INTRODUCTION

Every carpet with its pattern resembles a collection of messages, beliefs and symbols. They are declaration of wish on which all expectations are enriched. Every pattern that is woven onto carpet is a picture of feelings, desire or a wish. So far as that every carpet represents a living history from early ages to the present in which women have patently and untiringly written their joys and sorrows in amazing codes and magic letters which are to be read line by line. They contain voices of birds voices, of children, gently blowing spring, winds, flowers, leaves, figures, whims wishes and rebukes carpet has long been a precious gift item, migration on the roots of conquest and trade carrying its patterns from one place to another and this magic work of craft has finally traveled through ages to our times and its colours, symbol language. 1

There are at least four methods of making carpets. They include woven carpets, tufted carpets, needle punching, and knitted carpets. Both natural and man-made fibres are used in manufacturing carpet yarns. Wool, silk and other natural fibres are also used in carpet industry. Man made fibres, today dominate carpet industry with nylon and polypropylene accounting for approximately 65% of the total market. 2

Currently 93% of carpet waste is associated and used and remaining 7% are clean and potentially more valuable was5te resulting from processing and installation operations. Carpet is made of several complex components and is bulky and cumbersome to transport. It is estimated that about 3 to 4 billion pounds of carpet are removed from home and business each year in the United States. There are many challenges to reusing and recycling used or post-consumer carpets. So far, this has been an evasive goal. 3 Recycling efforts are drawn by both environmental and economic concerns. Many carpet manufacturers, recycling companies and academic institutions are actively pursuing various methods to recycle carpet waste. Used carpet recycling programs were first introduced to commercial carpet retailers as a tool that appealed to an ecologically conscious market e.g. Dupont Carpet Reclamation Program.

BASF CORP. 6 IX AGAIN EXPANSION PROGRAM: Program came out at Georgia Institute of Technology. These approached include depolymerization, waste characterization, material component separation and reinforcement for concrete and soil. This seminar provides some of technologies and activities for carpet waste utilization.

CARPET AND ITS USES

    • Carpet Composition 3

Carpet is a complex of materials. The tufted broadloom shown below consists of four major components: face yarn, primary backing, adhesive and secondary backing. The face yarn or pile may be nylon (type 6, 6 or 6), polypropylene, polyester, wool or acrylic and is approximately 50% by weight of a new carpet (see table given below).

Composition of Typical Broadloom Carpets

Components

Weight %

Most Common Materials

Face Yarn

40- 60

Nylon 6 and 6,6 PET, PP

Primary Backing

4- 6

Woven PP

Adhesive

38- 52

SB Latex + calcium carbonate

Secondary Backing

3- 5

PP, Jute

Nylon 6, 6 is used as the face fiber in approximately 75% of all carpets. However, one of the first problems to solve when recycling carpet is to identify the carpet construction and type of face yarn.

The primary backing is generally a woven polypropylene fabric through which the face yarn is tufted. The adhesive layer is generally made from water-based latex and mineral filter of calcium carbonate. The filter accounts for 70 to 83 percent of the total weight of the adhesive mixture. The secondary backing is a lightweight fabric that provides strength and dimensional stability to the carpet. In most carpets it consists of a polypropylene slit tape in the warp direction and a polypropylene spun yarn in the fill direction. In the case of some carpets, such as carpet tiles, a vinyl coating replaces the latex adhesive layer and secondary backing. This structure lends itself to easier recycling techniques. Several major fiber producer companies have had pilot recycling programs for nylon for many years. Under these programs carpets are collected at centers throughout North America. The collected carpets are then sent to a central facility for separation of the face fiber after which they go through a depolymerization process that converts the nylon back to its precursor ingredients. BASF, Dupont and Allied signal all have programs with this approach.

  • Types of Fibers Used and their Conversion to Yarns:

Both natural and man-made fibers are used in manufacturing carpet yarns.

  • Wool 4

Wool or fleece sheered from back of sheep is expensive to produce and limited by the available number of animals. However hardworking warm feeling and comfort are associated with wool fibers, which account for nearly 31% of the carpet market. The quantity of wool varies according to the climate, the breed of sheep and the time of year of sheering. Wool from sheep that live in warm and arid regions is normally dry and brittle and since it breaks so easily. It is normally dry and brittle and since it breaks so easily. It ends up being short and feels lifeless. Good quality of wool comes from healthy and well-feed sheep found in cold regions or at high elevations with good grazing lands and lots of water. In colder regions sheep grow a full fleece to keep warm and the wool so fleece obtained feels silky, smooth and wet sparingly. One unique property of wool is its ability to felt. Specially constructed carpets have been finished to produce an attractive felted texture akin to sheepskin.

  • Cotton 1

In carpet cotton is used as warp threads as well as wefts. Compared to wool, cotton is generally considered to be more resistant fibre and is less elastic, so tighter knots can be tied on cotton warps as opposed to wool. If very tight knots are tied to wool warp, the fibre will break most frequently than warps. Were or cotton. Consequently, woven pile rugs with high knotting density counts will normally have cotton warps.

  • Pure Silk 1

The best and finest hand-woven carpet in world is silk carpet. A normal quality of silk should have 1,000,000 knots per square meter. The best and finest carpets in the world are Hereke silk carpets. They are woven with 3,240,000 knots per square meter. This indicates how finely silk can be twisted and woven as well as how strong and resistant these piles can be. Man made fibres today; dominate the carpet industry with nylon and polypropylene accounting for approximately 65 % of total market.

