Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 ~ 5867~
INORGANIC FOAM
1. MD 31126
This invention relates to inorganic foams
and in particular to rigid foams comprising a
clay mineral. In particular the invention
relates to inorganic foam materials comprising a
S plurality of foam prills derived from one or more
layer minerals and a method for making such
products; inorganic foam materials comprising
certain layer minerals or a mixture of two or
more layer minerals and a method for their
production; uses of the inorganic foam products;
and an intermediate product for use in the
production of inorganic foam prod~ucts.
The layer minerals are naturally-occurring
forms of silica and are phyllosilicate materials,
i.e. they have a layer-structure. Included
! ~ within the term layer minerals are, for example,
vermiculite, kaolinite and other clay minerals,
montmorillonite, sepiolite, attapulgite, illite
and saponite.
The clay minerals occur in clays as particles
of the order of a few microns diameter which are
aggregates or agglomerates of small crystalline
units of the mineral of sub-micron size. Kaolin-
type clay is essentially an aggregation of
,; ~
fi7~ .
2. MD 31126
. . .
book-shaped units of sheets of the clay mineral
kaolinite; it is to be understood that as used
herein the term kaolinite includes kaolin-type
clays, ball clays, fire clays and chin~ clays in
which kaolin minerals~OCCUr in nature although
such clays may not comprise pure kaolinite. Fire
clays are a mixture of kaolinite and illite.
The layer minerals are well known and some at
least are used extensively in industry. Kaolinite
and kaolin-containing clays are used extensively
in numerous industries, for example in the ceramics
industries (the major usage) for the manufacture of
white-ware, porcelain and refractories, and as a
filler for paper, paints, adhesives, plastics and
rubbers. Vermiculite is used, commonly in heat-
exfoliated form (exfoliated vermiculite) as
loose-file insulation material, in bound form as
slabstock or boardstock for insulation and fire
protection applications, and ion Agricultrual
Applications. Delaminated vermiculite, by which
is meant vermiculite which has to be delaminated
by chemical treatment followed by swelling in
water and milling or grinding, has been proposed
for use in making sheet-like materials or papers,
as a coating material for substrates and for
making rigid inorganic foam products for insulation
and fire protection applications. Delaminated
vermiculite foam and uses thereof are described,
for example , in our United States Patent Specification
No 4 130 687. Montmorillonite is used extensively
in industry as a filler for paper, adhesives and
paints. Sepiolite is used extensively in the
ceramics industry.
-
1 ~58679
3. MD 31126
Rigid materials made from kaolinite, e.g
whiteware, porcelain and refractories, are
dense, brittle materials produced by processes
involving a firing or sintering operation.
Although kaolinite itself is a poor conductor
of heat, the high-density rigid materials
hitherto produced from it do not exhibit good
insulation properties. Because of their high
density (and hence heaviness), brittleness
and unexceptional insulation properties, products
made from kaolin - containing clays are not used
to any significant extent in thermal-insulation
or fire-protection applications. Rigid materials
made from heat-exfoliated vermiculite tend to be
dense (heavy), rather brittle materials and
whilst they are used in industry for the fire-
protection of structural steelwork they are not
used extensively as insulation materials. Rigid
foam materials made from delaminated (as opposed
to heat exfoliated) vermiculite are lightweight
and exhibit good fire protection and insulation
properties, but are difficult to make in large
sizes. Because such products tend to crack and
deform extensively upon drying, they are difficlt
to produce in the form of slabstock or boardstock
in sizes greater than about 30 cm square and 3 cm
thickness.
In a first embodiment, the present invention
resides in the discovery of a low-density product
form of layer minerals which is both lightweight
and exhibits good heat-insulation and fire
protection properties, and is readily produced in
the form of slabstock or boardstock of large
. ..
-
.
` 1 1586~9
4. MD 31126
sizes, for example up to 3 m x 1 m x 10 cm
thickness.
According to a first embodiment of the
invention there is provided a rigid inorganic
foam product preferably having a density of
less than 0.4g/ml and more preferably less than
0.2g/ml, comprising prills of one or more layer
minerals, each prill being of cellular structure.
By the term "prills" as used throughout this
specification we mean particles, beads, pieces or
small lumps of foam having an essentially continuous
: cellular structure in which the walls of the
cells are constituted by the layer mineral(s)
particles, although the term is not intended as
implying any particular size, shape or configur-
ation of the pieces of foam. Typically, and as a
guide only, the prills will be cylindrical or
essentially spherical pieces of foam of maximum
dimension below about 5 mm, for example from 0.5
to 5 mm.
; As will be described more fully herein-
after, the inorganic foam products are made by
.~ assembling the prills of cellular structure into
desired product forms such as slabstock or
- ~ 25 boardstock, such that the products have an
~ ~ :
essentially cellular structure although the true
~: cellular structure may not be contlnuous throughout
the product.: It i9 to be understood that the
term "rigid inorganic foam product" as used
: : 30 throughout this specification includes such
: products wherein the cellular structure is not
truly continuous; thus for example the term
: includes products wherein the prills are bound
together by means of an adhesive or by mutual
~. .
, ~
:.
I 158679
5. MD 31126
attraction and voids exist between prills within
the product structure.
The density of the foam products of the
invention is normally below 0.25 g/ml, and may be
as low as 0.06g/ml for especially lightweight
products. Typically, the products will have a
density in the range of 0.08g/ml to 0.15g/ml.
By the term "rigid foam" as applied to the
prills we mean a material having structural
integrity which is a two-phase dispersion of gas
in a solid matrix which is an essentially continuous
cellular structure, and by the term "rigid
inorganic foam" as applied to the prills we mean
a rigid foam which is essentially made of inorganic
material, though the presence of small amounts
of organic materials as impurity in the layer
mineral(s) or by deliberate addition (for example
an organic surfactant used in production of the
foam as described hereinafter) is not excluded.
Moreover, by the term "rigid inorganic foam
product" as applied to the products comprising
an assembly of prills, we do not exclude the
presence of a small amount, e.g up to 20% of an
organic material present in the prills or added
deliberately for example as a binder for uniting
the prills into a self-supporting structure.
The embodiment of the invention described
hereinbefore is a product of essentially cellular
structure comprising prills of cellular structure
made of one or more layer minerals. A further
embodiment of the invention is a product of true
cellular structure derived directly from a
suspension of certain layer minerals or mixtures
of layer minerals.
.
; ~
. ~
~ lS86~9
- 6. ~D 31126
.
- According to a second embodiment of the
invention there is provided a rigid inorganic
foam of cellular structure comprising a mixture
of layer minerals and preferably having a density
of less than 0.4 g/ml, more preferably less than
0.2 g/ml.
There is provided also a rigid inorganic
foam of cellular structure comprising montmorillonite
and preferably having a density of less than 0.4
g/ml, more preferably less than 0.2 g/ml.
There is provided in a further embodiment of
the invention a rigid inorganic foam of cellular
structure comprising sepiolite and preferably
having a density of less than 0.4 g/ml, more
preferably less than 0.2 g/ml.
There is also provided a rigid inorganic foam
of cellular structure comprising a ball clay
and/or a fire clay and preferably havi~g a
~ density of les than 0.4g/ml, more preferbly
: 20 below 0.2g/ml.
