Polypropylene composition as well as preparation method and application thereof

Abstract

The invention discloses a polypropylene composition as well as a preparation method and application thereof, and belongs to the technical field of materials. The polypropylene composition comprises 100 parts by weight of polypropylene; 0.1 to 0.8 part by weight of an antioxidant; 0.01 to 0.3 part by weight of a nucleating agent; 0.01 to 0.1 part by weight of an acid acceptor; 0.01 to 0.1 part by weight of an antistatic agent; the polypropylene is selected from homo-polypropylene, an ethylene-propylene random copolymer or a propylene-butylene random copolymer; the nucleating agent is selected from an organic phosphate nucleating agent or a beta-type nucleating agent; the antistatic agent is selected from fatty acid alkanolamide and / or fatty acid monoglyceride. Through the combined action of the nucleating agent, the antistatic agent and other components (polypropylene, the antioxidant and the acid acceptor), the polypropylene composition has good high temperature resistance, impact resistance and stiffness, and is suitable for preparing a thermoforming packaging material, especially a hot filling bottle under the ultrahigh temperature (121 DEG C) sterilization condition.

Description

Technical Field

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

[0002] At present, polyethylene terephthalate (PET) bottles are more commonly used in the hot filling market of beverages. However, the disadvantage of PET bottles is that they are extremely hygroscopic and need to be dried by special equipment before processing. Moreover, ordinary PET bottles are not resistant to high temperatures and cannot be used for packaging fruit juices and tea beverages. The main way to change their properties is to increase the crystallinity. Specifically, a heat setting process is added during bottle blowing, and at the same time, the manufacturing process of the preform also needs to be changed. By adjusting the process, the crystallinity of PET is increased, and thus its heat resistance temperature is increased. However, this method can only increase the heat resistance temperature of PET bottles from 85 °C to 93 °C. Although the heat resistance temperature of conventional transparent homopolypropylene (PP) is higher than that of highly crystalline PET, it is only 100 °C. And the impact strength of ordinary transparent PP is usually only 4-6 kJ / m 2 , with poor toughness, and it is easy to have the phenomenon of bottle body cracking when dropped from a height, which in turn leads to a decrease in the product qualification rate and a poor customer experience.

[0003] In the high-temperature hot filling process, the material is subjected to ultra-high temperature instantaneous sterilization (135-150 °C / 2-8 s), then cooled to 85 °C - 92 °C for filling, and then the filled material is transported to a sterilization kettle for re-sterilization of the material, bottle body, and bottle cap at 121 °C for 15-20 s. The high-temperature hot filling process uses the residual heat of the product to sterilize the inner wall of the container and the bottle cap. Its core is to integrate sterilization and packaging sterilization through high temperature, reducing the separate sterilization link. The high-temperature hot filling process has the advantages of efficient sterilization (effectively killing bacteria and microorganisms in a high-temperature environment and extending the shelf life), simplified process (no need to sterilize the bottle body and bottle cap separately, reducing the equipment complexity), and wide applicability (can be used for high-sugar or pectin-containing heat-sensitive products such as fruit juices, tea beverages, and functional beverages).

[0004] Therefore, it is of great significance to research and develop a new material with high heat resistance temperature and good impact resistance suitable for the high-temperature hot filling process for preparing food packaging such as hot filling bottles. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a polypropylene composition, a preparation method thereof, and an application thereof. The polypropylene composition has excellent high-temperature resistance, impact resistance, relatively high stiffness, and low haze.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a polypropylene composition, which comprises the following components by weight:

[0008] Polypropylene: 100 parts by weight;

[0009] Antioxidant: 0.1 - 0.8 parts by weight;

[0010] Nucleating agent: 0.01 - 0.3 parts by weight;

[0011] Acid scavenger: 0.01 - 0.1 parts by weight;

[0012] Antistatic agent: 0.01 - 0.1 parts by weight;

[0013] Preferably, the polypropylene is selected from homopolypropylene, ethylene - propylene random copolymer or propylene - butene random copolymer;

[0014] Preferably, the nucleating agent is selected from organic phosphate nucleating agents or β - type nucleating agents;

[0015] Preferably, the antistatic agent is selected from fatty acid alkanolamides and / or fatty acid monoglycerides; more preferably, it is a mixture of fatty acid alkanolamides and fatty acid monoglycerides. In some specific embodiments of the present invention, the mass ratio of the fatty acid alkanolamide to the fatty acid monoglyceride is 1:1.

