A method for preparing a polyvinyl butyral-ethanol-toluene mixed solution

Abstract

The present application relates to a kind of polyvinyl butyral-ethanol-toluene mixed solution preparation method, belong to multilayer ceramic capacitor technical field.The polyvinyl butyral-ethanol-toluene mixed solution preparation method of the present application, comprising the following steps: polyvinyl alcohol and n-butanol are reacted in solvent, then the mixed solution of toluene and ethanol is added, continue to react, separate organic phase, i.e.the polyvinyl butyral-ethanol-toluene mixed solution described above;The solvent includes eutectic solvent and water.The mixed solution obtained by the present application can be directly used in sheet multilayer ceramic capacitor casting forming production process.This method reduces the agglomeration of PVB product in the existing production process and the difficulty in separating unreacted PVA raw materials, while avoiding the slow dissolution of solid PVB in the casting forming production process of multilayer ceramic capacitor, time-consuming and laborious, and the defects such as bubble and crack caused by residual PVB micelle of incomplete dissolution.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of multilayer ceramic capacitors, and particularly relates to a preparation method of a polyvinyl butylal-methanol-toluene mixed solution. BACKGROUND

[0002] The tape casting is the key of the multilayer ceramic technology, is the supporting technology of the multilayer ceramic device, and is also the necessary technology for producing electronic components. The tape casting process mainly includes the preparation of slurry, tape casting, drying, debinding and sintering processes, and the preparation of slurry and the control of the tape casting process play a key role. In the tape casting process, firstly, the raw materials such as powder, solvent, dispersant, binder and plasticizer are treated by ball milling to obtain electronic slurry with suitable viscosity and stable dispersion performance, wherein the reagent for dispersion, bonding and inhibiting the sedimentation of inorganic particles is mainly polyvinyl butylal (PVB). The dissolution performance, bonding performance, dispersion performance and sedimentation inhibition performance of PVB are the key to form the electronic slurry with uniformity, stability and good dispersion.

[0003] However, in the actual production process, due to the inherent property limitation of the high molecular polymer, the swelling and dissolution process of PVB powder in the solvent is relatively slow, which seriously restricts the improvement of production efficiency. At the same time, it is often difficult to intuitively judge whether PVB has been completely dissolved in the operation process, and the partially swollen and not completely dissolved PVB is left in the system, which further causes the ceramic substrate to crack and be scrapped in the subsequent sintering process. In addition, in the traditional process of synthesizing PVB with water and ethanol as solvents, whether it is a two-step method or a one-step method, since the acetalization reaction is a dehydration process, a large amount of water exists, which is not conducive to the reaction; and since the product PVB is insoluble in water, as the acetalization degree increases, the solubility of PVA in water gradually decreases, PVB is precipitated from the system, and forms agglomerated blocky substances mixed with part of the unacetalized or low-acetalized PVA, and the product purity is not high; in addition, the catalyst used in the water system is inorganic acid such as sulfuric acid and hydrochloric acid, which can be wrapped in the precipitated PVB particles, causing the post-treatment process to be relatively complex.

[0004] Therefore, it is urgent to explore a simpler preparation method of PVB and overcome the problem of incomplete dissolution of PVB causing the ceramic substrate to be scrapped. SUMMARY

[0005] The purpose of the present application is to overcome the problems existing in the prior art, and to provide a preparation method of a polyvinyl butylal-methanol-toluene mixed solution.

[0006] The present application is realized by the following technical scheme:

[0007] The application aims to provide a preparation method of a polyvinyl butyral-ethanol-toluene mixed solution, comprising the following steps: reacting polyvinyl alcohol (PVA) and n-butanol in a solvent, then adding a mixed solution of toluene and ethanol, continuing the reaction, and separating the organic phase to obtain the polyvinyl butyral-ethanol-toluene mixed solution; the solvent comprises a deep eutectic solvent (DES) and water.

