Note: Descriptions are shown in the official language in which they were submitted.
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FLAME-RETARDANT YARN/FABRIC/CLOTHING
TECHNICAL FIELD
The present invention relates to the field of labor protection, and in
particular, to a flame-
retardant yarn/fabric/clothing.
BACKGROUND
Regarding modacrylic, cellulose fibers and polyimide in the prior art, the
three types of
fibers are totally different in physical and chemical properties and may be
produced by
different manufactures, so it is quite difficult to completely understand and
master their
properties to carry out proper blending processing. There is a
modacrylic/lyocell (one of
the cellulose fibers)/aromatic polyamide product available in the U.S. market.
The
company providing this product owns the patent on modacrylic/cotton/aromatic
polyamide
which, however, actually has not been put into mass production. Modacrylic may
produce
a flame-retardant gas as a barrier for oxygen during combustion, allowing a
blend to be
flame-retardant as a whole, and meanwhile, a certain amount of acid vapor may
be
produced. Due to weak acid resistance of aromatic polyamide, it is possible
that the char
length of a fabric is not ideal enough or unstable. Polyimide fibers are
expensive and have
been extensively used in the aerospace field with high radiation resistance,
good acid-base
resistance and excellent heat resistance and heat insulation property. In
recent years, the
polyimide fibers have been well developed, and begin to gradually step into
the civil field.
SUMMARY OF THE INVENTION
The technical problem to be solved by the present invention is to blend
modacrylic,
cellulose and polyimide in a certain ratio, allowing a smaller char length of
a fabric after
vertical burning, which is applicable to a flame-retardant
yarn/fabric/clothing.
A flame-retardant yarn contains the following three types of fibers in
percentage by weight
based on their total weight:
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modacrylic: 20% to 80%;
cellulose: 10% to 50%; and
polyimide: 1% to 50%.
The flame-retardant yarn in the present invention, contains the following
three types of
fibers in percentage by weight based on their total weight:
modacrylic: 25% to 75%;
cellulose: 15% to 45%; and
polyimide: 2% to 45%.
The flame-retardant yarn in the present invention contains anti-static staple
fibers or
filaments.
The flame-retardant yarn in the present invention contains anti-static staple
fibers.
In the flame-retardant yarn in the present invention, an anti-static component
of the anti-
static staple fibers is carbon or a metal.
In the flame-retardant yarn in the present invention, the anti-static
component is carbon.
In the flame-retardant yarn in the present invention, the modacrylic, in which
the content
of acrylon is 35% to 85%, comprises a vinyl chloride-acrylon copolymer, a
vinylidene
chloride-acrylon copolymer, or a vinyl chloride-vinylidene chloride-acrylon
copolymer.
When the weight of the vinyl chloride or the modacrylic or the total weight of
both in the
modacrylic accounts for 40-60% of that of the modacrylic, a better flame
retardance may
be achieved. In addition, dyeing groups containing sulfonic groups account for
0.5% to 1%.
The modacrylic also includes a modacrylic containing one or more antimony
oxides
selected from a group consisting of antimony trioxide, antimony tetroxide and
antimony
pentoxide, and a better flame retardance may be achieved when the content of
the antimony
oxide(s) accounts for above 2.5% of the weight of the modacrylic.
The limit oxygen index (LOT) of the modacrylic ranges from 28 to 33 (the LOI
is the
percentage of the minimum content of oxygen needed to support combustion;
generally,
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air contains about 20% of oxygen; materials having the LOI lower than 20 are
inflammable,
while those having the LOI above 26 are flame-retardant materials and those
having the
LOI above 40 are incombustible materials). The modacrylic, after being set
alight, may
give off a flame-retardant gas heavier than air to prevent contact between an
inflammable
material and oxygen, thereby improving the flame retardance of surrounding
articles. This
fiber is high in flame retardance, but low in temperature tolerance and
dimensional stability.
When the content of the modacrylic accounts for 20%-80% of the blend, a
significant effect
may be achieved. If the content of the modacrylic is lower than 20%, the flame-
retardant
gas produced is insufficient, leading to a failure in ensuring the overall
flame retardance of
the blend. If the content of the modacrylic is more than 80%, the blend is low
in heat
resistance, and may have an increased char length because the burning part may
be torn
apart due to thermal contraction during vertical burning. With an excessive
increase of the
modacrylic, the amount of the cheap cellulose fibers added is reduced
consequently, which
is unfavorable for cost control. When the content of the modacrylic accounts
for 25-75%
of the blend, a better flame retardance may be achieved.
