry out the first stage reaction, and the remaining second portion of butyraldehyde and the long-chain aldehyde B are added at the later stage of the reaction to regulate the viscosity change speed and size in the phase change stage, as well as the precipitation of phase change particles. The prepared polyvinyl acetal resin has a low discreteness ranging from 0.9 to 1.2, and its dispersibility is relatively better, which effectively improves the uniformity of the product; in addition, the particles are uniform, with a particle size range of 30-100 μm, and are in the form of white fine powder.

[0088] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0089] Although 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 the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing polyvinyl acetal resin for electronic ceramics, characterized in that: The steps include: Adding the first portion of butyraldehyde and aldehyde A to the aqueous solution of polyvinyl alcohol, mixing them evenly, and then adding an acidic catalyst to perform an acetalization reaction to obtain a mixture 1; Add the second portion of butyraldehyde and aldehyde B to the mixture 1, mix them evenly for secondary acetalization, and then add an alkaline solution to adjust the pH to 3-4; wash with water, filter, and air-dry to obtain a polyvinyl alcohol butyral resin; Aldehyde A is selected from the group consisting of the chemical formula I: Formula II: Any of the compounds; In formula I, x is any integer > 0, at least one of R1, R2, R3, and R4 is -CH3 or -Ph, and the rest are -H; In formula II, y is any integer ≥ 0, and R5 and R6 can be selected from any one of -H, -CH3, and -Ph; The chemical structural formula of aldehyde B is Formula III: Wherein z is any integer ≥3.

2. The method for preparing a polyvinyl acetal resin for electronic ceramics according to claim 1, characterized in that: The polyvinyl alcohol is at least one of polyvinyl alcohols of 0499, 0899, 1599, 1799 or 2699.

3. The method for preparing a polyvinyl acetal resin for electronic ceramics according to claim 1, characterized in that: The amounts of the first butyraldehyde and the second butyraldehyde are 15%-25% and 30%-40% of the amount of the polyvinyl alcohol respectively.

4. The method for preparing a polyvinyl acetal resin for electronic ceramics according to claim 1, characterized in that: The dosage of aldehyde A is 0.5%-5% of the dosage of polyvinyl alcohol; the dosage of aldehyde B is 1%-4% of the dosage of polyvinyl alcohol.

5. The method for preparing a polyvinyl acetal resin for electronic ceramics according to claim 1, characterized in that: The acidic catalyst includes at least one of concentrated hydrochloric acid, concentrated sulfuric acid or concentrated nitric acid; And / or, the amount of the acid catalyst used is 14%-35% of the amount of the polyvinyl alcohol used.

6. The method for preparing a polyvinyl acetal resin for electronic ceramics according to claim 1, characterized in that: The alkaline solution includes at least one of sodium hydroxide and potassium hydroxide solution; And / or, after the alkaline solution is added, the reaction system is kept warm for 30-60 minutes.

7. The method for preparing a polyvinyl acetal resin for electronic ceramics according to claim 1, characterized in that: The primary acetalization reaction adopts a constant temperature insulation reaction, specifically: the reaction temperature is 0-30°C, and the reaction time is 30-180min.

8. The method for preparing a polyvinyl acetal resin for electronic ceramics according to claim 1, characterized in that: The secondary acetalization reaction adopts a gradient heating and heat preservation reaction, specifically: the temperature is kept at 30-180°C under the temperature condition of 5-20°C, and then the temperature is increased to 40-50°C at a heating rate of 10-30°C / h, and the temperature is kept for 1-3h.

9. A polyvinyl acetal resin for electronic ceramics, characterized in that: Prepared by the preparation method described in any one of claims 1 to claim 8.

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