FR3140008A1 - Chamber for steam molding of expanded or cellular materials or foams. - Google Patents

Abstract

The invention relates to a chamber for steam molding (1) of expanded or cellular or foamed materials comprising an enclosure (3) comprising at least two parts (3a, 3b), at least one part being movable (3a) to allow its opening and closing, and part of the surfaces of which are covered with an insulating coating, in particular the interior surface of the enclosure or the exterior surface of the steam inlets. [FIG. 2]

Description

Chamber for steam molding of expanded or cellular materials or foams. Field of the invention

The invention generally relates to the steam molding of expanded or cellular or foamed materials.

Technical background

Traditionally, aluminum molds are used for the manufacture of molded parts made of expanded or cellular foams, for example expanded polystyrene. These molds are integrated into aluminum or steel steam chambers which undergo multiple temperature variations during their operation. In particular, after the injection of balls or cellular pearls into the impressions of a mold, steam is injected to heat and possibly expand the balls contained in the mold to obtain a body having the shape given by the impressions. The imprints are in fact microperforated to allow steam to penetrate the heart of the material. This is followed by a mold cooling phase to stabilize the molded body before removing it by opening the mold. Each cycle lasts a few tens of seconds to a few minutes and the temperature is alternately raised, for the molding of expanded polystyrene for example, to 110-120 °C by injection of steam under pressure into the chamber and the mold, then reduced to 80 °C. C by decompression and/or water spray to freeze the part. However, these incessant temperature variations cause significant energy dispersion in the molding device and the steam chamber generally made of steel or aluminum, on the one hand because of the large mass of metal present in the tool (several hundred kilograms of steel and aluminum), and also because of the large volume of steam circulating in the chamber. In the end, less than 10% of the energy supplied is used for molding the cellular material.

Some manufacturers have sought to reduce energy loss by insulating the chamber and/or the molds. However, this approach induces the formation of condensation in the mold, which is harmful to the quality of the final product, which can cause filling defects on subsequent cycles inducing defects on subsequent parts due to lack of filling in the mold. Indeed, we can for example observe the appearance of a film of water on the impressions preventing the air from escaping correctly when material is introduced into the impression in the following cycle, thus creating micro-pockets. of air preventing the honeycomb balls from being placed correctly in the impression. This results in malformed parts and/or non-uniform density.

Such molds for manufacturing products molded by a steam process are for example described in JP3874708. The steam chamber 109 and the mold inside which are placed impressions described in this document, reproduced here at , include in particular a water-resistant protective material 107, here a layer of stainless steel, and a thermal insulation material 108, here a layer of asbestos, resistant to compression fixed against the rear plates 106 of the steam chamber 109, plates kept at a distance between the two complementary parts of the mold 102 and 103 by supports 105. The layer 107 of water-resistant material makes it possible to protect the insulation layer from humidity by repelling this humidity thanks to with hydrophobic properties. The surface of this layer must be smooth to allow condensation to drain effectively. It is essential that the insulating layer 108 is resistant to compression since it supports the mold and therefore the impressions, and ensures the accuracy of the shape of the expanded product. The layers of material 107 and 108 are fixed using bolts between the rear plate and the edge of the side plates 112 and 113. These side plates are not insulated by the materials 107 and 108.

Such a mold helps reduce the amount of steam required for heating and expanding the material. A disadvantage of this type of mold is that it cannot control the condensation of steam inside the mold. However, the presence of condensation can cause filling defects in the following products.

Other disadvantages can be mentioned regarding condensation. When ejecting the molded part, it is known to use two types of ejector: mechanical ejector and/or air injection. When air is sent through the steam ports to eject the molded part, water droplets will also be sprayed onto the parts. This humidity will pose a conservation problem when storing parts in plastic bags for example. These parts must therefore undergo additional drying stages before they can be stored. In addition, cellular beads such as polystyrene absorb humidity, which causes weight variations of up to 10% of the weight. This seriously harms the quality of the product, which must generally meet precise humidity criteria. It is therefore important to generate as little water as possible in the molded part in order to avoid making it heavier.