In the flame-retardant yarn in the present invention, the polyimide is
expressed by a
molecular structural formula below:
o 0
N N R R ___
wherein bis(-CO-N-03-) is a core structure in a mass ratio above 50%. The
polyimide
decomposes at a temperature above 500 DEG C, has the characteristics of acid
and base
resistance, high flame retardance, high LOI above 36, good heat insulation
property, and
good thermal stability, and has extensive application in the aerospace field
due to high
radiation resistance.
In the flame-retardant yarn in the present invention, the cellulose is
expressed by a
molecular structural formula below:
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OH
,,C1
HO OH
0
HO 0
OH
OH
The cellulose in the present invention consists of D-glucopyranosyl groups
(anhydroglucoses) with a simple molecular formula (C61-11005)n, and may be in
following
specific forms: cotton, flax, viscose or rayon, lyocell, bamboo fiber, wood
fiber, and other
fibers derived from plant celluloses. The cellulose has the characteristics of
good water
absorbability and friendliness to human body, and is an inflammable fiber with
the LOI of
17 to 19.
The flame-retardant yarn in the present invention further contains various
types of fibers
having no influence on the effect of the present invention, such as terylene,
nylon 66, meta-
aramid, aramid, polyoxadiazole, acrylic, wool, cony hair, silk, carbon-
containing anti-static
components, and metallic anti-static components.
A flame-retardant fabric contains the following three types of fibers in
percentage by
weight based on their total weight:
modacrylic: 20% to 80%;
cellulose: 10% to 50%; and
polyimide: 1% to 50%.
The flame-retardant fabric in the present invention contains the following
three types of
fibers in percentage by weight based on the weight of the fabric:
modacrylic: 25% to 75%;
cellulose: 15% to 45%; and
polyimide: 2% to 45%.
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The flame-retardant fabric in the present invention has a char length of less
than 150 mm
measured in accordance with GB/T 5455-2014.
The flame-retardant fabric in the present invention has a char length of less
than 100 mm
measured in accordance with GB/T 5455-2014.
The flame-retardant fabric in the present invention has a char length of less
than 50 mm
measured in accordance with GB/T 5455-2014.
The flame-retardant fabric in the present invention contains an anti-static
component.
In the flame-retardant fabric in the present invention, the modacrylic, in
which the content
of acrylon is 35% to 85%, comprises a vinyl chloride-acrylon copolymer, a
vinylidene
chloride-acrylon copolymer, or a vinyl chloride-vinylidene chloride-acrylon
copolymer.
When the weight of the vinyl chloride or the modacrylic or the total weight of
both in the
modacrylic accounts for 40-60% of that of the modacrylic, a better flame
retardance may
be achieved. In addition, dyeing groups containing sulfonic groups account for
0.5% to 1%.
The modacrylic also includes a modacrylic containing one or more antimony
oxides
selected from a group consisting of antimony trioxide, antimony tetroxide and
antimony
pentoxide, and a better flame retardance may be achieved when the content of
the antimony
oxide(s) accounts for above 2.5% of the weight of the modacrylic.
The LOI of the modacrylic ranges from 28 to 33. The modacrylic, after being
set alight,
may give off a flame-retardant gas heavier than air to prevent contact between
an
inflammable material and oxygen, thereby improving the flame retardance of
surrounding
articles. This fiber is high in flame retardance, but low in temperature
tolerance and
dimensional stability. When the content of the modacrylic accounts for 20%-80%
of the
blend, a significant effect may be achieved. If the content of the modacrylic
is lower than
20%, the flame-retardant gas produced is insufficient, leading to a failure in
ensuring the
overall flame retardance of the blend. If the content of the modacrylic is
more than 80%,
the blend is low in heat resistance, and may have an increased char length
because the
burning part may be torn apart due to thermal contraction during vertical
burning. With an
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excessive increase of the modacrylic, the amount of the cheap cellulose fibers
added is
reduced consequently, which is unfavorable for cost control. When the content
of the
modacrylic accounts for 25-75% of the blend, a better flame retardance may be
achieved.
