U.S. patent application number 12/669739 was filed with the patent office on 2010-07-29 for heat-bondable composite fiber, process for producing the same, and fibrous mass.
This patent application is currently assigned to DAIWABO HOLDINGS CO., LTD.. Invention is credited to Akihiko Kawanaka, Koji Nagai, Yoshiji Usui.
Application Number | 20100190406 12/669739 |
Document ID | / |
Family ID | 40259679 |
Filed Date | 2010-07-29 |
United States Patent
Application |
20100190406 |
Kind Code |
A1 |
Usui; Yoshiji ; et
al. |
July 29, 2010 |
HEAT-BONDABLE COMPOSITE FIBER, PROCESS FOR PRODUCING THE SAME, AND
FIBROUS MASS
Abstract
A POM/POM thermoadhesive conjugate fiber is produced by
providing two kinds of POM-based polymers A and B which satisfy
30<MI.sub.A wherein MI.sub.A is a before-spinning melt index
(g/10 min) of the POM-based polymer A (conditions: 190.degree. C.,
load: 21.18N (2.16 kg)), and T.sub.B>T.sub.A+10 wherein T.sub.A
and T.sub.B are before-spinning fusion peak temperatures of the
POM-based polymers A and B respectively, compositely spinning a
first component containing the POM-based polymer A and a second
component containing the POM-based polymer B such that the first
component is exposed with an exposed length of not less than 20%
relative to a peripheral length of the fiber, subjecting the spun
fiber to a drawing treatment, and subjecting the drawn fiber to an
annealing treatment at a temperature of from 60.degree. C. to
110.degree. C.
Inventors: |
Usui; Yoshiji; (Hyogo,
JP) ; Nagai; Koji; (Hyogo, JP) ; Kawanaka;
Akihiko; (Hyogo, JP) |
Correspondence
Address: |
HAMRE, SCHUMANN, MUELLER & LARSON, P.C.
P.O. BOX 2902
MINNEAPOLIS
MN
55402-0902
US
|
Assignee: |
DAIWABO HOLDINGS CO., LTD.
DAIWABO POLYTEC CO., LTD.
|
Family ID: |
40259679 |
Appl. No.: |
12/669739 |
Filed: |
July 15, 2008 |
PCT Filed: |
July 15, 2008 |
PCT NO: |
PCT/JP2008/062760 |
371 Date: |
March 24, 2010 |
Current U.S.
Class: |
442/361 ;
264/172.17; 428/373 |
Current CPC
Class: |
D01D 10/02 20130101;
C09J 159/02 20130101; Y10T 428/2929 20150115; D01F 8/16 20130101;
D01D 5/12 20130101; D01D 5/30 20130101; Y10T 442/637 20150401 |
Class at
Publication: |
442/361 ;
428/373; 264/172.17 |
International
Class: |
D01D 5/30 20060101
D01D005/30; D01D 5/08 20060101 D01D005/08; D04H 13/00 20060101
D04H013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2007 |
JP |
2007-187960 |
Claims
1. A thermoadhesive conjugate fiber comprising a first component as
a thermoadhesive component which comprises a polyoxymethylene-based
polymer A and a second component which comprises a
polyoxymethylene-based polymer B, wherein the first component is
exposed with an exposed length of not less than 20% relative to a
peripheral length of the fiber, which fiber satisfies:
30<MI.sub.A wherein MI.sub.A is a before-spinning melt index
(g/10 min) of the polyoxymethylene-based polymer A, which is
determined according to JIS K 7210 (conditions: 190.degree. C.,
load: 21.18N (2.16 kg)), a before-spinning 150.degree. C. 1/2
crystallization time of the polyoxymethylene-based polymer B is not
less than 10 seconds and less than 30 seconds, and
Tf.sub.B>Tf.sub.A+10 wherein Tf.sub.A and Tf.sub.B are
after-spinning fusion peak temperatures of the
polyoxymethylene-based polymers A and B respectively, which are
determined according to JIS K 7121.
2. (canceled)
3. The thermoadhesive conjugate fiber according to claim 1, wherein
an after-spinning 150.degree. C. 1/2 crystallization time of the
polyoxymethylene-based polymer B is from 10 seconds to 100
seconds.
4. A thermoadhesive conjugate fiber comprising a first component as
a thermoadhesive component which comprises a polyoxymethylene-based
polymer A and a second component which comprises a
polyoxymethylene-based polymer B, wherein: the first component is
exposed with an exposed length of not less than 20% relative to a
peripheral length of the fiber, a before-spinning 150.degree. C.
1/2 crystallization time of the polyoxymethylene-based polymer B is
not less than 10 seconds and less than 30 seconds, and
Tf.sub.B>Tf.sub.A+10 wherein Tf.sub.A and Tf.sub.B are
after-spinning fusion peak temperatures of the
polyoxymethylene-based polymers A and B respectively, which are
determined according to JIS K 7121.
5. A thermoadhesive conjugate fiber comprising a first component as
a thermoadhesive component which comprises a polyoxymethylene-based
polymer A and a second component which comprises a
polyoxymethylene-based polymer B, wherein: the first component is
exposed with an exposed length of not less than 20% relative to a
peripheral length of the fiber, an after-spinning 150.degree. C.
1/2 crystallization time of the polyoxymethylene-based polymer B is
from 10 seconds to 100 seconds, and Tf.sub.B>Tf.sub.A+10 wherein
Tf.sub.A and Tf.sub.B are after-spinning fusion peak temperatures
of the polyoxymethylene-based polymers A and B respectively, which
are determined according to JIS K 7121.
6. The thermoadhesive conjugate fiber according to claim 4, wherein
a before-spinning Z-average molecular weight of the
polyoxymethylene-based polymer B is 500,000 or less.
7. The thermoadhesive conjugate fiber according to claim 5, wherein
an after-spinning Z-average molecular weight of the conjugate fiber
is 350,000 or less.
8. The thermoadhesive conjugate fiber according to claim 4, which
is a sheath-core conjugate fiber consisting of the first component
and the second component, the first component being a sheath
component and the second component being a core component.
9. The thermoadhesive conjugate fiber according to claim 8, which
has an eccentric sheath-core cross section in which a center
position of the second component is shifted from the center
position of the fiber.
10. A method for producing a thermoadhesive conjugate fiber which
comprises: providing two kinds of polyoxymethylene-based polymers A
and B which satisfy: 30<MI.sub.A wherein MI.sub.A is a
before-spinning melt index (g/10 min) of the polyoxymethylene-based
polymer A, which is determined according to JIS K 7210 (conditions:
190.degree. C., load: 21.18N (2.16 kg)), a before-spinning
150.degree. C. 1/2 crystallization time of the
polyoxymethylene-based polymer B is not less than 10 seconds and
less than 30 seconds, and T.sub.B>T.sub.A+10 wherein T.sub.A and
T.sub.B are before-spinning fusion peak temperatures of the
polyoxymethylene-based polymers A and B respectively, which are
determined according to JIS K 7121, compositely spinning a first
component comprising the polyoxymethylene-based polymer A and a
second component comprising the polyoxymethylene-based polymer B
such that the first component is exposed with an exposed length of
not less than 20% relative to a peripheral length of the fiber,
subjecting the spun fiber to a drawing treatment, and subjecting
the drawn fiber to an annealing treatment at a temperature of from
60.degree. C. to 110.degree. C.
11. (canceled)
12. A method for producing a thermoadhesive conjugate fiber, which
comprises: providing two kinds of polyoxymethylene-based polymers A
and B, the polymer B having a before-spinning 150.degree. C. 1/2
crystallization time of not less than 10 seconds and less than 30
seconds, and the polymers satisfying T.sub.B>T.sub.A+10 wherein
T.sub.A and T.sub.B are before-spinning fusion peak temperatures of
the polyoxymethylene-based polymers A and B respectively which
temperatures are determined according to JIS K 7121, compositely
spinning a first component comprising the polyoxymethylene-based
polymer A and a second component comprising the
polyoxymethylene-based polymer B such that the first component is
exposed with an exposed length of not less than 20% relative to a
peripheral length of the fiber, subjecting the spun fiber to a
drawing treatment, and subjecting the drawn fiber to an annealing
treatment at a temperature of from 60.degree. C. to 110.degree.
C.
13. The method for producing a thermoadhesive conjugate fiber
according to claim 12, wherein the annealing is conducted at a
temperature of from 60.degree. C. to 90.degree. C.
14. The method for producing a thermoadhesive conjugate fiber
according to claim 12, wherein spinning is conducted at a draft
ratio of from 100 times to 1000 times and the drawing is conducted
at a draw ratio of from 4 times to 10 times.
15. A fiber assembly comprising the thermoadhesive conjugate fiber
according to claim 4 in an amount of 10 mass % or more.
16. The fiber assembly according to claim 15, wherein the fibers
are thermally bonded to each other.
17. The fiber assembly according to claim 15, which is a
nonwoven.
18. A wiper which comprises the nonwoven according to claim 17.
19. The fiber assembly according to claim 15, which is a molded
article.
Description
TECHNICAL FIELD
[0001] The present invention is related to a thermoadhesive
conjugate fiber wherein a core component and a sheath component are
formed from polyoxymethylene-based polymers and the sheath
component has thermoadhesiveness and the production method of the
fiber, and a fiber assembly including the fiber.
BACKGROUND ART
[0002] Polyoxymethylene is called "polyacetal" and known as an
engineering plastic which is excellent in electrical insulation,
heat resistance and chemical resistance. The molded article of the
polyoxymethylene is widely used as, for example, a component of a
car. Since the polyoxymethylene has excellent crystallizability and
present a high crystallization speed and a large crystallinity, it
is said that it is difficult to produce a fiber from this resin.
Nevertheless, the production of the fiber from the polyoxymethylene
has been tried by i) selecting a particular polyoxymethylene resin,
ii) mixing a particular additive with the polyoxymethylene, or iii)
compositely spinning the polyoxymethylene combined with a
particular polymer, in order that the excellent properties of the
polyoxymethylene is utilized (Patent Literatures 1 to 5). Further,
a multi-layer oxymethylene-based copolymer fiber has been proposed,
wherein a cross-section structure has at least two layers, every
layer is exposed to a surface of the fiber and an amount of
comonomer in a copolymer that forms each layer is defined.
[0003] [Patent Literature 1] Unexamined Japanese Patent (Kokai)
Publication No. H1-272821
[0004] [Patent Literature 2] Unexamined Japanese Patent (Kokai)
Publication No. H8-144128
[0005] [Patent Literature 3] Unexamined Japanese Patent (Kokai)
Publication No. H11-293523
[0006] [Patent Literature 4] Unexamined Japanese Patent (Kokai)
Publication No. 2003-268627
[0007] [Patent Literature 5] Unexamined Japanese Patent (Kokai)
Publication No. 2006-9205
[0008] [Patent Literature 6] Unexamined Japanese Patent (Kokai)
Publication No. 2008-138331
DISCLOSURE OF INVENTION
Problems to be Solved by Invention
[0009] In the case where the polyoxymethylene is made into a fiber
and a product (such as civil engineering and construction material,
an interfacing, a cushion, and a mat) is manufactured of a
nonwoven, a woven fabric, or a knitted fabric which is formed of
the fibers, and a component other than the polyoxymethylene is not
included in the product, the properties of the polyoxymethylene is
utilized maximally. In other words, when the fibers are made into
the nonwoven or the like and another binder component is included
in the nonwoven, some binders make the chemical resistance of the
product poor as a whole, even though the fiber itself is formed
from the polyoxymethylene. The same is applicable to a conjugate
fiber which comprises of the polyoxymethylene and another polymer.
The present inventors considered that, in order to avoid such
inconvenience, it is only necessary to form the fiber only from the
polyoxymethylene and have the fiber itself function as the binder.
More specifically, when the two polyoxymethylenes which have
different melting points are compositely spun with one component
being a thermoadhesive component, a sheet, particularly a nonwoven,
wherein the fibers are integrally bonded can be obtained without
using the another binder component.
[0010] A sheath-core conjugate fiber wherein two kinds of
polyoxymethylenes are used is disclosed in Patent Literature 5. The
conjugate fiber described in Patent Literature is proposed for the
purpose of achieving a high knot strength retention and is not
intended to be used as the thermoadhesive fiber. Further, the
conjugate fiber produced by a method described in Patent Literature
5 does not necessarily have sufficient properties as the
thermoadhesive fiber. Furthermore, a fine fiber could not be
obtained when the present inventors produced the conjugate fiber by
the method described in Patent Literature 5. The multi-layer fiber
described in Patent Literature 6 is intended to have good
crimpability. Therefore, if a thermoadhesive nonwoven is produced
using this fiber, difference in area of the nonwoven between before
and after thermal treatment is large due to crimp of the fiber,
whereby it is difficult to obtain the nonwoven of a predetermined
dimension. The present invention was made in light of these
situations, and an object of the present invention is to provide a
thermoadhesive conjugate fiber formed mainly from the
polyoxymethylene.
Solution to Solve Problems
[0011] When the sheath component of the sheath-core conjugate fiber
produced only from the polyoxymethylenes by the method described in
Patent Literature 5 was melted or softened as the thermoadhesive
component to produce a sheet-shaped product, the core component
significantly shrank and it was difficult to obtain the sheet-like
product. Then, the present inventors have reviewed various kinds of
polyoxymethylenes and the various production conditions in order to
suppress the shrink of the core component. As a result, they have
found that a fiber which functions well as the thermoadhesive
conjugate fiber by using polyoxymethylenes which have a particular
difference in melting point, one polyoxymethylene having a high
melt index as the sheath component; and employing particular
drawing conditions and drying conditions. Further, the inventors
found that 150.degree. C. 1/2 crystallization time, and/or Mz
(Z-average molecular weight) of the core component effects
spinnablity of the conjugate fiber and that it is important to
select these parameters appropriately, particularly when a fine
fiber is produced.
[0012] In a first aspect, the present invention provides a
thermoadhesive conjugate fiber including a first component as a
thermoadhesive component which contains a polyoxymethylene-based
polymer A and a second component which contains a
polyoxymethylene-based polymer B, wherein the first component is
exposed with an exposed length of not less than 20% relative to a
peripheral length of the fiber,
[0013] which fiber satisfies:
[0014] 30<MI.sub.A wherein MI.sub.A is a before-spinning melt
index (g/10 min) of the polyoxymethylene-based polymer A, which is
determined according to JIS K 7210 (conditions: 190.degree. C.,
load: 21.18N (2.16 kg)), and
[0015] Tf.sub.B>Tf.sub.A+10 wherein Tf.sub.A and Tf.sub.B are
after-spinning fusion peak temperatures of the
polyoxymethylene-based polymers A and B respectively, which are
determined according to JIS K 7121.
[0016] Selecting two kinds of polyoxymethylene-based polymers so
that MI.sub.A, Tf.sub.A and Tf.sub.B satisfy the above
relationships suppresses the shrink of the second component when
the first component is heated so as to function as the
thermoadhesive component, which results in good adhesion between
the fibers.
