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Description  |
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This invention relates to sealant, adhesive and coating compositions and
especially to sealant formulations based on liquid polymers which are
convertible by curing agents to rubbery form and which are useful in
sealing cracks in and adhesively bonding cementitious materials used in
the construction of roads, airfields, docks, canals, buildings and the
like, and also in the adhesive bonding of substrates such as glass,
aluminum and the like, as well as to a method of converting such sealants
into rubber-like form. Still more particularly, the invention relates to a
low cost extender for use in such compositions.
Numerous types of sealant formulations and coating compositions based on
liquid organic polymers are known in the art for sealing joints in and
bonding cementitious materials, glass and metals and for a variety of
coating applications. The organic polymers of the sealant formulations are
commonly of the curable type, i.e., they are convertible to rubbery form
by chemical reaction with a curing agent. Typical sealant and coating
formulations may be based, for example, on liquid polythiopolymercaptans,
liquid polyepoxides and liquid organosilicon polymers. Representative
sealant formulations based on liquid organic polymers are disclosed, for
example, in U.S. Pat. Nos. 2,910,922; 3,225,017; 3,316,194; 3,349,047;
3,536,562; and 3,540,961.
In general, the liquid organic polymers on which such sealant and coating
compositions are based are relatively expensive materials. It is evident
that the cost of compositions based on such polymers can be reduced by
incorporation therein of inexpensive diluents or extenders which reduce
the proportion of the polymer required in the formulation. It is, of
course, necessary that the extender be of such a character that it does
not significantly reduce the sealing or coating effectiveness of the
composition and that it be compatible with the polymer either in and of
itself or in the presence of another ingredient of the composition. For
example, in cases where a sealant is to be used to seal joints or cracks,
the use of a volatile solvent as a diluent is unsatisfactory because
evaporation of the solvent causes excessive shrinkage of the cured sealant
bond. While particulate inert fillers such as calcium carbonate and silica
have been used in such sealant compositions, the amount of such fillers
that can be used without adversely affecting the physical properties of
the resulting seal is limited.
It is accordingly an object of the present invention to provide a novel
group of exceptionally inexpensive extenders which can be incorporated in
sealant compositions of the type referred to above without having any
substantial adverse effect on the adhesive and bonding properties of the
seals formed therefrom. It is another object of the invention to provide a
curable liquid sealant composition based on an organic polymer and
containing a substantial proportion of an inexpensive extender which is
compatible with or can be made compatible with the polymer on which the
sealant is based. It is a still further object of the invention to provide
a sealant, coating or adhesive composition based on a liquid curable
organic polymer, which composition contains a large proportion of
inexpensive extender that does not cause excessive shrinkage when the
composition is cured. It is still another object of the invention to
provide a process for converting a curable liquid polymer into solid form
which comprises mixing with the polymer prior to curing a relatively large
amount of a novel and inexpensive extender. Other objects of the invention
will be in part obvious and in part pointed out hereafter.
The present invention is based on the discovery that certain aqueous
colloidal dispersions or gels can be incorporated as extenders in sealant
and coating compositions of the general type referred to above and that
the resulting cured seals, joints and coatings exhibit little, if any,
shrinkage, notwithstanding the fact that the added extenders contain a
considerable proportion of water which would be expected to evaporate and
cause substantial shrinkage of the seal or coating. It appears that when
the aqueous extenders of the present invention are used, nearly all of the
water associated with the extender is bound in some manner such that it
becomes an integral part of the cured seal or coating. Thus the water
content of the aqueous dispersion itself acts as an extender.
The present extenders comprise in general aqueous colloidal dispersions of
certain inorganic oxides and oxide mixtures, in particular, aqueous
magnesium oxide and aqueous alkali metal silicates, e.g., sodium potassium
and lithium silicates, as well as aqueous dispersions of finely divided
silica. Because of their low cost and ready availability, the aqueous
sodium silicates are preferred. While the extenders are referred to herein
as aqueous colloidal dispersions, it has been found that the liquid phase
of the dispersion may contain, in addition to water, other liquids
miscible with water such as, e.g., ethylene glycol, polyglycols and
polyglycol ethers, and the phrase "aqueous dispersion" as used herein is
intended to include such mixtures.
