U.S. patent application number 13/384124 was filed with the patent office on 2012-05-17 for crimped composite fiber, and fibrous mass and testile product using the same.
This patent application is currently assigned to DAIWABO POLYTEC CO., LTD.. Invention is credited to Hiroshi Okaya.
Application Number | 20120121882 13/384124 |
Document ID | / |
Family ID | 43449485 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120121882 |
Kind Code |
A1 |
Okaya; Hiroshi |
May 17, 2012 |
CRIMPED COMPOSITE FIBER, AND FIBROUS MASS AND TESTILE PRODUCT USING
THE SAME
Abstract
A crimped conjugate fiber of the present invention is a
conjugate fiber containing a first component and a second
component, the first component containing polybutene-1 and linear
low density polyethylene, the linear low density polyethylene
content being 2 to 25 mass %, the second component 2 containing a
polymer having a melting peak temperature at least 20.degree. C.
higher than the melting peak temperature of polybutene-1 or a
polymer having a melting initiation temperature of 120.degree. C.
or higher, when viewed from a fiber cross-section, the first
component occupies at least 20% of the surface of the conjugate
fiber 10 and the centroid position of the second component not
overlapping the centroid position of the conjugate fiber, the
conjugate fiber is an actualized crimping conjugate fiber in which
three-dimensional crimps have been developed or a latently
crimpable conjugate fiber in which three-dimensional crimps are
developed by heating. Accordingly, a crimped conjugate fiber having
high elasticity, a high level of bulk recovery properties, and high
durability against repetitive compression as well as high
elasticity, a high level of bulk recovery properties, and high
durability when used at high temperatures, and a fiber assembly
that uses the crimped conjugate fiber are provided.
Inventors: |
Okaya; Hiroshi; (Hyogo,
JP) |
Assignee: |
DAIWABO POLYTEC CO., LTD.
Osaka-shi, Osaka
JP
DAIWABO HOLDINGS CO., LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
43449485 |
Appl. No.: |
13/384124 |
Filed: |
July 16, 2010 |
PCT Filed: |
July 16, 2010 |
PCT NO: |
PCT/JP2010/062103 |
371 Date: |
January 13, 2012 |
Current U.S.
Class: |
428/221 ;
428/370 |
Current CPC
Class: |
D01D 5/34 20130101; D01F
8/14 20130101; D04H 1/544 20130101; Y10T 428/249921 20150401; D01D
5/22 20130101; D04H 1/50 20130101; D01F 8/06 20130101; Y10T
428/2924 20150115 |
Class at
Publication: |
428/221 ;
428/370 |
International
Class: |
D01F 8/06 20060101
D01F008/06; D04H 1/40 20120101 D04H001/40 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 2009 |
JP |
2009-168773 |
Claims
1. A crimped conjugate fiber comprising a first component and a
second component, the first component comprising polybutene-1 and
linear low density polyethylene, the content of the linear low
density polyethylene in the first component is 2 to 25 mass %, the
second component comprising a polymer having a melting peak
temperature at least 20.degree. C. higher than a melting peak
temperature of polybutene-1 or a polymer having a melting
initiation temperature of 120.degree. C. or higher, when viewed
from a fiber cross-section, the first component occupies at least
20% of a surface of the conjugate fiber, and a centroid position of
the second component not overlapping a centroid position of the
conjugate fiber, and the conjugate fiber is an actualized crimping
conjugate fiber in which three-dimensional crimps have been
developed or a latently crimpable conjugate fiber in which
three-dimensional crimps are developed by heating.
2. The crimped conjugate fiber according to claim 1, wherein the
three-dimensional crimps are at least one selected from wavy crimps
and spiral crimps.
3. The crimped conjugate fiber according to claim 1, wherein the
linear low density polyethylene is a copolymer polymerized with
.alpha.-olefin using a metallocene catalyst.
4. The crimped conjugate fiber according to claim 1, wherein the
linear low density polyethylene has a melting peak temperature
obtained from DSC measured according to JIS-K-7121 of 80 to
130.degree. C. and a density measured according to JIS-K-7112 of
0.88 to 0.92 g/cm.sup.3.
5. The crimped conjugate fiber according to claim 1, wherein the
linear low density polyethylene has a flexural modulus measured
according to JIS-K-7171 of 20 to 300 MPa.
6. The crimped conjugate fiber according to claim 1, wherein the
polymer having a melting peak temperature at least 20.degree. C.
higher than a melting peak temperature of polybutene-1 or the
polymer having a melting initiation temperature of 120.degree. C.
or higher contained in the second component is a polyolefin-based
polymer.
7. The crimped conjugate fiber according to claim 6, wherein the
polyolefin-based polymer contained in the second component is
homopolypropylene, and the homopolypropylene is contained in the
second component in a proportion of 75 to 100 mass %, when the
entire second component being 100 mass %.
8. The crimped conjugate fiber according to claim 1, wherein the
polymer having a melting peak temperature at least 20.degree. C.
higher than a melting peak temperature of polybutene-1 or the
polymer having a melting initiation temperature of 120.degree. C.
or higher contained in the second component is a polyester-based
polymer.
9. A fiber assembly comprising a crimped conjugate fiber in a
proportion of 30 mass % or greater, the crimped conjugate fiber
comprising a first component and a second component, the first
component comprising polybutene-1 and linear low density
polyethylene, the content of the linear low density polyethylene in
the first component is 2 to 25 mass %, the second component
comprising a polymer having a melting peak temperature at least
20.degree. C. higher than a melting peak temperature of
polybutene-1 or a polymer having a melting initiation temperature
of 120.degree. C. or higher, when viewed from a fiber
cross-section, the first component occupies at least 20% of a
surface of the conjugate fiber, and a centroid position of the
second component not overlapping a centroid position of the
conjugate fiber, and the conjugate fiber is an actualized crimping
conjugate fiber in which three-dimensional crimps have been
developed or a latently crimpable conjugate fiber in which
three-dimensional crimps are developed by heating.
10. The fiber assembly according to claim 9, comprising, in
addition to the crimped conjugate fiber, at least one fiber
selected from synthetic fibers, chemical fibers, natural fibers,
and inorganic fibers.
11. A fiber product at least partially contains the fiber assembly
of claim 9 and formed into hard stuffing, bedding, a vehicle seat,
a chair, a shoulder pad, a brassiere pad, a cloth, a hygienic
material, a packaging material, a wet wipe, a filter, a sponge-like
porous wiping material, a sheet-like wiping material, or wadding.
Description
TECHNICAL FIELD
[0001] The present invention mainly relates to an actualized
crimping conjugate fiber and a latently crimpable conjugate fiber
suitable for a fiber assembly having high elasticity and a high
level of bulk recovery properties, in particular a nonwoven fabric,
and to a fiber assembly and a fiber product that use such a
conjugate fiber.
BACKGROUND ART
[0002] Thermally bonded nonwoven fabrics containing a thermally
fused conjugate fiber composed of a low-melting-point component
that is exposed at least partially on the surface of the fiber and
a high-melting-point component that has a melting point higher than
that of the low-melting-point component are used in various
applications, such as nonwoven fabrics used for hygienic materials,
packaging materials, wet tissue, filters, wipers, and the like,
nonwoven fabrics used for hard stuffing, chairs, and the like, and
molded articles. In particular, as a urethane foam substitute,
there is a growing demand for a nonwoven fabric having excellent
elasticity and excellent bulk recovery properties, i.e., having
excellent thickness-direction bulk recovery properties, and
extensive research has been made on a nonwoven fabric having
excellent bulk recovery properties and a conjugate fiber suitable
for such a nonwoven fabric having excellent bulk recovery
properties. Since a conjugate fiber suitable for a nonwoven fabric
for use in such applications has itself excellent elasticity and
shape recovery properties, research has been made on using the
conjugate fiber itself as wadding for various pieces of bedding
such blankets and mattresses as well as clothing articles.
[0003] Extensive research has been made on such a conjugate fiber
that itself has excellent elasticity and a thermally bonded
conjugate fiber that has excellent bulk recovery properties once it
has been processed into a fiber assembly such as a nonwoven fabric.
Patent Documents 1 and 2 below disclose a conjugate fiber composed
of a polyester component having a melting point of 200.degree. C.
or higher and a polyetherester block copolymer component, i.e., a
so-called elastomer component, having a melting point of
180.degree. C. or lower. Use of the elastomer component as a sheath
component enhances the degree of freedom of bonded points and
durability against compression deformation, and thus a fiber having
a high level of bulk recovery properties can be obtained.
[0004] Patent Document 3 discloses an actualized crimping conjugate
fiber composed of a first component containing a polytrimethylene
terephthalate (PTT)-based polymer and a second component that
contains a polyolefin-based polymer, in particular, polyethylene,
with crimping being obtained by arranging the centroid position of
the first component so as not to overlap the centroid position of
the fiber on the cross-section of the fiber. By including an
actualized crimping conjugate fiber in which a polymer having large
bending elasticity and small bending hardness is used as a first
component, in which the cross-section of the fiber is eccentric,
and in which the crimps are wavy, a nonwoven fabric that has a high
level of bulk recovery properties, that is flexible, and that has a
large initial bulk can be obtained.
[0005] Patent Documents 4 and 5 disclose a crimped conjugate fiber
containing a sheath component containing polybutene-1 (hereinafter
also referred to as PB-1) and a nonwoven fabric having excellent
bulk recovery properties and improved initial bulk recovery
properties that uses such a fiber.
[0006] In Patent Documents 1 and 2, a polyesterether elastomer is
used as a sheath component, and a nonwoven fabric having a high
level of bulk recovery properties is intended to be obtained by
taking advantage of the fact that this polymer has rubberlike
elasticity and a high degree of freedom from bonding point
deformation. However, since this polyesterether elastomer is a
copolymer of a hard polyester and a soft ether, and contains a soft
component having low thermal resistance, this polyesterether
elastomer is readily thermally softened, and the nonwoven fabric
undergoes bulk reduction, or so-called sagging, during thermal
processing. As a result, a conjugate fiber in which such a
polyesterether elastomer is used as a sheath component is
problematic in that the initial bulk when formed into a nonwoven
fabric is small, only giving a highly dense nonwoven fabric, and
its applications are thus limited. Furthermore, such a nonwoven
fabric being compressed while being heated, or such a nonwoven
fabric being repeatedly compressed is problematic in that, for
example, the points where pieces of the fiber are bonded to each
other and the fiber itself collapse or bend, and the fiber strength
is impaired, and thus the hardness of the nonwoven fabric is
significantly lower than that of the original nonwoven fabric.
[0007] In Patent Document 3, it is intended to obtain a nonwoven
fabric having a high level of bulk recovery properties by selecting
a specific polymer used for the core, a specific fiber
cross-section, and a specific crimp state. However, while the
initial thickness (initial bulk) of the nonwoven fabric is large,
the bulk recovery properties, in particular the initial bulk
recovery properties immediately after load removal, are not
sufficient, and thus there is a problem in that its applications
are limited.
[0008] The conjugate fiber disclosed in Patent Documents 4 and 5 is
problematic in that, when a fiber web that uses the conjugate fiber
is processed into a nonwoven fabric in which pieces of the
component fiber are bonded to each other by thermal processing, or
when pieces of the resulting nonwoven fabric are bonded to each
other by thermal processing, since the so-called sheath component
that occupies for most of the fiber surface is composed of
polybutene-1 and polypropylene, which has a higher melting point
than polybutene-1, a phenomenon occurs in which the apparent
melting point of the sheath component is increased, and thermal
bonding properties in a heat treatment at a low temperature and the
strength of the nonwoven fabric after thermal bonding are not
sufficient, and it is also difficult to adjust the temperature
conditions for thermal bonding processing.
[0009] In addition to Patent Documents 1 to 5, extensive research
has been made on a nonwoven fabric having excellent bulk recovery
properties, a conjugate fiber suitable for such a nonwoven fabric
having excellent bulk recovery properties, a nonwoven fabric that
uses such a fiber, and the like, but there is still a problem in
that deterioration of bulk recovery properties is observed when a
load is applied repetitively, and a fiber and a nonwoven fabric
that are suitable for use in applications such as cushioning
materials for which a high level of bulk recovery properties are
needed even after being repetitively compressed are not
obtained.
CITATION LIST
Patent Documents
[0010] Patent Document 1: JP H4-240219A
[0011] Patent document 2: JP H5-247724A
[0012] Patent document 3: JP 2003-3334A
[0013] Patent document 4: JP 2007-126806A
[0014] Patent document 5: JP 2008-248421A
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0015] In order to solve the above-described problems of the
conventional art, the present invention provides a crimped
conjugate fiber having high elasticity, a high level of bulk
recovery properties, and high durability against repetitive
compression as well as having high elasticity, a high level of bulk
recovery properties, and high durability when used at high
temperatures, and a fiber assembly and a fiber product that use
such a fiber.
Means for Solving the Problem
[0016] The crimped conjugate fiber of the present invention is a
conjugate fiber containing a first component and a second
component, the first component containing polybutene-1 and linear
low density polyethylene, the content of the linear low density
polyethylene in the first component is 2 to 25 mass %, the second
component containing a polymer having a melting peak temperature at
least 20.degree. C. higher than a melting peak temperature of
polybutene-1 or a polymer having a melting initiation temperature
of 120.degree. C. or higher, when viewed from a fiber cross-section
the first component occupies at least 20% of the surface of the
conjugate fiber and the centroid position of the second component
not overlapping the centroid position of the conjugate fiber, and
the conjugate fiber is an actualized crimping conjugate fiber in
which three-dimensional crimps have been developed or a latently
crimpable conjugate fiber in which three-dimensional crimps are
developed by heating. The melting initiation temperature as used
herein refers to an extrapolated melting initiation temperature
measured by differential scanning calorimetry (DSC) as defined in
JIS-K-7121. Also, the melting peak temperature as used herein
refers to a melting peak temperature obtained from a DSC curve
measured according to JIS-K-7121.
[0017] The fiber assembly of the present invention contains a
crimped conjugate fiber in a proportion of 30 mass % or greater,
and the crimped conjugate fiber is a conjugate fiber containing a
first component and a second component, the first component
containing polybutene-1 and linear low density polyethylene. The
content of the linear low density polyethylene in the first
component is 2 to 25 mass %. The second component contains a
polymer having a melting peak temperature at least 20.degree. C.
higher than the melting peak temperature of polybutene-1 or a
polymer having a melting initiation temperature of 120.degree. C.
or higher. When viewed from a fiber cross-section the first
component occupies at least 20% of the surface of the conjugate
fiber and the centroid position of the second component not
overlapping the centroid position of the conjugate fiber, and the
conjugate fiber is an actualized crimping conjugate fiber in which
three-dimensional crimps have been developed or a latently
crimpable conjugate fiber in which three-dimensional crimps are
developed by heating.
[0018] The fiber product of the present invention at least
partially contains the fiber assembly of the present invention and
is formed into hard stuffing, bedding, a vehicle seat, a chair, a
shoulder pad, a brassiere pad, a garment, a hygienic material, a
packaging material, a wet wipe, a filter, a sponge-like porous
wiping material, a sheet-like wiping material, or wadding.
Effects of the Invention
[0019] In the crimped conjugate fiber of the present invention, the
first component contains polybutene-1 and linear low density
polyethylene, and the second component contains a polymer having a
melting peak temperature at least 20.degree. C. higher than the
melting peak temperature of the polybutene-1 or a polymer having a
melting initiation temperature of 120.degree. C. or higher, and
accordingly the fiber exhibits excellent spinnability,
stretchability, crimp formability, and like properties.
Accordingly, use of the crimped conjugate fiber of the present
invention enables a conjugate fiber that has excellent bulk
recovery properties and excellent thermal processability with which
pieces of the fiber can be strongly thermally bonded to each other
even in low-temperature thermal bonding processing as well as a
fiber assembly and a fiber product that use the conjugate fiber to
be obtained.
[0020] A nonwoven fabric that uses the crimped conjugate fiber of
the present invention has both excellent initial bulk and excellent
bulk recovery properties, and can be suitably used for cushioning
materials and like hard stuffing, hygienic materials, packaging
materials, filters, materials for cosmetics, women's brassiere
pads, shoulder pads, and like low-density nonwoven fabric products.
