METHOD OF CONDITIONING WOOL FIBRE MATERIAL Technical field

This invention relates to a method of conditioning wool fibre material.

More specifically, the method according to this invention relates to the conditioning of wool fibre materials subjected to treatment using ionized gases and/or plasma, hereafter referred to also merely as plasma treatment.

The invention addresses the above mentioned method as applied to a wool fibre material of any kind: fibres in semi-processed form, yarns, knitwear, woven fabric or finished garments.

The invention also relates to a system for actuating the above-mentioned method of conditioning wool fibre material. Background art

Plasma treatment technology, in particular atmospheric plasma treatment, is known, for example from patent application WO201 1/095930, and consists in treating a continuous permeable substrate (made from natural or synthetic fibre or fabric or from polymeric membrane) with ionized gases or plasma, obtained by electric discharges in a controlled atmosphere, in particular air. This technology proved particularly effective because it was found that treating the substrate in this way improves its selling performance, minimizes production cost and improves the quality of subsequent treatments such as finishing, dyeing and the like.

According to the above mentioned patent application, the substrate is fed between two sets of rollers which are suitably offset from each other in such a way that electric discharges can be generated across successive rollers and made to pass through the material constituting the substrate. Although, as stated, the plasma treatment is able to bring numerous benefits to the treated substrates, it is not completely satisfactory in the case of wool fibre from other points of view.

Whilst, on the one hand, the plasma treatment gives the wool fibre materials improved characteristics such as, for example, non-shrink, water-resistant, anti-felting, reduced pilling effect (that is, the formation of small balls of fluff typical of wool), tensile strength of the web of fibre of thread, or ease of dyeing, the same treatment has been found to result in undesired effects from other points of view. More specifically, it has been found that after the plasma treatment, the wool fibre material loses its smoothness characteristics, resulting almost hursh to touch.

In the jargon of the trade, the typical smoothness of the hand on wool is also know simply as "handle" or "handle feel".

Experimental studies, also carried out by the same Applicant of this application, have shown how this worsening of the characteristics of the wool fibre derives in essence from the considerable reduction, due to oxidisation following the plasma treatment, of the lipid layer which coats the wool fibre.

It is, in effect, proven that the above-mentioned smoothness characteristic of the wool fibre derives from the presence of this lipid layer.

In other words, the lipid layer naturally present on the surface area of the wool fibre, subjected to plasma treatment, undergoes an oxidation and partially dissolves.

The practical implication of this circumstance has proved to be commercially undesirable for the manufacturers of woolen garments, who have therefore decided to forgo the welcome effects of the plasma treatment, until the above-mentioned drawback of the worsening of the smoothness to touch is overcome.

Attempts to recover the above-mentioned smoothness (also known in the jargon of the trade as "hand") have so far been based on the use of softening substances which, however, have resulted in drastically reducing also the beneficial effects generated by the plasma treatment. In effect, experimental studies, also developed by the same Applicant, have shown how most of these beneficial effects can be attributed to the nano- roughness generated, following the plasma treatment, on the surface of the wool fibre.

For example, if the shrinking typical of woolen garments is due to the unidirectional movement of the fibres, the non-shrink effect is a consequence of the fact that due to the above-mentioned nano-roughness the wool fibres adjacent to each other increase considerably the mutual friction, thus fixing their mutual position. This sort of cohesion between the fibres in practice makes the woolen fabric or garment substantially not exposed to the shrinkage which is typical of these materials when they are subjected to twisting or violent beating (such as washing in high speed washing machines).

Attempts have been made to overcome the above-mentioned drawback of a considerable reduction in the smoothness to touch of wool fibre when subjected to plasma treatment, by applying suitable softening substances. However, it has been observed that the application of the softeners produces a continuous or intermittent coating of the fibres, with the consequence of considerably reducing the effect of cohesion between the fibres produced by the nano-roughness induced by the plasma treatment.

In other words, whilst the use of the softeners improves the smoothness to touch of the wool fibre, it cancels out the beneficial effects of the plasma treatment and therefore, as a result, this route has been found to be not particularly advantageous.

