Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
The present invention relates to sealant compost-
lions and methods for encapsulating friable material used for
thermal insulation, fireproofing, acoustical insulation and
decorative finishes and is particularly applicable to the
treatment of asbestos-containing materials.
In recent years there has been an increasing aware-
news of the importance of environmental factors in Carson-
genesis. The recognition of widespread environmental con tam-
inaction by asbestos-containing materials has been of portico-
far concern.
Such concern is evidenced in approximately twenty Federal regulations under various laws which regulate human
and environmental exposure to asbestos. Despite these rug-
lotions, large segments of the population continue to be
exposed to this dangerous material especially material in
friable form.
The extensive use of asbestos in commerce and in-
dusty has created a health hazard of serious consequences
for persons inhaling or ingesting the substance. Since the
beginning of the century, asbestos has been used as a major
constituent or an important additive to many consumer products
so that there are many sources of exposure to the general public
For almost forty years asbestos has been widely used in building
construction having been sprayed or applied onto structural
steel to retard structural collapse during fire and to ceilings
and walls for purposes of acoustic and thermal insulation, decor-
lion and condensation control. Many insulation materials con-
sit of a mixture of asbestos an mineral-, rock-, slag-wool
or fibrous glass. In other formulations wood pulp and paper
fixers and non-fibrous binders such as plaster of Paris,
vermiculite, puerility and clay are used Asbestos has also
been used extensively as decorative and textured-spray finishes
or paints. The asbestos content of these materials is usually
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found in the range of 5 to 50 weight percent. Some of this
asbestos containing material is now known to be damaged or
deteriorating and releasing fibers into the building environ-
mint.
Unlike most chemical carcinogens asbestos mineral
fibers persist in the environment almost indefinitely and
represent a continuous source of exposure. Asbestos fibers
cannot be easily destroyed or degraded. The size and shape of
these fibers give them aerodynamic capability to permit them
to remain suspended in air for many hours. The fibers can
become suspended in the air and are then available for respire-
lion and retention in the lung. Fibers which have settled to
the floor can be reentrained by the slightest activity in the
area. Thus, even though the release of fibers may be inter-
mitten, there is a potential for continuous exposure.
Triable material is material that can be crumbled,
pulverized or reduced to powder under hand pressure Friable
material may be an asbestos-containing material or it may be
a material that contains other fibers such as cellulose and
glass fibers. Friable asbestos material draws particular
attention since it is likely to release fibers with minimum
disturbance of the surface, cause serious contamination and
exposure problems and it has been used in many buildings have
in high population densities including schools, office build-
ins and high-rise apartment buildings. Furthermore, as
friable asbestos material ages, it can lose its cohesive
strength and more readily releases fibers. These materials
were usually applied by spraying but have also been applied by
troweling and brushing. They are friable in varying degrees
depending on the components of the material, the amount of
cement or binder added, and the method of application
Sprayed material is usually soft. Cementitious material varies
from soft to relatively hard. Several methods have been
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I
proposed to eliminate or substantially reduce exposure of
friable asbestos material such as by removal, encapsulation
and enclosure. For encapsulation, the asbestos material is
coated with a sealant. The sealing of sprayed asbestos sun-
faces involves applying material that will penetrate and en-
velop the fiber matrix and coat the surface portions to elimin-
ate fallout and protect against abrasion damage as well as
physical damage due to impact.
Sealants for friable materials which are currently
available include water-based latex polymers, water soluble
epoxy resins and organic solvent-based polymers of various
types. However none of these sealants have been common-
Shelley successful because the fail to provide one or more of
the desirable properties required. Shortcomings associated
with the available sealant compositions include the need for
high-pressure application, lack of penetration, poor flex-
ability of the encapsulated asbestos-containing material,
unacceptable impact strength and abrasion resistance, poor
adhesive and cohesive strength. Also several sealant combo-
sessions have been found unacceptable since they are combust-
isle and during combustion they generate smoke and release
toxic gases.
Therefore a need persists for a sealant composition
for friable material which avoids all of the drawbacks of the
prior art compositions.
