Low shrinkage high transmission polypropylene composition and process for the preparation thereof

Abstract

The present application belongs to the technical field of polymer materials, and particularly relates to a low-shrinkage high-transmittance polypropylene composition and a preparation method thereof. The composition is composed of the following raw materials in percentage by weight: polypropylene resin: 29.2-79.85%; polyethylene resin: 10-25%; elastomer: 0-10%; light diffuser: 0-5%; inorganic filler: 10-30%; nucleating agent: 0.05-0.5%; antioxidant: 0.1-0.3%; wherein the polypropylene resin is an impact copolymer polypropylene, and the ratio of the characteristic viscosity of the rubber phase to that of the polypropylene resin is 1-1.2; the polyethylene resin is prepared by using a metallocene catalyst. The present application optimizes the formula of the composition, significantly improves the transmittance, impact resistance and dimensional stability of the polypropylene material on the basis of maintaining excellent mechanical properties, so as to meet the market demand for high-performance polypropylene materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a low-shrinkage, high-transmittance polypropylene composition and its preparation method. Background Technology

[0002] Polypropylene (PP), a thermoplastic polymer, occupies an important position in the field of plastic materials due to its numerous advantages, including low density, excellent mechanical properties, good heat resistance, and high chemical stability. It is one of the most widely used general-purpose plastics. The density of polypropylene is only 0.89-0.91 g / cm³. 3 It is one of the lightest types of plastics, and it also has good molding and processing properties, which makes it widely used in many industries such as household goods, automobile manufacturing, piping systems, and medical devices.

[0003] However, polypropylene also exhibits some significant drawbacks in applications, which limit its application range in specific fields. First, polypropylene has relatively low impact strength, especially at low temperatures, where its impact resistance decreases significantly, making it difficult to meet the requirements of applications with high impact resistance. Second, polypropylene has a relatively high shrinkage rate, typically between 1.8% and 2.5%. This characteristic makes it difficult to achieve ideal dimensional stability when manufacturing products with high dimensional accuracy requirements, thus affecting product quality and aesthetics. Furthermore, polypropylene has relatively poor light transmittance, especially homopolymer and random copolymer polypropylene. While homopolymer and random copolymer polypropylene have high light transmittance, their impact strength is insufficient; and while impact copolymer polypropylene has high impact strength, its light transmittance is significantly reduced, making it difficult to meet the requirements of applications with high light transmittance, such as translucent car bumpers, large light boxes, and large decorative boxes.

[0004] With advancements in technology and continuous market development, the performance requirements for polypropylene materials are constantly increasing. Especially in high-end applications such as automobiles, lighting, and architectural decoration, higher demands are placed on polypropylene materials, including high rigidity, high impact resistance, high light transmittance, low shrinkage, and good processability. These improved performance requirements make traditional polypropylene materials insufficient to meet market demands, necessitating the development of a novel polypropylene composition to overcome the shortcomings of existing technologies.

[0005] Currently, although various methods for modifying polypropylene have been proposed, such as adding toughening agents, nucleating agents, and inorganic fillers to improve polypropylene performance, these methods often struggle to simultaneously achieve high light transmittance, high impact resistance, and low shrinkage. Therefore, developing a polypropylene composition and its preparation method that possesses both high light transmittance and high impact resistance while exhibiting low shrinkage is of great significance for broadening the application areas of polypropylene materials and enhancing product performance and market competitiveness. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a low-shrinkage, high-transmittance polypropylene composition. By optimizing the formulation of the composition, the polypropylene material can significantly improve its transmittance, impact resistance, and dimensional stability while maintaining excellent mechanical properties, thereby meeting the market demand for high-performance polypropylene materials.

[0007] Another objective of this invention is to provide a method for preparing a low-shrinkage, high-transmittance polypropylene composition that is scientific, reasonable, simple, and easy to implement.

[0008] The technical solution adopted in this invention is as follows:

[0009] The low-shrinkage, high-transmittance polypropylene composition comprises the following raw materials in weight percentages:

[0010] Polypropylene resin: 29.2-79.85%;

[0011] Polyethylene resin: 10-25%;

[0012] Elastomer: 0-10%;

[0013] Light diffusing agent: 0-5%;

[0014] Inorganic fillers: 10-30%;

[0015] Nucleating agent: 0.05-0.5%;

[0016] Antioxidant: 0.1-0.3%;

[0017] The polypropylene resin is an impact-resistant copolymer polypropylene, and the intrinsic viscosity ratio of the rubber phase to the polypropylene resin is 1-1.2.

