A spray-paint-grade high-toughness recycled ABS and its preparation method

Abstract

The present invention relates to a paint-grade, high-toughness recycled ABS and a preparation method thereof. The preparation method comprises mixing recycled ABS, a high-flow additive, a tackifier, and a compatibilizer, melt-extruding, and cooling to obtain the recycled ABS product. Compared with existing technologies, this invention effectively addresses the industry pain points of low surface gloss and high paint rejection rates encountered during the secondary processing of recycled ABS. The resulting recycled ABS resin has mechanical properties and surface characteristics comparable to those of virgin ABS. This not only reduces environmental pollution caused by waste materials and increases the value of recycled materials, but also enhances the product competitiveness of plastic modification companies.

Description

Technical Field

[0001] The invention belongs to the technical field of ABS recovery and modification, and relates to a method for preparing spray-paint-grade high-toughness recycled ABS. Background Art

[0002] ABS, a terpolymer of styrene, acrylonitrile, and butadiene, combines excellent mechanical and processing properties, room-temperature and low-temperature toughness, and chemical resistance. Due to the high surface tension of the base material, it is also easy to paint, making it widely used in industries such as home appliances and automobiles. However, in recent years, the price of ABS raw materials has remained high, placing significant cost pressure on plastics modification companies and downstream enterprises. Furthermore, the amount of ABS waste generated annually is enormous. Processing recycled ABS to produce products that meet market demand would not only reduce costs to a certain extent but also alleviate the environmental problems caused by the difficulty in degrading waste ABS. Currently, there are numerous companies engaged in ABS resin recycling both domestically and internationally, including INEOS Styrolution, Indaver, and Jiangxi Green Cycle, with mature recycling technologies. These recycled ABS particles are typically obtained by recycling old household appliances, such as white goods casings, through pulverization, multiple cleaning, dehydration, and drying.

[0003] ABS recycled materials are mainly divided into two categories according to their sources: (1) scraps and waste materials from the injection molding process; and (2) various products that have been used beyond their expiration date. Generally, the main properties of the first type do not change much. After modification, they can meet the corresponding mechanical performance requirements. They are also the most common types of recycled ABS products on the market. However, due to the impurities that may be mixed in the raw material source itself and the inorganic or metallic impurities introduced during the product processing process, the recycled ABS will have low gloss and difficulty in painting during the secondary injection molding. This limits its use in some occasions where gloss requirements are high and painting is required. The reason for this phenomenon is that the impurities in the matrix have poor interfacial bonding with the ABS itself, and due to differences in density and fluidity, the impurities migrate to the surface of the material during the injection molding process to form defects such as pitting.

[0004] In the industry, there are three main approaches to addressing impurity spots (pitting): (1) blending new ABS with recycled materials from a formulation perspective; (2) improving processing techniques, such as increasing processing temperature and back pressure; and (3) post-processing, such as polishing the finished parts. However, these methods can only reduce the probability of pitting to a certain extent and are uneconomical, increasing production and processing costs. Summary of the Invention

[0005] The purpose of the present invention is to provide a spray-paint grade high-toughness recycled ABS and a preparation method thereof, so as to solve the problem of many pitting in ABS recycled materials.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for preparing spray-paint-grade high-toughness recycled ABS, comprising:

[0008] 85-92 wt% recycled ABS, 3-7 wt% high flow additive, 2-8 wt% tackifier and 2-3 wt% compatibilizer are uniformly mixed, melt-extruded and granulated in a screw extruder to obtain spray-paint grade high-toughness recycled ABS.

[0009] Preferably, during the mixing process, the components are mixed in a high-speed mixer for 5 to 20 minutes until the additive and the recycled ABS are uniformly mixed.

[0010] Preferably, during the melt extrusion process, the set temperatures of the twin-screw extruder used from the feeding port to the die head are: zone 1 temperature 180-200°C, zone 2 temperature 210-230°C, zone 3 temperature 220-230°C, zone 4 temperature 220-235°C, zone 5 temperature 220-235°C, zone 6 temperature 220-240°C, zone 7 temperature 220-240°C, zone 8 temperature 220-240°C, zone 9 temperature 220-240°C, zone 10 temperature 220-240°C, and the screw speed is 400-700rpm.

