An unfilled natural heat-resistant retention polypropylene composite, its preparation method and application

Abstract

The present invention discloses a non-filled natural heat-resistant retention polypropylene composite. By weight parts, the polypropylene composite comprises the following components: 58-91 parts of polypropylene resin, 10-40 parts of syndiotactic polypropylene, 0.05-1 part of a first primary antioxidant, 0.05-1 part of a second primary antioxidant, 0.05-1 part of a first secondary antioxidant, 0.05-1 part of a second secondary antioxidant, 0.05-1 part of a metal deactivator, 0.05-1 part of a hindered amine antioxidant, 0.5-2 parts of ultra-high melt index polypropylene. The first primary antioxidant is a hindered phenol antioxidant with a melting point of 150-230 °C, the second primary antioxidant is a hindered phenol antioxidant with a melting point of 40-60 °C, the first secondary antioxidant is a phosphite antioxidant, and the second secondary antioxidant is a thioether antioxidant. The present invention effectively improves the heat retention yellowing phenomenon of the polypropylene composite by adopting syndiotactic polypropylene and optimizing the combination of the antioxidant system and the lubricant system.

Description

Technical Field

[0001] The present invention belongs to the technical field of modified plastics, and more specifically, relates to a non-filled natural heat-resistant retention polypropylene composite and its preparation method and application. Background Art

[0002] With the development of the automotive industry, polypropylene materials are increasingly widely used in automobiles. Through the technology of replacing steel with plastics and the generalization technology of engineering plastics, they gradually replace metal materials and engineering plastic materials and have become the material type with the largest application quantity. At the same time, new technologies such as transparent polypropylene parts, in-vehicle atmosphere lights, and non-filled expansion tanks have emerged. These parts are all prepared with non-filled polypropylene, enriching the personalized choices of automotive users. For example, Patent CN112063057B prepared a polypropylene for an expansion tank with yellowing resistance by specifying special primary antioxidants, secondary antioxidants, and nucleating agents, and it can maintain good transparency and color after 150°C / 500h.

[0003] However, with the increasing market competition, the cost pressure of parts puts higher requirements on production efficiency and output rate. Many injection molding manufacturers have put forward requirements such as "producing good products in three molds" or even "producing good products in one mold", resulting in that after the injection molding machine stops due to abnormal situations such as breaks and shift handovers during the injection molding process, the parts produced after starting the machine are extremely prone to yellowing. This yellowing phenomenon is relatively rare in filled polypropylene, reinforced polypropylene, or dyed polypropylene, but for non-filled natural polypropylene materials, without the covering of fillers and colorants, it is extremely prone to yellowing (heat retention yellowing), especially the heat retention yellowing phenomenon generated during the injection molding of the injection molding machine.

[0004] Therefore, how to optimize the existing non-filled polypropylene materials and then improve the generation of their heat retention yellowing phenomenon has become an urgent technical problem to be solved. Summary of the Invention

[0005] Aiming at the above existing technical problems, the primary object of the present invention is to provide a non-filled natural heat-resistant retention polypropylene composite. The non-filled natural heat-resistant retention polypropylene composite effectively improves the heat retention yellowing phenomenon of the polypropylene composite by using syndiotactic polypropylene and optimizing the combination of the antioxidant system and the lubricant system.

[0006] The second object of the present invention is to provide a preparation method of a non-filled natural heat-resistant retention polypropylene composite.

[0007] The third object of the present invention is to provide an application of a non-filled natural heat-resistant retention polypropylene composite in the automotive field.

