2. (1) According to different classifications of oil types, it is usually divided into three categories: drying oil, semi-drying oil and non-drying oil according to the drying properties of the oil. The average number of double bonds of triglyceride molecules is 6 The above is dry oil, which can gradually dry into a film in the air. An average double bond number of 4 to 6 is a semi-drying oil, which can form a sticky film over a long period of time. An average double bond number of less than 4 is a non-drying oil. It cannot form a film. The dryness of oil is not only related to the number of double bonds, but also related to the position of double bonds. Oils in the copurine position, such as tung oil, have stronger drying properties. The iodine value, which is the number of grams of iodine that 100g of oil can absorb, is commonly used in industry to measure the degree of unsaturation of oils and to distinguish the drying properties of oils. The iodine value of drying oil is above 140, and commonly used ones include tung oil, catalpa oil, linseed oil, etc. The iodine value of semi-dry oil is between 100 and 140. Commonly used oils include soybean oil, sunflower oil, cottonseed oil, etc. The iodine value of non-drying oils is below 100. There are caster oil, coconut oil, rice bran oil, etc.
① Dry oil alkyd resin The resin modified mainly with unsaturated fatty acids or drying oils and semi-drying oils can be dissolved in fatty acids, terpene (turpentine) or aromatic smoke solvents. It dries quickly, has high hardness and strong luster. But easy to change color. Tung oil reacts too quickly and the paint film wrinkles easily. It can be mixed with other oils to increase the drying speed and hardness. Sesame oil is quite special. It is a non-drying oil, containing about 85% of sesame oil. In the presence of high temperature and catalyst, it removes a molecule of water and adds a double bond, of which 20%~
30% are copure double bonds. Therefore, dehydrated sesame oil becomes a drying oil. The alkyd resin modified by it has a larger proportion of conjugated double bonds, better water resistance and weather resistance, and does not discolor when baked and exposed. It is often combined with amino resin to make paint.
② Non-drying oil alkyd resin is an alkyd resin modified mainly with saturated fatty acids or non-drying oils. It cannot be cured to form a film at room temperature and needs to be heated with other resins. Cross-linking reaction can solidify into a film. Its main use is to be used with amino resin to make various amino alkyd paints, which have good gloss and color retention and are used in refrigerators, automobiles, bicycles, mechanical and electrical equipment, and have excellent performance; secondly, they can be used in nitro It is used as a toughening agent in paint and perchlorethylene paint to improve adhesion and weather resistance. Alkyd resin is added to nitrocellulose paint to increase gloss, make the paint film plump, and prevent the paint film from shrinking.
(2) The oil content in resin is classified according to different oil content and is expressed by oil degree. The definition of oiliness is the ratio of the weight of the oil used in the resin to the theoretical weight of the final alkyd resin 90
①The oiliness of short oil alkyd resin is 35%~45%, which can be made of soybean oil, Made of dry oils such as talline oleic acid, dehydrated sesame oil and linseed oil, the paint film sets quickly, has average self-propagation ability, medium zen properties, and good gloss and gloss retention. It dries quickly. It can be used as baking paint. After burning, short oil alkyd resin has better hardness, gloss, color retention, and anti-friction properties than long oil alkyd resin. It is used in automobiles, toys, machine parts, etc. Maker paint
⑵ The oil content of medium oil alkyd resin is 46%~60%. It is made from linseed oil and point oil, and is the main variety of alkyd resin. This kind The paint can be brushed or sprayed. Medium oil paint dries quickly, has excellent gloss, weather resistance, and elasticity. The paint film solidifies and dries quickly. It can be dried by itself. Nitrogen-based resin can also be added for drying. Medium oil paint is alcoholic. Acid resin is used to make self-drying or oven-drying paints, primers, metal decorative paints, vehicle paints, etc.
The oil content of long oil alkyd resin is 60% to 70% . It has good drying performance, and the paint film is elastic. It has good gloss, good gloss retention and weather resistance. But it is not as good as medium oil alkyd resin in terms of hardness, toughness and friction resistance. In addition, this paint f) Good brushability, can be used to make steel structure coatings, indoor and outdoor architectural coatings. Because it can be mixed with some oil-based paints, it can be used to enhance oil-based resin coatings, and can also be used to enhance latex paints,
①The oil content of ultra-high degree alkyd resin grease is above 70%, which dries slowly and is easy to apply. It is generally used as base material for tinting and coloring.
In short, for alkyd resins with different oil levels. Generally speaking, the higher the oil level, the more properties the coating will show, and it will be more durable than soft objects, and the paint film will be more elastic. It is suitable for outdoor coatings. The higher the oil level, the more flexible the paint film will be. Short, the coating film shows few characteristics. It is relatively hard and brittle, has good gloss, color retention, and anti-wear properties, and is easy to polish, but not durable. Suitable for indoor coatings.
