CN112094472B

CN112094472B - High-welding-strength polypropylene composition and preparation method and application thereof

Info

Publication number: CN112094472B
Application number: CN202011032114.6A
Authority: CN
Inventors: 张爽爽; 尹朝清; 王亚南; 杨泽; 周杰; 杨磊
Original assignee: Shanghai Kingfa Science and Technology Co Ltd; Jiangsu Kingfa New Material Co Ltd
Current assignee: Shanghai Kingfa Science and Technology Co Ltd; Jiangsu Kingfa New Material Co Ltd
Priority date: 2020-09-27
Filing date: 2020-09-27
Publication date: 2022-11-15
Anticipated expiration: 2040-09-27
Also published as: CN112094472A

Abstract

The invention relates to a high-welding-strength polypropylene composition, a preparation method and application thereof, wherein the composition comprises an ethylene-propylene block copolymer, an ethylene-propylene random copolymer, low-density polyethylene, cyclic polyolefin, an antioxidant and a lubricant. According to the invention, by adding the low-density polyethylene and the ethylene-propylene random copolymer, the synergistic effect on the improvement of the melt strength and the welding strength of the product is achieved, the thin-wall extruded pipe can be formed, and the product has excellent welding strength, good sealing property and good application prospect.

Description

High-welding-strength polypropylene composition and preparation method and application thereof

Technical Field

The invention belongs to the field of modified plastics, and particularly relates to a high-welding-strength polypropylene composition, and a preparation method and application thereof.

Background

Polypropylene is one of five general-purpose plastics, and is widely applied to the fields of household appliances, automobiles, daily necessities, chemical building materials and the like. The polypropylene material is mainly formed by three molding modes, namely injection molding, extrusion and blow molding, wherein the polypropylene material is more and more widely applied to the field of extrusion molding due to excellent temperature resistance and chemical stability of the polypropylene material.

However, the polypropylene structure is usually a linear molecular chain, and no branched chain exists in the molecular chain, so that the melt strength of the polypropylene structure is low, the melt fracture condition is easy to occur in the thin-wall extrusion molding process, and the difficulty in molding thin-wall corrugated pipes or sheets and other extrusion products is high. Chinese patent CN102477202B discloses a waste polypropylene modified thin-wall corrugated pipe, wherein peroxide master batches and micromolecule monomer master batches are added, the micromolecule monomer is grafted under the action of peroxide in the forming process to generate branched chains so as to improve the melt strength and improve the compatibility among polar impurity resins.

In addition, the extruded product usually needs to be further welded and molded, and because the polypropylene material is a crystalline polymer, the welding strength is reduced due to the reduction of the melt strength and the orientation problem of molecular chains in the welding and melting process, and the structural strength and the sealing property of the product are insufficient. Chinese patent CN110669287A discloses a polypropylene material suitable for vibration friction welding, which realizes high welding strength by adding ethylene-propylene random copolymer and nucleating agent to reduce molecular chain orientation and improve matrix strength, but the problem of polypropylene molecular chain orientation is not fundamentally changed by adding the random copolymer, and the improvement degree of crystallinity to matrix strength by adding the nucleating agent is limited.

Disclosure of Invention

The invention aims to solve the technical problem of providing a high-welding-strength polypropylene composition, and a preparation method and application thereof.

The invention provides a high-welding-strength polypropylene composition which comprises the following components in percentage by mass:

the melt index of the ethylene-propylene block copolymer is 0.3-5 g/10min under the test condition of 230 ℃/2.16 kg.

The melt index of the ethylene-propylene random copolymer is 0.5-20 g/10min under the test condition of 230 ℃/2.16 kg.

The low-density polyethylene has long chain branch and the melt index is 0.2-20 g/10min under the test condition of 190 ℃/2.16 kg.

The cyclic polyolefin is a copolymer of a bicycloheptene monomer and an ethylene monomer, and the melt index is 2-60 g/10min under the test condition of 260 ℃/2.16 kg.

The antioxidant is at least one of hindered phenol, hindered amine and phosphite ester, such as 3,5-di-tert-butyl-4-hydroxyphenylpropionyl-hexanediamine (antioxidant 1098), tris (2,4-di-tert-butylphenol phosphite) (antioxidant 168), and tetra [ beta- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester (antioxidant 1010).

The lubricant is at least one of stearate, such as zinc stearate or calcium stearate.

The invention also provides a preparation method of the polypropylene composition with high welding strength, which comprises the following steps:

according to the proportion, the raw materials are placed in a mixer to be uniformly mixed, the mixed raw materials are melted and mixed through a double-screw extruder, and are extruded and granulated to obtain the high-welding-strength polypropylene composition.

The process parameters of the mixer are as follows: the rotation speed is 100-300rpm, and the mixing time is 5-10min.

The technological parameters of the double-screw extruder are as follows: the rotating speed of the screw is 200-600 rpm, and the melting temperature of the extruder is set to be 180-250 ℃.

The invention also provides application of the polypropylene composition with high welding strength.

Advantageous effects

According to the invention, by adding the low-density polyethylene and the ethylene-propylene random copolymer, the synergistic effect on the improvement of the melt strength and the welding strength of the product is achieved, the molecular chain entanglement degree in a melt state is increased, the interface compatibility is excellent, the molecular chain movement capacity and the orientation degree are greatly reduced, the thin-wall extruded pipe can be formed, the product has excellent welding strength and good sealing performance, and the application prospect is good.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention can be made by those skilled in the art after reading the teaching of the present invention, and these equivalents also fall within the scope of the claims appended to the present application.

