Ecology And Environmental Issues In Coating And Laminated Textile.

Introduction

Fabric coating and lamination are technical processes and the products are, therefore, technical products which form an important sector of the textile industry. Much depends on definitions and how products are categorized, and it is difficult to find figures which specifically apply to coated and laminated .fabrics. Coated and laminated fabrics appear in most, if not all, of these areas, especially transportation, industrial, clothing, and medical uses. Significant growth is expected in all 12 application areas, especially in the geotextile, environment and protective clothing categories. Transportation textiles, which includes uses in automobiles, other road vehicles, aircraft, marine and rail, is the largest single area in technical textiles.

Coating

 

Coating is a process in which a polymer layer is applied directly to one or both surface of the fabric. The polymer coating must adhere to the textile and similar aperture to control the thickness of polymer .The technical textile required heavy coating than apparel coating .the coating has been applied to woven technical textile, but increasingly warp knitted, Rachel, weft knitted and nonwovens fabric must be coated on the same line considering advantage and disadvantages of selected fabric for particular application purpose. coating may be colored, reflective, repellent, according to the end use requirement. the chemicals which are generally use are:

1. Surfactants
2. Pigments
3. Plasticizer
4. Flame retardant
5. water repellent
6. Accelerators
7. Ant degradants
8. Fungicides

Coating Technology:

Transfer coating

It is an indirect coating technique in which coating technique formed on silicon coated release paper. the film may be formed before transferring the fabric by application of heat.

Direct coating

Coating is essentially spreading a polymer in the form of a thickened aqueous dispersion or an aqueous or solvent solution on to a fabric to form a continuous layer. It is necessary to thicken the liquid so that it does not sink into or through the fabric. Pre-prepared compounds should always bestirred and the viscosity checked and recorded before applying. The simplest coating procedure is the direct method, sometimes called the ‘floating knife’ or knife over air technique, where the fabric is stretched flat to form an even uniform surface and is transported under a stationary doctor blade. Direct coating is mainly used for fabric produced from smooth continuous filament yarns such as nylon or polyester. If fabrics made from spun yarns are direct coated, a raspy rough surface is generally obtained because the fibre ends protrude from the surface.

Foam finishing

Related to direct coating is ‘foam finishing’, which involves preparation of foam using a solution or a water dispersion of the textile chemical to be Coated and laminated textiles applied. The foam is direct coated in the same way as described above for compounded polymers. Foam processing was developed in the USA during the late  more environmentally friendly alternative to impregnation or padding with a pad mangle.Instead of fully immersing the fabric in an aqueous bath of the chemical finish and then squeezing out the excess water, the foamed chemical, at the appropriate concentration, is direct coated on to one side of the fabric. The foam processing method is especially useful for applying finishes to only one side of the fabric – the non-coated side. Foam processing may be a way of applying colour to one side of the fabric.

Aqueous coating

Aqueous based coating system are now more widely used to apply water soluble/water dispersible polymer to the fabric. The coating formulation must be dried by evaporation of water in hot air oven.

 Hot melt extrusion coating

This method is used for thermoplastic polymers such as polyurethane, polyolefins and PVC, which are applied by feeding granules of the material into the nip between moving heated rollers.

Calender Coating

Calenders are primarily used to produce unsupported films of PVC and rubbers from compounded polymer ‘dough’. The process can also be adapted to apply the freshly produced film to fabric. Calenders consist of a number of massive rollers, sometimes five or more in various configurations, which rotate to crush the ‘dough’ and smooth it into films of uniform thickness. 28,29 The thickness of the film is determined by the gap separation between the rollers, but there is usually a limit to the thinness of films which may be produced by this method. The more rollers, the more accurate and uniform is the film produced.

Lamination

Combines two materials and this very act results in modification of physical properties based on the individual characteristics of the separate components. If one component has limited stretch only in the warp and the other limited stretch only in the weft, the combined material will have limited stretch in both warp and weft.

Lamination Technology:

Flame lamination

The flame lamination process is in widespread use throughout the world. This lamination method was once used extensively to produce laminated fabric for garments, curtains and drapes, and it makes use of the polyurethane foam itself as the adhesive. It is a quick, economical process but requires a certain amount of technical skill, regular maintenance and abatement of the fumes produced.

