A high-strength black polyamide film and its preparation method

Abstract

The present invention discloses a high-strength black polyamide film and a preparation method thereof. First, the surface of carbon fiber is acid-treated in the present invention, and then carbon fiber after acidification and diatomite are modified with chloroacetyl chloride and ethylenediamine respectively, so that the surface of carbon fiber is rich in acyl chloride groups and the surface of diatomite is rich in amino groups. Under the catalytic action of N,N-dimethylformamide, the acyl chloride groups react with the amino groups, so that carbon fiber and diatomite are bonded together through chemical bonds, and black colorant A is prepared. Since diatomite has good dispersibility in polyamide 6, the prepared black colorant solves the problem of product color difference caused by uneven dispersion of carbon fiber in polyamide 6. In addition, carbon fiber can not only make the surface of the synthesized polyamide film smoother, but also effectively improve the mechanical strength of the polyamide film, prevent deformation and damage during subsequent forming and composite operations, and improve the quality of the product.

Description

Technical Field

[0001] The present invention relates to the technical field of polyamide films, and particularly to a high-strength black polyamide film and a preparation method thereof. Background Art

[0002] As an important material for encapsulating soft-packaged lithium battery cells, aluminum-plastic composite films are widely used in fields such as consumer electronics, new energy vehicles, power tools, medical devices, and drones. The aluminum-plastic composite film has extremely high barrier properties of metal aluminum foil and the flexibility of plastic film in its micro-structure. It can be prepared by a composite process, and its structure is polyamide film / aluminum foil / cast polypropylene film. Adhesives are used for composite between the three layers, or the MPP resin between the aluminum foil and the polypropylene film can be modified and then adhered first. The aluminum-plastic composite film generally appears silver. In digital products such as mobile phones, using a black aluminum-plastic film that is the same color as other internal parts can make the overall product beautiful and grand, and gain market favor. Therefore, the demand for black aluminum-plastic composite films is very large.

[0003] Currently, the production process of black aluminum-plastic composite films is to directly coat polyamide films with black ink and then perform composite. However, this method has two defects: ① When the black ink layer coated on the polyamide film is composite with the aluminum foil, it is easily scratched, causing damage to the black film layer, and the presence of the ink layer will affect the composite strength between the polyamide film and the aluminum foil; ② The black aluminum-plastic composite film uses a cold stamping forming process and is finally formed into a shell. During the forming process, the corners are subjected to the stretching effect of forming. When the forming depth is relatively deep, there will be situations such as the stretching black becoming lighter, decolorization, and color disconnection. Therefore, it is very necessary to invent a high-strength black polyamide film. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-strength black polyamide film and a preparation method thereof to solve the problems raised in the above background art.

[0005] To solve the above technical problems, the present invention provides the following technical solution: A high-strength black polyamide film, whose structure from top to bottom is successively: upper surface layer, sub-upper surface layer, black core layer, sub-lower surface layer, and lower surface layer. Its preparation method includes the following steps:

[0006] Step (1): Preparation of black colorant A:

[0007] S1: First, sinter carbon fiber powder at high temperature. After cooling, wash it with absolute ethanol and pure water, dry it, remove the protective slurry on the surface, perform strong acid acidification treatment, filter and dry to obtain acidified carbon fiber B. Using N,N-dimethylformamide as a catalyst, react acidified carbon fiber B with chloroacetyl chloride, filter, and wash with acetone and pure water until the filtrate is neutral, then dry and grind to obtain acyl chloride carbon fiber C;

[0008] S2: Add ethylenediamine into absolute ethanol, stir to disperse evenly, then add diatomite powder, filter after standing for 12 h, and obtain modified diatomite D after drying;

[0009] S3: Mix acyl chlorinated carbon fiber C and modified diatomite D, add chloroacetyl chloride, use N, N-dimethylformamide as a catalyst, stir evenly and then heat for reaction, filter and wash with acetone and pure water until the filtrate is neutral, dry and grind to obtain black colorant A;

[0010] Step (2): Carry out vacuum suction feeding and mixing according to the raw materials of each layer, melt and plasticize into a melt in an extruder respectively. The melt passes through a filter screen and a perforated plate, and is co-extruded from a circular die head into a multi-layer tubular film tube blank, and is rapidly cooled with cold water;

[0011] Step (3): Preheat the cylindrical film tube blank, then introduce compressed air for transverse blowing, and at the same time carry out longitudinal stretching through traction, and control the transverse and longitudinal stretching ratios;

[0012] Step (4): After the blown and stretched film tube blank is flattened by a traction roller, keep the longitudinal and transverse sides clamped in a relaxed state, carry out heat setting treatment and then corona treatment on the surface layer of the film, and obtain the finished product after winding, slitting and packaging.

