Phenolic antioxidantIt is the most non-polluting and non-discoloring antioxidant among all antioxidants. The best one, mainly used in the plastics and synthetic fiber industries. In the rubber processing industry, due to its weak protective effect, it is usually only used for products with low aging requirements. However, in recent years, phenolic antioxidants have been widely used as non-polluting raw rubber stabilizers for synthetic rubber. In this sense, the dosage of phenolic antioxidants in the rubber industry is also relatively large.
As antioxidants, they are mainly hindered phenols. Their structural feature is that there are one or two larger groups adjacent to the phenolic hydroxyl group.
Hindered phenols can also be divided into the following categories:
(1) Alkylene monophenol
This type The synthesis of antioxidants mainly uses the alkylation reaction of phenol. 2.6-Di-tert-butyl-4-methylphenol (264) is the most representative and widely used alkyl monophenol. It is a white to light yellow powder, m.p.68-70℃, non-toxic, and can be used in various polymers, as well as petroleum products and food processing industries. The disadvantage is that the molecular weight is low, the volatility is high, and it is not suitable for high-temperature processing of plastics. The general dosage is 0.1% in plastics and 0.5%~2% in rubber.
(2) Alkylene bisphenols, polyphenols and hindered phenol-substituted esters, triazine hindered phenols
The synthesis of this type of antioxidant generally involves the alkylation of phenols, in the ortho position of the phenolic hydroxyl group Introduce one or two larger groups, usually -C(CH3)3, to make hindered phenols, and then react with aldehydes or other compounds to produce alkylene bisphenols, polyphenols, or Hindered phenol substituted esters, triazine hindered phenols, etc. Below are typical examples.
①Alkylene bisphenol such as antioxidant 2264, white Powder, m.p.125~133℃.
②Alkylene polyphenols such as antioxidant CA are white crystalline powders, m.p. 185~188°C.
This type of antioxidant is commonly used in polyolefins, but also in other plastics, natural rubber and synthetic rubber. Because they have large molecular weight, low volatility, excellent heat resistance and antioxidant properties, and are non-toxic and non-polluting, they are widely used. Among them, antioxidant 1010 [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (white powder, m.p. 119~123℃) and antioxidant 1076 also have excellent water resistance to extraction properties, and also applies to fiber products. The general dosage is 0.1%~0.5%. In rubber, the dosage is larger, up to 2%.
(3) Thiobisphenol
Thiobisphenols also belong to hindered phenol antioxidants. They are compounds that use sulfur atoms to connect hindered phenols.
Thiobisphenols are generally synthesized by the reaction of hindered phenols and sulfur dichloride.
Halogen atoms can also be introduced into the benzene ring of hindered phenol and then react with sodium sulfide.
This type of antioxidant has higher antioxidant properties than 2246 and can be used in plastics and rubber. Because they have a thioether structure, Therefore, it has the functions of chain terminator and hydrogen peroxide decomposer.
