BOPP matt film and preparation method thereof

Abstract

The invention relates to a BOPP matt film and a preparation method thereof, and belongs to the technical field of matt films. The BOPP matt film comprises a matt layer, a core layer and a lower surface layer which are arranged in sequence, the matt layer comprises co-polypropylene, 46-51 wt% of high density polyethylene and 2-4 wt% of hyperbranched polyethylene, and the branching degree of the hyperbranched polyethylene is 8-12%; the core layer comprises homo-polypropylene and 6-10 wt% of a block copolymer of ethylene oxide and epoxypropane, the total proportion of ethylene oxide chain segments in the block copolymer of ethylene oxide and epoxypropane is 60-70 wt%, and the total proportion of epoxypropane chain segments in the block copolymer of ethylene oxide and epoxypropane is 30-40 wt%. According to the BOPP matt film, a certain proportion of hyperbranched polyethylene is added into the matt layer, a certain proportion of ethylene oxide and propylene oxide block copolymer is added into the core layer, and the hyperbranched polyethylene and the ethylene oxide and propylene oxide block copolymer cooperate with each other, so that the problem of bright spots on the film surface of the BOPP matt film is solved, and meanwhile, the matt effect is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of matt films, in particular to a BOPP matt film and a preparation method thereof. Background Art

[0002] BOPP matte film achieves its matte effect mainly by scattering light, which can significantly improve the texture and quality of printed outer packaging, and is therefore widely used in paper-plastic composite and electronic packaging industries. The matte matte performance of BOPP matte film gives it a soft, stylish and elegant high-end visual appearance, and can effectively relieve visual fatigue, so BOPP matte film is increasingly used in the packaging field.

[0003] In order to achieve the ideal matte effect, the matte layer of BOPP matte film is mainly composed of high-density polyethylene and copolymer polypropylene. Using the soft-hard principle, that is, copolymer polypropylene (soft phase) encapsulates high-density polyethylene (hard phase), during the biaxial stretching film making process, this structure will present an "island" structure at the microscopic level, and finally achieve the matte effect. However, during the processing of BOPP matte film, bright spots will appear on the film surface, resulting in appearance defects, which seriously affects the application of BOPP matte film; Reasons for bright spots on the film surface of BOPP matte film: (1) Mirror bright spots in the matt layer: Due to the high crystallinity of the high-density polyethylene in the matt layer, it is easy to form large-sized spherulites, resulting in the existence of high-density polyethylene-rich areas in the matt layer, which will reduce the scattering efficiency or form a "scattering blind area", destroying the uniform scattering structure and forming local bright spot defects.

[0004] (2) Bright spots: Since the main component of the core layer of BOPP matte film is homopolymer polypropylene, and the main components of the matte layer are high-density polyethylene and copolymer polypropylene, the interfacial tension between the core layer and the matte layer is large, and local stratification is prone to occur. Light in the stratified area directly passes through the core layer, forming bright spots. Summary of the invention

[0005] Based on this, the object of the present invention is to provide a BOPP matte film and a preparation method thereof, by adding a certain proportion of hyperbranched polyethylene in the matte layer and a certain proportion of block copolymer of ethylene oxide and propylene oxide in the core layer, the two work together to improve the bright spot problem on the film surface of the BOPP matte film while ensuring the matte effect.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a BOPP matting film, which comprises a matting layer, a core layer and a lower surface layer arranged in sequence; the matting layer comprises copolymerized polypropylene, 46-51 wt% of high-density polyethylene and 2-4 wt% of hyperbranched polyethylene, and the degree of branching of the hyperbranched polyethylene is 8-12%; the core layer comprises homopolypropylene and 6-10 wt% of a block copolymer of ethylene oxide and propylene oxide, and the total proportion of the ethylene oxide chain segments in the block copolymer of ethylene oxide and propylene oxide is 60-70 wt%, and the total proportion of the propylene oxide chain segments is 30-40 wt%.

[0007] In the BOPP matting film of the present invention, by adding the hyperbranched polyethylene into the matting layer, the crystallization of the high-density polyethylene in the matting layer is inhibited, and the mirror bright spot defect of the matting layer caused by the local "scattering blind area" caused by large-sized spherulites is reduced; by adding the block copolymer of ethylene oxide and propylene oxide into the core layer, a "molecular bridge" can be constructed at the interface between the core layer and the matting layer, the interlayer adhesion force is enhanced, the local delamination is inhibited, and the bright spot defect of the core layer of the BOPP matting film is improved; the two cooperate to improve the bright spot problem on the film surface of the BOPP matting film while ensuring the matting effect.

[0008] The hyperbranched polyethylene added in the extinction layer has short branches formed by the polymerization of ethylene chain walking randomly and densely distributed in its molecules, forming a three-dimensional dendritic compact structure. It inhibits the crystallization of high-density polyethylene in the extinction layer through two aspects: First, van der Waals forces are formed between the short branches of the hyperbranched polyethylene and the molecular chains of high-density polyethylene, so that the hyperbranched polyethylene is inserted between the linear molecular chains of high-density polyethylene during melt blending, destroying the regular arrangement of the high-density polyethylene molecular chains and hindering the crystallization of high-density polyethylene; Second, the dense distribution of the short branches of the hyperbranched polyethylene produces a steric hindrance effect, restricting the degree of freedom of movement of the high-density polyethylene molecular chains and the crystallization diffusion path, promoting high-density polyethylene to form small grains with uniform size, thereby reducing the crystallinity of high-density polyethylene and reducing the mirror bright spot defects in the extinction layer caused by the local "scattering blind area" caused by large-sized spherulites of high-density polyethylene. The present invention defines that the addition amount of the hyperbranched polyethylene in the extinction layer is 2-4wt%. If the addition amount of the hyperbranched polyethylene is less than 2wt%, due to the insufficient number of short branches, it cannot be fully inserted between the high-density polyethylene molecular chains to form effective interference, resulting in high-density polyethylene still forming large-sized spherulites through the regular arrangement of molecular chains, ultimately leading to uneven light scattering and bright spot defects in the BOPP extinction film; If the addition amount of the hyperbranched polyethylene in the extinction layer is greater than 4wt%, the short branches of the excessive hyperbranched polyethylene tightly wrap the high-density polyethylene molecular chains due to the highly dense distribution, making it impossible to crystallize regularly, resulting in the scattering structure of the extinction layer being anisotropic, the extinction effect becoming worse, causing uneven local light scattering and bright spot defects, and at the same time affecting the processing stability of the extinction film. The present invention defines that the degree of branching of the hyperbranched polyethylene is 8-12%. If the degree of branching of the hyperbranched polyethylene is less than 8%, the molecular chain of the hyperbranched polyethylene with too low degree of branching is close to a linear structure, with small steric hindrance and weak interference on the crystallization process of high-density polyethylene, resulting in high-density polyethylene still easily forming large-sized spherulites with high crystallinity, and a "scattering blind area" is formed in the local area due to the large-sized spherulites, ultimately leading to mirror bright spot defects in the extinction layer; If the degree of branching of the hyperbranched polyethylene is greater than 12%, the molecular chain of the hyperbranched polyethylene is highly branched and the intermolecular entanglement is strong, resulting in a significant reduction in the melt fluidity of the extinction layer, being prone to sticking to the roller and difficult to form a film during production, and affecting the extinction effect.

