Plant fiber for gypsum fiberboard as well as preparation method and application of plant fiber

Abstract

The invention relates to the technical field of gypsum fiberboard raw material treatment, in particular to a plant fiber for a gypsum fiberboard and a preparation method and application thereof. Compared with the prior art, the preparation method provided by the invention adopts specific process steps, plant fiber raw materials are softened by using a supersaturated calcium hydroxide solution to partially remove lignin, the treated plant fiber slurry is introduced into a sulfuric acid solution for neutralization in the water washing process, and generated nano-scale calcium sulfate particles are attached to the surfaces of the plant fibers, so that the surface of the plant fibers is uniform. The plant fiber coagulant plays a role of a coagulant during production of the gypsum fiberboard, and the plant fiber meeting the requirements of production of the gypsum fiberboard is prepared. The preparation method provided by the invention is low in cost, and the gypsum fiberboard prepared from the obtained plant fiber for the gypsum fiberboard has relatively high mechanical property indexes and meets the performance requirements of boards for building decoration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gypsum fiberboard raw material processing, and particularly relates to a plant fiber for gypsum fiberboard and a preparation method and application thereof. BACKGROUND

[0002] Plant fiber raw materials include bast fibers such as flax and paper mulberry bark, wood fibers such as poplar shavings, and stem fibers such as wheat straw and reed. Cotton fibers such as cotton are not directly used in the production of gypsum fiberboard without chemical pulping and softening treatment. Chemical pulping is a method of removing as much as possible the intercellular layer lignin that binds fibers together in plant fiber raw materials, so that the fiber cells are separated or easily separated to become true plant fibers. Therefore, without chemical pulping to remove lignin, the cell wall fibers are highly integrated, and only using physical crushing methods cannot form filamentous fibers.

[0003] Traditional chemical pulping processes are alkali pulping and sulfite pulping. The raw materials used are sodium hydroxide or sodium sulfite, and the cost of raw materials and the cost of wastewater treatment are high. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to provide a plant fiber for gypsum fiberboard and a preparation method and application thereof. The plant fiber for gypsum fiberboard provided by the present application has low preparation cost and does not produce waste liquid. The gypsum fiberboard prepared therefrom has high mechanical performance indicators and meets the performance requirements of building decoration boards.

[0005] The present application provides a preparation method of a plant fiber for gypsum fiberboard, comprising the following steps:

[0006] S1) softening treatment of plant fiber raw materials in a supersaturated calcium hydroxide solution, followed by filtration to obtain filter residue;

[0007] S2) acid-base neutralization of the filter residue obtained in step S1) with a sulfuric acid solution, followed by filtration to obtain wet pulp, and grinding of the obtained wet pulp to obtain a plant fiber for gypsum fiberboard.

[0008] The plant fiber raw material is first softened in a supersaturated solution of calcium hydroxide. The plant fiber raw material according to the present application is broken plant fiber raw material, with a length of less than 6 cm, preferably 1-6 cm, more preferably 1-5 cm, and even more preferably 2-3 cm. The plant fiber raw material according to the present application includes bast fiber such as flax and paper mulberry bark, wood fiber such as poplar shaving, bamboo fiber raw material such as bamboo, leaf fiber raw material such as sisal, stem fiber such as wheat straw and reed, and cotton fiber such as cotton, with stem fiber such as wheat straw and reed being preferred. In the supersaturated solution of calcium hydroxide according to the present application, the ratio of calcium hydroxide to water is 5-30 g / L, and preferably 10-30 g / L.

[0009] The plant fiber raw material is softened in a supersaturated solution of calcium hydroxide, with the softening temperature being 140-160°C, preferably 145-155°C, the softening pressure being 0.4-0.6 MPa, preferably 0.45-0.55 MPa, and the softening time being 60-180 min, preferably 120-180 min.

[0010] More specifically, the softening is performed in a high-pressure reactor, and the softening is divided into two stages of temperature increase, with the temperature first being increased to 100-110°C, then being depressurized, and then being further increased to 140-160°C and controlled at a pressure of 0.4-0.6 MPa for 60-180 min, or further increased to 145-155°C and controlled at a pressure of 0.45-0.55 MPa for 120-180 min.

[0011] In some embodiments of the present application, the softening is performed in a high-pressure steaming ball, with the temperature first being increased from room temperature to 105°C, then being depressurized by opening a pressure relief valve, and then being increased to 140-160°C after the pressure is reduced to zero and the pressure relief valve is closed. The steaming ball is under a pressure of 0.4-0.6 MPa for 60-180 min, or under a pressure of 0.45-0.55 MPa for 120-180 min.

