Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
lwl862
This invention relates to inorganic foams and
ln particular to rigid foams of minerals.
, Accordlng to the present invention there ls
provided a rigid foam comprising an inorganic
S cellular structure composed of lamellae of
, vermicullte.
Vermicullte ls a phylloslllcate mineral i.e. one having
a layer structure. Vermlculite may be swollen by
the action of aqueous salts and thereafter the structure
~" broken down (i.e. delaminated) by mechanical action
. ~
into extremely thin lamellae. Other phyllosilicate
, . ,
minerals for example hydrobiotites, or chlorite-
vermlculltes also contain a substantial proportion of
,~,', 15 vermlculite layers and these also may be exfoliated
~,' ln the same or similar manner. These minerals whlch
'`' contain vermiculite layers also give 'rise to thin
. ,;, .
lamellae and it is to be understood that they are
;~ inc}uded ln the present lnventlon. It ls preferred
~' 20 to use the lame,l}ae"~f venm~culite,ltself for the
formation of the inorganic foam of this invention.
Accordlng to a preerred aspect of the present
,- inventlon there ls provided a rlgid foam
', comprising a oellular structure having the cell walls
thereo~ composed of overlapping indlvidual vermiculite
lame~lae adhering together by mutually attractlve
, force~. -
~,` The cellular structure extends continuously and
".
:
,~ - 2 -
. -,
.. .
. ~ , . ..
. .
:., :. : . ......
. -
:: ~ :,- . . .
, -
.. .. . ~ , .
- 1091862
substantially uniformly ln all dimensions
throughout the volume of the foam formed. The
overlapplng lamellae constitute the boundary walls
of each cell in the cellular structure ~o that, in
the structure as a whole, the indlvldual lamellae
are present ln all possible orlentatlons with
respect to a glven plane of reference. Thus, the
foam of the present lnvention may be dlstinguished
from the heat exfollated vermicullte granules
w~ich have been produced hitherto. In these heated
granules a low denslty form of the mlneral is
; produced wherein, within each granule (which was a
separate particle before heat-exfoli~atlon) the layers
of the mineral are forced apart during the heatlng
proces~ but remaln substantlally parallel to oneanother
Furthermore, such a structure exists only wlthin each
granule and does not extend to a co~tinuous structure
between granules. This known form of low-density
vermiculite is not included within the scope of
,~
the present invention.
The aforementloned individual lamellae, which
may alternatively be termed platelets or flake-~,
- possess for example a small dlmension of less than
0.5~m , preferably less than 0.05~m,especially less than
0.005~m and have approximately similar length or
. , :
breadth dimensions of at least a hundred, preferably
at least a thousand,times greater than ~hat of the
.~ .
; small dimension.
''' .
... .
~ - 3 -
-
,~:. . : . :. - ..
. - ,
'~ ' ,, : ' ' ' ' . '
1091862
The density of the foams of this inventlon lies
in the range less than 0.5 g/ml and usually less
than 0.15 g/ml and for especlally "light" foams the-
density may be for example as low as 0.01 g/ml.
The density may be varled in several different
ways, for example by incorporatlng different amounts
of gas into the su~pension or by altering the solids
content of the su~penslon. For a low den~lty foam
the solids content may be suitably from S to 20% by weight
whereas if a hlgher density foam is requlred the
solids content may be lncreased to 30% w/w or more.
According to a further aspect of the present
inventlon there is provided a proceQs for producing
a rigid vermiculite foam comprislng the productlon
of a suspenslon of vermiculite lamellae ln a liquld
medlum,preferablj an agueous liguid medlum~ ga~ification
of the ~u~pension to form a froth and removal of the
liquld medlum from the froth by evaporation.
The swelllng and delamlnatlon of vermlculite to
give aqueous dlsperslons of vermicullte lamellae has
been described in several publications for example
UK Patent Speciflcations Nos. 1,016,385; 1,076,786
and 1,119,305 and by Baumeister and Hahn "Micron"
, .
