A matte film containing primer and preparation method thereof

Abstract

The present invention relates to the field of films, and in particular to a matte film containing a primer and a preparation method thereof, wherein the matte film containing a primer comprises a primer layer, a core layer and a matte layer which are sequentially arranged; the primer layer comprises 80-89.9wt% ethylene-octene copolymer and 10-20wt% propylene-butene copolymer, the melting point of the ethylene-octene copolymer is 75-95°C, and the melting point of the propylene-butene copolymer is 80-95°C; the core layer comprises homopolymerized polypropylene; the matte layer comprises random copolymerized polypropylene, 40-50wt% high-density polyethylene and 15-35wt% propylene-based copolymer, the melting point of the propylene-based copolymer is 140-160°C, and the crystallinity of the propylene-based copolymer is 5-10%. The matte film containing a primer of the present invention not only improves the quality problems of the matte film being scalded and sticking to a high-temperature steel roller and improving the temperature resistance of the primer layer and the matte layer, but also improves the matte effect of the matte film, and has good prospects for industrial application.

Description

Technical Field

[0001] The invention relates to the field of films, in particular to a matte film containing a primer and a preparation method thereof. Background Art

[0002] BOPP film is a packaging film that is first stretched longitudinally and then stretched transversely. It is generally a co-extruded composite structure of 3 to 5 layers. After multiple stretching, the film shows good mechanical and optical properties. It has the advantages of light weight, printing performance and good moisture resistance, so it is known as the "Queen of Packaging". The technological iteration and application of BOPP film have accelerated the rapid and high-quality development of the packaging industry, reduced the use of paper packaging materials in society, reduced carbon emissions and the protection of forest resources. At present, BOPP film is widely used in paper-plastic lamination, among which the thermal lamination of EVA (ethylene-vinyl acetate) hot melt adhesive film is a typical application of green packaging. When the traditional BOPP film is directly coated with EVA hot melt adhesive, the bonding strength between EVA and the homopolymer PP of BOPP film is poor. Therefore, before gluing, AC agent (high molecular weight polyethyleneimine aqueous solution) is generally applied offline, and then EVA coating is performed. Since the organic solvents used in the AC agent coating stage are harmful to the human body and the environment, and the process efficiency of offline gluing and laminating is low, a primer-coated BOPP film has been developed on the market. A surface layer of the primer-coated BOPP film contains a primer during extrusion, which can replace the traditional AC agent. EVA hot melt adhesive can be directly coated in downstream applications, which reduces one process compared to offline gluing and is more energy-saving and environmentally friendly.

[0003] However, the production of primer-coated BOPP films is much more difficult than that of ordinary BOPP films. The primer layer of existing primer-coated BOPP films is usually of low melting point and has a certain viscosity. Therefore, during production, on the one hand, the extrusion temperature of the primer layer cannot be too high, and on the other hand, the temperature of the primer layer's roller surface must be moderate to avoid adhesion and scratches on the primer layer. Therefore, when existing primer-coated BOPP films are produced and rolled up on traditional BOPP film production lines, since the primer layer is placed in a narrow and long flow channel with high temperature and pressure, not only will degradation products and cross-linking products be produced, but also problems such as film surface burns and difficulty in unwinding the parent roll after winding will occur, which restricts the large-scale production of primer-coated BOPP films.

[0004] Although there is a kind of primer-coated BOPP film with two surface layers, namely a primer layer and a matte layer, on the market, the roughness of the matte layer makes it relatively easy to unwind the mother roll after winding, but in actual production, the aforementioned problems of primer coating film surface burns or primer coating sticking to the roller still exist; if the production temperature of the primer coating is reduced as much as possible during longitudinal stretching, the core layer and the matte layer will have low stretching temperatures due to heat conduction, which may easily lead to cold drawing and uneven stretching of the film surface; if the longitudinal stretching temperature of the matte layer is increased as much as possible, since the main component of the matte surface layer is a random copolymer of high-density polyethylene and polypropylene, the melting point of high-density polyethylene is about 130°C, and the initial heat sealing temperature of random copolymer polypropylene is about 120-125°C, therefore, increasing the temperature of the longitudinal stretching area of ​​the matte layer will cause high-temperature burns to the matte layer during longitudinal stretching. On this basis, with the continuous commissioning and release of BOPP film production capacity in recent years, the pursuit of production efficiency and high output has become an industry trend. Therefore, the speed of BOPP film production lines is getting faster and faster, and the base coating and matte layer need to continue to heat up to match the higher production line speed, which will further aggravate the quality problem of burns on the base coating film surface. Summary of the invention

[0005] Based on this, the purpose of the present invention is to provide a matte film containing a primer, which improves the quality problems of scalding and sticking to high-temperature steel rollers of the matte film by optimizing the formula components of the matte layer containing a primer, improves the temperature resistance of the primer layer and the matte layer, and also improves the matte effect of the matte film, which has good prospects for industrial application.

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

[0007] A matte film containing a primer, comprising a primer layer, a core layer and a matte layer which are arranged in sequence; the primer layer comprises 80-89.9wt% of an ethylene-octene copolymer and 10-20wt% of a propylene-butene copolymer, the melting point of the ethylene-octene copolymer is 75-95°C, and the melting point of the propylene-butene copolymer is 80-95°C; the core layer comprises homopolymerized polypropylene; the matte layer comprises random copolymerized polypropylene, 40-50wt% of a high-density polyethylene and 15-35wt% of a propylene-based copolymer, the melting point of the propylene-based copolymer is 140-160°C, and the crystallinity of the propylene-based copolymer is 5-10%.

[0008] The matte film containing a primer coating of the present invention not only improves the quality problems of the matte film being scalded on a high-temperature steel roller and sticking to the roller, improves the temperature resistance of the primer coating and the matte layer, but also improves the matte effect of the matte film, and has good industrial application prospects.

