U.S. patent application number 16/978272 was filed with the patent office on 2021-01-14 for nonwoven fabric.
This patent application is currently assigned to Toray Industries, Inc.. The applicant listed for this patent is Toray Industries, Inc.. Invention is credited to Masaru Harada, Hiroshi Tsuchikura.
Application Number | 20210010175 16/978272 |
Document ID | / |
Family ID | 1000005123174 |
Filed Date | 2021-01-14 |
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United States Patent
Application |
20210010175 |
Kind Code |
A1 |
Harada; Masaru ; et
al. |
January 14, 2021 |
NONWOVEN FABRIC
Abstract
A nonwoven fabric that is fabricated is described, which
includes a non-melting fiber A having a high-temperature shrinkage
rate of 3% or less and a thermal conductivity conforming to
ISO22007-3 (2008) of 0.060 W/mK or less and a thermoplastic fiber B
having a LOI value conforming to JIS K 7201-2 (2007) of 25 or more
and having a density of more than 50 kg/m.sup.3 and less than 200
kg/m.sup.3, where the nonwoven fabric exhibits high flame-shielding
performance and has a heat insulating property.
Inventors: |
Harada; Masaru; (Otsu-shi,
Shiga, JP) ; Tsuchikura; Hiroshi; (Otsu-shi, Shiga,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toray Industries, Inc. |
Tokyo |
|
JP |
|
|
Assignee: |
Toray Industries, Inc.
Tokyo
JP
|
Family ID: |
1000005123174 |
Appl. No.: |
16/978272 |
Filed: |
March 13, 2019 |
PCT Filed: |
March 13, 2019 |
PCT NO: |
PCT/JP2019/010192 |
371 Date: |
September 4, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D04H 1/498 20130101;
D04H 1/435 20130101; D04H 1/4366 20130101 |
International
Class: |
D04H 1/4366 20060101
D04H001/4366; D04H 1/498 20060101 D04H001/498; D04H 1/435 20060101
D04H001/435 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2018 |
JP |
2018-067712 |
Claims
1. A nonwoven fabric comprising a non-melting fiber A having a
high-temperature shrinkage rate of 3% or less and a thermal
conductivity conforming to 15022007-3 (2008) of 0.060 W/mK or less
and a thermoplastic fiber B having a LOI value conforming to JIS K
7201-2 (2007) of 25 or more, wherein a density of the nonwoven
fabric is more than 50 kg/m.sup.3 and less than 200 kg/m.sup.3.
2. The nonwoven fabric according to claim 1, wherein a content of
the non-melting fiber A is 15% to 70% by mass.
3. The nonwoven fabric according to claim 1, comprising a fiber C
other than the non-melting fiber A and the thermoplastic fiber B at
20% by mass or less.
4. The nonwoven fabric according to claim 1, wherein the
non-melting fiber A is a flame resistant fiber or a
meta-aramid-based fiber.
5. The nonwoven fabric according to claims 1, wherein the
thermoplastic fiber B is a fiber formed of a resin selected from
the group consisting of anisotropic molten polyester, flame
retardant poly(alkylene terephthalate), flame retardant
poly(acrylonitrile butadiene styrene), flame retardant polysulfone,
poly(ether-ether-ketone), poly(ether-ketone-ketone), polyether
sulfone, polyarylate, polyarylene sulfide, polyphenylsulfone,
polyetherimide, polyamide-imide and any mixture of these
resins.
6. The nonwoven fabric according to claim 5, wherein the
thermoplastic fiber B is a fiber containing a sulfur atom at 15% by
mass or more.
7. The nonwoven fabric according to claims 1, wherein a density of
the nonwoven fabric is 70 to 160 kg/m.sup.3.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is the U.S. National Phase application of
PCT/JP2019/010192, filed Mar. 13, 2019, which claims priority to
Japanese Patent Application No. 2018-067712, filed Mar. 30, 2018,
the disclosures of these applications being incorporated herein by
reference in their entireties for all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to a nonwoven fabric.
BACKGROUND OF THE INVENTION
[0003] Conventionally, in applications required to exhibit flame
retardancy, a method in which a chemical having a flame retardant
effect is kneaded into polyester, nylon, and cellulose-based fibers
at the raw yarn stage and a method in which a chemical having a
flame retardant effect is applied to polyester, nylon, and
cellulose-based fibers in the post-processing have been
adopted.
[0004] As the flame retardant, halogen-based chemicals and
phosphorus-based chemicals are generally used, but replacement of
halogen-based chemicals with phosphorus-based chemicals have
recently proceeded because of the environmental regulations.
However, there are some phosphorus-based chemicals which do not
reach the flame retardant effect of conventional halogen-based
chemicals.
[0005] As a method for imparting higher flame retardancy, there is
a method in which a polymer exhibiting high flame retardancy is
combined. For example, paper formed of a composite of a flame
resistant yarn and a polyphenylene sulfide fiber (Patent Document
1) and a felt formed of a composite of a flame resistant yarn and a
polyphenylene sulfide fiber (Patent Document 2) are known.
PRIOR ART DOCUMENTS
Patent Documents
[0006] Patent Document 1: International Publication No.
