U.S. patent application number 12/097651 was filed with the patent office on 2009-07-23 for process for producing entangled object for artificial leather.
This patent application is currently assigned to KURARAY CO., LTD.. Invention is credited to Hidetaka Ebata, Masasi Meguro, Hisao Yoneda, Yasuhiro Yoshida.
Application Number | 20090186193 12/097651 |
Document ID | / |
Family ID | 38162934 |
Filed Date | 2009-07-23 |
United States Patent
Application |
20090186193 |
Kind Code |
A1 |
Yoshida; Yasuhiro ; et
al. |
July 23, 2009 |
PROCESS FOR PRODUCING ENTANGLED OBJECT FOR ARTIFICIAL LEATHER
Abstract
A method of producing an entangled fabric for artificial
leathers including a step of uniting a woven/knitted fabric and an
entangled nonwoven fabric by entanglement. The method includes (1)
a step of superposing the woven/knitted fabric on one surface of
the entangled nonwoven fabric; (2) a step of needle-punching the
superposed body from a side of the entangled nonwoven fabric so as
to allow fibers constituting the entangled nonwoven fabric to enter
into the woven/knitted fabric and then penetrate through the
woven/knitted fabric, thereby forming a nonwoven fabric layer
composed of the penetrated fibers on an outer surface of the
woven/knitted fabric; and (3) a step of needle-punching from a side
of the nonwoven fabric layer so as to allow a part of the fibers
which have penetrated through the woven/knitted fabric and form the
nonwoven fabric layer to turn back into the woven/knitted fabric,
thereby uniting the woven/knitted fabric and the entangled nonwoven
fabric together by entanglement. The method hardly causes wrinkles,
etc. and is good in process passing properties. The artificial
leathers produced from the entangled fabric for artificial leathers
have a good shape stability, a high-quality appearance and a soft,
high quality hand.
Inventors: |
Yoshida; Yasuhiro; (Okayama,
JP) ; Meguro; Masasi; (Okayama, JP) ; Ebata;
Hidetaka; (Hokkaido, JP) ; Yoneda; Hisao;
(Okayama, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
KURARAY CO., LTD.
OKAYAMA
JP
|
Family ID: |
38162934 |
Appl. No.: |
12/097651 |
Filed: |
December 13, 2006 |
PCT Filed: |
December 13, 2006 |
PCT NO: |
PCT/JP2006/324811 |
371 Date: |
July 23, 2008 |
Current U.S.
Class: |
428/151 ; 28/104;
442/59 |
Current CPC
Class: |
B32B 5/26 20130101; Y10T
428/24438 20150115; Y10T 442/20 20150401; D06N 3/0013 20130101;
B32B 5/06 20130101 |
Class at
Publication: |
428/151 ; 442/59;
28/104 |
International
Class: |
D06N 3/00 20060101
D06N003/00; D04H 11/08 20060101 D04H011/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2005 |
JP |
2005-359812 |
Claims
1. A method of producing an entangled fabric for artificial
leathers comprising a woven/knitted fabric and an entangled
nonwoven fabric which are united together by entanglement, which
comprises the following steps: (1) a step of superposing the
woven/knitted fabric on one surface of the entangled nonwoven
fabric; (2) a step of needle-punching the superposed body from a
side of the entangled nonwoven fabric so as to allow fibers
constituting the entangled nonwoven fabric to enter into the
woven/knitted fabric and then penetrate through the woven/knitted
fabric, thereby forming a nonwoven fabric layer comprising the
penetrated fibers on an outer surface of the woven/knitted fabric;
and (3) a step of needle-punching from a side of the nonwoven
fabric layer so as to allow a part of the fibers which have
penetrated through the woven/knitted fabric and form the nonwoven
fabric layer to turn back into the woven/knitted fabric, thereby
uniting the woven/knitted fabric and the entangled nonwoven fabric
together by entanglement.
2. The method according to claim 1, wherein the needle punching of
the step (2) is performed in a punching density of 300 to 2500
punch/cm.sup.2, and the needle punching of the step 3 is performed
in a punching density of 50 to 1000 punch/cm.sup.2.
3. The method according to claim 1, wherein the needle punching of
the step (2) is performed in a penetration depth such that a barb
nearest a tip of needles penetrates through the woven/knitted
fabric by 5 mm or more over the outer surface thereof.
4. The method according to claim 1, wherein the needle punching of
the step (3) is performed in a penetration depth such that a barb
nearest a tip of needles does not penetrate through the
woven/knitted fabric.
