The most popular synthetic resin and plastic produ

2022-08-05
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Safety in production of synthetic resin and plastics (III)

phenolic resin is a general term for synthetic resin prepared by polymerization of phenol and aldehyde, of which phenol formaldehyde resin is the most important. Phenolic resin has two types: thermoplastic and thermosetting. It is used to manufacture plastics, coatings, adhesives and synthetic fibers. Polymethylmethacrylate (PMMA) is a thermoplastic resin prepared by polymerizing methyl methacrylate (MMA). Most of them are amorphous polymers, and the relative molecular weight is often as high as 1million. The main variety is five color solid prepared by bulk polymerization. It is an excellent organic transparent material, commonly known as plexiglass. Main applications: manufacturing cockpit cover, windshield and extruded products, leather decoration, lamp coating, etc

in addition, there are urea formaldehyde resin, epoxy resin, alkyd resin, fluororesin, cellulose resin, silicone resin, furan resin and other synthetic resins, which are rich raw materials for plastic products

although the company structure has changed, the specific hazards of synthetic resin production are the same as those of oil refining production and petrochemical industry. It largely depends on the raw materials used in the production of synthetic resin, such as ethylene, propylene, hydrocyanic acid, styrene, benzene, p-xylene, vinyl chloride, formaldehyde and other substances, which are flammable, explosive and toxic. Fire and explosion are the main hazards in synthetic resin production. Various raw materials, catalysts and solvents for synthetic resins also have different properties of toxicity and occupational hazards

1. fire and explosion: because the monomer, solvent and catalyst of synthetic resin are flammable and explosive substances, the production unit is large-scale and the process is complex. The main production processes are carried out under the conditions of high temperature and high pressure. A little negligence will cause fire and explosion

triethyl aluminum, triisobutyl aluminum, isoamyl aluminum, and the mixture of monochloroethyl aluminum and dichloroethyl aluminum used in the synthetic resin can spontaneously ignite in the air and explode in the presence of water, which has a great fire risk. Once the catalyst is scattered on the ground, it shall be immediately sprinkled with dry yellow sand, swept into the iron container, moved to a safe area, and decomposed with water

polymerization is mostly carried out under high temperature, high pressure (even ultra-high pressure). If the proportioning of raw materials, polymerization temperature and reaction speed are not strictly controlled during operation, it is easy to cause a sharp increase in pressure in the reaction system, resulting in flushing or overtemperature polymerization. The explosion will cause equipment blockage and sudden pressure increase, resulting in equipment damage and material leakage, leading to fire and explosion. The corrosion, deformation, leakage, vibration and other conditions of reactors and pipe accessories of high-pressure and ultra-high pressure systems shall be regularly inspected to make them meet the requirements. The pressure gauge, safety valve, emergency vent, automatic alarm, interlocking and other safety accessories and control instruments shall be regularly checked to ensure sensitivity and reliability. In the negative pressure system, if the equipment is poorly sealed and the air leaks into the system, combustion and explosion will also occur. The efficiency of the condenser between the vacuum pump and the polymerizer is poor. The flammable liquid vapor cannot be condensed and discharged into the atmosphere to form an explosive mixture, which will also produce combustion and explosion in case of open fire. The failure of emergency discharge facilities for pressurized equipment and storage tanks, improper emergency discharge of flammable and explosive materials, and the absence of flame arresters in vent pipes all pose the risk of explosion and fire

in the process of resin production, the temperature of some reaction materials is higher than the spontaneous combustion point of the material. Once the equipment leaks, the materials will burn immediately. Most of the solvents used for polymerization are flammable, volatile and electrostatic substances. High speed leakage will produce electrostatic sparks and cause fire or explosion. Overflow occurs in suspension polymerization production. After the water evaporates, the unpolymerized monomer and initiator are attached to the surface of the equipment or the floor. It is very easy to burn and explode in case of fire source

after the resin polymerization reaction, during the discharge operation, the unresponsive monomers, solvents, emulsifiers, catalysts and initiators discharged will also cause fire and explosion hazards due to poor discharge operation mode or improper equipment material selection

most resins are flammable powder. When the concentration in the air reaches the explosion limit, the powder explosion accident will occur in case of fire source. The finer the dust particles, the greater the danger. Powder explosion is a threat to production in the process of pneumatic conveying, resin drying and product packaging of synthetic resin. Good anti-static measures shall be taken in the powder drying and conveying system, otherwise a large amount of static charge will accumulate and discharge, which will become the main fire source of resin conveying and drying system

in the whole production process of synthetic resin, burns may occur. Some additives and catalysts used in production will cause chemical burns when splashed into people's eyes and skin. There is a danger of scalding in the treatment and transportation of molten thermoplastics, and the monomer with low boiling point will absorb a large amount of domestic heat during the gasification of liquid materials, resulting in human frostbite accidents. For many mechanical equipment used in plastic forming processing, it is necessary to prevent mechanical injury accidents, such as three roll, four roll and multi roll extension press, which are easy to involve the operator's clothes, fingers, etc. Injection machine, laminator and blow molding machine are prone to hand injury accidents. Therefore, protective facilities shall be provided for the moving parts of the machine

