JPH0423597A - Acoustic diaphragm and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the physical characteristic of the diaphragm by employing a sheet-making material made of a cellulose subject to micro fibril processing for an acoustic diaphragm such as a speaker. CONSTITUTION:Cone paper of an acoustic diaphragm is made of a cellulose subject to micro fibril processing. When a micro fibril cellulose is made sheet, at first a sheet-making screen 2 is mounted to a bottom of a paper machine 1, a reinforcing member 3 is placed on the sheet-making screen 2 and a suspension 4 in which micro fibril cellulose is dispersed is supplied onto the member 3 to screen-make a sheet-made material 5. Since the micro fibril cellulose is sheet-made in this way, the physical characteristic is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an acoustic diaphragm used for speakers, etc., and a method for manufacturing the same, and particularly an acoustic diaphragm using microfibrillated cellulose and its manufacturing method. It is about the method.

[Summary of the Invention] The present invention aims to provide an acoustic diaphragm with excellent physical properties such as Young's modulus and tensile strength by making paper from microfibrillated cellulose.

Furthermore, by making paper while reinforcing microfibrillated cellulose with a reinforcing member placed on a papermaking net, the present invention enables handling even if the wet strength of the paper product is low, and provides an acoustic diaphragm with excellent physical properties. can be manufactured with high productivity.

[Conventional technology]

Conventionally, cone paper made from pulp has been widely used for acoustic diaphragms of speakers and the like.

Cone paper is made through a process of beating pulp, dispersing the beaten pulp in water and swelling it, and making paper into the required shape from the pulp dispersed in water. If paper is made by dispersing the pulp in water, it not only lacks a crisp feel but also has low strength, making it unsuitable for use as a diaphragm. This is because the fibers constituting the pulp are not firmly attached to each other.

Adhesive strength is obtained by softening the fibers and by performing so-called fibrillation, which increases the number of contact points between the fibers and increases hydrogen bonds, rather than unraveling the fibrils that make up the fibers.

This mechanical fibrillation of fibers is called beating, and is usually carried out using a device called a beater.

Incidentally, an acoustic diaphragm is required to have a high longitudinal wave propagation velocity (sound velocity C), and therefore, it is advantageous for the acoustic diaphragm to be made of a material that is light and has a large Young's modulus.

The physical properties of cone paper, such as Young's modulus and tensile strength, are determined by the degree of beating, as mentioned above, and in order to create cone paper with a high Young's modulus, cellulose with a high degree of beating with as much fibrillation as possible is used. There is a need. That is, in corn paper used as an acoustic diaphragm, it is thought that the higher the degree of beating of cellulose used in paper making, the higher the Young's modulus.

(Problems to be Solved by the Invention) However, when the degree of beating of cellulose used for making corn paper increases, its strength in a wet state during paper making is extremely reduced, making it difficult to handle and maintain the shape. If you try to transfer the paper product to another mold while it is still wet, there is a risk that the paper product will lose its shape.

In addition, cellulose tends to get mixed into the papermaking mesh, and when trying to peel off the paper product (cone paper) from the papermaking mesh after drying, due to the high rigidity of the papermaking mesh, an excessive force is applied to the cone at once. There is a risk of damaging the paper.

Alternatively, if the paper is made into a flat sheet and then tried to be molded into a desired shape by press working with a die, there is a high possibility that excessive force will be applied locally and breakage will occur.

Therefore, although it is expected to have advantages in terms of properties, it is difficult to make paper from highly fibrillated cellulose to make acoustic diaphragms due to manufacturing issues.
In particular, it is said that it is extremely difficult to realize a thin diaphragm.

The present invention was proposed in view of the above-mentioned conventional situation, and an object of the present invention is to provide an acoustic diaphragm having excellent physical properties such as Young's modulus and tensile strength. A further object of the present invention is to make it possible to handle even paper products with low wet strength, and to make it possible to efficiently produce a hollow acoustic diaphragm with a Young's modulus made of microfibrillated cellulose.

[Means for Solving the Problem] In order to achieve the above-mentioned object, the acoustic diaphragm of the present invention has the following features:
It is characterized by being made of a microfibrillated cellulose paper product, and further characterized by being made by laminating the microfibrillated cellulose paper product and a reinforcing member.

Further, the manufacturing method of the present invention is characterized in that a reinforcing member is placed on a papermaking net, and a paper is made of cellulose having a Canadian standard freeness of 300 ml or less on the reinforcing member.

In the present invention, the cellulose used in paper making is highly microfibrillated cellulose, and here it is cellulose with a Canadian standard freeness of 300 ml or less. The Canadian standard freeness is set to 300 ml or less because if the Canadian standard freeness exceeds 300 d, the Young's modulus of the acoustic diaphragm used to make paper will be insufficient, and there will be fewer problems with wet strength during paper making. .

