Peroxide modified high-haze bopp matt masterbatch and matt film and preparation process

Abstract

The present application relates to the technical fields of polymer material blending modification and polypropylene film, and discloses a peroxide modified high-haze BOPP matt masterbatch, matt film and preparation process.The matt masterbatch is composed of polypropylene, polyethylene, peroxide, antioxidant and anti-blocking agent, wherein the polypropylene is random copolymer polypropylene, the polyethylene is high-density polyethylene, and the peroxide is dialkyl organic peroxide.The matt masterbatch is prepared by high-speed mixing, double-screw melting blending extrusion, cooling and granulation.The matt film is a multi-layer co-extrusion biaxial stretching film, which at least includes a polypropylene core layer and a matt layer formed by the matt masterbatch.The matt film has an average haze of more than 84% and a glossiness as low as 6.5% by utilizing the differential synergistic modification effect of the controllable degradation of peroxide to polypropylene and the controllable cross-linking of peroxide to high-density polyethylene without any inorganic filler, and the film surface is fine and uniform, the mechanical properties are excellent, and the film can be directly and continuously produced on the existing BOPP production line.

Description

Technical Field

[0001] This invention relates to the field of polymer blending modification and polypropylene film technology, and particularly to a peroxide-modified high-haze BOPP matting masterbatch and matting film and its preparation process. Background Technology

[0002] Biaxially oriented polypropylene (BOPP) film is widely used in packaging, lamination, printing, and tape industries due to its advantages such as light weight, transparency, excellent mechanical properties, and good moisture resistance. Among these, matte BOPP film, with its delicate matte texture, effectively reduces specular reflection and improves printability, giving packaging products a high-end, soft appearance, and has seen continuous market demand growth in recent years. Currently, BOPP matte film is mainly produced by laminating a matte layer onto a polypropylene base film and simultaneously biaxially stretching it. This matte layer typically uses a polypropylene and polyethylene blend system, utilizing the differences in crystallization behavior and melt flow rate between the two to induce a microscopic uneven structure on the film surface during stretching, achieving diffuse light reflection and thus obtaining a basic matte effect.

[0003] However, to achieve higher film haze and superior matting quality, existing technologies commonly add inorganic fillers such as silica, talc, and calcium carbonate as synergistic agents to the matting layer. However, this approach has several inherent drawbacks. First, inorganic fillers readily agglomerate in the matrix, causing severe surface defects such as crystal points, white spots, and whitening streaks. Second, the continuous presence of rigid fillers causes severe wear on extruders and stretching equipment, significantly increasing equipment inspection and maintenance costs. More importantly, the introduction of large amounts of fillers disrupts the continuity of the polyolefin matrix, leading to a significant decrease in core mechanical properties such as tensile strength and toughness of the film, and filler precipitation severely restricts the continuous and stable mass production of films.

[0004] To address the aforementioned issues, the published patent application CN101121799A uses a peroxide crosslinking agent to crosslink polyethylene into microgels to reduce the gloss of the blend. However, this only performs unilateral crosslinking of polyethylene and does not address the functional regulation of the polypropylene matrix. Furthermore, this formulation still allows the addition of up to 30% inorganic fillers, failing to avoid the inherent drawbacks of filler-induced agglomeration, wear, and mechanical degradation. More importantly, this solution is geared towards general blend modification materials and differs fundamentally from biaxially oriented film forming processes, making it difficult to directly apply to the continuous production of BOPP films. Therefore, developing a matting masterbatch and matting film technology that requires no inorganic fillers, is specifically designed for the BOPP biaxially oriented process, and can achieve high haze matting effects through differentiated synergistic modification of polypropylene and polyethylene using peroxides, has significant industrial value. Summary of the Invention

[0005] The purpose of this invention is to provide a peroxide-modified high-haze BOPP matting masterbatch and matting film, as well as a preparation process. This invention solves the problems in the prior art where inorganic fillers are relied upon to achieve high haze matting effect, leading to film surface defects, equipment wear, and decreased mechanical properties. Furthermore, the existing peroxide crosslinking schemes cannot differentiate and synergistically regulate polypropylene and polyethylene to adapt to the biaxial stretching process, making it difficult to achieve stable and continuous production of high-haze matting films under filler-free conditions.

