CN111943217B - Preparation method of ultrafine wollastonite with high length-diameter ratio - Google Patents
Preparation method of ultrafine wollastonite with high length-diameter ratio Download PDFInfo
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Abstract
The invention provides a preparation method of ultrafine wollastonite with a high length-diameter ratio, and relates to the technical field of wollastonite preparation. The invention takes superfine acicular wollastonite as a matrix, takes mixed silicon source-water glass and ethyl orthosilicate as well as calcium source-calcium hydroxide suspension as reaction raw materials, takes a surfactant as a crystal form inducer, and performs homogeneous nucleation to construct new calcium silicate in the one-dimensional direction of the superfine acicular wollastonite by a hydrothermal method, so as to improve the length-diameter ratio of the original wollastonite, thereby obtaining the superfine wollastonite with high length-diameter ratio, wherein the length-diameter ratio of the superfine wollastonite is 12-18; the step of processing by matching with a coupling agent can effectively slow down the agglomeration trend of the high-length-diameter-ratio ultrafine wollastonite powder, improve the dispersibility of the high-length-diameter-ratio ultrafine wollastonite powder in downstream application, improve the compatibility with matrix resin and further improve the comprehensive performance of the product.
Description
Technical Field
The invention relates to the technical field of wollastonite preparation, in particular to a preparation method of ultrafine wollastonite with a high length-diameter ratio.
Background
Wollastonite is a metasilicate mineral with a modification cause, has a unique needle-shaped structure, good insulativity, excellent heat resistance and chemical stability, and is widely applied to the fields of modified plastics, papermaking, coatings, rubber, ceramics and the like.
The current wollastonite deep processing products mainly comprise two types, one type is a wollastonite product with a high length-diameter ratio, the unique one-dimensional structure is mainly utilized to replace other short fiber mineral raw materials (such as glass fibers) to serve as a polymer reinforcing and toughening functional material, and particularly, the bending strength and the impact strength of a product can be improved in the fields of plastics and rubber, and the thermal stability and the dimensional stability of the product are improved; the other is ultra-fine wollastonite, which is mainly used in the field of ceramics to impart excellent low thermal expansion and impact resistance to products.
Researches show that the ultrafine wollastonite with high length-diameter ratio has greater application value, and the ultrafine wollastonite with high length-diameter ratio can obviously improve the strength and the wear resistance of a product in a filler for rubber; in the plastic filler, the high length-diameter ratio ultrafine wollastonite can greatly improve the strength and toughness of the product.
The equipment for further processing the wollastonite mainly comprises an impact crusher, a jet mill, a stirring mill, a Raymond mill, a stirring mill and the like. The practical results show that the shearing and rubbing action has a tendency to cause the particles to peel along the crystalline cleavage plane, which is often the bonding plane with the weakest strength inside the particles, so that a suitable amount of shearing and rubbing will cause the wollastonite crystals to peel into a single fiber. Wherein, superfine wollastonite products with high length-diameter ratio (12-15) can be obtained by deep processing by using an air flow mill, but the product fineness is limited (D50 is more than 8 mu m); the superfine wollastonite product can be obtained by deep processing by using a stirring mill, but most of the fiber structure of the wollastonite is damaged, the length-diameter ratio (3-5) is small, and the reinforcing effect is weakened.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing ultra-fine wollastonite with a high aspect ratio. The preparation method provided by the invention can be used for preparing the ultrafine wollastonite with a high length-diameter ratio.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of ultrafine wollastonite with a high length-diameter ratio, which comprises the following steps:
(1) Mixing the superfine wollastonite slurry and a surfactant to obtain a first mixed slurry; the average grain diameter of the ultrafine wollastonite in the ultrafine wollastonite slurry is 0.8 to 1.0 μm, and the length-diameter ratio is 3 to 5;
(2) Mixing water glass, ethyl orthosilicate and water to obtain silicon prehydrolysis liquid; hydrolyzing the silicon prehydrolysis liquid under an acidic condition to obtain a silicon hydrolysis liquid;
(3) The silicon hydrolysate and the calcium hydroxide suspension are dripped into the first mixed slurry in a parallel flow manner to carry out liquid phase deposition reaction, so as to obtain second mixed slurry;
(4) After the second mixed slurry is subjected to hydrothermal reaction, mixing the hydrothermal reaction product with a coupling agent to obtain the ultra-fine wollastonite with the high length-diameter ratio, wherein the length-diameter ratio is 12-18;
the steps (1) and (2) are not limited in time sequence.
Preferably, the mass concentration of the ultrafine wollastonite slurry in the step (1) is 20 to 40 percent; the mass of the surfactant is 1.0-2.0% of that of the superfine wollastonite slurry.
Preferably, the surfactant is selected from one or more of an anionic surfactant, a nonionic surfactant and a cationic surfactant;
the anionic surfactant comprises sodium dodecyl benzene sulfonate and/or sodium stearate; the nonionic surfactant comprises one or more of polyoxypropylene-polyoxyethylene-polyoxypropylene triblock copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, sorbitan oleate and sorbitan monooleate polyoxyethylene ether; the cationic surfactant comprises one or more of dodecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride.
Preferably, the surfactant is a mixture of a nonionic surfactant and a cationic surfactant.
Preferably, the surfactant is a mixture of dodecyltrimethylammonium chloride and a polyoxypropylene-polyoxyethylene-polyoxypropylene triblock copolymer; the mol ratio of the dodecyl trimethyl ammonium chloride to the polyoxypropylene-polyoxyethylene-polyoxypropylene triblock copolymer is 10.
