JP2005092914A - Casing for recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure physical properties of stable moldability, satisfactory impact strength, etc. to reduce load to environment, and to heighten the reliability of a recording medium, in a casing for the recording medium. <P>SOLUTION: The casing for the recording medium is formed by using a constitution material containing a biodegradable resin or a constitution material containing the biodegradable resin, a filler and a hydrolysis inhibitor and the specific gravity of the casing is specified to be ≥1.3 g/cm<SP>3</SP>(e.g. the biodegradable resin having ≥1.3 g/cm<SP>3</SP>specific gravity is used). E.g. an aliphatic polyester (polylactic acid or the like), polysaccharide, polyamino acid, poly vinyl alcohol, polyalkylene glycol, etc. are used as the biodegradable resin, e.g. an inorganic filler (aluminum hydroxide or the like) having ≥2 g/cm<SP>3</SP>specific gravity is used as the filler and e.g. a carbodiimide compound, an isocyanate compound, an oxozoline compound, etc. are used as the hydrolysis inhibitor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a housing (cartridge) for a recording medium that enables recording / reproduction of information such as music, video, and various data, and at the same time, faithful recording / reproduction with a vibration damping effect and environmental consideration are simultaneously achieved. The present invention relates to a housing for a recording medium that can be used.

  Depending on the purpose of use of the recording medium, polystyrene resin (hereinafter referred to as PS resin), acrylonitrile-butadiene-styrene resin (hereinafter referred to as material) constituting the casing for the recording medium may be used. Polymer materials (organic polymer materials) such as polycarbonate resin (hereinafter referred to as PC resin) have been used as appropriate. For example, video for professional use to store important information, images, etc. For casings such as cassettes and general household DV cassettes, polymer materials and structures that provide sufficient impact resistance (for example, drop strength, etc.) and structures (for example, blending amount of each material, bonding structure, etc.) are applied. It is preferable to do.

  The production volume of recording media is increasing year by year, and not only the improvement of physical properties such as impact strength is required as described above, but also the recording method, housing shape, design, etc. are widely used. For this reason, not only a polymer material such as a resin is used as a constituent material of the casing of the recording medium, but also various fillers (for example, fillers made of an inorganic material for the purpose of coloring the casing (hereinafter referred to as a filler) A filler made of an inorganic material is referred to as an inorganic filler)).

  On the other hand, the production amount of a composition using a polymer material is not limited to the case of a recording medium, but a depleting resource such as a petroleum resource (for example, a resin) is often used although the production amount is increasing year by year. Therefore, it is preferable to recycle the used polymer material composition. However, since various components (for example, resin, inorganic filler, etc.) are contained in the polymer material composition, it is difficult to separate these components, and the recycling application is limited and the resin is recycled. It was also difficult to apply technology.

  At present, most of the polymer material compositions that are difficult to recycle as described above employ a method of disposal as, for example, heat treatment (for example, treatment by combustion or indirect heating) or incombustible waste. When heat treatment is performed as described above, there is a risk of generation of harmful gases such as dioxins and damage to the heat treatment equipment (for example, damage to the incinerator due to large combustion heat). Even if treatments and the like are performed to avoid the above-mentioned dangers and damages, carbon dioxide must be discharged and global warming will be caused. In addition, sulfur or nitrogen halogen contained in the polymer material may cause air pollution. Furthermore, when disposing as described above, most of the polymer material used in the casing of the current recording medium is likely to remain without being decomposed for a long time. And may cause problems such as soil and water pollution.

  As described above, research and development have been carried out to further reduce the burden on the environment in polymer material compositions obtained by using a depleting resource as a raw material and adding various fillers. For example, in polymer materials compositions mainly premised on disposables such as daily necessities, sanitary goods, play goods, stationery, and packaging, those using biodegradable resins have been put into practical use.

  This biodegradable resin is biochemically decomposed into carbon dioxide or water by microorganisms or enzymes. For example, when a composition composed of a biodegradable resin is discarded into the natural environment, the composition is easily decomposed, reduced in molecular weight, and changed into a harmless compound for the environment. For example, the burden on the global environment is low compared to a composition made of PS resin or the like.

  In addition, compositions composed of biodegradable resins often produce less carbon dioxide per unit volume when combusted and have relatively low combustion heat compared to compositions composed of, for example, PS resins. For this reason, even when the composition of the biodegradable resin is treated by incineration, the burden on the environment is small as compared with the conventional polymer material composition.

