Patent Publication Number: US-2023136642-A1

Title: Artificial turf, filler for artificial turf, and artificial turf production method

Description:
TECHNICAL FIELD 
     The present invention relates to artificial turf, artificial turf filler and artificial turf production method, and more particularly, to artificial turf, etc., comprising a filler layer with filler between a plurality of piles. 
     BACKGROUND ART 
     Artificial turf is currently used in various sports facilities. In addition, a variety of artificial turf has been developed. The following is a description of artificial turf commonly used in football grounds. 
     The natural turf used in the past required a lot of daily maintenance work, such as fertilization, watering and repair. In comparison, artificial turf is easy to maintain and manage. In addition, the use of artificial turf has been increasing in recent years because it is made of an organic polymer compound, which makes it highly durable and enables competitions to be played even after rain. 
     However, early artificial turf was hard and had poor shock-absorbing properties, which placed a heavy burden on the knees. In addition, there was a problem of burns and abrasions that could easily occur when sliding. 
     The history of the development of artificial turf is explained with reference to  FIG.  2 A ,  FIG.  2 B  and  FIG.  2 C .  FIG.  2 A ,  FIG.  2 B  and  FIG.  2 C  show cross-sectional views of conventional artificial turfs.  FIG.  2 A  shows the conventional artificial turf of first-generation.  FIG.  2 B  shows the conventional artificial turf of second-generation. And  FIG.  2 C  shows the conventional artificial turf of third-generation artificial turf. 
     Artificial turf was first introduced (first generation) in the world in 1966 at the Astrodome (baseball stadium) in Houston, USA. In Japan, it was introduced at Korakuen Stadium in 1976. As shown in  FIG.  1 A , the first-generation artificial turf  11  consists of a pile layer  13  and a cushioning layer  15  (synthetic polymer foam) called underpad to ensure the cushioning required for sports and has a two-layer structure. A number of piles  17  forming the pile layer  13  are raised from the cushion layer  15  in a carpet-like shape. 
     The first-generation artificial turf  11  was noted to have a safety problem in that it was prone to burns and abrasions when sliding. Furthermore, the underpads were locally indented due to their flexibility, making it difficult for players to stand on their feet when dashing or jumping, which was a problem that tended to cause strain on the player&#39;s feet and legs. 
     Due to the high safety and installation costs of the first-generation artificial turf  11 , sand-filled artificial turf was introduced in the 1980s as the second-generation artificial turf  21 . The second-generation artificial turf  21  consists of a pile layer  23 , a cushion layer  25 , a pile  27 , and further with a sand  29  in between piles  27 . In addition, the second-generation artificial turf  21  has a smaller number of piles  27  to be woven in than the first-generation artificial turf  11 , and it has sand between the artificial turf  29 , resulting in a cost that is said to be about 50% lower than first-generation artificial turf. As a result, it was widely used in baseball fields and tennis courts at the civic level. In addition, the second-generation artificial turf  21 , with the addition of sand  29 , reduced the localized denting of the underpad, as the impact received by the player&#39;s feet is transmitted downwards in a wider area and is mitigated. Therefore, the problem of fatigue in the player&#39;s feet and legs was improved. 
     However, another problem arose with the second-generation  21  artificial turf. When it was used for many years and the sand layer was hardened and tightened, it tended to transmit impact directly to the feet and knees during exercise. 
     In the late 1990s, third-generation artificial turf  31 , commonly known as high-tech artificial turf, was introduced. The third-generation artificial turf  31  has a pile layer  33 , a rubber chip layer  35 , sand  37  and a base layer  39 . The pile forming the pile layer  33  is a long pile  41 , longer than the artificial turf of the first-generation artificial turf  11  and the second-generation artificial turf  21 . The third-generation artificial turf  31  does not comprise the underpad. It has a base layer  39 , a rubber chip layer  35  and a sand  37 , which form three layers. The rubber chip layer  35  is cushioned and adjusted to be not too soft by adding sand  37 . This makes the deformability during exercise closer to that of natural grass, thereby reducing injuries. 
     For example, Patent Document 1 describes a technology for improving the shock absorbency of artificial turf by filling rubber chips made from crushed waste tires, industrial waste, etc. as filler between a number of piles resembling turf leaves rising on a base material constituting the artificial turf. 
     PRIOR ART LITERATURE 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Publication No. 2018-178499. 
       