It was suggested to evacuate the condensation using a drainage pump. This is for example what is described in document EP2227366 where the steam condensate formed in the chamber is sucked up. The disadvantage of this mold is the use of additional energy for the operation of such a device, which adds additional cost to the final product.

It was therefore deemed necessary by the applicant to improve steam injection molding systems, seeking to firstly avoid the formation of condensation.

To this end, the invention relates to a chamber for the steam molding of expanded or cellular materials or foams comprising:

- an enclosure comprising at least two parts, at least one part being movable to allow its opening and closing, and whose interior surface is at least partly covered with (thermal) insulation, characterized in that a plate made of material thermal conductor covers the insulation.

It has been observed that the internal insulation of a steam chamber induces the formation of condensation inside the chamber. The applicant has identified, surprisingly, that covering the thermal insulation with a plate of thermally conductive material overcomes this problem by preventing condensation from forming.

The thermal conductive material preferably comprises metal; it may be pure metal or a composite. Preferably, this metal is aluminum, copper and/or stainless steel. Preferably, the plate made of thermally conductive material (19) comprises aluminum, copper and/or stainless steel. In a particular mode, the plate is made of aluminum, copper and/or stainless steel.

The presence of this plate makes it possible to limit temperature variations on the internal surface of the enclosure. Thus, not only is it no longer necessary to heat several hundred kilograms of metal (the chamber frame) thanks to the insulating layer, but, during the cooling stage, the internal plate of conductive material maintains a temperature high enough during the mold cooling phase to avoid steam condensation in the next cycle. This not only results in a considerable energy saving, but a condensation evacuation system is no longer useful.

This also makes it possible to reduce cycle times while optimizing the steam molding process with an energy and economic gain significantly greater than existing systems but also makes it possible to reduce the carbon footprint of the steam molding process of expanded or cellular materials. or moss.

The chamber for the steam molding of expanded or cellular or foam materials can designate indifferently a traditional chamber inside which is arranged a mold with perforated impressions or a chamber with a so-called “monoblock” mold with perforated impressions, c that is to say a chamber whose walls (of the enclosure) coincide with the mold, or a hybrid system. In all cases, the enclosure includes a mold with at least one perforated cavity.

The perforated impression is the element used to obtain the desired part shape. Preferably, the imprint consists of a punch part and a die part which, when combined, delimit the shape of the part to be molded. The inside of the impressions is intended to be in contact with expanded or cellular or foam materials. The perforations in the impression are sized to be smaller than the beads of cellular material, but large enough to allow the passage of vapor through these beads.

The enclosure and the mold may be two distinct elements or the mold may, at least in part, be confused with the enclosure.

The enclosure designates a volume delimited by a rigid envelope, defined for example by a frame and walls. The enclosure preferably has a rectangular parallelepiped shape. In a particular mode, the enclosure is a cube.

The enclosure comprises at least two parts, at least one part of which is movable to allow it to be opened and closed. Generally, a fixed part cooperates with the moving part during its operation to ensure the stability of the system.

Each part of the enclosure is associated with a part of the mold.

A part of the mold supports a punch part of the impression composed of relief. The other part of the mold supports the matrix part of the perforated impression, arranged to complement the punch when closing the enclosure. Thus, the opening of the enclosure allows the opening of the mold and the impressions for the ejection of the molded parts when the enclosure was closed, in a conventional manner, well known to those skilled in the art.

The enclosure comprises fluidic connection systems between the interior of the enclosure and the exterior of the enclosure, preferably arranged on the side faces of the enclosure, such as at least one water inlet, at at least one steam inlet, and at least one injector of the cellular balls. These connection systems make it possible to bring the different materials directly into the enclosure, when it is closed. Preferably, the enclosure also includes at least one conduit for applying vacuum.

