High melt index, high modulus, high impact polypropylene composite and method of making same

Abstract

The application discloses a high-melt-index, high-modulus and high-impact polypropylene composite material and a preparation method thereof. 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 part by weight of antioxidant. The high-melt-index and low-melt-index polypropylenes and the high-melt-index and low-melt-index elastomers are compounded, the glass fiber is selectively distributed in the high-melt-index polypropylene matrix, the chain entanglement density of the elastomer particles is increased, the polypropylene composite material has the characteristics of high melt index, high modulus and high impact, the bending modulus is greater than 2000 MPa, the melt index is greater than 20 g / 10 min, the notched impact strength is greater than 20 KJ / m 2 , and 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] This invention belongs to the field of polymer material modification and processing technology, specifically relating to a high melt index, high modulus, and high impact resistance polypropylene composite material and its preparation method. Background Technology

[0002] Lightweighting and high-performance automotive components have been major development directions in the automotive industry in recent years. Bumpers and interior trim are primarily made of various modified polypropylene materials, and with the increasing demand for vehicle weight reduction, there is a growing trend towards expanding the use of polypropylene in vehicle production. Therefore, developing polypropylene materials that meet the needs of the automotive industry will help expand their application in the automotive sector.

[0003] Looking at the development direction of new polypropylene products by petrochemical companies in recent years, it's easy to see a continuous increase in the types of polypropylene with high melt flow index (MFI), high modulus, and high impact resistance. This is mainly due to the requirements of processability and lightweighting in automotive parts. To enable polypropylene to be used in injection molding and thin-walled applications, high MFI, high modulus, and high impact resistance polypropylene products are favored by automakers. High MFI polypropylene raw materials are beneficial for injection molding production and are preferred by manufacturers. However, a high MFI also means that the molecular weight of polypropylene is very low, making it difficult to improve its notched impact strength. Often, it is necessary to add a high content of elastomer to improve the notched impact strength of high MFI polypropylene, which inevitably leads to a significant decrease in the material modulus. Therefore, there is a certain conflict between high MFI and high modulus and high impact resistance. Therefore, it is necessary to improve polypropylene materials and develop high MFI, high modulus, and high impact resistance polypropylene materials as raw materials for automotive parts.

[0004] Chinese invention patent application publication CN102382375A discloses a special material for automobile bumpers or interior trim. The polypropylene raw material obtained has good notched impact strength and yield strength, but low flexural modulus. Chinese invention patent application publication CN112759845A discloses a polypropylene composite material prepared by adding a small amount of basic magnesium sulfate whiskers using a weak shear strong dispersion method. This improves the modulus of the polypropylene composite material, which can be used in automobile bumpers. However, this process requires a specially designed screw assembly to achieve both high modulus (above 2000 MPa) and high impact resistance (20 KJ / m²). 2 (Above), and it cannot be expected that the material will still have good impact resistance at low temperatures. Chinese invention patent application publication CN115926326A discloses an automotive interior material using bio-based straw powder to fill polypropylene. This polypropylene composite material has a high flexural modulus and melt index, but a low notched impact strength.

[0005] The polypropylene materials disclosed in the aforementioned patents cannot simultaneously possess the high melt index, high modulus, and high impact resistance required for automotive parts, or involve cumbersome processing steps and high production costs, hindering large-scale market application. Furthermore, existing technologies rarely address the low-temperature notched impact strength of polypropylene. Considering the time-temperature equivalence mechanism of polymer materials, the mechanical properties exhibited by the material during high-speed vehicle impacts are equivalent to its mechanical behavior in low-temperature environments. Therefore, improving the low-temperature toughness of polypropylene composites is more meaningful for practical applications. Thus, how to prepare higher-performance automotive polypropylene raw materials using simple raw materials and methods remains a challenge. Summary of the Invention

[0006] This invention provides a polypropylene composite material with high melt index, high modulus, and high impact resistance, which has a simple preparation process and widely available raw materials, as well as a preparation method thereof.

[0007] The technical solution adopted in this invention is:

[0008] A polypropylene composite material with high melt index, high modulus, and high impact resistance, wherein the polypropylene composite material comprises the following raw materials in parts by weight:

[0009] High melt flow index polypropylene 40-80 parts by weight, low melt flow index polypropylene 10-40 parts by weight, high melt flow index elastomer 5-20 parts by weight, low melt flow index elastomer 5-15 parts by weight, glass fiber 15-43 parts by weight, antioxidant 0.1-1 parts by weight.

[0010] Furthermore, the polypropylene composite material preferably comprises the following parts by weight of raw materials:

[0011] High melt index polypropylene 45-65 parts by weight, low melt index polypropylene 15-30 parts by weight, high melt index elastomer 15-20 parts by weight, low melt index elastomer 5-10 parts by weight, glass fiber 25-43 parts by weight, antioxidant 0.1-1 parts by weight.

[0012] More preferably, the polypropylene composite material comprises the following raw materials in parts by weight:

[0013] High melt index polypropylene 45-60 parts by weight, low melt index polypropylene 15-30 parts by weight, high melt index elastomer 15-20 parts by weight, low melt index elastomer 5-10 parts by weight, glass fiber 30-43 parts by weight, antioxidant 0.1-1 parts by weight.

