CN114956621A - Alpha-semi-hydrated gypsum composite material and preparation and application thereof - Google Patents

Alpha-semi-hydrated gypsum composite material and preparation and application thereof Download PDF

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CN114956621A
CN114956621A CN202210581555.4A CN202210581555A CN114956621A CN 114956621 A CN114956621 A CN 114956621A CN 202210581555 A CN202210581555 A CN 202210581555A CN 114956621 A CN114956621 A CN 114956621A
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hemihydrate gypsum
formula
gypsum composite
composite material
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CN114956621B (en
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周宏明
陈红霞
聂日煌
周梦成
张昕宇
许双午
杨雨甜
李程
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Central South University
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B11/00—Calcium sulfate cements
    • C04B11/02—Methods and apparatus for dehydrating gypsum
    • C04B11/028—Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained
    • C04B11/032—Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained for the wet process, e.g. dehydrating in solution or under saturated vapour conditions, i.e. to obtain alpha-hemihydrate
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B11/00—Calcium sulfate cements
    • C04B11/02—Methods and apparatus for dehydrating gypsum
    • C04B11/024—Ingredients added before, or during, the calcining process, e.g. calcination modifiers
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
    • C04B24/04—Carboxylic acids; Salts, anhydrides or esters thereof
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
    • C04B24/12—Nitrogen containing compounds organic derivatives of hydrazine
    • C04B24/121—Amines, polyamines
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
    • C04B24/12—Nitrogen containing compounds organic derivatives of hydrazine
    • C04B24/124—Amides

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  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

Abstract

The invention belongs to the field of gypsum materials, and particularly relates to an alpha-hemihydrate gypsum composite material which comprises alpha-hemihydrate gypsum and a compound shown in a formula 1;
Figure DDA0003664043260000011
in the formula 1, R 1 ～R 4 Wherein at least one substituent is carboxyl and its derivative carboxylate, amide or anhydride; the remaining substituent is H, C 1 ～C 6 Alkyl of (C) 1 ～C 6 Alkoxy, hydroxy or amino groups. In addition, the invention also comprises the preparation and application of the composite material. The research of the invention shows that by combining the compound shown in the formula 1 and the alpha-hemihydrate gypsum,can realize synergy, can effectively reduce the water consumption of standard consistency, and is favorable for further improving the flexural strength and the compressive strength of the water-based high-consistency material.

Description

Alpha-semi-hydrated gypsum composite material and preparation and application thereof
Technical Field
The invention belongs to a gypsum material, and particularly relates to the field of alpha-hemihydrate gypsum materials.
Technical Field
The alpha-semi-hydrated gypsum is a crystal form powder cementing material obtained by dihydrate gypsum in a saturated steam medium or a liquid water solution under the conditions of certain pressure, temperature or a crystal transformation agent and the like. The alpha-semi-hydrated gypsum has the excellent performances of good crystal growth, compact and complete crystallization, large specific surface area, stable chemical property, no toxicity, light weight, low water consumption for standard consistency, quick setting and hardening, high strength and the like, is widely used in the aspects of modern medical treatment, precision casting, high-rise building materials, ceramic materials, high-grade artware and the like, and has wide application prospect.
The preparation method of the alpha-hemihydrate gypsum is more: wherein, the aging method is formed by calcining, dehydrating and then aging dihydrate gypsum, and the product prepared by the method is not uniform and has low strength generally; the steam pressing method is that block-shaped dihydrate gypsum is placed in a steam pressing kettle, saturated steam is introduced at a certain pressure and temperature, after a period of steam pressing, the product is obtained through drying and crushing, and the method is actually a mixture of alpha-hemihydrate gypsum and beta-hemihydrate gypsum, and has the advantages of large energy consumption and high equipment cost; the pressurized aqueous solution method is to add the dihydrate gypsum into the aqueous solution containing the crystal modifier, and then carry out high-temperature and high-pressure reaction to obtain the product, and the process is relatively complex and has relatively high energy consumption cost; the normal pressure salt solution method mainly reduces the water activity by adding inorganic salt into the water solution, realizes the conversion reaction of the dihydrate gypsum to the alpha-hemihydrate gypsum at normal pressure and lower temperature, and has the advantages of mild preparation conditions, easy control of product quality, low equipment cost, short production period, industrialization and the like compared with other methods. However, the alpha-hemihydrate gypsum prepared by the normal pressure salt solution method has high water consumption at the standard consistency, so that the strength of the obtained alpha-hemihydrate gypsum is not high, and therefore, the alpha-hemihydrate gypsum prepared by the method has low water consumption at the standard consistency, so that the alpha-hemihydrate gypsum with high strength has higher added value and better application prospect.
