WO2012158054A1

WO2012158054A1 - A method of manufacturing foamed, amorphous, non- flammable insulating materials

Info

Publication number: WO2012158054A1
Application number: PCT/PL2012/050011
Authority: WO
Inventors: Dariusz HRENIAK; Magdalena SKRAJNOWSKA; Wiesław STRĘK; Edward Reszke
Original assignee: WROCŁAWSKIE CENTRUM BADAŃ EIT+ Sp z o.o.; Instytut Niskich Temperatur I Badań Strukturalnych
Priority date: 2011-05-13
Filing date: 2012-05-11
Publication date: 2012-11-22
Also published as: PL394854A1; EP2707341A1; PL218302B1

Abstract

A method of producing foamed, amorphous and non-flammable insulating materials, characterized in that the foaming is performed through subjecting a material to the flow of electrical current in order to increase the temperature of the material to a temperature required for foaming, whereas the foamed material is a granulate based on colloidal silica with a grain size from 1 to 20 mm with an addition of a foaming agent and water.

Description

A method of manufacturing foamed, amorphous, non-flammable insulating materials.

The subject of the present invention is a method of producing foamed, insulating, non-flammable and amorphous insulating materials based on colloidal silica and using a foaming agent as well as a device for performing the process.

Known are methods for producing foamed materials based on silicon oxides and industrial waste materials and mineral dust with the use of high temperatures, such as in patent application P.388764. Materials were mixed at a ratio from 3:5 to 1:1 (ratio of total dust mass to the mass of vitreous sodium silicates), along with an addition of specified amount of boric acid. After drying, the material was triturated into finer pieces and heated in a form at a temperature in the range of 250 - 600 °C. The silicates used in the process were such materials as: AEROSIL, T-30; the industrial waste used was SILIMIC, and the mineral dust was DIATOMIT. The goal of the indicated invention was to lower the costs of production by using waste resources. Depending on the form used, the resulting blocks of foamed glass assume a particular shape (plates, disks, cylinders, tubes, cubes, etc.) . To achieve a positive effect, the authors suggest the partial replacement of fired silicates with mineral dust and industrial waste resources in a dust form.

Likewise, known are methods of foaming materials based on silicon oxide using microwave radiation. For example, method described in patent application P.392889 is based on producing a homogeneous suspension in the form of a sol of colloidal silica with a fine grain of the size of 7 nm - 350 ]i and of aqueous sodium glass at a ratio from 2 to 1 to 10 to 1. Next, following the drying of the sol at a temperature of 80 - 90 °C for maximally 2 hours, such a prepared material is subjected to granulation into smaller pieces. The drying stage may be omitted in the process, but this depends on the composition of the material. The material is placed into a plastic mold and is subjected to microwave radiation. Depending on the material composition, various power levels and varying heating times are used. Microwave ovens may be used for this purpose. The forming makes use of plastic containers with increased heat resistance, as well as teflon pipes and containers. In effect, a porous, foamed material is obtained with a cellular structure. This synthesis makes use of such silicates as: AEROSIL^® OX-50, Evonik Degussa GmbH, Germany; AEROSIL^® A-380, Evonik Degussa GmbH, Germany; Arsil, Z . Ch . Rudniki S. A. In an example process, 690g of aqueous sodium glass and 200g of Arsil colloidal silica are mixed using a mechanical mixer until a sol is obtained. Next, the material is dried at a temperature of 90°C for 30 minutes. The substance is subjected to microwave radiation at 650W for 10 minutes in a microwave oven. This results in a block of foamed material.

Also known is a method of foaming polystyrene in a high frequency field, US 3,341,638. Prior to foaming the material, it is significant that the polystyrene is moistened with a moisturizing agent or an electrolyte dissolved in water, i.e. salt, such that it becomes conductive. The wetting process is performed in a mixer through misting the dissolved electrolyte via nozzles. It is important to initially moisten the molecules prior to foaming the material. These materials are produced in the form of sheets, via a continuous spraying process so as to form multiple layers of the material.

Furthermore, also known are methods of foaming plastic materials, which make use of high frequency electric fields, as in US 3,413,434. The foaming of materials under the control of a high frequency electric field has also been used in the production of parts of large materials (i.e. structural elements with a polystyrene core or a middle layer) . The advantage of said invention is that energy losses are limited to a minimum. The patent describes an apparatus for the production of materials containing synthetic materials using high frequency electric fields. The core of the produced materials is in the form of a plastic foam, and the external electrode is composed of two parts. A metallic screen with supplied high-frequency current is connected with the external electrode. An electrical connection of the lateral pieces of the device is enabled through the conducting material.

