U.S. patent application number 16/964243 was filed with the patent office on 2021-02-11 for spunbonded nonwoven fabric.
This patent application is currently assigned to Toray Industries, Inc.. The applicant listed for this patent is Toray Industries, Inc.. Invention is credited to Yoshitaka Aranishi, Yoshitsugu Funatsu, Kentaro Kajiwara, Hiroo Katsuta, Yuka Nishiguchi.
Application Number | 20210040660 16/964243 |
Document ID | / |
Family ID | 1000005206771 |
Filed Date | 2021-02-11 |
United States Patent
Application |
20210040660 |
Kind Code |
A1 |
Nishiguchi; Yuka ; et
al. |
February 11, 2021 |
SPUNBONDED NONWOVEN FABRIC
Abstract
The present invention relates to a spun-bonded nonwoven fabric
including a monocomponent fiber including a copolymerized polyester
based resin in which 5 weight % or higher and 40 weight % or lower
of a polyethylene glycol is copolymerized with a polyester based
resin, in which the spun-bonded nonwoven fabric has a .DELTA.MR of
0.5% or higher and 15% or lower.
Inventors: |
Nishiguchi; Yuka; (Shizuoka,
JP) ; Katsuta; Hiroo; (Shizuoka, JP) ;
Funatsu; Yoshitsugu; (Shiga, JP) ; Aranishi;
Yoshitaka; (Shizuoka, JP) ; Kajiwara; Kentaro;
(Otsu-shi, Shiga, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toray Industries, Inc. |
Tokyo |
|
JP |
|
|
Assignee: |
Toray Industries, Inc.
Tokyo
JP
|
Family ID: |
1000005206771 |
Appl. No.: |
16/964243 |
Filed: |
January 23, 2019 |
PCT Filed: |
January 23, 2019 |
PCT NO: |
PCT/JP2019/002142 |
371 Date: |
July 23, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D04H 3/011 20130101;
D04H 3/14 20130101; D01F 6/92 20130101 |
International
Class: |
D04H 3/011 20060101
D04H003/011; D01F 6/92 20060101 D01F006/92; D04H 3/14 20060101
D04H003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 25, 2018 |
JP |
2018-010254 |
Sep 28, 2018 |
JP |
2018-183755 |
Claims
1. A spun-bonded nonwoven fabric comprising a monocomponent fiber
comprising a copolymerized polyester based resin in which 5 weight
% or higher and 40 weight % or lower of a polyethylene glycol is
copolymerized with a polyester based resin, wherein the spun-bonded
nonwoven fabric has a .DELTA.MR of 0.5% or higher and 15% or
lower.
2. The spun-bonded nonwoven fabric according to claim 1, wherein
the polyester based resin is a polyethylene terephthalate.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is the U.S. National Phase application of
PCT/JP2019/002142, filed Jan. 23, 2019, which claims priority to
Japanese Patent Application No. 2018-010254, filed Jan. 25, 2018
and Japanese Patent Application No. 2018-183755, filed Sep. 28,
2018, the disclosures of each of these applications being
incorporated herein by reference in their entireties for all
purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to a spun-bonded nonwoven
fabric that is soft and excellent in sense of touch.
BACKGROUND OF THE INVENTION
[0003] Generally, a sanitary nonwoven fabric such as a paper diaper
or a sanitary napkin is required to have good texture and softness
for touch on skin when it is worn.
[0004] Filament nonwoven fabrics such as spun-bonded nonwoven
fabrics have been used for various applications owing to their
properties such as strength, air permeability and bending
resistance, and their high productivity. Various resins such as
polyester based resins or polyolefin based resins have been used as
the raw materials of the filament nonwoven fabrics. Among them,
copolymerized polyester based resins have been considered to be
used for spun-bonded nonwoven fabrics.
[0005] For example, a nonwoven fabric composed of fibers containing
a thermoplastic water-absorbing resin having polyalkylene glycol
copolymerized is proposed (see Patent Literature 1).
[0006] In addition, a nonwoven fabric composed of core-sheath
fibers having, as a sheath component, a copolymerized polyester
based resin of polyalkylene glycol and aromatic polyester and
having a polyester based resin as a core component is proposed (see
Patent Literature 2).
PATENT LITERATURE
[0007] Patent Literature 1: JP-A-2006-299424 [0008] Patent
Literature 2: JP-A-2003-336156
SUMMARY OF THE INVENTION
[0009] However, in the technique disclosed in Patent Literature 1,
there is a problem that when a resin in which 45 mass % of
polyethylene glycol has been copolymerized with polytetramethylene
terephthalate is used as the copolymerized polyester based resin as
shown in the description thereof by way of example, water
absorbency of fibers containing the resin is so high that a sticky
sense of touch is provided to a nonwoven fabric formed of the
fibers, thereby resulting in poor texture.
[0010] On the other hand, in the technique disclosed in Patent
Literature 2, there is a problem that since a rigid polyester resin
is used in a core portion, the bending rigidity of fibers is so
high that the softness deteriorates in a spun-bonded nonwoven
fabric formed of the fibers.
