A paper-plastic composite biaxially oriented polypropylene film and its preparation method and application

Abstract

The present invention relates to the technical field of biaxially oriented polypropylene film, and in particular to a paper-plastic composite biaxially oriented polypropylene film and a preparation method and application thereof, wherein the film comprises an imprintable surface layer, a core layer and a low-melting point thermal composite layer arranged in sequence, the imprintable surface layer comprises copolymerized polypropylene and 15-25wt% ethylene-norbornene copolymer A; the low-melting point thermal composite layer comprises 5-10wt% ethylene-norbornene copolymer B and ethylene-vinyl acetate copolymer, and the core layer comprises polypropylene. The paper-plastic composite biaxially oriented polypropylene film of the present invention can meet the laser holographic imprinting process requirements of the imprintable surface layer without affecting the performance of the low-melting point thermal composite layer, and can be directly thermally composited with aluminized cardboard without an adhesive layer, has high composite strength, has the advantages of energy saving and environmental protection, and has good barrier properties of the laser anti-counterfeiting cardboard obtained after lamination and aluminization, which is conducive to extending the shelf life of the packaged contents.

Description

Technical Field

[0001] The invention relates to the technical field of biaxially oriented polypropylene films, in particular to a paper-plastic composite biaxially oriented polypropylene film and a preparation method and application thereof. Background Art

[0002] In the current laser anti-counterfeiting cardboard manufacturing process, the laser surface of the BOPP laser film is obtained by the laser holographic embossing process. The thermoplastic polyolefin material on the surface of the laser film is hot-pressed and softened with a nickel plate or a laser PET film laser surface, presenting a laser holographic pattern on the surface of the working plate or transfer film, and then aluminizing or evaporating the surface through corona. BOPP laser film can be used with various types of coated substrates (such as aluminized cardboard) through paper-plastic thermal composite, which plays an anti-counterfeiting and decorative role, and is therefore widely used.

[0003] However, the BOPP laser film of the prior art still has the following problems: first, during the lamination process, it is often necessary to coat an adhesive layer after corona treatment on the smooth surface of the BOPP laser film before it can be composited with the aluminized cardboard. This lamination method, on the one hand, limits the promotion and application of the BOPP laser film. On the other hand, it is easy for the adhesive component to chemically react with the aluminized layer in the aluminized cardboard, thereby affecting the barrier properties of the aluminized layer, especially the moisture barrier properties, which is not conducive to the shelf life of the packaged contents (such as cigarettes and baked goods); second, the barrier properties of the BOPP laser film itself are not enough, which is not conducive to the synergy of the moisture barrier properties of the BOPP laser film as a base film and the vapor-deposited aluminum layer, that is, it is not conducive to the shelf life of the packaged contents.

[0004] Chinese patent CN108977107B discloses a moldable heat-composite polypropylene film and its preparation method and application, wherein the moldable heat-composite polypropylene film has both a laser moldable layer and a hot melt adhesive layer. After laser information mold printing and surface evaporation of the medium, it can be directly hot-pressed and laminated on paper printed materials and other materials without coating an adhesive layer. However, the patent does not involve how to regulate the temperature matching of the moldable layer and the hot melt adhesive layer so that the film can meet the laser holographic embossing process requirements of the moldable layer without affecting the thermal composite performance of the hot melt adhesive layer and the aluminum-plated cardboard, nor does it consider the barrier properties of the film as a whole and the insufficient aluminum plating applicability of the laser moldable layer of the film after corona treatment, which has an adverse effect on the barrier properties of the substrate for film packaging, and is not conducive to extending the shelf life of the packaged contents. Summary of the invention

[0005] Based on this, the object of the present invention is to provide a paper-plastic composite biaxially oriented polypropylene film. The film of the present invention can meet the laser holographic embossing process requirements of the embossable surface layer without affecting the performance of the low-melting point thermal composite layer, can be directly thermally composited with aluminum-plated cardboard without an adhesive layer, has high composite strength, has the advantages of energy saving and environmental protection, and the laser anti-counterfeiting cardboard obtained after lamination and aluminum plating has good barrier properties, which is beneficial to extending the shelf life of the packaged contents.

[0006] The technical solution of the present invention is achieved by the following methods:

[0007] A paper-plastic composite biaxially stretched polypropylene film comprises an embossable surface layer, a core layer and a low-melting-point thermal composite layer which are arranged in sequence, wherein the embossable surface layer comprises copolymerized polypropylene and 15-25wt% of ethylene-norbornene copolymer A, wherein the glass transition temperature of the ethylene-norbornene copolymer A is 90-100°C; the low-melting-point thermal composite layer comprises 5-10wt% of ethylene-norbornene copolymer B and ethylene-vinyl acetate copolymer, wherein the glass transition temperature of the ethylene-norbornene copolymer B is 85-95°C; and the core layer comprises polypropylene.

[0008] After a large number of experimental verifications and in-depth research, the inventors added ethylene-norbornene copolymers with different glass transition temperatures to the embossable surface layer and the low-melting-point thermal composite layer based on the temperature matching problem existing in the prior art due to the high molding temperature of the embossable surface layer and the low-melting-point thermal composite layer. By differentially designing and regulating the temperatures of the embossable surface layer and the low-melting-point thermal composite layer, the film can meet the laser holographic embossing process requirements of the embossable surface layer without affecting the thermal composite effect of the low-melting-point thermal composite layer and the aluminum-coated cardboard. It can be directly thermally composited with the aluminum-coated cardboard without an adhesive layer, and has high composite strength. At the same time, the special ring structure in the ethylene-norbornene copolymer is utilized, which is beneficial to improving the barrier properties of the entire film, ensuring the aluminum plating fastness, thereby ensuring the barrier properties of the packaging substrate after lamination, and extending the shelf life of the package contents.

