A high-temperature resistant plastic and its preparation method

Abstract

This invention discloses a high-temperature resistant plastic and its preparation method, belonging to the field of chemical technology. The high-temperature resistant plastic comprises polyethylene material, which includes: 20-65 wt% of a first polyethylene component, 20-60 wt% of a second polyethylene component, and 10-55 wt% of a third polyethylene component; the first polyethylene component is high molecular weight bimodal high-density polyethylene with a weight-average molecular weight of 280,000-430,000, and the percentage of components with a molecular weight per million obtained by GPC is not less than 10%; the second polyethylene component is L-R polyethylene obtained by blending low-density polyethylene and medium-density heat-resistant polyethylene solutions, with a weight-average molecular weight of 130,000-160,000; the third polyethylene component is low molecular weight high-density polyethylene with a weight-average molecular weight of 50,000-80,000. The polyethylene plastic formulation of this invention simultaneously satisfies the requirements of high-temperature resistance, good mechanical properties, and processing performance, and is easy to prepare and process.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a high-temperature resistant plastic and its preparation method. Background Technology

[0002] As the world's most produced general-purpose plastic, polyethylene (PE) is widely used in packaging, piping, and electronic devices due to its excellent chemical stability, ease of processing, and low cost. Polyethylene is a thermoplastic resin produced by the polymerization of ethylene monomers. Industrially, it also includes copolymers of ethylene with small amounts of α-olefins. Based on molecular weight and different chain structures, it can be classified into high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ultra-high molecular weight polyethylene (UHMWPE), among others.

[0003] However, conventional polyethylene alone has certain shortcomings in terms of heat resistance and mechanical strength. For example, low-density polyethylene (LDPE) has excellent processing properties, but its mechanical properties at high temperatures are significantly reduced due to the lack of long-chain support; while high-density polyethylene (HDPE) is difficult to achieve both good processing properties. This means that single-component polyethylene plastic formulations can hardly meet the requirements of high tensile strength at high temperatures while achieving processability, thus limiting their application in heat-resistant structural components.

[0004] Recent studies have found that regulating the molecular weight distribution of polyethylene may be a new direction for overcoming its heat resistance bottleneck. In polyethylene materials with a wide molecular weight distribution, long-chain molecules can form physical entanglement points to inhibit high-temperature creep, while short-chain polyethylene molecules are beneficial for maintaining processing fluidity. However, how to synergistically optimize the heat resistance, mechanical properties, and processing properties of polyethylene plastic products and expand their application range remains an urgent problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-temperature resistant plastic and its preparation method. The polyethylene plastic formulation of this invention can simultaneously meet the requirements of high temperature resistance, good mechanical properties, and processing performance, and is easy to prepare and process.

[0006] This invention provides a high-temperature resistant plastic, comprising polyethylene material, wherein the polyethylene material comprises: 20-65 wt% of a first polyethylene component, 20-60 wt% of a second polyethylene component, and 10-55 wt% of a third polyethylene component;

[0007] The first polyethylene component is high molecular weight bimodal high-density polyethylene with a weight-average molecular weight of 280,000-430,000, and the proportion of the component with a molecular weight of millions obtained by gel permeation chromatography (GPC) is not less than 10%; the second polyethylene component is LR polyethylene obtained by blending low-density polyethylene and medium-density heat-resistant polyethylene solutions with a weight-average molecular weight of 130,000-160,000; the third polyethylene component is low molecular weight high-density polyethylene with a weight-average molecular weight of 50,000-80,000.

[0008] Furthermore, the first polyethylene component has a number-average molecular weight of 50,000-70,000 and a micro-crosslinked structure, which can be subjected to radiation micro-crosslinking before further processing; the second polyethylene component has a number-average molecular weight of less than 50,000; and the third polyethylene component has a number-average molecular weight of 8,000-15,000.

[0009] In some embodiments of the present invention, the high-temperature resistant plastic further includes additives, which are one or more of lubricants, light stabilizers and antioxidants.

[0010] Furthermore, the additive is a lubricant, which is stearate and / or polyethylene wax.

[0011] Furthermore, the polyethylene material comprises: 55-65 wt% of a first polyethylene component, 20-40 wt% of a second polyethylene component, and 10-35 wt% of a third polyethylene component.

[0012] In some embodiments of the present invention, the high-temperature resistant plastic has a tensile strength of more than 20 MPa at 70°C and a puncture strength of more than 350 N at 70°C with a thickness of 2 mm, provided that the processing requirements are met.

[0013] This invention provides a method for preparing high-temperature resistant plastics as described above, comprising the following steps:

[0014] High molecular weight bimodal high-density polyethylene, LR polyethylene and low molecular weight high-density polyethylene are mixed in a mass ratio, melt extruded and dried to obtain the high temperature resistant plastic.