  • Nylon 4

Nylon fibre has traditionally been preferred for their resilience, good compressive recovery and low moisture uptake. Nylon in various forms is still dominant carpet fibre. The most preoccupation of nylon fibre producers has been with two properties, particularly static electricity and soil hiding. A slightly different approach was taken by ICI fibres, who developed what they termed epitropic fibres. Nylon fibres having their outer layer impregnated with carbon to provide an electrically conductive path. They also developed Trimbrelle, which was a whole range of fibres, rather than just one-type trimbrelle (ICI) fibres is highly luster nylon developed for elour carpets in plain shades. Nylon 6, 6 from rhone polulene which give a carpet a soft, velvet look and pile has shaded effect which walk on.

  • Polypropylene Fibre 4

Polypropylene with properties not too different to nylon and with additional advantage of availability in large quantities and hence low costs has become second most important manmade fibre in carpet manufacturing. One of the major market Merklon Polyprpylene launched a 'berber' bulked continuous filament yarn. This fibre has been achieved by eliminating luster to make it more wool like. Polypropylenes also have good covering power.

  • Polyester Fibre 4

One of reason for the interest in polyester fibre is the move to cut pile and Saxony textures and good heat setting properties of polyester fibre is kodel which is available in both deep and light dyeing types. The fibre is also dyed without carrier. Boyer polyester fibre marketed under name Veston 16 which is dye-able without carrier.

  • Acrylic fibres 4

Acrylic fibres are also used in carpet yarns but their relative consumption is low amounting to around 3%. Monsonto developed Acrilan type A76P. it is claimed that this fibre also resists pile deformation during printing.

Considerably less popular manmade fibres cover the remaining 1%.

  • Uses 5 & 6

As today's lifestyle and economy dictate spending more leisure time at home, the consumers are focusing on home decorating and use of lavish art carpet and nits as accents to create color and design effects to compliment traditional or modern décor. Carpets, which are decorated palaces of sultan, have also become an important means of investment today. The successful use of wool carpet by large educational institutions including libraries as well as residence halls and student unions. Between terms the halls of residence, lecture theatres and restaurants are used for special courses or seminar and to have tourists or businessman who expect the same high standard of aesthetics, quality and appearance found in traditional hospitality areas. Wool carpets provide a hygienic floor covering for all locations including hospitals. The studies showed that dust mites and micro-organisms both of which live on human skin flakes are not in general present to any great extent in carpets and therefore not a health hazard. The ultimate luxury is carpeting in the aerobic class. The 100% pure new wool plain cut pile tufted carpet was chosen because of its excellent appearance retention and soil resistance property and vitally important for center's smart fashion aware clientele- its superb looks!


Carpet Industry

While busily covering our floors the carpet and the rug industry addresses key carpet issues in order to provide the products possible and to promote a healthy environment.7 The Indian hand-knitted carpet industry is essentially a cottage industry in the unorganized sector. This industry is traditional bound and is rural based, highly labor intensive, export oriented giving employment to a half a million weavers and rural workers in their own home or villages spread over nearly 40,000 square kilometers in the district of Mirzapur, Varansi, Allahabad, Jaunpur in eastern Uttar-Pradesh. The industry is also spread in Shahajahanpur and Agra in Uttar-Pradesh, Jammu and Kashmir, Bihar, Punjab, Gujarat, Andhra- Pradesh, Tamilnadu. In export market, Indian carpets have certain strong points in their favour. These are,

  • Indian knots are Persian knots.

  • India can produce all types of knotting coarse, medium, fine and very fine, in different regions. India has finest, main and Isphahan designs.

  • India has the knowledge of all the techniques and processes to produce some of finest oriental carpets in the world. India has been weaving Persian designs since Mughal days.

  • India can produce carpets of any size as required by foreign importer, which is not possible in Afghanistan.

The main produces of hand knotted carpets in world are India, Iran, turkey, The Caucasian Republic of Soviet Union, Afghanistan, Pakistan, and China. The carpets from India are acceptable in U.S.A. and West Germany, the world's two largest markets for carpets price wise, quality wise, color wise and design wise. 8

United states tufted Carpet Industry, Centered in Dalton, Georgia has captured in to a boom period in 1950s and 1960s by introduction of polyester and nylon fibres and use of the tufted construction, making carpet affordable and within the reach of most of Americans. In 1996 the industry had net mill sales of almost ten million dollars and produced approximately 1.6 billion square yards of carpets. The number of consolidations and mergers among carpet producers over the last few years staggers the imagination. The present structure of industry shows that future opportunities for acquisition are limited, at best. Today three firms - Shaw, Mohawk and Beaulie- domonate the residential carpet business. On the commercial side of ledger, these three plus interface ship the majority of commercial products. Although overall financial results for the previous decade are mixed, most firms showed improved performance in 1999 and 2000. 9 & 7

The largest British Carpet manufacturer it currently produces about one third of all carpet manufactured in U.K. Carpet international recognizes that U.K. carpet's long term appeal makes it a key element in the business. Today carpet international has seven manufacturing sites. A plant at headquarters site in Bradford another at Donaghadee, site in Ireland allowed the company to launch range of polyester Saxony carpets- produced in considerable volume by U.S.A. carpet companies but previously only available as imports to consumer in U.K. and Europe.

Supplying the contract segment of carpet trade is growing activity for the group with CI contracts Drv. Expanding its target areas. CI contract recently added file product provided in U.K. to its commercial portfolio. The contract business now accounts for some of 15% groups total sales. 9 & 10

The industry challenges involve issues such as performance standards, statistical gathering, educational programs, industrial relations, export and international barriers, environmental issues and information about carpet for consumer shows a variety of profiles as between thus various types and different profiles overtime for individual types of carpet.


