A low-temperature resistant polypropylene matte film, its preparation method and cold laminating composite film

Abstract

The present invention relates to the field of thin films, and particularly to a low-temperature resistant polypropylene matte film, a preparation method thereof, and a cold laminating composite film. The matte film comprises a matte layer, a core layer, and an adhering layer arranged in sequence. The matte layer comprises 45-55 wt% of random copolymer polypropylene and 45-55 wt% of high-density polyethylene. The core layer comprises homopolypropylene and 5-10 wt% of poly(1,4-butylene glycol-1-butene) random copolymer. The adhering layer comprises homopolypropylene and 2-5 wt% of n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer. The matte film of the present invention has appropriate flexibility in a low-temperature environment, and there is still appropriate adhesion between the adhering layer and the adhesive layer. During manufacturing, the film can be smoothly unwound and rewound, and can be used as the base film of a low-temperature resistant cold laminating film.

Description

Technical Field

[0001] The present invention relates to the field of thin films, and particularly to a low-temperature resistant polypropylene matte film, a preparation method thereof, and a cold laminating composite film. Background Art

[0002] In the printing industry, in order to protect the printed pattern, laminating is generally carried out on the printed matter. The laminating process can not only enhance the picture texture of the printed matter, but also protect the picture, resist scratching and be water-resistant, and is widely used in labels, wedding photos, oil painting production, calligraphy and paintings, outdoor posters, advertisements, various pictures, document materials, etc.

[0003] At present, most of the laminating in the printing industry uses polyvinyl chloride (PVC) cold laminating film. The PVC cold laminating film usually includes a PVC base film layer and an adhesive layer arranged in sequence, and the main component is PVC. On the one hand, PVC will decompose at high temperatures, generating toxic hydrogen chloride and vinyl chloride, which have irritating effects on the eyes and respiratory tract, and long-term contact may cause harm to human health. On the other hand, PVC is prone to fading under long-term ultraviolet irradiation, resulting in the dull color of the product after laminating. Therefore, the industry is gradually developing polypropylene films to replace polyvinyl chloride (PVC) cold laminating films.

[0004] Chinese Patent CN202210038282.9 discloses a polypropylene film for cold laminating composite film, a preparation method thereof, and a cold laminating composite film, which has low surface tension, is easy to unwind, has a simple manufacturing method, and has high composite fastness with printed matter. However, through a large number of practices, the inventor found that this patent did not consider the problem that the polypropylene material becomes brittle in a low-temperature environment, resulting in a decline in the overall performance of the film. For example, in winter, the adhesive layer and the base film layer cannot be effectively bonded, and problems such as glue dropping and cracking may occur. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a low-temperature resistant polypropylene matte film, a preparation method thereof, and a cold laminating composite film. On the one hand, by adding 5-10 wt% of poly(1,4-butylene glycol-1-butene) random copolymer to the core layer, the prepared matte film still has appropriate flexibility in a low-temperature environment. On the other hand, by adding 2-5 wt% of n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer to the bonding layer, it is beneficial to maintain an appropriate adhesive force between the bonding layer and the adhesive layer, and the film unwinds and winds smoothly during the manufacturing process. Under the synergistic effect, the prepared polypropylene matte film can be used as the base film of a low-temperature resistant cold laminating film.

[0006] The technical solution of the present invention is realized as follows:

[0007] A low-temperature resistant polypropylene matte film comprises a matte layer, a core layer and a laminating layer arranged in sequence; the matte layer comprises 45-55wt% of random copolymer polypropylene and 45-55wt% of high-density polyethylene, the core layer comprises homopolypropylene and 5-10wt% of poly-1,4-butenediol-1-butene random copolymer, and the laminating layer comprises homopolypropylene and 2-5wt% of n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer.

[0008] Homopolymer polypropylene (PP) is a highly crystalline polymer with a highly regular molecular chain, which makes it exhibit glassy properties at low temperatures. However, as the ambient temperature decreases, the activity of the PP molecular chain decreases, and the main chain of the PP molecular chain becomes fixed, making it difficult to undergo significant deformation. This results in reduced flexibility and embrittlement.

[0009] Therefore, in the present invention, 5-10 wt% of poly(1,4-butylene glycol-1-butene) random copolymer is first added to the core layer. The poly(1,4-butylene glycol) segment itself has good flexibility, and there are strong intermolecular interactions, with a certain degree of crystallinity, endowing the core layer with certain mechanical properties. The introduction of 1-butene reduces the intermolecular interactions of the poly(1,4-butylene glycol) segment itself, making the poly(1,4-butylene glycol-1-butene) random copolymer as a whole exhibit more excellent low-temperature flexibility. On the one hand, the ethyl side group in the poly(1,4-butylene glycol-1-butene) random copolymer can, to a certain extent, inhibit the regular arrangement movement of the homopolypropylene molecular chain, so that the homopolypropylene still maintains a certain degree of flexibility at low temperatures, which is conducive to the core layer having appropriate low-temperature flexibility. On the other hand, the poly(1,4-butylene glycol-1-butene) random copolymer contains a certain amount of OH groups, which can interact with the polar components in the bonding layer, thereby enhancing the interfacial bonding force between the core layer and the bonding layer and ensuring no delamination during the biaxial stretching process. On the other hand, the 1-butene segment in the poly(1,4-butylene glycol-1-butene) random copolymer is weakly polar, ensuring the compatibility between the poly(1,4-butylene glycol-1-butene) random copolymer and the homopolypropylene, and avoiding affecting the appearance quality of the matte film (such as the appearance of white spots, etc.) due to phase separation between the core layer components. In addition, the 1-butene segment also ensures the overall thermal stability of the poly(1,4-butylene glycol-1-butene) random copolymer, making it applicable to the production process temperature of biaxial stretching. If the addition amount of the poly(1,4-butylene glycol-1-butene) random copolymer is less than 5 wt%, the low-temperature flexibility of the core layer cannot be effectively improved, which is not conducive to the overall low-temperature flexibility of the matte film. If the addition amount of the poly(1,4-butylene glycol-1-butene) random copolymer is higher than 10 wt%, on the one hand, the core layer will be too flexible, resulting in too low stiffness of the matte film and affecting the smoothness of winding and unwinding of the matte film itself. On the other hand, there will be a poor compatibility between the poly(1,4-butylene glycol-1-butene) random copolymer and the homopolypropylene, affecting the appearance quality of the matte film. On the other hand, the hydrogen bond force between the poly(1,4-butylene glycol-1-butene) random copolymers themselves is too strong, which is also not conducive to biaxial stretching and may cause cracks.

