Silicone composition for automobile interior and preparation method thereof

Abstract

The present invention relates to the field of silicone compositions, and discloses a silicone composition for automobile interior decoration and a preparation method thereof. The silicone composition comprises the following components by mass: 10-60 parts of polyolefin resin, 10-40 parts of methyl vinyl silicone rubber, 10-40 parts of methyl silicone rubber, 5-15 parts of compatibilizer, 1-10 parts of dimethyl silicone oil, 0.01-0.1 parts of catalyst, 1-2 parts of hydrogen-containing silicone oil, and 0.5-1 parts of dispersant. The technical scheme optimizes the raw material components, improves the scratch resistance of polypropylene, and avoids the occurrence of bright spot defects, and has excellent application prospects.

Description

Technical Field

[0001] The invention relates to the field of silicone compositions, and in particular to a silicone composition for automobile interior decoration and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is one of the commonly used materials for automotive interior parts due to its relatively low cost and excellent processability. However, the scratch resistance of this material is poor, and the dashboard, pillars, door panels and other parts of the car are in the area that is easy to scratch. Scratch-resistant modified PP materials have always been the focus of research. Major mainstream automobile OEMs have clear standards for PP materials in terms of scratch resistance. At present, OEMs have higher and higher requirements for surface scratch resistance, not only for the change in color difference after cross scratching of the material, but also for the change in gloss after scratch resistance.

[0003] In the prior art, there are three ways to improve the scratch resistance of PP materials: one is to add small molecular weight amide lubricants; the second is to add polyorganosiloxane lubricants of a certain molecular weight; the third is to add polytetrafluoroethylene self-lubricants or metal oxides. For example, Chinese patents CN101173074A, CN102807711A and CN109651711A can effectively reduce the surface friction coefficient of the material and improve the scratch resistance of polypropylene by using amide lubricants, but amide lubricants are easy to migrate out due to their small molecular weight, and the surface of the parts will have the risk of stickiness after heating, and the odor is large. Chinese patent CN103772818A adds nano-scale polytetrafluoroethylene powder to improve the scratch resistance of polypropylene, but the price of polytetrafluoroethylene is expensive, which limits its promotion and application. At present, the mainstream modification of polypropylene compositions is still achieved by adding high molecular weight polysiloxanes, which have good surface lubrication effects on polypropylene materials, low odor, easy to obtain, and excellent heat resistance and weather resistance, so they have received widespread attention. However, during the injection molding process, polysiloxane-modified polypropylene materials occasionally have bright spot defects. The probability of fine skin wrinkles with bright spots is relatively high. The bright spot defect is manifested in high gloss and a greasy feeling when touched by fingers, which seriously affects the appearance of the product. Summary of the invention

[0004] The present invention aims to provide a silicone composition for automobile interior decoration and a preparation method thereof, which can improve the scratch resistance of polypropylene and avoid the occurrence of bright spot defects.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a silicone composition for automobile interior, comprising the following components, by mass: 10-60 parts of polyolefin resin, 10-40 parts of methyl vinyl silicone rubber, 10-40 parts of methyl silicone rubber, 5-15 parts of compatibilizer, 1-10 parts of dimethyl silicone oil, 0.01-0.1 parts of catalyst, 1-2 parts of hydrogenated silicone oil, and 0.5-1 parts of dispersant.

[0006] Preferably, as an improvement, the polyolefin resin is at least one of copolymer polypropylene, homopolypropylene, random polypropylene and polyethylene, and the melt index of the polyolefin resin is 2-25 g / 10 min.

[0007] Preferably, as an improvement, the molecular weight of the methyl vinyl silicone rubber is 400,000-600,000 and the vinyl molar content is 0.04-0.24%.

[0008] Preferably, as an improvement, the molar vinyl content of the methyl vinyl silicone rubber is 0.16-0.24%.

[0009] In the present technical solution, too much vinyl molar content will lead to excessive crosslinking, which is not conducive to the dispersion of the crosslinked silicone, thereby affecting the bright spots and scratch resistance; too little vinyl molar content will lead to low crosslinking, which is not conducive to the improvement of scratch resistance.

[0010] Preferably, as an improvement, the molecular weight of the methyl silicone rubber is 400,000-600,000.

