BE1030784B1 - Expanded natural fiber molded parts - Google Patents

Abstract

The invention concerns the manufacture of rigid insulating materials, preferably 100% natural and/or biosourced, having a better thermal coefficient than existing natural and/or plant fiber plates, which are biodegradable and easy to work with (cutting, grooving, machining, etc.). coat…). This involves manufacturing an expanded molded part in cellulosic and/or lignocellulosic fibers whose surfaces are a crust enclosing a structure with open porosity, the constituents of the crust and the structure with open porosity being identical.

Description

1 BE2022/5638

Expanded molded parts in natural fibers.

The invention concerns the manufacture of insulating plates, preferably 100% natural and/or biosourced, having a thermal coefficient at least as good as existing natural and/or plant fiber plates, which are biodegradable and easy to work with (cutting, grooving, etc.). machining, coating, etc.).

Whether for applications in packaging or in construction, there are insulating materials, in the form of panels or flexible layers based on natural materials, such as natural fibers. However, the insulating performance of such materials is often disappointing compared to classic synthetic materials such as polystyrene or polyurethane, or mineral materials such as glass wool. These materials are often soft and cannot be grooved, and are difficult to cut cleanly.

Indeed, it is very difficult to form a sufficiently strong panel based on natural fibers, without adding at least one thermoplastic binder or other synthetic additive, to hold the fibers together, and/or facings on each side of the material to ensure this. cohesion, which then makes it impossible to recycle or compost such panels.

The applicant therefore considered it necessary to develop an insulating panel having excellent thermal properties, completely recyclable and biodegradable, which is both simple to produce and easy to work with.

Solution of the invention

To this end, the invention relates to an expanded molded part made of cellulosic and/or lignocellulosic fibers whose surfaces are a crust enclosing a structure with open porosity, the

2 BE2022/5638 constituents of the crust and the open porosity structure being identical.

Unlike known materials, the applicant has developed a composition based on cellulose fibers making it possible to obtain, following the cooking step of the initial composition, an expanded structure with open porosity with a denser and more rigid surface providing mechanical properties and a low density interior conferring insulating properties.

Unlike expanded synthetic materials such as polyurethane or polystyrene, in which air is captured in closed bubbles, the expanded part of the invention has open porosity, i.e. air can circulate in the material, between the fibers, thus giving it breathable properties.

The molded part of the invention comprises cellulosic and/or lignocellulosic fibers, at least one foaming agent and at least one binder.

In one embodiment the binder comprises at least one vegetable protein.

The room may also contain residual humidity. The humidity level in the room may vary over time and depends in particular on storage conditions and ambient humidity.

The crust can be defined as a surface film (thin layer on the surface of the object) inseparable from the material on which it is present. That is to say, it is not formed by bonding or assembly on the expanded structure with open porosity but results naturally from the manufacturing process of this expanded structure.

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According to the invention, this crust has the same constituents as the open porosity structure that it encloses, the proportions may however be different. Indeed, the constituents can for example present a gradient of proportions at the level of the crust, towards the surface.

The molded part of the invention is single-layer.

This is, for example, a single-layer rigid insulating panel.

A panel refers to a material having a thickness much less than its surface. It can be generally flat, or have reliefs, angles and/or curvatures.

This board is single-ply, meaning it only has one layer made at one time. Unlike known panels, no facing or surface layer is laminated, sprayed or glued to the panel. The crust is a denser portion of the same constituents as those of the internal structure.

Cellulosic and/or lignocellulosic fibers are natural and/or biosourced fibers, such as for example wood, coconut, linen, cotton, jute, kenaf or hemp fibers. It can also be recycled paper or recycled cellulose textiles (cellulose wadding).

Preferably, the cellulosic fibers have a length of at least 0.1 mm, preferably at least 0.5 mm, preferably at least 1 mm and more preferably at least 2 mm, or at least 4 mm. Fibers that are too short do not provide sufficient cohesion of the piece.

In some cases, the length of the fibers must be limited to be suitable for the mixing technique, for example it must be limited to 100 mm.

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The foaming agent or swelling agent is a surfactant, of natural or biosourced origin or not, which aims to expand the fibrous network of the material. Foaming agents are for example sodium alkyl sulfates, such as sodium docecyl sulfate (SDS) or lauryl sulfate, phospholipids, sorbitan or alginate derivatives.

The function of the binder is to ensure cohesion between fibers.

The binder may preferably comprise agents of natural or biosourced origin, such as for example polysaccharides, such as starch and/or modified starches. Preferably, the binder does not comprise calcium carbonate.

Surprisingly, it was found that plant proteins are particularly suitable for aqueous mixture expansion of fibers, preferably in combination with the foaming agent.