[0011] Therefore, in consideration of the aforementioned problems,
an object of the present invention is to provide a spun-bonded
nonwoven fabric that is soft and excellent in sense of touch.
[0012] The present inventors made intensive studies in order to
attain the foregoing objects. As a result, the present inventors
found that softness and a sense of touch can be improved on a large
scale in a copolymerized polyester based resin in which a specific
amount of polyethylene glycol has been copolymerized.
[0013] The present invention was completed based on the
aforementioned findings. In exemplary embodiments of the present
invention, the following inventive configurations are provided.
[0014] A spun-bonded nonwoven fabric according to an embodiment of
the present invention is a spun-bonded nonwoven fabric including a
monocomponent fiber including a copolymerized polyester based resin
in which 5 weight % or higher and 40 weight % or lower of a
polyethylene glycol is copolymerized with a polyester based resin,
in which the spun-bonded nonwoven fabric has a .DELTA.MR of 0.5% or
higher and 15% or lower.
[0015] According to a preferred embodiment of the present
invention, the polyester based resin is a polyethylene
terephthalate.
[0016] In the present invention, it is possible to obtain a
spun-bonded nonwoven fabric capable of further improving softness,
having a less sticky, smooth and excellent sense of touch. Further,
processability into a sheet is excellent because the strength of
fibers is enhanced, thereby improving productivity.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0017] A nonwoven fabric according to an embodiment of the present
invention is a spun-bonded nonwoven fabric including a
monocomponent fiber including a copolymerized polyester based resin
in which 5 weight % or higher and 40 weight % or lower of a
polyethylene glycol is copolymerized with a polyester based resin.
The spun-bonded nonwoven fabric is characterized in that a
.DELTA.MR of the spun-bonded nonwoven fabric is 0.5% or higher and
15% or lower.
[0018] Examples of the polyester based resin that can be used in
embodiments of the present invention include polyethylene
terephthalate, polypropylene terephthalate, polybutylene
terephthalate, and polylactic acid. Particularly, for a preferred
embodiment, polyethylene terephthalate is used. When polyethylene
terephthalate is used, the resin can be made into fibers that have
excellent softness and an excellent sense of touch. In addition,
since the resin can be drawn at a high spinning speed, the fibers
tend to develop orientation crystallization and also have
mechanical strength.
[0019] The number-average molecular weight of the polyethylene
glycol contained in the copolymerized polyester based resin used in
the present invention is preferably 4,000 or more and 20,000 or
less. When the number-average molecular weight of the polyethylene
glycol is set at 4,000 or more and more preferably at 5,000 or
more, moisture absorbency can be given to the copolymerized
polyester based resin so that a nonwoven fabric having a good sense
of touch can be obtained. On the other hand, when the
number-average molecular weight of the polyethylene glycol is set
at 20,000 or less and more preferably at 10,000 or less, the
copolymerized polyester based resin has an excellent fiber-forming
property. Thus, the spun-bonded nonwoven fabric has few defects.
Assume that the number-average molecular weight of the polyethylene
glycol contained in the copolymerized polyester resin in the
present invention designates a value measured and calculated in the
following method.
(1) Sampling about 0.05 g of the copolymerized polyester based
resin; (2) Adding 1 mL of 28% ammonia water to the sample, and
heating the sample at 120.degree. C. for 5 hours to melt the
sample; (3) After radiational cooling, adding 1 mL of purified
water and 1.5 mL of 6 mol/L hydrochloric acid, and making up a
constant volume of 5 mL with purified water; (4) Putting the
solution in a centrifugal separator, and then filtrating the
solution with a filter having a mesh hole diameter of 0.45 .mu.m;
(5) Measuring a molecular weight distribution in the filtrate by
GPC; (6) Determining the number-average molecular weight of
polyethylene glycol by use of a calibration curve of molecular
weight prepared using a standard sample having known molecular
weight; and (7) In addition, determining the quantity of the
polyethylene glycol by use of a calibration curve of solution
concentration prepared by a polyethylene glycol aqueous solution,
and calculating the copolymerization amount of the polyethylene
glycol in the copolymerized polymer.
[0020] The copolymerization amount of the polyethylene glycol
contained in the polymerized polyester based resin used in
embodiments of the present invention is characterized by being 5
weight % or higher and 40 weight % or lower. When the
copolymerization amount of the polyethylene glycol is set at 5
weight % or higher and more preferably at 7 weight % or higher, a
nonwoven fabric having excellent softness and an excellent sense of
touch can be obtained. On the other hand, when the copolymerization
amount of the polyethylene glycol is set at 40 weight % or lower
and more preferably at 20 weight % or lower, the resin can be
formed into fibers having heat resistance durable to practical use
and high mechanical strength. The copolymerization amount of the
polyethylene glycol contained in the copolymerized polyester resin
in the present invention designates a value measured by a method
which will be described in Examples.
[0021] Coloring pigment, an antioxidant, a lubricant such as
polyethylene wax, a heat-resistance stabilizer, etc. can be added
to the copolymerized polyester based resin used in the present
invention, so long as the addition thereof does not impair the
effects of the present invention.