Preferably, the water inlet is placed on a side face of the enclosure. It is connected to a water source and allows water to be conducted inside the enclosure, preferably in the form of a spray or spray directed towards at least one footprint. The water supply participates in the cooling system to cool the interior of the mold cavity in order to freeze the molded part before the vacuum stabilization step to remove water and steam residues prior to processing. ejection of the part. The water inlet is arranged to operate discontinuously and is well known to those skilled in the art.

Preferably, the cellular ball injector is placed on a side face of the enclosure to drive cellular balls inside at least one perforated cavity of the mold. The ball injector is designed to operate discontinuously and is well known to those skilled in the art.

Preferably, the steam inlet is placed on a side face of the enclosure to allow the introduction of steam into the enclosure, preferably towards at least one cavity. The steam inlet opens into the enclosure at a steam inlet. In certain cases, the steam inlet can also function as an air inlet, to help eject the part from the impression when it is opened.

Preferably, at least one steam deflector is arranged in the enclosure facing the steam inlet to guarantee faster dispersion of the steam in the enclosure. The deflector is for example positioned a few centimeters from the steam inlet, preferably at most 10 mm away, preferably 5 mm.

Preferably, the enclosure includes a frame ensuring its rigidity. For example, this frame can be made of aluminum, or any other material ensuring rigidity. The frame may also include reinforcement means.

The enclosure walls can be made from the same material as the frame, or from a different material.

Advantageously, the thickness of the enclosure can be between 10 and 40 mm, preferably between 20 and 30 mm.

In operational mode, the enclosure can have two positions, an open position and a closed position.

Advantageously, closing means are provided to keep the enclosure closed in a sealed manner during the successive injections of balls into the impressions, of steam and of water towards the impressions.

The chamber of the invention is characterized by the fact that the interior surface of the enclosure is at least partly covered with a layer of insulation. Preferably, the enclosure is covered at least 50% by a layer of insulation, preferably at least 70% by a layer of insulation, preferably at least 90% by a layer of insulation and preferably still in full.

If the insulation is a relatively rigid material, the layer of insulation can be assembled inside the enclosure using a mortise and tenon system at the corners in order to prevent steam access to the edges and /or at the corners of the frame, and thus avoid the formation of condensation.

Advantageously, an insulating layer broadly designates one or more superimposed insulating layers, possibly of different types. This makes it possible to increase and/or combine the thermal properties of the insulation.

An insulator can be a flexible or rigid material, possibly expanded, cellular or foam, such as those commonly used in other insulation applications (mineral wool, polystyrene, polyurethane, epoxy resin or glass, etc.), and/or an insulating covering. , and/or textile materials such as non-woven fabrics.

The insulation can have a total thickness of between 1 and 45mm, depending on the type of insulation used. For example, when it is an expanded, cellular or foam material, the thickness can be between 15 and 45 mm, preferably between 20 and 30 mm. When it comes to an insulating coating, the thickness required is generally less to obtain comparable thermal conductivity, for example between 1 mm and 10 mm, preferably between 1.5 mm and 5 mm.

The insulation is chosen according to technical criteria such as good thermal and mechanical resistance, a low coefficient of expansion, and good stability to heat and humidity over the time of use.

An expanded, cellular or foam material type insulation preferably has a density of between 1.70 and 2 g/cm ³ .

An insulating coating, here thermal insulating, preferably designates a fluid or semi-fluid material which can be spread, for example using a brush or paint roller or sprayed (using a paint roller). spray or a paint gun), to obtain, after drying, an insulating layer with a thickness ranging from a few microns to a few millimeters. Several coats can be applied one on top of the other, with drying time between applications.

Preferably, the thermal insulating coating comprises particles of insulating material, preferably mineral particles such as ceramic or glass. These are for example insulating microbubble microspheres, hollow glass microspheres, for example in borosilicate, hollow ceramic micro-bodies, etc.

These particles are suspended in an aqueous polymeric base which may contain formaldehyde, (methyl)acrylate, styrene, etc.

