Preparation method of silicate-impregnated washable flame-retardant paper

Abstract

The invention discloses a preparation method of silicate-impregnated washable flame-retardant paper, and relates to the technical field of pulping and papermaking. Comprising the following steps: 1, filling mineral particles in a suspension of plant fiber paper pulp, and carrying out raw paper making, 2, dipping the raw paper in a silicate colloid dipping material in the raw paper making process, and 3, heating, drying, curing and curling the raw paper to obtain a finished product, the washable flame-retardant paper prepared by the preparation method disclosed by the invention still has flame-retardant property after being impregnated and soaked in water, realizes flame-retardant and washable functions of the paper, and has wide application value in the fields of decoration and packaging.

Description

Technical Field

[0001] This invention discloses a method for preparing water-resistant flame-retardant paper impregnated with silicate, which relates to the field of pulp and paper technology. Background Technology

[0002] Certain specialty papers require fire-retardant properties, as well as water and moisture resistance, such as wallpaper, battery packaging paper, flammable chemicals, and other materials. However, flame retardancy contradicts the inherent organic and porous nature of paper. The porosity of paper provides convenient diffusion and mass transfer channels for air and oxygen, directly affecting the flame-retardant performance of the paper material. Furthermore, paper's main component is cellulose, a flammable organic material. Current methods for flame retardant paper involve adding flame retardants. Some of these flame retardants have synergistic effects such as heat absorption and cooling, oxygen isolation, blocking free radical chain reactions, diluting flammable gases, and catalyzing char formation. They can provide condensed phase isolation, gas phase inhibition, and interruption of heat exchange, such as chemical flame retardants. However, these are costly, easily cause environmental pollution, and their effectiveness in preventing water immersion or moisture penetration is not significant. Other flame retardants are simply added physically during papermaking. These flame retardants are lost, weakening or eliminating the paper's flame-retardant properties. Moreover, such flame-retardant paper is not water-resistant and cannot withstand washing, immersion, or moisture penetration, making it unsuitable for practical applications in daily life and production. Summary of the Invention

[0003] This invention addresses the problems of existing technologies by providing a method for preparing silicate-impregnated, washable, flame-retardant paper. The specific solution proposed by this invention is as follows:

[0004] This invention provides a method for preparing silicate-impregnated, washable, flame-retardant paper, comprising:

[0005] Step 1: Add mineral particles to the suspension of plant fiber pulp for papermaking. The mineral particles include one or more of the following mineral particles: calcium, aluminum, manganese, and iron. The amount added is 10-30% of the mass of the plant fiber pulp after addition.

[0006] Step 2: During the papermaking process, the base paper is impregnated in a silicate colloidal impregnating material. The preparation process of the silicate colloidal impregnating material is as follows:

[0007] Step 21: Mix sodium carbonate and / or potassium carbonate powder with silica particles in a specified ratio. When using sodium carbonate, the mass ratio of silica to sodium carbonate should be greater than 1.7; when using potassium carbonate, the mass ratio of silica to potassium carbonate should be greater than 1.3. Calcine the mixture in a kiln at 1400-1600℃ until completely melted.

[0008] Step 22: Cool the melt by water quenching, break it into particles >80 mesh, and send the particles into a high-temperature and high-pressure reactor. Add 10 times the mass of water, heat to 140-160℃ in a sealed environment, maintain saturated steam pressure, and stir continuously until completely dissolved. Cool to room temperature to obtain a dissolved silicate colloidal solution.

[0009] Step 23: Filter the silicate colloidal solution using a 200-mesh filter to remove particles and insoluble matter, then heat and concentrate to a solids concentration of 20-50%, obtaining a silicate colloidal solution with a modulus greater than 3.

[0010] Step 24: Add melamine-formaldehyde resin prepared under weak alkaline conditions to silicate colloidal solution and stir evenly to obtain silicate colloidal impregnating material. Add melamine-formaldehyde resin according to the dry basis resin addition amount being 5-20% of the dry basis silicate mass.

[0011] Step 3: Heat and dry the base paper to cure it, then roll it up to obtain the finished product.

