Patent Description:
Polyurethanes are nowadays used in many applications because of their broad property profile. Polyurethanes can be used both in compact form and in foamed form. Polyurethanes can, for example, be present in the form of thermosetting elastomers, thermoplastic elastomers, microcellular elastomers, integral foams, flexible foams, rigid foams or semi rigid foams. Further details on this subject may be found in "<NPL>.

<CIT> discloses the use of a hybrid material comprising a matrix of polyurethane and foamed particles of thermoplastic polyurethane comprised therein as floor covering, bicycle saddles, upholstery and shoe soles.

<CIT> describes a stall floorcovering comprising a foam mat comprising expanded thermoplastic polyurethane-bead foam for animals.

<CIT> relates to highly elastic PU foams suitable as functional material with thermally insulating properties, e.g. for diving suits, surfing wetsuits, swim suits, sea rescue wetsuits or boots in the marine sector.

It is well known that the dynamic interaction between the athlete and the sports flooring is significant to the performance and safety of the athlete. Therefore, the ability of the surface to reduce force (i.e. force reduction) is important.

It was therefore an object of the present invention to provide floorings having improved force reduction. It was found by the present inventors that the inclusion of expanded thermoplastic polyurethanes in the floorings is capable to improve the force reduction of floorings.

Thus, the present invention provides a composite, comprising (<NUM>) a bottom layer comprising expanded thermoplastic polyurethane particles; and (<NUM>) a surface layer on the bottom layer,.

The present invention also provides use of such composites in flooring surfaces, sports hall floorings, swimming pool hall floorings, running tracks, sports facilities, playgrounds, kindergartens, park walkway and pavements.

In one embodiment of the invention, a composite as defined above is provided, wherein the composite comprises (<NUM>) a bottom layer comprising expanded thermoplastic polyurethane particles; and (<NUM>) a surface layer on the bottom layer.

The bulk densities of the expanded thermoplastic polyurethane particles are preferably less than <NUM>/l, more preferably from <NUM>/l to <NUM>/l, even more preferably from <NUM> to <NUM>/l.

The expanded thermoplastic polyurethane particles have a closed cell content of preferably more than <NUM>% as measured by customary method (DIN ISO <NUM>) in the art.

The composites have good force reduction of more than <NUM>%, preferably from <NUM>% to <NUM>%.

The expanded thermoplastic polyurethane particles are generally spherical, and usually have an average diameter of from <NUM> to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>. In the case of non-spherical, e.g. ellipsoidal, elongate or cylindrical, particle diameter means the longest dimension.

Conventional materials in the art can be used in the surface layer. The surface layer comprises compact (i.e. non-foamed) elastomers, selected from the group consisting of mixtures of ethylene propylene diene monomer (EPDM) rubber and polyurethane (PU).

In one embodiment of the present invention, the content of the expanded thermoplastic polyurethane particles is in the range from <NUM> wt% to <NUM> wt%, preferably from <NUM> wt% to <NUM> wt% based on the weight of the composite.

Preferably, the ratio of bottom layer to surface layer in the composites is in the range from <NUM>:<NUM> to <NUM>:<NUM> by weight.

In the composites, the expanded thermoplastic polyurethane particles can be bonded to one another with an adhesive, for example with a matrix of reactive components. Preferably, the matrix of reactive components is selected from the group consisting of <NUM>-component or <NUM>-component polyurethane, urea, melamine, formaldehyde, and epoxy polymers. The matrix can be in the form of a foam, a compact elastomeric system or a gel.

In the composites, the expanded thermoplastic polyurethane particles can be also thermally-fused to one another by exposure to heat, without using an adhesive.

In one embodiment of the present invention, the expanded thermoplastic polyurethane particles can be randomly dispersed into a matrix of EPDM in the bottom layer of the composites.

For the purposes of the present invention, the expanded thermoplastic polyurethane particles are used for preparing the composites. Suitable foamed thermoplastic polyurethane particles (i.e. expanded thermoplastic polyurethane particles (E-TPU)) and production thereof are well known and are disclosed by way of example in <CIT>, <CIT>, <CIT>, and <CIT>.

From the TPUs, it is possible to produce expanded, i.e. foamed, TPU particles, in particular via the suspension or extrusion processes known to the person skilled in the art and described in the literature above. In these processes, the foamed E-TPU particles can be obtained directly or indirectly, i.e. by way of non-foamed expandable TPU particles comprising blowing agent as intermediate; (for the purposes of the present invention, the expressions "expanded TPU (or TPE) particles" and "foamed TPU (or TPE) particles" are used synonymously).

