U.S. patent application number 11/917836 was filed with the patent office on 2009-07-30 for piled sheet and process for producing the same.
This patent application is currently assigned to Kuraray Co., Ltd.. Invention is credited to Masasi Meguro, Tsuyoshi Yamasaki, Hisao Yoneda, Yasuhiro Yoshida.
Application Number | 20090191778 11/917836 |
Document ID | / |
Family ID | 37532320 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090191778 |
Kind Code |
A1 |
Yoshida; Yasuhiro ; et
al. |
July 30, 2009 |
PILED SHEET AND PROCESS FOR PRODUCING THE SAME
Abstract
A raised sheet composed of three layers which are united by
entanglement. The three layers are united in a layered structure of
entangled nonwoven fabric A made of microfine fibers/polyurethane
sheet B/woven or knitted fabric C or a layered structure of
entangled nonwoven fabric A made of microfine fibers/woven or
knitted fabric C/polyurethane sheet B. On the surface of the
entangled nonwoven fabric A, raised naps of the microfine fibers
are formed. A part of the microfine fibers constituting the
entangled nonwoven fabric A penetrates through the polyurethane
sheet B and the woven or knitted fabric C in this order, or
penetrates through the woven or knitted fabric C and the
polyurethane sheet B in this order. At least a part of the
penetrated microfine fibers bonds to polyurethane which constitutes
the polyurethane sheet B. The raised sheet is excellent in the
shape stability, for example, it does not lose its shape even after
a long term use. In addition, the raised sheet has a good surface
abrasion resistance and a soft and high-quality hand.
Inventors: |
Yoshida; Yasuhiro; (Okayama,
JP) ; Meguro; Masasi; (Okayama, JP) ; Yoneda;
Hisao; (Okayama, JP) ; Yamasaki; Tsuyoshi;
(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: |
37532320 |
Appl. No.: |
11/917836 |
Filed: |
June 14, 2006 |
PCT Filed: |
June 14, 2006 |
PCT NO: |
PCT/JP2006/311922 |
371 Date: |
January 7, 2009 |
Current U.S.
Class: |
442/268 ;
156/148; 442/319 |
Current CPC
Class: |
B32B 5/26 20130101; D06N
3/0004 20130101; Y10T 442/494 20150401; D06N 3/0013 20130101; Y10T
442/3707 20150401 |
Class at
Publication: |
442/268 ;
442/319; 156/148 |
International
Class: |
D06N 3/14 20060101
D06N003/14; D04H 13/00 20060101 D04H013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 2005 |
JP |
2005-178197 |
Claims
1. A raised sheet comprising three layers which are united by
entanglement, the raised sheet satisfying the following
requirements: (1) three layers are united in a layered structure of
entangled nonwoven fabric A made of microfine fibers/polyurethane
sheet B/woven or knitted fabric C or a layered structure of
entangled nonwoven fabric A made of microfine fibers/woven or
knitted fabric C/polyurethane sheet B; (2) the entangled nonwoven
fabric Ahas raised microfine fibers on its surface; (3) a part of
the microfine fibers constituting the entangled nonwoven fabric A
penetrates through the polyurethane sheet B and the woven or
knitted fabric C in this order, or penetrates through the woven or
knitted fabric C and the polyurethane sheet B in this order; and
(4) at least a part of the penetrated microfine fibers bonds to
polyurethane which constitutes the polyurethane sheet B.
2. The raised sheet according to claim 1, wherein an entangled
nonwoven fabric D is further united by entanglement to an outer
surface of the woven or knitted fabric C or the polyurethane sheet
B which is disposed on an outermost surface of the layered
structure, and a part of the microfine fibers constituting the
entangled nonwoven fabric A penetrates through the polyurethane
sheet B and the woven or knitted fabric C and is entangled with the
fibers constituting the entangled nonwoven fabric D.
3. The raised sheet according to claim 1, wherein an entangled
nonwoven fabric D is further united by entanglement to an outer
surface of the woven or knitted fabric C or the polyurethane sheet
B which is disposed on an outermost surface of the layered
structure; a part of the microfine fibers constituting the
entangled nonwoven fabric A penetrates through the polyurethane
sheet B and the woven or knitted fabric C and is entangled with the
fibers constituting the entangled nonwoven fabric D; and a part of
the fibers constituting the entangled nonwoven fabric D penetrates
through the polyurethane sheet B and the woven or knitted fabric C
and is entangled with the microfine fibers constituting the
entangled nonwoven fabric A.
4. The raised sheet according to any one of claims 1 to 3, wherein
the microfine fibers constituting the entangled nonwoven fabric A
are produced by converting microfine fiber-forming fibers which
comprises a water-soluble polymer and a sparingly water-soluble
polymer to the microfine fibers.
5. A covering fabric for vehicle seats produced from the raised
sheet as defined in any one of claims 1 to 3.
6. A method of producing a raised sheet, which comprises: (1) a
step of superposing a fiber web A' made of microfine fiber-forming
fibers, a polyurethane sheet B and a woven or knitted fabric C,
thereby obtaining a superposed body having a layered structure of
fiber web A'/polyurethane sheet B/woven or a layered structure of
knitted fabric C or fiber web A'/woven or knitted fabric
C/polyurethane sheet B; (2) a step of entangling the superposed
body such that at least a part of the microfine fiber-forming
fibers penetrates through the polyurethane sheet B and the woven or
knitted fabric C, thereby converting the fiber web A' to an
entangled nonwoven fabric A' to unite the superposed body; (3) a
step of converting the microfine fiber-forming fibers to microfine
fibers, thereby converting the entangled nonwoven fabric A'' to an
entangled nonwoven fabric A; and (4) a step of bonding at least a
part of the microfine fibers penetrating through the polyurethane
sheet B to polyurethane which constitutes the polyurethane sheet B
by heat treatment, and then, forming raised microfine fibers on a
surface of the entangled nonwoven fabric A; or (5) a step of
forming raised microfine fibers on a surface of the entangled
nonwoven fabric A, and then, bonding at least a part of the
microfine fibers penetrating through the polyurethane sheet B to
polyurethane which constitutes the polyurethane sheet E by heat
treatment.
Description
TECHNICAL FIELD
[0001] The present invention relates to a raised sheet with little
loss of shape even after a long term use having a good surface
abrasion resistance and a soft hand, which is suitably used as the
covering fabric for vehicle seats and interior furniture such as
cushion sheet, sofa and chair.
BACKGROUND ART
[0002] Artificial leathers have been used in various applications
such as interior, clothes, shoes, bags, gloves, and covering
fabrics for vehicle seats. Particularly in the field of the
covering fabric for vehicle seats such as railroad vehicle seat,
automotive seat, airplane seat and ship seat and the covering
fabric for interior furniture such as cushion sheet and sofa and
chair, artificial leathers which combine a good surface abrasion
resistance and a high shape stability resistant to elongation, loss
of elasticity and wrinkling even after a long term use have been
keenly required.