Preferably, the modulus of the water glass in the step (2) is 2.5-2.8, and the molar ratio of the water glass to the tetraethoxysilane is 1; with SiO 2 The mass concentration of the silicon prehydrolysis liquid is 20-30%; the pH value of the acidic condition is 2.5-6.5; the hydrolysis temperature is 30-80 ℃, and the hydrolysis time is 20-60 min.
Preferably, the mass concentration of the calcium hydroxide suspension in the step (3) is 30-70%, and the average particle size of the calcium hydroxide in the calcium hydroxide suspension is 0.1-0.2 μm; the dropping speed ratio of the calcium hydroxide suspension to the silicon hydrolysate is 1.2-1.5: 1.
preferably, the temperature of the liquid phase deposition reaction in the step (3) is 60-90 ℃, and the pH value of the reaction system is controlled to be 9.0-9.5 in the process of the liquid phase deposition reaction.
Preferably, the temperature of the hydrothermal reaction in the step (4) is 100-150 ℃ and the time is 6-8 h.
Preferably, the coupling agent in step (4) is selected from one or more of a silane coupling agent, a titanate coupling agent and an aluminate coupling agent; the silane coupling agent comprises one or more of aminopropyltriethoxysilane, vinyl triethoxysilane and methyl propyl acyloxy propyl triethoxysilane; the titanate coupling agent comprises isopropoxy tricarboxyacyl titanate and/or di (dioctyl pyrophosphate) ethylene titanate; the aluminate coupling agent comprises one or more of isopropyl bis (glyceryl distearate) aluminate, isopropyl bis (diglycolate stearate) aluminate and isopropyl bis (diglycolate oleate) aluminate.
Preferably, the coupling agent is a mixture of methylpropylacyloxypropyltriethoxysilane and isopropoxytricarboxyacyl titanate; the molar ratio of the methyl propyl acyloxy propyl triethoxy silane to the isopropoxy tricarboxyacyl titanate is 1-4.
The invention provides a preparation method of ultrafine wollastonite with a high length-diameter ratio, which takes ultrafine needle-shaped wollastonite as a matrix, takes mixed silicon source-sodium silicate, ethyl orthosilicate and calcium source-calcium hydroxide suspension as reaction raw materials, takes a surfactant as a crystal form inducer, and performs homogeneous nucleation on the ultrafine needle-shaped wollastonite in a one-dimensional direction by a hydrothermal method to construct new calcium silicate and improve the length-diameter ratio of the original wollastonite, thereby obtaining the ultrafine wollastonite with the high length-diameter ratio, wherein the length-diameter ratio of the ultrafine wollastonite is 12-18.
In addition, the hydrothermal method is to realize the growth of the nano-scale calcium silicate (synthesized by chemical reaction of a silicon source and a calcium source) on the surface of the primary micron-scale wollastonite in the one-dimensional direction through a crystal form inducer, so that the nano-scale to micron-scale conversion is realized, and the agglomeration effect of the calcium silicate is reduced; the step of processing by matching with a coupling agent can effectively slow down the agglomeration trend of the high-length-diameter-ratio ultrafine wollastonite powder, improve the dispersibility of the high-length-diameter-ratio ultrafine wollastonite powder in downstream application, improve the compatibility with matrix resin and further improve the comprehensive performance of the product.
Further:
the cationic surfactant and the nonionic surfactant are used as crystal form inducers and have synergistic effect, the cationic surfactant can realize the fast growth of rod-shaped micelles, the nonionic surfactant can realize the slow growth of the rod-shaped micelles, and the cationic surfactant and the nonionic surfactant can regulate the size of the rod-shaped micelles together, so that the new calcium silicate is effectively guided to preferentially grow along the one-dimensional direction of wollastonite, and the length-diameter ratio of the original wollastonite is improved;
the invention can reduce the temperature of hydrothermal reaction, shorten reaction time, and has milder reaction conditions, so that the raw materials are selected from mixed silicon source water glass and tetraethoxysilane, and different hydrolysis rates and reaction activities of the two silicon sources are utilized (the hydrolysis rate and the reaction activity of the water glass are higher than those of the tetraethoxysilane, and the tetraethoxysilane can preferentially grow along a certain direction under the regulation and control of a crystal form inducer due to the existence of steric hindrance effect and has lower reaction activity by utilizing the different hydrolysis rates and reaction activities of the two silicon sources, thereby generating synergistic effect and being beneficial to the growth of crystals in the hydrothermal reaction process; in addition, in a hydrothermal reaction system, ultrafine wollastonite (0.8-1.0 μm) is used as a nucleation matrix for crystal production, so that the nucleation process of calcium silicate crystals is omitted, and the reaction time is shortened;
the invention can also realize the regulation and control of the length-diameter ratio of the superfine wollastonite with high length-diameter ratio, and the length-diameter ratio of the superfine wollastonite can be conveniently regulated and controlled by regulating and controlling the proportion of the water glass and the ethyl orthosilicate in the silicon source mixture and regulating and controlling the type and proportion of the surfactant, thereby meeting the requirements of different products.
Detailed Description
The invention provides a preparation method of ultrafine wollastonite with a high length-diameter ratio, which comprises the following steps:
(1) Mixing the superfine wollastonite slurry and a surfactant to obtain a first mixed slurry; the average grain diameter of the ultrafine wollastonite in the ultrafine wollastonite slurry is 0.8 to 1.0 μm, and the length-diameter ratio is 3 to 5;
(2) Mixing water glass, tetraethoxysilane and water to obtain silicon prehydrolysis liquid; hydrolyzing the silicon prehydrolysis liquid under an acidic condition to obtain a silicon hydrolysis liquid;
(3) Dropwise adding the silicon hydrolysate and the calcium hydroxide suspension into the first mixed slurry in a parallel flow manner to perform a liquid phase deposition reaction, thereby obtaining second mixed slurry;
(4) After the second mixed slurry is subjected to hydrothermal reaction, mixing the hydrothermal reaction product with a coupling agent to obtain the ultrafine wollastonite with the high length-diameter ratio of 12-18;
the steps (1) and (2) are not limited in chronological order.
