Multilayer cross film and its preparation method and application

Abstract

The present invention provides a multi-layer cross film and a preparation method and application thereof, belonging to the technical field of polymer films. The multi-layer cross film is formed by cross-compounding at least two composite layers, the composite layers comprising a first polypropylene layer, a first polyethylene layer, a nylon layer, a second polyethylene layer, and a second polypropylene layer stacked in sequence; wherein the first polypropylene layer and the second polypropylene layer each independently comprise 70wt% to 100wt% of polypropylene and 0 to 30wt% of a compatibilizer, the compatibilizer being one or more of ethylene-octene copolymer elastomer, maleic anhydride grafted modified ethylene-octene copolymer, and metallocene linear low-density polyethylene, and the density of the metallocene linear low-density polyethylene is 0.915 to 0.935 g / cm 3 The first polyethylene layer and the second polyethylene layer each independently include high-density polyethylene, and the density of the high-density polyethylene is 0.94~0.965g / cm 3 ; The nylon layer includes 90wt%~100wt% of nylon and 0~10wt% of polyethylene grafted maleic anhydride.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer films, and in particular to a multi-layer cross film and a preparation method and application thereof. Background Art

[0002] Cross film is usually a composite film made by blowing polyethylene into a blank, then unidirectional stretching to form it, and then 45° rotary cutting and cross-compounding. It is often used in building waterproofing, packaging film and other fields.

[0003] In the related art, the preparation process of the cross membrane is complicated, and it generally has shortcomings such as poor heat resistance, insufficient toughness, and poor strength. Especially when used in the field of waterproof membranes, during the service process after outdoor laying, the above defects of the cross membrane can easily cause the waterproof membrane to warp, wrinkle, or even break. Summary of the invention

[0004] In view of this, the present invention provides a multi-layer cross film and a preparation method and application thereof.

[0005] According to an embodiment of one aspect of the present invention, a multilayer cross membrane is provided, wherein the multilayer cross membrane is cross-compounded by at least two composite layers, wherein the composite layer comprises a first polypropylene layer, a first polyethylene layer, a nylon layer, a second polyethylene layer, and a second polypropylene layer stacked in sequence.

[0006] According to an embodiment of another aspect of the present invention, a method for preparing a multi-layer cross film is provided, comprising: placing a first polypropylene layer material, a first polyethylene layer material, a nylon layer material, a second polyethylene layer material and a second polypropylene layer material into a five-layer co-extrusion film blowing machine for co-extrusion film blowing, and obtaining a composite layer after shaping; the composite layer is rotary cut and rolled, cross-compounded, and a multi-layer cross film is obtained.

[0007] According to another embodiment of the present invention, there is provided application of the above multi-layer cross film or the multi-layer cross film prepared by the above preparation method in the field of building waterproofing and packaging film.

[0008] According to the embodiments of the present invention, nylon has high mechanical strength, self-lubrication and wear resistance, and polypropylene has good high temperature resistance and chemical stability, but nylon and polypropylene have relatively high hardness; polyethylene has good flexibility but relatively poor heat resistance and strength. In view of this, the present invention uses polypropylene as the surface layer of the multi-layer cross membrane, nylon as the skeleton, and forms a composite layer by stacking the first polypropylene layer, the first polyethylene layer, the nylon layer, the second polyethylene layer, and the second polypropylene layer in sequence, and then cross-compounds at least two composite layers to form a multi-layer cross membrane, so that the multi-layer cross membrane of the present invention has good toughness, strength and heat resistance, and can solve the problems of warping, wrinkling and even breakage of the cross membrane during application.

[0009] According to an embodiment of the present invention, the first polypropylene layer material, the first polyethylene layer material, the nylon layer material, the second polyethylene layer material and the second polypropylene layer material are respectively placed in a five-layer co-extrusion film blowing machine for co-extrusion film blowing. After shaping, a composite layer is obtained. The composite layer does not need to be stretched twice, and can be directly rotary cut and rolled, cross-compounded, to obtain a multi-layer cross film, which simplifies the process steps and facilitates industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The schematic diagram of the multi-layer cross film provided by the embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0011] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0012] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0013] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0014] In the related technologies, cross membranes generally have shortcomings such as poor heat resistance, insufficient toughness, and poor strength. Especially when used in the field of waterproof membranes, during the service process after outdoor laying, the above defects of the cross membranes can easily cause the waterproof membranes to warp, wrinkle, or even break.

[0015] In the process of realizing the concept of the present invention, it was found that through the cross-film multi-layer design and the cross-film material selection, the toughness, strength and heat resistance of the cross-film can be effectively improved, and the warping, wrinkling and even breakage can be alleviated.

