Polyester fiber, process for the production and process for the dyeing of the fibrous structure of the polyester fiber

A fiber of a polyester, in which 80% or more of the repeating units are composed of ethylene terephthalate, characterized in that it satisfies the following inequalities: EQU 0.16<tan .delta..sub.max <0.22 1 EQU 115<T.sub.max <140 2 EQU D.sub.100 <-3.79.times.d.sup.1/2 +91 3 EQU D.sub.130 >-11.36.times.d.sup.1/2 +58 4 as well as a process for the production and dyeing of a fibrous structure of the polyester fiber. According to the present invention, especially in deep color dyeing at a high temperature, the degree of dye exhaustion is improved, and the utilization efficiency of the dye is enhanced, and moreover, especially in an extremely fine fiber yarn, a polyester fibrous structure having a concentration of a color shade equal to that of an ordinary yarn, which has never been obtained by the conventional process can be provided. In addition, there can be provided a polyester fiber and a fibrous structure thereof that are excellent in coloring properties and color fastness and can be used for various purposes.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a polyester fiber exhibiting excellent 
dyeing properties at a high temperature, although its normal pressure 
dyeability is low, and a process for the production as well as a process 
for the dyeing of the fibrous structure of the polyester fiber. 
2. Description of the Related Art 
A polyester fiber has a high refractive index among the various synthetic 
fibers, and is remarkably inferior to an acetate fiber in coloring 
properties, even when dyed with the same dye concentration. Since, in an 
extremely fine fiber of polyester, the surface area per a determined 
weight is increased, and irregular reflections of light (white light) on 
the fiber surface are increased, it has been said that a dyed product does 
not exhibit a high color value compared to an ordinary yarn, even if the 
same amount of dye is used. In order to obtain a dyed product having a 
deep color, a so-called "high concentration dyeing", becomes necessary in 
which a dye with a concentration 2 to 6 times as high as the dye 
concentration for an ordinary yarn is used. 
The disadvantages of the high concentration dyeing are as follows: 
(A) A large quantity of dye is required, and the utilization efficiency of 
the dye is lowered, resulting in high production costs. 
(B) Many hours are required for dyeing or the cleaning of a dyeing machine. 
(C) The fastnesses of a dyed product is lowered. 
That is, there are many problems with respect to coloring properties, 
qualities, workability and production cost, and refinements in these 
problems are in demand. 
With respect to refinement in the dyeability of a polyester fiber, 
examination of preliminary treatments of the polyester fiber with hot 
water and a solvent has been proposed by Kuwabara (Sen-i-gakkaishi 
[Journal of the Institute of Fibers], vol 34, No. 9, p. 56 (1978)), Wakita 
(Sen-i-gakkaishi, vol. 37, No- 5, p. 33 (1981)), and Katayama ("Senshoku 
Kogyo" [Dyeing Industry], vol. 24, No. 7, p. 10 (1976)). 
In addition, as property modification of a material fiber for making the 
fiber dyeable under normal or atmospheric pressures, there have been 
proposed a process for the copolymerization of a polyalkylene glycol with 
a polyethylene terephthalate in, e.g., Japanese Unexamined Patent 
Publication No. 52-63292 and Japanese Unexamined Patent Publication No. 
54-156861, and a process for the copolymerization of a polyalkylene glycol 
and isophthalic acid with a polyethylene terephthalate in Japanese 
Unexamined Patent Publication No. 53-35022. 
Furthermore, as a process for spinning a polyethylene terephthalate at a 
high speed so as to obtain a fiber that is dyeable under normal pressures, 
there has been proposed, in Japanese Unexamined Patent Publication No. 
57-161121, a normal pressure dyeable polyester fiber comprising a high 
speed spun polyethylene terephthalate fiber with a value of tan 
.delta..sub.max greater than 0,135 (0,135&lt;tan .delta..sub.max) and a value 
of T.sub.max (.degree. C.) not higher than 105 (T.sub.max (.degree. 
C.).ltoreq.105) in a mechanical loss tangent tan .delta.-temperature T 
curve obtained by a measurement of dynamic viscoelasticity. 
In the aforesaid Kuwabara's process, the preliminary treatment is effected 
at a temperature ranging from 106.degree. C. and 135.degree. C., and the 
dyeing is effected at a temperature of 105.degree. C. at the highest, and 
in the aforesaid Wakita's process, the preliminary treatment is effected 
at a temperature of 140.degree. C. at the highest, and the dyeing is 
effected at a temperature of 120.degree. C. at the highest. However, a 
deep color-improving effect for a polyester fiber has not been sufficient 
according to any of these processes. 
In other words, though the aforesaid hitherto known techniques are intended 
to improve the dyeing properties of a polyester at a low temperature, a 
notably high dyeability at a high temperature has not been obtained. 
On the other hand, Katayama's process has been a process in which a dye is 
added to a water soluble high boiling medium and dyeing is effected at a 
high temperature. This process has, however, a defect in the sublimability 
of the dye and the dyeing fastnesses. 
Also with respect to the aforesaid reforming process of a material fiber, 
when a polyalkylene glycol with a small repeating unit such as 
polyethylene glycol is copolymerized, the light exposure properties of the 
material fiber are likely to lower. 
In addition, in the high speed spun fiber disclosed in Japanese Unexamined 
Patent Publication No. 57-161121, that is, a fiber with T.sub.max 
(.degree. C.).ltoreq.105, T.sub.max of the conventional drawn yarn for 
clothing within the range between 135 and 140.degree. C., the packing 
density of a molecular chain belonging to an amorphous region is reduced 
owing to the lowering of the T.sub.max value and normal pressure 
dyeability has been obtained, but there is the problem in that the fiber 
is inferior in characteristics at a high ductility and has a high 
crystallization degree, which makes it difficult to control the degree of 
shrinkage and the like, and the utilization sphere of which is therefore 
narrow. 
