NZ235730A - Chitin acetate fibre and its production - Google Patents

Description

m 23 Priority Dats{s): .. AV?.V?; iS.ti: Complete Specification Filed:/' Class: .Db>.\£^J??" .\S.q£, Publication Date: P.O. Journal, No: Under the provisions of Regulation 23 (1) the Specification has been ante-dated to 19 J.2.

Initials Patents Form No. 5 This is a divisional out of application No. 222906 dated 14 December 1987 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION CHITIN ACETATE FIBERS WE, E.I. DU PONT DE NEMOURS AND COMPANY, organised and existing under the laws of the State of Delaware, of 10th & Market Streets, Wilmington, Delaware, United States of America, hereby declare the invention, for which we pray-that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: ^3/30 This invention relates to high strength fibers made of chitin acetate and a- process for making the-fibers.

Chitin (poly-N-acetyl-D-glucosamine) is a polysaccharide widely distributed in nature and is a major component of the cell vail of various fungi as well as the shell of insects and crustaceans. Chitin has been extracted and purified front its various sources and has been formed into potentially useful articles such as fibers for medical sutures. Chitin-based fibers having both high tensile strength and high modulus of elasticity prepared directly without post fiber treatment would be highly desirable.

Previous work to provide high strength chitin fibers has included the after-treatment of wet-spun chitin fibers in a second coagulation bath as described in U.S. Patent No. 4,431,601 or by drawing the fiber .'•••- Methods to produce chitosan (poly-D-glucosamine) and chitin acetate (poly-N-acetyl-O-acetyl-D-gl ucosamine) are known and methods for spinning chitosan and chitin acetate into fibers are known.

In the polysaccharide art, optically anisotropic spinning solutions from cellulose and cellulose acetate have been disclosed. An object in the cellulose art was to provide a concentrated solution of highly polymerized cellulose triacetate as well as a large degree of acetate substitutions in order to produce high strength fibers as described in U.S. Patent No. 4,464,323. la (followed by page 2) It has now been discovered that by forming a chitin acetate fiber that has a lower degree of substitution a significantly higher tenacity can be obtained. This is completely unexpected in the light of the teaching in U.S. patent 4464323.

Accordingly, this invention provides a chitin acetate fiber that has an as-spun tenacity of at least 4 g/den, a modulus of at least 100 g/den and a degree of O-acetylation of less than 2.2. The fiber is produced by extruding an optically anisotropic solution of chitin acetate that has a degree of O-acetylation of less than 2.2 through a spinneret, passing the extruded chitin acetate through an air gap, and passing the chitin acetate into a coagulating bath to form the fibers.

The chitin acetate fibers show increased strength when compared to non-derivatized chitin fibers or chitin acetate fibers with a higher degree of acetylation. 235 7 c Chitin, when isolated in high molecular weight form, is soluble at low concentration in only a limited • • number of specialized solvent systems. In order to enhance the solubility of chitin-based polymers, it is desirable to place organic substituents on the free amine or hydroxy groups of chitin or chitosan. These substituents perform two functions. First, they provide organic pendant groups to facilitate dissolution in organic solvent systems, e.g. trichloroacetic acid/methylene chloride. Second, the presence of such substituents disrupts the crystalline, strongly hydrogen-bonded structure of native chitin, which itself constitutes a significant barrier to dissolution.

Chitin refers to poly-N-acetyl-D-glucosamine wherein the degree of N-acetyl substitution is from 0.75-1.0. Though chitin is found naturally with the C5-C6 bond in the D-configuration, the chemistry defined herein would be just as applicable to an L-form and is not intended to be limited to the D-form.

Chitin acetate refers to poly-N-acetyl-O-acetyl-D-glucosamine wherein the O-acetyl group can be substituted at the C3 and C6 position of the monomer to a varying degree, with a degree of O-acetylation less than 2.2 and preferably ranging from about 0.05 to 2.0.

The total degree of acetyl group subs-titufcion- .onto the chitin acetate is determined by the types and concentration of reactants and catalysts used for the preparation of each polymer.

In the preparation of fibers, an optically anisotropic solution* of chitin acetate was prepared and then extruded through a spinneret into a coagulation bath to form fibers which were then wound onto bobbins.

The anisotropic spinning solutions were prepared by dissolving the chitin acetate into a solvent comprising trichloroacetic acid/methylene chloride. The solutions were judged to be anisotropic if', when C 235 7 30 sandwiched between a microscope slide and cover slip, they were birefringent when viewed between crossed polarizers. Generally, chitin acetate was . found to form optically anisotropic solutions when dissolved at weight percents 5 greater than 10% in a 60/40 (w/w) trichloroacetic acid/methylene chloride solvent.