[0012] The plant fiber raw material is softened in a supersaturated calcium hydroxide solution, and the cost of the calcium hydroxide raw material is much lower than that of sodium hydroxide or sodium sulfite, thereby greatly reducing the processing cost of the plant fiber. The softened material is filtered, and the obtained filtrate is a recyclable alkaline filtrate, further reducing the cost. The obtained filtrate after filtration is a supersaturated calcium hydroxide solution containing lignin. The obtained filter residue after filtration is an aqueous slurry, and the water content of the filter residue is 25% to 45%, preferably 30% to 40%. In some embodiments of the present application, the softened material is filtered using a filter press, and the filter press is specifically a roll filter dewatering machine.

[0013] After filtering the softened material, the obtained filter residue and a sulfuric acid solution are subjected to acid-base neutralization. Specifically, the obtained filter residue is washed with water, and a sulfuric acid solution is added for acid-base neutralization until the system material is neutral. More specifically, the acid-base neutralization is performed until the pH of the system material is 7.0 to 8.0. The mass concentration of the sulfuric acid solution is 10% to 50%, preferably 30% to 50%. The introduction of the sulfuric acid solution into the filter residue obtained by filtering the softened material during the water washing process can produce nanoscale calcium sulfate particles attached to the surface of the plant fiber. The nanoscale and microscale calcium sulfate dihydrate fine particles act as crystal seeds during the hydration of the building gypsum and play the role of a coagulant during the production of gypsum fiberboard.

[0014] After the acid-base neutralization of the obtained filter residue and the sulfuric acid solution, the obtained material after acid-base neutralization is filtered. The obtained filtrate after filtration is an aqueous solution containing calcium sulfate, which can be recycled after filtration. The obtained filter residue after filtration is a wet slurry, and the water content of the wet slurry is 40% to 70%, preferably 50% to 60%.

[0015] After obtaining the wet slurry, the obtained wet slurry is ground and dried to obtain plant fiber for gypsum fiberboard. Specifically, after drying, the material after drying is fed into a fiber mill for dispersion treatment, so that the plant fiber becomes fluffy and is easily mixed with building gypsum powder during the preparation of gypsum fiberboard. The grinding is performed at a speed of 150 r / min to 300 r / min, preferably at a speed of 200 r / min. The length of the obtained plant fiber for gypsum fiberboard is less than 5 mm, preferably 0.1 mm to 3 mm. The water content of the obtained plant fiber for gypsum fiberboard is 5% to 20%, preferably 5% to 15%, and preferably 7% to 13%.

[0016] The application provides the plant fiber for gypsum fiberboard prepared by the preparation method.

[0017] The application further provides a gypsum fiberboard prepared from gypsum powder and the plant fiber.

[0018] The application discloses a plant fiber for gypsum fiberboard and a preparation method and application thereof. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The particle size distribution diagram of the mechanical grinding seed obtained in the comparative example 1 of the application;

[0020] Figure 2 The particle size distribution diagram of the wet pulp seed obtained in step (4) of the example 2 of the application. DETAILED DESCRIPTION

[0021] The application discloses a kind of plant fiber for gypsum fiberboard and its preparation method and application. Those skilled in the art can improve process parameters appropriately to realize by referring to the content herein. It is particularly pointed out that all similar substitutions and changes are obvious to those skilled in the art, and they are considered to be included in the present application. The method and application of the present application have been described by preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application herein without departing from the content, spirit and scope of the present application to realize and apply the present application technology.

[0022] The application is further described below in conjunction with examples:

[0023] Example 1

[0024] (1) Breaking: the reed straw is broken into 1 cm~5 cm raw materials, and the broken raw materials are loaded into a high-pressure steaming ball.

[0025] (2) Cooking and softening: a supersaturated solution of calcium hydroxide is prepared, and the ratio of calcium hydroxide to water is 25 g / L. The above-mentioned supersaturated solution of calcium hydroxide is loaded into a high-pressure steaming ball, and two-stage temperature rising is performed, i.e., from room temperature to 105°C, and then the pressure relief valve is opened to relieve the pressure of the steaming ball; after the pressure relief is completed, the pressure relief valve is closed, and then the temperature is raised from 105°C to 145°C; the pressure of the steaming ball is 0.45 MPa; and the cooking time is 120 min.