2017/6807
[0007] Patent Document 2: Japanese Patent Laid-open
[0008] Publication No. 2013-169996
SUMMARY OF THE INVENTION
[0009] However, conventional flame retardant performance is
attained by testing how hardly the material itself is burned or
whether the material can shield the flames of the burner when being
heated from one surface using a burner prescribed in JIS, and it
cannot be said that the conventional flame retardant performance is
sufficient to prevent fire spread when the material is exposed to
flames raging furiously like an actual fire for a long time or when
other combustibles are present. In the method described in Patent
Document 1, the flame can be shielded by the burner prescribed in
JIS, but in a case in which the temperature of the heating source
is higher or combustibles which ignite by temperature rise are in
close contact with paper, ignition occurs when the temperature on
the back side that is not hit by the flame rapidly rises and
exceeds the ignition point of the combustibles which are in close
contact with the back side that is not hit by the flame as
polyphenylene sulfide carbonized by the flame transmits heat, and
there is thus room for improvement. Patent Document 2 discloses
felt formed of a composite of a flame resistant yarn and a
polyphenylene sulfide fiber, but the felt density is low and there
is a possibility that combustibles ignite when the air heated by
the burner escapes from the felt gap, the ambient temperature on
the opposite side that is not hit by the flame rapidly rises and
the combustibles are arranged on the opposite side that is not hit
by the flame.
[0010] Accordingly, an object of the present invention is to
provide a nonwoven fabric exhibiting high flame shielding
performance and heat insulating property.
[0011] The present invention adopts the following means in order to
solve the above problems.
[0012] (1) A nonwoven fabric including a non-melting fiber A having
a high-temperature shrinkage rate of 3% or less and a thermal
conductivity conforming to ISO22007-3 (2008) of 0.060 W/mK or less
and a thermoplastic fiber B having a LOI value conforming to JIS K
7201-2 (2007) of 25 or more, in which a density of the nonwoven
fabric is more than 50 kg/m.sup.3 and less than 200 kg/m.sup.3.
[0013] (2) The nonwoven fabric according to (1), in which a content
of the non-melting fiber A is 15% to 70% by mass.
[0014] (3) The nonwoven fabric according to (1) or (2), including a
fiber C other than the non-melting fiber A and the thermoplastic
fiber B at 20% by mass or less.
[0015] (4) The nonwoven fabric according to any one of (1) to (3),
in which the non-melting fiber A is a flame resistant fiber or a
meta-aramid-based fiber.
[0016] (5) The nonwoven fabric according to any one of (1) to (4),
in which the thermoplastic fiber B is a fiber formed of a resin
selected from the group consisting of anisotropic molten polyester,
flame retardant poly(alkylene terephthalate), flame retardant
poly(acrylonitrile butadiene styrene), flame retardant polysulfone,
poly(ether-ether-ketone), poly(ether-ketone-ketone), polyether
sulfone, polyarylate, polyarylene sulfide, polyphenylsulfone,
polyetherimide, polyamide-imide, and any mixture of these resins.
(6) The nonwoven fabric according to (5), in which the
thermoplastic fiber B is a fiber containing a sulfur atom at 15% by
mass or more.
[0017] (7) The nonwoven fabric according to any one of (1) to (6),
in which a density of the nonwoven fabric is 70 to 160
kg/m.sup.3.
[0018] The nonwoven fabric of the present invention has the
above-described configuration and thus exhibits high flame
shielding performance and heat insulating property.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The figure is a diagram for explaining a combustion test to
evaluate flame shielding performance and heat insulating
property.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0020] The present invention is a nonwoven fabric which includes a
non-melting fiber A having a high-temperature shrinkage rate of 3%
or less and a thermal conductivity conforming to ISO22007-3 (2008)
of 0.060 W/mK or less and a thermoplastic fiber B having a LOI
value conforming to JIS K 7201-2 (2007) of 25 or more and has a
density of more than 50 kg/m.sup.3 and less than 200
kg/m.sup.3.
[0021] <<High-Temperature Shrinkage Rate>>
[0022] In the present invention, the high-temperature shrinkage
rate is a numerical value determined by the following equation from
L0 and L1 attained as follows: a fiber, which is a raw material of
the nonwoven fabric, is left to stand in a standard state
(20.degree. C., 65% of relative humidity) for 12 hours, then a
tension of 0.1 cN/dtex is applied to the fiber, the original length
L0 is measured, the fiber is exposed to a dry heat atmosphere at
290.degree. C. for 30 minutes without applying a load to the fiber,
sufficiently cooled in the standard state (20.degree. C., 65% of
relative humidity), and a tension of 0.1 cN/dtex is applied to the
fiber, and the length L1 is measured.
[0023] High-temperature shrinkage rate =[(L0-L1)/L0] .times.100
(%)
[0024] The thermoplastic fiber melts when the flame approaches and
heat is applied thereto, and the molten thermoplastic fiber spreads
in a thin film shape along the surface of the non-melting fiber
(aggregate). When the temperature further rises, both fibers will
be eventually carbonized, but the high-temperature shrinkage rate
of the non-melting fiber is 3% or less, thus the vicinity of the
flame contact portion at which the temperature has increased hardly
shrinks, fracture of the nonwoven fabric due to the thermal stress
generated between the low temperature portion which is not in
contact with the flame and the high temperature portion hardly
occurs, and as a result, the flame can be shielded for a long time.
It is preferable that the high-temperature shrinkage rate is low
from this point, but the high-temperature shrinkage rate is
preferably -5% or more since fracture of the nonwoven fabric due to
thermal stress is caused even when the fiber does not shrink but
significantly expands by heat. Among others, the high-temperature
shrinkage rate is preferably 0% to 2%.