The foam product of the present invention,
whether in the form of prills or as direct
products, are made by a process involving incor-
: porating a gas in a suspension (or dispersion) of
:~ 25 a layer mineral in a liquid medium and a further
: feature of the invention resides in a process for
the production of a rigid inorganic foam of
; cellular structure comprising one or more layer
minerals which comprises gasification of a
suspension of one or more layer minerals in a
liquid medium containing a surface active agent
to form a stable wet foam or froth and removal of
at least part of the liquid medium from the
froth.
;: `~ :
.
::
`~ I 158679
7. MD 31126
. .
By the term "stable wet foam or froth"
we mean a gasified suspension which does not
collapse upon standing or upon removal of liquid
from it, and in particular which upon standing
does not collapse (no substantial reduction in
foam-height) within a period of 10 minutes. As
is discussed in more detail hereinafter, the
stability of the gasified suspension is dependent
mainly upon the particular surface active agent
used to form it and we have found that whilst
some surface active agents, for example fatty
amines and saponin, enable a froth to be produced
the resulting froth is not stable and collapses
within a few minutes; production of such an
; 15 unstable gasified suspension is not included
within the scope of the present invention.
As stated, the rigid foams are made by
a process involving gasification of a suspension
of one or more layer minerals and removal of the
liquid medium from the resulting froth. In the
case where the foam is produced in the form of
prills, the gasified suspension or froth may be
divided into droplets or wet particles before
:
removal of the liquid medium. Division of the
gasified suspension or froth into particles or
wet droplets may be effected in a variety of
ways, for example by spraying the froth through a
nozzle or other orifice, extrusion of the froth
through orifices in a belt or any other known
technique for dividing suspensions into droplet
or particle form. The wet particles or droplets
should be at least partially dried before they
have the opportunity to re-combine. Dry or
partially dry prills may be produced using a
:
- `~ I 1S8679
~. MD 31126
spray-drying apparatus. Partially dry prills may
be further dried by heating them under conditions
whereby they are prevented from combining, for
example in single layers or agitated beds such as
a fluid bed. Prills may also be formed by
shaping the froth into fibre-like lengths, drying
it, and chopping the dry or partially dried
material.
The density of the rigid foams (prills or
directly extruded products) produced by the
process of the invention may be varied in
; several different ways, for example by inOEorporat-
ing different amounts of gas into the suspension,
by using blowing agents and by varying the solids
content of the suspension. The solids content of
the suspension affects the viscosity of the
suspension, as also do the particular surface
active agents used and the temperature at which
gasification is effected, but in general increas-
ing the solids content of the suspension resùlts
in an increase in the density of the foam produced
from the suspension. Typically, the solids
content of the suspension will be from 10% to 60
by weight of the suspension, preferably from 20%
to 40% by weight. A deflocculating agent, for
example sodium tripolyphosphate may be added to
enable suspensions of high sollds content to be
produced.
The suspension of the layer mineral will
; ~ usually be aqueous and in particular will be a
suspension or dispersion of the layer mineral
particles in water, preferably distilled or
de-ionised water. Layer mineral are generally
readily suspended or dispersed in water to form
suspensions exhibiting colloidal properties. The
liquid medium of the suspension may if desired be
, .
.
.
-::
~ - ~
:~ ' ~ ` ; '
.
" I 15867~
9. MD 31126
a mixture of water and a water-miscible solvent
such as alcohol. If desired, however, the liquid
may be an organic liquid. In converting the
suspension into a froth and thereafter into a
rigid foam, it is necessary to incorporate a
surface active agent in the suspension and this
agent will normally be added to the water prior
to or during formation of the suspension. It is
to be understood that in the case of the layer
mineral vermiculite, delamination of the
mineral may result in a surface active agent
being incorporated in the delaminated material
and a separate agent may not be required. In
addition to a surface active agent, other agents
such as fillers, compressive strength improvers,
water-stability improvers and deflocculating
agents may be incorporated in the suspension
prior to, during or after production of the
. suspension.
Any surface active agent may be used which
upon gasification of the suspension results
in a wet foam or froth which is stable, by which
is meant does not collapse upon standing for a
period of at least 10 minutes or upon removal
from it of the liquid medium. Anionic, non-ionic
or cationic surface active agents may be used
provided they result in a stable froth. The
suitability of a surface active agent for
use in the process is thus readily determined
by simple experiment merely involving determin-
ation of whether the agent enables a wet foam or
froth to be created from a suspension of say 30%
solids content and if so whether the froth is
stable. As a guide, a wet foam or froth which
.
.
~ 158679
10. MD 31126
upon standing does not collapse (e.g. no sub-
stantial reduction in foam - height is observed)
within a period of 10 minutes, preferably within
a period of 1 hour, will in general be suitable
for drying to yield a rigid foam according to the
invention. For purposes of the test, the surface
active agent under test may be used in any
desired amount, or at various concentrations
provided that it does not flocculate the foam;
in general a large amount of the agent, for
example 2% by weight of the solution, will
provide an indication in an initial test as to
whether the agent is worth further testing.
Surface active agents which can be used at
low concentrations are preferred, though this is
not critical. It has been observed that a
surface active agent which provides a stable foam
from a suspension of one layer mineral may not
provide a foam of comparable stability from a
suspension of another layer mineral or of mixed
minerals such as a mixture of kaolinite and
delaminated vermiculite. Equally, a surface
active agent which fails to provide a stable foam
from a suspension of one layer mineral may
nevertheless provide a stable foam from a sus-
pension of another layer mineral or of mixed
minerals. For example the surface active agent
n-butyl ammonium chloride does not yield a
particularly stable foam from a suspension of
kaolinite alone but does yield a stable foam from
a suspension of delaminated vermiculite or of a
50:50 mixture by weight of kaolinite and delamin-
ated vermiculite. This must be born in mind when
;; testing the suitability of a surface active
agent, i.e. the test should preferably be
. ~ ,
''
, . .
- . . -
:. ~ . - - . ,
' . ~
1 158679
- 11. MD 31126
performed using the actual suspension it is
desired to gasify and later dry to a rigid
foam.
In respect of the surface active agent it has
been observed also that those surface active agents
which most readily produce a foam or froth do not
necessarily produce the most stable froth. In fact
we have found th~at, in general, surface active agents
which produce a~froth only with some difficulty (e.g.
after prolonged whisking of the suspension) tend to
produce the more stable froths. The ease with which
a surface active agent enables a froth to be created
is not, however, conclusive evidence as to the
suitability of that agent for use in the process of
the present invention and it is to be understood that
the invention is not limited to agents of low foaming
characteristics.
The amount used of the surface active agent
may vary within wide limits, depending for
example upon the solids content of the suspension,
the particular layer~mineral and surface active
agent, the particular gasification technique
employed and the temperature of gasification. As
a guide the amount of surface active agent will
~- 25 typically be from 0.1% to 5% by weight based on
the weight of the layer mineral in the suspension
to be gasified. Since the surface active
~ agent remains in the rigid foam upon removal of
; liquid~from the froth and its presence in the
rigid foam is undesirable, we prefer to use the
minimum possible amount of surface active agent
consistent with production of a stable froth
which does not collapse upon removal of liquid
from it.