Accordingly, by the processes of the aforesaid prior art, though normal 
pressure dyeability may be imparted to a polyester fiber, there have been 
defects in that the dyeing properties of the fiber at a low temperature 
cannot be said to be sufficient, that the color fastness is lowered, or 
that certain properties, such as the mechanical properties of the 
polyester fiber, are degraded. 
In addition, since dyeing of a polyester fiber is generally inferior in 
coloring properties, it is effected by increasing the concentration of the 
dye as a measure to counter this tendency. However, the utilization 
efficiency of the dye cannot be improved by such a measure, and therefore, 
there have been problems with respect to production costs, as well as 
drainage. 
Further, although it has been recognized that when a polyester fiber is 
dyed at a temperature of 120.degree. C. or more, adequate dyeing 
properties can be obtained, the present inventors' examination has proven 
that especially in the dyeing of an extremely fine fiber, improved dyeing 
properties become necessary to obtain a deep color. 
The aforesaid techniques of improving dyeing properties have been 
insufficient. 
SUMMARY OF THE INVENTION 
The object of the present invention is, to provide a polyester fiber with 
high dyeability and a production process and dyeing process, without 
impairing the properties (mechanical properties, chemical resistance, and 
color fastnesses) of the polyester fibers, and to prevent the utilization 
efficiency of the dye from being lowered under high temperature dyeing 
conditions. 
The present invention has the following constitution for the purpose of 
achieving the aforesaid object. 
That is, the present invention relates to a fiber of a polyester, in which 
80% or more of the repeating units are composed of ethylene terephthalate, 
characterized in that it satisfies the following inequalities 1 to 4. 
EQU 0.16&lt;tan .delta..sub.max &lt;0.22 1 
EQU 115&lt;T.sub.max &lt;140 2 
EQU D.sub.100 &lt;-3.79.times.d.sup.1/2 +91 3 
EQU D.sub.130 &gt;-11.36.times.d.sup.1/2 +58 4 
wherein 
tan .delta..sub.max : a peak value in a mechanical loss tangent tan 
.delta.-temperature T curve obtained by a measurement of dynamic 
viscoelasticity; 
T.sub.max (.degree. C.): a temperature at which tan .delta. in a mechanical 
loss tangent tan .delta.-temperature T curve obtained by a measurement of 
peak dynamic viscoelasticity; 
D.sub.100 : dye exhaustion degree at 3% o.w.f. of Resolin Blue FBL at 
100.degree. C.; 
D.sub.130 : dye exhaustion degree at 5% o.w.f. of Samaron GSL-400 at 
130.degree. C.; and 
d: monofilament denier. 
The present invention further relates to a process for the production of a 
polyester fibrous structure, comprising subjecting a fibrous structure of 
a polyester, in which 80% or more of the repeating units are composed of 
ethylene terephthalate, to a heat treatment at a temperature of 
160.degree. C. or more with water or steam. 
In addition, the present invention relates to a process for the production 
of a polyester fibrous structure comprising heat treating a fibrous 
structure of a polyester, in which 80% or more of the repeating units are 
composed of ethylene terephthalate, at a temperature of 160.degree. C. or 
higher in a medium, that is diffusible in said polyester fiber but has 
little swelling effect, and subsequently subjecting the structure to a 
medium-eliminating treatment. Furthermore, the present invention relates 
to a process for the dyeing of a fibrous structure of a polyester, in 
which 80% or more of the repeating units are composed of ethylene 
terephthalate, comprising effecting the aforesaid treatment before dyeing 
the fibrous structure, and subjecting the fibrous structure to exhaustion 
dyeing at a dyeing temperature .ranging from 120.degree. C. to 150.degree. 
C. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following, the present invention will be explained in detail. 
The present inventors have found that, since the excellent characteristics 
of a polyester fiber are degraded when normal pressure dyeability thereof 
is increased, by lowering the normal pressure dyeability, i.e., the dyeing 
properties at a low temperature, and by notably heightening the dyeability 
in high temperature dyeing, it becomes possible to make a polyester fiber 
deep colored without impairing the excellent properties of the polyester 
fiber, and the fiber becomes a polyester fiber with ideal high dyeability. 
Such a polyester fiber of high dyeability at a high temperature can be 
obtained by controlling the fiber structure by the preliminary treatment 
of a specific compound under specific conditions before the polyester 
fiber is preliminarily treated, as mentioned hereafter. 
The present invention has succeeded in fixing a highly concentrated dye 
into the inside of a polyester fiber by subjecting the polyester fiber to 
a preliminary treatment under specific conditions (as mentioned hereafter, 
when a solvent other than water or steam is used, it is preferable to 
subject the polyester fiber to a medium-eliminating treatment after the 
preliminary treatment has been completed) as a result of careful 
examination of the interrelation among the preliminary treatment, the 
fibrous structure, the degree of fineness (d) and the dependence on dyeing 
temperature, and subsequently, preferably subjecting the preliminarily 
treated polyester fiber to high temperature exhaustion dyeing. 
According to the present invention, there are advantages in that the 
utilization efficiency of the dye can be improved even in the case of high 
concentration dyeing, the amount of the dye used may be reduced as 
compared to the conventional process, and a dyed product excellent in 
fastnesses can be provided. 
The polyester fiber of the present invention, having good dyeing properties 
at a high temperature, is formed by changing and controlling the fibrous 
structure by the hereinafter mentioned preliminary treatment, and it is 
presumed that the number of dyeing seats is increased in the state such 
that the structure of the amorphous portion that is to become a dyed 
portion of the dye does not become too loose, which is also supported by a 
measurement of the dynamic viscoelasticity of the fiber. 
In the first place, a detailed explanation will be made of the polyester 
fiber of the present invention. 
