Patent Publication Number: US-2006000027-A1

Title: Method for modifying fibers and modified fibers

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2004-192527 filed in Japan on Jun. 30, 2004, the entire contents of which are hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      This invention relates to a method for modifying fibers and also to modified fibers.  
      For the purposes of preventing fibers from fluffing, improving tensile strength and wear resistance of fibers, imparting static resistance and water absorption to fibers, or providing good hand or texture to fibers, there has been proposed a method called “imitation linen finishing” wherein viscose is attached to fibers and is coagulated and regenerated, followed by rinsing with water and drying to cover the fiber surfaces with the regenerated cellulose.  
      In this connection, however, the method of modifying fibers by coverage with viscose-derived, regenerated fibers includes the steps of applying to fibers a solution, i.e., viscose, obtained by dissolving in a sodium hydroxide aqueous solution cellulose xanthate which is prepared by degenerating cellulose with highly toxic carbon disulfide, and subsequently coagulating and regenerating the cellulose. This presents a problem that in the steps of preparing cellulose xanthate and coagulating and regenerating the cellulose, workers undergo exposure to carbon disulfide. In addition, the regenerated cellulose per se used for the coverage according to this fiber modifying method is unsatisfactory with respect to water absorption, thus causing the problem in that improvements in static resistance, water absorption and shrink proofing are not satisfactory.  
      To solve the problems on the modification of fibers by coverage with viscose-derived, regenerated cellulose, a method of covering fiber surfaces with regenerated cellulose has been proposed, in which cellulose per se is dissolved in a sodium hydroxide aqueous solution and attached to fibers, followed by coagulation and regeneration (JP-A 61-252369).  
      However, the method needs not only the dissolution of cellulose in a sodium hydroxide aqueous solution at low temperature, but also the use of cellulose of the type which has a reduced degree of crystal structure sufficient to increase solubility, e.g. cellulose that is obtained by acid hydrolyzing wood pulp and grinding it in a ball mill, or regenerated cellulose that is prepared from viscose, thus imposing restrictions thereon.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an object of the invention to provide a method for modifying fibers which is free of a problem on toxicity based on carbon disulfide, allows an easy step of dissolution, and has an excellent washing resistance.  
      It is another object of the invention to provide modified fibers obtained by the method.  
      There has already been proposed a method wherein a cellulose ether having a low degree of substitution is dissolved in a solution of an alkali such as sodium hydroxide or the like and applied onto fibers, after which the solution is coagulated and regenerated (JP-A 2004-218102). Intensive studies have been further made so as to improve washing resistance and, as a result, it has been found that fiber modifying finish is enabled by a procedure which comprises adding a crosslinking agent and/or an aqueous resin emulsion to an aqueous solution of a cellulose ether having such a low degree of substitution that a molar degree of substitution with an alkyl group and/or a hydroxyalkyl group ranges from 0.05 to 1.3, applying the resulting solution onto fibers, coagulating the applied solution with an acid for coagulation, and thermally treating the resulting fibers. For the above purpose, another procedure may also be used, which comprises adding a crosslinking agent and/or an aqueous resin emulsion to an alkali aqueous solution dissolving a cellulose ether having a low degree of substitution, applying the resulting solution onto fibers, subjecting the fibers to heating treatment and then neutralizing with an acid. The resulting modified fibers are improved in washing resistance, have no problem on carbon disulfide, are prevented from fluffing, and have high tensile strength and excellent wear resistance, static resistance and water absorption.  
      The invention has been accomplished based on the above findings.  
      More particularly, according to one embodiment of the invention, there is provided a method for modifying fibers comprising steps of adding a crosslinking agent and/or an aqueous resin emulsion to an aqueous solution of an alkali dissolving therein a cellulose ether having such a low degree of substitution that a molar degree of substitution with an alkyl group and/or a hydroxyalkyl group ranges 0.05 to 1.3, applying the resulting solution to fibers, neutralizing the applied solution with an acid for coagulation, and thermally treating the fibers.  
      According to another embodiment of the invention, there is provided a method for modifying fibers comprising steps of adding a crosslinking agent and/or an aqueous resin emulsion to an aqueous solution of an alkali dissolving therein a cellulose ether having such a low degree of substitution that a molar degree of substitution with an alkyl group and/or a hydroxyalkyl group ranges 0.05 to 1.3, applying the resulting solution to fibers, thermally treating the thus applied fibers, and applying an acid to the fibers to neutralize the alkali left on the fibers.  
