U.S. patent application number 16/477920 was filed with the patent office on 2019-12-05 for sheet-like material.
This patent application is currently assigned to Toray Industries, Inc.. The applicant listed for this patent is Toray Industries, Inc.. Invention is credited to Takanori Furui, Gen Koide, Ryuji Shikuri.
Application Number | 20190368124 16/477920 |
Document ID | / |
Family ID | 62908948 |
Filed Date | 2019-12-05 |
United States Patent
Application |
20190368124 |
Kind Code |
A1 |
Furui; Takanori ; et
al. |
December 5, 2019 |
SHEET-LIKE MATERIAL
Abstract
The present invention provide a sheet-like material having a
highly soft texture, and further having high crease resistance
while being soft. The sheet-like material of the present invention
is a sheet-like material which includes a nonwoven fabric
containing ultrafine fibers having an average single fiber diameter
of 0.3 to 7 .mu.m, and an elastomer, and having nap on a surface,
in which the elastomer has a porous structure, and the porous
structure has a proportion of micropores with a pore size of 0.1 to
20 .mu.m of 60% or more in all pores.
Inventors: |
Furui; Takanori;
(Anpachi-gun, Gifu, JP) ; Shikuri; Ryuji;
(Anpachi-gun, Gifu, JP) ; Koide; Gen;
(Anpachi-gun, Gifu, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toray Industries, Inc. |
Tokyo |
|
JP |
|
|
Assignee: |
Toray Industries, Inc.
Tokyo
JP
|
Family ID: |
62908948 |
Appl. No.: |
16/477920 |
Filed: |
December 25, 2017 |
PCT Filed: |
December 25, 2017 |
PCT NO: |
PCT/JP2017/046354 |
371 Date: |
July 15, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D06N 3/14 20130101; D06N
3/00 20130101 |
International
Class: |
D06N 3/14 20060101
D06N003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 23, 2017 |
JP |
2017-009507 |
Claims
1. A sheet-like material comprising a nonwoven fabric containing
ultrafine fibers having an average single fiber diameter of 0.3 to
7 .mu.m, and an elastomer, and having nap on a surface, wherein the
elastomer has a porous structure, and the porous structure has a
proportion of micropores with a pore size of 0.1 to 20 .mu.m of 60%
or more in all pores.
2. The sheet-like material according to claim 1, wherein the
elastomer exists in an interior space in the nonwoven fabric.
3. The sheet-like material according to claim 1, wherein the
elastomer is a polycarbonate-based polyurethane resin.
4. The sheet-like material according to claim 3, wherein the
polyurethane resin has a weight-average molecular weight of 30,000
to 150,000.
5. The sheet-like material according to claim 2, wherein the
elastomer is a polycarbonate-based polyurethane resin
6. The sheet-like material according to claim 5, wherein the
polyurethane resin has a weight-average molecular weight of 30,000
to 150,000.
7. The sheet-like material according to claim 1, wherein a number
of pores per unit area in section is 50 pores/1600 .mu.m.sup.2 or
more in the porous structure in the elastomer.
8. The sheet-like material according to claim 2, wherein a number
of pores per unit area in section is 50 pores/1600 .mu.m.sup.2 or
more in the porous structure in the elastomer.
9. The sheet-like material according to claim 3, wherein a number
of pores per unit area in section is 50 pores/1600 .mu.m.sup.2 or
more in the porous structure in the elastomer.
10. The sheet-like material according to claim 4, wherein a number
of pores per unit area in section is 50 pores/1600 .mu.m.sup.2 or
more in the porous structure in the elastomer.
11. The sheet-like material according to claim 5, wherein a number
of pores per unit area in section is 50 pores/1600 .mu.m.sup.2 or
more in the porous structure in the elastomer.
12. The sheet-like material according to claim 6, wherein a number
of pores per unit area in section is 50 pores/1600 .mu.m.sup.2 or
more in the porous structure in the elastomer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is the U.S. National Phase application of
PCT/JP2017/046354, filed Dec. 25, 2017, which claims priority to
Japanese Patent Application No. 2017-009507, filed Jan. 23, 2017,
the disclosures 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 sheet-like material,
particularly to a napped leather-like sheet-like material.
BACKGROUND OF THE INVENTION
[0003] It is widely known to obtain a suede-like or nubuck-like,
napped leather-like sheet-like material by buffing with sandpaper a
surface of a sheet-like material in which a base material such as a
nonwoven fabric composed of fibers is impregnated with a
polyurethane resin to stand the fibers. Desired properties of the
napped leather-like sheet-like material can be arbitrarily and
widely designed by combination of a base material composed of
fibers and a polyurethane resin.
[0004] For example, it is proposed that when a polycarbonate-based
polyurethane resin is used which is obtained by a reaction of a
polycarbonate polyol having a specific structure with an aromatic
polyisocyanate, softness of the polycarbonate-based polyurethane
resin is improved, grindability obtained by using sandpaper is
improved whereby a preferable nap length of a ultrafine fiber is
expressed, and an artificial leather having an elegant appearance,
a supple surface touch and soft texture due to nap can be obtained
(see Patent Document 1).