[0009] The block copolymer of ethylene oxide and propylene oxide added to the core layer, which contains ethylene oxide segments and propylene oxide segments, can build a "molecular bridge" at the interface between the core layer and the matting layer. The propylene oxide segments in the block copolymer of ethylene oxide and propylene oxide can anchor the core layer interface through random chain segment entanglement and van der Waals forces because the side chain methyl groups thereof are similar in structure to the homopolypropylene segments in the core layer; while the ethylene oxide segments in the block copolymer of ethylene oxide and propylene oxide, with their weakly polar ether bonds, can connect the matting layer interface; the two (propylene oxide segments and ethylene oxide segments) are arranged directionally at the interface, reducing the interfacial tension between the core layer and the matting layer, converting the two layers from "high-tension repulsion" to "low-tension compatibility", enhancing the interlayer adhesion, inhibiting local delamination, and improving the defect of bright spots in the light transmission of the core layer of the BOPP matting film. The present invention defines that the addition amount of the block copolymer of ethylene oxide and propylene oxide in the core layer is 6-10 wt%. If the addition amount of the block copolymer of ethylene oxide and propylene oxide in the core layer is less than 6 wt%, a complete "molecular bridge" cannot be formed at the interface between the core layer and the matting layer, the interfacial anchor points are limited, the reduction of the interfacial tension and the enhancement of the interlayer adhesion are weak, local delamination still occurs, and the improvement of the bright spots in the core layer light transmission is not obvious; if the addition amount of the block copolymer of ethylene oxide and propylene oxide in the core layer is greater than 10 wt%, new phase separation interfaces will be generated inside the core layer, the interfacial tension between layers will rise, and the interlayer adhesion will decrease, exacerbating the defect of the bright spot problem. The present invention defines that the total proportion of the ethylene oxide segments in the block copolymer of ethylene oxide and propylene oxide is 60-70 wt%, and the total proportion of the propylene oxide segments is 30-40 wt%; by restricting the total proportions of the ethylene oxide segments and the propylene oxide segments in the block copolymer of ethylene oxide and propylene oxide within the above ranges respectively, it is beneficial to maintain the processing stability. If the total proportion of the ethylene oxide segments in the block copolymer of ethylene oxide and propylene oxide is less than 60 wt% and the total proportion of the propylene oxide segments is greater than 40 wt%, due to the insufficient ethylene oxide segments, the matting layer anchor points of the "molecular bridge" are missing, resulting in limited reduction of the interfacial tension and adhesion between the core layer and the matting layer, and "bright spot" defects appear on the film surface; if the total proportion of the ethylene oxide segments in the block copolymer of ethylene oxide and propylene oxide is greater than 70 wt% and the total proportion of the propylene oxide segments is less than 30 wt%, the melt fluidity of the core layer becomes poor, it is not easy to stretch and the film is easily broken, and the processing stability of the film becomes poor.

[0010] As a preferred embodiment of the present invention, in the matting layer, the melt index of the hyperbranched polyethylene at 190 °C under a load of 21.6 kg is 15 - 25 g / 10 min. Controlling the melt index of the hyperbranched polyethylene within the above range is beneficial to ensuring the matting effect and processability of the matting layer. If the melt index of the hyperbranched polyethylene is too low, it may lead to poor melt fluidity of the matting layer, difficulty in stretching and easy film breakage, affecting the processing stability of the matting film; if the melt index of the hyperbranched polyethylene is too high, the melt fluidity of the matting layer is good, which affects the matting effect of the matting film.

[0011] As a preferred embodiment of the present invention, in the matting layer, the preparation method of the hyperbranched polyethylene is the chain walking polymerization method. The chain walking polymerization method is a commonly used technical means in the art, and those skilled in the art can polymerize the hyperbranched polyethylene of the present invention based on this method, which will not be elaborated here. The molecular structure of the hyperbranched polyethylene prepared by the chain walking polymerization method has the following exemplary structural formula:

[0012] In the hyperbranched polyethylene molecule, short side chains (such as side chain 1, side chain 2,... side chain n shown in the above formula) are randomly and densely distributed, forming a three-dimensional dendritic compact structure.

[0013] As a preferred embodiment of the present invention, in the matting layer, the copolymerized polypropylene is one or more of ethylene-propylene binary copolymerized polypropylene or ethylene-propylene-butene terpolymer.

[0014] As a preferred embodiment of the present invention, in the matting layer, the melt index of the copolymerized polypropylene at 230 °C under a load of 2.16 kg is 6 - 12 g / 10 min, and the melt index of the high-density polyethylene at 190 °C under a load of 21.6 kg is 12 - 20 g / 10 min. Controlling the melt indexes of the above copolymerized polypropylene and high-density polyethylene within the above ranges respectively is beneficial to providing an excellent matting effect.

[0015] As a preferred embodiment of the present invention, in the core layer, the block copolymer of ethylene oxide and propylene oxide is at least one of ethylene oxide-propylene oxide diblock copolymer and ethylene oxide-propylene oxide-ethylene oxide triblock copolymer.

