Insulating panel comprising structural fibers and thermally bonding fibers.

Abstract

Title of the invention: Insulating panel comprising structural fibers and thermally bonding fibers. The present invention relates to an insulating panel comprising an interweaving of structural fibers (2, 6, 8) and thermally bonding fibers (4), the thermally bonding fibers (4) being formed of a sheath and a core, the core and the sheath being formed of two distinct materials each having a distinct melting point, the core having a diameter of at most 11 µm. (Figure 1)

Description

Title of the invention: Insulating panel comprising structural fibers and thermally bonding fibers.

[0001] The present invention relates to the field of construction materials, and more particularly to the field of construction materials intended for thermal and / or acoustic insulation. The present invention relates more particularly to an insulating panel comprising structural fibers bonded to each other by thermally bonding fibers.

[0002] Insulating panels are commonly used as insulation materials intended to provide thermal and / or acoustic insulation, for example during the construction of buildings.

[0003] Such insulating panels may, in particular, be formed of structural fibers bonded together by a binding agent so that air is trapped stably and immobile within the insulating panels. The structural fibers are fibers used to form the structure of the insulating panel. To this end, the structural fibers are intertwined and bonded together by a binding agent to form an insulating panel. These structural fibers may be chosen from mineral fibers such as glass fibers or rock fibers, or from natural fibers such as wood fibers or hemp fibers.Particularly when made with structural fibers in the form of glass fibers, these insulating panels can be obtained by an aerodynamic manufacturing system in which structural fibers and thermally bonding fibers are mixed together and deposited on a conveyor before passing through an oven.

[0004] The manufacture of these insulating panels, and in particular the manufacture of the structural fibers necessary for their production, has a carbon footprint that manufacturers are seeking to reduce. To this end, the structural fibers can be recovered from pre-existing insulating panels and recycled to form a new insulating panel.

[0005] It follows that in such an insulating panel made from recycled structural fibers, the primary factor increasing the carbon footprint of the insulating panel relates to the use of thermal bonding fibers. However, the quantity of thermal bonding fibers cannot be reduced without risking a decrease in the mechanical properties of the insulating panels.

[0006] The present invention falls within this context and aims to overcome at least some of the drawbacks of the prior art. The present invention proposes to find a solution for limiting the carbon footprint of an insulating panel without affecting its mechanical properties.

[0007] Thus, the present invention relates to an insulating panel comprising an entanglement of structural fibers, selected from mineral fibers and natural fibers, and thermally bonding fibers, the thermally bonding fibers being formed of a sheath and a core, the core and the sheath being formed of two distinct materials each having a distinct melting temperature, the core having a diameter of less than 11 pm.

[0008] The structural fibers can be selected from mineral fibers such as glass fibers and / or rock fibers. They can also be selected from natural fibers, that is, fibers of organic origin, such as woody plant fibers commonly referred to as "wood fibers," and in particular Douglas fir, beech, or pine fibers, or from cellulosic plant fibers such as straw, hemp, or cotton fibers. Within the insulating panel as it exits the manufacturing process, the structural fibers are bonded to one another by means of the molten sheath of the thermally bonding fibers. It is understood that the insulating panel is obtained after passing through an oven in which the thermally bonding fibers are heated to a temperature such that the sheath melts and expands while the core remains intact.The core then provides rigidity to the fiber entanglement and allows the sheath to be held locally, which expands into filaments attached to the core to adhere to the structural fibers present near the core. This characteristic of thermally bonded fibers is made possible by distinct melting temperatures for the core and the sheath.

[0009] It is therefore understood that the insulating panel has a configuration before oven curing in which the thermally bonded fibers are not permanently bonded to the structural fibers, and a configuration after oven curing in which the thermally bonded fibers are permanently bonded to the structural fibers. This bonding between the thermally bonded fibers and the structural fibers is achieved by the sheath, which connects at least part of the core to the structural fibers. It should be noted that within such an insulating panel, there are thermally bonded fibers that are only bonded to other thermally bonded fibers. Although these thermally bonded fibers are not bonded to the structural fibers, they contribute to strengthening the interconnectedness between the thermally bonded and structural fibers within the insulating panel.

[0010] The thermally bonding fibers are configured according to the invention such that they have a core with a diameter of less than 11 pm. In other words, the core diameter of the fibers is less than a threshold value of 11 pm, this threshold value having been determined by the inventors through tests and calculations demonstrating that compliance with this upper threshold value enables the achievement of the necessary mechanical properties of the insulating panel, and in particular resistance to the tensile strength and deflection of the insulating panel. It is then possible to adjust the core diameter of the thermal bonding fibers to optimize their use and reduce the mass percentage of thermal bonding fibers in the insulating panel without affecting its mechanical properties, with the understanding that reducing the quantity of thermal bonding fibers in the insulating panel thus reduces its carbon footprint.

[0011] According to a feature of the invention, the diameter of the core of the thermal bonding fibers is between 3 pm and 10 pm.

[0012] According to one feature of the invention, the core diameter of the thermally bonded fibers is between 4 pm and 9 pm. The inventors were able to determine that these core diameter values ​​of the thermally bonded fibers correspond to insulating panels that are both sufficiently rigid, i.e. within the target range during tensile strength tests or during flexural tests, and sufficiently flexible, i.e. within the target range during compression return tests, for example, and that the tests on these panels are carried out with thermally bonded fibers of the same length, the same dtex, or the same sheath / core ratio.