[0016] Specifically, according to an embodiment of one aspect of the present invention, a multi-layer cross film is provided, wherein the multi-layer cross film is formed by cross-compounding at least two composite layers, such as Figure 1 As shown, the composite layer includes a first polypropylene layer 100, a first polyethylene layer 200, a nylon layer 300, a second polyethylene layer 400, and a second polypropylene layer 500 which are stacked in sequence.

[0017] According to the embodiments of the present invention, nylon has high mechanical strength, self-lubrication and wear resistance, and polypropylene has good high temperature resistance and chemical stability, but nylon and polypropylene have relatively high hardness; polyethylene has good flexibility but relatively poor heat resistance and strength. In view of this, the present invention uses polypropylene as the surface layer of the multi-layer cross membrane, nylon as the skeleton, and forms a composite layer by stacking the first polypropylene layer 100, the first polyethylene layer 200, the nylon layer 300, the second polyethylene layer 400, and the second polypropylene layer 500 in sequence, and then cross-compounds at least two layers of the composite layer to form a multi-layer cross membrane, so that the multi-layer cross membrane of the present invention has good toughness, strength and heat resistance, and can solve the problems of warping, wrinkling and even damage of the cross membrane during application.

[0018] According to an embodiment of the present invention, the first polypropylene layer 100 and the second polypropylene layer 500 may have the same or different compositions. The first polyethylene layer 200 and the second polyethylene layer 400 may have the same or different compositions.

[0019] Specifically, according to an embodiment of the present invention, the first polypropylene layer 100 and the second polypropylene layer 500 each independently include 70wt% to 100wt% of polypropylene and 0 to 30wt% of a compatibilizer, preferably the first polypropylene layer 100 and the second polypropylene layer 500 each independently include 70wt% to 95wt% of polypropylene and 5 to 30wt% of a compatibilizer. Specifically, the first polypropylene layer 100 and the second polypropylene layer 500 may each independently include 70wt% of polypropylene and 30wt% of a compatibilizer, 80wt% of polypropylene and 20wt% of a compatibilizer, 90wt% of polypropylene and 10wt% of a compatibilizer, 95wt% of polypropylene and 5wt% of a compatibilizer, or 100wt% of polypropylene.

[0020] According to an embodiment of the present invention, the first polypropylene layer 100 and the second polypropylene layer 500 include polypropylene, with polypropylene as the surface layer, utilizing the high temperature resistance and chemical stability of polypropylene to improve the strength and heat resistance performance of the multilayer cross film. The first polypropylene layer 100 and the second polypropylene layer 500 may also include a compatibilizer, and the compatibility between the first polypropylene layer 100 and the first polyethylene layer 200, and between the second polypropylene layer 500 and the second polyethylene layer 400 is improved by adding the compatibilizer, so as to further improve the toughness, strength and heat resistance of the multilayer cross film. The proportion of compatibilizer addition can take into account the strength, heat resistance and cost of the multilayer cross film.

[0021] According to an embodiment of the present invention, the compatibilizer is one or more of ethylene-octene copolymer elastomer (POE), maleic anhydride grafted modified ethylene-octene copolymer (POE-g-MAH), and metallocene linear low-density polyethylene (mLLDPE), wherein the density of the metallocene linear low-density polyethylene is 0.915~0.935g / cm 3 .

[0022] According to the embodiment of the present invention, a suitable compatibilizer can further improve the compatibility between the first polypropylene layer 100 and the first polyethylene layer 200 and between the second polypropylene layer 500 and the second polyethylene layer 400 to further improve the performance of the multi-layer cross film.

[0023] According to an embodiment of the present invention, the first polypropylene layer 100 and the second polypropylene layer 500 each independently further include 0.01 wt % to 1 wt % of a nucleating agent.

[0024] According to an embodiment of the present invention, the nucleating agent may include at least one of dibenzylidene sorbitol (DBS), di(p-methylbenzylidene) sorbitol (PM-DBS), substituted aryl phosphate nucleating agent (TMP-6), and the like.

[0025] According to the embodiments of the present invention, a suitable nucleating agent can change the crystallization behavior of the resin, accelerate the crystallization rate, increase the crystallization density and promote the refinement of the grain size, shorten the molding cycle, and improve the physical and mechanical properties of the product such as transparency, tensile strength, rigidity, and toughness.

[0026] According to an embodiment of the present invention, the first polypropylene layer 100 and the second polypropylene layer 500 each independently further include 0.01 wt % to 0.1 wt % of an ultraviolet absorber.

