Interpenetrating network cross-linked polyvinyl chloride foam material and preparation method thereof

Abstract

The invention relates to the technical field of foam materials, in particular to an interpenetrating network cross-linked polyvinyl chloride foam material and a preparation method thereof. Comprising the following components in parts by weight: 60-70 parts of polyvinyl chloride resin, 3-7 parts of dibasic acid ester, 30-40 parts of isocyanate, 5-10 parts of a physical foaming agent, 1.5-3 parts of water, 1-3 parts of a nucleating agent, 0.1-0.3 part of a foam stabilizer, 0.5-1 part of a catalyst, 0-10 parts of hollow glass microspheres and 0.5-5 parts of a processing aid, the physical foaming agent is supercritical gas, and the air pressure is 8.5-15 MPa. The one-step mould pressing supercritical foaming process is adopted, the process is simple, the step that a foaming blank is prefabricated firstly and then cross-linked and foamed in a water area or a steam area in conventional mould pressing chemical foaming can be effectively avoided, the foaming time is short, the yield is large, and the production cost is relatively low.

Description

Technical Field

[0001] This invention relates to the field of foam materials technology, and in particular to an interpenetrating network cross-linked polyvinyl chloride foam material and its preparation method. Background Technology

[0002] Foamed plastics are a type of polymer material formed by dispersing a large number of gas micropores in solid plastic. They are lightweight, heat-insulating, sound-absorbing, and shock-absorbing, and their dielectric properties are superior to those of the matrix resin, making them widely used. Among them, structural foamed plastics are widely used in wind power generation, rail transportation, shipbuilding, aerospace, and building energy conservation due to their excellent properties such as high strength, low water absorption, light weight, corrosion resistance, and electrical insulation.

[0003] Polyvinyl chloride (PVC) foam is a general-purpose foam plastic with excellent properties such as low cost, flame retardancy, and insulation. However, compared with structural foam plastics, PVC foam has the disadvantages of low mechanical strength and poor heat resistance. Structural PVC foam materials are the research direction of PVC foam materials.

[0004] Currently, most of the cross-linked polyvinyl chloride (PVC) structural foams disclosed in patents use maleic anhydride and phthalic anhydride as essential formulation components. They are mainly IPN polymer foam materials composed of polyamide-polyimide-polyvinyl chloride-polyisocyanate-polyurea interpenetrating networks. This material is relatively brittle, and the preparation process mainly consists of two steps: the first step is to prepare a pre-foamed preform through a molding foaming process; the second step is to place the pre-foamed preform in a water bath or steam to expand and obtain the finished foam material. In this step, water needs to penetrate into the pre-foamed preform and react with the isocyanate to release carbon dioxide, achieving the purpose of secondary expansion and curing of the foamed preform. Due to this constraint, the cross-linking and curing time is longer as the thickness of the product increases, generally 4-6 days. A major drawback of this process is its inability to produce continuously, and the overall material preparation process involves two steps, resulting in extremely low production efficiency and significantly increasing the production cost for industrial-scale production. The invention patent CN113061310A, "A Crosslinked Polyvinyl Chloride Structural Foam Material and Its Preparation Method," discloses a method for preparing crosslinked polyvinyl chloride structural foam material using a physical foaming agent. This method includes: melting and mixing polyvinyl chloride resin, modified resin, isocyanate, acid anhydride, nucleating agent, and heat stabilizer to obtain a blank; impregnating the blank in a foaming gas to obtain a foam body; and crosslinking and curing the foam body to obtain the crosslinked polyvinyl chloride structural foam material. This invention employs a novel process route for preparing crosslinked polyvinyl chloride structural foam, allowing for a wide range of adjustable composition and proportions of PVC resin and other raw materials. This invention uses carbon dioxide or nitrogen for foaming, making the PVC foam preparation process safer and more environmentally friendly, and reducing costs. Although this crosslinking foaming uses carbon dioxide or nitrogen, the entire foaming process is still a two-step method. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing interpenetrating network crosslinked polyvinyl chloride foam material by a one-step supercritical foaming process. The method provided by this invention is simple, safe and environmentally friendly, has high production efficiency and low cost, and the foam material obtained has good mechanical properties.

