A matt modified bopp composite film and a preparation method thereof

Abstract

This application belongs to the field of biaxially oriented polypropylene (BOPP) film preparation, specifically providing a matte-modified BOPP composite film and its preparation method. The preparation method of the matte-modified BOPP composite film includes the following steps: co-extruding three layers in the order of matte layer melt, core layer melt, and lower surface layer melt, biaxially stretching, and then cooling to obtain the matte-modified BOPP composite film. The matte-modified BOPP composite film obtained by this application has excellent matte performance, and the composite film product has the advantages of high haze and low gloss.

Description

Technical Field

[0001] This application belongs to the field of biaxially oriented polypropylene film technology, and in particular relates to a matte modified BOPP composite film and its preparation method. Background Technology

[0002] BOPP (Biaxially Oriented Polypropylene) film is a polymer film material made by biaxially stretching polypropylene resin. It possesses core characteristics such as lightweight and high strength, high transparency, excellent barrier properties, good temperature resistance, and good chemical stability, and is widely used in food packaging, tobacco packaging, label printing, tapes, and flexible packaging.

[0003] To further reduce the gloss and increase the haze of BOPP films, thus achieving a better matting effect, the industry currently employs multi-layer composite technology. A matting layer is applied to the surface of the BOPP film to prepare a BOPP composite film. The matting layer typically uses polypropylene resin as the base resin, blended with inorganic matting agents or high-density polyethylene. By enhancing the absorption and scattering of light, the composite film achieves a matting effect. Patent application CN102807709A discloses a matting material for BOPP films and its preparation method. The composition and weight ratio of the raw materials in the matting material are as follows: 30-60 parts PP resin, 30-60 parts high-density polyethylene, 2-15 parts inorganic matting powder, 2-10 parts PBT, 1-3 parts dispersant, and 0.1-1.0 parts antioxidant, with a total weight of 100 parts. The method incorporates inorganic matting agents such as calcium carbonate and titanium dioxide to improve the matting performance of the BOPP composite film.

[0004] While the aforementioned proposed solutions can improve the matting effect of BOPP composite films, they also present compatibility issues between inorganic matting materials and the matrix. As the amount of inorganic matting material added increases, the tensile mechanical properties of the BOPP composite film decrease, which is not conducive to obtaining a more stable BOPP composite film. Therefore, it is necessary to find a matting modified BOPP composite film and its preparation method that can improve the matting effect of BOPP composite films while reducing compatibility issues. Summary of the Invention

[0005] To address the aforementioned issues and further improve the matting effect of BOPP film while reducing compatibility problems caused by the introduction of matting agents, this application provides a matting modified BOPP composite film and its preparation method.

[0006] This application first provides a method for preparing a matte-modified BOPP composite film, the preparation steps of which include the following:

[0007] S01. Take 25-30 parts of polypropylene, 15-20 parts of high-density polyethylene, 1-1.5 parts of anti-adhesion agent and 2.5-4 parts of crystallizing agent, mix them, and melt extrude at 235-245℃ to obtain a matte layer melt; the crystallizing agent is obtained by hydroxylated modified polyisoprene, which is mixed with dimethylglyoxime and polyisocyanate for catalytic reaction;

[0008] S02. Mix 90-95 parts of polypropylene and 2-5 parts of antistatic agent, and melt-extrude at 230-240℃ to obtain the core layer melt;

[0009] S03. Take 42-45 parts of polypropylene and 0.5-1.5 parts of anti-sticking agent, mix them, and melt extrude at 235-240℃ to obtain the lower surface melt;

[0010] S04. The matte-modified BOPP composite film is obtained by co-extruding three layers in the order of matte layer melt, core layer melt, and lower surface layer melt, followed by biaxial stretching and cooling.

[0011] Furthermore, in step S01, the preparation step of the crystallizing agent includes the following:

[0012] a. Take polyisoprene, disperse it in acetone, purge nitrogen to initiate the reaction, then add ethylene oxide dropwise using a syringe to continue the reaction, then precipitate it with anhydrous ethanol, filter and dry to obtain hydroxylated modified polyisoprene;

[0013] b. Dehydrate acetone, then add hydroxylated modified polyisoprene, disperse, add polyisocyanate and dimethylglyoxime, catalyze the reaction, precipitate again, and dry to constant weight to obtain the product;

[0014] In step a, the polyisoprene used has a molecular weight of 3000-5000.