[0003] Recently, artificial leathers having a substrate made of a
nonwoven fabric, particularly, artificial leathers having a
substrate made of a nonwoven fabric of microfine fibers have been
used as high-quality materials in various applications. However,
the artificial leathers having a substrate which is made only of a
nonwoven fabric of microfine fibers have a problem of easy
deformation. For example, a covering fabric of chair is likely
strained by person's weight which is loaded thereon repeatedly for
a long period of time. To prevent the strain, it has been generally
known to laminate a woven or knitted fabric onto a back surface of
artificial leathers. However, although the deformation is
effectively prevented, the hand becomes hard and the sewing is
difficult because of wrinkling in case of complicated design. An
artificial leather having a substrate made of an entangled body
which is composed of a nonwoven fabric of microfine fibers and a
hard twist woven or knitted fabric is known (for example, Patent
Document 1). This artificial leather has a soft hand as compared
with an artificial leather having a woven or knitted fabric on its
back surface, and has a high shape stability as compared with an
artificial leather having no woven or knitted fabric. However, the
entangled body having only a woven or knitted fabric united is poor
in the recovery from elongation and causes strain on the portion
repeatedly subjected to person's weight after use for several
years. In addition, the surface abrasion resistance cannot be
improved only by laminating a woven or knitted fabric.
[0004] To improve the elasticity, proposed are a nonwoven fabric
produced by laminating a short fiber web and a fleece made of
elastic long fibers of polyurethane, and a nonwoven fabric composed
of an elastic nonwoven fabric made of elastomer and short fiber
webs laminated on both surfaces of the elastic nonwoven fabric in
which the fibers in the short fiber webs on both the surfaces
penetrate through the interposed elastic nonwoven fabric layer and
the fibers in the short fiber webs on both the surfaces bond to one
another by adhesive or heat fusion (Patent Documents 2 and 3). The
sheets obtained from these nonwoven fabrics are surely improved in
the elasticity. However, if used in an application, such as a
covering fabric for chair, which is repeatedly subjected to
person's weight for a long period of time, the proposed sheet is
easily permanently stretched and does not fit for practical use
because of the lack of structure for preventing excessive
elongation which is possessed by a woven fabric. Therefore, the
sheets hitherto proposed are not sufficient in the shape stability
and surface abrasion resistance during a long term use.
[Patent Document 1] JP 4-1113B
[Patent Document 2] JP 4-257363A
[Patent Document 3] JP 7-70902A
DISCLOSURE OF THE INVENTION
[0005] An object of the present invention is to provide a raised
sheet for artificial leathers having a good shape stability of
preventing the loss of shape even after a long term use, a good
surface abrasion resistance and a good hand excellent in softness
and high quality, which is suitably used in the production of a
covering fabric for vehicle seats and interior furniture such as
cushion sheet, sofa and chair.
[0006] As a result of extensive researches, the inventors have
found a raised sheet achieving the above object and accomplished
the invention.
[0007] Thus, the present invention relates to a raised sheet
composed of three layers which are united by entanglement, the
raised sheet satisfying the following requirements:
(1) three layers are united in a layered structure of entangled
nonwoven fabric A made of microfine fibers/polyurethane sheet
B/woven or knitted fabric C or a layered structure of entangled
nonwoven fabric A made of microfine fibers/woven or knitted fabric
C/polyurethane sheet B; (2) the entangled nonwoven fabric A has
raised microfine fibers on its surface; (3) a part of the microfine
fibers constituting the entangled nonwoven fabric A penetrate
through the polyurethane sheet B and the woven or knitted fabric C
in this order, or penetrate through the woven or knitted fabric C
and the polyurethane sheet B in this order; and (4) at least a part
of the penetrated microfine fibers bonds to polyurethane which
constitutes the polyurethane sheet B.
[0008] The present invention further relates to a method of
producing a raised sheet, which includes:
(1) a step of superposing a fiber web A' made of microfine
fiber-forming fibers, a polyurethane sheet B and a woven or knitted
fabric C, thereby obtaining a superposed body having a layered
structure of fiber web A/polyurethane sheet B/woven or a layered
structure of knitted fabric C or fiber web A/woven or knitted
fabric C/polyurethane sheet B; (2) a step of entangling the
superposed body such that at least a part of the microfine
fiber-forming fibers penetrates through the polyurethane sheet B
and the woven or knitted fabric C, thereby converting the fiber web
A' to an entangled nonwoven fabric A'' to unite the superposed
body; (3) a step of converting the microfine fiber-forming fibers
to microfine fibers, thereby converting the entangled nonwoven
fabric A'' to an entangled nonwoven fabric A; and (4) a step of
bonding at least a part of the microfine fibers penetrating through
the polyurethane sheet B to polyurethane which constitutes the
polyurethane sheet B by heat treatment, and then, forming raised
microfine fibers on a surface of the entangled nonwoven fabric A;
or (5) a step of forming raised microfine fibers on a surface of
the entangled nonwoven fabric A, and then, bonding at least a part
of the microfine fibers penetrating through the polyurethane sheet
B to polyurethane which constitutes the polyurethane sheet B by
heat treatment.
BEST MODE FOR CARRYING OUT THE INVENTION
[0009] The fibers mainly composed of microfine fibers of 0.5 dtex
or less are preferably used for the entangled nonwoven fabric A
which forms at least one layer of the raised sheet of the
invention, because the resultant raised sheet has a natural leather
like hand, although not particularly limited thereto. The microfine
fibers may be those directly produced by spinning a single kind of
polymer or those obtained by converting microfine fiber-forming
composite fibers (also simply referred to as microfine
fiber-forming fibers) which are produced from at least two kinds of
polymers. The microfine fiber-forming fibers may include, for
example, extraction-type composite fibers which are capable of
forming fibrillates of the island component by the dissolution or
decomposition of the sea component and division-type composite
fibers which are capable of being fibrillated to microfine fibers
of each polymer component by a mechanical/physical method or a
chemical method using a treating agent.
[0010] The polymer for microfine fibers is at least one kind of
polymer sparingly soluble in water which is selected from
melt-spinnable polyamides such as 6-nylon, 66-nylon and 12-nylon,
and melt-spinnable polyesters such as polyethylene terephthalate,
polytrimethylene terephthalate, polybutylene terephthalate and
their copolymers. The component to be removed by extraction or
decomposition of the extraction-type composite fibers is a
water-soluble polymer which is different from the microfine
fiber-forming component in the solubility and decomposability,
which is less compatible with the microfine fiber-forming
component, and which has a melt viscosity or surface tension
smaller than those of the microfine fiber-forming component under
the spinning conditions. Talking the prevention of environmental
pollution and the shrinking properties upon dissolution into
consideration, a heat-melting, hot water-soluble polyvinyl alcohol
is preferably used as the component to be removed by extraction or
decomposition. The microfine fibers may be spinning-colored with an
inorganic pigment such as carbon black and titanium oxide or an
organic pigment or may be added with a known additive for fibers,
in an extent not adversely affecting the effect of the
invention.
