Polypropylene composite material with high melt index, high modulus and high impact resistance and preparation method thereof

Abstract

The invention discloses a high-melt-index, high-modulus and high-impact polypropylene composite material and a preparation method thereof, and the polypropylene composite material comprises the following raw materials by weight: 40-80 parts of high-melt-index polypropylene, 10-40 parts of low-melt-index polypropylene, 5-20 parts of a high-melt-index elastomer, 5-15 parts of a low-melt-index elastomer, and 15-43 parts of glass fiber. And 0.1-1 part by weight of an antioxidant. According to the invention, through compounding of the polypropylene with high and low melt indexes and the elastomer with high and low melt indexes, the glass fibers are selectively distributed in the polypropylene matrix with high melt index, and the chain entanglement density of elastomer particles is increased, so that the polypropylene composite material has the characteristics of high melt index, high modulus and high impact resistance, the bending modulus can be greater than 2000MPa, the melt index is greater than 20g / 10min, and the impact resistance can be improved. The notched impact strength is greater than 20 KJ / m < 2 >, the notched impact strength at-30 DEG C can be greater than 5 KJ / m < 2 >, and the performance is excellent.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material modification and processing, and particularly relates to a high melt index, high modulus, high impact polypropylene composite material and a preparation method thereof. Background Art

[0002] Lightweighting and enhancing vehicle performance have been key developments in the automotive industry in recent years. Bumpers and interior trims are primarily made from various modified polypropylene materials. With the demand for weight reduction, the use of polypropylene in vehicle production is increasing. Therefore, developing polypropylene that meets the needs of the automotive industry will help expand its application in the automotive sector.

[0003] Looking at the recent developments in new polypropylene products from petrochemical companies, it's not hard to see a growing number of polypropylenes with high melt index, high modulus, and impact resistance. This is primarily driven by the demands for processability and lightweighting in automotive parts. To enable polypropylene for injection molding and thin-wall production, automakers prefer polypropylene with high melt index, high modulus, and impact resistance. High melt index polypropylene raw materials are advantageous for injection molding, making them preferred by manufacturers. However, a high melt index also means a very low molecular weight, making it difficult to increase notched impact strength. This often requires the addition of high elastomer content, which inevitably leads to a significant decrease in the material's modulus. Consequently, there is a conflict between high melt index and high modulus and high impact resistance. Therefore, there is a need to improve polypropylene materials and develop high melt index, high modulus, and high impact polypropylene materials for automotive parts.

[0004] The Chinese invention patent application publication CN102382375A discloses a special material for automobile bumpers or interior decoration. The polypropylene raw material obtained has good notched impact strength and yield strength, but low flexural modulus. The Chinese invention patent application publication CN112759845A discloses a polypropylene composite material obtained by adding a small amount of basic magnesium sulfate whiskers in a weak shear and strong dispersion method, which improves the modulus of the polypropylene composite material. The obtained polypropylene composite material can be used in automobile bumpers, but this process requires a specially designed screw combination to achieve a material with high modulus (above 2000MPa) and high impact resistance (20KJ / m 2 The material is not expected to have good impact resistance at low temperatures. Chinese invention patent application publication CN115926326A discloses an automotive interior material using bio-based straw powder filled with polypropylene. This polypropylene composite material has a high flexural modulus and melt index, but low notched impact strength.

[0005] The polypropylene materials disclosed in the above-mentioned patents cannot simultaneously possess the high melt index, high modulus and high impact resistance required for automotive parts, or the processing steps involved are cumbersome and the production cost is high, which is not conducive to large-scale market applications. In addition, the existing technology rarely involves the low-temperature notched impact strength of polypropylene. Considering the time-temperature equivalence mechanism of polymer materials, the mechanical properties of the material when a vehicle collides at high speed are equivalent to its mechanical behavior in a low-temperature environment. Therefore, improving the low-temperature toughness of polypropylene composite materials is more meaningful for actual application scenarios. Therefore, how to prepare automotive polypropylene raw materials with better performance through simple raw materials and methods remains a challenge. Summary of the Invention

[0006] The present invention provides a polypropylene composite material with high melt index, high modulus and high impact resistance, which has simple preparation process and wide raw material sources, and a preparation method thereof.

[0007] The technical solution adopted in the present invention is: A polypropylene composite material with high melt index, high modulus and high impact resistance, comprising the following raw materials in parts by weight: 40-80 parts by weight of high melt index polypropylene, 10-40 parts by weight of low melt index polypropylene, 5-20 parts by weight of high melt index elastomer, 5-15 parts by weight of low melt index elastomer, 15-43 parts by weight of glass fiber, and 0.1-1 part by weight of antioxidant.

