Method for improving the demoulding effect of spray granulation powders

Abstract

The application provides a method for improving the demolding effect of spray granulation powder, and belongs to the technical field of non-metal ceramics. The method comprises the following steps: mixing a demolding material with non-metal ceramic slurry, performing ball milling to obtain mixed slurry, performing spray granulation on the mixed slurry to obtain powder, and performing press forming on the powder in a mold. The demolding material comprises oleic acid and glycerol, or aviation kerosene and zinc stearate. The ball milling time is 30-120 min. The method provided by the application has the characteristics of good demolding effect, difficulty in sticking to the mold, simple operation and continuous production for the dry press forming of non-metal ceramic powder after spray granulation.

Description

Technical Field

[0001] This invention belongs to the field of non-metallic ceramic technology, specifically relating to a method for improving the demolding effect of spray-granulated powder. Background Technology

[0002] Generally, spray-granulated powders tend to stick to the mold during continuous dry pressing, preventing continuous production. Most manufacturers add liquid release agents to the spray-granulated powder, then mix and stir before use. This process has low mixing efficiency, poor release effect, is prone to sticking to the mold, is cumbersome, and is not conducive to mass production. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a method for improving the demolding effect of spray-granulated powder. This method, used for dry pressing of non-metallic ceramic powder after spray granulation, features good demolding effect, less sticking to the mold, simple operation, and the ability to achieve continuous production.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for improving the demolding effect of spray-granulated powder, comprising the following steps:

[0006] The release material is mixed with a non-metallic ceramic slurry and ball-milled to obtain a mixed slurry.

[0007] The mixed slurry is spray-granulated to obtain powder;

[0008] The powder is placed in a mold and pressed into shape.

[0009] The release material includes oleic acid and glycerin, or aviation kerosene and zinc stearate; the ball milling time is 30 to 120 minutes.

[0010] Preferably, the mass ratio of oleic acid to glycerol is (1.5-4):1.

[0011] Preferably, the mass ratio of aviation kerosene to zinc stearate is 4:1.

[0012] Preferably, the mass of the release material in the mixed slurry accounts for 0.5 to 1.8% of the mass of the non-metallic ceramic powder.

[0013] Preferably, the preparation method of the non-metallic ceramic slurry includes the following steps:

[0014] Non-metallic ceramic powder is mixed with water and subjected to a first ball milling process to obtain the non-metallic ceramic slurry.

[0015] Preferably, the non-metallic ceramic powder includes alumina ceramic powder, zirconia ceramic powder, silicon carbide ceramic powder, or boron carbide ceramic powder.

[0016] Preferably, the mass ratio of the non-metallic ceramic powder to water is (1-1.5):1.

[0017] Preferably, the spray granulation is carried out in a centrifugal spray dryer; the centrifugal spray dryer has an inlet temperature of 170±10℃, an outlet temperature of 80±10℃, an atomization rate of 32Hz, a negative pressure of 0.2kPa, and a feeding rate of 12~17Hz.

[0018] Preferably, the pressing process includes dry pressing and / or cold isostatic pressing.

[0019] Preferably, the pressing pressure is 1 to 2 tons per square centimeter.

[0020] This invention provides a method for improving the demolding effect of spray-granulated powder, comprising the following steps: mixing a demolding material with a non-metallic ceramic slurry and ball milling it to obtain a mixed slurry; spray-granulating the mixed slurry to obtain powder; and placing the powder in a mold for pressing. The demolding material includes oleic acid and glycerin, or aviation kerosene and zinc stearate; the ball milling time is 30–120 min. In this invention, the demolding material mainly removes the molded object from the mold by forming a separation layer, reducing the adhesion between the mold and the powder surface, and accelerating the curing time. The method provided by this invention for dry pressing of non-metallic ceramic powder after spray granulation has the characteristics of good demolding effect, less sticking to the mold, simple operation, and continuous production capability. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 Image of the silicon carbide ceramic prepared in Example 1;

[0023] Figure 2 Image of the silicon carbide ceramic prepared in Comparative Example 2;

[0024] Figure 3 Image of silicon carbide ceramic prepared in Comparative Example 3. Detailed Implementation

[0025] This invention provides a method for improving the demolding effect of spray-granulated powder, comprising the following steps:

[0026] The release material is mixed with the non-metallic ceramic slurry and then ball-milled to obtain a mixed slurry.

