A ceramic filter slurry and its application

Abstract

The present invention belongs to the technical field of ceramic product preparation processes, and particularly relates to a ceramic filter slurry and the application of the slurry in ceramic slip casting. The inventor improves the stability of the produced ceramic filter by adding a thickener to the slurry for preparing the ceramic filter. Further, the inventor screens a variety of thickeners and selects the slurry components and the optimal component ratio that are most suitable for the sponge slip casting process. Compared with the slurries in the prior art, the ceramic filter prepared using the slurry provided by the present invention can increase the qualified rate of the ceramic filter by 2-10%.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic product preparation processes, and particularly relates to a ceramic filter slurry and the application of the slurry in ceramic slip casting. Background Art

[0002] At the present stage, ceramic filters used in casting are relatively mature, and ceramic filters have extremely strict requirements for appearance dimensions in practical applications. In order to achieve a better filtering effect, the dimensional errors between filters and between filters and runners need to be as small as possible. However, since the production process of filters is through a sponge slip casting process. The slurry currently used in the sponge slip casting process faces problems that when preparing ceramic filters, if the slurry viscosity is too small, it is not conducive to slip casting, and if the slurry viscosity is too large, it is easy to generate bumps on the surface after slip casting, thereby affecting the stability of the ceramic filter. The ceramic filter has strict requirements for its shape and size. Here, the stability refers to the dimensional stability of the filter, including the filter pore size, the length, width, and height of the filter, and the surface flatness of the filter.

[0003] Therefore, to meet the actual application requirements, there is an urgent need to develop a slurry that can stabilize the slip casting effect and improve the stability of the filter. Summary of the Invention

[0004] To solve at least one of the above problems, the present invention provides a slurry for a ceramic filter. The components of the slurry include a composite powder, a thickener, an aqueous sodium hydroxide solution, silica sol, polyvinyl alcohol, and a solvent.

[0005] Among them,

[0006] The thickener includes an alkali-swellable thickener and an associative thickener;

[0007] The composite powder includes silicon carbide, silica powder, and alumina.

[0008] According to a specific embodiment of the present invention, in the slurry, the weight ratio of the composite powder, the alkali-swellable thickener, the associative thickener, the aqueous sodium hydroxide solution, silica sol, polyvinyl alcohol, and the solvent is (70 - 80):(0.2 - 0.8):(1 - 2):(0.3 - 0.5):(5 - 8):(3 - 5):(6 - 10).

[0009] According to a specific embodiment of the present invention, in the composite powder, the mass ratio of silica powder, alumina, and silicon carbide is (20 - 40):(20 - 45):(150 - 250). Within this range, the stability of the filter prepared by the present invention is the best.

[0010] According to a specific embodiment of the present invention, the associative thickener includes an associative polyurethane leveling thickener.

[0011] According to a specific embodiment of the present invention, the solvent is water.

[0012] The second aspect of the present invention provides the use of the slurry described in the first aspect in the preparation of a ceramic filter.

[0013] The third aspect of the present invention provides a method for preparing a ceramic filter, comprising:

[0014] A. Dissolving and swelling sodium hydroxide aqueous solution, silica sol, and polyvinyl alcohol in water to obtain a mixed solution 1;

[0015] B. Adding an alkali-swellable thickener to swell in the mixed solution 1 to obtain a mixed solution 2;

[0016] C. Adding a composite powder to the mixed solution 2 to obtain a mixed solution 3;

[0017] D. Adding an associative thickener to the mixed solution 3 to obtain a ceramic filter slurry;

[0018] E. Injecting the ceramic filter slurry into a sponge mold for slip casting treatment to obtain the ceramic filter,

[0019] wherein,

[0020] the composite powder includes silicon carbide, silica powder, and alumina.

[0021] The present invention uses an associative leveling thickener and an alkali-swellable thickener to modify the slurry. The alkali-swellable thickener is used to increase the base viscosity of the slurry to ensure the slip casting performance of the slurry. The associative leveling thickener is used to change the flow performance of the slurry during slip casting, so that after the slurry is slip cast, the bumps can naturally level off in a short time. The two thickeners act together to achieve the effect of stable slip casting. Thereby improving the final stability of the filter.

[0022] According to a specific embodiment of the present invention, in the ceramic filter slurry, the weight ratio of the composite powder, alkali-swellable thickener, associative thickener, sodium hydroxide aqueous solution, silica sol, polyvinyl alcohol, and solvent is (70 - 80):(0.2 - 0.8):(1 - 2):(0.3 - 0.5):(5 - 8):(3 - 5):(6 - 10).

