Polyesters bleaching

The most effective method of bleaching polyester/cotton is sodium chlorite, which may be followed by peroxide bleaching. Chlorite bleaches the husk, but does not destroy them completely. Polyester/cotton blends may be bleached with sodium chlorite in long liquors and also by pad-steam process [Table 6.10]. The... 

Recipe for Bleaching Polyester/Cotton Blends with NaClO ... 

Peracetic acid can also be used for bleaching polyester/cotton blended fabrics with a solution containing 4 g/1 peracetic acid, 1 g/1 tetrasodium pyrophosphate (stabiliser) and 1 g/1 wetting agent with a liquor ratio of 5 1. Peracetic acid has a pH of about 1.5 and the bleaching bath solution is adjusted to pH 5.5 with the help of dilute alkali. The material is entered cold and run for 10 min. Then the temperature is raised to 65-70 C in 15 min and bleaching is continued at this temperature till the concentration of peracetic acid drops to 0.09 g/1. The fabric is then washed thoroughly... 

Polyester fibers have exceUent resistance to soap, detergent, bleach, and other oxidiziag agents. PET fibers are generally iasoluble ia organic solvents, including cleaning fluids, but are soluble ia some phenoHc compounds, eg, (9-chlorophenol. 

The most common chemical bleaching procedures are hypochlorite bleach for cotton hydrogen peroxide bleach for wool and cotton sodium chlorite bleach for cotton, polyamide, polyester, and polyacrylonitrile and reductive bleaching with dithionite for wool and polyamide. 

Preparation for Dyeing. A hot alkaline scour with a synthetic surfactant and with 1% soda ash or caustic soda is used to remove size, lubricants, and oils. Sodium hypochlorite is sometimes included in the alkaline scouring bath when bleaching is requked. After bleaching, the polyester fabric is given a bisulfite rinse and, when requked, a further scouring in a formulated oxahc acid bath to remove mst stains and mill dkt which is resistant to alkaline scouring. 

Other fibers blended with polyesters in numerous blended fabrics requke alternative methods of preparation. Generally, the scouring and bleaching procedures used for these blends are those employed for the primary component of the blended fiber or for the component that most influences aesthetic appearance. 

In a recent detailed evaluation of Cl Fluorescent Brightener 393 on polyester, this product was incorporated into the polymer melt. The prebrightened fibre was blended with cotton and fabric knitted from these yarns was scoured and bleached. It was demonstrated... 

FBA may be applied by exhaustion from the same bath. If the polyester portion of the blend is to be bleached with sodium chlorite, the cotton is usually brightened in a second step since most FBAs for cotton are destroyed by sodium chlorite. Both types of FBA are normally compatible with a hydrogen peroxide bleaching process. 

Cotton and Cotton-Polyester. Cotton is the principal fiber bleached today, and almost all cotton is bleached. About 80-90% of all cotton and cotton-polyester fabric is bleached with hydrogen peroxide. 

The best laundry procedure for 100% cotton and 65/35 polyester/cotton fabric is to presoak the fabric for 3 hours in the washing machine filled with warm water (70 liters at 50°C) to which 280 mL of chlorine bleach has been added. After the 3 hours, empty the machine, and give the fabric a single warm wash (at 50°C). Less than 0.1% chlorpyrifos residue remains on both cotton and polyester/cotton when the bleach soak pre-treatment is used however, when a single wash, without the bleach pre-soak is used, approximately 40% of the chlorpyrifos residue remains on the cotton fabric and 28% on the polyester/cotton blend. 

NOTE The bleach/soak procedure results in color loss that is severe for 100% cotton and less for the polyester/cotton blend in addition, after 25 bleach/soak launderings, a third to half of the original strength of the 100% cotton is lost, whereas there is no significant strength loss for the 65/35 polyester/cotton blend.7... 

Summaries of chemical and physical properties of different polyester fibers are available (107). Polyesters display excellent resistance to conventional textile bleaching agents and are most resistant to cleaning solvents (107). Mold, mildew, and fungi may grow on finishes applied to polyester fabrics but do not attack the fiber itself (3). Again, insects that devour natural fibers normally do not affect polyester fibers although they may cut their way out of the fabric if trapped. 

In the textile industry, because of its intense, but nevertheless fiber protecting, bleaching effect. Sodium Chlorite HOECHST is used for bleaching nearly all natural and synthetic fibers. The effects on synthetic fibers, e.g., polyamide, polyester, and polyacrylonitrile are extremely good and cannot be obtained by other bleaching products which are used in the textile industry. 

Post cleanup of polyester yarns and fabrics Bleaching of nylon... 

BURCO SCOUR VAR-DF3 is particularly effective for J-Box and Kler bleaching, and for prescouring, of 100% cotton and polyester/cotton blends. It combines the solvents and emulsifiers to penetrate and remove troublesome oils and waxes by holding them in suspension, thus preventing any redeposit on the fabric. 

Non-yellowing softener for bleached white and pastel dyed cotton, polyester/cotton and acrylic/cotton knit goods. 

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