Cellulose with the above Canadian standard freeness of 300 m1 or less (
Hereinafter, it will be referred to as microfibril cellulose. ) may be obtained by mechanically beating pulp using a beater or the like. In this case, by appropriately setting the beating conditions using the beater (for example, the beating time, the strength of the force applied during beating, etc.), it is easy to achieve a Canadian standard freeness of 300 ml.
It can be as follows.

Alternatively, bacterial cellulose produced microbiologically by culturing certain bacteria under defined conditions is also suitable.

The above-mentioned bacterial cellulose is composed of highly crystalline α-cellulose, has extremely high strength due to its extremely strong surface orientation, and is extremely fine, with a thickness of 200 to 500.

Bacteria that produce bacterial cellulose include
Acetobacter bacteria are typical, such as Acetobacter aceti and Acetobacter xyli.
num), Acetobacter 0 lances (Acetobacter
Bacterium xyl
oides).

Acetobacter passenarianus (8ce toba)
c terpasteurianus) + Agrobacterium tumefaciens (Agrobacterium
um tumefaciens), and further examples include the genus Pseudomonas and the genus Rhizobium.

The above-mentioned bacterial cellulose can be obtained by producing it as a gel-like substance with a certain thickness at the interface between the medium and air, or by the aeration agitation culture method, etc., but the bacterial cellulose obtained can be obtained by disintegrating it in water. Paper can be made.

When making paper, it is also possible to blend carbon fibers, glass fibers, and polymer fibers such as aramid fibers, polyolefin fibers, ultrastretched polyolefin fibers, and polyester fibers as reinforcing materials into the microfibril cellulose described above. Further, paper additives such as so-called sizing agents and fillers may be added as necessary.

On the other hand, the reinforcing member placed on the papermaking net is used to supplement the wet strength of the paper product made of microfibrillar cellulose, and is about 100 mesh (pore diameter 20
Woven fabrics, nonwoven fabrics, etc., which have voids of about 0 μm) and have some degree of flexibility are suitable.

The material, thickness, etc. of these woven or nonwoven fabrics are optional when they are simply used as reinforcement for paper products, but as described later, when they are integrated with microfibrillar cellulose paper to form an acoustic diaphragm. may be selected depending on the characteristics of the intended acoustic diaphragm. In addition, when the reinforcing member is used simply as reinforcement for a paper product as described above, the reinforcing member is the same.

In other words, it is preferable that the woven fabric or non-woven fabric be made of a material that can be easily peeled off from the microfibrillar cellulose, and when it is directly integrated with the microfibrillar cellulose paper making,
It is preferable to use a material that easily adheres to microfibril cellulose and has high strength and high elastic modulus.

Specifically, woven fabrics or non-woven fabrics such as carbon fiber, glass fiber, polyester fiber, aramid fiber, silk, etc. can be used, and the material may be selected from these in consideration of the above requirements.

In the present invention, in order to make paper from microfibrillar cellulose, first, as shown in FIG. It is placed on a screen (2), and a suspension (4) in which microfibril cellulose is dispersed is supplied thereon to form a paper product (5).

Next, the paper product (5) that has been made into paper is transferred to a drying step to dry it, but at this time, the paper product (5) made of microfibrillar cellulose is placed on the paper making net (2) together with the reinforcing member (3). You can move on to the drying process while it is placed, or you can remove it together with the reinforcing member (3) from the papermaking net (2).
The drying process may be started after this is placed on another mold. In the latter case, since the paper product (5) made of microfibrillar cellulose is handled together with the reinforcing member (3), there is little risk of damage or deformation even if the paper product (5) has low wet strength.

After drying, the reinforcing member may be peeled off from the microfibril cellulose paper (cone paper) and only the microfibril cellulose paper may be used as an acoustic diaphragm, or it may be integrated as it is to form a paper-woven fabric or a cone paper. It may also be a non-woven composite diaphragm.

In the case of the above-mentioned method, the shape of the obtained cone paper is determined by the shape of paper making WI (2), but in the present invention, for example, after making microfibrillar cellulose into a flat sheet, it is formed by drawing with a mold or the like. It is also possible to give it a desired shape.

Note that in any case, a normal paper mesh (2) can be used, such as a wire mesh or a metal plate that has been processed to form holes called punching.

[Effect]

In the acoustic diaphragm of the present invention, since the cone paper is composed of microfibrillated cellulose, there are many contact points between fibers, increasing hydrogen bonding, and improving physical properties such as Young's modulus and tensile strength. It will be done. Furthermore, by laminating and integrating the reinforcing member, the mechanical strength is further improved.

On the other hand, in the manufacturing method of the present invention, microfibrillar cellulose is paper-made on a reinforcing member placed on a paper-making net. Although the paper product made of microfibrillar cellulose has low wet strength, since it is reinforced by the reinforcing member, it is easy to handle even in a wet state, and its shape is maintained.

Furthermore, when the reinforcing member is peeled off from the paper product after drying, since the reinforcing member has flexibility, it can be gradually peeled off from the paper product.
A large force will not be applied inadvertently to the

〔Example〕

Hereinafter, specific examples to which the present invention is applied will be described.