[0009] The primer layer of the primer-containing matte film of the present invention uses ethylene-octene copolymer as the main raw material, and 10-20wt% of propylene-butene copolymer is added to the primer layer to improve the interface compatibility between the primer layer and the core layer. If the addition amount of the propylene-butene copolymer is less than 10wt%, the bonding force between the primer layer and the core layer is low, and the effect of improving the interface bonding force between the two phases is not obvious. If the addition amount of the propylene-butene copolymer is greater than 20wt%, it will cause poor compatibility between the primer layer and the EVA hot melt adhesive layer, which is not conducive to the bonding force between the primer layer and the EVA hot melt adhesive layer. The present invention defines the melting point of the ethylene-octene copolymer as 75-95°C. If the melting point of the ethylene-octene copolymer is less than 75°C, the primer layer is likely to stick to the roller during longitudinal stretching, causing defects on the film surface, and is likely to stick or even be unable to unwind when rolled up under a large tension; if the melting point of the ethylene-octene copolymer is greater than 95°C, the compatibility and interlayer bonding strength of the primer layer with the later-coated EVA hot melt adhesive decrease; further, the present invention also defines the melting point of the propylene-butene copolymer as 80-95°C. If the melting point of the propylene-butene copolymer is less than 80°C, it is not conducive to reducing the problem of the primer layer sticking to the roller during longitudinal stretching, and is prone to high-temperature burns. If the melting point of the propylene-butene copolymer is greater than 95°C, the melting point of the propylene-butene copolymer and the melting point of the ethylene-octene copolymer are too different, which is not conducive to the interlayer bonding strength of the primer layer and the later-coated EVA hot melt adhesive.

[0010] In order to improve the temperature resistance of the matt layer, the present invention adds a high-melting-point, low-crystallization and transparent propylene-based copolymer to the matt layer, adopts the high-melting-point propylene-based copolymer to replace the low-melting-point random copolymer polypropylene, partially covers the high-density polyethylene phase of the matt layer, reduces the high-temperature scalding quality problem of the matt layer during longitudinal stretching, and the melting point of the propylene-based copolymer is higher than the melting points of the high-density polyethylene and the random copolymer polypropylene, thereby increasing the temperature resistance of the matt layer; specifically, the melting point of the propylene-based copolymer is 140-160° C. If the melting point of the propylene-based copolymer is less than 140° C., the problem of high-temperature scalding of the matt layer during longitudinal stretching cannot be effectively improved; if the melting point of the propylene-based copolymer is greater than 160° C., the melting point difference between the components of the matt layer is too large, which easily causes poor stretching of the matt layer. In the present invention, a propylene-based copolymer is added to the matte layer as a continuous phase, and the crystallinity of the propylene-based copolymer is 5-10%. Its low crystallinity is conducive to the stretching protrusion of the high-density polyethylene phase, and improves the overall matte effect of the matte film. Specifically, when the crystallinity of the propylene-based copolymer is lower than 5%, the melt viscosity is very low, which has certain difficulties in production, processing and feeding. When the crystallinity of the propylene-based copolymer is higher than 10%, a large amount of addition is required to significantly reduce the total crystallization enthalpy of the continuous phase, and the cost is high. At the same time, the propylene-based copolymer is in a transparent form, has good compatibility with random copolymerized polypropylene and high-density polyethylene, and does not affect the transparency of the film. Adding 15-35wt% of propylene-based copolymer to the matt layer improves the temperature resistance of the matt layer while improving the matt effect of the matt layer. If the amount of propylene-based copolymer added is less than 15wt%, although the total crystallization enthalpy of the continuous phase decreases and the haze of the matt film is improved to a certain extent, the amount of propylene-based copolymer added is low, and it is not enough to form a continuous amorphous continuous phase after shear dispersion, and the effect of improving the temperature resistance of the matt layer is not obvious; if the amount of propylene-based copolymer added is higher than 35wt%, the tensile strength of the matt film containing the primer will be significantly reduced, and the thermal shrinkage ratio of the film will be increased. The present invention further defines the content of high-density polyethylene in the matt layer as 40-50wt%, and the content of random copolymer polypropylene as 17-50wt%, which is conducive to obtaining a more ideal matt effect. Preferably, the content of random copolymer polypropylene in the matt layer of the present invention is 17-37wt%.

[0011] Further, the propylene-based copolymer in the matt layer is propylene-1-butene copolymerized polypropylene, in which the isotacticity of the propylene sequence is 90-93%, and the isotacticity of the 1-butene sequence is 87-90%. It is well known to those skilled in the art that, generally for propylene-1-butene copolymerized polypropylene, the introduction of butene units destroys the sequence structure of the polypropylene chain molecular chain, reduces the crystallinity of the copolymer, and the melting temperature decreases significantly with the increase of butene-1. However, the propylene-1-butene copolymer polypropylene selected in the present invention is synthesized by using an optimized catalytic system of stereo-controlled polymerization. Specifically, alkyl aluminum or alkyl aluminum hydride, an external electron donor, a supported titanium catalyst and hydrogen are used as a catalyst system for isotactic polymerization to carry out bulk copolymerization to obtain the propylene-1-butene copolymer polypropylene. The isotacticity of the 1-butene sequence and the propylene sequence in the obtained propylene-1-butene copolymer polypropylene is greater than 85%, and with the increase of the 1-butene content, the melting temperature of the copolymer increases significantly, so that the propylene-1-butene copolymer polypropylene has a relatively high melting point while maintaining a relatively low crystallinity. Propylene-1-butene copolymer polypropylene composed of a propylene sequence with an isotacticity of 90-93% and a 1-butene sequence with an isotacticity of 87-90% is selected. If the isotacticity of the propylene sequence is too low, the melting point of the propylene-1-butene copolymer polypropylene is too low. When added to the matte layer, it cannot provide effective heat-resistant protection for the matte layer, and the improvement of high-temperature scald of the matte layer is not obvious enough. If the isotacticity of the propylene sequence is too high, the crystallinity of the propylene-1-butene copolymer polypropylene will increase, which is not conducive to improving the haze of the matte film; if the isotacticity of the 1-butene sequence is too low, the melting point of the 1-butene sequence in the propylene-1-butene copolymer polypropylene will be too low, which is not conducive to obtaining a relatively high melting point propylene-1-butene copolymer polypropylene. When added to the matte layer, it cannot provide effective heat-resistant protection for the matte layer. If the isotacticity of the 1-butene sequence is too high, the propylene-1-butene copolymer polypropylene may be too rigid and not conducive to biaxial stretching.

[0012] Furthermore, the content of 1-butene monomer in the propylene-1-butene copolymer polypropylene in the matt layer is 15-35wt%. If the 1-butene content is lower than 15wt%, the randomness of the propylene-1-butene copolymer polypropylene is reduced, the crystallinity is increased, and the matt effect of improving the matt layer is not obvious enough. When the 1-butene content is higher than 35wt%, due to the low crystallinity of the propylene-1-butene copolymer polypropylene, when the temperature rises, the internal stress of the propylene-1-butene copolymer polypropylene is easily released, resulting in an increase in the heat shrinkage of the primer-containing matt film during downstream lamination.