The requirements 1 and 2 for a high temperature -high dyeability polyester 
fiber referred to in the present invention will be explained. 
EQU 0.16&lt;tan .delta..sub.max &lt;0.22 1 
EQU 115&lt;T.sub.max &lt;140 2 
wherein tan .delta..sub.max indicates a peak value of tan .delta. in a 
mechanical loss tangent tan .delta.-temperature T curve obtained by a 
measurement of dynamic viscoelasticity, and T.sub.max (.degree. C.) 
indicates a temperature at which tan .delta. reaches a peak value. 
The value of tan .delta. referred to in the present invention can be 
obtained from a mechanical loss tangent Tan .delta.-temperature T curve 
obtained by a measurement of dynamic viscoelasticity. To be concrete, when 
this measurement is effected using Viblon ("DDV-II-EP produced by 
Orientech Co., Ltd.) and at a temperature rising rate of 3.degree. C./min, 
the values of tan .delta..sub.max and T.sub.max are, respectively, within 
the ranges as defined by the inequalities, although the value of tan 
.delta..sub.max of the conventional polyethylene terephthalate fiber with 
a monofilament fineness ranging from 2 to 3 deniers for clothing is within 
the range between about 0.145 and about 0.150, and T.sub.max thereof is 
within the range between about 135.degree. C. and about 140.degree. C. 
It has hitherto been said that the value of tan .delta..sub.max obtained by 
a measurement of dynamic viscoelasticity corresponds to the amorphous 
amount of the polyester fiber, while T.sub.max indicates the compactness 
or looseness (the weakness of the force of constraint of the polyester 
molecular chain) (see, e.g., Kamide et al., Senshoku Kogyo [Dyeing 
Industry], vol. 32, No. 7, p. 26, (1984)). The polyester fiber of the 
present invention has a tan .delta..sub.max value higher than an ordinary 
polyester fiber, and has a T.sub.max value ranging from a value equivalent 
to that of the ordinary polyester fiber to a value higher than that of the 
ordinary polyester fiber by 20.degree. C. 
That is, the above fact is presumed, with respect to the fibrous structure 
of the present invention, to indicate that the compactness of the 
amorphous region of the present fiber structure is not that different than 
the conventional polyester fiber, in relation to T.sub.max, and the amount 
of the amorphous region of the present fibrous structure is increased 
compared to that of the conventional polyester fiber, in relation to tan 
.delta..sub.max. 
That is, the high temperature - high dyeability polyester fiber of the 
present invention is characterized in that it has an increased value of 
tan .delta..sub.max without noticeable lowering the value of T.sub.max as 
compared to the conventional ordinary polyester fiber. 
Next, the requirements 3 and 4 of the high temperature - high dyeability 
polyester fiber referred to in the present invention will be explained: 
EQU D.sub.100 &lt;-3.79.times.d.sup.1/2 +91 3 
EQU D.sub.130 &gt;-11.36.times.d.sup.1/2 +58 4 
wherein 3 indicates a degree of dye exhaustion of Resolin Blue FBL 
(hereinafter referred to as "FBL degree of exhaustion") when dyeing is 
effected by the use of 3% o.w.f. of Resolin Blue FBL at a bath ratio of 
1:5 at 100.degree. C. for 60 min, and 4 indicates a degree of dye 
exhaustion of Samaron Blue GSL-400 (hereinafter referred to as "GSL degree 
of exhaustion") when dyeing is effected by using 5% o.w.f. of Samaron Blue 
GSL-400 at a bath ratio of 1:20 at 130.degree. C. for 60 min. 
That is, the FBL degree of exhaustion is one of the parameters such that if 
one of these parameters is 85% or more in an ordinary yarn, this parameter 
indicates normal pressure dyeability of the ordinary yarn, when the 
ordinary yarn is dyed under the dyeing conditions as defined in 3 (refer 
to Senshoku Kogyo [Dyeing Industry], vol. 32, No. 7, p. 26, (1984)). 
The GSL degree of exhaustion indicates a value approximate to the saturated 
dyed amount of Samaron Blue GSL-400 in the case of practical dyeing and 
also indicates dyeing properties in the case of high temperature dyeing. 
In the present invention, although the dyeing properties vary depending on 
the fineness (d), when e.g., a fiber having a monofilament fineness of 2.5 
deniers is used, this fiber is a high temperature - high dyeability 
polyester fiber with an FBL degree of exhaustion (D.sub.100) smaller than 
85% and a GSL degree of exhaustion (D.sub.130) of 40% or more. The value 
of D.sub.130 is preferably 50% or more. 
The D.sub.100 value of the conventionally used polyethylene terephthalate 
fiber (monofilament fineness: 2 to 3 deniers) is about 46% and the 
D.sub.130 value is about 26%, and the D.sub.100 value of an extremely fine 
yarn (single yarn fineness: 0.07 denier) is about 87% and the D.sub.130 
value thereof is about 47%. 
On the other hand, a known normal pressure dyeable yarn, e.g., a 
copolymerized or high speed spun polyester fiber exhibits a D.sub.100 
value of 85% or more, which is out of the scope of the present invention. 
Such a polyester fiber with high low temperature dyeing properties do not 
always exhibit high dyeing properties at a high temperature; in many of 
such polyester fibers, the D.sub.130 value is lower than 40%, and even in 
the case where D.sub.130 exhibits a value of 40% or more, if low 
temperature dyeing properties are high, the dyeing fastnesses 
deteriorates, which is not preferable. 
One of the features of the present invention is that D.sub.100 is lower 
than a definite value, that is, the fiber is not normal pressure dyeable 
is presumed to correspond to the characteristic that the degree of 
looseness of the amorphous region in the fiber structure, and the feature 
that the D.sub.130 value is large is presumed to correspond to some degree 
of the dyeing property of the fiber is high at a high temperature and high 
concentration, that is, the number of dyeing seats of the polyester fiber 
is increased. 
