What Is Synthetic Resin?

Synthetic resin is a kind of artificially synthesized high molecular weight polymer. It is a resin that has or exceeds the inherent characteristics of natural resins. ASTM D883-65T defines synthetic resins as solid, semi-solid, or pseudo (quasi) solid organic substances with an unrestricted molecular weight but often high molecular weight. They tend to flow when stressed, often have a softening or melting range and when broken Shell-shaped.

In practical applications, it is often used synonymously with polymers and even plastics, especially referring to the basic materials produced by the polymerization reaction of the monomers without any additives or with only a small amount of additives. In addition, it is sometimes used to represent uncured flowable thermosetting polymer materials. ^[1]

The world's three largest synthetic materials include synthetic resins, synthetic rubber and synthetic fibers. Synthetic resin is the synthetic material with the highest output and consumption.

Chinese name: Synthetic resin

Foreign name: synthetic resin

Application field of synthetic resin

The most important application of synthetic resins is the manufacture of plastics. In order to facilitate processing and improve performance, additives are often added, and sometimes they are also directly used for processing and forming, so they are often synonymous with plastics. The content of synthetic resin in plastic is generally 40 ~ 100%. Because of the large content, and the nature of resin often determines the nature of plastic, people often regard resin as a synonym for plastic. For example, polyvinyl chloride resin is mixed with polyvinyl chloride plastic, phenolic resin is mixed with phenolic plastic. In fact, resin and plastic are two different concepts. Resin is an unprocessed virgin polymer that is used not only to make plastics, but also to make coatings, adhesives, and synthetic fibers. In addition to a very small part of plastic containing 100% resin, most plastics, in addition to the main component resin, also need to add other substances.

Synthetic resin is also the basic raw material for the manufacture of synthetic fibers, coatings, adhesives, insulation materials, etc. The widely used resin concrete also uses synthetic resin as the cementing material. Because synthetic resin has obvious performance and cost advantages compared with other competitive materials, its application has penetrated into all aspects of the national economy. Packaging is the largest market for synthetic resins, followed by construction supplies. Electronics, electrical and automotive are also important applications for synthetic resins. Other markets include furniture, toys, entertainment, home appliances and medical supplies.

Basic types of synthetic resin

There are many types of synthetic resins.

Synthetic resin industrial products can be divided into general resins and special resins. General resin has large output and low cost. It is generally used for general consumer goods or durable goods. Typical varieties are polyethylene, polypropylene, polyvinyl chloride, polystyrene, and ABS. The five major types of synthetic resins are used for special purposes. The production of resin has a small output and a high production cost. For example, it can replace metals for machinery, electronics, and automobiles. Engineering plastics belong to the category of special resins. Important engineering plastics are polyamide, polycarbonate, polyoxymethylene, polybutylene terephthalate, modified polyphenylene ether and polytetrafluoroethylene. Another type of special resin is a thermoplastic elastomer, which has rubber-like elasticity and can be repeatedly molded when heated. ^[2]

According to the chemical composition, synthetic resins can be roughly divided into two categories: one kind of main chain is only composed of aliphatic carbon atoms, and general resins basically belong to this category; the other kind of synthetic resin contains in addition to carbon atoms in the main chain Oxygen, nitrogen, sulfur, etc., most engineering plastics are composed of hetero-chain polymers.

According to engineering properties, synthetic resins can be divided into thermoplastic resins and thermosetting resins. The difference mainly comes from the chemical composition and molecular structure of the polymer. The thermoplastic resin molecular chain structure is linear or branched, and can be plasticized (or softened, melted) and flowed after being heated. Typical thermoplastic resins are polyethylene, polypropylene, poly 1-butene, polyvinyl chloride, polystyrene, and the like. Thermoplastic resins can be formed quickly and repeatedly. Thermosetting resin is a three-dimensional high-molecular polymer. It contains multifunctional macromolecules in the molecular chain. It can be softened (or melted) under the presence of a curing agent, heated and pressurized, and simultaneously cured (or cured) to become insoluble Infusible polymer. Typical typical thermosetting resins are phenol-formaldehyde resin (commonly known as phenolic resin), urea-formaldehyde resin (commonly known as urea-formaldehyde resin), melamine formaldehyde resin (commonly known as melamine formaldehyde resin), epoxy resin, unsaturated polyester resin, polyurethane, etc.

Preparation method of synthetic resin

Synthetic resin is a high molecular compound, which is produced by combining low molecular raw materials-monomers (such as ethylene, propylene, vinyl chloride, etc.) into large molecules through polymerization. Polymerization methods commonly used in the industry include bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, slurry polymerization, and gas phase polymerization. There are abundant sources of raw materials for the production of synthetic resins. In the early days, coal tar products and calcium carbide were mainly used in calcium carbide. Nowadays, they are mostly oil and natural gas products, such as ethylene, propylene, benzene, formaldehyde and urea.