[0013] Furthermore, the content of octene in the ethylene-octene copolymer is 5-20wt%. By controlling the content of octene in the ethylene-octene copolymer, the compatibility and affinity between the primer layer and the EVA hot melt adhesive layer can be improved on the basis of ensuring the melting performance of the film; if the content of octene is too high, the melting point of the ethylene-octene copolymer will be reduced, and undesirable phenomena such as sticking to the roller will occur during the stretching process; if the content of octene is too low, the compatibility of the primer layer and EVA will be reduced, which is not conducive to the bonding force between the primer layer and the EVA hot melt adhesive layer.

[0014] Furthermore, under the conditions of 230°C and 2.16kg, the melt index of the propylene-butene copolymer in the primer layer and the propylene-1-butene copolymer polypropylene in the matte layer are both 5-10g / 10min. Controlling the propylene-butene copolymer in the primer layer to 5-10g / 10min is conducive to matching the melt index of the ethylene-octene copolymer, and the two can be dispersed more evenly. Controlling the melt index of the propylene-1-butene copolymer polypropylene in the matte layer to 5-10g / 10min, as a continuous phase, when the melt index of the propylene-1-butene copolymer polypropylene is lower than 5g / 10min, it is not conducive to the fluidity of the matte layer and the improvement of the uniformity of the matte of the edge of the film. When the melt index of the propylene-1-butene copolymer polypropylene is higher than 10g / 10min, the difference between the melt viscosity and the dispersed phase is too large, which is not conducive to shear dispersion and maintaining the mechanical strength of the system.

[0015] Furthermore, at 230°C and 2.16kg, the melt index of the random copolymer polypropylene in the matte layer is 7-12g / 10min, and at 190°C and 21.6kg, the melt index of the high-density polyethylene is 8-14g / 10min. If the melt index of the random copolymer polypropylene is lower than 7g / 10min, the viscosity difference between the high-density polyethylene phase and the random copolymer polypropylene phase is low, which is not conducive to the phase separation size of the high-density polyethylene phase, and the fluidity is also deteriorated. If the melt index of the random copolymer polypropylene is higher than 12g / 10min, the viscosity difference between the high-density polyethylene phase and the random copolymer polypropylene phase is too large, and the high-viscosity high-density polyethylene phase is difficult to effectively disperse in the low-viscosity random copolymer polypropylene phase. The present invention also defines that the melt index of the high-density polyethylene measured under the conditions of 190°C and 21.6kg is 8-14g / 10min. If the melt index of the high-density polyethylene is lower than 8g / 10min, the molecular weight of the high-density polyethylene is too large, and impurity points are likely to appear on the membrane surface. If the melt index of the high-density polyethylene is higher than 14g / 10min, the melt viscosity will be low, and the viscosity difference with the random copolymer polypropylene will be small, resulting in a small phase separation size of the high-density polyethylene in the matte layer and a poor matte effect.

[0016] Furthermore, the primer layer further includes 0.1-0.3wt% of an antioxidant, which is prepared by compounding antioxidant 1010 and antioxidant 168 at a ratio of 1:2. Adding 0.1-0.3wt% of an antioxidant to the primer layer is beneficial to reducing the thermal oxidation degradation and crosslinking of the low-melting-point polyolefin resin in the primer layer during high-temperature extrusion, and reducing the quality problem of uneven film stretching.

[0017] Furthermore, the random copolymer polypropylene in the matt layer is selected from one or both of ethylene-propylene copolymer polypropylene and ethylene-propylene-butylene copolymer polypropylene.

[0018] Furthermore, the core layer comprises 99wt% homopolypropylene and 1wt% antistatic masterbatch, the melt index of the homopolypropylene is 3-4g / 10min, the carrier of the antistatic masterbatch is homopolypropylene, and the effective concentration of the antistatic agent in the antistatic masterbatch is 40wt%.

[0019] The present invention also provides a method for preparing any of the above-mentioned matte films containing a primer, comprising the following steps: mixing the raw materials of each layer evenly through a high-speed mixer, then passing through a batcher and entering a screw extruder, and after being metered by a metering pump, the melts of each extruder are merged into a thick sheet at a T-die head, the thick sheet is cooled by a chilled roller and enters a chilled water tank, the thick sheet is longitudinally stretched after passing through a water blowing chamber, and then transversely stretched, and then corona treated after shaping, and then rolled up to an aging rack for treatment, and after the treatment is completed, it is cut and packaged into finished products.

[0020] In order to better understand and implement the present invention, the present invention is described in detail below. DETAILED DESCRIPTION

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] It should be understood that the embodiments of the present application are not limited to the precise structure described above, 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.

[0026] As an embodiment of the present invention, the matte film containing a primer in this embodiment optimizes the formula components of the matte layer containing a primer, thereby improving the quality problems of the matte film being burned and sticking to the high-temperature steel roller, improving the temperature resistance of the primer layer and the matte layer, and improving the matte effect of the matte film, and thus having a good prospect for industrial application.

[0027] Further, the propylene-based copolymer in the matt layer is propylene-1-butene copolymerized polypropylene, in which the isotacticity of the propylene sequence is 90-93%, and the isotacticity of the 1-butene sequence is 87-90%. It is well known to those skilled in the art that, generally for propylene-1-butene copolymerized polypropylene, the introduction of butene units destroys the sequence structure of the polypropylene chain molecular chain, reduces the crystallinity of the copolymer, and the melting temperature decreases significantly with the increase of butene-1. However, the propylene-1-butene copolymer polypropylene selected in the present invention is synthesized by using an optimized catalytic system of stereo-controlled polymerization. Specifically, alkyl aluminum or alkyl aluminum hydride, an external electron donor, a supported titanium catalyst and hydrogen are used as a catalyst system for isotactic polymerization to carry out bulk copolymerization to obtain the propylene-1-butene copolymer polypropylene. The isotacticity of the 1-butene sequence and the propylene sequence in the obtained propylene-1-butene copolymer polypropylene is greater than 85%, and with the increase of the 1-butene content, the melting temperature of the copolymer increases significantly, so that the propylene-1-butene copolymer polypropylene has a relatively high melting point while maintaining a relatively low crystallinity. Propylene-1-butene copolymer polypropylene composed of a propylene sequence with an isotacticity of 90-93% and a 1-butene sequence with an isotacticity of 87-90% is selected. If the isotacticity of the propylene sequence is too low, the melting point of the propylene-1-butene copolymer polypropylene is too low. When added to the matte layer, it cannot provide effective heat-resistant protection for the matte layer, and the improvement of high-temperature scald of the matte layer is not obvious enough. If the isotacticity of the propylene sequence is too high, the crystallinity of the propylene-1-butene copolymer polypropylene will increase, which is not conducive to improving the haze of the matte film; if the isotacticity of the 1-butene sequence is too low, the melting point of the 1-butene sequence in the propylene-1-butene copolymer polypropylene will be too low, which is not conducive to obtaining a relatively high melting point propylene-1-butene copolymer polypropylene. When added to the matte layer, it cannot provide effective heat-resistant protection for the matte layer. If the isotacticity of the 1-butene sequence is too high, the propylene-1-butene copolymer polypropylene may be too rigid and not conducive to biaxial stretching.

