JPS5820518B2 - Manufacturing method of speaker diaphragm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a low-density speaker diaphragm containing foam-containing fine particles.

As for the physical characteristics of a speaker diaphragm, it is desirable not only to theoretically analyze its operation but also to have a piston motion as much as possible from the standpoint of operational stability and frequency characteristics. It is necessary that the diaphragm has a large diaphragm and an appropriate mechanical internal loss, and that it is lightweight from the viewpoint of the acoustic radiation efficiency of the speaker, and a diaphragm that has high rigidity and low density is required.

Conventionally, in order to obtain such a low-density diaphragm, papermaking was performed using fibers with a low degree of beating, but diaphragms using such fibers had extremely weak bonds between the fibers, making them difficult to use as a diaphragm. The required rigidity cannot be met.

On the other hand, if fibers with a high degree of beating are used, the rigidity and density will increase, resulting in an increase in the weight of the diaphragm.

One of the solutions to these contradictory phenomena is a diaphragm whose density is lowered by mixing foam-containing fine particles, and the following methods are already known as methods for manufacturing this diaphragm.

(1) Mix unfoamed fine particles with fibers, add a sizing agent such as water-soluble polyamide resin or synthetic resin acid colloid to fix the fine particles to the fibers, and after papermaking, heat and pressurize in a mold to foam at the same time as forming. Method.

(2) A method in which foamed fine particles are mixed with fibers, a sizing agent such as a synthetic rubber emulsion or a synthetic resin acid colloid is added, the foamed fine particles are fixed to the fibers, and the paper is formed and then heated and pressure molded.

However, in the method (1) above, since there is no means to strongly bond the fibers and unfoamed fine particles, most of the unfoamed fine particles flow out into the waste water during paper making, resulting in a large loss of unfoamed fine particles. It is economically disadvantageous, and in method (2), the already foamed foam-containing fine particles tend to float and separate from the fibers, and in order to prevent this, a large amount of a keying agent such as a synthetic rubber emulsion is used. However, there is a drawback that the weight of the diaphragm increases and the weight reduction effect of the foam-containing fine particles is offset.

In addition, there are two possible functions of the foam-containing fine particles to lower the density of the diaphragm: one is simply due to the space corresponding to the volume of the foam-containing fine particles themselves, and the other is due to the space between the fibers. This function prevents the fibers from being densely deposited and creates new voids between the fibers below the spaces eliminated by the foam-containing fine particles.

From this point of view, in the method (1) in which foaming is performed after papermaking, a dense paper layer is formed once during papermaking and then expanded by foaming, so the volume corresponds to the volume of foam-containing fine particles expanded by foaming. Since only the amount of fibers removed is removed, no effect of forming voids other than the spaces created by the foam-containing fine particles between the fibers can be expected.

In addition, if the volume of the fine particles is smaller than the voids that are naturally formed in the paper layer during papermaking, the fine particles that fall into the voids simply fill the voids and do not contribute at all to lowering the density of the diaphragm. .

Furthermore, even if the particles are intervening between fibers, if they are adjacent to the voids that occur during papermaking, they will expand toward the voids with less resistance, rather than pushing the fibers up due to volume increase during foaming to create voids between the fibers. As a result, it cannot be involved in lowering the density.

As mentioned above, most of the structure of the diaphragm is determined at the moment the fibers are deposited on the papermaking screen, so how effectively the foam-containing particles are used at the time of paper making is a key factor in creating a diaphragm with a low density. This becomes a problem.

This invention is a manufacturing method that improves this point, and uses micro hollow spheres to effectively reduce the density of the diaphragm, as well as promoting the fixation of fine particles to the fibers, thereby minimizing material loss. .

To explain this invention in more detail, highly refined (C8F)
(200 to 300 cc), cellulose fibers or mixed fibers with non-cellulose fibers, unfoamed fine particles of vinylidene chloride acrylonitrile micro hollow spheres are mixed with the fibers, and a polymer flocculant such as polyethyleneimine or polyacrylamide is mixed into the fibers. After fixing the unfoamed fine particles to the fibers, the unfoamed fine particles are heated to foam them to form micro hollow spheres between the fibers.

Next, paper is made and the fiber layer deposited on the paper screen is dried or, if necessary, lightly pressed to shape it.

The mechanism for fixing fine particles to fibers according to the method of this invention is as follows.

That is, highly beaten and sufficiently fibrillated fibers or fine particles located between fine fibers adhere to the fibers so as to be wrapped around them when the fibers are aggregated by the action of the flocculant.

Therefore, the bond between fine particles and fibers is extremely poor.
In addition, since the fibers and fine particle substrates have a surface charge, they do not fall off easily even with a slight external force, so if a cationic flocculant is used as the flocculant, the bonding force due to electrostatic attraction is added and the adhesion can be made even stronger.

After fixing the fine particles in this way, they are heated and foamed to form microscopic hollow spheres, and then paper is made.In order to create a denser deposited layer of microscopic hollow spheres during paper making, microscopic hollow spheres exist between the fibers. However, in addition to the spaces created by the expanded micro hollow spheres between the fibers, it is also effective in creating other voids between the fibers by intervening between the fibers.

Next, an example of the present invention will be described. First, unfoamed fine particles of polyvinylidene acrylonitrile microscopic hollow spheres of 10 parts by weight were mixed with NBKP beaten into 260 cc of C3F, and further 2 to 3 parts by weight of polyethyleneimine was added. Coagulates fibers and fixes fine particles.

This is heated to 80° to 90°C to foam the fine particles,
Next, paper is made and dried.

Table 1 shows the physical properties of the diaphragm thus obtained and the diaphragm using only NBKP.

As is clear from the table, although the density of the diaphragm manufactured by the method of this invention is significantly reduced, the Young's modulus (E) remains almost unchanged, E/ρ increases, and the internal loss (tanδ) also slightly increases. I understand.

As described above, according to the manufacturing method of the present invention, not only the spaces excluded by the foam-containing fine particles, but also other voids can be formed between the fibers by the foam-containing fine particles interposed between the fibers. Not only can the densification effect be fully demonstrated, but since the fixation of fine particles to fibers utilizes the agglomeration and electrostatic effects of the fibers, only a small amount of coagulant is required, and the fixation by rubber emulsion is much easier. Since the method does not assume that the resin itself is deposited, there are no factors that offset the advantages of the low-density diaphragm, such as the weight increase due to adhesion of the fixing agent.

As described above, according to the manufacturing method of this invention, low density,
It has excellent advantages such as being able to provide a diaphragm with high rigidity and high internal loss, and having little loss of material and being very economically advantageous.

Claims (1)

[Claims] 1 Vinylidene chloride-acryloni) Unfoamed microparticles of IJ Le micro hollow spheres are beaten and mixed with sufficiently fibrillated cellulose fibers or non-cellulose fibers, and a polymer flocculant is further added. A method for manufacturing a diaphragm for a speaker, which comprises fixing the fine particles, followed by heating and foaming, paper-making, drying, or, if necessary, light press molding.