[0009] The embossable surface layer includes copolymerized polypropylene and 15-25wt% of ethylene-norbornene copolymer A, and the glass transition temperature of the ethylene-norbornene copolymer A is 90-100°C. Adding 15-25wt% of ethylene-norbornene copolymer A with a glass transition temperature of 90-100°C to the embossable surface layer can not only reduce the molding temperature of the embossable surface layer to a certain extent, thereby facilitating that the low-melting point thermal composite layer is not easily damaged during molding, but also based on the special ring structure of the ethylene-norbornene copolymer, it is also beneficial to the excellent barrier properties of the film as a whole. In addition, the embossable surface layer is also made suitable for aluminum plating after corona treatment, which is beneficial to ensuring the fastness of aluminum plating, further improving the barrier properties of the packaging substrate after lamination, and is beneficial to extending the shelf life of the packaged contents. If the amount of ethylene-norbornene copolymer A added to the imprintable surface layer is less than 15wt%, the molding temperature of the imprintable surface layer cannot be effectively reduced, which is not conducive to the low melting point thermal composite layer being not easily destroyed during molding; if the amount of ethylene-norbornene copolymer A added to the imprintable surface layer is higher than 25wt%, although it is more conducive to reducing the molding temperature of the imprintable surface layer, due to the rigid ring structure on the molecular chain of the ethylene-norbornene copolymer, the imprintable surface layer will be warped toward the imprintable surface layer after the film is subjected to the biaxial stretching process because the internal stress of the imprintable surface layer is greater than that of other layers, and even interlayer peeling occurs between the core layer due to the difference in stretchability, resulting in unsmooth biaxial stretching production. Selecting ethylene-norbornene copolymer A with a glass transition temperature of 90-100°C is conducive to reducing the molding temperature of the imprintable surface layer, while maintaining a certain melt fluidity, and obtaining a thick film suitable for biaxial stretching. If the glass transition temperature of the added ethylene-norbornene copolymer A is lower than 90°C, the difference in melting point between it and the copolymer polypropylene is too large, which is not conducive to obtaining a uniform thick sheet suitable for biaxial stretching, and may also cause the imprintable surface layer to adhere to the plate roller during molding, thereby reducing the printing speed; if the glass transition temperature of the added ethylene-norbornene copolymer A is higher than 100°C, it is not conducive to reducing the molding temperature of the imprintable surface layer, and the temperature matching between the imprintable surface layer and the low-melting-point thermal composite layer is poor, resulting in the low-melting-point thermal composite layer adhering to the preheating roller during molding, resulting in damage or the imprint cannot be used normally.

[0010] Adding 5-10wt% of ethylene-norbornene copolymer B with a glass transition temperature of 85-95°C to the low-melting point thermal composite layer is beneficial to increasing the thermal composite temperature of the low-melting point thermal composite layer to a certain extent, thereby ensuring that the printable surface layer and the low-melting point thermal composite layer have good temperature matching during molding, and will not damage the low-melting point thermal composite layer. At the same time, the stiffness of the low-melting point thermal composite layer is improved, which is beneficial to the smoothness of winding and unwinding, and further enhances the barrier properties of the film, which is beneficial to the barrier properties of the packaging substrate after lamination, and is beneficial to extending the shelf life of the packaging contents. If the amount of ethylene-norbornene copolymer B added is less than 5wt%, the thermal composite temperature of the low-melting thermal composite layer cannot be effectively increased. Even if the molding temperature of the imprintable surface layer is reduced, the surface of the low-melting thermal composite layer will still be damaged due to contact with the preheating roller at a higher temperature under the corresponding molding temperature conditions, resulting in damage or the imprint cannot be used normally; if the amount of ethylene-norbornene copolymer B added is higher than 10wt%, the concentration of EVA, the main effective component of the low-melting thermal composite layer, is low, resulting in low interface bonding between the film low-melting thermal composite layer and the aluminum-plated cardboard, which is not conducive to the firm composite with the aluminum-plated cardboard. Since the low-melting thermal composite layer is in direct contact with the stretching roller, the present invention selects the glass transition temperature of the ethylene-norbornene copolymer B to be 85-95°C, which is conducive to avoiding adhesion to the stretching roller or other chrome-plated rollers other than the Teflon roller in the molding process, resulting in damage or the imprint cannot be used normally, which is conducive to the smoothness of production and application processing. If the glass transition temperature of ethylene-norbornene copolymer B is lower than 85°C, the thermal composite temperature of the low-melting-point thermal composite layer cannot be effectively increased. Even if the molding temperature of the imprintable surface layer is lowered, the surface of the low-melting-point thermal composite layer will still be damaged due to contact with a high temperature preheating roller under the corresponding molding temperature conditions; if the glass transition temperature of ethylene-norbornene copolymer B is higher than 95°C, it will be detrimental to the heat-softening fluidity of ethylene-norbornene copolymer B and the main effective component EVA during hot pressing composite, detrimental to the interface bonding strength between the low-melting-point thermal composite layer and the aluminized cardboard, and detrimental to the firm composite with the aluminized cardboard.

[0011] Furthermore, the melt volume flow rate of the ethylene-norbornene copolymer A and the ethylene-norbornene copolymer B are both 10-20 cm 3 / 10min. The selection of ethylene-norbornene copolymer A and ethylene-norbornene copolymer B within the above melt volume flow rate range can ensure relatively good melt flow matching between ethylene-norbornene copolymer A and copolymerized polypropylene in the embossable surface layer, ensure relatively good melt flow matching between ethylene-norbornene copolymer B and EVA, the main component of the low-melting-point thermal composite layer, improve the lateral distribution of the melt in the T-die, avoid excessive viscosity differences between layers in the multi-layer co-extrusion process, and make the thick sheet "incompatible" and unable to obtain a thick sheet suitable for stable biaxial stretching and thus maintaining smooth and uniform film thickness after stretching, and also help to ensure the thermal composite interface bonding between the film and the aluminum-coated cardboard.

