Preparation method of active nano kaolin powder

Abstract

The invention discloses a preparation method of active nano kaolin powder. The preparation method comprises the following steps: drying kaolin concentrate; the dried kaolin concentrate is mixed with a chemical additive, the chemical additive comprises an intercalator and a surfactant, and the kaolin concentrate, the intercalator and the surfactant are mixed according to the mass ratio of 100: (5-60): (1-10); grinding the mixed kaolin and the chemical additive in a ball mill for 5-10 minutes, fully and uniformly mixing, transferring into ultrasonic or microwave, carrying out intercalation reaction for 1-3 hours, transferring the intercalated slurry into the sand mill again, carrying out superfine grinding for 10-60 minutes, washing the superfine ground slurry, and carrying out surface modification; carrying out centrifugal dewatering, drying and depolymerization on the modified material; the depolymerized powder is the active nano kaolin powder product; according to the preparation method, the nano kaolin is subjected to wet surface modification, so that agglomeration of nano particles in the drying process can be effectively reduced, and the dispersity of the nano kaolin is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of kaolin preparation, and particularly relates to a method for preparing active nano kaolin powder. Background Art

[0002] Kaolin products are widely used in fields such as paints, coatings, papermaking, rubber, plastics, cables, ceramics, enamel, refractory materials, textiles, cement, automobiles, chemistry, environmental protection, and agriculture due to their high whiteness, good crystal form, large porosity, small bulk density, good chemical stability and insulation, and strong covering power.

[0003] There are many types of kaolin products in our country, but the proportion of high-grade products is less than 20%. They are mainly used in papermaking, high-grade paints and the automotive industry, and partly replace titanium dioxide, etc. A large amount of high-grade kaolin still needs to be imported from abroad every year. Nano kaolin belongs to two-dimensional nano powder materials with a sheet thickness less than 100 nm, a sheet thickness of 20 - 100 nm, a particle size of 300 - 500 nm, and a typical hexagonal flake microstructure. Different from nano-spherical carbon black and silica, nano kaolin used in rubber products not only has excellent reinforcing properties in conventional properties such as mechanical properties and durability, but also shows unique advantages in enhancing specific properties such as flame retardancy and airtightness; nano kaolin has many characteristics such as fine particle size, high whiteness, large specific surface area, strong adsorption ability, and stable chemical properties, and is widely used as a special papermaking coating, a thickener for paints and coatings, a pigment, a catalyst carrier, a moisturizer for high-grade cosmetics, an additive for high-grade inks, and can replace silica and part of carbon black as a reinforcing agent in rubber and plastics.

[0004] The preparation processes of nano kaolin mainly include mechanical grinding method, classification sedimentation method and intercalation method, among which the intercalation method is currently the most effective method for preparing nano-scale kaolin. Nano kaolin particles are very fine, have a large surface area and high activity, and are prone to agglomeration during the dehydration and drying process.

[0005] Therefore, the present invention provides a method for preparing active nano kaolin powder, which prepares active nano kaolin powder by a process of intercalation - ultra-fine grinding - surface modification - centrifugal dehydration - drying - depolymerization. By performing wet surface modification on nano kaolin, the agglomeration of nano particles during the drying process can be effectively reduced, and the dispersibility of nano kaolin can be improved. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing active nano kaolin powder. By performing wet surface modification on nano kaolin, the agglomeration of nano particles during the drying process can be effectively reduced, and the dispersibility of nano kaolin can be improved.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A preparation method of active nano kaolin powder, comprising the following steps:

[0009] (1) Drying of raw materials: drying kaolin concentrate;

[0010] (2) Mixing the dried kaolin concentrate in step (1) with chemical additives, wherein the chemical additives include intercalating agents and surfactants, and mixing is carried out according to the mass ratio of kaolin concentrate: intercalating agent: surfactant = 100:5 - 60:1 - 10;

[0011] (3) Grinding the mixed kaolin and chemical additives in a ball mill for 5 - 10 min for thorough mixing, and then transferring to ultrasonic or microwave for intercalation reaction for 1 - 3 hours to obtain intercalated slurry;

[0012] (4) Transferring the intercalated slurry to a sand mill for ultrafine grinding for 10 - 60 min to obtain ultrafine ground slurry;

[0013] (5) Washing the ultrafine ground slurry and then performing surface modification;

[0014] (6) Centrifugally dewatering, drying, and depolymerizing the modified material;

[0015] (7) The depolymerized powder is the active nano kaolin powder product.