[0015] The weight-average molecular weight of the high molecular weight bimodal high-density polyethylene is 280,000-430,000; the weight-average molecular weight of the LR polyethylene is 130,000-160,000; and the weight-average molecular weight of the low molecular weight high-density polyethylene is 50,000-80,000.

[0016] In some embodiments of the present invention, the high molecular weight bimodal high-density polyethylene is irradiated with a high-energy electron beam in an air environment to form a micro-crosslinked structure.

[0017] In some embodiments of the present invention, the melt extrusion is carried out using a twin-screw extrusion granulation device, wherein the temperature of the melting section is 200~215°C.

[0018] In some embodiments of the present invention, the high-temperature resistant plastic is in granular form and undergoes high-temperature gel chromatography, rheological and mechanical testing, and the test data is normalized.

[0019] Compared with existing technologies, the high-temperature resistant plastic formulation provided by this invention is based on different molecular weights and their distributions, and is mainly composed of the following polyethylene material components: 20-65 wt% high molecular weight bimodal high-density polyethylene (HDPE), with a weight-average molecular weight (Mw) of 280,000-430,000; 20-60 wt% LR polyethylene (obtained by blending low-density polyethylene and medium-density heat-resistant polyethylene solutions), with a weight-average molecular weight of 130,000-160,000; and 10-60 wt% low molecular weight HDPE, with a weight-average molecular weight of 50,000-80,000. In this invention, the high molecular weight bimodal HDPE and LR polyethylene are synergistically compounded to form a suitable strong entanglement network. Furthermore, the high molecular weight bimodal HDPE has a wider molecular weight distribution than LR polyethylene. The short-chain molecules in the wide-distribution component can reduce melt viscosity and ensure processing fluidity, while the long-chain molecules inhibit high-temperature creep through physical cross-linking. The long-chain narrow-distribution component directionally enhances the tensile strength at high temperatures. The introduction of the low molecular weight HDPE component facilitates material processing and preparation, thereby effectively overcoming the contradiction that a single polyethylene component cannot simultaneously achieve processability and heat resistance.

[0020] Furthermore, this invention uses stearate and polyethylene wax as lubricants, which can form a synergistic lubrication system with low molecular weight high-density polyethylene in high-temperature resistant plastic formulations. This is significantly superior to traditional filled modified PE and can be directly applied to conventional processing equipment such as injection molding and extrusion, avoiding the increased costs caused by complex chemical modifications.

[0021] In addition, this invention establishes a novel evaluation system for multi-component blended plastic materials, which facilitates precise control and optimization. Attached Figure Description

[0022] Figure 1 The graph shows the Mw (weight-average molecular weight) test results for Examples 1-6 of this invention;

[0023] Figure 2 The graph shows the Mn (number average molecular weight) test results for Examples 1-6 of this invention;

[0024] Figure 3 The figures show the rheological test results of Examples 1-6 of the present invention;

[0025] Figure 4 The figures show the tensile test results of Examples 1-6 of the present invention;

[0026] Figure 5 The figures show the elongation test results of Examples 1-6 of the present invention;

[0027] Figure 6 These are tear test results from Examples 1-6 of the present invention;

[0028] Figure 7 The figures show the puncture test results of Examples 1-6 of the present invention;

[0029] Figure 8 These are the test result diagrams for embodiments 1-6 of the present invention;

[0030] Figure 9 This is a comprehensive performance evaluation diagram of embodiments 1-6 of the present invention. Detailed Implementation

[0031] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0032] This invention provides a high-temperature resistant plastic comprising polyethylene material, wherein the polyethylene material comprises: 20-65 wt% of a first polyethylene component, 20-60 wt% of a second polyethylene component, and 10-55 wt% of a third polyethylene component; wherein the first polyethylene component is high molecular weight bimodal high-density polyethylene with a weight-average molecular weight of 280,000-430,000, and the percentage of the component with a molecular weight per million obtained by GPC is not less than 10%; the second polyethylene component is low-density polyethylene (LR) obtained by blending low-density polyethylene and medium-density heat-resistant polyethylene solutions, with a weight-average molecular weight of 130,000-160,000; and the third polyethylene component is low molecular weight high-density polyethylene with a weight-average molecular weight of 50,000-80,000.

[0033] The polyethylene plastic provided by this invention can simultaneously meet the requirements of high temperature resistance and good mechanical properties, and is easy to prepare, process and apply.

[0034] The polyethylene plastic described in this invention is a high-temperature resistant plastic, comprising a multi-component polyethylene material. In this polyethylene material, a high-molecular-weight bimodal high-density polyethylene with a weight-average molecular weight (Mw) of 280,000-430,000 is used as the first polyethylene component, with a mass ratio of 20-65 wt%, further 55-65 wt%, for example 55 wt%, 60 wt%, 62 wt%, 65 wt%, etc., which helps ensure processing fluidity and high-temperature resistance. In some embodiments, its weight-average molecular weight can be 300,000-350,000, melt index is 0.3-1.5 g / 10 min, and density is 0.949-0.987 g / cm³.3 .