[0006] Inventive Idea

[0007] To achieve the primary technical objective mentioned above, this invention employs a simple process. Instead of using acid anhydrides as a component in the formulation of the interpenetrating network crosslinked polyvinyl chloride (PVC) foam material, a diester acid ester is used. The reaction principle of the components in the PVC mixture during the preparation of the interpenetrating network crosslinked PVC foam material is as follows:

[0008] Polyvinyl chloride resin can decompose when heated, releasing hydrogen chloride gas. The reaction process is shown in equation (1):

[0009]

[0010] The hydrogen chloride gas released in the above process can react with compounds having an epoxy structure to give compounds containing hydroxyl groups:

[0011]

[0012] In addition, diacid esters can decompose upon hydrolysis, releasing diacids and alcohols:

[0013]

[0014] The reaction of a dicarboxylic acid and a diisocyanate yields a polyamide:

[0015]

[0016] The isocyanate then reacts with the hydroxyl-containing compound obtained from the above reaction to give a urethane compound containing isocyanate:

[0017]

[0018] The urea ester obtained in the above reaction reacts with isocyanate to form a network of interconnected polyurea structures, as shown in the following reaction:

[0019]

[0020] To achieve the second objective of the aforementioned technology, safety and environmental protection are paramount. In the formulation of this invention, the dicarboxylic acid ester plays a role in dissolving and plasticizing PVC resin in the early stage of the foaming process. In the later stage, it decomposes and releases dicarboxylic acid anhydrides and alcohols as isocyanate reactants to generate polyamide and polyurea network structures. Therefore, there are no safety and environmental protection issues related to the recovery of organic waste gas. In addition, the supercritical physical foaming process solves the problems of low foaming ratio and toxic, unsafe, and environmentally unfriendly residual chemical foaming agents when using chemical foaming agents.

[0021] To achieve the third objective of the aforementioned technology, this invention offers high production efficiency and low cost. This invention achieves cross-linking and curing within the mold cavity in a single step, eliminating the need for a second step involving cross-linking and curing in water or steam. Therefore, it is a "one-step" process, significantly improving production efficiency compared to contrasting patents, resulting in a shorter process route, lower costs, and the ability to meet the needs of continuous production.

[0022] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0023] An interpenetrating network crosslinked polyvinyl chloride foam material comprises the following components in parts by weight: 60-70 parts polyvinyl chloride resin, 3-7 parts diester, 30-40 parts isocyanate, 5-10 parts physical blowing agent, 1.5-3 parts water, 1-3 parts nucleating agent, 0.1-0.3 parts foam leveling agent, 0.5-1 part catalyst, 0-10 parts hollow glass microspheres, and 0.5-5 parts processing aid. The polyvinyl chloride resin has a relative molecular weight of 60,000-160,000, and the physical blowing agent is a supercritical gas with a pressure of 8.5 MPa-15 MPa.

[0024] The relative molecular weight of the polyvinyl chloride resin ranges from 60,000 to 160,000.

[0025] The diester includes one or more of the following: diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethyl maleate, dibutyl maleate, dioctyl maleate, diisobutyl adipate, dihexyl adipate, dioctyl adipate, diethyl sebate, dibutyl sebate, dioctyl sebate, and dibutyl oxalate.

[0026] The isocyanate includes one or more of polyphenyl polymethylene polyisocyanate, methylene diphenyl diisocyanate, toluene diisocyanate, terephthalic diisocyanate, phenyl dimethylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0027] The physical foaming agent is one or both of supercritical carbon dioxide and supercritical nitrogen.

[0028] The nucleating agent includes one or more of calcium carbonate, silicon dioxide, calcium silicate, montmorillonite, kaolin, and talc.

[0029] The foaming agent includes one or more of silicone oils DC-193, DC-197, and L-580.

[0030] The catalysts include amine catalysts and / or organotin catalysts.

[0031] The amine catalysts include one or more of triethylenediamine, triethanolamine, N,N′-dimethylcyclohexylamine, N,N′,N"-tris(dimethylaminopropyl)-hexahydrotriazine, and triethylenediamine.

[0032] The organotin catalysts include one or more of stannous octoate, dibutyltin dilaurate, and dibutyltin thiolate.

[0033] The processing aids include one or more of the following: heat stabilizers, flame retardants, antioxidants, colorants, and reinforcing agents.

[0034] The heat stabilizer includes one or more of thiol methyltin, phosphite, and epoxidized soybean oil.

[0035] The flame retardant includes one or more of antimony pentoxide, magnesium hydroxide, aluminum hydroxide, zinc borate, and red phosphorus.

[0036] The antioxidants mentioned include one or more of antioxidant 1010, antioxidant DLTP, and antioxidant 264.

[0037] The colorant includes one or more of carbon black, iron oxide, chromium oxide, and phthalocyanine.

[0038] The reinforcing agent includes one of carbon nanotubes, wollastonite whiskers, basic magnesium sulfate whiskers, nylon fibers, and polyester fibers.