[0016] In the ethylene oxide-propylene oxide diblock copolymer, the ethylene oxide segment and the propylene oxide segment are respectively located at the "two ends" of the molecular structure; the propylene oxide segment at one end is anchored to the core layer interface by random segment winding and van der Waals force; the ethylene oxide segment at the other end is connected to the matte layer interface by its weak polar ether bond; the two (the propylene oxide segment at one end and the ethylene oxide segment at one end) are oriented at the interface to reduce the interfacial tension between the core layer and the matte layer, so that the two layers change from "high tension repulsion" to "low tension compatibility", enhance the interlayer adhesion, inhibit local delamination, and improve the bright spot defects of the core layer of the BOPP matte film.

[0017] In the ethylene oxide-propylene oxide-ethylene oxide triblock copolymer, the propylene oxide segment is located in the "middle" of the molecular structure, and the two ethylene oxide segments are respectively located at the two ends of the molecular structure; the propylene oxide segment located in the middle is anchored to the core layer interface by random segment entanglement and van der Waals force; the ethylene oxide segments located at the two ends are connected to the matt layer interface by their weak polar ether bonds. The present invention takes into account that the effect of the "weak polar ether bond" of the ethylene oxide segment is relatively weak compared to the effect of the "random segment entanglement and van der Waals force" of the propylene oxide segment. In addition to the design of the total proportion of the ethylene oxide segment and the propylene oxide segment, the present invention is designed into a triblock molecular structure of ethylene oxide segment-propylene oxide segment-ethylene oxide segment; the two (propylene oxide segment in the middle and ethylene oxide segments at both ends) are arranged in a directional manner at the interface, which can not only reduce the interfacial tension between the core layer and the matte layer, but also make the interfacial tension at each interface between the core layer and the matte layer more uniform, so that the two layers are transformed from "high tension repulsion" to more uniform "low tension compatibility", enhance the interlayer adhesion, further inhibit local delamination, and improve the bright spot defects of the core layer of the BOPP matte film. Therefore, as a more preferred solution, the block copolymer of ethylene oxide and propylene oxide in the present invention is more preferably an ethylene oxide-propylene oxide-ethylene oxide triblock copolymer. Of course, the ethylene oxide-propylene oxide diblock copolymer can also meet the demand for improving the bright spot defects of the core layer of the BOPP matte film.

[0018] Furthermore, in the ethylene oxide-propylene oxide-ethylene oxide triblock copolymer, the two ethylene oxide segments account for 30-35 wt % respectively, and the total account for 60-70 wt % of the two ethylene oxide segments.

[0019] As a preferred embodiment of the present invention, in the core layer, the block copolymer of ethylene oxide and propylene oxide (the ethylene oxide-propylene oxide diblock copolymer or the ethylene oxide-propylene oxide-ethylene oxide triblock copolymer) has a melt index of 1-3 g / 10 min at 230 °C under a load of 2.16 kg. Controlling the melt index of the block copolymer of ethylene oxide and propylene oxide (the ethylene oxide-propylene oxide diblock copolymer or the ethylene oxide-propylene oxide-ethylene oxide triblock copolymer) within the above range enables good melt flow matching with the homopolypropylene in the core layer, which is beneficial for reducing bright spots on the film surface and ensuring processing stability. If the melt index of the block copolymer of ethylene oxide and propylene oxide (the ethylene oxide-propylene oxide diblock copolymer or the ethylene oxide-propylene oxide-ethylene oxide triblock copolymer) is too low, the melt fluidity of the core layer becomes poor, which is not conducive to its dispersion in the core layer, and there may be an increase in light-transmitting bright spots; if the melt index of the block copolymer of ethylene oxide and propylene oxide (the ethylene oxide-propylene oxide diblock copolymer or the ethylene oxide-propylene oxide-ethylene oxide triblock copolymer) is too high, it is not conducive to the stable co-extrusion of the core layer melt and affects processing stability.

[0020] As a preferred embodiment of the present invention, in the core layer, the preparation method of the block copolymer of ethylene oxide and propylene oxide (the ethylene oxide-propylene oxide diblock copolymer or the ethylene oxide-propylene oxide-ethylene oxide triblock copolymer) is anionic ring-opening polymerization. Using a strong alkaline initiator (such as hydroxide, alkoxide) to initiate the anionic ring-opening polymerization of ethylene oxide or propylene oxide, and achieving the block structure by adding monomers step by step, the block copolymer of ethylene oxide and propylene oxide (the ethylene oxide-propylene oxide diblock copolymer or the ethylene oxide-propylene oxide-ethylene oxide triblock copolymer) is prepared.

[0021] As a preferred embodiment of the present invention, in the core layer, the core layer further includes 0.5-1.0 wt% antistatic masterbatch.

[0022] As a preferred embodiment of the present invention, the effective content of the antistatic agent in the antistatic masterbatch is 35-50 wt%, and the carrier is homopolypropylene.

[0023] As a preferred embodiment of the present invention, the homopolypropylene in the core layer has a melt index of 2-5 g / 10 min at 230 °C under a load of 2.16 kg.

[0024] As a preferred embodiment of the lower surface layer, the lower surface layer is a smooth lower surface layer, including homopolypropylene and 0.5-1.0 wt% antiblocking masterbatch.

[0025] As a preferred embodiment of the present invention, in the lower surface layer, the homopolypropylene has a melt index of 2 - 5 g / 10 min at 230°C under a load of 2.16 kg.

[0026] As a preferred embodiment of the present invention, the effective content of the anti-blocking agent in the anti-blocking agent masterbatch is 5 - 6 wt%, the anti-blocking agent is preferably fumed silica with an average particle size (D50) of 4.0 - 5.0 μm, and the carrier is homopolypropylene.

[0027] As another preferred embodiment of the lower surface layer, the lower surface layer is a matte lower surface layer, comprising copolymerized polypropylene, 46 - 51 wt% high-density polyethylene, and 2 - 4 wt% hyperbranched polyethylene, and the degree of branching of the hyperbranched polyethylene is 8 - 12%.

[0028] As a preferred embodiment of the present invention, in the lower surface layer, the hyperbranched polyethylene has a melt index of 15 - 25 g / 10 min at 190°C under a load of 21.6 kg. Controlling the melt index of the hyperbranched polyethylene within the above range is beneficial to ensuring the matte effect and processing performance of the lower surface layer.

