WO2008146320A2

WO2008146320A2 - Thermal and acoustic insulating material

Info

Publication number: WO2008146320A2
Application number: PCT/IT2008/000347
Authority: WO
Inventors: Marco Morocutti; Giuseppe Gianotti
Original assignee: Fincantieri Cantieri Navali Italiani S.P.A.; Santarossa S.P.A.
Priority date: 2007-05-25
Filing date: 2008-05-26
Publication date: 2008-12-04
Also published as: ITUD20070090A1; WO2008146320A3

Abstract

Insulating material of the type comprising mineral fibres variously mixed with each other characterised by the fact that said mineral fibres are consolidated with each 5other in a cellular structure by means of the addition of colloidal silica and without the addition of organic components. The novelty of the product lies in its cellular structure of variable density depending on the percentages of the components.

Description

DESCRIPTION "THERMAL AND ACOUSTIC INSULATING MATERIAL" fOOnSphere of application

[002]The present invention relates to a thermal-acoustic insulating material and the 5relative method for making it. The present invention also relates to a product containing the aforesaid insulating material.

[003] Advantageously, the material according to the invention is aimed specifically at thermal-acoustic insulation with anti-combustion or flameproof properties, especially though not exclusively, in the form of panels. io[OO4] By way of a non-limiting example, one sector of particular interest is the naval sector. The invention may, however, also be applied to other sectors, such as the construction industry. f0051State of the art

[006] Various materials for thermal-acoustic insulation are known which can I5basically be classified into two main categories according to their physical structure: fibrous materials and spongy (porous) materials.

[007] Within each of these main categories, various sub-categories may be attributed depending on the origin of the material: materials of natural origin; materials of synthetic origin; materials of mineral origin. 20[008]Among fibrous materials of natural origin for example, are cotton and hemp fibres.

[009]Among fibrous materials of synthetic origin among others are polyamide resins (such as nylon).

[0010]Among fibrous materials of mineral origin are rock wool/ fibre or glass 25wool/fibre. [0011]The fibrous materials may be used loose, in the form of fabric, or in the form of panels wherein the fibre is bound by rigid (rigid panels) or flexible (flexible panels) binding materials. [0012]Among the spongy materials of natural origin are cork and sea sponges for

5example.

[0013]Among the synthetic spongy materials are foam rubber, which has an open cell structure (in other words which transpires), and polystyrene and polyurethane foam, which has a closed cell structure. The polyurethane foam, which may be of the rigid or flexible type depending on the additives used, may either be in the form ioof granules or loose pellets (such as those used for example for insulation or packaging), or in the form of panels or products for the most varied uses, and especially for use as thermal and acoustic insulation.

[0014]Among the spongy materials (porous or foam) of mineral origin are expanded clay and vermiculite (phyllosilicate mineral of magnesium, trivalent iron isand aluminium, with oxydrils and water) which are generally in the form of loose foam granules or conglomerates, in other words bound to each other to form masses with varying degrees of porosity or to form compact masses in the form of panels and products, generally used for lightweight building structures. [0015]Considering, in general, the limits of the various materials mentioned above

20the following observations may be made:

[0016]a) the materials of natural and especially plant origin have the advantage of being biodegradable and lightweight (low specific weight), but have limited heat resistance, given that in general they are combustible; [0017]b) the materials of synthetic origin (plastic) are generally lightweight and 5have a low specific weight, but are not biodegradable or heat-resistant and are generally combustible;

[0018]c) the mineral materials are highly resistant to high temperatures, are not combustible, but are generally heavier than the former categories and have a slightly higher thermal and acoustic conductivity than the other materials

5mentioned.

[0019]ln the naval sphere, woven and non-woven mineral fibre materials, especially glass wool and rock wool, are widely used to make fire bulkheads and cabin panels. For the purposes of insulation, especially thermal, these materials offer the advantage of combining a low specific weight with incombustibility which iotherefore makes them resistant to high temperatures.

[0020]One of the limits of these materials lies in their transpiration properties, which reduce their insulation capacity, especially if compared to polystyrene or polyurethane foam panels. [0021]Another limit is connected with the potential risk to human health deriving

I5from direct or indirect contact with such materials. This second aspect in particular may lead to a limitation of the use of such materials.

[0022]As we know asbestos fibre, an excellent thermal insulation and fireproof material, is carcinogenic. [0023]Similarly, all artificial refractory fibres with a content of alkaline oxides or

2θalkaline-earth oxides of less than 18% in weight are considered carcinogenic (belonging to group 2 of the classification of carcinogenic materials with R49 status ("May cause cancer if inhaled"). Rock wools with a low content of alkaline-earth oxides or alkaline oxides fall within this category. [0024]Rock wools with a content of alkaline-earth oxides or alkaline oxides of over

2518 % in weight satisfy the biosolubility parameters DE 97/69/EC (note Q) and do not fall within the category of carcinogenic substances. They maintain solely the warning R38 (irritating substances).

[0025]The raw material of rock wool is natural basalt the chemical composition of which may vary according to the area of provenance and even along the same ,5vein. Rock wool is therefore constantly monitored by the bodies appointed in relation to the issues mentioned above. r00261Presentation of the invention

[0027]Consequently, the purpose of the present invention is to eliminate the drawbacks of the state of the art mentioned above by making available a new type ioof material which presents in a balanced manner the more advantageous properties of the said materials of natural origin, of the materials of plastic origin and of the materials of mineral origin but without the drawbacks and defects which the same present individually.

[0028] In other words, the purpose of the present invention is to provide a material lswhich is lightweight, which has thermal and acoustic insulation properties and which is resistant to high temperatures, in other words flame-resistant and therefore incombustible.

[0029JA material of such type would be extremely advantageous for a multiplicity of applications, especially in the making building and naval structures,

20[003O]A further purposi of the present invention is to make available a thermal and acoustic insulating mat ϊrial which constitutes an alternative to panels in rock wool or glass wool.

