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Патент USA US2407581

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Patented Sept. 10, 1946
. Marion F. Smith and Harold W. Greider, Wyo
ming, Ohio, assignors to The Philip Carey lYIan
ufacturing Company, a corporation of 01110
No Drawing. Application February 9, 1945,
Serial No. 577,162
9 Claims. (Cl. 117-—118)
This invention relates to asbestos products and
relates especially to products which comprise
consequent actual loss of strength of the resulting
asbestos paper. The strength of the asbestos
?brous material containing asbestiform mineral
paper can be somewhat increased by the employ
?bers disposed in intimately contacting relation
ment of asbestos ?bers which are longer‘ than the
as by felting or other operation adapted to form
5 asbestos ?bers usually used in the manufacture
a sheet or sheet-like body.
of asbestos paper. There are, however, objections
The asbestos products which ?nd most ex
to the use of long asbestos ?bers in the manufac
. tensive commercial use are asbestos sheet mate
ture of asbestos paper. In the first place, long
rials that are usually produced by water laying
asbestos ?bers are of much higher cost and are
and that are generally referred to as asbestos
usually reserved for spinning purposes. Asbestos
paper or asbestos “millboard,” which is referred
?bers of intermediate length, namely, between
to herein generally as “paper.” The bulk of the
the long spinning ?bers and the relatively short
asbestiform mineral ?ber that is used in asbestos
?bers used for making asbestos paper, are gener
paper usually runs from about T16” to 1/4" in
ally used for reinforcement purposes, e. g., as a
length, although the ?ber that is supplied for 15 reinforcement
in the manufacture of heat insu
paper making generally contains a considerable
lation materials and the like which consist in
quantity of shorter ?bers of varying lengths and
major proportion of ?nely-divided non-?brous
may contain a portion of longer ?bers. The most
heat~resistant material that is reinforced by the
generally accepted system of classi?cation of as
asbestos ?bers. Another reason why the long
bestos ?bers is that of the Quebec Asbestos Pro
ducers Association. , The asbestos ?bers which
_ are most commonly used for the manufacture of
asbestos paper are those which range from the
group 5 or paper classi?cation to the group 7
?bers are not used in the manufacture of asbestos
paper is the fact that long ?bers are diiiicult to
form into uniform sheets from the aqueous sus
pension in a paper-making operation. The long
?bers tend to form into clumps which result in
or shorts classi?cation of the Quebec Asbestos 25 the formed paper in slots of ?ber with thin or
Producers Association, or mixtures thereof.
open spaces de?cient in ?ber therebetween.
In the manufacture of asbestos paper from
Moreover, only a slight increase in strength is af
asbestos ?bers of the character aforesaid, the
forded by the employment of long asbestos ?bers
water-laying of the ?bers to produce the felt is
in the manufacture of asbestos paper. This in
somewhat more difficult than the water-laying‘
vention is of particular utility in the manufacture
of ordinary paper or felts from cellulosic ?bers
of products from the more common and less ex
due to the fact that the asbestos ?ber forms a
pensive ?bers of the paper-making ‘grades men
pulp which is “slow,” namely, a pulp from which
tioned above.
water does not drain readily. Consequently, as
It has heretofore been standard practice in
bestos paper is usually prepared on the multi
manufacture of asbestos paper to use starch
cylinder machine, each cylinder picking up a thin 35 as the binder material for imparting strength
layerof the felted asbestos ?bers from the water
to the paper, since starch has been found to be
suspension in the cylinder vat and these layers
most effective and economical binder for
being plied together on the machine to produce
webs comprising asbestos ?bers. The starch may
paper products of the desired thickness. The
be used in varying amounts depending upon the
plying of a plurality of thin layers of asbestos 40 strength to be imparted to the asbestos paper
?bers also tends to afford somewhat greater
and depending upon the purpose for which the
strength than otherwise would be the case if a
asbestos paper is intended.
single thick layer of corresponding weight were
When starch is used as a binder for asbestos
produced. Usually asbestos paper contains from
the resulting product has the serious draw
three to six plies of the relatively thin water
back of having virtually no resistance to water.