For example, a layer of insulating coating has a thickness between 0.3 and 0.7 mm. Advantageously, several layers, for example between 2 and 8 layers, for example 5 layers can be applied, to obtain a thickness of between 1 mm and 5 mm, for example between 2 mm and 3 mm.

The insulating coating is preferably applied to the interior surface of the enclosure and is covered by a plate of thermally conductive material.

The insulating coating can be applied to the interior surface of the enclosure and/or to the plate made of thermally conductive material.

The insulating coating is preferably applied to the plates made of thermally conductive material (Alu or Stainless Steel) which are then applied to the inside of the enclosure using a high temperature silicone and/or also screwed.

The insulation preferably has a thermal conductivity of between 0.001 and 0.40 W/mK, 0.01 and 0.40 W/mK, 0.05 and 0.40 W/mK, preferably between 0.10 and 0.35 W/mK.

The insulation preferably has a thermal resistance of between 150 and 250°C.

In some cases, the insulation may have a compressive strength of between 400 – 550 MPa.

In some cases, the insulation may have a flexural strength of between 350 – 450 MPa.

The insulation can have a dielectric strength of between 10 – 20 kV/mm.

A plate of thermally conductive material covers the insulating layer. The thermal conductive material preferably has a thermal conductivity of between 230 and 400 W/m.K.

Preferably, the plate made of thermally conductive material comprises aluminum and/or stainless steel. Preferably, the plate made of thermally conductive material is made of aluminum, stainless steel or copper.

The plate made of thermally conductive material preferably has a thermal conductivity coefficient of between 200 and 400 Wm ^-1 K ^-1 , preferably between 220 and 395 Wm ^-1 K ^-1 , and preferably between 230 and 300 Wm ^-1 K ^-1 .

The plate made of thermally conductive material preferably has a low linear expansion coefficient, that is to say the linear expansion coefficient from 20 to 100°C is between 15 x 10 ^-6 and 30 x 10 ^-6 .

Preferably, the plate of thermally conductive material preferably covers at least 70% of the insulating layer, preferably 80%, preferably 90%, preferably the entire insulating layer.

Preferably, the thickness of the plate made of thermal conductive material is between 1 and 5 mm, preferably between 1 and 3 mm. This provides sufficient rigidity for its integration into the enclosure and gives it good durability, without unnecessarily weighing down the device and the metal mass to be heated.

The plate made of conductive material can advantageously be mechanically reinforced by a layer of organic composite such as Bakelite and Frathernit.

The plate made of conductive material is fixed to the insulating layer using fixing means to ensure sufficient mechanical strength, such as a stainless steel screw for example.

The expanded or cellular material or foam molded in the steam chamber of the invention can for example be polystyrene, polypropylene, polyethylene and/or polystyrene/polyethylene.

The applicant was surprised by the effectiveness of the insulating coating in reducing steam consumption in the molding process. The implementation of this coating being simple, she imagined insulating other parts of the equipment.

The invention therefore also extends, more generally, to the use of a thermal insulating coating to insulate at least in part a device for steam molding expanded or cellular or foamed materials.

Advantageously, the insulating coating can be applied to the frame of the molding enclosure, inside and/or outside the steam chambers, whether fixed or mobile, and/or on the exterior surface of the ducts or steam passage areas.

Preferably, the insulating covering is not in contact with the steam. When applied to internal areas of the chamber, it is preferably covered watertight by a protective layer.

The invention also relates to a chamber for the steam molding of expanded or cellular or foam materials comprising an enclosure comprising at least two parts, at least one part being movable to allow its opening and closing, the enclosure comprising at least at least one steam inlet, and at least one injector of the cellular balls, characterized in that the surfaces of the enclosure and/or the steam inlet are at least partly covered by a thermal insulating coating.

Preferably, the exterior surface of the steam inlets is covered at least 50% by insulating coating, preferably at least 70%, preferably at least 90%.

Preferably, the interior surface of the enclosure is covered at least 50% by insulating coating, preferably at least 70%, preferably at least 90%.