Carpet manufacturing methods

Once fleece has undergone opening, cleaning and carding processes it can then spun into pure woolen yarns or blended with other fibers. Similarly after extrusion, drawing and crimping man made fibers are cut to suitable staple lengths and baled within the yarn-spinning mill, bails are opened and fibers carded and possibly blended before entering the spinning zone. Spinning traditionally been carried out by either ring or open-end methods. The ring spinning converts roving or finely combed, lightly twisted assemblies of fibers into yarns by drawing and inserting further twist .The open end method directly converts sliver or loose rope like continuous fibrous masses into yarns by entering a rotating drum from one end and exiting as yarns from the other. Spun yarns are wound on sized packages before going on creels to feed into tufting machines or wound on beams as warp yarns to be used for weaving. 2 & 11

The out line of a carpet loom looks like a wooden frame. Warp threads are vertically wound around the loom parallel to each other, depending on the type and the size of the carpet. After preparing the warp, a chain like plait called chiti is woven, leaving a margin for fringes and then 2-4 cm wide kilim weaving is done so as to prevent the pile knots from shifting and dropping out. Upon a completion of this procedure, the carpet is ready for weaving .The weaver hangs the colored knotting threads wound into small balls together with carpet design, drawn on a graph paper .The type of graph paper used depends on the type of carpet and density of its knots. Each knot on the carpet corresponds to one square on graph paper and its color is designed by the paint converting the respective square. Sitting on a small tool, weavers begin to weave the carpet from the upward .As the weaving progress, the carpet is shifted behind the loom. Upon completion of a row of knots, the weaver passes the horizontal thread called weft throughout the warp threads (below and above) across width of the carpet and firmly presses on the knots with the shed stick .The ends of knots which have been cut roughly with a knife at the time of each knotting are trimmed with a special pair of scissors to make them even with the face (pile) of carpet. The two methods used for carpet weaving are (Gordes) Turkish knot double knot and (sine) Persian knot single knot. Finally a chain plait is woven and the carpet is cut loose from its warp to be taken out of the loom .It is washed with sopy water to get rid of the dust and dirt collected during course of weaving and made ready for use. 1

On machine made carpets that which naturally demands the first mention is Brussels carpet. The yarn received from spinner in grease that is still containing the oil that was put into wool for the purpose of spinning and in skeins. Normal Brussels yarn may take a thread sharply twisted in the doubling, running about 100yards to the ounce .In dye house it is first scoured to get rid of oil then dyed .The skeins of dyed yarn are then dried. From drying room yarn passes to the winding room, to be wound on to bobbins. Winding frame consists of series of pulleys set on shaft. Opposite each pulley or drum is a swift on which the skein is adjusted, the end of the yarn from skein being led on the body of empty bobbin, which is held against and rotated by pulley. This bobbin called creel bobbin. The five sets of bobbin are placed one in each of five creel frames. The body and back of carpet are provided for normally by two warp beams, chain and stuffer .The object of chain is to form in combination with weft, the woven base of fabric all. The rest is chain ends being threaded or back affects either surface or back .The weave is effected by chain ends being threaded through eyelets mounted on two frames or gears which rise alternatively in such a way as to allow shuttle carrying weft to shot through shed. Both chains and stuffer beams lie between creel frames and the main part of the loom. Jacquard is an ingenious devise for selecting and many as the best of all machine made carpets regard raising the threads required to form pattern respects to Brussels Wilton carpet in its higher grades. 12

Wire loom: Looms are available in widths up to 5.5 m. This has a single shuttle sley of steel construction, having low weight but high stability. The sley performs a double beat up free from vibration at speeds of up to 70 picks/min. Various accessories are available for 100m, including electronic monitoring, automatic shuttle changing and jacquard controls for producing various unusual textures. Jacquard Wilton in loop or cut pile up to 4m wide. Insertion speeds of 50 picks/min were possible with the rapier driven by carefully designed cable and drum system. The warp let-off, take up, and lubrications were carefully designed for ease of use. 12

Face to face looms: This loom operates with flexible rapier system, the weft being inserted by the 'giver' rapier from large cone on left of machine after which it is picked up half way across shed by the gripper or 'taker' rapier. A Grosse hook jacquard is used for pile pattern mechanism and machine produces 'through-theback' carpet. This could be used for plain carpet or even as print base cloth. 12

Axminster loom: In this the machine was even faster since it was capable of speeds up to 50picks/min for 400cm loom weaving three shot carpet. An entirely new double eccentric needle drive mechanism is employed that allows for equal dwell periods at high operating speed. The majority of modifications to Axminster looms have been made by the loom builders, several developments have been carried out by individual carpet procedures. New life has been into gripper Axminster business by availability of electronic jacquards, controlled either by disc or direct from computer. 13

Tufted carpet manufacture

Ancillary equipment: Needles and loopers are two of most important parts on tufting machine. With the very wide range of yarns and fibres being tufted a wide range of needles is vital. Large eye needles have been developed for felted wool yarns. The cut pile knife block and conversion kit is available to many tufters. It is claimed that the kit improves the surface of the carpet but ensuring that same number of loops is cut on each looper. The sectional knife blocks also enable more accurate and faster settings to be obtained.

Broadloom carpet tufting machine has a bed plate giving better visibility and access to gauge parts. It also has simplified needle stroke mechanism. Other features are variable speed drive. The machine is available in wide variety of gauges in cut loop and cut and loop pile. British machine makers launched one heavy-duty machine for carpets. They also developed computer controlled pattern attachment for use on their machines. The system can store up to ten-patternsin memory. Tufters have been attempting to match the appearance of traditional woven carpets and for this purpose cut pile carpets are undoubtedly required. 13

Needle felt Manufacture 13

Needle design has become more specialized depending on nature of fibres to be processed. Singe offer triangular needles with ten small barbs. Each barb transports less fibre than is the case on conventional needle. Special needles are made for processing fine fibres. Forked needles are used for punching bundles of fibres from back to give a velour effect on surface. A strain gauge system has been used to measure the effect of needle force of distance along the web, needle position needle penetration web weight and fibre orientation.
WASTE ASSOCIATED TO PROCESS 14

The term waste is a collective expression usually meaning surplus or substandard left overs from fittings & replacement carpets. In fact waste occurs at all levels of production & increases exponentially along entire manufacturing route with post consumer waste accounting for most of this. The carpet waste is eventually incinerated or preferably, as is the case in UK, dumped into landfill sites. In manufacturing, the potential value of waste or loss factor increases the further it is created along the production route. Fig.1 shows the full processing route involved in carpet manufacturing & the amount of waste generated at each stage along the entire path.

