A scratch-resistant, glue-free matt film and a preparation method thereof

Abstract

The present application relates to the technical field of BOPP film, in particular to a scratch-resistant glue-free matt film and a preparation method thereof, the scratch-resistant glue-free matt film comprises a matt layer, a core layer and a thermal composite layer arranged in sequence, the matt layer comprises copolymerized polypropylene, high-density polyethylene, 2.0-2.5 wt% maleic anhydride modified aziridine as an end group of linear alkyl silicone (weight average molecular weight 120-150 thousand, surface tension 42-45 mN / m) and 2000-4000 ppm spherical polymethyl methacrylate (particle size D50 is 4.0-5.0 microns); the core layer comprises homopolymerized polypropylene; and the thermal composite layer comprises ethylene-vinyl acetate copolymer and 2000-4000 ppm spherical anti-blocking agent. Through the synergistic design of the components of the matt layer and the thermal composite layer, the scratch-resistant glue-free matt film realizes the balance of the surface scratch resistance of the matt layer, the high surface tension (printability) and the smoothness of the winding and unwinding, and provides a solution to the common problem of the scratch resistance of the matt surface for high-end BOPP matt film.

Description

Technical Field

[0001] The invention relates to the technical field of BOPP films, in particular to a scratch-resistant glue-free matte film and a preparation method thereof. Background Art

[0002] Matte film is a packaging film whose matte surface exhibits a low-gloss, matte appearance due to diffuse reflection of incident light. This film offers numerous advantages not achievable with ordinary packaging films, including a pleasant surface feel, an elegant appearance, and realistic color reproduction when printed. Existing BOPP matte films primarily consist of a first surface layer (matte layer), a core layer, and a second surface layer. Co-extruded composite structures with more than three layers are also available. In practice, these films undergo post-processing such as printing or coating on the matte layer. However, traditional pre-coated or ready-to-coat matte films, due to their use of energy-intensive, VOC-containing primer coating and drying or in-line gluing and drying processes for paper-plastic lamination, are being replaced by matte films that can be directly laminated to paper-plastics using a one-step process. These matte films typically consist of a three-layer structure: a matte layer, a core layer, and a thermal composite layer.

[0003] The matte layer of current matte film products that can be directly thermally laminated is primarily composed of high-density polyethylene (HDPE) and copolymerized polypropylene (PP). During film formation and stretching, the PP copolymer forms the "sea phase" and the crystallized HDPE forms the "island phase." Under external tensile forces, the HDPE in the matte layer protrudes relative to the copolymerized PP "sea phase," creating a microscopic "island" domain structure, thereby achieving a matte surface appearance. However, the matte layer of current BOPP matte film products that can be directly thermally laminated exhibits poor scratch resistance, leading to scratches from guide rollers during secondary slitting or lamination due to the common "film-roller speed difference." This is particularly susceptible to scratches and marks from packaging boxes rubbing against each other during transportation. These scratches are particularly noticeable when laminated against a dark background, creating a significant technical bottleneck that hinders the achievement of high-end aesthetics in paper-plastic laminated packaging.

[0004] Furthermore, the commonly used matte films that can be directly thermally laminated (hereinafter referred to as "glueless matte films") typically have a relatively low-melting-point hot-melt adhesive layer for their thermal lamination layer, primarily composed of ethylene-vinyl acetate copolymer (VA = vinyl acetate) with a relatively high VA content. During the film-making process, corona treatment is often applied to the film to synergistically ensure the lamination strength between the film and the printed workpiece. However, to improve the suitability of the matte layer (which also requires corona treatment) for lamination with post-print processing (such as UV varnish, hereinafter referred to as "UV varnish"), the surface tension of the matte layer is typically increased. This increased surface tension of the matte layer causes the polar components of the matte layer to interact with those of the thermal lamination layer during rewinding and unwinding, resulting in unsmooth rewinding and unwinding when the reel contacts the inside and outside, and when unwinding and reusing, including during storage in high-temperature environments in summer. Therefore, "maintaining a balance between smooth rewinding and unwinding and improving the suitability of the matte layer for post-print processing (such as UV varnish)" is a common technical issue that currently needs to be addressed. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a scratch-resistant, glue-free matte film and a preparation method thereof, which is a biaxially oriented polypropylene film, does not require secondary processing, is energy-saving and environmentally friendly, and achieves a balance between "scratch resistance, high surface tension (positively correlated with the "printing suitability" well known to technicians in the post-press processing industry) and smoothness of winding and unwinding" on the surface of the matte layer of the scratch-resistant, glue-free matte film through the collaborative innovative design of the matte layer components and the coordinated design of the matching thermal composite layer. It has good scratch resistance under both room temperature and low temperature environments, which is conducive to meeting the growing demand for high-performance films for high-performance packaging represented by high-definition and long-lasting identifiability of printed logo content of smart electronic products, and provides a solution to the common problem of matte surface scratch resistance for high-end BOPP matte films.

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

[0007] A scratch-resistant, glue-free matte film comprises a matte layer, a core layer, and a thermal composite layer arranged in sequence, wherein the matte layer comprises copolymerized polypropylene, 45-55 wt% high-density polyethylene, 2.0-2.5 wt% linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group, and 2000-4000 ppm spherical polymethyl methacrylate (PMMA), wherein the weight average molecular weight Mw of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group is 120,000 to 150,000, the surface tension of the linear alkyl silicone with maleic anhydride modified aziridine as the terminal group is 42 to 45 mN / m; the particle size D50 of the spherical polymethyl methacrylate is 4.0 to 5.0 μm; the core layer comprises homopolymer polypropylene; the thermal composite layer comprises ethylene-vinyl acetate copolymer and 2000 to 4000 ppm of spherical anti-blocking agent; the particle size D50 of the spherical anti-blocking agent is the thickness of the thermal composite layer + 2 μm.

