Note: Descriptions are shown in the official language in which they were submitted.
~ ~z,3~7~
(1)
The uresent invcntion relates to a multi-laycr board
and a process of preparing the same.
Multi-layer boards comprised of laminated layers are
know. U.S. Paten-t No. 2,806,811, for e~ample, describes
a paper-covered gypsum board wherein the paper layers are
bonded to the gypsum board with a resin adhesive.
Laminated boards taking advantage of the good qualities
of inorganic materials used for the core layer and organic
plastics for the cover layer or layers are very useful.
~owever, considerable difficulties have been encountered
in providing a true and lasting bond between layers of such
different materials since not only the adhesion but also the
mechanical properties of the materials cause problems.
Glueing or bonding with adhesive does not provide strong
enough lamination.
Attempts to bond the two layers to each other while
their materials were still wet and the layers were, there-
fore, in a plastic condition failed because when an organic
plastics layer was cast on a fresh core layer of concrete
or a like water-containing cementitious binder material,
which was not yet hardened, a water layer formed between the
layers. Similar disadvantages are found when a material in
a plastic condition was applied to a hardened layer.
It is the primary object of this invention to provide
a multi-layer board and a process of preparing the same,
in which a cementitious material core layer and at least
one cover layer of organic plastics are combined while
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i~.Z37~2
(2)
I assuring strong adhesion therebetween so that the~e is no
¦ danger of the cover l~yer separating fro~ the core layer when
I the multilayer board is in use, i.e. to connect the
¦ interfaces of the layers in a force-transmitting manner, the
! 5 board constituting an integral structure as ~ar as its
j m~chanical characteristics are concerned.
The above and other objects of one aspect of the present
invention are accomplished with a multi-layer board compris-
~ ing a core layer consisting at least primarily of a cement-
! ` lo itious binder material, and at least one cover layer consist-
ing of a fiber-reinforced material selected from the group
consisting of plastics and the binder material containing
plastics, the flexural stiffness factor of each of the
- layers being calculated to a desired mechanical on the basis
15 of the board on the basis of the following equation:
E bc3 + 2E ~ bl2t + bt (-2-)
wherein SB is the flexural stiffness of the multi-layer
board, E is the modulus of elasticity, index c signifies the
core layer, c is the thickness of the core layer, b is the
j width of-the structural part, index t signifies the cover
i layer(s), and t is the thickness of the cover layer, and
¦ the layers having interfaces connected in a force-transmit-
ting manner. The cementitious binder material is illustrated
25 by such materials as cement, lime, gypsum, magnesite, and/or
mixtures of magnesia and magnesium chloride, and may be
fiber-reinforced. The force-transmitted connection between
the layers is pro~ided by the structure of the interfaces,
.. . . ... . . . . . .
(3) ~'~ 2~7Z~
by fibers projecting therefrom into the adjclcent interface,
by cllemical or vander Waals forces, or by an intermediate
layer connecting the interfaces of the core layer and the
cover layer, the intermediate layer consisting of at least
one hydrophilic natural or synthetic resin and/or the
cementitious binder material containing plastics.
In a preferred embodiment, the board comprises another
one of the cover layers, the core layer being disposed
between the two cover layers.
According to another aspect of this invention, the
multi-layer board is prepared by forming a core layer con-
sisting at least primarily of a cementitious binder material,
adjacently forming a cover layer of a fiber-reinforced
material selected from the group consisting of plastics and
the binder material containing plastics, superposing the
layers while the material of at least one layer is still wet,
and permitting the wet material to harden at or above room
temperature until the layers are connected in a force-
transmitting manner. The material of one layer may be wet
and the other rigid, or the materials of both layers may be
wet. The wet material may be premitted to harden to an
elevated temperature, such as under infrared radiation of in
a furnace. The concept of contacting the layers while we-t
means that the layer materials have not yet hardened. The
concept of contacting a dry or rigid layer with a wet layer
means that the material of a layer which has not yet hardened
is applied to a layer of hardened material.