The insulating coating, particularly when applied to the interior surface of the enclosure, is arranged so as not to be in direct contact with the steam. This means that it can be covered with a waterproof protective layer. It may for example be a polymeric layer, a hydrophobic paint, a plastic plate or other suitable material, or a plate made of conductive material. Watertight seals can be added, especially when rigid materials are used, to seal the contours and prevent any steam infiltration.

Preferably, the insulating coating has a thickness of between 1 and 5 mm, preferably between 2 and 4 mm.

• La représente une chambre vapeur selon l’art antérieur (JP3874708)
• La représente, une vue en perspective, d’un premier mode de réalisation d’une chambre pour le moulage à la vapeur de matériaux expansés ou alvéolaires ou mousses en configuration ouverte selon l’invention
• La représente, une vue de côté de la chambre de la en configuration fermée.
• La est un schéma explosé en coupe de la chambre à vapeur de la en configuration ouverte.
• La est une vue en perspective d’un déflecteur de vapeur selon l’invention agence dans la chambre de la .
• La est une vue schématique en coupe d’un agencement des différentes couches de l’enceinte de la .

The invention will be better understood with the help of the description of several embodiments, corresponding to the drawing in which:

• There represents a vapor chamber according to the prior art (JP3874708)
• There represents, a perspective view, of a first embodiment of a chamber for the steam molding of expanded or cellular or foam materials in open configuration according to the invention
• There represents, a side view of the room of the in closed configuration.
• There is an exploded sectional diagram of the steam chamber of the in open configuration.
• There is a perspective view of a steam deflector according to the invention arranged in the chamber of the .
• There is a schematic sectional view of an arrangement of the different layers of the enclosure of the .

The characteristics, variants and different embodiments of the invention can be associated with each other, in various combinations, to the extent that they are not incompatible or exclusive with respect to each other. In particular, it will be possible to imagine variants of the invention comprising only a selection of characteristics sufficient to confer a technical advantage and/or to differentiate the invention from the prior state of the art.

With reference to Figures 2 to 6, a chamber 1 for the steam molding of expanded or cellular or foam materials comprises an enclosure 3 with at least two distinct parts, 3a and 3b. The part 3a is here mobile while the part 3b is fixed, to allow the opening and closing of the enclosure 3. The fixed part 3b here cooperates with the mobile part 3a during its operation to allow the production of molded part .

In this non-limiting example, the enclosure 3 comprises a mold 4 with perforated impressions 5, here four impressions 5 are represented. The mold 4 consists of a carcass whose role is to hold the perforated impressions 5 used to obtain the desired part shape.

The mold 4 is in two distinct parts with a part 4a associated with part 3a of the enclosure and another part 4b associated with part 3b of the enclosure.

Part 4a of the mold 4 supports a punch part of the impression 5. The other part 4b of the mold supports the matrix part 5b of the perforated impression 5. When the enclosure is closed, the two parts 5a and 5b of the impressions are associated so as to delimit the volume of the part to be molded.

The interior of the impressions 5 is intended to be in contact with expanded or cellular or foam materials. These imprints are here, for example, made of aluminum. They are perforated. The perforations of the impressions are sized so as to be smaller than the balls of cellular material, but large enough to allow the passage of steam towards the inside of the impression, through these balls.

The mold 4 includes an ejection system 6 of the molded part. The ejection system here comprises eight ejectors 6, crossing the large face of the movable part 3a of the enclosure and opening inside the indentations 5. The ejectors 6, when they are activated, when the mold 4 is open , exert pressure on the molded part to detach it.

The enclosure 3 comprises a rigid frame and side faces, on which fluidic connection systems are arranged between the interior of the enclosure and the exterior of the enclosure.

This concerns in particular a water inlet 7, here two water inlets, crossing the large face of the mobile part 3a of the enclosure and intended to conduct liquid water towards sprays arranged in the enclosure, oriented towards the impressions 5. This water is intended to cool the impressions 5 to freeze the material after cooking. The water inlet 7 contributes to the cooling of the cavity of the mold 4. The water inlet 7 is arranged to operate discontinuously and is well known to those skilled in the art.

