Precipitation-resistant and aging-resistant polypropylene composite material as well as preparation method and application thereof

Abstract

The invention discloses an anti-precipitation and anti-aging polypropylene composite material as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The anti-precipitation and anti-aging polypropylene composite material is prepared from the following components in parts by weight: 25 to 57 parts of homo-polypropylene resin, 10 to 20 parts of polypropylene random copolymer resin, 5 to 12 parts of high-density polyethylene, 25 to 40 parts of glass fiber, 2 to 5 parts of compatilizer, 1 to 4 parts of nucleating agent and 0.1 to 0.5 part of antioxidant. According to the polypropylene composite material disclosed by the invention, the homo-polypropylene resin, the polypropylene random copolymer resin and the high-density polyethylene are compounded, so that the precipitation resistance and the aging resistance of the polypropylene composite material can be improved while the rigidity of the polypropylene composite material is ensured, and the polypropylene composite material disclosed by the invention is suitable for preparing parts of an automobile thermal management system.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to an anti-precipitation and anti-aging polypropylene composite material and a preparation method and application thereof. Background Art

[0002] The coolant circulates in new energy electric vehicles and exchanges heat with the electric drive thermal management system, air conditioning thermal management system and battery thermal management system to ensure that the components are in a reasonable operating temperature range and prevent the system from being overcooled or overheated. The insulation of the coolant is crucial to the safe operation of new energy vehicles, and ion precipitation is an important factor affecting the insulation of the coolant.

[0003] Polypropylene materials have been widely used in automotive decorative parts due to their advantages such as low relative density, low price, good processing performance and good comprehensive performance. However, existing polypropylene materials have the defects of low tensile strength and poor aging resistance, which limits their application in parts working in high-temperature environments. The existing technology usually improves the aging resistance of polypropylene materials by increasing the content of antioxidants in polypropylene materials. However, with the increase of the antioxidant content in polypropylene materials, the amount of antioxidant precipitated from the polypropylene material increases under high-temperature working environment, and the precipitated antioxidant dissolves in the coolant to form ions, which deteriorates the insulation of the coolant, thereby affecting the normal operation of various thermal management systems in new energy vehicles.

[0004] Therefore, there is an urgent need to develop a polypropylene composite material with both anti-precipitation and aging resistance. Summary of the invention

[0005] Based on the defects of the prior art, the purpose of the present invention is to provide an anti-precipitation and aging-resistant polypropylene composite material and a preparation method and application thereof.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] In the first aspect, the present invention provides an anti-precipitation and aging-resistant polypropylene composite material, comprising the following components in parts by weight: 25 to 57 parts of homopolymer polypropylene resin, 10 to 20 parts of random copolymer polypropylene resin, 5 to 12 parts of high-density polyethylene, 25 to 40 parts of glass fiber, 2 to 5 parts of compatibilizer, 1 to 4 parts of nucleating agent, and 0.1 to 0.5 parts of antioxidant. The crystallinity of the homopolymer polypropylene resin is not less than 45%, the melt flow rate of the high-density polyethylene at 190° C. and 2.16 kg load is not more than 3 g / 10 min, the antioxidant comprises a complex of a hindered phenol antioxidant and a phosphite antioxidant, the solubility of the hindered phenol antioxidant is not less than 1 g / 100 g of n-hexane, the melting point of the hindered phenol antioxidant is greater than 110° C., the glass fiber is a flat glass fiber, and the nucleating agent is an α nucleating agent.

[0008] The present invention adopts homopolymerized polypropylene resin, random copolymerized polypropylene resin and high-density polyethylene as the matrix resin of the polypropylene composite material, which can ensure the rigidity of the polypropylene composite material while enabling the polypropylene composite material to quickly and effectively form a dense crystalline region on the surface layer during the injection molding process, thereby blocking the migration and precipitation of small molecular components (such as antioxidants), improving the precipitation resistance and aging resistance of the polypropylene composite material, and making the polypropylene composite material of the present invention suitable for preparing automotive thermal management system parts.

[0009] Compared with round glass fibers, flat glass fibers can play a better physical barrier role in the material system and improve the anti-precipitation performance of polypropylene composites.

[0010] Compared with other nucleating agents, the α-nucleating agent introduced in the present invention can not only improve the rigidity of the polypropylene composite material, but also improve the crystallization rate and crystallinity of the polypropylene composite material, thereby making the polypropylene composite material have better aging resistance and precipitation resistance.