The present invention provides a penetrating sealant
composition useful for encapsulating a friable material de-
signed to be stored in two parts which are mixed prior to use
comprising:
Part I an aqueous silicate solution component
comprising:
a) 20 to 40 weight percent of an aqueous alkali
metal silicate selected from potassium silicate or
a mixture of potassium silicate and sodium silicate;
b) 0.01 to 10 weight percent of a cat ionic or
non ionic surfactant,
c) 60 to 80 weight percent water; and
Part II an acrylic polymer dispersion component
comprising:
a) 45 to 65 weight percent of an acrylic polymer
latex having a solids content of 40 to 65 weight
percent, said acrylic polymer selected from the
group consisting of homopolymers and copolymers of
lower al~cyl esters of acrylic acid or lower alkyd
esters of an alpha-lower alkyd acid or mixtures
thereof;
b) 0.01 to 10 weight percent of a reagent
that reacts with said alkali silicate; and
c) 35 to 55 weight percent water, wherein the
ratio of Part I to Part II provides a blended compost-
tion having a solids content between 20 and 65 weight
percent.
The invention also provides a method for preparing
the penetrating sealant composition in the form of a two
component system wherein each of the components are prepared
separately and includes a method of preparing the encapsulate
in composition which contains optimal concentrations of the
foregoing ingredients. This two component system allows for
the moieties to be mixed at the work site providing for a
long pot life and insuring storage stability.
There is also provided a method of applying the
encapsulating material of this invention to friable material
which substantially improves the physical characteristics
of same.
It is an object of this invention to provide a
method of encapsulating friable insulating material by using
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the composition of this invention which affords rapid and
deep penetration into the insulating material matrix, which
improves adhesive and cohesive strength of the matrix by
converting the friable-containing material into a solid,
tough and flexible barrier having a cohesive mass of encamp-
sulfated friable material having good resistance to mechanical
abuse.
t is a particular object of the present invention
to provide a penetrating sealant composition having improved
characteristics for encapsulating asbestos-containing material
to prevent release of asbestos fibers into the environment.
It is a further object of the present invention to
provide a penetrating sealant composition for encapsulating
friable asbestos containing material which also enhances
physical properties of the asbestos-containing material.
According to this invention, useful products pro-
voiding effective encapsulating sealant compositions for
friable insulation materials are supplied as a two part
system. One part comprises an aqueous silicate dispersion
ox selected alkali metal silicates blended with a cat ionic
or non ionic surfactant. The other part comprises an acrylic
latex composition containing a water soluble reagent that is
reactive with the alkali metal silicate of the first part.
These two moieties are stored separately, have increased
storage life, are mixed shortly before use and preferably
are formulated so that equal parts by volume are fixed to
form the penetrating sealant composition that is ultimately
utilized.
While the individual materials that make up the
present encapsulating sealant compositions are well-known
and available commercially, the combination of these materials
in the proportions recited provide a tough coating which
adheres to the friable material, particularly with insulation
~2~g~
materials such as asbestos and mineral-, rock-, slag-wool
with sufficient penetration to encapsulate individual fibers
or particles.
PART I, the aqueous silicate component of the
penetrating sealant is prepared by blending potassium silicate
or a mixture of potassium silicate and sodium silicate with
a cat ionic or non ionic surfactant and then adding water to
form the aqueous silicate dispersion.
The concentration of the alkali metal silicates in
the aqueous silicate solution component of Part I can range
from 20 to 40 weight and preferably from 25 to 40 weight
percent and most preferably from 25 to 35 weight percent.
The concentration of the non ionic or cat ionic surfactant can
range from 0.01 to 10 weight percent, preferably 0.05 to 5.0
weight percent and most preferably from 0.1 to 1.0 weight
percent.
Aqueous potassium silicate is commercially avail-
able as a liquid containing 54 to 71 weight percent water and
the balance potassium silicate. The potassium silicate
that is used preferably has a molar ratio of K20/SiO2 between
about 1 to 4, preferably from 1~5 to 3~75 and most preferably
from 2.8 and 3.2.
Aqueous sodium silicate is commercially available
as a liquid containing 45 to 85 weight percent water and the
balance sodium silicate. The weight ratio of assay 2 is
from 1.5 to about 3.75 in the commercially available materials.
While it is preferable that all the soluble sift-
gate be in the form of potassium silicate i-t is not essential
in achieving the advances of this invention that the soluble
silicate consist entirely of potassium silicate. However, it
has been discovered that mixtures of potassium silicate and
sodium silicate having a major portion of potassium silicate
provide the advantages of this invention Preferably at
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least about 75 weight percent of the soluble silicate should
be potassium silicate and most preferably at least about 95
weight percent. Suitable soluble silicates include potassium
and sodium orthosilicate, potassium and sodium metasilicate,
potassium and sodium metasilicate pentahydrate and potassium
and sodium sequisilicate.
