GB1582121A

GB1582121A - Vermiculite suspension

Info

Publication number: GB1582121A
Application number: GB4173379A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1977-04-07
Filing date: 1977-04-07
Publication date: 1980-12-31

Description

(54) VERMICULITE SUSPENSION (71) We, IMPERIAL CHEMICAL INDUS TRIES LIMITED, Imperial Chemical House, Millbank, London SW1P 3JF, a British com- pany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to aqueous suspensions of inorganic materials useful in the production of inorganic foams and in particular of rigid foams.

Vermiculite is a phyllosilicate mineral i.e.

one having a layer structure. Vermiculite 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 chiorite-vermiculites also contain a substantial proportion of vermiculite layers and these also may be exfoliated in the same or similar manner. These minerals which contain vermiculite layers also give rise to thin lamellae and it is to be understood that they are included in the present invention. It is preferred to use the lamellae of vermiculite itself for the formation of the inorganic foams.

The aforementioned individual lamellae, which may alternatively be termed platelets or flakes, possess for example a small dimension of less than 0.5 Fm, preferably less than 0.05 ,,am, especially less than 0.005 ,am and have approximately similar length or breadth dimensions of at least a hundred, preferably at least a thousand, times greater than that of the small dimension.

According to the present invention we provide a process for the production of a suspension of swollen or expanded vermiculite ore in water which comprises the steps of (a) treating vermiculite ore with a saturated solution of sodium chloride in water under reflux conditions, (b) treating the sodium chloride-treated ore from step (a) with a solution of butyl ammonium chloride in water under reflux conditions and (c) allowing the treated ore from step (b) to swell in water The swelling and delamination of vermiculite to give aqueous dispersions of vermiculite lamellae has been described in several publications for example UK Patent Specifications Nos. 1,016,385; 1,076,786 and 1,119,305 and by Baumeister and Hahn "Micron" 7 247 (1976): the procedures disclosed therein are relevant to the present invention.However for the formation of foams we prefer to have a surface active agent or a foaming agent present in the suspension prior to the gasification of the suspension to form the froth; which term includes an expanded form of the whole suspension.

It is advantageous for the surface active agent or foaming agent to be one which is capable of penetrating the structure of the mineral and thus will swell the mineral and allow delamination to occur. Other types of foaming agents or foam-producing surfactants may also be employed as additives to the suspension of vermiculite lamellae, as adjuvants to other swelling agents for example long-chain aliphatic alcohols (e.g.

cetyl alcohol), alkyl sulphate salts, (e.g.

sodium lauryl sulphate) N-acyl sarcosinates, long-chain aliphatic amine oxides (e.g. oleyl dimethyl amine N-oxide), protein type foaming agents for example water-soluble proteins (such as albumin or gelatin) or water solubilised protein derivatives such as hydrolysed soya bean and hydrolysed blood or feathers.

The aqueous liquid medium may contain water miscible organic liquids for example the lower alcohols or acetone.

A foam may be produced from the suspension by gasification which is conveniently performed by mechanically entraining the gas in the suspension by rapid agitation for example by rapid churning or whisking of the suspension. Alternatively the suspension may be rapidly heated and the foam produced by gasification due either to steam produced by evaporation of water or to liberation of gas dissolved in the sample.

Foams produced from the suspensions of this invention are described and claimed in the specification of our co-pending U.K.

Application No. 14764/76.

The invention is illustrated by the following Examples.

Example I 1 Kg of vermiculite ore of South African origin know as Mandoval micron grade was refluxed in 5 litres of saturated sodium chloride solution for 30 minutes. Excess brine was decanted off and the vermiculite washed in 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 1.25 mole of butyl ammonium chloride made up to five litres volume with distilled water. After reflux, a washing procedure as described above was carried out during which a rapid expansion of the vermiculite to about six times its original volume occurred.After standing overnight the supernatant liquid was decanted off and the 6 litres of swollen vermiculite ore was divided into two portions of approximately 3 litres each and each made up to 4 litres with distilled water in a larger beaker.

Each suspension was then sheared for one hour using a rotary-bladed mixture dipping into each beaker and working at 6,500 r.p.m.

The suspension was maintained near to ambient temperature by a spray of cold water to the outside of each beaker. Air became entrained in the suspension of the lamellae during this process and a froth appeared on the surface of each suspension.

The depth of froth increased when the suspension was allowed to stand for 30 minutes and ca. 600 ml of foam was scraped from the suspension in each beaker.