[0011] The heat-melting, hot water soluble polyvinyl alcohol (PVA)
is produced by saponifying a resin mainly constituted by vinyl
ester units. Examples of vinyl monomers for the vinyl ester units
include vinyl formate, vinyl acetate, vinyl propionate, vinyl
valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl
benzoate, vinyl pivalate and vinyl versatate, with vinyl acetate
being preferred in view of easiness of production of PVA.
[0012] PVA may be homo PVA or modified PVA introduced with
co-monomer units, with the modified PVA being preferred in view of
a good melt spinnability, water solubility and fiber properties. In
view of a good copolymerizability; melt spinnability and water
solubility, preferred examples of the co-monomers are
.alpha.-olefins having 4 or less carbon atoms such as ethylene,
propylene, 1-butene and isobutene; and vinyl ethers such as methyl
vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl
vinyl ether and n-butyl vinyl ether. The content of the comonomer
units in PVA is preferably 1 to 20 mol %, more preferably 4 to 15
mol %, and still more preferably 6 to 13 mol % base on the total
constitutional units in the modified PVA. Particularly preferred is
ethylene-modified PVA, because the fiber properties are enhanced
when the comonomer unit is ethylene. The content of the ethylene
units is preferably 4 to 15 mol % and more preferably 6 to 13 mol
%.
[0013] PVA can be produced by a known method such as bulk
polymerization, solution polymerization, suspension polymerization,
and emulsion polymerization. Generally, a bulk polymerization or
solution polymerization in the absence or presence of a solvent
such as alcohol is employed. Examples of the solution for the
solution polymerization include lower alcohols such as methyl
alcohol, ethyl alcohol and propyl alcohol. The copolymerization is
performed in the presence of a known initiator, for example, an azo
initiator or peroxide initiator such as
a,a'-azobisisobutyronitrile,
2,2'-azobis(2,4-dimethyl-varelonitrile), benzoyl peroxide, and
n-propyl peroxycarbonate. The polymerization temperature is not
critical and 0 to 150.degree. C. is recommended.
[0014] The viscosity average polymerization degree of PVA is
preferably 200 to 500, more preferably 230 to 470, and still more
preferably 250 to 450. The polymerization degree (P) is measured
according to JIS-KG726, in which a PVA-based resin is re-saponified
and purified, and then, an intrinsic viscosity [.eta.] is measured
in water at 30.degree. C. The polymerization degree (P) is
calculated from the following equation:
P=([.eta.]10.sup.3/8.29).sup.(1/0.62).
[0015] The saporfication degree of the PVA is preferably 90 to
99.99 mol %, more preferably 93 to 99.98 mol %, still more
preferably 94 to 99.97 mol %, and particularly preferably 96 to
99.96 mol %. The melting point of PVA (Tm) is preferably 160 to
230.degree. C., more preferably 170 to 227.degree. C., still more
preferably 175 to 224.degree. C., and particularly preferably 180
to 220.degree. C. Using DSC (TA3000 manufactured by Mettler Co.
Ltd.), the sample was heated to 300.degree. C. at a temperature
rising rate of 10.degree. C./min in nitrogen atmosphere, cooled to
room temperature, and then, heated again to 300.degree. C. at a
temperature rising rate of 10.degree. C./min. The peak top
temperature of the obtained endothermic curve is taken as the
melting point.
[0016] After spinning, the microfnme fiber-forming fibers are cut
to staples of 20 to 120 mm long having a fineness of 1 to 15 dtex,
optionally after drawing, heat treatment and mechanical crimping.
The staples are carded and then made into the fiber web A' by a
webber. Alternatively, the fiber web A' may be made directly form
long fibers simultaneously with the spinning thereof by a spunbond
method without mechanically drawing so much. After superposing in a
desired weight and thickness, the fiber web A' is used in the
production of the raised sheet optionally after a pre-entangling
treatment by a known method such as needle punching and water
jet.
[0017] The mass per unit area of the fiber web A' is selected
according to the mass per unit area of the aimed raised sheet, and
preferably 80 to 2000 g/m.sup.2, more preferably 100 to 1500
g/m.sup.2. To make the entanglement with the woven or knitted
fabric C easy, the fiber web A' may be needle-punched in a punching
density of 20 to 100 punch/cm.sup.2, before superposing on the
woven or knitted fabric C. The punching density referred to herein
is a total number of felt needles which are punched to a web per
unit area during a needle punching treatment. For example, when a
needle board having felt needles in a density of 10/cm.sup.2 is
punched 50 times, the punching density is 500 punch/cm.sup.2.
[0018] In view of obtaining the surface abrasion resistance, it is
important that a part of the microfine fibers of the entangled
nonwoven fabric A penetrates through the polyurethane sheet E and
bonds to the polyurethane. To attain this, the polyurethane is
preferably present in the polyurethane sheet B in a highly
continuous state along the direction parallel to its surface,
namely, in a film state. To allow the microfine fibers constituting
the entangled nonwoven fabric A to penetrate through the
polyurethane sheet B and the woven or knitted fabric C, the
polyurethane sheet B is preferably a nonwoven fabric. Such a
polyurethane nonwoven fabric is obtained, for example, by a melt
blown method described below.
[0019] Polyurethane is preferably a thermoplastic polyurethane
which is produced from a polymer diol, an organic diisocyanate and
an optional chain extender each in a desired proportion by a melt
polymerization, a bulk polymerization or a solution polymerization.
Examples of the polymer diol include a polyester diol having an
average molecular weight of 600 to 3000 which is produced by the
reaction between at least one diol component selected from a
straight-chain aliphatic diol, a branched aliphatic diol or an
alicyclic aliphatic diol each having 2 to 12 carbon atoms such as
ethylene glycol, propanediol, 1,4-butanediol, 1,5-pentanediol,
3-methyl-1,5-pentanediol, neopentyl glycol and 1,6-hexanediol, and
at least one dicarboxylic acid component selected from an aliphatic
carboxylic acid such as succinic acid, glutaric acid, adipic acid
and their carboxylic esters. The organic diisocyanate is mainly
selected from an organic or alicyclic diisocyanate such as
phenylene diisocyanate, tolylene diisocyanate and
4,4'-diphenylmethane diisocyanate. An organic diisocyanate selected
from an aliphatic diisocyanate or a diisocyanate having a
naphthalene ring may be partly used, if necessary. The chain
extender may be selected from a low molecular compound having two
active hydrogen atoms such as diol, aminoalcohol, hydrazine and
diamine. The polyurethane is not limited to the polyester
polyurethane described above, and a polyether polyurethane, a
polycarbonate polyurethane, a copolymer polyurethane and their
mixture may be used according to the kind of aimed
polyurethane.