[0022] The melting point of the copolymerized polyester based resin
used in the present invention is preferably 200.degree. C. or
higher and 300.degree. C. or lower, and more preferably 220.degree.
C. or higher and 280.degree. C. or lower. When the melting point of
the copolymerized polyester based resin is set preferably at
200.degree. C. or higher and more preferably at 220.degree. C. or
higher, heat resistance durable to practical use can be obtained
easily. On the other hand, when the melting point of the
copolymerized polyester based resin is set preferably at
300.degree. C. or lower and more preferably at 280.degree. C. or
lower, each yarn ejected from a spinneret can be cooled easily to
inhibit fibers from being fused with each other. Thus, the obtained
spun-bonded nonwoven fabric has few defects. The melting point of
the copolymerized polyester based resin in the present invention
designates a value obtained from a peak top temperature in an
endothermic peak obtained by measurement on the condition of a
temperature rise rate of 16.degree. C./min under nitrogen by a
differential scanning calorimetry.
[0023] A method for manufacturing copolymerized polyester in
embodiments of the present invention is a known polymerization
method such as a transesterification method or an esterification
method. In the transesterification method, an ester-forming
derivative of terephthalic acid and ethylene glycol are charged in
a reaction vessel and brought into reaction within a range of
150.degree. C. or higher and 250.degree. C. or lower under the
existence of a transesterification catalyst. After that, a
stabilizer, a polycondensation catalyst, etc. are added, and heated
within a range of 250.degree. C. or higher and 300.degree. C. or
lower under reduced pressure of 500 Pa or lower so as to cause
reaction for 3 hours or more and 5 hours or less. Thus,
copolymerized polyester can be obtained.
[0024] On the other hand, in the esterification method,
terephthalic acid and ethylene glycol are charged in a reaction
vessel, and brought into esterification reaction at 150.degree. C.
or higher and 270.degree. C. or lower under a pressurized nitrogen
atmosphere. After the esterification reaction is terminated, a
stabilizer, a polycondensation catalyst, etc. are added, and heated
within a range of 250.degree. C. or higher and 300.degree. C. or
lower under reduced pressure of 500 Pa or lower so as to cause
reaction for 3 hours or more and 5 hours or less. Thus,
copolymerized polyester can be obtained.
[0025] In the method for manufacturing copolymerized polyester of
the present invention, the timing when the polyethylene glycol is
added is not particularly limited. The polyethylene glycol may be
added together with other raw materials before the esterification
reaction or the transesterification reaction. Alternatively, the
polyethylene glycol is added after the termination of the
esterification reaction or the transesterification reaction and
before the start of the polycondensation reaction.
[0026] In the method for manufacturing copolymerized polyester
according to an embodiment of the present invention, examples of
the transesterification catalyst include zinc acetate, manganese
acetate, magnesium acetate, and titanium tetrabutoxide. Examples of
the polycondensation catalyst include antimony trioxide, germanium
dioxide, and titanium tetrabutoxide.
[0027] It is essential that .DELTA.MR of the spun-bonded nonwoven
fabric according to embodiments of the present invention is 0.5% or
higher and 15% or lower. As a result of earnest researches, the
present inventors found that there is a high correlation between
.DELTA.MR which is a parameter conventionally used as an index of a
moisture absorbing-releasing property of a fiber and a sense of
touch on a spun-bonded nonwoven fabric. When the .DELTA.MR is set
at 0.5% or higher and more preferably at 2% or higher, the
spun-bonded nonwoven fabric is in a state where the surface thereof
moderately has absorbed moisture so that the sense of touch on the
surface thereof becomes a good feeling with moist feeling. On the
other hand, when the .DELTA.MR is set at 15% or lower, more
preferably at 10% or lower and even more preferably at 7% or lower,
the sense of touch is free from stickiness. In addition, when the
.DELTA.MR is set within the aforementioned range, the spun-bonded
nonwoven fabric can have smoothness and softness suitable for its
high-speed production. Thus, the spun-bonded nonwoven fabric can
have excellent high-degree processability.
[0028] The .DELTA.MR can be adjusted by the kind of the polyester
component, the number-average molecular weight of the contained
polyethylene glycol, and the copolymerization amount thereof.
[0029] Assume that the .DELTA.MR in the present invention
designates a value measured and calculated in the following
method.
(1) Freezing and crushing 3 g of a sample to be measured, drying
the sample in a vacuum at a drying temperature of 110.degree. C.
for 24 hours, and measuring absolute dry mass (W.sub.d) of the
sample; (2) Leaving the sample for 24 hours in a constant
temperature and humidity apparatus controlled in a state of
20.degree. C..times.65% R.H., and measuring mass (W.sub.20) of the
sample reaching an equilibrium state; and (3) Next, changing the
settings of the constant temperature and humidity apparatus to
30.degree. C..times.90% R.H., further leaving the sample for 24
hours, then measuring mass (W.sub.30) of the sample, and
calculating the .DELTA.MR based on the following equation.