[0008] The present invention comprehensively considers the problems that the surface of the matte layer of the BOPP matte film that can be directly thermally laminated has poor scratch resistance, the surface of the matte layer has improved applicability for post-printing processing, and it is difficult to achieve a good balance in the smoothness of film winding and unwinding. After in-depth research, the components of the matte layer of the film are functionally coordinated designed: First, in order to improve the scratch resistance, a straight-chain alkyl silicone with maleic anhydride-modified aziridine as the end group is added to the matte layer, which has excellent lubricity and anti-adhesion. When the surface of the matte layer is scratched, since the silicone molecules are not easy to form a strong attraction with other substances, it is equivalent to forming a lubricating isolation barrier on the surface of the matte layer, thereby reducing the possibility of scratches on the surface of the matte layer, and improving the scratch resistance of the surface of the matte layer of the film at room temperature and low temperature environments; second, it is well known to those skilled in the art that the surface of the silicone itself The surface tension is low. In order to improve the adverse effect of the low surface tension of silicone on the post-printing processing applicability of the matte layer surface, after research and analysis, a straight-chain alkyl silicone with aziridine as the end group was selected and modified with maleic anhydride. The obtained maleic anhydride-modified straight-chain alkyl silicone with aziridine as the end group has high surface tension, which is different from the low surface tension characteristics of general silicone. There is no problem of the adverse effect of the decrease in surface tension on the post-printing processing applicability caused by the addition of general silicone, which improves the post-printing processing applicability of the film matte layer. The straight-chain alkyl group is also conducive to the uniform dispersion of silicone in the matte layer; thirdly, the addition of spherical polymethyl methacrylate to the matte layer not only further ensures the post-printing processing applicability of the matte layer, but also cooperates with the effect of the thermal composite layer, which is beneficial to the smooth winding and unwinding of the film itself during production and application.

[0009] The Si-O bond in the main chain of the linear alkyl silicone molecule with maleic anhydride-modified aziridine as the terminal group in the present invention has a large molecular volume and a high degree of free rotation, and the aziridine terminal group has a longer linear alkyl group, which gives the silicone molecular chain better flexibility. The aziridine terminal group has unique reaction characteristics. After reacting with maleic anhydride, on the one hand, it has stronger intermolecular interaction capabilities, including hydrogen bonding and dipole interactions, which makes it easier for polar groups to be enriched on the surface, which is beneficial to increasing the surface tension of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group, thereby improving the post-printing processing applicability of the matte layer. On the other hand, after the ring-opening reaction, a pendant methyl group is formed, which inhibits its own low-temperature crystallization and is beneficial to improving its low-temperature resistance, thereby enabling the matte layer to obtain good low-temperature scratch resistance. The addition of 2.0-2.5wt% of maleic anhydride-modified aziridine-terminated linear alkyl silicone to the matte layer not only ensures the matte layer's scratch resistance (both at room and low temperatures), but also avoids the adverse effects of traditional silicones (surface tension 20-25mN / m) on post-print processing suitability due to the decrease in surface tension. Furthermore, the longer linear alkyl group facilitates its compatibility with the high-density polyethylene in the matte layer, ensuring uniform dispersion in the matte layer. This results in a uniform surface tension distribution for the matte layer, ensuring even adhesion of the ink to the surface. If the amount of linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group is added too low, the scratch resistance of the matte layer surface cannot be effectively improved. If the amount added is too high, it may not be effectively dispersed in the matte layer due to the difference in polarity, which is not conducive to the uniformity of the surface tension of the matte layer. In addition, the polarity of the matte layer is too large, which is not conducive to the smoothness of the winding and unwinding of the rolled film itself (matt layer and thermal composite layer). In addition, due to the presence of polar components, the polarity of the matte layer and the core layer may differ too much, thereby affecting the interlayer bonding strength and causing interlayer shear peeling during biaxial stretching.

[0010] The weight-average molecular weight of the maleic anhydride-modified aziridine-terminated linear alkyl silicone is controlled to be 120,000 to 150,000, and the surface tension of the maleic anhydride-modified aziridine-terminated linear alkyl silicone is controlled to be 42 to 45 mN / m. This is more conducive to the effective dispersion of the maleic anhydride-modified aziridine-terminated linear alkyl silicone and achieves a balance between excellent scratch resistance and high surface tension, so that the matte layer of the film has good scratch resistance and good printability. As the weight-average molecular weight increases, on the one hand, the elastic recovery ability of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group is enhanced, which is beneficial to the improvement of the scratch resistance. In addition, the mobility of the linear alkyl silicone with high molecular weight maleic anhydride-modified aziridine as the terminal group in the matrix will be reduced. Because the molecular chain is longer, there are more entanglements, and the diffusion rate is slower, it helps to maintain the stable presence of polar groups on the surface, and will not cause unstable surface performance due to excessive fluidity. It is more conducive to ensuring the surface tension of the matte layer. At the same time, during the winding and unwinding process, the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group will not migrate to the thermal composite layer and have an adverse effect on the composite fastness between the film and the printed part. On the other hand, relatively high molecular weight silicone has more molecular chain entanglements and higher melt viscosity, and can better maintain structural integrity during relatively high temperature processing or use, and can be suitable for the co-extrusion biaxial stretching preparation process of the present invention. If the molecular weight of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group is too low, the silicone molecules will easily migrate to the surface and may further migrate to the thermal composite layer during the winding and unwinding process, affecting the surface tension stability of the matte layer and the composite fastness between the thermal composite layer and the printed part; if the molecular weight of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group is too high, the refractive index of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group will become larger, which is not conducive to maintaining the transparency required for the application of the matte film, and there may be problems of uneven dispersion. The present invention controls the surface tension of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group to 42-45 mN / m, which is conducive to achieving a balance between improving the post-printing processing applicability of the matte layer and the smoothness of winding and unwinding of the rolled film. If the surface tension of the silicone is too low, it is not conducive to improving the surface tension of the matte layer and thus failing to improve the printability. If the surface tension of the silicone is too high, the surface tension of the matte layer of the film is too high, resulting in the matte layer surface being easily sticky between the longitudinal stretching metal roller in contact with it, and is detrimental to the smoothness of winding and unwinding of the film itself.

[0011] In order to further ensure the post-processing applicability of the matting layer, while taking into account the smoothness of the film itself during winding and unwinding, 2000-4000 ppm of spherical polymethyl methacrylate (PMMA) is added to the matting layer. On the one hand, PMMA belongs to polar ester polymers and has a high surface tension, which is beneficial to further ensure the post-processing applicability of the matting layer. On the other hand, the polar ester group is beneficial to form a strong polar interaction force with the maleic anhydride modified alkyl polysilicone. PMMA exists in the form of microspheres and has certain anti-sticking properties, which effectively inhibits the interaction between the polar groups in the maleic anhydride modified aziridine as the end group of the linear alkyl silicone and the certain adhesive ethylene-vinyl acetate in the thermal complex layer during winding, which is beneficial to ensure the smoothness of the film itself during winding and unwinding. In addition, PMMA has a similar refractive index to polypropylene and does not adversely affect the light transmittance of the film. If the amount of PMMA added is too small, the smoothness of the film during winding and unwinding cannot be effectively ensured, and if the amount of PMMA added is too large, it can cause uneven dispersion in the matting layer, which adversely affects the appearance of the film. The inventors have found through experiments that the particle size D50 of the spherical polymethyl methacrylate (PMMA) selected in the matting layer is 4.0-5.0 μm, which is beneficial to keep the difference between the particle size D50 of PMMA and the surface roughness (Rz, which is the maximum height of the profile obtained by the difference between the extreme peaks and valleys) of the matting layer within a certain range, which is beneficial to the smoothness of the high-polar matting layer surface and the high-polar thermal complex layer surface of the film after winding to ensure the smoothness of winding and unwinding, to obtain a suitable balance between the production smoothness of the film and the post-processing applicability of the matting layer, and to ensure that the matting effect of the film does not be significantly negatively affected, and to ensure the appearance quality. Preferably, the difference between the particle size D50 of PMMA and the surface roughness (Rz) of the matting layer is 0.5-1 μm.

