Production method and equipment of semi-hydrated gypsum material for 3D printing

Abstract

The invention discloses a production method and equipment of a semi-hydrated gypsum material for 3D printing, wherein a slurry is prepared with gypsum raw material, water and a crystal medium, and the temperature is raised to 115-125°C in a reactor for constant temperature reaction to obtain a semi-hydrated gypsum slurry with a fibrous crystal structure; the semi-hydrated gypsum slurry with a fibrous crystal structure is filtered, and the semi-hydrated gypsum with a fibrous crystal structure is obtained after the liquid in the reactor is discharged, and the semi-hydrated gypsum with a fibrous crystal structure in the reactor is repeatedly washed with hot water; hot water containing 1% of a crystal conversion agent is injected into the reactor, and the heated constant temperature reaction is performed to increase the diameter of the fibrous crystals of the semi-hydrated gypsum; the obtained slurry is discharged from the reactor, and then dried and ground. The invention combines two process parameters for producing a fibrous crystal structure of semi-hydrated gypsum and a short columnar crystal structure, and produces a semi-hydrated gypsum material having the advantages of high compressive strength, flexural strength, and bending strength, good toughness, high temperature resistance, chemical corrosion resistance, and easy surface treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of production of semi-hydrated gypsum materials, and in particular to a production method and device of semi-hydrated gypsum materials for 3D printing. Background Art

[0002] The hemihydrate gypsum currently used for 3D printing materials is ordinary α-hemihydrate gypsum, which has the following advantages: (1) relatively high compressive strength; (2) low price, only a few tens of times that of other materials; (3) no static electricity; (4) inorganic material, stable performance and no aging. However, since α-hemihydrate gypsum crystals are short columnar; therefore, its biggest disadvantage is low flexural strength, tensile strength and bending strength, which seriously affects the scope of use of hemihydrate gypsum as a 3D printing material.

[0003] If the fibrous crystal structure has high flexural strength, tensile strength and bending strength, combined with the high compressive strength of α-hemihydrate gypsum to produce a hemihydrate gypsum material for 3D printing, its use will be greatly expanded and the material cost of 3D printing will be reduced. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a production method and equipment for semi-hydrated gypsum material for 3D printing, so as to achieve the purpose of improving the flexural strength, tensile strength and bending strength of the material.

[0005] In order to solve the above technical problems, according to one aspect of the present invention, a method for producing a semi-hydrated gypsum material for 3D printing is provided, comprising the steps of:

[0006] Step 1, cultivating the fibrous crystal structure of hemihydrate gypsum;

[0007] The slurry is prepared with gypsum raw material, water and a crystallizing agent, wherein the mass concentration of the gypsum raw material in the slurry is 4%-6%, the initial pH value of the slurry is 9.8-10.1, and the crystallizing agent is 1%-2% of the mass of the water in the slurry. The prepared slurry is heated to 115-125° C. in a reactor for constant temperature reaction to obtain a semi-hydrated gypsum slurry with a fibrous crystal structure.

[0008] Step 2: cleaning;

[0009] The hemihydrate gypsum slurry with a fibrous crystal structure obtained in step 1 is filtered, and the liquid in the reaction kettle is discharged to obtain hemihydrate gypsum with a fibrous crystal structure, and then the hemihydrate gypsum in the reaction kettle is repeatedly washed with hot water at 90-110° C.;

[0010] Step 3, coarsening and cultivating the fibrous crystals of hemihydrate gypsum;

[0011] Inject 90-110°C hot water containing 1% of a crystal conversion agent into a reaction kettle and heat to 120-140°C for constant temperature reaction to increase the diameter of the fibrous crystals of the hemihydrate gypsum;

[0012] Step 4, drying and grinding;

[0013] The slurry obtained in step 3 is discharged from the reactor and then dried and ground.

[0014] Furthermore, in step 1, the prepared slurry is heated to 120° C. in the reactor and reacted at the constant temperature for 3 hours.

[0015] Furthermore, in step 1, calcium hydroxide is added to adjust the pH value in the reaction kettle.

[0016] Furthermore, in step 1, the particle size of the gypsum raw material is 38µm.

[0017] Furthermore, in step 2, the semi-hydrated gypsum in the reaction kettle is repeatedly washed with hot water at 100°C.

[0018] Furthermore, in step three, hot water at 100° C. containing a crystal conversion agent is injected into the reactor.

[0019] Furthermore, in step three, the crystal conversion agent includes 90 parts of aluminum sulfate, 5 parts of sodium citrate, and 5 parts of sodium hexadecane sulfonate, by weight.