The true connection of the layers is provided by an
(4) ~l~.Z37~Z
interface between the layers in which the layers actually
grow into each other or are mechanically locked to each
other, which is meant by the layers having interfaces
connected in a force-transmitted manner. In other words,
they form an integral multi-layered structure and no bond-
ing agent is used to adhere the layers to each other.
Rather, the connection between the layers is established
by making use of chemical bonding forces, such as van der
Waals forces, created by the materials of the layers and/or
the interlocking provided by projecting fibers forming
bridges between the layers. By suitably adjusting the
flexural stiffness of the board according to the equation,
the elongation, the modulus of elasticity and other mech-
anical properties of the individual layers, a substantial-
ly tension-free product is obtained which constitutes a
very advantageous laminated plate combining the advantages
; of inorganic materials with those of organic plastics.
The core layer has a high rigidity or stiffness and
there is no danger of aging since progressive hydration of
the aementitious binder material will actually improve it.
- Subsequent shrinkage and cracks caused thereby are avoided
and there is no decrease in rigidity because the evaporation
of the water is impeded.
The core has a resistance to deformation which imparts
to the multi-layer board the characteristics of a single-
layer board, or to a pipe made therefrom, that of homo-
geneous layer pipe. The cover layers are also load-carrying
,: .
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,
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and contribute to the hicJh quality of the board and enhance
it. I~eretofore, tlO sheet material of this type was known
which was so well adapted for the production of round bodies
and imparted to them the required ri~idity. seing resistant
5 to abrasion and wear, for instance by corrosion, the cover
layers operate as protective layers and simultaneously
provide a desired surface configuration.
They also absorb maxima of tensile forces. Using an
- intermediate layer will remove difficulties arising from
10 surface irregularities at the interfaces. An intermediate
~ layer transmits shearing forces, prevents the spreading
i of cracks and imparts great stability to the multi-board.
It is a connecting layer constituting an advanlageous
transition between the core an~ cover layers.
In contr~st to the cover layers in known multi-layer
boards, the cover layers in the boards of the invention
are load-carrying layers, whereby the load-carrying capabil-
ity of the board is increased. Since the board is a sub-
~^ stantially integral structure, it combines this mechanical
20 advantage with the advantages obtained by the use of
~ inorganic and organic structural materials.
; The multi-layer board of the present invention is far
superior in its mechanical properties to known laminates of
this type and will find particular application in the
" 25 construction industry, in water pipe systems, and in build-
ing tanks or like containers.
The binder material of the core layer may be cement,
.,~
,
3722
(~)
particularly a fast-hardenincJ type of cement, or a
magnesite type material, or a mixture of magnesia and
magnesium chloride. Other cementitious binder materials
useful for the board of the invention are burnt lime and
gypsum or liquid silicates which may be rapidly hardened
by the admixture of suitable additives. If desired, the
cementitious binder material may contain fillers of natural
or synthetic substances, such as sand, slag, bau~ite or
corundum and the like, as well as fibers of inorganic
substances, including glass fibers, asbestos fibers and/or
other mineral or metallic fibers, and fibers of organic
substances. It is also possible to add to the cementitious
binder material hydrophilic, self-hardening plastics, such
as a vinyl ester resin, a phenolic resin and/or other
15 plastics with or without suitable curing agents. Such
plastics additions to the cementitious binder material will
improve the extensibility of the inorganic binder material
matrix. Depending on the final purpose of the finished
board and the desired characteristics thereof, the matrix
20 may consist of plastics and the cementitious binder material
may be added thereto.
The cover layer comprises strong plastics and operates
not only as a protective layer but forms, in fact, an
integral part of the core layer in the multi-layer board,
25 the cover layer reinforcing the core at its weak points,
in addition to being resistant to abrasion, wear and cor-
rosion, as well as being capable to impart a desired surface
configuration to the board.
i~a
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(7) ~-2372Z
The ma-terials fornling the cover layer may contain the
same matrix material as thc cover layer. The matrix of the
cover layer may consist of curable plastics which may
contain inorganic fillers and/or carbon fibers. The fibers
may be filamen-ts, staple fibers, fibrous webs or rovings
arranged in parallel. Also, fibers may be arranged in the
core in one or several superposed layers.
