An outdoor inkjet printing base film and a printing material comprising the base film

Abstract

This application discloses an outdoor inkjet printing base film and printing materials containing the base film, belonging to the field of inkjet printing technology. The printing base film comprises: a core layer, a first surface layer, and a second surface layer, wherein the first and second surface layers are distributed on the front and back sides of the core layer; the first and second surface layers both contain a UV absorber and / or an antioxidant to improve the weather resistance of the base film; the density of the first and second surface layers is greater than that of the core layer, which can reduce material usage and effectively lower production costs.

Description

Technical Field

[0001] The present invention relates to the technical field of inkjet printing, and in particular to an outdoor inkjet printing base film and a printing material comprising the base film. Background Art

[0002] Inkjet printing technology boasts fast recording speeds, easy colorization, convenient application, and a pollution-free design. It is widely used in industries such as photo editing, advertising, and label printing. Outdoor advertising is a key application for this technology. Common outdoor advertising inkjet printing materials use a PVC base film coated with a suitable printing coating. However, PVC base films contain a large amount of organochlorine, making them environmentally unsuitable.

[0003] At present, biaxially oriented polypropylene foam film materials have the characteristics of being lightweight, environmentally friendly, and soft to the touch. They are environmentally friendly solutions to replace PVC base films. However, traditional biaxially oriented polypropylene foam film materials are usually prepared using a multi-layer co-extrusion process. The bonding strength between the layers is not ideal, and the strength of the core layer is not high enough. After long-term outdoor exposure, they are prone to delamination, aging, and peeling. There are also some methods that improve the overall outdoor weather resistance of the material by adding antioxidants or UV absorbers to the coating, but such methods have limited improvement on the weather resistance of the base film and are prone to yellowing of the coating, affecting the use effect of the final product. There are also some methods that improve the weather resistance by adding antioxidants or UV absorbers to the polypropylene base film, but the cost of the existing preparation process is high and it is difficult to be widely used. Summary of the Invention

[0004] In view of the above problems, the present invention proposes an outdoor inkjet printing base film with excellent weather resistance and a printing material containing the base film, which can effectively reduce production costs.

[0005] The technical solution adopted by the present invention is as follows: The present invention provides an outdoor inkjet printing base film, comprising: a core layer, a first surface layer and a second surface layer, wherein the first surface layer and the second surface layer are distributed on the front and back sides of the core layer;

[0006] The first surface layer and the second surface layer both contain ultraviolet absorbers and / or antioxidants and light stabilizers;

[0007] The densities of the first surface layer and the second surface layer are both greater than the density of the core layer.

[0008] Compared to conventional coating-based approaches to improve the weather resistance of the base film, this application significantly improves the weather resistance of the base film by adding UV absorbers and / or antioxidants and light stabilizers to both surface layers (i.e., the first and second surface layers) of the base film, thereby improving the delamination, aging, and peeling of the base film after long-term exposure to sunlight. Furthermore, the density of the core layer of this application is lower than that of the two surface layers. The relatively dense structure of the two surface layers can also better protect the inner core layer, and the low density of the inner core layer can effectively reduce the amount of material used, thereby reducing production costs.

[0009] Typically, the density of polypropylene-based films is about 0.90 g / cm 3 By introducing a core layer with a foam structure, the amount of material per unit area can be saved at the same thickness. The specific data is shown in Table 1 below:

[0010] Table 1. Savings of polypropylene base films with different densities

[0011]

[0012] Optionally, the first surface layer and the second surface layer comprise, by mass percentage, 50-97% polypropylene, 0-30% ethylene propylene copolymer, 0-30% polyethylene, 0.5-3% antioxidant, 0.5-3% ultraviolet absorber and 0.3-2% light stabilizer.

[0013] Optionally, the core layer comprises, by mass percentage, 70-94% polypropylene resin, 5-20% porogen, and 0-20% inorganic powder, wherein the inorganic powder may be titanium dioxide; and the porogen may be selected from calcium carbonate, butylene terephthalate, or a combination thereof.

[0014] The two surface layers in this application are not foamed and generally have a higher density, while the core layer has a lower density after foaming.