[0016] The polypropylene composition of the present invention has excellent high - temperature resistance, relatively high flexural modulus, notched impact strength and lower haze.

[0017] The flexural modulus of the polypropylene composition ≥ 1300 MPa;

[0018] The notched Izod impact strength of the polypropylene composition ≥ 8 kJ / m 2 ;

[0019] The heat distortion temperature of the polypropylene composition ≥ 110 °C;

[0020] The haze of the polypropylene composition ≤ 20%;

[0021] The melt flow rate of the polypropylene composition is 1.5 - 30 g / 10 min.

[0022] Preferably, in the polypropylene composition of the present invention, the mass ratio of polypropylene to the nucleating agent is 100:(0.03 - 0.2); more preferably 100:(0.05 - 0.18). In some specific embodiments of the present invention, it is preferably 100:0.1 or 100:0.18 or 100:0.05.

[0023] Preferably, the organic phosphate nucleating agent is selected from aluminum 2,2'-methylenebis(4,6-di-tert-butylphenoxy)phosphate or sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate.

[0024] Preferably, the β-nucleating agent is selected from rare earth nucleating agents or amide nucleating agents.

[0025] More preferably, the rare earth nucleating agent is selected from the mixture composed of lanthanum stearate, stearic acid and calcium phosphate, or the mixture composed of cerium stearate, stearic acid and calcium carbonate, or the mixture composed of rubidium stearate, stearic acid and calcium sulfate;

[0026] More preferably, the amide nucleating agent is selected from one or more of N,N'-dicyclohexyl terephthalamide, N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide, 2,6-bis(cyclopentylcarbamoyl)naphthalene.

[0027] Preferably, the mass ratio of polypropylene to antioxidant in the polypropylene composition is 100:(0.15 - 0.4); more preferably 100:0.15.

[0028] Preferably, the antioxidant is selected from the mixture of hindered phenol antioxidants and phosphate antioxidants.

[0029] More preferably, the mass ratio of the hindered phenol antioxidant to the phosphate antioxidant is 1:(0.5 - 2); further preferably 1:(1 - 2).

[0030] Preferably, the mass ratio of polypropylene to acid scavenger in the polypropylene composition is 100:(0.03 - 0.05); more preferably 100:0.03 or 100:0.05.

[0031] Preferably, the acid scavenger is selected from metal stearates or hydrotalcite.

[0032] The metal stearates include but are not limited to calcium stearate, zinc stearate, magnesium stearate, etc.

[0033] Preferably, the mass ratio of polypropylene to antistatic agent in the polypropylene composition is 100:(0.02 - 0.05); more preferably 100:0.02 or 100:0.03.

[0034] Preferably, the isotacticity of the homopolypropylene is 96% - 98%; more preferably 97% - 98%.

[0035] Preferably, the ethylene content of the ethylene-propylene random copolymer is 0.5% - 2.0%; more preferably 1% - 1.5%.

[0036] Preferably, the butene content in the propylene-butene random copolymer is 0.5% to 2.0%; more preferably 1% to 1.5%.

[0037] Preferably, the melt index of the polypropylene composition at 230 °C / 2.16 kg is 1.5 to 30 g / 10 min; more preferably 3 to 20 g / 10 min.

[0038] The present invention provides a method for preparing the above polypropylene composition, comprising the following steps:

[0039] (1) Mix the nucleating agent and the antistatic agent to obtain an activated nucleating agent;

[0040] (2) Mix polypropylene, an antioxidant, an acid absorbent and the activated nucleating agent obtained in step (1), melt extrude and pelletize to obtain the polypropylene composition.

[0041] Through the activation treatment of the nucleating agent by the antistatic agent, the polar groups of the antistatic agent are combined with the nucleating agent through chemical adsorption, reducing the agglomeration force between the nucleating agents, improving the dispersion of the nucleating agent, and better exerting the nucleating effect of the nucleating agent.

[0042] The present invention also provides the application of the above polypropylene composition or the polypropylene composition prepared by the above preparation method in the field of thermoformed food packaging.

