Impurity removal process of adhesive for preparation of multilayer ceramic capacitor
The dialysis bag operation simplifies the manufacturing process of multilayer ceramic capacitors, solving the problems of large water consumption and impurity residue in traditional water washing processes. It achieves efficient and environmentally friendly impurity removal, improving the production quality and economic benefits of capacitors.
Patent Information
- Application Number
- CN202511351560.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-22
- Publication Date
- 2025-11-25
AI Technical Summary
Traditional water washing processes in the fabrication of multilayer ceramic capacitors involve large water consumption and leave behind impurities, affecting production yield and sintering process.
After polyvinyl alcohol acetalization, dialysis is performed through a dialysis bag. Membrane separation technology is used to remove salts, surfactants, and excess unreacted aldehyde impurities, simplifying the impurity removal process.
Significantly reduces water consumption, improves desalination efficiency, increases production efficiency, reduces costs, and ensures capacitor yield.
Smart Images
Figure CN121006174A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of precision machining technology of electronic ceramic materials, and relates to a process for removing impurities from adhesives used in the fabrication of multilayer ceramic capacitors. Background Technology
[0002] Capacitors, as one of the three fundamental components, play a crucial role in modern industry. They are primarily used for storing and releasing electrical energy, and are applied in power supply filtering, signal filtering, signal coupling, harmonic filtering, compensation, charging and discharging, energy storage, and DC circuit isolation. Capacitors are classified according to their constituent materials, mainly into ceramic capacitors, aluminum electrolytic capacitors, and tantalum electrolytic capacitors, among which ceramic capacitors are the most widely used. Ceramic capacitors are further divided into single-layer ceramic capacitors and multilayer ceramic capacitors based on the number of stacked layers. Due to their high stability and miniaturization, multilayer ceramic capacitors are widely used in consumer electronics, automotive electronics, and communication equipment, gradually replacing traditional disc ceramic capacitors and becoming the mainstream ceramic capacitor in the market. In the manufacturing of ceramic capacitors, in addition to ceramic powder, binders are also used. These binders act like solvents during the slurry preparation process and must be residue-free during subsequent sintering, thus placing high technical requirements on the binders. To remove salts, surfactants, and excess unreacted aldehydes and other residues, appropriate impurity removal processes are required. The conventional method is to use large amounts of water for washing, i.e., water washing.
[0003] Traditional water washing processes have drawbacks such as high water consumption and easy residue of impurities during production. The former has a significant impact on cost, while the latter has a serious impact on the subsequent sintering process. Incomplete impurity removal will lead to a decrease in the yield of capacitor production. Summary of the Invention
[0004] To address the problems existing in current processes, this invention aims to provide a process for removing impurities from the adhesive used in the fabrication of multilayer ceramic capacitors. This invention employs a simpler impurity removal process, which effectively improves desalination efficiency and reduces water consumption.
[0005] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: to provide a process for removing impurities from the adhesive used in the fabrication of multilayer ceramic capacitors, the process comprising: Polyvinyl alcohol was used as a raw material for acetalization reaction. After the reaction was completed, alkali was added to the mixture to adjust the pH to neutral. After stirring evenly, the crude product was separated from the mother liquor by filtration. Water is added to the crude product and then transferred to a dialysis bag, which is then placed in a container. Water is added to the container to begin dialysis. After the dialysis is completed, the liquid obtained by filtering the dialysis bag is used as a binder for the preparation of multilayer ceramic capacitors.
[0006] The filtration method is one of gravity filtration, vacuum filtration, and pressure filtration.
[0007] The ratio of the amount of water added to the crude product to the mass of the crude product is (1-1.2):2.
[0008] The dialysis bag is made of either a regenerated cellulose membrane or a cellulose ester membrane.
[0009] The molecular weight cutoff of the dialysis bag is 3000-5000.
[0010] The process includes pretreatment of the dialysis bag before adding water to the crude product and transferring it to the dialysis bag. The pretreatment steps include: boiling the bag with 50% ethanol for 1 hour, washing it sequentially with 50% ethanol, 0.01 mol / L sodium bicarbonate and 1 mol / L disodium ethylenediaminetetraacetate solution, and finally rinsing it with distilled water.
[0011] The volume of the material into which water is added is 1 / 3 to 1 / 2 of the internal volume of the dialysis bag, wherein the material is an intermediate product obtained by adding water to the crude product.
[0012] The amount of water added to the container is at least 100 times the amount of water added to the dialysis bag.
[0013] The dialysis procedure involves changing the water every 8 hours, and ending the dialysis after 24 hours.
[0014] The conditions for the dialysis operation are as follows: continuous stirring during dialysis, and a temperature of 35-45℃.