Disclosure of the invention

The aim of this invention is therefore to provide a method of conditioning wool fibre material which comprises the plasma treatment of the material but which is able at the same time to not adversely affect the smoothness to touch of the finished product made of this type of material.

This aim is fully achieved by the method for conditioning wool fibre material according to this invention as characterized in the appended claims.

Detailed description of preferred embodiments of the invention

The technical features of the invention, with reference to the above aim, are clearly described in the appended claims and its advantages are apparent from the detailed description which follows.

The method of conditioning wool fibre material according to this invention has been developed on the basis of experimental observations on the phenomenon of migration of the lipids in the wool fibre.

As stated, lipids are present in wool fibre in the form of a substantially surface layer which, following the plasma treatment to which the fibre is subjected, appears considerably reduced, until considerably compromising the tactile sensation of smoothness to touch which is typical of woolen products.

It have been observed experimentally that the layer of lipids present in the wool fibre is subject to migration towards the inside of the fibre when the fibre is exposed to a moist environment whilst, on the hand, it is subject to migration towards the outside of the fibre when the fibre is exposed to a dry environment.

The method according to this invention therefore comprises treating a wool fibre material with plasma, so as to provoke on the surface of the fibre that nano-roughness of which the beneficial effects are desired so as to considerably improve the characteristics of the fibre, as described above. A subsequent step of the method according to this invention comprises subjecting the wool fibre to a moist environment to induce a compaction of the residual surface lipids (that is, those which have not been eliminated during the plasma treatment), inside the wool fibre.

Next, the method according to this invention comprises subjecting the wool fibre to a dry environment so as to stimulate the migration of a considerable quantity of lipids, from the inner layers, to the surface of the fibre.

It has been observed experimentally that the migration of the lipids towards the surface of the wool fibre is increased by an action of movement of the wool fibre material.

Advantageously, the above-mentioned migration of the lipids is improved by a vigorous action of movement of the wool fibre material.

A method of actuation of this vigorous action is the repeated beating and overturning of the wool fibre material.

Advantageously, this step of vigorously moving the wool fibre material is actuated by placing the material inside a rotary drum and rotating the drum.

According to a preferred embodiment of the method according to this invention, the rotary drum is substantially of the type provided in washing machines for garments, linen and the like.

For this reason, during rotation of the drum, the wool fibre material is overturned and beaten against the walls of the drum.

In other words, the rotation of the drum is advantageously such as to cause the repeated falling and overturning of the wool fibre material inside the drum, whilst soaked in water.

It is well known that this vigorous movement is to be avoided in the traditional wool fibre materials as it generates felting and shrinkage of the materials; these effects only occur to a residual extent with wool fibre material which has been subjected beforehand to plasma treatment.

The method according to this invention therefore overcomes a deep- rooted prejudice in the sector to the treatment of wool fibre materials, that is, the fact that wool fibre materials cannot be subjected to vigorous movements, without the deterioration of the materials due to shrinkage and/or felting.

It has also been observed experimentally that the above-mentioned migration of the lipids towards the surface of the wool fibre is improved by the fact that the water used for soaking the wool fibre material is at a temperature higher than ambient temperature.

Advantageously, it has been found that the above-mentioned soaking in water provides valid results using water at a temperature of between 50°C and 120°C.

Preferably, it has been found that more than satisfactory results are obtained with a water temperature of between 60°C and 100°C.

Still more preferably, it has been found that excellent results are obtained with water at approximately 90°C.

The use of hot water, at a temperature higher than 40°C is notoriously advised against, by manufacturers of woollen garments and fibres, by manufacturers of detergents and by washing machine manufacturers, in view of the possible deterioration of the characteristics of the wool fibre. Experimentally, in the development of the method according to this invention, it was found that the use, for soaking the wool fibre material, of hot water at a temperature higher than 40°C does not generate any significant deterioration of the material when the wool fibre material has been subjected beforehand to atmospheric plasma treatment.

