Scratch-resistant low-shrinkage modified polypropylene with flocking appearance and preparation method of scratch-resistant low-shrinkage modified polypropylene

Abstract

The invention discloses scratch-resistant low-shrinkage modified polypropylene with flocking appearance and a preparation method thereof. The modified polypropylene material is prepared from the following components in percentage by mass: 50 to 70 percent of polypropylene, 5 to 20 percent of flexibilizer, 5 to 10 percent of talcum powder, 3 to 10 percent of whisker, 0.2 to 1 percent of lubricant, 0.1 to 0.5 percent of antioxidant and 0 to 1 percent of toner. According to the invention, the lubricant is added into the PP matrix after coating the whisker, so that the material has excellent scratch resistance and is suitable for preparation of exposed parts, the flocking performance of the material is not influenced, and the special form of the filler can effectively endow the material with excellent mechanical properties and low shrinkage performance. Compared with a common talcum powder modified PP material, the method has the advantages that the formula is improved, the problems that a traditional material is exposed during flocking and is difficult to resist scratches are solved, meanwhile, the material has higher mechanical property and lower after-shrinkage rate, and the material has a better maintaining effect on the long-term use size change rate. The method is simple in process and suitable for flocking and preparation of parts needing to be partially exposed.

Description

Technical Field

[0001] The invention relates to a modified polypropylene with flockable appearance, scratch resistance and low shrinkage and a preparation method thereof. Background Art

[0002] Modified plastics are widely used in the field of automobile manufacturing, especially modified polypropylene, which can be used in the preparation of interior parts such as dashboards, door panels, pillar systems, etc., and exterior parts such as bumpers, bottom guard plates, etc. Although polypropylene materials are inexpensive, they have a high gloss and are not easy to reduce the gloss by adding matting agents. They have a strong plastic feel when viewed with the naked eye, especially in dashboard systems, where the look and feel are easily perceived. Therefore, in order to improve the texture, some OEMs have introduced flocking technology during design to increase the touch and feel of parts, especially flocking in glove boxes. To prepare flocked parts, first, the material parts need to be injection molded, and then, the oily primer and water-based glue are sprayed on the parts in sequence, and then a layer of dense fiber fluff is adsorbed on the surface of the parts through the electrostatic flocking process before the glue dries, and finally a complete flocked part is obtained after a drying process.

[0003] Although most flocked parts are designed as non-appearance parts and do not need to be colored or add other functional additives to give them scratch resistance, light resistance and color performance, in actual application, there are indeed cases where some areas of flocked parts are exposed. Since parts such as glove boxes usually have fine leather grains, it is easier to observe if the exposed surface is accidentally scratched, so non-flocking parts must have sufficient scratch resistance. However, the formula conventionally used to prepare leather grain appearance parts has a certain impact on the oily primer sprayed during flocking, which may cause the primer to spread unevenly, thereby causing the water-based glue to avoid the area where the primer is scattered when it is attached. When flocking, the glue-free areas cannot be flocked and gaps appear, resulting in a small area for the entire flocking, insufficient adhesion, and the flocking surface can be easily torn off, resulting in the part test NG and the entire part being scrapped. Parts with better flocking effects must be able to make the primer glue perfectly and evenly dispersed without voids. At the same time, due to its special location, the glove box is suspended vertically and often needs to be opened and closed. It needs sufficient mechanical properties to support its own gravity, and its rear shrinkage should be small to avoid the widening of the gap due to rear shrinkage and deformation of parts during long-term use, which may cause complaints from passengers.

[0004] In order to realize that automotive interior parts can be used for flocking, appearance and scratch tests at the same time, some people have also studied it. CN 109206744 adds glass fiber to the formula to increase the surface roughness when talcum powder modifies PP, adds flocking aids to help improve the flocking effect, and uses the more expensive α nucleating agent to improve the crystallization of the material. However, if the glass fiber is not dispersed well, it is easy to float the fiber and cause poor appearance. At the same time, the dispersion of glass fiber is anisotropic. When the shrinkage of the material in the horizontal and vertical directions is inconsistent, it will cause material stress concentration and warping deformation. Even if the invention can control the resistance to deformation below 0.5mm by adjusting the formula, it does not mean that there is no deformation. In addition, the invention only focuses on how to improve the flocking performance of the material, and does not take into account the need for sufficient scratch resistance when the flocked part of the part is exposed, and does not evaluate the scratch resistance of the material. Although CN114230958 uses whiskers and scratch resistance aids to evaluate the mechanical properties and scratch resistance of the material, it does not explore its flocking performance, nor does it pay attention to its subsequent shrinkage performance. Summary of the invention

[0005] Based on this, the purpose of the present invention is to provide a modified polypropylene with flockable appearance, scratch resistance and low shrinkage and a preparation method thereof, so as to solve the above technical problems of the prior art.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A modified polypropylene with flockable appearance, scratch resistance and low shrinkage, made from the following raw materials in percentage by mass:

[0008]

[0009] The polypropylene is a block copolymer polypropylene, the melt flow rate of which is 30-60g / 10min, and the simply supported beam notched impact strength at room temperature is >5kJ / m 2 .