The invention mixes the ultramicro wollastonite sizing agent and the surface active agent to obtain the first mixed sizing agent. In the present invention, the mean particle diameter of the ultrafine wollastonite in the ultrafine wollastonite slurry is 0.8 to 1.0 μm, preferably 0.9 μm; the aspect ratio is 3 to 5, preferably 4. In the invention, the superfine wollastonite slurry is preferably prepared by sequentially carrying out dry grinding, iron removal and stirring grinding on wollastonite concentrate and wet grinding. In the invention, the mass content of calcium silicate in the wollastonite concentrate is preferably more than or equal to 96%, and the wollastonite concentrate is not particularly required to be sourced, and the wollastonite concentrate from which the wollastonite concentrate is well known to those skilled in the art can be adopted. The invention has no special requirements on the specific mode of the dry grinding and iron removal, and adopts a corresponding mode which is well known by the technical personnel in the field; after said dry grinding, the particle size of the wollastonite concentrate preferably satisfies D50 < 35 μm. In the invention, the stirring mill is preferably a vertical stirring mill, and the invention has no special requirement on the vertical stirring mill and can adopt corresponding equipment well known by the technical personnel in the field; the invention has no special requirements on the technological parameters of the stirring mill, and the ultrafine wollastonite slurry with the particle size and the length-diameter ratio can be obtained; the stirring mill mainly uses shearing and friction force, so that wollastonite mineral can be peeled off along the cleavage plane to obtain an ultra-fine fiber structure. In the present invention, the mass concentration of the ultrafine wollastonite slurry is preferably 20 to 40%, more preferably 30%; in the present invention, it is preferable to dilute the slurry (mass concentration of 40 to 60%) directly obtained by the wet grinding with a stirring mill to obtain the ultrafine wollastonite slurry having the above-mentioned mass concentration range.
In the present invention, the mass of the surfactant is 1.0 to 2.0%, preferably 1.5% of the mass of the ultrafine wollastonite slurry; the mixing is preferably stirring mixing, the speed of stirring mixing is preferably 300rpm, and the time is preferably 10min.
In the present invention, the surfactant is preferably selected from one or more of an anionic surfactant, a nonionic surfactant and a cationic surfactant; the anionic surfactant preferably comprises sodium dodecylbenzene sulfonate and/or sodium stearate; the nonionic surfactant preferably comprises one or more of polyoxypropylene-polyoxyethylene-polyoxypropylene triblock copolymer (F127), polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), sorbitan oleate (Span 80) and sorbitan monooleate polyoxyethylene ether (Tween 80); the cationic surfactant preferably comprises one or more of Dodecyl Trimethyl Ammonium Chloride (DTAC), tetradecyl Trimethyl Ammonium Chloride (TTAC), hexadecyl trimethyl ammonium chloride (CTAC) and Octadecyl Trimethyl Ammonium Chloride (OTAC).
In the present invention, the surfactant is further preferably a mixture of the above-mentioned nonionic surfactant and cationic surfactant, more preferably a mixture of dodecyltrimethylammonium chloride (DTAC) and a polyoxypropylene-polyoxyethylene-polyoxypropylene triblock copolymer (F127); the molar ratio of the cationic surfactant to the nonionic surfactant is preferably 10. The source of the surfactant is not particularly required in the present invention, and commercially available products well known to those skilled in the art may be used.
In the invention, DTAC is used as a cationic surfactant, a negatively charged hydrophobic group and a positively charged amino hydrophilic group of a long carbon chain are formed after dissociation in water, wherein the positively charged amino group is preferentially adsorbed on the surface of a wollastonite matrix, when the concentration of the surfactant in a system is more than 20 times of the critical micelle concentration cmc (wherein the cmc of the DTAC is 0.03%, and the cmc of the F127 is 0.1%), rod-shaped micelles are formed, the F127 and the DTAC are synergistic, the DTAC can realize the fast growth of the rod-shaped micelles, the F127 can realize the slow growth of the rod-shaped micelles, the two can jointly regulate and control the size of the rod-shaped micelles, when a silicon hydrolysate and a calcium hydroxide suspension are subsequently added, the rod-shaped micelles adsorb silanol formed by hydrolysis in the silicon hydrolysate under the electrostatic action and react with calcium hydroxide to generate calcium silicate in situ to deposit on the surface of the wollastonite matrix, and the newly generated calcium silicate can preferentially grow along the one-dimensional direction of the wollastonite under the guidance of the rod-shaped micelles of the surfactant, and the calcium silicate is further cured after the hydrothermal reaction, so that the length-diameter ratio of the primary wollastonite is improved. In addition, the length-diameter ratio of the superfine wollastonite can be conveniently regulated and controlled by regulating the ratio of F127 to DTAC, different product requirements are met, specifically, wollastonite with a higher major axis can be obtained by increasing the addition ratio of DTAC, conversely, wollastonite with a smaller major axis can be obtained, and in addition, the wollastonite with a higher major axis can also be obtained by increasing the total addition of the surfactant.
