An artificial key material

Abstract: In composition of an artificial key material mainly made of synthetic resins, addition of ceramic whiskers in cluster form much improves workability, sweat absorption and texture.

Description: Background of the invention The present invention relates to the use of an artificial key material, and more particularly relates to its use for keyboard musical instruments such as pianos, organs and accordions. As well known, natural ivory is well suited for keys or surface covering of keys of keyboard musical instruments. In addition to the high price of the material, however, recently growing international trend for protection of natural animals disenables free and abundant use of ivory for these purposes. Ebony, which is also used to this end, is again very high in price and, moreover, its significant variation in quality and inevitable colour fading in use limit broader use of this material for keys. Out of such a background, use of synthetic resins as a substitute for these natural materials has acquired an enlarged market. Thermosetting resins such as phenol and urea as well as thermoplastic resins such as polymethyl methacrylate have been generally used for production of artificial keys. Use of the tliermosetting resins, however, is inevitably accompanied with the problem of poor workability in production processes. Whereas sole use of the thermoplastic resins tends to cause undesirable slippage of players' fingers on keys during performance due to the relatively low sweat absorption of the thermoplastic resins. In EP-A-0 291 056 an artificial key material for providing the lowest possible friction between internal moving parts of a key for a computer or the like is disclosed, comprising a resin reinforced with ceramic whiskers. Summary of the invention It is thus the basic object of the present invention to provide an artificial key material which is highly hygroscopic for rich absorption of human sweat, well suited for working in production and still provided with an excellent texture quite close to that of natural key materials. In accordance with the present invention, use is made of an artificial key material with the characteristics set forth in the appended single claim. Brief description of the drawing The attached drawing is a photographic representation of the surface of the artificial key material in accordance with the present invention enlarged with 1000 magnification. Description of the preferred embodiments The content of the ceramic whiskers per the total of the whiskers and the resin should preferably be in a range from 5 to 50 % by weight, and more preferably from 5 to 25% by weight. For the matrix resin is usable methacrylic ester resins such as polymethyl methacrylate, acrylic ester resins, acrylonitrile-stylene resins, acrylonitrile-butadiene-stylene resins, polyester resins, stylene-acrylic acid ester copolymer resins, stylene-methacrylic acid ester copolymer resins, epoxy resins or combinations of these resins. Most preferably are used polymethyl methacrylate, acrylonitrile-stylene resins and acrylonitrile-butadiene-stylene resins. The ceramic whiskers are given in the form of an oxide type, sulfide type, carbide type, nitride type, silicate type and mixtures of these types. More specifically, the ceramic whiskers have a composition such as, for example, MgSO 4 · 5Mg(OH) 2 · 3H 2 O, K 2 TiO 3 , K 2 TiO 3 or CaSO 4 · 2H 2 O. The length of the ceramic whiskers should preferably be in a range from 1 to 1000 µ m, and more preferably from 10 to 100 µ m. The diameter of the ceramic whiskers should preferably be 10 µ m or smaller, and more preferably 1 µ m or smaller. In accordance with the present invention, the ceramic whiskers are dispersed in the matrix resin in form of clusters of filaments but not in the form of individual filaments. There is no special limit for the number of filaments in each cluster. The length of each cluster should preferably be in a range from 1 to 1000 µ m, and more preferably from 10 to 100 µ m. The diameter of each cluster should preferably be in a range from 1 to 1000 µ m, and more preferably from 10 to 100 µ m. The artificial key material may further contain fillers, pigments, dyestuffs, plasticizers, lubricants, hardners, antioxidants and/or antistatics. In production of the artificial key material in accordance with the present invention, a mixture of the components are kneaded together and the kneaded mixture is shaped in a proper manner such as extrusion, injection, casting, pressing after rolling or pressing. For example in the case of practical shaping via extrusion or injection, resin pellets are first supplied to an extruder or an injector and the whiskers are supplied into the machine at a midpoint middle step in order to avoid possible breakage of the whiskers. In the case of shaping via casting, the whiskers are mixed and kneaded with liquid resin of polyester, acryl or epoxy. Since the clusters of whiskers appear on the surface of the shaped piece, polishing is applied to the surface of the shaped piece in order to remove the surface skin. Preferably buffing is further applied to the shaped piece for surface smoothness of the end product. The shaped piece so obtained can be used either as a key or, after proper slicing, as a surface covering of a key. As is well observed in the attached photographic representation, sub-micron size interspaces are left between whiskers in clusters dispersed within matrix resin and presence of such numerous fine interspaces well absorb sweat on hands of players just like porous natural ivory. Inclusion of the whiskers of excellent mechanical properties much improves strength, hardness, thermal transmission, appearance and rigidity of the material. The whiskers appearing on the surface of the material provide the surface with moderate frictional resistance which well prevents unintended slippage of fingers during performance. Examples Samples Nos.1 to 3 were prepared using three different materials. That is, Sample No.1 was made of the key material in accordance with the present invention, Sample No.2 was made of the same resin but without inclusion of ceramic whiskers and Sample No.3 was made of natural ivory. Each Sample was cut into test pieces each in the form of a rectangular sheet of 30mm length, 10mm width and 20 to 30µ m thickness. For measurement of hygroscopic property, the weight of each test piece was measured after drying at 35% RH and 20°C temperature for one week. The weight of the test piece was again measured after leaving in a dessicator saturated with steam at a temperature of 23°C for 24 hours. The results of the measurement are shown in Table 1 in which 5 to 7% increase in weight well indicates significant improvement in hygroscopic characteristics when compared with the conventional key material made of resin only. For measurement of tensile strength, a square block of 200x200mm 2 and 3mm thickness was prepared from each Sample via injection moulding. Test pieces cut out of the block were subjected to tension in the direction of resin flow during the injection (direction A) and in a direction normal to the resin flow (direction B). The results of the measurement are shown in Table 2 in which the tensile characteristics of the material of the present invention is close to that of natural ivory. Sample Change in weight (%) 1 5 to 7 2 0 3 15 to 18 Sample Tensile strength (kg/mm 2 ) Tensile elasticity (kg/mm 2 ) Elongation % 1 A 6.5 520 2.0 B 4.7 445 1.6 2 A 5.8 295 9.8 B 3.7 297 1.5 3 A 17.2 840 3.6 B 6.3 320 1.4 Frictional characteristics (coefficient of friction) of the Samples was measured under the following conditions. The results are shown in Table 3 in which the frictional characteristics of the material of the present invention is close to that of natural ivory. Rubbing material deerskin Sliding speed 5.6mm/sec Weight in g. 100 200 300 500 1000 Area of contact 2.5 x 6cm = 15cm 2 Temperature 23°C RH 50% Period 1 week Measurement A 23°C x 50% B deerskin wet with mist spray Sample A B 1 0.13 0.87 2 0.23 0.54 3 0.11 0.94

Claims: Use, in a keyboard musical instrument of an artificial key material in which ceramic whiskers are dispersed in a matrix resin, the whiskers are arranged in the form of clusters of filaments, the material is in the form of a shaped piece having a surface to which polishing has been applied to remove the surface skin, the clusters of whiskers appear on the polished surface of the shaped piece, and submicron size interspaces are left between whiskers in the clusters.

Inventors: OSHIMA YUTAKA, OSHIMA, YUTAKA
Applicants: YAMAHA CORP, YAMAHA CORPORATION
Application year: 1989
Main classification: C08K7
IPC codes: C08K7, G10C3