Method for producing an optimised loose insulating material, and insulating structure comprising such a material

Abstract

The invention relates to a method for producing a loose insulating material based on cereal straw, characterised in that it comprises the steps of: a) shredding the straw to obtain a defibred straw of which the strands have an average length of between 3 mm and 11 mm and of which the average diameter is between 0.5 mm and 2.5 mm; b) using cellulose wadding and untangling and aerating the cellulose wadding; c) mixing the straw defibred in step a) and the cellulose wadding prepared in step b), the cellulose wadding being introduced into the mixer 3 before the defibred straw, with a proportion by weight of between 1% and 30%; d) injecting compressed air to homogenise the mixture and to obtain a mixture having a density of between 55 kg / m3 and 65 kg / m3; and e) bagging the insulating material thus obtained.

Description

[0001] PROCESS FOR MANUFACTURING AN OPTIMIZED INSULATING MATERIAL

[0002] IN BULK AND INSULATING STRUCTURE COMPRISING SUCH A

[0003] MATERIAL

[0004] Technical field

[0005] The present invention relates to the general technical field of loose-fill insulating materials used in new buildings or in buildings undergoing renovation. These materials are generally intended to enhance the thermal performance of an unused attic space, an intermediate floor or an external wall. These loose-fill insulating materials can also be integrated into prefabricated modular wooden structures or into mixed prefabricated wood-concrete structures, by insufflation.

[0006] In France and other countries, public and private tender specifications increasingly require the use of bio-sourced insulation materials with the smallest possible ecological footprint. These insulating materials are, for example, made from renewable and recyclable raw materials, such as wood fibers, cellulose wadding, textile fibers, expanded cork, hemp, sheep's wool, or other bio-sourced materials.

[0007] “Bio-sourced materials” are materials derived from renewable organic matter (biomass) of plant or animal origin.

[0008] The invention relates more particularly to the manufacture of bulk bio-sourced insulating materials as well as the design and manufacture of insulating structures comprising such materials.

[0009] Prior art

[0010] For example, we know of the use of loose mineral wool intended to be blown into attics or inserted into a hollow partition wall.

[0011] However, such an insulating material has a density of approximately 40 kg / m 3 , which may prove insufficient, depending on the projects considered, to protect oneself from the summer heat if one wishes to obtain real thermal comfort.

[0012] Most known bulk materials are not bio-sourced. Examples include mineral or hybrid wools. Furthermore, these bulk materials have insufficient insulation performance in summer.

[0013] Bio-based products found on the market, such as cellulose wadding, have a fire reaction classification, generally E or F. This poor performance requires the addition of fire-retardant materials, for example in the design of insulating walls. This results in an increase in the cost of these solutions. In addition, the use of these non-bio-based fire-retardant materials has a negative impact on the carbon footprint of these solutions.

[0014] For example, document EP 2 204 483 discloses a method for manufacturing loose-fill insulation, in which cellulose wadding is mixed with animal or plant fibers. The weight ratio of cellulose wadding to the total mass is 35% to 60%. This high proportion of cellulose wadding is not likely to give the insulating material interesting thermal and ecological performance.

[0015] Presentation of the invention

[0016] The object of the invention therefore aims to overcome the drawbacks of the prior art by proposing a new process for manufacturing a bio-sourced insulating material in bulk, from ecological, renewable, recyclable raw materials available in almost all countryside.

[0017] Another object of the invention is to propose a method for manufacturing bulk insulating material, free from boron salt.

[0018] Another object of the invention is to propose a method for manufacturing bulk insulating material, which is easy to implement and economical.

[0019] Another object of the invention is to provide a new loose insulating material, capable of being blown or injected into cavities and having excellent thermal and sound insulation performance.

[0020] Another object of the invention is to provide prefabricated insulating modular elements, incorporating the new insulating material and exhibiting excellent fire resistance, thermal and sound insulation performance.

[0021] The objects assigned to the invention are achieved by means of a method for manufacturing a bulk insulating material based on cereal straw, characterized in that it comprises the steps: a) mechanically grinding the straw to obtain a defibrated straw whose strands have an average length of between 3 mm and 22 mm and preferably between 3 mm and 11 mm and whose average diameter is between 0.5 mm and 4.0 mm and preferably between 0.5 and 2.5 mm, b) using cellulose wadding and carrying out disentangling and aeration of said cellulose wadding, c) using a mixer and mixing the defibrated straw under a) and the cellulose wadding prepared under b), said cellulose wadding being introduced into the mixer with a mass proportion of between 1% and 30%, relative to the total mass of the defibrated straw and the cellulose wadding,d) injecting compressed air into the mixer to homogenize said mixture and to obtain a mixture having a density of between 55 kg / m, 3 and 65 kg / m 3 , and e) bagging the insulating material thus obtained.