[0027] According to an embodiment of the present invention, the ultraviolet absorber may include at least one of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), 2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole (UV-326), 2-(2′-hydroxy-3′,5′-dipentylphenyl)benzotriazole (UV-328), and the like.

[0028] According to the embodiments of the present invention, a suitable ultraviolet absorber can improve the aging resistance of the material by absorbing ultraviolet light.

[0029] According to an embodiment of the present invention, the first polypropylene layer 100 and the second polypropylene layer 500 each independently further include 0.01 wt % to 0.1 wt % of a light stabilizer.

[0030] According to an embodiment of the present invention, the light stabilizer may include at least one of the hindered amine light stabilizers. Specifically, the light stabilizer may include at least one of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (GW-480), tris(1,2,2,6,6-pentamethyl-4-piperidinyl) phosphite (GW-540), tris(2,2,6,6-tetramethyl-4-piperidinyl nitroxide) phosphite (GW-544), poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl] [2-(2,2,6,6-tetramethylpiperidinyl)-amino]-hexylene-[4-(2,2,6,6-tetramethylpiperidinyl)-imino]} (944FDL), etc.

[0031] According to an embodiment of the present invention, the light stabilizer can reduce the number of active free radicals causing aging in the entire system by reacting with free radicals generated during the aging process of the material, thereby achieving the purpose of inhibiting or slowing down the aging process of the material.

[0032] According to an embodiment of the present invention, the first polyethylene layer 200 and the second polyethylene layer 400 each independently include high-density polyethylene, wherein the density of the high-density polyethylene is 0.94-0.965 g / cm 3 .

[0033] According to an embodiment of the present invention, the first polyethylene layer 200 and the second polyethylene layer 400 include high-density polyethylene, and the performance of the multi-layer cross film is improved by utilizing the flexibility and strength of the high-density polyethylene.

[0034] According to an embodiment of the present invention, the nylon layer 300 includes 90wt% to 100wt% of nylon and 0 to 10wt% of polyethylene grafted maleic anhydride, which is 100wt% in total. Preferably, the nylon layer 300 includes 90wt% to 99wt% of nylon and 1 to 10wt% of polyethylene grafted maleic anhydride. Specifically, the nylon layer 300 may include 90wt% of nylon and 10wt% of polyethylene grafted maleic anhydride, 92wt% of nylon and 8wt% of polyethylene grafted maleic anhydride, 95wt% of nylon and 5wt% of polyethylene grafted maleic anhydride, 97wt% of nylon and 3wt% of polyethylene grafted maleic anhydride, 99wt% of nylon and 1wt% of polyethylene grafted maleic anhydride, or 100wt% of nylon.

[0035] According to an embodiment of the present invention, the nylon layer 300 includes nylon, and the nylon is used as a skeleton, and the mechanical strength, self-lubrication and wear resistance of nylon are utilized to improve the performance of the multi-layer cross film. The nylon layer 300 may also include polyethylene grafted maleic anhydride, and the compatibility between the first polyethylene layer 200 and the nylon layer 300, and between the second polyethylene layer 400 and the nylon layer 300 is improved by adding a compatibilizer, so as to further improve the toughness, strength and heat resistance of the multi-layer cross film.

[0036] According to an embodiment of the present invention, the melt index of the first polypropylene layer 100 and the second polypropylene layer 500 are independently 1-10 g·(10 min). -1 , preferably 3~4g·(10min) -1 Specifically, the melt index 500 of the first polypropylene layer 100 and the second polypropylene layer is independently 1 g·(10 min) -1 、2g·(10min) -1 、3g·(10min) -1 、4g·(10min) -1 、5g·(10min) -1 、7g·(10min) -1 or 10g·(10min) -1 .

[0037] According to an embodiment of the present invention, the melt index of the first polyethylene layer 200 and the second polyethylene layer 400 are independently 0.5 to 5 g·(10 min). -1 , preferably 1~3g·(10min) -1 Specifically, the melt index of the first polyethylene layer 200 and the second polyethylene layer 400 are each independently 0.5 g·(10 min) -1 、1g·(10min) -1 、2g·(10min) -1 、3g·(10min)-1 、4g·(10min) -1 or 5g·(10min) -1 .

[0038] According to an embodiment of the present invention, the melt indexes of the first polypropylene layer 100 and the second polypropylene layer 500 may be the same or different. The melt indexes of the first polyethylene layer 200 and the second polyethylene layer 400 may be the same or different.

[0039] According to an embodiment of the present invention, the melt index of the nylon layer 300 is 1-4 g·(10 min). -1 , preferably 2~4g·(10min) -1 Specifically, the melt index of the nylon layer 300 may be 1 g·(10 min) -1 、2g·(10min) -1 、3g·(10min) -1 or 4g·(10min) -1 .