The specific raw materials and their brands and manufacturers are shown in Table 1.

The compositions described herein and comparative compositions were prepared using the raw materials of Table 1 by the following methods:

step 1: weighing the components according to the mixture ratio (weight ratio) in the table 2;

step 2: ethylene-propylene block copolymer, ethylene-propylene random copolymer, polyethylene, cyclic polyolefin, antioxidant and lubricant, wherein the rotating speed of a mixer is 200rpm, and the mixing time is 5min;

and step 3: melting and mixing the mixed raw materials through a double-screw extruder, and extruding and granulating to obtain the product, wherein the screw rotating speed of the double-screw extruder is 450rpm; the melting temperature of the extruder is set to 180-250 ℃.

The compositions prepared in the above-mentioned specific examples and comparative examples were subjected to various performance tests in which tensile properties were evaluated according to ISO 527 standard at a tensile speed of 50mm/min; testing the impact performance of a cantilever notch according to the ISO180 standard; injection-molding a welded sample strip, and performing a welding tensile strength test under the test condition of 50mm/min according to the test standard ISO 527; the melt strength was determined using a melt extensional rheometer from Geottfert, germany, and the temperature was determined: at 200 ℃. The diameter of the die head is 2mm, the initial rotating speed of the roller is 30mm/s, the acceleration of the roller is 2.5mm/s, and the distance from the die head to the roller is 65mm; the effect of forming a 0.2mm thick tube was evaluated by a single screw extruder, where the extrusion temperature was set at 180-220 ℃.

TABLE 1 raw materials for examples and comparative examples, their designations and manufacturers

Name of raw materials	Number plate	Manufacturer of the product
			Ethylene-propylene block copolymer	K8003	Winnowing petrifaction
Propylene homopolymer	PPH-T03	Zhenhai refining
			Ethylene-propylene random copolymer	SM198	Malaysia danteng petrochemical
Low density polyethylene	LDPE 2426H	Zhonghai shell petrifaction
			Linear low density polyethylene	LLDPE 0220AA	Shanghai Saikai petrochemical
Cyclic polyolefins	APL613T	Mitsui chemical Co Ltd
			Antioxidant agent	Antioxidant 1010	Li Anlong New materials, inc
Lubricant agent	BS-3818	Zhongshan Mingtai chemical Co Ltd

TABLE 2 comparison of formulation and test Properties of the examples and comparative examples

As can be seen from Table 2, the polypropylene composition of the present invention has high welding strength, can be used for smoothly forming thin-walled pipes, and has good appearance, and the comparison between example 1 and comparative examples 1 and 2 shows that the low-density polyethylene and the ethylene-propylene random copolymer in the system of the present invention have synergistic effects on providing melt strength and welding strength. By comparing the properties of example 2 and comparative example 3, it can be seen that the propylene homopolymer does not function in the present system and the ethylene-propylene block copolymer has a better compatibilizing effect. By comparing example 2 with comparative example 4, it can be seen that linear low density polyethylene cannot perform good entanglement due to short molecular branch, resulting in poor system compatibility; it can be seen from comparison of example 3 with comparative example 5 that the weld strength of the system with excess low density polyethylene added also shows a decreasing trend; by comparing example 3 with comparative example 6, it can be found that the toughness of the system added by the pure cyclic polyolefin, low density polyethylene and ethylene-propylene random copolymer is reduced rapidly, and the ethylene-propylene block copolymer plays an important role in improving the toughness of the product.

Claims

1. A high weld strength polypropylene composition characterized by: the composite material comprises the following components in percentage by mass:

20-80% of an ethylene-propylene block copolymer;

5-20% of ethylene-propylene random copolymer;

5-10% of low-density polyethylene;

10-50% of cyclic polyolefin;

0.1 to 0.3 percent of antioxidant;

0.1 to 0.5 percent of lubricant;

wherein the melt index of the ethylene-propylene block copolymer is 0.3-5 g/10min at the test condition of 230 ℃/2.16 kg; the melt index of the ethylene-propylene random copolymer is 0.5-20 g/10min under the test condition of 230 ℃/2.16 kg; the low-density polyethylene has long chain branch, and the melt index is 0.2-20 g/10min under the test condition of 190 ℃/2.16 kg; the cyclic polyolefin is a copolymer of a bicycloheptene monomer and an ethylene monomer, and the melt index is 2-60 g/10min under the test condition of 260 ℃/2.16 kg; the sum of the mass percentages of the components is 100 percent.

2. The composition of claim 1, wherein: the antioxidant is at least one of hindered phenol, hindered amine and phosphite antioxidant.

3. The composition of claim 1, wherein: the lubricant is at least one of stearate.

4. A method for preparing the high weld strength polypropylene composition of claim 1, comprising:

5. The method of claim 4, wherein: the process parameters of the mixer are as follows: the rotating speed is 100-300rpm, and the mixing time is 5-10min; the technological parameters of the double-screw extruder are as follows: the rotating speed of the screw is 200-600 rpm, and the melting temperature of the extruder is set to be 180-250 ℃.

6. Use of the high weld strength polypropylene composition according to claim 1.