[0029] As a preferred embodiment of the present invention, in the lower surface layer, the preparation method of the hyperbranched polyethylene is the chain walking polymerization method.

[0030] As a preferred embodiment of the present invention, in the lower surface layer, the copolymerized polypropylene is one or more of ethylene-propylene binary copolymerized polypropylene or ethylene-propylene-butene terpolymer.

[0031] As a preferred embodiment of the present invention, in the lower surface layer, the copolymerized polypropylene has a melt index of 6 - 12 g / 10 min at 230°C under a load of 2.16 kg, and the high-density polyethylene has a melt index of 12 - 20 g / 10 min at 190°C under a load of 21.6 kg. Controlling the melt indices of the above copolymerized polypropylene and high-density polyethylene within the above ranges respectively is beneficial to providing an excellent matte effect.

[0032] As a preferred embodiment of the present invention, the thickness of the matte layer is 1.5 - 2.3 μm, the thickness of the lower surface layer is 0.7 - 0.9 μm or 1.5 - 2.3 μm (when the lower surface layer is a smooth lower surface layer, the thickness is 0.7 - 0.9 μm; when the lower surface layer is a matte lower surface layer, the thickness is 1.5 - 2.3 μm), and the total thickness of the BOPP matte film is 16 - 23 μm.

[0033] The present invention also provides a method for preparing the BOPP matte film described in any one of the above, comprising the following steps: Under dry conditions, the raw materials of the matte layer, the core layer, and the lower surface layer are weighed according to the ratio and added into respective extruders. After the raw materials of each layer are melted and plasticized in each extruder, they are metered by metering pumps, and then converge at a T-die according to different extruder channels to form a thick sheet. After the thick sheet is extruded, it is subjected to chill casting. After the casting is shaped, it first enters the longitudinal stretching zone for longitudinal stretching, and then enters the transverse stretching zone for transverse stretching. After the film is biaxially stretched, trimming, corona treatment, winding, and aging treatment are carried out, and finally, it is slit and packaged to obtain the BOPP matte film.

[0034] As a preferred embodiment of the present invention, the extrusion temperature of the matte layer is 230 - 255 °C; the extrusion temperatures of the core layer and the lower surface layer are 230 - 260 °C (when the lower surface layer is a smooth lower surface layer, the temperature is preferably 250 - 260 °C; when the lower surface layer is a matte lower surface layer, the temperature is preferably 230 - 255 °C); the temperature of the T-die is 230 - 245 °C, the temperature of the chill roll is 30 - 35 °C, the temperature of the longitudinal stretching preheating roll is between 128 - 145 °C, the temperature of the longitudinal stretching zone is 120 - 135 °C, the longitudinal stretching ratio is 4 - 5 times, the transverse stretching preheating temperature is 160 - 175 °C, the temperature of the transverse stretching zone is 155 - 165 °C, and the transverse stretching ratio is 7 - 9 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic structural diagram of the BOPP matte film of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0037] For the component and content of each layer of the BOPP matte film in the following examples or comparative examples, please refer to Table 1 below: Table 1 Formulations of BOPP Matte Films in Examples 1 - 5 and Comparative Examples 1 - 11

[0038] In the following examples or comparative examples: The homopolypropylene in the core layer and the lower surface layer: The melt index is 3 g / 10 min (230 °C, 2.16 kg).

[0039] The copolymerized polypropylene in the matte layer and the lower surface layer: Ethylene-propylene copolymerized polypropylene, the melt index is 9 g / 10 min (230 °C, 2.16 kg).

[0040] Antistatic masterbatch: The active ingredient is glycerol monostearate, the active content is 42 wt%, and the carrier is homopolypropylene.

[0041] Anti-blocking masterbatch: The active ingredient is fumed silica, the active content is 5.5 wt%, the average particle size (D50) is 4.5 μm, and the carrier is homopolypropylene.

[0042] Hyperbranched polyethylene: The preparation method is chain walking polymerization.

[0043] Ethylene oxide - propylene oxide diblock copolymer: The preparation method is anionic ring-opening polymerization. Using a strong alkaline initiator (such as hydroxide, alkoxide) to initiate the anionic ring-opening polymerization of ethylene oxide or propylene oxide, and achieving a block structure by adding monomers step by step, to prepare an ethylene oxide - propylene oxide diblock copolymer. The ethylene oxide - propylene oxide diblock copolymer has a diblock molecular structure (ethylene oxide chain segment - propylene oxide chain segment).

[0044] Ethylene oxide - propylene oxide - ethylene oxide triblock copolymer: The preparation method is anionic ring-opening polymerization. Using a strong alkaline initiator (such as hydroxide, alkoxide) to initiate the anionic ring-opening polymerization of ethylene oxide or propylene oxide, and achieving a block structure by adding monomers step by step, to prepare an ethylene oxide - propylene oxide - ethylene oxide triblock copolymer. The ethylene oxide - propylene oxide - ethylene oxide triblock copolymer has a triblock molecular structure (ethylene oxide chain segment - propylene oxide chain segment - ethylene oxide chain segment).

[0045] Example 1 This example provides a BOPP matting film. Please refer to Figure 1 , which includes a matting layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matting layer 1: 52 wt% copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% high-density polyethylene (melt index is 16 g / 10 min), and 2 wt% hyperbranched polyethylene (melt index is 15 g / 10 min, degree of branching is 8%).

[0046] Core layer 2: 89.5 wt% homopolypropylene (melt index is 3 g / 10 min), 10 wt% ethylene oxide - propylene oxide diblock copolymer (melt index is 3 g / 10 min, the total proportion of ethylene oxide chain segments is 60 wt%, and the total proportion of propylene oxide chain segments is 40 wt%), and 0.5 wt% antistatic masterbatch.

[0047] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% anti-blocking masterbatch.