Non ionic or cat ionic surfactants can be employed
as an ingredient in the aqueous polymer dispersion of Part II
or in the alkali metal silicate dispersion of Part I or in
both of the solutions, as desired However, it was found
that strongly cat ionic surfactants, have a tendency to pro-
cipitate the polyacrylic latex and should not be employed
in the polymer dispersion.
Non ionic synthetic surfactan-ts suitable for use
in the present composition include
1. The polyethylene oxide condensates of alkyd
phenols.
2. The condensation products of aliphatic
alcohols and ethylene oxide.
3. Thy condensation products ox ethylene oxide
with a hydrophobic base formed by the condemn-
station of propylene oxide with propylene
glycol.
4. Condensation products of amine, asides or
mercaptans with ethylene oxide or propylene
oxide.
5. Products formed by reacting ethanolamines
with fatty acids.
6. Amine oxide surfactants.
7. Phosphine oxide surfactants.
8. Sulfoxide surfactants.
Of all the above described types of non ionic sun-
fact ants, preferred non ionic surfactants include the
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,
condensation product of nonyl phenol with about 9.5 moles
of ethylene oxide per mole of nonyl phenol, the condensation
product of coconut fatty alcohol with about 6 moles of ethyl
tone oxide per mole of coconut fatty alcohol, the condensation
product of tallow fatty alcohol with about 11 moles of
ethylene oxide per mole of tallow fatty alcohol, the condemn-
station product of a secondary fatty alcohol containing about
15 carbon atoms with about 9 moles of ethylene oxide per
mole of fatty alcohol, dimethyldodecylamine oxide, dime thy-
ltetradecylamine oxide, dimethyldodecylphosphin~ oxide,
cetyldimethyl phosphine oxide, octa~ecylmethyl suffixed, and
tetradecylmethyl sulfoxide.
Cat ionic synthetic surfactants suitable for use in
the present composition include:
1. Amine salts.
20 Fatty esters of primary, secondary or tertiary
hydroxyalkyl amine.
3. Qua ternary ammonium compounds, pyridinium salts
and like compounds in which the qua ternary
nitrogen atom is part ox a ring system.
specific examples of cat ionic surfactants include
Seattle pyridinium chloride, Seattle trim ethyl ammonium chloride,
stroll dim ethyl bouncily ammonium chloride, laurel dim ethyl
bouncily ammonium chloride, qua ternary ammonium chloride,
trim ethyl octadecyl ammonium chloride, methyl polyethanol
qua ternary amine, didecyl dim ethyl ammonium chloride,
tetradecyl bouncily ammonium chloride dehydrate, coo hydra-
ethyl imidazoline, tall oil hydroxyethyl imidazoline and
oleic hydroxyethyl imidazoline.
Various other non ionic and cat ionic synthetic sun-
fact ants which can be employed are described in "Surface
Active Agents and Detergents", Vol. II by Schwartz, Perry
and Bench, Intrusions (1958) and "Detergents and Emulsifiers,"
I
1972 Annual (McCutcheon's Dive , Allured),
Part II, the acrylic polymer dispersion component,
is prepared by diluting the acrylic polymer latex with water
then adding a reagent that reacts with the alkali silicate
of the first part and blending until a homogeneous compost-
lion is formed. Adding a weak base such as ammonium hydroxide
to adjust the pi to about 4.2 may be necessary.
The concentration of acrylic polymer latexes may
range from 45 to 65 weight percent, preferably from 45 to 60
weigh percent and most preferably from 50 to 55 weight
percent. The concentration of -the reagent that reacts with
the alkali silicate of the first part may range from 0.01
to 10 weight percent, preferably from 0.1 to 5 weight percent
and most preferably 0.5 to 2 weight percent.
The acrylic polymer latexes used in Part II are
available commercially or can be readily prepared by well-
known polymerization procedures. Suitable acrylic polymer
latex compositions include ~omopolymers of lower alkyd
esters of acrylic acid, lower alkyd esters of an alpha-
lower alkyd acrylic acid or copolymers thereof, that is
polymers made of two or more different acrylic acid esters
and/or alpha-lower alkyd acrylic esters and copolymers of the
aforementioned acrylic esters with vinyl acetate. These
acrylic polymer latexes are available in emulsion form with
a solids content of about 45 to 65 weight percent, a pi of
to 5, a viscosity of 2 to 4 poises and ranging from 8.8
to 9.25 pounds per gallon.