There are also other known methods of producing porous materials i.e. those based on slag from an electric arc furnace US 2007/0133651. The goal of the cited description is to deliver a method of increasing the efficiency of the functioning of an electric arc furnace (EAF) used for controlling slag foaming. The authors present an improved method of stabilizing the arc in an arc furnace using an automated method based on the evaluation of an objective criterion. The device adds a foaming agent into slag in an automated fashion, or said agent is added by hand at a particular time. This agent may contain carbon, coke, graphite powder, calcium, MgO or combinations thereof and may be added such that the arc is stable: i.e. when the earlier defined arc stability criterion is not met, and the foaming agent is no longer added. The furnace contains at least one column electrode. The method supposes the use of at least one mobile electrode inside and one outside the electric furnace, as well as an appropriate power supply, ensuring voltage to the electrodes so as to cause an electric arc. There is also a method of foaming thermoplastic materials resistance-heated under high pressure disclosed in PCT WO2008/112813. The patent describes methods of reducing the density of thermoplastic materials and products similar to them, which possess improved mechanical properties in relation to solid bodies or non-cellular materials. The description also mentions an improved method of foaming materials with a cellular structure, with a cell size from 0,1 - 100 using an electric arc, and of forming the shapes of these materials, wherein the method consists of several stages: production of a thermoplastic material impregnated with a gas under a pressure from 1 MPa to 5 MPa, placing the material in a press and subjecting it to a pressure, heating the press such that cells form, and removing the gas from the material, such that the material becomes free of bubbles and surface deformations. The thermoplastic material placed in the press has a thickness of over 3 mm. The following actions are performed to produce the cellular structure: the first thermoplastic material is placed above the second (the surfaces are superimposed) , the material is gas-impregnated, the second material is heated to cause foaming in areas of higher gas concentration in the first and second thermoplastic material.

The goal of the present invention is to produce a foamed, amorphous, non-flammable insulating material with an open- celled structure. The characteristic differentiating the resulting product from similar materials is that the material is produced more economically, because the foaming is performed continuously without the need for large heating ovens .

According to the present invention, the method of producing foamed, amorphous and non-flammable insulating materials is characterized in that the foaming is performed by subjecting the material to the flow of current in order to increase the temperature of the material to a point required to foam it , whereas the foamed material consists of a granulate of colloidal silica with a grain size of from 1 to 20 mm with an addition of a foaming agent and water. The material is subjected to electrical current continuously or in impulses, wherein the process occurs at a pressure in the range from 1.5 to 100 Bar. The temperature at the input is contained in the range from 20 - 90 °C. The end temperature of the process is from 100 to 350 °C. The foamed material is is ejected from the reactor using an external force. The multiphase alternating or direct current frequency is in the range from 10 Hz to 20kHz.

Example 1

The raw material is composed of colloidal silica with grain sizes below 350 μηι and a foaming agent is formed in the shape of a pill 10 mm high and 20 mm in diameter. This tablet is placed in the foaming apparatus between steel pistons, of which one or both is connected to a steady compression force of 1000 kg. The pistons are connected to an alternating current source of 6 A at a frequency of 50 Hz. As a result of current flow, the foamed material is heated to a temperature above 300°C and at the same time it is violently foamed following a short time of 2-10 s, depending on current density. The foamed material is ejected from the apparatus via the force applied to the pistons through an appropriate ejection nozzle. This material is in the form of a foam, which is amorphous and with a pore size of from 0.1 to 1 mm. Example 2.

Using a pumping pressure through a channel with a rectangular cross-section, two opposite walls of the channel can be made of metal such that they constitute two electrodes supplying an alternating electrical current, with a frequency in the range from 10 Hz to 20kHz, to a material flowing through the channel.

Claims

1. A method of producing foamed, amorphous and non- flammable insulating materials, characterized in that the foaming is performed through subjecting a material to the flow of electrical current in order to increase the temperature of the material to a temperature required for foaming, whereas the foamed material is a granulate based on colloidal silica with a grain size from 1 to 20 mm with an addition of a foaming agent and water.

2. A method according to Claim 1, characterized in that the material is subjected to the flow of electrical current in constant or impulse fashion, wherein the process occurs at a pressure in the range of 1.5 to 100 Bar.

3. A method according to Claim 1, characterized in that the temperature at the input of the system is in the range of 20 to 90 °C.

4. A method according to Claim 1, characterized in that the end temperature of the process is in the range of 100 to 350

°C.

5. A method according to Claim 1 characterized in that the foamed material is ejected from the reactor due to an external force.

6. A method according to Claim 1. characterized in that the electrical current used for the foaming process is direct current or pulsed direct current, or alternating current, or multiphase electrical current.

7. A method according to Claim 6 characterized in that the frequency of the alternating or multiphase alternating current is in the range of 10 Hz to 20kHz.