[0031 ]A further purpose of the present invention is to make available a thermal and acoustic insulating material which does not present limits to its application with

25regard to the risks foπhuman health. fO0321Brief description of the figures

[0033]The technical characteristics of the invention, according to the aforesaid purposes can be seen clearly from the contents of the claims made below and the advantages of the same will be proven more clearly in the detailed description

5which follows, made with reference to the attached figures, which represent one or more forms of embodiment purely by way of example and not limited to such, wherein:

[0034]- Fig. 1 shows an enlarged schematic view of the structure of the insulating material according to a specific embodiment of the invention; iθ[OO35]- Fig. 2 shows a cross-section view of a panel formed with the insulating material according to the present invention in which one can clearly see the expanded cellular structure obtained from the fibre sponge; [0036]- Fig. 3 shows a two-layer panel according to a specific embodiment of the invention: a first layer in granular material made from silica aerogel (thermal and

I5acoustic insulant) and a second fibrous layer made according to the present invention (thermal and acoustic insulant);

[0037]- Fig.4 shows four graphs relative to the acoustic insulation capacity in dB at a specific frequency range of four insulant materials, of which two (curves a - b) state of the art and two (curves c - d) according to the invention.

20f00381Detailed description

[0039]According to a general embodiment of the invention, the method for making the thermal acoustic insulating material, comprises the following operative phases: [0040]- a) preparing a foamed watery emulsion comprising inorganic fibres, at least one silicate-based bine ng agent and at least one organic emulsifying- 25foaming agent; [0041]- b) subjecting the emulsion to a first heat treatment aimed at consolidating the foam ( expanded cellular) structure so as to obtain a dried foamed solid body ; and

[0042]- c) subjecting the foamed body to a second heat treatment aimed at

5eliminating the organic components present in it so as to obtain an inorganic foamed body.

[0043]As will be described in further detail below, the method according to the invention makes it possible to obtain a material substantially free of organic components (incombustible), having a fibrous matrix with expanded cellular iostructure (porous) which ensures that the material has good mechanical resistance and limited specific weight (density). Combined with these characteristics there is high performance in terms of thermal and acoustic insulation comparable, if not superior, to that of traditional insulating panels in rock wool. [0044]Advantageously, the method for making an insulating material according to isthe invention may include a sintering phase of the foam body. [0045]More specifically, such sintering phase is aimed at causing welding of the inorganic fibres to each other and between them and any inorganic materials present, and is performed subsequent to the aforesaid second heat treatment. [0046]Should the aforesaid sintering phase be foreseen, the insulating material

2θcontinues to present an expanded or porous cellular structure (i.e. comprising empty spaces or containing gas (2) similar to the case in which such phase is not foreseen, but compared to this latter case - as shown in the diagram of Figure 1 - the inorganic (mineral (1 )) fibres are substantially welded directly to each other in their points of contact (4) by heat fusion and/or thermoplastic fusion on contact or

25indirectly by the adjacent presence of other inorganic binding materials which operate at substantially similar or slightly inferior temperatures of incipient fusion and/or softening of the inorganic fibrous material, but in any case below its collapse temperature.

[0047]Advantageously, the method for making an insulating material according to 5the invention may comprise an aspersion phase of the inorganic foamed body with water-repellent compounds, independently of the fact that such is foreseen or not upstream of the aforesaid sintering phase.

[0048]To such purpose, as will be further explained below, silicone oils with a high combustion temperature may be used as water-repellent compounds. lo[0049]According to a preferred solution of the method, the preparation phase of the emulsion comprises the following sub-phases:

[0050]- a1 ) crushing the inorganic fibres in water;

[0051]- a2) preparing a mixture of water and the organic emulsifying-foaming agent; 15[OO52]- a3) adding the inorganic binding agent to the mixture of water and emulsifying-foaming agent;

[0053]- a4) adding the crushed inorganic fibres to the mixture of water and emulsifying-foaming agent and inorganic binding agent at the same time proceeding with an emulsifying -foaming treatment of the mixture preferably by 2θmeans of whisking and/or beating so as to obtain as homogeneous as possible an emulsion.

[0054]Advantageously, during the phase of crushing the fibres in water dispersant substances may be added to prevent the agglomeration of the fibres. To such purpose commercial dispersing agents known as Reotan®, Dolapix®, Zusoplast®, 25or Peg® may be used. [0055]According to an alternative embodiment of the method, the addition of the various components during the preparation phase of the emulsion may occur in a different order. More specifically one may proceed as follows: [0056] - mixing the inorganic fibres in water (preferably demineralised), optionally

5adding any dispersant substances to prevent the agglomeration of the fibres and at the same time proceeding with their crushing;

[0057] - adding the organic emulsifying-foaming agent to the watery suspension of fibres, beginning the emulsion-foaming treatment; [0058]- adding the inorganic binding agent to the water-fibre-emulsifying emulsion. iθ[0059]Advantageously, with specific but not exclusive reference to the two embodiments indicated above, during the treatment in water the fibres are soaked. This may facilitate the phase of mixing to an emulsion.

[0060]Advantageously, with specific but not exclusive reference to the two embodiments indicated above, to obtain as homogeneous an emulsion as possible

I5and at the same time crush the fibres, whisk-type devices (such as those used in the cake industry) may be used.

[0061]The time needed for the mixing-emulsifying operations depends on both the content in fibre and on the speed of the whisks. Advantageously, whisk mixers with

. a speed ranging from 250 to 1 ,900 revs/min may be used. 0[0062]Advantageously, during or subsequent to the phase of preparing the emulsion the addition of the following components may be foreseen: - a foam stabilising agent; - a synthetic foaming agent (in addition to the emulsifying- foaming agent); - an expanded inorganic material; - solid organic bodies (destined to generate cavities inside the mater/al by combustion, as will be described below). 5[0063]Of all these (optional) components one may foresee not only a combined use, but also individual use or use of a selection of the same depending on the requirements and final characteristics desired in the final insulant material. [0064] Preferably, as inorganic fibres ceramic type fibres are used. The term "ceramic" is taken to include non-metallic materials. Silicate-based ceramic fibres 5are especially preferred, such as for example glass wool or rock wool. Examples of this type of fibre, present on the market, are the rock wools produced by Rockwool and by Tervol.