The high temperature - high dyeing property fiber of the present invention 
has advantages in that it exhibits good dyeing properties to various kinds 
of disperse dyes, and it exhibits a degree of exhaustion 1.3 to 1.8 times 
as high as that of the conventional polyester fiber, for a deep color, and 
the color fastness is hardly lowered. The fiber of the present invention 
is effective for a fiber having an ordinary denier, and especially 
effective for an extremely fine fiber requiring an increased amount of a 
dye for the dyeing thereof, so that it becomes possible to express deep 
colors in a region that have never been attained. 
The polyester fiber referred to in the present invention is a fiber of an 
ethylene terephthalate polymer in which 80% or more of the repeating units 
are composed of ethylene terephthalate, and as a polyester component, 
polyethylene terephthalate, polybutylene terephthalate, and various 
modified polymers thereof are included. At least 90% of the repeating 
units synthesized from a dicarboxylic acid with a high heat resistance and 
a diol are preferably composed of polyethylene terephthalate, though not 
particularly limited. The present polyester fiber is preferably of 
polyethylene terephthalate. In addition, an ordinary additive such as a 
delustering agent, flame retarder, and light resisting agent may be 
contained in the present polyester fiber. 
Polyester fibers having a monofilament fineness of 20 deniers or less are 
used. The fiber that is preferably used in the present invention is a 
fiber having a monofilament fineness ranging preferably from 0.0001d to 
1d, more preferably from 0.0001d to 0.5d, and most preferably from 0.0001d 
to 0.1d. 
Such an extremely fine fiber as mentioned above may be a fiber produced by 
any process, generally, one produced of an islands-in-sea type composite 
fiber, one produced by direct spinning, one produced of a divided type 
composite fiber, or the like. 
Examples of the fibrous structure of the present invention include yarn, 
loose fiber, fabric, non-woven fabric, sheet and the like, and the present 
fibrous structure is not particularly limited. This fibrous product may be 
a mixed product of a polyester fiber and other fibers. 
In the following, the process for the production of high temperature - high 
dyeability polyester fibers of the present invention will be explained. 
The production process of the present invention is a process in which a 
polyester fiber is subjected to a preliminary treatment at a temperature 
of 160.degree. C. or higher using a gas or liquid diffusible in the 
polyester fiber, before dyeing the polyester fiber. When the treatment 
temperature is lower than 160.degree. C., the high temperature -high 
dyeability fiber of the present invention cannot be obtained, and this 
temperature range is not preferable. The preliminary treatment temperature 
is preferably 180.degree. C. or higher, and more preferably 190.degree. C. 
or higher. 
The treatment may be effected by optionally setting the treating time such 
that the aforesaid dynamic viscoelastic characteristic satisfies the 
requirements 1 and 2. 
As the preliminary treatment, a high temperature wet heat treatment with 
water or steam or a preliminary treatment using a water soluble 
hardly-swelling medium diffusible into a polyester fiber is preferably 
used. 
As a high temperature wet heat treatment, preliminary treatments at a 
temperature ranging from 160.degree. to 230.degree. C., respectively, 
using high temperature steam, superheated steam and high temperature hot 
water may be considered. 
As a preliminary treatment using a water soluble hardly-swelling medium 
diffusible in a polyester fiber, a preliminary treatment to be effected at 
a temperature ranging from 160.degree. to 210.degree. C. may be 
considered. In particular, when a water soluble high boiling solvent is 
used, the preliminary treatment can be effected under normal pressures. 
A high temperature wet heat treatment using water or steam is preferable 
because it is a non-polluting process, but the cost is high because of the 
device for treatment thereof. 
The water soluble hardly-swelling medium referred to in the present 
invention may be a medium that exhibits a solubility of 10% to water at 
room temperature and hardly exhibits a swelling capabability with respect 
to a polyester fiber at room temperature. 
As the water soluble hardly-swelling medium, there may be mentioned, e.g., 
alcohol type mediums such as methanol, ethanol, propanol, and butanol; 
glycol type mediums such as ethylene glycol, diethylene glycol, 
triethylene glycol, propylene glycol, dipropylene glycol, tripropylene 
glycol, polypropylene glycol, polyethylene glycol, hexylene glycol, and 
glycerine; and diols such as 1,3-butanediol, and 1,4-butanediol. 
Of the water soluble hardly-swelling mediums, those having a solubility 
parameter of 13.4 or more are preferable, and examples thereof are 
diethylene glycol, polyethylene glycol, propylene glycol, polypropylene 
glycol, hexylene glycol and the like. More preferably, mediums that have a 
high boiling point and a small molecular weight, i.e., polyethylene 
glycols or polypropylene glycols having a molecular weight of 300 or less, 
or the like may be considered. They can be used individually or as a blend 
of 2 or more and when the molecular weight of the medium is 600 or more, 
this medium is unlikely to be diffused into a polyester fiber. 
The aforesaid mediums may be used individually, or as a blend of 2 or more, 
or as an aqueous solution thereof. 
In addition, when a medium with a boiling point of 220.degree. C. or lower, 
e.g., a low boiling medium such as water, methanol, ethanol, and ethylene 
glycol is used for the preliminary treatment, this treatment is effected 
under pressure, although the kind of the medium used varies depending upon 
the treating temperature. When effecting a treatment under pressure, water 
or steam is preferably used, and water is particularly preferable. When 
the treatment is effected under normal pressures, glycerine, diethylene 
glycol, triethylene glycol, polyethylene glycol, and propylene glycol are 
preferably used, and diethylene glycol, triethylene glycol, and propylene 
glycol are most preferably used. By using this treating method under 
normal pressures, very advantageous results with respect to productivity, 
equipment and production cost may be obtained. 
