Oil pastels and their manufacturing method

Abstract

The present invention discloses an oil pastel and a manufacturing method thereof. The oil pastel is composed of 100 parts of a plant wax base, 8 - 25 parts of an environment-friendly pigment, and 0 - 90.05 parts of auxiliary materials. The plant wax base is composed of 50 - 90 parts of plant wax A and 10 - 50 parts of plant wax B. The hardness of plant wax A is higher than that of plant wax B to ensure the hardness of the oil pastel, and the viscosity of plant wax B is higher than that of plant wax A to enhance the saturation of the oil pastel. Plant wax A is selected as soybean wax with a melting point of 58 - 62°C. The oil pastel prepared by the present invention is more excellent in anti-chipping ability and high-temperature resistance, bringing a better painting experience to users. In addition, since the present invention can be prepared with only three main raw materials, the simple formula makes the processing procedure simple. Using soybean wax as the main raw material, it is convenient to obtain and has a low production cost. The prepared oil pastel is green, safe and degradable, and has the characteristic of not being easy to release oil at high temperatures. By adding a bittering agent, it can prevent young people from swallowing after biting, improve the use safety, and has a wider application range.

Description

Technical Field

[0001] The present invention relates to the technical field of art painting tools, and particularly relates to an oil pastel which is non-toxic, has a simple formula, and is made of easily obtainable raw materials, as well as a production method thereof. Background Art

[0002] An oil pastel is an oily colored painting pigment, which has the characteristics of delicate and smooth touch, good spreading property, excellent color overlapping and mixing performance, and bright colors. The coating has a certain thickness, and the adhesion and covering power of the coating on the paper surface are stronger, with texture, which can fully display the oil painting effect and meet the requirements of various painting skill difficulties.

[0003] However, traditional oil pastels are generally composed of industrial-grade raw materials such as wax, vegetable oil, fillers, plasticizers, pigments, etc. Although the prepared oil pastels meet the current safety requirements, the ingredients are complex and the raw materials still contain relatively more heavy metals such as lead, cadmium, barium, antimony, arsenic, mercury, selenium or other harmful substances, etc., which still pose a great safety hazard to young children and teenagers who use oil pastels more frequently. Summary of the Invention

[0004] In order to overcome the above defects, the present invention provides an oil pastel with a simple formula, easily obtainable raw materials, and capable of meeting painting requirements, as well as a production method of the oil pastel.

[0005] The technical solution adopted by the present invention to solve its technical problems is: to provide an oil pastel, by weight, the raw materials of the oil pastel include:

[0006] 100 parts of a plant wax base, the plant wax base is composed of 50 - 90 parts of plant wax A and 10 - 50 parts of plant wax B, the hardness of plant wax A is higher than that of plant wax B to ensure the hardness of the oil pastel, and the viscosity of plant wax B is higher than that of plant wax A to strengthen the saturation of the oil pastel;

[0007] 8 - 25 parts of environmentally friendly pigments;

[0008] 0 - 90.05 parts of auxiliary materials;

[0009] Among them, the plant wax A is selected from soybean wax with a melting point of 58 - 62°C.

[0010] As a further improvement of the present invention, the plant wax B is selected from at least one of palm wax, olive wax, candelilla wax, coconut wax, cottonseed wax, rapeseed wax, and soybean wax with a melting point of 42 - 52°C.

[0011] As a further improvement of the present invention, the plant wax B is composed of a compound of palm wax and soybean wax with a melting point of 42 - 52°C.

[0012] As a further improvement of the present invention, the plant wax B is compounded from palm wax, olive wax, and soybean wax with a melting point of 42 to 52 °C.

[0013] As a further improvement of the present invention, the environmentally friendly pigment is selected from at least one of sunset yellow, lemon yellow, quinoline yellow, amaranth red, carmine, erythrosine, allura red, new red, brilliant blue, indigo, and vegetable carbon black.

[0014] As a further improvement of the present invention, by weight, the auxiliary materials include 20 to 90 parts of a filler and 0.01 to 0.05 parts of a bittering agent.

[0015] As a further improvement of the present invention, the filler is selected from at least one of food-grade calcium carbonate, food-grade kaolin, food-grade barium sulfate, food-grade magnesium carbonate, and food-grade silica.

