Seam envelope can also be called envelope. Sewing thread is divided into civil sewing thread and industrial sewing thread. Sewing thread is a consumable, and the profit margin is very small. . So far, pure polyester chemical fiber is used as raw material, which has the characteristics of alkali resistance, corrosion resistance and acid resistance. Widely used in feed mills, fertilizer plants, cement plants, rice mills and building materials factories. It can be used for sewing seams and bottom seams of woven bags, paper bags, sacks and composite bags.