When a swelling agent with a solubility parameter approximate to that of 
the polyester fiber (10.7) is used, many hours are required for a swelling 
agent-eliminating treatment owing to its considerably greater affinity for 
the fiber, and therefore, use of such a swelling agent is not preferable. 
In the present invention, in order to obtain a high temperature - high 
dyeability, conditions that impart a sufficient change in fiber structure 
are required. According to the present inventor's examination, such a 
purpose can be achieved by the treatment under the aforesaid conditions, 
e.g., 160.degree. C..times.2 minutes or more, and a treatment of 5 minutes 
or more is more preferable. In the light of the shrinkage percentage of 
the fiber, it has been found that under the treatment conditions such that 
the shrinkage percentage of an ordinary polyethylene terephthalate 
oriented yarn (shrinkage in boiling water: 9%; monofilament fineness: 2 to 
3d) becomes 13% or more, a change in fibrous structure occurs, which is 
enough to exhibit the effect of the present invention. The fiber or fabric 
to be herein treated is not always required to be treated to have the 
above shrinkage percentage, and a sufficient effect has been recognized by 
the treatment under tension or under a determined length. 
Such treating conditions are preferably selected by synthetic judgement of 
not only the fixing rate and color development of the dye but by hand 
(shrinkage percentage), fiber strength and the like. 
Although the high temperature wet heat treatment and treatment by using a 
water soluble hardly-swelling medium according to the present invention is 
effected most preferably under no tension, its effects are sufficiently 
exhibited even by a treatment under tension. 
In the treatment using water or steam, a medium-eliminating treatment is 
not particularly required, but after a treatment using a water soluble 
hardly-swelling medium has been effected, it is preferable to effect a 
treatment for eliminating the medium. When the water soluble 
hardly-swelling medium remains in the polyester fiber, the solubility of 
the disperse dye becomes higher than required, thereby resulting in a 
noticeable lowering of the fixability of the dye, or discoloration of 
fabric. Therefore, it is preferable to eliminate the medium to the 
greatest possible extent. 
It is presumed that in the polyester fiber that has been subjected to the 
aforesaid treatment, there is formed a fiber structure that is likely to 
absorb the dye, and the formed fiber structure is apt to be easily broken 
by again being subjected to a heat treatment (high temperature heat 
treatment) and a return to the original state of the fiber before it is 
subjected to the preliminary treatment. Accordingly, since the dyeability 
of the fiber is likely to be lowered owing to the second heat treatment 
followed by the preliminary treatment, it is preferable to maintain a 
fiber structure capable of easily absorbing the dye and transferring the 
fiber having the thus maintained fiber structure into the subsequent 
dyeing step. For this purpose, it is preferable to eliminate the medium at 
a relatively low temperature in the medium-eliminating treatment. The 
condition of such a medium elimination is washing of the fiber with water 
or a solvent at a temperature of 160.degree. C. or lower, or treatment of 
the fiber with hot air at a temperature of 160.degree. C. or lower, and 
also in the subsequent drying step, treatment of the fiber at a 
temperature of 160.degree. C. or lower, preferably 130.degree. C. or 
lower, constitutes a preferable condition for obtaining high dyeability. 
In the present invention, the amount of such a remaining medium is 
controlled to preferably 5 wt-% or less, more preferably to 2 wt-% or 
less. 
By dyeing the thus obtained fiber at a high temperature, it is possible to 
apply the dye to the fiber by using the high fixability and high 
efficiency of the dye and thereby provide a colored fibrous structure 
having sufficient fastness, though it has high coloring properties. 
Subsequently, the fiber is transferred to a dyeing step followed by a 
medium-eliminating treatment. (When the fiber is to be subjected to a 
preliminary treatment with steam or water, the fiber is transferred to a 
dyeing step after the preliminary treatment has been completed, without 
effecting a medium-eliminating treatment.) As the dye, a disperse dye that 
has widely been used for a polyester fiber is used. 
As the dyeing method, any, e.g., continuous bath dyeing, printing, and 
exhaustion dyeing may be used, but the exhaustion dyeing method is most 
preferably used. In the exhaustion dyeing method, the dyeing is effected 
preferably at a temperature ranging from 120.degree. C. to 150.degree. C., 
more preferably from 130.degree. C. to 140.degree. C. 
In the present invention, there is adopted a temperature under which the 
dye is easily absorbed in the fiber and the fiber structure changes, and 
the fiber is subjected to a medium-eliminating treatment, while such a 
temperature is maintained, whereafter the greatest possible amount of the 
dye is absorbed into the fiber by an ordinary high temperature dyeing, so 
as to fix the dye to the fiber. This dyeing at a high temperature is 
considered to excite both the exhaustion of the dye and a change in the 
fiber structure (a change in the fiber to return to the original state 
before the preliminary treatment). In addition, if, when effecting the 
medium-eliminating treatment, the treating temperature is excessively 
high, the fiber structure becomes similar to the original state before the 
preliminary treatment, it is likely that improvement of the fixability of 
the dye cannot be expected. That is, it is considered that the present 
invention has the function of securely fixing a large quantity of a dye by 
exhausting the dye into the fiber, and returning the fiber to the original 
fiber structure while the dye-exhausted state is being retained, during a 
high temperature dyeing, and consequently, the obtained dyed product 
attains an excellent color fastness. 
According to the present invention, the utilization efficiency of the dye 
can be improved even in a high concentration dyeing, and the amount of dye 
used can be reduced compared to the conventional method, and a dyed 
product with excellent various fastness characteristics can be provided. 
By the present invention, a colored fibrous structure having sufficient 
fastnesses and high coloring properties can be provided, by exhausting the 
dye to a polyester fiber by making the fiber highly fixable and highly 
utilizable, and when an extremely fine fiber is used, the coloring 
properties are very low compared to an ordinary yarn, even at the same dye 
concentration, and therefore, an extremely fine fiber is dyed with a dye 
of an amount 2 to 6 times higher than when an ordinary yarn is to be dyed, 
so that the effect of the present invention is very significant. 
