JPH0451837B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a keyboard to which a surface material having characteristics extremely similar to ivory is attached. [Prior Art] Ivory is highly valued by experts as a material constituting at least the surface of the keys of keyboard instruments such as pianos, organs, and accordions. This is thought to be due to the fact that ivory ideally satisfies the following characteristics required as a keyboard material, rather than the fact that it is originally a high-quality art material. (a) Must have appropriate water absorption. This is required to absorb sweat from the player's fingers and prevent slippage due to sweat. (b) It must have appropriate surface smoothness and friction coefficient. This affects the tactile sensation when pressing a key. (c) It has an excellent appearance (despite its high whiteness,
(Excellent stain resistance). (d) Must have appropriate hardness. This is required to provide a tactile feel when pressing keys and to prevent wear due to long-term use. (E) Must have appropriate workability. [Problems to be Solved by the Invention] However, even natural ivory having such excellent properties has the disadvantage that demand cannot be met due to insufficient supply capacity. Particularly in recent years, African countries that produce the fish have begun banning their capture for animal welfare reasons, and the imbalance between supply and demand is even more significant. In view of these circumstances, synthetic resins are widely used as keyboard materials because they generally have no problems in terms of supply. However, although synthetic resin keyboards are somewhat satisfactory in terms of appearance and workability, the surface is too smooth, making it easy for fingers to slip on them, and because they lack water absorption, they become especially slippery when sweating, making it difficult to make mistakes. This caused some inconvenience. Furthermore, since the hardness is generally insufficient, wear during long-term use also becomes a problem. This invention provides a keyboard with an ivory-like surface material affixed with casein as a matrix resin, which, like ivory, satisfies various required properties as a keyboard material and solves the problem of supply. be. [Means for Solving the Problems] The method of kneading casein to which pigments or dyes have been added with water, molding, and hardening by formalin treatment is itself known as a method for producing casein plastics. However, there are problems in using such casein plastic as a keyboard material as it is. That is, such casein plastic does not have the feel, dimensional stability when dry or wet, hardness, thermal conductivity, and heavy feel that ivory as a keyboard material has. This invention uses casein as a matrix resin and blends a water-containing inorganic filler in a specific ratio, thereby taking advantage of the great water absorbency and compatibility with the human body (finger, etc.) of casein plastic, while solving the above-mentioned drawbacks. This work was completed based on the knowledge that a surface material with properties dramatically similar to those of ivory was obtained, and that an excellent keyboard could be obtained by attaching this material to a wood keyboard base material. That is, the keyboard of the present invention contains a specific hydrated material selected from the group consisting of aluminum hydroxide, calcium sulfate hydrate, hydrated magnesium silicate, and hydrated silicic acid in 100 parts by weight of a casein resin matrix hardened with formalin. The keyboard is characterized in that a thin plate containing 10 to 75 parts by weight of an inorganic filler dispersed therein is pasted onto the key-pressing area of a keyboard base material made of wood. This invention will be explained in more detail below. In the following description, "%" and "part" are based on weight unless otherwise specified. The casein used in this invention is preferably 100%
It is necessary that it is a fine powder pulverized to less than mesh size. This is because if the casein is coarse, it will not be mixed uniformly with the filler. Casein belongs to phosphoproteins, is a mixture of proteins that are similar to each other (complex protein), and has a molecular weight of 75,000.
~375,000, about 3% in milk, about 1% in human milk
Contains. Among these, the product obtained by coagulating milk with the enzyme rennin is mainly called rennet casein, and the product obtained by coagulating with acid is called acid casein. For the purposes of the present invention, the use of rennet casein, which has a folded and highly branched macromolecular structure, is particularly suitable. In the present invention, the term "hydrous inorganic filler" refers to an inorganic filler that has adsorption or water of crystallization by itself, or that becomes easily hydrated with water and has water of crystallization, such as aluminum hydroxide, aluminum hydroxide, A material selected from calcium sulfate hydrate, hydrated magnesium silicate, and hydrated silicic acid is used. These hydrous inorganic fillers are added at a ratio of 10 to 75 parts per 100 parts of casein. If the amount is less than 10 parts, the effect of addition will not be sufficient. On the other hand, when more than 75 parts are added, the tensile strength and elongation at break of the surface material obtained sharply decrease, and the tensile Young's modulus sharply increases. For this reason, the surface material cannot follow the dimensional changes due to the expansion and contraction of the wood.
