阅读说明：本技术 一种免喷涂美学塑料的制备方法 (Preparation method of spraying-free aesthetic plastic ) 是由 曾军堂 陈庆 司文彬 李钧 于 2021-08-06 设计创作，主要内容包括：本发明涉及功能塑料制备的技术领域,公开了一种免喷涂美学塑料的制备方法。包括如下制备过程：(1)将EVA、聚乙烯蜡搅拌混合成为浆状,得到浆料；(2)以聚乙二醇8000对金属粉进行分散改性,并以聚硅氮烷进行包覆,得到预包覆金属颜料；(3)将浆料、预包覆金属颜料、珠光粉、色料搅拌混合成浆,采用三辊研磨机研磨分散,并冷却、粉碎,得到颗粒状色料；(4)将颗粒状色料与基体树脂混合均匀,挤出造粒,得到一种免喷涂美学塑料。本发明的方法克服了免喷涂塑料的颜料分散性及抗氧化性较差的缺陷,制得的免喷涂美学塑料的注塑件光亮均匀、无流痕,浸酸放置后也保持表面光亮均匀、无流痕。(The invention relates to the technical field of functional plastic preparation, and discloses a preparation method of spraying-free aesthetic plastic. The preparation method comprises the following preparation processes: (1) stirring and mixing EVA and polyethylene wax into slurry to obtain slurry; (2) dispersing and modifying metal powder by using polyethylene glycol 8000, and coating by using polysilazane to obtain a pre-coated metal pigment; (3) stirring and mixing the slurry, the pre-coated metal pigment, the pearl powder and the pigment into slurry, grinding and dispersing by using a three-roll grinder, cooling and crushing to obtain a granular pigment; (4) and uniformly mixing the granular pigment and the matrix resin, and extruding and granulating to obtain the spraying-free aesthetic plastic. The method overcomes the defects of poor pigment dispersibility and oxidation resistance of the spraying-free plastic, and the prepared spraying-free aesthetic plastic injection molding piece has uniform brightness and no flow mark, and the surface of the injection molding piece can be kept uniform and bright after the injection molding piece is placed in an acid dipping mode.)

1. The preparation method of the spraying-free aesthetic plastic is characterized by comprising the following specific steps:

(1) adding EVA and polyethylene wax into a stirrer, and stirring for 15-20min at 110-120 ℃ to form slurry to obtain slurry;

(2) firstly adding metal powder and polyethylene glycol 8000 into a high-speed dispersion machine for dispersion for 20-30 min, fully dispersing the metal powder under the action of high-speed stirring friction, then uniformly spraying polysilazane into the high-speed dispersion machine, and continuously dispersing for 20-30 min to obtain a pre-coated metal pigment; the addition amount of the polyethylene glycol 8000 is 0.2-0.3% of the mass of the metal powder; the addition amount of the polysilazane is 1-1.5% of the mass of the metal powder;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2), pearl powder and pigment into slurry, then grinding and dispersing the slurry in a three-roll grinder for 25-30 min to obtain dispersed color paste, and then cooling and crushing the dispersed color paste to obtain granular pigment;

(4) and uniformly mixing the granular pigment and the matrix resin, and extruding and granulating to obtain the spraying-free aesthetic plastic.

2. The method for preparing the painting-free aesthetic plastic according to claim 1, wherein the painting-free aesthetic plastic comprises the following steps: the raw materials in the step (1) comprise, by weight, 2 parts of EVA and 1 part of polyethylene wax.

3. The method for preparing the painting-free aesthetic plastic according to claim 1, wherein the painting-free aesthetic plastic comprises the following steps: the melt index of the EVA in the step (1) is more than 50g/10 min.

4. The method for preparing the painting-free aesthetic plastic according to claim 1, wherein the painting-free aesthetic plastic comprises the following steps: the metal powder in the step (2) is one of aluminum powder, silver powder, copper powder and stainless steel powder; the particle size of the metal powder is 20-50 mu m.

