The primary raw material for acrylic staple fiber is acrylonitrile, which originates from the petrochemical industry chain. The specific production route involves distilling petroleum in a refinery's atmospheric and vacuum distillation unit to produce naphtha; cracking the naphtha in an ethylene cracker to generate propylene; and subsequently converting the propylene into acrylonitrile via ammoxidation.
The production process for acrylic staple fiber primarily comprises polymerization, spinning, and post-treatment stages. Specifically, acrylonitrile undergoes polymerization and monomer removal before being dissolved in a solvent to create the spinning dope. This dope is processed through a spinning machine to form nascent fibers. Finally, the fibers undergo a series of post-treatment steps-including stretching, drying, heat setting, crimping, cutting, and baling-to yield the finished product.
Acrylic production processes are categorized into dry spinning and wet spinning (such as the sodium thiocyanate two-step method) based on the spinning and forming technique employed. These methods rely on different formation mechanisms, resulting in distinct fiber properties. Dry-spun acrylic fibers, due to their unique formation mechanism, exhibit a "dog-bone" cross-sectional shape; this structure imparts properties-such as covering power, soft hand-feel, luster, moisture transport, and hygrothermal stability-that more closely resemble wool and generally outperform those of wet-spun acrylic fibers.
Solution dyeing (or dope dyeing) technology represents a significant innovation in the production process. This technique involves adding a specific proportion of colorant paste to the spinning dope and thoroughly mixing it before directly spinning the mixture into colored fibers. Compared to traditional post-dyeing methods, solution-dyed acrylic offers advantages such as uniform coloration, high color fastness, high dye uptake, and excellent resistance to fading from sunlight exposure. Furthermore, the process generates virtually no colored wastewater during production or subsequent processing, demonstrating significant eco-friendly characteristics.