High-bonding-strength prime-coat-free pre-coating base film for EVA (Ethylene Vinyl Acetate) as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of BOPP (Biaxially-oriented Polypropylene) film materials, and particularly relates to an EVA (Ethylene Vinyl Acetate) high-bonding-strength prime-coat-free pre-coating base film, a preparation method and application. The prime-coat-free pre-coating base film sequentially comprises a functional layer, a core layer and a prime-coat-free bonding layer from top to bottom, the functional layer is prepared from the following raw materials in parts by weight: a silicon dioxide type anti-blocking master batch and homo-polypropylene; the core layer is prepared from the following raw materials in percentage by mass: 0.5 to 1.6 percent of antistatic master batch and 98.4 to 99.5 percent of homo-polypropylene; the prime coat-free bonding layer is prepared from the following raw materials in parts by weight: a small-particle-size anti-blocking master batch and co-polypropylene. According to the EVA high-bonding-strength prime-coat-free pre-coating base film, good coating bonding fastness can be obtained under the condition of low EVA coating thickness (the EVA coating thickness is smaller than or equal to 6 microns), the EVA coating thickness is reduced, the production cost is saved, meanwhile, the bonding layer film has good paper-plastic composite fastness, and the use requirements of environment protection and low processing cost are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of BOPP film materials, and particularly relates to a bottom - coat - free pre - coated base film with high EVA bonding strength, a preparation method and an application thereof. Background Art

[0002] The EVA high - adhesion BOPP bottom - coat - free film is a specially treated film material. Its surface has a high gloss, capable of producing a bright and dazzling appearance effect, similar to specular reflection. "Bottom - coat - free" means that during the film manufacturing process, there is no need to coat a primer. After extrusion coating of EVA, it can be thermally laminated with paper, having excellent bonding strength. At the same time, this type of film has good scratch - resistant performance, a relatively high surface hardness, can effectively prevent scratches caused by sharp objects, and has good wear resistance and chemical corrosion resistance, with a long service life.

[0003] In the traditional production of bottom - coat - free pre - coated films, the EVA coating is prone to peeling, especially when the EVA coating thickness is low (EVA coating thickness ≤ 6um), and problems such as the paper laminating force value occur during paper lamination. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the object of the present invention can be achieved by the following technical solutions:

[0005] A bottom - coat - free pre - coated base film with high EVA bonding strength, the bottom - coat - free pre - coated base film sequentially includes a functional layer, a core layer, and a bottom - coat - free bonding layer from top to bottom;

[0006] The preparation raw materials of the functional layer include, by weight: 5 - 8% of silica - type anti - blocking masterbatch, 92 - 95% of homopolypropylene;

[0007] The preparation raw materials of the core layer include, by mass percentage: 0.5 - 1.6% of antistatic masterbatch, 98.4 - 99.5% of homopolypropylene;

[0008] The preparation raw materials of the bottom - coat - free bonding layer include, by weight: 4 - 6% of small - particle - size anti - blocking masterbatch, 94 - 96% of copolymerized polypropylene.

[0009] Further, the preparation raw materials of the silica - type anti - blocking masterbatch include, by mass percentage: 91.9 - 96.95% of homopolypropylene, 3 - 8% of synthetic silica, 0.05 - 0.1% of antioxidant;

[0010] Further, the melt index of the silica - type anti - blocking masterbatch under the standard test of 230℃ / 2.16KG is 4.0 - 9.0g / 10min.

[0011] Further, the raw materials for preparing the antistatic masterbatch include, by mass percentage: 59.9 - 79.5% of homopolypropylene, 20 - 40% of compound antistatic agent, and 0.05 - 0.1% of antioxidant.

[0012] Further, the melt index of the antistatic masterbatch under the standard test of 230°C / 2.16KG is 15.0 - 25.0 g / 10min.

