Low-temperature-resistant high-melt injection molding polypropylene composition as well as preparation method and application thereof

Abstract

The invention discloses a low-temperature-resistant high-melt injection molding polypropylene composition and a preparation method and application thereof.The preparation method comprises the steps that propylene serves as a raw material and is added into a single-loop reactor, a catalyst, a first cocatalyst and a second cocatalyst are added, then the mixture is stirred to be uniform, ethylene and hydrogen are introduced into a single-loop reactor, and polypropylene powder is obtained through flash evaporation, steaming and drying; and mixing the antioxidant, the acid acceptor and the slipping agent, extruding and granulating to obtain a granular composition, and mixing the granular composition with the polypropylene powder to obtain the low-temperature-resistant high-melt injection molding polypropylene composition. The low-temperature-resistant high-melt injection molding polypropylene composition provided by the invention has the advantages of high melt index, high tensile yield stress, high load deformation temperature and high Rockwell hardness. Due to the addition of ethylene, the low-temperature resistance of the product is improved, and the product can replace thin-wall injection-molded polypropylene produced by a degradation method and can be used for cold meal boxes in summer. Compared with common polypropylene injection molding materials in the market, the polypropylene injection molding material provided by the invention has the advantage that various indexes are obviously improved.

Description

Technical Field

[0001] The invention relates to a polymer material field, and in particular to a low-temperature resistant high-melt injection molding polypropylene composition, a preparation method and an application thereof. Background Art

[0002] Since 2019, with the successive commissioning of major refining and chemical integration projects and PDH projects, the downstream polypropylene industry has entered a new round of capacity expansion peak. The main uses of polypropylene are drawing, injection molding, impact copolymerization, transparent materials, pipes, film materials, etc. According to Zhuochuang Information data monitoring, from 2019 to 2023, the average growth rate of polypropylene thin-wall injection molding production reached 23%, far higher than the average growth rate of polypropylene of 9%.

[0003] Due to the low price, low density, high temperature resistance and easy processing of polypropylene, it is widely used in milk tea cups, fast food boxes and other fields. Starbucks, Bawang Chaji and other companies have gradually moved from first- and second-tier cities to fourth- and fifth-tier cities. The number of takeout orders from Meituan and Ele.me has increased year by year, which has led to an explosive growth in the demand for milk tea cups and fast food boxes. The price of thin-wall injection molding polypropylene is relatively strong.

[0004] Domestic thin-wall injection molding polypropylene previously relied mainly on imported raw materials. Later, as companies such as Luoyang Petrochemical, Shanghai Petrochemical, Shandong Lianhong, and Hengli Petrochemical developed alternative products, they gradually replaced imports.

[0005] Polypropylene is not resistant to low temperatures, but the milk tea cups made from it need to hold cold drinks, and fast food boxes need to be used in the Northeast in winter. At the same thickness, it will become brittle in low temperature areas. The higher the melt index of thin-walled injection molding polypropylene, the lower the energy consumption of downstream companies for reprocessing. Increasing the melt index will increase the difficulty in production, and the disadvantage of low-temperature brittleness of the product will become prominent. How to balance the relationship between melt index and low-temperature brittleness has become a difficult problem that major companies urgently need to solve. Based on the above problems, the present invention proposes a low-temperature resistant high-melt injection molding polypropylene composition and its preparation method and application are of great significance. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention proposes a low-temperature resistant high-melt injection molding polypropylene composition and a preparation method and application thereof, which balances the relationship between melt index and low-temperature brittleness, and effectively improves the competitiveness of the product.

[0007] To achieve the above object, the technical solution of the present invention is as follows: The present invention provides a method for preparing a low temperature resistant high melt injection molding polypropylene composition, comprising the following steps: 1) Propylene is used as a raw material, added into a single loop reactor, and a catalyst, a co-catalyst 1 and a co-catalyst 2 are added, and then stirred evenly, ethylene and hydrogen are introduced into the single loop, and polypropylene powder is obtained by flash evaporation, steam distillation and drying; 2) The antioxidant, acid absorbent and lubricant are first mixed and extruded to form a granular composition, and then mixed with the polypropylene powder obtained in step 1) to obtain a low-temperature resistant and high-melt injection molding polypropylene composition.