[0012] Furthermore, in step 1 of the method for preparing a silicate-impregnated water-resistant flame-retardant paper, the mineral particles include one or a combination of hematite, pyrolusite, diaspore, apatite, scheelite, barite, fluorite, calcite, and calcium carbonate.

[0013] Furthermore, in step 1 of the method for preparing silicate-impregnated water-washable flame-retardant paper, the preferred mineral particles are calcium carbonate with a particle size of 5-20 μm.

[0014] Furthermore, in step 2 of the method for preparing silicate-impregnated water-resistant flame-retardant paper, the base paper is dried to a dryness greater than 70% before being impregnated in silicate colloidal impregnating material, with an impregnation amount of 5-20 g / m³. 2 .

[0015] Furthermore, in step 24 of the method for preparing silicate-impregnated water-washable flame-retardant paper, the solid content of the melamine-formaldehyde resin solution added is 25-35%, and the silicate colloidal solution and the melamine-formaldehyde resin solution are stirred evenly at 3000-5000 r / m.

[0016] Furthermore, in step 3 of the method for preparing silicate-impregnated water-resistant flame-retardant paper, the base paper is dried and cured by a combination of drying and infrared heat source, and the temperature of the infrared drying section is 140°C.

[0017] The present invention also provides a silicate-impregnated water-washable flame-retardant paper, which is prepared by the aforementioned method for preparing silicate-impregnated water-washable flame-retardant paper.

[0018] The present invention also applies the silicate-impregnated, water-washable, flame-retardant paper described above in the fields of fireproof packaging and fireproof decoration.

[0019] The present invention also provides a silicate colloidal impregnating material, which is prepared according to the preparation process of the silicate colloidal impregnating material.

[0020] The present invention also utilizes a silicate colloidal impregnating material to impregnate plant fiber materials, thereby assisting the plant fiber materials in resisting water washing and flame retardancy.

[0021] The advantages of this invention are:

[0022] This invention involves adding mineral particles to the base paper, impregnating it in a silicate colloidal impregnating material, and finally drying and curing it to obtain a finished water-resistant flame-retardant paper. The silicate colloidal impregnating material used in this invention can fill the pores of the paper, prevent air penetration, and simultaneously coat plant fibers, thus playing a role in isolating combustion. On the one hand, sodium silicate or potassium silicate in the silicate colloid can react with the mineral particles inside the paper to form insoluble silicates that are firmly embedded in the paper, improving the paper's water resistance and ensuring its flame retardancy after washing. On the other hand, the sodium silicate or potassium silicate in the silicate colloid has a modulus higher than 3.0, and reacts with CO2 in the air during the paper drying process to form a dense silica structure that exists inside the paper. This dense silica liquid also improves the paper's water resistance and flame retardancy. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, some simple figures will be drawn below to describe the sample data characterization process in the implementation of the present invention.

[0024] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0026] Example 1

[0027] A method for preparing silicate-impregnated water-washable flame-retardant paper includes:

[0028] Step 1: Add mineral particles to the suspension of plant fiber pulp for papermaking. The plant fiber pulp is prepared by mixing 30% unbleached softwood chemical pulp and 70% chemically processed bamboo pulp, beating to a freeness of 40°SR, to obtain the plant fiber pulp.

[0029] Light calcium carbonate with a D50 particle size of 10μm is added to the pulp, and the mass ratio of pulp to calcium carbonate is 7:3.

[0030] Papermaking: Paper is made using a two-wire paper machine with a basis weight of 80 g / m³. 2 The retention rate of calcium carbonate in the paper is 67%. Calculations show that the amount of calcium carbonate added is 20%, which is the weight ratio of calcium carbonate to paper. After multiple drying cycles, the paper has a dryness of 70%.

