A one-step formed graphite crucible and a method and apparatus for making the same

Abstract

The application provides a one-step forming graphite crucible and a preparation method and device thereof, and the graphite crucible comprises the following raw materials in parts by mass: 70-80 parts of artificial graphite powder, 10-15 parts of mesophase carbon microbeads, 10-15 parts of vermicular graphite powder, 20-25 parts of thermosetting phenolic resin, 1-2 parts of additives, 1-2 parts of a release agent, and 1-3 parts of benzidine; in the patent, the thermosetting phenolic resin is used as a binder; the thermosetting resin has certain fluidity under heating and pressurization, and a solidification reaction occurs, so that a secondary powder grinding process after mixing is omitted, and the product does not need to be impregnated for densification and strength improvement, powder mixing is more uniform, and the product after forming has better homogeneity.

Description

Technical Field

[0001] This invention belongs to the field of crucible manufacturing, and particularly relates to a one-piece molded graphite crucible and its preparation method and apparatus. Background Technology

[0002] Graphite has advantages such as high strength, good lubricity and good plasticity. Graphite crucibles are also widely used in the chemical field. However, most traditional graphite crucibles currently use asphalt binders. When using asphalt binders, in order to improve the strength of the product, the product needs to be impregnated multiple times to increase density and strength. Furthermore, the casting process requires core removal, which makes the preparation method complex, the raw material cost high and the production efficiency low. Summary of the Invention

[0003] The technical problem to be solved by the present invention is that the traditional method of manufacturing graphite crucibles is complicated. To overcome the shortcomings and defects mentioned in the background art above, the present invention provides a one-time molding graphite crucible and its preparation method and apparatus.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0005] A one-piece molded graphite crucible, the graphite crucible comprising the following parts by weight of raw materials:

[0006] 70-80 parts of artificial graphite powder, 10-15 parts of mesophase carbon microspheres, 10-15 parts of worm-like graphite powder, 5-10 parts of polyvinyl butyral, 20-25 parts of thermosetting phenolic resin, 1-2 parts of additives, 1-2 parts of release agent, and 1-3 parts of curing agent.

[0007] In the artificial graphite powder, 60-100 mesh accounts for 70-80% of the artificial graphite powder, and 100-200 mesh accounts for 20-30% of the artificial graphite powder; the mesh size of the mesophase carbon microspheres is not less than 325 mesh, and the mesh size of the worm-like graphite powder is not less than 100 mesh.

[0008] Traditional isostatic pressing graphite production processes are complex and time-consuming, requiring steps such as grinding, kneading, secondary grinding, pre-pressing, isostatic pressing, and firing. Repeated impregnation and firing enhance strength and achieve graphitization. This application uses graphite powders of various mesh sizes as raw materials and thermosetting phenolic resin as a binder to prepare one-piece molded graphite crucibles. Thermosetting phenolic resin can be molded in one step during hot pressing and possesses higher strength, eliminating the need for repeated impregnation and firing to increase density and strength. Furthermore, because the raw material is graphite powder, the graphitization process is eliminated, thus optimizing the production process and raw materials for the graphite crucibles.

[0009] The raw materials are a combination of artificial graphite powder of different particle sizes, mesophase carbon microspheres (MCMB) and worm-like graphite powder, and an appropriate amount of thermosetting phenolic resin is selected. The resulting one-time sintered graphite crucible has a dense texture and high strength.

[0010] Preferably, the dispersant comprises sodium alginate, the release agent comprises a mixture of stearic acid and paraffin, and the curing agent is benzidine.

[0011] Sodium alginate was selected as an additive to improve the bonding between graphite particles, and benzidine was used as a curing agent for thermosetting phenolic resin. This ensures both the pass rate of the finished product during kneading and the final strength of the product.

[0012] Under the same technical concept, the present invention also provides a method for preparing a one-piece molded graphite crucible, comprising the following steps:

[0013] (1) Polyvinyl butyral ester was used to granulate artificial graphite powder, and mesophase carbon microsphere powder and worm-like graphite powder were added. The mixture was kneaded at room temperature for 20-40 min, then heated to 120-140℃, and additives were added and mixed for 20-40 min. The temperature was lowered to 60-70℃, and thermosetting phenolic resin was added and kneaded for 20-40 min. Then benzidine and release agent were added and kneaded for another 20-30 min. After cooling, crushing and sieving, 60-200 mesh graphite crucible powder raw material was obtained.

