CN111139552B - Preparation method of alumina short fiber - Google Patents
Preparation method of alumina short fiber Download PDFInfo
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- CN111139552B CN111139552B CN202010036322.7A CN202010036322A CN111139552B CN 111139552 B CN111139552 B CN 111139552B CN 202010036322 A CN202010036322 A CN 202010036322A CN 111139552 B CN111139552 B CN 111139552B
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
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Abstract
The invention provides a preparation method of alumina short fibers, which comprises the following steps: a) mixing polyaluminium chloride sol and silica sol, and then sequentially hydrolyzing and distilling and concentrating for the first time to obtain silicon-aluminum composite spinning solution; then adding a spinning auxiliary agent for secondary distillation and concentration, and controlling the viscosity to obtain a spinning solution with the room-temperature viscosity of 1500MPa & s-2200 MPa & s; b) spinning the spinning solution obtained in the step a) to obtain precursor fiber; c) carrying out heat treatment on the precursor fiber obtained in the step b) to obtain a fiber cotton blank; and finally, extruding to obtain the alumina short fiber. Compared with the prior art, the preparation method comprises the steps of firstly obtaining the spinning solution suitable for the spinning process by adopting a specific formula, then combining specific process steps and conditions to realize better interaction, obtaining the alumina short fiber with short length and easy dispersion, not easily causing the problems of doubling, adhesion and fiber curling in the spinning process, and simultaneously obtaining the cotton blank with small thickness deviation at two sides and good uniformity.
Description
Technical Field
The invention relates to the technical field of alumina fibers, in particular to a preparation method of alumina short fibers.
Background
The alumina fiber is used as a reinforcing material of other products in the main aspect of application, and the strength of the alumina fiber is higher than that of common ceramic fiber; if the fibers are too long and are wound, the fibers are not easy to uniformly disperse in the application process, and the labor intensity in the use process is increased.
The alumina short fiber has narrow application, can be prepared into alumina fiber blankets, modules and other products, and greatly widens the application field. The industry commonly adopts a thread throwing process, and the alumina fiber is prepared into an alumina fiber blanket by dry needling; therefore, high requirements are put on the preparation of the alumina short fiber. When the spinning process is used for forming fibers, the spinning disc rotates at a high speed, the fibers are too long and are easy to be doubled, adhered, curled and the like, and the fibers cannot be scattered in time, so that the uniformity of cotton distribution is influenced, and the problem of uneven thickness of the prepared alumina fiber blanket is caused.
Disclosure of Invention
In view of the above, the present invention aims to provide a preparation method of alumina short fibers, the alumina short fibers obtained by the preparation method provided by the present invention are short, easy to disperse, and difficult to cause the problems of doubling, adhesion and fiber curling in the spinning process, and the obtained cotton blank has small thickness deviation on both sides and good uniformity.
The invention provides a preparation method of alumina short fibers, which comprises the following steps:
a) mixing polyaluminum chloride sol and silica sol, and then sequentially carrying out hydrolysis and first distillation and concentration to obtain a silicon-aluminum composite spinning solution; then adding a spinning auxiliary agent for secondary distillation and concentration, and controlling the viscosity to obtain a spinning solution with the room-temperature viscosity of 1500MPa & s-2200 MPa & s;
b) spinning the spinning solution obtained in the step a) to obtain precursor fiber;
c) carrying out heat treatment on the precursor fiber obtained in the step b) to obtain a fiber cotton blank; and finally, extruding to obtain the alumina short fiber.
Preferably, Al of the polyaluminum chloride sol in step a)2O3The content is 18wt% -25 wt%.
Preferably, Al in the polyaluminum chloride sol of step a)2O3And SiO in silica sol2The mass ratio of (67-80): (20-33).
Preferably, the hydrolysis temperature in the step a) is 40-70 ℃ and the time is 1-2 h.
Preferably, the temperature of the first distillation and concentration in the step a) is 80-150 ℃, and the time is 2-3 h.
Preferably, the spinning auxiliary agent in the step a) is a polyvinyl alcohol aqueous solution with the mass concentration of 3-6%;
the addition amount of the spinning auxiliary agent is Al in the silicon-aluminum composite spinning solution2O3And SiO2The sum of the solid contents is 2 to 5 percent.
Preferably, the temperature of the second distillation and concentration in the step a) is 80-150 ℃, and the time is 0.5-1 h.
