Evaluating the Role of Hydrophobic and Cationic Appendages on the Laundry Performance of Modified Hydroxyethyl Celluloses

Abstract

Soil-release polymers (SRPs) are essential additives of laundry detergents whose function is to enable soil release from fabric and to prevent soil redeposition during the washing cycle. The currently used SRPs are petrochemical-based; however, SRPs based on biorenewable polymers would be preferred from an environmental and regulatory perspective. To explore this possibility, we have synthesized SRPs based on hydroxyethyl cellulose (amphiphilic HEC) appended with controlled compositions of hydrophobic and cationic appendages and assessed their cleaning abilities. The results demonstrate that the introduction of hydrophobic lauryl appendages onto the HEC backbone is essential to deliver anti-redeposition and soil-release performance. Conversely, further introduction of cationic groups onto hydrophobic modified HECs had no clear impact on soil-release performance but caused significant disadvantages on anti-redeposition performance. We speculate that this poor performance arises on account of coacervation formation between the cationic HEC polymer and the anionic surfactant in the detergent, negatively impacting soil suspension and suggests that the inclusion of cationic appendages on HECs can ultimately lead to detrimental effects on performance. Interestingly, in contrast to conventional SPRs that exhibit good soil-release performance exclusively on synthetic fabrics, amphiphilic HEC displayed encouraging results on both synthetic and cotton-based textiles, possibly as a result of a good chemical affinity with natural fabrics. This work highlights that the nature and hydrophobic content of HEC ethers are key variables that govern HEC applicability as SRPs, thus paving the way for the design and synthesis of new SRPs.

Figure 1

Synthesis of (A) hydrophobic modified HECs (1L–6L, 1E–2E, 1H) and (B) hydrophobic and cationic modified HECs (7LC–9LC, 3EC–4EC, 2HC).

Figure 2

Summary scheme of the soil-release test conditions.

Figure 3

Summary scheme of the anti-redeposition test conditions.

Figure 4

FTIR spectra of (a) hydroxyethyl cellulose (HEC), (b) hydrophobic modified HEC (3L), and (c) hydrophobic and cationic modified HEC (7LC).

Figure 5

¹H NMR spectra (700 MHz, D₂O) of (a) hydroxyethyl cellulose (HEC), (b) hydrophobic HEC (3L), and (c) hydrophobic and cationic HEC (7LC).

Figure 6

(A) Stain removal index (SRI) for polyester fabrics pretreated with hydrophobic modified HEC (3L–9L, blue), hydrophobic and cationic modified HEC (7LC–9LC, light blue), and unmodified HEC (red) compared with untreated fabrics (white). (B) Stain removal index for cotton fabrics treated with hydrophobic modified HEC (3L, blue) and hydrophobic and cationic modified HEC (7LC, light blue) compared with untreated fabrics (white). (C) Polyester fabrics were pretreated with pure unmodified HEC (left), hydrophobic HEC (3L, center), and amphiphilic HEC (7LC, right) and then stained and washed. (D) Cotton fabrics were treated with hydrophobic HEC (3L, center) and amphiphilic HEC (7LC, right) and then stained and washed.

Figure 7

(A) Test A results: whiteness index variation (ΔWI) of knit cotton (blue, CK), polycotton (light blue, PC), polyester (red, PE), and polyspandex (white, PS) tracers washed with a laundry detergent formulation in the presence of HEC ethers (3L–6L, 7LC–9LC). (B) Test B results: whiteness index variation (ΔWI) of knit cotton (blue, CK), polycotton (light blue, PC), polyester (red, PE), and polyspandex (white, PS) tracers washed with a laundry detergent formulation in the presence of HEC ethers (1E–2E, 3EC–4EC, 1H, 1HC). (C) Test C results: whiteness index variation (ΔWI) of knit cotton (blue, CK), polycotton (light blue, PC), polyester (red, PE), and polyspandex (white, PS) tracers washed with a laundry detergent formulation in the presence of HEC ethers (1L, 2L, and 3L).

Figure 8

Turbiscan stability Index (TSI) as a function of time (s). (A) Evolution of the TSI index of samples 3L and 7LC compared with the TSI index of a laundry detergent (200 ppm) in the absence of polymers. (B) Evolution of the TSI index of a typical laundry detergent solution (200 ppm) with samples 3L and 7LC compared with the TSI index of a typical laundry detergent solution (200 ppm) in the absence of polymers. (C) Evolution of the TSI index of typical laundry detergent solution (2000 ppm) with samples 3L and 7LC compared with the TSI index of a typical laundry detergent solution (2000 ppm) in the absence of polymers.

Figure 9

Transmission values for modified HEC solutions as a function of a laundry detergent concentration.

Figure 10

ζ-Potential values of polyester fabrics conditioned with modified HEC solutions. White: untreated polyester; red: unmodified HEC; blue: hydrophobic HEC (sample 3L); cyan: amphiphilic HEC (sample 7LC); light blue: laundry detergent.