[0027] The mixed slurry is spray-granulated to obtain powder;

[0028] The powder is placed in a mold and pressed to form a non-metallic ceramic.

[0029] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0030] This invention involves mixing a release material with a non-metallic ceramic slurry and then ball milling the mixture to obtain a mixed slurry.

[0031] In this invention, the release material comprises oleic acid and glycerin, or aviation kerosene and zinc stearate; the mass ratio of oleic acid to glycerin is preferably (1.5–4):1, more preferably (2–3.5):1, and even more preferably 3:1; the mass ratio of aviation kerosene to zinc stearate is preferably 4:1. In this invention, the mass of the release material in the mixed slurry preferably accounts for 0.5–1.8% of the mass of the non-metallic ceramic powder, more preferably 0.8–1.4%, and even more preferably 1.2%.

[0032] In this invention, the ball milling time is 30–120 min, preferably 50–100 min, and more preferably 60 min. The ball-to-material ratio in this invention is preferably 1:1. This invention does not have specific requirements for the ball milling speed; any speed well-known in the art can be used. In this invention, if the ball milling time is greater than 120 min, during dry pressing, the powder is prone to sticking to the mold during continuous automatic pressing, leading to product abnormalities and preventing continuous production. If the ball milling time is less than 30 min, the demolding material and slurry are not fully integrated, thus failing to achieve the final demolding effect.

[0033] In this invention, the method for preparing the non-metallic ceramic slurry preferably includes the following steps:

[0034] Non-metallic ceramic powder is mixed with water and subjected to a first ball milling process to obtain the non-metallic ceramic slurry.

[0035] In this invention, the non-metallic ceramic powder preferably includes alumina ceramic powder, zirconia ceramic powder, silicon carbide ceramic powder, or boron carbide ceramic powder; the mass ratio of the non-metallic ceramic powder to water is preferably (1-1.5):1, more preferably (1.2-1.4):1; the first ball milling time is preferably 8-10 hours, more preferably 8.5-9.5 hours; the ball-to-material ratio of the first ball mill is preferably 1:1. This invention does not have special requirements for the rotational speed of the first ball mill; speeds well-known in the art can be used.

[0036] After obtaining the mixed slurry, the present invention performs spray granulation on the mixed slurry to obtain powder.

[0037] In this invention, the spray granulation is preferably carried out in a centrifugal spray dryer; the inlet temperature of the centrifugal spray dryer is preferably 170±10℃, more preferably 170℃; the outlet temperature of the centrifugal spray dryer is preferably 80±10℃, more preferably 80℃; the atomization rate of the centrifugal spray dryer is preferably 32Hz, the negative pressure is preferably 0.2kPa, and the feeding rate is preferably 12~17Hz. The use of a centrifugal spray dryer for spray granulation in this invention has the characteristics of fast drying speed and spherical granulation, making it suitable for dry powder compression molding.

[0038] After obtaining the powder, the present invention places the powder in a mold for pressing and shaping.

[0039] In this invention, the pressing molding preferably includes dry pressing and / or cold isostatic pressing, more preferably including dry pressing and cold isostatic pressing; the pressing pressure is preferably 1-2 tons per square centimeter, more preferably 1.2-1.8 tons per square centimeter, and even more preferably 1.5 tons per square centimeter. In this invention, when the pressing pressure exceeds 2.5 tons per square centimeter, cracks will appear on the inner or outer circumference of the product after pressing.

