EP4092185A1

EP4092185A1 - Fibrillated regenerated cellulose fiber, and fabric using same

Info

Publication number: EP4092185A1
Application number: EP20913922.9A
Authority: EP
Inventors: Motoya MATSUBARA; Shogo JITSUMATSU
Original assignee: Asahi Kasei Corp; Asahi Chemical Industry Co Ltd
Current assignee: Asahi Kasei Corp; Asahi Chemical Industry Co Ltd
Priority date: 2020-01-14
Filing date: 2020-01-14
Publication date: 2022-11-23
Also published as: CN114929962B; JP7259088B2; JPWO2021144854A1; CN114929962A; WO2021144854A1; EP4092185A4

Abstract

Provided are a fibrillated regenerated cellulose fiber, and a fabric using the same, the fiber having a characteristic surface texture, softness, and a resilient feeling, being fibrillated by rubbing and tanning treatment in a wet state, and having an excellent surface texture and long-lasting feeling after being water-washed, thereby exhibiting high quality. Provided are: a regenerated cellulose fiber of which the surface is fibrillated and which has a degree of polymerization of 100-250, and a tensile strength of 1.0-3.0 cN/dtex (exclusive of 1.0 cN/dtex) at the time of drying; a fabric including the regenerated cellulose fiber as a constituent yarn; and a method for producing the regenerated cellulose fiber of which the surface is fibrillated, and the fabric including the regenerated cellulose fiber as a constituent yarn, the method comprising a step for modifying, in an acid solution, the regenerated cellulose fiber into yarn or fabric form, under the conditions of a temperature of 110-150 °C, a pH of 2.6-3.4, and a duration of 10-30 minutes.

Description

FIELD

The present invention relates to a fibrillated regenerated cellulose fiber having a characteristic surface texture, softness and a resilient feel, being fibrillated by rubbing and tanning treatment in a wetted state, and having an excellent surface texture after water washing and a long-lasting feel, thereby exhibiting high quality, as well as to a fabric including the fiber as constituent yarn.

BACKGROUND

Regenerated cellulose fibers include cuprammonium rayon and organic solvent-obtained cellulose fibers wherein the cellulose fibers all comprise aggregated fibrils composed mainly of cellulose microfibrils, and the fibers having a feature of splitting and becoming fibrillated in the fiber axis direction when subjected to rubbing or cloth kneading treatment in a wetted state.
In order to exhibit characteristic surface texture, softness and resilient feel for clothing articles produced using regenerated cellulose fibers, many types of products have been provided wherein these properties are utilized and the regenerated cellulose fibers forming the clothing are fibrillated, but when such fibrillated clothing articles are repeatedly washed the fibrils are shed and the surface texture and feel are impaired. Prior art documents relating to fibrillated regenerated cellulose fibers can also be found, but none of the prior art documents offer specific solution means for such problems.
For example, a processing method involving fibrillation is disclosed in PTL 1, as a method using impact during raising treatment and dyeing with a jet dyeing machine. However, since the expression level of the fibrils is not constant, being dependent on the dyeing conditions including the dyeing time, the liquor to goods ratio, the fabric speed and the concentration of the alkali used, there is a disadvantage in that products of consistent quality cannot be provided in a repeatable manner, and furthermore the polymerization degree of the regenerated cellulose fibers is specified to be 400 or greater and shedding of fibrils by water washing is not mentioned.
PTL 2 discloses fibrillation using an aqueous alkali solution. However, the polymerization degree of the regenerated cellulose fibers is specified to be 300 or greater, and since the treatment method is carried out in an aqueous alkali solution, the regenerated cellulose fibers are structurally modified to be easily fibrillated only in an aqueous alkali solution, while fibrillation is difficult by water washing with a weak degree of weak alkalinity, and furthermore, nothing is mentioned regarding shedding of the fibrils by water washing.
PTL 3 discloses a method using an aqueous acid solution or an aqueous oxidizing agent solution, but nothing is mentioned regarding the polymerization degree of the regenerated cellulose fibers. When the conditions for the treatment described in PTL 3 are compared to the conditions disclosed herein, while extended treatment is carried out at high temperature under ordinary pressure in a high-concentration acid solution with the aim of inhibiting reduction in strength, nothing is mentioned regarding the rate of strength reduction by the treatment method, and although it is stated that the strength is reduced by treatment under high pressure, the processing conditions are completely different from those disclosed in the present specification.
PTL 4 discloses a method using an aqueous acid solution, but nothing is mentioned regarding the polymerization degree of the regenerated cellulose fibers. PTL 4 describes tumbling treatment with an acid water-soluble solution for 30 to 80 minutes aimed at strength reduction, in order to remove long fibrils, and high-speed tumbling treatment in a dry state. However, the lyocell-containing fabric disclosed in PTL 4 has the long fibrils removed, which are responsible for producing a "hairy effect" on fabric surfaces as the characteristic surface texture that is disclosed in the present specification, while PTL 4 states that the short fibrils on the fabric surface have a characteristically "clean" surface finish, unlike a "hairy effect", and they are therefore different from the fibrillated regenerated cellulose fiber disclosed herein. In addition, PTL 4 completely fails to indicate the rate of strength reduction of the fabric by the treatment method used to remove the long fibrils, and also mentions nothing regarding shedding of the fibrils by water washing.