Ontology aggregation

Bulk polymerization is the polymerization process of monomers under the action of initiators or heat, light, and radiation without adding other media. It is characterized by pure product, no complicated separation and purification, simple operation and high utilization rate of production equipment. It can directly produce quality products such as pipes and plates, so it is also called block polymerization. Disadvantages are that the viscosity of the material increases with the progress of the polymerization and reaction, mixing and heat transfer are difficult, and the reactor temperature is not easy to control. Bulk polymerization is commonly used in the production of polymethyl methacrylate (commonly known as plexiglass), polystyrene, low density polyethylene, polypropylene, polyester and polyamide.

Suspension polymerization

Suspension polymerization refers to a polymerization process in which monomers are dispersed into droplets under the action of mechanical stirring or shaking and a dispersant, which is usually suspended in water, so it is also called bead polymerization. The characteristics are: there is a large amount of water in the reactor, the material has low viscosity, and it is easy to transfer heat and control; after polymerization, it only needs simple separation, washing, drying and other procedures to obtain resin products, which can be directly used for molding and processing; And even. The disadvantage is that the reactor production capacity and product purity are inferior to the bulk polymerization method, and furthermore, continuous production cannot be used. Suspension polymerization is widely used in industry.

Emulsion polymerization

Emulsion polymerization refers to the polymerization of monomers to form an emulsion in water with the aid of an emulsifier under mechanical stirring or shaking. The emulsion polymerization reaction product is a latex, which can be applied directly, or the latex can be destroyed, and a powder or needle-like polymer can be obtained through post-processing steps such as washing and drying. Emulsion polymerization can obtain polymers with higher molecular weights at higher reaction speeds, low viscosity of the materials, easy heat transfer and mixing, easy production control, and easy removal of residual monomers. The disadvantage of emulsion polymerization is that the emulsifiers added during the polymerization process affect the product performance. In order to obtain a solid polymer, it takes a coagulation, separation, washing and other processes. The production capacity of the reactor is lower than that of the bulk polymerization method.

Solution polymerization

Solution polymerization is carried out in the presence of a solvent. The solvent chosen must be capable of dissolving both monomers and polymers. During the polymerization process, the system was a homogeneous, viscous solution. The polymerization system was always homogeneous. The continuous operation cycle was long and easy to operate. However, the viscosity of the system is relatively large. The advantage is that the homogeneous reaction is easier to control, and the molecular weight and its distribution can also be controlled appropriately. However, the solution polymerization system is viscous, which makes heat and mass transfer difficult and uneven.

Slurry polymerization

In slurry polymerization, a solvent is used or the monomer itself is used as a dispersion medium. The resulting polymer is insoluble in the dispersion medium, and is dispersed in the form of particles in the form of a slurry. Some earlier literature has attributed it to heterogeneous solution polymerization. This polymerization is characterized by a small viscosity of the system, which is easy to stir, easy to dissipate heat, and a higher monomer concentration can be used to increase the unit equipment productivity. At present, this method can be used for the production of high-density polyethylene and polypropylene.

Gas phase polymerization

In the gas-phase polymerization, a gas-phase monomer and a catalyst are introduced into the reactor in a prescribed amount for one-step synthesis to obtain a dried polymer. The premise of gas phase polymerization is that the catalyst selectivity and yield must be sufficiently high, and the obtained product does not need to remove the residual catalyst, which can greatly shorten the process. With the advent of highly active support Ziegler catalysts, gas phase polymerization has hitherto become mainstream in the manufacture of polyethylene or polypropylene. In addition, it can be widely used for polymerization by a free radical mechanism.

Synthetic resin processing method

The curing of thermoplastic resin is generally achieved by cooling the product to a temperature below the glass transition temperature or melting point, while the thermosetting resin achieves the purpose of curing by chemical reactions that form a network structure by heating. The main processing methods are extrusion, compression molding, injection molding, blow molding, rotational molding, reaction injection molding, thermoforming, foaming, etc.

History of synthetic resin

The secretions of some trees often form resin, but amber is the fossil of resin. Although shellac is also regarded as resin, it is the sediment that lac insects secrete on the tree. Shellac lacquer made of shellac was originally only used as a preservative for wood, but became the earliest insulating varnish with the invention of the motor. However, since the 20th century, natural products have been unable to meet the needs of electrification, prompting people to find new cheap substitutes.

As early as 1872, the German chemist A. Bayer first discovered that phenol and formaldehyde could quickly form red-brown hard masses or stickies when heated under acidic conditions, but the experiment was stopped because they could not be purified by classical methods. After the 20th century, phenol has been obtained in large quantities from coal tar, and formaldehyde has also been produced in large quantities as preservatives. Therefore, the reaction products of the two have attracted more attention, and hope to develop useful products, although many people have spent huge labor for it. , But did not achieve the expected results.