[0016] As a further improvement of the present invention, the bittering agent is 0.05 parts of denatonium benzoate.

[0017] The technical solution adopted by the present invention to solve its technical problems is to provide the production method of the oil pastel, including the following steps:

[0018] Step 1: Weigh the formula portions of plant wax A and plant wax B, heat them to 70 °C to 75 °C until completely melted, and while maintaining the heating and stirring state, slowly add the formula portion of the environmentally friendly pigment for mixing and fully stir to obtain a uniform mixture;

[0019] Step 2: Grind the uniform mixture obtained in Step 1 by a three-roll mill to a fine particulate solid with a size of 5 to 25 μm;

[0020] Step 3: Heat the fine particulate solid obtained in Step 2 to 80 °C to 90 °C to complete melting, and while maintaining the heating and stirring state, add the formula portions of the filler and the bittering agent, and stir and disperse them by a disperser to form a uniform liquid slurry mixture;

[0021] Step 4: Inject the slurry mixture obtained in Step 3 into a molding machine, and after low-temperature condensation and demolding treatment at 6 to 15 °C, obtain the oil pastel.

[0022] As a further improvement of the present invention, in Step 3, the stirring speed and stirring duration of the disperser include:

[0023] First, stir continuously at a stirring speed of 250 to 500 revolutions per minute for 20 minutes to fully wet the added materials;

[0024] Secondly, increase the stirring speed from 250 to 500 revolutions per minute to 800 to 1000 revolutions per minute, and stir continuously for 20 to 30 minutes to fully mix and disperse the materials;

[0025] Finally, reduce the stirring speed from 800 - 1000 revolutions per minute to 250 - 300 revolutions per minute, and continuously stir for 15 - 25 minutes to stabilize the material and eliminate air bubbles, obtaining the slurry mixture.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. The present invention has all the properties required for use as an oil pastel. In particular, it is more excellent in anti - flaking ability and high - temperature resistance compared to ordinary oil pastels, bringing a better painting experience to users and being able to maintain the integrity of the painted works. In addition, since the present invention can be prepared with only three main raw materials, the simple formula makes the processing process simple. At the same time, using soybean wax as the main raw material, the raw materials are easily obtained, inexpensive, and the production cost is low. The prepared oil pastel is green, safe, degradable, and has the characteristic of not being prone to oil leakage at high temperatures;

[0028] 2. By adding a filler to adjust and control the drawing ability and anti - folding strength of the oil pastel;

[0029] 3. By adding a bittering agent to the product to prevent young children from swallowing after biting, thus improving the safety of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the state after the high - temperature resistance experiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] The following is a detailed description of a preferred embodiment of the present invention with reference to the accompanying drawings.

[0032] The present invention will be further described in detail through examples.

[0033] In the following examples, plant wax A is selected as soybean wax with a melting point of 62°C, and plant wax B is selected as soybean wax with a melting point of 42°C. The following is by weight.

[0034] Example 1:

[0035] Heat 90 parts of plant wax A and 10 parts of plant wax B to 75°C until completely melted. While maintaining the heating and stirring state, slowly add 8 parts of carmine aluminum lake and 1.2 parts of lemon yellow aluminum lake for mixing and fully stir to obtain a uniform mixture;

[0036] Grind the above - mentioned uniform mixture through a three - roll mill into fine particulate solids with a size of 5 - 25 μm;

[0037] Heat the above-mentioned fine granular solid to 90°C to complete melting, add 20 parts of food-grade calcium carbonate and 0.05 part of denatonium benzoate under stirring, keep heating and stir and disperse with a high-speed stirring disperser for 70 min to form a uniform liquid paste mixture, inject the paste mixture into a molding machine, and obtain the oil pastel through low-temperature condensation and demolding techniques at 13°C.

[0038] Example 2:

[0039] Heat 70 parts of plant wax A and 30 parts of plant wax B to 70°C to completely melt, keep heating and stirring, slowly add 25 parts of brilliant blue aluminum lake for mixing and fully stir to obtain a uniform mixture;

[0040] Grind the above-mentioned uniform mixture with a three-roll mill into fine granular solids with a size of 5 - 25 μm;

[0041] Heat the above-mentioned fine granular solid to 85°C to complete melting, add 75 parts of food-grade calcium carbonate and 0.05 part of denatonium benzoate under stirring, keep heating and stir and disperse with a high-speed stirring disperser for 70 min to form a uniform liquid paste mixture, inject the paste mixture into a molding machine, and obtain the oil pastel through low-temperature condensation and demolding techniques at 13°C.