Steam inlets 8, here four steam inlets, are also located opposite each other on the two opposite parts of the enclosure 3a and 3b, on the top of the enclosure. They are intended to allow the steam to penetrate into the enclosure 3, and into the mold 4 so that it passes through the impressions 5, for welding the cellular material.

Here also, as is generally the case, the steam inlets 8 can also function as air inlets, to participate in the ejection of the part from the impression when it opens.

Injectors of the cellular balls 9, here eight injectors, pass through the large face of the mobile part 3a of the enclosure and open out inside the perforated impressions 5 of the mold 4 (not shown).

The ball injector 9 is arranged to operate discontinuously and is well known to those skilled in the art.

Valves (not shown) allow these various injectors to be opened and closed at appropriate times during the molding cycle.

The expanded or cellular or foam material introduced into the impressions via the injectors 9 can for example be polystyrene, polypropylene, polyethylene and/or polystyrene/polyethylene.

The enclosure 3 also includes at least one conduit for the application of vacuum 10 to extract the air and gas still present in the mold after the water cooling phase. Preferably, the vacuum application conduit is connected to a vacuum pump placed near chamber 1. This equipment is well known to those skilled in the art.

The enclosure 3 comprises locking means 11 provided to keep the enclosure 3 closed in a sealed manner during the successive injections of balls into the indentations 5, of steam and water towards the indentations 5. These locking means 11 can be fasteners in two parts, placed opposite each other around the perimeter of parts 3a and 3b of the enclosure. They cooperate with each other when closing chamber 1. Here, twelve clips (three per side of the enclosure) are fixed on the side parts 3a and 3b of the enclosure. The number and/or type of fasteners may depend on the dimensions of the room.

The enclosure 3 includes reinforcement means such as, for example, here stiffeners 12 placed along the side face of part 3a of the enclosure. The ends of the stiffeners are fixed using screws 13 to the rear frame 14 of part 2a of the additional chamber. These screws 13 can for example be of type FH M12 x 60mm.

Part 3b of the enclosure includes on its rear part a watering circuit 15 in order to regulate the temperature of the mold 4.

Steam deflectors 16 arranged in the enclosure 3 facing the steam inlet to guarantee faster dispersion of the steam in the enclosure ( ). The deflector 16 is for example fixed a few centimeters from the steam inlet 8 on the plate using screws 16a.

A layer of insulation 17, here for example a rigid layer of epoxy resin, is placed on the interior faces of the enclosure 3 ( ), particularly on the side faces (on which the enclosure opens) as well as on the large faces. Plates 19 of conductive metal cover the insulator.

The insulating layer 17 here comprises two layers 17 and 17a. It is assembled inside enclosure 3 by a mortise and tenon system at the corners ( ) in order to prevent steam from reaching the edges and/or corners of the frame, and thus avoid the formation of condensation.

The insulating layer 17, 17a is positioned and fixed on the four sides of the enclosure frame 3, for example using screws 18.

The two-layer composition of the insulation makes it possible to increase and/or combine the thermal properties of the insulation. On the , an additional insulating layer 17a covers the insulating layer 17.

The insulation 17, 17a can have a total thickness of between 15 and 45 mm. It is possible to have different thicknesses between 17 and 17a. It is also possible to combine more than two layers.

The insulators 17 and 17a are chosen according to technical criteria such as good thermal and mechanical resistance, a low coefficient of expansion, and good stability to heat and humidity over the time of use. For example, an insulator can be an epoxy resin.

Examples of optimal ranges on the mechanical properties of insulators are described in Table 1 below:

Technical criteria Test method Value range Density (in g/cm ³ ) ISO 1183 1.70 – 2 Thermal conductivity (in W/mK) ISO 8302 0.20 - 0.40 Thermal resistance (in °C) IEC 216 150 – 250 Compressive strength (in MPa) ISO 604 400 - 550 Flexural strength (in MPa) ISO 178 350 - 450 Dielectric strength (in kV/mm) IEC 243-1 10 – 20

A non-limiting example of insulation suitable for the present invention is that sold under the trade name Deltherm 68.890 sold by the company BASFF Thermal Engineering SRL or even EPGM 203 by the company Melpro SAS.