[0015] The mass-to-volume ratio of the polyisoprene, acetone, and ethylene oxide used is (4.5-5.3) g:(10-15) mL:(1.2-1.4) mL;

[0016] The ethylene oxide dropping rate is 0.2-0.5 mL / min;

[0017] The initiation reaction is set to a water bath at 30-35°C and the reaction is carried out for 1-2 hours. The initiator is an organolithium initiator.

[0018] Furthermore, in step b, the mass ratio of hydroxylated modified polyisoprene, polyisocyanate and dimethylglyoxime used is (3-3.5):(1.8-2.1):(1-1.2);

[0019] The polyisocyanate is at least one of diphenylmethane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate;

[0020] The catalyst used in the catalytic reaction is dibutyltin dilaurate.

[0021] Furthermore, in step S04, the biaxial stretching is set with a stretching temperature of 130-140℃, a stretching rate of 30-40% / s, and a stretching aspect ratio of (1.8-2.3):1.

[0022] This application also provides a matte-modified BOPP composite film, which is prepared using the above-described preparation method.

[0023] Compared with the prior art, this application has the following beneficial effects:

[0024] 1. This application incorporates a small amount of crystallizing agent into the matting layer of the BOPP composite film, which can promote the regular crystallization of high-density polyethylene. The modified polyisoprene in the crystallizing agent induces crystallization during the biaxial stretching orientation stage, and the resulting seed crystals can regulate the crystallization behavior of high-density polyethylene, making the crystallization more uniform. When light passes through the BOPP matting layer, the uniform high-density polyethylene grains can effectively scatter the light, achieving a better matting effect.

[0025] 2. This application promotes the dynamic adjustment of the structure of polyisoprene through modification treatment. During the heating and stretching stage, the oxime ester group bonds in the molecular structure break, and the polyisoprene chain segments fold in an orderly manner. Subsequently, during the cooling process, the oxime ester bonds recombine, promoting the merging and reshaping of the folded crystal region structure to form irregular microcrystals. These microcrystals remain in the BOPP composite film and can also play a role in scattering light, thereby improving the matting effect of the matting film. Attached Figure Description

[0026] Figure 1 This study presents the extinction properties of BOPP composite films from Examples 1-3 and Control Groups 1-2 of this application.

[0027] Figure 2 The crystallinity of BOPP composite films in Examples 1-3 and Control Groups 1-2 of this application was tested. Detailed Implementation

[0028] To make the inventive objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments described herein. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0031] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.

[0032] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0033] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0034] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0035] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0036] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0037] In this application, room temperature refers to 0~40℃, including but not limited to 10~40℃, or further to 20~30℃.

[0038] Based on extensive experimental research, this application provides a matte-modified BOPP composite film and its preparation method.

[0039] In some specific embodiments of this application, the weight parts of the crystallizing agent can be 2.5-4 parts, 3-4 parts, or 3.5-4 parts; typically, but not limitingly, for example, it can be 2.5 parts, 3 parts, 3.5 parts, or 4 parts, wherein the BOPP composite film with the best matting effect is obtained when the weight parts of the crystallizing agent are 3 parts.

[0040] In some specific embodiments of this application, the ethylene oxide dropping acceleration rate can be 0.2-0.5 mL / min, 0.3-0.5 mL / min, or 0.4-0.5 mL / min; typically, but not limitingly, it can be 0.2 mL / min, 0.4 mL / min, or 0.5 mL / min; among these, the effect is best when the ethylene oxide dropping acceleration rate is 0.4 mL / min.

[0041] In some specific embodiments of this application, the biaxial stretching temperature of the composite membrane can be 130-140℃, 132-140℃, or 135-140℃; typically, but not limitingly, it can be 130℃, 140℃, or 145℃; among these, the membrane stretching effect is optimal when the biaxial stretching temperature is 135℃.

[0042] In some specific embodiments of this application, the biaxial stretching rate of the composite membrane can be 30-40% / s, 35-40% / s, or 37-40% / s; typically, but not limited to, it can be 30% / s, 32% / s, or 35% / s; among them, the membrane stretching effect is best when the biaxial stretching rate is 32% / s.

[0043] In some specific embodiments of this application, the biaxial stretching aspect ratio of the composite membrane can be (1.8-2.3):1, (1.9-2.3):1, or (2.2-2.3):1; typically, but not limited to, it can be 1.9:1, 2.1:1, or 2.3:1; among which, the membrane stretching effect is best when the biaxial stretching aspect ratio is 2.2:1.