Also, the crimped conjugate fiber of the present invention can be
suitably used for wadding for various pieces of bedding such as
mattresses and blankets and various clothes due to the sufficient
elasticity and repulsive force of the fiber itself.
BRIEF DESCRIPTION OF DRAWINGS
[0021] [FIG. 1] FIG. 1 shows the cross-section of a crimped
conjugate fiber according to one embodiment of the present
invention.
[0022] [FIG. 2] FIGS. 2A to 2C show forms of crimps of a crimped
conjugate fiber according to one embodiment of the present
invention.
[0023] [FIG. 3] FIG. 3 shows a form of conventional mechanical
crimps.
[0024] [FIG. 4] FIG. 4 shows a form of crimps of the crimped
conjugate fiber of the present invention in which wavy crimps and
serrated crimps are concomitantly present.
DESCRIPTION OF THE INVENTION
[0025] The crimped conjugate fiber of the present invention has
high elasticity, a high level of bulk recovery properties, and high
durability against repetitive compression as well as having high
elasticity, a high level of bulk recovery properties, and high
durability when used at high temperatures. In particular, a fiber
assembly that uses the crimped conjugate fiber of the present
invention that has actual crimps (hereinafter also referred to as
an actualized crimping conjugate fiber) has large initial bulk. A
fiber assembly that uses the crimped conjugate fiber of the present
invention that has latent crimps (hereinafter also referred to as a
latently crimpable conjugate fiber) develops crimps when multiple
layers are placed one over another and thermally processed.
Accordingly, entanglement of fibers between layers is enhanced,
thus further increasing elasticity and bulk recovery
properties.
[0026] First Component
[0027] In the crimped conjugate fiber of the present invention, the
first component contains polybutene-1 and linear low density
polyethylene. Disposing the first component such that the first
component occupies for at least 20% of the surface of the conjugate
fiber enables a crimped conjugate fiber that makes use of the
flexibility and the shape retainability (resilience after being
deformed) of polybutene-1 to be obtained.
[0028] It was found in the present invention that the first
component containing linear low density polyethylene in addition to
polybutene-1 improves spinnability such as uniform fiber formation
and stretchability during melt spinning as well as the
spreadability of a staple fiber, the crimp formability of a staple
fiber, and like properties. That is, it is thought that, when melt
spinning is performed solely with polybutene-1, the viscosity of
the polymer discharged from a nozzle is not likely to be stable,
thus making it difficult to obtain a uniform fiber. Also,
polybutene-1 has a high molecular weight, and the degree of freedom
of its molecular chain is poor and it is thus difficult to perform
a stretching step. In addition, polybutene-1 has very large heat
shrinkability. Therefore, it is thought that the fiber would shrink
during thermal processing, thus making it difficult to obtain a
nonwoven fabric having good texture. However, since the first
component contains linear low density polyethylene in addition to
polybutene-1, the aforementioned problems such as poor spinnability
and poor stretchability of polybutene-1 can be solved. Polybutene-1
has a large molecular weight. That is, the molecular chain
constituting polybutene-1 is long, and entanglement between
molecules is extensive, and it is thought that the aforementioned
problem, i.e., poor stretchability, is thus created. Here, it is
presumed that when the polymer component contains linear low
density polyethylene in addition to polybutene-1 as in the present
invention, linear low density polyethylene enters between the
molecular chains of polybutene-1 having high molecular weight, and
adequately suppresses the entanglement of the molecular chains of
polybutene-1, thus improving stretchability. In addition, due to
the use of the polymer that contains linear low density
polyethylene as the first component that occupies for most of the
surface portion of the crimped conjugate fiber, a fiber assembly
that uses the resulting crimped conjugate fiber exhibits excellent
thermal processability (thermal treatment accomplished in a short
period of time, uniform thermal bonding between component fibers)
due to the linear low density polyethylene contained in the first
component of the crimped conjugate fiber. That is, by adopting a
configuration in which the principal component of the first
component that occupies for most of the surface of the crimped
conjugate fiber is polybutene-1, and linear low density
polyethylene is added in a proportion of 2 to 25 mass % relative to
the first component, the phenomenon of an increase of the apparent
melting peak temperature of the first component resulting from
addition of a high melting point polymer, which can occur when a
polymer (for example, polypropylene) having a higher melting point
than polybutene-1 is added to polybutene-1, does not occur.
Accordingly, the crimped conjugate fiber of the present invention
can be thermally bonded so as to attain sufficient bonding strength
even when thermal processing is performed at a lower temperature
for a shorter period of time, and thus the post-processability of a
fiber assembly containing the crimped conjugate fiber is enhanced.
Moreover, since linear low density polyethylene has excellent
impact resistance, the fiber assembly of the present invention in
which pieces of the component fiber are thermally bonded by the
first component containing linear low density polyethylene of the
crimped conjugate fiber of the present invention is unlikely to
result in separation and delamination of bonded points of the fiber
even when used in applications where a load is repetitively
applied, and thus has excellent resistance to residual set from
repetitive compression as well as resistance to residual set from
compression.
[0029] The linear low density polyethylene is not particularly
limited, and for example, copolymers with .alpha.-olefins
polymerized using Ziegler catalysts and metallocene catalysts are
usable. From the viewpoint of attaining a narrow molecular weight
range and a uniform branch distribution, it is preferable to use
copolymers with .alpha.-olefins polymerized using metallocene
catalysts. A feature of linear low density polyethylene polymerized
using a metallocene catalyst is having a uniform distribution of
molecular weight, composition, and crystallinity. Due to the
foregoing feature, linear low density polyethylene polymerized
using a metallocene catalyst is likely to be uniformly dispersed
inside PB-1 even when added in an amount of 2 to 25 mass %, and it
is thus presumed that linear low density polyethylene demonstrates
an effect of improving the stretchability of PB-1. The
.alpha.-olefins are not particularly limited, and examples include
1-butene, 1-hexene, 1-octene, 1-pentene, 3,3-dimethyl-1-butene,
4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-decene, 1-dodecene,
1-tetradecene, 1-octadecene, and the like. As the copolymer
polymerized with an .alpha.-olefin using a metallocene catalyst,
commercially available products such as "Harmorex" (registered
trademark) NJ744N, "Kernel" (registered trademark) KS560T and KC571
manufactured by Japan Polyethylene Corporation, and 420SD
manufactured by Ube-Maruzen Polyethylene Co., Ltd., may be
used.
[0030] It is preferable that the linear low density polyethylene in
the first component has a ratio (Q value) of weight average
molecular weight (Mw) to number average molecular weight (Mn) of 6
or less. A more preferable Q value is 2 to 5, and a particularly
preferable Q value is 2.2 to 3.5. The stretchability of the crimped
conjugate fiber of the present invention containing polybutene-1 in
the first component is enhanced when the first component contains,
in addition to polybutene-1, linear low density polyethylene,
preferably linear low density polyethylene that is polymerized
using a metallocene catalyst and that satisfies the foregoing Q
value range. In addition, the first component that occupies for
most of the fiber surface, which contains linear low density
polyethylene, imparts a slide effect to the fiber surface, and the
resulting crimped conjugate fiber exhibits enhanced crimper
passability and, once cut so as to obtain a staple fiber having a
desired fiber length, enhanced spreadability of the staple fiber,
and thus such a first component is preferable.
[0031] From the viewpoint of attaining good compatibility with
PB-1, it is preferable that the density measured according to
JIS-K-7112 of the linear low density polyethylene is 0.930
g/cm.sup.3 or less, more preferably 0.920 g/cm.sup.3 or less, and
particularly preferably 0.915 g/cm.sup.3 or less. When the density
is within the foregoing range, compatibility with PB-1 is good and
heat resistance is high. The lower limit of the density of the
linear low density polyethylene is not particularly limited, and it
is preferably 0.870 g/cm.sup.3 or greater, more preferably 0.880
g/cm.sup.3 or greater, and particularly preferably 0.890 g/cm.sup.3
or greater. When the density of the linear low density polyethylene
is less than 0.870 g/cm.sup.3, the heat resistance of the first
component constituting the crimped conjugate fiber is likely to be
impaired, and it is likely that bulk recovery properties and
resistance to residual compression set at temperatures greater than
room temperature, for example in the range of 40 to 80.degree. C.,
are impaired.
[0032] From the view point of attaining good compatibility with
PB-1 and good elasticity of the resulting fiber as well as good
bulk recovery properties and resistance to residual compression set
of a fiber assembly prepared using the resulting crimped conjugate
fiber, it is preferable that the flexural modulus measured
according to JIS-K-7171 of the linear low density polyethylene is
800 MPa or less, more preferably 20 to 650 MPa, particularly
preferably 25 to 300 MPa, and most preferably 30 to 180 MPa. When
the flexural modulus is within the foregoing range, compatibility
with PB-1 is good and heat resistance is high, and the resulting
fiber assembly exhibits excellent bulk recovery properties and
resistance to residual compression set. When the flexural modulus
of the linear low density polyethylene is high, the flexibility of
the polymer is lost, and the elasticity of the resulting crimped
conjugate fiber tends to be impaired, and when the flexural modulus
of the linear low density polyethylene exceeds 800 MPa, the bulk
recovery properties and the resistance to residual compression set
of a fiber assembly prepared using the resulting crimped conjugate
fiber are likely to be impaired. Also, when the flexural modulus of
the linear low density polyethylene is high, the melting peak
temperature of the polymer tends to be low, and when the flexural
modulus of the linear low density polyethylene is less than 20 MPa,
heat resistance is impaired, and the bulk recovery properties of
the resulting fiber assembly at high temperatures are likely to be
impaired.
[0033] It is preferable that the linear low density polyethylene
has a melting peak temperature obtained from a DSC curve measured
according to JIS-K-7121 of 70 to 130.degree. C., more preferably 80
to 125.degree. C., and even more preferably 90.degree. C. to
123.degree. C. When the melting peak temperature is 70 to
130.degree. C., heat resistance is high, and bulk recovery
properties at high temperatures are good. The term "melting peak
temperature" as used herein refers to a melting peak temperature
obtained from a DSC curve measured according to JIS-K-7121. Herein,
the melting peak temperature obtained from a DSC curve is also
referred to as a melting point.
[0034] It is preferable that the linear low density polyethylene
has a melt flow rate
[0035] (MFR; a measurement temperature of 190.degree. C., a load of
2.16 kgf (21.18 N), hereinafter referred to as MFR190) according to
JIS-K-7210 of 1 to 30 g/10 min, more preferably an MFR190 of 3 to
25 g/10 min, and even more preferably 5 to 20 g/10 min. When the
MFR190 is 1 to 30 g/10 min, heat resistance is good and bulk
recovery properties at high temperatures are favorable, and spun
yam retrievability and stretchability are good.
[0036] It is preferable that polybutene-1 for use in the present
invention has a melting peak temperature obtained from a DSC curve
measured according to JIS-K-7121 of 115 to 130.degree. C., and more
preferably 120 to 130.degree. C. When the melting peak temperature
is 115 to 130.degree. C., heat resistance is high, and bulk
recovery properties at high temperatures are good.
[0037] It is preferable that the polybutene-1 has a melt flow rate
(MFR; a measurement temperature of 190.degree. C., a load of 2.16
kgf (21.18 N), hereinafter referred to as MFR190) according to
JIS-K-7210 of 1 to 30 g/10 min, more preferably an MFR190 of 3 to
25 g/10 min, and even more preferably 3 to 20 g/10 min. When the
MFR190 is 1 to 30 g/10 min, polybutene-1 has a high molecular
weight, and thus heat resistance is good and bulk recovery
properties at high temperatures are favorable, and thus this
configuration is preferable. Also, spun yarn retrievability and
stretchability are good.
[0038] In the first component, polybutene-1 is the principal
component and is contained in a proportion of 70 mass % or greater
relative to the entire first component. From the viewpoint of
attaining good productivity, good cushioning properties, and good
bulk recovery properties at high temperatures, it is preferable
that polybutene-1 is contained in a proportion of 75 to 98 mass %,
more preferably 80 to 97 mass %, particularly preferably 85 to 97
mass %, and most preferably 87 to 96 mass %.
[0039] By blending linear low density polyethylene that
demonstrates a sufficient compatibilizing effect with polybutene-1
as described above, a problem that occurs because the spinnability
and stretchability of polybutene-1 are not improved when the
compatibilizing effect on polybutene-1 is excessively low, i.e., a
uniform conjugate fiber is unlikely to be obtained, can be
solved.
[0040] The amount of the linear low density polyethylene added to
the first component is 2 to 25 mass %, when the entire first
component being 100 mass %, more preferably 3 to 20 mass %,
particularly preferably 3 to 15 mass %, and most preferably 4 to 12
mass %. When the amount is within the foregoing range, the
flowability of PB-1 is enhanced, stable and uniform spinning can be
performed, and stretchability is also improved.
[0041] The first component contains polybutene-1 and linear low
density polyethylene as described above, and further may contain an
ethylene-ethylenic unsaturated carboxylic acid copolymer. Since the
ethylene-ethylenic unsaturated carboxylic acid copolymer, as with
the linear low density polyethylene, shows, compatibility with
polybutene-1, the first component further containing an
ethylene-ethylenic unsaturated carboxylic acid copolymer is capable
of improving spinnability such as uniform fiber formation when melt
spinning, stretchability, and the like. Moreover, with a crimped
conjugate fiber in which the first component further contains an
ethylene-ethylenic unsaturated carboxylic acid copolymer in
addition to polybutene-1 and linear low density polyethylene, when
performing thermal processing such as thermal bonding on a fiber
web or a nonwoven fabric containing the fiber, a phenomenon in
which the sheath component undergoes shrinking and thermally bonded
points shrink, i.e., "bonding point shrinkage" (hereinafter also
simply referred to as bonding point shrinkage) is unlikely to occur
at the points where pieces of the constituting fiber are thermally
bonded to each other, even when the thermal processing is performed
for a long period of time at high temperatures. Accordingly, pieces
of the constituting fiber can be bonded firmly to each other, and a
thermally bonded nonwoven fabric having greater bonding strength
can be obtained.
[0042] The ethylenic unsaturated carboxylic acid constituting the
ethylene-ethylenic unsaturated carboxylic acid copolymer for use in
the crimped conjugate fiber of the present invention is not
particularly limited, and examples include acrylic acid,
methacrylic acid, ethacrylic acid, fumaric acid, maleic acid,
itaconic acid, monomethyl maleate, monoethyl maleate, maleic
anhydride, itaconic anhydride, and the like.
[0043] Specific examples of the ethylene-ethylenic unsaturated
carboxylic acid copolymer include ethylene-acrylic acid copolymer
(EAA), ethylene-methacrylic acid copolymer (EMAA),
ethylene-ethacrylic acid copolymer, ethylene-maleic acid copolymer,
ethylene-fumaric acid copolymer, ethylene-itaconic acid copolymer,
ethylene-maleic anhydride copolymer, ethylene-itaconic anhydride
copolymer, and the like. Among such examples, ethylene-acrylic acid
copolymer, ethylene-methacrylic acid copolymer, and ethylene-maleic
acid copolymer are preferable, and ethylene-acrylic acid copolymer
and ethylene-methacrylic acid copolymer are more preferable.
[0044] The ethylene-ethylenic unsaturated carboxylic acid copolymer
is not limited to a copolymer composed of ethylene and an ethylenic
unsaturated carboxylic acid, and may be a copolymer in which
another component is copolymerized, including, for example, a
terpolymer in which two or more components including an ethylenic
unsaturated carboxylic acid are copolymerized with ethylene.
[0045] Examples of monomers for use as the other copolymerization
components include ethylenic unsaturated carboxylic acid esters
such as vinyl acetate, vinyl propionate, and like vinyl esters,
methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl
acrylate, isobutyl acrylate, isooctyl acrylate, and like acrylic
acid esters, methyl methacrylate, isobutyl methacrylate, and like
methacrylic acid esters, and dim ethyl maleate, diethyl maleate,
and like maleic acid esters; carbon monoxide; sulfur dioxide; and
the like.
[0046] The copolymer in which ethylene, an ethylenic unsaturated
carboxylic acid, and an optional copolymerization component are
copolymerized is not particularly limited, and an example may be an
ethylene-acrylate-maleic acid polymer in which ethylene, maleic
anhydride and an acrylic ester are copolymerized ("Bondine"
(registered trademark) manufactured by Arkema Japan) or the
like.