[0043] The polypropylene composition has excellent high temperature resistance and can be used to prepare hot filling bottles under ultra-high temperature (121 °C) sterilization conditions or fresh food lunch boxes that need to be heated in a microwave oven.

[0044] Compared with the prior art, the polypropylene composition provided by the present invention, by weight, comprises the following components: polypropylene: 100 parts by weight; antioxidant: 0.1 to 0.8 parts by weight; nucleating agent: 0.01 to 0.3 parts by weight; acid absorbent: 0.01 to 0.1 parts by weight; antistatic agent: 0.01 to 0.1 parts by weight; the polypropylene is selected from homopolypropylene, ethylene-propylene random copolymer or propylene-butene random copolymer; the nucleating agent is selected from organic phosphate nucleating agents or β-type nucleating agents; the antistatic agent is selected from fatty acid alkanolamides and / or fatty acid monoglycerides. Through the combined action of the nucleating agent, the antistatic agent and other components (polypropylene, antioxidant, acid absorbent), the polypropylene composition has good high temperature resistance, impact resistance and stiffness, and is suitable for preparing thermoformed packaging materials, especially hot filling bottles under ultra-high temperature (121 °C) sterilization conditions, thereby solving the problems of insufficient heat resistance and easy breakage upon dropping of PET and conventional PP in ultra-high temperature hot filling. Detailed embodiments

[0045] To further illustrate the present invention, the polypropylene composition provided by the present invention, its preparation method and application will be described in detail below in conjunction with embodiments.

[0046] Example 1

[0047] According to the ratio shown in Table 1, the nucleating agent 2,2'-methylenebis(4,6-ditert-butylphenoxy) aluminum phosphate and the antistatic agent (the mass ratio of fatty acid alkanolamide to fatty acid monoglyceride is 1:1) are stirred and mixed in a high-speed mixer for 20 min to obtain the activated nucleating agent.

[0048] The isotactic polypropylene with an isotacticity of 97% - 98%, antioxidant, acid absorbent calcium stearate and the above-activated nucleating agent are placed in a high-speed mixer according to the ratio shown in Table 1 and mixed evenly to obtain a mixture.

[0049] The mixture is melt-blended and extruded through a twin-screw extruder and pelletized to obtain the polypropylene composition, and its performance parameters are shown in Table 2.

[0050] Example 2

[0051] According to the ratio shown in Table 1, the nucleating agent 2,2'-methylenebis(4,6-ditert-butylphenoxy) aluminum phosphate and the antistatic agent (the mass ratio of fatty acid alkanolamide to fatty acid monoglyceride is 1:1) are stirred and mixed in a high-speed mixer for 20 min to obtain the activated nucleating agent.

[0052] The ethylene-propylene random copolymer polypropylene with an ethylene content of 1% - 1.5%, antioxidant, acid absorbent calcium stearate and the above-activated nucleating agent are placed in a high-speed mixer according to the ratio shown in Table 1 and mixed evenly to obtain a mixture.

[0053] The mixture is melt-blended and extruded through a twin-screw extruder and pelletized to obtain the polypropylene composition, and its performance parameters are shown in Table 2.

[0054] Example 3

[0055] According to the ratio shown in Table 1, the nucleating agent 2,2'-methylenebis(4,6-ditert-butylphenoxy) aluminum phosphate and the antistatic agent (the mass ratio of fatty acid alkanolamide to fatty acid monoglyceride is 1:1) are stirred and mixed in a high-speed mixer for 20 min to obtain the activated nucleating agent.

[0056] The propylene-butene random copolymer polypropylene with a butene content of 1% - 1.5%, antioxidant, acid absorbent calcium stearate and the above-activated nucleating agent are placed in a high-speed mixer according to the ratio shown in Table 1 and mixed evenly to obtain a mixture.

[0057] The mixture is melt-blended and extruded through a twin-screw extruder and pelletized to obtain the polypropylene composition, and its performance parameters are shown in Table 2.

[0058] Example 4

[0059] According to the ratio described in Table 1, an amide nucleating agent (N,N′-dicyclohexyl terephthalamide) and an antistatic agent (the mass ratio of fatty acid alkanolamide to fatty acid monoglyceride is 1:1) are stirred and mixed in a high-speed mixer for 20 min to obtain an activated nucleating agent.

