A method for the production of ultrafine calcium carbonate for breathable films

Abstract

The application discloses a preparation method of superfine calcium carbonate for a breathable film, and relates to the technical field of nano calcium carbonate production. The method comprises the following steps: sending calcium hydroxide slurry to a carbonization kettle, adding a dispersing agent and a crystal form control agent into the carbonization kettle, then feeding kiln gas into the carbonization kettle to perform a preliminary carbonization reaction, stopping the feeding when the pH value of the slurry in the carbonization kettle is 7.2-8.0, and preparing slurry; putting a first modifier into the slurry, and continuing to feed kiln gas into the carbonization kettle, stopping the feeding of kiln gas when the pH value of the slurry in the carbonization kettle is less than or equal to 7, then putting a second modifier into the slurry, stirring uniformly, and reacting for 2-3 hours to prepare modified nano calcium carbonate suspension; and after the modified nano calcium carbonate suspension is subjected to pressure filtration, drying and crushing, the finished superfine calcium carbonate is obtained. Therefore, the problem of poor compatibility of superfine calcium carbonate with an organic polymer (such as PE or PVC) matrix is solved, and the dispersibility and interface combination are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nano calcium carbonate production, and particularly relates to a preparation method of superfine calcium carbonate for a breathable film. BACKGROUND

[0002] The breathable film is a kind of powerful polymer material, which can skillfully block liquid water, dust and bacteria while allowing air and water vapor to pass through. The film surface is full of a large number of nano-sized pores, and the pore size of the pores is greater than that of the gas molecules and smaller than that of the liquid water drops.

[0003] The breathable film commonly uses microporous agents such as heavy calcium, light calcium and nano calcium carbonate. However, the heavy calcium and light calcium have problems such as poor strength and elongation due to large particle size. The existing nano calcium carbonate has the problems of large particle size and easy agglomeration, which leads to small specific surface area of the nano calcium carbonate, and the number and size of micropores on the breathable film are difficult to control, which reduces the mechanical properties of the breathable film. SUMMARY

[0004] In view of the above defects, the purpose of the present application is to provide a preparation method of superfine calcium carbonate for a breathable film, which aims to solve the problem of mechanical property reduction of the breathable film caused by the large particle size and easy agglomeration of the nano calcium carbonate in the prior art.

[0005] To solve the above technical problems, the technical scheme of the present application is as follows:

[0006] A preparation method of superfine calcium carbonate for a breathable film, characterized in that it comprises the following steps:

[0007] Step one, the calcium hydroxide slurry is sent to a carbonization kettle, a dispersing agent and a crystal form control agent are added to the carbonization kettle, then kiln gas is sent into the carbonization kettle to carry out a preliminary carbonization reaction, and the feeding is stopped when the pH value of the slurry in the carbonization kettle is 7.2-8.0, and a slurry is prepared;

[0008] Step two, a first modifier is added to the slurry, and the kiln gas continues to be sent into the carbonization kettle, and the feeding of the kiln gas is stopped when the pH value of the slurry in the carbonization kettle is less than or equal to 7, then a second modifier is added to the slurry, and after stirring uniformly, the reaction is carried out for 2-3 hours to prepare a modified nano calcium carbonate suspension;

[0009] Step three, the modified nano calcium carbonate suspension is obtained after pressure filtration, drying and crushing to obtain finished superfine calcium carbonate;

[0010] The first modifier is composed of 20-30 parts by mass of stearic acid, 5-8 parts by mass of triisostearyl titanate, and 3-5 parts by mass of tetraisopropyl bis(dilauryl phosphite) titanate; and the amount of the first modifier is 2.3-4.8% of the mass fraction of the calcium carbonate dry substrate;

[0011] The second modifier is composed of 40-50 parts by weight of silane coupling agent, 10-20 parts by weight of surfactant and 10-20 parts by weight of silver-loaded hydroxyapatite; the amount of the second modifier is 1.5-2.4% of the mass fraction of the dry calcium carbonate matrix.

[0012] In step one, the volume concentration of calcium hydroxide in the calcium hydroxide slurry is 7-13%.