.DELTA.MR=(W.sub.30-W.sub.20)/W.sub.d (%)
[0030] It is essential that the copolymerized polyester based
fibers forming the spun-bonded nonwoven fabric according to
embodiments of the present invention are monocomponent fibers. When
the fibers are monocomponent fibers, the softness belonging to the
copolymerized polyester based resin is reflected on the spun-bonded
nonwoven fabric so that the spun-bonded nonwoven fabric can have a
soft sense of touch. Further, spinnability is improved in
comparison with composite fibers. Thus, the spun-bonded nonwoven
fabric has few defects.
[0031] The average single fiber diameter of the copolymerized
polyester based fibers forming the spun-bonded nonwoven fabric of
the present invention is preferably 10 .mu.m or more and 16 .mu.m
or less. When the average single fiber diameter is set at 10 .mu.m
or more and more preferably at 11 .mu.m or more, processability at
the time of post-processing can be improved so that the number of
defects can be reduced. On the other hand, when the average single
fiber diameter is set at 16 .mu.m or less and more preferably at 15
.mu.m or less, the sense of touch on the surface of the spun-bonded
nonwoven fabric obtained from the copolymerized polyester based
fibers becomes smooth. In addition, owing to the narrow average
single-fiber diameter, reduction in sectional secondary moment is
also exhibited so that the softness is further improved. However,
when the average single fiber diameter is less than 10 .mu.m,
processability at the time of post-processing deteriorates to
increase the number of defects. Assume that the average single
fiber diameter of the copolymerized polyester based fibers in the
present invention designates a value calculated as follows. That
is, 10 small-piece samples are sampled at random from a nonwoven
web pulled by an ejector, drawn and then collected on a net. The
surfaces of the samples are photographed at a magnification of 500
to 1,000 times by a microscope, and widths of 10 fibers from each
sample are measured. A value (.mu.m) calculated from an arithmetic
average value of the widths of a total of 100 fibers is regarded as
the average single fiber diameter.
[0032] The spun-bonded nonwoven fabric of the present invention has
preferably a bending return property of 0.2 cm-1 or more and 1.0
cm-1 or less. When the bending return property is 1.0 cm-1 or less,
a feeling of fitting to a hand can be obtained at the time of
bending return. When the bending return property is 0.2 cm-1 or
more, moderate resistance against the return can be obtained to
exhibit a natural texture. The bending return property is more
preferably 0.8 cm-1 or less, and even more preferably 0.6 cm-1 or
less. On the other hand, the bending return property is more
preferably 0.3 cm-1 or more, and even more preferably 0.4 cm-1 or
more.
[0033] The bending return property can be controlled by the
aforementioned thermoplastic resin, the additives and the fiber
diameter, and/or, the spinning speed, the mass per unit area, the
apparent density and the bonding method which will be described
later.
[0034] The bending return property of the spun-bonded nonwoven
fabric in the present invention designates a value obtained in the
following equation using bending rigidity (B) and bending
hysteresis (2HB) in each of two directions perpendicular to each
other measured by a bending tester (for example, "KES-FB2" made by
Kato Tech Co., Ltd.).
bending rigidity=(B in direction 1+B in direction 2)/2
bending hysteresis=(2HB in direction 1+2HB in direction 2)/2
bending return property=bending hysteresis/bending rigidity
[0035] The spun-bonded nonwoven fabric of the present invention has
preferably a bending rigidity of 10 .mu.Ncm.sup.2/cm or more and
300 .mu.Ncm.sup.2/cm or less. When the bending rigidity is 300
.mu.Ncm.sup.2/cm or less, the spun-bonded nonwoven fabric can be
bent easily so that a soft sense of touch can be obtained. When the
bending rigidity is 10 .mu.Ncm.sup.2/cm or more, moderate response
to bending can be obtained. The bending rigidity is more preferably
250 .mu.Ncm.sup.2/cm or less, and even more preferably 200
.mu.Ncm.sup.2/cm or less. On the other hand, the bending rigidity
is more preferably 20 .mu.Ncm.sup.2/cm or more, and even more
preferably 30 .mu.Ncm.sup.2/cm or more. The bending rigidity can be
controlled by the aforementioned thermoplastic resin, the additives
and the fiber diameter, and/or, the spinning speed, the mass per
unit area, the apparent density and the bonding method which will
be described later.
[0036] The bending rigidity of the spun-bonded nonwoven fabric in
the present invention designates a value obtained in the following
equation using bending rigidity (B) in each of two directions
perpendicular to each other measured by a bending tester (for
example, "KES-FB2" made by Kato Tech Co., Ltd.).
bending rigidity=(B in direction 1+B in direction 2)/2
[0037] The spun-bonded nonwoven fabric in the present invention has
preferably a tensile elasticity of 5 MPa or more and 100 MPa or
less. When the tensile elasticity is 100 MPa or less, the
spun-bonded nonwoven fabric can be deformed easily so that a sense
of touch on the spun-bonded nonwoven fabric following a hand can be
obtained. When the tensile elasticity is 5 MPa or more, a sense of
moderate resistance can be obtained. The tensile elasticity is more
preferably 80 MPa or less, and even more preferably 60 MPa or less.
