Block copolymerized polypropylene and method for producing the same, polypropylene material and method for producing the same, polypropylene film

Abstract

The present application relates to the field of polyolefin matt film, and discloses a block copolymerized polypropylene and a preparation method thereof, a polypropylene material and a preparation method thereof, and a polypropylene film.The method comprises the following steps: (1) carrying out homopolymerization reaction on first propylene in the presence of hydrogen, a main catalyst, alkyl aluminum and organosilane to obtain product I; the main catalyst is a Ziegler Natta catalyst; (2) mixing hydrogen, second propylene, ethylene and the product I to carry out copolymerization reaction under a protective atmosphere to obtain the block copolymerized polypropylene; the block copolymerized polypropylene provided by the present application is used to prepare a polypropylene material, and the polypropylene material can be directly used as the upper layer (temperature-resistant matt layer) of BOPP matt film when applied to the polypropylene film, that is, the polypropylene film simultaneously has good matt effect and temperature resistance without an additional temperature-resistant layer.

Description

Technical Field

[0001] This invention relates to the field of polyolefin matte films, specifically to block copolymer polypropylene and its preparation method, polypropylene materials and their preparation method, and polypropylene films. Background Technology

[0002] As people's aesthetic standards change and their demands for packaging materials constantly evolve, matte film is a new type of film developed by film manufacturers to meet consumers' numerous needs for comfortable handling, a serene and elegant appearance, and realistic color reproduction during printing. Matte film is a packaging film with a surface similar to paper, exhibiting very low gloss but high haze, resulting in a diffuse reflection and matte finish. Its surface reflects light weakly and softly, with a haze generally exceeding 70%, earning it the name "natural gloss film." It is primarily used for packaging high-end food, gifts, and candies, as well as for printing on large outdoor advertisements and for the covers of hardcover books.

[0003] Currently, the mainstream matte films on the market mainly consist of a matte layer, a heat-resistant layer, a core layer, and a heat-sealing layer (such as...). Figure 2 (As shown). The matte layer is also called the upper surface layer, and the heat-sealing layer is also called the lower surface layer. According to statistics, the melting temperature of the special materials used in the matte layer of matte film products is generally below 150℃. This has the following impact on existing processing technology:

[0004] In the heat-sealing process of packaging products, when using a heat-sealing machine to seal and cut the packaging, the film at the sealing area needs to be heated to allow the heat-sealing layer to adhere, thus achieving the sealing effect and facilitating subsequent packaging steps. However, in practical applications, it has been found that a high processing temperature is required for the heat-sealing layer to fully adhere during the sealing process. But at higher processing temperatures, the matte layer can also deform due to the high temperature, resulting in obvious wrinkles at the sealing point of the packaging. This has a greater impact on the printed packaging products, making it difficult to present a better appearance to consumers. Some larger wrinkles may form sharp edges, affecting the consumer's feel and safety, and also easily leading to significant waste for packaging product manufacturers.

[0005] CN102079841A discloses a high-flow, impact-resistant polypropylene composition. This technical solution contains 85-95 parts of block copolymer polypropylene, 5-15 parts of high-density polyethylene, and some processing aids. The formulation, by adding peroxide, makes the melt flow rate of the composition within the range of (60±5) g / 10min. The polypropylene composition of this technical solution is suitable for the field of thin-wall injection molding, but not for the field of matte film.

[0006] CN111806027A discloses a polypropylene matte film and its preparation method. The ordinary matte layer is made of matte masterbatch, which consists of 25-30 parts low-density polyethylene, 6-12 parts homopolymer polyethylene, 2-4 parts ethylene-propylene copolymer, 3.6-6.6 parts nano-silica, 2.4-4.4 parts nano-calcium oxide, and 0.2-0.8 parts antioxidant. The heat-resistant matte layer is made of any one or more of block copolymer polypropylene K7726H, EP5074, and M30RH. Therefore, this technical solution uses block copolymer polypropylene as a separate heat-resistant matte layer, which is then placed on top of the ordinary matte layer. However, when this technical solution is applied to polypropylene matte films, the process is complex and the product cost is high. Summary of the Invention