Disclosure of Invention
Aiming at the problems of large water consumption and low breaking strength of the conventional normal-pressure salt solution alpha-hemihydrate gypsum that the standard consistency is high, the invention provides an alpha-hemihydrate gypsum composite material and aims to reduce the water consumption of the standard consistency and improve the breaking strength of the alpha-hemihydrate gypsum composite material.
The second purpose of the invention is to provide the preparation and application of the alpha-hemihydrate gypsum composite material.
Aiming at the problems that the standard consistency water consumption of the short-distance alpha-hemihydrate gypsum prepared under normal pressure salt solution is large, and the breaking strength and the compressive strength are to be improved, the invention provides the following technical scheme:
an alpha-hemihydrate gypsum composite comprising alpha-hemihydrate gypsum and a compound of formula 1;
Figure BDA0003664043240000021
in the formula 1, R 1 ～R 4 Wherein at least one substituent is carboxyl and its derivative carboxylate, amide or anhydride; the remaining substituent is H, C 1 ～C 6 Alkyl of (C) 1 ～C 6 Alkoxy, hydroxy or amino groups.
The research of the invention shows that the compound of the formula 1 and the alpha-hemihydrate gypsum are combined to realize synergy, can effectively reduce the water consumption of standard consistency, and is beneficial to further improving the flexural strength and the compressive strength.
In the invention, the carboxyl is-COOH, and the carboxylate is sodium salt, potassium salt and the like derived from the carboxyl. The amide is, for example, -CON-, which may be a cyclic amide (lactam) or a non-cyclic amide. The acid anhydride is a cyclic acid anhydride (adjacent carboxyl forming acid anhydride) or a non-cyclic acid anhydride (forming acid anhydride with other carboxylic acid).
In the present invention, in the above formula 1, R 1 ～R 4 Wherein two substituents are carboxyl and the rest is H;
preferably, the carboxyl groups are located on the same or different rings. For example, the two carboxyl groups may be on the same phenyl ring or may be distributed on different phenyl rings.
Preferably, the compound of formula 1 is at least one of the compounds having the following structure;
Figure BDA0003664043240000022
in the present invention, the alpha-hemihydrate gypsum may be alpha-hemihydrate gypsum known in the industry.
For example, the alpha-hemihydrate gypsum is obtained by carrying out normal pressure salt solution crystal transformation on calcium sulfate dihydrate in a salt solution and a crystal transformation agent system. In the invention, the alpha-hemihydrate gypsum prepared by the preparation process of the normal-pressure salt solution and the compound of the formula 1 can obtain better synergistic effect.
The salt solution is an aqueous solution of inorganic salt;
preferably, the inorganic salt is at least one of water-soluble alkali metal salt and water-soluble alkaline earth metal salt; preferably at least one of sodium chloride and magnesium chloride;
preferably, the concentration of the solute in the salt solution is 2.2-3.5 mol/L;
preferably, the volume ratio of the calcium sulfate dihydrate pre-salt solution is 1: 4-1: 8 (g/mL).
In the invention, the crystal transformation agent is at least one of citric acid, succinic acid, fumaric acid and EDTA;
preferably, the mass of the crystal modifier is 0.1-0.6% of the mass of the calcium sulfate dihydrate.
In the invention, the temperature in the crystal transformation reaction process is 90-100 ℃, and preferably 93-99 ℃;
preferably, the crystal transformation stage is carried out under stirring, and the stirring speed is preferably 180-220 r/min;
preferably, the time of crystal transformation treatment is 2-6 h;
preferably, after the crystal transformation treatment, filtering while hot, and washing with hot water, fixing with ethanol and drying to obtain the product;
preferably, the drying temperature is 45-60 ℃, and the drying time is 6-15 h.