5. The method for preparing the painting-free aesthetic plastic according to claim 1, wherein the painting-free aesthetic plastic comprises the following steps: the raw materials in the step (3) comprise, by weight, 50-60 parts of slurry, 8-10 parts of pre-coated metal pigment, 1-2 parts of pearl powder and 0-1 part of pigment.

6. The method for preparing the painting-free aesthetic plastic according to claim 1, wherein the painting-free aesthetic plastic comprises the following steps: the pearl powder in the step (3) is one of mica powder and glass powder; the pigment is one of titanium dioxide, barium sulfate, carbon black, iron oxide red, iron oxide yellow and chromium oxide green.

7. The method for preparing the painting-free aesthetic plastic according to claim 1, wherein the painting-free aesthetic plastic comprises the following steps: and (3) the rotating speed ratio of the slow roller, the middle roller and the fast roller of the three-roller grinding machine is 1: 3: 9, controlling the roller temperature of the three-roller grinding machine to be 100-110 ℃.

8. The method for preparing the painting-free aesthetic plastic according to claim 1, wherein the painting-free aesthetic plastic comprises the following steps: the raw materials in the step (4) comprise, by weight, 1-2 parts of granular pigment and 8-9 parts of matrix resin.

9. The method for preparing the painting-free aesthetic plastic according to claim 1, wherein the painting-free aesthetic plastic comprises the following steps: and (4) the matrix resin is one of polypropylene, polyethylene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate, nylon, polylactic acid, polybutylene adipate-terephthalate and polybutylene succinate.

Technical Field

The invention relates to the technical field of functional plastic preparation, and discloses a preparation method of spraying-free aesthetic plastic.

Background

Plastics are widely used in automobiles, household appliances, electronic products, toys, artware and the like, and in order to achieve good quality and appearance, treatments such as spraying, gold plating and the like are mostly required. However, the plastic products coated with gold and coated with gold have poor scratch resistance, the surfaces of the plastic products are easy to age and turn dark, and the product quality improvement limitation is large. Especially, organic solvent paint must be used for spraying paint on the surface of plastic, which causes great pollution to the environment.

In order to further improve the quality of plastic products, the technology of painting-free aesthetic plastics has been rapidly developed in recent years. The spraying-free aesthetic plastic is a functional plastic which can be directly formed into a high-quality appearance through one-time injection molding by performing special modification treatment on the plastic, and can be designed to obtain different textures such as metal, pearlescence, glittering effect and the like according to requirements.

The core technology of the spraying-free aesthetic plastic is that the functional pigment is efficiently dispersed in the resin, surface spraying modification is not needed, and the spraying-free aesthetic plastic is environment-friendly and pollution-free. The plastic can greatly improve the quality of plastic products, and particularly meet the requirements of differentiated, personalized, diversified and differentiated customers.

In order to effectively disperse the functional pigment in the resin and form a good uniform effect, the spraying-free plastic has extremely high requirements on the dispersibility and the stability of the pigment. Due to the limitation of plastic modification technology, the dispersibility of the current spraying-free plastic has a plurality of problems. Mainly manifested by poor flow uniformity, easy generation of flow marks, poor compatibility and combination of functional pigments and resins, easy generation of powder removal, etc.

In addition, most of the functional pigments for spray-free plastics contain metal powder, which is easily oxidized and faded by the external environment, thereby affecting the color and luster, and the like, so that the weather resistance of the spray-free plastics needs to be solved.

Chinese patent publication No. CN102372904B discloses a method for preparing aesthetic resin for improving affinity of aluminum powder pigment, in order to improve the affinity of aluminum powder pigment and resin and increase the binding property of pigment and resin, the affinity of aluminum powder pigment and resin is improved by treating aluminum powder with organic solvent and then with coupling agent, but good uniform effect is still difficult to realize.

Chinese patent publication No. CN106317752B discloses a high weather-resistant aesthetic resin and a preparation method thereof, the weather resistance of the resin is improved by adding nano zinc oxide, nano silicon oxide, nano titanium oxide and the like, but the oxidation resistance of the metallic pigment cannot be effectively solved.