[0007] The purpose of this invention is to provide a polypropylene film that simultaneously meets the requirements of temperature resistance and matting effect, while simplifying the preparation process and reducing the product preparation cost.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for preparing block copolymer polypropylene, the method comprising:

[0009] (1) In the presence of hydrogen, a main catalyst, alkyl aluminum and organosilane, the first propylene is subjected to homopolymerization to obtain product I; the main catalyst is Ziegler-Natta catalyst;

[0010] (2) Under a protective atmosphere, hydrogen, second propylene, ethylene and product I are mixed to carry out a copolymerization reaction to obtain the block copolymer polypropylene;

[0011] In step (1), the weight ratio of the first propylene used to the second propylene used in step (2) is 0.5-1.2:1;

[0012] The weight ratio of the amount of ethylene used to the total amount of the first propylene and the second propylene used is 0.1-0.5:1.

[0013] A second aspect of the invention provides a block copolymer polypropylene obtained by the method described in the first aspect.

[0014] A third aspect of the present invention provides a method for preparing a polypropylene material, the method comprising: mixing block copolymer polypropylene with a density of 0.94-0.96 g / cm³. 3 High-density polyethylene, inorganic fillers, antioxidants and acid absorbers are mixed and then extruded into granules.

[0015] The block copolymer polypropylene is the block copolymer polypropylene described in the second aspect.

[0016] A fourth aspect of the present invention provides a polypropylene material prepared by the method described in the third aspect.

[0017] A fifth aspect of the present invention provides a polypropylene film prepared from the polypropylene material described in the fourth aspect.

[0018] The present invention has the following advantages through the above technical solution:

[0019] (1) The block copolymer polypropylene prepared by the method provided by the present invention is used to prepare polypropylene material. The polypropylene material has suitable melt flow properties. When applied to polypropylene film, it can be directly used as the upper surface layer of biaxially oriented polypropylene matte film (BOPP). That is, the matte film can be used as a heat-resistant matte layer without the need for an additional heat-resistant layer, and at the same time has good matting effect and heat resistance.

[0020] (2) The polypropylene film provided by the present invention has high haze and low gloss, good hand feel, and outstanding temperature resistance, and is not easily deformed by heat at high heat sealing temperature.

[0021] (3) The polypropylene material provided by the present invention not only satisfies the matting effect of matting film in actual processing and application, but also has a higher softening temperature, which can reduce wrinkles at the heat sealing of the film during the slitting and packaging process, reduce the frequency of matting film sticking to the cutter, and reduce the waste of manpower and material resources caused by the company stopping to clean the cutter; it can improve the aesthetics of the packaged products by improving the slitting effect.

[0022] (4) The polypropylene material provided by the present invention is suitable as a heat-resistant matting layer for preparing heat-resistant matting film. It can be used to prepare matting film products by casting or orientation stretching to obtain packaging cover material, and can be widely used in high-end food packaging, gift packaging and other application fields. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope image of the block copolymer polypropylene obtained in Preparation Example 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of existing matte film technology;

[0025] Figure 3 This is a schematic diagram of the polypropylene film prepared from the polypropylene material obtained in Example 1 of the present invention, which is used as a heat-resistant matting layer in a matting film. Detailed Implementation

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] In this invention, all pressures refer to gauge pressure; HDPE refers to high-density polyethylene.

[0028] As previously described, a first aspect of the present invention provides a method for preparing block copolymer polypropylene, the method comprising:

[0029] (1) In the presence of hydrogen, a main catalyst, alkyl aluminum and organosilane, the first propylene is subjected to homopolymerization to obtain product I; the main catalyst is Ziegler-Natta catalyst;

[0030] (2) Under a protective atmosphere, hydrogen, second propylene, ethylene and product I are mixed to carry out a copolymerization reaction to obtain the block copolymer polypropylene;

[0031] In step (1), the weight ratio of the first propylene used to the second propylene used in step (2) is 0.5-1.2:1;

[0032] The weight ratio of the amount of ethylene used to the total amount of the first propylene and the second propylene used is 0.1-0.5:1.