Preferably, the spinning process in the step b) adopts a spinning and cotton collecting device, which specifically comprises the following steps: the primary upward induced air pressure is 0.2-0.4 MPa, an included angle of 50-70 degrees is formed with the tangential direction of the spinning disc, the secondary upward induced air pressure is 0.05-0.2 MPa, an included angle of 70-90 degrees is formed with the tangential direction of the spinning disc, the primary downward induced air pressure is 0.3-0.5 MPa, the primary upward induced air pressure is 1-2 m above the cotton collecting net, the secondary downward induced air pressure is 0.1-0.3 MPa, the curing distance is 3-7 m, the temperature is 20-45 ℃, the humidity is controlled to be 30-40 RH%, the aperture of the spinning disc needle is 0.05-0.2 mm, the distance between the spraying needles is 2-3 cm, the upper row of needle holes and the lower row of needle holes are distributed in an S shape, and the rotating speed of the spinning disc is 10-30 Hz.
Preferably, the heat treatment process in step c) is specifically:
heating the precursor fiber to 450-550 ℃ according to the heating rate of 2-5 ℃/min, and then preserving the heat for 2-3 h; then heating to 1300-1400 ℃ according to the heating rate of 8-15 ℃/min, and roasting for 30-60 min to obtain the fiber cotton blank.
Preferably, the extrusion mode in the step c) is compression roller extrusion; the extrusion pressure is 5 kN/cm-10 kN/cm.
The invention provides a preparation method of alumina short fiber, which comprises the following steps: a) mixing polyaluminium chloride sol and silica sol, and then sequentially hydrolyzing and distilling and concentrating for the first time to obtain silicon-aluminum composite spinning solution; then adding a spinning auxiliary agent for secondary distillation and concentration, and controlling the viscosity to obtain a spinning solution with the room-temperature viscosity of 1500-2200 MPa.s; b) spinning the spinning solution obtained in the step a) to obtain precursor fiber; c) carrying out heat treatment on the precursor fiber obtained in the step b) to obtain a fiber cotton blank; and finally, extruding to obtain the alumina short fiber. Compared with the prior art, the preparation method provided by the invention firstly adopts a specific formula to obtain the spinning solution suitable for the spinning process, and then combines specific process steps and conditions to realize better interaction, so that the obtained alumina short fiber is shorter and easy to disperse, the problems of doubling, adhesion and fiber curling are not easy to occur in the spinning process, and meanwhile, the thickness deviation of two sides of the obtained cotton blank is small, and the uniformity is good. Experimental results show that the thickness deviation of two sides of the cotton blank obtained by the preparation method provided by the invention can be as low as 0.3cm, the fiber length of the obtained alumina short fiber is 3-5 cm, and the average length is 3.6 cm.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of alumina short fiber, which comprises the following steps:
a) mixing polyaluminium chloride sol and silica sol, and then sequentially hydrolyzing and distilling and concentrating for the first time to obtain silicon-aluminum composite spinning solution; then adding a spinning auxiliary agent for secondary distillation and concentration, and controlling the viscosity to obtain a spinning solution with the room-temperature viscosity of 1500MPa & s-2200 MPa & s;
b) spinning the spinning solution obtained in the step a) to obtain precursor fiber;
c) carrying out heat treatment on the precursor fiber obtained in the step b) to obtain a fiber cotton blank; and finally, extruding to obtain the alumina short fiber.
Firstly, mixing polyaluminium chloride sol and silica sol, and then sequentially hydrolyzing and distilling and concentrating for the first time to obtain the silicon-aluminum composite spinning solution. In the invention, the polyaluminum chloride sol is an aluminum source; al of the polyaluminum chloride sol2O3The content is preferably 18wt%25wt%, more preferably 20 wt%. In the present invention, the preparation process of the polyaluminum chloride sol is preferably specifically:
mixing aluminum powder, hydrochloric acid and distilled water, and heating and refluxing at 60-110 ℃ to obtain polyaluminum chloride sol;
more preferably:
mixing aluminum powder, hydrochloric acid and distilled water, and heating and refluxing at 100 ℃ to obtain polyaluminum chloride sol. The sources of the aluminum powder and hydrochloric acid are not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used. In the present invention, the purity of the powdery aluminum is preferably 99% or more, WFe2O3% preferably 0.01%; the particle size of the aluminum powder is preferably 200 to 600 meshes.
