A whisker-modified polypropylene composition and its preparation method and application

Abstract

The present invention provides a whisker-modified polypropylene composition, its preparation method, and application. The whisker-modified polypropylene composition comprises the following components in parts by weight: 65-88 parts of a polypropylene resin, 6-15 parts of a filler, 5-15 parts of a polyolefin elastomer, and 0-5 parts of an additive; the filler is a mixture of a whisker filler and a flaky filler in a weight ratio of (2-3) to 1; and the polypropylene resin has a melting enthalpy of 40-100 J / g. Through the combined effects of the whisker filler, the flaky filler, the polypropylene resin with a specific melting enthalpy, and the polyolefin elastomer, the whisker-modified polypropylene composition exhibits both excellent mechanical properties and low warpage.

Description

Technical Field

[0001] The present invention relates to the technical field of plastics, in particular to a whisker-modified polypropylene composition and a preparation method and application thereof. Background Art

[0002] With the recent growth of the new energy vehicle industry, lightweighting has become a key research topic for automotive manufacturers. Lightweighting can reduce vehicle energy consumption, increase range, and improve energy efficiency, with significant economic and social significance. Polypropylene (PP), due to its excellent overall performance, is widely used in a variety of automotive parts and is currently the most widely used automotive plastic. Therefore, achieving lightweighting for its injection molded parts is of great significance.

[0003] Currently, the main lightweighting solutions for polypropylene parts include: low density, thin-walling, foaming, and replacing steel with plastic. Low density is achieved by replacing traditional fillers with new fillers. At a lower addition ratio (lower density), these fillers can achieve similar performance to traditional fillers added at a higher ratio (higher density), achieving lightweight parts through their lower density. Commonly used new fillers include whiskers, wollastonite, sepiolite, and other types of nanofillers. Whiskers are widely used due to their excellent performance after addition, wide availability, and relatively low cost compared to other new fillers.

[0004] However, polypropylene materials using whiskers as fillers suffer from high warpage. Whiskers are fillers with a specific aspect ratio. Because they orient during the injection molding process, shrinkage in the flow direction and perpendicular to the flow direction differs, making them prone to warping and other phenomena that affect the appearance and functionality of parts. Whisker-modified polypropylene not only exhibits high initial warpage upon completion of injection molding, but also increases over time and after thermal aging, leading to quality issues after assembly.

[0005] Chinese patent application CN 104558843 A discloses a low-warpage, high-modulus modified polypropylene material and its preparation method. The material comprises polypropylene, whiskers, and an anti-warpage nucleating agent. The addition of the anti-warpage nucleating agent alleviates the warpage problem in the product to some extent. However, the maximum warpage of the modified polypropylene material, reaching 1.62 mm, is still too high, and the warpage increases further after thermal aging.

[0006] Therefore, it is necessary to develop a whisker-modified polypropylene composition with low warpage. Summary of the Invention

[0007] The purpose of the present invention is to overcome the high warpage defect of the prior art and provide a whisker-modified polypropylene composition. Through the combined action of whisker fillers, flaky fillers, a polypropylene resin with a specific melting enthalpy, and a polyolefin elastomer, the whisker-modified polypropylene composition of the present invention has both excellent mechanical properties and low warpage.

[0008] Another object of the present invention is to provide a method for preparing the whisker-modified polypropylene composition.

[0009] Another object of the present invention is to provide applications of the whisker-modified polypropylene composition.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A whisker-modified polypropylene composition comprises the following components in parts by weight:

[0012]

[0013] The filler includes a whisker filler and a flake filler, and the weight ratio of the whisker filler to the flake filler is (2-3):1;

[0014] The melting enthalpy of the polypropylene resin is 40 to 100 J / g.

[0015] In whisker modified polypropylene composition of the present invention, adopt the whisker filler and the flaky filler of specific ratio compounding as mixed filler, polypropylene resin is modified.The whisker filler has improved the mechanical property of material, and the flaky filler adds with less number, is scattered around the whisker filler, has reduced the orientation of whisker filler, thereby reduced the warpage of material.The flaky filler is owing to having special sheet structure, and excellent heat resistance, not only can improve the initial warpage of the application's whisker modified polypropylene composition when injection molding is completed, can also make injection molded part still keep low warpage after thermal aging.