[0040] According to the embodiments of the present invention, a suitable melt index can enable the material to have better processing performance while ensuring the performance of the composite layer.

[0041] According to an embodiment of the present invention, the total thickness of the composite layer is 50-100 μm, preferably 50-90 μm. Specifically, the total thickness of the composite layer can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0042] According to an embodiment of the present invention, the thicknesses of the first polypropylene layer 100 and the second polypropylene layer 500 may be the same or different. The thicknesses of the first polyethylene layer 200 and the second polyethylene layer 400 may be the same or different.

[0043] According to an embodiment of the present invention, the thickness of the first polypropylene layer 100 is 10-30 μm, preferably 15-25 μm. Specifically, the thickness of the first polypropylene layer 100 may be 10 μm, 15 μm, 20 μm, 25 μm, 27 μm or 30 μm.

[0044] According to an embodiment of the present invention, the thickness of the first polyethylene layer 200 is 5-15 μm, preferably 7-12 μm. Specifically, the thickness of the first polyethylene layer 200 may be 5 μm, 7 μm, 9 μm, 11 μm, 12 μm or 15 μm.

[0045] According to an embodiment of the present invention, the thickness of the nylon layer 300 is 5-15 μm, preferably 7-12 μm. Specifically, the thickness of the nylon layer 300 may be 5 μm, 7 μm, 9 μm, 11 μm, 12 μm or 15 μm.

[0046] According to an embodiment of the present invention, the thickness of the second polyethylene layer 400 is 5-15 μm, preferably 7-12 μm. Specifically, the thickness of the second polyethylene layer 400 may be 5 μm, 7 μm, 9 μm, 11 μm, 12 μm or 15 μm.

[0047] According to an embodiment of the present invention, the thickness of the second polypropylene layer 500 is 10-30 μm, preferably 15-25 μm. Specifically, the thickness of the second polypropylene layer 500 may be 10 μm, 15 μm, 20 μm, 25 μm, 27 μm or 30 μm.

[0048] According to an embodiment of the present invention, the total thickness of the composite layer and the thickness of each layer can be controlled by adjusting the extruder frequency and / or the pulling speed. The appropriate total thickness of the composite layer and the thickness of each layer can take into account the performance and cost of the multi-layer cross film.

[0049] According to an embodiment of another aspect of the present invention, a method for preparing a multi-layer cross film is provided, comprising: placing a first polypropylene layer material, a first polyethylene layer material, a nylon layer material, a second polyethylene layer material and a second polypropylene layer material into a five-layer co-extrusion film blowing machine for co-extrusion film blowing, and obtaining a composite layer after shaping; the composite layer is rotary cut and rolled, cross-compounded, and a multi-layer cross film is obtained.

[0050] According to an embodiment of the present invention, the peeling angle may be 30° to 60°, specifically, 30°, 40°, 45°, 50° or 60°, preferably 45°. The present invention does not limit the peeling angle.

[0051] According to an embodiment of the present invention, the first polypropylene layer material and the second polypropylene layer material each independently include 70wt% to 100wt% of polypropylene and 0 to 30wt% of a compatibilizer. The compatibilizer is one or more of ethylene-octene copolymer elastomer (POE), maleic anhydride grafted modified ethylene-octene copolymer (POE-g-MAH), and metallocene linear low-density polyethylene (mLLDPE), wherein the density of the metallocene linear low-density polyethylene is 0.915 to 0.935 g / cm 3 .

[0052] According to an embodiment of the present invention, the first polypropylene layer material and the second polypropylene layer material each independently further include 0.01wt% to 1wt% of a nucleating agent. The nucleating agent may include at least one of dibenzylidene sorbitol (DBS), di(p-methylbenzylidene) sorbitol (PM-DBS), substituted aryl phosphate salt nucleating agent (TMP-6), etc.

[0053] According to an embodiment of the present invention, the first polypropylene layer material and the second polypropylene layer material each independently further include 0.01wt% to 0.1wt% of an ultraviolet absorber. The ultraviolet absorber may include at least one of 2-hydroxy-4-n-octyloxybenzophenone (UV-531), 2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole (UV-326), 2-(2′-hydroxy-3′,5′-dipentylphenyl)benzotriazole (UV-328), and the like.