[0017] Further, in a second aspect, the present invention provides
a thermoadhesive conjugate fiber including a first component as a
thermoadhesive component which contains a polyoxymethylene-based
polymer A and a second component which contains a
polyoxymethylene-based polymer B, wherein:
[0018] the first component is exposed with an exposed length of not
less than 20% relative to a peripheral length of the fiber,
[0019] a before-spinning 150.degree. C. 1/2 crystallization time of
the polyoxymethylene-based polymer B is from 10 seconds to 100
seconds, and
[0020] Tf.sub.B>Tf.sub.A+10 wherein Tf.sub.A and Tf.sub.B are
after-spinning fusion peak temperatures of the
polyoxymethylene-based polymers A and B respectively, which are
determined according to JIS K 7121.
[0021] The crystallization time relates to a time until the molten
resin solidifies. By limiting the 150.degree. C. 1/2
crystallization time of the polyoxymethylene-based polymer for the
second component, the crystallization is accelerated and therefore
solidification proceeds during the discharge of the molten resin
from nozzles and the draft of the discharged resin at a
predetermined draft ratio. This increases the spinnablity and
particularly makes it possible to obtain a spun filament having a
small fineness.
[0022] The second aspect may be combined with the first aspect.
Such combination provides better spinnability and makes it possible
to obtain the fiber having a smaller fineness.
[0023] In any aspect (or another aspect) of the thermoadhesive
conjugate fiber of the present invention, the before-spinning
Z-average molecular weight (Mz) of the polyoxymethylene-based
polymer B is preferably 500,000 or less. Further, it is preferable
that, in any aspect, the thermoadhesive conjugate fiber of the
preset invention is one wherein the after-spinning Z-average
molecular weight (Mz) of the polyoxymethylene polymer B is 350,000
or less.
[0024] Mz is a parameter which relates to a high-molecular-weight
component of a polymer. As the value of Mz is larger, the
crystallization speed is higher. In the present invention, the
crystallization speed of the core component is adjusted by defining
the upper limit of before- and/or after-spinning Mz of the
polyoxymethylene-based polymer B, whereby the spinnability of the
entire conjugate fiber is improved.
[0025] In any aspect, the thermoadhesive conjugate fiber is
preferably a sheath-core conjugate fiber consisting of a first
component and a second component wherein the first component is a
sheath component and the second component is a core component.
Since the first component occupies all the length of the peripheral
surface in the sheath-core structure, the fiber having such
structure presents more favorable thermal adhesiveness.
[0026] In the case where the thermoadhesive conjugate fiber of the
present invention is the sheath-core conjugate fiber, it may have
an eccentric sheath-core cross section wherein a center position of
the second component is shifted from the center position of the
fiber. The fiber having such cross-sectional structure tends to
develop three-dimensional crimps and confers stretchability,
bulkiness and/or soft feeling to, for example, a nonwoven made of
the fibers.
[0027] In a third aspect, the present invention provides a method
for producing the thermoadhesive conjugate fiber of the first
aspect of the present invention, which includes:
[0028] providing two kinds of polyoxymethylene-based polymers A and
B which satisfy: [0029] 30<MI.sub.A wherein MI.sub.A is a
before-spinning melt index (g/10 min) of the polyoxymethylene-based
polymer A, which is determined according to JIS K 7210 (conditions:
190.degree. C., load: 21.18N (2.16 kg)), and [0030]
Tf.sub.B>Tf.sub.A+10 wherein T.sub.A and T.sub.B are
before-spinning fusion peak temperatures of the
polyoxymethylene-based polymers A and B respectively, which are
determined according to JIS K 7121,
[0031] compositely spinning a first component containing the
polyoxymethylene-based polymer A and a second component containing
the polyoxymethylene-based polymer B such that the first component
is exposed with an exposed length of not less than 20% relative to
a peripheral length of the fiber,
[0032] subjecting the spun fiber to a drawing treatment, and
[0033] subjecting the drawn fiber to an annealing treatment at a
temperature of from 60.degree. C. to 110.degree. C.
[0034] This production method is characterized in that the two
polyoxymethylene-based polymers are selected so that MI.sub.A,
T.sub.A and T.sub.B satisfy the above relationships and the
annealing treatment is conducted at a temperature of from
60.degree. C. to 110.degree. C. after spinning the fiber. These
characteristics make it possible to obtain the thermoadhesive
conjugate fiber which presents good cardability and small shrink of
the second component upon thermal adhesion of the first component.
A more preferable annealing treatment temperature is from
60.degree. C. to 90.degree. C.
[0035] In a fourth aspect, the present invention provides a method
for producing the thermoadhesive conjugate fiber of the second
aspect of the present invention, which comprises:
[0036] providing two kinds of polyoxymethylene-based polymers A and
B, the polymer B having a before-spinning 150.degree. C. 1/2
crystallization time of from 10 seconds to 100 seconds, and the
polymers satisfying Tf.sub.B>Tf.sub.A+10 wherein T.sub.A and
T.sub.B are before-spinning fusion peak temperatures of the
polyoxymethylene-based polymers A and B respectively which
temperatures are determined according to JIS K 7121,
[0037] compositely spinning a first component containing the
polyoxymethylene-based polymer A and a second component containing
the polyoxymethylene-based polymer B such that the first component
is exposed with an exposed length of not less than 20% relative to
a peripheral length of the fiber,
[0038] subjecting the spun fiber to a drawing treatment, and
[0039] subjecting the drawn fiber to an annealing treatment at a
temperature of from 60.degree. C. to 110.degree. C.
[0040] This production method is characterized in that the two
kinds of the polyoxymethylene-based polymers are selected so that
the before-spinning 150.degree. C. 1/2 crystallization time of the
polyoxymethylene-based polymer B satisfies the above relationship
and T.sub.A and T.sub.B satisfy the above relationship and that the
annealing treatment is conducted at a temperature of from
60.degree. C. to 110.degree. C. after spinning the fiber. These
characteristics make it possible to obtain the thermoadhesive
conjugate fiber which presents good cardability and has a small
fineness. A more preferable annealing temperature is from
60.degree. C. to 90.degree. C.
[0041] The fourth aspect may be combined with the third aspect.
Such combination makes it possible to produce the thermoadhesive
conjugate fiber which passes the carding machine well, has a small
fineness and presents a small thermal shrink upon the thermal
adhesion.
[0042] In the production method in any aspect of the present
invention, the spinning is preferably conducted with a draft ratio
of from 100 times to 1000 times and the drawing treatment is
preferably conducted with a draw ratio of from 4 times to 10 times.
Setting the draft ratio and the draw ratio within these ranges
gives the thermoadhesive conjugate fiber which has more favorable
cardability and presents less shrink of the second component upon
the thermal adhesion. Further, setting the draft ratio and the draw
ratio within these ranges enables the fineness to be small, for
example, from about 0.1 dtex to about 3 dtex.
[0043] In a fifth aspect, the present invention provides a fiber
assembly which contains the thermoadhesive conjugate fiber of the
first or the second aspect of the present invention in an amount of
10 mass % or more. This fiber assembly may be, for example, a
nonwoven or a molded article.
EFFECT OF INVENTION
[0044] The thermoadhesive conjugate fiber of the present invention
is one wherein both of the low-melting-point thermoadhesive
component and the high-melting-point component are formed of the
polyoxymethylene-based polymers. Therefore, when a sheet article
such as a nonwoven is made using this fiber, the fibers are
integrated with the polyoxymethylene-based component having the low
melting point and another binder component is not required. Such a
sheet article presents the heat resistance and the chemical
resistance of the polyoxymethylene-based polymer, particularly when
it is formed only from the thermoadhesive conjugate fibers of the
present invention. Further, the fiber assembly containing the
thermoadhesive conjugate fibers of the present invention has a high
water retentivity, slippability, crease resistance, and bulk
recoverability, and/or good wiping-ability. Therefore, the fiber
assembly is suitable for applications which require such
properties.
EMBODIMENT OF THE INVENTION
[0045] The thermoadhesive conjugate fiber includes at least two
components each of which contains the polyoxymethylene-based
polymer. In the present specification, the polyoxymethylene-based
polymer is a polymer wherein an oxymethylene unit is a main
repeating unit. The polyoxymethylene-based polymer may be a
so-called "POM homo-polymer" which is obtained by a polymerization
reaction wherein a main raw material is formaldehyde or trioxane,
or may be a so-called "POM copolymer" which is composed mainly of
the oxymethylene unit and contains an oxyalkylene unit which has
from two to eight adjacent carbon atoms, preferably
CH.sub.2CH.sub.2O, and may have a substituent. The oxyalkylene unit
is preferably contained in the POM copolymer in an amount of 10
mass % or less, and more preferably in an amount of from 0.5 mass %
to 8 mass % as an ethyleneoxide equivalent. The substituent which
can be bonded to the oxyalkylene group is, for example, an alkyl
group, a phenyl group, or another organic group. Further, the
polyoxymethylene-based polymer may be a copolymer which has another
constituent unit, that is, a block copolymer, a terpolymer, or a
cross-linked polymer.
[0046] The thermoadhesive conjugate fiber of the first aspect of
the present invention includes the first component containing the
polyoxymethylene-based polymer A and the second component
containing the polyoxymethylene-based polymer B. The
polyoxymethylene-based polymers A and B satisfy:
[0047] 30<MI.sub.A wherein MI.sub.A is a before-spinning melt
index (g/10 min) of the polyoxymethylene-based polymer A, which is
determined according to JIS K 7210 (conditions: 190.degree. C.,
load: 21.18N (2.16 kg)), and
[0048] Tf.sub.B>Tf.sub.A+10 wherein Tf.sub.A and Tf.sub.B are
after-spinning fusion peak temperatures of the
polyoxymethylene-based polymers A and B respectively which are
determined according to JIS K 7121.
[0049] In order that, MI.sub.A, Tf.sub.A and Tf.sub.B satisfy the
above formulae, the polyoxymethylene-based polymers A and B are
different from each other in at least one of a molecular weight,
the kind or the content of the comonomer which co-polymerizes with
the oxymethylene unit.
[0050] Specifically, the polyoxymethylene-based polymer A is, for
example, a polymer of which MI.sub.A is preferably from 40 to 75,
and more preferably from 50 to 70, and of which before-spinning
melting point T.sub.A is preferably from 140.degree. C. to
160.degree. C. and more preferably from 150.degree. C. to
158.degree. C. Such a polyoxymethylene-based polymer is, for
example, one which contains CH.sub.2CH.sub.2O in an amount of from
3 mass % to 10 mass % as the ethyleneoxide equivalent, preferably 5
mass % to 9 mass %. The polyoxymethylene-based polymer B is a
polymer of which before-spinning melting point MI.sub.B (g/10 min)
is preferably from 20 to 80 and more preferably from 50 to 70, and
of which before-spinning fusion peak temperature T.sub.B is
preferably from 160.degree. C. to 174.degree. C. and more
preferably from 165.degree. C. to 172.degree. C. Such a
polyoxymethylene-based polymer is, for example, one which contains
CH.sub.2CH.sub.2O in an amount of from 0.5 mass % to 3 mass % as
the ethyleneoxide equivalent, preferably from 0.5 mass % to 1.5
mass %.
[0051] "30<MI.sub.A" wherein MI.sub.A is the before-spinning
melt index MI (g/10 min) of the polyoxymethylene-based polymer A
means that a resin of a sheath component has high fluidity.
Therefore, when the thermoadhesive conjugate fibers of the present
invention are processed into a nonwoven and heated to be thermally
adhered, there is a tendency that the first component spreads over
a wide area, the adhesive strength becomes high and the strength of
the nonwoven is increased. Further, when the fineness is made
small, a take-over speed is higher during spinning (that is, a
drafting ratio is larger). Therefore, when the resin of the sheath
component satisfies 30<MI.sub.A, the resin has high fluidity,
which gives advantage that the resin is easy to melt and deform
during spinning.
[0052] Further, the draft ratio during spinning and the draw ratio
during a drawing treatment can be made high to give a finer fiber,
by setting MI.sub.B (g/10 min) within a range of from 20 to 80
wherein MI.sub.B is the before-spinning melt index of the
polyoxymethylene-based polymer B. As a result, crystal orientation
of the fiber is facilitated, and thereby the shrink of the fiber is
expected to be suppressed, whereby a non-woven shrinkability can be
suppressed upon processing the fibers into the non-woven.
[0053] Further, there is a 150.degree. C. 1/2 crystallization time
as the property for defining the polyoxymethylene-based polymer B.
In the conjugate fiber of the present invention, the
polyoxymethylene-based polymer B preferably has the 150.degree. C.
1/2 crystallization time of from 10 seconds to 100 seconds, which
time is determined as follow.
[0054] [A method for determining 150.degree. C. 1/2 crystallization
time]
[0055] A sample of 10 mg is put into an aluminum container and a
temperature is raised from 20.degree. C. to 200.degree. C. at a
temperature rising speed of 10.degree. C./min and the temperature
is retained for 2 minutes, using a differential scanning
calorimeter under a nitrogen atmosphere. Then the temperature is
lowered at a temperature falling speed of 50.degree. C./min and is
retained at 150.degree. C. The time period between the time at
which the retention of the temperature starts and the time at which
a crystallization heat-release peak (a peak which appears near
150.degree. C.) is determined as the 150.degree. C. 1/2
crystallization time.
[0056] The details of the conditions for determination are as
follow:
[0057] Differential scanning calorimeter: trade name "DSC 6200"
manufactured by SEIKO Instruments;
[0058] Atmosphere: nitrogen flow (50 mL/min)
[0059] Temperature calibration: pure water, and melting points of
high-purity indium and high-purity tin;
[0060] Sensitivity calibration: high-purity indium (.DELTA.Hm=6.86
cal/g).
[0061] Temperature range: 20.degree. C. to 220.degree. C.
[0062] When the before-spinning 150.degree. C. 1/2 crystallization
time of the polyoxymethylene-based polymer B is within the above
range, the crystallization is facilitated and thereby the
solidification proceeds to some extent during the discharge of the
molten resin and the drafting of the discharged resin at a
predetermined drafting ratio. This improves the spinnability of the
conjugate fiber and particularly enables the spun filament of a
small fineness. Particularly when the conjugate fiber is a
sheath-core conjugate fiber which is described below, the sheath
component tends to be solidified by being cooled by a chimney,
while the core component may not be cooled sufficiently, which
makes the solidification of the component difficult. This tendency
is a reason why it is preferable that the 150.degree. C. 1/2
crystallization time of the polyoxymethylene-based polymer B is
within the above ramge.
