PRODUCED BY THIS METHOD

The present invention relates to a method for the production of a carpet and to carpet produced by this method. In particular the invention relates to a carpet with different pile heights in which the pile heights are distributed in a predetermined manner, in particular according to a (decorative) pattern.

There are various techniques for applying patterns to carpet. Differently colored threads can be used, carpet can be printed and a difference in pile height can be achieved using weaving techniques or with different threads so that a visually perceivable design can also be achieved.

The influencing of the pile height and application of variations in height during weaving is a complex process, however, which is why in practice producers often choose to create differences in height of the piles in the carpet after weaving by means of shearing. Shearing is to be understood here as the reduction in pile length by means of a cutting process.

This is also a labor-intensive process which is furthermore characterized by a waste of material, since the part of the thread cut off is logically removed. The American patent applications US 2662558 and US 2790225, for example, also describe the use of carpet with a memory effect in which at least part of the threads used changes its form - in particular shrinks - after heating, with use being made of intrinsic polymer properties, or by using threads made of fibers with different properties. These techniques have the disadvantage that they are difficult to use for very specific threads, while it is desirable not to be limited in the choice of threads to be used during the production of carpet. One object of the present invention is therefore to provide a method for the production of carpet that does not have the above-mentioned disadvantages, and to provide a viable alternative to the existing methods of carpet production.

The invention thus presents a method for the production of carpet comprising reducing a fiber length of a thread; fixing the reduced fiber length such that a thermally activatable memory effect is created; temporary stretching the fixed thread; processing the temporarily stretched thread to produce carpet or semi-finished carpet and heating the carpet or semi-finished carpet produced in this way at least up to an activation temperature of the memory effect, wherein the fixing of the reduced fiber length comprises the use of a chemical process such as treatment with sulfite.

Permanently and temporarily fixed threads behave differently during a thermal post- treatment. Permanently fixed threads maintain their form. Temporarily fixed threads return to their initially fixed form. This initial form is stored in their form memory that is controlled by various parameters.

In one specific embodiment the chemical process comprises adding a sodium metabisulfite (Na2S ₂ 05) solution to the threads; these can be wool threads, but can also be made at least partially of polyamide. The connections, also referred to as bridges, that in these threads provide the specific stable keratin structure, can become tensioned by mechanical processes (spinning, twisting/cabling) during the production of the threads. Breaking down these bridges under tension and forming new bridges without tension, chemical setting, fixes the imposed tensioned thread structure. The length of the thread is stabilized by the complete fixing of the tensioned structure. In this imposed form, the bridges are no longer tensioned.

Sodium metabisulfite in solution with a pH of > 5 results predominantly in "bisulfite" (HSO3 ). The following oxidation quickly converts the thiols (-SH) into -S-S- bridges. Oxidation occurs already during coiling of the material at elevated temperature, but can be accelerated by the addition of perborate or other oxidation agents.

Depending on the desired pattern, weaving should be performed at each pile point with a temporarily or permanently fixed thread type (and this via the positioning of the threads with form memory in the loom). The permanently fixed threads and the temporarily fixed threads will behave differently during a thermal post-treatment. The permanently fixed threads will maintain their form (length). The form (length) of the temporarily fixed threads will be lost. These threads will return to their initial (well fixed) form. This initial form is stored in the thread memory (which is why they must also be regarded as memory materials). With this method, a (semi-finished) carpet can be produced using conventional weaving techniques and equipment wherein the patterns created during weaving are subsequently revealed by heating the (semi-finished) carpet to the activation temperature of the memory effect of the thread. An advantage of the inventive method is that no attention has to be paid to the special properties of the thread during weaving as these are - so to speak - temporarily suspended and stored in the memory of the thread. After activation of the memory effect, the pretreated thread shrinks and a difference in height is created between the piles. The pattern of this difference in height is determined by the method employed during the production of the (semi-finished) carpet. The use also of threads with unreduced fiber length creates a relatively large contrast and enhances the visibility of the pattern.