[0054] According to an embodiment of the present invention, the first polypropylene layer material and the second polypropylene layer material each independently further include 0.01 wt% to 0.1 wt% of a light stabilizer. The light stabilizer may include at least one of hindered amine light stabilizers. Specifically, the light stabilizer may include at least one of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (GW-480), tris(1,2,2,6,6-pentamethyl-4-piperidinyl) phosphite (GW-540), tris(2,2,6,6-tetramethyl-4-piperidinylnitroxide) phosphite (GW-544), poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl] [2-(2,2,6,6-tetramethylpiperidinyl)-amino]-hexylene-[4-(2,2,6,6-tetramethylpiperidinyl)-imino]} (944FDL), and the like.

[0055] According to an embodiment of the present invention, the first polyethylene layer material and the second polyethylene layer material each independently include high-density polyethylene, wherein the density of the high-density polyethylene is 0.94-0.965 g / cm 3 .

[0056] According to an embodiment of the present invention, the nylon layer material includes 90 wt % to 100 wt % of nylon and 0 to 10 wt % of polyethylene grafted maleic anhydride, which is 100 wt % in total.

[0057] According to an embodiment of the present invention, the melt index of the first polypropylene layer material and the second polypropylene layer material is independently 1-10 g·(10 min) -1 The melt index of the first polyethylene layer material and the second polyethylene layer material are independently 0.5~5g·(10min) -1 The melt index of the nylon layer material is 1~4g·(10min) -1 .

[0058] According to an embodiment of the present invention, the compositions of the first polypropylene layer material, the first polyethylene layer material, the nylon layer material, the second polyethylene layer material and the second polypropylene layer material are respectively the same as the compositions of the above-mentioned first polypropylene layer 100, the first polyethylene layer 200, the nylon layer 300, the second polyethylene layer 400 and the second polypropylene layer 500, and are not repeated herein.

[0059] According to an embodiment of the present invention, the first polypropylene layer material, the first polyethylene layer material, the nylon layer material, the second polyethylene layer material and the second polypropylene layer material are respectively placed in a five-layer co-extrusion film blowing machine for co-extrusion film blowing. After shaping, a composite layer is obtained. The composite layer does not need to be stretched twice, and can be directly rotary cut and rolled, cross-compounded, to obtain a multi-layer cross film, which simplifies the process steps and facilitates industrial production.

[0060] According to an embodiment of the present invention, in the step of co-extrusion blown film, the extrusion temperatures of the first polypropylene layer material and the second polypropylene layer material are independently 190-230°C.

[0061] According to an embodiment of the present invention, in the step of co-extrusion blown film, the extrusion temperatures of the first polyethylene layer material and the second polyethylene layer material are independently 190-240°C.

[0062] According to an embodiment of the present invention, in the step of co-extrusion film blowing, the extrusion temperature of the nylon layer material is 200-270°C.

[0063] According to an embodiment of the present invention, in the step of co-extrusion film blowing, the die temperature of the five-layer co-extrusion film blowing machine is 190-240°C.

[0064] According to the embodiment of the present invention, the appropriate extrusion temperature and the die temperature can take into account the plasticizing effect of the material, the production efficiency of the composite layer, and the performance of the composite layer.

[0065] According to another embodiment of the present invention, there is provided application of the above multi-layer cross film or the multi-layer cross film prepared by the above preparation method in the field of building waterproofing and packaging film.

[0066] According to the embodiments of the present invention, the multi-layer cross film provided by the present invention has good toughness, strength and heat resistance, and can effectively alleviate problems such as warping, wrinkling and even breakage of the multi-layer cross film.

[0067] The following lists a number of specific embodiments to illustrate the technical solution of the present invention in detail. It should be noted that the specific embodiments below are only used for illustration and are not used to limit the present invention.

[0068] Example 1

[0069] This embodiment 1 provides a multi-layer cross membrane, which is formed by cross-compounding two composite layers, and the composite layer includes a first polypropylene layer, a first polyethylene layer, a nylon layer, a second polyethylene layer, and a second polypropylene layer stacked in sequence.

[0070] The first polypropylene layer and the second polypropylene layer are both made of a blend of 89.36 wt% polypropylene, 10 wt% ethylene-octene copolymer elastomer, 0.5 wt% nucleating agent DBS, 0.07 wt% ultraviolet absorber UV-326 and 0.07 wt% light stabilizer GW-480, and the melt index of the blend is 4 g·(10 min). -1 The first polyethylene layer and the second polyethylene layer are both made of high-density polyethylene, and the melt index is 3g·(10min) -1 , where the density of high-density polyethylene is 0.95g / cm 3 The nylon layer is made of 95wt% nylon and 5wt% polyethylene grafted maleic anhydride blend, and the melt index of the blend is 2g·(10min) -1 The total thickness of the composite layer is 59.8 μm, the thickness of the first polypropylene layer is 15.6 μm, the thickness of the first polyethylene layer is 9.4 μm, the thickness of the nylon layer is 9.7 μm, the thickness of the second polyethylene layer is 9.6 μm, and the thickness of the second polypropylene layer is 15.5 μm.