[0063] In the case where the 150.degree. C. 1/2 crystallization
time of the polyoxymethylene-based polymer B is shorter than 10
seconds, the second component is solidified quickly, whereby the
drafting is not made during spinning; fiber breakage occurs just
under the nozzle; and many blocks tend to generate. In the case
where the 150.degree. C. 1/2 crystallization time of the
polyoxymethylene-based polymer B is longer than 100 seconds, the
cooling during spinning is not sufficient, which causes the
breakage during drafting due to the shortage of a melt tension.
[0064] In the case where the 150.degree. C. 1/2 crystallization
time of the polyoxymethylene-based polymer B is within the above
range, it is preferable that difference between the before-spinning
melt indexes MI (g/10 min) of the polyoxymethylene-based polymers B
and A is small. Specifically, the ratio (before-spinning
MI.sub.B/before-spinning MI.sub.A) is preferably from 0.8 to 1.2.
This is because the drafting smoothly proceeds when the fluidity of
the two components are more similar to each other during the
spinning drafting.
[0065] In the case where the conjugate fiber having the fineness of
about 1.7 dtex or less is produced, the before-spinning 150.degree.
C. 1/2 crystallization time of the polyoxymethylene-based polymer B
is preferably from 15 seconds to 50 seconds, more preferably from
20 seconds to 50 seconds, and still more preferably from not less
than 20 seconds to less than 30 seconds.
[0066] Alternatively, the 150.degree. C. 1/2 crystallization time
of the polyoxymethylene-based polymer B may be determined after
spinning. In this case, the preferable range of the 150.degree. C.
1/2 crystallization time is from 10 seconds to 100 seconds. The
after-spinning 150.degree. C. 1/2 crystallization time of the
polyoxymethylene-based polymer B is determined, by raising and
retaining the temperature according to the determination method
described above using the conjugate fiber as the sample. In the
conjugate fiber having the fineness of about 1.7 dtex or less, the
after-spinning 150.degree. C. 1/2 crystallization time of the
polyoxymethylene-based polymer B is preferably from 15 seconds to
50 seconds, and more preferably from 20 seconds to 50 seconds. The
polyoxymethylene-based polymer A is in a melted or softened state
during the determination of the 150.degree. C. 1/2 crystallization
time of the polyoxymethylene-based polymer B in the conjugate
fiber, and does not affect the determination as to the
polyoxymethylene-based polymer B.
[0067] The polyoxymethylene-based polymer B which has the
before-spinning or the after-spinning 150.degree. C. 1/2
crystallization time is not necessarily required to be used in
combination with the polyoxymethylene-based polymer A having the
before-spinning MI.sub.A within the above range. In other words,
even if the before-spinning melt properties of the
polyoxymethylene-based polymer A is not limited to particular ones,
the thermoadhesive conjugate fiber which is spun well and presents
good thermal adhesiveness can be obtained, as long as the
before-spinning or the after-spinning 150.degree. C. 1/2
crystallization time of the polyoxymethylene-based polymer B is
within the above range.
[0068] Further, the physical properties which define the
polyoxymethylene-based polymer B include a Z-average molecular
weight (Mz). In the conjugate fiber of the present invention, a
before-spinning Mz of the polyoxymethylene-based polymer B is
preferably 500,000 or less which is determined under the following
conditions.
[0069] <Conditions for Determination of Mz> [0070] Method:
GPC (Gel Permeation Chromatography) Conditions: [0071] Device: Gel
permeation chromatograph GPC (produced by Waters) [0072] Detector:
differential refractive index detector RI (Type 2414, sensitivity
256, produced by Waters) [0073] Column: Shodex-HFIP-806M two
columns (S/N A406246, A406247) (produced by Showa Denko K.K.,
.phi.8.0 mm.times.30 cm, number of theoretical plates of about
14,000 plates/two columns) [0074] Solvent: Hexafluoroisopropanol
(HFIP, produced by Central Glass Co., Ltd., NaTFA 5 mM added)
[0075] Flow speed: 0.5 mL/min [0076] Sample: [0077] (Dissolution)
Agitating gently at a room temperature, [0078] (Solubility) Visual
good [0079] (Concentration) 0.05 w/v % [0080] (Filtration) Membrane
filter with a pore diamter of 0.45 .mu.m (H-13-5, produced by Tosoh
Corporation) [0081] (Charged amount) 0.200 mL [0082] (Standard
specimen) polymethylmethacrylate produced by Showa Denko K.K.) and
[0083] Dimethylterephthalate (produced by Tokyo chemical industry
Co., Ltd.). [0084] Determination of Mz: Mz is determined from the
following formula:
[0084] Mz=.SIGMA.(NiMi.sup.3)/.SIGMA.(NiMi.sup.2) [0085] wherein Mi
is a molecular weight at an elution position of a GPC curve which
is obtained through a molecular weight calibration curve, and Ni is
a number of molecule.
[0086] The spinning was conducted, by the present inventors, in
which various polyoxymethylene-based polymers are used as the
second component. As a result, they found that difference in
distribution of the molecular weight affects the spinnability, even
though the before-spinning MI.sub.B, is the same. Further, they
found that as Mz which is a parameter relating to the
high-molecular-weight component of the polymer is larger, the
crystallization speed is higher. Specifically, when the Mz of the
polyoxymethylene-based polymer B is 500,000 or lower, good
spinnability is achieved. When the composite fiver having a
fineness of less than 2 dtex, particularly 1.8 dtex or less, more
particularly 1.6 dtex or less, and still more particularly 1.4
dtex, the Mz of the polyoxymethylene-based polymer B is preferably
390,000 or less, more preferably 380,000 or less and still more
preferably 360,000 or less. When the Mz of the
polyoxymethylene-based polymer B is over 500,000 or less, the
crystallization speed is high, resulting in deterioration of the
spinnability. Further, the polymer of such a high Mz generates
unmelted substance upon melting the polymer in an extruder, which
causes breakage of fiber during spinning.
[0087] Otherwise, the Mz of the polyoxymethylene-based polymer B
may be determined after spinning. In that case, the Mz is
preferably 500,000 or less. When the Mz is determined by the above
determination method wherein the sample is the conjugate fiber, the
Mz of the polyoxymethylene-based polymer A and the Mz of the
polyoxymethylene-based polymer B are combined and one Mz is
determined. However, it is considered that the most of the
determined Mz is occupied by the polyoxymethylene-based polymer B.
In the conjugate fiber having a fineness of about 1.7 dtex or less,
Mz is preferably 350,000 or less, and more preferably 300,000 or
less.
[0088] When the first component contains a component(s) other than
the polyoxymethylene-based polymer A, it preferably contains the
polyoxymethylene-based polymer A in an amount of at least 50 mass
%. When the content of the polyoxymethylene-based polymer is less
than 50 mass %, the fiber which presents the properties (for
example, chemical resistance) provided by the
polyoxymethylene-based polymer cannot be obtained. It is preferable
that the first component essentially consists of the
polyoxymethylene-based polymer A. The term "essentially" is used
considering that the content of the polyoxymethylene-based polymer
A is not completely 100 mass % in the case where the first
component contains an additive such as a stabilizer or the like.
The component other than the polyoxymethylene-based polymer A
contained in the first component is preferably, for example, a
high-density polyethylene, a low-density polyethylene,
ethylene-propylene copolymer, or polypropylene.
[0089] The above applies to the second component.
[0090] After-spinning Tf.sub.A is preferably in a range of from
138.degree. C. to 160.degree. C., and more preferably from
148.degree. C. to 156.degree. C.
[0091] After-spinning Tf.sub.B is higher than Tf.sub.A by
10.degree. C. or more, preferably 13.degree. C. or more, and more
preferably 15.degree. C. or more. When the difference between
Tf.sub.A and Tf.sub.B is small, the second component shrinks during
the heat adhesion and the fiber loses its form, whereby a nonwoven
having a shape cannot be formed upon producing the nonwoven, for
example.
[0092] The thermoadhesive conjugate fiber of the present invention
has a cross-sectional structure wherein the first component is
exposed with an exposed length of not less than 20% relative to a
peripheral length of the fiber. Such structure is preferably a
sheath-core conjugate fiber structure wherein the first component
is the sheath component and the second component is the core
component. The sheath-core structure gives favorable thermal
adhesiveness since the first component which is the thermoadhesive
component exists over the entire fiber surface in this structure.
The sheath-core conjugate fiber may have an eccentric sheath-core
cross section wherein the center position of the second component
(the core component) is shifted from the center position of the
fiber. A fiber having such cross section tends to develop
three-dimensional crimps and provides stretchability, bulkiness
and/or soft feeling to, for example, a nonwoven made of the fibers
when the nonwoven is made from this fiber. Further, the
thermoadhesive conjugate fiber having the eccentric sheath-core
cross section can be obtained as a fiber which develops the
three-dimensional crimps by subjecting it to a thermal
treatment.
[0093] In the sheath-core conjugate fiber, a composite ratio of the
first component to the second component is preferably in a range of
3:7 to 7:3 by volume. The more preferable range of the volume ratio
is from 4:6 to 6:4. When the ratio of the first component is less
than three, the thermoadhesiveness may be insufficient. When the
ratio of the first component is over seven, the cardability may be
deteriorated. Further, the large ratio of the first component makes
the bulk of the nonwoven prone to difficult to obtain (that is, the
nonwoven lacks for bulkiness), resulting in deterioration of
feeling, when the fibers are processed to form the nonwoven.
[0094] The thermoadhesive conjugate fiber of the present invention
may include the first component, the second component and possibly
a third component containing another polyoxymethylene-based polymer
to give a construction wherein all the components are disposed
concentrically, or a construction wherein the components are
disposed to be parallel to each other. In the case where the
thermoadhesive conjugate fiber includes another component other
than the first component and the second component, it is preferable
that the another component also contains another
polyoxymethylene-based polymer and the another
polyoxymethylene-based polymer and the polyoxymethylene-based
polymer A satisfy the same relationship as that between the
polyoxymethylene-based polymer B and the polyoxymethylene-based
polymer A, with respect to the after-spinning fusion peak
temperature.
[0095] The thermoadhesive conjugate fiber of the present invention
can be obtained as a fine fiber having a fineness of from about 0.1
dtex to about 3 dtex. Fibers of such a fineness is equivalent to
those of a polypropylene fiber and a polyester fiber which are
widely used as a fiber for producing a nonwoven (including a paper
(a wetlaid nonwoven)), and therefore makes it possible to produce a
fiber assembly (particularly the nonwoven) by a method which is
employed when using these widely-used fibers.
[0096] The thermoadhesive conjugate fiber presents the reduced
shrink of the second component upon the thermal adhesion due to the
use of the particular polyoxymethylene-based polymers. This is
shown by a single fiber dry heat shrinkage percentage determined
according to JIS L 1015 (dry heat shrinkage percentage) at a
temperature of 140.degree. C., for a time of 15 minutes under an
initial tension (load) of 0.018 mN/dtex (2 mg/d). The
thermoadhesive conjugate fiber of the present invention preferably
shows the single fiber dry heat shrinkage percentage of 15% or
less, and more preferably 12% or less, when the center position of
the second component almost coincide with the center position of
the fiber, that is, when the fiber is the concentric sheath-core
conjugate fiber.
[0097] Further, the thermoadhesive conjugate fiber of the present
invention tends to have a high knot strength retention.
Specifically, the thermoadhesive conjugate fiber of the present
invention has a knot strength retention of 90% or more, and more
specifically from 96% to 98%, when the center position of the
second component coincides with the center position of the fiber,
that is, when the fiber is the concentric sheath-core conjugate
fiber. The reason why the thermoadhesive conjugate fiber of the
present invention has the high knot strength retention is not
clear, but one reason may be that a smoothness of the fiber of the
present invention is high, and the fiber is orientationally
crystallized by drawing, resulting in hardening of the fiber. It is
considered that the knot strength retention tends to be lowered
when the fibers are damaged because they are rubbed on each other
upon knotting the fiber. It is presumed that since the
thermoadhesive conjugate fiber has a high surface smoothness and is
hard, the damage due to friction is small, leading to the high knot
strength retention.
[0098] Another reason is that the thermoadhesive conjugate fiber of
the present invention can be produced being drawn sufficiently at a
high draw ratio, and thereby can be obtained as a fine fiber. Since
the fine fiber of from about 0.1 dtex to about 3 dtex is
particularly flexible in general, it is presumed that the knot
strength retention of such a fine fiber becomes high.
[0099] It is presumed that the crystallization of each component of
the thermoadhesive conjugate fiber of the present invention
proceeds to harden the entire fiber, since the fiber is preferably
produced by a production method which involves drawing the fiber
sufficiently at a relatively high draw ratio during spinning and
drawing. In the hard fiber, mechanical crimps tend to be kept for a
long time after the crimps are given, whereby the fibers are
entangled well. This gives a tendency that, for example, uniformity
of a web which is obtained by carding the fibers is excellent.
[0100] Next, a method for producing the thermoadhesive conjugate
fiber of the present invention is described. Firstly, two kinds of
polyoxymethylene-based polymers A and B are prepared, which
satisfy: [0101] 30<MI.sub.A wherein MI.sub.A is a
before-spinning melt index (g/10 min) of the polyoxymethylene-based
polymer A, which is determined according to JIS K 7210 (conditions:
190.degree. C., load: 21.18N (2.16 kg)), and [0102]
T.sub.B>T.sub.A+10 wherein T.sub.A and T.sub.B are
before-spinning fusion peak temperatures of the
polyoxymethylene-based polymers A and B respectively after being
spun, which are determined according to JIS K 7121. Such
polyoxymethylene-based polymers A and B are as described above.
[0103] In addition to or as a substitute for MI.sub.A of the above
range, the 150.degree. C. 1/2 crystallization time of the
polyoxymethylene-based polymer B may be within a range of from 1
second to 100 seconds. Alternatively, in addition to MI.sub.A of
the above range and/or the 150.degree. C. 1/2 crystallization time
of the above range, the polyoxymethylene-based polymer B may have
Mz of 500,000 or less. Such a polyoxymethylene-based polymer B is
as described above.
[0104] Then, the first component containing the
polyoxymethylene-based polymer A and the second component
containing the polyoxymethylene-based polymer B are compositely
spun such that the first component is exposed with an exposed
length of not less than 20% relative to a peripheral length of the
fiber. A spinning temperature is preferably from 180.degree. C. to
200.degree. C. The spun filament having an after-drafting fineness
in a range of from 2 dtex to 15 dtex is made. In the case where the
fiber having a fineness of less than 2.0 dtex is intended to be
obtained, an after-drafting fineness is made 8 dtex or less. When
the after-drafting fineness of the spun filament is less than 2.0
dtex, the productivity of the fiber is lowered due to break of
filament. When the after-drafting fineness of the spun filament is
over 15 dtex, the filament is not drawn sufficiently and a fiber
with uniform fineness cannot be obtained due to necking. When an
orifice diameter of a spinning nozzle is from 0.3 mm to 1 mm, the
draft ratio (drawing ratio) during spinning is, for example,
preferably from about 100 times to about 1000 times, more
preferably from about 300 times to about 900 times, and still more
preferably about 400 times to about 800 times in order to obtain
the spun filament having the fineness in the above range. The
relatively high draft ratio during spinning can give, synergized
with a later drawing treatment, the thermoadhesive conjugate fiber
of which second component presents suppressed shrink upon the
thermal adhesion. The orifice diameter of the spinning nozzle may
be selected arbitrarily in order to achieve the above draft
ratio.