The plate made of thermally conductive material 19 covering it is here an aluminum plate, a material chosen for its properties as much as for its affordable price. Other materials are however possible, such as stainless steel or copper, or alloys or composites.

The characteristics of copper, stainless steel and aluminum are detailed as an example in table 2 below:

Aluminum Stainless steel Copper Thermal conductivity (Wm ^-1 -K ^-1 ) 237 15-20 390 Linear expansion coefficient from 20° to 100°C 15 x 10 ^-6 16.5 x 10 ^-6 30 x 10 ^-6 Density (in g/cm3) 2.7 7.8-7.9 8.96 Melting point (in °C) 660.3 1085 Poisson coefficient 0.24 to 0.33 0.33
Young's modulus (in GPa) 69 200 124 Specific heat (in Jk ^{-1.kg -1} ) 897 500 385

The thermal conductive material 19 preferably has a thermal conductivity of between 230 and 450 Wm ^-1 -K ^-1 . The thermal conductivity of a material is a physical quantity which characterizes its capacity to diffuse heat in environments without macroscopic movement of matter. Therefore, aluminum and copper have good conductivity.

The plate of thermally conductive material 19 preferably has a low linear expansion coefficient, that is to say the linear expansion coefficient from 20 to 100°C between 15 x 10 ^-6 and 30 x 10 ^-6 .

The plate of thermally conductive material 19 here covers almost the entire surface of the insulator, which itself covers almost the entire interior wall of the enclosure. Although less coverage would likely be less effective, it would still be more profitable than not having any. The conductive material therefore preferably covers at least 70% of the insulating layer 17 or 17a, preferably 80%, preferably 90%, preferably the entire insulating layer 17 or 17a.

Preferably, the thickness of the plate made of thermal conductive material 19 is here 5mm. This provides sufficient rigidity for its integration into enclosure 3 and gives it good durability, without unreasonably weighing down the device and the metal mass to be heated.

The plates 19 are fixed to the insulator 17, 17a using screws 20, here made of stainless steel to withstand the humid conditions expected inside the enclosure, and do not in any way hinder the properties of the plate 19.

A non-limiting example of a plate made of thermal conductive material 19 suitable for the present invention is that sold under the trade name AG 3C 5083 sold by Eyrolliage®.

The characteristics of the AG 3C 5083 plate are described in table 3 below:

AG plate 3C 5083 Modulus of elasticity (in MPa) 71000 Modulus of rigidity (in MPa) 26800 Poisson's ratio (in v) 0.33 Solidity temperature (in °C) 580 Melting temperature (°C) 640 Specific heat (in J kg-1 K-1) 899 Thermal expansion coefficient (in μm m-1 K-1) 23.8 Density (in kg m-3) 2660 Resistivity (in nΩm) 60 Thermal conductivity (in λ) 117 Electrical conductivity (in %IACS) 28.5

Figures 2 to 6 illustrate a particular embodiment of the chamber of the invention. Those skilled in the art generally know the operating principle of such chambers and the technical variations that can be made there, depending on the type of cellular material used, the size and shape of the parts to be molded, etc.

The innovation here lies at the level of the insulating layer 17 combined with a plate of thermally conductive material 19.

During a parts molding process, initially, the enclosure is closed, cellular foam balls are injected into the indentations 5, steam is then injected into the enclosure 3 and the mold 4 so as to to penetrate into the impressions 5 to weld the cellular balls. Liquid water is then projected using a spray onto the impressions to freeze the molded parts. A vacuum step extracts residual moisture and accelerates the stabilization of the molded part. The enclosure 3 is then opened, the coin ejectors 6 actuated and/or an air flow applied to eject the coins. Enclosure 3 is then closed for a new cycle.