[0033] It should be noted that the alkylaluminum refers to a large class of organometallic aluminum compounds formed by the direct combination of alkyl groups and aluminum, with the general formula AlR3, RnAlX. 3-n Or R3Al2X2 (R is alkyl, X is halogroup, n = 1, 2, 3), also known as trialkylaluminum; the Ziegler-Natta catalyst is composed of titanium tetrachloride-triethylaluminum [TiCl4-Al(C2H5)3].

[0034] Preferably, in step (1), the organosilane is selected from at least one of tetraethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane and n-propyltriethoxysilane, and is preferably diisobutyldimethoxysilane.

[0035] Preferably, in step (1), the weight ratio of the main catalyst, the alkylaluminum and the organosilane is 1:500-600:200-300.

[0036] In a preferred embodiment, the conditions for the homopolymerization reaction in step (1) include: a polymerization temperature of 60-80°C, a polymerization pressure of 0.04-1 MPa, and a polymerization time of 10-25 min.

[0037] Preferably, in step (2), the protective atmosphere is nitrogen.

[0038] Preferably, in step (2), the conditions for the copolymerization reaction include: a polymerization temperature of 55-85℃, a polymerization pressure of 1-8MPa, and a polymerization time of 0.5-3h.

[0039] In a preferred embodiment, the weight ratio of the amount of ethylene to the amount of hydrogen is 20-40:1; the amount of hydrogen refers to the total amount of hydrogen used in steps (1) and (2).

[0040] More preferably, the conditions for the copolymerization reaction include: a polymerization temperature of 60-70°C, a polymerization pressure of 2-5 MPa, and a polymerization time of 1-2 h.

[0041] As previously stated, a second aspect of the present invention provides a block copolymer polypropylene obtained by the method described in the first aspect.

[0042] In a preferred embodiment, based on the total weight of the block copolymer polypropylene, the content of the ethylene propylene rubber phase in the block copolymer polypropylene is 10-25% by weight, and the content of the ethylene structural unit is 5-15% by weight.

[0043] More preferably, based on the total weight of the block copolymer polypropylene, the content of the ethylene propylene rubber phase in the block copolymer polypropylene is 15-20% by weight; and the content of the ethylene structural unit is 7-11% by weight.

[0044] Preferably, in the block copolymer polypropylene, the average particle diameter of the ethylene propylene rubber phase is 0.7-1.3 μm.

[0045] In a preferred embodiment, the melt flow index of the block copolymer polypropylene at 230°C and 2.16 kg load is 1-8 g / 10 min, preferably 1.5-6 g / 10 min.

[0046] As previously described, a third aspect of the present invention provides a method for preparing a polypropylene material, the method comprising: mixing block copolymer polypropylene with a density of 0.94-0.96 g / cm³. 3 High-density polyethylene, inorganic fillers, antioxidants and acid absorbers are mixed and then extruded into granules.

[0047] The block copolymer polypropylene is the block copolymer polypropylene described in the second aspect.

[0048] Preferably, relative to 100 parts by weight of the block copolymer polypropylene, the amount of high-density polyethylene is 10-70 parts by weight, the amount of inorganic filler is 0.1-0.5 parts by weight, the amount of antioxidant is 0.05-0.2 parts by weight, and the amount of acid scavenger is 0.01-0.05 parts by weight. In this preferred embodiment, the polypropylene film obtained by the technical solution of the present invention has a better matting effect.

[0049] More preferably, relative to 100 parts by weight of the block copolymer polypropylene, the amount of high-density polyethylene is 17-47 parts by weight, the amount of inorganic filler is 0.2-0.4 parts by weight, the amount of antioxidant is 0.1-0.15 parts by weight, and the amount of acid scavenger is 0.02-0.04 parts by weight.

[0050] In a preferred embodiment, the molecular weight of the high-density polyethylene exhibits a unimodal or bimodal distribution.

[0051] Preferably, the melt flow index of the high-density polyethylene at 190°C and under a load of 21.6 kg is 5-20 g / 10 min.

[0052] Preferably, the high-density polyethylene has a weight-average molecular weight of 240,000-300,000 and a molecular weight distribution index of 17-28.

[0053] In a preferred embodiment, the high-density polyethylene is selected from at least one of 7000F, HTA001, DGDA-6098, and HDPE52090. In this preferred embodiment, the polypropylene film obtained by the technical solution of the present invention has higher haze, better matting effect, and a better feel.

