CA1061068A

CA1061068A - Process for producing pullulan fibers

Info

Publication number: CA1061068A
Application number: CA222,491A
Authority: CA
Inventors: Tatsuo Nomura; Nobuhiro Toyota; Seizo Nakashio; Kozo Tsuji; Fumio Fujita
Original assignee: Sumitomo Chemical Co Ltd; Hayashibara Biochemical Laboratories Co Ltd
Current assignee: Hayashibara Seibutsu Kagaku Kenkyujo KK; Sumitomo Chemical Co Ltd
Priority date: 1974-03-20
Filing date: 1975-03-19
Publication date: 1979-08-28
Also published as: JPS5335165B2; DE2512110B2; DE2512110A1; FR2264896A1; GB1496017A; FR2264896B1; JPS50123931A

Abstract

PROCESS FOR PRODUCING PULLULAN FIBERS

ABSTRACT OF THE DISCLOSURE
A pullulan-containing fiber is obtained by using as a spinning solution an aqueous solution of pullulan or a melt of pullulan plasticized with water, and extruding the spinning solution at a temporary up to 100°C through a nozzle into a gas phase.

Description

11~6~68 The present invention relates to a process for produc-ing a novel fiber containing pullulan, which is a polymer having repeated units of maltotriose.
Pullulan decomposes at about 2S0C when heated in an absolutely dry state, but does not melt at temperatures between room temperature and the thermal decomposition temperature there-of. A process as been disclosed in which the melting temperature of pullulan is lowered by addition of water as a plasticizer, and is then subjected to molding. According to said process, -it is known that a fiber can beobtained by subjecting pullulancontaining less than about 25% of water to extrusion at a temp-erature of 110 to 120C under a pressure of 100 to 150 kg/cm2.
The pullulan referred to in the present invention is a linear high poIymer in which units of maltotriose, which is a trimer of glucose, are repeatedly bonded through ~-linkages which are different from those of said trimer, and has the molecular structure represented by the formula CH20H CH20E~ CH20H ' ~ ~
O ~ O ~ O 2 C 2 2 ~ ~ ~ ~ t CH2 CH~OI CH~OH
~ O ~

