The present invention relates to a carpet for floor covering. The present invention relates particularly to a carpet which results in fine dust reduction in the space in which it is laid.

Due to increasing insulation, for instance for the purpose of air conditioning in buildings, the exchange of air in the space with outside air decreases and the concentration of fine dust and other contamination in the spaces increases.

Fine dust and endotoxins represent a great problem for people suffering from allergies. When breathed in, small particles have the effect of irritating the airways, particularly in the case of people with weak lungs. Contaminants such as allergens and endotoxins moreover adhere to these small particles and are breathed deeply into the lungs. Dust can also cause disease, for instance because floating dust ends up in the blood, whereby the blood thickness can increase, with a greater risk of a heart attack.

It is generally believed that floor covering comprising textile, such as carpet, is less suitable for people with asthmatic conditions.

So-called dust control carpets are known, which are not so much intended to prevent (fine) dust and dirt being stirred up into the air (of the space in which the carpet lies), but rather to remove it from footwear. It is known to apply tor this purpose relatively high piles with fine filaments and relatively low piles with coarse fibres or filaments, usually with cut piles, in order to brush the dirt off footwear.

The European patent application EP 0378 004 describes such a dust control carpet, which is composed of first areas with fine yarn and second areas with coarse yarn. The areas are preferably at least 2 mm wide. The fine yarn is made up of fibres of 15-60 dpf (16-55 dTex) and the coarse yarn of between 150 and 5000 dpf (160-5500 dTex). The carpet described in EP 0 378 004 however does not have for its object to reduce fine dust in the space, nor is it suitable for this purpose. The American patent US 4 820 566 likewise describes a dust control carpet including high, fine tufts and low, coarse tufts. The carpet described in US 4820 566 does not have the purpose of reducing or binding fine dust either. The fine fibres have a weight of 15-50 dpf and the coarse fibres a weight of 150-500 dpf.

It is however an object of the present invention to provide a carpet which does result in a decrease in the fine dust in the space, or contributes toward making such a decrease possible.

The present invention provides for this purpose a carpet with a base structure of a primary backing comprising high and low piles, wherein the greatest number of fibres of the high piles is lighter in weight than the smallest fibres which the low piles comprise, and wherein at least some of the fibres of the high piles have a weight per unit of length of less than 15, and preferably less than 5 dTex. The terms "high" and "low" must be understood here to be relative, the high piles thus being higher than the low piles. The high piles are however preferably a minimum of 1 mm higher than the low piles.

It is noted that in this application the dimensions in dTex stated in respect of the present invention relate to a filament (also referred to as dpf in the field). The yarns used can comprise a plurality of these filaments.

Because the carpet comprises both high and low piles, the effect of dust being trodden into the carpet is reduced. The fine dust enters the spaces which occur where low piles are situated between high piles. Having entered these spaces, the fine dust is held fast and no longer re-enters the room area. The high piles comprising the ultra-fine filaments adhere the smallest particles (< 10 μm) and hold them fast. The lower piles comprise the thicker yarns, in which coarser dust is collected. It is precisely by applying at least some of the fibres of the high piles with a weight per unit of length of less than 15, and preferably less than 5 dTex, that the effect is obtained of fine dust being bound. Fine dust is for instance understood to mean particles in the order of magnitude of PMlO or PM2.5 (particle matter). PMlO relates to particles which can be breathed in, with an aerodynamic diameter smaller than 10 μm. Particles of this size cause health problems because they are generally carried through the throat and nose and enter the lungs.

PM2.5 relates to particles which can be breathed in, with an aerodynamic diameter smaller than 2.5 μm. These particles can affect the vascular system and prolonged exposure thereto can result in a shortened lifespan.

The high piles, which form a contact surface of the carpet according to the present invention, are preferably manufactured from a thread which is made up of fibres with a diversity of weights per unit of length. It has been found particularly advantageous for the other fibres of the high piles to have a weight per unit of length of less than 25 dTex. The part with fibres of less than 15, and preferably less than 5, dTex is preferably higher than 30 percent, more preferably more than half, and still more preferably more than 70 percent.

The coarse fibres also have the purpose of arranging an open pile construction in the carpet, whereby a better airflow results during cleaning of the carpet. Measurements by means of sensors which are placed through the backing at the position of the base of the piles indicate that during vacuuming of the carpet according to the present invention this airflow, measured at the position just above the primary backing, is 28 m/s against 18 m/s in standard carpet, whereby the larger quantity of concentrated fine dust discharge can be substantiated.

It is a further object to collect the fine dust such that it can then be discharged, and herein prevent it from re-entering the space. It is advantageous for this purpose for the low piles to be manufactured from thread, at least some of the fibres of which have a weight per unit of length above 400 dTex. Use can be made for this purpose of a plurality of threads, each with a different weight per unit of length, by tufting thereof on a base structure from different bobbins or cones, and of a preparation made up of a plurality of different types of thread prior to being arranged.

Because the low piles are enclosed by high piles, the fine dust is prevented from being carried along again when the carpet is walked on or in the case of airflows parallel to the floor covered with the carpet. When the carpet is vacuumed however, the air flow is substantially perpendicular to the carpet and in a direction away from the carpet, whereby all piles are suctioned straight upward and the fine dust is picked up in simple manner. A suitable width of the space between the high piles has been found to be 5.1 mm (1/10" x2) and 6.4 mm (1/8" x2).

In order to further reduce a brushing action and the resulting stirring up of dust, at least the high or the low piles can consist of loop piles. Both the high and low piles are more preferably formed by loop piles.

