GB1578404A

GB1578404A - Production of expanded materail

Info

Publication number: GB1578404A
Application number: GB12502/78A
Authority: GB
Original assignee: Rhone Poulenc Industries SA
Current assignee: Rhone Poulenc Industries SA
Priority date: 1977-03-31
Filing date: 1978-03-30
Publication date: 1980-11-05
Also published as: PT67849A; DE2813473A1; NL7803379A; SE7803629L; LU79329A1; NO781092L; BE865516A; DE2813473C3; DK140978A; PT67849B; DE2813473B2; BR7801959A; IT7848658A0; FR2385656A1

Description

(54) PRODUCTION OF EXPANDED MATERIAL (71) We, RHONE-POULENC INDUSTRIES, a French body corporate, of 22, avenue Montaigne, 75 Paris (8), France, 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:- The present invention is concerned with expanded alkali-metal-silicate-based materials and their production.

U.S. Patent 1,944,007 describes a process comprising mixing a finely divided clay in a highly fluid sodium silicate solution, adding a foaming agent, stirring the solution in order to permit of the introduction of air into the material, then treating the solution with an acid agent so as to bring about flocculation of the particles and then gelling of the material until the latter has an adequate plasticity for moulding or injection moulding. However, this procedure has a certain number of problems, relating both to the actual process and to the product obtained.

It is generally required that the product should have good mechanical characteristics, as well as good thermal and acoustic insulation characteristics. As these two types of characteristics are not wholly compatible and do not vary in the same sense, it is necessary to make a compromise. It is also desirable that the process be easy and rapid to perform, whilst it must also be possible to check the properties of the product, and at the same time provide a degree of reliability permitting the process to be industrially performed.

In the above-mentioned Patent it is proposed that the process be controlled by controlling the flocculation and gelling by means of the acidification bias of the material. In this way it is possible to influence the degree of acidification by the choice of acidifying agent, whilst also utilising buffer compounds.

With regard to the thermicity of the reactions, the above Patent uses no compounds which are burnt during the final production stage.

Attempts have constantly been made to improve such processes, particular attention being paid to the nature of the pore-forming agents, both with regard to their influence on the qualities of the product obtained and on the ease of using them.

Thus, French Patent Specification Nos. 2,309,488 and 2,347,320 recommend the use of finely divided silicon and aluminium as the pore-forming agent, these substances being mixed with an active filler. The material is expanded during moulding without there being any need for an external supply of heat.

Such a process has proved to be interesting both from the thermal standpoint and with respect to the product obtained in that the Al-Si couple makes it possible to control, at least to a certain extent, the density and mechanical properties of the product. However, it is not possible to sufficiently control of the expansion process.

In all proposed processes expansion has taken place without being fully controlled, which is a serious disadvantage because the conditions that improve mechanical properties tend to cause insulation properties to deteriorate, and vice versa.

According to the present invention a solution of at least one alkali metal silicate and at least one pore-forming agent, preferably constituted by the aluminium-silica couple according to French Patent Specifications Nos. 2,309,488 and 2,347,320, is mixed and expansion is carried out without external heating in the presence of at least one methyl ester and, optionally propylene carbonate. These compounds act as expansion regulators. It is assumed that certain of them, particularly propylene carbonate, have a silicate-solubilisation action.

The compounds are used singly or mixed, optionally with other compounds. In particular it is possible to combine at least one methyl ester with propylene carbonate. The compounds can be introduced prior to the expansion or can be formed in situ during the expansion treatment. They are advantageously introduced in a proportion of 0.1 to 10% by weight relative to the silicate.

It is found that when proceeding according to the invention the small cavities that appear are much more regular, making it possible to improve the thermal conductivity coefficient and the compressive strength and to almost completely eliminate shrinkage.

The methyl esters used according to the invention can be but are not necessarily monoesters. In particular, they can be diesters.