[0054] Preferably, the inorganic filler is selected from at least one of talc, wollastonite, mica powder and silicon dioxide, and is preferably silicon dioxide.

[0055] Preferably, the inorganic filler has an average particle diameter of 4-5 μm.

[0056] In a preferred embodiment, the antioxidant is a hindered phenolic antioxidant and / or a phosphite antioxidant.

[0057] Preferably, the hindered phenolic antioxidant is selected from at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (hereinafter referred to as antioxidant 1010), 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxyphenyl)benzene (hereinafter referred to as antioxidant 330), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid (hereinafter referred to as antioxidant 3114) and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (hereinafter referred to as antioxidant 1076), preferably pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and / or 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxyphenyl)benzene.

[0058] Preferably, the phosphite antioxidant is selected from at least one of tris(2,4-di-tert-butylphenyl) phosphite (hereinafter referred to as antioxidant 168), bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite (hereinafter referred to as antioxidant 626), and bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, preferably tris(2,4-di-tert-butylphenyl) phosphite (hereinafter referred to as antioxidant PEP-36), and more preferably tris(2,4-di-tert-butylphenyl) phosphite.

[0059] According to a preferred embodiment, the antioxidant is a combination of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1.5-2.5.

[0060] In a preferred embodiment, the acid absorbent is selected from at least one of sodium stearate, calcium stearate, zinc stearate, and hydrotalcite, with hydrotalcite being the most preferred.

[0061] It should be noted that, in this invention, the extrusion granulation includes a melt blending process and a granulation process.

[0062] The present invention does not have any particular limitation on the equipment used for stirring and mixing, as long as the corresponding components are mixed evenly. For example, any one of a high-speed mixer, kneader, open mill, and internal mixer can be used to mix the corresponding components.

[0063] The present invention does not impose any particular limitation on the equipment used for the extrusion granulation, as long as the above raw materials can be fully mixed, melted and granulated. For example, the equipment used for the extrusion granulation is a twin-screw extruder, a single-screw extruder, or a melt mixer.

[0064] Preferably, the stirring and mixing conditions include: a time of 5-30 minutes, a temperature of 25-65°C, and a rotation speed of 50-300 rpm.

[0065] Preferably, the conditions for the extrusion granulation include: a temperature of 160-230℃ and a rotation speed of 100-400 rpm.

[0066] According to a preferred embodiment, the method further includes: first mixing inorganic filler, antioxidant, acid absorber and block copolymer polypropylene, then adding high-density polyethylene for a second mixing, and finally extruding and granulating.

[0067] As previously described, a fourth aspect of the present invention provides a polypropylene material prepared by the method described in the third aspect.

[0068] Preferably, the melt flow index of the polypropylene material at 230°C and 2.16 kg load is 1.5-5 g / 10 min, and more preferably 2-4 g / 10 min.

[0069] As previously described, a fifth aspect of the present invention provides a polypropylene film prepared from the polypropylene material described in the fourth aspect.

[0070] In this invention, the polypropylene film is suitable for the upper surface layer (heat-resistant matting layer) of BOPP matte film.

[0071] According to a preferred embodiment, the polypropylene film includes a heat-resistant matte layer, a core layer, and a heat-sealing layer, and the thickness ratio of the heat-resistant matte layer, the core layer, and the heat-sealing layer is 1-3:13-25:1.

[0072] Preferably, the average thickness of the heat-resistant matting layer is 1-3 μm.

[0073] Preferably, the haze of the polypropylene film is 90-92%.

[0074] Preferably, the polypropylene film has a mirror gloss of 2.5-3.5%.

[0075] Preferably, the relative roughness of the polypropylene film is 450-500 μm.

[0076] In a preferred embodiment, the heat-sealing temperature of the polypropylene film is 140-145°C.

[0077] The present invention will be described in detail below through embodiments.

[0078] In the following examples, unless otherwise specified, all compounds and reagents used are commercially available products, including:

[0079] Ziegler-Natta catalyst was purchased from Beijing Aoda Branch of Sinopec Catalyst Co., Ltd.