[0035] Weight-average molecular weight (Mw) is the average molecular weight calculated by mass, obtained by averaging per unit weight; while the molecular weight averaged by the number of molecules is called number-average molecular weight (Mn). Both can be measured in a single step by gel permeation chromatography. Bimodal polyethylene is a polyethylene resin with a special molecular weight distribution (exhibiting two peaks). Its molecular weight distribution curve shows two distinct peaks. Bimodal polyethylene can also be separated into two single-peaked polyethylene structures based on the corresponding peak positions, with the same effect. Melt index is defined as: the amount of thermoplastic material extruded under specified conditions within a certain time, that is, the mass of melt passing through a standard die capillary every 10 minutes, expressed as MFR, with units of g / 10 min. The test method follows the national standard GB / T 3682 (equivalent to international standard ISO 1133 and American ASTM D1238).

[0036] The high molecular weight bimodal high-density polyethylene described in this invention embodiment has a relatively wide molecular weight distribution and can be referred to as high molecular weight wide molecular weight distribution bimodal polyethylene, etc. Its number average molecular weight Mn can be 50,000-70,000, the first peak appears at around 30,000, the second peak appears at around 300,000, and the ultra-high molecular weight part (molecular weight greater than one million) accounts for 10%-15%, and it needs to be obtained through micro-crosslinking (having a micro-crosslinked structure).

[0037] The polyethylene material described in this embodiment of the invention includes: 20-60 wt% of a second polyethylene component, preferably 20-40 wt%; the second polyethylene component is LR polyethylene (obtained by solution blending of low-density polyethylene and medium-density heat-resistant polyethylene PE-RT), with a weight-average molecular weight (Mw) of 130,000-160,000, and also has a relatively narrow molecular weight distribution, which can be called long-chain narrow molecular weight distribution polyethylene, which is beneficial for improving tensile strength at high temperatures. For example, LDPE and PE-RT with similar molecular weights (around 150,000) can form a more uniform network structure through solution blending, resulting in better mixing effect and lower heat damage to the material than twin-screw extrusion; where normal twin-screw extrusion requires 200 degrees Celsius, solution blending requires 140 degrees Celsius. In some embodiments, its weight-average molecular weight (Mw) is 130,000-160,000, and its number-average molecular weight (Mn) is 30,000-50,000; the melt index is 0.5-2.2 g / 10 min, and the density is 0.92-0.96 g / cm³. 3 .

[0038] Furthermore, the polyethylene material includes a third polyethylene component of 10-55 wt%, preferably 10-35 wt% (e.g., 10%, 15%, 20%); the third polyethylene component is a low molecular weight high-density polyethylene with a weight-average molecular weight (Mw) of 50,000-80,000, a melt index of 17-20 g / 10 min, and a density of 0.95-0.98 g / cm³. 3 It has high liquidity, etc.

[0039] In a preferred embodiment, the polyethylene material comprises: 55-65 wt% of a first polyethylene component, 20-40 wt% of a second polyethylene component, and 10-35 wt% of a third polyethylene component.

[0040] This invention primarily addresses the harmonious performance of polyethylene plastics across multiple properties by optimizing molecular weight distribution and systematically studying the synergistic mechanism between multi-peak distribution morphology and heat resistance and mechanical properties. Specifically, it utilizes molecular weight distribution and other factors to achieve optimal performance across various aspects. In this invention, embodiments are developed that precisely control the proportions and topological structures of polyethylene components with different molecular weights, achieving synergistic optimization of high-temperature resistance, processing performance, and mechanical strength without the need for external reinforcing fillers or complex chemical modifications.

[0041] The high-temperature resistant plastic formulation based on molecular weight distribution and other controlled parameters described in this invention embodiment further includes additives, which are one or more of lubricants, light stabilizers, and antioxidants. The lubricant is preferably stearate (mainly zinc stearate) and / or polyethylene wax; the low molecular weight high-density polyethylene can act as a flow promoter, forming a synergistic lubrication system with polyethylene wax and zinc stearate, which is more beneficial to the processing.

[0042] In a preferred embodiment of the invention, the light stabilizer is hindered amine particles; the antioxidant is also in masterbatch form, for example, dilauryl thiodipropionate. In a preferred embodiment, the additive is a combination of lubricant, light stabilizer, and antioxidant. Preferably, the added additive is 100% polyethylene material, wherein: zinc stearate 1-3 wt%, polyethylene wax 2-4 wt%, hindered amine particles 1-3 wt%, and antioxidant masterbatch 1-3 wt%.

