Abstract:
The present invention relates to a grip tape ( 2 ) and replacement grip tape for sports implements, like tennis, squash, racketball and badminton rackets, or clubs, as well as to a process for producing the same. The grip tape and replacement grip tape according to the present invention comprise a phase change material for dissipating and/or storing body heat of a player, so that the grip feeling for the player is improved considerably.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a grip tape, i.e., a tape or strip to be wrapped around the handle of a sports implement, like a racket or club to be used for ball games, and to a replacement grip tape for such implements (ball game rackets or clubs), in particular tennis, squash, racketball, badminton rackets and golf clubs, as well as to processes for producing the same. 
     BACKGROUND OF THE INVENTION 
     Grip tapes of this kind for sports implements, which are also called “grips” in the art, are wrapped around the grip or handle of a sports implement so that a player can handle the sports implement in the most precise and comfortable manner. In this connection, different criteria such as, for example, tackiness or tack (adhesive force), carrying-off of moisture and cushioning effect are important. A conventional replacement grip tape is, for example, described in U.S. Pat. No. 5,695,418. This replacement grip tape comprises a felt layer, with a closed cell polyurethane layer applied to the one side thereof and an adhesive layer with a liner applied to the other side thereof. The closed cell polyurethane layer is said to improve the shock absorbing and cushioning effect. 
     The replacement grip tape described in U.S. Pat. No. 5,695,418 with its closed cell polyurethane layer cannot absorb moisture or can only absorb little moisture so that due to the sweat generated by the player the tackiness of the grip tape decreases as the duration of the handling of the sports implement during a match increases. Thus, the handling of the sports implement is worsened considerably. Moreover, U.S. Pat. No. 5,695,418 describes only replacement grip tapes. 
     Latent heat storing materials are also known in the prior art. For example DE-A-198 13 562 describes a latent heat body wherein a paraffin-based latent heat storing material is received in a support material having receiving spaces. The support material consists of individual support material elements which are, e.g., bonded together, wherein capillary receiving spaces for the latent heat storing material are formed at least between the support material elements. A further example for a latent heat storing material and the possible use thereof in low temperature protection suits, ski boot liners, thermal socks, gloves and face masks is mentioned in U.S. Pat. No. 5,722,482. Moreover, it is referred to WO-A-00/70983 which describes the use of latent heat storing materials in shoes. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved grip tape and replacement grip tape having in particular an improved tackiness and a better cushioning effect vis-à-vis known grip tapes. This object is achieved with the features of the claims. 
     In achieving this object, the invention starts out from the basic idea that for improving the tackiness, the moisture usually caused by sweat between the hand of the player and the grip tape should be avoided to a large extent. For this purpose, the grip tape according to the present invention comprises a latent heat storing material which dissipates body heat of the player and/or controls the temperature of the grip tape and/or the hand of the player during a match. In accordance with a preferred embodiment of the grip tape of the present invention, the outer layer of the grip tape, which is in contact with the hand of the player, is made of an open cell polyurethane material which is able to absorb and/or carry off moisture. 
     The latent heat storing materials being used in the present invention are often also called phase change materials (PCM). Examples for phase change materials of the kind useful in the present invention are described in U.S. Pat. No. 5,851,338, U.S. Pat. No. 5,955,188, U.S. Pat. No. 6,077,597 and U.S. Pat. No. 6,099,894. The phase change material used in accordance with the present invention preferably consists of fibers, fabrics or foams containing microspheres or microcapsules filled with the actual phase change material. The phase change material is selected such that the phase change from solid to liquid and vice versa, wherein heat is absorbed during liquefaction and released during solidification, takes place in a temperature range close to the body temperature of the player, e.g. at 34 to 36° C., preferably at about 35° C. Any suitable combination of phase change materials can also be used. 
     By means of the grip tape and replacement grip tape according to the present invention, the tackiness (adhesive force) of the grip can be improved permanently because due to the use of the phase change material the temperature of the grip tape is controlled such that the player&#39;s hand sweats less. Thus, the grip feeling and/or the tack remain more constant as compared with conventional grip tapes. 
