Note: Descriptions are shown in the official language in which they were submitted.
55421
BAC~GROUND OF THE INVENTION;
The present invention concerns a method for producing
shaped articles having a high mechanical strength by applying a
technique of electrodeposition on an aqueous suspension of a
fibrous substance having an electrophoretic property, and an
apparatus for producing the same.
The herein used term, "a fibrous substance having an
electrophoretic property" means a fibrous protein such as collagen
contained in skins and tendons of mammals, fibroin in silk,
lo keratin in hair, fibrinogen in blood, myosin in muscles and casein
in milk.
Hitherto, methods for producing shaped articles such as
casings for packing of sausages, threads for surgical operation,
guts for tennis-racket and sheets for artificial skin by electro-
depositionai shaping of a fibrous substance having an electro-
phoretic property, for instance, a proteinous fibril such as
collagen have been known. The above-mentioned publicly known
method, for instance as is disclosed in Japanese Patent Publica-
tion No. 13636/1971, comprises a process in which an aqueous
suspension of the above-mentioned proteinous fibril is supplied
into a vessel provided with at least.one cathode and at least one
ano~e, and by impressing a direct electric potential between the
two electrodes, the above-mentioned proteinous fibril is
accumulated electrodepositionally onto the surface of one of the
electro~es to form shaped articles,
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In the above-mentioned method, when the pH of the
above-mentioned aqueous suspension is adjusted to lower than 6,
the proteinous fibrils are electrically deposited selectively on
the surface of cathode, and on the other hand when it is adjusted
to higher than 9, the proteinous fibrils are electrically depositec
selectively onto the surface of the anode.
However, in the above-mentioned method of electrodeposi-
tion, when the operation is continuously carried out, since the
electrodeposited shaped articles are continuously removed away
lo fromthe electrode and the aqueous suspension of the proteinous
fibril is continuously supplied into the vessel of electrodeposi-
tion as a raw material, the proteinous fibrils in the aqueous
suspension electrophoretically move to the almost same direction
as the direction of the flow of the aqueous suspension (the
aqueous suspension flows to a fixed direction in the vessel of
electrodeposition) and deposit on the surface of electrode.
Accordingly, the electrodepositionally shaped articles
have a structure in which the proteinous fibrils are oriented
almost into one and same ~ixed direction and so, there is a defect
that the article is mechanically weaker.
In consideration of the above-mentioned situation,
Japanese Patent Publication No. 24257/1972 proposes the following
method according to which the mechanical strength of the shaped
articles obtained by the process of continuous electrodeposition
will be improved.
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That is, in the case where an aqueous suspension of
proteinous fibril of protein is continuously introduced into the
vessel of electrodeposition in the same procedures as described
above and the proteinous fibrils are electrically deposited from
the suspension to the prescribed surface of the electrode, and the
thus shaped articles by electrodeposition of the proteinous fibril
is continuously removed from the vessel, the aqueous suspension
in the vessel of electrodeposition is given a flow to the direc-
tion different from the direction of removing the shaped product
lo and thus the fibrils being deposition in the shaped article take
an entangled structure and the mechanical strength of the shaped
article is improved.
In addition, the apparatus for production of the above-
mentioned shaped articles disclosed in;th~ above-mentioned
Publication comprises a vessel for electrodeposition provided with
at least one pillar-shaped electrode for the base of electrodepo-
sition, at least one opposing electrode, a means for continuously
removing the pipe-shaped articles electrically deposited on the
surface of the above-mentioned electrode for the base of electro-
~o deposition from the vessel for electrodeposition and a means for
giving a flow of a different direction from the direction of
removing the above-mentioned formulated objects to the aqueous
suspension of proteinous fibrils, introduced into the vessel for
electrodeposition. The means for giving the above-mentioned flow
to the above-mentioned aqueous suspension disclosed in the above-
mentioned Publication comprises a method in which a spirally
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ascending flow is caused in -the above-mentioned aqueous suspension
by installing spiral ribbon(si in the inner surface of the vessel
for electrodeposition and by forwarding the aqueous suspension
from the lower region of the vessel to the tangential direction
against the cross section of the vessel, or a method in which a
rotary flow is caused in the above-mentioned aqueous suspension
by rotating a stirrer around the above-mentioned pillar shaped
electrode onto which the fibrous substance is to be electrodepo-
sited, the stirrer having been installed on the opposite electrode
lo or installed separately.
However, according to the method and the apparatus
disclosed in the above-mentioned Japanese Patent Publication No.
