Wiredrawing film and preparation method thereof

Abstract

The invention relates to the technical field of wiredrawing films, and discloses a wiredrawing film and a preparation method thereof.The wiredrawing film comprises a core layer and two surface layers arranged on the upper surface and the lower surface of the core layer; the wiredrawing film comprises one or two surface layers with wiredrawing textures; the raw materials of the surface layer with the wiredrawing textures comprise a crystalline polyester material and an amorphous polyester material, and the mass of the amorphous polyester material accounts for 5-95% of the total mass of the raw materials of the surface layer. According to the present invention, by using the crystallinity difference between the crystalline polyester material and the amorphous polyester material, the lasting wire drawing effect can be formed on the film, and the subsequent wire drawing process is not required after the film is prepared, such that the working efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of wire drawing films, and in particular to a wire drawing film and a preparation method thereof. Background Art

[0002] Brushed film is a film that has been specially processed to form a metal brushed fine texture on the surface of the film material. It feels delicate to the touch and is mainly used in the surface lamination process of various printing and packaging products. The excellent metal brushed fine texture can increase the three-dimensional sense of the product, make it more ornamental, and improve the grade and taste of the product. It also has excellent properties such as corrosion resistance, scratch resistance, and high temperature resistance.

[0003] The base film of the drawing film is a polyester film, which uses a crystalline polyester material. When the polyester film is biaxially stretched, the crystallinity of each position of the film is uniform, and the appearance is transparent and uniform. The usual practice of drawing film is to use a row knife to score the polyester film, and the linear scratches formed on the film surface are called drawing. Alternatively, UV ink is applied to the surface of the polyester film, and then a mold is used to emboss the drawing texture, which is then cured. Therefore, the drawing film must go through at least two processes. The first is the preparation of the base film, and the second is to artificially create scratches on the base film, thereby reducing production efficiency. In addition, the drawing texture formed by ink coating is easy to fall off. Summary of the invention

[0004] In order to solve the above-mentioned technical problems, the present invention provides a drawing film and a preparation method thereof. By utilizing the difference in crystallinity between crystalline polyester materials and amorphous polyester materials, a lasting drawing effect can be formed on the film. After the film is prepared, no subsequent drawing process is required, thereby improving work efficiency and reducing production costs.

[0005] The purpose of the present invention is achieved through the following technical solutions: In the first aspect, the present invention provides a drawing film, comprising a core layer and two surface layers arranged on the upper and lower surfaces of the core layer; the drawing film contains one or two surface layers with a drawing texture; the raw materials of the surface layer with a drawing texture include crystalline polyester material and amorphous polyester material, and the mass of the amorphous polyester material accounts for 5 to 95% of the total mass of the surface layer raw materials.

[0006] At present, conventional polyester films adopt ABA or ABC structure, in which layer B is the core layer, and layers A and C are surface layers. According to needs, the two surface layers of the film can be the same or different, and the brushed texture can be set on one or both surface layers of the film.

[0007] The present invention mixes crystalline polyester material and amorphous polyester material in a certain proportion. By utilizing the difference in crystallinity, the crystalline polyester material will undergo crystallization during the production process, while the amorphous polyester material remains in its original state, resulting in differences in transmittance, refractive index, glossiness, etc. between the two in the film, resulting in fine lines visually visible on the film, which appear as scratched bright lines under the irradiation of light, and its appearance effect is basically equivalent to a film treated with scratches. Conventional wire drawing films all use a single crystalline polyester, and if no subsequent wire drawing treatment is performed, wire drawing lines will not appear. The present invention can obtain a wire drawing film with a better wire drawing effect by optimizing and improving the raw materials. After the film is prepared, no subsequent wire drawing process is required, which improves work efficiency and reduces production costs. At the same time, the wire drawing effect of the wire drawing film can be maintained for a long time, extending the service life of the product.

[0008] Preferably, the mass of the amorphous polyester material accounts for 10 to 80% of the total mass of the surface layer raw materials; more preferably, the mass of the amorphous polyester material accounts for 15 to 70% of the total mass of the surface layer raw materials.

