Preparation method of polyvinyl chloride micro-foaming material capable of effectively reducing combustion smoke

Abstract

The invention discloses a preparation method of a polyvinyl chloride micro-foaming material capable of effectively reducing combustion smoke. The preparation method comprises the following steps: firstly, respectively adding expanded perlite, zinc borate and polyethylene wax in different proportions into a ball mill, and processing for 15-25 minutes at the rotating speed of 120-240 revolutions per minute to form composite powder A; and stirring and mixing PVC, calcium powder, a stabilizer, a foaming agent, a foaming regulator, stearic acid and the composite powder A at a high speed, and performing extrusion molding by using a twin-screw extruder to obtain the micro-foamed board. The preparation method of the polyvinyl chloride micro-foaming material is simple, environment-friendly and efficient, the prepared plate is environment-friendly, color-adjustable, high in cost performance and excellent in mechanical property, the amount of smoke formed by combustion is low, and the amount of residual carbon formed by combustion is high and stable.

Description

Technical Field

[0001] The present invention relates to a modification method for reducing smoke generated by the combustion of polymer materials, and in particular to a modification method for effectively reducing smoke generated by the combustion of polyvinyl chloride materials. The modification method is simple, rapid, environmentally friendly, and has high environmental and economic benefits. Background Art

[0002] Most deaths in fires are not caused by high temperatures, but rather by poisoning or oxygen deprivation caused by the release of toxic and harmful gases during combustion. Large amounts of smoke generated during fires, which reduces visibility and makes escape difficult, are also a significant contributing factor. Polymer materials are a significant source of toxic and harmful smoke during fires. Polyvinyl chloride (PVC), one of the three most common polymer plastics, boasts the lowest price and excellent mechanical properties, making it particularly widely used in construction, telecommunications, and decorative fabrics. However, its fire hazard is the highest among the three general-purpose polymers. Analysis of PVC combustion smoke reveals that the gas content of PVC is 69.3%, including significant amounts of hydrogen chloride, carbon dioxide, carbon monoxide, and acetylene, which are the primary sources of white smoke. These gases significantly reduce visibility at the fire scene. PVC combustion also produces a large amount of dense black smoke, typically measured by its maximum specific optical density. A higher maximum specific optical density indicates greater smokiness, resulting in denser black smoke and greater environmental pollution. The maximum specific optical density of PVC is as high as 720 dm, while that of polypropylene is only 41 dm, and that of PE is less than 40 dm (low-density polyethylene is 13 dm, and high-density polyethylene is 39 dm). Therefore, effectively reducing the smoke produced by PVC combustion is particularly important for fire escape.

[0003] The dense black smoke produced during polymer combustion primarily stems from the following: 1. Polymers with polyolefin structures or benzene rings in their side chains. The carbon chains of polyolefins can undergo cyclization and polycondensation to form graphitized carbon particles. 2. Polymers with benzene rings in their side chains easily generate conjugated double-bonded unsaturated hydrocarbons during combustion, which then undergo cyclization and polycondensation to form carbon, producing black smoke. 3. The removal of small molecule cyclization from polymers (for example, after dehydrochlorination of polyvinyl chloride) can easily form carbonized products that emit large amounts of smoke. During combustion, the flame diffuses, and air convection continuously carries the generated carbonized products into the air, which is the fundamental cause of the high smoke production. Therefore, the key to reducing smoke from PVC combustion is to firmly anchor the generated carbonized products to the surface of the burning material, rather than allowing them to diffuse into the air.

[0004] Adding ferrocene is currently an effective way to reduce smoke production in rigid PVC. This is primarily due to the rapid conversion of ferrocene to α-Fe₂O₃ during the PVC dehydrogenation process, which catalyzes the conversion of the carbonized layer into CO and CO₂, thereby reducing the amount of carbon black formed. However, ferrocene's high price and orange-red color have hindered its application and promotion. Therefore, developing environmentally friendly and non-toxic white or transparent formulations to reduce the combustion smoke concentration of PVC while maintaining the excellent mechanical properties of PVC microfoam is currently a demanding goal for green and safe PVC applications in the construction and communications sectors. Summary of the Invention