1.1S8679
12. MD 31126
Gasification of the suspension may be effected
in a variety of ways, for example by release of
gas or vapour in the suspension or by mechanically
entraining a gas in the suspension by rapid
agitation of the suspension. The gas will
normally be one which is inert to the (aqueous)
suspension for example air, nitrogen, carbon
dioxide, a hydrocarbon or a chlorofluorocarbon.
Mechanical entrainment of the gas in the suspension
can be achieved, for example, by rapid churning,
beating or whisking of the suspension.
Release of gas or vapour in the suspension can be
achieved by heating the suspension, preferably rapidly,
to release bubbles of the gasified liquid medium
(steam where the liquid medium is aqueous) or to
release bubbles of the vapour of a substance (blowing
agent) deliberately incorporated in the suspension as
a source of vapour for gasification of the foam. The
blowing agent may be, for example, a hydrocarbon,
chlorocarbon, a fluorocarbon, a chlorofluorocarbon
; or a source of carbon dioxide. The suspension
can be gasified by subjecting it to electromagnetic
radiation having a frequency in the range of from
104HZ to 1012HZ.
Production of the suspension, and gasification
of the suspension in the cases where gasification
does not involve a heating step, conveniently can be
carried out at room temperature, though higher or
lower temperatures may be employed if desired.
The removal of the liquid medium from the
gasified suspension will normally be mainly by
evaporation usually induced by heating the gasified
suspension. The rate of removal of liquid from the
froth can be controlled, for example by controlling
:
,~
I 15867~
13. MD 31126
the temperature of the froth or by use of a
drying vessel having provision for humidity
control, such that too rapid drying of the foam
leading to cracking or bowing of the foam is
avoided. If desired the wet foam may be allowed
to stand at room temperature for a prolonged
period, for example several days, to allow the
foam to dry out and attain a rigid structure.
Normally, however, the froth will be heated,
after shaping, at temperatures up to about
90C to remove the liquid medium. Control of the
drying conditions may be important in the production
of products such as slabstock or boardstock
directly by extrusion of the gasified suspension
and drying, but is less important in the production
of prills where rapid drying is possible for
example at temperatures up to 200C or even higher.
Rigid inorganic foams comprising layer
minerals tend to be soft and of low compressive
strength. Depending upon the particular layer
; mineral, the strength of the foams can be improved
by incorporating therein a compressive strength
improver and/or by heating the dry foam to sinter
it. Incorporation in mixed-mineral foam, e.g. by
incorporation in the suspension prior to gasific-
ation, of vermiculite lamellae (delaminated
` ~ ~ vermiculite) results in general in an increase in
the compressive strength of the foam. Except in
the case of wholly vermiculite foams, strong
: ::
foams are obtained by sintering the dry, rigid
foam obtained~by drying the gasified suspension,
for example by heating the dry foam at a temper~
ature of up to 1000C or even higher. Sintering
of the foam may result in densification of the foam
.
.
I 158679
14. ~ID 31126
but the sintered foam retains a cellular structure
and remains a lightweight material. Sintering of
mixed vermiculite/other mineral foams may result
in an increase or a decrease or very little
change in the density of the foams, depending
upon the proportion of vermiculite in the foam
and the weight of material lost upon heating the
foam at sintering temperatures.
Sintered layer mineral foams are included
within the scope of the present invention, as is
their process of production.
Unsintered rigid foams comprising layer
minerals exhibit little resistance to degradation
by liquid water and we prefer to subject the
foams to a treatment to improve their water
stability. For instance, the foams can be
water-proofed by incorporating a silicone polymer
precursor therein and subsequently creating
within the foam acidic conditions under which
polymerisation of the precursor occurs with
the formation of a silicone polymer in the
- foam. For example, sodium methyl siliconate can
be incorporated in an aqueous suspension of
kaolinite prior to or during gasification of the
suspension and the resulting foam whilst still
wet can be treated with an acidic gas such as
carbon dioxide gas to create the acid conditions
necessary for polymerisation of the siliconate to
yield a silicone polymer. Instead of treating
the foam with an acidic gas during the drying of
the rigid foam in the foam-making process, the
foam may be fully dried and then subsequently
wetted out with water to the desired extent. If
,
. .
, .
~,
- : ~
1,.158679
--- 15. MD 31126
desired, instead of a deliberate treatment with
an acidic gas, the wet foam may be allowed to
stand in air for a prolonged period
whereupon carbon dioxide in the air will be
absorbed to provide the necessary acidic conditions
in the foam. Sintered foams, where a silicone
polymer incorporated before sintering would be
destroyed, can be water proofed with a silicone
polymer after sintering.
The relative proportions of the layer minerals
- in suspension of mixed minerals, and hence in the
resulting rigid foam, may vary within wide
limits, depending for example upon the compressive
strength and thermal insulation properties
required in the rigid foam. The foams may
comprise, for example kaolinite or a kaolin-
containing clay and vermiculite in the relative
proportions of from 90:10 to 10:90 by weight. In
general, increasing the relative proportion of
vermiculite lamallae in the rigid foam results in
an increase in the compressive strength of the
rigid foam but also an increase in the thermal
insulation coefficient (R-value) of the rigid
foam,
Rigid foams of cellular structure comprising
~:~ lamallae of vermiculite and their production
by gasification of a suspension of vermiculite
lamellae to form a froth, extrusion of the froth
~- and removal of the liquid medium from the froth
are described in our Canadian Patent No. 1091862,
which issued December 23, 1980 and the corres-
; ponding United States Patent No. 4130687 which
- issued December 19, 1978 in which the production
of suspensions of vermiculite lamallae is also
described .
- , ~ ... _ .. . ..
.
~ 1S~6~
16
The rigid mixed-mineral foams of the present
invention containing delaminated vermiculite are
conveniently derived from a suspension of verm-
iculite lamallae by incorporating another layer
mineral in the suspension prior to gasification
thereof. As is described in aforesaid United States
Patent Specification No 4 130 68~, the suspension
: 10 of vermiculite lamellae will usually contain a
: surface active agent such as n-butyl ammonium
chloride used in production of the suspension so
that incorporation of another layer mineral
in the suspension provides both the suspension
; 15 and the surface active agent necessary for the
production of rigid foams as described herein.
Preferably mixed mineral foams containing
' vermiculite contain an agent for improving
. ~he compressive strength and water stability of
rigid foams comprising only vermiculite lamellae.
.~ The enhancement of the compressive strength and
water stability of vermiculite foams by incorpor-
ation of a compressive strength improver which is
~ a solid particulate material having a basic
:^. 25 reaction in water is described in our United
:~ States Patent No. 4,269,628 which issued
: ~,
:~ : May 26, 1981. As is described in the afore-
said United States Patent No. 4,269,628,
the preferred compressive strength and water
stability improver is particulate magnesium
oxide, and we prefer to incorporate particulate
;~ magnesium oxide in the mixed-mineral (containing
~ ~ vermiculite) foams of the present invention. As
1 158679
17. MD 31126
described hereinbefore, the compressive strength
of the mixed mineral foams can alternatively be
enhanced by sintering the foam.
