A polypropylene composite material and a preparation method thereof

Abstract

The application discloses a polypropylene composite material capable of being used for efficient spraying of water-based paint and a preparation method thereof. The polypropylene composite material is prepared from 45-61 parts of conventional polypropylene, 5-20 parts of porous polypropylene, 5-15 parts of a toughening agent, 15-30 parts of inorganic fillers, 2-10 parts of modified nanocellulose fibers, 0.2-0.4 parts of an antioxidant, 0.1-0.3 parts of a lubricant and 0.2-0.6 parts of color powder according to weight parts. The modified nanocellulose fibers are nanocellulose fibers subjected to dopamine surface modification treatment. The nanocellulose is subjected to surface modification by dopamine, the compatibility of the nanocellulose with polypropylene resin is improved, the water-based paint is more easily penetrated into the resin under the synergistic action of the porous polypropylene, the water-based paint is well solidified on the surface of a base material, and the efficient spraying use effect of the water-based paint on the polypropylene composite material is met.

Description

Technical Field

[0001] This invention relates to the field of polymer material modification technology, specifically a polypropylene composite material that can be used for efficient spraying of water-based paints and its preparation method. Background Technology

[0002] Polypropylene resin is widely used in the automotive, home appliance, and many other industries due to its low price, excellent mechanical properties, and simple processing. Especially in the automotive sector, polypropylene resin is used in a wide range of interior and exterior components, including bumpers, door panels, and pillars. Statistics show that the amount of polypropylene resin used per vehicle currently exceeds 50 kg. For exterior components like bumpers, surface coating processes are generally involved. Previously, oil-based paints were the primary method, but in recent years, with increased environmental awareness, water-based paints have been gradually adopted. Water-based paints have advantages such as low toxicity and low flammability; however, due to their high surface tension, they have poorer wetting and dispersion properties for pigments and substrates. Furthermore, their penetration into resin substrates is relatively weaker than oil-based paints, resulting in inferior adhesion to the substrate. To improve the penetration and adhesion of water-based paints to resin substrates, it is necessary to strengthen the research and development of high-end water-based paints, and at the same time, it is also necessary to develop composite polypropylene materials that are more compatible with water-based paints. Therefore, it is of great significance to develop a polypropylene composite material that can be used for efficient spraying of water-based paints. Summary of the Invention

[0003] In view of this, the present invention provides a polypropylene composite material and its preparation method that can be used for efficient spraying of water-based paints, in order to solve the problems mentioned in the background art. By modifying the surface of nanocellulose with dopamine, its compatibility with polypropylene resin is improved. On the one hand, the surface hydroxyl activity of nanocellulose is utilized to make it have good compatibility with water-based paints, thereby improving the adhesion between water-based paints and resin surfaces. On the other hand, under the synergistic effect of porous polypropylene, water-based paints can more easily penetrate into the interior of the resin, allowing the water-based paints to be well cured on the substrate surface, thus satisfying the high-efficiency spraying effect of water-based paints on polypropylene composite materials.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention discloses a polypropylene composite material that can be used for efficient spraying of water-based paints. It is prepared by weight proportions of 45-61 parts conventional polypropylene, 5-20 parts porous polypropylene, 5-15 parts toughening agent, 15-30 parts inorganic filler, 2-10 parts modified nanocellulose fibers, 0.2-0.4 parts antioxidant, 0.1-0.3 parts lubricant, and 0.2-0.6 parts colorant; wherein the modified nanocellulose fibers are nanocellulose fibers that have undergone dopamine surface modification treatment.

[0006] As a further aspect of the present invention: the conventional polypropylene is at least one of copolymer polypropylene or homopolymer polypropylene, and its melt index is 5 to 100 g / 10 min at 230℃ / 2.16 kg.

[0007] As a further aspect of the present invention, the porosity of the porous polypropylene is 10-30%.

[0008] As a further aspect of the present invention: the toughening agent is at least one of POE, EPDM, HDPE, LLDPE, and SEBS.