On the other hand, the tensile elasticity is more preferably 7 MPa
or more, and more preferably 9 MPa or more. The tensile elasticity
can be controlled by the aforementioned thermoplastic resin, the
additives and the fiber diameter, and/or, the spinning speed, the
mass per unit area, the apparent density and the bonding method
which will be described later.
[0038] The tensile elasticity of the spun-bonded nonwoven fabric in
the present invention is an arithmetic average of tensile
elasticities obtained in two directions perpendicular to each other
by tensile testing with a distance of at least 5 cm between grips
performed according to "6.3.1 Normal Time" of "6.3 Tensile Strength
and Elongation Rate (ISO method)" of "General Nonwoven Fabric
Testing Method" of JIS L1913: 2010. The tensile elasticity
designates a value obtained as follows. That is, a curve
(stress-stain curve) is obtained by a load and an elongation rate.
The largest inclination (where increase of the load is large
relatively to the elongation rate) in a region where the elongation
rate is 20% or lower is obtained. The obtained inclination is
divided by a sectional area to thereby obtain the tensile
elasticity. Incidentally, the sectional area in the present
invention is a product of a sample width and a thickness (T.sub.o)
measured under a load of 0.5 g/cm.sup.2 by a compression tester
(for example, "KES-FB3" made by Kato Tech Co., Ltd.).
[0039] In the spun-bonded nonwoven fabric of the present invention,
the tensile strength per unit mass per unit area is preferably 0.3
(N/5 cm)/(g/m.sup.2) or more, and 10 (N/5 cm)/(g/m.sup.2) or less.
When the tensile strength per unit mass per unit area is 0.3 (N/5
cm)/(g/m.sup.2) or more, the spun-bonded nonwoven fabric can
withstand the performance of passing through a process for
manufacturing a paper diaper or the like and use as a product. When
the tensile strength per unit mass per unit area is 10 (N/5
cm)/(g/m.sup.2) or less, the spun-bonded nonwoven fabric can also
have softness. The tensile strength per unit mass per unit area is
more preferably 8 (N/5 cm)/(g/m.sup.2) or less, and even more
preferably 6 (N/5 cm)/(g/m.sup.2) or less. On the other hand, the
tensile strength per unit mass per unit area is more preferably 0.4
(N/5 cm)/(g/m.sup.2) or more, and even more preferably 0.5 (N/5
cm)/(g/m.sup.2) or more. The tensile strength per unit mass per
unit area can be controlled by the aforementioned thermoplastic
resin, the additives and the fiber diameter, and/or, the spinning
speed, the mass per unit area, the apparent density and the bonding
method which will be described later.
[0040] The tensile strength of the spun-bonded nonwoven fabric in
the present invention is a value obtained by dividing, by the mass
per unit area, an average of tensile strengths (strengths at which
a sample is broken) obtained in two directions perpendicular to
each other by tensile testing with a distance of at least 5 cm
between grips performed according to "6.3.1 Normal Time" of "6.3
Tensile Strength and Elongation Rate (ISO method)" of "General
Nonwoven Fabric Testing Method" of JIS L1913: 2010.
[0041] For a preferred embodiment, the bending resistance of the
spun-bonded nonwoven fabric of the present invention is 70 mm or
lower. When the bending resistance is set preferably at 70 mm or
lower, more preferably at 67 mm or lower and even more preferably
at 64 mm or lower, satisfactory softness can be obtained
particularly when the spun-bonded nonwoven fabric is used as a
nonwoven fabric for a sanitary material. When the bending
resistance is made too low, handlability of the nonwoven fabric may
deteriorate. Therefore, the lower limit of the bending resistance
is preferably 10 mm or higher. The bending resistance can be
adjusted by the resin, the mass per unit area, the average
single-fiber diameter and embossing rolls (degree of press bonding,
temperature, and linear pressure). The bending resistance in the
present invention is calculated according to a "6.7.3 41.5.degree.
C. antilever Method" of "6.7 Bending Resistance" of "General
Nonwoven Fabric Testing Method" of JIS L1913: 2010. A calculation
method will be described. First, five test pieces each measuring 25
mm in width by 150 mm are sampled. Each test piece is placed on a
horizontal table having a slope of 45.degree. such that its short
sides are aligned with a base line of a scale. Next, the test piece
is manually slid along the slope. As soon as a center point of one
end of the test piece touches the slope, the moving length of the
position of the other end is read by the scale. Such moving lengths
are measured as to the both sides of the five test pieces. An
average value calculated from the moving lengths is used as the
bending resistance in the present invention.
[0042] The mass per unit area of the spun-bonded nonwoven fabric of
the present invention is preferably set at 5 g/m.sup.2 or more and
50 g/m.sup.2 or less. For a more preferred embodiment, the mass per
unit area is set at 10 g/m.sup.2 or more and 30 g/m.sup.2 or less.