5. A method of producing a substrate for artificial leathers, which
comprises a step of impregnating a solution or emulsion of an
elastic polymer into the entangled fabric for artificial leathers
produced by the method according to claim 1.
6. A suede-finished artificial leather which is produced by raising
at least one surface of the substrate for artificial leathers
produced by the method according to claim 5.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method of producing an
entangled fabric for artificial leathers. Particularly, the present
invention relates to a method of producing an entangled fabric for
artificial leathers and artificial leathers such as suede-finished
artificial leathers composed of the entangled fabric, which little
lose their shape even after long term use, have a high-quality
suede finished appearance, a soft hand, an excellent strength and
practical performances such as pilling resistance, and are suitable
for the production of upholstery of interior furniture such as
vehicle seats, cushion seats, sofas, and chairs.
BACKGROUND ART
[0002] Artificial leathers have been used in various applications
such as interior furniture, clothes, shoes, briefcases, gloves, and
upholstery of vehicle seats. In particular, in the application to
upholstery of vehicle seats such as rail road seats, automotive
seats, air-plane seats and watercraft seats and upholstery of
interior furniture such as cushion seats, sofas and chairs,
artificial leathers combining a good surface abrasion resistance
and a shape stability free from elongation, collapse and wrinkles
even after long term use have been keenly desired.
[0003] Artificial leathers having a substrate made of a fiber
nonwoven fabric, particularly, a microfine fiber nonwoven fabric
have found their application in various fields as high grade
materials because of their soft and dense feeling resembling
natural leathers. However, artificial leathers having a substrate
made of only a microfine fiber nonwoven fabric easily lose their
shape. For example, the upholstery of chairs produced from
artificial leathers having a substrate made of only a microfine
fiber nonwoven fabric are likely to be deformed by the long-term,
repeating load of user's weight.
[0004] To reduce the deformation, it has been generally employed to
bond a woven/knitted fabric to the back side of artificial
leathers. Although effective for preventing the deformation, the
hand becomes hard and a product having complicated design is
difficult to produce by sewing because wrinkles are easily
formed.
[0005] A method of producing artificial leathers having a laminated
substrate of a microfine fiber nonwoven fabric and a woven/knitted
fabric has been proposed (for example, Patent Document 1). The
artificial leathers produced by the proposed method have a hand
softer than that of artificial leathers having a woven/knitted
fabric bonded to the back side and a shape stability higher than
that of artificial leathers having no woven/knitted fabric.
However, in a known substrate laminated with a woven/knitted
fabric, fibers constituting the woven/knitted fabric are easily
exposed to the surface to deteriorate the process passing
properties (properties that the treatment intended in each process
is successfully made and the treated product is transferred to the
next process stably without causing any troubles) and the hand of
the obtained artificial leathers is not satisfactory.
[0006] [Patent Document 1] JP 4-1113B
DISCLOSURE OF THE INVENTION
[0007] An object of the present invention is to provide an
entangled fabric for artificial leather for use as a substrate for
artificial leathers which have a good shape stability resistant to
the loss of shape even after long term use and a soft hand and are
suitable for the production of upholstery of interior furniture
such as vehicle seats, cushion seats, sofas, and chairs.
[0008] As a result of extensive study for achieving the above
object, the inventors have reached the present invention.
[0009] Namely, the present invention relates to a method of
producing an entangled fabric for artificial leathers comprising a
woven/knitted fabric and an entangled nonwoven fabric which are
united together by entanglement, which comprises the following
steps: (1) a step of superposing the woven/knitted fabric on one
surface of the entangled nonwoven fabric; (2) a step of
needle-punching the superposed body from a side of the entangled
nonwoven fabric so as to allow fibers constituting the entangled
nonwoven fabric to enter into the woven/knitted fabric and then
penetrate through the woven/knitted fabric, thereby forming a
nonwoven fabric layer comprising the penetrated fibers on an outer
surface of the woven/knitted fabric; and (3) a step of
needle-punching from a side of the nonwoven fabric layer so as to
allow a part of the fibers which penetrate through the
woven/knitted fabric to form the nonwoven fabric layer to turn back
into the woven/knitted fabric, thereby uniting the woven/knitted
fabric and the entangled nonwoven fabric together by
entanglement.
[0010] The present invention further relates to a method of
producing an artificial leather, comprising a step of impregnating
a solution or an emulsion of an elastic polymer into the entangled
fabric for artificial leathers produced by the above method.