[0025] <<Thermal Conductivity>>
[0026] Thermal conductivity is a numerical value indicating the
ease of heat conduction, and a small thermal conductivity means
that the temperature rise at the unheated portion is small when the
material is heated from one surface. A material having a thermal
conductivity of 0.060 W/mK or less measured by a method conforming
to ISO22007-3 (2008) and using a felt having a weight per unit area
of 200 g/m.sup.2 and a thickness of 2 mm (density: 100 kg/m.sup.3)
measured by a method conforming to JIS L 1913 (2010) as a test body
hardly transmits heat, the temperature rise on the opposite side
that is not heated can be suppressed when the material is formed
into a nonwoven fabric and heated from one surface, and the
possibility that the combustible ignites decreases even when a
combustible is arranged on the opposite side. It is more preferable
as the thermal conductivity is lower, but the upper limit thereof
is about 0.020 W/mK for available fiber materials.
[0027] <<LOI Value>>
[0028] The LOI value is the volume percentage of the minimum amount
of oxygen required to sustain combustion of a substance in a mixed
gas of nitrogen and oxygen, and it can be said that it is less
likely to burn as the LOI value is higher. Hence, a thermoplastic
fiber having a LOI value conforming to JIS K 7201-2 (2007) of 25 or
more hardly burns, and even if the thermoplastic fiber catches
fire, the fire is extinguished immediately when the fire source is
separated from the thermoplastic fiber, and a carbonized film is
usually formed at the slightly flared portion, and this carbonized
portion can prevent fire spread. It is more preferable as the LOI
value is higher, but the upper limit of the LOI value for actually
available substances is about 65.
[0029] <<Ignition Temperature>>
[0030] The ignition temperature is a spontaneous ignition
temperature measured by a method conforming to JIS K 7193
(2010).
[0031] <<Melting Point>>
[0032] The melting point is a value measured by a method conforming
to JIS K 7121 (2012). The melting point refers to the value of the
melting peak temperature when heating performed at 10.degree.
C./min.
[0033] <<Non-Melting Fiber A>>
[0034] In the present invention, the non-melting fiber A refers to
a fiber which does not liquefy but maintains its shape when being
exposed to a flame, and those that do not liquefy or ignite at a
temperature of 800.degree. C. are preferable and those that do not
liquefy or ignite at a temperature of 1000.degree. C. or more are
more preferable. Examples of the non-melting fiber having the
high-temperature shrinkage rate in the range prescribed in the
present invention include a flame resistant fiber, a
meta-aramid-based fiber, and a glass fiber. The flame resistant
fiber is a fiber obtained by subjecting a fiber selected from an
acrylonitrile-based fiber, a pitch-based fiber, a cellulose-based
fiber, a phenol-based fiber or the like as a raw material to a
flame resistant treatment. These may be used singly or two or more
of these may be used at the same time. Among these, flame resistant
fibers, of which the high-temperature shrinkage rate is low and the
carbonization proceeds by the oxygen shielding effect of the film
formed by the thermoplastic fiber B to be described later at the
time of flame contact, and the heat resistance at a high
temperature is further improved, are preferable. Among various
flame resistant fibers, an acrylonitrile-based flame resistant
fiber is more preferably used as the fiber having a small specific
gravity, flexibility, and excellent flame retardancy, and this
flame resistant fiber is obtained by heating and oxidizing an
acrylic fiber as a precursor in high-temperature air. Examples of
commercially available products include Pyromex (registered
trademark) (manufactured by Toho Tenax Co., Ltd.) in addition to
flame resistant fiber PYRON (registered trademark) (manufactured by
Zoltek companies, Inc.) that is used in Examples and Comparative
Examples to be described later. Generally, a meta-aramid-based
fiber has a high high-temperature shrinkage rate and does not
satisfy the high-temperature shrinkage rate prescribed in the
present invention, but a meta-aramid-based fiber of which the
high-temperature shrinkage rate is adjusted to be in the range of
the high-temperature shrinkage rate prescribed in the present
invention by a suppression treatment can be preferably used. The
non-melting fiber preferably used in the present invention is used
in a method in which the non-melting fiber is used singly or is
combined with a different material, and the fiber length is
preferably in a range of 30 to 120 mm, more preferably in a range
of 38 to 70 mm. When the fiber length is in the range of 38 to 70
mm, it is possible to obtain a nonwoven fabric by a general needle
punching method or a water-jet interlacing method and it is easy to
combine with a different material. The thickness of the single
fiber of the non-melting fiber is also not particularly limited,
but the single fiber fineness is preferably in a range of 0.1 to 10
dtex from the viewpoint of carding process-passing.
[0035] When the content of the non-melting fiber in the nonwoven
fabric is too low, the function as an aggregate is insufficient,
and thus the mixing ratio of the non-melting fiber A in the
nonwoven fabric is preferably 15% by mass or more, more preferably
20% by mass or more. The upper limit is preferably 70% by mass or
less, and more preferably 60% by mass or less from the viewpoint of
the productivity and strength of the nonwoven fabric.
