A method for eliminating holes in multi-characterized silicate articles

Abstract

The application discloses a method for eliminating holes of a multi-feature silicate product, and comprises the following steps: sintering and solidifying a silicate product obtained after silicate degreasing, and then performing a subsequent heat process, wherein the heat process comprises the following continuous processes: second-step degreasing, vacuum residual slag, partial pressure sintering, positive pressure hole elimination, and temperature reduction super-cold tempering. The application has the following advantages and effects: under the condition of ensuring that the silicate product does not collapse, the internal holes of the multi-feature silicate product are successfully eliminated, and the quality of the obtained silicate product is stable and has good consistency.

Description

Technical Field

[0001] This invention relates to the field of chemical processing, and in particular to a method for eliminating pores in multi-feature silicate products. Background Technology

[0002] Traditional silicate products, if not subjected to appropriate working pressure to eliminate internal pores in the silicate material, will not only suffer from visual defects but also have their light transmittance, a requirement for optical properties, compromised by the pores. It is well known that the pores in multi-feature silicate products originate from a blank formed by extruding billions of tiny powder particles mixed with a binder. During the high-temperature curing process, these pores are encapsulated within the multi-feature silicate material product. Furthermore, multi-feature silicate products obtained through powder processing have surfaces with many characteristic angles. Using conventional methods of filling with crushed silicate powder and then extruding and heating the molten material is inefficient and dangerous. Molding methods using mass extrusion to obtain blanks result in an enormous number of products, making it impossible to eliminate pores using conventional contact pressure transmission methods. Moreover, the viscosity of molten silicate fluid is very high. If pores are to be removed using a vacuum-assisted static defoaming method, an environment exceeding the melting temperature of the silicate material must be used, which would cause the multi-feature silicate product to melt and lose its characteristics. Therefore, it is necessary to consider a method of pressurizing the blank of molded multi-feature silicate products at a temperature far below the melting point using fluid isostatic pressing to eliminate voids.

[0003] Furthermore, the process of eliminating voids in the simultaneous molding and curing of multi-feature silicate products requires control of several crucial parameters, including the rate and duration of temperature rise, pressure changes from atmospheric pressure to negative pressure and then to high pressure, the type of pressurizing gas, and finally, surface heat treatment tempering. Without establishing stable parameters and methods for continuous operation, the produced silicate products will be of inconsistent quality and cannot be made into uniform products.

[0004] Therefore, the key point revealed by the method for eliminating pores in molded multi-feature silicate articles of the present invention is to overcome the difficulty of efficiently eliminating internal pores in molded multi-feature silicate articles using common processes. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for eliminating pores in multi-feature silicate products, which can ensure the structural stability of silicate products while removing small pores.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for eliminating pores in multi-feature silicate products, wherein the gray blank obtained after silicate degreasing is subjected to a subsequent thermal process of sintering and solidification, the thermal process including a second degreasing step, vacuum residual residue, partial pressure sintering, positive pressure pore removal, and cooling and extreme cold tempering, etc.

[0007] The present invention is further configured such that: the temperature range of the second degreasing step is 25-550℃, multi-temperature segment heating and heat preservation are adopted, and the negative pressure is 10-40KPa, the gas flow rate is 10-40L / min, and the atmosphere is nitrogen or argon.

[0008] The present invention is further configured such that: the temperature range for vacuum residue removal is 500-700℃, a process of heating in one stage and holding in one stage is adopted, and the vacuum pressure is less than 0.1KPa, and the atmosphere is nitrogen or argon.

[0009] The present invention is further configured such that: the partial pressure sintering temperature range is 550-1600℃, the end-section heating and multi-section heat preservation method is adopted, and the partial pressure range is 10-60KPa, the gas flow rate is 10-60L / min, and the atmosphere is nitrogen or argon.

[0010] The present invention is further configured such that: the partial pressure sintering temperature range is 550-1600℃, the end-section heating and multi-section heat preservation method is adopted, and the partial pressure range is 10-60KPa, the gas flow rate is 10-60L / min, and the atmosphere is nitrogen or argon.

