阅读说明：本技术 综合性能优异的双壁波纹管用聚乙烯组合物及其制备方法 (Polyethylene composition with excellent comprehensive performance for double-wall corrugated pipe and preparation method thereof ) 是由 王群涛 王日辉 郭锐 高凌雁 许平 唐岩 苑东兴 裴晓静 石晶 于 2018-07-16 设计创作，主要内容包括：本发明涉及一种综合性能优异的双壁波纹管用聚乙烯组合物及其制备方法,属于聚乙烯改性技术领域。本发明所述的综合性能优异的双壁波纹管用聚乙烯组合物,包括以下重量份数的原料：聚乙烯树脂a 78-85份,聚乙烯树脂b 7-12份,抗氧剂0.1-0.5份,炭黑母粒0.5-3.5份,滑石粉母粒5-8份,吸酸剂0.05-0.15份,反应剂0.06-0.1份。所述反应剂为马来酰亚胺类哌啶基氧化物。本发明所述的聚乙烯组合物,熔体强度高、刚韧平衡性好、耐慢速裂纹增长性能优异,有利于提高管材的加工性能、抗耐内外压能力,延长了管材长期使用寿命；本发明同时提供了简单易行、节能环保的制备方法。(The invention relates to a polyethylene composition with excellent comprehensive performance for a double-wall corrugated pipe and a preparation method thereof, belonging to the technical field of polyethylene modification. The polyethylene composition with excellent comprehensive performance for the double-wall corrugated pipe comprises the following raw materials in parts by weight: 78-85 parts of polyethylene resin a, 7-12 parts of polyethylene resin b, 0.1-0.5 part of antioxidant, 0.5-3.5 parts of carbon black master batch, 5-8 parts of talcum powder master batch, 0.05-0.15 part of acid acceptor and 0.06-0.1 part of reactant. The reactant is maleimide piperidyl oxide. The polyethylene composition has high melt strength, good rigidity and toughness balance and excellent slow crack growth resistance, is beneficial to improving the processing performance and the internal and external pressure resistance of the pipe, and prolongs the long-term service life of the pipe; the invention also provides a simple, energy-saving and environment-friendly preparation method.)

1. The polyethylene composition for the double-wall corrugated pipe with excellent comprehensive performance is characterized by comprising the following raw materials in parts by weight: 78-85 parts of polyethylene resin a, 7-12 parts of polyethylene resin b, 0.1-0.5 part of antioxidant, 0.5-3.5 parts of carbon black master batch, 5-8 parts of talcum powder master batch, 0.05-0.15 part of acid absorbent and 0.06-0.1 part of reactant;

the reactant is maleimide piperidyl oxide;

the main chain end methyl group/1000C of the polyethylene resin a is 0.7-0.8; the weight average molecular weight is 19-23 ten thousand;

the density of the polyethylene resin b is 0.949-0.955g/cm³(ii) a The melt mass flow rate is 1.8-2.2g/10 min.

2. The polyethylene composition for double-wall corrugated pipe with excellent combination property according to claim 1, characterized in that: the polyethylene resin a is a copolymer of ethylene and 1-butene, or a copolymer of ethylene and 1-hexene, or a copolymer of ethylene, 1-butene and 1-hexene, and is produced by adopting a gas phase process and a chromium catalyst.

3. The polyethylene composition for double-wall corrugated pipe with excellent combination property according to claim 1, characterized in that: the density of the polyethylene resin a is 0.942-0.947g/cm³(ii) a The mass flow rate of the melt is 10.5-11.5g/10 min; the molecular weight distribution is 17-21.

4. The polyethylene composition for double-wall corrugated pipe with excellent combination property according to claim 1, characterized in that: the polyethylene resin a is in the form of powder and has an averageThe particle diameter is 0.87-0.94mm, and the bulk density is 0.45-0.48g/cm³。

5. The polyethylene composition for double-wall corrugated pipe with excellent combination property according to claim 1, characterized in that: the polyethylene resin b is in the form of powder, and has an average particle diameter of 0.87-0.94mm and a bulk density of 0.45-0.48g/cm³。

6. The polyethylene composition for double-wall corrugated pipe with excellent combination property according to claim 1, characterized in that: the antioxidant is a mixture of hindered phenol antioxidant and phosphite antioxidant.