[0005] The napped leather-like sheet-like material has an
appearance and a surface closely resembling to natural leather, and
is recognized to have advantages which do not exist in the natural
leather, such as uniformity and color fastness. Use of the napped
leather-like sheet-like material has recently been spread to
long-term uses such as covering materials for furniture such as
sofa and seat covers for automobiles, in addition to clothing use.
In the clothing use among them, artificial leather having both
excellent softness and crease resistance has been required.
[0006] According to the proposal described above, it is proposed
that soft artificial leather can be obtained by making a structure
of the polycarbonate polyol forming the polyurethane resin specific
to the hardness of the polycarbonate-based polyurethane resin which
is the conventional problem. In the use requiring the soft texture
as in the clothing use, however, the softness has been still
insufficient.
[0007] It is also proposed that when a polyurethane resin including
a bio-based polycarbonate polyol is used, synthetic leather having
excellent low-temperature flexing and contributing to environmental
loading reduction can be obtained (see Patent Document 2).
According to this proposal, however, synthetic leather composed of
layers of nonporous polyurethane resins having various molecular
weights and a fiber fabric has been studied in detail, but napped
artificial leather having a soft texture and crease resistance has
not been studied at all.
[0008] A method for obtaining a suede-like, leather-like sheet
whose color tone is not changed and which has an elegant appearance
is proposed, the sheet being obtained in a manner in which a porous
layer having micropores is formed by adding a specific coagulation
modifier to a polyurethane resin and the layer is napped by
grinding (see Patent Document 3). According to this proposal, a
good texture has been attained by controlling pore sizes in layers
of nonporous polyurethane resins having various molecular weights,
and in portions close to the surface layer and the fibrous base
layer, but coexistence of softness and crease resistance has not
been studied at all, and softness is impaired because of porous
polyurethane resin layer.
[0009] Separately, a method for obtaining a sheet-like material
having nap and elegant appearance in a manner in which a
polyurethane resin having good grindability is obtained by
containing pores having a diameter of 10 to 200 .mu.m inside a
water-dispersible polyurethane resin, and a sheet obtained
therefrom is ground with sandpaper, or the like is proposed (see
Patent Document 4). According to this proposal, however, when the
pores inside the polyurethane resin layer have a large pore size of
more than 20 .mu.m, the thickness of the polyurethane resin layer
between the pores is thick, so that an effect of improving the
grindability of the polyurethane resin and an effect of improving
softness are insufficiently exhibited. Accordingly, it has been
difficult to obtain sufficient softness in the use requiring
flexible deformation along a complicated shape such as in clothing
use. It has been also difficult to obtain ultrafine and uniform
pores.
[0010] It is also proposed that a leather-like base material having
lightweight and supple texture is obtained which is composed of a
porous elastomer having a specific pore size and a nonwoven fabric
of porous hollow fibers (see Patent Document 5). According to this
proposal, the material has a soft texture because of the porous
structure and is uniform, but it has been difficult to have both
softness and crease resistance due to remaining creases.
[0011] As described above, it has been very difficult to stably
obtain a napped leather-like sheet-like material having both
excellent softness and excellent crease resistance according to the
conventional techniques.
PATENT DOCUMENTS
[0012] Patent Document 1: WO2005/095706 [0013] Patent Document 2:
Japanese Patent Laid-open Publication No. 2014-1475 [0014] Patent
Document 3: Japanese Patent Laid-open Publication No. 2000-303368
[0015] Patent Document 4: Japanese Patent Laid-open Publication No.
2011-214210 [0016] Patent Document 5: Japanese Patent Laid-open
Publication No. 2012-214944
SUMMARY OF THE INVENTION
[0017] In view of the background of the prior art described above,
an object of the present invention is to provide a napped
leather-like sheet-like material having both a texture of excellent
softness and high crease resistance while it is soft.
[0018] The present invention is to solve the problems described
above, and the sheet-like material of the present invention is a
sheet-like material comprising a nonwoven fabric containing
ultrafine fibers having an average single fiber diameter of 0.3 to
7 .mu.m, and an elastomer, and having nap on a surface, wherein the
elastomer has a porous structure, and the porous structure has a
proportion of micropores with a pore size of 0.1 to 20 .mu.m of 60%
or more in all pores.
[0019] According to a preferable embodiment of the sheet-like
material of the present invention, the elastomer exists in an
interior space in the nonwoven fabric.
[0020] According to a preferable embodiment of the sheet-like
material of the present invention, the elastomer is a
polycarbonate-based polyurethane resin.
[0021] According to a preferable embodiment of the sheet-like
material of the present invention, the polyurethane resin has a
weight-average molecular weight of 30,000 to 150,000.
[0022] According to a preferable embodiment of the sheet-like
material of the present invention, a number of pores per unit area
in section is 50 pores/1600 .mu.m.sup.2 or more in the porous
structure in the elastomer.
