CA1324787C - Squid chitin formed material - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
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.

Description

TITLE OF THE INVENTION
SQUID CHI~IN FORMED MATERIAL
BACKGROUND OF THE INVEN~ION

Field of the Invention: :
This invention relates to a novel squid chitin formed material, and, more particularly, to a s~uid chitin formed material, such as a ~quid chitin sheet, a s~uid chitin fiber, and the like. The squid chitin formed material has excellent characteristics such a~
~uperior strength and the like.
Descri~tion of the Backqround:
Since formed materials made of chitin are fn 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 material~ formed of chitin, exoskeletons of a crustacean or an insect are first treated with .:~
hydro~hloric acid and sodium hydroxide, and chitin - .
separated is formed into a sheet or the like (Japane~e Patent Laid-open Nos. 53339/1986, 64256/1986, 129005/1986, and 212302/lY86).
Chitins made from oxoskeletons of crustacean or :-insects, however, exhibit only poor dope forming capability, resulting in form~d chitin materials having '~ ' '''`-, r inadequate characteristic~ such as in~ufficient strength, reduced elongation, or the like. Thus, chitins produced from conventional sources have problems still to be solved. In an attempt to improve the in~ufficient chitin properties, Japanese Patent Laid-open No~. 53339/1986 and 64256/1986 propo~e to employ a water soluble polymer as a binder. This method, however, does not necessarily provide a ~atisfactory solution.
In view of this situation, the pre~ent inventors have undertaken extensive studies in order to solve the above problems, and found that ~mong chitins produced from a number of raw materials ~quid chitins made from squid crust possessed excellent characteristics. The inventors have further found that among squid chitins those produced from squid galadius of ~ol l usca, Teutho~de~, 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.
SllMNARY OF THE INVENTION
Accordingly, An ob~ect of this invention is to provide a ~quid chitin formed material prepared from squid chitin which iB separated from squid crust.
Other ob~ects, features and advantage~ of the .
invention will hereinafter become more readily apparent from the following description.

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132~787 The present invention, in one aspect, resides in a process of preparing a squid chitin sheet comprising:
grinding squid chitin, suspending the ground squid chitin in water, forming a gel of said squid chitin, suspending the gel in water, submitting the suspension to ~iltration to eliminate water, and drying the residue.
In another aspect, the present invention resides in a process of preparing squid chitin fiber comprising:
dis~olving squid chitin in formic acid, subjecting the solution to a freeze-defrost treatment to produce a dope, defoaming the dope in vacuo, and extruding the defoamed dope into a solvent to coagulate the dope.

- 2a -1~24787 D~TAILED DESCRIP~ION OF THE INVENTION
AND PREF~RRED EMBODIMENTS
Any ~quid crusts can be used as a raw material for preparing the squid chitin formed material of thi~
invention 80 long as the crusts are those from squids belonging to the division of ~ollusca, the order of Decapoda. Specific examples of the squid~ are those from the suborder Sepioidea such as Spirula, Sep~a, Sepiola, from the suborder Teuthoidea such as Loligo, Doryteuthis, S~pioteuthis, Natasenfa, Onychoteuth~s, Architeuthis, ~adarode~, Chiroteuth~s, Ommastraph~s, Illex, Gon~topsis, and the like.
For preparing squid chitin from squid crust according to this invention, squid crust i8 first pulverized, and treated with caustic soda and h~drochloric acid to remove proteins and ashes. More specifically, taking the preparation of squid chitin from squid galadius a8 an example, the pulverized s~uid galadius is treated with sodium hydroxide solution of about 1 N at about 90C for approximately 1 hour. The treatMent with hydrochloric acid is performed u~ing an aquaous hydrochloric acid ~olution of around 0.1 N
concentration at room temperature for about 1 hour.
Squid chitin 18 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 ~uspended into water at a concentration of 5 to 20% by weight, ~tirred vigorously or sub~ected to a freeze-defrost tr~atment. Through these treatments the squid chitin absorb~ water and swells increasing it~
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 i8 something like non-woven cloth, which i8 quite different from the squid chitin sheets prepared by thi~ 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 di~solved into formic acid at a concentration of 2 ~-to 15% by weight. ( The specific squid chitin concentration in formic ac~d may vary depending on the purpose intended.) Freeze-defrost treatments are performed two or three times on this solution to di~integrate 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 ~quid chitin coagulating-solvent to produce squid chitin fiber. An alcohol such a~
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 a~ a ~quid chitin coagulating-solvent.
If the above procedure 16 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 de~ree of chitin molecules.
This makes it impossible to produce a fiber having sufficient strength.
Some of the characteristics of a squid chitin aheet and a s~uid 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 ~heet: prepared in Reference Example 2 ::

Table 1 Breaking Folding Weig~t Streng~h Endurance (g/m ) (RPa m~/g) ~ (Times) **
Squid chitin sheet29 9.0 > 16 (1 kg) ~ -Crab chitin sheet115 1.5 10 (500 g) :-.:' * Breaking Strength: The pressure (per unit weight of chitin sheet) required to pulverize a chitin .. ~
sheet. ~.
** Folding Endurance: A chitin sheet i5 folded while pressure is exerted on the sheet using a 500 g or 1 kg plumb. ~Folding Endurance~ is the number . :
of timeis for which the chitin sheet is folded before it is broken. .