[0048] The preparation method of the BOPP matte film in this embodiment includes the following steps: Under dry conditions, weigh the raw materials of each layer according to the ratio and add them to each extruder. The temperatures of the extruders for the core layer 2 and the lower surface layer 3 are both 250 °C, and the temperature of the extruder for the matte layer 1 is 240 °C. After the raw materials of each layer are melted and plasticized in each extruder, they are metered by a metering pump, and then enter different extruder channels, converge and are extruded at the T-die head, and are cast into a thick sheet through a chill roll. After the thick sheet is extruded, it is subjected to chill casting. After the casting is shaped, it first enters the longitudinal stretching zone for longitudinal stretching preheating, and then undergoes longitudinal stretching. The longitudinal stretching multiple is 5 times, and the longitudinal stretching temperature is 125 °C. After longitudinal stretching and shaping, it enters the transverse stretching zone for transverse stretching preheating, and then undergoes transverse stretching. The transverse stretching multiple is 8 times, and the transverse stretching temperature is 160 °C. After the film is biaxially stretched, it is trimmed and cut, then corona treated, wound, and aged, and finally slit and packaged to obtain the finished product.

[0049] The total thickness of the BOPP matte film in this embodiment is 21 µm, the thickness of the matte layer 1 is 1.5 µm, the thickness of the core layer 2 is 18.7 µm, and the thickness of the lower surface layer 3 is 0.8 µm.

[0050] Example 2 This embodiment provides a BOPP matte film. Please refer to Figure 1 , which includes a matte layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. For the components of each layer, please refer to Table 1 and the following specific components: Matte layer 1: 50 wt% copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% high-density polyethylene (melt index is 16 g / 10 min), and 4 wt% hyperbranched polyethylene (melt index is 20 g / 10 min, degree of branching is 10%).

[0051] Core layer 2: 93.5 wt% homopolypropylene (melt index is 3 g / 10 min), 6 wt% ethylene oxide - propylene oxide diblock copolymer (melt index is 1 g / 10 min, total proportion of ethylene oxide segments is 65 wt%, total proportion of propylene oxide segments is 35 wt%), and 0.5 wt% antistatic masterbatch.

[0052] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% antiblocking masterbatch.

[0053] The preparation method of the BOPP matte film in this embodiment is the same as that in Example 1.

[0054] The total thickness and the thickness of each layer of the BOPP matte film in this embodiment are the same as those in Example 1.

[0055] Example 3 This embodiment provides a BOPP matting film. Please refer to Figure 1 , which includes a matting layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matting layer 1: 51 wt% of copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% of high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% of hyperbranched polyethylene (melt index is 25 g / 10 min, degree of branching is 12%).

[0056] Core layer 2: 91.5 wt% of homopolypropylene (melt index is 3 g / 10 min), 8 wt% of ethylene oxide - propylene oxide diblock copolymer (melt index is 2 g / 10 min, total proportion of ethylene oxide segments is 70 wt%, total proportion of propylene oxide segments is 30 wt%), and 0.5 wt% of antistatic masterbatch.

[0057] Lower surface layer 3: 99.5 wt% of homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% of antiblocking masterbatch.

[0058] The preparation method of the BOPP matting film in this embodiment is the same as that in Embodiment 1.

[0059] The total thickness and the thickness of each layer of the BOPP matting film in this embodiment are the same as those in Embodiment 1.

[0060] Embodiment 4 This embodiment provides a BOPP matting film. Please refer to Figure 1 , which includes a matting layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matting layer 1: 51 wt% of copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% of high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% of hyperbranched polyethylene (melt index is 20 g / 10 min, degree of branching is 10%).

[0061] Core layer 2: 91.5 wt% of homopolypropylene (melt index is 3 g / 10 min), 8 wt% of ethylene oxide - propylene oxide diblock copolymer (melt index is 2 g / 10 min, total proportion of ethylene oxide segments is 65 wt%, total proportion of propylene oxide segments is 35 wt%), and 0.5 wt% of antistatic masterbatch.

[0062] Lower surface layer 3: 48 wt% of copolymerized polypropylene (melt index is 9 g / 10 min), 49 wt% of high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% of hyperbranched polyethylene (melt index is 20 g / 10 min, degree of branching is 10%).

[0063] The preparation method of the BOPP matting film in this example is basically the same as that in Example 1, except that the temperature of the lower surface layer 3 extruder is 240 °C.

[0064] The total thickness of the BOPP matting film in this example is 21.7 µm, the thickness of the matting layer 1 is 1.5 µm, the thickness of the core layer 2 is 18.7 µm, and the thickness of the lower surface layer 3 is 1.5 µm.

[0065] Example 5 This example provides a BOPP matting film. Please refer to Figure 1 , which includes a matting layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matting layer 1: 51 wt% copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% hyperbranched polyethylene (melt index is 25 g / 10 min, degree of branching is 12%).

[0066] Core layer 2: 91.5 wt% homopolypropylene (melt index is 3 g / 10 min), 8 wt% ethylene oxide-ethylene propylene-ethylene oxide triblock copolymer (melt index is 2 g / 10 min, the total proportion of ethylene oxide chain segments is 70 wt%, of which the two ethylene oxide chain segments at both ends account for 35 wt% respectively, and the total proportion of ethylene propylene chain segments is 30 wt%), and 0.5 wt% antistatic masterbatch.

[0067] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% antiblocking masterbatch.

[0068] The preparation method of the BOPP matting film in this example is the same as that in Example 1.

[0069] The total thickness and the thickness of each layer of the BOPP matting film in this example are the same as those in Example 1.

[0070] Comparative Example 1 This comparative example provides a BOPP matting film. Please refer to Figure 1 , which includes a matting layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matting layer 1: 53 wt% copolymerized polypropylene (melt index is 9 g / 10 min) and 47 wt% high-density polyethylene (melt index is 16 g / 10 min).

[0071] Core layer 2: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% antistatic masterbatch.

[0072] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% anti-blocking masterbatch.

[0073] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0074] The total thickness and the thickness of each layer of the BOPP matte film in this comparative example are the same as those in Example 1.

[0075] Comparative Example 2 This comparative example provides a BOPP matte film. Please refer to Figure 1 , which includes a matte layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matte layer 1: 48 wt% copolymerized polypropylene (melt index is 9 g / 10 min), 49 wt% high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% hyperbranched polyethylene (melt index is 20 g / 10 min, degree of branching is 10%).