[0016] Preferably, in step (1), the particle size of the kaolin concentrate is such that D90 is less than 2 microns.

[0017] Preferably, in step (2), the intercalating agent is selected from one or more of potassium acetate, dimethyl sulfoxide, dimethylformamide, thiourea, and urea, and the surfactant is selected from one or more of cetyltrimethylammonium bromide, sodium dodecylsulfonate, Tween 80, and Tween 40.

[0018] Preferably, in step (3), the temperature for the intercalation reaction by ultrasonic or microwave is 50 - 100 °C; the concentration of the intercalated slurry is 30% - 70%.

[0019] Preferably, in step (4), the sand grinding medium in the sand mill is zirconium balls with a size of 0.5 - 1 mm, and the medium filling rate is 50%.

[0020] Preferably, in step (5), the modifier for surface modification is selected from one or more of stearic acid, silane, titanate, aluminate, and silicone oil, the temperature for modification is 80 - 120 °C, and the time for modification is 10 - 60 min.

[0021] Preferably, in step (7), the lamellar thickness of the active nano kaolin powder product is 20 - 90 nm, and the particle size is 200 - 500 nm.

[0022] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0023] 1. The present invention prepares the active nano kaolin powder by the process of intercalation - ultrafine grinding - surface modification - centrifugal dehydration - drying - depolymerization. By wet surface modification of nano kaolin, the agglomeration of nano particles during the drying process can be effectively reduced, and the dispersibility of nano kaolin can be improved.

[0024] 2. The active nano kaolin powder product of the present invention can be used in composite materials such as rubber and plastic, playing a role in reinforcing and improving the flame retardancy, airtightness and insulation properties of the materials, and can partially replace silica and carbon black.

[0025] 3. The present invention performs surface modification after washing the slurry after ultrafine grinding, which can avoid or reduce the agglomeration of nano kaolin particles during the drying process of the slurry, and can obtain nano kaolin powder with finer and more uniform particle size. At the same time, the modified powder can be directly used in rubber and plastic composite materials to increase the compatibility with the matrix. Specific Embodiments

[0026] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0027] Example 1

[0028] This example provides a preparation method of active nano kaolin powder, including the following steps:

[0029] (1) Drying of raw materials: The kaolin concentrate is dried, and the particle size is D90 less than 2 microns.

[0030] (2) Mix the kaolin concentrate dried in step (1) with chemical additives. Among them, the chemical additives include an intercalating agent and a surfactant, and are mixed according to the mass ratio of kaolin concentrate: intercalating agent: surfactant = 100:30:4; the intercalating agent is dimethyl sulfoxide, and the surfactant is cetyltrimethylammonium bromide.

[0031] (3) The mixed kaolin and chemical additives are ground in a ball mill for 10 min to be fully and evenly mixed, and then transferred to an ultrasonic device for an intercalation reaction for 2 hours to obtain the intercalated slurry. Among them, the temperature for the ultrasonic intercalation reaction is 80 °C; the concentration of the intercalated slurry is 50%;

[0032] (4) The intercalated slurry is transferred to a sand mill again for ultra-fine grinding for 50 min to obtain the ultra-fine ground slurry. Among them, the sand grinding medium in the sand mill is zirconium balls with a size of 0.5 - 1 mm, and the medium filling rate is 50%;

[0033] (5) The ultra-fine ground slurry is washed and then surface-modified. The surface modifier is stearic acid, the temperature for modification is 100 °C, and the modification time is 30 min;

[0034] (6) The modified material is centrifuged for dehydration, dried, and depolymerized;

[0035] (7) The depolymerized powder is the active nano kaolin powder product; the lamellar thickness of the active nano kaolin powder product is 50 - 90 nm, and the particle size is 200 - 500 nm.