[0009] Both the crystalline polyester material and the amorphous polyester material in the drawing film can form fine linear textures. The difference in crystallinity and ratio between the two will affect the number and obviousness of the textures. Within the limited range of the present invention, a drawing film with better drawing effect can be obtained.

[0010] Preferably, when the drawing film comprises two surface layers with drawing textures, the raw material ratios in the two surface layers are the same or different.

[0011] Preferably, the crystallinity of the crystalline polyester material is 48-53%.

[0012] Preferably, the amorphous polyester material has a crystallinity of less than 5%.

[0013] Preferably, the crystalline polyester material is polyethylene terephthalate.

[0014] Preferably, the amorphous polyester material is an alcohol-modified polyester material or an acid-modified polyester material.

[0015] Preferably, the amorphous polyester material is polyethylene terephthalate modified with 1,4-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol accounts for 15 to 30% of the total molar amount of ethylene glycol and 1,4-cyclohexanedimethanol.

[0016] The study found that when the molar content of 1,4-cyclohexanedimethanol is between 15% and 30%, the obtained modified copolyester is basically in an amorphous state without a crystallization peak, and there is a large difference in crystallinity between it and the crystalline polyester material.

[0017] As the CHDM content in the copolymer increases, the melting point decreases, the glass transition temperature increases, the crystallinity decreases, and finally an amorphous polymer is formed.

[0018] Preferably, the raw material of the surface layer with a brushed texture further includes a lubricant accounting for 800 to 1500 ppm of the total mass of the raw material of the surface layer.

[0019] The addition of lubricants helps to achieve better processing results.

[0020] Preferably, the lubricant is micron-sized silicon dioxide.

[0021] In a second aspect, the present invention provides a method for preparing a drawn film, comprising the following steps: plasticizing and melting the raw materials of the core layer and the surface layer respectively, adding them into an extruder for three-layer co-extrusion to form a cast film; stretching the cast film longitudinally and transversely, and then post-processing it to obtain a drawn film.

[0022] The present invention mixes a crystalline polyester material and an amorphous polyester material in a certain proportion, and after melt extrusion, the mixture is used as the surface layer of the film, and after melt extrusion, the crystalline polyester material is used as the core layer of the film, and then a drawing film is formed through the steps of casting, stretching, shaping, etc. The method can combine the two steps of film making and drawing into one step, thereby improving work efficiency and reducing production costs.

[0023] Preferably, the stretching ratio of the longitudinal stretching is not less than 2.8; and the stretching ratio of the transverse stretching is not less than 3.0.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) By utilizing the difference in crystallinity between crystalline polyester materials and amorphous polyester materials, a durable wire drawing effect can be formed on the film, and no subsequent wire drawing process is required after the film is prepared, thereby improving work efficiency and reducing production costs; (2) The crystallinity and ratio of the crystalline polyester material and the amorphous polyester material are matched with each other, so that the number of drawn fibers in the obtained drawn film is greater and the degree of drawn fibers is more obvious. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described below with specific embodiments, but the protection scope of the present invention is not limited thereto: The wire drawing film in the present invention comprises a core layer and two surface layers arranged on the upper and lower surfaces of the core layer, each surface layer accounts for 5 to 15% of the total mass of the wire drawing film, and adopts an ABA or ABC structure, wherein layer B is the core layer, and layers A and C are surface layers. As required, the two surface layers of the film can be the same or different, and the wire drawing texture can be arranged on one or both surface layers of the film.

[0026] The raw materials of the core layer and the surface layer without the brushed texture are both crystalline polyester materials. The crystalline polyester material is polyethylene terephthalate, and the crystallinity is 48-53%.

[0027] The raw materials of the surface layer with the brushed texture include crystalline polyester material and amorphous polyester material, and the mass of the amorphous polyester material accounts for 5-95% of the total mass of the raw materials of the surface layer.

