Intrinsic flame-retardant high-transmittance PMMA (polymethyl methacrylate) film and preparation method thereof

Abstract

The invention discloses an intrinsic flame-retardant high-transmittance PMMA film and a preparation method thereof.The film comprises a first blending layer, a second blending layer and an organic silicon light diffusion layer, the flame retardant property of the film reaches V1 or above, almost no smoke is generated during combustion, the first blending layer and the second blending layer comprise matrix resin A, matrix resin B, modified resin A, an antioxidant and a flame retardant respectively, and the organic silicon light diffusion layer is formed by compounding an organic silicon light diffusion layer and an organic silicon light diffusion layer. The organic silicon light diffusion layer comprises matrix resins A and B, an organic silicon light diffusion agent, a lubricant and a flame retardant, the main component of the organic silicon light diffusion agent is a phosphazene compound with double bonds, and the preparation method comprises the following steps: S1, respectively adding raw materials of the first blending layer, the second blending layer and the organic silicon light diffusion layer into a double-screw extruder to prepare granules; s2, melting the granules, and feeding the melted granules into a three-layer co-extrusion film blowing machine to prepare a three-layer film blank; and S3, preparing the PMMA film. According to the invention, a double-bond phosphazene compound is adopted as the flame retardant, and reacts with PMMA in the film preparation process to generate stable chemical bonds, so that performance reduction caused by precipitation of the flame retardant in the storage and use processes of the film is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of PET films, and in particular to an intrinsic flame-retardant and highly transparent PMMA film and a preparation method thereof. Background Art

[0002] Polymethyl methacrylate (PMMA) films offer excellent UV resistance and weather resistance. Existing efforts to improve the flame retardancy of PMMA films primarily rely on adding powdered flame retardants to the PMMA material. While this approach can address the flame retardancy issue, it can easily increase the film's haze and prevent transparency. Furthermore, while powdered flame retardants can be evenly distributed within the film through blending and other methods to achieve a good flame retardant effect, they tend to leach out over time, weakening the film's flame retardant effectiveness and reducing the product's service life. Summary of the Invention

[0003] In response to the above-mentioned shortcomings, the present invention proposes an intrinsically flame-retardant and highly permeable PMMA film and a preparation method thereof. A phosphazene compound with a double bond is used as a flame retardant, which can react with PMMA to form a stable chemical bond during the film preparation process, thereby preventing the performance degradation caused by the precipitation of the flame retardant during the storage and use of the film.

[0004] To achieve the above object, the present invention provides the following technical solution: an intrinsic flame retardant and highly transparent PMMA film, comprising a first blending layer, an organic silicon light diffusion layer, and a second blending layer stacked in sequence; The light transmittance of the film is above 85%, the haze is above 90%, the flame retardancy reaches V1 and above, and it burns almost without smoke; The first blended layer and the second blended layer respectively comprise the following raw material components in weight percentage: Base resin A 50-65%; Base resin B 20%-30%; Modified resin A 5%-10%; Additive A 2%-5%; Additive C 3%-10%, The silicone light diffusion layer contains the following raw material components: Base resin A 50-60%; Base resin B 30%-45%; Silicone light diffuser 0.5-2%; Additive B 2%-5%, The auxiliary agent A is an antioxidant, the auxiliary agent B is a lubricant, and the auxiliary agent C is a flame retardant. The main component of the flame retardant is a phosphazene compound with a double bond.

[0005] As an improvement, the matrix resin A is polymethyl methacrylate polymer, and the molecular weight of the polymethyl methacrylate polymer is 5W-10W.

[0006] As an improvement, the matrix resin B is a polymer of methyl methacrylate and alkyl acrylate, the content of methyl methacrylate is not less than 95%wt, and the carbon chain length of the alkyl acrylate is 2-4.

[0007] As an improvement, the modified resin A is an acrylic core-shell modifier, the core layer component of the acrylic core-shell modifier is a methyl methacrylate / alkyl acrylate copolymer, and the carbon chain length of the alkyl acrylate is 2-4.

[0008] As an improvement, the shell modifier is a methyl methacrylate / styrene / alkyl acrylate copolymer, and the carbon chain length of the alkyl acrylate is 2-12.