[0015] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention introduces membrane separation technology, using dialysis bags to perform dialysis on crude binder products containing salts, surfactants, and excess unreacted aldehydes, thereby improving the impurity removal process. This dialysis operation simplifies the process flow, significantly reducing water consumption compared to traditional water washing processes and achieving better desalination. Therefore, this invention's impurity removal process is more environmentally friendly and efficient, generating significant economic benefits. Attached Figure Description
[0016] Figure 1 This is a flowchart of a process for removing impurities from the adhesive used in the fabrication of multilayer ceramic capacitors, provided in an embodiment of the present invention. Detailed Implementation
[0017] Please see Figure 1 , Figure 1This is a flowchart of a process for removing impurities from an adhesive used in the fabrication of multilayer ceramic capacitors, as provided in an embodiment of the present invention. As shown in the figure, the process for removing impurities from the adhesive in this embodiment includes: S1: Using polyvinyl alcohol as raw material, an acetalization reaction is carried out. After the reaction is completed, alkali is added to the mixture to adjust the pH to neutral. After stirring evenly, the crude product is separated from the mother liquor by filtration.
[0018] In specific implementation, the adhesive synthesis process includes: using polyvinyl alcohol as a raw material, and carrying out an acetalization reaction with aldehydes under the action of an acidic catalyst and a surfactant. Specifically, the aldehyde in the embodiments of this invention can be one of butyraldehyde and formaldehyde, preferably butyraldehyde; the acidic catalyst can be one of hydrochloric acid and sulfuric acid; and the surfactant can be one of sodium dodecylbenzenesulfonate, alkyl sulfonates, and composite surfactants.
[0019] After the adhesive synthesis process is completed, alkali is added to the mixture after the reaction to adjust the pH to neutral. Adding alkali can immediately terminate the acetalization reaction chain process, prevent excessive cross-linking that could lead to product embrittlement or gelation, and also improve product stability, prevent acetal bonds from hydrolyzing and degrading in an acidic environment, and significantly extend the adhesive's storage life.
[0020] Among these options, sodium hydroxide is preferred as an alkaline solution due to its high economic efficiency and ease of operation.
[0021] In neutralization reactions, acids and bases react to form salts, and these salts are the main targets for impurity removal.
[0022] After the neutralization reaction is complete, the mixture is stirred thoroughly and then filtered to separate the crude product from the mother liquor. The filtration method is one of gravity filtration, vacuum filtration, or pressure filtration.
[0023] As a preferred method, vacuum filtration is performed under stirring conditions.
[0024] S2: Add water to the crude product and transfer it to a dialysis bag, then place the dialysis bag in a container.
[0025] After separating and filtering to obtain the crude product, water is added and the product is transferred to a dialysis bag.
[0026] Dialysis relies on the concentration difference of solutes inside and outside the membrane to drive the diffusion of small molecule impurities outward. After dissolving in water, the small molecules in the filter residue create a high-concentration environment inside the dialysis bag, forming a gradient with the pure water outside, thus accelerating impurity removal. Furthermore, the solution state ensures uniform dispersion of target macromolecules, preventing excessively high local concentrations from affecting the selective retention of the semi-permeable membrane and ensuring complete removal of small molecule impurities. The filter residue is the crude product, specifically polyvinyl butyral; the impurities are salts.
[0027] The amount of water added should not be excessive; a small amount is sufficient. The ratio of water added to the crude product by mass is (1-1.2):2. For example, 1.05:2, 1.07:2, 1.12:2, etc. It is preferable to control the ratio of water added to crude product by mass to 1:2.
[0028] Optionally, the dialysis bag is made of either regenerated cellulose membrane or cellulose ester membrane; the preferred specification of the dialysis bag is a dialysis bag with a molecular weight cutoff of 3000-5000.
[0029] Within the temperature range that dialysis bags can withstand, higher dialysis temperatures are more conducive to the release of organic matter from the product, thereby accelerating the dialysis rate. Cellulose dialysis bags can withstand temperatures up to 37°C, while regenerated cellulose dialysis bags can withstand temperatures as high as 60°C.
[0030] As a preferred implementation, cellulose dialysis bags can be used for dialysis at 35°C, while regenerated cellulose dialysis bags can be used for dialysis at 45°C.
[0031] In addition, before transferring the crude product to the dialysis bag after adding water, the dialysis bag undergoes pretreatment. The pretreatment steps include: boiling with 50% ethanol for 1 hour, then washing with 50% ethanol, 0.01 mol / L sodium bicarbonate and 1 mol / L disodium ethylenediaminetetraacetate solution in sequence, and finally rinsing with distilled water. After the dialysis bag is selected and pretreated, it can be put into use.