[0020] Furthermore, in step three, the reactor is heated to 130° C. and reacted at a constant temperature for 2 hours.

[0021] Furthermore, in step three, the diameter of the fibrous crystals of the hemihydrate gypsum increases by 6 to 8 times.

[0022] According to another aspect of the present invention, there is provided an apparatus for the above production method, comprising a reaction kettle, wherein the reaction kettle comprises a slurry discharge pipe with a filter screen.

[0023] The present invention organically combines two process parameters for producing hemihydrate gypsum fibrous crystal structure and short columnar crystal structure through innovative equipment and perfect process links, and produces hemihydrate gypsum material with the advantages of high compressive strength, flexural strength, bending strength, good toughness, high temperature resistance, chemical corrosion resistance, and easy surface treatment. Using natural fibrous gypsum with a grade of about 98, the obtained product can have a dry compressive strength of more than 80 MPa, a dry flexural strength of 45 MPa, and a bending strength of 8 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the reaction kettle of the present invention;

[0025] Figure 2 This is the crystal form of the hemihydrate gypsum obtained in Example 1 of the present invention.

[0026] In the figure, 1-reactor body, 2-feed valve, 3-hot water cleaning pipe valve, 4-drain valve, 5-slurry discharge valve, 6-agitation shaft. DETAILED DESCRIPTION

[0027] A typical embodiment of the present invention provides a method for producing a semi-hydrated gypsum material for 3D printing, comprising the following steps.

[0028] Step 1, cultivating the fibrous crystal structure of hemihydrate gypsum;

[0029] The slurry is prepared with gypsum raw material, water and a crystal medium, the mass concentration of gypsum raw material in the slurry is 4%-6%, the initial pH value of the slurry is 9.8-10.1, and the crystal medium is 1%-2% of the mass of water in the slurry. The prepared slurry is heated to 115-125°C in a reactor for constant temperature reaction to obtain a semi-hydrated gypsum slurry with a fibrous crystal structure. The aspect ratio of the semi-hydrated gypsum with a fibrous crystal structure obtained after cultivation reaches more than 60.

[0030] In this step, when preparing the slurry, calcium hydroxide is added to adjust the initial pH value to 9.8-10.1. The particle size of the gypsum raw material is 38µm (400 mesh).

[0031] Preferably, the prepared slurry is heated to 120° C. in a reactor and reacted at a constant temperature for 3 hours.

[0032] Step 2: cleaning;

[0033] The fibrous crystal structure of the semi-hydrated gypsum slurry obtained in step 1 is filtered, and the liquid in the reactor is discharged to obtain the semi-hydrated gypsum with a fibrous crystal structure. The semi-hydrated gypsum in the reactor is repeatedly washed with hot water at 90-110°C, and the amount of washing water is generally 3 to 4 times that of the reaction liquid, preferably with hot water at 100°C.

[0034] In this step, the crystal conversion agent, by weight, includes 90 parts of aluminum sulfate, 5 parts of sodium citrate, and 5 parts of sodium hexadecane sulfonate.

[0035] Step 3, coarsening and cultivating the fibrous crystals of hemihydrate gypsum;

[0036] Inject 90-110°C hot water containing 1% of crystal conversion agent into the reactor and heat it to 120-140°C for constant temperature reaction, so that the diameter of the fibrous crystals of hemihydrate gypsum increases by 6 to 8 times.

[0037] A preferred embodiment is to inject 100°C hot water containing a crystal conversion agent into a reactor, and heat the reactor to 130°C for a constant temperature reaction for 2 hours.

[0038] Step 4, drying and grinding;

[0039] The slurry obtained in step 3 is discharged from the reactor and then dried and ground.

[0040] The slurry is dried by a conventional centrifuge and airflow dryer. The chemical bonds of the gypsum crystals produced by the rotary splitting mill are further improved to further improve the various properties of the hemihydrate gypsum material used for 3D printing.

[0041] like Figure 1 As shown, another typical embodiment of the present invention provides an apparatus for the above production method, including a reactor, wherein the reactor includes a slurry discharge pipe with a filter.

[0042] The invention improves the vertical stirring reactor, that is, based on the original vertical stirring reactor having only one discharge pipe, a water liquid discharge pipe with a filter is added to form a vertical stirring reactor for filtering and reaction.

[0043] like Figure 1 As shown, a feed pipe and a high-temperature water cleaning pipe are provided at the top of the reactor body 1, and corresponding feed valves 2 and high-temperature water cleaning pipe valves 3 are provided at the pipe openings. A drain pipe with a filter screen and a discharge pipe are provided at the bottom of the reactor body 1, and corresponding drain valves 4 and discharge slurry valves 5 are provided at the pipe openings. A stirring shaft 6 is provided inside the reactor.