[0043] This invention provides a method for preparing high-temperature resistant plastics as described above, comprising the following steps:

[0044] High molecular weight bimodal high-density polyethylene, low molecular weight polyethylene (LR) and low molecular weight high-density polyethylene are mixed in a mass ratio, with optional additives added, and then melt-extruded and dried to obtain the high-temperature resistant plastic; the weight average molecular weight of the high molecular weight bimodal high-density polyethylene is 280,000-430,000; the weight average molecular weight of the LR polyethylene is 130,000-160,000; and the weight average molecular weight of the low molecular weight high-density polyethylene is 50,000-80,000.

[0045] Regarding the raw materials involved, the high molecular weight bimodal polyethylene, LR polyethylene, and low molecular weight high density polyethylene correspond to the first polyethylene component, second polyethylene component, and third polyethylene component mentioned above, respectively, and will not be described in detail here. The raw materials used in the embodiments of the present invention can be commercially available products. The high molecular weight bimodal high density polyethylene can form its micro-crosslinked structure in an air environment by high-energy electron beam irradiation.

[0046] In some specific embodiments, the high molecular weight bimodal high-density polyethylene component undergoes micro-crosslinking, including the following steps:

[0047] The granules are evenly spread in the high-energy irradiation crosslinking inlet container to ensure that all granules are evenly dispersed in the bottom layer without overlapping.

[0048] The flat granules are irradiated with a high-energy electron beam in air at room temperature. Preferably, the irradiation time is 0.3s per irradiation, the absorbed dose is 1MGy, the duration is 30s, and the total absorbed amount is 9MGy, which can form a micro-crosslinked structure.

[0049] In some specific embodiments, the LR polyethylene component needs to be obtained by solution blending, including the following steps:

[0050] Place LDPE (70wt%) and PE-RT (30wt%) in a three-necked flask, and antioxidants 168 and 1018 can be added in combination, each at 0.1% (by mass).

[0051] The mixture was stirred for 2 hours in xylene solvent (the volume of the added solution was greater than 10 times the sum of the volumes of the added LDPE and PE-RT) at a constant temperature of 138 ℃ and a stirring rotor speed of 175 rpm.

[0052] After cooling, pour the mixture into a beaker and add sufficient methanol to precipitate the precipitate. Dry the precipitate in a vacuum oven at 40 °C for 24 hours to obtain LR polyethylene raw material. Crush the precipitate with a pulverizer to obtain small and uniform LR polyethylene raw material.

[0053] In some embodiments of the present invention, a twin-screw extrusion granulation device can be used to melt-extrude and granulate the mixed formulation raw materials, wherein the temperature of the melting section can be controlled between 200 and 215°C. Afterwards, the embodiments of the present invention can be dried, preferably with the moisture content after drying controlled to be below 0.2%. The embodiments of the present invention can directly use conventional processing equipment such as injection molding and extrusion, simplifying the preparation process and reducing costs.

[0054] In some embodiments of the present invention, the high-temperature resistant plastic is in granular or sheet form; wherein it can be extruded into sheet form by a single screw, thus producing a high-temperature resistant plastic sheet product. For example, the high-temperature resistant plastic described in the embodiments of the present invention, under the premise of meeting processing requirements, has a tensile strength of over 20 MPa at 70°C and a puncture strength of over 350 N (2 mm thickness) at 70°C, exhibiting good mechanical properties, high temperature resistance, and simple preparation.

[0055] Furthermore, the embodiments of the present invention have undergone high-temperature gel chromatography, rheological and mechanical testing, and the test data have been normalized. The key achievement is the establishment of a polyethylene material evaluation system, which, compared with single test judgment, can more scientifically and accurately evaluate the comprehensive performance of blended materials.

[0056] Furthermore, in the aforementioned evaluation system, the formula for evaluating the comprehensive performance of the components is as follows:

[0057] (1);

[0058] in:

[0059] G com(x,y,z) The score is the comprehensive performance evaluation score of the components;

[0060] (x,y,z) represents the ratio of the three polyethylene components, x+y+z=100; the components mixed in different proportions are extruded by a twin-screw extruder and then granulated.

[0061] x represents the proportion of high molecular weight bimodal polyethylene with a wide molecular weight distribution. The raw material is enhanced by pre-micro crosslinking (irradiation time is 0.3s per irradiation, absorbed dose is 1MGy, lasts for 30s, and the total absorbed amount is 9MGy).

[0062] y represents the proportion of long-chain, narrow molecular weight distribution (LR) polyethylene, which is obtained by solution mixing of LDPE (70wt%) and PE-RT (30wt%) at 138°C for 2 hours, followed by precipitation.

[0063] z represents the proportion of low molecular weight high-density polyethylene (HDPE).

