Discussion on the safety technology of coating and

Introduction

most of the raw materials used in the process of coating production and coating operations contain volatile organic solvents, resins, pigments that are easy to catch fire and harmful to human health. Therefore, there is always the possibility of fire and even explosion in paint production and painting operations

fire: 1. Gas fire; 2. The oil is on fire; 3. Inflammable fire; 4. Electrical fire; 5. Metal fire; 6. Excess oxygen fire

explosion: 1. Mixed gas explosion; 2. Explosion of gas decomposition; 3. Dust explosion; 4. Explosion caused by mixing dangerous substances; 5. Explosion of explosive compounds; 6. Vapor explosion

dangerous substances: 1. Combustible gas; 2. Flammable liquid; 3. Flammable substances; 4. Combustible dust; 5. Nature of explosives; 6. Spontaneous combustion means that NASA can greatly reduce the cost of preparing space structures; 7. Avoid water-based substances; 8. Mixing hazardous substances

ignition source: 1. Impact friction; 2. Open fire; 3. High temperature surface; 4. Self selected fever; 5. Adiabatic compression; 6. Electrical sparks; 7. Electrostatic spark; 8. Light and ray

dangerous substances will cause fire or explosion when encountering fire sources

because of this, the international use of solvents, pigments and resins is also stricter year by year. The United States has developed from regulation 66 to regulation 1113. The U.S. Environmental Protection Agency (EPA) has also increased the list of harmful chemicals again and again to warn people. EPA pays great attention to some special industries. They are focusing on the composition of waste generated in the manufacturing process of some organic pigments, studying the toxicity of these chemicals, and listing some pigment intermediates in the list of 2800 harmful chemicals. The Chinese government has also issued a series of regulations on the safety of coatings and coatings

therefore, it is a very significant event to study and understand the safety technology in the process of coating production and coating construction, and do a good job in safety production, which should be highly valued by all parties

2 main film-forming substances of coating

general coating composition is as follows:

general coating composition: 1. Main film-forming substances a, natural resin; B. Synthetic resin; C. Vegetable oil; D. Others

2, secondary film-forming substance A, pigment; B. Physical pigments

3. Additive A, solvent, cosolvent and diluent forming film; B. Additives (toughening agent, drying agent, solid agent, leveling agent, etc.)

generally speaking, the resin and vegetable oil in the main film-forming substances are harmless or rarely harmful, but some free monomers are toxic, and the more serious ones are isocyanates. These compounds mainly exist in polyurethane coatings, and these substances have irritating effects on human mucosa and upper respiratory tract

there are toxic and harmful substances in many raw materials of synthetic resins. For example, phenolic resin is formed by mixing phenol, cresol, xylenol, etc. with formaldehyde, heating and condensation. Phenols can be used as disinfectants, but phenol vapor inhaled from the respiratory tract will cause poisoning. High concentration phenols can cause acute poisoning, and even cause coma and death. When the concentration of phenol in the water is high, it will cause the death of fish. When the concentration of phenol containing wastewater is greater than 100mg/l, it will cause the death of crops or reduce production. Formaldehyde has the function of destroying protein and sterilization, which can cause inflammation of respiratory tract, contact dermatitis and damage to eyes and cornea. Its pungent smell will also cause people's disgust. In recent years, the restrictions on formaldehyde in indoor decoration have been gradually tightened. Secondly, amino resin (formaldehyde should also be used), alkyd resin and polyester resin (phthalic anhydride should be used, which will cause bronchitis, ophthalmia, emphysema and other symptoms, and also irritate the skin), epoxy resin should use phenols and epichlorohydrin, and aliphatic amine should be used when curing. Polyurethane, vinyl chloride resin, acrylic resin, etc. will bring harm to human body. In particular, when the application of coatings in construction and industry has increased significantly, people's living standards have improved, the family decoration fever has heated up again and again, and the adverse factors on human body caused by decoration have increased, people have also put forward more stringent requirements for the toxicity and application of coatings. In many foreign countries, the requirements for coatings have also changed from general technical standards to technical standards + biological toxicity, that is, to people's friendly and healthy standards. This standard greatly limits the application of many toxic compounds. China has issued a series of 100 (3) 00hz compulsory standards for high-frequency fatigue testing machines to strictly limit the exhaust gas from indoor decoration