[0016] The weight ratio of whisker filler to flake filler is a key factor influencing the mechanical and warpage properties of a material. The inventors found that when the amount of whisker filler is too high and the amount of flake filler is too low, the material's warpage is excessive. On the other hand, when the amount of whisker filler is too low and the amount of flake filler is too high, while the material's warpage is improved, the insufficient amount of whisker filler provides insufficient mechanical reinforcement, resulting in poor mechanical properties.

[0017] The enthalpy of fusion of a polypropylene resin reflects its crystallization properties to a certain extent. Polypropylene resins with lower enthalpy of fusion have lower crystallization rates and crystallinity. The present invention utilizes a polypropylene resin with a enthalpy of fusion ≤100 J / g as the base resin, leveraging its lower crystallization rate and crystallinity to reduce the warpage of the whisker-modified polypropylene composition. However, the enthalpy of fusion of the polypropylene resin should not be too low. The inventors have found that using a polypropylene resin with a enthalpy of fusion <40 J / g as the base resin results in poor mechanical properties of the resulting polypropylene material, making it difficult to meet practical application requirements.

[0018] The addition of polyolefin elastomer improves the toughness of the whisker-modified polypropylene composition and also enables the whisker filler and plate-like filler to be distributed in the polypropylene matrix in a more ideal manner.

[0019] The whisker-modified polypropylene composition of the present invention has both excellent mechanical properties and low warpage through the combined effects of whisker fillers, flake fillers, polypropylene resin with specific melting enthalpy and polyolefin elastomer.

[0020] The test method for the melting enthalpy of polypropylene resin is GB / T 16582-1996.

[0021] Preferably, the melting enthalpy of the polypropylene resin is 60 to 80 J / g.

[0022] The inventors have found that when the polypropylene resin is 60 to 80 J / g, the obtained whisker-modified polypropylene composition has a smaller warpage change after heat aging treatment, and the warpage after heat aging is even lower.

[0023] Preferably, the weight ratio of the whisker filler to the flake filler is (2.5-2.6):1.

[0024] When the whisker filler and the flake filler are in the above weight ratio, the compounding effect of the two is optimal, and the obtained whisker-modified polypropylene composition has both excellent flexural modulus and notched impact strength and low warpage.

[0025] Preferably, the aspect ratio of the whisker filler is (10-23):1.

[0026] More preferably, the aspect ratio of the whisker filler is (10-11):1.

[0027] Preferably, the average particle size of the flake filler is 2.5 to 40 μm.

[0028] More preferably, the average particle size of the flake filler is 2.5 to 10 μm.

[0029] More preferably, the average particle size of the flake filler is 2.6 to 5 μm.

[0030] Flake fillers with smaller particle sizes have better dispersibility and can be more tightly combined with whisker fillers, thus reducing the warpage of the material to a greater extent without affecting the mechanical properties of the material.

[0031] Preferably, the whisker filler is at least one of magnesium sulfate whiskers, potassium titanate whiskers, and calcium sulfate whiskers.

[0032] Preferably, the flaky filler is talc and / or mica.

[0033] More preferably, the whisker filler is magnesium sulfate whisker, and the flaky filler is talc.

[0034] Magnesium sulfate whiskers and talc powder can produce a synergistic effect and have a better anti-warping effect.

[0035] Optionally, the polyolefin elastomer is ethylene-butene copolymer and / or ethylene-octene copolymer.

[0036] Preferably, the polyolefin elastomer is ethylene-octene copolymer.

[0037] The inventors found that due to the difference in the comonomers of octene and butene, the carbon chain of octene is longer than that of butene, and the ethylene-octene copolymer has a better improvement in the orientation of the whisker filler. The resulting whisker-modified polypropylene composition has lower warpage and better mechanical properties.

[0038] Preferably, the Mooney viscosity of the polyolefin elastomer is ≥8.