Polyolefin foam

Polyolefin foams, which are used in car interiors, can also be flame laminated, especially to other materials with some thermoplastic nature. polyolefin foams have certain advantage over polyurethane foams such as no fogging in automobiles, better chemical resistance and ageing properties. Hot melt lamination is accomplished by two separate processes: first a means of applying the actual adhesive; and second bringing the two substrates together to form the actual  bond under the action of heat and pressure.

Hot melt lamination

When the issue of flame lamination being an environmentally unfriendly process arose, thoughts turned first to calendars and the hot melt adhesives, which had been used in the garment industry for many years. the two materials being joined are made into a sandwich with a hot melt adhesive film, web or powder in the centre. This is then fed into the calendar, which heats the materials and melts the adhesive to produce a laminate. Calendars are available from several manufacturers and with different designs, e.g. different layout of heater zones and heater arrangement, some with cooling inside the machine, others with the cooling unit outside. The main drawback of the calendar method is that the heat is supplied to the hot melt adhesive via the substrates themselves, which could be prone to damage by heat, especially fabrics with textured yarns or with a pile.

Adhesive in lamination

Adhesive are solution in a solvent or water or as desperation in water or soil, which

melt under the action of heat.

Solvent based and  Water based adhesive

Solvent based adhesive can be used to laminate micro porous membrane to textile fabric to provide a barrier against liquids.solvant based adhesive arte not eco friendly and harmful to health if breathed. it is more expensive than water .water based adhesive are safe and cause less pollution  to the environment.

The Mathematical Equation

IMPACT OF ENVIROMENT=POPULATION×AFFUENCE ×TECHNOLOGY

All human activity as some effect on the environment and coating and laminating industry  is no exception .however, the overall guiding principle, agreed by everyone, to protect the environment is to reduce ,reuse, repair or recycle.

Environmental  Issues

Significant fundamental environmental treads and issue that will have an impact on coating and laminating industry are needed attention. the environmental friendliness can be assessed in the manufacturing part o life cycle of the coated and laminated product. various factors are

• Chemical application to impact various material functions
• Binding material used to produce fibrous products.
• Renewable sources as the claim for environmental accepted product.
• Type of matrix used to produce fiber composite.
• For many application of technical textile are either coated or laminated with polymeric materials
• Most of coated technical technical textile requires manmade fiber which consumes level of power and energy.
• Hazardous part of machine fail safe so that function cannot be overruled to create a unsafe situation.
• The elimination of excessive noice from equipment by suitable design or insulation.
• The avoidance of the use of any toxic or chemical.

The greenhouse effect and global warming Human life depends on the ‘greenhouse effect’, which is caused by the presence of certain gases and water vapour in the atmosphere. If they were not there, the surface of the Earth would be about 30°C lower than it actually is. Small changes in their concentration are believed to cause changes in the surface temperature of the Earth. It is a very delicate balance, because an increase in surface temperature of only 1 °C is thought likely to change the world’s ecology and cause very significant changes in climate and sea water levels. The greenhouse effect happens because the Earth’s atmosphere and surface retain heat. The atmosphere as a whole, including greenhouse gases, allows sunshine, made up of both short and longer wavelength radiation, to pass through to heat the Earth’s surface.

The ‘greenhouse effect’. Global warming causes changing weather patterns and rising sea levels. Incineration of solvent fumes and emissions from coating and lamination operations must be carefully controlled and abatement of fumes is essential. All incineration processes, including municipal waste disposal, produce carbon dioxide, the main ‘greenhouse’ gas.

Air pollution

Harmful gases or vapours and solid particulate matter cause air pollution. There are many air polluting gases which are harmful to human, animal and plant life, but the main ones are oxides of sulphur, carbon monoxide, hydrocarbons and oxides of nitrogen Oxides of sulphur, produced mainly from industrial burning of fossil fuels, give rise to acid rain; this is harmful to human health and also damaging to agricultural crops, vegetation and materials including buildings. Oxides of nitrogen contribute to acid rain, and produce adverse physiological conditions including eye and throat irritation if present in high concentration. Carbon monoxide is toxic to human and animal life, because it combines with hemoglobin in the blood resulting in less oxygen being carried to body organs, heart patients being especially vulnerable.

Particulate matter

Particulate matter is mainly carbon in a wide range of particle sizes, but the most harmful to health are those which are smaller than 10 micrometers in diameter.8–11 These small particles do not settle rapidly as dust, but stay in the air for long periods and are, therefore, more available for breathing into the human body Particle matter is believed to be the cause of bronchitis, asthma ,other chest and breathing conditions and to contribute to lung cancer.