    
     SUMMARY OF THE INVENTION 
     Problem Solved by the Invention 
     However, when the inventor measured and compared the surface temperatures of natural and artificial turf under natural light, the surface temperature of conventional artificial turf was over 60° C., sometimes 20° C. higher than that of natural turf. 
       FIG.  3 A  and  FIG.  3 B  show the isothermal distribution of surface temperatures of a ground with third-generation artificial turf and a ground with natural grass.  FIG.  3 A  and  FIG.  3 B  show the distribution of surface temperatures near noon on a sunny day in September. 
     Note that the wind was blowing from the east (right side of the figure), so the surface temperature is lower on the right side of the figure due to the wind. Overall, the surface temperature of the third-generation artificial turf was approximately 20° C. higher than that of the natural turf, with some areas exceeding 60° C. 
     Thus, there remained room for improvement in order to use artificial turf as a substitute for natural grass. It is therefore an object of the present invention to provide an artificial turf or the like with a function to maintain the temperature of the artificial turf surface at a low temperature. 
     Means for Solving the Problems 
     A first aspect of the present invention is an artificial turf comprising a base material, a plurality of piles imitating turf leaves erected on the base material, and a filler layer formed by a filler material being filled between the plurality of piles, wherein the filler layer includes a water retaining layer, and a mineral having calcium carbonate as a major component. 
     A second aspect of the present invention is the artificial turf of the first aspect, wherein the water retaining layer has a porous material. 
     A third aspect of the present invention is the artificial turf of the first or second aspect, wherein the filling material has a plant-derived material. 
     A fourth aspect of the present invention is the artificial turf of the third aspect, further comprising a mineral layer between the filler layer and the base material, wherein the mineral is the main material of the mineral layer. 
     A fifth aspect of the present invention is the artificial turf of the third or fourth aspect, wherein the mineral is limestone. 
     A sixth aspect of the present invention is the artificial turf of the fifth aspect, wherein the plant-derived material is wood chips and sawdust derived from bark. 
     A seventh aspect of the present invention is the artificial turf of the fifth aspect, wherein the plant-derived material is coconut pete. 
     An eighth aspect of the present invention is an artificial turf filler, which is filled between a plurality of piles resembling turf leaves in the artificial turf, comprising a plant-derived material, and a mineral comprising calcium carbonate as a major component. 
     A ninth aspect of the invention is an artificial turf production method comprising a base material and a plurality of piles resembling turf leaves erected on the base material, and wherein the filler material comprises a plant-derived material, and a mineral comprising calcium carbonate as a major component, and the artificial turf production method includes filling the filler material on the base material and between the plurality of piles. 
     Effect of the Invention 
     According to each aspect of the present invention, it is possible to deprive the minerals of a lot of vaporization heat as the water contained in the water retaining layer vaporizes, and also to delay the temperature rise by providing moisture to the minerals. This makes it possible to provide artificial turf and the like with the ability to maintain the temperature of the artificial turf surface at a low temperature. As a result, it is possible to provide artificial turf with a high level of safety by suppressing burns and heat stroke of users. 
     The rubber chips forming the rubber chip layer used in the third-generation artificial turf are recycled from finely crushed car tires. Tires contain various chemicals such as zinc oxide, sulfur, carbon black, etc. And some reports indicate that benzopyrene, which is considered to be highly carcinogenic, has been detected in the rubber chips. According to the third, eighth or ninth aspect of the present invention, only natural resources are used for the filling material, without using rubber chips, which may cause environmental pollution and risk to the health of the user. This makes it possible to suppress the adverse effects on the user&#39;s health. 
     According to the fourth aspect of the invention, the relatively cushiony filling material layer and the relatively hard mineral layer reduce the physical burden on the user and maintain an adequate resilience. 
     Furthermore, according to the fifth to seventh aspects of the present invention, it is possible to provide a more effective artificial turf. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a cross-sectional view of the artificial turf of the present invention. 
         FIG.  2 A  is a cross-sectional view of conventional artificial turf, showing the first generation.  FIG.  2 B  is a cross-sectional view of conventional artificial turf, showing the second generation. And  FIG.  2 C  is a cross-sectional view of conventional artificial turf, showing the third-generation artificial turf. 
         FIG.  3 A  and  FIG.  3 B  are the isothermal distributions of surface temperatures of a ground with third-generation artificial turf and a ground with natural grass. 
     