24257/1972, although the proteinous fibrils in the shaped articles
obtained as the articles electrodeposited onto the electrode have
entangled mutually owing to the intra-vessel flow of the aqueous
suspension into the different direction to the direction of
removing the shaped articles, since the above-mentioned aqueous
suspension has only one direction of rotation, the shaped article
obtained as the electrodeposited body on the electrode is composed
~o of a single layer in which only one and same structure substantial
ly presents. Accordingly, the mechanical strength of the shaped
article obtained by the application of the above-mentioned method
and ap~aratus is not satisfactory.
The inventors of the present invention, as a result of
studies based on the presumption that the mechanical strength of
the electrodeposited shaped article consisting of the above-
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mentioned fibxous substance will be remarkably improved by giving
the shaped article a laminated layer structure of the fibrous
substance, each layer having direction of orientation of the
fibrous substance different from each other, have found that in
the process of electrodeposition, such laminated layers in the
deposited shaped articles are available and as a result, the
mechanical strength of the thus obtained shaped article is
extremely improved by causing at least two flows different from
each other in direction in the aqueous suspension of the above-
lo mentioned fibrous substance during the operation of electrodepo-
sition. .
Accordingly, one object of the present invention is to
offer a method for producing, from an aqueous suspension of an
electrophoretic fibrous substance, the shaped articles excellent
in mechanical strength comprising a structure of laminated layers
of the fibrous substance, in which the direction of orientation
of the fibrous substance in the layer is different from layer
after layer.
Another object of the present invention is to offer an
apparatus for producing continuously the above~mentioned shaped
articles from the above-mentioned aqueous suspension of the
fibrous substance.
Still another object of the present invention is to offe~
shaped articles having a high mechanical strength comprising
laminated layers of the above-mentioned fibrous substance, the
direction of the orientation of the fibrous substance in each
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layer of the la~inated la~ers being different from layer after
layer.
BRIEF EXPLANATION OF DRAWINGS:
Figure 1 is a vertical sectional plan for the exemplifi-
cation of the apparatus of the present invention, and Figure 2 is
a vertical sectional plan for another exemplification of the
apparatus of the present invention, Figure 3 is a sectional plan
in the direction of A-A' of Figure 2.
DETAILED DESCRIPTION OF THE INVENTION:
The characteristic feature of the present invention is,
in the electrodeposition ofa fibrous substance having an electo-
phore`tic property and having been suspended in an aqueous medium,
to cause at least two flows different in direction in the aqueous
Suspensionintroduced into a vessel for electrodeposition,
particularly in the vicinity of the surface of electrode onto whic~
the fibrous substance in the aqueous suspension is deposited.
Accordingly, the characteristic feature of the apparatus of the
present invention is the installation of the means for causing
the above-mentioned flows in the above~mentioned aqueous suspen-
` 20 sion within the vessel for electrodeposition.
The present invention will be explained in detail while
referring to the Drawings as follows-
According to the process of the present invention, at the
first place, an aqueous suspension of a fibrous substance having
an electrophoretic property, as the starting material, is prepared
by an ordinary procedure. For instance, in the case of using a
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raw hide of mamals as the startin~ material~ it is finely cut by
a slicer and after delining and fine-cutting by a refiner, it is
brought into suspension in water at a content of about 1~ of solid
in the thus prepared suspension and the pH of the aqueous suspen-
sion is adjusted to lower than 6, for instance 3.5 to be the
starting material.
In the next place, the thus prepared aqueous suspension
is introduced into a cylindrical vessel for electrodeposition
shown in Figure 1. The cylindrical vessel 1 for electrodeposition
lo (hereinafter referred to as E.D. vessel) for use in the process of
the present invention is provided with at least one c~lindrical
anode 2 within E.D. vessel 1 and at least one cylindrical cathode
3 in the central region of E.D. vessel. Around the cathode 3,
two spirally formed guide plates 4 and 4' are installed, these
guide plates being so designed that the flow of the above-mentionec
aqueO~ussuspension in E.D. vessel is deflected into at least 2
mutually different directions by them. In the lower region of
E.D. vessel 1, a supply port 5 for the aqueous suspension and in
the upper region of E.D. vessel 1, a roller 6 for taking out the
shaped articles electrodeposited onto cathode 3 from E.D. vessel
1 are respectively installed.
In addition, the apparatus shown in Figure 1 is provided
with a diaphragm 8 between anode 2 and cathode 3, and the acidic
solution such as an aqueous hydrochloric acid solution is place
between the diaphragm 8 and anode 2 to prevent the fluctuation of
pH in the liquids in the anode chamber and the cathode chamber.
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In Fig~ 1, the outlet of the effluent aqueous suspension, the
inlet for the acidic solution and the outlet for the acidic solu-
tion are shown by 7, 9 and 10, respectively.
