Polypropylene composition, and preparation method therefor and use thereof

Abstract

The present invention relates to a polypropylene composition, and a preparation method therefor and the use thereof. The polypropylene composition comprises the following components: a polypropylene resin, a composite filler, a compatibilizer, a lubricant and other auxiliaries. The polypropylene composition has a low density, a high notch impact strength and low molding shrinkage, and the surface of a large automobile part prepared therefrom by means of injection molding is free of pocking marks, and is smooth and glossy.

Description

A polypropylene composition and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of polymer materials, and more particularly to a polypropylene composition, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid development of the automotive industry in recent years, lightweighting, quality improvement, energy conservation, environmental protection, and functionalization have become key goals. Polypropylene, a versatile engineering plastic, is a key lightweight automotive material due to its low price, lightweight, solvent resistance, recyclability, and non-toxicity.

[0003] To significantly reduce the overall material density and weight, hollow glass microspheres can be added to polypropylene, as exemplified by the Chinese patent titled "A High-Rigidity, Low-Density, Low-Shrinkage Modified Polypropylene Material and Its Preparation Method." However, the hollow glass microspheres exhibit a certain degree of uneven particle size distribution. Larger hollow glass microspheres tend to sink to the bottom during the resin mixing process, while hollow glass microspheres of varying sizes have varying fluidity. These factors lead to uneven distribution of the hollow glass microspheres within the polypropylene material, reducing the impact resistance of the injection-molded product. Furthermore, they can cause surface pitting when large parts are injection-molded, impacting the appearance.

[0004] To this end, it is necessary to solve the problems of poor impact resistance of polypropylene materials using hollow glass microspheres as fillers and defects in appearance when injection molded into large parts. Summary of the Invention

[0005] The primary purpose of the present invention is to provide a polypropylene composition to overcome the problems of poor impact resistance and appearance defects when injection molded into large parts of polypropylene materials using hollow glass microspheres as fillers in the current technology.

[0006] A further object of the present invention is to provide a method for preparing the above-mentioned polypropylene composition.

[0007] A further object of the present invention is to provide use of the polypropylene composition in the preparation of automobile bumpers.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] A polypropylene composition comprising the following components in parts by weight:

[0010] The composite filler includes nano hollow barium sulfate and hollow glass particles in a mass ratio of 1:(1.2-2.5); the mass ratio of nano hollow barium sulfate and hollow glass particles can specifically be 1:1.2, 1:1.5, 1:1.8, 1:2.0, 1:2.3 or 1:2.5.

[0011] Through research, the inventors of the present invention have discovered that adding a composite filler made by compounding nano-hollow barium sulfate and hollow glass microspheres in a specific mass ratio to a polypropylene composition can effectively improve its impact strength while maintaining a low overall density. This is because, on the one hand, the nano-hollow barium sulfate has a nanoscale size and hollow structure, and has a high specific surface area, which can provide more interfacial area, thereby better interacting with the polypropylene resin; on the other hand, the different size characteristics of the nano-hollow barium sulfate and hollow glass microspheres can achieve a size matching effect between the fillers and avoid filler aggregation and accumulation. The combined effect of these two aspects can effectively improve the impact strength of the polypropylene composition while maintaining the overall density of the polypropylene composition within a low range. At the same time, when the polypropylene composition is injection molded into a large automobile part, the surface is smooth and glossy without pitting, and has a good appearance. The reasons for this may be: the size matching effect between the composite fillers and the reduction of filler aggregation and accumulation phenomena. At the same time, the combination with the compatibilizer and lubricant makes the filler more uniformly dispersed in the polypropylene composition, and can effectively improve the processing performance and melt fluidity of the polypropylene composition, thereby reducing the occurrence of surface defects.

[0012] In addition, the inventors of the present invention have also found that, unlike precipitated barium sulfate, the nano hollow barium sulfate in the composite filler of the present invention can play a nucleating role, thereby reducing the molding shrinkage of the polypropylene composition.

[0013] That is, the polypropylene composition of the present invention has low density, high notched impact strength and low molding shrinkage, and the surface of the large automobile parts obtained by injection molding has no pitting, is smooth and glossy.

[0014] Optionally, the polypropylene resin has a melt flow rate of 4 to 28 g / 10 min measured at 230° C. and 2.16 kg.

[0015] Preferably, the melt flow rate of the polypropylene resin measured at 230° C. and 2.16 kg is 4.8 to 8 g / 10 min. The polypropylene resin selected within this melt flow rate range can provide a polypropylene composition with higher notched impact strength.

[0016] The melt flow rate of the polypropylene resin of the present invention can be measured according to ISO 1133-2011.

