Potassium permanganate polylactic acid microcapsule, flame-free paintable polypropylene composite material, and preparation method and application thereof

Abstract

The present invention discloses a potassium permanganate polylactic acid microcapsule, a flame-free paintable polypropylene composite material, and a preparation method and application thereof. The potassium permanganate polylactic acid microcapsule of the present invention has a multi-layer wrapping structure, and the core material is wrapped with polylactic acid and polyoxyethylene sorbitan stearate; wherein, the mass ratio of potassium permanganate, polyoxyethylene sorbitan stearate to polylactic acid is 1:(3-5):(4-6). When the potassium permanganate polylactic acid microcapsule is added to polypropylene resin or a polypropylene composition for injection molding, not only can the cortex of the injection molded part be fully oxidized to improve the polarity of the surface of the part, thereby improving its surface tension and enhancing the bonding performance with the paint film, but also the generated manganese dioxide can significantly improve the toughness of the injection molded part.

Description

Technical Field

[0001] The present invention relates to the technical field of compositions of polymer compounds, and more specifically, to a potassium permanganate microcapsule, a flame-free paintable polypropylene composite material, and a preparation method and application thereof. Background Art

[0002] Polypropylene materials are widely used in the preparation of automotive parts, including bumpers, instrument panels, door panels, columns, and various decorative or functional parts, due to their low specific gravity, excellent mechanical properties, low cost, easy processing, etc. In particular, parts such as automotive bumpers, lower trim panels, and spoilers need to be painted to keep the color of the car body consistent. However, most of the paints used for painting contain oily solvents or water-based solvents, and polypropylene itself is non-polar, which results in difficult spreading of the paint on the surface of polypropylene materials, and problems such as paint peeling or paint flaking often occur after direct spraying.

[0003] Currently, the main solution is to perform flame treatment on polypropylene painted parts before painting to improve their polarity, thereby improving the painting effect of polypropylene parts. However, adding the flame treatment process makes the manufacturing cycle long and the cost high, so there is an urgent need to develop high-performance PP materials that are easy to paint without flame treatment.

[0004] For example, the prior art discloses a flame-free and hydrolysis-resistant polypropylene composite material, which comprises the following components: 50-90 parts of polypropylene resin, 5-20 parts of toughening agent, 8-25 parts of filling material, 0.3-3 parts of amide wax, 0.1-3 parts of antioxidant, 0.05-0.2 parts of phosphate ester salt, and 0.1-5 parts of other processing aids. By using the phosphate ester salt and amide wax in combination, the effect of rapid crystallization can be achieved. The higher the crystallinity, the denser layer can be formed on the surface of the parts, and the better the solvent resistance. At the same time, the surface tension of the material is high, and the paintability is good, ensuring that the paint film is tightly combined with the PP material. At the same time, a protective film can be formed on the surface of the material to prevent the intervention of water molecules and improve the water resistance of the material; however, amide wax belongs to an external lubricant, which will affect the crystallinity of polypropylene by the phosphate ester salt, and there is a certain contradiction in their interaction, resulting in limited improvement of the surface tension of the polypropylene composite material, and the binding performance between the paint film and the PP material needs to be improved. Summary of the Invention

[0005] The object of the present invention is to overcome the defects and deficiencies of the poor binding performance between the existing flame-free paintable polypropylene composite material and the paint film, and to provide a potassium permanganate polylactic acid microcapsule.

[0006] Another object of the present invention is to provide a preparation method of the potassium permanganate polylactic acid microcapsule.

[0007] Another object of the present invention is to provide an application of the above-mentioned potassium permanganate polylactic acid microcapsules in a polypropylene composite material.

[0008] Another object of the present invention is to provide a flame-free paintable polypropylene composite material.

[0009] Another object of the present invention is to provide a method for preparing a flame-free paintable polypropylene composite material.

[0010] Another object of the present invention is to provide an application of the above-mentioned flame-free paintable polypropylene composite material in automotive spray-painted parts.