[0011] Preferably, as an improvement, the compatibilizer is polypropylene grafted with vinyl triethoxysilane, and the grafting rate is 0.8-1.2%.

[0012] Preferably, as an improvement, the viscosity of the dimethyl silicone oil is 350-1000 mPa·s, and the molar content of hydrogen groups in the hydrogen-containing silicone oil is 0.5-1.5%.

[0013] In the present technical solution, if the hydrogen-based molar content of the hydrogen-containing silicone oil is too much, it will lead to excessive crosslinking, which is not conducive to the dispersion of the crosslinked silicone, thereby affecting the bright spots and scratch resistance; if the hydrogen-based molar content of the hydrogen-containing silicone oil is too little, the crosslinking degree is too low, which is not conducive to improving the scratch resistance.

[0014] Preferably, as an improvement, the catalyst is a Castaplatin catalyst, and the dispersant is silicone powder E525 or E550.

[0015] On the other hand, the present technical solution also provides a method for preparing a silicone composition for automotive interior, characterized in that it comprises the following steps:

[0016] Step 1, mixing and kneading methyl vinyl silicone rubber, methyl silicone rubber, dimethyl silicone oil, hydrogen-containing silicone oil, a catalyst and a dispersant;

[0017] Step 2: adding polyolefin resin and compatibilizer, mixing and kneading, and then melt-extruding by a twin-screw extruder, cooling after extrusion, and pelletizing to obtain silicone masterbatch.

[0018] Preferably, as an improvement, in step one, the mixing and kneading temperature is 80-90°C, and the kneading time is 40 minutes; in step two, the feeding section temperature of the twin-screw extruder is 130-160°C, the melting section temperature is 160-180°C, the conveying section temperature is 180-200°C, and the die head temperature is 190-200°C.

[0019] The principle and beneficial effect of this technical solution are as follows: In this technical solution, the purpose is to solve the bright spot defect and whitening problem of the product under the premise of ensuring the scratch resistance. Based on this, the inventor analyzed the causes of the bright spot defect and found that the bright spot and whitening problems of the product are mainly closely related to the dispersibility and compatibility of silicone rubber. In view of this, the inventor considered optimizing the formula and introduced special dispersants E525 and E550, which are filler dispersing aids based on amphiphilic copolymer polymers. They can effectively help the dispersion of fillers in the main resin and are conducive to the uniform dispersion of dynamically cross-linked silicone rubber. In addition, PP grafted silane can effectively improve the compatibility of silicone rubber and the matrix, thereby effectively solving the bright spot and whitening problems of the product. During the research and development process, the inventors found that the molecular weight of methyl vinyl silicone rubber also has a great influence on the dispersibility. The molecular weight distribution of methyl vinyl silicone rubber is achieved through partial cross-linking (methyl silicone rubber will not cross-link, but methyl vinyl silicone rubber and hydrogen-containing silicone oil will cross-link under the action of a catalyst). The molecular weight of methyl vinyl silicone rubber should not be too large, otherwise it will be detrimental to the dispersion of silicone rubber, but too small a molecular weight will be detrimental to scratch resistance. After repeated verification, it was determined that the molecular weight of methyl vinyl silicone rubber is 400,000-600,000. In addition, the technical solution allows part of the silicone rubber (methyl vinyl silicone rubber containing vinyl) to undergo dynamic cross-linking. By adjusting the amount of catalyst and hydrogen-containing silicone oil, the methyl vinyl silicone rubber is cross-linked, while the methyl silicone rubber will not cross-link. It was unexpectedly found that by broadening the molecular weight distribution of silicone rubber through such partial cross-linking, scratch resistance and silicone rubber dispersion can be better satisfied at the same time, and dynamic cross-linking can make silicone rubber form a uniformly dispersed and dense matte layer, which has a significant improvement effect on bright spots. DETAILED DESCRIPTION

[0020] The following is further described in detail through specific implementations, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following implementations are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; the materials, reagents, etc. used can all be obtained from commercial channels.

[0021] Program Overview:

[0022] A silicone composition for automobile interior decoration comprises the following components, measured by mass: 10-60 parts of polyolefin resin, 10-40 parts of methyl vinyl silicone rubber, 10-40 parts of methyl silicone rubber, 5-15 parts of compatibilizer, 1-10 parts of dimethyl silicone oil, 0.01-0.1 parts of catalyst, 1-2 parts of hydrogenated silicone oil and 0.5-1 parts of dispersant.