[0008] Furthermore, the specific process of step 1) is as follows: Propylene is used as a raw material, added into a single loop reactor, and a catalyst, a co-catalyst 1 and a co-catalyst 2 are added, and then stirred evenly, the reaction pressure of the single loop reactor is controlled to be 3.8-4.4MPa, the reaction temperature is 70±2°C, the ethylene concentration in the single loop reactor is 0.2-0.4% (wt), 0.1-0.3% (wt) of hydrogen is added, and subsequently flash evaporation, steam distillation and drying are performed to obtain a polypropylene powder with a melt flow rate of 80-90g / 10min.

[0009] Furthermore, the catalyst in step 1) is the fourth generation domestic ZN catalyst DQC-602; the co-catalyst 1 in step 1) is the electron donor cyclohexyl-methyl-dimethoxysilane; the co-catalyst 2 in step 1) is triethylaluminum.

[0010] Furthermore, in step 1), the mass ratio of raw material propylene to catalyst, co-catalyst 1 and co-catalyst 2 is 10000: 0.4-0.6: 0.05-0.35: 0.9-1.3.

[0011] Furthermore, in step 2), the amount of the antioxidant added is 0.1-0.2% (wt) of the total amount of polypropylene, and the antioxidant is a phosphate antioxidant, specifically tris (2,4-di-tert-butylphenyl) phosphite; the amount of the acid absorber added in step 2) is 0.05-0.1% (wt) of the total amount of polypropylene, and the acid absorber is calcium stearate; the amount of the lubricant added in step 2) is 0.05-0.1% (wt) of the total amount of polypropylene, and the lubricant is glyceryl monostearate.

[0012] Furthermore, the amount of antioxidant added in step 2) is 0.15% (wt) of the total amount of polypropylene; the amount of acid absorbent added in step 2) is 0.075% (wt) of the total amount of polypropylene; and the amount of lubricant added in step 2) is 0.075% (wt) of the total amount of polypropylene.

[0013] Furthermore, in step 2), when a twin-screw extruder is used for compounding and granulation, the temperature of the pre-melting section is 160-200°C, the temperature of the melting section is 170-210°C, and the temperature of the extrusion section is 170-190°C.

[0014] The invention provides a low-temperature resistant high-melt injection molding polypropylene composition prepared by the method.

[0015] Furthermore, the low temperature resistant high melt injection molding polypropylene composition comprises the following components in parts by weight: 99.7% (wt) polypropylene, 0.15% (wt) tris (2,4-di-tert-butylphenyl) phosphite, 0.075% (wt) calcium stearate, 0.075% (wt) glyceryl monostearate.

[0016] The invention also proposes the use of a low temperature resistant high melt injection molding polypropylene composition in a summer cold lunch box.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The present invention uses propylene as a raw material, adds a catalyst, a co-catalyst 1 and a co-catalyst 2 into a single loop reactor, and then stirs evenly, introduces ethylene and hydrogen into the single loop, flashes, steams, and dries to obtain polypropylene powder, then firstly mixes an antioxidant, an acid absorber and a lubricant, extrudes and granulates them into a granular composition, and then mixes them with the polypropylene powder to obtain a low-temperature resistant high-melt injection molding polypropylene composition; 2) The present invention achieves the purpose of preparing a low-temperature resistant thin-wall injection molding polypropylene powder by increasing the reactor pressure and adjusting the ratio of propylene, hydrogen and ethylene. The prepared polypropylene composition has a bonded ethylene content of 0.2-0.4% (wt) and a melt flow rate of 80-90g / 10min; 3) The polypropylene composition prepared by the present invention has a wide molecular weight distribution, is non-yellowing, has no odor, has good fluidity and rigidity-toughness balance, and is low in price. It can partially replace imported thin-wall injection molding polypropylene and can be used for cold lunch boxes in summer. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with embodiments, but the scope of protection of the present invention is not limited to the described scope.