[0020] To obtain a nonwoven fabric excellent in the uniformity, a
thermoplastic polyurethane which has a polymer diol for
constituting the soft segment in an amount of 45 to 75% by mass is
preferably used. Also preferred is a polyurethane produced by the
polymerization in the presence of a chain extender mainly composed
of a compound selected from a low molecular aliphatic diol and
isophoronediamine. The polymerization degree of polyurethane is
preferably controlled such that the intrinsic viscosity [.eta.] is
0.5 to 1.5 dl/g when measured in DMF. The content of the soft
segment in polyurethane is preferably 45% by mass or more, because
the spinnability of molten polymer is good, the conversion to
microfine fibers is easy, and the flexibility, elasticity, shape
stability and surface smoothness of the polyurethane sheet 13 are
good. To prevent the spinnability from being lowered and the
conversion to microfnme fibers from being difficult, the content of
the soft segment is preferably 75% by mass or less. If the
intrinsic viscosity [.eta.] is 0.5 dl/g or more, the spinnability
is good and the conversion to microfine fibers is easy. If being
1.5 dl/g or less, the melt viscosity is moderate and the fiber flow
is good. The polyurethane may be added with an additive such as
antiblocking agent, stabilizer, colorant and antistatic agent in a
suitable amount.
[0021] The softening temperature of polyurethane is preferably 100
to 220.degree. C. The softening temperature is defined as the end
point of a rubbery flat region in a curve showing the temperature
dependency of the storage elastic modulus, which is obtained by a
tensile dynamic viscoelastic measurement frequency: 11 Hz). The
softening temperature is largely dependent particularly upon the
molecular weight of polyurethane and the kinds and proportions of
the organic diisocyanate (hard segment) and chain extender.
Therefore it is preferred to select the molecular weight and the
hard segment so as to regulate the softening temperature of
polyurethane within the above range, while taking the easiness of
forming the polyurethane sheet B, aimed properties and the
adhesiveness with the microfine fibers in the production of the
raised sheet into consideration.
[0022] In the production of the nonwoven fabric for the above
polyurethane by a melt blow method, the spinning temperature is
selected from 220 to 280.degree. C. such the melt viscosity of
polyrethane is 500 P or less, and the amount of blowing air is
controlled so as to obtain a desired mass per unit area.
[0023] The mass per unit area of the polyurethane sheet B is
preferably 10 to 150 g/m.sup.2. If being 10 g/m.sup.2 or more, a
sufficient elasticity is obtained and the surface abrasion
resistance is good. If being 150 g/m.sup.2 or less, an excessively
large weight of the total raised sheet and a rubbery hand can be
avoided.
[0024] The woven or knitted structure of the woven or knitted
fabric C is not critical in the present invention. The fibers for
the woven or knitted fabric C may be selected from fibers of a
known polymer as long as the raised sheet having a strength which
fits for practical use in the intended application is obtained. In
view of the balance between the hand and properties of the woven or
knitted fabric which depends upon the count of yarns, multifilament
yarns are preferably used, although monofilament yarns and spun
yarns are also usable. If the woven or knitted fabric is made from
multifilament yarns composed of bundles of fibers, it is preferred
to twist or size the yarns so as to prevent the filament from being
disbundled. The number of twist is preferably about 10 to 900
turn/m in view of the hand of the resultant raised sheet, although
not limited thereto. The count of yarns is preferably 30 to 200
dtex, although suitably changed according to the intended use. If
being 200 dtex or less, the hand of the resultant raised sheet is
soft and the thickness can be reduced. If being 30 dtex or more, a
necessary strength is obtained even when the number of weaving is
small, and the fiber web A' and the woven or knitted fabric C are
sufficiently united by a needle punching or a hydroentanglement.
The number of filaments in a single multifilament yarn is
preferably 6 to 100. Although the yarns become soft as the number
of filament increases, the properties thereof are reduced and the
yarns become easily damaged in the step of fixing the penetrated
fibers described below. Therefore, the number of filament is
preferably selected from the above range according to the balance
between the intended hand and properties. If the microfine
fiber-forming fibers mentioned above are uses as the filament for
the multifilament yarns, the number of filament can be increased by
the conversion to microfine fibers in a stage after the penetrating
step. By conducting the penetrating step so as to prevent the
damage of yarns as much as possible, the raised sheet having a good
hand can be obtained. The mass per unit area of the woven or
knitted fabric C is preferably 30 to 200 g/m.sup.2 in view of the
hand of the resultant raised sheet. If being 30 g/m.sup.2 or more,
the woven or knitted fabric acquires a sufficient strength and the
loss of shape due to slippage of yarns is prevented. If being 200
g/m.sup.2 or less, the resultant raised sheet has a soft hand and
the woven or knitted fabric C and the fiber web A' are firmly
united.
[0025] The order of superposing the entangled nonwoven fabric A,
the polyurethane sheet B and the woven or knitted fabric C in the
raised sheet is not critical, and may be superposed in the order of
entangled nonwoven fabric A/polyurethane sheet B/woven or knitted
fabric C or entangled nonwoven fabric A/woven or knitted fabric
C/polyurethane sheet B. To improve the appearance and hand of the
back surface (surface opposite to the entangled non woven fabric A)
or regulating the thickness or mass per unit area of the raised
sheet, the entangled nonwoven fabric D may be disposed on the back
surface to obtain a layered structure of entangled nonwoven fabric
A/polyurethane sheet B/woven or knitted fabric C/entangled nonwoven
fabric D or a layered structure of entangled nonwoven fabric
A/woven or knitted fabric C/polyurethane sheet B/entangled nonwoven
fabric D. When the raised sheet has the above layered structure and
a part of the microfine fibers constituting the entangled nonwoven
fabric A penetrates through the polyurethane sheet B and the woven
or knitted fabric C thereby to be entangled with the fibers
constituting the entangled nonwoven fabric D, each layer is united
firmly and the raised sheet has good hand, touch and properties on
its both surfaces. Alternatively, a part of the fibers constituting
the entangled nonwoven fabric D may be allowed to penetrate through
the polyurethane sheet B and the woven or knitted fabric C so as to
be entangled with the microfine fibers constituting the entangled
nonwoven fabric A.
[0026] The kind and fineness of the fibers for constituting the
entangled nonwoven fabric D and the mass per unit area of the
entangled nonwoven fabric D may be selected from the polymer and
ranges which are described above with respect to the entangled
nonwoven fabric A. The kind and fineness of fibers and the mass per
unit area may be the same or different between the entangled
nonwoven fabric D and the entangled nonwoven fabric A.