    
    
     DETAILED DESCRIPTION 
     Form for Carrying Out the Invention 
     The embodiments of the invention are described in detail below with reference to the drawings. The embodiments of the invention are not limited to those described below. 
     Example 1 
       FIG.  1    shows a cross-sectional view of an artificial turf  1 . The artificial turf  1  (an example of “artificial turf” in the present claims) comprises a base material  3  (an example of “base material” in the present claims), a number of piles  5  (an example of “pile” in the present claims) imitating turf leaves standing on the base material  3 , a filler layer  7  (an example of a “water retaining layer” and a “filler layer” in the present claims) formed by filling the spaces between the numerous piles  5  with a filler material (an example of a “filler material” in the present claims), a mineral layer  9  (an example of a “mineral layer” in the present claims) made mainly of minerals (an example of a “mineral” in the present claims), being between the base material  3  and the filler layer  7 . 
     The filler material forming the filler layer  7  includes a plant-derived material (an example of a “porous material” and a “plant-derived material” in the present claims) and a mineral mainly composed of calcium carbonate. For the plant-derived material, dried and powdered coconut pete was used. For the minerals, Kansuiseki stone from Mt Kawaradake in lizuka, Fukuoka Prefecture, was used. Kansuiseki is a white crystalline limestone. 
     An artificial turf production method (an example of an “artificial turf production method” in the present claims) according to the present invention for producing an artificial turf  1  is as follows. The artificial turf  1  is produced through a pile planting step for planting a number of piles  5  on a substrate  3 , a mineral layer formation step for forming a mineral layer  9  made mainly of minerals between a number of piles  5 , and a filler layer forming step in which a filler layer  7  is formed by filling a filler material on top of the mineral layer  9  and between the numerous piles  5 . 
     For example, the overall thickness of the pile  5  may be 40-60 mm, including the substrate  3  being a 5-15 mm shock pad, the mineral layer  9  being 10-15 mm, and the filler layer  7  being 15-30 mm and the length of the pile  5  above the filler layer  7  being 10-15 mm. The thickness of each of these layers and the overall thickness may be other than the above if necessary. 
     Fillers and minerals can be further added later if necessary. 
     A flexible shock pad is used as the base material  3 , for example. Shock pads have a structure made of thread-like material and can retain a certain amount of water. Therefore, the water retaining layer may be realized by the base material  3  instead of a filler layer. Alternatively, the base material  3  may function as a water retaining layer together with the filler layer. The heat of vaporization of the moisture retained by the base material  3  can also be expected to cool the artificial turf, at least by the heat of vaporization. 
     The artificial turf  1  of the present invention has the same shock absorption, durability and ease of maintenance as conventional artificial turfs, and furthermore, the temperature rise of the artificial turf surface can be suppressed, thus providing players with a cooler and more comfortable environment. 
     Examples of actual measurement results comparing the surface temperature between the artificial turf of the present invention and the third-generation artificial turf are shown in Table 1. As shown in Table 1, the surface temperature of the artificial turf in this example is more stable than that of the third-generation artificial turf placed in the same environment and the temperature rise is suppressed by more than 10° C. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Artificial turf of 
                   
               
               
                 Measurement 
                 the present 
                 Third-generation 
               
               
                 environment 
                 invention (° C.) 
                 artificial turf (° C.) 
               
               
                   
               
             
            
               
                 1 
                 36.9 
                 48.6 
               
               
                 2 
                 35.0 
                 49.1 
               
               
                 3 
                 43.8 
                 60.1 
               
               
                   
               
            
           
         
       
     
     Here, the above surface temperature measurements were made using a non-contact thermometer, which measured the radiant temperature. It is expected that the sport players who is in direct contact with the artificial turf will feel even cooler on the artificial turf of the present example. 
     In addition, because coconut pete is used instead of rubber chips to enhance shock absorption, there is no risk of environmental pollution or health hazards. 
     Although powdered coconut pete was used as the plant-derived material, bark chips from cypress, cedar and other trees may also be used. By replacing the filling material with bark chips instead of rubber chips, the higher surface temperature can be suppressed. Wood chips and/or sawdust from crushed bark may also be used as a plant-derived material, or a mixture with coconut peat may be used. 
     Black rubber chips, which are recycled tire material, tend to produce black carbon particles and produce an unpleasant odor when the temperature rises. On the other hand, cypress and cedar bark chips give off a woody aroma and a pleasant feeling of forest bathing. Furthermore, bark chips are superior to rubber chips in terms of resource recycling. 
     Powdered coffee beans may also be used as a plant-derived material. 
     DESCRIPTION OF THE REFERENCE NUMBERS 
     ( 1 ) artificial turf, ( 3 ) base material, ( 5 ) pile, ( 7 ) filler layer, ( 9 ) mineral layer, ( 11 ) first-generation artificial turf, ( 13 ) pile layer, ( 15 ) cushion layer, ( 17 ) pile, ( 21 ) second-generation artificial turf, ( 23 ) pile layer, ( 25 ) cushion layer, ( 27 ) pile, ( 29 ) sand, ( 31 ) third-generation artificial turf, ( 33 ) pile layer, ( 35 ) rubber chip layer, ( 37 ) sand, ( 39 ) substrate layer, ( 41 ) long pile.