Polypropylene composition resistant to high-temperature creep, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a polypropylene composition resistant to high-temperature creep, and a preparation method therefor and the use thereof. The polypropylene composition resistant to high-temperature creep comprises the following components in parts by weight: 70-92 parts of a polypropylene resin; 5-20 parts of a branched linear low-density polyethylene resin; and 3-10 parts of an ultrahigh-molecular-weight polypropylene resin, wherein the branched linear low-density polyethylene resin is obtained by subjecting a linear low-density polyethylene resin to an irradiation treatment, and the ratio of M1 / M2 of the branched linear low-density polyethylene resin is not less than 10:1, with M2 being 3-45 g / 10 min. By adding a small amount of the branched linear low-density polyethylene resin and the ultrahigh-molecular-weight polypropylene resin to a polypropylene resin system, a super-entanglement structure is formed by means of a bridging effect, thereby making the polypropylene composition have good resistance to high-temperature creep; moreover, all the components are compatible with one another, and the polypropylene composition has a good fluidity.

Description

A high temperature creep resistant polypropylene composition and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of polymer materials, and more particularly to a high-temperature creep-resistant polypropylene composition, a preparation method thereof, and an application thereof. Background Art

[0002] Polypropylene, with its low density, acid and alkali resistance, and affordability, is widely used across various industries. Its use in the automotive industry is gradually expanding, driven by national policies on carbon peak and carbon neutrality and international public opinion on global carbon emissions. The auxiliary radiator of traditional fuel vehicles is made of polypropylene, with some specifications featuring pure polypropylene composites and others featuring PP and glass fiber reinforced polypropylene composites. Regardless of the technology approach, polypropylene suffers from relatively weak creep resistance at high temperatures. Therefore, thicker wall thicknesses are required in the design of components like the auxiliary radiator to mitigate this risk.

[0003] In the prior art, there are two main approaches to improving the high-temperature creep resistance of polypropylene composites: adding aspect-ratio fillers or nucleating agents to increase physical bonding points; and creating micro-crosslinking or molecular chain shuttling. However, both approaches are limited by the polypropylene resin and cannot achieve high-temperature creep resistance while maintaining high flowability, which in turn affects the processing performance of the polypropylene material. Therefore, there is a need in the art to develop a polypropylene composition that is resistant to high-temperature creep and also exhibits good flow properties.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to provide a high-temperature creep-resistant polypropylene composition in order to overcome the defects in the above-mentioned prior art. The polypropylene composition has good high-temperature creep resistance and good fluidity.

[0006] Another object of the present invention is to provide a method for preparing the high-temperature creep-resistant polypropylene composition.

[0007] Another object of the present invention is to provide application of the high temperature creep resistant polypropylene composition in automobiles.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A high-temperature creep-resistant polypropylene composition comprises the following components calculated in parts by weight: 70 to 92 parts of a polypropylene resin; 5 to 20 parts of a branched linear low-density polyethylene resin; 3 to 10 parts of an ultra-high molecular weight polypropylene resin;

[0010] The branched linear low-density polyethylene resin M1 / M2 is not less than 10:1; M1 is the melt flow rate of the branched linear low-density polyethylene resin at 190°C and a 10kg load; M2 is the melt flow rate of the branched linear low-density polyethylene resin at 190°C and a 2.16kg load; and M2 is 3 to 45g / 10min.

[0011] The invention provides a high-temperature creep-resistant polypropylene composition. The high-temperature creep-resistant polypropylene composition is prepared by adding a small amount of branched linear low-density polyethylene resin and an ultra-high molecular weight polypropylene resin to a polypropylene resin. The high-temperature creep-resistant polypropylene composition utilizes the bonding force between the ultra-high molecular weight polypropylene resin and the polypropylene resin and the high-temperature creep resistance of the ultra-high molecular weight polypropylene resin through a "bridging" effect, combines the high-temperature creep resistance of the branched linear low-density polyethylene resin with the high-temperature creep resistance of the ultra-high molecular weight polypropylene resin, and forms a super-entangled structure, so that the polypropylene composition has good high-temperature creep resistance. The ultra-high molecular weight polypropylene acts as an "entanglement link" between the polypropylene resin and the branched linear low-density polyethylene resin. When the ratio M1 / M2 of the branched linear low-density polyethylene resin is within a specific range, as M1 / M2 increases, it indicates that the branched linear low-density polyethylene resin has more long chain branches, more branches, and more entanglement physical points, thereby enabling the polypropylene composition to obtain better high-temperature creep resistance. At the same time, due to the addition of a small amount of branched linear low-density polyethylene resin, the fluidity of the composition will not be significantly reduced, and the composition has good high-temperature creep resistance.