According to the invention, water glass, tetraethoxysilane and water are mixed to obtain silicon prehydrolysis liquid; and hydrolyzing the silicon prehydrolysis liquid under an acidic condition to obtain a silicon hydrolysis liquid. In the present invention, the modulus of the water glass is preferably 2.5 to 2.8, more preferably 2.6 to 2.7; the molar ratio of the water glass to the Tetraethylorthosilicate (TEOS) is preferably 1 to 1; with SiO 2 The mass concentration of the silicon prehydrolysis liquid is 20-30%, and more preferably 25%. In the present invention, the pH value of the acidic condition is preferably 2.5 to 6.5, more preferably 3.5 to 5, and still more preferably 4.5, and the acidic condition is preferably adjusted by dropwise addition of 1mol/L of acetic acid. In the present invention, the temperature of the hydrolysis is preferably 30 to 80 ℃, more preferably 40 to 70 ℃, and still more preferablyPreferably 60 ℃; the time is preferably 20 to 60min, more preferably 25 to 35min, and still more preferably 30min. The invention takes the water glass and the tetraethoxysilane as a mixed silicon source, and the water glass and the tetraethoxysilane are hydrolyzed under the acid condition to obtain silanol Si (OH) with different activities 4 The synergistic effect can be generated, and the growth of crystals in the subsequent hydrothermal reaction process is facilitated; the length-diameter ratio of the ultrafine wollastonite can be conveniently regulated and controlled by regulating the proportion of the water glass and the tetraethoxysilane in the mixed silicon source, specifically, the wollastonite with a higher length-diameter ratio can be obtained by increasing the proportion of the water glass in the mixed silicon source, and conversely, the wollastonite with a lower length-diameter ratio can be obtained.
After the first mixed slurry and the silicon hydrolysate are obtained, the silicon hydrolysate and the calcium hydroxide suspension are dripped into the first mixed slurry in a parallel flow manner to carry out liquid phase deposition reaction, and the second mixed slurry is obtained. In the present invention, the mass concentration of the calcium hydroxide suspension is preferably 30 to 70%, more preferably 60%, and the average particle size of calcium hydroxide in the calcium hydroxide suspension is preferably 0.1 to 0.2 μm. The invention has no special requirements on the preparation method of the calcium hydroxide suspension, and the calcium hydroxide suspension can be prepared by adopting a method well known by a person skilled in the art, for example, calcined natural limestone is subjected to slaking reaction with water to prepare quicklime, the calcium hydroxide suspension is used as a calcium source, and the newly synthesized calcium hydroxide suspension has high reaction activity, so the calcium hydroxide suspension is preferably prepared in situ.
In the present invention, the concurrent dropwise addition is preferably carried out by a peristaltic pump, which is not particularly required in the present invention and is well known to those skilled in the art. In the present invention, the ratio of the dropping speed of the calcium hydroxide suspension to the silicon hydrolysate is preferably 1.2 to 1.5:1, in the specific embodiment of the invention, the dropping speed of the silicon hydrolysate is preferably 5.0mL/min, and the dropping speed of the calcium hydroxide suspension is preferably 6.0-7.5 mL/min; the molar ratio of calcium hydroxide in the calcium hydroxide suspension to silicon dioxide in the silicon hydrolysate is preferably 1 to 1.2.
In the present invention, the temperature of the liquid phase deposition reaction is preferably 60 to 90 ℃, more preferably 70 to 80 ℃. In the invention, the pH value of the reaction system is controlled to be preferably 9.0-9.5, more preferably 9.2-9.4, the calcium hydroxide suspension is alkaline, and the silicon hydrolysate is acidic in the liquid phase deposition reaction process, and the pH value of the reaction system is realized by adjusting the speed of dropwise adding the calcium hydroxide suspension and the silicon hydrolysate. After the parallel-flow dropwise addition is completed, the obtained reaction system is preferably stirred and dispersed for 30min. In the invention, the parallel-flow dropwise adding mode can realize the in-situ liquid phase deposition reaction of the calcium hydroxide suspension and the silicon hydrolysate on the surface of the wollastonite matrix to obtain uniform and stable calcium silicate.
After the second mixed slurry is obtained, the second mixed slurry is subjected to hydrothermal reaction, and a hydrothermal reaction product is mixed with a coupling agent to obtain the ultrafine wollastonite with the high length-diameter ratio. In the invention, the temperature of the hydrothermal reaction is preferably 100-150 ℃, more preferably 120 ℃, and the time is preferably 6-8 h, more preferably 7h; the hydrothermal reaction is preferably carried out in a polytetrafluoroethylene-lined hydrothermal reaction vessel.
The invention takes superfine needle-shaped wollastonite as a matrix, takes mixed silicon source-water glass and ethyl orthosilicate as well as calcium source-calcium hydroxide suspension as reaction raw materials, takes a surfactant as a crystal form inducer, and carries out homogeneous nucleation on the superfine needle-shaped wollastonite in the one-dimensional direction by a hydrothermal method to construct new calcium silicate and improve the length-diameter ratio of the original wollastonite, thereby obtaining the superfine wollastonite with high length-diameter ratio, wherein the length-diameter ratio of the superfine wollastonite is 12-18. In addition, the temperature of the hydrothermal reaction can be reduced, the reaction time is shortened, the mixed silicon source water glass and the tetraethoxysilane are selected for selecting raw materials, and the synergistic effect can be generated by utilizing different hydrolysis rates and reaction activities of the two silicon sources, so that the growth of crystals in the hydrothermal reaction process is facilitated; in addition, in the hydrothermal reaction system, ultrafine wollastonite (0.8-1.0 μm) is used as a nucleation matrix for crystal production, so that the nucleation process of calcium silicate crystals is omitted, and the reaction time is shortened.