[0023] According to the present invention, a napped leather-like
sheet-like material having both a highly soft texture and crease
resistance can be obtained. Specifically, a napped leather-like
sheet-like material having an elegant appearance obtained by
buffing, and further having excellent softness and crease
resistance can be obtained by the present invention. Here, the term
"highly soft texture" means, in clothing use, that the sheet-like
material can be tailored into a complicated three-dimensional shape
and can provide good feeling of wearing by deformation along with
the physical movement, and means, in use of furniture, automobile
interior materials, or the like, that the sheet-like material can
be molded or processed along with a complicated three-dimensional
shape and can provide good feeling of use by flexibly following
deformation caused, for example, when a person sits. The term
"crease resistance" refers to an excellent recovery from the
crease, and means that even if wrinkles are caused by applying a
load, for example, a deformation caused upon the use as described
above, the wrinkles disappear without leaving any trace after
removing the load. It is necessary to apply appropriate elasticity
to the sheet-like material in order to express the crease
resistance, which is conflict with the softness, and thus it has
been difficult to obtain both the softness and the crease
resistance.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0024] The sheet-like material of the present invention is a
sheet-like material comprising a nonwoven fabric containing an
ultrafine fibers having an average single fiber diameter of 0.3 to
7 .mu.m, and an elastomer, and having nap on a surface, in which
the elastomer has a porous structure, and the porous structure has
a proportion of micropores with a pore size of 0.1 to 20 .mu.m of
60% or more in all pores.
[0025] The sheet-like material of the present invention comprises,
as described above, a nonwoven fabric containing ultrafine fiber,
and an elastomer.
[0026] As a material of the ultrafine fiber forming the nonwoven
fabric used in the present invention, it is possible to use
thermoplastic resins capable of melt-spinning, for example,
polyesters such as polyethylene terephthalate, polybutylene
terephthalate, and polytrimethylene terephthalate, polyamides such
as 6-nylon and 66-nylon, and the like. Of these, a polyester is
preferably used from the viewpoint of the strength, dimensional
stability, and light resistance. The nonwoven fabric may be mixed
with ultrafine fibers of different other materials.
[0027] The cross-sectional shape of a single fiber forming the
nonwoven fabric may have a circular cross-section, and may be an
elliptical, plane, or polygonal such as triangle shape. A single
fiber having a modified cross-section such as a sector or cruciform
may also be used.
[0028] It is important that the ultrafine fibers that form the
non-woven fabric have an average single fiber diameter of 7 .mu.m
or less from the viewpoint of the softness and nap appearance of
the sheet-like material. The average single fiber diameter is
preferably 6 .mu.m or less, and more preferably 5 .mu.m or less. On
the other hand, it is important that the average single fiber
diameter is 0.3 .mu.m or more from the viewpoint of the chromogenic
property after dying, the dispersibility of fiber bundles during
buffing, and the easy handling. The average single fiber diameter
is preferably 0.7 .mu.m or more, and more preferably 1 .mu.m or
more.
[0029] The average single fiber diameter herein refers to a value
obtained by cutting the obtained sheet-like material in a thickness
direction, observing a cross-section with a scanning electron
microscope (SEM), measuring a fiber diameter of 50 arbitrary
ultrafine fibers at three points, and calculating an average value
of fiber diameters of a total of 150 fibers.
[0030] As a method for obtaining the ultrafine fiber used in the
present invention, use of an ultrafine fiber-generating fiber is a
preferable embodiment. As the ultrafine fiber-generating fiber, an
islands-in-the-sea fiber can be used in which two thermoplastic
resin components having solubility in a solvent different from each
other are used as a sea component and an island component, and the
island component can be used as the ultrafine fiber by dissolving
only the sea component in a solvent to be removed. A peelable
composite fiber or a multilayered composite fiber can also be used
in which two thermoplastic resin components are disposed
alternately in a radial pattern of a fiber cross-section or in a
layer pattern, and each component is peeled and divided to split
the composite fiber into an ultrafine fiber.
[0031] As the nonwoven fabric, it is possible to use a nonwoven
fabric in which single fibers of the ultrafine fibers are entangled
with one another, and a nonwoven fabric in which fiber bundles of
the ultrafine fibers are entangled. However, the nonwoven fabric in
which fiber bundles of the ultrafine fibers are entangled is
preferably used from the viewpoint of the strength and texture of
the sheet-like material. A nonwoven fabric having appropriate voids
between the ultrafine fibers inside the fiber bundle is
particularly preferably used from the viewpoint of the softness and
the texture. The nonwoven fabric in which fiber bundles of the
ultrafine fibers are entangled, as described above, can be obtained
by previously entangling the ultrafine fiber-generating fibers and
then generating the ultrafine fibers. The nonwoven fabric having
appropriate voids between the ultrafine fibers inside the fiber
bundle can be obtained by using islands-in-the-sea fibers which can
provide appropriate voids between the island components, i.e.,
between the ultrafine fibers inside the fiber bundle, by removing
the sea component.