[0047] The content of the ethylenic unsaturated carboxylic acid in
ethylene-ethylenic unsaturated carboxylic acid copolymer is 1 to 50
mass %, and preferably 1 to 29 mass %. In particular, in the case
of acrylic acid, it is preferably 5 to 25 mass %, and in the case
of methacrylic acid, it is preferably 5 to 20 mass %. The content
of the other copolymerizable component in the ethylene-ethylenic
unsaturated carboxylic acid copolymer is in the range of 0 to 30
mass %, and preferably 0 to 20 mass %.
[0048] In the present invention, as the ethylene-ethylenic
unsaturated carboxylic acid copolymer, an ionomer in which carboxyl
groups are partially or entirely in a metal salt form can be used
other than the ethylene-ethylenic unsaturated carboxylic acid
copolymer itself. Examples of metal species constituting metal
ionomers include lithium, sodium, potassium, and like monovalent
metals, magnesium, calcium, zinc, copper, cobalt, manganese, lead,
iron, and like polyvalent metals, and the like, with monovalent
metals or zinc being particularly preferable.
[0049] In the present invention, the ethylene-ethylenic unsaturated
carboxylic acid copolymers may be used singly, or may be used in a
combination of two or more.
[0050] The ethylene-ethylenic unsaturated carboxylic acid
copolymers can be obtained by, although not particularly limited
to, high pressure radical copolymerization. The ethylene-ethylenic
unsaturated carboxylic acid copolymer ionomers can be obtained by
ionizing the ethylene-ethylenic unsaturated carboxylic acid
copolymers by an ordinary method.
[0051] As described above, the first component of the crimped
conjugate fiber of the present invention contains an
ethylene-ethylenic unsaturated carboxylic acid copolymer that
demonstrates a sufficient compatibilizing effect on polybutene-1,
and accordingly a problem that occurs due to the poor spinnability
of polybutene-1 when the compatibilizing effect on polybutene-1 is
excessively low, i.e., a uniform conjugate fiber is unlikely
obtained, can be solved. Also, a problem that occurs when the
compatibilizing effect on polybutene-1 is excessive, i.e., a
conjugate fiber composed of a first component mainly containing
polybutene-1 can be obtained but bonding point shrinkage occurs due
to thermal processing when preparing a thermally bonded nonwoven
fabric from the resulting conjugate fiber, can be solved. That is,
by blending an ethylene-ethylenic unsaturated carboxylic acid
copolymer that demonstrates a sufficient compatibilizing effect on
polybutene-1, it is possible to obtain a uniform conjugate fiber
containing them. Moreover, the thermal bonding properties of the
resulting conjugate fiber is improved, and thus it is possible to
overcome bonding point shrinkage, which can occur when bonding is
performed by thermal processing at temperatures higher than the
melting point of polybutene-1.
[0052] In the case where an ethylene-ethylenic unsaturated
carboxylic acid copolymer is added to the first component, it is
preferable that the amount of the copolymer added is 0.5 to 20 mass
%, when the entire first component being 100 mass %, more
preferably 1 to 15 mass %, even more preferably 3 to 10 mass %, and
particularly preferably 4 to 9 mass %. When the amount is 0.5 mass
% or greater, a crimped conjugate fiber having excellent thermal
bonding properties can be obtained, the bonding strength between
pieces of the fiber is not impaired at high temperatures, for
example, a temperature of 190.degree. C. or higher, and the
aforementioned bonding point shrinkage does not occur. Moreover,
when the amount is 20 mass % or less, a fiber structure such as a
nonwoven fabric that has good hardness retainability (bulk recovery
properties) can be obtained.
[0053] It is preferable that the ethylene-ethylenic unsaturated
carboxylic acid copolymer has an MFR190 measured according to
JIS-K-7210 of 3 to 60 g/10 min. A more preferable MFR190 is 5 to 40
g/10 min, and even more preferably 5 to 30 g/10 min. With the
MFR190 being 60 g/10 min or less, the effect of suppressing bonding
point shrinkage that can occur when performing thermal processing
on a fiber web that contains the resulting crimped conjugate fiber
can be enhanced. Moreover, with the MFR190 being 3 g/10 min or
greater, it is easy to obtain a uniform crimped conjugate fiber
that has excellent operability during a spinning step and a
stretching step.
[0054] It is preferable that the ethylene-ethylenic unsaturated
carboxylic acid copolymer has a melting peak temperature obtained
from a DSC curve measured according to JIS-K-7121 of 60.degree. C.
or higher, more preferably 70.degree. C. or higher, and even more
preferably 70 to 120.degree. C. With the melting peak temperature
being 60.degree. C. or higher, the effect of suppressing bonding
point shrinkage is strong, and deterioration of cushioning
properties such as deterioration of bulk recovery properties and an
increase of a rate of compression set due to thermal processing are
unlikely to occur. Moreover, with the melting peak temperature
being 70 to 120.degree. C., the effect of suppressing bonding point
shrinkage, the effect of suppressing deterioration of cushioning
properties, and like effects can be more readily demonstrated.
[0055] It is preferable that the ethylene-ethylenic unsaturated
carboxylic acid copolymer has a softening temperature (Vicat
softening point) as measured according to JIS-K-7206 of 40.degree.
C. or higher, more preferably 50.degree. C. or higher, and
particular preferably 50 to 100.degree. C. With the softening
temperature being 40.degree. C. or higher, the effect of
suppressing bonding point shrinkage is strong, and deterioration of
cushioning properties such as deterioration of bulk recovery
properties and an increase of a rate of compression set due to
thermal processing are unlikely to occur. With the softening
temperature being 50 to 100.degree. C., the effect of suppressing
bonding point shrinkage, the effect of suppressing deterioration of
cushioning properties, and like effects can be more readily
demonstrated.
[0056] Examples of polymers that further can be blended with the
first component, as long as the effect of the present invention is
not impaired, include polyolefin-based polymers other than the
aforementioned polyolefin-based polymers, copolymerizable polymers
with olefins having a polar group such as a vinyl group, a carboxyl
group, or maleic anhydride; polyolefin-based, styrene-based,
polyester-based, and like various thermoplastic elastomers; and the
like.
[0057] It is possible to add various known additives to the first
component as long as the effect of the present invention is not
impaired, or fiber productivity, nonwoven fabric productivity,
thermal bonding properties, and texture are not affected. Depending
on the application, the first component can be mixed with, for
example, other polymers, known nucleating agents such as organic or
inorganic substances (for example, calcium carbonate, talc, and the
like), antistatic agents, pigments, delusterants, thermal
stabilizers, photostabilizers, flame retardants (halogen-based,
phosphorus-based, nonhalogen-based, antimony trioxide, and like
inorganic compound-based flame retardants, and the like),
bactericidal agents, lubricants, plasticizers, softening agents,
and the like. Adding a nucleating agent as such an additive brings
about the following advantages: an effect of preventing fusion
between pieces of the fiber when spinning can be further enhanced,
and a nonwoven fabric having soft texture can be obtained. The
amount of nucleating agent added is not particularly limited, and
it is preferable in light of fiber productivity to add a nucleating
agent in a proportion of 20 mass % or less relative to the total
mass of the first component, and it is more preferable to add in a
proportion of 10 mass % or less.
[0058] The first component constituting the crimped conjugate fiber
of the present invention has the above-described features. That is,
the first component contains PB-1 as the principal component in a
proportion of 70 mass % or greater, preferably 75 mass % or
greater, and contains linear low density polyethylene in a
proportion of 2 to 25 mass %. Accordingly, the melting point of the
first component after spinning is low, and thus a phenomenon in
which the apparent melting point of the first component is
increased, which can occur in the case where polypropylene in place
of linear low density polyethylene is added to PB-1, is unlikely to
occur. This can be verified by performing measurement with a
differential scanning calorimeter (DSC) using the obtained crimped
conjugate fiber and then obtaining the melting point of each
component after spinning from a heat of fusion curve obtained from
the measurement. That is, regarding the crimped conjugate fiber of
the present invention, the first component after spinning has a
melting point (Tf1) obtained from a DSC curve measured according to
JIS-K-7121 of 140.degree. C. or lower, preferably 90 to 135.degree.
C., more preferably 100 to 130.degree. C., particularly preferably
115 to 130.degree. C., and most preferably 120.degree. C. to
125.degree. C. As long as the melting point (Tf1) of the first
component after spinning is within this range, a thermally bonded
fiber assembly having sufficient bonding strength can be obtained
at a lower temperature in a shorter period of time when producing a
fiber assembly such as a nonwoven fabric by thermal bonding
processing. The higher the melting point of the first component
after spinning, the less likely the above-described effect is
obtained, and if multiple melting point peaks derived from the
first component appear, e.g., if the first component has a
so-called double peak, at a temperature lower than the melting
point (Tf2) of the second component after spinning, which occurs
when the melting point (Tf1) of the first component after spinning
exceeds 140.degree. C. or when a polyolefin-based polymer (for
example, polypropylene) having a high melting peak temperature is
added, low-temperature thermal bonding properties are likely to be
insufficient and a fiber assembly having sufficient bonding
strength is unlikely to be obtained. The lower limit of the melting
point (Tf1) of the first component after spinning is not
particularly limited, but when the lower limit is lower than
90.degree. C., heat resistance and bulk recovery properties at high
temperatures are likely to be impaired. As described above, in the
crimped conjugate fiber of the present invention, it is not
preferable, regarding the melting point of the first component of
the conjugate fiber after spinning, that the heat of fusion curve
has a so-called double-peak shape having multiple peaks derived
from the first component when performing thermal bonding
processing. Therefore, linear low density polyethylene is
preferable that has a melting point that mostly overlaps the
melting point of post-spinning PB-1, which is the principal
component of the first component, and that has a so-called single
peak having only one peak derived from the first component on a
heat of fusion curve.
[0059] Second Component
[0060] The second component of the crimped conjugate fiber of the
present invention is not particularly limited as long as it is a
polymer having a melting peak temperature at least 20.degree. C.
higher than the melting peak temperature of polybutene-1 or a
polymer having a melting initiation temperature of 120.degree. C.
or higher. Polymers having excellent bending strength and bending
elasticity are preferable, and examples include polyethylene
terephthalate, polybutylene terephthalate, polytrimethylene
terephthalate, polyethylene naphtahalate, polylactic acid, and like
polyester-based polymers, Nylon 6, Nylon 66, Nylon 11, Nylon 12,
and like polyamides, polypropylene, polymethylpentene, and like
polyolefin-based polymers, polycarbonates, polystyrenes, and the
like. When such polymers are used as the second component, polymers
may be used singly or may be used as a combination of two or more.
In the crimped conjugate fiber of the present invention, a
polyester-based polymer or a polyolefin-based polymer is preferable
as a polymer for use in the second component. The use of a
polyolefin-based polymer as the second component together with the
use of a polyolefin-based polymer as the first component as
described above makes it easy to recycle the crimped conjugate
fiber of the present invention. The crimped conjugate fiber of the
present invention that uses the polyester-based polymer as the
second component has a large melting point difference between the
second component that constitutes near the center of the conjugate
fiber and the first component that occupies for most of the fiber
surface, and therefore even when the conjugate fiber, a fiber web,
and a nonwoven fabric are subjected to thermal bonding at a
temperature at which the first component undergoes sufficient
thermal bonding, the second component maintains its shape, and
sagging caused by thermal processing is unlikely to occur, and it
is easy to manage the processing temperature in a thermal
processing step, allowing a fiber assembly having high bonding
strength to readily be obtained.
[0061] First, regarding the crimped conjugate fiber of the present
invention, a conjugate fiber now will be described that uses a
polyester-based polymer as a polymer constituting the second
component. In the case where a polyester-based polymer is used as
the second component of the crimped conjugate fiber of the present
invention, the polymer is not particularly limited insofar as it is
a polyester-based polymer having a melting peak temperature at
least 20.degree. C. higher than the melting peak temperature of
polybutene-1 or a polyester-based polymer having a melting
initiation temperature of 120.degree. C. or higher. Since polymers
having excellent bending strength and bending elasticity are
preferable, polyethylene terephthalate (hereinafter also referred
to as PET), polytrimethylene terephthalate (hereinafter also
referred to as PTT), and polybutylene terephthalate (hereinafter
also referred to as PBT) are preferable, with polyethylene
terephthalate or polytrimethylene terephthalate being more
preferable. A polymer that has physical properties suitable for the
application of the fiber is selected, and in the case where a
polyester-based polymer is used as the second component in the
crimped conjugate fiber of the present invention, it is most
preferable to use polyethylene terephthalate in light of the
availability, the high bulk recovery properties of the fiber, and
like features.
[0062] It is preferable that the polyester-based polymer has a
limiting viscosity [.eta.] of 0.4 to 1.2, and more preferably 0.5
to 1.1. When the limiting viscosity is less than 0.4, the molecular
weight of the polymer is excessively low, and therefore not only is
spinnability inferior but also fiber strength is poor, and such a
fiber is not practical. When the limiting viscosity exceeds 1.2,
the molecular weight of the polymer is increased, and the melt
viscosity is excessive. Therefore, single-yam breakage and like
phenomena occur, making it difficult to perform good spinning, and
thus such limiting viscosity is not preferable. A limiting
viscosity [.eta.] within the foregoing range enables a conjugate
fiber having excellent productivity and excellent bulk recovery
properties to be obtained. The limiting viscosity [.eta.] as
referred to herein is measured with an Ostwald viscometer using an
o-chlorophenol solution at 35.degree. C. and expressed as a value
obtained according to Expression 1 below:
[ .eta. ] = lim c -> o 1 { C .times. ( .eta. r - 1 ) } .
Expression 1 ##EQU00001##
[0063] In Expression 1 above, .THETA..sub.r is a value obtained by
dividing the viscosity at 35.degree. C. of a diluted solution of a
sample dissolved in o-chlorophenol having a purity of 98% or
greater by the concentration of the entire solvent measured at the
same temperature, and C is the weight value in grams of the solute
in 100 ml of the aforementioned solution.
[0064] It is preferable that the polyester has a melting peak
temperature obtained from a DSC curve measured according to
JIS-K-7121 of 180.degree. C. to 300.degree. C., and more preferably
200.degree. C. to 270.degree. C. A melting peak temperature of 180
to 300.degree. C. enables the weatherability to be increased and
the flexural modulus of the resulting conjugate fiber to be
increased.
[0065] Next, regarding the crimped conjugate fiber of the present
invention, a conjugate fiber will now be described that uses a
polyolefin-based polymer as a polymer constituting the second
component. In the case where a polyolefin-based polymer is used as
the second component of the crimped conjugate fiber of the present
invention, the polymer is not particularly limited insofar as it is
a polyolefin-based polymer having a melting peak temperature at
least 20.degree. C. higher than the melting peak temperature of
polybutene-1 or a polyolefin-based polymer having a melting
initiation temperature of 120.degree. C. or higher. Since polymers
having excellent bending strength and bending elasticity are
preferable, polypropylene (hereinafter also referred to as PP) is
preferable. Such polypropylene is not particularly limited, and for
example, homopolymers, random copolymers, block copolymers, or
mixtures thereof, and insofar as properties required for nonwoven
fabrics and cushioning materials, such as heat resistance and bulk
recovery properties, are not impaired, polypropylene in which
synthetic rubber or a like elastomer component is dispersed or
mixed therewith may be used. In light of heat shrinkability, it is
preferable that it is a homopolymer (homopolypropylene) or a block
copolymer. In particular, homopolypropylene is advantageous in
terms of the bulk recovery property and thus is preferable.
Examples of the random copolymers and the block copolymers include
copolymers of propylene and at least one .alpha.-olefin selected
from the group consisting of ethylene and .alpha.-olefins having 4
or more carbon atoms. Such .alpha.-olefins having 4 or more carbon
atoms are not particularly limited, and examples include 1-butene,
1-pentene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene,
4,4-dimethyl-1-pentene, 1-decene, 1-dodecene, 1-tetradecene,
1-octadecene, and the like. In particular, from the viewpoint of
attaining bulk recovery properties, one selected from the group
consisting of propylene homopolymers, ethylene-propylene
copolymers, and ethylene-butene-1-propylene terpolymers is
preferable, and in light of heat resistance of the resulting
crimped conjugate fiber, recycling efficiency after use, and
economical efficiency (production costs), in the case where a
polyolefin-based polymer is used as the second component, the
polyolefin-based polymer is particularly preferably
homopolypropylene. From the viewpoint of attaining bulk recovery
properties, in the case where a mixture of a homopolymer, a random
copolymer, and a block copolymer of polypropylene is used, the
homopolypropylene content is 73 to 100 mass %, more preferably 75
to 100 mass %, particularly preferably 85 to 100 mass %, when the
entire second component being 100 mass %.