[0064] α, β, +β=1, where β and β are the balance coefficients for the front and rear parts, respectively, and can be adjusted according to the product's processability. Here, we take β=1. =β=0.5.

[0065] I Ln(Vrheology(x,y,z)) Rheological viscosity (after normalization);

[0066] I Mw The weight-average molecular weight index (after normalization) was determined by high-temperature gel permeation chromatography (GPC).

[0067] Ten. represents the tensile strength index of a material (after normalization), at room temperature (25°C);

[0068] El represents the elongation at break of the material (after normalization), at room temperature (25°C);

[0069] Tea represents the tear strength index of the material (after normalization) at room temperature (25°C);

[0070] Pu represents the puncture strength index (normalized) of the material at room temperature (25°C).

[0071] The normalization calculations and specific implementation methods are as follows:

[0072] =[(LnV rheology(x,y,z) -LnV rheologyMin ) / (LnV rheologyMax -LnV rheologyMin )]×100 (2;

[0073] V rheology(x,y,z) For rheological test results (Pa·s) of any component, Ln VrheologyMin Ln is the minimum value of the test results for the system (which can be understood as all results in the rheological test). VrheologyMax The maximum value of the system test results; Test conditions: flat plate rheometer, 215℃, flow sweep, 215℃; Shear rate: 0.01-100s. -1 The shear rate is taken as 0.025 s. -1 The viscosity value corresponding to that time is the usable value. Rheological testing is conducted by measuring viscosity at a series of shear rates, and a suitable viscosity at a shear rate that indicates smooth processing of the extrusion process can be selected.

[0074] =[(Mw (x,y,z) -Mw Min ) / (Mw Max -Mw Min )]×100 (3;

[0075] Mw (x,y,z)For theoretical calculations of any component, Mw Min Mw is the minimum value of the theoretical calculation results for the system. Max The maximum value of the theoretical calculation result of the system is used. Test conditions: The molecular weights of components x, y, and z are calculated. The sample is fused in trichlorobenzene for 24 hours, and then tested using high-temperature gel permeation chromatography (GPC). The coefficients k and α use the standard values ​​for polyethylene. In determining the molecular weight of polymers using GPC, k and α are key parameters in the Mark-Houwink equation, used to establish the quantitative relationship between intrinsic viscosity η and molecular weight M. The k value is the Mark-Houwink constant, reflecting the flexibility and hydrodynamic volume of the polymer chain in a specific solvent, and is related to the interaction between the polymer and solvent system. The standard k value for polyethylene is 1.725. The α value is the Mark-Houwink exponent, used to describe molecular morphology (such as the degree of coil extension), and its value range is usually 0.5 ≤ α ≤ 2.0. The standard α value for polyethylene is 0.67. The formula is: η = K·M α (The calculation process can be obtained through computer software).

[0076] The molecular weight information of each component can then be calculated using formulas. The calculation formulas for blending the three components in different proportions are as follows: m1, m2, and m3 are the mass fractions of the three original, unblended polyethylenes in a given formulation; W1, W2, and W3 are the weight-average molecular weights (Mw) of the three original polyethylenes measured using the GPC testing method described above; and Mn1, Mn2, and Mn3 are the weight-average molecular weights (Mn) of the three original polyethylenes measured using the GPC testing method described above.

[0077] (4);

[0078] (5).

[0079] Ten. (x,y,z) =[(Tensile strength (x,y,z) -Tensile strength Min ) / (Tensilestrength Max -Tensile strength Min )]×100 (6);

[0080] Tensile strength (x,y,z) Tensile strength (MPa) is the test result for any component. Min The minimum value of the system test results, Tensile strength MaxThe maximum value of the system test results; Test conditions: GB / T 1040.1-2018 / ISO527-1:2012 "Determination of tensile properties of plastics", 250 mm / min, stretched to breakage, in accordance with national standards.

[0081] El. (x,y,z) =[(Elongation (x,y,z) -Elongation Min ) / (Elongation Max -Elongation Min )]×100 (7);

[0082] Elongation (x,y,z) Elongation test results for any component Min Elongation is the minimum value of the system test results. Max The maximum value of the system test results; Test conditions: GB / T 1040.1-2018 / ISO527-1:2012 "Determination of tensile properties of plastics", which conforms to the national standard.