[0011] The above objects of the present invention are achieved by the following technical solutions:

[0012] The present invention protects a potassium permanganate polylactic acid microcapsule, which has a multi-layer wrapping structure, with potassium permanganate as the core material, and the core material is wrapped with polylactic acid and polyoxyethylene sorbitan monostearate; wherein, the mass ratio of potassium permanganate, polyoxyethylene sorbitan monostearate to polylactic acid is 1:(3-5):(4-6).

[0013] In the present invention, polylactic acid and polyoxyethylene sorbitan monostearate are used as wall materials to wrap potassium permanganate to form microcapsules. When the microcapsules are mixed with polypropylene resin or polypropylene composite material and then injection-molded, the polylactic acid will gradually decompose and release potassium permanganate. Since the density of potassium permanganate is greater than that of other components, potassium permanganate is distributed at the front of the melt (i.e., the surface of the injection-molded part), and can fully oxidize the cortex of the injection-molded part to improve the polarity of its surface, thereby improving the surface tension of the injection-molded part to improve its bonding performance with the paint film. Moreover, potassium permanganate will generate manganese dioxide after the oxidation ends. Compared with potassium permanganate, manganese dioxide has a higher density and can be dispersed in the cortex of the injection-molded part as an inorganic filler to improve the mechanical properties of the injection-molded part. In addition, the applicant found that the manganese dioxide generated in the present invention also has a plasticizing effect and can significantly improve the toughness of the polypropylene composite material.

[0014] The polyoxyethylene sorbitan monostearate can be selected as polyoxyethylene sorbitan monostearate, and further preferably Tween 60.

[0015] The content of polylactic acid in the potassium permanganate polylactic acid microcapsules affects the thickness of the microcapsule wall material, and further affects the decomposition rate of the microcapsules during the injection molding process, thereby affecting the release of potassium permanganate. When the content of polylactic acid is too high, it is not conducive to the rapid decomposition of polylactic acid during the injection molding process, affecting the release of potassium permanganate. And injection molding is a process with a very short time. If potassium permanganate is not released in time, it is difficult to play the above role; when the content of polylactic acid is too low, it is difficult to fully wrap potassium permanganate to form a microcapsule structure.

[0016] Preferably, the mass ratio of potassium permanganate, polyoxyethylene sorbitan stearate to polylactic acid is 1:(3.5 - 4.5):(4.5 - 5.5).

[0017] Specifically, according to the ISO 1133-1:2012 standard, the melt mass flow rate of the above-mentioned polylactic acid is 3 - 5 g / 10 min at 190 °C under the condition of 2.16 kg.

[0018] Optionally, in the structural units of the main chain of the polylactic acid, the content of the structural units derived from D-lactic acid monomers is 2 wt% - 4 wt%. The content of the structural units derived from D-lactic acid monomers in polylactic acid has a certain influence on the decomposition performance of polylactic acid. It is found that when the content of the structural units derived from D-lactic acid monomers in polylactic acid is 2 wt% - 4 wt%, it is more conducive to the decomposition of polylactic acid.

[0019] The present invention also protects a method for preparing the above-mentioned potassium permanganate polylactic acid microcapsules, which includes the following steps:

[0020] First, dissolve polylactic acid in dichloromethane solution, and add polyoxyethylene sorbitan stearate to form a primary emulsion; then add potassium permanganate to the primary emulsion for encapsulation, and after removing the solvent, potassium permanganate polylactic acid microcapsules are obtained.

[0021] The application of the above-mentioned potassium permanganate polylactic acid microcapsules in polypropylene composites is also within the protection scope of the present invention.

[0022] The present invention protects a flame-free paintable polypropylene composite material, which comprises the following components in parts by weight: 100 parts of polypropylene resin, and 0.3 - 0.8 parts of the above-mentioned potassium permanganate polylactic acid microcapsules.