wherein n is an integer of 20 to 10,000 which has the polymeri-zation degree.
Heretofore, pullulan has been known merely as a water-soluble tacky substance, but has remained a substance which is entirely unknown in the field of fiber industry.
While the pullulan used in the present invention contains glucose units in its molecule, it is entirely different in molecular structure and greatly different in properties from starch, oxidized starch, enzymated starch, etherified starch, cationized starch, aminated starch, cellulose, alkyl cellulose, hydroxyalkyl cellulose, carboxymethyl cellulose and gum arabic which are conventional glucose derivatives composed mainly of glucose units, as in the case of pullulan.
Among the notewarthy properties of pullulan, those which are particularly outstanding are its specific water solub-ility and its excellent threading property.i.e. its ability toform filaments. The inventors have conducted extensive studies to find a process for converting pullulan into fibers and to con-firm that the resulting fibers possess excellent properties.
The present invention provides a novel fiber containing pullulan which has a strength capable of practical use and a specific water solubility.
The invention also provides a process for producing the said fiber.
The present invention provides a process for producing a fibrous substance, in which an aqueous solution containing pullulan or a melt of pullulan plasticized with water is adjusted to a temperature up to 100C. or less, preferably 70 to 20C, more preferably 50 to 20C and is extruded through a nozzle into a gas phase.
The present inventors have found that since pullulan has a specific affinity for water, it can be easily spun at a temperature lower than that disclosed inthe aforesaidknown process taking advantage of the facts that pullulan and cold water are homogeneously miscible with each other in any proportions, that ~0 an aqueous solution of pullulan has a high threading property, and that an aqueous pullulan solution is stable over a long period of time. A feature of the present invention is that a ;1068 spinning solution comprising an aqueous pullulan solution or a water-containing pullulan melt is spun at such a relatively low temperature as up to 100C.
Pullulan has excellent water solubility, and particul-arly the solubility of pullulan in the cold water is higher than that of any other water-soluble polymer. A conventional water-soluble polymer, e.g. polyvinyl alcohol, is sparingly soluble in cold water, in general, though the extent of water solubility varies depending on the degree of saponification of the polyvinyl alcohol, and it is ordinary practice to prepare an aqueous poly-vinyl alcohol solution by spraying steam maintained at above 110C.
into the system to dissolve the polyvinyl alcohol. Carboxymethyl cellulose, which is also a water soluble polymer, has the disad-vantage that when charged all at once into water, it exhibits a so-called "undissolved state" making it difficult to obtain a L
homegeneous aqueous solution. In contrast to this, the pullulan E
used in the present invention is specific in water solubility ~t as compared with polyvinyl alcohol or carboxymethyl cellulose, and hence has the characteristic of quickly dissolving even in cold water. Further, when compared with the viscosity of an aqueous solution of another water-soluble polymer, which is identical in molecular weight and concentration with pullulan, the viscosity of an aqueous solution of pullulan is far lower than that of an aqueous solution of not only carboxymethyl cellu-lose but also polyvinyl alcohol, which is known to be relatively low in viscosity. This low viscosity of aqueous pullulan solu-tion, coupled with the specific water solubility of pullulan, has made it possible that the aqueous pullulan solution, when used as a spinning solution, is easily spun into fibres by extrusion through a nozzle into air, nitrogen or other gas, while adjusting t the aqueous pullulan solution to such a low temperature as up to 100C.
- 3 - ~t ' No disclosure has yet been made as to the spinning of starches, in general, except the disclosure in Ooya et al: "Sen-i To Kogyo (Fibers and Industries)", Vol. 5, No. 9, page 441 (1972).
This literature teaches that corn starch, rice, millet flour, wheat flour or the like starch is charged with 10 to 50% of water, and the resulting mixture is subjected to a first heating operation and is then cooled to homogeneously obtain a gel-like spinning solution containing water, which is again heated to 90 to 120C and then extruded to obtain spun fibres. By contrast, the pullulan used in the present invention can homogeneously absorb a desired amount of water either in the form of steam or by water spraying, and does not require any preliminary heating operation for homogeneous dispersion of water. Starch is crystal-line and hence must be dissolved by heating in a single operation, whereas pullulan is non-crystalline and hence is easy in handling, and this has marked advantages in the production of pullulan fibers. Further, the crystallinity of starch and the non-crystal-linity of pullulan result in a great difference in stability between the two when converted into the form of aqueous solutions.
That is, an aqueous pullulan solution is stable over a long period of time at any concentration, and does not exhibit any such gela-tion or so-called "aging" phenomenon as observed in aqueous starch stolutions. Consequently, an aqueous pullulan solution or a melt of pullulan plasticized with water can easily be spun into fibres by extrusion through a nozzle into a gas such as air or nitrogen at relatively low temperature such as up to ~00C which cannot be expected in the case of starches.
It is a characteristic of pullulan that even when an aqueous pullulan solution or a pullulan melt has a relatively low temperature at the time of spinning, as compared with a solution of starch, the solution or melt is low in viscosity and nence can be extruded under a relatively low extrusion pressure.
The spinnability of an aqueous pullulan solution or a pullulan melt at a relatively low temperature ranging from 0 to 100C.
including room temperature is not only advantageous from the standpoint of thermal efficiency, but also gives such great prac-tical advantages that the temperature control of the spinning solution and the maintenance of uniform temperature distribution in the spinning solution can be facilitated to make the spun filaments free from unevenness and to make possible the production of fibers definite in quality.
The tensile strength of the starch fiber produced according to the process disclosed in the previously cited lit-erature is about 300 kg/cm2, whereas that of the pullulan fiber produced according to the process of the present invention is

2,520 kg/cm2 and thus is more than 8 times the strength of said starch fiber (refer to Example 1 as hereinafter described).
The water content of the pullulan spinning solution used in the present invention is in the range of 5 to 99 wt%, t preferably 30 to 80 wt% and spun fibres can be obtained by pro-perly adjusting the temperature of the spinning solution to the molecular weight of pullulan, the shape and size of spinning nozzle, and the extrusion pressure. For example, in case a spinning solution of pullulan having a molecular weight of ~`
150,000 is extruded through a cylindrical noz~le of 0.3 mm. in diameter and lmm. in length at room temperature under a pressure of 1 to 10 kg/cm2, the water content of the pullulan spinning solution is in the range of 30 to 80 wt%, preferably 50 to 70 wt~.
In the spinning according to the present invention, l~
pullulan may be mixed with, in addition tQ water, as a plasti- L
cizer or softener, a polyhydric alcohol such as glycerin, sor-bitol, maltitol, ethylene glycol, propylene glycol, polyethylene glycol or polypropylene glycol, or dimethyl sulfoxide.

