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JPH05247879

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DESCRIPTION JPH05247879
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
paper-made body obtained by forming microbially produced cellulose (so-called bacterial
cellulose) and a method for producing the same, and further to an acoustic diaphragm using
microbially produced cellulose and a method for producing the same It is about
[0002]
[Background Art] Cellulose produced by microorganisms such as bacteria is mainly composed of
highly crystalline α-cellulose, and has features such as very fine and strong orientation, and its
effective use is examined in various fields. It is done. For example, JP-A-59-120459 describes
that the sheet of the microorganism-produced cellulose is used as a medical pad, and JP-A-61281800 discloses a diaphragm for acoustic use. It is proposed to use.
[0003]
By the way, when using the above-mentioned microorganism-produced cellulose, it is necessary
to form a film or a sheet by some method. And conventionally, as a method of film-forming or
sheet-forming microorganism-produced cellulose, a method of dehydration and drying using a
press etc. as it is without breaking the microorganism-produced cellulose gel sheet obtained by
culturing, or the microorganism-produced cellulose cultured A method is known in which the gel
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is completely disintegrated by a mixer or the like to form a slurry, and then wet forming is
carried out similarly to paper.
[0004]
However, in the case of the former, when it is intended to obtain a sheet having a fixed shape,
production control from the culture stage is required, and the productivity is low and there are
many problems in terms of the manufacturing cost. For example, when the press method is
applied to the production of an acoustic diaphragm, it has the advantage that it has the
advantage that a specific structure that is built by bacteria and that exhibits excellent acoustic
characteristics is reflected in the diaphragm without being broken. It is necessary to culture the
microorganism-produced cellulose by matching the shape and weight to the vibrator plate to be
manufactured, and strict culture control is required for culture time and the like, which is not
suitable for industrial scale production.
[0005]
On the other hand, in the latter case, the microorganism-produced cellulose gel is subjected to
disaggregation using a mixer or the like, so the shape and weight during culture are not limited,
and the culture process becomes very productive. The slurry obtained by disaggregating the
microorganism-produced cellulose gel is in a state in which microfibrils with a diameter of about
0.02 μm and a length of several hundred μm are dispersed in water, so drainage and
dehydration take a long time during paper making, After all productivity is very bad.
[0006]
In addition, when applied to the production of an acoustic diaphragm, a structure that expresses
excellent acoustic characteristics built by bacteria is destroyed, and the excellent acoustic
property that is a feature of the bacterial cellulose diaphragm may be greatly impaired. There is.
[0007]
Accordingly, the present invention has been proposed in view of such conventional
circumstances, and it is an object of the present invention to eliminate the need for production
control at the culture stage and to facilitate drainage and dewatering during papermaking. It aims
at providing a paper-making object and an acoustic diaphragm excellent in productivity by this,
and also providing those manufacturing methods.
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Another object of the present invention is to provide an acoustic diaphragm capable of
maintaining the excellent physical properties of microorganism-produced cellulose and having
excellent acoustic characteristics, and a method for producing the same.
[0008]
[Means for Solving the Problems] As a result of intensive studies to achieve the above-mentioned
purpose, the present inventors finely cut the gel of microorganism-produced cellulose to make it
into a granular gel. The knowledge that water easily escapes and drainage and dehydration can
be completed in a short time has led to the completion of the present invention.
That is, the sheet-formed body of the present invention is characterized in that a slurry
containing particulate microbially-produced cellulose gel is formed into a sheet, and at least a
part of the cellulose-based fibers is microbially-produced cellulose. The method for producing a
paper-made body of the present invention is characterized in that the microorganism-produced
cellulose gel is finely divided into particles, and a slurry containing the microorganism-produced
cellulose gel particles formed thereby is formed into a paper.
[0009]
The acoustic diaphragm of the present invention is characterized in that a slurry containing
particulate microorganism-produced cellulose gel is formed into a paper, and at least a part of
the cellulose-based fiber is made of microorganism-produced cellulose. Furthermore, the method
for producing an acoustic diaphragm according to the present invention is characterized in that
the microorganism-produced cellulose gel is finely divided into particles, and a slurry containing
the microorganism-produced cellulose gel particles formed thereby is formed into a paper. .
[0010]
The microorganism-produced cellulose used in the present invention is produced microbially by
cultivating certain bacteria, and contains cellulose and cellulose-based heteropolysaccharide, and
β-1, And glucans such as β-1, 2 etc.
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Components other than cellulose in the case of heteropolysaccharides are mannose, fructose,
galactose, xylose, arabinose, hexacarbon sugars such as rhamnose, glucuronic acid etc., five
carbon sugars, organic acids and the like.
[0011]
The microorganism that produces the above-mentioned microorganism-produced cellulose is not
particularly limited, but there are no limitations, but Acetobacter aceti subspasi xylinum
(Acetobacter aceti subsp xylinum), Acetobacter pasteurian (Acetobacter pasteurian), Acetobacter
rancens (Acetobacter ranns), Sarcyna bentorikuri (Sarcina ventriculi), Bacterium xyloides,
Pseudomonas bacteria, Agrobacterium bacteria, etc. can be used.