[0013] Further, the raw materials for preparing the small - particle - size anti - blocking masterbatch include, by mass percentage: 93.9 - 95.95% of copolymerized polypropylene, 4 - 6% of inorganic silica, and 0.05 - 0.1% of antioxidant;

[0014] The melt index of the small - particle - size anti - blocking masterbatch under the standard test of 230°C / 2.16KG is 4.0 - 9.0 g / 10min, and the particle size is ≤4um.

[0015] Further, the thickness of the functional layer is 0.8 - 1.0μm, the thickness of the core layer is 10.2 - 10.6μm, and the thickness of the adhesive layer is 0.6 - 0.8μm.

[0016] A preparation method of an EVA high - bonding - strength bottom - coat - free pre - coated base film, the preparation method includes the following steps: respectively adding the raw materials of the functional layer and the bottom - coat - free adhesive layer into two auxiliary extruders, adding the raw materials of the core layer into the main extruder, heating and melting, then passing through die - head composite co - extrusion, cooling through a chill roll to form a cast sheet. After the cast sheet is longitudinally pre - heated, stretched and shaped and cooled, it enters the transverse pre - heating, stretching and shaping and cooling, and then is traction - wound and subjected to aging and slitting to obtain a finished film roll.

[0017] Further, the heating and melting temperature of the functional layer is 220 - 225°C, the heating and melting temperature of the core layer is 250 - 260°C, the heating and melting temperature of the adhesive layer is 235 - 245°C; the longitudinal stretching ratio is 4.8 - 5.2, and the temperature is 110 - 125°C; the transverse stretching temperature is 155 - 170°C.

[0018] The above - mentioned EVA high - bonding - strength bottom - coat - free pre - coated base film is applied to the paper - covering packaging industry.

[0019] Advantages of the present invention: For ordinary BOPP bottomless pre-coated films, when applying a low EVA thickness during use, the adhesion between the film and EVA is low and delamination is likely to occur. Moreover, when hot-pressing and laminating with paper or the like after applying EVA, the paper laminating force value is low, and the use fastness does not meet the requirements. When applying a thicker EVA fastness, although the coating fastness can be improved, the production cost of the film increases, which is not conducive to controlling the production and use costs of the film in the upstream and downstream. Therefore, on the basis of the original, through improving the formula and other means, the present invention has successfully obtained a BOPP bottomless coating with high EVA adhesion fastness. When applying a low EVA coating, the film still has good EVA adhesion fastness and paper-plastic composite fastness. The production and use costs of the film are controlled. The product also has characteristics such as good thickness flatness, low haze, high light transmittance, and high strength, and has high market application value. Detailed implementation mode

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0021] Embodiment 1

[0022] A functional layer of a BOPP bottomless coating film with high EVA adhesion fastness of the present invention comprises the following raw materials: 5% silica type anti-blocking masterbatch, 95% homopolypropylene; the core layer comprises the following raw materials: 1% antistatic masterbatch, 99% homopolypropylene; the bottomless coating adhesion layer comprises the following raw materials: 4% small particle size anti-blocking masterbatch, 96% copolymerized polypropylene;

[0023] The melt index of the silica type anti-blocking masterbatch under the standard test of 230°C / 2.16KG is 7.68 g / 10min.

[0024] The silica type anti-blocking masterbatch comprises the following raw materials in mass percentage: 94.95% homopolypropylene, 5% synthetic silica, 0.05% antioxidant.

[0025] The melt index of the small particle size anti-blocking masterbatch under the standard test of 230°C / 2.16KG is 7.47 g / 10min, and the particle size is 3um.

[0026] The small particle size anti-blocking masterbatch comprises the following raw materials in mass percentage: 96.95% homopolypropylene, 3% inorganic gauge stone, 0.05% antioxidant.

[0027] The antistatic masterbatch comprises the following raw materials by mass percentage: homopolypropylene 79.9%, compound antistatic agent 20%, antioxidant 0.1%; the melt index of the antistatic masterbatch under the standard test of 230°C / 2.16KG is 15.2 g / 10min.