[0013] In step one, the volume concentration of carbon dioxide in the kiln gas is 20-35%, and the flow rate of the kiln gas is 4-6 m / s. 3 / s, the temperature inside the carbonization kettle is 18-32℃, and the empty volume of the carbonization kettle is 20m³. 3 The volume of slurry is 14m³. 3 .

[0014] In step two, the volume concentration of carbon dioxide in the kiln gas is 30-35%, and the flow rate of the kiln gas is 2-4 m / s. 3 / s, the temperature inside the carbonization kettle is 35-45℃.

[0015] The crystal form control agent is composed of 5-8 parts citric acid, 6-10 parts sodium polyphosphate, 10-12 parts ethylene glycol and 2-3 parts polyethyleneimine by weight; the amount of the crystal form control agent is 1.6-3.2% of the dry matrix mass of calcium hydroxide.

[0016] The dispersant is composed of 2-6 parts by weight of sodium hexametaphosphate, 3-8 parts by weight of sodium dodecylbenzenesulfonate and 1-3 parts by weight of sodium polyacrylate; the amount of the dispersant is 0.5-0.8% of the dry matrix mass of calcium hydroxide.

[0017] The silane coupling agent is composed of 10-15 parts by weight of γ-mercaptopropyltrimethoxysilane, 3-8 parts by weight of vinyltriethoxysilane, and 2-4 parts by weight of perfluorooctyltriethoxysilane.

[0018] The ultrafine calcium carbonate has a particle size ≤150nm and a moisture content ≤0.3%.

[0019] After adopting the above technical solution, the beneficial effects of the present invention are:

[0020] First, the combined action of citric acid, sodium polyphosphate, ethylene glycol, and polyethyleneimine guides the transformation of calcium carbonate crystals towards a spherical-ellipsoidal morphology, thereby achieving a larger specific surface area. Second, the use of stearic acid, isopropyl triisostearoyl titanate, and tetraisopropyl di(dilauryl phosphite) titanate solves the problem of poor compatibility between ultrafine calcium carbonate and organic polymer matrices (such as PE and PVC), improving dispersibility and interfacial bonding. Third, materials such as γ-mercaptopropyltrimethoxysilane, vinyltriethoxysilane, and perfluorooctyltriethoxysilane endow ultrafine calcium carbonate with strong hydrophobic properties and enhanced interfacial chemical bonding. Fourth, silver-loaded hydroxyapatite solves the problem of high surface energy in calcium carbonate and endows it with antibacterial properties. Detailed Implementation

[0021] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0022] In this invention, all components are expressed in parts by mass.

[0023] A method for preparing ultrafine calcium carbonate for use in breathable membranes includes the following steps:

[0024] Step 1: Send the calcium hydroxide slurry to the carbonization reactor, add dispersant and crystal form control agent to the carbonization reactor, and then send kiln gas into the carbonization reactor to carry out the preliminary carbonization reaction. When the pH value of the liquid in the carbonization reactor is 7.2-8.0, stop sending and obtain the slurry.

[0025] Step 2: Add the first modifier to the slurry and continue to feed kiln gas into the carbonization kettle. When the pH of the slurry in the carbonization kettle is ≤7, stop feeding kiln gas. Then add the second modifier to the slurry, stir evenly, and react for 2-3 hours to obtain a modified nano calcium carbonate suspension.

[0026] Step 3: The modified nano-calcium carbonate suspension is filtered, dried, and crushed to obtain the finished ultrafine calcium carbonate.

[0027] In step one, the volume concentration of calcium hydroxide in the calcium hydroxide slurry is 7-13%.

[0028] In step one, the volume concentration of carbon dioxide in the kiln gas is 20-35%, and the flow rate of the kiln gas is 4-6 m / s. 3 / s, the temperature inside the carbonization kettle is 18-32℃, and the empty volume of the carbonization kettle is 20m³. 3 The volume of slurry is 14m³. 3 .

[0029] In step two, the volume concentration of carbon dioxide in the kiln gas is 30-35%, and the flow rate of the kiln gas is 2-4 m / s. 3 / s, the temperature in the carbonization kettle is 35-45℃.