It has been found that the range of proportions of magnesium oxide in the
dispersions made therefrom is desirably somewhat less than the proportion
of silicates in the silicate dispersions. More particularly, the magnesium
oxide dispersions preferably contain from about 5% to 40% by weight of
magnesium oxide. The magnesium oxide used has a sufficiently fine particle
size so that even when it is present in relatively small proportions, the
dispersion has a pasty consistency.
In the case of the silicate and silica dispersions, the solids content is
preferably from about 20% to 60% by weight of the colloidal dispersion.
Silicates having various ratios of alkali metal oxide to silica (M.sub.2
O:SiO.sub.2) may be used. Thus the ratio M.sub.2 O:SiO.sub.2 may vary from
0:1 to 1:1, with the initial ratio indicating silica per se. The preferred
ratio is from about 1:1 to 1:4.
As indicated above, the low cost extenders of the present invention may be
usefully employed in curable sealant, adhesive and coating compositions
based on various polymers such as the polysulfide, polyepoxide and
silicone polymers. As is known in the art, liquid polysulfide polymers may
be made by first preparing high molecular weight solid polymers and then
splitting the solid polymers to form liquid polymers. The solid polymers
may be prepared by reacting with alkali metal or alkaline earth metal
sulfide solutions difunctional organic compounds, usually containing a
small amount, say 1% to 4% of trifunctional compounds to provide
cross-links, to produce high molecular weight polymers having the
recurring unit (RSS) wherein R is a divalent organic radical that may vary
widely in its specific structure and SS represents a disulfide linkage
through which the organic radicals are interconnected. The polymers thus
obtained are high molecular weight polymers characterized by exceptional
resistance to acids, alkalis, petroleum hydrocarbons and atmospheric
oxidation.
The liquid polysulfide polymers can be obtained from the high molecular
weight polymers referred to above by a splitting process described in U.S.
Pat. No. 2,466,963. As disclosed in the latter patent, the high molecular
weight polymers can be split to form polythiopolymercaptan polymers having
molecular weights of the order of 500 to 25,000 which are viscous liquids
having viscosities in the range 300 to 100,000 centipoises at 25.degree.
C. Such liquid polymers can be cured by any of various curing agents
disclosed in U.S. Pat. No. 2,466,963 to form solid elastomers having the
exceptional resistance to solvents and atmospheric oxidation and moisture
referred to above.
In the commercially important liquid polymers the R of the (RSS) groups is
generally a hydrocarbon or oxahydrocarbon group, for example, a diethyl
formal group to produce polymers essentially composed of the recurring
--S.CH.sub.2.CH.sub.2.O.CH.sub.2.O.CH.sub.2.CH.sub.2 S--
groups and having free mercapto terminals through which they may be cured
to form a solid elastomer. Typical curing agents for such
mercapto-terminated liquid polysulfide polymers include inorganic
peroxides, particularly peroxides of lead, zinc, calcium, barium, sodium,
lithium, manganese and antiomony, as well as sodium carbonate peroxide.
Organic peroxides such as benzoyl peroxide, dicumyl peroxide and cumene
hydroperoxide may also be used. In order to achieve good dispersion of the
curing agent in the liquid polymer, it is often desirable to use the
curing agent in the form of a paste made by mixing the curing agent with a
plasticizer such as a chlorinated aromatic or paraffinic hydrocarbon or an
unsubstituted hydrocarbon such as poly-alpha-methylstyrene.
Sealant compositions based on such liquid polysulfide polymers are also
known in the art and are disclosed, for example, in certain of the U.S.
patents referred to above. Such sealant compositions commonly comprise in
addition to the liquid polysulfide polymer and curing agent therefor
various special purpose additives such as fillers, plasticizers, curing
rate modifiers, adhesion promoters and the like.
In cases where the present extenders are used in sealants based on liquid
polysulfide polymers, the sealant desirably contains an auxiliary resin
material to improve the compatibility of the liquid polymer and the
extender. Suitable resinous materials for this purpose include coal tar,
highly chlorinated hydrocarbons, polyalpha-methyl styrene, alpha-methyl
naphthalene, stage "B" phenolic resins, linear polyesters, acrylic resins,
rosin esters, aliphatic hydrocarbon resins, mixed aromatic resins, high
molecular weight polyalkylene glycols, polyvinyl alcohol and
hydroxyl-containing polybutadiene. The proportion of resinous material
incorporated in the sealant compositions may vary over a wide range in
terms of the liquid polysulfide polymer therein. Thus the resinous
material may vary from say 10% to 200% based on the weight of liquid
polymer in the sealant composition.