[0012]
The method of cultivating these microorganisms to produce microorganism-produced cellulose
may follow a general method of cultivating bacteria.
The resulting microorganism-produced cellulose has a structure in which microfibrils are
intertwined, and is obtained in the form of a gel. The obtained microorganism-produced cellulose
may be used as it is, or may be reformed by treating with an alkaline solution or a bleaching
agent, and the total nitrogen content is 1.5% by weight or less, and the α-cellulose content is
95% by weight You may use as above.
[0013]
In the present invention, the above-mentioned microorganism-produced cellulose is formed into
a paper-made body or an acoustic vibration plate, but at this time, the microorganism-produced
cellulose is finely divided while maintaining the state of gel without disaggregating the
microorganism-produced cellulose. A gel particle is formed into a slurry containing this. The
microorganism-produced cellulose gel particles retain water and maintain the gel state, and in
this respect, they are greatly different from those which are deaggregated.
[0014]
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The method of finely dividing the above-mentioned microorganism-produced cellulose into
microorganism-produced cellulose gel particles is arbitrary, and any method may be adopted.
However, if a specific method is exemplified, food chopper, food The method of mechanically
subdividing with a cutter, a meat chopper, etc. is mentioned. Alternatively, a method of rapidly
freezing the microorganism-produced cellulose gel with liquid nitrogen or the like and
pulverizing it with a freeze crusher is also suitable.
[0015]
Size (average particle size) of finely divided microorganism-produced cellulose gel particles. Here,
the average maximum length of particles is used. ) May be arbitrarily selected according to the
application, but from the viewpoint of shortening the drainage time at the time of sheet making
to improve the productivity, it is preferable to set the average particle diameter to 0.1 mm or
more. In addition, the average particle diameter is preferably 3 mm or less because the
uniformity of the obtained sheet-formed body or acoustic diaphragm is deteriorated.
[0016]
[Function] When microbially produced cellulose is disintegrated, microfibrils are dispersed in
water, and when it is made into paper, it takes a very long time for drainage and dehydration. On
the other hand, when a slurry containing gel particles obtained by finely dividing the cultured
microorganism-produced cellulose gel is formed into a sheet, water is easily released because it is
in the form of particles, and drainage and dewatering can be completed in a short time.
[0017]
Further, since the cultured microorganism-produced cellulose gel is finely divided and used, there
is no restriction on the shape and the like at the time of culture.
[0018]
On the other hand, the factors that microbe-produced cellulose exerts excellent physical
properties (for example, acoustic physical properties) are: (1) a specific network structure
constructed by bacteria (cellulose fibrils are branched because the bacteria divide and reproduce
while making cellulose; A mesh structure is formed.
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(2) Ultrafine fibers with a thickness of 0.02 to 0.05 μm (referred to as cellulose or fibrils). And
when forming a paper-made body, there are much more bonds between fibers that control
strength, ie, hydrogen bonds between cellulose fibers, than a paper-made body (eg, paper)
composed of thick fibers of 20 to 50 μm. Existence, (3) Dehydration, large surface orientation
simultaneously with drying.
[0019]
Here, disaggregation of the microorganism-produced cellulose completely destroys the features
of (1) and (2), so that the physical properties (for example, acoustic physical properties) are
greatly reduced. On the other hand, when the microorganism-produced cellulose gel is used in
the form of particles, the features of (1) to (3) are left in the particles, and the aggregate of the
particles is scaly which is surface-oriented by dehydration drying. The cellulose has a laminated
structure, and the physical properties are not greatly reduced.
[0020]
EXAMPLES Examples to which the present invention is applied will be described in detail with
reference to specific experimental results.
[0021]
Preparation of Microbe-Produced Cellulose Gel A medium having a composition comprising
sucrose 5 g / dl, yeast extract 0.5 g / dl, ammonium sulfate 0.5 g / dl, potassium hydrogen
phosphate 0.3 g / dl, and magnesium sulfate 0.05 g / dl pH 5.0) 50 ml was put into a 200 ml
Erlenmeyer flask, and steam-sterilized at 120 ° C. for 20 minutes to prepare a culture solution.
[0022]
Then, the culture solution is grown at 30 ° C. for 3 days in a test tube slope agar medium (pH
6.0) having a composition consisting of 0.5 g / dl of yeast extract, 0.3 g / dl of peptone and 2.5 g
/ dl of mannitol. One platinum loop of each of the prepared Acetobacter aceti subsp. Xylinum
(ATCC 10821) was inoculated and cultured at 30.degree.
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After culturing for 30 days under the above conditions, a gel containing white bacterial cellulose
polysaccharide was formed in the upper layer of the culture solution.
[0023]
The obtained gel was reformed by immersing in a 4% sodium hydroxide solution at 20 ° C. for 3
hours, and then washed with distilled water until the washing solution showed no alkalinity.
