MXPA98005021A - Material of mixed body of aerogel of formacionfibrosa that contains at least a thermoplastic material, procedure for its production and usodel - Google Patents

Abstract

The present invention relates to a mixed-body material which at least has a formation consisting of fibers and airgel particles and is characterized in that the fibrous formation contains at least one fibrous thermoplastic material to which the airgel particles are bonded and by which the fibers of the formation are bonded, also refers to a process for the production of said mixed-body material, and the use of the same.

Description

MATERIAL OF MIXED BODY OF AEROGEL OF FIBROUS FORMATION THAT CONTAINS AT LEAST ONE THERMOPLASTIC MATERIAL. PROCEDURE FOR YOUR PRODUCTION AND USE OF THE SAME DESCRIPTIVE MEMORY This invention relates to a mixed body material containing at least one formation of fibrous material and airgel particles, a process for its production and use thereof.

Due to their very low density, high porosity and small pore diameters, aerogels, in particular those with porosities greater than GO'Á and densities less than 0.4 g / cm3, show a very low thermal conductivity and for this reason are used as thermal insulating materials as described, for example, in the patent EPA-A-0 171 722. However »its high porosity results in a very weak mechanical stability» both in the gel from which the airgel dries »as well as in the same dry airgel. In the broadest sense »that is. when considered as "air gels as the dispersed material" »aerogels are produced by curing an appropriate gel. When used in this sense, the term "airgel" includes aerogels in the strictest sense, such as xerogels and cryogels. A gel is designated as an airgel in the strictest sense if the liquid is extracted from the gel at temperatures higher than the critical temperature and starting from temperatures that are higher than the critical temperature and starting with the pressures that are above the critical pressure. In comparison with this, if the liquid is extracted from the gel subenthically, for example with the formation of a liquid-vapor limit phase. then the resulting gel is. in many cases, called as xerogel. It should be noted that the gels according to this invention are aerogels in the sense that they are gels with air as the dispersed material. The procedure that forms the airgel is completed during the sol-gel transition. Once the solid gel structure has been formed, the external shape can only be changed by reducing the size, for example, by spraying. The material is very fragile for any other form of processing. However »for many applications it is necessary to use the airgel with certain shapes. In principle, the production of formed parts is possible even when the gel is being formed. However »the replacement of solvents» typically required during production »and that is governed by diffusion (with regard to aerogels» see »for example» US patents -4 610. BS3 and EP-A 0 396 076; to airgel mixed body materials »see eg WO 93/06044), and drying-which similarly is governed by diffusion at production times which are economically unacceptable. For this reason, it is appropriate to carry out a step to shape after the production of the airgel, that is, after it has been dried, and to do this without any essential change of the internal structure of the airgel that is made with respect to the particular application. For many applications. v. gr .. to isolate curved or irregularly shaped surfaces. It is necessary to use flexible panels or mats made of insulating material. DE-A 3346 1B0 describes rigid panels of shaped bodies based on silicic acid airgel obtained by flame pyrolysis combined with long mineral fiber effort. However, this silicic acid airgel that is extracted from flame pyrolysis is not an airgel in the above sense since it is not produced by curing a gel. and for this reason it has a completely different porous structure. Mechanically »is much more stable and for this reason can be pressed without destruction of the microstructure, although it has a higher thermal conductivity than the typical aerogels in the previous sense. The surface of a molded body like this is extremely of each and for this reason it must be hardened »as by the use of a binder, or being covered with a movie. In addition »the resulting formed body can not be compressed. DE-A-44 18 B43 describes a mat of a reinforced fiber airgel. It is true that »because of the high proportion of airgel, these mats show a very low level of thermal conductivity, but require relatively long production times due to the aforementioned diffusion problems. In particular, it is only possible to manufacture thicker mats by combining several thinners, and this involves additional costs. The task of this invention is to produce a mixed body material which is based on airgel granules. which has a lower level of thermal conductivity, and which is both mechanically stable and easy to produce in the form of mats or panels. This problem has been solved by a mixed-body material containing at least one formation of fibrous materials with which the airgel particles are connected and by which the fibers are connected together in the formation in such a way that the thermoplastic fibers of the surface are fused and when cooled they result in a union of the fibers between them and between the airgel particles. This thermal consolidation ensures a stable fibrous formation and ensures that the airgel particles are bound to the fibers. Here it is understood that a fibrous formation is any formation that can be produced