U.S. patent application number 10/566597 was filed with the patent office on 2007-03-15 for process for preparing elastic fiber having high modulus, alkali-resistance and heat-resistance.
Invention is credited to Joong Seong Jin, Yeon Soo Kang, Ik Hyeon Kwon, Seung Won Seo.
Application Number | 20070059523 10/566597 |
Document ID | / |
Family ID | 36204452 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070059523 |
Kind Code |
A1 |
Kang; Yeon Soo ; et
al. |
March 15, 2007 |
Process for preparing elastic fiber having high modulus,
alkali-resistance and heat-resistance
Abstract
Disclosed herein is a process for preparing an elastic fiber
having a high modulus and superior resistance to alkali and heat.
The process comprises the steps of adding 1.about.20% by weight of
a cellulose acetate to a polyurethane or polyurethaneurea solution,
based on the total weight of the polyurethane or polyurethaneurea,
homogeneously stirring the mixture to obtain a spinning solution,
and ripening and spinning the solution. According to the process, a
high modulus and highly heat resistant elastic fiber can be
prepared without a sudden change in conditions for preparation of
the polymer.
Inventors: |
Kang; Yeon Soo;
(Gyeonggi-Do, KR) ; Jin; Joong Seong;
(Gyeonggi-Do, KR) ; Seo; Seung Won; (Gyeonggi-Do,
KR) ; Kwon; Ik Hyeon; (Gyeonggi-Do, KR) |
Correspondence
Address: |
SALIWANCHIK LLOYD & SALIWANCHIK;A PROFESSIONAL ASSOCIATION
PO BOX 142950
GAINESVILLE
FL
32614-2950
US
|
Family ID: |
36204452 |
Appl. No.: |
10/566597 |
Filed: |
August 13, 2004 |
PCT Filed: |
August 13, 2004 |
PCT NO: |
PCT/KR04/02031 |
371 Date: |
June 22, 2006 |
Current U.S.
Class: |
428/364 |
Current CPC
Class: |
D01F 6/94 20130101; Y10T
428/2913 20150115; D01F 6/70 20130101 |
Class at
Publication: |
428/364 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 1, 2003 |
KR |
10-2003-0060810 |
Claims
1. A process for preparing an elastic fiber, comprising the steps
of: adding from 1 to 20% by weight of a cellulose acetate to a
polyurethane or polyurethaneurea solution, based on the total
weight of the polyurethane or polyurethaneurea, and homogeneously
stirring the mixture to obtain a spinning solution; ripening the
spinning solution; and spinning the ripened solution.
2. The process according to claim 1, wherein the cellulose acetate
is cellulose diacetate or cellulose triacetate having a degree of
acetylation of from 28 to 72%.
3. The process according to claim 1, wherein the polyurethane or
polyurethaneurea solution is obtained by reacting an organic
diisocyanate with a polymeric diol to form a polyurethane
precursor, dissolving the polyurethane precursor in an organic
solvent, and reacting the precursor solution with a diamine and a
monoamine sequentially.
4. The process according to claim 3, wherein the organic
diisocyanate is selected from the group consisting of
diphenylmethane-4,4'-diisocyanate, hexamethylenediisocyanate,
toluenediisocyanate, buthylenediisocyanate, and hydrogenated
p,p-methylenediisocyanate; the polymeric diol is selected from the
group consisting of polytetramethyleneether glycol,
polypropyleneglycol, and polycarbonatediol; the diamine is selected
from the group consisting of ethylenediamine, propylenediamine, and
hydrazine; and the monoamine is selected from the group consisting
of diethylamine, monoethanolamine, and dimethylamine; and the
organic solvent is selected from the group consisting of
N,N'-dimethylformamide, N,N'-dimethylacetamide, and
dimethylsulfoxide.
5. The process according to claim 1, wherein the spinning solution
further contains at least one additive selected from dulling
agents, UV stabilizers, antioxidants, NO.sub.x gas anti-yellowing
agents, anti-adhesion agents, dyeing promoters, and anti-chlorine
agents.
6. The process according to claim 1, wherein after the addition of
the cellulose acetate, the homogeneous stirring is carried out for
at least 2 hours, and the spinning solution is ripened by allowing
it to stand at 30.degree. C. to 70.degree. C. for 28 to 38
hours.