[0014] (2) Pour the graphite crucible powder raw material obtained in step (1) into the molding mold, and keep the pressure at 10MPa-15MPa at 150℃-170℃ for 5min-10min.

[0015] (3) Demold the molded sample and heat it to a temperature of not less than 900℃ for carbonization to obtain a one-time molded graphite crucible.

[0016] Preferably, the method for granulating artificial graphite powder includes:

[0017] Polyvinyl butyral was prepared into a 3-5 wt.% aqueous solution. Artificial graphite powder was added to the polyvinyl butyral aqueous solution and granulated. The granulated powder was dried, ground and crushed, and then sieved to obtain granulated artificial graphite powder of 200-60 mesh.

[0018] Under the same technical concept, the present invention also provides a preparation device for a one-time molding graphite crucible. The preparation device is a molding die, including a mold core, a base, and a demolding ejector. The base includes a pedestal and a hollow cylindrical outer cylinder disposed on the pedestal. The mold core is cylindrical and is nested with the base. The demolding ejector is disposed below the hollow cylindrical outer cylinder of the base and corresponds to the longitudinal axis of the mold core.

[0019] The preparation device for the one-time molding graphite crucible is designed according to the structure of the one-time molding graphite crucible. Conventional molding molds are mostly used to process solid cylindrical products. The mold and base used in this device can realize the shape of the graphite crucible in one process, forming a crucible shape with the center hollowed out, avoiding subsequent processing and modification, and greatly simplifying the preparation process.

[0020] Preferably, the mold core is provided with a plurality of longitudinal mold core heating holes, and the base is provided with a plurality of base heating holes. The base heating holes are provided in both the longitudinal and transverse structures of the base, and the base heating holes and the mold core heating holes are connected to a heating device.

[0021] Preferably, the heating device is an electric heating element and / or a thermocouple.

[0022] Preferably, there is an 11-12mm gap between the mold core and the inner wall of the hollow cylindrical outer cylinder of the base, and a 50-60mm wide protrusion is left on the top of the mold core cylinder to fill the gap, and a protruding pull handle is provided on the outer surface of the top surface of the mold core cylinder.

[0023] Preferably, the pull handle has threads, the pull handle is connected to a press, and the threads are adapted to the connection of the press.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) In this invention, thermosetting phenolic resin is used as a binder. Thermosetting resin has a certain fluidity under heating and pressure and will undergo a curing reaction. Compared with using asphalt or liquid resin, thermosetting phenolic resin as a binder eliminates the need for secondary grinding after mixing, and does not require impregnation of the product to increase density and strength. The powder is mixed more evenly, and the homogeneity of the molded product is better.

[0026] (2) The powder and binder selected in this invention work together, and the crucible is prepared by one-time firing molding, which saves processing and raw material costs and improves production efficiency compared with traditional core-removing crucibles.

[0027] (3) The one-time forming graphite crucible forming device provided by this patent is designed to meet the process requirements, has a simple operation method, high adaptability, and has high market value. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a front view of the molding die for the one-piece graphite crucible used in Embodiment 1 of the present invention.

[0030] Figure 2 This is a schematic diagram of the overall structure of the molding die for the one-time molding graphite crucible used in Embodiment 1 of the present invention;

[0031] Among them, 1. mold core; 2. mold core heating hole; 3. base heating hole; 4. base; 5. crucible; 6. demolding ejector pin. Detailed Implementation

[0032] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] Example 1

[0036] A one-piece molded graphite crucible comprising the following parts by weight of raw materials:

[0037] The composition includes 800g of artificial graphite powder, 100g of MCMB, 100g of worm-shaped graphite powder, 80g of polyvinyl butyral (PVB), 200g of thermosetting phenolic resin, 15g of additives, 15g of release agent, and 20g of benzidine. In the artificial graphite powder, 70% by weight is 60-100 mesh, and 30% by weight is 100-200 mesh. The mesophase carbon microspheres have a mesh size of 325, and the worm-shaped graphite powder has a mesh size of 100.

[0038] The apparatus used in the one-piece molding graphite crucible preparation method of this embodiment includes a molding mold, such as... Figure 1 , 2 As shown;

[0039] The molding die includes a core 1, a base 4, and a ejector pin 6. The base 4 includes a base and a hollow cylindrical outer cylinder set on the base. The core 1 is cylindrical and is nested with the base 4. The ejector pin 6 is set below the hollow cylindrical outer cylinder of the base 4 and corresponds to the longitudinal axis of the core 1.

