JP2006293260A - Moisture conditioning sheet for musical instrument and moisture conditioning set for musical instrument using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moisture conditioning sheet for a musical instrument which is lightweight and has high immediate effect properties, and a moisture conditioning set using the same. <P>SOLUTION: The moisture conditioning set 1 as an embodiment 1 of the present invention includes a moisture conditioning set 2 stored in a resin case 10. The moisture conditioning set 2 is obtained by constituting a felt 3 as a fiber structure by forming moisture conditioning fiber 301, having moisture absorbing and discharging polymers made of a vinyl copolymer etc., in a base of a polyol-based polymer material, in a sheet shape and incorporating it in exterior meshes 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a humidity control sheet for musical instruments and a humidity control set for musical instruments using the same, and more particularly to improvement of immediate effect of humidity control effect.

Conventionally, when storing stringed instruments such as violins, cellos, viola, bows used for this performance, brass instruments such as saxophones, trumpets, etc., or pianos, etc., moderate humidity adjustment to maintain the performance of the instrument Is required.
For this reason, for example, a bag containing granular silica gel is stored in a musical instrument storage case to remove excessive moisture immediately after use of the musical instrument or due to a change in the usage environment. Measures are taken to reduce humidity.

Further, when storing musical instruments, it is necessary not only to reduce humidity but also to maintain a constant humidity. This is because, due to the material properties of the above stringed instruments and bows, if the drying progresses too much, the sound quality may change, and in extreme cases, physical damage such as cracking or cutting may occur. .
For this reason, as shown in Patent Documents 1 to 3, for example, a moisture-absorbing / releasing polymer is used, and a rubber sheet is formed by mixing the polymer with a rubber material serving as a base. Measures have been taken to arrange and use the instrument storage case as “Dry Keeper” manufactured by Denki Kogyo Co., Ltd.
JP 2003-010631 A JP 2003-001050 A Japanese Patent Laid-Open No. 9-324119

However, the humidity control sheets for musical instruments according to the conventional techniques described in Patent Documents 1 to 3 have a problem that although a certain degree of humidity control effect can be expected, the immediate effect related to the humidity control is relatively slow.
Here, FIG. 6A shows a configuration of a humidity control sheet made of a conventional rubber sheet, and FIG. 6B shows a schematic enlarged cross-sectional view along the line xx ′ of the sheet.

The said humidity control sheet has the structure by which the said rubber sheet was affixed with respect to the confidential film surfaces, such as polyethylene, and this was accommodated in the nonwoven fabric bag. Therefore, although the nonwoven fabric bag itself has good circulation, the air permeability of the rubber sheet itself is not so high, and one main surface of the rubber sheet is covered with a confidential film.
For this reason, in fact, although there is a considerable amount of moisture-absorbing / releasing polymer contained in the rubber sheet, since the area that comes into contact with the outside air is small, the humidity is adjusted at a very slow speed. It can be said that there are still problems in terms of the immediate effect required as a humidity control effect.

In particular, in the case of a bow or the like used for a stringed musical instrument, a natural material (horse tail hair, etc.) that stretches rapidly depending on humidity is used.
In addition, it is necessary to use a humidity control sheet corresponding to a storage case for storing a relatively large musical instrument such as a cello or viola. In this case, the rubber sheet is used because it has a certain weight. There is also a problem that the weight tends to increase according to the number.

  This invention is made | formed in view of the above subject, Comprising: It aims at providing the moisture-control sheet | seat for musical instruments which is lightweight and highly effective compared with the past, and a humidity-control set using the same.

In order to solve the above problems, the present invention provides a musical instrument comprising a fibrous structure in which a fibrous material in which a hygroscopic polymer is dispersed in a substrate made of a polymeric material is formed in a sheet shape. A humidity control sheet was used.
Here, the substrate made of the polymer material is made of a material containing a polyol-based material, and the moisture-absorbing / releasing polymer includes a polymer formed by polymerizing a water-soluble vinyl monomer or a precursor thereof and a crosslinking agent. It can consist of materials.

Moreover, the said fiber structure can also have a nonwoven fabric structure.
Furthermore, the present invention can also be used as a humidity control sheet for musical instruments in which the fiber structure is housed in a tare.
Furthermore, this invention can also be set as the humidity control set for musical instruments in which a moisturizing agent and the said humidity control sheet for musical instruments are accommodated in the case which has a vent hole.