[0013] In step S1, the sintering temperature is 400 °C, the strong acid is a concentrated nitric acid solution with a mass concentration of 65-70%, the reaction temperature of the acidified carbon fiber B and chloroacetyl chloride is 65-70 °C, and the reaction time is 72 h.

[0014] Further, the raw materials of the acyl chlorinated carbon fiber C include the following components: by weight, 1-3 parts of acidified carbon fiber B, 16-25 parts of chloroacetyl chloride, and 5 parts of N, N-dimethylformamide.

[0015] In step S2, by weight, 20 parts of ethylenediamine and 30 parts of absolute ethanol.

[0016] In step S3, the raw materials of the black colorant A include the following components: 3-6 parts of acyl chlorinated carbon fiber C, 1-2 parts of modified diatomite D, 10-12 parts of chloroacetyl chloride, and 12 parts of N, N-dimethylformamide.

[0017] Further, the reaction temperature is 70-75 °C, and the reaction time is 60 h.

[0018] In step (2), the thickness of the film tube blank is 100-500 μm; the temperature of the cold water is 0-10 °C

[0019] Further, the raw materials of each layer include the following components, by weight:

[0020] Upper surface layer: 95 - 100 parts of polyamide 6, 2 - 8 parts of antioxidant, 3 - 7 parts of light stabilizer;

[0021] Sub - upper surface layer: 96 - 100 parts of polyamide 6, 3 - 7 parts of anti - sticking agent, 1 - 9 parts of antioxidant;

[0022] Black core layer: 70 - 80 parts of polyamide 6, 20 - 30 parts of black colorant A, 2 parts of antioxidant;

[0023] Sub - lower surface layer: 97 - 100 parts of polyamide 6; 1 - 9 parts of anti - sticking agent, 2 - 8 parts of antioxidant;

[0024] Lower surface layer: 96 - 100 parts of polyamide 6, 1 - 9 parts of anti - sticking agent, 1 - 9 parts of antioxidant, 3 - 8 parts of light stabilizer;

[0025] Furthermore, the proportion of the thickness of each layer is: upper surface layer 10%, sub - upper surface layer 15%, black core layer 50%, sub - lower surface layer 15%, lower surface layer 10%.

[0026] Furthermore, the antioxidant is one or more of 1010, 168, 1076, 626, 1790; the light stabilizer is one or more of 944, 2020, 119, XT - 55; the anti - sticking agent is one of paraffin, fatty acid metal salt, calcium carbonate, calcined silica.

[0027] In step (3), the pre - heating temperature is 75 - 120 °C; the draw ratio is 2.8 - 4.0.

[0028] In step (4), the heat - setting treatment temperature is 180 - 230 °C; the film thickness is 15 - 25 μm.

[0029] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention uses chloroacetyl chloride and ethylenediamine to modify carbon fiber and diatomite respectively, and uses N, N - dimethylformamide as a catalyst to bond the acyl - chlorinated carbon fiber and the modified diatomite together through chemical bonds to obtain black colorant A. Since diatomite has good dispersibility in polyamide 6, and carbon fiber is combined with polyamide 6, the problem of product color difference caused by uneven dispersion of carbon fiber is solved. In addition, carbon fiber can not only make the surface of the synthesized polyamide 6 film smoother, but also effectively improve the mechanical strength of the polyamide film, effectively avoiding the occurrence of deformation and damage during subsequent forming and composite operations due to stress, and improving the quality of the product. Specific embodiments

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] In the following examples, the material sources are as follows: carbon fiber (Wuxi Weisheng New Materials Co., Ltd.); diatomite (Henan Antong Environmental Protection Technology Co., Ltd.); acetone (CAS No.: 67-64-1, Wuxi Tensheng Chemical Co., Ltd.); concentrated nitric acid (CAS No. 7697-37-2, Wuxi Tensheng Chemical Co., Ltd.); chloroacetyl chloride (CAS No.: 201-171-6, Shandong Pulisi Chemical Co., Ltd.); N,N-dimethylformamide (CAS No.: 68-12-2, Wuxi Tensheng Chemical Co., Ltd.); absolute ethanol (CAS No.: 64-17-5, Wuxi Tensheng Chemical Co., Ltd.); polyamide 6 (CAS No.: 25038-54-4, Dongguan Shengtao Chemical Co., Ltd.); antioxidant 1010 (Shanghai Lingrui Chemical Co., Ltd.); light stabilizer 944 (Shanghai Lingrui Chemical Co., Ltd.); calcium carbonate (CAS No.: 207-439-9, Zhangjiagang Qinchang Calcium Carbonate Co., Ltd.).