[0015] Optionally, the average density of the base film is 0.52-0.85 kg / L, which can control costs while ensuring weather resistance.

[0016] Optionally, the density of the first surface layer and the second surface layer is 0.85-0.95 kg / L; the density of the core layer is 0.52 kg / L-0.85 kg / L, more preferably, the density of the core layer is 0.52-0.75 kg / L, most preferably, the density of the core layer is 0.52-0.7 kg / L.

[0017] The base film has a thickness of 40-500 μm, preferably 60-150 μm. The thicknesses of the first and second surface layers are 0.5-10 μm, preferably 0.5-5 μm, more preferably 0.5-3 μm, and most preferably 0.5-2 μm, respectively. The core layer has a thickness of 40-500 μm, preferably 60-150 μm. The core layer is much thicker than the two surface layers. By reducing the density of the core layer, the material consumption in its production can be significantly reduced. While the density of the two surface layers is relatively high, their thinness reduces the overall material consumption in the surface layer production, effectively reducing production costs.

[0018] Optionally, a transition layer is provided between the first surface layer and the core layer and / or between the second surface layer and the core layer to improve the adhesion between the two surface layers and the core layer, wherein the transition layer contains an ultraviolet absorber, an antioxidant, and a light stabilizer.

[0019] Optionally, the transition layer comprises 80-99% olefin copolymer, 0.1-5% UV absorber, antioxidant, and light stabilizer, and 0-18% inorganic powder. The properties of the transition layer are between the surface layer and the core layer, so it can connect the surface layer and the core layer and improve adhesion.

[0020] Optionally, the density of the transition layer is greater than that of the core layer. Specifically, the density of the transition layer is 0.60-0.85 kg / L, and most preferably, the density of the transition layer is 0.65-0.80 kg / L. The density of the transition layer can be between the surface layer and the core layer to better serve as a transition connection.

[0021] Optionally, the antioxidant is selected from any one or more combinations of phenols and phosphites.

[0022] Specifically, the antioxidant is selected from any one or more combinations of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and its derivatives, tris[2,4-di-tert-butylphenyl]phosphite and its derivatives.

[0023] Optionally, the ultraviolet absorber is selected from any one or more combinations of benzophenones, salicylates, benzotriazoles, substituted acrylonitriles, and triazines.

[0024] The present invention also provides an outdoor inkjet printing material, comprising the outdoor inkjet printing base film and an ink-absorbing coating, wherein the ink-absorbing coating is distributed on the first surface layer and / or the second surface layer.

[0025] Specifically, the ink-receptive coating has a thickness of 5-40 μm. By mass percentage, the ink-receptive coating comprises 40%-80% polyacrylic resin, 0.2%-5% substrate wetting agent, 15%-60% silica powder, and additives such as antioxidants, UV absorbers, film-forming aids, and antistatic agents. The acrylic resin has a glass transition temperature of 0-50°C, preferably 10-40°C. The silica powder is precipitated silica with a particle size of 1-20 μm, preferably 5-15 μm.

[0026] The preparation method of the outdoor inkjet printing base film described in the present invention is specifically as follows: the raw materials of the first surface layer, the second surface layer and the core layer are respectively sent into three extruders for co-extrusion, the extrusion temperature is controlled at 220-260°C, and they are merged at the die head after passing through the flow channel distributor, and then cooled by a chilled roller, and the cooling temperature is controlled at 30-35°C to prepare a three-layer resin sheet; then the resin sheet is introduced into the longitudinal stretching device in the biaxial stretching equipment, the surface is preheated to 135-150°C, the stretching temperature is controlled at 100-120°C, and the stretching ratio is 5 times; then it is introduced into the transverse stretching device, the surface is preheated to 170-185°C, stretched 7.5 times at 155-170°C, cooled by air shower, and then the surface of the first surface layer is corona treated or flame treated, the mother roll is collected, and finally cut and packaged to obtain the base film.