Here, the specific moisturizing agent may be selected from polyethylene glycol materials, plant leaves and leaves, or fiber materials impregnated with moisture, and the case further includes a hygrometer. It can also be stored.
Furthermore, the present invention can also be used as a piano key cover in which the humidity control sheet for musical instruments is included or supported in a belt-like breathable material.

According to the humidity control sheet for musical instruments of the present invention and the humidity control set for musical instruments using the same, the hygroscopic polymer is dispersed in the fibrous base material, so that the moisture absorption / release characteristics compared with the humidity control sheet of the conventional structure. The surface area where the polymer comes into contact with the outside air is remarkably increased, and the circulation of the outside air is ensured in the gap between the humidity control fibers.
As a result, both the moisture absorption and moisture removal characteristics are dramatically improved through the gaps of the humidity control fibers, and compared to a humidity control sheet (FIG. 6B) made of a conventional rubber sheet. The high immediate effect required as a humidity control sheet is exhibited.

In addition, since such a humidity control sheet is actually composed of a nonwoven fabric structure (so-called felt) using fibers, it can be made extremely light compared to the conventional rubber sheet structure.
For this reason, even if it stores in a musical instrument storage case, the bodily sensation which the weight increased is not felt at all. Therefore, it is possible to freely adjust the usage amount of the humidity control sheet according to the convenience of the internal space without worrying about the weight even for a large musical instrument storage case such as a viola or a cello.
In addition, if the humidity control sheet of the present invention is applied to a piano key cover, excessive humidity around the keyboard after use can be appropriately reduced, so that changes in sound quality over time can be suppressed and good at any time. The effect that the sound quality is demonstrated can also be expected.

Embodiments of the present invention will be described below.
<Embodiment 1>
FIG. 1 is a schematic diagram showing a configuration of a humidity control set according to Embodiment 1 of the present invention and an application example to a musical instrument storage case.
The humidity control set 1 according to the first embodiment is stored in a musical instrument storage case 5 and includes a resin case 10, a humidity control sheet 2, a digital hygrometer 110, etc., as shown in FIG. Composed.

  The resin case 10 is formed by injection-molding a polypropylene (PP) material, and a rectangular upper lid 101 and a lower lid 102 are arranged to face each other with an internal space therebetween. Windows 101a and 102a (not shown) are formed on the main surfaces of the upper lid 101 and the lower lid 102 as openings or meshed vents, respectively. Inside the resin case 10, a digital hygrometer 110 and a humidity control sheet 2 are accommodated.

  The digital hygrometer 110 has a known configuration in which a thermistor element and a capacitive humidity element are arranged together with a button battery on a one-chip substrate, and the humidity is displayed on the liquid crystal display together with the current temperature. It is like that. As shown in FIG. 1A, the digital hygrometer 110 is disposed at an easy-to-see position on the upper lid 101 of the resin case 10. Of course, the hygrometer is not limited to the digital method.

The humidity control sheet 2 is accommodated so as to be positioned in the window portions 101 a and 102 a of the resin case 10. In this invention, it has the characteristics in the structure of the said humidity control sheet 2, and this is explained in full detail behind. As an example of the size of the sheet 2, it can be 90 mm in length, 55 mm in width, and 2 mm in thickness.
On the other hand, as an example of the size of the resin case 10, it can be 120 mm in length, 75 mm in width, and 15 mm in thickness. However, this size is relatively large and can be further reduced.

The resin case 10 is made of a soft resin such as vinyl chloride or polyethylene (PE), or a porous paper or plastic bag, so that it can be flexibly applied to the curved inner wall of the instrument storage case. It is also possible to make it stick.
As shown in FIG. 1 (b), the humidity control set 1 having such a configuration actually includes, for example, a violin storage case 5, the interior of the case body 50b, the inner wall 51, the upper space 52, or the lid 50a. It can be arranged either inside. In addition, at the time of the arrangement, the resin case 10 can be fixed by a double-sided tape or detachably fixed by using a hook-and-loop fastener or the like.