[0013] It should be noted that the core dimension is here determined by the value of the core diameter, in relation to a core shape with a circular cross-section. Alternatively, and in order to consider slightly ovoid core shapes, for example, the core dimension can also be determined by the cross-sectional area of ​​the core obtained by a cut along a plane perpendicular to a principal elongation direction of a heat-bonding fiber. Equivalent to what has just been mentioned as the core dimension specific to the invention, the cross-sectional area of ​​the core has a maximum area of ​​95 pm². Preferably, the cross-sectional area of ​​the core is between 12.5 pm² and 63.5 pm².

[0014] According to a feature of the invention, the thermal bonding fibers have a decitex between 0.8 dtex and 1.7 dtex.

[0015] The decitex of a thermally bonded fiber allows for the characterization of the overall fineness of this thermally bonded fiber when it is not subjected to a melting temperature, i.e., before oven curing, notably by providing mass information for a fiber length of 10,000 meters. The decitex is measured with the unmelted cladding, and therefore with the cladding and core, which are coaxial cylindrical shapes. It is understood that with a core diameter of less than 11 µm and a fiber fineness between 0.8 dtex and 1.7 dtex, the structure of the thermally bonded fibers, and more specifically the cladding of said thermally bonded fibers, maximizes the formation of bond points between the core of the thermally bonded fibers and the structural fibers, as well as the strength of these bonds. For a given mass percentage, there are more thermally bonded fibers within the insulating panel, which has the effect of allowing a better distribution of the fiber cores within the insulating panel, between the structural fibers, and therefore a better distribution of the sheath filaments formed during the oven curing process and therefore a better distribution of the attachment points on the structural fibers formed by the deployment of the sheath filaments from the core.

[0016] According to a feature of the invention, the thermal bonding fibers have a decitex less than or equal to 1.5 dtex.

[0017] According to a feature of the invention, the thermal bonding fibers have a decitex less than or equal to 1.3 dtex.

[0018] According to a feature of the invention, the thermal bonding fibers have a decitex between 1 dtex and 1.3 dtex.

[0019] According to one feature of the invention, the mass percentage of the sheath is at least 65%. Preferably the mass percentage of the sheath is between 65% and 90%, and more preferably the mass percentage of the sheath is 80% plus or minus 5%.

[0020] According to one feature of the invention, the mass percentage of the core is at most 35%. Preferably the mass percentage of the core is between 10% and 35%, and more preferably, the mass percentage of the core is 20% plus or minus 5%.

[0021] It should be noted that, in relation to the mass percentages just mentioned, the mass percentage of the sheath added to the mass percentage of the core represents 100% of the mass percentage of a heat-bonding fiber. Therefore, the percentages mentioned above must be considered in combination with each other so that the total mass percentage of a heat-bonding fiber equals 100%.

[0022] In other words, the sheath-to-core ratio is at least 65 / 35. This mass percentage must be considered in relation to the total mass of a thermally bonded fiber formed jointly by the sheath and the core, such that the sheath then represents at least 65% of the mass of the thermally bonded fiber and the core at most 35% of the mass of the thermally bonded fiber. Having a sheath-to-core ratio that is greater than a given threshold value strengthens the bonds between the sheath and the structural fibers, since this results in more molten sheath for a given attachment point. This strengthens the attachments, and it is this rigidity of the insulating panel, rather than the size of the rigid core, that determines its rigidity.

[0023] According to one feature of the invention, the thermally bonded fibers have a length of between 8 mm and 20 mm. Preferably, the length of the thermally bonded fibers is between 9 mm and 15 mm. Even more preferably, the length of the thermally bonded fibers is equal to or substantially equal to 12 mm. By substantially equal, it is understood that the thermally bonded fibers are obtained by a cutting at regular intervals of a cylindrical or relatively cylindrical core / sheath assembly and that manufacturing tolerances can generate a deviation on the order of a millimeter from one fiber to another.

[0024] The inventors were able to determine through testing that, in the method of producing the insulating panel used for the tests—namely, an aerodynamic process—a length of 20 mm represents a limit beyond which the homogeneity of the resulting insulating panels is no longer guaranteed. Of course, if another embodiment, which does not generate a lack of homogeneity, is implemented, the threshold value of 20 mm for the length of the thermally bonding fibers could be increased.

[0025] According to a feature of the invention, the structural fibers and the thermally bonding fibers are distributed homogeneously within the insulating panel, the homogeneous distribution of the fibers being considered along a direction perpendicular to a principal longitudinal elongation direction of the mineral wool mat.

[0026] According to a feature of the invention, the coefficient of variation of the volumetric density of the insulating panel, representative of the distribution of fibers within the insulating panel between at least a first lateral zone of the insulating panel and a second lateral zone of the insulating panel, is less than 5%, preferably less than 3%. It should be noted that these zones more specifically form strips with identical dimensions ranging from 10 cm to 30 cm, depending on the protocols implemented. It should also be noted that the insulating panel can be cut into any number of strips whose width or thickness allows the coefficient of variation between each strip to be measured.