[0042] Example 3:

[0043] Heat 50 parts of plant wax A and 50 parts of plant wax B to 70°C to completely melt, keep heating and stirring, slowly add 8.5 parts of lemon yellow aluminum lake for mixing and fully stir to obtain a uniform mixture;

[0044] Grind the uniform mixture with a three-roll mill into fine granular solids with a size of 5 - 25 μm;

[0045] Heat the above-mentioned fine granular solid to 80°C to complete melting, add 90 parts of food-grade calcium carbonate and 0.05 part of denatonium benzoate under stirring, keep heating and stir and disperse with a high-speed stirring disperser for 75 min to form a uniform liquid paste mixture, inject the paste mixture into a molding machine, and obtain the oil pastel through low-temperature condensation and demolding techniques at 13°C.

[0046] Example 4:

[0047] Heat 80 parts of plant wax A and 20 parts of palm wax to 70°C to completely melt, keep heating and stirring, slowly add 8 parts of brilliant blue aluminum lake for mixing and fully stir to obtain fine granular solids;

[0048] Grind the above-mentioned fine granular solid with a three-roll mill into fine granular solids with a size of 5 - 25 μm;

[0049] Heat the above-mentioned fine granular solid to 90 °C to complete melting, add 80 parts of food-grade calcium carbonate and 0.05 part of denatonium benzoate under stirring, keep heating and stir and disperse with a high-speed stirring disperser for 55 min to form a uniform liquid paste mixture, inject the paste mixture into a molding machine, and obtain the oil pastel through low-temperature condensation and demolding techniques at 13 °C.

[0050] Example 5:

[0051] In this example, plant wax B is composed of 15 parts of palm wax and 20 parts of soybean wax at 42 - 52 °C by compounding;

[0052] Heat 75 parts of plant wax A and 35 parts of plant wax B to 70 °C to completely melt, keep heating and stirring, slowly add 10 parts of erythrosine aluminum lake for mixing and stir fully to obtain fine granular solid;

[0053] Grind the above-mentioned fine granular solid through a three-roll grinder to obtain fine granular solid with a size of 5 - 25 μm;

[0054] Heat the above-mentioned fine granular solid to 85 °C to complete melting, add 80 parts of food-grade calcium carbonate and 0.05 part of denatonium benzoate under stirring, keep heating and stir and disperse with a high-speed stirring disperser for 75 min to form a uniform liquid paste mixture, inject the paste mixture into a molding machine, and obtain the oil pastel through low-temperature condensation and demolding techniques at 13 °C.

[0055] Example 6:

[0056] In this example, plant wax B is composed of 15 parts of palm wax, 5 parts of olive wax and 30 parts of soybean wax at 42 - 52 °C by compounding;

[0057] Heat 50 parts of plant wax A and 50 parts of plant wax B to 75 °C to completely melt, keep heating and stirring, slowly add 8 parts of vegetable carbon black for mixing and stir fully to obtain fine granular solid;

[0058] Grind the above-mentioned fine granular solid through a three-roll grinder to obtain fine granular solid with a size of 5 - 25 μm;

[0059] Heat the above-mentioned fine granular solid to 85 °C to complete melting, add 85 parts of food-grade calcium carbonate and 0.05 part of denatonium benzoate under stirring, keep heating and stir and disperse with a high-speed stirring disperser for 60 min to form a uniform liquid paste mixture, inject the paste mixture into a molding machine, and obtain the oil pastel through low-temperature condensation and demolding techniques at 13 °C.

[0060] In addition to the above examples, the present invention also provides comparative examples to illustrate the effects of the present invention.

[0061] The oil pastels of the comparative example are compounded from 24 to 60 parts of matrix, 50 to 125 parts of filler, 3 to 25 parts of pigment, and 0 to 5 parts of other additives. Among them, the matrix consists of 3% to 10% paraffin wax, 3% to 10% microcrystalline wax, 15% to 30% hardened oil, 15% to 30% synthetic wax, and 30% to 55% white oil.