<Composition and effect of humidity control sheet>
Here, unlike the prior art, the humidity control sheet 2 in Embodiment 1 is made of a fiber material (absorbing and releasing resin dispersion) in which a hygroscopic polymer composed of B is dispersed in a polymer substrate in a sheet form. It is characterized in that it is configured as a structured fiber structure.
3A is an external view of the humidity control sheet 2, FIG. 3B is an AA ′ cross-sectional view of the humidity control sheet, and FIG. 3C is an enlarged cross-sectional view of the humidity control sheet.

The humidity control sheet 2 shown in FIG. 3A includes an exterior mesh 20 and a felt 3 included therein.
The exterior mesh 20 is a tare having a coarse mesh structure with a gap 201 having a diameter of about 2 mm. As shown in FIG. 3B, the inner felt 3 can sufficiently come into contact with the outside air. It is like that.

The felt 3 is a nonwoven fabric structure in which the humidity control fibers 301 are condensed at an appropriate density. Here, the humidity control fiber 301 is obtained by dispersing a hygroscopic polymer in a polymer substrate.
Here, the following polyol materials can be used as the polymer substrate.
That is, as the polyol material, polyether polyol, polyester polyol, polyether ester polyol, polyester amide polyol, acrylic polyol, polyurethane polyol, epoxy polyol, epoxy-modified polyol, polyhydroxyalkane, oil-modified polyol, castor oil, or Polyols whose main chain is a C—C bond, etherified products and esterified products in which the hydroxyl groups of the polyol are partially blocked with alcohol or carboxylic acid. Of these, polyether polyols and polyester polyols have been found to be suitable.

On the other hand, the following can be used as the hygroscopic polymer.
That is, a water-soluble vinyl monomer or a polymer of a vinyl monomer that becomes water-soluble by hydrolysis is formed by crosslinking with a crosslinking agent. In the present invention, the water-soluble vinyl monomer includes at least one carboxylic acid (salt) group, sulfonic acid (salt) group, phosphoric acid (salt) group, hydroxyl group, amide group, amino group, quaternary ammonium base and the like. A polymerizable monomer having a hydrophilic group is exemplified.

Here, examples of the vinyl monomer that becomes water-soluble by hydrolysis include monomers having at least one hydrolyzable group (such as an ester group, a nitrile group, and an amide group).
Examples of the monomer having an ester group include lower alkyl (C1-C3) esters of monoethylenically unsaturated carboxylic acids [for example, methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc.] And esters of monoethylenically unsaturated alcohols [for example, vinyl acetate, (meth) allyl acetate, etc.]. Examples of the monomer having a nitrile group include (meth) acrylonitrile.

Of these, water-soluble vinyl monomers are preferred. More preferred are monomers having a carboxylic acid (salt) group and a sulfonic acid (salt) group, and particularly preferred are acrylic acid and / or acrylate. These polymerizable monomers may be used alone or in combination of two or more if necessary.
<Method for producing humidity control fiber>
The following procedure can be taken as an example of a method for producing the humidity control fiber 301 using the polymer base material and the hygroscopic polymer material described above.

Specifically, the humidity control fiber 301 in the present invention can be produced by the following method.
(1) An aqueous solution or aqueous dispersion prepared by mixing a water-soluble vinyl monomer or a precursor thereof, a crosslinking agent, and, if necessary, another vinyl monomer is prepared. And the liquid which mixed the polyol material and the emulsifier as needed is dripped at this. After that, it is heated using a radical polymerization catalyst, if necessary, or irradiated with radiation, electron beam, ultraviolet rays or the like.

(2) A water-soluble vinyl monomer or a precursor thereof, a crosslinking agent and, if necessary, an aqueous solution or dispersion of another vinyl monomer are dropped into the polyol material, and if necessary, using a radical polymerization catalyst and an emulsifier, Thereafter, the same operation as in (1) is performed.
(3) A water-soluble vinyl monomer or a precursor thereof, a crosslinking agent and, if necessary, an aqueous solution or an aqueous dispersion of another vinyl monomer are dropped into a mixture of a polyol-based material and water, and radical polymerization catalyst and emulsifier as necessary. Then, the same operation as in (1) is performed.