[0011] The present invention still further relates to a method of
producing a suede-finished artificial leather, comprising a step of
raising at least one surface of the artificial leather produced by
the above method.
BEST MODE FOR CARRYING OUT THE INVENTION
[0012] The fibers (microfine fiber-forming fibers) convertible to
microfine fibers of 0.5 dtex or less, preferably 0.0001 to 0.5 dtex
are preferably used as the fibers for constituting the entangled
nonwoven fabric because the resultant artificial leathers acquire a
natural leather-like hand, although not particularly limited
thereto. Although the microfine fibers can be directly spun from a
single kind of polymer, it is preferred to convert microfine
fiber-forming fibers composed of at least two kinds of polymers to
microfine fibers in a later stage. Examples of the microfine
fiber-forming fibers include extraction-type fibers in which the
fibers are fibrillated to microfine fibers of the island component
by dissolving or decomposing the sea component and division-type
fibers in which the fibers are fibrillated to microfine fibers of
each polymer by a mechanical or chemical treatment. The microfine
fiber-forming fibers may be made into short fibers or long fibers
having a fineness of 1 to 15 dtex, if necessary, through steps of
stretching, heat treating, mechanical crimping and cutting.
[0013] The polymer for the microfine fibers may include at least
one polymer selected from melt-spinnable polyamide such as 6-nylon,
66-nylon and 12-nylon and melt-spinnable polyester such as
polyethylene terephthalate, polytrimethylene terephthalate,
polybutylene terephthalate and copolymers thereof. The component
for forming the microfine fibers may be included with a pigment
such as carbon black and a known additive for fibers as long as the
effect of the present invention is not adversely affected.
[0014] The component to be extracted or decomposed of the
extraction-type fibers is a polymer having a solubility to an
extraction solvent and a decomposability by a decomposing agent
different from those of the microfine fiber-forming component,
being less compatible with the microfine fiber-forming component,
and having a melt viscosity or a surface tension smaller than those
of the microfine fiber-forming component under spinning conditions.
In addition, the component to be extracted or decomposed is
required to have a solubility to an extraction solvent and a
decomposability by a decomposing agent different from those of the
elastic polymer to be impregnated into the entangled fabric for
artificial leathers. Preferred examples thereof include known
polymers based on polyvinyl alcohol or polyolefin.
[0015] When the short fibers are used to form the entangled
nonwoven fabric, the fibers are carded and then made into a web
through a webber. When the long fibers are used, a web is produced
simultaneously with spinning the long fibers by a spun-bonding
method, etc. The mass per unit area of the web depends upon the
desired mass per unit area of entangled fabric for artificial
leathers and the laminate structure of the entangled nonwoven
fabric and the woven/knitted fabric, and preferably from 80 to 2000
g/m.sup.2, more preferably from 100 to 1500 g/m.sup.2 because the
artificial leather combines a good hand and mechanical properties.
The obtained webs are superposed in a desired mass per unit area or
thickness, and pre-entangled, if necessary, by a known method such
as needle punching and jet water to obtain an entangled nonwoven
fabric which is to be united with a woven/knitted fabric by
entanglement. To enhance the entanglement with the woven/knitted
fabric, the needle punching density of the entangling treatment is
preferably from 20 to 100 punch/cm.sup.2 and more preferably from
25 to 80 punch/cm.sup.2. The punching density referred to herein is
a total number of felt needles punched on the web per unit area.
For example, when the web is punched 50 times by a needle board
having felt needles in a density of 10/cm.sup.2, the punching
density is 500 punch/cm.sup.2.
[0016] The structure of the woven/knitted fabric is not critical.
The fibers for forming the woven/knitted fabric are not
particularly limited and may be produced from a known polymer as
long as the resultant artificial leather has a practical strength
in a desired use. When bundles of fibers axe used to form the
woven/knitted fabric, the number of twist is not particularly
limited. In view of the hand of the resultant artificial leather,
the number of twist is preferably small, for example 900 T/m or
less, preferably from 80 to 900 T/m. The fineness is selected
according to the intended use and preferably from 30 to 200 dtex.
If being 200 dtex or less, the hand of the resultant artificial
leather is good and the thickness of the woven/knitted fabric can
be reduced. If being 30 dtex or more, the fabric density required
for sufficient strength can be reduced, the entangled nonwoven
fabric is easily united by needle punching, and the fibers
constituting the woven/knitted fabric are hardly broken.