In the invention, the molar ratio of the aluminum powder, hydrochloric acid (calculated as HCl) and distilled water is preferably (1.6-2): 1: (10-30), more preferably 1.8: 1: 22.2.
in the present invention, the silica sol, i.e., acidic silica (sol), is a silicon source; the silica sol is preferably prepared from tetraethoxysilane, the pH is preferably 2-4, the granularity is preferably 10-20 nm, and the WSiO is2% is preferably 15% to 30%. The source of the tetraethoxysilane is not particularly limited in the present invention, and a commercially available product well known to those skilled in the art may be used.
In the present invention, Al in the polyaluminum chloride sol2O3And SiO in silica sol2The mass ratio of (2) is preferably (67-80): (20 to 33), more preferably 67: 33.
the mixing process is not particularly limited, and the technical scheme of manual stirring or mechanical stirring well known to those skilled in the art can be adopted, so that the raw materials are uniformly mixed.
In the present invention, the temperature of the hydrolysis is preferably 40 ℃ to 70 ℃, more preferably 60 ℃; the hydrolysis time is preferably 1 to 2 hours, more preferably 1.5 hours.
In the present invention, the temperature of the first distillation concentration is preferably 80 ℃ to 150 ℃, more preferably 90 ℃; the time for the first distillation concentration is preferably 2 to 3 hours, and more preferably 2.5 hours.
The viscosity (50 ℃) of the obtained silicon-aluminum composite spinning solution is preferably 300 MPa.s to 600 MPa.s, more preferably 400 MPa.s, and the solution is transparent and uniform.
After the silicon-aluminum composite spinning solution is obtained, the spinning auxiliary agent is added into the obtained silicon-aluminum composite spinning solution for secondary distillation and concentration, and then the spinning solution with the room temperature viscosity of 1500MPa & s-2200 MPa & s is obtained through viscosity control. In the present invention, the spinning aid is preferably a polyvinyl alcohol aqueous solution having a mass concentration of 3% to 6%, and more preferably a polyvinyl alcohol aqueous solution having a mass concentration of 6%. In the invention, the polymerization degree of the polyvinyl alcohol is preferably 300-700, and the alkalization degree is preferably 75-95. The polyvinyl alcohol used in the present invention is not particularly limited in its source, and commercially available products known to those skilled in the art can be used.
In the invention, the addition amount of the spinning auxiliary agent is preferably Al in the silicon-aluminum composite spinning solution2O3And SiO22-5% of the sum of solid contents, more preferably Al in the silicon-aluminum composite spinning solution2O3And SiO22% of the sum of the solids contents.
In the present invention, the temperature of the second distillation concentration is preferably 80 ℃ to 150 ℃, more preferably 90 ℃; the time for the second distillation concentration is preferably 0.5h to 1h, and more preferably 0.7 h.
In the present invention, the process of viscosity control is preferably performed under sealed conditions; the process of viscosity control is preferably embodied as follows:
aging the product after the second distillation and concentration to obtain clear and transparent sol, and controlling the viscosity (at 50 ℃) of the sol to be 800 MPa.s-1000 MPa.s; then ageing at room temperature to obtain spinning solution with the room temperature viscosity of 1500MPa & s-2200 MPa & s;
more preferably:
aging the product after the second distillation and concentration to obtain clear and transparent sol, and controlling the viscosity (at 50 ℃) of the sol to be 900MPa & s; then aging at room temperature to obtain the spinning solution with the room temperature viscosity of 1800 MPa.s.
In the process of obtaining the spinning solution (sol) with the specific room temperature viscosity, firstly, mixing alumina and silica to prepare the sol (silicon-aluminum composite spinning solution) with a certain viscosity, then adding a spinning auxiliary agent, so that the fiber strength can be ensured, and meanwhile, selecting low-molecular-weight polyvinyl alcohol and keeping a lower addition amount, so that the fiber forming performance of the sol can be controlled to a certain degree, on one hand, the sol can meet the fiber forming requirement, and can be stretched into fibers, and on the other hand, the longer fiber forming length caused by the over-good fiber forming performance can be avoided; the viscosity of the prepared sol (silicon-aluminum composite spinning solution) cannot be too high, the preparation viscosity (50 ℃) is controlled to be 300MPa & s-600 MPa & s, too high viscosity means that the polymerization degree of the sol is too high, the sol with higher molecular weight is easy to generate, the molecular weight is high, the molecular chain is longer, and the fiber forming length is longer; therefore, the viscosity of the outlet kettle and the viscosity of fiber forming are further controlled, and finally the spinning solution with the room temperature viscosity of 1500MPa & s-2200 MPa & s is obtained.