Man-made fibre production, by virtue of its creation method, may be assumed to produce no water at all. In fact polymerization of the parent monomer and subsequent extrusion into fibres could give rise to as much as 15% wastes. The waste resulting from one or combination of the following factors:

  1. The operator

  2. Equipment breakdown

  3. Power failure

The processed carpet is eventually cut & trimmed along both edges. The waste, by this stage has considerably increased both in terms of size and value. Whether coloured yarn or pile printing methods is used, such faults as strips and streaks and similar defects caused by faulty needles or knives are picked up during inspection and subsequently discarded as yet more waste. By and large the biggest quantity of waste in newly processed carpet occurs during fitting with an average waste of up to 20% or more. In weaving, waste associated to beaming, breaks, weft insertion and subsequent inspection and fitting results in even greater loses, both ion terms of quality and value.


Figure1: Schematic Representation of the Full Carpet Manufacturing Route (S)

Fibre Production

Spinning

Drawing

Texturing

Cutting to staple lengths

Bales

Opening and Carding

Blending may be necessary

Yarn Formation

Winding to correct length

Creeling

Waste: Upto 4-15% due to incomplete conversion, stop & breaks

Waste: Upto 3% adjustment of measuring device

Base fabric: Primary Substrate

Woven

No woven

Usually PP or PET. Jute used

No waste, but as strong as woven

Waste: Edge fraying etc.

Tufting

Inspection

Mending

Dyeing & printing if uncoloured yarn

Adhesive Application

Backing & Drying

Shearing

Cutting & Trimming

Tiles

Cut to Size

Waste: Upto 12%

Waste:

2-3% short fibres etc.

Waste: Upto 4.8% due to drag

Nylon

(~35%)

Tufted

(~30%)

Needle

Punched

(~3%)

Others

(~1%)

Man-made

Total Production: 146.2 million sq. m.

12%

76%

9%

3%

Waste: Total loss 65 million/yr (pounds)

Woven

Tufted

Needle

Punched

Others

Natural

Wool (~31%)

Opening and Cleaning

Waste: Upto 5% i.e. twigs & short fibres

NEED FOR CARPET RECYCLING 15

According to US Environmental Protection Agency, the multiple solid waste generated in US is about 200 millions per year among them about 40% being paper products 8% plastic, 2% carpets and textiles. It is estimated that carpet waste disposed in landfill each year is about 4 million tons. This practice requires constant creation of new landfill spaces, which is in contraction to nations environmental goals including ecosystem protection. Carpet waste is in large strong pieces, which are difficult to handle with the landfill equipments. There is an urgent need to address this problem of carpet waste disposal.

The notion of recycling is almost entirely due to environmental demands for reducing waste. Carpets removed for disposal can have a very different overall composition since they contain significant amounts of contamination. A study carried out in Europe several years ago found that carpets removed from recycling were about 30po heavier than when they were first installed due to dirt that was trapped in the pile. The main effect of the additional dirt is to reduce the proportion of valuable components; such as face yarn and to complicate the waste disposal processes must be designed to work on the presence of dirt that will invariably be present.

Because of diversity and mixture of the materials used in carpets, there is no one obvious approach for their recycling. Many processes have been considered and these have resulted in a wide variety of techniques and potential products.
CARPET RECYCLING AND REUSE

It is estimated that 3 to 4 billion pounds of carpet are removed from homes and business each year in the United States. Less than one percent will be recycled. The rest will go to landfills and represent one percent of all materials sent to landfill. The challenge has been to find a way to recover value from old carpet using process that results in les cost to perform recycling than cost of removed materials. So far this has been an evasive goal. 16

Sixty five to eighty percent of scrap carpet consists of nylon pile (both polyamide66 and ployamide6). A styrene butadiene latex adhesive that is highly filled with calcium carbonate holds the nylon face fibre and baking material together. The fibres represent about half the weight of carpet, which is available for recycling. 16

    • Carpet Recycling Process

  1. Collection of Carpet

Post consumer carpet waste comes from domestic sector i.e. private households, as well as from trade. Dupont and BASF have initiated collection programmes and started processing carpet commercially. Duponts network of collection sites is by far the most extensive in industry, with 61 sites and new one being added all the time. BASF greatly expanded its collection program with commitment to taken in any carpet that is removed in the process of installing a new carpet with BASF's nylon fibre. BASF have specified 6 regional collection centers in North America. 16

  1. Sorting and Separation of used Carpet 17

  • Carpet Identification by Melting Point

The first carpet identification system uses the melting point of the polymer to identify the face fibre type. This allows for accurate distinction between polypropylene and nylon6 carpet. The low cost device is able to accurately identify a carpet's face fibre in approximately 10 seconds thus significantly reducing the cost of the carpet sorting process.

The device (a modified double soldering iron) has two heated probes that are permanently set slightly above the melting point of nylon6 and polypropylene (i.e. one probe is set to 255oC and other to 180oC). The heated probes are pressed against a small piece of aluminum foil that is in contact with the surface of the sample. If the carpet has nylon6 face fibres the probe will leave one mark on the surface of carpet. Whereas two melt marks will be left if the carpet has polypropylene face fibres. If the carpet has a fibre face of polyester, nylon66, wool or acrylic then no marks will be left on the face of the carpet. In order to differentiate the nylon66 and polyester from wool and acrylic a third probe with a permanent temperature setting of 280oC can be added which would leave a mark only on nylon66 and polyester carpet. The disadvantage of this method is that nylon66 and polyester polymers have comparable melting temperatures and such device cannot discriminate between these two fibre types.