[0027] The method of uniting the fiber web A' the polyurethane
sheet B and the woven or knitted fabric C is not particularly
limited. When the fiber web A' having a large mass per unit area is
used, a needle punching is preferably employed because the
microfine fiber-forming fibers in the fiber web A' are effectively
entangled and the three layers are united simultaneously. The
punching density is preferably 300 to 4000 punch/cm.sup.2 and more
preferably 500 to 3500 punch/cm.sup.2. If being 300 punch/cm.sup.2
or more, the three layers are firmly united. If being 4000
punch/cm.sup.2 or less, the fibers in the fiber web A' and the
woven or knitted fabric C are little damaged to prevent the
reduction of properties. The punching depth is set such that at
least a part of the fibers in the fiber web A' penetrates through
the polyurethane sheet B and the woven or knitted fabric C so as to
enhance the surface abrasion resistance of the resultant raised
sheet. Namely, when punching from the side of the fiber web A', the
punching depth is set so as to allow the barbs of needles to pass
through the polyurethane sheet B and the woven or knitted fabric C.
When the fibers constituting the woven or knitted fabric C are
extremely thick as compared with the microfine fibers which finally
constitute the entangled nonwoven fabric A, or when the color and
dyeability of the fibers constituting the woven or knitted fabric C
are different from those of the microfine fibers, it is preferred
to prevent the fibers of the woven or knitted fabric C from being
exposed to the surface. Therefore, when punching from the side of
the polyurethane sheet B or the side of the woven or knitted fabric
C, the punching depth is set such that the barb nearest to the tip
of needle does not project from the surface of the fiber web A'.
However, such may be not necessarily applied, if the fineness of
the fibers constituting the woven or knitted fabric C is the same
or smaller than that of the microfine fibers or if the appearance
such as color and dyeability is not disharmonious. Also, in the
production of the raised sheet having the entangled nonwoven fabric
D, the punching depth is set such that the fibers constituting the
woven or knitted fabric C are not exposed to the surface of the
entangled nonwoven fabric D, if the appearance is likely to become
disharmonious.
[0028] By the above needle punching, the microfine fiber-forming
fibers are sufficiently entangled to convert the fiber web A' to
the entangled nonwoven fabric A'' and simultaneously the three or
four layers are united by the entanglement. Optionally after
adjusting the apparent density to 0.2 to 0.7 g/cm.sup.3 and the
thickness to 0.6 to 4 mm by heat-pressing the entangled body, an
elastic polymer is provided at least to the interstices between the
entangled microfine fiber-forming fibers in the entangled nonwoven
fabric A''. By providing the elastic polymer, a hand and dense
feeling like natural leathers are obtained and the mechanical
properties are further enhanced. The elastic polymer is preferably
the polyurethane mentioned above in view of a hand and dense
feeling.
[0029] The elastic polymer is provided by impregnating or applying
its solution, dispersion or hot melt. However, the use of a
solution containing a solvent which dissolves the polyurethane
constituting the polyurethane sheet B much more than needed or the
use of a hot melt which melts the polyurethane much more than
needed is not recommended. If the polyurethane is used as the
elastic polymer, a 3 to 40% by mass aqueous emulsion prepared by
dispersing the polyurethane to a non-solvent for the polyurethane,
i.e., a liquid mainly composed of water, is preferably used. The
elastic polymer provided is coagulated by a wet method such as a
hot water treatment at 70 to 100.degree. C. and a steam treatment
at 100 to 200.degree. C. or a dry method such as a heat treatment
in a dryer at 50 to 200.degree. C., preferably by the dry
method.
[0030] The elastic polymer may be added, if necessary, with an
additive such as a colorant, for example, carbon black and pigment,
a thickening agent, an antioxidant and a dispersing agent. If the
polyurethane is used as the elastic polymer, the amount to be
provided is preferably 5 to 50% by mass, more preferably 10 to 40%
by mass (solid basis) of the entangled nonwoven fabric before the
conversion to microfine fibers, i.e., the entangled nonwoven fabric
A', in view of the soft hand and elasticity of the raised sheet.
Within the above range, the elastic polymer forms a dense spongy
structure (porous structure) to give a soft hand. In addition, the
effect of preventing the loss of shape by the woven or knitted
fabric C is enhanced.
[0031] If the fiber web A' is made of the microfine fiber-forming
composite fibers, the composite fibers are converted to microfine
fibers or bundles of microfine fibers by removing at least one of
the polymer components (for example, sea component) by the
treatment with a solvent or decomposer or by a mechanical or
chemical treatment, thereby converting the entangled nonwoven
fabric A'' to the entangled nonwoven fabric A. If the sea-island
composite fibers having PVA described above as the sea component
are used, the sea component PVA is removed by dissolution by
immersing the entangled body in a water bath of 80 to 95.degree. C.
for 5 to 120 min, thereby converting the composite fibers to the
microfine fibers or bundles of microfine fibers. The average single
fiber fineness of the microfine fibers is preferably 0.0003 to 0.5
dtex, more preferably 0.005 to 0.35 dtex, and still more preferably
0.01 to 0.2 dtex. The fineness of the bundles of microfine fibers
is preferably 0.25 to 5 dtex, and 4 to 10000 microfine fibers are
contained in a single bundle.
[0032] The conversion of the microfine fiber-forming fibers may be
conducted before the elastic polymer is provided. However, if the
elastic polymer is provided after the conversion to the bundles of
microfine fibers, the elastic polymer bonds to the microfine fibers
to likely make the hand hard. Therefore, the conversion to the
bundles of microfine fibers is preferably conducted after providing
the elastic polymer. In case of conducting the conversion to the
bundles of microfine fibers before providing the elastic polymer,
it is preferred to temporarily provide the entangled nonwoven
fabric with a filler such as polyvinyl alcohol which is removable
by dissolution so as to prevent the microfine fibers and the
elastic polymer from bonding to each other. Thereafter, the elastic
polymer is provided and then the filler is removed.
[0033] To enhance and adjust the hand, dense feeling and mechanical
properties including the surface abrasion resistance of the raised
sheet, a small amount of the elastic polymer may be provided, if
necessary, at any stage after the conversion to the bundles of
microfine fibers, i.e., at a stage after the conversion to
microfine fibers, at a stage after the raising treatment, at a
stage after the dyeing treatment, etc. However, the amount of the
elastic polymer to be provided at such stages should be controlled
to a minimum amount for obtaining the intended hand and properties,
for example, should be controlled to about 10% or less of the mass
per unit area of the entangled nonwoven fabric A, because the
elastic polymer bonds to the microfine fibers as described
above.