After the spinning solution is obtained, the spinning solution is spun to obtain the precursor fiber. In the invention, the spinning process preferably adopts spinning and cotton collecting equipment; the spinning process preferably comprises the following steps:
the primary upward induced air pressure is 0.2-0.4 MPa, an included angle of 50-70 degrees is formed with the tangential direction of the spinning disc, the secondary upward induced air pressure is 0.05-0.2 MPa, an included angle of 70-90 degrees is formed with the tangential direction of the spinning disc, the primary downward induced air pressure is 0.3-0.5 MPa, the primary upward induced air pressure is 1-2 m above the cotton collecting net, the secondary downward induced air pressure is 0.1-0.3 MPa, the curing distance is 3-7 m, the temperature is 20-45 ℃, the humidity is controlled to be 30-40 RH percent, the aperture of the spinning disc needle is 0.05-0.2 mm, the distance between the spraying needles is 2-3 cm, the upper row of needle holes and the lower row of needle holes are distributed in an S shape, and the rotating speed of the spinning disc is 10-30 Hz;
more preferably:
the primary upward induced air pressure is 0.3MPa, an included angle of 60 degrees is formed between the primary upward induced air pressure and the tangential direction of the spinning disc, the secondary upward induced air pressure is 0.1MPa, an included angle of 80 degrees is formed between the secondary upward induced air pressure and the tangential direction of the spinning disc, the primary downward induced air pressure is 0.4MPa, the secondary downward induced air pressure is 0.2MPa, the curing distance is 5m, the temperature is 35 ℃, the humidity is controlled at 35 RH%, the aperture of the spinning disc needle is 0.1mm, the distance between the spray needles is 2.5cm, the upper row of needle holes and the lower row of needle holes are distributed in an S shape, and the rotating speed of the spinning disc is 20 Hz.
The invention adopts the spinning process with the specific steps, conditions and parameters, wherein primary up-blowing is a fiber forming effect, secondary up-blowing is a blowing-off effect, and lower induced air is used for matching air flow; wind pressure is adjusted, namely wind power is adjusted, the fibers are blown away by the wind power within a certain range, and the force acted on the fibers can be effectively exerted only by matching with the fiber forming direction when the wind power is applied; meanwhile, the air flow stability in the cotton collecting chamber is ensured by the coordination of air induction and upward blowing. The matching adjustment of the spinning (fiber forming) process can ensure that the quality and the length of the fiber can be controlled within a required range, such as: the upper blowing is too large, the lower induced air is too small, so that the redundant air quantity cannot be discharged, cotton balls can float and float along with the air flow, and the temperature and humidity can not be maintained.
After the precursor fiber is obtained, carrying out heat treatment on the obtained precursor fiber to obtain a fiber cotton blank; and finally, extruding to obtain the alumina short fiber. In the present invention, the heat treatment process is preferably specifically:
heating the precursor fiber to 450-550 ℃ according to the heating rate of 2-5 ℃/min, and then preserving the heat for 2-3 h; then heating to 1300-1400 ℃ according to the heating rate of 8-15 ℃/min, and roasting for 30-60 min to obtain a fiber cotton blank;
more preferably:
heating the precursor fiber to 550 ℃ according to the heating rate of 5 ℃/min, and then preserving the heat for 2.5 h; and then heating to 1350 ℃ according to the heating rate of 10 ℃/min and roasting for 50min to obtain the fiber cotton blank. In the present invention, in the course of the temperature rise to 450 to 550 ℃, the adsorbed water contained in the precursor fiber is removed at 105 ℃, and the thermal decomposition product of the organic group and part of the coordinated water are further removed when the temperature reaches 450 to 550 ℃. In the invention, the fiber cotton blank is a finished product comprising alumina short fibers.
After the fiber cotton blank is obtained, the obtained fiber cotton blank is extruded to obtain the alumina short fiber. In the present invention, the extrusion process is preferably performed on the fiber cotton blank just after calcination (baking), the fiber in the fiber cotton blank just after calcination is brittle, and the extrusion can break the twisted fibers to reduce the fiber length. In the invention, the extrusion mode is preferably compression roller extrusion; the pressure of the extrusion is preferably 5kN/cm to 10kN/cm, more preferably 8 kN/cm.
