Insulating panel comprising structural fibres and thermal bonding fibres

Abstract

The present invention relates to an insulating panel comprising an entanglement of structural fibres (2, 6, 8) and thermal bonding fibres (4), the thermal bonding fibres (4) being formed of a sheath and a core, the core and the sheath being formed of two distinct materials, each material having a distinct melting temperature, and the core having a diameter of at most 11 µm.

Description

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 together by thermally bonding fibers.

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

[0003] Such insulating panels can be made of structural fibers bonded together by a binding agent, so that air is trapped stably and immobile within the panels. Structural fibers are the fibers that form the structure of the insulating panel. To achieve this, the structural fibers are interwoven and bonded together to form an insulating panel. These structural fibers can be mineral fibers such as glass or rock fibers, or natural fibers such as wood 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 manufacturing of these insulating panels, and in particular the production of the structural fibers needed to make them, has a carbon footprint that manufacturers are trying to reduce. To do this, the structural fibers can be recovered from existing insulating panels and recycled to form a new insulating panel.

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

[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 interweaving 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 jim.

[0008] Structural fibers can be chosen from mineral fibers such as glass and / or rock fibers. They can also be chosen from natural, or organic, fibers such as woody plant fibers, commonly referred to as "wood fibers," including Douglas fir, beech, and pine, or from cellulosic plant fibers such as straw, hemp, and cotton. Within the insulation panel as it exits the manufacturing process, the structural fibers are bonded together by means of the molten sheath of the thermally bonding fibers. The insulation panel is obtained after being placed in an oven where the thermally bonding fibers are heated to a temperature that causes the sheath to melt and expand while the core remains intact.The core provides rigidity to the fiber entanglement and locally holds the sheath in place. The sheath expands into filaments that bond to the core and adhere to the structural fibers located near the core. This characteristic of thermally bonded fibers is made possible by the distinct melting temperatures of the core and the sheath.

[0009] It is therefore understandable 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 and 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, some thermally bonded fibers are bonded only 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 thermal bonding fibers are configured according to the invention such that they have a core diameter of less than 11 µm. In other words, the core diameter of the fibers is less than a threshold value of 11 µm, this threshold value having been determined by the inventors through tests and calculations demonstrating that compliance with this upper threshold value allows for the achievement of the necessary mechanical properties of the insulation panel, and in particular the tensile strength and deflection of the insulation panel. It is therefore 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 insulation panel without affecting the mechanical properties of the insulation panel, it being understood that reducing the quantity of thermal bonding fibers in the insulation panel thus reduces the carbon footprint of the insulation panel.

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

[0012] According to one feature of the invention, the core diameter of the thermally bonded fibers is between 4 jam and 9 jam. 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 or 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 cutting it 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 of 95 square meters. 2 Preferably, the heart section has an area between 12.5 µm 2 and 63.5 jam 2 .

[0014] According to one 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 characterizes its overall fineness 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 less than 11 jim and a fiber fineness between 0.8 dtex and 1.7 dtex, the structure of the thermally bonded fibers, and more specifically the cladding, maximizes the formation of bond points between the core and the structural fibers, as well as the strength of these bonds.For a given mass percentage, there are more thermally bonding 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 one feature of the invention, the thermal bonding fibers have a decitex less than or equal to 1.5 dtex.

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

[0018] According to one 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 heart is at most 35%. Preferably the mass percentage of the heart is between 10% and 35%, and more preferably, the mass percentage of the heart 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 should be considered in combination with the others so that the total mass percentage of a thermal bonding fiber is equal to 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 by the sheath and core, such that the sheath represents at least 65% of the thermally bonded fiber's mass and the core at most 35% of the thermally bonded fiber's mass. Having a sheath-to-core ratio 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 bonds, and it is this rigidity, rather than the size of the rigid core, that determines the rigidity of the insulation panel.

[0023] According to one feature of the invention, the thermally bonded fibers have a length 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 cutting a cylindrical or relatively cylindrical core / sheath assembly at regular intervals, and that manufacturing tolerances may result in a variation on the order of a millimeter from one fiber to another.

[0024] The inventors were able to determine through testing that a length of 20 mm, in the method used to produce the insulating panel (namely, an aerodynamic process), is 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 one 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 one 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 is at Note that these zones form bands with identical dimensions, ranging from 10 cm to 30 cm depending on the protocols used. It should also be noted that the insulating panel can be cut into any number of strips, and the width or thickness of these strips allows for the measurement of the coefficient of variation between them.

[0027] According to one 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 layers of the mineral wool mat, relative to each other. In other words, the coefficient of variation of one zone is the same for every other zone of the mineral wool mat. Furthermore, it should be noted that the coefficient of variation can alternatively be applied to the mass distribution of the fibers within the insulation 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 places an additional constraint on the mechanical properties of the insulation panel, which is mitigated by using thermally bonding fibers with a core diameter of less than 11 jim. Indeed, the overrepresentation of the sheath relative to the core allows to maximize 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. 3It is understood that the insulating panel is a lightweight product. Preferably, the volumetric density of the insulating panel is between 20 kg / m³ and 20 kg / m³. 3 and 30kg. 3 .