  • Carpet Identification by Infrared

A more sophisticated carpet identification device is based on near infrared reflectance probe. This can identify carpet s face fibre in less than 10 seconds and can identify nylon6, Nylon66, polyester, wool or propylene with excellent accuracy.

The unit has a hand-held NIR probe that is placed directly against the carpet surface the acquired NIR spectrum is matched against a library containing over 300 spectra of carpets samples ranging from very new carpet heavily solid samples.

The hand held NIR probe is attached to fibre optic cable cup (upto 6m) and has a panel with coloured LEDs to allow the operator identify the carpet face quickly and easily with single button operation. The system is dust proof and vibration proof making it robust enough to withstand the environment of carpet sorting facility. The device acquires fine scans per second over 1200-2400 nm resolutions. It is interesting to note that while the NIR spectra of Nylon6 and Nylon66 are quite similar; their second derivative allows them to be easily distinguished.

Other development is rapid identification system it can be used in automatic sorting center. Carpets are automatically singled out and manually brought to clamps, which is integrated in hanging transport systems. The hanging system delivers each carpet to identification station. After identification they are automatically transported to different containers.

  • Grinding and Density Separation of Carpet

Figure2 shows a process for mechanical recycling of nylon carpet in which the sorted carpet is comminuted using a hammer mill in combination with grinding and then the nylon faces fibres are separated from latex adhesives polypropylene fillers and dirt by float sink process. Finally recovered nylon is reprocessed by extrusion and melts filtered.

  • Solvent Separation

Carpet to be recycled is taken to shredder section and sheared into small pieces. These pieces are separated by difference in solubility. The different type of solvents separates different types of fibres depending on the nature of solubility of fibres. Face fibre separation of nylon6 and nylon6,6 can be achieved by selective dissolution using appropriate solvents. Nylon6 can be successfully separated from mixture with nylon6,6 by dissolving nylon6 with aqueous solution of an aliphatic carboxylic acid. Water is added to enhance nylon precipitation. Alternatively both nylons can be dissolved and then nylon6,6 can be preferentially precipitated. Nylon6 can also be recovered from carpet waste by dissolving with 85% formic acid.

  • Wet and Dry SeparationCarpet Identification by Melting Point

A combination of wet and dry separation guarantees the technical realization. In dry process components chock dirt and styrene butadiene latex are separated. In the weight separation polypropylene and polyamide are separated and remaining impurities will be removed. Based on technology such as hydrocentrifuge and hydrocyclon weight separation can be carried out.

  1. Chemical Recycling

  • Acidolysis

Nylon6 can be catalytically depolymerised to its monomer-caprolactam. Using an acid catalyst, the cut nylon6 waste is melted in continuous reactor and treated with steam. The monomer, caprolactam is formed by hydrolysis. The caprolactam is distilled. While the caprolactam-water vapour mixture is concentrated and treated with potassium permanganate to oxidize impurities. After filtration the caprolactam is recovered and may be fed into a polymerization process with no deterioration of polymer product quality. The acidolysis of nylon6 can be efficiently catalysed by phosphoric acid according to the reaction.


  • Hydrolysis

Polyamide6 can be hydrolytically depolymerised in an aqueous system under pressure to give high yields (60-70%) of caprolactam. The reaction can be (reaction1) carried out at 250o C under nitrogen using ratio water: polymer of 10:1. Although no catalyst is necessary for this process, removing the water from the caprolactam requires distillation and is relatively expensive.

Higher reaction temperatures enhanced yield of caprolactuam (graph1), however, this also adds pressure to the closed system. Thus to achieve monomer yields greater than 70%. The yield of caprolactam increases as a function of water content of their reaction mixture as shown in graph2. At water: polymer ratios greater than 12:1 there is little increase in caprolactum yield obtained. For optimum conversion and lowest water content water: polymer ratio around 10:1 has been selected.

  • Amonolysis (or Aminolysis)

In this process nylon6 and nylon6,6 are reacted with ammonia and a phosphate catalyst to produce polyamide monomers (figure3). The nylon monomers can produce new nylon6 and nylon6,6 which can spun into bulked continuous filament to produce new carpet and thus enable true closed-loop recycling.

Collected carpet must be separated from PP backing, adherent dirt and any other contaminants. The carpet is shredded, chipped, passed through a hammer mill, screened and then ground to particles with an average diameter of 1.5mm. At this stage the carpet consists of a course powder compromising an 80:15:5 ratio of nylon, polypropylene and dirt respectively. This material is added to water to form slurry and then the constituents are separated on the basis of density. The separated nylon (98.5% purity) is transferred to the depolymerisation reactor while the polypropylene (98% purity) is mechanically recycled.

In the ammonolysis reactor, the nylon is mixed with ammonia gas and a phosphate catalyst. The reaction occurs at 330oC and 7 Mpa.

The reaction mixture is distilled to recycle the ammonia and remove carbamate by-products. The crude nylon monomers are fractionally distilled into three streams: -

  1. Caprolactam

  2. Hexamethylenediamine (HMD) and aminocapronitrile (CAN)

  3. Adiponitrile (ADN)

ACN and ADN are hydrogenated to give pure HMD while the caprolactam is converted to more CAN by further aminolysis, or directly refined to pure caprolactam. The HMD produced by this process is of high quality (>99.8%). The levels of the main impurities aminomethylenecyclopentylamine (ACM) and tetrahydroazine (THA) are expected to be reduced to lower levels by the full-scale plants, which operate with larger distillation columns.