The preparation method provided by the invention firstly adopts a specific formula to obtain the spinning solution suitable for the silk spinning process, and then combines specific process steps and conditions to realize better interaction, the obtained alumina short fiber is shorter and easy to disperse, the problems of doubling, adhesion and fiber curling are not easy to occur in the silk spinning process, and meanwhile, the thickness deviation of two sides of the obtained cotton blank is small, and the uniformity is good.
The invention provides a preparation method of alumina short fibers, which comprises the following steps: a) mixing polyaluminum chloride sol and silica sol, and then sequentially carrying out hydrolysis and first distillation and concentration to obtain a silicon-aluminum composite spinning solution; then adding a spinning auxiliary agent for secondary distillation and concentration, and controlling the viscosity to obtain a spinning solution with the room-temperature viscosity of 1500-2200 MPa.s; b) spinning the spinning solution obtained in the step a) to obtain precursor fiber; c) carrying out heat treatment on the precursor fiber obtained in the step b) to obtain a fiber cotton blank; and finally, extruding to obtain the alumina short fiber. Compared with the prior art, the preparation method provided by the invention firstly adopts a specific formula to obtain the spinning solution suitable for the spinning process, and then combines specific process steps and conditions to realize better interaction, so that the obtained alumina short fiber is shorter and easy to disperse, the problems of doubling, adhesion and fiber curling are not easy to occur in the spinning process, and meanwhile, the thickness deviation of two sides of the obtained cotton blank is small, and the uniformity is good. Experimental results show that the thickness deviation of two sides of the cotton blank obtained by the preparation method provided by the invention can be as low as 0.3cm, the fiber length of the obtained alumina short fiber is 3-5 cm, and the average length is 3.6 cm.
To further illustrate the present invention, the following examples are provided for illustration. The raw materials used in the following examples of the present invention are all commercially available; wherein the purity of the aluminum powder is 99 percentSupra, WFe2O3Less than or equal to 0.01 percent and 200-600 meshes; hydrochloric acid (HCl, 36.5%), analytical grade; the spinning auxiliary agent is prepared from a spinning aid, the mass concentration of the spinning aid is 3% -6%, the spinning aid is polyvinyl alcohol, the polymerization degree is 300-700, and the alkalization degree is 75-95; acidic silica (sol): the silica sol is prepared from tetraethoxysilane (analytically pure), the pH value is 2-4, the granularity is 10-20 nm, and the WSiO is2% is 15% -30%; the spinning process adopts a spinning and cotton collecting device (conventional, mobile cotton collecting mesh belt).
Example 1
(1) Aluminum powder, hydrochloric acid (calculated as HCl) and distilled water are mixed according to a molar ratio of 1.8: 1: 22.2, heating and refluxing at 100 ℃ to obtain Al2O3Polyaluminum chloride sol with the content of 20 wt%; according to the mass ratio of aluminum oxide in the aluminum source to silicon oxide in the silicon source of 67: 33, respectively weighing an aluminum source and silica sol, and uniformly mixing the aluminum source and the silica sol;
uniformly stirring the mixed solution, hydrolyzing at 60 ℃ for 1.5h, heating to 90 ℃, distilling and concentrating for 2.5h to obtain a transparent and uniform silicon-aluminum composite spinning solution with the viscosity of 400MPa & s (50 ℃);
then adding a spinning auxiliary agent with the mass concentration of 6% according to the proportion that the addition amount is 2% of the sum of the solid contents of the aluminum oxide and the silicon oxide; distilling and concentrating the mixed solution at 90 deg.C for 0.7h, taking out, and sealing; aging to obtain clear and transparent sol, and controlling the viscosity of the sol after being taken out of a kettle at 900MPa & s (50 ℃); aging at room temperature, and adjusting the spinning viscosity to 1800MPa · s (room temperature).
(2) The spinning process comprises the following steps: the primary upper induced air pressure is 0.3MPa, an included angle of 60 degrees is formed between the primary upper induced air pressure and the tangential direction of the spinning disc, the secondary upper induced air pressure is 0.1MPa, an included angle of 80 degrees is formed between the secondary upper induced air pressure and the tangential direction of the spinning disc, the primary lower induced air pressure is 0.4MPa (located 1.5m above the cotton collecting net), the secondary lower induced air pressure at the bottom of the cotton collecting net is 0.2MPa, the curing distance is 5m, the temperature is 35 ℃, the humidity is controlled at 35RH, the aperture of needles of the spinning disc is 0.1mm, the distance between every two spray needles is 2.5cm, the upper row of needle holes and the lower row of needle holes are distributed in an S shape, and the rotating speed of the spinning disc is 20 Hz; and obtaining the precursor fiber.