According to the above, the spraying-free plastic in the existing scheme has the defects of poor pigment dispersibility and oxidation resistance, so that the spraying-free plastic is difficult to keep lasting brightness.

Disclosure of Invention

The spraying-free plastic in the prior art has the defects of poor pigment dispersibility and oxidation resistance, and the invention solves the problems by the following technical scheme:

a preparation method of spraying-free aesthetic plastic comprises the following specific steps:

(1) adding EVA and polyethylene wax into a stirrer, and stirring for 15-20min at 110-120 ℃ to form slurry to obtain slurry;

(2) firstly adding metal powder and polyethylene glycol 8000 into a high-speed dispersion machine for dispersion for 20-30 min, fully dispersing the metal powder under the action of high-speed stirring friction, then uniformly spraying polysilazane into the high-speed dispersion machine, and continuously dispersing for 20-30 min to obtain a pre-coated metal pigment; the addition amount of the polyethylene glycol 8000 is 0.2-0.3% of the mass of the metal powder; the addition amount of the polysilazane is 1-1.5% of the mass of the metal powder;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2), pearl powder and pigment into slurry, then grinding and dispersing the slurry in a three-roll grinder for 25-30 min to obtain dispersed color paste, and then cooling and crushing the dispersed color paste to obtain granular pigment;

(4) and uniformly mixing the granular pigment and the matrix resin, and extruding and granulating to obtain the spraying-free aesthetic plastic.

In the step (1), EVA and polyethylene wax are adopted to prepare the slurry, wherein the EVA is a polymer with good fluidity at a lower temperature, and is melted into flowable liquid after being heated to a certain temperature, so that the slurry preparation is facilitated, and the polyethylene wax is not only a dispersing agent, but also is heated and melted into slurry, so that the pigment dispersion in the subsequent steps is facilitated. In order to ensure good fluidity of EVA, the melt index of EVA in step (1) is preferably greater than 50g/10 min. In a further preferred embodiment of the present invention, in the step (1), the raw materials are compounded in an amount of 2 parts by weight of EVA and 1 part by weight of polyethylene wax.

The step (2) is to pre-coat the metal pigment, and aims to improve the oxidation resistance and the corrosion resistance of the metal powder. As known, the surface of metal powder has hydroxyl, and the invention carries out dispersion modification on the metal powder by polyethylene glycol 8000 to activate the hydroxyl on the surface and increase the number of the hydroxyl. Furthermore, the invention utilizes polysilazane to carry out coating treatment on the metal powder, the polysilazane has Si-NH-Si bonds and is easy to solidify at room temperature, meanwhile, the Si-NH-Si bonds and-OH on the surface of the metal powder are easy to react to form a transparent coating layer, and the coating layer isolates the metal powder from the outside, thereby showing good oxidation resistance and corrosion resistance, and being used as a pigment for spraying-free plastics and having lasting brightness. Preferably, the metal powder in the step (2) is one of aluminum powder, silver powder, copper powder and stainless steel powder; the particle size of the metal powder is 20-50 mu m.

In general, in actual practice, a pigment is dispersed in a resin, and the resin has a high viscosity at the time of hot melting, so that the pigment is difficult to disperse, and the pigment is used in a small amount, so that if the pigment is not uniformly dispersed, the product is liable to be colored. Therefore, the invention firstly prepares the slurry with good fluidity, and the pigment is dispersed in the slurry and ground and dispersed in a three-roll grinder to form color paste, and then the color paste is dispersed with the matrix resin, so that the dispersibility of the pigment is greatly improved.

And (3) matching the pearl powder with the pre-coated metal pigment to obtain the granular pigment with glittering luster and free of spraying aesthetic resin, and optionally adding different pigments according to needs to prepare different colors. The pigment is an organic or inorganic pigment finished product meeting the requirement of high-temperature processing of plastics. Preferably, the pearl powder in the step (3) is one of mica powder and glass powder; the pigment is one of titanium dioxide, barium sulfate, carbon black, iron oxide red, iron oxide yellow and chromium oxide green. In a further preferable aspect of the present invention, the raw materials in step (3) include, by weight, 50 to 60 parts of a paste, 8 to 10 parts of a pre-coated metallic pigment, 1 to 2 parts of a pearl powder, and 0 to 1 part of a coloring material.