[0010] The toughening agent is ethylene-octene copolymer, and the melt flow rate is 0.5-2g / 10min.

[0011] The mesh number of the talcum powder is greater than 5000 meshes.

[0012] The whiskers are basic magnesium sulfate whiskers with a whisker diameter less than 1um and a length of 10-30um.

[0013] The lubricant is magnesium stearate.

[0014] The stabilizer is a primary antioxidant and a secondary antioxidant that are considered necessary by those skilled in the art, wherein the primary antioxidant is a hindered phenol or thioester antioxidant, and the secondary antioxidant is a phosphite antioxidant.

[0015] The method for preparing the above-mentioned modified polypropylene with flockable appearance, scratch resistance and low shrinkage comprises the following steps:

[0016] Step 1: Weigh magnesium stearate and whiskers according to the material ratio, and stir the whiskers and magnesium stearate lubricant evenly.

[0017] Step 2: Blend the modified whiskers obtained in step 1 evenly with 5-10 parts of polypropylene and add them through the side feed port. The remaining materials enter through the main feed port of the twin-screw extruder, and after being melted, they are mixed with the materials entering the side feed port, extruded, pelletized, dried, and other processes to obtain the finished product. The process parameters of the twin-screw extruder are as follows: the temperature of the first zone is 60-180℃, the temperature of the second zone is 60-180℃, and the temperature of the second zone is 60-180℃.

[0018] The temperature of zone eight is 180~210℃, and the extrusion temperature is 200±10℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 These are photos of Examples 1-4 and Comparative Examples 1-3. Specific implementation methods

[0021] The present invention is described below by means of specific examples, but the present invention is not limited to these examples.

[0022] The main raw materials used in the embodiments and comparative examples are as follows:

[0023] The polypropylene resin is copolymer polypropylene EP648U;

[0024] The mesh number of talcum powder is 10000 mesh;

[0025] The toughening agent is Dow LC168;

[0026] The functional filler basic magnesium sulfate is Yingkou Kangru WS-6VS;

[0027] The lubricant is magnesium stearate;

[0028] Antioxidant is 1010:168=1:1;

[0029] The color powder is Cabot Carbon Black 2014;

[0030] The comparative scratching aid used oleamide;

[0031] The formulas of the embodiments and comparative examples are shown in Table 1 below:

[0032] Table 1. Ratio of each sample formula

[0033] Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Example 4 Polypropylene (Phr) 84 84 69 81 79 74 68 Talc (Phr) 10 10 20 10 10 10 10 Toughener (Phr) 5 5 10 5 5 10 10 Whisker (Phr) 3 5 5 10 Scratch aid (phr) 0.2 Lubricant (Phr) 0.2 0.2 0.5 1 Antioxidant (Phr) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Toner 0.5 0.5 0.5 0.5 0.5 0.5 0.5

[0034] The embodiments and comparative examples are injected into standard specimens by an injection molding machine after being blended and extruded, and tested according to the standard. The test standards are as follows: density is tested according to ISO 1183; tensile strength is tested according to ISO 527, with a test speed of 50mm / min; flexural modulus is tested according to SO 178, with a test speed of 2mm / min and a span of 64mm; notched impact strength is tested at 23°C according to ISO 179; scratch resistance is tested on a fine leather grain board according to PV3952, 10N. Conventional mainstream OEMs basically require △L≤1.5, which means that the scratch resistance of the material can meet the needs of daily use; the post-shrinkage test method is in accordance with ISO294, and the FLOW / CROSS FLOW direction data is tested after 80°C*48h; the flocking effect verification method is to prepare the plastic particles into a flat plate, spray oil primer (transparent, no dispersion effect can be observed) and water-based glue (milky white after combining with oil primer) in sequence, and observe whether the glue is uniform on the plastic parts. If it is uniform and complete, it is judged as OK. If there are hollow oily spots scattered, it will cause the flocking to be shed due to insufficient contact surface, and it will be judged as NG.

[0035] The performance of Examples 1-5 and Comparative Example 1 is shown in Tables 2 and Figure 1 As shown;

[0036] Table 2. Comparison of formulation and performance of each sample

[0037]

[0038]

[0039] It can be seen from the above examples 1-5 and comparative examples 1-2 that by filling the whiskers with activated lubricants, the mechanical properties of the traditional PP+EPDM-T20 material can be achieved with a small amount of addition. At the same time, due to the special morphology of the whiskers, the material can have a lighter density and a lower post-shrinkage rate, which can better maintain the morphology of the material after it is made into parts. The activated whisker-filled modified PP material not only has better scratch resistance, meeting the requirements of conventional mainstream OEMs for scratch resistance, but also does not affect the adhesion of the flocking primer like the traditional scratch resistance system, resulting in flocking NG.

