Polypropylene composite material as well as preparation method and application thereof

Abstract

The invention discloses a polypropylene composite material which comprises the following components in parts by weight: 38-82 parts of polypropylene resin; 4 to 10 parts of a PA6 / PA66 copolymer; 0.2 to 0.6 part of carboxyl-terminated hyperbranched polyester; 0.5 to 5 parts of maleic anhydride grafted polypropylene; and 5-50 parts of long glass fiber. By utilizing the PA6 / PA66 copolymer, epiphytic crystallization of polypropylene resin on the surface of the glass fiber can be reduced, so that the anisotropy caused by crystallization non-uniformity is effectively improved. And meanwhile, the PA6 / PA66 copolymer can also make up the material rigidity reduction caused by crystallization reduction. The carboxyl-terminated hyperbranched polyester in the material can effectively reduce the stress generated in the crystallization process. And the combined action of the two can greatly improve the buckling deformation of the material and improve the light transmittance.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a polypropylene composite material, its preparation method, and its application. Background Technology

[0002] Long glass fiber reinforced polypropylene (GFRP) possesses numerous advantages such as high strength, low cost, and lightweight. Its use in large plastic products is already widespread, including automotive front-end frames, fans, and underbody protection panels. However, the inherent drawbacks of glass fiber reinforcement, such as warpage, severely limit its application. The warpage of glass fiber reinforced materials is fundamentally caused by the significant difference in the distribution of glass fibers along the flow direction and perpendicular to the flow direction. Furthermore, the epigenetic crystallization of crystalline polymers on the glass fiber surface further exacerbates the warpage. Addressing these inherent characteristics of glass fiber reinforced polypropylene is a common goal across the industry. Chinese patent CN103739932A discloses a high-rigidity, low-warpage glass fiber reinforced polypropylene material, comprising 100 parts polypropylene, 20-45 parts chopped glass fiber, 5-15 parts glass fiber powder, 5-15 parts inorganic filler, 2-8 parts compatibilizer (maleic anhydride-grafted polypropylene, maleic anhydride-grafted ethylene-butene copolymer, maleic anhydride-grafted ethylene-octene copolymer, glycidyl methacrylate-grafted ethylene-butene copolymer, glycidyl methacrylate-grafted ethylene-octene copolymer), and 2-5 parts toughening agent (ethylene-butene copolymer, ethylene-octene copolymer, ethylene-propylene-based elastomer). However, this patented solution is only applicable to chopped glass fiber and not to long glass fiber reinforced polypropylene composites. Chinese patent application CN107892772A discloses an anti-warping continuous glass fiber reinforced polypropylene composite material, comprising 42.5-65 parts of polypropylene, 25-35 parts of continuous glass fiber, 6-12 parts of hollow microspheres, and 2-5 parts of compatibilizer (maleic anhydride grafted polymer). However, this patent is only applicable to continuous glass fiber with a low content (maximum 35 wt%). When the content of continuous glass fiber is increased (to 40 wt% or more, especially 45 wt% or more), the low warping effect cannot be achieved.

[0003] In recent years, translucent materials have attracted widespread attention as a novel material property. For example, in laser welding, a certain level of light transmittance is required for the light-transmitting layer material. For crystalline materials, there are generally three methods to improve light transmittance: 1. reducing the material's crystallinity; 2. improving the uniformity of material crystallization. This invention attempts to improve the light transmittance of materials by adjusting their crystallization. Summary of the Invention

[0004] The purpose of this invention is to provide a long glass fiber reinforced polypropylene composite material with low warpage and high light transmittance, as well as its preparation method and application.

[0005] This invention is achieved through the following technical solution: A polypropylene composite material, by weight, comprises the following components: Polypropylene resin A: 38-82 parts; 4-10 parts of PA6 / PA66 copolymer; 0.2-0.6 parts of carboxyl-terminated hyperbranched polyester; 0.5-5 parts of maleic anhydride-grafted polypropylene; 5-50 parts of long glass fiber.

[0006] In the polypropylene composite material of the present invention, the content of polypropylene resin can be any value or a range of any two of 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, and 82 parts; the content of PA6 / PA66 copolymer can be any value or a range of any two of 4 parts, 4.5 parts, 5.0 parts, 5.5 parts, 6.0 parts, 7.0 parts, 8.0 parts, 9.0 parts, and 10.0 parts; and the content of carboxyl-terminated hyperbranched polyester can be 0.2 parts, 0.3 parts, or 0.4 parts. The content of maleic anhydride-grafted polypropylene can be any value or a range of two of the following: 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, 3.5 parts, 4.0 parts, 4.5 parts, and 5.0 parts. The content of long glass fibers can be any value or a range of two of the following: 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, and 50 parts.

