Compositions containing polypropylene, polypropylene materials and their preparation methods, polypropylene films

Abstract

This invention relates to the field of polypropylene film packaging technology, and discloses a polypropylene-containing composition, a polypropylene material, a method for preparing the same, and a polypropylene film. The polypropylene-containing composition of this invention contains a propylene polymer and an ethylene polymer; wherein, based on the total weight of the composition, the content of the ethylene polymer is 0.5-5% by weight; wherein, based on the total weight of the propylene polymer, the content of ethylene structural units in the propylene polymer is 0.3-5% by weight, the content of 1-butene structural units is 5-10% by weight, and the content of propylene structural units is 85-94% by weight. Polypropylene films prepared using the polypropylene-containing composition or polypropylene material of this invention, when used as packaging materials, better avoid contamination of the packaged goods by the precipitation of soluble substances during processing, and possess high transparency, high stiffness, and low-temperature heat-sealing performance, resulting in better packaging appearance, and are particularly suitable as the heat-sealing layer of multilayer films.

Description

Technical Field

[0001] This invention relates to the field of polypropylene film packaging technology, specifically to polypropylene-containing compositions, polypropylene materials and their preparation methods, and polypropylene films. Background Technology

[0002] Polypropylene film is widely used in the packaging materials field due to its excellent optical properties, mechanical properties, and packaging adaptability. Polypropylene film can be prepared using a unidirectional casting film processing technology. Whether in the preparation process or in its use as packaging, it is undesirable for the film to contain excessive soluble substances. This is because soluble substances have low molecular weights, cannot crystallize at room temperature, and easily migrate to the film surface. During film preparation, they can stick to the conveyor rollers, causing excessive stops for cleaning, and can contaminate the packaged goods during use. Furthermore, achieving higher heat-sealing strength at lower heat-sealing temperatures remains a development trend in heat-sealing materials. This meets the requirements of high-speed packaging and energy conservation and environmental protection, and also avoids wrinkling of cast polypropylene films due to high heat-sealing temperatures during rapid packaging. Therefore, for propylene polymers formed by the polymerization of propylene, ethylene, and α-olefins, the content of soluble and insoluble substances in hexane and the melting temperature of the propylene polymer have a significant impact on the initial heat-sealing temperature and anti-heat-blocking properties of the film formed from this propylene polymer, and also greatly affect the stiffness and gloss of the prepared film.

[0003] CN102453180A discloses that films prepared using butene-propylene copolymers have good transparency and low soluble content, but it does not study the heat-sealing temperature of the films.

[0004] CN 109265594A discloses an ethylene-propylene-butadiene ternary copolymer polypropylene, its preparation method, and its applications. The ethylene-propylene-butadiene ternary copolymer polypropylene has a weight-average molecular weight of 210,000-270,000, a molecular weight distribution of 3-4, an ethylene content of 2.5-3.3% by mass, and a butene content of 6.5-8.0% by mass. When used as a heat-sealing layer material, the heat-sealing temperature is 108-113℃. However, this invention does not address performance improvements in terms of lower heat-sealing temperatures, lower leachate, and higher film stiffness, thus failing to meet the current high-speed processing requirements of cast films. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of high heat-sealing temperature of polypropylene films in the prior art, and to provide a polypropylene-containing composition, polypropylene material and its preparation method, and polypropylene film. The polypropylene material of this invention has the characteristics of low melting temperature, and is suitable for the preparation of uniaxially stretched polypropylene film. The polypropylene film obtained has high transparency, high stiffness and low initial heat-sealing temperature, and can be used in the packaging of fast food, books and audio-visual products, wine, pharmaceuticals and other products.

[0006] To achieve the above objectives, a first aspect of the present invention provides a composition containing polypropylene, said composition comprising a propylene polymer and an ethylene polymer;

[0007] Wherein, based on the total weight of the composition, the content of the ethylene polymer is 0.5-5% by weight;

[0008] Based on the total weight of the propylene polymer, the propylene polymer contains 0.3-5% by weight of ethylene structural units, 5-10% by weight of 1-butene structural units, and 85-94% by weight of propylene structural units.

[0009] A second aspect of the present invention provides a method for preparing a polypropylene material, the method comprising melt-blending and extruding the above-mentioned polypropylene-containing composition into granules.

[0010] A third aspect of the present invention provides a polypropylene material obtained by the above preparation method.

[0011] A fourth aspect of the present invention provides a polypropylene film, which is obtained by unidirectional casting and stretching of the above-mentioned polypropylene-containing composition or polypropylene material.