[0012] In addition, in order to ensure that there is enough gap between the high-polarity matte layer surface and the high-polarity thermal composite layer surface of the film during the winding process to further ensure the smooth winding and unwinding of the film itself, 2000~4000ppm of spherical anti-blocking agent is added to the thermal composite layer. This is conducive to smooth film production and prevents the thermal composite layer from sticking to the roller. Preferably, the particle size D50 of the spherical anti-adhesive agent is controlled to be the thickness of the thermal composite layer T+2μm. On the one hand, it can effectively prevent the thermal composite layer from sticking to the roller during the production process, and cooperate with the role of the spherical PMMA in the matte layer to jointly ensure the smoothness of the film itself being wound and unwound. On the other hand, considering that the film edge material will be recycled to the film core layer after trimming in actual production, if the particle size of the spherical anti-adhesive agent is too different from the thickness of the thermal composite layer, it will be detrimental to the continuous and stable production of the film. Due to the poor compatibility between the polar anti-adhesive particles and the weak polar PP, phase separation will occur after biaxial stretching, resulting in film breakage, and it is not conducive to the appearance quality of the film. If the particle size of the spherical anti-adhesive agent is too small compared with the thickness of the thermal composite layer, it will not be able to prevent the thermal composite layer from sticking to the roller, nor will it be conducive to cooperating with the matte layer to ensure that there is an appropriate gap between the high-polarity matte layer surface and the high-polarity thermal composite layer surface in the rolled film to ensure the smoothness of winding and unwinding. If the content of the anti-blocking agent is less than 2000 ppm, it will not effectively prevent the thermal composite layer from sticking to the roller. If the content of the anti-blocking agent is higher than 4000 ppm, on the one hand, it is easy to increase the possibility of abnormal appearance of "white spots" in the film caused by the aforementioned "phase separation" or the loss of the anti-blocking agent during high-speed operation and the contamination of the contacting guide roller due to the common "film-roller speed difference" during the production process. On the other hand, it will increase the haze and reduce the gloss, affecting the appearance of the film.

[0013] Furthermore, the preparation of the maleic anhydride-modified aziridine-terminated linear alkyl silicone is obtained by a ring-opening reaction of the aziridine end group in the aziridine-terminated linear alkyl silicone with maleic anhydride under acidic conditions; the decomposition temperature of the maleic anhydride-modified aziridine-terminated linear alkyl silicone is ≥270°C. Aziridine, a three-membered nitrogen heterocycle, has a bond angle of approximately 60° and a rigid bridged ring structure. The lone pair of electrons on the nitrogen atom is located in an sp³ hybrid orbital, perpendicular to the ring plane. This structure gives it unique reactivity. Under acidic conditions (pH 6.5-7.5), aziridine is easily attacked by carboxylic acid nucleophiles (such as maleic anhydride), resulting in ring opening to form an N-substituted aminocarboxylic acid structure. The amide bond derived from aziridine has a thermal decomposition temperature of 270°C. This thermal stability makes maleic anhydride-modified aziridine-terminated linear alkyl silicones suitable for high-temperature processing conditions, such as the 180-245°C processing temperature of the matte film of the present invention.

[0014] Further, the maleic anhydride modified aziridine is end-group linear alkyl silicone, wherein the linear alkyl is any one of β-phenyl C12-C16. It should be noted that in the present application, β-phenyl C12-C16 is defined as follows: the first C in the linear alkyl group connected to the silicon atom in the silicone is defined as α-C, and the second C is defined as β-C, and one H on the β-C is replaced by a benzene ring. The linear alkyl is any one of β-phenyl C12-C16, on the one hand, the corresponding maleic anhydride modified aziridine end-group linear alkyl silicone has a refractive index of 1.48-1.50, which is very close to the refractive index of polypropylene, and will not adversely affect the light transmittance of the film, on the other hand, it is beneficial to ensure the appropriate flexibility of the maleic anhydride modified aziridine end-group linear alkyl silicone, which is conducive to forming an effective lubricating and isolating barrier on the surface of the matt layer, and improving the scratch resistance of the matt layer of the film. If the linear alkyl is too short, the maleic anhydride modified aziridine end-group linear alkyl silicone molecule is too rigid, which leads to a decrease in scratch resistance, and is not conducive to uniform dispersion in the matt layer, thereby not conducive to uniform distribution of surface tension, resulting in significant differences in subsequent UV varnish wetting. If the linear alkyl is too long, the maleic anhydride modified aziridine end-group linear alkyl silicone has a significant difference in melt flowability with other components in the matt layer, which is not conducive to obtaining a suitable bidirectional stretched thick sheet through co-extrusion, which is prone to film breakage, affecting the smoothness of production.

[0015] Further, the thermal composite layer further comprises 3-5wt% high-density polyethylene, and the melt index of the high-density polyethylene in the thermal composite layer is 20-30g / 10min under the condition of 190℃ and 21.6kg. The addition of 3-5wt% high-density polyethylene with a melt index of 20-30g / 10min in the thermal composite layer is conducive to further reducing the noise of slitting and unwinding, further improving the unwinding smoothness, ensuring the production and application efficiency, and not affecting the light transmittance of the film and the film covering firmness of the thermal composite layer and the printed part. If the amount of high-density polyethylene added is too low, the unwinding smoothness cannot be further improved, and if the amount of high-density polyethylene added is too high, on the one hand, it will adversely affect the film covering firmness of the thermal composite layer and the printed part, and on the other hand, due to the difference in polarity between the high-density polyethylene and the ethylene-vinyl acetate copolymer, the dispersion of the high-density polyethylene in the thermal composite layer is not conducive, which affects the appearance quality of the film. The selection of high-density polyethylene with a melt index of 20-30g / 10min not only plays a certain viscosity reduction role to further improve the unwinding smoothness, but also will not adversely affect the film covering firmness, and is conducive to ensuring the flow matching of the ethylene-vinyl acetate copolymer melt, which can be smoothly co-extruded.

