FR2931157A1 - SOLID MATERIAL CONTAINING AN ACTIVE LOAD AND ENABLING GREAT FACILITY OF ACCESS TO THIS LOAD - Google Patents

Abstract

The invention relates to a solid material containing an active charge and allowing great accessibility to this charge.This material comprises a matrix of microporous and open-pore shaped material, and a particulate active charge of which at least part is housed in the state in at least a portion of the pores of said matrix.The invention also relates to a method of manufacturing such a material.

Description

The present invention relates to a solid material containing an active charge and allowing great accessibility to this load; it also relates to a method of manufacturing such a material.

In many fields (industrial, medical, cosmetic, food, ...), substances with various properties (physical, chemical, biological, ...) are used to perform various tasks. They may be absorbent, reactive, insulating, etc. These are generally used in particulate form and depending on their nature, can be fixed or not on a support to facilitate its implementation. In certain applications, it is particularly advantageous for these substances to be dispersed, as fillers, in the vicinity of the surface of the wall of the structure (tube for example) intended to contain or convey the product with which these charges must react. The solutions of this type proposed to date are unsatisfactory since said product only reaches the load slowly and / or in a limited way because of the low permeability of said wall to this product. The object of the present invention is to remedy these drawbacks and to do this, it proposes a solid material, 25 containing an active charge and allowing great accessibility to this load; this material is characterized in that it comprises, on the one hand, a matrix of shapeable material, this matrix being microporous and with open pores, and, on the other hand, a particulate filler of which at least a part is housed in the free state in At least a portion of the pores of said matrix. Note that the matrix may for example be constituted by a thermoplastic (co) polymer, in which case the particulate filler is thermostable. The material according to the invention has many advantages. 35 It is light because of its microporous structure. It combines a considerable surface area due to the microporosity of the matrix (and possibly the filler) to an optimum accessibility to the particulate filler resulting from the open pore network of porosity; these pores, and thus the charge which is lodged there, are thus easily affected by any substance which one would seek to make act or react on this load.

Since the matrix of this material consists of a shapeable material, in particular a thermoplastic (co) polymer, it is possible to produce this material in the form desired by conventional shaping techniques, such as extrusion, injection molding, thermoforming, for example, this shape being able to be that of a tube, a sheet, a container, in addition, the particulate filler being in the free state, that is to say not totally coated by the matrix and not chemically linked to the latter, it is more easily accessible and therefore of optimum efficiency.

The particulate filler content of the material according to the invention may vary within wide limits. It will depend on the nature of this load and the function it is intended to fill, but nevertheless limited to maintain sufficient mechanical strength of the material and allow the implementation of the conventional techniques of shaping mentioned above. Generally, the weight ratio matrix / particulate filler is in the range of 0.1 to 4. The filled material according to the invention preferably has a porosity corresponding to a density of 0.3 to 1.2, the matrix having for its part, preferably a porosity corresponding to a density of 0.1 to 0.8. Furthermore, the particle size of the particulate filler is preferably in the range of 1 to 200 μm.

According to one embodiment of the invention, the particulate filler is polar and the constituent material of the matrix is a non-polar (co) polymer or having a polarity lower than that of the charge. In this case, said (co) polymer may for example be a polypropylene (PP) or a polyamide (PA). Alternatively, the particulate filler may be non-polar and the constituent material of the matrix may be a polar (co) polymer. The material according to the invention has applications in the most diverse fields depending on the nature of the particulate filler. Thus, this charge can be: an absorbent or adsorbent substance, in which case the material can be used for the collection of water, water vapor, gas, odors, dust, etc ..., - a substance with chemical or biological properties, the material can then be implemented in reactions involving a substrate sensitive to these properties, or a substance with conductive properties or electrical, thermal or acoustic insulation, the material then finding applications in the electrical, electronic, heat exchange and insulation fields.