[0030] The crystal form control agent is composed of 5-8 parts of citric acid, 6-10 parts of sodium polyphosphate, 10-12 parts of ethylene glycol and 2-3 parts of polyethyleneimine; the dosage of the crystal form control agent is 1.6-3.2% of the dry substrate mass fraction of calcium hydroxide.

[0031] The dispersant is composed of 2-6 parts of sodium hexametaphosphate, 3-8 parts of sodium dodecylbenzenesulfonate and 1-3 parts of sodium polyacrylate; the dosage of the dispersant is 0.5-0.8% of the dry substrate mass fraction of calcium hydroxide.

[0032] The first modifier is composed of 20-30 parts of stearic acid, 5-8 parts of triisostearyl titanate, 3-5 parts of tetraisopropyl bis(dilaurylphosphite) titanate; the dosage of the first modifier is 2.3-4.8% of the dry substrate mass fraction of calcium carbonate.

[0033] The second modifier is composed of 40-50 parts of silane coupling agent, 10-20 parts of surfactant and 10-20 parts of silver-loaded hydroxyapatite; the dosage of the second modifier is 1.5-2.4% of the dry substrate mass fraction of calcium carbonate.

[0034] The silane coupling agent is composed of 10-15 parts of γ-mercaptopropyl trimethoxysilane, 3-8 parts of vinyl triethoxysilane and 2-4 parts of perfluorooctyl triethoxysilane.

[0035] The particle size of the superfine calcium carbonate is ≤150nm, and the moisture content is ≤0.3%.

[0036] Example 1:

[0037] The superfine calcium carbonate is prepared by the above preparation method, wherein:

[0038] In step one, the feeding of kiln gas is stopped when the pH value of the material liquid in the carbonization kettle is 7.2. The volume concentration of calcium hydroxide in the calcium hydroxide slurry is 7%.

[0039] In step one, the volume concentration of carbon dioxide in the kiln gas is 20%, and the flow rate of the kiln gas is 4m 3 / s, and the temperature in the carbonization kettle is 18℃.

[0040] The crystal form control agent is composed of 5 parts of citric acid, 6 parts of sodium polyphosphate, 10 parts of ethylene glycol and 2 parts of polyethyleneimine; the dosage of the crystal form control agent is 1.6% of the dry substrate mass fraction of calcium hydroxide.

[0041] The dispersant is composed of 2 parts of sodium hexametaphosphate, 3 parts of sodium dodecyl benzene sulfonate and 1 part of sodium polyacrylate; the amount of the dispersant is 0.5% of the dry base mass fraction of calcium hydroxide.

[0042] The first modifier is composed of 20 parts of stearic acid, 5 parts of triisostearyl titanate, 3 parts of tetraisopropyl di(dilauryl phosphite) titanate; the amount of the first modifier is 2.3% of the dry base mass fraction of calcium carbonate.

[0043] The second modifier is composed of 40 parts of silane coupling agent, 10 parts of surfactant and 10 parts of silver-loaded hydroxyapatite; the amount of the second modifier is 1.5% of the dry base mass fraction of calcium carbonate.

[0044] The silane coupling agent is composed of 10 parts of γ-mercaptopropyl trimethoxysilane, 3 parts of vinyl triethoxysilane and 2 parts of perfluorooctyl triethoxysilane.

[0045] In step two, after stirring uniformly, the reaction is carried out for 2 hours.

[0046] In step two, the volume concentration of carbon dioxide in the kiln gas is 30%, the flow rate of the kiln gas is 2m / s, and the temperature in the carbonization kettle is 35℃. 3

[0047] Example 2:

[0048] The difference between this example and example 1 is that:

[0049] In step one, the kiln gas is stopped when the pH value of the material liquid in the carbonization kettle is 7.4. The volume concentration of calcium hydroxide in the calcium hydroxide slurry is 11%.

[0050] In step one, the volume concentration of carbon dioxide in the kiln gas is 22%, the flow rate of the kiln gas is 4.5m / s, and the temperature in the carbonization kettle is 24℃. 3

[0051] The crystal form control agent is composed of 6 parts of citric acid, 8 parts of sodium polyphosphate, 10.5 parts of ethylene glycol and 2.2 parts of polyethyleneimine; the amount of the crystal form control agent is 2% of the dry base mass fraction of calcium hydroxide.