[0006] To achieve the above objectives, the present invention provides a peroxide-modified high-haze BOPP matting masterbatch, which is composed of the following components in parts by weight: Polypropylene 50-60 parts, polyethylene 40-50 parts, peroxide 0.5-2.0 parts, antioxidant 0.1-0.6 parts, antiblocking agent 0.1-0.8 parts; The polypropylene is a random copolymer polypropylene with a melt index of 2.0–5.0 g / 10 min and an ethylene content of 3–8 wt%. The polyethylene is high-density polyethylene, and the melt flow index of the high-density polyethylene is 0.01 to 0.1 g / 10 min, and the density is ≥0.950 g / cm³. The peroxide is a dialkyl organic peroxide, and the 1-minute half-life temperature of the dialkyl organic peroxide is 175-195°C.

[0007] The matting masterbatch, by weight, is composed of the following components: 53-55 parts polypropylene, 43-47 parts polyethylene, 0.7-1.5 parts peroxide, 0.2-0.5 parts antioxidant, and 0.1-0.3 parts anti-blocking agent.

[0008] The peroxide is one or more of di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, or di-tert-butylperoxydiisopropylbenzene.

[0009] A process for preparing peroxide-modified high-haze BOPP matting masterbatch includes the following steps: Polypropylene, polyethylene, peroxide, antioxidant and antiblocking agent are added to a high-speed mixer according to the formula content and mixed for 30 to 50 minutes to obtain a premix. The premixed material is fed into a twin-screw extruder for melt blending and extrusion, with the extrusion temperature controlled at 180-230°C and the screw speed at 200-400 r / min. The extruded melt is cooled to 20-40°C in a water bath, and the cooled strip material is granulated and dried to obtain the matte masterbatch.

[0010] A matte film, wherein the matte film is a multilayer co-extruded biaxially oriented film, the matte film comprising at least a core layer and a matte layer, the core layer being polypropylene, and the matte layer being formed by melt co-extrusion of the matte masterbatch according to any one of claims 1-3.

[0011] The total thickness of the matting film is 10–60 μm, and the thickness of the matting layer is 1–6 μm.

[0012] A process for preparing an matte film includes the following steps: The matte masterbatch and the core layer polypropylene resin are melted and plasticized separately in an independent extruder, and then extruded into a cast sheet through a co-extrusion die. After cooling and shaping, a thick sheet is obtained. The extrusion melting temperature is 220-260°C, and the casting sheet cooling temperature is 20-40°C. The thick sheet is subjected to longitudinal stretching, transverse stretching, heat setting, and cooling setting in sequence to obtain the finished matte film. The longitudinal stretching temperature is 110-130℃ and the longitudinal stretching ratio is 4-5 times. The transverse stretching temperature is 150-170℃ and the transverse stretching ratio is 8-10 times. The heat setting temperature is 140-160℃.

[0013] This invention discloses a peroxide-modified high-haze BOPP matte masterbatch and matte film, and their preparation process. First, 50-60 parts of random copolymer polypropylene, 40-50 parts of high-density polyethylene, 0.5-2.0 parts of dialkyl organic peroxides, 0.1-0.6 parts of antioxidants, and 0.1-0.8 parts of anti-blocking agents are mixed at high speed, melt-blended by twin-screw extrusion, cooled, pelletized, and dried to obtain a matte masterbatch. Then, the matte masterbatch and polypropylene core resin are melt-plasticized separately using independent extruders, and integrally extruded into a cast sheet through a co-extrusion die. The film is then subjected to longitudinal stretching, transverse stretching, heat setting, and cooling setting to obtain a multi-layer co-extruded biaxially stretched matte film containing at least one matte layer formed by the matte masterbatch. This invention utilizes the differentiated synergistic modification effect of dialkyl peroxides to controllably degrade polypropylene at processing temperatures to enhance melt flowability and to moderately crosslink high-density polyethylene to form microgels. Without adding any inorganic fillers, a uniform and dense microphase separation structure and a micro-rough surface are formed during biaxial stretching. This completely solves the technical problems of existing technologies that require the addition of inorganic fillers to achieve high haze, resulting in film surface crystal points and white spots, equipment wear, decreased mechanical properties, and filler precipitation restricting continuous production. It also overcomes the shortcomings of existing peroxide crosslinking schemes, which only modify polyethylene unilaterally and cannot be adapted to biaxial stretching processes. Ultimately, it achieves an average haze of over 84%, a matte surface gloss as low as 6.5%, a fine, uniform, and defect-free film surface, excellent mechanical properties, and can be directly and stably produced continuously on existing BOPP production lines. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0015] Figure 1 This is a flowchart of the preparation process of the peroxide-modified high-haze BOPP matting masterbatch of the present invention.