[0008] In order to achieve the above objects, the present invention is realized through the following technical solutions:

[0009] An unfilled natural heat-resistant retention polypropylene composite, by weight parts, comprises the following components:

[0010]

[0011] The polypropylene resin includes one or two of random copolymerized polypropylene and isotactic polypropylene;

[0012] The first primary antioxidant is a high-melting-point hindered phenol antioxidant, and the melting point of the first primary antioxidant is 150 - 230°C; the second primary antioxidant is a low-melting-point hindered phenol antioxidant, and the melting point of the second primary antioxidant is 40 - 60°C;

[0013] The first secondary antioxidant is a phosphite antioxidant, and the melting point of the first secondary antioxidant is ≥225°C; the second secondary antioxidant is a thioether antioxidant, and the melting point of the second secondary antioxidant is 40 - 70°C;

[0014] The third secondary antioxidant is a metal deactivator;

[0015] The lubricant is ultra-high melt index polypropylene, and the melt flow rate of the ultra-high melt index polypropylene under the conditions of 230°C and 2.16 kg is 1000 - 1500 g / 10 min.

[0016] In the unfilled natural heat-resistant retention polypropylene composite of the present invention, syndiotactic polypropylene is adopted. Due to the particularity of the molecular chain segments of syndiotactic polypropylene, there is a certain degree of saturation and low activity, so that the degradation of syndiotactic polypropylene during heat shearing is very little, and the reaction participated by antioxidants is very little, thus generating very little yellowing substance and avoiding the occurrence of heat retention yellowing phenomenon. While isotactic polypropylene has a higher crystallinity, and the distribution of antioxidants in the amorphous phase and the crystalline phase is uneven, and the low-melting-point antioxidants are more likely to migrate, resulting in the aggravation of the heat retention yellowing phenomenon of the material; while random copolymerized polypropylene has a lower melting point and poor heat resistance, and the effect of resisting heat retention yellowing is also poor.

[0017] Furthermore, in the polypropylene composite system of the present invention, a high-melting-point first primary antioxidant is combined with a low-melting-point second primary antioxidant, a high-melting-point phosphite antioxidant is combined with a low-melting-point thioether antioxidant, and then combined with a specific metal deactivator and a hindered amine antioxidant, ensuring that the polypropylene composite generates less yellowing substance under high heat conditions and avoiding the occurrence of heat retention yellowing phenomenon. Even further, the present invention adopts ultra-high melt index polypropylene as the lubricant, reducing the promoting effect of using alkaline or acidic substances as lubricants on the yellowing of polypropylene and further improving the generation of heat retention yellowing phenomenon.

[0018] The present invention optimizes the compatibility of syndiotactic polypropylene, metal deactivator, ultra-high melt index polypropylene, hindered amine antioxidant, and antioxidants with different high and low melting points, effectively improving the heat retention yellowing phenomenon of unfilled natural heat retention polypropylene composites.

[0019] Specifically, the test method for the melt flow rate of the ultra-high melt index polypropylene is GB / T 3682-2018.

[0020] Preferably, in the unfilled natural heat retention polypropylene composite, the content of the polypropylene resin is not less than 58.7%.

[0021] Preferably, the melt flow rate of the syndiotactic polypropylene under the conditions of 230°C and 2.16 kg is 1-10 g / 10 min. The test standard for the melt flow rate of the syndiotactic polypropylene is: GB / T 3682-2018.

[0022] Preferably, the melt flow rate of the isotactic polypropylene under the conditions of 230°C and 2.16 kg is 0.1-12 g / 10 min. The test standard for the melt flow rate of the isotactic polypropylene is: GB / T 3682-2018.

[0023] Preferably, the melt flow rate of the random copolymer polypropylene under the conditions of 230°C and 2.16 kg is 0.1-12 g / 10 min. The test standard for the melt flow rate of the random copolymer polypropylene is: GB / T3682-2018.

[0024] Preferably, the first main antioxidant is selected from one or two of 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione and 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid. Further preferably, the first main antioxidant can be selected from the above substances with a purity ≥ 99.5%.

[0025] Preferably, the second main antioxidant is n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0026] Preferably, the first auxiliary antioxidant is selected from one or two of 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane and bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.

[0027] Preferably, the molecular weight of the first co-antioxidant is ≥600. More preferably, the molecular weight of the first co-antioxidant is ≥800. At this preferred molecular weight, the first co-antioxidant is more difficult to precipitate in the polypropylene composite, so it can better improve the heat retention yellowing phenomenon of the polypropylene composite.

