Patent Application
20140083636
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1. Field of the Invention
The announced depletion of petroleum resources has driven the industrial actors in the field of insulation to study the improvement of heat insulation, namely of the buildings, but also of the vehicles. The present invention falls within this field of heat insulation, although it cannot be said that it is limited in its applications to this field alone. In particular, this invention may also find an interest in the framework of sound insulation.
The present invention relates in particular to a sheet of vegetable wool fibers that can be used for heat and/or sound insulation of a wall. In the following part of the application and in order to simplify its reading, we will only cite heat insulation, but it should be understood that a large part of the sheets that can be used for heat insulation are also useful for sound insulation, and that such sheets can furthermore be implemented in cases where only sound insulation is looked for.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
The heat-insulation vegetable wools can be considered as products that can compete with the mineral (glass, stone) wools for application namely in the field of the durable eco-habitat. The mineral wools rely to a major extent on the use of thermosetting synthetic polymeric materials, such as for example phenol formaldehyde. FR2626597 introduces a heat- and sound-insulation panel with mineral wool bonded by means of a thermosetting melamine resin.
Further implementations of glass-wool-based panels have examined the replacement of the thermosetting matrices by thermoplastic polymeric binders. FR2731243 introduces a heat- and sound-insulation panel with glass wool bonded by means of a thermoplastic material, such as PVC.
Another document has proposed to replace within the mineral wools the petrochemical binders by a composition formed of a monosaccharide and/or a polysaccharide with a polycarboxylic organic acid having a molar mass lower than 1000. Such an invention is described in detail in FR2924719A1.
The already marketed vegetable wools are very often based on hemp or linseed fibers. A semi-crystalline thermoplastic polymer (polyethylene, polypropylene, polyethylene terephthalate) is in turn used as an inter-fiber binder, in order to ensure their mechanical cohesion for manufacturing an insulation sheet, even a panel, of vegetable wool. However, its petrochemical origin impedes these insulation sheets or panels from bearing a natural or ecologic product label.
The mechanical and thermal performances of the vegetable wools depend of course on various factors, some of which are directly related to the very nature of the fibers being used. In this respect can be cited:
As regards the polymeric binder, most commercial applications using vegetable fibers make use of polyolefin (polyethylene, polypropylene) or polyester (polyethylene terephthalate) thermoplastic polymers. Because of their semi-crystalline nature, these polymers may melt during a raise in temperature, which permits them to spread within the fiber network. After cooling down to room temperature, these polymers recover a high mechanical rigidity permitting to ensure the inter-fiber cohesion necessary for producing an insulating sheet.
The insulating sheets are often produced in the form of rigid or semi-rigid panels, which can for example be placed between a wall and a face, in order to improve the heat insulation of said wall. They may also be used for insulating a non-planar wall, such as a door of a vehicle. In this case, either a non-planar panel can be formed, for example by molding, or the sheet can be formed directly on its support. To this end, the fibers can be prepared on one side, the polymer on the other side. The polymer can then be deposited on the fibers, then the aggregate can be projected onto the wall to be cladded. The fibers and the polymer can also be projected at the same time, by means of an appropriate projection device. The choice of the method will depend on the characteristics of the polymers being chosen.
In the present application, the word ‘sheet’ will be used for describing a layer of fibers, bonded by means of a binder, of any shape, whether planar or not, whether preformed so as to form a separate part, or shaped at the time of its being applied onto the wall the heat and/or sound insulation of which it must improve. In the description, the word “panel” will often be used, since the panel represents the most common application. But here too, the described variants apply to any sheets whatsoever.
The choice of a thermosetting binder proceeding from petroleum has several drawbacks. Indeed, it is not possible to recycle these materials once they have been mixed with the vegetable fibers. Furthermore, because of their 100% petrochemical origin, these different classes of binders can in no way allow to provide the insulating material with a “green” label. Finally, the mechanical characteristics, close to the different types of thermoplastics being used, limit the implementation of a wide range of vegetable wools.
Besides the factors inherent to the fibers described above, the relative proportion of polymer permits to cause the physical properties of the fibrous panel to vary. However, in order not to alter the thermal aspect of the insulating panel, the mass percentage of the thermoplastic matrix should not exceed 10 to 20%. This thus highly limits the use of this means to provide a panel with the desired properties.