[CITATION LIST]

[PATENT LITERATURE]

[PTL 1] Japanese Unexamined Patent Publication HEI No. 08-113846
[PTL 2] Japanese Unexamined Patent Publication HEI No. 06-166956
[PTL 3] Japanese Unexamined Patent Publication HEI No. 11-315474
[PTL 4] UK Patent No. GB 2399094A

SUMMARY

[TECHNICAL PROBLEM]

In light of this prior art, the problem to be solved by the invention is to provide a fibrillated regenerated cellulose fiber having a characteristic surface texture, softness and resilient feel, being fibrillated by rubbing and tanning treatment in a wetted state, and having an excellent surface texture after water washing and a long-lasting feel, thereby exhibiting high quality, as well as a fabric using the fiber.

[SOLUTION TO PROBLEM]

Upon avid research with the goal of solving this problem, the present inventors have discovered that rather than modifying the expressed fibrils so that they are not shed it is more effective to modify them so that even if the fibrils are shed they are re-expressed during washing, and as a result of much further experimentation based on this discovery, studying methods of modification whereby even if the fibrils are shed they are re-expressed during washing, the present inventors have completed this invention upon finding, unexpectedly, that if the polymerization degree of regenerated cellulose fibers is controlled to 100 to 250, the fibrils can be easily expressed with only the weak rubbing effect of washing, and a lightweight feel, softness and a resilient feel are exhibited.
Specifically, the present invention is as follows.

[1] Regenerated cellulose fibers that are fibrillated on their surfaces, having a polymerization degree of 100 to 250, and a dry tensile strength of greater than 1.0 cN/dtex and 3.0 cN/dtex or lower.
[2] The regenerated cellulose fibers according to [1] above, wherein the regenerated cellulose fibers are organic solvent-obtained cellulose fibers.
[3] A fabric including regenerated cellulose fibers according to [1] or [2] above as constituent yarn.
[4] A method for producing the regenerated cellulose fibers according to [1] or [2] above or the fabric according to [3] above, which includes a step of modifying treatment of regenerated cellulose fibers in yarn or fabric form in an acid solution, under conditions with a temperature of 110°C to 150°C, a time of 10 to 30 minutes and a pH 2.6 to 3.4.

[ADVANTAGEOUS EFFECTS OF INVENTION]

The fibrillated regenerated cellulose fibers of the invention are fibers that have a characteristic surface texture, softness and resilient feel, and that are also fibrillated by rubbing and tanning treatment in a wetted state and exhibit an excellent surface texture after water washing and a long-lasting feel, thereby exhibiting high quality.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a photograph of the surface of a woven fabric, showing the fibrillated state of the regenerated cellulose fibers as the constituent yarn.
Fig. 2 is a magnified photograph of the fibrillated state of regenerated cellulose fibers.