[0022] According to an exemplary implementation, the method consists in step a) of using at least one grinder to shred and grind the straw into bales, said at least one grinder comprising adjustable shredding / grinding tools to define the shape and dimensional properties of the strands of defibrated straw obtained, said tools comprising in series cutters and hammers.

[0023] For example, the method consists in step c) of using at least one mixer of the rotating cylinder and / or drop cage type.

[0024] According to an exemplary implementation, the method consists of filtering the defibrated straw obtained under a) to remove dust and other impurities in a proportion by mass of at least 2% and preferably at least 5% to 10% of the defibrated straw. This filtration advantageously makes it possible to reduce the risks of explosion on the manufacturing site linked to a significant concentration of dust in the air.

[0025] According to an example of implementation, it consists of mixing cellulose wadding or the cellulose wadding - defibrated straw mixture, with one or more adjuvants including a fungicide product.

[0026] According to an example of implementation, the method consists of mixing the cellulose wadding or the cellulose wadding - defibrated straw mixture, with one or more adjuvants, comprising at least one fire-retardant product with a proportion by mass relative to the total mass of the products mixed under c), of between 10% and 30%.

[0027] The fire retardant product is, for example, chosen from a family of geo-sourced products.

[0028] According to another example of implementation of the method, the fire retardant product is in viscous or liquid form and comprises a geopolymer of the metakaolin type.

[0029] The objects assigned to the invention are also achieved using a prefabricated modular wooden structure for making a wall or a partition or for covering a wall of a building, on the exterior or interior side. This structure advantageously comprises at least one cavity containing the insulating material obtained according to the manufacturing method detailed above.

[0030] The objects assigned to the invention are also achieved using a mixed prefabricated modular structure made of wood and concrete to create a wall or to cover a wall of a building, on the outside or inside. This structure advantageously comprises at least one cavity containing the insulating material obtained according to the manufacturing method presented above.

[0031] The process according to the invention provides the remarkable advantage that the insulating material obtained comprises cereal straw, which is available in large quantities and in almost all regions.

[0032] Furthermore, the straw does not require any treatment prior to the manufacture of the bulk insulating material according to the process according to the invention. The straw can therefore be stored as is, as soon as it is harvested, while awaiting its processing to manufacture the insulating material.

[0033] Furthermore, the loose-fill insulating material obtained using the method according to the invention comprises a product that is very interesting from an ecological point of view, namely straw, which has CO2 storage / emission performance that is significantly superior to the performance of other insulating materials, namely wood wool, cellulose wadding, grass wool or hemp wool. Another advantage of the loose-fill insulating material obtained using the method according to the invention lies in the fact that it is perfectly suited to existing blowing devices that usually operate with other loose-fill insulating materials. Users of this new loose-fill insulating material can therefore keep their old blowing or insufflation equipment without modifying it.

[0034] The material obtained using the process according to the invention also exhibits remarkable performance. Indeed, this material has a thermal conductivity coefficient lambda- Â (W / mK) of 0.038, which is remarkable, knowing that the thermal conduction coefficient is between 0.052 and 0.080 for straw, between 0.037 and 0.044 for expanded cork and between 0.037 and 0.042 for cellulose wadding.

[0035] The material obtained according to the process according to the invention also surprisingly exhibits great lightness and great homogeneity.

[0036] Brief description of the figures

[0037] Other characteristics and advantages of the present invention will appear more clearly on reading the description which follows, given with reference to the appended drawing, given by way of non-limiting example, in which:

[0038] • Figure 1 is a schematic view of a flowchart of an example of implementation of the method for manufacturing a bulk insulating material in accordance with the invention.

[0039] Detailed description of the invention

[0040] Figure 1 illustrates, using a flowchart, an example of the implementation of a process for manufacturing a loose insulating material from cereal straw, such as wheat, barley, oats, rapeseed, miscanthus, rice straw or various mixtures thereof.

[0041] The installation includes, for example, a crushing and defibering unit 1 for transforming raw straw into defibered straw by shredding and crushing.

[0042] The crushing and defibering unit 1 advantageously comprises tools for cutting and splitting the straw strands. For example, the crushing and defibering unit 1 comprises two crushers connected in series. The first crusher comprises, for example, tools for cutting the straw strands, such as knives. The second crusher comprises, for example, tools for splitting the straw strands, such as hammers.

[0043] Defibrated straw means straw comprising non-homogeneous strands with an average length of between 3 mm and 22 mm and preferably between 3 mm and 11 mm and an average diameter of between 0.5 mm and 4.0 mm and preferably between 0.5 and 2.5 mm.