[0039] More preferably, the Mooney viscosity of the polyolefin elastomer is ≥13.

[0040] The test method for Mooney viscosity of polyolefin elastomers is ASTM D1646-2004.

[0041] More preferably, the Mooney viscosity of the polyolefin elastomer is 20-26.

[0042] The higher Mooney viscosity of the polyolefin elastomer helps to reduce the orientation of the whisker filler during dispersion, thereby improving the warpage of the polypropylene composition to a certain extent.

[0043] Optionally, the auxiliary agent is a functional auxiliary agent commonly used in the polypropylene field.

[0044] Preferably, the auxiliary agent includes an antioxidant.

[0045] More preferably, the antioxidant comprises at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and tris[2,4-di-tert-butylphenyl]phosphite. The present invention also provides a method for preparing the whisker-modified polypropylene composition, comprising the following steps:

[0046] The polypropylene resin, filler, polyolefin elastomer and additives are mixed and added to an extruder, and the mixture is melt-mixed and extruded into granules to obtain the whisker-modified polypropylene composition.

[0047] Preferably, the extruder is a twin-screw extruder; the screw length-diameter ratio of the twin-screw extruder is 36:1 to 56:1; the temperature of the twin-screw extruder is 80-120°C in zone 1, 190-210°C in zone 2, 210-230°C in zone 3, 210-230°C in zone 4, 210-230°C in zone 5, 210-230°C in zone 6, 210-230°C in zone 7, 210-230°C in zone 8, 210-230°C in zone 9, and the speed is 200-800 rpm.

[0048] The present invention also protects the use of the whisker-modified polypropylene composition in preparing automobile instrument panels, bumpers and door panels.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention develops a whisker-modified polypropylene composition. Through the combined action of whisker fillers, flaky fillers, a polypropylene resin with a specific melting enthalpy, and a polyolefin elastomer, the whisker-modified polypropylene composition of the present invention has both excellent mechanical properties and low warpage.

[0051] The flexural modulus of the whisker-modified polypropylene composition of the present invention is ≥1800 MPa and the notched impact strength is ≥10 kJ / m 2 The initial warpage after injection molding is ≤0.9mm. After heat aging at 100℃ for 1000h, the warpage increase is ≤0.2mm. DETAILED DESCRIPTION

[0052] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any form.

[0053] The sources of raw materials used in the embodiments and comparative examples of the present invention are as follows:

[0054] PP-1, polypropylene resin, CNOOC Shell EP548R, melting enthalpy is 63 J / g;

[0055] PP-2, polypropylene resin, Fujian Petrochemical Z30S, melting enthalpy is 91 J / g;

[0056] PP-3, polypropylene resin, Zhenhai Petrochemical M60RHC, melting enthalpy is 80J / g;

[0057] PP-4, polypropylene resin, Korean SK BX3800, melting enthalpy is 40 J / g;

[0058] PP-5, polypropylene resin, Lanzhou Petrochemical SP179, melting enthalpy is 30J / g;

[0059] PP-6, polypropylene resin, Shanghai Petrochemical manufacturer M1200HS, melting enthalpy is 118J / g;

[0060] Whisker-1, whisker filler, magnesium sulfate whisker, Fengzhu NP-YW2, aspect ratio of 11:1;

[0061] Whisker-2, whisker filler, magnesium sulfate whisker, Liaoning Weiske WS-1S2, aspect ratio is 23:1,

[0062] Whisker-3, whisker filler, potassium titanate whisker, Fengzhu NP-TW4, aspect ratio of 12:1;

[0063] Whisker-4, whisker filler, calcium sulfate whisker, Fengzhu NP-M02, aspect ratio of 16:1;

[0064] Talc-1, flake filler, Liaoning Tianyuan HTP Ultra 5L, 5000 mesh, i.e., average particle size of 2.6 μm;

[0065] Talc-2, flake filler, Liaoning Tianyuan 8875B, 1250 mesh, i.e. average particle size of 10 μm;