[0018] The polyethylene resin was prepared by catalysis using a metallocene catalyst.

[0019] The polypropylene resin has a melt flow rate of 1-30 g / 10 min (2.16 kg weight, 230 °C); a copolyethylene monomer content of 4-7%, preferably 5-6%; and a weight-average molecular weight of (15-50) × 10⁻⁶. 4 The molecular weight distribution is 3-7, preferably 4-6; the rubber phase content is 14-18%.

[0020] The polyethylene resin is linear ultra-low density polyethylene, and the comonomer is hexene; the melt flow rate is 1-5 g / 10 min (with a weight of 2.16 kg and a temperature of 190 °C); the monomer bonding content is 1-6%, preferably 3-5%; and the density is 0.910-0.915 g / cm³. 3 The molecular weight distribution is 2-7, preferably 3-5.

[0021] The elastomer is a copolymer of propylene and ethylene, with a melt flow rate of 1-10 g / 10 min, preferably 5-7 g / 10 min; and a density of 0.860-0.890 g / cm³. 3 The preferred dosage is 4-7%.

[0022] The light diffusing agent is an organosilicon powder, the main component of which is a vinyl polydimethylsiloxane / polymethylsiloxane sesquioxane crosslinked polymer; the average particle size is 2-10 μm, preferably 2-5 μm.

[0023] The inorganic filler is glass fiber with a radial dimension of 8-12 μm and a length of 30-50 mm.

[0024] The nucleating agent is one or more of sorbitol-based or phosphate-based nucleating agents, preferably used at an amount of 0.2-0.4%.

[0025] The antioxidant is a compound antioxidant composed of one of the following: phenolic antioxidants (such as antioxidant 1010 or antioxidant 1076) and phosphite antioxidants (such as antioxidant 168) or thioester antioxidants (such as DLTP or DSTP), with a compounding ratio of 1:1.

[0026] The polypropylene resin, polyethylene resin, elastomer, light diffusing agent, nucleating agent and antioxidant of the formulation are mixed and stirred for 4-6 minutes. Then, inorganic filler is added and stirred evenly. The mixture is then melt-extruded, stretched and pelletized by a twin-screw extruder to obtain a low-shrinkage and high-transmittance polypropylene composition.

[0027] The temperature of the twin-screw extruder is 150-230℃.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The high light transmittance and high impact resistance polypropylene composition prepared by this invention has a notched impact strength of 15-40 kJ / m² for simply supported beams. 2 With a flexural modulus of 1500-4000MPa, a light transmittance (2mm thick sheet) greater than 70%, and a shrinkage rate of 0.3-0.6%, this high-transmittance, high-impact polypropylene composition can be used in injection molding, compression molding, and other processing methods to produce translucent car bumpers, large light boxes, large decorative boxes, etc. The products have low shrinkage and high flatness, effectively improving the matching between the products and other parts and the appearance of the products, while greatly reducing direct light from the products. Detailed Implementation

[0030] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.

[0031] Unless otherwise specified, the raw materials used in the examples and comparative examples are all commercially available materials, and the process methods used in the examples and comparative examples are all conventional methods in the art.

[0032] The following is a description of some of the raw materials used in the examples and comparative examples:

[0033] Phosphate nucleating agent NA-11: purchased from Adico (China) Investment Co., Ltd.;

[0034] Sorbitol nucleating agent NX8000 was purchased from Milliken.

[0035] Example 1

[0036] The low-shrinkage, high-transmittance polypropylene composition comprises the following raw materials in weight percentages:

[0037] Polypropylene resin 1: 60.6%;

[0038] Polyethylene resin 1:20%;

[0039] Elastomer 1: 9%;

[0040] Inorganic filler 1:10%;

[0041] Nucleating agent 1: 0.2%;

[0042] Antioxidant: 0.2%.