[0012] Furthermore, the melting point of the ethylene-vinyl acetate copolymer is 83-88°C, the melt index is 15-25g / 10min, and the vinyl acetate content of the ethylene-vinyl acetate copolymer is 15-20wt%. Controlling the melting point of the ethylene-vinyl acetate copolymer to 83-88°C and the melt index to 15-25g / 10min is conducive to ensuring good melt fluidity during the processing and production process, and is conducive to the effective extrusion of the low-melting point thermal composite layer resin melt without being too sticky, so that the production is smooth, and the processing applicability requirements can be met during the subsequent film thermal composite. The vinyl acetate content of the ethylene-vinyl acetate copolymer is 15-20wt%, which can ensure a smooth preparation process of the polypropylene film. If the content of vinyl acetate (VA) in the ethylene-vinyl acetate copolymer (EVA) is lower than 15wt%, the adhesion of the obtained polypropylene film is insufficient. If the content of vinyl acetate (VA) in the ethylene-vinyl acetate copolymer (EVA) is higher than 20wt%, it is easy to degrade and break the film during stretching during the coextrusion process, and it is easy to stick to the roller during longitudinal stretching, resulting in imprinting or damage on the surface of the functional layer, which in turn leads to an inability to smoothly produce or the film cannot be used normally.

[0013] Furthermore, the melting point of the copolymerized polypropylene is 130-140° C. and the softening point is 105-115° C. Selecting copolymerized polypropylene with a melting point of 130-140° C. and a softening point of 105-115° C. is conducive to ensuring the temperature resistance of the imprintable surface layer, and can ensure the thermoplasticity and fluidity of the imprintable surface layer, and ensure the processing speed and quality of the imprinting.

[0014] Furthermore, the copolymerized polypropylene is one or both of ethylene-propylene-butene copolymer and ethylene-propylene copolymer; the ethylene content of the ethylene-propylene-butene copolymer is 2-4wt%, and the butene content is 5-6wt%; the ethylene content of the ethylene-propylene copolymer is 3.5-4.5wt%. Selecting the above copolymerized polypropylene is conducive to ensuring the temperature resistance of the imprintable surface layer, and can ensure the thermoplasticity and fluidity of the imprintable surface layer, ensure the processing speed and quality of the imprinting, and also help to ensure the compatibility and interface bonding force between the imprintable surface layer and the core layer, and avoid the phenomenon of interlayer peeling of the film.

[0015] Furthermore, the polypropylene in the core layer is isotactic polypropylene, the isotacticity of the isotactic polypropylene is 95-97%, and the melt index is 2.8-3.8 g / 10 min. Using the above isotactic polypropylene as the core layer is conducive to ensuring the excellent mechanical properties of the film as a whole.

[0016] Furthermore, the imprintable surface layer also includes 0.1-0.3wt% of an anti-adhesive agent, which is one or a mixture of two or more of silicon dioxide, zeolite, and polymethyl methacrylate. Adding a suitable anti-adhesive agent to the imprintable surface layer can improve the anti-adhesive performance of the imprintable surface layer, avoid adhesion between the inner and outer layers of the polypropylene roll film that are in contact with each other (i.e., between the imprintable surface layer and the low-melting-point thermal composite layer) to cause film breakage during slitting and unwinding, and ensure smooth winding and unwinding.

[0017] Furthermore, the surfaces of the embossable surface layer and the low-melting point thermal composite layer are both subjected to corona treatment. The two surface layers of the polypropylene film are subjected to corona treatment, and the film prepared therefrom has excellent processing applicability. In addition, since the ethylene-norbornene copolymer, whose six-membered ring structure containing a bridge bond, has a large ring tension, adding a suitable proportion of ethylene-norbornene copolymer to the embossable surface layer and the low-melting point thermal composite layer, after corona treatment, has a relatively durable high surface energy, which is conducive to further improving the interfacial bonding strength between the embossable surface layer of the film and the vapor-deposited layer, and the thermal composite interfacial bonding strength between the low-melting point thermal composite layer and the aluminum-coated layer of the aluminum-coated cardboard.

[0018] Furthermore, the thickness of the embossable surface layer is 1.5-3 μm, the thickness of the low-melting-point thermal composite layer is 2-5 μm, and the total thickness of the film is 10-20 μm.

[0019] The present invention also provides a method for preparing any of the above-mentioned paper-plastic composite biaxially oriented polypropylene films, comprising the following steps: putting component raw materials of an imprintable surface layer, a core layer, and a low-melting-point thermal composite layer into a batching unit, co-extruding them through an extruder after metering, merging them in a three-layer die head after passing through a flow channel distributor, and then cooling them through a chilled roller to form a resin sheet, biaxially stretching the resin sheet to form a film, cooling the film through an air shower, controlling the thickness through a trimmer, and then corona treating the film to obtain a film mother roll, and the film mother roll is subjected to aging treatment, slitting, and packaging, and is stored as a finished product.

[0020] Furthermore, Teflon coatings are provided on the surface of the feed chute of the extruder and on the surface of the stretching roller used for biaxial stretching.

[0021] The present invention also provides an application of any of the above-mentioned paper-plastic composite biaxially oriented polypropylene films, which is applied to laser anti-counterfeiting cardboard. The laser anti-counterfeiting cardboard includes a sequentially arranged vapor-deposited layer, any of the above-mentioned paper-plastic composite biaxially oriented polypropylene films processed by laser holographic image embossing, and an aluminum-coated cardboard. The aluminum-coated cardboard includes an aluminum-coated layer, and the aluminum-coated layer is adjacent to the low-melting-point thermal composite layer of the paper-plastic composite biaxially oriented polypropylene film.

[0022] Furthermore, the embossable surface layer of the paper-plastic composite biaxially oriented polypropylene film is passed through, and the evaporation medium of the evaporation layer is aluminum.

[0023] The paper-plastic composite biaxially oriented polypropylene film of the present invention has ethylene-norbornene copolymers with different glass transition temperatures added to the embossable surface layer and the low-melting point thermal composite layer. The embossable surface layer and the low-melting point thermal composite layer are differentially designed and regulated in temperature, so that the film can meet the laser holographic embossing process requirements of the embossable surface layer without affecting the thermal composite performance of the low-melting point thermal composite layer and the aluminum-plated cardboard, can be directly thermally composited with the aluminum-plated cardboard without an adhesive layer, and has high composite strength. At the same time, the special ring structure in the ethylene-norbornene copolymer is utilized, which is beneficial to improving the barrier property of the entire film, and improving the aluminum plating applicability of the embossable surface layer of the film after corona treatment, which is beneficial to ensuring the aluminum plating fastness, thereby ensuring the barrier property of the packaging substrate after lamination, and facilitating the extension of the shelf life of the packaged contents.

