Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/44—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds
  • D01F6/46—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds of polyolefins
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/42—Formation of filaments, threads, or the like by cutting films into narrow ribbons or filaments or by fibrillation of films or filaments
  • D01D5/426—Formation of filaments, threads, or the like by cutting films into narrow ribbons or filaments or by fibrillation of films or filaments by cutting films
• • E—FIXED CONSTRUCTIONS
  • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
  • E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
  • E01C13/00—Pavings or foundations specially adapted for playgrounds or sports grounds; Drainage, irrigation or heating of sports grounds
  • E01C13/08—Surfaces simulating grass ; Grass-grown sports grounds

Definitions

• the present invention relates to a thermoplastic synthetic fiber to be used in the production of artificial grass mats or the like, to a process for the production thereof and to mats or the like incorporating said fiber. More in particular, the invention relates to a thermoplastic synthetic fiber constituting the bundles or tufts that protrude, in use, from the upper side of a backing layer in mats, particularly artificial grass mats.
• Artificial grass mats, or artificial lawns constitute a valid alternative to natural grass lawns in many cases, especially in the field of sporting facilities. Unlike natural grass lawns, artificial or synthetic grass mats do not require costly and constant maintenance operations and are not subject to easy wear and tear caused by intense mechanical stresses associated with sports use.
• This type of mats, for use as artificial grass, as a doormat or as a covering for walking surfaces in a domestic environment, an urban environment and the like usually comprises a flat flexible backing composed of one or more layers of synthetic material, attached to which are a plurality of bundles or tufts, which project from the upper side of the backing and cover the entire surface thereof, to form a resilient and relatively soft walking layer.
• the aforesaid bundles or tufts simulate the tufts of grass and perform the same function.
• These tufts are in turn composed of bundles of fibers or strips made of plastic material, produced separately from the flat backing and fixed thereto with techniques known to those skilled in the art.
• the fibers or strips intended to form these tufts must have properties of mechanical strength, flexibility and resilience suitable for the purpose for which they are intended.
• Patent application WO 99/04074 discloses the production of fibers or strips for artificial grass mats constituted by polymers or mixtures of polymers such as polyamide, polypropylene and LLDPE.
• fibers or strips for artificial grass for example, structures obtained by coextrusion of different polymers in order to form filaments having a polyolefin inner core and a polyamide surface layer, or vice versa.
• Preferred structures are composite structures in which fibers of different plastic materials are joined and twisted.
• European patent application EP 1 378 592 Al discloses the production of fibers or strips for the production of artificial grass composed of a binary mixture of a polymer and a plastomer.
• the polymer is composed of polyethylene or polypropylene and the plastomer is composed of a homopolymer or copolymer of ethylene obtained with metallocene catalysis or in any case with single-site catalysts.
• the quantity of plastomer varies from 30 to 80% by weight with respect to the mixture.
• the object of the present invention is therefore to provide a thermoplastic synthetic fiber for the production of mats, particularly artificial grass mats, provided with excellent properties of tenacity, resilience and softness, sufficient to eliminate or reduce possibilities of abrasion to the skin of persons who accidentally come into contact with the surface of the mat, and which is obtained with an inexpensive material.
• Another object of the invention is to provide a mat, particularly an artificial grass mat, or a doormat, incorporating synthetic fibers provided with excellent properties of tenacity, resilience and softness, which are also such as to eliminate or reduce possibilities of abrasion to the skin of persons in the event of falls, slipping or more generally in the event of contact with the surface of this mat.
• thermoplastic synthetic fiber for the production of mats, artificial grass and the like characterized in that it comprises from 90 to 50% by weight of polyethylene and from 5 to less than 30% by weight of a plastomer having a modulus of flexural rigidity between 5 and 100 MPa, said plastomer being chosen from an ethylene copolymer obtained by single- site catalysis and a heterophasic copolymer containing prevalently propylene.
• the polyethylene is chosen from high density or medium density polyethylene.
• Polyethylene with a density between 0.930 e 0.945 g/cc is particularly preferred.
• the plastomer When the plastomer is an ethylene copolymer obtained through metallocene catalysis or single-site catalysis, it can be an ethylene copolymer with a comonomer such as butene, hexene, 5-methylpentene-l or octene.
• Single-site catalysts are well known to those skilled in the art and are described, for example, in the patents EP 129 368 and US 4752597. They are capable of generating polymers with a narrow distribution of molecular weights, which, expressed as Mw/Mn, can be below 3. Plastomers having these characteristics are marketed, for example, with the trademark EXACT by ExxonMobil.
• the plastomer When the plastomer is a heterophasic copolymer containing prevalently propylene, it is typically composed of a mixture of copolymers obtained directly in the reactor, comprising a random copolymer of propylene with ethylene and an ethylene -propylene rubber, optionally also comprising a third monomer.
• These heterophasic copolymers at times also called thermoplastic olefins (TPO), are marketed, for example, by Basell Polyolefins with the trademark SOFTELL.
• the plastomer according to the invention is characterized by a modulus of flexural rigidity of between 5 and 100 MPa, preferably between 8 and 80 MPa, more preferably between 10 and 60 MPa, measured according to ASTM D - 790.