[0023] Specifically, in the above-mentioned flame-free paintable polypropylene composite material, the mass percentage of polypropylene resin ≥ 60%, and the polypropylene resin can be homopolypropylene and / or copolymerized polypropylene, and its melt mass flow rate is 20 - 35 g / 10 min at 230 °C under the condition of 2.16 kg according to the ISO 1133-1:2022 standard, preferably 25 - 30 g / 10 min.

[0024] Optionally, the above-mentioned flame-free paintable polypropylene composite material further comprises a filler, an elastomer and a processing aid, and the filler is one or more of talc powder, mica powder or calcium carbonate.

[0025] The present invention protects a method for preparing the above-mentioned flame-free paintable polypropylene composite material, which includes the following steps: first, mix other components except potassium permanganate polylactic acid microcapsules in proportion and melt-extrude to obtain a polypropylene composition, and then mix it with potassium permanganate polylactic acid microcapsules to obtain a flame-free paintable polypropylene composite material.

[0026] The application of the above flame-free paintable polypropylene composite material in automotive painted parts is also within the protection scope of the present invention. Specifically, the automotive painted parts can be bumpers, lower trim panels or spoilers.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] In the present invention, polylactic acid and polyoxyethylene sorbitan stearate are used as the wall materials, and potassium permanganate is used as the core material to form potassium permanganate polylactic acid microcapsules. When the polypropylene composite material formed by adding the microcapsules into polypropylene resin or polypropylene composition is injection-molded, the polylactic acid will gradually decompose and release the potassium permanganate it encapsulates. The potassium permanganate is used to fully oxidize the cortex of the injection-molded part to improve the polarity of the surface of the part, thereby improving the surface tension of the injection-molded part and further improving the bonding performance with the paint film. Moreover, the potassium permanganate will be reduced to generate manganese dioxide, which can not only be dispersed in the cortex of the injection-molded part as an inorganic filler to improve the mechanical properties of the injection-molded part, but also has a certain plasticizing effect, significantly improving the toughness of the polypropylene composite material part. Specific embodiments

[0029] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw material reagents used in the embodiments of the present invention are conventionally purchased raw material reagents.

[0030] 1. Raw material reagents

[0031] PP-1, homopolypropylene, melt mass flow rate of 25 g / 10 min, grade PP SZ30S, manufacturer Zhongke Huake Petrochemical Co., Ltd.;

[0032] PP-2, copolymer polypropylene, melt mass flow rate of 30 g / 10 min, grade PP EP548R, manufacturer CNOOC Shell Petrochemical Co., Ltd.;

[0033] Polylactic acid-1, content of dextrorotatory lactic acid 4 wt%, grade PLA FY804, manufacturer Anhui Fengyuan Futailai Polylactic Acid Co., Ltd.;

[0034] Polylactic acid-2, content of dextrorotatory lactic acid 2 wt%, grade PLA FY802, manufacturer Anhui Fengyuan Futailai Polylactic Acid Co., Ltd.;

[0035] Potassium permanganate and polyoxyethylene sorbitan stearate (Tween 60), commercially available.

[0036] 2. The flame-free paintable polypropylene composite materials of each embodiment and comparative example of the present invention are prepared by the following preparation method:

[0037] Weigh each component according to the formula, and mix the polypropylene resin and the potassium permanganate polylactic acid microcapsules evenly to obtain the flame-free paintable polypropylene composite material.

[0038] 3. Performance Testing

[0039] (1) Mechanical property testing: Refer to the ISO standard, the notched impact strength ISO 180-2019 (Type 1A notch).

[0040] (2) Surface tension testing: Injection mold a 100mm * 100mm sample plate of the flame-free paintable polypropylene composite material, and conduct the test with reference to GB / T14216-2008.