[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 made 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, the insulating panel has thickness recovery properties of at least 75%. This thickness recovery is determined by a compression test, under conditions similar to those applied to the insulating panel during its packaging for marketing, and by measuring the recovered thickness after a specified period following the removal 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 is understood that the insulating 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 one feature of the invention, said insulating panel has a deflection of no more than 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 attached 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.21 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. 31 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 thermally bonding fibers 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 the 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 the 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, they 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 may be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may include only a selection of features, described hereafter in isolation from the other features described, 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 schematically represents 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 is described below.

[0054] Structural fibers 2 can be formed from natural fibers from woody plants, such as beech or Douglas fir, or from cellulosic plants, such as the Hemp or wheat. Alternatively, structural fibers 2 can be formed from mineral fibers, such as rock fibers or glass fibers. In this embodiment, structural fibers 2 are formed from mineral fibers, and more specifically from glass fibers. It should be noted that 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, as shown in the embodiment depicted, at least some of the structural fibers 2 can be derived from the recycling of pre-existing insulation panels. The use of recycled structural fibers reduces the carbon footprint of the insulation 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 noticeable in Figure 1 that the insulating panel comprises virgin structural fibers 6 and recycled structural fibers 8. The recycled fibers 8 are distinguished from the virgin structural fibers 6 by the fact that they contain residues of a binding agent used in the manufacture of pre-existing insulating panels. Thus, the residues of this binding agent are visible on the recycled structural fiber 8 shown in Figure 1, which exhibits a slightly deformed surface due to these binding agent residues compared to a virgin structural fiber 6. For 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 bonded fibers, as will be described in more detail below, consist of a core and a sheath, made of materials distinct in particular by their melting temperature.

[0060] The interweaving of structural fibers 2 and thermally bonding fibers 4, as shown for example in Figure 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 all the fibers are mixed and then blown into a depositing area on a conveyor belt, the accumulation of blown fibers settling on the conveyor, forming layer by layer 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 in 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 involves 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 yet 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, particularly the heat-bonding fibers, which at the end of the second stage maintain a shape and dimensions virtually 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 point of the heat-bonding fiber sheath and the melting point of the heat-bonding fiber core. At this heating temperature, the sheath melts around the core, which remains solid. The molten sheath material acts as a binder between the structural fibers, while the unmelted core material provides the mechanical strength of the heat-bonding fiber and contributes to the overall strength of the insulation panel. It should be noted that these different melting temperatures will be described in more detail later.

[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.m 3Preferably, the volumetric density of the insulating panel is between 20 kg.m 1 and 30 kg.m

[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 points. More specifically, the sheath 12 has a lower melting point than the core 10. This difference in melting point 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 stage 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 oven-baking the thermal bonding fibers 4 and the structural fibers 2. As seen in Figure 1, oven-baking the thermal 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, thus controlling 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 thermally 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 thermal bonding fibers 4, in their original shape and dimensions, constitute parameters that significantly influence the mechanical properties of the insulating panel after the structural and thermal bonding fibers have been oven-cured. In particular, the decitex, i.e., the fineness of the thermal bonding fibers, and / or the length of the thermal bonding fibers have an effect on these mechanical properties.

[0073] More specifically, 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 precisely, 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 specific characteristic of the thermally bonding fibers on a mechanical property of the insulation panel. It should be noted that, in relation to these Figures 3 to 7, the tests are performed on insulation panels that are similar in terms of density, homogeneity, origin of the structural fibers 2, and mass percentage of thermally bonding fibers 4; only the specific characteristic under consideration is modified.

[0075] Thus, Figure 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 corresponds to a target threshold value that an insulating panel conforming to the present invention must reach, and the value C corresponds to a critical value from which the tensile strength of the insulating panel does not meet expectations.

[0077] During their tests, the inventors demonstrated 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 contain thermally bonding fibers 4 with 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 be based solely on the decitex of the thermally 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 achieve the target threshold value B. 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 may not be sufficient to provide adequate mechanical properties to the insulation panel, particularly in terms of tensile strength. More specifically, the inventors determined that the decitex value of the thermal bonding fibers is optimal between 1 dtex and 1.3 dtex.

[0080] This optimization of the thermal bonding fibers 4, with a dtex 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 with a decitex conforming to the invention in the insulating panel is greater than the number of thermal bonding fibers with 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 allows 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 insulation 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 through tensile tests in accordance with the procedure described in relation to Figure 3.

[0082] It is particularly noteworthy in Figure 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] The 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 for the thermal bonding fibers 4, the target threshold value B is reached, whereas with a length of thermal bonding fibers shorter than this value of 8 mm, 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 observed, as illustrated in Figure 4 by the hatched area 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 longer than 20 mm.