It is recognized that both the molecular weight and pattern of substitution of chitin acetate polymers ' will probably determine their 10 solubility in any particular solvent and also the concentrations at which optical anisotropy is observed. . Also, even though a 60/40 (w/w) trichloroacetic aeid/methylene chloride solvent is used for mos^of the work described herein, other solvents for chitin acetate 15 1 could be used. 235 7 30 The coagulation bath used during fiber formation consisted of cold methanol, which is a non-solvent for chitin and its derivatives. The coagulation bath was between 20 and 30 inches in length. Any suitable non-solvent for chitin or its derivatives could be used in place of methanol for the purpose of coagulating the fiber spinning solution.

There are many parameters which can be varied in the spinning scheme and one could readily adjust spinneret orifice diameters, length of the air gap spacing, jet velocity, bath conditions, ratio of windup speeds to jet velocity, as well as other parameters in order to optimize various physical properties of the fibers of this invention.

The chitin derivative polymers produced according to the present invention are spun from anisotropic solution and form high strength fibers.

It is expected that articles other than fibers, such as cast or molded products, could be produced from the polymers described herein and may also demonstrate high strength properties.

Fig. 1 is a scnematic diagram of an apparatus for air-gap spinning of anisotropic solutions of chitin and chitin derivatives. 235730 Fig. 2 is a schematic diagram of a twin cell apparatus for air-gap spinning of anisotropic solutions of chitin derivatives.

Fig. 3 is a schematic diagram of a mixing plate used in conjunction with the apparatus of Fig. 2.

In using the apparatus of Fig. 1 an anisotropic solution of chitin or a chitin derivative was placed in spin cell (G). A piston (D) activated by hydraulic press (F) and associated with piston travel indicator (E) was positioned over the surface of the solution, excess air . expelled from the top of the cell and the cell sealed. The spin cell was fitted at the bottom with the following screens (A) for solution filtration: four to six 325-mesh screens. The filtered solution was then passed into a spinneret pack (B) containing two or three 325-mesh screens. Solutions were extruded through an air gap at a controlled rate into a static bath (C) using a metering pump to supply pressure at piston (D). The fiber was passed around a pin (H), pulled through the bath, passed under a second pin (I) and wound onto a bobbin. The air gap between the spinneret face and the coagulation bath was typically 0.6 to 2.0 cm. The coagulation bath temperature was generally held below 100eC with specific values as given in the examples.

In using the apparatus of Fig. 2, filter plate (J) is replaced by mixing plate (R). Polymer dope is placed in cylinder bore (T) and then piston (D) and cap plate (L) i6 fitted to the spin cell (G). A driver fluid (e.g. water) is pumped into the upper part of bore (T) through feed line (F). The piston (D) is displaced by the driver fluid, thereby pushing the polymer dope through passages (W), (S) in mixing plate (R) and then through passage (K) in distribution plate (M) into second cylinder bore (U). This process is then reversed by pumping fluid through feed line (X). The aforementioned forward and 7 30 reverse process is repeated several times to effect a nixing of the polymer dope. Component (E) acts to sense the position of cylinder (D).

After mixing is complete (about 30 cycles), mixing plate (R) is replaced by filter plate (J) and polymer dope is extruded from bore (T) through passage (W), through filter pack (A) containing 2 Dutch Twill Heave 165 x 800 mesh screens, through passage (Y) in filter plate (J) and passage (Z) in spinneret mounting plate (0) and out of spin cell (G) through spinneret (B). The extruded dope is spun into a bath and taken up as . _ described for Fig. 1. Pressure of the polymer dope during spinning is measured by pressure transducer (P).

TEST METHODS Inherent viscosity (I.V.) is calculated using the formula: Inherent viscosity n. . - (In h , )/C where C is • inn r t i the polymer concentration in grams of polymer per deciliter of solvent. The relative viscosity (*lr#1) is determined by measuring the flow time in seconds using a standard viscometer of a solution of 0.5 g (except where indicated) of the polymer in 100 ml hexafluoroisopropanol at 30°C and dividing by the flow time in seconds for the pure solvent. The units of inherent viscosity are dl/g.

Jet Velocity (J.V.) is the average exit velocity of the spinning solution from the spinneret capillary as calculated from the volume of solution passing through an orifice per unit time and from the cross-sectional area of the orifice and is reported as meters per minute.

Filament tensile properties were measured using a recording stress-strain analyzer at 70°F (21.1*C) and 65% relative humidity. Gauge length was 1.0 in (2.54 cm), and rate of elongation was 10%/min. Results are reported as T/E/M. Tenacity T is break tenacity in g/den, Elongation (E) is elongation-at-break expressed as the *30/50 percentage by which initial length increased, and Modulus (M) is initial tensile modulus in g/den. Average tensile «• properties for at least three filament samples are reported. The test is further described in ASTM D2101-79 part 33, 1981.