[0007] Based on the total weight percentage of the polypropylene composite material of the present invention, the content of polypropylene resin is not less than 35 wt%, and the weight percentage content of PA6 / PA66 copolymer ranges from 2 to 10 wt%.

[0008] The polypropylene resin is selected from homopolymer polypropylene resin or copolymer polypropylene resin. The melt index of the polypropylene resin is in the range of 10-100 g / 10 min. The test conditions are 230℃, load 2.16 kg, and the test standard is ISO 1133.

[0009] The PA6 segment accounts for 75-99% by weight percentage of the PA6 / PA66 copolymer.

[0010] The molar percentage of each unit in the PA6 / PA66 copolymer was determined by proton nuclear magnetic resonance spectroscopy.

[0011] The weight percentage of PA6 segments in the PA6 / PA66 copolymer can be any value or a range of any two of the following: 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0012] Preferably, the PA6 segment accounts for 80-90% by weight percentage of the PA6 / PA66 copolymer.

[0013] The relative viscosity range of the PA6 / PA66 copolymer is 2.5-3.0, and the test conditions are 25℃, 96% sulfuric acid, and m:V=1:100.

[0014] PA6 / PA66 copolymer is a copolymer of PA6 and PA66. It can be a commercially available product or it can be obtained by making it in-house. The in-house preparation method is as follows: Nylon 66 brine and caprolactam solutions were added separately to a concentration vessel, along with acetic acid and defoamer. Medium-pressure steam was used to heat the solution via a reboiler, creating a self-flowing circulation process to raise the brine temperature to 148-158°C and the concentration to 70-80%. The material was then pressurized into a polymerization reactor (using either concentrated brine vapor or high-pressure nitrogen). The material was heated and pressurized in the polymerization reactor, completing the pressure-holding prepolymerization process at approximately 17.5 bar. After a gradual depressurization and dehydration stage (also known as the maturation stage), a polymer with a viscosity of approximately 2.5-3.0 was formed, yielding the PA6 / PA66 copolymer.

[0015] This invention does not have any particular limitation on long glass fibers; a linear density of 1000-2400 tex is sufficient to achieve the purpose of this invention.

[0016] Those skilled in the art may choose to add 0-2 parts of an additive as needed, wherein the additive is selected from at least one of antioxidants and lubricants.

[0017] Antioxidants can be tris(2,4-di-tert-butylphenyl) phosphite; 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; 2,5-di-tert-butyl-4-hydroxybenzyl dimethylamine; diethyl-3,5-di-tert-butyl-4-hydroxybenzyl phosphate; stearyl-3,5-di-tert-butyl-4-hydroxybenzyl phosphate; 3,5-di-tert-butyl-4-hydroxyphenyl-3,5-distearate-thiotriazolylamine; 2,6-di-tert-butyl-4-hydroxymethylphenol; 2,4-di-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylglycerol allyl ether)-1,3,5-triazine; N,N'-Hexamethylene di(3,5-di-tert-butyl-4-hydroxy-hydrogenated cinnamamide); N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine; β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl ester; triethylene glycol di[3-(3,5-dimethyl-4-hydroxyphenyl)propionate]; triethylene glycol di[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate]; 2,2'-thiodiethyl-di[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester; etc.

[0018] The lubricant may be at least one of stearate lubricants, fatty acid lubricants, and stearate ester lubricants; the stearate lubricant is selected from at least one of calcium stearate, magnesium stearate, and zinc stearate; the fatty acid lubricant is selected from at least one of fatty acids, fatty acid derivatives, and fatty acid esters; and the stearate ester lubricant is selected from pentaerythritol stearate.

[0019] The preparation method of the polypropylene composite material of the present invention includes the following steps: polypropylene resin, PA6 / PA66 copolymer, carboxyl-terminated hyperbranched polyester, and maleic anhydride-grafted polypropylene are mixed uniformly according to the specified ratio, and then compounded in a twin-screw extruder. The mixture is then impregnated with long glass fibers through a wetting die, and extruded and granulated to obtain the polypropylene composite material. The temperature range of the twin-screw extruder is 210-300℃, and the temperature range of the wetting die is 270-320℃.

[0020] The polypropylene composite material of the present invention is used in the manufacture of automotive parts.