[0040] The method provided by this invention is used for dry pressing of non-metallic ceramic powder after spray granulation. It has the characteristics of good demolding effect, not easy to stick to the mold, simple operation and continuous production.

[0041] To further illustrate the present invention, the release material and its application method provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] Silicon carbide ceramic powder was added to a ball mill, followed by an equal amount of water, and the first ball milling was performed for 10 hours. ， A non-metallic ceramic slurry was obtained;

[0044] The release material (the mass ratio of oleic acid to glycerin is 3:1, and the mass of the release material accounts for 1.2% of the mass of the non-metallic ceramic powder) is added to a ball mill for a second ball milling process. The second ball milling time is 60 minutes to obtain a mixed slurry.

[0045] The mixed slurry was removed from the ball mill and then spray-granulated using a centrifugal spray dryer. The inlet temperature of the centrifugal spray dryer was 170℃±10℃, the outlet temperature was 80℃±10℃, the atomization rate was 32Hz, the negative pressure was 0.2kPa, and the feeding rate was 15Hz to obtain powder.

[0046] The powder is formed in a continuous automatic dry press by first dry pressing and then isostatic pressing. The forming pressure is 1.5 tons / square centimeter, resulting in non-metallic ceramics with a water content of 0.8-1.2%. Figure 1 The image shows the silicon carbide ceramic prepared in Example 1. It can be seen from the image that... ， The silicon carbide ceramic prepared according to the method of the present invention has a regular surface.

[0047] Example 2

[0048] The preparation steps are the same as in Example 1, except that the second ball milling time is 30 min.

[0049] Example 3

[0050] The preparation steps are the same as in Example 1, except that the release material is a mixture of aviation kerosene and zinc stearate, with a mass ratio of aviation kerosene to zinc stearate of 4:1.

[0051] Comparative Example 1

[0052] The preparation steps are the same as in Example 1, except that the second ball milling time is 130 min.

[0053] Comparative Example 2

[0054] The preparation steps are the same as in Example 1, except that no release material is added. Figure 2 The image shows the silicon carbide ceramic prepared in Comparative Example 2. From the image, it can be seen that... ， Without adding release material, its surface is uneven.

[0055] Comparative Example 3

[0056] The preparation steps are the same as in Example 1, except that the second ball milling time is 15 min. Figure 3 The image shows the silicon carbide ceramic prepared in Comparative Example 3. From the image, it can be seen that... ， If the second ball milling time is less than 30 minutes, the product is abnormal.

[0057] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for improving the demolding effect of spray-granulated powder, characterized in that, The specific steps are as follows: The release material is mixed with a non-metallic ceramic slurry and ball-milled to obtain a mixed slurry. The mixed slurry is spray-granulated to obtain powder; The powder is placed in a mold and pressed into shape. The release material is oleic acid and glycerin, the mass ratio of oleic acid to glycerin is 3:1, and the ball milling time is 30~120min; The mass of the release material in the mixed slurry accounts for 1.2% of the mass of the non-metallic ceramic powder; The preparation method of the non-metallic ceramic slurry specifically includes the following steps: Non-metallic ceramic powder is mixed with water and subjected to a first ball milling process to obtain the non-metallic ceramic slurry. The spray granulation is carried out in a centrifugal spray dryer; the inlet temperature of the centrifugal spray dryer is 170℃, the outlet temperature is 80℃, the atomization rate is 32Hz, the negative pressure is 0.2kPa, and the feeding rate is 12~17Hz. The pressing process includes dry pressing and cold isostatic pressing.

2. The method according to claim 1, characterized in that, The non-metallic ceramic powder includes alumina ceramic powder, zirconia ceramic powder, silicon carbide ceramic powder, or boron carbide ceramic powder.

3. The method according to claim 1 or 2, characterized in that, The mass ratio of the non-metallic ceramic powder to water is (1~1.5):

1.

4. The method according to claim 1, characterized in that, The pressing pressure is 1 to 2 tons per square centimeter.

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