[0105] Next, the spun filament is subjected to a drawing treatment
to give a drawn filament. The drawing treatment is preferably
conducted at a temperature lower than the fusion peak temperature
of the polyoxymethylene-based polymer A. Specifically, the drawing
temperature is preferably set at a temperature of from 130.degree.
C. to 150.degree. C. The draw ratio is preferably from 4 times to
10 times, and more preferably from 4.2 times to 7 times. The
drawing method is preferably a dry drawing method. Alternatively,
the drawing may be conducted by a wet drawing method.
[0106] A predetermined amount of a fiber treatment agent is applied
to the resultant drawn filament and then mechanical crimps are
given to the filament with a crimper (a crimp-giving machine) in
the case where the fiber is one for being opened and forming a web
with a carding machine or for forming an airlaid web. The number of
crimps is preferably in a range of from 12 peaks/25 mm to 19
peaks/25 mm. When the number of crimps is less than 12 peaks/25 mm,
the cardability of the fiber is deteriorated since winding on a
cylinder and fly tend to occur in the card. Further, a small number
of crimps makes a web strength low, which indicates a degree of
entanglement of fibers, and tends to cause trouble in the carding
process. When the number of crimps is more than 19 peaks/25 mm,
unevenness such as nep and cloudy tends to generate due to bad
openability of the fibers in the carding process. The number of
crimps is more preferably in a range of from 14 peaks/25 mm to 16
peaks/25 mm. In the case where the conjugate fiber is intended to
be obtained as a short-length fiber (particularly, a short fiber
for making paper) having a fiber length of less than 10 mm, the
mechanical crimps may not be given to the fiber.
[0107] After forming the crimps (or applying the fiber treatment
agent without forming the crimps), the filament is subjected to an
annealing treatment at a temperature in a range of from 60.degree.
C. to 110.degree. C. for a several seconds to about 30 minutes.
When the annealing treatment is conducted after the fiber treatment
agent is applied, the annealing treatment is preferably conducted
at an annealing temperature in a range of from 60.degree. C. to
110.degree. C. for a treatment time of at least 5 minutes in order
that the fiber treatment agent is dried at the same time. When the
annealing treatment is conducted at a temperature in the
above-described range, the crimp shape is stabilized which results
in, for example, reduced thinning of the nonwoven, whereby a bulky
and bouncy nonwoven is obtained when the nonwoven is produced.
Further, the annealing treatment at such a relatively low
temperature can suppress the single fiber dry heat shrinkage
percentage of the resultant fiber. The annealing treatment may be
omitted when the short fiber for making paper.
[0108] After completing the annealing treatment (after applying the
fiber treatment agent in the case of the short fiber for making
paper), the filament is cut so that the fiber length is from 3 mm
to 100 mm depending on use. The thermoadhesive conjugate fiber of
the present invention may be used as a long fiber, if necessary.
The thermoadhesive conjugate fiber of the present invention can be
produced by a meltblown method and a spunbond method as long as the
particular polyoxymethylene-based polymers as described above are
used for the first and the second components.
[0109] The present invention also provides a fiber assembly which
contains the thermoadhesive conjugate fiber of the present
invention as described above in an amount of 10 mass % or more. The
fiber assembly is preferably one wherein the fibers are bonded by
the first component. The fiber assemblies include a woven fabric, a
knitted fabric and nonwoven. The fiber assembly contains the
thermoadhesive conjugate fiber more preferably in an amount of 50
mass % or more and most preferably 100 mass %.
[0110] Then, the nonwoven is described as an example of the fiber
assembly of the present invention, together with the production
method of the nonwoven. The nonwoven is produced by making a web
containing the thermoadhesive conjugate fiber of the present
invention in an amount of 10 mass % or more and subjecting the web
to a thermal treatment to melt or soften the first component of the
fiber so that the fibers are bonded. The nonwoven may be produced
using a web which is obtained by mixing the thermoadhesive
conjugate fiber of the present invention and another fiber(s), or a
laminate wherein a web of another fiber(s) is stacked on the web of
the fiber of the present invention. As the another fiber, one or
more fibers may be selected from a natural fiber such as cotton,
silk, wool, hemp and pulp; a regenerated fiber such as rayon and
cupraammonium rayon (Cupra); and a synthetic fiber such as an
acrylic fiber, a polyester fiber, a polyamide fiber, a polyolefin
fiber and a polyurethane fiber, depending on use and so on of the
nonwoven.
[0111] The fiber mixed with the fiber of the present invention may
be a splittable conjugate fiber consisting of two or more resin
components. The splittable conjugate fiber has a fiber
cross-sectional structure wherein at least one component is divided
into two or more segments and at least a portion of each component
is exposed on a surface of the fiber and the exposed portion
extends continuously in the longitudinal direction of the fiber.
The preferable polymer combination for constituting the splittable
conjugate fiber is, polyethylene terephthalate/polyethylene,
polyethylene terephthalate/polypropylene, polyethylene
terephthalate/ethylene-propylene copolymer,
polypropylene/polyethylene, and polyethylene
terephthalate/nylon.
[0112] The webs used for producing the nonwoven include a carded
web such as a parallel web, a semi-random web, a random web, a
cross-laid web, and crisscross-laid web; a wetlaid web; and an
airlaid web. Two or more fiber webs of different types may be
stacked. Further, the fiber web may be optionally subjected to a
second process such as a hydroentangling treatment or a
needle-punching treatment before and/or after the thermal treatment
in order to entangle the fibers.
[0113] The fiber web is subjected to a thermal treatment with a
known thermal treating means. It is preferable to employ at least
one thermal treating technique selected from a hot air-through
technique and a thermocompression bonding technique as the thermal
treating means. The conditions for the thermal treatment such as a
thermal treatment temperature and soon are optimally selected
depending on the thermal treating technique employed. When the hot
air-through technique is employed, the thermal treatment
temperature may be set at a temperature at which the first
component of the thermoadhesive conjugate fiber is melted or
softened, preferably in a range of from 145.degree. C. to
170.degree. C., a more preferably in a range of from 150.degree. C.
to 165.degree. C., and still more preferably in a range of
155.degree. C. to 165.degree. C. This thermal treatment temperature
is preferably employed when the fiber assembly of another
embodiment (for example, the woven fabric or the knitted fabric) is
produced.
[0114] A mass per unit area is not limited to a particular one, and
may be selected from a range of from 10 g/m.sup.2 to 5000 g/m.sup.2
depending on the use. Further, a density of the nonwoven may be
selected from a range of from 0.01 g/cm.sup.3 to 1.0 g/cm.sup.3
depending on the use.
[0115] The resultant nonwoven has excellent slippability because
the smoothness of the surface of the thermoadhesive conjugate fiber
is high. Further, the nonwoven is bulky and has cushioning
properties. Furthermore, this nonwoven presents high water
retentivity, high bulk recoverability, and high crease resistance.
Therefore, this nonwoven is favorably suitable for applications
such as hygiene products (menstrual sanitary products and paper
diaper), paper, a wiper, a wet tissue, a mask, an interfacing, a
brassiere pad, a civil engineering and construction material, a
buffer (including a cushion), a wrapping material, clothes, a mat
and a sponge-like nonwoven material. Further, the fiber assembly of
another embodiment (for example, the woven fabric and the knitted
fabric) may be used for the same applications.
[0116] Particularly when the nonwoven for the wiper is produced, it
is preferable to combine the thermoadhesive conjugate fiber of the
present invention with the splittable conjugate fiber. The
splittable fiber gives ultrafine fibers by dividing the fiber, for
example, by means of the hydroentangling treatment, resulting in a
nonwoven wherein the fibers of the present invention and the
ultrafine fibers exist on the surface. Such a nonwoven has high
slippability which is conferred by the fiber of the present
invention, and is excellent in wiping-ability. Alternatively, a
fiber which is widely used for forming the wiper may be used
instead of the splittable conjugate fiber. The conjugate fiber of
the present invention is preferably contained in an amount of from
20 mass % to 70 mass %, and more preferably in an amount of from 30
mass % to 50 mass % regardless of the type of the fiber which is
mixed with the conjugate fiber of the present invention.
[0117] The thermoadhesive conjugate fiber of the present invention
is not necessarily required to be used for bonding the fibers in
the fiber assembly. Particularly when the fiber assembly is used as
the nonwoven for the wiper, the fiber assembly is integrated by the
fiber entanglement (for example, the hydroentanglement) without
being subjected to the thermal treatment, so that a softer and a
better feeling are obtained.
[0118] The fiber assembly of the present invention may be a molded
article which is produced by conducting the thermal treatment with
the fibers or the fiber web within a mold. For example, the molded
article can be simply formed by making the fiber web containing the
thermoadhesive conjugate fiber of the present invention with a
carding machine, and putting the web into the mold followed by the
thermal treatment. The kinds of the carded webs are described as
above. The thermal treatment may be conducted employing the hot
air-through technique. The fiber web may be put into the mold after
being subjected to the hydroentangling treatment. The molded
article having a large thickness may be produced by laminating the
fiber webs using a cross-layer machine and putting the laminated
web into the mold. The laminated web may be optionally subjected to
the needle-punching treatment and/or the hydroentangling
treatment.
[0119] The density of the molded article is selected depending on
the use of the article, regardless of the method for producing the
molded article. Specifically, the density of the molded article is
preferably from 0.01 g/cm.sup.3 to 1.0 g/cm.sup.3, more preferably
from 0.02 g/cm.sup.3 to 0.8 g/cm.sup.3, and still more preferably
from 0.04 g/cm.sup.3 to 0.6 g/cm.sup.3. The mass per unit area is
also selected depending on the use. Specifically, it is preferably
from 10 g/m.sup.2 to 5000 g/m.sup.2.
[0120] The molding process is conducted at a thermal treatment
temperature in a range of from 140.degree. C. to 180.degree. C. for
the thermal treatment time in a range of from 5 seconds from 120
minutes depending on the mass per unit area of the fiber web and
the intended density of the resultant molded article. Specifically,
the thermal treatment temperature is preferably at least the
melting point of the first component of the thermoadhesive
conjugate fiber of the present invention and at most (the melting
temperature of the second component -5.degree. C.). More
specifically, in the case where the mass per unit area is 100
g/m.sup.2 or less, the thermal treatment is preferably conducted
using a conveyer type hot air-through thermal treating machine and
setting the thermal treatment time within a range of from 5 seconds
to 20 minutes. In the case where the mass per unit area is over 100
g/m.sup.2, the thermal treatment is preferably conducted using a
batch type hot air-through thermal treating machine and setting the
thermal treatment time within a range of from 1 minute to 120
minutes.
[0121] The molding process is preferably conducted using a mold
formed from a air-permeable material such as a metal mesh or a
resin mesh sheet so that the thermal treatment is conducted evenly
in a thickness direction of the fiber web when using a hot
air-through thermal treating machine. For example, the molding
process may be conducted by a method wherein the mold is made by
shaping the air-permeable sheet into a predetermined shape, and
then the fiber web is put into this mold. Alternatively, the fiber
web may be mold-processed by a method wherein the fiber web is
sandwiched with two air-permeable sheets (for example, the metal
mesh) and then the sandwiched web is shaped into a desired shape
and subjected to the thermal treatment. The shape of the molded
article is not limited to a particular one, and it may be any of a
flat plate shape, a shape with a curbed surface, a box shape, a
convex shape, a hat shape, a glass shape, a cup shape, a columnar
shape and a spherical shape.
EXAMPLES
[0122] Hereinafter, the present invention is specifically described
by examples. In the following examples, the melting points T.sub.A
and T.sub.B of the polyoxymethylene-based polymers A and B which
were used as a first and a second components respectively in the
production of fiber. The after-spinning melting point Tf.sub.A of
the first component, the after-spinning melting point Tf.sub.B of
the second component, the single fiber strength and rupture
elongation, the number of crimps, the percentage of crimp, the knot
strength, the knot strength retention, the single fiber dry heat
shrinkage percentage, the cardability, the area shrinkage
percentage of nonwoven, the thickness and the strength of nonwoven
were determined as described below.
[0123] [Determination of T.sub.A and T.sub.B]
[0124] A differential scanning calorimeter (manufactured by Seiko
Instruments Inc.) was employed. A sample amount was 5.0 mg. The
sample was maintained at 200.degree. C. for 5 minutes, and cooled
to 40.degree. C. at a temperature falling speed of 10.degree.
C./min and then melted at a temperature rising speed of 10.degree.
C./min so that a curve for heat of fusion was obtained for each of
the first component and the second component. From the curve for
heat of fusion, the fusion peak temperatures T.sub.A and T.sub.B
were determined as the melting points, respectively.
[0125] [Determination of Tf.sub.A and Tf.sub.B]
[0126] A differential scanning calorimeter (manufactured by Seiko
Instruments Inc.) was employed. A sample amount was 6.0 mg. The
temperature of fiber was risen from a room temperature to
200.degree. C. at a temperature rising speed of 10.degree. C./min
to be melted, and Tf.sub.A and Tf.sub.B were determined from a
resultant curve for heat of fusion.
[0127] [Mz and 150.degree. C. 1/2 crystallization time]
[0128] These were determined according to the methods which are
described in "Embodiment for Carrying Out Invention."
[0129] [Spinnability]
[0130] The spinnablity was estimated according to the following
standards:
[0131] .smallcircle. No fiber breakage occurred during 1-hour
spinning;
[0132] .DELTA. The filament could be take off even though the fiber
breakage occurred;
[0133] x The filament could not be taken off because fiber breakage
occurred frequently.
[0134] [Tensile Strength and Rupture Elongation of a Single
Fiber]
[0135] A load and an elongation when the fiber broke were measured
according to JIS L 1015 using an extension tensile tester with a
sample gage length of 20 mm and they were determined as the single
fiber strength and the single fiber rupture elongation
respectively.
[0136] [Knot Strength and Knot Strength Retention]
[0137] The knot strength of a single filament was determined
according to JIS L 1013 and the knot strength retention which was a
ratio of the knot strength to the filament strength (the fiber
tensile strength) was calculated.
[0138] [Number of Crimps, and Percentage of Crimp]
[0139] They were determined according to JIS L 1015.
[0140] [Single Fiber Dry Heat Shrinkage Percentage]
[0141] Dry heat shrinkage percentages were determined according to
JIS L 1015 with a gage length of 100 mm at a treatment temperature
of 140.degree. C. for a treatment time of 15 minutes under an
initial tension of 0.018 mN/dtex (2 mg/d).