On carrying the electrodepositional shaping with the
introduction of the aqueous suspension of the above-mentioned
fibrous substance into the above-mentioned apparatus for electro-
deposition, the aqueous suspension is introduced into E.D. vessel
1 from the supply port 5, and a direct electrical potential is
applied between the above-mentioned anode 2 and cathode 3.
Then the introduced aqueous suspension flows along the
above-mentioned guide plates 4 and 4' with a spiral motion, the
direction of the spiral motion being, as is shown in Figure 1,
counter clock-wise in the region at the lower part of cathode 3
by the guide plate 4, and on the other hand, clock-wise in the
region at the upper part of cathode 3 by the guide plate 4'.
Naturally, almost all the length-wise directions of the respective
fibrils in the aqueous suspension are equal to the direction
of spiral motion of flow of the aqueous suspension, and
accordingly, the shaped article formed by the electrodeposited
fibrous substance onto the cathode 3 comprises laminated layers
having different orientation of the fibrous substance from layer
after layer.
The apparatus according to the present invention, as is
shown in Figure 1, in the case where the fibrous substance is to
be electrodeposited onto the outer circum~erence of one electrode,
may be provided with at least more than two guide plates 4(s) in
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spiral with at least more than one pitch, for instance four or
six plates with their direction of spiral inversed alternately.
In addition, it is preferable that the guide plates 4 are
installed almost all over the surface cf the electrode onto
which the fibrous substance is electrodeposited, however, there
are some cases where the guide pla es are installed only at the
end parts of the electrode. The lead angle of the above-mentioned
guide plate 4 is preferably 30 to 60, more preferably 40 to 50.
In the case of the angle of smaller than 30 , since the
resistence of the plate to the liquid is too large, the liquid
goes straight between the electrode and the guide plate with the
result that the orientation of the fibrous substance is directed
to the direction of the flow of the liquid. Accordingly, the
purpose of installing the guide plate is not achieved. On the
other hand, in the case of the angle of larger than 60, the
effect of directing the orientation of the length-wise direction
of the fibrous substance is too weak. Accordingly, the angle of
larger than 60 is also unfavorable.
In addition, it is preferableto install the guide plates
~O at a distance of 1 to 13 mm, more preferably 3 to 8 mm apart from
the surface of the electrode onto which the fibrous substance
accumulates.
Figures 2and 3 show the other instances of the apparatus
of the present invention, in which the E.D. ~essel 1 is provided
with two plate-shape electrodes 11 and 12 placed face to face.
Of these electrodes, in the vicinity of the surface of the
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electrode onto which the fibrous substance is to be electro
deposited (electrode 11 in Figure~, more than two guide plates
13, 13' .. are installed, the plates having different directions.
In addition, as the apparatus shownin Figure 1, the
apparatus shown in Figures 2 (and 3 ) has the inlet 5 of the
aqueous suspension, the roller 6 for taking out of the shaped
articles, the supply port 9 for the acidic solution and the outlet
10 of the solution.
On carrying out electrodeposition by the use of the
apparatus shown in Figures 2 ~and 3), the similar procedures to
those taken in the operation of the apparatus shwon in Figure 1
may be preferably taken. In this case, since the aqueous
suspension of the fibrous substance introduced into E.D. vessel 1
flows along the guide plates 13, 13' ... , the shaped articles,
comprising laminated layers with each layer comprising the
deposited fibrous substance haivng different direction of orienta-
tion from layer after layer corresponding to the number of guide
plates installed in E.D. vessel 1, are obtained. For instance,
with four guide plates so installed that their directions are
different among them, the shaped articles with a four-layered
struc~ure in which the direction of orientation of the deposited
fibrous substance is different from layer after layer are obtained
Moreover, the multi-layered shaped articles are also
available by altering the lead angle of the above mentioned lead
plates 13, 13' ... in the range between 30 to 60 while altering
the flow rate of the above-mentioned aqueous suspension in the
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range between 5 to 50 cm/sec during the operation of electrodeposi
tion.
By the way, it is naturally possible, in cases of
electrodeposition of the ahove-mentioned fibrous ~ubstance using
the apparatus shown in Figure 1 or 2, to have the fibrous
substance deposited on the surface of anode by adjusting the pH
of the aqueous suspension in an alkaline region.
According to the present invention, the
proteinous fibers such as collagen, fibroin, keratin, fibrinogen,
myosin and casein are possibly electrodeposited to be shaped
articles, as has been described.
In addition, the aqueous suspension of each substance
. for use in electrodeposition may contain several additives unless
they give harmful effects on the operation of electrodeposition.
As such an additive, for instance, reinforcing fibers, fillers,
defoaming agents, surfactants, etc. may be mentioned.