The suspensions containing a surface active
agent used to form the rigid mixed layer mineral
foams of the invention are provided according to
a still further feature of the present invention,
including the following suspensions of mixed
layer minerals:
(i) a suspension in a liquid medium containing
a surface active agent of vermiculite
lamellae and one or more other layer
mineral.
(ii) a suspension in a liquid medium containing
a surface active agent of vermiculite
lamellae, one or more other layer minerals
and a compressive strength and water
stability improver, e.g. magnesium oxide,
(iii) a suspension as (i) or (ii) above
additionally containing a deflocculating
; agent, for example a tripolyphosphate, and
(iv) a suspension in a liquid medium contain-
ing a surface active agent of two or more
layer minerals.
Preferably the liquid medium in each of
the suspensions is aqueous and in particular
is water. Preferably, also, in each of the
suspensions of mixed layer minerals, one of the
layer minerals is kaolinite.
; 30 Each of the above suspensions (i) to (iv)
; can be dried as also can similar suspensions free
fromm surface active agents, for example by
spray-drying, to yield a corresponding free-flow-
ing, dry-powder material and such materials are
.
-
..
,
,~
~ 158679
18. MD 31126
also provided according to the invention. These
dry-powder materials are readily re-dispersed in
a liquid medium, particularly water, to form a
suspension suitable for conversion into a rigid
foam by the process described herein. In the
case of dry-powder materials containing magnesium
oxide, it is preferred to dry a suspension free
from magnesium oxide and to add dry magnesium
oxide to the dried suspension. It will be
appreciated that the dry powders according to the
invention may also be produced by mixing dry-powder
comprising vermiculite lamellae with another
powdered layer mineral ~optionally mixed with
sodium tripolyphosphate) and optionally with
dry, powdered magnesium oxide.
The rigid foam products provided by the
invention, whether made wholly of one layer
mineral or comprising mixed minerals, for example
kaolinite and vermiculite,.are heat-resistant
and heat-insulating materials which are useful
in a wide variety of fire-protection and thermal
insulation applications. The products may be
produced as slab stock or board stock for use
in subsequent fabrication processes, for example
for formation of laminates with sheets of a
wide variety of materials such as wood, veneers,
asbestos, mica, plastics, vermiculite board
(foamed or made from heat-exfoliated vermiculite
granules), glass fibre scrim impregnated with
vermiculite and polymers. Such laminates from
useful decorative construction panels for the
building industry. Slab stock may be used
directly, without lamination to another material,
for example for cladding wood, cement or steel
-. -
.:
.
~.~58679
19. MD 31126
construction elements to provide a fire-protection
barrier and heat-insulation layer around the
elements, and as roofing boards, lining boards
and ceiling tiles.
The rigid foams may be subjected to high
temperatures, for example up to 1000C for
prolonged periods without disintegration although
prolonged exposure to high temperatures results
in embrittlement of the products. Press-moulding
of the surface of the rigid foams after or during
drying thereof produces a smooth surface which
may be sculptured for decorative effect if
desired.
The rigid foams, if desired in the form of
a laminate with another material, may be used in
fire-doors or fire-barrier partitions. In the
form of prills they may be used as loose-filling
for cavities, voids and the like.
The prills of foam may be glued together
to form the desired products. A variety of
inorganic and organic (but preferably inorganic)
; adhesives may be used to glue the prills together
to ~ake slab stock to form laminates from the
rigid foam or to apply slab stock as a coating or
cladding to substrates such as wood, cement and
steel construction elements. Slab stock of
thickness up to 10 cm or more can be produced
by cementing together prills of dry foam.
Examples of inorganic binders which may be used
are phosphoric acid, aqueous solutions of
phosphates and silicates cements and plasters.
Eamples of organic binders which may be used are
aqueous emulsions of vinyl and vinylidene polymers
and copolymers.
1 158679
20. MD 31126
Prills of the foams, especially those com-
prising wholly or partially delaminated vermiculite
(vermiculite lamellae) can be dry-pressed into
products having structural integrity without the
need to employ an adhesive or binder. Preferably
products obtained by dry-pressing prills are in
the form of laminates wherein the prill product
is faced with or sandwiched between layers, for
example of paper or sheet. Whilst products may
; 10 be formed by dry-pressing the prills we preer to
moisten or dampen the prills before pressing them
into products.
The wet foam (i.e. the gasified suspension)
and the suspension prior to gasification may be
used as a binder in cementing together rigid foam
prills. For use as an adhesive, we prefer that
the wet foam or suspension should comprise
or contain vermiculite lamellae and preferably
an appreciable proportion of vermiculite lamellale,
for example at least 50% by weight of the total
solids content of the wet foam or suspension.
According to one embodiment of the invention
for making prill products,there is provided a
process for the production of shaped articles
from prills of rigid inorganic foam comprising
one or more layer minerals, which process
comprises applying a solution containing phosphate
ions or silicate ions to the prills and drying
the resulting wet prills whilst they are retained
in the desired shape.
The solution containing phosphate ions may
be a phosphoric acid or a solution of a phosphate
salt. Organic and inorganic phosphates may be
.,
~ ~ '
:
- 1 158679 ` `; . ~
21. MD 31126
.
used, including complex phosphates, although
since the shaped article produced by the process
is desirably wholly or at least essentially
inorganic we prefer to use inorganic phosphates
or a phosphoric acid. The preferred solution
containing phosphate ions is orthophosphoric
acid. Sodium silicate solution is the preferred
~solution containing silicate ions.
In carrying out the process of the invention,
prills of foam are assembled into the shape of
the desired product, for example a slab or board,
and~whilst in this shape are dried in the presence
of a solution containing phosphate or silicate
ions~such that after drying the prills are
~ glued together and the shaped article formed from
them has structural integrity. The solution may
be applied to the individual prills before the
latter are assembled into the desired shape or
the solution may be applied to the assembled
prills whilst they are retained in the desired
configuration to produce a shaped article.
Alternatively the solution may be applied to the
prills, before or after assembly of the prills
into the desired shape, by creating on the prills
a dry coating of a phosphoric acid, phosphate
- salt or silicate and subsequently wetting the
coated prills to create the solution containing
phosphate or silicate ions.
It is preferred to apply the solution to the
; 30 individual prills prior to assembling the prills
into the desired shape. It is especially preferred
to produce prills having thereon a dry coating of
~ a phosphoric acid, phosphate salt or silicate and
:.
,
58679
22. MD 31126
which are readily stored and transported, and
which simply require wetting by a fabricator of
shaped articles before or after assembly of the
prills into the desired shaped articles. It is
usually more convenient in practice to wet the
individual prills prior to assembly into desired
shapes than to wet the prills after assembly, and
it is also easier in this way to control the
amount of solution applied to the individual
prills and to ensure a uniform concentration of
the solution throughout an assembly of the
prills.
Prills of a layer mineral foam having thereon
a dry coating of a phosphoric acid, a phosphate
salt or a silicate are provided according to a
preferred feature of the invention. Such coated
prills are readily prepared by applying a phosphoric
acid or a solution of a phosphate salt or silicate
to the prills and drying them by evaporation of
the liquid medium from the coating under conditions
whereby gluing together of the prills is avoided;
re-wetting of the dry, coated prills recreates
the solution containing phosphate or silicate
ions on the prills. Drying of the prills may be,
for example, by fluid-bed drying.