[0142] [Cardability]
[0143] A parallel carding machine was used. A carded web having a
mass per unit area of about 30 g/m.sup.2 was discharged at a line
speed of 10 m/min and uniformity of the carded web, presence or
absence of fly, and transferability of web (continuousness of web
transferring from a roller to a roller) were observed and
cardability was evaluated according to the following criteria:
[0144] .smallcircle.: Favorable as to all of the uniformity of the
carded web, the fly, winding and the transferability of the
web;
[0145] .DELTA.: Bad as to one of the uniformity of the web, the
fly, winding and the transferability of the web; and
[0146] x: Bad as to two or more of the uniformity of the carded
web, the fly, winding and the transferability of the web.
[0147] [Nonwoven-Area Shrinkage Percentage: Samples 1 to 9 and 11
to 16]
[0148] The Nonwoven-area shrinkage percentage was determined by the
following method.
[0149] (1) A carded web having a mass per unit area shown in Tables
1 to 4 using a parallel carding machine and it was cut into a
square with a size of 20 cm in the lengthwise direction.times.20 cm
in a crosswise direction. The size (cm) of the web before a
shrinking treatment was determined.
[0150] (2) The carded web was subjected to a thermal treatment
without being restricted in order to be shrunk, at a thermal
treatment temperature shown in Tables 1 to 4 and an air flow rate
of 1.5 m/sec (upper flow) using a hot air-through thermal treating
machine. The thermal treatment time was set at 12 seconds.
[0151] (3) The size (cm) of the nonwoven after the treatment was
determined.
[0152] (4) The area shrinkage percentage was calculated based on a
following formula:
Nonwoven - areashrinkagepercentage ( % ) = ( Before - shrinking
lengthwise - direction size .times. crosswise - direction size ) -
( After - shrinking lengthwise - directionsize .times. crosswise -
direction size ) Before - shrinking lengthwise - direction size
.times. crosswise - direction size ##EQU00001##
[0153] [Nonwoven-Area Shrinkage Percentage: Sample 10]
[0154] The Nonwoven-area shrinkage percentage was determined by the
following method.
[0155] (1) 2 L water was put into a household mixer, and 4.4 g
fibers were put into the mixer followed by the mixing for 1 minute.
Then, a wet-laid web of 70 g/m.sup.2 was obtained using a 25
cm.times.25 cm hand-made paper device. The size of the web was
determined.
[0156] (2) The thermal treatment was conducted at a thermal
treatment shown in Table 3 (150.degree. C.) using a Yankee drier.
The thermal treatment time was set at 45 seconds.
[0157] (3) The size of the nonwoven after the thermal treatment was
determined.
[0158] (4) The area shrinkage percentage was calculated from the
above formula.
[0159] [Thickness of Nonwoven]
[0160] The thickness of the nonwoven after the thermal treatment
was determined using a thickness meter (manufactured by Daiei
Kagaku Seiki Seisakusho Co., Ltd., trade name: THICKNESS GAUGE
model CR-60A) under a load of 2.94 cN/cm.sup.2.
[0161] [Tensile strength of Nonwoven]
[0162] A sample piece of 5 cm in width is held at a grasp interval
of 10 cm and extended at a pulling rate of 30.+-.2 cm/min with a
constant speed extension tensile tester in accordance with JIS L
1096 6.12.1 A method (strip method). The value of load at break is
taken as the tensile strength. The tensile test was made for each
of a lengthwise direction (a machine direction) of the nonwoven and
a crosswise direction (a cross direction). The extension tensile
test of the nonwoven produced from the fibers of Sample 10 was made
only for one direction.
Experimental Example 1
Evaluation of Fiber Properties and the Nonwoven-Processability
(Sample 1)
[0163] A polyoxymethylene-based polymer was prepared as the first
component (the sheath component), of which T.sub.A was
156.0.degree. C., MI.sub.A was 51, and content of CH.sub.2CH.sub.2O
as the comonomer was 7.1 mass % as the ethylene oxide equivalent
(trade name: V40EX-1 produced by Mitsubishi Engineering-Plastics
Corporation). A polyoxymethylene-based polymer was prepared as the
second component (the core component), of which T.sub.B was
169.0.degree. C., MI.sub.B was 28, and content of CH.sub.2CH.sub.2O
as the comonomer was 0.9 mass % as the ethylene oxide equivalent
(trade name: A30EX-1 produced by Mitsubishi Engineering-Plastics
Corporation). These two components were melted and extruded using a
sheath-core composite nozzle (an office diameter 0.6 mm: this was
the same in the production of the following samples) at a
sheath-component spinning temperature of 190.degree. C. and a
core-component spinning temperature of 200.degree. C. The composite
ratio (volume ratio) of first component/second component was 50/50.
The draw ratio (spinning draft) was 440 times. As a result, a spun
filament having a fineness of 9.9 dtex was obtained.
[0164] The spun filament was drawn in hot air of 140.degree. C.
with a draw ratio of 4.7 times to give a drawn filament having a
fineness of about 2 dtex. Next, a fiber treatment agent was applied
to the drawn filament and mechanical crimps were formed in the
filament with a stuffing box type crimper. Then, the filament in a
relaxed state was subjected to an annealing treatment and a drying
treatment at the same time for about 15 minutes, in a hot
air-through thermal treatment machine wherein a temperature was set
at 110.degree. C. The filament was then cut into a fiber length of
51 mm and a thermoadhesive conjugate fiber in form of a staple
fiber was obtained.
[0165] [Sample 2]
[0166] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
1, except that the setting temperature of the hot air-through
thermal treatment (that is, the temperature for the annealing
treatment and the drying treatment) was 90.degree. C.
[0167] [Sample 3]
[0168] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
1, except that the setting temperature of the hot air-through
thermal treatment (that is, the temperature for the annealing
treatment and the drying treatment) was 60.degree. C.
[0169] [Sample 4]
[0170] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
1, except that the spun filament was dry-drawn in the hot air of
140.degree. C. at 5.7 times to obtain a drawn filament having a
fineness of about 1.7 dtex and the setting temperature of the hot
air-through thermal treatment (that is, the temperature for the
annealing treatment and the drying treatment) was 60.degree. C.
[0171] [Sample 5]
[0172] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
1, except that a eccentric sheath-core composite nozzle was used
and the cross-sectional structure was made an eccentric sheath-care
structure having an eccentricity of 40%.
[0173] [Sample 6]
[0174] A polyoxymethylene-based polymer was prepared as the first
component (the sheath component), of which T.sub.A was
156.0.degree. C., MI.sub.A was 51, and content of CH.sub.2CH.sub.2O
as the comonomer was 7.1 mass % as the ethylene oxide equivalent
(trade name: V40EX-1 produced by Mitsubishi Engineering-Plastics
Corporation). A polyoxymethylene-based polymer was prepared as the
second component (the core component), of which T.sub.B was
169.4.degree. C., MI.sub.B was 53, and content of CH.sub.2CH.sub.2O
as the comonomer was 0.9 mass % as the ethylene oxide equivalent
(trade name: A40EX-1 produced by Mitsubishi Engineering-Plastics
Corporation). These two components were melted and extruded using a
sheath-core composite nozzle at a sheath-component spinning
temperature of 190.degree. C. and a core-component spinning
temperature of 200.degree. C. The composite ratio (volume ratio) of
first component/second component was 50/50. The draw ratio
(spinning draft) was 495 times. As a result, a spun filament having
a fineness of 8 dtex was obtained.
[0175] The spun filament was drawn on a hot plate of 140.degree. C.
with a draw ratio of 4.7 times to give a drawn filament having a
fineness of about 1.7 dtex. Next, a fiber treatment agent was
applied to the drawn filament and mechanical crimps were formed in
the filament with a stuffing box type crimper. Then, the filament
in a relaxed state was subjected to an annealing treatment and a
drying treatment at the same time for about 15 minutes, in a hot
air-through thermal treatment machine wherein a temperature was set
at 60.degree. C. The filament was then cut into a fiber length of
51 mm and a thermoadhesive conjugate fiber in form of a staple
fiber was obtained.
[0176] [Sample 7]
[0177] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
6, except that the setting temperature of the hot air-through
thermal treatment (that is, the temperature for the annealing
treatment and the drying treatment) was 80.degree. C.
[0178] [Sample 8]
[0179] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
6, except that the setting temperature of the air-through thermal
treatment (that is, the temperature for the annealing treatment and
the drying treatment) was 100.degree. C.
[0180] [Sample 9: Comparative]
[0181] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
1, except that a polyoxymethylene-based polymer was prepared as the
second component (the core component), of which T.sub.B was
164.degree. C., MI.sub.B was 51, and content of CH.sub.2CH.sub.2O
as the comonomer was 2.6 mass % as the ethylene oxide equivalent
(trade name: F40-73R-1 produced by Mitsubishi Engineering-Plastics
Corporation) and the setting temperature of the hot air-through
thermal treatment (that is, the temperature for the annealing
treatment and the drying treatment) was 60.degree. C.
[0182] The properties of the staple fibers obtained as Samples 1 to
9 are shown in Tables 1 and 2. In the tables, "-" means that the
item was not measured, and a box wherein "/" is indicated entirely
means that the item could not be measured since the spinning could
not be conducted or the nonwoven could not be produced.
TABLE-US-00001 TABLE 1 Sample 1 Sample 2 Sample 3 Sample 4 Sample 5
Sheath MI.sub.A (g/10 min) 51 51 51 51 51 Component Melting Point
(T.sub.A) (.degree. C.) 156.0 156.0 156.0 156.0 156.0 Melting Point
(Tf.sub.A) (.degree. C.) 153.6 153.6 153.8 154.0 154.7 Core
MI.sub.B (g/10 min) 28 28 28 28 28 Component Melting Point
(T.sub.B) (.degree. C.) 169.0 169.0 169.0 169.0 169.0 Melting Point
(Tf.sub.B) (.degree. C.) 167.7 168.2 169.5 170.0 170.1 Eccentric
Eccentricity (%) 0 0 0 0 40 Form Production Spinning Temperature
(.degree. C./.degree. C.) 190/200 190/200 190/200 190/200 190/200
Conditions (Sheath/Core) Fineness of Spun (dtex) 9.0 9.0 9.0 9.0
9.0 Filament Drawing Temperature (.degree. C.) 140 140 140 140 140
Draw Ratio (times) 4.7 4.7 4.7 5.7 4.7 Annealing/Drying Temp.
(.degree. C.) 110 90 60 60 110 Fiber Length (mm) 51 51 51 51 51
Single Fiber Fineness (dtex) 2.0 2.0 2.0 1.7 2.0 Properties
Strength (cN/dtex) 4.76 4.78 4.81 4.93 2.85 Elongation (%) 94.1
96.3 103.6 87.6 132.7 Number of Crimps (peaks/25 mm) 116 12.2 16.7
16.5 21.3 Percentage Crimps (%) 7.3 8.8 11.0 13.8 16.4 Knot
Strength (cN) 8.83 8.96 8.94 8.08 4.82 Knot Strength Retention (%)
92.75 93.72 92.93 96.41 84.56 Single Fiber Initial Tension 0.018
mN/dtex (%) 8.11 9.15 10.73 10.01 18.33 Dry Heat Shrinkage
Percentage Cardability .DELTA. .smallcircle.~.DELTA. .smallcircle.
.smallcircle. .DELTA. Nonwoven Process Temperature (.degree. C.)
153 153 153 153 153 Nonwoven Area Shrinkage Percentage (%) 7.4 9.9
8.1 2.7 36.4 Nonwoven Mass Per Unit Area (g/m.sup.2) 29.5 30.1 31.6
30.3 -- Properties Thickness (mm) 0.61 0.68 0.81 1.01 -- Specific
Volume (cm.sup.3/g) 20.5 22.7 25.6 33.3 -- Strength MD 65.1 53.0
45.6 56.7 -- (N/5 cm) CD 15.5 15.4 13.5 15.1 --
TABLE-US-00002 TABLE 2 Sample 6 Sample 7 Sample 8 Sample 9 Sheath
MI.sub.A (g/10 min) 51 51 51 51 Component Melting Point (T.sub.A)
(.degree. C.) 156.0 156.0 156.0 156.0 Melting Point (Tf.sub.A)
(.degree. C.) 154.5 154.6 154.6 156.5 Core MI.sub.B (g/10 min) 53
53 53 51 Component Melting Point (T.sub.B) (.degree. C.) 168.3
168.3 168.3 164.0 Melting Point (Tf.sub.B) (.degree. C.) 171.4
171.5 171.8 162.7 Eccentric Eccentricity (%) 0 0 0 0 Form
Production Spinning Temperature (.degree. C./.degree. C.) 190/200
190/200 190/200 190/200 Conditions (Sheath/Core) Fineness of Spun
Filament (dtex) 8.0 8.0 8.0 9.0 Drawing Temperature (.degree. C.)
140 140 140 140 Draw Ratio (times) 5.0 5.0 5.0 4.7 Annealing/Drying
Temp. (.degree. C.) 60 80 100 60 Fiber Length (mm) 51 51 51 51
Single Fiber Fineness (dtex) 1.68 1.72 1.73 2.0 Properties Strength
(cN/dtex) 3.87 3.69 3.67 2.31 Elongation (%) 36.50 35.90 43.90
134.0 Number of Crimps (peaks/25 mm) 15.20 12.40 18.90 16.5
Percentage Crimps (%) 8.50 6.80 10.00 11.3 Knot Strength (cN) 6.31
6.11 6.20 3.32 Knot Strength Retention (%) 97.05 96.27 97.65 71.86
Single Fiber Initial Tension 0.018 mN/dtex (%) 10.20 9.80 8.60
43.41 Dry Heat Shrinkage Percentage Cardability .smallcircle.
.smallcircle. .DELTA. .smallcircle. Nonwoven Process Temperature
(.degree. C.) 155 155 155 155 Nonwoven Area Shrinkage Percentage
(%) 2.0 1.8 1.8 Nonwoven Mass Per Unit Area (g/m.sup.2) 31.4 29.0
30.4 Properties Thickness (mm) 0.72 0.63 0.55 Specific Volume
(cm.sup.3/g) 23.5 21.7 18.1 Strength MD 90.3 75.6 89.9 (N/5 cm) CD
20.0 14.8 15.3
[0183] The conjugate fibers of Samples 2 to 4, 6 and 7 presented
good cardability and small shrinkage upon the thermal adhesion
treatment, which means favorable processability. In contrast, the
conjugate fibers of Samples 1, 5 and 8 presented a slightly
deteriorated cardability. It is considered that this is because the
annealing temperatures for the conjugate fibers of Samples 1, 5 and
8 were slightly high. The measurement of knot strengths and knot
strength retentions of Samples 6 to 8 showed that knot strength
retentions of Samples 6 to 8 were high.
[0184] The fiber of Sample 9 could not give a nonwoven because of
the shrink of the fiber upon the thermal adhesion treatment,
although the fiber could be produced.