[0027] According to a feature of the invention, the coefficient of variation of the volumetric density of the insulating panel, representative of the distribution of fibers within the insulating panel between at least a first vertical zone of the insulating panel and a second lateral zone of the insulating panel, is less than 10%, preferably less than 5%. The first vertical zone and the second vertical zone are offset from each other within the thickness of the panel, along a vertical direction perpendicular to the transverse direction and to the principal longitudinal elongation direction, and perpendicular to a conveyor plane on which the insulating panel is formed during the manufacturing process.

[0028] It is understood that the coefficient of variation is established between each of the strips of the mineral wool mat, relative to each other. In other words, the coefficient of variation of one zone is the same for each other zone of the mineral wool mat. Furthermore, it should be noted that alternatively, the coefficient of variation can be applied to the mass distribution of the fibers within the insulating panel, and in the same percentages.

[0029] According to one feature of the invention, the structural fibers are mineral fibers, in particular glass fibers or rock fibers, and preferably glass fibers.

[0030] According to one feature of the invention, the structural fibers are recycled structural fibers.

[0031] The use of recycled structural fibers reduces the carbon footprint of the insulation panel. These recycled structural fibers contain residues of a pre-existing binder that play little or no role in the bonding of the recycled structural fibers to the thermally bonding fibers. The use of recycled structural fibers represents an additional constraint on the mechanical properties of the insulation panel, which is mitigated by the use of thermally bonding fibers with a core diameter of less than 11 µm. Indeed, the overrepresentation of the sheath relative to the core maximizes the bonding points between the recycled structural fibers and the core of the thermally bonding fibers without binder residues significantly influencing these bonds.

[0032] According to one feature of the invention, the volumetric density of the insulating panel is less than 40 kg / m³. It is understood that the insulating panel is a lightweight product. Preferably, the volumetric density of the insulating panel is between 20 kg / m³ and 30 kg / m³.

[0033] According to one feature of the invention, the sheath of the heat-bonding fibers is made of polyethylene.

[0034] According to one feature of the invention, the core of the thermal bonding fibers is formed of polypropylene or polyethylene terephthalate.

[0035] According to one feature of the invention, the mass of thermally bonding fibers represents between 10% and 20% of the mass of the insulating panel. Preferably, the mass of the thermally bonding fibers represents 15%, or approximately 15% to within + / - 1%, of the mass of the insulating panel.

[0036] According to one feature of the invention, said insulating panel has a tensile strength of at least 4 N / g. The tensile strength of the insulating panel is determined by a tensile test in which the insulating panel is stretched along its principal elongation direction in two opposite directions until it breaks, the force exerted at the moment of breakage allowing the tensile strength value to be determined.

[0037] According to one feature of the invention, said insulating panel has thickness recovery properties of at least 75%. The thickness recovery is determined by a compression test, under conditions similar to the compression exerted on the insulating panel during its packaging for marketing, and This is achieved by measuring the recovered thickness after a given period following the release of compression. Typically, the compression ratio is 4.5:1, where the compression ratio is defined as the ratio of the nominal thickness to the thickness under compression. It follows that the insulation panel, with at least the properties of the thermally bonding fiber core mentioned above, is capable of recovering at least 75% of its thickness after compression.

[0038] According to a feature of the invention, said insulating panel has a deflection of at most 100 mm.

[0039] The present invention also relates to an aerodynamic process for manufacturing an insulating panel as mentioned above, said process implementing at least: - a first step during which the structural fibers are mixed with the thermally bonding fibers, - a second stage during which the mixture obtained at the end of the first stage is deposited onto a conveyor to form a fiber mat, - a third stage during which the fiber mat is heated in an oven to a temperature between the melting temperature of the heat-bonding fiber sheath and the melting temperature of the heat-bonding fiber core to form the insulating panel.

[0040] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and the illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings on the other hand, in which:

[0041] [Fig. 1] schematically represents a detailed view of an entanglement of structural fibers and thermally bonding fibers after passing through an oven and forming an insulating panel according to the present invention;

[0042] [Fig.2] schematically represents a cross-sectional view of a heat-bonding fiber before passing through an oven, highlighting the original structure of the heat-bonding fiber;

[0043] [Fig.3] graphically represents the effect of the decitex of the thermally bonding fibers on the tensile strength of the insulating panel, as determined by the inventors through appropriate tests;

[0044] [Fig.4] graphically represents the effect of the length of the thermally bonding fibers on the tensile strength of the insulating panel, as determined by the inventors through appropriate tests;

[0045] [Fig.5] graphically represents the effect of the decitex of the thermally bonding fibers on the deflection of the insulating panel, as determined by the inventors through appropriate tests;

[0046] [Fig.6] graphically represents the effect of the decitex of the thermally bonding fibers on the thickness recovery of the insulating panel, as determined by the inventors through appropriate tests;

[0047] [Fig.7] graphically represents the effect of the ratio between the sheath and the core of the fibers thermal bonding on the tensile strength of the insulating panel, as determined by the inventors through appropriate tests;

[0048] [Fig.8] is a first graphical representation of the effect of the core diameter of thermally bonding fiber on the tensile strength of the insulating panel, as determined by the inventors through appropriate tests; and

[0049] [Fig.9] is a second graphical representation of the effect of the core diameter of thermally bonding fiber on the tensile strength of the insulating panel, as determined by the inventors through appropriate tests.