[0032] Example 1:

[0033] Step (1): Preparation of black colorant A:

[0034] S1: Sinter 1 part of carbon fiber powder at 400 °C. After cooling, wash it with absolute ethanol and pure water, dry it, remove the protective slurry on the surface, then acidify it with a 65% mass concentration of concentrated nitric acid solution, filter it, and rinse it with clear water until the surface is neutral to obtain acidified carbon fiber B. Add 5 parts of N,N-dimethylformamide as a catalyst and react with 16 parts of chloroacetyl chloride at 65 °C for 72 h. After filtration, wash it with acetone and pure water until the filtrate is neutral, dry it, and grind it to obtain acyl chloride carbon fiber C;

[0035] S2: Add 20 parts of ethylenediamine to 30 parts of absolute ethanol, stir to disperse it evenly, then add diatomite powder, let it stand for 12 h, filter it, and dry it to obtain modified diatomite D;

[0036] S3: Mix 3 parts of acyl chloride carbon fiber C and 1 part of modified diatomite D, add 10 parts of chloroacetyl chloride, use 12 parts of N,N-dimethylformamide as a catalyst, stir evenly, then heat it to 70 °C and react for 60 h. After filtration, wash it with acetone and pure water until the filtrate is neutral, dry it, and grind it to obtain black colorant A;

[0037] Step (2): Vacuum suction feeding and mixing are carried out according to the raw materials of each layer, and they are respectively melted and plasticized into a melt in an extruder. The melt passes through a filter screen and a perforated plate, and is co-extruded from a circular die head into a multi-layer tubular film blank with a thickness of 196 μm, and is rapidly cooled with cold water at 0 °C. Among them, the upper surface layer: 95 parts of polyamide 6, 8 parts of antioxidant 1010, 3 parts of light stabilizer 944; the sub-upper surface layer: 96 parts of polyamide 6, 3 parts of calcium oxide, 9 parts of antioxidant 1010; the black core layer: 70 parts of polyamide 6, 20 parts of black colorant A, 2 parts of antioxidant 1010; the sub-lower surface layer: 97 parts of polyamide 6; 1 part of calcium oxide, 8 parts of antioxidant 1010; the lower surface layer: 96 parts of polyamide 6, 1 part of calcium oxide, 1 part of antioxidant 1010, 8 parts of light stabilizer 944; the proportion of the thickness of each layer is: the upper surface layer 10%, the sub-upper surface layer 15%, the black core layer 50%, the sub-lower surface layer 15%, the lower surface layer 10%;

[0038] Step (3): Preheat the cylindrical film blank to 75 °C, then introduce compressed air for transverse blowing, and at the same time conduct longitudinal stretching through traction. The stretching ratio in the transverse and longitudinal directions is 2.8;

[0039] Step (4): After the blown and stretched film blank is flattened by a traction roller, keep the longitudinal and transverse sides in a relaxed state of clamping, and conduct heat setting treatment at 180 °C. The thickness of the film is 25 μm; then corona treatment is carried out on the surface layer of the film, and the corona-treated film is wound up, slit, and packaged to obtain the finished product.

[0040] Example 2:

[0041] Step (1): Preparation of black colorant A:

[0042] S1: Sinter 2.4 parts of carbon fiber powder at 400 °C. After cooling, wash it with absolute ethanol and pure water, dry it, remove the protective slurry on the surface, then acidify it with a nitric acid solution with a mass concentration of 68%, filter it, and rinse it with clean water until the surface is neutral to obtain acidified carbon fiber B. Add 5 parts of N,N-dimethylformamide as a catalyst, and react with 20 parts of chloroacetyl chloride at 68 °C for 72 h. After filtration, wash it with acetone and pure water until the filtrate is neutral, dry it, and grind it to obtain acyl chloride carbon fiber C;