[0076] Core layer 2: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% antistatic masterbatch.

[0077] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% anti-blocking masterbatch.

[0078] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0079] The total thickness and the thickness of each layer of the BOPP matte film in this comparative example are the same as those in Example 1.

[0080] Comparative Example 3 This comparative example provides a BOPP matte film. Please refer to Figure 1 , which includes a matte layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matte layer 1: 50 wt% copolymerized polypropylene (melt index is 9 g / 10 min) and 50 wt% high-density polyethylene (melt index is 16 g / 10 min).

[0081] Core layer 2: 91.5 wt% homopolypropylene (melt index is 3 g / 10 min), 8 wt% ethylene oxide - propylene oxide diblock copolymer (melt index is 2 g / 10 min, the total proportion of ethylene oxide segments is 65 wt%, and the total proportion of propylene oxide segments is 35 wt%), and 0.5 wt% antistatic masterbatch.

[0082] The lower surface layer 3: 99.5 wt% of homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% of anti-blocking masterbatch.

[0083] The preparation method of the BOPP matte film of this comparative example is the same as that of Example 1.

[0084] The total thickness and the thickness of each layer of the BOPP matte film of this comparative example are the same as those of Example 1.

[0085] Comparative Example 4 This comparative example provides a BOPP matte film. Please refer to Figure 1 , which includes a matte layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matte layer 1: 51 wt% of copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% of high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% of hyperbranched polyethylene (melt index is 20 g / 10 min, degree of branching is 10%).

[0086] Core layer 2: 84.5 wt% of homopolypropylene (melt index is 3 g / 10 min), 15 wt% of ethylene oxide - propylene oxide diblock copolymer (melt index is 2 g / 10 min, the total proportion of ethylene oxide segments is 65 wt%, and the total proportion of propylene oxide segments is 35 wt%), and 0.5 wt% of antistatic masterbatch.

[0087] The lower surface layer 3: 99.5 wt% of homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% of anti-blocking masterbatch.

[0088] The preparation method of the BOPP matte film of this comparative example is the same as that of Example 1.

[0089] The total thickness and the thickness of each layer of the BOPP matte film of this comparative example are the same as those of Example 1.

[0090] Comparative Example 5 This comparative example provides a BOPP matte film. Please refer to Figure 1 , which includes a matte layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matte layer 1: 51 wt% of copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% of high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% of hyperbranched polyethylene (melt index is 20 g / 10 min, degree of branching is 10%).

[0091] Core layer 2: 96.5 wt% homopolypropylene (melt index is 3 g / 10 min), 3 wt% ethylene oxide - propylene oxide diblock copolymer (melt index is 2 g / 10 min, total ethylene oxide segment proportion is 65 wt%, total propylene oxide segment proportion is 35 wt%) and 0.5 wt% antistatic masterbatch.

[0092] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% antiblocking masterbatch.

[0093] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0094] The total thickness and the thickness of each layer of the BOPP matte film in this comparative example are the same as those in Example 1.

[0095] Comparative Example 6 This comparative example provides a BOPP matte film, please refer to Figure 1 , which includes a matte layer 1, a core layer 2 and a lower surface layer 3 arranged in sequence, and the components of each layer are shown in Table 1 and the following specific components: Matte layer 1: 44 wt% copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% high-density polyethylene (melt index is 16 g / 10 min) and 10 wt% hyperbranched polyethylene (melt index is 20 g / 10 min, degree of branching is 10%).

[0096] Core layer 2: 91.5 wt% homopolypropylene (melt index is 3 g / 10 min), 8 wt% ethylene oxide - propylene oxide diblock copolymer (melt index is 2 g / 10 min, total ethylene oxide segment proportion is 65 wt%, total propylene oxide segment proportion is 35 wt%) and 0.5 wt% antistatic masterbatch.

[0097] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% antiblocking masterbatch.

[0098] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0099] The total thickness and the thickness of each layer of the BOPP matte film in this comparative example are the same as those in Example 1.

[0100] Comparative Example 7 This comparative example provides a BOPP matte film, please refer to Figure 1 , which includes a matte layer 1, a core layer 2 and a lower surface layer 3 arranged in sequence, and the components of each layer are shown in Table 1 and the following specific components: Matte layer 1: 53.5 wt% copolymerized polypropylene (melt index of 9 g / 10 min), 46 wt% high-density polyethylene (melt index of 16 g / 10 min), and 0.5 wt% hyperbranched polyethylene (melt index of 20 g / 10 min, degree of branching of 10%).

[0101] Core layer 2: 91.5 wt% homopolypropylene (melt index of 3 g / 10 min), 8 wt% ethylene oxide - propylene oxide diblock copolymer (melt index of 2 g / 10 min, total proportion of ethylene oxide segments is 65 wt%, total proportion of propylene oxide segments is 35 wt%), and 0.5 wt% antistatic masterbatch.

[0102] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index of 3 g / 10 min) and 0.5 wt% antiblocking masterbatch.

[0103] The preparation method of the BOPP matte film of this comparative example is the same as that of Example 1.

[0104] The total thickness and the thickness of each layer of the BOPP matte film of this comparative example are the same as those of Example 1.

[0105] Comparative Example 8 This comparative example provides a BOPP matte film. Please refer to Figure 1 , which includes a matte layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matte layer 1: 51 wt% copolymerized polypropylene (melt index of 9 g / 10 min), 46 wt% high-density polyethylene (melt index of 16 g / 10 min), and 3 wt% hyperbranched polyethylene (melt index of 7 g / 10 min, degree of branching of 4%).

[0106] Core layer 2: 91.5 wt% homopolypropylene (melt index of 3 g / 10 min), 8 wt% ethylene oxide - propylene oxide diblock copolymer (melt index of 2 g / 10 min, total proportion of ethylene oxide segments is 65 wt%, total proportion of propylene oxide segments is 35 wt%), and 0.5 wt% antistatic masterbatch.

[0107] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index of 3 g / 10 min) and 0.5 wt% antiblocking masterbatch.

[0108] The preparation method of the BOPP matte film of this comparative example is the same as that of Example 1.

[0109] The total thickness and the thickness of each layer of the BOPP matte film of this comparative example are the same as those of Example 1.