Advantageously 5 to 50%, or even up to 150%, by weight, relative to the alkali metal silicate, of an active filler constituted by a finely divided material, e.g. a cement, synthetic anhydrite or slaked lime, is added to the mixture of silicate and pore-forming agent. The cement can for example be of type CPA, CPAC or CPAL or even CPALC, as defined in French Standard NF P 15302 of October, 1964 and its supplement of March 1967. The term 'active filler' means a compound that has an alkaline dehydrating reaction that in known manner accelerates the action of the pore-forming agents.

In addition it is possible to add up to 150% and preferably 10 to 120% by weight, relative to the alkali metal silicate, of a so-called inactive filler, i.e. one that is inert under the expansion reaction conditions. Such an inactive charge can be a kaolin, particularly a colloidal kaolin, which may be calcined, a natural kaolin, a clay, bentonite, a silica derivative, a dihydrated calcium sulphate from any source, an alumina, a silicate, a carbonate or fly ash. In general a grain size below 200 microns is chosen.

As has already been stated the pore-forming agent is advantageously constituted by the elements Al and Si in finely divided form. Preferably the Al/Si couple is used and the pore-forming agent is in present in the form of a powder with a grain size between 10 and 100 microns.

The pore-forming agent may contain only these elements or may be in the form of a composition. In particular the silicon can be in the form of a composition containing approximately 35 to 75% of pure silicon.

The quantity of pore-forming agent, compared with the silicate, is advantageously between 2 and 15%. The silicate can be any soluble silicate, but generally a silicate is used having a molar ratio SiO2:Na > O close to 2:1.

Advantageously a composition according to the invention comprises: 5 to 50% by weight of active filler, 10 to 120% by weight of inactive filler, 2 to 15% of pore-forming agent, 0.1 to 10% of the methyl ester or methyl ester plus propylene carbonate.

Moreover certain properties can be improved by a subsequent treatment, such as with water.

The invention will be better understood from the following examples, which illustrate but in no way limit the invention.

In the following examples the following basic composition is used, the figures relating to parts by weight: Silicate of molar ratio SiO2 ;Na2O = 2.1 100 Fly ash 40 Slaked lime 7 Finely ground silicon 10 to 100 7 Al(Prolabo4018) 10to 100toe 2 Regulator x The fly ash is produced from the flue gases of power stations and have the following grain size: < 40 1% Oversize at 40 2% Oversize at 50 6 ' Oversize at 74 15% Oversize at 100 17% Oversize at 125 48% Oversize at 200 11% and a specific gravity d:0.4 Moulding is carried out in a wooden mould covered with a PVC film and of dimensions 34.9 x 34.9 x 20 cm.

