Basic components of paint (raw materials)
1. Base resin
3. Pigments and fillers
The function of the coating: coated on the surface of the object to be coated, through the formation of a coating film to play a protective role, decorative role and give the object to be coated a special function.
(1) Base resin (main film-forming substance)
It is to combine pigments and fillers to form a uniform and dense coating film on the substrate and form a coating after curing.
Type: Natural resin (rosin, asphalt, shellac), phenolic resin, alkyd resin, nitrocellulose, amino resin, polyester resin, epoxy resin, polyurethane resin, acrylic resin, other resins
The main properties and uses of common base materials
1. Acrylic emulsion (aqueous): According to the different emulsions, it can be divided into pure acrylic, styrene acrylic, silicon acrylic, acetic acid acrylic, self-crosslinking acrylic acid, etc.
Advantages: moderate cost, excellent weather resistance, good performance adjustability, no organic solvent release, etc.
Uses: mainly used for interior and exterior wall coating of buildings, leather coating, wood coatings, etc.
2. Solvent-based acrylic resin: It can be divided into self-drying acrylic resin (thermoplastic type) and cross-linking curing acrylic resin (thermosetting type). The cross-linking and curing acrylic paint mainly includes acrylic amino paint, acrylic polyurethane paint, acrylic alkyd paint, radiation curing acrylic paint and other varieties.
Advantages: Self-drying acrylic has quick surface drying, easy construction, obvious protection and decoration. Crosslinking-curable acrylic paints have a high solid content, a thick coating film can be obtained in one coating, and excellent mechanical properties, can be made into a coating with high weather resistance, high fullness, high elasticity and high hardness .
Disadvantages: The solid content of the self-drying acrylic paint is not easy to be too high, the hardness and elasticity are not easy to take into account, a thick coating film cannot be obtained in one application, and the fullness of the coating film is not ideal. Cross-linking and curing acrylic paints are troublesome to construct. Many varieties also require heat curing or radiation curing. They require relatively high environmental conditions, and generally require better equipment and more skilled coating techniques.
Uses: mainly used in architectural coatings, plastic coatings, electronic coatings, road marking coatings, automotive coatings, electrical appliance coatings, wood coatings, architectural coatings, etc.
3. Polyurethane resin: Polyurethane paint can be divided into two-component polyurethane and single-component polyurethane.
Advantages: higher solid content, hard and wear-resistant paint film, generally have good mechanical properties, excellent chemical resistance, good oil resistance and solvent resistance.
Disadvantages: the construction process is complicated, the requirements on the construction environment are very high, and the paint film is prone to defects.
Uses: The application direction includes wood coatings, floor coatings, automotive repair coatings, anti-corrosion coatings, floor coatings, electronic coatings, special coatings, etc.
Nitro paint: The main film-forming material is mainly nitrocellulose, combined with alkyd resin, modified rosin resin, acrylic resin, amino resin and other soft and hard resins.
Advantages: good decorative effect, easy construction, rapid drying, low requirements for coating environment, good hardness and brightness, easy to avoid paint film defects, easy to repair.
Disadvantages: lower solids content, requires more construction channels to achieve better results; durability is not very good, especially the internal nitro paint, its light and color retention is not good, it is easy to use for a long time There are disadvantages such as loss of light, cracking, discoloration, etc.; the protective effect of the paint film is not good, and it is not resistant to organic solvents, heat, or corrosion.
Uses: Nitro paint is mainly used in the coating of wood and furniture, home decoration, general decorative coating, metal coating, general cement coating, etc.
5. Epoxy resin: The main variety of epoxy paint is two-component paint, which is composed of epoxy resin and curing agent.
6. Advantages: strong adhesion to inorganic materials such as cement and metals; the coating itself is very resistant to corrosion; excellent mechanical properties, wear resistance and impact resistance; can be made into solvent-free or high-solids coatings; organic solvent resistance, heat resistance , Water resistant; non-toxic coating.