In the invention, the compound of the formula 1 accounts for 0.5 to 2 percent of the mass of the alpha-hemihydrate gypsum; preferably 0.5-1.5%; more preferably 1 to 1.5%.
The invention also provides a preparation method of the alpha-hemihydrate gypsum composite material, which is obtained by compounding alpha-hemihydrate gypsum and the compound shown in the formula 1.
The preparation method of the preferred alpha-hemihydrate gypsum composite material comprises the following steps:
step 1, preparing an inorganic salt solution with a certain concentration, adding calcium sulfate dihydrate into the salt solution, then adding a crystal modifier, and uniformly stirring at normal temperature to obtain a reaction system; the inorganic salt is one of sodium chloride and magnesium chloride, and the concentration is 2.2-3.5 mol/L. The mass ratio of the calcium sulfate dihydrate to the salt solution is 1: 4-1: 8 (g/mL). The crystal modifier is at least one of citric acid, succinic acid, fumaric acid and EDTA. The mass of the crystal modifier is 0.1-0.6% of the mass of the calcium sulfate dihydrate.
Step 2, stirring the reaction system at a certain temperature and a certain stirring speed for reaction for a certain time to obtain alpha-hemihydrate gypsum slurry; wherein the crystal transformation reaction temperature is 90-100 ℃, the stirring speed is 180-220 r/min, and the reaction time is 2-6 h.
Step 3, filtering the obtained alpha-hemihydrate gypsum slurry while the slurry is hot, washing the slurry with boiling water, fixing the slurry with ethanol, and then drying the slurry; wherein the drying temperature is 45-60 ℃, and the drying time is 3-12 h.
And 4, uniformly mixing the obtained alpha-hemihydrate gypsum with the compound shown in the formula 1 to obtain the alpha-hemihydrate gypsum composite material with low standard consistency water. The compound of the formula 1 is at least one of the formulas 1-a to 1-f; the mass of the compound shown in the formula 1 is 0.5-2% of the mass of the alpha-hemihydrate gypsum.
The method can prepare the alpha-hemihydrate gypsum composite material with low water consumption of standard consistency, high strength, high purity, stable structure and uniform particles by using the compound shown in the formula 1.
The invention also provides application of the alpha-semi-hydrated gypsum composite material, which is characterized by being used in the fields of precision manufacturing, high-end ceramics, medical treatment, functional fillers, decorative materials, industrial art and the like.
Action and effects of the invention
The compound of formula 1 and the alpha-hemihydrate gypsum can realize synergy, reduce water consumption of standard consistency, improve strength and purity, have stable structure and uniform particles. Researches find that the compressive strength of the composite material is more than or equal to 25MPa, the water consumption for the standard consistency is less than or equal to 38 percent, and the high-strength normal-pressure saline solution gypsum standard is obtained. The technical scheme of the invention has the advantages of simple process, convenient operation, short reaction time and low energy consumption, and is very suitable for industrialization.
Drawings
FIG. 1 is a scanning electron micrograph of alpha-hemihydrate gypsum prepared in example one;
FIG. 2 is an XRD pattern of alpha-hemihydrate gypsum prepared in example one;
FIG. 3 is a TGA profile of alpha-hemihydrate gypsum prepared in example one;
Detailed Description
The following describes in detail a specific embodiment of the method for producing alpha-hemihydrate gypsum according to the present invention with reference to the accompanying drawings.
In the following cases, the water consumption at the standard consistency is determined by referring to the GB/T17669.4-1999 determination of physical properties of building gypsum neat paste; the flexural strength and the compressive strength are measured by adopting the JC/T2038-2010 alpha-type high-strength gypsum.
