Note: Descriptions are shown in the official language in which they were submitted.
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Title: hAMINATION BETWEEN PLASTIC RESINS AND CEMENT
Fiend of the Invention
This invention relates to composite structures
made from layers of material that will not normally bond
readily to each other. More particularly, it relates to
a method and resulting structure whereby a polymeric
plastic surface layer, formed from a setting resin, will
bond more readily to a hydraulic cement-based layer of
mortar, concrete or the like.
Background to the Invent~nn
It is, on occasion, desirable to bond to a
concrete surface a polymeric plastic finish. An example
is the concrete burial vault with plastic liner described
in Canadian patent application 2,062,518 by Michael
Davidian (laid-open September 14, 1992). In that
reference a thermo-setting epoxy resin adhesive with
solvent and surfactant is applied to the outer surface of
a preformed thermoplastic resin liner. Before the
adhesive is fully cured, wet flowable concrete is applied
to the adhesive layer. The result is to bond the
concrete to the liner. Earlier United States patents
addressing similar technology are U.S. 3,439,461 and U.S.
3,787,545.
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In another United States patent No. 3,949,144
to Duff a reinforced concrete construction is formed from
alternate, integrally bonded layers of epoxy concrete
containing resin and fibre reinforced epoxy resin. The
resulting laminate is a thin-walled construction of
reduced cost, due to the use of concrete.
According to one variant of the Duff invention
a gel coat is spread over a mold, followed by a layer of
chopped glass fibres and epoxy resin. To this last layer
while still wet is then applied the resin-containing, wet
cement mixture. This is followed by alternate layers of
reinforced resin and cement to build-up strength. Thus,
in the Duff invention, a polymeric resin with glass
fibres imbedded therein is bonded to a hydraulic cement
layer that, as well, contains a bonding resin.
Thin structures based on the use of polymer-
enriched concrete have also been employed using a fine
wire matrix for reinforcing. Sold under the trade mark
PERMA PLATE, by Ferro-Mesh of Canada Inc. the technology
for fabrication of a three dimensional reinforcing mesh
is described in Canadian patent No. 1,145,228.
Applications of this technology have been directed to
providing a finishing layer to concrete structures such
as bridge decks and industrial flooring. The PERMA PLATE
(TM) finish has also been applied over wooden decking,
such as on a pier. PERMA PLATE technology is ideally
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suited to forming thin-shelled structures having the
dimensional stability associated with hydraulic cement
and concrete. Problems may be encountered, however, in
bonding such material to resin finishes that are
organically-based. For example, a more or less complete
curing of the concrete at the interface between the resin
layer and the concrete layer may be required for maximum
bond strength. In an actual production scenario, this
delay could amount to a week or longer, and would be
unacceptable, particularly if the parts being produced
were fairly large and had to be moved for further
processing or assembly.
This invention is directed to an improved means
for bonding a hydraulic cement-based material to a
polymeric plastic surface. It further has as an
objective the production of thin walled structures having
a high quality resin-based finish on at least one
surface, and the dimensional stability of concrete.
The invention in its general form will first be
described, and then its implementation in terms of
specific embodiments will be detailed with reference to
the drawings following hereafter. These embodiments are
intended to demonstrate the principle of the invention,
and the manner of its implementation. The invention in
its broadest and more specific forms will then be further
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described, and defined, in each of the individual claims
which conclude this Specification.
According to one broad aspect of the invention,
a thin walled structure is formed by:
(1) laying a resinous, polymeric coat over a
mold, such coat being preferably supported by
reinforcing fibres imbedded in resin;
(2) distributing a coupling agent, preferably a
preformed wire grid or optionally silica sand,
chopped glass or mineral fibres, or a
combination thereof over the surface of the
resin while such resin is soft enough to bind
to and retain such coupling agent across its
surface without absorbing such coupling agent
fully within the resin so that parts of the
coupling agent remain partially exposed;
(3) allowing the resin to set to form an interface
surface: and
(4) applying a hydraulic cement based layer over
the surface of the resin to bond with the
exposed parts of the coupling agent.
The coupling agent should be compatible with bonding to
both the resinous coat and to a hydraulic cement mixture.
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By this method a composite is produced having alternate
resin and cement layers with the coupling agent present,
and providing bonding, at the interface of the two
layers.
Preferably, the hydraulic cement based layer is
polymer-modified and may be reinforced by reinforcing
planar wire mesh or a three dimensional matrix imbedded
therein. Where a wire grid coupling agent is employed,
such coupling agent may be attached to the reinforcing
wire mesh or matrix to improve bonding of the cement
layer to the resin coat.