[0062] In the experiment, the oil pastels of Examples 1 to 6 and the oil pastels of the comparative example were evaluated by depicting smoothness, flaking, coloring power, adhesion, folding resistance, coating thickness, and high temperature resistance tests. The test results are shown in Table 1 and the appendix Figure 1 。

[0063] Among them, the method for measuring the folding resistance refers to the industry standard of oil pastels QB / T 2586-2014, and the requirement for the folding resistance is >4N.

[0064] For the flaking test, the sample is evenly coated on a sketch paper with an area of 50mm*50mm, and the state of powder debris falling from the sample is observed during the coating process:

[0065] A: The coating adheres well to the paper surface without debris;

[0066] B: A small amount of powder debris falls;

[0067] C: More powder debris falls on the paper surface.

[0068] For the coloring power test, the sample is used to coat a single area of 50mm*50mm on a sketch paper, and the uniformity of the coating color on the sketch paper is observed:

[0069] A: The color is uniform, and the sketch paper under the coating is not revealed;

[0070] B: The color is uniform, the sketch paper under the coating cannot be completely covered, and a small amount is revealed;

[0071] C: The color is uneven, and more of the sketch paper under the coating is revealed.

[0072] For the adhesion test, it is painted on various surfaces such as paper, cloth, plastic, glass, marble, and metal, and the adhesion is scored (A-C):

[0073] A: It can be painted and adhered on various medium surfaces;

[0074] B: It is easy to adhere and color on rough surfaces such as paper and cloth, and it is not easy to adhere on other smooth surfaces. The color can only be shown after repeated painting;

[0075] C: It can only be painted and adhered on paper and cloth, and cannot be adhered on other smooth surfaces.

[0076] The coating thickness test is carried out by evenly coating a 50mm*50mm area on the sketch paper with the sample. The coating weight = (the weight of the sketch paper + the coated sample) - the weight of the sketch paper, with the unit of g / cm.

[0077]

[0078] In addition, the above Examples 1, 4, 5, 6 and the comparative examples were subjected to a high-temperature resistance test, that is, the oil pastels obtained in the above examples were placed in a constant-temperature drying oven and continuously heated at 60°C for 4H, and the oil leakage situation on the packaging paper of the oil pastels was observed. For the results of this experiment, see the appendix Figure 1 .

[0079] Appendix Figure 1 Specific description: The four groups of oil pastels on the left show the states of Examples 1, 4, 5, and 6, and the two groups of oil pastels on the right show the states of the comparative examples; it can be seen that the packaging papers of Examples 1, 4, 5, and 6 are brighter in color, indicating that the oil leakage is not obvious, and the packaging papers of the comparative examples are darker in color, indicating that the oil leakage is obvious. It can be seen that the oil pastels of the present invention have durable high-temperature resistance.

[0080] From Table 1 and the results shown in the appendix Figure 1 It can be seen that the oil pastels of Examples 1 to 6 of the present invention are comparable to the comparative examples in terms of performance such as smooth drawing, coloring power, adhesion, folding resistance, and coating thickness. At the same time, the examples of the present invention are superior in terms of anti-chipping ability and high-temperature resistance.

[0081] In terms of chipping, the examples of the present invention will not chip during the painting process, which can bring a better painting experience to users and at the same time maintain the integrity of the painted works; in terms of coating thickness, the coating thickness of the examples of the present invention is thicker than that of the comparative examples, which can bring a stronger three-dimensional sense to the painting.

[0082] Based on the test results, combined with the composite materials and preparation methods of the present invention, among them, plant wax A is selected as soybean wax with a melting point of 62°C to ensure the hardness of the oil pastel, and plant wax B is used to enhance the saturation of the oil pastel. In addition, the molecular structure of the soybean wax with a melting point of 62°C forms a support, enabling the present invention to meet the requirements of the folding resistance of the oil pastel without adding auxiliary agents such as fillers or plasticizers.