[0028] The amorphous polyester material is a modified polyester with a crystallinity of less than 5%. The modified polyester includes an alcohol-modified polyester material or an acid-modified polyester material, and the modified monomers used can be one or more. Taking alcohol-modified amorphous polyester as an example, the commonly used modified monomer is 1,4-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol accounts for 15-30% of the total molar amount of ethylene glycol and 1,4-cyclohexanedimethanol.

[0029] The synthesis route (esterification-polycondensation process) of the amorphous polyester material (polyethylene terephthalate modified with 1,4-cyclohexanedimethanol) is as follows: S1: Slurry preparation: The raw materials involved in the production process of PETG mainly include terephthalic acid (PTA), ethylene glycol (EG) and 1,4-cyclohexanedimethanol (CHDM). After 1,4-cyclohexanedimethanol is heated and melted, it is added with terephthalic acid and ethylene glycol according to the set molar ratio. After adding, the three raw materials are fully stirred and mixed in the slurry preparation tank before entering the next esterification reactor.

[0030] S2: Esterification I: The slurry feed rate is determined according to the esterification reaction. The reaction temperature of the esterification reactor I is controlled at 249-263°C, and the reaction pressure is controlled at 120-150 kPa (a). In the esterification reactor, the carboxyl group -COOH in the PTA structure combines with the hydroxyl group -OH in the EG and CHDM structures to produce small molecules and water. The water generated by the reaction at high temperature exists as gas, and the gas produced by the reaction enters the process tower for separation. In the esterification reactor I, the esterification conversion rate is controlled at 91-93%.

[0031] S3: Esterification II: The esterified product generated in the esterification I system is transported to the esterification II system through a pipeline for further esterification. The reaction temperature of the esterification II reactor is controlled at 252-268°C, and the reaction pressure is controlled at 100-118 kPa (a). In the esterification II reactor, the esterification conversion rate is controlled at 95-98%.

[0032] S4: Polycondensation I: The materials generated by the esterification II system are transported to the polycondensation I system through a pipeline for polycondensation reaction. The reaction temperature of the polycondensation I reactor is controlled at 267-272°C, and the reaction pressure is controlled at 10-15 kPa(a).

[0033] S5: Polycondensation II: The prepolymer generated in the polycondensation I system is transported to the polycondensation II reactor through a pipeline. The reaction temperature of the polycondensation II reactor is controlled at 269-274°C, and the reaction pressure is controlled at 2-4 kPa(a). In the polycondensation II reactor, the prepolymer is further polycondensed, the molecular weight continues to increase, and the viscosity of the prepolymer gradually increases.

[0034] S6: Final polycondensation: The prepolymer generated in the polycondensation II system is filtered by a prepolymer pump and a prepolymer filter and then transported to the final polycondensation reactor. The reaction temperature of the final polycondensation reactor is controlled at 273-280°C, and the reaction pressure is controlled at 100-150 Pa (a).

[0035] The preparation of the above-mentioned drawing film comprises the following steps: (1) Drying the crystalline polyester chips to a moisture content of less than 50 ppm, and feeding the dried chips into a main extruder for plasticization and melting (as a core layer raw material); (2) mixing the crystalline polyester chips with the amorphous polyester chips, and feeding the mixture into an auxiliary extruder for plasticization and melting (as a surface layer raw material); (3) The melts from the main and auxiliary extruders are co-extruded in three layers according to the ABA structure or ABC structure ratio of the drawing film. The melt extrusion temperature is 270-290°C. After filtration, they converge at the die head and flow out from the die mouth. With the help of the attachment system, they are evenly attached to the cold roller and quickly cooled to form a cast film. (4) placing the cast film into a longitudinal stretching machine, and after being heated to 80-125° C., stretching it between a slow roller and a fast roller, with the longitudinal stretching ratio set to be no less than 2.8; (5) The film that has completed longitudinal stretching enters a transverse stretching machine, is heated again to 100-150° C., and then is transversely stretched. The transverse stretching ratio is set to be not less than 3.0; (6) After the transverse stretching, the film enters the traction machine and is collected into a mother roll after edge trimming, dust removal, static electricity elimination, corona treatment, etc.