[0050] It should first be noted that while the figures illustrate the invention in detail for its implementation, these figures can of course also serve to further define the invention, if necessary. It should also be noted that these figures only show examples of embodiments of the invention.

[0051] The features, variants, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0052] As previously mentioned, the present invention relates to an insulating panel, particularly used in building construction, comprising an entanglement of fibers including thermally bonding fibers whose shape and dimensions are specifically determined to enable the achievement of insulation and mechanical performance while minimizing the carbon impact of the product obtained.

[0053] Figure 1 represents, very schematically, a detail of a fiber entanglement within such an insulating panel. More specifically, Figure 1 illustrates an entanglement of structural fibers 2 and thermally bonding fibers 4 after the insulating panel has been placed in an oven, this oven curing step being disclosed below.

[0054] The structural fibers 2 can be formed from natural fibers derived from woody plants, such as beech or Douglas fir, or from cellulosic plants, such as hemp or wheat. Alternatively, the structural fibers 2 can be formed from mineral fibers, such as rock fibers or glass fibers. In the embodiment, the structural fibers 2 are formed from mineral fibers, and more particularly from glass fibers. It should be noted that the structural fibers 2 do not exhibit thermoplastic properties.

[0055] The structural fibers 2 can be derived from recycled raw materials, in this case from the recycling of household and industrial products such as windshields or glass bottles. Alternatively, and as is the case in the embodiment shown, at least some of the structural fibers 2 can be derived from the recycling of pre-existing insulating panels. The use of recycled structural fibers reduces the carbon footprint of the insulating panel by limiting the carbon dioxide emissions resulting from the manufacture of these structural fibers 2.

[0056] The recycling of pre-existing insulating panels is carried out by defibrating said pre-existing insulating panels, for example by means of a defibration unit, so as to recover the structural fibers 2 composing these pre-existing insulating panels.

[0057] It is particularly noteworthy in [Fig. 1] that the insulating panel comprises virgin structural fibers 6 and recycled structural fibers 8, which can be distinguished from the virgin structural fibers 6 insofar as they contain residues of a binding agent used in the manufacture of pre-existing insulating panels. Thus, the residues of this binding agent are distinguishable on the recycled structural fiber 8 visible in [Fig. 1], which exhibits a surface condition slightly deformed by these binding agent residues compared to a virgin structural fiber 6. As an example, these residues can be observed by electron microscopy.

[0058] It should be noted that the insulating panel may consist exclusively of virgin structural fibers 6. Alternatively, the insulating panel may consist exclusively of recycled structural fibers 8.

[0059] Thermally bonding fibers, as will be described in more detail below, comprise a core and a sheath, made of materials distinct in particular by their melting temperature.

[0060] The interlocking of structural fibers 2 and thermally bonding fibers 4, as seen for example in [Fig. 1], is advantageously obtained by an aerodynamic process. More specifically, in the embodiment shown, this aerodynamic process is an "Airlaid" type process, that is to say, a process in which The entire set of fibers is mixed and then blown into a depositing area onto a conveyor belt; the accumulation of blown fibers depositing on the conveyor allows for the formation, layer by layer, of a thickness of non-woven insulating material.

[0061] It should be noted that according to one aspect of the invention, the aerodynamic process for manufacturing an insulating panel implemented to obtain an insulating panel according to the present invention implements at least a first step during which the structural fibers 2 are mixed with the thermal bonding fibers 4. This mixing is carried out so as to obtain a homogeneous distribution of the thermal bonding fibers 4 with respect to the structural fibers 2 in the desired proportions.

[0062] Following this first step, the aerodynamic manufacturing process incorporates at least one second step in which the mixture obtained at the end of the first step is deposited onto a conveyor to form a fiber mat. This fiber mat represents an entanglement of structural fibers 2 and thermally bonding fibers 4 before being placed in an oven. In other words, at the end of this second step, the thermally bonding fibers 4 and the structural fibers 2 are not bonded to each other; only the entanglement of these fibers provides mechanical strength to the fiber mat.

[0063] It is noteworthy that during these first two stages, the fibers retain their original shape, and in particular the heat-bonding fibers, which at the end of the second stage maintain a shape and dimensions substantially identical to those they had at the beginning of the first stage. In other words, before the third stage, the sheath has retained its original shape around the core and its original dimensions.

[0064] Then, the aerodynamic manufacturing process incorporates at least a third step in which the fiber mat is heated in an oven to a temperature between the melting temperature of the heat-bonding fiber sheath and the melting temperature of the heat-bonding fiber core. At this heating temperature, the sheath is able to melt around the core, which remains solid, so that the molten material of the sheath acts as a binder between the structural fibers, while the unmelted material of the core provides the mechanical strength of the heat-bonding fiber and contributes to the mechanical strength of the insulating panel. It should be noted that these different melting temperatures will be described in more detail in the following description.

[0065] Such an aerodynamic manufacturing process thus makes it possible to obtain a lightweight insulating panel conforming to the present invention, that is to say with a volumetric density of at most 40 kg.m3, preferably this volumetric density of the insulating panel is between 20 kg.m3 and 30 kg.m3.

[0066] Figure 2 illustrates a cross-sectional view of a heat-bonding fiber 4 before it has been placed in an oven, i.e., in its original form. Like the heat-bonding fiber 4 shown in Figure 2, all heat-bonding fibers 4 comprise a core 10 and a sheath 12 surrounding the core 10.