[0011] Preferably, the density of the recycled ABS is 1.04-1.08 g / cm 3 The melt index at a temperature of 220°C and a pressure of 10kg is 5-40g / 10min, the notched impact strength is 50-200J / m, and the color is black or natural.

[0012] Preferably, the high flow aid is prepared from the following components calculated by weight:

[0013] Polybutylene terephthalate (PBT): 50-85 parts,

[0014] Polyethylene terephthalate (PET): 5-30 parts,

[0015] Styrene and acrylonitrile copolymer (SAN): 5-20 parts,

[0016] Ethylene methyl acrylate copolymer (EMA): 5-10 parts,

[0017] Transesterification accelerator: 0.05-0.3 parts,

[0018] Lubricant: 0.2-2 parts,

[0019] Antioxidant: 0.1-1 part;

[0020] The total weight of the four components of PBT, PET, SAN and EMA is 100 parts.

[0021] Preferably, the viscosity of the PBT at 25°C is 0.6-1.2 dL / g; the viscosity of the PET at 25°C is 0.6-1 dL / g; the weight-average molecular weight of the SAN is 20,000-80,000, of which the acrylonitrile (AN) content is 22-35 wt%; the melt index of the EMA at a temperature of 190°C and a pressure of 2.16 kg is 2-15 g / 10 min, of which the methyl acrylate (MA) content is 20-30 wt%; the transesterification accelerator is a titanate transesterification accelerator, including at least one of butyl titanate, tetrabutyl titanium, and isopropyl tri(diethoxy)titanium; the lubricant is pentaerythritol stearate; and the antioxidant is composed of a mixture of IG-1076 antioxidant and IG-168 antioxidant in a mass ratio of 1:1.

[0022] Preferably, the preparation method of the high flow aid comprises: uniformly mixing PBT, PET, SAN, EMA, an ester exchange promoter, a lubricant, and an antioxidant according to parts by weight, and then melt-extruding, cooling, and pelletizing to obtain the high flow aid; during the melt extrusion process, the operating temperature of the twin-screw extruder used is 180-260°C. More preferably, the setting temperature of the twin-screw extruder from the feed port to the die is: zone 1 temperature 180-200°C, zone 2 temperature 220-240°C, zone 3 temperature 230-250°C, zone 4 temperature 230-255°C, zone 5 temperature 230-255°C, zone 6 temperature 230-260°C, zone 7 temperature 230-260°C, zone 8 temperature 230-250°C, zone 9 temperature 230-250°C, and zone 10 temperature 230-260°C; the screw speed is 400-800rpm. Properly increasing the processing temperature can promote the ester exchange of PBT and PET, thereby increasing the processing temperature of the material. However, too high a temperature may cause the material to decompose. Therefore, it is preferable to use the upper limit temperature of the temperature range while ensuring that the material can withstand the temperature.

[0023] Preferably, the tackifier includes one or more of styrene-butadiene-styrene block copolymer (SBS) elastomer, acrylonitrile-butadiene-styrene copolymer (ABS) high rubber powder, and acrylonitrile-styrene-acrylate rubber graft copolymer (ASA) high rubber powder.

[0024] Preferably, in the SBS elastomer, the weight ratio of styrene to butadiene is (2:8) to (4:6), the weight average molecular weight is 100,000 to 200,000, and the SBS has a star-shaped structure;

[0025] The ABS high-density rubber powder has a butadiene content of 50-65 wt%, a weight-average molecular weight of 90,000-150,000, and an AN content of SAN in the rubber powder of 18-35 wt%.

[0026] The ASA high-rubber powder has an acrylate rubber content of 45-65wt%, a rubber particle size of 100-500nm, a grafting rate of 60-90%, and a cross-linking degree of 70-90%.

[0027] Preferably, the compatibilizer is styrene-acrylonitrile-glycidyl methacrylate (AS-GMA), with a weight average molecular weight of 40,000 to 100,000 and a glycidyl methacrylate content of 1 to 8 wt%.