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~061068 If necessary, the spinning solution may be subjected, in order to improve the physical properties of spun fibres and fabrics obtained therefrom, to mixed-spinning in admixture with other water-soluble polymer such as polyvinyl alcohol, polyethyl-eneimine, polyacrylamide, polyacrylic acid, sodium polyacrylate, ' polyvinyl pyrrolidone, polyethylene oxide, sodium alginate, car- .
boxymethyl cellulose or hydroxyethyl cellulose, or an emulsion of a water-insoluble polymer such as polyvinyl acetate, polyethyl acrylate, polypropyl acrylate, poly n-butyl acrylate, polymeth-acrylic acid, polymethyl methacrylate, polypropyl methacrylate, polybutyl methacrylate, polystyrene, polyvinyl chloride, poly-vinylidene chloride, polyacrylonitrile or ethylenevinyl acetate copolymer.
Further, the spinning solution may properly include inorganic and organic additives which include colorants such as ~.
pigments and dyes; antioxidants such as phenyl-~-naphthylamine, phenyl-~-naphthylamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-~-naphthyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, aldol-~-naphthylamine, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, 1,1-bis(4-hydroxy-phenyl) cyclohexane, 2,6-di-tert-butyl-p-cresol,2,2'-methylene- , bis-(4-methyl-6-tert-butylphenol),4,4'-thiobis-(6-tert-butyl-3-methylphenol),styrenated phenol; ultraviolet light absorbers such as phenylsalicylate, p-octylphenyl-salicylate, 4-tert-butylphenyl-salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzo-phenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxy-benzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-benzophenone, resorcinol monobenzoate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole; fillers such as calcium carbonate, clay, activated calcium fluoride, dolomite, '~`
talc, alumina white, mica powder, aluminum sulfate and barium F
sulfate; and flame retardants such as antimony oxide, antimony ~.

. ~

silico oxide, tris~ chloroethyl)-phosphate, tris(chloropropyl) phosphate, tris(dichloropropyl)phosphate, tris(2-bromoethyl) phosphate, triphenylphosphite, tris(2-chloroethyl)phosphite, chlorinated paraffin and tetrabromoethane.
Fibers spun according to the present invention may be stretched in steam at 60 to 120C., whereby they are further enhanced in strength, Young's modulus and knot strength.
Pullulan fibers are useful in various fields. However, they have high water solubility, so that it is necessary to control the degree of water solubility or to insolubilize the pullulan fibers according to the practical uses thereof. For this purpose, the pullulan fibers can be insolubilized by crosslinking with crosslinking agents for hydroxy group containing compounds including aldehydes such as formaldehyde, acetaldehyde, n-butyl-aldehyde and glyoxal, various epoxy resins, diisocyanates, and methylol compounds such as dimethylol ureaand dimethylol ethylene urea. Alternatively, the pullulan fibers can be insolubilized by incorporating bichromates into the fibers and then crosslinking the fibers with light.
It is also possible to insolubilize pullulan fibers by previously incorporating into the pullulan spinning solution a mixture comprising a monofunctional monomers such as acrylamide, acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate or N-vinyl pyrrolidone, and a polyfunctional monomers such as ethylene glycol dimethacrylate and polyethylene glycol dimeth-acrylate such as diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, nonaethylene glycol dimethacrylate, or methylene-bis-acrylamide and an initiator such as hydrogen perox-ide, ammonium persulfate, potassium persulfate, cerium (IV) ammonium nitrate, cerium (IV) ammonium sulfate, azobis-isobutyron-itrile, t-butyl-peroxide, di-t-butyl peroxide, dicumyl peroxide, cumen hydroperoxide and t-butyl hydroperoxide, spinning the resulting mixture to obtain pullulan fibers, and then cross-linking the fibers by application of heat, light or radiation.
Further, in order to properly control the water solubility of pullulan fibers, there may be used a modified pullulan prepared by subjecting the pullulan to esterification, alkyl etherifica-tion, hydroxyalkyl etherification, carboxyalkyl etherification, phosphatization, oxidation, reduction or graft-copolymerization with a vinyl monomer.
Characteristic features of a pullulan fiber obtained by the spinning process of the present invention are as follows;
(1) The fiber dissolves quite quickly not only in hot water but also in cold water.
(2) The strength and Young's modulus of a single fiber have such values that the fiber can successfully be put into practical use even when it has not been stretched. (refer to Examples 1 and 2 as hereinafter described).