[0044] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0045] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0046] Example 1

[0047] In this embodiment, the preparation steps of the matte-modified BOPP composite film are as follows:

[0048] Matte layer melt: Take 1.25 kg of Baofeng 550J polypropylene (MFR: 3.2 g / 10 min, 230℃), 0.75 kg of HD5290HLFL high-density polyethylene (MFR: 9.0 g / 10 min, 230℃), 50 g of anti-blocking masterbatch ABPP905A and 125 g of crystallizing agent and mix them in a high-speed mixer. Then, melt the mixture in the homogenization zone of the extruder at 235℃ and discharge the matte layer melt.

[0049] Core layer melt: Take 4.5 kg of Baofeng 550J polypropylene and 100 g of antistatic masterbatch AT4040-HC and mix them in a high-speed mixer. Then, melt the mixture in the homogenization zone of the extruder at 230℃ and discharge the core layer melt.

[0050] Lower surface melt: Take 2.1 kg of Baofeng 550J polypropylene and 25 g of silica and mix them in a high-speed mixer. Then, melt them in the homogenization zone of the extruder at 235℃ and discharge the lower surface melt.

[0051] The melt layers, namely the matte layer melt, the core layer melt, and the lower surface layer melt, are sequentially placed in a three-layer co-extrusion extruder to obtain a cast sheet. Then, the biaxial stretching process temperature is set to 130℃, the stretching rate is 30% / s, and the aspect ratio is 1.8:1. After cooling, a matte modified BOPP composite film with a thickness of 30 micrometers is obtained.

[0052] In this embodiment, the preparation steps of the matting layer melt using the crystallizing agent are as follows:

[0053] Mix 4.5g of polyisoprene (molecular weight 3000) with 10mL of acetone, purge with nitrogen to remove air, and dissolve completely. Then add 0.01mL of n-butyllithium (concentration 1.6M), heat in a water bath at 30℃ for 1h, and then add 1.2mL of ethylene oxide at a rate of 0.2mL / min using a syringe. Adjust the magnetic stirring speed to 100rpm and react for 5h. Then precipitate with ethanol, filter, dry the precipitate, and take 3g of the product. Add it back to 50mL of fully dehydrated acetone for dispersion, then add 1.8g of diphenylmethane diisocyanate, 1g of butanedione oxime, and 0.02g of catalyst dibutyltin dilaurate. React at 45℃ overnight, then add 200mL of ethanol for precipitation, filter, and dry the filtrate under vacuum at 50℃ to constant weight to obtain the crystal agent.

[0054] Example 2

[0055] In this embodiment, the preparation steps of the matte-modified BOPP composite film are as follows:

[0056] Matte layer melt: Take 1.35 kg of Baofeng 550J polypropylene, 0.82 kg of HD5290HLFL high-density polyethylene, 65 g of anti-blocking masterbatch ABPP905A and 150 g of crystallizing agent and mix them in a high-speed mixer. Then, melt the mixture in the homogenization zone of the extruder at 242℃ and discharge the matte layer melt.

[0057] Core layer melt: Take 4.6 kg of Baofeng 550J polypropylene and 150 g of antistatic masterbatch AT4040-HC and mix them in a high-speed mixer. Then, melt the mixture in the homogenization zone of the extruder at 235℃ and discharge the core layer melt.

[0058] Lower surface melt: Take 2.2 kg of Baofeng 550J polypropylene and 50 g of silica and mix them in a high-speed mixer. Then, melt them in the homogenization zone of the extruder at 240℃ and discharge the lower surface melt.

[0059] The melt layers, namely the matte layer melt, the core layer melt, and the lower surface layer melt, are sequentially placed in a three-layer co-extrusion extruder to obtain a cast sheet. Then, the biaxial stretching process temperature is set to 135℃, the stretching rate is 32% / s, and the aspect ratio is 2.2:1. After cooling, a matte modified BOPP composite film with a film thickness of 32 micrometers is obtained.

[0060] In this embodiment, the preparation steps of the matting layer melt using the crystallizing agent are as follows:

[0061] Mix 5.2 g of polyisoprene (molecular weight 4000) with 12 mL of acetone, purge with nitrogen to remove air, and dissolve completely. Then add 0.015 mL of n-butyllithium (concentration 1.6 M), heat in a water bath at 34 °C for 1.2 h. Then add 1.2 mL of ethylene oxide at a rate of 0.4 mL / min using a syringe, adjust the magnetic stirring speed to 100 rpm, and react for 5.5 h. Then precipitate with ethanol, filter, dry the precipitate, and take 3.5 g of the product. Add it back to 55 mL of fully dehydrated acetone for dispersion, then add 1.8 g of isophorone diisocyanate, 1.2 g of butanedione oxime, and 0.03 g of catalyst dibutyltin dilaurate. React at 50 °C overnight, then add 200 mL of ethanol for precipitation, filter, and dry the filtrate under vacuum at 50 °C to constant weight to obtain the crystal agent.