[0012] Through the above technical solutions, the polypropylene material made from the polypropylene-containing composition of the present invention has a lower hexane-soluble content and a lower melting temperature. The polypropylene film made from the polypropylene-containing composition or polypropylene material of the present invention can better avoid the precipitation of soluble substances during the processing and contamination of the packaged product. It also has high transparency, high stiffness and low temperature heat-sealing performance, and can obtain a better packaging appearance. It is especially suitable as a heat-sealing layer of multilayer films. Detailed Implementation

[0013] 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.

[0014] A first aspect of the present invention provides a composition containing polypropylene, said composition comprising a propylene polymer and an ethylene polymer;

[0015] Wherein, based on the total weight of the composition, the content of the ethylene polymer is 0.5-5% by weight;

[0016] Based on the total weight of the propylene polymer, the propylene polymer contains 0.3-5% by weight of ethylene structural units, 5-10% by weight of 1-butene structural units, and 85-94% by weight of propylene structural units.

[0017] The inventors discovered in their research that when the composition contains the aforementioned amount of ethylene polymer, it is beneficial to maintain the mechanical properties of the cast polypropylene film at a lower processing temperature, reduce processing defects, and at the same time lower the initial heat-sealing temperature and widen the heat-sealing window.

[0018] In this invention, the "propylene polymer" refers to a polymer containing propylene structural units, ethylene structural units and 1-butene structural units, namely, ethylene-propylene-butene random copolymer polypropylene.

[0019] In this invention, unless otherwise specified, the propylene structural unit refers to the structural unit provided by propylene monomer, the ethylene structural unit refers to the structural unit provided by ethylene monomer, and the 1-butene structural unit refers to the structural unit provided by 1-butene monomer.

[0020] In some embodiments of the present invention, based on the total weight of the propylene polymer, the content of ethylene structural units in the propylene polymer is 1.5-3% by weight, the content of 1-butene structural units is 5-8% by weight, and the content of propylene structural units is 89-93.5% by weight. When the content of ethylene, 1-butene, and propylene structural units in the propylene polymer is within the above range, the prepared polypropylene material has a high flexural modulus, and the prepared polypropylene cast film has higher transparency, high stiffness, and low-temperature heat-sealing performance, resulting in a better packaging appearance.

[0021] In some embodiments of the present invention, the melt index of the propylene polymer at 230°C and 2.16 kg load is 1-15 g / 10 min.

[0022] In this invention, the ethylene polymer can be obtained commercially or prepared by various methods known to those skilled in the art.

[0023] In this invention, the propylene polymer can be prepared by the propylene polymer preparation method provided in the second aspect of this invention.

[0024] In some embodiments of the present invention, to further improve the transparency of the obtained polypropylene film, the content of the ethylene polymer is 1-3% by weight, based on the total weight of the composition. More preferably, the content of the ethylene polymer is 1-2% by weight.

[0025] In this invention, "ethylene polymer" refers to a polymer containing ethylene structural units. The ethylene polymer may also contain 1-butene structural units. That is, the ethylene polymer can be homopolymer polyethylene or ethylene-butene random copolymer polyethylene. More preferably, the ethylene polymer is ethylene-butene random copolymer polyethylene. The ethylene structural units and 1-butene structural units are as described above.

[0026] In some embodiments of the present invention, the melt index of the ethylene polymer at 190°C and a load of 2.16 kg is 10-20 g / 10 min, and the density of the ethylene polymer is 0.945-0.956 g / cm³. 3 .

[0027] In some embodiments of the present invention, based on the total weight of the ethylene polymer, the content of ethylene structural units in the ethylene polymer is 99-100% by weight, and the content of 1-butene structural units is 0-1% by weight. The inventors have found that when the ethylene polymer is ethylene-butene random copolymer polyethylene, it is beneficial to reduce the initial heat-sealing temperature. Preferably, based on the total weight of the ethylene polymer, the content of ethylene structural units in the ethylene polymer is 99-99.5% by weight, and the content of 1-butene structural units is 0.5-1% by weight.

[0028] In some embodiments of the present invention, the composition further comprises a processing aid, which is at least one selected from antioxidants, acid absorbers, opening agents, and slip agents.

[0029] In some embodiments of the present invention, the antioxidant content is 0.05-0.2% by weight, based on the total weight of the composition.

[0030] In some embodiments of the present invention, the acid absorbent content is 0.01-0.05% by weight, based on the total weight of the composition.