[0016] Furthermore, the copolymerized polypropylene in the matte layer is an ethylene-propylene-butene random copolymer and / or an ethylene-propylene random copolymer, and the melt index of the copolymerized polypropylene is 7-12 g / 10 min at 230°C and 2.16 kg; the melt index of the high-density polyethylene in the matte layer is 10-15 g / 10 min at 190°C and 21.6 kg. Controlling the melt indexes of the copolymerized polypropylene and high-density polyethylene in the matte layer within the above ranges facilitates obtaining a polypropylene film with more ideal surface gloss and haze for the matte layer.

[0017] Furthermore, the vinyl acetate VA content in the ethylene-vinyl acetate copolymer is 16-21 wt%, and the melt index of the ethylene-vinyl acetate copolymer is 15-25 g / 10 min at 190°C and 2.16 kg. Selecting an ethylene-vinyl acetate copolymer with the above VA content as the thermal composite layer, on the one hand, prevents the thermal composite layer from being too sticky as a whole, and on the other hand, helps the thermal composite layer and the core layer maintain a certain interlayer bonding force, does not cause interlayer shear peeling, can be biaxially stretched at a large ratio, and maintains the smoothness of normal production, while maintaining the adhesion between the thermal composite layer and the printed part. Controlling the melt index of the ethylene-vinyl acetate copolymer within the above range is conducive to ensuring good melt fluidity during the processing and production process, and is conducive to the effective extrusion of the thermal composite layer melt without being too sticky, so that production is smooth and the subsequent film thermal composite can meet the composite fastness requirements.

[0018] Furthermore, the spherical anti-blocking agent has a particle size D50 of 3.5 to 5.5 μm and is selected from either or both spherical polysiloxane and spherical polymethyl methacrylate. Adding a spherical anti-blocking agent of the appropriate type and particle size to the thermal composite layer can improve the anti-blocking properties of the thermal composite layer, ensuring smooth reeling and unreeling between the inner and outer contacting layers of the rolled film (i.e., between the thermal composite layer and the matte layer). Considering the overall light transmittance of the film, the spherical anti-blocking agent is preferably spherical polymethyl methacrylate, as its refractive index is closer to that of polypropylene.

[0019] Furthermore, the homopolypropylene in the core layer is isotactic polypropylene, and the isotacticity of the isotactic polypropylene is 95.5-97.5%, and the melt index is 2.8-3.8 g / 10 min at 230°C and 2.16 kg. Limiting the homopolypropylene in the core layer to isotactic polypropylene, and controlling the isotacticity of the isotactic polypropylene to 95.5-97.5% and the melt index to 2.8-3.8 g / 10 min, helps ensure excellent mechanical properties of the film as a whole, and also helps improve the affinity between the homopolypropylene in the core layer and the ethylene-vinyl acetate copolymer, avoiding interlayer shear peeling.

[0020] Furthermore, the thickness of the thermal composite layer is 1.5 to 4.0 μm, and the total thickness of the scratch-resistant adhesive-free matte film is 10 to 30 μm. The present invention sets the thickness of the thermal composite layer to 1.5 to 4.0 μm, which can effectively achieve the bonding effect of the thermal composite layer and is conducive to ensuring the composite effect between the film and the printed part.

[0021] The present invention also provides a method for preparing any of the above-mentioned scratch-resistant, glue-free matte films, comprising the following steps: the component raw materials of the matte layer, the core layer, and the thermal composite layer are put into a dosing unit, and after metering, they are co-extruded through an extruder respectively, and then merged in a three-layer die head after a flow channel distributor, and then cooled by a chilled roller to form a resin sheet; the resin sheet is biaxially stretched to form a film, and the film is cooled by an air shower and the thickness is controlled by a trimming machine; the film is then corona-treated and / or flame-treated, and then collected into a film mother roll; the film mother roll is subjected to aging treatment, slitting, and packaging, and is stored as a finished product.

[0022] Furthermore, the surfaces of the matt layer and the thermal composite layer are subjected to corona and / or flame treatment. After the corona and / or flame treatment, the prepared film has better applicability for deep processing.

[0023] Furthermore, the extruder's thermal composite layer discharge chute and the stretching rollers used for biaxial stretching are both coated with Teflon. This prevents the ethylene-vinyl acetate copolymer from sticking to the rollers during extrusion and stretching, respectively, thereby preventing smooth processing and compromising film surface integrity. The ethylene-vinyl acetate copolymer's moderate stickiness also reduces the risk of film slippage and scratches on the Teflon-coated stretching rollers.

[0024] The scratch-resistant, glue-free matte film of the present invention is a biaxially oriented polypropylene film, does not require secondary processing, is energy-saving and environmentally friendly, and achieves a balance between scratch resistance, high surface tension (positively correlated with printability) and smoothness of winding and unwinding of the matte layer surface of the scratch-resistant, glue-free matte film through the collaborative innovative design of the matte layer components and the coordinated design of the matching thermal composite layer. It has good scratch resistance in both room temperature and low temperature environments, and does not affect the smoothness of unwinding during storage in summer, which is conducive to meeting the growing demand for high-performance films for high-end packaging represented by high-definition and long-lasting identifiability of printed logo content of smart electronic products, and provides a typical solution to the common problem of matte surface scratch resistance for high-end BOPP matte films.

[0025] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of the scratch-resistant non-adhesive matte film described in Examples 1 to 5 and the non-adhesive matte film described in Comparative Examples 1 to 10. DETAILED DESCRIPTION

[0027] It should be clear that the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the embodiments of the present invention.

[0028] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the embodiments of the present invention. The singular forms "a," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. 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.

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

[0030] As used in the present specification and the appended claims, "thickness" refers to the thickness of the matrix formed by the polypropylene and / or polyethylene in the film or its layers.

[0031] The present invention provides a scratch-resistant, glue-free matte film, comprising a matte layer, a core layer, and a thermal composite layer arranged in sequence, wherein the matte layer comprises copolymerized polypropylene, 45-55 wt% high-density polyethylene, 2.0-2.5 wt% linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group, and 2000-4000 ppm spherical polymethyl methacrylate, wherein the weight average molecular weight of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group is 12 ~150,000, the surface tension of the linear alkyl silicone with maleic anhydride modified aziridine as the terminal group is 42~45mN / m; the particle size D50 of the spherical polymethyl methacrylate is 4.0~5.0μm; the core layer includes homopolymer polypropylene; the thermal composite layer includes ethylene-vinyl acetate copolymer and 2000~4000ppm of spherical anti-blocking agent; the particle size D50 of the spherical anti-blocking agent is the thickness of the thermal composite layer + 2μm.