[0012] Specifically, the M2 is 3 to 45 g / 10 min, for example, it can be 5, 7, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40 or 42 g / 10 min, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0013] Specifically, the mass parts of the polypropylene resin are 70 to 92 parts, for example, 72 parts, 75 parts, 77 parts, 80 parts, 82 parts, 85 parts, 88 parts or 90 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0014] The mass parts of the branched linear low-density polyethylene resin are 5 to 20 parts, for example, 7 parts, 10 parts, 12 parts, 15 parts or 18 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0015] The mass parts of the ultra-high molecular weight polypropylene resin are 3 to 10 parts, for example, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts or 9 parts, as well as specific point values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0016] Furthermore, the high temperature creep resistant polypropylene composition comprises the following components calculated in parts by weight:

[0017] Furthermore, the M2 is 10 to 25 g / 10 min.

[0018] It should be noted that the melt flow rate described in the present invention is measured in accordance with ISO 1133-2011.

[0019] It should be noted that the content of polypropylene resin in the polypropylene composition of the present invention is not less than 65 wt%.

[0020] It should be understood by those skilled in the art that the weight average molecular weight of the ultra-high molecular weight polypropylene resin in the present invention is not less than 100w.

[0021] In a specific embodiment, the weight average molecular weight of the ultra-high molecular weight polypropylene resin is 100w to 150w.

[0022] The weight average molecular weight of the polypropylene resin in the present invention is 10w to 35w.

[0023] The present invention also protects a branched linear low-density polyethylene resin, characterized in that the M1 / M2 of the branched linear low-density polyethylene resin is not less than 10:1; M1 is the melt flow rate of the branched linear low-density polyethylene resin at 190°C and a 10kg load; M2 is the melt flow rate of the branched linear low-density polyethylene resin at 190°C and a 2.16kg load; the M2 is 3 to 45 g / 10min; further, the M2 is 10 to 25 g / 10min.

[0024] Furthermore, the preparation method of the branched linear low-density polyethylene resin is as follows:

[0025] The linear low-density polyethylene was obtained by irradiating it with 60Co gamma rays under vacuum conditions.

[0026] Furthermore, the irradiation dose is 5 to 8 kgy, and the irradiation time is 20 to 28 hours.

[0027] In a specific embodiment, the preparation method is as follows:

[0028] All linear low-density polyethylene samples were compression-molded into 1 mm thick flat sheets using a hydraulic press at 170–190°C for 1–5 minutes at a maximum pressure of 10 MPa. The sheets were then cooled at room temperature and placed in a Pyrex tube connected to a vacuum glass line, where they were placed under high vacuum for 20–28 hours. The samples were then sealed in the same Pyrex tube. Sample irradiation was performed at room temperature using a 60Co gamma-ray source.

[0029] Specifically, the radiation dose is measured using a red organic glass dosimeter. After irradiation, the sample is annealed at 130-150° C. for 1.5-2.5 hours, and the sample is crushed to obtain branched linear low-density polyethylene.

[0030] Furthermore, the M1 / M2 of the branched linear low-density polyethylene resin is (13-20):1.

[0031] Furthermore, the polypropylene resin has a melt flow rate of 3.0 to 35.0 g / 10 min at 230° C. and 2.16 kg.

[0032] Furthermore, the polypropylene resin is a homopolymer polypropylene resin or a copolymer polypropylene resin.

[0033] Furthermore, the ultra-high molecular weight polypropylene resin is a homopolymer ultra-high molecular weight polypropylene resin or a copolymer ultra-high molecular weight polypropylene resin.

[0034] Furthermore, the ultra-high molecular weight polypropylene resin has a melt flow rate of 0.1 to 15 g / 10 min at 230° C. and a load of 2.16 kg.

[0035] Specifically, the melt flow rate of the ultra-high molecular weight polypropylene resin at 230° C. and a load of 2.16 kg is 0.1 to 15 g / 10 min, for example, but not limited to, 0.2, 0.3, 0.5, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5 g / 10 min, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention no longer exhaustively lists the specific points included in the range.

[0036] Furthermore, the antioxidant can be selected from commonly used antioxidants, including hindered phenol antioxidants, phosphite antioxidants, diphenylamine antioxidants, copper salt antioxidants or thioether antioxidants.

[0037] Specifically, the hindered phenol antioxidant is one or more of N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide (Irganox 1098), pentaerythritol tetrakis[1093,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010), triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate (Iragnox 259), β-(4-hydroxy-3,5-di-tert-butylphenyl) propionate n-octadecyl (Iragno 1076) or spiroethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] (ADK AO-80).