[0043] The polypropylene resin 1 is an impact-resistant copolymer polypropylene with a melt flow rate of 10 g / 10 min (weight 2.16 kg, temperature 230℃); the content of copolyethylene monomer is 5.1%; and the weight-average molecular weight is 23 × 10⁻⁶. 4 The molecular weight distribution is 6; the rubber phase content is 15.6%; the intrinsic viscosity ratio of the rubber phase to the polypropylene resin is 1.05; and the size of the rubber phase is 300±100nm.

[0044] The polyethylene resin 1 is linear ultra-low density polyethylene, obtained by catalysis with a metallocene catalyst, and the comonomer is hexene; the melt flow rate is 1.1 g / 10 min (with a weight of 2.16 kg and a temperature of 190 °C); the monomer bonding content is 3.5%; and the density is 0.914 g / cm³. 3 The molecular weight distribution is 3.6.

[0045] The elastomer 1 is a copolymer of propylene and ethylene; the melt flow rate is 5.2 g / 10 min; and the density is 0.863 g / cm³. 3 .

[0046] The inorganic filler 1 is glass fiber with a radial dimension of 10μm and a length of 40mm.

[0047] The light diffusing agent 1 is an organosilicon powder, the main component of which is a vinyl polydimethylsiloxane / polymethylsiloxane sesquioxane crosslinked polymer; the average particle size is 2μm.

[0048] The nucleating agent 1 is a phosphate nucleating agent NA-11, specifically sodium 2,2-methylene-bis(4,6-di-n-butylphenol) phosphate.

[0049] The antioxidant is a compound antioxidant of antioxidant 1010 and antioxidant 168, with a compounding ratio of 1:1.

[0050] The preparation method of the low-shrinkage, high-transmittance polypropylene composition is as follows: Mix and stir the raw materials other than the inorganic filler for 5±1 min, then add the inorganic filler, stir evenly, and then melt-extrude, stretch, and pelletize through a twin-screw extruder to obtain the low-shrinkage, high-transmittance polypropylene composition. The extrusion screw temperature is set at 150℃, 160℃, 180℃, 200℃, 220℃, 230℃, and 220℃ from the feed end to the extrusion end, respectively.

[0051] Example 2

[0052] The low-shrinkage, high-transmittance polypropylene composition comprises the following raw materials in weight percentages:

[0053] Polypropylene resin 1: 59.6%;

[0054] Polyethylene resin 1:15%;

[0055] Elastomer 1: 7%;

[0056] Light diffusing agent 1:3%;

[0057] Inorganic filler 1:15%;

[0058] Nucleating agent 1: 0.1%;

[0059] Antioxidant: 0.3%.

[0060] Everything else is the same as in Example 1.

[0061] Example 3

[0062] The low-shrinkage, high-transmittance polypropylene composition comprises the following raw materials in weight percentages:

[0063] Polypropylene resin 1: 64.6%;

[0064] Polyethylene resin 1:10%;

[0065] Elastomer 1:3%;

[0066] Light diffusing agent 1:2%;

[0067] Inorganic filler 1:20%;

[0068] Nucleating agent 1: 0.3%;

[0069] Antioxidant: 0.1%.

[0070] Everything else is the same as in Example 1.

[0071] Example 4

[0072] The low-shrinkage, high-transmittance polypropylene composition comprises the following raw materials in weight percentages:

[0073] Polypropylene resin 1: 39.75%;

[0074] Polyethylene resin 1:25%;

[0075] Light diffusing agent 1:5%;

[0076] Inorganic filler 1:30%;

[0077] Nucleating agent 1: 0.05%;

[0078] Antioxidant: 0.2%.

[0079] Everything else is the same as in Example 1.

[0080] Example 5

[0081] The low-shrinkage, high-transmittance polypropylene composition comprises the following raw materials in weight percentages:

[0082] Polypropylene resin 2: 79.3%;

[0083] Polyethylene resin 2: 10%;

[0084] Inorganic filler 2: 10%;

[0085] Nucleating agent 2: 0.5%;

[0086] Antioxidant: 0.2%.