[0032] Furthermore, the preparation of the maleic anhydride-modified aziridine-terminated linear alkyl silicone is obtained by a ring-opening reaction of the aziridine end group in the aziridine-terminated linear alkyl silicone with maleic anhydride under acidic conditions; the decomposition temperature of the maleic anhydride-modified aziridine-terminated linear alkyl silicone is ≥270°C.

[0033] Furthermore, in the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group, the linear alkyl group is any one of β-phenylated C12 to C16 groups.

[0034] Furthermore, the thermal composite layer further comprises 3-5 wt% of high-density polyethylene, and the melt index of the high-density polyethylene in the thermal composite layer is 20-30 g / 10 min at 190° C. and 21.6 kg.

[0035] Furthermore, the copolymerized polypropylene in the matt layer is an ethylene-propylene-butene random copolymer and / or an ethylene-propylene random copolymer, and the melt index of the copolymerized polypropylene is 7~12g / 10min under the conditions of 230°C and 2.16kg; the melt index of the high-density polyethylene in the matt layer is 10~15g / 10min under the conditions of 190°C and 21.6kg.

[0036] Furthermore, the vinyl acetate (VA) content in the ethylene-vinyl acetate copolymer is 16-21 wt %, and the melt index of the ethylene-vinyl acetate copolymer is 15-25 g / 10 min at 190° C. and 2.16 kg.

[0037] Furthermore, the particle size D50 of the spherical anti-adhesion agent is 3.5-5.5 μm, and the spherical anti-adhesion agent is any one or both of spherical polysiloxane and spherical polymethyl methacrylate.

[0038] Furthermore, the homopolymer polypropylene in the core layer is isotactic polypropylene, the isotacticity of the isotactic polypropylene is 95.5-97.5%, and the melt index is 2.8-3.8 g / 10 min at 230° C. and 2.16 kg.

[0039] Furthermore, the thickness of the thermal composite layer is 1.5-4.0 μm, and the total thickness of the scratch-resistant adhesive-free matte film is 10-30 μm.

[0040] The present invention also provides a method for preparing any of the above-mentioned scratch-resistant glue-free matte films, comprising the following steps: feeding the raw materials of each layer component into a batching unit and metering them into an extruder respectively, and co-extruding them through the extruder respectively, the extrusion temperature of the matte layer is controlled at 180~220℃, the extrusion temperature of the core layer is controlled at 230~245℃, the extrusion temperature corresponding to the thermal composite layer is controlled at 200~240℃, and after passing through a flow channel distributor, they are merged at a multi-layer die head to form a resin melt with a multi-layer structure, and then cooled by a chilled roller at 25~35℃ to form a resin sheet with a multi-layer structure; introducing the resin sheet into the longitudinal stretching device in the biaxial stretching equipment, and the The surface of the light layer is preheated at 130-135°C, the stretching temperature of the matte layer and the core layer is controlled at 110-130°C, the thermal composite layer is preheated at 50-90°C, the stretching temperature of the thermal composite layer is controlled at 50-90°C, and the stretching is 4.8-5.2 times, which is conducive to obtaining a relatively higher stiffness and facilitating smooth winding and unwinding; then a transverse stretching device is introduced, after being preheated at 165-175°C, it is stretched 8-10 times at 156-160°C, and then shaped at 165-170°C to form a film, the film is cooled by air shower, and the thickness is controlled by a trimming machine; the matte surface of the film is first corona treated in order (energy density is 1.5KJ / m 2 ) and then corona treatment (energy density of 1.0KJ / m 2 ), the film master roll is collected, and finally the film master roll is subjected to aging treatment, slitting and packaging to obtain the scratch-resistant glue-free matte film as a finished product and put into storage.

[0041] Furthermore, the extruder's thermal composite layer discharge chute and the stretching rollers used for biaxial stretching are both coated with Teflon. This prevents the ethylene-vinyl acetate copolymer from sticking to the rollers during extrusion and stretching, respectively, thereby preventing smooth processing and compromising film surface integrity. The ethylene-vinyl acetate copolymer's moderate stickiness also reduces the risk of film slippage and scratches on the Teflon-coated stretching rollers.

[0042] The physical properties and testing methods of the embodiments and comparative examples of the present invention are as follows:

[0043] Film thickness is measured according to GB / T6672-2001, unit is μm;

[0044] Melt index (melt mass flow rate MFR) is in accordance with GB / T3682-2018, unit is g / 10min;

[0045] Scratch resistance evaluation: The scratch resistance of the matte layer surface was tested using a friction tester, including room temperature scratch resistance and low temperature scratch resistance. The index was haze reduction rate. Specifically, under constant temperature and humidity conditions of 25°C and 55% humidity and under constant temperature and humidity conditions of -20°C and 55%, a 200g weight (square area below the weight: 50mm×50mm) was wrapped with a 20μm thick BOPP matte film (the glossiness of the matte layer surface was 7%, the glossy surface was in contact with the weight, and the periphery was effectively fixed with tape). The outer periphery of the glue-free matte film sample prepared by the invention is effectively fixed on the metal plate of the friction coefficient tester with tape (to ensure the flatness of the film), and the matte layer surface of the tested film is facing upward. Then, referring to the friction coefficient test method, the weight is fixed at the same position of the tested film and dragged unidirectionally 50 times. The haze of the glue-free matte film of the present invention before and after scratching is measured, and the haze reduction rate δH (%) is calculated. The greater the haze reduction rate, the worse the scratch resistance of the matte layer surface of the tested sample film, and the smaller the haze reduction rate, the better the scratch resistance of the matte layer surface of the tested sample film.

[0046] Haze reduction rate δ H (%) = (H0-H 50 ) / H0, H0 is the initial haze of the film being tested, H 50 The haze value is the haze value of the tested film after the surface of the matt layer of the matt film wrapped with a standard weight is scratched 50 times. The haze value is measured in accordance with GB / T10003-2008.

[0047] The surface roughness (Rz) test of the matt layer is carried out according to GB / T3505-2009, and the unit is μm;

[0048] The light transmittance is tested according to GB / T2410-2008 and the unit is %.

[0049] The surface tension is measured according to GB / T14216. The surface tension of the matt layer of the film is measured with a dyne pen (the surface of the matt layer is corona treated with an energy density of 1.5KJ / m 2 ), the unit is dyn / cm.