[0032] When transferring crude product with a small amount of water to a dialysis bag, it is essential to leave one-third to one-half of the space. This is primarily to prevent the dialysis bag from rupturing and to ensure dialysis efficiency. During dialysis, the low-concentration solution outside the bag will permeate into the high-concentration solution inside, causing a significant expansion of the liquid volume inside the bag. If the space is insufficient, the internal pressure may exceed the dialysis bag's tolerance limit, leading to rupture. Furthermore, the semi-permeable membrane only allows small molecules to diffuse outward, while large molecules are trapped inside the bag. As small molecules continue to permeate, the solute concentration inside the bag increases, further exacerbating the osmotic pressure gradient of water infiltration and making the volume expansion more pronounced. Leaving space also allows the dialysis bag to fully expand, preventing folding or compression that would reduce the effective membrane area, ensuring rapid permeation of small molecules, and avoiding localized high-concentration areas that hinder uniform solute diffusion.
[0033] Therefore, to ensure more thorough dialysis, the volume of water added to the crude product should be controlled to be 1 / 3 to 1 / 2 of the internal volume of the dialysis bag. For example, 2 / 5, 3 / 8, 4 / 9, etc. Preferably, the volume of water added is 1 / 3 of the internal volume of the dialysis bag.
[0034] Seal the dialysis bag and then place it in the container.
[0035] A dialysis bag is a container used for dialysis, in which the dialysis bag is completely immersed to facilitate the diffusion of small molecules. This container typically contains water, a buffer solution, or distilled water, known as the dialysate.
[0036] Preferably, the dialysate is water, which is economical and practical.
[0037] S3: Add water to the container to start dialysis. After the dialysis is completed, filter the liquid in the dialysis bag to obtain polyvinyl butyral, which can be used as an adhesive for the preparation of multilayer ceramic capacitors.
[0038] First, a large volume of dialysate maintains a stable concentration gradient, ensuring continuous diffusion of small molecules from inside the bag to the outside. Second, sufficient volume prevents excessively high local concentrations outside the bag from creating "dead zones," maintaining efficient exchange through agitation or flow. Finally, this ratio has been optimized through practice, reducing the operational costs of frequent fluid changes while ensuring efficient removal. Based on these three reasons, the volume of dialysate should be chosen within a suitable range.
[0039] In one preferred embodiment, the amount of water added to the container is at least 100 times the amount of water added to the crude product.
[0040] The application of stirring technology in dialysis operations can significantly improve dialysis efficiency and optimize process quality. Through forced convection, stirring can eliminate the stagnant layer on the membrane surface, increase the diffusion rate of small molecule impurities by more than 30%, prevent the stratification of high-viscosity materials, and improve the residual aldehyde removal rate by 40%.
[0041] Heating can be applied appropriately during dialysis to improve its efficiency. Dialysis can be performed at 35℃, or at 45℃ using regenerated cellulose dialysis bags.
[0042] As a preferred implementation, when using a cellulose dialysis bag, the dialysis conditions are set to heating to 35°C and continuous stirring; when using a regenerated cellulose dialysis bag, the dialysis conditions are set to heating to 45°C and continuous stirring.
[0043] During dialysis, regularly changing the dialysate can maintain the concentration difference between the internal and external solutions, thereby maintaining separation efficiency and ensuring system stability.
[0044] As a preferred implementation, the water change operation in this embodiment is to change the water once every 8 hours, and to end dialysis after three water changes and 24 hours.
[0045] Once the dialysis operation is completed, the impurity removal process is finished. Subsequently, filtration is performed to obtain the adhesive for preparing multilayer ceramic capacitors after impurity removal and separation. The filtration is one of gravity filtration, vacuum filtration, and pressure filtration. As a preferred method, vacuum filtration is performed under stirring conditions.
[0046] The above describes the impurity removal process for the adhesive used in the fabrication of multilayer ceramic capacitors provided by this invention. Impurities are removed from the synthesized adhesive using membrane separation technology. This simplified and upgraded impurity removal process utilizes dialysis and concentration differences to streamline the process. Only about 400-600 mL of water is needed to reduce salt residues to the ppm level. Compared to traditional water washing methods, this significantly improves desalination efficiency and greatly reduces water consumption to only 10%-35% of the original amount. Reduced water consumption directly contributes to cost reduction and environmental protection, resulting in substantial economic benefits.