As indicated above, the present extenders may also be advantageously used
in connection with coating and adhesive compositions based on liquid
curable polyepoxides. A wide variety of such epoxides is commercially
available. For example, the polyepoxides with which the present extenders
are used may be the normally liquid glycidyl ethers of polyhydric phenols
or polyhydric alcohols. The glycidyl ethers of polyhydric phenols are
commonly obtained by reacting epichlorhydrin with the desired polyhydric
phenol, e.g., 2,2-bis(4-hydroxyphenyl)-propane. Other useful polyepoxides
are epoxidized polyethylenically unsaturated hydrocarbons such as
epoxidized 2,2'-bis(2-cyclohexenyl)-propane, epoxidized vinylcyclohexene,
epoxidized dimer of cyclopentadiene, epoxidized polymers and copolymers of
diolefins such as polybutadiene, butadiene-acrylonitrile copolymers,
butadiene-styrene copolymers and the like.
As is known in the art, curing of the liquid polyepoxides to solid form can
be effected with a variety of curing or cross-linking agents including
primary, secondary and tertiary amines, such as triethylamine,
ethylenediamine, diethylamine, diethylenetriamine, N-phenylenediamine,
dicyandiamide and melamine and carboxylic acids or their anhydrides such
as oxalic acid or phthalic anhydride. It has been found that as in the
case of the compositions based on the liquid polysulfide polymers, when
the present extenders are incorporated in liquid polyepoxide compositions,
nearly all of the water content of the extender is in some manner bound to
the polymer and does not evaporate as would be expected. Thus when the
compositions based on the polyepoxide and containing the present extenders
are cured in the usual manner, the water associated with the extender
surprisingly remains in the compositions and little, if any, shrinkage of
the cured composition occurs.
The present extenders may also be used with advantage in sealant
compositions based on liquid silicone polymers. The silicone polymers used
in such compositions may be curable liquid polysiloxane polymers having
viscosities within the range 10,000 to about 100,000 c.p. They may be
cured in known manner with metal soap curing agents, e.g., stannous
octoate. When the present extenders are incorporated in such sealant
compositions and the compositions are cured with conventional curing
agents, nearly all of the water associated with the extender remains in
the cured composition and does not evaporate therefrom. Thus, as in the
case of the polysulfide and polyepoxide compositions, little, if any,
shrinkage of the cured composition occurs.
The quantity of the present extenders that is added to the sealant
composition depends in part on the nature of the polymer on which the
sealant is based and may vary over a wide range, particularly in the case
of the polysulfide sealants where a compatability promoter is desirably
used. Thus the quantity of extender may vary from about 10% to about 200%
of the weight of liquid polymer in the sealant composition.
In general, the compositions of the present invention are so-called
"two-package" sealants, that is, the components of the sealant are
separately packaged and mixed at the point of use to produce a mixture
that reacts to form an elastomeric seal or coating having the desired
properties. Thus in the case of the liquid sealant compositions based on
liquid polysulfide polymers, the liquid polymer and curing agent therefor
are packaged separately. The extender and compatibility-promoting resinous
material may be included in either package, or partially in each package,
but are preferably premixed with the liquid polymer with the curing agent
being separately packaged. Similarly in the case of compositions based on
liquid polyepoxides and polysiloxanes, the curing agent is separately
packaged with the extender being included in either package or partially
in each package.
In order to point out more fully the nature of the present invention, the
following specific examples are given to illustrate the manner in which
the present extenders can be used.
EXAMPLE 1
A curable sealant formulation was made by mixing the indicated parts by
weight of the ingredients listed below:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
33
Coal Tar (Allied Chemical 439 - 85%
CP 440 - 15%) 33
Aqueous sodium silicate (Silicate "N"
Phila. Quartz Co.) SiO.sub.2 :Na.sub.2 O ratio
3.22:1, 37.6% silicate
33
Lead dioxide curing agent
1.5
______________________________________
The liquid polysulfide polymer was of the type described above and is
commercially identified as LP-2. It has an average molecular weight of
about 4,000 and about 2% of cross-linking. The curing agent was a paste
comprising equal parts by weight of lead dioxide and chlorinated biphenyl.