As described above, since the biodegradable resin itself is a material that is easily decomposed, the biodegradable resin itself has hardly been applied to a polymer material composition used in electrical products, electronic devices, and the like on the premise of repeated use. Therefore, in recent years, attempts have been made to adjust the biodegradation rate of the biodegradable resin by using an additive that suppresses hydrolysis of the biodegradable resin (for example, Patent Document 1, Patent Document). 2).
JP 2003-87721 A (paragraph [0012] and the like). JP 2003-87751 A (paragraph [0012] etc.).

  However, since most of the casings for recording media are intended for long-term storage and storage, biodegradable resins have not been applied until environmental load reduction is taken into consideration.

  In addition, when a recording medium is used (for example, recording, reproduction, etc.), vibrations of various frequencies (particularly low frequency) generated from a drive system such as a recording medium deck, a drive, or various structures, for example. Vibration), and any movement (such as a vehicle equipped with a deck, a drive, etc., or a vehicle) that causes vibrations or sound resonances to cause some influence (for example, sound skipping, modulation noise, wow and flutter) Etc.). For this reason, it has been desired to increase the reliability of the recording medium (for example, to be able to perform desired recording and reproduction) by applying a material and a structure capable of obtaining a vibration damping effect.

  Generally, as a method for obtaining a vibration damping effect of a composition, a technique for increasing the specific gravity of the material of the composition is known. For example, in the case of a casing of a recording medium, if a large amount of barium sulfate having a high specific gravity is added to a polymer material (for example, ABS resin, PC resin, a mixture of ABS resin and PC resin, etc.) and molded, the casing The vibration damping effect is improved.

  However, when a large amount of material with a high specific gravity is added to the polymer material (for example, exceeding the optimum blending amount), the flowability (MFI) of the polymer material at the time of molding is reduced, the mold is damaged ( For example, not only the mold inner surface may be worn) but also the interfacial adhesiveness of the polymer material composition may be lowered (the blending balance of each material may be lowered), causing problems such as impact strength deterioration. For this reason, a technique for adding a large amount of a material having a high specific gravity as described above has not been widely used in a case for a recording medium to which various fillers are added.

  Among the polymer materials, the ABS resin is generally known as a material having good impact resistance. As described above, the rubber contained in the ABS resin can be obtained without adding a large amount of a material having a high specific gravity. Since a sufficiently good vibration damping effect can be obtained depending on the component, it is frequently used in the current case for recording media.

  The present invention has been made based on the above-mentioned problems, and can secure physical properties such as stable moldability and sufficiently good impact strength, and can reduce the burden on the environment and increase the reliability of the recording medium. An object of the present invention is to provide a housing for a recording medium (for example, having a vibration damping effect equal to or higher than that using an ABS resin).

In order to solve the above-described problems, the present invention is characterized in that the recording medium casing is made of a constituent material containing a biodegradable resin and has a specific gravity of 1.3 g / cm ³ or more.

  The constituent material includes a biodegradable resin, a filler, and a hydrolysis inhibitor.

As described above, a case using a constituent material containing a biodegradable resin and having a specific gravity of 1.3 g / cm ³ or more (or a case using a biodegradable resin having a specific gravity of 1.3 g / cm ³ or more. ), It is possible to obtain a high logarithmic decay rate without using a large amount of a high specific gravity filler, and to ensure physical properties such as stable moldability and sufficiently good impact strength. The casing itself is easily decomposed, and when burned, it is burned with a small amount of carbon dioxide generation and low combustion heat.

  Moreover, the logarithmic decay rate can be further increased by including a filler in the constituent material.

  Furthermore, the biodegradation rate can be adjusted according to the intended use of a housing | casing by containing a hydrolysis inhibitor in the said structural material.

  In addition, the above-mentioned filler is preliminarily surface-treated in consideration of ensuring physical properties such as balance in constituent materials, compatibility with biodegradable resin, stability of moldability, impact strength of molded products, etc. It is preferable to do.

  As described above, according to the present invention, physical properties such as stable moldability and sufficiently good impact strength can be ensured, and a vibration damping effect equivalent to or higher than that of a conventional recording medium casing can be obtained. The reliability of the recording medium can be increased and the burden on the environment is reduced.

  Hereinafter, the constituent materials, manufacturing methods, specific examples after molding, etc. of the recording medium casing according to the present invention will be described.