[0010] Secondly, in order to take into account both the low-temperature flexibility and adhesion of the laminating layer in direct contact with the adhesive layer, the present invention adds 2-5wt% of n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer to the laminating layer. N-alkyl maleate grafted modified ethylene-vinyl acetate copolymer is a non-crystalline polymer with good low-temperature fluidity. On the one hand, the long n-alkyl chain in the n-alkyl maleate has a large steric hindrance, which to a certain extent limits the close stacking of the molecular chains in the laminating layer, which is beneficial to reducing the crystallinity of the laminating layer resin, thereby improving the low-temperature flexibility of the laminating layer, and is also beneficial to ensuring the compatibility of the homopolymer polypropylene between the copolymer and the matrix resin; on the other hand, the n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer also interacts with the hydroxyl groups of the poly-1,4-butene diol-1-butene random copolymer in the core layer through hydrogen bonds to form a tangled network structure, which is beneficial to improving the interfacial bonding strength between the core layer and the laminating layer. On the one hand, the ethylene-vinyl acetate chain segment itself has good low-temperature fluidity, which can improve the low-temperature flexibility of the laminating layer. On the other hand, the polar ester group therein can enhance the adhesion between the laminating layer and the adhesive layer, which is beneficial to ensure that the laminating layer and the adhesive layer still have appropriate adhesion in a low-temperature environment, reducing the problem of cold laminating film failure caused by glue falling off.

[0011] If the addition amount of the ethylene-vinyl acetate copolymer modified by grafting of n-alkyl maleate is less than 2wt%, on the one hand, it cannot effectively reduce the crystallinity of the laminating layer resin, and thus cannot effectively give the laminating layer suitable low-temperature flexibility. On the other hand, it is not conducive to improving the adhesion between the laminating layer and the adhesive layer, thereby affecting the low-temperature laminating effect; if the addition amount of the ethylene-vinyl acetate copolymer modified by grafting of n-alkyl maleate is higher than 5wt%, although it can improve the low-temperature flexibility of the laminating layer, it may be too sticky and not conducive to the smoothness of the matte film itself in the manufacturing and slitting process.

[0012] Furthermore, the melt index of the poly(1,4-butene glycol)-1-butene random copolymer measured at 190°C and 2.16 kg was 40-100 g / 10 min. A melt index within the range of 40-100 g / 10 min facilitates melt flow compatibility between the poly(1,4-butene glycol)-1-butene random copolymer, the core homopolypropylene, and the laminating layer, enabling effective coextrusion and meeting biaxial stretching process requirements. Furthermore, the copolymer can be effectively and evenly dispersed in the core layer, resulting in a matte film with more suitable low-temperature flexibility.

[0013] Furthermore, the poly-1,4-butenediol-1-butene random copolymer has a glass transition temperature (Tg) of -75°C to -40°C. Controlling the glass transition temperature within the range of -75°C to -40°C ensures the overall low-temperature flexibility of the matte film while also providing it with more suitable flexibility at room temperature, thereby ensuring smooth winding and unwinding of the matte film at room temperature.

[0014] Furthermore, the content of 1-butene in the poly(1,4-butanediol-1-butene) random copolymer is 10-30 wt%. If the content of 1-butene is lower than 10 wt%, the glass transition temperature of the poly(1,4-butanediol-1-butene) random copolymer is too high due to too strong hydrogen bond interaction, which is not conducive to improving the low-temperature flexibility of the core layer. If the content of 1-butene is higher than 30 wt%, the poly(1,4-butanediol-1-butene) random copolymer will make the core layer too flexible, resulting in too low stiffness of the matte film and affecting the smoothness of winding and unwinding of the matte film itself. Moreover, it is not conducive to ensuring the polarity matching between the core layer and the bonding layer and cannot ensure the bonding force.

[0015] Furthermore, the number-average molecular weight of the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is 40,000-60,000 g / mol, and the grafting rate of the n-alkyl maleate in the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is 12-30 wt%. On the one hand, it is conducive to ensuring that the bonding layer has a certain flexibility at low temperature and can be effectively bonded to the adhesive layer. On the other hand, it is conducive to ensuring that there is an appropriate adhesive force between the bonding layer and the adhesive layer. If the grafting rate of the n-alkyl maleate is higher than 30 wt%, the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer will be too severely entangled or even form a crosslinked network structure, unable to effectively improve the low-temperature flexibility of the bonding layer and not conducive to effective bonding with the adhesive layer. If the grafting rate of the n-alkyl maleate is lower than 12 wt%, the number of grafted n-alkyl long chains is too small, unable to effectively inhibit the crystallization performance of the homopolypropylene in the bonding layer, not conducive to playing the role of improving the low-temperature flexibility, and also not conducive to the mutual penetration between the bonding layer and the adhesive layer to improve the adhesive force.

[0016] Furthermore, the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is obtained by free radical polymerization of n-alkyl maleate and ethylene-vinyl acetate copolymer. The n-alkyl maleate has a double ester group structure and is obtained by esterification reaction of n-alkyl alcohol and maleate. The n-alkyl alcohol is any one of n-tetradecyl alcohol, n-hexadecyl alcohol, and n-octadecyl alcohol. The obtained n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer has a more appropriate steric hindrance, which is conducive to the mutual penetration with the adhesive layer to improve the adhesive force.

[0017] Furthermore, the preparation method of the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer includes the following steps: First, n-alkyl maleate is synthesized by esterification reaction of maleic anhydride and n-alkyl alcohol, and then, using benzoyl peroxide as an initiator, n-alkyl maleate and ethylene-vinyl acetate copolymer are subjected to free radical polymerization reaction to synthesize the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer.

[0018] Furthermore, the ethylene-vinyl acetate copolymer used to prepare the n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer has a melting point of 80-90°C, and a melt index of 20-25 g / 10 min, measured at 190°C and 2.16 kg. Controlling the melting point and melt index of the ethylene-vinyl acetate copolymer within the above ranges helps ensure that the prepared n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer has good melt flowability during processing and production, facilitates the efficient extrusion of the laminating layer resin melt without excessive viscosity, and ensures smooth production. It also helps ensure that the laminating layer has suitable low-temperature flexibility, thereby ensuring that the laminating layer and the adhesive layer still have suitable adhesion at low temperatures.

[0019] Furthermore, the melt index of the high-density polyethylene (HDPE) measured at 190°C and 21.6 kg is 9-20 g / 10 min; the melt index of the random copolymer polypropylene (PP) measured at 230°C and 2.16 kg is 6-10 g / 10 min. Selecting HDPE and random copolymer polypropylene with melt indexes within these ranges facilitates achieving an overall excellent matte effect.

[0020] Furthermore, the core layer further comprises 0.5-1 wt% of an antistatic agent masterbatch, wherein the effective content of the antistatic agent in the antistatic agent masterbatch is 20-40 wt%; and the isotacticity of the homopolypropylene of the core layer is 90-99%.