If desired, the cover layers may consist of several
plies which differ from each other in their mechanical
properties. If the core is covered on both surfaces with
a cover layer, one of the cover layers may consist of
plastics binder material and the other cover layer may
consist of a cementitous binder material.
The favourable properties of the multi-layer board of
the present invention are further enhanced by the use of
intermediate layers between the core and cover layers, the
intermediate layer being comprised of hydrophilic plastics
which may be cold hardening or thermosetting resins of
the type of natural or synthetic elastomers. The inter-
mediate layer may have a thickness of about 0.1 to about5 mm or more. It may be reinforced with inorganic fibers,
fabrics or webs.
Such an intermediate layer does not only add to the
rigidity of the multi-layer board but it also transmits
shearing forces, reduces such forces, and impedes tears
and cracks, thus increasing the stability of the board and
shaped structures made therefrom. The intermediate layers
also operate as bonding layers which provide a favourable
interface between the core and cover layers.
3~7~
(~)
rhe stress in the intcrmediate layer clue to a ]oad on the
board is preferably adjuste~d to the parameters of the core
and cover Layers, the following tension value being desir-
able: ~ ~ c x bt
z
wherein ~z is the stress of the intermediate layer, ~c
is the stress of the core layer and ~t is the stress of
the cover layer.
The calculated stress value ~z, which is given by the
product ~z x Ez, is then to be adjusted so that ~z is high
with respect to -the extensibilities of the core and cover
layers, and Ez is small with respect to the other moduli of
elasticity.
~z is the strain in the intermediate layers and E is
lS the modulus of elasticity.
Obviously, the possibilities of varying the composition
of the layers are quite manifold and may be suitably
selected by those skilled in the art to match the desired
requirements of the finished board. In any case, it is es-
sential to keep in mind the desired bending resistance,
modulus of elasticity, elongation and other mechanical
properties. It will be possible to adjust the flexural
stiffness of the several layers of the board in each case
on the basis of the above equation.
As indicated, we have found that the multi-layer
board may be prepared wet-on-wet, i.e. the core layer with
a matrix of a cementitious binder material may not yet be
hardened when it is laminated with a cover layer of plastics
not yet polymerized. The process of the invention has over-
~.23~
(~)
come the well known di~Liculties of binding inoryanic and
organic materials in their still workablc condition, so
that it i5 now possible to particularly deposite orgallic
lay~rs in tlle workable condition on inorganic layers in the
workable condition, that is wet-on-wet and also wet-on-dry.
The accompanying drawing illustrates, by way of
example, some embodiments of a multi-layer board according
to the present invention.
FIG. 1 is a cross sectional view of a portion of a
flat board comprised of a core faced by two cover layers.
FIG. 2 is a like cross section of such a board further
comprising intermediate layers between the core and cover
layers.
FIG. 3 is a like cross section showing a modification
of the embodiment of FIG. 2.
FIG. 4 is a side view of a portion of a multi-layer
board constructed according to any of the preceding embodi-
ments but being arcuately curved and indented, rather than
extended rectilinearly.
FIG. 5 is an end view of such a board shaped into a
pipe.
FIGS. 6 to 9 are end views of variously shaped boards
incorporating the structu~e of the embodiments of FIGS. 1, 2
or 3-
The multi-layer board of FIG. 1 is comprised of core
layer 1 and two cover layers 2 and 3.
The board of FIG. 2 is comprised of core layer 10, a
cover layer 11 bonded to the core layer by intermediate
layer 12, and another cover layer 13 bonded to the core
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(10)
layer by intermediate layer 14.