[0028] The melt index of the antistatic masterbatch under the standard test of 230°C / 2.16KG is 15.2 g / 10min.

[0029] The thickness of the functional layer is 1.0μm, the thickness of the core layer is 11.3μm, and the thickness of the bottom-coatless adhesive layer is 0.7μm.

[0030] A preparation method of an EVA high-adhesion BOPP bottom-coatless film comprises the following steps: adding the raw materials of the functional layer and the bottom-coatless adhesive layer into two auxiliary extruders respectively, adding the raw materials of the core layer into the main extruder, heating and melting, then performing co-extrusion through a die head for compounding, cooling through a chill roll to form a cast sheet, after the cast sheet is preheated, stretched and shaped and cooled longitudinally, entering the transverse stretching process including preheating, stretching and shaping and cooling, and finally obtaining a finished film roll through traction winding and aging slitting.

[0031] For the EVA high-adhesion BOPP bottom-coatless film described above, the heating and melting temperature of the functional layer is 230°C, the heating and melting temperature of the core layer is 250°C, and the heating and melting temperature of the adhesive layer is 230 - 235°C;

[0032] The longitudinal stretching ratio of the film is 4.9, and the longitudinal stretching temperature range is 110 - 125°C;

[0033] Preferably, the transverse stretching temperatures are: the preheating temperature is 170°C, the stretching temperature is 155°C, and the shaping temperature is 168°C.

[0034] Example 2

[0035] The functional layer of an EVA high-adhesion BOPP bottom-coatless film of the present invention comprises the following raw materials: 8% silica anti-blocking masterbatch, 92% homopolypropylene; the core layer comprises the following raw materials: 0.5% antistatic masterbatch, 99.5% homopolypropylene; the bottom-coatless adhesive layer comprises the following raw materials: 6% small-particle-size anti-blocking masterbatch, 94% copolymerized polypropylene;

[0036] The melt index of the silica anti-blocking masterbatch under the standard test of 230°C / 2.16KG is 7.68 g / 10min.

[0037] The silica anti-blocking masterbatch comprises the following raw materials by mass percentage: homopolypropylene 94.95%, synthetic silica 5%, antioxidant 0.05%.

[0038] The small-particle-size anti-blocking masterbatch comprises the following raw materials in percentage by mass: 96.95% of homopolypropylene, 3% of inorganic guishi, and 0.05% of antioxidant.

[0039] The small-particle-size anti-blocking masterbatch has a melt index of 6.89 g / 10 min under the standard test of 230 °C / 2.16 KG, and a particle size of 6 μm.

[0040] The antistatic masterbatch comprises the following raw materials in percentage by mass: 79.9% of homopolypropylene, 20% of compound antistatic agent, and 0.1% of antioxidant;

[0041] The antistatic masterbatch has a melt index of 15.2 g / 10 min under the standard test of 230 °C / 2.16 KG.

[0042] The thickness of the upper surface layer is 1.0 μm, the thickness of the core layer is 11.3 μm, and the thickness of the lower surface layer is 0.7 μm.

[0043] A preparation method of an EVA high-adhesion BOPP bottomless coating film comprises the following steps: adding the raw materials of the functional layer and the bottomless coating adhesive layer into two auxiliary extruders respectively, adding the raw materials of the core layer into the main extruder, heating and melting, then performing die head composite co-extrusion, cooling through a chill roll to form a cast sheet, after the cast sheet is longitudinally drawn, preheated, stretched and shaped and cooled, entering the transverse drawing preheating, stretching and shaping and cooling, and obtaining a finished film roll after traction winding and aging slitting.

[0044] For the EVA high-adhesion BOPP bottomless coating film described above, the heating and melting temperature of the functional layer is 230 °C, the heating and melting temperature of the core layer is 250 °C, and the heating and melting temperature of the adhesive layer is 230 - 235 °C;

[0045] The draw ratio of the longitudinal stretching of the film is 4.9, and the longitudinal stretching temperature range is 110 - 125 °C;

[0046] Preferably, the temperature of the transverse stretching is: the preheating temperature is 170 °C, the stretching temperature is 155 °C, and the shaping temperature is 168 °C.