;:
` 7 247 (1976): the procedures dlsclosed therein are
appllcable to the present invent~on. However for the
formation of foams we prefer to have a surface actlve
agent or a foaming agent present in the suspension
prior to the gaslflcatlon of the suspension to form
- 4 -
. ~ .
. , : ,
,: . , . , -
.. . .. .
:
. ,,
, - :
.
109~86~
the froth;which term includes an expanded form of
the whole suspension.
It i8 advantageous for the surface actlve agent
or foaming agent to be one which ls capable of
; 5 penetrating the structure of the mlneral and thus will
3well the mlneral and allow delaminatlon to occur.
We especially prefer to use a catlonic organic salt
which ls capable of undergolng lon exchange wlth the
catlons present in the vermlcullte layers. Cationic
surface actlve agents which are eqpecially favoured
are the hydrocarbon substltuted ammonium group of
surfactants. For example the substitution may be of
from l to 4 hydrogen atoms on the ammonium cation by
alkyl, aryl, alicyclic, or heterocyclic groups.
Examples of préferred cationic aalts are
n-butyl ammonlum chloride
isobutyl ammonium chloride
isoamyl ammonium chloride
cetyl pyrldlnium bromide
,.
cety~ trimethyl ammonium bromide
.. ; ,
2-ethyl hexyl ammonium chloride
dodecyl ammonium chloride
,
lysine monohydrochloride
ornithine monohydrochloride
and polypeptides in cationic form. Other types of
... .
foaming agents or foam-producing surfactants~may also
be employed as additives to the suspens~on of vermiculite
~`~ lamellae,as adjuvants to other swelling agents e.g.
,
- 5 -
.. . . . .
.
,
, ,~
- 1091862
alkali metal chlorides orin combination with the
aforementioned cationic salts, for example long-chaln
aliphatlc alcohols (e.g. cetyl alcohol), alkyl
- sulphate salts, le.g- sodium lauryl sulphate) N-acyl
sarcosinates and long-chain aliphatlc amine oxides
~e.g. oleyl dimethyl amine N-oxide).
An alternative class of foaming agents which may
be used with advantage a~ additlves to the suspension
of vermicullte lamellae are the protein type foaming
agents for example water-soluble proteins (such as
albumin or gelatln) or water qolubilised protein
derlvatives such as hydrolysed soya bean and hydrolysed
blood or feathers.
The liquid medium, if aqueous, may contain water-
miscible organic liquids for example the lower alcohols
or acetone. Alternatively the foam may be produced
in a non-aqueous medium using suitably modified vermiculites
-,~ as described in UK Patent 1,076,786.
. The gasification process may be performed by means
of a release of gas or vapour ln the suspension of
. .
vermicullte lamellae preferably one whlch ls substantially
inert to the aqueous suspension for example air, nitrogen,
argon, carbon dioxide,a hydrocarbon, chlorocarbon,
.;~
-` fluorocarbon or chlorofluorocarbon. The gaslfication may
- more conveniently be performed by mechanically entraining
the gas in the suspension by rapid agitation -for
example by rap~d churnlng or whisking of the suspension.
,
Alternatively the suspension may be rapidly heated
-~;
',''' '
- 6 -
, .
. .
.~ . . . ;
~ , . : .
.,, , -
' ;' . , ' ' ' ~ ' ' '
: - : ' . .
1091862
and the foam produced by gasification due either to
steam produced by evaporation of water or to liberation
of gas dissolved ln the sample.
By the term rigid foam we mean a two phase
- 5 dispèrslon of gas in solld, the solld phase belng an
essentlally contlnuous lnorganlc cellular structure.
Small quantities of organlc materials may be present
ln the foam, whlch may be elther dellberately added
or lnadvertently present, but the organic materlal is
not fundamental to the coheslon of the cellular structure
although it may usefully modlfy the properties thereof.