[0009] As a further aspect of the present invention: the inorganic filler is at least one of talc, calcium carbonate, wollastonite, mica, and magnesium sulfate whiskers.

[0010] As a further aspect of the present invention: the modification method of the modified nanocellulose fiber includes the following steps:

[0011] The nanocellulose fibers were placed in a dopamine solution and stirred for 1-3 hours. The pH of the system was adjusted to 8-9, and the stirring was continued for 3-6 hours. After filtration, washing and drying, the modified nanocellulose fibers were obtained.

[0012] The concentration of the dopamine solution is 1-2 g / L, and the ratio of the modified nanocellulose fiber to the dopamine solution is 1 g:(20-40) mL.

[0013] As a further aspect of the present invention: the antioxidant is a compound of a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant is one of antioxidant 1010 or antioxidant 1076, and the secondary antioxidant is antioxidant 168.

[0014] As a further aspect of the present invention, the lubricant is at least one of calcium stearate, zinc stearate, and stearate ester.

[0015] Another aspect of the present invention discloses a method for preparing a polypropylene composite material that can be used for efficient spraying of water-based paints as described in any of the preceding claims, comprising the following steps:

[0016] The conventional polypropylene, porous polypropylene, toughening agent, modified nanocellulose fiber, inorganic filler, antioxidant, lubricant and color powder are mixed evenly according to the weight parts, and then fed into a twin-screw extruder. After melting, extrusion, water cooling, air drying and granulation, and baking at 80-100℃ for 2-6 hours, a high-efficiency water-based paint spraying polypropylene composite material is obtained.

[0017] As a further aspect of the present invention: the extrusion temperatures of each zone in the twin-screw extruder are 80±10℃, 190±10℃, 200±10℃, 210±10℃, 210±10℃, 200±10℃, 200±10℃, 200±10℃, 200±10℃, 200±10℃, the screw speed is 350~450r / min, the length-to-diameter ratio of the twin-screw extruder is (36~48):1, the vacuum degree of the extrusion process is -0.05~-0.1MPa, and the extruder die head has a double-layer 80~120 mesh filter screen.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] (1) This invention utilizes dopamine to modify the surface of nanocellulose to improve its compatibility with polypropylene resin. It also utilizes the surface hydroxyl activity of nanocellulose fibers to make it compatible with water-based paint, thereby improving the adhesion between water-based paint and resin surface.

[0020] (2) The present invention introduces a porous polypropylene raw material. This polypropylene raw material has a porous structure on its surface. After being made into a composite material, it can continue to maintain its porous structure on its surface, so that the water-based paint can penetrate into the resin more easily and cure well on the substrate surface, thus satisfying the high-efficiency spraying effect of water-based paint on polypropylene composite materials. Detailed Implementation

[0021] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0023] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0024] Polypropylene, specifically copolymer polypropylene, grade BX3800, purchased from SK in South Korea;

[0025] Porous polypropylene, grade Hifax CA 7153S, has a porosity of 23% vol and an apparent density of 0.36 kg / dm³. 3 Purchased from Basel;

[0026] The nanocellulose fiber (CNF) is branded as MFC and manufactured by Zhejiang Hanghua New Material Technology Co., Ltd.

[0027] The talc powder is grade AHCP250 and manufactured by Liaoning Aihai Talc Co., Ltd.

[0028] The POE grade is LC565, and the manufacturer is LG Chem.

[0029] The LLDPE grade is 7042, and the manufacturer is Zhong'an United.

[0030] Antioxidant 1010, manufactured by BASF;

[0031] Antioxidant 168, manufactured by BASF;

[0032] Carbon black, grade X30B, manufactured by Dexin Fine Chemical Co., Ltd.

[0033] The antioxidant is a compound system of 1010 and 168 in a weight ratio of 1:2.