[0032] As the nonwoven fabric, any of a staple fiber nonwoven
fabric and a filament fiber nonwoven fabric can be used, and a
staple fiber nonwoven fabric is preferably used from the viewpoint
of the texture and the appearance.
[0033] A staple fiber in the staple fiber nonwoven fabric
preferably has a fiber length of 25 to 90 mm. When the fiber length
is set to 25 mm or more, the sheet-like material having the
excellent abrasion resistance can be obtained by entanglement. When
the fiber length is set to 90 mm or less, the sheet-like material
having a more excellent texture and appearance can be obtained. The
fiber length is more preferably 35 to 80 mm, and particularly
preferably 40 to 70 mm.
[0034] When the ultrafine fibers or the fiber bundles thereof form
the nonwoven fabric, a woven fabric or a knitted fabric may be
inserted into the fabric in order to improve the strength. Fibers
that form the woven fabric or the knitted fabric used have
preferably an average single fiber diameter of about 0.3 to 10
.mu.m.
[0035] The elastomer used in the present invention has a porous
structure, and a proportion of micropores with a pore size of 0.1
to 20 .mu.m in all pores in the porous structure is 60% or more.
The ratio of the micropores is more preferably 70% or more, and
still more preferably 80% or more. The porous structure may have
either open cells or closed cells. When the elastomer has a certain
ratio or more of the micropores, the softness of the elastomer can
be increased, and the sheet-like material having a highly soft
texture can be obtained. In order to make the elastomer have the
porous structure having micropores, it is preferable to use wet
coagulation described below as a method for fixing the elastomer in
the nonwoven fabric.
[0036] Further, by making the elastomer have the porous structure
having micropores, a deformation force can be dispersedly received
by not a part of the elastomer but by the whole elastomer when a
crease deformation is applied to the sheet-like material.
Accordingly, the generation of the creases with buckling of the
elastomer is suppressed, and the sheet-like material having the
excellent crease resistance can be obtained.
[0037] It is important that 60% or more of the pores with respect
to all pores in the porous structure of the elastomer have a pore
size of 0.1 .mu.m or more. The pore size is preferably 0.5 .mu.m or
more, and more preferably 1 .mu.m or more. When the pore size is
set to 0.1 .mu.m or more, the softness of the elastomer is
increased and, at the same time, the cushioning against the
deformation can be increased. On the other hand, it is also
important that 60% or more of the pores with respect to all pores
in the porous structure of the elastomer have a pore size of 20
.mu.m or less. The pore size is preferably 15 .mu.m or less, and
more preferably 10 .mu.m or less. When the pore size is set to 20
.mu.m or less, the pore density of the porous structure can be
increased, both the softness and the appropriate strength can be
obtained, and a deformation force can be dispersedly received by
the whole elastomer, so that the sheet-like material having the
excellent softness and the crease resistance can be obtained.
[0038] The number of pores per unit area in the porous structure of
the elastomer is 50 pores/1600 .mu.m.sup.2 or more, preferably 70
pores/1600 .mu.m.sup.2 or more, and more preferably 100 pores/1600
.mu.m.sup.2 or more. On the other hand, the number of pores per
unit area in the porous structure of the elastomer is preferably
1000 pores/1600 .mu.m.sup.2 or less, and more preferably 800
pores/1600 .mu.m.sup.2 or less.
[0039] When the number of pores per unit area is set to 50
pores/1600 .mu.m.sup.2 or more, the porous structure having a soft
texture is obtained and a crease deformation force of the sheet can
be received by a plurality of pores. Accordingly, the excellent
crease resistance can be obtained. When the number of pores per
unit area is too small, the deformation force is concentrated to
specific pores to cause buckling, and the crease recovery is poor.
When the number of pores per unit area is too large, a deformation
space of the pores is too small, the deformation force cannot be
dispersed, and the crease recovery is poor.
[0040] The elastomer used in the present invention holds the
ultrafine fibers in the sheet-like material. It is a preferable
embodiment that the elastomer exists in an interior space of the
nonwoven fabric from the viewpoint of having nap on at least one
surface of the sheet-like material.
[0041] As the elastomer used in the present invention, a
polyurethane resin is preferably used in the point of obtaining
uniform micropores in the sheet-like material. As the polyurethane
resin, a polyurethane resin obtained by a reaction of a polymer
diol with an organic diisocyanate is preferably used.
[0042] Examples of the polymer diol may include
polycarbonate-based, polyester-based, polyether-based,
silicone-based, and fluorine-based polymer diols, and copolymers of
combinations of these may also be used.
[0043] A polycarbonate-based polymer diol is preferably used,
because it can provide the appropriate rigidity to the polyurethane
resin, the excellent softness can be exhibited by forming the
porous structure having micropores, and the high crease resistance
can be exhibited without buckling of the polyurethane resin.
[0044] The polycarbonate-based diol can be produced by
transesterification of an alkylene glycol with a carbonic acid
ester, or a reaction of phosgene or chloroformic acid ester with an
alkylene glycol, or the like.
