Squid chitin formed material

A novel squid chitin formed material is disclosed. Squid chitin is prepared by pulverizing squid crust and treating the pulverized chitin with caustic soda and then with hydrochloric acid to remove proteins and ashes. Squid chitin formed material such as sheet or fiber is then prepared by a freeze-defrost treatment. The squid chitin sheet and fiber have better physical properties than conventional crab chitin formed materials in terms of strength and folding endurance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a novel squid chitin formed material, and, more 
particularly, to a squid chitin formed material, such as a squid chitin 
sheet, a squid chitin fiber, and the like. The squid chitin formed 
material has excellent characteristics such as superior strength and the 
like. 
2. Description of the Background 
Since formed materials made of chitin are in vivo decomposable, they are 
widely used as suture threads, wound covering or protecting materials, 
dialysis membranes, molecular filters, ultra-membrane filters, and the 
like. 
According to a conventionally known method for preparing materials formed 
of chitin, exoskeletons of a crustacean or an insect are first treated 
with hydrochloric acid and sodium hydroxide, and chitin separated is 
formed into a sheet or the like (Japanese Patent Laid-open Nos. 
53339/1986, 64256/1986, 129005/1986, and 212302/1986). 
Chitins made from exoskeletons of crustacean or insects, however, exhibit 
only poor dope forming capability, resulting in formed chitin materials 
having inadequate characteristics such as insufficient strength, reduced 
elongation, or the like. Thus, chitins produced from conventional sources 
have problems still to be solved. In an attempt to improve the 
insufficient chitin properties, Japanese Patent Laid-open Nos. 53339/1986 
and 64256/1986 propose to employ a water soluble polymer as a binder. This 
method, however, does not necessarily provide a satisfactory solution. 
In view of this situation, the present inventors have undertaken extensive 
studies in order to solve the above problems, and found that among chitins 
produced from a number of raw materials squid chitins made from squid 
crust possessed excellent characteristics. The inventors have further 
found that among squid chitins those produced from squid galadius of 
Mollusca, Teuthoidea, had exceptionally superior characteristics, and 
could be formed into superb chitin sheets and the like. Such a finding has 
led to the completion of this invention. 
SUMMARY OF THE INVENTION 
Accordingly, an object of this invention is to provide a squid chitin 
formed material prepared from squid chitin which is separated from squid 
crust. 
Other objects, features and advantages of the invention will hereinafter 
become more readily apparent from the following description.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS 
Any squid crusts can be used as a raw material for preparing the squid 
chitin formed material of this invention so long as the crusts are those 
from squids belonging to the division of Mollusca, the order of Decapoda. 
Specific examples of the squids are those from the suborder Teuthoidea 
such as Spirula, Sepia, Sepiola, from the suborder Teutoidea such as 
Loligo, Doryteuthis, Sepioteuthis, Watasenia, Onychoteuthis, Architeuthis, 
Tadarodes, Chiroteuthis, Ommastrephes, Illex, Gonatopsis, and the like. 
For preparing squid chitin from squid crust according to this invention, 
squid crust is first pulverized, and treated with caustic soda and 
hydrochloric acid to remove proteins and ashes. More specifically, taking 
the preparation of squid chitin from squid galadius as an example, the 
pulverized squid galadius is treated with sodium hydroxide solution of 
about 1 N at about 90.degree. C. for approximately 1 hour. The treatment 
with hydrochloric acid is performed using an aqueous hydrochloric acid 
solution of around 0.1 N concentration at room temperature for about 1 
hour. Squid chitin is then obtained by drying the treated material thus 
prepared. 
For preparing the squid chitin sheet of this invention squid chitin 
sufficiently ground as fine as 16 mesh is suspended into water at a 
concentration of 5 to 20% by weight, stirred vigorously or subjected to a 
freeze-defrost treatment. Through these treatments the squid chitin 
absorbs water and swells increasing its viscosity, and ultimately becomes 
a gel. The gel is suspended into water and the suspension is submitted to 
a paper-making operation; i.e., it is fed onto a filter to eliminate 
water. The residue is then dried to produce a squid chitin sheet. 