[0023] According to a specific embodiment of the present invention, in the composite powder, the mass ratio of silica powder, alumina, and silicon carbide is (20 - 40):(20 - 45):(150 - 250).

[0024] According to a specific embodiment of the present invention, the pH of the ceramic filter slurry is 8.8 - 9.5.

[0025] The third aspect of the present invention provides a ceramic filter prepared by the method described in the second aspect.

[0026] The present invention uses an associative leveling thickener and an alkali-swellable thickener to modify the slurry. The alkali-swellable thickener is used to increase the base viscosity of the slurry to ensure the slurry hanging property. The associative leveling thickener is used to change the flow property of the slurry during hanging, so that after the slurry is hung, the bumps can naturally level out in a short time. The two thickeners act together to achieve the effect of stable slurry hanging, thereby improving the final stability of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0028] Figure 1 Surface morphology of the ceramic filter prepared by the method of Embodiment 1 of the present invention;

[0029] Figure 2 Intermediate morphology of the slurry prepared by the method of Comparative Example 1 of the present invention;

[0030] Figure 3 Surface morphology of the ceramic filter prepared by the method of Comparative Example 2 of the present invention;

[0031] Figure 4 Surface morphology of the ceramic filter prepared by the method of Comparative Example 3 of the present invention;

[0032] Figure 5 Surface morphology of the ceramic filter prepared by the method of Comparative Example 4 of the present invention;

[0033] Figure 6 Surface morphology of the ceramic filter prepared by the method of Comparative Example 5 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following details the embodiments of the present invention, and the examples are shown in the drawings. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0035] It should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present invention, unless otherwise specified, "a plurality of" means two or more.

[0036] In this text, the terms "comprising", "including" or "containing" are open expressions, that is, they include the content specified in the present invention, but do not exclude other aspects.

[0037] In this text, the terms "optionally", "optional" or "option" generally mean that the subsequent events or conditions may but do not necessarily occur, and this description includes the cases where such events or conditions occur and the cases where such events or conditions do not occur.

[0038] In this text, the term "polyvinyl alcohol" is an organic compound with the chemical formula [C2H4O]n. It appears as white flakes, flocs or powdery solids and is odorless. It is soluble in water (above 95 °C), slightly soluble in dimethyl sulfoxide, and insoluble in gasoline, kerosene, vegetable oil, benzene, toluene, dichloroethane, carbon tetrachloride, acetone, ethyl acetate, methanol, ethylene glycol, etc. Polyvinyl alcohol is an important chemical raw material and is used to manufacture polyvinyl acetal, gasoline-resistant pipes, vinylon, fabric treatment agents, emulsifiers, paper coatings, adhesives, glues, etc.

[0039] In this text, the term "silica powder" is a non-toxic, odorless and pollution-free inorganic non-metallic material. Due to its excellent properties such as good heat resistance, acid and alkali corrosion resistance, high thermal conductivity, high insulation, low expansion, stable chemical properties, and high hardness, it is widely used in the fields of chemical industry, electronics, integrated circuits (ICs), electrical appliances, plastics, coatings, high-grade paints, rubber, national defense, etc. With the rapid development of high-tech fields, silica powder will also enter a new historical development period. Silica powder is made from natural quartz (SiO2) or fused quartz (non-crystalline SiO2 after natural quartz is melted at high temperature and cooled) through multiple processes such as crushing, ball milling (or vibration, air jet milling), flotation, pickling purification, and high-purity water treatment.

[0040] In the present invention, silicon carbide includes silicon carbide C-DUST and silicon carbide (325 mesh). By weight, the silicon carbide C-DUST is 40 - 60 parts and the silicon carbide (325 mesh) is 100 - 200 parts.

[0041] To make the technical means, creative features, achieved objectives and functions of the present invention easy to understand, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. They are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention.