[0050] Peel strength of laminated digital printed materials: measured according to GB / T8808 (Method A), unit: N / 15mm; the laminated digital printed materials used in this invention are 250g white cardstock with black spot color printed materials, which are aged at 45°C for 2 hours after lamination and measured under constant temperature and humidity conditions of 25°C and 55%.

[0051] Test method for slitting and unwinding noise: Wind a 6000-meter film roll with a Shore hardness of 86 at 40°C and 60±5% humidity, store it at an ambient temperature of 40°C for 30 days, and unwind it on a slitting machine at a line speed of 200 meters per minute. Use a GM1356 noise meter to measure the noise at a position 500±50 meters from the bottom of the roller (matt layer surface / thermal composite functional surface). Test the noise at the surface, middle, and bottom of the roll separately, and take the average of the noise at these three positions in decibels (dB).

[0052] It should be noted that 1000 ppm corresponds to 0.1 wt % and the proportions described in the embodiments or comparative examples of the present invention are all weight percentages. The components and contents of each layer in the embodiments and comparative examples of the present invention are shown in Table 1 below.

[0053] Table 1

[0054]

[0055] It should be noted that, in the embodiments and comparative examples of the present invention, the copolymerized polypropylene in the matt layer is an ethylene-propylene random copolymer with a melt index of 7 g / 10 min (230°C, 2.16 kg), and the melt index of the high-density polyethylene is 10 g / 10 min (190°C, 21.6 kg); the homopolymerized polypropylene in the core layer is an isotactic polypropylene having an isotacticity of 95.5% and a melt index of 3.8 g / 10 min (230°C, 2.16 kg); in the thermal composite layer, the VA content in the ethylene-vinyl acetate copolymer is 20 wt%, the melt index is 20 g / 10 min (190°C, 2.16 kg), the thickness of the thermal composite layer is 3 μm, and the spherical anti-blocking agent is spherical polysiloxane in Example 4, while the other embodiments and all comparative examples are spherical polymethyl methacrylate with a particle size D50 of 5 μm.

[0056] Example 1

[0057] This embodiment provides a scratch-resistant, glue-free matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The method for preparing the scratch-resistant, glue-free matte film of this embodiment comprises the following steps:

[0058] Preparation of matt layer 1 resin: 52.8 wt% copolymerized polypropylene, 45 wt% high-density polyethylene, 2.0 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 150,000, surface tension of 45 mN / m, linear alkyl of C16), and 2000 ppm spherical polymethyl methacrylate (particle size D50 of 5.0 μm) were mixed uniformly to obtain matt layer 1 resin.

[0059] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0060] Preparation of thermal composite layer 3 resin: 99.8 wt % of ethylene-vinyl acetate copolymer and 2000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0061] The preparation method of the scratch-resistant non-adhesive matte film of this embodiment comprises the following steps: feeding the raw materials of each layer into a batching unit, metering them, and then respectively entering an extruder for co-extrusion, wherein the extrusion temperature of the matte layer 1 is controlled at 180-220°C, the extrusion temperature of the core layer 2 is controlled at 230-245°C, and the extrusion temperature of the thermal composite layer 3 is controlled at 200-240°C.

[0062] After passing through the flow channel distributor, the melt is merged at the three-layer die head to form a three-layer resin melt, which is then cooled by a chilled roller at 25-35°C to form a three-layer resin sheet; the resin sheet is introduced into the longitudinal stretching device in the biaxial stretching equipment, the surface of the matt layer 1 is preheated to 130-135°C, the stretching temperature of the matt layer 1 and the core layer 2 is controlled at 110-130°C, the thermal composite layer 3 is preheated to 50-90°C, the stretching temperature of the thermal composite layer 3 is controlled at 50-90°C, and the stretching is 4.8-5.2 times; then the transverse stretching device is introduced, after being preheated to 165-175°C, it is stretched 8-10 times at 156-160°C, and then shaped at 165-170°C to form a film, the film is cooled by air shower and the thickness is controlled by a trimming machine; the matt surface of the film is first corona treated in order (energy density is 1.5KJ / m 2 ), and then the surface of the thermal composite layer of the film is corona-treated (energy density is 1.0KJ / m 2 ), the film mother roll is collected, and finally the film mother roll is aged, slit, and packaged to obtain the scratch-resistant, glue-free matte film as the finished product for storage. This preparation method has a smooth process and smooth collection and unloading of the film.

[0063] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0064] Example 2

[0065] This embodiment provides a scratch-resistant, glue-free matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The method for preparing the scratch-resistant, glue-free matte film of this embodiment comprises the following steps:

[0066] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 130,000, surface tension of 44 mN / m, linear alkyl group of C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0067] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0068] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0069] The preparation method of the scratch-resistant non-adhesive matte film of this embodiment is the same as that of embodiment 1, so it is not described in detail. This preparation method has a smooth process and can be rolled up and unrolled smoothly.

[0070] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0071] Example 3

[0072] This embodiment provides a scratch-resistant, glue-free matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The method for preparing the scratch-resistant, glue-free matte film of this embodiment comprises the following steps:

[0073] Preparation of matt layer 1 resin: 42.1 wt% copolymerized polypropylene, 55 wt% high-density polyethylene, 2.5 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 120,000, surface tension of 42 mN / m, linear alkyl group of C12), and 4000 ppm spherical polymethyl methacrylate (particle size D50 of 4.0 μm) were mixed uniformly to obtain matt layer 1 resin.

[0074] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0075] Preparation of thermal composite layer 3 resin: 99.6 wt % of ethylene-vinyl acetate copolymer and 4000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0076] The preparation method of the scratch-resistant non-adhesive matte film of this embodiment is the same as that of embodiment 1, so it is not described in detail. This preparation method has a smooth process and can be rolled up and unrolled smoothly.

[0077] The total thickness of the film is 15 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 11 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0078] Example 4

[0079] This embodiment provides a scratch-resistant, glue-free matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The method for preparing the scratch-resistant, glue-free matte film of this embodiment comprises the following steps:

[0080] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 130,000, surface tension of 44 mN / m, linear alkyl group of C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0081] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0082] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical polysiloxane (particle size D50: 5 μm) were mixed uniformly to obtain thermal composite layer 3 resin.

[0083] The preparation method of the scratch-resistant non-adhesive matte film of this embodiment is the same as that of embodiment 1, so it is not described in detail. This preparation method has a smooth process and can be rolled up and unrolled smoothly.