[0024] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the paper-plastic composite biaxially oriented polypropylene film according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the laser anti-counterfeiting cardboard according to an embodiment of the present invention;

[0027] Among them, the surface layer 1, the core layer 2, the low melting point thermal composite layer 3, the cardboard 4, the aluminum-plated layer 5, the holographic pattern layer 6, and the vapor-deposited layer 7 can be embossed. DETAILED DESCRIPTION

[0028] It should be clear that the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the embodiments of the present application.

[0029] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of the present application. The singular forms of "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0030] When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the attached claims. In the description of the present application, it should be understood that the terms "first", "second", "third", etc. are only used to distinguish similar objects, and do not have to be used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0031] In addition, in the description of this application, unless otherwise specified, "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0032] It should be understood that the embodiments of the present application are not limited to the precise structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the embodiments of the present application is limited only by the appended claims.

[0033] See also Figure 1As an embodiment of the present invention, the paper-plastic composite biaxially oriented polypropylene film of this embodiment includes an imprintable surface layer 1, a core layer 2 and a low-melting point thermal composite layer 3 which are arranged in sequence, the imprintable surface layer 1 includes copolymerized polypropylene and 15-25wt% ethylene-norbornene copolymer A, the glass transition temperature of ethylene-norbornene copolymer A is 90-100°C; the low-melting point thermal composite layer 3 includes 5-10wt% ethylene-norbornene copolymer B and ethylene-vinyl acetate copolymer, the glass transition temperature of ethylene-norbornene copolymer B is 85-95°C; the core layer 2 includes polypropylene.

[0034] Furthermore, the melt volume flow rate of the ethylene-norbornene copolymer A and the ethylene-norbornene copolymer B are both 10-20 cm 3 / 10min.

[0035] Furthermore, the melting point of the ethylene-vinyl acetate copolymer is 83-88° C., the melt index is 15-25 g / 10 min, and the vinyl acetate content of the ethylene-vinyl acetate copolymer is 15-20 wt %.

[0036] Furthermore, the copolymerized polypropylene has a melting point of 130-140°C and a softening point of 105-115°C.

[0037] Furthermore, the copolymerized polypropylene is one or both of ethylene-propylene-butene copolymer and ethylene-propylene copolymer; the ethylene content in the ethylene-propylene-butene copolymer is 2-4wt%, and the butene content is 5-6wt%; the ethylene content in the ethylene-propylene copolymer is 3.5-4.5wt%.

[0038] Furthermore, the polypropylene in the core layer 2 is isotactic polypropylene, the isotacticity of the isotactic polypropylene is 95-97%, and the melt index is 2.8-3.8 g / 10 min.

[0039] Furthermore, the embossable surface layer 1 further comprises 0.1-0.3 wt% of an anti-adhesive agent, wherein the anti-adhesive agent is one or a mixture of two or more of silicon dioxide, zeolite, and polymethyl methacrylate, and the particle size D50 of the anti-adhesive agent is 4-6 μm.

[0040] Furthermore, the surfaces of the embossable surface layer 1 and the low-melting-point thermal composite layer 3 are both subjected to corona treatment.

[0041] Furthermore, the thickness of the embossable surface layer 1 is 1.5-3 μm, the thickness of the low-melting-point thermal composite layer 3 is 2-5 μm, and the total thickness of the film is 10-20 μm.

[0042] The present invention also provides a method for preparing any of the above-mentioned paper-plastic composite biaxially oriented polypropylene films, comprising the following steps: feeding the raw materials of each layer component into a batching unit and then entering an extruder after metering, the extrusion temperature corresponding to the surface layer 1 and the core layer 2 can be embossed and controlled at 240-260°C, the extrusion temperature corresponding to the low-melting-point thermal composite layer 3 can be controlled at 210-240°C, and after passing through a flow channel distributor, they are merged at a multi-layer die head to form a resin melt with a multi-layer structure, and then cooled by a chilled roller at 25-35°C to form a resin sheet with a multi-layer structure; introducing the resin sheet into a longitudinal stretching device in a biaxially oriented device, and the surface layer 1 can be embossed and the core layer 2 can be embossed. The surface is preheated at 130-135°C, the stretching temperature of the imprintable surface layer 1 and the core layer 2 is controlled at 110-130°C, the low-melting point thermal composite layer 3 is preheated at 50-90°C, the stretching temperature is controlled at 50-90°C, and the stretching ratio is 4.8-5.2 times; then a transverse stretching device is introduced, after being preheated at 165-175°C, it is stretched 8-10 times at 156-160°C, and then shaped at 165-170°C, cooled by air shower, and then the surface of the low-melting point thermal composite layer 3 is corona treated to obtain the film mother roll, and finally aging treatment, slitting and packaging are performed to obtain the paper-plastic composite biaxially oriented polypropylene film.

[0043] Furthermore, Teflon coatings are provided on the surface of the feed chute of the extruder and on the surface of the stretching roller used for biaxial stretching.

[0044] The present invention also provides an application of any of the above-mentioned paper-plastic composite biaxially oriented polypropylene films, which is applied to laser anti-counterfeiting card paper 4. Figure 2 The laser anti-counterfeiting card paper 4 includes an aluminum-plated card paper 4, any of the above-mentioned paper-plastic composite biaxially stretched polypropylene films processed by laser holographic image embossing, and a vapor-deposited layer 7, and the aluminum-plated card paper 4 includes a card paper 4 and an aluminum-plated layer 5, and the aluminum-plated layer 5 is adjacent to the low-melting-point thermal composite layer 3 of the paper-plastic composite biaxially stretched polypropylene film. Specifically, any of the above-mentioned paper-plastic composite biaxially stretched polypropylene films processed by laser holographic image embossing includes a holographic pattern layer 6, an embossable surface layer 1, a core layer 2, and a low-melting-point thermal composite layer 3, which are arranged in sequence.

[0045] Furthermore, the evaporation medium of the evaporation layer 7 is aluminum.

[0046] Furthermore, the preheating rollers that the low-melting-point thermal composite layer 3 contacts during the laser embossing and aluminum evaporation processes are all provided with Teflon coatings to prevent the low-melting-point thermal composite layer 3 from sticking to the rollers.