[0021] The present invention has the following beneficial effects: This invention utilizes PA6 / PA66 copolymer dispersed at the interface between the resin matrix and long glass fibers, effectively improving anisotropy caused by uneven crystallization. Simultaneously, the PA6 / PA66 copolymer can compensate for the decrease in material rigidity due to reduced crystallinity. The carboxyl-terminated hyperbranched polyester in the material effectively reduces stress generated during the crystallization process. The combined effect of these two factors significantly improves the material's warpage and increases light transmittance. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0023] The raw materials used in this invention are sourced from the following sources: Polypropylene-1: from Zhenhai Petrochemical, typical grade Z30S, melt flow index 30g / 10min (230℃, 2.16kg); Polypropylene-2: from Basel, grade HP500N, melt flow index 10g / 10min (230℃, 2.16kg); PA6 / PA66 copolymer A: PA6 segments account for 75%, relative viscosity range is 2.62, self-made; PA6 / PA66 copolymer B: PA6 segments account for 80%, relative viscosity range is 2.65, self-made; PA6 / PA66 copolymer C: PA6 segments account for 90%, relative viscosity range is 2.67, self-made; PA6 / PA66 copolymer D: PA6 segments account for 99%, relative viscosity range is 2.69, self-made; Nylon 66 brine and caprolactam solutions were added separately to a concentration vessel, along with acetic acid and defoamer. Medium-pressure steam was used to heat the solution via a reboiler, creating a self-flowing circulation process to raise the brine temperature to 148-158°C and the concentration to 70-80%. The material was then forced into a polymerization reactor. The material underwent heating and pressurization in the reactor, completing the prepolymerization process at approximately 17.5 bar. After a gradual depressurization and dehydration stage (also known as a maturation stage), the process was stopped once the set viscosity was reached, yielding the PA6 / PA66 copolymer.

[0024] PA6: HY-2500A, relative viscosity range is 2.5, supplied by Haiyang Chemical Fiber; PA66: EP-158, relative viscosity range is 2.6, provided by Huafeng Company; Long glass fiber: sourced from Taishan Fiberglass, with a linear density of 2400 tex, grade EDR240-T838JH; Maleic anhydride-grafted polypropylene: Model CA100, purchased from Arkema. Carboxyl-terminated hyperbranched polyester A: HyPer C100, Wuhan Hyperbranched Resin Technology Co., Ltd.; Carboxyl-terminated hyperbranched polyester B: HyPer C201, Wuhan Hyperbranched Resin Technology Co., Ltd.; Hydroxyl-terminated hyperbranched polyester: HyPer H102, Wuhan Hyperbranched Resin Technology Co., Ltd.; Antioxidant: The main antioxidant and auxiliary antioxidant are compounded in a 1:1 mass ratio and are commercially available; Lubricant: Zinc stearate, commercially available.

[0025] The preparation method of the polypropylene composite material in the examples and comparative examples includes the following steps: Polypropylene resin, PA6 / PA66 copolymer, carboxyl-terminated hyperbranched polyester, and maleic anhydride-grafted polypropylene are mixed uniformly according to the specified ratio, and then compounded in a twin-screw extruder. The mixture is then impregnated with long glass fibers through a wetting die, extruded, and granulated to obtain the polypropylene composite material. The temperature range of the twin-screw extruder is 210-300℃, and the temperature range of the wetting die is 270-320℃.

[0026] Test methods: (1) Warpage Deformation: The linear expansion coefficient CLTE in the flow direction and perpendicular direction of the sample was determined according to ISO 11359. The closer the CLTE values ​​in the two directions are, the closer the transverse and longitudinal shrinkage rates of the sample are, and the smaller the material warpage. In the example table, CLTE represents the flow direction / perpendicular to the flow direction, 10E -6 μm / (m℃), -30-100℃.

[0027] (2) Light transmittance: The transmittance of a 1.5mm injection molded square plate was tested with infrared light at 980nm and recorded.

[0028] Table 1: Weight parts and test results of each component in the polypropylene composite material of the example Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Polypropylene-1 40 60 60 60 60 60 Polypropylene-2 80 PA6 / PA66 copolymer A 10 8 4 8 PA6 / PA66 copolymer B 8 PA6 / PA66 copolymer C 8 PA6 / PA66 copolymer D 8 Carboxyl-terminated hyperbranched polyester A 0.4 0.2 0.6 0.2 0.2 0.2 Carboxyl-terminated hyperbranched polyester B 0.2 Maleic anhydride-grafted polypropylene 0.5 2 5 2 2 2 2 Long glass fiber 5 30 50 30 30 30 30 antioxidants 0.5 0.5 lubricant 0.5 0.5 CLTE 60 / 165 35 / 115 37 / 115 45 / 120 46 / 115 38 / 112 41 / 120 CLTE ratio in the flow direction / CLTE in the vertical flow direction 0.36 0.30 0.32 0.38 0.40 0.34 0.34 Light transmittance (%) 35 29 26 31 33 29 31 As can be seen from Examples 2 / 4-6, when the proportion of PA6 segments in the PA6 / PA66 copolymer is preferred, there is less warping and deformation, and the light transmittance is higher.

