JPS6250037B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cabinet material for a sound reproduction device, etc., and more particularly to a cabinet material with excellent acoustic properties that is effective as a baffle plate for a speaker box or the like.

The above-mentioned sound reproduction device etc. refers to a speaker system, television, radio, etc.

In general, it is considered desirable for a sound reproduction device to have little resonance with the sound generated by a speaker, to absorb sound from the back of the speaker, and to have excellent sound insulation properties.

Therefore, the properties required of the cabinet material for the above-mentioned devices, etc. are that the internal loss against vibration is moderately large, that vibration is quickly absorbed and attenuated, that it has high density and rigidity, and that it is difficult to vibrate. etc.

Therefore, in order to satisfy the above-mentioned attributes, conventional cabinet materials have been made of hardwood such as cherry tree or birch, or particle board made by hardening hardwood chips with resin.

However, these materials have relatively low specific gravity and poor sound insulation, resulting in poor acoustic properties in the mid- and low-frequency ranges.Since they are natural materials, it is difficult to obtain homogeneity in the material, and in addition, they are extremely hygroscopic. Due to its large size, it has drawbacks such as being susceptible to the effects of humidity, and it cannot at all satisfy the above-mentioned attributes as a cabinet material.

Furthermore, in order to improve sound insulation properties, in recent years, cabinet materials have been developed in which aggregates mainly composed of inorganic substances are hardened using a binder such as resin or cement.

However, although these materials have excellent sound insulating properties, they not only require a lot of work to process, but also are extremely troublesome to bond the sound absorbing materials, fix the speakers, and connect them when assembling the box. Moreover, due to the non-uniformity of the material, it was difficult to design curved surfaces such as corners, and there were also problems in terms of mass production.

In addition, these materials have many drawbacks when used as cabinet materials for sound reproducing devices, such as the fact that in addition to the resonance of the materials themselves, they tend to cause "box noise" and the like, which often significantly impairs sound quality.

As a result of various studies to eliminate the above-mentioned drawbacks, the inventors of the present invention have developed a rigid polyurethane foam that is easy to process to fully express even complex designs and is mass-producible due to the ease of the manufacturing process. discovered that the inorganic fiber content and resin density improve sound insulation properties, improve damping properties, and prevent "box noise" when used in cabinets such as sound reproduction devices, This completes the present invention.

That is, in the present invention, the fibrous inorganic material is used in a weight ratio of 5 to 5.
Rigid polyurethane foam containing 80%, its density is 1.5≦d _M /d _F ≦16, 3.0≦d _M ≦1.3 (however, d _F
= free foam density, d _M = mold density)
It is characterized by being shaped so that it has the following relationship.

Hereinafter, the cabinet material according to the present invention will be specifically explained.

Fibrous inorganic materials that can be used in the present invention include:
Glass fibers, metal fibers, mineral fibers (PMF), ceramic fibers, single crystal fibers (whiskers), etc. are used.

It is desirable that these fibers have good dispersibility in hard urethane, and if necessary, they are treated to improve the dispersibility.

In addition, the above fibers have a length of 5 mm or less and a diameter (d) of
The ratio of length (l) to
~500 range is used.

If the above-mentioned inorganic fiber is outside the above range, for example, if it is too long or the l/d value is too large, it will become floc-like lumps when dispersed in rigid urethane foam and will not be uniformly dispersed, resulting in uncured portions. Therefore, when these materials are used as a cabinet material, the sound quality becomes distorted.

Contrary to the above, if the l/d value of the fiber is too small, the rigidity of the final molded product will decrease and the brittleness will increase. This is not preferable because it tends to occur easily.

The inorganic fibers are contained in the rigid foam polyurethane in a weight ratio of 5 to 80%.

If the content of this inorganic fiber is less than 5%, it will lack the rigidity necessary for cabinet materials for sound reproduction devices, etc., the resonance frequency will become low, the sound insulation performance in the mid-bass region will decrease, and as a result, the acoustic properties will be distorted. If it exceeds 80%, the material will have high rigidity and sufficient acoustic properties will be obtained, but the high viscosity of the raw material will increase the difficulty of manufacturing, and the wear resistance of the material surface will also decrease. In order to do so, reinforcement such as pasting a PVC sheet on the surface is required, so 5~
A range of 80% is good.