[0009] As an improvement, the antioxidant component is one of hindered phenols, phosphites or thiols.

[0010] As an improvement, the organosilicon light diffuser is nano-silica microspheres, and the particle size of the nano-silica microspheres is 5-40 nm.

[0011] As an improvement, the lubricant is composed of hydrocarbons or silicones.

[0012] A method for preparing an intrinsically flame-retardant and highly transparent PMMA film comprises the following steps: S1: adding the raw materials of the first blending layer, the silicone light diffusion layer and the second blending layer to a twin-screw extruder after measurement, and extruding and granulating to obtain pellets; S2: After the pellets are melted, they are fed into a three-layer co-extrusion film blowing machine to prepare a three-layer film blank; S3: The three-layer film ingredients are formed into a PMMA film by a biaxial film drawing machine.

[0013] Compared with the prior art, the advantages of the present invention are: (1) Using a phosphazene compound with a double bond as a flame retardant, it can react with PMMA to form a stable chemical bond during the film preparation process, thereby preventing the film from precipitating out the flame retardant during storage and use, causing performance degradation. The film's flame retardancy reaches V1 and above, and it burns almost smokeless. This not only improves product safety, but also meets modern environmental protection requirements, reducing fire risks and environmental pollution. (2) A twin-screw extruder is used for granulation, a three-layer co-extrusion film blowing machine is used to prepare the film blank, and then a bidirectional film stretching machine is used to form the film. This preparation method not only simplifies the production process, but also improves production efficiency and product quality; (3) The selection of matrix resin A (polymethyl methacrylate polymer) and matrix resin B (methyl methacrylate and alkyl acrylate oligomer) ensures the basic performance and stability of the film. The introduction of acrylic core-shell modifier in modified resin A further enhances the mechanical properties and processing properties of the film. (4) The light transmittance of the film reaches over 85%, ensuring good light transmittance and suitable for various applications requiring high transparency. At the same time, the haze is over 90%, which can effectively scatter light and provide a soft and uniform lighting effect. DETAILED DESCRIPTION

[0014] An intrinsically flame-retardant and highly transparent PMMA film comprises a first blending layer, an organic silicon light diffusion layer, and a second blending layer stacked in sequence; The light transmittance of the film is above 85%, the haze is above 90%, the flame retardancy reaches V1 and above, and it burns almost without smoke; The first blended layer and the second blended layer respectively comprise the following raw material components in weight percentage: Base resin A 50-65%; Base resin B 20%-30%; Modified resin A 5%-10%; Additive A 2%-5%; Additive C 3%-10%, The silicone light diffusion layer contains the following raw material components: Base resin A 50-60%; Base resin B 30%-45%; Silicone light diffuser 0.5-2%; Additive B 2%-5%, The auxiliary agent A is an antioxidant, the auxiliary agent B is a lubricant, and the auxiliary agent C is a flame retardant. The main component of the flame retardant is a phosphazene compound with a double bond.

[0015] The matrix resin A is a polymethyl methacrylate polymer, and the molecular weight of the polymethyl methacrylate polymer is 5W-10W.

[0016] The matrix resin B is a polymer of methyl methacrylate and alkyl acrylate, the content of methyl methacrylate is not less than 95% by weight, and the carbon chain length of the alkyl acrylate is 2-4.

[0017] The modified resin A is an acrylic core-shell modifier, the core layer component of the acrylic core-shell modifier is a methyl methacrylate / alkyl acrylate copolymer, and the carbon chain length of the alkyl acrylate is 2-4.

[0018] The shell modifier is a copolymer of methyl methacrylate / styrene / alkyl acrylate, and the carbon chain length of the alkyl acrylate is 2-12.

[0019] The antioxidant component is one of hindered phenols, phosphites or thiols. Preferably, the antioxidant component is one of 168, DSTP, 1010, CA or 1076.

[0020] The organosilicon light diffuser is nano-silica microspheres, and the particle size of the nano-silica microspheres is 5-40 nm. Preferably, the particle size of the nano-silica microspheres is 10-25 nm.

[0021] The lubricant is composed of hydrocarbons or silicones. Preferably, the lubricant is high-boiling point paraffin or microcrystalline paraffin.