[0044] In addition, the system also includes conventional hot water (100°C) boilers and drying equipment, as well as grinding equipment and heat sources.

[0045] The technical solution claimed in the present invention is further described below by a relatively specific embodiment. However, the embodiment is used to explain the embodiment of the present invention and does not exceed the scope of the subject matter of the present invention. The protection scope of the present invention is not limited by the embodiment. Unless otherwise specified, the materials and reagents used in the present invention can be obtained from commercial products in the art.

[0046] A slurry suitable for cultivating a fibrous crystal structure of hemihydrate gypsum is prepared in a reactor. First, 80% of the volume of pure water is added to the reactor, and then calcium hydroxide is added to adjust the pH in the reactor so that the initial pH value of the reaction slurry is between 9.8 and 10.1; at the same time, 1.5% by mass (relative to the mass of pure water) of copper chloride is added as a crystal medium, and a gypsum raw material with a particle size of 400 mesh (38µm) is added at a mass concentration of 5%; after the slurry for cultivating a fibrous crystal structure of hemihydrate gypsum is prepared in the reactor, the stirring function and the heating function of the reactor are started at the same time, the slurry is gradually heated to 120°C, and kept at this temperature for 3 hours to obtain hemihydrate gypsum with a fibrous (aspect ratio of 60 or more) crystal structure.

[0047] After that, stirring and heating are stopped, the drain valve 5 is opened, and the reaction liquid with a pH value of 9.8 to 10.1 and containing the crystallization medium copper chloride in the reactor is discharged through the drain valve 4 with a filter, and then the semi-hydrated gypsum in the reactor is repeatedly cleaned three times with hot water at 100°C.

[0048] After cleaning, close the drain valve 4, inject 100°C hot water containing 1% (mass concentration) crystal conversion agent into the reactor, start stirring, and heat the new reaction slurry to 130°C and keep it at a constant temperature for 2 hours to increase the diameter of the fibrous crystals of the hemihydrate gypsum by 6 to 8 times, wherein the crystal conversion agent is 90 parts of aluminum sulfate, 5 parts of sodium citrate, and 5 parts of 1,6-diphenylsulfonate sodium.

[0049] Finally, the stirring is stopped, the discharge valve 5 of the reactor is opened to discharge the slurry, and the slurry is dried by a centrifuge and an air flow dryer, and is then impact-ground by a rotary splitting mill.

[0050] Obviously, those skilled in the art can make changes and modifications to the present invention. If these changes and modifications do not depart from the principles of the present invention and fall within the scope of the claims of the present invention and their equivalent technologies, the protection scope of the present invention also includes these changes and modifications.

Claims

1. A method for producing a semi-hydrated gypsum material for 3D printing, characterized in that: Includes steps: Step 1, cultivating the fibrous crystal structure of hemihydrate gypsum; The slurry is prepared with gypsum raw material, water and a crystal medium, and calcium hydroxide is added to adjust the pH value in the reaction kettle so that the initial pH value of the slurry is 9.8-10.

1. The mass concentration of the gypsum raw material in the slurry is 4%-6%, and the particle size of the gypsum raw material is 38µm; the crystal medium is 1%-2% of the mass of the water in the slurry. The prepared slurry is heated to 120° C. in a reactor and reacted at a constant temperature for 3 hours to obtain a semi-hydrated gypsum slurry with a fibrous crystal structure; Step 2: cleaning; The hemihydrate gypsum slurry with a fibrous crystal structure obtained in step 1 is filtered, and the liquid in the reaction kettle is discharged to obtain hemihydrate gypsum with a fibrous crystal structure, and the hemihydrate gypsum in the reaction kettle is repeatedly washed with hot water at 100° C.; Step 3, coarsening and cultivating the fibrous crystals of hemihydrate gypsum; Pour 100°C hot water containing 1% crystal conversion agent into the reactor, continue heating to 130°C and keep the reaction at a constant temperature for 2 hours, so that the diameter of the fibrous crystals of hemihydrate gypsum increases by 6 to 8 times; In parts by mass, the crystal conversion agent includes 90 parts of aluminum sulfate, 5 parts of sodium citrate, and 5 parts of sodium hexadecylbenzenesulfonate; Step 4, drying and grinding; The slurry obtained in step 3 is discharged from the reactor and then dried and ground.

2. An apparatus for the production method according to claim 1, comprising a reaction kettle, characterized in that: The reactor comprises a slurry discharge pipe with a filter screen.

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