[0011] The inventors have found through research that the present invention uses a compound of a hindered phenol antioxidant and a phosphite antioxidant as an antioxidant for a polypropylene composite material. When the solubility of the hindered phenol antioxidant is not less than 1g / 100g n-hexane and the melting point is not less than 100°C, the antioxidant can not only be better compatible with the matrix resin, making it difficult for the antioxidant to precipitate, but also improve the efficiency of the antioxidant and improve the aging resistance of the polypropylene composite material.

[0012] In the present invention, the sum of the weight percentages of the homopolymer polypropylene resin, the random copolymer polypropylene resin and the high-density polyethylene in the polypropylene composite material is not less than 55%.

[0013] Preferably, the crystallinity of the homopolymer polypropylene resin is 45-70%. The inventors have found that controlling the crystallinity of the homopolymer polypropylene resin within an appropriate range can improve the rigidity of the polypropylene composite material while allowing the polypropylene composite material to form a stable crystalline region on the surface after injection molding, thereby improving the precipitation resistance and aging resistance of the polypropylene composite material.

[0014] In the present invention, the crystallinity of the homopolymer polypropylene resin may be 45%, 46%, 48%, 50%, 55%, 57%, 60%, 65%, 70% or a range consisting of any two groups of values ​​therein.

[0015] Further preferably, the homopolymer polypropylene resin has a crystallinity of 50-57%, and the comprehensive performance of the polypropylene composite material is better.

[0016] Preferably, the melt mass flow rate of the homopolypropylene resin at 230° C. and 2.16 kg load is 5 to 45 g / 10 min. The melt mass flow rate of the homopolypropylene resin at 230° C. and 2.16 kg load can be 5 g / 10 min, 8 g / 10 min, 10 g / 10 min, 12 g / 10 min, 15 g / 10 min, 20 g / 10 min, 25 g / 10 min, 30 g / 10 min, 35 g / 10 min, 40 g / 10 min, 45 g / 10 min, or a range consisting of any two groups of values.

[0017] Preferably, the melt mass flow rate of the random copolymer polypropylene resin at 230°C and 2.16Kg load is 0.9 to 3.8 / 10min. In the present invention, the melt mass flow rate of the random copolymer polypropylene resin at 230°C and 2.16Kg load can be 0.9g / 10min, 1.0g / 10min, 1.2g / 10min, 1.5g / 10min, 1.8g / 10min, 2.0g / 10min, 2.1g / 10min, 2.2g / 10min, 2.5g / 10min, 2.8g / 10min, 3.0g / 10min, 3.5g / 10min, 3.8g / 10min or a range consisting of any two groups of values.

[0018] Further preferably, the random copolymer polypropylene resin has a melt mass flow rate of 2 to 2.8 g / 10 min at 230° C. and a load of 2.16 kg.

[0019] The inventors have found that the present invention introduces random copolymer polypropylene and controls the melt mass flow rate of the random copolymer polypropylene within the range of 2.1 to 2.8 g / 10 min, which can more effectively enhance the compatibility of the base resin with other components (such as antioxidants) and inhibit the precipitation of small molecular components.

[0020] Preferably, the melt flow rate of the high-density polyethylene at 190°C and 2.16kg load is 0.5-3g / 10min. In the present invention, the melt flow rate of the high-density polyethylene at 190°C and 2.16kg load can be 0.5g / 10min, 1g / 10min, 1.2g / 10min, 1.5g / 10min, 2g / 10min, 2.1g / 10min, 2.5g / 10min, 3g / 10min or a range consisting of any two groups of values.

[0021] The inventors have found that introducing high-density polyethylene with a melt mass flow rate in the range of 0.5 to 3 g / 10 min into a polypropylene composite material can accelerate the formation of a surface crystallization zone of the material during the injection molding process, making the crystallization zone structure denser and more effectively preventing the precipitation of small molecules.

[0022] Further preferably, the high-density polyethylene has a melt flow rate of 1.2 to 3 g / 10 min at 190° C. and a load of 2.16 kg.

[0023] Preferably, the compatibilizer includes at least one of maleic anhydride grafted polypropylene, glycidyl methacrylate grafted polypropylene, and glycidyl acrylate grafted polypropylene.

[0024] In the present invention, the α-nucleating agent may include at least one of a sorbitol nucleating agent, a phosphate nucleating agent, and a carboxylic acid nucleating agent.