[0028] Furthermore, the content of 1-butene monomer in the propylene-1-butene copolymer polypropylene in the matt layer is 15-35wt%. If the 1-butene content is lower than 15wt%, the randomness of the propylene-1-butene copolymer polypropylene is reduced, the crystallinity is increased, and the matt effect of improving the matt layer is not obvious enough. When the 1-butene content is higher than 35wt%, due to the low crystallinity of the propylene-1-butene copolymer polypropylene, when the temperature rises, the internal stress of the propylene-1-butene copolymer polypropylene is easily released, resulting in an increase in the heat shrinkage of the primer-containing matt film during downstream lamination.

[0029] Furthermore, the content of octene in the ethylene-octene copolymer is 5-20wt%. By controlling the content of octene in the ethylene-octene copolymer, the compatibility and affinity between the primer layer and the EVA hot melt adhesive layer can be improved on the basis of ensuring the melting performance of the film; if the content of octene is too high, the melting point of the ethylene-octene copolymer will be reduced, and undesirable phenomena such as sticking to the roller will occur during the stretching process; if the content of octene is too low, the compatibility of the primer layer and EVA will be reduced, which is not conducive to the bonding force between the primer layer and the EVA hot melt adhesive layer.

[0030] Furthermore, under the conditions of 230°C and 2.16kg, the melt index of the propylene-butene copolymer in the primer layer and the propylene-1-butene copolymer polypropylene in the matte layer are both 5-10g / 10min. Controlling the propylene-butene copolymer in the primer layer to 5-10g / 10min is conducive to matching the melt index of the ethylene-octene copolymer, and the two can be dispersed more evenly. Controlling the melt index of the propylene-1-butene copolymer polypropylene in the matte layer to 5-10g / 10min, as a continuous phase, when the melt index of the propylene-1-butene copolymer polypropylene is lower than 5g / 10min, it is not conducive to the fluidity of the matte layer and the improvement of the uniformity of the matte of the edge of the film. When the melt index of the propylene-1-butene copolymer polypropylene is higher than 10g / 10min, the difference between the melt viscosity and the dispersed phase is too large, which is not conducive to shear dispersion and maintaining the mechanical strength of the system.

[0031] Furthermore, at 230°C and 2.16kg, the melt index of the random copolymer polypropylene in the matte layer is 7-12g / 10min, and at 190°C and 21.6kg, the melt index of the high-density polyethylene is 8-14g / 10min. If the melt index of the random copolymer polypropylene is lower than 7g / 10min, the viscosity difference between the high-density polyethylene phase and the random copolymer polypropylene phase is low, which is not conducive to the phase separation size of the high-density polyethylene phase, and the fluidity is also deteriorated. If the melt index of the random copolymer polypropylene is higher than 12g / 10min, the viscosity difference between the high-density polyethylene phase and the random copolymer polypropylene phase is too large, and the high-viscosity high-density polyethylene phase is difficult to effectively disperse in the low-viscosity random copolymer polypropylene phase.

[0032] Furthermore, the primer layer further includes 0.1-0.3wt% of an antioxidant, which is prepared by compounding antioxidant 1010 and antioxidant 168 at a ratio of 1:2. Adding 0.1-0.3wt% of an antioxidant to the primer layer is beneficial to reducing the thermal oxidation degradation and crosslinking of the low-melting-point polyolefin resin in the primer layer during high-temperature extrusion, and reducing the quality problem of uneven film stretching.

[0033] Furthermore, the random copolymer polypropylene in the matt layer is selected from one or both of ethylene-propylene copolymer polypropylene and ethylene-propylene-butylene copolymer polypropylene.

[0034] Furthermore, the core layer comprises 99wt% homopolypropylene and 1wt% antistatic masterbatch, the melt index of the homopolypropylene is 3-4g / 10min, the carrier of the antistatic masterbatch is homopolypropylene, and the effective concentration of the antistatic agent in the antistatic masterbatch is 40wt%.

[0035] Furthermore, the total thickness of the primer-containing matte film of the present invention is 14-25 μm, the thickness of the primer layer is 1-2 μm, and the thickness of the matte layer is 1.6-2.0 μm.

[0036] The invention also provides a method for preparing any of the above-mentioned matte films containing a primer, comprising the following steps: mixing the raw materials of each layer evenly through a high-speed mixer, then passing through a batcher and entering a screw extruder, and after being metered by a metering pump, the melts of each extruder are merged into a thick sheet at a T-die head, and the thick sheet is cooled by a chilled roller and enters a chilled water tank, and the thick sheet is longitudinally stretched after passing through a water blowing chamber, and then transversely stretched, and then corona treated after shaping, and then rolled up to an aging rack for treatment, and after the treatment is completed, it is cut and packaged into finished products.

[0037] It should be noted that the random copolymer polypropylene in the matte layer of the present invention and the comparative example is ethylene-propylene binary copolymer polypropylene, the melt index of ethylene-propylene binary copolymer polypropylene is 8g / 10min (230°C, 2.16kg), and the melt index of high-density polyethylene is 11g / 10min (190°C, 21.6kg). The antioxidant in the core layer of the present invention and the comparative example is a mixture of BASF 1010 and 168, wherein 1010:168=1:2, and the carrier resin is an ethylene-octene copolymer with a melting point of 85°C.

[0038] The physical properties and test methods of the embodiments or comparative examples of the present invention are as follows:

[0039] The melting point and crystallinity are both tested by DSC; the gloss test is carried out according to GB / T8807-1988, the haze test is carried out according to GB / T2410-2008, and the mechanical property test is carried out according to GB / T1040.3-2006.

[0040] Thermal shrinkage: In the thermal shrinkage test, a film sample of 10*10 cm in size was placed in an oven at 110°C for 120 seconds and then cooled at room temperature to test the longitudinal and transverse shrinkage of the film.

[0041] Defect point detection: The statistical cycle is 10,000 meters of online detector winding, and the particle size of the defect points counted is 1mm² and above.