[0022] Example 1 As shown in Table 1, a method for preparing an intrinsically flame-retardant and highly transparent PMMA film comprises the following steps: S1.1: Preparation of first blended layer pellets. The first blended layer comprises the following raw material components: 55% PMMA, 25% methyl methacrylate and ethyl acrylate copolymer, 8% core-shell modifier comprising a core layer of methyl methacrylate and ethyl acrylate copolymer and a shell layer of methyl methacrylate and butyl acrylate copolymer, 3% 168, and 10% phosphazene compound. The raw materials are added to a twin-screw extruder according to the composition and extruded into pellets to produce the first pellets. S1.2: Preparation of organic silicon light diffusion layer pellets. The organic silicon light diffusion layer comprises the following raw material components: 52% PMMA, 43% methyl methacrylate and ethyl acrylate copolymer B, 1% nano-silica microspheres, and 4% paraffin wax. The raw materials are added to a twin-screw extruder according to the composition and extruded into pellets to produce a second pellet. S1.3: Preparation of pellets for the second blended layer. The second blended layer comprises the following raw material components: 60% PMMA, 24% copolymer of methyl methacrylate and ethyl acrylate, 7% core-shell modifier comprising a copolymer of methyl methacrylate and ethyl acrylate as a core layer and a copolymer of methyl methacrylate and butyl acrylate as a shell layer, 2% DSTP, and 9% phosphazene compound. The raw materials are added to a twin-screw extruder according to the composition and extruded and pelletized to produce a third pellet. S2: The first, second, and third pellets obtained by extrusion granulation are added to the corresponding feed ports of a film blowing machine in a ratio of 1:3:1, heated and melted at 195°C, and the die head temperature is controlled at 180°C for film blowing with a blowing ratio of 3:1 to obtain a three-layer film blank; S3: The three-layer film blank is subjected to a biaxial stretching process to obtain a PMMA film.

[0023] The thickness of the film prepared in the present invention is measured using the GB / T 6672-2001 method, the transmittance and haze are measured using the GB / T 2410-2008 method, and the flame retardant property is measured using the GBT 2408-2021 method. The measurement shows that the film prepared in Example 1 has a thickness of 190 μm, a transmittance of 85%, a haze of 90%, and a flame retardant property of V0.

[0024] Example 2 As shown in Table 1, a method for preparing an intrinsically flame-retardant and highly transparent PMMA film comprises the following steps: S1.1: Preparation of first blended layer pellets. The first blended layer comprises the following raw material components: 60% PMMA, 28% copolymer of methyl methacrylate and propyl acrylate, 7% core-shell modifier comprising a copolymer of methyl methacrylate and ethyl acrylate as a core layer and a copolymer of methyl methacrylate and butyl acrylate as a shell layer, 4% 168, and 8% phosphazene compound. The raw materials are added to a twin-screw extruder according to the composition and extruded into pellets to produce the first pellets. S1.2: Preparation of organic silicon light diffusion layer pellets. The organic silicon light diffusion layer comprises the following raw material components: 55% PMMA, 40% methyl methacrylate and ethyl acrylate copolymer, 1.5% nano-silica microspheres, and 3.5% W microcrystalline wax. The raw materials are added to a twin-screw extruder according to the composition and extruded into pellets to produce a second pellet. S1.3: Preparation of pellets for the second blended layer. The second blended layer comprises the following raw material components: 58% PMMA, 26% methyl methacrylate and ethyl acrylate copolymer, 6% core-shell modifier comprising a core layer of methyl methacrylate and ethyl acrylate copolymer and a shell layer of methyl methacrylate and butyl acrylate copolymer, 3% 168, and 10% phosphazene compound. The raw materials are added to a twin-screw extruder according to the composition and extruded into pellets to produce a third pellet. S2: The first, second, and third pellets obtained by extrusion granulation are added to the corresponding feed ports of the film blowing machine in a ratio of 1:3:1, heated and melted at 200°C, and the die head temperature is controlled at 185°C for film blowing with a blow-up ratio of 3.2:1 to obtain a three-layer film blank; S3: The three-layer film blank is subjected to a biaxial stretching process to obtain a PMMA film.