In the modlfication of tl~is board s}lown in ~IC. 3,
the ~ore layer has two plies 20 and 22 wllerebetweel- there
extended a fibrous layer 21, cover layer 24 being bonded to
the t~70-ply core by intermediate layer 23 and cover layer
26 being bonded to the core by intermediate layer 25.
In FIG. 6, the board has a U-shaped section, in
FIG. 7 it has a truncated V-shape with longitudinal flang~s,
the board of FIG. 8 is corrugated, and FIG. 9 is a rectang-
ular hollow cross section. Other shapes may obviously befabricated.
The following specific examples further illustrate the
practice of this invention, all parts being by wei~ht unless
otherwise indicated.
~xample 1 (Board according to FIG. 1)
A flat one-square meter multi-layer board according to
FIG. 1 was produced in the following manner. Core 1 was
glass fiber-reinforced concrete having a thickness of 20mm
and consisting of a very rapidly hardening modified Portland
cement having a water cement value (ratio of water to cement)
of 0.4 and containing 5%, by volume, of alkali-resistant
glass staple fibers. Each cover layer 2 and 3 had the
following composition:
One hundred grams of a styrene-containing vinyl ester
resin (a polymerized adduct of an epoxy resin and acrylic
acid dissolved in styrene, with a styrene content of 45-50~)
were dissolved with two grams of 50~ methyl ethyl ketone
Z 37~;?d2
(11)
peroxide in a plasticizer, 0.125 g of cobalt octoate
~6% Co in styrene) and 1.2 g of dimethyl aniline (10% in
styrene) being added as catalysts and activators. A glass
fiber web weighing 450 g/m2was disposed in the vinyl ester
resin and the fiber-reinforced layer was cured on the core
after the latter has been aged for 48 hours.
The core layer was aged in a mold for 48 hours and the
two cover layers were applied to the aged, hardened core
layer before they were cured and were then cured in contact
with the core layer.
The parameters of the layers calculated according to
the above equation were as f~llows:
Modulus of elasticity of the cover layers,
Et = 260,000 kp/cm2
Modulus of elasticity of the core layer,
Ec = 200,000 kp/cm2
Thickness of the cover layer, t = 0.1 cm
Thickness of the core layer, c = 2.00 cm
Thickness of the structural part, b = 1.00 cm
SB = 190,707 kp/cm
EXample 2 (Board according to FIG. 2)
., .
The multi-layer board of FIG. 2 was prepared from the
sam~e preformed core layer and cover layers as in Example 1,
but bonded by interp~sed intermediate layers, each of said
;~ 25 intermediate layers 12 and 14 having the following composit-
ion:
Hundred parts of "Beckopox" (T.M.) VEP 22 ("Beckopox"
' ' '
~.237~2
(12)
being liquid or solid epo~y resin of Farbwerke lloechst,
Germany, whicll may be cured with the addition of commercial-
ly available curing agents or special "Beckopox" curing
agents and/or in conjunction with phenolic or amino resins
at ambient or elevated temperatures), 80 parts of
"Beckopox" special curing agent (also available from
Farbwerke Hoechst, as a variety of modified polyamines and
polyamide amines capable if imparting to the "Beckopox"
epoxy resins different curing conditions and properties of
the cured product), and 10 parts of alkali-resistant glass
fibers having a length of 5 to 10 mm.
The surfaces of the cover layers facing the intermediate
layer were roughened before the cover material was cured.
The components of the intermediate layer were mixed and the
mixture was deposited as intermediate layer 12 onto the
not yet cured but roughened cover layer 11. Then the pre-
formed core 10 was pressed onto the intermediate layer 12.
Then the following intermediate layer 14 was deposited
between the core 10 and the cover layer 13.
Modifications of the compositions were made by replac-
ing the rapidly hardening modified Portland cement by an
ordinary cement to which an accelerator was added, the
specific accelerating agent used being calcium chloride.
In either cement formulation, the vinyl ester resin was
replaced by an unsaturated polyester or any epoxy resin.