[0028] Preferably, in the first co-antioxidant, the phosphorus content is ≥7%. More preferably, the phosphorus content is ≥9%, or the phosphorus content is ≥12%. The higher the phosphorus content, the higher the ability to decompose hydrogen peroxide, and thus the higher the ability to prevent heat retention yellowing.

[0029] Preferably, the second co-antioxidant is pentaerythritol tetrakis(3-laurylthiopropionate).

[0030] Preferably, the molecular weight of the second co-antioxidant is ≥800. At this preferred molecular weight, the second co-antioxidant is more difficult to precipitate in the polypropylene composite, so it can better improve the heat retention yellowing phenomenon of the polypropylene composite.

[0031] Preferably, the metal deactivator is bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazine. More preferably, the metal deactivator can be selected from the above substances with a purity of ≥99.5%.

[0032] Preferably, the hindered amine antioxidant is selected from one or more of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidyl)imino]]), and poly(6-morpholino-5-triazine-2,4-diyl)(2,2,6,6-tetramethylpiperidyl)iminohexamethylene[(2,2,6,6-tetramethylpiperidyl)-imino].

[0033] Preferably, the lubricant, syndiotactic polypropylene, the first main antioxidant, the first co-antioxidant, and the third co-antioxidant can be added in the form of masterbatch. The preparation method of the masterbatch is: mix the lubricant and syndiotactic polypropylene, then add the first main antioxidant, the first co-antioxidant, and the third co-antioxidant and mix, and prepare the masterbatch by vacuum extrusion granulation.

[0034] Preferably, the polypropylene resin, the second main antioxidant, the second co-antioxidant, and the hindered amine antioxidant can be added in the form of masterbatch. The preparation method of the masterbatch is: mix the polypropylene resin, the second main antioxidant, the second co-antioxidant, and the hindered amine antioxidant, and obtain the masterbatch by vacuum extrusion granulation.

[0035] Furthermore, the present invention claims a method for preparing an unfilled natural heat-resistant retention polypropylene composite, comprising the following steps:

[0036] (1) Mix the lubricant and syndiotactic polypropylene evenly, then add the first main antioxidant, the first auxiliary antioxidant, and the third auxiliary antioxidant and mix them. Prepare antioxidant masterbatch by vacuum extrusion granulation;

[0037] (2) Mix the polypropylene resin, the second main antioxidant, the second auxiliary antioxidant, and the hindered amine antioxidant evenly, and obtain the polypropylene composite masterbatch by vacuum extrusion granulation;

[0038] (3) Mix the antioxidant masterbatch and the polypropylene composite masterbatch to obtain the heat-resistant retention polypropylene composite.

[0039] Preferably, in the step (1), the vacuum degree of the vacuum extrusion granulation is ≤ -0.08 MPa.

[0040] Preferably, a twin-screw extruder is used for extrusion, and the length-diameter ratio of the twin-screw extruder is 40 - 48:1.

[0041] Preferably, the screw speed of the twin-screw extruder is 400 - 600 rpm.

[0042] Preferably, the extrusion temperature is 120 - 220 °C.

[0043] Furthermore, the present invention claims an application of the unfilled natural heat-resistant retention polypropylene composite in the automotive field. Specifically, the heat-resistant retention polypropylene composite is applicable to transparent or translucent parts such as transparent interior trim, transparent exterior trim, in-vehicle atmosphere lights, expansion tanks, and wash bottles, especially in occasions with high requirements for transparency and translucency performance.

[0044] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses syndiotactic polypropylene, metal deactivator, ultra-high melt index polypropylene, hindered amine antioxidant, and antioxidants with different high and low melting points in combination, effectively improving the heat retention and yellowing phenomenon of the unfilled natural heat-resistant retention polypropylene composite. Specific Embodiments

[0045] The following further illustrates the present invention in conjunction with the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0046] "Unfilled" in the present invention means that only functional additives such as antioxidants and lubricants are added to the polypropylene resin, and no fillers (such as talc powder, calcium carbonate, mica, glass fiber, plant fiber, etc.) are added.