Degree of Substitution (DS) of acetate is determined by proton-NMR in the following manner: The spectra are determined in deuterated trifluoracetic acid solvent and using tetramethylsilane (TMS) as a standard. The D.S. is determined by integrating the area due to the protons on carbons Cx through C6 of the glucosamine derivative (6.0 to 3.0 ppm) and comparing it with the total area due to the methyl group protons (2.5 to 2.0 ppm) using the following formula: D.S. - (M/(G/7))/3 where: M - area of methyl group protons G - area of the protons on carbons C4 through Cs of the glucosamine derivative EXAMPLES RUN A Chitin was isolated from shrimp shells and spun into fiber according to the following procedures: Isolation of Chitin V ^ / J u Shrimp shells obtained from Gulf Cities Fisheries of Pascagoula, Miss, were placed in large containers and soaked in acetone for 5 to 7 days, after 5 which the acetone was filtered off and the shells rinsed with additional acetone to remove as much pigment as « possible. The shells were then air dried for 72 hours. > The dried shells were ground into a flake using an Abbe ■ cutter. The ground shells (500 g) were decalcified by treatment with ice cold 10% hydrochloric acid (4 to 6 1) with stirring for 20 minutes. The liquid was then removed by filtering and the shells rinsed with water. This acid treatment was repeated and the decalcified shells were • rinsed with water until neutral and allowed to air dry.

- The dry solid was suspended in 2.5 1 of 3% sodium hydroxide in a 5 1 flask and heated at 100°C for 2 hours. The suspension was then filtered and the remaining solid washed with water. This caustic treatment was repeated and the chitin obtained was washed with water until 20 neutral. The chitin was then washed successively with methanol and acetone, air dried and lastly dried in a vacuum oven for about 12 hours at 120eC.

Spinning Chitin obtained by the above procedure was 25 dissolved at 24°C in a 60/40 (w/w) trichloroacetic w* acid/methylene chloride mixture, to form a solution containing 13.5% solids. The solution was tested and found to be anisotropic.

The chitin solution above was extruded into 30 fibers using the apparatus represented by Fig. 1 and described previously. The solution was extruded through 0.004" diameter holes of a 10-hole spinneret at a jet velocity of 15.2 M/nin., passed through a 1.25 cm air gap, into a 0#C methanol bath and wound onto bobbins at a rate 35 of 15.5 M/min.

Fiber properties were measured as described above and are reported in Table I. 235 7 3 RUN B Chitin acetate wj.th a high degree of substitution of acetyl groups was synthesized and spun into fiber by the following method: Preparation of Chitin Acetate 200 ml of reagent grade methylene chloride, 400 ml of reagent grade acetic anhydride/ and 125 ml of glacial acetic acid were added to a 1 1 resin kettle equipped with a stirrer and nitrogen inlet. The mixture was cooled to about 0"C in a methanol bath and 20 g of chitin, prepared as in Run A, were added. 6 ml of 70% , perchloric acid were then added slowly and the mixture was stirred about 12 hours. After stirring, the mixture was filtered on a fritted Buchner funnel and excess acetic anhydride was removed by aspiration. The solid was washed thoroughly with methanol, acetone, 10% sodium bicarbonate, water, and lastly acetone, after which the solvent was removed by aspiration. The remaining solid was then air dried for about 12 hours to give 25 g of chitin acetate as a white solid. The inherent viscosity of the polymer was 5.72 dl/g and the degree of substitution was 2.95.

Spinning Chitin acetate prepared by the above procedure was spun as in Run A using the apparatus represented by Fig. 2 with the different spinnning parameters listed in Table 2.

Fiber properties were measured as described above and reported in Table I.

EXAMPLE 1 Chitin acetate with a relatively low degree of substitution of acetyl groups on chitin was synthesized and spun into fiber by the following method: Preparation of Chitin Acetate 200 ml of reagent grade methylene chloride, 400 ml of reagent grade acetic anhydride, and 125 ml of glacial acetic acid were added to a 1 1 resin kettle 235 7 3 equipped with a stirrer and nitrogen inlet. The mixture was cooled to about 0°C in a methanol bath and 20 g of chitin, prepared as in Example 1, were added. 3 ml of 70% perchloric acid were then added slowly and the mixture was stirred about 12 hours. After stirring, the mixture was filtered on a fritted Buchner funnel and excess acetic anhydride was removed by aspiration. The solid was washed-thoroughly with methanol, acetone, 10% sodium bicarbonate, water, and lastly acetone, after which all of the solvent was removed by aspiration for about 12 hours to give 25 g of chitin acetate as a white solid. The inherent ,, viscosity of the polymer was 6.76 and the degree of substitution was 2.0 Spinning Chitin acetate prepared by the above procedure was spun as in Bun A using the apparatus represente d by Fig. 2 with the different spinnning parameters listed in Table 2.