In the flame-retardant yarn in the present invention, the polyimide is
expressed by a
molecular structural formula below:
(0 0
--"N itis Ev- R --)---f-- R' +
0 a m n
wherein bis(-CO-N-00-) is a core structure in a mass ratio above 50%. The
polyimide
decomposes at a temperature above 500 DEG C, has the characteristics of acid
and base
resistance, high flame retardance, high LOI above 36, good heat insulation
property, and
good thermal stability, and has extensive application in the aerospace field
due to high
radiation resistance.
In the flame-retardant fabric in the present invention, the cellulose is
expressed by a
molecular structural formula below:
-( OH
! OH
0 HO
HO ',
. 1
,
OH
OH n
The cellulose in the present invention consists of D-glucopyranosyl groups
(anhydroglucoses) with a simple molecular formula (C6Hio05)n, and may be in
following
specific forms: cotton, flax, viscose or rayon, lyocell, bamboo fiber, wood
fiber, and other
fibers derived from plant celluloses. The cellulose has the characteristics of
good water
absorbability and friendliness to human body, and is an inflammable fiber with
the LOI of
17 to 19.
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The flame-retardant fabric in the present invention further contains various
types of fibers
having no influence on the effect of the present invention, such as terylene,
nylon 66, meta-
aramid, aramid, polyoxadiazole, acrylic, wool, cony hair, silk, carbon-
containing anti-static
components, and metallic anti-static components.
A flame-retardant clothing contains the following three types of fibers in
percentage by
weight based on their total weight:
modacrylic: 20% to 80%;
cellulose: 10% to 50%; and
polyimide: I% to 50%.
The flame-retardant clothing in the present invention contains the clothing
three types of
fibers in percentage by weight based on the weight of the clothing:
modacrylic: 25% to 75%;
cellulose: 15% to 45%; and
polyimide: 2% to 45%.
In the flame-retardant clothing in the present invention, the modacrylic, in
which the
content of acrylon is 35% to 85%, comprises a vinyl chloride-acrylon
copolymer, a
vinylidene chloride-acrylon copolymer, or a vinyl chloride-vinylidene chloride-
acrylon
copolymer. When the weight of the vinyl chloride or the modacrylic or the
total weight of
both in the modacrylic accounts for 40-60% of that of the modacrylic, a better
flame
retardance may be achieved. In addition, dyeing groups containing sulfonic
groups account
for 0.5% to 1%. The modacrylic also includes a modacrylic containing one or
more
antimony oxides selected from a group consisting of antimony trioxide,
antimony tetroxide
and antimony pentoxide, and a better flame retardance may be achieved when the
content
of the antimony oxide(s) accounts for above 2.5% of the weight of the
modacrylic.
The LOI of the modacrylic ranges from 28 to 33. The modacrylic, after being
set alight,
may give off a flame-retardant gas heavier than air to prevent contact between
an
inflammable material and oxygen, thereby improving the flame retardance of
surrounding
articles. This fiber is high in flame retardance, but low in temperature
tolerance and
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dimensional stability. When the content of the modacrylic accounts for 20%-80%
of the
blend, a significant effect may be achieved. If the content of the modacrylic
is lower than
20%, the flame-retardant gas produced is insufficient, leading to a failure in
ensuring the
overall flame retardance of the blend. If the content of the modacrylic is
more than 80%,
the blend is low in heat resistance, and may have an increased char length
because the
burning part may be torn apart due to thermal contraction during vertical
burning. With an
excessive increase of the modacrylic, the amount of the cheap cellulose fibers
added is
reduced consequently, which is unfavorable for cost control. When the content
of the
modacrylic accounts for 25-75% of the blend, a better flame retardance may be
achieved.
In the flame-retardant clothing in the present invention, the polyimide is
expressed by a
molecular structural formula below:
o
i
N 0 141111 N- ( R
o '
..4 R)
wherein bis(-CO-N-00-) is a core structure in a mass ratio above 50%. The
polyimide
decomposes at a temperature above 500 DEG C, has the characteristics of acid
and base
resistance, high flame retardance, high LOI above 36, good heat insulation
property, and
good thermal stability, and has extensive application in the aerospace field
due to high
radiation resistance.