[0065]According to a favourite embodiment, for the purpose of resolving, for example, the limits of bio-compatibility of many rock wools, fibres of the biosoluble lOtype, in other words having chemical compositions such as not to pose a risk to human health, are used as inorganic fibres.

[0066]To such purpose for example, ceramic fibres made from silicon oxide (SiO₂) with content of alkaline oxides and/or alkaline earth oxides over 18% in weight may be used. An example of such fibre is the fibre Insulfrax ®, having the following

I5average composition (percentages in weight): SiO₂ 61-67%; AI₂O₃ <1%; CaO 27- 33%; MgO 2,5-6,5%.

[0067] Preferably, the inorganic fibres are present in a percentage ranging from 20% to 40% in weight of the emulsion. Advantageously the fibres are added in staple, preferably^* with a length ranging from 500 μm to 5 cm, and even more θpreferably from 0.2 cm and 5 cm. The fibres have a diameter preferably not greater than 3 μm.

[0068] Preferably a protein is used as the emulsifying-foaming agent. [0069]The emulsifying-foaming capacities of the protein derive from its amphiphilic nature, common to surfactant compounds.

I 5[007O]As regards the bonding properties however it is known how proteins (which are substantially the condensation products of amino acids) act differently from conventional binding agents. The main chain of the protein molecule (primary structure) is characterised by the presence of covalent peptide bonds, while the steric folded conformation (typical of proteins, secondary and tertiary structure) is

5stabilised by the weak bonds substantially of the non-covalent type. A modification in the configuration of such bonds leads to a radical change in the chemical- physical properties of the molecule.

[0071]The phenomenon of loss of structure caused by heat connected with the aforesaid weak bonds is called denaturation. Owing to heating to temperatures of lOnot less than 50-60⁰C (variable limit depending on the protein) modifications of the weak links (hydrogen and disulphide bridges) which stabilise the steric structure of the proteins (secondary and tertiary structure) take place. Therefore there is a partial or total loss of the folded configuration and consequently a random formation of new bonds between the non-folded protein chains. This leads to the

15formation of an interconnecting structure between the denatured protein molecules and to the loss of solubility.

[0072] This property of the proteins is exploited in the first heat treatment, which in fact is aimed at provoking denaturing of the protein and consequent consolidation of the expanded cellular structure (foamed) generated by it during the emulsifying-

20foaming phase.

[0073]This way at the end of the first heat treatment, one has a dried, foamed, solid body (porous or expanded cellular structure) which can be handled and subjected to further processing without collapsing or without suffering fractures or breakage thanks to the mechanical resistance deriving from the binding effect of

25the denatured protein. [0074]According to a favourite embodiment, albumin is used as the emulsifying- foaming agent. Albumin (especially ovoalbumin) may be synthetic or of natural origin. In the latter case the albumin may be in the form of powder (dried or lyophilised), or in its natural state, that is albumen. [0075]Natural albumin is not pure, but contains various types of proteins and other compounds (such as fats and carbohydrates).

0

Table 1

[0076]Table 1 above shows the composition of the albumen of a hen's egg (percentages in weight). Note how the content of water is practically 90% of the weight. [0077] Preferably, the emulsifying-foaming agent is present with a percentage in weight ranging from 3% to 6% in weight of the emulsion.

[0078] With particular (but not exclusive) reference to the use of protein, the first heat treatment is conducted at a temperature ranging from 70⁰C to 120⁰C, and preferably between 8O⁰C and 100⁰C. Preferably the length of time of this first heattreatment ranges from 2 to 20 hours, and decreases as the temperature is increased.

[0079] According to a favourite solution of the invention, the silicate-based binding agent is colloidal silica. The function of the colloidal silica is to sustain the fibrous- porous (expanded cellular) structure of the material after the elimination of the

5protein following the second heat treatment.

[0080]During the second heat treatment the colloidal silica polymerises forming chains of tetrahedrons in an amorphous structure which withholds and binds the fibres substantially conserving the expanded cellular matrix of the material intact. [0081]Alternatively, as inorganic binding agents potassium and /or sodium silicate iosolutions may be used. It must, however, be pointed out that these specific binding agents while encouraging cohesion with the fibres following the reactions between the silicate and ceramic fibres (with advantages in terms of compactness of the material) seem to slow down the combustion kinetics of the organic components (during the second heat treatment). The use of such binding agents imposes an

I5increase both of temperature and duration of the second heat treatment. [0082]Preferably, the silicate-based binding agent is present in a percentage in weight ranging from 15% to 25% in weight of the emulsion. [0083] With particular (but not exclusive) reference to the use of colloidal silica as the organic binding agent, the second heat treatment is conducted at a

20temperature ranging from 400⁰C to 800⁰C₁ and preferably 500⁰C to 550⁰C. [0084]The duration of this second heat treatment preferably ranges from 30 minutes to 4 hours and even more preferably from 60 to 120 minutes. Over 500 - 550⁰C no substantial improvements in terms of reducing the treatment time are observed.

25[0085]Preferably, as already mentioned, during the aforesaid preparation phase of the emulsion at least one foam stabilising agent is added to the mixture of water and organic emulsifying-foaming agent.

[0086]According to a favourite solution, with particular reference to the use of protein and especially of albumin, sugar is used as the stabilising agent, added 5preferably at a percentage in weight ranging from 2% to 5% in weight of the emulsion.

[0087]Preferably, the sugar is added before or during the formation of the emulsion. As a result of the mechanical stress connected with the mixing operations the local temperature may reach up to 40-50⁰C making the sugar iofluidify (partial melting - solvation action of the water). In this way, thanks to the mixing movements, fluid filaments of sugar are formed which are dispersed in the mass of material. A (minimal) sudden fall in temperature (such as that caused by interruption of the mixing action) is sufficient to solidify the filaments of sugar in a vitreous manner. The sugar thus presents a rigid framework (organised in the short

I5range and amorphous in the long range) which helps to support the expanded cellular structure (foam) before the denaturation of the proteins (following the first heat treatment ).