[0028] A spray-paint-grade high-toughness recycled ABS is prepared by the method described above.

[0029] Compared with the prior art, the present invention has the following characteristics:

[0030] 1) The present invention addresses the characteristics of different types of impurities in recycled ABS by introducing rubber powder, particularly a star-shaped SBS elastomer, to increase the viscosity of the matrix, thereby reducing the possibility of impurities migrating to the surface during processing and improving the toughness of the material to a certain extent;

[0031] 2) The high-flowability additive used in this invention is precisely compatible with the substrate, allowing for interaction without fusion. This promotes high material flow and allows the additive to easily flow to the surface during the injection molding process, smoothing out surface irregularities caused by impurities. It also improves the chemical resistance of the base resin, preventing excessive corrosion during contact between the paint layer and the recycled ABS during the painting process, ensuring a smooth, pit-free surface. Furthermore, PBT's rapid crystallization prevents impurities from migrating to the surface during cooling, and its high surface tension also facilitates painting.

[0032] 3) The AS-GMA compatibilizer used in the present invention can effectively solve the material brittleness problem caused by the addition of low molecular weight PBT, thereby improving the overall compatibility and toughness of the material;

[0033] 4) The modification method used in the present invention effectively reduces the problem of impurity points (pitting) on ​​the surface of recycled ABS injection molded parts, effectively reduces the number of pitting and improves the impact toughness of the recycled ABS. The paint yield rate is also increased from 30% to over 90%;

[0034] 5) This invention addresses the industry pain points of low surface gloss and high paint rejection rates encountered during the secondary processing of recycled ABS. The resulting recycled ABS resin has mechanical properties and surface characteristics comparable to those of new ABS. This not only reduces environmental pollution caused by waste materials, increases the value of recycled materials, but also enhances the product competitiveness of plastic modification companies. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to specific embodiments.

[0036] In the following examples, the sources of raw materials used are as follows:

[0037] Recycled ABS 1: Recycled ABS from Qingdao Bailimei New Materials Co., Ltd., with a density of 1.06 g / cm 3 ;Surface pit density 4.5 / cm 2 , surface pit size is 0.3-1.3μm; notched impact strength is 120J / m (ASTM D256, 6.4mm, 23℃); color is black, melt index (220℃, 10kg condition) is 25g / 10min.

[0038] Recycled ABS2: Recycled ABS from Qingdao Bailimei New Materials Co., Ltd., with a density of 1.06g / cm 3 ;Surface pit density 2.1 / cm 2 , surface pit size 0.2~1.1μm, notched impact strength 95J / m, black, melt index (220℃, 10kg condition) 20g / 10min;

[0039] PBT: Sinopec Yizheng Chemical Fiber Co., Ltd., viscosity 0.8 dL / g (25°C); PET, viscosity 0.85 dL / g (25°C), Jinshan Petrochemical Co., Ltd.; SAN, AN content 24 wt%, weight-average molecular weight 40,000, Shanghai Rizhisheng Fine Chemical Co., Ltd.; EMA, MA content 25 wt%, melt index 3 g / 10 min at 190°C and 2.16 kg, Dupont; transesterification accelerator: butyl titanate; lubricant: pentaerythritol stearate; antioxidant: IG-1076 and IG-168, mixed in a 1:1 ratio;

[0040] SBS: melt index 0.40 / 10min (200°C*5kg), Hunan Yueyang Baling Petrochemical Co., Ltd.; weight ratio of styrene to butadiene is 3:7, weight-average molecular weight 111,000;

[0041] AS-GMA: SAG002, manufactured by Rizhisheng Fine Chemical Co., Ltd., with a weight average molecular weight of 90,000 and a glycidyl methacrylate content of 2 wt%.

[0042] The test characterization method is as follows:

[0043] Surface pitting density: ABS high-gloss board was prepared by mixing recycled ABS pellets in a high-gloss mold. The high-gloss board was used as the observation object. The size of the high-gloss board was 100mm×100mm×3mm. The number of pitting on the surface was counted and then the number of pitting was divided by 100cm. 2 The surface pit density was obtained. A total of 20 samples were evaluated and the average value was taken.