[0016] Figure 2 This is a flowchart of the preparation process of the matte film of the present invention. Detailed Implementation

[0017] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0018] Please refer to Figure 1 and Figure 2 This invention is prepared according to a unified formula for matte masterbatch, masterbatch preparation process and biaxial stretching molding process for BOPP matte film. The types of raw materials and equipment parameters are kept consistent, and the component ratio and type of peroxide are only adjusted according to experimental requirements.

[0019] Matting masterbatch preparation process: According to the formula ratio, each raw material component is added to a high-speed mixer and thoroughly mixed at room temperature for 30-50 minutes to ensure uniform dispersion of the components, thus obtaining a premix. The obtained premix is ​​then fed into a twin-screw extruder via a precision metering feeding system for melt blending extrusion. The length-to-diameter ratio of the twin-screw extruder is 32:1 to 48:1, the extrusion temperature is controlled at 180-230 ℃, and the screw speed is 200-400 r / min. The extruded strip is cooled in a water bath (cooling water temperature 20-40 ℃). After cooling, the strip is subjected to air knife or dehumidification device to remove surface moisture, and then fed into a pelletizer for pelleting. The pellet size is 2-4 mm. The pelletized material is then graded by a vibrating screen and dried to obtain the finished matte masterbatch. The matte masterbatch prepared by the above method is milky white granules with uniform particle size and no adhesion; the melt index is 2.0-4.0 g / 10 min (230℃ / 2.16 kg).

[0020] Matting film preparation process: BOPP matte film is a multi-layer co-extruded biaxially oriented film, comprising at least one core layer and one matte layer; the matte layer is formed by melt co-extrusion of the aforementioned matte masterbatch; the core layer is polypropylene.

[0021] The preferred matte BOPP film is an ABB three-layer co-extrusion structure, but an ABC-type multi-layer co-extrusion structure can also be used, wherein: The A layer is a matting layer, which is made from the matting masterbatch; The B layer consists of a core layer and a lower surface layer, and is made of film-grade polypropylene resin; The C layer can be selected as a functional layer (such as a heat-sealing layer, a printing layer, or a second matte layer), and heat-sealing resin, printing agent, or matte masterbatch can be added according to application requirements.

[0022] When the matte film adopts an ABB-type three-layer co-extrusion biaxial stretching structure, the total film thickness is set to 12 μm, the thickness of the surface matte layer is controlled at 1–4 μm, and the core layer is polypropylene resin. During the processing, the extrusion melting temperature is 220–260 ℃, the casting cooling temperature is 20–40 ℃, the longitudinal stretching temperature is 110–130 ℃ with a stretching ratio of 4–5 times, the transverse stretching temperature is 150–170 ℃ with a stretching ratio of 8–10 times, the heat setting temperature is 140–160 ℃, and finally, the finished matte film is obtained by corona treatment and winding.

[0023] All sample performance tests were conducted in accordance with industry-standard enterprise specifications. The main test indicators included film haze, melt flow rate, thickness deviation, film surface defects, mechanical properties, and appearance uniformity.

[0024] Example 1 (Preferred Formula Ratio) This embodiment provides a peroxide crosslinked modified BOPP high haze matting masterbatch. By weight, the raw material ratio of each component is as follows: 53.2 parts polypropylene, 45 parts polyethylene, 1.5 parts di-tert-butyl peroxide (DTBP), 0.15 parts antioxidant 1010, and 0.15 parts antiblocking agent.

[0025] The above process is followed to complete the mixing, extrusion granulation, and preparation of matte masterbatch; then the matte masterbatch is compounded with polypropylene, and a BOPP matte film with a thickness of 12 μm is prepared by ABB-type three-layer co-extrusion and biaxial stretching process.