The casing for a recording medium according to the present invention uses a constituent material containing a biodegradable resin and having a specific gravity of 1.3 g / cm ³ or more. For example, a constituent material containing only a biodegradable resin having a specific gravity of 1.3 g / cm ³ or more may be used. However, by adding an inorganic filler having a high specific gravity to the biodegradable resin, the constitution The specific gravity of the material may be adjusted as appropriate.

In particular, biodegradable resins with large specific gravity as a single substance and inorganic fillers with high specific gravity such as aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium carbonate, barium sulfate, titanium oxide, mica, talc, glass, kaolin, etc. According to the constituent material in combination with an inorganic filler of 2 g / cm ³ or more, good characteristics (characteristics with a low environmental load and good vibration damping effect) can be obtained. Each said inorganic filler may use only 1 type, and can also use multiple types together. In addition to the biodegradable resin and the inorganic filler, a rubber-based component may be blended with the constituent materials in order to further improve the mechanical strength necessary for the casing. This rubber component is preferably biodegradable from the viewpoint of environmental considerations.

  The case for the recording medium is a recording of a generally used DV cassette (mini digital video cassette), video cassette, disk cartridge, HDD or IC device (for example, IC card). Shows shells and mechanical parts of media products, and shows all parts that protect built-in media of all recording methods and shapes such as magnetic recording, magneto-optical recording, optical recording methods such as disks, tapes, hard disks, and IC devices. Is.

  From the viewpoint of reducing the environmental load, it is preferable to replace all the constituent materials used in the casing of the current recording medium product (the casing not using biodegradable resin) with the constituent material according to the present invention. For example, from the viewpoint of improving not only the vibration damping effect but also the impact strength, etc., the constituent material used in the current product and the constituent material according to the present invention are combined (for example, using each constituent material and laminating the composition) , A casing formed by coating one of the constituent material compositions with the other constituent material, composite molding), a contact portion with a recording / reproducing device (deck, drive, etc.), a tape reel portion, a disc holder portion A casing that is used only for a specific part of the casing may be used.

  The biodegradable resin (organic polymer compound) of the present invention can be molded and processed with a low environmental impact like existing thermoplastic resins, such as microorganisms, natural products (plant-derived), and chemical synthesis systems. These biodegradable resins can be mentioned. Considering reduction of exhaustible resources, reduction of production energy of recording media casing, recycling, disposal, incineration, etc. (considering environmental load), it is preferable to use natural product-based biodegradable resin There is no limitation as long as it is generally treated as a biodegradable resin (for example, a biodegradable polymer compound, a biodegradable resin, etc.). Specifically, for example, any one of aliphatic polyester, polysaccharide, polyamino acid, polyvinyl alcohol, polyalkylene glycol and the like, or a copolymer containing at least one of each of the above biodegradable resins, A well-known thing, such as a mixture, can be applied.

  The aliphatic polyester is excellent in mixing property and mass productivity, and polylactic acid such as poly-L-lactic acid (PLLA), random copolymer of L-lactic acid and D-lactic acid, and derivatives thereof are particularly preferable. preferable. In addition, polycaprolactone, polyhydroxybutyric acid, polyhydroxyvaleric acid, polyethylene succinate, polybutylene succinate, polybutylene adipate, polymalic acid, microbial synthetic polyester (for example, 3-hydroxybutyrate (3HB)) classified into polyester , 3-hydroxyvalerate (3HV)) or a copolymer thereof can also be applied.

  The polysaccharide may be any saccharide that produces at least one monosaccharide by hydrolysis, and may be a saccharide that simultaneously produces a derivative of monosaccharide upon hydrolysis. It is not specifically limited, For example, cellulose, cellulose ester (acetylcellulose, cellulose propionate, cellulose butyrate, nitrocellulose, cellulose sulfate, cellulose phosphate, these copolymers or a mixture thereof), cellulose ether (methyl cellulose, ethyl cellulose, carboxymethyl cellulose, Carboxyethyl cellulose, hydroxyethyl cellulose or hydroxypropyl cellulose), starch, chitosan, chitin chitosan, mannan, carrageenan, alginic acid, amylose, amylopectin, pectin, lentinan, hyaluronic acid, hylan, agarose, pullulan, dextran, derivatives thereof (for example, cellulose) Propionate, cellulose acetate propionate, cellulose butyrate, cell Loin acetate butyrate, cellulose derivatives such as hydroxyethyl cellulose or hydroxypropyl cellulose, etc.), etc. These copolymers or their mixtures thereof.

