[Plastic] General situation of the development of domestic polyethylene pipe special materials

At present, polyethylene (PE) pipe has become the second-largest plastic pipe variety in the world after polyvinyl chloride (PVC).

PE pipe materials in the Chinese market are mainly concentrated in water supply pipes, gas pipes, floor heating pipes and other fields.

Although the total amount can meet the current demand, there are still certain shortcomings.

According to the international standards ISO9080-2012 and ISO 12162-2009, PE pipes are divided into PE32, PE40, PE63, PE80, PE100, PE112 and PE125 grades.

In 2019, the output of PE pipes in the domestic market was about 2.

1.

PE pipe has the advantages of good hygiene, environmental protection, flexibility, weldability, convenient and economical laying, safe and reliable use, etc.

For drinking water supply pipes, the color of the pipes is blue or black pipes with blue strips.

2.

Because polyethylene pipe has good resistance to rapid crack transmission, it has become the first choice for medium and low pressure buried gas pipes in cities and towns.

According to the requirements of the international standard ISO4437-1:2014 "Buried Polyethylene Pipe (PE) for Gas-Metric Standard-Specification" and GB 15558.

In the 21st century, my country has begun to implement the energy structure adjustment plan, make full use of natural gas resources, and greatly increase the proportion of natural gas in energy.

On March 19, 2019, the seventh meeting of the Central Comprehensive Deepening Reform Committee was held to deliberate and pass the "Implementation Opinions on the Reform of Oil and Gas Pipeline Network Operation Mechanism.

In China, Qilu Petrochemical Company, Shanghai Petrochemical Company, Yanshan Petrochemical Company, Yangzi Petrochemical Company and Dushanzi Petrochemical Company have all started the development of special materials for polyethylene gas pipes, but only YHG041T of Shanghai Petrochemical Company and Dushanzi Petrochemical Company are mass-produced.

At present, safety issues are serious, and the quality requirements for gas pipes are very strict.

3.

PE100-RC resin is known as the 4th generation pipe resin.
Under the full-notch creep test (FNCT) test conditions, its resistance to slow crack growth exceeds 8760h.
Because of its excellent resistance to slow crack growth (as shown in Figure 1), it is also called "super tough PE100 resin".

Compared with ordinary PE100 pipes, under the same conditions, this product can not only bring longer service life and higher safety, but also adopts modern non-traditional pipeline installation technology, which can be used for pipeline renewal, trenchless installation and pipeline Construction such as rapid laying can reduce the difficulty of pipe construction and greatly reduce construction costs.

In terms of polymerization process, PE100-RC resin is produced by optimizing the balance between polyethylene chain entanglement and crystallinity through the design of molecular structure.
Among them, the bimodal polymerization process generally uses 1-hexene as a comonomer, and Lyondell Basel Industries uses Hostalen ACP (Advanced Cascade Process) three-pot tandem process technology and 1-butene as a comonomer to produce crack-resistant polyethylene.

In China, Sinosand (Tianjin) Petrochemical, Dushanzi Petrochemical, and Sino-Korea (Wuhan) Petrochemical Company produced PE100-RC pipe material using the InnoveneTMS double-ring pipe slurry polymerization process, and Shanghai Petrochemical Company adopted the patented technology of Borstar.
The crack-resistant polyethylene PE100-RC pipe special material YHG041RC is used.

In the relevant domestic standards, GB15558.
1-2015 "Buried Polyethylene (PE) Piping System for Gas Use Part 1: Pipes" in Appendix D, it is recommended to adopt some special laying environment (such as backfill without sand bed) or non-opening In areas such as excavation and construction, it may be necessary to use PE100 blends with high resistance to slow crack growth.

4.
Low melt sag and large diameter polyethylene pipe material

Compared with traditional ductile iron, large-diameter polyethylene pipes have the advantages of sanitation, corrosion resistance and good welding performance.
Therefore, they are widely used in sewage discharge, marine aquaculture, seawater desalination projects, and industrial cooling water supply.

However, in the production of large-caliber polyethylene pipes, with the increase of the maximum working pressure, the wall thickness of the pipes gradually increases, the cooling and solidification speed is slow, and the melt will sag under the action of gravity, resulting in a small upper wall thickness and a lower wall thickness.
Thickness is the sag effect.

Therefore, it is necessary to select special raw materials, that is, special materials for low-melting polyethylene pipes, to make the wall thickness of the produced pipes uniform.
For bimodal polyethylene pipes, in order to obtain products with good sag resistance, it is necessary to increase the weight-average relative molecular mass of the pipe material to increase the content of the high-molecular-weight part.