[0083] For the selection of raw materials, the present invention adopts plant wax base to replace the paraffin base extracted from petroleum as the raw material of oil pastel. The main raw material of plant wax is vegetable oil, such as soybean oil, palm oil, sunflower seed oil, peanut oil, coconut oil, etc., and such grease is processed by hydrogenation to become plant wax. Soybean wax is a natural material with a relatively low melting point. Compared with traditional paraffin wax, soybean wax is more easily melted. Except the characteristics of easy melting and easy handling, soybean wax is extracted from natural plants, is cheap, does not contain harmful substances, can be completely degraded, will not pollute the environment, make the obtained oil pastel safe and environmentally friendly, conform to the trend of green and low-carbon economy, and the vegetable oil in soybean wax makes the oil pastel of the present invention carry fragrance.

[0084] In Example 1, 50 parts of soybean wax with a melting point of 62°C and 50 parts of soybean wax with a melting point of 42°C are respectively mixed and melted and dispersed to form a molten plant wax base, and then 18 parts of environmentally friendly pigments are added to the molten plant wax base and stirred, which can significantly improve the dispersibility of the pigments and obtain more brilliant colors.

[0085] Specifically, the hardness of 62°C soybean wax ensures the hardness of the finished oil pastel, so that it meets the requirement of QB / T 2586-2014 oil pastel industry standard, flexural strength> 4N, and ensures that the oil pastel is not easy to break during the painting process; while 52°C soybean wax enhances the softness and ductility of the oil pastel to ensure color saturation, and also improves the adhesion and spreading performance of the oil pastel on paper and cloth; two soybean waxes with different melting points are compounded by 100 parts to form a plant wax base, which ensures that the plant wax base has good plasticity, and the oil pastels are designed with different shapes to meet the use needs of different groups; in addition, the adhesion of soybean wax enables the oil pastels to adhere better when the layers of colors are thick, thus having excellent anti-chipping performance.

[0086] In addition, since soybean oil contains unsaturated fatty acids such as palmitic acid, stearic acid, arachidic acid, oleic acid, linoleic acid, and linolenic acid, the soybean wax obtained after hydrogenation of soybean oil naturally contains oil, which is beneficial to the uniform fusion of various raw materials in the manufacturing process of oil pastels, ensuring uniform dispersion of pigments, and at the same time can improve the gloss of the finished oil pastels and the lubricity of painting.

[0087] In Example 4, palm wax is selected as vegetable wax B, because the viscosity of palm wax can adjust the hardness of the plant wax base after compounding with vegetable wax A, thereby adjusting the bending resistance of the oil pastel; in addition, because palm wax has good adhesion, friction and lubricity, it can ensure the dispersion of pigments during the production process, the adhesion of painting, and the smoothness of the oil pastel.

[0088] In Example 5, the plant wax B is a compound of palm wax and soybean wax with a melting point of 42°C. After compounding two soybean waxes with different melting points, it can not only adjust the hardness and saturation, but also improve the flexural strength and anti-chipping performance of the oil pastel.

[0089] In Example 6, the plant wax B is composed of palm wax, olive wax, and soybean wax with a melting point of 42°C. Olive wax further improves the adhesion, and at the same time plays a role in moisturizing and lubricating the finished oil pastel, further ensuring that the finished oil pastel is not easy to release oil at high temperatures and maintaining good gloss. The effect is the best under this compounding.

[0090] The plant wax B of the present invention can also be selected as candelilla wax. The candelilla wax has a certain degree of extensibility, which can further improve the extensibility, pigment dispersibility, anti-chipping and other properties of the oil pastel. At the same time, the overall gloss and plasticity of the prepared oil pastel meet the processing requirements, and it also plays a role in adjusting the hardness of the oil pastel.

[0091] Therefore, as can be seen from Table 1, by selecting one or more plant waxes to compound the obtained plant wax B, the functional cooperation with the plant wax A can ensure the smoothness, coloring power, adhesion, flexural strength and coating thickness adhesion and other properties of the oil pastel during painting. In addition, the anti-chipping and high-temperature resistance of the oil pastel are significantly improved.

[0092] In addition, according to the positioning and usage requirements of the oil pastel, auxiliary materials can be compounded on the basis of plant wax A and plant wax B: fillers and bitter agents. The fillers are added in different amounts to further adjust and control the painting ability and flexural strength of the oil pastel. The bitter agent is preferably 0.05 parts of denatonium benzoate. The bitter agent plays a role in preventing young people from swallowing after biting, and improves the safety of use.