using a surface forming technique. Examples of these surface formations are textile fabrics, matting of mats with fibers arranged at random. woven fabrics and fleeces, the fleeces being preferred. It is understood that the fleeces include the so-called stable fiber mats, that is, mats with randomly arranged fibers of finite length, as well as spunbond mats, that is, those that are continuous fissures. In the case of thermoplastic fibers, hereinafter referred to as the first fiber material, they may be fibers of organic thermoplastic material, such as, for example, polyolefin fibers, polyester fibers or, preferably, polyester fibers. The fibers can be round, trilobal, »pent-lobed» octalobular »in the form of strips» or have the shape of pine trees »of weights» or others. The recessed fibers can also be used. The first fiber materials can be lso or curly. Further »the fibrous formation may contain at least one extra fiber material which is bonded to the first thermoplastic material fibers during the thermal consolidation process. For this purpose, the melting point of the material from which these fibers are made may not be less than the temperature at which the fleece is thermally consolidated. In the case of fibers, these can be inorganic fibers such as mineral or glass fibers or organic fibers, such as polyolefin. polyamide or polyester fibers or mixtures thereof. It is preferred that the additional fibers be of a material identical to that of the first fibers, but of another profile, "another diameter" or that they show another type of ripple and / or another degree of stretch. The fibers can be modified by conventional additives, for example antistatic agents such as soot. The fibers that are contained in the formation may contain IR opacifiers »such as carbon black» titanium dioxide »iron oxide or zirconium dioxide. as well as mixtures of these »to reduce the contribution of radiation to thermal conductivity. The fibers can also be dyed to be colorful. The diameter of the fibers that are used in the mixed body material should preferably be less than the average diameter of the airgel particles so that a high proportion of airgel can be allocated to the mixed body material. The selection of very fine fibers makes it possible to produce mats that are very flexible. Also the use of thicker fibers results in heavier mats that are stiffer considering their greater resistance to bending. The diameter of the fibers is preferably between 0.8 and 40 d ?. Mixtures of fibers that are of different materials »with different profiles and / or different d ners can also be used. The mixture of thicker fibers results in a greater resistance to bending. On the one hand, in order to achieve good consolidation of the fleece and to ensure good adhesion of the airgel granulate, on the other hand, the proportion by weight of the first fibrous thermoplastic material must be between 10 and 100 J in weight, preferably between 40 and 10054 in weight, relative to the total amount of fiber. Of the spunbonded fleeces, those that are made of synthetic polymer fibers, the so-called spun bonds * are preferred; these are produced from filaments or sides randomly cast in fresh. These consist of continuous synthetic fibers that are made of polymeric materials that can be melt spinning. Suitable polymeric materials are, for example, polyamides such as poly hexadedand polyamide, polyprolactam, aromatic or partially aromatic polyamides (aramides), aliphatic polyamides such as nylon, partially aromatic or fully aromatic polyesters, polyphenyl isulfide (PPS), polymers with groups ether or keto, such as polyetherketones (PEK) and polyteretherketone (PEEK), or pol ibenzimidazoles. It is preferred that the spun mats consist of melt-spun polyesters. In principle, all known polyester materials that are suitable for the production of fibers can be used. Polyesters of this type consist mainly of building blocks which are derivatives of aromatic bicarboxylic acids and aliphatic diols. The common building blocks of aromatic dicarboxylic acid are the divalent radicals of benzenediacarboxylic acids. in particular of terephthalic acid and isophthalic acid. Common diols have 2 to 4 B atoms coal »eti lengl col being particularly suitable. Particularly advantageous are the spunbonded webs consisting of at least 85 mol% of polyethylene terephthalate. The remaining 15 mole is then formed of dicarboxylic acid units and units of glycol which act as the so-called modifying agents and which enable the person skilled in the art to alter the physical and chemical properties of the filaments that are produced. Examples of these carboxylic acid units are radicals of isophthalic acid or of carboxylic acids to the phatics, for example »glutaric acid» adipic acid »sebacic acid; Examples of diol radical modifiers are those of the long chain of diols such as propanediols or butanediols. of di- or triet lengl icol o »as long as they are present in small quantities. polyglycol with a molar weight of approximately 500 to 2000. Particularly preferred are polyesters containing at least 95 mol% polyethylene terephthalate (PET) »in particular those of unmodified PET. If the mixed body materials according to this invention should also have a flame retardant effect, it is an advantage if they have been spun from modified flame retardant polyesters. These modified flame retardant polyesters are well known. They contain additives of halogen compounds, in particular bromine compounds or, which is particularly advantageous. they contain phosphonic compounds that are condensed in the polyester chain.