[0031] Step 2: During the papermaking process, the base paper is impregnated in a silicate colloidal impregnating material. The preparation process of the silicate colloidal impregnating material is as follows:

[0032] Step 21: Mix sodium carbonate and / or potassium carbonate powder with silica particles in a specified ratio. The silica particles should be >80 mesh. If using sodium carbonate, the mass ratio of silica to sodium carbonate should be higher than 1.7; if using potassium carbonate, the mass ratio should be higher than 1.3. Adjust the material mass ratio so that the modulus of the subsequently generated silicate material is 3.2. Calcine the mixture in a kiln at 1400-1600℃ until completely melted.

[0033] Step 22: Cool the melt by water quenching, crush it into particles >80 mesh, send the particles into a high temperature and high pressure reactor, add 10 times the mass of water, heat to 140-160℃ in a closed environment, maintain saturated steam pressure, and stir continuously at 20 r / m until completely dissolved. Cool to room temperature to obtain a dissolved silicate colloidal solution, the solute components being potassium silicate and / or sodium silicate.

[0034] Step 23: Filter the silicate colloidal solution using a 200-mesh filter to remove particles and insoluble matter, then heat and concentrate to a solids concentration of 30%, obtaining a silicate colloidal solution with a modulus of 3.2.

[0035] Step 24: Add melamine-formaldehyde resin prepared under weak alkaline conditions to silicate colloidal solution and stir evenly. The solid content of melamine-formaldehyde resin solution is 35%, and silicate colloidal impregnating material is obtained. Melamine-formaldehyde resin is added according to the dry basis resin addition amount being 10% of the dry basis silicate mass.

[0036] Step 3: Heat and dry the base paper to cure it, then roll it to obtain the finished product. After the base paper is formed, it undergoes pressing and drying in a drying cylinder until its dryness reaches 70%. It is then impregnated with silicate impregnating material, increasing the paper's basis weight by 12 g / m³. 2 The impregnation amount is 12g / m 2 The impregnated paper enters the drying device and is dried using a combination of drying cylinder and infrared drying. The temperature of the infrared drying section is 140℃, which completes the curing of the impregnating material.

[0037] The chemical reactions that occur during the paper drying process in this invention are as follows:

[0038] CaCO3 + Na2SiO3 → CaSiO3 + Na2CO3

[0039] Calcium carbonate is added to the pulp of paper. The reaction is relatively slow, which converts sodium silicate in silicate impregnating material into calcium silicate. Calcium silicate is insoluble in water, which improves the washability of silicate impregnated paper and ensures the flame retardancy of the paper after washing.

[0040] Furthermore, Na₂OnSiO₂ + CO₂ + mH₂O → Na₂CO₃ + nSiO·mH₂O

[0041] The silicate impregnating material is composed of Na₂OnSiO₂. During the drying process, it reacts with CO₂ in the air at a relatively fast rate, forming a dense silica structure that exists within the paper. This dense silica solution improves the paper's washability and flame retardancy.

[0042] Three comparative examples are used to compare with Example 1 to illustrate the water resistance and flame retardancy of the paper of the present invention.

[0043] Table 1

[0044] Processing steps Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Calcium carbonate addition × √ √ √ Silicate modulus > 3 × × √ √ Adding melamine-formaldehyde resin × × × √

[0045] Other parameters are the same as those in Example 1.

[0046] According to the national standard GB / T14656-2009, the flame retardancy of the four paper examples in Table 1 was evaluated. The paper was washed (i.e., immersed in water) using Test Method A of GB / T14656-2009, and the change in flame retardant properties after washing was evaluated. Test Method B of GB / T14656-2009 did not involve washing. In addition, the limiting oxygen index (OI) of the flame-retardant paper was tested according to the oxygen index (OI) test method under the national standard GB / T2406. The results are shown in Table 2.

[0047] Table 2

[0048]

[0049] *The water washing of the sample, i.e., water immersion, shall be conducted in accordance with Test Method A of GB / T14656-2009. The technical indicators refer to the indicators required by GB / T14656-2009. Materials with an oxygen index higher than 27% are flame retardant, and the higher the oxygen index, the better the flame retardant effect.