The manufacturing process can also be used to cause the physical properties of the panel to vary. For example, the compacting pressure will have an impact namely on the density of the vegetable wool, but at the same time also on its insulating nature. The dispersion mode of the polymeric matrix (in the form of powder or fibers) within the vegetable network is another element having an influence. The means for action prove however extremely limited.
The present invention pretends to cope with at least part of the above-mentioned drawbacks and proposes to replace the thermoplastic binder of petrochemical origin by a thermosetting polymeric formulation derived from green chemistry. The latter is based on the reactive mixture of an epoxidized vegetable oil with a hardener.
To this end, the invention relates to a sheet of vegetable wool fibers. This sheet is impregnated with an epoxidized vegetable oil and a hardener. The association of epoxidized vegetable oil and the hardener constitutes a binder permitting the sheet of vegetable wool fibers to constitute an integral and coherent unit. This concept permits a very wide implementation of formulations depending on the intrinsic chemical nature of its components, the composition of the mixture or also the associated conditions of polymerization (time, temperature).
According to further features:
The present invention also relates to a heat-insulation panel including a sheet according to the invention, wherein said epoxidized vegetable oil and said hardener form a binder, so as to provide said panel with sufficient mechanical cohesion; such a panel can easily be used in the building industry.
Finally, the present invention relates to a method for manufacturing a sheet or a panel according to the invention, including the following steps:
According to further features:
The advantage deriving from the present invention resides in that the binder being used is to a large extent from biologic origin and, according to some preferred embodiments, entirely of biologic origin.
Further features and advantages of the invention will become clear from the following detailed description, which refers to an exemplary embodiment given by way of non-restrictive indication.
This description will be better understood when referring to the attached drawing.
The present invention relates to a sheet of vegetable wool fibers. Such fibers are known for their insulating characteristics. Nevertheless, in order to be able to be formed into a sheet or even a panel, a binder should be added thereto. According to the invention, this binder is formed of an epoxidized vegetable oil and a hardener.
A vegetable oil is a triglyceride unit: it is in this respect formed of three fatty acids grafted onto a glycerol unit. Only the fatty chains carrying double carbon-carbon (C═C) bonds are qualified as unsaturated. The transformation of these double bonds (C═C) through peroxidizing will permit to create epoxy groups and, hence, epoxidizing the oil. In other words, only the vegetable oils containing unsaturated fatty acids can be epoxidized. This method serves as a basis for the synthesis of the binder according to the invention, which will be used in the manufacture of the heat-insulating vegetable wool panels.
Some exemplary unsaturated fatty chains grasses are shown in table 1. The associated fatty acids are naturally present in the vegetable oils of linseed, sunflower, soya beans, olive, tung wood, cotton, colza, ricin, cashew nuts, peanuts, grape seeds, which have thus been identified as possible solutions for the invention. The oil may be used pure or as a mixture of the above-cited oils.
Among the different oils cited, the one extracted from the linseeds is particularly interesting, because it is very rich in unsaturated fatty acids (>90%), namely with a high proportion of linoleic and linolenic fatty acids (see table 2). Furthermore, since it is not edible, its valorization results in no way into a conflict with a production initially for food.
The epoxidizing of a linseed oil permits for example to provide access to a molecule carrying 2 to 6 epoxy groups, which will be as many groups that can react with hardener groups such as anhydride or polyamine. The selection of the oil can thus have an influence on the rigidity of the seed by the choice of the number of epoxy groups present: the more epoxy groups there are, the higher will be the rigidity of the sheet.
The invention encompasses two categories of hardeners. The first one is formed of the polyamines (molecules carrying several amine functions), the second one of the acid anhydrides and the acids.
A primary amine is capable of opening two epoxy groups in order to form two covalent bonds. Thus, a diamine of the standard chemical formula H2N—R—NH2 can react with four epoxy groups (NH2 is a primary amine terminus and R is the central bloc). This reaction can generate the forming of a three-dimensional polymer network when these two epoxy groups are carried by two different macromolecular chains. The transformation is referred to as crosslinking. The schematic diagram is proposed in
Within the framework of our invention, the polyamine-epoxy reaction is implemented through the mixture formed of an epoxidized vegetable oil with a diamine hardener, in order to produce a thermosetting formulation. For a pair of oil and polyamine, the proportion of each compound in the reaction mixture can be chosen depending on the desired extent of crosslinking, in order to adjust, if necessary, the rigidity of the material or its stickiness by default of the hardener. But for a complete consumption of the reagents leading to a stable product, ii is important to work with stoichiometric quantities. For example, for an epoxidized linseed oil carrying 5.45 epoxy functions per triglyceride unit, the stoichiometry of the formulation is 1.36 mole of primary diamine per 1 mole of oil.