[0110] Comparative Example 9 This comparative example provides a BOPP matting film. Please refer to Figure 1 , which includes a matting layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matting layer 1: 51 wt% copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% hyperbranched polyethylene (melt index is 35 g / 10 min, degree of branching is 18%).

[0111] Core layer 2: 91.5 wt% homopolypropylene (melt index is 3 g / 10 min), 8 wt% ethylene oxide - propylene oxide diblock copolymer (melt index is 2 g / 10 min, total proportion of ethylene oxide segments is 65 wt%, total proportion of propylene oxide segments is 35 wt%), and 0.5 wt% antistatic masterbatch.

[0112] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% anti-blocking masterbatch.

[0113] The preparation method of the BOPP matting film in this comparative example is the same as that in Example 1.

[0114] The total thickness and the thickness of each layer of the BOPP matting film in this comparative example are the same as those in Example 1.

[0115] Comparative Example 10 This comparative example provides a BOPP matting film. Please refer to Figure 1 , which includes a matting layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matting layer 1: 51 wt% copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% hyperbranched polyethylene (melt index is 20 g / 10 min, degree of branching is 10%).

[0116] Core layer 2: 91.5 wt% homopolypropylene (melt index is 3 g / 10 min), 8 wt% ethylene oxide - propylene oxide diblock copolymer (melt index is 4 g / 10 min, total proportion of ethylene oxide segments is 40 wt%, total proportion of propylene oxide segments is 60 wt%), and 0.5 wt% antistatic masterbatch.

[0117] Lower surface layer 3: 99.5 wt% homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% anti-blocking masterbatch.

[0118] The preparation method of the BOPP matting film in this comparative example is the same as that in Example 1.

[0119] The total thickness and the thickness of each layer of the BOPP matting film of this comparative example are the same as those of Example 1.

[0120] Comparative Example 11 This comparative example provides a BOPP matting film. Please refer to Figure 1 , which includes a matting layer 1, a core layer 2, and a lower surface layer 3 arranged in sequence. The components of each layer are shown in Table 1 and the following specific components: Matting layer 1: 51 wt% of copolymerized polypropylene (melt index is 9 g / 10 min), 46 wt% of high-density polyethylene (melt index is 16 g / 10 min), and 3 wt% of hyperbranched polyethylene (melt index is 20 g / 10 min, degree of branching is 10%).

[0121] Core layer 2: 91.5 wt% of homopolypropylene (melt index is 3 g / 10 min), 8 wt% of ethylene oxide - propylene oxide diblock copolymer (melt index is 0.8 g / 10 min, total proportion of ethylene oxide segments is 90 wt%, total proportion of propylene oxide segments is 10 wt%), and 0.5 wt% of antistatic masterbatch.

[0122] Lower surface layer 3: 99.5 wt% of homopolypropylene (melt index is 3 g / 10 min) and 0.5 wt% of antiblocking masterbatch.

[0123] The preparation method of the BOPP matting film of this comparative example is the same as that of Example 1.

[0124] The total thickness and the thickness of each layer of the BOPP matting film of this comparative example are the same as those of Example 1.

[0125] Performance detection The BOPP matting films of Examples 1 - 5 and Comparative Examples 1 - 11 were respectively subjected to the following performance tests: Glossiness: Measured by the 45° angle method according to the standard of GB / T 10003 - 2008; Haze: Measured according to the standard of GB / T 10003 - 2008; Highlight density: The test method is to use a high-speed linear array camera for on-line visual inspection of the number of visible highlights per unit area, and the unit is pieces / m².

[0126] The results are shown in Table 2: Table 2 Performance test results of the BOPP matting films of Examples 1 - 5 and Comparative Examples 1 - 11

[0127] It can be seen from the above performance test data that: For the BOPP matte film of Examples 1-5 of the present invention, by adding 2-4 wt% of hyperbranched polyethylene (degree of branching is 8-12%) to the matte layer and adding 6-10 wt% of a block copolymer of ethylene oxide and propylene oxide (such as ethylene oxide-propylene oxide diblock copolymer, ethylene oxide-propylene oxide-ethylene oxide triblock copolymer, where the total proportion of ethylene oxide segments is 60-70 wt% and the total proportion of propylene oxide segments is 30-40 wt%) to the core layer, the two cooperate to improve the problem of bright spots on the film surface of the BOPP matte film, while ensuring the matte effect and smooth production process. The BOPP matte film of Example 5 adds an ethylene oxide-propylene oxide-ethylene oxide triblock copolymer to the core layer, and has the best effect in improving the problem of bright spots on the film surface.

[0128] In the BOPP matte film of Comparative Example 1, no hyperbranched polyethylene was added to the matte layer, and no block copolymer of ethylene oxide and propylene oxide (such as ethylene oxide-propylene oxide diblock copolymer, ethylene oxide-propylene oxide-ethylene oxide triblock copolymer) was added to the core layer. The BOPP matte film of Comparative Example 1 has many bright spots.

[0129] In the BOPP matte film of Comparative Example 2, no block copolymer of ethylene oxide and propylene oxide (such as ethylene oxide-propylene oxide diblock copolymer, ethylene oxide-propylene oxide-ethylene oxide triblock copolymer) was added to the core layer. The interfacial tension between the core layer and the matte layer is high, and the interlayer adhesion is weak. The improvement of bright spots on the matte film is not obvious.

[0130] In the BOPP matte film of Comparative Example 3, no hyperbranched polyethylene was added to the matte layer. The high-density polyethylene has a high crystallinity and is easy to form large-sized spherulites. The local "scattering blind area" caused by the large-sized spherulites of high-density polyethylene results in bright spot defects on the matte film, and the improvement of bright spots on the matte film is not obvious.

[0131] In the BOPP matte film of Comparative Example 4, the addition amount of the ethylene oxide-propylene oxide diblock copolymer in the core layer is greater than 10 wt%. New phase separation interfaces are generated inside the core layer, the interfacial tension between layers rebounds, and the interlayer adhesion decreases, exacerbating the defect of the bright spot problem.

