WO2016001790A1

WO2016001790A1 - Heat insulating device

Info

Publication number: WO2016001790A1
Application number: PCT/IB2015/054637
Authority: WO
Inventors: Giorgio Tlustos; Paolo Gozzi
Original assignee: Plastidite Srl
Current assignee: Plastidite Srl
Priority date: 2014-07-01
Filing date: 2015-06-19
Publication date: 2016-01-07
Anticipated expiration: 2017-01-01

Abstract

Heat insulating device comprising at least two sheets (11) of polymer material, distanced by at least an intermediate support frame (12) to define, between the sheets (11), at least a heat insulating hollow space (13), sealed with respect to the outside by one or more packing elements (15, 16).

Description

"HEAT-INSULATING DEVICE"

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FIELD OF THE INVENTION

The present invention concerns a heat-insulating device formed by sheets distanced so as to define a hollow space that acts as a heat-insulating chamber and which can be used to make a furnishing element, a refrigeration apparatus, in particular a cooling display case, or a closing element such as a door or window.

BACKGROUND OF THE INVENTION

Heat-insulating devices are known, used for the heat insulation of spaces at different temperatures, known as insulating glass units and consisting, in their minimal configuration, of two sheets of glass distanced by an intermediate support frame to define a hollow space that is sealed with respect to the outside and that can contain air, an inert gas or can be under a vacuum. This configuration can be repeated modularly, thus providing three, four or more sheets of glass separated by respective hollow spaces.

Insulating glass units can be used for a wide range of applications, such as for example installation in the fixtures of houses, in refrigerated display cases or in various furnishing elements.

However, known insulating glass units are very heavy, due to the specific weight of the glass sheets: they are therefore difficult to handle and consequently dangerous if they are required to be installed in conditions where there is little mobility, such as for example at great heights.

Furthermore, so that the glass sheets can be associated with the intermediate frame, or other structures such as for example when making refrigeration apparatuses, it is necessary to work the glass mechanically, for example holing it, cutting it to size and possibly shaping it.

However, since the behavior of glass when broken is the brittle type, breaking into cutting fragments, there is always the possibility that, during installation and the various operations, there may be very dangerous breakages for the operators and which can increase costs due to wastage.

Moreover, in the case of glass that has first been heat tempered, it is more resistant to impacts but is in any case brittle, breaking into micro-fragments, but more blunt. Finally, tempered glass is intrinsically tensioned, and although its resistance to impact is greater, it makes working more difficult. It must also be said that there are limits to the colors, also because it is known to be slightly greenish, not colorless.

Cast sheets of polymethyl methacrylate (PMMA) are also known, but these have disadvantages connected to the fact that they can easily be scratched or incised. In fact, standard PMMA in itself is not resistant to scratching.

In particular, one of the most common or recurrent scratching stresses in PMMA articles is that due to the so-called "brush effect", or "brushed effect", that is, the presence of thin scratches, elongated in shape, often parallel to each other, or with a concentric circular shape or spiral, which cause the surfaces to lose their brilliance and appear opaque. This "brush effect", or "brushed effect" can be rather annoying and un-esthetic, and also considerably worsens the performance of clarity and visibility of the PMMA articles in question, making them opaque and emphasizing their aging. Generally, to solve the problem of scratches caused by "brush effect", or "brushed effect", renovating creams or polishes are used for automobile bodywork. However, if the scratches or incisions are deep, the damage is often irreparable, and in any case the restoration work is delicate and costly.

In the state of the art, to try to overcome these disadvantages, it is known to apply an anti-scratch coating on the surface of the PMMA sheet, for example using a film or varnish. This solution can be effective for reducing or eliminating the risk of scratches, but it is costly since it requires an additional operation, that is, the application of the anti-scratch coating, in the production cycle of a PMMA sheet or article in general. Furthermore, the increased cost due to the coating material used is not negligible.

Coatings are known that are hardened by UV irradiation, or heat treatment or evaporation of solvents. The compositions that confer resistance to abrasion provide nano-sized compounds, normally of silica, aluminum and titanium.