DESCRIPTION OF EMBODIMENTS

An embodiment of the invention will now be described in detail.
One embodiment of the invention is regenerated cellulose fibers that are fibrillated on their surfaces, having a polymerization degree of 100 to 250, and a dry tensile strength of greater than 1.0 cN/dtex and 3.0 cN/dtex or lower.
Regenerated cellulose fibers are regenerated cellulose fibers spun from a molten cellulose starting material such as cuprammonium rayon or organic solvent-obtained cellulose fibers, and they are preferably cuprammonium rayon or organic solvent-obtained cellulose fibers, and more preferably organic solvent-obtained cellulose fibers.
The yarn form of the regenerated cellulose fibers may be staple fibers or long fibers, but long-fiber multifilament yarn is preferred. The single fiber size is not particularly restricted but is preferably 0.5 to 5.0 dtex. The total fineness is not particularly restricted but is preferably 22 to 330 dtex, and the yarn count is not particularly restricted but is preferably 5 to 100. The monofilament cross-section shape is also not particularly restricted. There are likewise no particular restrictions on the state of twisting, which may be without twists, false-twisting or with twisting, or on the number of twists, which is preferably no more than 2000 added twists. Lack of twisting is preferred from the viewpoint of the tactile feel.
Combination with other materials is likewise not particularly restricted since this embodiment is not affected by other materials, but acryl, diacetate or wool is not preferred for such other combined materials since the processing method involves treatment under high pressure which can lead to strength reduction, hardened feel and loss of transparency.
The proportion of regenerated cellulose fibers used in a fabric that includes a woven or knitted fabric or nonwoven fabric is not particularly restricted, but in order to satisfactorily exhibit the desired effect it is preferably 10 wt% or greater, more preferably 20 wt% or greater and even more preferably 30 wt% or greater of the total weight of the fabric. If the amount used is 10 wt% or lower, fibrillation will be observed but it will be more difficult to obtain softness and a resilient feel. The yarn combination method may be combined twisting, interlaced filament combination, Taslan filament combination, covering, cotton blending, worsted or woollen spinning or fine spun yarn doubling.
The fibrillated regenerated cellulose fibers according to this embodiment have a polymerization degree of 100 to 250, preferably 150 to 250 and more preferably 200 to 250. If the polymerization degree is less than 100 the dry tensile breaking strength will fall below 1.0 cN/dtex, and the physical properties necessary for post-treatment and for use as a clothing article will not be exhibited. However, a polymerization degree of higher than 250 is not preferred since re-expression of the fibrils by water washing will not be possible. The polymerization degree is the value measured by the viscosity method using a copper-ammonia solution.
The fabric may be a woven fabric, warp knit fabric, circular knit fabric, horizontal knit fabric or nonwoven fabric, and is preferably a woven fabric, warp knit fabric, circular knit fabric or horizontal knit fabric, and more preferably a woven fabric or circular knit fabric. The texture and density of the fabric are also not particularly restricted. The method of combination with other materials may be mixed weaving, mixed knitting, composite yarn or insertion of weft yarn into warp yarn.
There are no particular restrictions on the method of modifying treatment to adjust the polymerization degree of the fibrillated regenerated cellulose fiber of this embodiment to 100 to 250. For regenerated cellulose fibers having a polymerization degree of 250 or higher and a dry tensile strength of 2.0 cN/dtex or greater, however, it is especially preferred to use modifying treatment to adjust the polymerization degree to 100 to 250 and the dry tensile strength to greater than 1.0 cN/dtex and 3.0 cN/dtex or lower by treatment in an acid solution, since adjustment of the physical properties of the yarn and the polymerization degree will thus be facilitated. The type of acid used is not particularly restricted and may be citric acid, malic acid, acetic acid, formic acid, sulfuric acid, nitric acid, hydrochloric acid or oxalic acid, preferred among which are acids with low corrosivity for metals, with formic acid, citric acid and malic acid being more preferred. The treatment temperature is preferably 110°C to 150°C, more preferably 120°C to 150°C and even more preferably 130°C to 140°C, for modification to the desired polymerization degree and tensile strength. A temperature range of lower than 110°C is not preferred because a longer treatment time will be necessary for modification and the tensile strength will be significantly reduced even with successful modification to the desired polymerization degree. A short period treatment time at lower than 110°C is also not preferred because it requires a lower pH, and treatment for a short period at a low pH results in local reduction in polymerization degree and strength reduction making it difficult to achieve homogeneous modification, while variation in quality between different modifying treatments also occurs. A temperature above 150°C or higher, on the other hand, is also not preferred because temperature management becomes more difficult and homogeneous modification is more difficult to achieve. The treatment pH and treatment time must be adjusted depending on the regenerated cellulose fibers used, but the treatment pH is preferably 2.6 to 3.4 and more preferably 2.8 to 3.2, while the treatment time is preferably 10 to 30 minutes, more preferably 12 to 28 minutes and even more preferably 15 to 25 minutes. For example, when regenerated cellulose fibers having a polymerization degree of about 450 to 600 and a dry tensile strength of 2.0 cN/dtex or greater are treated using formic acid, 20 minutes of treatment at 130°C in an acid bath at pH 2.8 having a 76% formic acid concentration of 1.0 g/L can modify the polymerization degree to 100 to 250 and can maintain a dry tensile strength of greater than 1.0 cN/dtex and 3.0 cN/dtex or lower. In order to lower the polymerization degree to the desired polymerization degree in a short period while modifying the dry tensile strength to greater than 1.0 cN/dtex and 3.0 cN/dtex or lower, it is necessary to use a low-concentration acid for short-period modifying treatment, which requires high-temperature, high-pressure treatment at 110°C or higher.
The form used in the modifying treatment is not particularly restricted, but it is preferably a yarn or fabric form, and more preferably a fabric form. The equipment used for processing is not particularly restricted for either yarn or fabrics, but for yarn forms it is preferred to use a cheese dyeing machine or skein dyeing machine and for fabric forms it is preferred to use a jet dyeing machine, airflow dyeing machine, beam dyeing machine, jigger dyeing machine, paddle dyeing machine, drum dyeing machine, washer dyeing machine or winch dyeing machine, with a jet dyeing machine or airflow dyeing machine being preferred.
Since fibrillation treatment in water is necessary to express fibrils after modifying treatment, either the fibrillation treatment must be carried out simultaneously with the modifying treatment, or the fibrillation treatment must be carried out after modifying treatment. The form used in the fibrillation treatment is not particularly restricted but is preferably a fabric form. The equipment used for processing is not particularly restricted, but it is preferred to use a jet dyeing machine, airflow dyeing machine, paddle dyeing machine, drum dyeing machine, washer dyeing machine or winch dyeing machine, with a jet dyeing machine or airflow dyeing machine being preferred. The fibrillation treatment in water is not particularly restricted, and examples of performed fibrillation treatment are with a jet dyeing machine, airflow dyeing machine or winch dyeing machine as the equipment, at a temperature of 10 to 130°C, a fabric speed of 100 m/min or greater and a treatment time of 20 minutes or longer, or paddle dyeing machine, drum dyeing machine or washer dyeing machine as the equipment, at a temperature of 10 to 130°C and a treatment time of 20 minutes or longer. After fibrils have been expressed it is necessary to avoid removal of the fibrils, and therefore it is preferred to either omit texture treatment in a dry state after fibrils have been expressed, or when texture treatment is carried out in a dry state, it is preferably carried out using an airflow dyeing machine or air tumbler drier as the equipment under conditions with a fabric speed of 800 m/min or lower and a treatment time of 60 minutes or less, or using a batch process tumbler drier as the equipment with a treatment time of 60 minutes or less.
The regenerated cellulose fibers of this embodiment have a dry tensile strength of greater than 1.0 cN/dtex and 3.0 cN/dtex or lower, preferably 1.3 cN/dtex to 2.5 cN/dtex and more preferably 1.5 cN/dtex to 2.0 cN/dtex. If the dry tensile strength is 1.0 cN/dtex or lower, the fibers will suffer damage during the steps up until production of the fabric, making it difficult to obtain a practical fabric and impairing the resilient feel, while if it is greater than 3.0 cN/dtex the softness will be impaired.
The term "fibrillated" as regards the fibrillated regenerated cellulose fibers of this embodiment refers to a state in which aggregated fibrils composed mainly of cellulose microfibrils on the surfaces of the regenerated cellulose fibers are split in the fiber axis direction. Fig. 1 is a photograph of the surface of a woven fabric, showing the fibrillated state of the regenerated cellulose fibers as the constituent yarn, with arrow 1 indicating a state where aggregated fibrils composed mainly of cellulose microfibrils are split in the fiber axis direction (a fibrillated state). Fig. 2 is a magnified photograph of the fibrillated state of regenerated cellulose fibers, with arrow 2 indicating cellulose microfibrils.