[0042] Evaluation of the bonding strength between the primer layer and the hot-melt adhesive layer: Take the primer-containing matte film prepared in the present invention, and coat EVA hot-melt adhesive (VA content of 18 wt %, melt index of 15 g / 10 min) on the surface of the primer layer with a coating thickness of 8 μm. After coating, use 3M adhesive tape to perform an interlayer peeling test to observe whether the EVA hot-melt adhesive layer peels off.

[0043] Example 1

[0044] This embodiment provides a matte film containing a primer, including a primer layer, a core layer and a matte layer arranged in sequence. The method for preparing the resin layers of the matte film containing a primer in this embodiment includes the following steps:

[0045] Preparation of primer resin: 84.7 wt% of ethylene-octene copolymer (octene content is 18 wt%, melt index is 6.5 g / 10 min, melting point is 85°C), 15 wt% of propylene-butene copolymer (butene content is 33 wt%, melt index is 7 g / 10 min, melting point is 75°C) and 0.3 wt% of antioxidant are mixed evenly in a high-speed mixer to obtain a primer resin.

[0046] Preparation of core layer resin: 99 wt% homopolypropylene (melt index is 3.2 g / 10 min) and 1 wt% antistatic masterbatch (the carrier is homopolypropylene, the effective concentration is 40 wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0047] Preparation of matt layer resin: 48wt% of high-density polyethylene, 37wt% of ethylene-propylene copolymer polypropylene and 15wt% of propylene-based copolymer (propylene-based copolymer is propylene-1-butene copolymer polypropylene, with a melt index of 7.1g / 10min, in which the copolymer ratio of 1-butene is 31.3wt%, the crystallinity is 7.46%, and the melting point is 160°C; in propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 93%, and the 1-butene sequence isotacticity is 90%) are mixed evenly in a high-speed mixer to obtain a matt layer resin.

[0048] The preparation method of the BOPP film of this embodiment comprises the following steps:

[0049] The resin of each layer is transported to three screw extruders through a batcher (the base coating and the matte layer are both single-screw extruders, the core layer is a twin-screw extruder, the extrusion temperature of the base coating is 235°C, the extrusion temperature of the matte layer is set to 245°C, and the extrusion temperature of the core layer is 250°C). The melt of the three extruders is metered by a melt metering pump, passes through a narrow flow channel and merges into a thick sheet at the T-die head. The thick sheet is cooled by a chilled roller and enters a chilled water tank, and then enters the longitudinal stretching area after passing through a water blowing chamber. It is stretched longitudinally (primer layer: preheating zone temperature is 70℃, stretching zone temperature is 60℃, shaping zone temperature is 65℃; matte layer: preheating zone temperature is 135℃, stretching zone temperature is 130℃, shaping zone temperature is 130℃; longitudinal stretching ratio is 5 times), and then enters the transverse stretching area for transverse stretching (stretching temperature is 160℃, transverse stretching ratio is 8 times), and then trimming and corona treatment are carried out after shaping, and then it is rolled up to the aging rack for treatment. After the treatment is completed, it is slit and packaged into finished products.

[0050] The total thickness of the matte film containing primer in this embodiment is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0051] Example 2

[0052] This embodiment provides a matte film containing a primer, including a primer layer, a core layer and a matte layer arranged in sequence. The method for preparing the resin layers of the matte film containing a primer in this embodiment includes the following steps:

[0053] Preparation of primer resin: 84.7wt% of ethylene-octene copolymer (octene content is 18wt%, melt index is 6.5g / 10min, melting point is 85℃), 15wt% of propylene-butene copolymer (butene content is 33wt%, melt index is 7g / 10min, melting point is 75℃) and 0.3wt% of antioxidant are mixed evenly in a high-speed mixer to obtain primer resin. Preparation of core layer resin: 99wt% of homopolypropylene (melt index is 3.2g / 10min) and 1wt% of antistatic masterbatch (carrier is homopolypropylene, effective concentration is 40wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0054] Preparation of matt layer resin: 48wt% of high-density polyethylene, 27wt% of ethylene-propylene copolymer polypropylene and 25wt% of propylene-based copolymer (propylene-based copolymer is propylene-1-butene copolymer polypropylene, with a melt index of 7.1g / 10min, in which the copolymer ratio of 1-butene is 31.3wt%, the crystallinity is 7.46%, and the melting point is 160°C; in propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 93%, and the 1-butene sequence isotacticity is 90%) are mixed evenly in a high-speed mixer to obtain a matt layer resin.

[0055] The preparation method of the primer-containing matte film of this embodiment is the same as that of Embodiment 1, so it is not described in detail.

[0056] The total thickness of the matte film containing primer in this embodiment is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0057] Example 3

[0058] This embodiment provides a matte film containing a primer, including a primer layer, a core layer and a matte layer arranged in sequence. The method for preparing the resin layers of the matte film containing a primer in this embodiment includes the following steps:

[0059] Preparation of primer resin: 84.7wt% of ethylene-octene copolymer (octene content is 18wt%, melt index is 6.5g / 10min, melting point is 85℃), 15wt% of propylene-butene copolymer (butene content is 33wt%, melt index is 7g / 10min, melting point is 75℃) and 0.3wt% of antioxidant are mixed evenly in a high-speed mixer to obtain primer resin. Preparation of core layer resin: 99wt% of homopolypropylene (melt index is 3.2g / 10min) and 1wt% of antistatic masterbatch (carrier is homopolypropylene, effective concentration is 40wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0060] Preparation of matte layer resin: 48wt% of high-density polyethylene, 22wt% of ethylene-propylene copolymer polypropylene and 30wt% of propylene-based copolymer (propylene-based copolymer is propylene-1-butene copolymer polypropylene, with a melt index of 7.1g / 10min, in which the copolymer ratio of 1-butene is 31.3wt%, the crystallinity is 7.46%, and the melting point is 160°C; in propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 93%, and the 1-butene sequence isotacticity is 90%) are mixed evenly in a high-speed mixer to obtain a matte layer resin.

[0061] The preparation method of the primer-containing matte film of this embodiment is the same as that of Embodiment 1, so it is not described in detail.