7. An elastic fiber prepared by a process comprising the steps of:
adding from 1 to 20% by weight of a cellulose acetate to a
polyurethane or polyurethaneurea solution, based on the total
weight of the polyurethane or polyurethaneurea, and homogeneously
stirring the mixture to obtain a spinning solution: ripening the
spinning solution; and spinning the ripened solution.
8. A velvet fabric manufactured using an elastic fiber prepared by
a process comprising the steps of: adding from 1 to 20% by weight
of a cellulose acetate to a polyurethane or polyurethaneurea
solution, based on the total weight of the polyurethane or
polyurethaneurea, and homogeneously stirring the mixture to obtain
a spinning solution; ripening the spinning solution; and spinning
the ripened solution.
Description
TECHNICAL FIELD
[0001] The present invention relates to a process for preparing an
elastic fiber having a high modulus and superior resistance to
alkali and heat. More specifically, the present invention relates
to a process for preparing a high modulus and highly alkali and
heat resistant elastic fiber by adding 1.about.20% by weight of a
cellulose acetate to a polyurethane or polyurethaneurea solution,
based on the total weight of the polyurethane or polyurethaneurea,
to obtain a spinning solution, and ripening and spinning the
solution. According to the process, a high modulus and highly heat
resistant elastic fiber can be prepared without a sudden change in
conditions for preparation of the polymer.
BACKGROUND ART
[0002] An elastic fiber is used in a wide variety of applications.
For example, the elastic fiber acts to tightly hold a polyester
yarn of a 3-way warp knitted velvet fabric, together with a
polyester fiber. The elastic fiber is required to have a modulus
high enough to form and maintain a good raised state, and at the
same time, to have heat resistance sufficient to endure dyeing and
setting treatments at high temperature in subsequent
post-processing steps of a polyester velvet fabric. An embossing
technique has been recently in the spotlight as a technique for
increasing the added value of a velvet fabric. For embossing of
various patterns, raised yarns of the velvet fabric must undergo
burning-out and printing into a desired color. For the processes,
superior alkali resistance is inevitably necessary for the elastic
fiber. Specifically, since a high concentration alkaline solution
(e.g., mainly caustic soda solution) is used to dissolve polyester
raised yarns at desired sites in the burning-out process, a
printing solution is applied thereto, followed by high temperature
treatment for dye fixing, the elastic fiber is required to have
superior alkali resistance in order to prevent it from being
degraded by alkaline solution remaining on the fabric at high
temperatures.
[0003] Problems often encountered in manufacturing a velvet fabric
using common elastic fibers are as follows. Since the common
elastic fibers have a low modulus, there occurs a phenomenon
wherein raised yarns are flattened after shearing, and thus the
elastic fibers exhibit poor velvet effects. In addition, since the
elastic fibers lose their inherent elastic recovery due to high
temperature post-processing, the fabric spreads out, and in extreme
cases, breakage of the elastic fibers takes place. Particularly,
the elastic fibers are severely broken by a high concentration
alkaline solution and a high temperature treatment employed in an
embossing technique requiring burning-out and printing, causing
occurrence of a number of holes on the velvet fabric.
[0004] Due to these problems, manufacturers of velvet fabrics make
a demand for high modulus and highly heat resistant elastic fibers
from manufacturers of elastic fibers. Furthermore, manufacturers of
burnt-out and printed velvet fabrics call for the supply of elastic
fibers having superior alkali resistance as well as high modulus
and superior heat resistance.
[0005] The most common processes adopted by manufacturers of
elastic fibers in order to solve the above-mentioned problems are
associated with the presence of a high content of hard segment in a
polymer solution for the preparation of an elastic fiber, and the
use of a chain extender having a high binding force and containing
no side chain. The higher the content of the hard segment, the
higher the modulus of the elastic fiber. The use of the chain
extender improves heat resistance of the elastic fiber. However,
since these processes have a difficulty in the management of the
viscosity of the polymer solution, they cause non-uniform physical
properties of the elastic fiber to be prepared using the polymer
solution, and are not suitable where small-scale preparation of the
elastic fiber is required. On the other hand, elastic fibers have
alkali resistance to some extent due to their inherent
characteristics, but are likely to easily degrade when caustic soda
at a high concentration of about 25% to about 30% is applied at a
temperature as high as 160.degree. C..about.180.degree. C.
Accordingly, burning-out and printing processes have been
separately carried out. No technique has been established that can
simultaneously proceed burning-out and printing processes to
date.
[0006] Thus, there is a need in the art for a process for easily
preparing an elastic fiber having a high modulus and superior
resistance to heat and alkali, without any problem associated with
non-uniform physical properties.