[0026] (3) Pressure filtration and neutralization: the mixed slurry obtained in step (2) is subjected to pressure filtration to remove water, and the alkaline filtrate is recycled; the obtained filter cake is placed in a washing tank for water washing and stirring, and a 30% sulfuric acid solution is added for acid-base neutralization to a pH of 7.8.

[0027] (4) Filtration and pulp grinding: the neutralized raw material slurry obtained in step (3) is filtered to obtain wet pulp, and the calcium sulfate-containing filtrate is recycled. The wet pulp obtained in step (4) is placed in a pulp grinder for pulp grinding to obtain reed straw fibers below 3 mm, which are dried and then subjected to dispersing treatment in a fiber mill for the production of gypsum fiberboard.

[0028] Example 2

[0029] (1) Breaking: the wheat straw is broken into 1 cm~5 cm raw materials, and the broken raw materials are loaded into a high-pressure steaming ball.

[0030] (2) Cooking softening: prepare a supersaturated solution of calcium hydroxide, the ratio of calcium hydroxide to water is 15 g / L, the above-mentioned supersaturated solution of calcium hydroxide is loaded into a high-pressure steaming ball, two-stage temperature rising, first from room temperature to 105℃, then open the pressure relief valve to relieve the pressure of the steaming ball; after the pressure relief is completed, close the pressure relief valve, then raise the temperature from 105℃ to 145℃; the pressure of the steaming ball is 0.45 MPa; the cooking time is 120 min.

[0031] (3) Pressure filtration and neutralization: the mixed slurry obtained in step (2) is subjected to pressure filtration to remove water, and the alkaline filtrate is recycled; the obtained filter cake is placed in a washing tank for water washing and stirring, and a 30% sulfuric acid solution is added for acid-base neutralization to a pH of 7.6.

[0032] (4) Filtration and pulping: the raw material slurry obtained in step (3) is filtered to obtain wet pulp, and the filtrate containing calcium sulfate is recycled. The wet pulp obtained in step (4) is put into a pulping machine for pulping to obtain wheat straw fibers below 3 mm, which is dried and then put into a fiber mill for dispersion treatment, and used for the production of gypsum fiberboard.

[0033] Example 3

[0034] (1) Breaking: the balsa tree bark is broken into raw materials of 1 cm-5 cm, and the broken raw materials are loaded into a high-pressure steaming ball.

[0035] (2) Cooking softening: prepare a supersaturated solution of calcium hydroxide, the ratio of calcium hydroxide to water is 15 g / L, the above-mentioned supersaturated solution of calcium hydroxide is loaded into a high-pressure steaming ball, two-stage temperature rising, first from room temperature to 105℃, then open the pressure relief valve to relieve the pressure of the steaming ball; after the pressure relief is completed, close the pressure relief valve, then raise the temperature from 105℃ to 145℃; the pressure of the steaming ball is 0.45 MPa; the cooking time is 120 min.

[0036] (3) Pressure filtration and neutralization: the mixed slurry obtained in step (2) is subjected to pressure filtration to remove water, and the alkaline filtrate is recycled; the obtained filter cake is placed in a washing tank for water washing and stirring, and a 40% sulfuric acid solution is added for acid-base neutralization to a pH of 7.2.

[0037] (4) Filtration and pulping: the raw material slurry obtained in step (3) is filtered to obtain wet pulp, and the filtrate containing calcium sulfate is recycled. The wet pulp obtained in step (4) is put into a pulping machine for pulping to obtain balsa tree bark fibers below 3 mm, which is dried and then put into a fiber mill for dispersion treatment, and used for the production of gypsum fiberboard.

[0038] The length screening of the plant fibers obtained in the above Examples 1-3 is shown in Table 1:

[0039] Table 1

[0040]

[0041] From the data in Table 1, it can be seen that after the plant fibers cooked by saturated calcium hydroxide solution at high temperature, after the refining treatment, the fiber length is mainly concentrated in 0-1mm, the plant fibers are effectively softened and dispersed.

[0042] The plant fibers obtained in the above Examples 1-3 are used to prepare gypsum fiber boards, specifically, the mass ratio of plant fibers and building gypsum powder is 18:72, and the gypsum fiber boards are prepared by using a semi-dry process, the forming pressure is 12 MPa, and reed straw fiber boards, wheat straw fiber boards and broussonetia papyrifera fiber boards are obtained respectively.

[0043] The physical performance test results of the gypsum fiber boards obtained above are shown in Table 2:

[0044] Table 2

[0045]

[0046] As can be seen from the data in Table 2, the gypsum fiber boards prepared by using the above plant fibers have high mechanical performance indexes, which meet the performance requirements of building decoration boards.

