Enzymes in textile processing

2 12 2011

Humankind has used enzymes for thousands of years to carry out important chemical reactions for making products such as cheese, beer, and wine. Bread and yogurt also owe their flavor and texture to a range of enzyme producing organisms that were domesticated many years ago.

In the textile industry, one of the first areas which enzyme research opened up was the field of desizing of textiles.  A size is a substance that coats and strengthens the fibers to prevent damage during the weaving process. Size is usually applied to the warp yarn, since this is particularly prone to mechanical strain during weaving.   The size must be removed before a fabric can be bleached and dyed, since it affects the uniformity of wet processing. Previously, in order to remove the size, textiles were treated with acid, alkali or oxidising agents, or soaked in water for several days so that naturally occurring microorganisms could break down the starch. However, both of these methods were difficult to control and sometimes damaged or discoloured the material. But by using enzymes, which are specific for starch, the size can be removed without damaging the fibers.

Enzymes used in textile processing - photo from Novozymes

It represented great progress, therefore, when crude enzyme extracts in the form of malt extract, or later, in the form of pancreas extract, were first used to carry out desizing.  Bacterial amylase derived from Bacillus subtilis  was used for desizing  as early as 1917. Amylase is a hydrolytic enzyme which catalyses the breakdown of dietary starch to short chain sugars, dextrose  and maltose.

Enzymes have been used increasingly in the textile industry since the late 1980s. Many of the enzymes developed in the last 20 years are able to replace chemicals used by mills. The first major breakthrough was when enzymes were introduced for stonewashing jeans in 1987 – because more than one billion pairs of denim jeans require some sort of pre-wash treatment every year. Within a few years, the majority of denim finishing laundries had switched from pumice stones to enzymes.

Today, enzymes are used to  treat and modify fibers, particularly during textile processing and in caring for textiles afterwards.  They are used to enhance the preparation of cotton for weaving, reduce impurities, minimize “pulls” in fabric, or as pre-treatment before dying to reduce rinsing time and improve color quality.  New processing applications have been developed for:

  • Scouring (the process of removing natural waxes, pectins, fats and other impurities from the surface of fibers), which gives a fabric a high and even wet ability so that it can be bleached and dyed successfully. Today, highly alkaline chemicals (such as caustic soda) are used for scouring. These chemicals not only remove the non-cellulosic impurities from the cotton, but also attack the cellulose leading to heavy strength loss and weight loss in the fabric. Furthermore, using these hazardous chemicals result in high COD (chemical oxygen demand) and BOD (biological oxygen demand)  in the waste water. Recently a new enzymatic scouring process known as ‘Bio-Scouring’ is being used in textile wet-processing with which all non-cellulosic components from native cotton are completely or partially removed. After this Bio-Scouring process, the cotton has an intact cellulose structure, with lower weight loss and strength loss. The fabric gives better wetting and penetration properties, making the subsequent bleach process easy and  giving much better dye uptake.
    • One of the newest products, PrimaGreen® EcoScour from Genencor, offers sustainability advantages for eco-scouring in cotton pretreatment, including 30 percent water savings and 60 percent energy savings compared to standard processing. In addition, the mild processing conditions result in improved fabric quality and enhanced color brightness after dyeing.
  • Bleaching – When bleaching cotton, a lot of chemicals, energy and water are part of the process. The company Huntsman has developed a wetter/stabilizer that maximizes the wetting and detergency of the bleaching process and a one-bath caustic neutralizer and peroxide remover in order to shorten the bleaching cycle, reduce energy and water required and deliver more consistent bleaching results. They have developed surfactants that are environmentally friendly (in that they do not contain Alkylphenol ethoxylates), and the system is both Oeko-Tex and GOTS approved.  After fabric or yarn bleaching, residues of hydrogen peroxide are left in the bath, and need to be completely removed prior to the dyeingprocess, using a step called bleach cleanup.  The traditional method is to neutralize the bleach with a reducing agent, but the dose has to be controlled precisely. Incomplete peroxide removal results in poor dyeing with distinct change of color shade and intensity, as well as patchy, inconsistent dye distribution. Enzymes used for bleach clean-up ensure that residual hydrogen peroxide from the bleaching process is removed efficiently – a small dose of catalase breaks hydrogen peroxide into water and oxygen.  This results in cleaner waste water and reduced water consumption.
    • In 2010, a life-cycle assessment was completed comparing PrimaGreen enzymatic bleaching to conventional textile bleaching methods. According to this LCA, if the enzymatic system were to see wide scale global adoption, the potential savings in freshwater consumption could be up to 10 trillion liters of water annually, and greenhouse gas reductions could range from 10-30 million metric tons. (1)
  • Biofinishing or biopolishing (removing fiber fuzz and pills from fabric surface) –  enzymatic biofinishing yields a cleaner surface, softer handfeel, reduces pilling and increases luster;
  • Denim finishing – In the traditional stonewashing process, the blue denim was faded by the abrasive action of pumice stones on the garment surface. Nowadays, denim finishers are using a special cellulase.  Cellulase works by loosening the indigo dye on the denim in a process known as ‘Bio-Stonewashing’. A small dose of enzyme can replace several kilograms of pumice stones. The use of less pumice stones results in less damage to garment, machine and less pumice dust in the laundry environment; in addition, it’s possible to fade denim without risk of damaging the garment.
  • European scientists have just announced a new and environmentally friendly way to produce textile dyes using enzymes from fungi. (2)