[0007] Japanese Patent Laid-open No. 2000-303259 issued to Fujibo
discloses a polyurethane elastic fiber having improved
moisture-absorbing properties and biodegradability. According to
this publication, the polyurethane elastic fiber is prepared by
adding a cellulose acetate to a polyurethane or polyurethaneurea
solution, homogeneously stirring the mixture to obtain a spinning
solution, spinning the solution to prepare an
acetylcellulose-containing elastic fiber, and treating the
acetylcellulose-containing elastic fiber with an alkali. However,
the publication does not mention the alkali or heat resistance of
the elastic fiber. In addition, the modulus of the elastic fiber is
far too low to solve the above-mentioned problems.
DISCLOSURE OF THE INVENTION
[0008] The present inventors have earnestly and intensively
conducted research to solve the above-mentioned problems, and as a
result, have found that when 1.about.20% by weight of a cellulose
acetate (diacetate or triacetate) having a degree of acetylation of
about 28% to about 72% is added to a polymer solution, based on the
solid content (i.e., polymeric components) of the polymer solution,
homogeneously stirring the mixture to obtain a spinning solution,
ripening the solution for a predetermined period of time, and
spinning the ripened solution, an elastic fiber having a high
modulus and superior resistance to heat and alkali can be easily
prepared without a sudden change in polymerization viscosity or
non-uniform physical properties of the fibrous product. The present
invention is based on this finding.
[0009] Therefore, it is an object of the present invention to
provide a process for preparing an elastic fiber having a high
modulus and superior resistance to heat and alkali under mild
process conditions.
[0010] In accordance with one aspect of the present invention,
there is provided a process for preparing an elastic fiber
comprising the steps of: adding 1.about.20% by weight of a
cellulose acetate to a polyurethane or polyurethaneurea solution,
based on the total weight of the polyurethane or polyurethaneurea,
to obtain a spinning solution; ripening the solution for a
predetermined period of time; and spinning the ripened
solution.
[0011] In accordance with another aspect of the present invention,
there is provided a high modulus and highly alkali and heat
resistant elastic fiber, which is prepared by the process.
[0012] Hereinafter, the present invention will be explained in more
detail.
[0013] The polyurethane or polyurethaneurea solution for use in the
present invention is obtained by procedures known in the art. For
example, an organic diisocyanate is reacted with a polymeric diol
to form a polyurethane precursor. After the polyurethane precursor
is dissolved in an organic solvent, the resulting precursor
solution is reacted with a diamine for chain extension. The chain
extension reaction is terminated by using a monoamine to obtain the
polyurethane or polyurethaneurea solution.
[0014] Examples of organic diisocyanates usable in the present
invention include diphenylmethane-4,4'-diisocyanate,
hexamethylenediisocyanate, toluenediisocyanate,
buthylenediisocyanate, hydrogenated p,p-methylenediisocyanate, and
the like. As the polymeric diol, there may be used, for example,
polytetramethyleneether glycol, polypropyleneglycol, or
polycarbonatediol, all of which preferably have a number-average
molecular weight of 1,750 to 2,050. Meanwhile, the diamine employed
as a chain extender may be ethylenediamine, propylenediamine,
hydrazine, or the like, and the monoamine employed as a chain
terminator may be diethylamine, monoethanolamine, dimethylamine, or
the like. Examples of suitable organic solvents that can be used to
obtain the polymer solution include, but are not particularly
limited to, N,N'-dimethylformamide, N,N'-dimethylacetamide,
dimethylsulfoxide, and the like.
[0015] If necessary, the polyurethane or polyurethaneurea solution
may further contain at least one additive selected from dulling
agents, UV stabilizers, antioxidants, NO, gas anti-yellowing
agents, anti-adhesion agents, dyeing promoters, and anti-chlorine
agents.
[0016] According to the process of the present invention,
1.about.20% by weight of the cellulose acetate is added to the
polyurethane or polyurethaneurea solution, based on the total
weight of the polymer, and the mixture is homogeneously stirred to
obtain a spinning solution. If the amount of the cellulose acetate
added is below 1% by weight, the addition effect is negligible. On
the other hand, if the amount of the cellulose acetate exceeds 20%
by weight, homogeneous mixing is difficult. The cellulose acetate
may be cellulose diacetate or cellulose triacetate, and preferably
has a degree of acetylation of about 28% to about 72%. The spinning
solution is ripened by allowing it to stand at 30.degree.