Example one
The preparation method comprises the following steps:
preparing 3.3M sodium chloride solution, adding calcium sulfate dihydrate, wherein the solid-to-liquid ratio is 1: 5(g: ml), stirring, adding 0.2 percent of citric acid relative to the mass of the calcium sulfate dihydrate, and stirring for 10 min; and then putting the mixture into a water bath kettle with the temperature of 99 ℃, stirring for reaction for 3 hours, rotating at the speed of 200r/min, then filtering while the mixture is hot, washing the mixture for 4 times by boiling water, fixing the mixture once by absolute ethyl alcohol, and drying the mixture for 12 hours in an oven at the temperature of 55 ℃ to obtain alpha-hemihydrate gypsum powder (the SEM, XRD and TGA of the product are respectively shown in figures 1 to 3). Then the alpha-hemihydrate gypsum composite material is evenly mixed with 1 percent (based on alpha-hemihydrate gypsum powder) of the formula 1-d to obtain the alpha-hemihydrate gypsum composite material.
And (3) performance characterization:
as shown in FIG. 1, the alpha-hemihydrate gypsum prepared in the first embodiment is hexagonal prism-shaped crystal, and has uniform particle size, high regularity, length of 10-20 microns and length-diameter ratio of less than 1.5. As shown in fig. 2 and 3, XRD and TGA characterization results.
The water consumption of the prepared composite material sample at the standard consistency is 37 percent, the breaking strength is 8.7MPa, and the compressive strength is 26.6 MPa.
Example two
The only difference compared to example 1 is that the amount of formula 1-d is halved (formula 1-d is 0.5% by weight of the alpha-hemihydrate gypsum powder obtained).
The water consumption of the prepared alpha-hemihydrate gypsum composite material sample with the standard consistency is 38 percent, the breaking strength is 8.0 MPa, and the compressive strength is 25.4 MPa.
EXAMPLE III
The only difference compared to example 1 is that the amount of formula 1-d is increased by 50% (formula 1-d is 1.5% by weight of the alpha-hemihydrate gypsum powder).
The water consumption of the prepared composite material sample at the standard consistency is 37 percent, the breaking strength is 8.2MPa, and the compressive strength is 25.9 MPa.
Example four
The only difference compared to example 1 is that formula 1-e replaces formula 1-d.
The water consumption of the prepared composite material sample at the standard consistency is 36 percent, the breaking strength is 9.0MPa, and the compressive strength is 26.9 MPa.
EXAMPLE five
The preparation method comprises the following steps:
preparing 3.3M sodium chloride solution, adding calcium sulfate dihydrate, wherein the solid-to-liquid ratio is 1: 5(g: ml), stirring, adding EDTA (ethylene diamine tetraacetic acid) accounting for 0.3 percent of the mass of the calcium sulfate dihydrate, and stirring for 10 min; then putting the mixture into a water bath kettle with the temperature of 99 ℃, stirring and reacting for 3 hours, rotating at the speed of 200r/min, then filtering while the mixture is hot, washing for 4 times by boiling water, fixing once by absolute ethyl alcohol, drying for 12 hours in an oven at the temperature of 55 ℃, and then uniformly mixing the obtained alpha-semi-hydrated gypsum powder with 0.5 percent of formula 1-d to obtain the alpha-semi-hydrated gypsum composite material.
And (3) performance characterization:
the alpha-hemihydrate gypsum prepared in the fifth embodiment is hexagonal prism-shaped crystal, and has uniform particle size, high regularity, length of 5-25 microns and length-diameter ratio of less than 5. The water consumption of the prepared alpha-hemihydrate gypsum composite material sample in the standard consistency is 38%, the breaking strength is 7.8MPa, and the compressive strength is 25.1 MPa.
Example six
The preparation method comprises the following steps:
preparing 2.5M magnesium chloride solution, adding calcium sulfate dihydrate, wherein the solid-to-liquid ratio is 1: 5(g: ml), stirring, adding fumaric acid accounting for 0.4 percent of the mass of the calcium sulfate dihydrate, and stirring for 10 min; and then putting the mixture into a water bath kettle with the temperature of 95 ℃, stirring and reacting for 6 hours at the rotating speed of 200r/min, then filtering while the mixture is hot, washing the mixture for 4 times by boiling water, fixing the mixture once by absolute ethyl alcohol, drying the mixture for 12 hours at the temperature of 55 ℃ in an oven, and then uniformly mixing the obtained powder with 1 percent of the formula 1-d to obtain the alpha-semi-hydrated gypsum composite material.