The operating conditions and results are explained in the following tables. Type of Regulator Reaction Vapour Appearance of Ex. compound level time Expansion given off foam surface 1 Monopropylene 8 5 mn Disordered Slight Delaminated in glycol material - foam with poor appearance 2 Control without 0 3 mn Good (10.3 cm) Large Good ester 3 Composition 1 2 5 mn Slight Average Good 1 5 mn Average Average Good 4 Methyl lactate 2 7 mn Slight Average Good 1 6 mn Average Average Good 5 Propylene carbonate 4 6 mn Slight Slight Good 3 6 mn Slight Average Good 2 5 mn Average Large Average (cavernous) 6 Composition2 10 8 mn Slight (8 cm) Slight Good 8 6 mn Slight (4.2 cm) Slight Good 6 6 mn Average (8 cm) Slight Good 4 5 mn Average (8 cm) Average Good 2 5 mn Good (8.5cm) Large Good 7 Methyl acetate 4 3 mn Slight Slight Good 3 3 mn Slight Slight Good 2 3 mn Good Average Good 8 Methyl formate 2 6 mn Slight Average Good 1 4 mn Average Average Good Type of Regulator Reaction Vapour Appearance of Ex. compound level time Expansion given off foam surface 9 Formaldehyde 6 6 mn Average Average Good 10 Ethyl succinate 4 5 mn Good Average Poor 11 Composition 3 6 4 mn Average Slight Average 5 4 mn Average Slight Average 4 3 mn Good Average Average 12 Ethyl acetate 10 4 mn Good Average Average 13 Mixture of 10 4 mn Good Slight Average 30% monopropylene glycol and 70% ethyl acetate Small cavities Compressive K Shrinkage strength in # in in Ex. as % Appearance Size in mm Density Kg/cm2 Kcal W observations 1 DELAMINATED IN MATERIAL - FOAM WITH VERY POOR APPEARANCE 2 4 Small, average, 80% between 0.26 6.5 0.0630 0.6 irregular 0.75 - 1 3 2 Small, regular 0.3 0.39 22 0.0630 2.47 Use of small amounts 2.8 Small, regular 0.4 0.32 16 0.0620 2.00 4 2.2 Small, regular 0.2 0.38 26 0.671 2.41 Use of small amounts 2.8 Small, regular 0.2 0.29 15 0.0635 2.22 5 1.4 Small, regular 0.1 - 0.2 0.49 27 0.0784 3.60 2.2 Small, regular 0.8 0.37 20 0.0705 2.81 8 Small, regular 0.3 0.36 13 0.0663 1.72 6 1 Small, regular 0.2 0.52 21 0.0869 2.70 Possibility of obtaining a range 1 Small, regular 0.2 0.36 14 0.0726 1.91 of products with 1 Small, regular 0.5 0.29 8 0.0600 0.87 a good appearanc 1 Small, regular 0.7 0.32 7 0.0610 0.80 1 Small, regular 0.8 0.28 4.5 0.0580 0.70 7 0.3 Small, regular 0.2 0.36 22 0.0703 2.28 0.3 Small, regular 0.2 0.31 20 0.694 2.77 0.8 Small, regular 0.3 0.26 18 0.0697 2.46 8 0.7 Small, regular 0.1 0.38 22 0.0687 2.65 2.8 Small, regular 0.3 0.32 16 0.0654 2.42 Small cavities Compressive K Shrinkage strength in # in in Ex. as % Appearance Size in mm Density Kg/cm2 Kcal W Observations 9 2.8 Small, regular 0.3 0.37 14 0.747 2.62 10 1.2 Small, regular 0.2 0.25 5 0.0650 2.25 delaminated appearance 11 0.3 Small, regular 0.3 0.28 12 0.0718 2.50 0.6 but delaminated 0.3 0.28 11 0.0643 2.28 appearance 0.6 0.3 0.23 6 0.0648 1.98 12 0 Small, average, 0.3 - 2 0.22 6 0.0747 1.97 irregular 13 0.9 Regular 1 0.24 8 0.0626 1.65 In these tables: Composition 1 is constituted by 85 parts by weight of propylene carbonate and 15 parts by weight of methyl lactate, marketed by the Rhone-Poulenc Company under the Trade Mark PCL.

Composition 2 comprises 40% propylene glycol and 60% of a mixture of 20 parts by weight of methyl succinate, 60 parts by weight of methy glutarate and 20 parts by weight of methyl adipate and is marketed by Rhone-Poulenc under the Trade Mark MD 40.

Composition 3 contains 20 parts by weight of methyl succinate 60 parts by weight of methyl glutarate and 20 parts by weight of methyl adipate.

The tests were performed in the following manner: (a) The compound according to the invention is poured into the silicate in a cup and the solution is homogenized using a Rayneri stirrer. The inert charges, porophoric agents and finally the active filler (lime), are added in succession.

Depending on the reactivity of the mixtures introduction and mixing take between 2 and 5 mn.

(b) The thermal insulation coefficient measurements are carried out using a # type apparatus. The apparatus used measures the thermal conductivity or K factor according to Standard ASTM C 518.

The A is determined by measuring the quantity of heat passing through a known thickness of material having a known temperature gradient.

In the tables the term slight or small expansion means expansion between 3 and 5 cm, average expansion means expansion between 5 and 8 cm and good expansion an expansion in excess of 8 cm.

The tables indicate two control tests in one of which there is no compound according to the invention (ester-test 2) and the other where it is replaced by monopropylene glycol. It can be seen that the results are negative in both cases.