[0060] An ethylene-propylene random copolymer polypropylene with an ethylene content of 1% - 1.5%, an antioxidant, an acid absorbent calcium stearate, and the above-activated nucleating agent are placed in a high-speed mixer according to the ratio in Table 1 and mixed evenly to obtain a mixture.

[0061] The mixture is melt-blended and extruded through a twin-screw extruder and pelletized to obtain the polypropylene composition, and its performance parameters are shown in Table 2.

[0062] Example 5

[0063] According to the ratio described in Table 1, a rare earth nucleating agent (a mixture composed of lanthanum stearate, stearic acid, and calcium phosphate) and an antistatic agent (the mass ratio of fatty acid alkanolamide to fatty acid monoglyceride is 1:1) are stirred and mixed in a high-speed mixer for 30 min to obtain an activated nucleating agent.

[0064] An ethylene-propylene random copolymer polypropylene with an ethylene content of 1% - 1.5%, an antioxidant, an acid absorbent calcium stearate, and the above-activated nucleating agent are placed in a high-speed mixer according to the ratio in Table 1 and mixed evenly to obtain a mixture.

[0065] The mixture is melt-blended and extruded through a twin-screw extruder and pelletized to obtain the polypropylene composition, and its performance parameters are shown in Table 2.

[0066] Example 6

[0067] According to the ratio described in Table 1, the nucleating agent 2,2'-methylenebis(4,6-di-tert-butylphenoxy) aluminum phosphate and an antistatic agent (the mass ratio of fatty acid alkanolamide to fatty acid monoglyceride is 1:1) are stirred and mixed in a high-speed mixer for 20 min to obtain an activated nucleating agent.

[0068] An ethylene-propylene random copolymer polypropylene with an ethylene content of 1.5% - 2%, an antioxidant, an acid absorbent hydrotalcite, and the above-activated nucleating agent are placed in a high-speed mixer according to the ratio in Table 1 and mixed evenly to obtain a mixture.

[0069] The mixture is melt-blended and extruded through a twin-screw extruder and pelletized to obtain the polypropylene composition, and its performance parameters are shown in Table 2.

[0070] Comparative Example 1

[0071] According to the ratio described in Table 1, ethylene-propylene random copolymer polypropylene with an ethylene content of 1.5% to 2%, an antioxidant, an acid absorbent calcium stearate, a nucleating agent 2,2'-methylenebis(4,6-di-tert-butylphenoxy) aluminum phosphate, and an antistatic agent monoglyceride are placed in a high-speed mixer according to the ratio in Table 1 and mixed evenly to obtain a mixture.

[0072] The mixture is melt-blended and extruded through a twin-screw extruder and pelletized to obtain the polypropylene composition, and its performance parameters are shown in Table 2.

[0073] Comparative Example 2

[0074] According to the ratio described in Table 1, a sorbitol-based transparent nucleating agent and an antistatic agent monoglyceride are stirred and mixed in a high-speed mixer for 20 min to obtain an activated nucleating agent.

[0075] Ethylene-propylene random copolymer polypropylene with an ethylene content of 1% to 1.5%, an antioxidant, an acid absorbent calcium stearate, and the above-activated nucleating agent are placed in a high-speed mixer according to the ratio in Table 1 and mixed evenly to obtain a mixture.

[0076] The mixture is melt-blended and extruded through a twin-screw extruder and pelletized to obtain the polypropylene composition, and its performance parameters are shown in Table 2.

[0077] Comparative Example 3

[0078] According to the ratio described in Table 1, ethylene-propylene random copolymer polypropylene with an ethylene content of 1.5% to 2%, an antioxidant, an acid absorbent calcium stearate, an amide-based nucleating agent, and an antistatic agent monoglyceride are placed in a high-speed mixer according to the ratio in Table 1 and mixed evenly to obtain a mixture.

[0079] The mixture is melt-blended and extruded through a twin-screw extruder and pelletized to obtain the polypropylene composition, and its performance parameters are shown in Table 2.