[0071] This embodiment 1 also provides a method for preparing the above-mentioned multi-layer cross film, comprising the following steps:

[0072] (1) The first polypropylene layer material, the first polyethylene layer material, the nylon layer material, the second polyethylene layer material and the second polypropylene layer material are respectively placed in a five-layer co-extrusion film blowing machine for co-extrusion film blowing, wherein the extrusion temperature of the first polypropylene layer material and the second polypropylene layer material are both 210°C, and the extrusion temperature of the first polyethylene layer material and the second polyethylene layer material are both 220°C; the extrusion temperature of the nylon layer material is 240°C, and the die temperature of the five-layer co-extrusion film blowing machine is 210°C; after setting at 100°C for 100s, a composite layer is obtained.

[0073] (2) The composite layer is rolled up by 45° rotary cutting and cross-compounding to obtain a multi-layer cross-film.

[0074] Example 2

[0075] This embodiment 2 provides a multi-layer cross membrane, which is formed by cross-compounding two composite layers, and the composite layer includes a first polypropylene layer, a first polyethylene layer, a nylon layer, a second polyethylene layer, and a second polypropylene layer stacked in sequence.

[0076] The first polypropylene layer and the second polypropylene layer are both made of a blend of 89.85wt% polypropylene, 10wt% compatibilizer POE-g-MAH, 0.05wt% nucleating agent TMP-6, 0.05wt% ultraviolet absorber UV-531, and 0.05wt% light stabilizer 944FDL, and the melt index of the blend is 4g·(10min) -1 The first polyethylene layer and the second polyethylene layer are both made of high-density polyethylene, and the melt index is 3g·(10min) -1 , where the density of high-density polyethylene is 0.95g / cm 3 The nylon layer is made of 97wt% nylon and 3wt% polyethylene grafted maleic anhydride blend, and the melt index of the blend is 2g·(10min) -1 .

[0077] The total thickness of the composite layer is 59.2 μm, the thickness of the first polypropylene layer is 15.3 μm, the thickness of the first polyethylene layer is 9.4 μm, the thickness of the second polyethylene layer is 9.5 μm, the thickness of the nylon layer is 9.4 μm, and the thickness of the second polypropylene layer is 15.6 μm.

[0078] This embodiment 2 also provides a method for preparing the above-mentioned multi-layer cross film, comprising the following steps:

[0079] (1) The first polypropylene layer material, the first polyethylene layer material, the nylon layer material, the second polyethylene layer material and the second polypropylene layer material are respectively placed in a five-layer co-extrusion film blowing machine for co-extrusion film blowing, wherein the extrusion temperature of the first polypropylene layer material and the second polypropylene layer material are both 210°C, and the extrusion temperature of the first polyethylene layer material and the second polyethylene layer material are both 220°C; the extrusion temperature of the nylon layer material is 240°C, and the die temperature of the five-layer co-extrusion film blowing machine is 210°C; after setting at 100°C for 100s, a composite layer is obtained.

[0080] (2) The composite layer is rolled up by 45° rotary cutting and cross-compounding to obtain a multi-layer cross-film.

[0081] Example 3

[0082] This embodiment 3 provides a multi-layer cross membrane, which is formed by cross-compounding two composite layers, and the composite layer includes a first polypropylene layer, a first polyethylene layer, a nylon layer, a second polyethylene layer, and a second polypropylene layer stacked in sequence.

[0083] The first polypropylene layer and the second polypropylene layer are both made of a blend of 84.85wt% polypropylene, 15wt% compatibilizer POE-g-MAH, 0.05wt% nucleating agent TMP-6, 0.05wt% ultraviolet absorber UV-531, and 0.05wt% light stabilizer 944FDL, and the melt index of the blend is 3g·(10min) -1 The first polyethylene layer and the second polyethylene layer are both made of high-density polyethylene, and the melt index is 3g·(10min) -1 , where the density of high-density polyethylene is 0.95g / cm 3 The nylon layer is made of 97wt% nylon and 3wt% polyethylene grafted maleic anhydride blend, and the melt index of the blend is 2g·(10min) -1 .

[0084] This embodiment 3 also provides a method for preparing the above-mentioned multi-layer cross film, comprising the following steps:

[0085] (1) The first polypropylene layer material, the first polyethylene layer material, the nylon layer material, the second polyethylene layer material and the second polypropylene layer material are respectively placed in a five-layer co-extrusion film blowing machine for co-extrusion film blowing, wherein the extrusion temperature of the first polypropylene layer material and the second polypropylene layer material are both 210°C, and the extrusion temperature of the first polyethylene layer material and the second polyethylene layer material are both 220°C; the extrusion temperature of the nylon layer material is 240°C, and the die temperature of the five-layer co-extrusion film blowing machine is 210°C; after setting at 100°C for 100s, a composite layer is obtained.