[0008] The method of the application uses DES as a solvent and a catalyst, a small amount of water as a cosolvent, and PVA and n-butyraldehyde are reacted in the DES to obtain polyvinyl butyral (PVB). During the reaction, a toluene-ethanol mixed solution is added. Since the polarity of the product PVB is much lower than that of the raw material PVA, the PVB can be well dissolved in the toluene-ethanol mixed solvent. Therefore, when the PVA acetalization reaction reaches a certain degree, the PVB will be transferred from the strong-polarity deep eutectic solvent into the organic extraction phase, realizing the separation of the product and the raw material, and directly obtaining a PVB-ethanol-toluene mixed solution with a certain mass concentration. After the viscosity is properly adjusted, the solution can be directly applied to the flow casting process of a multilayer ceramic capacitor (MLCC). Moreover, the separated DES can be reused.

[0009] The strong dissolving and catalytic properties of the DES make the PVA dissolved in the DES with a small amount of water, and the acetalization can be quickly carried out after the addition of n-butyraldehyde. The low water content in the DES system is conducive to the acetalization reaction. After the acetalization reaction reaches a certain degree, a good solvent of PVB, i.e., a toluene-ethanol mixed solution, is added, and the high-acetalization PVB greatly reduces the polarity and is transferred from the strong-polarity DES to the toluene-ethanol mixed solution. Since this process is an extraction and dissolution transfer process, and the PVA is insoluble in toluene-ethanol, the product will not wrap the unreacted PVA and acid impurities, and the product purity is high. At the same time, the agglomeration of PVB is avoided, and the acetalization degree is controllable.

[0010] As a preferred embodiment of the preparation method of the polyvinyl butyral-ethanol-toluene mixed solution, the weight average molecular weight of the polyvinyl alcohol is 10000-50000.

[0011] Preferably, the alcoholysis degree of the polyvinyl alcohol is not less than 98%; more preferably, the alcoholysis degree of the polyvinyl alcohol is not less than 99%.

[0012] As a preferred embodiment of the preparation method of the polyvinyl butyral-ethanol-toluene mixed solution, the mass ratio of the polyvinyl alcohol to the solvent is 1:(5-20).

[0013] Preferably, the mass ratio of the polyvinyl alcohol to the solvent is 1:(5-15), and further, the mass ratio of the polyvinyl alcohol to the solvent is 1:(10-15).

[0014] As a preferred embodiment of the preparation method of the polyvinyl butyral-ethanol-toluene mixed solution of the present application, the molar ratio of the n-butyraldehyde to the hydroxyl group in the polyvinyl alcohol is (1-2):1.

[0015] As a preferred embodiment of the preparation method of the polyvinyl butyral-ethanol-toluene mixed solution of the present application, the eutectic solvent comprises choline chloride and p-toluenesulfonic acid, and the mass ratio of the choline chloride to the p-toluenesulfonic acid is 1:(1-3); more preferably, the mass ratio of the choline chloride to the p-toluenesulfonic acid is 1:(1-1.5).

[0016] The present application uses a eutectic solvent as a solvent and a catalyst, preferably, choline chloride as a hydrogen bond acceptor of the eutectic solvent, and p-toluenesulfonic acid as a hydrogen bond donor, and the eutectic solvent formed by the two can swell and dissolve PVA, and a small amount of water added can help the p-toluenesulfonic acid in the system to play a better catalytic role, and under heating conditions, cause the hydroxyl group in the PVA and the aldehyde group of the n-butyraldehyde to undergo acetalization reaction to form PVB.

[0017] Specifically, the preparation method of the eutectic solvent comprises the following steps: heating and mixing choline chloride and p-hydroxybenzoic acid to obtain a eutectic solvent. Preferably, the heating temperature is 100-120°C; the mixing method is preferably stirring mixing; and the mixing time is preferably 1-2h.

[0018] As a preferred embodiment of the preparation method of the polyvinyl butyral-ethanol-toluene mixed solution of the present application, in the solvent, the mass ratio of the water to the eutectic solvent is 1:(5-15); more preferably, the mass ratio of the water to the eutectic solvent is 1:(5-10).

[0019] As a preferred embodiment of the preparation method of the polyvinyl butyral-ethanol-toluene mixed solution of the present application, the temperature of the reaction and the continued reaction is 50-75°C.

[0020] As a preferred embodiment of the preparation method of the polyvinyl butyral-ethanol-toluene mixed solution of the present application, the reaction time is 0.1-0.5h, and the continued reaction time is 0.5-4h.