[0011] The present invention is further configured such that: the positive pressure pore removal operation system is pressurized immediately after the heat preservation process of the partial pressure sintering, the temperature does not change during the pressurization process, the positive pressure is in the range of 101KPa-15MPa, and nitrogen, argon or a mixture of both atmospheres are used.

[0012] The present invention is further configured such that: the cooling and rapid cooling tempering system rapidly cools down from the positive pressure hole removal end temperature to the range of 100-150°C at a rate of more than 50°C per minute, the furnace pressure is first reduced to 101 kPa and then increased to the range of 15 MPa, and nitrogen, argon or a mixture of both atmospheres are used.

[0013] The present invention is further configured such that: the preparation process of the gray blank is to mix silicate powder with a binder, wherein the silicate powder has a particle size between 0.5-60μm and a melting temperature between 650-1600℃, and the binder includes a lubricant and activator, a powder entrainer, a skeleton agent, and a graft toughening agent.

[0014] The present invention is further configured such that: the lubricant and activator is one or more of stearic acid, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, ethylene bis-stearamide, and pentaerythritol stearate; the powder entrainer is copolyoxymethylene; the skeleton agent is one or more of polyethylene and polypropylene; and the graft toughening agent is one or more of ethylene-vinyl acetate copolymer and butadiene rubber.

[0015] The present invention is further configured such that the weight ratio of the lubricant and activator is 0.2-20%;

[0016] The powder entrainer accounts for 60-93% by weight;

[0017] The weight percentage of the skeleton agent is 3-25%;

[0018] The toughening grafting agent accounts for 0.5-10% by weight.

[0019] Compared with the prior art, the beneficial effect of the present invention is that it can ensure the structural stability of silicate products while removing small pores. Attached Figure Description

[0020] Figure 1 This is a manufacturing process diagram of the present invention;

[0021] Figure 2 This refers to the thermal process curve and parameter settings of Embodiment 1 of the present invention;

[0022] Figure 3 This refers to the thermal process curve and parameter settings of Embodiment 2 of the present invention. Detailed Implementation

[0023] The technical solutions described in this invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described in this specification are only some feasible technical solutions of this invention. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without any creative effort should be considered to fall within the scope of protection of this invention.

[0024] A method for eliminating pores in multi-feature silicate products involves sintering and solidifying the resulting gray blank after silicate degreasing, followed by a thermal process including a second degreasing step, vacuum residue removal, pressure sintering, positive pressure pore removal, and cooling and ultra-cold tempering.

[0025] The second step of degreasing involves a temperature range of 25-550℃, multi-stage heating and heat preservation, and a negative pressure of 10-40KPa, a gas flow rate of 10-40L / min, and a nitrogen or argon atmosphere to sequentially vaporize and remove all the binders in the gray blank.

[0026] The vacuum residue removal process involves a temperature range of 500-700℃, employing a combination of heating and heat preservation, and using a vacuum pressure of less than 0.1KPa and an atmosphere of nitrogen or argon. The main purpose is to eliminate residual skeletonizing agents in the blank and to bring silicate powders into close contact with each other.

[0027] The partial pressure sintering temperature range is 550-1600℃, and the end-section heating and multi-section heat preservation method is adopted. The partial pressure range is 10-60KPa, the gas flow rate is 10-60L / min, and the atmosphere is nitrogen or argon. The main purpose is to sinter and densify the silicate powder.

[0028] The partial pressure sintering temperature range is 550-1600℃, and the end-section heating and multi-section heat preservation method is adopted. The partial pressure range is 10-60KPa, the gas flow rate is 10-60L / min, and the atmosphere is nitrogen or argon. The main purpose is to sinter and densify the silicate powder.