[0067] The core 10 forms the rigid element of the heat-bonding fibers 4 compared to the sheath 12. In the embodiment shown, the core 10 is made of polypropylene and the sheath 12 of polyethylene. Alternatively, the core 10 can be made of polyethylene terephthalate.

[0068] As mentioned previously, the sheath 12 and the core 10, whether the latter is made of polypropylene or polyethylene terephthalate, have distinct melting temperatures. More specifically, the sheath 12 has a lower melting temperature than the core 10. This difference in melting temperature between the core 10 and the sheath 12 allows the sheath 12 to melt without affecting the rigidity of the core 10 during the third step of the aerodynamic process described above.

[0069] More specifically, in the embodiment shown, the polypropylene core 10 has a melting point of 160°C and the polyethylene sheath 12 has a melting point of 130°C. When the heat-bonding fibers 4 are placed in an oven, the temperature is chosen between 130°C and 160°C so as to reach only the melting point of the sheath 12. It should be noted that the temperature to which the heat-bonding fibers 4 are heated is preferably slightly above 130°C, for example 135°C, so as to ensure that it does not approach the melting point of the core 10 and alter its mechanical properties.

[0070] As mentioned, the melting of the sheath 12 is achieved by passing the heat-bonding fibers 4 and the structural fibers 2 through an oven. As seen in [Fig. 1], the oven-baking of the heat-bonding fibers 4 melts the sheath 12, which expands radially from the core 10 in the form of filaments, while remaining bonded to the core 10. The surface tension forces between the sheath and the core allow the sheath 12, filament by filament, to remain locally bonded to the core 10, which makes it possible to control the distribution of the bonding element in the insulating panel.

[0071] This expansion of the sheath 12 allows the structural fibers 2 to be linked with the thermal bonding fibers 4 at a plurality of bonding points 14. It should be noted that the presence of the core 10 contributes to the rigidity of the insulating panel and prevents the sheath 12 from flowing freely in the entanglement of fibers.

[0072] The inventors were able to demonstrate, through appropriate tests and comparative measurements, that the characteristics of the heat-bonding fibers 4 in their original shape and dimensions constitute parameters that significantly influence the Mechanical properties of the insulating panel after oven curing of the structural and thermally bonding fibers. In particular, the decitex, i.e., the fineness of the thermally bonding fibers, and / or the length of the thermally bonding fibers have an effect on these mechanical properties.

[0073] In particular, the inventors were able to demonstrate through these same calculations that the diameter of the core of the thermally bonded fibers has a significant effect on the mechanical properties of the insulating panel after the structural and thermally bonded fibers have been oven-cured. More specifically, the inventors were able to demonstrate that the mechanical properties of the insulating panel are maximized when the core 10 of the thermally bonded fibers 4 has a diameter 16 that is less than a threshold value of 11 µm. The optimal values ​​for the core diameter 16 of the thermally bonded fiber will be given below, with reference to Figures 8 and 9.

[0074] Initially, Figures 3 to 7 graphically illustrate the effect of modifying a given characteristic of the thermally bonding fibers on a mechanical property of the insulating panel. It should be noted that, in relation to these Figures 3 to 7, the tests are carried out on insulating panels that are similar in terms of density, homogeneity, origin of the structural fibers 2, and mass percentage of thermally bonding fibers 4, with only the given characteristic being modified.

[0075] Thus, [Fig. 3] graphically illustrates the effect of the decitex of the thermally bonding fibers 4 on the tensile strength, expressed in N / g, of the insulating panel. As mentioned previously, it should be considered that the decitex is defined as the mass in grams of a length of 10,000 meters of thermally bonding fibers 4.

[0076] The tensile strength of the insulating panel is determined by a tensile test in which the insulating panel is stretched along its principal elongation direction in two opposite directions. During these tests, the inventors were able to determine three values, A, B, and C. Value A corresponds to a theoretical optimal value, value B to a target threshold value that an insulating panel conforming to the present invention must achieve, and value C to a critical value beyond which the tensile strength of the insulating panel does not meet expectations.

[0077] During their tests, the inventors were able to demonstrate that reducing the decitex of the thermally bonding fibers 4 increases the tensile strength of the insulating panel. It is understood that the lower the decitex of the thermally bonding fibers 4, the greater the tensile strength of the insulating panel. More specifically, the target threshold value B is reached when the decitex of the thermally bonding fibers 4 is less than 1.7 dtex. Thus, the inventors determined that an insulating panel according to the invention, which must exhibit a tensile strength greater than the target threshold value B, must include thermally bonding fibers 4 presenting a decitex between 0.8 dtex and 1.7 dtex, preferably less than 1.5 dtex, and more preferably less than 1.3 dtex, if the selection criterion were to focus solely on the decitex of the thermal bonding fibers.

[0078] More specifically, in the tests carried out, the inventors chose a theoretical optimum value of 6N / g, a target threshold value B of 4 N / g and a critical value of 2N / g.

[0079] The table of values ​​determined by the inventors' tests highlights the fact that using thermal bonding fibers with a decitex value greater than 1.5 dtex does not allow the target threshold value B to be achieved. It should also be noted that the inventors determined that if the thermal bonding fibers have a decitex value less than 0.8 dtex, the stiffness of the thermal bonding fibers 4 may not be sufficient to impart adequate mechanical properties to the insulating panel, particularly in terms of tensile strength. More specifically, the inventors were able to determine that the decitex value of the thermal bonding fibers was optimal between 1 dtex and 1.3 dtex.