[0021] As a preferred embodiment of the preparation method of the polyvinyl butyral-ethanol-toluene mixed solution of the present application, the mass ratio of the mixed solution of toluene and ethanol to the polyvinyl alcohol is 200:(10-25), and more preferably, the mass ratio of the mixed solution of toluene and ethanol to the polyvinyl alcohol is 200:(12-20).

[0022] As a preferred embodiment of the preparation method of the polyvinyl butyral-ethanol-toluene mixed solution, the volume ratio of ethanol to toluene in the mixed solution of ethanol and toluene is (3:7)-(7:3); more preferably, the volume ratio of ethanol to toluene is (4:6)-(6:4).

[0023] Preferably, the organic phase is separated and dried to obtain the polyvinyl butyral-ethanol-toluene mixed solution; more preferably, the drying uses anhydrous sodium sulfate.

[0024] Specifically, in the preparation method, the PVB is first heated and fully dissolved in the solvent, and then n-butyl aldehyde is added and stirred for reaction, preferably, the heating temperature is 50-75℃, and the time is 0.5-5h.

[0025] The present application has the following beneficial effects:

[0026] The method for preparing PVB has simple operation, controllable concentration and quality, and can be directly used for the preparation of MLCC electronic paste, thereby avoiding problems such as time-consuming and low efficiency in the on-site use of PVB and difficulty in monitoring the complete dissolution process of PVB, effectively improving the production efficiency, avoiding the phenomenon that PVB which is not completely dissolved but partially swells remains in the system to cause cracks in the ceramic substrate, and improving the product yield. At the same time, the DES after separation of the organic phase can be continuously used, thereby reducing the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The molecular weight distribution diagram of PVB obtained in Examples 1, 2, 4, 5 and 6;

[0028] Figure 2 The thermal decomposition curve of PVB obtained in Example 3;

[0029] Figure 3 The photo of the PVB-toluene-ethanol mixed solution obtained in Example 3 for inhibiting the sedimentation of ceramic powder inorganic particles for MLCC. DETAILED DESCRIPTION

[0030] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in combination with specific examples. Those skilled in the art should understand that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0031] Unless otherwise specified, the test methods used in the examples are conventional methods; and unless otherwise specified, the materials, reagents, etc. used are commercially available.

[0032] Example 1

[0033] A preparation method of a polyvinyl butyral-ethanol-toluene mixed solution, comprising the following steps:

[0034] Choline chloride and p-toluenesulfonic acid are mixed according to a mass ratio of 1:1.6, and a eutectic solvent is obtained by stirring at 110°C for 1h; PVA is uniformly mixed with the solvent (the solvent is obtained by mixing the eutectic solvent and water according to a mass ratio of 10:1) according to a mass ratio of 1:20, and dissolved by stirring at 70°C for 1h; n-butyraldehyde is added, and the reaction is carried out at 70°C for 0.3h; a mixed solution of toluene and ethanol is added, and the reaction is continuously stirred for 0.5h; the organic phase is separated, and anhydrous sodium sulfate is added for drying, to obtain a PVB-ethanol-toluene mixed solution.

[0035] In this embodiment, the PVA has a weight average molecular weight of 31000 and an alcoholysis degree of 99%, is purchased from Macklin, the molar ratio of n-butyraldehyde to the hydroxyl groups in the polyvinyl alcohol is 2:1, the mass ratio of the mixed solution of toluene and ethanol to the PVA is 10, and the volume ratio of ethanol to toluene in the mixed solution of toluene and ethanol is 3:7.

[0036] The acetal degree of the PVB is determined by alcoholysis and sodium hydroxide back titration, and the test result shows that the acetal degree of the obtained PVB is 52%, and the polydispersity index is 1.12.