[0043] S2: Add 20 parts of ethylenediamine to 30 parts of absolute ethanol, stir to disperse it evenly, then add diatomaceous earth powder, let it stand for 12 h, filter it, and dry it to obtain modified diatomaceous earth D;

[0044] S3: Mix 4.8 parts of acyl chloride carbon fiber C and 1.8 parts of modified diatomaceous earth D, add 11.5 parts of chloroacetyl chloride, use 12 parts of N,N-dimethylformamide as a catalyst, stir evenly, heat it to 72 °C, react for 60 h, filter it, and wash it with acetone and pure water until the filtrate is neutral, dry it, and grind it to obtain black colorant A;

[0045] Step (2): Vacuum suction feeding and mixing are carried out according to the raw materials of each layer, and they are respectively melted and plasticized into a melt in an extruder. The melt passes through a filter screen and a perforated plate, and is co-extruded from a circular die head into a multi-layer tubular film blank with a thickness of 205 μm, and is rapidly cooled with cold water at 7 °C. Among them, the upper surface layer: 98 parts of polyamide 6, 3 parts of antioxidant 1010, 5 parts of light stabilizer 944; the sub-upper surface layer: 97 parts of polyamide 6, 4 parts of calcium oxide, 7 parts of antioxidant 1010; the black core layer: 75 parts of polyamide 6, 25 parts of black colorant A, 2 parts of antioxidant 1010; the sub-lower surface layer: 98 parts of polyamide 6; 4 parts of calcium oxide, 5 parts of antioxidant 1010; the lower surface layer: 97 parts of polyamide 6, 4 parts of calcium oxide, 5 parts of antioxidant 1010, 5 parts of light stabilizer 944; the proportion of the thickness of each layer is: the upper surface layer 10%, the sub-upper surface layer 15%, the black core layer 50%, the sub-lower surface layer 15%, the lower surface layer 10%;

[0046] Step (3): Preheat the cylindrical film blank to 100 °C, then introduce compressed air for transverse blowing, and at the same time conduct longitudinal stretching through traction. The stretching ratio in the transverse and longitudinal directions is 3.2;

[0047] Step (4): After the blown and stretched film blank is flattened by a traction roller, keep the longitudinal and transverse sides in a relaxed state of clamping, and conduct heat setting treatment at 200 °C. The film thickness is 20 μm; then corona treatment is carried out on the surface layer of the film, and the corona-treated film is wound up, slit, and packaged to obtain the finished product.

[0048] Example 3:

[0049] Step (1): Preparation of black colorant A:

[0050] S1: Sinter 3 parts of carbon fiber powder at 400 °C. After cooling, wash it with anhydrous ethanol and pure water, dry it, remove the protective slurry on the surface, then acidify it with a 70% mass concentration of concentrated nitric acid solution, filter, and rinse with clear water until the surface is neutral to obtain acidified carbon fiber B. Add 5 parts of N,N-dimethylformamide as a catalyst, and react with 25 parts of chloroacetyl chloride at 70 °C for 72 h. After filtration, wash it with acetone and pure water until the filtrate is neutral, dry and grind it to obtain acyl chloride carbon fiber C;

[0051] S2: Add 20 parts of ethylenediamine to 30 parts of anhydrous ethanol, stir to disperse it evenly, then add diatomaceous earth powder, let it stand for 12 h, filter and dry to obtain modified diatomaceous earth D;

[0052] S3: Mix 6 parts of acyl chloride carbon fiber C and 2 parts of modified diatomite D, add 12 parts of chloroacetyl chloride, use 12 parts of N,N-dimethylformamide as a catalyst, stir evenly, then heat to 75 °C and react for 60 h. After filtration, wash with acetone and pure water until the filtrate is neutral, dry and grind to obtain black colorant A;

[0053] Step (2): Perform vacuum suction feeding and mixing according to the raw materials of each layer, melt and plasticize them into a melt in an extruder respectively. The melt passes through a filter screen and a perforated plate, and is co-extruded from a circular die head into a multi-layer tubular film blank with a thickness of 240 μm, and is quenched and cooled with 10 °C cold water. Among them, the upper surface layer: 100 parts of polyamide 6, 8 parts of antioxidant 1010, 3 parts of light stabilizer 944; the second upper surface layer: 100 parts of polyamide 6, 7 parts of calcium oxide, 1 part of antioxidant 1010; the black core layer: 80 parts of polyamide 6, 30 parts of black colorant A, 2 parts of antioxidant 1010; the second lower surface layer: 98 parts of polyamide 6; 4 parts of calcium oxide, 5 parts of antioxidant 1010; the lower surface layer: 97 parts of polyamide 6, 4 parts of calcium oxide, 5 parts of antioxidant 1010, 5 parts of light stabilizer 944; the proportion of the thickness of each layer is: the upper surface layer 10%, the second upper surface layer 15%, the black core layer 50%, the second lower surface layer 15%, the lower surface layer 10%;

