U.S. patent number 3,628,995 [Application Number 04/764,935] was granted by the patent office on 1971-12-21 for flame resistant cloth.
This patent grant is currently assigned to The Carborundum Company. Invention is credited to James Economy, Francis J. Frechette, Luis C. Wohrer.
United States Patent |
3,628,995 |
Economy , et al. |
December 21, 1971 |
FLAME RESISTANT CLOTH
Abstract
A flame resistant cloth or fabric comprising synthetic fibers
prepared from resin condensation products of phenols and aldehydes
which can be fiberized and cured. These fabrics may include blends
of phenolic resin fibers with other fire-resistant fibers such as
wool, silk, polyamide fibers, polyacrylonitrile fibers, mineral and
glass fibers, among others.
Inventors: |
Economy; James (Eggertsville,
NY), Frechette; Francis J. (Tonawanda, NY), Wohrer; Luis
C. (Lewiston, NY) |
Assignee: |
The Carborundum Company
(Niagara Falls, NY)
|
Family
ID: |
25072206 |
Appl.
No.: |
04/764,935 |
Filed: |
October 3, 1968 |
Current U.S.
Class: |
428/421; 428/525;
428/921; 442/146 |
Current CPC
Class: |
C01B
32/00 (20170801); D06M 15/41 (20130101); A41D
31/08 (20190201); D03D 15/513 (20210101); D01F
6/76 (20130101); Y10S 428/921 (20130101); Y10T
428/31946 (20150401); Y10T 428/3154 (20150401); Y10T
442/2713 (20150401) |
Current International
Class: |
A41D
31/00 (20060101); D06M 15/41 (20060101); D03D
15/12 (20060101); D01F 6/58 (20060101); D01F
6/76 (20060101); D06M 15/37 (20060101); C01B
31/00 (20060101); B32h 027/08 (); B32b
027/42 () |
Field of
Search: |
;117/136,138.8G
;8/115.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Ernest R. Kaswell, Wellington Sears Handbook of Industrial
Textiles, (1963) pgs. 233 & 234. .
Herbert A. Pohl, "Reaction Spinning of Fibers," Textile Research
Journal, pgs. 473-477 (1958)..
|
Primary Examiner: Martin; William D.
Assistant Examiner: Sofocleous; M.
Claims
We claim:
1. A flame-resistant fabric comprising phenolic fibers of cured
novolac resin condensation products of phenols and aldehydes, and a
liquid impenetrable coating thereon.
2. A flame resistant fabric according to claim 1 in which the
coating is a layer of resin selected from the group consisting of
phenolic and fluorocarbon resins.
3. A flame-resistant fabric consisting essentially of phenolic
fibers of cured novolac resin condensation products of phenols and
aldehydes, and a liquid impenetrable coating thereon.
4. A Flame-resistant fabric according to claim 3 in which the
coating is a layer of resin selected from the group consisting of
phenolic and fluorocarbon resins.
Description
BACKGROUND OF THE INVENTION
Man's concern with the hazards associated with the ready
combustibility of textiles has been continuous since the discovery
and utilization of fire. Today it is desirable that certain fabrics
such as curtains and drapes, decorative fabrics and sometimes
upholstery and floor coverings in public buildings be flame
resistant. It is highly desirable that certain clothing items such
as children's pajamas be flame resistant. Many special purpose
garments, such as welders'and steelworkers'overalls, fire fighters'
clothing, and certain types of military clothing must be flame
resistant.
Several factors generally affect flame resistance of a textile.
First, the composition of the fibers must be considered. Natural
fibers (such as cotton, flax, silk, wool), regenerated fibers (such
as rayon), the man made fibers (such as nylons, vinyls, acrylics),
and the inorganic fibers (such as glass and asbestos) have a
varying combustibility and flame resistance depending on their
chemical makeup. Of course, the weight and construction pattern of
the fabric makes a significant difference in ease of burning.
Lightweight, loose weave fabrics usually burn much faster than
heavier fabrics.
The terms used in connection with flame resistant fabrics are
sometimes confusing. "Fire-resistance" and "flame-resistance" are
very often used in the same context as the terms "fireproof" and
"flameproof." A textile which is flame-resistant or fire-resistant
will not continue to burn or glow once the source of ignition has
been removed although there will be some change in the physical and
chemical characteristics. Fireproof or flameproof, on the other
hand, refers to a material which is so resistant to flames that no
appreciable change in physical or chemical properties is noted.
Glass is an example of a fireproof material; however, if flame is
applied long enough, it will melt.