It is particularly preferred that the spun mat contain modified flame retardant polyesters that are condensed in the chain component group of formula (I) O O II II -O-P-R-C- (I) R wherein R represents alkylene or polymethylene with 2 to 6 carbon atoms or phenyl, and Rx means alkyl having 1 to 6 carbon atoms, "aryl or aralkyl" being condensed. It is preferred that in Formula (1) R means ethylene and R - * - signify methyl »ethyl, phenyl» or o- »m- or p-methyl-1-enyl, in particular methyl. Spun mats of this type are described, for example, in DE-A-3940 713. It is an advantage that the polyesters contained in the spunbonded webs have a molecular weight corresponding to the intrinsic viscosity (VI) of 0.6 to 1.4. as measured in a solution of 1 g of polymer in 100 ml of dichloracetic acid at 25 ° C. The individual die of the polyester filaments in the spun mats is between 1 to 16 dtex. preferably from 2 to 8 dtex. In another embodiment of this invention, the spunbonded fiber may also contain another fiber material such as conductive fibers. Spun mats of this type are described in EP-A-0,446 > 822, EP-A-0.530,769 and EP-A-0 590, 629. Examples of polymers from which the conductive fibers can be derived are pol acri loni ri lo. polyolefins such as polyethylene »essentially aliphatic polyamides such as nylon 6.6» essentially aromatic polyamides (aramides) »such as pol- (p-phenol terephthalate) or copolymers containing a portion of aromatic n-diamine units to improve solubility, or pol i- ( m-phen or isophthalate). essentially aromatic esters such as pol i- (p-hydroxy benzoate) or preferably essentially aliphatic polyesters such as poly terephthalephthalate. The ratio of two types of fibers relative to each other can be selected from a wide variety "although attention should be paid to the fact that the proportion of the thermoplastic fibers must be large enough for the adhesion of the conductive fibers to the fibers thermoplastics make the fleece material strong enough for the intended application. Then »the proportion of thermoplastic fibers generally amounts to less than 50 '/. in weight relative to the weight of the material of the mat. Suitable thermoplastic fibers are, in particular, modified polyesters with a melting point of 10 to 50 ° C., and preferably from 30 to 50 ° C lower than the starting material used for the fleece material. Examples of such fiber materials are polypropylene, polybutylene or refractory polystyrene modified by condensing into long chain diols and / or iso-thalic acid or aliphatic acid dicarboxylic acid. The conductive fibers of the thermoplastic fibers are preferably made of a kind of polymer. It must be understood that all the fibers that are used have to be chosen from a class of substances that once the fleece reaches the end of its useful life »can be recycled without any problem. The individual fiber diner of the conductive fibers and the thermoplastic fibers can be selected within very wide limits. Examples of the variations of said diner are from 1 to 16 dtex, preferably from 2 to 6 dtex. In another embodiment, the spunbonded web can be finely consolidated after mechanical consolidation by sewing and / or by means of fluid swaths optionally with the aid of a chemical binder, for