Further, a three-roll grinder is adopted in the step (3) for grinding and dispersing, and grinding and dispersing effects are achieved by mutual extrusion of the surfaces of the three horizontal rollers and friction at different speeds. Preferably, in the step (3), the rotating speed ratio of the slow roller, the middle roller and the fast roller of the three-roller grinder is 1: 3: 9. in order to ensure grinding in a slurry state, the roller temperature of the three-roller grinding machine is controlled to be 100-110 ℃.

The matrix resin in the step (4) is selected according to specific needs, and as a preferable aspect of the present invention, the matrix resin in the step (4) is one of polypropylene (PP), Polyethylene (PE), acrylonitrile-butadiene-styrene copolymer (ABS), polyethylene terephthalate (PET), nylon (PA), polylactic acid (PLA), polybutylene adipate-terephthalate (PBAT), and polybutylene succinate (PBS). In a further preferred embodiment of the present invention, in the step (4), the raw materials are mixed in an amount of 1 to 2 parts by weight of the particulate coloring material and 8 to 9 parts by weight of the matrix resin.

The invention provides a preparation method of spraying-free aesthetic plastic, which comprises the steps of stirring and mixing EVA and polyethylene wax into slurry to obtain slurry; then, carrying out dispersion modification on the metal powder by using polyethylene glycol 8000, and coating by using polysilazane to obtain a pre-coated metal pigment; further stirring and mixing the slurry, the pre-coated metal pigment, the pearl powder and the pigment into slurry, grinding and dispersing by a three-roll grinder, cooling and crushing to obtain granular pigment; and finally, uniformly mixing the granular pigment and the matrix resin, and extruding and granulating.

The invention provides a preparation method of spraying-free aesthetic plastic, which has the outstanding characteristics and excellent effects compared with the prior art that:

1. provides a method for preparing spraying-free aesthetic plastics by adopting pre-coated metal pigment and EVA and polyethylene wax mixed slurry.

2. The polysilazane hydrolysis coating is carried out on the surface of the dispersed metal powder pigment to form a transparent coating layer, so that the metal pigment can be effectively prevented from being oxidized and corroded, the lasting gloss is kept, and the dispersibility and the stability of the metal pigment are improved.

3. By selecting the EVA and the polyethylene wax for matching, slurry is easily formed at a lower temperature, and the metal pigment and the pearl powder are dispersed in the slurry by a three-roll grinder, so that the pigment is well dispersed.

4. Because the EVA and the polyethylene wax have good thermal fluidity, the processing fluidity can be improved when the EVA and the polyethylene wax are used for the final matrix resin.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.

Example 1

(1) Adding EVA (DuPont EVA 420) and polyethylene wax (Chengdu and 203X polyethylene wax) into a stirrer, and stirring at 110 deg.C for 15min to obtain slurry; in the slurry, the weight portions of EVA 2 and polyethylene wax 1 are counted;

(2) firstly, adding metal powder and polyethylene glycol 8000 into a high-speed dispersion machine for dispersion for 20min, fully dispersing the metal powder under the action of high-speed stirring friction, then uniformly spraying polysilazane into the high-speed dispersion machine, and continuously dispersing for 30min to obtain a pre-coated metal pigment; the metal powder is aluminum powder with the particle size of 20-50 mu m; in the pre-coated metal pigment, by weight, 100 parts of metal powder, 0.2 part of polyethylene glycol and 1.5 parts of polysilazane are calculated;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2), pearl powder and pigment into slurry, then grinding and dispersing in a three-roll grinder for 30min to obtain dispersed color paste, and then cooling and crushing to obtain granular pigment; the pearl powder is mica powder; the pigment is titanium dioxide; the rotating speed ratio of the slow roller, the middle roller and the fast roller of the three-roller grinder is 1: 3: 9; the roller temperature of the three-roller grinder is controlled at 100 ℃; in the granular pigment, by weight, 50 parts of slurry, 10 parts of pre-coated metal pigment, 1 part of pearl powder and 1 part of pigment;