When the mass per unit area is within the aforementioned range,
softness can be exhibited suitably in the spun-bonded nonwoven
fabric. Assume that the mass per unit area in the present invention
designates a value obtained as follows. That is, in accordance with
"6.2 Mass per Unit Area" of "General Nonwoven Fabric Testing
Method" of JIS L1913: 2010, three test pieces each measuring 20 cm
by 25 cm are sampled per sample width of 1 m, mass (g) of each test
piece in a normal state is measured. An arithmetic average value of
the measured masses is expressed by mass per m.sup.2 (g/m.sup.2).
The value obtained thus is regarded as the mass per unit area.
[0043] The spun-bonded nonwoven fabric of the present invention has
preferably an apparent density of 0.01 g/cm.sup.3 or more and 0.30
g/cm.sup.3 or less. When the apparent density is 0.01 g/cm.sup.3 or
more, form stability applicable to practical use can be obtained
easily, and the bending return rate can be reduced easily. When the
apparent density is 0.30 g/cm.sup.3 or less, air permeability and
softness can be obtained easily. The apparent density is more
preferably 0.25 g/cm.sup.3 or less, and even more preferably 0.20
g/cm.sup.3 or less. On the other hand, the apparent density is more
preferably 0.03 g/cm.sup.3 or more, and even more preferably 0.05
g/cm.sup.3 or more.
[0044] The apparent density of the spun-bonded nonwoven fabric in
the present invention is a value obtained by dividing the mass per
unit area by the thickness.
[0045] The spun-bonded nonwoven fabric of the present invention can
be used broadly for a medical sanitary material, a living material,
an industrial material, etc. The spun-bonded nonwoven fabric is
excellent in softness and good in sense of touch and is also good
in processability owing to few defects as a product. Therefore, the
spun-bonded nonwoven fabric can be used suitably particularly for a
sanitary material. Specifically, the spun-bonded nonwoven fabric
can be used as a disposable diaper, a sanitary item, a base fabric
of a poultice material, etc.
[0046] Next, a method for manufacturing the spun-bonded nonwoven
fabric of the present invention will be described along its
specific example.
[0047] A spun-bonding method for manufacturing a spun-bonded
nonwoven fabric is a manufacturing method requiring the steps of:
melting a resin; spinning the resin from a spinneret; then cooling
and solidifying the resin to obtain yarns; pulling the yarns by an
ejector to draw the yarns; collecting the yarns on a moving net to
thereby form the yarns into a nonwoven fiber web; and thermally
bonding the nonwoven fiber web.
[0048] Various shapes such as round shapes or rectangular shapes
can be used as the shapes of the spinneret and the ejector to be
used. Among them, a combination of a rectangular spinneret and a
rectangular ejector are used in a preferred embodiment because the
use amount of compressed air can be comparatively reduced and the
yarns can be prevented from being easily fused with each other or
from easily rubbing on each other.
[0049] In the present invention, after the copolymerized polyester
based rein is dried in a vacuum, the spinning temperature at which
the copolymerized polyester based resin is melted and spun is
preferably 240.degree. C. or higher and 320.degree. C. or lower,
more preferably 250.degree. C. or higher and 310.degree. C. or
lower, further preferably 260.degree. C. or higher and 300.degree.
C. or lower. When the spinning temperature is set within the
aforementioned range, the resin can be brought into a stable
melting state to obtain excellent spinning stability.
[0050] The copolymerized polyester based resin is melted and
weighed in an extruder, fed to the spinneret, and spun out as
filament fibers.
[0051] Yarns of the filament fibers spun out are next cooled.
Examples of methods for cooling the yarns spun out include a method
for forcibly blowing cool air to the yarns, a method for naturally
cooling the yarns at an atmospheric temperature around the yarns,
and a method for adjusting the distance between the spinneret and
the ejector. A method in which those methods are combined may be
used. In addition, the cooling conditions may be suitably adjusted
and used in consideration of the discharge rate per single-hole of
the spinneret, the spinning temperature, the atmospheric
temperature, etc.
[0052] Next, the yarns cooled and solidified are pulled and drawn
by compressed air sprayed from the ejector.
[0053] The spinning speed is preferably 2,000 m/min or higher, more
preferably 3,000 m/min or higher, and even more preferably 4,000
m/min or higher. When the spinning speed is set at 2,000 m/min or
higher, high productivity can be provided, and the fibers develop
orientation crystallization so that filament fibers with high
strength can be obtained.
[0054] The mass per length of 10,000 m was calculated from the
average single fiber diameter and the solid density of the resin
used, and the calculated value was rounded off to the first decimal
place to obtain the single-fiber fineness. The spinning speed in
the present invention was calculated from the single-fiber fineness
(dtex) and the discharge rate of resin discharged from the
spinneret single hole (hereinafter referred to as "single-hole
discharge rate") (g/min) set under each set of conditions, by using
the following equation.
Spinning speed=(10,000.times.single-hole discharge
rate)/single-fiber fineness
[0055] Successively, the obtained filament fibers are collected on
a moving net to be formed into a nonwoven fiber web. In the present
invention, the filament fibers are drawn at a high spinning speed
so that the fibers ejected from the ejector can be collected on the
net in a state where the fibers are controlled by a high-speed air
flow. Thus, a nonwoven fabric which is highly uniform with reduced
entanglement among the fibers can be obtained.