In the flame-retardant clothing in the present invention, the cellulose is
expressed by a
molecular structural formula below:
sKOH
I
bH
OH n
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The cellulose in the present invention consists of D-glucopyranosyl groups
(anhydroglucoses) with a simple molecular formula (C61-11005)n, and may be in
following
specific forms: cotton, flax, viscose or rayon, lyocell, bamboo fiber, wood
fiber, and other
fibers derived from plant celluloses. The cellulose has the characteristics of
good water
absorbability and friendliness to human body, and is an inflammable fiber with
the LOI of
17 to 19.
The flame-retardant fabric in the present invention further contains various
types of fibers
having no influence on the effect of the present invention, such as terylene,
nylon 66, meta-
aramid, aramid, polyoxadiazole, acrylic, wool, cony hair, silk, carbon-
containing anti-static
components, and metallic anti-static components.
The flame-retardant clothing in the present invention further contains various
types of
fibers having no influence on the effect of the present invention, such as
terylene, nylon 66,
meta-aramid, aramid, polyoxadiazole, acrylic, wool, cony hair, silk, carbon-
containing
anti-static components, and metallic anti-static components.
The flame-retardant yarn, fabric or clothing in the present invention differs
from the prior
art in that:
For the flame-retardant yarn, fabric or clothing in the present invention, the
three types of
fibers are blended to form a blend, wherein the modacrylic, which is low in
heat resistance,
is a gas-phase flame-retardant material and may be blended with the
inflammable cellulose
fibers, such as cotton, flax, viscose or rayon, lyocell, bamboo fiber, wood
fiber, and other
fibers derived from plant celluloses like these. The blend has flame
retardance as a whole.
The modacrylic, when burning, may give off a flame-retardant gas to fully
prevent contact
between the cellulose fibers and oxygen, and the combustion of the cellulose
fibers may
promote charring of the modacrylic to prevent further combustion of the
modacrylic,
thereby forming a mechanism of continuous combustion suppression. Once the
source of
ignition is removed, combustion ends fast, thus achieving the purpose of
automatic fire
extinguishment. As the cellulose may improve the overall moisture
absorbability and
comfort of the blend, the skin-friendliness of the yarn, fabric or clothing
produced from the
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blend is greatly improved. Furthermore, the polyimide has excellent heat
resistance and
extremely high flame retardance with extensive application in the fields of
aerospace and
electronics, and can still maintain such properties after being made into
fibers; besides,
after the polyimide is blended with the modacrylic and the cellulose fibers,
the thermal
stability, dimensional stability and heat insulation property of the blend may
be improved.
The fabric produced from the blend may be quickly charred with high flame
retardance.
The polyimide fiber high in heat resistance serves as a flexible stiffener in
the charred film
such that the charred film is not prone to breakage and further combustion of
the fabric is
prevented more effectively, thus achieving the purpose of reducing the char
length.
Vertical burning tests are carried out in accordance with GB/T 5455-2014 to
test the flame
retardance of fabric woven using the flame-retardant yarns provided in the
present
invention and the fabric or clothing provided in the present invention,
wherein the
measured char length is lower than 150 mm, 100 or 50 mm. The char length is
reduced to
different extents, and thus different flame retardance requirements are met.
The flame-retardant yarn, fabric or clothing provided in the present invention
will be
further described below in conjunction with the accompanying drawings and
specific
examples.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a weave diagram of 2/2 right-hand diagonal twill in an example of
the present
invention; and
Fig. 2 is a diagram of 10 mm x 10 mm fabric checks formed by 48 warps and 24
wefts in
example 10 of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, Modacrylic is PROTEX-C fiber from KANEKA
CORPORATION, which has the fineness of 1.7 dtex and the length of 38 mm;
cotton is
combed cotton available on the open market; lyocell is Tencel fiber from
Lenzing AG,
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which has the fineness of 1.5 dtex and the length of 38 mm; viscose or rayon
is common
viscose or rayon available on the open market, which has the fineness of 1.5
dtex and the
length of 38 mm; polyimide is 2.2 dtex gray fiber from Lianyungang Aoshen
company,
with the length of 38 mm; and anti-static fiber is 5.5 dtex polyester-based
carbon-
containing anti-static fiber from Wuxi Textile Research Institute, which has
the length of
38 mm and the electrical resistivity of 106 to 107 12/cm.