(4) uniformly mixing the granular pigment and polyethylene resin, feeding the mixture into a single-screw extruder, and setting the screw temperature to 135 ℃, 155 ℃, 175 ℃, 180 ℃, 170 ℃ and 165 ℃ from the feeding section to the discharging section; extruding and bracing, air cooling and cutting into granules by a hob to obtain the spraying-free aesthetic plastic; the spraying-free plastic comprises 1 part by weight of granular pigment and 9 parts by weight of polyethylene resin.

Example 2

(1) Adding EVA (DuPont EVA 420) and polyethylene wax (Chengdu and 203X polyethylene wax) into a stirrer, and stirring at 115 deg.C for 15min to obtain slurry; in the slurry, the weight portions of EVA 2 and polyethylene wax 1 are counted;

(2) firstly, adding metal powder and polyethylene glycol 8000 into a high-speed dispersion machine for dispersion for 30min, fully dispersing the metal powder under the action of high-speed stirring friction, then uniformly spraying polysilazane into the high-speed dispersion machine, and continuously dispersing for 30min to obtain a pre-coated metal pigment; the metal powder is stainless steel powder with the particle size of 20-50 mu m; in the pre-coated metal pigment, by weight, 100 parts of metal powder, 0.2 part of polyethylene glycol and 1.5 parts of polysilazane are calculated;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2), pearl powder and pigment into slurry, then grinding and dispersing in a three-roll grinder for 28min to obtain dispersed color paste, and then cooling and crushing to obtain granular pigment; the pearl powder is glass powder; the pigment is chromium oxide green; the rotating speed ratio of the slow roller, the middle roller and the fast roller of the three-roller grinder is 1: 3: 9; the roller temperature of the three-roller grinder is controlled at 100 ℃; in the granular pigment, 55 parts by weight of slurry, 8 parts by weight of pre-coated metal pigment, 1 part by weight of pearl powder and 0 part by weight of pigment are calculated according to the parts by weight;

(4) uniformly mixing the granular pigment and polyethylene resin, feeding the mixture into a single-screw extruder, and setting the screw temperature to 135 ℃, 155 ℃, 175 ℃, 180 ℃, 170 ℃ and 165 ℃ from the feeding section to the discharging section; extruding and bracing, air cooling and cutting into granules by a hob to obtain the spraying-free aesthetic plastic; the spraying-free plastic comprises 2 parts by weight of granular pigment and 8 parts by weight of polyethylene resin.

Example 3

(1) Adding EVA (DuPont EVA 420) and polyethylene wax (Chengdu and 203X polyethylene wax) into a stirrer, and stirring at 110 deg.C for 20min to obtain slurry; in the slurry, the weight portions of EVA 2 and polyethylene wax 1 are counted;

(2) firstly, adding metal powder and polyethylene glycol 8000 into a high-speed dispersion machine for dispersion for 22min, fully dispersing the metal powder under the action of high-speed stirring friction, then uniformly spraying polysilazane into the high-speed dispersion machine, and continuously dispersing for 22min to obtain a pre-coated metal pigment; the metal powder is silver powder with the particle size of 20-50 mu m; in the pre-coated metal pigment, by weight, 100 parts of metal powder, 0.22 part of polyethylene glycol and 1.2 parts of polysilazane are calculated;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2), pearl powder and pigment into slurry, then grinding and dispersing for 27min in a three-roll grinder to obtain dispersed color paste, and then cooling and crushing to obtain granular pigment; the pearl powder is mica powder; the pigment is barium sulfate; the rotating speed ratio of the slow roller, the middle roller and the fast roller of the three-roller grinder is 1: 3: 9; the roller temperature of the three-roller grinder is controlled at 110 ℃; in the granular pigment, by weight, 60 parts of slurry, 9 parts of pre-coated metal pigment, 1.4 parts of pearl powder and 0.3 part of pigment;

(4) uniformly mixing the granular pigment and polyethylene resin, feeding the mixture into a single-screw extruder, and setting the screw temperature to 135 ℃, 155 ℃, 175 ℃, 180 ℃, 170 ℃ and 165 ℃ from the feeding section to the discharging section; extruding and bracing, air cooling and cutting into granules by a hob to obtain the spraying-free aesthetic plastic; the spraying-free plastic comprises 1.5 parts by weight of granular pigment and 8.5 parts by weight of polyethylene resin.