[0044] The average diameter must be understood as being the largest dimension of the straw blade, taken in a plane orthogonal to the longitudinal direction of said blade.

[0045] For example, a defibrated straw comprises from 29% to 33% of strands having an average length of 9.633 mm with an average diameter greater than 2 mm, from 32% to 37% of strands having an average length of 6.951 mm with an average diameter greater than 1 mm and from 16% to 20% of strands having an average length of 3.960 mm with an average diameter greater than 0.5 mm.

[0046] The remainder of this sample sample is considered dust, which is preferably removed by filtration using a filtration / dosing unit 2.

[0047] The process is implemented, for example, using an installation illustrated schematically with the flowchart in Figure 1.

[0048] The installation comprises a crushing and defibration unit 1 fed with straw, for example packaged in bales or bundles. The crushing and defibration unit 1 comprises, for example, two crushers in series, which may comprise crushing tools having specific shapes or settings. The or each crusher thus comprises adjustable cutting, splitting and / or shredding tools to define the shape and size parameters of the strands of the defibrated straw.

[0049] According to another embodiment of the installation, the crushing and defibration unit 1 comprises knives for cutting the straw strands and hammers for splitting said strands. In the context of the implementation of the crushing of the straw, one or more passages may be provided in the crushing and defibration unit 1. The number of passages depends on the morphology (shape, length and diameter) sought for the defibrated straw strands. A defibrated straw is thus obtained, at the outlet of the crushing and defibration unit 1, composed of dimensionally optimized strands and shapes to promote their mixing with the cellulose wadding on the one hand and to improve the thermal and sound insulation properties of the insulating material obtained on the other hand.

[0050] According to an exemplary embodiment, the installation also comprises a filtering and dosing unit 2 which directly feeds a mixer 3.

[0051] The filtering operation is carried out, for example, by using a vibrating screen and / or a cyclonic separator. The latter can advantageously be used to transfer the defibrated straw to the mixer 3. Filtering makes it possible to separate the defibrated straw from dust and other impurities by gravity or by cyclonic filtering.

[0052] The mixer 3 comprises, for example, at least one mixer of the rotating cylinder and / or drop cage type.

[0053] The installation also comprises a first dosing and spraying unit 4a for supplying the mixer 3 with adjuvants. These adjuvants comprise at least one fungicidal adjuvant F. These adjuvants may also comprise a fire-retardant adjuvant R.

[0054] The installation also comprises a second metering and spraying unit 4b for feeding the mixer 3 with cellulose wadding. The installation advantageously comprises a disentangling and aeration unit 5 for decompacting the cellulose wadding before it is metered and sprayed into the mixer 3. The one disentangling and aeration unit 5 comprises for example a carding system.

[0055] The installation also includes a compressor 6 to inject compressed air into the mixer 3, thus promoting the homogenization and aeration of the mixture.

[0056] The installation also includes a bagging and palletizing unit 7 for the insulating material at the outlet of the mixer 3.

[0057] The loose insulating material is therefore manufactured according to the manufacturing process in accordance with the invention and detailed below.

[0058] The process for manufacturing bulk insulating material based on cereal straw comprises a step a) consisting of mechanically shredding and grinding the straw to obtain a defibrated straw whose strands preferably have an average length of between 3 mm and 11 mm and whose average diameter is between 0.5 mm and 2.5 mm.

[0059] Advantageously, the method consists of filtering the defibrated straw obtained under a) to remove dust and other impurities in a proportion by mass of at least 2% and preferably 5% to 10% of the defibrated straw. The separation of undesirable residues and dust or other materials affecting the performance of the insulating material can therefore be carried out by gravity using a sieve, for example a vibrating sieve, or using cyclonic filtering.

[0060] According to a step b), the method consists of using cellulose wadding and carrying out disentangling and aeration of said cellulose wadding. This phase of disentangling and aeration of the cellulose wadding can be carried out separately in an ancillary installation or directly in the mixer 3, before the introduction of the defibrated straw into said mixer 3.

[0061] According to step c), the process consists of mixing the defibrated straw under a) and the cellulose wadding prepared under b).

[0062] The cellulose wadding is therefore introduced into the mixer 3, before the defibrated straw, for example by spraying, with a mass proportion of between 1% and 30% relative to the total mass of the defibrated straw and the cellulose wadding.

[0063] According to a step d), the method consists of injecting compressed air into the mixer 3 to homogenize the mixture and to obtain an insulating material having a density of between 55 kg / m 3 and 65 kg / m 3 This is the density that must be achieved, for example, when blowing bulk material into cavities.

[0064] The duration of the mixing operation depends on the size of the mixer 3.