A wide variety of reagents can be employed to react
with the alkaline metal silicate to enhance the film forming
and encapsulating properties of the present sealant compost-
lion. The reagents suitably employed for this purpose include
water syllable and water dispersible inorganic or organic
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2~6
salts and oxides of polyvalent and alkali metals. Preferred
compounds are those which impart flame retardant properties
to the sealant composition. Such agents include metal salts
of hydroxycarboxylic acids, salts of organic acids, e.g.
garlic acid, citric acid and tartaric acid. Water soluble
salts are preferred inclusive of which include the borate,
halide, nitrate and phosphate salts of aluminum, antimony,
barium, beryllium, cadmium, calcium, sodium, chromium, cobalt,
copper, lead, magnesium, mercury, silver and zinc. Most
preferred reagent compounds are those which impart flame
retardant properties such as potassium silicofluoride, zinc
silicofluoride and hydrated sodium borate (borax).
Obviously, it may be desirable to include or add
additional materials to facilitate the preparation or apply-
cation of the impregnating or treating composition, or to
impart collateral benefits or properties to asbestos products.
In certain applications it may be advantageous to include
anti-freeze compositions, foam inhibitors, corrosion in-
hibitors, fungicides, mildewcides, etc. Additionally if a
colored product is desired, a water dispensable pigment may
be added to Part II to give the composition a desirable
color.
In accordance with the method of the invention,
Part I and Part II formulations are separately prepared and
subsequently mixed. Preferably, each part is formulated so
that equal parts of each are fixed to provide ease of pro-
parathion of the sealant composition and minimize formulating
errors at the job site. In any event, each moiety should be
formulated within the Sp2Ci~iC proportions given to yield a
blended sealant having a total solids content between 20 and
65 weight percent preferably between 30 and 60 weight percent
and most preferably between 35 and 55 weight percent.
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The mixing of the two moieties may occur in several
ways. The materials may be introduced into a common con-
trainer and blended by agitation. The two liquid materials
may be sprayed separately at low pressure with the sprays of
the two materials impinging upon one another to provide a
combined spray in which the spray particles are homogeneously
admixed The two liquids may be introduced into spraying
equipment which has a common mixing chamber preceding the
spray nozzle.
Application of the penetrating sealant composition
of this invention can also be 'by brushing. The viscosity
of the sealant composition which can be obtained by blending
an aqueous acrylic resin dispersion with an aqueous potassium
silicate or potassium silicate and sodium silicate mixtures
is expediently so adjusted that a readily crushable mixture
can be obtained.
Low pressure spraying is preferred. The penetrate
in sealant composition should be applied with as much caution
and at as low a nozzle pressure as possible to reduce surface
contact disturbance on friable asbestos-containing material
since a potentially high concentration of small asbestos
fibers could cause serious exposure to the worker. In any
event workers should require protection with respiratory
devices and decontamination. Low pressure airless spray
units available commercially are suitable for such apply-
cation The application of this composition does not no-
urea any particular skill.
The coverage of the penetrating sealant composition
varies depending on the condition of the friable material
from about 10 to 50 square feet per gallon with a penetration
of 1 3/4 inches For example, a highly friable material
(could be damaged by hand contact) but having no loose
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~l2~L2~6
material hanging free would require a coverage of about 40
square feet with the same penetration.
Exposure of the coated material to ambient tempera-
lures (e.g. 55F or a period of three hours is ordinarily
sufficient for the accomplishment of the desired curing and
drying. Of course, variations in ambient temperatures will
effect length of cure.
Upon curing, the present silicate-polymer compost-
lion provides an effective sealant for friable materials such
as glass fibers, cellulose, mineral wool, synthetic resin
foams polyurethane polystyrene, polyvinyl chloride,
etc.), and particularly friable asbestos-containing materials.
The active ingredients in the final composition form a
product which eliminates fiber dispersal by adhering to the
fibrous substrate with sufficient penetration into the
friable asbestos-containing material matrix to prevent
separation of the sealant from the asbestos material; to
lock in the asbestos fibers to provide excellent abrasion
and impact resistance to the enclosed asbestos material;
yet to maintain good flexibility to accommodate atmospheric
change, vibration and structural setting. The cured come
position also provides sufficient permeability -to water vapor
to prevent condensation accumulation, in the asbestos material
beneath the coating or the substrate. Additionally, the
composition of this invention provides high flame retardant
characteristics and does not release excessive smoke or
toxic fumes under conditions of direct flame impingement
Likewise, the composition is neither noxious or toxic per so.