[0047] The paper-plastic composite biaxially oriented polypropylene film of the present invention has ethylene-norbornene copolymers with different glass transition temperatures added to the imprintable surface layer 1 and the low-melting point thermal composite layer 3. By differentially designing and regulating the temperatures of the imprintable surface layer 1 and the low-melting point thermal composite layer 3, the film can meet the laser holographic imprinting process requirements of the imprintable surface layer 1 without affecting the thermal composite performance of the low-melting point thermal composite layer 3 and the aluminum-plated cardboard 4. The film can be directly thermally composited with the aluminum-plated cardboard 4 without an adhesive layer, and has high composite strength. At the same time, the special ring structure in the ethylene-norbornene copolymer is utilized, which is beneficial to improving the barrier properties of the entire film, and improving the aluminum plating applicability of the imprintable surface layer of the film after corona treatment, which is beneficial to ensuring the aluminum plating fastness, thereby ensuring the barrier properties of the packaging substrate after lamination, and facilitating the extension of the shelf life of the packaged contents.

[0048] The physical properties and test methods of the embodiments or comparative examples of the present invention are as follows:

[0049] Film thickness is measured according to GB / T6672-2001;

[0050] Melt index (melt mass flow rate MFR): According to GB / T3682-2018, polypropylene is measured at 2.16kg and 230°C, and ethylene-vinyl acetate copolymer is measured at 2.16kg and 190°C, the unit is g / 10min;

[0051] Glass transition temperature (Tg) is measured according to ISO11357, in °C;

[0052] Melting point and softening point are determined according to GB / T16582-2008, in °C;

[0053] Ethylene-norbornene copolymer melt volume flow rate (MVR), measured at 2.16 kg and 190°C;

[0054] The surface energy is measured according to GB / T14216, and the surface energy of the imprintable surface layer 1 after the film corona treatment is measured with a dyne pen, and the unit is dyn / cm;

[0055] The peel strength of aluminized cardboard 4 is measured according to GB / T8808 (Method A), and the unit is N / 15mm;

[0056] Film appearance: Observe the appearance of the film with the naked eye, such as the uniformity of thickness.

[0057] Whether the embossable surface layer 1 is scalded during the embossing process, and whether the low-melting-point thermal composite layer 3 is sticky to the roller: Observe with the naked eye the scalding degree of the embossable surface layer 1 and whether the low-melting-point thermal composite layer 3 is sticky to the roller during the molding process.

[0058] Evaluation of production smoothness: whether there is stratification, film breaking, and smoothness of winding and unwinding.

[0059] Film moisture barrier evaluation: GB / T30412-2013 plastic film and sheet water vapor transmission rate measurement (38°C, 90%RH), unit is g / (m 2 ·24h).

[0060] It should be noted that the proportions described in the embodiments of the present invention or comparative examples are all weight percentages. The components and contents of each layer in the embodiments of the present invention and comparative examples are shown in Table 1 below.

[0061] Table 1

[0062]

[0063] Example 1

[0064] This embodiment provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. The specific structure can be referred to Figure 1 The method for preparing each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this embodiment comprises the following steps:

[0065] Preparation of the imprintable surface resin: 84.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 15wt% ethylene-norbornene copolymer A (Tg 90℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0066] Preparation of core layer resin: 100 wt % isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken as the core layer resin.

[0067] Preparation of low melting point thermal composite layer resin: 90wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 10wt% ethylene-norbornene copolymer B (Tg of 85℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0068] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of the present embodiment comprises the following steps:

[0069] The components of the imprintable surface layer, the core layer, and the low-melting-point thermal composite layer are put into the batching unit and then enter the extruder after being metered. The extrusion temperature of the imprintable surface layer and the core layer is controlled at 240-260°C, and the extrusion temperature of the low-melting-point thermal composite layer is controlled at 210-240°C. After passing through the flow channel distributor, they are merged at the multi-layer die head to form a multi-layer structure of resin melt, which is then cooled by a chilled roller at 25-35°C to form a multi-layer structure of resin sheet; the resin sheet is introduced into the longitudinal stretching device in the biaxial stretching equipment, and the surface of the imprintable surface layer is subjected to Preheat at 130-135℃, the stretching temperature of the imprintable surface layer and core layer is controlled at 110-130℃, the low melting point thermal composite layer is preheated at 50-90℃, the stretching temperature is controlled at 50-90℃, and the stretching ratio is 4.8-5.2 times; then introduce the transverse stretching device, after preheating at 165-175℃, stretch 8-10 times at 156-160℃, and then shape at 165-170℃, cool by air shower, and then perform corona treatment on the surface of the low melting point thermal composite layer (the energy density of corona treatment is 1.875KJ / m 2 ), the film mother roll is collected, and finally the paper-plastic composite biaxially oriented polypropylene film is obtained through aging treatment, slitting and packaging.

[0070] The total thickness of the prepared paper-plastic composite biaxially oriented polypropylene film is 15 μm, of which the thickness of the imprintable surface layer is 1.5 μm, the thickness of the core layer is 11 μm, and the thickness of the low-melting-point thermal composite layer is 2.5 μm. The preparation method has a smooth process and smooth winding and unwinding.

[0071] Example 2

[0072] This embodiment provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. The specific structure can be referred to Figure 1 The method for preparing each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this embodiment comprises the following steps:

[0073] Preparation of the imprintable surface resin: 79.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 20wt% ethylene-norbornene copolymer A (Tg 95℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0074] Preparation of core layer resin: 100 wt % isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken as the core layer resin.

[0075] Preparation of low melting point thermal composite layer resin: 92wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 8wt% ethylene-norbornene copolymer B (Tg of 90℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0076] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this embodiment is the same as that of Embodiment 1, so it is not described in detail.

[0077] The total thickness of the prepared paper-plastic composite biaxially oriented polypropylene film is 15 μm, of which the thickness of the imprintable surface layer is 1.5 μm, the thickness of the core layer is 11 μm, and the thickness of the low-melting-point thermal composite layer is 2.5 μm. The preparation method has a smooth process and smooth winding and unwinding.