      In these methods of the invention, the crosslinking agent used should preferably be an isocyanate crosslinking agent, and the aqueous resin emulsion should preferably be an aqueous urethane resin emulsion or an O/W emulsion of a reactive organopolysiloxane.  
      In the practice of the invention, the cellulose ether having a low degree of substitution should preferably be a low-substituted hydroxypropyl cellulose having a molar degree of substitution ranging from 0.1 to 0.7. Preferably, the aqueous solution of an alkali is a sodium hydroxide aqueous solution.  
      Moreover, according to a further embodiment of the invention, there is also provided a modified fiber article which includes fibers individually covered with a cellulose ether having such a low degree of substitution that a molar degree of substitution with an alkyl group and/or a hydroxyalkyl group ranges from 0.05 to 1.3, and also with a crosslinked product and/or an aqueous emulsion-derived resin component.  
      According to the invention, there can be obtained modified fibers without an appreciable problem on safety because of no use of a toxic solvent such as carbon disulfide and without involving a complicated step of dissolution. Such modified fibers can be appropriately prevented from fluffing or fuzzing, and have high tensile strength and excellent wear resistance, static resistance and water absorption. Moreover, the modified fibers obtained according to the invention have improved air permeability, a smooth feeling, and a solid touch with good resilience. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The fibers used in the invention are not critical in type. Examples of the fibers include synthetic fibers such as polyethylene fibers, polypropylene fibers, polyester fibers, nylon fibers, acrylic fibers, vinylon fibers, rayon fibers, polyvinyl chloride fibers, and polyvinylidene chloride fibers; natural fibers such as of cotton, cellulose, and hemp; and animal fibers such as of wool, silk, and cashmere. The term “fibers” used herein include thread-shaped fibers, woven fabrics or textiles of thread-shaped fibers, or non-woven fabrics or textiles of thread-shaped fibers.  
      The cellulose ether having a low degree of substitution used in the invention means a cellulose ether wherein the hydrogen atoms of the hydroxyl groups of glucose rings of cellulose are partially substituted with an alkyl group and/or a hydroxyalkyl group provided that a molar degree of substitution ranges from 0.05 to 1.3, preferably from 0.1 to 0.7 and which should not be dissolved in water but dissolved in an alkali aqueous solution. If the molar degree of substitution is lower than 0.05, such a cellulose ether is unlikely to dissolve in an alkali aqueous solution. On the contrary, when the molar degree/exceeds 1.3, dissolution in water increases with a decrease in solubility in an alkali solution.  
      In the present specification, the cellulose ether of a low degree of substitution is referred as a low-substituted cellulose ether hereinafter.  
      Examples of the cellulose ether of a low degree of substitution include low-substituted alkyl celluloses such as low-substituted methyl cellulose, and low-substituted ethyl cellulose; low-substituted hydroxyalkyl celluloses such as low-substituted hydroxyethyl cellulose, and low-substituted hydroxypropyl cellulose; low-substituted hydroxyalkylalkyl celluloses such as low-substituted hydroxypropylmethyl cellulose, low-substituted hydroxyethylmethyl cellulose, and low-substituted hydroxyethylethyl cellulose. Of these, low-substituted hydroxypropyl cellulose is preferred.  
      The modification of fibers according to the invention may be carried out by two different procedures. A first procedure comprises adding a crosslinking agent and/or an aqueous resin emulsion to an aqueous solution of an alkali dissolving therein a low-substituted cellulose ether as mentioned above, applying the solution to fibers by coating or dipping, if necessary, removing an excessive applied solution from the fibers by a suitable means such as a centrifugal dehydrator, a mangle, a knife coater or the like, coagulating the applied solution by neutralization with an acid, and thermally treating the resulting fibers after washing with water and drying, if necessary. A second procedure comprises adding a crosslinking agent and/or an aqueous resin emulsion to an aqueous solution of an alkali dissolving therein a low-substituted cellulose ether as mentioned above, applying the solution to fibers by coating or dipping, if necessary, removing an excessive applied solution from the fibers by a suitable means such as a centrifugal dehydrator, a mangle, a knife coater or the like, thermally treating the fibers, neutralizing an alkali left in the fibers with an acid, and drying the fibers. In either procedure, the crosslinking reaction and the cured film formation from the aqueous resin emulsion proceed in the course of the thermally treating step. Either of the crosslinking reaction or the cured film formation contributes to enhancing the adhesion between the fibers and the low-substituted cellulose ether, thus resulting in an improved washing resistance.  