By way of non-limiting examples of absorbing or adsorbent substances, mention may be made of zeolites, CaO, CaSO4, silica gel and alginates. Examples of substances with chemical or biological properties are iron powder (oxygen scavenger), enzymes, catalysts, electrolytes, bacteria. It will be noted that the particulate filler may be constituted by the abovementioned substances themselves or by those substances supported by a particulate substrate. The present invention furthermore relates to a method of manufacturing the above material in which the matrix consists of a (co) polymer, characterized in that it comprises the operations of: mixing in the molten state under shear, two thermoplastic (co) polymers and a particulate filler, these two (co) polymers being incompatible with each other and chosen to be divided into two co-continuous phases in the mixture obtained, the filler being for its part selected for be essentially distributed within the phase constituted by one of the two (co) polymers, possibly shaping said mixture to give it the desired shape, and 4 - after solidification of said mixture, selectively removing at least partially the phase of polymer in which the charge is distributed. As is well known in the field of polymers, in a mixture of two incompatible (co) polymers divided into two co-continuous phases, the level of dispersion one in the other of the two (co) polymers is molecular order, that is to say with no nodules of one of the (co) polymers, dispersed in the other (co) polymer.

It follows that by selectively removing one of the (co) polymer phases, an open pored microporous polymer matrix is formed, the charge remaining housed at least partially in at least a portion of the pores thus formed. . The weight ratio between the two (co) polymers used in the initial mixing operation may vary within wide limits; However, it is preferable that the initial concentration of polymer to be removed is as high as possible to obtain, after its selective removal, a matrix as porous as possible, the limit may however be the desired strength of the final material. Thus, the weight ratio between the (co) polymer to be selectively removed and the other (co) polymer may be from 1 to 9, and preferably from 2 to 4. The weight ratio sum of (co) polymers / charge Preferably, the shear rate is 1 to 9, and preferably 2 to 4. As for shear, it is usually such that the shear rate is in the range of 10 to 300 sec -1. According to one embodiment of the process according to the invention, the (co) polymers have different polarities, the charge having a polarity for its part such that after the initial mixing operation, it is found essentially in the phase (co) polymer to be selectively removed. Thus, for example, if the (co) polymer to be selectively removed is polar, the remaining (co) polymer being non-polar, the charge will be chosen to be polar.

The (co) polymer pair may for example be polypropylene (PP) / poly (vinyl chloride) (PVC), polypropylene (PP) / poly (methyl methacrylate) (PMMA) or polyamide (PA) / poly (methacrylate). methyl) (PMMA), PP being a non-polar polymer and PA, PVC and PMMA being polar polymers. In fact, the pair of (co) polymers can easily be determined by those skilled in the art on the basis of the following parameters. ratio of the respective viscosities of the (co) polymers: equal to or close to 1, and ratio of the respective surface tensions of the (co) polymers: equal to or close to 1. The operation of shaping the molten mixture obtained according to the process, can for example, be an injection, extrusion, coextrusion or thermoforming operation. It can in particular be a coextrusion of said molten mixture with a nonporous (co) polymer that can be of the same chemical nature as the (co) polymer not selectively removed in the aforementioned process. It is thus possible to obtain, for example, a tube whose inner part consists of the microporous material according to the invention and whose overall mechanical strength can be high because of the highly resistant tubular part surrounding the relatively more fragile microporous inner tubular part. It will be added that the same type of bilayer tubular material could be obtained by eliminating the (co) polymer phase to be extracted, only over a certain thickness from the inside of the tube. The selective removal operation can take different forms. It can be a decomposition of the (co) polymer to be removed, for example a thermal decomposition (catalyzed or not) or a chemical decomposition using an appropriate decomposition agent whose nature is a function of the chemical composition of said (co) polymer. This type of decomposition leads to depolymerization of the (co) polymer concerned. Thus, from 180 ° C, the PMMA will depolymerize by releasing the starting monomer, methyl methacrylate, easily removable. The above-mentioned decomposition thus allows the creation of porosity without resorting to an extraction solvent. The presently preferred form of removal, however, is an extraction with an appropriate solvent capable of selectively dissolving the (co) polymer to be removed and having little or no effect on the other (co) polymer. Thus, in the case where the (co) polymer to be removed is PVC, this solvent may be tetrahydrofuran and in the case where this (co) polymer is PMMA, the solvent may be acetone. Alternatively, the extraction can also be carried out using a supercritical fluid (especially supercritical CO2), the advantage of this technique over those using an organic solvent, being to be able to exonerate any removal operation of the solvent after extraction, since this fluid (CO2) is removed spontaneously by passage to the gas phase, without leaving a toxic residue. The present invention is illustrated hereinafter by some nonlimiting examples of preparation of the material according to the invention. Example 1 Preparation of an absorbent microporous material from a ternary mixture PP / PVC / Zeolite 41.6 g of PVC, 10.4 g of PP and 13 g of zeolite (particle size: 1 to 200 μm) are mixed in a Rheocord Haake 90 mixer at a temperature of about 190 ° C. at a speed of the rotors. about 40 rpm and about 5 min. This results in a molten ternary mixture consisting of 64% by weight of PVC, 16% by weight of PP and 20% by weight of zeolite. This molten mixture is brought into the form of a plate (or film) by compression at 190 ° C. (maximum pressure: 9 tons). The plate thus obtained, once cooled, is introduced into an Erlenmeyer flask containing THF and an extraction of the PVC phase is carried out at 23 ° C. with gentle stirring. The extraction may alternatively be carried out by means of a Soxhlet extractor. After extraction of the PVC with THF, the analyzes carried out on the final material shows that the PVC was extracted in full; It should be noted, however, that the physico-chemical characteristics of PP differ slightly from those of pure PP, due to the high porosity of the material, which corresponds to a density of 0.37. It should be noted that the zeolite has not been extracted and it will be noted that the porosity of the organic phase, that is to say of the PP matrix, is of the order of 80%. The core morphology of the final material or external surfaces thereof was observed by SEM (low pressure scanning electron microscopy) and microtomography.