[0021] Furthermore, the laminating layer further comprises 0.5-1wt% of an anti-blocking agent masterbatch, wherein the effective content of the anti-blocking agent in the anti-blocking agent masterbatch is 5wt%, and the anti-blocking agent is one or more of silicon dioxide, polymethyl methacrylate, and polysiloxane, and the isotacticity of the homopolypropylene of the laminating layer is 90-99%. Preferably, the isotacticity of the homopolypropylene of the laminating layer is 95-99%. Adding 0.5-1wt% of the anti-blocking agent to the laminating layer can further prevent adhesion between the films during winding, which is conducive to the smooth winding and unwinding of the matte film itself.

[0022] The present invention also provides a method for preparing any of the above-mentioned low-temperature resistant polypropylene matte films, comprising the following steps: feeding the raw materials and additives into respective extruders according to the recipes of the respective layers, mixing and plasticizing them into a melt, distributing the melt to a die head for co-extrusion to form a co-extruded body, stretching the co-extruded body to form a matte film, further subjecting the matte film to corona treatment or flame treatment to obtain a matte film mother roll, and subjecting the mother roll to aging treatment and slitting to obtain a matte film product.

[0023] The present invention also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film described in any one of the above, an adhesive layer coated on the bonding layer, and a release layer covering the adhesive layer. The cold laminating composite film of the present invention still has appropriate flexibility in a low-temperature environment, and an appropriate adhesive force is still maintained between the bonding layer and the adhesive layer, which can ensure effective bonding with the printed matter in a low-temperature environment, and the winding and unwinding are smooth during the manufacturing and application processes.

[0024] For better understanding and implementation, the present invention will be described in detail below. Detailed implementation manners

[0025] It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the embodiments of the present application.

[0026] 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 "a", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term " / and / " used herein refers to and includes any or all possible combinations of one or more related listed items.

[0027] The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present application. On the contrary, they are only examples of devices and methods consistent with some aspects of the present application as detailed in the appended 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 specific circumstances.

[0028] In addition, in the description of the present application, unless otherwise specified, "a plurality of" means two or more. " / and / " describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0029] It should be understood that the embodiments of the present application are not limited to the exact structures described above, and various modifications and changes can be made without departing from its scope. The scope of the embodiments of the present application is only limited by the appended claims.

[0030] As an embodiment of the present invention, this embodiment provides a low-temperature resistant polypropylene matte film, which includes a matte layer, a core layer, and an adhesion layer arranged in sequence; the matte layer includes 45-55wt% of random copolymerized polypropylene and 45-55wt% of high-density polyethylene, the core layer includes homopolypropylene and 5-10wt% of poly(1,4-butylene glycol-1-butene) random copolymer, and the adhesion layer includes homopolypropylene and 2-5wt% of n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer.

[0031] Further, the melt index of the poly(1,4-butylene glycol-1-butene) random copolymer is measured to be 40-100 g / 10 min under the conditions of 190 °C and 2.16 kg.

[0032] Further, the glass transition temperature of the poly(1,4-butylene glycol-1-butene) random copolymer is -75 °C to -40 °C.

[0033] Further, the content of 1-butene in the poly(1,4-butylene glycol-1-butene) random copolymer is 10-30wt%.

[0034] Further, the number average molecular weight of the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is 40000-60000 g / mol, and the grafting rate of n-alkyl maleate in the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is 12-30wt%.

[0035] Further, the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is obtained by free radical polymerization of n-alkyl maleate and ethylene-vinyl acetate copolymer; the n-alkyl maleate has a double ester group structure and is obtained by esterification of n-alkyl alcohol and maleate, and the n-alkyl alcohol is any one of n-tetradecyl alcohol, n-hexadecyl alcohol, and n-octadecyl alcohol.

[0036] Further, the preparation method of the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer includes the following steps: first, n-alkyl maleate is synthesized by esterification of maleic anhydride and n-alkyl alcohol, and then, using benzoyl peroxide as an initiator, n-alkyl maleate and ethylene-vinyl acetate copolymer are subjected to free radical polymerization reaction to synthesize the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer.

[0037] Further, the melting point of the ethylene-vinyl acetate copolymer used to prepare the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is 80-90 °C, and the melt index of the ethylene-vinyl acetate copolymer is measured to be 20-25 g / 10 min under the conditions of 190 °C and 2.16 kg.

[0038] Further, the melt index of the high-density polyethylene is measured to be 9-20 g / 10 min under the conditions of 190 °C and 21.6 kg; the melt index of the random copolymer polypropylene is measured to be 6-10 g / 10 min under the conditions of 230 °C and 2.16 kg.

[0039] Further, the core layer further comprises 0.5-1 wt% of an antistatic masterbatch, wherein the effective content of the antistatic agent in the antistatic masterbatch is 20-40 wt%; the isotacticity of the homopolypropylene in the core layer is 90-99%.

[0040] Further, the bonding layer further comprises 0.5-1 wt% of an anti-blocking masterbatch, wherein the effective content of the anti-blocking agent in the anti-blocking masterbatch is 5 wt%, the anti-blocking agent is one or more of silicon dioxide, polymethyl methacrylate, and polysiloxane, and the isotacticity of the homopolypropylene in the bonding layer is 90-99%. Preferably, the isotacticity of the homopolypropylene in the bonding layer is 95-99%.

[0041] The present invention also provides a method for preparing the low-temperature resistant polypropylene matte film described above, comprising the following steps: feeding each raw material and additive into each extruder according to the formula of each layer, mixing and plasticizing into a melt, distributing the melt to a die head for co-extrusion to form a co-extruded body, stretching the co-extruded body to form a matte film, corona treating or flame treating the matte film, harvesting a matte film master roll, and aging and slitting the master roll to obtain a matte film product.

[0042] The present invention also provides a cold laminating composite film, comprising the low-temperature resistant polypropylene matte film described above, an adhesive layer coated on the bonding layer, and a release layer covering the adhesive layer.

[0043] The physical property indexes and their test methods of the examples or comparative examples of the present invention are specifically as follows:

[0044] The matte film thickness (μm) is measured according to GB / T6672-2001;

[0045] The low-temperature flexibility is characterized by the elongation at break (%) under low-temperature tension. Referring to ASTM D638: Standard Test Method for Tensile Properties of Plastics, the specific test method is as follows: Cool the matte film sample to 0 °C and keep it at this temperature for 15-20 minutes to ensure uniform temperature. Start the testing machine, stretch the sample at a constant speed (usually 50 mm / min), record the stress-strain curve during the stretching process until the sample breaks, and calculate the elongation at break. Generally, the higher the low-temperature elongation at break, the better the flexibility.