Samples of the foregoing formulation were applied to a concrete substrate
and cured in air. In spite of the fact that a substantial amount of water
was incorporated in the composition with the aqueous silicate, the cured
compositions were homogeneous elastomeric coatings showing good adhesion
to the concrete, i.e., when the coating was stripped from the substrate,
failure occurred in the coating material and not at the interface between
the coating and the substrate. Such failure is commonly designated
"cohesive failure," as distinguished from "adhesive failure" which occurs
when the coating separates at its interface with the substrate.
When heat aged at 50.degree. C. for 300 hours, the cured formulation showed
some loss in weight, but little, if any, shrinkage.
EXAMPLE 2
A curable sealant formulation having a reduced amount of the polysulfide
polymer was prepared by mixing the following ingredients in the indicated
parts by weight:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
28.57
Coal Tar (Allied Chemical 439)
35.71
Aqueous sodium silicate (Silicate "N")
SiO.sub.2 :Na.sub.2 O ratio 3.22:1
35.71
Lead dioxide curing agent
1.5
______________________________________
The adhesion to concrete and heat aging properties of the cured composition
were similar to those obtained in Example 1.
EXAMPLE 3
A curable sealant formulation was prepared by mixing the following
ingredients in the indicated parts by weight:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
33
Coal Tar (Allied Chemical 439)
33
Magnesium Oxide paste,
10% MgO in equal parts of
water and ethylene glycol
33
Lead dioxide curing agent
1.5
______________________________________
Samples of this formulation were applied to concrete substrates and cured
in air for 7 days to give an elastomeric coating with little, if any,
shrinkage. Good adhesion to the concrete was obtained as evidenced by the
fact that the coatings exhibited cohesive failure.
EXAMPLE 4
A number of sealant formulations were prepared having the following
formulation wherein various resins other than the coal tar of Examples 1
and 2 were used:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
20
Aqueous sodium silicate (Silicate "N")
5
Resin 5
Lead dioxide curing agent
2.4
______________________________________
The curing agent in these formulations was a mixture of 7.5 parts of lead
dioxide and 4.4 parts of liquid poly-alpha-methyl styrene. The resins used
were:
1. A stage "B" phenolic resin (Methylon resin 75121, General Electric Co.),
2. A triethylene glycol ester of hydrogenated rosin (Staybelite ester "3",
Hercules, Inc.),
3. A petroleum hydrocarbon resin with aliphatic characteristics (Piccopale
100, Penn. Ind. Chem. Corp.),
4. A mixed aromatic resin (piccovar-420, Penn. Ind. Chem. Corp.),
5. An acrylic resin (Acryloid AT-70), Rohm & Haas Chem. Co.),
6. A hydroxy-terminated polyester made by condensing adipic acid with a
mixture of ethylene and propylene glycols (ZL-634, Thiokol Chemical
Corporation),
7. A high molecular weight polyethylene glycol (Carbowax-400),
8. A hydroxyl-containing polybutadiene resin (R-45M, Arco Chem. Co.),
9. A fluorocarbon-modified polybutadiene resin,
10. Polyvinyl alcohol, and
11. A 5-carbon fluoro-alcohol.
In each case the composition cured at room temperature within one hour
after mixing to a uniform tough rubber having the water associated with
the aqueous silicate bound therein.
EXAMPLE 5
A sealant composition was prepared having the following formulation:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
20
Coal Tar (Allied Chemical 439)
10
Aqueous sodium silicate (Silicate "N")
SiO.sub.2 :Na.sub.2 O ratio 2:1, 54% silicate
10
Lead dioxide curing paste
2.4
______________________________________
A room temperature cure to a rubber was obtained in about 1 hour.
EXAMPLE 6
Sealant compositions were made using three different types of colloidal
silica dispersions in the following formulations:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
10
Coal Tar (Allied Chemical 439)
5
Silica 5
Lead dioxide curing paste
1.2
______________________________________
The silicas used were:
1. A 50% aqueous colloidal dispersion of silica containing about 0.35%
Na.sub.2 O and having a pH of 9.0 (Nalcoag 1050),
2. A 50% colloidal dispersion of silica in ethylene glycol ethyl ether
(Nalcoag 40D04), and
3. A 15% aqueous colloidal dispersion of silica containing about 0.80%
Na.sub.2 O and having a pH of 10.4 (Nalcoag D-2195).
In each case curing to a rubber occurred at room temperature within about
an hour of mixing.