  • Depolymerisation in Vacuo

This method of depolymerization is particularly attractive in that the caprolactam end product is of high purity and no distillation of water is necessary in contrast to hydrolytic depoymerisation method. A catalyst is necessary in vaccum depolymerisation of polyamide since in the absence of catalyst a number of byproducts are formed such as cyclic olefins and nitrides, which reduce the quality of the caprolactam, obtained. It can be seen that potassium carbonate gives high yield of caprolactam in short reaction times, which equates to high throughput, at relatively low levels of catalyst addition. Another feature of this method is that the distillate is essentially pure caprolactam. This is important in fibre applications since even ppm levels of impurities can produce off colour fibres.

Vaccum depolymerisation of polyamide6 has a number of advantages over hydrolytic depolymerisation including

      1. Higher yield of caprolactam

      2. High purity caprolactam is produced

      3. Short reaction time

      4. Distillation to remove water is not necessary

There are some disadvantages associated with the vaccum depolymerisation of polyamide6 and these include

  1. A catalyst is necessary and it is important that the catalyst is evenly

distributed throughout the polymer to avoid inhomogeneous

reactions.

  1. The residues of fillers polymer and catalyst must be disposed of.

  2. Organic residue that is produced cannot be fed back into the

process since tar formation can result.

  1. Mechanical Recycling

Ford in conjunction with Dupont, have developed a grade of nylon6,6 with 25 wt. % recycled content from reclaimed carpets, to be used in the production of automotive air cleaning housings. A range of polyamide resins is also commercially available containing 100% recycled resins (Nypel TM, allied signal). Unreinforecd grades of recycle polyamide exhibit excellent melt stability and regrind levels as high as 50% can be used. Components made from post consumer nylon have been tested in under the applications for recycled nylon resins include automotive timing belt covers, power tool housings and office chair basis.

    • Other Methods of Tackling Carpet Waste

  • Shearing 3

The most valuable component carpets is the face yarn. One way to recover it is to shear it, leaving behind the backings and adhesive. Unfortunately, this approach does not lead to complete recovery because a substantial portion of the face yarn is trapped under the primary backing. In the case of used carpets the dirt trapped in the carpet must be removed before shearing. One company in the US presently recycles sheared face yarn from broadloom carpets using a biocomponent spinning technique. In this case the core of the fibre is 70% recycled nylon and the sheath of the fibre is 30% virgin nylon. The core nylon contains the dye from the recycled carpet fibres; however, when the sheath polymer is dyed, the color is covered and the recycled fibre is virtually indistinguishable from a virgin fibre.

  • Glass Mat Thermoplastics 18 & 20

Glass mat reinforced thermoplastics (GMT) using virgin materials have been attracting growing attention, particularly for use in the automotive sector. Polypropylene is a commonly used thermoplastic matrix in GMTs. Carpet typically consists of two layers of backing (usually polypropylene), joined by CaCo3 filled styrene-butadiene latex (SBR), and face fibbers (the majority being nylon 6 and nylon6,6) tufted into the primary backing. In the studies led by Drs. J. Muzzy and S. Kumar, two types of carpet waste have been used; one is edge trim carpet waste, other is separated polypropylene from post-consumer carpet waste.

The GMT preparation included three steps: debunking, stacking with glass mats and consolidation. The properties of GMT using carpet waste have been compared with the commercial GMT, which uses virgin polypropylene, and similar (or better) results in tensile strength modulus and elongation have been observed. GMTs manufactured using carpet and other textile waste are currently being studied in greater depth from the point of view of optimization of consolidation and processing parameters.


  • Composite and Laminates from Carpet and Exile Waste 18

The face yarn in carpets and the fibres in textiles as fibrous filler for a composite or laminate and the polypropylene component to supply the necessary flow in processing. Because of the fine diameter of fibres involved, a low viscosity prepolymer in a water base is used to insure complete coverage of the fibres. The proper choice of the adhesive will result in a high modulus material that is creep resistant and has good weathering characteristics.

The initial work emphasized shredded carpet selvage to which various amount of cut waste fibre such as nylon6, nylon6,6 polyester and cotton were added. Fabric bits of waste denims and cotton polyester fabrics were used. The waste carpet blend was then coated with phenolic or urea formaldehyde resins that were dispersed in a water base. The fibres were spray coated and molded in a heated press at 150 to 200 0 C and 3.4 MPa. Test results show that one can achieve high flexural moduli of 2.4-2.8 Gpa with face yarn, i.e. fibres that bind to the matrix such as nylon, polyester and cotton. These values together with flexural strengths of 34-48 MPa can find many outdoor applications in the replacement of marine plywood in the transportation area.

Laminates directly from waste carpet pieces were also made. The mechanical properties of laminates made by coating the face yarn with a phenol formaldehyde resin and molding the carpet pieces back to back with the face yarn on the outside to achieve the higher flexural modulus. It was observed that the interfacial strength between the carpet backing and the face yarn is somewhat low. Pressing holes into the carpet prior to spray coating the face yarn so that protrusions of the matrix material flows into the backing during the molding process doubles the flexural modulus of the material.

  • Reactive Extrusion of Carpet Waste 19

The basic polymeric components (nylon and polypropylene) in carpet do not mix and bond well when melted. The use of maleic anhydride grafted polypropylene (PP-g-MAH) as a compatibilizer for reactive extrusion of carpet face (nylon) and backing (polypropylene) could produce low cost plastic parts with reasonable mechanical properties. Experimental work on the reactive extrusion at Monsanto15 and at Georgia Tech, has demonstrated a potential for the utilization of carpet as a plastic resin. The initial experiments showed that by blending, compatibilizing and extruding the carpet, the tensile strength as good as or better than the tensile strength of polypropylene could be achieved. However, the tensile failure strain of the extruded carpet was rather low. Attempts to improve the tensile strain have been made by altering the composition and processing conditions.