[0047] Comparative Example 1

[0048] The functional layer of an EVA high-adhesion BOPP bottomless coating film of the present invention comprises the following raw materials: 3% of silica-type anti-blocking masterbatch, 97% of homopolypropylene; the core layer comprises the following raw materials: 0.1% of antistatic masterbatch, 99.9% of homopolypropylene; the bottomless coating adhesive layer comprises the following raw materials: 2% of small-particle-size anti-blocking masterbatch, 98% of copolymerized polypropylene;

[0049] The silica-type anti-blocking masterbatch has a melt index of 7.68 g / 10 min under the standard test of 230 °C / 2.16 KG.

[0050] The silica-based anti-blocking masterbatch comprises raw materials in the following mass percentages: homopolypropylene 94.95%, synthetic silica 5%, and antioxidant 0.05%.

[0051] The bottom-coatless adhesive layer comprises the following raw materials in mass percentages: anti-blocking masterbatch; the anti-blocking masterbatch has a melt index of 7.52 g / 10 min under the standard test of 230°C / 2.16 KG, and a particle size of 4 μm.

[0052] The small-particle-size anti-blocking masterbatch comprises the following raw materials in mass percentages: homopolypropylene 96.95%, inorganic stone 3%, and antioxidant 0.05%.

[0053] The small-particle-size inorganic silica-based anti-blocking masterbatch comprises the following raw materials in mass percentages: homopolypropylene 94.9%, silica 5%, and antioxidant 0.1%.

[0054] The core layer of the EVA high-adhesion BOPP bottom-coatless film has the following characteristics: the core layer comprises 0.5% antistatic masterbatch and 99.5% polypropylene.

[0055] The core layer of the EVA high-adhesion BOPP bottom-coatless film has the following characteristics: the antistatic masterbatch comprises the following raw materials in mass percentages: homopolypropylene 79.9%, compound antistatic agent 20%, and antioxidant 0.1%; the antistatic masterbatch has a melt index of 15.2 g / 10 min under the standard test of 230°C / 2.16 KG.

[0056] The core layer of the EVA high-adhesion BOPP bottom-coatless film has the following characteristics: the antistatic masterbatch comprises the following raw materials in mass percentages: homopolypropylene 69.92%, compound antistatic agent 30%, and antioxidant 0.08%; the antistatic masterbatch has a melt index of 15.2 g / 10 min under the standard test of 230°C / 2.16 KG.

[0057] The thickness of the functional layer is 1.0 μm, the thickness of the core layer is 11.3 μm, and the thickness of the bottom-coatless adhesive layer is 0.7 μm.

[0058] The preparation method of the EVA high-adhesion BOPP bottom-coatless film comprises the following steps: adding the raw materials of the functional layer and the bottom-coatless adhesive layer into two auxiliary extruders respectively, adding the raw materials of the core layer into the main extruder, heating and melting, then performing die head composite co-extrusion, cooling through a chill roll to form a cast sheet, after the cast sheet is longitudinally preheated, stretched and shaped and cooled, entering the transverse preheating, stretching and shaping and cooling, and obtaining a finished film roll after traction winding and aging slitting.

[0059] For the EVA high - adhesion BOPP bottomless coated film described above, the heating melting temperature of the functional layer is 230°C, the heating melting temperature of the core layer is 250°C, and the heating melting temperature of the adhesive layer is 230 - 235°C;

[0060] The draw ratio of the longitudinal stretching of the film is 4.9, and the longitudinal stretching temperature range is 110 - 125°C;

[0061] Preferably, the temperatures for the transverse stretching are: the pre - heating temperature is 170°C, the stretching temperature is 155°C, and the setting temperature is 168°C.