[0185] A polyoxymethylene-based polymer was prepared as the first
component (the sheath component), of which T.sub.A was
155.4.degree. C., MI.sub.A was 55, and content of CH.sub.2CH.sub.2O
as the comonomer was 7.1 mass % as the ethylene oxide equivalent
(trade name: V40-EX1 produced by Mitsubishi Engineering-Plastics
Corporation). A polyoxymethylene-based polymer was prepared as the
second component (the core component), of which T.sub.B was
170.4.degree. C., MI.sub.B was 55, Mz was 320000, 150.degree. C.
1/2 crystallization time was 25 seconds and content of
CH.sub.2CH.sub.2O as the comonomer was 0.9 mass % as the ethylene
oxide equivalent (trade name: A40-EX1 produced by Mitsubishi
Engineering-Plastics Corporation). These two components were melted
and extruded using a sheath-core composite nozzle at a
sheath-component spinning temperature of 185.degree. C. and a
core-component spinning temperature of 190.degree. C. The composite
ratio (volume ratio) of first component/second component was 50/50.
The draw ratio (spinning draft) was 705 times. As a result, a spun
filament having a fineness of 4.7 dtex was obtained.
[0186] The spun filament was drawn in hot air of 140.degree. C.
with a draw ratio of 6.5 times to give a drawn filament having a
fineness of about 0.8 dtex. Next, a fiber treatment agent was
applied to the drawn filament then cut into a fiber length of 5 mm
and a thermoadhesive conjugate fiber in form of a short fiber was
obtained.
[0187] [Sample 11]
[0188] A polyoxymethylene-based polymer was prepared as the first
component (the sheath component), of which T.sub.A was
155.0.degree. C., MI.sub.A was 58, and content of CH.sub.2CH.sub.2O
as the comonomer was 7.1 mass % as the ethylene oxide equivalent
(trade name: V40-EF produced by Mitsubishi Engineering-Plastics
Corporation). A polyoxymethylene-based polymer was prepared as the
second component (the core component), of which T.sub.B was
170.5.degree. C., MI.sub.B was 58, Mz was 349000, 150.degree. C.
1/2 crystallization time was 19 seconds and content of
CH.sub.2CH.sub.2O as the comonomer was 0.9 mass % as the ethylene
oxide equivalent (trade name: A40-EF produced by Mitsubishi
Engineering-Plastics Corporation). These two components were melted
and extruded using a sheath-core composite nozzle at a
sheath-component spinning temperature of 185.degree. C. and a
core-component spinning temperature of 190.degree. C. The composite
ratio (volume ratio) of first component/second component was 50/50.
The draw ratio (spinning draft) was 417 times. As a result, a spun
filament having a fineness of 8.0 dtex was obtained.
[0189] The spun filament was drawn in hot air of 140.degree. C.
with a draw ratio of 5.0 times to give a drawn filament having a
fineness of about 1.8 dtex. Next, a fiber treatment agent was
applied to the drawn filament and mechanical crimps were formed in
the filament with a stuffing box type crimper. Then, the filament
in a relaxed state was subjected to an annealing treatment and a
drying treatment at the same time for about 15 minutes, in a hot
air-through thermal treatment machine wherein a temperature was set
at 60.degree. C. The filament was then cut into a fiber length of
51 mm and a thermoadhesive conjugate fiber in form of a staple
fiber was obtained.
[0190] [Sample 12]
[0191] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
11, except that the spinning temperature of the second component
was 200.degree. C. and the draw ratio of the spun filament was 4.3
times so as to obtain the drawn filament having a fineness of about
1.9 dtex.
[0192] [Sample 13]
[0193] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
11, except that the draw ratio (the spinning draft) during the melt
extrusion was 572 times to obtain the spun filament having a
fineness of 5.8 dtex and the fineness of the spun filament after
the dry drawing was about 1.3 dtex.
[0194] [Sample 14]
[0195] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
11, except that the draw ratio (the spinning draft) during the melt
extrusion was 572 times to obtain the spun filament having a
fineness of 5.8 dtex and the draw ratio of the spun filament was
6.5 times to obtain the drawn filament having a fineness of about
1.0 dtex.
[0196] [Sample 15]
[0197] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
11, except that a polyoxymethylene-based polymer was prepared as
the second component (the core component), of which T.sub.B was
170.8.degree. C., MI.sub.B was 59, Mz was 357000, 150.degree. C.
1/2 crystallization time was 10 seconds and content of
CH.sub.2CH.sub.2O as the comonomer was 0.9 mass % as the ethylene
oxide equivalent (trade name: A40-EF produced by Mitsubishi
Engineering-Plastics Corporation), the draw ratio (the spinning
draft) during the melt extrusion was 572 times to obtain the spun
filament having a fineness of 5.8 dtex and the draw ratio of the
spun filament was 4.3 times to obtain the drawn filament having a
fineness of about 1.3 dtex.
[0198] [Sample 16]
[0199] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
11, except that a polyoxymethylene-based polymer was prepared as
the second component (the core component), of which T.sub.B was
170.8.degree. C., MI.sub.B was 59, Mz was 357000, 150.degree. C.
1/2 crystallization time was 10 seconds and content of
CH.sub.2CH.sub.2O as the comonomer was 0.9 mass % as the ethylene
oxide equivalent (trade name: A40-EF produced by Mitsubishi
Engineering-Plastics Corporation), the draw ratio (the spinning
draft) during the melt extrusion was 370 times to obtain the spun
filament having a fineness of 9.0 dtex and the draw ratio of the
spun filament was 4.7 times to obtain the drawn filament having a
fineness of about 2.0 dtex.
[0200] [Sample 17]
[0201] A polyoxymethylene-based polymer was prepared as the first
component (the sheath component), of which T.sub.A was
155.0.degree. C., MI.sub.A was 61, and content of CH.sub.2CH.sub.2O
as the comonomer was 7.1 mass % as the ethylene oxide equivalent
(trade name: V40-EF produced by Mitsubishi Engineering-Plastics
Corporation). A polyoxymethylene-based polymer was prepared as the
second component (the core component), of which T.sub.B was
171.0.degree. C., MI.sub.B was 40, Mz was 400000, 150.degree. C.
1/2 crystallization time was 18 seconds and content of
CH.sub.2CH.sub.2O as the comonomer was 0.9 mass % as the ethylene
oxide equivalent (trade name: A40-EF-L, produced by Mitsubishi
Engineering-Plastics Corporation). These two components were melted
and extruded using a sheath-core composite nozzle at a
sheath-component spinning temperature of 185.degree. C. and a
core-component spinning temperature of 190.degree. C. The composite
ratio (volume ratio) of first component/second component was 50/50.
The draw ratio (spinning draft) was 396 times. As a result, a spun
filament having a fineness of 8.4 dtex was obtained.
[0202] The spun filament was drawn in hot air of 140.degree. C.
with a draw ratio of 4.7 times to give a drawn filament having a
fineness of about 1.8 dtex. Next, a fiber treatment agent was
applied to the drawn filament and mechanical crimps were formed in
the filament with a stuffing box type crimper. Then, the filament
in a relaxed state was subjected to an annealing treatment and a
drying treatment at the same time for about 15 minutes, in a hot
air-through thermal treatment machine wherein a temperature was set
at 60.degree. C. The filament was then cut into a fiber length of
51 mm and a thermoadhesive conjugate fiber in form of a staple
fiber was obtained.
[0203] [Sample 18]
[0204] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
17, except that the draw ratio (the spinning draft) was 370 times
to obtain the spun filament having a fineness of 9.0 dtex and the
resultant fiber having a fineness of about 2.0 dtex was
obtained.
[0205] [Sample 19]
[0206] A polyoxymethylene-based polymer was prepared as the first
component (the sheath component), of which T.sub.A was
155.8.degree. C., MI.sub.A was 29, and content of CH.sub.2CH.sub.2O
as the comonomer was 7.1 mass % as the ethylene oxide equivalent
(trade name: V30-EF produced by Mitsubishi Engineering-Plastics
Corporation). The polyoxymethylene-based polymer which was used as
the second component in the production of Sample 15 was prepared as
the second component (the core component). These two components
were melted and extruded using a sheath-core composite nozzle at a
sheath-component spinning temperature of 185.degree. C. and a
core-component spinning temperature of 190.degree. C. The composite
ratio (volume ratio) of first component/second component was 50/50.
The draw ratio (spinning draft) was 370 times. As a result, a spun
filament having a fineness of 9.0 dtex was obtained.
[0207] The spun filament was drawn in hot air of 140.degree. C.
with a draw ratio of 4.7 times to give a drawn filament having a
fineness of about 2.0 dtex. Next, a fiber treatment agent was
applied to the drawn filament and mechanical crimps were formed in
the filament with a stuffing box type crimper. Then, the filament
in a relaxed state was subjected to an annealing treatment and a
drying treatment at the same time for about 15 minutes, in a hot
air-through thermal treatment machine wherein a temperature was set
at 60.degree. C. The filament was then cut into a fiber length of
51 mm and a thermoadhesive conjugate fiber in form of a staple
fiber was obtained.
[0208] [Sample 20]
[0209] A thermoadhesive conjugate fiber was produced according to
the same procedures as those employed in the production of Sample
19, except that the draw ratio (the spinning draft) was 417 times
to obtain the spun filament having a fineness of 8.0 dtex and the
resultant fiber having a fineness of about 1.7 dtex was
obtained.
[0210] [Sample 21]
[0211] A thermoadhesive conjugate fiber having a fineness of 5.8
dtex was intended to be produced with the draw ratio (the spinning
draft) of 572 times, but the spinning could not be conducted.
[Sample 22]
[0212] The polyoxymethylene-based polymer which was used as the
first component in Sample 19 (trade name: V30-EF produced by
Mitsubishi Engineering-Plastics Corporation) was prepared as the
first component (the sheath component). A polyoxymethylene-based
polymer was prepared as the second component (the core component),
of which T.sub.B was 161.9.degree. C., MI.sub.B was 31, 150.degree.
C. 1/2 crystallization time was 353 seconds and content of
CH.sub.2CH.sub.2O as the comonomer was 2.6 mass % as the ethylene
oxide equivalent (trade name: F30-EF produced by Mitsubishi
Engineering-Plastics Corporation). These two components were melted
and extruded using a sheath-core composite nozzle at a
sheath-component spinning temperature of 185.degree. C. and a
core-component spinning temperature of 190.degree. C. The composite
ratio (volume ratio) of first component/second component was 50/50.
The draw ratio (spinning draft) was 370 times. Under the spinning
conditions, a spun filament having a fineness of 9.0 dtex was
intended to be produced, but the spinning could not be
conducted.
[0213] [Sample 23]
[0214] The spun filament having a fineness of 33.0 dtex was
intended to be obtained by setting the draw ratio (the spinning
ratio) at 100 times, but the spinning could not be conducted.
[0215] The properties of the staple fibers obtained as Samples 10
to 23 are shown in Tables 3 to 5. In the tables, "-" means that the
item was not measured, and a box wherein "/" is indicated entirely
means that the item could not be measured since the spinning could
not be conducted or the nonwoven could not be produced.
TABLE-US-00003 TABLE 3 Sample 10 Sample 11 Sample 12 Sample 13
Sheath MI.sub.A (g/10 min) 55 58 58 58 Component Melting Point
(T.sub.A) (.degree. C.) 154.4 155.0 155.0 155.0 Melting Point
(Tf.sub.A) (.degree. C.) 155.1 155.5 156.2 156.3 Core MI.sub.B
(g/10 min) 55 58 58 58 Component Melting Point (T.sub.B) (.degree.
C.) 170.4 170.5 170.5 170.5 Before- Z-Average Molecular Weight Mz
320,000 349,000 349,000 349,000 Spinning 150.degree. C. 1/2
Crystallization Time (seconds) 25 19 19 19 Core Wetting Poing
(Tf.sub.B) (.degree. C.) 171.4 171.7 172.8 171.1 Component
Z-Average Molecular Weight Mz -- -- -- 289,000 After- 150.degree.
C. 1/2 Crystallization Time (seconds) 33.0 20.4 27.0 24.0 Spinning
Eccentric Eccentricity (%) 0 0 0 0 Form Production Spinning
Temperature (.degree. C./.degree. C.) 185/190 185/190 185/200
185/190 Conditions (Sheath/Core) Fineness of Spun Filament (dtex)
4.7 8.0 8.0 5.8 Drawing Temp. (.degree. C.) 140 140 140 140 Draw
Ratio (times) 6.5 5.0 4.3 5.0 Annealing/Drying Temp. (.degree. C.)
60 60 60 60 Fiber Length (mm) 5 51 51 51 Spinnablity .smallcircle.
.smallcircle. .smallcircle. .smallcircle. Single Fiber Fineness
(dtex) 0.8 1.8 1.9 1.3 Properties Strength (cN/dtex) 4.4 4.2 4.0
4.3 Elongation (%) 18 26 22 21 Number of Crimps (peaks/25 mm) 17.1
16.4 16.7 16.9 Percentage Crimps (%) 12.6 12.4 12.7 12.5 Knot
Strength (cN) -- -- -- -- Knot Strength Retention (%) -- -- -- --
Single Fiber Initial Tension 0.018 mN/dtex (%) 6.7 2.4 0 1.8 Dry
Heat Shrinkage Percentage Cardability -- .smallcircle.
.smallcircle. .smallcircle. Nonwoven Process Temperature (.degree.
C.) 150 140 140 140 Nonwoven-Area Shrinkage Percentage (%) 12.3 5.2
0 3.5 Nonwoven Mass Per Unit Area (g/m.sup.2) 70 28 28 28
Properties Thickness (mm) 0.20 0.71 0.82 060 Specific Volume
(cm.sup.3/g) 2.85 25.1 29.2 21.6 Strength MD 23 99 98 98 (N/5 cm)
CD -- 20 18 18
TABLE-US-00004 TABLE 4 Sample 14 Sample 15 Sample 16 Sample 17
Sample 18 Sheath MI.sub.A (g/10 min) 58 58 58 61 61 Component
Melting Point (T.sub.A) (.degree. C.) 155.0 155.0 155.0 155.0 155.0
Melting Point (Tf.sub.A) (.degree. C.) 156.7 155.6 155.2 155.4
155.3 Core MI.sub.B (g/10 min) 58 59 59 40 40 Component Melting
Point (T.sub.B) (.degree. C.) 170.5 170.8 170.8 171.0 171.0 Resin
Z-Average Molecular Weight Mz 349,000 357,000 357,000 400,000
400,000 150.degree. C. 1/2 Crystallization Time (seconds) 19 24 24
18 18 Core Melting Poing (Tf.sub.B) (.degree. C.) 172.5 172.2 171.8
171.9 171.7 Component Z-Average Molecular Weight Mz -- -- -- -- --
Fiber 150.degree. C. 1/2 Crystallization Time (seconds) 31.8 13.8
24.0 18.0 18.0 Eccentric Eccentricity (%) 0 0 0 0 0 Form Production
Spinning Temperature (.degree. C./.degree. C.) 185/200 185/190
165/190 185/195 185/195 Conditions (Sheath/Core) Fineness of Spun
Filament (dtex) 5.8 5.8 9.0 8.4 9.0 Drawing Temp. (.degree. C.) 140
140 140 140 140 Draw Ratio (times) 6.5 4.3 4.7 4.7 4.7
Annealing/Drying Temp. (.degree. C.) 60 60 60 60 60 Fiber Length
(mm) 51 51 51 51 51 Spinnability .smallcircle. .smallcircle.