[0056] Successively, the obtained nonwoven fiber web is integrated
by heat bonding. Thus, an intended spun-bonded nonwoven fabric can
be obtained.
[0057] Examples of methods for integrating the nonwoven fiber web
by heat bonding include methods of heat bonding with various rolls
such as: hot embossing rolls which are a pair of upper and lower
rolls each having an engraved surface (have recesses and
protrusions on the surface); hot embossing rolls including a
combination of a roll having a flat (smooth) surface and a roll
having an engraved surface (has recesses and protrusions on the
surface); and hot calendar rolls including a combination of a pair
of upper and lower flat (smooth) rolls.
[0058] A proportion of an embossed bonding area in the heat bonding
is preferably 5% or higher and 30% or lower. When the proportion of
the bonding area is set preferably at 5% or higher and more
preferably at 10% or higher, strength applicable to practical use
as the spun-bonded nonwoven fabric can be obtained. Meanwhile, when
the proportion of the bonding area is set preferably at 30% or less
and more preferably at 20% or less, sufficient softness can be
obtained particularly for use as a spun-bonded nonwoven fabric for
a sanitary material.
[0059] When the heat bonding is performed by a pair of rolls each
having recesses and protrusions, the bonding area herein means a
proportion of parts where the protrusions of the upper roll and the
protrusions of the lower roll overlap each other and abut against
the nonwoven fiber web, with respect to the whole nonwoven fabric.
On the other hand, when heat bonding is performed by a roll having
recesses and protrusions and a flat roll, the bonding area means a
proportion of parts where, of the roll having recesses and
protrusions, the protrusions abut against the nonwoven fiber web,
with respect to the whole nonwoven fabric.
[0060] The shape engraved in the hot embossing rolls may be any of
circular, elliptic, square, rectangular, parallelogrammic, rhombic,
regularly hexagonal, and regularly octagonal shapes and the
like.
[0061] The linear pressure of the hot embossing rolls during the
heat bonding is preferably 5 to 70 N/cm. When the linear pressure
of the rolls is set preferably at 5 N/cm or higher, more preferably
at 10 N/cm or higher and even more preferably at 20 N/cm or higher,
sufficient heat-bonding can be performed to obtain strength
applicable to practical use as a nonwoven fabric. Meanwhile, when
the linear pressure of the rolls is set preferably at 70 N/cm or
lower, more preferably at 60 N/cm or lower and even more preferably
at 50 N/cm or lower, sufficient softness can be obtained
particularly for use as a nonwoven fabric for a sanitary
material.
EXAMPLES
[0062] Next, the present invention will be described specifically
based on its examples. Incidentally, each physical property was
measured based on a corresponding one of the aforementioned methods
as long as no particular mention is made. However, the present
invention is not limited to only those examples.
(1) To measure number-average molecular weight and copolymerization
amount of polyethylene glycol contained in copolymerized polyester
based resin
[0063] The number-average molecular weight of the polyethylene
glycol was measured by the following GPC measuring apparatus and on
the following conditions.
[0064] Apparatus: gel permeation chromatograph GPC
[0065] Detector: differential refractive index detector RI (RI-8020
made by Tosoh Corporation, sensitivity 128.times.)
[0066] Photodiode array detector (SPD-M20A made by Shimadzu
Corporation)
[0067] Column: TSK gel G3000PWXL (one column) (Tosoh
Corporation)
[0068] Solvent: 0.1 M sodium chloride aqueous solution
[0069] Flow rate: 0.8 mL/min
[0070] Column Temperature: 40.degree. C.
[0071] Injection volume: 0.05 mL
[0072] Standard sample: polyethylene glycol, polyethylene oxide
(2) .DELTA.MR (%)
[0073] .DELTA.MR was measured by use of "LHU-123" made by Espec
Corp. as a constant temperature and humidity apparatus.
(3) Thickness T.sub.o (mm)
[0074] Thickness T.sub.o was measured by use of "KES-FB3" made by
Kato Tech Co., Ltd. as a compression tester.
(4) Bending Rigidity (.mu.Ncm.sup.2/cm), Bending Return Property
(cm.sup.-1)
[0075] Bending rigidity and bending return property were measured
by use of "KES-FB2" made by Kato Tech Co., Ltd. as a bending
tester.
(5) Tensile Elasticity (MPa)
[0076] Tensile elasticity was measured by use of "AGS1KNX" made by
Shimadzu Corporation as a tensile tester. Incidentally, the sample
thickness T.sub.o (mm) was measured by the same apparatus as in the
aforementioned (2).
(6) Apparent Density (g/cm.sup.3)
[0077] Apparent density was calculated by dividing mass per unit
area by thickness T.sub.o (mm). Incidentally, the sample thickness
T.sub.o (mm) was measured by the same apparatus as in the
aforementioned (2).