[0062] Comparative Example 2

[0063] The functional layer of the EVA high - adhesion BOPP bottomless coated film of the present invention comprises the following raw materials: 15% silica - type anti - blocking masterbatch, 85% homopolypropylene; the core layer comprises the following raw materials: 5% antistatic masterbatch, 95% homopolypropylene; the bottomless coating adhesive layer comprises the following raw materials: 15% small - particle - size anti - blocking masterbatch, 85% copolymerized polypropylene;

[0064] The melting index of the silica - type anti - blocking masterbatch under the standard test of 230°C / 2.16KG is 7.68 g / 10min.

[0065] The silica - type anti - blocking masterbatch comprises the following raw materials by mass percentage: 94.95% homopolypropylene, 5% synthetic silica, 0.05% antioxidant.

[0066] The melting index of the small - particle - size anti - blocking masterbatch under the standard test of 230°C / 2.16KG is 7.85 g / 10min, and the particle size is 4μm.

[0067] The small - particle - size anti - blocking masterbatch comprises the following raw materials by mass percentage: 96.95% copolymerized polypropylene, 3% inorganic gauge stone, 0.05% antioxidant.

[0068] The antistatic masterbatch comprises the following raw materials by mass percentage: 79.9% homopolypropylene, 20% compound antistatic agent, 0.1% antioxidant; the melting index of the antistatic masterbatch under the standard test of 230°C / 2.16KG is 15.2 g / 10min.

[0069] The thickness of the functional layer is 1.0μm, the thickness of the core layer is 11.3μm, and the thickness of the bottomless coating adhesive layer is 0.7μm.

[0070] Preparation method of EVA high-bonding-strength BOPP bottomless coated film, comprising the following steps: adding the raw materials of the functional layer and the bottomless coating adhesive layer into two auxiliary extruders respectively, adding the raw materials of the core layer into the main extruder, heating and melting, then co-extruding through a die head composite, cooling through a chill roll to form a cast sheet, after the cast sheet is longitudinally preheated, stretched and shaped and cooled, entering the transverse preheating, stretching and shaping and cooling, and obtaining the finished film roll after traction winding and aging slitting.

[0071] For the EVA high-bonding-strength BOPP bottomless coated film described above, the heating and melting temperature of the functional layer is 230 °C, the heating and melting temperature of the core layer is 250 °C, and the heating and melting temperature of the adhesive layer is 235 °C;

[0072] The stretching ratio of the longitudinal stretching of the film is 5.1, and the longitudinal stretching temperature range is 125 °C;

[0073] Preferably, the temperature of the transverse stretching is: the preheating temperature is 170 °C, the stretching temperature is 155 °C, and the shaping temperature is 168 °C.

[0074] Perform performance tests on the bottomless pre-coated base films with high EVA bonding strength prepared in Example 1 and 2 and Comparative Example 1 and 2: specifically, test by the cross-cut method. The specific test steps are as follows:

[0075] Cross-cut method

[0076] Principle: By cutting out small squares on the surface of the coated film and observing the peeling situation of the coated film in the squares after the tape is pasted and torn off, the adhesion of the coated film is evaluated, and then its peeling performance is reflected.

[0077] Operation steps:

[0078] Prepare a test plate with a clean, dry surface, free of oil stains and impurities, coat the bottomless pre-coated film on the test plate and dry and cure it.

[0079] Use a cross-cut knife to cut a set of cross-shaped or specified-shaped scratches on the surface of the coated film, and the scratch depth is usually 1 / 3 to 1 / 2 of the coating thickness to form small squares 1.

[0080] Paste the tape on the scratches, press it firmly with fingers and nails to ensure full contact between the tape and the coated film, and then quickly peel off the tape. When peeling off, it should be perpendicular to the surface of the test plate.

