Polypropylene composition as well as preparation method and application thereof

Abstract

The invention discloses a polypropylene composition which comprises the following components in parts by weight: 59-81 parts of polypropylene; 8-30 parts of a water carrier talcum powder; 2-12 parts of a toughening agent; and 3-10 parts of polyethylene. By selecting the water carrier talcum powder, the polypropylene composition has good dispersity, and can improve pocking marks easily occurring in the processing process of the polypropylene composition and reduce TVOC (Total Volatile Organic Compounds).

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a polypropylene composition, a preparation method thereof, and an application thereof. Background Art

[0002] With the increase in the number of automobiles owned in China and the enhancement of consumers' health awareness, the air quality in the cockpit has attracted more and more extensive attention from consumers. Some low-boiling-point volatile substances existing in the cockpit will directly affect the physical and mental health of drivers and passengers. In view of this, many vehicle manufacturers and parts suppliers have put forward control requirements for VOC (volatile organic compounds) and TVOC (total volatile organic compounds) of parts and materials.

[0003] Due to its excellent comprehensive performance, the proportion of modified polypropylene materials in modified plastics for automobiles has been on the rise. Interior parts such as instrument panels, glove boxes, pillars, seat peripheries, and door panels mostly use modified polypropylene materials for injection molding at present. The main sources of volatile substances in polypropylene materials are as follows: First, monomers and catalysts remaining in the synthesis process of polypropylene resin; second, degradation products of polypropylene macromolecular chains after experiencing high temperature and strong shear during modification and injection molding; third, some processing and functional additives added during modification and their decomposition products after experiencing high temperature and shear. Controlling the volatile small molecules generated by polypropylene materials and developing low-VOC modified polypropylene products are important issues that need to be urgently solved for automotive interior polypropylene materials and are also the development direction of automotive interior materials in recent years.

[0004] At the same time, as automotive interior parts, inorganic fillers are usually added to play a role in filling and strengthening. Since common fillers such as talcum powder and calcium carbonate exist in powder form, when directly added during the modification of polypropylene, it is easy to cause agglomeration of the powder due to poor dispersion uniformity of the filled powder, resulting in raised pockmarks on the surface of the injection-molded part due to local filler agglomeration. In view of the fact that the current requirements of each parts manufacturer and vehicle manufacturer for the aesthetics of appearance parts are gradually increasing, it is necessary to develop a polypropylene modified product with good appearance and no pockmarks. In order to improve the dispersion of talcum powder during extrusion and avoid the generation of pockmarks, talcum powder masterbatch is usually used to replace the powder during modification in the industry. And the preparation of talcum powder masterbatch usually requires kneading the resin matrix and talcum powder with a mixer and then extruding and pelletizing. During the process of talcum powder masterbatch, the resin will be decomposed by high temperature and strong shear, increasing the VOC level, and it is difficult to balance the appearance of the product and a low TVOC level at the same time. Summary of the Invention

[0005] The purpose of the present invention is to provide a polypropylene composition with few pockmarks and low TVOC.

[0006] The present invention is achieved through the following technical solutions: A polypropylene composition, by weight, comprises the following components: 59 - 81 parts of polypropylene; 8 - 30 parts of water - carried talc powder; 2 - 12 parts of toughening agent; 3 - 10 parts of polyethylene.

[0007] In the polypropylene composition of the present invention, the weight content of polypropylene can be 59 parts, 61 parts, 63 parts, 65 parts, 67 parts, 69 parts, 71 parts, 73 parts, 75 parts, 77 parts, 80 parts, etc.; the water - carried talc powder can be 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, etc.; the toughening agent can be 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, etc.; the polyethylene can be 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.

[0008] Preferably, the polyethylene is selected from at least one of high - density polyethylene and linear low - density polyethylene; more preferably, the polyethylene is selected from linear low - density polyethylene.

[0009] The melt index range of the linear low - density polyethylene is 1 - 25 g / 10min, at 190 °C, 2.16 kg. The test standard is ISO 1133 - 1:2022.

[0010] The melt index range of the high - density polyethylene is 1 - 10 g / 10min, at 190 °C, 2.16 kg.

[0011] The melt index range of the polypropylene is 9 - 90 g / 10min, at 230 °C, 2.16 kg. In the polypropylene composition of the present invention, the percentage of polypropylene in the total weight is not less than 48 wt%.