The result obtained is generally satisfactory, but, since these are hard coatings, problems are normally encountered during working, such as cracking and chipping. Moreover, it must be said that the coating protects the sheet on only one of the two flat faces, and also that the coating operation must be carried out in "clean rooms", so as to prevent particles of dust on the surface layer of the coating itself.

Document FR-A-2.978.525 describes a door for furnishing elements to keep food or drinks cold, formed by two sheets of organic or mineral glass possibly associated with a protective film, in particular anti-scratching.

Document GB-A- 1.227.943 describes a rolled element formed by two glass or standard PMMA panels disposed distanced from each other.

There is therefore a need to perfect a heat-insulating device which can overcome at least one of the disadvantages of the state of the art.

In particular, one purpose of the present invention is to obtain a heat-insulating device that is light and resistant to mechanical working, without risk of cracks or fissures, or in any case brittle fracture in general.

Another purpose of the present invention is to obtain a heat- insulating device that has a heat transmittance at least comparable with that of an insulating glass unit traditionally provided with sheets of glass.

Another purpose of the present invention is to obtain a heat-insulating device that is transparent, optionally colorless and possibly characterized by clarity and good optical properties and at a relatively limited cost.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purposes, forms of embodiment described here concern a heat-insulating device comprising at least two sheets of polymer material, distanced by an intermediate support frame to define, between said sheets, at least a heat-insulating hollow space, sealed with respect to the outside by one or more packing elements. In one form of embodiment, the polymer material has a density less than 1.3 g/cm .

In another form of embodiment, the polymer material is selected from the group of optical polymers. In possible implementations, the group of optical polymers comprises polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene terephthalate copolymer (PETG), styrene-acrylonitrile (SAN), polystyrene (PS).

Using polymer material with a density lower than 1.3 g/cm³, and therefore much lighter than glass, the density of which can vary from 2.2 g/cm³ to 6.3 g/cm , makes the heat-insulating device according to the present description much lighter than known insulating glass units, also given the same weight of the other components like the intermediate connection frame and the packing, and is therefore easy to handle, both to displace and to install, even in conditions where balance is precarious.

Furthermore, since the polymer material that the panels are made of is easy to work, without getting damaged or suffering brittle fracture, the production of the heat-insulating devices does not cause any working waste and avoids relative additional costs, above all conferring greater operating safety.

Other forms of embodiment concern a heat-insulating device comprising at least two sheets of polymethyl methacrylate comprising one or more anti-scratch additives selected from among polydimethylsiloxanes or derivatives thereof. The two sheets are distanced by at least an intermediate support frame to define, between the two sheets, at least a heat-insulating hollow space, sealed with respect to the outside by one or more packing elements.

According to one form of embodiment, the one or more polydimethylsiloxanes or derivatives thereof are selected from a group consisting of: polyether polydimethylsiloxane, alkylmethyl trisiloxane, non-ionic polyoxyethylene polydimethylsiloxane.

According to another form of embodiment, the one or more polydimethylsiloxanes or derivatives thereof are provided between 0.1 % and 1 % w/w with respect to the overall weight of each sheet.

According to another form of embodiment, the one or more polydimethylsiloxanes or derivatives thereof are selected with a molecular weight less than or equal to 500.

Other forms of embodiment concern a method to make a heat-insulating device. According to one form of embodiment, the method comprises: - making available at least two sheets of polymethyl methacrylate comprising one or more anti-scratch additives selected from among polydimethylsiloxanes or derivatives thereof;

- disposing the two sheets distanced by at least an intermediate support frame to define, between the sheets, at least a heat-insulating hollow space, sealed with respect to the outside by one or more packing elements.

The heat-insulating device according to the present invention advantageously has a heat transmittance comparable with that of a traditional insulating glass unit, with the same structural configuration of the frame, hollow space and packing.

Advantageously, moreover, the polymer material that the sheets of the heat- insulating device according to the present invention are made of can have a cost comparable with that of glass, making it suitable for a vast range of applications.

Advantageously, moreover, the polymer material that the sheets of the heat- insulating device according to the present invention are made of can have optical properties equal or superior to traditional glass, in particular with regard to transparency, clarity and possibly also absence of color.