[0036] Example 1 In order to verify the effect of the crystallinity of copolyester on the drawing effect, three kinds of amorphous polyester materials with CHDM content were prepared, named PETG1, PETG2, and PETG3, and their crystallinity was evaluated. The crystallinity was evaluated using a DSCⅠ differential scanning calorimeter from Mettler, Switzerland. Test conditions: nitrogen atmosphere, gas flow rate 40mL / min, heating rate 10K / min. The evaluation results are shown in Table 1.

[0037] Table 1 name CHDM molar content Crystallinity PETG1 8％ 13％ PETG2 18％ 0％ PETG3 25％ 0％ Note: CHDM molar content is the percentage of the molar amount of 1,4-cyclohexanedimethanol to the total molar amount of ethylene glycol and 1,4-cyclohexanedimethanol.

[0038] The synthesis route (esterification-polycondensation process) of the above-mentioned amorphous polyester material (polyethylene terephthalate modified with 1,4-cyclohexanedimethanol) is as follows: S1: Slurry preparation: After heating and melting 1,4-cyclohexanedimethanol, add it with terephthalic acid and ethylene glycol according to the set molar ratio (the total amount of ethylene glycol and 1,4-cyclohexanedimethanol is 1.2 times the amount of terephthalic acid). After adding, the three raw materials are fully stirred and mixed in the slurry preparation tank before entering the next esterification reactor.

[0039] S2: Esterification I: The reaction temperature of the esterification reactor I is controlled at 252±2°C, and the reaction pressure is controlled at 135 kPa(a). In the esterification reactor I, the esterification conversion rate is controlled at 91%.

[0040] S3: Esterification II: The esterified product generated in the esterification I system is transported to the esterification II system through a pipeline for further esterification. The reaction temperature of the esterification II reactor is controlled at 260±2°C, and the reaction pressure is controlled at 110kPa(a). In the esterification II reactor, the esterification conversion rate is controlled at 97%.

[0041] S4: Polycondensation I: The materials generated by the esterification II system are transported to the polycondensation I system through a pipeline for polycondensation reaction. The reaction temperature of the polycondensation I reactor is controlled at 268±2℃, and the reaction pressure is controlled at 12kPa(a).

[0042] S5: Polycondensation II: The prepolymer generated in the polycondensation I system is transported to the polycondensation II reactor through a pipeline. The reaction temperature of the polycondensation II reactor is controlled at 272±2°C, and the reaction pressure is controlled at 3kPa(a).

[0043] S6: Final polycondensation: The prepolymer generated in the polycondensation II system is filtered by the prepolymer pump and the prepolymer filter and then transported to the final polycondensation reactor. The reaction temperature of the final polycondensation reactor is controlled at 275±2°C and the reaction pressure is controlled at 140Pa(a).

[0044] Example 2 The preparation of the drawing film (ABA structure) includes the following steps: (1) Drying crystalline polyester chips (PET, crystallinity 50%) at a temperature of 155° C. for 4.5 h. The moisture content after drying is within 50 ppm. The dried chips are fed into a main extruder for plasticization and melting (as core layer raw material); (2) Crystalline polyester chips (PET, with a crystallinity of 50%), amorphous polyester chips (PETG1 or PETG3), and a masterbatch containing micron-sized silica (obtained by melt-mixing micron-sized silica and crystalline polyester chips (PET, with a crystallinity of 50%)) are mixed, wherein the silica content in the obtained mixture is controlled to be 1300 ppm, the mass content of amorphous polyester is shown in Table 2, and the rest is crystalline polyester; the mixture is sent to an auxiliary extruder for plasticization and melting (as a surface layer raw material); (3) The melts of the main and auxiliary extruders are proportioned according to the ABA structure of the drawing film (a single surface layer accounts for 10% of the total mass of the drawing film), and three-layer co-extrusion is carried out at a melt extrusion temperature of 280°C. After filtration, the melts are combined at the die head and flow out from the die mouth. With the help of an attachment system, the melts are evenly attached to a cold roller and rapidly cooled to form a cast film; (4) placing the cast film into a longitudinal stretching machine, and after being heated to 110° C., stretching it between a slow roller and a fast roller, setting the longitudinal stretching ratio; (5) The film that has completed longitudinal stretching enters a transverse stretching machine, is heated to 130°C again, and then is stretched transversely. The transverse stretching ratio is set; (6) After the transverse stretching, the film enters the traction machine and is collected into a mother roll after edge trimming, dust removal, static electricity elimination, corona treatment, etc.