[0047] In the present invention, "natural color" means that no colorant is added to the polypropylene resin for color adjustment, and the polypropylene resin presents its inherent color, namely, translucent milky white.

[0048] The raw materials for the examples and comparative examples are as follows:

[0049]

[0050]

[0051]

[0052] Unless otherwise specified, the components (such as antioxidants and lubricants) selected in each parallel example and comparative example are the same commercially available products.

[0053] Example 1

[0054] The weight parts of the raw materials used in Example 1 are shown in Table 1.

[0055] A preparation method of a non-filled natural color heat-resistant retention polypropylene composite, the specific steps include:

[0056] (1) Add the lubricant and syndiotactic polypropylene into a high-speed mixer for low-speed mixing (≤200 rpm), then add the first main antioxidant, the first auxiliary antioxidant, and the third auxiliary antioxidant and continue to mix evenly. Use a twin-screw extruder (length-diameter ratio 40:1, rotation speed 550 rpm) to extrude and pelletize under vacuum (vacuum degree ≤ -0.08 MPa) to obtain an antioxidant masterbatch;

[0057] (2) Add polypropylene resin (random copolymerized polypropylene and / or isotactic polypropylene), the second main antioxidant, the second auxiliary antioxidant, and a hindered amine antioxidant into a high-speed mixer for low-speed mixing (≤200 rpm) until evenly mixed. Use a twin-screw extruder (length-diameter ratio 40:1, rotation speed 550 rpm) to extrude and pelletize under vacuum to obtain a polypropylene composite masterbatch;

[0058] (3) Mix the above antioxidant masterbatch and polypropylene composite masterbatch to obtain a non-filled natural color heat-resistant retention polypropylene composite.

[0059] Examples 2 to 13

[0060] The weight parts of the raw materials used in the following examples are shown in Table 1.

[0061] The specific preparation steps of the following examples are the same as those of Example 1.

[0062] Comparative Examples 1 to 7

[0063] The weight parts of the raw materials used in the following comparative examples are shown in Table 2.

[0064] The difference between Comparative Example 6 and Example 1 is that the lubricant is isotactic polypropylene-1.

[0065] The difference between Comparative Example 7 and Example 1 is that the first main antioxidant and the second main antioxidant use the common main antioxidant 1010, and the first auxiliary antioxidant, the second auxiliary antioxidant, and the third auxiliary antioxidant use the common auxiliary antioxidant 168.

[0066] The specific preparation steps of the other comparative examples are the same as those of Example 1.

[0067] Table 1

[0068]

[0069]

[0070]

[0071] Table 2 shows the formula components of each comparative example:

[0072] Table 2

[0073] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Isotactic polypropylene - 1 60 60 60 60 60 61 60 Random copolymer polypropylene - 1 20 20 20 20 20 20 20 Syndiotactic polypropylene - 1 0 20 20 20 20 20 20 Primary antioxidant - 1 0.2 0 0.2 0.2 0.2 0.2 0 Primary antioxidant - 2 0.2 0.4 0.2 0.2 0.2 0.2 0 Common primary antioxidant 0 0 0 0 0 0 0.8 Common secondary antioxidant 0 0 0 0 0 0 0.8 Secondary antioxidant - 1 0.2 0.2 0 0.2 0.2 0.2 0 Secondary antioxidant - 2 0.2 0.2 0.4 0.4 0.2 0.2 0 Secondary antioxidant - 3 0.2 0.2 0.2 0 0.2 0.2 0 Hindered amine - 1 0.2 0.2 0.2 0.2 0.2 0.2 0 Lubricant - 1 1 1 1 1 0 0 1 Lubricant - 2 0 0 0 0 1 0 0

[0074] The raw materials used in the above examples and comparative examples and the unfilled natural heat-resistant retention polypropylene composites prepared were tested according to the following test methods: The unfilled natural heat-resistant retention polypropylene composites prepared in the above examples and comparative examples were used, and a Haitian 80T injection molding machine was used. According to the injection molding conditions of the conventional process (temperature 210°C, injection speed 20 g / s, injection pressure 20 MPa, holding pressure 20 MPa, holding time 8 s) and the heat retention process (temperature 210°C, heat retention 30 min, injection speed 20 g / s, injection pressure 20 MPa, holding pressure 20 MPa, holding time 8 s), they were respectively injection molded into color plates of 50*80*2 mm, the color difference values of the color plates were detected, and the color difference change value △b = b value (heat retention color plate) - b value (conventional color plate) was calculated.