[0017] In view of the hand of the resultant artificial leather, the
mass per unit area of the woven/knitted fabric is preferably from
30 to 200 g/m.sup.2. If being 30 g/m.sup.2 or more, the
woven/knitted fabric has a sufficient strength and little loses its
shape by a shift of fibers. If being 200 g/m.sup.2 or less, the
resultant artificial leather has a good hand and the woven/knitted
fabric and the entangled nonwoven fabric are easily united
together.
[0018] After superposing the woven/knitted fabric on one surface of
the entangled nonwoven fabric, the entangling treatment is
performed. Known methods of entangling the entangled nonwoven
fabric and the woven/knitted fabric include a needle punching
method and a hydroentangling method (water jet method). The
hydroentangling method is generally applicable to a fiber web
comprising short fibers with a fiber length of about 1 to 10 mm and
having a mass per unit area of about 20 to 150 g/m.sup.2. When
producing an artificial leather, particularly a suede-finished
artificial leather having a high-quality surface appearance, the
hydroentanglement is performed by two methods according to the
fiber length.
[0019] A first method is a method generally employed in the
production of suede-finished artificial leathers, in which
microfine short fibers having a fiber length of about 1 to 10 mm
are made into a fiber web having a mass per unit area of about 20
to 150 g/m.sup.2 by a paper-making method, and after superposing
one fiber web thus obtained on the woven/knitted fabric or
interposing the woven/knitted fabric between two fiber webs, the
entangling treatment is performed by water-jetting from the side of
fiber web.
[0020] In the first method, since the fibers are short, the fibers
moves and entangled sufficiently by the water jetting. However, to
achieve an entangling degree required for obtaining a
suede-finished artificial leather having an excellent appearance,
the pressure of water jet is limited. Therefore, the mass per unit
area of the resultant entangled body is reduced. Even in case of
entangling a superposed body of one fiber web and one woven/knitted
fabric, the amount of fibers which penetrate though the
woven/knitted fabric to its outer surface is limited. Therefore,
the fibers do not move enough to form a nonwoven fabric layer on
the outer surface of the woven/knitted fabric. In addition, since
the fibers are short, the raised fibers on the surface of the
finally obtained suede-finished artificial leather are easily
pulled out. If the foot of raised fibers is anchored by a binder to
prevent the pilling, the hand becomes hard.
[0021] In the second method, microfine fiber-forming fibers of
about 30 to 100 mm are made into a fiber web having a mass per unit
area of about 200 to 600 g/m.sup.2 by a carding method, etc. and
the fiber web is then sufficiently entangled by a mechanical
entangling method such as needle punching. The entangled fiber web
as obtained or after converting the microfine fiber-forming fibers
to microfine fibers is used to obtain a superposed body by
superposing one fiber web on the woven/knitted fabric or
interposing the woven/knitted fabric between two fiber webs. If
exceeding 150 g/m.sup.2, the total mass per unit area is reduced to
150 g/m.sup.2 or less by slicing in two or other methods. Then, the
entangling treatment is performed by water jetting from the side of
fiber web.
[0022] In the second method, since the fibers are long, the fibers
are not moved and entangled in a degree attained in the first
method by a water jetting under conditions not damaging the fibers.
Namely, the fibers in the fiber web merely enter into the space
between the fibers of the woven/knitted fabric and hardly penetrate
through the woven/knitted fabric to its outer surface. In addition,
the fibers do not move enough to form a nonwoven fabric layer on
the outer surface of the woven/knitted fabric. When a superposed
body of one fiber web and one woven/knitted fabric is water-jetted
from the side of fiber web, the fibers in the fiber web enter into
the space between fibers of the woven/knitted fabric and then
project on the outer surface of the woven/knitted fabric, thereby
making the outer surface of the woven/knitted fabric rough.
Therefore an additional water jet treatment for smoothing the outer
surface of the woven/knitted fabric is optionally employed. In
addition, the fiber web and the woven/knitted fabric are easily
peeled off at their boundary because they are hardly entangled by
the water jetting.
[0023] Therefore, the entanglement is preferably performed by a
needle punching method in the present invention because the
entangled nonwoven fabric and the woven/knitted fabric are
effectively entangled.
