High-performance low-haze coating film for printing and preparation method thereof

Abstract

The invention discloses a high-performance low-haze coating film for printing and a preparation method thereof, the coating film comprises a BOPET base film and coating layers arranged on the upper surface and the lower surface of the BOPET base film, and coating liquid used by the coating layers is a waterborne polyurethane system. By adding the silica sol coating and simplifying the extrusion design of the base film, a good opening effect is achieved, a uniform microcosmic rough structure is formed on the surface of the base film, the haze is reduced while high light transmittance and high definition are kept, the coating film has the optical characteristics of high light transmittance (larger than or equal to 91%), high definition (99.9%) and low haze (smaller than or equal to 1%), and the application prospect is wide. The high-quality coating film for printing has the advantages that the stability is high, the wetting tension is high (the stability is 60dyn / cm), the coating has excellent ink matching performance, the subsequent processing adhesive force is good, and the requirement of the market on the high-quality coating film for printing is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin films and relates to a coating film, in particular to a high-performance low-fog coating film for printing and a preparation method thereof. Background Art

[0002] BOPET biaxially oriented polyester film has the characteristics of high strength, good rigidity, transparency, high gloss, etc. It is also odorless, tasteless, colorless, non-toxic, and has outstanding toughness.

[0003] In the field of high-end printing (such as precision labels, packaging printing, optical displays, etc.), the optical properties (light transmittance, clarity, haze) and surface properties (wetting tension, adhesion) of BOPET coating films directly determine the printing quality.

[0004] However, traditional BOPET coating films have the following core defects:

[0005] 1. Light transmittance: The light transmittance of existing products is mostly below 90%, which affects color reproduction and is difficult to meet the product display requirements of high-end packaging.

[0006] 2. Clarity: The clarity of existing products is usually less than 99%. After printing and other processing, the color saturation decreases, and the product quality is defective.

[0007] 3. Haze: The haze of existing products is generally higher than 1%, resulting in blurred edges of printed patterns, especially significant defects in high-resolution printing.

[0008] 4. Surface treatment defects: Corona treatment is used to increase the wetting tension (>60dyn / cm), but the corona effect is easily attenuated, and the film surface is prone to adsorb dust during the treatment process, resulting in problems such as ink pattern defects during printing.

[0009] 5. Adhesion: The surface free energy of traditional BOPET film is low, making it difficult for ink to wet and adhere to the surface of traditional BOPET film. Poor adhesion often occurs due to poor adaptation of post-processing. Summary of the Invention

[0010] In order to solve the low optical performance and surface treatment defects of existing BOPET coating films, the present invention provides a high-performance low-haze coating film for printing. The coating film of the present invention has high light transmittance (≥91%), high clarity (99.9%), low haze (≤1%), and high wetting tension (60 dyn / cm).

[0011] The present invention also provides a method for preparing the above-mentioned coating film. The present invention solves the defects of the existing BOPET coating film in terms of optical performance and poor adhesion in subsequent processing by synergistic optimization of the formula and process.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] The present invention provides a high-performance low-fog coating film for printing, which comprises a BOPET base film and coating layers arranged on the upper and lower surfaces of the BOPET base film, and the coating liquid used for the coating layer is an aqueous polyurethane system.

[0014] As a preferred embodiment of the present invention, the raw materials of the coating liquid include, by weight: 8-10 parts of waterborne polyurethane resin, 86.3-91 parts of deionized water, 0.2-0.6 parts of organic metal catalyst, 0.1-1 parts of alcohol compound, 0.3-0.8 parts of carbodiimide, 0.2-1 parts of methyl melamine and 0.1-0.3 parts of silica sol, and the pH of the coating liquid is adjusted to 9-11.

[0015] As a preferred embodiment of the present invention, the alcohol compound includes one of 2-tert-butoxyethanol, 2-tert-butoxypropanol, dimethyloctyne diol, and tetramethyldecyne diol.

[0016] As a preferred embodiment of the present invention, the organic metal catalyst is one of dibutyltin dilaurate, bis(cyclopentadienyl)zirconium dimethyl, and bismuth laurate.

[0017] As a preferred embodiment of the present invention, the pH regulator for adjusting the coating solution includes sodium carbonate or sodium bicarbonate.

[0018] As a preferred solution of the present invention, the raw material of the BOPET base film is 100% polyester chips.

[0019] As a preferred embodiment of the present invention, the thickness of the coating layer is 30-200 nm.