laid asbestos ?ber web produced on the individual
Thus, when a piece of starch-bonded asbestos
paper forming cylinders of a multi-cylinder ma
paper is placed in water, the ?bers are liberated
and become dissociated into a pulpy mass in only
An asbestos paper of the character aforesaid
has very little strength in the absence of a bind 50 a few seconds time. It is a matter of not in
frequent occurrence for an installation utilizing
er. Hydration by “beating,” as employed for the
asbestos paper to become moistened by water as
development of strength in cellulosic papers, is
a result of accidental exposure to the weather or
ineffective with the inorganic asbestos ?ber and
merely results in the shortening of the ?ber With 55 the breaking or leaking of a water or steam line.
Starch-bonded paper has such extremely low wa
into the paper. Preferably, however, the paper
ter resistance that serious damage may result
is substantially completely dried (so that it will
from such casual contacts with water. Starch
contain less than about 5% by weight of mois
bonded paper is likewise adversely affected by
ture) before the oxalic acid is applied, since by 7
humid atmosphere and when subjected to humid
so doing the absorption of the oxalic acid into
atmosphere becomes greatly weakened with re Cl the paper is more complete and is more uniform.
sultant sagging and likelihood of permanent
After the oxalic acid has been applied, the paper
damage- It is because of poor resistance to hu—
is again dried as by passing it over drying rolls
mid atmosphere that starch-bonded asbestos pa
which may be heated to conventional drying tem
per is not recommended for use below grade,
10 perature such as 200 to 300° F., although the.
e. g., in basements, tunnels, underground con
duits; etc.
' heating is not material and, if desired, maybe
‘There are known binders which are water
insoluble and that have been used to a very lim
ited extent for bonding asbestos paper. For ex
omitted. The dried paper may, for example,‘
contain. about 5% or less of retained moisture
although the extent of drying is not critical.
paper has been dried, it ordinarily is
ample, rubber latex and synthetic rubber-like 15 woundthe‘
on a reel, trimmed to desired width and
materials which are generally referred to as elas- '
made up into rolls as is conventional in paper
tomers have been used. However, such mate
rnaking, operations.
rials are considerably more expensive than
The above-described process can advanta-'_
starch. Moreover, asbestos paper is generally
geously be carried out in a single and continuous
used in situations where there is likelihood of
operation by applying the oxalic acid to the as- .
exposure to high temperatures and rubber or
bestos paper at an intermediate stage during the
rubber-like compounds are objectionable for such
passage of the asbestos paper over the drying
purpose, because of the malodorous vapors and
rolls of a conventional machine for the manu
smoke that are evolved when such compounds are
facture of asbestos paper products.
subjected to heat. Ordinary organic binders
The concentration of the oxalic acid that is
such as casein, soya protein, glue, rosin. and the
applied to the asbestos paper is not critical. Usu
like have not been found to be suitable for the
ally, the acid is applied to the paper when di
manufacture of asbestos paper.
There’ are cer
tain types of water-resistant synthetic resins
luted with water so as to be of about 10% :to
about 20% concentration.
_ which are used to bond asbestos paper, but their 30
cost is so great that their use is impractical for
. any but specialized uses.
It is a purpose of this invention to provide a
binder for'asbestos paper which is inexpensive,
which can be readily applied, and which, after _
application, affords‘ an asbestos paper or other
asbestos containing ?brous body which is highly
resistant to moisture and to water.
We have discovered that certain oxalates have
the property of bonding asbestiform mineral
?bers and that the bonded ?bers resist disinte
'gration when subjected'to water so as to provide
highly water-resistant asbestos products such as
asbestos paper. As typical of such substances,
oxalic acid has been found to possess this peculiar
property of bonding asbestos ?bers, and of pro
viding a bond which is resistant to moisture.
The strength of the
asbestos paper product is increased somewhat
upon increasing the concentration of the oxalic
acid that is applied thereto up to a concentration .
of about 30%, but the amount of strength that
is imparted to the asbestos paper is not propor
tional to the concentration of .the oxalic acid
that is employed.