[0084] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0085] Example 5

[0086] This embodiment provides a scratch-resistant, glue-free matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The method for preparing the scratch-resistant, glue-free matte film of this embodiment comprises the following steps:

[0087] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 130,000, surface tension of 44 mN / m, linear alkyl group of C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0088] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0089] Preparation of thermal composite layer 3 resin: 95.7 wt% ethylene-vinyl acetate copolymer, 4 wt% high-density polyethylene (melt index of 25 g / 10 min) and 3000 ppm spherical anti-blocking agent (particle size D50 of 5 μm) were mixed uniformly to obtain thermal composite layer 3 resin.

[0090] The preparation method of the scratch-resistant non-adhesive matte film of this embodiment is the same as that of embodiment 1, so it is not described in detail. This preparation method has a smooth process and can be rolled up and unrolled smoothly.

[0091] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0092] Comparative Example 1

[0093] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0094] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% linear alkyl silicone (Mw of 130,000, surface tension of 25 mN / m, linear alkyl of C14) and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0095] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0096] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0097] The preparation method of the non-adhesive matte film of this comparative example is the same as that of Example 1, so it will not be described in detail. This preparation method has a smooth process and can be rolled up and unrolled smoothly.

[0098] The total thickness of the film is 15 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 11 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0099] Comparative Example 2

[0100] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0101] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% aziridine-terminated linear alkyl silicone (Mw of 130,000, surface tension of 35 mN / m, linear alkyl group of C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0102] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0103] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0104] The preparation method of the non-adhesive matte film of this comparative example is the same as that of Example 1, so it will not be described in detail. This preparation method has a smooth process and can be rolled up and unrolled smoothly.

[0105] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0106] Comparative Example 3

[0107] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0108] Preparation of matt layer 1 resin: 49.2 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 0.5 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 130,000, surface tension of 44 mN / m, linear alkyl group of C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0109] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0110] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0111] The preparation method of the non-adhesive matte film of this comparative example is the same as that of Example 1, so it will not be described in detail. This preparation method has a smooth process and can be rolled up and unrolled smoothly.

[0112] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0113] Comparative Example 4

[0114] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0115] Preparation of matt layer 1 resin: 45.7 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 4 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 130,000, surface tension of 44 mN / m, linear alkyl group of C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0116] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0117] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0118] The preparation method of the adhesive-free 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 film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0120] Comparative Example 5

[0121] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0122] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 80,000, surface tension of 44 mN / m, linear alkyl group of C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0123] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0124] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0125] The preparation method of the non-adhesive matte film of this comparative example is the same as that of Example 1, so it will not be described in detail. This preparation method has a smooth process and can be rolled up and unrolled smoothly.

[0126] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0127] Comparative Example 6

[0128] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0129] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 300,000, surface tension of 44 mN / m, linear alkyl group of C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0130] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0131] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0132] The preparation method of the adhesive-free matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0133] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0134] Comparative Example 7

[0135] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0136] Matting layer 1 resin preparation: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw 130,000, surface tension 44 mN / m, linear alkyl group C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 3.5 μm) were mixed uniformly to obtain matting layer 1 resin.

[0137] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0138] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0139] The preparation method of the adhesive-free matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0140] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0141] Comparative Example 8

[0142] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0143] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 130,000, surface tension of 44 mN / m, linear alkyl group of C14), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 5.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0144] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0145] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0146] The preparation method of the adhesive-free matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0147] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0148] Comparative Example 9

[0149] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0150] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 130,000, surface tension of 44 mN / m, linear alkyl group of C6), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0151] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0152] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0153] The preparation method of the adhesive-free matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0154] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0155] Comparative Example 10

[0156] This comparative example provides a non-adhesive matte film, comprising a matte layer 1, a core layer 2, and a thermal composite layer 3 arranged in sequence. The preparation method of the non-adhesive matte film of this comparative example comprises the following steps:

[0157] Preparation of matt layer 1 resin: 47.5 wt% copolymerized polypropylene, 50 wt% high-density polyethylene, 2.2 wt% maleic anhydride-modified aziridine-terminated linear alkyl silicone (Mw of 130,000, surface tension of 44 mN / m, linear alkyl group of C20), and 3000 ppm spherical polymethyl methacrylate (particle size D50 of 4.5 μm) were mixed uniformly to obtain matt layer 1 resin.

[0158] Preparation of core layer 2 resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was mixed uniformly to serve as core layer 2 resin.

[0159] Preparation of thermal composite layer 3 resin: 99.7 wt % of ethylene-vinyl acetate copolymer and 3000 ppm of spherical anti-blocking agent (particle size D50 is 5 μm) are mixed uniformly to obtain thermal composite layer 3 resin.

[0160] The preparation method of the adhesive-free matte film of this comparative example is the same as that of Example 1, so it is not described in detail.

[0161] The total thickness of the film is 12 μm, wherein the matt layer 1 has a thickness of 1 μm, the core layer 2 has a thickness of 8 μm, and the thermal composite layer 3 has a thickness of 3 μm.

[0162] The performance tests of the scratch-resistant non-adhesive matte films described in Examples 1 to 5 and the non-adhesive matte films described in Comparative Examples 1 to 10 are shown in Table 2 below.

[0163] Table 2

[0164]

[0165] The data from Examples 1 to 5 indicate that the scratch-resistant, glue-free matte film of the present invention exhibits excellent scratch resistance at both room and low temperatures, achieving a balance between scratch resistance, high surface tension (positively correlated with printability), and smooth unwinding of the matte layer surface. In Example 4, the spherical anti-blocking agent is a spherical polysiloxane. Although the transmittance of the resulting film is lower than that of Example 2, the film's slitting and unwinding noise is significantly reduced, and the overall performance meets the objectives of this application. In Example 5, high-density polyethylene with an appropriate melt index is added to the thermal composite layer. The resulting scratch-resistant, glue-free matte film exhibits lower slitting and unwinding noise, better unwinding smoothness, and does not adversely affect the film's transmittance or the peel strength between the thermal composite layer and the printed part.