  Further, for example, even an organic polymer compound having sufficient biodegradability at a low molecular weight and low biodegradability at a high molecular weight can be produced by graft copolymerization with each of the above-described polymer materials having biodegradability. If degradability is obtained, it can be applied as the biodegradable resin of the present invention. Specific examples include polyethylene, polyacrylic acid derivatives, polypropylene, and polyurethane. Moreover, there is no restriction | limiting in particular about the molecular weight and terminal group of each said biodegradable resin, if mechanical strength is acquired.

  The inorganic filler used as the filler of the present invention is not particularly limited as long as it has a high specific gravity. That is, it is not limited to the above-mentioned aluminum hydroxide and the like, for example, other than general metal oxides, carbonates, nitrides, sulfides, sulfates, phosphorus oxides, chlorides, hydroxides, silicates, etc. Carbon, graphite, glass fiber, etc. can be used. Moreover, you may apply the filler which consists of organic substance instead of the said inorganic filler. Furthermore, as the particle shape of each of the fillers, various shapes such as a spherical shape and a needle shape may be applied, and the particle size, particle size distribution, and the like can be set as appropriate. Pretreatment or the like can be applied as appropriate for the purpose of interfacial reinforcement or the like.

  From the viewpoint of environmental consideration, it is preferable to apply the above-mentioned hydroxide compound-based and silica-based fillers. In addition, the amount of filler added is within a range that can ensure physical properties such as balance in the constituent materials, compatibility with the biodegradable resin, stability of moldability, and impact strength of the molded product (component material composition). It can be set as appropriate within the range, and it is also possible to apply a combination of a plurality of these fillers. In a specific addition amount, for example, a hydroxide-based or silica-based filler is preferably used within a range of 5 wt% to 70 wt%. Moreover, also when using the above-mentioned general purpose filler, it is preferable to use within the range of 5 wt%-70 wt%.

The specific gravity of the constituent material to which the inorganic filler is added is preferably larger from the viewpoint of obtaining a vibration damping effect. Specifically, it is 1.3 g / cm ³ or more, preferably 1.5 g / cm ³ or more.

  In addition, considering the balance of the constituent materials (optimal blending amount of each component in the constituent materials), surfactants, dispersants, antistatic agents, antibacterial agents, coloring pigments, etc. are added to the constituent materials as necessary. You may mix | blend suitably.

  As the hydrolysis inhibitor for the biodegradable resin in the constituent material, for example, a compound having reactivity with a carboxylic acid and a hydroxyl group which are terminal functional groups of the biodegradable resin is used. Specifically, carbodiimide compounds, isocyanate compounds, oxozoline compounds, and the like can be applied. In particular, a carbodiimide compound is preferable because melt kneading is possible and a sufficient effect can be obtained by adding a small amount.

  The carbodiimide compound used for the constituent material according to the present invention is a compound (including a polycarbodiimide compound) having one or more carbodiimide groups in the molecule of the carbodiimide compound. For example, an organic phosphorus compound or an organometallic compound is used as the catalyst. Specific examples thereof include those capable of synthesizing various polymer isocyanates by decarboxylation polycondensation in a solvent-free or inert solvent having a temperature of about 70 ° C. or higher. Specific examples of the monocarbodiimide compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, diphenylcarbodiimide, naphthylcarbodiimide and the like.

  As a method for adding the hydrolysis inhibitor, for example, a method by melt kneading is preferably applied, but it is also possible to add by any method. In addition, the amount of hydrolysis inhibitor added to the constituent material is adjusted according to the intended use of the recording medium (for example, for storing or storing important information, images, etc. for a long period of time) and the biodegradation rate (for example, (Adjust so that the recording medium is disassembled after the quality assurance period has elapsed).

  In the filler used in the present invention, it is indispensable to improve the dispersibility in consideration of the balance in the constituent materials, the compatibility with the biodegradable resin, the stability of the moldability, the maintenance of the impact strength of the molded product, etc. It is. For example, in the inorganic filler, it is desirable to perform surface treatment using a silane, titanate or aluminate coupling agent. Thereby, the interaction at the interface of the constituent materials is enhanced, and further improvement in physical properties can be expected.