[0088]Advantageously, as already mentioned, during the preparation phase of the emulsion a second, synthetic foaming agent may be added so as to modify the

20dimensions of the expanded cellular structure and thus the final density of the material. For example, anionic surfactants in a watery solution may be used. [0089]Preferably the synthetic foaming agent is added up to a content ranging from 0.3 % to 1% in weight of the emulsion. [0090]Advantageously, as already mentioned, during the preparation phase of the 5emulsion, and preferably after the addition of the inorganic fibres, at least one expanded inorganic material is added, preferably in the form of granules. [0091 ]Preferably the aforesaid inorganic expanded material may be of the siliceous, alumino-silicate, alumino-magnesium-silicate, calcareous and/or calcic type, and is preferably chosen from the group comprising expanded clay and

5vermiculite.

[0092]Advantageously, such inorganic expanded material is added in a percentage of not more than 20% - 25% in weight of the inorganic fibres. [0093]Preferably, during the preparation phase of the emulsion, preferably after the addition of the fibres, solid bodies in organic material are added, destined to be iocombusted during the second heat treatment so as to generate cavities of controlled dimensions inside the material, in addition to the porosity present in the expanded cellular structure.

[0094]Advantageously, such cavities may act as acoustic resonators so as to reduce acoustic transmission through the material. The dimensions of such solid isbodies are chosen so that the cavities left by them are substantially tuned with predefined sound frequencies.

[0095]According to a specific embodiment of the invention, the method for making the thermal acoustic insulating material foresees the following phases: [0096]a) one starts from an inorganic material in the form of fibre, such as θrock wool or other equivalent, for example SiO₂-based in the form of staple fibre; [0097]b) an expanded inorganic material such as expanded clay or equivalent, for example granular expanded mineral or vermiculite in a maximum quantity of 20% is preferably added to the fibres; [0098]c) the mineral fibres in staples are mixed using a whisk mixer

25maintaining the length of the fibres over 5 microns and in any case with a length: cross- section ratio of over 3;

[0099]d) dispersing agents are added during the mixing phase to prevent agglomeration of the fibres during crushing, such as commercial dispersing agents known as Reotan®, Dolapix®, Zusoplast®, Peg®;

5[00100]e) an organic emulsifying-foaming agent such as albumin is added; [00101]f) an emulsifying treatment by means of whisking is performed so obtain a foam. At this stage colloidal silica is also added in a percentage of up to 30% in weight of the mixture, as the binding agent of the fibres; [00102]g) the foam or mixture thus obtained is poured into a mould; iθ[OO1O3]h) a first heat treatment at a low temperature is performed to consolidate the product and maintain the foam structure by subjecting it to a temperature such as not to interfere with the organic material but such as to remove most of the water, therefore a temperature preferably ranging from 80-100⁰C for approx. 12 hours, said treatment having both a foaming or foaming adjuvant function and

I5consolidation function of the same;

[00104]i) the material thus treated is subjected to a second heat treatment at a high temperature, therefore to a higher temperature between 500⁰C and 600°C for 60-120 minutes to eliminate the organic components of the material. The product thus obtained and cooled is used for subsequent applications or undergoes further

2θprocessing for the completion of the product, cutting, gluing to other panels etc.

* * *

[00105]Reference will now be made to three specific embodiments of the insulating material according to the invention.

Table 2

[00106] Table 2 above shows the initial composition of the emulsion before the 5heat treatments and the characteristics of the final material in terms of thickness of the panel and of density after the heat treatments.

[00107]For all three examples, the preparation of the panel from the raw materials involved the following phases:

[00108] a) Mixing of the fibres (rock wool or artificial SiO₂-based fibres with iocontent of alkaline oxides or alkaline earth oxides in a variable quantity from 20 to

30% in weight of the final mixture). Specifically, fibres of the Insulfrax ® type were used. The mixing was performed in demineralised water in quantities ranging from

40-50 % weight of the final mixture.

[00109] b) Mixing was performed using mechanical whisks (cake-making

I5type).

[00110] c) Addition to the mixture of powdered albumin in quantities from 4 to 5% weight of the final mixture. [00111] d) Addition of sugar in a similar quantity to the albumin in quantities of 3- 3.5 % in weight of the final mixture.

[00112] e) Addition of colloidal silica with contents in silica of 30% colloid weight. Specifically colloidal silica of the type Lithosol ® 1530 produced by 5Zschimmer&Schwarz was used. The quantity of colloidal silica determines the density of the final panel. The quantity of colloidal silica at 30% may vary from 20 to 30% weight of the final mixture.

[00113] f) The addition, if any, of expanded vermiculite (example 1) with average size of granule less than 1 mm. Pull-Rhenen expanded vermiculite was loused. The quantity of vermiculite may vary from 1 to 8% weight of the final mixture.

[00114] g) Mixing so as to obtain an emulsified, homogeneous paste. Mixing time depends both on the fibre contents and the speed of the whisks. Emulsion techniques using whisk mixers were adopted. 15[OO115] h) Casting of the mixture into flat moulds of the desired height (15-

30 mm).

[00116] i) Drying of the organic components (sugar and albumin) in the furnace at a temperature of approx. 80 ⁰C for 8-12 hours depending on the thickness. 20[00117] j)heat treatment in the air at 500⁰C for 120 minutes to eliminate all the organic components.

[00118] The process was performed in lots, but can be performed in continuous cycle processing.

[00119] The material obtained by mixing the silicates and foaming agents

25has a porous (expanded cellular) structure with low density and lightness of the panel. The low density obtained of 150-210 Kg/m³ combined with the low thermal conductivity ranging indicatively from 0.033-0.045 W/mk and total incombustibility make the material particularly suitable for insulation applications in naval constructions.

5[00120]The extensive surface area of the cellular structure makes for high performance of the material in thermal and acoustic insulation. [00121]The material itself is also extremely resistant to melting. [00122]Thanks to the thermal pre-treatment, according to the present invention, which not only permits maintenance of the expansion but also stabilisation of the ioconglomerate materials, a working temperature is ensured which may vary indicatively from -50 to +800⁰C, even though it's even possible to exceed 1 ,000⁰C. The material obtained thus has good thermal stability.