[0034] To improve the surface abrasion resistance of the raised
sheet, at least a part of the microfine fibers of the entangled
nonwoven fabric A which penetrate through the polyurethane sheet B
is bonded and fixed to the polyurethane by heat-treating the
polyurethane sheet B at any stage after the conversion to the
microfine fibers (step of fixing the penetrated fibers). The
heating treatment may be conducted by any method as long as the
polyurethane can be heated to a temperature at which the
polyurethane is plasticized and capable of bonding to the microfine
fibers of the entangled nonwoven fabric A, i.e., the heat softening
temperature of the polyurethane or higher. The heat treatment may
be conducted by using a tenter or net hot-air dryer or a
far-infrared dryer, although not limited thereto. During the heat
treatment, the sheet may be compressed by a press roll. The
compression is preferably conducted because the heat-treating
temperature can be set lower than not compressed. The heating
treatment may be conducted at once in a single step or separately
in several steps. The heat treatment is preferably conducted at the
heat softening temperature of the polyurethane or higher, fore
example, at 120 to 200.degree. C. for 20 s to 20 min, although
depending upon the mass per unit area, thickness and density of the
resultant raised sheet and the mass per unit area of the
polyurethane sheet B. If the entangled nonwoven fabric A is made of
the microfine fibers which are directly spun, it is preferred to
pre-heat the fiber web A', the polyurethane sheet B and the woven
or knitted fabric C after the entanglement to a united body,
because the surface abrasion resistance of the raised sheet is
further improved. In case of providing the bask surface with the
entangled nonwoven fabric D as describe above, a part of the fibers
constituting the entangled nonwoven fabric D may be allowed to
penetrate through the polyurethane sheet B and woven or knitted
fabric C, and at least a part of the penetrated fibers may be fixed
to the polyurethane in the manner described above.
[0035] The sheet thus produced is then sliced or buffed so as to
have a desired thickness. Thereafter, the surface of the entangled
nonwoven fabric A is buffed by a known method using a sand paper or
a card clothing, thereby forming a surface having raised microfine
fibers. After optionally conducting a post-treatment such as
dyeing, the raised sheet having a desired appearance and hand is
obtained.
[0036] The thickness of the raised sheet thus obtained is, although
depending upon its final use, preferably 0.4 to 3 mm for use as the
covering fabric of chairs. The apparent density is preferably 0.1
to 0.8 g/cm.sup.3, because a good dense feeling, drapeability and
mechanical properties are obtained. The mass per unit area is
preferably 100 to 1500 g/m.sup.2. The thickness of each layer in
the raised sheet is preferably 0.3 to 2.5 mm for the entangled
nonwoven fabric A, preferably 0.03 to 0.2 mm for the polyurethane
sheet B, preferably 0.05 to 0.2 mm for the woven or knitted fabric
C, and preferably 0.2 to 1.0 mm for the entangled nonwoven fabric
D.
[0037] The raised sheet has a constant load elongation of 10% or
less in both MD and TD and a residual strain of 3% or less in both
MD and TD, when measured in the methods described below. Within the
above ranges, the raised sheet exhibits a good shape stability.
EXAMPLES
[0038] The present invention will be described in more detail with
reference to the examples. However, it should be noted that the
scope of the present invention is not limited thereto. The
"part(s)" and "%" used in the examples to indicate the amounts and
ratios are based on the mass unless otherwise noted. The measuring
methods are described below.
(1) Constant Load Elongation and Residual Strain
[0039] The measurement was made according to JASO M 403-88 6.5
(Test Method for Automotive Seat-Trim Fabrics) by Society of
Automotive Engineers of Japan, Inc.
[0040] Three test pieces (width; 80 mm, length: 250 mm) were cut
out of a raised sheet along each of the machine direction and the
transverse direction. Two gage marks perpendicular to the machine
direction were drawn at the central portion of each test pieces at
a distance of 100 mm. Then, the test piece was clipped onto an
upper grip of Martens fatigue tester at its lengthwise end and held
vertically. The lower end of the test piece was clipped onto a
lower grip at a clip distance of 150 mm. A load of 98.1 N (10 kgf)
inclusive of the lower grip was put on the lower end of the test
piece. After 10 min, the distance between gage marks (mm) was
measured and the load was removed. The test piece was placed on a
flat stand and the distance between gage marks was measured after
10 min from the removal of load. The constant load elongation (%)
and residual strain (%) were calculated from the following
equations:
Constant load elongation
(%)=(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 (mm) between gage marks before the
test, L.sub.1 is the distance (mm) between gage marks after 10 min
of the loading, and L.sub.2 is the distance (mm) between gage marks
after 10 min from the removal of load.
[0041] The result is expressed by an average of three calculated
values for each of the machine direction and transverse direction
of the raised sheet.
[0042] The covering fabric for chair shows a better shape stability
in long term use, if the constant load elongation and residual
strain are smaller.
(2) Surface Abrasion Resistance
[0043] The abrasion loss was measured according to Martindale
abrasion test of JIS L1096 under a load of 12 kPa and the number of
abrasion of 5000 times.
Production Example 1
Production of Polyurethane Sheet B
[0044] Into a screw kneading polymerizer, poly-3-methyl-1,5-pentyl
adipate glycol having an average molecular weight of 1150,
polyethylene glycol having an average molecular weight of 2000,
4,4'-diphenylmethane diisocyanate, and 1,4-butanediol were charged
in a molar ratio of 0.9:0.1:4:3 (4.63% of theoretical amount of
nitrogen when calculated based on the amount of isocyanate group),
and then the melt polymerization was allowed to proceed to produce
polyurethane. The heat softening point of polyurethane was
125.degree. C. The molten polyurethane was melt-blown to form a
random web as follows. The molten polyurethane was extruded from
the slots on a die orifice heated at 260.degree. C. The fibrous
molten polyurethane was made into fine fibers Abets by an air jet
of 260.degree. C. and collected on a wire cloth moving at 2 m/min
at a collection distance of 40 cm. The obtained melt-blown
polyurethane nonwoven fabric B was composed of fine fibers of about
0.13 dtex and had an average mass per unit of 45 g/m.sup.2, an
average thickness of 1.8 mm and an apparent density of 0.25
g/cm.sup.3.
Production Example 2
Production of Woven Fabric C
[0045] Polyester yarns (80 dtex/36 f) subjected to false twisting
were further subjected to additional twisting by 600 turn/m and
then woven at a weaving density of 82 yarns/inch (warp).times.76
yarns/inch (weft), to obtain a woven fabric C having a mass per
unit area of 70 g/m.sup.2, a thickness of 0.17 mm and an apparent
density of 0.412 g/cm.sup.3.
Production Example 3
Production of Water-Soluble, Thermoplastic Polyvinyl Alcohol
[0046] A 100-L pressure reactor equipped with a stirrer, a nitrogen
inlet, an ethylene inlet and an initiator inlet was charged with
29.0 kg of vinyl acetate and 31.0 kg of methanol. After raising the
temperature to 60.degree. C., the reaction system was purged with
nitrogen by bubbling nitrogen for 30 min. Then, ethylene was
introduced so as to adjust the pressure of the reactor to 5.9
kgf/cm.sup.2. A 2.8 g/L methanol solution of
2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) was purged with
nitrogen by nitrogen gas babbling. After adjusting the temperature
of reactor to 60.degree. C., 170 mL of the initiator solution was
added to initiate the polymerization. During the polymerization,
the pressure of reactor was maintained at 5.9 kgf/cm.sup.2 by
introducing ethylene, the polymerization temperature was maintained
at 60.degree. C., and the initiator solution was continuously added
at a rate of 610 mL/h. When the conversion of polymerization
reached 70% after 10 h, the polymerization was terminated by
cooling.