[0025] In the present invention, the phosphite antioxidant may include at least one of (2,4-di-tert-butylphenyl) phosphite triester, tris(4-nonylphenyl) phosphite and triphenyl phosphite.

[0026] Preferably, the hindered phenol antioxidant has a melting point of 159-242° C. and a solubility of 1.7-1.9 g / 100 n-hexane.

[0027] Preferably, the weight ratio of the hindered phenol antioxidant to the phosphite antioxidant is (0.5-1.5): 1. In the present invention, the weight ratio of the hindered phenol antioxidant to the phosphite antioxidant can be 0.5: 1, 0.6: 1, 0.7: 1, 0.8: 1, 1: 1, 1.2: 1, 1.5: 1 or a range consisting of any two weight ratios thereof.

[0028] Preferably, in the components of the polypropylene composite material, the weight portion of the hindered phenol antioxidant is 0.05 to 0.2 parts, and the weight portion of the phosphite antioxidant is 0.05 to 0.3 parts.

[0029] Further preferably, in the components of the polypropylene composite material, the weight portion of the hindered phenol antioxidant is 0.1 to 0.15 parts, and the weight portion of the phosphite antioxidant is 0.1 to 0.2 parts.

[0030] Preferably, the anti-precipitation and aging-resistant polypropylene composite material comprises the following components in parts by weight: 37 to 48 parts of homopolymer polypropylene resin, 12 to 15 parts of random copolymer polypropylene resin, 7 to 10 parts of high-density polyethylene, 30 to 35 parts of glass fiber, 3 to 4 parts of compatibilizer, 2 to 3 parts of nucleating agent, and 0.3 to 0.4 parts of antioxidant.

[0031] Preferably, in the present invention, the length of the flat glass fiber is 1 to 5 mm, and the aspect ratio of the cross section of the flat glass fiber is (3 to 4):1.

[0032] In a second aspect, the present invention provides a method for preparing the anti-precipitation and aging-resistant polypropylene composite material as described in the first aspect, comprising the following steps:

[0033] The components are mixed, melt-blended, extruded, granulated and dried to obtain the precipitation-resistant and aging-resistant polypropylene composite material.

[0034] In a third aspect, the present invention provides a use of the anti-precipitation and aging-resistant polypropylene composite material as described in the first aspect in preparing automobile thermal management system parts.

[0035] In the present invention, the automotive thermal management system parts may be electric drive thermal management system parts, air conditioning thermal management system parts, battery thermal management system parts, and the like.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention adopts homopolymer polypropylene resin, random copolymer polypropylene resin and high-density polyethylene to compound, which can improve the precipitation resistance and aging resistance of the polypropylene composite material while ensuring the rigidity of the polypropylene composite material, so that the polypropylene composite material of the present invention is suitable for preparing automobile thermal management system parts. DETAILED DESCRIPTION

[0038] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples, the purpose of which is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] In the present invention, the test method for the melt mass flow rate of the homopolypropylene resin is the method specified in the standard ISO1133-2011, the test temperature is 230° C., and the load is 2.16 Kg.

[0040] The crystallinity test method of the homopolypropylene resin is differential scanning calorimetry, the test temperature is from room temperature to 230°C, the heating rate is 10°C / min, and the melting enthalpy △H is obtained according to the DSC curve. Crystallinity=△H1 / △H2*100%, wherein △H2 is the melting heat of 100% crystallization of the sample (the melting heat of 100% crystallization of homopolypropylene is 209J / g).

[0041] The test method for the melt mass flow rate of the random copolymer polypropylene resin is the method specified in the standard ISO1133-2011, the test temperature is 230° C., and the load is 2.16 Kg.

[0042] The test method for the melt flow rate of the high-density polyethylene is the method specified in the standard ISO1133-2011, the test temperature is 190° C., and the load is 2.16 kg.

[0043] The solubility test method is as follows: add 100g of n-butane solvent into a container at room temperature (25°C); gradually add a certain amount of hindered phenol antioxidant solute (mass m1), stir continuously, fully dissolve, filter out the undissolved solute and dry, weigh the mass of the undissolved solute m2, and calculate the solubility according to the following formula: solubility = (m1-m2) / 100g.

[0044] The melting point was tested by differential scanning calorimetry at a heating rate of 10°C / min.

[0045] The source information and performance parameters of the components described in each embodiment and comparative example are shown in Table 1 below.

[0046] Table 1

[0047]

[0048]

[0049] Unless otherwise specified, the components and raw materials used in the embodiments and comparative examples of the present invention are all commercially available raw materials, and the components and raw materials used in each parallel experiment are all of the same kind.