[00123]Depending on the composition elements, after heat treatment the material is also resistant to chemical aggression and especially to acids. The material later

I5formed has good elasticity and sufficient compressibility, not being completely rigid. Workability of the material is excellent.

* * *

[00124]From a comparison of the insulant materials made according to example 1 and example 2 shown in Table 2 one may observe how the presence of vermiculite

20determines an increase in density.

[00125]A similar effect of increasing density accompanies an increase in the quantity of sugar in the emulsion. An opposite effect on the final density of the material is produced however by the synthetic foaming agents. [00126]To highlight the effects on density of the sugar and synthetic foaming

25agents, three panels in insulant material according to the invention were made, varying the quantity of sugar and including or excluding the presence of foaming agents . The results are shown in table 3 below.

Table 3

5[00127]The Example 1 panel is taken as reference; in the Example 2 panel a quantity of foaming agent was added, leaving the quantity of sugar unvaried; in the Example panel 3 the quantity of sugar was doubled while the other conditions remained unchanged; The anionic surfactant made from a sulphate of a fat alcohol W53 Fl produced by Zschimmer&Schwarz was used as the synthetic foaming loagent.

[00128]For the purpose of evaluating the impact of the presence of solid bodies in the material according to the invention as regards mechanical resistance and density, samples of material were produced introducing varying quantities of solid I5bodies.

[00129]The material indicated in Example 1 of Table 3 above was taken as the reference sample. Spheroid, starch-based particles having an average diameter of approx. 3mm were used as solid bodies. Three samples of material were then made, following the same composition and method of production used for the reference sample. Spheroid solid bodies were added to a first sample in a percentage of 16% of the volume of the mixture; spheroid solid bodies were added to the second sample in a percentage of 10% of the volume of the mixture; while in the third sample spheroid solid bodies were added in a percentage of 20% of the

5volume of the mixture.

[00130]The first and second samples show properties of mechanical resistance similar to those of the reference sample without solid bodies. The third sample is however extremely fragile, and substantially lacking in mechanical resistance. As regards the density of the material, the three samples have a density substantially iocomparable to that of the reference sample, with values measured for all three samples of about 185 kg/m³.

[00131]l_astly, a fourth and fifth sample were made, using in this case starch- based solid bodies of a (hollow) cylindrical shape having an average diameter of 5 mm and average height of 7 mm. As reference sample once again the material vindicated in Example 1 of Table 3 above was used. These samples too were made using the same composition and the same method of production as that of the reference sample.

[00132]ln the fourth sample cylindrical solid bodies were added to a percentage of the volume of the mixture of 10 %; in the fifth sample spherical solid bodies were

2θadded to a percentage of the volume of the mixture of 15 %. [00133]The fourth sample had similar mechanical resistance properties to that of the reference sample, with no solid bodies. While the fifth sample proved very fragile, and substantially lacking mechanical resistance. As regards the density of the material, the two samples had a lower density than that of the reference

25sample, of approx. 160 kg/m³. [00134]Experimental tests were carried out to identify the acoustic insulation properties of the acoustic material according to the invention, comparing it to state of the art materials.

5[00135]Specifically two panels were made in insulant material according to the invention following the instructions given for Examples 2 and 3 above: a first panel was 40mm thick and weighed about 12.9 kg, while a second panel was 30mm thick and weighed about 13.2 kg. As materials for comparison a panel in rock wool (20mm thick and weighing 10.7kg) and a panel in vermiculite (30 mm iothick and weighing 13.2 kg) were used.

[00136]ln Figure 4 attached hereto the insulation curves of the various samples are shown across a range of frequencies of 200 - 3.150 Hz. Curve (a) refers to the panel in rock wool, curve (b) to the panel in vermiculite, curves (c) and (d) to the first and second panels according to the invention respectively. i5[00137]Measurements were taken by positioning the panels in the aperture existing between a reverberation room (where sound is generated; volume 14.4 m³) and a semi-anechoic room (where noise is measured; volume 75 m³, with walls treated with soundproof material to prevent reflections). The levels of sound intensity (dB) were measured in both rooms, assessing the acoustic insulation

2θpower from the difference in levels of intensity in the two rooms. [00138]As can be seen from the graphs in Figure 4, the material according to the invention has acoustic insulation properties comparable to those of traditional materials currently used. In the range of frequencies between 200 and 1600 Hz the best insulation is given by the second panel made according to the invention 5(curve d). In the range of frequencies between 1600 and 6300 Hz it was seen that the best performance was by the panel in rock wool and that the first panel made according to the invention had substantially similar levels of performance. [00139]Lastly, the evaluation index of RW insulation calculated on the range of frequencies from 200 to 6300 Hz was assessed. The following figures were 5observed in relation to a frequency of 500 Hz: panel in rock wool RW = 30; panel in vermiculite RW = 33; first panel according to the invention RW = 33; second panel according to the invention RW = 34. The panels according to the invention generally show higher acoustic insulation properties.

* * *

iθ[00140]Advantageously the material according to the invention may be used loose in granules, for example scattered inside a cavity.

[00141]Preferably, the insulating material according to the invention is pre-formed in panels. Given the flexible characteristics of the material the panels prove semirigid i5[00142]Advantageously, the panels may be covered on at least one side with a layer of mineral fabric and/or be joined to a sheet of metal sheeting. The metal sheeting may in turn be covered with a finishing surface, for example in PVC. [00143]Advantageously, the material may be pre-formed in panels inserted like a sandwich between two layers of covering.

20[00144]Advantageously, the insulating material according to the invention - in the form of a panel - may be joined to at least one layer of covering modelled externally in a shape conducive to acoustic absorption, for example undulated. [00145]According to the invention an embodiment of panel of a thickness of approx. 15-20 mm backed with pre-painted metal sheeting or pre-covered in PVC

25produces a panel suitable for the realisation of decorative ship's bulkheads class BO, B15.