[0034] The pigment used is carbon black;

[0035] The dopamine solution was purchased from Sinopharm Guorui Pharmaceutical Co., Ltd.

[0036] Other dopamine, antioxidants, lubricants, and carbon black are all commercially available materials.

[0037] All materials are commercially available, commonly used products.

[0038] It is understood that the above-mentioned raw materials and reagents are merely examples of some specific embodiments of the present invention, making the technical solution of the present invention clearer, and do not mean that the present invention can only use the above-mentioned reagents. The specific scope shall be determined by the claims. In addition, unless otherwise specified, "parts" in the examples and comparative examples refer to parts by weight.

[0039] Any range described in this invention includes the endpoint, any value between the endpoints, and any subrange consisting of the endpoint or any value between the endpoints.

[0040] Examples 1-5 were carried out according to the following steps:

[0041] (1) Prepare a dopamine solution with a concentration of 1.5 g / L, place the nanocellulose fiber in the dopamine solution, the ratio of the two is 1 g: 30 ml, mix and stir for 2 h, add Tris buffer to the obtained nanocellulose fiber-dopamine solution, adjust the pH of the system to 8.5, continue stirring for 5 h, then filter, wash and dry to obtain modified nanocellulose fiber.

[0042] (2) Weigh all components according to the proportions in Table 1, and add them sequentially to a high-speed mixing pot and mix for 3 minutes to obtain a premix. Then, add the premix to a twin-screw extruder through the main feed port. After melt extrusion, cooling, and granulation, bake at 90°C for 4 hours in a drying tank to obtain a polypropylene composite material for high-efficiency spraying of water-based paints. The twin-screw extruder speed is set to 400 rpm, and the temperatures from the feeding section to the die head are 80°C, 190°C, 200°C, 210°C, 210°C, 200°C, 200°C, 200°C, 200°C, and 200°C, respectively. The screw speed is 400 r / min, the length-to-diameter ratio of the twin-screw extruder is 40:1, the vacuum degree during extrusion is -0.08 MPa, and the extruder die head uses a double-layer 100-mesh filter.

[0043] The obtained polypropylene composite material for high-efficiency water-based paint spraying was made into a test sample with dimensions of 210*140*2.5mm. Water-based paint, selected from the Onwaves brand of Donglai Coatings, was sprayed onto the sample. The specific spraying process was as follows: the sample surface was first washed with water, dried, and then sprayed three times back and forth using a spraying fixture. It was then baked in an 80℃ oven for 30 minutes, removed, and cooled to room temperature for 48 hours, resulting in a paint film thickness of approximately 0.1mm. All tests listed in Table 2 were then performed. The water resistance test was conducted using a constant-temperature digital display water bath at a temperature of 40±2℃. The results are shown in Table 2.

[0044] Table 1

[0045]

[0046]

[0047] Table 2

[0048]

[0049] As can be seen from the test results in Tables 1 and 2, the present invention obtains a polypropylene composite material that can be efficiently sprayed with water-based paint by using conventional polypropylene, porous polypropylene, modified nanocellulose fiber, inorganic filler, toughening agent, antioxidant, lubricant and carbon black in a specific ratio. As can be seen from the test results of Example 1 and Comparative Examples 1-2, the present invention uses dopamine to modify the surface of nanocellulose fibers, which can effectively improve their compatibility with polypropylene resin. Furthermore, the surface hydroxyl activity of nanocellulose enables it to have good compatibility with water-based paints, thereby improving the adhesion between the water-based paint and the resin surface. In addition, it also significantly improves the mechanical properties of the polypropylene composite material. As can be seen from Example 1 and Comparative Example 3, the introduction of porous polypropylene raw materials can maintain the porous structure of the material surface, making it easier for water-based paint to penetrate into the resin and allowing the water-based paint to cure well on the substrate surface. The combined use of modified nanocellulose fibers and porous polypropylene improves the adhesion between the water-based paint and the resin substrate in the early stages, while the latter enhances the penetration ability of the water-based paint. Together, they effectively increase the high-efficiency spraying effect of the water-based paint on the polypropylene composite material, exhibiting extremely strong adhesion. The water boiling resistance test, cross-cut adhesion test, and steam jet test all meet the stringent testing requirements for spray-painted products.

