According to the source of ingredients, biodegradable plastics can be divided into bio-based degradable plastics and petroleum-based degradable plastics. At present, they have begun to be used in many fields such as disposable tableware, packaging, agriculture, automobiles, medical treatment, and textiles. Deploy biodegradable plastics one after another, and strive to seize market opportunities ahead of time. So if our friends in the plastics industry want to get a share of the biodegradable materials industry, how should we proceed? How to distinguish between bio-based and petroleum-based degradable plastics? Which ingredients and technologies in the product formula are the key, and under what conditions can the degradable materials decompose to reach the standard......
Polypropylene (Polypropylene) is a widely used polymer material, referred to as PP, which has better thermoplastic properties. Due to its colorless, odorless and non-toxic physical properties, it is currently used as a lightweight general-purpose plastic. Polypropylene has excellent performance, safety and non-toxicity, low-cost and easy-to-obtain raw materials, and the prepared products are light and environmentally friendly materials. It has been used in product packaging, chemical raw materials, auto parts, construction pipes and other fields.
1. Introduction to the production process of polypropylene products
In the 1950s, research on polypropylene synthesis technology began. From the most traditional solvent polymerization method (also known as mud method) to a more advanced solution polymerization method, it has developed to the current liquid phase bulk and gas phase bulk polymerization method. With the continuous development of the production process, the most primitive solvent polymerization The law is no longer used in the industry.
Throughout the world’s advanced production technology of polypropylene, basell’s annual production of polypropylene exceeds 50% of the world’s total output, mainly using the Spheripol double-loop gas phase polymerization process; in addition, the Spherizone polypropylene synthesis pioneered by basell has been developed and put into production. The technology, the Borstar polypropylene synthesis process developed and put into production by Borealis have been widely used.
1.1 Spheripol process
The Spheripol double-loop gas phase polypropylene technology developed and put into operation by basell is the most experienced new type of polypropylene synthesis process. Compared with the traditional production process, the produced polypropylene products have better quality and larger output.
A total of four generations of catalysts have been improved. At present, a polypropylene synthesis reactor with a double-loop structure has been formed, and a variety of excellent polypropylene products have been produced on the basis of this process. The double-loop tube structure can obtain polypropylene products with better performance by changing the pressure in the synthesis process, and realize the regulation of the mass of polypropylene macromolecules and the morphology of polypropylene macromolecules; the fourth-generation catalyst obtained after multiple improvements, The catalyzed polypropylene product has higher purity, better mechanical properties, and higher wear resistance.
Due to the use of the double-ring tube reaction structure, the production operation can be more convenient; the reaction pressure is increased, so the hydrogen content in the entire production process is increased, which improves the various properties of polypropylene products to a certain extent; at the same time, based on the excellent double-ring tube structure It is capable of producing relatively higher-quality macromolecules and smaller-quality polypropylene products, so that the molecular weight distribution range of the produced polypropylene products is larger, and the obtained polypropylene products are more homogeneous.
This structure can better promote the heat transfer between the reaction materials. If combined with the more advanced metallocene catalysts, polypropylene products with better performance will be prepared in the future. The double loop reactor structure improves production efficiency, makes the production process more convenient and flexible, and to a certain extent increases the output of polypropylene products.
1.2 Spherizone process
Due to the current rising demand for bimodal polypropylene, basell has developed a brand new production process. The Spherizone process is mainly used for the production of bimodal polypropylene. The main innovation of the production process is that in the same reactor, the reactor is partitioned, and the reaction temperature, reaction pressure and reaction pressure in each reaction zone can be individually controlled. The hydrogen concentration is circulated in the reaction zone with different production conditions and controllable production conditions during the continuous growth of polypropylene molecular chain when synthesizing polypropylene. On the one hand, bimodal polypropylene with better performance is synthesized. On the other hand, the obtained polypropylene product has better uniformity.
1.3 Borstar process
The Borstar polypropylene synthesis process is based on the polypropylene synthesis process of basell Corporation by Borealis, based on the double-loop structure reactor, and the gas-phase fluidized bed reactor is connected in series at the same time, thereby producing polypropylene with better performance. product.
Prior to this, all polypropylene synthesis processes controlled the reaction temperature at about 70°C to avoid the generation of bubbles during the production process and make the polypropylene products more homogeneous. The Borstar process designed by Borealis allows a higher operating temperature, which can even exceed the critical value of propylene operation. The increase in temperature also promotes the increase in operating pressure, and there are almost no bubbles in the process, which is a kind of performance. It is an excellent polypropylene synthesis process.
The current characteristics of the process are summarized as follows: First, the catalyst activity is higher; second, the gas phase reactor is connected in series on the basis of the double loop tube reactor, which can more conveniently control the molecular mass and the morphology of the synthesized macromolecule ; Third, each peak obtained during the production of bimodal polypropylene can achieve a narrower molecular mass distribution, and the quality of bimodal products is better; fourth, the operating temperature is increased to prevent the polypropylene molecules from being dissolved in The phenomenon of propylene will not cause polypropylene products to stick to the inner wall of the reactor.