Example 4

(1) Adding EVA (DuPont EVA 420) and polyethylene wax (Chengdu and 203X polyethylene wax) into a stirrer, and stirring at 120 deg.C for 15min to obtain slurry; in the slurry, the weight portions of EVA 2 and polyethylene wax 1 are counted;

(2) firstly, adding metal powder and polyethylene glycol 8000 into a high-speed dispersion machine for dispersion for 25min, fully dispersing the metal powder under the action of high-speed stirring friction, then uniformly spraying polysilazane into the high-speed dispersion machine, and continuously dispersing for 30min to obtain a pre-coated metal pigment; the metal powder is aluminum powder with the particle size of 20-50 mu m; in the pre-coated metal pigment, by weight, 100 parts of metal powder, 0.2 part of polyethylene glycol and 1.5 parts of polysilazane are calculated;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2), pearl powder and pigment into slurry, then grinding and dispersing in a three-roll grinder for 26min to obtain dispersed color paste, and then cooling and crushing to obtain granular pigment; the pearl powder is mica powder; the pigment is iron oxide yellow; the rotating speed ratio of the slow roller, the middle roller and the fast roller of the three-roller grinder is 1: 3: 9; controlling the roller temperature of the three-roller grinder to be 108 ℃; in the granular pigment, by weight, 50 parts of slurry, 8 parts of pre-coated metal pigment, 2 parts of pearl powder and 0.7 part of pigment;

(4) uniformly mixing the granular pigment and polyethylene resin, feeding the mixture into a single-screw extruder, and setting the screw temperature to 135 ℃, 155 ℃, 175 ℃, 180 ℃, 170 ℃ and 165 ℃ from the feeding section to the discharging section; extruding and bracing, air cooling and cutting into granules by a hob to obtain the spraying-free aesthetic plastic; the spraying-free plastic comprises 1.2 parts by weight of granular pigment and 8.8 parts by weight of polyethylene resin.

Example 5

(1) Adding EVA (DuPont EVA 420) and polyethylene wax (Chengdu and 203X polyethylene wax) into a stirrer, and stirring at 110 deg.C for 20min to obtain slurry; in the slurry, the weight portions of EVA 2 and polyethylene wax 1 are counted;

(2) firstly, adding metal powder and polyethylene glycol 8000 into a high-speed dispersion machine for dispersion for 25min, fully dispersing the metal powder under the action of high-speed stirring friction, then uniformly spraying polysilazane into the high-speed dispersion machine, and continuously dispersing for 25min to obtain a pre-coated metal pigment; the metal powder is copper powder with the particle size of 20-50 mu m; in the pre-coated metal pigment, by weight, 100 parts of metal powder, 0.25 part of polyethylene glycol and 1.5 parts of polysilazane are calculated;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2) and the pearl powder to form slurry, then grinding and dispersing the slurry in a three-roll grinder for 25min to obtain dispersed color paste, and then cooling and crushing the dispersed color paste to obtain granular pigment; the pearl powder is glass powder; the rotating speed ratio of the slow roller, the middle roller and the fast roller of the three-roller grinder is 1: 3: 9; the roller temperature of the three-roller grinder is controlled at 106 ℃; in the granular pigment, 55 parts by weight of slurry, 8 parts by weight of pre-coated metal pigment and 1 part by weight of pearl powder are calculated according to the parts by weight;

(4) uniformly mixing the granular pigment and polyethylene resin, feeding the mixture into a single-screw extruder, and setting the screw temperature to 135 ℃, 155 ℃, 175 ℃, 180 ℃, 170 ℃ and 165 ℃ from the feeding section to the discharging section; extruding and bracing, air cooling and cutting into granules by a hob to obtain the spraying-free aesthetic plastic; the spraying-free plastic comprises 1.4 parts by weight of granular pigment and 8.6 parts by weight of polyethylene resin.