Thanks to the insulation combined with the plates made of conductive material 19, the energy loss of the process is considerably reduced. Only the plates made of conductive material 19 are subject to temperature variations at each cycle, which represents a volume of material much lower than the frame and walls of the enclosure. In addition, the temperature of the plates made of conductive material 19 does not drop considerably during the cooling phase of the part, thus allowing the humidity introduced into the room (steam, water spray) not to condense on these walls and in the room in general, avoiding manufacturing defects due to condensation.

Another implementation of the invention has also been carried out, by replacing the insulating plates 17 and 17a with an insulating coating.

The thermal insulating coating here is a white hydrophobic paint comprising a mixture of styrene and acrylic polymers (formaldehyde, methylacrylate and styrene) in an aqueous base, fire inhibitors and retardants and closed-cell microgranular ceramic additives having a thermal conductivity around 1 mW/m.°C per layer was applied with a brush in several layers (typically 5 layers of 0.5 mm) until a layer of 2-3 mm was obtained on the interior surface of the enclosure (instead of insulator 17 and 17a) and covered with a conductive aluminum plate (2.5 mm thick). A waterproof seal, here an acetic silicone seal for high temperature application, is placed around the edge so as to prevent any contact between the process steam and the paint.

Paint was also applied with a brush with a thickness of 1.5 to 5 mm on the external and visible parts of the machine, in which steam circulates.

A standard production cycle was conducted. It was observed that the temperature recorded on the external face of the enclosure is 50% lower than the temperature recorded for the same production without paint (43.8°C compared to 84.2°C without insulation). Steam consumption is reduced by 39% compared to a cycle without insulation.

It is anticipated that by insulating the entire chamber, the steam saving can reach 50%.

The paint could also have been applied with a spray gun.

To improve the adhesion of the paint to different surfaces, the first coat can be diluted with water, for example to 50% by volume.

Claims (13)

Chamber for steam molding (1) of expanded or cellular or foam materials comprising an enclosure (3) comprising at least two parts (3a, 3b), at least one part being movable (3a) to allow its opening and closing , the enclosure (3) comprising at least one steam inlet (8), and at least one cellular ball injector (9), characterized in that the surfaces of the enclosure and/or the steam inlet are at less partly covered by a thermal insulating coating. Chamber according to claim 1, in which the external surface of the steam inlets is covered at least 50% by insulating coating, preferably at least 70%, preferably at least 90%. Chamber according to one of claims 1 and 2, in which the interior surface of the enclosure (3) is covered at least 50% by insulating coating, preferably at least 70%, preferably at least 90% . Chamber according to claim 3, in which the insulating coating applied to the interior surface of the enclosure is arranged so as not to be in direct contact with the steam. Chamber according to one of claims 3 or 4, in which the insulating coating applied to the interior surface of the enclosure is covered by a plate of thermally conductive material. Chamber according to claim 5 in which the plate of thermally conductive material (19) comprises aluminum, stainless steel and/or copper. Chamber according to one of claims 5 to 6, in which the plate of thermally conductive material (19) has a thermal conductivity coefficient of between 200 and 400 W.m-1K-1. Chamber according to one of claims 5 to 7, in which the plate of thermally conductive material (19) has a linear expansion coefficient of 20 to 100°C between 15 x 10-6 and 30 x 10-6. Chamber according to one of claims 5 to 8, in which the thickness of the plate of thermally conductive material (19) is between 2 and 5 mm. Chamber according to one of claims 1 to 9, in which the insulating coating has a thickness of between 1 and 5 mm, preferably between 2 and 4 mm. Chamber according to one of claims 1 to 10, in which the insulating coating comprises mineral particles. Use of a thermal insulating coating to at least partially insulate a steam molding chamber of expanded or cellular or foam materials. Use according to claim 12, according to which the insulating coating is applied to the frame of the molding enclosure, inside the steam chambers, and/or to the exterior surfaces of the conduits or steam passage areas, the coating not being in contact with the steam.