[0027] The ink-receptive coating preparation method of the present invention comprises the following steps: 200 parts by weight of an acrylic emulsion (50% solids) and 300 parts by weight of deionized water are mixed, and 60 parts of silica powder is gradually added while stirring. Then, 0.2 parts of a brightener, 10 parts of a film-forming aid, 10 parts of an antistatic agent, 1.5 parts of a wetting agent, and 2.5 parts of a thickener are added in that order to obtain an ink-receptive coating solution. The mixed ink-receptive coating solution is then applied to the base film using a wire rod and then dried in an 80°C oven for 10 minutes to produce the final outdoor inkjet advertising printing material.

[0028] The present invention has the following beneficial effects: by directly adding antioxidants, UV absorbers, and light stabilizers to the first and second surface layers of the base film, the base film's weather resistance is significantly improved, thereby alleviating the delamination, aging, and peeling problems of the base film after long-term exposure to sunlight. Furthermore, the core layer of the present invention has a lower density than the two surface layers. The relatively dense structure of the two surface layers also better protects the inner core layer, while the lower density of the inner core layer effectively reduces material usage, thereby reducing production costs. DETAILED DESCRIPTION

[0029] The present invention is described in detail and completely below through specific examples. Unless otherwise specified, all percentage units are weight percentages.

[0030] Example 1

[0031] The first and second surface layers in this embodiment comprise, by mass, 46 parts of polypropylene resin, 22 parts of polyethylene resin, 32 parts of ethylene-propylene copolymer resin, 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.5 parts of tris[2,4-di-tert-butylphenyl]phosphite, 1.4 parts of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol, and 0.7 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate. The first and second surface layers have a thickness of 3-5 μm and a density of approximately 0.9 kg / L.

[0032] The core layer comprises, by mass, 75.9 parts of polypropylene resin, 21 parts of calcium carbonate, and 3.1 parts of titanium dioxide. The core layer has a thickness of 60 μm and a density of 0.55 kg / L.

[0033] The ink-absorbing coating comprises: 100 parts of acrylic resin, 60 parts of silica powder, 0.2 parts of whitening agent, 10 parts of film-forming aid, 10 parts of antistatic agent, 1.5 parts of wetting agent, and 2.5 parts of thickener. The acrylic resin has a glass transition temperature (Tg) of 23°C.

[0034] Example 2

[0035] The first and second surface layers in this embodiment comprise, by mass, 46 parts of polypropylene resin, 22 parts of polyethylene resin, 32 parts of ethylene-propylene copolymer resin, 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.5 parts of tris[2,4-di-tert-butylphenyl]phosphite, 1.4 parts of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol, and 0.7 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate. The first and second surface layers have a thickness of 3-5 μm and a density of approximately 0.9 kg / L.

[0036] The core layer comprises, by weight percentage, 81.9 parts of polypropylene resin, 15 parts of calcium carbonate, and 3.1 parts of titanium dioxide. The core layer has a thickness of 80 μm and a density of 0.65 kg / L.

[0037] The ink-absorbing coating comprises: 100 parts of acrylic resin, 60 parts of silica powder, 0.2 parts of whitening agent, 10 parts of film-forming aid, 10 parts of antistatic agent, 1.5 parts of wetting agent, and 2.5 parts of thickener. The acrylic resin has a glass transition temperature (Tg) of 23°C.

[0038] Example 3

[0039] The first and second surface layers in this embodiment comprise, by mass, 46 parts of polypropylene resin, 22 parts of polyethylene resin, 32 parts of ethylene-propylene copolymer resin, 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.5 parts of tris[2,4-di-tert-butylphenyl]phosphite, 1.4 parts of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol, and 0.7 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate. The first and second surface layers have a thickness of 3-5 μm and a density of approximately 0.9 kg / L.

[0040] The core layer comprises, by weight percentage, 85.3 parts of polypropylene resin, 11 parts of calcium carbonate, and 3.7 parts of titanium dioxide. The core layer has a thickness of 90 μm and a density of 0.70 kg / L.

[0041] The ink-absorbing coating comprises: 100 parts of acrylic resin, 60 parts of silica powder, 0.2 parts of whitening agent, 10 parts of film-forming aid, 10 parts of antistatic agent, 1.5 parts of wetting agent, and 2.5 parts of thickener. The acrylic resin has a glass transition temperature (Tg) of 23°C.