[0041] (3) Cross-cut test: Use the flame-free painting process, refer to the GB / T 9286-2021 standard, use a cross-cut knife to draw 10 * 10 small grids on the surface of the test sample piece, the scribing length is about 20MM, and the depth should be appropriate to cut through the paint layer. Use a brush to clean the paint layer powder or filaments at the scribing edge. Prepare a 3M tape (model 610#) with a length of about 75MM. Slowly and flatly attach one end of the 3M tape from the outermost edge of the cross-cut to the cross-cut, and then gently press it with your finger to ensure that there are no residual air bubbles between the tape and the sample piece. After pressing it flat, wait for 90 ± 30 seconds, then hold the sample piece with your left hand and pinch the free end of the tape with your right hand, and quickly tear off the 3M tape in the opposite direction by about 180 degrees. Repeat the above test 2 times on other flat parts of the sample piece. Use a magnifying glass to carefully check the peeling situation of the coating on the cross-cut.

[0042] Cross-cut test grade classification:

[0043] ISO grade 0: The edges of the cuts are completely smooth, and there is no peeling at the edges of the grids;

[0044] ISO grade 1: There are small pieces of peeling at the intersections of the cuts, and the actual damage in the cross-cut area does not exceed 5%;

[0045] ISO grade 2: The edges and / or intersections of the cuts have peeling, and the area is greater than 5%, but less than 15%;

[0046] ISO grade 3: There is partial peeling or large pieces of peeling along the edges of the cuts, and / or some grids are peeled off entirely, and the peeled area exceeds 15%, but less than 35%;

[0047] ISO grade 4: Large pieces of peeling at the edges of the cuts / or some squares are partially or completely peeled off, and the area is greater than 35% of the cross-cut area, but does not exceed 65%;

[0048] ISO grade 5: Exceeds the previous grade.

[0049] 3. The potassium permanganate polylactic acid microcapsules can be prepared by the following preparation method:

[0050] S1. Dissolve polylactic acid in dichloromethane solution, add surfactant Tween 60, and stir to form a primary emulsion.

[0051] S2. Add potassium permanganate to the primary emulsion in S1 and perform ultrasonic emulsification (ultrasonic power 400 W, ultrasonic time 200 s) to encapsulate potassium permanganate, and then mechanically stir to completely volatilize the dichloromethane solvent to obtain potassium permanganate microcapsules, as shown in Table 1 specifically.

[0052] Table 1 Weight parts of each component in potassium permanganate - polylactic acid microcapsules

[0053]

[0054] Examples 1 - 9 and Comparative Examples 1 - 2

[0055] The weight parts of each component in the flame - free paintable polypropylene composite materials in Examples 1 - 9 and Comparative Examples 1 - 2 are shown in Table 2 and Table 3.

[0056] Table 2 Weight parts of each component in the flame - free paintable polypropylene composite materials in Examples 1 - 9

[0057]

[0058] The performance test results of the flame - free paintable polypropylene composite materials in each example and comparative example according to the method mentioned above are shown in Table 3.

[0059] Table 3 Test results of each example and comparative example

[0060]

[0061] According to the data in Table 2, the flame - free paintable polypropylene composite materials in Examples 1 - 9 not only have excellent bonding properties with the paint film, with the surface tension reaching more than 40 mN / m and the cross - cut test all being grade 0; but also have good toughness, with the notch impact strength reaching 9 KJ / m 2 or more, indicating that the flame - free paintable polypropylene composite material of the present invention not only has good toughness but also has excellent bonding properties with the paint film.

[0062] At the same time, it can be seen from Examples 1 and 2 that the type of polypropylene has little effect on the surface tension of the injection molded part and its bonding performance with the paint film; according to Examples 1 and 3, it can be found that the dextrorotatory lactic acid content of the polylactic acid in the potassium permanganate polylactic acid microcapsules affects the surface tension of the injection molded part, and the reason may be that the dextrorotatory lactic acid content affects the decomposition of the polylactic acid, thereby affecting the release of potassium permanganate in the core layer, and then affecting the surface tension of the injection molded part. It can be seen from Examples 4 and 5 that when the mass ratio of potassium permanganate, polyoxyethylene sorbitan stearate and polylactic acid is 1:(3-5):(4-6), the flame-free paintable polypropylene composite material not only has good surface tension and bonding performance with the paint film, but also has excellent mechanical properties. It can be found from Examples 6 and 7 that when the mass ratio of potassium permanganate, polyoxyethylene sorbitan stearate and polylactic acid is 1:(3.5-4.5):(4.5-5.5), the flame-free paintable polypropylene composite material has better surface tension, bonding properties with the paint film and mechanical properties.