[0050] Table 2 shows that with the addition of calcium carbonate and a silicate modulus >3, the addition of melamine-formaldehyde resin shortened the afterflame time and increased the oxygen index, indicating that the flame retardant effect was enhanced. Comparative Example 1, without calcium carbonate and a silicate modulus below 3, showed a significant decrease in flame retardant effect after washing. Comparative Example 2, with calcium carbonate added and a silicate modulus below 3, showed preliminary water-resistant properties. Comparative Example 3, with calcium carbonate added and a silicate modulus greater than 3, exhibited water resistance; washing had minimal impact on its flame retardancy, and the afterflame time, ignition time, char length, and oxygen index all met the required specifications. In Example 1, with calcium carbonate added, a silicate modulus greater than 3, and melamine-formaldehyde resin added, the flame retardant performance was further enhanced; washing had almost no effect on the flame retardant performance, resulting in stronger water-resistant flame retardant properties.

[0051] This demonstrates that the water-resistant flame-retardant paper prepared by the method of the present invention not only meets the technical specifications, but also has a more obvious water-resistant and flame-retardant effect.

[0052] Example 2

[0053] A method for preparing silicate-impregnated water-washable flame-retardant paper includes:

[0054] Step 1: Add mineral particles to the suspension of plant fiber pulp for papermaking. The plant fiber pulp is prepared by mixing 30% bleached softwood chemical pulp and 70% bleached eucalyptus chemical pulp, beating to a freeness of 35°SR, to obtain the plant fiber pulp.

[0055] Barite with a D50 particle size of 10μm is added to the pulp, and the mass ratio of pulp to barite is 7:4.

[0056] Papermaking: Paper is made using a two-wire paper machine with a basis weight of 60 g / m³. 2 The retention rate of barite in the paper is 60%. Through calculation, the amount of barite added is 28.5%, which is the weight ratio of barite to paper. After the paper is dried in multiple batches, the dryness is 70%.

[0057] Step 2: During the papermaking process, the base paper is impregnated in a silicate colloidal impregnating material. The preparation process of the silicate colloidal impregnating material is as follows:

[0058] Step 21: Mix sodium carbonate powder and silica particles in a specified ratio. The silica particles should be >80 mesh. If using sodium carbonate, the mass ratio of silica to sodium carbonate should be higher than 1.7. Adjust the material mass ratio so that the modulus of the subsequently generated silicate material is 3.5. Calcine the mixture in a kiln at 1400-1600℃ until completely melted.

[0059] Step 22: Cool the melt by water quenching, crush it into particles >80 mesh, send the particles into a high temperature and high pressure reactor, add 10 times the mass of water, heat to 140-160℃ in a closed environment, maintain saturated steam pressure, and stir continuously at 20 r / m until completely dissolved. Cool to room temperature to obtain a dissolved silicate colloidal solution, the solute components being potassium silicate and / or sodium silicate.

[0060] Step 23: Filter the silicate colloidal solution using a 200-mesh filter to remove particles and insoluble matter, then heat and concentrate to a solids concentration of 30%, obtaining a silicate colloidal solution with a modulus of 3.5.

[0061] Step 24: Add melamine-formaldehyde resin prepared under weak alkaline conditions to silicate colloidal solution and stir evenly. The solid content of melamine-formaldehyde resin solution is 35%, and silicate colloidal impregnating material is obtained. The amount of melamine-formaldehyde resin added is 20% of the mass of sodium silicate.

[0062] Step 3: Heat and dry the base paper to cure it, then roll it to obtain the finished product. After the base paper is formed, it undergoes pressing and drying in a drying cylinder until its dryness reaches 70%. It is then impregnated with silicate impregnating material, increasing the paper's basis weight by 20 g / m². 2 The impregnation amount is 20g / m 2 The impregnated paper enters the drying device and is dried using a combination of drying cylinder and infrared drying. The temperature of the infrared drying section is 140℃, which completes the curing of the impregnating material.

[0063] Paper washing and flame retardant effect test: According to the test method A of GB / T14656-2009, after washing and drying, the flame retardant paper has an average afterflame time of 0.9s, an average ignition time of 2.2s, an average char length of 15mm, and no dripping phenomenon during the combustion process. According to the oxygen index (OI) test method under GB / T2406 standard, the limiting oxygen index of the flame retardant paper is 34.8%.