[0037] Example 2

[0038] A preparation method of a polyvinyl butyral-ethanol-toluene mixed solution, comprising the following steps:

[0039] Choline chloride and p-toluenesulfonic acid are mixed according to a mass ratio of 1:1.4, and a eutectic solvent is obtained by stirring at 110°C for 0.2h; PVA is uniformly mixed with the solvent (the solvent is obtained by mixing the eutectic solvent and water according to a mass ratio of 10:1) according to a mass ratio of 1:20, and dissolved by stirring at 70°C for 1h; n-butyraldehyde is added, and the reaction is carried out at 70°C for 0.3h; a mixed solution of toluene and ethanol is added, and the reaction is continuously stirred for 0.5h; the organic phase is separated, and anhydrous sodium sulfate is added for drying, to obtain a PVB-ethanol-toluene mixed solution.

[0040] In this embodiment, the PVA has a weight average molecular weight of 27000 and an alcoholysis degree of 99%, is purchased from Macklin, the molar ratio of n-butyraldehyde to the hydroxyl groups in the polyvinyl alcohol is 2:1, the mass ratio of the mixed solution of toluene and ethanol to the PVA is 10, and the volume ratio of ethanol to toluene in the mixed solution of toluene and ethanol is 4:6.

[0041] The test result shows that the acetal degree of the obtained PVB is 62%, and the polydispersity index is 1.09.

[0042] Example 3

[0043] A preparation method of a polyvinyl butyral-ethanol-toluene mixed solution, comprising the following steps:

[0044] Choline chloride and p-toluenesulfonic acid are mixed in a mass ratio of 1:1.2, and a eutectic solvent is obtained by stirring at 110 DEG C for 0.3 h; PVA is uniformly mixed with the solvent (the solvent is obtained by mixing the eutectic solvent and water in a mass ratio of 10:1) in a mass ratio of 1:20, and dissolved by stirring at 70 DEG C for 1 h; n-butyraldehyde is added, and the reaction is carried out at 70 DEG C for 0.3 h; a mixed solution of toluene and ethanol is added, and the reaction is carried out by stirring for 0.5 h; the organic phase is separated, anhydrous sodium sulfate is added for drying, and a PVB-ethanol-toluene mixed solution is obtained.

[0045] In the example, the weight average molecular weight of PVA is 27000, the alcoholysis degree is 99%, and the PVA is purchased from Macklin; the molar ratio of the molar amount of n-butyraldehyde to the molar amount of hydroxyl groups in the polyvinyl alcohol is 2:1; the mass ratio of the mixed solution of toluene and ethanol to PVA is 15; and the volume ratio of ethanol to toluene in the mixed solution of toluene and ethanol is 4:6.

[0046] Test results show that the acetal degree of the obtained PVB is 68%, and the polydispersity index is 1.02.

[0047] Example 4

[0048] A preparation method of a polyvinyl butyral-ethanol-toluene mixed solution, comprising the following steps:

[0049] Choline chloride and p-toluenesulfonic acid are mixed in a mass ratio of 1:1.2, and a eutectic solvent is obtained by stirring at 110 DEG C for 0.2 h; PVA is uniformly mixed with the solvent (the solvent is obtained by mixing the eutectic solvent and water in a mass ratio of 12:1) in a mass ratio of 1:15, and dissolved by stirring at 70 DEG C for 1 h; n-butyraldehyde is added, and the reaction is carried out at 70 DEG C for 0.3 h; a mixed solution of toluene and ethanol is added, and the reaction is carried out by stirring for 0.5 h; the organic phase is separated, anhydrous sodium sulfate is added for drying, and a PVB-ethanol-toluene mixed solution is obtained.

[0050] In the example, the number average molecular weight of PVA is 47000, the alcoholysis degree is 99%, and the PVA is purchased from Macklin; the molar ratio of the molar amount of n-butyraldehyde to the molar amount of hydroxyl groups in the polyvinyl alcohol is 2:1; the mass ratio of the mixed solution of toluene and ethanol to PVA is 20; and the volume ratio of ethanol to toluene in the mixed solution of toluene and ethanol is 4:6.

[0051] Test results show that the acetal degree of the obtained PVB is 54%, and the polydispersity index is 1.12.