[0029] The positive pressure pore removal process involves applying pressure immediately after the heat preservation procedure of partial pressure sintering. The temperature remains unchanged during the pressure application process, and the positive pressure ranges from 101 kPa to 15 MPa. Nitrogen, argon, or a mixture of both atmospheres are used. The main purpose is to eliminate small pores in silicate products and improve their light transmittance.

[0030] The rapid cooling tempering system rapidly cools the temperature from the positive pressure hole removal end temperature to the range of 100-150°C at a rate of more than 50°C per minute. The pressure inside the furnace is first reduced to 101 kPa and then increased to the range of 15 MPa. Nitrogen, argon, or a mixture of both atmospheres are used. The main purpose is to rapidly cool and temper silicate products.

[0031] In this application, the feedstock for the gray blank is prepared from silicate powder and binder. The particle size of the silicate powder is between 0.5 and 0.6 μm, and the binder includes lubricants and activators, powder entrainers, skeleton agents, and graft toughening agents.

[0032] The preparation of feed includes the following steps:

[0033] Step 1: Preparation of silicate powder: Select silicate powder with a particle size of 0.5-60μm;

[0034] Step 2: Preparation of binder powder: This includes lubricant and activator, skeleton agent, and powder entrainer. After mixing the above raw materials, use a pulverizer to pulverize them so that the particle size reaches between 10-30μm.

[0035] Step 3, Preparation of feed precursor: Mix the silicate powder from Step 1 with the binder powder from Step 2 at a certain volume ratio;

[0036] Step 4, Mixing: Place the feed precursor from Step 3 into the mixing chamber and form the feed precursor into feed lumps;

[0037] Step 5: Granulation: Cool the feed clumps appropriately and extrude and cut them into small granules or powder;

[0038] Step 6: Catalytic degreasing: to obtain porous yellow blanks from white blanks.

[0039] In step one, the silicate powder used is commercially available conventional silicate powder. The powder shape should preferably be equiaxed, including spherical and irregular shapes. Specifically, the sources of silicate powder include, but are not limited to:

[0040] Various transparent and opaque silicate materials, as well as materials of different colors and with added inorganic powders;

[0041] Silicate sheet materials and their scraps;

[0042] Defective or scrapped products from the manufacturing process of conventional silicate products;

[0043] Recycled materials from commercial silicate products, etc.

[0044] The binder powder used in step two is also a commercially available conventional polymer material;

[0045] In step three, the ratio of silicate powder and binder powder is calculated, weighed, and mixed according to Archimedes' principle, and then put into a premixer for mixing to form a feed precursor.

[0046] Furthermore, in the components of the adhesive powder in step two, the lubricant and activator are specifically one or more of stearic acid, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, ethylene bis-stearamide, and pentaerythritol stearate; the softening temperature range of the above lubricant and activator is between 50-120°C. In the technical solution of this application, its main function is to fill the pores and wet the surface of the silicate powder, thereby enabling it to bond with other adhesives.

[0047] Furthermore, the powder entrainer is copolymerized polyoxymethylene, i.e., polyoxymethylene plastic, with a softening temperature range of 160-170℃. In the technical solution of this application, its main function is to coat the powder and carry the powder along with it during the feeding and melting process.

[0048] Furthermore, the skeleton agent is one or more of polyethylene and polypropylene, with a softening temperature range of 140-160℃. Its main function is to support the powder-molded preform during the process of 25-600℃.

[0049] Furthermore, in the technical solution of this application, the lubricant and activator also includes a toughening grafting agent, specifically one or more of ethylene-vinyl acetate copolymer and butadiene rubber. Its main function is to assist in the mutual solubility of the powder entrainer and the skeleton agent, and to make the blank elastic so as not to crack when it leaves the mold.

[0050] Furthermore, the weight percentage of lubricant and activator is 0.2-20%;

[0051] The weight percentage of the powder entrainer is 60-93%;

[0052] The weight percentage of the matrix agent is 3-25%;

[0053] The toughening grafting agent accounts for 0.5-10% by weight.