[0080] This optimization of the thermal bonding fibers 4 with a dtex that is preferably between 1 dtex and 1.3 dtex allows, for a given mass percentage of thermal bonding fibers 4 in the insulating panel, the maximization of the number of bonding points 14 between the thermal bonding fibers 4 and the structural fibers 2. Indeed, for the same mass percentage, the number of thermal bonding fibers 4 having a decitex according to the invention in the insulating panel is greater than the number of thermal bonding fibers having a decitex greater than 1.3. This increase in the number of thermal bonding fibers 4 thus makes it possible to increase the number of bonding points 14 in the insulating panel, which makes it possible to increase the mechanical strength of the insulating panel, and in particular the tensile strength of the insulating panel.

[0081] Figure 4 illustrates the effect of the length, expressed in millimeters (mm), of the thermally bonding fibers 4 on the same mechanical characteristic, namely the tensile strength, expressed in N / g, of the insulating panel. It should be noted that the values ​​A, B, and C determined in Figure 4 are the same as those in Figure 3. Furthermore, the values ​​presented were obtained by tensile tests in accordance with what has been described in relation to Figure 3.

[0082] It is particularly remarkable on [Fig.4] that the tensile strength of the insulating panel increases significantly with increasing length of thermal bonding fibers 4. Thus, the inventors were able to demonstrate that the tensile strength of the insulating panel is maximum when the length of thermal bonding fibers 4 is on the order of 20 mm.

[0083] Tests conducted by the inventors led to the conclusion that the optimal length of the thermal bonding fibers 4 is between 8 mm and 20 mm. Indeed, it is noteworthy that with a length of 8 mm of the thermal bonding fibers 4 the target threshold value B is reached, whereas with a length of thermal bonding fibers less than this value of 8mm, for example a commonly recommended length of 6 mm, the target threshold value B is not reached.

[0084] It is understood that the greater the length of the thermally bonding fibers 4, the greater the tensile strength of the insulating panel. However, a compromise must be found between an optimal length for increasing the tensile strength of the insulating panel and an optimal length for maximizing the homogeneity of the insulating panel obtained by an aerodynamic manufacturing process. Indeed, the inventors have observed, as illustrated in [Fig. 4] by the hatched portion of the graph, that aerodynamic manufacturing processes for insulating panels do not allow for the formation of an insulating panel with optimal homogeneity using thermally bonding fibers 4 with a length greater than 20 mm.

[0085] The inventors were thus able to demonstrate that this compromise is achieved with a length of the thermal bonding fibers 4 between 8 mm and 20 mm, preferably between 9 mm and 15 mm and more preferably 12 mm. In other words, the inventors determined that an insulating panel according to the invention, which must have a tensile strength greater than the target threshold value B, must have thermal bonding fibers 4 with a length between 8 mm and 20 mm, preferably between 9 mm and 15 mm and more preferably 12 mm, if the selection criterion were to be based solely on the length of the thermal bonding fibers.

[0086] The concept of homogeneity mentioned above is particularly important for ensuring good mechanical properties of the insulating panel. Therefore, an insulating panel conforming to the present invention exhibits optimal homogeneity. This homogeneity is reflected in the insulating panel by a distribution of structural and thermally bonding fibers such that the fiber distribution from one end of the insulating panel to the other has a coefficient of variation of less than 5%, and preferably less than 3%.

[0087] In other words, the homogeneity of the insulating panel is such that the volumetric density, or quantity of fibers, of one zone of the insulating panel is substantially equal to the quantity of fibers present in another zone of the dimensions of the insulating panel, whether in a transverse or vertical cut of the insulating panel, with a variation in the quantity of fibers from one zone to another which is less than 10%, preferably less than 5%, with regard to the vertical variation and which is less than 5%, preferably less than 3%, with regard to the lateral variation.

[0088] The coefficient of variation is calculated by weighing and measuring each of the relevant zones. It should be noted that these zones are divided according to standard EN 1602. An average density and a standard deviation are then deduced, considering the difference between the average density and the density of each zone. The coefficient of variation is obtained by dividing the standard deviation by the average density.

[0089] Figure 5 illustrates the effect of the decitex of the thermally bonding fibers 4 on the deflection of the insulation panel, expressed in millimeters. The deflection of the insulation panel is obtained by measuring the deflection of the insulation panel, i.e., the inclination of the insulation panel relative to its principal elongation direction, when a load is applied to one end of the insulation panel, the opposite end being fixed.

[0090] Thus, it is noteworthy in [Fig. 5] that the inventors observed that the lower the decitex of the thermally bonding fibers 4, the lower the deflection of the insulating panel. More specifically, during these tests, the inventors considered three values ​​D, E, and F. The value D corresponds to a theoretical optimum value, the value E corresponds to a target threshold value that an insulating panel conforming to the present invention must achieve, and the value F corresponds to a critical value beyond which the deflection of the insulating panel does not meet expectations.

[0091] As shown in [Fig. 5], the decitex of the thermally bonding fibers 4 linearly influences the deflection of the insulating panel. More specifically, the inventors have observed that from a decitex of the thermally bonding fibers equal to 1.7 dtex, the mechanical strength of the insulating panel is such that the target threshold value E is reached.