Disadvantages: weather resistance is not good, powdering may occur after long-term sunlight exposure, so it can only be used as a primer or internal paint; poor decoration, gloss is not easy to maintain; high requirements for the construction environment, low temperature coating The film curing is slow, and the effect is not good; many varieties need high temperature curing, and the investment in painting equipment is large.
Uses: mainly used for floor coating, automobile primer, metal anti-corrosion, chemical anti-corrosion, etc.
6. Amino resin: mainly butyl etherified melamine formaldehyde resin, methyl etherified melamine formaldehyde resin, butyl etherified urea-formaldehyde resin and other resins. Amino baking varnish is mainly composed of two parts: one is amino resin, and the other is hydroxy resin part (mainly alkyd resin, polyester resin, hydroxyl-containing acrylic resin, epoxy resin and other resins).
Advantages: The cured film has excellent performance after curing, the film is hard and full, bright and bright, firm and durable, and has a good decorative and protective effect.
Disadvantages: high requirements for painting equipment, high energy consumption, not suitable for small-scale production.
Uses: mainly used for car topcoat, coil, furniture coating, household appliance coating, various metal surface coating, instrumentation and industrial equipment coating.
7. Alkyd resin: ①Short oil non-drying alkyd resin (mainly used for nitro paint, polyurethane paint, amino and polyester baking paint, etc.) ②Long oil dry alkyd resin (for self-drying alkyd paint) .
Advantages: Alkyd paint has the advantages of low price, simple construction, low requirements on the construction environment, full and hard coating, good durability and weather resistance, and good decoration and protection.
Disadvantages: Alkyd paint dries slowly, the coating film is not easy to meet the high requirements, and is not suitable for high decorative occasions.
Uses: Alkyd paint is mainly used for the coating of general wood, furniture and home decoration, general metal decorative coating, less demanding metal anti-corrosion coating, general agricultural machinery, automobile, instrumentation, industrial equipment and other aspects.
8. Unsaturated polyester resin: Unsaturated polyester paint is divided into two categories: air-drying unsaturated polyester and radiation curing (light curing) unsaturated polyester.
Advantages: It can be made into solvent-free paint, and a thick paint film can be obtained in one painting. The requirements on the coating temperature are not high, and the decoration effect of the paint film is good, the paint film is tough and wear-resistant, and easy to maintain.
Disadvantages: the shrinkage of the paint film during curing is large, and the adhesion to the substrate is prone to problems. The air-drying unsaturated polyester generally needs polishing treatment, the procedures are more cumbersome, and the radiation curing unsaturated polyester requires more coating equipment High, not suitable for small production.
Uses: Unsaturated polyester paint is mainly used in furniture, wooden floors, metal anti-corrosion, etc.
9. Vinyl resin and rubber resin: including vinyl chloride copolymer resin, polyvinyl butyral, vinylidene chloride, perchloroethylene, chlorosulfonated poly-Zene paint, chlorinated rubber and other varieties.
Advantages: mainly weather resistance, chemical resistance, water resistance, insulation, mildew resistance, and good flexibility.
Disadvantages: mainly in terms of general heat resistance, difficult to make high-solid coatings, mechanical properties, poor decorative performance, etc.
Uses: mainly used in industrial anti-corrosion coatings, electrical insulation coatings, phosphating primers, metal coatings, external coatings, etc.
10. Phenolic resin: Phenolic resin is a product formed by condensation of phenol and aldehyde in the presence of a catalyst.
Advantages: Phenolic paint dries quickly, the paint film is bright and hard, good water resistance and chemical resistance.
Disadvantages: Phenolic paint is easy to turn yellow, so it is not suitable to make light-colored paint, and its weather resistance is not good.
Uses: used in anti-corrosion coatings, insulating coatings, ordinary metal coatings, ordinary decorative coatings, etc.
It is to dissolve or disperse the film-forming materials into a uniform and stable liquid dispersion system, which is convenient for the preparation of coatings, film formation during construction, and then volatilization into the atmospheric environment.
Requirements for solvents used in coatings:
(1) It has good solubility and volatility, the solvent and the main film-forming substance should be miscible evenly, and the volatilization speed should meet the construction requirements.
(2) No chemical changes occur in the components of the paint.
