DMDHEU

This resin was most popular in Europe, partiy because of its lower requirements of glyoxal. However, because of increased availabiHty and lower glyoxal costs plus certain appHcation weaknesses, it has been generally replaced by DMDHEU. 

It is important that the amino resins used in the postcure process should ( /) not react with the fabric before it has been fashioned into a garment, and (2) release a minimum amount of formaldehyde into the atmosphere, especially while the goods are in storage or during the cutting and sewing operations. These requirements are met, at present, with the diethylene glycol modified DMDHEU resin. 

Control of Formaldehyde Release. Once the sealed-jar test became a factor in measuring the formaldehyde release of fabrics suppHed to garment cutters, limitations were placed on the allowable limits acceptable to the garment producers. These limits brought to the fore two classes of reagents those based on DMDHEU, and those based on the /V, /V- dim ethyl o1 ca rh am a tes (4) (88). 

Prior to 1965, it was not unusual for unwashed finished fabrics to release 3—5000 ppm of formaldehyde when tested by an AATCC test method. Formaldehyde release was reduced to the level of 2000 or less by appHcation of DMDHEU or dimethyl olcarhama tes. This level was reduced to approximately 1000 in the mid-1970s. Modification of the DMDHEU system and use of additives demonstrated that release values below 100 ppm were achievable. As of this writing (1997), good commercial finishing ranges between 100 and 200 ppm of formaldehyde release. 

Nonformaldehyde Finishing. The concern for formaldehyde release prompted interest in the development of cross-linking systems that did not contain formaldehyde. A number of systems were investigated but generally these systems seemed to fall short in performance (106,107). For example, l,3-dimethyl-4,5-dihydroxyethyleneurea (DMeDHEU) (5) has been used in Japan since 1974. This same agent has been marketed in the United States and elsewhere, but generally the level of smooth-dry performance is substantially lower than the level achievable with DMDHEU. The cost of dimethylurea also raises the overall cost of DMeDHEU above that of DMDHEU. 

As of this writing (1997), researchers are exploring combinations of acids, additives, and catalysts to achieve a suitable economic finish. However, commercial appHcation of these finishes would require costs akin to that of DMDHEU as well as compliance with formaldehyde release levels by consumers, regulators, and the textile industry. Another possible impetus could be marketing considerations. Nevertheless, this work has sparked intense effort in the use of cross-linkers containing ester cross-links and has broadened the scope of cross-linker research. 

A number of after-treatments with polyester copolymers carried out after sodium hydroxide processing are reported to produce a more hydrophilic polyester fabric (197). Likewise, the addition of a modified cellulose ether has improved water absorbency (198). Other treatments used on cotton and blends are also effective on 100% polyester fabrics (166—169). In this case, polymeri2ation is used between an agent such as DMDHEU and a polyol to produce a hydrophilic network in the synthetic matrix (166—169). 

Combined dyeing and easy-care finishing of cotton using bis-nicotinotriazine reactive dyes and DMDHEU in a pad-dry-HT steam process [325]... 

HOH2C CH2OH Figure 7.2 Cross-linking of cell wall polymers by reaction with dimethyloldihydroxyethyleneurea (DMDHEU). 

Ahmed Kabir etal. (1992) treated wood with DMDHEU as well as DMDHEU combined with a vinyl polymer, and determined the dimensional stability of the wood. Methane sulphonic acid was used as a catalyst in both cases. DMDHEU treatment resulted in a 50 % reduction in radial swelling following immersion in water for 100 minutes, with the combined treatment being snperior. However, the ASE (one cycle) of DMDHEU treated wood (30%) was snperior to that fonnd for the combined treatment (17%). DMDHEU appeared to be stable to hydrolysis over a number of wetting cycles. When DMDHEU-treated samples were exposed in ontdoor weathering trials, they exhibited considerable variation in moistnre content and developed severe surface checks, whereas the combined treatment showed snperior performance. 

Militz (1993) treated European beech with DMDHEU and evaluated the effectiveness of a variety of commercial catalysts. It was found that temperatures of 100 °C were necessary for effective curing of the resin. The ASE was calculated from the dimensions at 100 % RH in comparison to the sample dimensions at 30 % RH, rather than in a water-soak test, so that any possible effect of leaching was not determined. The highest ASE measured in this way was 75 %. The EMC of the treated samples was also determined and found to be higher than unmodified samples in all cases. 

The only treatments that are likely to be viable commercially are aqueous delivery systems. Of the systems described in this chapter, furfurylation is the most advanced commercially and appears to show great promise. There has also been the recent introduction of the DMDHEU-based modified wood Belmadur on the market by BASF. At the present time, no other systems appear to offer any immediate prospects for commercial exploitation. The use of silicone treatments has apparently received little attention, which is very surprising due to the ready commercial availability of these systems for masonry treatment. Whether this apparent lack of activity is due to an oversight, represents a lack of real potential or perhaps is due to commercial sensitivity will become clearer in the future. However, silicone treatments are confined to the wood surface only and are not capable of penetrating the cell wall, and would therefore provide little improvement in dimensional stability. Similarly, no significant improvement in biological durability would be expected, since the relatively thin envelope of the treatment would be breached easily. However, the use of silicones in combination with other treatments that may be teachable in service (e.g. borates) would be an area well worth exploring. 

Zee, M.E. van der, Beckers, E.P.J. and Mditz, H. (1998a). Influence of concentration, catalyst, and temperature on dimensional stability of DMDHEU modified Scots pine. International Research Group on Wood Preservation, Doc. No. IRGAVP 98-40119. 

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