[0092] This improvement in the mechanical strength of the insulating panel by reducing the decitex of the thermal bonding fibers 4 results, in accordance with what has been described in connection with [Fig.3], from the increase in the creation of bonding points 14 within the insulating panel.

[0093] Thus, a decitex of the thermal bonding fibers between 0.8 dtex and 1.7 dtex makes it possible to limit the deflection of the insulating panel to a maximum of 100mm.

[0094] Figure 6 illustrates the effect of the decitex of the thermally bonding fibers 4 on the thickness recovery of the insulation panel. The thickness recovery is measured after compression of the insulation panel perpendicular to its principal elongation direction for a given duration, here 1 month, and at a given compressive force.

[0095] As can be seen in [Fig. 6], the lower the decitex value of the thermally bonding fibers 4, the greater the thickness recovery of the insulating panel. Indeed, during their measurements, the inventors were able to determine three values: G, H, and I. The value G corresponds to a theoretical optimum value, close to 100% thickness recovery; the value H corresponds to a target threshold value that an insulating panel conforming to the present invention must reach; and the value I corresponds to a critical value beyond which the thickness recovery of the insulating panel does not meet expectations.

[0096] More specifically, the inventors were able to determine that the use of thermally bonding fibers 4 having a decitex between 0.8 dtex and 1.7 dtex allows to improve the thickness recovery of the insulating panel and to reach the target threshold value H. Such a configuration of the thermally bonding fibers 4 allows the insulating panel to have recovery properties of at least 75%. In other words, an insulating panel conforming to the present invention recovers, following compression perpendicular to its principal elongation direction for 1 month and an appropriate rest period, at least 75% of its original thickness before compression.

[0097] It should be noted that the compression applied corresponds to a compression commonly used to condition insulating panels for storage. More specifically, the compression ratio is such that the nominal thickness of an insulating panel is 4.5 times the thickness of a compressed insulating panel, i.e., the compression ratio is 4.5 / 1.

[0098] Fig. 7 illustrates the effect of the mass ratio between the core 10 and the sheath 12 of the thermally bonding fibers 4 on the mechanical properties of the insulating panel, in particular the tensile strength.

[0099] Through their experiments, the inventors were able to demonstrate that the sheath 12 of the thermally bonding fibers 4 plays a crucial role in the mechanical strength of the insulating panel. More specifically, the inventors were able to demonstrate that the core 10 of the thermally bonding fibers 4 controls the dispersion of the sheath 12 within the insulating panel after oven curing. Therefore, the larger the sheath 12 of a thermally bonding fiber 4, the greater the number of bonding points 14 formed by this thermally bonding fiber 4, as well as the strength of the bonds at said bonding points 14. However, the core 10 must be sufficiently large to ensure that the sheath 12 remains bonded to the core 10 after oven curing.

[0100] It is particularly noteworthy from the study that a mass percentage of the sheath 12 of at least 50% makes it possible to reach the target threshold value B, and that producing a thermally bonded fiber with at least 80% of the fiber's mass devoted to the sheath, and therefore consequently a mass percentage of the core 10 of at most 20% of this thermally bonded fiber 4 in a sheath / core ratio of approximately 80 / 20, makes it possible to significantly improve the mechanical properties of the insulating panel. This improvement in the mechanical properties of the insulating panel makes it possible, on the one hand, to improve the tensile strength of the insulating panel and, on the other hand, to limit the deflection of the insulating panel.

[0101] It follows that an insulating panel with a sheath / core ratio of 80 / 20 has better mechanical properties in terms of tensile strength and deflection than an insulating panel with a more balanced sheath / core ratio and for example of the order of 60 / 40.

[0102] During their experiments, the inventors determined that an insulating panel with a sheath 12 mass percentage of 80% plus or minus 5% and a core 10 mass percentage of 20% plus or minus 5% further improves the aforementioned mechanical properties of the insulating panel. However, a core 10 mass percentage of less than 5% does not guarantee that the sheath 12 remains bonded to the core 10 after oven curing, which negatively affects the homogeneity of the insulating panel and therefore its mechanical properties, as illustrated schematically in [Fig. 7] by the hatched area.

[0103] Thus, the optimization of the thermal bonding fibers, whether independently in terms of decitex, structure, and length in accordance with what has been described in connection with figures 3 to 7, makes it possible to improve the mechanical properties of the insulating panel and to reach target threshold values ​​and even to exceed these target threshold values.

[0104] Figures 8 and 9 highlight the impact of the core diameter of the thermally bonded fibers, regardless of the variable used during the tests. In particular, [Fig. 8] illustrates the impact of the thermally bonded fiber core diameter, which is measured by imaging in the finished product, when the decitex of the thermally bonded fibers is modified and the sheath / core ratio and length remain constant from one measurement to the next, while [Fig. 9] illustrates the impact of the thermally bonded fiber core diameter, again measured by imaging in the finished product, when the sheath / core ratio of the thermally bonded fibers is modified and the decitex and length remain constant from one measurement to the next.

[0105] In both cases, the measured mechanical property of the insulating product is tensile strength, but it should be noted that the inventors have observed that the diameter of the fiber core also has an impact on the other mechanical properties previously mentioned, and in particular deflection.