[0080] Alkyl aluminum was purchased from Beijing Aoda Branch of Sinopec Catalyst Co., Ltd.

[0081] Diisobutyldimethoxysilane was purchased from Beijing Aoda Branch of Sinopec Catalyst Co., Ltd.

[0082] HDPE(Ⅰ), purchased from Lotte Chemical Co., Ltd., South Korea, grade 7000F; density 0.956 g / cm³. 3 The melt flow index was 9 g / 10 min at 190℃ and 21.6 kg load, the weight-average molecular weight was 270,000, and the molecular weight distribution index was 20.

[0083] HDPE (ⅠⅠ), purchased from ExxonMobil Chemical Company, grade HTA001; density 0.954 g / cm³ 3 The melt flow index was 10 g / 10 min at 190℃ and 21.6 kg load, the weight-average molecular weight was 294,000, and the molecular weight distribution index was 27.2.

[0084] HDPE (ⅠⅢⅠ), purchased from Sinopec Qilu Petrochemical Company, grade DGDA-6098; density 0.952 g / cm³ 3 The melt flow index was 10.6 g / 10 min at 190℃ and 21.6 kg load, the weight-average molecular weight was 250,000, and the molecular weight distribution index was 18.

[0085] HDPE(Ⅳ), purchased from Sinopec (Guangdong) Refining & Chemical Co., Ltd., grade HDPE52090; density 0.953 g / cm³. 3 The melt flow index was 7 g / 10 min at 190℃ and 21.6 kg load, the weight-average molecular weight was 240,000, and the molecular weight distribution index was 19.

[0086] HDPE(V), purchased from Lotte Chemical Co., Ltd., South Korea, grade HDPE5000S; density 0.953 g / cm³. 3 The melt flow index was 8 g / 10 min at 190℃ and 21.6 kg load, the weight-average molecular weight was 240,000, and the molecular weight distribution index was 19.

[0087] The hydrotalcite was purchased from Dalian Haichen Chemical & Mineral Co., Ltd.

[0088] The silica was purchased from Guangzhou Lingwei Technology Co., Ltd., with an average particle diameter of 4.5 μm.

[0089] The testing methods involved in the following examples are as follows:

[0090] (1) Melt flow index: determined according to the method specified in GB / T 3682-2000. Specifically, the test temperature is 230℃ and the load is 2.16kg.

[0091] (3) Haze: The haze shall be determined in accordance with the method specified in GB / T2410-2008, wherein the thickness of the test sample film shall be 30 micrometers.

[0092] (4) Mirror gloss: The gloss is determined according to the method specified in GB / T8807-1998, wherein the thickness of the test sample film is 30 micrometers.

[0093] (5) Relative roughness: The prepared film was measured in an area of ​​100 square micrometers using the tapping mode of an atomic force microscope.

[0094] (6) Heat sealing temperature: The film is heat sealed using a heat sealing machine at different temperatures under different conditions of pressure of 3MPa and time of 1s, wherein the heat sealing strength is greater than 2.5N / 15mm.

[0095] (7) Scanning electron microscopy: The block copolymer polypropylene sample was subjected to low-temperature brittle fracture in liquid nitrogen. The block copolymer polypropylene was etched with a solvent (o-xylene). The ethylene propylene rubber phase was dissolved and detached by the solvent, forming pores, which made the two-phase structure of homopolymer polypropylene and ethylene propylene rubber more clearly visible.

[0096] The specific testing method for the scanning electron microscope images is as follows: a scanning electron microscope manufactured by Hitachi Scientific Instruments Co., Ltd., model S-3400N, is used, and the tests are conducted in accordance with the methods specified in GB / T 16594-2008.

[0097] In the following preparation examples, the weight ratio of ethylene to hydrogen is 30:1.

[0098] Preparation Example 1: Preparation of Block Copolymer Polypropylene

[0099] (1) In the presence of hydrogen, main catalyst (Zigler-Natta catalyst), alkyl aluminum and organosilane, the first propylene was placed in a reactor (reactor level was 70%) for homopolymerization to obtain product I;

[0100] (2) Under a protective atmosphere (nitrogen), hydrogen, second propylene, ethylene and product I are mixed to carry out a copolymerization reaction to obtain block copolymer polypropylene.