Because of the properties of enzymes, they make the textile manufacturing process much more  environmentally benign. (3)   Generally, they:

  1. operate under milder conditions (temperature and pH) than conventional process chemicals – this results in lower energy costs ( up to 120 kg CO2 savings per ton of textile produced) (4) ;
  2. save water – reduction of water usage up to 19,000 liters per ton of textiles bleached;
  3. are an alternative for toxic chemicals, making wastewater easier and cheaper to treat.
  4.  are easy to control;  do not attack the fiber structure with resulting loss of weight, resulting in better quality of material;
  5. better and more uniform affinity for dyes;
  6. contribute to safer working conditions through elimination of chemical treatments during production processes;
  7. are fully biodegradable.

So why is there a ruckus about enzymes being used in textile processing by GOTS and other organic certifying agencies?

(1)   http://primagreen.genencor.com/sustainability/lca_results/

(2)   http://www.just-style.com/news/eco-friendly-textile-dyes-use-enzymes-from-fungi_id112195.aspx

(3)   http://www.textiletodaybd.com/index.php?pid=magazine&id=52

(4)  http://www.europabio.org/sites/default/files/pages/lutz-walter-benefits-from-white-biotechnology-applications-in-the-european-textile-and-clothing-industry.pdf

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Toxic textiles by Walt Disney

27 01 2011

The Walt Disney Corporation,  in a letter to Greenpeace in 2003, said that “the Walt Disney Company is always concerned with quality and safety”.

Greenpeace decided to test that statement, so – as part of their campaign to show how dangerous chemicals are out of control, turning up in house dust, in household products, food, rain water, in our clothes……and ultimately in our bodies – they decided to test Disney’s childrenswear for the presence of toxic chemicals.

Disney garments, including T-shirts, pajamas and underwear, were bought in retail outlets in 19 different countries around the world and  analyzed  by the independent laboratory Eurofins, an international group of companies which provides testing, certification and consulting on the quality and safety of products and one of the largest scientific testing laboratories in the world. 

Greenpeace asked Eurofins to test the Disney childrenswear for:

1.      Phthalates

2.      Alkylphenol ethoxylates

3.      Organotins

4.      Lead

5.      Cadmium

6.      Formaldehyde

We don’t have the space to fill you in on why each of these six chemicals is of grave concern, but please believe us – they’re not good.  Any one of these chemicals can interfere with a child’s neurological development, for example, or can set the path for a cascade of health problems as they age.   

This is what they found:

1.      Phthalates:  Found in all the garments tested, from 1.4 mg/kg to 200,000 mg/kg – or more than 20% of the weight of the sample.

2.      Alkylphenol ethoxylates: Found in all the garments tested, in levels ranging from 34.1 mg/kg to 1,700 mg/kg

3.      Organotins:  found in 9 of the 16 products tested; the Donald Duck T shirt from The Netherlands had 474 micrograms/kg

4.      Lead:  Found in all the products tested, ranging from 0.14 mg/kg to 2,600 mg/kg for a Princess T shirt from Canada.  With Denmark’s new laws on the use, marketing and manufacture of lead   and products containing lead, the Princess T shirt from Canada would be illegal on the Danish market.  Canada has set a limit of 600 mg/kg for children’s jewelry containing lead – why not Disney T shirts?

5.      Cadmiun:  Identified in 14 of the 18 products tested, ranging from 0.0069 mg/kg in the Finding Nemo T shirt bought in the UK to 38 mg/kg in the Belgian Mickey Mouse T shirt.

6.      Formaldehyde:  Found in 8 of the 15 products tested for this chemical in levels ranging from 23 mg/kg to 1,100 mg/kg.

One sample stands out: a German Winnie the Pooh PVC raincoat.  This contained an astounding 320,000 mg/kg of total phthalates, or 32% by weight of the raincoat!  This raincoat also contained 1,129 micrograms/kg organotins.

Greenpeace urged Disney to take responsibility for avoiding or substituting harmful chemicals in their products and to demand that their licensees implement a chemical policy that protects children’s heath.  Disney reacted by stating that their products are in line with the law.    The only action taken was to put labels on some products with a warning that those clothes contain toxic chemicals – but  only in the UK (which has more stringent laws regarding chemical use than does the US), and only on a few items.  Greenpeace Toxics Campaigner Oliver Knowles said, “”Their complete disregard for children’s health smacks of a Mickey Mouse company, and it’s now down to us to let the public know that these pyjamas contain dangerous chemicals.

“Perhaps it would be more apt if Buzz Lightyear’s catchphrase became   “To infertility and beyond!”

SAFbaby.com has asked a variety of children’s clothing companies whether their clothing contained formaldehyde.  Disney responded that they comply with all Consumer Product Safety Commission (CPSC) regulations.   But (as SAFbaby commented): CPSC has NO regulations set for formaldehyde levels, so that reply was not helpful to us in the slightest.  We are not impressed with their follow up response to us.

Disney’s refusal to be pro active in insisting their suppliers phase out hazardous substances demonstrates why voluntary initiatives don’t work.  We support Greenpeace in asking that legislation  to require mandatory substitution of hazardous chemicals with safer alternatives be put in place.

Read the Greenpeace report on Disney’s childrenswear here.