Next, a description will be given of how the cabinet material for the sound reproduction device and the like according to the present invention is manufactured.

First, we will discuss the raw materials for rigid urethane foam.

Examples of polyether polyols suitably used in the present invention include those obtained by adding oxides such as polyethylene oxide, polypropylene oxide, butylene oxide, styrene oxide, epichlorohydrin, etc. to a normal active hydrogen compound having 2 to 8 functional groups as a starting material. Those with a hydroxyl value of 300 to 600 are used as a mixture of two or more types, or used alone, but the more preferred ones are those with a functional group number of 3.1 to 5.0 and a hydroxyl value of 350 to 450. It is.

Furthermore, polyester polyols having the same number of functional groups and hydroxyl value as described above can be used.

Isocyanate compounds include 4,4'-diphenylmethane diisocyanate and/or its isomers, polymethylene (polyphenyl isocyanate), 2,4- and/or 2,6-tolylene diisocyanate.

It is also possible to use polyisocyanates containing carbodiimide groups, biuret groups, uretdione groups, uretonimine groups, isocyanurate groups, and the like.

Further, it is also possible to use a prepolymer consisting of the above-mentioned isocyanate and the above-mentioned polyether.

As the chain extender or crosslinking agent, short chain diols such as 1,4-butanediol, dipropylene glycol, diethylene glycol, or
4,4′-methylenebis(0-chloroaniline),
Amines such as trimethylene glycol-di-P-aminobenzoate are preferred, and the amount added is preferably 3% by weight or more based on the total active hydrogen compound.

Further, the reaction equivalent ratio of these active hydrogen compounds and isocyanate compounds is usually desirably NCO/active hydrogen compound of 0.95 to 1.20, but it can be set to a maximum of 20.0 depending on the selection of the reaction accelerator.

Examples of the reaction accelerator include dimethylbenzylamine, N-methyl-N'-(N,N-dimethylaminoethyl)-piperazine, triethylenediamine, N-ethylmorpholine, N-methylmorpholine, dimethylcyclohexylamine. , or an organotin compound such as dibutyltin dilaurate, stannath octoate, or an alkali metal salt such as potassium acetate or sodium octylate, furthermore, N,N′,N″-tris(dimethylaminopropyl), hexahydro
Strong bases such as S-triazine and 1,8-diazabicycloundecene-7 and their salts can be used.

These reaction accelerators may be used alone or in an appropriate mixture.

As a blowing agent, a low boiling point solvent such as trichloromonofluoromethane, dichlorodifluoromethane, methylene chloride, etc. is used at a rate of 1% per total reaction mixture.
It is preferable to add up to 15% by weight.

Further, as a blowing agent, it is of course possible to use a gas (such as CO ₂ gas) generated by reaction with isocyanate, or an inert gas such as water vapor, air, or nitrogen.

In addition, polysiloxane polyether, etc. are added as cell stabilizers, and flame retardants,
Pigments etc. are used.

Next, the production of rigid polyurethane foam will be described.

Rigid foam polyurethane is easily produced by injecting raw materials into a mold using a conventional foaming machine.

Incidentally, the fibrous inorganic material is homogeneously dispersed in the raw material in the mold by an appropriate method. The temperature of the mold needs to be 25℃ or higher, but it is 30 to 70℃.
It is preferably within the range of °C.

In addition, it is also possible to integrally foam and mold reinforcing materials such as glass cloth, chopped strands, expanded metal, and non-woven fabric on the inner surface of the skin of these rigid polyurethane foams, and it is also possible to foam-mold reinforcing materials such as glass cloth, chopped strands, expanded metal, and non-woven fabric on the inner surface of the skin. It is also possible to integrally foam and mold face materials such as boards, felt, and Japanese paper.

Furthermore, if necessary, a reinforcing material can be applied to the mold and coated with a so-called mold coat.

In order to obtain a suitably homogeneous rigid polyurethane foam used in the present invention, it is important to consider the following manufacturing conditions depending on the thickness of the molded product. This is particularly important for rigid polyurethane foam.

