Thermosol Process

In heat fixation of disperse dyes, hot air and contact heat are used most commonly. Steam has a swelling effect on the fiber. If superheated steam is used for fixation, the temperature can be lowered in comparison with hot air, the fixing times being the same. This is an advantage especially with articles made of textured fibers. 

In the case of PES-CEL fiber blends, the larger part of the liquor is absorbed by the CEL fiber during drying, because of its higher absorption capacity. Nevertheless, in the subsequent thermofixing step, disperse dyes are almost completely fixed to the PES fiber. Transfer from the CEL to the PES fiber occurs both by migration via direct fiber contact and through the gas phase. The type of transfer depends on the sublimation behavior of the dyes [120], 

---

Antlblaze 19. Antiblaze 19 (Mobil), a flame retardant for polyester fibers (134), is a nontoxic mixture of cycHc phosphonate esters. Antiblaze 19 is 100% active, whereas Antiblaze 19T is a 93% active, low viscosity formulation for textile use. Both are miscible with water and are compatible with wetting agents, thickeners, buffers, and most disperse dye formulations. Antiblaze 19 or 19T can be diffused into 100% polyester fabrics by the Thermosol process for disperse dyeing and printing. This requires heating at 170—220°C for 30—60 s. 

Although polyester is always brightened with disperse-type products, the methods of application vary. FBAs are marketed for incorporation in the polymer mass, for exhaust application with or without carrier and for use in the pad-thermosol process at a temperature within the range 160-220 °C. Most products are applicable by more than one method, although none can he applied satisfactorily by all methods and cost-effective products introduced in the 1950s still remain important today. 

Many other compounds have been marketed as polyester brighteners for application by exhaustion or in the pad-thermosol process. No account would be complete without mention of the important class of coumarin disperse FBAs, of which structure 11.39 is a typical example. Many commercial brighteners for polyester contain one or two benzoxazole groups, including compounds 11.31, 11.35, 11.36, 11.40 and 11.41. 

Fixation is performed by steaming under various conditions, depending on the fibers and dyes involved. Generally, saturated steam at ca. 100°C is applied. Pressure steamers permit a reduction of the steaming time. Disperse dyes are fixed in polyester fibers by the Thermosol process the fabric is heated in a infrared unit by radiation, by hot air, or with contact heat to 210-220°C for 30-60 s. Superheated steam facilitates rapid fixation at lower temperatures. 

Polyester fibers are dyed to a considerable extent by selected low-molecular vat dyes with satisfactory fastness properties. They can be applied on CEL -PES fiber blends by the Thermosol process (see Section 4.12.4). 

PES fibers are almost exclusively colored with disperse dyes. For some time, dia-zotization dyes were used for dark shades. They are coupled in the fiber with suitable components (e.g., 2-hydroxynaphthoic acid). Although fast colors are obtained, the dyeing process is time-consuming and susceptible to failure, and dyeing reproducibility is poor. Vat dyes are also occasionally used for PES dyeing. Small molecular thioindigo derivatives, in particular, diffuse into PES fibers if they are applied in the thermosol process. 

Thermosol Process. The most important continuous dyeing process for PES fibers is the thermo sol process. It is applied primarily to PES-CEL blends (see Section 4.12.4). The thermosol process consists of four individual steps (1) Padding of the dye liquor on the fabric, (2) Drying, (3) Fixing of the dyes in the fiber, (4) Aftertreatment. The four individual steps usually follow one another in one pass. Systems also exist that include the subsequent overdyeing of the cellulose component in blended fabrics [e.g., by using the pad steam technique (see Section 4.1.1)]. 

After the dyes are fixed, dyes and auxiliaries that adhere superficially must be washed out, if necessary, by an alkaline reductive treatment. In the case of PES-CEL fiber blends, this washing can be combined conveniendy with afterdyeing of the cellulose component, e.g., simply by overdyeing with vat dyes (see Section 4.4.3). For details of the thermosol process, see [85, pp. 122-131],... 

In the thermosol pad batch process, a semicontinuous process, alkali-sensitive disperse dyes can be used if the alkali is applied after the thermosol process. Conversely, if the thermosol process is carried out after the pad batch step, the pH must be lowered before the thermosol process so that the disperse dye is not destroyed. 

In terms of dyeing and finishing, CT is more similar to purely synthetic fibers than CA. It can be permanently pleated. For stress relaxation, articles made of CT, like those made of PES, are heat set (thermofixed) after dyeing [80, pp. 92-100], CT, like PES, can be dyed by the thermosol process (see Section 4.12.1). 

SOLIDOKOLL N is a synthetic thickener for the prevention of dyestuff migration during the Intermediate drying of the fabric. It is particularly recommended for drying of synthetic fiber fabrics and its blends by the thermosol process. 

SOLIDOKOLL N does not become insoluble or lose it swell-ability as some natural products during the drying or thermosol process. 

Antimigrant for thermosol processes using pigments and dyes on cotton and polyester/cotton fabrics. 

The Thermosol process of Du Pont, or similar thermofix methods, are used extensively for continuous dyeing of materials made of polyester alone or when mixed with other fibres. The process, see Fig. 23.11, is... 

The Thermosol process (Chapter 23) is applied extensively to the continuous dyeing of cloth made of blends of polyester and cellulosic fibres. 

Emigen . [Hoechst Celanese/Colorants Surf. Hoechst AG] Acrylamide deriv. prevents frosting effect during thermosol process on polyester/cellulo-sic fiber blend. 

Simultaneous dyeing and flame retardation of 100% polyester fabric has always been a commercially successful aim and while research has been undertaken in this area with reasonable levels of durability achieved, either in a dye bath or by thermosol process, potential commercial exploitation depends on the costs relative to the cost of using an inherently low flammable polyester. Currently in the UK, for example, Solvay (formerly Rhodia) market Amgard CU which is the same as the former Antiblaze IQ " for finishing polyester textiles based on the cyclic phosphonate structure where n=l ... 

Textile production traditionally involves a number of wet processes that may use solvents. Emissions of volatile organic compounds (VOCs) mainly arise from textile finishing, drying processes, and solvent use. VOC concentrations vary from 10 milligrams of carbon per cubic meter (mg/m ) for the thermosol process to 350 mg carbon/m for the drying and condensation process. 

---