Advantageously, moreover, the polymer material that the sheets of the heat- insulating device according to the present invention are made of can be scratch- resistant.

The heat-insulating device can be used to produce opening elements, such as for example doors and windows, or to produce refrigeration apparatuses such as fridge counters and freezers, or refrigerated display cases in general, or again furnishing elements, like furniture.

These and other aspects, characteristics and advantages of the present disclosure will be better understood with reference to the following description, drawings and attached claims. The drawings, which are integrated and form part of the present description, show some forms of embodiment of the present invention, and together with the description, are intended to describe the principles of the disclosure.

The various aspects and characteristics described in the present description can be applied individually where possible. These individual aspects, for example aspects and characteristics described in the attached dependent claims, can be the object of divisional applications.

It is understood that any aspect or characteristic that is discovered, during the patenting process, to be already known, shall not be claimed and shall be the object of a disclaimer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of some forms of embodiment, given as a non- restrictive example with reference to the attached drawings wherein:

- fig. 1 is a perspective view of a heat-insulating device according to some forms of embodiment described here;

- fig. 2 is a cross section of fig. 1 ;

- fig. 3 is a perspective view of a window comprising a heat-insulating device according to forms of embodiment described here;

- fig. 4 is a perspective view of a refrigeration apparatus comprising a heat- insulating device according to forms of embodiment described here;

- fig. 5 is a perspective view of a furnishing element comprising a heat- insulating device according to forms of embodiment described here.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications.

DETAILED DESCRIPTION OF A FORM OF EMBODIMENT

We shall now refer in detail to the various forms of embodiment of the present invention, of which one or more examples are shown in the attached drawing. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, the characteristics shown or described insomuch as they are part of one form of embodiment can be adopted on, or in association with, other forms of embodiment. It is understood that the present invention shall include all such modifications and variants. Figs. 1-5 are used to describe forms of embodiment of a heat-insulating device 10 according to the present description, configured to heat insulate two environments, for example at different temperatures.

According to some forms of embodiment, the heat-insulating device 10 comprises at least two sheets 1 1 made of polymer material disposed distanced from each other and connected by an intermediate support frame 12, for example configured closed, like a frame, or the type with an open profile, for example formed by transverse elements and/or vertical uprights. In this way it is possible to define, between the sheets 1 1, an internal hollow space 13 which functions as a heat- insulating chamber, sealed with respect to the outside by one or more packing elements, such as a first sealant 15 and/or a second sealant 16, which can also define the stable connection of the sheets 1 1 with the intermediate support frame 12.

The one or more packing elements, such as a first sealant 15 and/or a second sealant 16, can advantageously be provided along the perimeter of the frame 12, at interface with the sheets 1 1 and/or the external environment (see for example fig. 2), or integrated or comprised in the frame 12. In other forms of embodiment, the frame 12 itself can be formed by one or more packing elements, such as a first sealant 15 and/or a second sealant 16, suitably shaped and sized and made with materials suitable to obtain desired structural, mechanical and sealing properties, based on specific requirements of size, design or application of the heat- insulating device 10. We believe that the heat-insulating device 10 according to the forms of embodiment described here constitutes an advantageous alternative to traditional insulating glass units with sheets of glass, since, given a heat transmittance comparable with or slightly higher than that of traditional insulating glass units, and in any case sufficient to prevent condensation, the heat- insulating device 10 is much lighter and therefore more manageable and less expensive to transport, and is also more easily worked, without risks of damage caused by brittle fracture, and therefore entails many fewer discards.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the hollow space 13 can contain air, inert gas or can be under vacuum. The polymer material that make up the sheets 1 1 can be selected from a group of polymer materials with a density of less than 1.3 g/cm³.

The polymer material in particular can be highly transparent and clear, and does not degrade following exposure to ultraviolet radiations.