The amount of the solution containing phos-
phate or silicate ions and the concentration of
ions in the solution applied to the prills
may vary within wide limits but affect the
physical properties of shaped articles formed
from the prills. In particular the amount of
solution applied and the concentration of the
solution affects the density of the shaped
products; in general increasing the amount of a
.
.: ~
- ;-
I 158679
23. MD 31126
particular solution applied to the prills will
result in an increase in the density of shaped
products made from the prills and likewise
increasing the concentration of ions in the
solution will result in an increase in the
density of shaped products made from the prills.
Another physical property of the products
which may be affected by the amount and concen-
tration of the solution applied to the prills, at
least in the case of phosphate solutions,
the strength of the products. We have observed
that as the amount of phosphate ions (at least
the amount in the surface region of the prills)
increases there exists a peak in the strength of
the product formed from the prilrs and that
increasing the amount beyond that which provides
the peak, either by increasing the amount of
solution applied or the concentration of the
solution, tends to result in a decrease in the
strength of the products.
The amount of solution applied to the prills
may depend to some extent upon the method by
which the solution is applied, but for a particular
application technique the optimum combination of
amount of solution applied and solution concen-
tration is readily determined by simple trial
and experiment. Application of the solution to
the prills may be by any convenient technique,
for example immersion, brushing or roller coating,
but by far the preferred application technique is
spraying. Spraying has the advantage of most
readily enabling control to be exercised over the
amount of solution applied to the prills and in
particular enables the prills to be surface
:
'
~ 158679
24 . MD 31126
coated with minimum impregnation of the prill
structure by the solution. Layer mineral foam
prills are generally highly porous structures
which readily absorb liquids and unless steps are
taken to avoid it any solution applied to the
prills will rapidly penetrate the structure to
the interior of the prills. This is undesirable
in the present invention from the standpoints of
the density of products made from the prills and
the thermal conductivity properties of such
products. A spraying technique operated in a
controlled manner to apply the minimum amount of
solution necessary to surface-coat the prills is
therefore preferred.
In addition to applying the minimum amount
of solution required to surface-coat the prills,
we prefer to employ fairly dilute solutions of
the phosphoric acid or phosphate or silicate salt
so as to again restrict the amount of phosphoric
acid, phosphate or silicate applied to the
prills. As a guide we prefer to employ solutions
of concentration from 5% to 20% by weight,
especially solutions of concentration from 7% to
15% by weight. In the embodiment of the invention
2S in which dry, coated prills are wetted out with
water for formation into products, the amount of
water added will normally be about 60-70% by
weight of the prills.
The wet prills, either as individual prills
or assembled into shaped products, may be allowed
to dry at ambient (room) temperature but usually
will be heated to increase the rate of drying.
The temperature employed is not critical and may
be up to several hundred C if desired. In
:
. ~ .. -~ .
1 15~679
25. ~D 31126
general the wet prills will be heated at about
the boiling point of the liquid to be removed
when drying shaped products made of the wet
prills, for example at about 90C to llO~C where
the liquid is water, but for drying individual
prills there may be an advantage in employing
higher temperatures, for example up to 600C.
The physical properties of the dry coated prills,
and dry shaped products made from them does not
appear to be dependent upon the temperature used
to dry the coated prills or the shaped products.
The process may be produced by gasifying a
- suspension of vermiculite lamellae to fo~m a
froth and removing the liquid from the froth
under conditions such that the rigid foam obtained
is in the form of prills or a product form which
can be converted to prills. An example of a
suitable product form for conversion into prills
by chopping e.g. using a gas jet is a fibre-like
extrusion of froth which may be chopped into
prilIs before drying or dried and then chopped
into prills. A wide variety of direct prill-form-
ing techniques may be employed, for example
spray-drying, belt-extrusion in which the froth
is caused to pass through holes in a belt to form
The chemical delamination of vermiculite
to produce suspensions, usually aqueous suspensions,
of vermiculite lamellae suitable for conversion
into rigid vermiculite-foam prills is known;
delamination processes are described for example
in United Kingdom Patent Specifications Nos
1,016,38S; 1,076,786; and 1,119,305; and by
Baumeister and Hahn in "Micron" 7 247 (1976).
Prills of foam made from the suspensions produced
-:
.
, .
.
`` I 1~8679 ` -~;
26. MD 31126 -
.
by any of the known processes may be employed in
the present invention.
For use in the preparation of foam prills
it 1s preferred to employ suspensions of vermiculite
lamellae which have been wet-classified to remove
all particles of size greater than 50 microns,
preferably 20 microns and which contain a high
proportion, for example 40% to 60% by weight, of
lamellae of size below 5 microns.
~ The strength of the shaped products of the
invention and particularly their flexural strength
can be improved by laminating the layer of bonded
prills with a surface layer of a flexible sheet
material such as paper (e.g. Kraft paper or
vermiculite paper or glass fibre scrim impregnated
with vermiculite) or metal strip or foil. Such a
facing layer or facing layers may be applied by
conventional laminating techniques to pre-formed
foam articles but for convenience the facing
; 20 layer(s) is applied during production of the foam
article. Thus, for example, slabs or boards can
be produced by laying wet phosphate or silicate-coated
~prills down between layers of a facing material,
slightly compressing the assembly, and drying the
2~ prills to form a laminate of foam core with
integral facing layers.
Slab stock (or board stock) comprising rigid
foam prills bound in a cellular matrix are another
feature of the present invention, including the
following materials:
.
.
.
- I 158679
~7. MD 31126
(i) Prills of foam made of one layer mineral in
a cellular matrix comprising the same or
another layer mineral,
(ii) Mixtures of foam prills of different
layer minerals in a cellular matrix
comprising one or more layer minerals,
(iii) Prills of kaolini-te foam in a cellular
matrix comprising vermiculite,
(iv) Prills of vermiculite foam in a cellular
matrix comprising vermiculite or kaolinite,
or both
(v) Prills of kaolinite foam in a cellular
matrix comprising kaolinite, and
(vi) Prills of kaolinite/vermiculite foam in
a cellular matrix comprlsing vermiculite
or kaolinite or a mixture of kaolinite
and vermiculite.
Production of products having prills of foam
embedded in a cellular matrix involves incorporating
pre-formed prills into a gasified suspension or
froth of a layer mineral and drying the resulting
~; prill-filled froth. The prills can be incorporated
in the froth by gently stirring them into the
froth and the filled froth may be shaped e.g. by
extrusion into the desired product form and
~ 25 dried. Alternatively the prills may be assembled
-~ ~ into the desired shape in, say, a mould, and the
froth may be forced into the assembled prills by
the applicatlon of pressure or drawn into the
prills by the application of suction, e.g. in a
vacuum-forming technique. The pressing of prills
into a pre-formed layer of froth to form boards
or slab stock is also possible, though in general
such a technique tends to result in collapse of
.
.
` ~ 15867~
28. MD 31126
the prills and/or the froth, leading to a denser
product than is obtainable by other techniques.
The amount of froth used may vary within wide
limits but will usually be just sufficient to
completely fill the voids between the packed
prills,, for example about an equal weight of
froth after drying based on the weight of the
prills.