[0040] In Example 1 and Comparative Example 1-2, the addition of a small amount of special morphology whiskers activated by magnesium stearate has higher mechanical properties and better scratch resistance when the density is almost the same as that of PP+EPDM-T10 material. At the same time, although the scratch resistance can be improved by adding traditional scratch resistance additives, it has a great influence on the adhesion of flocking primer, causing the primer to be scattered in hollow points, resulting in flocking NG. The embodiment does not have this defect.

[0041] In Examples 1-3 and Comparative Examples 1-3, as the special form filling content increases, the density increases slightly, but its mechanical properties show a great growth, even directly and significantly exceeding the traditional PP+EPDM-T20 material. Thereafter, the shrinkage rate is also gradually reduced, even less than 0.1%. Although the whiskers are long needle-shaped, their smaller size and the formula of the formula make their shrinkage rate in the horizontal and vertical directions no different from the talcum powder filling trend. It is believed that it does not have anisotropy, which is beneficial to the warping and deformation of parts. At the same time, in the formula, the increase in the content of the activating auxiliary agent magnesium stearate is positively helpful for the overall mechanical properties and scratch resistance, and will not affect the overall flocking performance, meeting the requirements of major mainstream OEMs for the scratch resistance of leather grain parts, and is suitable for flocking at the same time and direct exposure of leather grains in some areas.

[0042] In Example 4 and Comparative Example 3, when a large amount of whisker filling is added, its density is still significantly lower than that of PP+EPDM-T20 material, but its mechanical properties and post-shrinkage rate are the best among all the examples and comparative examples. Generally, the more filling, the easier it is to be scratched during the scratch resistance test, and the performance is relatively poor. However, in Example 4, because there is enough lubricant to activate and wrap the whiskers, and it has sufficient strength, the overall scratch resistance is close to 1.0, which is about 2 / 3 lower than that of Comparative Example 3. It is more suitable for lightweight design of automobiles, suitable for the preparation of parts with high overall mechanical performance requirements, flocking operations and scratch resistance that can be exposed at the same time.

[0043] In the above embodiment, the type of PP substrate and the filling ratio can be replaced or matched according to the actual needs of each OEM. On the premise of having sufficient mechanical properties, it has a lower shrinkage rate than traditional materials and meets the requirements of flocking operation and partial exposure of leather texture.

Claims

1. A modified polypropylene with flockable appearance, scratch resistance and low shrinkage, characterized in that: The invention is made of the following raw materials in percentage by mass: 50-70% polypropylene; 5-20% toughening agent; 5-10% talcum powder; 3-10% whisker; 0.2-1% lubricant; 0.1-0.5% antioxidant; and 0-1% color powder.

2. The modified polypropylene with flockable appearance, scratch resistance and low shrinkage according to claim 1, characterized in that: The polypropylene is a block copolymer polypropylene, the melt flow rate of which is 30-60g / 10min, and the simply supported beam notched impact strength at room temperature is >5kJ / m 2 .

3. The modified polypropylene with flockable appearance, scratch resistance and low shrinkage according to claim 1, characterized in that: The toughening agent is ethylene-octene copolymer, and the melt flow rate is 0.5-2g / 10min.

4. The modified polypropylene with flockable appearance, scratch resistance and low shrinkage according to claim 1, characterized in that: The mesh number of the talcum powder is greater than 5000 meshes.

5. The modified polypropylene with flockable appearance, scratch resistance and low shrinkage according to claim 1, characterized in that: The whiskers are basic magnesium sulfate whiskers with a whisker diameter less than 1um and a length of 10-30um.

6. The modified polypropylene with flockable appearance, scratch resistance and low shrinkage according to claim 1, characterized in that: The lubricant is magnesium stearate.

7. The modified polypropylene with flockable appearance, scratch resistance and low shrinkage according to claim 1, characterized in that: The stabilizer is a primary antioxidant and a secondary antioxidant that are considered necessary by those skilled in the art, wherein the primary antioxidant is a hindered phenol or thioester antioxidant, and the secondary antioxidant is a phosphite antioxidant.

8. The method for preparing the modified polypropylene with flockable appearance, scratch resistance and low shrinkage according to any one of claims 1 to 7, characterized in that: The steps include: Step 1: Weigh magnesium stearate and whiskers according to the material ratio, and stir the whiskers and magnesium stearate lubricant evenly. Step 2: The modified whiskers obtained in step 1 are evenly blended with 5-10 parts of polypropylene and added through the side feed port; the remaining materials enter through the main feed port of the twin-screw extruder, and after being melted, they are mixed with the materials entering through the side feed port and then extruded, pelletized, dried, and other processes to obtain the finished material; the process parameters of the twin-screw extruder are as follows: the temperature of zone 1 is 60-180°C, the temperature of zones 2-8 is 180-210°C, and the extrusion temperature is 200±10°C.

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