Reuse dyebath

A further advantage of spectrophotometers is the ready availability of a number of low-cost instruments with sufficient accuracy and reproductivity for dyebath analysis. Much of the work in the current study was carried out on a single-beam grating spectrophotometer costing approximately 2,000. The computations necessary in the analysis can be conveniently carried out on low-cost desk calculators or microprocessors. The calculations necessary for a four-dye mixture (or three dyes plus background) can be handled on a system costing less than 1,000. The least-squares fit of 16 points of the absorption spectrum can be carried out on a 3,000 minicomputer. Development of these low-cost instrument-minicomputer systems is largely responsible for consideration of dyebath reuse as a practical reality for the textile industry. 

Table III. Color Uniformity in Polyester Carpet Dyeings with Dyebath Reuse...

The estimated cost for a medium size (ten beck) carpet mill to convert 50% of dyeing capacity to the dyebath reuse system is shown in Table X. The calculation assumes the purchase of new equipment with a separate holding tank and pumping system for each of the five becks. At an estimated savings of one cent per pound of carpet dyed (considerably less than indicated in the Table VIII cost analysis and therefore conservative) the recovery of capital investment is still less than one year. 

Table X. Payback on Capital Costs for Carpet Dyebath Reuse...

No additional personnel required Savings using dyebath reuse, H per lb. of carpet dyed... 

Table XII. Modified Procedure for Dyebath Reuse Pantyhose Operations...

Table XV. Chemical, Water, and Energy Savings in Application of Dyebath Reuse to Disperse Dyeing of Nylon 66 Pantyhose ...

Using the savings figures from Table XV, a model pantyhose finishing plant incorporating dyebath reuse was constructed with the following assumptions ... 

The mill contained 16 rotating drum machines, all of 200-pound capacity, and 50% of the mill s production (Nylon 66) was adaptable to dyebath reuse. Eight of the machines would thus be equipped for reuse. 

Using vender information and best estimates, Table XVT was compiled to estimate the capital investment required to convert the eight 200-pound rotary drum machines of the model hosiery plant to dyebath reuse, the tools required to attain the proper analytical capabilities, and the cost of operating supplies for one year. The assumption was made that two machines could be operated from one holding tank. 

Hosiery Plant on Incorporation of Dyebath Reuse to 3.6 x 10° lb./yr. Production... 

Georgia Tech did not possess modern pressure fabric dyeing equipment at the initiation of the dyebath reuse research. Therefore, to determine the feasibility of dyebath reuse in the general area of coloration of 100% polyester under pressure with disperse dyes, research was initiated on available package yarn equipment. 

To further determine the effect of reusing the re-duction/clearing bath on the dyed yarn properties, lightfastness and crockfastness tests were performed on standard-dyed fabrics, dyebath reuse-dyed fabrics, and dyebath reuse plus reduction bath reuse-dyed fabrics. Lightfastness was performed according to AATCC Test Method 16A-1974, which called for forty hours of exposure to a carbon arc. Crockfastness was performed according to AATCC Test Method 8-1972. All fabrics exhibited the same fastness properties, indicating that the semiquantitative replenishment of the caustic/hydrosulfite bath did not affect the yarn quality. 

For a ten-cycle dyebath reuse sequence, the average energy consumption was calculated, using plant data and Table XXIV, to be 2.85 x 103 BTU/lb. Ten cycles was conservatively assumed to be the maximum number of cycles that the model plant could adequately schedule. 

Table XXV. Capital Equipment and Operating Cost Estimate for Dyebath Reuse Applied to Polyester Package Dyeing...

Figure 1. Dyebath reuse 100% cotton/low-temperature reactive dyes...

Table XXVII. Dyebath Reuse Color Difference Calculations 100% Cotton/One Low-Temperature Reactive Dye...

Figure 2. Dyebath reuse 50/50 cotton/polyester, high energy reactive/base-...

Table XXXII. Direct Savings in Two-Step Dyebath Reuse Coloration of Cotton/Polyester Knits Based on 3.6 x 10 Lb./Yr. Production...

An in-plant demonstration of dyebath reuse applied to coloration of nylon pantyhose has recently been completed, and the results will be published elsewhere (14). 

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