As special curing agents, "Beckopox" VEH 29 or VEH 14
were used, as well as the aliphatic polyamine "H 105 B"
sold by Rutgerswerke Meiderich, Germany (curing period 20 to
.
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Z37.~d2
(13)
40 hours at 25C). The "Beckopox" resins or curing agents
were replaced by epoxy resins and curing agents therefor,
sold by Ciba, of ~asle, Switzerland, with substantially the
same results.
Any suitable thermosetting plastics containing suit-
able curing agents may be used. Also, in addition to the
mentioned glass fibers, it is possible to use resin-covered
glass fibers, carbon fibers, graphite fibers, steel fibers
or organic fibers.
The residual contents of water in the cementitious
binders of the core layer had no perceptible influence on
the bonding quality of the intermediate or cover layers to
the core. No delamination occurred under mechanical stress
and the mechanical quality of the multi-layer boards was
excellent. Even higher qualities were obtained by adding
to the cementitious binder material of the core layer about
5 to lO percent by weight of the plastics used in the cover
or intermediate layers.
Example 3 (Board according to FIG. 2)
The composition of the core layer was as follows:
100 parts of magnesia, 6 parts of a urea-formaldehyde conde-
sation product, 142 parts of 20% aqueous solution of magne-
sium chJoride, 0.6 parts of glycerol or butyl glycol as a
plasticizer. All components were thoroughly mixed and the
mixture was placed into a mold for hardening.
The composition of the cover layer was as follows:
100 parts epoxy resin "Ciba (T.M.) X20", 90 parts of "Ciba
HT 907" epoxy resin curing agent, lO parts of "DY 040"
~a
~L~.Z37.~2
(14)
(an accelerator sold by Ciba), 1 part o~ Cib~'s DY 062
epoxy resin accelerator, 50 parts of hydrocarbon resin E
"Lithoplast") (T.M.) and lOO parts of a glass fiber web.
The components were mixed, the mixture was molded into a
plate and cured at a temperature 130C in 90 minutes.
"Lithoplast" is dark brown resin with a softening point of
100C and a melting temperature of about 120C to 140C,
having a molecular weight of 1000 to 2000. It is a hydro-
carbon resin of aromatic character which contains hydro-
carbons condensed in a ring, direct C-C bonds, secondary and
tertiary C-atoms, and 2 to 3 double bonds per molecule.
It is weakly polar.
The composition of the intermediate layer was as fol-
lows: 100 parts of Ciba's hydantoin resin, 100 parts of
Ciba's curing agent for hydantoin resin, 20 parts of glass
fibers and 1 part of polyester fiber unwoven web (KT 1751"
of the firm Freudenberg, Weinheim, Germany).
The intermediate layer composition is poured in the
liquid state over the shaped core and the formed cover
layer was placed thereover, and the laminate was subjected
to a temperature of 80C for two hours.
A water-soluble epoxy resin, with a suitable curing
agent therefor, was used instead of the hydantoin resin with
the same results.
Example 4 (Board according to FIG. 2)
The core layer had the following composition:
100 parts of Portland cement ("PZ 550"), 20 parts of mineral
aggregates having a maximum dimension of 2 mm, 50 parts of
water, 0.06 parts of liquefier, 6 parts of zirconium glass
3 ~ Z~
(15)
fibers, O.l parts o~ lO~ liquicl sodium silic~te.
~ \s is w~ nown, tlle nlineral ~gcJreclates use~l ill cerllcnt
include such materials as aranaceous quartz, ~3ranite,
diorite, quartz porphyry, basalt, quartzite, quart~itic
sandstone, other sandstones, dense limestone, other lime-
stones and blast-furnace slag, as well as mixtures thereof,
in grain sizes of 0.1 to 30 mm, preerably 0.8 to 8 mm.
Such aggregate additions may also be used with advantage up
to about lO~, by weight, in the cover and intermediate
layer materials, fine cement also having been used as an
advantageous additive in the intermediate layers.