Cracking or peeling of the surface material occurs. The present invention addresses the requirements for suitability as a keyboard surface material, the manufacturing process requirement of applying adhesive onto a wooden key base material, and the integrity required with the base material wood when used as a keyboard. In view of the requirements, 10 to 75 parts by weight of filler is used per 100 parts by weight of casein (filler content in the composition is 9 to 43% by weight). Incidentally, Figure 1 shows the rate of change in dimensions (solid line) corresponding to the rate of decrease in water content, using the filler content of filler-containing casein plastic as a parameter.
This is shown in a graph together with a similar dimensional change rate range (dotted line) accompanying drying in the direction (T direction) parallel to the growth rings of the wood key base material to be pasted. In this way, in the process of attaching a surface material made of a casein plastic molded body to wood using an adhesive and drying it as in the present invention, the shrinkage rate of the surface material must be equal to or smaller than that of the wood. Cracking of the surface material occurs, and for this purpose a filler content of 25% or more is particularly desirable. On the other hand, changes in physical properties due to changes in the filler content of casein plastics are shown in the attached Figure 2, and the tensile elongation (curve a) and tensile strength (curve The decrease in b) and the increase in Young's modulus (curve c) both make it impossible for the surface material to follow the dimensional changes caused by the absorption and drainage of the wood base material in the keyboard material of the pasted structure.
This means that it may eventually lead to cracking or destruction of the surface material. Therefore, in order to obtain a keyboard material with a stable pasted structure, the filler content range of the present invention is extremely critical. Next, FIG. 3 shows the relationship between the immersion time in water and the water absorption rate, using the filler content of the filler-containing casein plastic as a parameter. Ivory as a sample
25×25×1.5mmt, casein composite molded plate 25×25×
Using 1.5mmt, a water absorption test was conducted from an absolutely dry state. The water temperature was 23℃. According to this, the water absorption rate of the filler-containing plastic of the present invention changes depending on the content of the filler, and the value of the water absorption rate characteristic of ivory, which is the target of the present invention, is within the content range of the filler of the present invention. It turns out that it is almost included in Similarly, FIG. 4 shows the relationship between filler content and thermal conductivity of filler-containing casein plastics.
Two samples with a size of 50 x 50 x 30 mm were used, and a thermal conductivity measuring device manufactured by Kyoto Electronics Industry Co., Ltd. was used as the device. Natural ivory has a moisture content of 3 to 12% and its thermal conductivity varies. According to this, it can be seen that the filler-containing casein plastic can have properties corresponding to the thermal conductivity properties of ivory when the filler content of the present invention is at least 10%, which is the lower limit value. Therefore, it turns out that the filler content range of the present invention is very critical for the water absorption and thermal conductivity properties as well as for the shrinkage rate mentioned above. In addition to the above ingredients, the raw material mixture contains pigment acid dyes such as titanium oxide (if titanium oxide is not used as a filler) and zinc white to adjust the color tone per 100 parts of casein. 1-10
up to 100% can be added. Each of the above components is kneaded with, for example, 10 to 40 parts of water per 100 parts of casein using a grinder or the like. After this kneading, it is preferable to leave the mixture at room temperature for about 5 to 24 hours to expand the casein and improve subsequent moldability. Next, the mixture is molded, and the molding can be performed by extrusion, post-roll pressing, pressing, or other methods. Extrusion molding is performed at a pressure of about 100 to 200 kg/cm ² and a temperature range of about 20 to 100°C, with an increasing temperature gradient from the base of the cylinder of the extruder to the die. In addition, press molding is preferably performed at a pressure of 100 to 200.
Kg/cm ² and a temperature of 85 to 95°C. Next, the molded body is immersed in formalin having a concentration of about 3 to 10% at around room temperature to harden the casein. The immersion time varies depending on the dimensions of the molded object, but in the case of a plate-like object, as an example, the immersion time is 6 days at a thickness of 3 mm.
16 days for 10mm, and 50 days for 10mm. A surface material is obtained by drying the molded cured product at a temperature of about 20 to 45° C., and further performing post-processing such as cutting, cutting, and polishing as necessary. The keyboard material of the present invention can be obtained by attaching the surface material thus obtained to the key-pressing portion of the surface of a key base material made of wood. The keyboard material according to the present invention can also be used as a black key (material) by coloring it, but it is more preferable to use it as a white key (material) like ivory.
used as. [Operation and Effects of the Invention] As described above, according to the present invention, powdered casein and a hydrous inorganic filler are kneaded with water,
An excellent keyboard material can be obtained by attaching a key surface material extremely similar to natural ivory, obtained by hardening with formalin treatment after molding, to a wood key base material.
