Manufacture[edit]
There are two types of alkyd resins, drying (including semi drying) and nondrying. Both types are typically produced from dicarboxylic acids or anhydrides, such as phthalic anhydride or maleic anhydride, and polyols, such as trimethylolpropane, glycerine, or pentaerythritol. Alkyds are also used in items such as resins and paints.
Main article: drying oil
For the "drying" resins, triglycerides are derived from polyunsaturated fatty acids (often derived from plant and vegetable oils, e.g. linseed oil). These drying alkyds are cured in air. The drying speed and the nature of the coatings depends on the amount and type of drying oil employed (more polyunsaturated oil means faster reaction in air) and use of metal salts, the so-called oil drying agents. These metal complex that catalyze crosslinking of the unsaturated sites.
Alkyd coatings are produced in two processes; fatty acid process and the alcoholysis or mono-glyceride process. Higher quality higher performance alkyds are produced in the fatty acid process where the composition of the resulting resin can be more precisely controlled. In this process an acid anhydride, a polyol and an unsaturated fatty acid are combined and cooked together until the product has achieved a predetermined level of viscosity. Penta alkyds are made this way. More economical alkyd resins are produced from the alcoholysis or glyceride process where end product quality control is not as paramount. In this process raw vegetable oil, high in unsaturated component, is combined with additional polyol and heated to cause transesterification of the triglycerides into a mixture of mono- and diglyceride oils. To this resulting mixture acid, anhydride is added to build the molecular weight of the resin into roughly the same product as in the fatty acid process. However, the alcoholysis process, also known as the glyceride process, produces a more randomly oriented structure. To remove the water produced as a by-product and to increase the reaction rate, surplus phthalic anhydride was added. Water was thus removed with the unreacted acid by heating the bulk to a temperature needed to do this. It meant that the reaction was not as controllable as would be desired. A new process was introduced, in which Xylene was added to produce an azeotrope with the water. This gave greater control at a lower temperature, this also produced resins at a lower viscosity, useful in making high solids paints; this process was known as the AZO process. In both cases the resulting product is a polyester resin to which pendant drying oil groups are attached. At the conclusion of both processes the resin is purified, diluted in solvent and sold to paint and varnish makers.[2]
[แก้] การผลิตมีสองประเภทของอัลคิดเรซิน แห้ง (รวมกึ่งแห้ง) และ nondrying ทั้งสองชนิดโดยทั่วไปผลิตจาก dicarboxylic กรด หรือ ไดรด์ เช่น phthalic anhydride หรือ maleic anhydride และ polyols เช่น trimethylolpropane กลีเซอรีน หรือ pentaerythritol Alkyds มีใช้ในรายการเช่นเรซิ่นและสีด้วยบทความหลัก: น้ำมันอบแห้งไตรกลีเซอไรด์มาจากกรดไขมันไม่อิ่มตัว (มักจะมาจากพืชและน้ำมันพืช น้ำมันเมล็ดฝ้ายเช่น) สำหรับเรซิ่น "แห้ง" การอบ alkyds เหล่านี้จะหายในอากาศ แห้งเร็วและลักษณะของการเคลือบขึ้นอยู่กับจำนวนและชนิดของน้ำมันอบแห้งที่ใช้ (น้ำมันไม่อิ่มตัวทำ ปฏิกิริยาเร็วขึ้นในอากาศ) และใช้เกลือของโลหะ น้ำมันเรียกว่าแห้งแทน เหล่านี้โลหะซับซ้อนที่กระตุ้น crosslinking ไซต์ไม่อิ่มตัวAlkyd coatings are produced in two processes; fatty acid process and the alcoholysis or mono-glyceride process. Higher quality higher performance alkyds are produced in the fatty acid process where the composition of the resulting resin can be more precisely controlled. In this process an acid anhydride, a polyol and an unsaturated fatty acid are combined and cooked together until the product has achieved a predetermined level of viscosity. Penta alkyds are made this way. More economical alkyd resins are produced from the alcoholysis or glyceride process where end product quality control is not as paramount. In this process raw vegetable oil, high in unsaturated component, is combined with additional polyol and heated to cause transesterification of the triglycerides into a mixture of mono- and diglyceride oils. To this resulting mixture acid, anhydride is added to build the molecular weight of the resin into roughly the same product as in the fatty acid process. However, the alcoholysis process, also known as the glyceride process, produces a more randomly oriented structure. To remove the water produced as a by-product and to increase the reaction rate, surplus phthalic anhydride was added. Water was thus removed with the unreacted acid by heating the bulk to a temperature needed to do this. It meant that the reaction was not as controllable as would be desired. A new process was introduced, in which Xylene was added to produce an azeotrope with the water. This gave greater control at a lower temperature, this also produced resins at a lower viscosity, useful in making high solids paints; this process was known as the AZO process. In both cases the resulting product is a polyester resin to which pendant drying oil groups are attached. At the conclusion of both processes the resin is purified, diluted in solvent and sold to paint and varnish makers.[2]
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