The study of the reactivity can be performed by means of differential scanning calorimetry by following the evolution of the heat released by the crosslinking reaction. The dynamic rheometry can also be used to determine the characteristics of the polymerization kinetics at a given temperature, such as its speed or also the duration permitting to reach the balance of the reaction. This key information obtained at different temperatures is useful to determine the optimal implementation factors (temperature and duration) necessary for constructing the thermal cycle of implementation.
A first generation of epoxidized vegetable oil based binders can thus be developed by using polyamines proceeding from petrochemistry. In comparison with the present thermoplastic solution, this kind of binders has already the advantage of being based on a much higher renewable carbon rate, because of the presence of vegetable oil in the thermosetting formulation.
The exact nature of the central block R of the polyamine permits to modulate to measure the properties of the final matrix, namely at the level of the mechanical or thermal properties. It is then possible to implement a wide range of vegetable wools depending on the desired mechanical flexibility or rigidity.
The simplest case is represented by the polyamines carrying two amine functions. Consider diamine. A diamine having a rigid central block R—i.e. based on cyclic or aromatic chemical units—should be preferred for producing “structural” binders. Cite for example p-phenylenediamine, isophoronediamine (also called 5-amino-1,3,3-trimethylcyclohexanemethylamine), m-xylylenediamine. The binder derived from this kind of polyamine is particularly suitable for the production of dense and rigid heat-insulation wool panels. It should be noted that some aromatic diamines such as “methylene diamine” should be discarded, because of their health risk.
On the other hand, a diamine exhibiting an aliphatic central block will permit to manufacture more flexible binders. This very flexibility can be modulated through the length of the aliphatic unit, even the presence of flexible chemical rotulae such as ethers. Cite for example ethylenediamine, 1,4-diaminobutane, hexamethylene-diamine, bis(3-aminopropyl)amine, 1-(2-aminoethyl)piperazine, Jeffamines. In this case, the flexibility of the binder permits to produce much more flexible wool panels capable of adapting to an installation in areas with complex geometry. These same fibrous panels exhibit a residual deformation after compression much smaller than the one observed with the panels based on a rigid binder. It should be noted that the proportion of binder in the fibrous mass nevertheless permits to modulate the difference between these two kinds of hardener.
Furthermore, the reaction between an amine terminus and an epoxy group can also be performed with an epoxidized oil hardened by means of a polyamine, i.e. a chemical compound having more than two amine functions. This solution is a new lever permitting to extend the range of binders, in particular in order to meet specific constraints at mechanical or thermal level. Several commercially available polyamines can serve as a basis for this concept, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, T-Jeffamines.
A second generation of binders for vegetable wool can be obtained by causing the epoxidized vegetable oil to react with diamines produced from biologic sources. For example, the above-cited compound “1-4 diaminobutane” can also be obtained by Green Chemistry, namely by hydrolysis of animal proteins. Another compound that can be produced from biologic components is 1,5-diaminopentane. In a different register, some amino-acids carry several amine functions, which enable them to fulfill the function of hardener. Let's cite for example lysine, arginine, asparagine, glutamine. All these hardeners permit, like their homologues proceeding from petrochemistry, to cause the epoxidized oil to crosslink during a raise in temperature. The thus obtained binders permit to make heat-insulating panels of 100% biologic origin. The latter point is interesting, because this kind of product is perfectly compatible with the expectations from the durable habitat market.
The present invention also encompasses the vegetable wools, the binder of which has been obtained by polymerizing the epoxidized vegetable oil with an anhydride hardener. Different anhydride compounds have been tested in order to extend the range of the binders intended for vegetable wools. Some examples can be cited, namely phthalic anhydride, maleic anhydride, succinic anhydride, hexahydrophthalic anhydride or also methylhexahydrophthalic anhydride. Each of them requires of course to define the adapted crosslinking temperatures in order to take into consideration the reactivity of the mixture. In any case, the speed of reaction of the anhydride hardener with the oil is slower than that observed with the polyamine hardeners. This point is important within the framework of an industrial production, even though the crosslinking reaction can be catalyzed, in particular by using an amine derivate.
