What safety precautions should be paid attention to in synthetic resin processing?

Synthetic resin processing involves melting, mixing, molding, curing and other processes. In the process, it will come into contact with high temperature, high pressure, flammable and volatile monomers/additives, and may also produce dust and toxic gases. Fire prevention, explosion prevention, poisoning prevention, mechanical injury prevention and high temperature burn prevention are the core safety points. The details of different processing technologies (injection molding, extrusion, molding, winding, gluing, etc.) are slightly different. The following are general and must be observed.

First, preliminary preparation: material and environment control

Material classification management

Synthetic resins (such as epoxy resin, polyurethane, phenolic resin and acrylic resin) and auxiliary agents (curing agents, diluents, plasticizers and solvents) are mostly flammable, explosive and toxic substances (such as benzene solvents, isocyanates and amine curing agents), which need to be stored according to the requirements of hazardous chemicals: stored separately in a cool and ventilated warehouse away from fire sources/heat sources. It is forbidden to mix acid, alkali and oxidant, and equipped with leakage-proof cofferdams and. The principle of "small quantity and multiple times" is followed, and there is no hoarding on site.

The working environment is up to standard

The processing workshop must be well ventilated, equipped with a forced exhaust system (especially in the closed molding area), and equipped with a special tail gas treatment device for toxic and harmful gases (such as formaldehyde, styrene and isocyanate); Smoking, naked flame and kindling are strictly prohibited in the workshop. Fire and explosion warning and electrostatic discharge device are set at the entrance of the workshop.

Inspection of equipment and tools

Before starting, check whether the temperature control, pressure and transmission system of processing equipment (injection molding machine, extruder, mixer, hot press, etc.) are normal and whether the safety protection devices (protective cover, emergency stop button, overtemperature/overpressure alarm) are in good condition; Check the pipelines (raw material conveying, cooling water and steam) for no leakage, and the electrical equipment is explosion-proof (suitable for the process with solvent volatilization) to avoid the danger caused by electrical sparks.

Second, the core process: operating safety specifications

(1) Melting/mixing/plasticizing (high temperature processes such as injection molding, extrusion and granulation)

Strictly control the temperature, rotating speed and pressure according to the process parameters of the resin, so as to avoid the decomposition and carbonization of the resin caused by overtemperature, producing toxic gases (such as formaldehyde released by phenolic resin overtemperature and hydrogen chloride released by PVC overtemperature), and even causing spontaneous combustion of materials.

Wear high-temperature protective gloves, goggles and anti-scalding work clothes when operating high-temperature equipment to avoid direct contact with molten resin, high-temperature barrel and mold to prevent burns; It is forbidden to clean the sticky materials in the equipment directly by hand, and use special tools (copper scraper to avoid sparks).

In case of material blockage and overpressure during equipment operation, stop the machine for cooling and pressure relief before handling, and it is forbidden to operate under pressure; When cleaning the equipment surplus materials, it shall be carried out after the materials are completely cooled to prevent the residual high-temperature materials from splashing.

(2) Forming/curing (molding, pouring, winding, gluing, etc.)

During the construction of resins (such as unsaturated polyester and epoxy resin) involving solvent dilution, ventilation must be ensured, and gas masks/activated carbon masks and nitrile gloves must be worn to avoid solvent vapor inhalation and skin contact (some solvents/curing agents are corrosive and allergenic, such as isocyanate can irritate respiratory tract and skin).

If there is exothermic reaction in the curing process (such as polyurethane and epoxy resin curing at room temperature), it is necessary to control the feeding amount and curing environment temperature to avoid local heat accumulation leading to material explosion, expansion and even mold explosion; When curing large products, temperature measuring points should be set to monitor the temperature in real time.

When manual operations (such as paving and pouring) are carried out, it is necessary to avoid the mess at the site and prevent tripping and falling; When using pressure molding equipment (such as hot press and hydraulic press), make sure that the mold is firmly positioned, and it is forbidden to put hands and arms into the mold clamping area to prevent extrusion injury.

(3) Cutting/grinding/post-treatment

Resin dust will be produced when resin products are cut and polished. Wear dust masks and goggles, and install dust collection devices in the operation area to clean the dust regularly to avoid respiratory diseases caused by dust inhalation or dust explosion (such as polystyrene and polypropylene dust) when dust accumulates in an open flame.

When using cutting and grinding equipment, check that the protective cover is in good condition, and it is forbidden to remove the protective device for operation; Keep a safe distance between the hand and the cutter/grinding wheel during operation to prevent mechanical injury.

When it comes to post-treatment of chemicals (such as glue removal and cleaning), use special cleaning solvent to avoid reacting with resin or additives and producing toxic gas; The waste liquid after cleaning shall be collected according to the requirements of hazardous chemicals, and it is strictly prohibited to discharge it at will.