(4) A radical polymerization catalyst is present in a dispersion composed of a polyol-based material, an emulsifier and water, if necessary, and a water-soluble vinyl monomer or a precursor thereof, a crosslinking agent and, if necessary, another vinyl monomer are dropped. And then operate in the same way.
Here, the content of the moisture absorbing / releasing polymer in the humidity control fiber 301 is usually in the range of 1% by weight to 70% by weight, preferably 5% by weight, from the viewpoint of dispersibility of the moisture absorbing / releasing polymer. It is desirable to set in the range of 65% by weight, particularly preferably in the range of 10% by weight to 60% by weight.

The humidity control fiber 301 of the present invention can be obtained by mixing and processing various materials by such a method.
In addition, about the structure of the humidity control fiber 301 and the said preparation method itself, it is disclosed by Unexamined-Japanese-Patent No. 9-324119 and Unexamined-Japanese-Patent No. 2003-1050, for example, and is a well-known thing. However, these publications do not disclose or suggest the configuration or application examples of the humidity control sheet and humidity control set for musical instruments of the present invention using the humidity control fiber 301.

In addition, although the nonwoven fabric structure (felt) is shown here as the condensation structure of the humidity control fiber 301, this invention is not limited to this, You may produce as a woven fabric structure.
<Effect of humidity control sheet 2>
According to the humidity control sheet 2 having such a configuration, since the moisture absorbing / releasing polymer is dispersed in the fibrous substrate, the surface area of the moisture absorbing / releasing polymer in contact with the outside air as compared with the humidity controlling sheet having the conventional structure. Is significantly increased, and the circulation of the outside air is ensured in the gap 201 of the exterior mesh 20 and the gap of the humidity control fiber 301. As a result, as shown in FIG. 3 (c), both moisture absorption and moisture removal are successfully performed through the gap 201 of the exterior mesh 20 and the gap of the humidity control fiber 301, and the conventional structure (FIG. 6 (b)). Compared to, it has a much higher immediate effect.

  Moreover, since the humidity control sheet 2 is composed of the felt 3 using the humidity control fibers 301, it is extremely light compared to the conventional rubber sheet structure (for example, when compared with the same size, the rubber sheet structure is 20 g. About 1 g or less can be produced in the present invention. For this reason, even if it stores in a musical instrument storage case, the bodily sensation which the weight increased is not felt at all.

Therefore, according to the present invention, it is possible to store a large amount of the humidity control sheet 2 even in a large musical instrument storage case such as a viola or a cello as long as there is room in the internal space without worrying about the weight. is there.
In the first embodiment, the configuration example using the humidity control set 1 in which the humidity control sheet 2 and the digital hygrometer 110 are arranged in the resin case 10 has been described. However, in the present invention, the resin case 10 and the digital case are digitally displayed. The hygrometer 110 can be used arbitrarily and is not an essential element.

In the case of using a case made of a soft material (porous nylon or the like) without using a hard case, such as the resin case 10 or the like, or omitting the case itself and using only the humidity control sheet 2, the instrument case Since the humidity control sheet 2 and the case for storing it can be bent and pasted freely according to the inner surface shape, it is considered that good convenience can be expected in that respect.
Further, the humidity control sheet 2 does not necessarily require a configuration in which the felt 3 is stored in the exterior mesh 20, and may be a configuration using at least the felt 3.

  Further, FIG. 1 shows an example in which the humidity control set 1 is arranged inside the instrument storage case 5, but in addition to this, as shown in FIG. 2, the linings 501 and 502 of the instrument storage case 5 and the instrument case A plurality of humidity control sheets 2 may be interposed between the main body 503 and the main body 503. In this case, if the digital hygrometer 110 or the like is unnecessary, the use of the humidity control set 1 can be omitted.

Further, the linings 501 and 502 themselves can be configured as the humidity control sheet 2 and can be used by being attached to the inside of the musical instrument storage case 5.
<Example>
FIG. 4 shows data comparing the performance of the humidity control sheet of the present invention with the performance of each conventional humidity control sheet. FIG. 4A shows data of the example, and FIG. 4B shows data of the conventional example. As a conventional example, the characteristic about Furukawa Electric Co., Ltd. "dry keeper" which is a rubber sheet-like humidity control sheet is shown.