[0045] Examples of the alkylene glycol include linear alkylene
glycols such as ethylene glycol, propylene glycol, 1,4-butane diol,
1,5-pentane diol, 1,6-hexane diol, 1,9-nonane diol, and 1,10-decane
diol, branched alkylene glycols such as neopentyl glycol,
3-methyl-1,5-pentane diol, 2,4-diethyl-1,5-pentane diol, and
2-methyl-1,8-octane diol, alicyclic diols such as 1,4-cyclohexane
diol, aromatic diols such as bisphenol A, glycerol, trimethylol
propane, and pentaerythritol. Either polycarbonate-based diols
obtained from alkylene glycol alone, or copolymerized
polycarbonate-based diol obtained from two or more kinds of
alkylene glycols may be used.
[0046] Examples of the polyester-based diol may include polyester
diols obtained by condensation of a polybasic acid with various low
molecular weight polyols.
[0047] As the low molecular weight polyols, it is possible to use
one or more kinds of polyols selected from, for example, ethylene
glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butane
diol, 1,4-butane diol, 2,2-dimethyl-1,3-propane diol, 1,6-hexane
diol, 3-methyl-1,5-pentane diol, 1,8-octane diol, diethylene
glycol, triethylene glycol, dipropylene glycol, tripropylene
glycol, cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol. As
the low molecular weight polyols, it is possible to use an adduct
in which bisphenol A is added with various alkylene oxides.
[0048] Examples of the polybasic acid include one or more kinds of
acids selected from, for example, succinic acid, maleic acid,
adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic
acid, sebacic acid, dodecane dicarboxylic acid, phthalic acid,
isophthalic acid, terephthalic acid, and hexahydroisophthalic
acid.
[0049] Examples of the polyether-based diol may include
polyethylene glycol, polypropylene glycol, polytetramethylene
glycol, and copolymerized diols obtained by combination of
these.
[0050] The polymer diol preferably has a number-average molecular
weight of 500 to 5000. When the number-average molecular weight is
set to 500 or more, and more preferably 1500 or more, it is
possible to prevent the texture from being hardened. When the
number-average molecular weight is set to 5000 or less, and more
preferably 4000 or less, the strength as the polyurethane resin can
be maintained.
[0051] Examples of the organic diisocyanate used in the synthesis
of the polyurethane resin may include aromatic diisocyanates such
as 4,4'-diphenylmethane diisocyanate, praraphenylene diisocyanate,
1,5-naphthalene diisocyanate, paraxylene diisocyanate, and
methylene diisocyanate, alicyclic diisocyanates such as
4,4'-dicyclohexylmethane diisocyanate and isophorone diisocyanate,
and aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate.
Of these, aromatic diisocyanates, particularly 4,4'-diphenylmethane
diisocyanate, are preferably used from the viewpoint of the
strength and durability such as heat resistance of the obtained
polyurethane resin.
[0052] As a chain extender used in the synthesis of the
polyurethane resin, it is possible to use organic diols, organic
diamines, hydrazine derivatives, and the like.
[0053] Examples of the organic diol may include aliphatic diols
such as ethylene glycol, propylene glycol, 1,4-butane diol,
neopentyl glycol, 1,5-pentane diol, methylpentane diol, 1,6-hexane
diol, 1,7-heptane diol, 1,8-octane diol, 1,9-nonane diol, and
1,10-decane diol, alicyclic diols such as 1,4-cyclohexane diol and
hydrogenated xylylene glycol, and aromatic diols such as xylene
glycol.
[0054] Examples of the organic diamine may include ethylene
diamine, isophorone diamine, xylene diamine, phenyl diamine, and
4,4'-diaminodiphenyl methane.
[0055] Examples of the hydrazine derivative may include hydrazine,
adipic acid dihydrazide, and isophthalic acid dihydrazide.
[0056] In order to improve the water resistance, the abrasion
resistance, and the hydrolysis resistance, a cross-linking agent
can be added to the polyurethane resin. The cross-linking agent may
be an external cross-linking agent that is added to the
polyurethane as a third component, or an internal cross-linking
agent can be used which previously introduces a reaction point
forming a cross-linked structure into a polyurethane molecular
structure.
[0057] In the synthesis of the polyurethane resin, it is possible
to use, as a catalyst, amines such as triethyl amine and
tetramethyl butane diamine, metal compounds such as potassium
acetate, zinc stearate, and tin octylate, and the like, for
example.
[0058] The polyurethane resin used in the present invention
preferably has a weight-average molecular weight (Mw) of 30,000 to
150,000, and more preferably 50,000 to 130,000. When the
weight-average molecular weight (Mw) is set to 30,000 or more, the
strength of the obtained sheet-like material can be maintained, and
the loss of nap and the occurrence of pilling can be prevented.