In some forms of embodiment, the polymer material that makes up the sheets 1 1 can be selected in the group consisting of polymers made by the reaction of radical polymerization of the poly addition type. In particular, the polymer material that make up the sheets 1 1 can have a luminous transmission of more than 85%, in particular 90% and a refraction index lower than 1.60, in particular lower then 1.55, advantageously in the case of colorless material or sheet.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the polymer material that makes up the sheets 1 1 can be an optical polymer. Examples of optical polymers are polymethyl methacrylate (PMMA, density about 1.19 g/cm , luminous transmission about 92%, refraction index about 1.49), polycarbonate (PC, density about 1.20 g/cm³, luminous transmission about 88%, refraction index about 1.58), polyethylene terephthalate (PET, density about 1.34 g/cm³, luminous transmission about 89%, refraction index about 1.58), polyethylene terephthalate copolymer (PETG, density about 1.27 g/cm³, luminous transmission about 88%, refraction index about 1.57), styrene acronitrile (SAN, density about 1.08 g/cm³, luminous transmission about 86%, refraction index about 1.56), polystyrene (PS density about 1.05 g/cm³, luminous transmission about 89%, refraction index about

I .59).

The polymer material that makes up the sheets 1 1 , if it is PMMA, can have a heat transmittance of about 5.0 W/m²-K while for a sheet of glass this is about 5.7 W/m²-K, considering for both a thickness of 6 mm.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the optical polymer that makes up the sheets 1 1 can also comprise additives to modify determinate mechanical characteristics of the polymer material produced, in particular the mechanical properties of the sheets

I I , for example anti-scratch, which can advantageously be incorporated into the polymer material and emerge on its external surface. Examples of anti-scratch additives, for example if the optical polymer that makes up the sheets is PMMA, can be selected from among the polydimethylsiloxanes (PDMS) or derivatives thereof, as described for example in the application for a patent of industrial invention UD2014A000107 filed by the present Applicant and incorporated here in its entirety by way of reference. Therefore, possible forms of embodiment, which can be combined with all the forms of embodiment described here, provide that the heat-insulating device 10 comprises at least two of said sheets 1 1 and that the sheets 1 1 are made of PMMA comprising one or more anti-scratch additives selected from among PDMS or derivatives thereof.

According to possible forms of embodiment, which can be combined with all the forms of embodiment described here, each of the sheets 1 1 can have two opposite surfaces 20 connected by a perimeter edge 21 which defines a thickness of the sheets 1 1. The frame 12 can be associated with the sheets 1 1 in correspondence with the perimeter edges 21. The sheets 1 1 can have for example a regular shape, such as polygonal, for example quadrangular, rectangular, square, or a curvilinear shape, for example circular or oval, or a mixed polygonal/curvilinear shape.

In possible implementations, the surfaces 20 of the sheets 1 1 can be modified to obtain different esthetic properties, such as for example a satin effect.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the surfaces 20 of the sheets 1 1 can be cast in particular molds to obtain, for example, a satin effect; they can be subjected to metallization for example, which can provide to deposit metal layers on the plastic material, generally aluminum to produce for example plates, panels, reflecting coverings; they can be subjected to trademark applications, to partial mirroring or partial screen printing to confer recognition of the producer, esthetic effects, or suitable coverings of technical details inside the construction on which they are mounted, or a combination of the above effects.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the sheets 1 1 can normally filter the ultraviolet radiation, but they can also be partly transparent to ultraviolet radiation, conferring a performance that glass cannot achieve.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the sheets 1 1 can be transparent, or have reduced luminous transmission in various degrees, allowing to diffuse the light transmitted; they can be colored transparent, colored fluorescent transparent, colored opal with different degrees of diffusion of the light transmitted, or colored with a full, covering color, adding additives and dye pigments to the starting mixture.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the sheets 1 1 can be selected with a thickness varying between 2 and 40 mm, for example about 3 mm, 3.5 mm, 4 mm, 5 mm or even more.

In particular, this thickness can be selected to obtain a compromise between rigidity of the heat-insulating device, heat insulation effect and easy working.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the frame 12 can be made of aluminum or an alloy thereof, containing merely by way of example silica, iron, copper, manganese and zinc, as well as aluminum.

In possible implementations, the frame 12 can have a quadrangular cross section for example, in particular square, rectangular, trapezoid, or curvilinear, or a mixed section, as described for example using fig. 2.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the frame 12 can also have a tubular structure, that is, hollow inside, to maintain the lightness of the heat-insulating device 10, or alternatively it can be solid.