[0024] First, a superposed body of an entangled nonwoven fabric and
a woven/knitted fabric is needle-punched from the side of the
entangled nonwoven fabric to allow the fibers constituting the
entangled nonwoven fabric to enter into the woven/knitted fabric
and then penetrate though the woven/knitted fabric (first needle
punching step). In the first needle punching step, the superposed
body is not needle-punched from the side of the woven/knitted
fabric. If needle-punched from the side of the woven/knitted
fabric, the resultant artificial leather is poor in mechanical
properties because of insufficient entanglement between the
woven/knitted fabric and the entangled nonwoven fabric.
[0025] The fibers which penetrate though the woven/knitted fabric
form a nonwoven fabric layer on the outer surface (the surface of
the woven/knitted fabric not facing the entangled nonwoven fabric).
With this nonwoven fabric layer, the resultant artificial leather
has sufficient mechanical properties and a natural leather-like
hand. In addition, the defect such as surface wrinkles is avoided
in the steps after the entangling treatment.
[0026] Then, the needle punching is performed from the side of the
nonwoven fabric layer which is formed on the outer surface of the
woven/knitted fabric, thereby allowing the fibers penetrated
through the woven/knitted fabric and forming the nonwoven fabric
layer to turn back (second needle punching step). The term "turn
back" means that at least a part of the fibers penetrated through
the woven/knitted fabric and forming the nonwoven fabric layer are
moved toward the side of the woven/knitted fabric by the needle
punching. By allowing the fibers constituting the nonwoven fabric
layer to turn back, the fibers penetrated through the woven/knitted
fabric enter again into the woven/knitted fabric. Therefore, the
fibers constituting the entangled nonwoven fabric are effectively
locked to prevent the fiber pull-out of the resultant
suede-finished artificial leather. Effect of preventing the fibers
on the back side from pilling during dyeing and hot-water
relaxation treatment can be additionally obtained.
[0027] The ratio of the nonwoven fabric layer formed on the outer
surface of the woven/knitted fabric by the two-stage needle
punching step of the present invention is preferably 5 to 40% of
the mass per unit area of the entangled nonwoven fabric which is
superposed to the woven/knitted fabric in the first needle punching
step. If being 5% or more, the minimum uniformity of the entangled
nonwoven fabric and the woven/knitted fabric acceptable in the
present invention is obtained and the defect such as peeling and
slippage between the layers of the entangled fabric for artificial
leather is difficult to occur. If being 40% or less, the fiber
damage is prevented in the entangled nonwoven fabric and the
woven/knitted fabric, and a unified, soft suede-fished artificial
leather having a natural leather-like, high-quality appearance and
hand is obtained.
[0028] The punching density (P1) in the first needle punching step
is preferably from 300 to 2500 punch/cm.sup.2, and more preferably
from 600 to 1300 punch/cm.sup.2. If being 300 punch/cm.sup.2 or
more, the entangled nonwoven fabric and the woven/knitted fabric
are entangled sufficiently. If being 2500 punch/cm.sup.2 or less,
the fiber damage is prevented in the entangled nonwoven fabric and
the woven/knitted fabric. In view of obtaining a sufficient
nonwoven fabric layer, the penetration depth of needles is selected
so that the barb nearest the tip of needles penetrates through the
woven/knitted fabric preferably by 5 mm or more, and more
preferably by 5 to 20 mm over the outer surface thereof.
[0029] The punching density (P2) in the second needle punching step
is preferably from 50 to 1000 punch/cm.sup.2, more preferably from
80 to 700 punch/cm.sup.2, and particularly preferably from 100 to
500 punch/cm.sup.2. If being 50 punch/cm.sup.2 or more, a part of
the fibers successfully turns back, and the hand and mechanical
properties are prevented from becoming uneven. If being 1000
punch/cm.sup.2 or less, the fiber damage is prevented in the
woven/knitted fabric. The penetration depth of needles is
preferably selected so that the barb nearest the tip of needles
does not penetrate through the entangled nonwoven fabric outer
surface.
[0030] The ratio of the punching density (P1) and the punching
density (P2) is preferably larger than 1/1, because the resultant
artificial leather has a uniform and natural leather-like hand. The
ratio is preferably 2/1 or more and particularly preferably 3/1 or
more, because the fiber pull-out of the suede-finished artificial
leather is effectively prevented. The ratio is more preferably 20/1
or less, because wrinkles hardly occur and a sufficient
entanglement is combined with mechanical properties.
