Bleaching and dyeing; fluid treatment and chemical modification – Bleaching – Wave energy
Patent
1995-08-16
1997-01-21
Howard, Jacqueline V.
Bleaching and dyeing; fluid treatment and chemical modification
Bleaching
Wave energy
8107, 8111, D06M 1004, D06L 302, D06L 304
Patent
active
055955720
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to wool and wool blend fabric treatments and in particular to novel methods of treating fabrics to give good colour yields when printed and/or to reduce pilling.
BACKGROUND
Wool and wool-blend fabrics have been processed and treated for many years to improve and/or enhance a wide range of characteristics. For example, the pre-treatment of fabrics, such as wool, before printing is essential to achieve good colour yields, levelness and brightness. Similarly a range of processes and treatments have been proposed to reduce or eliminate pilling.
Traditionally, chlorination has been used and several variants of the chlorination process are still used almost exclusively to prepare wool fabrics for printing. Dichloroisocyanuric acid (DCCA) is the most common chlorination reagent currently in use, and can be applied by both batch (the most common) and continuous processes. The batch method involves chlorination with 3-4% DCCA on mass of fibre (omf), at pH 3.5-4.5 and a temperature of 20.degree.-40.degree. C. for about 1 hour, followed by an antichlor aftertreatment with sodium bisulphite and acetic acid. The continuous process involves padding DCCA (35-50 gl.sup.-1), followed by a dwell time of 2-5 minutes before rinsing and an antichlor treatment similar to the batch process. The alternative to DCCA is Kroy chlorination, originally introduced for treatment of wool tops, which uses a solution of chlorine gas in water in a continuous fabric treatment process. Chlorine reacts with water to give a mixture of hypochlorous and hydrochloric acids, which is sprayed directly onto the fabric with a wetting agent. The reaction is more rapid than DCCA, but a rinsing and antichlor treatment are still necessary. Processing speeds of 10-15 m min.sup.-1 at a chlorine dose rate of 4% omf are typical and give similar performance to fabrics treated with 4% DCCA.
Typical problems with fabric chlorination include: yellowing, achieving an even application, and fibre damage. It is also very often necessary to bleach chlorine-treated fabrics, usually with hydrogen peroxide, to remove yellowness before printing. However, it is the environmental pressure on processes involving chlorine, particularly when absorbable organohalogens (AOX) are present in the plant effluent, which is leading to the replacement of chlorination by alternative technologies.
Other methods used to treat fabrics prior to printing are not common. Two polymer treatment routes, one for top and one for fabric are currently known, they are:
This polymer is applied to wool top after a prechlorination stage. Fabrics produced from treated top have an increased affinity for anionic dyes. The further mechanical processing which occurs during gilling, spinning and weaving results in a level preparation. However the colour yields tend to be lower since less chlorine is used. Further, care must be taken in washing off since treated wool has a high affinity for loose anionic dyes.
This polymer may be applied to a fabric without the need for a prechlorination step. The treatment of fabrics with this polymer prior to printing provides the fabric with a high affinity for hydrophobic dyes. However, the lack of a chlorination step reduces the penetration of printing paste into the fibres, and control over the steaming conditions is critical. This method has been used to print wool/cotton blends, but not pure wool fabrics to date.
Other methods avoiding the use of chlorine have been developed but are not considered to be commercially viable despite their reduced environmental impact. To summarise, the only prior art methods widely used commercially for pretreating wool fabrics for printing involve chlorination, followed by rinsing and an antichlor treatment, which then may require a bleaching treatment to remove yellowness.
Pilling is a term used to describe the formation of small, tight balls of fibre on a fabric surface. Pilling is highly detrimental to garments, resulting in a worn and unkempt appearance, and is a particular problem for knitwear.
The
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Howard Jacqueline V.
The Commonwealth of Australia Commonwealth Scientific and Indust
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