Study On The Synthesis Of Light Stabilizer 2908

With the gradual expansion of the demand for synthetic polymeric materials,additives that inhibit the aging of polymeric materials have also developed rapidly.Hindered phenol light stabilizers perform better in commercial stabilizers.Light stabilizer 2908,i.e.3,5-Di-tert-butyl-4-hydroxybenzoic acid n-hexadecyl ester is a typical representative.Light stabilizer 2908 has antioxidant activity,and it can provide effective protection for synthetic polymeric materials.It has the advantages of low toxicity,low volatility,small product colorability,and relatively good compatibility.Light stabilizer 2908 has obvious effects on olefins,especially for colored and opaque products;It can be used synergically with antioxidants and hindered amine light stabilizers to improve the weatherability of polymeric materials.It is of great significance to study and optimize its synthetic process.In this paper,2,6-di-tert-butylphenol and 3,5-di-tert-butyl-4-hydroxybenzoate were synthesized from 2,6-di-tert-butylphenol.Then it was reacted with n-hexadecanol to synthesize 2908 light stabilizer.In this paper,two methods were attempted to synthesize 3,5-di-tert-butyl-4-hydroxybenzoic acid.One synthetic route is using carbon dioxide as carboxylating agent via Kolbe-Schmidt reaction.3,5-Di-tert-butyl-4-hydroxybenzoic acid was synthesized using 2,6-di-tert-butylphenol as a raw material,n-butyl ether as a solvent,and sodium methoxide as a base,the preferred conditions of this method are:n(2,6-ditert-butylphenol):n(sodium methoxide)=11:1,carboxylation time was 2 h,carboxylation temperature was 165 ?,carboxylation pressure was 0.4 MPa.Under these conditions,the yield of 3,5-di-tert-butyl-4-hydroxybenzoic acid was 93.2 %,and the purity was 99.8 %.Another synthetic route is using 2,6-di-tert-butylphenol as a raw material and carbon tetrachloride as a carbon source via carbonylation and hydrolysis.This method can be carried out under atmospheric pressure and can be an alternative supplement to the Kolbe-Schmidt method.The optimized conditions for the synthesis of 3,5-di-tert-butyl-4-hydroxybenzoic acid are:n(2,6-di-tert-butylphenol):n(carbon tetrachloride):n(sodium hydroxide)=1:1.3:6.5,reaction temperature was 70 ?,reaction time was 2 h,hydrolysis temperature was 88 ?,hydrolysis time was 6 h.Under these conditions,the yield of 3,5-di-tert-butyl-4-hydroxybenzoic acid was 92.5 % and the purity was 96.4 %.When carbon tetrachloride was used as the carbonylation reagent to synthesize acid,the synthesis method of methyl ester was obtained by controlling the reaction conditions.The reaction conditions are:n(2,6-di-tert-butylphenol):n(carbon tetrachloride)n(sodium hydroxide)=1:1.3:4.6,the reaction time temperature was 70 ?,and the reaction time was 15 min.Under these conditions,the yield of methyl 3,5-ditert-butyl-4-hydroxybenzoate was 92.5 % and the purity was 96.4 %.When synthesizing light stabilizer 2908,two methods were attempted in this paper.The first method is via 3,5-di-tert-butyl-4-hydroxybenzoyl chloride prepared from 3,5-di-tert-butyl-4-hydroxybenzoic acid and phosphorus oxychloride.The reaction conditions are:n(3,5-di-tert-butyl-4-hydroxybenzoic acid):n(phosphor oxychloride):n(n-hexadecanol):=1:0.5:1.2;reaction temperature was 100 ?;reaction time was 11.5 h.The yield of the product obtained by this method was 95.5 % and the purity was 99.6 %.The second method is via transesterifcaion reaction from methyl 3,5-di-tert-butyl-4-hydroxybenzoate.The optimal reaction conditions are:n(methyl 3,5-di-tert-butyl-4-hydroxybenzoate):n(n-hexadecanol)=1:1.15;The amount of catalyst tetrabutyl titanate was 0.6 g / 20.0 g of methyl 3,5-di-tert-butyl-4-hydroxybenzoate;reaction time was 6h;reaction temperature was 105 ?.Under these conditions,the yield was 97.2 % and the purity was 99.5 %.