[0031] By the above entangling method, the entangled fabric for
artificial leathers of the present invention having excellent
properties can be produced. The mass per unit area of the entangled
fabric for artificial leathers is preferably from 80 to 1200
g/m.sup.2 and the total thickness is preferably from 0.35 to 8.0
mm. In the entangled fabric for artificial leathers, the thickness
of the entangled nonwoven fabric is preferably from 0.2 to 7.5 mm,
the thickness of the woven/knitted fabric is preferably from 0.1 to
1.5 mm, and the thickness of the nonwoven fabric layer formed on
the outer surface of the woven/knitted fabric is preferably from
0.05 to 1.5 mm.
[0032] In view of obtaining a natural leather-like hand, the
entangled fabric for artificial leathers thus obtained is made into
a substrate for artificial leathers preferably by impregnating and
coagulating an elastic polymer. Any of known polyurethane resins,
acrylic resins and other polymers which are used as an impregnant
for artificial leathers are usable as the elastic polymer, with
polyurethane resins being preferred in view of a hand and
properties. Preferred examples of polyurethane resins include
polyester ether-based polyurethane, polylactone-based polyurethane
and polycarbonate-based polyurethane, which are produced by the
solution polymerization, melt polymerization or bulk polymerization
of a polymer diol and an organic diisocyanate in the presence of a
compound having two active hydrogen atoms. The polymer diol is
preferably at least one compound selected from polyester diol,
polyether diol, polyester ether diol, polylactone diol and
polycarbonate diol, each having an average molecular weight of from
700 to 3000. The organic diisocyanate is preferably at least one
compound selected from organic diisocyanates, aliphatic
diisocyanates and alicyclic diisocyanates. Another organic
diisocyanate or triisocyanate may be combinedly used, if needed.
Examples of the compound having two active hydrogen atoms include
low molecular diols, low molecular diamines, hydrazine, and
hydroxylamine.
[0033] The method for impregnating polyurethane is not particularly
limited. For example, usable are a method in which the entangled
fabric for artificial leathers is dipped and nipped in a solution
or dispersion (emulsion, etc.) of polyurethane and a method in
which a solution or dispersion of polyurethane is coated on the
entangled fabric for artificial leathers and rubbed therein by a
roll rotating at a high speed. The polyurethane concentration in
the solution or dispersion is preferably from 5 to 50% by mass. The
impregnated polyurethane is coagulated by a wet coagulation in
which the entangled fabric for artificial leathers is immersed in a
liquid containing a non-solvent for polyurethane or by a dry
coagulation in which an aqueous emulsion (dispersion) of
polyurethane is gelled and dried under heating. The immersion time
and temperature and the heat-drying temperature and time are
selected from those employed in the known production of artificial
leathers.
[0034] The solution or dispersion of the elastic polymer may be
included with, if needed, an additive such as colorant, for
example, carbon black and pigment, coagulation regulator,
antioxidant and dispersant. In view of a soft hand and elastic
recovery of the artificial leather, the content of the elastic
polymer (solid basis) in the entangled fabric for artificial
leathers is preferably from 5 to 50% by mass and more preferably
from 10 to 40% by mass of the amount of the entangled fabric for
artificial leathers before the conversion to microfine fibers. If
being 5% by mass or more, a dense, elastic sponge (porous
structure) is formed and a soft hand is obtained. If being 50% by
mass or less, the hand is prevented from becoming rubber-like, and
the shape stability is enhanced by the woven/knitted fabric to
prevent the loss of shape.
[0035] When the entangled nonwoven fabric and/or the woven/knitted
fabric are formed by microfine fiber-forming fibers, the microfine
fiber-forming fibers are converted to microfine fibers or bundles
of microfine fibers, to obtain an artificial leather. The
conversion is performed by a method of removing at least one
polymer from the microfine fiber-forming fibers (sea component
polymer in case of sea-island fibers) by dissolution in a solvent
or decomposition by a decomposer, or a mechanical or chemical
treatment. The details of the operations and conditions are
selected from those employed in the known production of artificial
leathers.
[0036] The conversion to microfine fibers may be carried out before
the impregnation of the elastic polymer. However, if the solution
of the elastic polymer is impregnated and coagulated after the
conversion to bundles of microfine fibers, the elastic polymer
adheres to the microfine fibers to likely harden the hand.
Therefore, the conversion to microfine fibers is preferably carried
out after the impregnation of the elastic polymer. If the
conversion to microfine fibers is carried out before the
impregnation of the elastic polymer, it is preferred to
provisionally impregnate a filler such as polyvinyl alcohol, which
can be removed by dissolution in the later steps, into the
entangled fabric for artificial leathers to prevent the adhesion
between the microfine fibers and the elastic polymer. Then the
elastic polymer is impregnated and thereafter the filler is
removed. The apparent density of the artificial leather thus
obtained is preferably from 0.2 to 0.7 g/cm.sup.3 in view of
hand.