On removal of water rom an aqueous disperslon of
vermicullte lamellae, the lamellae come together to
form a coherent fllm. Accordlngly the cell walls of the
cellular structure of the present inventlon derive thelr
mechanical strength largely or wholly from the self-
adheslon of the flakes when water ls removed. The
resultlng structure ls a non-brittle foam i.e. under
atress the structure may deform without crumbllng.
The cellular vermlcullte is a useful heat-
reslstant and heat lnsulatlng materlal whlch may be
cast as a foam-fllllng for cavltles and voldæ or whlch
.,
- - may be used as a coatlng for the outslde of materials
for example wood or steelwork,in both cases the vermlculite
foam acting inter alia as a fire-protective layer. The
vermiculite foam may be produced as a slab stock for
;.
~ubse~uent fabricatlon or other lamination. An lnner
sandwich of vermiculite foam as hereln provided,
, . ,
., ~
.~ ,
':,'
. , , . .,. . - . : . .
.. , .... .- ., . . ,~. - :
.:. , ... .-' . ~ .: , . . :
i. ~ , .. .. . . .
',, ~. ' ~' ' ~' ., ' ,:
'. : : .: '~'. . ' ' ' ~ ':
, 109~86Z
optionally bounded for example by sheets of wood-
veneer, paper, asbestos, mi ca or plastic ~ or by
vermiculite sheet, forms useful decorative construction
panels: the vermiculite foam may be sandwiched between
plaster-board or sheets of thermo-setting resin e.g.
melamine resin. The fore-going structures form
useful fire-reslstant and/or souna insu~ating panels
for the building industry, panels which may bé maintained
at temperatures of ca.1000C without disintegration.
Sheets of vermiculite foam may be applied as facings to
polyurethane foam panels by conventional lamination
techniques in order to improve the fire resistance of
the polyurethane foam core. The froth i.e. the
gas1fied suspenslons before drylng may be con~eniently
~-~ 15 used to bond together previously formed ~ermiculite
, ~
- structures e.g. sheets or slabs of foam already in
drled form and so cement ~everal sheets together and
build up larger structures. In a similar way the heat-
,~
exfoliated vermiculite granules may be cemented together
by means of thé same froth and thus a composite
-
structure is formed consisting of the foam of the
.
present invention as a continuous cement between granules
of heat-exfoliated vermiculite.
For some applications the vermlculite foam may
require a water-proofing treatment for example a
treatment with ammonia a~ described in our copending
Canadian application Serial No. 300,521, ~iled April 5,
;~:
1978
..
,
- 8 -
.~
109186Z
The inventlon is lllustrated by the following
Examples.
Exam~Ie~
1 Kg of vermiculite ore of South Africa origin known
as Man~doval micron grade wa~ refluxed in 5 litres of
saturated sodium chlorlde solutlon for 30 minutes.
Excess brine was decanted off and the vermlculite washed
ln 5 litres of distilled water. This was followed by
five separate washings of the solid with one litre
aliquots of distilled water on a Buchner filter funnel.
The wet cake of vermiculite was returned to the
- refluxing vessel and refluxed for two hours with 1.25mole of butyl ammonium chloride made up to five litres
,
volume with distilled water. After reflux, a washing
procédure as descrlbed above was carried out durlng
whlch a rapid expansion of the vermiculite to about
six times its original volume occurred. After standing
overnlght the supernatant ll~uld was decanted off and
the 6 litres of swollen vermiculite ore was divided
into two portions of approximately 3 lltres each and
- each made up to 4 litres with distllled water ln a large
beaker.
-; Each suspension was then sheared for one hour
, .
using a rotary-bladed mixer dlpping into each beaker
and working at 6,500 rpm. The suspenslon was maintained
-
near to ambient temperature by a spray of coId water ,
` to the outside of each beaker. Air became entrained
in the suspension of the lamellae during this process
,'~.;
.;
. , .