Fiber properties were measured as described above and reported in Table I.

EXAMPLE 2 Isolation of Chitin Wet shrimp shell waste (25 kg) was sorted manually to remove extraneous substances and boiled in water for 2 hours. The shells were collected by vacuum filtration and placed into cheesecloth pouches. Using one-half of the batch at a time, the shells were then boiled in 2% NaOH (50 1) under a nitrogen atmosphere for 1 hour, collected, pressed out and washed once with water. The shells were then boiled for 9 hours in 2% NaOH (50 1) under nitrogen for a second time, collected, pressed out, washed in water and immersed in 50 1 10% acetic acid for 1 hour at room temperature. The shells were collected by filtration, washed twice more in water and pressed out.

They were finally suspended in acetone (4 1), collected by 23 5 7 30 filtration, washed once more with clean acetone and allowed to air dry. The .yield was 1.2 kg dry chitin.

Preparation of Chitin Acetate Chitin (50 g) prepared as described above was ground in two steps to pass through a 0.5 mm screen. The ground chitin was placed in a Soxhlet extractor and extracted with acetone until the extract was clear. After' air drying, the chitin powder was washed twice with methanol, pressed out and heated to 77°C in 15% methanolic potassium hydroxide for 1 hour under nitrogen. The powder was collected by filtration, pressed out, washed once with water followed by two washes in glacial acetic acid.

After the final wash, the powder was pressed out and suspended using methods described above in cooled acetic anhydride (500 ml) and methylene chloride (500 ml) containing perchloric acid (2 ml) all at -22°C. After 16 hours, the temperature was raised to 13°C and the reactants allowed to stir for an additional 24 hours reaching a final temperature of 18°C. The polymer was collected by filtration, pressed out and washed twice with methyl alcohol. The product was then washed once in 5% sodium bicarbonate, followed by two washes in water and a final wash in acetone. The product was dried in a vacuum at 55°C. The yield was 57 g. D.S. - 1.4 based on NMR analysis.

Spinning Chitin acetate prepared as described above was spun using the method of Run A and the equipment described by Figure 1. The spinning solvent was 60/40 w/w trichloroacetic acid/methylene chloride. Pertinent spinning parameters appear in Table II.

Fiber properties were measured as described above and appear in Table I. 235730 TABLE I EX. DESCRIPTION D.S.

ACETATE FIBER PROPERTIES TENSILE PROPERTIES DPF TEN./ELONG./MOD.

Chitin 1.0 .7 1.3gpd/2.6%/107gpd B 1 2 Chitin Acetate Chitin Acetate Chitin Acetate 2.9. 2.0 1.4 7.0 2. 5gpd/7.3 l/90gpd 4.5 4. 3gpd/4.5%/169gpd .4 5.9gpd/6.4*/206gpd D.S. - degree of substitution, these fiber values can differ from those of the starting polymer because some partial deesterification may occur during conversion to fibers DPF » denier per filament Ex. ■ Example or run designation G 255730 O Parajneters % Solids Spinneret No. of Holes Dia. of Holes (cm) Jet Velocity (N/min) Air Gap (ant Pun A 13.5% 0.0102 .2 1.25 Coagulation Bath 0 Tenp. (.°C) Wind-up Fate (H/min) .5 TABLE II SPINNING PARAMETERS Run B Ex. 1 % 29.9 1.4 1 24 % 16.6 1.1 8 40 Ex. 2 15% 115 0.0076 0.0076 0.0076 1.5 1.3 16 21.3 C ■ m 235730

Claims (4)

WHAT WE CLAIM IS:

1. A chitin acetate fiber having an as-spun tenacity of at least 4 g/den, a modulus of at least 100 g/den and a degree of O-acetylation of less than 2.2, the fiber being produced by extruding an optically anisotropic solution of chitin acetate that has a degree of O-acetylation of less than 2.2 through a spinneret, passing the extruded chitin acetate through an air gap, and passing the chitin acetate into a coagulating bath to form the fibers.

2. A chitin acetate fiber according to claim 1 in which the optically anisotropic solution of chitin acetate comprises chitin acetate in trichloroacetic acid and methylene chloride.

3. A chitin acetate fiber according to claim 1 or claim 2 in which the chitin acetate has a degree of O-acetylation in the range 0.5 to 2.0.

4. A chitin acetate fiber according to claim 1 and substantially as described in this specification with reference to example 1 or example 2. t t*T;E.I..DU PONT DE NEMOURS;by tneir attolcntgyt Baldwin), son & carey ix..^ , ^ ... , _ . -i* •s.i'V'' —