[0052] Example 5

[0053] A preparation method of a polyvinyl butyral-ethanol-toluene mixed solution, comprising the following steps:

[0054] Choline chloride and p-toluenesulfonic acid were mixed in a mass ratio of 1:1.2, stirred at 110°C for 0.3h to obtain a eutectic solvent, PVA was mixed with the solvent (the solvent was obtained from a eutectic solvent and water in a mass ratio of 8:1) in a mass ratio of 1:10, stirred and dissolved at 70°C for 1h, then n-butyraldehyde was added, reacted at 70°C for 0.3h, then a mixed solution of toluene and ethanol was added, and the stirring reaction was continued for 0.5h, the organic phase was separated, anhydrous sodium sulfate was added and dried to obtain a PVB-ethanol-toluene mixed solution.

[0055] The PVA used in this example had a weight average molecular weight of 27000 and was purchased from Macklin, the molar ratio of n-butyraldehyde to the hydroxyl groups in the polyvinyl alcohol was 1:1, the mass ratio of the mixed solution of toluene and ethanol to PVA was 20, and the volume ratio of ethanol to toluene in the mixed solution of toluene and ethanol was 4:6.

[0056] Test results showed that the acetalization degree of the obtained PVB was 53% and the polydispersity index was 1.09.

[0057] Example 6

[0058] A preparation method of a polyvinyl butyral-ethanol-toluene mixed solution, comprising the following steps:

[0059] Choline chloride and p-toluenesulfonic acid were mixed in a mass ratio of 1:1.2, stirred at 110°C for 0.3h to obtain a eutectic solvent, PVA was mixed with the solvent (the solvent was obtained from a eutectic solvent and water in a mass ratio of 8:1) in a mass ratio of 1:10, stirred and dissolved at 70°C for 1h, then n-butyraldehyde was added, reacted at 70°C for 0.3h, then a mixed solution of toluene and ethanol was added, and the stirring reaction was continued for 0.5h, the organic phase was separated, anhydrous sodium sulfate was added and dried to obtain a PVB-ethanol-toluene mixed solution.

[0060] The PVA used in this example had a weight average molecular weight of 27000 and was purchased from Macklin, the molar ratio of n-butyraldehyde to the hydroxyl groups in the polyvinyl alcohol was 1:1, the mass ratio of the mixed solution of toluene and ethanol to PVA was 20, and the volume ratio of ethanol to toluene in the mixed solution of toluene and ethanol was 4:6.

[0061] Test results showed that the acetalization degree of the obtained PVB was 53% and the polydispersity index was 1.09.

[0062] Example 7

[0063] A preparation method of a polyvinyl butyral-ethanol-toluene mixed solution, comprising the following steps:

[0064] Choline chloride and p-toluenesulfonic acid were mixed in a mass ratio of 1:1.2, stirred at 110°C for 0.3h to obtain a eutectic solvent, PVA was mixed with the solvent (the solvent was obtained by mixing the eutectic solvent and water in a mass ratio of 8:1) in a mass ratio of 1:10, stirred at 75°C for 1h to dissolve, then n-butyraldehyde was added, and the reaction was continued at 75°C for 0.3h, then a mixed solution of toluene and ethanol was added, and the reaction was continued at 75°C for 0.5h, then the organic phase was separated, anhydrous sodium sulfate was added, and the mixture was dried to obtain a PVB-ethanol-toluene mixed solution.

[0065] The PVA used in the example had a weight average molecular weight of 27000 and an alcoholysis degree of 99%, and was purchased from Macklin. The molar ratio of n-butyraldehyde to the hydroxyl groups in the polyvinyl alcohol was 2:1. The mass ratio of the mixed solution of toluene and ethanol to PVA was 15. In the mixed solution of toluene and ethanol, the volume ratio of ethanol to toluene was 6:4.

[0066] The acetal degree of the obtained PVB was 68%, and the polydispersity index was 1.05.

[0067] Example 8

[0068] A method for preparing a polyvinyl butyral-ethanol-toluene mixed solution, comprising the following steps:

[0069] Choline chloride and p-toluenesulfonic acid were mixed in a mass ratio of 1:1.2, stirred at 110°C for 0.3h to obtain a eutectic solvent, PVA was mixed with the solvent (the solvent was obtained by mixing the eutectic solvent and water in a mass ratio of 8:1) in a mass ratio of 1:10, stirred at 75°C for 1h to dissolve, then n-butyraldehyde was added, and the reaction was continued at 75°C for 0.3h, then a mixed solution of toluene and ethanol was added, and the reaction was continued at 75°C for 0.5h, then the organic phase was separated, anhydrous sodium sulfate was added, and the mixture was dried to obtain a PVB-ethanol-toluene mixed solution.