[0039] The hollow glass microspheres have a particle size range of 25-95 μm and an actual density of 0.15-0.25 g / cm³. 3 Softening temperature less than or equal to 600℃

[0040] The method for preparing interpenetrating network crosslinked polyvinyl chloride foam material by a one-step supercritical foaming process includes the following steps in sequence:

[0041] 1. Weigh all components except for the physical foaming agent and water according to the composition and weight parts, disperse them at high speed for 5-10 minutes in a high-speed dispersion mixing tank at a speed of 500rpm-1500rpm, and degas to obtain the premix.

[0042] 2. Preheat the molding die to 80-120℃, then measure the premixed material, physical foaming agent and water according to the proportion, and inject them into the mold after instantaneous impact mixing in the mixing head.

[0043] 3. Heat the mold to 160-180℃, heat treat for 15-20 minutes, then cool to 30-40℃ to demold and cure, to obtain interpenetrating network cross-linked polyvinyl chloride foam material.

[0044] The "one-step method" refers to the process of producing interpenetrating network cross-linked polyvinyl chloride foam material in a single step within a mold.

[0045] The degassing is performed under vacuum with a vacuum degree of 0.06-0.08 MPa.

[0046] The mixing head includes one of the following: countercurrent impact type, parallel impact type, and rotary mixing type, and has a self-cleaning function.

[0047] The curing process involves the residual isocyanate in the cross-linked polyvinyl chloride foam material that has not been completely consumed by water reacting with water in the air for 1-2 days after contact with the external environment, eventually curing and shaping it to achieve maximum hardness and strength.

[0048] Beneficial effects

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The present invention adopts a one-step supercritical foaming molding process, which is simple and can effectively avoid the two-step production process of conventional chemical foaming, which involves first pre-forming the foamed preform and then cross-linking and foaming in water or steam. This process is characterized by low production efficiency, high cost, and is not conducive to large-scale production. Molding foaming uses a large-sized mold cavity, and at the same time, the foaming time is short, generally only 15-20 minutes, which is sufficient for cooling and demolding. The output is large, the actual production efficiency of foaming is improved and increased, the production cost is relatively low, and it is very easy to scale up industrial production in the later stage.

[0051] (2) Conventional chemical cross-linking PVC foaming uses expensive chemical foaming agents and leaves residues that are not environmentally friendly. This invention uses supercritical physical foaming, which uses inexpensive physical foaming agents that leave no residues and have no impact on the environment, making it safer and more environmentally friendly.

[0052] (3) By adding inorganic hollow glass microspheres and reinforcing materials, the material has excellent mechanical properties. Attached Figure Description

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, and the above advantages of the present invention will become clearer.

[0054] Figure 1 Electron microscope image of Embodiment 1 of the present invention

[0055] Figure 2 Electron microscope image of Comparative Example 1 of this invention

[0056] Figure 3This invention provides a one-step supercritical foaming process for preparing interpenetrating network crosslinked polyvinyl chloride foam material, as described in Example 1 of this invention. Detailed Implementation

[0057] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0058] In the following embodiments, the gas ratio is a pressure ratio.

[0059] Example 1

[0060] An interpenetrating network crosslinked polyvinyl chloride foam material is composed of 70 parts by weight of polyvinyl chloride paste resin with a degree of polymerization of 1650, 7 parts by weight of dioctyl phthalate, 40 parts by weight of polyphenylene polymethylene polyisocyanate, 10 parts by weight of 8.5 MPa carbon dioxide, 3 parts by weight of water, 1 part by weight of calcium silicate, 0.1 parts by weight of silicone oil DC-193, 0.5 parts by weight of stannous octoate, and 0.5 parts by weight of epoxidized soybean oil.

[0061] Preparation of the above-mentioned interpenetrating network crosslinked polyvinyl chloride foam material: According to the weight requirements, dioctyl phthalate (DOP), polyphenylene polymethylene polyisocyanate (PAPI), silicone oil DC-193, stannous octoate, and epoxidized soybean oil are first stirred at 500 rpm for 5 minutes. Then, calcium silicate is added and mixed, stirred for 10 minutes, and homogenized for 5 minutes. Finally, polyvinyl chloride paste resin is added and stirred for 10 minutes. After the above components are mixed evenly, the mixture is degassed under vacuum at 0.08 MPa for 10 minutes to obtain a premix. Then, the mold is preheated to 80°C, and the premix, carbon dioxide, and water are added under high pressure and metered. The three raw materials are mixed by high-speed impact through a mixing head and then injected into the mold. The mold is then heated to 170°C, molded at 17 MPa, and heat-treated for 20 minutes. Finally, it is cooled to 30°C, demolded, and cured to obtain interpenetrating network crosslinked polyvinyl chloride foam.