      The alkali aqueous solutions include a sodium hydroxide aqueous solution, and a potassium hydroxide aqueous solution. The concentration of the caustic alkali depends on the type of substituent of a low-substituted cellulose ether used and the degree of substitution and may be appropriately determined. In general, the concentration ranges from 2 to 25% by weight, preferably from 3 to 15% by weight. If the concentration is smaller than 2% by weight the low-substituted cellulose ether may not be dissolved in some case. On the other hand, if the concentration exceeds 25% by weight, a solution of the low-substituted cellulose ether becomes gelled, with some possibility that a difficulty is involved in coating or dipping operation. Typically, low-substituted hydroxypropyl cellulose having a molar degree of substitution as low as 0.2 is dissolved in a sodium hydroxide aqueous solution having a concentration of 9 to 10% by weight.  
      On the other hand, the concentration of the low-substituted cellulose ether in an alkali aqueous solution is in the range of from 1 to 20% by weight, preferably from 1 to 10% by weight. If the concentration is smaller than 1% by weight, little effect of improving the hand of fibers is expected. Over 20% by weight, the resulting solution becomes too high in viscosity, so that the solution may be unlikely to be attached to the fibers in a given amount throughout the fibers.  
      The solution can be coated by use of coaters such as a blade coater, a transfer coater, an air doctor coater and the like. For dipping of fibers in a solution, there may be used dipping machines such as of one thread sizing type, a pre-wetting type, a floating type, a doctor bar type and the like.  
      The amount of the low-substituted cellulose solution on fibers is appropriately determined, and a pickup, i.e., [amount of an applied low-substituted cellulose ether solution/weight of fiber substrate]×100, is in the range of 10 to 500% by weight, preferably 20 to 300% by weight. If the pickup is smaller than 10% by weight, a coverage of fibers with a low-substituted cellulose ether becomes small, with the possibility that a satisfactory effect of modifying the fibers cannot be expected. On the contrary, when the pickup exceeds 500% by weight, the texture or hand of the resulting fibers becomes worsened, with some case where improvements in air permeability, hand such as a smooth feeling and the like may not be obtained as being commensurate with the amount of the cellulose ether added.  
      With the coagulation by neutralization with an acid according to the first procedure, the acids used include mineral acids such as hydrochloric acid, sulfuric acid and the like, and organic acids such as citric acid, malic acid, formic acid, acetic acid and the like. In this case, the concentration of the acid in the aqueous solution ranges from 1 to 50% by weight, preferably 2 to 15% by weight. It will be noted that if necessary, a salting-out method may be used in combination wherein the attached solution is coagulated by dipping in an aqueous solution of a salt such as ammonium chloride, ammonium sulfate, sodium sulfate, sodium chloride, zinc sulfate, magnesium sulfate, sodium phosphate, ammonium phosphate, sodium thiosulfate, sodium carbonate, sodium bicarbonate, sodium salts of aliphatic acids, and sodium benzenesulfonate. If the salting-out method is used in combination, an initially applied solution may be coagulated by neutralization, followed by further coagulation by salting-out. Alternatively, after coagulation by salting-out, further coagulation by neutralization may be carried out. Coagulation may be performed in an aqueous solution containing both an acid and a salt.  
      The crosslinking agents used in the invention may be ones which cause crosslinking reaction through reaction with hydroxyl groups left in the low-substituted cellulose ether. Such crosslinking agents include those agents to carry out reaction with hydroxyl group as described in “HANDBOOK OF CROSSLINKING AGENTS” (published by Kabushiki Kaisha Taiseisha., on Oct. 20, 1981). Specific examples include: epoxy compounds such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, sorbitol polyglycidyl ether, allyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, alkylphenol glycidyl ethers, polyethylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycidyl ether, 1,6-hexanediol, diglycidyl ether, glycerine polyglycidyl ether, diglycerine polyglycidyl ether, cresyl glycidyl ether, aliphatic diglycidyl ethers having 3 to 15 carbon atoms, monoglycidyl ether, epoxy acrylate, bisphenol A, butylglycidyl ether acrylate, ethylene glycol diglycidyl ether acrylate, trimethylolpropane polyglycidyl ether polyacrylate, terephthalic acid diglycidyl ester acrylate, phthalic acid diglycidyl ester, spiroglycol diglycidyl ether and the like; dialdehydes such as glyoxal; formaldehyde crosslinking agents such as urea formaldehyde; and isocyanate crosslinking agents such as toluidine isocyanate, dimer of 2,4-toluidine isocyanate, naphthylene-1,5-diisocyanate, o-toluidine isocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, tris(p-isocyanatephenyl)thiophosphite, polymethylenepolyphenyl isocyanate, polyfunctional aromatic isocyanates, aromatic polyisocyanates, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, blocked polyisocyanates, xylylene diisocyanate, ether group and urethane group-bearing, blocked isocyanate-containing prepolymers, polyisocyanate prepolymers, blocked isocyanates, polyisocyanates, two-component polyisocyanates, yellowing-free, two-component polyisocyanates, thermosetting polyisocyanates and the like. Moreover, there may be mentioned silanes of the general formula SiR1R 2 R 3 R 4  wherein R 1  represents an alkyl group, an alkoxy group or an acyloxy group each having 1 or 2 carbon atoms, and R 2 , R 3  and R 4  independently represent an alkoxy group or an acyloxy group having 1 or 2 carbon atoms.  