When the weight-average molecular weight (Mw) is set to 150,000 or
less, the polyurethane resin in the sheet-like material can have
uniform micropores. When the polyurethane resin has such a
weight-average molecular weight (Mw) range, the uniform and
ultrafine porous structure can be obtained by the temporary
softening of the polyurethane resin with heating and the
evaporation of the soluble and insoluble solvents contained in the
polyurethane resin after wet coagulation described below as the
starting point, in the production steps usually used where the
polyurethane resin is fixed into the nonwoven fabric in the wet
coagulation, and then the sheet-like material containing a
insoluble solvent such as water is dried with heating.
[0059] The elastomer may contain polyester-based, polyamide-based,
and polyolefin-based elastomers, acrylic resins, and ethylene-vinyl
acetate resins within a range in which the performance and the
texture are not impaired. In addition, the elastomer may also
contain various additives, for example, pigments such as carbon
black, flame retardants such as phosphorus-based, halogen-based,
and inorganic flame retardants, antioxidants such as phenol-based,
sulfur-based, and phosphorus-based antioxidants, UV absorbers such
as benzotriazole-based, benzophenone-based, salicylate-based,
cyanoacrylate-based, and oxalic acid anilide-based UV absorbers,
light stabilizers such as hindered amine-based and benzoate-based
light stabilizers, hydrolysis stabilizer such as polycarbodiimide,
plasticizers, antistatic agents, surfactants, coagulation
modifiers, dyes, and the like.
[0060] In the sheet-like material of the present invention, an
amount of the elastomer in the sheet-like material is preferably 10
to 50% by mass, and more preferably 15 to 35% by mass. When the
amount of the elastomer is set to 10% by mass or more, the
sheet-like material obtains the strength, and it is possible to
prevent fiber falling. When the amount of the elastomer is set to
50% by mass or less, it is possible to prevent the texture from
being hardened, and the desired good nap appearance can be
obtained.
[0061] Examples of the method of fixing the elastomer into the
nonwoven fabric include methods in which the nonwoven fabric is
impregnated with a solution of the elastomer, followed by wet
coagulation or dry coagulation. The wet coagulation is preferably
used from the viewpoint of obtaining the uniform and ultrafine
porous structure as in the present invention. As the solvent used
when the polyurethane resin is given as the elastomer,
N,N'-dimethyl formamide, dimethyl sulfoxide, and the like may be
used. Specifically, the nonwoven fabric is immersed in a solution
in which the elastomer is dissolved in the solvent to give the
elastomer to the nonwoven fabric, and is immersed in the insoluble
solvent for the coagulation. It is also possible to perform the
coagulation by immersing the nonwoven fabric in a mixture of the
soluble solvent and the insoluble solvent.
[0062] The sheet-like material of the present invention may also be
obtained by dividing the material in half or into several sections
in the thickness direction of the sheet-like material before
buffing.
[0063] The addition of the antistatic agent before buffing is
preferably performed, because grinded powder generated from the
sheet-like material by grinding tends to be hardly accumulated on
the sandpaper.
[0064] The sheet-like material of the present invention is
eventually used suitably as a napped leather-like sheet-like
material in which ultrafine fibers are buffed on at least one
surface of the sheet-like material. The buffing is performed by a
method in which grinding is conducted using sandpaper, a roll
sander, or the like. In order to obtain good fiber nap on the
surface, it is a preferable embodiment that a lubricant such as a
silicone emulsion is applied before the buffing.
[0065] The sheet-like material of the present invention is
eventually used suitably as a napped leather-like sheet-like
material in which ultrafine fibers are buffed on at least one
surface of the sheet-like material.
[0066] The sheet-like material of the present invention can be
suitably used as covering materials used in furniture, chairs, wall
covering, and seats, ceilings and interior finishing products in
interior of vehicles such as automobiles, trains and airplanes, and
further covering materials having a very elegant appearance of
clothes.
EXAMPLES
[0067] The sheet-like material of the present invention is more
specifically described by way of Examples below.
[Evaluation Method]
(1) Average Single Fiber Diameter:
[0068] A cross-section of a nonwoven fabric containing fibers of a
sheet-like material, which was vertical to the thickness direction
of the fabric, was observed at 3000 magnifications using a scanning
electron microscope (SEM, VE-7800-type manufactured by Keyence
Corporation), and diameters of 50 single fibers that were randomly
extracted from a 30 .mu.m.times.30 .mu.m visual field were measured
at a unit of .mu.m up to the first decimal place. The measurement
was performed at three points, diameters of 150 single fibers in
total were measured, and an average value up to the first decimal
place was calculated. In the case where fibers having a fiber
diameter of more than 50 .mu.m are present, it is considered that
those fibers do not correspond to the ultrafine fibers, and they
were excluded from objects to be measured for the average fiber
diameter. When the ultrafine fiber had a modified cross-section,
first, a cross-sectional area of a single fiber was measured, and
supposing that the cross-section had a circle, the diameter was
calculated to obtain a diameter of the single fiber. An average
value was calculated considering the values above as a population,
which was defined as an average single fiber diameter.