[00146]The thicker panels of approx. 40-50mm may be used to make walls / bulkheads of class A60.

[00147]Obviously the material can also be used in panels which have not been 5pre-covered, as a thermal acoustic insulating material.

[00148]The panel backed with protective mineral fabric can be used in the service areas.

[00149]The method for making a panel with the panel covered in fabric is as follows: io[OO15O]a) mixing of the material in a watery solution,

[00151]b) rolling out of the mixture onto continuously rotating metal trays,

[00152] c) maintaining in multilevel drying furnace for elimination of water and formation of the spongy panel with period of about 10 hours for 25mm thickness and 12 hours for 80mm thickness, 15[00153Jd) cutting to measure of the panels formed (for example using a band saw for a number of sandwich panels or using a trimming saw with a slitting disc),

[00154]e) processing at high temperature of 500⁰C for 120 minutes in air,

[00155]f) gluing of external covering such as fabric, or metal sheeting or another layer of finishing material. This last phase may be inverted with the one above. 20[00156]The panel glued to steel sheeting or made into a sandwich between two steel sheets is particularly useful for fire-resistant naval bulkheads. In such case they have fire resistance class BO or B15 with noise reduction of RW42

SBISO140/3, 717/1 by a double panel.

[00157]As already mentioned earlier, to improve its resistance to water the panel in

25insulant material is subjected to an aspersion treatment with water-repellent products such as silicone oils with a high combustion temperature. Such treatment enables a reduction of the hygroscopic properties of the material.

[00158]According to a particular embodiment of the invention, the insulant material comprises granules of colloidal silica in the form of aerogel. 5[00159]Advantageously, the granules of aerogel are used as a low density filler in the same way as vermiculite or expanded clay, in combination with such or in place of such. Preferably the contents of silica aerogel in volume is over 20%.

Formulations containing respectively 20-30-50 vol.% of granules of aerogel are advantageous. iθ[OO16O]Materials of the silica aerogel type have a low conductivity (0.011-0.013

WVmK at 38⁰C for a material with a density of 100 Kg/m³, maximum temperature of

800⁰C).

[00161]ln addition inside the aerogel materials the speed of sound decreases at the same frequency to 100 m/sec, so that a panel of aerogel of the same thickness isand density favours absorption of low frequencies.

[00162]The aerogels also have the property of lightness (density 20-150 kg/m³) and revolutionary thermal insulation. Their main limit is in their elevated fragility and high cost.

[00163]According to a particular embodiment of the invention, illustrated in Figure 203 hereto attached, a thermal-acoustic insulating panel may be made comprising at least one first layer 6 of insulant material with an expanded cellular structure as described in precedence, and at least one second layer 5 of granular thermal and acoustic insulating material made from silica aerogel.

[00164]According to an alternative embodiment, a thermal-acoustic insulating 25panel may be made comprising at least a first layer with sound absorption and heat resistant functions (for example: shaped structure in ceramic oxide material or granular material made from silica aerogel) and a second fibrous layer made according to the present invention( thermal and acoustic insulation). [00165]Advantageously, according to a further embodiment, the insulating panel 5may be thought of as composed of two separate parts:

[00166]- a structure specially-shaped so as to attenuate sound and tuned for the relevant frequencies.

[00167]- a filled part for thermal insulation corresponding to the material as per the present invention, of significantly lesser density than the rock wool used today, iothus creating a sound-absorbent structure (such as the Helmholtz resonator) in lightweight fire-resistant material, like a traditional, low density ceramic.

* * *

[00168]The cellular structure of the insulating material according to the invention offers a better noise deadening effect especially for low frequencies, indicating

I5better attenuation by the cellular structure compared to the conventional rock wool mat.

[00169]The final panel is composed of non-combustible material (preferably, silica and colloidal silica-based fibre), given that the final heat treatment (500⁰C) totally eliminates the organic compounds. The siliceous mineral fibre and colloidal silica 0have a thermal conductivity no greater than the thermal conductivity of basalt. [00170]The density of the material is no greater than the density of the rock wool mat currently used. One may therefore reasonably assume that the fire-resistant properties are better or at most the same as the rock wool mat. [00171]Drying at low temperature and subsequent treatment eliminating the 5emulsifying organic compounds (albumin) are aspects of certain advantage. [00172]The use of low cost materials (especially albumin, colloidal silica and artificial fibres, vermiculite) reducing the cost of producing the panel, is also a possible technological aspect.

[00173]An advantageous embodiment is to make the product in a double layer, 5that is one layer designed mainly to reduce the noise in other words for acoustic insulation, of a more foamed and/or cellular nature and a layer designed more for thermal insulation. Such embodiment makes it possible to significantly lighten the weight of the insulating materia).

[00174]This solution makes it possible to produce a lighter panel with the same iothermal barrier characteristics BO and/or B15, and acoustic insulation of 43 db.

[00175]This way one has the advantage of :

[00176]- improving functionality and performance;

[00177]- improving quality while containing costs.

[00178]With the present inventions one may therefore produce a variation of the I5state of the art rock wool fibre panels or mats, achieving according to the present invention a slight reduction of density by means of the cellular structure.

Claims

1. Thermal-acoustic insulating material, characterised by the fact of having a cellular structure comprising fibres and by the fact of being made from a foamed watery emulsion comprising inorganic fibres, at least one silicate- based binding agent and at least one organic emulsifying-foaming agent, said emulsion being subjected to a first heat treatment aimed at consolidating the foam structure to obtain a dried, foamed solid body, said body being then subjected to a second heat treatment aimed at eliminating the organic components present in said foamed body.

2. Material according to claim 1, wherein said inorganic fibres are silicate-based.

3. Material according to claim 2, wherein said fibres are biosoluble and, specifically , have a content of alkaline metals and/or alkaline-earth metals of over 18% in weight .

4. Material according to any of the previous claims, wherein said inorganic fibres are present with a percentage ranging from 20% to 40% in weight of said emulsion.

5. Material according to any of the previous claims, wherein said inorganic fibres are in staple, preferably with a length ranging from 500 μm to 5 cm, and even more preferably from 0.2 cm to 5 cm.

