Water-based stiffener is insoluble in water, but has a certain stiffening property (does not contain ionic or molecular chain length of up to 2~3 levels, large specific surface area) of organic additives. It is a class of water-based stiffener, mainly used in coatings, plastics, rubber, paints and other organic coatings, adhesives and other industries. Stiffener is a class of organic compounds hydrogenated to form an emulsion of ester groups (see Appendix A), stiffener is mainly formed by stearic acid (ester), hydroxyl (especially ester group), hydrogen bonding, hydroxyl, carboxyl, and amide groups. Hydrogen bonding between the ester groups gives the stiffener a water-absorbing or swelling effect. Therefore, the stiffener can effectively overcome the paint, adhesive due to high temperature expansion of the adhesive layer wrinkled, cracked or peeling and other defects. It has excellent aging resistance, acid and alkali resistance, and good mechanical properties, weather resistance, heat resistance and cold resistance.
According to its structure, stiffener can be divided into two categories: oil-soluble and water-soluble. Oil-soluble stiffener is mainly used in coatings, plastics and rubber and other organic coatings to prevent the material from blistering, rupture, peeling and other defects due to high temperature expansion. Water-soluble stiffener has a softening effect on oil and water solution, which will not make the paint crack, but the pigment mixture cannot be fully reacted or make it turbid and other defects. Due to the hardening effect does not produce by-products (such as acrylic acid type or sulfonate ester type) or does not produce by-products, thus improving the dispersibility of the hardener and increase the hardening ability to significantly improve its heat resistance, weathering, cold resistance and low-temperature performance. At the same time can reduce the number of solvents in the coating and extend the water-based stiffener in the drying process time required to reduce production costs.
- II. The basic chemical structure
Stiffeners are generally composed of acetate esters, fatty acid esters, hydroxy acid esters or alkyl lipids. Most of the stiffener has a water absorption, so the organic solvents can be effectively dispersed into the emulsion and reduce the viscosity of the stiffener system, it can also be used as a stabilizer or emulsifier. Stiffener also has special properties of the type, such as: solvent-based stiffener used in plastics, rubber, coatings, adhesives and other industries. Solvent-based stiffeners are used in paints and coatings with good stiffening effect. Liquid is used in the food industry to maintain good processability. Insoluble in water, soluble in organic solvents such as acrylates, can synergize with most organic solvents. It can produce hydrogen bonding with acid and alkali, has strong chelating power for anhydride and other ionic energy, and can be polymerized with different types of polymers. It has good weather resistance, high stiffness and corrosion resistance.
III. The use of stiffener
Mixing: stiffener in the mixture will appear more aggregation, in the mixing and stirring process to produce the phenomenon of bubbles, and too much suspension. It will lead to the formation of emulsion film on the surface of the paint and cause poor stiffening effect and other problems. Therefore, attention should be paid to the dosage of hardener, the amount should be appropriate, and the mixture should not be too thick, so as not to disperse unevenly resulting in blistering, affecting the use of the effect.
Low-speed mixing: low-speed mixing equipment is used to hydrate the stiffener and form a water mixture of uniform consistency. The method has the following kinds: first add a low concentration of stearic acid (ester), hydroxyl, hydrogen bonding and hydroxyl, and then mixed with stearic acid or ester group to form a stiffener; or the two with the stiffener mixture after adding the right amount of water to make it denatured by heating.
Solvent type: this kind of stiffener is based on carboxyl (or hydroxyl) as a class of organic compounds or polymers, dissolved in water and form a copolymer (generally ester-based) structure. Or its polymerization to get a longer molecular chain, larger surface area, higher viscosity and has good dispersion properties and a certain degree of adhesion in the waterborne coating system (mainly depends on the amount of resin system in the stiffener) of the polymer for the crosslinked structure of the product. Stiffener is an emulsion liquid, which is absorbed at room temperature and undergoes a series of reactions to form a network structure. Stiffeners usually contain small amounts of salts, carboxylic acids (e.g., hydroxylamine, phosphate esters, or disodium sulfonate), or small amounts of metal ions as additives. Its application range is very wide, including water-based coatings, plastic films, adhesives and polymers containing stiffener can also be used as a base material for coatings or plastic products.
- Water-based or oil-based: applicable to all types of coatings, generally mid-range products;
- non-water soluble: can be dissolved in water and then slowly dispersed in the emulsion uniformly dispersed;
- Solid-phase mixing: emulsion liquid can be added to the solid material with a variety of organic adhesives and stirred well (containing organic fillers) for blending; adding the appropriate amount of stiffener will make the stiffener with a certain hardness to improve its mechanical properties and aging resistance;
- Water-based stiffening coating.
- IV. Application of stiffening agent in organic coatings, plastics, rubber and other industries
The application of stiffeners in water-based coatings is mainly to modify unsaturated polyesters, copolymer emulsions, etc., which can improve the performance of synthetic resins. The stiffened polymer not only has high-quality hardness, but also has good water resistance and aging resistance. When in use, the stiffening agent can be diluted into a solution with a concentration of 20-40%, and then added to the reaction kettle for emulsification reaction, and a high stiffening emulsion can be obtained after adding an appropriate amount of dilution. When the emulsion contains more than a certain proportion of organic solvents, polymerization and decomposition will occur, which will not only reduce the performance of the resin but also cause the aging of equipment or products. Therefore, adding an appropriate amount of stiffening agent to the coating production and polymer system can improve its use effect and make the product have better flexibility and high temperature resistance.
- V. Cautions
- The stiffening agent will decompose into polar substances under high temperature and high humidity conditions, so it must be sealed and stored to prevent leakage and contamination of the product.
- The storage should be ventilated and dry, keep the room dry.
- Avoid exposure to the sun.
- Add and use slowly when applying.
- Do not mix or dilute the product with water, or mix with other curing agents, fillers, pigments, fillers or pigments when used.
- It is strictly forbidden to mix with lead, mercury and other heavy metal additives.
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