[0066] When polypropylene is used as the second component, it is
preferable that the polypropylene has a melt flow rate (MFR; a
measurement temperature of 230.degree. C., a load of 2.16 kgf
(21.18 N), hereinafter referred to as MFR230) according to
JIS-K-7210 of 3 to 40 g/10 min, and a more preferable MFR230 is 5
to 35 g/10 min. When the MFR230 is 3 to 40 g/10 min, heat
resistance is good and bulk recovery properties at high
temperatures are favorable, and spun yarn retrievability and
stretchability are good.
[0067] When polypropylene is used as the second component, it is
preferable that the polypropylene has a ratio (Q value) of weight
average molecular weight (Mw) to number average molecular weight
(Mn) of 2 or greater. A more preferable Q value is 3 to 12. A more
preferable value of the ratio (Q value) of the weight average
molecular weight (Mw) to the number average molecular weight (Mn)
of polypropylene in the second component can be selected according
to the kind of three-dimensional crimps which are developed in the
resulting crimped conjugate fiber. For example, in the case where
an actualized crimping conjugate fiber in which a crimped conjugate
fiber has actualized three-dimensional crimps is to be obtained,
the Q value of polypropylene of the second component is preferably
4 to 12, and more preferably 5 to 9. In the case where a latently
crimpable conjugate fiber that develops three-dimensional crimps
once heated is to be obtained, the Q value is preferably 3 to
5.
[0068] When a polyolefin-based polymer such as polypropylene is
used as the second component, in addition to the polyolefin-based
polymer having a melting peak temperature at least 20.degree. C.
higher than the melting peak temperature of polybutene-1, a
thermoplastic elastomer may also be contained. That is, in a
constituent fiber of a fiber assembly suitable for applications
where excellent bulk recovery properties and resistance to
repetitive compression set are required, such as cushioning
materials and clothing pads, and in a crimped conjugate fiber for
use as wadding of various pieces of bedding such as blankets and
mattresses and clothing articles in which elasticity, shape
recovery properties, and light-weight properties of the fiber
itself are required, the second component that contributes to the
hardness, the bulk recovery properties, and the resistance to set
of a crimped conjugate fiber itself and those of a fiber assembly
containing the crimped conjugate fiber, or in other words, a
component that is disposed more toward the center in a
core-in-sheath conjugate fiber (also referred to as a core
component in a core-in-sheath conjugate fiber, encompassing an
eccentric conjugate fiber) preferably contains a thermoplastic
elastomer. Known thermoplastic elastomers can be used, and
styrene-based elastomers, olefin-based elastomers, ester-based
elastomers, amide-based elastomers, urethane-based elastomers, and
vinyl chloride-based elastomers are usable. Among such elastomers,
in the crimped conjugate fiber of the present invention, in the
case where a polyolefin-based polymer is used as the second
component, in light of recycling efficiency after use, it is
preferable to use a polypropylene homopolymer, a random copolymer,
a block copolymer, or a mixture thereof as the polyolefin-based
polymer that has a melting peak temperature at least 20.degree. C.
higher than the melting peak temperature of polybutene-1, and it is
preferable to use an olefin-based thermoplastic elastomer as the
thermoplastic elastomer. Olefin-based thermoplastic elastomers are
thermoplastic elastomers that use a polyolefin resin such as
polyethylene or polypropylene as a hard segment, and an
ethylene-propylene-based rubber such as ethylene-propylene rubber
(EPM), ethylene-butene rubber (EBM), ethylene-propylene-diene
rubber (EPDM) as a soft segment. Usable examples of commercially
available olefin-based thermoplastic elastomers include
"Milastomer" (registered trademark) and "Notio" (registered
trademark) manufactured by Mitsui Chemicals, Inc., "Espolex"
(registered trademark) manufactured by Sumitomo Chemical Co., Ltd.,
"Thermorun" (registered trademark) and "Zelas" (registered
trademark) manufactured by Mitsubishi Chemical Corporation, and the
like. In the crimped conjugate fiber of the present invention, it
is presumed that, in the case where the second component
constituting the crimped conjugate fiber is a polyolefin-based
polymer, adding a suitable amount of a thermoplastic elastomer,
such as an olefin-based thermoplastic elastomer, to the second
component imparts bending elasticity that seems to be derived from
the thermoplastic elastomer to the second component containing the
polyolefin-based polymer, and recoverability from bending and
resistance to repetitive bending fatigue, which are likely to be
insufficient in a conjugate fiber in which the second component is
composed solely of a polyolefin-based polymer, are enhanced, and
durability against repetitive compression required in cushioning
materials or the like are enhanced. Moreover, when the
thermoplastic elastomer to be added is an olefin-based
thermoplastic elastomer, the first component and the second
component are both composed of polyolefin-based polymers, thus
making it easy to recycle the fiber assembly after use.
[0069] In the crimped conjugate fiber of the present invention, in
the case where the second component is a polyolefin-based polymer,
it is preferable that the olefin-based thermoplastic elastomer
added to the second component is an .alpha.-olefin-based
thermoplastic elastomer containing an .alpha.-olefin-based
rubber-like polymer as a soft segment. Moreover, it is preferable
that the olefin-based thermoplastic elastomer and the
.alpha.-olefin-based thermoplastic elastomer are olefin-based
thermoplastic elastomers polymerized using metallocene
catalysts.
[0070] The .alpha.-olefin-based rubber-like polymer is not
particularly limited, and for example, it is preferable to use a
copolymer of ethylene and an .alpha.-olefin having 3 to 20 carbon
atoms. Examples of the .alpha.-olefin include propylene, 1-butene,
1-pentene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene,
4,4-dimethyl-1-pentene, 1-decene, 1-dodecene, 1-tetradecene,
1-octadecene, and the like. The hard segment contained in the
olefin-based thermoplastic elastomer is not particularly limited,
and for example, polyolefin-based polymers such as polypropylene
and polypropylene are usable. The polypropylene is not particularly
limited, and for example, homopolymers, random copolymers, block
copolymers, or mixtures thereof are usable. Examples of the random
copolymers and the block copolymers include copolymers of propylene
and at least one .alpha.-olefin selected from the group consisting
of ethylene and .alpha.-olefins having 4 or more carbon atoms. Such
.alpha.-olefins having 4 or more carbon atoms are not particularly
limited, and examples include 1-butene, 1-pentene,
3,3-dimethyl-1-butene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene,
1-decene, 1-dodecene, 1-tetradecene, 1-octadecene, and the
like.
[0071] When a polyolefin-based polymer such as polypropylene is
used as the second component, the content of the olefin-based
thermoplastic elastomer added to the second component is preferably
3 to 25 mass %, more preferably 3 to 20 mass %, and particularly
preferably 5 to 15 mass %, when the entire second component being
100 mass %. In the second component, when the olefin-based
thermoplastic elastomer content is 3 mass % or greater, the second
component as a whole exhibits elasticity due to the addition of the
elastomer component to the second component, and the resistance to
residual repetitive compression set and the resistance to residual
compression set of a fiber assembly that uses the crimped conjugate
fiber of the present invention can be increased. In the second
component, when the olefin-based thermoplastic elastomer content is
25 mass % or less, a crimped conjugate fiber from which a fiber
assembly that has excellent resistance to residual repetitive
compression set and resistance to residual compression set is
obtained is produced without adversely affecting the spinnability
and the stretchability of the crimped conjugate fiber.
[0072] The density of the olefin-based thermoplastic elastomer is
preferably 0.8 to 1.0 g/cm.sup.3, and more preferably 0.85 to 0.88
g/cm.sup.3. When the density is within the foregoing range,
excellent heat resistance is obtained, and regarding a fiber
assembly that uses the crimped conjugate fiber, a lighter fiber
assembly can be obtained if the volume is the same, and is thus
preferably used in applications where a light weight is
required.
[0073] The Shore A hardness of the olefin-based thermoplastic
elastomer measured according to ASTM D 2240 using a type A
durometer is preferably 50 to 95, more preferably 60 to 90, and
particularly preferably 65 to 85. When the Shore A hardness of the
olefin-based thermoplastic elastomer added to the second component
satisfies the foregoing range, the heat resistance and the
durability against repetitive bending of a nonwoven fabric that
uses the resulting crimped conjugate fiber is well-balanced. When
the Shore A hardness is less than 50, the added olefin-based
thermoplastic elastomer itself is excessively soft, and the
resulting crimped conjugate fiber and a fiber assembly deform
easily, and thus bending recovery properties and bulk recovery
properties can be poor. When the Shore A hardness exceeds 95, the
added olefin-based thermoplastic elastomer is excessively hard,
bending elasticity attributable to the addition of the olefin-based
thermoplastic elastomer to the second component is not
demonstrated, and bending recovery properties and bulk recovery
properties against repetitive compression tend to be impaired.
[0074] The melting peak temperature of the olefin-based
thermoplastic elastomer used in the present invention is not
particularly limited, but in light of the heat treatment performed
when producing a fiber assembly from the resulting crimped
conjugate fiber as well as the application of the fiber assembly
and the heat resistance of the fiber assembly, the melting peak
temperature of the olefin-based thermoplastic elastomer is
preferably 70.degree. C. or higher and 170.degree. C. or lower,
more preferably 100.degree. C. or higher and 160.degree. C. or
lower, and particularly preferably greater than or equal to the
melting peak temperature of polybutene-1 contained in the first
component and 160.degree. C. or lower. When the melting peak
temperature of the olefin-based thermoplastic elastomer contained
in the second component is 70.degree. C. or higher and 170.degree.
C. or lower, heat resistance is high, and bulk is not likely to be
reduced in a thermal treatment performed when obtaining a fiber
assembly from the resulting crimped conjugate fiber, thus enabling
a bulky fiber assembly to be readily obtained. In actual use of the
fiber assembly, since the bulk recovery properties at high
temperatures are good, the crimped conjugate fiber and the fiber
assembly are particularly suitable for applications where heat
resistance is required.
[0075] The melt flow rate of the olefin-based thermoplastic
elastomer is not particularly limited, and it is preferable that a
melt flow rate (MFR; a measurement temperature of 230.degree. C., a
load of 2.16 kgf (21.18 N), hereinafter referred to as MFR230)
measured according to JIS-K-7210 of 1 to 30 g/10 min, and a more
preferable MFR230 is 3 to 20 g/10 min, and a particularly
preferable MFR 230 is 5 to 15 g/10 min. With the MFR230 of the
olefin-based thermoplastic elastomer being within the foregoing
range, spun yarn retrievability and stretchability are good. Also,
in addition to the MFR230, with the melting peak temperature
satisfying the foregoing range, the olefin-based thermoplastic
elastomer used have good heat resistance, and therefore bulk is not
likely to be reduced in a thermal treatment performed when
obtaining a fiber assembly from the resulting crimped conjugate
fiber, thus enabling a bulky fiber assembly to be readily obtained.
In actual use of the fiber assembly, since the bulk recovery
properties at high temperatures are good, the crimped conjugate
fiber and the fiber assembly are particularly suitable for
applications where heat resistance is required.
[0076] While there are a variety of olefin-based thermoplastic
elastomers that satisfy the aforementioned density, Shore A
hardness, melting peak temperature, and melt flow rate, among such
olefin-based thermoplastic elastomers, it is preferable to use an
olefin-based thermoplastic elastomer that is polymerized using a
metallocene catalyst. In an olefin-based thermoplastic elastomer
that is polymerized without using a metallocene catalyst,
crystalline structure and amorphous structure portions having a
size of 300 nm to 1 .mu.m are scattered throughout the elastomer.
With an elastomer in which such hard segments and soft segments
having the aforementioned size are scattered throughout the
polymer, the bending elasticity of the elastomer itself and the
bending elasticity and the bulk recovery properties of a fiber and
a nonwoven fabric that contain the elastomer tend to be poor, and
in addition, it tends to be difficult to perform melt spinning. In
contrast, in an olefin-based thermoplastic elastomer polymerized
using a metallocene catalyst, crystalline structure and amorphous
structure portions having a size of 5 to 50 nm are scattered
throughout in the elastomer. By adding an elastomer having such a
structure to the second component (core component) of a crimped
conjugate fiber, it is likely that the resulting crimped conjugate
fiber has ample heat resistance and excellent bulk recovery
properties and resistance to set after repetitive deformation. An
example of the olefin-based thermoplastic elastomer polymerized
using a metallocene catalyst may be "Notio" (registered trademark)
manufactured by Mitsui Chemicals, Inc., or the like, but the
olefin-based thermoplastic elastomer is not limited thereto.
[0077] In the case where a polyester-based polymer is used as the
principal component of the second component as well as in the case
where a polyolefin-based polymer is used as the principal component
of the second component, the second component can be further
blended with a polymer insofar as the effect of the present
invention is not impaired. In addition, known various additives can
be added also to the second component insofar as the effect of the
present invention is not impaired and insofar as fiber
productivity, nonwoven fabric productivity, thermal bonding
properties, and texture are not adversely affected. Known
nucleating agents, antistatic agents, pigments, delusterants,
thermal stabilizers, photostabilizers, flame retardants,
bactericidal agents, lubricants, plasticizers, softening agents,
and the like can be mixed as additives that can be added to the
second component according to the applications.
[0078] In the crimped conjugate fiber of the present invention, the
centroid position of the second component does not overlap the
centroid position of the conjugate fiber. FIG. 1 shows a schematic
diagram of the cross-section of a crimped conjugate fiber according
to one embodiment of the present invention. A first component 1 is
disposed around a second component 2, and the first component 1
occupies for at least 20% of the surface of a conjugate fiber 10.
Accordingly, the surface of the first component 1 melts during
thermal bonding. A centroid position 3 of the second component 2
does not overlap a centroid position 4 of the conjugate fiber 10.
As seen in an enlarged image of the cross-section of the crimped
conjugate fiber captured with an electron microscope or the like,
the shift ratio (hereinafter also referred to as eccentricity) is a
value represented by Expression 2 below, where the centroid
position 3 of the second component 2 is C1, the centroid position 4
of the conjugate fiber 10 is Cf, and a radius 5 of the conjugate
fiber 10 is rf:
Eccentricity (%)=[|Cf-c1|/rf].times.100 Expression 2
[0079] The fiber cross-section in which the centroid position 3 of
the second component 2 does not overlap the centroid position 4 of
the conjugate fiber is preferably in an eccentric core-in-sheath
type as shown in FIG. 1 or a parallel type. In some cases, even
when the cross-section is in a multi-core type, a fiber in which
the centroid position of a multi-core portion as a whole does not
overlap the centroid position of the fiber is usable. In
particular, it is preferable that the fiber has an eccentric
core-in-sheath cross-section because the desired wavy crimps and/or
spiral. crimps are readily developed. The eccentricity of the
eccentric core-in-sheath conjugate fiber is preferably 5 to 50%,
and more preferably 7 to 30%. The shape of the fiber cross-section
of the second component 2 may be, other than being circular, oval,
Y, X, #, polygonal, star, and various other shapes, and the shape
of the cross-section of the conjugate fiber 10 may be, other than
being circular, oval, Y, X, #, polygonal, star, and various other
shapes, or hollow.
[0080] With the cross-section of the crimped conjugate fiber of the
present invention as shows in FIG. 1, in the case of an eccentric
core-in-sheath structure where the first component is disposed as a
sheath component of the conjugate fiber, the second component is
disposed as a core component, and the centroid position of the
second component does not overlap the centroid position of the
conjugate fiber. It is preferable that the second component and the
first component (core/sheath) are combined in a volume ratio of 8/2
to 2/8, more preferably 7/3 to 3/7, and even more preferably 6/4 to
4/6. The second component that serves as a core component
contributes mainly to bulk recovery properties, and the first
component that serves as a sheath component contributes mainly to
the strength of the nonwoven fabric and the hardness of the
nonwoven fabric. A combination ratio of 8/2 to 2/8 enables the
strength, the hardness, and the bulk recovery properties of the
nonwoven fabric to be satisfied simultaneously. When the first
component that serves as a sheath component is excessive, the
strength of the nonwoven fabric is increased, but the resulting
nonwoven fabric tends to be hard, and the bulk recovery properties
tend to be poor. On the other hand, when the second component that
serves as a core component is excessive, bonding points are
excessively reduced, and the strength of the nonwoven fabric tends
to be lowered, and the bulk recovery properties tend to be
poor.