example, one based on a polyacrylate. The ratio of weight to area of the spunbond is between and 500 g / cm "*" and preferably between 30 and 250 g / cm "*. The volumetric percentage of the airgel within the mixed body material should be as high as possible "and should add at least 40% and preferably more than 60%. To achieve mechanical stability of the mixed body material »the percentage should not» however. exceed 95% and preferably should not be more than 90%. Aerogels which are suitable for the compounds according to this invention are those which are based on metal oxides which are suitable for the sol-gel technique (CJ Brinker, GW Scherer, Sol-Gel Science, 1990, Chapters 2 and 3). ). for example, Si or Al compounds. or those based on organic substances which are suitable for the sol-gel technique »as melamine-formaldehyde condensates (US Pat. No. 5,086,055) or condensates resorcincolformaldehyde (US-A-4 patent B73. 218). They can also be based on mixtures of the above mentioned materials. It is preferred that aerogels containing Si compounds. especially SiO "8 aerogels, and in particular SiO3 aerogels" are used, and the airgel may contain IR opacifiers such as carbon black, titanium dioxide, iron oxide or zirconium dioxide, and mixtures of these, for reduce the contribution of radiation to the thermal conductivity.Also, the thermal conductivity of aerogels decreases when the porosity increases and the density increases, for this reason, aerogels with porosities greater than 60% and densities less than 0.4 g / cm * » they are especially preferred The thermal conductivity of the airgel granulate should be less than 40mW / mK, and in particular less than 25mW / mK In a preferred embodiment »the airgel particles have hydrophobic surface groups To avoid some subsequent collapse of aerogels due to the condensation of moisture inside the pores, it is advantageous »if the hydrophobic groups that are not separated when they act by water are present covalently on the inner surface of the airgel. Preferred groups for permanent hydrophobisation are the silyl trisubstituted groups of the general formula -Si (R) 3. with trialkyls and / or trian groups "Isi 1 being preferred, with each R independently being an unreactive organic radical such as C ^ -C ^ -alkyl or CC ,, - aryl, preferably C., .- Ca alkyl or in particular methyl, ethyl, cyclohexyl or phenyl which can be further substituted with more functional groups Particularly advantageous for the permanent hydrophobisation of airgel is the use of trimethylsilyl groups The incorporation of these groups can be carried out as described above. described in patent WO 94/25149, or it can be done by reaction of gas phase between the airgel and a derivative of tri al qui Isi laño activated, such as clortrialqui Isi laño or a hexaalqui Isi lazano, for example (Cf. Iler, The Chemistry of Silica, Wiley &Sons, 1979.) The size of the grains will depend on the use given to the material, however, in order to be able to agglutinate in a large percentage of aerosol granules, the particles must be larger than the diameter of the fibers, p more preferably 30 μm. To achieve a high level of stability, the granulate should not be so thick, and the grains should preferably be smaller at 2 cm.