(2) Chitin fiber Squid chitin flber: prepared in Example 2 Crab chitin fiber: prepared in Reference Exzmple 1 Table 2 Strength Elongation (g/d) * (~
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Squid chitin fiber 5.0 5.0 Crab chitin fiber 1.6 4.3 * Strength (Pulling strength): The force required to break 50 ~tringis of fiber.
** Elongation: A ratio of elongation (as per the original length) when 50 strings o~ fiber i5 pulled and broken.
~ s demonstrated in the above test, the squid chitin formed materials of thi3 invention have better physical properties than conventional crab chitin formed materials in terms of ~trength, folding endurance, etc. Although the details are still to be elucidated, these superior characteri~tic~ are presumed to be a result of the more oriented nature o~ squid chitin crystals than crab chitin crystals.
Other feature~ of the invention will become apparent in the course of the following description of the exemplary embodiment~ which are given for illustration of the invention and are not intended to be limiting thereof.
EXAMPLES
Example l (i) One (1) kg of Tadarodes galadiuQ was ground -by a feather mill (5 m/m screen pas~ he ground ~ -galadius was put into a 1 N NaO~ solution, heated at 90C for 1 hour, washed with water, and dipped into a 0.1 N HCl solution at room temperature for 1 hour. The ground material then was washed with water and again heated nt 90C in a 1 N NaOH ~olution for 1 hour.
After washing with water, the material was dried in an oven ~t 50C for 5 hours to produce lOO g of squid chitin.
(ii) Ten (10) g of the ~quid chitin produced in ., .

1324787 :~
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(i) above was pulverized by an"Osterizer"* The pulverized chitin wa~ suspended into 400 ml of water and vigorou~ly ~tirred to increase the viscosity. The viscous gel-like product thus obtained was sub~ected to a conventional water ~et 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/m2 had breaking strength of 9 gPa m2/g and folding endurance of at least 16 at a 1 kg plumb weight.
Letters were printed with ink onto the s~uid chitin sheet. The ink wa~ well attached onto the sheet with no run or blur.
Example 2 Twenty (20) g of the squid chitin produced in Example l(i) was pulverized by an'~sterize~'to produce a homogeneous chitin particles. S00 ml of formic acid was added to the chitin particles. The mixture was stirred slowly, and allowed to qtand at room temperature until needle-like solid materials contained therem disappeared. After freezing at -20C, the fro~en material was thawed, gently stirred, and wa~ 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 8 '~
*Trade mark of 1.5 Rgf/cm2, and an extender having a first roller rotating at o.1 m/sec. and a second roller rotating at 0.11 m/sec., to produce wet squid fiber. The squid fiber was neutxalized 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 th~ method po~sessed silky gloss.
Reference Example 1 (Preparation of crab chitin fiber) -(1) One (1) kg of C~ionaecetes opilio crab shell -~exoskeleton) was ground by a coffee grinder. The ground crab ~hell was put into a 1 N NaOH solution, heated at 90C for 1 hour, washed with water, dipped into a 2 N HCl solution at room temperature for 6 hours, and then was washed with water. This ~ame proceduxe was performed 3 times. After washing with water, the finally obtained material was dried in an oven at 50C 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'~sterizer"
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 ~aterials contained therein disappeared. 12 hours after ~n ~
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freezing at -20C, the frozen material was thawed at room temperature. The thawed material was gently stirred, and again frozen to produce a dope. ~hi~
frozing-thawing operation wa~ once more repeated. The dope finally obtained was deaerated in vacuo, and extruded into a mixed 301vent of ethyl acetate and water through a nozzle with 30 hole~, each hole having a diameter of 0.09 m/m, at an extrusion pressure of 1.3 Rgf/cm2, and extended at an ex~ension 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 ~et 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 ch~tin sheet.
Obviously, numerous modification~ and variations o the pre~ent Invention are pos~ible 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.

Claims (8)

1. A process of preparing a squid chitin sheet comprising: grinding squid chitin, suspending the ground squid chitin in water, forming a gel of said squid chitin, suspending the gel in water, submitting the suspension to filtration to eliminate water, and drying the residue.

2. A process according to claim l, wherein said gel of squid chitin is formed by stirring the ground squid chitin suspension.

3. A process according to claim 1, wherein said gel of squid chitin is formed by subjecting the ground squid chitin suspension to a freeze-defrost treatment.

4. A squid chitin sheet prepared by the process claimed in claims 1, 2 or 3.

5. A process of preparing squid chitin fiber comprising: dissolving squid chitin in formic acid, subjecting the solution to a freeze-defrost treatment to produce a dope, defoaming the dope in vacuo, and extruding the defoamed dope into a solvent to coagulate the dope.

6. A process according to claim 5, wherein said solvent is an alcohol, a ketone, or a mixture thereof.

7. A process according to claim 5, wherein the alcohol is methanol, ethanol, propanol or butanol, and the ketone is acetone or methyl ethyl ketone.

8. Squid chitin fiber prepared by the process claimed in claims 5, 6 or 7.