Description:

The invention pertains a process for producing tufted carpets comprising primary backings with a built in precoat. The invention also pertains tufted carpets comprising primary backings with a built in precoat.

Tufted carpet comprises 90% of all carpet manufactured today. Tufting is most prominent because of its low cost, high quality and the variety of styling and design that can be achieved.

Four basic components are used in tufted carpet: the pile fiber or carpet face; the primary backing; the precoat, in most cases made of latex; and the secondary backing.

Basically, precoating a carpet is the application of a coating on the tufted or dyed/printed carpet fabric in order to:

• Bond the piles to the primary backing, referred as pile bonding or stitch lock.

• Bond the individual filaments of the carpet yarn, necessary for good wear resistance of carpet face, referred as filament bonding Dependent on the requirements of the end product the precoat can also have some other functions in the carpet:

• Give good bonding to further backing materials

• Improve fire retardancy

• Improve electrical conductivity and anti-static performance

• Prevent fraying

• Improve dimensional stability

• Reduce permeability

Precoating is always followed by other coat steps. Details are dependent on the application.

A precoat type that is commonly used in the carpet industry is a latex and in particular Styrene Butadiene (S/B) latex. In Western Europe this is more than 80%. The carpet is wetted by a fluid polymer dispersion, penetrating in the piles and towards the primary backing. By removing the water at elevated temperatures (>110 0C) the polymer forms a network and interconnects the piles, filaments and the primary backing.

The following reasons show why latex is currently the first binder choice of the carpet industry:

• an effective binder with adhesion to a wide range of substrates

• the low viscosity of the aqueous medium provides excellent wetting and it is easy to increase viscosity by frothing.

• low prize • carrier for additives, can accept high quantities of inorganic fillers and functional additives

Disadvantages of latex are:

• high energy consumption because of the curing mechanism

• relatively high waste water volumes, especially for cleaning

• large volume of the application equipment

• potential reduction in tear strength

• Odor of latex (contains volatile organic compounds)

• Emission of monomers (styrene) during and after curing (health aspects)

• Low recycleability of selvedges, latex sludge and the final carpet (ashes of filler by incineration)

• Cleaning and disposal costs for latex storage and formulation tanks

• Interruption during carpet manufacturing can be a disaster for latex coated carpet in the oven

• High transport costs for latex formulations (high content of water)

The disadvantages of latex regarding recycling, energy consumption, VOCs, etc. have given reason for the carpet manufacturers to investigate alternatives. There are several initiatives for latex-free carpets.

Most of the developments in others markets are directed towards using thermoplastic binders and fibers (low melting), preferably of one polymer family for recycling reasons. Disadvantages of these developments compared to latex precoats are • weaknesses • pilling/fuzzing • higher overall running costs

It is an object of the invention presented herein to overcome the disadvantages of the prior art and to provide an alternative to latex precoats.

According to the present invention a solution for the object described is a process for producing tufted carpets characterised in that the primary backing of the carpet receives a finish which contains radical polymerisable organic substances and an initiator and that after tufting polymerisation of the finish to form a precoat is carried out by activating the initiator to fast a radical chain polymerisation reaction. Contrary to prior art polymerisation of the precoat is carried out in situ. Not the polymer is applied on the primary backing as built in precoat but the reactants for a polymerisation reaction form the built in precoat. A solution for the object described is also a tufted carpet characterised in that the carpet is obtained by the process for producing tufted carpets as described above.

A "finish" according to the present invention is a treatment of textile products with an agent or a formulation of various chemical substances.

In an embodiment the primary backing of the carpet receives a finish containing radical polymerisable unsaturated organic substances and an initiator. In another embodiment the primary backing of the carpet receives a finish containing olefins and an initiator. Suitable olefins have to be chosen regarding boiling point, toxicity as well as applicability. It is thus preferred that the number of carbon atoms in the olefin molecules is at least seven. A person skilled in the art would be able to choose suitable olefins. In another embodiment the primary backing of the carpet receives a finish containing unsaturated fatty acids and an initiator. In a preferred embodiment the primary backing of the carpet receives a finish containing vegetable oils or fats and an initiator.

Fatty acids according to the invention are aliphatic carboxylic acids containing at least 10 carbon atoms. Vegetable fats or oils are glycerol esters of fatty acids, i.e. mono-, di- and triglycerides, derived from vegetable raw materials which are liquid (oils) or solid (fats) at room temperature.

As an initiator AIBN (2,2'-azoisobutyronitrile) may be used. It is however preferred to use organic peroxides such as peroxyesters, dialkyl peroxides and peroxyketals as initiator.

The initiator is activated by energy supplying in the form of thermal energy, radiation or ultrasound.

As primary backing woven and nonwoven materials may be used. Such materials are known. They are typically made from polyethylene terephthalate.

In a preferred embodiment, however, a finish of vegetable oil and initiator is applied on Colback®. This finish polymerizes after heat input after the tufting machine to a firm network around and in the tuft piles.

Colback® is a thermally bonded, spunlaid nonwoven, made from bicomponent filaments having a polyester core and a polyamide (PA6) nylon skin. The incorporation of a precoat function or a part of it into the primary backing makes several advantages for the carpet manufacturers possible:

• saving of the efforts and costs of a separate process step;

• decrease of the vulnerability of the tufted carpet for piles loss during further processing steps;

• improvement of the stability after tufting;

• improvement on environmental impact of the carpet manufacturing process;

• elimination of latex systems; this is necessary for some automotive customers because of a negative smell aspect.

The built in precoat according to the present invention can replace latex precoats in all areas where tufted carpets are used:

• tufted car carpets • modular carpet tiles • walk off mats • broad loom carpet • synthetic turf • dust control mats