GB1598468A

GB1598468A - Process for producing insulating sheets from finely dispersed material

Info

Publication number: GB1598468A
Application number: GB1109578A
Authority: GB
Original assignee: Gruenzweig und Hartmann AG
Current assignee: Saint Gobain Isover G+H AG
Priority date: 1977-03-23
Filing date: 1978-03-21
Publication date: 1981-09-23
Also published as: CH632729A5; FR2384731B3; DE2712625A1; AT369726B; ATA114678A; BE865174A; FR2384731A1

Abstract

The invention relates to a process for producing insulating panels from finely disperse material, consisting of a mixture of pyrogenic silica and an opacity agent such as TiO2, which is pressed and enveloped. Such insulating panels of microporous silica are, because of their specifically high heat conduction resistance and their resistance to very high and low temperatures, used increasingly in technical apparatus, especially if a high insulation effect against heat and cold is demanded with little space available. To obtain a homogeneous heat insulation panel, the pressing step should be carried out according to the invention in a heated mould or between at least two press plates, at least one of which is heated. In addition, the finely disperse material can be pressed under a pressure of from 5 to 10 kp/cm<2> and the envelope can be heated to about 70 DEG C to 350 DEG C during pressing.

Description

(54) PROCESS FOR PRODUCING INSULATING SHEETS FROM FINELY DISPERSED MATERIAL (71) We, GRUNZWEIG + HARTMANN UND GLASFASER AG, a German Company, of Burgermeister Grunzweig-Strasse I - 47, 6700 Ludwigshafen am Rhein, Germany, 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 a process for producing a thermally insulating sheet from finely dispersed, particulate material comprising a mixture of pyrogenic silicic acid and an pacifying agent, for example TiO2, which is pressed in a casing.

Due to their specifically high resistance to thermal conductivity and their resistance to very high and low temperatures, insulating sheets of the above-mentioned kind, made from micro-porous silicic acid, are widely used in technical equipment, patti- cularly when an insulation effect against heat and cold is required and there is little space available.

In the hitherto known processes for making these sheets, the finely dispersed material was placed in casings in the form of bags made of spun glass fabric, paper or similar material. The bags were then sewn up and pressed. Attempts have ibeen made to achieve a tensioning of the casing during this pressing process by the transverse flow of the material as it was being pressed.

However, tests show that this tensioning depends to a great extent on the gross density and the fluidity of the particulate material during the pressing process, so that frequently the desired goal is not attained.

The present invention aims to provide an improved process for producing the above described insulating sheets.

According to the invention a process for producing a thermally insulating sheet from finely dispersed, particulate material com- prising a mixture of pyrogenic silicic acid and opacifying agent, which is pressed in a casing, is characterised in that the pressing process is carried out between two pressing plates, at least one of which is heated.

In the process in accordance with the invention the following physical processes are produced: 1. Due to a temperature time function, the casing is brought up to a specific tem perature so that when, for example spun glass fabric is used as the casing, expansion of the surface results.

2. Due to the simultaneous pressing pro cess, the insulating particulate material is compressed through its thickness and forced out in the direction of the large surfaces, i.e. length and breadthwise, corresponding to the extension of the casing. The subsequent cooling of the casing causes it to shrink, so that the particulate material is enclosed firmly and under tension. Since the particulate material itself has poor thermal con ductivity, heat is concentrated in the casing during the pressing process whilst the insulating material remains relatively cold.

The finely dispersed material may be pressed with a pressure of 5 to 10 kpl/cm2 and the casing may Ibe heated to a temperature of from around 70" C to 3500 C during the pressing stage. Temperatures of up to 350" C are intended for casings made of spun glass fabric and similar temperature resistant materials, for example metallic aloth or metallic foil.Naturally, temperatures of very much more than 350" C can also be used, but in this case the heating up time must be reduced and, where appropriate, the pressure increased so that the casing is brought to the desired temperature in a shorter period of time and the desired minimum pressure necessary for binding the particulate material is applied throughout the latter when the pressure is transmitted.

Since the insulating sheets may be used not only for insulation against heat but also against cold, the casing need not be made from heat-resistant material, for example spun glass fabric, but from a casing material which is only resistant to cold, for example shrinkable foil or fabric. In this case temperatures of from 70" C to 100" C may be used during the pressing, and the pressure against the shrinkable foil causes tensioning. As the shrinkable foil shrinks, the finely dispersed material is simultaneously compressed through its thickness and forced out in the surface planes, i.e. in length and breadth. In this case as well, by using the process in accordance with the invention an insulating sheet is produced with the casing firmly enclosing the particulate material.

WHAT WE CLAIM IS: 1. A process for producing a thermally insulating sheet from finely dispersed, particulate material comprising a mixture of pyrogenic silicic acid and opacifying agent, which is pressed in a casing, characterised in that the pressing process is carried out between two pressing plates, at least one of which is heated.

2. A process according to claim 1, in which the finely dispersed material is pressed with a pressure of from 5 to 10 kp/cm2, and that the casing is heated during the pressing process to a temperature of from 70" C to 350" C.

3. A process according to claim 2, in which the casing is made of spun glass fabric, paper, metallic cloth or metallic foil.

4. A process according to claim 1, in which the casing is heated during the pressing process to a temperature of from 700 C to 100" C.

5. A process according to claim 1, in which the casing is made of shrinkable foil or fabric.

6. A process according to any of the preceding claims, in which the opacifying agent in the particulate material is TiO2.

7. A thermally insulating sheet when made by the proecss claimed in any oF the preceding claims.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. this case temperatures of from 70" C to 100" C may be used during the pressing, and the pressure against the shrinkable foil causes tensioning. As the shrinkable foil shrinks, the finely dispersed material is simultaneously compressed through its thickness and forced out in the surface planes, i.e. in length and breadth. In this case as well, by using the process in accordance with the invention an insulating sheet is produced with the casing firmly enclosing the particulate material. WHAT WE CLAIM IS:

1. A process for producing a thermally insulating sheet from finely dispersed, particulate material comprising a mixture of pyrogenic silicic acid and opacifying agent, which is pressed in a casing, characterised in that the pressing process is carried out between two pressing plates, at least one of which is heated.