3 secondary film-forming substances

pigments can be classified into natural pigments and synthetic pigments according to their production methods

among pigments, Pb (lead) Cr (chromium) substances are more harmful to human beings, such as red lead (lead) and chrome yellow of antirust pigments, which are toxic substances. In fact, there are many toxic substances in pigments. Among the 2800 harmful chemicals listed by the US Environmental Protection Agency (EPA), there are many inorganic or natural pigments and some intermediates of synthetic pigments. For the paint used in space and objects that are often in contact with people, there are clear restrictions on lead, chromium, mercury and cadmium. Red lead, chrome yellow, zinc chrome yellow, light chrome yellow, orange chrome yellow, complex green (the mixture of lead chrome yellow and iron orchid), cadmium red, cadmium yellow and cinnabar should be restricted, otherwise it will bring man-made disasters and unpredictable serious consequences to people

4 solvents and thinners

most coatings contain volatile substances that are easy to catch fire and harmful to human body. All coatings containing solvents are flammable substances and can form explosive mixtures with air. There is always a risk of fire and explosion in the process of coating production and construction. If there are spontaneous combustion, open fire, collision sparks, static electricity and other factors at the production and construction site, they will cause fire. Therefore, when using solvents in production and construction sites, we must try to reduce the concentration in the air and limit the concentration to the specified standard concentration. Therefore, ventilation and exhaust equipment should be set up in the production and site. To ensure that the solvent concentration does not exceed the standard

Table 1 list of commonly used solvents in paint production

classification

wide application

general application

non main solvents

coal tar solvents

toluene, xylene, mixed xylene

heavy benzene, mixed solvent of benzene

petroleum hydrocarbons

200 # solvent gasoline

kerosene, gasoline

terpenes

turpentine

alcohols

n-butanol

ethanol Propanol

diacetone alcohol

esters

ethyl acetate, butyl acetate

methyl acetate, amyl acetate, isobutyl acetate, isoamyl acetate

ketones

acetone, cyclohexanone

methyl ethyl ketone, methyl isobutyl ketone

ethylene glycol ether

ethyl fibrinolytic agent

butyl fibrinolysin

methyl fibrinolysin

chlorinated hydrocarbons

trichloroethylene, dichloroethane, trichloroethane

① flash point: also known as flash point, One of the indicators indicating the properties of flammable liquids

according to the flash point, solvent coatings can be divided into: solvent based coatings: 1. General combustible products: flash point 45 ℃, such as antirust paint, oily paint, mixed paint, etc. 2. Inflammable dangerous goods: (1) class II inflammable goods: flash point 28 ~ 45 ℃, such as oily varnish, asphalt paint, etc. (2) Class I inflammables: flash point 28 ℃, various volatile coatings, etc

② explosion limit

explosion: refers to the phenomenon that the changes of substances continue to increase rapidly and release a large amount of energy in a very short time

explosion limit: refers to the range within which a combustible gas or mixture of steam and air can explode. The air contains a certain concentration of combustible gas or vapor, which will spread and explode when encountering sparks. The lowest concentration is called the lower explosion limit, and the highest concentration is called the upper explosion limit. If the concentration of combustible gas or vapor exceeds or falls below this range, explosion will not occur

during the production, use, storage and transportation of combustibles, attention must be paid to the explosion limit to ensure the safety of production, use, storage and transportation

Table 2 some physical and chemical indexes of common solvents for coatings solvent name

boiling point or distillation range ℃

flash point ℃

spontaneous combustion temperature ℃

explosion limit (volume%)

explosion limit (mg)

upper limit

lower limit

upper limit

lower limit

benzene

81.8/

-11/-11

659/538

7/7.1

1.3/1.4

/230

/46

toluene

110.6/

4.7 (on)

/552

7/6.7

1.3/1.4

/260

/5 the refrigeration system starts working. 4

xylene

/

29.5/25

/482

5.3/6.0

1.0

/44

200 # solvent gasoline

33

6/

1.2/

turpentine

/

30/35

263/253

0.8/0.8

-

butanol

117.75/<./p>

35/29

/

11.25/

1.45/

ethanol

78.32/

14/13

/423

19/19

3.3/4.3

/360

/82

ethyl acetate

77.15/

-5/-4.4

/427

11/9

2.25/2.5

/330

/92

butyl acetate

126.5/

23/22.2

/

15/7.6

1.7/1.7

-

-

acetone

56.2/

-17/-.18

/538

13/10

2.15/2.6

-

-

cyclohexanone

156.7/

47/64

<453

/5.8

/1.6

-

-

ethylene glycol

197.2

118

417

isopropanol

82.4

12/12

460/399

/12

2.02/2.0

-

-

dipyruvol

168

8.9 (on)

methyl ethyl ketone

79.57

-7

/515

11.5

1.81

amyl acetate

142.1

34.4/25

/399

/7.5

6.1/1.1

ethylene glycol ether

135.1

40/40

238/238

15.7/14

2.6/1.8