[0075] Table 3 shows the performance test results of each example and comparative example respectively.

[0076] Table 3

[0077] Color difference value △B Example 1 0.21 Example 2 0.26 Example 3 0.04 Example 4 0.18 Example 5 0.16 Example 6 0.19 Example 7 0.18 Example 8 0.18 Example 9 0.14 Example 10 0.15 Example 11 0.19 Example 12 0.20 Example 13 0.23 Comparative Example 1 0.41 Comparative Example 2 0.44 Comparative Example 3 0.49 Comparative Example 4 0.38 Comparative Example 5 1.76 Comparative Example 6 1.05 Comparative Example 7 3.58

[0078] As can be seen from the data of Examples 1 to 13, using syndiotactic polypropylene, a combination of high-melting-point and low-melting-point antioxidants, a metal deactivator, a hindered amine material, and high-melt-index polypropylene as a lubricant ensures that less yellowing substances are generated in the unfilled natural heat-resistant retention polypropylene composite under high-temperature conditions, reducing the occurrence of heat-retention yellowing phenomenon. The color difference value △B of the prepared unfilled natural heat-resistant retention polypropylene composite is ≤0.26, and the heat-retention yellowing phenomenon of the polypropylene composite has been greatly improved.

[0079] As can be seen from Example 1 and Comparative Example 1, when syndiotactic polypropylene is missing in the polypropylene composite, the color difference value △B > 0.4, and the heat-retention yellowing phenomenon of the polypropylene composite is aggravated.

[0080] As can be seen from Example 1, Comparative Example 2, and Comparative Example 3, when any antioxidant in the antioxidant system is missing in the polypropylene composite and a high-melting-point and low-melting-point combined antioxidant system is not used, the color difference value △B > 0.38, and the heat-retention yellowing phenomenon of the polypropylene composite is aggravated. Comparative Example 4 also reflects the importance of the selection of the metal deactivator in the system. When the metal deactivator is replaced with a conventional antioxidant, the heat-retention yellowing phenomenon of the polypropylene composite is aggravated.

[0081] As can be seen from Example 1, Comparative Example 5, and Comparative Example 6, when the polypropylene composite does not use ultra-high-melt-index polypropylene as a lubricant but uses a conventional lubricant (zinc stearate) or low-melt-index polypropylene, the color difference value △B > 1.0, and the heat-retention yellowing phenomenon of the polypropylene composite is aggravated. The reason is that zinc stearate is produced by the water method and is acidic, and acidic substances accelerate the progress of thermal-oxidative aging. Conventional polypropylene does not have a lubricating effect, which increases the friction between polypropylene molecules and between polypropylene and the extruder barrel, accelerating the degradation of the polypropylene molecular weight and aggravating the yellowing phenomenon.

[0082] As can be seen from Example 1 and Comparative Example 7, when the polypropylene composite uses a conventional primary antioxidant 1010 and a secondary antioxidant 168 in combination, the antioxidant is prone to phenolic yellowing or quinone yellowing, making the heat-retention yellowing phenomenon of the prepared polypropylene composite significantly aggravated.

[0083] The foregoing examples are illustrative only and are used to explain some features of the method of the present invention. The appended claims are intended to claim the broadest scope conceivable, and the examples presented herein are supported by the applicant's actual test results. Therefore, the applicant's intention is that the appended claims are not limited by the selection of examples that illustrate the features of the present invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be construed as being covered by the appended claims whenever possible.