Fabrics comprising mineral fibers such as asbestos or glass fibers,
while flameproof, have several drawbacks. They are uncomfortable
when in contact with the skin; they are highly heat conductive; and
usually they must be blended with other fibers such as cotton to
provide adequate strength and flexibility to the fabric. When the
cotton or other fabric becomes burned or charred, the asbestos or
glass fabric becomes very brittle and may fall apart. Glass fibers
begin to lose their strength around 350.degree. C., and asbestos
fibers dehydrate and become friable at about 550.degree. C. In
intense heat they melt away. Wool and other animal fiber fabrics
have a relatively high ignition temperature and burn slowly. Wool
has a bulky ash which is very brittle and, therefore, burnt wool
falls apart easily. Cotton and other cellulose-type fabrics are
extremely flammable without chemical treatment which is of limited
value.
Most man made fabrics melt rapidly when in contact with flames or
at temperatures somewhat above 150.degree. C. For example,
polyethylene fabrics melt between 110.degree. and 120.degree. C;
polyvinylidene chloride fabrics melt between 140.degree. and
150.degree. C; modacrylics (copolymers) melt at about 170.degree.
C; polyesters (terephthalic acid derivatives) melt at around
250.degree. C; polyacrylonitrile (P.A.N.) fabrics soften at about
250.degree. C. The common polyamides melt at low temperature, for
example, nylon 6 melts at 210.degree. C., and nylon 66 at
250.degree. C. It should be understood that synthetic fibers lose
their strength at temperatures much below their melting points.
Of the synthetic fabrics, only special polyamides,
polyacrylonitriles and fluorocarbons have generally been considered
flame resistant. There are special polyamide fabrics that are more
resistant to a flame than the common nylons but only retain their
strengths to temperature of about 225.degree. C, and at about
325.degree. C., decompose into a friable char. The
polyacrylonitriles shrink at elevated temperatures and might under
unusual conditions be the source of poisonous gases. The
fluorocarbon fabrics (polytetrafluoroethylene) give off a poisonous
vapor above 200.degree. C.
According to the teachings of this invention, there is provided a
fabric having the following advantages: It is flame resistant. It
does not melt. It has a low thermal conductivity. It is not
uncomfortable when adjacent the skin as are mineral or woolen
fabrics. The flexibility of the fabric is substantially equivalent
to nylon. It chars producing carbon fibers with sufficient strength
to maintain an integral protective cloth. It is chemically
resistant and gives off no poisonous gases on heating.
THE INVENTION
Flame-resistant fabrics according to this invention comprise
synthetic fibers prepared from resin condensation products of
phenols and aldehydes which can be fiberized and cured. (Hereafter,
these synthetic fibers will be referred to as phenolic fibers.) The
flame-resistant fabrics may include blends of phenolic fibers with
other fire-resistant fibers such as wools, silks, polyamide fibers,
polyacrylonitrile fibers, mineral and glass fibers, fluorocarbon
fibers, and chemically treated cotton and rayon, among others.
These fabrics may have additional wear-resistance and better
moisture regain. In some instances, less fire-resistant fibers, for
example, cottons, can be blended with phenolic fibers in the
manufacture of fire-resistant fabrics. The amount of such fibers
added and the manner of addition affects the properties of the
composite fabric. Preferably, the more flammable fibers are added
as coring in yarns. Alternatively, any suitable conventional
technique for sheathing such fibers with phenolic fibers may be
employed. Even small percentages of phenolic fiber will eliminate
the dripping of molten polymer encountered in the burning of some
fabrics. It is preferable that the fabrics according to this
invention be at least 35percent by weight phenolic fibers.
Phenolic resins are the condensation products resulting from the
reaction between phenols and aldehydes. The various phenols and
aldehydes that can be used to make phenolic resins are well known.
(See, for example, Phenolic Resins by David F. Gould, Reinhold
Publishing Company, New York, 1959. ) Primarily, phenolic resins
are products of phenol and formaldehyde. The reaction of phenol
itself with formaldehyde in the absence of any other reagent is
slow, and a catalyst is almost always added to accelerate the
reaction. The nature of the reaction products depends considerably
upon whether an acidic or a basic catalyst is used and upon the
ratio of phenol to formaldehyde. When alkaline catalysts are used
and the molar ratio of formaldehyde to phenol is greater than 1:1,
the primary reaction products are phenol alcohols having reactive
methylol groups which products are referred to as resoles. When
acid catalysts are used and the molar ratio of formaldehyde to
phenol is somewhat less than 1: 1, the primary reaction products
are probably also phenol alcohols but they rearrange rapidly to
yield diphenyl methane derivatives to which the name novolac has
been given. It has generally been accepted that phenol alcohols
condense, with the elimination of water, to yield three dimensional
macromolecules cross-linked by methylene bridges. Hence, resoles on
heating polymerize resulting in an insoluble and infusible product.
On the other hand, novolacs on heating remain viscous, and are
permanently fusible. The novolac resins may be made rigid by curing
with additional formaldehyde or with hexamethylene tetramine, among
others, in the presence of an appropriate catalyst.