The binder preferably comprises at least one vegetable protein.

Plant proteins have surfactant and film-forming properties which fully participate in the stabilization of the expanded material in the wet state. Preferably, the vegetable protein is a legume protein, such as soy, pea or bean protein, an oilseed protein such as rapeseed or sunflower protein, or a cereal protein such as wheat or sunflower protein. rice, or a combination of vegetable proteins.

The molded part of the invention preferably has a density of between 15 and 80 kg/m², preferably between 20 and 65 kg/m². It is therefore particularly balanced to have a good ratio between density (lightness), insulation, solidity (mechanical properties) and cost, which has until now never been obtained with exclusively natural and/or biosourced materials.

The molded part of the invention preferably has a thermal conductivity of 0.060 W/m*K or less and preferably 0.050

W/m*K or less, measured by hot wire method. 5 The invention therefore also relates to this particular composition for the formation of an expanded part having a crust on the surface and an expanded core with open porosity. The composition comprises cellulosic or lignocellulosic fibers, at least one foaming agent and at least one binder and water.

In one embodiment, the binder may comprise at least one plant protein.

Preferably, the binder and the foaming agent are cold soluble in water to save energy during the manufacture of the composition.

The composition may include a pH adjuster, preferably a base such as sodium hydroxide, to facilitate solubilization of the protein.

The composition preferably comprises between 50 and 85% by weight of water, preferably between 60% and 82%, preferably between 70% and 80% by weight of water. Too little water means a composition lacking fluidity for mixing the ingredients and expanding the mixture, with the water being absorbed by the fibers.

Too much water implies too much energy demand for drying, and can pose a problem with settling of constituents, creating cavities within the material leading to fragile, heterogeneous and unusable materials.

The composition preferably comprises between 10% and 35% by mass of cellulosic or lignocellulosic fibers, and preferably between 11% and 30% by mass, preferably between 12% and 25%.

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The composition preferably comprises between 1% and 25% by weight of binder, preferably between 2% and 20%, more preferably between 3% and 15%.

Concerning the binder, the vegetable protein can preferably represent between 1% and 25% by weight of the composition, preferably between 2% and 20%, more preferably between 3% and 15%.

The composition preferably comprises between 0.1% and 3% by weight of foaming agent, preferably between 0.2% and 2%, more preferably between 0.25% and 1.5%.

All the constituents of the composition are preferably recyclable and/or biodegradable. The molded parts of the invention can thus also be recyclable and/or biodegradable or even compostable. The parts of the invention can for example be recycled to serve as a fully biodegradable substrate for cultivation and/or germination.

The parts of the invention can be burned without releasing toxic fumes unlike polyurethanes or PVC.

The invention also relates to the method of manufacturing the molded part of the invention. It includes the steps of: “Cellulosic and/or lignocellulosic fibers, at least one binder, at least one foaming agent, and water are mixed; = The mixture obtained is introduced into a mold; and - The mold is heated to a temperature between 80°C and 200°C, preferably between 100°C and 150°C.

The mixing step may include mixing the components.

Fibers are preferably introduced gradually into

7 BE2022/5638 the mixture to ensure the homogeneity of the humidification of the fibers.

Preferably, the binder is dissolved cold in water. It is possible to work hot, but the cold solution saves energy.

The binder may comprise at least one vegetable protein.

The heating step freezes the expanded structure and forms the crust present on the surface of the part. It also allows some or even almost all of the humidity to escape. Too low a temperature can lead to the formation of mold; above 200°C, the part is thermally damaged.

Optionally, for energy saving reasons, the heating step can be shortened and a drying step can be added at the end of the process, in order to obtain the desired humidity level in the room. This drying can be active, that is to say by placing the part in a dryer where hot air passes, or progressive by applying a temperature gradient.

Preferably, the mold is perforated on at least part of its surface to facilitate the evacuation of humidity, and accordingly reduce the necessary drying time. The perforations have any shape and are for example perforations whose diameter is between 1 mm and 5 min, to prevent the composition from escaping from the mold.

Advantageously, the perforations are distributed homogeneously over at least one face of the mold.

These perforations give relief to the surface of the crust, which gives this crust adhesion properties, for example for coatings.

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Preferably the mold is a closed mold, that is to say it covers the entire shape. This prevents a portion of the molded part obtained from exhibiting uncontrolled swelling. This avoids additional steps of polishing, sanding or reslitting.

The parts of the invention can be used for thermal insulation in buildings, planes, vehicles, components in machines such as heat pumps or air conditioning, etc.