Although a single application of the coating come
position may be sufficient in certain instances, it may be desirable to apply additional applications. Since the cured
composition produces a cohesive mass of encapsulated friable
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material which is stable to weathering and aging, it provides
an excellent substrate for conventional coatings and good
resistance against solution by common cleaning agents.
While this invention is not to be limited by any
theory or explanation it is believed that polymers are formed
by certain of the ingredients which also react in the case of
asbestos to etch the fibers to impart a strong cohesive bond.
However, it should be understood that the many advantages
and improvements provided by this invention are the result
of a combination of all the component ingredients in the above
approximate specified percentages
The following are examples of various composition
formulations for specific and general use, and their general
method of application. It is to be understood that the come
positions for and method of applying the same to specific
asbestos articles or products are exemplary and are not con-
ridered to limit the invention to any of the particular
compositions or operating conditions outlined. Percentages
and parts are by weight unless otherwise indicated.
0 Preparation ox penetration sealant composition
EXAMPLE 1
PART I Silicate Component
A mixture of 2~5 parts of an aqueous potassium
silicate solution having a K20/SiO2 ratio of 3.13 and a
solids content of 33% (KSIL No. 6, Philadelphia Quartz Co.,
Philadelphia, Pa.) is blended with a 1% aqueous solution of
octylphenoxy polyethoxy ethanol and then is diluted with
11 parts of water and is stirred until a homogeneous mixture
is formed
PART II Acrylic Polymer Latex Component
To 7.5 parts of an acrylic latex having a solids
content of 45%, a viscosity of 6 poises and a pi of about 4.5
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: I
(SCAR Latex 879, Union Carbide Corporation, New York, N. Y.)
is blended with 6 parts of water. After a homogeneous disk
pension is formed, 1% potassium silicofluoride is added with
agitation. Then the pi is adjusted to about 4.2 by -the
addition ox ammonium hydroxide.
Parts I and II are stored separately until use.
Both parts are quite stable. No change occurs within one
i week (minimum) at temperatures of 30 I. to 120F. The final
formulation is prepared by simple mixing of the components
I 10 prior to use.
j EXAMPLE 2
t This example shows another formulation of Part I silicate component which is compatible with the Part II of
¦ Example 1.
A mixture of 2.5 parts of an aqueous silicate come
potent consisting of 95% potassium silicate and 5% sodium
silicate is blended with a 1% aqueous solution of octal-
phonics polyethoxy ethanol and then is diluted with 11 parts
of water and is stirred until a homogeneous mixture is formed.
The application of the penetrating sealant composition to
friable asbestos-corltaining material
EXAMPLE 3
The test substrates were friable asbestos-contain-
in material (30-35 percent crystal) approximately 3 inches
thick over a precise cement sample and 2 inches thick on a
steel support I-beam specimen. The material was highly
friable (could be damaged by hand contact) but had no loose
material.
Equal volume portions of silicate component (Part
I) the acrylic latex component (Part II) are thoroughly
blended with agitation to form a spray able penetrating seal-
ant composition. This composition is charged to a supply
l * Trade Mark - 15 -
tank of an airless spray gun. the nozzle has a 0.013 inch
opening which gave a fan width of 8 to 10 inches, one foot
from the spray tip. The pump pressure is approximately
30psi (as low a setting as possible to get a uniform spray
pattern). The pump pressure resulted in an average nozzle
pressure of 450 psi. It should be noted that although the
nozzle pressure is high, it is hydraulic pressure and the
liquid has an immediate pressure drop once it leaves the
spray nozzle. The sealant composition is applied in one
coat at a coverage rate of 1 gallon per 40 square inches to a
depth of 3/4 inch.
After curing at room temperature for 12 hours, a
core sample from the coated friable asbestos material on the
precast cement indicated a penetration of 2 inches in the -
3 inch coating. Furthermore, this sample had a strong co-
hornet mass, and is flexible and had excellent resistance to
mechanical abuse. A core sample from the steel support
I-beam specimen indicates a penetration to the steel I-beam
(i.e. 2 inch penetration) and an enhancement of the adhesion
of the asbestos-containing material to the I-beam substrate.
The properties of cohesion, flexibility and resistance to
mechanical abuse are similar to the other test specimen.
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