.smallcircle. .DELTA. .smallcircle. Single Fiber Fineness (dtex)
1.0 1.3 2.0 1.8 2.0 Properties Strength (cN/dtex) 4.2 4.1 3.8 3.6
3.9 Elongation (%) 19 19 23 20 21 Number of Crimps (peaks/25 mm)
17.3 16.6 17.2 16.7 17.1 Percentage Crimps (%) 12.3 11.9 12.2 11.8
12.1 Knot Strength (cN) -- -- -- -- -- Knot Strength Retention (%)
-- -- -- -- -- Single Fiber Initial Tension 0.018 mN/dtex (%) 0 0 0
0 0 Dry Heat Shrinkage Percentage Cardability .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle. Nonwoven
Process Temperature (.degree. C.) 156 156 156 156 156 Nonwoven-Area
Shrinkage Percentage (%) 0 0 0 0 0 Nonwoven Mass Per Unit Area
(g/m.sup.3) 30 29 30 28 29 Properties Thickness (mm) 0.55 0.61 0.80
0.78 0.79 Specific Volume (cm.sup.3/g) 18.3 21.2 26.7 27.9 27.2
Strength MD 96 97 96 99 95 (N/5 cm) CD 20 18 19 20 19
TABLE-US-00005 TABLE 5 Sample 19 Sample 20 Sample 21 Sample 22
Sample 23 Sheath MI.sub.A (g/10 min) 29 29 29 29 29 Component
Melting Point (T.sub.A) (.degree. C.) 155.8 155.8 155.8 155.8 155.8
Melting Point (Tf.sub.A) (.degree. C.) 156.1 156.1 156.1 156.1
156.1 Core MI.sub.B (g/10 min) 59 59 59 31 31 Component Melting
Point (T.sub.B) (.degree. C.) 170.8 170.8 170.8 161.9 161.9 Resin
Z-Average Molecular Weight Mz 357,000 357,000 357,000 -- --
150.degree. C. 1/2 Crystallization Time (seconds) 24 24 24 353 353
Core Melting Poing (Tf.sub.B) (.degree. C.) 171.4 171.4 171.4 163.1
163.1 Component Z-Average Molecular Weight Mz -- -- -- -- -- Fiber
150.degree. C. 1/2 Crystallization Time (seconds) 26.3 26.3 26.3
366.0 366.0 Eccentric Eccentricity (%) 0 0 0 0 0 Form Production
Spinning Temperature (.degree. C./.degree. C.) 185/190 185/190
185/190 185/190 185/190 Conditions (Sheath/Core) Fineness of Spun
Filament (dtex) 9.0 8.0 5.8 9.0 33.0 Drawing Temp. (.degree. C.)
140 140 Draw Ratio (times) 4.7 4.7 Annealing/Drying Temp. (.degree.
C.) 60 60 Fiber Length (mm) 51 51 Spinnablity .smallcircle.
.smallcircle. x x x Single Fiber Fineness (dtex) 2.0 1.7 Properties
Strength (cN/dtex) 3.6 3.7 Elongation (%) 20 19 Number of Crimps
(peaks/25 mm) 16.3 15.5 Percentage Crimps (%) 11.0 9.9 Knot
Strength (cN) -- -- Knot Strength Retention (%) -- -- Single Fiber
Initial Tension 0.018 mN/dtex (%) 0 0 Dry Heat Shrinkage Percentage
Cardability .smallcircle. .smallcircle. Nonwoven Process
Temperature (.degree. C.) 156 156 Nonwoven-Area Shrinkage
Percentage (%) 0 0 Nonwoven Mass Per Unit Area (g/m.sup.2) 29.3
28.8 Properties Thickness (mm) 066 0.59 Specific Volume
(cm.sup.3/g) 22.5 20.5 Strength MD 94 98 (N/5 cm) CD 20 18
[0216] All of Samples 10 to 16 presented good spinnability and
relatively small single fiber dry heat shrinkage percentages.
Further, all of Samples 11 to 16 presented good cardability and
small shrinkage upon the thermal adhesion. As to Sample 10, the
wet-laid nonwoven was produced and the shrinkage of this nonwoven
was determined. For this reason, the area shrinkage percentage was
slightly high, but the percentage was a sufficiently practical
level. Sample 17 was an example wherein the Z-average molecular
weight of 400000 was used as the second component, and the
spinnability was slightly deteriorated. Sample 18 wherein the same
second component was used and the spun filament was 9.0 dtex to
give the resultant fiber having a fineness of 2.0 dtex, was spun
well.
[0217] Samples 19 and 20 were spun well, although the
before-spinning melt index was 30 or less. This was because the
before-spinning 150.degree. C. 1/2 crystallization time of the
second component was 24 seconds. However, when the fineness of the
spun filament was made small so that a finer fiber is obtained, the
spinning could not be conducted (Sample 21). In Sample 22, the
spinning could not be conducted when the spun filament was set at
9.0 dtex, since the before-spinning melt index of the first
component was 30 or less and the before-spinning 150.degree. C. 1/2
crystallization time of the second component was long. In Sample
23, the spun filament was set at a relatively large fineness to
improve the spinnability, using the same resins as those used in
Sample 22, but the spinning could not be conducted.
Experimental Example 2
Evaluation of Water Retentivity of Nonwoven
[0218] (Sample NW-1)
[0219] The water retentivity of a nonwoven of the fibers of the
present invention was evaluated. Sample 12 produced in Experimental
Example 1 was used to make a parallel web having a mass per unit
area of about 70 g/m.sup.2 and then the web was subjected to a
hydroentangling treatment. The hydroentangling treatment was
conducted using a nozzle wherein orifices each having a 0.1 mm
diameter were provided in a line at intervals of 0.6 mm. Water
streams were applied once to one surface of the web at a water
pressure of 3 MPa and the water streams were applied once to the
other surface of the web at a water pressure of 3.5 MPa. Then, the
web after the hydroentangling treatment was dried with a hot
air-through thermal treating machine at 160.degree. C. to give a
thermally bonded nonwoven. The resultant nonwoven was cut into a
size of 10 cm.times.10 cm and put into a water bath. The nonwoven
was impregnated with water sufficiently not to float and left in
the water bath for 10 minutes. Then, the nonwoven was taken out and
three corners of the four corners are pinched with clothespins and
suspended. After suspending the nonwoven for 10 minutes, a mass of
the nonwoven was determined and the water retentivity was
calculated from a difference in mass between the nonwoven before
and after being immersed in water. The results are shown in Table
6.
[0220] (Sample NW-2; Comparative)
[0221] A thermoadhesive conjugate fiber (trade name: NBF(H)
produced by Daiwabo Polytec Co., ltd.) wherein the sheath
component/the core component was a high-density
polyethylene/polypropylene, having a fiber length of 51 mm and the
fineness of 1.7 dtex, was prepared. The thermally bonded nonwoven
was produced according to the same procedures as those employed in
the production of Sample NW-1, except that the drying temperature
was set at 140.degree. C. Further, the water retentivity of this
nonwoven was determined by the same method as that employed in
Sample NW-1. The results are shown in Table 6.
TABLE-US-00006 TABLE 6 Mass after Mass per Mass in Leaving Sample
Water Unit Area Thickness Density Dry State in Water for Retention
Sample (g/m.sup.2) (mm) (g/cm.sup.3) (g) 10 min. (g) (%) NW-1 65
0.65 0.100 0.65 4.70 623 NW-2 67 0.86 0.078 0.67 3.98 494
[0222] In general, as the thickness of the nonwoven is larger, the
water retentivity is higher. Although Sample NW-1 is thinner than
Sample NW-2, it showed higher water retentivity. This means that
the conjugate fiber of the present invention can confer excellent
water retentivity to the fiber assembly. The nonwoven showing such
water retentivity is suitable for a wet tissue, a wiper, a mask and
so on.
Experimental Example 3
Evaluation of Slippability of Nonwoven
[0223] (Sample NW-3)
[0224] The slippability of the nonwoven formed from the fibers of
the present invention was evaluated. Sample 1 produced in
Experimental Example 150 mass % and rayon fiber (trade name: Corona
produced by DAIWABO RAYON Co., Ltd., fineness 1.7 dtex, fiber
length 40 mm) 50 mass % were mixed and a parallel web having about
a mass per unit area of about 60 g/m.sup.2 was made using the mixed
fibers. The web was subjected to the hydroentangling treatment. The
hydroentangling treatment was conducted using a nozzle wherein
orifices each having a 0.1 mm diameter were provided in a line at
intervals of 0.6 mm. Water streams were applied to one surface of
the web once at a water pressure of 3 MPa and the water streams
were applied to the other surface of the web once at a water
pressure of 3.5 MPa. Then, the web after the hydroentangling
treatment was dried with a hot air-through thermal treating machine
at 160.degree. C. to give a thermally bonded nonwoven.
[0225] (Sample NW-4; Comparative)
[0226] The thermoadhesive conjugate fiber (trade name: NBF(H)
produced by Daiwabo Polytec Co., ltd.) wherein the sheath
component/the core component was a high-density
polyethylene/polypropylene, having the fiber length of 51 mm and
the fineness of 1.7 dtex was prepared. The thermally bonded
nonwoven was produced according to the same procedures as those
employed in the production of Sample NW-3, except that the drying
temperature was set at 140.degree. C.
[0227] The slippability of Samples NW-3 and NW-4 were evaluated
according to the following procedures:
[0228] (1) The nonwoven was cut into a size of 10 cm.times.10
cm;
[0229] (2) The nonwoven was placed on a glass plate so that the
surface to which the water streams of 3.5 MPa were applied
contacted with the glass plate, and an acrylic plate having a
thickness of 1 mm was placed on the nonwoven and a weight of 200 g
was further placed on the acrylic plate;
[0230] (3) The nonwoven and the acrylic plate were pinched with a
clip and a spring scale (produced by Sankou Seikohjyo Co. Ltd.)
which could measure a load of up to 196 cN was attached to the
clip; and
[0231] (4) The average load when a laminate of the nonwoven and the
acrylic plate was slid 10 cm on the glass plate was read off.
[0232] Sample NW-3 showed 44.1 cN as the load described in (4).
Sample NW-4 showed 53.9 cN as the load described in (4). From these
results, it was found that the nonwoven produced using the
thermoadhesive conjugate fiber of the present invention presented
excellent slippablity and the nonwoven was suitable for a wiper or
the like used in a dry state.
Experimental Example 4
Production and Evaluation of Personal Wiper
[0233] [Sample WP-1]
[0234] 8-segment splittable conjugate fiber consisting of a
combination of PET/HDPE (trade name: DFS(SH) produced by Daiwabo
Polytec Co., ltd.) which has a fineness of 2.2 dtex and a fiber
length of 51 mm was prepared. This splittable conjugate fiber 70
mass % and the conjugate fiber of Sample 1 30 mass % were mixed and
then a parallel web having a mass per unit area of 50 g/m.sup.2 was
made. The web was subjected to the hydroentangling treatment to
entangle the fibers and divide the splittable conjugate fiber to
form ultrafine fibers, using a nozzle wherein orifices each having
a 0.1 mm diameter were provided in a line at intervals of 0.6 mm.
Water streams were applied to one surface of the web once at a
water pressure of 3 MPa, and the water streams were applied to the
other surface of the web once at a water pressure of 3 MPa. Next,
the web after the hydroentangling treatment was dried with a hot
air-through thermal treating machine at 100.degree. C. to give a
hydroentangled nonwoven. In this nonwoven, the fibers were not
thermally bonded.
[0235] [Sample WP-2: Comparative]
[0236] A parallel web having a mass per unit area of 50 g/m.sup.2
was made only from the splittable conjugate fibers used in the
production of Sample WP-1. This web was subjected to the
hydroentangling treatment to divide the splittable conjugate fiber.
The hydroentangling treatment was conducted using a nozzle wherein
orifices each having a 0.1 mm diameter were provided in a line at
intervals of 0.6 mm. Water streams were applied to the one surface
of the web once at a water pressure of 3 MPa and the water streams
were applied to the other surface of the web once at a water
pressure of 3 MPa. Then the web after the hydroentangling treatment
was dried with a hot air-through thermal treating machine at
100.degree. C. to give a hydroentangled nonwoven.
[0237] [Sample WP-3: Comparative]
[0238] A parallel web having a mass per unit area of 50 g/m.sup.2
was made only from cotton (trade name: MS-D produced by MARUSAN
INDUSTRY CO., LTD.) and this web was subjected to the
hydroentangling treatment. The hydroentangling treatment was
conducted using a nozzle wherein orifices each having a 0.1 mm
diameter were provided in a line at intervals of 0.6 mm. Water
streams were applied to one surface of the web once at a water
pressure of 2.5 MPa and the water streams were applied to the other
surface of the web once at a water pressure of 2.5 MPa. Next, the
web after the hydroentangling treatment was dried using a hot
air-through thermal treating machine at 100.degree. C. to give a
hydroentangled nonwoven.
[0239] The properties of the three samples were evaluated when the
samples were used as the wiper for removing blot from skin of a
person. Specifically, the evaluation was conducted according to the
following procedures:
[0240] (1) Lip rouge was over painted three times on a left palm
and left for three minutes;
[0241] (2) The sample was cut into a size of 5 cm.times.10 cm
[0242] (the lengthwise direction (MD).times.crosswise direction
(CD));
[0243] (3) The lip rouge was wiped off by rubbing the left palm
three times by means of the sample applying a little pressure. The
sample and the left palm were observed and the wiping-ability was
evaluated according to the following standards;
[0244] 1: Much blot remained;
[0245] 2: Blot left on the left palm was noticeable;
[0246] 3: Much blot was transferred to the surface of the sample,
but a little blot remained (slightly noticeable);
[0247] 4: Much blot was transferred to the surface of the sample
and a tiny amount of blot remained (not noticeable);
[0248] 5: Much blot was transferred into the sample and a tiny
amount of blot remained (not noticeable).
[0249] Further, the similar wiping-ability was evaluated by
over-painting eyebrow on the left palm.
[0250] Furthermore, the feel of each sample was evaluated according
to the following standards:
[0251] 1: Hard and rough;
[0252] 2: Hard and slightly rough;
[0253] 3: Slightly hard and slightly rough;
[0254] 4: Soft and slightly rough;
[0255] 5: Soft and not rough.