[0014] The high melt flow index polypropylene and the low melt flow index polypropylene are each independently block copolymer polypropylene or random copolymer polypropylene.

[0015] Furthermore, the high melt index polypropylene has a melt index of 60-100 g / 10 min, and the low melt index polypropylene has a melt index of 30-60 g / 10 min. The test conditions for the melt index are 230°C and a load of 2.16 kg.

[0016] The high melt flow index elastomer and the low melt flow index elastomer are polyolefin elastomers, each being one or more of ethylene-propylene rubber, ethylene-octene rubber, or polystyrene-ethylene-propylene-polystyrene rubber. Preferably, the high melt flow index elastomer or the low melt flow index elastomer is ethylene-propylene rubber, i.e., ethylene propylene diene monomer (EPDM) rubber.

[0017] 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 for the elastomer are 230℃ and a load of 2.16 kg.

[0018] The glass fiber has an aspect ratio of 100-300 and an average length of 3-6 mm. Furthermore, the glass fiber is alkali-free.

[0019] The antioxidant is one or a mixture of antioxidant 1010 and antioxidant 1076.

[0020] The high melt index, high modulus, and high impact strength polypropylene composite material provided by this invention can be used as automotive polypropylene material to manufacture automotive parts, including but not limited to automotive bumpers, automotive interior shells, and air intake grilles.

[0021] The polypropylene composite material with high melt index, high modulus, and high impact resistance can be prepared by the following method:

[0022] (1) First, add high melt flow index polypropylene, low melt flow index polypropylene, high melt flow index elastomer, low melt flow index elastomer and antioxidant to a high speed mixer according to the formula ratio and mix evenly to obtain a blend.

[0023] (2) The blend obtained in step (1) is fed into a twin-screw extruder through the main feed port, and glass fiber is fed into the extruder through the side feed port. The mixture is then melt-extruded and granulated to obtain the polypropylene composite material with high melt index, high modulus and high impact resistance.

[0024] The glass fiber content is adjusted by the feeding amount through the main feed port and the side feed port.

[0025] Furthermore, melt extrusion granulation is generally carried out at a temperature of 90–230°C. More specifically, a typical extrusion process can be adopted with the following parameters: conveying section temperature 90–140°C, melting section temperature 160–230°C (preferably 180–220°C), homogenization section temperature 180–230°C (preferably 200–220°C), die temperature 180–230°C (preferably 200–220°C), and screw speed 100–200 rpm.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention utilizes a blend of high melt flow index (FRI) and low melt flow index (LRI) polypropylene. By leveraging the different viscosity gradients of the materials during processing, glass fibers are selectively distributed within the high melt flow index polypropylene, thus better utilizing the stiffening effect of the glass fibers. This results in a polypropylene composite material with a flexural modulus superior to that of a polypropylene composite material using a single matrix.

[0028] This invention employs a blend of high melt flow index (MFI) and low melt flow index (MFI) elastomers, resulting in excellent bonding between the high MFI elastomer and high MFI polypropylene, and vice versa. Furthermore, the high MFI and low MFI polypropylene exhibit excellent compatibility due to their similar chemical structures, leading to suitable viscosity ratios and smaller interparticle spacing, thus enhancing the toughening effect of the elastomers. In addition, some of the low MFI elastomers used in this invention possess greater molecular chain entanglement and lower glass transition temperatures, significantly improving the room temperature and low temperature notched impact strength of the polypropylene composite material. Therefore, this polypropylene composite material exhibits excellent low temperature notched impact strength. In principle, the blending of high and low melt flow index polypropylene and elastomers regulates the filler distribution, alters the molecular chain entanglement of the elastomer particles, constructs a suitable structure, and ultimately improves the performance of the composite material.

[0029] The processing technology used in this invention is simple, easy to implement, and low in cost. The resulting polypropylene composite material has a flexural modulus greater than 2000 MPa, a melt flow index greater than 20 g / 10 min, and a notched impact strength greater than 20 KJ / m. 2 The notched impact strength at -20℃ can be greater than 7KJ / m 2 The notched impact strength at -30℃ can be greater than 5KJ / m 2 It possesses characteristics of high melt index, high modulus, and high impact resistance, and can be widely used in the automotive parts industry, possessing great market value. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments. However, the scope of protection of the present invention is not limited to these embodiments.

[0031] In the following examples, the high melt flow index polypropylene is BX3900 (SK Group, South Korea, 100g / 10min), the low melt flow index polypropylene is EP5074 (Polymirae Co., Ltd., South Korea, 30g / 10min), the high melt flow index elastomer is 6502 (ExxonMobil, 45g / 10min), the low melt flow index elastomer is 2032PM (Shanghai Sinopec Mitsui Chemicals Co., Ltd., 0.8g / 10min), the glass fiber has an aspect ratio of 150 and a diameter of 3mm, and the antioxidant is a 1:1 blend of 1010 and 1076.