In the present invention, the coupling agent is preferably selected from one or more of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent; the silane coupling agent preferably comprises one or more of aminopropyltriethoxysilane, vinyltriethoxysilane and methylpropyl acyloxy propyltriethoxysilane; the titanate coupling agent preferably comprises an isopropoxy tricarboxy titanate and/or di (dioctyl pyrophosphate) ethylene titanate; the aluminate coupling agent preferably comprises one or more of isopropyl bis (glyceryl distearate) aluminate, isopropyl bis (diglycolate stearate) aluminate and isopropyl bis (diglycolate oleate) aluminate. In the present invention, the coupling agent is further preferably a mixture of methylpropylacyloxypropyltriethoxysilane and isopropoxytricarboxyacyl titanate; the molar ratio of the methylpropanoyloxypropyltriethoxysilane to the isopropoxytricarboxyacyl titanate is preferably 1 to 4, and specifically may be 1. After the hydrothermal reaction, directly adding a coupling agent into the hydrothermal reaction product for mixing, wherein the hydrothermal reaction product does not need to be additionally treated; the mass of the coupling agent is preferably 2 to 4% of the mass of the hydrothermal reaction product. The method of mixing is not particularly limited in the present invention, and the coupling agent may be sufficiently dispersed, and in the present invention, the mixing time is preferably 10min.
The coupling agent is used for modifying wollastonite products after hydrothermal reaction, so that the agglomeration tendency of the high-length-diameter-ratio ultrafine wollastonite powder can be effectively slowed down, the dispersibility of the high-length-diameter-ratio ultrafine wollastonite powder in downstream application is improved, the compatibility with matrix resin is improved, and the comprehensive performance of the product is further improved.
After the wollastonite modified product is mixed with a coupling agent, the obtained wollastonite modified product is preferably sequentially washed, filtered and dried in a solid phase to obtain the ultrafine wollastonite with the high length-diameter ratio. In the present invention, the washing is preferably water washing, and the present invention is not particularly limited to the conditions for drying the solid phase, and water may be sufficiently removed.
The method for producing wollastonite having an ultra-fine aspect ratio according to the present invention will be described in detail with reference to examples, but the scope of the present invention is not limited to these examples.
Example 1
Selecting wollastonite concentrate with calcium silicate content of more than or equal to 96wt%, carrying out primary dry grinding and deironing, and carrying out vertical stirring and grinding wet grinding to obtain superfine wollastonite slurry, wherein the average particle size of the superfine wollastonite slurry is 0.9 mu m, and the length-diameter ratio is 4;
diluting the superfine wollastonite slurry to 30wt%, adding a surfactant accounting for 1.0wt% of the slurry, wherein the surfactant is DTAC: f127=6 (molar ratio), stirring and dispersing at a stirring speed of 300rpm for 10min for standby;
preparing 25wt% (in SiO) 2 Metering) silicon prehydrolysis liquid, wherein the molar ratio of water glass (the modulus is 2.6) to tetraethoxysilane is 1;
respectively dropwise adding newly synthesized 60wt% calcium hydroxide suspension and silicon hydrolysate into the superfine wollastonite slurry added with the surfactant by adopting a parallel flow method through a peristaltic pump (the dropwise adding speed of the silicon hydrolysate is 5.0mL/min, and the dropwise adding speed of the calcium hydroxide suspension is 6.0 mL/min), controlling the pH value of the system to be 9.0, controlling the reaction temperature to be 60 ℃, and continuously stirring and dispersing for 30min after the dropwise adding is finished; transferring the slurry into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and keeping the hydrothermal temperature at 120 ℃ for 6.5 hours; after the hydrothermal reaction is finished, adding a coupling agent (the molar ratio is 3.
Example 2
Selecting wollastonite concentrate with calcium silicate content of more than or equal to 96wt%, carrying out primary dry grinding and deironing, and carrying out vertical stirring and grinding wet grinding to obtain superfine wollastonite slurry, wherein the average particle size of the superfine wollastonite slurry is 0.9 mu m, and the length-diameter ratio is 4;
diluting the superfine wollastonite slurry to 30wt%, adding a surfactant accounting for 1.5wt% of the slurry, wherein the surfactant is DTAC: f127=6 (molar ratio), stirring and dispersing at a stirring speed of 300rpm for 10min for standby;
preparing 25wt% (in SiO) 2 Metering) silicon prehydrolysis liquid, wherein the molar ratio of water glass (the modulus is 2.6) to tetraethoxysilane is 1;
respectively dropwise adding newly synthesized 60wt% calcium hydroxide suspension and silicon hydrolysate into the superfine wollastonite slurry added with the surfactant by adopting a parallel flow method through a peristaltic pump (the dropwise adding speed of the silicon hydrolysate is 5.0mL/min, and the dropwise adding speed of the calcium hydroxide suspension is 6.0 mL/min), controlling the pH value of the system to be 9.0, controlling the reaction temperature to be 60 ℃, and continuously stirring and dispersing for 30min after the dropwise adding is finished; transferring the slurry into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and keeping the hydrothermal temperature at 120 ℃ for 6.5 hours; after the hydrothermal reaction is finished, adding a coupling agent of methyl propyl acyloxy propyl triethoxysilane and isopropoxy tricarboxyacyl titanate (the molar ratio is 2.