Example 1
A flame-retardant yarn is composed of materials in percentage by weight as
follows:
modacrylic: 75%;
cellulose (cotton): 10%;
polyimide: 13%; and
polyester-based carbon-containing anti-static fibers: 2%.
Example 2
A flame-retardant yarn is composed of materials in percentage by weight as
follows:
modacrylic: 48%;
cellulose (cotton): 49%;
polyimide: 1%; and
polyester-based carbon-containing anti-static fibers: 2%.
Example 3
A flame-retardant yarn is composed of materials in percentage by weight as
follows:
modacrylic: 45%;
cellulose (cotton): 45%;
polyimide: 8%; and
polyester-based carbon-containing anti-static fibers: 2%.
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Example 4
A flame-retardant yarn is composed of materials in percentage by weight as
follows:
modacrylic: 48%;
cellulose (cotton): 35%;
polyimide: 15%; and
polyester-based carbon-containing anti-static fibers: 2%.
Example 5
A flame-retardant yarn is composed of materials in percentage by weight as
follows:
modacrylic: 48%;
cellulose (cotton): 20%;
polyimide: 30%; and
polyester-based carbon-containing anti-static fibers: 2%.
Example 6
A flame-retardant yarn is composed of materials in percentage by weight as
follows:
modacrylic: 38%;
cellulose (cotton): 10%;
polyimide: 50%; and
polyester-based carbon-containing anti-static fibers: 2%.
Example 7
A flame-retardant yarn is composed of materials in percentage by weight as
follows:
modacrylic: 25%;
cellulose (cotton): 28%;
polyimide: 45%; and
polyester-based carbon-containing anti-static fibers: 2%.
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Example 8
A flame-retardant yarn is composed of materials in percentage by weight as
follows:
modacrylic: 25%;
cellulose (lyocell): 28%;
polyimide: 45%; and
polyester-based carbon-containing anti-static fibers: 2%.
Example 9
A flame-retardant yarn is composed of materials in percentage by weight as
follows:
modacrylic: 48%;
cellulose (viscose or rayon): 35%;
polyimide: 15%; and
polyester-based carbon-containing anti-static fibers: 2%.
Examples 1 to 9 are instances for composition in the present invention, and
various
compositions within the scope of the present invention shall all fall into the
scope of
protection of the present invention. For example, the modacrylic may also be
20% or 80%;
the polyimide may also be 2%; and the cellulose may also be 50% or 15%.
To make the advantages of the present invention more prominent, comparative
tests are
carried out.
Besides the examples, para-aramid from Yantai Taihe company is also used,
which is 2.2
dtex and 51 mm.
Comparative example 1
A blend is composed of materials in percentage by weight as follows:
modacrylic: 48%;
cellulose (cotton): 35%;
para-aramid: 15%; and
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polyester-based carbon-containing anti-static fibers: 2%.
Comparative example 2
A yarn is composed of materials in percentage by weight as follows:
modacrylic: 53%;
cellulose (cotton): 45%; and
polyester-based carbon-containing anti-static fibers: 2%.
Comparative example 3
A yarn is composed of materials in percentage by weight as follows:
modacrylic: 10%;
cellulose (cotton): 38%;
polyimide: 50%; and
polyester-based carbon-containing anti-static fibers: 2%.
In the examples and the comparative examples of the present invention, the
same test
parameters are used: 16/1 (cotton count/single yarn), 2/2 right-hand diagonal
twill, warp
density of 120 warps/inch, weft density of 60 wefts/inch, and the final grams
per square
meter of the fabrics: 250 g/gsm. The char length is measured in accordance
with GB/T
5455-2014.
Notes: 16/1 (cotton count/single yarn) represents that one pound of cotton
yarns have 16
840-yard lengths under the commercial moisture regain, which is a unit of
measurement
for thickness of yarns; and the greater the value, the finer the yarns. /I
represents a single
yarn without being stranded.
2/2 right-hand diagonal twill is one of general weaves of woven fabrics with a
weave
diagram as shown in Fig. 1.
