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Description  |
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BACKGROUND OF THE INVENTION
1. Field Of The Invention
This invention relates to the use of silanes having capped functional
groups as adhesivizing agents, especially for between organic polymers and
substances having inorganic oxidic and/or metal surfaces.
2. Discussion Of The Prior Art
It is known to coat sheet metals or glass fibers or glass fiber fabrics
with a variety of organic polymers on one or both sides and thus to
prepare laminates of these materials. It has furthermore long been known
to use condensation products of the phenol-formaldehyde and amine resin
type as binding agents, for example in foundry practice.
However, good adhesion between the organic and the inorganic components
cannot be achieved without adhesives, because the anchoring together of
the two components at their boundary surfaces without other media is not
sufficient to achieve the mechanical characteristics which the materials
require. For example, German Pat. No. 1,010,941 described the pretreatment
of oxidic material with organic silicon compounds containing vinyl
radicals. Furthermore, in German Pat. No. 1,242,358, the use of
organosilane compounds containing amino groups is described for this
purpose. For many applications, however, the strength of adhesion achieved
with these adhesivizing agents is insufficient, or else the transparency
is inadequate, especially in glass laminates. It is also desirable for the
film on the inorganic, metallic or oxidic surface to be highly resistant
to mechanical stress.
It has furthermore been found in practice that, for example, when
.gamma.-aminopropyltriethoxysilane is used as the adhesive component, the
initially positive adhesivizing effect of the aminosilane becomes
ineffectual after relatively long storage in a variety of resins other
than furan resins, such as, for example, in phenol resol resins or epoxy
resins.
SUMMARY OF THE INVENTION
In accordance with the foregoing the present invention contemplates a
process for protecting the surface of an inorganic oxidic or metallic
surface against corrosion or for improving its adhesion to an organic
polyaddition and/or polycondensation and/or polymerization compound which
comprises contacting said surface with a silane having a capped functional
group.
This invention is also directed to a treated object having an inorganic,
oxidic or metallic surface, said object having on said surface a coating
of a silane having a capped functional group.
Also contemplated herein is a laminate comprising an inorganic oxidic or
metallic surface and a polymer, said laminate having in the region of the
interface between the inroganic oxidic or metallic surface and the polymer
a silane having a capped functional group.
The term, "silanes containing capped functional groups," as used herein,
refers to compounds of the following formulas:
##STR1##
wherein n can be from 1 to 8, preferably 2 to 4, R represents an oxygen
moiety or two hydrogen atoms, X represents oxygen or sulfur, R' represents
identical or different alkyl moieties of 1 to 8 carbon atoms which can be
interrupted by an oxygen atom if desired, and a can be equal to 0 or 1.
The preparation of the compounds of Formula I is generally performed in the
manner described in German "Offenlegungsschrift" No. 2,159,991. The
compounds of Formula II can be prepared, for example, by the reaction of
the corresponding .omega.-halogenalkyltrialkoxysilanes with aminoacetals.
The silanes are generally used in the acid range. They thus become cleaved
and form the corresponding diols or carbonyl-group-containing silanes. One
can also use the silanes in the alkaline range, especially when an amine
or melamine resin is used as the organic polymer. When the silane is
employed: in an acidic medium, this medium can be either a water solution
or the resin in which the silane is incorporated; it has normally
pH-values between 3.5 and 6.5. But other values below 7.0 can be accepted.
When the silane is employed in an alcaline medium, this medium is either a
water solution with pH-values from 7.5 to 10.0 or a resin.
The following compounds are given as examples of the silanes:
##STR2##
The laminates made from organic binding agents and inorganic oxides or
metals with the use, in accordance with the invention, of silanes having
capped functional groups display substantially improved mechanical
strengths as a result of improved adhesion, as shown by wet strength
measurements in bending experiments performed on standardized test
specimens.
The organic binding agents whose adhesion to inorganic substrates is
improved include polyaddition products, such as, for example, epoxy
resins, urethane resins or polyester resins, polycondensation products,
such as for example the cold setting and/or thermosetting resins obtained
by the condensation of aldehydes with phenols and/or ureas or the
derivatives thereof, and polymerization products, such as, for example,
those based on polyvinylhalides and/or copolymers of vinyl chloride and
vinyl acetate, ethylene and methacrylic acid esters. Also, the adhesion of
polymers based on caprolactam or the adhesion of other polyamides can be
improved in accordance with the invention.
Examples of components having inorganic, oxidic surfaces are glass, quartz,
diatomaceous earth, sand, asbestos, mica, corundum, iron oxides, calcium
carbonate, calcium sulfate, etc. Suitable metallic surfaces are, for
example, those of iron, copper, zinc, aluminum, tin and titanium.
The inorganic components can be, for example, in the form of fibers, mats,
rovings, powders, or fabrics, etc.; the metals are used, for example, in
the form of powders, sheets or wires.
Of special technical interest is the pretreatment of glass fabrics and
fibers and of glass surfaces and metal surfaces which are made into
laminates with numerous organic polymers.