[0025] The thickness of the film prepared in the present invention is measured using the GB / T 6672-2001 method, the transmittance and haze are measured using the GB / T 2410-2008 method, and the flame retardant property is measured using the GBT 2408-2021 method. The measurement shows that the film prepared in Example 1 has a thickness of 120 μm, a transmittance of 85%, a haze of 92%, and a flame retardant property of V0.

[0026] Example 3 As shown in Table 1, a method for preparing an intrinsically flame-retardant and highly transparent PMMA film comprises the following steps: S1.1: Preparation of first blended layer pellets. The first blended layer comprises the following raw material components: 50% PMMA, 30% copolymer of methyl methacrylate and butyl acrylate, 9% core-shell modifier comprising a copolymer of methyl methacrylate and ethyl acrylate as a core layer and a copolymer of methyl methacrylate and butyl acrylate as a shell layer, 2.5% 1076, and 7.5% phosphazene. The raw materials are added to a twin-screw extruder according to the composition and extruded into pellets to produce the first pellets. S1.2: Preparation of organic silicon light diffusion layer pellets. The organic silicon light diffusion layer comprises the following raw material components: 50% PMMA, 45% methyl methacrylate and butyl acrylate copolymer, 2% nano-silica microspheres, and 3% paraffin wax. The raw materials are added to a twin-screw extruder according to the composition and extruded into pellets to produce a second pellet. S1.3: Preparation of pellets for the second blended layer. The second blended layer comprises the following raw material components: 62% PMMA, 22% copolymer of methyl methacrylate and butyl acrylate, 5% core-shell modifier comprising a copolymer of methyl methacrylate and ethyl acrylate as the core layer and a copolymer of methyl methacrylate and butyl acrylate as the shell layer, 4% 1076, and 8% phosphazene. These raw materials are added to a twin-screw extruder according to their composition and extruded and pelletized to produce a third pellet. S2: The first, second, and third pellets obtained by extrusion granulation are added to the corresponding feed ports of a film blowing machine in a ratio of 1:3:1, heated and melted at 205°C, and the die head temperature is controlled at 190°C for film blowing with a blow-up ratio of 3.5:1 to obtain a three-layer film blank; S3: The three-layer film blank is subjected to a biaxial stretching process to obtain a PMMA film.

[0027] The thickness of the film prepared in the present invention is measured using the GB / T 6672-2001 method, the transmittance and haze are measured using the GB / T 2410-2008 method, and the flame retardant property is measured using the GBT 2408-2021 method. The measurement shows that the film prepared in Example 1 has a thickness of 80 μm, a transmittance of 90%, a haze of 95%, and a flame retardant property of V0.

[0028] Example 4 As shown in Table 1, a method for preparing an intrinsically flame-retardant and highly transparent PMMA film comprises the following steps: S1.1: Preparation of first blended layer pellets. The first blended layer comprises the following raw material components: 63% PMMA, 27% methyl methacrylate and butyl acrylate copolymer, 6% core-shell modifier comprising a core layer of methyl methacrylate and ethyl acrylate copolymer and a shell layer of methyl methacrylate and butyl acrylate copolymer, 3.5% 168, and 9.5% phosphazene compound. The raw materials are added to a twin-screw extruder according to the composition and extruded into pellets to produce the first pellets. S1.2: Preparation of organic silicon light diffusion layer pellets. The organic silicon light diffusion layer comprises the following raw material components: 58% PMMA, 37% methyl methacrylate and butyl acrylate copolymer, 1% nano-silica microspheres, and 4% microcrystalline wax. The raw materials are added to a twin-screw extruder according to the composition and extruded into pellets to produce a second pellet. S1.3: Preparation of pellets for the second blended layer. The second blended layer comprises the following raw material components: 59% PMMA, 29% copolymer of methyl methacrylate and dodecyl propylene ester, 8% core-shell modifier comprising a copolymer of methyl methacrylate and ethyl acrylate as the core layer and a copolymer of methyl methacrylate and butyl acrylate as the shell layer, 2% 1076, and 7% phosphazene. These raw materials are added to a twin-screw extruder according to their composition and extruded into pellets to produce a third pellet. S2: The first, second, and third pellets obtained by extrusion granulation are added to the corresponding feed ports of a film blowing machine in a ratio of 1:3:1, heated and melted at 210°C, and the die head temperature is controlled at 195°C for film blowing with a blow-up ratio of 3.8:1 to obtain a three-layer film blank; S3: The three-layer film blank is subjected to a biaxial stretching process to obtain a PMMA film.