[0045] According to the preparation method in Example 2, as shown in Table 2, the type, content, longitudinal stretching ratio, and transverse stretching ratio of the amorphous polyester chips were adjusted respectively, and the resulting drawn film was inspected against a light source (ordinary fluorescent light source), and the number of drawn lines and their obviousness were evaluated. The number of drawn lines was judged as 1, 2, 3, 4, and 5, respectively, and the larger the number, the more drawn lines there were; the obviousness of the drawn lines was judged as 1, 2, 3, 4, and 5, respectively, and the larger the number, the more obvious it was.

[0046] Table 2 Example 3 The preparation of the drawing film (ABA structure) includes the following steps: (1) Drying crystalline polyester chips (PET, crystallinity 52%) at a temperature of 155° C. for 4.5 h. The moisture content after drying is within 50 ppm. The dried chips are fed into a main extruder for plasticization and melting (as core layer raw material); (2) Crystalline polyester chips (PET, with a crystallinity of 52%), amorphous polyester chips (PETG1 or PETG3), and a masterbatch containing micron-sized silica (obtained by melt-mixing micron-sized silica and crystalline polyester chips (PET, with a crystallinity of 52%)) are mixed, wherein the silica content in the obtained mixture is controlled to be 1300 ppm, the mass content of amorphous polyester is shown in Table 3, and the rest is crystalline polyester; the mixture is sent to an auxiliary extruder for plasticization and melting (as a surface layer raw material); (3) The melts of the main and auxiliary extruders are proportioned according to the ABA structure of the drawing film (a single surface layer accounts for 10% of the total mass of the drawing film) and three-layer co-extruded at a melt extrusion temperature of 280°C. After filtration, the melts are combined at the die head and flow out from the die mouth. With the help of an attachment system, the melts are evenly attached to a cold roller and rapidly cooled to form a cast film; (4) placing the cast film into a longitudinal stretching machine, and after being heated to 100° C., stretching it between a slow roller and a fast roller, setting a longitudinal stretching ratio; (5) The film that has completed longitudinal stretching enters a transverse stretching machine, where it is heated again to 120°C and then stretched transversely. The transverse stretching ratio is set; (6) After the transverse stretching, the film enters the traction machine and is collected into a mother roll after edge trimming, dust removal, static electricity elimination, corona treatment, etc.

[0047] According to the preparation method in Example 3, as shown in Table 3, the type, content, longitudinal stretching ratio, and transverse stretching ratio of the amorphous polyester chips were adjusted respectively, and the resulting drawn film was inspected against a light source (ordinary fluorescent light source), and the number of drawn lines and their obviousness were evaluated. Regarding the number of drawn lines, 1, 2, 3, 4, and 5 were used for evaluation, and the larger the number, the more drawn lines there were; regarding the obviousness of the drawn lines, 1, 2, 3, 4, and 5 were used for evaluation, and the larger the number, the more obvious it was.