And (3) performance characterization:
the alpha-hemihydrate gypsum prepared in the sixth embodiment is hexagonal prism-shaped crystal, has uniform particle size and high regularity, is 10-20 microns long and has the length-diameter ratio of less than 1.5. The water consumption of the prepared alpha-hemihydrate gypsum composite material sample in the standard consistency is 36%, the breaking strength is 9.7MPa, and the compressive strength is 28.1 MPa.
EXAMPLE seven
The preparation method comprises the following steps:
preparing 3.0M magnesium chloride solution, adding calcium sulfate dihydrate, and mixing the solution in a solid-to-liquid ratio of 1: 4(g: ml), stirring, adding succinic acid accounting for 0.1 percent of the mass of the calcium sulfate dihydrate, and stirring for 10 min; then putting the mixture into a water bath kettle with the temperature of 97 ℃, stirring for reaction for 4 hours, rotating at the speed of 200r/min, then filtering while the mixture is hot, washing for 4 times by boiling water, fixing once by absolute ethyl alcohol, drying for 12 hours in an oven at the temperature of 55 ℃, and then uniformly mixing the obtained powder with 1.25 percent of the formula 1-c to obtain the alpha-hemihydrate gypsum composite material.
And (3) performance characterization:
the alpha-hemihydrate gypsum prepared in the seventh embodiment is hexagonal prism-shaped crystal, and has uniform particle size, high regularity, length of 20-50 microns and length-diameter ratio of less than 10. The water consumption of the prepared alpha-hemihydrate gypsum composite material sample in the standard consistency is 38%, the breaking strength is 8.3MPa, and the compressive strength is 26.2 MPa.
Example eight
The preparation method comprises the following steps:
preparing 3.5M sodium chloride solution, adding calcium sulfate dihydrate, wherein the solid-to-liquid ratio is 1: 7(g: ml), stirring, adding succinic acid accounting for 0.4 percent of the mass of the calcium sulfate dihydrate, and stirring for 10 min; then putting the mixture into a water bath kettle with the temperature of 99 ℃, stirring and reacting for 3 hours, rotating at the speed of 150r/min, then filtering while the mixture is hot, washing for 4 times by boiling water, fixing once by absolute ethyl alcohol, drying for 8 hours in an oven at the temperature of 50 ℃, and then uniformly mixing the obtained powder with 1.0 percent of the formula 1-b to obtain the alpha-hemihydrate gypsum composite material.
And (3) performance characterization:
the alpha-hemihydrate gypsum prepared in the eighth embodiment is hexagonal prism-shaped crystal, has uniform particle size and high regularity, and has the length of 20-50 microns and the length-diameter ratio of less than 10. The water consumption of the prepared alpha-hemihydrate gypsum composite material sample with the standard consistency is 37 percent, the breaking strength is 8.1MPa, and the compressive strength is 26.1 MPa.
Example nine
The preparation method comprises the following steps:
preparing 2.5M sodium chloride solution, adding calcium sulfate dihydrate, wherein the solid-to-liquid ratio is 1: 5(g: ml), stirring, adding fumaric acid accounting for 0.4 percent of the mass of the calcium sulfate dihydrate, and stirring for 10 min; and then putting the mixture into a water bath kettle with the temperature of 95 ℃, stirring and reacting for 4 hours, rotating at the speed of 220r/min, filtering while the mixture is hot, washing the mixture for 4 times by boiling water, fixing the mixture once by absolute ethyl alcohol, drying the mixture for 6 hours in an oven at the temperature of 55 ℃, and then uniformly mixing the obtained powder with 0.75 percent of the formula 1-c to obtain the alpha-hemihydrate gypsum composite material.
And (3) performance characterization:
the alpha-hemihydrate gypsum prepared in this example nine is hexagonal prism-shaped crystal, and has uniform particle size, high regularity, length of 10-20 microns, and length-diameter ratio of less than 1.5. The water consumption of the prepared alpha-hemihydrate gypsum composite material sample in the standard consistency is 36%, the breaking strength is 8.8MPa, and the compressive strength is 26.4 MPa.