(2) Pore Size of Porous Structure of Elastomer and Proportion of
Micropores with Pore Size of 0.1 to 20 .mu.m in all Pores in Porous
Structure:
[0069] A cross-section of a nonwoven fabric containing elastomers
of a sheet-like material, which was vertical to the thickness
direction of the fabric, was observed at 2000 magnifications using
a scanning electron microscope (SEM, VE-7800-type manufactured by
Keyence Corporation), and pore sizes (diameter) of 50 pores in
elastomers that were randomly extracted from a 40 .mu.m.times.40
.mu.m visual field were measured at a unit of .mu.m up to the first
decimal place. The measurement was performed at three points, pore
sizes of 150 pores in total were measured, and the proportion of
the number of pores with a pore size of 0.1 to 20 .mu.m in 150
pores was calculated, and the proportion was defined as the
proportion of micropores with a pore size of 0.1 to 20 .mu.m in the
porous structure. When the pores in the elastomers were variant
pores, first, a cross-sectional area of a pore was measured, and
supposing that the cross-section had a circle, the diameter was
calculated to obtain a pore size (diameter) of the pore.
(3) The Number of Pores Per Unit Area in Porous Structure of
Elastomer:
[0070] A cross-section of a nonwoven fabric containing elastomers
of a sheet-like material, which was vertical to the thickness
direction of the fabric, was observed at 2000 magnifications using
a scanning electron microscope (SEM, VE-7800-type manufactured by
Keyence Corporation), and the number of pores in the elastomer was
counted in a 40 .mu.m.times.40 .mu.m visual field. The count was
performed at three points, and an arithmetic average value of the
number of pores was defined as the number of pores per unit area in
the porous structure. When the area of the elastomer containing the
porous structure is less than the 40 .mu.m.times.40 .mu.m visual
field, the number of pores in the visual field was divided by an
effective area of the elastomer, and the obtained value was
converted into the number of pores per 1600 .mu.m.sup.2, which was
defined as the number of pores per unit area in the porous
structure. When the pore size of the pore is larger than the 40
.mu.m.times.40 .mu.m visual field, the number of pores in the
porous structure was defined as 1.
(4) Weight-Average Molecular Weight of Polyurethane Resin:
[0071] The polyurethane resin was extracted from the obtained
sheet-like material using N,N'-dimethylformamide (hereinafter may
sometimes be referred to as "DMF"), the concentration of the
polyurethane resin was set to 1% by mass, and a weight-average
molecular weight of the polyurethane resin was measured by gel
permeation chromatography (GPC) under the following conditions:
[0072] Apparatus: GPC measuring apparatus HLC-8020 (manufactured by
Tosoh).
[0073] Column: TSK gel GMH-XL (manufactured by Tosoh)
[0074] Solvent: N,N-dimethylformamide (hereinafter referred to as
"DMF"
[0075] Standard sample: polystyrene (TSK standard polystyrene
manufactured by Tosoh)
[0076] Temperature: 40.degree. C.
[0077] Flow rate: 1.0 ml/minute
(5) Softness:
[0078] Five specimens each having a size of 2.times.15 cm (a
vertical direction.times.a horizontal direction) were made in
accordance with the A method (450 Cantilever Method) described in
8.21.1 in 8.21 "Bending Stiffness" in JIS L 1096:2010 "Testing
Methods for Woven and Knitted Fabrics". Each of the specimens was
put on a horizontal table having a slope with an angle of
45.degree.. The specimen was slid, and the scale was read when the
central point on one end of the specimen was brought into contact
with the slope. An average value of the five specimens was
obtained. When the value was 45 mm or less, the softness was
evaluated as good.
(6) Crease Resistance:
[0079] Crease recovery angles for five specimens were measured
using a 10 N load apparatus in accordance with JIS L 1059-1:2009
"Testing Methods for Crease Recovery of Textiles--Part 1:
Determination of the Recovery from Creasing of a Horizontally
Folded Specimen by Measuring the Angle of Recovery (Monsant
Method)", the crease resistance was calculated by the formula of
crease resistance ratio described in section 10 "Calculation of
Crease Recovery Angle and Crease Resistance Ratio", and an average
value of the five specimens was obtained. When the value was 90% or
more, the crease resistance was evaluated as good.
[Expression of Chemical Substance]
[0080] Abbreviations of chemical substances used in Examples and
Comparative Examples have the following meanings:
[0081] PU: polyurethane
[0082] DMF: N,N-dimethylformamide
Example 1
[0083] An islands-in-the-sea fiber including a polystyrene as a sea
component and a polyethylene terephthalate as an island component
was drawn, crimped, and cut to obtain a raw stock for a nonwoven
fabric. Subsequently, the obtained raw stock was formed into fiber
webs using a cross-lapper, and needle punching was performed to
obtain a nonwoven fabric.
[0084] The thus obtained nonwoven fabric composed of the
islands-in-the-sea fiber was impregnated with an aqueous solution
of polyvinyl alcohol, dried, and then the polystyrene as the sea
component was extracted in trichloroethylene to be removed. The
resulting material was dried to obtain a nonwoven fabric composed
of ultrafine fibers having an average single fiber diameter of 2.0
.mu.m.