[0023] The polyolefin resin is at least one of copolymer polypropylene, homopolypropylene, random polypropylene and polyethylene, and the melt index of the polyolefin resin is 2-25 g / 10 min, and the test conditions are 2.16 kg×230° C.

[0024] The molecular weight of the methyl vinyl silicone rubber is 400,000-600,000, and the molar content of vinyl is 0.04-0.24%, more preferably 0.16-0.24%.

[0025] The molecular weight of methyl silicone rubber is 400,000-600,000.

[0026] The compatibilizer is polypropylene grafted with vinyl triethoxysilane, and the grafting rate is 0.8-1.2%.

[0027] The viscosity of dimethyl silicone oil is 350-1000mPa·s.

[0028] The catalyst is a Castaplatin catalyst.

[0029] The hydrogen molar content of the hydrogen-containing silicone oil is 0.5-1.5%.

[0030] The dispersant is silicone powder E525 or E550.

[0031] A method for preparing a silicone composition for automobile interior decoration comprises the following steps:

[0032] Step 1: first, knead methyl vinyl silicone rubber, methyl silicone rubber, dimethyl silicone oil, hydrogen-containing silicone oil, catalyst and dispersant together, control the temperature at 80-90°C, and knead for 40 minutes.

[0033] Step 2: Add polyolefin resin and compatibilizer and knead together for 5 minutes, then force feed into a twin-screw extruder for melt extrusion and granulation. The temperatures of each extrusion section are as follows: feeding section 130-160°C, melting section 160-180°C, conveying section 180-200°C, die head temperature 190-200°C, water cooling after extrusion, and pelletizing to obtain silicone masterbatch.

[0034] Example 1

[0035] A silicone composition for automobile interior decoration comprises the following components, measured by mass: 42 parts of polyolefin resin, 30 parts of methyl vinyl silicone rubber, 15 parts of methyl silicone rubber, 10 parts of compatibilizer, 2 parts of dimethyl silicone oil, 0.015 parts of catalyst, 1 part of hydrogenated silicone oil and 0.5 parts of dispersant.

[0036] Among them, the polyolefin resin is copolymer polypropylene, the melt index of the copolymer polypropylene is 10g / 10min, and the test conditions are 2.16kg×230℃; when the polyolefin resin selects homopolymer polypropylene, random polypropylene or polyethylene, the effect is basically equivalent to selecting copolymer polypropylene.

[0037] The molecular weight of methyl vinyl silicone rubber is 500,000 and the vinyl molar content is 0.20%;

[0038] The molecular weight of methyl silicone rubber is 500,000;

[0039] The compatibilizer is PP grafted vinyl triethoxysilane, with a grafting rate of 1.0%;

[0040] The viscosity of dimethyl silicone oil is 550 mPa·s;

[0041] The catalyst is a Castaplatin catalyst;

[0042] The molar content of hydrogen groups in hydrogen-containing silicone oil is 1.0%;

[0043] The dispersant is silicone powder E525; after testing, when the dispersant is E550, the effect is basically the same.

[0044] Examples 2 to 7 are examples of the present invention, and Comparative Examples 1 to 5 are comparative examples of the present invention. The difference between each example and comparative example and Example 1 is the amount of each component added (by mass), as shown in the following table. The preparation methods of each example and comparative example, except for the specific selection of raw materials, are the same as the preparation method in the above scheme summary to obtain silicone masterbatches of Examples 1 to 7 and Comparative Examples 1 to 5.

[0045] Table 1

[0046]

[0047] Comparative Example 6

[0048] The difference between this comparative example and Example 1 is that the molecular weight of the methyl vinyl silicone rubber in this comparative example is 300,000.

[0049] Comparative Example 7

[0050] The difference between this comparative example and Example 1 is that the molecular weight of the methyl vinyl silicone rubber in this comparative example is 700,000.

[0051] Comparative Example 8

[0052] The difference between this comparative example and Example 1 is that in this comparative example, PP-grafted vinyl triethoxysilane is not added.

