Preparation method of superfine calcium carbonate for breathable film

Abstract

The invention discloses a preparation method of superfine calcium carbonate for a gas-permeable membrane, and relates to the technical field of nano calcium carbonate production.The preparation method comprises the steps that calcium hydroxide slurry is fed into a carbonization kettle, a dispersing agent and a crystal form control agent are added into the carbonization kettle, then kiln gas is fed into the carbonization kettle, and a preliminary carbonization reaction is conducted; when the pH value of the feed liquid in the carbonization kettle is 7.2-8.0, conveying is stopped, and slurry is prepared; putting a first modifier into the slurry, continuously feeding kiln gas into the carbonization kettle, stopping conveying the 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, uniformly stirring, and reacting for 2-3 hours to prepare a modified nano calcium carbonate suspension; and carrying out filter pressing, drying and crushing on the modified nano calcium carbonate suspension to obtain the finished product superfine calcium carbonate. Therefore, the problem that the compatibility of superfine calcium carbonate and organic polymer (such as PE and PVC) matrixes is poor is solved, and the dispersity and the interface bonding property 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 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 is greater than that of gas molecules and smaller than that of liquid water drops.

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

[0004] In view of the above defects, the present application aims to provide a preparation method of superfine calcium carbonate for a breathable film, and 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: A preparation method of superfine calcium carbonate for a breathable film, characterized in that the method comprises the following steps: 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 perform a preliminary carbonization reaction, 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; Step two, a first modifier is added to the slurry, and the kiln gas is continuously sent into the carbonization kettle, 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 the modified nano calcium carbonate suspension is prepared after uniform stirring and reaction for 2-3 hours; Step three, the modified nano calcium carbonate suspension is obtained after pressure filtration, drying and crushing to obtain finished superfine calcium carbonate; The first modifier consists of 20-30 parts of stearic acid, 5-8 parts of triisostearyl titanate and 3-5 parts of tetraisopropyl bis(dilauryl phosphite) titanate by mass fraction; and the amount of the first modifier is 2.3-4.8% of the mass fraction of the calcium carbonate dry substrate. 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.

[0006] In step one, the volume concentration of calcium hydroxide in the calcium hydroxide slurry is 7-13%.

[0007] 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 .

[0008] 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℃.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] The ultrafine calcium carbonate has a particle size ≤150nm and a moisture content ≤0.3%.

[0013] After adopting the above technical solution, the beneficial effects of the present invention are: 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

[0014] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0015] In this invention, all components are expressed in parts by mass. A method for preparing ultrafine calcium carbonate for use in breathable membranes 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.

[0016] In step one, the volume concentration of calcium hydroxide in the calcium hydroxide slurry is 7-13%.

[0017] 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 .

[0018] 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℃.

[0019] 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; the amount of the crystal form control agent is 1.6-3.2% of the dry matrix mass fraction of calcium hydroxide.

[0020] The dispersant is composed 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 matrix mass fraction of calcium hydroxide.

[0021] The first modifier is composed 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 mass fraction.

[0022] 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 amount of the second modifier is 1.5-2.4% of the mass fraction of the dry calcium carbonate matrix.

[0023] The silane coupling agent is composed of 10-15 parts of γ-mercaptopropyltrimethoxysilane, 3-8 parts of vinyltriethoxysilane, and 2-4 parts of perfluorooctyltriethoxysilane.

[0024] The ultrafine calcium carbonate has a particle size ≤150nm and a moisture content ≤0.3%.

[0025] Example 1: Ultrafine calcium carbonate was prepared using the above preparation method, wherein: In step one, the kiln gas supply is stopped when the pH of the feed liquid in the carbonization reactor reaches 7.2. The volume concentration of calcium hydroxide in the calcium hydroxide slurry is 7%.

[0026] In step one, the volume concentration of carbon dioxide in the kiln gas is 20%, and the flow rate of the kiln gas is 4 m / s. 3 / s, the temperature inside the carbonization vessel is 18℃.

[0027] The crystal form control agent is composed of 5 parts citric acid, 6 parts sodium polyphosphate, 10 parts ethylene glycol and 2 parts polyethyleneimine; the amount of the crystal form control agent is 1.6% of the dry matrix mass of calcium hydroxide.

[0028] The dispersant is composed of 2 parts sodium hexametaphosphate, 3 parts sodium dodecylbenzenesulfonate and 1 part sodium polyacrylate; the amount of the dispersant is 0.5% of the dry matrix mass fraction of calcium hydroxide.

[0029] The first modifier consists of 20 parts stearic acid, 5 parts triisostearoyl titanate isopropyl ester, and 3 parts tetraisopropyl di(dilauryl phosphite) titanate; the amount of the first modifier is 2.3% of the dry calcium carbonate matrix mass fraction.