[0080] Table 1 Component ratios of Examples 1 to 6 and Comparative Examples 1 to 3

[0081] Polypropylene / kg Antioxidant / g Nucleating agent / g Acid absorbent / g Antistatic agent / g Example 1 10 15 10 5 2 Example 2 10 15 10 5 2 Example 3 10 15 10 5 2 Example 4 10 15 5 5 2 Example 5 10 15 10 5 2 Example 6 10 15 18 3 3 Comparative Example 1 10 15 10 5 2 Comparative Example 2 10 15 25 3 3 Comparative Example 3 10 15 10 5 3

[0082] Table 2 Performance parameters of polypropylene compositions of Examples 1 to 6 and Comparative Examples 1 to 3

[0083]

[0084]

[0085] The test methods for the performance in Table 2 above:

[0086] Melt mass flow rate (MFR): Determined with reference to GB / T 3682.1-2018, load 2.16 kg, test temperature 230 °C; flexural modulus: Determined with reference to GB / T 9341; heat distortion temperature: Determined with reference to GB / T 1634; haze: Determined with reference to GB / T 2410; notched Izod impact strength (23 °C): Determined with reference to GB / T 1043.

[0087] Comparisons between Examples 1 to 6 and Comparative Examples 1 to 3 show that the organic phosphate nucleating agent or β-type nucleating agent after antistatic agent activation treatment can better exert the nucleating effect. The polypropylene prepared by this method has higher heat distortion temperature, flexural modulus, notched impact strength and lower haze.

[0088] In Comparative Example 2, when a sorbitol-based nucleating agent was selected, although it had an advantage in haze, its effect of increasing stiffness and heat resistance was significantly insufficient and could not meet the requirements of high stiffness and temperature resistance in packaging materials.

[0089] The descriptions of the above examples are only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A polypropylene composition, characterized in that By weight, it includes the following ingredients: Polypropylene: 100 parts by weight; Antioxidant: 0.1-0.8 parts by weight; Nucleating agent: 0.01-0.3 parts by weight; Acid absorbent: 0.01-0.1 parts by weight; Antistatic agent: 0.01-0.1 parts by weight; The polypropylene is selected from homopolypropylene, ethylene-propylene random copolymer or propylene-butylene random copolymer; The nucleating agent is selected from an organic phosphate nucleating agent or a β-type nucleating agent; The antistatic agent is selected from fatty acid alkanolamide and / or fatty acid monoglyceride.

2. The polypropylene composition according to claim 1, characterized in that The organic phosphate nucleating agent is selected from 2,2'-methylenebis(4,6-di-tert-butylphenoxy)aluminum phosphate or 2,2'-methylenebis(4,6-di-tert-butylphenyl)sodium phosphate; The β-type nucleating agent is selected from rare earth nucleating agents or amide nucleating agents.

3. The polypropylene composition according to claim 2, characterized in that The rare earth nucleating agent is selected from a mixture of lanthanum stearate, stearic acid and calcium phosphate, or a mixture of cerium stearate, stearic acid and calcium carbonate, or a mixture of rubidium stearate, stearic acid and calcium sulfate; The amide nucleating agent is selected from one or more of N,N′-dicyclohexylterephthalamide, N,N′-dicyclohexyl-2,6-naphthalene diamide, and 2,6-di(cyclopentylamido)naphthalene.

4. The polypropylene composition according to claim 1, characterized in that The antioxidant is selected from a mixture of hindered phenol antioxidants and phosphate antioxidants.

5. The polypropylene composition according to claim 4, characterized in that The mass ratio of the hindered phenol antioxidant to the phosphate antioxidant is 1:(0.5-2).

6. The polypropylene composition according to claim 1, characterized in that The acid absorbent is selected from stearate or hydrotalcite.

7. The polypropylene composition according to claim 1, characterized in that The isotacticity of the homopolypropylene is 96% to 98%; The ethylene content of the ethylene-propylene random copolymer is 0.5% to 2.0%; The butene content in the propylene-butene random copolymer is 0.5% to 2.0%.

8. The polypropylene composition according to any one of claims 1 to 7, characterized in that The polypropylene composition has a melt index of 1.5 to 30 g / 10 min at 230° C. / 2.16 kg.

9. The method for preparing the polypropylene composition according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) mixing a nucleating agent and an electrostatic agent to obtain an activated nucleating agent; (2) Mixing polypropylene, an antioxidant, an acid absorbent and the activated nucleating agent obtained in step (1), melt-extruding, and granulating to obtain the polypropylene composition.

10. Use of the polypropylene composition according to any one of claims 1 to 8 or the polypropylene composition prepared by the preparation method according to claim 9 in the field of thermoforming food packaging.

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