      It will be noted that the concentration of these crosslinking agents in the alkali solution is not critical and is preferably within a range of from 1 to 30% by weight, especially 5 to 10% by weight. If the concentration is smaller than 1% by weight, washing resistance may not be improved satisfactorily. When the concentration exceeds 30% by weight, there is the possibility that a further improvement in washing resistance as being commensurate with too much an amount is not expected.  
      For crosslinkage of a low-substituted cellulose ether according to the first procedure, there may be used a method wherein an alkali aqueous solution dissolving therein a low-substituted cellulose ether and a crosslinking agent is applied to fibers, and the thus applied fibers are treated with an acid aqueous solution to permit coagulation of the cellulose ether, followed by washing with water, drying and heating at 100 to 170° C. at which crosslinking reaction is allowed to proceed. The heating time is not critical and is preferably within a range of from 1 to 20 minutes.  
      On the other hand, for the crosslinkage of a low-substituted cellulose ether in the second procedure, there is used a method wherein an alkali aqueous solution dissolving therein a low-substituted cellulose ether and a crosslinking agent is applied to fibers, and the fibers are heated at 100 to 170° C. to cause crosslinking reaction to proceed, after which the fibers are treated with an acid aqueous solution, for example, by immersion to cause the alkali left in the fibers to be neutralized, followed by washing with water and drying, if necessary. The heating time is not critical and is preferably within a range of 1 to 20 minutes. It will be noted that re-heating treatment may be carried out after the drying, if necessary.  
      The acids used for the neutralization in the second procedure may be ones as used in the first procedure, and this is true of the concentration of an acid in the aqueous solution.  
      In either of the first or second procedure, in order to permit a crosslinking agent to be readily infiltrated into fibers, surface active agents including alkyl ether penetrants such as propylene glycol, ethylene glycol and the like, and penetrants of block copolymers of propylene glycol and ethylene glycol may be added in an amount of 0.5 to 1% by weight along with a crosslinking agent.  
      In the first procedure of the invention, the aqueous resin in the emulsion is fixed to fibers along with a low-substituted cellulose ether in the course of coagulation of the low-substituted cellulose ether and the aqueous resin is formed as a cured film in a subsequent heating step. In the second procedure, the aqueous resin in the emulsion is fixed to fibers and formed as a cured film during the heating step to cover the fiber surfaces along with the low-substituted cellulose ether, thereby improving the physical properties of fibers such as a washing resistance. In this sense, the aqueous resin emulsion used may be one which is converted to film by heating to enhance adhesion between the fibers and the low-degree substituted cellulose ether. To this end, those emulsions ordinarily used for resin finishing for fibers are used including aqueous urethane resin emulsions, aqueous acrylic resin emulsions, aqueous vinyl acetate resin emulsions, aqueous ethylene/vinyl acetate emulsions, aqueous epoxy resin emulsions, reactive organopolysiloxane O/W emulsions, SBR latices and the like. Of these, aqueous urethane resin emulsions and reactive oganopolysiloxane O/W emulsions are preferred.  
      The aqueous urethane resin emulsions include various types of emulsions prepared by reaction between polyethers such as polyoxyethylene glycol, polyoxypropylene glycol, and polyoxybutylene glycol and diisocyanates such as tolylene diisocyanate, 3,3′-bistolylene-4,4′-diisocyanate, diphenylmethane diisocyanate, 3,3-dimetyldiphenylmethane diisocyanate, and 4,4′-diisocyanate.  
      With the first procedure, there is adopted a method wherein an aqueous resin emulsion is added to an alkali solution dissolving therein a low-substituted cellulose ether and is applied to fibers along with the low-substituted cellulose ether upon coating of the low-substituted cellulose ether to the fibers. Thereafter, the cellulose ether on the fibers is coagulated by means of an acid aqueous solution, followed by washing with water and heating for film formation. In this case, the heating temperature may be one at which the resin component in the aqueous emulsion is formed as a cured film. The heating conditions preferably include a temperature ranging from 80 to 150° C. and a time ranging from 1 to 20 minutes. It will be noted that the concentration of the aqueous resin in the alkali aqueous solution is preferably from 1 to 30% by weight, especially 5 to 10% by weight. When the concentration is smaller than 1% by weight, a satisfactory improvement in washing resistance may not be obtained in some case. On the other hand, when the concentration exceeds 30% by weight, a further improvement in washing resistance may not be attained as being commensurate with such a large amount.  
      With the second procedure, an aqueous resin emulsion is added to an alkali solution dissolving a low-substituted cellulose ether, and is attached to fibers along with the low-substituted cellulose ether upon coating of the low-substituted cellulose ether. The resulting fibers are heated to convert the aqueous resin to a cured film, followed by treating the fibers with an acid aqueous solution such as by immersion to neutralize a remaining alkali, washing with water, if necessary, and drying. It is to be noted that the cured film conversion conditions are similar to those as used in the first procedure.  