(7) Bending Resistance (mm)
[0078] Bending resistance was calculated according to the "6.7.3
41.5.degree. C. antilever Method" of "6.7 Bending Resistance" of
"General Nonwoven Fabric Testing Method" of JIS L1913: 2010.
[0079] Five test pieces each measuring 25 mm in width by 150 mm
were sampled from the manufactured nonwoven fabric. Each test piece
was placed on a horizontal table having a slope of 450 such that
its short sides were aligned with a base line of a scale. The test
piece was manually slid along the slope. As soon as a center point
of one end of the test piece touched the slope, the moving length
of the position of the other end was read by the scale. Such moving
lengths were measured as to the both sides of the five test pieces.
An average value was calculated from the moving lengths.
(8) Evaluation of Sense of Touch
[0080] Ten persons selected arbitrarily touched a surface of each
nonwoven fabric by their hands, and made evaluation in accordance
with the following criteria. The total points of the evaluation
results for each nonwoven fabric was regarded as evaluation of a
sense of touch on the nonwoven fabric. [0081] 3: The surface was
especially smooth, and the sense of touch was very excellent.
[0082] 2: The surface was smooth, and the sense of touch was
excellent. [0083] 1: The surface was sticky, and the sense of touch
was poor.
Example 1
[0084] Copolymerized polyethylene terephthalate in which the
number-average molecular weight and the copolymerization amount of
contained polyethylene glycol were 5,500 and 12 weight % was melted
by an extruder. Yarns spun out from a rectangular spinneret having
a hole diameter .phi. of 0.30 mm at a spinning temperature of
290.degree. C. and at a single-hole discharge rate of 0.6 g/min
were cooled and solidified. The yarns were pulled and drawn by
compressed air from a rectangular ejector having an ejector
pressure of 0.30 MPa, and then collected on a moving net. Thus, a
nonwoven fiber web composed of copolymerized polyester filament
fibers was obtained. The obtained web was heat-bonded at a heat
bonding temperature of 230.degree. C. and at a linear pressure of
50 N/cm by use of a pair of upper and lower heat embossing rolls.
The upper embossing roll was a metallic embossing roll having polka
dots engraving thereon and having a proportion of bonding area of
16%, and the lower embossing roll was a metallic flat roll. Thus, a
spun-bonded nonwoven fabric having a mass per unit area of 18
g/m.sup.2 was obtained. The obtained spun-bonded nonwoven fabric
was evaluated and the results thereof are shown in Table 1.
Example 2
[0085] A spun-bonded nonwoven fabric was obtained in the same
method as in Example 1, except that the copolymerization amount of
contained polyethylene glycol was 8 weight %. The obtained
spun-bonded nonwoven fabric was evaluated and the results thereof
are shown in Table 1.
Comparative Example 1
[0086] A spun-bonded nonwoven fabric was obtained in the same
method as in Example 1, except that the copolymerization amount of
contained polyethylene glycol was 45 weight %. The obtained
spun-bonded nonwoven fabric was evaluated and the results thereof
are shown in Table 1.
Comparative Example 2
[0087] A spun-bonded nonwoven fabric was obtained in the same
method as in Example 1, except that the copolymerization amount of
contained polyethylene glycol was 2 weight %. The obtained
spun-bonded nonwoven fabric was evaluated and the results thereof
are shown in Table 1.
TABLE-US-00001 TABLE 1 Comparative Comparative unit Ex. 1 Ex. 2 Ex.
1 Ex. 2 resin -- PET PET PET PET PEG number-average molecular
weight -- 5500 5500 5500 5500 copolymerization ratio weight % 12 8
45 2 average single fiber diameter .mu.m 11.6 11.5 13.4 11.5
spinning speed m/min 4114 4186 3083 4186 mass per unit area
g/m.sup.2 18 18 18 18 .DELTA.MR % 2.4 0.8 18.6 0.3 bending return
property cm.sup.-1 0.35 0.41 0.16 0.38 tensile elasticity MPa 12.0
15.0 8.0 60.0 bending rigidity .mu.N cm.sup.2/cm 90 100 68 520
apparent density g/cm.sup.3 0.15 0.15 0.15 0.15 bending resistance
mm 62 64 63 80 evaluation of sense of touch -- 2.8 2.5 1.3 2.0
[0088] Examples 1 and 2 had an excellent sense of touch and high
softness.
[0089] On the other hand, when the copolymerization amount of
polyethylene glycol was too large as in Comparative Example 1, the
softness was indeed provided but there arose a problem that the
surface of the nonwoven fabric was sticky, and the sense of touch
was extremely poor. On the other hand, when the copolymerization
amount was too small as in Comparative Example 2, the bending
resistance was so high that the sheet was hard and poor in
texture.
[0090] The present invention has been described in detail and with
reference to its specific embodiments, but it is obvious for those
in the art that various changes or modifications can be made
without departing from the spirit and scope of the present
invention. The present application is based on a Japanese patent
application (Japanese Patent Application No. 2018-010254) filed on
Jan. 25, 2018, and a Japanese patent application (Japanese Patent
Application No. 2018-183755) filed on Sep. 28, 2018, the contents
of which are incorporated herein by reference.
* * * * *