:
g _
,..... - . : . - , . ~ ,
,~ . . . . . . . .
', . -,,' , ~ , . ' : . ..
,,
loals6z
and a froth appeared on the surface of each suspension.
The depth of froth lncreased when the suspension was
allowed to stand for 30 minutes and ca. 600 ml of
foam was scraped from the suspension in each beaker.
S The foam was placed ln a mould and drled ln a
well ventllated oven at 60C. A hard foam of
vermiculite having a density of 0.08 g/ml was removed
from the mould. The foam had adopted the peImanent
shape of the mould and had acqulred a skin film o~
vermlcullte over the surface.
'1 The suspenslon of lamellae was churned at high-
speed again for a period of 60 minutes and allowed
~o stand for a further 30 minutes whereupon a fresh
'~ quantlty of froth appeared. The process was repeated
several times and ~hereby several batches of foam
wers made from the same suspen~ion. Thsse were
combinsd and removsd to a mould and dried in the oven
to form a solld foam of denslty 0.08 g/ml and average
cell diameter 0.7 mm
,:
~ 20 Example 2 -
,:
; A sample of ground vermicullte ore from the
."
~,, deposlts ln North America (Zonollte No 4) was refluxed
,` for 30 minutes in a saturated solution of sodium chloride
and thoroughly washed with several portions of distilled
, .. ..
- 25 water. The particles were then given a two hour reflux
in an aqusous solution of n-butyl ammonium chloride -
followed again by a thorough washing in distilled water.
During this second washing (which may last conveniently
.
:`ii -- 10
~ `~i ' .
, , , , : -
. - , . . .
-.:
. ~ . . . . ..
, ~ , .
10~1862
-
between a few minutes and several hours) a pronounced
swelling of the particles occurred to approx~mately
six times their original wet volume. ThlS was then a
sample of expanded vermlculite.
The weight ratio of the aqueous suspension of
the swollen vermiculite was adjusted by removal of
water by filtration until the weight ratio was
approximately 10% vermicullte sollds to 90% liquid
water. The suspension was placed in a high-shear
mixer (manufactured by Greaves Limited) which had a
blade capable of rotating at 6,500 rpm and the suspension
was mechanically milled or macerated for a period of
10 minutes. During this process air was entrained in
,
the suspension and when the rotation of the blade was
; 15 - stopped and the suspension allowed to stand for 5
~,
minute~ several inches depth of froth was present '
above the suspenslon. The froth was taken off ~ith a knife
and spread on a tray. The tray containing the froth
~ was placed in a well-ventilated oven at ca. 60C and
,t,~,., 20 and the water removed by evaporation,optionally aided
, ,.: . ..
by a fan or extractor in the oven. When dry the foam
,
could be removed from the tray as a solld cellular
vermiculite structure having a density of less than
~, 0.1 g/ml and average cell diameter of 0.5 mm.
-~ 25 Example_3 ~~~- -
~ A sample of Zonolite No 4 ver~iculite was treated
. . ~,
as described in Example 2 the suspension being milled
for 60 minutes. The density of the resultant foam was
. .,
.:
; - 11 -
:;
..
. ~ .
.
;,: - , . . . .
: ~ - .- .
; . . - ~
:,: ' .' : ` .,
,
, . .
:: :
109~86Z
0.035 g/ml and the average cell diameter was 0.5 mm.
ExamPle_4 _ --
South Afrlcan vermiculite was expanded as
described in the flrst paragraph of Example 1. After
ad~ustlng the solids content of the swollen vermiculite
suspension to 20~ w/w it was stirred until homogeneous
and subjected to a single pass through a mill of the
type known as a "rotor-in-stator" mill, runnlng at a
speed of 20,000 rpm. Before passing into the shearing
zone of the mill, alr was metered into the suspension
at a rate of 10 litre/min. The whole suspension was
converted to a thick froth which on standing overnight
separated out into a lower liquid layer containing
some of the larger sized vermlculite particles and
another layer of wet vermicullte froth. The froth
twhlch was observed to be stable for several weeks in
the wet stage) was collected and dried in a wire-mesh
, . . .