[0078] Example 3

[0079] This embodiment provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. The specific structure can be referred to Figure 1 The method for preparing each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this embodiment comprises the following steps:

[0080] Preparation of the imprintable surface resin: 74.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 25wt% ethylene-norbornene copolymer A (Tg 100℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0081] Preparation of core layer resin: 100 wt % isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken as the core layer resin.

[0082] Preparation of low melting point thermal composite layer resin: 95wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 5wt% ethylene-norbornene copolymer B (Tg of 95℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0083] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this embodiment is the same as that of Embodiment 1, so it is not described in detail.

[0084] The total thickness of the prepared paper-plastic composite biaxially oriented polypropylene film is 15 μm, of which the thickness of the imprintable surface layer is 1.5 μm, the thickness of the core layer is 11 μm, and the thickness of the low-melting-point thermal composite layer is 2.5 μm. The preparation method has a smooth process and smooth winding and unwinding.

[0085] Comparative Example 1

[0086] This comparative example provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. Figure 1 The preparation method of each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this comparative example comprises the following steps:

[0087] Preparation of printable surface layer resin: Take 99.9wt% ethylene-propylene-butene copolymer (melting point of 130°C, softening point of 115°C, melt index of 5g / 10min, ethylene content of 2mol%, butene content of 5mol%) and 0.1wt% silica (D50 of 4μm) and mix them evenly to obtain a printable surface layer resin.

[0088] Preparation of core layer resin: 100 wt % of isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken to obtain core layer resin.

[0089] Preparation of low melting point thermal composite layer resin: 100 wt % ethylene-vinyl acetate copolymer (melt index of 20 g / 10 min, VA content of 20 wt %, melting point of 83° C.) was taken as the low melting point thermal composite layer resin.

[0090] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0091] The total thickness of the film is 30 μm, of which the thickness of the imprintable surface layer is 2 μm, the thickness of the core layer is 26 μm, and the thickness of the low melting point thermal composite layer is 2 μm. The preparation method has a smooth process and smooth winding and unwinding.

[0092] Comparative Example 2

[0093] This comparative example provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. Figure 1 The preparation method of each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this comparative example comprises the following steps:

[0094] Preparation of printable surface layer resin: Take 99.9wt% ethylene-propylene-butene copolymer (melting point of 130°C, softening point of 115°C, melt index of 5g / 10min, ethylene content of 2mol%, butene content of 5mol%) and 0.1wt% silica (D50 of 4μm) and mix them evenly to obtain a printable surface layer resin.

[0095] Preparation of core layer resin: 100 wt % of isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken to obtain core layer resin.

[0096] Preparation of low melting point thermal composite layer resin: 92wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 8wt% ethylene-norbornene copolymer B (Tg of 90℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0097] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0098] The total thickness of the film is 30 μm, of which the thickness of the imprintable surface layer is 2 μm, the thickness of the core layer is 26 μm, and the thickness of the low melting point thermal composite layer is 2 μm. The preparation method has a smooth process and smooth winding and unwinding.

[0099] Comparative Example 3

[0100] This comparative example provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. Figure 1 The preparation method of each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this comparative example comprises the following steps:

[0101] Preparation of the imprintable surface resin: 59.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 40wt% ethylene-norbornene copolymer A (Tg 95℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0102] Preparation of core layer resin: 100 wt % of isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken to obtain core layer resin.

[0103] Preparation of low melting point thermal composite layer resin: 92wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 8wt% ethylene-norbornene copolymer B (Tg of 90℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0104] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0105] The total thickness of the film is 30 μm, of which the thickness of the imprintable surface layer is 2 μm, the thickness of the core layer is 26 μm, and the thickness of the low melting point thermal composite layer is 2 μm. In this preparation method, interlayer peeling occurs.

[0106] Comparative Example 4

[0107] This comparative example provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. Figure 1 The preparation method of each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this comparative example comprises the following steps:

[0108] Preparation of the imprintable surface resin: 79.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 20wt% ethylene-norbornene copolymer A (Tg 95℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0109] Preparation of core layer resin: 100 wt % of isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken to obtain core layer resin.

[0110] Preparation of low melting point thermal composite layer resin: 100 wt % ethylene-vinyl acetate copolymer (melt index of 20 g / 10 min, VA content of 20 wt %, melting point of 83° C.) was taken as the low melting point thermal composite layer resin.

[0111] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0112] The total thickness of the film is 30 μm, of which the thickness of the imprintable surface layer is 2 μm, the thickness of the core layer is 26 μm, and the thickness of the low melting point thermal composite layer is 2 μm. The preparation method has a smooth process and smooth winding and unwinding.

[0113] Comparative Example 5

[0114] This comparative example provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. Figure 1 The preparation method of each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this comparative example comprises the following steps:

[0115] Preparation of the imprintable surface resin: 79.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 20wt% ethylene-norbornene copolymer A (Tg 95℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0116] Preparation of core layer resin: 100 wt % isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken as the core layer resin.

[0117] Preparation of low melting point thermal composite layer resin: 80wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 20wt% ethylene-norbornene copolymer B (Tg of 90℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0118] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0119] The total thickness of the prepared paper-plastic composite biaxially oriented polypropylene film is 15 μm, wherein the thickness of the imprintable surface layer is 1.5 μm, the thickness of the core layer is 11 μm, and the thickness of the low-melting-point thermal composite layer is 2.5 μm. The preparation method has a smooth process.

[0120] Comparative Example 6

[0121] This comparative example provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. Figure 1 The preparation method of each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this comparative example comprises the following steps:

[0122] Preparation of the imprintable surface resin: 79.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 20wt% ethylene-norbornene copolymer A (Tg 80℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0123] Preparation of core layer resin: 100 wt % of isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken to obtain core layer resin.

[0124] Preparation of low melting point thermal composite layer resin: 92wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 8wt% ethylene-norbornene copolymer B (Tg of 90℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0125] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0126] The total thickness of the film is 30 μm, of which the thickness of the imprintable surface layer is 2 μm, the thickness of the core layer is 26 μm, and the thickness of the low melting point thermal composite layer is 2 μm. The film prepared by this method has poor appearance and poor thickness uniformity.