  Each of the above coupling agents is appropriately selected and used according to the components of the constituent materials. In particular, the silane coupling agent is a surface modification at the interface between the inorganic filler and the polymer material (particularly, organic resin). It is said that the effect is good and is generally widely used.

  For the surface treatment, a known technique can be applied. Among these, the wet treatment method modifies the surface of the inorganic filler by, for example, immersing the inorganic filler in a dilute alcohol solution of a silane coupling agent and performing sufficient heat drying. Therefore, the interaction with the biodegradable resin interface is enhanced, and the physical properties of the molded product can be further improved.

  Also, instead of the wet processing method, a dry processing method is applied. For example, the inorganic filler is stirred with a dilute solution of the titanate coupling agent with a high-speed mixer or the like, and the dilute solution is uniformly dispersed in the inorganic filler. After spraying (vapor phase spraying), surface treatment may be performed by heat drying. Furthermore, when the direct method is applied and the biodegradable resin and the inorganic filler are kneaded, the surface treatment may be performed by directly adding the coupling agent to the kneaded material and then drying. In any treatment method, it is necessary to perform sufficient heat treatment and drying treatment as pretreatment in order to avoid generation of low molecular gas components during molding. In addition to the surface treatment with the coupling agent, hydrophilic treatment by oxidation or high concentration kneading method (master batch method) may be used in combination.

  In addition, when the surface-treated filler is simply applied to a conventional recording medium casing, a good vibration damping effect can be obtained, but the casing itself is difficult to be disassembled when disposed of, for example, When the combustion treatment is performed, a large amount of carbon dioxide is generated and burned with high combustion heat, so that there is a possibility that the energy burden and the environmental load are increased as compared with the recording medium casing of the present invention.

  Next, the recording medium casing of the present invention will be described using samples obtained by the methods shown in Examples 1 to 3 and Comparative Examples 1 to 4. The present invention is not limited to these examples.

[Example 1]
In Example 1, 80 weights each of polylactic acid (Laisia manufactured by Mitsui Chemicals; H100J), surface-treated aluminum hydroxide, and carbodilite (reagent; 8CA) were used as biodegradable resins, inorganic fillers, and hydrolysis inhibitors. Parts, 20 parts by weight, and about 2 parts by weight, and mixed by a melt kneading method to obtain a constituent material (a constituent material intended to obtain a sample having a specific gravity of about 1.5 g / cm ³ ).

  The surface treatment was performed by mixing aluminum hydroxide with 0.5 parts by weight of γ-aminopropyltriethoxysilane (manufactured by Nihon Unicar Co., Ltd .; A-1100) in Henschel and performing sufficient heat treatment. To do. In addition, as the mixing conditions, a minimax-mix ruler (manufactured by Toyo Seiki Co., Ltd.) is used as a kneader, the nozzle temperature is 170 ° C. to 175 ° C., the torque is 4 to 6 kg, and the residence time is within 3 seconds. did.

Then, the above constituent materials are pulverized and then pressed at a temperature of 170 ° C. and a pressure of 300 kg / cm ² to form a 1.0 mm thick plate, and the plate is 1.0 mm × 10.0 mm × 100 mm. The member obtained by cutting was taken as sample S1.

[Example 2]
In Example 2, the same polylactic acid, surface-treated aluminum hydroxide, and carbodilite as in Example 1 were used in proportions of 60 parts by weight, 40 parts by weight, and 2 parts by weight, respectively, and mixed by melt kneading. A constituent material (a constituent material intended to obtain a sample having a specific gravity of about 1.7 g / cm ³ ) was obtained. This constituent material was pulverized, pressed, and cut in the same manner as in sample S1, and the resulting member was designated as sample S2.

[Example 3]
In Example 3, the same polylactic acid and carbodilite as in Example 1 were used in proportions of about 100 parts by weight and 1 part by weight, respectively, and mixed by a melt-kneading method to form a constituent material (specific gravity about 1.3 g / cm ^3). A constituent material for the purpose of obtaining a sample was obtained. This component material was pulverized, pressed, and cut in the same manner as for sample S1, and the resulting member was designated as sample S3.

[Comparative Example 1]
In Comparative Example 1, a polyoxymethylene resin was used as a constituent material (a constituent material intended to obtain a sample having a specific gravity of about 1.4 g / cm ³ ), and the constituent material was 1.0 mm × 10.0 mm by injection molding. It processed into the member of * 100mm, and the obtained member was made into the sample P1.