[0054] Step (3): Preheat the cylindrical film blank to 120 °C, then introduce compressed air for transverse blowing, and at the same time perform longitudinal stretching through traction. The transverse and longitudinal stretching ratios are 4.0;

[0055] Step (4): After the blown and stretched film blank is flattened by a traction roller, keep the longitudinal and transverse sides clamped in a relaxed state, and perform heat setting treatment at 230 °C. The film thickness is 15 μm; then corona treat the surface layer of the film, wind up, slit and package the corona-treated film to obtain the finished product.

[0056] Comparative Example 1

[0057] Directly color the polyamide film with black paint to obtain a black polyamide film.

[0058] Among them, the upper surface layer: 100 parts of polyamide 6, 8 parts of antioxidant 1010, 3 parts of light stabilizer 944; the second upper surface layer: 100 parts of polyamide 6, 7 parts of calcium oxide, 1 part of antioxidant 1010; the core layer: 80 parts of polyamide 6; the second lower surface layer: 98 parts of polyamide 6; 4 parts of calcium oxide, 5 parts of antioxidant 1010; the lower surface layer: 97 parts of polyamide 6, 4 parts of calcium oxide, 5 parts of antioxidant 1010, 5 parts of light stabilizer 944; the proportion of the thickness of each layer is: the upper surface layer 10%, the second upper surface layer 15%, the black core layer 50%, the second lower surface layer 15%, the lower surface layer 10%;

[0059] The remaining operations are the same as those in Example 1.

[0060] Comparative Example 2

[0061] No diatomaceous earth is added, and only carbon fiber is used as the black colorant.

[0062] Step (1): Vacuum suction feeding and mixing are carried out according to the raw materials of each layer, and they are respectively melted and plasticized into a melt in an extruder. The melt passes through a filter screen and a perforated plate, and is co-extruded from a circular die head into a multi-layer tubular film blank with a thickness of 196 μm, and is rapidly cooled with cold water at 7 °C. Among them, the upper surface layer: 95 parts of polyamide 6, 8 parts of antioxidant 1010, 3 parts of light stabilizer 944; the sub-upper surface layer: 96 parts of polyamide 6, 3 parts of calcium oxide, 9 parts of antioxidant 1010; the black core layer: 70 parts of polyamide 6, 20 parts of carbon fiber, 2 parts of antioxidant 1010; the sub-lower surface layer: 97 parts of polyamide 6; 1 part of calcium oxide, 8 parts of antioxidant 1010; the lower surface layer: 96 parts of polyamide 6, 1 part of calcium oxide, 1 part of antioxidant 1010, 8 parts of light stabilizer 944; the proportion of the thickness of each layer is: the upper surface layer 10%, the sub-upper surface layer 15%, the black core layer 50%, the sub-lower surface layer 15%, the lower surface layer 10%;

[0063] The remaining operations are the same as those in Example 1.

[0064] Comparative Example 3

[0065] The carbon fiber is not acid-treated, and is directly modified with chloroacetyl chloride to obtain acyl chloride carbon fiber C.

[0066] Step (1): Preparation of black colorant A:

[0067] S1: Sinter 2.4 parts of carbon fiber powder at 400 °C. After cooling, wash it with absolute ethanol and pure water, dry it, remove the protective slurry on the surface, add 5 parts of N,N-dimethylformamide as a catalyst, and react with 20 parts of chloroacetyl chloride at 70 °C for 72 h. After filtration, wash it with acetone and pure water until the filtrate is neutral, dry and grind to obtain acyl chloride carbon fiber C

[0068] S2: Add 20 parts of ethylenediamine to 30 parts of absolute ethanol, stir to disperse it evenly, then add diatomaceous earth powder, filter and dry it after standing for 12 h to obtain modified diatomaceous earth D;

