Insoluble sulfur is a sulfur polymer, which can α- It is prepared by heating sulfur to a high temperature close to the boiling point and turning it into a dark brown viscous liquid, then rapidly cooling and polymerization, or by spraying hot sulfur vapor into cold water and rapidly cooling it to below 90 ℃. Insoluble sulfur will be evenly dispersed in the rubber mixture and insoluble in rubber, so it is difficult to spray frost when the amount is large. Therefore, it is recommended to use insoluble sulfur when there is a large amount of sulfur in reclaimed rubber products.
1. Role of insoluble sulfur in recycled rubber products
When insoluble sulfur is used as the vulcanizing agent of reclaimed rubber, it exists in a dispersed state, which effectively resists sulfur accumulation, reduces the scorching tendency of rubber during storage, and makes the rubber free of frost and has good viscosity. When using reclaimed rubber 2ELYY121 to produce light colored rubber products, the appearance of the products can be better guaranteed. From the perspective of production process, the use of insoluble sulfur can maintain the viscosity among semi-finished parts, facilitate molding operation, shorten the curing time, reduce the amount of curing agent, and ensure the uniformity of vulcanization of recycled rubber. Insoluble sulfur has no migration in adjacent rubber layers, which can further improve the aging resistance of recycled rubber products.
2. Precautions for using insoluble sulfur in reclaimed rubber
(1) Inappropriate storage of insoluble sulfur will transform into soluble sulfur
Insoluble sulfur will change into soluble sulfur when exposed to some alkaline materials or exposed to above 40 ℃ for a long time. Hyposulphonamide accelerants such as CBS, TBBS, DCBS and MBS will release amines during the storage period, and insoluble sulfur will rapidly change into soluble sulfur in contact with such accelerants. In addition, insoluble sulfur is flammable, so open fire shall be avoided during storage and use.
(2) Key points for processing reclaimed rubber with insoluble sulfur
Insoluble sulfur is a typical fine powder material. Once electrostatic collection occurs during mixing, sulfur particles will agglomerate and it is difficult to disperse evenly; It is suggested to use low processing temperature and rapidly add insoluble sulfur to promote its uniform dispersion. Unlike ordinary sulfur, which should be added to the cold roll of the open mill, insoluble sulfur can be directly added to the rubber during mixing. When the recycled rubber is mixed in the internal mixer, it shall be added at a temperature lower than 90 ℃ before discharging.
Recycled rubber is widely used in rubber products such as tires, tapes, rubber hoses, rubber shoes, rubber sheets, waterproof rolls, auto parts, hard rubber, etc. Insoluble sulfur is recommended when there is a large amount of sulfur. Generally, the amount of insoluble sulfur in soft rubber is 0.2-5.0 phr. When the reclaimed rubber is used to prepare hard rubber, the amount of insoluble sulfur can be increased to 40 phr. Later, Xiaobian will continue to share with you the specific amount of insoluble sulfur in various rubber products and the key points for coordination.
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