Such piles can be formed by means of tufting, wherein many methods for manufacturing the carpet are possible. The high and the low piles can be produced in diverse design variants and for instance be arranged mixed together, or altematingly in one or more rows, or optionally in pairwise manner in a chessboard pattern, or have a random structure.

The invention will now be elucidated with reference to the following figures, in which: Figure 1 shows a carpet according to the present invention; Figure 2 shows a carpet according to the present invention during the removal of fine dust;

Figures 3a-3f show a number of comparative tests between the carpet according to the present invention and a standard carpet or a hard floor covering such as a laminate or linoleum.

Figure 1 shows a carpet 1 according to the present invention situated in a space 4 in which fine dust particles 5 and 6 are present. The fine dust particles drop downward as a result of the force of gravity and come to lie on carpet 1. A small part of the finest particles 6 here adheres to high piles 2 of carpet 1 and the somewhat coarser particles 5 to low piles 3 of carpet 1. It can be seen that particles 5 come to lie in a space enclosed between two high piles. In this way they are not entrained by an airflow parallel to carpet 1 (a direction generated by walking in the space or for instance by draught) and so not taken up again into the air in the space either. Figure 2 shows the directions of displacement of dust particles 5 and 6 from the high and low piles as a result of a substantially vertical airflow in a direction away from carpet 1. Such an airflow is caused during vacuuming and, as shown, results in concentrated discharge of the collected dust being possible. The carpet thus functions as a regenerative fine dust reservoir.

Figures 3a-3d show the quantity of dust in a space in which the carpet according to the present invention (A) is laid as a function of time, relative to a standard carpet (B).

Figure 3a shows a comparison between the carpet according to the present invention (A) and a standard carpet (B), wherein the quantity of particles with a size PMlO is shown as a function of time. The graph shows that an airflow is generated several times in order to cause a turbulence corresponding to wind current caused by walking or to draught. It can be seen that in the carpet according to the present invention (A) the dust which is hereby stirred up is relatively much lower after a period of time than in the standard carpet (B), even in the case of a higher quantity of fine dust at the start of the test.

Figure 3b shows a comparison between the carpet according to the present invention (A) and a standard carpet (B) ₅ wherein the quantity of particles with a size PM2.5 is shown as a function of time. The quantity of fine dust introduced into the test space in the case of (A) is roughly equal to the quantity in the case of (B). No difference can be seen in the sedimentation after the quantity of fine dust PM2.5 has been introduced. After a longer time there are moreover differences in the swirling as a result of airflows such as caused by people walking on the carpet or by draught, and there is a lower final concentration of fine dust in the space. As in figure 3a, an airflow is generated several times in order to cause a turbulence corresponding to wind current caused by walking or to draught. It can be seen that in the carpet according to the present invention (A) the dust hereby stirred up is relatively much lower after a period of time than in the standard carpet (B).

Figure 3c shows a comparison between the carpet according to the present invention (A) and a standard carpet (B), and in addition a hard floor covering such as laminate or linoleum (D), as well as a standard carpet (C). As in figure 3a, a quantity of particles with a size PMlO is introduced into the space. It can be seen that the reduction in fine dust particles brought about by the carpet according to the present invention amounts to more than a factor 10 relative to a hard floor covering.

Figure 3d shows a comparison similar to the comparison of figure 3a, but wherein particles with a size PM2.5 are now used instead of particles with a size PMlO. It can also be seen here that the reduction in fine dust particles brought about by the carpet according to the present invention amounts to more than a factor 10 relative to a hard floor covering.

Figure 3e shows the average result of a comparison, repeated 15 times, between the fine dust reduction carpet according to the present invention and a hard floor covering. It can be seen that the carpet according to the invention results in a concentration B of PMlO particles in the air which is 8 times lower compared to the hard floor covering A.

Figure 3f shows the average result of a comparison, repeated 15 times, between the fine dust reduction carpet according to the present invention and a hard floor covering. It can be seen that the carpet according to the invention results in a concentration B' of PM2.5 particles in the air which is 3 times lower compared to the hard floor covering A'.

It is noted by way of comparison that, compared to a hard floor covering, standard "low level loop" carpets only result in an improvement of a concentration which is 1.3 respectively 2 times lower than a hard floor covering.

It can be concluded on the basis of the above figures that the carpet according to the present invention is much less susceptible to swirling and turbulence in the air of the space in which it is laid, on the one hand because it ensures that the fine dust is held fast in the spaces created between the long piles, and on the other due to the increased capturing capacity of the fine filaments in the high pile.

An embodiment which functions very well in practice is obtained by manufacturing the high piles from a yarn of 700 dTex with 30 filaments (so 23.3 dTex or dpf per filament) in a 3:5 ratio with a yarn of 320 dTex with 72 filaments (so 4.4 dTex or dpf per filament) and by manufacturing the low piles from a yarn with 1600 dTex with 4 filaments (so 400 dTex or dpf per filament) in a 5:3 ratio with a yarn of 1000 dTex with 42 filaments (so 23.8 dTex or dpf per filament).

In addition to the shown embodiments, several variations are possible which are all deemed to fall within the scope of protection of the following claims. It is particularly noted that the carpet according to the present invention can be manufactured both as wall-to-wall carpet and as carpet tile, wherein the piles are fixed to a tuft base by means of a precoating and a heavy coating or for instance through fusing, and wherein a protective and/or strengthening layer can for instance consist of bitumen, polyolefins, PVC, SBR or EVA.