Example 3
Selecting wollastonite concentrate with calcium silicate content more than or equal to 96wt%, carrying out primary dry grinding and deironing, and carrying out vertical stirring and grinding wet grinding to obtain superfine wollastonite slurry, wherein the average particle size of the superfine wollastonite slurry is 0.9 mu m, and the length-diameter ratio is 4;
diluting superfine wollastonite slurry to 30wt%, adding a surfactant accounting for 1.0wt% of the slurry, wherein the surfactant is DTAC: f127=2 (molar ratio), stirring and dispersing at a stirring speed of 300rpm for 10min for standby;
25wt% (in terms of SiO) of 2 Metering) silicon prehydrolysis liquid, wherein the molar ratio of water glass (the modulus is 2.6) to ethyl orthosilicate is 1;
respectively dropwise adding the newly synthesized 60wt% calcium hydroxide suspension and the newly synthesized silicon hydrolysate into the superfine wollastonite slurry added with the surfactant by adopting a parallel flow method through a peristaltic pump (the dropwise adding speed of the silicon hydrolysate is 5.0mL/min, and the dropwise adding speed of the calcium hydroxide suspension is 6.5 mL/min), controlling the pH value of the system to be 9.0, controlling the reaction temperature to be 60 ℃, and continuously stirring and dispersing for 30min after dropwise adding is finished; transferring the slurry into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and keeping the hydrothermal temperature at 120 ℃ for 6.5 hours; after the hydrothermal reaction is finished, adding a coupling agent of methyl propyl acyloxy propyl triethoxysilane and isopropoxy tricarboxyacyl titanate (the molar ratio is 1).
Example 4
Selecting wollastonite concentrate with calcium silicate content of more than or equal to 96wt%, carrying out primary dry grinding and deironing, and carrying out vertical stirring and grinding wet grinding to obtain superfine wollastonite slurry, wherein the average particle size of the superfine wollastonite slurry is 0.9 mu m, and the length-diameter ratio is 4;
diluting the superfine wollastonite slurry to 30wt%, adding a surfactant accounting for 2.0wt% of the slurry, wherein the surfactant is DTAC: f127=4 (molar ratio), stirring and dispersing at a stirring speed of 300rpm for 10min for standby;
25wt% (in terms of SiO) of 2 Metering) silicon prehydrolysis liquid, wherein the molar ratio of water glass (the modulus is 2.6) to ethyl orthosilicate is 1;
respectively dropwise adding newly synthesized 60wt% calcium hydroxide suspension and silicon hydrolysate into the superfine wollastonite slurry added with the surfactant by adopting a parallel flow method through a peristaltic pump (the dropwise adding speed of the silicon hydrolysate is 5.0mL/min, and the dropwise adding speed of the calcium hydroxide suspension is 6.5 mL/min), controlling the pH value of the system to be 9.0, controlling the reaction temperature to be 60 ℃, and continuously stirring and dispersing for 30min after the dropwise adding is finished; transferring the slurry into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and keeping the hydrothermal temperature at 120 ℃ for 6.5 hours; after the hydrothermal reaction is finished, adding a coupling agent of methyl propyl acyloxy propyl triethoxysilane and isopropoxy tricarboxyacyl titanate (the molar ratio is 3.
Example 5
Selecting wollastonite concentrate with calcium silicate content of more than or equal to 96wt%, carrying out primary dry grinding and deironing, and carrying out vertical stirring and grinding wet grinding to obtain superfine wollastonite slurry, wherein the average particle size of the superfine wollastonite slurry is 0.9 mu m, and the length-diameter ratio is 4;
diluting the superfine wollastonite slurry to 30wt%, adding a surfactant accounting for 1.5wt% of the slurry, wherein the surfactant is DTAC: f127=5 (molar ratio), stirring and dispersing at a stirring speed of 300rpm for 10min for standby;
25wt% (in terms of SiO) of 2 Metering) silicon prehydrolysis liquid, wherein the molar ratio of water glass (modulus is 2.6) to ethyl orthosilicate is 1, and hydrolysis is carried out for 30min under the conditions that the temperature is 60 ℃ and the pH value is 4.5 (adjusted by dropwise adding 1mol/L acetic acid), so as to obtain silicon hydrolysis liquid;
respectively dropwise adding newly synthesized 60wt% calcium hydroxide suspension and silicon hydrolysate into the superfine wollastonite slurry added with the surfactant by adopting a parallel flow method through a peristaltic pump (the dropwise adding speed of the silicon hydrolysate is 5.0mL/min, and the dropwise adding speed of the calcium hydroxide is 7.0 mL/min), controlling the pH value of the system to be 9.0, controlling the reaction temperature to be 60 ℃, and continuously stirring and dispersing for 30min after dropwise adding is finished; transferring the slurry into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and keeping the hydrothermal temperature at 120 ℃ for 6.5 hours; after the hydrothermal reaction is finished, adding a coupling agent of methyl propyl acyloxy propyl triethoxysilane and isopropoxy tricarboxyacyl titanate (the molar ratio is 2.
Example 6
Selecting wollastonite concentrate with calcium silicate content of more than or equal to 96wt%, carrying out primary dry grinding and deironing, and carrying out vertical stirring and grinding wet grinding to obtain superfine wollastonite slurry, wherein the average particle size of the superfine wollastonite slurry is 0.9 mu m, and the length-diameter ratio is 4;
diluting superfine wollastonite slurry to 30wt%, adding a surfactant accounting for 2.0wt% of the slurry, wherein the surfactant is DTAC: f127=3 (molar ratio), stirring and dispersing at a stirring speed of 300rpm for 10min for standby;
25wt% (in terms of SiO) of 2 Metering) silicon prehydrolysis liquid, wherein the molar ratio of water glass (the modulus is 2.6) to tetraethoxysilane is 1;
respectively dropwise adding the newly synthesized 60wt% calcium hydroxide suspension and the newly synthesized silicon hydrolysate into the superfine wollastonite slurry added with the surfactant by adopting a parallel flow method through a peristaltic pump (the dropwise adding speed of the silicon hydrolysate is 5.0mL/min, and the dropwise adding speed of the calcium hydroxide suspension is 7.0 mL/min), controlling the pH value of the system to be 9.0, controlling the reaction temperature to be 60 ℃, and continuously stirring and dispersing for 30min after dropwise adding is finished; transferring the slurry into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and keeping the hydrothermal temperature at 120 ℃ for 6.5 hours; after the hydrothermal reaction is finished, adding a coupling agent (the molar ratio is 2.