[0048] Table 3 Example 4 The preparation of the drawing film (ABC structure) includes the following steps: (1) Drying crystalline polyester chips (PET, crystallinity 50%) at a temperature of 155° C. for 4.5 h. The moisture content after drying is within 50 ppm. The dried chips are fed into a main extruder for plasticization and melting (as core layer raw material); (2) Mixing crystalline polyester chips (PET, with a crystallinity of 50%), amorphous polyester chips (PETG1), and a masterbatch containing micron-sized silica (obtained by melt-mixing micron-sized silica and crystalline polyester chips (PET, with a crystallinity of 50%)), wherein the silica content in the obtained mixture is controlled to be 1300 ppm, the mass content of amorphous polyester is 50%, and the rest is crystalline polyester; feeding the mixture into an auxiliary 1 extruder for plasticization and melting (as a raw material for the surface layer 1); (3) Mixing crystalline polyester chips (PET, with a crystallinity of 50%), amorphous polyester chips (PETG3), and a masterbatch containing micron-sized silica (obtained by melt-mixing micron-sized silica and crystalline polyester chips (PET, with a crystallinity of 50%)), wherein the silica content in the obtained mixture is controlled to be 1300 ppm, the mass content of amorphous polyester is 50%, and the rest is crystalline polyester; the mixture is fed into the auxiliary 2 extruder for plasticization and melting (as the raw material for the surface layer 2); (4) The melts from the main and auxiliary extruders are mixed according to the ABC structure of the drawing film (a single surface layer accounts for 7% of the total mass of the drawing film) and three-layer co-extruded at a melt extrusion temperature of 280°C. After filtration, they converge at the die head and flow out from the die mouth. With the help of the attachment system, they are evenly attached to the cold roller and quickly cooled to form a cast film. (5) placing the cast film into a longitudinal stretching machine, and after being heated to 110° C., stretching it between a slow roller and a fast roller, setting the longitudinal stretching ratio; (6) The film that has completed longitudinal stretching enters a transverse stretching machine, is heated to 130°C again, and then is stretched transversely. The transverse stretching ratio is set; (7) After the transverse stretching, the film enters the traction machine and is collected into a mother roll after edge trimming, dust removal, static electricity elimination, corona treatment, etc.

[0049] According to the preparation method in Example 4, as shown in Table 4, the obtained wire drawing film was inspected against a light source (ordinary fluorescent light source), and the number of wire drawing and its obviousness were evaluated. The number of wire drawing was judged by 1, 2, 3, 4, and 5, and the larger the number, the more wire drawing; the obviousness of wire drawing was judged by 1, 2, 3, 4, and 5, and the larger the number, the more obvious it was.

[0050] Table 4 The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A drawing film, comprising a core layer and two surface layers arranged on the upper and lower surfaces of the core layer, characterized in that: The brushed film contains one or two surface layers with brushed textures; the raw materials of the surface layer with brushed textures include crystalline polyester materials and amorphous polyester materials, and the mass of the amorphous polyester material accounts for 5-95% of the total mass of the surface layer raw materials.

2. The wire drawing film according to claim 1, characterized in that: When the drawing film comprises two surface layers with drawing textures, the raw material ratios in the two surface layers are the same or different.

3. The wire drawing film according to claim 1, characterized in that: The crystallinity of the crystalline polyester material is 48-53%.

4. The wire drawing film according to claim 1, characterized in that: The amorphous polyester material has a crystallinity of less than 5%.

5. The wire drawing film according to any one of claims 1 to 4, characterized in that: The crystalline polyester material is polyethylene terephthalate.

6. The wire drawing film according to claim 1, characterized in that: The amorphous polyester material is an alcohol-modified polyester material or an acid-modified polyester material.

7. The drawing film according to claim 1 or 6, characterized in that: The amorphous polyester material is polyethylene terephthalate modified with 1,4-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol accounts for 15-30% of the total molar amount of ethylene glycol and 1,4-cyclohexanedimethanol.

8. The wire drawing film according to any one of claims 1 to 4, characterized in that: The raw material of the surface layer with a brushed texture also includes a lubricant accounting for 800-1500 ppm of the total mass of the raw material of the surface layer.

9. A method for preparing a drawing film according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: plasticizing and melting the raw materials of the core layer and the surface layer respectively, adding them into an extruder for three-layer co-extrusion to form a cast film; longitudinally stretching and transversely stretching the cast film, and then post-treating it to obtain a drawn film.

10. The method for preparing a drawing film according to claim 9, characterized in that: The stretching ratio of the longitudinal stretching is not less than 2.8; the stretching ratio of the transverse stretching is not less than 3.0.

Images