1 to 4 represent four warps, and A to D represent 4 wefts; the colored
portions represent
that when warps and wefts are interlaced, the warps are in the surface of the
fabric, while
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the wefts are on the reverse side. The uncolored portions represent that the
wefts are in the
surface of the fabric, while the warps are sunk under the wefts. When the
colored portions
go towards the upper right by a regular pattern, it is called right-hand
diagonal.
The warp density of 120 warps/inch and the weft density of 60 wefts/inch
represent the
number of the warps and the number of the wefts in each I inch which is equal
to 25.4 mm.
The greater the number, the denser the yarns.
250 g/gsm grams per square meter represents that the weight of one square
meter of fabric
is 250 g, i.e., the total weight of the warps and the wefts in one square
meter of fabric. This
parameter is closely related to the warp density and the weft density.
Blends shown in examples 1 to 9 and comparative examples 1 to 3 are fully
opened and
uniformly blended by means of conventional devices, and then conventionally
carded, and
spun in a compact Siro spinning mode. Perfect control is carried out on the
hairness of the
yarns and the uniformity of the yarns such that the results of the comparative
tests are not
influenced by the spinning quality of the yarns.
The yarns shown in the same example or comparative example are woven using a
widely
popularized rapier loom in accordance with the above-mentioned warp density
and weft
density and the above-mentioned weave. Before weaving, the warps are subject
to
necessary slashing using a compound slashing agent of starch and PVC.
The woven gray fabric is conventionally dyed using a reactive dye through a
one bath
process. The uncolored fibers are not dyed again. The dyed fabric undergoes
conventional
after-treatment such as setting, drying and the like. Any after-treatment that
may possibly
influence the flame retardance of the fabric is avoided.
Vertical burning tests are carried out on the obtained fabrics in accordance
with GB/T
5455-2014. The measured char lengths are shown below.
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Char Length mm
Warp Weft
Example 1 35 55
Example 2 124 123
Example 3 64 68
Example 4 55 53
Example 5 42 50
Example 6 31 37
Example 7 45 51
Example 8 28 44
Example 9 49 57
Comparative 85 92
example 1
Comparative 165 177
example 2
Comparative 153 Burning through
example 3
At least the following explicit conclusions can be drawn from the test
results.
I. The char length has no inevitable relationship with the type of the
inflammable cellulose
fibers.
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Blending ratio % Char
length
mm
Modacrylic Polyimide Cellulose Fibers Para- Polyester- Warp
Weft
aramid based
carbon-
Cotton Lyocell Viscose containing
or anti-static
rayon fibers
Example
4
48 15 35 2 55 53
Example
9
48 15 35 2 49 57
Example
7
25 45 28 2 45 51
Example
8
25 45 28 2 28
44
Example 4 is compared with example 9, and example 7 is compared with example
8. Every
two compared examples are the same in types and proportions of other fibers
than the types
of the cellulose fibers, and have quite close maximum char lengths after
burning. Hence, it
may be basically regarded that the char length is correlated to test errors,
and unrelated to
the type of the cellulose.
2. Even though a small quantity of polyimide is blended, it may still greatly
impact the char
length, leading to reduction of the char length.
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Blending ratio % Char
length
mm
Modacrylic Polyimide Cellulose Fibers Para- Polyester- Warp
Weft
aram id based
carbon-
Cotton Lyocell Viscose containing
or anti-static
rayon fibers
Example 2
48 1 49 2 124
123
Comparative
example 2
53 45 2 165
177
In example 2, 49% of inflammable cotton and 2% of inflammable polyester-based
carbon-
containing anti-static fibers, 51% in total, are included; in comparative
example 2, the
summation of the inflammable fibers is 47%, which is 4% less than that in
embodiment 2.
However, according to the char lengths measured through actual burning tests,
the
maximum char length in example 2 is 53 mm less than that in comparative
example 2. It
thus can be seen that the 1% of polyimide in example 2 has a significant
effect on reduction
of the char length.