[0050] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0051] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A polypropylene composite material that can be used for high efficiency spray coating of water-based paint, characterized by, The water-based paint high-efficiency spraying polypropylene composite material is prepared from 45-61 parts of conventional polypropylene, 5-20 parts of porous polypropylene, 5-15 parts of toughening agent, 15-30 parts of inorganic filler, 2-10 parts of modified nanocellulose fiber, 0.2-0.4 parts of antioxidant, 0.1-0.3 parts of lubricant, and 0.2-0.6 parts of color powder according to weight parts; wherein the modified nanocellulose fiber is a nanocellulose fiber treated by dopamine surface modification.

2. The polypropylene composite material for high-efficiency spraying of water-based paint according to claim 1, characterized in that, The conventional polypropylene is at least one of copolymerized polypropylene or homopolymerized polypropylene, and the melt index thereof is 5-100 g / 10 min under the condition of 230℃ / 2.16 kg.

3. The polypropylene composite material for high-efficiency spraying of water-based paint according to claim 1, characterized in that, The porosity of the porous polypropylene is 10-30%.

4. The polypropylene composite material for high-efficiency spraying of water-based paint according to claim 1, characterized in that, The toughening agent is at least one of POE, EPDM, HDPE, LLDPE, and SEBS.

5. The polypropylene composite material for high-efficiency spray of water-based paint according to claim 1, characterized in that, The inorganic filler is at least one of talc, calcium carbonate, wollastonite, mica, and magnesium sulfate whisker.

6. The polypropylene composite material for high-efficiency spraying of water-based paint according to claim 1, characterized in that, The modification method of the modified nanocellulose fiber comprises the following steps: The nanocellulose fiber is stirred in a dopamine solution for 1-3 h, the pH value of the system is adjusted to 8-9, and the stirring is continued for 3-6 h, and then the modified nanocellulose fiber is obtained by filtration, washing, and drying; wherein the concentration of the dopamine solution is 1-2 g / L, and the dosage ratio of the modified nanocellulose fiber to the dopamine solution is 1 g:(20-40) mL.

7. The polypropylene composite material for high-efficiency spraying of water-based paint according to claim 1, characterized in that, The antioxidant is compounded from a main antioxidant and an auxiliary antioxidant, the main antioxidant is one of antioxidant 1010 or antioxidant 1076, and the auxiliary antioxidant is antioxidant 168.

8. The polypropylene composite material for high-efficiency spraying of water-based paint according to claim 1, characterized in that, The lubricant is at least one of calcium stearate, zinc stearate, and stearate.

9. The method for preparing polypropylene composite material for high efficiency spray of water-based paint according to any one of claims 1-8, characterized in that, The method comprises the following steps: The conventional polypropylene, porous polypropylene, toughening agent, modified nanocellulose fiber, inorganic filler, antioxidant, lubricant, and color powder are mixed uniformly according to weight parts, and then are put into a double-screw extruder to be melted, extruded, water-cooled, air-dried, granulated, and baked at 80-100℃ for 2-6 h, so as to obtain the water-based paint high-efficiency spraying polypropylene composite material.

10. The production method according to claim 9, wherein The extrusion temperatures of the double-screw extruder in each zone are 80±10℃, 190±10℃, 200±10℃, 210±10℃, 210±10℃, 210±10℃, 200±10℃, 200±10℃, 200±10℃, and 200±10℃ in sequence, the screw rotation speed is 350-450 r / min, the length-diameter ratio of the double-screw extruder is (36-48):1, the vacuum degree during the extrusion process is -0.05 to -0.1 MPa, and the double-layer 80-120 mesh filter screen is arranged at the head of the extruder.

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