A process for making a catalytically decomposable silicate feed for pressure forming

Abstract

The application discloses a kind of silicate feed preparation methods for pressure forming catalytically decomposable, comprising the following steps: step one, silicate powder preparation: select the silicate powder of powder particle size 0.5-60 μm;Step two, binder powder preparation: including lubrication and activator, skeleton agent, powder carrier agent, after the above raw materials are mixed, using pulverizer to crush, so that particle size reaches 10-30 μm between;Step three, feed precursor preparation: the silicate powder in step one is mixed with the binder powder in step two according to certain volume ratio;Step four, mixing: the feed precursor in step three is placed into mixing chamber, and the feed precursor is made into feed briquetting;Step five, granulation: extrusion cutting into small particles or powder after proper cooling feed briquetting;Step six, catalytic debinding: make white blank obtain porous yellow blank.The application has the following advantages and effects: while preparing feed, effectively removing binder, and ensuring the forming of feed blank.

Description

Technical Field

[0001] This invention relates to the field of chemical processing, and in particular to a method for preparing catalytically decomposable silicate feedstock for pressure forming. Background Technology

[0002] Silicate materials are transparent and belong to the category of disordered supercooled liquid substances in materials science. After melting at high temperatures, they form a smooth and high-density state on a free surface. Therefore, if silicate materials can be molded into specific shapes, they can be used by humans to provide items such as cups, bowls, pots, water bottles, wine bottles, etc. If the silicate materials are purified, they can be used for biological and chemical experiments. After use, they can be reused after cleaning. If they are accidentally broken or there are defects in the manufacturing process, these silicate materials can be recycled to make new utensils. They are an environmentally friendly and green circular material.

[0003] Powder molding is a method of manufacturing products by shaping powdered materials. While most existing materials can be made into powder, for materials with high hardness and no plasticity, such as cemented carbides and silicates, powder processing requires the use of powder encapsulants and binders to encapsulate the powder. The binders work by pressing and bonding the powder together, helping to form a specific shape. The binders are then removed to obtain a final shaped preform of the powder material, which is then cured at high temperatures to obtain the final product. This process involves the preparation of the mixture of binder and powder, i.e., the feedstock.

[0004] The considerable amount of binder added to the feedstock is crucial for powder molding. However, the binder's assistance during the molding process becomes a burden after high-temperature curing and debinding. Removing the binder cannot safely and effectively guarantee the shape of the powder preform during the curing process. Improper debinding can lead to preform cracking and powder preform collapse, which is very troublesome.

[0005] Therefore, how to develop a silicate powder feedstock for pressure forming to obtain a molded blank, and how to properly degrease and remove glue to obtain the final product, is an urgent problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for preparing catalytically decomposable silicate feedstock for pressure forming, thereby achieving smooth debinding of the silicate feedstock and effectively ensuring the shape of the solidified powder blank.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for producing a catalytically decomposable silicate feedstock for pressure forming, characterized by comprising the following steps:

[0008] Step 1: Preparation of silicate powder: Select silicate powder with a particle size of 0.5-60μm;

[0009] 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.

[0010] 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;

[0011] Step 4, Mixing: Place the feed precursor from Step 3 into the mixing chamber and form the feed precursor into feed lumps;

[0012] Step 5: Granulation: Cool the feed clumps appropriately and extrude and cut them into small granules or powder;

[0013] Step 6: Catalytic degreasing: to obtain porous yellow blanks from white blanks.

[0014] The present invention is further configured such that: the lubricant and activator in step two 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; and the skeleton agent is one or more of polyethylene and polypropylene.

[0015] The present invention is further configured such that the lubricant and activator also includes a toughening grafting agent, specifically one or more of ethylene-vinyl acetate copolymer and butadiene rubber.

[0016] The present invention is further configured such that the weight ratio of the lubricant and activator is 0.2-20%;

[0017] The powder entrainer accounts for 60-93% by weight;

[0018] The weight percentage of the skeleton agent is 3-25%;

[0019] The toughening grafting agent accounts for 0.5-10% by weight.

[0020] The present invention is further configured such that the volume ratio of the silicate powder to the binder is (2-1):1.

[0021] The present invention is further configured such that step four specifically includes steps such as preheating the feed precursor, heating the feed precursor, accelerating the stirring of the feed, and cooling the feed, wherein the preheating temperature is 110℃, the holding time is 20-40 minutes, and the stirring speed is 3-5 RPM.

[0022] The present invention is further configured such that: when the feed precursor is heated to 170°C, the movement state of the pressure hammer is observed at every 1°C increase, and the pressure hammer maintains up-and-down undulating motion. This step is repeated until the temperature rises to 180°C.

[0023] The present invention is further configured such that the stirring speed of the so-called feeding acceleration stirring step is 20-40 RPM and the stirring time is 20-40 minutes.