[0031] In some embodiments of the present invention, the content of the opening agent is 0-0.2% by weight, based on the total weight of the composition.

[0032] In some embodiments of the present invention, the content of the slip agent is 0-0.15% by weight, based on the total weight of the composition.

[0033] In some embodiments of the present invention, the antioxidant is a hindered phenolic and / or phosphite antioxidant, preferably one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (abbreviated as: Antioxidant 1010), octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl) phosphite (abbreviated as: Antioxidant 168), bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, and 2,6-di-tert-butyl-4-methylbenzene.

[0034] In some embodiments of the present invention, the acid absorbent is at least one of calcium stearate, zinc stearate, and hydrotalcite, preferably hydrotalcite.

[0035] In some embodiments of the present invention, the opening agent is silicon dioxide.

[0036] In some embodiments of the present invention, the slip agent is at least one of erucamide, oleamide, stearamide and N,N-ethylenebis-stearamide, preferably erucamide.

[0037] A second aspect of the present invention provides a method for preparing polypropylene materials, characterized in that the method includes melt blending, extrusion granulation of the polypropylene-containing composition as described above.

[0038] In some embodiments of the present invention, the propylene polymer contained in the polypropylene-containing composition is obtained by polymerizing propylene, ethylene and butene in the presence of a catalyst and hydrogen.

[0039] In some embodiments of the present invention, the butene contains not less than 99.0% by weight of 1-butene, not more than 20 mg / kg of water, and not more than 5 mg / kg of total sulfur.

[0040] In some embodiments of the present invention, based on the total amount of propylene, butene, and ethylene, the amount of propylene is 85-94% by weight, the amount of ethylene is 1-5% by weight, and the amount of butene is 5-10% by weight. More preferably, based on the total amount of propylene, butene, and ethylene, the amount of propylene is 90-93% by weight, the amount of ethylene is 2-3% by weight, and the amount of butene is 5-7% by weight.

[0041] In some embodiments of the present invention, the conditions for the polymerization reaction include: a polymerization temperature of 55-85°C, a polymerization pressure of 1-8 MPa, and a polymerization time of 0.5-3 h.

[0042] In some embodiments of the present invention, the weight ratio (H2 / C3) of the hydrogen to the propylene monomer is 0.01-0.02:1. Preferably, the weight ratio of the hydrogen to the propylene monomer can be 0.013-0.018:1.

[0043] In this invention, the catalyst can be a commonly used catalyst for olefin polymerization, such as a Ziegler-Natta catalyst. The amount of Ziegler-Natta catalyst can be selected based on the total amount of monomers. For example, based on 100 parts by weight of the total weight of propylene, ethylene, and butene, the amount of Ziegler-Natta catalyst can be 0.001-0.01 parts by weight. The type of Ziegler-Natta catalyst can be conventionally selected in the art, as long as the activity of the polymerization reaction is ensured; this is well known to those skilled in the art and will not be elaborated upon here.

[0044] In some embodiments of the present invention, the extrusion granulation conditions are: a temperature of 200-230°C.

[0045] A third aspect of the present invention provides a polypropylene material obtained by the preparation method described above.

[0046] In some embodiments of the present invention, the melt index of the polypropylene material is 1-15 g / 10 min, preferably 4-8 g / 10 min. The melt index is determined according to the method specified in GB / T3682-2000. The test conditions include a temperature of 230°C and a load of 2.16 kg.

[0047] In some embodiments of the present invention, the hexane-soluble content of the polypropylene material is 1-10% by weight, preferably 3-5% by weight.

[0048] In this invention, the content of n-hexane-soluble matter is determined by the following method: 4g of polypropylene material (with an error range of ±0.001g), 1mm × 1mm × 1mm in shape, is weighed and added to a Soxhlet extractor. 200mL of n-hexane is then added to the Soxhlet extractor, and the mixture is heated until the n-hexane boils. After boiling for 2 hours, the material is washed with the same batch of n-hexane for 4 hours, cooled, and then weighed. The difference between the original weight of the polypropylene material and the weight after washing is the content of n-hexane-soluble matter.

[0049] In some embodiments of the present invention, the melting temperature of the polypropylene material is 125-140°C.