The frame 12 can have a width L which during use defines the thickness of the hollow space 13 and the distance between the sheets 1 1 (fig. 2).

The width L can be comprised for example between 4 and 26.5 mm, in particular between 7.5 and 16.5 mm, more in particular between about 9 and about 13 mm. The width L can represent a compromise between stability and ease of construction of the heat- insulating device 10, and at the same time can be a thickness suitable for heat insulation. Examples of the width L are 10 mm, 1 1 mm, 1 1 .5 mm, 12 mm.

In possible implementations, the hollow space 13 can be filled with a gas, for example air or an inert gas such as argon, xenon, krypton, for example with low heat conductivity, in particular less than 0.025 W/(m-K). In some forms of embodiment, the air can be dehydrated to prevent phenomena of condensation forming inside the hollow space 13.

In other forms of embodiment, the hollow space 13 can be put under vacuum, for example to cancel the heat transmission effect through convection between the heat insulated environments.

As described above, in some forms of embodiment the hollow space 13 can also be sealed with respect to the outside by means of one or more packing elements, that is, it can be made hermetic, for example to prevent any gases, if present, from escaping from the hollow space 13, or the vacuum condition from being compromised, and also to prevent the humidity contained in the atmospheric air from infiltrating into the hollow space 13, in particular to prevent condensation.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the heat-insulating device 10 can contain, for example in the cross section of the respective frame 12, a dehydrating material, such as for example molecular sieves configured to absorb a limited quantity of humidity infiltrating into the hollow space 13.

According to some forms of embodiment, which can be combined with all the forms of embodiment described here, the one or more packing elements with which the heat-insulating device 10 is provided can comprise a first sealant 15, for example located between the sheets 1 1 and the frame 12.

In particular, the first sealant 15 can be activated thermally, for example by heating before application, for example between 1 10°C and 130°C.

The first sealant 15 can be in the form of a ribbon or strip and, in possible implementations, it can also have the function of a stable connection between sheets 1 1 and frame 12. An example of the material of the first sealant 15 is a polymer material, for example polyisobutylene.

Furthermore, according to some forms of embodiment, which can be combined with all the forms of embodiment described here, the one or more packing elements with which the heat-insulating device 10 is provided can comprise a second sealant 16, which can be applied to a perimeter portion of the heat-insulating device 10, for example in correspondence with the perimeter edges 21 of the sheets 1 1 , typically to fill the external perimeter space comprised between the sheets 1 1 and the frame 12 toward the outside, see for example fig. 2.

An example of the material of the second sealant 16 can be a packing material with a gluing function, such as for example silicone based, a silicone glue, a foam polymer or other.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the second sealant 16 can be used in the state of aggregation of a paste and can be applied for example by a pistol, an air pistol or other industrial devices suitable for the purpose. The second sealant 16 can define the stable connection between the sheets 1 1 and the frame 12.

Finally, in some forms of embodiment, which can be combined with all the forms of embodiment described here, the heat-insulating device 10 can comprise a cover profile 18, disposed along the whole of its perimeter, which can be provided both for esthetic reasons, so as to hide the inside of the heat-insulating device 10 from view, and also to keep the one or more packaging elements in position, like the first sealant 15 and/or the second sealant 16.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the cover profile 18 can comprise an external covering strip 18a, which for example partly overlaps the sheets 1 1 and covers the interspace between them, a connection portion 18b protruding from the external covering strip 18a, which can be provided with gripping or holding fins 18c, and which is inserted between the sheets 11, as can be seen for example in fig. 2.

In possible implementations, the covering profile 18 can be made of a material resistant to wear, exposure to the outside, corrosion, such as for example a metal material, such as aluminum, or plastic, such as polyvinyl chloride (PVC) or other polymers.

Some forms of embodiment, which can be combined with all the forms of embodiment described here, also concern a heat-insulating device 10 provided with a plurality of hollow spaces 13, for example two, three or even more than three, delimited by respective sheets 1 1 associated with corresponding frames 12 and packing elements. In other words, the configuration of the heat-insulating device 10 can be the modular type, providing a repetition of heat-insulating modules formed by the insulation chambers that are defined by the hollow spaces 13. For example, if "n" is the number of hollow spaces 13, "n" frames 12 and "n+1 " sheets will be provided.

