Environment-friendly flame-retardant polyvinyl alcohol high-temperature film and processing method thereof

Abstract

The invention discloses an environment-friendly flame-retardant polyvinyl alcohol high-temperature film and a processing method thereof, and relates to the technical field of film processing, modified polyvinyl alcohol is prepared in a copolymerization modification mode from the molecular structure of polyvinyl alcohol, good water solubility and biodegradability of the polyvinyl alcohol can be reserved to the maximum extent, and the environment-friendly flame-retardant polyvinyl alcohol high-temperature film has the advantages of being environmentally friendly, good in flame retardance and good in flame retardance. The heat resistance of the polyvinyl alcohol can be remarkably improved, the problem of poor compatibility between the heat stabilizer and the polyvinyl alcohol is solved compared with physical addition of the heat stabilizer, and meanwhile, the comprehensive performance of the polyvinyl alcohol film is improved by adding auxiliaries such as the flame retardant, the plasticizer and the reinforcing agent.

Description

Technical Field

[0001] The invention relates to the technical field of film processing, and in particular to an environmentally friendly flame-retardant polyvinyl alcohol high-temperature film and a processing method thereof. Background Art

[0002] Polyvinyl alcohol (PVA) film has the advantages of good water solubility, high transparency, good gas barrier properties, excellent physical and mechanical properties, good biocompatibility, and biodegradability. It has broad application prospects in packaging materials, reinforced fibers, liquid crystal displays, drug coating materials, medical devices and other fields.

[0003] The temperature resistance of PVA is mainly reflected in its thermal stability and decomposition temperature. PVA softens when heated, and there is no obvious change below 40°C, and the glass transition temperature is 75-85°C. When heated to above 100°C, PVA will slowly change color and become brittle; when heated for a long time above 160°C, it will gradually color, dehydrate and etherify, and lose solubility; when heated to above 220°C, it will decompose to produce water, acetic acid, acetaldehyde and crotonaldehyde; when it exceeds 250°C, it will become a polymer containing conjugated double bonds. Furthermore, the temperature resistance of PVA is also affected by its alcoholysis degree and polymerization degree. PVA with an alcoholysis degree of less than 95% can be dissolved in water at room temperature, while PVA with an alcoholysis degree of more than 99.5% needs to be dissolved in hot water above 95°C. An increase in the degree of polymerization will increase the viscosity of the aqueous solution, and the strength and solvent resistance after film formation will increase, but the solubility in water and the elongation after film formation will decrease. In addition, PVA has poor flame retardancy, and its limiting oxygen index (LOI) is only 19.7%. PVA is composed of C, H, and O elements and is a flammable material. It produces a lot of black smoke when burning, which limits its application in situations where high flame retardancy is required. Therefore, improving the flame retardancy and temperature resistance of PVA film is of great practical significance. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for processing an environmentally friendly flame-retardant polyvinyl alcohol high-temperature film. The obtained polyvinyl alcohol high-temperature film exhibits excellent comprehensive properties (such as physical and mechanical properties, flame retardancy, heat resistance, water solubility, biodegradability, etc.) and can be widely used in multiple technical fields.

[0005] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0006] One of the purposes of the present invention is to provide a method for processing an environmentally friendly flame-retardant polyvinyl alcohol high-temperature film, comprising the following steps:

[0007] (1) in the presence of an initiator, subjecting vinyl acetate and 4-propylenethiosemicarbazide to a free radical polymerization reaction to obtain a copolymer;

[0008] (2) alcoholyzing the copolymer to obtain modified polyvinyl alcohol;

[0009] (3) The modified polyvinyl alcohol and the additive are melt-blended and extruded into granules through a twin-screw extruder, and then blow-molded into a film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film.

[0010] A second object of the present invention is to provide an environmentally friendly flame-retardant polyvinyl alcohol high-temperature film obtained by the aforementioned environmentally friendly flame-retardant polyvinyl alcohol high-temperature film processing method.