[0046] Evaluation of low-temperature lamination: The printed part to be laminated (250g white card with black spot color print) and the cold-mounted composite film are cooled to 0°C for half an hour. The printed part and the cold-mounted composite film are then fed simultaneously into a laminating machine, which automatically presses the cold-mounted composite film onto the substrate surface and removes air bubbles using rollers to obtain laminated printed part samples. The samples are then placed in a test environment (temperature 0±1°C; relative humidity 50±5%) for 2 hours. The laminated printed part samples are then cut into strips 100mm wide and 100mm long. The strips are pulled at a speed of 10mm / s under a force of 2.5N / 15mm and visually observed for peeling. Specifically, if the combined area of peeling between the laminating layer, the adhesive layer, and the printed part is less than 30%, the low-temperature lamination is considered effective and can meet the requirements for low-temperature use.

[0047] Production smoothness and appearance evaluation: smoothness of winding and unwinding, presence of white spots, etc.

[0048] It should be noted that the proportions described in the embodiments or comparative examples of the present invention are all percentages by weight.

[0049] The high-density polyethylene used in the examples and comparative examples of the present invention is ExxonMobil's HTA001HD5 (melt index of 10 g / 10 min measured at 190° C. and 21.6 kg).

[0050] The random copolymer polypropylene used in the examples and comparative examples of the present invention is F800E produced by Shanghai Petrochemical (melt index is 7.5 g / 10 min measured at 230° C. and 2.16 kg).

[0051] The homopolypropylene used in the laminating layer and the core layer of the embodiments of the present invention and the comparative examples is L5D98C (isotacticity of 95%, melt index of 3.4 g / 10 min measured at 230° C. and 2.16 kg) produced by China National Petroleum Corporation.

[0052] The melt index of the poly-1,4-butene diol-1-butene random copolymers of the examples and comparative examples of the present invention is 40 g / 10 min (measured at 190° C. and 2.16 kg).

[0053] The number average molecular weight of the n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer in the examples and comparative examples of the present invention is 50,000 g / mol, and n-tetradecyl alcohol is used to prepare the n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer. The melting point of the ethylene-vinyl acetate copolymer used to prepare the n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer is 85° C., and the melt index measured at 190° C. and 2.16 kg is 25 g / 10 min.

[0054] The effective content of the anti-blocking agent in the anti-blocking agent masterbatch of the embodiment of the present invention and the comparative example is 5 wt %, the anti-blocking agent is silicon dioxide, and the carrier of the anti-blocking agent masterbatch is homopolypropylene.

[0055] The effective content of the antistatic agent in the antistatic agent masterbatch of the embodiment of the present invention and the comparative example is 40 wt %, the antistatic agent is a quaternary ammonium salt-based methacrylate copolymer, and the carrier of the antistatic agent masterbatch is homopolypropylene.

[0056] The adhesive layers of the embodiments of the present invention and the comparative examples are composed of an acrylic adhesive.

[0057] The components and contents of each layer in the embodiments and comparative examples of the present invention are shown in Table 1 below.

[0058] Table 1

[0059]

[0060] Example 1

[0061] This embodiment provides a low-temperature resistant polypropylene matte film, comprising a matte layer, a core layer, and a laminating layer arranged in sequence. The method for preparing the resin layers of the low-temperature resistant polypropylene matte film of this embodiment comprises the following steps:

[0062] Preparation of matt layer resin: 50 wt% random copolymer polypropylene and 50 wt% high-density polyethylene were mixed evenly to obtain matt layer resin.

[0063] Preparation of core layer resin: 94 wt% homopolypropylene, 5 wt% poly-1,4-butene diol-1-butene random copolymer (Tg is -75°C, 1-butene content is 30 wt%) and 1 wt% antistatic agent masterbatch are mixed evenly to obtain core layer resin.

[0064] Preparation of bonding layer resin: 94.5wt% homopolypropylene, 5wt% n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer (the grafting rate of n-alkyl maleate is 12wt%) and 0.5wt% anti-blocking agent masterbatch are mixed evenly to obtain bonding layer resin.

[0065] The preparation method of the low-temperature resistant polypropylene matte film in this embodiment is a co-extrusion and biaxial stretching process, which includes the following steps: premix the selected raw materials for each layer (including main raw materials, modified materials, additive masterbatches, etc.) according to the designed formula, and stir evenly to obtain the resins for each layer. After the resins for each layer are metered, they are fed into each extruder, and are plasticized into uniform melts in the extrusion process. Each melt is transported through pipelines, filtered by filters, and distributed to the die head through the flow channel for co-extrusion to form a co-extruded body. The co-extruded body is quenched on a chill roll to form a thick sheet, and the thick sheet is formed into a matte film through a biaxial stretching process. The matte film is cooled, trimmed on both sides, traction thickness measured, and then corona treated to obtain a matte film master roll. The matte film master roll undergoes aging treatment and slitting process to finally form the finished matte film product.

[0066] The temperatures of the used extruder, flow channel, pipeline, filter, and die head are controlled at 230 - 260 °C, the quenching temperature of the chill roll is at 25 - 40 °C, the process temperatures for longitudinal and transverse stretching are 130 - 180 °C, the longitudinal stretching ratio is 4.0 - 6.0 times, and the transverse stretching ratio is 7.0 - 10.0 times. After the biaxial stretching process, the matte film can be cooled at room temperature, trimmed and thickness measured on both sides, and the surface of the bonding layer of the matte film is corona treated.

[0067] The total thickness of the low-temperature resistant polypropylene matte film in this embodiment is 23 µm, among which the thickness of the matte layer is 1 µm, the thickness of the core layer is 20 µm, and the thickness of the bonding layer is 2 µm.

[0068] This embodiment also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film of this embodiment arranged in sequence, an adhesive layer coated on the bonding layer, and a release layer covering the surface of the adhesive layer. The thickness of the adhesive layer in this embodiment is 5 µm, and the release layer in this embodiment is a release base paper.

[0069] During preparation, first coat a 5-µm adhesive layer on the bonding layer of the low-temperature resistant polypropylene matte film, and then cover a release base paper on the surface of the adhesive layer to obtain the cold laminating composite film of this embodiment.

[0070] Example 2

[0071] This embodiment provides a low-temperature resistant polypropylene matte film, which includes a matte layer, a core layer, and a bonding layer arranged in sequence. The preparation method of the resins for each layer of the low-temperature resistant polypropylene matte film in this embodiment includes the following steps:

[0072] Preparation of matte layer resin: Take 50 wt% of random copolymer polypropylene and 50 wt% of high-density polyethylene, mix them evenly to obtain the matte layer resin. Preparation of core layer resin: Take 91 wt% of homopolypropylene, 8 wt% of poly(1,4-butylene glycol-1-butene) random copolymer (Tg is -60 °C, and the 1-butene content is 20 wt%), and 1 wt% of antistatic masterbatch, mix them evenly to obtain the core layer resin.