[0036] <<Thermoplastic Fiber B>>
[0037] The thermoplastic fiber B used in the present invention is
one of which the LOI value is in the range prescribed in the
present invention and the melting point is lower than the ignition
temperature of the non-melting fiber A, and specific examples
thereof include fibers formed of thermoplastic resins selected from
the group consisting of anisotropic molten polyester, flame
retardant poly(alkylene terephthalate), flame retardant
poly(acrylonitrile butadiene styrene), flame retardant polysulfone,
poly(ether-ether-ketone), poly(ether-ketone-ketone), polyether
sulfone, polyarylate, polyarylene sulfide, polyphenylsulfone,
polyetherimide, polyamide-imide, and any mixture of these. These
may be used singly or two or more of these may be used at the same
time. As the LOI value is in the range prescribed in the present
invention, combustion in the air is suppressed and the polymer is
likely to be carbonized. As the melting point is lower than the
ignition temperature of the non-melting fiber A, the molten polymer
forms a film on the surface of the non-melting fiber A and between
the fibers and the film is further carbonized, thus the effect of
shielding oxygen is enhanced, oxidative deterioration of the
non-melting fiber A can be suppressed, and the carbonized film
exerts excellent flame shielding performance. The melting point of
the thermoplastic fiber B is lower than the ignition temperature of
the non-melting fiber A by preferably 200.degree. C. or more, more
preferably 300.degree. C. or more. Among these, polyphenylene
sulfide fiber (hereinafter, also referred to as PPS fiber) is most
preferable from the viewpoint of high LOI value, melting point
range, and easy availability. Even a polymer of which the LOI value
is not in the range prescribed in the present invention can be
preferably used by being treated with a flame retardant as long as
the LOI value of the polymer after the treatment is in the range
prescribed in the present invention. PPS is most preferable since
PPS contains a sulfur atom in the polymer structure or the flame
retardant, thus generates sulfuric acid at the time of the thermal
decomposition of the polymer or flame retardant, and develops a
mechanism for dehydration carbonization of the polymer substrate,
and a sulfur-based flame retardant is preferable in the case of
using a flame retardant. As the thermoplastic fiber B, it is
preferable to use a fiber containing sulfur atoms at 15% by mass or
more. Specific examples thereof include PPS and polyester to which
a sulfur-based flame retardant is added. The upper limit is
preferably 50% by mass or less from the viewpoint of fiber
strength.
[0038] The ratio of sulfur atom herein is determined by raising the
temperature of about 10 mg of the sample from room temperature to
800.degree. C. at 10.degree. C./min under an air stream condition,
oxidizing and decomposing the thermoplastic fiber using a
thermogravimetric analyzer, and quantitatively analyzing sulfur
oxide in the decomposition gas by gas chromatography.
[0039] The thermoplastic fiber B used in the present invention is
used in a method in which the thermoplastic resin is used singly or
is combined with a different material, and the fiber length is
preferably in a range of 30 to 120 mm, more preferably in a range
of 38 to 70 mm. When the fiber length is in the range of 38 to 70
mm, it is possible to obtain a nonwoven fabric by a general needle
punching method or a water-jet interlacing method and it is easy to
combine with a different material. The thickness of the single
fiber of the thermoplastic fiber B is also not particularly
limited, but the single fiber fineness is preferably in a range of
0.1 to 10 dtex from the viewpoint of carding process-passing.
[0040] The PPS fiber preferably used in the present invention is a
synthetic fiber formed of a polymer of which the polymer structural
unit includes --(C.sub.6H.sub.4--S)-- as the main structural unit.
Typical examples of these PPS polymers include polyphenylene
sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide
ketone, random copolymers and block copolymers of these, and any
mixtures of these, etc. As a particularly preferred PPS polymer, a
polyphenylene sulfide containing a p-phenylene sulfide unit
represented by --(C.sub.6H.sub.4--S)-- as the main structural unit
of the polymer preferably at 90% by mole or more is desirable. From
the viewpoint of mass, polyphenylene sulfide containing a
p-phenylene sulfide unit at 80% by mass, still more preferably at
90% by mass or more is desirable.
[0041] The PPS fiber preferably used in the present invention is
used in a method in which the PPS fiber is used singly or is
combined with a different material, and may be in the form of
filament or staple. In the case of using the PPS fiber in the form
of staple, the fiber length is preferably in a range of 30 to 120
mm, more preferably in a range of 38 to 70 mm. When the fiber
length is in the range of 38 to 70 mm, it is possible to obtain a
nonwoven fabric by a general needle punching method or a water-jet
interlacing method and it is easy to combine with a different
material. The thickness of the single fiber of PPS is also not
particularly limited, but the single fiber fineness is preferably
in a range of 0.1 to 10 dtex from the viewpoint of carding
process-passing.
[0042] The method for producing the PPS fiber used in the present
invention is preferably a method in which a polymer having the
above-mentioned phenylene sulfide structural unit is melted at a
temperature equal to or higher than its melting point and spun from
a spinneret to form a fiber. The spun fiber is an undrawn PPS fiber
as it is. Most of the undrawn PPS fibers have an amorphous
structure and a high fracture elongation. On the other hand, such
fibers are inferior in dimensional stability due to heat, and thus
drawn fibers in which the strength and thermal dimensional
stability of the fibers are improved by hot drawing and orientation
after spinning are commercially available. As PPS fibers, a
plurality of PPS fibers such as "TORCON" (registered trademark)
(manufactured by TORAY INDUSTRIES, INC.) and "PROCON" (registered
trademark) (manufactured by TOYOBO CO., LTD.) are in
circulation.
[0043] In the present invention, the undrawn PPS fiber and the
drawn fiber can be used concurrently in the range satisfying the
range of the present invention. Instead of the PPS fiber, it is of
course possible to concurrently use a drawn fiber and an undrawn
fiber of a fiber satisfying the range of the present invention.
[0044] When the mixing ratio of the thermoplastic fibers B in the
nonwoven fabric is too low, the thermoplastic fibers do not
sufficiently spread in a film shape between the non-melting fibers
of the aggregate, and thus the mixing ratio of the thermoplastic
fibers B in the nonwoven fabric is preferably 10% by mass or more,
more preferably 20% by mass or more. When the mixing ratio of the
thermoplastic fiber B is too high, the carbonized portion is likely
to be brittle at the time of flame contact and the flame shielding
performance decreases, thus the upper limit of the mixing ratio is
preferably 80% by mass or less, more preferably 70% by mass or
less.