7. The polyethylene composition for double-wall corrugated pipe with excellent combination property according to claim 1, characterized in that: the acid absorbent is metal soap, metal oxide or stearic acid.

8. The polyethylene composition for double-wall corrugated pipe with excellent combination property according to claim 1, characterized in that: the maleimide piperidyl oxide is one or two of 4-maleimide-tetramethylpiperidine oxide or 1-oxy-3-maleimide-tetramethylpiperidine oxide.

9. A method for preparing the polyethylene composition for double-wall corrugated pipe with excellent combination property according to any one of claims 1 to 8, characterized by comprising the steps of:

(1) putting the polyethylene resin a, the antioxidant and the acid absorbent into a high-speed mixer, stirring and mixing, stopping stirring, adding the reactant, and stirring again; finally, adding the polyethylene resin b, the carbon black master batch and the talcum powder master batch, and stirring and mixing;

(2) and (2) adding the material finally mixed in the step (1) into a double-screw extruder for melting, plasticizing, extruding and granulating to obtain the polyethylene composition with excellent comprehensive performance for the double-wall corrugated pipe.

10. The method of preparing the polyethylene composition for double-wall corrugated pipe with excellent combination property according to claim 9, characterized in that: in the step (1), the reaction agent is added and stirred at the stirring temperature of 50-60 ℃.

Technical Field

The invention relates to a polyethylene composition with excellent comprehensive performance for a double-wall corrugated pipe and a preparation method thereof, belonging to the technical field of polyethylene modification.

Background

At present, the domestic large-caliber pipe for municipal drainage and sewage systems mainly adopts a double-wall corrugated pipe and a stretching winding pipe, and the diameter of the double-wall corrugated pipe is not less than 500 mm. The pipe, especially the double-wall corrugated pipe, is required to have higher ring stiffness and cracking resistance, and simultaneously, higher melt strength is required to meet the requirement of on-line flaring during forming. The polyethylene pipe has the characteristics of light weight, good corrosion resistance, small resistance, strong weather resistance and the like, is successfully applied to a large-caliber drainage and pollution discharge system at present, and occupies a market leading position.

The large-caliber drainage and pollution discharge pipe belongs to an outer pressure-bearing pipe, and the material is required to have good rigidity so as to meet the requirement of bearing an external acting force, and meanwhile, the material is required to have good flexibility in order to meet the requirements of transportation, construction and the like. As a buried pipe, the buried pipe has a complex use environment, and needs a material with excellent slow crack growth resistance (namely environmental stress cracking resistance) to meet the long-term use requirement. How to improve the cracking resistance of the material while ensuring the good rigidity and toughness balance of the material is a difficult problem which needs to be solved urgently in the industry.

A certain number of long branched chains are formed in a molecular chain to improve the slow crack growth resistance and the melt strength of the resin, so that the production requirement of the material can be met, and the long-term use requirement can also be met. At present, polyolefin production enterprises mainly introduce long-chain branches into molecular chains by means of adjusting catalysts, polymerization process technologies and the like, but the technical process is complex, the molecular chain structure is difficult to control, and the cost is high.

CN105237861A discloses a rigidity-toughness balanced polyethylene composition, which provides a rigidity-toughness balanced polyethylene composition, comprising the following components in parts by weight: 88-93 parts of polyethylene resin a, 7-12 parts of polyethylene resin b, 0.1-0.4 part of antioxidant, 0.5-3.5 parts of carbon black master batch and 0.05-0.15 part of acid acceptor; wherein the polyethylene resin a is a copolymer of ethylene and 1-butene and/or 1-hexene, and the density is 0.951-0.955 g/cm³(ii) a The mass flow rate of the melt is 4.5-5.5 g/10 min; the relative branching degree is 0.04-0.08; the crystallinity is 67-70%; the thickness of the lamella is 21-24 nm; the polyethylene resin b is a copolymer of ethylene and 1-hexene, and the density is 0.916-0.920 g/cm³(ii) a The mass flow rate of the melt is 41-47 g/10 min.