[0062] Example 3

[0063] In this embodiment, the preparation steps of the matte-modified BOPP composite film are as follows:

[0064] Matte layer melt: Take 1.5 kg of Baofeng 550J polypropylene, 1 kg of HD5290HLFL high-density polyethylene, 75 g of anti-blocking masterbatch ABPP905A and 200 g of crystallizing agent and mix them in a high-speed mixer. Then, the extruder is set to the homogenization zone temperature of 245℃ to melt and discharge the matte layer melt.

[0065] Core layer melt: Take 4.75 kg of Baofeng 550J polypropylene and 250 g of antistatic masterbatch AT4040-HC and mix them in a high-speed mixer. Then, melt the mixture in the homogenization zone of the extruder at 240℃ and discharge the core layer melt.

[0066] Lower surface melt: Take 2.25 kg of Baofeng 550J polypropylene and 75 g of silica and mix them in a high-speed mixer. Then, melt them in the homogenization zone of the extruder at 240℃ and discharge the lower surface melt.

[0067] The melt layers, namely the matte layer melt, the core layer melt, and the lower surface layer melt, are sequentially placed in a three-layer co-extrusion extruder to obtain a cast sheet. Then, the biaxial stretching process temperature is set to 140℃, the stretching rate is 40% / s, and the aspect ratio is 2.3:1. After cooling, a matte modified BOPP composite film with a film thickness of 35 micrometers is obtained.

[0068] In this embodiment, the preparation steps of the matting layer melt using the crystallizing agent are as follows:

[0069] Mix 5.3 g of polyisoprene (molecular weight 5000) with 15 mL of acetone, purge with nitrogen to remove air, and dissolve completely. Then add 0.015 mL of n-butyllithium (concentration 1.6 M), heat in a water bath at 35 °C for 2 h. Then add 1.2 mL of ethylene oxide at a rate of 0.5 mL / min using a syringe, adjust the magnetic stirring speed to 200 rpm, and react for 5 h. Then precipitate with ethanol, filter, dry the precipitate, and take 3 g of the product. Add it back to 60 mL of fully dehydrated acetone for dispersion, then add 2.1 g of hexamethylene diisocyanate, 1.2 g of dimethylglyoxime and 0.05 g of catalyst dibutyltin dilaurate. React at 50 °C overnight, then add 200 mL of ethanol to precipitate, filter, and dry the filtrate under vacuum at 50 °C to constant weight to obtain the crystal agent.

[0070] Control group 1

[0071] The specific preparation steps of the matte-modified BOPP composite film in this control group are as follows:

[0072] 1.25 kg of Baofeng 550J polypropylene, 0.75 kg of HD5290HLFL high-density polyethylene, 50 g of anti-blocking masterbatch ABPP905A, and 125 g of silica were mixed in a high-speed mixer. The mixture was then melted in the homogenization zone of an extruder at 235°C, and the matte layer melt was discharged. The matte layer melt, core layer melt, and lower surface layer melt were then extruded in a three-layer co-extrusion extruder to obtain a cast film. The biaxial stretching process was then set at 130°C, with a stretching rate of 30% / s and an aspect ratio of 1.8:1. After cooling, a matte modified BOPP composite film with a thickness of 32.2 micrometers was obtained.

[0073] The remaining steps are the same as in Example 1.

[0074] Control group 2

[0075] The only difference between this control group and Example 1 is that the preparation steps of the crystallizing agent are as follows:

[0076] Mix 4.5g of polyisoprene (molecular weight 5000) with 10mL of acetone, purge with nitrogen to remove air, and dissolve completely. Then add 0.01mL of n-butyllithium (concentration 1.6M), heat in a water bath at 30℃ for 1h, and then add 1.2mL of ethylene oxide at a rate of 0.2mL / min using a syringe. Adjust the magnetic stirring speed to 100rpm and react for 5h. Then precipitate with ethanol, filter, dry the precipitate to obtain the crystal agent.

[0077] The remaining steps are the same as in Example 1.