[0052] The dispersant is composed of 3 parts of sodium hexametaphosphate, 4 parts of sodium dodecyl benzene sulfonate and 1.5 parts of sodium polyacrylate; the amount of the dispersant is 0.55% of the dry base mass fraction of calcium hydroxide.

[0053] The first modifier is composed of 22 parts of stearic acid, 5.5 parts of triisostearyl titanate, 3.5 parts of tetraisopropyl di(dilauryl phosphite) titanate; the amount of the first modifier is 2.8% of the dry base mass fraction of calcium carbonate.​​

[0054] The second modifier is composed of 44 parts of silane coupling agent, 14 parts of surfactant and 14 parts of silver-loaded hydroxyapatite; the amount of the second modifier is 1.8% of the dry mass fraction of calcium carbonate.

[0055] The silane coupling agent is composed of 11 parts of γ-mercaptopropyl trimethoxysilane, 4 parts of vinyl triethoxysilane and 2.5 parts of perfluorooctyl triethoxysilane.

[0056] In step two, the reaction is stirred for 2.4 hours.

[0057] In step two, the volume concentration of carbon dioxide in the kiln gas is 31%, the flow rate of the kiln gas is 2.5 m / s, and the temperature in the carbonization kettle is 38℃. 3

[0058] Example 3:

[0059] The difference between this example and Example 1 is that:

[0060] In step one, the kiln gas is stopped when the pH value of the material liquid in the carbonization kettle is 7.8. The volume concentration of calcium hydroxide in the calcium hydroxide slurry is 12%.

[0061] In step one, the volume concentration of carbon dioxide in the kiln gas is 26%, the flow rate of the kiln gas is 5 m / s, and the temperature in the carbonization kettle is 28℃. 3

[0062] The crystal form control agent is composed of 7 parts of citric acid, 9 parts of sodium polyphosphate, 11 parts of ethylene glycol and 2.6 parts of polyethyleneimine; the amount of the crystal form control agent is 3% of the dry mass fraction of calcium hydroxide.

[0063] The dispersant is composed of 4 parts of sodium hexametaphosphate, 5 parts of sodium dodecylbenzenesulfonate and 2 parts of sodium polyacrylate; the amount of the dispersant is 0.65% of the dry mass fraction of calcium hydroxide.

[0064] The first modifier is composed of 26 parts of stearic acid, 6 parts of triisostearyl titanate, 4 parts of tetraisopropyl bis (dilauryl phosphite) titanate; the amount of the first modifier is 3.5% of the dry mass fraction of calcium carbonate.

[0065] The second modifier is composed of 46 parts of silane coupling agent, 16 parts of surfactant and 16 parts of silver-loaded hydroxyapatite; the amount of the second modifier is 2% of the dry mass fraction of calcium carbonate.

[0066] The silane coupling agent is composed of 13 parts of γ-mercaptopropyl trimethoxysilane, 6 parts of vinyl triethoxysilane and 3 parts of perfluorooctyl triethoxysilane.​​

[0067] In step two, the reaction was carried out for 2.8 hours after the stirring was uniform.

[0068] In step two, the volume concentration of carbon dioxide in the kiln gas was 33%, the flow rate of the kiln gas was 3 m / s, and the temperature in the carbonation kettle was 40℃. 3

[0069] Example 4:

[0070] The difference between this example and Example 1 is that:

[0071] In step one, the kiln gas was stopped when the pH value of the material liquid in the carbonation kettle was 8.0. The volume concentration of calcium hydroxide in the calcium hydroxide slurry was 13%.

[0072] In step one, the volume concentration of carbon dioxide in the kiln gas was 35%, the flow rate of the kiln gas was 6 m / s, and the temperature in the carbonation kettle was 32℃. 3

[0073] The crystal form control agent was composed of 8 parts of citric acid, 10 parts of sodium polyphosphate, 12 parts of ethylene glycol, and 3 parts of polyethyleneimine; the amount of the crystal form control agent was 3.2% of the mass fraction of the dry calcium hydroxide substrate.