[0020] The present invention also provides a method for preparing the above-mentioned high-performance, low-haze coating film for printing, which comprises the following steps: melting the raw materials and subjecting them to single-layer extrusion or three-layer co-extrusion, film casting, longitudinal stretching, coating, transverse stretching, traction and winding, and slitting to obtain a high-performance, low-haze coating film for printing.

[0021] As a preferred embodiment of the present invention, the melting temperature is 260-290°C, the longitudinal stretching ratio is 2.6-3.6, the longitudinal stretching temperature is 75-95°C; the transverse stretching ratio is 3-4, the transverse stretching temperature is 90-130°C; and the setting temperature is 200-230°C.

[0022] As a preferred embodiment of the present invention, during coating, the coating speed matches the line speed; after coating, curing is completed in a preheating zone at 90-130°C.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The present invention achieves a good opening effect by adding a silica sol coating and simplifying the base film extrusion design, forming a uniform microscopic rough structure on the base film surface, reducing haze while maintaining high transmittance and high clarity.

[0025] 2) The coating liquid of the present invention reacts with the surface of the base film to form a chemical bond, thereby stably increasing the wetting tension to 60 dyn / cm, avoiding the attenuation and contamination problems of corona treatment.

[0026] 3) The coating film of the present invention has optical properties of high light transmittance (≥91%), high clarity (99.9%), and low haze (≤1%).

[0027] 4) The present invention improves the coating liquid formula, increases the surface energy of the coating film, and enhances the bonding force between different inks and the coating film surface; by forming a uniform microscopic rough structure on the coating film surface, the contact area between the ink and the coating film surface is increased, thereby improving the wettability. Therefore, the coating film of the present invention has higher adaptability and good matching with subsequent printing processing, meeting the market demand for high-quality coating films for printing.

[0028] 5) The present invention improves the raw material formula, enhances the optical properties of the product, reduces production costs, and improves the market competitiveness of the coating film of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] The present invention provides a high-performance, low-fog coating film for printing. The coating film comprises a BOPET base film and coating layers arranged on the upper and lower surfaces of the BOPET base film. The coating liquid used in the coating layer is an aqueous polyurethane system.

[0031] Preferably, the raw materials of the coating liquid include, by weight: 8-10 parts of waterborne polyurethane resin, 86.3-91 parts of deionized water, 0.2-0.6 parts of organic metal catalyst, 0.1-1 parts of alcohol compound, 0.3-0.8 parts of carbodiimide, 0.2-1 parts of methyl melamine and 0.1-0.3 parts of silica sol, and the pH of the coating liquid is adjusted to 9-11 by sodium bicarbonate.

[0032] More preferably, the alcohol compound includes one of 2-tert-butoxyethanol, 2-tert-butoxypropanol, dimethyloctyne diol, and tetramethyldecyne diol.

[0033] More preferably, the organometallic catalyst is one of dibutyltin dilaurate, bis(cyclopentadienyl)zirconium dimethyl, and bismuth laurate.

[0034] More preferably, the adjusting agent for adjusting the pH of the coating liquid includes sodium carbonate or sodium bicarbonate.

[0035] Most preferably, the raw materials of the coating liquid include, by weight: 9.5 parts of waterborne polyurethane resin, 88.6 parts of deionized water, 0.3 parts of organic metal catalyst dibutyltin dilaurate, 0.8 parts of 2-tert-butoxyethanol, 0.3 parts of carbodiimide, 0.1 parts of methyl melamine, 0.1 parts of sodium bicarbonate added to adjust the actual pH to 9-11, and 0.3 parts of silica sol.

[0036] Preferably, the coating layer has a thickness of 30-200 nm.

[0037] The present invention also provides a method for preparing the above-mentioned high-performance, low-haze coating film for printing, which comprises the following steps: melting the raw materials and subjecting them to single-layer extrusion or three-layer co-extrusion, film casting, longitudinal stretching, coating, transverse stretching, traction and winding, and slitting to obtain a high-performance, low-haze coating film for printing.

[0038] Preferably, the raw materials are melted and then extruded in a single layer. Therefore, the present invention can also simplify the equipment, thereby saving costs and improving work efficiency.

[0039] Preferably, the melting temperature is 260-290°C, the longitudinal stretching ratio is 2.6-3.6, the longitudinal stretching temperature is 75-95°C; the transverse stretching ratio is 3-4, the transverse stretching temperature is 90-130°C; and the setting temperature is 200-230°C.

[0040] Preferably, during coating, the coating speed matches the line speed; and after coating, curing is completed in a preheating zone at 90-130°C.

[0041] Example 1

[0042] This embodiment provides a method for preparing a high-performance, low-haze coating film for printing.