-- mould in a well ventilated oven at 80~. A slab of
foam of dimensions 12" x 12" x 2" was formed and was
; 20 found to have the following properties:
Density 0.22 g/ml
Compressive strength 0.11 MNm 2
Thermal conductivity 0.060 Wm -lR-
% closed cells 12%
.
~ 25 Average cell diameter 1.5 mm
.
Example 5 _
3 Kg of American vermlculite was expanded in a
similar manner to that described in the flrst paragraph
; of Example 2.
.
~i. - 12 -
'. . ,
109186Z
The swollen vermiculite was then divided lnto 9
batches, each of whlch was milled for 45 minutes ln
a Greaves mill, in order to produce suspensions of
delamlnated vermlculite. The 9 batches were then
ccmbined and the larger particles of vermiculite
removed by passing the suspension through a 50 ~m
sleve. The resultant "classified" suspension which
contained approxlmately 5% solids by weight, was
evaporated on a large heated tray to increase the
solids content to 20%. Air was then beaten into the
thick suspension using a culinary mixer, using the
whisking attachment. An approximately two fold volume
.
increase of the suspension took place and a small
bubble size ~ wet foam was produced from the whole
" .
'h. 15 suspension. The foam was spread on a heated tray and
~ dried overnlght to form a board 6' x 4' x l/4". The
.. . .
;; dried foam had the following properties:
~ Density 0.12 g/ml
; Compresslve strength 0.30 MNm 2
,
Thermal conductlvity 0.060 Wm lK 1
% closed cells 41%
Average cell diameter 0.2 mm
ExamPle 6
3 Kg of South African vermiculite was expanded
as described in the first paragraph of Example 1.
-~hen the expansion was complete the supernatant water
~, ,~
was decanted off and the swollen vermiculite milled
in 750 ml aliguots in a domestic liquldiser for lO
. . .
:
:;:
~vi - 13 -
, .
.: :, . ,
''.': ' ' ~ '' . :'
,
, . . .. . .
1~)9~862
minutes. The thlck, but pourable suspension was
found to have solids content of 20% w/w. The
suspenslon wa~ foamed using a culinary mixer as
described ln Example 5. The foam was then dried in
an oven at 90C overnight to form slabs of dlmensions
24" x 12" x 1/4". Several slabs were laminated
using wet froth and a larger slab of dimensions 12"
x 12" x 1~" was formed and dried ln an oven. The
- physical properties of the larger slab were measured as
Density 0.07 g/ml
Compressive strength 0.05 MN~ 2
Thermal conductivity 0.048 Wm lK 1
% closed cells 6%
Average cell dlameter 0.5 mm
Exam~le 7
A non-foamed su8pension of American vermiculite
(20% w/w solids con~ent~ was prepared as described in
Example 5. In this case the suspension was not aerated
but was placed in an oven at 140C for 3 hours, causing
, 20 rapid evolution of water vapour which produced a dry
foam of denslty 0.10 g/ml.
.,
Example 8
170 g of South African vermiculite suspension
" prepared according to the method described in Example 5
, -
. 25 the solids csntent adjusted to 13% w/w and placed in an
"Aerosol" container which was adapted to be
pressurised. A mixture of 18 g of dichloro difluoromethane
and 12 g of dichloro tetrafluoroethane was forced under
'
- 14 -
: .
,., : - ~ . .. ,:
. .
--
. . .
109186~
pressure into the Aerosol can and mixed with the
vermiculite paste. upon activation of the ejection
nozzle of the can a wet froth was applied to a tray
and dried in air over a period of 24 hours. The
S rigld foam of vermiculite produced was observed to have
a very fine pore size (average diameter of bubbles
-~ = 350~m) and a density of 0.05 g/ml.