[0083] Tea. (x,y,z) =[(Tear strength (x,y,z) -Tear strength Min ) / (Tear strength Max -Tear strength Min )]×100 (8);

[0084] Tear strength (x,y,z) Tear strength is the result of a tear strength test for any component. Min The minimum value of the system test results, Tear strength Max The maximum value of the system test results; Test conditions: GB / T 529-2008 "Determination of tear strength of vulcanized rubber or thermoplastic rubber (trouser-shaped, right-angled, crescent-shaped specimens)", 25 mm / min, stretched to breakage, in accordance with national standards;

[0085] Pu. (x,y,z) =[(Puncture strength (x,y,z) -Puncture strength Min ) / Puncturestrength Max -Puncture strength Min )]×100 (9;

[0086] Puncture strength (x,y,z) For breakdown strength test results of any component, Puncturestrength Min The minimum value of the system test results, Puncture strength Max The maximum value of the system test results; Test conditions: TB / T 3360.1-2014 "Railway Tunnel Waterproofing Materials Part 1: Waterproof Membrane", 100 mm / min, puncture to breakage, in accordance with industry standards.

[0087] In addition to the calculation results above, some performance data under extreme conditions should also be excluded. The performance testing limit here is taken at room temperature as an example; the limit for the final sample can be:

[0088] Weight-average molecular weight Mw ≥ 120,000;

[0089] 20000≤Number-average molecular weight Mn≤50000;

[0090] V rheology(x,y,z) ≤500000 Pa·s;

[0091] Tensile strength ≥ 20 MPa.

[0092] In some embodiments, the above G is selected. com(x,y,z) The highest-ranking component within the restricted range is used as the specific implementation component. The components are then physically mixed uniformly and extruded through a twin-screw extruder to obtain the finished plastic product. Alternatively, a high-temperature resistant plastic product can be obtained by extruding sheets through a single screw extruder.

[0093] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention. The substances used in the embodiments of this invention are commercially available; zinc stearate, polyethylene wax, hindered amine particles, and antioxidant masterbatch are all common additives on the market, meeting the basic requirements for materials.

[0094] High molecular weight bimodal high-density polyethylene component x: melt index 0.3-1.5 g / 10 min, density 0.949-0.987 g / cm³. 3 Specifically, the selectable grade is Sinopec Tianjin Zhongsha Petrochemical PN049-030-122, or it can be obtained by mixing two HDPEs with narrow distribution, such as 2911 from PetroChina Fushun Petrochemical Branch and 5000s from PetroChina Dushanzi Petrochemical Branch, mixed at a mass ratio of 1:1.

[0095] The above-mentioned high molecular weight bimodal high-density polyethylene component x is first subjected to micro-crosslinking, with a melt index of 0.34~0.36 g / 10min. The steps include: uniformly spreading the x component granules in a high-energy irradiation crosslinking inlet container to ensure that all particles are uniformly dispersed in the bottom layer without overlap; irradiating the granules in air at room temperature with a high-energy electron beam; the irradiation time is 0.3s per irradiation, the absorbed dose is 1MGy, the duration is 30s, and the total absorbed dose is 9MGy.

[0096] LR polyethylene (y): This component is a blend of LDPE and PE-RT solution. The melt index of LR polyethylene is 1.8-2.1 g / 10 min, and the density is 0.930-0.950 g / cm³. 3 Specifically, the available grades are 3711 (PE-RT) from Daqing Petrochemical Company of China National Petroleum Corporation or 2388 (PE-RT) from Dow Chemical Company of the United States. For LDPE, Ube Chemical of Japan can choose F222.

[0097] Low molecular weight high-density polyethylene (HMWPE): melt index 17-20 g / 10 min, density 0.950-0.980 g / cm³ 3 The specific grades that can be selected are Dow Chemical Company's 9820, China National Petroleum Corporation's Dushanzi Petrochemical Branch's 8920, or Saudi Basic Industries Corporation's M200056.

[0098] Example

[0099] (1) Configure an instance group containing a sufficient number of implementation cases, specifically expressed as a percentage by quality, as shown in the table below.

[0100] Table 1 Component formulations for different specific examples

[0101]

[0102] (2) By subjecting the raw materials of the above different comparative examples and embodiments to twin-screw co-extrusion granulation, polyethylene plastic material can be obtained, including the following steps:

[0103] S1. The mixed formula is granulated and extruded using a twin-screw extruder. The extrusion granulation process parameters are shown in the table below.

[0104] Table 2 Specific process parameters for melt extrusion granulation

[0105]

[0106] S2. After granulation and extrusion, the granules are dried at 60°C, and the moisture content of the dried material is 0.20%.

[0107] (3) The material obtained after twin-screw co-extrusion granulation is subjected to high-temperature gel chromatography, rheology and different types of mechanical tests, and the obtained data is normalized, including the following steps:

[0108] Step A: Perform high-temperature gel permeation chromatography and normalize the Mn and Mw values, as detailed below:

[0109] Test conditions: Samples of components x, y, and z were melted in trichlorobenzene and subjected to high-temperature gel permeation chromatography after 24 hours. Coefficients k and α were calculated using standard values ​​for polyethylene. The molecular weights of each component were then calculated using the aforementioned formula. The test results for Mw and Mn, combined with the calculation results, are shown in [reference to relevant documentation]. Figure 1 , Figure 2 Then use I Mw The formula was used to normalize the data, resulting in the results shown in Table 3.