[0024]
Measurement of papermaking drainage time The microorganism-produced cellulose gel
(hereinafter referred to as BC gel) obtained as described above.
) Was rapidly frozen with liquid nitrogen, pulverized and granulated by a freeze pulverizer (A10,
manufactured by JANKE & KUNEL), and fractionated by particle diameter using a sieve (TESTING
SIEVE).
[0025]
Next, paper making was performed using the crushed and granulated BC gel particles, and the
drainage time was measured.
In the measurement, as shown in FIG. 1, a 150 mesh paper mesh 2 is provided at the bottom of a
cylindrical body 1 having a height of 150 mm and a diameter of 80 mm so as to have a paper
diameter of 70 mm. The solution was suctioned and drained from the conical suction unit 3
under a suction vacuum pressure of 400 mmHg.
[0026]
The results are shown in Table 1. In addition, it measured also about the slurry which
disaggregated the same BC gel for comparison.
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[0028]
As apparent from this table, when BC gel particles are used, the drainage time is significantly
shortened as compared to the deaggregated slurry, and the drainage time is shorter as the
average particle diameter is larger. . Although not described in Table 1, when BC gel particles
having an average particle diameter of 3 μm or more were used, the drainage time was short,
but the obtained sheet tended to have poor uniformity. The
[0029]
Measurement of Acoustical Properties The acoustical properties of the sheet obtained by the
above-described method were measured. The measurement items are internal loss tan δ,
Young's modulus E, density d, and longitudinal wave propagation velocity C. The measurement
was performed by the vibration lead method. Further, for comparison, the same measurement
was performed on a sheet obtained by dewatering and drying BC gel by a press and a sheet
obtained by forming a slurry obtained by disaggregating BC gel. The results are shown in Table
2.
[0031]
When the longitudinal wave propagation velocity C is compared on the basis of a sheet
dewatered and dried by BC gel, the sheet obtained by forming a slurry from which the BC gel is
disintegrated is reduced by about 40%. In the sheet obtained by forming the particles, the
decrease is about 10 and the excellent properties are maintained.
[0032]
Preparation of Acoustic Vibrating Plate A cone-type vibrating plate was prepared by a papermaking method using BC gel particles having an average particle diameter of 1 to 0.5 mm, and a
full-range speaker unit having a diameter of 12 cm was made.
The weight of the diaphragm was 2.0 g. A diaphragm was produced without breaking the
cultured gel, and a full range speaker unit similar to that of Example 1 was made on a trial basis.
A diaphragm was manufactured using disaggregated BC gel, and a full range speaker unit similar
to that of Example 1 was made on a trial basis.
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[0033]
The frequency characteristics of the output sound pressure level of these speaker units were
measured. As shown in FIG. 2, in Example 1, substantially the same characteristics as in
Comparative Example 1 were obtained, and the diaphragm by the same paper-making method
(Comparative Example 2) In comparison with the above, it was found that the high frequency
reproduction limit frequency is shifted to the high frequency side by the effect of the high
Young's modulus, and the reproduction frequency band is expanded.
[0034]
Example 2 A mixture of BC gel particles having an average particle diameter of 1 to 0.5 mm and
pulp (KP) was mixed at a weight of 1: 1, and a speaker unit similar to that of Example 1 was
made on a trial basis.
A softwood kraft pulp (N. B. KP) was beaten with a Horender-type beater to a Canadian standard
freeness of 560 ml, a diaphragm was produced by a normal paper-making method, and a speaker
unit similar to that of Example 1 was produced.
[0035]
The frequency characteristics of the output sound pressure level of the embodiment 2 and the
comparative example 3 are shown in FIG. 3, but the regeneration frequency band is expanded
also in the embodiment 2 due to the effect of the Young's modulus as in the embodiment 1. The
acoustic properties of the diaphragms of Example 2 and Comparative Example 3 are shown in
Table 3.
[0037]
Further, in Example 2 and Comparative Example 3, when the paper-making drainage time when
producing the diaphragm was performed in the same manner as the previous experiment, it was
75 seconds in Example 2 and 20 seconds in Comparative Example 3. The In the case of mixing
with BC gel particles, although a slight drainage time is required as compared with the case of
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pulp alone, the drainage speed is greatly improved as compared with the case of disaggregation
and sheet making.
[0038]
As apparent from the above description, in the present invention, since the BC gel is formed into
particles and formed into a sheet, there is no restriction on the shape at the time of culture, and
culture management can be carried out. Not only it becomes easy, but the drainage and
dewatering time at the time of sheet making become short, and the productivity can be greatly
improved.
[0039]
For example, in the case of an acoustic diaphragm, culture in a shape conforming to the shape of
the diaphragm is not necessary, and weight control is eased. In addition, since the drainage speed
at the time of paper making, which influences the productivity of the diaphragm, is high, the
paper making time can be reduced to about 1/3.
Moreover, since the acoustic diaphragm obtained has left the structure which the bacteria
constructed | assembled in particle | grain inside, it can maintain the outstanding physical
property.
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