[0040] The mold core 1 is provided with multiple longitudinal mold core heating holes 2, and the base 4 is provided with multiple base heating holes 3. The base heating holes 3 are provided in both the longitudinal and transverse structures of the base 4. The base heating holes 3 and the mold core heating holes 2 are connected to the heating device.

[0041] Both the mold core and the base are designed with heating holes. Electric heating tubes and thermocouples are placed in the holes to control the required heating temperature and achieve the effect of over-pressing and heating molding.

[0042] A 10-12mm gap is provided between the mold core 1 and the inner wall of the hollow cylindrical outer cylinder of the base 4 for filling the crucible 5 and its preparation raw materials. A 50-60mm wide protrusion is left on the top of the cylinder of the mold core 1 to fill the gap. A protruding cylindrical pull handle is provided on the top surface of the cylinder of the mold core 1 to facilitate the removal of the mold core 1 after preparation. The protruding pull handle has a threaded structure and is inserted into the pressing platform of the press.

[0043] The ejector pin 6 is cylindrical, with a ring of cylindrical protrusions on top, which fits into the base 4, facilitating the insertion and removal of the ejector pin 6 and the demolding of the crucible 5.

[0044] The method for preparing the one-piece molded graphite crucible in this embodiment includes the following steps:

[0045] (1) Dissolve PVB in water to prepare a 3wt.% PVB aqueous solution. Add artificial graphite powder to the PVB aqueous solution according to the particle size ratio for granulation treatment. After drying, the granulated powder is ground and crushed to 60 mesh. Add the granulated artificial graphite powder, MCMB powder and worm-shaped graphite powder to a mixing pot in sequence and knead at room temperature for 30 min. Then heat to 120℃ and add additives and mix for 30 min. When the raw material temperature drops to 60-70℃, add thermosetting phenolic resin and knead for 30 min. Then add benzidine and release agent and knead for another 20-30 min. Crush and sieve to 60 mesh to obtain graphite crucible powder raw material.

[0046] (2) Molding: After the mold temperature is constant, pour the mixed raw materials into the aforementioned molding mold (mold temperature set at 150-170℃); the operation steps of the molding mold are as follows:

[0047] 1. Before molding, turn on the mold heating switch, set the heating temperature, and wait for the temperature to stabilize. 2. Operate the press, moving the press head upwards to pour the raw material into the mold cavity. 3. Then operate the press, moving the press head downwards until it reaches the lower limit. 4. Maintain the temperature and pressure for a certain period of time to allow the sample to solidify. 5. Operate the press, moving the press head upwards, and simultaneously operate the press to eject and demold the sample.

[0048] The resin has a certain fluidity at high temperature. Start the press connected to the molding die, press the head down to the set stroke, maintain the pressure at 10-15MPa, and hold the pressure for 5 minutes. Under high temperature and high pressure, the resin is cured and pressed into the shape of a crucible. After 5 minutes, demold and take out the sample.

[0049] (3) Calcination: The shaped sample needs to be calcined and carbonized. The sample is placed in a calcining furnace and heated to 900°C. After cooling, it is taken out to become a finished one-time shaped graphite crucible.

[0050] Comparative Example 1:

[0051] The rest of this comparative example is the same as that of Example 1, except that the aggregate is entirely made of artificial graphite powder, and the particle size distribution of the artificial graphite powder is consistent with the ratio of artificial graphite powder / MCMB and worm graphite powder in Example 1. This comparative example provides a one-piece molded graphite crucible containing the following parts by weight of raw materials:

[0052] 1000g of artificial graphite powder, 80g of polyvinyl butyral (PVB), 200g of thermosetting phenolic resin, 15g of additives, 15g of release agent, and 20g of benzidine; in the artificial graphite powder, 60-100 mesh accounts for 56% by mass, 100 mesh accounts for 10%, 100-200 mesh accounts for 24% by mass, and 325 mesh accounts for 10%.

[0053] Comparative Example 2:

[0054] The rest of this comparative example is the same as that of Example 1, except that the granulation step of artificial graphite powder is omitted. This comparative example provides a one-piece molded graphite crucible containing the following parts by weight of raw materials:

[0055] The composition includes 800g of artificial graphite powder, 100g of MCMB, 100g of worm-shaped graphite powder, 200g of thermosetting phenolic resin, 15g of additives, 15g of release agent, and 20g of benzidine. In the artificial graphite powder, 70% by weight is 60-100 mesh, and 30% by weight is 100-200 mesh. The mesophase carbon microspheres have a mesh size of 325, and the worm-shaped graphite powder has a mesh size of 100.