[0062] The total thickness of the matte film containing primer in this embodiment is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0063] Example 4

[0064] This embodiment provides a matte film containing a primer, including a primer layer, a core layer and a matte layer arranged in sequence. The method for preparing the resin layers of the matte film containing a primer in this embodiment includes the following steps:

[0065] Preparation of primer resin: 84.7wt% of ethylene-octene copolymer (octene content is 18wt%, melt index is 6.5g / 10min, melting point is 85℃), 15wt% of propylene-butene copolymer (butene content is 33wt%, melt index is 7g / 10min, melting point is 75℃) and 0.3wt% of antioxidant are mixed evenly in a high-speed mixer to obtain primer resin. Preparation of core layer resin: 99wt% of homopolypropylene (melt index is 3.2g / 10min) and 1wt% of antistatic masterbatch (carrier is homopolypropylene, effective concentration is 40wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0066] Preparation of matte layer resin: 48wt% high-density polyethylene, 17wt% ethylene-propylene copolymer polypropylene and 35wt% propylene-based copolymer (the propylene-based copolymer in this embodiment is propylene-1-butene copolymer polypropylene, with a melt index of 8.3g / 10min, wherein the comonomer ratio of 1-butene is 23.5wt%, the crystallinity is 6.1%, and the melting point is 140°C; in the propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 90%, and the 1-butene sequence isotacticity is 87%) are mixed evenly in a high-speed mixer to obtain a matte layer resin.

[0067] The preparation method of the primer-containing matte film of this embodiment is the same as that of Embodiment 1, so it is not described in detail.

[0068] The total thickness of the matte film containing primer in this embodiment is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0069] Comparative Example 1

[0070] This comparative example provides a matte film containing a primer, comprising a primer layer, a core layer and a matte layer arranged in sequence. The preparation method of each layer of the resin of the matte film containing a primer in this comparative example comprises the following steps:

[0071] Preparation of primer resin: 84.7 wt% of ethylene-octene copolymer (octene content is 18 wt%, melt index is 6.5 g / 10 min, melting point is 85°C), 15 wt% of propylene-butene copolymer (butene content is 33 wt%, melt index is 7 g / 10 min, melting point is 75°C) and 0.3 wt% of antioxidant are mixed evenly in a high-speed mixer to obtain a primer resin.

[0072] Preparation of core layer resin: 99 wt% homopolypropylene (melt index is 3.2 g / 10 min) and 1 wt% antistatic masterbatch (the carrier is homopolypropylene, the effective concentration is 40 wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0073] Preparation of matt layer resin: 48 wt% of high-density polyethylene and 52 wt% of ethylene-propylene copolymer polypropylene are mixed evenly in a high-speed mixer to obtain a matt layer resin.

[0074] The preparation method of the primer-containing matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0075] The total thickness of the primer-containing matte film of this comparative example is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0076] Comparative Example 2

[0077] This comparative example provides a matte film containing a primer, comprising a primer layer, a core layer and a matte layer arranged in sequence. The preparation method of each layer of the resin of the matte film containing a primer in this comparative example comprises the following steps:

[0078] Preparation of primer resin: 84.5 wt% of ethylene-octene copolymer (octene content is 18 wt%, melt index is 6.5 g / 10 min, melting point is 85°C), 15 wt% of propylene-butene copolymer (butene content is 33 wt%, melt index is 7 g / 10 min, melting point is 75°C) and 0.5 wt% of antioxidant are mixed evenly in a high-speed mixer to obtain a primer resin.

[0079] Preparation of core layer resin: 99 wt% homopolypropylene (melt index is 3.2 g / 10 min) and 1 wt% antistatic masterbatch (the carrier is homopolypropylene, the effective concentration is 40 wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0080] Preparation of matt layer resin: 48wt% of high-density polyethylene, 47wt% of ethylene-propylene copolymer polypropylene and 5wt% of propylene-based copolymer (propylene-based copolymer is propylene-1-butene copolymer polypropylene, with a melt index of 7.1g / 10min, in which the copolymer ratio of 1-butene is 31.3wt%, the crystallinity is 7.46%, and the melting point is 160°C; in propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 93%, and the 1-butene sequence isotacticity is 90%) are mixed evenly in a high-speed mixer to obtain a matt layer resin.

[0081] The preparation method of the primer-containing matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0082] The total thickness of the primer-containing matte film of this comparative example is 18 μm, of which the thickness of the primer layer is 5.5 μm and the thickness of the matte layer is 2 μm.

[0083] Comparative Example 3

[0084] This comparative example provides a matte film containing a primer, comprising a primer layer, a core layer and a matte layer arranged in sequence. The preparation method of each layer of the resin of the matte film containing a primer in this comparative example comprises the following steps:

[0085] Preparation of primer resin: 84.7 wt% of ethylene-octene copolymer (octene content is 18 wt%, melt index is 6.5 g / 10 min, melting point is 85°C), 15 wt% of propylene-butene copolymer (butene content is 33 wt%, melt index is 7 g / 10 min, melting point is 75°C) and 0.3 wt% of antioxidant are mixed evenly in a high-speed mixer to obtain a primer resin.

[0086] Preparation of core layer resin: 99 wt% homopolypropylene (melt index is 3.2 g / 10 min) and 1 wt% antistatic masterbatch (the carrier is homopolypropylene, the effective concentration is 40 wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0087] Preparation of matt layer resin: 48wt% of high-density polyethylene, 14wt% of ethylene-propylene copolymer polypropylene and 38wt% of propylene-based copolymer (propylene-based copolymer is propylene-1-butene copolymer polypropylene, with a melt index of 7.1g / 10min, in which the copolymer ratio of 1-butene is 31.3wt%, the crystallinity is 7.46%, and the melting point is 160°C; in propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 93%, and the 1-butene sequence isotacticity is 90%) are mixed evenly in a high-speed mixer to obtain a matt layer resin.

[0088] The preparation method of the primer-containing matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0089] The total thickness of the primer-containing matte film of this comparative example is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0090] Comparative Example 4

[0091] This comparative example provides a matte film containing a primer, comprising a primer layer, a core layer and a matte layer arranged in sequence. The preparation method of each layer of the resin of the matte film containing a primer in this comparative example comprises the following steps:

[0092] Preparation of primer resin: 84.7 wt% of ethylene-octene copolymer (octene content is 18 wt%, melt index is 6.5 g / 10 min, melting point is 85°C), 15 wt% of propylene-butene copolymer (butene content is 33 wt%, melt index is 7 g / 10 min, melting point is 75°C) and 0.3 wt% of antioxidant are mixed evenly in a high-speed mixer to obtain a primer resin.

[0093] Preparation of core layer resin: 99 wt% homopolypropylene (melt index is 3.2 g / 10 min) and 1 wt% antistatic masterbatch (the carrier is homopolypropylene, the effective concentration is 40 wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0094] Preparation of matt layer resin: 48wt% of high-density polyethylene, 37wt% of ethylene-propylene copolymer polypropylene and 15wt% of propylene-based copolymer (propylene-based copolymer is propylene-1-butene copolymer polypropylene, with a melt index of 7.1g / 10min, in which the copolymer ratio of 1-butene is 31.3wt%, the crystallinity is 4.1%, and the melting point is 120°C; in propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 70%, and the 1-butene sequence isotacticity is 80%) are mixed evenly in a high-speed mixer to obtain a matt layer resin.