[0005] To address the problem of PVC combustion producing large amounts of toxic smoke and black smog, which reduces visibility, this invention proposes a modification method for effectively reducing PVC combustion smog. Expanded perlite (powder) is used as the primary ingredient for smoke reduction. This method utilizes a high content of silica (65-75%) in the expanded perlite, which acts as a flame retardant through a cohesive phase and forms a silica film that prevents the escape of loose carbon layers. The expanded perlite also contains 10% alumina, which absorbs smoke during combustion and melting. Furthermore, the expanded perlite contains a small amount of ferric oxide (0.5-3.5%), which catalyzes the more complete conversion of the ring-shaped carbonized products that cause black smoke into CO and CO₂. However, expanded perlite is highly water-absorbent and has poor compatibility with PVC, prone to agglomeration and precipitation. Therefore, the expanded perlite must be modified to seal its porous structure and reduce water absorption, while also improving its bonding with PVC. In addition, a small amount of zinc borate is added to the system as a synergist. Zinc borate begins to release crystalline water above 300°C. This crystalline water will promote the expansion of perlite, thereby forming an expanded carbon layer, effectively preventing the carbon layer from fragmenting and being peeled off with the airflow; in addition, during the combustion process, zinc borate can combine with chlorine radicals to form boron chloride radicals, inhibiting the free radical reaction of the combustion process.

[0006] The invention prepares the smoke suppression formula by modifying expanded perlite and compounding it with zinc borate, and adopts polyethylene wax to perform surface hydrophobicity and compatibility modification by ball milling, thereby developing an environmentally friendly, efficient and economically valuable smoke suppression formula and process for a polyvinyl chloride micro-foam material system.

[0007] The technical solution adopted by the present invention to solve the technical problem comprises the following steps: Step 1: adding expanded perlite, zinc borate and polyethylene wax in different proportions into a ball mill, and processing at a speed of 120 to 240 rpm for 15 to 25 minutes to form a composite powder A; Step 2: PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A are mixed at high speed and formed into a micro-foamed board by twin-screw extrusion.

[0008] In the step 1, the mass ratio of expanded perlite, zinc borate and polyethylene wax is 100:5:150 to 100:20:180 In the step 2, the mass ratio of PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A is 100:40:2:0.7:1.5:0.8:1 to 100:50:3:1.4:5:1.5:8.

[0009] In the step 2, the twin-screw extrusion temperature is 170-190° C., and the pressure is 20-30 MPa.

[0010] The polyvinyl chloride micro-foam material prepared by the method of the present invention has the following advantages compared with the polyvinyl chloride micro-foam material prepared by the conventional method: the tensile strength is increased by 29%, the impact strength is increased by 35%, the smoke density level is increased by 22%, and the carbon residue rate at 800°C is increased to a maximum of 131% of the original.

[0011] The beneficial effects of the present invention are: (1) The present invention uses expanded perlite, zinc borate and polyethylene wax modified materials, which are widely available, inexpensive, have a white base color (adjustable later), and are environmentally friendly.

[0012] (2) The polyvinyl chloride micro-foam material prepared by the present invention has good mechanical properties and can simultaneously improve the strength and toughness of the material.

[0013] (3) The present invention does not use volatile solvents in the preparation process of the polyvinyl chloride micro-foam material, which is environmentally friendly and efficient.

[0014] (4) The present invention prepares polyvinyl chloride micro-foam materials and effectively reduces the smoke from the combustion of polyvinyl chloride micro-foam materials. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below through specific embodiments, but this should not be construed as limiting the scope of the present invention to the following examples. Various substitutions or modifications made according to common technical knowledge and customary means in the art without departing from the above-mentioned method concept of the present invention are intended to be included within the scope of the present invention.

[0016] The embodiments of the present invention are as follows: Example 1

[0017] The formula and process for effectively reducing the combustion smoke of polyvinyl chloride micro-foam material used in the following examples are as follows: Step 1: Add expanded perlite, zinc borate, and polyethylene wax (the mass ratio of expanded perlite, zinc borate, and polyethylene wax is 100:5:150) into a ball mill, and process at a speed of 120 rpm for 25 minutes to obtain composite powder A; Step 2: PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid, and composite powder A (the mass ratio of PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid, and composite powder A is 100:40:2:0.7:1.5:0.8:1) were mixed at high speed and extruded using a twin-screw extruder at an extrusion temperature of 190°C and a pressure of 30 MPa to form a micro-foamed sheet. This was to prepare the sample for Experimental Example 1.

[0018] Among them, the stabilizer is a calcium-zinc composite stabilizer, purchased from Jinan Junteng Chemical Co., Ltd.; the foaming agent is acrylate ACR (HF-401), purchased from Dongguan Hongfu Zinc Material Co., Ltd.; and the foaming regulator is copolymer acrylate (P-530A), purchased from Mitsubishi Rayon Co., Ltd. of Japan.

[0019] To prepare polyvinyl chloride micro-foam material, PVC, calcium powder, stabilizer, foaming agent, foaming regulator, and stearic acid (the mass ratio of PVC, calcium powder, calcium-zinc composite stabilizer, acrylate ACR, copolymerized polyacrylate P-530A, and stearic acid is 100:40:2:0.7:1.5:0.8) are mixed at high speed and extruded using a twin-screw extruder at a temperature of 190°C and a pressure of 30 MPa to form a micro-foam sheet. This sheet is designated as polyvinyl chloride reference sheet A.