[0087] The polypropylene resin 2 is an impact-resistant copolymer polypropylene with a melt flow rate of 22 g / 10 min (weight 2.16 kg, temperature 230℃); the copolyethylene monomer content is 5.6%; and the weight-average molecular weight is 21 × 10⁻⁶. 4 The molecular weight distribution is 6.2; the rubber phase content is 16.3%; the intrinsic viscosity ratio of the rubber phase to the polypropylene resin is 1.09; and the size of the rubber phase is 300±100nm.

[0088] The polyethylene resin 2 is linear ultra-low density polyethylene, obtained by catalysis with a metallocene catalyst, and the comonomer is hexene; the melt flow rate is 2 g / 10 min (weight 2.16 kg, temperature 190℃); the monomer bonding content is 3.7%; and the density is 0.915 g / cm³. 3 The molecular weight distribution is 3.5.

[0089] The elastomer 2 is a copolymer of propylene and ethylene; the melt flow rate is 5.5 g / 10 min; and the density is 0.87 g / cm³. 3 .

[0090] The inorganic filler 2 is glass fiber with a radial dimension of 8μm and a length of 40±5mm.

[0091] The light diffusing agent 2 is an organosilicon powder, the main component of which is a vinyl polydimethylsiloxane / polymethylsiloxane sesquioxane crosslinked polymer; the average particle size is 5 μm.

[0092] The nucleating agent 2 is a sorbitol-based nucleating agent NX8000.

[0093] The antioxidant is a compound antioxidant of antioxidant 1076 and antioxidant 168, with a compounding ratio of 1:1.

[0094] The preparation method of the low-shrinkage, high-transmittance polypropylene composition is the same as that in Example 1.

[0095] Example 6

[0096] The low-shrinkage, high-transmittance polypropylene composition comprises the following raw materials in weight percentages:

[0097] Polypropylene resin 2: 44.5%;

[0098] Polyethylene resin 2: 15%;

[0099] Elastomer 2: 10%;

[0100] Inorganic filler 2:30%;

[0101] Nucleating agent 2: 0.3%;

[0102] Antioxidant: 0.2%.

[0103] The rest is the same as in Example 5.

[0104] Example 7

[0105] The low-shrinkage, high-transmittance polypropylene composition comprises the following raw materials in weight percentages:

[0106] Polypropylene resin 2: 53.4%;

[0107] Polyethylene resin 2: 20%;

[0108] Elastomer 2:3%;

[0109] Light diffusing agent 2:3%;

[0110] Inorganic filler 2: 20%;

[0111] Nucleating agent 1: 0.1%;

[0112] Nucleating agent 2: 0.3%;

[0113] Antioxidant: 0.2%.

[0114] The rest is the same as in Example 5.

[0115] Example 8

[0116] The low-shrinkage, high-transmittance polypropylene composition comprises the following raw materials in weight percentages:

[0117] Polypropylene resin 2: 37.5%;

[0118] Polyethylene resin 2: 25%;

[0119] Elastomer 2: 7%;

[0120] Light diffusing agent 2:5%;

[0121] Inorganic filler 2: 25%;

[0122] Nucleating agent 1: 0.1%;

[0123] Nucleating agent 2: 0.2%;

[0124] Antioxidant: 0.2%.

[0125] The rest is the same as in Example 5.

[0126] Comparative Example 1

[0127] The difference from Example 1 is that an equal amount of polyethylene resin 3 is used instead of polyethylene resin 1. The polyethylene resin 3 used is prepared by titanium-based catalyst, and the comonomer is butene. The melt flow rate (with a weight of 2.16 kg and a temperature of 190 °C) is 1.1 g / 10 min. The monomer bonding content is 1.5%. The density is 0.920 g / cm³. 3 The molecular weight distribution is 5.7. Other parameters are the same as in Example 1.

[0128] Comparative Example 2

[0129] The difference from Example 2 is that an equal amount of lightweight calcium carbonate is used instead of glass fiber. Everything else is the same as in Example 2.

[0130] Comparative Example 3

[0131] The difference from Example 3 is that an equal amount of talc powder (1250 mesh) is used instead of glass fiber. Everything else is the same as in Example 3.