Densified nylon6 carpet in the form of pellets was extruded with two compatibilizers: PolybondTM (PP-g-MAH) from BP chemicals and Kraton G1921x (SEBS-g-MAH) from Shell Co. The carpet waste and the compatibilizer were blended in a twin-screw extruder. Extruded samples were compression molded at 235 and 2600C. Variation in extrusion temperatures and in the molding temperatures result in small variation in properties.

  • Molding Compounds 3 & 18

The most straightforward way to convert carpets into a new form is to chop and grind them into small pieces (which often removes about half of the latex filler), and fed the size-reduced material into an extruder. The pellets formed have voids and an unpleasant odor due to decomposition of the latex during processing. The molded parts also have to a rubbery feel. In most cases, additional amounts of polyolefin materials are added during the extrusion process.

United Recycling Inc. has introduced two grades of molding compounds based on old nylon6 carpets using proprietary blends containing added polypropylene. The compounds contain about half of the latex and filler of the original carpet. The first application developed for this compound was a carpet tack strip. Monsanto developed a similar process for making a molding compound from nylon6,6 carpet. A key feature is the high intensity mixing provided by a twin-screw extruder.

Collin & Akman took another innovative approach; however, it is limited only to carpet tiles. In the C&A carpet construction, the primary backing filler and secondary backing are all replaced by vinyl. The face yarn is exclusively nylon. The recycled carpet is size reduced and extruded. Post consumer low-density polyethylene (LDPE) is added during the extrusion process to improve the finish of the product. The properties of the extruded material is similar to wood and is being used in plastic lumber, industry block flooring, and parking blocks.

In the injection molding shredded selvage trim was debulked at 2040 C in the compression molding press. The debulked sheets were cut or ground into small pieces suitable for injection molding. Tensile bars were injection molded at temperature profile of 2040C (rear) and 2600C (nozzle). This sample contained polypropylene, nylon6, nylon6,6 and calcium carbonate. The molded samples resulted in a tensile strength of 180 MPa and a strain failure of 9.4%. These samples exhibited brittle tensile fractures. Injections molding experiments have also been carried out on nylon lint from several carpet mills. Test results indicate that the lint samples have tensile strength similar to that of virgin nylon, through the strain to failure is much lower than the virgin material.

In the press study, carpet waste was debulked at 2040C using a compression molding press. The surface of these debulked sheets was quite rough. To give a smooth finish to these sheets, the debulked sheets from carpet waste were hot pressed between virgin polyethylene films. The carpet sheets sandwiched between the virgin polyethylene films. The carpet sheets sandwiched between the virgin polyethylene sheets had an excellent texture. Such are excellent candidates for potential vinyl floor tile replacement. The density of these sheets was measured to be 1.15 gm/cm3 . further processing development work is needed to reliably measure the properties of such sheet material and compare them to the properties of the currently used vinyl floor tiles.

  • Carpet Waste Fibre for Concrete Reinforcement 21

A carpet typically consists of two layers of backing (usually fabrics from polypropylene tape yarns), joined by CaCo3 filled styrene-butadiene latex rubber (SBR), and face fibres (majority being nylon6 and nylon6,6 textured yarns).Such nylon and polypropylene fibres can be used for concrete reinforcement. A laboratory study led by Dr. Y. Wang on concrete reinforcement with carpet waste fibres was carried out at Georgia Tech. The concrete mix weight ratios are Type I Portland cement (1.0), river sand (0.85), crushed granite (0.61), water (0.35) and a small amount of Superplasticizer. Recycled carpet waste fibres used were disassembled from hard carpet waste (Typical length 12 to 25mm). Fibre volume fractions for the waste fibres were 1% and 2%. Only the actual fibre portion was included for calculating fibre volume fractions for the waste fibre reinforced concrete. FibreMesh, a virgin polypropylene fibre (19 mm long), at 0.5% and 1% volume fractions was also included in this study for comparison purposes.

Four point flexural test and cylinder compressive test were conducted on a hydraulic testing machine. In the compressive tests, the plain concrete specimens failed in a brittle manner and shattered into pieces. In contrast, all the FRC samples after reaching the peak load could still remain as an integral piece, with fibres holding concrete matrices tightly together. In the flexural test, it was observed that the plain concrete samples broke into two pieces once the peak load was reached, very little energy absorption. The FRC specimens, on the other hand, exhibited a pseudo ductile behavior and fibres bridging the beam crack can be seen. Because of the fibre bridging mechanism, the energy absorption during flexural failure was significantly higher than for plain concrete.

The laboratory study has indicated that the carpet waste fibre was very effective in improving the toughness and shrinkage properties of concrete. Shaw Industries Inc. in 1994 completed an 11,000m2 R&D Center in Dalton, Georgia, which used concrete, reinforced with carpet waste fibres in the construction project. About 20 tons of carpet production waste was consumed in the project, which would otherwise be sent to a landfill. The concrete mix followed a typical design for concrete with a 28MPa (4000 psi) compressive strength, consisting of cement, sand and rock. The water cement ratio was 0.5 and the cement content was about 260 kg/m3. Superplasticizer was added to maintain the desired workability. The amount of waste fibre included was 5.95 kg/m3. Adding fibres to the mixing truck directly did mixing, after which the fibres were found to be uniformly dispersed in the concrete without balling or clumping. Mixing, pouring and finishing followed standard procedures, used conventional equipment, and went smoothly. The compressive and flexural strengths exceeded specifications, and reduced shrinkage cracking was observed. Such concrete containing waste fibres was used for floor slabs, driveways, and walls of the building. Besides reducing the need for landfilling, the use of low-cost waste fibre for concrete reinforcement could lead to improved infrastructure with better durability and reliability.