Merely by way of example, we shall now describe a method for making the heat-insulating device 10 according to the present description.

First of all, the sheets 1 1 made of polymer material according to the present description can be suitably shaped to adapt to the final shape of the heat- insulating device 10, according to its application and final use.

In particular, the sheets 1 1 can be shaped easily using milling techniques, laser techniques or other known techniques suitable for the purpose, without risk of damage, cracks, fissures or general brittle fracture.

Subsequently, a decorative treatment as already described can optionally be applied to the sheets 1 1.

Depending on the size of the heat-insulating device 10 and its subsequent application and final use, the profile of the frame 12 is designed and shaped.

If desired, inside the tubular profile of the frame 12, material to capture humidity can possibly be inserted, such as for example molecular sieves.

In some forms of embodiment, which can be combined with all the forms of embodiment described here, the frame 12 and the sheets 1 1 are associated with each other and the one or more packing elements are put between them, also with a stable connection function, for example the first sealant 15 and second sealant 16.

Finally, the covering profile 18 is positioned on the perimeter of the heat- insulating device 10.

In some forms of embodiment, the heat-insulating device 10 according to the present invention can advantageously be used to make elements or apparatuses that are configured for heat-insulation, refrigeration, heating and/or thermal conditioning. To this purpose, the heat-insulating device 10 can be configured as a panel with a heat insulation chamber defined by the hollow space 13.

In forms of embodiment described using fig. 3, which can be combined with all the forms of embodiment described here, an opening element 30 can be provided, such as for example a door or a window, comprising one or more heat- insulating devices 10 according to the present description. The opening element 30 can be provided with a frame-type support structure 31, typically square or rectangular, without excluding other polygonal or curvilinear shapes, or mixed shapes, inside which the heat-insulating device 10 can be installed or positioned, advantageously constrained stably and stationary. The opening element 30 can also comprise a containing case, or perimeter frame 32, which can be attached to walls for example, see for example fig. 3, and to which the frame-type support structure 31 can be associated.

In forms of embodiment described using fig. 4, which can be combined with all the forms of embodiment described here, a refrigeration apparatus 40 can be provided, comprising one or more heat-insulating devices 10 according to the present description, such as for example a fridge, a fridge counter, a freezer or refrigerated display case in general, configured to contain foodstuffs of the cold chain for example, or in any case products to be kept refrigerated or frozen.

The refrigeration apparatus 40 can also comprise a containing element 42, for example box-like, such as a cabinet, accessible from the outside through an aperture, upper or lateral, and configured to contain the products to be kept refrigerated or frozen, see for example fig. 4. The containing element 42 can be closed, at the top or even only at the sides, by a lid or sides made for example with the heat- insulating device 10 according to the present invention. Moreover, one or more of the components of the containing element 42, for example front or lateral, can be made by the heat-insulating device 10 according to the present invention.

In forms of embodiment described using fig. 5, which can be combined with all the forms of embodiment described here, a furnishing element 50 can be provided, made by one or more heat-insulating devices 10 according to the present description. The furnishing element 50 comprises a hollow container 52, generally formed by lateral shoulders, a back, a top and a bottom, configured for example to place objects or articles of various kinds, accessible from the outside and provided with panels 54 configured to close it. The heat-insulating device 10 according to the present invention can be used for example to make the panels 54 and/or one or more of the components of the main body 52.

Experimental data Applicant has carried out experiments to evaluate the heat-insulating performance of the heat-insulating device 10 by detecting the heat transmittance, comparing it with that of insulating glass units available on the market.

Applicant used a heat-insulating device 10 according to the present description configured with two sheets 1 1 of PMMA about 4 mm thick and a hollow space 13 of 12 mm filled with air. The weight of the heat-insulating device 10 was about 50% of the weight of a similar configuration built with glass sheets of equal thickness.

A similar configuration was also used for the insulating glass unit compared, but using sheets of glass and not PMMA.