[0036] Example 2

[0037] This example provides a preparation method of active nano kaolin powder, including the following steps:

[0038] (1) Drying of raw materials: The kaolin concentrate is dried, and the particle size is such that D90 is less than 2 microns;

[0039] (2) The dried kaolin concentrate in step (1) is mixed with chemical additives. Among them, the chemical additives include an intercalating agent and a surfactant, and they are mixed according to the mass ratio of kaolin concentrate:intercalating agent:surfactant = 100:40:4; the intercalating agent is dimethylformamide, and the surfactant is cetyltrimethylammonium bromide;

[0040] (3) The mixed kaolin and chemical additives are ground in a ball mill for 10 min to be fully and evenly mixed, and then transferred to an ultrasonic device for an intercalation reaction for 3 hours to obtain the intercalated slurry. Among them, the temperature for the ultrasonic intercalation reaction is 80 °C; the concentration of the intercalated slurry is 50%;

[0041] (4) The intercalated slurry is transferred to a sand mill again for ultra-fine grinding for 50 min to obtain the ultra-fine ground slurry. Among them, the sand grinding medium in the sand mill is zirconium balls with a size of 0.5 - 1 mm, and the medium filling rate is 50%;

[0042] (5) Wash the ultrafinely ground slurry and then conduct surface modification. The modifier for surface modification is silane, the modification temperature is 100 °C, and the modification time is 30 min;

[0043] (6) Centrifuge and dehydrate, dry, and depolymerize the modified material;

[0044] (7) The depolymerized powder is the active nano kaolin powder product; the lamellar thickness of the active nano kaolin powder product is 20 - 90 nm, and the particle size is 200 - 500 nm.

[0045] Example 3

[0046] This example provides a preparation method of active nano kaolin powder, including the following steps:

[0047] (1) Drying of raw materials: Dry the kaolin concentrate, with a particle size of D90 less than 2 microns;

[0048] (2) Mix the kaolin concentrate dried in step (1) with chemical additives. Among them, the chemical additives include an intercalating agent and a surfactant, and they are mixed according to the mass ratio of kaolin concentrate: intercalating agent: surfactant = 100:55:4; the intercalating agent is urea, and the surfactant is sodium dodecyl sulfonate;

[0049] (3) Grind the mixed kaolin and chemical additives in a ball mill for 20 min to mix them evenly, and then transfer them to an ultrasonic device for an intercalation reaction for 3 hours to obtain an intercalated slurry. Among them, the temperature for the ultrasonic intercalation reaction is 60 °C; the concentration of the intercalated slurry is 50%;

[0050] (4) Transfer the intercalated slurry to a sand mill again for ultrafine grinding for 60 min to obtain an ultrafinely ground slurry. Among them, the sand grinding medium in the sand mill is zirconium balls with a size of 0.5 - 1 mm, and the medium filling rate is 50%;

[0051] (5) Wash the ultrafinely ground slurry and then conduct surface modification. The modifier for surface modification is titanate, the modification temperature is 95 °C, and the modification time is 25 min;

[0052] (6) Centrifuge and dehydrate, dry, and depolymerize the modified material;

[0053] (7) The depolymerized powder is the active nano kaolin powder product; the lamellar thickness of the active nano kaolin powder product is 20 - 70 nm, and the particle size is 300 - 500 nm.

[0054] Example 4

[0055] This example provides a preparation method of active nano kaolin powder, including the following steps:

[0056] (1) Drying of raw materials: The kaolin concentrate is dried, and the particle size is such that D90 is less than 2 microns.

[0057] (2) Mix the dried kaolin concentrate from step (1) with chemical additives. Among them, the chemical additives include an intercalating agent and a surfactant, and they are mixed according to the mass ratio of kaolin concentrate: intercalating agent: surfactant = 100:50:6; the intercalating agent is dimethyl sulfoxide, and the surfactant is cetyltrimethylammonium bromide.

[0058] (3) The mixed kaolin and chemical additives are ground in a ball mill for 10 min to be fully and evenly mixed, and then transferred to an ultrasonic bath for an intercalation reaction for 3 hours to obtain an intercalated slurry. Among them, the temperature for the ultrasonic intercalation reaction is 80 °C; the concentration of the intercalated slurry is 50%.

[0059] (4) The intercalated slurry is transferred to a sand mill again for ultrafine grinding for 60 min to obtain an ultrafine ground slurry. Among them, the grinding medium in the sand mill is zirconium balls with a diameter of 0.5 - 1 mm, and the medium filling rate is 50%.

[0060] (5) The ultrafine ground slurry is washed and then surface-modified. The modifier for surface modification is stearic acid, the temperature for modification is 100 °C, and the time for modification is 25 min.

[0061] (6) The modified material is centrifugally dehydrated, dried, and depolymerized.