[0024] The present invention is further configured such that: during the feeding and cooling step, the stirring speed is reduced to 3-5 RPM, and the mixing operation is completed after the temperature drops to 165°C.

[0025] The present invention is further configured such that the catalytic degreasing step is carried out under an oxalic acid or nitric acid atmosphere, and the temperature range is between 90-150°C.

[0026] Compared to existing technologies, the beneficial effects of this invention are as follows: In the final catalytic degreasing step, polyoxymethylene (POM) plastic can be decomposed in an oxalic acid or nitric acid atmosphere at a temperature range of 90-150°C. POM thus decomposes into formaldehyde gas, achieving complete removal of the powder entrainer. Simultaneously, the lower-temperature fusible lubricant and activator are also liquefied during this stage and separated from the blank by gravity settling. After removing most of the powder entrainer, lubricant, and activator, the blank becomes a porous yellow blank. The porous yellow blank, supported by the skeleton agent and toughening grafting agent, can maintain the geometric shape of the molded blank. In the degreased yellow blank, the removed powder entrainer, lubricant, and activator form continuous pores, like tunnel-like paths, providing channels for airflow and heat flow in subsequent thermal processes, preparing the silicate powder blank for sintering shrinkage. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the silicate feeding process of this application;

[0028] Figure 2 This is a schematic diagram of the silicate feed manufacturing process of this application. Detailed Implementation

[0029] 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.

[0030] A method for preparing catalytically decomposable silicate feedstock for pressure forming is proposed, which enables the smooth degreasing of silicate feedstock and effectively ensures the shape of the solidified powder blank.

[0031] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for manufacturing a catalytically decomposable silicate feedstock for pressure forming, comprising the following steps:

[0032] Step 1: Preparation of silicate powder: Select silicate powder with a particle size of 0.5-60μm;

[0033] 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.

[0034] 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;

[0035] Step 4, Mixing: Place the feed precursor from Step 3 into the mixing chamber and form the feed precursor into feed lumps;

[0036] Step 5: Granulation: Cool the feed clumps appropriately and extrude and cut them into small granules or powder;

[0037] Step 6: Catalytic degreasing: to obtain porous yellow blanks from white blanks.

[0038] 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:

[0039] Various transparent and opaque silicate materials, as well as materials of different colors and with added inorganic powders;

[0040] Silicate sheet materials and their scraps;

[0041] Defective or scrapped products from the manufacturing process of conventional silicate products;

[0042] Recycled materials from commercial silicate products, etc.

[0043] The binder powder used in step two also uses commercially available conventional polymer materials;

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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℃.

[0048] 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.

[0049] Furthermore, the weight percentage of lubricant and activator is 0.2-20%;

[0050] The weight percentage of the powder entrainer is 60-93%;

[0051] The weight percentage of the matrix agent is 3-25%;

[0052] The toughening grafting agent accounts for 0.5-10% by weight.

[0053] 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.

[0054] Furthermore, the mixing process includes the following steps:

[0055] (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.

[0056] 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.

[0057] (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.

[0058] (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℃.

[0059] (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.

[0060] (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;

[0061] (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.

[0062] (7) Stop the equipment and remove the feed clumps.

[0063] 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.

[0064] Furthermore, the catalytic degreasing step is carried out in an oxalic acid or nitric acid atmosphere at a temperature range of 90-150°C. The effectiveness of the catalytic degreasing can be determined by measuring the weight difference of the feed before and after the catalytic degreasing operation. In this step, polyoxymethylene (POM) separates into formaldehyde gas, thereby achieving the complete removal of powder entrainers. Simultaneously, the lower-temperature fusible lubricants and activators are also liquefied during this stage and separated from the blank by gravity settling. After removing most of the powder entrainers, lubricants, and activators, the blank becomes a porous yellow blank. The porous yellow blank, supported by the skeleton agent and toughening grafting agent, can maintain the geometric shape of the blank during molding. The removed powder entrainers, lubricants, and activators form continuous pores, like tunnels, in the degreased yellow blank, providing channels for airflow and heat flow in subsequent thermal processes, as preparation for the sintering and shrinkage of the silicate powder blank.

[0065] It should be noted that the calculation of the weight loss rate of catalytic degreasing is determined by the amount of binder powder entrainer in the formula with different shrinkage ratios, which is determined by the total amount of polyoxymethylene, i.e., the weight difference before and after degreasing.

[0066] Weight before degreasing: silicate powder + powder entrainer + lubricant and activator + skeleton agent + toughening grafting agent.

[0067] Weight after degreasing: silicate powder + skeleton agent + toughening grafting agent.