EXAMPLES

The present invention will now be described in greater detail by examples, with the understanding that the invention is not limited to these examples. The performance parameters of the yarns and fabrics in the Examples were evaluated by the following methods.

(1) Measurement of polymerization degree

The "viscosity method" was used for the viscosity of a solution of the cellulose fibers dissolved in copper-ammonia, using the Standinger viscosity rule represented by the following formula: $η sp / c = KmM$
{ηsp: relative viscosity, c: fiber substance concentration (basic number of moles/100 ml), Km: constant (5 × 10^-4), M: fiber substance molecular weight}.
Cellulose fiber samples with different polymerization degrees were each dissolved in a copper-ammonia solution as a molecular dispersion and the polymerization degree was measured based on the formula shown above in a Nakano viscosity tube, after which the viscosity of the fiber substance sample dissolved in a copper-ammonia solution at a fixed concentration in a Tappy viscosity tube was measured, the relationship between viscosity and polymerization degree was determined, the actual viscosity dissolved in a copper-ammonia solution at the same fixed concentration in a Tappy viscosity tube was measured, and the polymerization degree was calculated from a prepared relationship table for viscosity and polymerization degree.
The method of measuring the viscosity with a Tappy viscosity tube is as follows. The sample is allowed to stand for 24 hours or longer in a constant temperature and humidity room at 20°C, 65% humidity for equilibration of the moisture content. A 0.1 g portion of the sample is weighed out. The sample is placed in a Tappy viscosity tube with a wedge, and then a copper-ammonia solution (composition = ammonia: 205 g/L, copper (I) hydroxide: 11.0 g/L, sucrose: 10 g/L) is drawn into the viscosity tube which is then plugged. The viscosity tube is set in a rotating device and rotated for 30 minutes at a speed of 3 rpm to dissolve the sample. The viscosity tube is removed from the rotating device and immersed for 5 minutes in a thermobath at 20°C. The lower plug of the viscosity tube is removed and set in a thermobath, inserting the whole into a jacket. The plug cock at the top of the viscosity tube is opened and the time for flow of the solution between gauge marks A and B of the viscometer is measured. The absolute viscosity (V) is calculated by the following formula: $V = d / C (t - K / t)$
{V: absolute viscosity (cP), d: solution specific gravity (g/cm³), C: Tappy viscosity tube constant, t: flow time between gauge marks A and B (sec), K: flow energy constant for Tappy viscosity tube}. The value calculated for the absolute viscosity is then compared with the aforementioned relationship table for viscosity and polymerization degree, to determine the polymerization degree.

(2) Dry tensile strength test method

The sample was allowed to stand for 24 hours or longer in a constant temperature and humidity room at 20°C, 65% humidity for equilibration of the moisture content. Using a TENSILON RTC Series universal material tester (product of A&D Co., Ltd.), the sample was stretched to a sample length (yarn length) of 200 mm at a pull speed of 200 mm/min, and the breaking strength was recorded.