CN200480016156 discloses a method of forming a polyolefin resin having a relatively high density and a long chain branching index ("LCB") greater than about 1. The process of the present invention comprises forming a reaction mixture that can form a polyolefin resin by mixing molecular hydrogen, a first olefin, an optional second olefin, a diluent, and a catalyst system comprising vanadium at a sufficient temperature, and initiating polymerization of the reaction mixture.

In the above patent, CN105237861A discloses a formulation of a polyethylene composition with balanced rigidity and toughness, but the rigidity and toughness balance, melt strength and slow crack growth resistance of the final product are all required to be further improved.

Disclosure of Invention

The invention aims to provide a polyethylene composition with excellent comprehensive performance for a double-wall corrugated pipe, which has high melt strength, good balance of rigidity and toughness and excellent slow crack growth resistance, is beneficial to improving the processing performance and the internal and external pressure resistance of the pipe, and prolongs the long-term service life of the pipe; the invention also provides a simple, energy-saving and environment-friendly preparation method.

The polyethylene composition with excellent comprehensive performance for the double-wall corrugated pipe comprises the following raw materials in parts by weight: 78-85 parts of polyethylene resin a, 7-12 parts of polyethylene resin b, 0.1-0.5 part of antioxidant, 0.5-3.5 parts of carbon black master batch, 5-8 parts of talcum powder master batch, 0.05-0.15 part of acid acceptor and 0.06-0.1 part of reactant.

Preferably, the feed comprises the following raw materials in parts by weight: 78-85 parts of polyethylene resin a, 7-12 parts of polyethylene resin b, 0.2-0.4 part of antioxidant, 1-2 parts of carbon black master batch, 5-8 parts of talcum powder master batch, 0.05-0.15 part of acid absorbent and 0.07-0.09 part of reactant.

The polyethylene resin a is a copolymer of ethylene and 1-butene, or a copolymer of ethylene and 1-hexene, or a copolymer of ethylene, 1-butene and 1-hexene, and is produced by adopting a gas phase process and a chromium catalyst.

The density, melt mass flow rate and molecular weight distribution of the polyethylene resin a and the polyethylene resin b are defined by combining the basic requirements of forming processing and rigidity-toughness balance of double-wall corrugated pipes with diameter of more than 500 mm. The density of the polyethylene resin a is 0.942-0.947g/cm³Preferably 0.943 to 0.945g/cm³. The polyethylene resin a has a melt Mass Flow Rate (MFR) of 10.5 to 11.5g/10min, preferably 10.8 to 11.3g/10min under a load of 21.6 kg; the polyethylene resin a has a molecular weight (Mw/MD) distribution D of 17-21, preferably 18.5-20.5. The density of the polyethylene resin b is 0.949-0.955g/cm³Preferably 0.951 to 0.953g/cm³(ii) a The melt Mass Flow Rate (MFR) is from 1.8 to 2.2g/10min, preferably from 1.9 to 2.1g/10 min.

The weight average molecular weight (Mw) of the polyethylene resin a is 19 to 23 ten thousand; the ratio of main chain terminal methyl group/1000C is 0.7-0.8, preferably 0.72-0.78. The Mw and the number of methyl groups at the end of the backbone affect the reaction efficiency and cooperativity of the reactants, i.e., the number and distribution of long chain branches introduced into the resin.

The polyethylene resin a and the polyethylene resin b are both in powder form, the average particle diameter is 0.87-0.94mm, and the bulk density is 0.45-0.48g/cm³And the dispersion of the auxiliary agent and the introduction of long-chain branches are facilitated.

When the tube material is in contact with air, it is oxidized by a chemical reaction with oxygen in the air, which is a typical radical reaction. The antioxidant is added into the pipe material and can react with oxidation free radicals R and ROO generated by oxidation in the plastic material to interrupt the growth of an active chain, thereby effectively inhibiting or reducing the degradation and aging processes of the plastic material and prolonging the service life of plastic products. The antioxidant is a mixture of hindered phenol antioxidant and phosphite antioxidant, and the mixing ratio is preferably 1: 1. Amine antioxidants hinder the chain reaction effect of the reactants with the resin and are not favorable for introducing long chain branches.

