JPS6366478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flame retardant center cap for a speaker.

Generally speaking, speaker diaphragms are made mainly from cellulose fibers, but as they are inherently flammable, they are vulnerable to flames, and are susceptible to heat generated by the speaker voice coil due to excessive input, or to high-temperature environments such as those found in television cabinets. Therefore, there was a risk of ignition and other fires. Therefore, various proposals have been made to make the diaphragm flame retardant, but the center cap of the speaker tends to be overlooked, and like the diaphragm, it is necessary to make it flame retardant. Therefore, it is possible to use inorganic asbestos as a flame retardant material for the center cap.
Since this has a large mass, speaker sensitivity deteriorates, which is not desirable in terms of sound quality. On the other hand, when the center cap is made of cellulose fiber, examples of flame retardant treatment agents include boric acid, boron, or chlorine compounds, but boric acid, boron, etc. are highly hygroscopic and cause a significant decrease in strength and weight. Because of this increase, the speaker sensitivity deteriorates, which is unfavorable in terms of characteristics. In addition, chlorinated compounds have a major disadvantage in that they are hygroscopic and also generate harmful gases when ignited.

The present invention has been made in view of the above-mentioned points, and provides a flame-retardant center cap for a speaker that has stable quality, does not adversely affect the vibration characteristics of the speaker, and can be manufactured at low cost without requiring special equipment. The purpose is to

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an example of a cone speaker. In the figure, reference numeral 1 designates a back plate, on which a pole piece 2 is placed in the center and a magnet 3 is provided on the periphery. Plate 4 includes magnet 3, pole piece 2, and back plate 1.
Together they form a magnetic cap. A voice coil bobbin 6 carrying a voice coil 5 is inserted into the magnetic cap so as to be able to vibrate freely, and is supported by a damper 7. A cone 8 is connected to the bobbin 6 at its center hole, and a center cap 9 is further attached to the bobbin 6. The upper peripheral edge of the cone 8 is supported on the frame 11 via an edge 10, which is further connected to the frame 11 by a gasket 12.
It is fixed at 1. Note that the lead wire of the voice coil 6 is connected to a terminal 14 on the side surface of the frame 11 via a tinsel wire 13.

The above is a known structure, but in the present invention, the center cap 9 includes a flame-retardant cone 8,
A flame-retardant material is used together with the gasket 12.

In other words, the center cap 9 is made by impregnating a paper made of cellulose fibers such as wood pulp or bast fibers with an organic phosphorus-containing nitrogen compound mixed with a low-form melamine resin, and then drying it by heat treatment. This makes it flame retardant.

In the present invention, the reason why paper molding is used instead of a simple sheet as the material for the center cap is as follows.

In other words, in order to increase the specific elastic modulus (E/ρ) and moderate internal loss like the diaphragm, the center cap is pressed by instant heat (mold) after paper making, or by instant heat in an oven, etc. It is for drying. Therefore, the surface is hard and the inside is soft. In contrast,
In the case of a sheet, it is gradually dried over a period of time on a roll, so that it has approximately uniform physical properties both on the surface and inside.

Therefore, when impregnating a center cap with resin, etc., the degree of impregnation and adhesion to the surface and inside will vary depending on the concentration of the solution, the type of resin, the hardening agent, etc. However, in the case of a sheet, the There is no significant difference.

In order to impart flame retardancy to such a center cap by impregnating it with a flame retardant, it is only necessary that the surface of the center cap be covered with the flame retardant, and it is not necessarily necessary for the flame retardant to penetrate into the inside of the center cap. Therefore, in the present invention, impregnation in the case of impregnating a flame retardant to make it flame retardant includes not only normal impregnation but also simply covering the center cap surface. It is possible to achieve flame retardancy by minimizing the amount of flame retardants, which tend to change significantly and cause a decrease in Young's modulus, and to add other components such as resins to improve non-water absorption, Young's modulus, and suppress weight increase. becomes important.