[0019] Comparative Example 1 1) Preparation of catalyst: 220L No. 68 white oil and 110L fat are made into a grease mixture, heated to 70°C, 80kg of catalyst is added, stirred for 120min, cooled to 10°C, and a catalyst suspension is prepared; 2) Preparation of co-catalyst Donor-C: 200L white oil and 200L Donor-C, prepared into 50% (v / v) Donor-C; 3) Prepolymerization: The prepolymerization reactor R200 was maintained at 20°C and the catalyst (0.4 kg / h, pump stroke 29%), co-catalyst Donor-C (0.08 kg / h), and co-catalyst TEAL (1 kg / h) were added; 4) Polymerization reaction: Polymerization reactor R201 was maintained at 70°C and 3.9MPa, and propylene (8.26t / h), hydrogen (1.54kg / h), and prepolymer were added; 5) Degassing: After flash evaporation, steaming and drying, 5.6t of powder is produced; 6) preparing additives: mixing 8.4 kg of antioxidant tris(2,4-di-tert-butylphenyl)phosphite, 4.2 kg of acid absorber calcium stearate, and 4.2 kg of lubricant monostearate glyceryl, and extruding and granulating into a granular composition; 7) Granulation: Add additives to the powder, mix evenly, and then mix and granulate in a twin-screw extruder; the pre-melting section temperature is 160-200°C, the melting section temperature is 170-210°C, and the extrusion section temperature is 170-190°C, and finally 5.6t of pellets are obtained.

[0020] Comparative Example 2 1) Preparation of catalyst: 220L No. 68 white oil and 110L fat are made into a grease mixture, heated to 70°C, 80kg of catalyst is added, stirred for 120min, cooled to 10°C, and a catalyst suspension is prepared; 2) Preparation of co-catalyst Donor-C: 200L white oil and 200L Donor-C, prepared into 50% (v / v) Donor-C; 3) Prepolymerization: The prepolymerization reactor R200 was maintained at 20°C, and catalyst (0.36 kg / h, pump stroke 25.3%), co-catalyst Donor-C (0.29 kg / h), and co-catalyst TEAL (0.86 kg / h) were added; 4) Polymerization reaction: Polymerization reactor R201 was maintained at 70°C and 3.95MPa, and propylene (8.7t / h), hydrogen (1.46kg / h), ethylene (34.6kg / h), and prepolymer were added; 5) Degassing: After flash evaporation, steaming and drying, 5.1t of powder is produced; 6) preparing additives: mixing 7.65 kg of antioxidant tris(2,4-di-tert-butylphenyl)phosphite, 3.825 kg of acid absorber calcium stearate, and 3.825 kg of lubricant monostearate glyceryl, and extruding and granulating into a granular composition; 7) Granulation: Add additives to the powder, mix evenly, and then mix and granulate in a twin-screw extruder. The pre-melting section temperature is 160-200°C, the melting section temperature is 170-210°C, and the extrusion section temperature is 170-190°C. Finally, 5.1t of pellets are obtained. Example 1

[0021] 1) Preparation of catalyst: 220L No. 68 white oil and 110L fat are made into a grease mixture, heated to 70°C, 80kg of catalyst is added, stirred for 120min, cooled to 10°C, and a catalyst suspension is prepared; 2) Preparation of co-catalyst Donor-C: 200L white oil and 200L Donor-C, prepared into 50% (v / v) Donor-C; 3) Prepolymerization: The prepolymerization reactor R200 was maintained at 20°C, and catalyst (0.42kg / h, pump stroke 29%), co-catalyst Donor-C (0.08kg / h), and co-catalyst TEAL (1kg / h) were added; 4) Polymerization reaction: Polymerization reactor R201 was maintained at 70°C and 4.0MPa, and propylene (8.26t / h), hydrogen (1.7kg / h), and prepolymer were added; 5) Degassing: After flash evaporation, steaming and drying, 5.6t of powder is produced; 6) preparing additives: mixing 8.4 kg of antioxidant tris(2,4-di-tert-butylphenyl)phosphite, 4.2 kg of acid absorber calcium stearate, and 4.2 kg of lubricant monostearate glyceryl, and extruding and granulating into a granular composition; 7) Granulation: Add additives to the powder, mix evenly, and then mix and granulate in a twin-screw extruder. The pre-melting section temperature is 160-200°C, the melting section temperature is 170-210°C, and the extrusion section temperature is 170-190°C. Finally, 5.6t of pellets are obtained; Example 2