      For the O/W emulsions of reactive organopolysiloxanes, mention is made of those emulsions obtained by dispersing in water methylhydrogenpolysiloxane, terminal hydroxyl group-blocked dimethylpolysiloxane and vinyl group-containing polysiloxane that are described in U.S. Pat. No. 4,221,688 and SILICONE HANDBOOK, pages 248 to 251, edited by Kunio Ito (published by Nikkan Kogyo Shimbun Ltd., on Aug. 31, 1990) and organopolysiloxanes having at least two hydroxyl groups bonded to a silicon atom as described in JP-B 3-67145. For a catalyst of promoting the crosslinking reaction of these reactive organopolysiloxanes in the form of an O/W emulsion, mention is made of salts of metals such as tin, lead, zinc, cobalt, manganese chromium, zirconium, titanium, and platinum. Especially, zirconium acetate as described in JP-B 34-4199 and chloroplatinic acid as described in JP-B 51-9440 are favorably used. The amount of the catalyst is not critical and an effective amount for promoting the crosslinking reaction is within a range of from 0.001 to 120 parts by weight, preferably from 0.005 to 110 parts by weight per 100 parts by weight of reactive organopolysiloxane in an emulsion used. The particle size in the O/W emulsion is not critical and is within a range of from 0.01 to 100 μm. From the standpoint of stability, the particle size is preferably within a range of 0.1 to 80 μm.  
      It will be noted that where an O/W emulsion of reactive organopolysiloxane is used, film formation may be carried out under the same curing conditions as for the above-stated aqueous urethane resin emulsion.  
      The clothes or fabrics obtained by use of the modified fibers of the invention is improved in air permeability and becomes smooth and flexible to the touch. Moreover, it is possible to provide fibers or clothes having a photocatalytic function by addition of about 1 to 20% by weight of titanium oxide to an alkali solution of low-substituted cellulose ether. Alternatively, dyes or pigments may be added to an alkali solution of low-substituted cellulose ether for coloration. Besides, all types of inorganic materials, organic material, and natural materials may be added to an alkali solution of low-substituted cellulose ether within ranges of amounts not impeding the purposes of the invention, modified fibers may be obtained.  
     EXAMPLES  
      Examples and Comparative Examples are shown to more particularly illustrate the invention, and the examples should not be construed as limiting the invention thereto.  
     Examples 1 to 11  
      50 parts by weight of an 18 wt % sodium hydroxide aqueous solution was added to 50 parts by weight of an aqueous solution dispersing 10 parts by weight of each low-substituted cellulose ether indicated in Table 1, thereby dissolving the low-substituted cellulose ether therein. Thereafter, 9 parts by weight of diphenylmethane diisocyanate was added to and dissolved in the mixture to prepare an alkali solution of the low-substituted cellulose ether dissolving the crosslinking agent therein. Next, “Knit Comber” cotton thread #30/1 made by Omikenshi Co., Ltd, or a polyester thread #30 made by Asahi Kuma Kabushiki Kaisha, were immersed in the sample solution by use of KHS Universal Sizer made by Kabushiki Kaisha Kakinoki so that a pickup reached 200 to 300% by weight. The thread was immediately removed from the sizer and immersed in a 10 wt % formic acid aqueous solution to cause the low-substituted cellulose ether to be coagulated. Subsequently, after sufficient washing well with water, the resulting thread was dried and heated at 145° C. for 5 minutes to obtain a sample fiber thread.  
      The samples obtained in this way were assessed according to the following testing methods with respect to fluffing property, tensile strength, wear resistance, static resistance, water absorption and washing resistance. The results are shown in Table 1.  
     Examples 12 to 18  
      The general procedure of Examples 1 to 11 was repeated except that an aqueous urethane resin emulsion of a crosslinked type of polyoxyethylene glycol and diphenylmethane diisocyanate was used, as an aqueous urethane resin emulsion of a crosslinked structure type, in place of the diphenylmethane diisocyanate and the fiber used was “Knit Comber” cotton thread #30/1 made by Omikenshi Co., Ltd, thereby obtaining sample fiber threads for evaluation. The results are shown in Table 1.  
     Example 19  
      50 parts by weight of an 18 wt % sodium hydroxide aqueous solution was added to 50 parts by weight of an aqueous solution dispersing 10 parts by weight of low-substituted hydroxy cellulose ether indicated in Table 1 to dissolve the low-substituted hydroxy cellulose ether. Thereafter, 3.2 parts by weight of methylhydrogen polysiloxane and 3 g of zirconium acetate acting as a crosslinking catalyst were added to the mixture to provide a solution. Next, “Knit Comber” cotton thread #30/1 made by Omikenshi Co., Ltd was immersed in the sample solution by use of KHS Universal Sizer made by Kabushiki Kaisha Kakinoki, so that a pickup reached 200 to 300% by weight. The thread was immediately removed from the sizer and immersed in a 10 wt % formic acid aqueous solution to coagulate the low-substituted cellulose ether. Subsequently, the thread was washed well with water, dried and thermally treated at 145° C. for 5 minutes to obtain a sample fiber thread.  