The organic phosphorus-containing nitrogen-containing compound used as a flame retardant in the present invention is an alcohol containing a phosphonic acid derivative as a main component (e.g. ethanol, methanol).
It is soluble and does not contain harmful gas-generating components such as chlorine and bromine, unlike conventional products. As this organic phosphorus-containing nitrogen-containing compound, for example, a commercially available alcoholic solution of a compound containing 17.1% by weight of phosphorus and 7.7% by weight of nitrogen can be used.

A flame-retardant diaphragm can be obtained by impregnating the organic phosphorous-containing nitrogen compound, but in the present invention, a low phosphorus melamine resin and an organic amine salt added thereto as a catalyst are also used. Low-form type melamine resin refers to so-called 3-methylol melamine obtained by reacting formalin and melamine.
It has a lower formalin content than methylolmelamine, and is used in an alcohol-soluble state through condensation. The use of this low-hol type melamine resin improves water absorption by impregnating it with flame retardant, making it non-hygroscopic.It also improves heat resistance and compressive strength of 31%.
A product with excellent mechanical strength such as tensile strength can be obtained.

That is, according to the present invention, since the material is mainly composed of cellulose fiber, the internal loss is large, and the mechanical strength (Young's modulus) is increased by impregnation with the low-hol type melamine resin, so it has excellent frequency characteristics. You can get a center cap.

Next, a method for manufacturing a flame-retardant center cap will be explained.

First, a center cap sheet mainly made of cellulose fibers such as wood pulp is paper-molded, and a center cap is obtained by die cutting. After this cap is immersed in a methanol mixed solution of an organic phosphorus-containing nitrogen-containing compound and a low phosphoric melamine resin, or is coated with a spray, brush, etc.,
A flame-retardant center cap can be obtained by heat treatment and drying for 15 minutes.
The desired flame retardancy and hardness of the center cap can be obtained by changing the amount of phosphorus-containing and nitrogen-containing compounds attached to the cap or their blending ratio, but the total amount attached to the cap should be 8 to 20% by weight. is appropriate. In addition, the organic phosphorus-containing nitrogen-containing compound uses a 5-20% alcohol solution, and the compounding ratio of the compound, low-form melamine resin, and organic amine salt is 5-20:0.1-5:0.1-3 by weight. Prepare a mixed solution so that As described above, in the present invention, since alcohol such as methanol is used as a solvent, even cellulose fibers that easily swell in an aqueous system can be rapidly processed while maintaining their shape.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 A center cap with a diameter of 10 cm was formed using paper and FLAMEGARD5527 was used as an organic phosphorus-containing nitrogen-containing compound.
(manufactured by Dainippon Ink KK.) and BECAMINE PM~N (manufactured by the same company) as a low-hol type melamine resin.
A combustion test was conducted on a center cap that was impregnated with methanol diluted to 8% with a blending ratio of 1 (by weight) and dried at 100℃ for 15 minutes.The flame-retardant center cap did not catch fire immediately after being removed from the disaster. I got it. This center cap is UL rated 94
-Excellent flame retardancy meeting the requirements of V-O.

Example 2 A center cap with a diameter of 8 cm was made from paper,
A combustion test was conducted on a center cap impregnated with an alcohol mixed solution containing 10% by weight BECAMINE, 0.5% organic amine salt, and 20% FLAMEGARD 5527, and dried at 100℃ for 15 minutes. We were able to obtain a flame-retardant center cap that does not catch fire.

As described above, according to the present invention, flame retardancy can be imparted by impregnating an inherently flammable center cap made mainly of cellulose fibers with a treatment solution, which may reduce the possibility of heat generation in speaker voice coils or It can be used without any danger even in cases where it is easily exposed to high temperatures, such as in a cabinet.

[Brief explanation of drawings]

The drawing is a longitudinal sectional view of a cone speaker according to the present invention. 7... Damper, 8... Cone, 9... Center cap, 10... Edge, 11... Frame,
12...Gasket.

Claims (1)

[Scope of Claims] 1. A flame-retardant speaker center cap made by impregnating a paper-molded cap mainly made of cellulose fibers with an organic phosphorus-containing nitrogen-containing compound mixed with a low-hol type melamine resin, and drying this by heating. . 2. The flame-retardant center cap for a speaker according to claim 1, wherein the low-form melamine resin is used together with an organic amine salt catalyst.