[0093] In summary, the present invention has all the performance requirements for the use of oil pastels. Especially, it is more excellent in anti-chipping ability and high-temperature resistance compared with ordinary oil pastels, bringing a better painting experience for users, and at the same time being able to maintain the integrity of the painted works. In addition, since the present invention can be prepared with only three main raw materials, the formula is simple, making the processing process simple. At the same time, using soybean wax as the main raw material, the raw materials are easily obtained, the price is low, and the production cost is low. The prepared oil pastel is green, safe, degradable, and has the characteristic of not being easy to release oil at high temperatures. By adding a bitter agent, it can prevent young people from swallowing after biting, improve the safety of use, and has a wider application range.

[0094] Numerous specific details are set forth in the foregoing description in order to provide a thorough understanding of the present invention. However, the above description is merely a preferred embodiment of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed above. At the same time, any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes, without departing from the scope of the technical solution of the present invention. All simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. An oil pastel, characterized in that, By weight, the raw materials of the oil pastel include: 100 parts of a plant wax base, which is composed of 50 - 90 parts of plant wax A and 10 - 50 parts of plant wax B. The hardness of plant wax A is higher than that of plant wax B to ensure the hardness of the oil pastel, and the viscosity of plant wax B is higher than that of plant wax A to enhance the saturation of the oil pastel; 8 - 25 parts of environmentally friendly pigments; 0 - 90.05 parts of auxiliary materials; Among them, the plant wax A is selected as soybean wax with a melting point of 58 - 62°C; the plant wax B is selected from at least one of palm wax, olive wax, candelilla wax, coconut wax, cottonseed wax, rapeseed wax, and soybean wax with a melting point of 42 - 52°C.

2. The oil pastel according to claim 1, wherein: The plant wax B is compounded by palm wax and soybean wax with a melting point of 42 - 52°C.

3. The oil pastel according to claim 1, wherein: The plant wax B is compounded by palm wax, olive wax, and soybean wax with a melting point of 42 - 52°C.

4. The oil pastel according to claim 1, wherein: The environmentally friendly pigments are selected from at least one of sunset yellow, lemon yellow, quinoline yellow, amaranth, carmine, erythrosine, allura red, new red, brilliant blue, indigo, and vegetable carbon black.

5. The oil pastel according to claim 1, characterized in that: By weight, the auxiliary materials include 20 - 90 parts of fillers and 0.01 - 0.05 parts of bittering agents.

6. The oil pastel according to claim 5, wherein: The fillers are selected from at least one of food-grade calcium carbonate, food-grade kaolin, food-grade barium sulfate, food-grade magnesium carbonate, and food-grade silica.

7. The oil pastel according to claim 6, wherein: The bittering agent is 0.05 parts of denatonium benzoate.

8. A method for manufacturing an oil pastel according to any one of claims 1 to 7, characterized in that , including the following steps: Step 1: Weigh the formulated parts of plant wax A and plant wax B, heat them to 70°C - 75°C until completely melted, and while maintaining the heating and stirring state, slowly add the formulated parts of environmentally friendly pigments for mixing and fully stir to obtain a uniform mixture; Step 2: Grind the uniform mixture obtained in Step 1 through a three-roll mill to obtain fine granular solids with a size of 5 - 25 μm; Step 3: Heat the fine granular solids obtained in Step 2 to 80°C - 90°C to complete melting, and while maintaining the heating and stirring state, add the formulated parts of fillers and bittering agents, and stir and disperse them through a disperser to form a uniform liquid slurry mixture; Step 4: Inject the slurry mixture obtained in Step 3 into a molding machine, and after low-temperature condensation and demolding treatment at 6 - 15°C, obtain the oil pastel.

9. The manufacturing method according to claim 8, characterized in that: In Step 3, the stirring speed and stirring duration of the disperser include: First, continuously stir at a stirring speed of 250 - 500 revolutions per minute for 20 minutes to fully wet the added materials; Secondly, increase the stirring speed from 250 - 500 revolutions per minute to 800 - 1000 revolutions per minute and continuously stir for 20 - 30 minutes to fully mix and disperse the materials; Finally, reduce the stirring speed from 800 - 1000 revolutions per minute to 250 - 300 revolutions per minute and continuously stir for 15 - 25 minutes to stabilize the materials and eliminate bubbles, obtaining the slurry mixture.

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