As a further variant, the wire grid coupling
agent may be pre-formed to facilitate such attachment.
Thus, a field of protruding wire stubs on a base may be
bonded in place by the resin to provide means to locate
the reinforcing wire mesh prior to the application of the
hydraulic cement, and to further improve bonding between
the resin and cement layers. Alternately or
simultaneously, the wire grid coupling agent may be in
the form of a planar grid with raised or corrugated
portions intended to protrude above the resin. Such
field or corrugated grid may be anchored within the
resinous coat by applying and imbedding fibre
reinforcement above the portion of the coupling agent
imbedded in the resin.
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As a further variant, part of the reinforcing
planar wire mesh or matrix of the cement-based layer may
be embedded in the layer of wet resin laid over the
interface surface before the hydraulic cement based layer
has been applied, thereby serving as the coupling agent
and providing a bond directly between the resinous layer
and the hydraulic cement based layer.
Preferably, the resin coat has an outer gel-
coat layer to provide an external surface with a high-
quality finish, as well as inner, fibre reinforcement.
As a further variant, silica sand and/or
chopped, silica-based or mineral-based fibres are
partially imbedded in the resinous polymeric coat as the
coupling agent and provide bonding between the resin and
cement layers.
Where silica sand or other particulate coupling
agent is used alone to bond the resin and cement layers
the cement layer should allowed to cure thoroughly before
the part is moved or disturbed as premature handling
could destroy the bond. With wire grid as coupling agent
the part may be carefully moved much sooner. Maximum
bonding effect is achieved when the wire grid and
particulate matter coupling agents are used together.
Maximum panel strength is achieved when the cement layer
is reinforced with a wire matrix or two layers of flat
wire mesh.
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By this method, a thin walled structure of
substantial size, such as a projection screen or a hollow
shelter, can be formed, the gel coat providing a smooth
finish. Because of the use of the hydraulic cement to
provide body and support, such thin-walled structures
exhibit improved dimensional stability under variable
temperature conditions.
The foregoing summarizes the principal features
of the invention and some of its optional aspects. The
invention may be further understood by the description of
the preferred embodiments, in conjunction with the
drawings, which now follow.
Figure 1 illustrates configurations of wire
grid coupling agents, bent so they may be partly embedded
in the resin layer and partly in the hydraulic cement-
based layer. Typical dimensions would be up to two
inches wide by up to six inches long with a height of
one-eight to one-half inch. Much larager wire grids may
be used.
Figure 2 illustrates a construction using a
wire grid coupling agent in corrugated form, partially
embedded in the resin layer and partially in the cement
layer. A portion of the wire grid coupling agent has
been additionally secured to the resin layer by fibre
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reinforced resin placed over portions of the resin-
embedded coupling agent. The hydraulic cement layer is
reinforced with a three dimensional wire matrix and is
bonded to the resin layer through its bond with the
embedded wire grid coupling agent.
Figure 3 illustrates a construction using
silica sand as the coupling agent. typically, the silica
sand will be 1/4 inch or 1/8 inch in diameter.
Approximately half the depth of the particles of sand are
embedded in the resin. Also illustrated is a wire anchor
with its base secured to the resin layer by resin
impregnated fibreglass cloth or roving which is placed
over or around the stub of the anchor. The anchor serves
to position the reinforcing for the hydraulic cement
layer which rests on the embedded sand particles.
Figure 4 is a cross-section of the structure of
Figure 3 in which the anchor stub is bent down over the
reinforcing to anchor it during placing of the cement.
Figure 5 illustrates a construction wherein the
bottom grid of a wire mesh matrix 7 serves as the
coupling agent, being partially embedded in the resin
layer 4.
Descr~nt~an cf t_he PreferrP~ F hnr3;ma"+
In Figure 2 a gel coat 1 has been laid over the
surface of a mold 2. Bonded to the gel coat 1 in the
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normal way is a resinous coating layer 4 of resin-based
plastic with one or more layers of fibreglass reinforcing
3 contained therein.
The resin-based plastic layer 4 terminates at
a surface 9 that is formed on the side opposite the gel
coat 1. While this surface is still tacky, or after
placing additional wet resin, a pre-formed wire mesh grid
5, as further depicted in Figure 1, is pressed into the
surface of the resin layer 4 and held there until the
resin has set. The wire grid 5 of Figure 2 is provided
with regular elevated portions 5a, 5b, 5c, 5d which are
intended to protrude from the resin layer 4. These
elevated portions may occur regularly, undulating in a
corrugated-like manner. Their role is to serve as a
coupling agent to bond to the hydraulic cement layer 8
which is to follow. The wire mesh grid 5 also serves to
support and provide attachment means for the cement layer
reinforcing mesh or matrix 7. (Wire mesh may be planar;
a wire matrix is three dimensional.)