[0085] The thus obtained nonwoven fabric composed of ultrafine
fibers was immersed in a resin solution in which a concentration of
a solution of a polycarbonate-based polyurethane resin in DMF was
adjusted to 11%, and an adhesion amount of the polyurethane (PU)
resin solution was controlled by using a squeeze roll. Then, the PU
resin was coagulated in an aqueous solution having a DMF
concentration of 30%, subsequently, polyvinyl alcohol and DMF were
removed by hot water, and the resulting material was dried to
obtain a sheet-like material having a PU resin content of 17% by
mass. One side of the thus obtained sheet-like material was
subjected to buffing using 180-mesh endless sandpaper, and then was
dyed with a dispersion dye to obtain a napped leather-like
sheet-like material.
[0086] When a cross-section in the thickness direction of the
inside of the obtained leather-like sheet-like material was
observed with a scanning electron microscope (SEM), it was found
that the polyurethane resin existed only in the inside of the
nonwoven fabric, the polyurethane resin had a porous structure
having micropores, the proportion of micropores with a pore size of
0.1 to 20 .mu.m in all pores in the porous structure was 85%, and
the number of pores per unit area in the porous structure was 247
pores/1600 .mu.m.sup.2. The polyurethane resin extracted from the
napped leather-like sheet-like material had a weight-average
molecular weight of 110,000.
[0087] The obtained napped leather-like sheet-like material had a
good nap length and dispersibility of the fibers, and had the
excellent softness and the crease resistance. The results are shown
in Table 1.
Examples 2 to 7 and Comparative Examples 1 to 5
[0088] A napped leather-like sheet-like material was manufactured
in the same manner as in Example 1, except that the average single
fiber diameter of the ultrafine fiber, the kind of the polyurethane
resin, and the weight-average molecular weight of the polyurethane
resin were changed to values shown in Table 1.
[0089] When a cross-section in the thickness direction of the
inside of the leather-like sheet-like material in each of Examples
and Comparative Examples was observed with a scanning electron
microscope (SEM), it was found that the polyurethane resin had a
porous structure having micropores, and the polyurethane resin
existed only in the inside of the nonwoven fabric.
[0090] Table 1 shows the average single fiber diameter of the
ultrafine fiber, the kind of the polyurethane resin, the
weight-average molecular weight of the polyurethane resin, the
average particle size of the porous structure of the polyurethane
in the obtained sheet-like material, the proportion of micropores
with a pore size of 0.1 to 20 .mu.m in all pores in the porous
structure, the softness, and the crease resistance in each Example
and each Comparative Example.
TABLE-US-00001 TABLE 1 Average pore Proportion of Weight-average
size of micropores with Number of pores per Average single Kind of
molecular weight porous pore size of 0.1 unit area in porous Crease
fiber diameter polyurethane of polyurethane structure to 20 .mu.m
in pore structure Softness resistance (.mu.m) resin resin (.mu.m)
structure (%) (pores/1600 .mu.m) (mm) (%) Example 1 2.0
polycarbonate-based 110,000 3.3 85 247 35 96 Example 2 2.0
polycarbonate-based 70,000 7.2 71 92 31 91 Example 3 2.0
polycarbonate-based 140,000 14.5 63 53 43 90 Example 4 4.4
polycarbonate-based 110,000 3.1 81 252 41 94 Example 5 5.5
polycarbonate-based 110,000 3.2 83 245 42 93 Example 6 2.0
polyether-based 110,000 8.5 68 76 30 90 Example 7 2.0
polyester-based 110,000 4.7 74 160 32 91 Comparative 2.0
polycarbonate-based 160,000 19.4 52 12 50 86 Example 1 Comparative
2.0 polycarbonate-based 200,000 38.0 30 1 54 82 Example 2
Comparative 2.0 polycarbonate-based 260,000 71.8 14 1 57 80 Example
3 Comparative 2.0 polyether-based 200,000 58.7 19 1 48 78 Example 4
Comparative 2.0 polyester-based 200,000 41.3 26 1 52 80 Example
5
[0091] In all of the napped leather-like sheet-like materials in
Examples 1 to 7, the polyurethane resin had the porous structure
having micropores, and both the excellent softness and the
excellent crease resistance were obtained by adjusting the
weight-average molecular weight of the polyurethane resin, the
average pore size of the pores in the porous structure, the
proportion of micropores with a pore size of 0.1 to 20 .mu.m in all
pores in the porous structure, and the number of pores per unit
area in the porous structure. On the other hand, in the sheet-like
materials in Comparative Examples 1 to 5, the porous structure was
formed in the polyurethane resin by the increase of the
weight-average molecular weight of the polyurethane resin, but the
pores were large and ununiform, and the thickness of the
polyurethane resin between the pores became thick, thus resulting
in the reduced softness. Also the pore size was not uniform, and
thus the crease deformation could not be received by the whole
polyurethane resin, thus resulting in the poor crease
resistance.
* * * * *