A LUMINESCENT MATERIAL

Technical Field

The present invention relates to a composition comprising polypropylene and at least one luminescent material particularly for manufacturing threads, and to a method for manufacturing a thread starting from such composition. Background Art

It is known that all the uniforms used by individuals working for example in the road maintenance and/or rescue sector, in civil protection and in police forces include reflective bands composed of films which reflect light in order to make the individual who wears them more visible in situations of poor visibility and at night. The same bands are applied to items of sports clothing and ordinary clothing.

However, these uniforms suffer the drawback of being invisible in the absence of a light source which illuminates them, and therefore cannot ensure adequate safety for the individuals who wear them. It would be desirable, therefore, to have a thread or monofilament which is particularly adapted to manufacture, for example, items of clothing capable of ensuring better visibility and therefore higher safety for those who wear them.

Disclosure of the Invention The aim of the present invention is to provide a composition particularly for manufacturing filaments which overcomes the drawbacks of the background art.

Within this aim, an object of the invention is to provide a composition particularly for manufacturing threads which is visible in conditions of poor or no lighting without the aid of external light sources.

Another object is to provide a thread which comprises a composition as above and is particularly adapted to produce articles characterized by high visibility in conditions of poor or no lighting and in the absence of external light sources. Another object is to provide a thread as described above which is also characterized by combustion-retardant properties, antibacterial or antiodorant properties, is inalterable over time, is environmentally compatible and is easy and cheap to manufacture and work.

A further object is to provide a method for preparing a thread starting from a composition as described above.

This aim and these and other objects which will become better apparent hereinafter are achieved by a composition, particularly for manufacturing threads, which comprises polypropylene and at least one luminescent material. The aim and objects of the invention are also achieved by a thread which can be obtained from a composition as described above.

The aim and objects of the invention are also achieved by a method for manufacturing a thread which comprises a composition defined as above, wherein the method comprises the step of incorporating at least one luminescent material within polymeric cells of polypropylene.

The aim and objects of the invention are also achieved by an article which comprises a thread as defined above.

The characteristics mentioned exclusively with reference to one of the aspects of the invention must be understood as valid, where applicable, also with reference to the other aspects even though they are not explicitly repeated. Ways of carrying out the Invention

The term "thread", unless otherwise specified, is understood here as the product of spinning, both in the form of a monofilament and as a bundle of two or more filaments possibly interwoven, twisted, texturized or

taslanized. In a first aspect, the invention relates to a composition which comprises polypropylene and at least one luminescent substance, such luminescent substance being advantageously in a quantity comprised between 1% and 40%, preferably between 10% and 20%, even more preferably equal to 15% by weight on the total weight of the composition.

The term "luminescence" is used here to designate the phenomena of phosphorescence, fluorescence or chemiluminescence, preferably phosphorescence. The expression "luminescent substance" is used to designate any substance characterized by an electron structure such that the absorption of photons by said substance leads to an emission of radiation in the visible spectrum which lasts over time, preferably as a consequence of a phosphorescence phenomena.

Preferably, said at least one luminescent material is selected from the group that consists of phosphorus and compounds which belong to the family of aluminate oxides of alkaline earth metals doped with europium. These compounds are per se known.

The expression "aluminate oxides of alkaline earth metals doped with europium" is used to designate luminescent compounds which substantially comprise oxides of alkaline earth metals and alumina (Al ₂ O ₃ ), doped with europium. Preferably, in addition to oxides of alkaline metals and alumina, the luminescent compounds used also comprise boron oxide (B ₂ O ₃ ).

Preferably, doping occurs with a combination of europium and dysprosium.

The composition can comprise advantageously also one or more optional ingredients selected from the group which comprises colors, pigments, fire-resistant substances, such as for example antimony trioxide, antibacterial substances, and mixtures thereof.

In a preferred embodiment, the polypropylene is in granules (here referenced also as cells). In this embodiment, a first part of the granules is constituted exclusively by propylene, while a second part of the granules incorporates the at least one luminescent substance and the other optional

ingredients, if present. In this manner, the luminescent material incorporated in the polymeric cells of polypropylene cannot be dispersed into the environment (for example by washing or abrasion).

A second aspect of the invention is constituted by a thread characterized by great visibility even in complete darkness, which can be manufactured for example by extruding a composition as defined above.