[0038] The phosphite antioxidant is one or more of 2,4-di-tert-butylphenol (Irganox 168), bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol phosphite (PEP-36) or 627A.

[0039] It should be noted that the polypropylene composition of the present invention may further include one or more of a lubricant, a colorant, an anti-ultraviolet agent or a filler without impairing the effects of the present invention.

[0040] The method for preparing the high-temperature creep-resistant polypropylene composition of the present invention comprises the following steps:

[0041] Polypropylene resin, branched linear low-density polyethylene resin, ultra-high molecular weight polypropylene resin and antioxidant are mixed and added into an extruder, and granulated by melt extrusion to obtain a high-temperature creep-resistant polypropylene composition.

[0042] Furthermore, the mixing speed is 300-400 rpm.

[0043] Furthermore, the mixing time is 120 to 240 seconds.

[0044] Furthermore, the melting temperature is 200-220°C.

[0045] The present invention protects the use of the high-temperature creep-resistant polypropylene composition in automobiles, for example, in the preparation of materials for cold air outlet pipes, water chambers or cooling fans in automobiles.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention provides a high-temperature creep-resistant polypropylene composition. The high-temperature creep-resistant polypropylene composition is prepared by adding a small amount of branched linear low-density polyethylene resin and ultra-high molecular weight polypropylene resin to a polypropylene resin system. A super-entangled structure is formed through a "bridging" effect, so that the polypropylene composition has good high-temperature creep resistance. At the same time, since the small amount of branched linear low-density polyethylene resin does not significantly reduce the fluidity of the polypropylene composition, the melt flow rate of the polypropylene composition is not less than 10 g / 10 min, the composition has good processing performance, and the creep rupture time is not less than 200 h. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with specific embodiments, but the examples do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the examples of the present invention are conventionally purchased raw materials and reagents.

[0049] The raw materials used in the embodiments and comparative examples of the present invention are:

[0050] Polypropylene resin:

[0051] Polypropylene resin 1: melt flow rate at 230°C and 2.16 kg: 12.0 g / 10 min, weight average molecular weight: 24w, PP HP500N, CNOOC Shell Petrochemical Co., Ltd.

[0052] Polypropylene resin 2: 230°C, melt flow rate at 2.16 kg: 26.0 g / 10 min, weight-average molecular weight: 19w, PPH-Y26 (ZHONGKE), Zhongke (Guangdong) Refining and Chemical Co., Ltd.

[0053] Branched linear low density polyethylene resin:

[0054] Linear low-density polyethylene resin 1: 190°C, melt flow rate at 2.16 kg: 20.0 g / 10 min, LLDPE-7144, Maoming Petrochemical;

[0055] Linear low-density polyethylene resin 2: 190°C, melt flow rate at 2.16 kg: 50.0 g / 10 min, TJZS-2650, Tianjin Petrochemical;

[0056] The branched linear low-density polyethylene resin used in the present invention is prepared by the following method:

[0057] All linear low-density polyethylene samples were compression-molded into 1 mm thick flat sheets using a hydraulic press at 180°C for 2 minutes at a maximum pressure of 10 MPa. These were then cooled at room temperature and placed in a Pyrex tube connected to a vacuum glass line, where they were placed under high vacuum for 24 hours. The samples were then sealed in the same Pyrex tube. The samples were irradiated at room temperature using a 60Co gamma-ray source.

[0058] Specifically, the radiation dose was measured using a red organic glass dosimeter. After irradiation, the sample was annealed at 140°C for 2 hours and then crushed to obtain branched linear low-density polyethylene.

[0059] Branched linear low-density polyethylene resin 1: Linear low-density polyethylene resin 1 was used as raw material for treatment, and the M1 / M2 after treatment was 13:1; the melt flow rate of branched linear low-density polyethylene resin 1 at 190°C and a 10 kg load was 205 g / 10 min (M1); the melt flow rate of branched linear low-density polyethylene resin 1 at 190°C and a 2.16 kg load was 15.7 g / 10 min (M2), the irradiation dose was 5 kgy, and the irradiation time was 24 h;

[0060] Branched linear low-density polyethylene resin 2: Linear low-density polyethylene resin 2 was used as the raw material for treatment, and the M1 / M2 after treatment was 17:1; the melt flow rate of branched linear low-density polyethylene resin 2 at 190°C and a 10 kg load was 682 g / 10 min (M1); the melt flow rate of branched linear low-density polyethylene resin 2 at 190°C and a 2.16 kg load was 40.11 g / 10 min (M2). The irradiation dose was 8 kgy, and the irradiation time was 24 h.