3. The higher the content of polyimide, the smaller the char length.
Blending ratio % Char length
mm
Modacrylic Polyimide Cellulose Fibers Para- Polyester- Warp Weft
aram id based
carbon-
Cotton Lyocell Viscose containing
or rayon anti-static
fibers
Example
3
45 8 45 2 64 68
Example
1
75 13 10 2 35 55
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Example
4
48 15 35 2 55 53
Example
48 30 20 2 42 50
Example
7
25 45 28 2 45 51
Example
6
38 50 10 2 31 57
The worst values of the char length are put in an order basically consistent
with that of the
contents of the polyimide. It may be estimated that if the content of the
polyimide is more
than 50%, the char length may be smaller. The test results for example 6 are
already able
to meet the highest flame-retardant level requirement of less than 50 mm, and
therefore, it
is unnecessary to increase the content of the expensive polyimide.
4. The content of the modacrylic fibers should not be too low and may not be
out of
reasonable balance with the content of the inflammable cellulose fibers;
otherwise, the
entire blend can not maintain the flame retardance.
Blending ratio % Char length
mm
Modacrylic Polyimide Cellulose Fibers Para- Polyester- Warp Weft
aramid based
carbon-
Cotton Lyocell Viscose containing
or rayon anti-static
fibers
Example 7
25 45 28 2 45 51
Comparative
example 3
Burning
50 38 2 153 through
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From example 7, it can be seen that with 25% of modacrylic and 30% in total of
inflammable cotton and inflammable polyester-based carbon-containing anti-
static fibers,
the entire blend can automatically stop burning with outstanding char length
data. From
example 3, it can be seen that even though the content of the polyimide is up
to 50% with
10% of modacrylic and 40% in total of inflammable cotton and inflammable
polyester-
based carbon-containing anti-static fibers, the blend cannot automatically
stop burning, and
the test result is burning through, i.e., infinite char length. If the content
of the modacrylic
is increased to 20% and the content of the inflammable cotton and inflammable
polyester-
based carbon-containing anti-static fibers is reduced to 30%, the fabric may
maintain the
characteristic of automatically stopping burning with fine char length data.
5. Under the same circumstance, the polyimide in the same proportion as the
para-aramid
is more advantageous for reduction of the char length.
Blending ratio %
Char length
mm
Modacrylic Polyimide Cellulose Fibers
Para- Polyester- Warp Weft
aram id based
carbon-
Cotton Lyocell Viscose containing
or rayon anti-static
fibers
Example 4
48 15 35 2 55 53
Comparative
example 1
48 35 15 2 85 92
Under normal circumstances, the tensile strength of the para-aramid is in a
range of about
15 to 22 cN/dtex or above, and the tensile strength of the polyimide is above
4 cN/dtex. It
is apparent that the para-aramid is much stronger. However, the polyimide may
have higher
temperature endurance when burning and may decompose at a temperature above
500 DEG
C which is almost 100 DEG C higher than that of the para-aramid. The LO! (the
minimum
percentage content of oxygen needed to support combustion) of the para-aramid
is above
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28, while that of the polyimide is above 36. After being set alight, the
modacrylic may give
off hydrochloric acid (HC1) vapor. The para-aramid is worse than the polyimide
in acid
resistance, and when the char length is tested by using a tearing method, the
polyimide,
instead, is much stronger than the para-aramid. It can be seen that in the
blend system with
the modacrylic and cellulose fibers, the polyimide is more suitable than the
para-aramid.
In the comparative example, no meta-aramid is blended because the meta-aramid
is lower
than the para-aramid in both tensile strength and heat resistance in spite of
identical acid
resistance, and also cannot be compared to the polyimide in controlling the
char length.
The above descriptions are examples having the same warp and weft blending
proportions.
The example of a checked weave will be shown below.
Example 10
Yarn 1 is composed of materials in percentage by weight as follows:
polyimide: 98%; and
polyester-based carbon-containing anti-static fibers: 2%.
Yarn 2 is composed of materials in percentage by weight as follows:
modacrylic: 49%;
cellulose (cotton): 49%; and
polyester-based carbon-containing anti-static fibers: 2%.
Fabric parameters in the example are shown below:
16/1 (cotton count/single yarn), 2/2 right-hand diagonal twill, warp density
of 120
warps/inch, weft density of 60 wefts/inch, and the final grams per square
meter of the
fabrics: 250 g/gsm. The char length is measured in accordance with GB/T 5455-
2014.