[0062] Comparative Example 1

[0063] It consists of 100 parts by weight of polyvinyl chloride paste, 18 parts by weight of methyl hexahydrophthalic anhydride, 4 parts by weight of epoxy resin, 54 parts by weight of polyphenyl polymethylene polyisocyanate (PAPI), and 8 parts by weight of azobisisobutyronitrile.

[0064] Preparation of the above-mentioned cross-linked polyvinyl chloride foam material: According to the weight requirements, methyl hexahydrophthalic anhydride, epoxy resin, and polyphenylene polymethylene polyisocyanate (PAPI) are first stirred for 5 minutes. Then, azobisisobutyronitrile (AIBN) is added and mixed for 10 minutes, followed by homogenization for 5 minutes. Finally, polyvinyl chloride paste resin is added and stirred for 15 minutes. After the above components are mixed evenly, vacuum degassing is performed for 15-17 minutes. Then, the mixture is poured into a mold, preheated at 70°C for 25 minutes, then pressurized to 13 MPa, heated to 170°C, and molded for 300 seconds. Finally, the mold is opened after cooling to 30°C to obtain a preform block. Then, secondary foaming and curing are carried out in a constant temperature and humidity chamber. The secondary foaming temperature is 89°C, and the curing temperature is 60°C to obtain an interpenetrating network cross-linked polyvinyl chloride foam material.

[0065] Example 2

[0066] The interpenetrating network crosslinked polyvinyl chloride foam material is composed of 60 parts by weight of polyvinyl chloride paste resin with a degree of polymerization of 1250, 5 parts by weight of dibutyl phthalate, 15 parts by weight of polyphenylene polymethylene polyisocyanate (PAPI), 15 parts by weight of toluene diisocyanate (TDI), 5 parts by weight of 10 MPa carbon dioxide, 1.5 parts by weight of water, 1 part by weight of silica, 0.1 parts by weight of silicone oil DC-197, 1 part by weight of dibutyltin dilaurate, and 0.5 parts by weight of epoxidized soybean oil.

[0067] Preparation of the above-mentioned interpenetrating network crosslinked polyvinyl chloride foam material: According to the weight requirements, dibutyl phthalate (DBP), polyphenylene polyisocyanate (PAPI), toluene diisocyanate (TDI), silicone oil DC-197, dibutyltin dilaurate, and epoxidized soybean oil are first stirred at 750 rpm for 5 minutes. Then, silica is added and mixed, stirred for 10 minutes, and homogenized for 5 minutes. Finally, polyvinyl chloride paste resin is added and stirred for 10 minutes. After the above components are mixed evenly, the mixture is degassed under vacuum at 0.07 MPa for 10 minutes to obtain a premix. The mold is then preheated to 100°C, and the premix, carbon dioxide, and water are added under high pressure and metered. The three raw materials are mixed by high-speed impact through a mixing head and then injected into the mold. The mold is then heated to 165°C, molded at 15 MPa, and heat-treated for 15 minutes. Finally, it is cooled to 35°C, demolded, and cured to obtain the interpenetrating network crosslinked polyvinyl chloride foam material.

[0068] Comparative Example 2

[0069] The cross-linked polyvinyl chloride foam material is composed of 100 parts by weight of polyvinyl chloride paste resin, 10 parts by weight of hexahydrophthalic anhydride, 11 parts by weight of phthalic anhydride, 8 parts by weight of epoxy resin, 30 parts by weight of TDI, 32 parts by weight of PAPI, 8 parts by weight of azobisisobutyronitrile, 2 parts by weight of azodicarbonamide, and 8 parts by weight of montmorillonite.

[0070] Preparation of the above-mentioned cross-linked polyvinyl chloride foam material: According to the weight requirements, hexahydrophthalic anhydride, phthalic anhydride, epoxy resin, TDI and PAPI are first stirred. After stirring for 5 minutes, azobisisobutyronitrile, azodicarbonamide and montmorillonite are added and mixed, stirred for 10 minutes, homogenized for 5 minutes, and finally polyvinyl chloride paste resin is added and stirred for 15 minutes. After the above components are mixed evenly, vacuum degassing is carried out for 15-17 minutes, and then poured into a mold. It is first preheated at 90℃ for 20 minutes, then pressurized to 13MPa, heated to 182℃, and molded for 300 seconds. Finally, it is cooled to 30℃ and then the mold is opened to obtain a preform block. Then, it is subjected to secondary foaming and curing in a constant temperature and humidity chamber. The secondary foaming temperature is 95℃ and the curing temperature is 60℃ to obtain an interpenetrating network cross-linked polyvinyl chloride foam material.