[0050] In this invention, the melting temperature is determined using differential scanning calorimetry: approximately 5 mg of sample is heated to 200 °C at a rate of 10 °C / min under N2 protection, held at that temperature for 10 min to eliminate the influence of the sample's thermal history, and then cooled at a rate of 10 °C / min to obtain the crystallization temperature (T). c ) and heat of crystallization (ΔH) c The temperature was then increased to 180℃ at a rate of 10℃ / min to obtain the melting peak and melting point (T0) of the sample. m ) and heat of fusion (ΔH) m Tm is the melting temperature of the sample.

[0051] In some embodiments of the present invention, the flexural modulus of the polypropylene material is 500-800 MPa, preferably 700-800 MPa.

[0052] The flexural modulus of the polypropylene material was tested according to GB / T 9341-2000.

[0053] A fourth aspect of the present invention provides a polypropylene film, said polypropylene film being prepared by unidirectional casting and stretching of a polypropylene-containing composition as described above or a polypropylene material as described above.

[0054] In some embodiments of the present invention, the thickness of the polypropylene film is <100μm, preferably 30-50μm, and more preferably 30μm.

[0055] In some embodiments of the present invention, when the thickness of the film is 30 μm, the haze of the film is 0.5-5%, preferably 1-1.5%.

[0056] In some embodiments of the present invention, when the thickness of the film is 30 μm, the initial heat sealing temperature of the film is 105-110°C, preferably 106-108°C.

[0057] In this invention, the haze of the film is tested according to GB / T 2410-2008.

[0058] In this invention, taking a film thickness of 30 μm as an example, the test method for the initial heat-sealing temperature of the film is as follows: Polypropylene material is used to make a film with a width of 15 mm and a thickness of 30 μm. Two films are pressed together at 1°C intervals, with 105°C as the initial test temperature. The heat-sealing time is 1 second, the heat-sealing pressure is 0.3 MPa, and after being placed under constant temperature and humidity for 48 hours, the force required to peel off the sample is measured using an Instron 5566 material testing machine with a clamp distance of 50 mm and a test speed of 300 mm / min. The initial test temperature at which the measured force is above 2.5 N is taken as the initial heat-sealing temperature.

[0059] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials and reagents are all commercially available.

[0060] In the following examples, the content of 1-butene in butene is not less than 99.0% by weight, the water content is not greater than 20 mg / kg, and the total sulfur content is not greater than 5 mg / kg.

[0061] Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (abbreviated as Antioxidant 1010) was purchased from Ciba Specialty Chemicals.

[0062] Tris(2,4-di-tert-butylphenyl) phosphite (abbreviated as Antioxidant 168) was purchased from Ciba Specialty Chemicals.

[0063] The hydrotalcite was purchased from Kyowa Corporation of Japan.

[0064] Triethylaluminum was purchased from Beijing Aoda Petrochemical Co., Ltd.

[0065] The following embodiments involve the following test methods:

[0066] 1. Melt Flow Index: This is determined according to the method specified in GB / T 3682-2000. Specifically, the test temperature for polypropylene or propylene polymers or polypropylene materials is 230℃, and the load is 2.16 kg; the test temperature for polyethylene or ethylene polymers is 190℃, and the load is 2.16 kg.

[0067] 2. Hexane-soluble content of polypropylene material: Weigh 4g of polypropylene material (error range ±0.001g), with a shape of 1mm×1mm×1mm, and add it to a Soxhlet extractor. Add 200mL of hexane to the Soxhlet extractor and heat until the hexane boils. After boiling for 2 hours, rinse with the same batch of hexane for 4 hours, cool, and weigh the rinsed material. The difference between the original weight and the weight after rinsing is the hexane-soluble content.

[0068] 3. Content of propylene, ethylene, and 1-butene structural units in the propylene polymer: determined by carbon nuclear magnetic resonance (CMR) spectroscopy. The solvent was deuterated o-dichlorobenzene. CMR spectroscopy was performed on a BRUKER 400 NMR spectrometer purchased from Bruker, Switzerland. Test conditions included: operating frequency 100.62 MHz, 30° pulse, pulse duration 3 s, full decoupling of proton noise, spectral width 15000 Hz, 4000 stoichiometric iterations, and calibration using isolated methylene carbon at 30.0 ppm.

[0069] 4. The test method for the initial heat-sealing temperature is as follows: Polypropylene material is prepared into a film with a width of 15 mm and a thickness of 30 μm. Two films are pressed together at 1℃ intervals, with an initial test temperature of 105℃. The heat-sealing time is 1 second, and the heat-sealing pressure is 0.3 MPa. After being placed under constant temperature and humidity for 48 hours, the force required to peel off the sample is measured using an Instron 5566 material testing machine with a clamp distance of 50 mm and a test speed of 300 mm / min. The initial test temperature at which the measured force is above 2.5 N is taken as the initial heat-sealing temperature.