[0095] The preparation method of the primer-containing matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0096] The total thickness of the primer-containing matte film of this comparative example is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0097] Comparative Example 5

[0098] This comparative example provides a matte film containing a primer, comprising a primer layer, a core layer and a matte layer arranged in sequence. The preparation method of each layer of the resin of the matte film containing a primer in this comparative example comprises the following steps:

[0099] Preparation of primer resin: 84.7 wt% of ethylene-octene copolymer (octene content is 18 wt%, melt index is 6.5 g / 10 min, melting point is 85°C), 15 wt% of propylene-butene copolymer (butene content is 33 wt%, melt index is 7 g / 10 min, melting point is 75°C) and 0.3 wt% of antioxidant are mixed evenly in a high-speed mixer to obtain a primer resin.

[0100] Preparation of core layer resin: 99 wt% homopolypropylene (melt index is 3.2 g / 10 min) and 1 wt% antistatic masterbatch (the carrier is homopolypropylene, the effective concentration is 40 wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0101] Preparation of matt layer resin: 48wt% of high-density polyethylene, 37wt% of ethylene-propylene copolymer polypropylene and 15wt% of propylene-based copolymer (propylene-based copolymer is propylene-1-butene copolymer polypropylene, with a melt index of 7.1g / 10min, in which the copolymer ratio of 1-butene is 31.3wt%, the crystallinity is 40%, and the melting point is 165°C; in propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 97%, and the 1-butene sequence isotacticity is 93%) are mixed evenly in a high-speed mixer to obtain a matt layer resin.

[0102] The preparation method of the primer-containing matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0103] The total thickness of the primer-containing matte film of this comparative example is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0104] Comparative Example 6

[0105] This comparative example provides a matte film containing a primer, comprising a primer layer, a core layer and a matte layer arranged in sequence. The preparation method of each layer of the resin of the matte film containing a primer in this comparative example comprises the following steps:

[0106] Preparation of primer resin: 99.7 wt% of ethylene-octene copolymer (octene content: 18 wt%, melt index: 6.5 g / 10 min, melting point: 85°C) and 0.3 wt% of antioxidant were mixed evenly in a high-speed mixer to obtain primer resin.

[0107] Preparation of core layer resin: 99 wt% homopolypropylene (melt index is 3.2 g / 10 min) and 1 wt% antistatic masterbatch (the carrier is homopolypropylene, the effective concentration is 40 wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0108] Preparation of matt layer resin: 48wt% of high-density polyethylene, 37wt% of ethylene-propylene copolymer polypropylene and 15wt% of propylene-based copolymer (propylene-based copolymer is propylene-1-butene copolymer polypropylene, with a melt index of 7.1g / 10min, in which the copolymer ratio of 1-butene is 31.3wt%, the crystallinity is 7.46%, and the melting point is 160°C; in propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 93%, and the 1-butene sequence isotacticity is 90%) are mixed evenly in a high-speed mixer to obtain a matt layer resin.

[0109] The preparation method of the primer-containing matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0110] The total thickness of the primer-containing matte film of this comparative example is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0111] In this comparative example, the film production process was not smooth enough and delamination occurred.

[0112] Comparative Example 7

[0113] This comparative example provides a matte film containing a primer, comprising a primer layer, a core layer and a matte layer arranged in sequence. The preparation method of each layer of the resin of the matte film containing a primer in this comparative example comprises the following steps:

[0114] Preparation of primer resin: 69.7 wt% of ethylene-octene copolymer (octene content is 18 wt%, melt index is 6.5 g / 10 min, melting point is 85 ° C), 30 wt% of propylene-butene copolymer (butene content is 33 wt%, melt index is 7 g / 10 min, melting point is 75 ° C) and 0.3 wt% of antioxidant are mixed evenly in a high-speed mixer to obtain a primer resin.

[0115] Preparation of core layer resin: 99 wt% homopolypropylene (melt index is 3.2 g / 10 min) and 1 wt% antistatic masterbatch (the carrier is homopolypropylene, the effective concentration is 40 wt%) are mixed evenly in a high-speed mixer to obtain core layer resin.

[0116] Preparation of matt layer resin: 48wt% of high-density polyethylene, 37wt% of ethylene-propylene copolymer polypropylene and 15wt% of propylene-based copolymer (propylene-based copolymer is propylene-1-butene copolymer polypropylene, with a melt index of 7.1g / 10min, in which the copolymer ratio of 1-butene is 31.3wt%, the crystallinity is 7.46%, and the melting point is 160°C; in propylene-1-butene copolymer polypropylene, the propylene sequence isotacticity is 93%, and the 1-butene sequence isotacticity is 90%) are mixed evenly in a high-speed mixer to obtain a matt layer resin.

[0117] The preparation method of the primer-containing matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0118] The total thickness of the primer-containing matte film of this comparative example is 18 μm, of which the thickness of the primer layer is 1.8 μm and the thickness of the matte layer is 2 μm.

[0119] The performance test results of the primer-containing matte films of Examples 1 to 4 and Comparative Examples 1 to 7 are shown in Table 1 below.

[0120] Table 1

[0121]

[0122] Since BOPP matte film is generally stretched transversely from the middle first, and then gradually stretched to both sides after reaching a certain tensile stress, the BOPP matte film has always had the problem that the stretching in the middle of the film is better than that on both sides, which is reflected in the matte effect, resulting in poor matte effect or even uneven matte.

[0123] From the analysis of the above test results, it can be seen that the matte film containing a primer of the present invention, with the increase of the amount of propylene-based copolymer added in the matte layer, whether it is Example 1 to Example 4, or Comparative Example 1 to Comparative Example 3, the haze data of the matte film is significantly improved. In particular, when the amount of propylene-based copolymer added in the matte layer is more than 15wt%, it is effective in improving the matte and uneven dispersion problems on both sides of the film. This is because the added propylene-based copolymer is a low-crystalline material, and its crystallinity is much lower than that of random copolymer polypropylene and high-density polyethylene. The propylene-based copolymer forms a low-crystalline continuous phase. During high-speed stretching production, the presence of the low-crystalline continuous phase makes the fast-crystallizing high-density polyethylene phase more likely to protrude, thereby increasing the roughness of the matte layer. Therefore, the problem of uneven edge matte is effectively improved, and the overall matte effect is improved.