[Comparative Example 2]
In Comparative Example 2, an ABS-PC (polycarbonate) resin containing about 10 parts by weight of barium sulfate was used as a constituent material (a constituent material intended to obtain a sample having a specific gravity of about 1.5 g / cm ³ ). Was processed into a 1.0 mm × 10.0 mm × 100 mm member by injection molding, and the obtained member was used as a sample P2.

[Comparative Example 3]
In Comparative Example 3, an ABS resin for recording medium containing about 10% by weight of a butadiene rubber component was used as a constituent material (a constituent material intended to obtain a sample having a specific gravity of about 1.1 g / cm ³ ). Was processed into a 1.0 mm × 10.0 mm × 100 mm member by injection molding, and the obtained member was used as a sample P3.

[Comparative Example 4]
In Comparative Example 4, polystyrene resin (hereinafter referred to as PS resin) was used as a constituent material (a constituent material intended to obtain a sample having a specific gravity of about 1.0 g / cm ³ ), and the constituent material was injected by injection molding. A member having a size of 0.0 mm × 10.0 mm × 100 mm was processed, and the obtained member was used as a sample P4.

[Specific gravity measurement]
For the samples S1 to S3 and P1 to P4 obtained in Examples 1 to 3 and Comparative Examples 1 to 4, the weight and volume (the volume obtained by measuring and multiplying the length, width and height; 0.0 mm × 10.0 mm × 100 mm) was accurately measured, and the specific weights were calculated by dividing the obtained weights by the respective volumes.

[Vibration control test]
Next, based on the method and principle shown below, the damping properties (vibration damping effect) of the samples S1 to S3 and P1 to P4 are expressed as logarithmic attenuation rates (logarithmic attenuation rates obtained by the equation (5) described later). Quantitative evaluation was made by δ).

  First, in the method of measuring the logarithmic decay rate, as shown in FIG. 1, for example, one end of a measurement object (samples S1 to S3, P1 to P4) 1 is fixed with a jig 4 (fixed in a cantilever shape) Then, an acceleration sensor (acceleration pickup manufactured by EMIC; model 710-C) 2 was fixed to the other end of the measuring object 1 with a screw 3.

  The measurement object 1 is vibrated at various frequencies by flipping one end of the measurement object 1 fixed as described above on the acceleration sensor 2 side. By detecting with sampling (for example, 500 μsec to 5000 μsec) through an apparatus (NR2000 manufactured by Keyence Corporation) 5, the attenuation characteristic of the single vibration of the measurement object 1 was measured.

  The operation of flipping one end of the measurement object 1 is based on the assumption that low-frequency vibrations that can be generated from electrical appliances (recording medium decks, drives, etc.) and various buildings are used. The vibration was performed at 60 Hz. The frequency was changed by adjusting the length of the measuring object 1 (for example, cutting the measuring object 1 or shortening the distance between the acceleration sensor 2 and the jig 4).

By such a method, for example, an acceleration damped oscillation curve as shown by the solid line in FIG. 2 is obtained. The change in the maximum value (minimum value) of the damped oscillation curve can be generally approximated by a geometric series, where the first displacement maximum value is x ₁ , the maximum value after 2π / ω in one cycle is x ₂ , Assuming that the maximum after n cycles is x _n , the logarithmic decay rate δ is as shown in the following equation (1).

  FIG. 3 shows a one-dimensional viscous damping vibration theoretical model, and the equation of motion of the system having such viscous damping can be expressed by the following equation (2).

  Moreover, the general solution of said Formula (2) can be represented by the following (3) Formula.

In the above equation (3), when sin (ω _d t + φ) = ± 1, the damped oscillation curve as shown in FIG. 2 is considered to be in contact with the envelope, and can be assumed to decrease in an equal ratio. When the first displacement maximum value is x ₁ , the maximum value after 2π / ω in one cycle is x ₂ , and the maximum value after n cycles is x _n , the following equation (4) is established.

  The logarithmically expressed value for the above equation (4) can be regarded as the logarithmic attenuation factor δ as shown in the following equation (5).

  For example, when the logarithmic attenuation rate δ obtained by the equation (5) is large in the measurement object 1, the vibration attenuation effect of the measurement object 1 is good, and it is excellent as a casing for a recording medium. Can be considered.