For greater panel strength, additional fibre-
reinforced resin 6 may be placed over the embedded wire
grid 5 coupling agent.
When the resin has set a reinforcing wire mesh
or matrix 7 is located atop the embedded wire grid 5
coupling agent and attached thereto. A hydraulic cement-
based mortar mix is then placed over the resin surface 9,
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embedding both the reinforcing matrix 7 and the exposed
portions of the wire mesh coupling agent 5, to form the
cement layer 8. Suitable dimensions for the resin layer
4 and cement layer 8 are one eighth (1/8) of an inch and
5 seven eighths (7/8) of an inch respectively.
In Figure 3 silica sand 13 is used as the
coupling agent. While this surface 9 is still tacky, but
stiff enough to provide support at its surface, silica
sand 10 is broadcast over it to serve as a further
10 coupling agent for the hydraulic cement which is to
follow. Such sand 3 works well where time is not a
constraint or where the part may be moved without risk of
disturbing the interface 9 between the resin and cement
layers until the cement 8 is fully cured.
While fine silica sand 13 has been found to
work well in this application, any finely divided
particulate material that bonds both to the resin surface
9 and to the hydraulic cement 8 may be employed. This
includes finely chopped glass or mineral fibres which may
be used alone or in addition to sand 13. The coupling
agent should in all cases sit on the surface 9 partially
immersed in the resin 4 to which it is bonded, leaving an
exposed upper portion protruding for bonding to the
cement layer 8. Therefore such granules or fibres 13
should not be submerged totally into the resin layer 4.
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Optionally, wire anchors or, as shown in Figure
3, an array of protruding wire stubs 14 to serve as
anchors 14 may be partially embedded in the resin layer
4. Over these stubs 14 may be applied fibreglass
cloth/roving 6 which may be pierced by the wire stubs 14,
or be placed intermediate the protruding portions of any
such coupling agents 5. The anchors 14 are laid in wet
resin which is allowed to set. The protruding wire stubs
14 may then be bent over a reinforcing wire matrix 7
provided for the hydraulic cement layer 8 and serve to
hold such reinforcing 7 in place until the cement mix 8
has been placed and set.
Figure 4 illustrates a construction similar to
Figure 3 except that in this variant, wire stub coupling
agent 14 has a foot 14b that is bent to extend on both
sides of the stub 14 with fibreglass 3 overlaying such
feet.
In Figure 4, the hook ends 14a of stubs 14,
which may be partially pre-bent, are shown as closed over
parts of the wire matrix 7 to secure it in place. Once
the reinforcing wire mesh 7 is properly located, a
filling of hydraulic cement preferably in the form of
polymer-modified concrete, may be applied to Porm the
cement layer 8. If suitably stiff when applied, this
cement layer 8 may be laid-on over near vertically
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oriented surfaces permitting molds with substantial
curvature to be employed.
In Figures 3 and 4 the anchor 14 is shown
singly, with a foot 14b. As an alternative, a wire
substrate having a field of protruding wire stubs to
serve as anchors 4 may be prepared to which is applied
fibreglass roving 6 with the stubs 14 protruding through
the roving 6. By the use of fine, soft wire in the
substrate, the combined substrate and fiber reinforcing
can be sufficiently flexible to be laid over a curved
surface on a mold. The substrate also allows for the
bulk placement of stubs which serve as anchors 5.
As a further alternative, in Figure 5 the
bottom portion 7a reinforcing layer of mesh in the matrix
7 is partially embedded in the resin layer 4 and acts as
the coupling agent in the bonding to that layer.
While it is preferred to use a preformed, three
dimensional reinforcing matrix of the PERMA PLATE type
described above for the cement reinforcing wire mesh 7
2o the same final result can be obtained by using any planar
or dual layer cement reinforcing wire matrix 7.
The foregoing has constituted a description of
specific embodiments showing how the invention may be
applied and put into use. These embodiments are only
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exemplary. The invention in its broadest, and more
specific aspects, is further described and defined in the
claims which now follow.
These claims, and the language used therein,
are to be understood in terms of the variants of the
invention which have been described. They are not to be
restricted to such variants, but are to be read as
covering the full scope of the invention as is implicit
within the invention and the disclosure that has been
provided herein.