     Moreover, it surprisingly turned out to be favorable that by the use of the phase change material also the cushioning effect is influenced advantageously. Thus, by the use of the grip tape and replacement grip tape according to the present invention the handling of sports implements can be improved considerably. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a first embodiment of a grip tape according to the present invention; 
         FIG. 2  is a cross-sectional view of a second embodiment of a grip tape according to the present invention; 
         FIG. 3  is a cross-sectional view of a first embodiment of a replacement grip tape according to the present invention; 
         FIG. 4  is a cross-sectional view of a second embodiment of a replacement grip tape according to the present invention; and 
         FIG. 5  is a diagram comparing the equilibrium temperatures of conventional grip tapes and grip tapes according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a cross-sectional view of a grip tape  2  according to the present invention. The grip tape  2  is suitable for any kind of sports implement like ball game rackets, e.g. tennis, squash, racketball or badminton rackets, or clubs, and has an essentially longitudinal shape so that it can be wrapped around the grip or handle of a sports implement. According to the embodiment shown in  FIG. 1 , the grip tape  2  according to the present invention consists of three layers. This layer structure comprises an outer layer  4 , a center layer  6  and an inner layer  8 . When the sports implement is in use, the outer layer  4  contacts the hand of the player and should therefore be made of a suitable material which can absorb and/or carry off moisture. Particularly preferable for outer layer  4  is an open cell polyurethane material which has particularly advantageous properties as regards storing and carrying-off of moisture as well as dampening. The thickness d 1  of the outer layer  4  is preferably about 0.10 to 0.50 mm, particularly preferably about 0.15 to 0.25 mm. 
     The center layer  6  of  FIG. 1  comprises at least one phase change material (PCM). Preferably, the center layer  6  consists essentially completely of PCM. Suitable phase change materials which are contained in layer  6  or are used for forming this layer can, for example, be obtained from Outlast Technologies, Inc., Frisby Technologies, Inc. or BASF company. The phase change material is typically used in an amount of about 15 to 200 g/m 2 , preferably about 25 to 80 g/m 2 , and more preferably about 50 to 60 g/m 2 . The preferred phase change material is provided in the form of microspheres being arranged in a binder material in order to form the center layer  6 . 
     The embodiment of the grip tape  2  according to the present invention and as shown in  FIG. 1  additionally comprises an inner layer  8  that is preferably made of felt and serves as a base or support layer. The inner layer  8  has preferably a trapezoidal cross-section so that wrapping the grip tape around the grip of a sports implement is facilitated. The center layer  6  and the inner layer  8  together have a thickness d 2 +d 3  of preferably about 1.05 to 1.85 mm. Thus, the grip tape  2  has an overall thickness of preferably about 1.3 to 2.3 mm, more preferably about 1.3 to 2.0 mm. The inner layer  8 , which serves as the base layer, can directly be connected with the center layer  6 , e.g. by laminating, or can include a separate connecting layer  10 , e.g. in the form of an adhesive layer. The same holds true for the connection between the outer layer  4  and the center layer  6 , in which a connecting layer  12  can also be provided. 
       FIG. 2  shows another preferred embodiment of a grip tape  2   a  according to the present invention. The structure of the grip tape  2   a  of  FIG. 2  essentially corresponds to that of the grip tape  2  described with reference to  FIG. 1 ; however, the grip tape  2   a  comprises an outer layer  4   a , which is essentially a combination of layers  4  and  6  of  FIG. 1 , in other words, in the grip tape  2   a  the phase change material is integrated in the outer layer  4   a . The layer  4   a  is preferably made of an open cell polyurethane material into which the phase change material is included. The amount of phase change material in the layer  4   a  preferably ranges between 15 and 200 g/m 2 , more preferably between 25 to 80 g/m 2  and most preferably between 50 and 60 g/m 2 . An optimum of the mass amount of phase change material in the layer  4   a  lies preferably in the range of about 5 to 20%, more preferably 10 to 15%. The grip tape  2   a  also has an inner layer  8  serving as the base or support layer and being made preferably of felt, on which the outer layer  4   a  is provided. 
     The embodiment of the grip tape  2   a  according to the present invention, as shown in  FIG. 2 , is configured of two main layers only, so that it can be produced more easily and at the same time the phase change material is arranged more closely to the player so that the desired cooling effect is achieved more quickly. Moreover, it surprisingly turned out that the cushioning effect in the grip tape  2   a  is particularly favorable as compared with conventional grip tapes. 
     The grip tape  2   a  according to  FIG. 2  has an overall thickness of preferably about 1.3 to 2.3 mm, particularly preferably about 1.3 to 2.0 mm, wherein the outer layer  4  is about 0.10 to 0.80 mm thick, preferably about 0.15 to 0.50 mm, and the inner layer  8  is about 0.50 to 1.50 mm thick, preferably about 0.75 to 1.25 mm. In the embodiment according to  FIG. 2  the outer layer  4   a  can be directly applied to the inner layer  8 , or alternatively a connecting layer  10  can be present. 