[0068] The weight loss rate of catalytic degreasing, expressed as a percentage, varies depending on the weight proportion of silicate. The main difference lies in the feeding design and adjustment required for product molding due to variations in silicate powder particle size. The weight loss portion is at least 60% of the total weight of the powder entrainer, lubricant, and activator.

[0069] Example 1

[0070] Formula ratio:

[0071]

[0072] Mixing parameters:

[0073]

[0074]

[0075] Defatting parameters:

[0076]

[0077] Result: The weight loss rate of the adhesive is >90% of the total weight of the adhesive.

[0078] Example 2

[0079] Formula ratio:

[0080]

[0081] Mixing parameters:

[0082]

[0083]

[0084] Defatting parameters:

[0085]

[0086] Result: The weight loss rate of the adhesive was >84% of the total weight of the adhesive.

[0087] Example 3

[0088] Formula ratio:

[0089]

[0090] Mixing parameters:

[0091]

[0092]

[0093] Defatting parameters:

[0094]

[0095] Result: The weight loss rate of the adhesive is >81% of the total weight of the adhesive.

[0096] Example 4

[0097] Formula ratio:

[0098]

[0099] Mixing parameters:

[0100]

[0101] Defatting parameters:

[0102]

[0103] Result: The weight loss rate of the adhesive was >78% of the total weight of the adhesive.

[0104] Example 5

[0105] Formula ratio:

[0106]

[0107] Mixing parameters:

[0108]

[0109]

[0110] Defatting parameters:

[0111]

[0112] Result: The weight loss rate of the adhesive is >73% of the total weight of the adhesive.

[0113] Example 6

[0114] Formula ratio:

[0115]

[0116]

[0117] Mixing parameters:

[0118]

[0119] Defatting parameters:

[0120]

[0121] Result: The weight loss rate of the adhesive is >68% of the total weight of the adhesive.

[0122] The above description is only a preferred embodiment of the present invention. Furthermore, the application field of the present invention is not limited to blanks made of silicate powder by injection molding machines, but can also be applied to blanks made by other types of powder forming equipment such as extruders, extruders, 3D printing filament extruders and powder blank presses. 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 process for the production of a catalytically decomposable silicate feedstock for pressure forming, characterized in that, It comprises the following steps: Step one, silicate powder preparation: select the powder particle size of 0.5-60 μm silicate powder; Step two, binder powder preparation: composed of lubricating and activating agent, skeleton agent, powder carrier agent, toughening grafting agent, after mixing the above raw materials, use the pulverizer to crush, make the particle size reach 10-30 μm; Step three, feed precursor preparation: mix the silicate powder in step one with the binder powder in step two according to a certain volume ratio; Step four, mixing: put the feed precursor in step three into the mixing chamber, and make the feed precursor into a feed block; Step five, granulation: cool the feed block appropriately and extrude and cut into small particles or powder; Step six, catalytic debinding: make the white body obtain porous yellow body; The lubricating and activating agent in step two is one or more of stearic acid, paraffin, microcrystalline wax, fischer-tropsch wax, polyethylene wax, ethylene bis-stearamide, pentaerythritol stearate, the powder carrier agent is copolymer 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; The weight percentage of the lubricating and activating agent is 0.2-20%, and the softening temperature range is 50-120℃; The weight percentage of the powder carrier agent is 60-93%, and the softening temperature range is 160-170℃; The weight percentage of the skeleton agent is 3-25%, and the softening temperature range is 140-160℃; The weight percentage of the toughening grafting agent is 0.5-10%; The catalytic debinding step in step six is carried out in oxalic acid or nitric acid atmosphere, and the temperature range is 90-150℃.

2. A process for making a catalytically decomposable silicate feedstock for pressure forming according to claim 1, characterised in that: The volume ratio of the silicate powder to the binder is (2-1):

1.

3. A process for making a catalytically decomposable silicate feedstock for pressure forming according to claim 1, characterized in that: The step four further comprises the steps of feed precursor preheating, feed precursor warming, feed accelerating stirring, and feed cooling, wherein the preheating temperature is 110℃, the holding time is 20-40 minutes, and the stirring speed is 3-5 RPM.

4. A process for making a catalytically decomposable silicate feedstock for pressure forming according to claim 3, characterized in that: When the feed precursor is warmed to 170℃, the movement state of the press hammer is observed while increasing 1℃, the press hammer keeps up and down movement, and the step is repeated until the temperature rises to 180℃.

5. A process for making a catalytically decomposable silicate feedstock for pressure forming according to claim 3, characterized in that: The stirring speed of the feed accelerating stirring step is 20-40 RPM, and the stirring time is 20-40 minutes.

6. A process for making a catalytically decomposable silicate feedstock for pressure forming according to claim 3, characterized in that: In the feed cooling step, the stirring speed is reduced to 3-5 RPM, and the mixing operation is completed after the temperature is reduced to 165℃.

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