Example 7
Selecting wollastonite concentrate with calcium silicate content of more than or equal to 96wt%, carrying out primary dry grinding and deironing, and carrying out vertical stirring and grinding wet grinding to obtain superfine wollastonite slurry, wherein the average particle size of the superfine wollastonite slurry is 0.9 mu m, and the length-diameter ratio is 4;
diluting superfine wollastonite slurry to 30wt%, adding a surfactant accounting for 1.0wt% of the slurry, wherein the surfactant is DTAC: f127=6 (molar ratio), stirring and dispersing at a stirring speed of 300rpm for 10min for standby;
25wt% (in terms of SiO) of 2 Measured) silicon prehydrolysis solution, in which water glass (modulus 2.6) andhydrolyzing the tetraethoxysilane at a molar ratio of 1;
respectively dropwise adding the newly synthesized 60wt% calcium hydroxide suspension and the newly synthesized silicon hydrolysate into the superfine wollastonite slurry added with the surfactant by adopting a parallel flow method through a peristaltic pump (the dropwise adding speed of the silicon hydrolysate is 5.0mL/min, and the dropwise adding speed of the calcium hydroxide suspension is 6.5 mL/min), controlling the pH of the system to be 9.0, controlling the reaction temperature to be 60 ℃, and continuously stirring and dispersing for 30min after the dropwise adding is finished; transferring the slurry into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and keeping the hydrothermal temperature at 120 ℃ for 6.5 hours; after the hydrothermal reaction is finished, adding a coupling agent (the molar ratio is 2.
Example 8
Selecting wollastonite concentrate with calcium silicate content of more than or equal to 96wt%, carrying out primary dry grinding and deironing, and carrying out vertical stirring and grinding wet grinding to obtain superfine wollastonite slurry, wherein the average particle size of the superfine wollastonite slurry is 0.9 mu m, and the length-diameter ratio is 4;
diluting superfine wollastonite slurry to 30wt%, adding a surfactant accounting for 2.0wt% of the slurry, wherein the surfactant is DTAC: f127=6 (molar ratio), stirring and dispersing at a stirring speed of 300rpm for 10min for standby;
preparing 25wt% (in SiO) 2 Metering) silicon prehydrolysis liquid, wherein the molar ratio of water glass (the modulus is 2.6) to tetraethoxysilane is 1;
respectively dropwise adding newly synthesized 60wt% calcium hydroxide suspension and silicon hydrolysate into the superfine wollastonite slurry added with the surfactant by adopting a parallel flow method through a peristaltic pump (the dropwise adding speed of the silicon hydrolysate is 5.0mL/min, and the dropwise adding speed of the calcium hydroxide suspension is 7.5 mL/min), controlling the pH value of the system to be 9.0, controlling the reaction temperature to be 60 ℃, and continuously stirring and dispersing for 30min after the dropwise adding is finished; transferring the slurry into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and keeping the hydrothermal temperature at 120 ℃ for 6.5 hours; after the hydrothermal reaction is finished, adding a coupling agent (the molar ratio is 3.
Example 9
Selecting wollastonite concentrate with calcium silicate content more than or equal to 96wt%, carrying out primary dry grinding and deironing, and carrying out vertical stirring and grinding wet grinding to obtain superfine wollastonite slurry, wherein the average particle size of the superfine wollastonite slurry is 0.9 mu m, and the length-diameter ratio is 4;
diluting superfine wollastonite slurry to 30wt%, adding a surfactant accounting for 1.5wt% of the slurry, wherein the surfactant is DTAC: f127=3 (molar ratio), stirring and dispersing at a stirring speed of 300rpm for 10min for standby;
preparing 25wt% (in SiO) 2 Metering) silicon prehydrolysis liquid, wherein the molar ratio of water glass (the modulus is 2.6) to tetraethoxysilane is 1;
respectively dropwise adding the newly synthesized 60wt% calcium hydroxide suspension and the newly synthesized silicon hydrolysate into the superfine wollastonite slurry added with the surfactant by adopting a parallel flow method through a peristaltic pump (the dropwise adding speed is respectively 5.0mL/min for the silicon hydrolysate and 7.5mL/min for the calcium hydroxide suspension), controlling the pH value of the system to be 9.0 and the reaction temperature to be 60 ℃, and continuously stirring and dispersing for 30min after the dropwise adding is finished; transferring the slurry into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and keeping the hydrothermal temperature at 120 ℃ for 6.5 hours; after the hydrothermal reaction is finished, adding a coupling agent (the molar ratio is 1.
The high aspect ratio ultrafine wollastonite prepared in examples 1 to 9 was observed with a microscope, and the aspect ratio thereof was counted, and the average particle size (malvern laser particle size), oil absorption and whiteness thereof were measured (generally, the more perfect the needle-like structure of wollastonite, the higher the aspect ratio, the higher the oil absorption thereof, and therefore, the aspect ratio thereof can be indirectly characterized by the oil absorption). The results are shown in table 1:
TABLE 1 particle size, aspect ratio, oil absorption and whiteness of ultra-fine wollastonite having a high aspect ratio, prepared in examples 1 to 9
It can be seen from the above examples that ultrafine acicular wollastonite is prepared by stirring and grinding, mixed silicon source-water glass, ethyl orthosilicate and calcium source-calcium hydroxide suspension are used as reaction raw materials, a surfactant is used as a crystal form inducer, and a hydrothermal method is used for homogeneously nucleating and constructing new calcium silicate in one-dimensional direction of the ultrafine acicular wollastonite, so that ultrafine acicular wollastonite with a high length-diameter ratio can be obtained.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.