C..about.70.degree. C. for 28.about.38 hours, and is then spun to
prepare the final elastic fiber having a high modulus and superior
resistance to heat and alkali. According to a study undertaken by
the present inventors, since the homogeneous stirring of the
cellulose acetate as an additive and the polymer solution and the
ripening enable formation of urethane, urea and hydrogen bonds
between the polymer and the cellulose acetate, the steps have a
direct influence on the increase of the modulus and improvement in
the resistance to alkali and heat of the electric yarn.
Accordingly, it is important to set optimized conditions for the
steps. According to the process of the present invention, the
cellulose acetate is dissolved in the same organic solvent as that
used to obtain the polymer solution, the resulting solution is
homogeneously stirred for 7.about.8 hours, and then the homogeneous
solution is added to the polymer solution. Thereafter, the
resulting mixture is homogeneously stirred for at least 2 hours. At
this time, the stirring time is extended by 30 minutes with
increasing percentage of the cellulose acetate added. After
stirring, the mixture of the cellulose acetate and the polymer
solution is ripened for about 28.about.38 hours, and is then spun
through a spinning nozzle to prepare the final elastic fiber.
[0017] The constitution and effects of the present invention will
be described in more detail with reference to the following
specific examples and comparative examples. However, these examples
are given for the purpose of illustration and are not to be
construed as limiting the scope of the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Example 1
[0018] 518 g of diphenylmethane-4,4'-diisocyanate, and 2,328 g of
polytetramethyleneetherglycol having a number-average molecular
weight of 1,800 were reacted with each other at 85.degree. C. for
90 minutes with stirring to form a polyurethane precursor
containing isocyanate groups at both terminal positions. The
polyurethane precursor was allowed to cool to room temperature, and
was then dissolved in 4,643 g of N,N'-dimethylacetamide to obtain a
polyurethane precursor solution. Thereafter, 54 g of
propylenediamine, and 9.1 g of diethylamine were dissolved in 1,889
g of N,N'-dimethylacetamide, and the resulting solution was added
to the polyurethane precursor solution at 10.degree. C. or less to
produce a segmented polyurethaneurea solution.
[0019] To the polymer solution was added a UV stabilizer, an
antioxidant, a NO.sub.x gas anti-yellowing agent, a dyeing
promoter, a magnesium-based anti-adhesion agent and a
titanium-based dulling agent. The resulting solution was
homogeneously stirred. To the homogeneous solution was added a
solution of 1 wt % of cellulose diacetate having a degree of
acetylation of 45% in N,N'-dimethylacetamide, based on the solid
content of the polymer solution. Thereafter, the mixture was
defoamed for 2 hours, and ripened at 40.degree. C. for 35 hours to
obtain a spinning solution. The spinning solution was dry spun at a
spinning temperature of 250.degree. C., and drawn at a draw ratio
of 1.3 to prepare a polyurethaneurea elastic fiber having a
thickness of 40 deniers. The polyurethaneurea elastic fiber thus
prepared was wound.
[0020] 590 polyurethaneurea elastic fibers were warped, knitted
with 50-denier polyester yarns, and dyed to manufacture a velvet
fabric. The velvet fabric was subjected to burning-out and printing
processes. The yarns of the velvet fabric were measured for
resistance to heat and allcali, and the velvet fabric was measured
for power retention. In addition, the raised state of the fabric
before burning-out, and occurrence of holes on the fabric after
burning-out were evaluated. The results are shown in Table 1.
Example 2
[0021] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that a solution of 5% by weight of cellulose diacetate
(degree of acetylation: 45%) in N,N'-dimethylacetamide was added to
the polymer solution, based on the solid content of the polymer
solution, and homogeneous stirring was carried out for 4 hours.
Thereafter, a velvet fabric was manufactured in the same manner as
in Example 1, and was then subjected to burning-out and printing.
The properties of the velvet fabric were measured and evaluated,
and the results are shown in Table 1.
Example 3
[0022] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that a solution of 10% by weight of cellulose diacetate
(degree of acetylation: 45%) in N,N'-dimethylacetamide was added to
the polymer solution, based on the solid content of the polymer
solution, and homogeneous stirring was carried out for 6.5 hours.
Thereafter, a velvet fabric was manufactured in the same manner as
in Example 1, and was then subjected to burning-out and printing.
The properties of the velvet fabric were measured and evaluated,
and the results are shown in Table 1.