[0017] Optionally, the particle size D50 of the hollow glass microspheres is 3 to 20 μm.

[0018] In the present invention, the particle size D50 of the hollow glass microspheres can be measured according to ISO 13320-2020.

[0019] Preferably, the particle size D50 of the hollow glass microspheres is 5 to 10 μm. By selecting hollow glass microspheres within this particle size D50 range, the resulting polypropylene composition has higher impact strength and lower molding shrinkage.

[0020] The nano hollow barium sulfate of the present invention can be obtained commercially or prepared in-house; the preparation can be made in-house by referring to patent CN113697838A. Optionally, the preparation method of the nano hollow barium sulfate is as follows: a) adding 1 to 5 parts by weight of hydrochloric acid and 1 to 4 parts by weight of an auxiliary agent to 400 to 700 parts by weight of a barium carbonate slurry to obtain a pre-reaction mixture A, wherein the auxiliary agent is at least one of sodium hexametaphosphate, sodium pyrophosphate, or potassium tripolyphosphate; b) adding 100 parts by weight of water to 1 to 3 parts by weight of the sodium hexametaphosphate solution to obtain a pre-reaction mixture B; c) adding sulfuric acid solution to the pre-reaction mixture A and the pre-reaction mixture B simultaneously, reacting at a pH of 1.5 to 1.8 for more than 30 minutes, and then adjusting the pH to 7 to 9 to terminate the reaction; d) filtering, washing with water, and drying to obtain the nano hollow barium sulfate.

[0021] Typically, the average particle size of the nano hollow barium sulfate is 50 to 500 nm.

[0022] Preferably, the average particle size of the nano hollow barium sulfate is 100-130 nm.

[0023] More preferably, the average particle size of the nano hollow barium sulfate is 120-130 nm. By regulating the average particle size of the nano hollow barium sulfate within this range, the obtained polypropylene composition has higher impact strength and lower molding shrinkage.

[0024] Preferably, the nano hollow barium sulfate is a nano hollow barium sulfate whose surface is modified with a silane coupling agent.

[0025] By selecting nano hollow barium sulfate whose surface is modified with a silane coupling agent, the obtained polypropylene composition has higher notched impact strength and lower molding shrinkage.

[0026] The preparation process of the nano hollow barium sulfate with the surface modified by the silane coupling agent is as follows: slurrying the nano hollow barium sulfate, adding the silane coupling agent, adjusting the pH to 3.5-4.0, stirring for 10-20 minutes, and dehydrating and drying to obtain the nano hollow barium sulfate with the surface modified by the silane coupling agent; wherein the mass ratio of the nano hollow barium sulfate to the silane coupling agent is 1:(0.3-0.6).

[0027] Optionally, the compatibilizer is at least one of styrene-anhydride-butadiene copolymer (SMA), methyl methacrylate-butadiene-styrene copolymer (MBS), acrylonitrile-butadiene-styrene-acrylate copolymer (ASA), maleic anhydride grafted polypropylene or maleic anhydride grafted ethylene-octene copolymer.

[0028] Preferably, the compatibilizer is maleic anhydride grafted polypropylene.

[0029] By selecting maleic anhydride grafted polypropylene as a compatibilizer, the obtained polypropylene composition has higher notched impact strength and lower molding shrinkage.

[0030] Typically, the grafting rate of maleic anhydride in the maleic anhydride grafted polypropylene is 0.9-1.15%.

[0031] The grafting rate of maleic anhydride in the maleic anhydride-grafted polypropylene can be measured by acid-base titration. The specific testing process is: the sample is dissolved in xylene and then titrated with potassium hydroxide methanol solution. The grafting rate is calculated as follows: GD = 98.06(V2-V1)C / 2000m×100%; where: GD is the grafting rate, %; C is the concentration of potassium hydroxide methanol solution, mol / L; V2 is the amount of potassium hydroxide methanol solution used to titrate the sample, mL; V1 is the amount of potassium hydroxide methanol solution used to titrate the blank sample, mL; and m is the mass of the titrated sample, g.

[0032] Optionally, the lubricant is at least one of graphite oxide, calcium stearate, mineral white oil or erucamide.

[0033] Preferably, the lubricant is graphite oxide.

[0034] Selecting the right lubricant is more conducive to improving the processing performance and appearance quality of the composition. Graphite oxide's unique layered structure can lubricate, disperse, and reduce pitting. Its excellent thermal conductivity effectively transfers heat from the melt to the mold surface, thereby improving the cooling rate and uniformity of the injection molded part. This also further reduces defects such as bubbles and shrinkage cavities that may occur in the composition, resulting in fewer defects in the finished injection molded product and better impact resistance.