[0050] Examples 1 to 13

[0051] The embodiments of the anti-precipitation and aging-resistant polypropylene composite material of the present invention, the components and weight proportions of the anti-precipitation and aging-resistant polypropylene composite material are shown in Table 2.

[0052] The method for preparing the anti-precipitation and aging-resistant polypropylene composite material comprises the following steps:

[0053] After mixing the components, the components are melt-blended, extruded and granulated through a twin-screw extruder, and dried to obtain the anti-precipitation and aging-resistant polypropylene composite material. The temperatures of the zones of the twin-screw extruder from the feeding section to the die are: 220° C. for zone 1, 235° C. for zone 2, 235° C. for zone 3, 235° C. for zone 4, 235° C. for zone 5, 235° C. for zone 6, 230° C. for zone 7, 230° C. for zone 8, 225° C. for zone 9 and 225° C. for zone 10. The screw speed of the twin-screw extruder is 180 rpm, and the aspect ratio of the screw is 40:1.

[0054] Table 2 (Unit: parts by weight)

[0055]

[0056]

[0057]

[0058] Comparative Examples 1 to 9

[0059] The difference between the comparative examples and the embodiments is only in the types and proportions of components, as shown in Table 3.

[0060] Table 3 (Unit: weight parts)

[0061]

[0062]

[0063] In order to verify the performance of the composite material of the present invention, the composite materials prepared in each embodiment and comparative example were used as samples to perform the following performance tests:

[0064] (1) Tensile strength: The samples were injection molded into ISO 527 1A specimens and tested according to the ISO 527-2012 method at a test temperature of 23 °C and a tensile rate of 10 mm / min.

[0065] (2) Aging resistance: The samples were injection molded into ISO 527 1A specimens, and the specimens were placed in an oven at 120°C for 1000 h. The test was performed according to the ISO 527-2012 method at a test temperature of 23°C and a tensile rate of 10 mm / min, and the tensile strength retention rate was calculated.

[0066] (3) Anti-precipitation property: The sample was injection molded into ISO 527 5A specimens, and deionized water was prepared and tested with a conductivity tester. The conductivity of the deionized water was 1.0 uS / cm. Five specimens were immersed in 1 L of deionized water. After being stored in an oven at 90°C for 1008 h, the conductivity of the deionized water in which the specimens were immersed was tested with a conductivity tester. The smaller the conductivity obtained by the test, the better the anti-precipitation performance of the sample.

[0067] The test results are shown in Tables 4 and 5.

[0068] Table 4

[0069]

[0070] Table 5

[0071]

[0072] As can be seen from Tables 4 to 5, the embodiments of the present invention adopt homopolymerized polypropylene resin, random copolymerized polypropylene resin and high-density polyethylene compounding, which can ensure the rigidity of the polypropylene composite material while enabling the polypropylene composite material to quickly and effectively form a dense crystalline region on the surface layer during the injection molding process, blocking the migration and precipitation of small molecular components (such as antioxidants), and improving the precipitation resistance and aging resistance of the polypropylene composite material. The tensile strength of the polypropylene composite material of the embodiment of the present invention is not less than 94MPa, and the tensile strength retention rate is not less than 93% after aging at 120°C for 1000h, and the conductivity of the deionized water soaked with the sample strip is not greater than 1.9uS / cm after being stored in an oven at 90°C for 1008h.

[0073] It can be seen from Example 1, Examples 5 to 7 and Comparative Example 1 that controlling the crystallinity of the homopolymerized polypropylene resin within an appropriate range can improve the rigidity of the polypropylene composite material while enabling the polypropylene composite material to form a stable crystalline region on the surface after injection molding, thereby improving the precipitation resistance and aging resistance of the polypropylene composite material; when the crystallinity of the homopolymerized polypropylene resin is 50 to 57%, the comprehensive performance of the polypropylene composite material is better.

[0074] It can be seen from Example 1, Examples 11 to 12, Comparative Examples 2 and Comparative Examples 5 to 7 that introducing a high-density polyethylene with a melt mass flow rate in the range of 0.5 to 3 g / 10 min into the polypropylene composite material and controlling the addition amount of the high-density polyethylene within an appropriate range can accelerate the formation of a surface crystallization zone of the material during the injection molding process, make the structure of the crystallization zone denser, and more effectively block the precipitation of small molecules, thereby improving the aging resistance and precipitation resistance of the polypropylene composite material.