In addition, the deeper the color of a dyed product to be obtained, the 
more the true merit of the present invention is proven. For example, deep 
color dyeing, in which the dye concentration (by the standard of 100% in 
the case of a commercially available dye) of preferably 2 wt-% or more, 
more preferably 3 wt-% or more is applied to a fabric, can be stably 
achieved with good reproducibility. Furthermore, when the same color 
concentration is to be obtained, the color fastness is improved in the 
dyed product obtained in the present invention, compared to the dyed 
product obtained by the conventional method. 
In addition, after the dyeing has been completed, the dyed product may be 
subjected to an ordinary soaping step, if necessary.

The present invention will be explained in more detail with reference to 
the following non-limitative working examples. 
EXAMPLES 1 TO 14, AND COMATIVE EXAMPLES 1 to 5 
As a fabric composed of a regular yarn (ordinary yarn), a fabric (taffeta) 
was used, the warp and weft of which were, respectively, polyethylene 
terephthalate fiber (150 deniers-48 filaments), which had been scored and 
heat set (Examples 1, 3, 5, 7, 9, 11). 
In addition, as an extremely fine yarn, a fabric composed of an extremely 
fine fiber with a monofilament fineness of 0.07 denier was used and was 
obtained by subjecting a fabric (taffeta) of a 50 deniers-9 filaments 
yarn) consisting of a polyethylene terephthalate copolymerized with 4 
mol-% of 5-sodium sulfoisophthalic acid as a sea component and a 
polyethylene terephthalate as an island component (70 islands per 
filament; the ratio of sea to islands: 10:90) to a treatment with an 
alkali (Examples 2, 4, 6, 8, 10, and 12). 
These fabrics were, respectively, subjected to a preliminary treatment 
under the conditions set forth in Table 1. The preliminary treatment using 
high temperature hot water (Examples 5 to 8) and that using a high boiling 
water soluble solvent (Examples 9 to 12) were, respectively, effected by 
immersion of the fabrics. In addition, as the high boiling water soluble 
solvent, a polyethylene glycol (PEG) with a molecular weight of 200 was 
used, and after the preliminary treatment had been completed, the fabrics 
were washed with water, again washed with hot water at 80.degree. C., and 
dried for 3 minutes at a temperature of 100.degree. C. (Examples 9 to 12). 
After the preliminary treatments had been completed, the fabrics were dyed 
under the following conditions, and subsequently subjected to ordinary 
reduction cleaning (80.degree. C.), following which the thus treated 
fabrics were again washed with water and washed with hot water at a 
temperature of 60.degree. C., whereafter the washed fabrics were dried for 
3 minutes at a temperature 100.degree. C. With respect to the thus treated 
fabrics, dynamic viscoelastic characteristics (tan .delta..sub.max, 
T.sub.max), and degrees of dye exhaustion (D.sub.100, D.sub.130) were 
obtained using the following methods. The results are also set forth in 
Table 1. 
tan .delta..sub.max, T.sub.max 
Using "Viblon" (DDV-11-EP produced by Orientech Co., Ltd.) and at a 
temperature elevating rate of 3.degree. C./min, a mechanical loss tangent 
tan .delta.-temperature T curve was measured and obtained. With respect to 
an ordinary yarn, a yarn of 150 deniers was subjected to the measuring, 
and with respect to the extremely fine yarn, the yarns decomposed from a 
fabric were gathered to form a yarn of 150 deniers, which was then 
subjected to a measuring. The values in the parenthesis are the results 
obtained after dyeing. 
D.sub.100 
Using 3% o.w.f. of Resolin Blue FBL (C.I.Disperse Blue 56) (produced by 
Bayer A.G.; disperse dye), dyeing was effected for 60 minutes at a bath 
ratio of 1:50, and at a temperature of 100.degree. C. 
With respect to exhaustion percentage, the remaining liquid was collected 
and dissolved in an acetone/water (1:1) solution, and the degree of dye 
exhaustion (D.sub.100) was evaluated by applying a calorimetric method to 
the remaining liquid. 
D.sub.130 
Using 5% o.w.f. of Samaron Blue GSL-400 (C.I.Disperse Blue 165) (produced 
by Hoechst GmbH; disperse dye), dyeing was effected for 60 minutes at a 
bath ratio of 1:20 and at a temperature of 130.degree. C. 
With respect to the degree of exhaustion of GSL, the dyed fabric was 
dissolved by a solution of phenol/ethane tetrachloride (6:4), and a 
calibration curve was obtained by the dissolution calorimetric method, and 
from the graph thus obtained, a degree of dye exhaustion (D.sub.130) was 
evaluated. 
Shrinkage Percentage (ordinary yarn alone) 
As one of the indices estimating the conditions of the preliminary 
treatment, the shrinkage percentage was obtained using the following 
method. 
With respect to shrinkage percentage, using as a yarn an ordinary 
polyethylene terephthalate yarn (48 filaments of 150 deniers) having a 
boiled water shrinkage percentage of about 9%, this yarn was treated under 
no tension at a preliminary treatment temperature and time with hot water 
under each condition. Yarn lengths before and after the treatment were 
measured under a load of 0.1 g/d (15 g), so as to obtain a shrinkage 
percentage. 
With respect to the dyed fabrics, color fastnesses were evaluated according 
to JIS L0844 (color fastness to washing) and JIS L0849 (color fastness to 
rubbing), and the results were also set forth in Table 1. 
In addition, in order to evaluate the coloring properties, L* values were 
obtained a multiilluminant spectrophotometric colorimeter (produced by 
Suga Test Machine Co., Ltd.). The results were set also forth in Table 1. 
The L* values indicate that the smaller the value, the higher the color 
value. 