That is, the rigid polyurethane foam of the present invention is produced by curing a stock solution of rigid polyurethane foam having a free density (d _F ) of 0.03 to 0.5 g/cm ³ in a mold, and
It is molded so that the mold density (d _M ) is 0.3 to 1.3 g/cm ³ , but the above density ratio d _M /d _F is 1.5 to 1.3 g/cm 3 .
Molding is performed so that the density ratio d _M /d _F has a value of 16, more preferably, a value of 5 to 12.

A molded product molded so that the density ratio d _M /d _F is 1.5 to 16 has a suitably homogeneous density distribution in the thickness direction, and as a result provides acoustic characteristics with little distortion.

In particular, a molded article molded so that the density ratio d _M /d _F is between 5 and 12 has excellent acoustic properties.

In this way, a cabinet material for a sound reproduction device or the like according to the present invention can be obtained. and,
Speaker cabinets made from this cabinet material exhibit great rigidity and can increase the resonant frequency, resulting in good sound insulation.
In addition, the hard urethane foam used has a reasonably uniform density distribution in the thickness direction (small difference in density between the skin and corners), which increases the internal loss of the cabinet and reduces the vibrations emitted from the speaker. It is possible to prevent "box noise" etc. and obtain distortion-free acoustic characteristics.

Therefore, the above-mentioned speaker cabinet can provide good reproduction sound with extremely high fidelity in acoustic characteristics, particularly in the mid-to-low frequency range.

As described above, the cabinet material for the sound reproducing device, etc. of the present invention has the above-mentioned attributes required of the cabinet material, namely, it has a suitably large internal loss against vibrations, and quickly absorbs and attenuates vibrations. It has high density and rigidity and is difficult to vibrate.
Moreover, since it is made of rigid polyurethane foam, it is easy to process and can fully express complex designs.
The manufacturing process is simple and mass production is possible, and various practical effects are achieved.

An embodiment of the present invention will be shown below.

Polyether polyol (OH value 400) 90 parts Crosslinking agent 10 parts Triethylenediamine 0.3 parts Silicone 1.0 parts Freon 11 10 parts Glass fiber (length, 0.5 to 2.0 mm, thickness 10
μ) 50 parts Pigment 3 parts Crude 4,4'-diphenylmethane diisocyanate was added at a ratio of 110 parts to the above formulation, stirred for about 30 seconds, and then placed in a mold at 30°C. Injected and foam molded. The foam molding conditions at this time were set so that the d _M /d _F value was 8.2. In this example, the free density (d _F ) of the rigid foam was 0.10, and the foam molding conditions were set so that the mold density (d _M ) of the molded plate material was 0.82 g/cm ³ .

Thereafter, the mold was released after about 60 minutes to obtain a cabinet material for a sound reproduction device or the like according to the present invention. The size of this cabinet material is 650mm x 400mm x 18mm.
(Density (d _M ) 0.82 g/cm ³ ).

This cabinet material has a compressive strength of 440Kg/cm ³
The bending strength was 480Kg/cm ² .

Cut out this cabinet material to a height of 640 mm.
A speaker box with a width of 356 mm and a depth of 295 mm was assembled, a 30 cm woofer, a horn-shaped speaker, and a horn-shaped tweeter were attached, and glass wool about 5 cm thick was lined inside the box, similar to commercially available products, to create a speaker system. .

This speaker system was compared with a commercially available particle board speaker system of the same shape.

Trial listening was performed using a stereo playback device in an approximately 20 m ² room with various music records, and by switching the speaker system. The results are as follows.

It has been revealed that the speaker system made of the cabinet material of the present invention has a more extended and beautiful sound in the bass range than the above-mentioned commercial products, and has less distortion.

In addition, in the above comparison, a speaker system made of a cabinet material in which the content of glass fiber in the cabinet material composition of the present invention was zero or less than 5% was used instead of a commercially available product. The system suffered from significant distortion due to the vibration of the speaker box in response to high-level input, and I could not feel any extension in the bass range.

Claims (1)

[Claims] 1 Rigid polyurethane foam containing 5 to 80% by weight of fibrous inorganic material, whose density is 1.5≦d _M /
A cabinet material for a sound reproduction device, etc., which is molded to satisfy the following relationships: d _F ≦16, 0.3≦d _M ≦1.3 (where d _F = free foam density, d _M = mold density).