[0032] Table 1. Composition and Formulation of Comparative Examples and Examples

[0033] 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 flow 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 elastomers 15 25 15 0 0 15 15 15 20 15 Low melt index elastomers 10 0 10 25 25 10 10 10 5 10 Fiberglass 43 43 43 (Talc as a substitute for fiberglass) 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

[0034] According to the formula shown in Table 1, a twin-screw extruder was used for melt extrusion. The extrusion conditions were: conveying section temperature 100℃, melting section temperature 220℃, homogenization section temperature 220℃, die temperature 220℃, and screw speed 120rpm.

[0035] Table 2 presents the performance characterization results for the comparative examples and embodiments.

[0036] Comparative Example 1 used only high melt flow index polypropylene as the matrix, which could not achieve selective dispersion of glass fibers, and the compatibility between the polypropylene matrix and the low melt flow index elastomer was not improved. However, because no low melt flow index polypropylene was added, the overall flowability was better. Therefore, the resulting polypropylene composite material had a higher melt flow index than Example 1, but the room temperature and low temperature notched impact strength, flexural modulus, and yield strength were all significantly reduced.

[0037] Comparative Example 2 used only a high melt flow index elastomer. The molecular chain entanglement density of the elastomer in the composite material was low, and the compatibility between the low melt flow index polypropylene and the high melt flow index elastomer was also limited. Therefore, the notched impact strength, flexural modulus, and yield strength of the resulting polypropylene composite material at room temperature and low temperature were significantly reduced, while the melt flow index was slightly increased.

[0038] Comparative Example 3 replaced glass fiber with another widely used filler, talc. The results showed that, compared with glass fiber, talc had a greater adverse effect on the notched impact strength, flexural modulus, and yield strength of the material.

[0039] Comparative Example 4 uses a high melt index matrix and a low melt index elastomer. Due to the significant lack of compatibility between the two, the low-temperature notched impact strength and melt index of the polypropylene composite material are both poor.

[0040] Comparative Example 5 did not use a high melt index elastomer, so the compatibility between the polypropylene matrix and the low melt index elastomer was relatively limited, and the notched impact, flexural modulus and melt index of the material need to be improved.

[0041] The results of Examples 1-4 show that when both high and low melt flow index polypropylene and high and low melt flow index elastomers are used simultaneously, the flexural modulus of the materials can reach over 2000 MPa, significantly higher than that of the comparative sample. The materials also exhibit a high melt flow index and good room temperature and low temperature notched impact strength. The results of Example 5 show that when the mass fraction of glass fiber in the sample prepared using this technology is reduced from approximately 30% to approximately 20%, the flexural modulus of the material decreases significantly, but it is still comparable to that of the comparative sample 3 with 30% glass fiber filling.

[0042] The data from the above comparative examples and embodiments show that by compounding high and low melt flow index polypropylene and high and low melt flow index elastomers, the compatibility between the polypropylene matrix and the elastomer can be effectively improved, and the glass fiber can be selectively distributed. This makes the polypropylene composite material have high melt flow index, high modulus and high impact resistance, which can well meet the application requirements of some automotive polypropylene.

[0043] Table 2. Performance characterization results of comparative examples and embodiments

[0044] 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[Izod impact strength (KJ / m 2 -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 flow 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. A polypropylene composite material with high melt index, high modulus, and high impact resistance, characterized in that, The polypropylene composite material comprises the following raw materials in parts by weight: High melt index polypropylene 45~65 parts by weight, low melt index polypropylene 15~30 parts by weight, high melt index elastomer 15~20 parts by weight, low melt index elastomer 5~10 parts by weight, glass fiber 25~43 parts by weight, antioxidant 0.1~1 parts by weight. The high melt flow index polypropylene is a block copolymer polypropylene with a melt flow index of 60 g / 10min; The low melt flow index polypropylene is a block copolymer polypropylene with a melt flow index of 30 g / 10min; The high melt index elastomer mentioned is 6502 manufactured by ExxonMobil. The low melt index elastomer is 2032PM produced by Shanghai Sinopec Mitsui Chemicals Co., Ltd. The melt flow index was tested at 230°C with a load of 2.16 kg.

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

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

4. The method for preparing the high melt index, high modulus, and high impact resistance polypropylene composite material according to any one of claims 1 to 3, characterized in that... The method includes the following steps: (1) First, add high melt flow index polypropylene, low melt flow index polypropylene, high melt flow index elastomer, low melt flow index elastomer and antioxidant to a high speed mixer according to the formula ratio and mix evenly to obtain a blend. (2) The blend obtained in step (1) is fed into a twin-screw extruder through the main feed port, and glass fiber is fed into the extruder through the side feed port. The mixture is then melt-extruded and granulated to obtain the polypropylene composite material with high melt index, high modulus and high impact resistance.

5. The method according to claim 4, characterized in that... Twin-screw extruders granulate at temperatures ranging from 90 to 230°C.

6. The application of the high melt index, high modulus, and high impact resistance polypropylene composite material according to any one of claims 1 to 3 in the preparation of automotive parts.

7. The application according to claim 6, characterized in that... The automotive parts include automotive bumpers, automotive interior shells, or air intake grilles.