[0062] (7) The depolymerized powder is the active nano-kaolin powder product; the lamellar thickness of the active nano-kaolin powder product is 20 - 70 nm, and the particle size is 200 - 500 nm.

[0063] Comparative Example 1

[0064] This comparative example is based on Example 1 above. The difference from Example 1 is that the ultrafine ground slurry is not surface-modified after washing, and the other steps are the same as those in Example 1; the lamellar thickness of the obtained active nano-kaolin powder product is 70 - 100 nm, and the particle size is 500 - 1000 nm.

[0065] Comparative Example 2

[0066] This comparative example is based on Example 1 above. The difference from Example 1 is that only the surfactant is added and the intercalating agent is not added when the kaolin concentrate is mixed with the chemical additives, and the other steps are the same as those in Example 1. The lamellar thickness of the obtained active nano-kaolin powder product is 100 - 200 nm, and the particle size is 500 - 1000 nm.

[0067] It can be seen from Example 1, Comparative Example 1 and Comparative Example 2 that the thickness and particle size of the active nano kaolin powder product prepared by the preparation method of the present invention are more excellent.

[0068] In summary, the present invention prepares active nano kaolin powder by a process of intercalation - ultrafine grinding - surface modification - centrifugal dehydration - drying - depolymerization. By wet surface modification of nano kaolin, the agglomeration of nano particles during the drying process can be effectively reduced, and the dispersibility of nano kaolin can be improved. The active nano kaolin powder product of the present invention can be used in composite materials such as rubber and plastics, playing a role in reinforcing and improving the flame retardant performance, airtight performance and insulation performance of the materials, and can partially replace white carbon black and carbon black. By performing surface modification after washing the slurry after ultrafine grinding in the present invention, the agglomeration of nano kaolin particles during the drying process of the slurry can be avoided or reduced, and nano kaolin powder with finer and more uniform particle size can be obtained. At the same time, the modified powder can be directly used in rubber and plastic composite materials to increase the compatibility with the matrix.

[0069] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing active nano-kaolin powder, characterized in that: The steps include: (1) Drying of raw materials: drying the kaolin concentrate; (2) mixing the kaolin concentrate dried in step (1) with a chemical additive, wherein the chemical additive comprises an intercalating agent and a surfactant, and the mixture is mixed in a mass ratio of kaolin concentrate: intercalating agent: surfactant = 100:5-60:1-10; (3) The mixed kaolin and chemical additives are ground in a ball mill for 5 to 10 minutes to be fully mixed, and then transferred to an ultrasonic or microwave for intercalation reaction for 1 to 3 hours to obtain an intercalated slurry; (4) the intercalated slurry is transferred to a sand mill again for ultrafine grinding for 10 to 60 minutes to obtain an ultrafinely ground slurry; (5) washing the ultrafinely ground slurry and performing surface modification; (6) The modified material is centrifuged for dehydration, drying, and depolymerization; (7) The deagglomerated powder is the active nano-kaolin powder product.

2. The method for preparing an active nano-kaolin powder according to claim 1, characterized in that: In step (1), the particle size of the kaolin concentrate is D90 less than 2 microns.

3. The method for preparing an active nano-kaolin powder according to claim 1, characterized in that: In step (2), the intercalant is selected from one or more of potassium acetate, dimethyl sulfoxide, dimethylamide, thiourea and urea, and the surfactant is selected from one or more of hexadecyltrimethylammonium bromide, sodium dodecylsulfonate, Tween 80 and Tween 40.

4. The method for preparing an active nano-kaolin powder according to claim 1, characterized in that: In step (3), the temperature of the ultrasonic or microwave intercalation reaction is 50-100° C.; the concentration of the slurry after the intercalation is 30%-70%.

5. The method for preparing an active nano-kaolin powder according to claim 1, characterized in that: In step (4), the sand milling medium is a zirconium ball with a diameter of 0.5 to 1 mm, and the medium filling rate is 50%.

6. The method for preparing an active nano-kaolin powder according to claim 1, characterized in that: In step (5), the surface modification agent is selected from one or more of stearic acid, silane, titanate, aluminate, and silicone oil, the modification temperature is 80 to 120° C., and the modification time is 10 to 60 minutes.

7. The method for preparing an active nano-kaolin powder according to claim 1, characterized in that: In step (7), the active nano-kaolin powder product has a sheet thickness of 20 to 90 nm and a particle size of 200 to 500 nm.