Claims

1. An unfilled natural heat-resistant retention polypropylene composite, characterized in that, By weight parts, it includes the following components: The polypropylene resin includes one or two of random copolymerized polypropylene and isotactic polypropylene; The first main antioxidant is a high melting point hindered phenol antioxidant, and the melting point of the first main antioxidant is 150 - 230 °C; the second main antioxidant is a low melting point hindered phenol antioxidant, and the melting point of the second main antioxidant is 40 - 60 °C; The first auxiliary antioxidant is a phosphite antioxidant, and the melting point of the first auxiliary antioxidant is ≥225 °C; the second auxiliary antioxidant is a thioether antioxidant, and the melting point of the second auxiliary antioxidant is 40 - 70 °C; The third auxiliary antioxidant is a metal deactivator; the metal deactivator is bis(3,5 - di - tert - butyl - 4 - hydroxy - benzoyl) hydrazine; The lubricant is ultra - high melt index polypropylene, and the melt flow rate of the ultra - high melt index polypropylene under the conditions of 230 °C and 2.16 kg is 1000 - 1500 g / 10 min; The hindered amine antioxidant is selected from one or more of bis(2,2,6,6 - tetramethyl - 4 - piperidyl) sebacate, poly[[6 - [(1,1,3,3 - tetramethylbutyl)amino] - 1,3,5 - triazine - 2,4 - diyl][(2,2,6,6 - tetramethyl - 4 - piperidyl)imino] - 1,6 - hexanediyl[(2,2,6,6 - tetramethyl - 4 - piperidyl)imino]]), and poly(6 - morpholino - 5 - triazine - 2,4 - diyl)(2,2,6,6 - tetramethylpiperidyl) iminohexamethylene[(2,2,6,6 - tetramethylpiperidyl) - imino]; 2. The unfilled natural heat-resistant retention polypropylene composite according to claim 1, characterized in that, The melt flow rate of the syndiotactic polypropylene under the conditions of 230 °C and 2.16 kg is 1 - 10 g / 10 min.

3. The unfilled natural heat-resistant retention polypropylene composite according to claim 1, wherein The first main antioxidant is selected from one or two of 1,3,5 - tris(4 - tert - butyl - 3 - hydroxy - 2,6 - dimethylbenzyl) - 1,3,5 - triazine - 2,4,6 - (1H,3H,5H) - trione and 1,3,5 - tris(3,5 - di - tert - butyl - 4 - hydroxybenzyl) isocyanuric acid.

4. The unfilled natural heat-resistant retention polypropylene composite according to claim 1, characterized in that, The second main antioxidant is n - octadecyl β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl) propionate.

5. The unfilled natural heat-resistant retention polypropylene composite according to claim 1, characterized in that, The first auxiliary antioxidant is selected from one or two of 3,9 - bis(2,4 - di - cumylphenoxy) - 2,4,8,10 - tetraoxa - 3,9 - diphosphaspiro[5.5]undecane and bis(2,6 - di - tert - butyl - 4 - methylphenyl) pentaerythritol diphosphate.

6. The unfilled natural heat-resistant retention polypropylene composite according to claim 1, wherein The second auxiliary antioxidant is pentaerythritol tetrakis(3 - laurylthiopropionate).

7. The preparation method of the unfilled natural heat-resistant retention polypropylene composite according to any one of claims 1 to 6, characterized in that It includes the following steps: (1) Mix the lubricant and syndiotactic polypropylene evenly, then add the first main antioxidant, the first auxiliary antioxidant, and the third auxiliary antioxidant and mix them, and prepare an antioxidant masterbatch by vacuum extrusion granulation; (2) Mix the polypropylene resin, the second main antioxidant, the second auxiliary antioxidant, and the hindered amine antioxidant evenly, and obtain a polypropylene composite masterbatch by vacuum extrusion granulation; (3) Mix the antioxidant masterbatch and the polypropylene composite masterbatch to obtain a heat - resistant retention polypropylene composite.

8. Use of the unfilled natural heat-resistant retention polypropylene composite according to any one of claims 1 to 6 in the automotive field.

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