Land and water

Pollution of waters by the textile industry is caused by manufacturing processes such as dyeing and finishing and the washing of pesticides from cotton. Toxic liquors will harm marine life and could be harmful to humans on beaches. Pollutants are broken down chemically and biologically in the water, but both mechanisms require action by the dissolved oxygen in the water. This reduces the amount of oxygen available for fish and other marine life. Measures of these effects are the oxygen demand indices, biological oxygen demand (BOD) and carbon oxygen demand (COD).

Environmental Aspects

The considerable interest in environmental heath and safety issues .many technical textile are temporary solutions to many environmental problems .the use of various polymer ,their formulation, the use of equipment and the carrying out of the industrial process, serious condition must be give at all the stages on the design. construction, installation, operation in machinery in coating and laminating field. it includes;

• The elimination of excessive noise from equipment
• All the hazardous part of machine such as drive, all working part of machine, nips all are failsafe so that functions cannot be overruled to create situation
• Avoid the use of toxic chemical
• Water based polymer used for fabric coating include polyvinyl acetate , pvc dispersions ,acrylics, polyurethane, silicon and rubber .aqueous polymer dispersion system contains up to 50% solids suspended in water and although they avoid the problem and solvent they require large amount of heat energy to drive off water to dry and the film which results.

 The advantage of water based coating polymer are:               

• Low environmental impact
• Low odor during application
• Low toxicity of discharge vapors
• Surfactant free- no adhesive problem
• Easy to use-no reactant needed
• Can be thermoplastic or thermosetting
• Heat resistance coating
• Low temperature flexibility
• Water vapour permeable

Environmental legislation

The earliest environmental laws in the UK were passed during the thirteenth century to control the burning of coal. However, times change and accepted standards become more demanding with the increase in the quality of life. Environmental regulations have become stricter to meet new circumstances and, in addition to UK law, there is now EU legislation, which takes the form of directives and regulations. Directives are guidelines to be used by individual countries to form their own laws, while regulations are  Coated and laminated textiles

themselves legislative acts which apply across the EU without further action by individual countries. The EU in 1973 (then called the EEC) started the mechanism for programmes of action to reduce pollution and nuisances, to tackle environmental problems caused by depletion of natural resources, to promote education and awareness of environmental problems, and also

to improve the natural and urban environment. Since this date the EU has been one of the leaders in the world community in protecting the environment.

European legislation

The European Integrated Pollution Prevention and Control Directive (IPPC), based on Part 1 of the UK EPA 1990, concerns major industrial operators who are to be licensed in an integrated way to control emissions to the air and water and to manage waste, in order to protect the environment as a whole. In addition IPPC is also concerned with the use and nature of raw materials, including water, energy efficiency, prevention of accidents, low waste technology, noise, and also restoration of a factory site to a satisfactory condition when production ceases. The overall concept is to make industry aware of the process as a whole, in order to ensure adoption of clean technology, careful management of resources (especially energy) and acceptance of the principle that the ‘polluter pays’.

Manufacturing concerns

In common with most major industries, textile producers take environmental and health and safety issues very seriously. All major manufacturers have established environmental policies and environmental management systems.

Coating and lamination

Joining methods using solvent-based adhesive spray application methods and flame lamination are potentially highly polluting, and many solvent based adhesives have been replaced and continue to be replaced with hot melt, high solids content and water-based varieties. However, fabric coating and joining using solvent-based resins and adhesives is still widespread. In the fabric coating industry, water-based resins are used whenever possible, but in some cases it is proving difficult at present to obtain the high standards of performance and durability normally achieved with solvent-based types. PVC factories need abatement for the fumes emitted during the gelling process. The fumes are likely to contain plasticizer and traces of the stabilizers and possibly other additives.

Health and safety aspects

Control of hazardous substances

All chemicals and materials used in the textile and automotive industries are subject to the Control of Substances Hazardous to Health regulations(COSHH) of 1994 (which replaced the original 1988 regulations) and March 1999, which cover all aspects of purchase, handling, transportation, storage, use and disposal. The most important issue is that an employer cannot carry out any activity which exposes employees to any hazardous substance unless a ‘suitable and sufficient’ assessment has first been made. The assessment must be reviewed regularly and whenever any significant modification to the process has been made. Hazardous material may include gases, vapours, liquids, fumes, dusts, solids or micro-organisms.