The content of solid matter in the above-mentioned aqueouc
suspension for use in electrodepositional shaping according to the
present invention is not specifically limitative, and as in
conventional methods, the content in percentage of 0.3 to 1.0% by
weight based on the fibrous substance in dryness may be preferable.
In addition, the temperature and the flow rate of the
aqueous suspension inthe process of electrodeposition according to
the present invention as well as the voltage of direct current in
that case may be adjusted not limitatively in accordance with the
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conventional method.
According to the present invention, by selecting the
form and shape of the electrode onto which the fibrous substance
is electrodeposited, not only the pipe-form shaped articles
but also variously shaped articles such as sheets for artificial
skin, threads for surgical operations and guts for rac~et are
optionally produced.
Since the shaped articles obtained according to the
present invention comprise, as has been described, laminated
lo la~ers with the direction of orientation of the layer-forming
fibrous substance different from layer after layer, their
mechanical strength in longitudinal direction is scarcely
. different from that in transversal direction, and they are
extremely higher than the mechanical strength of the shaped
articles obtained according to the conventional methods, and
particularly, the tear-strength of the shaped articles
obtained according to the present invention has been remarkably
improved.
The followings are the concrete explanation of the
20 present invention while referring to Examples, and the superiority
of the present invention to the conventional methods is explained
by the comparison to Comparative examples of the conventional
methods.
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EXAMpLE 1:
._ . .
An E,D, yessel comprising a cylindrical vessel made of
vinyl chloride resin, 100 mm in inner diameter and 700 mm in
height, provided with a cylindrical platinum wire netting of 75 mm
in diameter as the anode therein, a diaphragm within the wire
netting, a stainless-steel tube of 17 mm in outer diameter as the
cathode in the central region of the vessel and a spiral-form guide
plate around the above-mentioned anode, as shown in Figure 1 was
used for electrodeposition. The lead angle of the above-mentioned
lo guide plate was 45, and the spiral had 4 pitches so that the
aqueous suspension introduced into E.D. vessel rotated counter-
clockwise in the region at the lower part of the cathode and
rotated clock-wise in the region at the upper part of the cathode.
After introducing an aqueous hydrochloric acid solution
of pH of 2.5 between the cathode and the diaphragm, an aqueous
suspension of 0.5% by weight of fibrous collagen prepared in
advance at pH of 3.6 was introduced from the supply port into the
space between the cathode and the diaphragm at a flow rate of
25 cm/sec while applying a potential of 500 V between the electrode s
to electrically deposit the fibrous collagen onto the cathode.
The thus deposited tubular shaped articles were taken ou. from Eo
D. vessel by a roller installed at the upper part of the vessel at
a pull;ng-up velocity of 8 m/min to be a collagen-casing~A) of 15
microns in thickness as the product.
E~AMPT~ 2
In E.D. vessel used in Example 1, instead of the spiral
:
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guide plate, four plates designed to ~iYe xotating motions
successively of counter clock-wise, clock-wise, counter clock-
wise and then clock-wise to the flow of the aqueous suspension
were installed.
Collagen casing (B)(with the thickness of 15 microns)
was produced in the thus modified apparatus under the same
conditions as in Example 1.
COMPARATIVE EXAMPLE 1:
Except for using an E.D. vessel without the installation
of spiral guide plate instead of using E.D vessel of Example 1,
collagen casing (C) was produced in the same procedures as in
Example 1.
COMPARATIVE EXAMPLE 2:
Using an E.D. vessel provided with a stirrer around the
cathode instead of the spiral guide plate for giving a rotary flow
to the aqueous suspension, collagen casing (D) was produced by the
same procedures as in Example 1.
COMPARISON OF THE PRODUCTS OF EXAMPLES 1 AND 2 AND
_,
COMPARATIVE EXAMPLES lAND 2:
Tensile strength and tear strength of the respective
products (A~, (B), (C), and (D) were determined in accordance with
the respective methods of the Japane~e Industrial Standard (JIS)
P8113 and P8116. The results are shown in the following Table:
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,. ~
. Table
~,
Item Tensile s2trength Tear strength
(kg/mm ) (g cm/cm)
Specimen Long~itud nal trans~versal longl ~ inal transversal
(A) 2.7 2.8 30 32
_._ ._
(B) 2.7 2.9 38 . 35
_. . __ .. . ,. . .
(C) 2.8 1.5 12 20
(D) 2.5 1.8 15 - 21
From the above-mentioned Table, it will be easily
understood that the collagen casings (A) and (B) obtained by
~ the method of the present lnvention are-remarkably superior
to those (C) and (D) obtained in Comparative examples according
to the conventional methods in their tensile strength and tear
strength~
,