[0078] Performance testing

[0079] 1. Mechanical property testing

[0080] Referring to standard Astm D-882, tensile strength and elongation at break of BOPP composite films from Examples 1-3 and Control Groups 1-2 were tested, and the test results are shown in Table 1.

[0081] Table 1. Test results of tensile strength and elongation at break of BOPP composite films in Examples 1-3 and Control Group 1-2

[0082]

[0083] 2. Extinction property test

[0084] Referring to the national standard GB / T2410-2008, haze and gloss tests were conducted on BOPP composite films from Examples 1-3 and Control Groups 1-2. Each group was tested three times, and the average value was taken as the final data. The test results are as follows: Figure 1 As shown.

[0085] 3. Crystallinity test

[0086] Referring to the national standard GB / T19466.3-2004, 5 mg of BOPP composite film samples from Examples 1-3 and Control Groups 1-2 were placed in aluminum crucibles. DSC was performed under a nitrogen atmosphere at a heating rate of 10℃ / min. The test data were recorded and processed to obtain the crystallinity. The test results are as follows: Figure 2 As shown.

[0087] Examples 1-3 and control groups 1-2 were taken and compared with Table 1 and... Figures 1-2 It can be concluded that the matting layer prepared using the organic crystal agent in the example scheme achieves a better matting effect than control group 1, while also avoiding compatibility issues caused by the introduction of inorganic components to a certain extent; combined with Figure 2 Crystallinity data shows that by modifying polyisoprene, the main component of the crystallizing agent, the crystallization of the composite film can be improved, and the matting effect can be enhanced.

[0088] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a matt modified BOPP composite film, characterized by, The preparation steps include the following: S01. Take 25-30 parts of polypropylene, 15-20 parts of high-density polyethylene, 1-1.5 parts of anti-adhesion agent and 2.5-4 parts of crystallizing agent, mix them, and melt extrude at 235-245℃ to obtain a matte layer melt; the crystallizing agent is obtained by hydroxylated modified polyisoprene, which is mixed with dimethyl ethyl oxime and polyisocyanate for catalytic reaction; S02. Mix 90-95 parts of polypropylene and 2-5 parts of antistatic agent, and melt-extrude at 230-240℃ to obtain the core layer melt; S03. Take 42-45 parts of polypropylene and 0.5-1.5 parts of anti-sticking agent, mix them, and melt extrude at 235-240℃ to obtain the lower surface melt; S04. The matte-modified BOPP composite film is obtained by co-extruding three layers in the order of matte layer melt, core layer melt, and lower surface layer melt, followed by biaxial stretching and cooling.

2. The method of claim 1, wherein the method is characterized by, In step S01, the preparation steps of the crystallizing agent include the following: a. Take polyisoprene, disperse it in acetone, purge the air with nitrogen, then add n-butyllithium, heat in a water bath at 30-35℃ for 1-2 hours, then add ethylene oxide dropwise with a syringe to continue the reaction, then precipitate with anhydrous ethanol, filter and dry to obtain hydroxylated modified polyisoprene. b. Dehydrate acetone, then add hydroxylated modified polyisoprene, disperse, add polyisocyanate and dimethylglyoxime, catalyze the reaction, precipitate again, and dry to constant weight to obtain the product.

3. The method of claim 2, wherein the method is characterized by, In step a, the polyisoprene used has a molecular weight of 3000-5000.

4. The method of claim 2, wherein the method is characterized by, In step a, the mass-to-volume ratio of polyisoprene, acetone and ethylene oxide is (4.5-5.3) g:(10-15) mL:(1.2-1.4) mL.

5. The method of claim 2, wherein the method is characterized by, In step a, the ethylene oxide dropping rate is 0.2-0.5 mL / min.

6. The method of claim 2, wherein the method is characterized by, In step b, the mass ratio of hydroxylated modified polyisoprene, polyisocyanate and dimethylglyoxime is (3-3.5):(1.8-2.1):(1-1.2); the polyisocyanate is at least one of diphenylmethane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate.

7. The method of claim 2, wherein the method is characterized by, In step b, the catalyst used for the catalytic reaction is dibutyltin dilaurate.

8. The method for preparing a matte-modified BOPP composite film according to claim 1, characterized in that, In step S04, the biaxial stretching is set with a stretching temperature of 130-140℃, a stretching rate of 30-40% / s, and a stretching aspect ratio of (1.8-2.3):

1.

9. A matte-modified BOPP composite film, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.

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