• the plastomer according to the invention is preferably present in a quantity between 10 and 25% by weight of the total mixture.
• thermoplastic fiber obtained according to the invention is characterized by a tenacity between 3 and 1 gf/denier, preferably between 2 and 1.2 gf/denier, and by a breaking load between 3000 and 1000 gf, more preferably between 2500 and 1500 gf.
• the aforesaid mechanical properties of the mixture of polymers according to the invention is such as to ensure that the fibers or strips have an adequate mechanical impact resistance, necessary to prevent the tufts of grass from breaking as a consequence of the continuous trampling and the violent mechanical stresses to which they are subjected, particularly in the event of the mat being used for sports.
• the mixture of polymers also has good properties of resilience, so that the tuft, which is stressed in compression when trampled, can regain its substantially erect position when compression ceases.
• thermoplastic fiber according to the invention can contain other components such as additives, colorants, stabilizers, fillers and the like, as it is known in the art.
• thermoplastic synthetic fibers With reference to Figure 1, the steps of a particularly advantageous method for the production of thermoplastic synthetic fibers according to the invention will now be schematically described.
• the granules of polymer mixture 1 which are to form the fiber (10) according to the invention are fed, through loss-in-weight gravimetric feeders 2, into a Bandiera double screw extruder E at a temperature of 220-230 0 C.
• the mixture is formulated with suitable additive packages, as it is known in the art.
• the molten mixture is filtered through filters 3 to separate gels and any particles of dirt, and then fed to a flat headed spinnerette S, from which a molten film is delivered.
• the hot film delivered from the spinnerette S is then subjected to a cooling step C in a water tank kept at a constant temperature.
• the film is dried with a fan system and then cut into fibers or strips that are subjected to a hot stretching step D by means of two series of rollers 4, 4' and 5, 5' with different speeds, intercalated by a heating oven maintained at controlled temperature.
• a hot stretching step D the speed Vi of the first series of rollers 4, 4' is lower than the speed V 2 of the second series of rollers 5, 5'.
• the fiber is then subjected to a thermosetting step TF in another two series of hot rollers at controlled temperature 6, 6' and 7, 7', in which the speed V 3 of the first series of rollers 6, 6' is greater than the speed V 4 of the second series of rollers 7, T.
• the subsequent step F is a lubrication step in which the fiber is lubricated by means of a finishing oil to make it suitable for the subsequent processing operations.
• the final fiber obtained (10) has a count of between 200 and 2000 dtex, for the product named "monotape”, and between 4000 and 15000 dtex for the product named "fibrillated".
• the difference between the two articles is due to the width of the final strip and the fibrillation, which is required to generate a particular mesh pattern in the fiber and which is produced between stretching and thermosetting by means of a roller provided with special needle inserts, not shown.
• this is joined in tufts of 4, 6 or 8 fibers, and these groups of fibers are twisted in a step T and optionally subjected to curling.
• a bundle of fibers (28) with a suitable count to form tufts of synthetic grass in a mat is thus generated.
• a monofilament product can also be produced, with similar properties to the monotape, by direct extrusion in the spinnerette, i.e. without the need to cut a sheet as the fibers are delivered from several holes, of different shape, positioned on the extrusion head. Also with this product the monofilaments obtained are joined in bundles of 4, 6 or 8 fibers.
• the final product is strong, flexible and soft, and therefore suitable to form the upper surface of a mat, for example an artificial grass mat.
• the cross section of a detail thereof is shown schematically in Figure 2.
• the fibers 10 grouped together and twisted in the bundles 28 are then fixed to one or more backing layers 30, 32 of a mat, in order to form a strong, flexible and soft upper covering layer simulating the properties of tufts of natural grass.
• the bundles of fibers 28 are fixed to the backing layers of the mat 40 preferably by passing the bundles through one or more of these layers and making them protrude from the upper side thereof.
• Fibers can be fixed to the backing of the mat using other methods, as it is known to those skilled in the art.
• a filling material such as sand or granules of an elastic material 34, such as rubber, in particular recycled rubber, can be deposited on the upper surface of the mat backing, and which is capable of improving the general elastic properties of the mat, particularly in the case of an artificial grass mat intended for sports use. Examples
• the fibers obtained had a count of 1350 denier.
• the tenacity of these fibers was determined with the method UNI EN ISO 2062 and the breaking load with the method UNI EN ISO 2062. The results are set down in Table 2:
• thermoplastic synthetic fiber according to the invention allow the task and preset objects to be fully accomplished.
• the characteristics of mechanical strength and softness required to solve the technical problem highlighted in the preamble are obtained through the use of materials that allow a considerable reduction in the final production costs.
• the production method of the synthetic fiber is simple and low-cost, although providing a fiber structure that associates, in an extremely advantageous manner, the characteristics of strength and durability with softness, which are very important from the viewpoint of accident prevention and comfort of the user.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Architecture (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Mechanical Engineering (AREA)
• Artificial Filaments (AREA)
• Nonwoven Fabrics (AREA)

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Cited By (6)

Citations (4)

• 2007
  • 2007-02-13 IT ITMI20070266 patent/ITMI20070266A1/it unknown
• 2008
  • 2008-02-11 WO PCT/EP2008/051621 patent/WO2008098905A2/en active Application Filing

Patent Citations (4)

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