The effectiveness of the bonding, that may be
aiiorded between the?bers of an asbestos paper
may be illustrated in connection with the follow
ing example. If asbestos paper is made by a
conventional paper-making operation so as to _
weigh about ten pounds per 100 square feet,'the '
resulting web or sheet when dried and without
having had any binder included in the furnish,
has a tensile strength of only about two pounds
per linear inch of width in the machine direction
of the sheet and a tensilestrength of only about
one-half pound per linear inch of width across
The action of the oxalic acid is not understood
but appears to be speci?c between the substance
the sheet. Upon applying oxalic acid of about
of the asbestiform mineral ?bers and the oxalic 50
20% concentration to the sheetmaterial sothat
the sheet materialwill take up about seventy
The manufacture of a strong, coherent and
pounds of the dilute oxalic acid solution for each
water-resistant asbestos paper according to this
one hundred pounds of the asbestos sheet and
invention may be illustrated as follows: Asbestos
paper, which may be any of the usual paper
then drying the sheet, the resulting product has
grades of asbestos ?ber heretofore used in the
manufacture of asbestos paper products, is made
sheet of about thirteen pounds per linear inchlot
width and about ?ve pounds per linear inch of
width across the sheet. The tensile strengths
up into an aqueous furnish according to conven
tional methods used in the manufacture of as
bestos paper and the furnish is made up into
sheet material on a paper-making machine in the
usual way until an asbestos paper is produced
having the ultimate thickness and weight de
sired. The paper thus produced is free of any
binder, and, after it has been formed, it is sub- ;
jected to drying as by passing it over a plurality
of drying rolls. According to this invention, the
asbestos paper, which has been formed and dried,
has a solution of oxalic acid applied thereto by
any suitable means which may be in the form of
a transfer roll for contacting one or both sides
of the sheet, spray application, tub sizing or the
like. The extent to which the paper is dried be
fore the oxalic acid is applied may be merely
su?icient to enable the oxalic acid to penetrate -75
a tensile strength in the machine direction of the
that are given aboveand elsewhere herein are as
by the
A. s. T. M. standard 13202-411‘ using a Scott
tensile testing machine, the test specimens'of
paper having been conditioned at 45% relative
‘humidity at ‘77° F. for four hours before testing.
The asbestos paperwhich has been bonded by
the application ofoxalic acid thereto is notablev
for its capacity to retain its structural integrity
and a substantial part of its dry strength when
contacted with water. A very severe accelerated
test for determining the resistance of asbestos pa-,
per to water consists in immersing a small sam-'
ple of the product (about 1 x 2 inches) in boiling
water. Failure, if it occurs, is taken as the point
at which the binder no longer acts to hold the
?bers together, the ?bers becoming liberated to
form a pulpy mass.
‘merits of this invention will take up 30% or more
of water and preferably 40% or‘ more of water
when immersed in water at 77° F. for live min
When subjected to the boil
ing water test, the asbestos paper, wherein the
absestos ?bers had been bonded together by the
action of the oxalic acid, successfully withstood
utes. In referring to the sheet materialproduced
according to this invention as being ?exible, it
may be mentioned as typical that sheets having
the boiling water test for over 90 minutes. The
test was discontinued at that time because the
a thickness up to .050 inch or less may be bent
paper had not disintegrated and there was no in
180° ‘around a mandrel 1.5 inches in diameter in
dication that longer exposure to boiling water
two seconds at 77° F. without rupture or breaking
would result in disintegration of the paper. Un 10 at the surface and are thus of a. suitable degree
der similar conditions, a starch-bonded asbestos
of ?exibility for fabrication purposes. Thin
paper 'disintegrates virtually immediately.
sheets are, of course, more flexible than thick
In addition to oxalic acid, we have found that
ones and the ?exibility can, if desired, be further
the water-soluble acid salts of oxalic acid, name
increased by calendering or other manipulative
ly, ammonium acid oxalate, sodium acid oxalate 15 treatment of the sheet after it has been dried.