[0012] The water content of the water - carried talc powder is 1.5 - 7.5 wt%; preferably 3 - 5 wt%.

[0013] The water - carried talc powder can be a commercially available product or obtained by self - preparation. The self - preparation method is: according to the water content of the water - carried talc powder, mix water and talc powder evenly, and then press into tablets to obtain the water - carried talc powder.

[0014] In the water - carried talc powder, the average particle size of the talc powder is 3 - 20 microns. The average particle size is tested by a laser particle size analyzer.

[0015] The toughening agent can be selected from copolymers of ethylene and α - olefins, including but not limited to one or more of ethylene - butene copolymer, ethylene - hexene copolymer, and ethylene - octene copolymer.

[0016] The toughening agent is selected from at least one of POE (polyolefin elastomer), POP (polyolefin plastomer), and mPE (metallocene PE).

[0017] For the purpose of reducing pits, POP is further preferably selected as the toughening agent.

[0018] According to actual requirements, at least one of 0 - 3 parts of antioxidant, color powder, and light stabilizer can be selected and added.

[0019] The antioxidant can be a hindered phenol antioxidant, a phosphite antioxidant, etc.

[0020] The light stabilizer can be a hindered amine light stabilizer, a benzophenone light stabilizer, etc.

[0021] The preparation method of the polypropylene composition of the present invention includes the following steps: According to parts by weight, mix each component evenly, and extrude and pelletize through a twin - screw extruder to obtain the polypropylene composition. The melting and extrusion conditions of the twin - screw extruder are as follows: the temperature of the first zone is 100 - 120 °C, the temperature of the second zone is 190 - 210 °C, the temperature of the third zone is 210 - 230 °C, the temperature of the fourth zone is 210 - 230 °C, the temperature of the fifth zone is 210 - 230 °C, the temperature of the sixth zone is 210 - 230 °C, the temperature of the seventh zone is 210 - 230 °C, the temperature of the eighth zone is 210 - 230 °C, the temperature of the ninth zone is 210 - 230 °C, the main machine speed is 250 - 600 revolutions per minute; the length - to - diameter ratio of the twin - screw extruder is 32:1 - 40:1.

[0022] The polypropylene composition of the present invention is applied to the preparation of automotive interior accessories, such as door panels, instrument panels, lower instrument panels, pillars, and seats.

[0023] The present invention has the following beneficial effects: In the present invention, by selecting water - borne talc powder with good dispersibility, and further selecting a toughening agent and high - density polyethylene or linear low - density polyethylene, the toughness is improved, and the pits that are likely to appear during the processing of the polypropylene composition can be reduced, and TVOC can be lowered. The specific mechanism of action may be as follows: 1. The water - borne talc powder used in the present invention, due to the addition of a water - injection process during the manufacturing process, its product can be kneaded into granular form. This form makes it easier to feed and transport during the melt - blending process than powder, so it has more excellent dispersibility, is not prone to powder agglomeration, and reduces the probability of appearance defects of pit appearance.

[0024] 2. The use of water-carried talcum powder in the present invention eliminates the generation of small molecule decomposition products due to the resin matrix in the masterbatch passing through the machine for the second time, and also avoids the addition of auxiliaries such as lubricants that have a negative effect on the odor emission. At the same time, some of the water contained in the talcum powder can also be miscible with organic small molecule substances such as aldehydes, ketones, and alcohols or form an azeotrope during the extrusion process, and these substances will be carried away together during the post-treatment process. The combined effect of the above three points can significantly reduce the content of odor-emitting organic substances generated by the material. Detailed Embodiments

[0025] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all fall within the protection scope of the present invention.

[0026] Polypropylene A: PP EP548R produced by CNOOC and Shell; Polypropylene B: BX3900 produced by SK of South Korea; HDPE: HDPE 7260 produced by Guangdong Petrochemical, with a melt flow rate of 8 g / 10 min at 190 °C and 2.16 kg; LLDPE: PE-L M2320 produced by Guangzhou Petrochemical, with a melt flow rate of 20 g / 10 min at 190 °C and 2.16 kg; Water-carried talcum powder A-1: with a water content of 1.5 wt%, self-made; Water-carried talcum powder A-2: with a water content of 3.0 wt%, self-made; Water-carried talcum powder A-3: with a water content of 5.0 wt%, self-made; Water-carried talcum powder A-4: with a water content of 7.5 wt%, self-made; The preparation method of water-carried talcum powder A is as follows: according to the water content, mix water / talcum powder evenly and then press into tablets. The above talcum powder is sourced from Tianyuan Chemical Industry, TYT-777A; Water-carried talcum powder B: LAmax E05W of AiHai Group, with a water content of 4%; Talcum powder: TYT-777A of Tianyuan Chemical Industry.