Comparative example 1
The only difference compared to example 1 is that formula 1-d is not added.
The water consumption of the prepared alpha-hemihydrate gypsum sample in standard consistency is 49%, the flexural strength is 6.3MPa, and the compressive strength is 21.5 MPa.
It can be seen that the combination of the compounds of formula 1 is effective in reducing the amount of water used for standard consistency and, in addition, contributes to a synergistic improvement in flexural and compressive strength.
Comparative example No. two
The only difference compared to example 1 is that an equal weight of FDN-C was added instead of formula 1-d.
The water consumption of the prepared composite material sample at the standard consistency is 40 percent, the breaking strength is 7.4MPa, and the compressive strength is 23.6 MPa.
The above embodiments are merely illustrative of the technical solutions of the present invention. The method for preparing the alpha-hemihydrate gypsum according to the present invention is not limited to the contents described in the above examples, but is subject to the scope defined by the claims. Any modification or supplement or equivalent replacement made by the person skilled in the art on the basis of this embodiment is within the scope of the invention as claimed in the claims.

Claims (10)

1. An alpha-hemihydrate gypsum composite comprising alpha-hemihydrate gypsum and a compound of formula 1;
Figure FDA0003664043230000011
the formula isIn 1, R 1 ～R 4 Wherein at least one substituent is carboxyl and its derivative carboxylate, amide or anhydride; the remaining substituent is H, C 1 ～C 6 Alkyl of (C) 1 ～C 6 Alkoxy, hydroxy or amino groups.
2. The alpha-hemihydrate gypsum composite of claim 1 wherein in formula 1, R is 1 ～R 4 Wherein two substituents are carboxyl and the rest is H;
preferably, the carboxyl groups are located on the same or different rings.
3. The alpha-hemihydrate gypsum composite of claim 2 wherein the compound of formula 1 is at least one of the following structures;
Figure FDA0003664043230000012
4. the alpha-hemihydrate gypsum composite of claim 1 wherein the alpha-hemihydrate gypsum is obtained by normal pressure salt solution recrystallization of calcium sulfate dihydrate in a salt solution, a crystal modifier system.
5. The alpha-hemihydrate gypsum composite of claim 4 wherein the salt solution is an aqueous solution of an inorganic salt;
preferably, the inorganic salt is at least one of water-soluble alkali metal salt and water-soluble alkaline earth metal salt; preferably at least one of sodium chloride and magnesium chloride;
preferably, the concentration of the solute in the salt solution is 2.2-3.5 mol/L;
preferably, the volume ratio of the calcium sulfate dihydrate pre-salt solution is 1: 4-1: 8 (g/mL).
6. The alpha-hemihydrate gypsum composite of claim 4 wherein the crystallization agent is at least one of citric acid, succinic acid, fumaric acid, EDTA;
preferably, the mass of the crystal modifier is 0.1-0.6% of the mass of the calcium sulfate dihydrate.
7. The alpha-hemihydrate gypsum composite of claim 5 wherein the temperature of the crystal transformation reaction is from 90 ℃ to 100 ℃;
preferably, the crystal transformation stage is carried out under stirring, and the stirring speed is preferably 180-220 r/min;
preferably, the time of crystal transformation treatment is 2-6 h;
preferably, after the crystal transformation treatment, filtering while hot, and washing with hot water, fixing with ethanol and drying to obtain the product;
preferably, the drying temperature is 45-60 ℃, and the drying time is 6-15 h.
8. An alpha-hemihydrate gypsum composite as claimed in any one of claims 1 to 7 wherein the compound of formula 1 is 0.5-2% by mass of the alpha-hemihydrate gypsum; preferably 0.5-1.5%; more preferably 1 to 1.5%.
9. A method for preparing an alpha-hemihydrate gypsum composite material as claimed in any one of claims 1 to 8, wherein the alpha-hemihydrate gypsum is obtained by compounding alpha-hemihydrate gypsum with a compound of formula 1.
10. Use of the α -hemihydrate gypsum composite material according to any one of claims 1 to 8, for producing at least one of precision manufacturing materials, ceramic materials, medical materials, functional fillers, decorative materials and industrial art materials.
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