[0026] Testing revealed that the average thickness of the matte film prepared in this embodiment was 12.01 μm, with a thickness deviation of ±0.05 μm, far exceeding the enterprise standard's allowable deviation range of ±4.0 μm; the surface matte layer thickness was 2.29 μm. The film exhibited a haze of 84.6% and a gloss level as low as 6.5%, demonstrating excellent optical matting effects. The film surface had 16.5 defects per 100 μm. 2 The film surface is fine and uniform, free of crystal points, precipitation, and whitening defects. Simultaneously, the film surface tension meets the standards, mechanical properties are stable, and tensile strength and dimensional stability are excellent. In summary, the BOPP high-haze matte film prepared in this embodiment exhibits excellent overall performance, fully meeting the requirements for high-end packaging, printing, and lamination applications.

[0027] Comparative Example 1: No peroxide added The difference between this comparative example and Example 1 is that no peroxide was added to the system, the amount of polypropylene was adjusted to 54.7 parts, and the remaining components, ratios and preparation processes were kept the same as in Example 1, resulting in a 12 μm thick BOPP matte film.

[0028] Test results showed that the average haze of the film in Comparative Example 1 was 71.3%, and the gloss of the matte surface was 12.5%, indicating insufficient matting effect. The film surface exhibited obvious streaky unevenness ("blooming") and poor transverse uniformity. The longitudinal thermal shrinkage rate of the film reached 5.2%, exceeding the company's control standard. This is because the lack of peroxide prevented effective cross-linking between the polypropylene and high-density polyethylene phases, resulting in insufficient phase separation and difficulty in forming a uniform and fine micro-rough structure on the film surface. Simultaneously, due to the lack of a cross-linking network to regulate melt rheological behavior, the flowability difference between the PP and HDPE phases during transverse stretching was too large, causing uneven stress distribution on the film surface, thus triggering the "blooming" phenomenon and deterioration of transverse uniformity. Ultimately, this resulted in a matting effect and dimensional stability inferior to Example 1.

[0029] Comparative Example 2: Using inorganic fillers to replace peroxides In Example 1, 1.5 parts of DTBP were replaced with 1.5 parts of silica matting powder with an average particle size of 2.5 μm, and 2.0 parts of dispersant (zinc stearate) were added simultaneously to improve the dispersibility of inorganic fillers in the resin matrix. At the same time, the amount of polypropylene was adjusted to 51.5 parts to maintain the total balance. The remaining components and preparation process were the same as in Example 1, and comparative matting masterbatch and 12 μm thick BOPP matting film were obtained.

[0030] Testing revealed that the average haze of the matte film prepared in Comparative Example 2 was 76.8%, and the gloss of the matte surface was 11.2%. Although this was an improvement over Comparative Example 1, it still showed a significant difference compared to Example 1. Furthermore, the longitudinal tensile strength of the film decreased by approximately 18% compared to Example 1, and the elongation at break decreased by approximately 22%, indicating a significant deterioration in mechanical properties. The number of defects on the film surface increased to 42 per 100 μm. 2 The main defects are crystal points and white spots formed by the agglomeration of inorganic fillers; the overall evaluation of extinction uniformity is good, but there are localized uneven extinction phenomena on the film surface.

[0031] Despite the addition of dispersants, the large difference in interfacial tension between silica and the resin matrix leads to the easy aggregation of inorganic particles within the matrix. During biaxial stretching, these aggregated particles form stress concentration points, inducing microcracks and resulting in a decrease in mechanical properties. Uneven filler distribution also contributes to inconsistent matting effects. Furthermore, the surface protrusion structure is difficult to control precisely, resulting in an overall matting effect inferior to the uniform microgel network formed by the peroxide crosslinking system in Example 1.

[0032] Example 2: Effect of different peroxide addition amounts on product performance Referring to the formulation and preparation process of Example 1, only the amount of DTBP added was adjusted to prepare matting masterbatches with DTBP amounts of 1.0 parts, 1.5 parts, and 2.0 parts, respectively, and correspondingly processed to obtain 12 μm thick BOPP matting films; at the same time, a group without added DTBP was set as Comparative Example 1, and the key performance test results of each group of samples are shown in Table 1.