      The samples obtained in this way were assessed according to the following testing methods with respect to fluffing property, tensile strength, wear resistance, static resistance, water absorption and washing resistance. The results are shown in Table 1.  
     Examples 20 to 23  
      50 parts by weight of an 18 wt % sodium hydroxide aqueous solution was added to 50 parts by weight of an aqueous solution dispersing 10 parts by weight of each low-substituted hydroxylpropyl cellulose ether indicated in Table 1 to dissolve the low-substituted cellulose ether. Thereafter, 9 parts by weight of diphenylmethane diisocyanate and 9 parts by weight of a crosslinked product of polyoxyethylene glycol and diphenylmethane diisocyanate that is an aqueous urethane resin emulsion of a crosslinked structure type were added to and dissolved in the solution. Thus, an alkali solution of the low-substituted hydroxypropyl cellulose dissolving the crosslinking agent and the aqueous resin emulsion was prepared to provide each sample solution. Next, “Knit Comber” cotton thread #30/1 made by Omikenshi Co., Ltd was immersed in the sample solution by use of KHS Universal Sizer made by Kabushiki Kaisha Kakinoki so that a pickup reached 200 to 300% by weight. The thread was immediately removed from the sizer and immersed in a 10 wt % formic acid aqueous solution to coagulate the low-substituted cellulose ether. Subsequently, the thread was washed well with water, dried and thermally treated at 145° C. for 5 minutes to obtain a sample fiber thread.  
      The samples obtained in this way were assessed according to the following testing methods with respect to fluffing property, tensile strength, wear resistance, static resistance, water absorption and washing resistance. The results are shown in Table 1.  
     Comparative Example 1  
      A sample was made and evaluated in the same manner as in Examples 1 to 6 except that a sample solution used was comprised of 100 parts by weight of a viscose containing 8% by weight, calculated as cellulose, of powdery cellulose KC FLOCK W 100 made by Nippon Paper Industries Co., Ltd., 6% by weight of sodium hydroxide and 2.5% by weight of carbon disulfide. The results are shown in Table 1.  
     Examples 24 to 27  
      50 parts by weight of an 18 wt % sodium hydroxide aqueous solution was added to 50 parts by weight of an aqueous solution dispersing 10 parts by weight of each low-substituted hydroxypropyl cellulose indicated in Table 2 to dissolve the low-substituted hydroxypropyl cellulose. Thereafter, 9 parts by weight of diphenylmethane diisocyanate was added to and dissolved in the solution. Thus, an alkali solution of the low-substituted hydroxypropyl cellulose dissolving the crosslinking agent was prepared to provide each sample solution. Next, “Knit Comber” cotton thread #30/1 made by Omikenshi Co., Ltd was immersed in the sample solution by use of KHS Universal Sizer made by Kabushiki Kaisha Kakinoki so that a pickup reached 200 to 300% by weight, followed by thermally treating at 145° C. for 5 minutes. The thermally treated thread was immersed in a 10 wt % formic acid aqueous solution to neutralize sodium hydroxide left in the thread. Subsequently, the fiber thread was washed well with water and dried to obtain a sample thread.  
      The samples obtained in this way were assessed according to the following testing methods with respect to a fluffing property, tensile strength, wear resistance, static resistance, water absorption and washing resistance. The results are shown in Table 2.  
     Examples 28 to 31  
      The general procedure of Examples 20 to 23 were repeated using, instead of diphenylmethane diisocyanate, a crosslinked product of polyoxyethylene glycol and diphenylmethane diisocyanate serving as an aqueous urethane resin emulsion of a crosslinked structure type, thereby obtaining sample fiber threads for evaluation. The results are shown in Table 2.  
     Example 32  
      50 parts by weight of an 18 wt % sodium hydroxide aqueous solution was added to 50 parts by weight of an aqueous solution dispersing 10 parts by weight of low-substituted hydroxypropyl cellulose indicated in Table 2 to dissolve the low-substituted hydroxypropyl cellulose. Thereafter, 3.2 parts by weight of methylhydrogen polysiloxane and 3 g of zirconium acetate acting as a crosslinking catalyst were added to the mixture to provide a solution. Next, “Knit Comber” cotton thread #30/1 made by Omikenshi Co., Ltd was immersed in the sample solution by use of KHS Universal Sizer made by Kabushiki Kaisha Kakinoki, so that a pickup reached 200 to 300% by weight, followed by thermally treating at 145° C. for 5 minutes. The thermally treated thread was immersed in a 10 wt % formic acid aqueous solution to neutralize sodium hydroxide left in the thread. Subsequently, the fiber thread was washed with water and dried to obtain a sample thread. The samples obtained in this way were assessed according to the following testing methods with respect to fluffing property, tensile strength, wear resistance, static resistance, water absorption and washing resistance. The results are shown in Table 2.  
     Examples 33 to 36  