(3) Low toxicity, low price and rich source of raw materials.
Classification of solvent varieties There are many types of solvents, which can be divided into the following categories according to their chemical composition and source:
(1) Terpene solvent: most of it comes from pine secretions. Commonly used are turpentine and pine oil. Turpentine's ability to dissolve natural resins and resins is greater than ordinary banana water and less than benzene. Its volatilization rate is moderate, which meets the requirements of paint brushing and drying.
(2) Petroleum solvent: This type of solvent is a hydrocarbon. It is fractionated from petroleum. Commonly used are gasoline, rosin, kerosene, etc. Gasoline evaporates very quickly and is dangerous. Generally, it is not used as a solvent.
Rosin is a commonly used solvent in paints. It is characterized by its low toxicity and is generally used in oil paints and magnetic paints.
(3) Coal coke solvent: This type of solvent also belongs to hydrocarbons. It is obtained by dry distillation of coal. Commonly used are benzene, toluene, xylene and so on. Benzene has a strong dissolving power. It is a strong solvent for natural dry oils and resins. It can not dissolve shellac, but it is highly toxic and volatile quickly. It is not commonly used in paints and is generally used as a detergent. The dissolving power of toluene is similar to benzene. It is mainly used as a solvent for alkyd paints, and can also be used as a thinner for epoxy resins and spray paints. It is used in a small amount in detergents. The solubility of xylene is slightly lower than that of toluene, and its volatilization is slower than toluene. As a powerful solvent instead of rosin.
(4) Ester solvent: It is a combination of low-carbon organic acids and alcohols. Commonly used are J acetate, ethyl acetate, ethyl acetate, amyl acetate, etc. Ethyl acetate has better solubility than butyl ester. J acetate has low toxicity, and is generally used in spray paint for easy construction and can also prevent the precipitation of resin and nitrocellulose; pentyl acetate evaporates slowly, and can be used in fiber paint to improve the leveling and whitening of the paint film.
(5) Ketone solvent: It is an organic solvent, mainly used to dissolve nitrocellulose.
Commonly used are acetone, methyl ethyl ketone, methyl isoacetone, cyclohexanone and so on. Acetone has extremely strong dissolving power, and can be dissolved in water in any proportion quickly, so it is easy to absorb water and make the paint film white and dry after drying. It is generally used with solvents that evaporate slowly. Mostly used in spray paint and quick-drying adhesives. However, acetone is extremely flammable, and attention should be paid to fire prevention when using it; methyl ethyl ketone evaporates slower than acetone and has a slightly poor solubility, and can be used alone; methyl isopropyl acetone has high solubility and moderate volatility, and has a strong ability to prevent paint whitening; cyclohexanone Slow volatilization and good solubility can make the paint film form a bright and smooth surface during drying to prevent the generation of air bubbles.
(6) Alcohol solvent: It is an organic solvent that can be mixed with water. Commonly used are ethanol and butanol. Alcoholic solvents have poor dissolving power to coatings and can only dissolve shellac or butyral resins. When used in combination with ester and ketone solvents, it can increase its dissolving power, so they are called cosolvents of nitrolacquer. Ethanol can not dissolve general resin, but can dissolve ethyl fiber, shellac and so on. It can also be used to make alcohol varnish, wood stain, washing primer, etc. J The dissolving power of alcohol is slightly lower than that of ethanol, and it evaporates more slowly. Commonly used with ethanol to prevent the paint film from whitish and eliminate defects such as pinholes, orange peels, and air bubbles. The special effect of butanol is to prevent the gelation of paint, reduce the viscosity and at the same time can also be used as a solvent for amino resins.
(7) Other solvents: Commonly used chlorine-containing solvents, nitrated alkane solvents, ether alcohol solvents.
Chlorine-containing solvents have a strong dissolving power, but are relatively toxic, and are only used in certain special requirements and paint strippers; the volatilization rate of nitrated alkane solvents is about the same as that of J acetate, and at the same time, they can dissolve nitrocellulose; ether alcohol solvents It is an emerging solvent, including ethylene glycol ether, ethylene glycol butyl ether and its esters. Commonly used in nitro paint, phenolic resin paint and epoxy resin paint. Ethyl butyl ether is commonly used as white water.