[0042] Comparative Example 1

[0043] The first and second surface layers in this embodiment comprise, by mass, 46 parts of polypropylene resin, 22 parts of polyethylene resin, and 32 parts of ethylene-propylene copolymer resin. The first and second surface layers have a thickness of 3-5 μm and a density of approximately 0.9 kg / L.

[0044] The core layer comprises, by weight percentage, 81.9 parts of polypropylene resin, 15 parts of calcium carbonate, and 3.1 parts of titanium dioxide. The core layer has a thickness of 60 μm and a density of 0.65 kg / L.

[0045] The ink-absorbing coating comprises: 100 parts of acrylic resin, 60 parts of silica powder, 0.2 parts of whitening agent, 10 parts of film-forming aid, 10 parts of antistatic agent, 1.5 parts of wetting agent, and 2.5 parts of thickener. The acrylic resin has a glass transition temperature (Tg) of 23°C.

[0046] Comparative Example 2

[0047] The first and second surface layers in this embodiment comprise, by mass, 46 parts of polypropylene resin, 22 parts of polyethylene resin, and 32 parts of ethylene-propylene copolymer resin. The first and second surface layers have a thickness of 3-5 μm and a density of approximately 0.9 kg / L.

[0048] The core layer comprises, by mass, 86.5 parts of polypropylene resin, 10 parts of calcium carbonate, and 3.5 parts of titanium dioxide. The core layer has a thickness of 90 μm and a density of 0.75 kg / L.

[0049] The ink-absorbing coating comprises: 100 parts of acrylic resin, 60 parts of silica powder, 0.2 parts of whitening agent, 10 parts of film-forming aid, 10 parts of antistatic agent, 1.5 parts of wetting agent, and 2.5 parts of thickener. The acrylic resin has a glass transition temperature (Tg) of 23°C.

[0050] Comparative Example 3

[0051] The first and second surface layers in this embodiment comprise, by mass, 46 parts of polypropylene resin, 22 parts of polyethylene resin, 32 parts of ethylene-propylene copolymer resin, 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.5 parts of tris[2,4-di-tert-butylphenyl]phosphite, 1.4 parts of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol, and 0.7 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate. The first and second surface layers have a thickness of 3-5 μm and a density of approximately 0.9 kg / L.

[0052] The core layer comprises, by mass percentage, 73 parts of polypropylene resin, 25 parts of calcium carbonate, and 2 parts of titanium dioxide. The core layer has a thickness of 60 μm and a density of 0.50 kg / L.

[0053] The ink-absorbing coating comprises: 100 parts of acrylic resin, 60 parts of silica powder, 0.2 parts of whitening agent, 10 parts of film-forming aid, 10 parts of antistatic agent, 1.5 parts of wetting agent, and 2.5 parts of thickener. The acrylic resin has a glass transition temperature (Tg) of 23°C.

[0054] Comparative Example 4

[0055] The first and second surface layers in this embodiment comprise, by mass, 46 parts of polypropylene resin, 22 parts of polyethylene resin, 32 parts of ethylene-propylene copolymer resin, 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.5 parts of tris[2,4-di-tert-butylphenyl]phosphite, 1.4 parts of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol, and 0.7 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate. The first and second surface layers have a thickness of 3-5 μm and a density of approximately 0.9 kg / L.

[0056] The core layer comprises, by weight percentage, 81.9 parts of polypropylene resin, 15 parts of calcium carbonate, and 3.1 parts of titanium dioxide. The core layer has a thickness of 80 μm and a density of 0.65 kg / L.

[0057] The ink-absorbing coating comprises: 100 parts of acrylic resin, 60 parts of silica powder, 0.2 parts of whitening agent, 10 parts of film-forming aid, 10 parts of antistatic agent, 1.5 parts of wetting agent, and 2.5 parts of thickener. The acrylic resin has a glass transition temperature (Tg) of 65°C.

[0058] The outdoor advertising printed materials of Examples 1-3 and Comparative Examples 1-4 were attached to the outside of glass windows with tape and subjected to a real outdoor exposure test. The exposure direction was perpendicular to the south direction of the facade. The exposure location was in Jiashan County, Zhejiang Province, and the exposure time was from March 1 to August 31. The test results are shown in Table 2 below.