Notes: 16/1 (cotton count/single yarn) represents that one pound of cotton
yarns have 16
840-yard lengths under the commercial moisture regain, which is a unit of
measurement
for thickness of yarns; and the greater the value, the finer the yarns. /1
represents a single
yarn without being stranded.
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2/2 right-hand diagonal twill is one of general weaves of woven fabrics with a
weave
diagram as shown in Fig. 1.
Three yarns 1 are woven in the warp and weft of fabric at an equal interval of
10 mm with
the yarns 2 being woven therewith. Looping is carried out according to the
weave diagram
shown in Fig. 2. Forty-eight warps and 24 wefts just form 10 mm x 10 mm fabric
checks.
The blending proportions of various fibers in the fabric may be calculated
conveniently
based on the blending ratio of yarns 1 and yarns 2 and the number of the yarns
used:
modacrylic: 44.9%;
cellulose (cotton): 44.9%;
polyimide: 8.2%; (3+3)/(48+24)*98%=8.2%; and
polyester-based carbon-containing anti-static fibers: 2%.
The yarns are woven using a widely popular rapier loom in accordance with the
above-
mentioned warp density and weft density and the above-mentioned weave. Before
weaving,
the warps are subject to necessary slashing using a compound slashing agent of
starch and
PVC.
The woven gray fabric is conventionally dyed using a reactive dye through a
one bath
process. The uncolored fibers are not dyed again. The dyed fabric undergoes
conventional
after-treatment such as setting, drying and the like. Any after-treatment that
may possibly
influence the flame retardance of the fabric is avoided.
Burning tests are carried out in accordance with GB/T 5455-2014. The measured
char
lengths are: warp: 60 mm, and weft 65 mm.
Comparison between example 10 and example 3 is shown below.
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Blending ratio % Char
length mm
Modacrylic Polyimide Cellulose Fibers Para-
Polyester- Warp Weft
aram id based
carbon-
Cotton Lyocell Viscose containing
or rayon anti-static
fibers
Example
3
45 8 45 2 64 68
Example
44.9 8.2 44.9 2 60 65
From the table above, it can be seen that the char lengths are basically
identical although
the design methods of the fabrics are different. The blending proportions of
various fibers
in the blend determine the basic level of the char length.
The flame retardance of the flame-retardant clothing provided in the present
invention is
determined by the flame retardance of the fabric, and therefore, it is
unnecessary to show
examples and comparative examples of the flame-retardant clothing, which may
not impact
the scope of the present invention.
The examples described above are merely intended to describe the preferred
embodiments
of the present invention, and not limit to the scope of the present invention.
Various
variations and improvements made by those of ordinary skill in the art to the
technical
solutions of the present invention without departing from the design spirit of
the present
invention shall all fall into the scope of protection of the present invention
defined by the
appended claims.
Industrial Applicability
According to the flame-retardant yarn, fabric or clothing provided in the
present invention,
three types of fibers modacrylic, cellulose and polyimide are blended to form
a blend,
wherein the modacrylic, when burning, may give off a flame-retardant gas to
fully isolate
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the cellulose fibers from oxygen, and the combustion of the cellulose fibers
may promote
charring of the modacrylic to prevent further combustion of the modacrylic,
thereby
forming a mechanism of continuous combustion suppression. Once the source of
ignition
is removed, combustion ends fast, thus achieving the purpose of automatic fire
extinguishment. As the cellulose may improve the overall moisture
absorbability and
comfort of the blend, the skin-friendliness of the yarn, fabric or clothing
produced from the
blend is greatly improved. Furthermore, the polyimide has excellent heat
resistance and
extremely high flame retardance, and after being blended with the modacrylic
and the
cellulose fibers, may improve the thermal stability, dimensional stability and
heat
insulation property of the blend. The fabric in the present invention may be
quickly charred
with high flame retardance. The polyimide fibers high in heat resistance
serves as a flexible
stiffener in the charred film such that the charred film is not prone to
breakage and further
combustion of the fabric is prevented more effectively, thus achieving the
purpose of
reducing the char length. The flame-retardant yarn, fabric or clothing
provided in the
present invention is significant in flame retardance effect, and thus has good
industrial
applicability.
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