[0081] Check the situation of the coated film peeled off on the tape and the remaining coated film on the test plate, and evaluate the adhesion grade according to the area of the coated film peeled off, and then judge the peeling performance. Generally speaking, the smaller the peeling area, the better the adhesion and the worse the peeling performance.

[0082] The test results are shown in Table 1:

[0083] Table 1: Test results of Example 1, Example 2, Comparative Example 1 and Comparative Example 2.

[0084]

[0085] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0086] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. An EVA high bonding strength non-primer pre-coated base film, characterized in that: The primer-free pre-coated base film comprises a functional layer, a core layer and a primer-free adhesive layer from top to bottom; The raw materials for preparing the functional layer include, by weight: 5-8% of silica anti-adhesion masterbatch and 92-95% of homopolymer polypropylene; The raw materials for preparing the core layer include, by mass percentage: 0.5-1.6% antistatic masterbatch, 98.4-99.5% homopolymer polypropylene; The raw materials for preparing the primer-free adhesive layer include, by weight: 4-6% of small-particle anti-adhesion masterbatch and 94-96% of copolymerized polypropylene.

2. The EVA high-bonding strength non-primer pre-coated base film according to claim 1, characterized in that: The raw materials for preparing the silicon dioxide type anti-adhesion masterbatch include, by mass percentage, 91.9-96.95% of homopolypropylene, 3-8% of synthetic silicon dioxide, and 0.05-0.1% of antioxidant.

3. The EVA high bonding strength non-primer pre-coated base film according to claim 1, characterized in that: The melting index of the silica-based anti-adhesive masterbatch under a 230° C. / 2.16KG standard test is 4.0 to 9.0 g / 10 min.

4. The EVA high-bonding strength non-primer pre-coated base film according to claim 1, characterized in that: The raw materials for preparing the antistatic masterbatch include, by mass percentage, 59.9-79.5% of homopolypropylene, 20-40% of compound antistatic agent, and 0.05-0.1% of antioxidant.

5. The EVA high-bonding strength non-primer pre-coated base film according to claim 1, characterized in that: The antistatic masterbatch has a melt index of 15.0 to 25.0 g / 10 min under a 230° C. / 2.16 kg standard test.

6. The EVA high-bonding strength non-primer pre-coated base film according to claim 1, characterized in that: The raw materials for preparing the small-particle anti-adhesion masterbatch include, by mass percentage, 93.9-95.95% copolymerized polypropylene, 4-6% inorganic silica, and 0.05-0.1% antioxidant; The small-particle anti-adhesion masterbatch has a melt index of 4.0-9.0 g / 10 min under a 230° C. / 2.16 kg standard test, and a particle size of ≤4 um.

7. The EVA high-bonding strength non-primer pre-coated base film according to claim 1, characterized in that: The thickness of the functional layer is 0.8-1.0 μm, the thickness of the core layer is 10.2-10.6 μm, and the thickness of the bonding layer is 0.6-0.8 μm.

8. A method for preparing an EVA primer-free pre-coated base film with high bonding strength as claimed in any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: respectively adding the raw materials of the functional layer and the primer-free adhesive layer into two auxiliary extruders, adding the raw materials of the core layer into the main extruder, heating and melting, and then co-extruding through a die head, cooling through a quenching roller to form a cast sheet, preheating the cast sheet through longitudinal drawing, stretching and shaping cooling, and then preheating, stretching and shaping cooling through transverse drawing, and then traction and winding and aging and slitting to obtain a finished film roll.

9. The method for preparing an EVA primer-free pre-coating base film with high bonding strength according to claim 8, characterized in that: The heating and melting temperature of the functional layer is 220-225°C, the heating and melting temperature of the core layer is 250-260°C, and the heating and melting temperature of the bonding layer is 235-245°C; the longitudinal stretching ratio is 4.8-5.2, and the temperature is 110-125°C; the transverse stretching temperature is 155-170°C.

10. The EVA primer-free pre-coated base film with high bonding strength as described in any one of claims 1 to 8 is used in the paper-covered packaging industry.

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