The porosity of the matrix is regular, the average pore diameter is of the order of 21 μm (the mean distance between two nearest cavities being 35 μm) and the zeolite is retained in the pores of the matrix without being chemically bound to it. . Example 2: Preparation of a microporous absorbent material from a PP / PMMA / zeolite ternary mixture. 38.1 g of PMMA, 16.3 g of PP and 13.6 g of zeolite (particle size: 1 to 200 μm) are mixed as in Example 1, except that the reaction is carried out at 220 ° C. instead of 190 ° C. The resulting molten ternary mixture consists of 56% weight of PMMA, 24% by weight of PP and 20% by weight of zeolite. It is brought in the form of a plate (or a film) as in Example 1, but working at 220 ° C instead of 190 ° C. The PMMA is then extracted using the technique described in Example 1, but using acetone instead of THF. The material obtained has a porosity corresponding to a density of 0.41, the average pore diameter is 28 μm and the average distance between two nearest cavities is 38 μm, the matrix (PP) having a porosity of 30 μm. 70%. Example 3: Preparation of a microporous absorbent material from a ternary PA / PMMA / zeolite mixture. 27.3 g of PMMA, 18.2 g of PA and 19.5 g of zeolite (particle size: 1 to 200 μm) are mixed as in Example 1, except that the mixture is produced at 230 ° C. instead of 190 ° C. The resulting ternary mixture consists of 42% PMMA, 28% PA and 30% zeolite. It was brought as a plate (or film) as in Example 1, but operating at 230 ° C instead of 190 ° C. The PMMA phase is then extracted as in Example 2. The material obtained has a high porosity corresponding to a density of 0.51, the average pore diameter of this material being 30 m and the average distance between two cavities the highest. close to this material is 31 m. Example 4: Water Absorption Properties of the Materials Subject of Examples 1 to 3

The technique used to measure the moisture absorption of these materials is thermogravimetric analysis (TGA). This measurement is performed under an air atmosphere until a maximum plateau is obtained: isothermal at 40 ° C for 150 min in air at a rate of 451 / min at 50% humidity.