[0033] Table 1. Effect of different peroxide addition amounts on matting film performance 0 (Comparative Example 1) 4.52 71.3 12.5 8.0 The blooming is obvious and uneven. 0.5 3.86 76.2 10.8 10.0 Mostly uniform, with slight streaks in some areas. 1.0 3.25 80.1 8.3 13.0 Mostly uniform, with slight streaks 1.5 (Example 1) 2.83 84.6 6.5 16.5 Fine and even texture, superior quality 2.0 2.41 86.2 5.8 28.0 Fine and even texture, but with an increase in some individual gel spots. Table 1 shows that when the peroxide content is 0.5 parts and 1.0 parts, the film exhibits a certain matting effect but low haze, and the film surface has varying degrees of streak defects, with average uniformity. When the peroxide content is increased to 1.5 parts (Example 1), the melt index of the matting masterbatch is 2.83 g / 10min, the film surface haze reaches 84.6%, the gloss is as low as 6.5%, and the number of defects on the film surface is only 16.5 / 100m², with uniform matting and excellent overall performance. This indicates that at this addition amount, the degree of crosslinking between the PP and HDPE phases is moderate, the micro-rough structure is uniform and dense, and the overall performance is optimal. When the peroxide content is further increased to 2.0 parts, the matting effect and film surface uniformity are still good, but the number of individual gel points increases, and the number of defects on the film surface increases to 28.0 / 100m². 2 This is due to excessive local cross-linking caused by excessive peroxide. In summary, the optimal amount of peroxide added is 1.5 parts, under which the matte film exhibits the best balance of haze, gloss, and film surface quality.

[0034] Example 3: Effect of different types of peroxides on the performance of matting films Referring to the formulation and preparation process of Example 1, the amount of peroxide added was fixed at 1.5 parts. Dicumyl peroxide (DCP), bis-tert-butyl peroxide (BIPB), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH), and benzoyl peroxide (BPO) were selected as peroxides for the experiment. DTBP in Example 1 was used as a reference to prepare corresponding matting masterbatch and 12 μm thick BOPP matting film. The performance test results of each group are shown in Table 2.

[0035] DCP 175 2.95 80.3 28.0 The extinction effect is generally uniform, but the haze is low, and there are slight longitudinal streaks on the film surface. BIPB 182 2.76 85.1 18.0 Fine and uniform texture, high haze, clean film surface, comparable to DBPH performance. DBPH 179 2.79 85.6 17.5 Fine and uniform texture, high haze, and clean film surface. DTBP (Example 1) 193 2.83 84.6 16.5 Fine and even texture, meeting the superior standard. BPO 131 4.51 72.4 135 Uneven matting, with numerous gel particles and precipitates appearing on the film surface. Table 2 shows that the half-life temperature has a certain impact on the decomposition behavior and crosslinking efficiency of peroxides within the BOPP processing window. DCP has a relatively low half-life temperature (175℃), resulting in a faster decomposition rate during melt blending and insufficient crosslinking reaction. This leads to a higher melt index (2.95 g / 10min) in the matting masterbatch, with a haze of only 80.3%, insufficient gloss reduction, and longitudinal streaks on the film surface. BIPB (182℃) and DBPH (179℃) have half-life temperatures that match the BOPP extrusion processing temperature window well, resulting in high crosslinking efficiency. The resulting matting films have hazes of 85.1% and 85.6%, respectively, with fine, uniform, and clean film surfaces, comparable to DTBP, and both achieving ideal matting effects. When BPO with an excessively low half-life temperature (131℃) is selected, the peroxide decomposes prematurely and in large quantities during the mixing and feeding stages, resulting in premature consumption of free radicals, extremely low crosslinking efficiency, and the decomposition products easily remain in the film to form precipitates. This leads to a melt index of the matting masterbatch as high as 4.51 g / 10min, a decrease in film haze to 72.4%, and a sharp increase in defects to 135 per 100m. 2 A large number of gel particles and precipitates appeared on the membrane surface, and the uniformity of extinction was significantly deteriorated.