[0110] Table 3 Test and normalization results of Mw in Example 1

[0111]

[0112] Step B: Perform rheological tests according to the aforementioned test conditions, and normalize V. rheology(x,y,z) Numerical values; see the rheological test results combined with the calculation results. Figure 3 Then use I Ln(Vrheology(x,y,z)) The formula was used to normalize the data, resulting in the results shown in Table 4.

[0113] Table 4. Rheological test and normalization results of the examples

[0114]

[0115] Step C: Perform a tensile test under the aforementioned test conditions and normalize the tensile strength. (x,y,z) Numerical values. For tensile test results, please refer to... Figure 4 Then use Ten. (x,y,z) The formula, after normalizing the data, yields the following table.

[0116] Table 5 Tensile test and normalized results of the examples

[0117]

[0118] Step D: Perform a tensile test and normalize the elongation. (x,y,z) Numerical values. For elongation test results, please refer to... Figure 5 Then use El. (x,y,z) The formula, after normalizing the data, yields the following table.

[0119] Table 6. Elongation Test and Normalization Results of Examples

[0120]

[0121] Step E: Perform a tear test and normalize the tear strength. (x,y,z) Numerical values. For tear test results, please refer to... Figure 6 Then use Tea. (x,y,z) The formula, after normalizing the data, yields the following table.

[0122] Table 7. Tear Test and Normalization Results of Examples

[0123]

[0124] Step F: Perform a puncture test and normalize the puncture strength. (x,y,z) Numerical values. For the puncture test results, please refer to... Figure 7 Then use Pu. (x,y,z) The formula is used to normalize the data, resulting in the table below.

[0125] Table 8. Puncture test and normalization results of the examples

[0126]

[0127] Substituting the above parameters into the final material evaluation system formula yields the following tables. For the test results, please refer to [link to relevant documentation]. Figure 8 .

[0128]

[0129] Table 9 Evaluation test results of Comparative Examples 1-8

[0130]

[0131] Table 10 Evaluation test results of Comparative Examples 9-19

[0132]

[0133] Table 11 Evaluation Test Results of the Example

[0134]

[0135] Based on the above calculations, some materials with extreme data in certain aspects should be excluded because they would strongly affect the material's processing and performance. The performance testing limits here are: Mw ≥ 120000, 20000 ≤ Mn ≤ 50000, V rheology(x,y,z)≤500000 Pa·s, Tensile strength ≥20 MPa. Combining the above constraints with G... com(x,y,z) By drawing the diagram, we can obtain... Figure 9 .

[0136] Based on the above results and the limitations of the restricted domain, the shaded area in the final graphic is a display of the overall performance under the premise of meeting individual requirements. Figure 9 As can be seen, the system reaches its maximum value in the upper left corner. Therefore, the plastic formulation of this application embodiment includes: high molecular weight bimodal polyethylene (x): 55-65 wt%, long-chain narrow molecular weight polyethylene (LR): 20-40 wt%, and low molecular weight high-density polyethylene (z): 10-35 wt%; its overall performance is good.

[0137] Of the above combinations, Example 1 is the optimal ratio. The superior performance of Example 1 can be demonstrated by comparisons of various performance aspects with other examples, so there is no need for further elaboration.

[0138] Example 7

[0139] High molecular weight bimodal polyethylene with broad molecular weight distribution (x): 60wt%; long-chain narrow molecular weight distribution (LR) polyethylene (y): 20wt%; low molecular weight high-density polyethylene (z): 20wt%.

[0140] Additional additives: 1 wt% zinc stearate, 2 wt% polyethylene wax, 1.5 wt% histamine particles, and 1.5 wt% antioxidant masterbatch, to ensure the overall performance of the material. The table below provides a detailed description of the additives:

[0141] Table 12 Types of Additives in the Examples

[0142]

[0143] Then, twin-screw extrusion of the sheet material is carried out to a thickness of 2mm, using the same process as before.

[0144] Comparative Example 20: High molecular weight bimodal polyethylene with a wide molecular weight distribution (x): 60 wt%, long-chain narrow molecular weight distribution (LR) polyethylene (y): 20 wt%, low molecular weight high-density polyethylene (z): 120 wt%; no additives. The mixture was then extruded using a twin-screw extruder to a thickness of 2 mm, following the same process as before.

[0145] The resulting sheet material was subjected to 70-degree heat aging and ultraviolet irradiation for 144 hours, with a xenon lamp at 550W / m. 2 After 250 hours of irradiation, tensile, tear, and puncture tests were performed at room temperature. The test methods were the same as before, and the test temperature was room temperature. Tensile and tear samples were taken along the extrusion direction. Three sets of parallel tests were performed for each test. The data were compiled into the table below.