  First, as shown in FIG. 4B, in the conventional example, it takes about 50 hours until the saturation associated with moisture absorption of the sheet. As described above with reference to FIG. 6B, such a result is a rubber-like substrate having a relatively dense substrate shape, and one side of the rubber sheet is covered with a film. This is probably because it takes time for moisture to enter the interior. In addition, even if the film is not provided, as long as the rubber sheet is used, substantial moisture absorption and desorption is performed in the vicinity of the surface in a short time. It is thought that it is not fully demonstrated.

  Of course, depending on the amount of the moisture absorbing / releasing polymer mixed into the rubber sheet (more specifically, depending on the amount of the moisture absorbing / releasing polymer contacting the outside air on the rubber sheet surface), this characteristic changes, If the amount of the polymer is increased, it is considered that the moisture absorption / release property is increased accordingly, but here, for comparison with the examples, a uniform material is used without distinguishing the surface and the inside of the rubber sheet. It is mentioned in terms of characteristics.

  On the other hand, as shown in FIG. 4A, in the example, saturation of moisture absorption is achieved in about 30 minutes, and it can be confirmed that it has higher immediate effect than the conventional example. Similarly, the moisture removal performance was confirmed to exhibit the same immediate effect as the moisture absorption characteristics, and neither the moisture absorption nor the moisture removal is superior to the other characteristics. It is confirmed that good performance is exhibited as well.

As shown in FIG. 3 (c), such an effect is achieved by the humidity control sheet 2 of the present invention including the felt 3, allowing the outside air to circulate to every corner inside the felt 3, and an effective surface area related to humidity control. This is probably due to the fact that this is secured.
<Embodiment 2>
FIG. 5 shown next is a diagram showing a configuration of a piano key cover having a humidity control function according to Embodiment 2 of the present invention. FIG. 5A and FIG. 5B show different key cover configurations. FIG. 5A shows a state of a key cover arranged on a schematic piano keyboard, and partially shows the inside of the key cover along the line BB ′.

  First, the key cover 4 shown in FIG. 5A is used by being sandwiched between a piano keyboard and a keyboard lid, and is provided inside a long belt-like felt exterior 40 which is an example of a breathable material. The humidity control sheet 2 covered with the exterior mesh 20 is accommodated. The humidity control sheet 2 uses a long sheet whose size is changed in accordance with the felt exterior 40. However, as shown in FIG. You may make it accommodate in 40.

  In the felt exterior 40, the felt material is a polyester nonwoven fabric similar to a conventional key cover, and has a certain air permeability by adjusting the fiber density of the nonwoven fabric. Thereby, the humidity control sheet 2 included in the felt exterior 40 can maintain good air permeability with the outside. In addition, as a breathable material, you may comprise using materials (felt craft paper etc. with fixed intensity | strength and breathability) other than a felt material.

  The key cover 4 may have any size, for example, it can be adjusted to the size of a keyboard composed of 88 keys of a standard grand piano. Further, as described in the first embodiment, the humidity control sheet 2 can be configured to be thin enough in units of several millimeters, so that the keyboard lid does not float even when the piano keyboard lid is closed, and the keyboard lid is securely closed. Thus, it can be satisfactorily sandwiched between the keyboard and the keyboard lid.

  According to the key cover 4 having the above configuration, even after the keyboard containing the moisture is covered with the keyboard lid after use by the user's finger or outside air, excessive moisture is absorbed from the periphery of the keyboard and when the keyboard is dried, A humidity control effect is made by appropriately releasing the taken-in water. In general, the piano is made of a material that is relatively resistant to moisture, such as metal, wood, felt, and the like. In particular, the periphery of the keyboard is made of felt and laminated wooden material to form a piano wire and a hammer mechanism. For this reason, the acoustic effect may change due to the influence of the user's sweat and humid environment, and these components contain moisture, so that tuning and fine maintenance are required as appropriate, etc. It may be difficult to maintain a certain sound quality. On the other hand, in the present invention, in the sealed space of the keyboard and the keyboard lid, the humidity control effect is exerted mainly on the surface of the keyboard and between adjacent keyboards, so that the condition of the keyboard is always kept good and stable at any time. It becomes possible to perform with sound quality.