6. Material according to any of the previous claims, wherein said inorganic fibres have a diameter of not more than 3 μm.

7. Material according to any of the previous claims, wherein said silicate-based binding agent is colloidal silica.

8. Material according to any of the previous claims, wherein said silicate-based binding agent is present with a percentage ranging from 15% to 25% in weight of said emulsion.

9. Material according to any of the previous claims, wherein said emulsifying- foaming agent is a protein.

10. Material according to any of the previous claims, wherein said emulsifying- foaming agent is albumin.

11. Material according to the previous claim, wherein albumin is of natural and/or synthetic origin, the natural albumin being in the form of powder and/or albumen.

12. Material according to any of the previous claims, wherein said emulsifying- foaming agent is present with a percentage ranging from 3% to 6% in weight of said emulsion.

13. Material according to any of the previous claims, wherein said first heat treatment is conducted at temperatures ranging from 70⁰C to 120⁰C, and preferably from 80°C to 100⁰C.

14. Material according to any of the previous claims, wherein said first heat treatment is conducted for a period of time ranging from 2 to 20 hours.

15. Material according to any of the previous claims, wherein said second heat treatment is conducted at temperatures ranging from 400°C to 800⁰C, and preferably from 500°C to 550°C.

16. Material according to any of the previous claims, wherein said second heat treatment is conducted for a period of time ranging from 30 minutes to 4 hours, and preferably from 60 to 120 minutes.

17. Material according to any of the previous claims, wherein said emulsion comprises at least one foam stabilising agent.

18. Material according to the previous claim, wherein said foam stabilising agent is sugar, and is preferably present in a percentage ranging from 2% to 5% in weight of said emulsion.

19. Material according to any of the previous claims, wherein said emulsion comprises a second synthetic foaming agent, preferably present in a percentage ranging from 0.3 % to 1% in weight of said emulsion.

20. Material according to any of the previous claims, wherein said emulsion comprises at least one inorganic expanded material, preferably in the form of granules.

21. Material according to any of the previous claims, wherein said inorganic expanded material is of the siliceous, alumino-silicate, alumino-magnesium- silicate, calcareous and/or calcic type, preferably chosen from the group comprising expanded clay and vermiculite.

22. Material according to any of the previous claims, wherein said inorganic expanded material in the form of granules is present in a percentage not exceeding 20% - 25% in weight of said fibres.

23. Material according to any of the previous claims, wherein said emulsion comprises solid bodies in organic material, destined to be combusted during said second heat treatment so as to generate cavities inside said material.

24. Material according to the previous claim, wherein said cavities act as acoustic resonators so as to reduce acoustic transmission through said material, the dimensions of such solid bodies being chosen so that the cavities left by them are substantially tuned with predefined sound frequencies.

25. Material according to any of the previous claims, wherein said foamed body is subjected to sintering treatment aimed at connecting said fibres directly to each other.

26. Material according to any of the previous claims, wherein said foamed body is subjected to aspersion treatment with water-repellent compounds, preferably silicone oils, so as to reduce the hygroscopic properties of said material.

27. Material according to any of the previous claims, wherein said material has a density ranging from 130 kg/m³ to 210 Kg/m³.

28. Thermal-acoustic insulating material of the type comprising variously mixed mineral fibres characterised by the fact that the said mineral fibres are (1) welded to each other in their points of contact (4) by heat-fusion and/or heat-plasto-fusion on contact by the same material or the adjacent presence of other binding material substantially operating slightly below or near the temperature of incipient melting and/or softening of the inorganic material, but below the collapse temperature of said inorganic material in fibre.

29. Material according to claim 28, characterised by the fact that it comprises internally empty spaces or spaces containing gas (2) therefore practically forming a mixed fibrous-expanded structure (1-2).

30. Material according to any of the claims from 28 to the previous, characterised by the fact that the weldings with each other in the respective points of contact entail the presence of colloidal silica.

31. Material according to any of the claims from 28 to the previous, characterised by the fact that the weldings with each other in the respective points of contact entail the presence of hardened and/or carbonised plastic material produced by subjection to temperatures above 600-800⁰C.

32. Material according to any of the claims from 28 to the previous, characterised by the fact that it comprises scattered granules of expanded mineral material (3), said expanded mineral material preferably being siliceous, alumino-silicate, alumino-magnesium-silicate, calcareous and/or calcic.

33. Material according to any of the claims from 28 to the previous, characterised by the fact that said mineral fibres are longer than 5 μm and have a length: diameter ratio of over 3.

34. Material according to any of the previous claims, characterised by the fact of being substantially loose granules.

35. Material according to any of the previous claims, characterised by the fact of being substantially pre-formed in semi-rigid panels.

36. Material according to any of the previous claims, characterised by the fact of being substantially pre-formed in panels with at least one side covered by a layer of mineral fabric.

37. Material according to any of the previous claims characterised by the fact of being substantially pre-formed in panels with at least one side covered in at least one sheet of metal sheeting.

38. Material according to any of the previous claims, characterised by the fact of being substantially pre-formed in panels with at least one side covered in at least one sheet of metal sheeting, said sheeting in turn being covered on its surface, preferably by a layer of PVC.

39. Material according to any of the previous claims, characterised by the fact of being substantially pre-formed in panels inserted like a sandwich between two layers of covering.

40. Material according to any of the previous claims, characterised by the fact of being substantially in the form of a panel and of being joined to at least one layer of covering modelled externally in a shape favouring acoustic absorption.

41. Material according to any of the previous claims, characterised by the fact of comprising silica aerogel, preferably in a granular form.

42. Material according to the previous claim, characterised by the fact that said silica aerogel is present in a percentage of over 20% in volume of said material.

43. Panel for thermal-acoustic insulation according to any of the previous claims, characterised by the fact of comprising at least a first layer of material according to any of the previous claims.

44. Panel for thermal-acoustic insulation according to the previous claims, comprising at least a second layer of granular, thermo-acoustic insulating material made from silica aerogel.