Claims (9)
1. A preparation method of ultrafine wollastonite with a high length-diameter ratio is characterized by comprising the following steps:
(1) Mixing the superfine wollastonite slurry and a surfactant to obtain a first mixed slurry; the average grain diameter of the ultrafine wollastonite in the ultrafine wollastonite slurry is 0.8 to 1.0 μm, and the length-diameter ratio is 3 to 5; the surfactant is a mixture of a nonionic surfactant and a cationic surfactant, and the nonionic surfactant comprises one or more of polyoxypropylene-polyoxyethylene-polyoxypropylene triblock copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, sorbitan oleate and sorbitan monooleate polyoxyethylene ether; the cationic surfactant comprises one or more of dodecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride;
(2) Mixing water glass, ethyl orthosilicate and water to obtain silicon prehydrolysis liquid; hydrolyzing the silicon prehydrolysis liquid under an acidic condition to obtain a silicon hydrolysis liquid;
(3) The silicon hydrolysate and the calcium hydroxide suspension are dripped into the first mixed slurry in a parallel flow manner to carry out liquid phase deposition reaction, so as to obtain second mixed slurry;
(4) After the second mixed slurry is subjected to hydrothermal reaction, mixing a product of the hydrothermal reaction with a coupling agent to obtain the ultrafine wollastonite with the high length-diameter ratio, wherein the length-diameter ratio is 12-18;
the steps (1) and (2) are not limited in chronological order.
2. The process according to claim 1, wherein the mass concentration of the ultra-fine wollastonite slurry in the step (1) is 20 to 40%; the mass of the surfactant is 1.0-2.0% of that of the superfine wollastonite slurry.
3. The method of claim 1, wherein the surfactant is a mixture of dodecyltrimethylammonium chloride and a polyoxypropylene-polyoxyethylene-polyoxypropylene triblock copolymer; the mol ratio of the dodecyl trimethyl ammonium chloride to the polyoxypropylene-polyoxyethylene-polyoxypropylene triblock copolymer is 10.
4. The preparation method according to claim 1, wherein the modulus of the water glass in the step (2) is 2.5-2.8, and the molar ratio of the water glass to the tetraethoxysilane is 1; the mass concentration of the silicon prehydrolysis liquid is 20-30% calculated by SiO 2; the pH value of the acidic condition is 2.5-6.5; the hydrolysis temperature is 30-80 ℃ and the hydrolysis time is 20-60 min.
5. The method according to claim 1, wherein the calcium hydroxide suspension in the step (3) has a mass concentration of 30 to 70%, and the calcium hydroxide suspension has an average particle size of 0.1 to 0.2 μm; the dropping speed ratio of the calcium hydroxide suspension to the silicon hydrolysate is 1.2-1.5: 1.
6. the production method according to claim 1 or 5, wherein the temperature of the liquid phase deposition reaction in the step (3) is 60 to 90 ℃, and the pH value of the reaction system is controlled to be 9.0 to 9.5 during the liquid phase deposition reaction.
7. The method according to claim 1, wherein the hydrothermal reaction in step (4) is carried out at a temperature of 100 to 150 ℃ for 6 to 8 hours.
8. The method according to claim 1, wherein the coupling agent in step (4) is one or more selected from the group consisting of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent; the silane coupling agent comprises one or more of aminopropyltriethoxysilane, vinyl triethoxysilane and methyl propyl acyloxy propyl triethoxysilane; the titanate coupling agent comprises isopropoxy tricarboxyacyl titanate and/or di (dioctyl pyrophosphate) ethylene titanate; the aluminate coupling agent comprises one or more of isopropyl bis (glyceryl distearate) aluminate, isopropyl bis (diglycol distearate) aluminate and isopropyl bis (diglycol oleate) aluminate.
9. The method of claim 8, wherein the coupling agent is a mixture of methylpropanoyloxypropyltriethoxysilane and isopropoxytricarboxyacyltitanate; the molar ratio of the methyl propyl acyloxy propyl triethoxy silane to the isopropoxy tricarboxyacyl titanate is 1-4.
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| JPH06128412A (en) * | 1992-09-01 | 1994-05-10 | Ube Ind Ltd | Calcium silicate hydrate and its production |
| JP2003286025A (en) * | 2002-03-28 | 2003-10-07 | Nippon Paper Industries Co Ltd | Fibrous calcium silicate carbonate and method for manufacturing the same |
| CN110964389A (en) * | 2019-11-14 | 2020-04-07 | 江西广源化工有限责任公司 | Preparation method of sol-gel-based interior wall coating containing needle-shaped wollastonite |
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| JPH06128412A (en) * | 1992-09-01 | 1994-05-10 | Ube Ind Ltd | Calcium silicate hydrate and its production |
| JP2003286025A (en) * | 2002-03-28 | 2003-10-07 | Nippon Paper Industries Co Ltd | Fibrous calcium silicate carbonate and method for manufacturing the same |
| CN110964389A (en) * | 2019-11-14 | 2020-04-07 | 江西广源化工有限责任公司 | Preparation method of sol-gel-based interior wall coating containing needle-shaped wollastonite |
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