[0075] It can be seen from Example 1, Example 13 and Comparative Examples 3 to 4 that the present invention adopts a composite of a hindered phenol antioxidant and a phosphite antioxidant as an antioxidant for a polypropylene composite material. When the melting point and solubility of the hindered phenol antioxidant simultaneously satisfy that the solubility is not less than 1 g / 100 g of n-hexane and the melting point is greater than 110°C, the antioxidant can not only be better compatible with the matrix resin, making it difficult for the antioxidant to precipitate, but also improve the action efficiency of the antioxidant and improve the aging resistance of the polypropylene composite material.

[0076] It can be seen from Example 1 and Comparative Examples 8 to 9 that, compared with round glass fibers, flat glass fibers can play a better physical barrier role in the material system and improve the anti-precipitation performance of the polypropylene composite material; compared with other nucleating agents, the introduction of an α nucleating agent in the present invention can better improve the rigidity of the polypropylene composite material, and improve the aging resistance and anti-precipitation performance of the polypropylene composite material.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A precipitation-resistant and aging-resistant polypropylene composite material, characterized in that: The invention comprises the following components in parts by weight: 25-57 parts of homopolypropylene resin, 10-20 parts of random copolymer polypropylene resin, 5-12 parts of high-density polyethylene, 25-40 parts of glass fiber, 2-5 parts of compatibilizer, 1-4 parts of nucleating agent and 0.1-0.5 parts of antioxidant. The crystallinity of the homopolypropylene resin is not less than 45%. The melt flow rate of the high-density polyethylene under 190° C. and 2.16 kg load is not more than 3 g / 10 min. The antioxidant comprises a complex of a hindered phenol antioxidant and a phosphite antioxidant. The solubility of the hindered phenol antioxidant is not less than 1 g / 100 g of normal hexane. The melting point of the hindered phenol antioxidant is greater than 110° C. The glass fiber is a flat glass fiber. The nucleating agent is an α-nucleating agent.

2. The anti-precipitation and aging-resistant polypropylene composite material according to claim 1, characterized in that: The crystallinity of the homopolymer polypropylene resin is 45 to 70%, and more preferably 50 to 57%.

3. The anti-precipitation and aging-resistant polypropylene composite material according to claim 1, characterized in that: The homopolymer polypropylene resin has a melt mass flow rate of 5 to 45 g / 10 min at 230° C. and a load of 2.16 kg.

4. The anti-precipitation and aging-resistant polypropylene composite material according to claim 1, characterized in that: The random copolymer polypropylene resin has a melt mass flow rate of 0.9 to 3.8 g / 10 min at 230° C. and a load of 2.16 kg, and more preferably 2 to 2.8 g / 10 min.

5. The anti-precipitation and aging-resistant polypropylene composite material according to claim 1, characterized in that: The high-density polyethylene has a melt flow rate of 0.5 to 3 g / 10 min at 190° C. and a load of 2.16 kg, and more preferably 1.2 to 3 g / 10 min.

6. The anti-precipitation and aging-resistant polypropylene composite material according to claim 1, characterized in that: The compatibilizer includes at least one of maleic anhydride grafted polypropylene, glycidyl methacrylate grafted polypropylene, and glycidyl acrylate grafted polypropylene.

7. The anti-precipitation and aging-resistant polypropylene composite material according to claim 1, characterized in that: In the components of the polypropylene composite material, the weight portion of the hindered phenol antioxidant is 0.05 to 0.2 parts, and the weight portion of the phosphite antioxidant is 0.05 to 0.3 parts.

8. The anti-precipitation and aging-resistant polypropylene composite material according to claim 1, characterized in that: The invention comprises the following components in parts by weight: 37-48 parts of homopolymer polypropylene resin, 12-15 parts of random copolymer polypropylene resin, 7-10 parts of high-density polyethylene, 30-35 parts of glass fiber, 3-4 parts of compatibilizer, 2-3 parts of nucleating agent and 0.3-0.4 parts of antioxidant.

9. A method for preparing the anti-precipitation and anti-aging polypropylene composite material according to any one of claims 1 to 8, characterized in that: The following steps are involved: The components are mixed, melt-blended, extruded, granulated and dried to obtain the precipitation-resistant and aging-resistant polypropylene composite material.

10. Use of the precipitation-resistant and aging-resistant polypropylene composite material according to any one of claims 1 to 8 in the preparation of automotive thermal management system parts.

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