LU85822A1 - PROCESS FOR PRODUCING A POROUS STRUCTURE COMPRISING ORGANIC MATERIAL DISPERSED IN A BINDER - Google Patents

Abstract

1. A process for producing a porous structure containing as a minimum an organic material, biologically active or of biological origin, dispersed in a binder, characterized by a sequence of operations as follows : the organic material, biologically active or of biological origin, in powder form, and the pulverulent binder in the dry state are mixed together to form a mixture ; this mixture is subjected to an agglomeration treatment in order to form agglomerates ; the agglomerates thus formed are subjected to a crushing treatment in order to form crushed agglomerates and the crushed agglomerates are compressed together in order to form a tablet, all these operations being performed at a temperature below 340 degrees Kelvin.

Description

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The present invention relates to a method for producing a porous structure comprising an organic material dispersed in a binder.

There are several embodiments of 5 porous structures comprising an organic material dispersed in a binder. Such structures have numerous applications in particular in chemical and more particularly biochemical methods and analyzes, in biological tests, pharmacology and the food industry.

The known processes for the production of these porous structures generally comprise a phase of treatment at a temperature substantially above ambient temperature and destructive of the organic material or of the bond between the latter and its support in the structure.

It follows that the fixing of organic matter on the support is necessarily the final phase of production; fixation is then more difficult to achieve and the regularity of the desired distribution of organic matter through the structure suffers. Especially if the organic material is to be fixed on a pulverulent support to be incorporated into the binder, the fixing of the material on the support is more easily controlled if it is carried out on the pulverulent support not yet incorporated in the binder. As the coupling between the support and the organic material is preferably to be carried out in the form of a covalent bond, it is to be avoided that this must occur with the support 30 already incorporated.

US-A-3,766,013 which describes methods for producing a porous structure comprising a binder according to which the coupling of organic matter.

4, - 2 - in this case an enzyme, is done on an organic support already incorporated in a binder, in this case polytetrafluoroethylene, points out that the coupling can also be carried out after fibrillation of the binder, 5 therefore with a support already incorporated, if the enzyme supports high temperature, but in practice the enzymes, and in general the biological materials to be incorporated, are destroyed at the temperatures required for the other phases of the production process.

The object of the invention is essentially to provide a process which can be carried out under conditions such that the organic material, therefore optionally the organic material already fixed on a support, can be incorporated into the binder without this material and / or its mounting on the support are not destroyed.

To this end, the method according to the invention comprises the following sequence of operations: - the organic material in the form of a powder and the pulverulent binder in the dry state are mixed together to form a dry mixture, - this dry mixture is subjected to an agglomeration treatment to form agglomerates, - the agglomerates formed are subjected to a grinding treatment to form crushed agglomerates "and - the crushed agglomerates are pressed together to form a tablet.

Preferably, all of the operations are carried out at ambient temperature.

In an advantageous embodiment of the invention, the tablet is subjected to rolling until a film is obtained.

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In a particular embodiment of the invention, the organic material is fixed on a pulverulent support and the pulverulent support laden with the organic material and the pulverulent binder in the dry state are mixed together to form a dry mixture.

It should be noted that a process comprising a succession of operations comparable to that according to the invention is known for the production of an electrode layer for a fuel cell. According to this method known from EU-A-43 632, a fine inorganic electrically conductive powder and the binder are mixed. It has been found according to the invention that, surprisingly, a comparable succession of operations also makes it possible to incorporate an organic material in a binder for the production of a porous structure intended for biological and similar applications.

Other details and particularities of the invention will emerge from the description of several embodiments of a process for producing a porous structure comprising an organic material dispersed in a binder according to the invention given below by way of description. 'nonlimiting example.

The structure to be produced by the process according to the invention is generally a structure in the form of a film or a disc therefore extending essentially in two dimensions, but can also be a three-dimensional structure. The porous structure is constituted by the dispersion of the organic material or of a pulverulent support loaded with this organic material within a porous matrix constituted by the binder. The aforementioned support can also be microporous.

Organic matter is for example a protein and more particularly an enzyme. Examples of organic materials are found in US-A-3,766,013 incorporated herein by reference. Another example of an organic material which can be used in the process according to the invention is cellulose.

The organic material, in particular the enzyme, can be coupled to a pulverulent support. Examples of such supports are found in US-A-3,766,013. The coupling between the pulverulent support and the organic material is carried out before the support is incorporated into the structure by the process according to the invention. The particularities of the coupling reaction are not part of this patent application.

It should however be noted that the coupling of the organic material to the support is preferably a covalent bond and that the coupling reaction known as such is a difficult and complex reaction. It is important according to the invention that this reaction is carried out on the organic material and the support not incorporated in the structure. The dosage is then more easily and more precisely controlled.

The binder should lend itself to the formation of a porous matrix. It can in particular be chosen from polyethylene, polypropylene, polyvinyl chloride, carbon polyfluorides and polytetrafluoroethylene.