[0042] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0043] Example 1

[0044] 1. At room temperature, add 830 g of water, 30 g of sodium hydroxide aqueous solution (32% sodium hydroxide solution), 600 g of silica sol (purchased from Shandong Baite New Materials Co., Ltd.), and 400 g of polyvinyl alcohol (purchased from Anhui Wanwei High-Tech Materials Co., Ltd.) into a high-speed dispersion stirring device for dissolution and swelling, and stir evenly;

[0045] 2. Add 40 g of alkali-swellable thickener TT-935 (purchased from Dow Chemical), stir for 30 minutes, fully swell and dissolve, and stir evenly;

[0046] 3. Add 80 g of mixed powder and stir evenly. The mixed powder is composed of 30 parts of silica powder (purchased from Tianjin Yuye International Trade Co., Ltd.), 40 parts of alumina (purchased from Shandong Aotai Electric Co., Ltd.), 50 parts of silicon carbide C-DUST (purchased from Tianjin Yuye International Trade Co., Ltd.), and 150 parts of silicon carbide (325 mesh) (purchased from Tianjin Yuye International Trade Co., Ltd.) by mass;

[0047] 4. Add 100 g of associative polyurethane leveling thickener N-150 (purchased from Hefei Huayue New Materials Technology Co., Ltd.) and stir evenly;

[0048] 5. Perform sizing. Through the dipping sizing process, press the mixed slurry onto a polyurethane sponge (purchased from Weihai Jingsheng). After multiple roller press sizing, the slurry is evenly distributed on the sponge, and a ceramic filter is obtained after drying.

[0049] The inventor found that for the ceramic filter prepared according to this step (as shown in Figure 1 ), the viscosity between the slurries and between the slurry and the sponge for sizing is such that the surface of the ceramic filter is flat, without obvious protrusions and not easily collapsible, the powder is evenly distributed, and there is no obvious phenomenon of pore blockage.

[0050] Comparative Example 1

[0051] Compared with Example 1, the difference in this comparative example is that a cellulose thickener was used in Step 2.

[0052] The inventors found that using a cellulose thickener would result in too high a viscosity in the early stage. During the powder dispersion process, the temperature was too high, and the slurry formed a skin before use (as Figure 2 shown), making it impossible to carry out subsequent slurry coating treatment.

[0053] Comparative Example 2

[0054] Compared with Example 1, the difference in this comparative example is that Step 4 was removed, and no associative polyurethane leveling thickener N-150 was added to the entire slurry.

[0055] The inventors found that for the ceramic filter prepared without adding the associative polyurethane leveling thickener (as Figure 3 shown), the viscosity between the slurries and between the slurry and the sponge for slurry coating was insufficient, the surface of the slurry showed a tendency to collapse, and it was easy to break and shed slag at the collapsed part.

[0056] Comparative Example 3

[0057] Compared with Example 1, the difference in this comparative example is that Step 2 was removed, and no alkali-swellable thickener TT-935 was added to the entire slurry.

[0058] The inventors found that for the ceramic filter without adding the alkali-swellable thickener (as Figure 4 shown), the viscosity of the slurry was too low in the early stage, and the powder was not evenly dispersed.

[0059] Comparative Example 4

[0060] Compared with Example 1, the difference in this comparative example is that 1 part of alkali-swellable thickener TT-935 was added in Step 2.

[0061] The inventors found that when the added alkali-swellable thickener was in excess, for the ceramic filter prepared (as Figure 5 shown), the viscosity of the slurry was too high, and it was easy to block the pores on the surface of the sponge during sponge slurry coating, thereby affecting the molten iron pouring passing rate.

[0062] Comparative Example 5

[0063] Compared with Example 1, the difference in this comparative example is that 4 parts of associative polyurethane leveling thickener N-150 were added in Step 4.

[0064] The inventors found that when the added associative polyurethane leveling thickener N-150 was in excess, for the ceramic filter prepared (as Figure 6As shown in the figure, the viscosity of the slurry is too high, and there are many protrusions on the surface. The protrusions are prone to breakage, and the prepared ceramic filter is unstable.

[0065] Comparative Example 6

[0066] Compared with Example 1, the difference in this comparative example is that no thickener is added to the slurry.

[0067] The inventor found that the surface of the ceramic filter prepared without adding any thickener does not have significant defects, but the average compressive strength after molding is only 1.18 mpa, while the average compressive strength in Example 1 is increased to 2.87 mpa, which does not meet the strength requirements of the filter.

[0068] Take 100 ceramic filters prepared from the slurries in the above examples and comparative examples respectively, and determine the qualification rate of the ceramic filters. When there are convex points, blocked holes, or collapses on the surface of the ceramic filter, and the compressive strength of the prepared ceramic filter is not higher than 1.2 mpa, it is determined as unqualified. The test results are shown in Table 1.