[0070] 5. Haze of polypropylene film: determined according to GB / T 2410-2008.

[0071] 6. Flexural modulus of polypropylene material: determined according to GB / T 9341-2000.

[0072] 7. The melting temperature of polypropylene material was determined using differential scanning calorimetry: Approximately 5 mg of sample was heated to 200 °C at a rate of 10 °C / min under N2 protection, held at that temperature for 10 min to eliminate the influence of the sample's thermal history, and then cooled at a rate of 10 °C / min to obtain the crystallization temperature (T). c ) and heat of crystallization (ΔH) c The temperature was then increased to 180℃ at a rate of 10℃ / min to obtain the melting peak and melting point (T0) of the sample. m ) and heat of fusion (ΔH) m Tm is the melting temperature of the sample.

[0073] Preparation Example 1

[0074] (1) The solid catalyst component (titanium tetrachloride supported on magnesium chloride, purchased from Beijing Aoda Petrochemical Co., Ltd.) was continuously added to 50m³ at a rate of 0.61 g / h. 3 In a continuous horizontal stirred bed gas-phase reactor, triethylaluminum is continuously added by a pump (the amount of triethylaluminum added makes the molar ratio of aluminum in triethylaluminum to titanium in the solid catalyst component Al / Ti = 30).

[0075] (2) Propylene, ethylene, butene, and hydrogen are introduced into the reactor for polymerization. The conditions of the polymerization reaction include: the pressure inside the reactor is 1.4 MPa, the temperature inside the reactor is 65°C, and the hydrogen / propylene weight ratio (H2 / C3) in the reactor is 0.015. Based on the total amount of propylene, ethylene, and butene, the amount of propylene is 89% by weight, the amount of ethylene is 3% by weight, and the amount of butene is 8% by weight. The average residence time of ethylene, propylene, butene, and hydrogen in the reactor is 60 min, and the reactor material level is 70%. Propylene polymer is obtained. During the polymerization process, there is no phenomenon of polymer particles clogging the material discharge pipe of the reactor.

[0076] (3) The propylene polymer was blended with the ethylene polymer, antioxidant 1010, antioxidant 168, and hydrotalcite. Based on the total weight of the composition, the amount of propylene polymer added was 98.8% by weight. The ethylene polymer C1 (a random copolymer of ethylene-butadiene polyethylene, purchased from Yanshan Petrochemical Company, with a melt index of 10 g / 10 min and a density of 0.945 g / cm³ at 190°C and a load of 2.16 kg) was also blended. 3 Based on the total weight of the ethylene polymer, the following additives were used: ethylene structural units (99% by weight), 1-butene structural units (1% by weight), antioxidant 1010 (0.05% by weight), antioxidant 168 (0.1% by weight), and hydrotalcite (0.05% by weight). The blended materials were then granulated at 220°C using a twin-screw extruder. This melt-mixing and granulation process yielded polypropylene material A1.

[0077] The contents of ethylene, propylene, and 1-butene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of polypropylene material A1 are shown in Table 2.

[0078] Preparation Example 2

[0079] Polypropylene material A2 was prepared in a manner similar to that used in Preparation Example 1, except that in step (2), based on the total amount of propylene, ethylene and butene, the amount of propylene was 90.5% by weight, the amount of ethylene was 1.8% by weight, and the amount of butene was 7.7% by weight.

[0080] In step (3), ethylene polymer C1 is replaced with an equal mass of ethylene polymer C2 (ethylene-butadiene random copolymer polyethylene, purchased from Yanshan Petrochemical Company, with a melt index of 10 g / 10 min and a density of 0.950 g / cm³ at 190℃ and 2.16 kg load). 3Based on the total weight of the ethylene polymer, the content of ethylene structural units is 99.5% by weight, and the content of 1-butene structural units is 0.5% by weight.

[0081] The contents of ethylene, propylene, and 1-butene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of polypropylene material A2 are shown in Table 2.

[0082] Preparation Example 3

[0083] Polypropylene material A3 was prepared in a manner similar to that used in Preparation Example 1, except that in step (2), based on the total amount of propylene, ethylene and butene, the amount of propylene was 90.1% by weight, the amount of ethylene was 2.9% by weight, and the amount of butene was 7% by weight.