[0008] Furthermore, it is preferred that the polypropylene composite material comprises the following raw materials in parts by weight: 45-65 parts by weight of high melt index polypropylene, 15-30 parts by weight of low melt index polypropylene, 15-20 parts by weight of high melt index elastomer, 5-10 parts by weight of low melt index elastomer, 25-43 parts by weight of glass fiber, and 0.1-1 part by weight of antioxidant.

[0009] More preferably, the polypropylene composite material comprises the following raw materials in parts by weight: 45-60 parts by weight of high melt index polypropylene, 15-30 parts by weight of low melt index polypropylene, 15-20 parts by weight of high melt index elastomer, 5-10 parts by weight of low melt index elastomer, 30-43 parts by weight of glass fiber, and 0.1-1 part by weight of antioxidant.

[0010] Wherein, the high melt index polypropylene and the low melt index polypropylene are each independently block copolymer polypropylene or random copolymer polypropylene.

[0011] Furthermore, the melt index of the high melt index polypropylene is 60-100 g / 10 min, the melt index of the low melt index polypropylene is 30-60 g / 10 min, and the test conditions of the melt index are 230° C. and a load of 2.16 kg.

[0012] The high melt index elastomer and the low melt index elastomer are polyolefin elastomers, and each is independently one or more of ethylene-propylene rubber, ethylene-octene rubber or polystyrene-ethylene-propylene-polystyrene rubber. Preferably, the high melt index elastomer or the low melt index elastomer is ethylene-propylene rubber, i.e., EPDM rubber.

[0013] Furthermore, the high melt index elastomer has a melt index of 20-50 g / 10 min, the low melt index elastomer has a melt index of 0.5-5 g / 10 min, and the melt index test conditions of the elastomer are 230° C. and a load of 2.16 kg.

[0014] The aspect ratio of the glass fiber is 100-300, the average length of the glass fiber is 3-6 mm, and the glass fiber is alkali-free glass fiber.

[0015] The antioxidant is one of antioxidant 1010 and antioxidant 1076, or a mixture of the two.

[0016] The high melt index, high modulus, and high impact polypropylene composite material provided by the present invention can be used as a polypropylene material for automobiles to prepare automobile parts, including but not limited to automobile bumpers, automobile interior shells, air intake grilles, etc.

[0017] The high melt index, high modulus, high impact polypropylene composite material can be prepared by the following method: (1) First, high melt index polypropylene, low melt index polypropylene, high melt index elastomer, low melt index elastomer and antioxidant are added into a high-speed blender according to the formula ratio and mixed evenly to obtain a blend; (2) The blend obtained in step (1) is fed into a twin-screw extruder through a main feed port, and glass fiber is fed into a side feed port of the extruder for melt extrusion and granulation to obtain the polypropylene composite material with high melt index, high modulus and high impact resistance.

[0018] The glass fiber content is adjusted by the feed amount of the main feed port and the side feed port.

[0019] Furthermore, melt extrusion granulation is generally performed at a temperature of 90 to 230° C., and further, a typical extrusion process can be adopted as follows: conveying section temperature 90 to 140° C., melting section temperature 160 to 230° C. (preferably 180 to 220° C.), homogenizing section temperature 180 to 230° C. (preferably 200 to 220° C.), die temperature 180 to 230° C. (preferably 200 to 220° C.), and screw speed 100 to 200 rpm.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention compounds high melt index polypropylene and low melt index polypropylene, and through the different viscosity gradients of the materials during processing, the glass fibers are selectively distributed in the high melt index polypropylene, thereby better exerting the rigidity-increasing effect of the glass fibers and making the flexural modulus of the polypropylene composite material better than that of a polypropylene composite material using a single matrix.

[0021] The present invention uses a compound of a high melt index elastomer and a low melt index elastomer, so that the high melt index elastomer is well combined with the high melt index polypropylene, and the low melt index elastomer is well combined with the low melt index polypropylene, and the high melt index polypropylene and the low melt index polypropylene have excellent compatibility due to similar chemical structures, so each phase has a suitable viscosity ratio and a smaller distance between the elastomer particles, thereby improving the toughening effect of the elastomer. In addition, some of the low melt index elastomers selected by the present invention have larger molecular chain entanglements and lower glass transition temperatures, which greatly improve the room temperature and low temperature notched impact strength of the polypropylene composite material. Therefore, the polypropylene composite material has good low temperature notched impact strength. In principle, the compounding of high and low melt index polypropylene and elastomers regulates the distribution of fillers, changes the molecular chain entanglements of the elastomer particles, constructs a suitable structure, and ultimately achieves an improvement in the performance of the composite material.