[0127] Comparative Example 7

[0128] This comparative example provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. Figure 1 The preparation method of each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this comparative example comprises the following steps:

[0129] Preparation of the imprintable surface resin: 79.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 20wt% ethylene-norbornene copolymer A (Tg 120℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0130] Preparation of core layer resin: 100 wt % of isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken to obtain core layer resin.

[0131] Preparation of low melting point thermal composite layer resin: 92wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 8wt% ethylene-norbornene copolymer B (Tg of 90℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0132] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0133] The total thickness of the film is 30 μm, of which the thickness of the imprintable surface layer is 2 μm, the thickness of the core layer is 26 μm, and the thickness of the low-melting-point thermal composite layer is 2 μm. The preparation method has a smooth process.

[0134] Comparative Example 8

[0135] This comparative example provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. Figure 1 The preparation method of each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this comparative example comprises the following steps:

[0136] Preparation of the imprintable surface resin: 79.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 20wt% ethylene-norbornene copolymer A (Tg 95℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0137] Preparation of core layer resin: 100 wt % of isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken to obtain core layer resin.

[0138] Preparation of low melting point thermal composite layer resin: 92wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 8wt% ethylene-norbornene copolymer B (Tg of 75℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0139] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0140] The total thickness of the film is 30 μm, of which the thickness of the imprintable surface layer is 2 μm, the thickness of the core layer is 26 μm, and the thickness of the low melting point thermal composite layer is 2 μm. In the preparation method, the roller sticks during the preparation process, and the winding and unwinding are not smooth.

[0141] Comparative Example 9

[0142] This comparative example provides a paper-plastic composite biaxially oriented polypropylene film, comprising an embossable surface layer, a core layer and a low melting point thermal composite layer arranged in sequence. Figure 1 The preparation method of each layer of resin of the paper-plastic composite biaxially oriented polypropylene film of this comparative example comprises the following steps:

[0143] Preparation of the imprintable surface resin: 79.9wt% ethylene-propylene-butene copolymer (melting point 130℃, softening point 115℃, melt index 5g / 10min, ethylene content 2mol%, butene content 5mol%), 20wt% ethylene-norbornene copolymer A (Tg 95℃, melt index 20cm 3 / 10min) and 0.1wt% silica (D50 is 4μm) are uniformly mixed to obtain an imprintable surface resin.

[0144] Preparation of core layer resin: 100 wt % of isotactic polypropylene (isotacticity is 97%, melt index is 3.8 g / 10 min) is taken to obtain core layer resin.

[0145] Preparation of low melting point thermal composite layer resin: 92wt% ethylene-vinyl acetate copolymer (melt index of 20g / 10min, VA content of 20wt%, melting point of 83℃) and 8wt% ethylene-norbornene copolymer B (Tg of 105℃, melt index of 20cm 3 / 10min) and evenly mix to obtain a low melting point thermal composite layer resin.

[0146] The preparation method of the paper-plastic composite biaxially oriented polypropylene film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0147] The total thickness of the film is 30 μm, of which the thickness of the imprintable surface layer is 2 μm, the thickness of the core layer is 26 μm, and the thickness of the low melting point thermal composite layer is 2 μm. The film prepared by this method has poor appearance and poor thickness uniformity.

[0148] The method for applying the paper-plastic composite biaxially oriented polypropylene film to laser anti-counterfeiting cardboard of the present invention comprises the following steps:

[0149] A nickel plate containing a laser holographic image is obtained, and the nickel plate is mounted on a plate roller of a molding device to form a working plate. Then, the imprintable surface layer of the paper-plastic composite biaxially oriented polypropylene film described in any one of Examples 1-3 and Comparative Examples 1-9 is preheated by a Teflon roller and transported to between the plate roller and the pressing roller of the molding device for imprinting. The imprinting temperature of the imprintable surface layer of the film is controlled at 105° C., the plate roller temperature is controlled at 50° C., and the pressing roller pressure is controlled at 12 kg / cm 2 , the embossing speed is controlled at 45m / min, thereby embossing the laser holographic image on the embossable surface layer, and then vapor-depositing an aluminum protective layer in a vacuum aluminum plating device to obtain a paper-plastic composite biaxially oriented polypropylene film with a holographic pattern layer and a vapor-deposited layer;

[0150] The paper-plastic composite biaxially oriented polypropylene film with the holographic pattern layer and the vapor-deposited layer is directly thermally laminated with the aluminum-coated cardboard on a paper-plastic laminating machine at 100° C., 10 MPa, and 20 m / min to obtain laser anti-counterfeiting cardboard.

[0151] The performance test results of the paper-plastic composite biaxially oriented polypropylene films of Examples 1 to 3 and Comparative Examples 1 to 9 are shown in Table 2 below.

[0152] Table 2

[0153]