[0073] Preparation of the bonding layer resin: 96 wt% of homopolypropylene, 3.5 wt% of ethylene-vinyl acetate copolymer graft-modified with n-alkyl maleate (the grafting rate of n-alkyl maleate is 20 wt%), and 0.5 wt% of anti-blocking masterbatch are mixed evenly to obtain the bonding layer resin.

[0074] The preparation method of the low-temperature resistant polypropylene matte film in this example is the same as that in Example 1, so it will not be elaborated here.

[0075] The total thickness of the low-temperature resistant polypropylene matte film in this example is 23 µm, among which the thickness of the matte layer is 1 µm, the thickness of the core layer is 20 µm, and the thickness of the bonding layer is 2 µm.

[0076] This example also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film of this example arranged in sequence, an adhesive layer coated on the bonding layer, and a release layer covering the surface of the adhesive layer. The thickness of the adhesive layer in this example is 5 µm, and the release layer in this example is a release base paper.

[0077] During preparation, first coat a 5-µm adhesive layer on the bonding layer of the low-temperature resistant polypropylene matte film, and then cover a release base paper on the surface of the adhesive layer to obtain the cold laminating composite film of this example.

[0078] Example 3

[0079] This example provides a low-temperature resistant polypropylene matte film, which includes a matte layer, a core layer, and a bonding layer arranged in sequence. The preparation methods of the resins of each layer of the low-temperature resistant polypropylene matte film in this example include the following steps:

[0080] Preparation of the matte layer resin: 50 wt% of random copolymerized polypropylene and 50 wt% of high-density polyethylene are mixed evenly to obtain the matte layer resin. Preparation of the core layer resin: 89 wt% of homopolypropylene, 10 wt% of poly(1,4-butylene glycol-1-butene) random copolymer (Tg is -40 °C, and the 1-butene content is 10 wt%), and 1 wt% of antistatic masterbatch are mixed evenly to obtain the core layer resin.

[0081] Preparation of the bonding layer resin: 97.5 wt% of homopolypropylene, 2 wt% of ethylene-vinyl acetate copolymer graft-modified with n-alkyl maleate (the grafting rate of n-alkyl maleate is 30 wt%), and 0.5 wt% of anti-blocking masterbatch are mixed evenly to obtain the bonding layer resin.

[0082] The preparation method of the low-temperature resistant polypropylene matte film in this example is the same as that in Example 1, so it will not be elaborated here.

[0083] The total thickness of the low-temperature resistant polypropylene matte film in this embodiment is 23 µm, among which the thickness of the matte layer is 1 µm, the thickness of the core layer is 20 µm, and the thickness of the bonding layer is 2 µm.

[0084] This embodiment also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film of this embodiment arranged in sequence, an adhesive layer coated on the bonding layer, and a release layer covering the surface of the adhesive layer. The thickness of the adhesive layer in this embodiment is 5 µm, and the release layer in this embodiment is a release base paper.

[0085] During preparation, first coat an adhesive layer with a thickness of 5 µm on the bonding layer of the low-temperature resistant polypropylene matte film, and then cover a release base paper on the surface of the adhesive layer to obtain the cold laminating composite film of this embodiment.

[0086] Comparative Example 1

[0087] This comparative example provides a low-temperature resistant polypropylene matte film, which includes a matte layer, a core layer, and a bonding layer arranged in sequence. The preparation method of the resins of each layer of the low-temperature resistant polypropylene matte film in this comparative example includes the following steps:

[0088] Preparation of the matte layer resin: Take 50 wt% of random copolymerized polypropylene and 50 wt% of high-density polyethylene and mix them evenly to obtain the matte layer resin.

[0089] Preparation of the core layer resin: Take 99 wt% of homopolypropylene and 1 wt% of antistatic masterbatch and mix them evenly to obtain the core layer resin.

[0090] Preparation of the bonding layer resin: Take 99.5 wt% of homopolypropylene and 0.5 wt% of antiblocking masterbatch and mix them evenly to obtain the bonding layer resin.

[0091] The preparation method of the low-temperature resistant polypropylene matte film in this comparative example is the same as that of Example 1, so it will not be elaborated here.

[0092] The total thickness of the low-temperature resistant polypropylene matte film in this comparative example is 23 µm, among which the thickness of the matte layer is 1 µm, the thickness of the core layer is 20 µm, and the thickness of the bonding layer is 2 µm.

[0093] This comparative example also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film of this comparative example arranged in sequence, an adhesive layer coated on the bonding layer, and a release layer covering the surface of the adhesive layer. The thickness of the adhesive layer in this comparative example is 5 µm, and the release layer in this comparative example is a release base paper.

[0094] During preparation, first coat an adhesive layer with a thickness of 5 µm on the bonding layer of the low-temperature resistant polypropylene matte film, and then cover a release base paper on the surface of the adhesive layer to obtain the cold laminating composite film of this comparative example.

[0095] Comparative Example 2

[0096] This comparative example provides a low-temperature resistant polypropylene matte film, which includes a matte layer, a core layer, and an adhesive layer arranged in sequence. The preparation method of the resins for each layer of the low-temperature resistant polypropylene matte film in this comparative example includes the following steps:

[0097] Preparation of the matte layer resin: Take 50 wt% of random copolymer polypropylene and 50 wt% of high-density polyethylene, mix them evenly to obtain the matte layer resin.

[0098] Preparation of the core layer resin: Take 91 wt% of homopolypropylene, 8 wt% of poly(1,4-butylene glycol-1-butene) random copolymer (Tg is -60 °C, and the 1-butene content is 20 wt%), and 1 wt% of antistatic masterbatch, mix them evenly to obtain the core layer resin.

[0099] Preparation of the adhesive layer resin: Take 99.5 wt% of homopolypropylene and 0.5 wt% of anti-blocking masterbatch, mix them evenly to obtain the adhesive layer resin.

[0100] The preparation method of the low-temperature resistant polypropylene matte film in this comparative example is the same as that in Example 1, so it will not be elaborated here.

[0101] The total thickness of the low-temperature resistant polypropylene matte film in this comparative example is 23 µm, among which the thickness of the matte layer is 1 µm, the thickness of the core layer is 20 µm, and the thickness of the adhesive layer is 2 µm.

[0102] This comparative example also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film of this comparative example arranged in sequence, an adhesive layer coated on the adhesive layer, and a release layer covering the surface of the adhesive layer. The thickness of the adhesive layer in this comparative example is 5 µm, and the release layer in this comparative example is a release base paper.

[0103] During preparation, first coat a 5-µm adhesive layer on the adhesive layer of the low-temperature resistant polypropylene matte film, and then cover a release base paper on the surface of the adhesive layer to obtain the cold laminating composite film of this comparative example.