[0047] After releasing ethylene from the reactor, ethylene was
completely removed by bubbling nitrogen gas. The non-reacted vinyl
acetate monomer was removed under reduced pressure to obtain a
methanol solution of polyvinyl acetate, which was then diluted to
50% concentration with methanol To 200 g of the 50% methanol
solution of polyvinyl acetate (100 g of polyvinyl acetate in the
solution), 46.5 g of a 10% methanol solution of NaOH was added. The
molar ratio of NaOH/vinyl acetate unit was 0.10. After about 2 min
of the addition of the alkali solution, the system was gelated. The
gel was crushed by a crusher and allowed to stand at 60.degree. C.
for one hour to allow the saponification to further proceed. Then,
1000 g of methyl acetate was added. After confirming the completion
of neutralization of the remaining alkali by phenolphthalein
indicator, white solid (modified PVA) was separated by filtration.
The white solid (modified PVA) was added with 1000 g of methanol
and allowed to stand at room temperature for 3 h for washing. After
repeating the above washing operation three times, the liquid was
centrifugally removed and the solid remained was dried at
70.degree. C. for 2 days to obtain a dried modified PVA.
[0048] The saponification degree of the ethylene-modified PVA was
98.4 mol %. The modified PVA was incinerated and dissolved in an
acid for analysis by atomic-absorption spectroscopy. The content of
sodium was 0.03 part by mass based on 100 parts by mass of the
modified PVA. After repeating three times the
reprecipitation-dissolution operation in which n-hexane is added to
the methanol solution of polyvinyl acetate obtained by removing the
non-reacted vinyl acetate monomer after the polymerization to cause
precipitation and acetone is then added for dissolution, the
precipitate was vacuum-dried at 80.degree. C. for 3 days to obtain
a purified polyvinyl acetate. The polyvinyl acetate was dissolved
in d6-DMSO and analyzed by 500 MHz H-NMR (JEOL GX-500) at
80.degree. C. The content of ethylene unit was 10 mol %.
[0049] The above methanol solution of polyvinyl acetate was added
with a 10% methanol solution of NaOH. The molar ratio of NaOH/vinyl
acetate unit was 0.5. The resultant gel was crushed and the
saponification was allowed to further proceed by standing at
60.degree. C. for 5 h. The saponification product was extracted by
Soxhlet with methanol for 3 days and the obtained extract was
vacuum-dried at 80.degree. C. for 3 days to obtain a purified,
ethylene-modified PVA. The average polymerization degree of the
purified, modified PVA was 330 when measured by a method of JIS
K6726. The content of 1,2-glycol linkage and the content of three
consecutive hydroxyl groups in the purified, modified PVA were
respectively 1.50 mol % and 83% when measured by 5000 MHz H-NMR
(JEOL GX-500). A 5% aqueous solution of the purified, modified PVA
was made into a cast film of 10 .mu.m thick, which was then
vacuum-dried at 80.degree. C. for one day and then measured for the
melting point in the manner described above. The melting point was
206.degree. C.
Production Example 4
Production of Microfine Fiber-Forming Fibers
[0050] The water-soluble, thermoplastic PVA (sea component)
produced above and an isophthalic acid-modified polyethylene
terephthalate (degree of modification of 8 mol %, island component)
having a melting point of 234.degree. C. and an intrinsic viscosity
of 0.65 (measured at 30.degree. C. in an equiamount mixed solution
of phenol/tetrachloroethane) were extruded form a spinneret for
melt composite spinning (0.25 mm .phi., 37 islands, 550 holes) at a
spinning temperature of 260.degree. C. in a sea component/island
component ratio of 30/70 (by mass). The spun fibers were drawn in a
roller plate manner under usual conditions. The spinning
properties, continuous running properties and drawability were good
and no problem was caused. The sea-island composite fibers were
crimped and cut to staples of 51 mm long. The staples of sea-island
composite fibers had a single fiber fineness of 4.13 dtex and good
mechanical properties such as a strength of 3.2 cN/dtex and an
elongation of 40%.
Example 1
(1) Preparation of Fiber Web A'
[0051] The staples of sea-island composite fibers (microfine
fiber-forming fibers) were made into a web through a carding step
and a crosslapping step. The web was pre-entangled by a needle
punching at a density of 40 punch/cm.sup.2, to obtain a fibrous web
A' made of Microfine fiber-forming fibers which had a mass per unit
area of 300 g/m.sup.2, a thickness of 2.5 mm and an apparent
density of 0.12 g/cm.sup.3.
(2) Preparation of Raised Sheet
[0052] The fibrous web A', the polyurethane nonwoven fabric B and
the plain woven fabric C were superposed in this order. The
superposed body was needle-punched with single barb felt needles
first from the side of the fibrous web A' at a punching density of
1200 punch/cm.sup.2 and then from the side of the plain woven
fabric C at a punching density of 400 punch/cm.sup.2 to convert the
fibrous web A' to an entangled nonwoven fabric A'' and
simultaneously unite the entangled nonwoven fabric A'', the
polyurethane nonwoven fabric B and the plain woven fabric C,
thereby obtaining a three-dimensionally entangled fibrous body
having a mass per unit area of 430 g/m.sup.2. The needle punching
from the side of the fibrous web A' was conducted such that the
barbs of felt needles passed through the plain woven fabric C, and
the needle punching from the side of the plain woven fabric C was
conducted such that the barbs of felt needles did not come out on
the surface of the fibrous web A'. The three-dimensionally
entangled fibrous body thus obtained was heated in a hot air of
200.degree. C. and pressed by a metal roll, to regulate the
apparent density to 0.45 g/cm.sup.3 (1.07 mm thick). Then, the
three-dimensionally entangled fibrous body was impregnated with a
40% aqueous emulsion of polyether-type polyurethane (Evafanol AP-12
manufactured by Nicca Chemical Co., Ltd.) and the impregnated
amount was adjusted to a pickup degree of 65% by squeezing with a
mangle. Successively thereafter, the three-dimensionally entangled
fibrous body was dried in a pin tenter dryer at 150.degree. C. for
7 min.
[0053] The polyurethane-impregnated, three-dimensionally entangled
fibrous body was repeatedly immersed in a hot water of 90.degree.