[0101] The methods used in the examples of this invention for preparing block copolymer polypropylene are the same, except that the raw material ratios and process parameters are different, resulting in block copolymer polypropylene with different characteristic parameters. The raw material ratios and process parameters of the block copolymer polypropylene are listed in Table 1. The parts not listed are the same as those in preparation example 1.

[0102] Table 1 (Ethylene dosage is 300g, main catalyst dosage is 20mg)

[0103]

[0104]

[0105] Example 1: Preparation of polypropylene material

[0106] First, inorganic filler (silica), antioxidant (a combination of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:2), acid absorber (hydrotalcite) and block copolymer polypropylene prepared in Preparation Example 1 are added to a high-speed mixer for the first mixing. Then, high-density polyethylene is added for the second mixing. Finally, the mixture is extruded and granulated.

[0107] For specific materials and reaction conditions in this embodiment, please refer to Table 2.

[0108] The remaining embodiments were prepared using the same method as in Example 1, except that the materials and reaction conditions were different, as shown in Table 2.

[0109] Table 2 (each part by weight represents 30g)

[0110]

[0111]

[0112] Comparative Example 1

[0113] The method is the same as in Example 1, except that Q1 is replaced with DQ1.

[0114] Comparative Example 2

[0115] The method is the same as in Example 1, except that Q1 is replaced with DQ2, and everything else is the same.

[0116] Test case

[0117] The melt flow index of the polypropylene materials prepared in the test examples is shown in Table 3.

[0118] The polypropylene material prepared in the example was used to prepare polypropylene film. The haze, specular gloss, relative roughness, and heat sealing temperature of the polypropylene film were tested. The degree of edge dispersion, feel, and appearance of the polypropylene film were also recorded. The results are shown in Table 3.

[0119] The method for preparing polypropylene film is the casting method, as detailed below:

[0120] The specific process for preparing polypropylene film is as follows: The polypropylene material prepared in the example is extruded into a film through a slit (slit gap of 0.4-0.65 mm) on a T-shaped die head. The extruded film is then adhered to a cooling roller using compressed air sprayed from an air knife. During the process of the extruded film passing through the cooling roller, the film is stretched and thinned to ultimately form a film with a thickness of 30 micrometers.

[0121] The present invention exemplarily in Figure 1 The image provided is a scanning electron microscope (SEM) image of the block copolymer polypropylene prepared in Example 1. Figure 1 It can be seen that the average particle diameter of the ethylene propylene rubber phase in the block copolymer polypropylene is 0.7-1.3 μm; this indicates that the method for preparing block copolymer polypropylene provided by the present invention can produce a relatively uniform ethylene propylene rubber phase. This ethylene propylene rubber phase enables the polypropylene material to have suitable matting performance when used as a temperature-resistant matting layer of a matting film, and can also ensure that the polypropylene film has high dispersibility and a good feel.

[0122] The present invention exemplarily in Figure 2 The diagram provides a schematic of existing matting films. Figure 3 The diagram provided illustrates the preparation of a polypropylene film from the polypropylene material obtained in Example 1 of this invention, which is then used as a heat-resistant matting layer in a matting film. (Comparison) Figure 2 and Figure 3 As can be seen, the polypropylene film provided by the present invention includes a heat-resistant matting layer (upper surface layer), a core layer, and a heat-sealing layer (lower surface layer), wherein the thickness of the heat-resistant matting layer is 2 μm; while the total thickness of the matting layer and the heat-resistant layer in the prior art matting film is 2 μm. This indicates that the polypropylene film provided by the present invention does not require an additional heat-resistant layer, which can meet the requirements of heat resistance and matting effect, while simplifying its preparation process and reducing product preparation costs.

[0123] Table 3

[0124]

[0125] The results above demonstrate that the block copolymer polypropylene prepared by the method provided in this invention exhibits suitable melt flow properties and outstanding temperature resistance when applied to the preparation of polypropylene materials. It is not easily deformed by heat at high heat-sealing temperatures. Furthermore, the polypropylene film possesses high haze and low gloss. Therefore, this polypropylene material can be directly used as the upper surface layer (temperature-resistant matting layer) of a BOPP matting film, meaning that the polypropylene film simultaneously achieves good matting effect and temperature resistance without the need for an additional temperature-resistant layer.