[0035] When graphite oxide is used as a lubricant, the obtained polypropylene composition has higher notched impact strength and lower molding shrinkage.

[0036] Optionally, the other auxiliary agent is at least one of an antioxidant or a UV stabilizer.

[0037] Preferably, the antioxidant is a composite antioxidant composed of a primary antioxidant and a secondary antioxidant in a mass ratio of 1:(0.5-1).

[0038] Optionally, the primary antioxidant is a phenolic antioxidant, including but not limited to at least one of alkylene bisphenols, polyphenols, hindered phenol-substituted esters, and triazine hindered phenols.

[0039] Optionally, the auxiliary antioxidant is a phosphite antioxidant, including but not limited to at least one of poly(dipropylene glycol) phenyl phosphite, dipropylene glycol bisphosphite, and trioctyl phosphite.

[0040] Optionally, the UV stabilizer includes but is not limited to at least one of derivatives of compounds such as benzophenone, benzotriazole and salicylate.

[0041] The preparation method of the above-mentioned polypropylene composition comprises the following steps: mixing polypropylene resin, a compatibilizer and a lubricant to obtain a first premix; mixing the remaining components to obtain a second premix; melt-blending the first premix and the second premix, and extruding and granulating to obtain the polypropylene composition.

[0042] Typically, the melting temperature is 200-240°C.

[0043] The use of the polypropylene composition in the preparation of automobile bumpers also falls within the protection scope of the present invention.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The polypropylene composition of the invention has low density, high notched impact strength and low molding shrinkage, and the surface of the large automobile parts obtained by injection molding has no pitting and is smooth and glossy. DETAILED DESCRIPTION

[0046] In order to more clearly and completely describe the technical solution of the present invention, the present invention is further described in detail through specific embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Various changes can be made within the scope of the rights of the present invention.

[0047] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0048] Polypropylene resin 1#: T30S, Lanzhou Petrochemical, melt flow rate 4.8g / 10min;

[0049] Polypropylene resin 2#: Z30S, Maoming Petrochemical, melt flow rate 25g / 10min;

[0050] Polypropylene resin 3#: STM866, Li Changrong Chemical, melt flow rate 8g / 10min;

[0051] Hollow glass microsphere 1#: HM-10, Zhengzhou Shenglaite, particle size D50 is 5μm,

[0052] Hollow glass microsphere 2#: HM-15, Zhengzhou Shenglaite, particle size D50 is 10μm,

[0053] Hollow glass microsphere 3#: HM-30, Zhengzhou Shenglaite, particle size D50 is 20μm,

[0054] Nano hollow barium sulfate 1#, homemade, preparation method is as follows:

[0055] 1) adding 100 parts by mass of nano-barium carbonate to 400 parts by mass of water and mixing to obtain a nano-barium carbonate slurry; adding 1 part by mass of 31% hydrochloric acid and 1.5 parts by mass of an auxiliary agent to the barium carbonate slurry; and mixing thoroughly to obtain a pre-reaction mixture A, wherein the auxiliary agent comprises sodium hexametaphosphate, sodium pyrophosphate, and potassium tripolyphosphate, wherein the mass ratio of sodium hexametaphosphate: sodium pyrophosphate: potassium tripolyphosphate is 4.5:1.5:2;

[0056] 2) adding 2 parts by mass of sodium hexametaphosphate to 100 parts by mass of water to prepare a sodium hexametaphosphate solution, and then adding 1 part by mass of 31% hydrochloric acid to obtain a pre-reaction mixture B;

[0057] 3) Pre-reaction mixture A and pre-reaction mixture B were added to the sulfuric acid solution simultaneously, with the pH value being stabilized at 3 during the addition; after all the mixtures were mixed, the pH value was 1.5; the sulfuric acid solution was prepared by mixing 50 parts by mass of 98% concentrated sulfuric acid with 300 parts by mass of water;

[0058] 4) Stirring the mixture obtained in step 3) for more than 30 minutes, and adjusting the pH to 8 to terminate the reaction;

[0059] 5) After filter pressing, washing with water, and drying, nano hollow barium sulfate 1# is obtained, with an average particle size of 120 nm.

[0060] Nano hollow barium sulfate 2# was prepared in-house using a method similar to that for nano hollow barium sulfate 1#, except that in step 1), 80 parts by weight of nano barium carbonate, 3 parts by weight of 31% hydrochloric acid, and 2.5 parts by weight of the additive were used. The resulting nano hollow barium sulfate 2# had an average particle size of 100 nm (measured using a Malvern laser particle size analyzer, similarly below).