[0020] The mechanical and smoke release data of the polyvinyl chloride micro-foam material prepared according to Example 1 are summarized in Table 1.

[0021] As shown in the table, adding expanded perlite, zinc borate, and polyethylene wax composite powder to the PVC system maintains essentially unchanged tensile strength while increasing impact strength by 15.6%. This demonstrates that the additive not only does not reduce the strength of the PVC microfoam but also helps improve its toughness. Smoke density decreases by 15%, while residual carbon increases by 7%. This is primarily due to the dense expanded carbon layer formed during the PVC combustion process, which effectively prevents fragmentation and subsequent separation with the gas. Example 2

[0022] The formula and process for effectively reducing the combustion smoke of polyvinyl chloride micro-foam material used in the following examples are as follows: Step 1: Add expanded perlite, zinc borate, and polyethylene wax (the mass ratio of expanded perlite, zinc borate, and polyethylene wax is 100:20:180) into a ball mill, and process at a speed of 240 rpm for 15 minutes to obtain composite powder A; Step 2: PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A (the mass ratio of PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A is 100:50:3:1.4:5:1.5:8) are stirred and mixed at high speed, and a twin-screw extruder is used at an extrusion temperature of 170°C and a pressure of 20MPa to form a micro-foamed board.

[0023] Among them, the stabilizer is a calcium-zinc composite stabilizer, purchased from Jinan Junteng Chemical Co., Ltd.; the foaming agent is acrylate ACR (HF-401), purchased from Dongguan Hongfu Zinc Material Co., Ltd.; and the foaming regulator is copolymer acrylate (P-530A), purchased from Mitsubishi Rayon Co., Ltd. of Japan.

[0024] The mechanical and smoke release data of the polyvinyl chloride micro-foam material prepared according to Example 2 are summarized in Table 2.

[0025] As shown in the table, the addition of expanded perlite, zinc borate, and polyethylene wax composite powder to the PVC system increased tensile strength by 29.9% and impact strength by 9.4%, demonstrating that the additives not only do not reduce the strength of the PVC microfoam but also help improve its toughness. Smoke density decreased by 19.4%, and residual carbon content increased by 31.2%. This is primarily due to the formation of a dense expanded carbon layer during PVC combustion, which effectively prevents fragmentation and subsequent separation with the gas. Example 3

[0026] The formula and process for effectively reducing the combustion smoke of polyvinyl chloride micro-foam material used in the following examples are as follows: Step 1: Add expanded perlite, zinc borate, and polyethylene wax (the mass ratio of expanded perlite, zinc borate, and polyethylene wax is 100:15:160) into a ball mill, and process at a speed of 150 rpm for 20 minutes to obtain composite powder A; Step 2: PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A (the mass ratio of PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A is 100:45:2.5:1:3:1:5) are stirred and mixed at high speed, and a twin-screw extruder is used at an extrusion temperature of 180°C and a pressure of 25MPa to form a micro-foamed board.

[0027] Among them, the stabilizer is a calcium-zinc composite stabilizer, purchased from Jinan Junteng Chemical Co., Ltd.; the foaming agent is acrylate ACR (HF-401), purchased from Dongguan Hongfu Zinc Material Co., Ltd.; and the foaming regulator is copolymer acrylate (P-530A), purchased from Mitsubishi Rayon Co., Ltd. of Japan.

[0028] The mechanical and smoke release data of the polyvinyl chloride micro-foam material prepared according to Example 3 are summarized in Table 3.

[0029] As shown in the table, adding expanded perlite, zinc borate, and polyethylene wax composite powder to the PVC system increased tensile strength by 25.3% and impact strength by 11.2%, demonstrating that the additives not only do not reduce the strength of the PVC microfoam material but also help improve its toughness. Smoke density decreased by 22.2%, and residual carbon content increased by 23.7%. This is primarily due to the formation of a dense expanded carbon layer during PVC combustion, which effectively prevents fragmentation and subsequent separation with the gas. Example 4

[0030] The formula and process for effectively reducing the combustion smoke of polyvinyl chloride micro-foam material used in the following examples are as follows: Step 1: Add expanded perlite, zinc borate, and polyethylene wax (the mass ratio of expanded perlite, zinc borate, and polyethylene wax is 100:10:170) into a ball mill, and process at a speed of 200 rpm for 20 minutes to obtain composite powder A; Step 2: PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A (the mass ratio of PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A is 100:48:1.6:0.8:4.5:1.2:6) are stirred and mixed at high speed, and a twin-screw extruder is used at an extrusion temperature of 190°C and a pressure of 30MPa to form a micro-foamed board.