First, bacterial cellulose produced by acetic acid bacteria is disintegrated using a mixer, and then paper is made onto a paper making wire mesh (11) attached with a polyester fiber woven fabric (12) as shown in Figure 2A. A composite consisting of cellulose (13) and woven fabric (12) was prepared. Note that the papermaking conditions, the type of polyester fiber woven fabric (12) that is the reinforcing member, and the drying conditions are as follows.

Microfibril cellulose: Disintegrated product of bacterial cellulose produced by acetic acid bacteria Paper density: 1 g/42 Polyester fiber woven fabric: 100 mesh (pore diameter 200 μm) manufactured by NBC Kogyo Co., Ltd., No. 120 S Drying conditions: Mold temperature 140°C, 5 minutes Next, as shown in FIG. 2B, the cellulose (13) and the woven fabric (12
), a mold with a hemispherical recess (
14A) and a mold (
14B) to obtain a dome-shaped composite diaphragm as shown in FIG. 2C.

Actual m% After paper making and drawing processing were performed under the same conditions as in Example 1, the polyester fiber woven fabric (12) was peeled off to obtain a dome-shaped diaphragm made only of cellulose (13).

Jitsu Itsu 1 Softwood bleached kraft pulp (N, B, KP) was beaten with a Hollender type beater to a Canadian standard freeness of 300, and then subjected to paper making and drawing processing in the same manner as in Example 1, and cellulose and A composite diaphragm made of polyester fiber woven fabric was obtained.

In the above-mentioned Examples 1 and 3, in order to improve the adhesion between cellulose and polyester fiber woven fabric, a binder (manufactured by Nippon Zeon Co., Ltd., Nipole Latex) was added to the cellulose suspension before paper making. LX-300) at a cellulose solid ratio of 10% by weight, a retention improver (wet paper strength enhancer) (manufactured by Dick Vercules, Kaimen 557-
H) was added at a cellulose solid ratio of 5% by weight.

Regarding the diaphragm obtained by the above method, internal loss (tan δ), Young's modulus E, and sound velocity C were measured by the vibration reed method. The results are shown in the table below. The measurement results for a paper diaphragm (a diaphragm made from cellulose paper with a Canadian standard freeness of 560) are also shown in the following table as a comparative example.

Table Comparing the characteristics of the diaphragm obtained in each example and a general paper diaphragm, the diaphragm obtained in each example has a Young's modulus that is 2 to 3 times that of a general paper diaphragm. It turns out that it has.

In addition, unlike conventional paper diaphragms, the diaphragms obtained in each example were film-like and had no pinholes, so we applied J2 a material called a filler, which was essential for paper diaphragms. Impregnation was not necessary, and it was possible to create a thin film diaphragm with a thickness of about 10 μm.

〔Effect of the invention〕

It is clear from the above explanation that the acoustic diaphragm of the present invention is made from microfibrillated cellulose, and furthermore, it is laminated and integrated with reinforcing members, so the physical properties are significantly improved. It is possible to provide an acoustic diaphragm with excellent Young's modulus, tensile strength, etc.

In addition, in the manufacturing method of the present invention, the reinforcing member is placed on the papermaking net and cellulose is made into paper on this, so when making paper from cellulose with low wet strength such as microfibrillar cellulose, can also be easily handled. Therefore, 1. It is possible to efficiently manufacture an acoustic diaphragm with a high Young's modulus.

Furthermore, in the manufacturing method of the present invention, it is possible to easily create a diaphragm made of a composite material made of microfibrillated cellulose mixed with various materials, and diaphragms with various characteristics can be manufactured depending on the application. It is possible to do so.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a papermaking process using a cone-shaped papermaking net. Figures 2A to 2C show the manufacturing process of a dome-shaped diaphragm by drawing. Figure 2A is a schematic cross-sectional view of a flat cellulose-woven fabric composite, and Figure 2B is a schematic cross-sectional view of a flat cellulose-woven fabric composite. FIG. 2C is a schematic cross-sectional view showing the drawing process, and FIG. 2C is a schematic cross-sectional view of a cellulose woven fabric composite formed into a dome shape. 2... Paper mesh 3... Reinforcement member 5... Paper product (cellulose)

Claims (5)

[Claims] (1) Acoustic diaphragm made of microfibrillated cellulose paper. (2) An acoustic diaphragm made by laminating a microfibrillated cellulose paper product and a reinforcing member. (3) A method for producing an acoustic diaphragm, which comprises placing a reinforcing member on a paper-making net, and paper-making microfibrillated cellulose onto the reinforcing member. (4) The method for producing an acoustic diaphragm according to claim (3), wherein the microfibrillated cellulose is cellulose obtained by beating pulp to a Canadian standard freeness of 300 ml or less. (5) The method for manufacturing an acoustic diaphragm according to claim (3), wherein the microfibrillated cellulose is bacterial cellulose produced by culturing bacteria.