Comparative example 1

(1) Adding EVA (DuPont EVA 420) and polyethylene wax (Chengdu and 203X polyethylene wax) into a stirrer, and stirring at 110 deg.C for 15min to obtain slurry; in the slurry, the weight portions of EVA 2 and polyethylene wax 1 are counted;

(2) firstly, adding metal powder and polyethylene glycol 8000 into a high-speed dispersion machine for dispersion for 20min, fully dispersing the metal powder under the action of high-speed stirring friction, then uniformly spraying polysilazane into the high-speed dispersion machine, and continuously dispersing for 30min to obtain a pre-coated metal pigment; the metal powder is aluminum powder with the particle size of 20-50 mu m; in the pre-coated metal pigment, by weight, 100 parts of metal powder, 0.2 part of polyethylene glycol and 1.5 parts of polysilazane are calculated;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2), pearl powder and pigment into slurry, cooling and crushing to obtain granular pigment; the pearl powder is mica powder; the pigment is titanium dioxide; in the granular pigment, by weight, 50 parts of slurry, 10 parts of pre-coated metal pigment, 1 part of pearl powder and 1 part of pigment;

(4) uniformly mixing the granular pigment and polyethylene resin, feeding the mixture into a single-screw extruder, and setting the screw temperature to 135 ℃, 155 ℃, 175 ℃, 180 ℃, 170 ℃ and 165 ℃ from the feeding section to the discharging section; extruding and bracing, air cooling and cutting into granules by a hob to obtain the spraying-free aesthetic plastic; the spraying-free plastic comprises 1 part by weight of granular pigment and 9 parts by weight of polyethylene resin.

The procedure (3) of comparative example 1 was carried out without three-roll grinding, but the mixture was directly cooled and pulverized, and the other preparation conditions were the same as in example 1, and the initial appearance and the appearance after pickling of the resulting spray-free aesthetic plastic were as shown in Table 1.

Comparative example 2

(1) Adding EVA (DuPont EVA 420) and polyethylene wax (Chengdu and 203X polyethylene wax) into a stirrer, and stirring at 110 deg.C for 15min to obtain slurry; in the slurry, the weight portions of EVA 2 and polyethylene wax 1 are counted;

(2) adding metal powder and polyethylene glycol 8000 into a high-speed dispersion machine for dispersion for 20min, and fully dispersing the metal powder under the action of high-speed stirring friction to obtain a pre-coated metal pigment; in the pre-coated metal pigment, by weight, 100 parts of metal powder and 0.2 part of polyethylene glycol are calculated;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2), pearl powder and pigment into slurry, then grinding and dispersing in a three-roll grinder for 30min to obtain dispersed color paste, and then cooling and crushing to obtain granular pigment; the pearl powder is mica powder; the pigment is titanium dioxide; the rotating speed ratio of the slow roller, the middle roller and the fast roller of the three-roller grinder is 1: 3: 9; the roller temperature of the three-roller grinder is controlled at 100 ℃; in the granular pigment, by weight, 50 parts of slurry, 10 parts of pre-coated metal pigment, 1 part of pearl powder and 1 part of pigment;

(4) uniformly mixing the granular pigment and polyethylene resin, feeding the mixture into a single-screw extruder, and setting the screw temperature to 135 ℃, 155 ℃, 175 ℃, 180 ℃, 170 ℃ and 165 ℃ from the feeding section to the discharging section; extruding and bracing, air cooling and cutting into granules by a hob to obtain the spraying-free aesthetic plastic; the spraying-free plastic comprises 1 part by weight of granular pigment and 9 parts by weight of polyethylene resin.

Step (2) of comparative example 2 was carried out without coating treatment with polysilazane and the other preparation conditions were the same as in example 1, and the initial appearance and appearance after pickling of the obtained spray-free aesthetic plastic were as shown in Table 1.