[0037] The substrate for artificial leathers is made into either
suede-finished artificial leathers or grain-finished artificial
leathers. Particularly, in the production of suede-finished
artificial leathers, after regulating the thickness of the
substrate for artificial leathers to a desired level by slicing or
buffing, the surface is buffed by a known method using sandpaper,
etc. to form a raised surface comprising the microfine fibers or
the bundles of microfine fibers and then the raised surface is
dyed. By using the entangled fabric for artificial leathers of the
present invention, the fiber pull-out and the fall of raised fibers
are markedly prevented in the steps until the suede-finished
artificial leathers are finally obtained. If the apparent density
of the resultant artificial leather is as relatively low as 0.35
g/cm.sup.3 or less, the obtained suede-finished artificial leather
has a sufficient strength and is excellent in practically important
performance such as pilling resistance, abrasion resistance and
fastness of dyeing even when the content of the elastic polymer is
as relatively low as 25% by mass or less.
[0038] In view of the shape stability, the resultant suede-finished
artificial leathers and grain-finished artificial leathers
preferably have an elongation at constant load of 10% or less and a
residual strain of 3% or less.
EXAMPLES
[0039] The present invention will be described with reference to
the example. However, it should be noted that the scope of the
present invention is not limited thereto. The "part(s)" and a "%"
in the following examples are based on mass unless otherwise
noted.
[0040] The elongation at constant load and the residual strain were
measure as follows according to JASO M 403-88 6.5 (Test Method for
Automotive Seat-Ti Fabrics) by Society of Automotive Engineers of
Japan, Inc.
[0041] Three test pieces (width: 80 mm, length: 250 mm) were cut
out of an artificial leather along each of the machine direction
and the transverse direction (total 9 test pieces). Two gage marks
were drawn at the central portion in the width direction of each
test piece at a distance of 100 mm L). Then, the test piece was
clipped onto an upper grip of Martens fatigue tester at its
lengthwise end. A load of 98.1 N (10 kgf) inclusive of the lower
grip was put on the other lengthwise end at a grip distance of 150
mm. After 10 min, the distance between gage marks L.sub.1 (mm) was
measured and the load was removed. The test piece was placed on a
flat stand and the distance between gage marks L.sub.2 (mm) was
measured after 10 min from the removal of load. The elongation at
constant load (%) and the residual strain (%) were calculated from
the following equations and the results are expressed by an average
on 9 test pieces.
Elongation at constant load
(%)=(L.sub.1-L.sub.0)/L.sub.0.times.100
Residual strain (%)=(L.sub.2-L.sub.0)/L.sub.0.times.100
wherein L.sub.0 is the distance (100 mm) between gage marks before
the test, L.sub.1 is the distance (mm) between gage marks after 10
min of loading, and L.sub.2 is the distance (mm) between gage marks
after 10 min from the removal of load.
[0042] The upholstery of chair shows a better shape stability even
after long term use, if the elongation at constant load and
residual strain are smaller.
Example 1
Preparation of Entangled Nonwoven Fabric
[0043] Staples of sea-island composite fibers composed of
polyethylene terephthalate as the island component and a low
density polyethylene as the sea component (number of islands of 20;
polyethylene terephthalate:low density polyethylene=60:40; fineness
of 4.0 dtex; fiber length of 51 mm; 12 crimp/inch) ware made into a
web by carding and cross lapping. The web was entangled by needle
punching in a density of 40 punch/cm.sup.2, to obtain an entangled
nonwoven fabric comprising microfine fiber-forming fibers, which
had a mass per unit area of 300 g/mz.
Preparation of Woven Fabric
[0044] Polyester yarns (56 dtex/24 f) subjected to false twisting
were further subjected to additional twisting by 600 T/m and then
woven by a water jet weaving machine at a fabric density of
120.times.95/inch, to obtain a plain-woven fabric having a mass per
unit area of 60 g/m.sup.2.
First Needle Punching Step
[0045] The entangled nonwoven fabric and the plain-woven fabric
were superposed to each other. The superposed body was
needle-punched from the side of the entangled nonwoven fabric using
single barb felt needles in a punching density of 1200
punch/cm.sup.2 and a penetration depth which allowed the barb
nearest the tip of needles to penetrate through the plain-woven
fabric by 6 mm over the outer surface thereof, thereby allowing the
fibers constituting the entangled nonwoven fabric to penetrate
through the plain-woven fabric and form a nonwoven fabric layer on
the outer surface of the plain-woven fabric.