(3) Washing test method

This was conducted according to the method of JIS L0217-103. Clothing detergent is added and dissolved in water at a liquid temperature of 40°C in a proportion of 2 g per 1 L for use as a washing solution. The sample yarn and a dummy cloth are loaded into the washing solution to a liquor to goods ratio of 1:30, and operation is initiated. After 5 minutes of washing and dewatering, water rinsing for 2 minutes in ordinary temperature water with the same liquor to goods ratio, dewatering, and further water rinsing for 2 minutes in ordinary temperature water with the same liquor to goods ratio and dewatering, the first washing cycle is complete. The drying method used was tumbler drying at 80°C for 20 minutes.

(4) Fibrillation degree

The sample is set in a VHX-6000 microscope (product of Keyence Corp.), and with the magnification of a VH-Z20 lens (product of Keyence Corp.) set to 200x and the luminance and sensitivity adjusted, the sample is both irradiated and photographed with light that produces white dots on the fibril portions. The proportion of white dot area with respect to photographed area was calculated and the degree of fibrillation was evaluated based on the following 3-level evaluation scale.

G (fibrillated): White dot area proportion of ≥10%
F (insufficient fibrillation): white dot area proportion of ≥5% and <10%
P (non-fibrillated): White dot area proportion of <5%

(5) Change in fibrillation degree by washing

The sample, both before washing and after washing, is set in a VHX-6000 microscope (product of Keyence Corp.), and with the magnification of a VH-Z20 lens (product of Keyence Corp.) set to 200x and the luminance and sensitivity adjusted, the sample is both irradiated and photographed with light that produces white dots on the fibril portions. The proportion of white dot area with respect to the photographed area was then calculated for the same both before and after washing, and the rate of change in the fibrillation degree was calculated by the following formula: $X = AW - BW$

{X: Change in fibrillation degree by washing (%), AW: white dot area proportion of sample after washing (%), BW: white dot area proportion of sample before washing (%)},
after which the degree of change in the fibrillation degree was evaluated on the following 3-level evaluation scale.
- G (No change in fibrillation): change of ≥-10% and <+10%
- P (Change in fibrillation): change of <-10% or ≥+10%

(6) Feel

The sample before washing was examined for feel by a tactile sensory test with repeated gripping and evaluated based on the following 3-level evaluation scale, also evaluating the sample after washing when the evaluation of the sample before washing was G or F.

G: Excellent softness and resilient feel
F: Somewhat inadequate softness or resilient feel
P: Inferior softness or resilient feel

[Example 1]

An 84 dtex/45 cuprammonium rayon filament was prepared with a polymerization degree of 580 and a dry tensile strength of 2.3 cN/dtex. The raw yarn was subjected to modifying treatment with a cheese dyeing machine at 130°C for 20 minutes using 76% formic acid at 1.0 g/L, to convert the polymerization degree to 200 and obtain modified cuprammonium rayon. The obtained modified cuprammonium rayon raw yarn was used as warp yarn and weft yarn for weaving of a 2/1 twill weave fabric, having a warp density of 144/2.54 cm and a weft density of 100/2.54 cm. The obtained greige was subjected to scouring relaxation and fibrillation treatment at 80°C for 20 minutes with a jet dyeing machine using 1 g/L of nonionic surfactant, after which dyeing of the cuprammonium rayon was again carried out for 60 minutes with a jet dyeing machine at a dyeing temperature of 60°C, followed by soaping for 10 minutes at 80°C. After dyeing and drying, the fabric was impregnated with a 1 wt% aqueous silicon-based softener solution, padded with a pickup of 80%, dried for 1 minute at 150°C, subjected to texture treatment with an air tumbler for 30 minutes at 80°C at a speed of 700 m/min, and provided for final setting at 130°C for 1 minute to obtain a dyed fabric with a warp density of 153/2.54 cm and a weft density of 104/2.54 cm. The polymerization degree of the 84 dtex/45 filament cuprammonium rayon of warp yarn removed from the woven fabric was 200.

[Example 2]

An 84 dtex/45 cuprammonium rayon filament with a polymerization degree of 580 and a dry tensile strength of 2.3 cN/dtex was used as warp yarn and weft yarn for weaving of a 2/1 twill weave fabric, having a warp density of 144/2.54 cm and a weft density of 100/2.54 cm. The obtained greige was subjected to modifying and fibrillation treatment for 20 minutes with a jet dyeing machine at 130°C using 1.0 g/L of 76% formic acid, to adjust the polymerization degree to 200, after which dyeing of the cuprammonium rayon was again carried out for 60 minutes with a jet dyeing machine at a dyeing temperature of 60°C, followed by soaping for 10 minutes at 80°C. After dyeing and drying, the fabric was impregnated with a 1 wt% aqueous silicon-based softener solution, padded with a pickup of 80%, dried for 1 minute at 150°C, subjected to texture treatment with an air tumbler for 30 minutes at 80°C at a speed of 700 m/min, and provided for final setting at 130°C for 1 minute to obtain a dyed fabric with a warp density of 153/2.54 cm and a weft density of 104/2.54 cm. The polymerization degree of an 84 dtex/45 cuprammonium rayon filament of warp yarn removed from the woven fabric was 200.