[0061] Nano hollow barium sulfate 3# was prepared in-house using a method similar to that used for nano hollow barium sulfate 1#, with the following differences: in step 1), 140 parts by weight of nano barium carbonate, 5 parts by weight of 31% hydrochloric acid, and 4 parts by weight of the additive were used. The resulting nano hollow barium sulfate 3# had an average particle size of 130 nm.

[0062] Nano hollow barium sulfate 4# was prepared in-house using a method similar to that used for nano hollow barium sulfate 1#, with the following differences: in step 1), 260 parts by weight of nano barium carbonate, 3 parts by weight of 31% hydrochloric acid, and 2 parts by weight of the additive were used. The resulting nano hollow barium sulfate 4# had an average particle size of 450 nm.

[0063] Nano hollow barium sulfate 5#: 2 parts by mass of nano hollow barium sulfate 1# were taken and slurried. 1 part by mass of silane coupling agent (γ-aminopropyltriethoxysilane, Yunsheng Chemical, KH550) was added. The pH was adjusted to 4, stirred for 1 hour, and dehydrated to obtain nano hollow barium sulfate 5#.

[0064] Ordinary barium sulfate: Dongguan Zhenming Chemical, precipitated barium sulfate;

[0065] Composite fillers 1 to 13# are homemade, and the preparation process is as follows: according to the formula in Table 1, mix the components to obtain the composite fillers.

[0066] Table 1 Composite filler formula (parts by weight)

[0067] Lubricant 1#: graphite oxide, Shanghai Zhenzhun Biological;

[0068] Lubricant 2#: erucamide, Lion;

[0069] Compatibilizer 1#: Maleic anhydride grafted polypropylene, B2, Coase;

[0070] Compatibilizer 2#: Maleic anhydride grafted POE, W1A, Koruida;

[0071] Antioxidant: prepared by mixing antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1; wherein antioxidant 1010 and antioxidant 168 are both commercially available products;

[0072] UV stabilizer: UV-326, commercially available.

[0073] Unless otherwise specified, the components (eg, antioxidant, UV stabilizer) used in the parallel examples and comparative examples are all the same commercially available products.

[0074] The properties of the polypropylene compositions provided in the embodiments and comparative examples of the present invention were measured according to the following test methods:

[0075] (1) Surface Inspection of Large Injection-Molded Parts: The polypropylene compositions prepared in the Examples and Comparative Examples were used to injection-mold large automobile bumpers, and the surface conditions of the molded parts were observed. Parts with smooth surfaces free of pitting were rated as Grade 1. Parts with smooth surfaces that had pitting, with 1 to 5 pitting spots within a 10 cm*10 cm area, were rated as Grade 2. Parts with smooth surfaces that had pitting, with 6 to 10 pitting spots within a 10 cm*10 cm area, were rated as Grade 3. Generally speaking, a Grade 1 surface condition is required for injection-molded parts to meet application requirements.

[0076] (2) Tensile strength: tested in accordance with ISO 527-2-2016, with a tensile speed of 50 mm / min;

[0077] (3) Izod notched impact strength: tested in accordance with ISO180-2000 standard;

[0078] (4) Molding shrinkage: Molding shrinkage: tested according to GB / T17037.4-2003, refers to the dimensional difference between the dry sample and the mold cavity of the sample, measured at laboratory temperature within 16 to 24 hours after the sample is molded. The sample is a small square piece of 60×60×2mm. The length l1 and width b1 of the test sample and the length l0 and width b0 of the mold cavity are tested. The molding shrinkage SMp parallel to the melt flow direction is measured in the middle of the sample width; the molding shrinkage SMn perpendicular to the melt flow direction is measured in the middle of the sample length. The calculation formula is: SMp = 100(l0-l1) / l0 and SMn = 100(b0-b1) / b0, and then the average of the two is taken as the molding shrinkage.

[0079] (5) Density: tested in accordance with ASTM D792.

[0080] The polypropylene compositions of the examples and comparative examples of the present invention were prepared by the following preparation method:

[0081] Weigh the components according to the formula; mix polypropylene, a compatibilizer (if any), and a lubricant (if any) to obtain a first premix; mix the remaining components (components other than polypropylene, the compatibilizer, and the lubricant) to obtain a second premix; then uniformly mix the first premix and the second premix, add the mixture into a twin-screw extruder, and obtain a polypropylene composition through melt blending and extrusion granulation (the extrusion temperature of the twin-screw extruder is 200-240°C: 200°C for the first section, 240°C for the second to fourth sections, 220°C for the fifth to eighth sections, and 240°C for the ninth section of the die).