[0166] In Comparative Example 1, a linear alkyl silicone was used to replace the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group. Although the scratch resistance was good, the surface tension of the matte layer was too low to meet the application requirements of printing on the matte layer surface. Moreover, due to its migration, it was not conducive to the peel strength of the laminated digital printed part. In Comparative Example 2, a linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group was used to replace the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group. Although the scratch resistance was good, the surface tension of the matte layer was still low and still could not meet the application requirements of printing on the matte layer surface. In Comparative Example 3, the amount of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group was too low, which was not conducive to the scratch resistance of the matte layer surface. Performance, and the surface tension of the matte layer cannot be effectively improved, which is not conducive to the post-printing processing applicability of the film; in Comparative Example 4, the amount of linear alkyl silicone with maleic anhydride modified aziridine as the terminal group is too high. Although the scratch resistance and surface tension of the matte layer are significantly improved, the slitting and unwinding noise is too high, and the winding and unwinding are not smooth enough, and the matte layer surface sticks to the roller during the production process; in Comparative Example 5, the molecular weight of the linear alkyl silicone with maleic anhydride modified aziridine as the terminal group is too low, resulting in its migration being too high, affecting the surface tension of the matte layer and the composite fastness between the thermal composite layer and the printed part; in Comparative Example 6, the molecular weight of the linear alkyl silicone with maleic anhydride modified aziridine as the terminal group is too high. , which is not conducive to the scratch resistance of the matte layer surface, and the overall light transmittance of the film is reduced, affecting the appearance quality of the film itself and the transparency required for application; in Comparative Example 7, the PMMA particle size D50 in the matte layer is too small, and the difference between the particle size D50 and the roughness of the matte layer is 0, resulting in a gap between the matte layer and the thermal composite layer in the rolled film that is too small, and cannot effectively inhibit the interaction between the polar group in the linear alkyl silicone with maleic anhydride modified aziridine as the terminal group and the ethylene-vinyl acetate with a certain viscosity in the thermal composite layer, which is not conducive to the smoothness of the film unwinding; in Comparative Example 8, the PMMA particle size D50 in the matte layer is too large, and the difference between the particle size D50 and the roughness of the matte layer is too large. Although the matte layer and the thermal composite layer in the rolled film are The gap between the thermal composite layers is sufficient to ensure smooth unwinding. However, due to the excessively large PMMA particle size, firstly, uneven dispersion in the matte layer is easily caused, affecting the appearance quality of the film itself (appearing "bright spots" and "white spots" as appearance defects). Secondly, the excessively large PMMA particles circulate into the core layer with the edge material, causing film breakage due to uneven stress with the polypropylene of the core layer during biaxial stretching. In Comparative Example 9, the linear alkyl group in the maleic anhydride-modified aziridine-terminated linear alkyl silicone is too short, resulting in reduced scratch resistance on the matte layer surface and poor dispersion of the maleic anhydride-modified aziridine-terminated linear alkyl silicone in the matte layer, which is detrimental to the appearance quality and uniformity of surface tension distribution of the film.In Comparative Example 10, the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group had an excessively long linear alkyl group, resulting in a significant difference in fluidity between the silicone and the other components of the matte layer, and film breakage occurred during biaxial stretching.

[0167] 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 scratch-resistant, glue-free matte film, characterized by: The invention comprises a matte layer, a core layer and a thermal composite layer which are arranged in sequence, wherein the matte layer comprises copolymerized polypropylene, 45-55wt% high-density polyethylene, 2.0-2.5wt% linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group and 2000-4000ppm spherical polymethyl methacrylate, the weight-average molecular weight of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group is 120,000-150,000, the surface tension of the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group is 42-45mN / m; the particle size D50 of the spherical polymethyl methacrylate is 4.0-5.0μm; the core layer comprises homopolypropylene; the thermal composite layer comprises ethylene-vinyl acetate copolymer and 2000-4000ppm spherical anti-blocking agent; the particle size D50 of the spherical anti-blocking agent is the thickness of the thermal composite layer + 2μm.

2. The scratch-resistant, glue-free matte film according to claim 1, characterized in that: The preparation of the maleic anhydride-modified aziridine-terminated linear alkyl silicone is obtained by a ring-opening reaction of the aziridine end group in the aziridine-terminated linear alkyl silicone with maleic anhydride under acidic conditions; the decomposition temperature of the maleic anhydride-modified aziridine-terminated linear alkyl silicone is ≥270°C.

3. The scratch-resistant, glue-free matte film according to claim 1, characterized in that: In the linear alkyl silicone with maleic anhydride-modified aziridine as the terminal group, the linear alkyl group is any one of β-phenyl C12 to C16.

4. The scratch-resistant, glue-free matte film according to claim 1, characterized in that: The thermal composite layer further comprises 3-5 wt% high-density polyethylene. The melt index of the high-density polyethylene in the thermal composite layer is 20-30 g / 10 min at 190° C. and 21.6 kg.

5. The scratch-resistant, glue-free matte film according to claim 1, characterized in that: The copolymerized polypropylene in the matt layer is an ethylene-propylene-butene random copolymer and / or an ethylene-propylene random copolymer, and the melt index of the copolymerized polypropylene is 7~12g / 10min under the conditions of 230°C and 2.16kg; the melt index of the high-density polyethylene in the matt layer is 10~15g / 10min under the conditions of 190°C and 21.6kg.

6. The scratch-resistant, glue-free matte film according to claim 1, characterized in that: The vinyl acetate content in the ethylene-vinyl acetate copolymer is 16-21 wt %, and the melt index of the ethylene-vinyl acetate copolymer is 15-25 g / 10 min at 190° C. and 2.16 kg.

7. The scratch-resistant, glue-free matte film according to claim 1, characterized in that: The particle size D50 of the spherical anti-adhesion agent is 3.5-5.5 μm, and the spherical anti-adhesion agent is any one or both of spherical polysiloxane and spherical polymethyl methacrylate.

8. The scratch-resistant, glue-free matte film according to claim 1, characterized in that: The homopolymer polypropylene in the core layer is isotactic polypropylene, the isotacticity of the isotactic polypropylene is 95.5-97.5%, and the melt index is 2.8-3.8 g / 10 min at 230° C. and 2.16 kg.

9. The scratch-resistant adhesive-free matte film according to claim 1, characterized in that: The thickness of the thermal composite layer is 1.5-4.0 μm, and the total thickness of the scratch-resistant adhesive-free matte film is 10-30 μm.

10. A method for preparing the scratch-resistant, glue-free matte film according to any one of claims 1 to 9, characterized in that: The following steps are involved: The component raw materials of the matt layer, the core layer and the thermal composite layer are put into the batching unit, and after being measured, they are co-extruded through the extruder respectively, merged in the three-layer die head after passing through the flow channel distributor, and then cooled by the chilled roller to form a resin sheet; the resin sheet is biaxially stretched to form a film, and the film is cooled by air shower and the thickness is controlled by the trimming machine; the film is then corona-treated and / or flame-treated and then collected into a film mother roll, and the film mother roll is subjected to aging treatment, slitting, packaging, and stored as a finished product.

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