Example 4
[0023] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that a solution of 15% by weight of cellulose diacetate
(degree of acetylation: 45%) in N,N'-dimethylacetamide was added to
the polymer solution, based on the solid content of the polymer
solution, and homogeneous stirring was carried out for 9.5 hours.
Thereafter, a velvet fabric was manufactured in the same manner as
in Example 1, and was then subjected to burning-out and printing.
The properties of the velvet fabric were measured and evaluated,
and the results are shown in Table 1.
Example 5
[0024] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that a solution of 20% by weight of cellulose diacetate
(degree of acetylation: 45%) in N,N'-dimethylacetamide was added to
the polymer solution, based on the solid content of the polymer
solution, and homogeneous stirring was carried out for 12 hours.
Thereafter, a velvet fabric was manufactured in the same manner as
in Example 1, and was then subjected to burning-out and printing.
The properties of the velvet fabric were measured and evaluated,
and the results are shown in Table 1.
Example 6
[0025] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that cellulose triacetate (degree of acetylation: 65%) was
dissolved in N,N'-dimethylacetamide at 110.degree. C. for 30
minutes and then the resulting solution was added to the polymer
solution so that the amount of the cellulose triacetate was 1% by
weight, based on the solid content of the polymer solution, and
homogeneous stirring was carried out for 2 hours. Thereafter, a
velvet fabric was manufactured in the same manner as in Example 1,
and was then subjected to burning-out and printing. The properties
of the velvet fabric were measured and evaluated, and the results
are shown in Table 1.
Example 7
[0026] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that cellulose triacetate (degree of acetylation: 65%) was
dissolved in N,N'-dimethylacetamide at 110.degree. C. for 30
minutes and then the resulting solution was added to the polymer
solution so that the amount of the cellulose triacetate was 5% by
weight, based on the solid content of the polymer solution, and
homogeneous stirring was carried out for 2 hours. Thereafter, a
velvet fabric was manufactured in the same manner as in Example 1,
and was then subjected to burning-out and printing. The properties
of the velvet fabric were measured and evaluated, and the results
are shown in Table 1.
Example 8
[0027] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that cellulose triacetate (degree of acetylation: 65%) was
dissolved in N,N'-dimethylacetamide at 110.degree. C. for 30
minutes and then the resulting solution was added to the polymer
solution so that the amount of the cellulose triacetate was 10% by
weight, based on the solid content of the polymer solution, and
homogeneous stirring was carried out for 2 hours. Thereafter, a
velvet fabric was manufactured in the same manner as in Example 1,
and was then subjected to burning-out and printing. The properties
of the velvet fabric were measured and evaluated, and the results
are shown in Table 1.
Example 9
[0028] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that cellulose triacetate (degree of acetylation: 65%) was
dissolved in N,N'-dimethylacetamide at 110.degree. C. for 30
minutes and then the resulting solution was added to the polymer
solution so that the amount of the cellulose triacetate was 15% by
weight, based on the solid content of the polymer solution, and
homogeneous stirring was carried out for 2 hours. Thereafter, a
velvet fabric was manufactured in the same manner as in Example 1,
and was then subjected to burning-out and printing. The properties
of the velvet fabric were measured and evaluated, and the results
are shown in Table 1.
Example 10
[0029] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that cellulose triacetate (degree of acetylation: 65%) was
dissolved in N,N'-dimethylacetamide at 110.degree. C. for 30
minutes and then the resulting solution was added to the polymer
solution so that the amount of the cellulose triacetate was 20% by
weight, based on the solid content of the polymer solution, and
homogeneous stirring was carried out for 2 hours. Thereafter, a
velvet fabric was manufactured in the same manner as in Example 1,
and was then subjected to burning-out and printing. The properties
of the velvet fabric were measured and evaluated, and the results
are shown in Table 1.
Comparative Example 1
[0030] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that a solution of 25% by weight of cellulose diacetate
(degree of acetylation: 45%) in N,N'-dimethylacetamide was added to
the polymer solution, based on the solid content of the polymer
solution, and homogeneous stirring was carried out for 9.5 hours.
Thereafter, a velvet fabric was manufactured in the same manner as
in Example 1, and was then subjected to burning-out and printing.
The properties of the velvet fabric were measured and evaluated,
and the results are shown in Table 1.