      50 parts by weight of an 18 wt % sodium hydroxide aqueous solution was added to 50 parts by weight of an aqueous solution dispersing 10 parts by weight of low-substituted hydroxypropyl cellulose indicated in Table 2 to dissolve the low-substituted hydroxypropyl cellulose. Thereafter, 9 parts by weight of diphenylmethane diisocyanate and 9 parts by weight of a crosslinked product of polyoxyethylene glycol and diphenylmethane diisocyanate that is an aqueous urethane resin emulsion of a crosslinked structure type were added to and dissolved in the mixture. Thus, an alkali solution of the low-substituted hydroxypropyl cellulose dissolving the crosslinking agent and the aqueous resin emulsion therein was prepared to provide each sample solution. Next, “Knit Comber” cotton thread #30/1 made by Omikenshi Co., Ltd was immersed in the sample solution by use of KHS Universal Sizer made by Kabushiki Kaisha Kakinoki so that a pickup reached 200 to 300% by weight, followed by thermally treating at 145° C. for 5 minutes. The thermally treated thread was immersed in a 10 wt % formic acid aqueous solution to neutralize sodium hydroxide left in the thread. Subsequently, the fiber thread was washed with water and dried to obtain a sample thread.  
      The samples obtained in this way were assessed according to the following testing methods with respect to fluffing property, tensile strength, wear resistance, static resistance, water absorption and washing resistance. The results are shown in Table 2.  
      Fluffing Property  
      Using an optical fluffing test device of F-INDEX TESTER made by Shikibo Ltd., a ratio of a total weight of fluffs having levels of 2 mm or below, 3 mm or below and 4 mm or below to an initial weight of a non-treated thread was determined.  
      Tensile Strength  
      Using Tensilon tensile strength measuring device made by A&amp;D Co., Ltd., the tensile strength of 10 threads with a length of 100 mm was measured to determine a ratio to that of non-treated threads.  
      Wear Resistance  
      Hiruta&#39;s wear resistance tester was used to determine a number of cycles before a sample thread was broken, from which a value obtained by dividing the number by a number of cycles before breakage of a non-treated thread is calculated.  
      Static Resistance  
      A half life was measured according to a method described in JIS L 1094-1980 to determine a static resistance as a ratio to that of a non-treated thread.  
      Water Absorption Rate  
      According to a method described in JIS L 1096-1979, a water absorption length in ten minutes was measured to determine a ratio to that of a non-treated thread.  
      Washing Resistance  
      A thread was washed according to a method described in JIS L 0844 and, after the washing, observed through a microscope to determine such that the degree of fluffing of a treated thread which was less than that of a non-treated thread was evaluated as ∘ and the degree which was not less than that of the non-treated thread was evaluated as X.  
                           TABLE 1                                  Name and Molar Degree of                   Substitution of               Low-substituted               Cellulose Ether   Evaluation                                                                                             Ratio in                           Hydroxy-   Ratio in   Ratio in   Ratio in   Ration in   Water       Target           Methyl   propyl   Fluffing   Tensile   Wear   Static   Absorption   Washing       fiber       Name   group   group   Degree   Strength   Resistance   Resistance   Rate   Resistance                                                                 Cotton   Example 1   Low-substituted       0.18   0.03   1.1   38   0.05   1.1   ◯       Thread   Example 2   Hydroxpropyl       0.26   0.04   1.1   40   0.08   1.1   ◯           Example 3   Cellulose       0.35   0.02   1.1   35   0.07   1.1   ◯           Example 4           0.5   0.06   1.1   38   0.07   1.1   ◯           Example 5   Low-substituted   0.7   0.14   0.03   1.1   37   0.05   1.1   ◯           Example 6   Hydroxypropyl-   1.1   0.10   0.04   1.1   42   0.07   1.1   ◯               methyl Cellulose           Example 7   Low-substituted   0.21       0.1   1.2   33   0.07   1.4   ◯               Methyl cellulose       Poly-   Example 8   Low-substituted       0.18   0.2   1.1   28   0.03   1.3   ◯       ester   Example 9   Hydroxypropyl       0.26   0.3   1.1   25   0.02   1.7   ◯       thread   Example 10   Cellulose       0.35   0.2   1.1   21   0.01   1.8   ◯           Example 11           0.5   0.1   1.1   20   0.02   1.8   ◯       Cotton   Example 12   Low-substituted       0.18   0.03   1.3   40   0.08   1.2   ◯       Thread   Example 13   Hydroxypropyl       0.26   0.03   1.4   38   0.07   1.5   ◯           Example 14   Cellulose       0.35   0.04   1.4   52   0.06   1.5   ◯           Example 15           0.50   0.05   1.5   38   0.08   1.5   ◯           Example 16   Low-substituted   0.7   0.14   0.03   1.3   45   0.08   1.2   ◯           Example 17   Hydroxypropyl   1.1   0.10   0.03   1.3   41   0.06   1.5   ◯               methyl Cellulose           Example 18   Low-substituted   0.21       0.08   1.2   38   0.07   1.2   ◯               Methyl cellulose           Example 19   Low-substituted       0.26   0.08   1.1   45   0.09   0.9   ◯           Example 20   Hydroxypropyl       0.18   0.02   1.3   53   0.08   1.2   ◯           Example 21   Cellulose       0.26   0.02   1.3   62   0.08   1.2   ◯           Example 22           0.35   0.01   1.2   60   0.08   1.3   ◯           Example 23           0.5   0.03   1.2   59   0.07   1.1   ◯           Comparative   —   —   —   0.7   1.1   10   0.1   1   X           Example 1                  
 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                   
               