[0059] Table 2 Exposure test results

[0060]

[0061] The thickness of the core layer is controlled by extruder equipment parameters. Using the controlled variable method to study the effect of core layer thickness parameters on weather resistance (with core layer thickness as the independent variable), it was found that core layer thickness had little effect on weather resistance. Comparison of Examples 1, 2, and 3 shows that increasing the amount of porogen added results in a lower core layer density. All three groups of examples showed no delamination after outdoor exposure testing, demonstrating that the base films prepared in these three examples achieve excellent weather resistance.

[0062] Comparison of Example 2 and Comparative Example 1 shows that adding an antioxidant to the first surface layer and the second surface layer can significantly improve the problems of delamination, aging and peeling of the base film and improve the weather resistance.

[0063] Comparison of Example 2 and Comparative Example 4 shows that the glass transition temperature of the acrylic resin in the ink-absorbing coating has a significant impact on the weather resistance. When the glass transition temperature is too high, the weather resistance of the material will be reduced.

[0064] Comparing Example 1 and Comparative Example 3, it can be seen that the higher the porogen content, the lower the core layer density, the lower the strength, and the easier it is to delaminate. When the core layer density is too low, reaching 0.5 kg / L, the weather resistance is poor. As shown in Comparative Example 3, when the density is low, even with the addition of antioxidants, UV absorbers, and light stabilizers, serious delamination problems still exist. As shown in Comparative Example 2, despite the high core layer density, delamination problems still exist without the addition of antioxidants. This shows that improving weather resistance cannot be achieved simply by adding antioxidants or increasing the core layer density, but requires the synergistic effect of antioxidants and density.

[0065] The above description is only a preferred embodiment of the present invention and does not limit the scope of patent protection of the present invention. Any equivalent structural transformation made by using the contents of the present invention specification, directly or indirectly used in other related technical fields, is also included in the scope of protection of the present invention.

Claims

1. An outdoor inkjet printing base film, characterized in that: include: A core layer, a first surface layer and a second surface layer, wherein the first surface layer and the second surface layer are distributed on the front and back sides of the core layer; The first surface layer and the second surface layer both contain an ultraviolet absorber, an antioxidant and a light stabilizer; wherein the density of the first surface layer and the second surface layer is greater than the density of the core layer; and the core layer contains 5-30% porogen by mass percentage; A transition layer is provided between the first surface layer and the core layer and / or between the second surface layer and the core layer, wherein the transition layer contains an ultraviolet absorber, an antioxidant and a light stabilizer; The density of the first surface layer and the second surface layer is 0.85-0.95 kg / L; the density of the core layer is 0.52-0.70 kg / L; the density of the transition layer is 0.65-0.80 kg / L; Wherein, the antioxidant is selected from any one or more combinations of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol and its derivatives, tris[2,4-di-tert-butylphenyl] phosphite and its derivatives; The ultraviolet absorber is selected from any one or more combinations of benzophenones, salicylates, benzotriazoles, substituted acrylonitriles, and triazines; The light stabilizer is selected from hindered amine compounds.

2. The outdoor inkjet printing base film according to claim 1, characterized in that In terms of mass percentage, the first surface layer and the second surface layer include 20-97% polypropylene, 0-50% ethylene propylene copolymer, 0-50% polyethylene, 0.05-5% antioxidant, 0.05-4% ultraviolet absorber and 0.03-3% light stabilizer.

3. The outdoor inkjet printing base film according to claim 1 or 2, characterized in that: Calculated by mass percentage, the core layer comprises 70-94% polypropylene resin, 5-30% porogen, and 0-20% inorganic powder.

4. The outdoor inkjet printing base film according to claim 1, characterized in that The transition layer comprises 80-99% of olefin polymer, 0-18% of inorganic powder and 0.1-5% of ultraviolet absorber, antioxidant and light stabilizer.

5. An outdoor inkjet printing material, characterized in that: The outdoor inkjet printing base film comprises the outdoor inkjet printing base film according to any one of claims 1 to 4 and an ink-absorbing coating, wherein the ink-absorbing coating is distributed on the first surface layer and / or the second surface layer.

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