EXAMPLE 7
A sealant composition was prepared having the following formulation:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
10
Alpha-methyl naphthalene
10
Aqueous sodium silicate (Silicate "N")
10
Lead dioxide curing paste
2.6
______________________________________
A good rubber cure was obtained at room temperature.
EXAMPLE 8
A sealant composition was prepared having the following formulation:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
10
Aqueous sodium silicate (Silicate "N")
10
Chlorinated biphenyl (Arochlor 1254)
10
Lead dioxide curing paste
2.6
______________________________________
A good rubber cure was obtained at room temperature.
EXAMPLE 9
A sealant composition was prepared having the following formulation:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
10
Poly-alpha-methyl styrene (Dow 276-V2)
10
Aqueous sodium silicate (Silicate "N")
10
Zinc peroxide curing paste
2.2
______________________________________
The zinc peroxide paste was a 50:50 mixture of zinc peroxide and
chlorinated biphenyl.
A good white rubber cure was obtained.
EXAMPLE 10
A magnesium oxide paste was prepared by mixing 30 parts of finely divided
MgO with 135 parts of water and 135 parts of ethylene glycol. The
resulting paste was mixed with an equal weight of coal tar-439.
A curing agent was prepared by mixing equal parts of lead dioxide and coal
tar-439.
20 parts of the magnesium oxide/coal tar paste were then mixed with 10
parts of liquid polysulfide polymer and 2.6 parts of the curing agent. The
mixture cured at room temperature to give a rubber of good quality.
EXAMPLE 11
A magnesium oxide paste was prepared containing 17% by weight of finely
divided MgO in a 50:50 mixture of ethylene glycol and water. This paste
was mixed with an equal weight of aqueous sodium silicate (Silicate "N").
10 parts of the resulting silicate/magnesium oxide mixture was then mixed
with 10 parts of a 75/25 mixture of coal tars CP 440 and 439 and 1.5 parts
of the curing agent of Example 10. Thereafter the resulting mixture was
mixed with 10 parts of liquid polysulfide polymer (LP-2).
This formulation cured at room temperature to give a rubber having good
properties.
EXAMPLE 12
A master batch was prepared having the following formulation:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-32)
100
CaCO.sub.3 (Multiflex M.M.)
25
Precipitated CaCO.sub.3 (Icecap K)
30
TiO.sub.2 (Titanox RA 50)
10
Chlorinated biphenyl (Arochlor 1254)
35
______________________________________
The liquid polymer LP-32 of this Example is similar to polymer LP-2, except
that it has about 0.5% of cross-linking instead of 2% cross-linking.
A sealant composition was prepared incorporating a quantity of the
foregoing master batch and having the following composition:
______________________________________
Component Parts by Weight
______________________________________
MgO paste (14% MgO in 50:50 mixture of
ethylene glycol and water)
10
Master batch 20
Lead dioxide curing paste
1.5
______________________________________
This composition gave an exceptionally fast cure to a rubber having good
properties.
EXAMPLE 13
A sealant composition was prepared having the following composition:
______________________________________
Component Parts by Weight
______________________________________
MgO paste (14% paste as in Ex. 12)
10
Poly-alpha-methyl styrene (Dow 276-V-2)
10
Zinc peroxide curing paste (as in Ex. 9)
2.2
Liquid polysulfide polymer (LP-2)
10
______________________________________
The MgO paste, poly-alpha-methyl styrene and curing paste were premixed and
then mixed with the polysulfide polymer. A good white, tough rubber cure
was obtained.
EXAMPLE 14
A sealant composition was prepared having the following formulation:
______________________________________
Component Parts by Weight
______________________________________
Magnesium oxide (14% paste as in Ex. 12)
5
Aqueous sodium silicate (Silicate "N")
5
Poly-alpha-methyl styrene (Dow 276-V2)
10
Zinc peroxide curing paste (as in Ex. 9)
2.2
Liquid polysulfide polymer (LP-2)
10
______________________________________
The components, other than the polysulfide polymer, were premixed and then
mixed with the polysulfide polymer. A spongy, white cured rubber was
obtained.
EXAMPLE 15
In this Example a silicone sealant material was modified with aqueous
sodium silicate having an SiO.sub.2 :Na.sub.2 O ratio of 3.75:1 and a
solids content of about 32% by weight (Silicate S-35, Phila. Quartz Co.).