[0022] The processing technology adopted by the present invention is simple and easy to implement, with low cost. The obtained polypropylene composite material has a flexural modulus greater than 2000MPa, a melt index greater than 20g / 10min, and a notched impact strength greater than 20KJ / m 2 , -20℃ notched impact strength can be greater than 7KJ / m 2 , -30℃ notched impact strength can be greater than 5KJ / m 2 It has the characteristics of high melt index, high modulus and high impact resistance, can be widely used in the field of automotive parts, and has great market value. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to specific examples, but the scope of protection of the present invention is not limited by these examples.

[0024] In the following examples, the high melt index polypropylene is BX3900 (SK Group, South Korea, 100 g / 10 min), the low melt index polypropylene is EP5074 (Polymirae Co., Ltd., South Korea, 30 g / 10 min), the high melt index elastomer is 6502 (ExxonMobil, 45 g / 10 min), the low melt index elastomer is 2032PM (Shanghai Sinopec Mitsui Chemicals Co., Ltd., 0.8 g / 10 min), the aspect ratio of the glass fiber is 150, the diameter is 3 mm, and the antioxidants are 1010 and 1076 compounded in a ratio of 1:1.

[0025] Table 1. Comparative Examples and Examples Composition Formula parts by weight Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Example 1 Example 2 Example 3 Example 4 Example 5 High melt index PP 75 60 60 75 60 60 53 46 60 60 Low melt index PP 0 15 15 0 15 15 22 30 15 15 High melt index elastomer 15 25 15 0 0 15 15 15 20 15 Low melt index elastomer 10 0 10 25 25 10 10 10 5 10 glass fiber 43 43 43 (talcum powder replaces glass fiber) 43 43 43 43 43 43 25 antioxidants 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 According to the formulation shown in Table 1, a twin-screw extruder was used for melt extrusion. The extrusion conditions were: conveying section temperature 100°C, melting section temperature 220°C, homogenizing section temperature 220°C, die temperature 220°C, and screw speed 120 rpm.

[0026] Table 2 shows the performance characterization results of the comparative examples and examples. Comparative Example 1, using only high-melt-finger polypropylene as the matrix, failed to achieve selective dispersion of glass fibers, and the compatibility between the polypropylene matrix and the low-melt-finger elastomer was not improved. However, the absence of low-melt-finger polypropylene resulted in better overall flowability. Consequently, the resulting polypropylene composite material exhibited a higher melt index than Example 1, but exhibited significantly lower room-temperature and low-temperature notched impact strength, flexural modulus, and yield strength.

[0027] Comparative Example 2, using only a high-melt-index elastomer, resulted in a low molecular chain entanglement density within the composite, and limited compatibility between the low-melt-index polypropylene and the high-melt-index elastomer. Consequently, the resulting polypropylene composite exhibited significantly decreased room-temperature and low-temperature notched impact strength, flexural modulus, and yield strength, while exhibiting a slight improvement in melt index.

[0028] In Comparative Example 3, the glass fiber was replaced with another widely used filler, talc powder. The results showed that compared with glass fiber, talc powder had a greater adverse effect on the material's notched impact strength, flexural modulus and yield strength.

[0029] Comparative Example 4 uses a high melt index matrix and a low melt index elastomer. Since the compatibility between the two is obviously insufficient, the low-temperature notched impact strength and melt index of the polypropylene composite material are relatively poor.

[0030] Comparative Example 5 does not use a high melt index elastomer, so the compatibility between the polypropylene matrix and the low melt index elastomer is relatively limited, and the notched impact, flexural modulus and melt index of the material need to be improved.

[0031] The results of Examples 1-4 show that when high- and low-melt index polypropylene and high- and low-melt index elastomers are used simultaneously, the flexural modulus of the materials reaches over 2000 MPa, significantly higher than that of the comparative example samples. The materials also exhibit a high melt index and good room- and low-temperature notched impact strength. The results of Example 5 show that for samples prepared using this technology, the flexural modulus of the materials decreases significantly when the mass fraction of glass fiber is reduced from approximately 30% to approximately 20%, but remains comparable to that of the 30% glass fiber-filled sample in Comparative Example 3.