[0022] 1) Preparation of catalyst: 220L No. 68 white oil and 110L fat are made into a grease mixture, heated to 70°C, 80kg of catalyst is added, stirred for 120min, cooled to 10°C, and a catalyst suspension is prepared; 2) Preparation of co-catalyst Donor-C: 200L white oil and 200L Donor-C, prepared into 50% (v / v) Donor-C; 3) Prepolymerization: The prepolymerization reactor R200 was maintained at 20°C, and the catalyst (0.38 kg / h, pump stroke 25.3%), co-catalyst Donor-C (0.29 kg / h), and co-catalyst TEAL (0.86 kg / h) were added; 4) Polymerization reaction: Polymerization reactor R201 was maintained at 70°C and 4.05MPa, and propylene (8.7t / h), hydrogen (1.66kg / h), ethylene (34.6kg / h), and prepolymer were added; 5) Degassing: After flash evaporation, steaming and drying, 5.1t of powder is produced; 6) preparing additives: mixing 7.65 kg of antioxidant tris(2,4-di-tert-butylphenyl)phosphite, 3.825 kg of acid absorber calcium stearate, and 3.825 kg of lubricant monostearate glyceryl, and extruding and granulating into a granular composition; 7) Granulation: Add additives to the powder, mix evenly, and then mix and granulate in a twin-screw extruder. The pre-melting section temperature is 160-200°C, the melting section temperature is 170-210°C, and the extrusion section temperature is 170-190°C. Finally, 5.1t of pellets are obtained. Example 3

[0023] 1) Preparation of catalyst: 220L No. 68 white oil and 110L fat are made into a grease mixture, heated to 70°C, 80kg of catalyst is added, stirred for 120min, cooled to 10°C, and a catalyst suspension is prepared; 2) Preparation of co-catalyst Donor-C: 200L white oil and 200L Donor-C, prepared into 50% (v / v) Donor-C; 3) Prepolymerization: The prepolymerization reactor R200 was maintained at 20°C, and catalyst (0.44 kg / h, pump stroke 25.3%), co-catalyst Donor-C (0.32 kg / h), and co-catalyst TEAL (0.96 kg / h) were added; 4) Polymerization reaction: Polymerization reactor R201 was maintained at 70°C and 4.1MPa, and propylene (9.8t / h), hydrogen (1.8kg / h), ethylene (18kg / h), and prepolymer were added; 5) Degassing: After flash evaporation, steaming and drying, 5.6t of powder is produced; 6) preparing additives: mixing 8.4 kg of antioxidant tris(2,4-di-tert-butylphenyl)phosphite, 4.2 kg of acid absorber calcium stearate, and 4.2 kg of lubricant monostearate glyceryl, and extruding and granulating into a granular composition; 7) Granulation: Add additives to the powder, mix evenly, and then mix and granulate in a twin-screw extruder. The pre-melting section temperature is 160-200°C, the melting section temperature is 170-210°C, and the extrusion section temperature is 170-190°C. Finally, 5.6t of pellets are obtained.

[0024] The process parameters of the low temperature resistant high melt injection molding polypropylene resin of comparative example 1 to example 3 are shown in Table 1: Table 1: Process parameters of low temperature resistant high melt injection molding polypropylene resin

[0025] It can be seen from Table 1 that in Comparative Example 2, when ethylene is added, in order to ensure stable production of the device, the load needs to be reduced. In addition, if the melt index of the product is to be increased, the reactor pressure needs to be increased. Example 3 achieves a balance between output and ethylene content. Under the premise of not changing the catalyst and the co-catalyst, a load of 5.6 t / h is achieved at a reaction pressure of 4.1 MPa, and an ethylene content of 0.3% (wt) in the product is achieved.

[0026] The performance characterization results of the low temperature resistant high melt injection molding polypropylene resin of Comparative Example 1 to Example 3 are shown in Table 2: Table 2: Performance parameters of low temperature resistant high melt injection molding polypropylene resin

[0027] It can be seen from Table 2 that the low-temperature resistant high-melt injection molding polypropylene composition provided by the present invention has a high melt index, a high tensile yield stress, a high load deformation temperature, and a high Rockwell hardness.