[0104] Comparative Example 3

[0105] This comparative example provides a low-temperature resistant polypropylene matte film, which includes a matte layer, a core layer, and an adhesive layer arranged in sequence. The preparation method of the resins for each layer of the low-temperature resistant polypropylene matte film in this comparative example includes the following steps:

[0106] Preparation of the matte layer resin: Take 50 wt% of random copolymer polypropylene and 50 wt% of high-density polyethylene, mix them evenly to obtain the matte layer resin.

[0107] Preparation of the core layer resin: Take 91 wt% of homopolypropylene, 8 wt% of poly(1,4-butylene glycol-1-butene) random copolymer (Tg is -60 °C, and the 1-butene content is 20 wt%), and 1 wt% of antistatic masterbatch, mix them evenly to obtain the core layer resin.

[0108] Preparation of bonding layer resin: 89.5 wt% homopolypropylene, 10 wt% n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer (n-alkyl maleate grafting rate is 20 wt%) and 0.5 wt% anti-blocking agent masterbatch are mixed evenly to obtain bonding layer resin.

[0109] The preparation method of the low-temperature resistant polypropylene 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 low-temperature resistant polypropylene matte film of this comparative example is 23 μm, of which the matte layer thickness is 1 μm, the core layer thickness is 20 μm, and the laminating layer thickness is 2 μm.

[0111] This comparative example also provides a cold-mounted composite film, comprising the low-temperature resistant polypropylene matte film of this comparative example, an adhesive layer coated on the laminating layer, and a release layer covering the surface of the adhesive layer, which are arranged in sequence. The thickness of the adhesive layer of this comparative example is 5 μm, and the release layer of this comparative example is a release base paper.

[0112] During preparation, a 5 μm thick adhesive layer was first coated on the laminating layer of the low-temperature resistant polypropylene matt film, and then a release paper was covered on the surface of the adhesive layer to obtain the cold-mounted composite film of this comparative example.

[0113] Comparative Example 4

[0114] This comparative example provides a low-temperature resistant polypropylene matte film, comprising a matte layer, a core layer, and a laminating layer arranged in sequence. The method for preparing the resin layers of the low-temperature resistant polypropylene matte film of this comparative example comprises the following steps:

[0115] Preparation of matt layer resin: 50 wt% random copolymer polypropylene and 50 wt% high-density polyethylene were mixed evenly to obtain matt layer resin.

[0116] Preparation of core layer resin: 99 wt% of homopolymer polypropylene and 1 wt% of antistatic agent masterbatch were mixed evenly to obtain core layer resin.

[0117] Preparation of bonding layer resin: 96 wt% homopolypropylene, 3.5 wt% n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer (n-alkyl maleate grafting rate is 20 wt%) and 0.5 wt% anti-blocking agent masterbatch are mixed evenly to obtain bonding layer resin.

[0118] The preparation method of the low-temperature resistant polypropylene matte 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 low-temperature resistant polypropylene matte film of this comparative example is 23 μm, of which the matte layer thickness is 1 μm, the core layer thickness is 20 μm, and the laminating layer thickness is 2 μm.

[0120] This comparative example also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film of this comparative example arranged in sequence, an adhesive layer coated on the bonding layer, and a release layer covering the surface of the adhesive layer. The thickness of the adhesive layer in this comparative example is 5 μm, and the release layer in this comparative example is a release base paper.

[0121] During preparation, first coat a 5-μm adhesive layer on the bonding layer of the low-temperature resistant polypropylene matte film, and then cover a release base paper on the surface of the adhesive layer to obtain the cold laminating composite film of this comparative example.

[0122] Comparative Example 5

[0123] This comparative example provides a low-temperature resistant polypropylene matte film, which includes a matte layer, a core layer, and a bonding layer arranged in sequence. The preparation methods of the resins of each layer of the low-temperature resistant polypropylene matte film in this comparative example include the following steps:

[0124] Preparation of the matte layer resin: Take 50 wt% of random copolymer polypropylene and 50 wt% of high-density polyethylene, mix them evenly to obtain the matte layer resin.

[0125] Preparation of the core layer resin: Take 84 wt% of homopolypropylene, 15 wt% of poly(1,4-butylene glycol-1-butene) random copolymer (Tg is -60 °C, and the 1-butene content is 20 wt%), and 1 wt% of antistatic masterbatch, mix them evenly to obtain the core layer resin.

[0126] Preparation of the bonding layer resin: Take 96 wt% of homopolypropylene, 3.5 wt% of n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer (the grafting rate of n-alkyl maleate is 20 wt%), and 0.5 wt% of antiblocking masterbatch, mix them evenly to obtain the bonding layer resin.

[0127] The preparation method of the low-temperature resistant polypropylene matte film in this comparative example is the same as that in Example 1, so it will not be elaborated here.

[0128] The total thickness of the low-temperature resistant polypropylene matte film in this comparative example is 23 µm, among which the thickness of the matte layer is 1 µm, the thickness of the core layer is 20 µm, and the thickness of the bonding layer is 2 µm.

[0129] This comparative example also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film of this comparative example arranged in sequence, an adhesive layer coated on the bonding layer, and a release layer covering the surface of the adhesive layer. The thickness of the adhesive layer in this comparative example is 5 μm, and the release layer in this comparative example is a release base paper.

[0130] During preparation, first coat a 5-μm adhesive layer on the bonding layer of the low-temperature resistant polypropylene matte film, and then cover a release base paper on the surface of the adhesive layer to obtain the cold laminating composite film of this comparative example.

[0131] Comparative Example 6

[0132] This comparative example provides a low-temperature resistant polypropylene matte film, comprising a matte layer, a core layer, and a laminating layer arranged in sequence. The method for preparing the resin layers of the low-temperature resistant polypropylene matte film of this comparative example comprises the following steps:

[0133] Preparation of matt layer resin: 50 wt% random copolymer polypropylene and 50 wt% high-density polyethylene were mixed evenly to obtain matt layer resin.

[0134] Preparation of core layer resin: 91 wt% homopolypropylene, 8 wt% poly-1,4-butene diol-1-butene random copolymer (Tg is -20°C, 1-butene content is 5 wt%) and 1 wt% antistatic agent masterbatch are mixed evenly to obtain core layer resin.

[0135] Preparation of bonding layer resin: 96 wt% homopolypropylene, 3.5 wt% n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer (n-alkyl maleate grafting rate is 20 wt%) and 0.5 wt% anti-blocking agent masterbatch are mixed evenly to obtain bonding layer resin.

[0136] The preparation method of the low-temperature resistant polypropylene matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0137] The total thickness of the low-temperature resistant polypropylene matte film of this comparative example is 23 μm, of which the matte layer thickness is 1 μm, the core layer thickness is 20 μm, and the laminating layer thickness is 2 μm.

[0138] This comparative example also provides a cold-mounted composite film, comprising the low-temperature resistant polypropylene matte film of this comparative example, an adhesive layer coated on the laminating layer, and a release layer covering the surface of the adhesive layer, which are arranged in sequence. The thickness of the adhesive layer of this comparative example is 5 μm, and the release layer of this comparative example is a release base paper.