[0061] Branched linear low-density polyethylene resin 3: Linear low-density polyethylene resin 1 was used as raw material for treatment, and the M1 / M2 after treatment was 20:1; the melt flow rate of branched linear low-density polyethylene resin 3 at 190°C and a 10 kg load was 300 g / 10 min (M1); the melt flow rate of branched linear low-density polyethylene resin 3 at 190°C and a 2.16 kg load was 15 g / 10 min (M2), the irradiation dose was 10 kgy, and the irradiation time was 24 h;

[0062] Branched linear low-density polyethylene resin 4: Linear low-density polyethylene resin 1 was used as raw material for treatment, and the M1 / M2 after treatment was 12:1; the melt flow rate of branched linear low-density polyethylene resin 4 at 190°C and a 10 kg load was 192 g / 10 min (M1); the melt flow rate of branched linear low-density polyethylene resin 4 at 190°C and a 2.16 kg load was 16 g / 10 min (M2), the irradiation dose was 4 kgy, and the irradiation time was 24 h;

[0063] Ultra-high molecular weight polypropylene resin: BA202E, weight-average molecular weight 102w, Borealis;

[0064] Antioxidants:

[0065] Antioxidant 1010, Tianjin Li'anlong; the parallel tests of Examples 1 to 11 and Comparative Examples 1 to 3 all used the same antioxidant.

[0066] Examples 1 to 11 and Comparative Examples 1 to 3

[0067] According to the formulations in Tables 1 to 3, a high-temperature creep-resistant polypropylene composition was prepared according to the following preparation method:

[0068] Polypropylene resin, branched linear low-density polyethylene resin, ultra-high molecular weight polypropylene resin and antioxidant are placed in a premix and stirred at a speed of 350 rpm / min for 180 seconds. The mixture is then added to a twin-screw extruder for melt blending and extrusion granulation to obtain a high-temperature creep-resistant polypropylene composition. The feeding section temperature is 180°C, the melt temperature is 210°C, the screw length-diameter ratio is 48:1, and the screw speed of the twin-screw extruder is 400 rpm.

[0069] Table 1 Amount of each component in the high temperature creep resistant polypropylene composition in Examples 1 to 7 (parts by weight)

[0070] Table 2 Amount of each component in the high temperature creep resistant polypropylene composition in Examples 8 to 11 (parts by weight)

[0071] Table 3 Amount of each component in the high temperature creep resistant polypropylene composition in Comparative Examples 1 to 3 (parts by weight)

[0072] Performance Testing

[0073] 1. Test method

[0074] The high temperature creep resistant polypropylene composition prepared above was subjected to performance tests:

[0075] (1) Melt flow rate test: The high temperature creep resistant polypropylene composition prepared above was tested according to the standard ISO 1133-2011, wherein the test conditions were 230°C / 2.16kg;

[0076] (2) High-temperature creep resistance test: The high-temperature creep-resistant polypropylene composition prepared above was injection molded to obtain ISO 1A tensile test bars. The injection molding conditions were: injection temperature of 200°C throughout the entire range, injection pressure of 70% throughout the entire range, holding pressure of 70% throughout the entire range, holding time of 15 seconds, and cooling time of 8 seconds. The injection mold was: ISO 1A bending test bar.

[0077] Step 1: Use ISO mechanics 1A tensile specimens to test the static tensile strength at 80°C; Step 2: Calculate 80% of the static tensile strength at 80°C as the tensile creep set load; Step 3: Set the environmental chamber temperature to 80°C and place the specimen in the creep environmental chamber for 4 hours; Step 4: Fix the tensile specimen on the clamp, reset the force to zero, and start the tensile creep test; Step 5: Observe the equipment rupture time, test until the specimen breaks, and record the creep rupture time.

[0078] 2. Test Results The test results of the high temperature creep resistant polypropylene composition prepared by the above method are shown in Table 4.

[0079] Table 4 Performance test results of various embodiments and comparative examples

[0080] As can be seen from Table 4, the high-temperature creep-resistant polypropylene compositions prepared in various embodiments of the present invention have good high-temperature creep resistance and a good melt flow rate. Specifically, the creep rupture time is not less than 200 hours; the melt flow rate at 230°C and 2.16 kg is not less than 10 g / 10 min, and the compositions have good processing performance and can be well injection molded.