[0045] <<Fiber C other than Non-Melting fiber A and
Thermoplastic Fiber B>>
[0046] A fiber C other than the non-melting fiber A and the
thermoplastic fiber B may be contained in the nonwoven fabric in
order to further impart specific performance. For example, a
vinylon fiber, a polyester fiber other than the thermoplastic fiber
B, a nylon fiber, and the like may be used in order to improve the
hygroscopic property and water absorbing property of the nonwoven
fabric. The mixing ratio of the fiber C is not particularly limited
as long as the effect of the present invention is not impaired, and
the mixing ratio of the fiber C other than the non-melting fibers A
and the thermoplastic fibers B is preferably 20% by mass or less,
more preferably 15% by mass or less. The lower limit in the case of
using the fiber C is not particularly limited as long as the
desired performance is imparted, but the lower limit is usually
preferably about 10% by mass.
[0047] The thickness of the nonwoven fabric of the present
invention is measured by a method conforming to JIS L 1913 (2010)
and is preferably 0.08 mm or more. When the thickness of the
nonwoven fabric is too thin, sufficient flame shielding performance
and heat insulating performance cannot be attained.
[0048] As the morphology of the fibers used in the nonwoven fabric
of the present invention, the number of crimp of the fibers is
preferably 7 crimps/2.54 cm or more, still more preferably 12
crimps/2.54 cm or more in order to sufficiently attain entanglement
of the fibers. The number of crimp in the present invention is
measured conforming to JIS L 1015 (2000).
[0049] The lengths of the short fibers of the non-melting fiber A
and the thermoplastic fiber B are preferably the same as each other
in order to obtain a more uniform nonwoven fabric. The same length
does not have to be exactly the same, and the length of the
thermoplastic fiber B may have a difference of about .+-.5% from
the length of the non-melting fiber A. From this viewpoint, the
fiber length of the non-melting fiber and the length of the
thermoplastic fiber B or the fiber C are all preferably in a range
of 30 to 120 mm, more preferably in a range of 38 to 70 mm.
[0050] The nonwoven fabric of the present invention is produced by
a needle punching method, a water-jet interlacing method or the
like using the above short fibers. The structure of the nonwoven
fabric is not limited as long as it is in the range prescribed in
the present invention, but the density of the nonwoven fabric is
required to be more than 50 kg/m.sup.3 and less than 200
kg/m.sup.3, and is preferably 55 to 180 kg/m.sup.3, more preferably
70 to 160 kg/m.sup.3, particularly preferably 75 to 160 kg/m.sup.3.
The density is calculated by dividing the weight of a 30 cm square
sample by the thickness measured by a method conforming to JIS L
1913 (2010).
[0051] The density of the nonwoven fabric is important for the
nonwoven fabric of the present invention to exhibit both excellent
flame shielding performance and heat insulating property. The heat
transmission includes that generated through a solid substance,
that generated through a gas, and that caused by radiation. When
the density increases, the volume occupied by the fibers
constituting the nonwoven fabric in the unit volume increases and
the contact points between the fibers increase, and thus the
thermal conductivity increases. Specifically, when the density is
more than 200 kg/m.sup.3, heat is likely to be transmitted by the
polyphenylene sulfide carbonized by the flame and the temperature
on the back side that is not hit by the flame is likely to rapidly
rise. On the other hand, when the density is less than 50
kg/m.sup.3, when one surface of the nonwoven fabric is heated, the
heated high-temperature air is likely to escapes to the opposite
side of the nonwoven fabric, heat conduction due to the flow of air
is promoted, and the temperature on the back side that is not hit
by the flame is likely to rapidly rise. In other words, by setting
the density of the nonwoven fabric to a range more than 50
kg/m.sup.3 and less than 200 kg/m.sup.3, the PPS fibers
appropriately forms a carbonized film to exert a flame shielding
performance at the portion hit by the flame and an appropriately
fine air layer is maintained in the thickness direction of the
nonwoven fabric, as a result, heat conduction through solid
substances and gas is suppressed and excellent heat insulating
property is exhibited. That is, it is important that the density
value is in a certain range. On the other hand, heat transmission
by radiation is suppressed when the density is high. In other
words, heat transmission by radiation is further suppressed as the
reciprocal of the density is smaller. Considering the above,
excellent heat insulating property is achieved by setting the sum
of the density and the reciprocal of the density, namely,
{density+(1/density)} to be in an appropriate range. The degrees of
influence of the heat transmission effect through solid substances,
heat transmission effect through gas, and heat transmission effect
by radiation are different from one another, strictly speaking, it
is thus necessary to experimentally determine the weighting of each
of the density term and the (1/density) term, but in the range of
the present invention, the value of density (kg/m.sup.3)+1/density
(kg/m.sup.3) is preferably 20 to 400, more preferably 25 to 350,
still more preferably 30 to 300 in order to attain excellent flame
shielding performance and heat insulating property. As the
thickness of the nonwoven fabric holding such a structure
increases, the heat insulating property is proportionally
improved.
[0052] After the nonwoven fabric is produced, heat setting may be
performed using a stenter or calendering may be performed in the
range prescribed in the present invention. As a matter of course,
the gray fabric may be used as it is. The setting temperature is
preferably a temperature at which the effect of suppressing the
high-temperature shrinkage rate is attained, and is preferably
160.degree. C. to 240.degree. C., more preferably 190.degree. C. to
230.degree. C. The calendering is to adjust the thickness, namely
the density of the nonwoven fabric, and the speed, pressure, and
temperature for calendering are not limited as long as a nonwoven
fabric having physical properties in the ranges prescribed in the
present invention is obtained.