and potassium acid oxalate are likewise effective
It is not ‘necessary that the new product of this
in affording a water-resistant bonded asbestos
invention be fabricated in the manner above de
paper or other body comprising asbestiiorm min
scribed, namely, by the water-laying of a felted
eral ?bers. Ammonium oxalate is likewise satis
sheet of asbestos ?bers. Thus, the asbestos ?bers
factory. These substances di?er somewhat in
may be brought into intimately associated felted
their effectiveness and the concentration of the
relationship in other ways either wet or dry. In
solution that is applied to the asbestos paper will
this connection, operations such as carding, gar
vary somewhat, depending upon the particular
oxalate used, but the concentration is generally
netting and the like, which accomplish a deposi
tion of air~borne ?bers to form a sheet-like body,
of the order of that above mentioned in connec
tion with the use of oxalic acid.
Sodium oxalate and potassium oxalate also
are to be regarded as providing “felted” ?bers as
the term “felted” is used herein and in the claims.
More'generally, all that is required is the dispo
have the peculiar property of bonding asbestos
sition of the asbestiform mineral fibers in inti
ma-tely contacting relation in a ?brous body and
paper or the like so that it will have good dry
strength; but these particular oxalates do not -.
provide a large increase in water resistance.
the application thereto of a solution of an oxalate
so that the action that occurs between the as
bestiform mineral ?ber and the oxalate occurs
However, since the employment of such oxalates
is new and is of advantage under some ‘circum
in situ with resultant bonding action of the char~
stances, the employment of water-soluble oxal
ates for bonding ?brous'bodies comprising asbes
acter herein described.
It-is not essential that the oxalate be applied
tiform mineral ?bers is to be regarded as coming
during the production of the asbestos paper. For
within the scope of this invention in its broad
example, if desired, asbestos paper may be ?rst
est aspects. In this connection, oxalic acid is re
incorporated in a product, e. g., as a surfacing for
garded as hydrogen oxalate and as being included
a heat insulation, and thereafter may be treated
within the term oxalate.
40 with a solution of oxalic acid, an acid salt of 0x
When oxalic acid or other oxalate is used to
alio acid, or ammonium oxalate, as by brush ap
bond the ?bers of asbestos paper, it is not essen
plication. After drying, the asbestos paper will
tial that starch be omitted. When the oxalate is
be found to be highly resistant to moisture.
of the class aforesaid which affords high wet
It is not essential that the asbestos paper or
strength, the presence of starch does not detract IP :41. other sheet-like body or product be composed en
from the obtainment of high wet strength and
tirely of asbestos paper. For example, asbestos
improves the dry strength. For example, as
paper may, and frequently does, contain a minor
bestos paper weighing about 10 pounds per 100
proportion of organic ?ber such as ordinary cel
square feet may be made containing about 1% of
lulosic paper ?ber. It is also possible to include
starch and, after drying, have applied thereto a
in the asbestos paper mineral ?bers such as rock
10% solution of oxalic acid. The tensile strength
wool, slag Wool, glass ?bers and the like which
of such product in the machine direction of the
are heat-resistant, but such ?bers have the dis_
sheet is about 12 pounds per linear inch of width,
advantage of being more brittle and frangible
as compared with about 5 pounds per linear inch
than asbestos ?bers. It is normally desirable that
of width when the starch was not present. The
the asbestiform mineral ?bers constitute the ma
effect of the starch is considerably in excess of
jor proportion by Weight of the ?bers and of the
the purely additive effects of the starch and oxalic
?nished product.
acid, for asbestos paper containing 1% of starch
In the ordinary case, according to this inven
only has a tensile strength of about 3 pounds per
tion, the usual asbestos ?ber of commerce may
linear inch of width. In other words, there is a
be used, namely, chrysotile asbestos ?ber. In ad
special coaction which results from the combina
dition to chrysotile asbestos ?ber, other asbesti
tion of the starch with the oxalic acid.
form mineral ?bers may be used, such as antho
When this invention is practiced using starch,
phyllite, actinolite, tremolite, crocidolite, amosite,
any amylaceous material may be employed such
as cornstarch, wheat starch, potato starch, tapi
oca starch, rice starch, etc. Modi?ed starches,
including those that have been modi?ed by heat
treatment, oxidation, enzyme action, acid treat
ment or other analogous treatment may be em
ployed and are to be regarded as embraced by
the term amylaceous material.