(3) Pigments and fillers
Give the coating hiding power and the required color to enhance its mechanical physical properties.
Type: coloring pigments (organic pigments, inorganic pigments), physical fillers, anti-rust functional pigments, special pigments and functional pigments
Common varieties and characteristics of pigments and fillers
1. Coloring pigment: It has good hiding power and can improve the coating's resistance to sunlight, durability and weather resistance. Some pigments can improve the wear resistance of the coating. The most important thing is that the coloring pigment can give the coating various colors.
(1) White pigment: titanium white TIO2, zinc barium white;
(2) Red pigments: iron red, toluidine red, cadmium red;
(3) Yellow pigment: iron yellow, chrome yellow;
(4) Green pigments: phthalocyanine green and chrome green;
(5) Blue pigments: phthalocyanine blue, Buddha blue, ultramarine blue, iron blue, Prussian blue;
(6) Violet pigments: toluidine violet, quinacridone violet;
(7) Black pigments: carbon black, iron black...
2. Anti-rust pigment: This kind of pigment can make the coating have good anti-rust ability and prolong life. It is the main raw material of anti-rust primer.
(1) Red lead: / lead lead: can passivate steel. Toxic, acid and alkali resistant and high temperature.
(2) Zinc chrome yellow: can passivate steel. Toxic.
(3) Zinc phosphate/phosphor zinc white: Phosphating of metal surface.
(4) Iron red and iron yellow: chemically inert, improve the density of the coating film, and reduce the permeability of the coating film.
(5) Aluminum powder, mica iron oxide: the surface is scaly, which enhances the sealing of the coating film, and has good anti-aging and UV reflection functions.
(6) Zinc powder: It has great activity and is corroded first to protect it.
(7) Other anti-rust pigments: four basic zinc chrome yellow, zinc oxide, basic lead chromate.
3. Body pigments: mainly used to increase the thickness of the coating, improve wear resistance and mechanical strength.
(1) Barium compounds: natural and precipitated barium sulfate
(2) Calcium compounds: heavy and light calcium carbonate
(3) Aluminum compounds: mica powder, kaolin, etc.
(4) Magnesium compounds: talc, light magnesium carbonate, etc.
(5) Silica: diatomite, quartz powder, white carbon black, etc.
4. Special pigments and functional pigments: a function of putty paint.
(1) Gold powder, silver powder, pearl powder, fluorescent pigment
(2) Luminous and light-storing pigments
(3) Temperature indicating pigment
(4) Cuprous oxide (antifouling)
(5) High temperature resistant composite pigment
Adjust and improve the overall performance of paints and coatings
Common additives are as follows:
1. Wetting and dispersion: The pigment is an aggregate of primary particles. The result of grinding and dispersing is to disperse this aggregate into the original particles and disperse it into the paint. Poor dispersion will result in incomplete depolymerization or re-flocculation. , Causing floating hair color, sunken bottom, gloss decline and so on.
Pigments must undergo three steps of wetting, crushing, and stabilization when dispersed.
Wetting aids enhance the wetting of pigment agglomerates, dispersing aids stabilize pigment dispersions to prevent flocculation, and a product often has both wetting and dispersing functions.
2. Leveling agent: The leveling aid improves the flow method by reducing the surface tension of the coating film to obtain a good appearance of the coating film. Some special additives can also provide smooth, hardening, anti-scratch and anti-blocking effects.
The main varieties are: silicone leveling agent, acrylate leveling agent, other types of leveling agent (fluorine modified leveling agent, high boiling point solvent)
3. Antifoaming agent: divided into antifoaming agent and foam breaking agent. Foam inhibitor mainly controls the generation of foam and eliminates the generated foam, and most of them play a role in the production and use of paint; the foam breaker mainly changes the small bubbles generated from small to large, making the bubble film gradually thin and Breaking bubbles by itself, such additives play a role in the entire process of coating.
Main products: silicone defoamer, non-silicon defoamer, fluorine modified defoamer