It is thus possible to plot for each material, the curve of the mass of absorbed water relative to the weight of the material (in%) as a function of time (in minutes). The curves of the following materials are shown in the appended single figure: 0 material obtained from the ternary mixture PP / PVC / Zeolite where PP / PVC = 20/80 and (PP + PVC) / Zeolite = 70/30. x material obtained from the ternary mixture PMMA / PP / zeolite where PMMA / PP = 70/30 and (PMMA + PP) / zeolite = 70/30. + material according to Example 3.

The tested materials have a moisture absorption kinetics equivalent to that of pure zeolite. Moreover, these same materials exhibit very high moisture absorption rates. above existing products currently on the market and mentioned at the beginning of this description.

Claims (15)

REVENDICATIONS1. Solid material containing an active charge and allowing great accessibility to this charge, characterized in that it comprises a matrix of microporous and open-pore shaped material, and a particulate active charge of which at least a portion is housed in the free state in at least a portion of the pores of said matrix. Material according to claim 1, characterized in that the matrix consists of a thermoplastic (co) polymer and the particulate filler is heat stable. 3. Material according to claim 1 or 2, characterized in that the weight ratio matrix / particulate filler is in the range of 0.1 to 4. Material according to any one of claims 1 to 3, characterized in that it has a porosity corresponding to a density of 0.3 to 1.2. Material according to any one of the preceding claims, characterized in that the matrix has a porosity corresponding to a density of 0.1 to 0.8. 6 material according to any one of claims 2 to 5, characterized in that the particulate filler is polar, the (co) polymer constituting the matrix being non-polar or having a polarity less than that of said load. 25 7. Material according to claim 6, characterized in that the (co) polymer is a polypropylene (PP) or a polyamide (PA). 8. Material according to any one of claims 2 to 5, characterized in that the particulate filler is non-polar and the (co) polymer constituting the matrix is polar. 30 9. Material according to any one of the preceding claims, characterized in that the filler comprises or consists of a substance selected from the group consisting of absorbing or adsorbent substances, substances with chemical properties, substances with properties 35 substances with conductive properties or electrical insulation, substances with thermal properties and substances with acoustic properties. 10. A method of manufacturing the material according to any one of the preceding claims, characterized in that it comprises the steps of: - melt blending, under shear, two thermoplastic (co) polymers and an active load thermostable particle, these two (co) polymers being incompatible with each other and chosen to be divided into two co-continuous phases in the mixture obtained, the charge being for its part selected to be distributed essentially within the phase constituted by one of the two (co) polymers, - possibly shaping said mixture to give it the desired shape, and - after solidification of said mixture, selectively at least partially eliminate the (co) polymer phase in which the charge is distributed. 11. Process according to claim 10, characterized in that the weight ratio (co) polymer to be selectively removed / (co) polymer not removed is in the range of 1 to 9. 12. The method of claim 10 or 11, characterized in that the sum weight ratio of (co) polymers / particulate filler is in the range of 1 to 9. 13. Method according to any one of claims 10 to 12, characterized in that the (co) polymers have different polarities, the charge having a polarity such that after the initial mixing operation, it is found for the first time. distributed within the (co) polymer phase to be removed. 14. Process according to any one of claims 10 to 13, characterized in that the pair of (co) polymers is selected from the group consisting of polypropylene (PP) / poly (vinyl chloride) (PVC) pairs, polypropylene (PP) / poly (methyl methacrylate) (PMMA) and polyamide (PA) / poly (methyl methacrylate) (PMMA). 15. Process according to any one of claims 10 to 14, characterized in that the step of forming the molten mixture is a co-extrusion of said mixture with a non-porous (co) polymer. Process according to any one of claims 10 to 15, characterized in that the selective removal operation is selected from the group consisting of thermal decomposition, chemical decomposition and extraction with a suitable solvent. 17. The method of claim 16 wherein the selective elimination is constituted by extraction with a solvent, characterized in that the (co) polymer to eliminate / solvent pair consists of poly (vinyl chloride) (PVC) / tetrahydrofuran (THF) or poly (methyl methacrylate) (PMMA) / acetone.