If the above-mentioned procedure is applied to crab chitin, even though it 
is submitted to the stirring operation or the freeze-defrost treatment, 
crab chitin does not form a gel. It is therefore necessary to manufacture 
a crab chitin sheet first to prepare crab chitin fiber and then to make 
the fiber into a sheet, as will be discussed later. Accordingly, a chitin 
sheet made from crab chitin is something like non-woven cloth, which is 
quite different from the squid chitin sheets prepared by this invention. 
Squid chitin fiber can be prepared by the following method according to 
this invention. The squid chitin separated by the procedure mentioned 
above is dissolved into formic acid at a concentration of 2 to 15% by 
weight. (A specific squid chitin concentration in formic acid may vary 
depending on the purpose intended ) Freeze-defrost treatments are 
performed two or three times on this solution to disintegrate inter- or 
intra-molecular hydrogen bonds of squid chitin and to produce a 
transparent and homogeneous dope. The dope is defoamed in vacuo and is 
extruded into a squid chitin coagulating-solvent to produce squid chitin 
fiber. An alcohol such as methanol, ethanol, propanol, butanol, or the 
like, or a ketone such as acetone, methyl ethyl ketone, or the like, or a 
mixture of two or more of these solvents can be used as a squid chitin 
coagulating-solvent. 
If above procedure is to be applied to a chitin from exoskeletons of crabs, 
for example, 20 to 30 times freeze-defrost treatments are required. This 
takes a much longer period of time for the treatment. In addition, this 
long period treatment with formic acid reduces the polymerization degree 
of chitin molecules. This makes it impossible to produce a fiber having a 
sufficient strength. 
Some of the characteristics of a squid chitin sheet and a squid chitin 
fiber prepared from the squid chitin of this invention are compared with 
those produced from a conventional crab chitin. 
(1) Chitin sheet 
Squid chitin sheet: prepared in Example 1 
Crab chitin sheet: prepared in Reference Example 2 
TABLE 1 
______________________________________ 
Breaking Folding 
Weight Strength Endurance 
(g/m.sup.2) 
(KPa m.sup.2 /g)* 
(Times)** 
______________________________________ 
Squid chitin sheet 
29 9.0 &gt;16 (1 kg) 
Crab chitin sheet 
115 1.5 10 (500 g) 
______________________________________ 
*Breaking Strength: The pressure (per unit weight of chitin sheet) 
required to pulverized a chitin sheet. 
**Folding Endurance: A chitin sheet is folded while a pressure is exerted 
to the sheet using a 500 g or 1 kg plumb. "Folding Endurance" is the 
number of times for which the chitin sheet is folded before it is broken. 
(2) Chitin fiber 
Squid chitin fiber: prepared in Example 2 
Crab chitin fiber: prepared in Reference Example 1 
TABLE 2 
______________________________________ 
Strength 
Elongation 
(g/d)* (%)** 
______________________________________ 
Squid chitin fiber 
5.0 5.0 
Crab chitin fiber 
1.6 4.3 
______________________________________ 
*Strength (Pulling strength): The force required to break 50 strings of 
fiber. 
**Elongation: A ratio of elongation (as per the original length) when 50 
strings of fiber is pulled and broken. 
As demonstrated in the above test, the squid chitin formed materials of 
this invention have better physical properties than conventional crab 
chitin formed materials in terms of strength, folding endurance, etc. 
Although the details are still to be elucidated, these superior 
characteristics are presumed to be a result of a more oriented nature of 
squid chitin crystals than crab chitin crystals. 
Other features of the invention will become apparent in the course of the 
following description of the exemplary embodiments which are given for 
illustration of the invention and are not intended to be limiting thereof. 
EXAMPLES 
Example 1 
(i) One (1) kg of Tadarodes galadius was ground by a feather mill (5 m/m 
screen pass). The ground galadius was put into a 1 N NaOH solution, heated 
at 90.degree. C. for 1 hour, washed with water, and dipped into a 0.1 N 
HC1 solution at room temperature for 1 hour. The ground material then was 
washed with water and again heated at 90.degree. C. in a 1 N NaOH solution 
for 1 hour. After washing with water, the material was dried in an oven at 
50.degree. C. for 5 hours to produce 100 g of squid chitin. 
