Phthalic acid is used as an active ingredient in polyesters and alkyd resins. It is also used as plasticizers for polyvinyl chloride and other polymers. It is also useful in the production of anthraquinone, phenolphthalein and phthalocyanine pigments. It serves as an organic reagent in the production of phthalates. It is used to prepare 1,3-cyclohexadiene by reduction using sodium amalgam.

Qingdao Sigma Chemical Co., Ltd.is a global chemical industry manufacturers and suppliers of pharmaceuticals and intermediates, food and feed additives, herbal extracts, agrochemicals and fine chemicals etc.

The aim of Qingdao Sigma Chemical Co., Ltd is a quality policy that "Elements in the system all have been satisfied, Personnel has been trained; Every batch of material is checked, Each procedure guarantees the quality; Every bag of our products is top grade, Service is thoughtful all the time, quality and reputation to increase market share and promote enterprise development. The quality, colors and forms of our products have reached a high level in related chemical industry, which relies on characteristic and advanced processing technology and it has gained a high and reliable reputation from customers at both quality and services.