[0011] The beneficial effects of the present invention are as follows: starting from the molecular structure of polyvinyl alcohol, the present invention prepares modified polyvinyl alcohol by copolymerization modification, which can not only retain the good water solubility and biodegradability of polyvinyl alcohol to the greatest extent, but also significantly improve the heat resistance of polyvinyl alcohol, and compared with the physical addition of heat stabilizers, the problem of poor compatibility between heat stabilizers and polyvinyl alcohol is solved, and at the same time, the comprehensive performance of the polyvinyl alcohol film is improved by adding additives such as flame retardants, plasticizers, and reinforcing agents. DETAILED DESCRIPTION

[0012] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0013] The present invention provides a method for processing an environmentally friendly flame-retardant polyvinyl alcohol high-temperature film, comprising the following steps:

[0014] (1) in the presence of an initiator, subjecting vinyl acetate and 4-propylenethiosemicarbazide to a free radical polymerization reaction to obtain a copolymer;

[0015] (2) alcoholyzing the copolymer to obtain modified polyvinyl alcohol;

[0016] (3) The modified polyvinyl alcohol and the additive are melt-blended and extruded into granules through a twin-screw extruder, and then blow-molded into a film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film.

[0017] Furthermore, the molar ratio of vinyl acetate to 4-propylene thiosemicarbazide is (5-10):1. In the present invention, an appropriate amount of 4-propylene thiosemicarbazide is added as a comonomer during the synthesis of polyvinyl alcohol, with the purpose of improving the heat resistance of polyvinyl alcohol. 4-propylene thiosemicarbazide has a unique molecular structure, and is used to prepare modified polyvinyl alcohol through free radical polymerization and alcoholysis process with vinyl acetate, and the obtained modified polyvinyl alcohol still has good water solubility.

[0018] Furthermore, the initiator is a commonly used initiator for free radical polymerization reaction well known to those skilled in the art, including but not limited to one or more of peroxide initiators and azo initiators.

[0019] Furthermore, the amount of the initiator used is 0.5-5% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide.

[0020] Furthermore, the alcoholysis uses sodium hydroxide or potassium hydroxide as a catalyst. Methanol is usually used as a solvent, and the catalyst is dissolved in methanol.

[0021] Furthermore, the degree of polymerization of the modified polyvinyl alcohol is 1000-3000, and the degree of alcoholysis is 88-99%.

[0022] Furthermore, the additives are plastic additives well known to those skilled in the art, including but not limited to one or more of flame retardants, plasticizers, reinforcing agents, antioxidants, light stabilizers, antistatic agents, lubricants, and colorants.

[0023] In the present invention, the flame retardant may be a flame retardant known to those skilled in the art, including but not limited to at least one of phosphorus flame retardants, nitrogen flame retardants, silicon flame retardants, and metal hydroxide flame retardants. Flame retardants mainly achieve flame retardant effects by reducing flammability, increasing thermal decomposition temperature, inhibiting flame spread, absorbing heat, and generating non-combustible gas.

[0024] In the present invention, the plasticizer can be a plasticizer well known to those skilled in the art, including but not limited to at least one of phthalate plasticizers, epoxy plasticizers, citrate plasticizers, aliphatic dibasic acid esters, and phosphate plasticizers. Plasticizer molecules can be inserted into polymer molecular chains, weaken intermolecular forces, increase the distance and activity space between polymer molecular chains, increase the plasticity of polymers, and reduce the processing temperature of polymers.

[0025] In the present invention, the reinforcing agent may be an inorganic filler and / or inorganic fiber well known to those skilled in the art, wherein the inorganic filler includes but is not limited to one or more of calcium carbonate, talc, mica powder, silicon dioxide, kaolin, diatomaceous earth, white carbon black, and carbon black; the inorganic fiber includes but is not limited to one or more of carbon fiber, glass fiber, graphite fiber, and ceramic fiber. The purpose of adding a reinforcing agent to polyvinyl alcohol is to improve the physical and mechanical properties, heat resistance, and flame retardancy of the composite material.

[0026] In the present invention, the antioxidant may be an antioxidant known to those skilled in the art, including but not limited to at least one of a phenolic antioxidant and an amine antioxidant. The purpose of adding an antioxidant to polyvinyl alcohol is to delay the oxidation process of the composite material, thereby extending the service life of the composite material.

[0027] In the present invention, the light stabilizer can be a light stabilizer known to those skilled in the art, including but not limited to at least one of benzophenone light stabilizers and benzotriazole light stabilizers. The purpose of adding a light stabilizer to polyvinyl alcohol is to inhibit and delay light aging of the film caused by ultraviolet rays and improve the durability of the film.