The commercial advantages of the invention can be achieved either by a
treatment of the inorganic metallic substrates with the claimed silanes by
applying them either by spraying, dipping, atomizing or brushing, or by
adding the claimed silanes to the polymers as adhesivizing adjuvants.
If the silanes are applied directly to the surface, they are preferably
used in the form of solutions. The solutions used contain the dissolved
adhesivizer in a concentration of 0.05 to 5 wt.-%, preferably 0.1 to 2
wt.-%. The application of the silanes is performed preferably by immersing
the products to be treated into the acid or alkaline solution of the
silane. If an acid aqueous solution is used, then in the case of the
compounds of the above-given Formula II, the acetal groups or ketal groups
are transformed to aldehyde and diol groups, respectively.
Alcohols, ethers, benzines, chlorinated hydrocarbons and aromatic
hydrocarbons can be used as solvents. Preferably, however, incombustible
solvents are used, such as, for example, water and mixtures of water with
the above-named organic solvents.
When the treatment with the silanes is completed, the impregnation can be
followed by evaporation of the solvent and, if desired, a heat treatment
for hardening purposes.
If, however, the silane is added to the organic polymer or is incorporated
into the polymer by known methods prior to the addition of the inorganic
materials, the silane concentrations in the polymer can be between 0.05
and 10% by weight, preferably 0.1 to 2% by weight, with respect to the
polymer, depending on the size of the surface area of the inorganic
substances. The amount to be used in each case depends on the nature of
the binding agents used and on the inorganic material. In the case of
cold-setting furan resins for example, which are used as binding agents in
foundry molds and cores, amounts between 0.1 and 0.3% by weight are added.
For the incorporation of the silanes into the binder it is sufficient to
mix them with the resin by known methods such that a uniform distribution
is brought about.
The mixture of the resins with the named silanes has an additional
advantage over resin-aminosilane mixtures. The shelf life of these
mixtures, especially when a phenol resol resin is used as the resin, is
significantly better than in the case of comparable resins to which
silanes containing amino groups have been added.
In order to more fully illustrate the nature of the invention and the
manner of practicing the same the following examples are presented:
EXAMPLES
EXAMPLE 1
Water-sized glass fibers are immersed for one minute in a 0.25% solution of
(CH.sub.3 --CH.sub.2 --O).sub.2 --CH--CH.sub.2 --NH.sub.1 --CH.sub.2
--CH.sub.2 --CH.sub.2 --Si(OCH.sub.3).sub.3 which has been acidified with
acetic acid. Then, after allowing the excess solution to drain off, the
fibers are dried for 15 minutes at 130.degree. C.
The glass filaments sized in this manner are then dipped in epoxy resin and
made into round fiber-reinforced rods. The curing of these rods is
performed at 130.degree. C. for 17 hours. The bending strength of the test
specimens obtained in this manner is determined in accordance with DIN 53
452, one determination being performed directly after curing and the other
after letting specimens stand in boiling water for 72 hours.
A test specimen prepared in the same manner, but reinforced with glass
filaments sized with .omega.-aminopropyltriethoxysilane, was used for
purposes of comparison. The blank specimen contains only water-sized glass
filaments. The results are given in the following table.
__________________________________________________________________________
BENDING STRENGTH OF GLASS FIBER-REINFORCED EPOXY RODS
(in kp/cm.sup.2)
Bending strength
Directly after
After stand-
Silane used curing ing in water
__________________________________________________________________________
None 9800 3500
H.sub.2 N (CH.sub.2).sub.3 --Si(OC.sub.2 H.sub.5).sub.3
9500 7900
(C.sub.2 H.sub.5 -O).sub.2 --CH--CH.sub.2 --NH--(CH.sub.2).sub.3 --Si(OCH.
sub.3).sub.3 11400 9600
__________________________________________________________________________
EXAMPLE 2
1000 weight-parts of Halterner Sand H 32 are mixed thoroughly with 15
weight-parts of a furan resin containing 0.3 wt.-% of adhesivizing agent,
and 6 weight-parts of a hardener (75% H.sub.3 PO.sub.4). The mixture is
charged into a +GF+ test bar mold and compressed with three blows of the
ram of a +GF+ ram apparatus. Then the bars are allowed to set at room
temperature, the initial bending strength being tested 5 hours later by
means of the +GF+ strength testing apparatus.
The second half of the bars is exposed for 24 hours to a
water-vapor-saturated atmosphere and then subjected to the bending test.
The following are used as the adhesivizing agents:
##STR3##
The results are given in the following table:
______________________________________
Bending strength of test bars
(in kp/cm.sup.2)
After 5 h plus
Resin component + silane 24 h exposure
(Experiment No.) After 5 h to moisture
______________________________________
0 (no silane) 16 12
a 35 36
b 33 25
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EXAMPLE 3
Degreased copper plates measuring 15 .times. 8 cm were repeatedly dipped
into a 10% alcoholic acetic acid solution of
4-3'-trimethoxysilylpropoxymethyl)-1,3-dioxolane and then dried for one
hour at 130.degree. C. On the surface there is then a firmly adherent,
hard film, which cannot be removed by scratching with a knife.
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