[0044] Defect density of painted surface pitting: Use a commercially available acrylic primer commonly used for ABS to paint the high-gloss board and evaluate the surface defect density of the sample after painting.

[0045] Paint yield rate: 50 sample panels are sprayed for each scheme for verification. The number of samples without pitting is considered as good paint. The ratio of good paint to the total number of samples sprayed is the paint yield rate.

[0046] IZOD notched impact strength: tested according to ASTM D256-10 (2018) standard, impact energy is 5.5J, and the test temperature is 23°C.

[0047] Example:

[0048] A high flow aid, the preparation method of which comprises:

[0049] According to the mass ratio in Table 1, PBT, PET, transesterification promoter, EMA, SAN, lubricant and antioxidant were added to a high-speed mixer and fully mixed. The mixed sample was then added to a twin-screw extruder for melt extrusion. The setting temperatures of the twin-screw extruder from the feed port to the die were: zone 1 temperature 190°C, zone 2 temperature 230°C, zone 3 temperature 240°C, zone 4 temperature 240°C, zone 5 temperature 245°C, zone 6 temperature 250°C, zone 7 temperature 250°C, zone 8 temperature 240°C, zone 9 temperature 240°C, zone 10 temperature 250°C; the screw speed was 600rpm, and the high flow additive was obtained by cooling and pelletizing.

[0050] Table 1: Distribution ratio of high flow additive components (parts by weight)

[0051]

[0052]

[0053] A spray-paint-grade high-toughness recycled ABS, the preparation method of which comprises:

[0054] According to the mass ratios in Tables 2 and 3, the recycled ABS, high flow additive, tackifier, and compatibilizer were added to a high-speed mixer and stirred for 5 minutes to fully mix. The mixed sample was then added to a twin-screw extruder for melt extrusion. The set temperatures of the twin-screw extruder from the feed port to the die were: zone 1 temperature 190°C, zone 2 temperature 220°C, zone 3 temperature 225°C, zone 4 temperature 230°C, zone 5 temperature 230°C, zone 6 temperature 230°C, zone 7 temperature 230°C, zone 8 temperature 230°C, zone 9 temperature 230°C, and zone 10 temperature 230°C; the screw speed was 600 rpm, and the recycled ABS product was obtained by cooling and pelletizing.

[0055] Table 2 Proportions (mass percentage) and properties of Examples 1-6

[0056]

[0057]

[0058] Table 3 Comparative Examples 1-5 Proportions (mass percentage) and performance

[0059]

[0060] Table 4 Comparative Examples 6 to 9 Proportions (mass percentage) and properties

[0061]

[0062] By comparing Table 2 with Table 3 and Table 4, it can be seen that: compared with Example 1, the high flow aid is removed in Comparative Example 1: the number of pits increases and the paint yield decreases; compared with Example 1, when the high flow aid is not used with the ester exchange promoter, the fluidity of the ABS finished product prepared with it decreases, and although the paint yield of Comparative Example 2 is significantly improved compared with Comparative Example 1, it is still poorer than that of Example 1; similarly, by comparing Comparative Examples 3 to Comparative Examples 6 with Example 1, it can be seen that the introduction of PET, SAN, and EMA into the high flow aid has certain benefits on the fluidity, compatibility, and toughness of the finished product, thereby achieving a higher final paint yield and excellent surface effect of the product. In Comparative Example 6, only PBT was used to prepare the high flow additive. Although there was some effect, it was difficult to achieve a significant improvement in the appearance effect and the paint yield: PBT was difficult to migrate to the surface, and the number of pits increased; in Comparative Example 7, compared with Example 1, the tackifier was removed: impurities migrated to the surface, the number of pits increased, and the paint yield decreased; in Comparative Example 8, the compatibilizer AS-GMA was removed: the product impact strength was very low; in Comparative Example 9, compared with Example 1, recycled ABS had the most pits.

[0063] It can be seen that the present invention is very effective in reducing the number of pits and improving the toughness of recycled materials, and has a relatively obvious improvement in the yield of spray painting.