  In addition, the structure of the key cover 4 is not limited to what completely covers the humidity-control sheet | seat 2 with the felt exterior 40 like Fig.5 (a), You may take a structure other than this. Here, FIG. 5B shows a configuration of a key cover according to another variation of the second embodiment. The key cover 6 shown in FIG. 5 (b) has a feature that the humidity control sheet 2 is arranged in plural inside, but the back surface of the felt exterior 40 is formed of a mesh 401. Thereby, since the air permeability is further improved as compared with FIG. 5A, excellent immediate effect can be expected.

FIG. 5 shows a configuration in which the humidity control sheet 2 is included in the felt exterior 40. However, the felt exterior 40 does not need to be formed in a bag shape. For example, the felt exterior 40 is formed into a belt-like body and directly adjusted on the surface of the belt-like felt. The wet sheet 2 may be carried by a technique such as sticking or sewing.
<Other matters>
In the first embodiment, the configuration in which only the humidity control set is put in the musical instrument storage case is shown. However, when the musical instrument is stored in a dry environment for a long period of time, the musical instrument is stored only with the moisture held by the humidity control sheet. It may be difficult to cover the humidity inside the case. In this case, it is preferable to separately provide a moisturizing agent in the humidity control set because this problem can be solved.

As the humectant, for example, a known cold bag having hydrophilicity and cold keeping properties such as polyethylene glycol (PEG) can be used.
As other moisturizing agents, a fiber material impregnated with moisture or the like (a configuration similar to a so-called paper towel) or plant branches and leaves can be used.
The plant branch and leaf is a kind of leaf vegetable represented by Chinese cabbage used in the preservation of Japanese musical instruments (such as shakuhachi), and the leaf has a considerable thickness, water retaining ability, and less odor. It is.

  The humidity control sheet for musical instruments of the present invention and the humidity control set for musical instruments using the same are humidity control sheets for various musical instruments such as stringed instruments such as violins, violas, and cellos, and brass instruments such as trombone, saxophone, and trumpet. It can be used as a wet set. Alternatively, the humidity control sheet for musical instruments can be used as a piano key cover having a humidity control function, or can be used by being arranged inside a piano. The types of musical instruments are not limited to those described above, and can be used for various percussion instruments, woodwind instruments, and the like.

It is a schematic diagram which shows the example of a structure of the humidity control set in Embodiment 1 of this invention, and an instrument storage case. It is a figure which shows the example of application (variation) of the humidity control sheet | seat to a musical instrument storage case. It is a figure which shows the structure of a humidity control sheet. It is the data which compared the performance of this invention and each conventional humidity control sheet. It is a figure which shows the structure of the key cover for pianos in Embodiment 2 of this invention. It is a figure which shows the typical structure of the conventional humidity control sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Humidity control set 2 Humidity control sheet 3 Felt 4, 6 Piano key cover 5 Violin musical instrument storage case 10 Storage case 20 Exterior mesh 40 Felt exterior 101 Upper lid 101a Window portion 102 Lower lid 110 Digital hygrometer 201 Mesh gap 301 tone Wet fiber 501, 502 Liner 503 Musical instrument storage case body

Claims (8)

A humidity control sheet for musical instruments, comprising: a fiber structure in which a fiber material in which a moisture-absorbing / releasing polymer is dispersed in a base made of a polymer material is formed into a sheet shape. The substrate made of the polymer material is made of a material containing a polyol-based material, and the moisture-absorbing / releasing polymer is made of a material containing a water-soluble vinyl monomer or a precursor thereof and a cross-linking agent. The humidity control sheet for musical instruments according to claim 1. The humidity control sheet for musical instruments according to claim 1 or 2, wherein the fiber structure has a nonwoven fabric structure. The humidity control sheet for musical instruments, wherein the fiber structure according to any one of claims 1 to 3 is housed in a tare. A humidity control set for musical instruments, characterized in that a case having an air vent contains the moisturizing agent and the humidity control sheet for musical instruments according to any one of claims 1 to 4. The humidity control set for musical instruments according to claim 5, wherein the humectant is selected from polyethylene glycol materials, plant leaves and leaves, or fiber materials impregnated with moisture. The humidity control set for musical instruments, further comprising a hygrometer stored in the case. The key cover for a piano, wherein the humidity control sheet for musical instruments according to any one of claims 1 to 3 is enclosed or supported by a belt-shaped breathable material.

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