[0030] 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 mass fraction of the dry calcium carbonate matrix.

[0031] The silane coupling agent is composed of 10 parts of γ-mercaptopropyltrimethoxysilane, 3 parts of vinyltriethoxysilane, and 2 parts of perfluorooctyltriethoxysilane.

[0032] In step two, after stirring evenly, react for 2 hours.

[0033] In step two, the volume concentration of carbon dioxide in the kiln gas is 30%, and the flow rate of the kiln gas is 2m. 3 / s, the temperature inside the carbonization kettle is 35℃.

[0034] Example 2: The difference between this embodiment and Embodiment 1 is that: In step one, the kiln gas supply is stopped when the pH of the feed liquid in the carbonization kettle reaches 7.4. The volume concentration of calcium hydroxide in the calcium hydroxide slurry is 11%.

[0035] In step one, the volume concentration of carbon dioxide in the kiln gas is 22%, and the flow rate of the kiln gas is 4.5 m / s. 3 / s, the temperature inside the carbonization kettle is 24℃.

[0036] The crystal form control agent is composed of 6 parts citric acid, 8 parts sodium polyphosphate, 10.5 parts ethylene glycol and 2.2 parts polyethyleneimine; the amount of the crystal form control agent is 2% of the dry matrix mass of calcium hydroxide.

[0037] The dispersant is composed of 3 parts sodium hexametaphosphate, 4 parts sodium dodecylbenzenesulfonate and 1.5 parts sodium polyacrylate; the amount of the dispersant is 0.55% of the dry matrix mass fraction of calcium hydroxide.

[0038] The first modifier is composed of 22 parts stearic acid, 5.5 parts triisostearoyl titanate isopropyl ester, and 3.5 parts tetraisopropyl di(dilauryl phosphite) titanate; the amount of the first modifier is 2.8% of the dry calcium carbonate matrix mass fraction.

[0039] 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 calcium carbonate matrix mass fraction.

[0040] The silane coupling agent is composed of 11 parts γ-mercaptopropyltrimethoxysilane, 4 parts vinyltriethoxysilane, and 2.5 parts perfluorooctyltriethoxysilane.

[0041] In step two, the mixture is stirred until homogeneous and then reacted for 2.4 hours.

[0042] In step two, the volume concentration of carbon dioxide in the kiln gas is 31%, and the flow rate of the kiln gas is 2.5 m / s. 3 / s, the temperature inside the carbonization kettle is 38℃.

[0043] Example 3: The difference between this embodiment and Embodiment 1 is that: In step one, the kiln gas supply is stopped when the pH of the feed liquid in the carbonization reactor reaches 7.8. The volume concentration of calcium hydroxide in the calcium hydroxide slurry is 12%.

[0044] In step one, the volume concentration of carbon dioxide in the kiln gas is 26%, and the flow rate of the kiln gas is 5 m / s. 3 / s, the temperature inside the carbonization vessel is 28℃.

[0045] The crystal form control agent is composed of 7 parts citric acid, 9 parts sodium polyphosphate, 11 parts ethylene glycol and 2.6 parts polyethyleneimine; the amount of the crystal form control agent is 3% of the dry matrix mass of calcium hydroxide.

[0046] The dispersant is composed of 4 parts sodium hexametaphosphate, 5 parts sodium dodecylbenzenesulfonate and 2 parts sodium polyacrylate; the amount of the dispersant is 0.65% of the dry matrix mass fraction of calcium hydroxide.

[0047] The first modifier is composed of 26 parts stearic acid, 6 parts triisostearoyl titanate isopropyl ester, and 4 parts tetraisopropyl di(dilauryl phosphite) titanate; the amount of the first modifier is 3.5% of the dry calcium carbonate matrix mass fraction.

[0048] 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 calcium carbonate matrix mass fraction.

[0049] The silane coupling agent is composed of 13 parts γ-mercaptopropyltrimethoxysilane, 6 parts vinyltriethoxysilane, and 3 parts perfluorooctyltriethoxysilane.

[0050] In step two, after stirring evenly, the reaction proceeds for 2.8 hours.

[0051] In step two, the volume concentration of carbon dioxide in the kiln gas is 33%, and the flow rate of the kiln gas is 3m. 3 / s, the temperature inside the carbonization kettle is 40℃.

[0052] Example 4: The difference between this embodiment and Embodiment 1 is that: In step one, the kiln gas supply is stopped when the pH of the feed liquid in the carbonization reactor reaches 8.0. The volume concentration of calcium hydroxide in the calcium hydroxide slurry is 13%.

[0053] In step one, the volume concentration of carbon dioxide in the kiln gas is 35%, and the flow rate of the kiln gas is 6 m / s. 3 / s, the temperature inside the carbonization vessel is 32℃.