[0071] Example 3

[0072] The interpenetrating network crosslinked polyvinyl chloride foam material is composed of 39 parts by weight of polyvinyl chloride paste resin with a degree of polymerization of 1650, 26 parts by weight of vinyl chloride paste resin with a degree of polymerization of 1250, 3 parts by weight of diethyl phthalate, 24 parts by weight of polyphenylene polymethylene polyisocyanate (PAPI), 16 parts by weight of liquefied MDI, 8 parts by weight of 15 MPa carbon dioxide, 2.5 parts by weight of water, 2 parts by weight of montmorillonite, 0.3 parts by weight of silicone oil L-580, 1 part by weight of triethanolamine, 0.5 parts by weight of epoxidized soybean oil, and 1 part by weight of phosphite.

[0073] Preparation of the above-mentioned interpenetrating network crosslinked polyvinyl chloride foam material: According to the weight requirements, diethyl phthalate, polyphenylene polyisocyanate (PAPI), liquefied MDI, silicone oil L-580, triethanolamine, epoxidized soybean oil, and phosphite are first stirred at 500 rpm for 2 minutes. Montmorillonite is then added and mixed for 10 minutes, followed by homogenization for 5 minutes. Finally, polyvinyl chloride paste resin is added and stirred for 10 minutes. After the components are thoroughly mixed, the mixture is degassed under vacuum at 0.06 MPa for 10 minutes to obtain a premix. The mold is then preheated to 120°C, and the premix, carbon dioxide, and water are added under high pressure and metered. The three raw materials are mixed by high-speed impact through a mixing head and then injected into the mold. The mold is then heated to 160°C, molded at 16 MPa for 20 minutes, and finally cooled to 40°C to open, demold, and cure, yielding the interpenetrating network crosslinked polyvinyl chloride foam material.

[0074] Comparative Example 3

[0075] The cross-linked polyvinyl chloride foam material is composed of 100 parts by weight of polyvinyl chloride paste resin, 9 parts by weight of methyl hexahydrophthalic anhydride, 13 parts by weight of succinic anhydride, 4 parts by weight of epoxy resin, 40 parts by weight of liquefied MDI, 26 parts by weight of PAPI, 7 parts by weight of azobisisobutyronitrile, 3 parts by weight of azodicarbonamide, and 12 parts by weight of montmorillonite.

[0076] Preparation of the above-mentioned cross-linked polyvinyl chloride foam material: According to the weight requirements, methyl hexahydrophthalic anhydride, epoxy resin, liquefied MDI and PAPI are first stirred. After stirring for 5 minutes, succinic anhydride, azobisisobutyronitrile, azodicarbonamide and montmorillonite are added and mixed. The mixture is stirred for 10 minutes and homogenized for 5 minutes. Finally, polyvinyl chloride paste resin is added and stirred for 15 minutes. After the above components are mixed evenly, vacuum degassing is performed for 15-17 minutes. Then, the mixture is poured into a mold, preheated at 90°C for 20 minutes, then pressurized to 14 MPa, heated to 182°C, and molded for 300 seconds. Finally, the mold is opened after cooling to 30°C to obtain a preform block. Then, secondary foaming and curing are carried out in a constant temperature and humidity chamber. The secondary foaming temperature is 97°C and the curing temperature is 60°C to obtain the cross-linked polyvinyl chloride foam material.

[0077] Example 4

[0078] The interpenetrating network cross-linked polyvinyl chloride foam material is composed of 60 parts by weight of polyvinyl chloride paste resin with a degree of polymerization of 1650, 10 parts by weight of polyvinyl chloride resin with a degree of polymerization of 1650 and 2500, 4 parts by weight of diethyl maleate, 24 parts by weight of toluene diisocyanate (TDI), 16 parts by weight of liquefied MDI, 9 parts by weight of 15MPa nitrogen, 3 parts by weight of water, 2 parts by weight of calcium carbonate, 0.3 parts by weight of silicone oil DC-193, 1 part by weight of dibutyltin mercaptan, 1 part by weight of hollow glass microspheres, and 0.5 parts by weight of epoxidized soybean oil.