45. Method for the production of thermo-acoustic insulating material comprising the following phases: a) preparing a foamed watery emulsion comprising inorganic fibres, at least one silicate based binding agent and at least one organic emulsifying- foaming agent; b) subjecting said emulsion to a first heat treatment aimed at consolidating the foam structure so as to obtain a dried solid foam body; c) subjecting said foamed body to a second heat treatment aimed at eliminating the organic components present in said foamed body to obtain an inorganic foamed body.

46. Method according to the previous claim, comprising an aspersion phase of said inorganic foamed body with water-repellent compounds, preferably silicone oils.

47. Method according to any of the previous claims comprising a sintering phase of said foamed body.

48. Method according to any of the previous claims wherein said preparation phase of the emulsion comprises the following sub-phases: a) crushing the inorganic fibres in water, preferably adding dispersing substances to prevent the agglomeration of said fibres; b) preparing a mixture of water and said organic emulsifying-foaming agent; c) adding said inorganic binding agent to said mixture of water and emulsifying-foaming agent; d) adding said crushed inorganic fibres to said mixture of water, emulsifying- foaming agent and inorganic binding agent obtaining a mixture and at the same time proceeding with an emulsifying-foaming treatment of said mixture, preferably by means of whisking and/or beating so as to obtain said emulsion.

49. Method according to any of the previous claims wherein said inorganic fibres are silicate-based, preferably of the bio-soluble type and even more preferably with a content of alkaline metals and/or alkaline-earth metals of over 18% in weight.

50. Method according to any of the previous claims wherein said inorganic fibres are present in a percentage ranging from 20% to 40% in weight of said emulsion.

51. Method according to any of the previous claims wherein said inorganic fibres are in staple, preferably with a length ranging from 500 μm to 5 cm, and even more preferably from 0.2 cm to 5 cm.

52. Material according to any of the previous claims, wherein said inorganic fibres have a diameter of not more than 3 μm.

53. Method according to any of the previous claims, wherein said silicate-based binding agent is colloidal silica.

54. Method according to any of the previous claims, wherein said silicate-based binding agent is present in a percentage ranging from 15% to 25% in weight of said emulsion.

55. Method according to any of the previous claims, wherein said emulsifying- foaming agent is a protein, said first heat treatment being aimed at causing the denaturation of said protein with consequent consolidation of the foamed structure generated by it during the emulsifying-foaming phase.

56. Method according to any of the previous claims, wherein said emulsifying- foaming agent is albumin, of natural and/or synthetic origin, the natural albumin being in the form of powder and/or albumen.

57. Method according to any of the previous claims, wherein said emulsifying- foaming agent is present in a percentage ranging from 3% to 6% in weight of said emulsion.

58. Method according to any of the previous claims, wherein said first heat treatment is conducted at temperatures ranging from 70⁰C to 120⁰C₁ and preferably from 80⁰C to 100⁰C, and for a time ranging preferably from 2 to 20 hours.

59. Method according to any of the previous claims, wherein said second heat treatment is conducted at temperatures ranging from 400⁰C to 800°C, and preferably from 500⁰C to 55O⁰C, and for a time preferably ranging from 30 minutes to 4 hours, and even more preferably from 60 to 120 minutes.

60. Method according to any of the previous claims, wherein during said preparation phase of the emulsion at least one foam stabilising agent is added to said mixture of water and organic emulsifying-foaming agent.

61. Method according to the previous claim, wherein said foam stabilising agent is sugar, and is preferably present in a percentage ranging from 2% to 5% in weight of said emulsion.

62. Method according to any of the previous claims, wherein during said preparation phase of the emulsion a second synthetic foaming agent is added, preferably present in a percentage ranging from 0.3% to 1% in weight of said emulsion, in the aim of modifying the dimensions of the cellular structure and thus the final density of the material.

63. Method according to any of the previous claims, wherein during said preparation phase of the emulsion, preferably after the addition of said fibres, at least one inorganic expanded material is added, preferably in the form of granules.

64. Method according to the previous claim, wherein said inorganic expanded material is of the siliceous, alumino-silicate, alumino-magnesium-silicate, calcareous and/or calcic type, preferably chosen from the group comprising expanded clay and vermiculite, preferably being added in a percentage of not more than 20% - 25% in weight of said fibres.

65. Method according to any of the previous claims, wherein during said preparation phase of the emulsion, preferably after the addition of said fibres, solid bodies in organic material are added, destined to be combusted during said second heat treatment so as to generate cavities inside said material.

66. Method according to the previous claim, wherein said cavities act as acoustic resonators so as to reduce acoustic transmission through said material, the dimensions of such solid bodies being chosen so that the cavities left by them are substantially tuned with predefined sound frequencies.

67. Method for making a fire-resistant, thermal-acoustic insulating material characterised by the fact of comprising at least the following phases: a) using an inorganic material in the form of fibre or in the form of staple fibre; b) subjecting the mineral staple fibres to grinding by breaking up in water; c) providing for any addition of dispersant substances to prevent agglomeration of the of the fibres during crushing; d) adding an organic emulsifying-foaming agent; e) performing an emulsifying-foaming treatment of the mixture by whisking and/or beating;

/f) subjecting such foamed mixture to a first heat treatment at a low temperature to consolidate the product and maintain the foam structure by subjection to a temperature such as not to interfere with the organic material ' but such as to consolidate such foam, substantially a temperature preferably around 180-200⁰C; g) subjecting the material obtained to a second heat treatment at a high temperature, therefore at a much higher temperature not under 400⁰C and

not over 600⁰C, preferably around 500°C so as to eliminate by calcination all . the organic components present.

68. Method for the production of insulating material according to the previous claim, characterised by the fact of adding before sintering and/or consolidation an expanded inorganic material, such as for example expanded clay or equivalent , such as granular expanded mineral or vermiculite.

69. Method for the production of insulating material according to the previous claim, characterised by the fact that the addition of said expanded granular mineral material is in the maximum quantity of 20% in weight .

70. Ship comprising a structural component made, totally or partially, with an insulating material and/or panel according to any of the previous claims.