[0036] Therefore, the choice of peroxide type is crucial to its decomposition behavior and crosslinking efficiency within the processing temperature window. The half-life temperatures of BIPB, DBPH, and DTBP are highly compatible with the BOPP processing temperature (180–230°C), effectively initiating the crosslinking reaction at the PP / HDPE interface to obtain a uniform, dense, micro-rough structure, thus achieving excellent matting effects. Considering all factors, BIPB and DBPH exhibit matting performance comparable to DTBP and can be considered preferred peroxide components in this invention, while DCP is less effective, and BPO is unsuitable for this system due to premature decomposition.

[0037] In summary, the peroxide in the matting masterbatch system of this invention is preferably a dialkyl peroxide, with di-tert-butyl peroxide (DTBP), di-tert-butyl peroxide diisopropylbenzene (BIPB), and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH) being the most preferred. All three can stably produce high-quality matting films with a haze ≥84% and a fine, uniform surface under conventional BOPP processing temperatures without the addition of any inorganic fillers, exhibiting both excellent matting effect and processing adaptability. Furthermore, this formulation and process can be flexibly adapted to various multilayer co-extrusion structures such as ABA, ABB, and ABC, meeting the application requirements of different scenarios and possessing good prospects for industrial application.

[0038] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A peroxide-modified high-haze BOPP matting masterbatch, characterized in that, It consists of the following components in parts by weight: Polypropylene 50-60 parts, polyethylene 40-50 parts, peroxide 0.5-2.0 parts, antioxidant 0.1-0.6 parts, antiblocking agent 0.1-0.8 parts; The polypropylene is a random copolymer polypropylene with a melt index of 2.0–5.0 g / 10 min and an ethylene content of 3–8 wt%. The polyethylene is high-density polyethylene, and the melt flow index of the high-density polyethylene is 0.01 to 0.1 g / 10 min, and the density is ≥0.950 g / cm³. The peroxide is a dialkyl organic peroxide, and the 1-minute half-life temperature of the dialkyl organic peroxide is 175-195°C.

2. The peroxide-modified high-haze BOPP matting masterbatch as described in claim 1, characterized in that, The matting masterbatch, by weight, is composed of the following components: 53-55 parts polypropylene, 43-47 parts polyethylene, 0.7-1.5 parts peroxide, 0.2-0.5 parts antioxidant, and 0.1-0.3 parts antiblocking agent.

3. The peroxide-modified high-haze BOPP matting masterbatch as described in claim 1, characterized in that, The peroxide is one or more of di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, or di-tert-butylperoxydiisopropylbenzene.

4. A preparation process for peroxide-modified high-haze BOPP matting masterbatch, used to prepare the peroxide-modified high-haze BOPP matting masterbatch as described in any one of claims 1-3, characterized in that, Includes the following steps: Polypropylene, polyethylene, peroxide, antioxidant and antiblocking agent are added to a high-speed mixer according to the formula content and mixed for 30 to 50 minutes to obtain a premix. The premixed material is fed into a twin-screw extruder for melt blending and extrusion, with the extrusion temperature controlled at 180-230°C and the screw speed at 200-400 r / min. The extruded melt is cooled to 20-40°C in a water bath, and the cooled strip material is granulated and dried to obtain the matte masterbatch.

5. A matte film, characterized in that, The matte film is a multi-layer co-extruded biaxially oriented film, comprising at least a core layer and a matte layer, wherein the core layer is polypropylene, and the matte layer is formed by melt co-extrusion of the matte masterbatch as described in any one of claims 1-3.

6. The matte film as described in claim 5, characterized in that, The total thickness of the matting film is 10–60 μm, and the thickness of the matting layer is 1–6 μm.

7. A process for preparing a matte film, used to prepare the matte film as described in claim 5, characterized in that, Includes the following steps: The matte masterbatch and the core layer polypropylene resin are melted and plasticized separately in an independent extruder, and then extruded into a cast sheet through a co-extrusion die. After cooling and shaping, a thick sheet is obtained. The extrusion melting temperature is 220-260°C, and the casting sheet cooling temperature is 20-40°C. The thick sheet is subjected to longitudinal stretching, transverse stretching, heat setting, and cooling setting in sequence to obtain the finished matte film. The longitudinal stretching temperature is 110-130℃ and the longitudinal stretching ratio is 4-5 times. The transverse stretching temperature is 150-170℃ and the transverse stretching ratio is 8-10 times. The heat setting temperature is 140-160℃.

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