[0079] Preparation of the above-mentioned interpenetrating network crosslinked polyvinyl chloride foam material: According to the weight requirements, diethyl maleate, toluene diisocyanate (TDI), liquefied MDI, silicone oil DC-193, dibutyltin mercaptan, and epoxidized soybean oil are first stirred at 500 rpm for 2 minutes. Then, calcium carbonate and hollow glass microspheres are added and mixed, stirred for 10 minutes, and homogenized for 5 minutes. Finally, polyvinyl chloride resin is added and stirred for 10 minutes. After the above components are mixed evenly, the mixture is degassed under vacuum at 0.08 MPa for 10 minutes to obtain a premix. Then, the mold is preheated to 110°C, and the premix, nitrogen, and water are added under high pressure and metered. The three raw materials are mixed by high-speed impact through a mixing head and then injected into the mold. The mold is then heated to 168°C, molded at 18 MPa, and heat-treated for 20 minutes. Finally, it is cooled to 35°C, demolded, and cured to obtain the crosslinked polyvinyl chloride foam material.

[0080] Comparative Example 4

[0081] The interpenetrating network crosslinked polyvinyl chloride foam material is composed of 100 parts by weight of polyvinyl chloride resin, 10 parts by weight of polyether polyol (molecular weight 8500), 30 parts by weight of maleic anhydride, 7 parts by weight of bisphenol A epoxy resin, 60 parts by weight of liquefied MDI, 8 parts by weight of dimethyl azobisisobutyrate, 2 parts by weight of azodicarbonamide, 20 parts by weight of methyl methacrylate, and 5 parts by weight of calcium stearate.

[0082] Preparation of the above-mentioned interpenetrating network crosslinked polyvinyl chloride foam material: According to the weight requirements, polyether polyol, bisphenol A epoxy resin, liquefied MDI and methyl methacrylate are first stirred for 5 minutes. Then, maleic anhydride, dimethyl azobisisobutyrate, azodicarbonamide and calcium stearate are added and mixed, stirred for 10 minutes, homogenized for 5 minutes, and finally polyvinyl chloride resin is added and stirred for 15 minutes. After the above components are mixed evenly, vacuum degassing is carried out for 15-17 minutes. Then, the mixture is poured into a mold, preheated at 90°C for 20 minutes, then pressurized to 18 MPa, heated to 175°C, and molded for 300 seconds. Finally, the mold is opened after cooling to 30°C to obtain a preform block. Then, secondary foaming and curing are carried out in a constant temperature and humidity chamber. The secondary foaming temperature is 95°C and the curing temperature is 80°C to obtain the interpenetrating network crosslinked polyvinyl chloride foam material.

[0083] Example 5

[0084] The interpenetrating network crosslinked polyvinyl chloride foam material is composed of 40 parts by weight of polyvinyl chloride resin with a degree of polymerization of 1000, 30 parts by weight of polyvinyl chloride paste resin with a degree of polymerization of 1650, 6 parts by weight of dibutyl maleate, 20 parts by weight of toluene diisocyanate (TDI), 20 parts by weight of polyphenylene polymethylene polyisocyanate (PAPI), 5 parts by weight of nitrogen gas at 8.5 MPa, 5 parts by weight of carbon dioxide, 3 parts by weight of water, 1 part by weight of talc, 0.3 parts by weight of silicone oil DC-193, 1 part by weight of N,N′,N"-tris(dimethylaminopropyl)-hexahydrotriazine, 5 parts by weight of hollow glass microspheres, 0.5 parts by weight of methyl tin mercaptan, and 0.5 parts by weight of epoxidized soybean oil.

[0085] Preparation of the above-mentioned interpenetrating network crosslinked polyvinyl chloride foam material: According to the weight requirements, first, dibutyl maleate, toluene diisocyanate (TDI), polyphenylene polymethylene polyisocyanate (PAPI), silicone oil DC-193, N,N′,N"-tris(dimethylaminopropyl)-hexahydrotriazine, methyltin mercaptan, and epoxidized soybean oil are stirred at 1500 rpm for 2 minutes. Then, talc powder and hollow glass microspheres are added and mixed, stirred for 10 minutes, homogenized for 5 minutes, and finally, polyvinyl chloride is added. Ethylene resin was stirred for 10 minutes to ensure uniform mixing of all components. The mixture was then degassed under vacuum at 0.07 MPa for 10 minutes to obtain a premix. The mold was preheated to 90°C, and then the premix, nitrogen, carbon dioxide, and water were added under high pressure and metered. The three raw materials were mixed by high-speed impact through a mixing head and then injected into the mold. The mold was then heated to 164°C, molded at 20 MPa for 20 minutes, and finally cooled to 36°C to allow for demolding and curing, resulting in an interpenetrating network cross-linked polyvinyl chloride foam material.