[0069] S3: Mix 6 parts of acyl chloride carbon fiber C and 2 parts of modified diatomaceous earth D, add 12 parts of chloroacetyl chloride, use 12 parts of N,N-dimethylformamide as a catalyst, stir evenly and heat to 75 °C for reaction for 60 h. After filtration, wash it with acetone and pure water until the filtrate is neutral, dry and grind to obtain black colorant A;

[0070] Step (2): Vacuum suction feeding and mixing are carried out according to the raw materials of each layer, and they are respectively melted and plasticized into a melt in an extruder. The melt passes through a filter screen and a perforated plate and is co-extruded from a circular die head into a multi-layer tubular film blank with a thickness of 205 μm, and is rapidly cooled with 10°C cold water. Among them, the upper surface layer: 98 parts of polyamide 6, 3 parts of antioxidant 1010, 5 parts of light stabilizer 944; the sub-upper surface layer: 97 parts of polyamide 6, 4 parts of calcium oxide, 7 parts of antioxidant 1010; the black core layer: 75 parts of polyamide 6, 25 parts of black colorant A, 2 parts of antioxidant 1010; the sub-lower surface layer: 98 parts of polyamide 6; 4 parts of calcium oxide, 5 parts of antioxidant 1010; the lower surface layer: 97 parts of polyamide 6, 4 parts of calcium oxide, 5 parts of antioxidant 1010, 5 parts of light stabilizer 944; the proportion of the thickness of each layer is: the upper surface layer 10%, the sub-upper surface layer 15%, the black core layer 50%, the sub-lower surface layer 15%, the lower surface layer 10%;

[0071] The remaining operations are the same as those in Example 2.

[0072] Comparative Example 4

[0073] Do not modify the diatomite.

[0074] Step (1): Preparation of black colorant A:

[0075] S1: Sinter 2.4 parts of carbon fiber powder at 400°C. After cooling, wash it with absolute ethanol and pure water, dry it, remove the protective slurry on the surface, then acidify it with a 65% mass concentration of concentrated nitric acid solution, filter it, and rinse it with clear water until the surface is neutral to obtain acidified carbon fiber B. Add 5 parts of N,N-dimethylformamide as a catalyst and react with 20 parts of chloroacetyl chloride at 70°C for 72 h. After filtration, wash it with acetone and pure water until the filtrate is neutral, dry it, and grind it to obtain acyl chloride carbon fiber C;

[0076] S2: Mix 4.5 parts of acyl chloride carbon fiber C and 1 part of diatomite, add 10 parts of chloroacetyl chloride, use 12 parts of N,N-dimethylformamide as a catalyst, stir evenly, heat it to 72°C and react for 60 h. After filtration, wash it with acetone and pure water until the filtrate is neutral, dry it, and grind it to obtain black colorant A;

[0077] Step (2): Vacuum suction feeding and mixing are carried out according to the raw materials of each layer, and they are respectively melted and plasticized into a melt in an extruder. The melt passes through a filter screen and a perforated plate, and is co-extruded from a circular die head into a multi-layer tubular film blank with a thickness of 205 μm, and is rapidly cooled with cold water at 7 °C. Among them, the upper surface layer: 98 parts of polyamide 6, 3 parts of antioxidant 1010, 5 parts of light stabilizer 944; the sub-upper surface layer: 97 parts of polyamide 6, 4 parts of calcium oxide, 7 parts of antioxidant 1010; the black core layer: 75 parts of polyamide 6, 25 parts of black colorant A, 2 parts of antioxidant 1010; the sub-lower surface layer: 98 parts of polyamide 6; 4 parts of calcium oxide, 5 parts of antioxidant 1010; the lower surface layer: 97 parts of polyamide 6, 4 parts of calcium oxide, 5 parts of antioxidant 1010, 5 parts of light stabilizer 944; the proportion of the thickness of each layer is: upper surface layer 10%, sub-upper surface layer 15%, black core layer 50%, sub-lower surface layer 15%, lower surface layer 10%;

[0078] The remaining operations are the same as those in Example 2.

[0079] Comparative Example 5

[0080] The modified carbon fiber and diatomite are directly mixed to prepare a black colorant.