(ii) Ten (10) g of the squid chitin produced in (i) above was pulverized by 
an Osterizer. The pulverized chitin was suspended into 400 ml of water and 
vigorously stirred to increase the viscosity. The viscous gel-like product 
thus obtained was subjected to a conventional water jet fall-type paper 
machine, each 20 ml a batch, and the sheet produced was air-dried at room 
temperature. The squid chitin sheet prepared having a weight of 29 
g/m.sup.2 had breaking strength of 9 KPa m.sup.2 /g and folding endurance 
of at least 16 at a 1 kg plumb weight. 
Letters were printed with ink onto the squid chitin sheet. The ink was well 
attached onto the sheet with no run or blur. 
Example 2 
Twenty (20) g of the squid chitin produced in Example (i) was pulverized by 
an Osterizer to produce a homogeneous chitin particles. 500 ml of formic 
acid was added to the chitin particles. The mixture was stirred slowly, 
and allowed to stand at room temperature until needle-like solid materials 
contained disappeared. After freezing at -20.degree. C., the frozen 
material was thawed, gently stirred, and was again frozen and thawed to 
produce a transparent and homogeneous dope. This dope was deaerated in 
vacuo, and extruded into a mixed solvent of acetone and 50% ethanol 
through a nozzle with 30 holes, each hole having a diameter of 0.09 m/m, 
at an extrusion pressure of 1.5 Kgf/cm.sup.2, and an extender having a 
first roller rotating at 0.1 m/sec. and a second roller rotating at 0.11 
m/sec., to produce wet squid fiber. The squid fiber was neutralized with a 
0.5 N NaOH-methanol mixture, washed with methanol, and air-dried at room 
temperature to obtain dried squid chitin fiber. 
The squid chitin fiber had strength (pulling strength) of 5.0 g/d and 
elongation of 5.0%. The squid chitin fiber produced according to this 
method possessed silky gloss. 
Reference Example 1 
(Preparation of crab chitin fiber) 
(i) One (1) kg of Chionaecetes opilio crab shell (exoskeleton) was ground 
by a coffee grinder. The ground crab shell was put into a 1 N NaOH 
solution, heated at 90.degree. C. for 1 hour, washed with water, dipped 
into a 2 N HC1 solution at room temperature for 6 hours, and then was 
washed with water. This same procedure was performed 3 times. After 
washing with water, the finally obtained material was dried in an oven at 
50.degree. C. for 3 hours to produce 150 g of crab chitin. 
(ii) Twenty-three (23) g of the crab chitin produced in (i) above was 
pulverized by an Osterizer and 490 ml of formic acid was added to the 
chitin particles. The mixture was stirred slowly, and allowed to stand at 
room temperature until needle-like solid materials contained disappeared. 
12 hours after freezing at -20.degree. C., the frozen material was thawed 
at room temperature. The thawed material was gently stirred, and again 
frozen to produce a dope. This frozing-thawing operation was once more 
repeated. The dope finally obtained was deaerated in vacuo, and extruded 
into a mixed solvent of ethyl acetate and water through a nozzle with 30 
holes, each hole having a diameter of 0.09 m/m, at an extrusion pressure 
of 1.3 Kgf/cm.sup.2, and extended at an extension ratio of 1.29. The crab 
fiber was washed in a stream of water overnight to obtain wet crab chitin 
fiber. 
(iii) The wet crab chitin fiber was air-dried at room temperature to obtain 
dried crab chitin fiber. 
Reference Example 2 
Preparation of crab chitin sheet) 
The crab chitin fiber prepared in Reference Example 2 was cut into 5 m/m 
length, and a prescribed amount of the cut crab chitin fiber was suspended 
into water. A conventional water jet fall-type paper milling was performed 
on the crab chitin suspension, and a sheet produced was air-dried at room 
temperature to produce a crab chitin sheet. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that the scope of the appended claims, the invention may be 
practiced otherwise than as specifically described herein.