[Example 3]

An 89 dtex/30 organic solvent-obtained cellulose fiber filament was prepared with a polymerization degree of 490 and a dry tensile strength of 3.5 cN/dtex. The raw yarn was subjected to modifying treatment with a cheese dyeing machine at 130°C for 20 minutes using 76% formic acid at 1.0 g/L, to convert the polymerization degree to 220 and obtain modified organic solvent-obtained cellulose fibers. The obtained modified organic solvent-obtained cellulose fibers were used as warp yarn and weft yarn for weaving of a plain woven fabric having a warp density of 105/2.54 cm and a weft density of 89/2.54 cm. The obtained greige was subjected to scouring relaxation and fibrillation treatment for 20 minutes with a jet dyeing machine using 1 g/L of nonionic surfactant at 80°C, after which dyeing of the organic solvent-obtained cellulose fibers was again carried out for 60 minutes with a jet dyeing machine at a dyeing temperature of 60°C, followed by soaping for 10 minutes at 80°C. After dyeing and drying, the fabric was impregnated with a 1 wt% aqueous silicon-based softener solution, padded with a pickup of 80%, dried for 1 minute at 150°C, subjected to texture treatment with an air tumbler for 30 minutes at 80°C at a speed of 700 m/min, and provided for final setting at 130°C for 1 minute to obtain a dyed fabric with a warp density of 109/2.54 cm and a weft density of 92/2.54 cm. The polymerization degree of the 89 dtex/30 filament organic solvent-obtained cellulose fibers of warp yarn removed from the woven fabric was 220.

[Example 4]

The 89 dtex/30 filament organic solvent-obtained cellulose fibers with a polymerization degree of 490 and a dry tensile strength of 3.5 cN/dtex were used as warp yarn and weft yarn for weaving of a plain woven fabric having a warp density of 105/2.54 cm and a weft density of 89/2.54 cm. The obtained greige was subjected to modifying and fibrillation treatment for 20 minutes with a jet dyeing machine at 130°C using 1.0 g/L of 76% formic acid, to adjust the polymerization degree to 220, after which dyeing of the organic solvent-obtained cellulose fibers was again carried out for 60 minutes with a jet dyeing machine at a dyeing temperature of 60°C, followed by soaping for 10 minutes at 80°C. After dyeing and drying, the fabric was impregnated with a 1 wt% aqueous silicon-based softener solution, padded with a pickup of 80%, dried for 1 minute at 150°C, subjected to texture treatment with an air tumbler for 30 minutes at 80°C at a speed of 700 m/min, and provided for final setting at 130°C for 1 minute to obtain a dyed fabric with a warp density of 109/2.54 cm and a weft density of 92/2.54 cm. The polymerization degree of the 89 dtex/30 filament organic solvent-obtained cellulose fibers of warp yarn removed from the woven fabric was 220.

[Comparative Example 1]

An 84 dtex/45 cuprammonium rayon filament with a polymerization degree of 580 and a dry tensile strength of 2.3 cN/dtex was used as warp yarn and weft yarn for weaving of a 2/1 twill weave fabric, having a warp density of 144/2.54 cm and a weft density of 100/2.54 cm. The obtained greige was dye finished in the same manner as Example 2, except that modifying treatment and fibrillation treatment were not carried out, to obtain a dyed fabric having a warp density of 153/2.54 cm and a weft density of 104/2.54 cm. The polymerization degree of an 84 dtex/45 cuprammonium rayon filament of warp yarn removed from the woven fabric was 580.

[Comparative Example 2]

The 89 dtex/30 filament organic solvent-obtained cellulose fibers with a polymerization degree of 490 and a dry tensile strength of 3.5 cN/dtex were used as warp yarn and weft yarn for weaving of a plain woven fabric having a warp density of 109/2.54 cm and a weft density of 92/2.54 cm. The obtained greige was dye finished in the same manner as Example 4, except that modifying and fibrillation treatment were not carried out, to obtain a dyed fabric having a warp density of 109/2.54 cm and a weft density of 92/2.54 cm. The polymerization degree of the 89 dtex/30 filament organic solvent-obtained cellulose fibers of warp yarn removed from the woven fabric was 490.

[Comparative Example 3]

An 84 dtex/45 cuprammonium rayon filament with a polymerization degree of 580 and a dry tensile strength of 2.3 cN/dtex was used as warp yarn and weft yarn for weaving of a 2/1 twill weave fabric, having a warp density of 144/2.54 cm and a weft density of 100/2.54 cm. The obtained greige was subjected to fibrillation treatment for 120 minutes with a jet dyeing machine using 40 g/L of sodium hydroxide at 80°C, after which dyeing of the cuprammonium rayon was again carried out for 60 minutes with a jet dyeing machine at a dyeing temperature of 60°C, followed by soaping for 10 minutes at 80°C. After dyeing and drying, the fabric was impregnated with a 1 wt% aqueous silicon-based softener solution, padded with a pickup of 80%, dried for 1 minute at 150°C, subjected to texture treatment with an air tumbler for 30 minutes at 80°C at a speed of 700 m/min, and provided for final setting at 130°C for 1 minute to obtain a dyed fabric with a warp density of 153/2.54 cm and a weft density of 104/2.54 cm. The polymerization degree of an 84 dtex/45 cuprammonium rayon filament of warp yarn removed from the woven fabric was 440.