Obtaining luminescence entails the necessary exposure of the composition, of the thread or, more advantageously, of the article manufactured with the thread to an external light source during the period in which they are not used, and can last up to three hours after the end of the exposure. In particular, the luminescence is due to the presence of the at least one luminescent substance, which is capable of absorbing photons in a broad range of wavelengths and of reemitting the energy in the form of a radiation in the visible range for a period which follows the end of the exposure to the external light source. Accordingly, the high- visibility effect is obtained even in the absence of a light source. Li this regard, the solution constituted by the invention differs distinctly from the threads used up to now for similar purposes, which do not emit, but are exclusively capable of reflecting, light that arrives from an external source (headlights of a vehicle or others).

The thread according to the invention is employed usefully wherever it is desirable or advantageous to have luminescent articles, such as for example in the manufacture of items of clothing, preferably for safety workers. However, it is also possible to use the thread according to the invention to manufacture fabrics for curtains, fabrics for interior decoration, for producing night-time special effects, fishing nets, ropes and others.

The thread of the invention can also be usefully employed in the manufacture of unique-identifiers for instance for clothing or other goods. In fact, a manufacturer of items of clothing could for example insert a length of the thread of the invention within the fabric so as to identify its

items and distinguish them from similar items manufactured by others. This use can also be advantageous for the identification of commercial counterfeitings as products lacking the unique-identifier made with the luminescent thread of the invention would be immediately and unambiguously identified.

The thread according to the invention has many other advantages, including the inalterability of its characteristics over time, the property of being slow-burning or flame retardant, and of being workable by means of the most widespread technologies for the ordinary working of threads. It is further possible to give the thread the most desired coloring by simply embedding inside it pigments and colors or to give it antibacterial and antiodorant characteristics.

The polypropylene thread according to the present invention is perfectly environmentally compatible, since it does not lose into the environment any luminescent substance and does not entail the emission of harmful or polluting radiation.

In another aspect, the invention relates to the production of a thread starting from a composition as defined above which is based on polypropylene and at least one luminescent substance, said method comprising substantially the step of incorporating the at least one luminescent substance within polymeric cells of polypropylene.

The method according to the present invention can be performed with conventional machines for manufacturing polypropylene threads. Such machines, provided with extruders and spinners, allow to manufacture a thread with the required characteristics. It is particularly preferable for extrusion through a spinneret to occur with a denier-filament value which is higher than conventional values and in particular is comprised between 10 and 30. To achieve this effect, it is possible for example to reduce the number of holes of the spinnerets with respect to conventional spinnerets. Preferably, the number of holes of the spinnerets used within the method is

comprised between 1 and 40.

In a preferred embodiment, the method comprises a step for feeding to said machines a mixture, here referenced as master, which advantageously comprises granules (or cells) of one or more materials selected from the group which comprises neutral propylene, polyethylene, preferably low-density polyethylene, granules of polypropylene incorporating various elements (color, pigments, fire-retardant material, antibacterial products) and mixtures thereof. The master then receives the addition, in a step which follows feeding to the machines but before extrusion, of the at least one luminescent substance in the quantities described above. As a consequence of the extrusion, the luminescent material is incorporated within the polypropylene cells.

In another aspect, the invention relates to an article which comprises a thread as defined above. Although only some preferred embodiments of the invention are described explicitly in the text, the person skilled in the art will understand immediately that numerous modifications are possible without thereby abandoning the inventive concept on which the present invention is based.

Other characteristics and advantages of the present invention will become better apparent from the description of the following preferred embodiments and corresponding applications, understood exclusively as non-limiting examples.

When providing a luminescent yellow thread, it is possible to produce fabrics adapted for making work jackets and overalls with high nighttime visibility for road maintenance workers.

A fabric manufactured with luminescent thread can be used to produce bands to be applied to items of sports clothing, in order to make the athlete visible even with poor ambient lighting.

By producing a luminescent colored thread and another thread of the same color which is not luminescent, it is possible to produce fabrics for

curtains and interior decoration or for the fashion sector in which lettering or images appear only in the absence of light.

A luminescent white thread can be used to produce deep-sea fishing nets; the fish is attracted by the luminescence of the article and is trapped by it.

A luminescent white thread can be used to produce cables for mooring watercraft in ports; in this manner, in case of night-time mooring it is always possible to find the ropes even if they are immersed in the water.

Shoelaces or items of clothing manufactured or woven with said thread can produce interesting effects in discos or in the presence of black light.

Schoolbags made with said thread can be another example of use.

The disclosures in Italian Patent Application No. MI2005A000471 from which this application claims priority are incorporated herein by reference.