For this reason, the use of water at temperatures much higher than ambient temperature in the treatment of wool fibre materials constitutes the overcoming of a prejudice rooted in the sector.

In this way, with the adoption of the conditioning method according to this invention, without substantially introducing alterations to the nano- roughness present on the surface of the wool fibre (which, on the contrary, occurs with the adoption of softening substances), the advantageous result is achieved of re-establishing a lipid layer such as to guarantee a sufficient tactile sensation of smoothness in the wool fibre material.

In other words, with the method according to this invention, it is possible to enjoy the beneficial effects of the plasma treatment without, however, having to forgo the smoothness to touch which is typical of the wool fibre materials which the users consider to be indispensable.

In effect, due to the above-mentioned conditioning method, there is substantial recovery of the smoothness to touch of the wool fibre materials which undergo plasma treatment, by regenerating the surface lipid layer of the wool fibre.

This invention also relates to a system for actuating the above-mentioned conditioning method.

The system for conditioning wool fibre material according to this invention comprises a station, not illustrated, for treating the wool fibre material using ionized gases and/or plasma. By way of an example, a station for atmospheric plasma treatment compatible with the system according to this invention is described in the above-mentioned patent application No. WO201 1/095930, in the name also of the same Applicant.

The wool fibre material subjected to plasma treatment is sent to a station for soaking in water, at which the material undergoes a soaking which is able to activate the migration of the residual lipid layer (that is, the remains of the lipid layer after the plasma treatment) towards the inside of the wool fibre.

The system comprises a thermal unit for heating the water to be used for soaking the wool fibre material, the thermal unit defining, for the conditioning system, respective means for heating the water.

Advantageously, the wool fibre material is moved at the soaking station by suitable movement means, described in more detail below.

The conditioning system according to this invention also comprises drying means designed to dry the wool fibre material previously subjected to soaking.

The above-mentioned drying means, not illustrated, are of the type normally used in drying machines for garments and linen, for example of an industrial type.

The above-mentioned soaking station usefully comprises a rotary drum substantially of the type used in washing machines for garments and linen. Advantageously, the rotary drum integrates the above-mentioned means for moving the material which, in a fashion not unlike the prior art rotary drums used in washing machines, comprises a plurality of recesses distributed on the peripheral surface of the drum.

During the rotation - advantageously about a horizontal axis of rotation - which the drum undergoes, these recesses allow the pulling upward and the consequent falling of the wool fibre material, thereby resulting in the above-mentioned vigorous movement.

Advantageously, the above-mentioned drying means act on the wool fibre material still located inside the drum, the conditioning system comprising for this purpose suitable means for introducing into and discharging water from the drum.

The experimental results achieved with the actuation of the method according to this invention have confirmed the effectiveness of the method for the purpose of recovering the smoothness to touch, or handle feel, of wool fibre materials previously subjected to plasma treatment.

More specifically, by way of example, it has been observed experimentally that the application of the method according to this invention to a piece of knitwear made of raw wool, following an atmospheric plasma treatment to achieve the non-shrink effect, a soaking cycle in water at 90°C and at the same time vigorous movement in a washing machine drum, and subsequent drying, has generated a substantial restoring of the handle feel of that piece, to the level of that of the same piece before being subjected to the plasma treatment, with a shrinkage value of the area quantifiable as about 6.5% (which should be compared with the much higher values of 30% achieved when subjecting an identical piece to the same steps which has not undergone plasma treatment).

The present invention therefore achieves the preset aims, overcoming the drawbacks of the prior art.

Wool fibre material means without distinction material made from wool fibre or even wool blend material.

In the system according to this invention the plasma treatment station is not necessarily located close to the soaking station, and can also be in a remote location.

It has also been found experimentally that the wool fibre materials subjected to the method according to this invention are substantially stable when treated with softeners. In other words, the beneficial effects of plasma treatment of the wool fibre material subjected to the method according to this invention do not decline following a subsequent treatment with softening substances.

For the purpose of this specification, the term "water" means any aqueous solution which can be used in the treatment of wool fibre materials, with the exception of solutions based on softeners.