[0027] POE: POE ENGAGE 7467 of Dow Chemical Company, with a melt flow rate of 1 g / 10 min at 190 °C and 2.16 kg; POP: VL0005 of Daelim Technology, with a melt flow rate of 5 g / 10 min at 190 °C and 2.16 kg; mPE: ExxonMobil EXCEED 3518PA, melt flow rate of 3.5 g / 10 min, at 190 °C, 2.16 kg; Color powder: commercially available carbon black; Antioxidant: Antioxidant 1010 and Antioxidant 168 are composed in a mass ratio of 1:1. Both Antioxidant 1010 and Antioxidant 168 are commercially available products.

[0028] Light stabilizer: Solvay UV-3808PP5.

[0029] Preparation method of the polypropylene compositions of the examples and comparative examples 1-4: Mix the components evenly to obtain a premix, and then add the premix to the main feed port of a twin-screw extruder for melt extrusion, pelletizing and drying to obtain the polypropylene composite. The melt extrusion conditions of the twin-screw extruder are as follows: the temperature of the first zone is 100-120 °C, the temperature of the second zone is 190-210 °C, the temperature of the third zone is 210-230 °C, the temperature of the fourth zone is 210-230 °C, the temperature of the fifth zone is 210-230 °C, the temperature of the sixth zone is 210-230 °C, the temperature of the seventh zone is 210-230 °C, the temperature of the eighth zone is 210-230 °C, the temperature of the ninth zone is 210-230 °C, and the main machine speed is 250-600 revolutions per minute; the length-diameter ratio of the twin-screw extruder is 32:1.

[0030] Testing methods for each item: (1) Pockmarks: Inject the polypropylene composition into 4 combustion plates of 360 mm * 100 mm * 3 mm, observe the number of pockmarks on a single plate under a magnifying glass, and count the total amount.

[0031] (2) Appearance: Rate the appearance of the above 4 combustion plates according to the following criteria. When at least one of the plates shows air marks or water splash defects, it is judged as grade 2-4: Grade 1: The surface is good, without appearance defects such as air marks and water splashes; Grade 2: There are slight air marks and water splashes on the surface; Grade 3: The air mark and water splash phenomena are obvious; Grade 4: The air mark and water splash phenomena are serious.

[0032] (3) TVOC: Determine with reference to MS300-55, where the sampling bag capacity is 100 L, the heating temperature is 65 °C, and the heating time is 2 hours.

[0033] Table 1: Weight fraction content and test results of the polypropylene compositions of Examples 1-6 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Polypropylene A 80 70 70 70 70 Polypropylene B 60 Water-carrier talc A-2 15 8 30 8 8 8 POP 8 8 POE 2 12 8 mPE 8 LLDPE 10 10 10 HDPE 3 7 10 Color powder 0.8 0.8 0 0.8 0.8 0.8 Antioxidant 0.4 0.4 0 0.4 0.4 0.4 Light stabilizer 0.2 0.2 0 0.2 0.2 0.2 Number of pits 4 0 7 3 2 1 Appearance grade Grade 1 Grade 1 Grade 1 Grade 1 Grade 1 Grade 1 <![CDATA[TVOC (μg / m 3 )]]> 2935 3030 3178 3231 3457 3362 It can be seen from Examples 2 / 4 that polyethylene is preferably LLDPE and the TVOC is also less.

[0034] It can be seen from Examples 2 / 5 / 6 that when the toughening agent is preferably POP, there are fewer pockmarks and less TVOC.

[0035] Table 2: Parts by weight content and test results of polypropylene compositions in Examples 7 - 10 Example 7 Example 8 Example 9 Example 10 Polypropylene A 70 70 70 70 Label of water-carrier talc A-1 A-3 A-4 B Content of water-carrier talc 8 8 8 8 POP 8 8 8 8 LLDPE 10 10 10 10 Color powder 0.8 0.8 0.8 0.8 Antioxidant 0.4 0.4 0.4 0.4 Light stabilizer 0.2 0.2 0.2 0.2 Number of pits 3 0 0 0 Appearance grade Grade 1 Grade 1 Grade 2 Grade 1 <![CDATA[TVOC (μg / m 3 )]]> 3405 2866 2675 2973 As can be seen from Examples 2 / 7 - 9, fewer pits are preferred when using talcum powder with appropriate water content. If the water content of talcum powder is too high, some water splash phenomena will occur.