Phenolic fibers may be made from resoles and novolacs or a
combination of each in varying proportions. Additives and
modifiers, either reactive or nonreactive, can be used to alter the
fiber characteristics either for attenuation or their end use
properties. When resoles are used as a starting material, they
should be dried prior to fiberization. The fibers are drawn from
the viscous mass and made infusible by the careful and gentle
application of heat. No additional methylol groups or catalysts are
required for a complete cure. However, the fibers remain tacky
until cured and must be kept from contact with each other or they
will coalesce. The addition of a novolac will decrease the tendency
to coalesce.
When a pure novolac is fiberized no coalescence occurs even though
the fibers are tightly wound on a spool. Curing of novolac fibers
can be accomplished quite readily. The curing cycle is determined
by the average molecular weight of the resin. The manufacture of
phenolic fibers from novolacs is described in copending U.S. Pat.
application Ser. No. 710,292, filed Mar. 4, 1968 entitled "Fibers
from Novolacs and Method for Their Production" by Economy and
Clark. That application and this application are assigned to a
common assignee.
Fabrics may be woven or knitted from continuous strands of phenolic
fiber or may be woven or knitted from yarns which are prepared from
phenolic fiber staples. Staples are made into yarn by the common
textile making practices of opening, picking, carding, breaker
drawing, finisher drawing, roving, spinning, twist setting and
winding. When other fibers are to be blended with the phenolic
fibers they can either be added as staples prior to the picking
operation, introduced as a core yarn or during weaving as warp or
fill. Worsted systems comprising gilling, pin drafting, roving,
spinning, twist setting and winding are also suitable for preparing
yarn.
The following tests were performed to demonstrate the superior
fire-resistance of phenolic fiber fabrics. In order to eliminate
the variables such as type and tightness of weave, staple fibers
were tested. Two grams of staples of the following fibers were
formed into balls having a diameter of 2 inches. The fibers
compared were cotton, rayon, wool, high temperature polyamide,
polyacrylonitrile and phenolic fibers. The test balls were placed
on a screen 1inch above the blue portion of a gas flame. The burner
had a capacity of 10,500B.t.u.' s per hour and consisted of 155
orificed cones. The height of flame caused by combustion of the
fiber balls and the change of weight and shape after a 10 second
test and a 60 second test are given in the following table.
##SPC1##
The table establishes that phenolic fibers have superior
flame-resistance to the other fibers tested. Surprisingly, phenolic
fibers did not produce a flame on ignition. Most important,
phenolic fibers retain their shape, that is, they shrink only
slightly and char or carbonize and hence, when woven into a fabric,
provide protection even after having been subjected to a direct
flame. All other fibers shrank. (The tabulated data show that the
balls of phenolic staples are larger after testing. This was due to
unraveling of the balls and not to expansion of the fibers which
actually shrink slightly. On the other hand, the remaining fiber
balls shrank due to considerable shrinking or melting of the fibers
themselves.) In a similar test, glass and asbestos fibers were
compared with phenolic fibers. Of course, the mineral fibers did
not ignite; however, after about 20 seconds in the flame they
melted away.
Phenolic fiber fabrics provide more protection against heat in
fire-fighting clothes than asbestos or glass fabric because the
phenolic fibers have a thermal conductivity only one-fifth of that
of mineral fibers.
Phenolic fiber fabrics have been found to be resistant even to
burning liquids in direct contact with them if coated with a liquid
impenetrable coating. Suitable coatings would comprise, for
example, firm and flexible layers of phenolic resin or fluorocarbon
resin.
It should be understood that this invention is not limited to
fabrics made 100percent from phenolic fibers. Considerable
advantage can be gained by combining these fibers with other
fire-resistant fibers such as wool, special polyamides,
polyacrylonitrile fibers, and asbestos or glass. By blending the
phenolic fibers with a natural fiber such as wool, the fabric can
be provided with increased moisture regain which contributes to the
comfort of the wearer of the fabric. By blending with special
polyamides and polyacrylonitriles, the wear resistance of the
fabric can be increased. Even though the polyamides have a tendency
to melt, the structure provided by the phenolic fibers will retain
the melt in place until it chars. The resistance of phenolic fiber
fabrics against longer time exposure to intermediate temperatures
(200.degree.-800.degree. C) can be improved by blending the
phenolic fibers with mineral fibers such as glass, asbestos or
boron nitride. In certain instances, even cotton, rayon, polyester
fibers, polyolefin fibers, polyvinyl fibers, an other less
fire-resistant fibers can be advantageously blended with phenolic
fibers to provide a fire-resistant fabric.
Having thus described our invention what is desire to be covered by
Letters Patent is as follows:
* * * * *