[0082] Examples 1 to 16

[0083] Examples 1 to 16 provide a series of polypropylene compositions, the formulations of which are shown in Tables 2 and 3.

[0084] Table 2: Formulas of Examples 1 to 7 (parts by weight)

[0085] Table 3 Formula of Examples 8 to 16 (parts by weight)

[0086] Comparative Examples 1 to 8

[0087] Comparative Examples 1 to 8 provide a series of polypropylene compositions, the formulations of which are shown in Table 4.

[0088] Table 4 Formulas of Comparative Examples 1 to 8 (parts by weight)

[0089] The properties of the polypropylene compositions of the embodiments and comparative examples were measured according to the above-mentioned test methods. The test results are shown in Table 5.

[0090] Table 5 Performance test results of polypropylene compositions of various embodiments and comparative examples

[0091] From Table 5 we can see that:

[0092] By matching the components and their amounts, the density of the polypropylene compositions of Examples 1 to 16 is 1 g / cm 3 Below, the notched impact strength is higher than 13KJ / m 2 , molding shrinkage was less than 0.52%, and surface testing results of large injection-molded parts all reached Grade 1, demonstrating that the polypropylene composition of the present invention has low density, high notched impact strength, and low molding shrinkage. The surfaces of the large automotive parts obtained by injection molding are pit-free, smooth, and glossy. Furthermore, the tensile strength of the polypropylene composition of the present invention is above 30 MPa, meeting the requirements of conventional application scenarios.

[0093] In Comparative Example 1, no composite filler was added, resulting in a low notched impact strength and high shrinkage for the polypropylene composition. In Comparative Example 2, precipitated barium sulfate was used as the composite filler, resulting in poor notched impact strength, high density, and high shrinkage for the polypropylene composition. The surface inspection of the large automotive part obtained by injection molding was poor. In Comparative Examples 3 and 4, the composite fillers were added in inappropriate ratios, resulting in poor surface inspection for the large automotive part obtained by injection molding. The polypropylene composition in Comparative Example 4 exhibited poor notched impact strength and high mold shrinkage. In Comparative Example 5, hollow glass microspheres were used as fillers, resulting in low notched impact strength and high mold shrinkage for the polypropylene composition. The surface inspection of the large automotive part obtained by injection molding was poor. In Comparative Example 6, hollow nano-barium sulfate was used as fillers, resulting in poor surface inspection for the large automotive part obtained by injection molding. In Comparative Example 7, no lubricant was added, resulting in poor notched impact strength for the polypropylene composition, resulting in poor surface inspection for the large automotive part obtained by injection molding. In Comparative Example 8, no compatibilizer was added, resulting in low notched impact strength for the polypropylene composition, resulting in poor surface inspection for the large automotive part obtained by injection molding.

[0094] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A polypropylene composition, characterized in that The composition comprises the following components in parts by weight: The composite filler comprises nano hollow barium sulfate and hollow glass microspheres in a mass ratio of 1:(1.2-2.5).

2. The polypropylene composition according to claim 1, characterized in that The melt flow rate of the polypropylene resin measured at 230° C. and 2.16 kg is 4 to 28 g / 10 min.

3. The polypropylene composition according to claim 1, characterized in that: The particle size D50 of the hollow glass microspheres is 3 to 20 μm.

4. The polypropylene composition according to claim 1, characterized in that: The nano hollow barium sulfate is a nano hollow barium sulfate with its surface modified by a silane coupling agent.

5. The polypropylene composition according to claim 1, characterized in that: The compatibilizer is at least one of styrene-anhydride-butadiene copolymer, methyl methacrylate-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene-acrylate copolymer or maleic anhydride grafted ethylene-octene copolymer.

6. The polypropylene composition according to claim 1, characterized in that: The lubricant is at least one of graphite oxide, calcium stearate, mineral white oil or erucamide.

7. The polypropylene composition according to claim 1, characterized in that: The average particle size of the nano hollow barium sulfate is 50-500nm.

8. The polypropylene composition according to claim 1, characterized in that: The other auxiliary agent is at least one of an antioxidant or a UV stabilizer.

9. The method for preparing the polypropylene composition according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: mixing polypropylene resin, compatibilizer and lubricant to obtain a first premix; mixing the remaining components to obtain a second premix; and melt-blending the first premix and the second premix, extruding and granulating to obtain the polypropylene composition.

10. Use of the polypropylene composition according to any one of claims 1 to 8 in the preparation of automobile bumpers.

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