[0139] During preparation, a 5 μm thick adhesive layer was first coated on the laminating layer of the low-temperature resistant polypropylene matt film, and then a release paper was covered on the surface of the adhesive layer to obtain the cold-mounted composite film of this comparative example.

[0140] Comparative Example 7

[0141] This comparative example provides a low-temperature resistant polypropylene matte film, comprising a matte layer, a core layer, and a laminating layer arranged in sequence. The method for preparing the resin layers of the low-temperature resistant polypropylene matte film of this comparative example comprises the following steps:

[0142] Preparation of matt layer resin: 50 wt% random copolymer polypropylene and 50 wt% high-density polyethylene were mixed evenly to obtain matt layer resin.

[0143] Preparation of core layer resin: 91 wt% homopolypropylene, 8 wt% poly-1,4-butene diol-1-butene random copolymer (Tg is -90°C, 1-butene content is 40 wt%) and 1 wt% antistatic agent masterbatch are mixed evenly to obtain core layer resin.

[0144] Preparation of laminating layer resin: 96 wt% homopolypropylene, 3.5 wt% n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer (n-alkyl maleate grafting rate is 20 wt%) and 1.5 wt% anti-blocking agent masterbatch are mixed evenly to obtain laminating layer resin.

[0145] The preparation method of the low-temperature resistant polypropylene matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0146] The total thickness of the low-temperature resistant polypropylene matte film of this comparative example is 23 μm, of which the matte layer thickness is 1 μm, the core layer thickness is 20 μm, and the laminating layer thickness is 2 μm.

[0147] This comparative example also provides a cold-mounted composite film, comprising the low-temperature resistant polypropylene matte film of this comparative example, an adhesive layer coated on the laminating layer, and a release layer covering the surface of the adhesive layer, which are arranged in sequence. The thickness of the adhesive layer of this comparative example is 5 μm, and the release layer of this comparative example is a release base paper.

[0148] During preparation, a 5 μm thick adhesive layer was first coated on the laminating layer of the low-temperature resistant polypropylene matt film, and then a release paper was covered on the surface of the adhesive layer to obtain the cold-mounted composite film of this comparative example.

[0149] Comparative Example 8

[0150] This comparative example provides a low-temperature resistant polypropylene matte film, comprising a matte layer, a core layer, and a laminating layer arranged in sequence. The method for preparing the resin layers of the low-temperature resistant polypropylene matte film of this comparative example comprises the following steps:

[0151] Preparation of matt layer resin: 50 wt% random copolymer polypropylene and 50 wt% high-density polyethylene were mixed evenly to obtain matt layer resin.

[0152] Preparation of core layer resin: 91 wt% homopolypropylene, 8 wt% poly-1,4-butene diol-1-butene random copolymer (Tg is -60°C, 1-butene content is 20 wt%) and 1 wt% antistatic agent masterbatch are mixed evenly to obtain core layer resin.

[0153] Preparation of laminating layer resin: 96 wt% homopolypropylene, 3.5 wt% n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer (the grafting rate of n-alkyl maleate is 5 wt%) and 0.5 wt% anti-blocking agent masterbatch were mixed evenly to obtain laminating layer resin.

[0154] The preparation method of the low-temperature resistant polypropylene matte film of this comparative example is the same as that of Example 1, so it will not be elaborated here.

[0155] The total thickness of the low-temperature resistant polypropylene matte film of this comparative example is 23 µm, among which the thickness of the matte layer is 1 µm, the thickness of the core layer is 20 µm, and the thickness of the bonding layer is 2 µm.

[0156] This comparative example also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film of this comparative example arranged in sequence, an adhesive layer coated on the bonding layer, and a release layer covering the surface of the adhesive layer. The thickness of the adhesive layer of this comparative example is 5 µm, and the release layer of this comparative example is a release base paper.

[0157] During preparation, first coat an adhesive layer with a thickness of 5 µm on the bonding layer of the low-temperature resistant polypropylene matte film, and then cover a release base paper on the surface of the adhesive layer, thus obtaining the cold laminating composite film of this comparative example.

[0158] Comparative Example 9

[0159] This comparative example provides a low-temperature resistant polypropylene matte film, which includes a matte layer, a core layer, and a bonding layer arranged in sequence. The preparation method of each layer of resin of the low-temperature resistant polypropylene matte film of this comparative example includes the following steps:

[0160] Preparation of matte layer resin: Take 50 wt% of random copolymerized polypropylene and 50 wt% of high-density polyethylene, mix them evenly, and obtain the matte layer resin.

[0161] Preparation of core layer resin: Take 91 wt% of homopolypropylene, 8 wt% of poly(1,4-butylene glycol-1-butene) random copolymer (Tg is -60 °C, and the 1-butene content is 20 wt%), and 1 wt% of antistatic masterbatch, mix them evenly, and obtain the core layer resin.

[0162] Preparation of bonding layer resin: Take 96 wt% of homopolypropylene, 3.5 wt% of n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer (the grafting rate of n-alkyl maleate is 40 wt%), and 0.5 wt% of anti-blocking masterbatch, mix them evenly, and obtain the bonding layer resin.

[0163] The preparation method of the low-temperature resistant polypropylene matte film of this comparative example is the same as that of Example 1, so it will not be elaborated here.

[0164] The total thickness of the low-temperature resistant polypropylene matte film of this comparative example is 23 µm, among which the thickness of the matte layer is 1 µm, the thickness of the core layer is 20 µm, and the thickness of the bonding layer is 2 µm.

[0165] This comparative example also provides a cold laminating composite film, which includes the low-temperature resistant polypropylene matte film of this comparative example arranged in sequence, an adhesive layer coated on the bonding layer, and a release layer covering the surface of the adhesive layer. The thickness of the adhesive layer in this comparative example is 5 μm, and the release layer in this comparative example is a release base paper.

[0166] During preparation, first coat a 5-μm adhesive layer on the bonding layer of the low-temperature resistant polypropylene matte film, and then cover a release base paper on the surface of the adhesive layer to obtain the cold laminating composite film of this comparative example.

[0167] The performance test results of the low-temperature resistant polypropylene matte films of Examples 1 to 3 and Comparative Examples 1 to 9 are shown in Table 2 below.