(3) The surface of the fiber has a beautiful silk-like gloss.

(4) The fiber is colorless and transparent, and the sur-face and interior thereof are excellent in dyeability.

(5) The fiber is hydrophilic and moisture-absorptive, so that it generates no static electricity and thus is antistatic.

(6) The fiber is edible, non-toxic, tasteless and odorless, and is of course non-irritative to the skin.

(7) Even when burned, the fiber does not generate any such poisonous gases as nitrogen oxides and chlorides. Further, the fiber, after use, can be discarded as is, since it spontaneously decomposes in water and soil, without causing any such problem in its disposal such as with other waste matter.

In view of such characteristic properties as mentioned 106~068 above, pullulan fibers can be put into various uses. For example, pullulan fibers can be made into paper by subjecting them to paper-making, either singly or in admixture with wood pulp, hemp or ramie fibers, using as a dispersant a hydrophilic low mole-cular weight alcohol such as methanol, ethanol or isopropanol, or a hydrophilic organic solvent such as acetone which does not dissolve pullulan. The thus obtained paper is quickly soluble ln water and excellent in printability, and hence can be used as paper for secret documents. Further, they are water-soluble, edible and indigestive, and hence can directly be used as inner packings for medicines and as small bags for packing seasonings for instantly-serviceable foodstuffs and for tea powder, coffee, cocoa and the like foods. Furthermore, they are water-soluble and non-irritative to the skin, and hence can be used as women's sanitary cotton, toilet paper and tissue paper.
Alternatively, the pullulan fibers can be used as binders for non-woven fabrics, taking advantage of their tacki-ness. When fibers obtained from pullulan which has partly been water-insolubilized, or pullulan fibers which have partly been water-insolubilized, are spun either singly or in admixture with other fibers, the resulting fibers can be used as underwear and other clothes, taking advantage of the moisture-absorptivity, antistatic properties and dyeability of the fibers.
The particular method of production of the pullulan used in the present invention is not critical. At present, it can be isolated and recovered as a tacky substance secreted in a culture liquor of a strain belonging to the genus Pullularia which is an incomplete microorganism. Thus, a strain of the species Pullularia pullulans is subjected to a shaking culture (i.e. culture is carried out in a manner in which the container with the culture liquid is shaken to cause ready mixing of the culture liquid with air), at 24C for 5 days in a medium contain-~ _ g_ 1~6~068 ing 10% of partially hydrolyzed starch, 0.5% of K2HPO4, 0.1% ofNaCl, 0.02% of MgSO4. 7H2O, 0.06% of (NH4)2SO4 and 0.04% of yeast extract, whereby - 9a -1C~61068 p~llulan is obtained as a tacky subtance secreted from the cells into the culture liquor. If necessary, the cells are removed by centrifugation from the culture liquor, and the supernatant is charged with methanol to deposit a pullulan precipitate. After repeating water dissolution and methanol precipitation, purified pullulan can be obtained. Pullulan somewhat varies in physical properties depending on the kind of strain used. This, however, is not greatly connected to the properties of pullulan as fiber.
The molecular weight of the pullulan used in the present invention is not particularly limited, but is preferably in the range of 10,000 to 5,000,000.
The present invention is illustrated in detail below with reference to Examples.
Example 1 Pullulan having a molecular weight of about 150,000 was dissolved in water to prepare a s pinning solution containing 40 wt~ of said pullulan. The spinning solution was extruded at room temperature (23C.) under a pressure of 2 kg/cm2 through a E
cylindrical nozzle of 0.3 mm. in diameter and 1 mrn. in length into air at room temperature. The fibre from the nozzle was wound up by means of a winding machine, whereby spun fibres were obtained while evaporating water from the fibres into air. The thus obtained fibres were about 20 microns in diameter, and the unstretched fiber had a tensile strength of 2,520 kg/cm , an elongation of 20~ and a Young's modulus of 15,000 kg/cm2. When dipped into water at room temperature, the fiber dissolved there-in instantaneously.
Example 2 A pullulan fiber spun under the same conditions as in Example 1 was stretched in steam at 90C. to three times the original length thereof. The thus stretched pullulan fiber had a tensile strength of 2,900 kg/cm2, an elongation of 17~, and a ~,; i Young's modulus of 28,000 kg/cm2. When dipped into water at room temperàture, the fiber dissolved therein instantaneously.
Example 3 Pullulan having a molecular weight of about 200,000 was adjusted to a water content of 30 wt~ by spraying water thereto.
The pullulan thus treated was extruded at 70C. under a pressure of 30 kg/cm2 through a cylindrical--nozzle of 0.5 mm. in diameter and 1 mm. in length into air at room temperature, and the result-ing fibres were wound up. The fibres were about 30 microns in diameter, and the unstretched fiber had a tensile strength of 2,610 kg/cm2, an elongation of 18%, and a Young's modulus of -16,500 kg/cm2. When dipped into water at room temperature, the fiber dissolved therein instantaneously.
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for producing a pullulan-containing fiber, characterized by using as a spinning solution an aqueous solution of pullulan or a melt of pullulan plasticized with water, and extruding the spinning solution at a temperature up to 100°C.
through a nozzle into a gas phase.