The parts of the invention can also be used in the manufacture of insulated packaging intended to transport fresh, cold or frozen products.

The mechanical properties of the parts also allow their use as protective packaging, for example to transport fragile objects. The isothermal and protective properties can also be combined.

The formulation and manufacturing process makes it possible to add a flame retardant treatment/agent thanks to the film-forming properties of the protein binders.

The invention will be better understood with the help of the description of several embodiments detailed in the examples below.

Example 1 - preparation of compositions according to the invention

Several compositions have been prepared based on natural fibers of different origins:

Cellulose wadding supplied by Soprema;

Paper pulp supplied by Smurfit Kappa; scutched flax tows supplied by Albert Brille (Belgium);

9 BE2022/5638 wood fibers Thermofibres supplied by GUTEX (Germany); chopped flax fibers (Linum usitatissimum), jute (Corchorus capsularis), coconuts (Cocos nucifera), kenaf (Hibiscus cannabinus)

The diameter of the fibers is included in 10 um and 200 um.

The length of the fibers here is between 100 um and several millimeters, up to 8 mm, the equipment used here being laboratory equipment. Industrial equipment could, however, allow the mixing of longer fibers.

The binders used in these compositions are a pea protein isolate (IPP) supplied by Cosucra (Be), modified starch (Tackidex I123) chosen for its good cold solubility and supplied by Ravago-Roquette (Fr).

The foaming agent used is Sodium Lauryl Sulfate (SDS) supplied by Sigma.

The fibers are gradually added to a solution at room temperature containing the binder(s) and the dissolved foaming agent.

The compositions produced are shown in Table 1. % ref fiber fiber starch | %IPP % SDS % total water

A176 linen | 13.04% | 0.00% | 6.06% | 0.07% | 80.83% | 100.00%

A186 linen | 11.37% | 0.00% | 6.14% | 0.07% | 82.42% | 100.00%

B160 linen | 15.17% | 3.03% | 3.03% | 0.65% | 78.11% | 100.00%

B162 linen | 19:11% | 3.06% | 2.58% | 0.72% | 74.53% | 100.00%

B184 linen | 18.89% | 3.12% | 2.55% | 0.80% | 74.63% | 100.00%

B196 linen | 14.25% | 0.00% 5.70% | 0.28% | 79.77% | 100.00% CAD in | 16.64% | 6.66% | 0.00% | 1.00% | 75.71% | 100.00%

C86 linen | 21.41% | 0.00% | 8.57% | 0.43% | 69.59% | 100.00%

A84b linen | 14.68% | 0.00% | 5.87% | 0.18% | 79.27% | 100.00% 687 linen | 15.50% | 0.00% | 5.43% | 1.55% | 77.52% | 100.00%

10 BE2022/5638

A194 linen/coconut 2/1 11.43% 0.00% 6.17% 0.07% | 82.32% | 100.00%

A182 linen/coconut 2/1 11.43% 6.17% 0.00% 0.07% | 82.32% | 100.00%

A184 linen/coconut 3/1 14.68% 5.95% 0.00% 0.07% | 79.30% | 100.00% 17.18% | 0.00% 5.15% | 0.34% | 77.32% | 100.00%

C118 17.35% | 0.00% | 5.20% | 0.26% | 77.19% | 100.00%

C128 17.62% | 0.00% 5.29% | 0.44% | 76.65% | 100.00%

C178 17.64% | 2.65% | 2.65% | 0.32% | 76.75% | 100.00%

A192 13.04% | 0.00% | 6.06% | 0.07% | 80.83% | 100.00%

A196 linen/jute 1/1 13.03% 0.00% 6.06% 0.13% | 80.78% | 100.00%

A198 13.04% | 0.00% | 6.06% | 0.07% | 80.83% | 100.00%

A200 lin/kenaf 1/1 13.04% 0.00% 6.06% 0.07% | 80.83% | 100.00%

G110b 17.86% | 0.00% | 4.46% | 1.79% | 75.89% | 100.00%

Table 1.

Example 2 - process for manufacturing parts in the form of plates

Plates measuring 40*35*4 cm were prepared in several successive steps, with the compositions listed in Table 1.

In a first step, the lignocellulosic wood fibers (220 g) are added by kneading with slow stirring to an aqueous solution (920 g) containing the proteins (33 g) and starch (33 g) previously dissolved in water.

The foaming agent (sodium dodecyl sulfate, 4 g) dissolved in 70 grams of water is then added and the mixture stirred.

The expanded mixture is then completely transferred into the 40*35*4 cm perforated mold which is then placed at 110°C for 6 to 8 hours, until a constant mass is obtained.