[0256] Furthermore, the rigidity of each sample was determined
using a handleometer (model type HOM-200, manufactured by Daiei
Kagaku Seiki Seisakusho Co., Ltd.). More specifically, a test piece
of 20 cm.times.17.5 cm (the lengthwise direction (MD).times.the
crosswise direction (CD)) was set on a slit of a 10 mm width
perpendicular to the slit and the test piece was pushed by 8 mm at
a position shifted by 6.7 cm from the side of the test piece (at a
position of one third of the testing width) using a blade of a
penetrator and a resistance value was measured as the stiffness.
The resistance values during the push were measured at two
different points for each of the lengthwise direction and the
crosswise direction (CD) respectively of one sample, and the sum of
the measured four values was evaluated as the rigidity.
[0257] The evaluation results are shown in Table 7.
TABLE-US-00007 TABLE 7 Mass per Unit Area Thickness Rigidity
Wiping-Ability Sample (g/m.sup.2) (mm) Feeling (g) Rouge Eyebrow
WP-1 54 0.72 5 18.9 5 5 WP-2 54 0.76 5 22.1 5 5 WP-3 48 0.65 3 26.1
3 3
[0258] Sample WP-3 made of cotton that is widely used in a sheet
for removing cosmetics were inferior in feeling and wiping-ability
compared to the other samples and had a large rigidity and hard and
rough feeling. In contrast, Sample WP-2 which contains ultrafine
fibers formed by division of the splittable conjugate fiber had
good feeling and wiping-ability, as already known to those skilled
in the art. Sample WP-1 containing the conjugate fiber of the
present invention presented the feeling and the wiping-ability
equivalent to those of Sample WP-2 although the content of the
splittable fibers (that is, the ultrafine fibers) in Sample WP-1
was smaller than that in Sample WP-2. Further, the rigidity of
Sample WP-1 is the smallest among the three samples. Therefore,
Sample WP-1 was very soft. Furthermore, as shown in Experimental
Example 3, since the conjugate fiber of the present invention
improved the slippability of the nonwoven, Sample WP-1 was an
excellent wiper which enabled the blot to be removed by lightly
wiping the skin therewith. These mean that the conjugate fiber of
the present invention is suitable for constituting the wiper.
Experimental Example 5
Evaluation of Impersonal Wiper
[0259] [Sample WP-4]
[0260] 8-segment splittable conjugate fiber consisting of a
combination of PET/HDPE (trade name: DFS(SH) produced by Daiwabo
Polytec Co., ltd.) having a fineness of 2.2 dtex and a fiber length
of 51 mm was prepared. This splittable conjugate fiber 70 mass %
and the conjugate fiber of Sample 1 30 mass % were mixed and then
two parallel webs each of which had a mass per unit area of 27
g/m.sup.2 were made. A tissue (produced by Havix Corporation)
having a mass per unit area of 17 g/m.sup.2 which was made from
wood pulp was sandwiched with these two webs to give a a laminated
web of three-layer structure.
[0261] This laminated web was subjected to the hydroentangling
treatment to entangle the fibers and divide the splittable
conjugate fiber to form ultrafine fibers. The hydroentangling
treatment was conducted using a nozzle wherein orifices each having
a 0.1 mm diameter are provided in a line at intervals of 0.6 mm.
Water streams were applied to one surface of the web once at a
water pressure of 3 MPa and the water streams were applied to the
other surface of the web once at a water pressure of 3.5 MPa. Then
the web after the hydroentangling treatment was dried with a hot
air-through thermal treating machine at 100.degree. C. to give a
hydroentangled nonwoven. In this nonwoven, the fibers were not
thermally bonded.
[0262] [Sample WP-5]
[0263] 16-segment splittable conjugate fiber consisting of a
combination of PET/PP (trade name: DF-1 produced by Daiwabo Polytec
Co., ltd.) having a fineness of 3.3 dtex and a fiber length of 51
mm was prepared. A hydroentangled nonwoven of laminated structure
was produced according to the same procedures as those employed in
the production of Sample WP-4, except that only this splittable
conjugate fiber was used.
[0264] [Sample WP-6]
[0265] A hydroentangled nonwoven of laminate structure was produced
according to the same procedures as those employed in the
production of Sample WP-4, except that only the splittable fiber
used in the production of Sample WP-4 was used.
[0266] The performance of each of these samples was evaluated when
using each sample as a wiper to remove dirt adhered to a surface of
a impersonal object. Specifically, the evaluation was conducted
according to the following procedures:
[0267] The nonwoven was cut into a size of 20 cm.times.60 cm (the
crosswise direction (CD).times.the lengthwise direction (MD)) and
folded in eightmo. Then, the sample was impregnated with a 50%
aqueous solution wherein "Fukupika Spray Wax" (trade name)
(produced by SOFT 99 Corporation) was diluted with water. The
sample was impregnated with the aqueous solution of 250 mass %
relative to the mass of the sample. The wetted sample was moved
back and forth ten times on a portion of painted surface of a car
body to remove the dirt. The operation for removing the dirt was
repeated twice. Further, the sample was moved back and forth ten
times on another portion of the painted surface of the car body,
while lightness of wiping, how liquid is released, kink, fuzz,
liquid remain, and wiping-ability were evaluated according to the
following standards:
[0268] [Lightness]
[0269] 1 Heavy and difficult to use for wiping operation;
[0270] 2 Little heavy, but no problem to use for wiping
operation;
[0271] 3 Light, but little resistance feeling;
[0272] 4 Light and easy to use for wiping operation.
[0273] [How Liquid is Discharged]
[0274] 1 Liquid is discharged at one time, and can be used for
wiping only a small area;
[0275] 2 Liquid is discharged slightly more, and can be used for
wiping a not-large area;
[0276] 3 Liquid is discharged adequately, but can be used for
wiping a slightly-reduced area;
[0277] 4 Liquid is discharged adequately, and can be used for
wiping a large area broad.
[0278] [Kink]
[0279] 1 Kink starts to be made just after starting wiping;
[0280] 2 Kink does not occur when starting wiping, but kink occurs
slightly after a short time;
[0281] 3 kink does not occur when starting wiping, but very slight
kink occurs after a short time;
[0282] 4 Very slight kink occurs when liquid in the sample starts
to evaporate.
[0283] [Fuzz]
[0284] 1 Fuzz generates;
[0285] 2 A little fuzz generates during the use of the sample;
[0286] 3 Fluff generates on the sample surface, but fuzz does not
generate during the use of the sample;
[0287] 4 A little fluff generates.
[0288] [Liquid Remain]
[0289] 1 Water droplets on the object being wiped after wiping are
large and difficult to dry;
[0290] 2 Water droplets on the object being wiped after wiping are
slightly large and require a slightly long time for drying;
[0291] 3 Water droplets on the object being wiped after wiping are
small and dry in a little while;
[0292] 4 Water droplets on the object being wiped after wiping are
minute and dry in a little while.
[0293] [Wiping-Ability]
[0294] 1 Dirt cannot be wiped off cleanly;
[0295] 2 Dirt can be wiped off cleanly after moving the sample back
and forth five or six times;
[0296] 3 Dirt can be wiped off cleanly after moving the sample back
and forth two or three times;
[0297] 4 Dirt can be wiped off cleanly after moving one or two
times.
[0298] The results of evaluation are shown in Table 8.
TABLE-US-00008 TABLE 8 Lightness How Liquid (Wiping Is Liquid
Wiping- Sample Comfortableness) Discharged Kink Lint Remain Ability
Total WP-4 3 4 3 3 4 3 20 WP-5 4 2 2 2 2 2 14 WP-6 4 4 2 3 4 3
20
[0299] Although Sample WP-4 had a construction wherein the upper
and the lower layers contained the conjugate fibers of the present
invention which were not the splittable fibers, it presented more
excellent wiping-ability than Sample WP-5 wherein the upper and the
lower layers consist only of the splittable fibers. Further, Sample
WP-4 showed better results for all items except for "lightness"
than Sample WP-5. Sample WP-6 was formed only from the splittable
conjugate fiber which constituted Sample 4 and had more ultrafine
fibers than Sample WP-4. Nevertheless, Sample WP-4 presented the
same properties as those of Sample WP-6. These mean that the
conjugate fiber of the present invention is suitable for
constituting the wiper.
Experimental Example 6
Evaluation of Compression Recoverability of Nonwoven
[0300] [Sample MA-1: Comparative]
[0301] A high-elastic PET fiber (trade name: elk produced by TEIJIN
FIBERS LIMITED, fineness 6.6 dtex, fiber length 64 mm) 30 mass %
and a hollow PET fiber (trade name: H18F produced by Unitika Ltd.,
fineness 6.7 dtex, fiber length 51 mm) 50 mass % and a latently
crimpable PET fiber (trade name: C81, produced by Unitika Ltd.,
fineness 2.8 dtex, fiber length 51 mm) 20 mass % were mixed, and a
parallel web was made using this mixed fibers and then the webs
were laminated using a cross layer to give a laminated web having a
mass per unit area of 800 g/m.sup.2. The laminated web was
subjected to a thermal treatment for seven minutes with an oven at
200.degree. C. to give a bulky sponge-like nonwoven having a
thickness of 28 mm.
[0302] [Sample MA-2]
[0303] A parallel web was made from the sheath-core conjugate fiber
of Sample 3 produced in Experimental Example 1. Then, the webs were
laminated with a cross layer to give a laminated web having a mass
per unit area of 800 g/m.sup.2. The laminated web was subjected to
a thermal treatment for seven minutes at 156.degree. C. to give a
bulky sponge-like nonwoven having a thickness of 25 mm.
[0304] Each of the samples was cut into a size of 10 cm.times.10 cm
and a weight of 5.6 kg was placed thereon and left for 24 hours.
Then, the weight was removed and the thickness of the nonwoven was
determined over time to evaluate the bulk recoverability. The
results of the evaluation are shown in Table 9.
TABLE-US-00009 TABLE 9 After Removing Weight 0 5 10 20 60 150 360
24 Sample Initial Weighted min. min min. min. min min min. hours
MA-1 Thickness 28.0 8.0 24.0 25.0 25.5 26.0 26.5 26.5 27.0 27.0
(mm) Recovery -- -- 85.7 89.3 91.1 92.9 94.6 94.6 24.0 96.4 Rate
(%) MA-2 Thickness 25.0 15.0 19.0 20.0 21.0 22.0 23.0 23.5 24.0
25.0 (mm) Recovery -- -- 76.0 80.0 84.0 88.0 92.0 94.0 96.0 100.0
Rate (%)
[0305] Sample MA-1 made for comparison containing the high elastic
fiber and the latently crimpable fiber was bulky enough to be used
as, for example, a bed mat, and had high compression
recoverability, particularly high initial bulk recoverability. On
the other hand, the thermoadhesive conjugate fiber of the present
invention showed a bulk recovery percentage of 100% 24 hours after
removing weight and presented high bulk recoverability although it
does not have latently crimpability and elasticity. The nonwoven
presenting such bulk recoverability is suitable for using as a
cushion material, a brassier pad and so on.
Experimental Example 7
Evaluation of Crease Resistance and Rigidity of Nonwoven
[0306] [Sample WR-1: Comparative]
[0307] A parallel carded web having a mass per unit area of 28.7
g/m.sup.2 was made from a concentric sheath-core conjugate fiber
wherein sheath/core was HDPE/PET and sheath:core (mass ratio) was
1:1 (trade name: NBF(SH) produced by Daiwabo Polytec Co., ltd.,
fineness 2.2 dtex, fiber length 51 mm). This web was subjected to a
thermal treatment using a hot air-through thermal treating machine
at 140.degree. C. for 12 seconds to give a thermally bonded
nonwoven with a thickness of 1.45 mm.
[0308] [Sample WR-2]
[0309] A parallel carded web having a mass per unit area of 27.4
g/m.sup.2 was made from the sheath-core conjugate fiber of Sample 3
produced in Experimental Example 1. This web was subjected to a
thermal treatment at 156.degree. C. for 12 seconds to give a
thermally bonded nonwoven having a thickness of 0.85 mm.
[0310] As to each of the two samples, the crease resistance
percentage (wire method) was determined according to JIS L 1085,
and the rigidity was determined according to JIS L 1096 (45.degree.
cantilever method). The results are shown in Table 10.
TABLE-US-00010 TABLE 10 Mass per Crease Unit Area Thickness Angle
.alpha. Resistance Rigidity Sample (g/m.sup.2) (mm) (.degree.)
Percentage (%) (mm) WR-1 28.7 1.45 145 80.6 120 WR-2 27.4 0.85 178
99.0 160
[0311] Sample WR-1 made from a general thermoadhesive conjugate
fiber was soft and had a tendency of creasing. In contrast, Sample
WR-2 made from the thermoadhesive conjugate fiber of the present
invention had a higher rigidity than Sample WR-1. Further, this
sample presented high crease resistance such that, when the sample
was released from folded state, the sample opened instantly and
returned to an original shape without crease. The nonwoven having
such high crease resistance is suitable for a constituent for a
hygiene product such as a menstrual sanitary product and a paper
diaper (for example, a sheet for retaining a shape of the hygiene
product) and an interfacing.
Experimental Example 8
Production of Molded Article
[0312] A parallel carded web was made from the fiber of Sample 12
produced in Experimental Example 1 and the webs were laminated
using a cross layer to give a laminated web having a mass per unit
area of 200 g/m.sup.2. Then, the laminated web was cut into a size
of 20 cm.times.20 cm.
[0313] Two hemisphere tea strainers made of metal mesh were
prepared, one being of a dimension of 060 mm.times.a depth of 60
mm, and the other being of a dimension of 050 mm.times.a depth of
55 mm. The two tea strainers were stacked with the laminated web
interposed between the strainers. The web sandwiched with the two
tea strainers was subjected to a thermal treatment at 161.degree.
C. for 15 minutes with a batch-type hot air-through thermal
treating machine. After the thermal treatment, the tea strainers
were removed, and thereby a cup-shaped molded article having a wall
thickness of 5 mm and a round bottom was obtained. Such a molded
article is suitable for being used as, for example, a filter.
INDUSTRIAL APPLICABILITY
[0314] The thermoadhesive conjugate fiber of the present invention
is one wherein the respective components are formed from
polyoxymethylene-based polymers, whereby a fiber assembly
(particularly a nonwoven) wherein the fibers are bonded only with a
polyoxymethylene-based polymer can be produced. Further, the
thermoadhesive conjugate fiber of the present invention confers, to
the fiber assembly, high water retentivity, high slippability,
crease resistance, and bulk recoverability and favorable
wiping-ability. Therefore, the thermoadhesive conjugate fiber of
the present invention is useful for producing the fiber assembly
applicable to various uses for which heat resistance and chemical
resistance are desired.
* * * * *