[0066] Mica, flake filler, Suzhou Shenwei YM-SW500, average particle size 40μm;

[0067] Ethylene-octene copolymer-1, polyolefin elastomer, Dow Chemical 8842, Mooney viscosity 26;

[0068] Ethylene-octene copolymer-2, polyolefin elastomer, Dow Chemical 8100, Mooney viscosity 20;

[0069] Ethylene-octene copolymer-3, polyolefin elastomer, Dow Chemical 8452, Mooney viscosity 13;

[0070] Ethylene-octene copolymer-4, polyolefin elastomer, Dow Chemical 8200, Mooney viscosity 8;

[0071] Ethylene-butene copolymer, polyolefin elastomer, Dow Chemical 7086, Mooney viscosity 25;

[0072] Additive, antioxidant 1010, commercially available.

[0073] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. Unless otherwise specified, the reagents and materials used in the present invention are commercially available.

[0074] Examples 1 to 17

[0075] Examples 1 to 17 provide a polypropylene composition, the component contents of which are shown in Table 1, and the preparation method is as follows:

[0076] After mixing the components according to Table 1, the mixture was added to a twin-screw extruder having a screw length-to-diameter ratio of 42:1; the temperatures of the twin-screw extruder were as follows: zone 1 temperature 80-120° C., zone 2 temperature 190-210° C., zone 3 temperature 210-230° C., zone 4 temperature 210-230° C., zone 5 temperature 210-230° C., zone 6 temperature 210-230° C., zone 7 temperature 210-230° C., zone 8 temperature 210-230° C., zone 9 temperature 210-230° C., and the rotation speed was 500 rpm; and the mixture was subjected to melt mixing and extrusion granulation to obtain a polypropylene composition.

[0077] Table 1

[0078]

[0079] Table 1

[0080]

[0081]

[0082] Comparative Examples 1 to 5

[0083] Comparative Examples 1 to 5 provide a polypropylene composition, the component contents of which are shown in Table 2, and the preparation method is as follows:

[0084] After mixing the components according to Table 2, the mixture was added to a twin-screw extruder having a screw length-to-diameter ratio of 42:1; the temperatures of the twin-screw extruder were as follows: zone 1 temperature 80-120° C., zone 2 temperature 190-210° C., zone 3 temperature 210-230° C., zone 4 temperature 210-230° C., zone 5 temperature 210-230° C., zone 6 temperature 210-230° C., zone 7 temperature 210-230° C., zone 8 temperature 210-230° C., zone 9 temperature 210-230° C., and the rotation speed was 500 rpm; and the mixture was subjected to melt mixing and extrusion granulation to obtain a polypropylene composition.

[0085] Table 2

[0086]

[0087] Performance Testing

[0088] The properties of the polypropylene compositions obtained in the above examples and comparative examples were characterized. The specific test items, test methods, and results are as follows:

[0089] Flexural modulus: tested in accordance with ISO178-2019, specimen size 80mm*10mm*4mm, span 64mm, speed 2mm / min;

[0090] Notched impact strength: tested in accordance with ISO179-1-2010, specimen size 80mm*10mm*4mm, A-type notch;

[0091] Warpage: The polypropylene composition was injection molded into a specimen with a size of 100*100*2mm. One corner of the specimen was fixed against a horizontal table. The height of the warpage at the opposite corner was measured with a vernier caliper and recorded as the initial warpage. The specimen was subjected to heat aging treatment: placed at 100°C for 1000h, and then the heat aging warpage was tested using the same method. The increase in heat aging warpage = heat aging warpage - initial warpage.

[0092] The test results of the embodiments are shown in Table 3, and the test results of the comparative examples are shown in Table 4.

[0093] Table 3 Test results of the embodiment

[0094]

[0095] Table 4 Test results of comparative examples

[0096]

[0097] According to the test results in Table 3, the polypropylene compositions prepared in the embodiments of the present invention have good mechanical properties: flexural modulus ≥ 1800 MPa, notched impact strength ≥ 10 kJ / m 2 ; The initial warpage is low, and the increase in warpage after thermal aging is small: the initial warpage after injection molding is ≤0.9mm, and after thermal aging at 100℃ and 1000h, the increase in warpage is ≤0.2mm.