The foam was placed in a mould and dried in a well ventilated oven at 600 C. A hard foam of vermiculite having a density of 0.08 g/ml was removed from the mould.

The foam had adopted the permanent shape of the mould and had acquired a skin film of vermiculite over the surface.

The suspension of lamellae was churned at high-speed again for a period of 60 minutes and allowed to stand for a further 30 minutes whereupon a fresh quantity of froth appeared. The process was repeated several times and thereby several batches of foam were made from the same suspension.

These were combined and removed to a mould and dried in the oven to form a solid foam of density 0.08 g/ml and average cell diameter 0.7 mm.

Example 2 A sample of ground vermiculite ore from the deposits in North America CZonolite No.

4) was refluxed for 30 minutes in a saturated solution of sodium chloride and thoroughly washed with several portions of distilled water. The particles were then given a two hour reflux in an aqueous solution of n-butyl ammonium chloride followed again by a thorough washing in distilled water. During this second washing (which may last conveniently between a few minutes and several hours) a pronounced swelling of the particles occurred to approximately six times their original wet volume. This was then a sample of expanded vermiculite.

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% vermiculite solids 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 stopped and the suspension allowed to stand for 5 minutes several inches depth of froth was present above the suspension. The froth was taken off with a knife and spread on a tray. The tray containing the froth was placed in a well-ventilated oven at ca. 600C 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 solid cellular vermiculite structure having a density of less than 0.1 g/ml and average cell diameter of 0.5 mm.

Example 3 A sample of Zonolite No. 4 vermiculite was treated as described in Example 2 the suspension being milled for 60 minutes.

The density of the resultant foam was 0.035 g/ml and the average cell diameter was 0.5 mm.

Example 4 South African vermiculite was expanded as described in the first paragraph of Example 1. After adjusting 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, running at a speed of 20,000 rpm.

Before passing into the shearing zone of the mill, air 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 vermiculite particles and another layer of wet vermiculite froth.The froth (which 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"C. A slab of foam of dimensions 12" X 12" X 2" was formed and was found to have the following properties: Density 0.22 g/ml Compressive strength 0.11 MNm-2 Thermal conductivity 0.060 Wm-1K-1 % closed cells 12% Average cell diameter 1.5 mm Example 5 3 Kg of American vermiculite was expanded in a similar manner to that described in the first paragraph of Example 2. The swollen vermiculite was then divided into 9 batches, each of which was milled for 45 minutes in a Greaves mill, in order to produce suspensions of delaminated vermiculite.

The 9 batches were then combined and the larger particles of vermiculite removed by passing the suspension through a 50 Fm sieve. The resultant "classified" suspension which contained approximately 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 suspension. The foam was spread on a heated tray and dried over night to form a board 6' X 4' X 14w*. k,'. The dried foam had the following properties: Density 0.12 g/ml Compressive strength 0.30 MNm-2 Thermal conductivity 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. When the expansion was complete the supernatant water was decanted off and the swollen vermiculite milled in 750 ml aliquots in a domestic liquidiser for 10 minutes.The thick, but pourable suspension was found to have solids content of 20% w/w. The suspension was foamed using a culinary mixer as described in Example 5. The foam was then dried in an oven at 900C overnight to form slabs of dimensions 24' X 12" x L4s. Several slabs were laminated using wet froth and a larger slab of dimensions 12" x 12" X 1X2" was formed and dried in an oven. The physical properties of the larger slab were measured as Density 0.07 g/ml Compressive strength 0.05MNm-2 Thermal conductivity 0.048 Wm-1K'1 % closed cells 6% Average cell diameter 0.5 mm Example 7 A non-foamed suspension of American vermiculite (20% w/w solids content) was prepared as described in Example 5.In this case the suspension was not aerated but was placed in an oven at 140"C for 3 hours, causing rapid evolution of water vapour which produced a dry foam of density 0.10 g/ml.

Example 8 170 g of South African vermiculite suspension prepared according to the method described in Example 5 the solids content adjusted to 13% w/w and placed in an "Aerosol" container which was adapted to be pressurised. A mixture of 18 g dichloro difluoromethane and 12 g of dichloro tetrafluoroethane was forced under 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 rigid foam of vermiculite produced was observed to have a very fine pore size (average diameter of bubbles = 350,ss1m) and a density of 0.05 g/ml.