Comparative Example 2
[0031] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that cellulose triacetate (degree of acetylation: 65%) was
dissolved in N,N'-dimethylacetamide at 110.degree. C. for 30
minutes and then the resulting solution was added to the polymer
solution so that the amount of the cellulose triacetate was 25% by
weight, based on the solid content of the polymer solution, and
homogeneous stirring was carried out for 2 hours. Thereafter, a
velvet fabric was manufactured in the same manner as in Example 1,
and was then subjected to burning-out and printing. The properties
of the velvet fabric were measured and evaluated, and the results
are shown in Table 1.
Comparative Example 3
[0032] A polyurethaneurea elastic fiber having a thickness of 40
deniers was prepared and wound in the same manner as in Example 1,
except that cellulose diacetate was not added. Thereafter, a velvet
fabric was manufactured in the same manner as in Example 1, and was
then subjected to burning-out and printing. The properties of the
velvet fabric were measured and evaluated, and the results are
shown in Table 1. TABLE-US-00001 TABLE 1 Evaluation of Fabrics
Occurrence of Evaluation of Yarns Raised state holes on Modulus
Heat Alkali Power before fabric after Exa. No. (g)
resistance.sup.1) resistance.sup.2) retention.sup.3)
burning-out.sup.4) burning-out.sup.5) Remarks Ex. 1 5.4 47% 117
min. 39.7% .DELTA. Occurred Ex. 2 6.2 65% 130 min. 47.3%
.largecircle. Few occurred Ex. 3 5.9 63% 133 min. 44.5%
.largecircle. Few occurred Ex. 4 5.7 54% 125 min. 42.7% .DELTA. Few
occurred Ex. 5 5.4 48% 121 min. 40.4% .DELTA. Occurred Ex. 6 5.5
50% 129 min. 41.6% .DELTA. Few occurred Ex. 7 6.5 69% 145 min.
48.8% .largecircle. Few occurred Ex. 8 6.1 67% 152 min. 46.0%
.largecircle. Few occurred Ex. 9 5.8 58% 136 min. 42.9% .DELTA. Few
occurred Ex. 10 5.3 53% 135 min. 41.1% .DELTA. Few occurred Comp.
4.9 42% 115 min. 38.5% .DELTA. Many Homogeneous Ex. 1 occurred
mixing was difficult Comp. 4.6 45% 127 min. 39.0% .DELTA. Few
occurred Homogeneous Ex. 2 mixing was difficult Comp. 5.1 45% 113
min. 39.2% .DELTA. Many Ex. 3 Occurred Notes: .sup.1)The heat
resistance of the yarns was evaluated by the following procedure: A
yarn sample is stretched by 100%, and wet-heat treated at
130.degree. C. for 1 hour. The heat treatment is repeated five
times (5 cylces). The heat resistance of the yarn sample is
expressed as percentage of the difference between the length
("initial length") of the yarn sample before the heat treatment and
that ("download value") after the fifth cycle. .sup.2)The alkali
resistance of the yarns was evaluated by the following procedure: A
yarn sample is dipped in an 25% aqueous NaOH (25 wt %) solution,
and heated to 150.degree. C. The alkali resistance of the yarn
sample is expressed as the time taken for the yarn sample to
decompose. .sup.3)The power retention of the fabrics was measured
by the following procedure: A finally processed fabric is cut into
a fabric sample (1 inch .times. 30 cm). The fabric sample is held
by grips from Instron Co., so that the length of the fabric sample
for measurement is 20 cm. The # holding is repeated five times (5
cycles). The power retention of the fabric sample is expressed as
percentage of the difference between the length ("upload value") of
the fabric sample after the first cycle and that ("download value")
after the fifth cycle. .sup.4)The raised state before burning-out
was evaluated by visually examining the degree of uprightness of
raised yarns after the velvet fabrics were subjected to shearing
and background dyeing. When the raised yarns were straight and
upright, the raised state was judged as ".largecircle.". On the
other hand, when some of the raised yarns were flattened, the state
was judged as ".DELTA.". .sup.5)The occurrence of holes on the
fabrics after burning-out was evaluated by visual examination.
[0033] As shown in Table 1, since the process of the present
invention enables uniform management of polymerization and spinning
viscosity, the elastic fibers show uniform physical properties, a
high modulus, and improved resistance to heat and alkali.
Accordingly, when the process of the present invention is applied
to general velvet fabrics or special velvet fabrics requiring
continuous burning-out and printing, it has advantages that no
degradation of elastic fibers arises, and the state of raised yarns
and fabrics is stably maintained.
[0034] Although the preferred embodiments of the present invention
have been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *