Papery product

A papery product consisting essentially of a fibrous web, at least part of said web being made of a wholly aromatic polyamide fiber having a readily soluble skin layer and a sparingly soluble or insoluble core layer, and pressure and heat being applied to said web. Said product is excellent in its mechanical and heat-resisting properties.

This invention relates to a papery product. More particularly, this 
invention relates to a papery product having an excellent heat-resisting 
property and a superior flame retardant property. 
Heretofore, it has been widely known to produce a papery product using a 
substrate of a synthetic fiber such as polyester or nylon or a chemical 
fiber such as rayon and bonding or matting the fiber using a binder or a 
suitable plasticizer. The resulting product is inferior in its 
heat-resisting property and flame retardant property and is not suitable 
for uses in the fields of a building material, an interior material, an 
electrical insulating material, etc. 
For these uses, there has been proposed a papery product formed mainly of a 
fiber made of wholly aromatic polyamide, especially, poly-m-phenylene 
isophthalamide, which is excellent in its heat-resisting property and 
flame retardant property. 
For example, a poly-m-phenylene isophthalamide solution in an amide polar 
solvent is dispersed into a dispersing medium formed mainly of water to 
prepare a thin foliated body having a specific configuration, the thin 
foliated body is then mixed and intertwined with a fiber in water and 
dried, and the materials are subjected to heat and pressure to prepare a 
papery product (Japanese Patent Publication No. 35-11851). 
According to this method, a papery product which is compact in structure 
and excellent, especially, in its electrical insulating property can be 
obtained, but since the process for preparing the thin foliated body and 
the papermaking step use a large amount of water, this method requires a 
considerably large amount of energy in the solvent recovering step and the 
drying step. 
To solve this problem, it has been desirable to produce a papery product of 
high density without employing a papermaking process which requires a 
specific binder and a complicated system and it has been proposed to apply 
heat and pressure to wholly aromatic polyamide fiber having a low degree 
of orientation and a low degree of crystallinity (Japanese Laid-open 
Patent Application No. 52-105975). 
However, according to this method, since the wholly aromatic polyamide 
fiber used is inferior in mechanical strength and heat-resistance, the 
thus obtained papery product inevitably has poor mechanical strength and 
poor heat-resistance. To improve these properties, it has been proposed to 
apply heat-treatment or blend a fiber of high orientation degree and 
crystallinity, but the heat-resisting property and the mechanical 
properties inherent in the wholly aromatic polyamide have not successfully 
been developed until now. 
The inventors have previously proposed a wholly aromatic polyamide fiber 
having a readily soluble skin layer and a sparingly soluble or insoluble 
core layer (Japanese Patent Application No. 54-49779). Now, it has been 
found that the skin layer effectively acts as a bonding agent when applied 
with heat and pressure and yet the core layer effectively strengthens the 
mechanical property and heat-resisting property thereof. Thus, the present 
invention has been achieved. 
Thus, this invention provides a papery product consisting essentially of a 
fibrous web, at least part of said web being made of a wholly aromatic 
polyamide fiber having a readily soluble skin layer and a sparingly 
soluble or insoluble core layer, said web being formed with application of 
pressure and heat. 
The wholly aromatic polyamide usable for the present invention contains 
repeating units of formulae (I) and (II), 
##STR1## 
wherein Ar.sub.1, Ar.sub.2 and Ar.sub.3 respectively represent, 
independently from each other, an unsubstituted or substituted divalent 
aromatic radical which comprises a single aromatic ring, or two or more 
aromatic rings that are condensed together, or are linked together by a 
single bond, or by a bridging atom or radical, and which is oriented 
either meta or para, and R.sub.1, R.sub.2 and R.sub.3 respectively 
represent, independently from each other, a hydrogen atom or an alkyl 
radical having 1 to 3 carbon atoms. 
In the formulae (I) and (II), it is preferable that Ar.sub.1, Ar.sub.2 and 
Ar.sub.3 be respectively selected, independently from each other, from the 
group consisting of the radicals of the formulae: 
##STR2## 
wherein R represents a member selected from the group consisting of lower 
alkyl radicals having 1 to 6 carbon atoms, lower alkoxy radicals having 1 
to 6 carbon atoms, halogen atoms and a nitro radical, n represents zero or 
an integer of from 1 to 4 and X.sup.1 represents a member selected from 
the group consisting of: 
##STR3## 
wherein Y.sup.2 represents a member selected from the group consisting of 
a hydrogen atom and lower alkyl radicals having 1 to 6 carbon atoms. 
Also, in the formulae (I) and (II), it is more preferable that Ar.sub.1, 
Ar.sub.2 and Ar.sub.3 respectively represent, independently from each 
other, a member selected from p-phenylene radical, m-phenylene radical, 
biphenylene and radicals of the formulae: 
##STR4## 
wherein X.sup.2 represents a member selected from 
##STR5## 
in which Y.sup.2 represents a hydrogen atom or an alkyl radical having 1 
to 3 carbon atoms. 
Furthermore, in the formulae (I) and (II), it is still more preferable that 
Ar.sub.1, Ar.sub.2 and Ar.sub.3 be respectively a p-phenylene or 
m-phenylene radical. 
Moreover, it is preferable that the aromatic polyamide contain the 
repeating units of the formula (II) in which Ar.sub.2 and Ar.sub.3 are 
respectively a p-phenylene or m-phenylene radical, most preferably, a 
m-phenylene radical. 
The aromatic polyamide may contain 30 molar % or less of one or more 
comonomers, for example, aliphatic diamines, such as hexamethylene diamine 
and piperazine, and aliphatic dicarboxylic acid, such as adipic acid, 
based on the entire molar amount of the comonomers contained in the 
polyamide. 
The wholly aromatic polyamide fiber, having a readily soluble skin layer 
and a sparingly soluble or insoluble core layer which is employable in the 
present invention, exhibits various characteristic properties as described 
in Japanese Patent Application No. 54-49779. 
First, the fiber exhibits remarkable characteristics in its dyeing 
property. The fiber can be colored deep by an ordinary dyeing method and 
in an ordinary dyeing time, but, when a section of the fiber is observed 
using a light microscope, it is evident that the dye is dispersed only 
within the skin layer and is not dispersed into the core layer. There is 
caused no change in this characteristic even after the fiber has been 
subjected to dyeing for a time longer than the ordinary dyeing time, e.g., 
more than five hours. 
Second, the fiber exhibits remarkable solubility characteristics. It has 
been known that, for example, a polymer of poly-m-phenylene isophthalamide 
or a poly-m-phenylene isophthalamide which has not been subjected to heat 
treatment or hot drawing is soluble in concentrated sulfuric acid or 
N-methyl-2-pyrrolidone (NMP), while a common, heat-treated or hot drawn 
poly-m-phenylene isophthalamide fiber is dissolved in concentrated 
sulfuric acid but is not dissolved in NMP because of its high-degree of 
orientation and crystallization. By contrast, the fiber having a readily 
soluble skin layer and a sparingly soluble or insoluble core layer shows a 
characteristic whereby only the skin layer thereof is dissolved in NMP at 
room temperature but the core layer is not dissolved thereinto. 
Of course, the fiber is wholly dissolved in concentrated sulfuric acid at 
room temperature. More particularly, although it is natural that the 
dissolution behavior is varied depending upon conditions such as the kind 
of solvent, temperature, time, etc., a common, heat-treated and hot-drawn 
poly-m-phenylene isophthalamide fiber is not substantially dissolved, 
under dissolution conditions (kind of solvent temperature, time, etc.) 
while a polymer powder of poly-m-phenylene isophthalamide having a low 
degree of crystallinity or a poly-m-phenylene isophthalamide fiber which 
has not been heat-treated or hot-drawn is completely dissolved, as in the 
case of a fiber where only the skin layer is dissolved and the core layer 
remains undissolved. This is a second substantiation for a double-layer 
structure of the fiber. In this case, the percentage of the undissolved 
portion of the fiber on the basis of the entire fiber is determined by the 
ratio of the core layer to the skin layer and the dissolution conditions 
(kind of solvent, temperature, time, etc.). 
For example, when the fiber in a solvent of N-methyl pyrrolidone is stirred 
at a temperature of 35.degree. C. for one hour, a drawn and heat-treated 
poly-m-phenylene isophthalamide fiber is not substantially dissolved under 
these conditions, whereas a polymer powder of poly-m-phenylene 
isophthalamide or a poly-m-phenylene isophthalamide fiber which has not 
been subjected to heat-treating or a drawing operation is substantially 
100% dissolved. In the double-layer structural fiber employed in the 
present invention, the cross-sectional area of the dissolved portion 
corresponds to from 10 to 80% and the cross-sectional area of the 
undissolved portion corresponds to from 90 to 20%. 
This shows that the skin layer of the double-layer structural fiber has a 
lower degree of crystallinity as compared with the drawn or heat-treated 
poly-m-phenylene isophthalamide fiber or the core layer of the 
double-layer structural fiber. Accordingly, when a web formed partially of 
such a double-layer structural fiber is subjected to heat and pressure, 
hot-fusion bonding is effected on the skin layer and the core layer having 
a high degree of orientation and crystallinity imparts a high 
heat-resisting property, improved mechanical properties, etc. to the web. 
As a result, a desirable papery product excellent in its heat-resisting 
property, mechanical property, etc. and free from residual solvent etc. 
can be obtained. 
A process for producing a wholly aromatic polyamide fiber having the 
double-layer structure as described above will now be described using 
examples, but the present invention is by no means limited to these 
processes. 
While there have been known several methods for producing a 
poly-m-phenylene isophthalamide fiber, one example of the process for 
producing the double-layer structural fiber used in the present invention 
is such that a spinning solution of poly-m-phenylene isophthalamide is 
extruded into a coagulating bath to form a filament, the filament is 
washed with water, the washed filament is drawn in boiling water and then 
wound while being drawn. The conditions for obtaining a common, strong 
poly-m-phenylene isophthalamide fiber differ, in various points, from the 
conditions for obtaining the double-layer structural fiber used in the 
present invention. 
This is summarized as follows: 
To obtain the double-layer structural fiber of the present invention, the 
kind of solvent for the spinning stock of poly-m-phenylene isophthalamide 
is not critical so long as it can dissolve poly-m-phenylene 
isophthalamide. The spinning stock may contain a salt known as a 
solubilizing auxiliary agent, e.g., calcium chloride, magnesium chloride, 
zinc chloride, lithium chloride, etc. 
While the formulation of the spinning solution is determined by a 
percentage composition of poly-m-phenylene isophthalamide, solvent, 
solubilizing auxiliary agent, etc., it is not critical for the purpose of 
obtaining the fiber of the present invention. Such a formulation is not 
suitable if the viscosity of the spinning solution is too high or too low. 
While the coagulating conditions are determined by the kind, formulation 
and viscosity of the coagulating bath, it is preferred that the 
coagulating bath be an aqueous solution of an inorganic salt. As the 
inorganic salts, there can be mentioned calcium chloride, zinc chloride, 
magnesium chloride, etc. The aqueous solution of the inorganic salt may 
contain the solvent or the solubilizing auxiliary agent, etc., which are 
contained in the spinning stock. The temperature of the coagulating bath 
suitably ranges from room temperature to 150.degree. C., and a preferable 
temperature is determined according to the temperature, kind and 
formulation of the spinning stock and the kind and formulation of the 
coagulating solution. 
The coagulated filament is washed with water at a temperature of 0.degree. 
to 50.degree. C., preferably at a temperature of 0.degree. to 25.degree. 
C. The amount of the solvent retained in the filament under washing, prior 
to drawing in boiling water is preferably reduced as much as possible. It 
is not desirable for preparing the double-layer structural fiber of the 
present invention to retain a large amount of solvent in the filament 
being washed. The upper limit of the solvent which is retained in the 
filament being washed varies depending on other conditions such as the 
drawing conditions in boiling water or at an elevated temperature. To 
obtain a common, strong fiber, the content of the solvent retained in the 
filament under washing should be within a range between a certain upper 
limit and a certain lower limit. However, to obtain the fiber of the 
present invention, it is generally preferred that the content be lower 
than the lower limit of said range. 
The washed filament is drawn in hot water and further subjected to hot 
drawing or heat treatment. The boiling water may be water of a temperature 
higher than 90.degree. C. The temperature of hot drawing or heat treatment 
is from 200.degree. to 390.degree. C., preferably, 250.degree. to 
360.degree. C., more preferably, 320.degree. to 360.degree. C. Assuming 
that the draw ratio in the drawing in the boiling water is DR.sub.1 and 
the drawing ratio in the heat drawing is DR.sub.2, the desired conditions 
for obtaining the fiber of the present invention is DR.sub.1 
.times.DR.sub.2 &lt;4.3 and DR.sub.1 &gt;1.5, preferably, DR.sub.1 
.times.DR.sub.2 &lt;3.5 and DR.sub.1 &gt;2.5. If DR.sub.1 .times.DR.sub.2 is 4.3 
or more while DR.sub.1 is 1.5 or less, the formation of the double-layer 
structure of the fiber of the present invention is not advantageously 
effected or the strength of the fiber is so deteriorated that the fiber 
cannot have sufficient utility. It is necessary to obtain the fiber of the 
present invention, to dry the filament between the steps of drawing in the 
boiling water and the heat drawing or the heat treatment. The drying 
temperature is lower than 180.degree. C., preferably, lower than 
150.degree. C., most preferably, lower than 120.degree. C. A higher drying 
temperature is not desirable for obtaining the double-layer structure of 
the fiber of the present invention. 
While the characteristic features of one process for obtaining the fiber of 
the present invention is described above, these features are generally 
different, in various points, from the conditions for obtaining a common, 
strong fiber of poly-m-phenylene isophthalamide. This is because the 
object of the present invention is not to obtain a common, strong fiber, 
but to obtain a fiber having a double-layer structure. 
The fiber usable for the present invention may contain, in a skeleton of 
poly-m-phenylene isophthalamide, as a copolymer component, other monomers, 
for example, diamines or dicarboxylic acids in such an amount that the 
double-layer structure of the invention is not impaired. As typical 
examples of such a monomer, there can be mentioned p-phenylene diamine, 
terephthalic acid, 2,4- or 2,6-tolylene diamine, etc. 
The double-layer structural fiber may contain various additives such as a 
flame-retarding agent, anti-static agent, etc. or a small amount of 
diverse polymers. 
In the present invention, there may be blended, as fiber components of the 
web, fibers other than wholly aromatic polyamide fibers having a readily 
soluble skin layer and a sparingly soluble or insoluble core layer as 
described above, unless they will not impair the heat-resisting property, 
the electrical property or mechanical property. 
As fibers employable, there can be mentioned: 
(1) Common, single-layer structural fibers made of wholly aromatic 
polyamide as described above; 
(2) Fibers made of a nitrogen-containing poly heterocyclic compound such 
as; Fibers of aromatic polyamide imide, polyazole, polybenzazole, 
polyhydantoin, polyparabanic acid, polyquinazolinedione, polyquinazolone, 
polyquinoxaline, polyoxazinone and the like. 
(3) Aromatic polyether fibers such as; Fibers of polyphenylene oxide, 
polyarylene oxide and the like. 
(4) Polyester fibers such as; Fibers of polyethylene-2,6-naphthalate, 
polyethylene-2,7-naphthalate, polyethylene terephthalate and the like. 
(5) Polyamide fibers; 
(6) Fibers made of inorganic compounds such as; glass fiber, asbestos 
fiber, rock wool fiber, slag cotton, silica fiber, bauxite fiber, kainite 
fiber, boron fiber, potassium titanate fiber and magnesia fiber, and 
whiskers such as alumina and silicon dioxide. 
(7) Natural fibers such as; Cellulose fiber, regenerated fiber, cellulose 
acetate fiber, etc. 
Particles of wholly polyamide polymer may be contained to improve the 
mechanical strength and/or the surface smoothness of the papery product. 
The "web" used in the present invention means a papermade sheet using an 
ordinary web-forming system such as a method in which crimp is imparted to 
a fiber, the cut staple fiber is matted by a card; a method for opening 
the tow of a long fiber; or a method wherein a fiber is cut into short 
filaments of 5 to 20 mm and dispersed with water or pressurized air. The 
thickness of the web may be selected as desired. The web may have been 
treated with an additive for retaining the configuration of the web. 
As the tow opening method for long fiber, there can be mentioned a method 
wherein, for example, sheets of long fiber are laid on each other and 
over-fed by a feeding roller and the fiber laminate is expanded in the 
direction of its width using a divergent belt with needles fixed thereto 
to form a web. This method is advantageously employed to form a web. 
Application of heat and pressure to the obtained web is suitably carried 
out according to the desired properties required for the product. 
The equipment for applying heat and pressure may be an ordinary heat and 
pressure applying equipment such as a heat-and-pressure calender, 
hot-press, etc. The conditions for the heating and pressing may vary 
depending upon the type and speed of the equipment used. However, in 
general, the heating and pressing treatment may preferably be carried out 
at a temperature of 200.degree. to 350.degree. C. and a pressure of higher 
than 50 kg/cm.sup.2. 
According to the process of the present invention, the skin layer of 
aromatic polyamide fiber having a skin-core layer is softened and fused, 
at the heat and pressure applying step, to bind fibers for forming a 
papery product having excellent heat-resisting and flame-retarding 
properties and sufficient strength and elongation characteristics. 
The thus obtained papery product has no color development and keeps 
sufficient tensile strength and elongation even after it has been left at 
a temperature of 250.degree. C. for a long time. 
The obtained papery product can suitably be used not only for ordinary 
purposes, but also as a building material, interior material and 
electrical insulating material all of which are required to have heat 
resistance and flame-retarding properties. 
Embodiments of the present invention will now be described with reference 
to the following examples. In the examples, the solubility of the fiber is 
measured in accordance with the following procedures. Fibers having a 
length of 5 mm were opened, subjected to an operation for removing oily 
materials, using methanol and chloroform at a temperature equal to their 
boiling points for 30 minutes, respectively, and then, dried at a 
temperature of 105.degree. C., for two hours, under a vacuum condition. 
About 0.5 g of the sampled fibers were accurately weighed (W.sub.0). The 
fibers were stirred in 20 cc of NMP at a temmperature of 30.degree. C. for 
one hour and the undissolved portion was put into a glass filter and 
washed sufficiently with NMP and, then, with water and with methanol. The 
portion was dried at a temperature of 105.degree. C., for two hours, under 
a vacuum condition. The dried undissolved portion was then weighed 
(W.sub.1). The dissolved amount % by weight of the fibers was calculated 
in accordance with the equation: 
##EQU1## 
The inherent viscosity (I.V.) of the polymer was determined in such a 
manner that about 50 mg of the polymer was accurately weighed, and, then, 
dissolved in 10.0 ml of concentrated sulphuric acid at room temperature. A 
time necessary for passing a predetermined amount of solvent and solution 
through an Ostwald's viscometer was measured, and the inherent viscosity 
was calculated in accordance with the equation: 
##EQU2## 
t: the time in seconds for solution t.sub.o : the time in seconds for 
sulfuric acid 
C: the concentration of the solution, g/100 ml

EXAMPLES 1 TO 3 
A spinning solution prepared from 22 parts of poly-m-phenylene 
isophthalamide (I.V.=1.85) polymerized from m-phenylene diamine and 
isophthalic acid chloride, 77 parts of calcium chloride and 100 parts of 
N-methyl-2-pyrrolidone was extruded through a spinneret having 100 
spinning holes, each having a diameter of 0.08 mm, into a bath consisting 
mainly of an aqueous solution of 50% by weight of calcium chloride, at a 
rate of 2 g/min, to coagulate the extruded materials. The coagulated 
filaments were washed with water at a temperature of 15.degree. C., and, 
then, washed with hot water. The washed filaments were drawn in hot water, 
at a draw ratio of 2.63 and dried at a temperature of from 110.degree. C. 
to 120.degree. C. on drying rollers. The filaments were drawn on a hot 
plate of 350.degree. C. at a draw rate of 1.20. The filaments were wound 
by a winder. The resultant yarn had a fineness of 200 denier, 4.5 g/de of 
tensile strength and 68% of ultimate elongation. The dissolved amount of 
the filaments was 31%. 
The filaments were crimped 11 or 12 times/20 mm, then, cut into staple 
fibers 51 mm long, carded using a cloth-laid webber, and needled at a 
punching density of 81/cm.sup.2 to obtain a web 1 m wide. The web was 
subjected to heat and a pressure applying operation on a hot press under 
conditions of various heat temperatures and 200 kg/cm.sup.2 pressure, for 
four minutes. The properties of the resultant papery product are 
summarized in Table 1. In the table, the properties measured after 
heat-treatment at 250.degree. C. for 500 hours are also shown. 
TABLE 1 
__________________________________________________________________________ 
Strength after 
Elongation after 
Press Thickness. 
Density, 
Strength, 
Elongation, 
heat-treatment 
heat-treatment 
Example 
Temp., .degree.C. 
.mu. g/cm.sup.3 
kg/mm.sup.2 
% kg/mm.sup.2 
% 
__________________________________________________________________________ 
Example 1 
290 204 0.60 6.2 13.8 6.1 13.5 
Example 2 
310 182 0.70 10.2 33.0 10.0 32.0 
Example 3 
330 105 0.92 10.2 18.6 10.1 18.0 
__________________________________________________________________________ 
COMATIVE EXAMPLE 1 
A N-methyl-2-pyrrolidone solution of 22% by weight of poly-m-phenylene 
isophthalamide (I.V.=1.80) was used as a spinning solution, and the 
solution was extruded into an aqueous solution consisting mainly of 43% by 
weight of calcium chloride at a temperature of 95.degree. C. through a 
spinneret having 100 spinning holes, each having a diameter of 0.08 mm, at 
a rate of 2 g/min to coagulate the material. The coagulated filaments were 
washed with an aqueous solution at a temperature of 20.degree. C., and, 
then, washed with hot water at a temperature of 70.degree. C. The washed 
filaments were drawn in boiling water at a draw ratio of 2.30 and dried at 
a temperature of 130.degree. C. on drying rollers. The dried filaments 
were further drawn on a hot plate at a temperature of 350.degree. C. at a 
draw ratio of 1.82. The filaments were then wound by a winder. The 
resultant yarn had a strength of 5.50 g/de and an elongation of 36%. The 
dissolved amount of the filaments was 0%. 
The filaments were crimped, cut into fibers 51 mm long and fed to a carding 
machine to obtain a web. The obtained web was subjected to a heat and 
pressure applying operation, using a hot press, at a temperature of 
330.degree. C. and at a pressure of 200 kg/cm.sup.2, for four minutes. The 
filaments were not sufficiently bound and a papery product could not be 
obtained. 
COMATIVE EXAMPLE 2 
A N-methyl-2-pyrrolidone solution of 22% by weight of poly-m-phenylene 
isophthalamide (I.V.=1.80) was used as a spinning solution, and the 
solution was extruded into an aqueous solution consisting mainly of 43% by 
weight of calcium chloride at a temperature of 95.degree. C., through a 
spinneret having 100 spinning holes, each having a diameter of 0.08 mm, at 
a rate of 2 g/min to coagulate the material. The coagulated filaments were 
washed with an aqueous solution at a temperature of 20.degree. C., and, 
then, washed with hot water at a temperature of 70.degree. C. The washed 
filaments were dried at a temperature of 130.degree. C. on drying rollers 
to obtain an undrawn yarn (A). The resultant yarn had a strength of 1.0 
g/de and an elongation of 400%. The dissolved amount of the filaments was 
100%. 
The above-mentioned procedure was repeated, except that the filaments 
washed with water at 70.degree. C. were drawn in boiling water at a draw 
ratio of 2.75, to obtain a drawn yarn (B). The obtained yarn had a 
strength of 3.0 g/de and an elongation of 50%. The dissolved amount of the 
filaments was 100%. 
The filaments were crimped and cut into staple fibers 51 mm long, as 
described in Example 1. The obtained fibers (A) or (B) or a blend of the 
fibers (A) or (B) with the fibers (C) obtained in Comparative Example 1 of 
a weight ratio or 60:40 were formed into a web having a width of 1 m and a 
weight of 150 g/m.sup.2 in the same manner as in Example 1. Each web was 
hot-pressed, using a hot press, at a temperature of 330.degree. C. and at 
a pressure of 200 kg/cm.sup.2, for 4 minutes. The properties of the 
obtained products are shown in Table 2 together with the properties 
measured after heat-treatment at 250.degree. C. for 500 hours. 
TABLE 2 
______________________________________ 
Strength 
Elongation 
Thick- Elon- after heat- 
after heat- 
Web-com- 
ness Strength gation 
treatment 
treatment 
posing fiber 
.mu. kg/mm.sup.2 
% kg/mm.sup.2 
% 
______________________________________ 
A 140 7.2 5 3.2 2 
B 157 6.7 7 not measurable 
A/C 180 4.8 10 4.4 6 
(60/40) 
B/C 192 4.5 12 4.2 8 
(60/40) 
______________________________________ 
The webs obtained using the fibers (A) and (B) were both inferior in their 
heat-resisting property. The webs obtained using the blend fibers 
necessitated a blending operation and, further, were inferior in the 
initial properties. 
EXAMPLE 4 
The filaments used in Example 1 were blended with the filaments used in 
Comparative Example 1 at a ratio of 60 to 40 to prepare a web. The web was 
subjected to a heat and pressure applying operation at a temperature of 
310.degree. C. and at a pressure of 200 kg/cm.sup.2 for four minutes, the 
resultant papery product had a strength of 6.0 kg/mm.sup.2 and an 
elongation of 16%. The strength and elongation after heat-treatment at 
250.degree. C. for 500 hours was 5.8 kg/mm.sup.2 and 15.5%, respectively. 
EXAMPLE 5 
Filaments obtained by similar procedures to those of Example 1 were cut 
into short filaments 7 mm long. The short filaments were dispersed by 
pressurized air using an ejector having an air supply conduit, a fiber 
supply conduit and a discharging slit, and, then, caught on a metal net to 
form a sheet. The sheet was subjected to a pressure and heat applying 
operation at a temperature of 310.degree. C. and a pressure of 200 
kg/cm.sup.3 for four minutes to obtain a papery product having such 
properties as a strength of 7.0 kg/mm.sup.2 and an elongation of 10%. The 
strength and elongation after heat-treatment at 250.degree. C. for 500 
hours was 6.7 kg/mm.sup.2 and 9.7%, respectively. 
EXAMPLE 6 
Tows of the filaments obtained in Example 1 were laminated and guided 
through a feed roller. The laminate was held, at ends thereof, by a pair 
of divergent belts with needles provided thereon which were disposed just 
after the feed roller, after overfeeding twice the normal feeding 
distance. The laminate was expanded in the width direction 10 times as 
wide as the original width, to form an expanded web having a weight of 100 
g/m.sup.2. The web was subjected to a heat-and-pressure processing, using 
a press roller, at a temperature of 250.degree. C. at a pressure of 100 
kg/cm.sup.2 to obtain a papery product having an excellent surface 
smoothness. The obtained papery product had a strength of 9.2 kg/mm.sup.2 
and an elongation of 23%. The strength and elongation after heat-treatment 
at 250.degree. C. for 500 hours was 9.1 kg/mm.sup.2 and 20%, respectively. 
EXAMPLE 7 
Filaments obtained by procedures similar to those of Example 1 were cut 
into short filaments 7 mm long, dispersed into water and formed into a 
sheet having a weight of 100 g/m.sup.2, using a TAPPI standard sheet 
machine. The resultant sheet was subjected to a heat and pressure applying 
operation at a temperature of 310.degree. C. and a pressure of 200 
kg/cm.sup.2 for four minutes to obtain a papery product having properties 
a strength of 6.8 kg/mm.sup.2 and an elongation of 10%. The strength and 
elongation after heat-treatment at 250.degree. C. for 500 hours was 6.5 kg 
and 9.5%, respectively. 
EXAMPLES 8 TO 12 
Using procedures as in Example 3, various wholly aromatic polyamide 
filaments as given below were blended with the filaments used in Example 1 
at a ratio of 40 to 60 to obtain webs, each having a weight of 100 
g/m.sup.2. The webs were subjected to heat and pressure applying operation 
at a temperature of 310.degree. C. at a pressure of 200 kg/cm.sup.2 for 
four minutes to obtain papery products each having an excellent heat 
resistance and a good surface smoothness. 
When the following wholly aromatic polyamide fibers above were used and 
pressed in a manner as described above, the dimension stability was 
deteriorated and no desired papery product was obtained. 
__________________________________________________________________________ 
Wholly aromatic Properties 
polyamide of single yarn 
Main acid 
Main amine Strength,Elongation, 
Example 
component 
component g/de% Web preparing method 
__________________________________________________________________________ 
##STR6## 
##STR7## 255 Wet type preparation, using short 
filaments 7 mm long 
##STR8## 
9 
##STR9## 
##STR10## 224 Preparation by carding, using crimped 
filaments 51 mm long 
10 
##STR11## 
##STR12## 1.54 (undrawn and non-heat-treated) 
Preparation by carding, using crimped 
filaments 51 mm long 
11 
##STR13## 
##STR14## 3.042 (drawn in hot water but non-heat-treated) 
Preparation by carding, using crimped 
filaments 51 mm long 
12 
##STR15## 
##STR16## 814 Preparation by carding, using crimped 
filaments 51 mm long 
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EXAMPLE 13 
95% of the crimped filaments used in Example 1 (51 mm long) which had been 
opened by a card was blended with potassium titanate filaments to prepare 
a web. The web was pressed at a temperature of 290.degree. C. to obtain a 
papery product having a strength of 6.0 kg/mm.sup.2 and an elongation of 
10%. 
EXAMPLE 14 
50% of the crimped filaments used in Example 1 (51 mm long) was 
preliminarily blended with 50% of crimped filaments (51 mm long) made of 
polyethylene-2,6-naphthalate and formed into a web using a card. The web 
was pressed at a temperature of 290.degree. C. to obtain a papery product 
having a strength of 6.4 kg/mm.sup.2 and an elongation of 12%.