[0081] Step (1): Preparation of black colorant A:

[0082] S1: Sinter 2.4 parts of carbon fiber powder at 400 °C. After cooling, wash it with absolute ethanol and pure water, dry it, remove the protective slurry on the surface, then acidify it with a 70% mass concentration of concentrated nitric acid solution, filter it, and rinse it with clear water until the surface is neutral to obtain acidified carbon fiber B. Add 5 parts of N,N-dimethylformamide as a catalyst, and react with 20 parts of chloroacetyl chloride at 70 °C for 72 h. After filtration, wash it with acetone and pure water until the filtrate is neutral, dry it, and grind it to obtain acyl chloride carbon fiber C;

[0083] S2: Add 20 parts of ethylenediamine to 30 parts of absolute ethanol, stir to disperse it evenly, then add diatomite powder, let it stand for 12 h, filter it, and dry it to obtain modified diatomite D;

[0084] S3: Mix 5 parts of acyl chloride carbon fiber C and 2 parts of modified diatomite D, and grind to obtain black colorant A;

[0085] Step (2): Vacuum suction feeding and mixing are carried out according to the raw materials of each layer, and they are respectively melted and plasticized into melts in an extruder. The melts pass through a filter screen and a perforated plate, and are co-extruded from a circular die head into a multi-layer tubular film blank with a thickness of 240 μm, and are rapidly cooled with cold water at 7°C. Among them, the upper surface layer: 100 parts of polyamide 6, 8 parts of antioxidant 1010, 3 parts of light stabilizer 944; the second upper surface layer: 100 parts of polyamide 6, 7 parts of calcium oxide, 1 part of antioxidant 1010; the black core layer: 80 parts of polyamide 6, 30 parts of black colorant A, 2 parts of antioxidant 1010; the second lower surface layer: 98 parts of polyamide 6; 4 parts of calcium oxide, 5 parts of antioxidant 1010; the lower surface layer: 97 parts of polyamide 6, 4 parts of calcium oxide, 5 parts of antioxidant 1010, 5 parts of light stabilizer 944; the proportion of the thickness of each layer is: the upper surface layer 10%, the second upper surface layer 15%, the black core layer 50%, the second lower surface layer 15%, the lower surface layer 10%;

[0086] The remaining operations are the same as those in Example 3.

[0087] Experiment: Perform relevant performance test experiments on the black polyamide films prepared in Examples 1 to 3 and Comparative Examples 1 to 5. Under the standard light source daylight D65 (color temperature 6500K), the color difference of the black polyamide films is evaluated from a fixed angle. According to the test conditions of Part 3 of "GB / T 1040.3-2006 Determination of Tensile Properties of Plastics", a static tensile load is applied to the black polyamide films to measure the tensile strength; the specimen is a long strip with a length of 150 mm and a width of (15 ± 0.1) mm, the distance between the clamps is 100 mm, and the test speed is (250 ± 25) mm / min. The change in color of the black polyamide film under the ultimate tensile condition is tested. The experimental results are as follows:

[0088]

[0089] Conclusion: The data in Examples 1 to 3 show that the black polyamide film prepared by using the reaction product of chlorinated carbon fiber and modified diatomaceous earth as a black colorant has better effect, no obvious color difference, and has good tensile strength. The color is basically unchanged under extreme stretching conditions, and the effect of preparing aluminum-plastic composite film with aluminum foil is better; Taking Example 1 as the control group, the data in Comparative Example 1 show that only coating the surface of the polyamide film with black ink has poor tensile strength, ink penetration causes color difference in the film, and color disjointed areas appear on the surface of the film under extreme stretching conditions, and the subsequent preparation of aluminum-plastic composite film is not satisfactory. When the film is formed, the coated ink has scratches and the synthesis effect is poor; the data of comparative example 2 show that only carbon fiber is used as a black colorant, and the dispersion ability in polyamide 6 is poor, and the prepared polyamide film has poor performance; taking Example 2 as the control group, the data of comparative examples 3 to 4 show that the unmodified carbon fiber and diatomaceous earth are difficult to combine together through reaction, and the performance of the prepared black polyamide film is poor; taking Example 3 as the control group, comparative example 5 shows that simply adding chlorinated carbon fiber and modified diatomaceous earth has little effect on improving the performance of the polyamide film, and the effect is better if the two are added after reaction.