On the other hand, for comparison, the results of the evaluation of 
characteristics were set forth in Table 1 also with respect to the case 
where no preliminary treatment was effected (Comparative Examples 1 and 2) 
and the case where a treatment with high temperature hot water at 
130.degree. C. was effected (Comparative Examples 3 and 4). 
Furthermore, evaluations were also made with respect to a fabric (taffeta) 
composed of a copolymerized polyethylene terephthalate yarn (48 filaments 
of 150 deniers) obtained by copolymerizing 7.5 wt-% of polyethylene glycol 
as a conventional normal pressure dyeable yarn, and the obtained results 
were set forth in Table 1 (Comparative Example 5). 
As may be clearly seen from Table 1, the yarns according to the present 
invention (Examples 1 to 12) exhibited a low degree of dye exhaustion 
(D.sub.100) in the case of low temperature dyeing, while they exhibited a 
high degree of dye exhaustion (D.sub.130) in the case of high temperature 
dyeing (satisfying the aforesaid requirements 3 and 4), high color 
fastness, and were excellent in coloring properties. 
In contrast, in Comparative Examples 1 and 3, the dyeing properties at a 
high temperature and a low temperature were low (not satisfying the 
aforesaid requirement 4), and the coloring properties were inferior. 
In addition, when an extremely fine yarn was used, the dyeing properties at 
a high temperature were low as shown in Comparative Examples 2 and 4 (not 
satisfying the aforesaid requirement 4), and the coloring properties 
especially were inferior, which shows that the effect of the present 
invention is noticeable. 
Further, the normal pressure dyeable yarn in Comparative Example 5 
exhibited a very high degree of dye exhaustion at a low temperature (not 
satisfying aforesaid requirement 3), and was inferior in color fastness. 
EXAMPLES 13 TO 18 AND COMATIVE EXAMPLES 6 TO 11 
Using the same ordinary yarn and extremely fine yarn as in Examples 1 and 
2, a preliminary treatment was effected for 2 minutes at a temperature of 
180.degree. C. using hexylene glycol, and these yarns were washed with 
water in the same manner as in Example 11, washed with hot water at a 
temperature of 80.degree. C., and dried for 3 minutes at a temperate of 
100.degree. C. Dyeing was effected with each of the dyes set forth in 
Table 2 for 60 minutes (bath ratio: 1:20) at a dye concentration of 20% 
o.w.f. Subsequently, the dyed products were subjected to ordinary 
reduction cleaning, washed with water, washed with hot water at a 
temperature of 60.degree. C., and dried for 3 minutes at a temperature of 
100.degree. C. L* values of the obtained fabrics were determined, and the 
results were set forth also in Table 2. Comparative Examples 6 to 11 are 
the examples where no preliminary treatment was effected. 
As may be clearly seen from Table 2, it can be understood that the fibrous 
structures obtained by the dyeing method according to the present 
invention (Examples 13 to 18) are singnificantly high in coloring 
properties in any of the dyes, compared to the comparative examples. 
EXAMPLES 19 TO 24, AND COMATIVE EXAMPLES 12 AND 13 
Using the same ordinary yarn as in Example 1, a preliminary treatment was 
effected using diethylene glycol or triethylene glycol for 2 minutes at a 
temperature ranging from 130.degree. to 200.degree. C. as shown in Table 
3, and the dyed product was washed with water, washed with hot water, and 
dried in the same manner as in Example 11. Dyeing was effected using 5% 
o.w.f. of Samaron Blue GSL-400 (produced by Hoechst GmbH) for 60 minutes 
at a temperature of 130.degree. C. (bath ratio: 1:20), and the dyed 
product was subsequently subjected to ordinary reduction washing at a 
temperature of 80.degree. C., whereafter it was washed with water, washed 
with hot water at a temperature of 60.degree. C., and dried for 3 minutes 
at a temperature of 100.degree. C. L* values of the obtained fabrics were 
determined, and the results were set forth also in Table 3. 
As is clear from Table 3, it may be seen that the fibrous structures 
obtained by the dyeing method according to the present invention (Examples 
19 to 24) have a high L* value, and exhibit significantly high coloring 
properties. In contrast, when the treatment temperature was 130.degree. C. 
(Comparative Examples 12 and 13), the fibrous structures were inferior in 
coloring properties. 
In addition, the fibrous products obtained by the dyeing method according 
to the present invention exhibited color fastness equal to that of the 
fibrous product that had not been subjected to a preliminary treatment 
(Comparative Example 1); this color fastness being excellent. 
According to the present invention, especially in deep color dyeing, the 
degree of dye exhaustion is improved, and utilization efficiency of the 
dye is enhanced, and moreover, especially when an extremely fine yarn is 
used, a polyester fibrous structure with a concentration of a color shade 
equal to that of an ordinary yarn can be provided, which has never been 
obtained by the conventional method. In addition, a polyester fiber and a 
fibrous structure thereof, that are excellent in coloring properties and 
color fastness that may be used for various purposes can be obtained. 
TABLE 1 
______________________________________ 
Dynamic 
Mono- viscoelastic 
Degree of 
filament 
characteristics 
exhaustion 
Preliminary fineness T.sub.max 
of dye (%) 
treatment (d) tan .delta..sub.max 
(.degree.C.) 
D.sub.100 
D.sub.130 
______________________________________ 
Ex. 1 high 3.1 0.176 130 57.1 58.5 
temperature (0.194) 
(122) 
steam 200.degree. C., 
2 min. 
Ex. 2 high 0.07 0.180 135 81.1 65.1 
temperature 
steam 200.degree. C., 
2 min. 