[0053] The nonwoven fabric of the present invention thus obtained
is excellent in flame shielding performance and heat insulating
property and exerts a fire spread preventing effect particularly by
being combined with a combustible, thus is suitable for use in
clothing materials, wall materials, floor materials, ceiling
materials, covering materials, and the like that are required to
exhibit flame retardancy, and is particularly suitable for use in
fireproof protective clothing and fire spread preventive covering
materials for urethane sheet materials and fire spread prevention
for bed mattresses of motor vehicles and aircraft.
EXAMPLES
[0054] Next, the present invention will be specifically described
based on Examples. However, the present invention is not limited to
only these Examples. Various changes and modifications can be made
without departing from the technical scope of the present
invention. Incidentally, the methods for measuring various
properties used in the present Examples are as follows.
[0055] [Weight Per Unit Area]
[0056] The weight of a 30 cm square sample was measured and
expressed in weight per 1 m.sup.2 (g/m.sup.2).
[0057] [Thickness]
[0058] The thickness was measured conforming to JIS L 1913
(2010).
[0059] [Evaluation on Flame Shielding Performance and Heat
Insulating Property]
[0060] Soft urethane foam commercially available from Fuji Gomu
co., Ltd. is cut into a length of 20 cm, a width of 20 cm, and a
thickness of 20 cm to obtain urethane foam 1. The nonwoven fabric 2
of the present invention is covered on the surface of the urethane
foam 1, and the place indicated by 3 in the figure is sewn with a
cotton thread to form the sewn portion 3. The sample is heated
using a burner 4 for 2 minutes at a distance of 5 cm from the
sample. As the burner 4, Power Torch RZ-730 manufactured by
Shinfuji Burner co., ltd. was used. The temperature of the flame is
adjusted to 1000 degrees using a thermocouple. After 2 minutes of
heating, the flame of the burner was extinguished, and the state of
the nonwoven fabric and the internal urethane was observed. A case
in which a hole is not formed in the nonwoven fabric after 2
minutes of heating is evaluated "to exhibit flame shielding
performance" and graded A. A case in which a hole is formed in the
nonwoven fabric during 2 minutes of heating and the flame reaches
the internal urethane foam is evaluated "not to exhibit flame
shielding performance" and graded F. A case in which the flame of
the burner is extinguished after 2 minutes of heating, the sample
is cooled at room temperature for 10 minutes, and the internal
urethane foam is flashed and the fire spreads or the urethane foam
is completely burned is evaluated "not to exhibit heat insulating
property" for the urethane foam and graded F. A case in which the
fire is self-extinguished after the flame of the burner is
extinguished and the urethane foam remains is graded B, and a case
in which the fire is self-extinguished and the weight reduction
rate of urethane foam is 5% by mass or less is graded A.
[0061] Next, terms in the following Examples and Comparative
Examples will be described.
[0062] <<Drawn Fiber of PPS Fiber>>
[0063] As a drawn PPS fiber, "TORCON" (registered trademark),
product number S371 (manufactured by TORAY INDUSTRIES, INC.) having
a single fiber fineness of 2.2 dtex (diameter: 14 .mu.m) and a cut
length of 51 mm was used. This PPS fiber has a LOI value of 34, a
melting point of 284.degree. C., and a number of crimp of 11
crimps/2.54 cm. The ratio of sulfur atoms in the fiber was 26.2% by
mass.
[0064] <<Flame Resistant Yarn>>
[0065] A 1.7 dtex flame resistant fiber PYRON (manufactured by
Zoltek companies, Inc.) cut into 51 mm was used. The
high-temperature shrinkage rate of PYRON was 1.6%. When PYRON was
heated by a method conforming to JIS K 7193 (2010), ignition was
not observed even at 1000.degree. C., and the ignition temperature
thereof was 1000.degree. C. or more. The thermal conductivity was
0.042 W/mK. The number of crimp is 10 crimps/2.54 cm.
[0066] <<Polyethylene Terephthalate (PET) Fiber>>
[0067] As a drawn PET fiber, "TETORON" (registered trademark)
(manufactured by TORAY INDUSTRIES, INC.) having a single fiber
fineness of 2.2 dtex (diameter: 14 .mu.m) and a cut length of 51 mm
was used. This PET fiber has an LOI value of 22 and a melting point
of 267.degree. C. The number of crimp is 17 crimps/2.54 cm. A
sulfur atom was not detected in the fiber.
[0068] <<Carbon fiber>>"TORAYCA" (registered trademark)
(manufactured by TORAY INDUSTRIES, INC.) with a diameter of 30
microns cut into 51 mm was used. The thermal conductivity was 8.4
W/mK.
Example 1
[0069] (Fabrication of Nonwoven Fabric)
[0070] The drawn fiber of PPS fiber and the flame resistant yarn
were mixed together using an opener, then were further mixed
together using a blower, and then passed through a carding machine
to fabricate a web. The web obtained was stacked using a
cross-lapper and formed into a felt using a water-jet interlacing
machine to obtain a nonwoven fabric including a drawn fiber of PPS
fiber and a flame resistant yarn. The weight mixing ratio of the
drawn fiber of PPS fiber to the flame resistant yarn in the
nonwoven fabric was 60:40, the weight per unit area of the nonwoven
fabric was 100 g/m.sup.2, and the thickness thereof was 1.21
mm.