[0063] In addition, it can be seen from Comparative Examples 1 and 2 that when the content of polylactic acid in potassium permanganate polylactic acid microcapsules is too high, it is not conducive to the rapid decomposition of polylactic acid during the injection molding process, thereby affecting the release rate of potassium permanganate, and injection molding is a very short process. If potassium permanganate is not released in time, it is difficult to play the above-mentioned role; moreover, the undecomposed potassium permanganate polylactic acid microcapsules are equivalent to impurity particles in the polypropylene resin, and due to the poor compatibility of polylactic acid and polypropylene, the notched impact strength of the flame-free paintable polypropylene composite material is greatly reduced.

[0064] When the content of polylactic acid in potassium permanganate polylactic acid microcapsules is 0, it is difficult for polyoxyethylene sorbitan stearic acid to effectively encapsulate potassium permanganate, resulting in excessively fast and premature release of potassium permanganate, causing potassium permanganate to begin to oxidatively decompose before reaching the cortex of the injection-molded part. This not only makes it difficult to fully oxidize the cortex of the injection-molded part to increase its surface polarity, but also leads to a sharp decrease in notched impact strength and poor toughness.

[0065] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A potassium permanganate polylactic acid microcapsule, characterized in that, the potassium permanganate polylactic acid microcapsule has a multi-layer coating structure, with potassium permanganate as the core material, and the core material is coated with polylactic acid and polyoxyethylene sorbitan monostearate; wherein, the mass ratio of potassium permanganate, polyoxyethylene sorbitan monostearate to polylactic acid is 1:(3 - 5):(4 - 6); in the structural unit of the main chain of the polylactic acid, the content of the structural unit derived from the D-lactic acid monomer is 2wt% - 4wt%.

2. The potassium permanganate polylactic acid microcapsule according to claim 1, characterized in that, the mass ratio of potassium permanganate, polyoxyethylene sorbitan monostearate to polylactic acid is 1:(3.5 - 4.5):(4.5 - 5.5).

3. A method for preparing the potassium permanganate polylactic acid microcapsule according to any one of claims 1 - 2, characterized in that, comprises the following steps: first dissolve polylactic acid in dichloromethane solution, and add polyoxyethylene sorbitan monostearate, and mix to form a primary emulsion; then add potassium permanganate to the primary emulsion for encapsulation, and after removing the solvent, the potassium permanganate polylactic acid microcapsule is obtained.

4. An application of the potassium permanganate polylactic acid microcapsule according to any one of claims 1 - 2 in a polypropylene composite material.

5. A flame-free paintable polypropylene composite material, characterized in that, by weight, comprises the following components: 100 parts of polypropylene resin, 0.3 - 0.8 parts of the potassium permanganate polylactic acid microcapsule according to any one of claims 1 - 2.

6. The flame-free paintable polypropylene composite material according to claim 5, characterized in that, the polypropylene resin is homopolypropylene and / or copolymerized polypropylene.

7. The flame-free paintable polypropylene composite material according to claim 5, characterized in that, further comprises a filler, an elastomer and a processing aid, and the filler is one or more of talc powder, mica powder or calcium carbonate.

8. A method for preparing the flame-free paintable polypropylene composite material according to any one of claims 5 - 7, characterized in that, comprises the following steps: first mix the other components except the potassium permanganate polylactic acid microcapsule in proportion and melt-extrude to obtain a polypropylene composition, and then mix it with the potassium permanganate polylactic acid microcapsule to obtain the flame-free paintable polypropylene composite material.

9. An application of the flame-free paintable polypropylene composite material according to any one of claims 5 - 7 in automotive spray-painted parts.

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