[0081] FIG. 2 shows forms of crimps of a crimped conjugate fiber
according to one embodiment of the present invention. The phrase
"conjugate fiber in which three-dimensional crimps have been
developed" as used herein means that the crimp shape have been
developed in the crimped conjugate fiber includes wavy crimps
and/or spiral crimps. The term "wavy crimps" as used herein refers
to crimps having curved crests as shown in FIG. 2A. The term
"spiral crimps" refers to crimps having spirally curved crests as
shown in FIG. 2B. Crimps in which wavy crimps and spiral crimps are
concomitantly present as shown in FIG. 2C are encompassed within
the crimp form of the three-dimensional crimps developed in the
crimped conjugate fiber of the present invention. In the case of
ordinary mechanical crimps as shown in FIG. 3, the crests of crimps
are sharply angled, i.e., retaining serrated crimps, and it tends
to be difficult to attain large initial bulk when processed into a
nonwoven fabric. Moreover, planar elasticity against compression,
i.e., a spring effect, is inferior, and in particular, sufficient
initial bulk recovery properties are not likely to be obtained.
Crimps in which acutely angled crimps by mechanical crimping and
wavy crimps are concomitantly present as shown in FIG. 4 and,
although not shown in the figures, crimps in which acutely angled
crimps of mechanical crimping and spiral crimps are concomitantly
present are also encompassed within the crimp form of the
three-dimensional crimps which are developed in the crimped
conjugate fiber of the present invention.
[0082] Regarding the crimped conjugate fiber of the present
invention, crimps in which wavy crimps and spiral crimps are
concomitantly present as shown in FIG. 2C are particularly
preferable because cardability, initial bulk, and bulk recovery
properties can be satisfied simultaneously.
[0083] Hereinbelow, a method for producing the crimped conjugate
fiber of the present invention will now be described.
[0084] First, a method for producing an actualized crimping
conjugate fiber, which is one embodiment of the crimped conjugate
fiber of the present invention, will now be described.
[0085] First, a first component containing polybutene-1 and linear
low density polyethylene and a second component containing a
polymer having a melting peak temperature at least 20.degree. C.
higher than the melting peak temperature of polybutene-1 or a
polymer having a melting initiation temperature of 120.degree. C.
or higher are provided. Next, the first component and the second
component are supplied to a compound nozzle, for example, an
eccentric core-in-sheath compound nozzle, such that on the fiber
cross-section, the first component occupies for at least 20% of the
surface of a conjugate fiber, and the centroid position of the
second component does not overlap the centroid position of the
conjugate fiber, and the second component is subjected to melt
spinning at a spinning temperature of 220 to 350.degree. C., and
the first component at a spinning temperature of 200 to 300.degree.
C. The spinning temperature of the second component is selected
according to the polymer, and it is preferable to perform melt
spinning at a spinning temperature of 220.degree. C. to 330.degree.
C. in the case where a polyolefin-based polymer such as
polypropylene or polymethylpentene is used, and at a spinning
temperature of 240 to 350.degree. C. in the case where a
polyester-based polymer such as polyethylene terephthalate,
polytrimethylene terephthalate, or polybutylene terephthalate is
used.
[0086] The first component and the second component are supplied to
an eccentric core-in-sheath compound nozzle at the aforementioned
spinning temperatures, and retrieved at a retrieving rate of 100 to
1500 m/min to give an unstretched spinning filament having a
fineness of 2 to 120 dtex. Next, a stretching treatment is carried
out at a stretch ratio of 1.8 or greater at a stretching
temperature of 40.degree. C. or higher and lower than the melting
point of the first component. A more preferable lower limit of the
stretching temperature is 50.degree. C. or higher, and a more
preferable upper limit of the stretching temperature is a
temperature 10.degree. C. lower than the melting point of the first
component. When the stretching temperature is lower than 40.degree.
C., crystallization of the first component barely proceeds, and
thus thermal shrinkage tends to be increased and bulk recovery
properties tend to be reduced. When the stretching temperature is
greater than or equal to the melting point of the first component,
pieces of the fiber tend to fuse to each other. A more preferable
lower limit of the stretch ratio is 2. A more preferable upper
limit of the stretch ratio is 4. When the stretch ratio is 1.8 or
greater, the stretch ratio is not excessively small, making it easy
to obtain a fiber in which the above-described wavy crimps and/or
spiral crimps are developed, and the initial bulk and the rigidity
of the fiber itself are not small, and nonwoven fabric
processability such as cardability and bulk recovery properties are
not inferior. The stretching method is not particularly limited,
and known stretching treatments can be performed, such as wet
stretching in which stretching is performed while heating with high
temperature fluid such as hot water; dry stretching in which
stretching is performed while heating in high temperature gas or
with a high temperature metal roll; and water vapor stretching in
which stretching is performed while heating a fiber by water vapor
having a temperature of 100.degree. C. or higher under ordinary
pressure or increased pressure. Among such methods, wet stretching
using hot water is preferable because of its productivity and
economical efficiency and because it allows the entire unstretched
fiber bundle to be readily and uniformly heated. Before or after
the above-described stretching, an annealing treatment may be
performed as necessary under a dry heat, wet heat, or steaming
atmosphere at 90 to 120.degree. C.
[0087] In an actualized crimping conjugate fiber that is one
embodiment of the crimped conjugate fiber of the present invention,
in the case where the polymer having a melting peak temperature at
least 20.degree. C. higher than the melting peak temperature of
polybutene-1 or the polymer having a melting initiation temperature
of 120.degree. C. or higher contained in the second component
constituting the actualized crimping conjugate fiber is a
polyolefin-based polymer such as homopolypropylene, an
ethylene-propylene copolymer, or an ethylene-butene-1-propylene
terpolymer, the stretching temperature is preferably 40.degree. C.
or higher and lower than or equal to the melting peak temperature
of polybutene-1 contained in the first component, more preferably
50.degree. C. or higher and 100.degree. C. or lower, and
particularly preferably 60.degree. C. or higher and 90.degree. C.
or lower. In contrast, in an actualized crimping conjugate fiber
that is one embodiment of the crimped conjugate fiber of the
present invention, in the case where the polymer having a melting
peak temperature at least 20.degree. C. higher than the melting
peak temperature of polybutene-1 or the polymer having a melting
initiation temperature of 120.degree. C. or higher contained in the
second component constituting the actualized crimping conjugate
fiber is a polyester-based polymer such as polyethylene
terephthalate, polytrimethylene terephthalate, or polybutylene
terephthalate, the stretching temperature is preferably 60.degree.
C. or higher and lower than or equal to the melting peak
temperature of polybutene-1 contained in the first component, more
preferably 70.degree. C. or higher and 100.degree. C. or lower, and
particularly preferably 75.degree. C. or higher and 95.degree. C.
or lower.
[0088] Next, before or after adding a fiber treating agent as
necessary 5 to 25 crimps per 25 mm are formed using a known crimper
such as a stuffer-box crimper. A more preferable number of crimps
is 8 to 20 per 25 mm, and a particularly preferable number of
crimps is 10 to 18 per 25 mm. It is preferable that the shape of
crimps after a fiber has passed through a crimper is serrated
crimps and/or wavy crimps. When the number of crimps is less than 5
per 25 mm, cardability tends to be impaired, and the initial bulk
and the bulk recovery properties of the nonwoven fabric tend to be
poor. On the other hand, when the number of crimps is greater than
25 per 25 mm, the number of crimps is excessive, and not only does
cardability tend to be impaired and the texture of the nonwoven
fabric tend to deteriorate, but also the initial bulk of the
nonwoven fabric tend to be reduced.
[0089] Moreover, after crimps are formed by the aforementioned
crimper, it is preferable to perform an annealing treatment at a
temperature at which an unstretched fiber bundle does not undergo
thermal bonding and at which three-dimensional crimps are
developed. For a conjugate fiber that is encompassed within the
crimped conjugate fiber of the present invention and in which the
first component is composed of a polymer containing polybutene-1,
it is preferable to perform an annealing treatment in a dry heat,
wet heat, or steaming atmosphere in a preferable temperature range
of 90 to 120.degree. C. Specifically, it is preferable that, after
a fiber treating agent is added, crimps are formed by a crimper,
and then an annealing treatment and simultaneously a drying
treatment are performed in a dry heat atmosphere of 90 to
120.degree. C. because the process can be simplified. When an
annealing treatment is performed at a temperature of 90.degree. C.
or higher, dry thermal shrinkage is not large, specific actual
crimps are readily obtained, the texture of the resulting nonwoven
fabric is not roughened, and productivity can be increased. In the
annealing treatment, a more preferable range of the treatment
temperature is 90 to 115.degree. C., and particularly preferably 95
to 110.degree. C.
[0090] An actualized crimping conjugate fiber obtained by the
above-described method mainly has at least one type of crimp
selected from wavy crimps and spiral crimps shown in FIG. 2.
Preferably, the actualized crimping conjugate fiber has at least
one type of crimp selected from wavy crimps only, spiral crimps
only, crimps where wavy crimps and spiral crimps are concomitantly
present, and crimps where wavy crimps and serrated crimps are
concomitantly present, and particularly preferably, the actualized
crimping conjugate fiber has at least one type of crimp selected
from wavy crimps only, spiral. crimps only, and crimps where wavy
crimps and spiral crimps are concomitantly present. The number of
crimps of the actualized crimping conjugate fiber is preferably 5
per 25 mm or greater, and 25 per 25 mm or less, because a bulky
nonwoven fabric can be obtained without reducing cardability. Then,
the fiber is cut into a desired fiber length, giving an actualized
crimping conjugate fiber. A more preferable number of crimps is 8
to 20 per 25 mm, and a particular preferable number of crimps is 10
to 18 per 25 mm.
[0091] With the actualized crimping conjugate fiber, crimps appear
on a conjugate fiber, and at least one type of three-dimensional
crimps selected from wavy crimps and spiral crimps are developed
and made visible, and therefore the actualized crimping conjugate
fiber has actual crimps. In the state of the fiber, the crimps may
be actualized crimps in which three-dimensional crimps fully have
been developed, or may be actualized crimps in which slightly more
crimping that will be developed (that will be developed when the
fiber is heated) remains. However, if crimps are developed to such
an extent that the number of crimps exceeds 25 per 25 mm when heat
is applied to the fiber (for example, when heat is applied for
processing into a nonwoven fabric as described later), cardability
may deteriorate, and it is thus not preferable.
[0092] Next, a method for producing a latently crimpable conjugate
fiber, which is another embodiment of the crimped conjugate fiber
of the present invention, will now be described.
[0093] First, a first component containing polybutene-1 and linear
low density polyethylene and a second component containing a
polymer having a melting peak temperature at least 20.degree. C.
higher than the melting peak temperature of polybutene-1 or a
polymer having a melting initiation temperature of 120.degree. C.
or higher are provided. Next, the first component and the second
component are supplied to a compound nozzle, for example, an
eccentric core-in-sheath compound nozzle, such that in the fiber
cross-section, the first component occupies for at least 20% of the
surface of a conjugate fiber, and the centroid position of the
second component does not overlap the centroid position of the
conjugate fiber, and the second component is subjected to melt
spinning at a spinning temperature of 220 to 350.degree. C., and
the first component at a spinning temperature of 200 to 300.degree.
C. The spinning temperature of the second component is selected
according to the polymer, and it is preferable to perform melt
spinning at a spinning temperature of 220.degree. C. to 330.degree.
C. in the case where a polyolefin-based polymer such as
polypropylene or polymethylpentene is used, and at a spinning
temperature of 240 to 350.degree. C. in the case were a
polyester-based polymer such as polyethylene terephtha late,
polytrimethylene terephthalate, or polybutylene terephthalate is
used.
[0094] The first component and the second component are supplied to
an eccentric core-in-sheath compound nozzle at the aforementioned
spinning temperatures, and retrieved at a retrieving rate of 100 to
1500 m/min to give an unstretched spinning filament having a
fineness of 2 to 120 dtex. Next, a stretching treatment is carried
out at a stretch ratio of 1.5 or greater at a stretching
temperature of 40.degree. C. or higher and lower than the melting
point of the first component. A more preferable lower limit of the
stretching temperature is 50.degree. C. or higher. A more
preferable upper limit of the stretching temperature is a
temperature 10.degree. C. lower than the melting point of the first
component. When the stretching temperature is lower than 40.degree.
C., crystallization of the first component barely proceeds, and
thus thermal shrinkage tends to be increased and bulk recovery
properties tend to be reduced. When the stretching temperature is
greater than or equal to the melting point of the first component,
fibers each other tend to fuse. A more preferable lower limit of
the stretch ratio is 2. A more preferable upper limit of the
stretch ratio is 4. When the stretch ratio is 1.5 or greater, the
stretch ratio is not excessively small, crimps are likely to appear
when a thermal treatment is performed, and the initial bulk and the
rigidity of the fiber itself are not small, and nonwoven fabric
processability such as cardability and bulk recovery properties are
not inferior. The stretching method is not particularly limited,
and known stretching treatments can be performed, such as wet
stretching in which stretching is performed while heating with high
temperature fluid such as hot water; dry stretching in which
stretching is performed while heating in high temperature gas or
with a high temperature metal roll; and water vapor stretching in
which stretching is performed while heating a fiber by water vapor
having a temperature of 100.degree. C. or higher under ordinary
pressure or increased pressure. Among such methods, wet stretching
using hot water is preferable because of its productivity and
economical efficiency and because it allows the entire unstretched
fiber bundle to be readily and uniformly heated.
[0095] In a latently crimpable conjugate fiber that is one
embodiment of the crimped conjugate fiber of the present invention,
in the case where the polymer having a melting peak temperature at
least 20.degree. C. higher than the melting peak temperature of
polybutene-1 or the polymer having a melting initiation temperature
of 120.degree. C. or higher contained in the second component
constituting the latently crimpable conjugate fiber is a
polyolefin-based polymer such as a propylene homopolymer, an
ethylene-propylene copolymer, or an ethylene-butene-1-propylene
terpolymer, the stretching temperature is preferably 40.degree. C.
or higher and lower than or equal to the melting peak temperature
of polybutene-1 contained in the first component, more preferably
50.degree. C. or higher and 100.degree. C. or lower, and
particularly preferably 60.degree. C. or higher and 90.degree. C.
or lower. In contrast, in a latently crimpable conjugate fiber that
is one embodiment of the crimped conjugate fiber of the present
invention, in the case where the polymer having a melting peak
temperature at least 20.degree. C. higher than the melting peak
temperature of polybutene-1 or the polymer having a melting
initiation temperature of 120.degree. C. or higher contained in the
second component constituting the latently crimpable conjugate
fiber is a polyester-based polymer such as polyethylene
terephthalate, polytrimethylene terephthalate, or polybutylene
terephthalate, the stretching temperature is preferably 60.degree.
C. or higher and lower than or equal to the melting peak
temperature of polybutene-1 contained in the first component, more
preferably 70.degree. C. or higher and 100.degree. C. or lower, and
particularly preferably 75.degree. C. or higher and 95.degree. C.
or lower.
[0096] Next, before or after adding a fiber treating agent as
necessary 5 to 25 crimps per 25 mm are formed using a known crimper
such as a stuffer-box crimper. Amore preferable number of crimps is
8 to 20 per 25 mm, and a particularly preferable number of crimps
is 10 to 18 per 25 mm. When the number of crimps is less than 5 per
25 mm or the number of crimps exceeds 25 per 25 mm, cardability is
likely to be impaired.
[0097] Furthermore, after crimps are formed by the aforementioned
crimper, it is preferable to perform an annealing treatment in a
dry heat, wet heat, or steaming atmosphere at 50 to 100.degree. C.,
preferably 60 to 90.degree. C., more preferably 60 to 80.degree.
