Thermal stableagent Its function is to prevent polymer materials from being damaged during processing or use Pricing or cross-linking occurs due to heat, to extend its service life. The processing and use of many high-tech materials, such as polyvinyl chloride, some engineering plastics and certain rafter rubbers (such as neoprene), often require the application of heat stabilizers. Among them, polyvinyl chloride is the most prominent. Next, Chemical Industry will introduce to you an introduction to the types of heat stabilizers.
1.Saline-based lead Salt
Basic lead salt refers to lead monoxide containing unsalted lead (commonly known as salt base) Lead inorganic acid and lead organic acid. Lead oxide also has a strong ability to bind chlorine, and it can also be used as a heat stabilizer itself, but it has a yellow color and will color the product. Most of the alkaline lead salts are white.
Basic lead salts generally react with lead oxide and inorganic acid or organic acid in the presence of acetic acid or acetic anhydride Become.
Suitable heat stabilizers generally have excellent heat resistance and weather resistance, good electrical insulation and low cost. The disadvantages are poor transparency, toxicity, susceptibility to hydrogen sulfide pollution, poor dispersibility, and large specific gravity, so the dosage is also large, often reaching more than 5%.
2. Fatty acid soap (metal soap)
Fatty acid soapAlso called metal soap, mainly barium, cadmium, lead, calcium, Metal salts of zinc, magnesium, strontium, etc. Commonly used fatty acids include stearic acid, lauric acid, palmitic acid, etc. Industrial stearic acid soap is actually a mixture of stearic acid soap and palmitic acid soap.
Fatty acid soap is mainly produced by metathesis of soluble salts of metals (such as barium chloride, calcium sulfate, etc.) and sodium salts of fatty acids. have to.
In this type of stabilizer, metals such as magnesium, calcium, and barium are elements of Group IA in the periodic table, and they produce All soaps have the common characteristics of small initial stabilization and good long-term heat resistance; soaps made of zinc, cadmium, etc., which are in group TB of the periodic table, all have the characteristics of large initial stability and poor long-term heat resistance. . These two types of metal soaps have their own strengths. When used together, they have obvious synergistic effects. Generally, the combination of barium soap and cadmium soap is widely used in polyvinyl chloride products; while the combination of calcium soap and zinc soap is mainly used in non-toxic soft products.
3. Organotin stabilizer
In the general formula of organotin, R is an alkyl group, and Y is an organic group connected to Sn through an oxygen atom or a sulfur atom.
According to different Y, there are three main types of organotin stabilizers: fatty acid salt type, maleate type ,
Thiolate type.
The synthesis method of organotin stabilizer It is to prepare alkyltin halide, which reacts with sodium hydroxide to form alkyltin oxide, and finally reacts with carboxylic acid, maleic anhydride, mercaptan, etc. to obtain fatty acid salts, maleates, and sulfides of organotin. Alcoholates, etc. The most important thing in synthesis is the synthesis of alkyltin halide.
There are two ways to synthesize alkyltin halides, one is the Grignard method and the other is the direct method
Grignard method uses alkyl chloride as raw material, but there are many reaction steps; direct method uses alkyl iodide as raw material, and the price is higher.
Other organotin stabilizers can be prepared in the same way.
In addition to being used as heat stabilizers, organotin stabilizers also have light stabilizing effects. Fatty acid-type organotin has slightly poor heat resistance, but has good processability, good weather resistance, and good transparency. Maleate type organotin has a good initial hue, long-term heat resistance and transparency, and has the best weather resistance among organotins, so it is widely used. However, because tin maleate has tear-inducing properties, maleic acid monoester salts are most commonly used. Alcohol-type organotin has a good initial hue, excellent long-term heat resistance and transparency, and ranks first among organotins. However, it has poor weather resistance and has an odor.
Organotin stabilizers are mainly used in transparent products of polyvinyl chloride, especially hard transparent products. Most of them are toxic. However, many varieties of dioctyltin compounds are considered non-toxic. In recent years, some new organotin stabilizers have been developed abroad, such as various ester tins, lauryl tin, etc., which are said to be low-toxic and efficient.