[0086] Example 6

[0087] The interpenetrating network crosslinked polyvinyl chloride foam material is composed of 30 parts by weight of polyvinyl chloride paste resin with a degree of polymerization of 1650, 30 parts by weight of polyvinyl chloride paste resin with a degree of polymerization of 1250, 6 parts by weight of dioctyl maleate, 20 parts by weight of toluene diisocyanate (TDI), 20 parts by weight of liquefied MDI, 2.5 parts by weight of nitrogen gas at 10 MPa, 7.5 parts by weight of carbon dioxide, 2 parts by weight of water, 1 part by weight of kaolin, 0.2 parts by weight of silicone oil DC-193, 1 part by weight of N,N′-dimethylcyclohexylamine, 10 parts by weight of hollow glass microspheres, 0.5 parts by weight of stannous octoate, and 0.5 parts by weight of epoxidized soybean oil.

[0088] Preparation of the above-mentioned interpenetrating network crosslinked polyvinyl chloride foam material: According to the weight requirements, dioctyl maleate, toluene diisocyanate (TDI), liquefied MDI, silicone oil DC-193, N,N′-dimethylcyclohexylamine, stannous octanoate, and epoxidized soybean oil are first stirred at 1300 rpm for 2 minutes. Then, kaolin and hollow glass microspheres are added and mixed, stirred for 10 minutes, and homogenized for 5 minutes. Finally, polyvinyl chloride resin is added and stirred for 10 minutes. After the above components are mixed evenly, the mixture is degassed under vacuum at 0.08 MPa for 10 minutes to obtain a premix. The mold is then preheated to 105°C, and the premix, nitrogen, carbon dioxide, and water are added under high pressure and metered. The three raw materials are mixed by high-speed impact through a mixing head and then injected into the mold. The mold is then heated to 165°C, molded at 18 MPa, and heat-treated for 20 minutes. Finally, it is cooled to 40°C, demolded, and cured to obtain the interpenetrating network crosslinked polyvinyl chloride foam material.

[0089] Example 7

[0090] Based on Example 1, the only difference is that the total amount of 10 parts of 8.5 MPa supercritical carbon dioxide is replaced with a total amount of 10 parts of 8.5 MPa supercritical nitrogen and supercritical carbon dioxide composite gas foaming agent, wherein the ratio of supercritical nitrogen to supercritical carbon dioxide is 1:3.

[0091] Example 8

[0092] Based on Example 2, only the total amount of 5 parts of 10MPa supercritical carbon dioxide was changed to a total amount of 5 parts of 10MPa supercritical nitrogen and supercritical carbon dioxide composite gas foaming agent, wherein the ratio of supercritical nitrogen to supercritical carbon dioxide was 1:1.

[0093] Example 9

[0094] Based on Example 3, only the total amount of 8 parts of 15MPa supercritical carbon dioxide was changed to a total amount of 8 parts of 10MPa supercritical nitrogen and supercritical carbon dioxide composite gas foaming agent, wherein the ratio of supercritical nitrogen to supercritical carbon dioxide was 1:3.

[0095] Example 10

[0096] Based on Example 4, the only difference is that the total amount of 9 parts of 15MPa supercritical nitrogen gas is changed to a total amount of 9 parts of 15MPa supercritical nitrogen gas and supercritical carbon dioxide composite gas foaming agent, wherein the ratio of supercritical nitrogen gas and supercritical carbon dioxide gas is 1:2.

[0097] Example 11

[0098] Based on Example 1, one part by weight of antimony pentoxide flame retardant was added to the formulation.

[0099] Example 12

[0100] Based on Example 1, 1 part by weight of antioxidant 1010 was added to the formulation.

[0101] Example 13

[0102] Based on Example 1, 0.1 parts by weight of carbon black colorant was added to the formulation.

[0103] Example 14

[0104] Based on Example 1, 3 parts by weight of reinforcing carbon nanotubes were added to the formulation.

[0105] Example 15

[0106] Based on Example 1, 10 parts by weight of hollow glass microspheres were added to the formulation.

[0107] The PVC foam materials obtained in the above embodiments were tested, and the results are shown in Table 1.

[0108] Table 1

[0109]

[0110] Based on the data in Table 1 and the phenomena observed during the experiment, the following conclusions can be drawn:

[0111] 1. Examples 1-4 are supercritical gas foaming, and Examples 5-10 are two supercritical gas combination foaming. From the comparison of apparent density, it can be concluded that the density of the two supercritical gas combination foaming is relatively lower and the thermal conductivity is relatively smaller than that of the one supercritical gas foaming.