C., and particularly preferably 60 to 75.degree. C. Specifically,
it is preferable that, after a fiber treating agent is added,
crimps are formed by a crimper, and then an annealing treatment and
simultaneously a drying treatment are performed in a dry heat
atmosphere of 50 to 90.degree. C. because the process can be
simplified. An annealing temperature of 50 to 90.degree. C. allows
desired heat shrinkage to be obtained, and a latently crimpable
conjugate fiber can be obtained in which crimps are developed
during heating. Also, a fiber that has high cardability can be
obtained.
[0098] The crimped conjugate fiber of the present invention, i.e.,
the actualized crimping conjugate fiber or the latently crimpable
conjugate fiber of the present invention, is subjected to the
aforementioned annealing treatment and dried, and then the filament
is cut according to the application. The cut fiber length is 1 to
120 mm, but is selected according to the application. If a nonwoven
fabric is produced by a known nonwoven fabric production method
such as air-through, needle punching, or hydro-entanglement, after
producing a fiber web with a carding machine, the filament is cut
into fiber lengths of 20 to 100 mm, preferably 30 to 90 mm, and
more preferably 40 to 80 mm. If a nonwoven fabric is produced by a
fiber web production method by air spreading, i.e., a so-called
air-laid method, the filament is cut into fiber lengths of 1 to 40
mm, preferably 1 to 30 mm, and more preferably 3 to 25 mm. If a wet
nonwoven fabric is produced by a paper making method, the filament
is cut into fiber lengths of 1 to 20 mm, preferably 1 to 10 mm, and
more preferably 3 to 8 mm. It is also possible with the crimped
conjugate fiber of the present invention that, depending on the
application, the filament after an annealing treatment is not cut
and used as it is.
[0099] The fineness of the crimped conjugate fiber of the present
invention, i.e., the actualized crimping conjugate fiber or the
latently crimpable conjugate fiber of the present invention, is not
particularly limited. The crimped conjugate fiber is processed so
as to have a fineness suitable for applications, for example,
various nonwoven fabric applications such as hard stuffing that
serves as a material substituted for urethane foam, mattresses for
bedding, vehicle seats and various chairs, cushioning materials for
clothing such as a shoulder pad and a brassiere pad, sanitary
materials, packaging materials, wet wipes, filters, sponge-like
porous wiping materials, sheet-like wiping materials; applications
as wadding for various kinds of bedding such as blankets and
mattresses and clothing articles that make use of the elasticity
and the shape recovery properties of the conjugate fiber itself,
and like applications, but a fineness of 1 to 60 dtex is preferable
because elasticity as well as bulk recovery properties and texture
when processed into a nonwoven fabric are excellent. Amore
preferable fineness range is 2 to 50 dtex, particularly preferably
4 to 30 dtex, and most preferably 4 to 20 dtex.
[0100] The fiber assembly of the present invention contains at
least 30 mass % of the crimped conjugate fiber. When the crimped
conjugate fiber is contained in a proportion of 30 mass % or
greater, the elasticity, the bulk recovery properties, and like
properties of the fiber assembly can be maintained at a high level.
Examples of the fiber assembly include knitted fabrics, woven
fabrics, nonwoven fabrics, fillings, pads, fiber webs, and the
like. It is preferable that the fiber assembly contains 30 to 100
mass % of the crimped conjugate fiber and 0 to 70 mass % of fibers
other than the crimped conjugate fiber. Such fibers other than the
crimped conjugate fiber contained in the fiber assembly are not
particularly limited insofar as the performance of the crimped
conjugate fiber is not impaired, including, for example, at least
one fiber selected from synthetic fibers, chemical fibers, natural
fibers, and inorganic fibers.
[0101] The method for producing a fiber assembly containing the
crimped conjugate fiber of the present invention is not
particularly limited. After forming a fiber web by a known method,
the fiber web can be processed into a nonwoven fabric by a known
nonwoven fabric production method such as air-through, needle
punching, or hydro-entanglement. In addition, it is also possible
that the crimped conjugate fiber is processed into a fiber ball,
and the fiber ball is blown into a frame mold and subjected to a
thermal treatment to give a fiber assembly having a specific shape
as disclosed in JP 2001-207360A and JP2002-242061A. A production
method is preferable in which a fiber web is formed and then
processed into a nonwoven fabric. Examples of forms of the fiber
web constituting the nonwoven fabric of the present invention
include a parallel web, a semi-random web, a random web, a
cross-laid web, a criss-cross web, an air-laid web, and the like.
The fiber web demonstrates a greater effect when the first
component is bonded due to a thermal treatment. If necessary, the
fiber web may be subjected to needle punching or hydro-entanglement
before thermal processing. The means of thermal processing is not
particularly limited insofar as the function of the crimped
conjugate fiber of the present invention is sufficiently
demonstrated, and it is preferable to use a heating machine that
does not impose much pressure such as wind pressure, for example, a
heating machine that lets hot air through, a heating machine that
vertically blows hot air, an infra-red heating machine, and the
like.
[0102] Fibers that can be blended with a fiber web that uses the
crimped conjugate fiber of the present invention (hereinafter also
referred to as blend fibers) are not particularly limited insofar
as the performance of the crimped conjugate fiber of the present
invention is not impaired. Examples include single fibers of
polyesters such as polyethylene terephthalate, polybutylene
terephthalate, polytrimethylene terephthalate, polyethylene
naphthalate, polylactate, and polybutylene succinate; single fibers
of polyethylenes such as low density polyethylene, high density
polyethylene, and linear low density polyethylene; single fibers of
isotactic, atactic, syndiotactic, and like polypropylenes
polymerized using ordinary Ziegler-Natta catalysts and metallocene
catalysts; single fibers of polyolefins such as polymers in which
monomers of such polyolefins are copolymerized, or polyolefins for
which metallocene catalysts (also referred to as Kaminsky
catalysts) are used when polymerizing such polyolefins; single
fibers of polyamides such as Nylon 6, Nylon 66, Nylon 11, and Nylon
12; single fibers of (poly)acryls composed of acrylonitrile; and
single fibers of engineering plastics such as polycarbonate,
polyacetal, polystyrene, and cyclic polyolefin. Here, the term
"single fiber" refers to a fiber composed solely of one polymer
component. As the blend fiber, a conjugate fiber containing at
least one or more polymer components can also be used insofar as
the performance of the crimped conjugate fiber of the present
invention is not impaired. Examples of such a conjugate fiber
include conjugate fibers in which different types of resins among
polyesters, polyolefins, polyamides and engineering plastics, or
resins composed of different polymer components of the same type
(for example, polyethylene terephthalate and polytrimethylene
terephthalate) are mutually combined. In the conjugate fiber, the
combined state is not particularly limited. In terms of the
cross-sectional shape of the fiber, core-in-sheath conjugate
fibers, eccentric core-in-sheath conjugate fibers, parallel
conjugate fibers, sectional conjugate fibers in which resin
components having a shape of citrus fruit clusters are disposed
alternately, and sea-island conjugate fibers may be used. In the
crimped conjugate fiber of the present invention, in the case where
the second component is a polyolefin-based polymer, most of the
polymer components constituting the crimped conjugate fiber are
polyolefin-based polymers, and thus use of a single fiber composed
of a polyolefin-based polymer, or use of a conjugate fiber in which
polyolefin-based polymers are mutually combined, as a blend fiber
is preferable from the viewpoint of recycling efficiency of the
fiber assembly.
[0103] Since the crimped conjugate fiber of the present invention
has excellent thermal bonding properties, the crimped conjugate
fiber exhibits thermal bonding properties for not only synthetic
fibers having the thermoplastic resins as the components, but also
natural fibers including cellulose-based fibers, semi-synthetic
fibers (also referred to as regenerated fibers) such as viscose
rayon, Tencel (registered trademark), Iyocel (registered
trademark), and cuprammonium rayon, inorganic fibers such as glass
fibers, and carbon fibers. Examples of the natural fibers include
vegetable-based natural fibers and animal-based natural fibers.
Examples of vegetable-based natural fibers include fibers of ramie
(China grass), linen (flax), kenaf, abaca (Manila hemp), henequen
(sisal hemp), jute, hemp (cannabis), coconut, palm, paper mulberry,
paper bush, bagasse, and the like. Examples of animal-based natural
fibers include fibers of silk, sheep wool, angora, cashmere,
mohair, and the like. As a fiber to be blended with the crimped
conjugate fiber of the present invention, a vegetable-based natural
fiber and an animal-based natural fiber can both be used, but a
vegetable-based natural fiber is preferable since the cost of
cultivation is inexpensive.
[0104] A fiber web containing the crimped conjugate fiber of the
present invention can be processed into a bulky fiber assembly by
performing thermal processing on the fiber web in a monolayer
state, but a fiber assembly having superior bulkiness can be
readily obtained by forming a laminate web in which fiber webs are
stacked before performing thermal processing, or a laminate of
fiber assemblies by stacking fiber assemblies after thermal
processing. It is preferable that in the fiber assembly, fibers
constituting the fiber assembly are arranged parallelly in the
thickness direction of the fiber assembly, or in other words,
fibers are arranged in the longitudinal direction of the fiber
assembly. This is because fibers constituting the fiber assembly
arranged parallelly in the thickness direction afford good bulk
recovery properties and cushioning properties against pressure
applied in the thickness direction. Herein, the phrase "fibers
constituting the fiber assembly are arranged parallelly in the
thickness direction of the fiber assembly (arranged in the
longitudinal direction of the fiber assembly)" means that the sharp
angle formed by the fibers constituting the fiber assembly and the
thickness direction of the fiber assembly is 45.degree. or less, or
in other words, when the fiber assembly is cut in the thickness
direction and the cut surface is viewed with an optical microscope
or a scanning electron microscope for enlargement, the sharp angle
formed by the fibers constituting the fiber assembly and the
thickness direction of the fiber assembly is 45.degree. or less. It
is more preferable that 80% or greater of the total number of the
entire fibers constituting the fiber assembly viewed on a specific
area of the cut surface are arranged in the longitudinal direction
of the fiber assembly. The fiber assembly described above in which
fibers constituting the fiber assembly are arranged parallelly in
the thickness direction can be produced by a known production
method, and examples include so-called Strute nonwoven fabrics
produced by shaping a fiber web into a wave form and subjecting it
to thermal bonding while compressing it in the length direction,
but the fiber assembly is not limited thereto.
[0105] In the case where the crimped conjugate fiber contained in a
fiber web is the actualized crimping conjugate fiber, the
temperature of thermal processing on the fiber web is set so as to
be within a range in which the developed wavy crimps and/or spiral
crimps of the crimped conjugate fiber do not disappear during
thermal processing. For example, if the melting peak temperature of
polybutene-1 is Tm, the thermal processing temperature is Tm-10
(.degree. C.) to lower than the melting peak temperature of the
second component, preferably Tm-10 (.degree. C.) to Tm+80 (.degree.
C.), particularly preferably Tm (.degree. C.) to Tm+50 (.degree.
C.), and most preferably 130 to 160.degree. C. Due to the thermal
processing, at least one resin component contained in the first
component of the actualized crimping conjugate fiber melts, and
pieces of the constituent fiber are thermally fused to each other.
In particular, it is preferable that when pieces of the constituent
fiber are thermally fused to each other by allowing at least
polybutene-1 of the actualized crimping conjugate fiber to melt,
more rigid intersections where pieces of the fiber meet each other
can be formed, and bulk recovery properties are enhanced.
[0106] In the case where the crimped conjugate fiber contained in a
fiber web is the latently crimpable conjugate fiber, the
temperature is set so as to be within a range in which crimps are
developed. For example, if the melting peak temperature of
polybutene-1 is Tm, the temperature is set so as to be within a
range of Tm-10 (.degree. C.) to lower than the melting point of the
second component, preferably Tm-10 (.degree. C.) to Tm+60 (.degree.
C.), particularly preferably Tm (.degree. C.) to Tm+50 (.degree.
C.), and most preferably 130 to 160.degree. C. Due to the thermal
processing, at least one resin component contained in the first
component of the latently crimpable conjugate fiber melts, and
pieces of the constituent fiber are thermally fused to each other.
In particular, it is preferable that when pieces of the constituent
fiber are thermally fused to each other by allowing at least
polybutene-1 of the latently crimpable conjugate fiber to melt,
more rigid intersections where pieces of the fiber meet each other
can be formed, and bulk recovery properties are enhanced.
[0107] It is preferable that the nonwoven fabric has a residual
compression set rate measured according to JIS-K-6400-4 A of 45% or
less, and more preferably 35% or less. The residual compression set
rate shows the extent of change of the hardness of the nonwoven
fabric when heated to 70.degree. C. The smaller the value, the more
the deterioration of the fiber or the nonwoven fabric by heat is
suppressed, thus indicating excellent bulk recovery properties.
[0108] It is preferable that the nonwoven fabric has a residual
repetitive compression set rate measured according to JIS-K-6400-4
B of 15% or less, and more preferably 12% or less. The residual
repetitive compression set rate shows the extent of change of the
hardness of the nonwoven fabric when 50% compression is repeated
80000 times. The smaller the value, the more the deterioration of
the fiber or the nonwoven fabric caused by compression is
suppressed, thus indicating excellent bulk recovery properties.
[0109] The fiber product of the present invention at least
partially contains the fiber assembly, and is formed into hard
stuffing, bedding, vehicle seats, chairs, shoulder pads, brassiere
pads, garments, sanitary materials, packaging materials, wet wipes,
filters, sponge-like porous wiping materials, sheet-like wiping
materials, and wadding.
EXAMPLE
[0110] The present invention shall be described in more detail
below by way of examples. However, the present invention is not
limited to these examples.
[0111] The measurement methods and the evaluation methods used in
the examples are as follows.
[0112] Q value
[0113] I. Analyzers used
[0114] (i) Cross-fractionation apparatus "CFC T-100" (hereinafter
referred to as CFC) manufactured by DIA Instruments Co., Ltd.
[0115] (ii) Fourier transform infrared absorption spectrometer
(FT-IR) "1760X" manufactured by PerkinElmer, Inc.
[0116] A fixed wavelength infrared spectrophotometer attached as a
detector of the CFC was removed and replaced by the FT-IR
spectrometer, and the FT-IR spectrometer was used as a detector.
The transfer line from the outlet for a solution eluted from the
CFC to the FT-IR spectrometer was 1 m, and the temperature was
maintained at 140.degree. C. during measurement. The flow cell
attached to the FT-IR spectrometer had an optical path length of 1
mm and an optical path diameter of 5 mm .phi., and the temperature
was maintained at 140.degree. C. during measurement.
[0117] (iii) Gel permeation chromatography (GPC)
[0118] Three GPC columns "AD806MS" manufactured by Showa Denko K.K.
connected in series were used in the latter portion of the CFC.
[0119] II. CFC measurement conditions
[0120] (i) Solvent: ortho-dichlorobenzene (ODCB)
[0121] (ii) Sample concentration: 1 mg/ml
[0122] (iii) Injection amount: 0.4 ml
[0123] (iv) Column temperature: 140.degree. C.
[0124] (v) Solvent flow rate: 1 ml/min
[0125] III. FT-IR measurement conditions
[0126] After the beginning of elution of a sample solution from the
GPC in the latter portion of the CFC, FT-IR measurement was
performed under the following conditions, and GPC-IR data was
collected.
[0127] (i) Detector: MCT
[0128] (ii) Resolution: 8 cm.sup.-1
[0129] (iii) Measurement interval: 0.2 min (12 sec)
[0130] (iv) Number of scans per measurement: 15
[0131] IV. Post-processing and analysis of measurement results
[0132] The molecular weight distribution was determined using the
absorbance at 2945 cm.sup.-1 obtained by the FT-IR spectrometer as
a chromatogram. The retention volume was converted to the molecular
weight using a standard curve prepared in advance with standard
polystyrenes. The standard polystyrenes used were "F380", "F288",
"F128", "F80", "F40", "F20", "F10", "F4", "F1", "A5000", "A2500",
and "A1000", all manufactured by Tosoh Corporation. A calibration
curve was created by injecting 0.4 ml of a solution in which 0.5
mg/ml of a standard polystyrene was dissolved in
[0133] ODCB (containing 0.5 mg/ml of BHT). The calibration curve
employed a cubic equation obtained by approximation using the
least-squares method. The conversion to the molecular weight
employed a universal calibration curve in reference to Sadao Mori,
"Size Exclusion Chromatography" (Kyoritsu Shuppan). The following
numerical values were used in the viscosity formula
([.theta.]=K.times.M.alpha.) used herein.