[0047] It can be seen that the method of the present application uses cheap calcium hydroxide instead of sodium hydroxide or sodium sulfite, greatly reducing the processing cost of plant fiber raw materials, and the prepared plant fibers meet the production of gypsum fiber boards; at the same time, the plant fiber slurry after treatment is neutralized by introducing sulfuric acid solution in the washing process, and the generated nano-sized calcium sulfate particles are attached to the surface of the plant fibers, which plays a role of coagulant in the production of gypsum fiber boards, and improves the mechanical properties of the gypsum fiber boards.

[0048] Comparative Example 1

[0049] According to the method of Example 2, the difference is that no sulfuric acid is added, and the water washing is directly carried out to PH 7.6, and 3mm or less wheat straw fibers are obtained;

[0050] The natural gypsum is mechanically ground by a ball mill, the mechanical grinding adopts a small ball mill, the equipment size is φ800*2980mm, the grinding body is a steel ball with a diameter of 25mm, the grinding body loading amount is 400Kg, and the grinding time is 1 hour, and the mechanical grinding seed is obtained.

[0051] The obtained plant fibers and building gypsum powder are mixed according to a mass ratio of 18:72, and 0.3% of the mechanical grinding seed is added as a coagulant, and the gypsum fiber board is prepared by using a semi-dry process, the forming pressure is 12 MPa, and the gypsum fiber board is obtained.

[0052] The physical performance test results of the gypsum fiber boards obtained above are shown in Table 3:

[0053] Table 3

[0054]

[0055] a: The data in this column is from the column containing the wheat straw fiberboard in Table 2.

[0056] The particle size distribution of the mechanically milled seed crystals obtained in Comparative Example 1 of this invention was tested, and the results are as follows: Figure 1 As shown, Figure 1 The particle size distribution diagram of the mechanically ground seed crystals obtained in Comparative Example 1 of the present invention shows that the proportion of 0-10 micrometer particles in the mechanically ground seed crystals is only 57.12%.

[0057] The wet pulp obtained in step (4) of Example 2 of this invention was dispersed in anhydrous ethanol to obtain nanocrystals adsorbed on paper fibers. The ethanol solution from which the seed crystals were extracted was then subjected to particle size distribution testing using a laser force distribution analyzer, and the results are as follows: Figure 2 As shown, Figure 2 This is a particle size distribution diagram of the seed crystals extracted with anhydrous ethanol in step (4) of Example 2 of the present invention. Figure 2 It is evident that the seed crystals formed in the reaction between calcium hydroxide solution and sulfuric acid solution are much finer, with 0-10 micrometer particles accounting for 97.89%.

[0058] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing plant fibers for gypsum fiberboard, characterized in that, Includes the following steps: S1) The plant fiber raw material is softened in a supersaturated solution of calcium hydroxide, and then filtered to obtain filter residue; S2) Neutralize the filter residue obtained in step S1) with sulfuric acid solution, then filter to obtain wet slurry. Grind the obtained wet slurry to obtain plant fiber for gypsum fiberboard.

2. The preparation method according to claim 1, characterized in that, In step S1), the ratio of calcium hydroxide to water in the supersaturated solution of calcium hydroxide is 5 g / L to 30 g / L.

3. The preparation method according to claim 1, characterized in that, In step S1), the softening temperature is 140℃~160℃, the softening pressure is 0.4 MPa~0.6 MPa, and the softening time is 60 min~180 min.

4. The preparation method according to claim 1, characterized in that, In step S1), the length of the plant fiber raw material is less than 6 cm.

5. The preparation method according to claim 1, characterized in that, In step S1), the moisture content of the filter residue is 25% to 45%.

6. The preparation method according to claim 1, characterized in that, In step S2), the mass concentration of the sulfuric acid solution is 10% to 50%.

7. The preparation method according to claim 1, characterized in that, In step S2), the moisture content of the wet slurry is 40% to 70%.

8. The preparation method according to claim 1, characterized in that, In step S2), the length of the plant fibers used in the resulting gypsum fiberboard is less than 5 mm; The moisture content of the plant fibers used in the resulting gypsum fiberboard is 5%~20%.

9. Plant fibers for gypsum fiberboard obtained by any of the preparation methods described in claims 1 to 8.

10. A gypsum fiberboard, characterized in that, It is prepared from gypsum powder and plant fiber; The plant fiber is the plant fiber for gypsum fiberboard obtained by any of the preparation methods described in claims 1 to 8.

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