[0146] Table 13 Performance Comparison with and without Additives

[0147]

[0148] Example: High temperature resistance test - 70 degrees Celsius test

[0149] High molecular weight bimodal polyethylene (x): 60wt%, long-chain narrow molecular weight polyethylene (y): 20wt%, low molecular weight high-density polyethylene (z): 20wt%; Additives: zinc stearate 1wt%, polyethylene wax 2wt%, histamine particles 1.5wt%, antioxidant masterbatch 1.5wt%, to ensure the overall performance of the material.

[0150] The sheet material is then extruded using a twin-screw extruder to a thickness of 2mm. The process temperatures are set to be the same, but the temperatures of the three-roll calender after extrusion are different, as detailed below:

[0151] Example 8: The temperatures of the three rollers are 50 ℃ / 75 ℃ / 60 ℃ respectively.

[0152] Example 9: The temperatures of the three rollers are 75 ℃ / 75 ℃ / 60 ℃ respectively.

[0153] Example 10: The temperatures of the three rollers are 75 ℃ / 80 ℃ / 60 ℃ respectively.

[0154] Tensile and puncture tests were conducted at 70℃, using the same method as before. Five parallel tests were performed for each test, and the data were compiled into the table below, demonstrating its ability to withstand high temperatures (provided that processing and usage performance are met).

[0155] Table 14 High Temperature Resistance Test Results

[0156]

[0157] As can be seen from the above embodiments, the polyethylene plastic formulation of the present invention can simultaneously meet the requirements of high temperature resistance, good mechanical properties and processing performance, and is easy to prepare and process.

[0158] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be noted that due to the limitations of textual expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A high-temperature resistant plastic, comprising polyethylene material, characterized in that, The polyethylene material comprises: 20-65 wt% of a first polyethylene component, 20-60 wt% of a second polyethylene component, and 10-55 wt% of a third polyethylene component; The first polyethylene component is high molecular weight bimodal high-density polyethylene with a weight-average molecular weight of 280,000-430,000, and the proportion of components with a molecular weight of at least one million obtained by gel permeation chromatography is not less than 10%; the second polyethylene component is LR polyethylene obtained by blending low-density polyethylene and medium-density heat-resistant polyethylene solutions, with a weight-average molecular weight of 130,000-160,000; the third polyethylene component is low molecular weight high-density polyethylene with a weight-average molecular weight of 50,000-80,000; the first polyethylene component has a number-average molecular weight of 50,000-70,000 and has a micro-crosslinked structure; the second polyethylene component has a number-average molecular weight of less than 50,000; and the third polyethylene component has a number-average molecular weight of 8,000-15,000.

2. The high-temperature resistant plastic according to claim 1, characterized in that, The high-temperature resistant plastic also includes additives, which are one or more of lubricants, light stabilizers, and antioxidants.

3. The high-temperature resistant plastic according to claim 2, characterized in that, The additive is a lubricant, which is stearate and / or polyethylene wax.

4. The high-temperature resistant plastic according to claim 1, characterized in that, The polyethylene material comprises: 55-65 wt% of a first polyethylene component, 20-40 wt% of a second polyethylene component, and 10-35 wt% of a third polyethylene component.

5. The high-temperature resistant plastic according to claim 1, characterized in that, The high-temperature resistant plastic, under the premise of meeting processing requirements, has a tensile strength of over 20 MPa at 70℃ and a puncture strength of over 350 N at 70℃ with a thickness of 2 mm.

6. The method for preparing high-temperature resistant plastic according to any one of claims 1-5, characterized in that, Includes the following steps: High molecular weight bimodal high-density polyethylene, LR polyethylene and low molecular weight high-density polyethylene are mixed in a mass ratio, melt extruded and dried to obtain the high temperature resistant plastic. The weight-average molecular weight of the high molecular weight bimodal high-density polyethylene is 280,000-430,000; the weight-average molecular weight of the LR polyethylene is 130,000-160,000; and the weight-average molecular weight of the low molecular weight high-density polyethylene is 50,000-80,000.

7. The preparation method according to claim 6, characterized in that, The high molecular weight bimodal high-density polyethylene forms a micro-crosslinked structure by high-energy electron beam irradiation in an air environment.

8. The preparation method according to claim 6, characterized in that, The melt extrusion is carried out using a twin-screw extrusion granulation equipment, wherein the temperature of the melting section is 200~215℃.

9. The preparation method according to any one of claims 6-8, characterized in that, The high-temperature resistant plastic is in granular or plate form, and undergoes high-temperature gel chromatography, rheological and mechanical testing, followed by normalization of the test data.

Images