Another form of slab stock according to the
invention comprises heat-exfoliated granules
of vermiculite in a prill matrix or in a cellular
matrix comprising kaolinite or a mixture of
kaolinite and vermiculite.
The invention is illustrated by the following
Examples.
EXAMPLE 1
A mixture of kaolin clay (60g), de-ionised water
(240 ml) and "Forafac" 1157 foaming agent (0.2~ by
weight of the kaolin) was beaten for 40 minutes in
a Kenwood Chef food mixer. The Forafac foaming agent
is a fluorochemical surface active agent containing
a C~F15 - group and an amphoteric group and is
available from Ugine Kuhlmann Company. A wet foam
or froth was produced of wet density 240 kg/m3.
The wet foam was laid down in a mould and allowed
. ::
to stand for 24 hours, after which time it was heated
at about 60C in an air oven to dry it. The density
of the resulting dry rigid foam was 75 kg/m3.
Linear shrinkage of the foam during the oven drying
step was observed to be 9~.
EXAMPLE 2
A dryj rigid foam produced as described in
Example 1 was placed in a furnace at 600C and
the temperature was raised to 1150C. After
5 g 6 7 '3
- 29. MD 31126
30 minutes at 1150C the foam was removed
and was found to be a sintered foam of density
90 kg/m3 and having a compressive strength
of 200 KN/m2 at 20% compression.
EXAMPLE 3
A mixture of kaolin (60g), de-ionised water
(240 ml) and "Empigen" BB*foaming agent ~0.45%
by weight of the kaolin) was beaten in a Kenwood
food mixer for 30 minutes. The foaming agent is
available from Albright and Wilson and is an
amphoteric hydrocarbon surfactant having
; carboxylic groups. A wet foam or froth was
produced of density 195 kg/m3. After standing
for 24 hours and drying at 60C as described in
Example 1, the froth yielded a dry, rigid foam of
density 63 kg/m3.
EXAMPLE 4
A mixture of kaolin (lOOg), de-ionised water
~200 ml), sodium tripolyphosphate (O.lg) deflocculat-
!` 20 ing agent and ~Forafac~ 1157 foaming agent (0.1%
by weight of the kaolin) was beaten in a Kenwood
food mixer for 10 minutes, after which time a
stable wet foam or froth has been produced. The
froth was dried as described in Example 1 to
~25 yield a dry, rigid foam of density 200 kg/m3.
EXAMPLE 5
A suspension (152g) of delaminated vermiculite
(vermiculite lamellae) in de-ionised water ~21.
solids content) was mixed with de-ionised water
(1259) in a Kenwood food mixer using the wire
attachment. Sodium tripolyphosphate deflocculating
agent (0.5g) and kaolin (33.3g of light grade
kaolin available from BDH Chemicals) were added
and mixed into the suspension. The mixture was
.
~ ~ Trade Mark
~,. . .
.~." . I
_ . . , ,, . . ~ ` _ .
, . ~ .
,
~ 1~867g
30. MD 31126
whisked at maximum speed for about 10 minutes
until the resulting froth had attained maximum
height, whereupon the mixing speed was reduced
and magnesium oxide (37g of light grade available
from BDH Chemicals) was added to and mixed into
the froth. The mixing speed was again increased
to maximum for about 1 minute.
The resulting stable wet foam, or froth, was
spread in a polyethylene-film lined aluminium tray
of dimensions 15 cm x 15 cm x 2.5 cm. The
froth was allowed to stand at room temperature for
about 12 hours and was then dried at 80C in an
air oven. The dry, rigid foam had a density of
150 kg/m3 and its compressive strength was
445 KN/m2 at 20~ compression.
EXAMPLE 6
A dry rigid foam was produced as described in
Example S except that 70g of de-iQnised water were
used instead of lOOg. The dry rigid foam produced
had a density of 202 kgjm3 and its compressive
strength was 800 KN/m2 at 20% compression.
EXAMPLE 7
A dry, rigid foam was produced as described in
~; Example S except that 67g of kaolin were used
instead of 33.3g. The dry, rigid foam had a
density of 215 kg/m3 and its compressive strength
at 20% compression was 6~0 KN/m
: EXAMPLE 8
. A dry, rigid foam was produced as described in
Example 5 except that lOOg of kaolin were used
instead of 33.3g. The density of the dry, rigid
foam was 302 kg/m3 and its compressive strength
was 587 KN/m2 (20% compression).
. ~ :
.~ -
.
1 1S8679
31. MD 31126
EXAMPLE 9
A dry, rigid foam was produced as described in
Example 5 except that the weight of kaolin was
133.3g instead of 33.3g. The foam had a density
of 375 kg/m3 and its compressive strength (20%
compression) was 943 KN/m2.
EXAMPLES 10 to 12
In these examples the vermiculite prills employed
were made by the following géneral procedure:
Prill-Formation:
An aqueous suspension of vermiculite lamellae
obtained by swelling vermiculite using consecutive
treatments with refluxing salt solution, refluxing
n-butylammonium chloride solution and water was
~-15 milled and wet-classified by removal of all
particles greater than 50 microns. The suspension
was gasified by heating in an Oakes Mixer or
; Kenwood Food Mixer to form a froth and magnesium
oxide powder (10% by weight based on the vermiculite~
was incorporated during the gasification operation.
The wet froth was cast immediately onto a
perforated 'Melinex'*belt, the froth passing
through the holes in the belt and forming 'beads'
on the underside of the belt. The beads were
allowed to cure and partially dry for a few
minutes before being dislodged from the belt by
scraping. The beads were then oven-dried on
trays to provide prills of dry, rigid foam for
fabrication into products. By varying the
concentration of vermiculite in the suspension
employed, prills of foam of various density were
obtained. The prills were of roughly cylindrical
shape and of average dimensions 2-3 mm diameter
* Trade Mark
, . .. .
-
.
1 1S8679
32. MD 31126
and 3-5mm length. They had a uniform cellular
structure.
EXAMPLE 10
Vermiculite foam prills (20 g) of density
112 kg/m3 were stirred carefully with an
aqueous solution (66.5 g) of concentrated phos-
phoric acid (5 g) in de-ionised water. The
thus-moistened prills were spread on a flat drying
tray and oven-dried at 60C for 16 hours. Any
agglomerates of the prills were broken up by hand
and any fine dust was removed by sieving.
Dry, phosphate-coated prills (8 g) were mixed
thoroughly with deionised water (16 g) and the
moistened prills were lightly compacted into two
cylindrical tubes lined with 'Melinex' plastic of
diameter 4.35 cm and height 2.0 cm using a knife
spatula. The flat top and bottom surfaces of the
prill assembly were skimmed with the spatula to
produce a smooth finish and the tubes were heated
in an oven at 150C for 4 hours.
The tubes were removed from the oven and the
foam cylinders were removed from the tubes and
immediately their compressive strengths (10%
compression) were determined using a Houndsfield
Tensometer. The article had a 20% by weight
loading of phosphate binding agent and its
density (mean of the two samples) was 206 kg/m
and compressive strength 274.8 KN/m .