[Comparative Example 4]

An 84 dtex/45 cuprammonium rayon filament with a polymerization degree of 580 and a dry tensile strength of 2.3 cN/dtex was used as warp yarn and weft yarn for weaving of a 2/1 twill weave fabric, having a warp density of 144/2.54 cm and a weft density of 100/2.54 cm. The obtained greige was subjected to fibrillation treatment for 60 minutes with a jet dyeing machine using 50 g/L of 75% phosphoric acid at 100°C, after which dyeing of the cuprammonium rayon was again carried out for 60 minutes with a jet dyeing machine at a dyeing temperature of 60°C, followed by soaping for 10 minutes at 80°C. After dyeing and drying, the fabric was impregnated with a 1 wt% aqueous silicon-based softener solution, padded with a pickup of 80%, dried for 1 minute at 150°C, subjected to texture treatment with an air tumbler for 30 minutes at 80°C at a speed of 700 m/min, and provided for final setting at 130°C for 1 minute to obtain a dyed fabric with a warp density of 153/2.54 cm and a weft density of 104/2.54 cm. The polymerization degree of an 84 dtex/45 cuprammonium rayon filament of warp yarn removed from the woven fabric was 400.

[Comparative Example 5]

An 84 dtex/45 cuprammonium rayon filament with a polymerization degree of 580 and a dry tensile strength of 2.3 cN/dtex was used as warp yarn and weft yarn for weaving of a 2/1 twill weave fabric, having a warp density of 144/2.54 cm and a weft density of 100/2.54 cm. The obtained greige was subjected to fibrillation treatment for 60 minutes with a jet dyeing machine using 30 g/L of aqueous 35% hydrogen peroxide at 100°C, after which dyeing of the cuprammonium rayon was again carried out for 60 minutes with a jet dyeing machine at a dyeing temperature of 60°C, followed by soaping for 10 minutes at 80°C. After dyeing and drying, the fabric was impregnated with a 1 wt% aqueous silicon-based softener solution, padded with a pickup of 80%, dried for 1 minute at 150°C, subjected to texture treatment with an air tumbler for 30 minutes at 80°C at a speed of 700 m/min, and provided for final setting at 130°C for 1 minute to obtain a dyed fabric with a warp density of 153/2.54 cm and a weft density of 104/2.54 cm. The polymerization degree of an 84 dtex/45 cuprammonium rayon filament of warp yarn removed from the woven fabric was 180.

[Comparative Example 6]

An 84 dtex/45 cuprammonium rayon filament with a polymerization degree of 580 and a dry tensile strength of 2.3 cN/dtex was used as warp yarn and weft yarn for weaving of a 2/1 twill weave fabric, having a warp density of 144/2.54 cm and a weft density of 100/2.54 cm.
The obtained greige was subjected to fibrillation treatment for 45 minutes with an airflow dyeing machine at 130°C using 6.4 g/L of acetic acid, after which dyeing of the cuprammonium rayon was again carried out for 360 minutes with an airflow dyeing machine at a dyeing temperature of 60°C, followed by soaping for 10 minutes at 80°C. After dyeing and drying, the fabric was impregnated with a 1 wt% aqueous silicon-based softener solution, padded with a pickup of 80%, dried for 1 minute at 150°C, subjected to texture treatment with an air tumbler for 30 minutes at 100°C at a speed of 900 m/min, and provided for final setting at 130°C for 1 minute to obtain a dyed fabric with a warp density of 153/2.54 cm and a weft density of 104/2.54 cm. The polymerization degree of an 84 dtex/45 cuprammonium rayon filament of warp yarn removed from the woven fabric was 190.

For the woven fabrics obtained in Examples 1 to 4 and Comparative Examples 1 to 6, a sample fabric repeatedly washed 10 times by the washing test method described above and a sample fabric without washing were both evaluated for degree of fibrillation, and change in fibrillation degree and feel after washing. An 84 dtex/45 cuprammonium rayon filament and an 89 dtex/30 organic solvent-obtained cellulose fiber filament that had been subjected to modifying and fibrillation treatment, from warp yarn removed from the woven fabric samples of Examples 1 to 4, and an 84 dtex/45 cuprammonium rayon filament and an 89 dtex/30 organic solvent-obtained cellulose fiber filament from warp yarn that had not been subjected to modifying treatment or had been subjected to different fibrillation treatment, removed from the woven fabric samples of Comparative Examples 1 to 6, were measured for tensile strength of the dry warp yarns. Table 1 shows the sample yarn materials, modifying treatment and fibril treatment used in Examples 1 to 4 and Comparative Examples 1 to 6, and the evaluation results are shown in Table 2.