[0106] In each of these two measurement sets, it is noteworthy that tensile strength and flexural strength are improved with the decrease in the fiber core diameter, and having such a diameter of a value less than 11 pm makes it possible to meet the target threshold value.

[0107] These tests enabled the inventors to determine that for thermal bonding fibers with a polypropylene (PP) core and a polyethylene (PE) sheath, optimal values ​​are obtained with a fiber core diameter of approximately 6 pm when the sheath / core ratio is 80 / 20 and the decitex is 1.3. By favoring a sheath / core ratio of around 90 / 10, with a decitex still less than 1.3, the core diameter of thermal bonding fibers can advantageously be between 3.5 pm and 4.5 pm, and in particular 4 pm.

[0108] Furthermore, for thermally bonding fibers with a polyethylene terephthalate (PET) core, the inventors were able to determine that optimal values ​​are obtained with a fiber core diameter of approximately 4.5 pm when the sheath / core ratio is 80 / 20 and the decitex is 1.3.

[0109] Also, the inventors were able to establish that according to the heat-bonding fibers chosen, in accordance with the sheath / core ratios previously mentioned, the diameter of the core of the heat-bonding fibers is optimal between 3 pm and 10 pm, and preferentially between 4 pm and 9 pm.

[0110] This optimization results in a reduction in the mass percentage of thermally bonding fibers 4 in the insulating panel while maintaining optimal mechanical properties of the insulating panel. Thus, using thermally bonding fibers with a decitex density, length, core diameter, and / or sheath-to-core ratio as described above makes it possible to reduce the quantity of thermally bonding fibers required in the insulating panel to achieve the desired insulation and mechanical performance, since these thermally bonding fibers are more efficient. Advantageously, an insulating panel according to the invention comprises at most 20% thermally bonding fibers 4. Preferably, the insulating panel comprises between 10% and 20% thermally bonding fibers 4, and more preferably, the insulating panel comprises at most 15% thermally bonding fibers 4.

[0111] It should be noted that the percentage of thermal bonding fibers 4 mentioned represents a mass percentage of thermal bonding fibers 4 relative to the mass of the insulating panel considered after oven drying.

[0112] The present invention achieves its objective by proposing an insulating panel in which the thermal bonding fibers are more efficient so that the quantity needed to reach target threshold values ​​is reduced, which allows isoperformance to decrease the quantity of thermal bonding fibers in the insulating panel and to reduce the carbon footprint of the insulating panel.

[0113] The present invention is not limited to the means and configurations described and illustrated herein and also extends to any equivalent means and configuration as well as to any technically operative combination of such means.

Claims

Demands

1. Insulating panel comprising an interweaving of structural fibers (2, 6, 8), selected from mineral fibers and natural fibers, and thermally bonding fibers (4), the thermally bonding fibers (4) being formed of a sheath (12) and a core (10), the core (10) and the sheath (12) being formed of two distinct materials each having a distinct melting temperature, the core (10) having a diameter (16) less than 11 pm.

2. Insulating panel according to claim 1, wherein the core (10) has a diameter (16) between 4 pm and 9 pm.

3. Insulating panel according to claim 1 or 2, in which the thermal bonding fibers (4) have a decitex between 0.8 dtex and 1.7 dtex.

4. Insulating panel according to any one of claims 1 to 3, wherein the mass percentage of the sheath (12) is at least 65%.

5. Insulating panel according to any one of claims 1 to 4, wherein the thermal bonding fibers (4) have a length between 8 mm and 20 mm.

6. Insulating panel according to any one of claims 1 to 5, wherein the structural fibers (2, 6, 8) are mineral fibers, in particular glass fibers or rock fibers, and preferably glass fibers.

7. Insulating panel according to any one of claims 1 to 6, wherein the structural fibers (2) are recycled structural fibers (8).

8. Insulating panel according to any one of claims 1 to 7, wherein the volumetric density of the insulating panel is less than 40kg.m3.

9. Insulating panel according to any one of claims 1 to 8, wherein the sheath (12) of the thermal bonding fibers (4) is formed of polyethylene (PE).

10. Insulating panel according to any one of claims 1 to 9, wherein the core (10) of the thermal bonding fibers (4) is formed of polypropylene (PP) or polyethylene terephthalate (PET).

11.

12.

13.

14.

15. Insulating panel according to any one of claims there 10, wherein the bundle of thermally bonding fibers (4) represents between 10% and 20% of the mass of the insulating panel. Insulating panel according to any one of claims 1 to 11, said insulating panel having a tensile strength of at least 4 N / g. Insulating panel according to any one of claims 1 to 12, said insulating panel having thickness recovery properties of at least 75%. An insulating panel according to any one of claims 1 to 13, said insulating panel having a deflection of at most 100 mm. An air-handling process for manufacturing an insulating panel according to any one of claims 1 to 14, the air-handling manufacturing process employing at least: - a first step during which the structural fibers (2, 6, 8) are mixed with the thermally bonding fibers (4), - a second stage during which the mixture obtained at the end of the first stage is deposited onto a conveyor to form a fiber mat, - a third step during which the fiber mat is heated in an oven to a temperature between the melting temperature of the sheath (12) of the thermal bonding fibers (4) and the melting temperature of the core (10) of the thermal bonding fibers (4) to form the insulating panel.

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