Second Needle Punching Step
[0046] Then, the superposed body was needle-punched from the side
of the nonwoven fabric layer in a punching density of 300
punch/cm.sup.2 and a penetration depth so that the barb nearest the
tip of needles did not penetrate through the entangled nonwoven
fabric to the outer surface thereof, thereby allowing the fibers
which had penetrated through the plain-woven fabric and formed the
nonwoven fabric layer to turn back into the plain-woven fabric. By
this treatment, an entangled fabric for artificial leathers having
a mass per unit area of 370 g/m.sup.2 which was composed of the
entangled nonwoven fabric and the plain-woven fabric united by
entanglement was obtained.
Impregnation of Elastic Polymer/Conversion to Microfine Fibers
[0047] A 15% solution of a polyether-based polyurethane in
dimethylformamide (DMF) was impregnated into the obtained entangled
fabric for artificial leathers. Then, the entangled fabric was
immersed in a mixed bath of DMF and water to wet-coagulate
polyurethane. After removing the remaining DE by washing with
water, the sea component polyethylene was removed by extraction in
a toluene bath at 85.degree. C. Immediately thereafter, the
remaining toluene was azeotropically removed in a hot water bath at
100.degree. C. and then the fabric was dried, to obtain a substrate
for artificial leathers having a mass per unit area of 295
g/m.sup.2 and a thickness of 0.8 mm. In the steps of impregnating
the elastic polymer and converting to microfine fibers, no wrinkle
was formed and the production was performed stably.
Suede-Finished Artificial Leather
[0048] The surface of the nonwoven fabric layer on the obtained
substrate for artificial leathers was buffed by #180 sandpaper
twice to regulated the thickness to 0.7 mm while smoothening the
surface. Then the surface of the entangled nonwoven fabric was
buffed by #240 sandpaper twice and #400 sandpaper twice
successively to form a raised surface comprising the microfine
fibers of polyethylene terephthalate. The fiber pull-out was hardly
observed during the suede-finishing treatment and the
suede-finished surface was covered with dense raised fibers.
[0049] Then, the suede-finished artificial leather was immersed in
a hot water bath at 80.degree. C. for 20 min to allow it to be well
wetted with hot water and relaxed, and thereafter, dyed with a
disperse dye using a high-pressure jet dyeing machine at a bath
ratio of 1:15 and dried, to obtain a dyed suede-finished artificial
leather. The obtained suede-finished artificial leather had an
elongation at constant load of 4% and a residual strain of 1% or
less. In addition, the surface of the suede-finished artificial
leather was covered with the raised fibers without causing pull-out
of the raised fibers, to present a high-quality suede-finished
appearance.
Comparative Example 1
[0050] A substrate for artificial leathers was obtained in the same
manner as in Example 1 except for needle-punching a superposed body
of an entangled nonwoven fabric and a plain-woven fabric in a
punching density of 750 punch/cm.sup.2 simultaneously from both
sides of the entangled nonwoven fabric and the plain-woven fabric.
Using the obtained substrate for artificial leathers, a dyed
suede-finished artificial leather was produced in the same manner
as in Example 1. The obtained suede-finished artificial leather had
an elongation at constant load of 4% and a residual strain of 1%.
Although the degree of strain was the same as that of Example 1,
the hand was hard as compared with Example 1 and fine wrinkles were
formed on the surface. In addition, unlike Example 1, the fiber
pull-out occurred in the relaxation and dyeing steps and many
raised fibers fell. Therefore the raised surface was rough and
polyurethane was exposed to the surface.
INDUSTRIAL APPLICABILITY
[0051] By using the entangled fabric for artificial leathers of the
present invention, a suede-finished artificial leather which little
loses its shape even after long term use and has a high-quality
suede-finished appearance and a soft hand is produced. In addition,
wrinkles, etc. are hardly formed during the production thereof, and
therefore, the process passing properties are good. The entangled
fabric for artificial leathers of the present invention is
particularly useful as the materials for the upholstery of vehicle
seats such as rail road seats, automotive seats, airplane seats and
watercraft seats and the upholstery of interior furniture such as
sofas, cushions and chairs. The entangled fabric for artificial
leathers is effectively used in other uses, for example, the
production of clothes, shoes, briefcases, pouches, or gloves.
* * * * *