A formulation was prepared having the following composition:
______________________________________
Component Parts by Weight
______________________________________
Sealant based on liquid polysiloxane
polymer (RTV-631, Part "A",
General Electric Co.)
22.5
Tin octoate curing agent (RTV-631,
Part "B", General Electric Co.)
2.5
Aqueous sodium silicate, SiO.sub.2 :Na.sub.2 O
ratio 3.75:1, 32% solids
7.5
______________________________________
The curing properties of the foregoing composition were compared with those
of a similar composition containing no aqueous sodium silicate and it was
found that while the formulation containing the aqueous silicate cured
somewhat more slowly than the control formulation, it cured to a good
quality of rubber similar to that of the control.
EXAMPLE 16
A composition was prepared using the silicone sealant and curing agent of
Example 15, but substituting aqueous magnesium oxide containing 37% by
weight magnesium oxide for the aqueous silicate of Example 15 to give the
following formulation:
______________________________________
Component Parts by Weight
______________________________________
Sealant based on liquid polysiloxane
22.5
Tin octoate curing agent
2.5
37% aqueous magnesium oxide
7.5
______________________________________
Upon mixing of the components of the foregoing formulation, the mixture
cured at room temperature to a somewhat spongy rubber in which the water
of the aqueous magnesium oxide was bound and no trace of solid magnesium
oxide could be detached.
EXAMPLE 17
A coating composition was prepared having the following formulation:
______________________________________
Component Parts by Weight
______________________________________
Diglycidyl ether of Bisphenol A,
(EPON 828) 20
Aqueous sodium silicate (Silicate "N")
10
2,4,6-tri-dimethylaminomethyl phenol,
(DMP-30) 2
______________________________________
The components were mixed and allowed to stand at room temperature. After
standing for a few days the mixture turned into a hard mass with the water
associated with the aqueous silicate bound therein.
EXAMPLE 18
A coating composition was prepared having the following formulation:
______________________________________
Component Parts by Weight
______________________________________
Diglycidyl ether of Bisphenol A,
(EPON 828) 10
Aqueous sodium silicate (Silicate "N")
10
Liquid polysulfide polymer (LP-32)
10
2,4,6-tri-dimethylaminomethyl phenol
(DMP-30) 2
______________________________________
The liquid polyepoxide was mixed with the aqueous sodium silicate and the
liquid polysulfide polymer was mixed with the amine curing agent, after
which the two mixtures were combined and allowed to stand at room
temperature. After 24 to 48 hours the mixture was somewhat rubbery and
easy to cut. After several days it set to a hard, plastic-appearing
material having relatively good impact resistance.
EXAMPLE 19
A coating composition was prepared having the following formulation:
______________________________________
Component Parts by Weight
______________________________________
Diglycidyl ether of Bisphenol A,
(EPON 828) 20
Aqueous sodium silicate (Silicate "N")
11
2,4,6-tri-dimethylaminomethyl phenol
1
______________________________________
The foregoing components were mixed and cured at room temperature to yield
a very hard yellow plastic.
EXAMPLE 20
A composition was prepared by mixing the following ingredients in the
indicated proportions:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
20
Aqueous potassium silicate,
SiO.sub.2 :K.sub.2 O ratio 2.5:1, about 29%
solids content (Kasil No. 1)
10
Lead dioxide curing agent
2.4
______________________________________
When the foregoing components were mixed, the mixture cured rapidly at room
temperature to yield a tough rubber in which the water content of the
aqueous silicate was bound.
EXAMPLE 21
A composition was prepared by mixing the following ingredients in the
indicated proportions:
______________________________________
Component Parts by Weight
______________________________________
Liquid polysulfide polymer (LP-2)
20
Aqueous potassium silicate,
SiO.sub.2 :K.sub.2 O ratio 2.1:1, about 39%
solids content (Kasil No. 6)
10
Lead dioxide curing agent
2.4
______________________________________
When the foregoing components were mixed, the mixture cured rapidly at room
temperature to yield a rubber similar to the product of Example 20.
It is of course to be understood that the foregoing Examples are intended
to be illustrative only and that numerous changes can be made in the
ingredients, proportions and conditions disclosed therein without
departing from the spirit of the invention as defined in the appended
claims. For example, various special purpose additives such as fillers,
curing rate modifiers, adhesion promoters, plasticizers and the like
previously known and used in the sealant art can be added to the above
formulations as desired. Other modifications within the scope of the
invention will be apparent to those skilled in the art.
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