[0043] Selected raw materials: 100% polyester chips are used. The raw materials of the coating liquid include, by weight: 8.7 parts of water-based polyurethane resin, 89.1 parts of deionized water, 0.5 parts of organic metal catalyst dibutyltin dilaurate, 0.5 parts of 2-tert-butoxyethanol, 0.5 parts of carbodiimide, 0.5 parts of methyl melamine, 0.1 parts of sodium bicarbonate are added to adjust the actual pH to 9-11, and 0.1 parts of silica sol.

[0044] The polyester film was produced using a biaxially oriented process, with melt extrusion, film casting, longitudinal stretching, double-sided coating, transverse stretching, transverse shaping, winding, and slitting. The extrusion temperature was 280°C, the longitudinal stretching temperature was 90°C, the longitudinal stretching ratio was 3.1, the transverse stretching temperature was 130°C, the transverse stretching ratio was 3.5, and the transverse shaping temperature was 230°C. The resulting coated film had a thickness of 188 μm.

[0045] Example 2

[0046] This embodiment provides a method for preparing a high-performance, low-haze coating film for printing.

[0047] Selected raw materials: 100% polyester chips are used. The raw materials of the coating liquid include, by weight: 9.1 parts of water-based polyurethane resin, 88.3 parts of deionized water, 0.5 parts of organic metal catalyst dibutyltin dilaurate, 0.8 parts of 2-tert-butoxyethanol, 0.5 parts of carbodiimide, 0.5 parts of methyl melamine, 0.1 parts of sodium bicarbonate are added to adjust the actual pH to 9-11, and 0.2 parts of silica sol.

[0048] The coated polyester film is obtained by adopting a planar biaxial stretching process, through melt extrusion, film casting, longitudinal stretching, double-sided coating, transverse stretching, transverse shaping, traction and winding, and slitting process; the extrusion temperature is 275°C, the longitudinal stretching temperature is 87°C, the longitudinal stretching ratio is 3.0, the transverse stretching temperature is 128°C, the transverse stretching ratio is 3.5, and the transverse shaping temperature is 225°C.

[0049] The thickness of the obtained coating film was 188 μm.

[0050] Example 3

[0051] This embodiment provides a method for preparing a high-performance, low-haze coating film for printing.

[0052] Selected raw materials: 100% polyester chips are used. The raw materials of the coating liquid include, by weight: 9.5 parts of water-based polyurethane resin, 88.6 parts of deionized water, 0.3 parts of organic metal catalyst dibutyltin dilaurate, 0.8 parts of 2-tert-butoxyethanol, 0.3 parts of carbodiimide, 0.1 parts of methyl melamine, 0.1 parts of sodium bicarbonate are added to adjust the actual pH to 9-11, and 0.3 parts of silica sol.

[0053] The coated polyester film is obtained by adopting a planar biaxial stretching process, through melt extrusion, film casting, longitudinal stretching, double-sided coating, transverse stretching, transverse shaping, traction and winding, and slitting process; the extrusion temperature is 275°C, the longitudinal stretching temperature is 90°C, the longitudinal stretching ratio is 3.1, the transverse stretching temperature is 125°C, the transverse stretching ratio is 3.5, and the transverse shaping temperature is 225°C.

[0054] The thickness of the obtained coating film was 188 μm.

[0055] Comparative Example 1

[0056] The coating film provided in this comparative example is as follows: the selected raw material is 100% polyester chips.

[0057] The polyester film is obtained by adopting a planar biaxial stretching process, through the process of melt extrusion, film casting, longitudinal stretching, transverse stretching, transverse shaping, traction and winding, and slitting; the extrusion temperature is 280°C, the longitudinal stretching temperature is 90°C, the longitudinal stretching ratio is 3.1, the transverse stretching temperature is 130°C, the transverse stretching ratio is 3.5, and the transverse shaping temperature is 230°C.

[0058] The thickness of the obtained coating film was 188 μm.

[0059] Comparative Example 2

[0060] The coating film provided in this comparative example is as follows: the raw materials selected are: the first layer and the third layer both use 5% silica opening agent and 95% polyester chips, and the second layer uses 100% polyester chips.

[0061] The polyester film is obtained by adopting a planar biaxial stretching process and undergoing a three-layer co-extrusion melt extrusion, film casting, longitudinal stretching, transverse stretching, transverse shaping, traction and winding, and slitting process; the extrusion temperature is 275°C, the longitudinal stretching temperature is 90°C, the longitudinal stretching ratio is 3.1, the transverse stretching temperature is 125°C, the transverse stretching ratio is 3.5, and the transverse shaping temperature is 225°C.