[0168] Table 2

[0169]

[0170] It can be seen from the above performance test data that:

[0171] Compared with Comparative Example 1 in which no poly(1,4-butylene glycol)-1-butene random copolymer is added to the core layer and no n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is added to the bonding layer, the low-temperature resistant polypropylene matte films of Examples 1 to 3 are added with 5-10 wt% poly(1,4-butylene glycol)-1-butene random copolymer in the core layer and 2-5 wt% n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer in the bonding layer, so that the prepared matte film has appropriate flexibility in a low-temperature environment. The elongation at break (test temperature is 0 °C) of Examples 1 to 3 is greater than that of Comparative Example 1, and it can still maintain an appropriate adhesive force with the adhesive layer at low temperature. The low-temperature peeling area of the cold laminating films of Examples 1 to 3 is lower than that of Comparative Example 1, and the unwinding and rewinding are smooth during the manufacturing process, and the appearance quality has no defects.

[0172] According to the data of Comparative Example 2 and Example 2, the content of n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer in the bonding layer of Comparative Example 2 is too low, and the prepared matte film has low flexibility in a low-temperature environment, and the low-temperature peeling area of the laminated printed matter is too high.

[0173] According to the data of Comparative Example 3 and Example 2, the content of n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer in the bonding layer of Comparative Example 3 is too high, and the flexibility of the prepared matte film in a low-temperature environment has no obvious improvement compared with Example 2. Although the low-temperature peeling area of the laminated printed matter is better than that of Example 2, there is a problem of poor unwinding and rewinding smoothness during the production process.

[0174] According to the data of Comparative Example 4 and Example 2, the content of poly 1,4-butene diol-1-butene random copolymer in the core layer of Comparative Example 4 is too low, and the flexibility of the prepared matte film is relatively low in a low-temperature environment, resulting in poor adhesion between the cold lamination film and the printed part, a high low-temperature peeling area of the laminated printed part, and delamination problems during the production process.

[0175] According to the data of Comparative Example 5 and Example 2, the content of poly 1,4-butene diol-1-butene random copolymer in the core layer of Comparative Example 5 is too high. Although the flexibility of the prepared matte film is significantly improved in a low-temperature environment and the low-temperature peeling area of the coated printed part is better than that of Example 2, the problem of poor smoothness of winding and unwinding occurs during the production process, and white spots appear on the obtained product.

[0176] According to the data of Comparative Example 6 and Example 2, the glass transition temperature of the poly 1,4-butenediol-1-butene random copolymer in the core layer of Comparative Example 6 is too high and the content of 1-butene is too low. The flexibility of the prepared matte film in a low-temperature environment is inferior to that of Example 2, resulting in poor adhesion between the cold lamination film and the printed part and a high low-temperature peeling area.

[0177] According to the data of Comparative Example 7 and Example 2, the glass transition temperature of the poly 1,4-butenediol-1-butene random copolymer in the core layer of Comparative Example 7 is too low and the content of 1-butene is too high. Although the flexibility of the prepared matte film is significantly improved in a low-temperature environment and the low-temperature peeling area of the laminated printed part is better than that of Example 2, the stiffness is insufficient due to the improvement of the overall flexibility of the film during the production process, resulting in poor smoothness of winding and unwinding.

[0178] According to the data of Comparative Example 8 and Example 2, the grafting rate of n-alkyl maleate used to prepare n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer in the laminating layer of Comparative Example 8 is too low, the flexibility of the prepared matte film in a low-temperature environment is not as good as that of Example 2, and the low-temperature peeling area of the laminated printed part is relatively high.

[0179] According to the data of Comparative Example 9 and Example 2, the grafting rate of n-alkyl maleate used to prepare the n-alkyl maleate grafted modified ethylene-vinyl acetate copolymer in the laminating layer of Comparative Example 9 is too high, resulting in excessive self-entanglement and even the formation of a cross-linked network structure, which cannot effectively improve the low-temperature flexibility of the laminating layer and is not conducive to biaxial stretching. The flexibility of the prepared matte film in a low-temperature environment is inferior to that of Example 2, which is not conducive to the adhesion between the cold laminating film and the printed part, and the low-temperature peeling area is relatively high.

[0180] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, and the present invention is intended to encompass such modifications and variations.

Claims

1. A low-temperature resistant polypropylene matte film, characterized in that, It includes an extinction layer, a core layer, and an adhesion layer arranged in sequence; the extinction layer includes 45-55 wt% of random copolymerized polypropylene and 45-55 wt% of high-density polyethylene, the core layer includes homopolypropylene and 5-10 wt% of poly(1,4-butylene glycol-1-butene) random copolymer, and the adhesion layer includes homopolypropylene and 2-5 wt% of n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer; the glass transition temperature of the poly(1,4-butylene glycol-1-butene) random copolymer is -75°C to -40°C, the content of 1-butene in the poly(1,4-butylene glycol-1-butene) random copolymer is 10-30 wt%, and the grafting rate of n-alkyl maleate in the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is 12-30 wt%.

2. The low-temperature resistant polypropylene matte film according to claim 1, wherein Under the conditions of 190°C and 2.16 kg, the melt index of the poly(1,4-butylene glycol-1-butene) random copolymer is measured to be 40-100 g / 10 min.

3. The low-temperature resistant polypropylene matte film according to claim 1, wherein The number-average molecular weight of the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is 40,000-60,000 g / mol.

4. The low-temperature resistant polypropylene matte film according to claim 1, wherein, The n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is obtained by radical polymerization of n-alkyl maleate and ethylene-vinyl acetate copolymer; the n-alkyl maleate has a double ester group structure and is obtained by esterification of n-alkyl alcohol and maleate, and the n-alkyl alcohol is one of n-tetradecyl alcohol, n-hexadecyl alcohol, and n-octadecyl alcohol.

5. The low-temperature resistant polypropylene matte film according to claim 1, characterized in that, The melting point of the ethylene-vinyl acetate copolymer used to prepare the n-alkyl maleate graft-modified ethylene-vinyl acetate copolymer is 80-90°C, and under the conditions of 190°C and 2.16 kg, the melt index of the ethylene-vinyl acetate copolymer is measured to be 20-25 g / 10 min.

6. The low-temperature resistant polypropylene matte film according to claim 1, wherein, Under the conditions of 190°C and 21.6 kg, the melt index of the high-density polyethylene is measured to be 9-20 g / 10 min; under the conditions of 230°C and 2.16 kg, the melt index of the random copolymerized polypropylene is measured to be 6-10 g / 10 min.

7. A method for preparing a low-temperature resistant polypropylene matte film according to any one of claims 1 to 6, characterized in that, It includes the following steps: Feed each raw material and additive into each extruder according to the formula of each layer, mix and plasticize them into a melt, distribute the melt to the die head for co-extrusion to form a co-extruded body, stretch the co-extruded body to form an extinction film, corona-treat or flame-treat the extinction film, wind it into an extinction film master roll, and obtain an extinction film product after aging treatment and slitting.

8. A cold laminating composite film, characterized in that, It includes the low-temperature-resistant polypropylene extinction film as described in any one of claims 1-6, an adhesive layer coated on the adhesion layer, and a release layer provided to cover the adhesive layer.

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