[0029] As can be seen from the above embodiments, the ratio of CLTE in the flow direction to CLTE in the vertical flow direction of the polypropylene composite material of the present invention is ≥0.30, and the light transmittance is ≥26%.

[0030] Table 2: Weight parts of each component and test results of comparative polypropylene composite materials Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Polypropylene-1 60 60 60 60 60 60 60 PA6 / PA66 copolymer A 0 18 8 8 8 PA6 8 PA66 8 Carboxyl-terminated hyperbranched polyester A 0.2 0.2 0.2 0.2 0 0.2 Hydroxyl-terminated hyperbranched polyester 0.2 Maleic anhydride-grafted polypropylene 2 2 2 2 2 2 0 Long glass fiber 30 30 30 30 30 30 30 CLTE 25 / 133 35 / 130 29 / 127 28 / 150 20 / 168 20 / 173 26 / 163 CLTE ratio in the flow direction / CLTE in the vertical flow direction 0.19 0.27 0.23 0.19 0.12 0.12 0.16 Light transmittance (%) 18 22 19 17 21 22 23 As shown in Comparative Example 1, the absence of PA6 / PA66 copolymer results in high warpage and low light transmittance.

[0031] As shown in Comparative Example 2, when the content of PA6 / PA66 copolymer is too high, it will also cause warping deterioration and a decrease in light transmittance.

[0032] As can be seen from Comparative Example 3 / 4, neither PA6 nor PA66 can achieve the purpose of this invention.

[0033] As shown in Comparative Example 5, hydroxyl-terminated hyperbranched polyester cannot synergistically improve warpage and light transmittance simultaneously and significantly with PA6 / PA66 copolymer.

[0034] As shown in Comparative Example 6, the hyperbranched polyester without terminal hydroxyl groups exhibits severe warping and low light transmittance.

[0035] As shown in Comparative Example 7, polypropylene grafted without maleic anhydride exhibits severe warping and low light transmittance.

Claims

1. A polypropylene composite material, characterized in that, By weight, it includes the following components: 38-82 parts of polypropylene resin; 4-10 parts of PA6 / PA66 copolymer; 0.2-0.6 parts of carboxyl-terminated hyperbranched polyester; 0.5-5 parts of maleic anhydride-grafted polypropylene; 5-50 parts of long glass fiber.

2. The polypropylene composite material according to claim 1, characterized in that, The polypropylene resin is selected from homopolymer polypropylene resin or copolymer polypropylene resin, and the melt index of the polypropylene resin is in the range of 10-100 g / 10 min. The test conditions are 230℃ and load 2.16 kg.

3. The polypropylene composite material according to claim 1, characterized in that, The PA6 segment accounts for 75-99% by weight percentage of the PA6 / PA66 copolymer.

4. The polypropylene composite material according to claim 3, characterized in that, The PA6 segment accounts for 80-90% by weight percentage of the PA6 / PA66 copolymer.

5. The polypropylene composite material according to claim 1, characterized in that, The relative viscosity range of the PA6 / PA66 copolymer is 2.5-2.7, and the test conditions are 25℃, 96% sulfuric acid, and m:V=100:

1.

6. The polypropylene composite material according to claim 1, characterized in that, The linear density of the long glass fiber is 1000-2400 tex.

7. The polypropylene composite material according to claim 1, characterized in that, The product also includes 0-2 parts by weight of additives, wherein the additives are selected from at least one of antioxidants and lubricants.

8. The method for preparing the polypropylene composite material according to any one of claims 1-7, characterized in that, The process includes the following steps: According to the formula, polypropylene resin, PA6 / PA66 copolymer, carboxyl-terminated hyperbranched polyester, and maleic anhydride-grafted polypropylene are mixed evenly, compounded in a twin-screw extruder, impregnated with long glass fibers through an impregnation die, and extruded and granulated to obtain a polypropylene composite material.

9. The application of the polypropylene composite material according to any one of claims 1-7, characterized in that, Used for manufacturing automotive parts.