[0084] In step (3), the amount of propylene polymer added is 97.8% by weight and the amount of ethylene polymer added is 2% by weight, based on the total weight of the composition.

[0085] The contents of ethylene, propylene, and 1-butene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of polypropylene material A3 are shown in Table 2.

[0086] Preparation Example 4

[0087] Polypropylene material A4 was prepared in a manner similar to that used in Preparation Example 1, except that in step (2), based on the total amount of propylene, ethylene and butene, the amount of propylene was 89.7 wt%, the amount of ethylene was 0.3 wt%, and the amount of butene was 10 wt%.

[0088] The contents of ethylene, propylene, and 1-butene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of polypropylene material A4 are shown in Table 2.

[0089] Preparation Example 5

[0090] Polypropylene material A5 was prepared in a manner similar to that of Preparation Example 1, except that in step (3), the amount of propylene polymer added was 96.8% by weight and the amount of ethylene polymer added was 3% by weight, based on the total weight of the composition.

[0091] The contents of ethylene, propylene, and 1-butene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of polypropylene material A5 are shown in Table 2.

[0092] Preparation Example 6

[0093] Polypropylene material A6 was prepared in a manner similar to that used in Preparation Example 1, except that in step (2), based on the total amount of propylene, ethylene and butene, the amount of propylene was 88.5 wt%, the amount of ethylene was 1.5 wt%, and the amount of butene was 10 wt%.

[0094] In step (3), ethylene polymer C1 is replaced with ethylene polymer C2 (which is ethylene-butadiene random copolymer polyethylene, purchased from Yanshan Petrochemical Company, with a melt index of 10 g / 10 min and a density of 0.950 g / cm³ at 190℃ and 2.16 kg load). 3 Based on the total weight of the ethylene polymer, the content of ethylene structural units is 99.5% by weight and the content of 1-butene structural units is 0.5% by weight, and based on the total weight of the composition, the amount of propylene polymer added is 97.8% by weight and the amount of ethylene polymer C2 added is 2% by weight.

[0095] The contents of ethylene, propylene, and 1-butene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of polypropylene material A6 are shown in Table 2.

[0096] Preparation Example 7

[0097] Polypropylene material A7 was prepared in a manner similar to that of Preparation Example 1, except that in step (3), the components to be blended also included an opening agent and a slip agent. Based on the total weight of the composition, the amount of the opening agent silica added was 0.1 wt%, the amount of the slip agent erucamide added was 0.1 wt%, the amount of the propylene polymer added was 98.6 wt%, and the amount of the ethylene polymer added was 1 wt%.

[0098] The contents of ethylene, propylene, and 1-butene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of polypropylene material A7 are shown in Table 2.

[0099] Preparation Example 8

[0100] Polypropylene material A8 was prepared in a similar manner to that used in Preparation Example 1, except that in step (3), ethylene polymer C1 was replaced with an equal mass of ethylene polymer C3 (homopolymer polyethylene, purchased from Yanshan Petrochemical Company, with a melt index of 10 g / 10 min and a density of 0.953 g / cm³ at 190 °C and a load of 2.16 kg). 3 ).

[0101] The contents of ethylene, propylene, and 1-butene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of polypropylene material A8 are shown in Table 2.

[0102] Preparation of Comparative Example 1

[0103] Polypropylene material DA1 was prepared in a manner similar to that used in Preparation Example 1. The difference was that in step (2), propylene, butene, and hydrogen were introduced into the reactor to carry out the polymerization reaction. Based on the total weight of ethylene, propylene, and butene, the amount of propylene was 88% by weight, the amount of ethylene was 0.5% by weight, and the amount of butene was 11.5% by weight.

[0104] In step (3), based on the total weight of the composition, the amount of ethylene polymer C1 added is 10% by weight, and the amount of propylene polymer added is 89.8% by weight.

[0105] The contents of ethylene, propylene, and 1-butene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of the prepared polypropylene material DA1 are shown in Table 2.

[0106] Preparation of Comparative Example 2

[0107] Polypropylene material DA1 was prepared in a manner similar to that used in Preparation Example 1. The difference was that in step (2), propylene, ethylene and hydrogen were introduced into the reactor to carry out a polymerization reaction. Based on the total amount of propylene and ethylene, the amount of propylene was 95% by weight and the amount of ethylene was 5% by weight.

[0108] In step (3), no ethylene polymer C1 is added, and the amount of propylene polymer added is 99.8% by weight.