[0074] The dispersant was composed of 6 parts of sodium hexametaphosphate, 8 parts of sodium dodecylbenzenesulfonate, and 3 parts of sodium polyacrylate; the amount of the dispersant was 0.8% of the mass fraction of the dry calcium hydroxide substrate.

[0075] The first modifier was composed of 30 parts of stearic acid, 8 parts of isopropyl triisostearoyl titanate, and 5 parts of tetraisopropyl di(dilauryl phosphite) titanate; the amount of the first modifier was 4.8% of the mass fraction of the dry calcium carbonate substrate.

[0076] The second modifier was composed of 50 parts of a silane coupling agent, 20 parts of a surfactant, and 20 parts of silver-loaded hydroxyapatite; the amount of the second modifier was 2.4% of the mass fraction of the dry calcium carbonate substrate.

[0077] The silane coupling agent was composed of 15 parts of γ-mercaptopropyl trimethoxysilane, 8 parts of vinyl triethoxysilane, and 4 parts of perfluorooctyl triethoxysilane.

[0078] In step two, the reaction was carried out for 3 hours after the stirring was uniform.

[0079] In step two, the volume concentration of carbon dioxide in the kiln gas was 35%, the flow rate of the kiln gas was 4 m / s, and the temperature in the carbonation kettle was 45℃. 3

[0080] Comparative Example 1: ​​​

[0081] The difference between this comparative example and Example 1 is that the first modifier is not used.

[0082] Comparative Example 2:

[0083] The difference between this comparative example and Example 1 is that the second modifier is not used.

[0084] Comparative Example 3:

[0085] A commercially available calcium carbonate with the brand name of Sennewerth was purchased, and the product parameters were: specific surface area 25000 cm 3 / g, average particle size D50 0.9-1.1, -2 μm passing rate >80%.

[0086] The calcium carbonate of the above examples and comparative examples was extrusion granulated according to the formula 52% PE + 47% calcium carbonate + 1% polyethylene wax, and then a breathable film was obtained by processing through a casting machine, and a test sample of 100 mm x 45 mm was prepared for testing. Among them, the tensile properties were tested according to GB / T1040-2018, the porosity of the breathable film was determined by the liquid absorption method of ASTM D-2873, the air permeability was determined by a microporous membrane Gurley value tester, and the smaller the Gurley value, the higher the air permeability. The test results are as follows:

[0087]

[0088] Note: (1) BET specific surface area was measured by Beijing Piao De Electronic Rapid Specific Surface Area Instrument, Model KB-1000;

[0089] (2) The average particle size of the ultrafine calcium carbonate was a theoretical empirical formula:

[0090]

[0091] In the formula, dp is the average diameter (μm), s is the specific surface (m 2 / g), wherein: s is the BET nitrogen adsorption specific surface area of the particles.

[0092] (3) Laser particle size was measured by Dandong Bitai Instrument Co., Ltd., Model BT-2000 instrument. First, the powder was wetted with white cat detergent, then dispersed with water, and then ultrasonicated for 3 minutes, and then added to the instrument for detection.

[0093] (4) The detection of activation degree was carried out according to 3.19

[0094] The surface coating degree of calcium carbonate was determined by the hydrophobicity of the surface treated calcium carbonate.

[0095] From the examples 1-4 and the comparative examples 1-2, it can be seen that: first, the first modifier can significantly improve the specific surface area of the superfine calcium carbonate. Second, the second modifier can effectively improve the hydrophobicity of the superfine calcium carbonate, and its water content is also greatly reduced.

[0096] From the examples 1-4 and the comparative example 3, it can be seen that, due to the larger specific surface area and water content, a higher air permeability is obtained, and under the action of titanate coupling agent and silane coupling agent, the product has better dispersibility and reduces the probability of agglomeration.