[0054] Furthermore, in step four, the mixing equipment is a common commercially available mixing equipment, including a pressure hammer driven by an adjustable reciprocating servo cylinder and a U-shaped mixing chamber. Several heating tubes are installed in the U-shaped mixing chamber for heating. A mixing space is formed between the pressure hammer and the U-shaped mixing chamber, with a certain exhaust gap. Several spiral rotors are also installed in the mixing space for stirring.

[0055] Furthermore, the mixing process includes the following steps:

[0056] (1) Preheating of feed precursors: The temperature gradually rises to about 110℃ and the preheating time is 20-40 minutes. The stirring speed is 3-5 RPM and the pressure hammer does not press down during this stage.

[0057] The preheating stage of the feed precursor is mainly to remove the moisture in the feed precursor. The heating of the mixing chamber and slow stirring allow the moisture in the various raw materials to be discharged smoothly. At the same time, the pressure hammer does not press down during this stage, which also ensures that the various raw materials have enough space to be heated and stirred.

[0058] (2) Heating of feed precursor: In this stage, the temperature is further heated to 170°C, so that the feed precursor can absorb heat and heat up. At the same time, the pressure hammer begins to press down to help remove the air and moisture contained in the precursor. At this time, the speed is still 3-5 RPM, which can be slightly reduced compared to the preheating stage. The slight reduction in speed is mainly to prevent powder from splashing and leaking.

[0059] (3) Fine adjustment of the temperature of the feed precursor: 170℃ is the temperature at which polyoxymethylene begins to melt into mud. Therefore, after the temperature reaches 170℃, in order to avoid excessive high temperature causing the polyoxymethylene to vaporize and decompose, the movement state of the pressure hammer is observed for every 1℃ increase until it increases by another 1℃. This step is repeated until the temperature reaches 180℃.

[0060] (4) Observe whether the feed forms clumps: By observing whether the hammer moves up and down, determine that the temperature has continued to increase until the hammer has moved up and down. When the hammer is raised, sort out the material in the mixing chamber and clean the powder that overflows around the chamber.

[0061] (5) Accelerate feeding and mixing: Maintain the agglomeration temperature and press the hammer down onto the feed agglomeration, increase the rotor speed to 20-40 RPM and maintain it for 20-40 minutes to ensure that all materials are mixed so that the silicate feed is uniform;

[0062] (6) Feeding and cooling: Stop the heater and keep the hammer pressing down. Adjust the rotor speed to 3-5 RPM and wait for the temperature to drop to 165℃ to complete the feeding and mixing operation.

[0063] (7) Stop the equipment and remove the feed clumps.

[0064] Furthermore, it also includes a granulation step, where the appropriately cooled feed agglomerates are extruded and cut into small particles or powder for subsequent molding. It is not recommended to use a crusher here, as it can easily lead to uneven particle size and excessively fine particles, resulting in feed loss.

[0065] Furthermore, it also includes the molding step, which uses pressure extrusion molding, including but not limited to compression molding, extrusion molding and injection molding. The feed made of silicate mixture is heated and pressure is applied to liquefy it and injected into a mold cavity. After cooling and solidification, the molded product is taken out and called a blank. The blank already has multiple features in multiple directions.

[0066] The first step is degreasing, which aims to remove the binder from the blank. The degreasing method of the present invention can be adapted to different binder formulations and is suitable for hot degreasing, catalytic degreasing, solvent degreasing, and combined degreasing operation modes. The main purpose of the first step of degreasing is to remove the lubricant, activator and powder entrainer from the blank, so that the blank forms a porous structure, but the skeleton agent and graft toughening agent support the blank to maintain the correct multi-feature shape.

[0067] The specific steps and parameters for the subsequent hot processing of the blank after the first degreasing step in this application are shown in Table 1 below:

[0068] Table 1. Procedures for using the same dedicated furnace without interruption in the hot process.