[0062] The thickness of the obtained coating film was 188 μm.

[0063] Comparative Examples 1 and 2 were not subjected to the coating process.

[0064] The coating films obtained in Examples 1-3 and Comparative Examples 1-2 were compared in terms of performance (optical performance was tested using a BYK tester in ASTM-C mode, and wetting tension was tested using GB / T14216). The results are shown in Table 1.

[0065] Table 1. Performance and effect comparison

[0066] Light transmittance (%) Clarity (%) Haze (%) Adhesion effect Opening effect Comparative Example 1 89.1 96.5 0.5 Difference Difference Comparative Example 2 88.6 95.4 1.0 Difference generally Example 1 91.1 99.9 0.4 good generally Example 2 91.2 99.9 0.5 good generally Example 3 91.5 99.9 0.7 good good

[0067] The performance of the coating film of the present invention was compared with that of commercially available BOPET coating film. The results are shown in Table 2.

[0068] Table 2. Performance comparison

[0069] Test items The present invention Existing BOPET coating film Test standards Light transmittance ≥91％ ≤90％ ASTM-C Haze 0.4-0.7％ ≥1％ ASTM-C Clarity 99.9％ 95％-99％ ASTM-C Wetting tension 60dyn / cm 52-65dyn / cm(fluctuation) GB / T14216

[0070] It can be seen that the coating film of the present invention has optical properties of high transmittance (≥91%), high clarity (99.9%), low haze (≤1%) and stable high wetting tension (stable 60dyn / cm). The present invention improves the surface energy of the coating film and improves the bonding force between different inks and the surface of the coating film; by forming a uniform microscopic rough structure on the surface of the coating film, the contact area between the ink and the surface of the coating film is increased, thereby improving the adhesion. Therefore, the coating film of the present invention has higher adaptability and good post-processing glue and printing matching, meeting the market demand for high-quality printing coating films; the present invention improves the raw material formula, improves the optical properties and meets the excellent adhesion required for post-processing, reduces production costs, and improves the market competitiveness of the present invention.

[0071] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A high-performance, low-haze coating film for printing, characterized in that: The coating film comprises a BOPET base film and coating layers arranged on the upper and lower surfaces of the BOPET base film, and the coating liquid used for the coating layer is an aqueous polyurethane system.

2. The high-performance, low-haze coating film for printing according to claim 1, characterized in that: The raw materials of the coating liquid include, by weight, 8-10 parts of waterborne polyurethane resin, 86.3-91 parts of deionized water, 0.2-0.6 parts of organic metal catalyst, 0.1-1 parts of alcohol compound, 0.3-0.8 parts of carbodiimide, 0.2-1 parts of methyl melamine and 0.1-0.3 parts of silica sol. The pH of the coating liquid is adjusted to 9-11.

3. The high-performance, low-haze coating film for printing according to claim 2, characterized in that: The alcohol compound includes one of 2-tert-butoxyethanol, 2-tert-butoxypropanol, dimethyloctyne diol, and tetramethyldecyne diol.

4. The high-performance, low-haze coating film for printing according to claim 2, characterized in that: The organic metal catalyst is one of dibutyltin dilaurate, bis(cyclopentadienyl) zirconium dimethyl and bismuth laurate.

5. The high-performance, low-haze coating film for printing according to claim 2, characterized in that: The pH regulator for adjusting the coating liquid includes sodium carbonate or sodium bicarbonate.

6. The high-performance, low-haze coating film for printing according to claim 1, characterized in that: The raw material of the BOPET base film is 100% polyester chips.

7. A high-performance, low-haze coating film for printing according to any one of claims 1 to 6, characterized in that: The thickness of the coating layer is 30-200 nm.

8. A method for preparing a high-performance, low-haze coating film for printing according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: melting the raw materials, extruding through single-layer or three-layer co-extrusion, casting, longitudinal stretching, coating, transverse stretching, traction and winding, and slitting to obtain a high-performance low-fog coating film for printing.

9. The method for preparing a high-performance, low-haze coating film for printing according to claim 8, characterized in that: The melting temperature is 260-290°C, the longitudinal stretching ratio is 2.6-3.6, the longitudinal stretching temperature is 75-95°C; the transverse stretching ratio is 3-4, the transverse stretching temperature is 90-130°C; and the setting temperature is 200-230°C.

10. The method for preparing a high-performance, low-haze coating film for printing according to claim 9, characterized in that: During coating, the coating speed matches the line speed; after coating, the material is cured in the preheating zone at 90-130°C.