If it is desired to limit or avoid the hydrophobic nature of the binder, the powder constituting the binder can be hydrophilized before the other operations of the process. This hydrophilization can consist of a treatment with a known hydrophilic liquid such as the liquids mentioned in US-A-4,252,878 incorporated herein by reference.

The process itself consists of a succession of the following operations.

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In a first operation, the organic material in the form of a powder is mixed together or the pulverulent support loaded with the organic material and the pulverulent binder in the dry state to form a dry mixture.

The percentages of the constituents to be mixed depend on the nature of the binder and the nature of the support and / or of the organic matter, but the amount of binder by weight relative to the whole of the mixture normally remains less than 30%. The mixing is carried out in any powder mixer 10, for example in a ball mixer in which the balls have a speed of the order of 0.1 to 1 m / sec relative to the tank. In a second operation, the dry mixture is subjected to an agglomeration treatment to form agglomerates. This is done in a ball mill in which the balls have a speed substantially higher than that applied to form the mixture, for example a speed of the order of 4 to 6 m / sec relative to the tank.

This agglomeration treatment can have a duration of several hours. After this operation, the crusher comprises 20 agglomerates in the form of a skin and 2 having an area of the order of a few cm to a few hundred crn ^.

In a third operation, the agglomerates are subjected to a grinding treatment to form crushed agglomerates, for example in a mixer or in a grinder of the coffee grinder type.

In a fourth operation, the crushed agglomerates or their useful fraction, for example the fraction passing through a 0.5 mm screen, are compressed in a press to a thickness of a few centimeters.

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In a fifth operation, the tablet is subjected to laminations until its thickness is reduced in a ratio of 1/10 to 1/50. The successive rolling steps are carried out on a tablet displaced by 90 °.

5 All operations are carried out at room temperature s and in any case at a temperature below 340 ° K.

Example 1.

50 grams of polytetrafluoroethylene powder (sold commercially under the brand name Teflon 10 N) and 10 50 grams of cellulose powder are introduced into a laboratory ball mill.

4 stainless steel balls with a diameter of 30 mm are also introduced into the mill.

After 2 hours of rotation the crusher is open; 15 its walls are covered with a "skin" formed by cellulose and polytetrafluoroethylene.

The skin is removed and ground in a kitchen mixer.

20 grams are taken and introduced into a press by means of which a tablet of 3.5 x 70 x 70 mm is formed.

The tablet is cold-rolled until a sheet 0.2 mm thick and 510 x 135 mm in surface is obtained 2.

-2 25 This sheet has 9.5 mg.cm of polytetra-. fluoroethylene and cellulose.

After soaking in water, it is found that after 12 hours the sheet has adsorbed 20% of its volume in water.

Example 2.

30 The procedure is as in Example 1, but the polytetrafluoroethylene powder is hydrophilized before it is introduced into the mill.

To this end, the polytetrafluoroethylene powder is immersed in a solution at 40% by weight of the product 4 - 7 - known in the trade under the name "Zonyl FSN" and is kept there for five days.

When a sample of the sheet produced according to this second example is immersed in water, it is found that after 30 seconds the sheet has adsorbed 50% of its volume in water.

The invention is in no way limited to the embodiments described above and in the context of this patent application numerous modifications can be made to it.

Claims (11)

1. Method for producing a porous structure comprising an organic material dispersed in a binder "characterized by the following sequence of operations: 5. the organic material in the form of a powder and the pulverulent binder are mixed together dry state to form a dry mixture, - this dry mixture is subjected to an agglomeration treatment to form agglomerates, 10. the agglomerates formed are subjected to a grinding treatment to form crushed agglomerates and - the crushed agglomerates are pressed together to form a tablet. 2. Method according to the preceding claim, characterized in that all the operations are carried out at a temperature below 340 ° K. 3. Method according to the preceding claim, characterized in that all the operations are carried out at room temperature. 4. Method according to either of the preceding claims, characterized in that the tablet is subjected to rolling until a film is obtained. 5. Method according to either of the preceding claims, characterized in that - fixes the organic material on a powdery support and that the powdery support loaded with organic matter and the powdery binder is mixed together with the 30 dry state to form a dry mixture. 6. Method according to the preceding claim, characterized in that the organic matter is fixed on the pulverulent support by covalent bond. βι. ** - 9 - 7. Method according to either of the preceding claims, characterized in that the carrier of the organic material is cellulose. 8. Method according to either of the preceding claims, characterized in that polytetrafluoroethylene is used as binder. 9. Method according to either of the preceding claims, characterized in that the pulverulent binder is hydrophilized and that the organic material in the form of a powder and the hydrophilized pulverulent binder are mixed together. 10. Method according to either of the preceding claims, characterized in that a biologically active material is used as organic material. 11. Method according to the preceding claim, characterized in that an enzyme is used as the biologically active material. * at