[0126] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing block copolymer polypropylene, characterized in that, The method includes: (1) In the presence of hydrogen, a main catalyst, alkyl aluminum and organosilane, the first propylene is subjected to homopolymerization to obtain product I; the main catalyst is Ziegler-Natta catalyst; (2) Under a protective atmosphere, hydrogen, second propylene, ethylene and product I are mixed to carry out a copolymerization reaction to obtain the block copolymer polypropylene; In step (1), the weight ratio of the first propylene used to the second propylene used in step (2) is 0.5-1.2:1; The weight ratio of the amount of ethylene used to the total amount of the first propylene and the second propylene used is 0.1-0.5:

1.

2. The method according to claim 1, wherein, In step (1), the conditions for the homopolymerization reaction include: polymerization temperature of 60-80℃, polymerization pressure of 0.04-1MPa, and polymerization time of 10-25min.

3. The method according to claim 1 or 2, wherein, In step (2), the conditions for the copolymerization reaction include: polymerization temperature of 55-85℃, polymerization pressure of 1-8MPa, and polymerization time of 0.5-3h.

4. Block copolymer polypropylene prepared by the method according to any one of claims 1-3.

5. The block copolymer polypropylene according to claim 4, wherein, Based on the total weight of the block copolymer polypropylene, the content of the ethylene propylene rubber phase in the block copolymer polypropylene is 10-25% by weight; the content of the ethylene structural unit is 5-15% by weight. And / or, in the block copolymer polypropylene, the average particle diameter of the ethylene propylene rubber phase is 0.7-1.3 μm; And / or, the melt flow index of the block copolymer polypropylene at 230°C and 2.16 kg load is 1-8 g / 10 min.

6. A method for preparing polypropylene material, characterized in that, The method includes: using block copolymer polypropylene with a density of 0.94-0.96 g / cm³. 3 High-density polyethylene, inorganic fillers, antioxidants and acid absorbers are mixed and then extruded into granules. The block copolymer polypropylene is the block copolymer polypropylene as described in claim 4 or 5.

7. The method according to claim 6, wherein, The amount of high-density polyethylene is 10-70 parts by weight relative to 100 parts by weight of the block copolymer polypropylene, the amount of inorganic filler is 0.1-0.5 parts by weight, the amount of antioxidant is 0.05-0.2 parts by weight, and the amount of acid scavenger is 0.01-0.05 parts by weight.

8. The method according to claim 6 or 7, wherein, The molecular weight of the high-density polyethylene exhibits a unimodal or bimodal distribution. And / or, the melt index of the high-density polyethylene at 190°C and under a load of 21.6 kg is 5-20 g / 10 min; And / or, the weight-average molecular weight of the high-density polyethylene is 240,000-300,000, and the molecular weight distribution index is 17-28.

9. The method according to any one of claims 6-8, wherein, The high-density polyethylene is selected from at least one of 7000F, HTA001, DGDA-6098 and HDPE52090.

10. The method according to any one of claims 6-9, wherein, The inorganic filler is selected from at least one of talc, wollastonite, mica powder and silica; And / or, the antioxidant is a hindered phenolic antioxidant and / or a phosphite antioxidant; And / or, the acid absorber is selected from at least one of sodium stearate, calcium stearate, zinc stearate and hydrotalcite.

11. The method according to any one of claims 6-10, wherein, The mixing conditions include: time of 5-30 min, temperature of 25-65℃, and rotation speed of 50-300 rpm; And / or, the conditions for the extrusion granulation include: a temperature of 160-230°C and a rotation speed of 100-400 rpm.

12. A polypropylene material prepared by the method according to any one of claims 6-11.

13. The polypropylene material according to claim 12, wherein, The melt flow index of the polypropylene material at 230℃ and under a load of 2.16kg is 1.5-5g / 10min.

14. A polypropylene film, characterized in that, The polypropylene film is prepared from the polypropylene material described in claim 12 or 13.

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