WHAT WE CLAIM IS: 1. A process for the production of a suspension of swollen or expanded vermiculite ore in water which comprises the steps of (a) treating vermiculite ore with a saturated solution of sodium chloride in water under reflux conditions, (b) treating the sodium chloride-treated ore from step (a) with a solution of butyl ammonium chloride in water under reflux conditions and (c) allowing the treated ore from step (b) to swell in water.

2. A process as claimed in claim 1 wherein the treated vermiculite ore from step (b) is thoroughly washed with water prior to step (c).

3. A process as claimed in claim 1 wherein the treated vermiculite ore is thoroughly washed with water between steps (a) and (b) and between steps (b) and (c).

4. A process as claimed in any one of claims 1-3 inclusive wherein the treated ore is allowed to swell to about six times its original volume.

5. A suspension of swollen vermiculite ore in an aqueous medium produced by a process according to any one of claims 1--4 inclusive.

6. A process for the production of a suspension of vermiculite lamellae in an

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Claims

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a wire-mesh mould in a well ventilated oven at 80"C. A slab of foam of dimensions 12" X 12" X 2" was formed and was found to have the following properties: Density 0.22 g/ml Compressive strength 0.11 MNm-2 Thermal conductivity 0.060 Wm-1K-1 % closed cells 12% Average cell diameter 1.5 mm Example 5

3 Kg of American vermiculite was expanded in a similar manner to that described in the first paragraph of Example 2. The swollen vermiculite was then divided into 9 batches, each of which was milled for 45 minutes in a Greaves mill, in order to produce suspensions of delaminated vermiculite.

The 9 batches were then combined and the larger particles of vermiculite removed by passing the suspension through a 50 Fm sieve. The resultant "classified" suspension which contained approximately 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 suspension. The foam was spread on a heated tray and dried over night to form a board 6' X 4' X 14w*. k,'. The dried foam had the following properties: Density 0.12 g/ml Compressive strength 0.30 MNm-2 Thermal conductivity 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. When the expansion was complete the supernatant water was decanted off and the swollen vermiculite milled in 750 ml aliquots in a domestic liquidiser for 10 minutes.The thick, but pourable suspension was found to have solids content of 20% w/w. The suspension was foamed using a culinary mixer as described in Example 5. The foam was then dried in an oven at 900C overnight to form slabs of dimensions 24' X 12" x L4s. Several slabs were laminated using wet froth and a larger slab of dimensions 12" x 12" X 1X2" was formed and dried in an oven. The physical properties of the larger slab were measured as Density 0.07 g/ml Compressive strength 0.05MNm-2 Thermal conductivity 0.048 Wm-1K'1 % closed cells 6% Average cell diameter 0.5 mm Example 7 A non-foamed suspension of American vermiculite (20% w/w solids content) was prepared as described in Example 5.In this case the suspension was not aerated but was placed in an oven at 140"C for 3 hours, causing rapid evolution of water vapour which produced a dry foam of density 0.10 g/ml.

Example 8

170 g of South African vermiculite suspension prepared according to the method described in Example 5 the solids content adjusted to 13% w/w and placed in an "Aerosol" container which was adapted to be pressurised. A mixture of 18 g dichloro difluoromethane and 12 g of dichloro tetrafluoroethane was forced under 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 rigid foam of vermiculite produced was observed to have a very fine pore size (average diameter of bubbles = 350,ss1m) and a density of 0.05 g/ml.

WHAT WE CLAIM IS: 1. A process for the production of a suspension of swollen or expanded vermiculite ore in water which comprises the steps of (a) treating vermiculite ore with a saturated solution of sodium chloride in water under reflux conditions, (b) treating the sodium chloride-treated ore from step (a) with a solution of butyl ammonium chloride in water under reflux conditions and (c) allowing the treated ore from step (b) to swell in water.
2. A process as claimed in claim 1 wherein the treated vermiculite ore from step (b) is thoroughly washed with water prior to step (c).
3. A process as claimed in claim 1 wherein the treated vermiculite ore is thoroughly washed with water between steps (a) and (b) and between steps (b) and (c).
4. A process as claimed in any one of claims 1-3 inclusive wherein the treated ore is allowed to swell to about six times its original volume.
5. A suspension of swollen vermiculite ore in an aqueous medium produced by a process according to any one of claims 1--4 inclusive.
6. A process for the production of a suspension of vermiculite lamellae in an

aqueous medium by shearing a suspension as claimed in claim 5.
7. A process for the production of a suspension of vermiculite lamellae substantially as described herein by reference to any one of the foregoing Examples.