[0086] (2) The composite layer is rolled up by 45° rotary cutting and cross-compounding to obtain a multi-layer cross-film.

[0087] Example 4

[0088] This embodiment 4 provides a multilayer cross film and a preparation method thereof, referring to embodiment 3, except that: in the multilayer cross film provided in this embodiment 4, the nylon layer is made of a blend of 95wt% nylon and 5wt% polyethylene grafted maleic anhydride, and the melt index of the blend is 3g·(10min) -1 .

[0089] Comparative Example 1

[0090] This comparative example 1 provides a multilayer cross film and a preparation method thereof, referring to Example 2, except that:

[0091] In the multi-layer cross membrane provided in this comparative example 1, the nylon layer in the composite layer is replaced by an ultra-high molecular weight polyethylene layer, and the ultra-high molecular weight polyethylene layer is made of ultra-high molecular weight polyethylene, and the weight average molecular weight of the ultra-high molecular weight polyethylene layer is 2 million.

[0092] In the extrusion film blowing step of the method for preparing the multi-layer cross film provided in this comparative example 1, the extrusion temperature of the ultra-high molecular weight polyethylene layer material is 210°C.

[0093] Comparative Example 2

[0094] This comparative example 2 provides a multilayer cross film and a preparation method thereof, referring to Example 2, except that:

[0095] The multilayer cross film provided in Comparative Example 2 removes the first polypropylene layer and the second polypropylene layer in the composite layer. The total thickness of the composite layer is 59.1 μm, the thickness of the first polyethylene layer is 24.6 μm, the thickness of the nylon layer is 9.8 μm, and the thickness of the second polyethylene layer is 24.7 μm.

[0096] Comparative Example 3

[0097] This comparative example 3 provides a multi-layer cross film and a preparation method thereof, referring to Example 2, except that:

[0098] The cross film provided in this comparative example 3, the first polyethylene layer and the second polyethylene layer in the composite layer are removed. The total thickness of the composite layer is 59.2 μm, the thickness of the first polypropylene layer is 25.7 μm, the thickness of the nylon layer is 24.8 μm, and the thickness of the second polypropylene layer is 9.7 μm.

[0099] Comparative Example 4

[0100] Comparative Example 4 provides a cross film, which is made of two polyethylene layers cross-compositely, wherein the polyethylene layer is made of 99.9wt% of a high-density polyethylene, 0.05wt% of an ultraviolet absorber UV-531, and 0.05wt% of a light stabilizer 944FDL blended material, and the melt index of the blended material is 3g·(10min) -1 ; The total thickness of the cross-film is 59.5μm.

[0101] This comparative example 4 also provides a method for preparing the above-mentioned cross-film, comprising the following steps:

[0102] (1) The blended material is placed in a single-layer film blowing machine for film blowing at an extrusion temperature of 220°C, followed by secondary stretching and shaping at 100°C for 100s to obtain a polyethylene layer.

[0103] (2) The polyethylene layer is rolled up by 45° rotary cutting and cross-laminating to obtain a cross-laminated film.

[0104] Comparative Example 5

[0105] The cross film and the preparation method thereof provided in this comparative example 5 refer to comparative example 4, except that in step (1) of the preparation method provided in this comparative example 5, no secondary stretching is performed.

[0106] The multi-layer cross films provided in Examples 1 to 4 were observed to have no problems of warping, wrinkling, or damage. However, the cross film prepared in Comparative Example 4 had warping and wrinkling, and some of the prepared batches even had damage.

[0107] The cross membranes provided in the embodiments and comparative examples of the present invention are tested as follows:

[0108] 1. Mechanical properties test: According to GB / T 1040.3-2006 test, the specimen adopts type 2, with a length of 150 mm, a width of 15 mm, a test speed of 500 mm / min, and three data are tested for each sample to calculate the average value.

[0109] 2. 110°C oven dimensional change rate test: Cut the prepared cross film into 10×10cm square samples and put them into a 110°C oven for 2h. After the samples are cooled, accurately measure and record the dimensional changes. Measure each sample 3-6 times and calculate the average value.

[0110] 3. Artificial climate aging test: Tested in accordance with GB / T 18244-2000, the aging time is 1000h.