[0154] From the above performance test data, it can be seen that in Comparative Example 1, since the corresponding ethylene-norbornene copolymer was not added to the stampable surface layer and the low-melting point thermal composite layer, the low-melting point thermal composite layer of the prepared film showed a sticking phenomenon during the stamping process, and the stamping effect of the stampable surface layer was poor, the barrier property of the film decreased, and the surface energy of the stampable surface layer after corona treatment was too low, which was not conducive to ensuring the aluminum plating fastness; in Comparative Example 2, no appropriate amount of ethylene-norbornene copolymer A was added to the stampable surface layer, and the stamping temperature of the stampable surface layer of the prepared film was too high, so the stamping effect obtained at the stamping temperature of 105°C was poor, and the barrier property of the film was also unreasonable. The surface energy of the embossable surface layer after corona treatment is too low, which is not conducive to ensuring the fastness of aluminum plating; in Comparative Example 3, due to the addition of excessive ethylene-norbornene copolymer A to the embossable surface layer, the prepared film has the problem of scalding of the embossable surface layer during the embossing process due to the low molding temperature of the embossable surface layer, and the phenomenon of warping toward the embossable surface layer occurs, and interlayer peeling occurs between the core layer due to the difference in stretchability, resulting in unsmooth biaxial stretching production; in Comparative Example 4, an appropriate amount of ethylene-norbornene copolymer B is not added to the low-melting-point thermal composite layer, resulting in the low melting point of the low-melting-point thermal composite layer. The low-melting-point thermal composite layer sticks to the roller during the embossing process. Phenomenon; In Comparative Example 5, due to the addition of excessive ethylene-norbornene copolymer B to the low-melting-point thermal composite layer, the composite fastness between the low-melting-point thermal composite layer and the aluminum-coated cardboard is reduced, and the low-melting-point thermal composite layer appears to stick to the roller during the embossing process, which is not conducive to the smoothness of production and the thickness uniformity of the appearance of the prepared film; In Comparative Example 6, the glass transition temperature of the ethylene-norbornene copolymer A added to the embossable surface layer is too low, resulting in too low a molding temperature of the embossable surface layer, and the embossable surface layer is scalded during the embossing process; In Comparative Example 7, the glass transition temperature of the ethylene-norbornene copolymer A added to the embossable surface layer is too low. If the temperature is too high, the molding temperature of the imprintable surface layer cannot be effectively reduced, resulting in poor imprinting effect and is not conducive to the thickness uniformity of the film appearance; the glass transition temperature of the ethylene-norbornene copolymer B added to the low-melting-point thermal composite layer in Comparative Example 8 is too low, and the melting point of the low-melting-point thermal composite layer cannot be effectively increased, and the low-melting-point thermal composite layer sticks to the roller during the imprinting process; the glass transition temperature of the ethylene-norbornene copolymer B added to the low-melting-point thermal composite layer in Comparative Example 9 is too high, which is not conducive to a firm composite with the aluminized cardboard, resulting in a decrease in the composite fastness between the low-melting-point thermal composite layer and the aluminized cardboard, and is not conducive to the thickness uniformity of the film appearance.

[0155] From the data of Examples 1 to 3, it can be seen that the paper-plastic composite biaxially oriented polypropylene film of the present invention meets the laser holographic embossing process requirements of the embossable surface layer without affecting the performance of the low-melting-point thermal composite layer, can be directly thermally composited with aluminized cardboard without an adhesive layer, has high composite strength, has the advantages of energy saving and environmental protection, and the laser anti-counterfeiting cardboard obtained after lamination and aluminization has good barrier properties, which is beneficial to extending the shelf life of the packaged contents.

[0156] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. A paper-plastic composite biaxially oriented polypropylene film, characterized in that: The invention comprises a stampable surface layer, a core layer and a low-melting-point thermal composite layer which are arranged in sequence, wherein the stampable surface layer comprises copolymerized polypropylene and 15-25wt% ethylene-norbornene copolymer A, wherein the glass transition temperature of the ethylene-norbornene copolymer A is 90-100°C; the low-melting-point thermal composite layer comprises 5-10wt% ethylene-norbornene copolymer B and ethylene-vinyl acetate copolymer, wherein the glass transition temperature of the ethylene-norbornene copolymer B is 85-95°C, and the glass transition temperatures of the ethylene-norbornene copolymer A and the ethylene-norbornene copolymer B are different; and the core layer comprises polypropylene.

2. The paper-plastic composite biaxially oriented polypropylene film according to claim 1, characterized in that: The melt volume flow rates of the ethylene-norbornene copolymer A and the ethylene-norbornene copolymer B measured at 2.16 kg and 190° C. are both 10-20 cm 3 / 10min.

3. The paper-plastic composite biaxially oriented polypropylene film according to claim 1, characterized in that: The melting point of the ethylene-vinyl acetate copolymer is 83-88° C., the melt index of the ethylene-vinyl acetate copolymer measured at 2.16 kg and 190° C. is 15-25 g / 10 min, and the vinyl acetate content of the ethylene-vinyl acetate copolymer is 15-20 wt %.

4. The paper-plastic composite biaxially oriented polypropylene film according to claim 1, characterized in that: The melting point of the copolymerized polypropylene is 130-140°C and the softening point is 105-115°C.

5. The paper-plastic composite biaxially oriented polypropylene film according to claim 1, characterized in that: The copolymerized polypropylene is one or both of ethylene-propylene-butene copolymer and ethylene-propylene copolymer; the ethylene content in the ethylene-propylene-butene copolymer is 2-4wt%, and the butene content is 5-6wt%; the ethylene content in the ethylene-propylene copolymer is 3.5-4.5wt%.

6. The paper-plastic composite biaxially oriented polypropylene film according to claim 1, characterized in that: The polypropylene in the core layer is isotactic polypropylene, the isotacticity of the isotactic polypropylene is 95-97%, and the melt index of the polypropylene measured at 2.16 kg and 230° C. is 2.8-3.8 g / 10 min.

7. The paper-plastic composite biaxially oriented polypropylene film according to claim 1, characterized in that: The embossable surface layer further comprises 0.1-0.3 wt % of an anti-adhesive agent, wherein the anti-adhesive agent is one of silicon dioxide, zeolite, and polymethyl methacrylate, or a mixture of two or more thereof.

8. The paper-plastic composite biaxially oriented polypropylene film according to claim 1, characterized in that: The surfaces of the embossable surface layer and the low-melting-point thermal composite layer are both subjected to corona treatment.

9. A method for preparing a paper-plastic composite biaxially oriented polypropylene film according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: putting component raw materials of the embossable surface layer, the core layer and the low-melting-point thermal composite layer into a batching unit, co-extruded through an extruder after metering, merged in a three-layer die head after passing through a flow channel distributor, and then cooled by a chilled roller to form a resin sheet, biaxially stretching the resin sheet to form a film, cooling the film through an air shower, controlling the thickness through a trimming machine, and then performing a corona treatment on the film to obtain a film master roll, which is subjected to aging treatment, slitting, and packaging before being put into storage as a finished product.

10. An application of the paper-plastic composite biaxially oriented polypropylene film according to any one of claims 1 to 8, characterized in that: Applicable to laser anti-counterfeiting card paper, the laser anti-counterfeiting card paper comprises a vapor-deposited layer, a paper-plastic composite biaxially oriented polypropylene film as claimed in any one of claims 1 to 8, and an aluminized card paper arranged in sequence, the aluminized card paper comprises an aluminized layer, and the aluminized layer is adjacent to a low-melting-point thermal composite layer of the paper-plastic composite biaxially oriented polypropylene film.

Images