[0053] Comparative Example 9

[0054] The difference between this comparative example and Example 1 is that in this comparative example, the added dispersant is ethylene bisstearamide.

[0055] Comparative Example 10

[0056] The difference between this comparative example and Example 1 is that in this comparative example, the added polyolefin resin is homopolypropylene.

[0057] Application Examples

[0058] 61 parts of polypropylene, 8 parts of POE elastomer, 8 parts of HDPE, 20 parts of talc, 1 part of light yellow masterbatch, 0.4 parts of antioxidant and 2 parts of silicone masterbatch prepared in the above examples / comparative examples were mixed uniformly, melt-extruded in an extruder at 150-200°C and cooled to granulate.

[0059] Meanwhile, the silicone masterbatch prepared in the comparative example and the embodiment without addition was used as a blank control group.

[0060] The modified particles for automotive interior prepared in the above application examples and the blank control group were dried in a vacuum drying oven at 80°C for 2 hours, and then the dried particles were molded into samples and samples on a flat vulcanizer, and finally cut into corresponding test specimens by a cutter for performance testing.

[0061] The performance test method and test results are as follows:

[0062] 1. Mechanical properties test

[0063] Impact strength test: carried out in accordance with the provisions of GB / T1843-2008.

[0064] 2. Scratch resistance test

[0065] The scratch resistance was tested according to Volkswagen PV3952. ERICHSEN430P-1 was used with a load of 10N and a metal scratch head with a diameter of 1mm to perform a scratch test on the sample surface. The scratch interval was 2mm, and 20 lines were made vertically and horizontally. The color difference of the crossed material was tested using the Japanese Minolta CM-3600A color testing system, and the ΔL value of the material was recorded. The smaller the ΔL value, the better the scratch resistance.

[0066] 3. Evaluation of stress whitening resistance

[0067] The stress whitening resistance is tested according to Volkswagen PV3966. A 500g stainless steel ball is dropped from a height of 50cm to impact a 3mm thick sample. The color difference of the sample before and 48h after the ball is dropped is tested using the Japan Minon CM-3600A color testing system. The ΔL value of the material is recorded. The smaller the ΔL value, the better the stress whitening resistance.

[0068] 4. Bright spot evaluation

[0069] A fine leather grain square plate was selected, and the injection temperature was 180°C. The bright spots of the leather grain plate were visually evaluated, and the levels were divided into: none, slight, obvious and severe.

[0070] The application examples of the above embodiments and comparative examples were tested, and each group was repeated three times. The test results are shown in Table 2.

[0071] Table 2

[0072]

[0073]

[0074] From the test results of Examples 1-7 above, it can be seen that the silicone masterbatch of the present invention can effectively improve the scratch resistance of automotive interior parts and better solve the bright spot defect of silicone, and some examples can even completely solve the bright spot problem. In addition, it has basically no adverse effects on the impact resistance and stress whitening of the formulation system.

[0075] In combination with Example 1, Comparative Example 1 and Comparative Example 2, it can be found that by adding a catalyst and hydrogen-containing silicone oil, the methyl vinyl silicone rubber in the silicone masterbatch is dynamically cross-linked, which can broaden the molecular weight distribution of the silicone rubber in the silicone masterbatch, better meet the scratch resistance of automotive interior parts and the dispersion problem of the silicone rubber in the formula system, and form a uniformly dispersed and dense matte layer, thereby perfectly solving the bright spot defect of the silicone rubber. In combination with Example 1, Comparative Example 3 and Comparative Example 4, it can be seen that the addition of special dispersant E525 has a significant improvement effect on bright spots and stress whitening. The silicone rubber in Comparative Example 4 has neither added a special dispersant to promote dispersion, nor added a catalyst and hydrogen-containing silicone oil for cross-linking, and cannot form a certain degree of molecular weight distribution and a uniform matte effect layer. Its bright spot defect is relatively serious, and its stress whitening and scratch resistance are also average. The results of Comparative Examples 6-7 show that the molecular weight distribution of methyl vinyl silicone rubber should not be too large, otherwise it is not conducive to the dispersion of silicone rubber, but too small a molecular weight is not conducive to scratch resistance. In addition, the selection and type of compatibilizer, dispersant and resin have a certain influence on the mechanical properties, bright spots and whitening of silicone masterbatch.