[0132] Comparative Example 4

[0133] The polypropylene composition comprises the following raw materials in weight percentages:

[0134] Polypropylene resin 1: 67.75%;

[0135] Polyethylene resin 1:25%;

[0136] Zinc oxide: 2%;

[0137] Light diffusing agent 1:5%;

[0138] Nucleating agent 1: 0.05%;

[0139] Antioxidant: 0.2%.

[0140] Everything else is the same as in Example 1.

[0141] Comparative Example 5

[0142] The polypropylene composition comprises the following raw materials in weight percentages:

[0143] Polypropylene resin 3: 64.6%;

[0144] Polyethylene resin 1:10%;

[0145] Elastomer 1:3%;

[0146] Light diffusing agent 1:2%;

[0147] Inorganic filler 1:20%;

[0148] Nucleating agent 1: 0.3%;

[0149] Antioxidant: 0.1%.

[0150] The polypropylene resin 3 used is an impact-resistant copolymer polypropylene with a melt flow rate of 12 g / 10 min (weight 2.16 kg, temperature 230℃); the copolyethylene monomer content is 7%; and the weight-average molecular weight is 21 × 10⁻⁶. 4 The molecular weight distribution is 6.2; the rubber phase content is 15.3%; and the intrinsic viscosity ratio of the rubber phase to the polypropylene resin is 1.6.

[0151] Everything else is the same as in Example 1.

[0152] The polypropylene compositions prepared in Examples 1-8 and Comparative Examples 1-5 were subjected to performance tests. Injection-molded samples were used, with an injection screw temperature of 200°C. The conditioning of the samples and the standard testing environment were performed according to GB / T 2918-2018, with a temperature of 23±2°C and a relative humidity of 50±5%. The specific test methods are as follows:

[0153] Melt mass flow rate (g / 10min): Refer to GB / T 3682-2018;

[0154] Notched impact strength of simply supported beam (23℃, kJ / m) 2 (Refer to GB / T 1043.1-2008)

[0155] Flexural modulus of elasticity (MPa): Refer to GB / T 9341-2008;

[0156] Light transmittance (2mm thick sample, %): Refer to GB / T 2410-2008;

[0157] Haze (2mm thick sample, %): Refer to GB / T 2410-2008;

[0158] Shrinkage rate (parallel flow channel, %): Refer to GB / T 17037.4-2003; The test specimens were prepared using a D2 type standard mold, and the specimens were small square pieces with dimensions of 60mm×60mm×2mm.

[0159] Shrinkage rate (vertical flow channel, %): Refer to GB / T 17037.4-2003; The test specimens were prepared using a D2 type standard mold, and the specimens were small square pieces with dimensions of 60mm×60mm×2mm.

[0160] The test results are shown in Table 1-3:

[0161] Table 1 Performance test results of Examples 1-4

[0162] project Example 1 Example 2 Example 3 Example 4 melt mass flow rate 7.0 5.3 4.7 4.1 Notched impact strength of simply supported beam 37.2 28.8 16.5 31.4 Flexural modulus 1590 2260 2930 3850 Light transmittance 71 72 72 73 Haze 93.6 97.8 96.6 98.5 Shrinkage rate (parallel flow channel) 0.5 0.4 0.4 0.3 Shrinkage rate (vertical flow channel) 0.6 0.5 0.5 0.4

[0163] As can be seen from the data in Table 1, the polypropylene compositions prepared in Examples 1-4 have a light transmittance of over 70%, and possess high flexural modulus and impact strength, while the shrinkage rate can be controlled to below 0.6%, achieving a good balance between light transmittance, mechanical properties, and shrinkage rate.

[0164] Table 2 Performance test results of Examples 5-8

[0165] project Example 5 Example 6 Example 7 Example 8 melt mass flow rate 9.9 5.8 7.5 6.3 Notched impact strength of simply supported beam 15.1 30.4 25.1 34.3 Flexural modulus 2180 3530 2890 2620 Light transmittance 75 70 72 71 Haze 66.8 63.9 98.0 98.7 Shrinkage rate (parallel flow channel) 0.5 0.4 0.4 0.3 Shrinkage rate (vertical flow channel) 0.6 0.5 0.5 0.4

[0166] As can be seen from the data in Table 2, the polypropylene prepared in Examples 5-8 has a light transmittance of over 70%, high flexural modulus and impact strength, and low shrinkage.