2. toxicity: the production of synthetic resin is generally carried out in a closed system, which usually does not endanger human health. In case of poor industrial hygiene of the production environment or a large amount of leakage, the different nature of various chemical raw materials will also bring different hazards to human health

ethylene is an anesthetic. In case of a large amount of leakage, it is necessary to be alert to the anesthetic effect on the human body, but it can play a role quickly and recover quickly. Only when oxygen contains 94% ethylene can it be fatal

in the production of styrene copolymer, the most dangerous substances are acrylonitrile, styrene and methyl methacrylate. In case of serious leakage or overflow, these compounds can cause acute poisoning, coma and sequelae, such as toxic encephalopathy and severe toxic hepatitis

the alkyl aluminum used in the polymerization of olefins is particularly harmful to human body, because they can spontaneously ignite in the air, and will explode violently when encountering water. Their smoke can cause serious lung damage. Their solution is a hydrolysate containing HCl, which can cause painful burns

vinyl chloride (VCM) is a monomer with high toxicity, which is (8000 ~ 10000) × The concentration of 10-6 can cause acute poisoning, and when the concentration is as high as 0.12, people may die. Its chronic poisoning is also serious. Long term exposure to high concentration of vinyl chloride can cause "vinyl chloride disease" syndrome. It is characterized by neurotoxic symptoms, terminal microcirculation disorders, scleroderma, acrolytic osteolysis, liver and spleen diseases and so on. It has been confirmed that vinyl chloride is an industrial carcinogen. When PVC is burned, it can form some highly irritating substances, such as hydrochloric acid gas, phosgene, carbon monoxide and other toxic gases

the raw materials for the production of phenolic resin, amino resin and polyester resin have different degrees of irritation to human skin and mucous membrane, and can cause skin allergic reaction and inflammation; At the same time, pay attention to the harm of resin dust to human body. Long term inhalation of high concentration of resin dust will cause lung diseases

preventive measures

1. the design and layout of the plant shall be properly considered, and the fire and explosion-proof spacing shall comply with the requirements of fire prevention regulations in the design of petrochemical enterprises and code for fire protection design of buildings. The production of alkyl aluminum shall be separately arranged in a safe area away from the main production plant. The design of raw material storage area and material handling system should be reliable, which can greatly reduce the risk in production

2. training and education on safety technology and production technology shall be provided to the factory staff. The operators of each post must be trained and pass the examination before they can take up the post and operate independently. The factory shall regularly check the implementation of safety technical regulations and post operation methods. Each worker shall understand the flammable, explosive and toxic factors of his post, master the skills of troubleshooting and accident handling, and realize safe production

3. contingency activities should be carried out to prevent all kinds of accidents, especially major and catastrophic disasters. Emergency response plans should be developed, and sufficient fire-fighting equipment and anti-virus equipment should be equipped at the post. The fire-fighting capacity of the volunteer fire brigade composed of post workers, workshop managers and technicians should be regularly checked. Once an accident occurs, accident rescue should be carried out in time to avoid the expansion of the accident and reduce accident losses

4. eliminate running, emitting, dripping and leakage, and install combustible gas monitoring alarm at the position where combustible gas and combustible material vapor may accumulate to avoid accidents

5. install fixed and mobile ventilation and exhaust equipment in the synthetic resin production unit, increase the ventilation times in the plant or in a local area, and reduce the content of harmful substances in the air of the plant, so as to reduce the harm to workers; Regularly monitor the concentration of hazardous substances in the air near the plant, check the pollution source on the site according to the monitoring data, and plug the loopholes in time to reduce the concentration of hazardous substances in the air below the national industrial hygiene standards

6. strengthen personal protection measures for operators. The first is to educate workers to understand personal anti-virus measures and anti-virus principles of various equipment, consciously implement self-protection measures, and learn self-help and mutual help methods. The factory shall regularly conduct physical examination for the personnel exposed to toxic and harmful substances, transfer them from the on-site post for treatment as soon as possible in case of any abnormality, and gradually implement the regular off-duty recuperation system in the posts with high poison risk and serious harm, so as to effectively reduce the time of workers exposed to poisons

source: Encyclopedia of safety science and technology should be powered on and operated once a month.

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