[0109] The contents of ethylene and propylene structural units in the propylene polymer obtained in step (2) and the melt index of the propylene polymer at 230℃ and 2.16kg load are shown in Table 1. The properties of the prepared polypropylene material DA2 are shown in Table 2.

[0110] Preparation of Comparative Example 3

[0111] Polypropylene material DA3 was prepared in a manner similar to that used in Preparation Example 1. The difference was that in step (2), propylene and hydrogen were introduced into the reactor to carry out a polymerization reaction. The amount of propylene used was 100% by weight. The melt index of the polypropylene obtained at 230°C and 2.16 kg load is shown in Table 1.

[0112] The properties of the prepared polypropylene material DA3 are shown in Table 2.

[0113] Preparation of Comparative Example 4

[0114] Polypropylene material B9 was prepared in a manner similar to that of Preparation Example 1, except that ethylene polymer C1 was not added, and the amount of propylene polymer added was 99.8% by weight, based on the total weight of the composition.

[0115] The properties of the prepared polypropylene material DA4 are shown in Table 2.

[0116] Example 1

[0117] This example illustrates a polypropylene film prepared using the composition of the present invention.

[0118] Polypropylene material A1 is used to form a polypropylene film using a casting method. The specific process flow is as follows:

[0119] Polypropylene material A1 is melted in an extruder, and the melt is extruded through a slit in a T-shaped die head (slit gap 0.4-0.65mm) to form a film. The extruded film is then pressed onto a cooling roller by 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, eventually forming a 30μm thick film, namely polypropylene film B1.

[0120] The properties of the prepared polypropylene film B1, including initial heat-sealing temperature, haze, and light transmittance, are shown in Table 3.

[0121] Examples 2-8

[0122] Polypropylene films B2-B8 were prepared in a manner similar to that in Example 1, except that polypropylene materials A2-A8 were used.

[0123] The properties of the prepared polypropylene films B2-B8, such as initial heat-sealing temperature, haze, and light transmittance, are shown in Table 3.

[0124] Comparative Examples 1-4

[0125] Polypropylene films DB1-DB4 were prepared in a manner similar to that in Example 1, except that polypropylene materials DA1-DA4 were used.

[0126] The properties of the prepared polypropylene films DB1-DB4, including initial heat-sealing temperature, haze, and light transmittance, are shown in Table 3.

[0127] Table 1

[0128]

[0129] Table 1 (continued)

[0130]

[0131] Table 2

[0132] polypropylene material A1 A2 A3 A4 A5 A6 Melting temperature (°C) 131 134 132 134 130 135 Melt index (g / 10min) 7.1 7.4 7.3 5.9 8.3 8.5 Content of n-hexane solubles (wt%) 4.6 3.4 4.1 3.5 4.9 4.4 Flexural modulus (MPa) 750 728 735 731 781 798

[0133] Table 2 (continued)

[0134] polypropylene material A7 A8 DA1 DA2 DA3 DA4 Melting temperature (°C) 132 132 141.8 144 166 131 Melt index (g / 10min) 7.1 7.1 5.9 6.1 7.9 7.2 Content of n-hexane solubles (wt%) 4.8 4.6 6.2 5.9 1.5 5.8 Flexural modulus (MPa) 754 740 760 810 1450 650

[0135] Table 3

[0136] Polypropylene film B1 B2 B3 B4 B5 B6 Initial heat sealing temperature (°C) 105 105 105 106 105 108 Haze (%) 1.0 0.9 1 1.1 1.5 1.3 Light transmittance (%) 93.1 92.9 93.3 92.8 90.5 92.9 Cast film processing speed (m / min) 200 220 210 190 230 220

[0137] Table 3 (continued)

[0138] Polypropylene film B7 B8 DB1 DB2 DB3 DB4 Initial heat sealing temperature (°C) 106 106 118 121 125 110 Haze (%) 1 1.2 3.0 2.5 4.0 1.2 Light transmittance (%) 93.5 92.3 89.8 90.5 88.9 93.1 Cast film processing speed (m / min) 200 220 150 160 200 160

[0139] As can be seen from the preparation examples and comparative examples, the polypropylene material of the present invention has a low melting point, low precipitation, and high modulus. As can be seen from the examples and comparative examples, the polypropylene film of the present invention has a low initial heat-sealing temperature, low haze, and fast processing speed.

[0140] As can be seen from the preparation of Comparative Example 3 and Comparative Example 3, although the polypropylene material prepared by homopolymer polypropylene has a low content of hexane-soluble matter, the polypropylene film prepared by it has high haze and does not meet the requirement of transparent appearance; the initial heat sealing temperature is high and the heat sealing performance is poor, so it cannot be used as a packaging film.