[0070] The PVA used in the example had a weight average molecular weight of 27000 and an alcoholysis degree of 99%, and was purchased from Macklin. The molar ratio of n-butyraldehyde to the hydroxyl groups in the polyvinyl alcohol was 2:1. The mass ratio of the mixed solution of toluene and ethanol to PVA was 13. In the mixed solution of toluene and ethanol, the volume ratio of ethanol to toluene was 5:5.

[0071] The acetal degree of the obtained PVB was 65%, and the polydispersity index was 1.08.

[0072] The molecular weight of the PVB obtained in Examples 1, 2, 4, 5, and 6 was tested, and the test results are shown in Table 1. Figure 1 Table 1 Figure 1It can be seen from the above table that by controlling the molecular weight of PVA and the synthesis process, PVB with specific molecular weight and acetalization degree can be obtained. The molecular weight distribution index of the synthesized PVB is relatively narrow, and the distribution index is between 1.02 and 1.12, and the acetalization degree is controllable. For PVB used for MLCC, specific acetalization degree, molecular weight and its molecular weight distribution are the key to good solubility, dispersibility and thermal decomposition performance.

[0073] Figure 2 The thermal decomposition curve of the PVB prepared in Example 3 is shown in Figure 2. It can be seen from the figure that the thermal decomposition residue of the synthesized PVB is low, and the thermal decomposition residue at 600 degrees Celsius is less than 3%. Figure 2

[0074] Figure 3 The photos of the PVB-toluene-ethanol mixed solution prepared in Example 3 for inhibiting the settlement of ceramic powder inorganic particles for MLCC, and the ratio of ceramic powder inorganic particles to the PVB-toluene-ethanol mixed solution is 30% (g / mL), and 1#, 2# are parallel samples synthesized twice by the same process. It can be seen from the figure that after 7 days of placement, it still has good effect of inhibiting the settlement of ceramic powder. Figure 3

[0075] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.​​

Claims

1. A method for preparing a mixed solution of polyvinyl butyral, ethanol, and toluene, characterized in that, Includes the following steps: Polyvinyl alcohol and n-butyraldehyde are reacted in a solvent, and then a mixed solution of toluene and ethanol is added. The reaction continues, and the organic phase is separated to obtain the polyvinyl butyraldehyde-ethanol-toluene mixed solution. The solvent includes a eutectic solvent and water. The mass ratio of water to the eutectic solvent in the solvent is 1:(5-15). The mass ratio of the polyvinyl alcohol to the solvent is 1:(5-20). The eutectic solvent includes choline chloride and p-toluenesulfonic acid, wherein the mass ratio of choline chloride to p-toluenesulfonic acid is 1:(1-3). The mass ratio of the toluene and ethanol mixture to the polyvinyl alcohol is 200:(10-25).

2. The method for preparing the polyvinyl butyral-ethanol-toluene mixed solution according to claim 1, characterized in that, The weight-average molecular weight of the polyvinyl alcohol is 10,000-50,000.

3. The method for preparing the polyvinyl butyral-ethanol-toluene mixed solution according to claim 1, characterized in that, The molar ratio of the butyraldehyde to the hydroxyl groups in the polyvinyl alcohol is (1-2):

1.

4. The method for preparing the polyvinyl butyral-ethanol-toluene mixed solution according to claim 1, characterized in that, The temperature for the reaction and the continued reaction is 50℃-75℃.

5. The method for preparing the polyvinyl butyral-ethanol-toluene mixed solution according to claim 1, characterized in that, The reaction time is 0.1h-0.5h, and the continued reaction time is 0.5h-4h.

6. The method for preparing the polyvinyl butyral-ethanol-toluene mixed solution according to claim 1, characterized in that, In the mixed solution of toluene and ethanol, the volume ratio of ethanol to toluene is (3:7) to (7:3).

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