Some domestic petrochemical enterprises have developed special materials for low-melting large-diameter polyethylene pipes by optimizing the process conditions of bimodal polyethylene polymerization and balancing the relationship between product processing performance and mechanical properties.

Jilin Petrochemical Company used the Hostalen slurry polymerization device to optimize the process based on the process of the bimodal PE100 pipe material JHMGC100S, and successfully developed a special material for low melting and large diameter polyethylene pipes, and the product quality has been recognized by users.

Dushanzi Petrochemical Company developed a single-reactor bimodal low-melting large-diameter polyethylene pipe special material UHXP-4808 using imported PRODIGY BMC-200 catalyst on the Unipol full-density polyethylene plant.

Shanghai Petrochemical Company used Borealis' Borstar technology to successfully develop YHG041LS special material on the 4PE device.
The specific production situation of domestic low-melting large-diameter pipe materials is shown in Table 2.

5.
Heat-resistant polyethylene (PE-RT) pipe material

PE-RT is a copolymer of ethylene and α-olefin.
It has the advantages of environmental protection, high temperature resistance, easy installation, and recyclability, making it the main material for floor heating pipes, aluminum-plastic composite pipes, and oil pipelines.

The international standard ISO22391-2:2009 divides PE-RT pipes into two types, namely Type I and Type II.
According to the requirements of the standard, the hydrostatic curve of type I PE-RT pipe can have an inflection point under the temperature conditions below 110 ℃; the hydrostatic curve of type II PE-RT pipe cannot have an inflection point under the temperature conditions of 110 ℃ or less, that is to say, it is clear that Ⅱ Type PE-RT pipe has better temperature and pressure resistance than Type I PE-RT pipe.

In recent years, domestic petrochemical companies have accelerated the pace of research and development of PE-RT pipe special materials, breaking the monopoly of foreign petrochemical companies.

Fushun Petrochemical Company used the Sclaritech solution process of Canadian NOVE to develop a special resin for ethylene and octene copolymerized PE-RT pipes, which filled the gap in my country's polyethylene products with octene as a comonomer.

Qilu Petrochemical Company uses metallocene catalysts to produce ethylene and hexene copolymer product QHM22F in Unipol gas phase polyethylene plant, and then develops QHM32F.
In 2019, the output of QHM32F surpassed QHM22F, realizing the upgrade and replacement of PE-RT products.

Lanzhou Petrochemical Company and Yangzi Petrochemical Company developed Sanfeng PE-RT pipe material by using Mitsui CX process, through technological transformation and technological innovation.
Table 3 shows the production status of PE-RT from major domestic manufacturers.

6.
Development suggestions

Inspired by my country's urbanization pipeline network construction and coal-to-gas policy, the country has increased investment in agriculture and water conservancy and other infrastructure construction, which has promoted the development of my country's plastic pipeline industry.
However, with the successive commissioning of refining and chemical integration projects in the next few years, the market competition for PE pipes will become more intense.

If you want to stand out in a highly competitive market, it is recommended to work in the following areas:

(1) Increase the research and development of high-end catalysts and realize localization.
As the core technology of polyethylene production, catalyst directly affects the final performance of the product.
At present, some pipe catalysts still rely on foreign imports, which are relatively expensive.
Therefore, realizing the localization of high-end catalysts is of great significance for improving the level of technological innovation in the field or improving product quality.

(2) Develop high-performance and high-value-added pipe special materials.
Compared with foreign manufacturers, there are fewer manufacturers of special materials for gas pipes, and the color is single.
It is necessary to develop orange or yellow pipe materials with advantages in color management and water absorption.
In addition, for PE100-RC pipe material, although some manufacturers have produced small batches and completed relevant certification work, it will take some time to cultivate the market, and it is necessary to increase market development efforts.

(3) Gradually establish a perfect integrated technical service system for production, marketing and research to improve the level of technical support.
In the face of ever-increasing market competition, how to provide high-level technical services and stabilize the user base is extremely important.
The major domestic petrochemical companies should establish a working idea of ​​integrating production, marketing and research, starting from the production of materials, polymer structure analysis and characterization, pipe processing and construction quality, etc.
, to provide customers with strong technical support.

(4) Overall planning and rational layout of industrial development.
All petrochemical companies should establish a departmental coordination mechanism, do a good job in top-level design and planning, and conduct scientific demonstrations in terms of raw material sources, technology selection, production capacity layout, etc.
, to reduce investment risks and avoid disorderly competition among homogeneous products.

(Keyword: polyethylene pipe)