EXAMPLE 11
Articles were made as described in Example 1
except that they had a 10% by weight loading of
the phosphate binding agent instead of a 20%
loading; this 10% loading was achieved by mixing
20 g of the foam prills with a solution (62.5 g) of
,- :
.;
- ` I 158679
- 33. MD 31126
.
concentrated orthophosphoric acid (2.22 g) in
deionised water.
The article had a density (mean of the two
samples) of 154 kg/m3 and a compressive strength
of 126.4 KN/m2.
EXAMPLE 12
Vermiculite foam prills (50 g) of density 104
kg/m3 were coated with orthophosphoric acid
using a laboratory-scale fluid bed drier, (Model
FBD/L7~ by PR Engineering Ltd). To coat the
prills they were placed in a fluidised cylindrical
bed of height 30 cm and diameter 13 cm held in
the head of the fluid bed drier and were heated
at 140C. 2.5 m orthophosphoric acid (12 ml) was
sprayed onto the fluidised prills using a
"Delavan" air atomizing syphon nozzle (model
30610-1) at a delivery rate of 0.22 cm3/second.
A prill loading of 2.5~ by weight orthophosphoric
acid was thus achieved.
The dry, coated prills (8 g) were formed into
cylindrical articles and tested as is described
in Example 1. The finished articles had a -
density (average for the two samples) of 127 ~g/m
; ~ and a compressive strength of 386 KN/m2.
EXAMPLES 13-15
Dry, rigid ball clay foams were produced by
the method generally described in Example 1
from the following ball clay suspensions.
Example I Ball Clay(g) Water Forafac(g j Beating
¦ ~__~) time (mins)
. 13 n Hymod"/AT~100 200 2 20
14 BSK/L(371)* 200 2.4 20
;~ ~ - 15 "Hycast/VC(100200 2 20
* Trade Mark
... . .. .. .. ... . . , . . ~ . . . . . . . .
.
: . .
~ ,
.. - .
,
:
~ 1158679
34 MD 31126
"~YMOD"/AT is a ball clay of Dorset origin
available from English China Clay.
"HYCAST"VC is a ba~l clay of Devon origin available
from English China Clay.
BSK/L*is a ball clay of North Devon original
available from Watson Blake.
Deionised water and "Forafac" 1157*were employed.
The wet foams were converted into day,
rigid foams as described in Example 1 and
the dry foams were sintered at 1050C as in
Ex~nple 2. The properties of the wet and dry
foams were determined and are shown below.
EXA~PLE
. .
13 14 15
PROPERTY
Wet density(Kg/m3) 245 198 196
Dry density(Kg/m3) 124 99 ~8
Sintering time ~mins) 5 5 5
Sintered density(Kg/m3) 128 101 99
*CS sintered foam(KN/m ) 700 114 172
*CS at 100 Kg/m3 420 114 150
*CS at 200 Kg/m3 1340 _ 630
*CS unsintered foam 40 _ 10.8
,: _
C.S. - Compressive Stren gth in KN/m2
CS at 100 Kg/M3 and 200 Kg/m3 are respectively
the Compressive Strengths of foams of density
; 100 Kg/m3 and 200 Kg/m3.
In a further series of experiments, the wet
foams produced in Examp}es 13, 14 and 15 were
converted into dry, rigid-foam prills by the
belt-extrusion technique described for making
~ Trade Y~rk
. . .
,
,- . . :
~. . .
~ ,. . . .
.
.
- I 158679
35- MD 31126
vermiculite foam prills in Examples 10-12. In
each case, handleable prills of cellular
structure were obtained.
In a still further series of experiments, the
wet foams were made into prills of cellular
structure in a spray-drying apparatus.
The prills from all six experiments were
sintered at 1050C and in each case the
cellular structure of the prill was retained.
EXAMPLE 16
A fire clay (kaolinite/illite) slip was
passed through a 20 micron sieve to remove any
large particles of quartz and 201 g of the sieved
slip (47% by weight solids) was mixed with 128 g
of de-ionised water and 2.4 g of "Forafac" 1157*
(0.63%) by weight based on the clay). The
resulting slurry (30~ solids) was whisked in a
Kenwood Chef Food ~ixer for about 20 minutes to
form a stable wet foam.
Samples of the wet foam were converted into an
extruded dry, rigid foam by the procedure of
Example 1 and the foam was sintered at 1150C as
in Example 2. The wet foam had a density of 190
Kg/m3 and the sintered foam had a density of
116 Rgjm3 and a Compressive Strength of 70KN/m2
(at 10~ compression~.
EXAMPLE 17
7.04 Kg of ball clay EWVA, 12.9 Kg of de-ionised
water and 169 ml of "Forafac" 1157*(0.6% on the
clay) were mixed to form a slurry of 35~ solids
content. The slurry was whisked in a Kenwood Chef
Food mixer for 20 minutes and the resulting
stable wet foam was converted into prills of foam
in a conventional spray-drying ap~aratus. The
~ Trade Mark
:
-: ~
. . .
-" I 1586~9 ;-
36. MD 31126
resulting prills were sintered at 1150C for 5
minutes. The wet foam had a density of 256
Kg/m3 and the sintered prills had a density of
150 Kg/m3.
f
' ' ' , -
;
f
~ ' ', ,.~ .
,' : ,f'
~,
:: I ' ,,/
~ ~ /
:
~ / :
.~ /
.
, ::, : ~: . , : . . :
-
, : ~
1 158679
37.
Example 18
Sepiolite (38g) was mixed with de-ionised water tl62g)
and "Forafac" 1157*(0.069 - 0.4% on the clay) in a
Kenwood Chef Food Mixer for 15 minutes to form a stable
wet foam. The wet foam, of density 195 Kg/m3, was
converted into prills of celluiar structure by the belt-
extrusion technique described in Examples 10-12. The
prills were sintered at 10~0C for ~ minutes and the
sintered prills had a density of 58 Kg/m3.
Example 19
:
18.9% delaminated vermiculite slurry in de-ionised water
(116g) was mixed with de-ionised water (789) and sodium
tripolyphosphate (0.5g). Light Grade Kaolin clay, ex BDH
(67g) was added to the mixture which was then whisked in
a Kenwood Chef mixed for about 15 minutes. Light Grade
Magnesium oxide powder, ex BDH (3.7g) was added and the
- mixture was whisked to dispense the powder. The wet
foam was made into prills by the belt-extrusion method
of Examples 10-12, and the prills were sintered at 1500C
for 10 minutes. The density of the sintered prills was
238 Kg/m3.
Example 20
Montmorillonite (50g) was dispersed in de-ionised water
(338g) and 18.3% delaminated vermiculite slurry (137g)
were added to the dispersion, followed by "Forafac" 1157*
(3g). The mixture was whisked in a Kenwood Chef Mixer
for 1 hour to produce a stable wet foam. The wet foam
* Trade Mark
~ ' ~ ` ' :
158679
38 .
was converted into dry prills of cellular structure by
the belt-extrusion method of Examples 10-12. The prills,
dried at 90C, had a density of 108 Kg/m3.