[0056] The performance of the crucibles prepared in Example 1 and Comparative Examples 1 and 2 was tested according to national standards. The results are shown in Table 1 below:

[0057] Table 1. Performance of Example 1 and Comparative Example

[0058]

[0059] As can be seen from Table 1, the crucible material prepared in Example 1 of this invention has met the performance requirements of graphite crucible products on the market and can be applied in the field of crucibles. Compared with Comparative Examples 1 and 2, Example 1 uses granulation and adds MCMB and worm graphite powder to the aggregate, which can significantly improve the bulk density and mechanical properties of the crucible. In addition, the preparation method of this invention has high homogeneity, and the products prepared with the same formula have negligible differences in performance, such as the standard deviation of resistivity being around 0.15-0.20.

Claims

1. A method for preparing a one-piece molded graphite crucible, characterized in that, Includes the following steps: (1) Polyvinyl butyral ester is used to granulate artificial graphite powder, and mesophase carbon microsphere powder and worm-like graphite powder are added. The mixture is kneaded at room temperature for 20-40 min, then heated to 120-140℃, and additives are added and mixed for 20-40 min; the temperature is lowered to 60-70℃, thermosetting phenolic resin is added and kneaded for 20-40 min, then benzidine and release agent are added and kneaded for another 20-30 min. After cooling, crushing, and sieving, 60-200 mesh graphite crucible powder raw material is obtained; The method for granulating artificial graphite powder includes: Polyvinyl butyral was prepared into a 3-5 wt.% aqueous solution of polyvinyl butyral. Artificial graphite powder was added to the aqueous solution of polyvinyl butyral and granulated. The granulated powder was dried, ground and crushed, and then sieved to obtain granulated artificial graphite powder of 200-60 mesh. (2) Pour the graphite crucible powder raw material obtained in step (1) into the molding mold, and keep the pressure at 10MPa-15MPa at 150℃-170℃ for 5min-10min. (3) Demold the molded sample and heat it to a temperature of not less than 900℃ for carbonization to obtain a one-time molded graphite crucible; The graphite crucible contains the following parts by weight of raw materials: 70-80 parts of artificial graphite powder, 10-15 parts of mesophase carbon microspheres, 10-15 parts of worm-like graphite powder, 5-10 parts of polyvinyl butyral, 20-25 parts of thermosetting phenolic resin, 1-2 parts of additives, 1-2 parts of release agent, and 1-3 parts of curing agent. In the artificial graphite powder, 60-100 mesh accounts for 70-80% of the artificial graphite powder, and 100-200 mesh accounts for 20-30% of the artificial graphite powder; the mesh number of the mesophase carbon microspheres is not less than 325 mesh, and the mesh number of the worm-like graphite powder is not less than 100 mesh. The additive is sodium alginate, the release agent includes a mixture of stearic acid and paraffin, and the curing agent is benzidine.

2. The preparation method according to claim 1, characterized in that, In step (2), the molding die includes a core (1), a base (4) and a demolding ejector (6). The base (4) includes a base and a hollow cylindrical outer cylinder set on the base. The core (1) is cylindrical and nested with the base (4). The demolding ejector (6) is set below the hollow cylindrical outer cylinder of the base (4) and corresponds to the longitudinal axis of the core (1).

3. The preparation method according to claim 2, characterized in that, The mold core (1) is provided with multiple longitudinal mold core heating holes (2), and the base (4) is provided with multiple base heating holes (3). The base heating holes (3) are provided in both the longitudinal and transverse structures of the base (4). The base heating holes (3) and the mold core heating holes (2) are connected to the heating device.

4. The preparation method according to claim 3, characterized in that, The heating device is an electric heating element and / or a thermocouple.

5. The preparation method according to claim 2, characterized in that, An 11-12mm gap is provided between the inner wall of the hollow cylindrical outer cylinder of the mold core (1) and the base (4). A 50-60mm wide protrusion is left on the top of the cylinder of the mold core (1) to fill the gap. A protruding plug-in handle is provided on the top surface of the cylinder of the mold core (1).

6. The preparation method according to claim 5, characterized in that, The pull handle is threaded and connected to a press, with the threaded connection adapted to the press.

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