TECHNICAL FIELD
[0001] The present invention relates to a nonwoven fabric.
BACKGROUND ART
[0002] 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.
[0003] 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.
[0004] 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
[0005]
Patent Document 1: International Publication No. 2017/6807
Patent Document 2: Japanese Patent Laid-open Publication No. 2013-169996
SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0006] 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.
[0007] Accordingly, an object of the present invention is to provide a nonwoven fabric exhibiting
high flame shielding performance and heat insulating property.
SOLUTIONS TO THE PROBLEMS
[0008] The present invention adopts the following means in order to solve the above problems.
- (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/m-K 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/m3 and less than 200 kg/m3.
- (2) The nonwoven fabric according to (1), in which a content of the non-melting fiber
A is 15% to 70% by mass.
- (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.
- (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.
- (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.
- (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/m3.
EFFECTS OF THE INVENTION
[0009] 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
[0010] Fig. 1 is a diagram for explaining a combustion test to evaluate flame shielding
performance and heat insulating property.
EMBODIMENTS OF THE INVENTION
[0011] 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/m-K 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
3 and less than 200 kg/m
3.
<<High-temperature shrinkage rate>>
[0012] 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°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°C for 30 minutes without applying a load to the fiber, sufficiently
cooled in the standard state (20°C, 65% of relative humidity), and a tension of 0.1
cN/dtex is applied to the fiber, and the length L1 is measured.
[0013] 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%.
<<Thermal conductivity>>
[0014] 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/m·K 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
2 and a thickness of 2 mm (density: 100 kg/m
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/m-K for available fiber materials.
<<LOI value>>
[0015] 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.
<<Ignition temperature>>
[0016] The ignition temperature is a spontaneous ignition temperature measured by a method
conforming to JIS K 7193 (2010) .
<<Melting point>>
[0017] 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°C/min.
<<Non-melting fiber A>>
[0018] 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°C are preferable and those that do not liquefy
or ignite at a temperature of 1000°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.
[0019] 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.
<<Thermoplastic fiber B>>
[0020] 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°C or more, more preferably
300°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.
[0021] The ratio of sulfur atom herein is determined by raising the temperature of about
10 mg of the sample from room temperature to 800°C at 10°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.
[0022] 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.
[0023] 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
6H
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
6H
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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
<<Fiber C other than non-melting fiber A and thermoplastic fiber B>>
[0028] 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.
[0029] 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.
[0030] 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).
[0031] 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.
[0032] 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
3 and less than 200 kg/m
3, and is preferably 55 to 180 kg/m
3, more preferably 70 to 160 kg/m
3, particularly preferably 75 to 160 kg/m
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).
[0033] 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
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
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
3 and less than 200 kg/m
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
3) + 1/density (kg/m
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.
[0034] 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°C to 240°C, more preferably 190°C
to 230°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.
[0035] 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
[0036] 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.
[Weight per unit area]
[0037] The weight of a 30 cm square sample was measured and expressed in weight per 1 m
2 (g/m
2).
[Thickness]
[0038] The thickness was measured conforming to JIS L 1913 (2010) .
[Evaluation on flame shielding performance and heat insulating property]
[0039] 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 Fig. 1 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.
[0040] Next, terms in the following Examples and Comparative Examples will be described.
<<Drawn fiber of PPS fiber>>
[0041] 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
µm) and a cut length of 51 mm was used. This PPS fiber has a LOI value of 34, a melting
point of 284°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.
<<Flame resistant yarn>>
[0042] 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°C, and the ignition temperature thereof was 1000°C or more. The thermal
conductivity was 0.042 W/m-K. The number of crimp is 10 crimps/2.54 cm.
<<Polyethylene terephthalate (PET) fiber>>
[0043] As a drawn PET fiber, "TETORON" (registered trademark) (manufactured by TORAY INDUSTRIES,
INC.) having a single fiber fineness of 2.2 dtex (diameter: 14 µm) and a cut length
of 51 mm was used. This PET fiber has an LOI value of 22 and a melting point of 267°C.
The number of crimp is 17 crimps/2.54 cm. A sulfur atom was not detected in the fiber.
<<Carbon fiber>>
[0044] "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/m·K.
[Example 1]
(Fabrication of nonwoven fabric)
[0045] 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
2, and the thickness thereof was 1.21 mm.
(Evaluation on flame shielding performance and heat insulating property)
[0046] 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]
[0047] 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
2 and a thickness of 1.53 mm.
[0048] 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]
[0049] 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
2 and a thickness of 1.64 mm.
[0050] 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]
[0051] 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
2 and a thickness of 1.63 mm.
[0052] 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]
[0053] The weight per unit area of the nonwoven fabric was changed to 50 g/m
2 in Example 1 to obtain a nonwoven fabric having a thickness of 0.89 mm.
[0054] 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]
[0055] The weight per unit area of the nonwoven fabric was changed to 120 g/m
2 in Example 1 to obtain a nonwoven fabric having a thickness of 1.91 mm.
[0056] 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]
[0057] 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
2, and the thickness thereof was 3.12 mm.
[0058] 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]
[0059] 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
2 and a thickness of 1.87 mm.
[0060] 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]
[0061] 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
2 and a thickness of 1.30 mm.
[0062] 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]
[0063] 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°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°C to obtain a nonwoven fabric. The nonwoven fabric obtained had a weight per
unit area of 100 g/m
2 and a thickness of 0.15 mm.
[0064] 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]
[0065] The weight per unit area of the nonwoven fabric was changed to 50 g/m
2 and the thickness thereof was changed to 10 mm in Example 7 to obtain a nonwoven
fabric.
[0066] 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]
[0067] 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
2 and a thickness of 1.89 mm.
[0068] 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.
INDUSTRIAL APPLICABILITY
[0069] 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
[0070]
- 1:
- Urethane foam
- 2:
- Nonwoven fabric
- 3:
- Sewn portion
- 4:
- Burner