The cover layer had the following composition:
lO0 parts of unsaturated, highly reactive polyester ("P 8"
of BASF) of medium viscosity, having a double bond value of
0.20, 0.3 parts of a cobalt acceleratox solution con-tain-
ing 1% Co, 2 parts of a catalyst paste (methyl ethylketone
peroxide), and lO0 parts of a roving fabric, the rovings
consisting of short staple glass fibers.
The intermediate layer had the following composition:
lO0 parts of "Beckopox" VEP 22 epoxy resin, 50 parts of
"Beckopox" VEH 14 curing agent, and l part of a polyester-
cotton fabric, the denier of the polyester fibers being 5
to lO mm.
The multi-layer board of FIG. 2 was produced wet-on-
wet from the core, intermediate and cover layers of Examples3 and 4, i.e. cover layer ll was the lowest layer and the
subsequent layer was superimposed thereon in the illustrat-
ed sequence.
(16)
Instead of t~le "P3" polyester, we used mixtures of
this resin w1th resin "E~ 200" of BASF, with the same result.
Also useful for this purpose were the alkali-resistant
product "A 410" of BASF as well as such resins as "W 41"
or "W 45" of sayer Leverkusen or similar resins of Hoechst.
By preparing the laminates in the wet~on-wet process,
i.e. by superimposing the layers in the given sequence
before the individual layers are hardened, the mechanical
properties and resistance to peeling of the board are con-
siderably improved. In this connection, it has provenparticularly useful to place a polyester or polyethylene
web or fabric in the intermediate layer, which contains wool
or cotton fibers, i.e. fibers which will absorb the resin
and produce a defined intermediate layer. Very good results
15 are obtained with three-dimensional fabrics.
The thicknesses of the layers may be freely chosen to
suit the end use of the multi-layer board, practical ranges
encompassing 3 to 300 mm for the core layer, 2 to 10 mm for
the cover layer, and 0.5 to 2 mm for the intermediate layer.
In the wet-to-wet process, several plies of the cover
layer may be applied to providing superposed plies of
plastics on the core layer and/or the core itself may con-
sist of a plurality of superpose plies. In the latter case,
as shown in FIG. 3, a fibrous layer may be disposed central-
25 ly in the core layer, which will prevent any propagation of
cracks from ply to ply.
In providing multi-ply cover layers, the outer ply
composition may be so selected as to make it resistant to
chemical reactions and/or this ply may be mixed with sand to
(17) ~37~z
make the board useful in an abrasive environment. The
surface layer of the outer cover layer in a multi-ply
cover layer can be formed of a thermoplastic material, such
as polyethylene, polypropylene, polyvinyl chloride, poly-
vinylidene fluoride, or other thermoplastics or also poly-
imides. For a good adhesion between the surface layer and
the adjacent thermosetting resins, i.e. the resins of the
cover layers ~Example 3), it is preferred to press a thin
fibrous reinforcement - in the main glass fiber - into the
thermoplastic material so that upon curing a strong
bonding is obtained. With polyvinyl chloride a known
binder may be used for applying the thin glass fiber fabric.
With such surface film or layer of the above thermo-
plastics an excellent corrosion-resistant layer is obtained.
At the same time, said thermoplastics - which may have a
thinkness of preferably 0.1 to about 10 mm - are useful in
sealing shapes, as shown in Figures 4 to 9. As illustrated,
the board may be shaped into any desired form, including
tubes. They may be molded into the desired shapes at the
time of manufacture and various methods may be used in pre-
paring tubes or pipes, including a centrifugal method in
which layer after layer is consecutely applied in a continu-
ous process from nozzles supplying the compositions of the
respective layers. The multi-layer tube is then cured by
means of warm air or infrared radiation, at a maximum
temperature of about 80C.
The tube may also be produced by winding the cover
layers over the core layer which is produced on a mandrel
72~2
(1~)
which receives a ribbon of the core layer composition wound
about the mandrel.
~ fter the multi-layer board has been finished, it
may be subjccted to desired sur:face treatments, for
instance a plastic coating and/or polishing.
~2a