[0076] By comparing Example 3, Example 4 and Example 7, it is found that the addition amount of methyl vinyl silicone rubber should not be too low, otherwise the amount of silicone rubber that can participate in cross-linking will be too small, which is not conducive to the improvement of scratch resistance. At the same time, it is difficult to form a uniformly dispersed and dense matte layer and the bright spot defect cannot be completely solved, even if more dispersant is used.

[0077] By comparing Example 2, Example 5 and Example 6, it can be found that a higher total content of organic silicon is beneficial to scratch resistance. Under the premise of no precipitation, adding more dimethyl silicone oil also helps scratch resistance to a certain extent. Too much methyl vinyl silicone rubber and hydrogen-containing silicone oil will lead to excessive cross-linking, increase the difficulty of organic silicon dispersion, and further affect the improvement effect of bright spots and whitening of the product.

[0078] By comparing Example 1 with Comparative Examples 6-10, it can be seen that too low a molecular weight of the methyl vinyl silicone rubber is not conducive to improving the scratch resistance, and too high a molecular weight is not conducive to improving the bright spots and whitening; not adding a compatibilizer or adding too little of the compatibilizer is not conducive to improving the bright spots and stress whitening of the parts; the dispersant ethylene bisstearamide has no significant dispersing effect on silicone, and the bright spots and whitening of Comparative Example 9 are not significantly improved compared with Comparative Example 3; using homopolymer PP as a carrier, the impact strength of the formula system is slightly lower than that of copolymer PP as a carrier, and other properties are basically equivalent.

[0079] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A silicone composition for automobile interior, characterized in that: The invention comprises the following components in parts by mass: 10-60 parts of polyolefin resin, 10-40 parts of methyl vinyl silicone rubber, 10-40 parts of methyl silicone rubber, 5-15 parts of compatibilizer, 1-10 parts of dimethyl silicone oil, 0.01-0.1 parts of catalyst, 1-2 parts of hydrogen-containing silicone oil and 0.5-1 parts of dispersant; the catalyst is a Castaplatin catalyst and the dispersant is silicone powder E525 or E550.

2. The silicone composition for automobile interior decoration according to claim 1, characterized in that: The polyolefin resin is at least one of copolymerized polypropylene, homopolymerized polypropylene and polyethylene, and the melt index of the polyolefin resin is 2-25 g / 10 min.

3. The silicone composition for automobile interior decoration according to claim 2, characterized in that: The molecular weight of the methyl vinyl silicone rubber is 400,000-600,000, and the molar content of vinyl is 0.04-0.24%.

4. The silicone composition for automobile interior decoration according to claim 3, characterized in that: The molar content of vinyl in the methyl vinyl silicone rubber is 0.16-0.24%.

5. The silicone composition for automobile interior decoration according to claim 4, characterized in that: The molecular weight of the methyl silicone rubber is 400,000-600,000.

6. The silicone composition for automobile interior decoration according to claim 5, characterized in that: The compatibilizer is polypropylene grafted with vinyl triethoxysilane, and the grafting rate is 0.8-1.2%.

7. The silicone composition for automobile interior decoration according to claim 6, characterized in that: The viscosity of the dimethyl silicone oil is 350-1000 mPa·s, and the molar content of hydrogen groups in the hydrogen-containing silicone oil is 0.5-1.5%.

8. A method for preparing a silicone composition for automobile interior decoration according to any one of claims 1 to 7, characterized in that: The steps include: Step 1, mixing and kneading methyl vinyl silicone rubber, methyl silicone rubber, dimethyl silicone oil, hydrogen-containing silicone oil, a catalyst and a dispersant; Step 2: adding polyolefin resin and compatibilizer, mixing and kneading, and then melt-extruding by a twin-screw extruder, cooling after extrusion, and pelletizing to obtain silicone masterbatch.

9. The method for preparing a silicone composition for automobile interior according to claim 8, characterized in that: In step 1, the mixing and kneading temperature is 80-90°C, and the kneading time is 40 minutes; in step 2, the feeding section temperature of the twin-screw extruder is 130-160°C, the melting section temperature is 160-180°C, the conveying section temperature is 180-200°C, and the die head temperature is 190-200°C.

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