The resulting keyboard material has the following characteristics in particular. (a) The surface material exhibits high water absorption of approximately 10% when immersed in water at 25°C for 24 hours, so it sufficiently absorbs sweat from fingers during performance and prevents mishits due to slipping during sweating. (b) The surface material has a feel, weight, and coefficient of friction comparable to natural ivory. (c) The surface material can be molded by changing the blending ratio of pigments or dyes during or after the formation process, or it can be piece-dyed with dyes to give it a free pattern. (d) The surface material has high dimensional stability during dry and wet conditions and excellent physical properties. Therefore, there is no inconvenience such as cracking or peeling of the surface material when manufacturing a keyboard material by pasting it onto a wood key base material and drying it, as well as during subsequent use. [Example] Hereinafter, an example of molding the surface material will be described. Example 1 Reinetz casein (particle size: 150-250 mesh) 100 parts Water 30 parts Titanium oxide 5 parts Aluminum hydroxide 50 parts After thoroughly kneading the above ingredients in a crusher, leave at room temperature for 12 hours to swell the casein. Ta. This mixture was filled into a mold and heated by a heat press machine for 95 minutes.
After molding at 150 Kg/cm ² at 150 Kg/cm 2 , it was cured with a 5% formalin solution to obtain a homogeneous ivory-colored molded product measuring 50 x 200 x 5 mm. When various properties required for a keyboard were measured for this molded body, the following effects were obtained. Specific gravity 1.58 Hardness Hr (M) ^* 70~80 (20℃, 60%) Hr (M) 40~50 (immersed in water at 25℃ for 24 hours) *Rotsuwell hardness (M scale) measurement results Water absorption rate 6~10% (Immersed in water at 25℃ for 24 hours) Bending strength 7~8Kg/mm ^2Bending modulus 500~600Kg/mm ^2Thermal conductivity 0.5kcal/m.hr.℃ Static friction coefficient dry state 0.2~0.25 (23℃ 35% Material: deerskin) Wet state 0.95-1.00 Compressive strength 30-40 Kg/mm ² The following results were obtained for a molded article formed in the same manner from the above raw materials except that only aluminum hydroxide was removed. Specific gravity 1.34 Hardness Hr (M) 99 (20℃ 60%) Hr (M) 16 (after immersion in water at 25℃) Bending strength 7~8Kg/mm ² Bending modulus 500~600Kg/mm ² Compressive strength 19~30Kg /mm ^2Tensile strength 7Kg/mm ^2Static friction coefficient Dry state 0.2 to 0.25 (23℃ 35% Compatible material: Deerskin) Wet state 0.80 to 0.90 Thermal conductivity 0.18kcal/m.hr.℃ Example 2 Example 1 described above All molding methods were carried out with the same dimensions except that the type of filler was changed to each of the fillers shown in Table 1 below compared to the composition to obtain molded bodies.

[Table] The results show that various fillers are almost equally effective for the present invention.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the rate of decrease in water content and the rate of change in wood dimensions using the filler content of filler-containing carbon plastic as a parameter. Figure 2 is a graph showing the change in filler content and various physical properties of casein plastic. Figure 3 is a graph showing the relationship between immersion time in water and water absorption of ivory and casein composite molded plates. Figure 4 is the graph showing the relationship between filler content and thermal conductivity of casein plastic containing fillers. It is a graph showing the relationship between.

Claims (1)

[Claims] 1. 100 parts by weight of a casein resin matrix hardened with formalin, containing a hydrous inorganic filler selected from the group consisting of aluminum hydroxide, calcium sulfate hydrate, hydrous magnesium silicate, and hydrous silicic acid. This keyboard is made by pasting a thin plate containing 10 to 75 parts by weight of a dispersing agent on the key-pressing part of a key base material made of wood. 2. The keyboard according to claim 1, wherein the inorganic filler is a hydrous inorganic filler selected from the group consisting of aluminum hydroxide, calcium sulfate hydrate, and hydrous silicic acid.