[0054] The crystal form control agent is composed of 8 parts citric acid, 10 parts sodium polyphosphate, 12 parts ethylene glycol and 3 parts polyethyleneimine; the amount of the crystal form control agent is 3.2% of the dry matrix mass of calcium hydroxide.

[0055] The dispersant is composed of 6 parts sodium hexametaphosphate, 8 parts sodium dodecylbenzenesulfonate and 3 parts sodium polyacrylate; the amount of the dispersant is 0.8% of the dry matrix mass fraction of calcium hydroxide.

[0056] The first modifier is composed of 30 parts stearic acid, 8 parts triisostearoyl titanate isopropyl ester, and 5 parts tetraisopropyl di(dilauryl phosphite) titanate; the amount of the first modifier is 4.8% of the dry calcium carbonate matrix mass fraction.

[0057] The second modifier is composed of 50 parts of silane coupling agent, 20 parts of surfactant and 20 parts of silver-loaded hydroxyapatite; the amount of the second modifier is 2.4% of the mass fraction of the dry calcium carbonate matrix.

[0058] The silane coupling agent is composed of 15 parts of γ-mercaptopropyltrimethoxysilane, 8 parts of vinyltriethoxysilane, and 4 parts of perfluorooctyltriethoxysilane.

[0059] In step two, after stirring evenly, react for 3 hours.

[0060] In step two, the volume concentration of carbon dioxide in the kiln gas is 35%, and the flow rate of the kiln gas is 4 m / s. 3 / s, the temperature inside the carbonization kettle is 45℃.

[0061] Comparative Example 1: The difference between this comparative example and Example 1 is that the first modifier was not used.

[0062] Comparative Example 2: The difference between this comparative example and Example 1 is that no second modifier was used.

[0063] Comparative Example 3: Purchase commercially available calcium carbonate from the brand name Senxin. Product specifications: specific surface area 25000 cm². 3 / g, with an average particle size D50 of 0.9-1.1 and a -2μm throughput of >80%.

[0064] The calcium carbonate samples from the above examples and comparative examples were extruded and granulated according to a formulation of 52% PE + 47% calcium carbonate + 1% polyethylene wax. The granules were then processed using a casting machine to obtain a breathable film, and 100mm × 45mm samples were prepared for testing. Tensile properties were tested according to GB / T1040-2018. The porosity of the breathable film was determined using the ASTM D-2873 liquid absorption method, and the air permeability was determined using a microporous membrane Gurley value tester. A lower Gurley value indicates higher air permeability. The test results are summarized below:

[0065] Note: (1) The BET specific surface area was measured using a Beijing Bio-Tech Electronics rapid specific surface area meter, model KB-1000; (2) The average particle size of ultrafine calcium carbonate is given by the theoretical empirical formula:

[0066] In the formula, dp The average diameter is (μm). s For specific surface area (m) 2 / g), where: s denoted as the BET nitrogen adsorption specific surface area of ​​the particles.

[0067] (3) Laser particle size was measured using a BT-2000 instrument from Dandong Better Instrument Co., Ltd. The powder was first moistened with White Cat dishwashing liquid, then dispersed with water, and then sonicated for 3 minutes before being added to the instrument for detection.

[0068] (4) Detection of activation degree, according to 3.19 of GB / T19281-2014, "Analytical Methods for Calcium Carbonate". The degree of coating on the surface of calcium carbonate was determined by utilizing the hydrophobicity characteristics of calcium carbonate after surface treatment.

[0069] From Examples 1-4 and Comparative Examples 1-2, it can be seen that: First, the first modifier can significantly increase the specific surface area of ​​ultrafine calcium carbonate. Second, the second modifier can effectively improve the hydrophobicity of ultrafine calcium carbonate, while its water content is also greatly reduced.

[0070] As can be seen from Examples 1-4 and Comparative Example 3, due to its larger specific surface area and water content, it achieves higher air permeability. At the same time, under the action of titanate coupling agent and silane coupling agent, this product has better dispersibility and reduces the probability of agglomeration.

[0071] In summary, the advantages of this scheme are as follows: 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 action 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 (such as PE and PVC) matrices, improving dispersibility and interfacial bonding. Third, the action of materials such as γ-mercaptopropyltrimethoxysilane, vinyltriethoxysilane, and perfluorooctyltriethoxysilane endows ultrafine calcium carbonate with strong hydrophobicity 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.

[0072] This invention is not limited to the specific embodiments described above. Any modifications made by those skilled in the art based on the above concept without creative effort are within the scope of protection of this invention.

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 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.

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 2, characterized in that, 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.

6. The method for preparing ultrafine calcium carbonate for a breathable membrane according to claim 2, characterized in that, 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.

7. The method for preparing ultrafine calcium carbonate for a breathable membrane according to claim 1, characterized in that, 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.

8. 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%.

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