[0134] (i) In formation of calibration curve using standard
polystyrenes
[0135] K=0.000138, .alpha.=0.70
[0136] (ii) In measurement of polypropylene samples
[0137] K=0.000103, .alpha.=0.78
[0138] Above, measurements were performed according to gel
permeation chromatography (GPC), but measurements may be performed
using another model. In such a case, measurements are performed
simultaneously with "MG03B" manufactured by Japan Polypropylene
Corporation as described in the 2005 Catalogue for Commercial
Transaction of Plastic Molding Materials (Chemical Daily Co., Ltd.,
published on Aug. 30, 2004), the value when the MG03B shows 3.5 is
used as a blank condition, and the conditions are adjusted to
perform the measurements.
[0139] Spinnability During Melt Spinning
[0140] The spinnability of each crimped conjugate fiber was
evaluated based on the conditions of occurrence and the frequency
of occurrence of a thread break when melt spinning was continuously
performed for 30 minutes using the following criteria:
[0141] A: The number of thread breaks was 0 to 2 during continuous
melt spinning for 30 minutes, and spinnability was good.
[0142] B: The number of thread breaks was 3 to 5 during continuous
melt spinning for 30 minutes, but not detrimental to the
processing.
[0143] C: The number of thread breaks was 6 or greater during
continuous melt spinning for 30 minutes, or a large number of
thread breaks occurred, making it impossible to carry out
spinning.
[0144] Stretchability
[0145] The stretchability of a crimped conjugate fiber was
evaluated based on the conditions of occurrence of a thread break
in a stretching step and the passability through a starer-box
crimper used for imparting crimps using the following criteria:
[0146] A: Few thread breaks occurred in a stretching step, and a
thread readily passed through a stuffer-box crimper, and thus there
was absolutely no productivity problem.
[0147] B: Thread breaks occurred in a stretching step or
stuffer-box crimper clogging occurred, but not detrimental to
productivity.
[0148] C: Thread breaks occurred frequently, and a thread wound
around a stretching bath and a stretching roll, or clogging inside
a stuffer-box crimper or at the outlet frequently occurred, and
thus severely impaired productivity.
[0149] Staple Fiber Spreadability
[0150] The staple fiber spreadability of a crimped conjugate fiber
was evaluated based on the card processability (cardability,
conditions of nep generation, and texture of resulting web) when
collecting a web by subjecting 100 mass % of a crimped conjugate
fiber to a parallel card using the following criteria:
[0151] A: A fiber easily passed through a parallel card, few neps
were produced, and thus a web having good texture was obtained.
[0152] B: Some neps were generated, but the texture of a web was
not affected that much.
[0153] C: Cardability was poor, or large amounts of neps were
generated, and thus no web was obtained.
[0154] Staple fiber crimp formability of actualized crimping
conjugate fiber
[0155] A tow after completion of a drying step (annealing and
drying step at 100.degree. C. for 15 minutes) was visually
inspected, and the staple fiber crimp formability of actualized
crimping conjugate fibers was evaluated using the following
criteria:
[0156] A: Three-dimensional crimps were developed, and it was easy
to identify the shape of spiral crimps and/or wavy crimps.
[0157] B: Three-dimensional crimps were developed, but it was
fairly difficult to identify the shape of spiral crimps and/or wavy
crimps, and serrated crimps were also concomitantly present.
[0158] C: It was not possible to identify either mechanical crimps
(serrated crimps) or three-dimensional crimps (spiral crimps and/or
wavy crimps), and most of the crimps had disappeared.
[0159] Staple fiber crimp formability of latently crimpable
conjugate fiber
[0160] A tow after completion of a drying step (annealing and
drying step at 100.degree. C. for 15 minutes) was visually
inspected, and the staple fiber crimp formability of latently
crimpable conjugate fibers was evaluated using the following
criteria:
[0161] A: Mechanical crimps imparted by a stuffer-box crimper had
not disappeared, and it was easy to identify the serrated
shape.
[0162] B: Mechanical crimps imparted by a stuffer-box crimper had
slightly disappeared, and there were portions where the serrated
shape was not observed.
[0163] C: It was not possible to identify either mechanical crimps
(serrated crimps) or three-dimensional crimps (spiral crimps and/or
wavy crimps), and most of the crimps had disappeared.
[0164] Crimp formability after thermal processing of actualized
crimping conjugate fiber
[0165] Each crimped conjugate fiber (100 mass %) was subjected to a
parallel card to collect a web, and the web was treated at a
processing temperature of 150.degree. C. for 30 seconds with a
convection heating machine and then visually inspected in order to
evaluate the crimp formability after thermal processing of an
actualized crimping conjugate fiber using the following
criteria:
[0166] A: Developed three-dimensional crimps had not disappeared,
and it was easy to identify the shape of spirals crimp and/or wavy
crimps.
[0167] B: Developed three-dimensional crimps had partially
disappeared, but it was possible to identify the shape of spiral
crimps and/or wavy crimps.
[0168] C: Developed three-dimensional crimps had mostly
disappeared, and it was difficult to identify the shape of
crimps.
[0169] Crimp formability after thermal processing of latently
crimpable conjugate fiber
[0170] A crimped conjugate fiber (100 mass %) was subjected to a
parallel card to collect a web, and the web was treated at a
processing temperature of 150.degree. C. for 30 seconds with a
convection heating machine and then visually inspected in order to
evaluate the crimp formability after thermal processing of a
latently crimpable conjugate fiber using the following
criteria:
[0171] A: Three-dimensional crimps were developed due to thermal
treatment, and it was easy to identify the shape of spiral crimps
and/or wavy crimps.
[0172] B: Three-dimensional crimps were poorly developed, or
three-dimensional crimps developed due to heat were partially
disappeared, but it was possible to identify the shape of spiral
crimps and/or wavy crimps.
[0173] C: Three-dimensional crimps were poorly developed, or
three-dimensional crimps were developed due to heat were mostly
disappeared, and it was difficult to identify the shape of
crimps.
[0174] Measurement of melting points (Tf1, Tf2) of each component
after spinning
[0175] Using a DSC manufactured by Seiko Instruments Inc., a sample
in an amount of 3.2 mg was heated at a heating rate of 10.degree.
C./min from ordinary temperature to 200.degree. C. (provided that
the temperature was increased to 300.degree. C. in the case where a
polyester-based polymer was used as the second component), and then
cooled at a cooling rate of 10.degree. C./min to 40.degree. C. From
the resulting heat of fusion curve, the melting point Tf1 of the
first component after spinning and the melting point Tf2 of the
second component after spinning were obtained. Regarding the
melting point after spinning, in the case where two peaks appeared,
the peak on the lower temperature side was regarded as the melting
point (Tf1) of the first component, and the peak on the higher
temperature side was regarded as the melting point (Tf2) of the
second component. In the case where three or more peaks appeared
when measuring the melting point after spinning, the last peak,
i.e., the peak on the higher temperature side, was regarded as the
melting point (Tf2) of the second component, and the other peaks
were regarded as the melting points (Tf1) after spinning of the
respective polymers constituting the first component.
[0176] Residual Compression Set Rate
[0177] The set rate after compression at a temperature of
70.degree. C..+-.1.degree. C. at a compression rate of 50% for 22
hours was measured according to JIS-K-6400-4 A and was regarded as
a residual compression set rate. All the thickness measurement was
carried out while no load was applied to the test pieces in the
thickness direction, and a metal bench rule as specified in
JIS-B-7516 was used for measurement.
[0178] Residual Repetitive Compression Set Rate
[0179] The set rate after compression 80000 times at a temperature
of 23.degree. C. at a compression rate of 50% was measured
according to JIS-K-6400-4 B and was regarded as a residual
repetitive compression set rate. All the thickness measurement was
carried out while no load was applied to the test pieces in the
thickness direction, and a metal bench rule as specified in
JIS-B-7516 was used for measurement.
[0180] Polymers used in the examples are as follows:
[0181] (1) PET ("T200E" manufactured by Toray Industries, Inc.,
melting peak temperature (melting point): 255.degree. C., IV value:
0.64)
[0182] (2) PP-A ("SA03E" manufactured by Japan Polypropylene
Corporation, melting peak temperature (melting point): 160.degree.
C., MFR230: 20 g/10 min, Q value: 5.6)
[0183] (3) PP-B ("SAOlA" manufactured by Japan Polypropylene
Corporation, melting peak temperature (melting point): 160.degree.
C., MFR230: 9 g/10 min, Q value: 3.2)
[0184] (4) PB-1 ("DPO401M" manufactured by SunAllomer Ltd., melting
peak temperature (melting point): 123.degree. C., MFR190: 20 g/10
min)
[0185] (5) LLDPE-A ("Kernel" (registered trademark) "KS560T"
manufactured by Japan Polyethylene Corporation [linear low density
polyethylene synthesized by a high-pressure method using a
metallocene catalyst], melting peak temperature (melting point):
90.degree. C., MFR190: 16.5 g/10 min, density: 0.898 g/cm.sup.3, Q
value: 2.5, flexural modulus: 62 MPa)
[0186] (6) LLDPE-B ("420SD" manufactured by Ube Maruzen
Polyethylene Co., Ltd. [linear low density polyethylene synthesized
by a gas phase method using a metallocene catalyst], melting peak
temperature (melting point): 118.degree. C., MFR190.degree. C.: 7
g/10 min, density: 0.918 g/cm.sup.3, Q value: 3.0, flexural
modulus: 280 MPa)
[0187] (7) LLDPE-C ("Kernel" (registered trademark) "KC571"
manufactured by Japan Polyethylene Corporation [linear low density
polyethylene synthesized by a high-pressure method using a
metallocene catalyst], melting peak temperature (melting point):
100.degree. C., MFR190: 12 g/10 min, density: 0.907 g/cm.sup.3, Q
value: 2.2, flexural modulus: 110 MPa)
[0188] (8) LLDPE-D ("Harmorex" (registered trademark) "NJ744N"
manufactured by Japan Polyethylene Corporation [linear low density
polyethylene synthesized by a gas phase method using a metallocene
catalyst], melting peak temperature (melting point): 120.degree.
C., MFR190: 12 g/10 min, density: 0.911 g/cm.sup.3, Q value: 2.5,
flexural modulus: 120 MPa)
[0189] (9) LLDPE-E ("631J" manufactured by Ube Maruzen Polyethylene
Co., Ltd. [linear low density polyethylene synthesized by a gas
phase method using a metallocene catalyst], melting peak
temperature (melting point): 121.degree. C., MFR190: 20 g/10 min,
density: 0.931 g/cm.sup.3, Q value: 2.9, flexural modulus: 600 MPa)
(10) LDPE ("LJ802" manufactured by Japan Polyethylene Corporation,
melting peak temperature (melting point): 106.degree. C., MFR190:
22 g/10 min, density: 0.918 g/cm.sup.3)
[0190] (11) PPR-1 (polypropylene-based thermoplastic elastomer,
"Notio" (registered trademark) "2070" manufactured by Mitsui
Chemicals, Inc., [olefin-based thermoplastic elastomer synthesized
using a metallocene catalyst], melting peak temperature (melting
point): 138.degree. C., Shore A hardness (ASTM D 2240): 75, MFR230:
6 g/10 min, density: 0.867 g/cm.sup.3)
[0191] (12) PPR-2 (polyolefin-based thermoplastic elastomer,
"Adflex V109F" manufactured by Basell, melting peak temperature
(melting point): 143.degree. C., Shore D hardness (ASTM D 2240):
41, MFR230: 12 g/10 min, density: 0.880 g/cm.sup.3) (13) BP
(butene-propylene copolymer, "5C37F" manufactured by SunAllomer
Ltd., melting peak temperature (melting point): 132.degree. C.,
MFR230: 6 g/10 min) (14) EMAA ("Nucrel" (registered trademark)
manufactured by Du Pont-Mitsui, density: 0.940 g/cm.sup.3, melting
peak temperature (melting point): 88.degree. C., MFR190: 10 g/10
min)
[0192] Above, the IV value refers to the above-described limiting
viscosity, and MFR230 refers to a melt flow rate measured at
230.degree. C. under 21.18N (2.16kgf) in accordance with
JIS-K-7210. MFR190 refers to a melt flow rate measured at
190.degree. C. under 21.18N (2.16kgf) in accordance with
JIS-K-7210.
[0193] A description of the manufacturing conditions of crimped
conjugate fibers is as follows.
[0194] (A) Extrusion temperature: 300.degree. C. for the second
component polymer, 250.degree. C. for the first component polymer,
nozzle spinneret temperature: 270.degree. C.
[0195] (B) Withdrawing rate: 500 m/min
[0196] (C) Number of nozzle holes: 600
[0197] (D) Combination ratio: core/sheath =55/45 (volume ratio)
[0198] (E) Unstretched fiber fineness: 10 dtex
[0199] (F) Stretching temperature: wet 80.degree. C.
[0200] (G) Stretch ratio: 2.3
[0201] (H) Crimps: 12 to 16 per 25 mm
[0202] (I) Annealing temperature (drying temperature), time:
100.degree. C., 15 min
[0203] (J) Product fineness (single fiber): 6.0 dtex
[0204] (K) Fiber length: 51 mm
[0205] Production Conditions of Nonwoven Fabric
[0206] A crimped conjugate fiber (100 mass %) was subjected to a
parallel card to collect a web, and the web was treated at a
processing temperature of 150.degree. C. for 30 seconds with a
convection heating machine, thus giving a nonwoven fabric having a
unit weight of 500 g/m.sup.2.
Example 1
[0207] A crimped conjugate fiber was prepared under the
above-described crimped conjugate fiber production conditions using
only PP-A as the second component and a mixture of PB-1 and LLDPE-A
having a mass ratio of PB-1/LLDPE-A=92/8 as the first component.
Next, a nonwoven fabric was prepared under the above-described
nonwoven fabric production conditions using the resulting crimped
conjugate fiber.
Example 2
[0208] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=85/15 was used
as the second component and a mixture of PB-1 and LLDPE-A having a
mass ratio of PB-1/LLDPE-A=97/3 was used as the first
component.
Example 3
[0209] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=85/15 was used
as the second component and a mixture of PB-1 and LLDPE-A having a
mass ratio of PB-1/LLDPE-A=95/5 was used as the first
component.
Example 4
[0210] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=85/15 was used
as the second component.
Example 5
[0211] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=85/15 was used
as the second component and a mixture of PB-1 and LLDPE-A having a
mass ratio of PB-1/LLDPE-A=80/20 was used as the first
component.
Example 6
[0212] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=85/15 was used
as the second component and a mixture of PB-1 and LLDPE-B having a
mass ratio of PB-1/LLDPE-B=92/8 was used as the first
component.
Example 7
[0213] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=85/15 was used
as the second component and a mixture of PB-1 and LLDPE-C having a
mass ratio of PB-1/LLDPE-C=92/8 was used as the first
component.
Example 8
[0214] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=95/5 was used
as the second component.
Example 9
[0215] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=75/25 was used
as the second component.
Example 10
[0216] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-B and PPR-1 having a mass ratio of PP-B/PPR-1=85/15 was used
as the second component.
Example 11
[0217] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-2 having a mass ratio of PP-A/PPR-2=85/15 was used
as the second component.
Example 12
[0218] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PB-1 and LLDPE-D having a mass ratio of PB-1/LLDPE-D=92/8 was
used as the first component.
Example 13
[0219] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PB-1 and LLDPE-E having a mass ratio of PB-1/LLDPE-E=92/8 was
used as the first component.
Example 14
[0220] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PB-1, LLDPE-D, and EMAA having a mass ratio of
PB-1/LLDPE-D/EMAA=90/5/5 was used as the first component.
Example 15
[0221] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that only PET
was used as the second component and a mixture of PB-1 and LLDPE-D
having a mass ratio of PB-1/LLDPE-D=92/8 was used as the first
component.
Example 16
[0222] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that only PET
was used as the second component.
Example 17
[0223] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that only PET
was used as the second component and a mixture of PB-1, LLDPE-D,
and EMAA having a mass ratio of PB-1/LLDPE-D/EMAA=90/5/5 was used
as the first component.
Example 18
[0224] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that only PET
was used as the second component and a mixture of PB-1, LLDPE-A,
and EMAA having a mass ratio of PB-1/LLDPE-A/EMAA=90/5/5 was used
as the first component.