In 1904, Bakerland and his assistant also carried out this research. The original purpose was only to hope that it could be made of insulating paint instead of natural resin. After three years of hard work, not only the insulating paint was produced in the summer of 1907. And also made a real synthetic plastic material-Bakelite, it is known as "bakelite" "bakelite" or phenolic resin. Once Bakelite came out, manufacturers soon discovered that it can not only manufacture a variety of electrical insulation products, but also daily necessities. T. Edison was used to make records, and soon announced in the advertisement that thousands of them had been made with Bakelite. This kind of product, for a time, praised Beckland's invention as the "alchemy" of the 20th century.

Before 1940, coal tar-based phenolic resins always ranked first in the production of various synthetic resins, reaching more than 200,000 tons per year. However, with the development of petrochemicals, polymerized synthetic resins such as polyethylene The production of polypropylene, polyvinyl chloride, and polystyrene has also continued to expand. With the establishment of many large factories with an annual output of more than 100,000 tons of these products, they have become the four types of synthetic resins with the largest output today.

To this day, synthetic resins and additives are used to obtain plastic products through various molding methods. There are dozens of types of plastics. The world's annual output is about 120 million tons. China is also more than 5 million tons. They have become production, Basic materials for life and national defense.

Status of synthetic resin in China

In 2013, there were nearly 830 synthetic resin manufacturers in China, with an output of 58.37 million tons, an increase of 9.5% year-on-year.

In recent years, the engineering synthetic resin industry has developed strongly, and the output growth rate is significantly faster than that of general synthetic resins, resulting in a decline in the proportion of the five general synthetic resin production in the total synthetic resin output, from 84.1% in 2010 to 2013. 79.5% of the year.

Nonetheless, the five major synthetic resins maintained a rapid expansion in 2013. With the commissioning of large-scale ethylene plants in Wuhan and Ningbo Fude's outsourcing of methanol to propylene projects, the production capacity of the five major domestic synthetic resins increased sharply. By the end of 2013, The five synthetic resins have a production capacity of more than 64 million tons per year. Affected by the market recovery and the release of new plant capacity, the output of the top five domestic synthetic resins in 2013 was approximately 46.62 million tons, a year-on-year increase of 11.1%. Among them, polyethylene output was 112.43 million tons, an increase of 7.3% year-on-year; polypropylene output was 12.62 million tons, an increase of 9.6% year-on-year; polyvinyl chloride production was 15.3 million tons, an increase of 16.1% year-on-year. ^[3]

China's synthetic resin industry has made remarkable achievements in terms of domestic catalysts, processes and equipment development. Compared with foreign advanced level, China's synthetic resin industry still has a certain gap. Many new large-scale synthetic resin installations also rely on the introduction of technology. In order to produce high-end products, some units must also purchase foreign catalysts; the number of domestic high-end products cannot meet market demand, such as the low number of domestic resins for shed film and low output. It is far from meeting the demand for functional shed film production, and imported raw materials account for about 50%; there is still a certain gap between domestic PP-R pipe materials and imported materials, and the quality needs to be improved and improved.

The world's synthetic resin industry is facing competition from low-cost products from the Middle East. To cope with the competition, the world's large-scale resin production companies are allocating assets to the Middle East region with low-cost raw materials; building world-class large-scale production facilities to take full advantage of economies of scale; adopting more advanced Catalysts, process technology and more advanced computer control, optimization and management solutions. The resin industry is highly competitive. Under this situation, China's resin industry should further strengthen its independent innovation capabilities, better digest and absorb imported technologies, and produce more high-end products that cannot be produced by Middle East installations, do everything possible to reduce production costs, and respond to the Middle East, neighboring countries and major multinational companies. Competition for synthetic resin products. ^[4]

Development prospects of synthetic resins

With the changes in the world economic structure, the drastic adjustment of the US energy structure, and the changes in China's economic growth mode, in the context of energy conservation and environmental protection, changes in the competitive landscape of the chemical market and demand upgrades will bring about great changes in the industry.

From the perspective of the raw materials for the upstream device of synthetic resin, it is more diversified and lighter in order to improve the competitiveness of products. From the demand side, green, functional and differentiated requirements are put forward for synthetic resin products. From the perspective of trade, due to the low cost advantages brought by the US shale gas to its chemical industry, exports to China will increase in the future. From the perspective of domestic competition, coal chemical industry, propane dehydrogenation to propylene, and methanol to olefins will pose huge challenges to the traditional petrochemical industry. In the short term, domestic synthetic resin production capacity has grown significantly, and demand continues to be sluggish. Synthetic resin will still be in a low profit period within 2 to 3 years.

Facing the severe market, China's synthetic resin must take the road of technological innovation. China's synthetic resin companies must first improve the technical content of their products, break through high-tech barriers, and lock in users; second, they must strengthen product technical services and after-sales services, so that users have the highest cost-effectiveness under the premise of appropriate purchase costs; Competitive users can choose to visit, tailor-made products, strengthen quality management, increase certification, etc. according to the requirements of the other party, binding high-end customers.