[0111] The relevant test data are detailed in Table 1. From the analysis of Table 1, it can be seen that compared with the polyethylene cross film prepared in Comparative Example 4, the cross film provided by the embodiment of the present invention has better heat resistance; and without secondary stretching, the tensile strength is not much different from that of the polyethylene cross film; and its elongation at break is significantly higher than that of the polyethylene cross film. It can be seen that using polypropylene with higher heat resistance as the surface layer, nylon with higher mechanical strength as the skeleton, and polyethylene as the middle layer effectively improves the heat resistance and mechanical properties of the cross film. Compared with the multi-layer cross films provided in Comparative Examples 1 to 5, the multi-layer provided by the embodiment of the present invention exhibits more excellent comprehensive performance.

[0112] Table 1

[0113]

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made to the technical method by any technician familiar with the art within the spirit and principle of the present invention is still included in the protection scope of the technical solution of the present invention.

Claims

1. A multi-layer cross film, characterized in that: The multi-layer cross film is formed by cross-compounding at least two composite layers, and the composite layer is composed of a first polypropylene layer, a first polyethylene layer, a nylon layer, a second polyethylene layer, and a second polypropylene layer stacked in sequence; The first polypropylene layer and the second polypropylene layer independently comprise 70 wt% to 95 wt% of polypropylene and 5 wt% to 30 wt% of a compatibilizer, wherein the compatibilizer is one or more of ethylene-octene copolymer elastomer, maleic anhydride grafted modified ethylene-octene copolymer, and metallocene linear low-density polyethylene, and the density of the metallocene linear low-density polyethylene is 0.915 to 0.935 g / cm 3 ; The first polyethylene layer and the second polyethylene layer each independently comprise high-density polyethylene, and the density of the high-density polyethylene is 0.94-0.965 g / cm 3 ; The nylon layer comprises 90wt% to 99wt% of nylon and 1wt% to 10wt% of polyethylene grafted maleic anhydride; The total thickness of the composite layer is 50-100 μm; The thickness of the first polypropylene layer is 10-30 μm; The thickness of the first polyethylene layer is 5-15 μm; The thickness of the nylon layer is 5-15 μm; The thickness of the second polyethylene layer is 5-15 μm; The thickness of the second polypropylene layer is 10-30 μm.

2. The multi-layer cross film according to claim 1, characterized in that The first polypropylene layer and the second polypropylene layer each independently include 0.01wt% to 1wt% of a nucleating agent, wherein the nucleating agent is one or more of dibenzylidene sorbitol, di(p-methylbenzylidene) sorbitol, and substituted aryl phosphate nucleating agents.

3. The multi-layer cross film according to claim 1, characterized in that The first polypropylene layer and the second polypropylene layer each independently include 0.01wt% to 0.1wt% of an ultraviolet absorber, wherein the ultraviolet absorber is one or more of 2-hydroxy-4-n-octyloxybenzophenone, 2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole, and 2-(2′-hydroxy-3′,5′-dipentylphenyl)benzotriazole.

4. The multi-layer cross film according to claim 1, characterized in that The first polypropylene layer and the second polypropylene layer each independently further include 0.01 wt % to 0.1 wt % of a light stabilizer, and the light stabilizer is a hindered amine light stabilizer.

5. The multilayer cross film according to any one of claims 1 to 4, characterized in that The melt index of the first polypropylene layer and the second polypropylene layer is independently 1 to 10 g·(10 min) -1 ; The melt index of the first polyethylene layer and the second polyethylene layer are independently 0.5 to 5 g·(10 min) -1 ; The melt index of the nylon layer is 1~4g·(10min) -1 .

6. A method for preparing the multilayer cross film according to any one of claims 1 to 5, characterized in that: The preparation method comprises: The first polypropylene layer material, the first polyethylene layer material, the nylon layer material, the second polyethylene layer material and the second polypropylene layer material are respectively placed in a five-layer co-extrusion film blowing machine for co-extrusion film blowing, and after shaping, a composite layer is obtained; The composite layer is rolled up and cross-compounded through rotary cutting to obtain a multi-layer cross-film.

7. The preparation method according to claim 6, characterized in that: In the step of co-extrusion blown film, the extrusion temperatures of the first polypropylene layer material and the second polypropylene layer material are independently 190-230° C.; The extrusion temperatures of the first polyethylene layer material and the second polyethylene layer material are independently 190-240° C.; The extrusion temperature of the nylon layer material is 200-270°C; The die temperature of the five-layer co-extrusion film blowing machine is 190-240°C.

8. Application of the multi-layer cross film described in any one of claims 1 to 5 or the multi-layer cross film prepared by the preparation method described in claim 6 or 7 in the field of building waterproofing and packaging film.

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