[0069]

[0070]

[0071] Example 1: Silicate powder with a melting point of 650℃ was used, and the sintering temperature was 580℃. This temperature was derived from thermogravimetric analysis and observation of the highest temperature at which the gray blank of a multi-characteristic silicate product did not collapse during high-temperature furnace testing. Specific thermal process curves and parameter settings are as follows: Figure 2 As shown.

[0072] Example 2: Silicate powder with a melting point of 1550℃ was used, and the sintering temperature was 1400℃. This temperature was derived from thermogravimetric analysis and observation of the highest temperature at which the gray blank of the multi-characteristic silicate product did not collapse during high-temperature furnace testing. Specific thermal process curves and parameter settings are as follows: Figure 3 As shown.

[0073] As mentioned above, the technical solution of this application eliminates the internal pores in molded multi-feature silicate products, and the resulting products have stable quality and good consistency.

[0074] The above description is only a preferred embodiment of the present invention. In addition, the application field of the present invention is not limited to molding processes, but can also be applied to other non-molding processes. For example, multi-feature silicate products made by powder 3D printing can also use the solution of the present invention to eliminate pores. It should be noted that for those skilled in the art, several improvements and additions can be made without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method of eliminating holes in a multi-component silicate article, characterized by, The prepared ash blank after silicate degreasing is sintered and solidified for subsequent heat treatment, and the heat treatment includes a second step of degreasing, vacuum residue removal, partial pressure sintering, positive pressure hole removal, and continuous processes of temperature reduction and rapid cooling and toughening; The positive pressure hole removal operation is immediately pressurized after the holding procedure of the partial pressure sintering, the temperature does not change during the pressurization process, the positive pressure is in the range of 5 MPa-15 MPa, and nitrogen or argon or a mixed atmosphere of the two is used; The temperature range of the second step of degreasing is 25-550℃, and multi-temperature section heating and holding are adopted, the negative pressure is 10-40 kPa, the gas flow is 10-40 L / min, and nitrogen or argon is used as the atmosphere; The temperature range of the vacuum residue removal is 500-700℃, and one-stage heating and one-stage holding are adopted, the vacuum degree is less than 0.1 KPa, and nitrogen or argon is used as the atmosphere.

2. The method of eliminating holes in multi-featured silicate articles according to claim 1, characterized in that: The temperature range of the partial pressure sintering is 550-1600℃, and end-section heating and multi-section holding are adopted, the partial pressure is in the range of 10-60 kPa, the gas flow is 10-60 L / min, and nitrogen or argon is used as the atmosphere.

3. The method of eliminating holes in multi-featured silicate articles of claim 2, wherein: The temperature reduction and rapid cooling and toughening are rapidly cooled from the temperature at which the positive pressure hole removal ends to the range of 100-150℃ at more than 50℃ per minute, the furnace pressure is first reduced to 101 kPa and then increased to 15 MPa, and nitrogen or argon or a mixed atmosphere of the two is used.

4. The method of eliminating holes in multi-featured silicate articles of claim 3, wherein: The preparation process of the ash blank is to mix silicate powder and a binder, the particle size of the silicate powder is 0.5-60μm, the melting temperature is 650-1600℃, and the binder includes lubricating and activating agents, powder carrying agents, skeleton agents, and toughening grafting agents.

5. The method of eliminating holes in multi-featured silicate articles of claim 4, wherein: The lubricating and activating agents are one or more of stearic acid, paraffin, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, ethylene bis-stearamide, and pentaerythritol stearate, the powder carrying agent is copolymerized formaldehyde, the skeleton agent is one or more of polyethylene and polypropylene, and the toughening grafting agent is one or more of ethylene-vinyl acetate copolymer and butadiene rubber.

6. The method of eliminating holes in multi-featured silicate articles of claim 5, wherein: The weight percentage of the lubricating and activating agents is 0.2-20%; The weight percentage of the powder carrying agent is 60-93%; The weight percentage of the skeleton agent is 3-25%; The weight percentage of the toughening grafting agent is 0.5-10%.

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