Ex. 3 superheated 3.1 0.170 133 56.2 56.2 
steam 220.degree. C., 
2 min 
Ex. 4 superheated 0.07 0.175 130 75.6 68.4 
steam 220.degree. C., 
2 min 
Ex. 5 high 3.1 0.165 131 51.8 51.9 
temperature hot 
water 160.degree. C., 
2 min 
Ex. 6 high 0.07 0.170 135 81.5 56.3 
temperature hot 
water 160.degree. C., 
2 min 
Ex. 7 high 3.1 0.174 133 59.1 53.7 
temperature hot (0.192) 
(124) 
water 190.degree. C., 
2 min 
Ex.8 high 0.07 0.178 134 84.7 63.4 
temperature hot 
water 190.degree. C., 
2 min 
Ex. 9 water soluble 
3.1 0.160 137 57.2 51.8 
hardly-swelling 
medium 
160.degree. C., 2 min 
Ex. 10 
water soluble 
0.07 0.170 135 83.5 57.7 
hardly-swelling 
medium 
160.degree. C., 2 min 
Ex. 11 
water soluble 
3.1 0.164 139 78.7 77.5 
hardly-swelling (0.212) 
(118) 
medium 
190.degree. C., 2 min 
Ex. 12 
water soluble 
0.07 0.190 127 81.9 73.2 
hardly-swelling 
medium 
190.degree. C., 2 min 
C.E. 1 
no 3.1 0.147 139 45.7 25.3 
(0.158) 
(135) 
C.E. 2 
no 0.07 0.159 138 86.8 47.2 
C.E. 3 
no 3.1 0.148 138 46.0 26.0 
C.E. 4 
no 0.07 0.160 137 87.0 47.5 
C.E. 5 
no 3.1 0.133 103 96.9 39.6 
______________________________________ 
Color Fastness (grade) 
washing Coloring Shrinkage 
stain- change in 
rubbing properties 
percentage 
ing color dry wet (L* value) 
(%) 
______________________________________ 
Ex. 1 4 4-5 4-5 4-5 22.5 23.6 
Ex. 2 4 4-5 4-5 4-5 23.5 
Ex. 3 4 4-5 4-5 4-5 23.1 18.0 
Ex. 4 4 4-5 4-5 4-5 27.5 
Ex. 5 4 4-5 4-5 4-5 24.2 13.1 
Ex. 6 4 4-5 4-5 4-5 24.0 
Ex. 7 4 4-5 4-5 4-5 23.1 16.1 
Ex. 8 4 4-5 4-5 4-5 24.8 
Ex. 9 4 4-5 4-5 4-5 24.1 13.0 
Ex. 10 
4 4-5 4-5 4-5 23.1 
Ex. 11 
4 4-5 4-5 4-5 21.0 22.6 
Ex. 12 
4 4-5 4-5 4-5 23.0 
C.E. 1 
4 4-5 4-5 4-5 26.8 9.0 
C.E. 2 
4 4-5 4-5 4-5 32.1 
C.E. 3 
4 4-5 4-5 4-5 26.1 11.0 
C.E. 4 
4 4-5 4-5 4-5 31.2 
C.E. 5 
3 4-5 4 4 26.0 
______________________________________ 
Ex. = Example, C.E. = Comparative Example 
TABLE 2 
______________________________________ 
Mono- Coloring 
Preliminary 
filament properties 
Dye treatment fineness (d) 
(L* value) 
______________________________________ 
Ex. 13 C.I. Disperse 
hexylene 3.1 32.9 
Red 279 glycol 
180.degree. C., 2 min 
C.E. 6 C.I. Disperse 
no 3.1 38.1 
Red 279 
Ex. 14 C.I. Disperse 
hexylene 0.07 34.3 
Red 279 glycol 
180.degree. C., 2 min 
C.E. 7 C.I. Disperse 
no 0.07 39.3 
Red 279 
Ex. 15 Palanil Blue 
hexylene 3.1 21.1 
2 G produced 
glycol 
by BASF) 180.degree. C., 2 min 
C.E. 8 Palanil Blue 
no 3.1 24.9 
2 G produced 
by BASF) 
Ex. 16 Palanil Blue 
hexylene 0.07 19.1 
2 G produced 
glycol 
by BASF) 180.degree. C., 2 min 
C.E. 9 Palanil Blue 
no 0.07 23.9 
2 G produced 
by BASF) 
Ex. 17 C.I. Disperse 
hexylene 3.1 25.1 
Red 167 glycol 
180.degree. C., 2 min 
C.E. 10 
C.I. Disperse 
no 3.1 29.8 
Red 167 
Ex. 18 C.I. Disperse 
hexylene 0.07 25.3 
Red 167 glycol 
180.degree. C., 2 min 
C.E. 11 
C.I. Disperse 
no 0.07 29.2 
Red 167 
______________________________________ 
Ex. = Example, C.E. = Comparative Example 
TABLE 3 
______________________________________ 
Coloring Shrinkage 
Preliminary Monofilament 
properties 
percentage 
treatment fineness (d) 
(L* value) 
(%) 
______________________________________ 
C.E. 12 
diethylene 3.1 26.1 7.8 
glycol 
130.degree. C., 2 min 
C.E. 13 
triethylene 
3.1 26.2 8.5 
glycol 
130.degree. C., 2 min 
Ex. 19 diethylene 3.1 24.0 16.5 
glycol 
160.degree. C., 2 min 
Ex. 20 triethylene 
3.1 24.1 16.6 
glycol 
160.degree. C., 2 min 
Ex. 21 diethylene 3.1 22.2 20.3 
glycol 
180.degree. C., 2 min 
Ex. 22 triethylene 
3.1 21.9 18.1 
glycol 
180.degree. C., 2 min 
Ex. 23 diethylene 3.1 20.6 32.0 
glycol 
200.degree. C., 2 min 
Ex. 24 triethylene 
3.1 20.6 30.9 
glycol 
200.degree. C., 2 min 
______________________________________ 
Ex. = Example, C.E. = Comparative Example