Comparative Example 1
[0225] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=85/15 was used
as the second component and only PB-1 was used as the first
component.
Comparative Example 2
[0226] An attempt was made to prepare a crimped conjugate fiber in
the same manner as in Example 1 except that a mixture of PP-A and
PPR-1 having a mass ratio of PP-A/PPR-1=85/15 was used as the
second component and a mixture of PB-1 and LLDPE-A having a mass
ratio of PB-1/LLDPE-A=70/30 was used as the first component, but
spinnability was poor, and thread breaks frequently occurred
immediately below the spinning nozzle, and it was thus not possible
to prepare a spun filament.
Comparative Example 3
[0227] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=99/1 was used
as the second component and a mixture of PB-1 and LDPE having a
mass ratio of PB-1/LDPE =90/10 was used as the first component.
Comparative Example 4
[0228] An attempt was made to prepare a crimped conjugate fiber and
a nonwoven fabric in the same manner as in Example 1 except that a
mixture of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=85/15
was used as the second component and a mixture of PB-1 and EMAA
having a mass ratio of PB-1/EMAA=94/6 was used as the first
component, but the stretchability of the spun filament was poor. In
addition, crimp formability after performing thermal processing in
order to form a nonwoven fabric was poor, and it was thus not
possible to prepare thermally adhered nonwoven fabric having good
cushioning properties.
Comparative Example 5
[0229] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that a mixture
of PP-A and PPR-1 having a mass ratio of PP-A/PPR-1=85/15 was used
as the second component and a mixture of PB-1 and BP having a mass
ratio of PB-1/BP=85/15 was used as the first component.
Comparative Example 6
[0230] An attempt was made to prepare a crimped conjugate fiber and
a nonwoven fabric in the same manner as in Example 1 except that
only PET was used as the second component and a mixture of PB-1,
PP-A, and EMAA having a mass ratio of PB-1/PP-A/EMAA=85/10/5 was
used as the first component. Although a conjugate fiber having high
spinnability, stretchability, and crimp formability was obtained,
pieces of the constituent fiber did not thermally bond sufficiently
to each other in thermal bonding processing at 150.degree. C., and
thus it was not possible to obtain a thermally bonded nonwoven
fabric.
Comparative Example 7
[0231] A crimped conjugate fiber and a nonwoven fabric were
prepared in the same manner as in Example 1 except that only PET
was used as the second component and a mixture of PB-1 and EMAA
having a mass ratio of PB-1/EMAA=92/8 was used as the first
component.
[0232] Tables 1 to 4 below show the results of the eccentricity,
spinnability during melt spinning, staple fiber spreadability,
staple fiber crimp formability, and crimp formability after thermal
processing of the resulting crimped conjugate fibers as well as the
initial thickness, unit weight, residual repetitive compression
set, and residual compression set of the nonwoven fabrics of
Examples 1 to 18 and Comparative Examples 1 to 7. The crimped
conjugate fibers of Examples 1 to 4, 6 to 9, and 11 to 18 were
actualized crimping conjugate fibers, have wavy crimps as shown in
FIG. 2A or spiral crimps, or have both wavy crimps and spiral
crimps, and the number of crimps was 12 to 18 per 25 mm. The
crimped conjugate fibers of Examples 5 and 10 were latently
crimpable conjugate fibers in which three-dimensional crimps have
been developed due to thermal processing performed when preparing a
nonwoven fabric, have at least one of the wavy crimps as shown in
FIG. 2A and the spiral crimps.
TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Second
Resin 1 PP-A PP-A PP-A PP-A PP-A PP-A component Resin 2 -- PPR-1
PPR-1 PPR-1 PPR-1 PPR-1 (Core resin) Resin 1:Resin 2 100:0 85:15
85:15 85:15 85:15 85:15 Melting point (Tf2) 163.5 -- -- -- -- 162.9
after spinning (.degree. C.) First Resin 1 PB-1 PB-1 PB-1 PB-1 PB-1
PB-1 component Resin 2 LLDPE-A LLDPE-A LLDPE-A LLDPE-A LLDPE-A
LLDPE-B (Sheath Resin 3 -- -- -- -- -- -- resin) Resin 1:Resin
2:Resin 3 92:8 97:3 95:5 92:8 80:20 92:8 Melting point (Tf1) 123.2
-- -- -- -- 121.7 after spinning (.degree. C.) Eccentricity (%) 25
25 25 25 25 25 Spun thread A-C A A A A B A break Stretchability A-C
A A A A A A Staple fiber A-C A A A A B A spreadability Staple fiber
A-C A A A A A A crimp formability Crimp (A-C) A A A A A A formation
Actual or latent Actual Actual Actual Actual Latent Actual after
thermal crimps crimps crimps crimps crimps crimps processing
Initial (mm) 25 25 25 25 25 25 thickness Unit weight (g/m.sup.2)
500 500 500 500 500 500 Residual (%) 11.7 10.3 11.2 9.7 11.8 11.9
repetitive compression set Residual (%) 33.4 26.1 29.2 30.0 33.5
33.7 compression set
TABLE-US-00002 TABLE 2 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12
Second Resin 1 PP-A PP-A PP-A PP-B PP-A PP-A component Resin 2
PPR-1 PPR-1 PPR-1 PPR-1 PPR-2 -- (Core resin) Resin 1:Resin 2 85:15
95:5 75:25 85:15 85:15 100:0 Melting point (Tf2) 162.6 -- -- -- --
162.0 after spinning (.degree. C.) First Resin 1 PB-1 PB-1 PB-1
PB-1 PB-1 PB-1 component Resin 2 LLDPE-C LLDPE-A LLDPE-A LLDPE-A
LLDPE-A LLDPE-D (Sheath Resin 3 -- -- -- -- -- -- resin) Resin
1:Resin 2:Resin 3 92:8 92:8 92:8 92:8 92:8 92:8 Melting point (Tf1)
123.5 -- -- -- -- 121.9 after spinning (.degree. C.) Eccentricity
(%) 25 25 25 25 25 25 Spun thread A-C A A A A A A break
Stretchability A-C A A A A A A Staple fiber A-C A A A A B A
spreadability Staple fiber A-C A A A A A A crimp formability Crimp
(A-C) A A A A A A formation Actual or latent Actual Actual Actual
Latent Actual Actual after thermal crimps crimps crimps crimps
crimps crimps processing Initial (mm) 25 25 25 25 25 25 thickness
Unit weight (g/m.sup.2) 500 500 500 500 500 500 Residual (%) 9.5
10.5 10.7 11.4 11.2 11.0 repetitive compression set Residual (%)
28.5 30.0 31.3 31.8 29.2 31.4 compression set
TABLE-US-00003 TABLE 3 Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18
Second Resin 1 PP-A PP-A PET PET PET PET component Resin 2 -- -- --
-- -- -- (Core resin) Resin 1:Resin 2 100:0 100:0 100:0 100:0 100:0
100:0 Melting point (Tf2) 163.0 -- -- -- -- -- after spinning
(.degree. C.) First Resin 1 PB-1 PB-1 PB-1 PB-1 PB-1 PB-1 component
Resin 2 LLDPE-E LLDPE-D LLDPE-D LLDPE-A LLDPE-D LLDPE-A (Sheath
Resin 3 -- EMAA -- -- EMAA EMAA resin) Resin 1:Resin 2:Resin 3 92:8
90:5:5 92:8 92:8 90:5:5 90:5:5 Melting point (Tf1) 120.8 -- -- --
-- -- after spinning (.degree. C.) Eccentricity (%) 25 25 25 25 25
25 Spun thread A-C A A A A A A break Stretchability A-C A A A A A A
Staple fiber A-C A A A A A A spreadability Staple fiber A-C A A A A
A A crimp formability Crimp (A-C) A A A A A A formation Actual or
latent Actual Actual Actual Actual Actual Actual after thermal
crimps crimps crimps crimps crimps crimps processing Initial (mm)
25 25 25 25 25 25 thickness Unit weight (g/m.sup.2) 500 500 500 500
500 500 Residual (%) 12.2 10.8 10.1 10.4 9.8 9.7 repetitive
compression set Residual (%) 35.0 31.2 39.8 39.8 39.5 39.8
compression set
TABLE-US-00004 TABLE 4 Comp. Comp. Comp. Comp. Comp. Comp. Comp.
Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Second Resin 1 PP-A PP-A
PP-A PP-A PP-A PET PET component Resin 2 PPR-1 PPR-1 PPR-1 PPR-1
PPR-1 -- -- (Core resin) Resin 1:Resin 2 85:15 85:15 99:1 85:15
85:15 100:0 100:0 Melting point (Tf2) -- -- -- -- -- 250.4 -- after
spinning (.degree. C.) First Resin 1 PB-1 PB-1 PB-1 PB-1 PB-1 PB-1
PB-1 component Resin 2 -- LLDPE-A LDPE EMAA BP PP-A EMAA (Sheath
Resin 3 -- -- -- -- -- EMAA -- resin) Resin 1:Resin 2:Resin 3 100:0
70:30 90:10 94:6 85:15 85:10:5 92:8 Melting point (Tf1) -- -- -- --
-- 162.7 -- after spinning (.degree. C.) 119.0 Eccentricity (%) 25
25 25 25 25 25 25 Spun thread A-C A C A B B A B break
Stretchability A-C B -- A B B A C Staple fiber A-C A -- B A B A A
spreadability Staple fiber A-C A -- A A B A A crimp formability
Crimp (A-C) A -- A C A A A formation Actual or latent Latent Latent
Latent Actual Actual after thermal crimps crimps crimps crimps
crimps processing Initial (mm) 25 -- 25 -- -- -- 25 thickness Unit
weight (g/m.sup.2) 500 -- 500 -- -- -- 500 Residual (%) 11.6 --
12.4 -- -- -- 9.7 repetitive compression set Residual (%) 33.8 --
34.7 -- -- -- 39.8 compression set
[0233] A comparison of Examples 1 to 18 of Tables 1 to 3 with
Comparative Examples 1 to 7 of Table 4 confirms that, with crimped
conjugate fibers in which the first component contained PB-1,
addition of linear low density polyethylene to PB-1 brought about
the effect of enhancing the stretchability, the staple fiber
spreadability, the staple fiber crimp formability, and like
properties of PB-1. This can be confirmed from the fact that
conjugate fibers in which the first component was composed solely
of PB-1 and conjugate fibers in which polymers other than linear
low density polyethylene were added to PB-1 as shown in Comparative
Examples 1, 4, 5, and 7 of Table 4 had poor stretchability (B
evaluation), whereas stretchability was good (A evaluation) in all
Examples. The conjugate fiber to which low density polyethylene
(LDPE) was added to the first component did not have good staple
fiber spreadability, thus confirming that addition of linear low
density polyethylene as a polymer to be added to the first
component containing polybutene-1 as the main ingredient enables
crimped conjugate fibers having not only good spinnability and
stretchability but also good staple fiber crimp formability, and
crimp formability after thermal processing, i.e., all such
properties were good, to be obtained.
[0234] It can be confirmed from Examples 1 to 18 that, with the
crimped conjugate fiber of the present invention, when the first
component was a resin component containing polybutene-1 and linear
low density polyethylene, a nonwoven fabric that used the resulting
conjugate fiber had little residual repetitive compression set
irrespective of whether the second component was either a
polyolefin-based polymer or a polyester-based polymer. Therefore,
in the crimped conjugate fiber of the present invention, the second
component that constitutes the inner portion of the conjugate fiber
is not particularly limited, and it appears that the second
component, while not being limited to a polyester-based polymer or
a polyolefin-based polymer, is usable insofar as it is a polymer
having a melting peak temperature at least 20.degree. C. higher
than the melting peak temperature of polybutene-1 or a polymer
having a melting initiation temperature of 120.degree. C. or higher
and having excellent bending strength and bending plasticity.
[0235] Regarding crimped conjugate fibers in which the first
component contained PB-1, for adding linear low density
polyethylene to the first component, conjugate fibers in which
linear low density polyethylene was added in a proportion of 20
mass % relative to the first component had good spinnability,
whereas conjugate fibers to which linear low density polyethylene
was added in a proportion of 30 mass % to the first component had
very poor spinnability. Therefore, it can be presumed from a
comparison of Example 5 and Comparative Example 2 that there is an
upper limit to the amount of linear low density polyethylene added,
and the upper limit to the amount is less than 30 mass %, and
preferably 25 mass % or less.
[0236] It can be confirmed that, with the crimped conjugate fibers
of Examples 1 to 18, the crimp formability of the resulting crimped
conjugate fibers and the resistance to residual repetitive
compression set and the resistance to residual compression set of
nonwoven fabrics that used the crimped conjugate fibers were
enhanced. In particular, it can be confirmed that the crimped
conjugate fibers of Examples 2 to 4, 7 to 9, 11, 12 and 14 and
nonwoven fabrics that used the crimped conjugate fibers had a rate
of residual repetitive compression set of 11.5% or less and a rate
of residual compression set of 31.5% or less, which were
significantly more improved than those of the nonwoven fabric of
Comparative Example 1. A comparison of Examples 2 to 4, 7 to 9, 11,
12, and 14 with Examples 6 and 13 shows that the residual
repetitive compression set and the residual compression set of
nonwoven fabrics that used the crimped conjugate fibers of Examples
6 and 13 in which linear low density polyethylenes having a
relatively high density and a high flexural modulus were used were
increased, and therefore it is presumed that it is preferable for
the crimped conjugate fiber of the present invention that linear
low density polyethylene to be added to the first component is
linear low density polyethylene having a lower density and a lower
flexural modulus insofar as thermal bonding properties and heat
resistance are not affected.
[0237] As shown in Comparative Example 6, it can be confirmed that
regarding a crimped conjugate fiber in which the first component
containing PB-1, the spinnability and the stretchability of PB-1
were enhanced also in a conjugate fiber in which polypropylene was
added to the first component, and a crimped conjugate fiber having
excellent staple fiber spreadability, staple fiber crimp
formability, and staple fiber crimp formability after thermal
processing was obtained. However, since polypropylene, which had a
higher melting point than PB-1, was added to the first component in
the crimped conjugate fiber of Comparative Example 6, the apparent
melting point of the first component was increased. As a result, it
was confirmed that pieces of the conjugate fiber were not
sufficiently bond to each other under this thermal bonding
processing condition. Therefore, a comparison of the melting points
(Tf1) of the first components after spinning of Examples 1 to 18
and Comparative Example 6, in particular Examples 1, 6, 7, 12, and
13 and Comparative Example 6 confirms that, in the case of
performing thermal bonding processing at lower temperatures or
thermal processing to attain higher bonding strength in a shorter
period of time, it is most suitable to add linear low density
polyethylene to the first component in a crimped conjugate fiber in
which the first component contains PB-1.
INDUSTRIAL APPLICABILITY
[0238] A fiber assembly that uses the crimped conjugate fiber of
the present invention has both excellent initial bulk and bulk
recovery properties and is preferably used in applications such as
cushioning materials and like hard stuffing, sanitary materials,
packaging materials, materials for cosmetic products, low-density
non-woven fabric products such as women's brassiere pads and
shoulder pads, wiping materials for people and non-human objects
for which urethane foam and urethane sponge have generally been
used, powdery or liquid cosmetic coating materials, heat insulating
materials, and sound absorbing materials. Moreover, the crimped
conjugate fiber of the present invention has excellent elasticity
and shape recoverability, and is therefore preferably used as
wadding for various kinds of bedding such as blankets and
mattresses and clothing articles. In the crimped conjugate fiber of
the present invention in which a polyolefin-based polymer is used
as the second component, which is one embodiment of the crimped
conjugate fiber of the present invention, all the resin components
constituting the conjugate fiber are composed of polyolefin-based
polymers, and therefore after being used as the hard stuffing,
wadding, and low-density nonwoven fabric products, it is easy to
collect the crimped conjugate fiber as a component composed of
polyolefin-based polymers, reuse it as a resin material, or reuse
it as a polyolefin-based fiber, and preferably is used as various
fiber assembly products for which separate collection after use and
reuse of components are desired.
LIST OF REFERENCE NUMERALS
[0239] 1 First component [0240] 2 Second component [0241] 3
Centroid position of second component [0242] 4 Centroid position of
conjugate fiber [0243] 5 Radius of conjugate fiber [0244] 10
Conjugate fiber
* * * * *