WO2004071986A1

WO2004071986A1 - Cement and foam polymer mix and method for its manufacturing

Info

Publication number: WO2004071986A1
Application number: PCT/SE2003/000250
Authority: WO
Inventors: Håkan DACKEFJORD
Original assignee: Eps Cement Svenska Ab
Priority date: 2003-02-14
Filing date: 2003-02-14
Publication date: 2004-08-26
Also published as: AU2003217090A1

Abstract

The invention concerns a method for manufacturing a cement and foam polymer mix, whereby the foam polymer comprises separate particles. Th foam polymer is treated so that the surface binds dry cement whereafter dry cement is mixed with the separate particles of foam polymer and the cement becomes bound at the surface of the foam polymer particles. The invention also concerns a cement and foam polymer mix, comprising separate particles of foam polymer The separate particles of he foam polymer, treated so that its surface melts, are mixed with cement, whereby the cement is bount at the surface of the separate particles of foam polymer.

Description

CEMENT AND FOAM POLYMER MIX AND METHOD FOR ITS MANUFACTURING

The present invention concerns a cement and foam polymer mix and a method for its manufacturing.

Background of the invention Since some years it is known to cast for example floors and systems of joists in buildings of cement and finely disintegrated foam polymer, usually expanded polystyrene polymer. This material, a kind of low density concrete, has many advantages, such as low density, quick drying, low shrinking, is heat insulating and easy to cast.

To the building site cement and finely disintegrated foam polymer are separately transported, the latter is preferably anti-static treated and sometimes cured, for example hardening by partial melting, so that a higher tensile strength in the completed material, the low density concrete, may be achieved.

At the site cement, finely disintegrated foam polymer and water are mixed in a forced paddle mixer. A forced paddle mixer is a mixerdrum, which comprises a through going, rotating axle provided with a number of large knife blades which force the contents in the drum towards one end of the drum and a number of smaller knife blades arranged so that they force the contents in the drum towards the other end of the drum. In this way the materials to be mixed will be moved back and forth in the drum until a homogeneous mix have been achieved.

Thereafter the mixed composition is blown into a chosen cast mould whereafter the composition will dry.

The problem

It is not possible to mix cement, finely disintegrated foam polymer and water in a conventional concrete mixer, such as a rotating drum provided with mixing ribs along the inside of the drum due to the large density difference between the cement and the foam polymer. It is not possible to obtain a homogeneous mix.

Forced paddle mixers are expensive and bulky and not many private people or smaller companies have the possibility to have such a mixer. At the same time this material has such important building technical advantages that it is interesting also for the consumer market. The problem the present invention aim to solve is to provide a consumer product, which with certainty will give these positive properties that can be obtained at large building sites.

Many people have tried to solve this problem during the last years but not succeeded until now.

Summary of the invention

The invention solves the problem by means of a manufacturing method according to claim 1 and a consumer product according to claim 8.

Thanks to the invention the cement is already evenly distributed in relation to the foam polymer at the time when water shall be added to form the low density concrete composition. This means that the consumer product may be mixed with water in, for example, a bucket and it suffices to stir with a stick to make the composition homogeneously mixed and thus give the desired properties of the material. If the material is not homogeneously mixed, different portions of the low density concrete will have different technical properties. Particularly, the co pressive strength will fluctuate through the material, which is very negative.

The essence of the invention is that the dry cement binds to the foam polymer.

Detailed description of a preferred embodiment

In order to manufacture a consumer product, which comprises a cement and foam polymer mix, you start with finely disintegrate, for example by grating, foam polymer, preferably expanded polystyrene, to particles, for example in the size range 5-8 mm. Preferably the finely disintegrated foam polymer is anti-static treated and sometimes also cured.

Or instead polymer particles may be used, which arise at polymerization of the polymer, i.e. polymer particles that have not been used already in for example packaging. The polymer particles are expanded before they are mixed with the cement. A wide range of particle-sizes may be used, for example particles in the size range up to 0,5 mm in the unexpanded state. Preferably these polymer particles are not expanded as much as is normal for making expanded foam polymers. Preferably, they are expanded to a size range up to 1,0 mm. It is of course conceivable to use polymer particles of larger sizes, too.

The surface of the foam polymer particles must be treated so that the dry cement will bind to the surface. One way to accomplish this is to treat the surface so that it melts, i.e. a local softening of the surface of the foam polymer particles occurs, whereby the surface becomes sticky. This can be accomplished by heating the surface by means of, for example, hot air. The heating of the surface may instead or also be accomplished by means of a reaction at the surface between a chemical and the foam polymer. Another way to accomplish a cement-binding surface is to apply an adhesive.

The surface of the foam polymer particles ought to reach a temperature of 45-60°C, preferably 50-55°C, in order to achieve best possible adherence between cement and foam polymer surface. When the right temperature is obtained at the surface of the foam polymer the finely disintegrated foam polymer is mixed with cement, the cement adhere to the surface of the foam polymer, more specifically all around the whole surface of each particle of the foam polymer.

Since no water is added when using the treatment of melting the surface but it is the foam polymer in itself that melts, the cement will not start to burn, i.e. cure, but only adhere to the foam polymer particles in order to at a later stage be able to cure when mixed with water.

When instead the alternative treatment is used it is important that the adhesive does not cause the cement to cure. Examples of adhesives that do not cause the cement to cure are non-water containing adhesives, such as non-water solution of a water-soluble polymer.

The completed product according to the invention thus comprises particles of foam polymer, which are covered with cement. The consumer then mixes the product according to the invention with water and a homogeneous mix of cement and foam polymer arise automatically when all cement has been wet. Thereafter the consumer can cast according to his/her own desire something that gives a low density concrete that will dry in 1-3 days.

Claims

1. A method for manufacturing a cement and foam polymer mix, whereby the foam polymer comprises separate particles, characterized in that the foam polymer is treated so that the surface binds dry cement whereafter dry cement is mixed with the separate particles of foam polymer and the cement is bound at the foam polymer particles .

2. A method according to claim 1, wherein the foam polymer is treated so that the surface melts.

3. A method according to claim 2, wherein the foam polymer is treated by heating so that the surface melts.

4. A method according to claim 3, wherein the heating is accomplished by means of hot air.

5. A method according to claim 1 or 2, wherein the foam polymer is treated with chemicals so that the surface melts.

6. A method according to any of the claims 1-5, wherein the temperature of the surface reaches 45-60 °C, preferably 50-

7. A method according to claim 1, wherein the foam polymer is treated by applying adhesive to the surface of the separate particles.

8. A cement and foam polymer mix, comprising separate particles of foam polymer, characterized in that the separate particles of the foam polymer, treated so that the surface binds dry cement, is mixed with dry cement, whereby the cement is bound at the surface of the separate particles of foam polymer.

9. A cement and foam polymer mix according to claim 8, wherein the foam polymer is expanded polystyrene.