(3) Heating to 550 ℃ according to the heating rate of 5 ℃/min, removing the thermal decomposition product of the organic group and part of the coordinated water, and preserving the heat for 2.5h at 550 ℃; then heating to 1350 ℃ according to the heating rate of 10 ℃/min, and roasting for 50min at the temperature to obtain a calcined cellucotton blank; through measurement, the thickness deviation of two sides of the cotton embryo is 0.3cm, the fiber length is 3 cm-5 cm, and the average fiber length is 3.9 cm.
(4) Finally, extruding the fiber cotton blank which is just calcined by a compression roller, wherein the pressure is 8kN/cm, and obtaining alumina short fibers; the fiber length of the alumina short fiber is 3 cm-4 cm through measurement, and the average length is 3.6 cm.
Comparative example 1 (Change of Sol-gel Process)
(1) Aluminum powder, hydrochloric acid (as HCl) and distilled water are mixed according to a molar ratio of 1.8: 1: 22.2, heating and refluxing at 100 ℃ to obtain Al2O3Polyaluminum chloride sol with the content of 20 wt%; according to the mass ratio of aluminum oxide in the aluminum source to silicon oxide in the silicon source of 67: 33, respectively weighing an aluminum source and silica sol, and uniformly mixing the aluminum source and the silica sol;
then adding a spinning auxiliary agent with the mass concentration of 6% according to the proportion that the addition amount is 2% of the sum of the solid contents of the aluminum oxide and the silicon oxide;
then uniformly stirring the mixed solution, hydrolyzing at 60 ℃ for 1.5h, heating to 90 ℃, distilling and concentrating for 3.2h, taking out, and sealing; aging to obtain clear and transparent sol, and controlling the viscosity of the sol in a kettle at 1200 MPa.s (50 ℃); aging at room temperature, and adjusting the spinning viscosity to 2500MPa s (room temperature).
(2) The spinning process comprises the following steps: the primary upper induced air pressure is 0.3MPa, an included angle of 60 degrees is formed between the primary upper induced air pressure and the tangential direction of the spinning disc, the secondary upper induced air pressure is 0.1MPa, an included angle of 80 degrees is formed between the primary upper induced air pressure and the tangential direction of the spinning disc, the primary lower induced air pressure is 0.4MPa (located 1.5m above the cotton collecting net), the secondary lower induced air pressure at the bottom of the cotton collecting net is 0.2MPa, the curing distance is 5m, the temperature is 35 ℃, the humidity is controlled at 35RH, the aperture of needles of the spinning disc is 0.1mm, the distance between every two spray needles is 2.5cm, the upper row of needle holes and the lower row of needle holes are distributed in an S shape, and the rotating speed of the spinning disc is 20 Hz; and obtaining the precursor fiber.
(4) Heating to 550 ℃ according to the heating rate of 5 ℃/min, removing the thermal decomposition product of the organic group and part of the coordinated water, and preserving the heat for 2.5h at 550 ℃; then heating to 1350 ℃ according to the heating rate of 10 ℃/min, and roasting for 50min at the temperature to obtain a calcined cellucotton blank; through measurement, the thickness deviation of two sides of the cotton embryo is 1.4cm, the fiber length is 4 cm-6 cm, and the average fiber length is 5.2 cm.
(5) Finally, extruding the fiber cotton blank which is just calcined by a compression roller, wherein the pressure is 8kN/cm, and obtaining alumina short fibers; the fiber length of the alumina short fiber is 3 cm-5 cm through measurement, and the average length is 4.6 cm.
Comparative example 2 (changing the spinning process)
(1) Aluminum powder, hydrochloric acid (calculated as HCl) and distilled water are mixed according to a molar ratio of 1.8: 1: 22.2, heating and refluxing at 100 ℃ to obtain Al2O3Polyaluminum chloride sol with the content of 20 wt%; according to the mass ratio of aluminum oxide in an aluminum source to silicon oxide in a silicon source of 67: 33, respectively weighing an aluminum source and silica sol, and uniformly mixing the aluminum source and the silica sol;
uniformly stirring the mixed solution, hydrolyzing at 60 ℃ for 1.5h, heating to 90 ℃, distilling and concentrating for 2.5h to obtain a transparent and uniform silicon-aluminum composite spinning solution with the viscosity of 400MPa & s (50 ℃);
then adding a spinning auxiliary agent with the mass concentration of 6% according to the proportion that the addition amount is 2% of the sum of the solid contents of the aluminum oxide and the silicon oxide; distilling and concentrating the mixed solution at 90 deg.C for 0.7h, taking out, and sealing; aging to obtain clear and transparent sol, and controlling the viscosity of the sol after being taken out of a kettle at 900MPa & s (50 ℃); aging at room temperature, and adjusting the spinning viscosity to 1800MPa s (room temperature).