[0090] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-strength black polyamide film, characterized in that: Its structure from top to bottom is as follows: upper surface layer, sub-upper surface layer, black core layer, sub-lower surface layer and lower surface layer, including the following steps: Step (1): Preparation of black colorant A: S1: After high-temperature sintering, remove the protective slurry on the surface of carbon fiber. Treat the carbon fiber with strong acid to obtain acidified carbon fiber B. React with chloroacetyl chloride using N,N-dimethylformamide as a catalyst to obtain acyl-chlorinated carbon fiber C; S2: Modify diatomite powder with ethylenediamine solution to obtain modified diatomite D; S3: Using N,N-dimethylformamide as a catalyst, mix and react acyl-chlorinated carbon fiber C and modified diatomite D. After washing, filtering, and drying, grind the product to obtain black colorant A; Step (2): Vacuum suction-feed and mix the raw materials of each layer, extrude them through an extruder into a multi-layer tubular film tube blank, and then rapidly cool and lower the temperature; Step (3): Preheat the cylindrical film tube blank, blow it up horizontally by introducing compressed air, and at the same time perform longitudinal stretching through traction, and control the stretching ratio in the horizontal and vertical directions; Step (4): The blown and stretched film tube blank is flattened by a traction roller, keeping the relaxed state of clamping on both the longitudinal and horizontal sides. After heat setting treatment, corona treatment is performed on the surface layer of the film, and the film after corona treatment is wound, slit, and packaged to obtain the finished product; Among them, the raw materials of each layer include the following components, by weight: Upper surface layer: 95 - 100 parts of polyamide 6, 2 - 8 parts of antioxidant, 3 - 7 parts of light stabilizer; Sub-upper surface layer: 96 - 100 parts of polyamide 6, 3 - 7 parts of anti-blocking agent, 1 - 9 parts of antioxidant; Black core layer: 70 - 80 parts of polyamide 6, 20 - 30 parts of black colorant A, 2 parts of antioxidant; Sub-lower surface layer: 97 - 100 parts of polyamide 6; 1 - 9 parts of anti-blocking agent, 2 - 8 parts of antioxidant; Lower surface layer: 96 - 100 parts of polyamide 6, 1 - 9 parts of anti-blocking agent, 1 - 9 parts of antioxidant, 3 - 8 parts of light stabilizer.

2. The method for preparing a high-strength black polyamide film according to claim 1, characterized in that: In step S1, the high-temperature sintering temperature is 400 °C, the strong acid is a concentrated nitric acid solution with a mass concentration of 65 - 70%, the reaction temperature between acidified carbon fiber B and chloroacetyl chloride is 65 - 70 °C, and the reaction time is 72 h.

3. The method for preparing a high-strength black polyamide film according to claim 2, characterized in that: In step S1, the raw materials of the acyl-chlorinated carbon fiber C include the following components: by weight, 1 - 3 parts of acidified carbon fiber B, 16 - 25 parts of chloroacetyl chloride, 5 parts of N,N-dimethylformamide.

4. The method for preparing a high-strength black polyamide film according to claim 1, characterized in that: In step S2, each component of the ethylenediamine solution is by weight, 20 parts of ethylenediamine and 30 parts of absolute ethanol.

5. The method for preparing a high-strength black polyamide film according to claim 1, characterized in that: In step S3, the raw materials of the black colorant A include the following components: 3 - 6 parts of acyl-chlorinated carbon fiber C, 1 - 2 parts of modified diatomite D, 10 - 12 parts of chloroacetyl chloride, 12 parts of N,N-dimethylformamide; the reaction temperature is 70 - 75 °C, and the reaction time is 60 h.

6. The method for preparing a high-strength black polyamide film according to claim 1, characterized in that: In step (2), the thickness of the film tube blank is 100 - 500 μm; the cold water temperature is 0 - 10 °C; The antioxidant is one of 1010, 168, 1076, 626, and 1790; the light stabilizer is one or more of 944, 2020, 119, and XT-55; the anti-blocking agent is one of paraffin, fatty acid metal salt, calcium carbonate, and calcined silica; the proportion of the thickness of each layer is: the upper surface layer 10%, the sub-upper surface layer 15%, the black core layer 50%, the sub-lower surface layer 15%, and the lower surface layer 10%.

7. The method for preparing a high-strength black polyamide film according to claim 1, characterized in that: In step (3), the preheating temperature is 75 - 120 °C; the stretching ratio is 2.8 - 4.

0.

8. The method for preparing a high-strength black polyamide film according to claim 1, characterized in that: In step (4), the heat setting treatment temperature is 180 - 230 °C; the film thickness is 15 - 25 μm.

9. A high-strength black polyamide film prepared by the method for preparing a high-strength black polyamide film according to any one of claims 1 to 8.

Images