[0064] The above are preferred embodiments of the present invention. Within the scope of the technical solution of the present invention, the effects produced by the present invention can be obtained by adjusting the type and amount of reagents according to the actual situation.

[0065] Unless otherwise specified, all reagents used in the method of this invention were purchased or obtained through legitimate channels.

[0066] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing silicate-impregnated water-washable flame-retardant paper, characterized in that: include: Step 1: Add mineral particles to the suspension of plant fiber pulp for papermaking. The mineral particles include one or more of the following mineral particles: calcium, aluminum, manganese, and iron. The amount added is 10-30% of the mass of the plant fiber pulp after addition. Step 2: During the papermaking process, the base paper is impregnated in a silicate colloidal impregnating material. The preparation process of the silicate colloidal impregnating material is as follows: Step 21: Mix sodium carbonate and / or potassium carbonate powder with silica particles in a specified ratio. When using sodium carbonate, the mass ratio of silica to sodium carbonate should be greater than 1.7; when using potassium carbonate, the mass ratio of silica to potassium carbonate should be greater than 1.

3. Calcine the mixture in a kiln at 1400-1600℃ until completely melted. Step 22: Cool the melt by water quenching, break it into particles >80 mesh, and send the particles into a high-temperature and high-pressure reactor. Add 10 times the mass of water, heat to 140-160℃ in a sealed environment, maintain saturated steam pressure, and stir continuously until completely dissolved. Cool to room temperature to obtain a dissolved silicate colloidal solution. Step 23: Filter the silicate colloidal solution using a 200-mesh filter to remove particles and insoluble matter, then heat and concentrate to a solids concentration of 20-50%, obtaining a silicate colloidal solution with a modulus greater than 3. Step 24: Add melamine-formaldehyde resin prepared under weak alkaline conditions to silicate colloidal solution and stir evenly to obtain silicate colloidal impregnating material. Add melamine-formaldehyde resin according to the dry basis resin addition amount being 5-20% of the dry basis silicate mass. Step 3: Heat and dry the base paper to cure it, then roll it up to obtain the finished product.

2. The method for preparing silicate-impregnated water-washable flame-retardant paper according to claim 1, characterized in that: The mineral particles in step 1 include one or more of the following: hematite, pyrolusite, diaspore, apatite, scheelite, barite, fluorite, calcite, and calcium carbonate.

3. The method for preparing silicate-impregnated water-washable flame-retardant paper according to claim 2, characterized in that: In step 1, the preferred mineral particles are calcium carbonate with a particle size of 5-20 μm.

4. The method for preparing silicate-impregnated water-resistant flame-retardant paper according to claim 1, characterized in that in step 2, the base paper is dried to a dryness of greater than 70% before being impregnated in silicate colloidal impregnating material, with an impregnation amount of 5-20 g / m³. 2 .

5. The method for preparing silicate-impregnated water-washable flame-retardant paper according to claim 1, characterized in that: The solid content of the melamine-formaldehyde resin solution added in step 24 is 25-35%. The silicate colloidal solution and the melamine-formaldehyde resin solution are stirred evenly at 3000-5000 r / m.

6. The method for preparing silicate-impregnated water-resistant flame-retardant paper according to claim 1, characterized in that the base paper is dried and cured in step 3 by a combination of drying and infrared heat source, and the temperature of the infrared drying section is 140°C.

7. A silicate-impregnated, water-washable, flame-retardant paper, characterized in that... It is prepared using the method for preparing silicate impregnated water-washable flame-retardant paper according to any one of claims 1-6.

8. The application of the silicate-impregnated, water-washable, flame-retardant paper as described in claim 7 in the fields of fire-resistant packaging and fire-resistant decoration.

9. A silicate colloidal impregnating material, characterized in that... The silicate colloidal impregnating material is prepared according to the preparation process described in claim 1.

10. Impregnating plant fiber materials with the silicate colloidal impregnating material according to claim 9 to assist the plant fiber materials in water resistance and flame retardancy.

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