Method for producing shaped articles by electrodepositional shaping from fibrous substance having electrophoretic property and apparatus for same

Disclosed herein a method for producing shaped articles by electrodeposition utilizing the electrophoretic fibrous substance suspended in an aqueous medium, wherein by deflecting the direction of the flow of the above-mentioned aqueous suspension of the fibrous substance into at least two mutually different direction in the vicinity of the surface of electrode onto which the fibrous substance is deposited electrically in the course of electrodeposition, the thus obtained shaped articles are given a laminated layer-structure of the deposited fibrous substance, in which the direction of orientation of the fibrous substance in the layer is different from layer after layer resulting in a highly raised mechanical strength of the thus shaped articles, and a means for installing the device deflecting the direction of flow of the above-mentioned aqueous suspension into at least two mutually different directions.

BACKGROUND 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, keratin in hair, fibrinogen in blood, 
myosin in muscles and casein in milk, as well as polysaccharides having a 
fiber-forming property such as chitin and alginic acid. 
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 electrodepositional shaping of a fibrous 
substance having an electrophoretic 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 Publication 
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 anode, 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 electrodes to form shaped articles. 
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 deposited selectively onto the surface of the anode. 
However, in the above-mentioned method of electrodeposition, when the 
operation is continuously carried out, since the electrodeposited shaped 
articles are continuously removed away from the electrode and the aqueous 
suspension of the proteinous fibril is continuously supplied into the 
vessel of electrodeposition 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 fixed 
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. 
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 
direction different from the direction of removing the shaped product 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 the above-mentioned Publication comprises a vessel 
for electrodeposition provided with at least one pillar-shaped electrode 
for the base of electrodeposition, 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 
electrodeposition 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 ascending flow is caused in the above-mentioned aqueous 
suspension by installing spiral ribbon(s) 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 electrodeposited, the stirrer having been installed on the 
opposite electrode 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 of a single layer in which only one and same structure 
substantially presents. Accordingly, the mechanical strength of the shaped 
article obtained by the application of the above-mentioned method and 
apparatus 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-mentioned fibrous 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-mentioned fibrous substance during the 
operation of electrodeposition. 
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 offer 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 layer of the laminated layers being different 
from layer after layer.

DETAILED DESCRIPTION OF THE INVENTION 
The characteristic feature of the present invention is, in the 
electrodeposition of a fibrous substance having an electophoretic property 
and having been suspended in an aqueous medium, to cause at least two 
flows different in direction in the aqueous suspension introduced into a 
vessel for electrodeposition, particularly in the vicinity of the surface 
of electrode onto which 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 suspension 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 raw hide of mamals as the starting 
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 
suspension 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 FIG. 1. The 
cylindrical vessel 1 for electrodeposition (hereinafter referred to as 
E.D. vessel) for use in the process of the present invention is provided 
with at least one cylindrical 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-mentioned 
aqueous suspension 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 FIG. 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. In FIG. 1, the outlet of the effluent aqueous suspension, 
the inlet for the acidic solution and the outlet for the acidic solution 
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 electrodeposition, 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 FIG. 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 FIG. 1, in 
the case where the fibrous substance is to be electrodeposited onto the 
outer circumference of one electrode, may be provided with at least more 
than two guide plates 4(s) in 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 of the electrode onto which the 
fibrous substance is electrodeposited, however, there are some cases where 
the guide plates are installed only at the end parts of the electrode. The 
lead angle of the above-mentioned guide plate 4 is preferably 30.degree. 
to 60.degree. , more preferably 40.degree. to 50.degree.. In the case of 
the angle of smaller than 30.degree., 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.degree., 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.degree. is also unfavorable. 
In addition, it is preferable to install the guide plates 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. 
FIGS. 2 and 3 show the other instances of the apparatus of the present 
invention, in which the E.D. vessel 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 electrode onto which the fibrous substance 
is to be electrodeposited (electrode 11 in Figure), more than two guide 
plates 13, 13' . . . are installed, the plates having different 
directions. 
In addition, as the apparatus shown in FIG. 1, the apparatus shown in FIGS. 
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 
FIGS. 2 (and 3), the similar procedures to those taken in the operation of 
the apparatus shown in FIG. 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 desposited 
fibrous substance having different direction of orientation 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 structure 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.degree. to 60.degree. while altering the flow rate of the 
above-mentioned aqueous suspension in the range between 5 to 50 cm/sec 
during the operation of electrodeposition. 
By the way, it is naturally possible, in cases of electrodeposition of the 
above-mentioned fibrous fubstance using the apparatus shown in FIG. 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, other fiber-formable substances such as 
chitin and alginic acid than 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 aqueous 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 in 
the 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 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 
racket are optionally produced. 
Since the shaped articles obtained according to the present invention 
comprise, as has been described, laminated layers 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 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. 
EXAMPLE 1 
An E.D. vessel 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 FIG. 1 was used for electrodeposition. The lead angle of the 
above-mentioned guide plate was 45.degree., and the spiral had 4 pitches 
so that the aqueous suspension introduced into E.D. vessel rotated 
counterclockwise 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 electrodes to electrically deposit the fibrous collagen onto the 
cathode. The thus deposited tubular shaped articles were taken out from E. 
D. vessel by a roller installed at the upper part of the vessel at a 
pulling-up velocity of 8 m/min to be a collagen-casing (A) of 15 microns 
in thickness as the product. 
EXAMPLE 2 
In E.D. vessel used in Example 1, instead of the spiral guide plate, four 
plates designed to give rotating 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. 
COMATIVE 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. 
COMATIVE 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. 
COMISON OF THE PRODUCTS OF EXAMPLES 1 and 2 AND COMATIVE EXAMPLES 1 
AND 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 Japanese Industrial Standard (JIS) P8113 and P8116. The results are 
shown in the following Table: 
TABLE 
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Tensile strength Tear strength 
Item (kg/mm.sup.2) (g . cm/cm) 
Specimen 
Longitudinal 
transversal 
longitudinal 
transversal 
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(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 
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From the above-mentioned Table, it will be easily understood that the 
collagen casings (A) and (B) obtained by the method of the present 
invention are remarkably superior to those (C) and (D) obtained in 
Comparative examples according to the conventional methods in their 
tensile strength and tear strength.