[0036] The number of pits of the polypropylene composition of the present invention is less than 10, the appearance grade ≥ 2, and the TVOC content is lower than 3600 μg / m 3 。

[0037] Table 3: Parts by weight content and test results of polypropylene compositions in Comparative Examples 1 - 2 Comparative Example 1 Comparative Example 2 Polypropylene A 70 70 Water-carrier talc A-2 8 Talc 8 POP 8 POE 15 LLDPE 10 10 Color powder 0.8 0.8 Antioxidant 0.4 0.4 Light stabilizer 0.2 0.2 Number of pits 31 12 Appearance grade Grade 1 Grade 1 <![CDATA[TVOC (μg / m 3 )]]> 4565 3756 As can be seen from Comparative Example 1, if ordinary talcum powder is selected, excessive pits will be caused due to insufficient dispersion of talcum powder.

[0038] As can be seen from Comparative Example 2 and Example 5, if the content of the toughening agent is too high, the number of pits will also increase. At the same time, since the toughening agent volatilizes VOC, the TVOC is also increased.

[0039] Comparative Example 3: 70 parts of polypropylene A, 7.76 parts of talcum powder, 0.24 parts of water, 8 parts of POP, 10 parts of LLDPE, 0.8 parts of color powder, 0.4 parts of antioxidant, and 0.2 parts of light stabilizer were mixed evenly to obtain a premix. Then the premix was added to the main feeding port of a twin - screw extruder for melt extrusion, pelletizing and drying to obtain the polypropylene composite. The melt extrusion conditions of the twin - screw extruder were: the temperature of zone 1 was 100 - 120°C, the temperature of zone 2 was 190 - 210°C, the temperature of zone 3 was 210 - 230°C, the temperature of zone 4 was 210 - 230°C, the temperature of zone 5 was 210 - 230°C, the temperature of zone 6 was 210 - 230°C, the temperature of zone 7 was 210 - 230°C, the temperature of zone 8 was 210 - 230°C, the temperature of zone 9 was 210 - 230°C, and the main machine speed was 250 - 600 revolutions per minute; the length - to - diameter ratio of the twin - screw extruder was 32:1.

[0040] The test results were: the number of pits was 28, the appearance grade was 2, and the TVOC was 3750 μg / m 3 。It can be seen that if the same amount of water is added in the traditional blending stage, it hardly improves the pits and TVOC, and instead causes the appearance defect of water streaks.

Claims

1. A polypropylene composition, characterized in that By weight, it includes the following components: Polypropylene 59-81 parts; 8-30 parts of water carrier talc; 2-12 parts of toughening agent; Polyethylene 3-10 parts.

2. The polypropylene composition according to claim 1, characterized in that The polyethylene is selected from at least one of high-density polyethylene and linear low-density polyethylene; preferably, the polyethylene is selected from linear low-density polyethylene.

3. The polypropylene composition according to claim 1, characterized in that The melting index range of the polypropylene is 9-90 g / 10 min, 230° C., 2.16 kg.

4. The polypropylene composition according to claim 1, characterized in that The water content of the water carrier talc is 1.5-7.5wt%, preferably 3-5wt%.

5. The polypropylene composition according to claim 1, characterized in that The average particle size of the talc in the water-carrier talc is 3-20 microns.

6. The polypropylene composition according to claim 1, characterized in that The toughening agent is selected from at least one of POE, POP and mPE.

7. The polypropylene composition according to claim 6, characterized in that The toughening agent is selected from POP.

8. The polypropylene composition according to claim 1, characterized in that By weight, it also includes 0-3 parts of at least one of an antioxidant, a colorant, and a light stabilizer.

9. The method for preparing the polypropylene composition according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: uniformly mixing the components according to weight, and extruding and granulating the components through a twin-screw extruder to obtain a polypropylene composition.

10. Use of the polypropylene composition according to any one of claims 1 to 8, characterized in that: Used to prepare automotive interior accessories.