The asbestos paper that is produced according
to this invention is ?exible and bibulous and is
well adapted for the various uses to which asbes
tos paper is particularly suited. Typical embodi
various amphibole ?bers, Canadian picrolite, and
the like.‘
In addition to the ?ber and the bonding com
ponents of the asbestos products produced accord
ing to this invention, the product mayv include a
minor quantity of ?ller material. For example,
a small quantity, e. g., of the order of 5% to 10%
of the weight of the ?ber, of a material such as
diatomaceous earth, may be employed. A ?ller
such as diatomaceous earth does not have an ad
verse e?ect on the porosity and absorptiveness of
75 the paper and usually increases these properties,
Another ?ller that affords considerable porosity
is pumice. Moreover, other ?llers such as clay,
talc, pigments to impart suitable color, etc., may
be employed.
Ordinarily, the ?ller, like the as
bestos, will be heat resistant, namely, will not de- _
compose or char when exposed to temperatures
of the order of 900° F. It is usually desirable that
the major proportion of the ?ber plus any ?ller
contained in the product should consist of as
bestiform mineral fibers and, for providing re
"sistance to heat, the ?ber plus any ?ller con
tained therein should contain less than 10% of
organic material or other nonheat resistant ma
terial. For most fabrication purposes, the as
body comprising asbestiform mineral ?bers which
constitute the major proportion by weight of the
?ber plus any ?ller contained in said sheet-like
body, said asbestiform mineral ?bers being bond~
ed by the interaction in situ between said asbesti
form mineral ?bers and an acid salt of oxalic acid.
5. A product comprising felted ?bers disposed
in a sheetdike water-resistant body, said sheet
like body comprising asbestiform mineral ?bers
10 which constitute the major proportion by weight
of the ?ber plus any ?ller contained in said sheet
like body, said asbestiform mineral ?bers being
bonded by the interaction in situ between said
asbestiform mineral ?bers and ammonium ox.
bestos 'productshould contain vless than about 15 alate.
6. A flexible coherent bibulous sheet-like body
20% by weight of material other than the ?ber
which consists in major proportion by weight of
plus any ?ller contained therein.
asbestiform mineral ?bers, the asbestiform min;
We claim:
eral ?bers in said sheet-like body being bonded
1. YA coherent ?brous body wherein the ?bers
consist in major proportion by weight of asbesti 20 by the interaction in situ between said asbesti
form mineral ?bers and a water-soluble oxalate.
vform mineral ?bers, said asbestiform mineral
7. A product comprising felted ?bers disposed
?bers being bonded by ‘the interaction in situ
in a sheet-like ‘water-resistant body according to
between said asbestiform mineral ?bers and a
claim 3 wherein said asbestiform mineral ?bers
water-soluble oxalate.
2. A coherent ?brous body according to claim 25 are bonded by said oxalic acid in the presence of
1 wherein said asbestiform mineral fibers are
bonded by said oxalate in combination with an
amylaceous material.
3. A product comprising felted ?bers disposed
in a sheet-like Water-resistant body, said sheet
an amylaceous material.
8. A product comprising felted ?bers disposed
in a sheet-like water-resistant body according to
claim 4 wherein said asbestiform mineral ?bers
30 are bonded by said acid salt of oxalic acid in the
presence of an amylaceous material.
9. -A product comprising felted ?bers disposed
in a sheet-like water-resistant body, according to
of the ?ber plus any ?ller contained in said sheet
claim 5 wherein said asbestiform mineral ?bers
like body, said asbestiform mineral ?bers being
are bonded by said ammonium oxalate in the
bonded by the interaction in situ between said
presence of an amylaceous material.
asbestiform mineral ?bers and oxalic acid.
like body comprising asbestiform mineral ?bers
which constitute the major proportion by weight
4. A product comprising felted ?bers disposed in
a sheet-like water-resistant body, said sheet-like
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