[0112] 2. A comparison of the mechanical properties of the examples and comparative examples shows that, under the same density level, supercritical gas foaming exhibits higher mechanical properties than chemical foaming. This can also be seen from the attached figures. Figure 1-2 Electron microscopy images show that the average particle size of supercritical foam is less than 100 μm, while that of ordinary chemical foaming agents is greater than 500 μm. The finer the pores, the higher the porosity and specific strength of the foam.

[0113] 3. A comparison of the mechanical properties of Examples 4-6, 10, 14 and 15 with that of Example 1 shows that the introduction of hollow glass microspheres and reinforcing materials can improve the mechanical properties of foamed materials, which is more pronounced than in the comparative examples.

[0114] 4. From the comparison of the oxygen index of the examples and comparative examples, it can be concluded that the oxygen index of supercritical gas cross-linked PVC foam material is greater than or equal to 28, which belongs to the B1 grade flame-retardant material, while the oxygen index of ordinary chemical foaming agent cross-linked PVC foam material is less than or equal to 25, which belongs to the B2 grade combustible material.

[0115] This invention provides a "one-step" PVC cross-linked foam material and its preparation method for the field of foam materials. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. An interpenetrating network cross-linked polyvinyl chloride foam material, characterized in that... The product comprises the following components in parts by weight: 60-70 parts polyvinyl chloride resin, 3-7 parts diester, 30-40 parts isocyanate, 5-10 parts physical foaming agent, 1.5-3 parts water, 1-3 parts nucleating agent, 0.1-0.3 parts foam leveling agent, 0.5-1 part catalyst, 0-10 parts hollow glass microspheres, and 0.5-5 parts processing aid. The polyvinyl chloride resin has a relative molecular weight of 60,000-160,000, and the physical foaming agent is a supercritical gas with a pressure of 8.5 MPa-15 MPa.

2. The interpenetrating network cross-linked polyvinyl chloride foam material according to claim 1, characterized in that: The supercritical gas is one or both of supercritical carbon dioxide and supercritical nitrogen.

3. The interpenetrating network cross-linked polyvinyl chloride foam material according to claim 1 or 2, characterized in that: The diester is one or more of diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethyl maleate, dioctyl adipate, dibutyl sebacate, or dibutyl oxalate.

4. The interpenetrating network cross-linked polyvinyl chloride foam material according to claim 1 or 2, characterized in that: The nucleating agent is at least one of calcium carbonate, silicon dioxide, montmorillonite, or talc.

5. The interpenetrating network cross-linked polyvinyl chloride foam material according to claim 1 or 2, characterized in that: The foaming agent is at least one of silicone oils DC-193, DC-197, and L-580.

6. The interpenetrating network cross-linked polyvinyl chloride foam material according to claim 1 or 2, characterized in that: The catalyst is at least one of an amine catalyst and an organotin catalyst, wherein the amine catalyst is triethylenediamine, triethanolamine or triethylenediamine; and the organotin catalyst is selected from stannous octoate or dibutyltin dilaurate.

7. The interpenetrating network cross-linked polyvinyl chloride foam material according to claim 1 or 2, characterized in that: The hollow glass microspheres have a particle size of 25-95 μm and an actual density of 0.15-0.25 g / cm³. 3 Softening temperature ≤600℃.

8. The interpenetrating network cross-linked polyvinyl chloride foam material according to claim 1 or 2, characterized in that: The processing aids include at least one of heat stabilizers, flame retardants, antioxidants, and reinforcing agents, wherein: the heat stabilizer is methyltin mercaptan or epoxidized soybean oil; the flame retardant is aluminum hydroxide, zinc borate, or red phosphorus; and the reinforcing agent is carbon nanotubes or basic magnesium sulfate whiskers.

9. A method for preparing any one of the interpenetrating network cross-linked polyvinyl chloride foam materials according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Weigh all components except physical foaming agent and water according to their composition and weight, disperse them at high speed for 5-10 minutes in a high-speed dispersion mixing tank at a speed of 500 rpm-1500 rpm, and degas to obtain a premix. The degassing is vacuum degassing with a vacuum degree of 0.06-0.08 MPa. Step 2: Preheat the molding die to 80-120℃, then measure the premixed material, physical foaming agent and water according to the proportion, mix them instantly in the mixing head and then inject them into the mold; Step 3: Heat the mold to 160-180℃, heat-treat for 15-20 minutes, then cool to 30-40℃ to demold and cure, to obtain interpenetrating network cross-linked polyvinyl chloride foam material.

10. The method for preparing an interpenetrating network cross-linked polyvinyl chloride foam material according to claim 9, characterized in that: The mixing head mentioned in step 2 is a countercurrent impact type, a parallel impact type, or a rotary mixing type.

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