Example 21
Sodium Montmorillonite (509 - Wyoming bentonite) and
Kaolin clay (509) were mixed with de-ionised water
~450g) in a Kenwood Chef Mixer until the Montmorillonite
had been thoroughly dispersed. "Forafac" 115?*(6g) was
added and the mixture was whisked for 1 hour at maximum
speed to produce a stable wet foam. Prills o dry foam
made from the wet foam by belt-extrusion as in Examples
10-12 and then sintered at 1050C for 10 minutes had a
density of 118 Kg/m3.
Example 22
Sodium Montmorillonite (Wyoming bentonite - 509) and
de-ionised water (4509) were stirred in a Kenwood Chef
Mixer until the Montmorillonite was thoroughly dispersed.
"Forafac" 11$7*(6g) was added and the mixture was beaten
with the whisk attachment at maximum speed setting for
about 1 hour to produce a stable wet foam. Prills were
made from the wet foam by the belt-extrusion method of
Examples 10-12 and sintered at 1000C for 10 minutes.
The sintered prills had a density of 110 Kg/m3.
Example 23
Sodium Montmorillonite (200g) and a 60% aqueous solution
of butylammonium chloride chloride (360g) and de-ionised
water (7509) were heated at 80C with stirring for
4 hours. The resulting butylammonium Montmorillonite
(solid) was separated by filtration and washed free of
.~-
* ~llrade Mark
' '
- I 158679
.. '
chloride lon One quarter of the solid was whisked
with de-ionised water ~1209) and "Forafac" 1157 (129)
in a Kenwood Chef Mixer for 1 hour to produce a stable
wet foam. The wet foam was transferred to a mould and
dried as described in Example 1 to yield a rigid foam
of cellular structure.
Example 24
Magnesium Montmorillonite was prepared by heating sodium
Montmorillonite (Wyoming bentonite - 2009) with magnesium
chloride (MgCl2.6H20 - 203g) in de-ionised water (1 litre)
at 80C for 4 hours. The magnesium Montmorillonite ~olid)
was separated by filtration and washed free of chloride
ion One quarter of the solid was whisked with de-ionised
water (lOOg) and "Forafac" 1157 (0.8g) in a Kenwood Chef
! 15 Mixer to produce a stable wet foam. The wet foam was
formed into a dry slab as described in Example 1. Ihe
dry foam had a cellular structure.
Example 25
Aluminium Montmorillonite was prepared by heating sodium
Montmorillonite ~Wyoming bentonite - 200g) with aluminium
nitrate (Al(NO3)3.9H20 - 375g) in de-ionised water
(1.1 litre) at 80C for 4 hours. The aluminium
Montmorillonite (solid) was separated by filtration and
washed free of nitrate ion. One quarter of the solid
was whis~ed in a Kenwood Chef Mixer with de-ionised
water (lOOg) and "Forafacl' llS7 (0.89) to produce a
stable wet foam. The wet foam was cast and dried as
~ * Trade ~lark
.. - ~.,
- : . - . ~ ~ : : .
~ 1586`79
40.
in Example 1 to yield a dry, rigid foam of cellular
structure.
Example 26
A board measuring 15 cm x 15 cm x 2.5 cm was made from
approximately spherical, dry prills of delaminated
vermiculite foam of diameter 3 mm prepared as described
in Examples 10-12. The prills had a true density of
65 Kg/m3 and a packing density of 45 Kg/m3.
The dry prills (22g) were placed in a steel mould of
size 15 cm x 15 cm x 2.5 cm and a force of 15 Kg/m3
was applied using a steel plate to compress the assembly
of prills. Pressure was applied until the volume of the
assembly of prills was reduced by about one half. The
product was a board of essentially cellular structure
and had a density of 90 Kg/m3, a flexural strength of
30 KN/m2 and a compressive strength of 100 KN/m2.
The board was pushed from the mould and its two major
faces were coated with a 35% aqueous solution of sodium
.
silicate. Glass fibre scrim of weight 50g/m3 was pressed
onto the coated surfaces and the resulting laminate was
dried in an oven for 2 hours. The laminate had a density
of 95 Kgim3, a flexural strength of 300 KN/m2 and a
compressive strength of 150 KN/m2. The thermal
conductivity of the laminate measured according to BS 874
was 0.056.
;
:: .
I 158679
41,
Example 27
A board measuring 15 cm x 15 cm x 2.5 cm was~prepared
as described in Example 26 except that the prills were
moistened with de-ionised water (44g) before being
S placed in the mould. The resulting board had an
essentially cellular structure and its density was
90 Kg/m3. The flexural strength of the board was
60 KN/m2 compressive strength was 110 KN/m3.
The board was laminated with glass fibre scrim as
described in Example 26 and the dry laminate had a
density of 95 Kg/m3, a flexural strength of 400 KN/m2
and a compressive strength of 130 KN/m2.
Example 28
A dry, rigid foam was produced by the procedure described
in Example 1 from 50g of Kaolin clay (light grade), 200 ml
of de-ionised water and 0.3g of "Vantoc" CL (a quaternary
ammonium bromide surface active agent available from
Imperial Chemical Industries Limited).
~:
The density of the dry foam was 88 Kg/m3.
Example 29
A composite board containing dry prills made from
vermiculite foam and a matrix of vermiculite foam was
made as follows.
~:
-~ ~ Vermiculite foam was generated by b~eating a 20 wt %
suspension of delaminated vermiculite. 2~09 of
suspension was beate~ for 5 minutes using a Kenwood mixer
at 60 revolutions/minute. The resulting foam was then
:
.
:, . : ,
. , ~ ': : '
1 ~8679
42.
mixed with 50g of prills made from foamed vermiculite
and stirred with a large mechanical stirrer at
5 revolutions/minute. The vermiculite prills had a
density of 70 Kg/m3, a compressive strength of 100 KN/m2
and a diameter of 3 mm,
The resulting mixture was smoothed into a metal tray
measuring 2.5 cm x 2.5 cm x 2.5 cm, dried at room
temperature for 24 hours and then at 50C for 2 days.
The resulting block had a compressive strength of
200 KN/m2, a flexural strength of 350 KN/m2 and a density
of 95 Kg/m3. Thermal conductivity of the board was 0.059
W/mk at 20C.
Example 30
A composite board containing dry beads of expanded
perlite and a matrix of vermiculite foam was made as
follows.
Vermiculite wet foam was made as described in Example 29.
The resulting foam was then mixed with lOOg of beads made
from expanded perlite. The beads had a density of
~:
- 20 130 Kg/m3, a compressive strength of 250 KN/m2 and a
diameter of 2-5 mn.
The resulting block had a compressive strength of 250 KN/m2,
a flexural strength of 300 KN/m2 and a density of 110 Kg/m3.
Thermal conductivity of the board was 0.046 ~/mk at 20C.
Example 31
A composite board containing dry prills made from foamed
Kaolin and a matrix of vermiculite foam was made as follows.
. ' '
1 158679
43.
Vermiculite foam was generated as described in Example 29.
The resulting foam was then mixed with 50g of prills made
of oamed Kaolin. The prills had a density of 65 Kg/m3,
a compressive strength of 90 KN/m2 and a diameter of
3 mm,
The resulting block had a compressive strength of 110 KN/m2,
a flexural strength of 250 KN/m2 and a density ~ 85 Kg/m3.
Thermal conductivity of the block was 0.045 W/mk at 20C.
:'
,
;