[Table 1]

		Sample yarn	Modifying treatment					Fibrillation treatment
		Sample yarn	Treatment form	Treatment solution	Treatment pH	Treatment time	Treatment temperature	Treatment solution	Treatment time	Treatment temperature
Present invention	Example 1	Cuprammonium rayon	Yarn	1.0 g/L 76% Formic acid	2.8	20 minutes	130°C	In water	20 min	80°C
	Example 2	Cuprammonium rayon	Fabric	1.0 g/L 76% Formic acid	2.8	20 minutes	130°C	No treatment	No treatment	No treatment
	Example 3	Organic solvent-obtained cellulose fibers	Yarn	1.0 g/L 76% Formic acid	2.8	20 minutes	130°C	In water	20 min	80°C
	Example 4	Organic solvent-obtained cellulose fibers	Fabric	1.0 g/L 76% Formic acid	2.8	20 minutes	130°C	No treatment	No treatment	No treatment
Prior art	Comp. Example 1	Cuprammonium rayon	Fabric	No treatment	No treatment	No treatment	No treatment	In water	20 min	80°C
	Comp. Example 2	Organic solvent-obtained cellulose fibers	Fabric	No treatment	No treatment	No treatment	No treatment	In water	20 min	80°C
	Comp. Example 3	Cuprammonium rayon	Fabric	No treatment	No treatment	No treatment	No treatment	40 g/L Sodium hydroxide	120 min	80°C
	Comp. Example 4	Cuprammonium rayon	Fabric	No treatment	No treatment	No treatment	No treatment	50 g/L 75% phosphoric acid	60 min	100°C
	Comp. Example 5	Cuprammonium rayon	Fabric	No treatment	No treatment	No treatment	No treatment	30 g/L 35% Hydrogen peroxide solution	60 min	100°C
	Comp. Example 6	Cuprammonium rayon	Fabric	No treatment	No treatment	No treatment	No treatment	6.4 g/L Acetic acid	45 min	130°C

[Table 2]

		Polymerization degree	Performance
			Fibrillation degree before washing	Change in fibrillation degree before and after washing	Feel		Tensile strength
			Fibrillation degree before washing	Change in fibrillation degree before and after washing	Before washing	After washing	Tensile strength
Present invention	Example 1	200	G	G	G	G	1.5 cN/dtex
	Example 2	200	G	G	G	G	1.5 cN/dtex
	Example 3	220	G	G	G	G	1.8 cN/dtex
	Example 4	220	G	G	G	G	1.8 cN/dtex
Prior art	Comp. Example 1	580	P	P	P	-	2.3 cN/dtex
	Comp. Example 2	490	P	P	P	-	3.7 cN/dtex
	Comp. Example 3	440	G	P	G	F	1.4 cN/dtex
	Comp. Example 4	400	G	P	G	P	1.2 cN/dtex
	Comp. Example 5	180	G	G	P	-	0.2 cN/dtex
	Comp. Example 6	190	P	P	P	-	1.0 cN/dtex

The fabrics using the modified cellulose fibers of Examples 1 to 4 had satisfactory textures that were soft and resilient with no change in fibril feel by washing, and the tensile strengths were shown to be greater than 1.0 cN/dtex. In other words, Examples 1 to 4 had characteristic surface texture, softness and resilient feel after washing, and excellent persistence of surface texture and feel even after washing.
In contrast, the fabrics of Comparative Examples 1 to 6 had tensile strengths of 1.0 cN/dtex or lower, or had loss of fibrils at the stage before washing, or had a polymerization degree of greater than 250 and change in fibrillation degree due to shedding of fibrils after washing. In other words, in Comparative Examples 1 to 6, the change in surface texture or feel after washing was large, or strength as a fabric failed to be maintained, with holes being opened by friction during wear or washing, or the fibrils were removed at the stage before washing, making the fabric unsuitable as a fiber product with fibrils which must exhibit satisfactory texture.

INDUSTRIAL APPLICABILITY

The present invention can provide regenerated cellulose fibers having a characteristic surface texture, softness and resilient feel, being easily fibrillated by rubbing and tanning treatment in a wetted state, and having an excellent surface texture after water washing and a long-lasting feel, thereby exhibiting high quality, as well as a fabric using the fibers, and the invention therefore has industrial applicability.

REFERENCE SIGNS LIST

1 State of aggregated fibrils composed mainly of cellulose microfibrils split in the fiber axis direction (fibrillated state)
2 Cellulose microfibrils

Claims

Regenerated cellulose fibers that are fibrillated on their surfaces, having a polymerization degree of 100 to 250, and a dry tensile strength of greater than 1.0 cN/dtex and 3.0 cN/dtex or lower.
The regenerated cellulose fibers according to claim 1, wherein the regenerated cellulose fibers are organic solvent-obtained cellulose fibers.
A fabric including regenerated cellulose fibers according to claim 1 or 2 as constituent yarn.
A method for producing the regenerated cellulose fibers according to claim 1 or 2 or the fabric according to claim 3, which includes a step of modifying treatment of regenerated cellulose fibers in yarn or fabric form in an acid solution, under conditions with a temperature of 110°C to 150°C, a time of 10 to 30 minutes and a pH 2.6 to 3.4.