In the suspension process, the TPU in the form of granulated material is heated with water, a suspending agent, and a blowing agent in a closed reactor, to above the softening temperature of the granulated material. The polymer particles here become impregnated with the blowing agent. One possibility then is to cool the hot suspension, whereupon the particles harden with inclusion of the blowing agent, and depressurize the reactor. The resultant expandable particles comprising blowing agent are foamed in a subsequent step via heating to give the expanded particles. In an alternative, the hot suspension can be depressurized suddenly without cooling (explosion expansion process), whereupon the softened particles comprising blowing agent foam immediately to give the expanded particles, see by way of example <CIT>.

In the extrusion process, the TPU is mixed in an extruder, with melting, with a blowing agent that is introduced into the extruder. In one possibility, the mixture comprising blowing agent is extruded and granulated under conditions of pressure and of temperature such that the granulated TPU material does not foam (expand), and by way of example this can be achieved by using an underwater pelletizer operated at a water pressure of more than <NUM> bar. This gives expandable particles which comprise blowing agent and which are foamed via heating in a subsequent step to give the expanded particles. In an alternative, it is also possible to extrude and granulate the mixture without using super atmospheric pressure. In this process, the melt strand foams, and the expanded particles are obtained via granulation.

The expanded TPU particles can be used in the process that is in principle known to the person skilled in the art to produce expanded TPU sheets; (for the purposes of the present invention, the expression "expanded TPU sheets" describes a prefabricated sheet obtainable via adhesive bonding and/or fusion of individual foamed TPU particles). By way of example, the expanded TPU particles can be adhesive-bonded to one another with the aid of an adhesive in continuous or batch processes, for example by using the polyurethane adhesives known to the person skilled in the art. The expanded TPU particles can be fused to one another with exposure to heat in continuous or batch processes, where it is also possible in principle to add adhesives during fusion. In one embodiment, the expanded TPU particles are fused by means of hot air or in particular steam without the use of adhesives.

The expanded TPU particles can be used to produce expanded TPU prefabricated sheets by fusing the E-TPU-particles with exposure to heat in a closed mold, in particular in a molding machine, for example as described in <CIT>. For this, the particles are charged to a mold and, after the mold has been closed, hot air, or preferably steam, is introduced, and the particles therefore undergo further expansion and, at temperatures that are preferably between <NUM>° C. and <NUM>° C. , are fused to one another to give the expanded TPU sheets.

In one embodiment of the present invention, the composites are prepared by the customary methods in the art, for example, placing the compact elastomers on the expanded TPU sheets by hand lay-up, spraying, spreading, and like.

The composites can also comprise other layers if appropriately, such as middle layer, substrate layer and/or fabric layer.

The composites can be in the form of prefabricated molded parts, which can be produced from the composites by the customary methods in the art. The molded parts comprising expanded TPU particles have low weight and can easily be subjected to mechanical operations via sawing, milling, or punching. Individual molded part can therefore be laid and/or connected to one another relatively easily via a very wide variety of techniques, e.g. via tongue-and-groove connections or dovetail connections.

The molded part can be used in flooring surfaces such as sports flooring surfaces, sports hall floorings, swimming pool hall floorings, running tracks, sports facilities, playgrounds, kindergartens, park walkway and pavements.

There is no particular limit for the thickness of the composite or the molded part. The thickness of the composite or the molded part is generally in the range from <NUM> to <NUM>, preferred in the range from <NUM> to <NUM>, more preferred in the range from <NUM> to <NUM>, depending on the specific use. Higher or lower thickness of the molded part is also possible.

All percentages and ratios are mentioned by weight unless otherwise indicated.

The present invention is now further illustrated by reference to the following examples, however, the examples are used for the purpose of explanation and not intended to limit the scopes of the present invention.

E-TPU particles were bonded to one another by a PU prepolymer as a bottom layer, and the bottom layer were then cured at ambient temperature and moisture for no less than <NUM> hours. EPDM particles were bonded via hand lay-up on the bottom layer to form a surface layer, and the surface layer was kept at ambient temperature and moisture for final curing.

Example <NUM> was carried out in a manner analogous to Example <NUM>, except that a middle layer made from polyurethane resin was used for sealing purpose and the surface layer was applied by spraying process.