III. Material Contact: Poisoning Prevention and Protection

Skin protection: Avoid direct contact with chemicals such as resin, curing agent and solvent. Wear chemical-resistant gloves (NBR and neoprene, avoid using latex gloves, which are easy to be corroded by solvents), long-sleeved work clothes and protective shoes when working. If the skin comes into contact with chemicals, rinse with plenty of water immediately. After contacting corrosive materials (such as strong acid curing agent), rinse with weak alkaline solution (such as soapy water) first, and then seek medical treatment.

Respiratory protection: choose protective articles according to the working environment: wear an activated carbon respirator/semi-mask when the solvent volatilizes, and wear a positive pressure air respirator when the concentration of toxic gas is high; Wear KN95 and above dust mask in dust environment to avoid inhaling dust for a long time.

Eye protection: Wear goggles all the time to prevent resin liquid, solvent, dust and debris from splashing into eyes; If eyes come into contact with pollutants, immediately rinse with clean water for more than 15 minutes, and seek medical attention in time.

Emergency eye washer and shower device shall be set at the job site, and they shall be available at any time; Regularly carry out occupational health examination for operators, and investigate respiratory tract, skin and eye injuries.

Fourth, equipment and electricity: the key to fire and explosion prevention

In all processing areas involving solvent volatilization and combustible gas generation, combustible gas detectors and smoke alarms must be installed, which are linked with the exhaust system and fire fighting equipment, and will automatically give an alarm and start the exhaust when exceeding the standard.

Electrical equipment, lines and switches are all explosion-proof grade (such as Ex d IIB T4) to avoid fire and explosion caused by electrical sparks and electrostatic sparks; Operators shall wear anti-static work clothes and shoes, and the raw materials shall be conveyed and the equipment shall be grounded well to prevent static electricity accumulation.

The workshop is equipped with dry powder fire extinguishers, carbon dioxide fire extinguishers and fire-proof sand (suitable for resin fires, and it is forbidden to use water to put out molten resin and solvent fires), and the fire-fighting equipment is placed in an easy-to-access position, and its effectiveness is checked regularly.

When the equipment is overhauled, stop the machine, cut off the power and give a warning, clean and replace the flammable materials in the barrel and pipeline, and then carry out the overhaul operation after the concentration of flammable gas reaches the standard, so as to avoid the danger caused by sparks in the overhaul process.

V. Waste and Emergency: Follow-up Management Requirements

Waste disposal: waste materials (waste resin, adhesive, solvent waste liquid and dust) generated during processing are collected according to hazardous chemicals and handed over to qualified units for disposal. It is strictly forbidden to throw away or burn them at will (some resins will produce toxic gases such as dioxin); Wastes such as rags and gloves stained with chemicals shall be sealed for centralized treatment.

Leakage emergency: in case of resin and solvent leakage, immediately stop the machine, cut off the fire source and evacuate the site personnel; Use sand and absorbent cotton to absorb the leakage, and it is forbidden to use water to shower (the solvent will spread with the water flow, expanding the danger range); The leaked area shall be cleaned after ventilation, and the cleaned waste shall be treated as hazardous waste.

Accident handling: In case of fire, immediately start the fire-fighting equipment, cut off the power supply, evacuate people and call 119; In case of personnel poisoning, burns and mechanical injuries, take immediate emergency measures (washing and bandaging) and send them to hospital for medical treatment; The workshop formulates special emergency plans and organizes emergency drills regularly.

VI. Personnel Management: Training and System

All operators must undergo professional safety training and operation training, be familiar with the physical and chemical properties, process parameters and safety risks of the processed resin, master emergency disposal methods, and take up their posts only after passing the examination; Unlicensed operation and illegal operation are strictly prohibited.

Establish and improve the safety management system, including equipment operation procedures, hazardous chemicals management system and work permit system (such as hot work and confined space operation need approval); Maintain the equipment, protective devices and fire-fighting equipment regularly and make records.

Clear safety warning signs (fire prevention, explosion prevention, gas protection, mechanical injury prevention, etc.) shall be set on the job site, and irrelevant personnel are strictly prohibited from entering the processing area.

Seven, special resin: targeted safety points

Some synthetic resins have exclusive safety requirements, which require extra attention:

Polyurethane resin: isocyanate monomer is easy to absorb moisture and decompose to produce toxic gas, which will react violently when it comes into contact with amines and water. It should be kept dry during storage and operation, and it is strictly forbidden to mix with water, acid and alkali; The heat release is obvious during curing, and the feeding amount is strictly controlled.

Phenolic resin: high-temperature processing releases formaldehyde, so it is necessary to strengthen ventilation and wear a special gas mask for formaldehyde; The resin is brittle after curing, and there is more dust when polishing, so dust prevention measures should be strengthened.

Unsaturated polyester resin: Styrene is used as cross-linking agent, which is volatile, flammable and toxic. Open fire is strictly prohibited in the operation area, and the ventilation should be strengthened to prevent vapor accumulation.

Polyvinyl chloride (PVC): It is easy to decompose and release hydrogen chloride when processed at high temperature (over 180℃), and the processing temperature is strictly controlled. It is equipped with an acid gas absorption device, and the operators wear acid protection articles.