[0031] Among them, the stabilizer is a calcium-zinc composite stabilizer, purchased from Jinan Junteng Chemical Co., Ltd.; the foaming agent is acrylate ACR (HF-401), purchased from Dongguan Hongfu Zinc Material Co., Ltd.; and the foaming regulator is copolymer acrylate (P-530A), purchased from Mitsubishi Rayon Co., Ltd. of Japan.

[0032] The mechanical and smoke release data of the polyvinyl chloride micro-foam material prepared according to Example 4 are summarized in Table 4.

[0033] As shown in the table, adding expanded perlite, zinc borate, and polyethylene wax composite powder to the PVC system increased tensile strength by 12.1% and impact strength by 35.5%, demonstrating that the additives not only do not reduce the strength of the PVC microfoam material but also help improve its toughness. Smoke density decreased by 17.2%, and residual carbon content increased by 25.8%. This is primarily due to the formation of a dense expanded carbon layer during PVC combustion, which effectively prevents fragmentation and subsequent peeling with the gas. Example 5

[0034] The formula and process for effectively reducing the combustion smoke of polyvinyl chloride micro-foam material used in the following examples are as follows: Step 1: Add expanded perlite, zinc borate, and polyethylene wax (the mass ratio of expanded perlite, zinc borate, and polyethylene wax is 100:20:175) into a ball mill, and process at a speed of 220 rpm for 20 minutes to obtain composite powder A; Step 2: PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A (the mass ratio of PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A is 100:50:2.5:1:2.5:1:3) are stirred and mixed at high speed, and a twin-screw extruder is used at an extrusion temperature of 180°C and a pressure of 25MPa to form a micro-foamed board.

[0035] Among them, the stabilizer is a calcium-zinc composite stabilizer, purchased from Jinan Junteng Chemical Co., Ltd.; the foaming agent is acrylate ACR (HF-401), purchased from Dongguan Hongfu Zinc Material Co., Ltd.; and the foaming regulator is copolymer acrylate (P-530A), purchased from Mitsubishi Rayon Co., Ltd. of Japan.

[0036] The mechanical and smoke release data of the polyvinyl chloride micro-foam material prepared according to Example 5 are summarized in Table 5.

[0037] As shown in the table, the addition of expanded perlite, zinc borate, and polyethylene wax composite powder to the PVC system significantly increased tensile strength by 29.2% and impact strength by 6.6%. This demonstrates that the additives not only do not reduce the strength of the PVC microfoam material but also help improve its toughness. Smoke density decreased by 10.8%, while residual carbon content increased by 10.2%. This is primarily due to the formation of a dense expanded carbon layer during PVC combustion, which effectively prevents fragmentation and subsequent separation with the gas.

Claims

1. A method for preparing a polyvinyl chloride micro-foam material that effectively reduces combustion smoke, characterized in that The following steps are involved: Step 1: adding expanded perlite, zinc borate and polyethylene wax in different proportions into a ball mill, and processing at a speed of 120 to 240 rpm for 15 to 25 minutes to form a composite powder A; Step 2: PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A are mixed at high speed and formed into a micro-foamed board by twin-screw extrusion.

2. The method for preparing a polyvinyl chloride micro-foam material that effectively reduces combustion smoke according to claim 1, characterized in that: In the step 1, the mass ratio of expanded perlite, zinc borate and polyethylene wax is 100:5:150 to 100:20:

180. Expanded perlite adopts closed-pore micro-powder structure powder with a particle size of 50-70 mesh. It needs to be dried at 60-90℃ for 3-6 hours before use.

3. The method for preparing a polyvinyl chloride micro-foam material that effectively reduces combustion smoke according to claim 1, characterized in that: In the step 2, the mass ratio of PVC, calcium powder, stabilizer, foaming agent, foaming regulator, stearic acid and composite powder A is 100:40:2:0.7:1.5:0.8:1 to 100:50:3:1.4:5:1.5:

8.

4. The method for preparing a polyvinyl chloride micro-foam material that effectively reduces combustion smoke according to claim 1, characterized in that: In the step 2, the stabilizer is a calcium zinc composite stabilizer The foaming agent is acrylic acid ester ACR The foaming regulator is a copolymerized polyacrylate.

5. The method for preparing a polyvinyl chloride micro-foam material that effectively reduces combustion smoke according to claim 1, characterized in that: In the step 2, the twin-screw extrusion temperature is 170-190° C., the screw speed is 30-50 rpm / min, and the pressure is 20-30 MPa.

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