The production of bottom layer was separated into <NUM> steps. First of all, a <NUM>-component PU sublayer was casted and cured for about <NUM>-<NUM> mins at ambient temperature and moisture to be still viscous but not fully gelled. Then, E-TPU particles are spread evenly on the gel. Afterwards, a third sublayer of <NUM>-component PU was casted. After the bottom layer was cured at ambient condition for no less than <NUM> hours, EPDM particles and PU prepolymer are sprayed on the bottom layer.

A microfoamed <NUM>-component PU elastomer system was prepared as a bottom layer. After curing, the same microfoamed PU layer was casted. Finally, EPDM particles were spread manually on it and cured.

E-TPU particles were randomly mixed with EPDM particles and then bonded with PU prepolymer adhesive as a bottom layer. After cured for no less than <NUM> hours at ambient temperature and moisture, layer of EPDM particles and PU prepolymer was sprayed on the bottom layer.

Example <NUM> was carried out in a manner analogous to Example <NUM>, except that a prefabricated E-TPU layer, rather than randomly embedded E-TPU particles, was laid in the middle of bottom layer. The prefabricated E-TPU layer was prepared in a same method as described in Example <NUM>.

Comparative example <NUM> was carried out in a manner analogous to comparative example <NUM>, except that a compact <NUM>-component PU elastomer, rather than microfoamed system, was used to prepare the composite.

Comparative example <NUM> was carried out in a manner analogous to comparative example <NUM>, except that the compact <NUM>-component PU elastomer was blended with EPDM particles to prepare the bottom layer.

Comparative example <NUM> was carried out in a manner analogous to example <NUM>, except that no E-TPU particles were used in the bottom layer.

The production of bottom layer was separated into <NUM> steps. First of all, a <NUM>-component PU sublayer was casted and cured for about <NUM>-<NUM> mins at ambient temperature and moisture to be still viscous but not fully gelled. Then, a prefabricated E-TPU sheet was laid on the surface of the PU sublayer as the second sublayer. Prefabricated E-TPU layer was prepared by adding 40wt% PU binder (Elastan® CC8004) to E-TPU particles to create a single layer sheet, and then curing for more than <NUM> hours. Afterwards, a third sublayer of <NUM>-component PU was casted.

After the bottom layer was cured at ambient condition for no less than <NUM> hours, PU elastomer was casted and kept for about <NUM>-<NUM> mins. Finally, EPDM particles were spread and bonded with PU elastomer layer and cured.

Examples in Table <NUM> supplemented with an asterisk * are not according to the invention.

The composites of examples <NUM> and <NUM> show a very attractive force reduction performance which can protect the injury of human body and joints in abrupt fall. It is high deformability of E-TPU particles that offers a relatively long "collision time", which improves the cushion effect and force reduction.

Compared with comparative example <NUM> and <NUM>, the composites of example <NUM> shows a significantly improvement of force reduction, from <NUM>% or <NUM>% to <NUM>%. Although force reduction may also be improved to certain degree in the case of comparative example <NUM>, where the bottom layer is microfoamed via recipe modification, from <NUM>% or <NUM>% to <NUM>%, however, the microfoamed process is strongly influenced by local moisture and temperature during construction, and therefore is more challenging to be practically well controlled. Prefabricated E-TPU sheet between the PU elastomer sublayers is used in the bottom layer in Example <NUM>, the force reduction is also significantly improved. The composites of inventive example <NUM> and example <NUM> improve the force reduction by either randomly mixing E-TPU particles or inserting a prefabricated E-TPU sheet into EPDM in the bottom layer, compared with the traditional composite of comparative example <NUM>. Randomly mixing E-TPU particles or inserting a prefabricated E-TPU sheet into PU elastomer can similarly improve the force reduction.

The use of ETPU provides an improved force reduction, but also a more environment friendly solution, which is urgently requested in this traditional application fields.

In addition, the addition of E-TPU does not reduce or destroy other properties of the composites, such as deformation, friction, tensile strength, abrasion, and elongation. In certain circumstance, the tensile and elongation properties are even improved.

Claim 1:
A composite comprising:
(<NUM>) a bottom layer comprising expanded thermoplastic polyurethane particles; and
(<NUM>) a surface layer on the bottom layer,
wherein the composite has a force reduction of more than <NUM>% measured according to EN <NUM>:<NUM>,
wherein the expanded thermoplastic polyurethane particles are dispersed into a matrix of EPDM in the bottom layer of the composite; and
wherein the surface layer comprises compact elastomers, wherein the compact elastomers are selected from the group consisting of mixtures of ethylene propylene diene monomer (EPDM) rubber and polyurethane (PU).