Example 3 — characterization of the plates obtained

The density and conductivity of the plates made from the different compositions were measured according to the following methods.

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The density of dry materials was calculated by dividing their weight by their volume.

The thermal conductivity of the materials was determined using a NEOTIM FP2C conductivity meter (ALBI, France) by the hot wire method provided by the manufacturer. This method makes it possible to estimate the thermal conductivity of a material from the change in temperature measured by a thermocouple placed near a resistive wire. The measurements were carried out on sample plates of at least 60x40 mm, and at least 20 mm thick. The values indicated present an average of at least 4 measurements, with an uncertainty of around 5%.

Commercial samples were also evaluated to compare their performance under the same measurement conditions.

The results are collected in table 2. plate obtained from the composition: density (kg/m?) | conductivity (W/m.K)

A176 0.051 + 0.001

A186 0.05 + 0.001

B160 0.043 + 0.002

B162 0.044 + 0.003

B196 0.047 + 0.002

A84b 0.052 + 0.001

A194 0.047 + 0.003

A182 0.047 + 0.003

A184 0.048 + 0.003 0.044 + 0.002

C118 0.045 + 0.002

C128 0.045 + 0.002

C178 0.046 + 0.002

A192 0.053 + 0.004

A196 0.048 + 0.001

A198 0.059 + 0.001

A200 0.058 + 0.001 0.040 + 0.001

G110b 0.052 + 0.004

Commercial Insulators

Glass wool (IRRM-440) 0.038 + 0.001

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Flexible Hemp Insulation (Thermo Hanf) 38 0.051 + 0.001

Flexible Hemp Insulation (Naturtherm) 0.051 + 0.001

Flexible Thermoflex Wood Fiber Insulation (GUTEX) 50 0.051 + 0.001

Cellulose Wadding Insulation (Soprema) 0.049 + 0.001

Table 2.

The plates formed according to the invention make it possible to obtain density and thermal conductivity properties comparable to existing natural or mineral flexible solutions. However, they are rigid and entirely biosourced as well as completely biodegradable. The plates of the invention can be worked and coated for use in construction.

They can also be molded with a specific shape, for a multitude of applications including packaging or specific insulation parts, for example for aeronautics, heat pumps or air conditioners, etc.

Claims (18)

13 BE2022/5638 Claims 1. Expanded molded part made of cellulosic and/or lignocellulosic fibers whose surfaces are a crust enclosing an open porosity structure, the constituents of the crust and of the open porosity structure being identical. 2. Expanded molded part according to claim 1, comprising cellulosic and/or lignocellulosic fibers, at least one foaming agent and at least one binder. 3. Expanded molded part according to claim 2, in which the binder comprises at least one vegetable protein. 4. Expanded molded part according to one of claims 1 to 3, in which the constituents have a gradient of proportions at the level of the crust, towards the surface. 5. Expanded molded part according to one of claims 1 to 4, in the form of a single-layer rigid insulating panel. 6. Expanded molded part according to one of claims 1 to 5, in which the cellulosic and/or lignocellulosic fibers are natural and/or biosourced fibers, such as for example wood, coconut, linen, cotton fibers, jute, kenaf or hemp. 7. Composition comprising cellulosic or lignocellulosic fibers, at least one foaming agent and at least one binder and water. 8. Composition according to claim 7, in which the binder comprises at least one vegetable protein. 14 BE2022/5638 9. Composition according to one of claims 7 and 8, comprising between 50 and 85% by weight of water. 10. Composition according to one of claims 7 to 9, comprising between 10% and 35% by mass of cellulosic or lignocellulosic fibers. 11. Composition according to one of claims 7 to 10, comprising between 1% and 25% by weight of binder. 12. Composition according to one of claims 7 to 11 comprising between 0.1% and 3% by mass of foaming agent. 13. Composition according to one of claims 7 to 12, in which the foaming agent comprises at least one sodium alkyl sulfate, for example sodium docecyl sulfate. 14. Composition according to one of claims 7 to 13, in which the binder comprises a polysaccharide and/or a protein of plant origin. 15. Composition according to claim 14, in which the vegetable protein is a reserve or legume protein, an oilseed protein or a cereal protein. 16. Process for manufacturing the molded part according to one of claims 1 to 6 comprising the steps of: “Cellulosic and/or lignocellulosic fibers, at least one binder, at least one foaming agent, and water are mixed. ; - The mixture obtained is introduced into a mold; and - The mold is heated to a temperature between 80°C and 200°C. 15 BE2022/5638 17. Method according to claim 16, according to which the fibers are gradually introduced into the mixture. 18. Method according to one of claims 16 or 17, in which the mold is perforated on at least part of its surface.