The anhydride way can also be explored by Green Chemistry. For example, itaconic anhydride can be obtained by treatment of citric acid. Mixed with epoxidized vegetable oil, it permits to produce a new binder proceeding entirely from biologic sources.
The preparation of the binder consists in mixing the epoxidized vegetable oil and its hardener. If the latter is solid at room temperature, it can be heated beyond its melting point, but below its vaporization and breakdown temperature. The oil will of course be heated at the same temperature, in order to avoid any crystallization of the hardener during the “oil/hardener” mixing. The stoichiometry of the mixture depends on the rate of epoxidizing of the oil (i.e. of the quantity of epoxy groups per triglyceride group), but also on the functionality of the hardener (diamine, polyamine, acid anhydride . . . ). It should be noted that an amine group can react with two epoxy groups. The same relationship 1:2 is observed with the reaction of an anhydride group on an epoxy group.
When the hardener is solid at room temperature, it is necessary to pre-heat the epoxidized oil alone at a temperature slightly higher than the melting temperature of said hardener. The oil is stirred mechanically by means of a blade mixer, in order to homogenize its temperature. The hardener is then added progressively, in order to permit its easier incorporation into the mixture. The mechanical stirring is maintained at low speed for 5 to 10 minutes until a mixture of a homogenous color is obtained. A degasing of the solution can be carried out in a vacuum enclosure, in order to eliminate any trace of air bubbles in the mixture. All these steps carried out by hand can also be carried out by means of a metering/mixing machine.
Generally, the viscosity of the “oil/hardener” mixture is sufficiently low to permit its vaporizing onto the vegetable fibers by means of nozzles. Should the case arise, it can be lowered by adding a solvent the choice of which must be defined depending on the kind of hardener used. A wide range exists, since the epoxidized oil is indeed soluble in many solvents: chloroform, ethyl acetate, some alkanes (hexane, heptane), petroleum ether, diethyl ether, dichloromethane, toluene, THF or also dioxane, . . . .
The wetting of the fibers can be carried out by different methods. A first technique consists in vaporizing the thermosetting formulation onto the fibers previously arranged on a conveyor belt. The flow rate of pulverization of the material and/or the speed of movement of the belt permit to regulate the oil/fibers ratio. An aspiration of the resin through the fibrous network can be carried out in order to permit a better penetration, then diffusion of the binder through the fibrous cloth.
In the second technique, the previously dried vegetable fibers are placed in a horizontal rotor in which they are stirred and dispersed. The phase of impregnation with the oil/hardener mixture can then occur through direct pulverization.
Irrespective of the mode of impregnation being chosen, the thus wetted sheet of fibers is then pressed either by means of a rolling machine permitting to regulate the thickness of the fibrous sheet, or by means of a mold formed by a set of mold form/counterpart. Then, the whole is subjected to a thermal treatment, in order to permit the crosslinking of the “oil-hardener” mixture. The final heating step can be carried out by means of lamps emitting in the infrared range, a hot-air tunnel or through direct heat contact. Once the polymerization of the binder has been carried out, the vegetable panel exhibits a good mechanical cohesion. The binder having become rigid provides the panel with a good tensile strength. The homogenous diffusion of the binder within the fibrous sheet ensure in turn a uniform color and a good dimensional stability.
The thus manufactured vegetable wool panels can be used as heat-insulation elements for the traditional building works in replacement of the mineral (glass or stone) wool panels. Based to a large extent or entirely on products of biologic origin, the vegetable wools provide a very interesting alternative for the lignocellulose wools based on a petrochemical binder, namely within the framework of the durable habitat (house with wooden skeleton). It is important to specify that besides the only thermal aspect, the vegetable wool panels also permit to ensure a sound-insulation function. This permits to achieve several advantages:
Although the invention has been described with respect to a particular embodiment, it is obvious that it is in no way limited thereto and that various modifications of shapes, materials and combinations of these various elements can be made without therefore departing from the scope and sprit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1152967 | Apr 2011 | FR | national |
| 1154264 | May 2011 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2012/050744 | 4/5/2012 | WO | 00 | 12/11/2013 |