The granulate with a favorable bimodal grain size can be used to achieve a high volumetric percentage of airgel. Other distributions can also be used. The fire capacity of the mixed body material is determined by the fire capacity of the airgel and the fibers. To achieve a more favorable fire rating for mixed body material, non-flammable fibers such as glass or mineral fibers or fibers that are difficult to ignite, such as TREVIRA CS, should be used. consists only of the fibrous formation containing the airgel particles, the airgel granulate can be broken when the mixed body material is subjected to mechanical loads, or it can be separated from the fibers so that the fragments can leave the formation. For this reason, for specific applications, it is advantageous that the fiber fleece be covered on one or both sides with. in each case, at least one cover layer »whose cover layers may be identical or different. As an example, the cover layers can be cemented onto the thermoplastic fibers by means of another adhesive during thermal consolidation, the cover layer being, for example, preferably a sheet of metal or a metallized plastic film. In addition, the particular cover layer can itself consist of several layers.

What is preferred is a mixed-body fiber-airgel material in the form of mats or panel, which has a fibrous formation containing an airgel as the middle layer and on each side has a cover layer, at least one of those Coating layers containing layers of thin thermoplastic fibers. with the layers of individual fibers being thermally consolidated in them and with each other. The cover layer may also contain bicomponent fibers. Bicomponent fibers are chemical fibers of two rigidly connected polymers that are of different chemical and / or physical structure, which has areas with different melting points, that is, areas of a low melting point and areas of a higher melting point. high. Typically, these fibers are in the form of a core and shell structure in which the low melting components form the shell, or otherwise have a side-by-side structure. The choice of fibers for the cover layer is governed by the same factors as those governing the choice of fibers for the formation of fibers in which the airgel particles are bound. To obtain the most dense cover layer possible. The fibers must have a diameter smaller than 30 μm. and preferably be less than 15 μm. To achieve the greatest stability or density of the surface layers, the layers of the cover layer can be sewn. A further objective of this invention is to describe a process for manufacturing the mixed body material in accordance with this invention. The production of the mixed body material according to this invention is described in detail below with respect to the preferred fiber mat, although it is not restricted to this Yorker period. Both short fibers with the carded form or commercially available cards are used to produce the fiber fleece. Considering that the fleece can be laid using the methods known to the person skilled in the art, the airgel granulate is spread. Care must be taken to achieve a distribution as even as possible of the granulated grains when the airgel granulate is introduced into the mixed fiber body. This can be done using commercially available spray equipment. When a cover layer is used, it is possible to lay the fiber fleece in a cover layer when the airgel is being sprayed; once this procedure is finished »then the top cover layer is put in place. If cover layers which are made of fine fiber material are used, the cover layer which is made of fine fibers and / or bicomponent fibers is laid using concisely and optionally stitched processes as described above, the mixed fiber body containing the Airgel is then placed on it. For an additional top cover layer »a layer can be placed using fine fibers and / or bicomponent fibers» for the lower cover layer »and then optionally stitched. The resulting mixed fiber body is thermally bonded »optionally under pressure, at temperatures above the melting point of the fiber material having the lowest melting point. The pressure is between the normal pressure and the compressive force of the airgel that is used. The length of time the temperature acts on the material must be selected to ensure that only the surfaces of the fibers are fused. The complete processing methods may, if preferred, be performed continuously using facilities known to those skilled in the art. Due to its low thermal conductivity, the panels and the mat according to this invention are suitable for use as thermal insulation material. In addition, the panels and the mat according to this invention can be used as a good absorption material, either directly or in the form of resonance absorbers since they have a low acoustic velocity and »compared to monolithic aerogels» provide greater attenuation acoustics. In addition to the cushioning effect caused by air friction between the pores of the fibrous formation. The permeability of the fiber fleece can be adjusted by changing the diameter of the fibers, the density of the fleece, and IB the size of the grains of airgel particles. If the fibrous formation also contains cover layers, these cover layers must allow the sound waves to penetrate the fibrous formation and not reflect the sound waves to any greater degree. In addition to the above, since the porosity of the fibrous formation and »in particular. the large porosity of the surface to volume ratio of the aerogels, the panels and the mat according to this invention are also suitable as absorption materials for liquids, vapors and gases. A specific absorption effect can be achieved by modifying the surface of the airgel. This invention will be described in greater detail based on the modalities, without being restricted to them.

EMP p A fiber mat with a surface to weight ratio of 100 g / m2 was laid 50% by weight of TREVIRA 290 0.8 dtex / 3B mm hm and 50% by weight of TREVIRA of fused adhesive fiber of 3.3 dtex / 60 mm hm (test fiber). During the laying process, an airgel granulate based on tetraeti lortosi 1 icato with a density of 150 kg / ma and a thermal conductivity of 23 mW / mK. and a grain size of 1 to 2 mm in diameter was applied to it by spraying. The resulting mixed body material was thermally bonded at a temperature of 160 ° C for 5 minutes and compressed with a width of 1.4 cm. The resulting panel was easily flexed. Its thermal conductivity was measured by a panel method in accordance with DIN 52612 Part 1, and determined to be 27 mW / mK.