[0028] The addition of ethylene in the product improves the low temperature resistance, and can replace the thin-wall injection-molded polypropylene produced by the degradation method, and can be used for summer cold lunch boxes. Compared with the commonly used polypropylene injection molding materials on the market, the polypropylene injection molding materials provided by the present invention have significantly improved various indicators.

Claims

1. A method for preparing a low temperature resistant high melt injection molding polypropylene composition, characterized in that The steps include: 1) Propylene is used as a raw material, added into a single loop reactor, and a catalyst, a co-catalyst 1 and a co-catalyst 2 are added, and then stirred evenly, ethylene and hydrogen are introduced into the single loop, and polypropylene powder is obtained by flash evaporation, steam distillation and drying; 2) The antioxidant, acid absorbent and lubricant are first mixed and extruded to form a granular composition, and then mixed with the polypropylene powder obtained in step 1) to obtain a low-temperature resistant and high-melt injection molding polypropylene composition.

2. The method for preparing the low temperature resistant high melt injection molding polypropylene composition according to claim 1, characterized in that The specific process of step 1) is as follows: Propylene is used as a raw material, added into a single loop reactor, and a catalyst, a co-catalyst 1 and a co-catalyst 2 are added, and then stirred evenly, the reaction pressure of the single loop reactor is controlled to be 3.8-4.4MPa, the reaction temperature is 70±2°C, the ethylene concentration in the single loop reactor is 0.2-0.4% (wt), 0.1-0.3% (wt) of hydrogen is added, and subsequently flash evaporation, steam distillation and drying are performed to obtain a polypropylene powder with a melt flow rate of 80-90g / 10min.

3. The method for preparing the low temperature resistant high melt injection molding polypropylene composition according to claim 1, characterized in that The catalyst in step 1) is the fourth generation domestic ZN catalyst DQC-602; the co-catalyst 1 in step 1) is the electron donor cyclohexyl-methyl-dimethoxysilane; the co-catalyst 2 in step 1) is triethylaluminum.

4. The method for preparing the low temperature resistant high melt injection molding polypropylene composition according to claim 1, characterized in that In step 1), the mass ratio of raw material propylene to catalyst, co-catalyst 1 and co-catalyst 2 is 10000: 0.4-0.6: 0.05-0.35: 0.9-1.

3.

5. The method for preparing the low temperature resistant high melt injection molding polypropylene composition according to claim 1, characterized in that The amount of the antioxidant added in step 2) is 0.1-0.2% (wt) of the total amount of polypropylene, and the antioxidant is a phosphate antioxidant, specifically tris (2,4-di-tert-butylphenyl) phosphite; the amount of the acid absorber added in step 2) is 0.05-0.1% (wt) of the total amount of polypropylene, and the acid absorber is calcium stearate; the amount of the lubricant added in step 2) is 0.05-0.1% (wt) of the total amount of polypropylene, and the lubricant is glyceryl monostearate.

6. The method for preparing the low temperature resistant high melt injection molding polypropylene composition according to claim 5, characterized in that The amount of antioxidant added in step 2) is 0.15% (wt) of the total amount of polypropylene; the amount of acid absorbent added in step 2) is 0.075% (wt) of the total amount of polypropylene; the amount of lubricant added in step 2) is 0.075% (wt) of the total amount of polypropylene.

7. The method for preparing the low temperature resistant high melt injection molding polypropylene composition according to claim 1, characterized in that When a twin-screw extruder is used for compounding and granulation in step 2), the temperature of the pre-melting section is 160-200°C, the temperature of the melting section is 170-210°C, and the temperature of the extrusion section is 170-190°C.

8. A low temperature resistant high melt injection molding polypropylene composition prepared by the method of claim 1.

9. The low temperature resistant high melt injection molding polypropylene composition according to claim 8, characterized in that The polypropylene composition comprises the following components in parts by weight: 99.7% (wt) polypropylene, 0.15% (wt) tris (2,4-di-tert-butylphenyl) phosphite, 0.075% (wt) calcium stearate, 0.075% (wt) glyceryl monostearate.

10. Use of the low temperature resistant high melt injection molding polypropylene composition according to claim 8 in summer cold lunch boxes.

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