[0029] The thickness of the film prepared in the present invention is measured using the GB / T 6672-2001 method, the transmittance and haze are measured using the GB / T 2410-2008 method, and the flame retardant property is measured using the GBT 2408-2021 method. The measurement shows that the film prepared in Example 1 has a thickness of 50 μm, a transmittance of 95%, a haze of 95%, and a flame retardant property of V1.

[0030] Table 1 Measurement results of the films obtained from Examples 1 to 4 As shown in Examples 1 to 4, the film prepared by the present invention has a light transmittance of more than 85%, a haze of more than 90%, and a flame retardant performance of V1 or above.

[0031] The above description is merely a description of the preferred embodiment of the present invention and is not to be construed as limiting the scope of the claims. The present invention is not limited to the above embodiment, and variations in the specific structure are permitted. Any variations within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

Claims

1. An intrinsically flame-retardant and highly transparent PMMA film, characterized in that: The invention comprises a first blending layer, an organic silicon light diffusion layer and a second blending layer which are sequentially stacked; The film has a light transmittance of more than 85%, a haze of more than 90%, a flame retardancy of V1 or above, and burns almost smokelessly; In terms of weight percentage, the first blended layer and the second blended layer respectively comprise the following raw material components: Base resin A 50-65%; Base resin B 20%-30%; Modified resin A 5%-10%; Additive A 2%-5%; Additive C 3%-10%, The organic silicon light diffusion layer comprises the following raw material components: Base resin A 50-60%; Base resin B 30%-45%; Silicone light diffuser 0.5-2%; Additive B 2%-5%, The auxiliary agent A is an antioxidant, the auxiliary agent B is a lubricant, and the auxiliary agent C is a flame retardant. The main component of the flame retardant is a phosphazene compound with a double bond.

2. The intrinsic flame retardant and highly transparent PMMA film according to claim 1, characterized in that: The matrix resin A is polymethyl methacrylate polymer, and the molecular weight of the polymethyl methacrylate polymer is 5W-10W.

3. The intrinsic flame retardant and highly transparent PMMA film according to claim 1, characterized in that: The matrix resin B is a polymer of methyl methacrylate and alkyl acrylate, the content of the methyl methacrylate is not less than 95%wt, and the carbon chain length of the alkyl acrylate is 2-4.

4. The intrinsic flame retardant and highly transparent PMMA film according to claim 1, characterized in that: The modified resin A is an acrylic core-shell modifier, the core layer component of the acrylic core-shell modifier is a methyl methacrylate / alkyl acrylate copolymer, and the carbon chain length of the alkyl acrylate is 2-4.

5. The intrinsic flame retardant and highly transparent PMMA film according to claim 1, characterized in that: The shell modifier is a methyl methacrylate / styrene / alkyl acrylate copolymer, and the carbon chain length of the alkyl acrylate is 2-12.

6. The intrinsically flame-retardant and highly transparent PMMA film according to claim 1, characterized in that: The antioxidant component is one of hindered phenols, phosphites or thiols.

7. The intrinsically flame-retardant and highly transparent PMMA film according to claim 1, characterized in that: The organosilicon light diffuser is nano-silicon dioxide microspheres, and the particle size of the nano-silicon dioxide microspheres is 5-40 nm.

8. The intrinsically flame-retardant and highly transparent PMMA film according to claim 1, characterized in that: The lubricant is composed of hydrocarbons or silicones.

9. The method for preparing an intrinsically flame-retardant and highly transparent PMMA film according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: adding the raw materials of the first blending layer, the silicone light diffusion layer and the second blending layer to a twin-screw extruder after measurement, and extruding and granulating to obtain pellets; S2: After the pellets are melted, they are fed into a three-layer co-extrusion film blowing machine to prepare a three-layer film blank; S3: The three-layer film ingredients are formed into a PMMA film by a biaxial film drawing machine.

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