[0081] As can be seen from Examples 1 and 3-4, as the M1 / M2 ratio in the branched linear low-density polyethylene resin increases, the overall performance of the resulting polypropylene composition improves. This is because within this range, the branched linear low-density polyethylene resin contains more long chain branches and more physical entanglement points. When M1 / M2 is (13-20):1, the polypropylene composition can exhibit higher high-temperature creep resistance while maintaining good fluidity, with a creep rupture time of not less than 280 hours.

[0082] In Example 2, due to the high fluidity of the branched linear low-density polyethylene resin, its creep resistance is reduced.

[0083] It can be seen from Examples 1, 5 and 6 that as the amount of branched linear low-density polyethylene resin increases, the melt flow rate of the obtained polypropylene composition gradually decreases and the high-temperature creep performance gradually increases. When the amount of branched linear low-density polyethylene resin is 12 to 15 parts, the comprehensive performance of the obtained polypropylene composition is better.

[0084] It can be seen from Examples 1, 8 and 9 that as the amount of ultra-high molecular weight polypropylene resin increases, the melt flow rate of the obtained polypropylene composition gradually decreases, but the high-temperature creep resistance gradually improves. When the amount of ultra-high molecular weight polypropylene resin is 5 to 8 parts, the comprehensive performance of the obtained polypropylene composition is better.

[0085] Comparison of Example 7 and Comparative Example 1 shows that when a linear low-density polyethylene resin is used instead of a branched linear low-density polyethylene resin, the high-temperature creep performance of the resulting polypropylene composition is significantly reduced. This is because ordinary linear low-density polyethylene has a straight-chain structure without long branches and cannot synergistically produce a "bridging" effect with the ultra-high molecular weight polypropylene resin, resulting in poor high-temperature creep resistance.

[0086] Comparison of Example 7 and Comparative Example 2 shows that if the ultra-high molecular weight polypropylene resin is not added, even if the branched linear low-density polyethylene resin is added, the high-temperature creep resistance of the obtained polypropylene composition is still poor, and the creep rupture time is only 65 hours, which is significantly reduced compared to Example 7.

[0087] Comparison of Example 7 and Comparative Example 3 shows that if the branched linear low-density polyethylene resin is not added, the flow rate and high-temperature creep properties of the polypropylene composition obtained are poor even if the ultra-high molecular weight polypropylene resin is added.

[0088] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A polypropylene composition, characterized in that The composition comprises the following components calculated by weight: Polypropylene resin 70-92 parts; 5-20 parts of branched linear low-density polyethylene resin; 3-10 parts of ultra-high molecular weight polypropylene resin; The branched linear low-density polyethylene resin M1 / M2 is not less than 10:1; M1 is the melt flow rate of the branched linear low-density polyethylene resin at 190°C and 10kg load; M2 is the melt flow rate of the branched linear low-density polyethylene resin at 190°C and 2.16kg load; and M2 is 3-45g / 10min.

2. The polypropylene composition according to claim 1, characterized in that The composition comprises the following components calculated by weight:

3. The polypropylene composition according to claim 1 or 2, characterized in that: The preparation method of the branched linear low-density polyethylene resin is as follows: The linear low-density polyethylene was irradiated with 60Co gamma rays under vacuum conditions.

4. The polypropylene composition according to claim 3, characterized in that: The irradiation dosage is 5 to 8 kgy, and the irradiation time is 20 to 28 hours.

5. The polypropylene composition according to claim 1 or 2, characterized in that: The melt flow rate of the polypropylene resin at 230° C. and 2.16 kg is 3.0 to 35.0 g / 10 min.

6. The polypropylene composition according to claim 1 or 2, characterized in that: The polypropylene resin is a homopolymer polypropylene resin or a copolymer polypropylene resin.

7. The polypropylene composition according to claim 1 or 2, characterized in that: The branched linear low-density polyethylene resin M1 / M2 is (13-20):

1.

8. A branched linear low-density polyethylene resin, characterized in that The M1 / M2 of the branched linear low-density polyethylene resin is not less than 10:1; M1 is the melt flow rate of the branched linear low-density polyethylene resin at 190°C and 10kg load; M2 is the melt flow rate of the branched linear low-density polyethylene resin at 190°C and 2.16kg load; and M2 is 3 to 45g / 10min.

9. The method for preparing the polypropylene composition according to any one of claims 1 to 7, characterized in that: The steps include: The polypropylene resin, the branched linear low-density polyethylene resin, the ultra-high molecular weight polypropylene resin and the antioxidant are mixed and added into an extruder, and granulated by melt extrusion to obtain a high-temperature creep-resistant polypropylene composition.

10. Use of the polypropylene composition according to any one of claims 1 to 7 in automobiles.

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