2. A process according to Claim 1, wherein the spinning solution contains 5 to 99 wt% of water.

3. A process according to Claim 1, wherein in the spinning solution is incorporated a plasticizer or a softener.

4. A process according to Claim 3, wherein the plasti-dizer or softener is glycerin, sorbitol, maltitol, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene gly-col or dimethyl sulfoxide.

5. A process according to Claim 1, wherein the spinning solution is used in admixture with a water-soluble polymer or an emulsion of water-insoluble polymer.

6. A process according to Claim 5, wherein the water-soluble polymer is polyvinyl alcohol, polyethyleneimine, poly-acrylamide, polyacrylic acid, sodium polyacrylate, polyvinyl pyrrolidone, polyethylene oxide, sodium alginate, carboxymethyl cellulose or hydroxyethyl cellulose.

7. A process according to Claim 5, wherein the water-insoluble polymer is polyvinyl acetate, polyethylacrylate, poly-propylacrylate, poly-n-butylacrylate, polymethacrylic acid, poly-methylmethacrylate, polypropylmethacrylate, polybutylmethacrylate, polystyrene, polyvinylchloride, polyvinylidenechloride, poly-acrylonitrile or ethylene-vinylacetate copolymer.

8. A process according to Claim 1, wherein in spinning solution is incorporated at least one member selected from the group consisting of colorants, antioxidants, ultraviolet light absorbers, fillers, and flame-retardants.

9. A process according to Claim 1, wherein in the spinning solution is incorporated a monofunctional monomer, a polyfunctional monomer and an initiator.

10. A process according to Claim 9, wherein the mono-functional monomer is selected from the group consisting of acrylamide, acrylic acid, methacrylic acid, 2-hydroxyethyl meth-acrylate, and N-vinyl pyrrolidone.

11. A process according to Claim 9, wherein the poly-functional monomer is ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, non-aethylene glycol dimethacrylate or methylene-bis-acrylamide.

12. A process according to Claim 9, wherein the initia-tor is hydrogen peroxide, ammonium persulfate, potassium persul-fate, cerium (IV) ammonium nitrate, cerium (IV) ommonium sulfate, azobis-isobutyronitrile, t-butylperoxide, dicumylperoxide, cumene hydroperoxide or t-butyl hydroperoxide.

13. A process as claimed in Claim 1, 2 or 3 in which the temperature is from 70°C to 20°C.

14. A process as claimed in Claim 1, 2 or 3 in which the temperature is from 50°C to 20°C.

15. A process as claimed in Claim 1, 2 or 3 in which the pullulan has a molecular weight of from 10,000 to 5,000,000.

16. A process according to Claim 1 in which the fibre is stretched at a temperature in the range of 60° to 120°C.

17. A process according to Claim 1 in which the fibre is insolubilized by crosslinking with formaldehyde, acetaldehyde, n-butylaldehyde, glyoxal, epoxy resin, diisocyanate, dimethyl-olurea or dimethylolethyleneurea.

18. A process according to Claim 1 in which the fibre is insolubilized with a bichromate and light.

19. A process as claimed in Claim 9 in which the fibre is insolubilized by crosslinking, after spinning, with heat, light or radiation.