Automotive fabric recycling

The car seat laminate is generally made up from polyester face fabric, polyurethane foam and a scrim fabric which is either nylon or polyester. These chemically dissimilar materials are not easily separated and, therefore, cannot be easily recycled. The use of polyester scrim reduces the number of chemical types to two, but even this presents a problem. Chemical hydrolysis can be used to break down the three polymers into simpler chemicals which can be used as fresh raw materials, but at present this is not commercially feasible.68 Several different types of nonwoven and knitted fabric (for example ‘spacer fabric’,Kunit, Multiknit (by Karl Mayer) and wool/polyester blends) have been evaluated as substitutes for laminate polyurethane foam. Karl Mayer manufacture the machines on which they are made. Some materials have been made from garment waste and are being used commercially in German made cars.79–87 These foam substitutes do not need a scrim backing and using one made of polyester together with a polyester face fabric produces a seat cover laminate all in one polymer type. These materials provide a soft touch to the laminate and compression properties initially comparable to foam, but they all lose significant thickness in compression and heat ageing tests.88,89 The thickness loss would be easily noticeable with thick layers, but may be less noticeable in thinner layers. Fibre producers have demonstrated the possibility of using recycled polyester face fabric into nonwoven material.

PVC recycling

The use of PVC has been questioned by some environmentalists, especially Greenpeace, because of the possible risk to health of phthalate plasticizers, and also because of the possible formation of dioxin chemicals during PVC manufacture and eventual disposal. Disposal of PVC is difficult because it cannot be land filled or incinerated without certain risks. The high chlorine content produces hydrochloric acid gas (HCl), and if it is not controlled, the combustion process may also produce dioxins. Many incinerators are not built to cope with large amounts of HCl gas which could not be released to atmosphere without treatment. Landfilling PVC poses the risk of additives being leached out and eventually entering water courses and even drinking water. In addition, the covering properties of discarded tarpaulins could change soil morphology, and could be harmful to earthworms and other soil dwelling creatures by reducing the level of oxygen or by restricting the flow of water. PVC coated fabric biodegrades slowly, and its disposal has become a problem which has contributed to the search for ways of recycling the material and also for alternative covering materials.

Recycling of textiles

At present, ‘recycling’ of textiles generally means cotton rags into paper, recovered wool (e.g. shoddy, mungo), charity shops selling second-hand clothing. Clothing which is too degraded for use is made into rags for wipes.123–126 However, these ‘rags’ will eventually have to be disposed of – probably with heavy soiling on them – and in addition disposable paper and

non-woven textiles are reducing the need for rags as wipes. Other textile waste is shredded and used for filler and insulation in automotive components, and some is used in the flocking industry. Recycling of coated and laminated fabrics is generally not easy, because by definition they are frequently made from at least two different polymers or materials and separation is likely to be a difficult if not an impossible commercial process for certain articles. Even standard articles of clothing such as shirts are likely to be made from polyester and cotton – two very different fibres

Recycling and waste disposal

The problem of waste disposal. Material remaining after reusing (second hand clothing), recycling and composting must be disposed of either by incineration or by landfill. Incineration with energy recovery (EfW — energy from waste) requires careful control to prevent the formation of dioxins; emissions must be rigorously treated according to legislation, and preferably with the approval of local residents. Incineration residues, which may contain a high

concentration of toxic substances, must be disposed of in some way. Landfill sites are filling up and landfill poses the risk of toxic leach ate to underground waters, which may eventually reach rivers and drinking water. Landfill taxes are due to rise significantly. In addition, methane, a ‘greenhouse’ gas, is produced in landfills. The logistical problems of waste collection, dismantling, sorting and identification of different chemical types, and the transport costs are formidable Routes may be possible, but they need to be commercially viable.

Use of natural fibers and materials

In recent years there has been a revival of the use of natural materials in the automotive industry. The reasoning is that use of raw materials from renewable sources is more environmentally responsible than the use of synthetic fibres and plastics produced from non-renewable oil reserves.140,141 In addition, natural materials are more biodegradable, and there are also technical advantages. Bast fibres, flax, sisal, kenaf and hemp are being explored as replacements for the more expensive glass as long fibre reinforcement in polyurethane injection moldings’ for door panels and in other applications.

 Conclusion:

The aim of this study was to analyze the current situation of coating and  laminating  industry to increase the awareness for making it more healthy and hazardous free. it can be concluded that starting from the product design stage, raw material selection, to the processing and production decisions, transportation, retailing and waste management, it is possible to make textile and clothing production more environmentally friendly by taking precautions.

 

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