[0028] In the present invention, the antistatic agent may be an antistatic agent known to those skilled in the art, including but not limited to one or more of cationic antistatic agents, anionic antistatic agents, nonionic antistatic agents, and amphoteric antistatic agents. The antistatic agent can form a conductive network inside the film to prevent the generation and accumulation of static electricity inside the film, and effectively avoid the problem of film adhesion and dust contamination.

[0029] In the present invention, the lubricant may be a lubricant known to those skilled in the art, including but not limited to one or more of paraffin wax, polyethylene wax, oxidized polyethylene wax, stearamide, calcium stearate, zinc stearate, and ethylene bis stearamide. Lubricants play a role in improving resin fluidity, increasing film gloss, and reducing friction in plastic film processing.

[0030] In the present invention, the colorant may be a colorant well known to those skilled in the art, including natural colorants and synthetic colorants.

[0031] Furthermore, the temperature of the twin-screw extruder is 140-200° C., and the screw speed is 50-300 rpm. The twin-screw extruder drives the material forward by the rotation of the screw in the barrel, thereby achieving efficient mixing and plasticization of the material.

[0032] Furthermore, the temperature of the blow molding machine is 180-200° C., and the screw speed is 50-300 rpm.

[0033] The present invention provides an environmentally friendly flame-retardant polyvinyl alcohol high-temperature film obtained by the aforementioned environmentally friendly flame-retardant polyvinyl alcohol high-temperature film processing method.

[0034] Example 1

[0035] (1) Adding vinyl acetate, 4-propylenethiosemicarbazide and azobisisobutyronitrile to methanol, heating to 75° C. for reaction, and obtaining a copolymer, wherein the molar ratio of vinyl acetate to 4-propylenethiosemicarbazide is 5:1, and the amount of azobisisobutyronitrile is 1% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide.

[0036] (2) adding a methanol solution of sodium hydroxide to the copolymer, wherein the amount of sodium hydroxide used is 10% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide, and alcoholyzing at 60° C. to obtain a modified polyvinyl alcohol having a degree of polymerization of 1800 and an alcoholysis degree of 95%.

[0037] (3) 100 parts of modified polyvinyl alcohol, 5 parts of aluminum hydroxide, 10 parts of tributyl citrate, 10 parts of calcium carbonate, 1 part of antioxidant BHT, and 1 part of polyethylene wax are melt-blended and extruded into granules through a twin-screw extruder, and then blow-molded into a film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film. The temperature of the twin-screw extruder is 140-200°C, the screw speed is 100 rpm; the temperature of the blow molding machine is 180-200°C, and the screw speed is 100 rpm.

[0038] Example 2

[0039] (1) Adding vinyl acetate, 4-propylenethiosemicarbazide and azobisisobutyronitrile to methanol, heating to 75° C. for reaction, and obtaining a copolymer, wherein the molar ratio of vinyl acetate to 4-propylenethiosemicarbazide is 8:1, and the amount of azobisisobutyronitrile is 2% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide.

[0040] (2) adding a methanol solution of potassium hydroxide to the copolymer, wherein the amount of potassium hydroxide used is 10% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide, and alcoholyzing at 65° C. to obtain a modified polyvinyl alcohol having a degree of polymerization of 2200 and an alcoholysis degree of 89%.

[0041] (3) 100 parts of modified polyvinyl alcohol, 10 parts of zinc borate, 12 parts of dioctyl phthalate, 15 parts of mica powder, 1 part of antioxidant 264, and 0.5 parts of stearamide were melt-blended and extruded into granules through a twin-screw extruder, and then blown into a film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film. The temperature of the twin-screw extruder is 140-200°C, the screw speed is 150rpm; the temperature of the blow molding machine is 180-200°C, and the screw speed is 100rpm.

[0042] Example 3

[0043] (1) Adding vinyl acetate, 4-propylenethiosemicarbazide and benzoyl peroxide to methanol, heating to 75° C. for reaction, and obtaining a copolymer, wherein the molar ratio of vinyl acetate to 4-propylenethiosemicarbazide is 10:1, and the amount of benzoyl peroxide is 1.5% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide.

[0044] (2) adding a methanol solution of sodium hydroxide to the copolymer, wherein the amount of sodium hydroxide used is 15% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide, and alcoholyzing at 55° C. to obtain a modified polyvinyl alcohol having a degree of polymerization of 2400 and an alcoholysis degree of 98%.