A semi-finished carpet is to be understood in this context as a not or not yet fully finished carpet, in particular a carpet to which no or not all of the backing has yet been applied. Backing is understood as a finish applied to what is seen as the underside of the carpet during use. In many cases this finish is applied in several steps with both a primary and a secondary backing being applied. The primary backing serves hereby to fix fibers on a tuft fabric and consists, for example, of a (latex) hot melt, while the secondary backing serves to give the carpet weight and sturdiness and is frequently made of bitumen or an ecological bitumen variant. Particularly in that case, the step of heating of the carpet can be combined with a further production step that is necessary anyway for the production process in which the semi-finished carpet has to be heated, such as during the application of a precoating, a hot melt or a heavy coating. In order to achieve the possibility of bringing even more variety into the patterns to be created, the method can also comprise processing of different temporarily stretched threads with different reduced fiber lengths to produce carpet or semi-finished carpet. In this way a pattern can be achieved with a multitude of fiber heights. In one embodiment, the step of reducing a fiber length of a thread can comprise spinning, twisting and/or cabling and stranding of fibers or threads. It has been observed that good results can be achieved using these techniques. The temporary stretching of the fixed thread can comprise the torsion relief and setting of the thread, but other techniques are equally possible.

Various techniques can be applied on the basis of the work steps described above. For example, the processing of the temporarily stretched thread to produce carpet or semi- finished carpet can comprise weaving of the thread. Weaving is a technique that is preferred for the production of so-called Axminster carpet, wherein a backing of the carpet is also produced by means of this weaving process.

The invention will now be explained using a practical example in which an Axminster carpet with structural difference is produced. The first step is the blending of the wool and the PA fibers. After the homogeneous blending of the fibers, 80% wool and 20% PA, the fibers are spun before being twisted to form composite threads with 2 or 3 threads. On the one hand these are permanently fixed A threads with standard torsion and on the other temporarily fixed B threads with high torsion. The permanently fixed A threads and temporarily fixed B threads are both dyed, after which a form memory is created in the temporarily fixed B threads by means of a treatment with sodium metabisulfite. This sodium metabisulfite treatment causes thiols (-SH) to be converted into -S-S- bridges. After creation of the form memory, the torsion is relieved in the temporarily fixed B threads. These threads are mechanically deformed so that they have the same torsion as the permanently fixed A thread.

The mechanically deformed C thread is temporarily fixed so that this form is maintained for weaving. The permanent A thread and temporarily fixed C thread are processed together in the Axminster weaving process. The Axminster weaving process does not change with this method so that the existing machine park can be employed. The thermal treatment of the woven carpet allows the lightly fixed C thread to return to its initial form, temporarily fixed B thread, due to the memory effect or form memory. The thermal treatment and application of latex backing is a One-step process'. The desired high-low effect in the carpet is finally achieved in this way.

The steps and sub-steps mentioned in the example above can be employed in the manner described here, in other words in this combination or sequence, but each step or sub- step can also be otherwise, in other words separately from other steps or in a different sequence, combined with any other of the measures mentioned in this description. The invention is now explained in further detail by reference to the following figures. Here:

Figure 1 shows a carpet according to the present invention before heat treatment has taken place;

Figure 2 shows a carpet according to the present invention after heat treatment has taken place; and

Figure 3 shows a flowchart of the the method as claimed in the present invention.

Figure 1 shows a carpet 1 produced by reducing a fiber length of a thread, the fixing of the reduced fiber length by applying a chemical process, such as a treatment with sulfite, such that a thermally activatable memory effect is created, and the temporary stretching of the fixed thread. It can be seen that the piles 2, 3 manufactured from different fibers all have the same length A.

Figure 2 shows the carpet 1 from Figure 1 after heating of the carpet to at least an activation temperature of the memory effect. It can be seen that a part 2 of the piles has a shorter length than a part 3 of the piles.

Figure 3 shows a flowchart of the the method as claimed in the present invention.