[0069] Table 1

[0070]

[0071] The inventor used the slurry described in Example 1 to coat the sponge and found that the qualification rate of coating was significantly improved. In Comparative Example 1, the inventor initially tried to use cellulose thickeners such as hydroxymethyl cellulose and hydroxyethyl cellulose. In the actual process, it was found that using cellulose thickeners would cause the viscosity of the system to be too high, and the powder in the slurry was prone to form agglomerates, and the dispersion effect was extremely poor. Subsequently, the thickener in Step 2 was changed to this alkali-swellable thickener, and the aggregates in the slurry could be stably dispersed. The inventor also tried to add two thickeners A / B in this step. Since there was a large amount of powder in this system and the powder was not wetted during the initial powder dispersion process, the internal friction was too large and the temperature of the slurry was too high. Cooling was required. Otherwise, normal subsequent production could not be carried out.

[0072] In Comparative Example 2, the inventor tried not to add an associative thickener in the last step for comparison. The inventor found that if only the front-end thickening was used, the coating could be carried out relatively stably, but the unqualified rate of the filter due to convex points was about 10 - 12%, while after adding an associative thickener in the last step, the unqualified rate of the filter due to convex points was about 6 - 8%.

[0073] Alkali-swellable thickeners can rapidly increase the viscosity of the system under alkaline conditions, combine with powders under high-shear conditions, and evenly disperse the powders in the mixed emulsion, maintaining good dispersibility of the powder materials. The biggest feature of associative thickeners is that they can ensure excellent viscosity stability under high shear, while having good fluidity under low-shear conditions. The combination of the two thickeners ensures the stability of the slurry viscosity under shear conditions during the sponge coating process. After the coating is completed, during the standing process, due to the disappearance of the shear force, the associative thickener ensures the natural leveling of the bumps.

[0074] In summary, the inventors of this application improve the stability of the produced ceramic filters by adding thickeners to the slurry for preparing the ceramic filters. Further, the inventors screen various thickeners and select the slurry components and the best component ratios that are most suitable for the sponge coating process. Compared with the slurries in the prior art, the ceramic filters prepared using the slurry provided by the present invention have increased the qualified rate of the ceramic filters by 2-10%.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a ceramic filter slurry, characterized in that: include: A. dissolving and swelling a sodium hydroxide aqueous solution, silica sol, and polyvinyl alcohol in a solvent to obtain a mixed solution 1; B. adding an alkali-swellable thickener to the mixed solution 1 to swell the mixed solution to obtain a mixed solution 2; C. adding the composite powder to the mixed solution 2 to obtain a mixed solution 3; D. adding an associative thickener to the mixed solution 3 to obtain a ceramic filter slurry; in, The composite powder includes silicon carbide, silicon powder and aluminum oxide; In the slurry, the weight ratio of the composite powder, the alkali swelling thickener, the associative thickener, the sodium hydroxide aqueous solution, the silica sol, the polyvinyl alcohol and the solvent is (70-80): (0.2-0.8): (1-2): (0.3-0.5): (5-8): (3-5): (6-10).

2. The method according to claim 1, characterized in that In the composite powder, the mass ratio of silicon powder, aluminum oxide and silicon carbide is (20-40): (20-45): (150-250).

3. The method according to claim 1, characterized in that The associative thickener includes an associative polyurethane leveling thickener; The solvent is water.

4. Use of the slurry prepared by the method according to any one of claims 1 to 3 in preparing a ceramic filter.

5. A method for preparing a ceramic filter, characterized in that: include: A. dissolving and swelling sodium hydroxide aqueous solution, silica sol and polyvinyl alcohol in water to obtain a mixed solution 1; B. adding an alkali-swellable thickener to the mixed solution 1 to swell the mixed solution to obtain a mixed solution 2; C. adding the composite powder to the mixed solution 2 to obtain a mixed solution 3; D. adding an associative thickener to the mixed solution 3 to obtain a ceramic filter slurry; E. injecting the ceramic filter slurry into a sponge mold for slurry treatment, and drying to obtain the ceramic filter, in, The composite powder includes silicon carbide, silicon powder and aluminum oxide; In the ceramic filter slurry, the weight ratio of the composite powder, the alkali swelling thickener, the associative thickener, the sodium hydroxide aqueous solution, the silica sol, the polyvinyl alcohol and the solvent is (70-80): (0.2-0.8): (1-2): (0.3-0.5): (5-8): (3-5): (6-10).

6. The method according to claim 5, characterized in that In the composite powder, the mass ratio of silicon powder, aluminum oxide and silicon carbide is (20-40): (20-45): (150-250).

7. The method according to claim 5, characterized in that The pH of the ceramic filter slurry is 8.8-9.

5.

8. A ceramic filter, characterized in that: Prepared by the method described in any one of claims 5 to 7.

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