[0085] The inventors were thus able to demonstrate that this compromise is achieved with a length of the thermally 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 include fibers thermal bonding 4 having 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 area of ​​the insulating panel is substantially equal to the quantity of fibers present in another area of ​​the same 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 area to another that is less than 10%, preferably less than 5%, with regard to the vertical variation and that 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 defined according to standard EN 1602. From this, an average density and a standard deviation are derived, 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, with the opposite end fixed.

[0090] Thus, it is noteworthy in Figure 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, and the value E corresponds to a target threshold value that an insulating panel conforming to the present invention, and the value F corresponds to a critical value from which the deflection of the insulating panel does not conform to expectations.

[0091] As shown in Figure 5, the decitex of the thermally bonding fibers 4 linearly influences the deflection of the insulation panel. More specifically, the inventors observed that from a decitex of the thermally bonding fibers equal to 1.7 dtex, the mechanical strength of the insulation 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 figure 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 shown in Figure 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 with a decitex density between 0.8 dtex and 1.7 dtex improves the thickness recovery of the insulation panel, enabling it to reach the target threshold value H. This configuration of thermally bonding fibers 4 allows the insulation panel to have recovery properties of at least 75%. In other words, an insulation panel according to the present invention recovers, following compression perpendicular to its principal elongation direction for one month and an appropriate rest period, at least 75% of its original thickness before compression.

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

[0098] Figure 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 these 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 sheath mass percentage of at least 50% allows the target threshold value B to be reached, and that producing a thermally bonded fiber with at least 80% of the fiber mass dedicated to the sheath, and therefore a core mass percentage of no more than 20% of this thermally bonded fiber 4 in a sheath / core ratio of approximately 80 / 20, significantly improves the mechanical properties of the insulating panel. This improvement in the mechanical properties of the insulating panel allows, on the one hand, for an increase in the tensile strength of the insulating panel and, on the other hand, for a reduction in the deflection of the insulating panel.

[0101] The result is that an insulating panel with a sheath / core ratio of 80 / 20 has better mechanical properties, particularly in terms of tensile strength and deflection, than an insulating panel with a more balanced sheath / core ratio, for example, of around 60 / 40.

[0102] During their experiments, the inventors determined that an insulating panel with a sheath 12 mass percentage of 80% ± 5% and a core 10 mass percentage of 20% ± 5% further improves the aforementioned mechanical properties of the insulating panel. However, a core 10 mass percentage below 5% does not guarantee that the sheath 12 remains bonded to the core 10 after oven curing, which negatively impacts the homogeneity of the insulating panel and therefore the mechanical properties of the latter, which is shown schematically in figure 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 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. Specifically, Figure 8 illustrates the impact of the thermally bonded fiber core diameter, measured by imaging in the finished product, when the decitex of the thermally bonded fibers is modified and the cladding-to-core ratio and length remain constant between measurements. Figure 9 illustrates the impact of the thermally bonded fiber core diameter, again measured by imaging in the finished product, when the cladding-to-core ratio of the thermally bonded fibers is modified and the decitex and length remain constant between measurements.

[0105] In both cases, the measured mechanical property of the insulating product is tensile strength, but it should be noted that the inventors were able to find that the diameter of the fiber core also has an impact on the other mechanical properties previously mentioned, including deflection.

[0106] In each of these two measurement sets, it is noteworthy that tensile strength and bending strength are improved with decreasing fiber core diameter, and having such a diameter of less than 11 jim allows the target threshold value to be met.

[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 gm 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 gm and 4.5 jam, and in particular 4 jam.

[0108] Furthermore, for thermally bonded 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 jam when the sheath / core ratio is 80 / 20 and the decitex is 1.3.

[0109] Also, the inventors were able to establish that, depending on 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 gm and 10 jam, and preferentially between 4 jam and 9 jam.

[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. Thus, using thermally bonding fibers with a decitex density, length, core diameter, and / or sheath-to-core ratio as described above allows for a reduction in 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. [YES] 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 intended goal 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 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 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 thermal bonding fibers (4), the thermal 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 jim.

2. Insulating panel according to claim 1, in which the core (10) has a diameter (16) between 4 jim and 9 jam.

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, in which 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 40 kg / m³.

9. Insulating panel according to any one of claims 1 to 8, in which 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, in which the core (10) of the thermal bonding fibers (4) is formed of polypropylene (PP) or polyethylene terephthalate (PET).

11. Insulating panel according to any one of claims 10, wherein the mass of thermally bonding fibers (4) represents between 10% and 20% of the mass of the insulating panel.

12. Insulating panel according to any one of claims 1 to 11, said insulating panel having a tensile strength of at least 4 N / g.

13. Insulating panel according to any one of claims 1 to 12, said insulating panel having thickness recovery properties of at least 75%.

14. An insulating panel according to any one of claims 1 to 13, said insulating panel having a deflection of at most 100 mm.

15. An air-handling method for manufacturing an insulating panel according to any one of claims 1 to 14, the air-handling manufacturing method 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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