[0045] (3) 100 parts of modified polyvinyl alcohol, 15 parts of ammonium polyphosphate, 10 parts of epoxy soybean oil, 20 parts of white carbon black, 0.5 parts of antioxidant BHT, 0.5 parts of antioxidant 264, 1 part of polyethylene wax, and 0.5 parts of 2,4-dihydroxybenzophenone were melt-blended and extruded into granules through a twin-screw extruder, and then blow-molded into a film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film. The temperature of the twin-screw extruder is 140-200°C, the screw speed is 100rpm; the temperature of the blow molding machine is 180-200°C, and the screw speed is 150rpm.

[0046] Example 4

[0047] (1) Adding vinyl acetate, 4-propylenethiosemicarbazide and benzoyl peroxide to methanol, heating to 75° C. for reaction, and obtaining a copolymer, wherein the molar ratio of vinyl acetate to 4-propylenethiosemicarbazide is 6:1, and the amount of benzoyl peroxide is 3% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide.

[0048] (2) adding a methanol solution of sodium hydroxide to the copolymer, wherein the amount of sodium hydroxide used is 20% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide, and alcoholyzing at 60° C. to obtain a modified polyvinyl alcohol having a degree of polymerization of 1800 and an alcoholysis degree of 99%.

[0049] (3) 100 parts of modified polyvinyl alcohol, 12 parts of melamine, 15 parts of tributyl citrate, 18 parts of calcium carbonate, 1 part of antioxidant 264, and 0.5 parts of polyethylene wax are melt-blended and extruded into granules through a twin-screw extruder, and then blow-molded into a film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film. The temperature of the twin-screw extruder is 140-200°C, the screw speed is 200 rpm; the temperature of the blow molding machine is 180-200°C, and the screw speed is 100 rpm.

[0050] Example 5

[0051] (1) Add vinyl acetate, 4-propylenethiosemicarbazide and azobisisobutyronitrile to methanol, and heat to 75° C. to react to obtain a copolymer, wherein the molar ratio of vinyl acetate to 4-propylenethiosemicarbazide is 8:1, and the amount of azobisisobutyronitrile is 2.5% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide.

[0052] (2) adding a methanol solution of sodium hydroxide to the copolymer, wherein the amount of sodium hydroxide used is 25% of the total mass of vinyl acetate and 4-propylenethiosemicarbazide, and alcoholyzing at 65° C. to obtain a modified polyvinyl alcohol having a degree of polymerization of 2600 and an alcoholysis degree of 93%.

[0053] (3) 100 parts of modified polyvinyl alcohol, 10 parts of zinc borate, 10 parts of dioctyl phthalate, 10 parts of white carbon black, 0.5 parts of p-phenylenediamine, and 2 parts of calcium stearate are melt-blended and extruded into granules through a twin-screw extruder, and then blow-molded into a film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film. The temperature of the twin-screw extruder is 140-200°C, and the screw speed is 120 rpm; the temperature of the blow molding machine is 180-200°C, and the screw speed is 180 rpm.

[0054] Comparative Example 1

[0055] The method of Example 5 is followed, except that acrylamide is used instead of 4-propenylthiosemicarbazide when preparing the modified polyvinyl alcohol.

[0056] (1) Adding vinyl acetate, acrylamide and azobisisobutyronitrile to methanol, heating to 75° C. for reaction, and obtaining a copolymer, wherein the molar ratio of vinyl acetate to acrylamide is 8:1, and the amount of azobisisobutyronitrile is 2.5% of the total mass of vinyl acetate and acrylamide.

[0057] (2) adding a methanol solution of sodium hydroxide to the copolymer, wherein the amount of sodium hydroxide used is 25% of the total mass of vinyl acetate and acrylamide, and alcoholyzing is carried out at 65° C. to obtain a modified polyvinyl alcohol having a degree of polymerization of 2700 and a degree of alcoholysis of 95%.

[0058] (3) 100 parts of modified polyvinyl alcohol, 10 parts of zinc borate, 10 parts of dioctyl phthalate, 10 parts of white carbon black, 0.5 parts of p-phenylenediamine, and 2 parts of calcium stearate are melt-blended and extruded into granules through a twin-screw extruder, and then blow-molded into a film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film. The temperature of the twin-screw extruder is 140-200°C, and the screw speed is 120 rpm; the temperature of the blow molding machine is 180-200°C, and the screw speed is 180 rpm.