C. and then squeezed to remove the sea component (water-soluble,
thermoplastic PVA) and then dried in a pin tenter dryer at
140.degree. C. for 5 min, thereby converting the entangled nonwoven
fabric A'' to an entangled nonwoven fabric A. After raising the
surface of the entangled nonwoven fabric A by buffing with a sand
paper, the three-dimensionally entangled fibrous body was dyed gray
by a jet dyeing with a disperse dye at 130.degree. C. for 1 h. The
dyed three-dimensionally entangled fibrous body was dried in a pin
tenter dryer at 140.degree. C. for 5 mm and finally the raised naps
were ordered, to obtain a raised sheet having a thickness of 0.9 mm
and a mass per unit area of 400 g/m.sup.2. The thickness of each
layer of the raised sheet was 0.63 mm for the entangled nonwoven
fabric A, 0.1 mm for the polyurethane nonwoven fabric B, and 0.17
mm for the plain woven fabric C.
[0054] The obtained raised sheet was cross-sectionally observed
under an electron microscope. The polyurethane nonwoven fabric B
was melted to form a film. The microfine fibers of the entangled
nonwoven fabric A which penetrated through the polyurethane
nonwoven fabric B were partly bonded and fixed to polyurethane. The
constant load elongation of the raised sheet was 2% in both MD and
TD, and the residual strain was 1% or less in both MD and TD. The
raised sheet had a rounded hand and a moderate elasticity. The seat
portion of a vehicle seat was completely covered using the raised
sheet as the covering fabric. After sitting on the obtained seat
continuously for 1 h, the surface of the seat portion was observed.
Particular deformation and wrinkles which largely impaired the
quality of covering fabric were not found. The abrasion loss of
raised sheet after Martindale abrasion test was 3 mg or less and
the change in appearance such as piling was not found.
Example 2
[0055] Using the microfine fiber-forming fibers produced in
Production Example 4, a fibrous web D' having a mass per unit area
of 200 g/m.sup.2, a thickness of 2 mm and an apparent density of
0.10 g/cm.sup.3 was prepared. Using the fibrous web D' together
with the polyurethane nonwoven fabric B, the plain woven fabric C
and the fibrous web A' each being obtained in Production Examples 1
and 2 and Example 1, a superposed body of fibrous web
A'/polyurethane nonwoven fabric B/plain woven fabric C/fibrous web
D' was obtained. Then, the superposed body was needle-punched with
single barb felt needles first from the side of the fibrous web A'
at a punching density of 800 punch/cm.sup.2, next from the side of
the fibrous web D' at a punching density of 600 punch/cm.sup.2, and
finally again from the side of the fibrous web A' at a punching
density of 200 punch/cm.sup.2. With such a needle punching, the
fibrous web A' and the fibrous web D' were converted to an
entangled nonwoven fabric A'' and entangled nonwoven fabric D'',
respectively, and simultaneously, the entangled nonwoven fabric
A'', the polyurethane nonwoven fabric B, the plain woven fabric C
and the entangled nonwoven fabric D'' were united together, to
obtain a three-dimensionally entangled fibrous body having a mass
per unit area of 630 g/m.sup.2. The needle punching from the side
of the fibrous web A' and the needle punching from the side of the
fibrous web D' were conducted such that the barbs of felt needles
passed through the fibrous web D' and the fibrous web A',
respectively. Thereafter, in the same manner as in Example 1, the
apparent density was adjusted to 0.45 g/cm.sup.3, polyurethane was
impregnated, and the microfine fiber-forming fibers were converted
to microfine fibers. Then, the obtained three-dimensionally
entangled fibrous body was made into a double-raised sheet in the
same manner as in Example 1 except for raising the surfaces of both
the entangled nonwoven fabric A and the entangled nonwoven fabric D
by buffing with a sand paper.
[0056] The obtained raised sheet was cross-sectionally observed
under an electron microscope. The polyurethane nonwoven fabric B
was melted to form a film. The microfine fibers of the entangled
nonwoven fabric A and the entangled nonwoven fabric D which
penetrated through the polyurethane nonwoven fabric L were partly
bonded and fixed to polyurethane. The constant load elongation of
the raised sheet was 2% in both MD and TD, and the residual strain
was 1% or less in both MD and TD. The seat portion of a vehicle
seat was completely covered using the raised sheet as the covering
fabric with the entangled nonwoven fabric A or the entangled
nonwoven fabric D being out. After sitting on the obtained seat
continuously for 1 h, the surface of the seat portion was observed.
In both the cases, particular deformation and wrinkles which
largely impaired the quality of covering fabric were not found. The
abrasion loss of raised sheet after Martindale abrasion test was 3
mg or less in both the sides of the entangled nonwoven fabric A and
the entangled nonwoven fabric D, and the change in appearance such
as piling was not found.
Comparative Example 1
[0057] A raised sheet and a seat were produced in the same manner
as in Example 1 except for omitting the polyurethane nonwoven
fabric B. The hand of the obtained raised sheet was not rounded.
After sitting on the obtained seat continuously for 1 h, the
covering fabric was deformed and took several minutes to restore to
its original state. The abrasion loss of raised sheet after
Martindale abrasion test was 5 mg and the pilling occurred.
Comparative Example 2
[0058] A raised sheet and a seat were produced in the same manner
as in Example 1 except for omitting the plain woven fabric C. The
hand of the obtained raised sheet was good. However, after sitting
on the obtained seat continuously for 1 h, the covering fabric was
deformed and took 1 h or more to restore to its original state. The
abrasion loss of raised sheet after Martindale abrasion test was 5
mg and the change in appearance such as piling was not found.
Comparative Example 3
[0059] A raised sheet was produced in the same manner as in Example
1 except that the penetrated fibers are fixed at 110.degree. C. for
2 min. After dyeing, the sheet was dried in a pin tenter dryer at
110.degree. C. for 2 min, and finally the raised naps were ordered,
to obtain the raised sheet. The obtained raised sheet was
cross-sectionally observed under an electron microscope. The
microfine fibers of the entangled nonwoven fabric A which
penetrated through the polyurethane sheet B were not bonded to
polyurethane.
[0060] The hand of the raised sheet was the same as that of the
raised sheet obtained in Example 1. After sitting on the seat
produced in the same manner as in Example 1 continuously for 1 h,
particular deformation and wrinkles which largely impaired the
quality of covering fabric were not found. However, the abrasion
loss of raised sheet after Martindale abrasion test was 5 mg and
the pilling occurred.
INDUSTRIAL APPLICABILITY
[0061] The raised sheet of the present invention is excellent in
the shape stability, for example, it does not lose its shape even
after a long term use. In addition, the raised sheet has a good
surface abrasion resistance and a soft and high-quality hand. With
such excellent properties, the raised sheet is particularly useful
as the covering fabric for vehicle seats such as railroad vehicle
seat, automotive seat, airplane seat and ship seat and the covering
fabric for interior furniture such as sofa, cushion and chair which
are required to have a good shape stability. The raised sheet is
also effectively used in other applications, for example, wide
applications such as clothes, shoes, bags, pouches and gloves.
* * * * *