The hindered phenol antioxidant is tetra [ methyl-beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] pentaerythritol ester, beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) n-octadecyl propionate, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene or 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione; the phosphite antioxidant is tris [2, 4-di-tert-butylphenyl ] phosphite, bis (2, 4-di-tert-butylphenol) pentaerythritol diphosphite or pentaerythritol distearate diphosphite.

The acid absorbent is metal soap, metal oxide or stearic acid, such as zinc stearate, calcium stearate or zinc oxide, preferably zinc stearate.

The pipe material is required to have certain ultraviolet aging resistance due to the fact that the pipe material needs to be stored in the open air, and the pipe material is improved in ultraviolet aging resistance due to the fact that carbon black is added to have the ultraviolet absorption capacity. The mass content of the carbon black in the added master batch is 45%, and the carbon black can be uniformly dispersed in the resin.

The talcum powder is added into the composition to improve the modulus, namely the rigidity, but is not beneficial to the flexibility and the cracking resistance of the material, the talcum powder is added into the composition by adopting a mode of adding talcum powder master batches, and the mass content of the talcum powder in the master batches is 35%.

The reactant is maleimide piperidyl oxide. Preferably, the maleimide oxide is one or two of 4-maleimide-tetramethylpiperidine oxide and 1-oxy-3-maleimide-tetramethylpiperidine oxide, and the mixing mass ratio is 1:1 when the maleimide oxide and the 1-oxy-3-maleimide-tetramethylpiperidine oxide are mixed.

The preparation method of the polyethylene composition with excellent comprehensive performance for the double-wall corrugated pipe comprises the following steps:

(1) putting the polyethylene resin a, the antioxidant and the acid absorbent into a high-speed mixer, stirring and mixing, stopping stirring, adding the reactant, and stirring at the temperature of 50-60 ℃; finally, adding the polyethylene resin b, the carbon black master batch and the talcum powder master batch, and stirring and mixing;

(2) and (2) adding the material finally mixed in the step (1) into a double-screw extruder for melting, plasticizing, extruding and granulating to obtain the polyethylene composition with excellent comprehensive performance for the double-wall corrugated pipe.

In the steps, the first three components are mixed, then the stirring is stopped, and then the reactant is added, so that the reactant is favorably and uniformly dispersed in the resin and fully reacted with the resin, and the content and the performance of the long-chain branch in the resin are improved.

The polyethylene compositions produced according to the invention have the following performance parameters:

the impact strength of the cantilever beam is more than or equal to 45kJ/m²(ii) a The melt strength is more than or equal to 0.42N; the hydrostatic strength of the mixture is more than or equal to 500 hours at 80 ℃ and under 4.1 MPa; the hydrostatic strength of the mixture is more than or equal to 1490h at 80 ℃ and under 2.9 MPa; the environmental stress cracking resistance (50 ℃,10 percent TX-10) is more than 1000 h; the ring stiffness of the prepared pipe is more than or equal to 9.0kN/m²(ii) a The impact performance (TIR) is less than or equal to 7 percent.

The invention has the following beneficial effects:

(1) the invention limits the molecular structure and components of two polyethylene resins, adds maleimide oxide in the pipe material, adds a small amount of other auxiliary agents, and introduces long-chain branch on the resin molecular chain through blending and melt extrusion, so that the prepared polyethylene composition has the characteristics of high melt strength, good balance of rigidity and toughness, excellent slow crack growth resistance and the like;

(2) the double-wall corrugated pipe prepared from the polyethylene composition has good ESCR performance, and the obtained double-wall corrugated pipe has high hydrostatic strength and ring stiffness, thereby being beneficial to improving the processing performance and the internal and external pressure resistance of the pipe and prolonging the long-term service life of the pipe;

(3) the polyethylene composition is widely applied to the production of large-caliber pipes of municipal drainage and sewage systems;

(4) the preparation method of the polyethylene composition is energy-saving and environment-friendly, and is simple and feasible.

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the practice of the invention.