Example 9
South African (Mandoval "micron~ grade) vermiculite
(1 Kq.) was refluxed for 10 hours in a mixture of water -
(4 -~.) manganese dichloride tetrahydrate (130 g.) and
concentrated hydrochloric acid (0.25 ml.). The product
was washed with water and then made up to a total volume
;s o~ 20 1. wlth water. Hydrochloric acid ~75 ml. lN
~, 15 801ution) and hydrogen peroxide (2 l. of 30~ solutlon)
' were then added and the stirred mixture warmed to 60C
for ~ hours whereupon the vermicullte expanded to take
.~,
up most of the llquld present. The mixture was then
cooled, flltered, washed with water, and made up
, 20 to lO l. wlth added fresh water. The resulting
- suspension was divided lnto 4 equal batches and each
sheared for one hour at 6500 rpm ln a 5 1. vessel wlth
~- a Greaves H5-Series mlxer (Mark III). The combined
suspension was then diluted to 16 l. with water and
. .
classlfied by passage through a sleve o aperture
: ;,j
.'! size 50 ~m to give a vermicull~e suspension containing
2.9~i by weight of solids (all water added was distilled).
The concentration of the suspension was then
.
- 15 -
. . .
,, .
1091862
increased to 20% by weight by evaporation of water
by the application of heat, the mixture was cooled
and a protein surfactant known commercially as
"Nicerol" was then added at a concentration of 10%
by volume relative to the weight of the solid
vermiculite and portions of the mixture
beaten in a culinary mixer to form a foam. The
foam when dried in a well-ventilated oven at 90C
had a density of 0.1 g/ml.
" 10 Example 10
~' 1 Kg. of South African vermiculite was refluxed
in a 20% w/w aque~us solutio~ of lithium chloride for 2
hours and after thorough washing in a Buchner funnel
and standing overnight in distilled water, an eight-
fold volume expansion of the orlginal ore took place.
~" Th~ mixtur,e of expanded ore and water (10% w/w of ore)
', was then mllled for 1 houF. The larger particles of
vermiculite were then removed by flltration through a
",l 50~m sieve and the concentration of the suspension,
/ 20 ad~usted to 20% w/w by evaporatlon. A protein surfactant
.i. *
,,x,, known commercially as "Nicerol" at a concentration of
`"' 10% by volume relative to the weight of vermiculite
- was then added and portions of the mixture beaten
~-, in a culinary mixer to form a foam. The foam when
dried ln a well ventilated oven at 90C had a density
of 0.1 g~ml~ '
'~ Exa~plo 11 ~---
., .
~ A dried foam based on North American vermiculite
,.
'~ *Trade Mark.
", - 16 -
. .
.; ~ . ,
~ ~ '
~C~9~6z
was prepared as describea in Example 4 ana found
to have an average size of 3.00mmand a density of
O.ol g/ml.
ExamPle 12
A sample of wet foam as prepared in Example 6
was blended with granules of heat expanded
vermiculite such that in the resultant blend the
wet foam occupied 34% of the total volume and the
granules 66% of the total volume. The blend was dried
; 10 in an oven at 90C. The resultant composite
structure had a density of 0.22g/ml and a compressive
strength of 0.12 MNm 2
.....
~ ExamPle 13
~, .,
, A slab of foam of dimensions 62 mm x 135 mm
x 4 mm cut from the foam produced ln Example 5 havlng
a density of 0.12 g/ml was placed in a furnace-at
, 1000C for 10 minute~. On removal from the furnace
the slab was observed not to have distorted at all
visibly as a result of the intense heat, the resultant
dimension-~ being 61 mm x 134 mm x 4 mm. The density
;; decreased to 0.09 g/ml and the compressive strength
-- was 0.22 MNm2.
-~ These results demonstrate that the foams of this
.;
invention resist heat well and therefore can be used
as a fire-protective material because they have good
` dimensional stability with little loss in compressive
-` strength.
r
~ '
.
.