[0059] Comparative Example 2

[0060] The method of Example 5 was followed, except that commercially available polyvinyl alcohol 2699 was used to replace the modified polyvinyl alcohol when preparing the film.

[0061] Polyvinyl alcohol 2699 was melt-blended with 10 parts of zinc borate, 10 parts of dioctyl phthalate, 10 parts of white carbon black, 0.5 parts of p-phenylenediamine and 2 parts of calcium stearate through a twin-screw extruder, extruded into granules, and then blown into film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film. The temperature of the twin-screw extruder was 140-200°C, the screw speed was 120rpm; the temperature of the blow molding machine was 180-200°C, and the screw speed was 180rpm.

[0062] The films prepared in the above examples and comparative examples were tested for heat resistance and flame retardancy. The test results are shown in Table 1.

[0063] The heat deformation temperature of the film was tested according to the standard ASTM D648. The higher the heat deformation temperature, the better the heat resistance.

[0064] The oxygen index of the film is tested according to the standard GB / T 2406.2-2009. The higher the oxygen index, the better the flame retardancy.

[0065] Table 1 Test results of heat resistance and flame retardancy of films

[0066] Heat deformation temperature / ℃ Oxygen index / % Example 1 119 28.7 Example 2 125 29.8 Example 3 123 31.5 Example 4 121 30.9 Example 5 128 30.4 Comparative Example 1 104 29.3 Comparative Example 2 100 28.5

[0067] It can be seen from Table 1 that the modified polyvinyl alcohol prepared by copolymerization modification in the present invention has better heat resistance and can slightly improve the flame retardancy of polyvinyl alcohol.

[0068] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for processing an environmentally friendly flame-retardant polyvinyl alcohol high-temperature film, characterized in that: The following steps are involved: (1) in the presence of an initiator, subjecting vinyl acetate and 4-propylenethiosemicarbazide to a free radical polymerization reaction to obtain a copolymer; (2) alcoholyzing the copolymer to obtain modified polyvinyl alcohol; (3) The modified polyvinyl alcohol and the additive are melt-blended and extruded into granules through a twin-screw extruder, and then blow-molded into a film through a blow molding machine to obtain a polyvinyl alcohol high-temperature film.

2. The method for processing the environmentally friendly flame-retardant polyvinyl alcohol high-temperature film according to claim 1, characterized in that: The molar ratio of vinyl acetate to 4-propylenethiosemicarbazide is (5-10):

1.

3. The method for processing the environmentally friendly flame-retardant polyvinyl alcohol high-temperature film according to claim 1, characterized in that: The initiator is selected from one or more of peroxide initiators and azo initiators.

4. The method for processing the environmentally friendly flame-retardant polyvinyl alcohol high-temperature film according to claim 3, characterized in that: The amount of the initiator used is 0.5-5% of the total mass of vinyl acetate and 4-propylene thiosemicarbazide.

5. The method for processing the environmentally friendly flame-retardant polyvinyl alcohol high-temperature film according to claim 1, characterized in that: The alcoholysis uses sodium hydroxide or potassium hydroxide as a catalyst.

6. The method for processing the environmentally friendly flame-retardant polyvinyl alcohol high-temperature film according to claim 1, characterized in that: The polymerization degree of the modified polyvinyl alcohol is 1000-3000, and the alcoholysis degree is 88-99%.

7. The method for processing the environmentally friendly flame-retardant polyvinyl alcohol high-temperature film according to claim 1, characterized in that: The auxiliary agent is selected from one or more of flame retardants, plasticizers, reinforcing agents, antioxidants, light stabilizers, antistatic agents, lubricants, and colorants.

8. The method for processing the environmentally friendly flame-retardant polyvinyl alcohol high-temperature film according to claim 1, characterized in that: The temperature of the twin-screw extruder is 140-200° C., and the screw speed is 50-300 rpm.

9. The method for processing the environmentally friendly flame-retardant polyvinyl alcohol high-temperature film according to claim 1, characterized in that: The temperature of the blow molding machine is 180-200° C., and the screw speed is 50-300 rpm.

10. An environmentally friendly flame-retardant polyvinyl alcohol high-temperature film obtained by the method for processing an environmentally friendly flame-retardant polyvinyl alcohol high-temperature film according to any one of claims 1 to 9.