Test 3 shows that a compound according to the invention comprising a methyl ester and a propylene carbonate gives excellent results.

Tests 5 and 6 show the influence of the regulator level on the expansion of the foam, its shrinkage and the size of the cavities, i.e. its density, mechanical properties (R/C and A) and the vapour given off.

Tests 7 and 8 correspond to two other ester-type compounds.

Test 9 explains a case where the ester is formed in situ.

Test 10 describes a control example relating to an ethyl ester, where the low compressive strength should be noted.

Example 11 shows the influence of monopropylene glycol, the results being inferior to those of Example 6.

Example 12 should be compared with Example 7. It is clear that when substituting the ethyl radical for the methyl radical there is a definite deterioration of the properties, even when the quantity of regulator is increased.

Finally Example 14 shows the interest of a water treatment.

EXAMPLE 14.

According to this example the 4% MD 40 product of test 6 is treated with water under the following conditions: Dry weight of the block after stoving for 4 hours at 50 C: 1790g Immersion in water for 24 hours, followed by drying in a ventilated oven at 500C for 24 hours.

Weight of the block after stoving treatment: 1620 g i.e. a loss of 9%.

For comparison purposes the compressive strength, thermal conductivity and density before and after water treatment were determined.

Before After Density 0.32 0.29 Compressive strength (kg/cm2) 7 9 A 0.0610 kcal 0.0474 kcal A very definite improvement in the compressive strength and thermal conductivity is apparent.

In conclusion it can be stated that the Examples show that the presence of a regulator according to the invention leads to: a smaller quantity of vapour being given off; a controllable expansion as a function of the regulator level, making it possible to regulate in a random manner the size of the cavities, which is very important from a practical standpoint; A shrinkage level of about 1%, which is negligible and permits good moulding; great uniformity of the size of the cavities, i.e. a better appearance; a controllable density as a function of the regulator level; very similar compressive strength values for identical densities; improved thermal conductivity coefficient, due to a better uniformity of the cavities.

Thus, the regulator according to the invention can achieve a double objective of improving the quality of the product and the reliability of the process, making it possible to obtain a range of specific products covering the maximum number of possible applications and in particular building, motor and space vehicles, industry, mines, foundries and refractory materials.

WHAT WE CLAIM IS: 1. A method of producing an expanded alkali-metal-silicate-based material comprising mixing at least one alkali metal silicate and at least one pore-forming agent and expanding the resulting mixture without external heating in the presence of at least one methyl ester and, optionally, propylene carbonate.

2. A method as claimed in Claim 1, in which the pore-forming agent comprises aluminium and/or silicon.

3. A method as claimed in Claim I or 2, in which at least one methyl ester and propylene carbonate are both present.

4. A method as claimed in any preceding claim, in which the ester together with any propylene carbonate, is formed in situ during the expansion.

5. A method as claimed in any preceding claim, in which, based on the weight of silicate, the following are used: 5 to 50% of an active filler as herein defined, 10 to 120% of an inactive filler, 2 to 15% of a pore-forming agent, and 0.1 to 10% of methyl ester or methyl ester plus propylene carbonate.

6. A method as claimed in any preceding claim, in which the alkali metal silicate has a molar ratio SiO2:Na2O of about 2:1.

7. A method as claimed in any preceding claim, in which the product subsequently undergoes treatment with water.

8. A method as claimed in Claim I substantially as hereinbefore described in any one of the Examples.

9. A product obtained by the method as claimed in any one of Claims I to 6.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Thus, the regulator according to the invention can achieve a double objective of improving the quality of the product and the reliability of the process, making it possible to obtain a range of specific products covering the maximum number of possible applications and in particular building, motor and space vehicles, industry, mines, foundries and refractory materials. WHAT WE CLAIM IS:

1. A method of producing an expanded alkali-metal-silicate-based material comprising mixing at least one alkali metal silicate and at least one pore-forming agent and expanding the resulting mixture without external heating in the presence of at least one methyl ester and, optionally, propylene carbonate.

9. A product obtained by the method as claimed in any one of Claims I to 6.