[0141] 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 polypropylene material, characterized in that, The preparation method of polypropylene material includes melt blending, extrusion granulation, and granulation of a polypropylene-containing composition; The hexane-soluble content of the polypropylene material is 3-4.8% by weight. The composition contains a propylene polymer and an ethylene polymer; The content of the ethylene polymer is 1-2% by weight, based on the total weight of the composition. Based on the total weight of the propylene polymer, the propylene polymer contains 0.3-5% by weight of ethylene structural units, 5-10% by weight of 1-butene structural units, and 89-93.5% by weight of propylene structural units. Based on the total weight of the ethylene polymer, the content of ethylene structural units in the ethylene polymer is 99-99.5% by weight, and the content of 1-butene structural units is 0.5-1% by weight.

2. The polypropylene material according to claim 1, wherein, Based on the total weight of the propylene polymer, the content of ethylene structural units in the propylene polymer is 1.5-3% by weight, and the content of 1-butene structural units is 5-8% by weight.

3. The polypropylene material according to claim 1 or 2, wherein, The composition further comprises a processing aid, which is at least one of an antioxidant, an acid absorber, an opening agent, and a slip agent.

4. The polypropylene material according to claim 3, wherein, Based on the total weight of the composition, the antioxidant content is 0.05-0.2% by weight. And / or, based on the total weight of the composition, the content of the acid absorbent is 0.01-0.05% by weight. And / or, based on the total weight of the composition, the content of the opening agent is 0-0.2% by weight. And / or, based on the total weight of the composition, the content of the slip agent is 0-0.15% by weight.

5. The polypropylene material according to claim 4, wherein, The antioxidant is a hindered phenolic and / or phosphite antioxidant; And / or, the acid absorbent is at least one of calcium stearate, zinc stearate, and hydrotalcite; And / or, the opening agent is silicon dioxide; And / or, the slip agent is at least one of erucamide, oleamide, stearamide and N,N-ethylenebis-stearamide.

6. The polypropylene material according to claim 5, wherein, The antioxidant is at least one selected from pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, and 2,6-di-tert-butyl-4-methylbenzene.

7. The polypropylene material according to claim 6, wherein, The acid absorbent is hydrotalcite; And / or, the slip agent is erucamide.

8. The polypropylene material according to claim 7, wherein, The polypropylene-containing composition contains a propylene polymer obtained by polymerizing propylene, ethylene, and butene in the presence of a catalyst and hydrogen. And / or, the butene contains not less than 99% by weight of 1-butene, not more than 20 mg / kg of water, and not more than 5 mg / kg of total sulfur; And / or, the conditions for the polymerization reaction include: a polymerization temperature of 55-85°C, a polymerization pressure of 1-8 MPa, and a polymerization time of 0.5-3 h; And / or, the conditions for the extrusion granulation are: a temperature of 200-230°C.

9. The polypropylene material according to claim 1, wherein, The polypropylene material has a melt flow index of 1-15 g / 10 min at 230°C and 2.16 kg load; And / or, the melting temperature of the polypropylene material is 125-140°C; And / or, the flexural modulus of the polypropylene material is 500-800 MPa.

10. The polypropylene material according to claim 9, wherein, The polypropylene material has a melt flow index of 4-8 g / 10 min at 230°C and 2.16 kg load; And / or, the melting temperature of the polypropylene material is 125-140°C; And / or, the flexural modulus of the polypropylene material is 700-800 MPa.

11. A polypropylene film, characterized in that, The polypropylene film is obtained by unidirectional casting and stretching of the polypropylene material according to claim 1.

12. The polypropylene film according to claim 11, wherein, The thickness of the film is <100μm.

13. The polypropylene film according to claim 12, wherein, The thickness of the film is 30-50 μm.

14. The polypropylene film according to claim 13, wherein, The thickness of the film is 30 μm.

15. The polypropylene film according to claim 13, wherein when the thickness of the film is 30 μm, the haze of the film is 0.5-5%; And / or, when the thickness of the film is 30 μm, the initial heat sealing temperature of the film is 105-110 °C.

16. The polypropylene film according to claim 15, wherein when the thickness of the film is 30 μm, the haze of the film is 1-1.5%; And / or, when the thickness of the film is 30 μm, the initial heat sealing temperature of the film is 106-108 °C.

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