       FIG. 3  shows an embodiment of a replacement grip tape  2   b  according to the present invention. The basic structure of the replacement grip tape  2   b  of  FIG. 3  essentially corresponds to that of the grip tape  2  described with reference to  FIG. 1 . However, the replacement grip tape  2   b  additionally comprises an adhesive strip  14  extending essentially along the length of the grip tape. The adhesive strip  14  is provided on the inner surface of the layer  8 , i.e. on the surface of the layer  8  facing away from the layers  4  and  6 . Moreover, the adhesive strip  14  is preferably provided with a liner  16  which covers the exposed adhesive surface of the adhesive strip  14 . For applying the replacement grip tape  2   b  to a grip of a sports implement, the liner  16  must first be removed in order to expose the adhesive surface of the adhesive strip  14 , so that subsequently the replacement grip tape  2   b  can be wrapped about the grip of the sports implement. 
       FIG. 4  shows a further embodiment of a replacement grip tape  2   c  according to the present invention. The structure of this replacement grip tape  2   c  essentially corresponds to the structure of the grip tape  2   a  described with reference to  FIG. 2 . Additionally, in this grip tape  2   c  an adhesive strip  14 , which is preferably provided with a liner  16 , is present on the surface of the layer  8  facing away from the phase change material. 
     The diagram of  FIG. 5  shows the equilibrium temperature which is provided between the hand of a player and a grip tape, depending on time, for a conventional grip tape and a grip tape or replacement grip tape according to the present invention. The structure of the conventional grip tape used for the comparison of  FIG. 5  is that of the grip tape according to the present invention without a phase change material. The structure of the grip tape according to the present invention which was used for the measurement corresponds to that of the grip tape  2   a  shown in  FIG. 2 , in which the phase change material is integrated in the outer layer  4   a . The mass amount of phase change material in the grip tape  2   a  used for this measurement example is 10%, and the outer layer  4   a  is made of open cell polyurethane material. This mass amount corresponds to about 55 g/m 2 . As can be taken from the diagram of  FIG. 5 , already after about 5 minutes an equilibrium temperature is found for both the conventional grip tape and also for the grip tape according to the present invention. While in the conventional grip tape, however, the equilibrium temperature is about 34° C., in the grip tape according to the present invention, which comprises about 10% phase change material, the equilibrium temperature is about 32° C. Thus, due to the use of the phase change material, the equilibrium temperature of the grip tape according to the present invention is about 2° C. lower than that of a conventional grip tape. Consequently, the hand of the player sweats less with the grip tape according to the present invention, so that less liquid has to be absorbed by the grip tape. This leads to an improved grip feeling because the characteristic of the grip tape (e.g., tack, cushioning effect) is constant or is at least retained over a longer period of time. Moreover, it turned out that the addition of the phase change material does not change the liquid carrying-off and/or the liquid storing capacity. It is a further surprising effect that due to the use of the phase change material the cushioning effect is influenced in a particularly favorable manner which leads to an additional improvement of the grip feeling. 
     For producing the grip tape according to the present invention, the heat change material can, as already discussed above, be integrated in the outer layer  4   a  consisting preferably of open cell polyurethane material or foam (according to the embodiments of  FIGS. 2 and 4 ) or be applied to the inner layer  8  as a separate layer  6  (according to the embodiments of  FIGS. 1 and 3 ). Alternatively or additionally, a separate phase change material layer can also be applied to the outside of the outer layer  4 . However, the application to the inner layer  8  is preferred because this offers the additional possibility to needle punch the inner layer  8 , which is preferably made of felt, so that it has improved moisture absorption properties. 
     Furthermore, the surface of the grip tape can be provided with a pattern, for example in the form of a stroke or symbol, for example by embossing. Moreover, openings or holes can be formed in the grip tape in order to improve moisture absorption and/or ventilation. 
     Under the inner layer  8  at least a further layer may be formed, said further layer having, for example, a different color, shock-absorbing effect and/or a particularly good cushioning effect. Felt, non-woven or elastomeric materials can, e.g., be used for this/these additional layer(s). Even with the additional layer(s), the overall thickness of such grip tapes according to the present invention should range preferably between 1.3 and 2.3 mm, particularly preferably 1.3 and 2.0 mm.