[0047] To further illustrate the technical solution of the present invention, specific embodiments are described below. The specific proportions, material selections, and reaction conditions mentioned below are all specific examples and are not intended to limit the scope of protection of the present invention. Example
[0048] An acetalization reaction was carried out using 50g of PVA as raw material. After the reaction, an alkaline solution was added to adjust the pH to 7. After stirring evenly, the mixture was filtered. The resulting filter residue was mixed with a small amount of water (2g filter residue: 1mL water) and transferred to a cellulose dialysis bag with a molecular weight cutoff of 3000-5000. The volume of the material was 1 / 3 of the total volume of the dialysis bag. After sealing, the bag was transferred to a 1000mL beaker, and 300mL of water was added. Dialysis was carried out under stirring conditions, with the water changed every 8 hours. After 24 hours, the liquid in the dialysis bag was filtered to obtain the target product. Example
[0049] An acetalization reaction was carried out using 50g of PVA as raw material. After the reaction, an alkaline solution was added to adjust the pH to 7. After stirring evenly, the mixture was filtered. The resulting filter residue was mixed with a small amount of water (2g filter residue: 1mL water) and transferred to a regenerated cellulose dialysis bag with a molecular weight cutoff of 3000-5000. The volume of the material was 1 / 3 of the total volume of the dialysis bag. After sealing, the bag was transferred to a 1000mL beaker, and 300mL of water was added. Dialysis was carried out under the conditions of heating to 45℃ and stirring. The water was changed every 8 hours. After 24 hours, the liquid in the dialysis bag was filtered to obtain the target product.
[0050] Comparative Example 1: An acetalization reaction was carried out using 50g of PVA as raw material. After the reaction was completed, an alkaline solution was added to adjust the pH to 7. After stirring evenly, the mixture was filtered. The filter residue was washed with 1000mL of water each time, for a total of 5 washes, to obtain the target product.
[0051] Comparative Example 2: An acetalization reaction was carried out using 50g PVA as raw material. After the reaction was completed, an alkaline solution was added to adjust the pH to 7. After stirring evenly, the mixture was filtered. The resulting residue was added to a flask, and 1000mL of water was added. The mixture was heated to 45℃ and stirred for 1 hour. After filtration, the product was washed four times to obtain the target product.
[0052] Impurity removal effect: After drying, the butyraldehyde content was tested by gas chromatography, and the sodium ion content was measured by ICP-MS to determine the residual amount of impurities.
[0053] Table 1. Impurity Detection Results
[0054] As shown in Table 1 of the impurity detection results, the residual amounts of butyraldehyde and sodium ions in the examples are both lower than those in the comparative examples. Specifically, the residual amount of sodium ions in the examples is significantly lower than that in the comparative examples, with a difference of up to 1000 ppm. Comparing the impurity removal results of the four technical solutions, it is clear that Example 2, using a regenerated cellulose dialysis bag under heating conditions, exhibits the best dialysis effect and the lowest residual impurities. In summary, it can be concluded that the adhesive impurity removal process for multilayer ceramic capacitors using membrane separation technology significantly improves the impurity removal effect compared to the traditional water washing method.
[0055] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A process for removing impurities from adhesives used in the fabrication of multilayer ceramic capacitors, characterized in that, The impurity removal process includes the following steps: Polyvinyl alcohol was used as a raw material for acetalization reaction. After the reaction was completed, alkali was added to the mixture to adjust the pH to neutral. After stirring evenly, the crude product was separated from the mother liquor by filtration. Water is added to the crude product and then transferred to a dialysis bag, which is then placed in a container. Water is added to the container to begin dialysis. After the dialysis is completed, the liquid obtained by filtering the dialysis bag is used as a binder for the preparation of multilayer ceramic capacitors.
2. The impurity removal process according to claim 1, characterized in that, The filtration method is one of gravity filtration, vacuum filtration, and pressure filtration.
3. The impurity removal process according to claim 1, characterized in that, The ratio of the amount of water added to the crude product to the mass of the crude product is (1-1.2):
2.
4. The impurity removal process according to claim 1, characterized in that, The dialysis bag is made of either a regenerated cellulose membrane or a cellulose ester membrane.
5. The impurity removal process according to claim 1, characterized in that, The molecular weight cutoff of the dialysis bag is 3000-5000.
6. The impurity removal process according to claim 4, characterized in that, Before transferring the crude product to the dialysis bag after adding water, the dialysis bag is pretreated. The pretreatment steps include: boiling with 50% ethanol for 1 hour, washing with 50% ethanol, 0.01 mol / L sodium bicarbonate and 1 mol / L disodium ethylenediaminetetraacetate solution in sequence, and finally rinsing with distilled water.
7. The impurity removal process according to claim 1, characterized in that, The volume of the material into which water is added is 1 / 3 to 1 / 2 of the internal volume of the dialysis bag, wherein the material is an intermediate product obtained by adding water to the crude product.
8. The impurity removal process according to claim 1, characterized in that, The amount of water added to the container is at least 100 times the amount of water added to the dialysis bag.
9. The impurity removal process according to claim 1, characterized in that, The dialysis procedure involves changing the water every 8 hours, and ending the dialysis after 24 hours.
10. The impurity removal process according to claim 1, characterized in that, The conditions for the dialysis operation are: continuous stirring during dialysis, and a temperature of 35-45℃.