(2) The spinning process comprises the following steps: secondary upper induced air of 0.1MPa forms an included angle of 80 degrees with the tangential direction of the throwing disc, secondary lower induced air of 0.2MPa is arranged at the bottom of the cotton collection, the curing distance is 5m, the temperature is 35 ℃, the humidity is controlled at 35 RH%, the aperture of needles of the throwing disc is 0.1mm, the distance between spray needles is 1cm, and the single-row needle holes are sequentially arranged, and the rotating speed of the throwing disc is 20 Hz; and obtaining the precursor fiber.
(3) Heating to 550 ℃ according to the heating rate of 5 ℃/min, removing the thermal decomposition product of the organic group and part of the coordinated water, and preserving the heat for 2.5h at 550 ℃; heating to 1350 ℃ according to the heating rate of 10 ℃/min, and roasting for 50min at the temperature to obtain a calcined fiber cotton blank; through measurement, the thickness deviation of two sides of the cotton embryo is 2cm, the fiber length is 3 cm-7 cm, and the average fiber length is 4.8 cm.
(4) Finally, extruding the fiber cotton blank which is just calcined by a compression roller, wherein the pressure is 8kN/cm, and obtaining alumina short fibers; the fiber length of the alumina short fiber is 3 cm-5 cm through measurement, and the average length is 4.2 cm.
Comparative example 3 (Heat treatment System changed and No pressure roller applied)
(1) Aluminum powder, hydrochloric acid (as HCl) and distilled water are mixed according to a molar ratio of 1.8: 1: 22.2, heating and refluxing at 100 ℃ to obtain Al2O3Polyaluminum chloride sol with the content of 20 wt%; according to the mass ratio of aluminum oxide in the aluminum source to silicon oxide in the silicon source of 67: 33, respectively weighing an aluminum source and silica sol, and uniformly mixing the aluminum source and the silica sol;
uniformly stirring the mixed solution, hydrolyzing at 60 ℃ for 1.5h, heating to 90 ℃, distilling and concentrating for 2.5h to obtain a transparent and uniform silicon-aluminum composite spinning solution with the viscosity of 400MPa & s (50 ℃);
then adding a spinning auxiliary agent with the mass concentration of 6% according to the proportion that the addition amount is 2% of the sum of the solid contents of the aluminum oxide and the silicon oxide; distilling and concentrating the mixed solution at 90 deg.C for 0.7h, taking out, and sealing; aging to obtain clear and transparent sol, and controlling the viscosity of the sol in a kettle at 900 MPa.s (50 ℃); aging at room temperature, and adjusting the spinning viscosity to 1800MPa s (room temperature).
(2) The spinning process comprises the following steps: the primary upper induced air pressure is 0.3MPa, an included angle of 60 degrees is formed between the primary upper induced air pressure and the tangential direction of the spinning disc, the secondary upper induced air pressure is 0.1MPa, an included angle of 80 degrees is formed between the secondary upper induced air pressure and the tangential direction of the spinning disc, the primary lower induced air pressure is 0.4MPa (located 1.5m above the cotton collecting net), the secondary lower induced air pressure at the bottom of the cotton collecting net is 0.2MPa, the curing distance is 5m, the temperature is 35 ℃, the humidity is controlled at 35RH, the aperture of needles of the spinning disc is 0.1mm, the distance between every two spray needles is 2.5cm, the upper row of needle holes and the lower row of needle holes are distributed in an S shape, and the rotating speed of the spinning disc is 20 Hz; obtaining the precursor fiber.