[0032] The data from the above comparative examples and embodiments show that the compounding of high and low melt index polypropylenes and high and low melt index elastomers can effectively improve the compatibility of the polypropylene matrix and the elastomer, and selectively distribute the glass fiber, so that the polypropylene composite material has high melt index, high modulus, and high impact resistance, which can well meet the use requirements of some automotive polypropylenes.

[0033] Table 2. Performance characterization results of comparative examples and examples Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[Notched impact strength (KJ / m 2 at 23℃)]]> 18.4 17.7 11.3 19.1 18.7 20.8 23.4 23.3 20.4 21.1 <![CDATA[Notched impact strength (KJ / m 2 at -20 °C)]]> 5.3 5.1 4.2 5.5 5.6 7.6 7.9 8.1 7.2 6.8 <![CDATA[Izod impact strength (KJ / m 2 - 30 °C)]]> 4.6 4.5 3.4 4.9 4.8 5.1 5.2 5.4 4.8 4.4 Flexural modulus (MPa 23℃) 1902 1866 1651 1962 1950 2135 2225 2140 2012 1512 Yield strength (MPa 23℃) 21 21.3 22.5 22.3 22.4 24.5 24.8 24.1 22.1 22 Melt index (g / 10min 230℃ 2.16kg) 26.1 35 25.1 17.8 18.2 24 23.2 21.7 20.8 24.3

Claims

1. High melt index, high modulus, high impact polypropylene composite material, characterized by The polypropylene composite material comprises the following raw materials in parts by weight: 40-80 parts by weight of high melt index polypropylene, 10-40 parts by weight of low melt index polypropylene, 5-20 parts by weight of high melt index elastomer, 5-15 parts by weight of low melt index elastomer, 15-43 parts by weight of glass fiber, and 0.1-1 parts by weight of antioxidant; The melt index of the high melt index polypropylene is 60-100 g / 10 min, the melt index of the low melt index polypropylene is 30-60 g / 10 min, the melt index of the high melt index elastomer is 20-50 g / 10 min, and the melt index of the low melt index elastomer is 0.5-5 g / 10 min.

2. The high melt index, high modulus, high impact polypropylene composite material according to claim 1, characterized in that The polypropylene composite material comprises the following raw materials in parts by weight: 45-65 parts by weight of high melt index polypropylene, 15-30 parts by weight of low melt index polypropylene, 15-20 parts by weight of high melt index elastomer, 5-10 parts by weight of low melt index elastomer, 25-43 parts by weight of glass fiber, and 0.1-1 part by weight of antioxidant.

3. The high melt index, high modulus, high impact polypropylene composite material according to claim 1, characterized in that The high melt index polypropylene and the low melt index polypropylene are independently block copolymer polypropylene or random copolymer polypropylene.

4. The high melt index, high modulus, high impact polypropylene composite material according to claim 1, characterized in that The high melt index elastomer and the low melt index elastomer are independently one of ethylene-propylene rubber, ethylene-octene rubber or polystyrene-ethylene-propylene-polystyrene rubber or a combination of several of them.

5. The high melt index, high modulus, high impact polypropylene composite material according to claim 1, characterized in that The aspect ratio of the glass fiber is 100-300, and the average length of the glass fiber is 3-6 mm.

6. The high melt index, high modulus, high impact polypropylene composite material according to claim 1, characterized in that The antioxidant is one of antioxidant 1010 and antioxidant 1076 or a mixture of both.

7. The method for preparing a polypropylene composite material with high melt index, high modulus and high impact resistance according to any one of claims 1 to 6, characterized in that The method comprises the following steps: (1) First, high melt index polypropylene, low melt index polypropylene, high melt index elastomer, low melt index elastomer and antioxidant are added into a high-speed blender according to the formula ratio and mixed evenly to obtain a blend; (2) The blend obtained in step (1) is fed into a twin-screw extruder through a main feed port, and glass fiber is fed into the extruder from a side feed port for melt extrusion granulation to obtain the polypropylene composite material with high melt index, high modulus and high impact resistance.

8. The method according to claim 7, characterized in that The twin-screw extruder extrudes and granulates at a temperature of 90-230°C.

9. Use of the high melt index, high modulus, and high impact polypropylene composite material according to any one of claims 1 to 6 in the preparation of automotive parts.

10. The use according to claim 9, characterized in that The automobile parts include automobile bumpers, automobile interior shells or air intake grilles.