[0065] The method then consists, according to a step e), in bagging the insulating material thus obtained and, if necessary, palletizing it. According to an exemplary implementation, the method consists in filtering the defibrated straw obtained under a) to remove dust and other impurities in a proportion by mass of at least 2% and preferably 5% to 10% of the defibrated straw.

[0066] According to an example of implementation, the method consists of mixing the cellulose wadding, or the cellulose wadding - defibrated straw mixture, with one or more adjuvants comprising a fungicidal product, for example with a proportion by mass relative to the total mass of the mixture, of between 0.03% and 11% and preferably of between 0.5 and 4%.

[0067] For example, the additives include at least one fire retardant product with a mass proportion relative to the total mass of the mixed products, between 10% and 30%. The precise proportion can be chosen according to the properties and performance required for the bulk material.

[0068] For example, the fire-retardant product, viscous or liquid, comprises a geopolymer of the metakaolin type.

[0069] According to another example of implementation of the process, one or more adjuvants, fungicides and / or fire retardants can be mixed with the cellulose wadding prior to the mixing operation with the defibrated straw.

[0070] The invention also relates to a prefabricated modular wooden structure for making a wall or a wall or for covering a wall of a building, on the exterior or interior side. Such a structure comprises at least one cavity containing the insulating material obtained according to the manufacturing method detailed above.

[0071] The invention also relates to a mixed prefabricated modular structure made of wood and concrete for making a wall or a wall or for covering a wall of a building, on the exterior or interior side. Such a structure comprises at least one cavity containing the insulating material obtained according to the manufacturing method detailed above.

[0072] According to an exemplary implementation, the cellulose wadding used is made entirely from recycled paper or from recycled paper incorporating recycled cardboard. It is obvious that the present description is not limited to the examples explicitly described, but also includes other embodiments and implementations. Thus, a described technical characteristic, or a described method step, can be replaced by an equivalent technical characteristic, respectively an equivalent step, without departing from the scope of the present invention as defined by the claims.

Claims

CLAIMS 1. A method of manufacturing a bulk insulating material based on cereal straw, characterized in that it comprises the steps: a) mechanically grinding the straw to obtain a defibrated straw whose strands have an average length of between 3 mm and 22 mm and preferably between 3 mm and 11 mm and whose average diameter is between 0.5 mm and 4.0 mm and preferably between 0.5 and 2.5 mm, b) using cellulose wadding and carrying out disentangling and aeration of said cellulose wadding, c) using a mixer (3) and mixing the defibrated straw under a) and the cellulose wadding prepared under b), said cellulose wadding being introduced into the mixer (3) before the defibrated straw with a mass proportion of between 1% and 30%, relative to the total mass of the defibrated straw and the cellulose wadding,d) injecting compressed air into the mixer (3) to homogenize said mixture and to obtain a mixture having a density of between 55 kg / m, 3 and 65 kg / m 3 , and e) bagging the insulating material thus obtained.

2. Method according to claim 1, characterized in that it consists in step a) of using at least one grinder to shred and grind the straw into bales, said at least one grinder comprising adjustable shredding / grinding tools to define the shape and size properties of the strands of defibrated straw obtained, said tools comprising knives and hammers in series.

3. Method according to claim 1 or 2, characterized in that it consists in step c) of using at least one mixer (3) of the rotating cylinder and / or dropping cage type.

4. Method according to any one of claims 1 to 3, characterized in that it consists of filtering the defibrated straw obtained under a) to remove dust and other impurities up to a mass proportion of at least 2%. and preferably at least 5% to 10% of the defibrated straw.

5. Method according to any one of claims 1 to 4, characterized in that it consists of mixing the cellulose wadding or the cellulose wadding - defibrated straw mixture, with one or more adjuvants comprising a fungicidal product.

6. Method according to any one of claims 1 to 5, characterized in that it consists of mixing the cellulose wadding or the cellulose wadding - defibrated straw mixture, with one or more adjuvants comprising at least one fire-retardant product with a proportion by mass relative to the total mass of the mixed products, of between 10% and 30%.

7. Method according to claim 6, characterized in that the fire-retardant product is chosen from a family of geo-sourced products.

8. Method according to claim 6, characterized in that the fire-retardant product is in viscous or liquid form and comprises a geopolymer of the metakaolin type.

9. Prefabricated modular wooden structure for making a wall or a wall or for covering a wall of a building, on the exterior or interior side, characterized in that it comprises at least one cavity containing the insulating material obtained according to the manufacturing method in accordance with any one of claims 1 to 8.

10. Prefabricated mixed modular structure made of wood and concrete for making a wall or a wall or for covering a wall of a building, on the exterior or interior side, characterized in that it comprises at least one cavity containing the insulating material obtained according to the manufacturing method in accordance with any one of claims 1 to 8.

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