               
                   
                   
                 Name and Molar Degree of 
                   
               
               
                   
                   
                 Substitution of 
               
               
                   
                   
                 Low-substituted 
               
               
                   
                   
                 Cellulose Ether 
                 Evaluation 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Ratio in 
                   
               
               
                   
                   
                   
                   
                 Hydroxy- 
                 Ratio in 
                 Ratio in 
                 Ratio in 
                 Ration in 
                 Water 
               
               
                 Target 
                   
                   
                 Methyl 
                 propyl 
                 Fluffing 
                 Tensile 
                 Wear 
                 Static 
                 Absorption 
                 Washing 
               
               
                 fiber 
                   
                 Name 
                 group 
                 group 
                 Degree 
                 Strength 
                 Resistance 
                 Resistance 
                 Rate 
                 Resistance 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Cotton 
                 Example 24 
                 Low-substituted 
                   
                 0.18 
                 0.03 
                 1.2 
                 42 
                 0.05 
                 1.4 
                 ◯ 
               
               
                 Thread 
                 Example 25 
                 Hydroxypropyl 
                   
                 0.26 
                 0.03 
                 1.3 
                 39 
                 0.06 
                 1.4 
                 ◯ 
               
               
                   
                 Example 26 
                 Cellulose 
                   
                 0.35 
                 0.02 
                 1.3 
                 37 
                 0.09 
                 1.3 
                 ◯ 
               
               
                   
                 Example 27 
                   
                   
                 0.5 
                 0.03 
                 1.3 
                 40 
                 0.08 
                 1.4 
                 ◯ 
               
               
                   
                 Example 28 
                   
                   
                 0.18 
                 0.03 
                 1.3 
                 35 
                 0.07 
                 1.8 
                 ◯ 
               
               
                   
                 Example 29 
                   
                   
                 0.26 
                 0.03 
                 1.4 
                 40 
                 0.07 
                 1.5 
                 ◯ 
               
               
                   
                 Example 30 
                   
                   
                 0.35 
                 0.02 
                 1.7 
                 41 
                 0.05 
                 1.4 
                 ◯ 
               
               
                   
                 Example 31 
                   
                   
                 0.5 
                 0.02 
                 1.5 
                 45 
                 0.06 
                 1.4 
                 ◯ 
               
               
                   
                 Example 32 
                   
                   
                 0.26 
                 0.03 
                 1.6 
                 39 
                 0.06 
                 1.7 
                 ◯ 
               
               
                   
                 Example 33 
                   
                   
                 0.18 
                 0.04 
                 1.4 
                 59 
                 0.05 
                 1.2 
                 ◯ 
               
               
                   
                 Example 34 
                   
                   
                 0.26 
                 0.03 
                 1.7 
                 68 
                 0.06 
                 1.4 
                 ◯ 
               
               
                   
                 Example 35 
                   
                   
                 0.35 
                 0.04 
                 1.7 
                 70 
                 0.07 
                 1.2 
                 ◯ 
               
               
                   
                 Example 36 
                   
                   
                 0.5 
                 0.02 
                 1.8 
                 72 
                 0.06 
                 1.3 
                 ◯ 
               
               
                   
               
            
           
         
       
     
      Japanese Patent Application No. 2004-192527 is incorporated herein by reference.  
      Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.