[0071] (Evaluation on Flame Shielding Performance and Heat
Insulating Property)
[0072] The flame did not penetrate the nonwoven fabric for 2
minutes, the internal urethane foam did not catch fire, and the
weight reduction rate of the urethane foam was 0.7% by mass,
indicating that the nonwoven fabric exhibited sufficient flame
shielding performance and heat insulating property.
Example 2
[0073] The weight mixing ratio of the drawn fiber of PPS fiber to
the flame resistant yarn in the nonwoven fabric was changed to
90:10 in Example 1 to obtain a nonwoven fabric having a weight per
unit area of 100 g/m.sup.2 and a thickness of 1.53 mm.
[0074] The flame did not penetrate the nonwoven fabric for 2
minutes, the internal urethane foam did not catch fire, and the
weight reduction rate of the urethane foam was 15.2% by mass,
indicating that the present nonwoven fabric exhibited sufficient
flame shielding performance and heat insulating property.
Example 3
[0075] The weight mixing ratio of the drawn fiber of PPS fiber to
the flame resistant yarn in the nonwoven fabric was changed to
30:70 in Example 1 to obtain a nonwoven fabric having a weight per
unit area of 100 g/m.sup.2 and a thickness of 1.64 mm.
[0076] The flame did not penetrate the nonwoven fabric for 2
minutes, the internal urethane foam did not catch fire, and the
weight reduction rate of the urethane foam was 1.2% by mass,
indicating that the present nonwoven fabric exhibited sufficient
flame shielding performance and heat insulating property.
Example 4
[0077] The weight mixing ratio of the drawn fiber of PPS fiber to
the flame resistant yarn in the nonwoven fabric was changed to
10:90 in Example 1 to obtain a nonwoven fabric having a weight per
unit area of 100 g/m.sup.2 and a thickness of 1.63 mm.
[0078] The flame did not penetrate the nonwoven fabric for 2
minutes, the internal urethane foam did not catch fire, and the
weight reduction rate of the urethane foam was 5.6% by mass,
indicating that the present nonwoven fabric exhibited sufficient
flame shielding performance and heat insulating property.
Example 5
[0079] The weight per unit area of the nonwoven fabric was changed
to 50 g/m.sup.2 in Example 1 to obtain a nonwoven fabric having a
thickness of 0.89 mm.
[0080] The flame did not penetrate the nonwoven fabric for 2
minutes, the internal urethane foam did not catch fire, and the
weight reduction rate of the urethane foam was 3.2% by mass,
indicating that the present nonwoven fabric exhibited sufficient
flame shielding performance and heat insulating property.
Example 6
[0081] The weight per unit area of the nonwoven fabric was changed
to 120 g/m.sup.2 in Example 1 to obtain a nonwoven fabric having a
thickness of 1.91 mm.
[0082] The flame did not penetrate the nonwoven fabric for 2
minutes, the internal urethane foam did not catch fire, and the
weight reduction rate of the urethane foam was 0.3% by mass,
indicating that the present nonwoven fabric exhibited sufficient
flame shielding performance and heat insulating property.
Example 7
[0083] The felting method was changed to needle punching in Example
1 to obtain a nonwoven fabric including a drawn fiber of PPS fiber
and a flame resistant yarn. The weight mixing ratio of the drawn
fiber of PPS fiber to the flame resistant yarn in the nonwoven
fabric was 60:40, the weight per unit area of the nonwoven fabric
was 300 g/m.sup.2, and the thickness thereof was 3.12 mm.
[0084] The flame did not penetrate the nonwoven fabric for 2
minutes, the internal urethane foam did not catch fire, and the
weight reduction rate of the urethane foam was 0.1% by mass,
indicating that the present nonwoven fabric exhibited sufficient
flame shielding performance and heat insulating property.
Example 8
[0085] The nonwoven fabric obtained in Example 7 passed through a
resin roll-resin roll calender one time at room temperature, a
linear pressure of 50 N/cm, and a roll rotation speed of 5 m/min to
obtain a nonwoven fabric having a weight per unit area of 300
g/m.sup.2 and a thickness of 1.87 mm.
[0086] The flame did not penetrate the nonwoven fabric for 2
minutes, the internal urethane foam did not catch fire, and the
weight reduction rate of the urethane foam was 0.1% by mass,
indicating that the present nonwoven fabric exhibited sufficient
flame shielding performance and heat insulating property.
Example 9
[0087] A PET fiber was mixed other than the drawn fiber of PPS
fiber and the flame resistant yarn and the weight mixing ratio of
the drawn fiber of PPS fiber to the flame resistant yarn and the
PET fiber was set to 40:40:20 in Example 1 to obtain a nonwoven
fabric having a weight per unit area of 100 g/m.sup.2 and a
thickness of 1.30 mm.
[0088] The flame did not penetrate the nonwoven fabric for 2
minutes, the internal urethane foam did not catch fire, and the
weight reduction rate of the urethane foam was 4.7% by mass,
indicating that the present nonwoven fabric exhibited sufficient
flame shielding performance and heat insulating property.