Comparative example 3

(1) Adding EVA (DuPont EVA 420) and polyethylene wax (Chengdu and 203X polyethylene wax) into a stirrer, and stirring at 110 deg.C for 15min to obtain slurry; in the slurry, the weight portions of EVA 2 and polyethylene wax 1 are counted;

(2) adding metal powder into a high-speed dispersion machine for dispersion, uniformly spraying polysilazane into the high-speed dispersion machine, and dispersing for 30min to obtain a pre-coated metal pigment; the metal powder is aluminum powder with the particle size of 20-50 mu m; in the pre-coated metal pigment, by weight, 100 parts of metal powder and 1.5 parts of polysilazane;

(3) stirring and mixing the slurry obtained in the step (1), the pre-coated metal pigment obtained in the step (2), pearl powder and pigment into slurry, then grinding and dispersing in a three-roll grinder for 30min to obtain dispersed color paste, and then cooling and crushing to obtain granular pigment; the pearl powder is mica powder; the pigment is titanium dioxide; the rotating speed ratio of the slow roller, the middle roller and the fast roller of the three-roller grinder is 1: 3: 9; the roller temperature of the three-roller grinder is controlled at 100 ℃; in the granular pigment, by weight, 50 parts of slurry, 10 parts of pre-coated metal pigment, 1 part of pearl powder and 1 part of pigment;

(4) uniformly mixing the granular pigment and polyethylene resin, feeding the mixture into a single-screw extruder, and setting the screw temperature to 135 ℃, 155 ℃, 175 ℃, 180 ℃, 170 ℃ and 165 ℃ from the feeding section to the discharging section; extruding and bracing, air cooling and cutting into granules by a hob to obtain the spraying-free aesthetic plastic; the spraying-free plastic comprises 1 part by weight of granular pigment and 9 parts by weight of polyethylene resin.

The metal powder of step (2) of comparative example 3 was not treated with polyethylene glycol, the uniformity and fastness of the polysilazane coated metal powder were somewhat affected, and the initial appearance and the appearance after pickling of the resulting spray-free aesthetic plastic were as shown in table 1.

And (3) performance testing:

the spraying-free aesthetic plastics obtained in the examples 1-5 and the comparative examples 1-3 are subjected to injection molding, and the injection molding process comprises the following steps: barrel temperature: 190 ℃, injection pressure: 15MPa, tip temperature: 195 ℃ and mold temperature: at 60 ℃. The initial appearance of the injection molded part was observed. Immersing the injection molding piece in 0.1mol/L dilute sulfuric acid, soaking for 24h, then placing the injection molding piece outside a natural room, placing for 1 week, wiping the injection molding piece clean, and observing the appearance condition after the injection molding piece is placed in acid. The results obtained are shown in table 1. As can be seen from table 1:

before pickling: the injection molded parts obtained in the embodiments 1 to 5 are uniform in brightness and free of flow marks; the injection molding obtained in the comparative example 1 has bright surface and flow marks; the injection molding obtained in the comparative example 2 is bright and uniform and has no flow mark; the injection molding obtained in comparative example 3 was bright and uniform and had flow marks.

After pickling: the injection molded parts of examples 1 to 5 were uniform in brightness and free from flow marks; the injection molding of comparative example 1 had a bright surface and flow marks; the injection-molded part of comparative example 2 had a dark color. The injection moldings obtained in comparative example 3 had a slightly darker gloss.

Table 1:

test sample	Initial appearance	Appearance after pickling and standing
			Example 1	Bright and without flow mark	Bright and without flow mark
Example 2	Bright and without flow mark	Bright and without flow mark
			Example 3	Bright and without flow mark	Bright and without flow mark
Example 4	Bright and without flow mark	Bright and without flow mark
			Example 5	Bright and without flow mark	Bright and without flow mark
Comparative example 1	Bright and having flow marks	Bright and having flow marks
			Comparative example 2	Bright, uniform and no flow mark	Color and luster become dark
Comparative example 3	Bright, even and with flow marks	Slightly darker colour