[0098] According to Examples 1 to 4, when the melting enthalpy of the polypropylene resin is ≤100 J / g, the warpage of the polypropylene composition is good. When the melting enthalpy of the polypropylene resin is low (40 J / g), the flexural modulus and notched impact strength of the polypropylene composition are relatively poor. When the melting enthalpy of the polypropylene resin is 60 to 80 J / g, the warpage change of the polypropylene composition after thermal aging treatment is smaller, and the warpage after thermal aging is lower.

[0099] In Comparative Example 1, the melting enthalpy of the polypropylene resin is too low (30 J / g), and the mechanical properties of the obtained polypropylene composition are poor; in Comparative Example 2, the melting enthalpy of the polypropylene resin is too high (118 J / g), and the initial warpage and the warpage after heat aging of the obtained polypropylene composition are both too high.

[0100] According to Examples 1 and 8 to 9, when the particle size of the flake filler is smaller, it is more tightly combined with the whisker filler, and the warpage can be reduced to a greater extent without affecting the mechanical properties of the polypropylene composition.

[0101] According to Example 1 and Examples 10 to 12, it can be seen that when the polyolefin elastomer is an ethylene-octene copolymer, the initial warpage of the polypropylene composition is relatively lower. When the Mooney viscosity of the ethylene-octene copolymer is 20 to 26, the warpage change of the polypropylene composition after heat aging treatment is smaller.

[0102] According to Examples 1 and 14 to 17, when the weight ratio of the whisker filler to the flaky filler is (2 to 3): 1, the whisker filler and the flaky filler have a good synergistic effect, and the mechanical properties and warpage properties of the obtained polypropylene composition can meet the requirements. When the weight ratio of the whisker filler to the flaky filler is 2.5 to 2.6: 1, the synergistic effect of the whisker filler and the flaky filler is more significant, and the warpage of the polypropylene composition is lower.

[0103] The weight ratio of the whisker filler to the flaky filler in Comparative Examples 3 and 4 exceeds the range of (2 to 3):1. Comparative Example 5 does not contain a flaky filler and only uses a whisker filler. The initial warpage and the warpage after heat aging of the polypropylene compositions obtained in Comparative Examples 3 to 5 are both too high.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A whisker-modified polypropylene composition, characterized in that The composition comprises the following components in parts by weight: 65-88 parts of polypropylene resin, 6 to 15 parts of filler, 5-15 parts of polyolefin elastomer, 1 to 5 parts of additives; The filler includes a whisker filler and a flake filler, and the weight ratio of the whisker filler to the flake filler is (2.5-2.6):1; The melting enthalpy of the polypropylene resin is 40 to 91 J / g; The Mooney viscosity of the polyolefin elastomer is ≥20; the polyolefin elastomer is ethylene-butene copolymer and / or ethylene-octene copolymer.

2. The whisker-modified polypropylene composition according to claim 1, wherein The melting enthalpy of the polypropylene resin is 60 to 80 J / g.

3. The whisker-modified polypropylene composition according to claim 1, wherein The aspect ratio of the whisker filler is (10-23):

1.

4. The whisker-modified polypropylene composition according to claim 1, wherein The average particle size of the flake filler is 2.5 to 10 μm.

5. The whisker-modified polypropylene composition according to claim 1, wherein The whiskers are at least one of magnesium sulfate whiskers, potassium titanate whiskers, and calcium sulfate whiskers; and the flaky filler is talc and / or mica.

6. The method for preparing the whisker-modified polypropylene composition according to any one of claims 1 to 5, characterized in that: The steps include: The polypropylene resin, filler, polyolefin elastomer and additives are mixed and added to an extruder, and the mixture is melt-mixed and extruded into granules to obtain the whisker-modified polypropylene composition.

7. Use of the whisker-modified polypropylene composition according to any one of claims 1 to 5 in the preparation of automobile instrument panels, bumpers and door panels.

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