  The logarithmic damping rate δ of each frequency (and the average value of each logarithmic damping rate δ) in each of the samples S1 to S3 and P1 to P4 obtained by the above-described method is the vibration damping with respect to the specific gravity shown in Table 2 and FIG. This is shown in the rate characteristic diagram.

  From the results shown in Table 2 and FIG. 4, the sample P3 using the ABS resin obtained a relatively high logarithmic damping factor δ and average value than the sample P4 using the PS resin, but at each frequency. It can be read that the variation in the measured vibration attenuation rate δ is large.

On the other hand, the samples S1 to S3, P1, and P2 having a specific gravity of 1.3 g / cm ³ or more have a logarithmic decay rate δ (logarithmic decay rate δ is about 0.1 or more) and an average value that are equal to or greater than those of the sample P3. It can be seen that the variation in the vibration damping rate δ measured at each frequency is small and stable. In particular, it can be seen that the sample having a higher specific gravity has a smaller variation in the vibration damping rate δ and tends to be stable and improved.

  Samples S1 to S3 made of a constituent material containing a biodegradable resin have the same physical properties such as impact strength as sample P3, have good flowability at the time of molding, and damage to the mold (for example, metal mold) No wear on the inner surface of the mold was observed.

Therefore, according to the composition having a specific gravity of 1.3 g / cm ³ or more made of a constituent material containing a biodegradable resin as in the samples S1 to S3, the load on the environment can be reduced and a high specific gravity can be achieved. Even if a large amount of material was not added, it was confirmed that a stable vibration damping effect could be obtained at the same level or higher compared to the composition made of ABS resin. Incidentally, the composition and the specific gravity is made of the material containing 1.3 g / cm ³ or more biodegradable resins, the composition having a specific gravity comprises a biodegradable resin is made of 1.3 g / cm ³ or more constituent materials If so, it is clear that the same stable vibration damping effect as the samples S1 to S3 can be obtained.

  In addition, by pre-treating the filler used for the constituent material in advance, sufficient physical properties such as balance in the constituent material, compatibility with the biodegradable resin, stability of the moldability, and impact strength of the molded product can be secured. Was confirmed.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

  For example, in Examples 1 to 3, a sample was prepared from a constituent material using polylactic acid, surface-treated aluminum hydroxide, and carbodilite. However, the biodegradable resins, fillers, and hydrolysis inhibitors listed above were used. The same effects as those of the samples S1 to S3 can be obtained even when the constituent materials blended by appropriately selecting etc. are used, or when the above-mentioned surface treatment is performed to constitute the casings of various recording media products. It is clear.

Schematic explanatory drawing of the apparatus used in the vibration damping test. The characteristic view which shows an example of the damping vibration curve of the acceleration obtained by the apparatus of FIG. Schematic explanatory drawing of a one-dimensional viscous damping vibration theory model. The vibration damping-rate characteristic view with respect to specific gravity in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Measuring object 2 ... Acceleration sensor 3 ... Screw 4 ... Jig 5 ... Data collection device

Claims (7)

A recording medium casing comprising a constituent material containing a biodegradable resin and having a specific gravity of 1.3 g / cm ³ or more.   The recording medium casing according to claim 1, wherein the constituent material includes a biodegradable resin, a filler, and a hydrolysis inhibitor.   The biodegradable resin may be any one of aliphatic polyester, polysaccharide, polyamino acid, polyvinyl alcohol, and polyalkylene glycol, or a co-polymer containing at least one of the biodegradable resins. The recording medium casing according to claim 1, wherein the recording medium casing is a combination or a mixture. The recording medium casing according to claim 2, wherein the filler is an inorganic filler having a specific gravity of 2 g / cm ³ or more.   3. The casing for a recording medium according to claim 2, wherein the hydrolysis inhibitor contains at least one of a carbodiimide compound, an isocyanate compound, and an oxozoline compound.   The aliphatic polyester includes at least one of polylactic acid, polycaprolactone, polyhydroxybutyric acid, polyhydroxyvaleric acid, polyethylene succinate, polybutylene succinate, polybutylene adipate, polymalic acid, and microbial synthetic polyester. The recording medium casing according to claim 3, wherein the casing is a recording medium casing.   The inorganic filler contains at least one of aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium carbonate, barium sulfate, titanium oxide, mica, talc, glass, and kaolin. 4. A casing for a recording medium according to 4.

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