  • Carpet Waste Fibres for Soil Reinforcement 18

At Georgia Tech, Drs. Y. Wang and J.D. Frost are investigating the feasibility of using shredded carpet waste for soil reinforcement in road construction. It has been widely reported that the properties (especially the shear strength) of soil can be enhance by fibre reinforcement, resulting in a more stable soil structure with improved durability. The novel approach, if proven feasible, could lead to the4 significant impact on the textile solid waste dispose problem, as it could lead to the use of large amount of carpet waste. It would also lead to improved durability and performance of road; reduced cost for road constructions less land, soil and chemical stabilizers are needed.

The study involves the carpet/fibre industry, several Georgia countries. Georgia Dept. of Transportation Institute of Technology along with other government agencies. Field trail sites for unpaved country roads were selected to represent typical types of solids found in Georgia. Trial sections with carpet waste fibres and virgin fibres were installed in a few unpaved roads. Preliminary assessment by visual inspections confirms that fibres in soil can indeed improve the durability

Of unpaved roads, thus reducing the need for frequent regarding. Base on the experience gained during these trials, installations procedures and equipment are being improved.

  • Incineration to recover Energy 22

Generally speaking low chalk content means an increase of net calorific value (n.c.v.) depending on face fibre material three levels of n.c.v. occur.

PP carpets: n.c.v. upto 42 MJ/kg

PA carpets: n.c.v. upto 27 MJ/kg

Wool carpet: n.c.v. upto 19 MJ/kg

An average mixture of carpet waste has a n.c.v. level between 18 to 20 MJ/kg.

Especially in view of finding alternative to traditional fossil fuel the calorific value is most important factor.

The locked in potential or LIP in carpets can be as high as those attained from normal fuel. The table shows comparative calorific values for a range of fibres and those of more common sources of diesel oil and naptha.

Comparative calorific values

Calorific values, MJ/kg

Fibres

Other sources of fuel

Polypropylene 46

Diesel 46

Polyethylene 46

Naphtha 42-46

Polystyrene 41

Carbon 21-33

Polyurethane 24-31

Wood 16-21

Polyester 19-30

Paper 16-19

Polyvinyl Chloride 20

However, burning carpets generate energy also produces its own waste commonly referred to as ash, which is also hard to dispose of. The ash consists of inorganic metals and halogens that are often included in the binder material to increase bulk. Efforts to replace these with organic substances has already led to some composite backing structures where polypropylene is used as the main binder with reinforcing threads to secure the carpet assembling.

Paralysis or burning in absence of oxygen is another process which carpet waste is carbonized at high temperatures to generate synthetic coal. The manufactured has quite high calorific value and can be burnt with or instead of regular coal, leaving relatively small quantities of ash. The carbonization is rather energy intensive and, therefore as yet, not economical.

Today most important field for employment for thermal reclamation for carpet is the cement industry. In contrast material such as tyres there is an advantage that carpets can led to the cement oven together with fuel. The organic components of carpets (e.g. Latex or PP) substitute fossil fuels in as much as the chalk substitutes the raw mixture from cement. Several cement industries are planning subsequent incineration of carpets.

  • Old Carpets becomes new Backing 23

Collin & Aikman developed a process for using used carpet to produce new backing for its carpet tiles. Nylon has much higher melting temperature than PVC, so C&A is able to melt the PVC backing from used carpet, while keeping the nylon fibres intact. The resulting product makes up as much as 75%of the new ER3 backing, which is essentially a PVC backing reinforced with short lengths of nylon fibres from the old facing. Virgin PVC and low-density polyethylene are added to the recycled mixture and the product is shaped into backing using calendaring technology borrowed from wallpaper industry. Tiles with ER3 backing are now being sold at the same price and with the same warranty as C&As conventional product.

  • Reuse in alternative Forms 24

Short and unprocessable from different stages of manufacturing used in soft furniture fillings, mattresses and pillows. Other utilization schemes include shredding granulation and mixing of the waste with binders to produce sheets or panels suitable for thermal; and sound insulation material in building industry. Other ideas include use of cutting edges and trim materials to produce needle-felt structures to replace foams or secondary backings in tufted carpets.

CONCLUSION

The most effective way of preventing waste is to avoid or minimize its creation in the first place. This in itself, however, calls for new and novel technologies as well as processing techniques that will have to come with time. The long-term strategy for eradication of waste however cannot be left to manufacturers alone, but it needs to grow out of partnership between the manufacturers, consumers and the governments working together towards common goal.

Manufacturers need to concentrate effort on:

  1. Creating homogenous as opposed to heterogeneous carpet structures, which would simplify manufacturing processes and reduce subsequent separation difficulties and hence recycling costs.

  2. New and novel approaches to carpet marking.

The consumer's role could include

  1. Adaptation to single fibre carpets and acceptance of perhaps less variety in choice at possibly higher costs.

  2. Acceptance of carpet tiles rather than full length carpets whenever possible.

  3. Use of reconditioned carpets where new designs and colors are applied on old carpets.

  4. Responding favorably to cash back incentives for recycling purpose.

Government's co-operation can be reinforced by

  1. subsiding and supporting companies who take initiatives in recycling programs.

  2. Legislating and implementing strict roles and regulations with regards to waste and its environmental aspects.

  3. Increasing tax levels on landfill.

In next century waste of all types will be one of the biggest challenges facing man. Synthetic carpets will only account for small but significant portion of waste of today's standard of living are to be maintained and even improved, delay tactics and hale-hearted measures to tackle waste will only postpone rather than solve the problem. What needs to be done is collective long term planning, supported by serious investment commitments that would run waste in to valuable commodity essential for substantial development and ultimately preservation of balance in nature.

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