[0132] In the BOPP matte film of Comparative Example 5, the addition amount of the ethylene oxide-propylene oxide diblock copolymer in the core layer is less than 6 wt%. It is impossible to form a complete "molecular bridge" at the interface between the core layer and the matte layer. The number of interfacial anchor points is limited, and the effects of reducing the interfacial tension and enhancing the interlayer adhesion are weak. Local delamination still occurs, and the improvement of light-transmitting bright spots is not obvious.

[0133] In the BOPP matting film of Comparative Example 6, the addition amount of hyperbranched polyethylene in the matting layer is greater than 4 wt%. The excessive hyperbranched polyethylene causes the scattering structure of the matting layer to be anisotropic, resulting in a deteriorated matting effect, uneven local light scattering, and the generation of bright spot defects, while affecting the processing stability of the matting film.

[0134] In the BOPP matting film of Comparative Example 7, the addition amount of hyperbranched polyethylene in the matting layer is less than 2 wt%. Due to the insufficient number of short branched chains, it is unable to effectively interfere by fully inserting into the high-density polyethylene molecular chains, ultimately resulting in uneven light scattering of the BOPP matting film and being unable to effectively reduce the bright spots on the matting film.

[0135] In the BOPP matting film of Comparative Example 8, the degree of branching of hyperbranched polyethylene in the matting layer is lower than 8%. Due to the too low degree of branching, the hyperbranched polyethylene molecular chains are close to a linear structure, with a small steric hindrance, weak interference on the crystallization process of high-density polyethylene, large-sized spherulites in local areas, forming a "scattering blind area", and there are still many bright spots on the matting film, and it is easy to break the film and difficult to form a film.

[0136] In the BOPP matting film of Comparative Example 9, the degree of branching of hyperbranched polyethylene in the matting layer is greater than 12%. Due to the highly branched hyperbranched polyethylene molecular chains and too high melt index, strong molecular entanglement occurs, resulting in a significant reduction in the fluidity of the matting layer, being prone to sticking to the roller and difficult to form a film, and affecting the matting effect.

[0137] In the BOPP matting film of Comparative Example 10, the proportion of the ethylene oxide chain segment in the ethylene oxide-propylene oxide diblock copolymer in the core layer is less than 60 wt%, and the proportion of the propylene oxide chain segment is greater than 40 wt%. The melt index is too high, and due to the insufficient ethylene oxide chain segment, the anchoring points of the "molecular bridge" in the matting layer are missing, resulting in limited improvement in the interfacial tension and adhesion between the core layer and the matting layer, and the appearance of "bright spot" defects on the film surface.

[0138] In the BOPP matting film of Comparative Example 11, the proportion of the ethylene oxide chain segment in the ethylene oxide-propylene oxide diblock copolymer in the core layer is greater than 70 wt%, and the proportion of the propylene oxide chain segment is less than 30 wt%. The melt index is too low, the fluidity of the core layer components becomes poor, it is not easy to stretch and is prone to film breakage, and the processing stability of the film becomes poor.

[0139] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and the present invention also intends to include these changes and modifications.

Claims

1. A BOPP matting film, characterized in that: It includes a matte layer, a core layer, and a lower surface layer arranged in sequence; the matte layer includes copolymerized polypropylene, 46-51wt% high-density polyethylene, and 2-4wt% hyperbranched polyethylene, and the degree of branching of the hyperbranched polyethylene is 8-12%; the core layer includes homopolypropylene and a block copolymer of 6-10wt% ethylene oxide and propylene oxide, and the total proportion of the ethylene oxide chain segment in the block copolymer of ethylene oxide and propylene oxide is 60-70wt%, and the total proportion of the propylene oxide chain segment is 30-40wt%.

2. The BOPP matting film according to claim 1, wherein: The melt index of the hyperbranched polyethylene at 190°C under a load of 21.6 kg is 15-25 g / 10 min.

3. The BOPP matting film according to claim 1, characterized in that: In the matte layer, the melt index of the copolymerized polypropylene at 230°C under a load of 2.16 kg is 6-12 g / 10 min, and the melt index of the high-density polyethylene at 190°C under a load of 21.6 kg is 12-20 g / 10 min.

4. The BOPP matting film according to claim 1, wherein: The block copolymer of ethylene oxide and propylene oxide is at least one of an ethylene oxide-propylene oxide diblock copolymer and an ethylene oxide-propylene oxide-ethylene oxide triblock copolymer.

5. The BOPP matting film according to claim 4, wherein: The melt index of the ethylene oxide-propylene oxide diblock copolymer and / or the ethylene oxide-propylene oxide-ethylene oxide triblock copolymer at 230°C under a load of 2.16 kg is 1-3 g / 10 min.

6. The BOPP matte film according to claim 1, wherein: The core layer further includes 0.5-1.0wt% antistatic masterbatch; the effective content of the antistatic agent in the antistatic masterbatch is 35-50wt%, and the carrier is homopolypropylene.

7. The BOPP matting film according to claim 1, wherein: The lower surface layer includes homopolypropylene and 0.5-1.0wt% antiblocking masterbatch.

8. The BOPP matte film according to claim 1, characterized in that: The lower surface layer includes copolymerized polypropylene, 46-51wt% high-density polyethylene, and 2-4wt% hyperbranched polyethylene, and the degree of branching of the hyperbranched polyethylene is 8-12%.

9. The BOPP matting film according to claim 1, wherein: The thickness of the matte layer is 1.5-2.3 μm, the thickness of the lower surface layer is 0.7-0.9 μm or 1.5-2.3 μm, and the total thickness of the BOPP matte film is 16-23 μm.

10. A method for preparing a BOPP matte film as described in any one of claims 1-9, characterized in that: It includes the following steps: Under dry conditions, weigh the raw materials of the matte layer, the core layer, and the lower surface layer according to the ratio and add them into each extruder. The raw materials of each layer are melt-plasticized in each extruder and then metered by a metering pump. Then, they converge at the T-die according to different extruder channels to form a thick sheet. After the thick sheet is extruded, it is quenched and cast into a sheet. After the sheet is shaped, it first enters the longitudinal stretching zone for longitudinal stretching, and then enters the transverse stretching zone for transverse stretching. After the film is biaxially stretched, it is trimmed, corona-treated, wound, aged, and finally slit and packaged to obtain the BOPP matte film.

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