[0124] In addition, since binary random copolymer polypropylene is used as a conventional heat-sealing material, the initial heat-sealing temperature is generally between 120-125°C. After replacing part of the random copolymer polypropylene with a high melting point propylene copolymer, the temperature resistance of the matte layer can be improved, and the scalding or sticking roller problems of the matte layer under high-temperature rollers can be reduced; and as the amount of propylene copolymer added increases, the decrease in the defect point data becomes more and more obvious. When the content of the propylene copolymer reaches more than 30wt%, not only a good matte effect can be obtained, but also low defects can be achieved, the quality of the matte film can be guaranteed, and the appearance problems of dots or sesames when the paper and plastic are coated with a dark background can be reduced. However, when the content of the propylene copolymer is increased, the film surface defect point data does not change much, which may be related to the high-temperature scalding of the high-density polyethylene phase in the matte layer. From the data of Example 4, it can also be concluded that the propylene copolymer with a melting point of 140°C is less effective than the propylene copolymer with a melting point of 160°C in improving the film surface scalding, but it is also better than the effect of Comparative Example 1 without the addition of the propylene copolymer.

[0125] In addition, due to the low crystallinity of propylene-based copolymers, after film stretching, film forming, shaping and slitting, the stretching orientation of the polymer chain segments is an unstable state, and the existence of stress in the chain segments has a tendency to return to random coils. This trend is particularly obvious at a certain heating temperature, and the thermal shrinkage and the crystallinity of the system are generally inversely proportional. Therefore, the greater the amount of propylene-based copolymer added, the lower the crystallinity of the continuous phase of the matte layer, and the greater its thermal shrinkage ratio. When the lateral thermal shrinkage ratio exceeds 4.5%, the paper-plastic coating will have obvious edge warping, and even affect the application of UV varnish or cause printing overprinting errors. Therefore, it is more appropriate to keep the proportion of propylene-based copolymers within 35wt%.

[0126] In Comparative Example 4, the isotacticity of the propylene sequence and the 1-butene sequence in the propylene-based copolymer are too low, resulting in lower melting point and crystallinity of the propylene-based copolymer, and significantly increased defect points on the matte surface of the prepared film, i.e., the matte layer cannot be effectively protected against temperature, and the heat shrinkage rate increases. Downstream manufacturers will experience serious quality problems such as film curling and large overprint positioning deviation during lamination. However, as the crystallinity of the propylene-based copolymer is further reduced, the total crystallization enthalpy of the continuous phase decreases more significantly, and thus the matte effect of Comparative Example 4 is improved.

[0127] In Comparative Example 5, the isotacticity of the propylene sequence and the 1-butene sequence in the propylene-based copolymer are too high, resulting in an increase in the melting point and crystallinity of the propylene-based copolymer, which is not conducive to the compatibility of the propylene-based copolymer with other materials of the matte layer, resulting in a thick sheet that is incompatible, causing poor stretching of the matte surface, poor matte uniformity, and affecting the appearance of the film.

[0128] In Comparative Example 6, no propylene-butene copolymer was added to the primer layer, resulting in poor compatibility between the primer layer and the core layer, and stratification occurred during the production process; in Comparative Example 7, an excessive amount of propylene-butene copolymer was added, which reduced the bonding strength between the primer layer and the hot melt adhesive layer, and interlayer peeling occurred in the peeling test.

[0129] 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 matte film containing a primer, characterized in that: The invention comprises a primer layer, a core layer and a matte layer which are arranged in sequence; the primer layer comprises 80-89.9wt% of ethylene-octene copolymer and 10-20wt% of propylene-butene copolymer, the melting point of the ethylene-octene copolymer is 75-95°C, and the melting point of the propylene-butene copolymer is 80-95°C; the core layer comprises homopolymerized polypropylene; the matte layer comprises random copolymerized polypropylene, 40-50wt% of high-density polyethylene and 15-35wt% of propylene-based copolymer, the melting point of the propylene-based copolymer is 140-160°C, the crystallinity of the propylene-based copolymer is 5-10%, the propylene-based copolymer is propylene-1-butene copolymerized polypropylene, in which the isotacticity of the propylene sequence is 90-93%, and the isotacticity of the 1-butene sequence is 87-90%.

2. The matte film containing primer according to claim 1, characterized in that: The content of 1-butene monomer in the propylene-1-butene copolymer polypropylene in the matt layer is 15-35wt%.

3. The matte film containing primer according to claim 1, characterized in that: The octene content in the ethylene-octene copolymer is 5-20wt%.

4. The matte film containing primer according to claim 1, characterized in that: Under the conditions of 230° C. and 2.16 kg, the melt index of the propylene-butene copolymer in the primer layer and the propylene-1-butene copolymer polypropylene in the matte layer is both 5-10 g / 10 min.

5. The matte film containing primer according to claim 1, characterized in that: The melt index of the random copolymer polypropylene in the matte layer is 7-12 g / 10 min at 230° C. and 2.16 kg, and the melt index of the high-density polyethylene is 8-14 g / 10 min at 190° C. and 21.6 kg.

6. The matte film containing primer according to claim 1, characterized in that: The primer layer further includes 0.1-0.3 wt % of an antioxidant, and the antioxidant is prepared by compounding antioxidant 1010 and antioxidant 168 in a ratio of 1:

2.

7. The matte film containing primer according to claim 1, characterized in that: The random copolymer polypropylene in the matt layer is selected from one or both of ethylene-propylene copolymer polypropylene and ethylene-propylene-butene copolymer polypropylene.

8. The matte film containing primer according to claim 1, characterized in that: The core layer comprises 99wt% homopolypropylene and 1wt% antistatic masterbatch, the melt index of the homopolypropylene is 3-4g / 10min at 230°C and 2.16kg, the carrier of the antistatic masterbatch is homopolypropylene, and the effective concentration of the antistatic agent in the antistatic masterbatch is 40wt%.

9. A method for preparing a matte film containing a primer as claimed in any one of claims 1 to 8, characterized in that: The method comprises the following steps: the raw materials of each layer are mixed evenly by a high-speed mixer respectively, and then enter into a screw extruder through a batcher, and the melts of each extruder are metered by a metering pump and merged into a thick sheet at a T-die head, and the thick sheet is cooled by a chilling roller and enters a chilling water tank, and the thick sheet is longitudinally stretched after passing through a water blowing chamber, and then transversely stretched, and then corona treated after shaping, and then rolled up to an aging rack for treatment, and after the treatment is completed, it is cut and packaged into finished products.

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