[0167] Table 3 Performance test results for Comparative Examples 1-5

[0168] project Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 melt mass flow rate 7.2 10.1 9.8 16.5 4.5 Notched impact strength of simply supported beam 18.8 35.0 8.3 32.6 20.2 Flexural modulus 1610 1220 1740 1150 2580 Light transmittance 53 39 23 22 37 Haze 94.7 100 100 100 98.5 Shrinkage rate (parallel flow channel) 0.5 0.7 0.6 0.6 0.4 Shrinkage rate (vertical flow channel) 0.6 0.8 0.7 0.7 0.5

[0169] As can be seen from the test data in Table 3, Comparative Example 1 used polyethylene resin 3, and the transmittance of the prepared polypropylene composition was 53%, which was significantly lower than that of Example 1. After changing the type of inorganic filler in Comparative Examples 2-4, the transmittance of the resulting resins was lower, and the shrinkage rate, flexural modulus, etc., also differed from those of the examples. In Comparative Example 5, the use of polypropylene resin 3 resulted in a significant decrease in the transmittance of the obtained resin.

Claims

1. A low-shrinkage, high-transmittance polypropylene composition, characterized in that, It consists of the following raw materials by weight percentage: Polypropylene resin: 29.2-79.85%; Polyethylene resin: 10-25%; Elastomer: 0-10%; Light diffusing agent: 0-5%; Inorganic fillers: 10-30%; Nucleating agent: 0.05-0.5%; Antioxidant: 0.1-0.3%; The polypropylene resin is an impact-resistant copolymer polypropylene, and the intrinsic viscosity ratio of the rubber phase to the polypropylene resin is 1-1.

2. The polyethylene resin was prepared by catalysis using a metallocene catalyst.

2. The low-shrinkage, high-transmittance polypropylene composition according to claim 1, characterized in that, The polypropylene resin has a melt flow rate of 1-30 g / 10 min (2.16 kg weight, 230 °C), a copolyethylene monomer content of 4-7%, and a weight-average molecular weight of (15-50) × 10⁻⁶. 4 The molecular weight distribution is 3-7; the rubber phase content is 14-18%.

3. The low-shrinkage, high-transmittance polypropylene composition according to claim 1, characterized in that, The polyethylene resin has hexene as its comonomer, a melt flow rate of 1-5 g / 10 min (with a 2.16 kg weight and a temperature of 190 °C), a monomer bonding content of 1-6%, and a density of 0.910-0.915 g / cm³. 3 The molecular weight distribution is 2-7.

4. The low-shrinkage, high-transmittance polypropylene composition according to claim 1, characterized in that, The elastomer is a copolymer of propylene and ethylene, with a melt flow rate of 1-10 g / 10 min and a density of 0.860-0.890 g / cm³. 3 .

5. The low-shrinkage, high-transmittance polypropylene composition according to claim 1, characterized in that, The light diffusing agent is an organosilicon powder, the main component of which is a vinyl polydimethylsiloxane / polymethylsiloxane sesquioxane crosslinked polymer.

6. The low-shrinkage, high-transmittance polypropylene composition according to claim 1, characterized in that, The inorganic filler is glass fiber.

7. The low-shrinkage, high-transmittance polypropylene composition according to claim 1, characterized in that, The nucleating agent is one or more of sorbitol-based nucleating agents or phosphate-based nucleating agents.

8. The low-shrinkage, high-transmittance polypropylene composition according to claim 1, characterized in that, The antioxidant is a compound antioxidant composed of phenolic antioxidants and one of phosphite antioxidants or thioester antioxidants.

9. A method for preparing a low-shrinkage, high-transmittance polypropylene composition according to any one of claims 1-8, characterized in that, The steps are as follows: Mix the polypropylene resin, polyethylene resin, elastomer, light diffusing agent, nucleating agent and antioxidant of the formulation components, then add inorganic filler, stir evenly, and then melt extrude, stretch and pelletize through a twin-screw extruder to obtain a low-shrinkage and high-transmittance polypropylene composition.

10. The method for preparing the low-shrinkage, high-transmittance polypropylene composition according to claim 9, characterized in that, The temperature of the twin-screw extruder is 150-230℃.