Comparative Example 1
[0089] A 1.7 dtex flame resistant fiber PYRON (manufactured by
Zoltek companies, Inc.), a 1.0 dtex PPS drawn fiber, "TORCON"
(registered trademark) (manufactured by TORAY INDUSTRIES, INC.),
and a 3.0 dtex PPS undrawn fiber "TORCON" (registered trademark)
(manufactured by TORAY INDUSTRIES, INC.) were each cut into 6 mm
and these flame resistant fiber, undrawn fiber of PPS fiber, and
drawn fiber of PPS fiber were prepared at a weight ratio of 40:30:
30 (namely, flame resistant yarn to PPS fiber =40:60). These were
dispersed in water to prepare a dispersion. Wet paper was
fabricated from the dispersion using a handmade paper machine. The
wet paper was heated and dried at 110.degree. C. for 70 seconds
using a rotary dryer, and subsequently heated and pressed one time
for each side at a linear pressure of 490 N/cm and a roll rotation
speed of 5 m/min a total of two times by setting the surface
temperature of the iron roll to 200.degree. C. to obtain a nonwoven
fabric. The nonwoven fabric obtained had a weight per unit area of
100 g/m.sup.2 and a thickness of 0.15 mm.
[0090] The flame did not penetrate the nonwoven fabric for 2
minutes, but the present nonwoven fabric ignited from the internal
urethane foam after 1 minute and 30 seconds of heating, and the
urethane foam was completely burned in 10 minutes after the flame
of the burner was extinguished.
Comparative Example 2
[0091] The weight per unit area of the nonwoven fabric was changed
to 50 g/m.sup.2 and the thickness thereof was changed to 10 mm in
Example 7 to obtain a nonwoven fabric.
[0092] The flame did not penetrate the nonwoven fabric for 2
minutes, but the present nonwoven fabric ignited from the internal
urethane foam after 1 minute of heating, and the urethane foam was
completely burned in 10 minutes after the flame of the burner was
extinguished.
Comparative Example 3
[0093] A carbon fiber was used instead of the flame resistant yarn
and the ratio of the drawn PPS fiber to the carbon fiber was set to
60:40 in Example 7 to obtain a nonwoven fabric having a weight per
unit area of 100 g/m.sup.2 and a thickness of 1.89 mm.
[0094] The flame did not penetrate the nonwoven fabric for 2
minutes, but the present nonwoven fabric ignited from the internal
urethane foam after 1 minute and 50 seconds of heating, and the
urethane foam was completely burned in 10 minutes after the flame
of the burner was extinguished.
TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 Nonwoven Nonwoven Water-jet Water-jet Water-jet
Water-jet Water-jet Water-jet fabric fabric interlacing interlacing
interlacing interlacing interlacing interlacing design producing
method Non-melting Flame Flame Flame Flame Flame Flame fiber A
resistant resistant resistant resistant resistant resistant Mixing
yarn yarn yarn yarn yarn yarn ratio 40 wt % 10 wt % 70 wt % 90 wt %
40 wt % 40 wt % (%) Thermoplastic PPS PPS PPS PPS PPS PPS fiber B
fiber fiber fiber fiber fiber fiber Mixing 60 wt % 90 wt % 30 wt %
10 wt % 60 wt % 60 wt % ratio (%) Other None None None None None
None fiber C Mixing ratio (%) Weight 100 100 100 100 50 120 per
unit area (g/m.sup.2) Thickness 1.21 1.53 1.64 1.63 0.89 1.91 (mm)
Density 83 65 61 61 56 63 (kg/m.sup.3) Density + 82.7 65.4 61.0
61.4 56.2 62.8 (1/density) Performance Flame A A A A A A shielding
With flame With flame With flame With flame With flame With flame
performance shielding shielding shielding shielding shielding
shielding performance performance performance performance
performance performance Heat A B A B A A insulating 0.7 wt % 15.2
wt % 1.2 wt % 5.6 wt % 3.2 wt % 0.3 wt % property Comparative
Comparative Comparative Example 7 Example 8 Example 9 Example 1
Example 2 Example 3 Nonwoven Nonwoven Needle Needle Water-jet Wet
Needle Needle fabric fabric punching punching + interlacing
papermaking punching punching design producing calendaring method
Non-melting Flame Flame Flame Flame Flame None fiber A resistant
resistant resistant resistant resistant Mixing yarn yarn yarn yarn
yarn ratio 40 wt % 40 wt % 40 wt % 40 wt % 40 wt % (%)
Thermoplastic PPS PPS PPS PPS PPS PPS fiber B fiber fiber fiber
fiber fiber fiber Mixing 60 wt % 60 wt % 40 wt % 60 wt % 60 wt % 60
wt % ratio (%) Other None None PET fiber None None Carbon fiber C
20 wt % fiber Mixing 40 wt % ratio (%) Weight 300 300 100 100 50
100 per unit area (g/m.sup.2) Thickness 3.12 1.87 1.3 0.15 10 1.89
(mm) Density 96 160 77 667 5 53 (kg/m.sup.3) Density + 96.2 160.4
76.9 666.7 5.2 52.9 (1/density) Performance Flame A A A A A A
shielding With flame With flame With flame With flame With flame
With flame performance shielding shielding shielding shielding
shielding shielding performance performance performance performance
performance performance Heat A A A F F F insulating 0.1 wt % 0.1 wt
% 4.7 wt % Flashing of Flashing of Flashing of property urethane
urethane urethane Complete Complete Complete burning of burning of
burning of urethane urethane urethane
INDUSTRIAL APPLICABILITY
[0095] The present invention is effective in fire spread
prevention, is suitable for use in clothing materials, wall
materials, floor materials, ceiling materials, covering materials,
and the like that are required to exhibit flame retardancy, and is
particularly suitable for use in fireproof protective clothing and
fire spread preventive covering materials for urethane sheet
materials and fire spread prevention for bed mattresses of motor
vehicles and aircraft.
DESCRIPTION OF REFERENCE SIGNS
[0096] 1: Urethane foam
[0097] 2: Nonwoven fabric
[0098] 3: Sewn portion
[0099] 4: Burner
* * * * *