EXAMPLE 2 A mat used as the bottom layer was laid 50% by weight of TREVIRA 120 short fibers with a diameter of 1.7 decitex, length of 35 mm, black yarn and 50% by weight of melted adhesive fiber of TREVIRA, 3.3 dtex / 60 mm hm (test fibers). This cover layer had a surface to weight ratio of 100 g / m2. A TREVIRA 292 fiber mat of 50% by weight, 40 dtex / 60 mm hm and 50% by weight of TREVIRA fused adhesive fiber of 3.3 dtex / 60 mm hm (test fiber) with a surface to weight ratio of 100 g / ma was placed on it. During the laying process, an airgel granulate based on tetraeti lortosi 1 icato with a density of 150 kg / m3 and a thermal conductivity of 23 mW / mK, and with a grain size of 2 to 4 mm in diameter was applied to it by spraying. A cover layer structured in the same manner as the lower cover layer was then placed on this fiber mat containing the airgel. The resulting fiber composite body material was thermally bonded at a temperature of 160 ° C for 5 minutes, and compressed with a thickness of 1.5 cm. The airgel percentage of the consolidated mat increased to 51%. Its thermal conductivity was measured by a panel method in accordance with DIN 52612 Part 1. and determined to be 29 mW / mK.

Claims (7)

NOVELTY OF THE INVENTION R? LVINDTCAC? QNES

1. - A mixed body material containing at least one fiber and airgel particle formation »further characterized in that the fiber formation contains at least one fibrous thermoplastic material to which the airgel particles are bonded and by which the fibers are agglutinated within the formation.

2. A mixed body material as defined in claim 1. < . Also characterized because the fibrous formation is a fiber fleece.

3. A mixed body material as defined in claim 1 or claim 2. further characterized in that the fibrous formation further contains at least one other fiber material.

4. A mixed body material as defined in at least one of the rei indications from 1 to 3. further characterized because the diner of the thermoplastic fiber material varies from 0.8 to 40 dtex.

5. A mixed body material as defined in at least one of claims 1 to 4, further characterized in that the proportion of airgel particles within the mixed body material is at least 40% in volume.

6. - A mixed body material as defined in at least one of claims 1 to 5 »further characterized in that the airgel is an SiOß airgel.

7. A mixed body material as defined in at least one of claims 1 to 6 »further characterized in that the fiber thermoplastic material and / or the airgel particles contain at least one infrared opacher. B. - A mixed body material as defined in at least one of claims 1 to 7, further characterized in that the airgel particles have porosities of densities greater than 60%, densities less than 0.4 g / cm3 »and conductive Thermal values of less than 40 mW / mK »preferably less than the 25 mW / mK period. 9. A mixed body material as defined in at least one of the claims 1 to 8 »further characterized in that the airgel particles have hydrophobic surface groups. 10. A mixed body material as defined in at least one of claims 1 to 9 »further characterized in that the fiber fleece has a cover layer on one or both sides» these cover materials being identical or different . 11. A mixed body material as defined in claim 10 further characterized in that the cover layers containing plastic films, metallic films, metallized plastic films or preferably layers of ester that are of simple fine fibers and / or fine fibers of two-component 12. A mixed body material as defined in at least one of claims 1 to 11 in the form of a panel or mat. 13. A process for producing a mixed-body material as defined in claim 1, further characterized in that the airgel particles are sprayed in a fibrous formation, preferably on a fiber mat, containing at least one thermoplastic material of fiber and the resulting mixed fiber body being then thermally consolidated at temperatures above the lowest melting point, optionally under pressure. 14. The use of a mixed body material as defined in at least one of the claims from 1 to 12 for thermal insulation »sound insulation and / or as absorption material for gases» vapors and liquids.