2. Progress in the application of polypropylene
Polypropylene (Polypropylene) has been used in many fields such as product packaging, daily necessities production, automobile manufacturing, building materials, medical equipment, etc. due to its mature production process, cheap and easy-to-obtain raw materials, safe, non-toxic and environmentally friendly products. Due to the current pursuit of green life and more requirements for environmental protection, polypropylene has replaced many materials with poor environmental friendliness.
2.1 Development of polypropylene products for pipes
Random copolymer polypropylene pipe, also known as PPR, is one of the most demanded polypropylene products at present. It has good mechanical properties and strong impact resistance. The pipe prepared from it as a raw material has high mechanical strength, light weight, and wear resistance. Corrosion resistant and convenient for further processing. Because it can withstand high temperature and hot water, it has a long service life based on quality inspection, good product quality and high stability, and it has been widely used in cold and hot water transportation.
Due to its stable performance, safety and reliability, and reasonable price, it is listed as the recommended pipe fitting material by the Ministry of Construction and other relevant departments. It should gradually replace traditional pipes with green environmental protection pipes such as PPR. Under the government’s initiative, my country is currently under construction. More than 80% of residences use PPR green pipes. With the rapid development of my country's construction industry, the demand for PPR pipes is also increasing. According to statistics, the average annual demand is about 200kt.
2.2 Development of film polypropylene products
Film products are also one of the most in demand polypropylene products. Film manufacturing is an important way for polypropylene applications. According to statistics, about 20% of the polypropylene produced each year is used to produce films. As polypropylene film is stable and environmentally friendly, it can be used in a variety of product packaging, as various insulating materials in precision products, and can also be used in many fields such as building materials. Especially in recent years, more polypropylene film materials with higher added value have been developed. For example, propylene-ethylene-1-butene ternary copolymer polypropylene film can be used for low-temperature heat-sealing layer, which has greater market demand.
Compared with traditional film-type heat-sealing layer materials, it can also achieve better mechanical strength and impact resistance. There are many types of film products, and representative films that are in greater demand are: biaxially oriented BOPP film, cast polypropylene CPP Film, CPP film is mostly used for food and pharmaceutical product packaging, BOPP film is mostly used for product packaging and the production of adhesive products. According to data, my country currently needs to import about 80kt of film-like polypropylene materials every year.
2.3 Development of polypropylene products for vehicles
After being modified, polypropylene material has better processing properties, high mechanical strength, and can maintain good performance after multiple impacts. It conforms to the development concept of safety and environmental protection. Therefore, it has been widely used in the automotive field.
At present, polypropylene products are used in various auto parts such as dashboards, interior materials, and bumpers. Modified polypropylene products have now become the main plastic products for auto parts. Especially, there is still a large gap in high-end polypropylene materials, and the development prospects are optimistic.
With the continuous improvement of my country's current requirements for automobile production and increased awareness of environmental protection in the field of automobile manufacturing, the development of the automobile industry must solve the problem of recycling and reuse of polypropylene materials for automobiles. The main problems of polypropylene products used in the automobile industry are currently Because of the lack of supply of high-end polypropylene products, it is required that polypropylene products should be green, environmentally friendly, pollution-free, have higher heat resistance, higher mechanical strength, and stronger chemical corrosion resistance.
In 2020, my country will implement the "National VI" standard, and the development of lightweight cars will be implemented. Polypropylene products are cost-effective and lightweight. They will have more advantages and will be more widely used in the automotive industry.
2.4 Development of medical polypropylene products
Polypropylene synthetic material is safe and non-toxic, and has lower production costs, and is more environmentally friendly in use. Therefore, it is mostly used in the preparation of various disposable medical products such as drug packaging, syringes, infusion bottles, gloves, and transparent tubes in medical equipment. The replacement of traditional glass materials has basically been achieved.
With the increasing requirements of the general public for medical conditions and my country’s increasing investment in scientific research on medical equipment, the consumption of polypropylene products in the medical market will greatly increase. In addition to the manufacture of such relatively low-end medical products, Used to prepare high-end medical materials such as medical non-woven fabrics and artificial kidney splints.
3. Summary
Polypropylene is a widely used polymer material with mature production technology, cheap and easy-to-obtain raw materials, safe, non-toxic and environmentally friendly products. It has been used in product packaging, daily necessities production, automobile manufacturing, construction materials, medical equipment and other fields. .
At present, most of the polypropylene production equipment, production processes, and catalysts in our country still use foreign technology. The research on polypropylene production equipment and processes should be accelerated, and a better polypropylene production process should be designed on the basis of absorbing foreign experience. At the same time, it is necessary to increase scientific research investment, research and develop polypropylene products with better performance and higher added value, and improve my country's core competitiveness.
Driven by environmental protection policies, the application of biodegradable plastics in disposable tableware, packaging, agriculture, automobiles, medical treatment, textiles and other fields is ushering in new opportunities for market development.