[0064] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing spray-paint-grade high-toughness recycled ABS, characterized in that: include: 85-92 wt% recycled ABS, 3-7 wt% high flow additive, 2-8 wt% tackifier, and 2-3 wt% compatibilizer are uniformly mixed, melt-extruded and granulated in a screw extruder to obtain spray-paint grade high-toughness recycled ABS; The high flow additive is prepared from the following components calculated by weight: PBT 50~85 parts, PET 5~30 parts, SAN 5~20 servings, EMA 5-10 copies, 0.05~0.3 parts of transesterification accelerator, 0.2~2 parts of lubricant, 0.1~1 part of antioxidant; The total weight of the four components of PBT, PET, SAN and EMA is 100 parts.

2. The method for preparing a spray-paint-grade high-toughness recycled ABS according to claim 1, characterized in that: The density of the recycled ABS is 1.04~1.08g / cm 3 The melt index at a temperature of 220°C and a pressure of 10kg is 5~40g / 10min, and the notched impact strength is 50~200J / m.

3. The method for preparing a spray-paint-grade high-toughness recycled ABS according to claim 1, characterized in that: The viscosity of the PBT at 25° C. is 0.6-1.2 dL / g; the viscosity of the PET at 25° C. is 0.6-1 dL / g; the weight-average molecular weight of the SAN is 20,000-80,000, wherein the acrylonitrile content is 22-35wt%; the melt index of the EMA at a temperature of 190° C. and a pressure of 2.16 kg is 2-15 g / 10 min, wherein the methyl acrylate content is 20-30wt%.

4. The method for preparing a spray-paint-grade high-toughness recycled ABS according to claim 1, characterized in that: The transesterification accelerator is a titanate transesterification accelerator.

5. The method for preparing a spray-paint-grade high-toughness recycled ABS according to claim 4, characterized in that: The titanate ester exchange promoter includes at least one of butyl titanate, tetrabutyl titanate, and isopropyl tri(diethoxy) titanate.

6. The method for preparing a spray-paint-grade high-toughness recycled ABS according to claim 1, characterized in that: The tackifier includes one or more of styrene-butadiene-styrene block copolymer elastomer, acrylonitrile-butadiene-styrene copolymer high-rubber powder or acrylonitrile-styrene-acrylate rubber graft copolymer high-rubber powder.

7. The method for preparing a spray-paint-grade high-toughness recycled ABS according to claim 6, characterized in that: The styrene-butadiene-styrene block copolymer elastomer is a star-shaped SBS, wherein the weight ratio of styrene to butadiene is (2:8) to (4:6), and the weight-average molecular weight is 100,000 to 200,000; the acrylonitrile-butadiene-styrene copolymer high-rubber powder has a butadiene content of 50 to 65% by weight, a weight-average molecular weight of 90,000 to 150,000, and an AN content of SAN in the rubber powder of 18 to 35% by weight; the acrylonitrile-styrene-acrylate rubber graft copolymer high-rubber powder has an acrylate rubber content of 45 to 65% by weight, a rubber particle size of 100 to 500 nm, a grafting rate of 60 to 90%, and a cross-linking degree of 70 to 90%.

8. The method for preparing a spray-paint-grade high-toughness recycled ABS according to claim 1, characterized in that: The compatibilizer is styrene-acrylonitrile-glycidyl methacrylate, with a weight average molecular weight of 40,000 to 100,000 and a glycidyl methacrylate content of 1 to 8 wt%.

9. The method for preparing a spray-paint-grade high-toughness recycled ABS according to any one of claims 1 to 8, characterized in that: In the melt extrusion process, the set temperatures of the twin-screw extruder used from the feed port to the die head are: zone 1 temperature 180-200°C, zone 2 temperature 210-230°C, zone 3 temperature 220-230°C, zone 4 temperature 220-235°C, zone 5 temperature 220-235°C, zone 6 temperature 220-240°C, zone 7 temperature 220-240°C, zone 8 temperature 220-240°C, zone 9 temperature 220-240°C, and zone 10 temperature 220-240°C; the screw speed is 400-700rpm.

10. A spray-paint grade high-toughness recycled ABS, characterized in that: The method is prepared by the method according to any one of claims 1 to 9.

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