[0097] In summary, the advantages of the present scheme are: first, under the joint action of citric acid, sodium polyphosphate, ethylene glycol and polyethyleneimine, the crystal of calcium carbonate is guided to change to a spherical-ellipsoidal shape, thereby obtaining a larger specific surface area. Second, under the action of stearic acid, titanium isopropyl triisostearoyl titanate, tetraisopropyl di(dilauryl phosphite) titanate, the problem of poor compatibility of superfine calcium carbonate with organic polymer (such as PE, PVC) matrix is solved, and the dispersibility and interfacial bonding are improved. Third, under the action of γ-mercapto propyl trimethoxysilane, vinyl triethoxysilane, perfluoro octyl triethoxysilane and other materials, the superfine calcium carbonate obtains strong hydrophobic and enhanced interfacial chemical bonding function. Fourth, silver-loaded hydroxyapatite solves the problem of high surface energy of calcium carbonate and endows calcium carbonate with antibacterial properties.

[0098] The present application is not limited to the above specific embodiments, and those skilled in the art can make various modifications without creative labor, which are all within the scope of the present application.

Claims

1. A method for preparing ultrafine calcium carbonate for use in breathable membranes, characterized in that, Includes the following steps: Step 1: Send the calcium hydroxide slurry to the carbonization reactor, add dispersant and crystal form control agent to the carbonization reactor, and then send kiln gas into the carbonization reactor to carry out the preliminary carbonization reaction. When the pH value of the liquid in the carbonization reactor is 7.2-8.0, stop sending and obtain the slurry. Step 2: Add the first modifier to the slurry and continue to feed kiln gas into the carbonization kettle. When the pH of the slurry in the carbonization kettle is ≤7, stop feeding kiln gas. Then add the second modifier to the slurry, stir evenly, and react for 2-3 hours to obtain a modified nano calcium carbonate suspension. Step 3: The modified nano-calcium carbonate suspension is filtered, dried, and crushed to obtain the finished ultrafine calcium carbonate product. The first modifier, by weight, consists of 20-30 parts stearic acid, 5-8 parts triisostearoyl titanate isopropyl ester, and 3-5 parts tetraisopropyl di(dilauryl phosphite) titanate; the amount of the first modifier is 2.3-4.8% of the dry calcium carbonate matrix. The second modifier, by weight, consists of 40-50 parts of silane coupling agent, 10-20 parts of surfactant, and 10-20 parts of silver-loaded hydroxyapatite; the amount of the second modifier is 1.5-2.4% of the dry calcium carbonate matrix. The crystal form control agent, by weight, consists of 5-8 parts citric acid, 6-10 parts sodium polyphosphate, 10-12 parts ethylene glycol, and 2-3 parts polyethyleneimine; the amount of the crystal form control agent is 1.6-3.2% of the dry calcium hydroxide matrix. The dispersant, by weight, consists of 2-6 parts sodium hexametaphosphate, 3-8 parts sodium dodecylbenzenesulfonate, and 1-3 parts sodium polyacrylate; the amount of the dispersant is 0.5-0.8% of the dry calcium hydroxide matrix. The silane coupling agent is composed of 10-15 parts by weight of γ-mercaptopropyltrimethoxysilane, 3-8 parts by weight of vinyltriethoxysilane, and 2-4 parts by weight of perfluorooctyltriethoxysilane.

2. The method for preparing ultrafine calcium carbonate for a breathable membrane according to claim 1, characterized in that, In step one, the volume concentration of calcium hydroxide in the calcium hydroxide slurry is 7-13%.

3. The method for preparing ultrafine calcium carbonate for a breathable membrane according to claim 1, characterized in that, In step one, the volume concentration of carbon dioxide in the kiln gas is 20-35%, and the flow rate of the kiln gas is 4-6 m / s. 3 / s, the temperature inside the carbonization kettle is 18-32℃, and the empty volume of the carbonization kettle is 20m³. 3 The volume of slurry is 14m³. 3 .

4. The method for preparing ultrafine calcium carbonate for a breathable membrane according to claim 1, characterized in that, In step two, the volume concentration of carbon dioxide in the kiln gas is 30-35%, and the flow rate of the kiln gas is 2-4 m / s. 3 / s, the temperature inside the carbonization kettle is 35-45℃.

5. The method for preparing ultrafine calcium carbonate for a breathable membrane according to claim 1, characterized in that, The ultrafine calcium carbonate has a particle size ≤150nm and a moisture content ≤0.3%.

Images