(3) Heating to 500 ℃ according to the heating rate of 5 ℃/min, removing the thermal decomposition product of the organic group and part of the coordinated water, and preserving the heat for 2.5h at 500 ℃; heating to 750 ℃ according to the heating rate of 10 ℃/min, and roasting for 50min at the temperature to obtain a calcined cellucotton blank, wherein the cellucotton blank comprises alumina short fibers; through measurement, the thickness deviation of two sides of the cotton embryo is 0.29cm, the fiber length is 3 cm-7 cm, and the average fiber length is 4.5 cm.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (5)
1. A preparation method of alumina short fiber comprises the following steps:
a) mixing polyaluminium chloride sol and silica sol, and then sequentially hydrolyzing and distilling and concentrating for the first time to obtain silicon-aluminum composite spinning solution; then adding a spinning auxiliary agent for secondary distillation and concentration, and controlling the viscosity to obtain a spinning solution with the room-temperature viscosity of 1500MPa & s-2200 MPa & s; the spinning auxiliary agent is a polyvinyl alcohol aqueous solution with the mass concentration of 3% -6%;
the addition amount of the spinning auxiliary agent is Al in the silicon-aluminum composite spinning solution2O3And SiO2The sum of the solid contents is 2% -5%;
al of the polyaluminum chloride sol2O3The content is 18wt% -25 wt%;
al in the polyaluminum chloride sol2O3And SiO in silica sol2The mass ratio of (67-80): (20 to 33);
b) spinning the spinning solution obtained in the step a) to obtain precursor fiber; the spinning process adopts the equipment for spinning and collecting cotton, and specifically comprises the following steps: the primary upward induced air pressure is 0.2MPa to 0.4MPa, an included angle of 50 degrees to 70 degrees is formed between the primary upward induced air pressure and the tangential direction of the spinning disc, the secondary upward induced air pressure is 0.05MPa to 0.2MPa, an included angle of 70 degrees to 90 degrees is formed between the primary upward induced air pressure and the tangential direction of the spinning disc, the primary downward induced air pressure is 0.3MPa to 0.5MPa, the primary upward induced air pressure is 1m to 2m above the cotton collecting net, the secondary downward induced air pressure is 0.1MPa to 0.3MPa, the curing distance is 3m to 7m, the temperature is 20 ℃ to 45 ℃, the humidity is controlled to be 30RH percent to 40RH percent, the aperture of a spinning disc needle is 0.05mm to 0.2mm, the distance between the spinning needles is 2cm to 3cm, the upper and lower rows of needle holes are distributed in an S shape, and the spinning disc rotating speed is 10Hz to 30 Hz;
c) carrying out heat treatment on the precursor fiber obtained in the step b) to obtain a fiber cotton blank; finally, extruding to obtain alumina short fibers; the heat treatment process specifically comprises the following steps:
heating the precursor fiber to 450-550 ℃ according to the heating rate of 2-5 ℃/min, and then preserving heat for 2-3 h; and then heating to 1300-1400 ℃ according to the heating rate of 8-15 ℃/min, and roasting for 30-60 min to obtain the cellucotton blank.
2. The preparation method of claim 1, wherein the hydrolysis in step a) is carried out at a temperature of 40 ℃ to 70 ℃ for 1h to 2 h.
3. The preparation method of claim 1, wherein the temperature of the first distillation concentration in the step a) is 80-150 ℃ and the time is 2-3 h.
4. The preparation method of claim 1, wherein the temperature of the second distillation concentration in the step a) is 80-150 ℃ and the time is 0.5-1 h.
5. The method of claim 1, wherein the pressing in step c) is a roll pressing; the extrusion pressure is 5-10 kN/cm.
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| CN1236832A (en) * | 1998-05-22 | 1999-12-01 | 中国科学院山西煤炭化学研究所 | Process for preparing Al2O3-SiO2 compound fibre |
| CN104086200A (en) * | 2014-07-22 | 2014-10-08 | 南京理工大学 | Preparation method of mullite fiber |
| CN106048780A (en) * | 2016-05-24 | 2016-10-26 | 天津工业大学 | Method for preparing alumina-based continuous fiber |
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| CN1236832A (en) * | 1998-05-22 | 1999-12-01 | 中国科学院山西煤炭化学研究所 | Process for preparing Al2O3-SiO2 compound fibre |
| CN104086200A (en) * | 2014-07-22 | 2014-10-08 | 南京理工大学 | Preparation method of mullite fiber |
| CN106048780A (en) * | 2016-05-24 | 2016-10-26 | 天津工业大学 | Method for preparing alumina-based continuous fiber |
| CN106544757A (en) * | 2016-11-25 | 2017-03-29 | 陕西聚洁瀚化工有限公司 | Get rid of the method that a method prepares polycrystalline alumina fiber |
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