In particular, tests were carried out to determine the properties of heat transmission in stationary conditions according to regulation UNI EN ISO 8990 ( 1999) and to determine the heat transmittance with the method of the hot chamber according to regulation UNI EN ISO 12567- 1 (2010).

The apparatuses and methods used to carry out the tests provide to use two cells, one hot (sizes: height 2.6 m, width 3.2 m, depth 2.2 m) and one cold (sizes: height 2.6 m, width 3.2 m, depth 2.2 m) simulating the internal and external environments. Inside the hot cell another cell is positioned, defined as the measuring cell, smaller in size (height 1.6 m, width 2.2 m, depth 0.4 m). Moreover, the walls have a thickness of 0.1 m.

The sample tested is integrated in a suitable frame located between the hot cell and the cold cell.

The data obtained from the test are summarized as follows:

- Average speed of air on hot side 0.08 m/s

- Average speed of air on cold side 1.90 m/s

- Average temperature on hot side 20.10°C

- Average temperature on cold side 0.70°C

- Average temperature of sample on hot side 1 1.47°C

- Average temperature of sample on cold side 5.07°C

From the tests carried out with the heat-insulating device 10 according to the present invention, Applicant obtained a heat transmittance value of 3.3 W/m -K. The insulating glass unit used for the comparison having a similar configuration to the heat-insulating device 10, but with the sheets made of glass, after the same verifications gave a heat transmittance value of 2.9 W/m -K.

Applicant then verified that, in the experimental case examined, the difference between the two heat transmittance values is about 13% greater for the heat- insulating device 10, which in any case guarantees an absence of condensation in the hollow space 13 also for the heat-insulating device 10 itself, as in the case of traditional insulating glass units.

However, this difference can be modified and improved not only by varying the thickness of the sheet used and of the hollow space 13 but, given the same data, by inserting into the hollow space 13 the specific insulating gases already described.

Therefore, the transmittance value, although slightly higher for the heat- insulating device 10, and in any case totally acceptable in terms of heat performance, can be obtained with a product that weighs a lot less, at least half, if not more, depending on the type of glass it is compared with, than a traditional insulating glass unit with sheets of glass, and which is essentially exempt from brittle fracture deriving from the working to which it is subjected for production or installation, such as shaping or holing.

One can therefore deduce that improvements can be obtained in terms of heat transmittance guaranteeing the absence of condensation with adequate interruption of the heat bridge also with other geometric configuration, thickness of the sheets 1 1 and widths of the hollow space 13, or with the introduction of insulating gases, compared with traditional insulating glass units with homogeneous parameters of size.

Advantageously, moreover, as discussed above, forms of embodiment described here can provide to use the anti-scratch additives PDMS or derivatives thereof, which are incorporated in the PMMA material and emerge on the external surface of the cast sheet 1 1 of PMMA in the course of its production process, and not subsequently applied on the external surface, by means of films or varnishes, as in the state of the art. In fact, the cast sheet 1 1 of PMMA, in some variants, can have no coating, either varnishes or films, applied after the production of the cast sheet 1 1 of PMMA in question. Therefore we believe that the cast sheet 1 1 of PMMA including the anti-scratch additives described here supplies the desired resistance to scratches or incisions, thus allowing a production process with reduced costs and higher productivity, since additional operations to provide anti-scratch resistance to the cast sheet 1 1 of PMMA produced may not be necessary.

According to possible forms of embodiment, which can be combined with all the forms of embodiment described here, the polydimethylsiloxanes or derivatives thereof can be provided between 0.1% and 1% w/w with respect to the weight of the cast sheet 1 1 of PMMA, in particular between 0.2% and 0.9%, more in particular between 0.25% and 0.85%, even more in particular between 0.3% and 0.8% w/w.

According to possible forms of embodiment, which can be combined with all the forms of embodiment described here, the polydimethylsiloxanes or derivatives thereof are selected with a low molecular weight, less than or equal to 500, in particular less than or equal to 400, more in particular less than or equal to 350. Applicant has found that, during the polymerization process of the oligomer, these values of molecular weight allow an effective migration of the PDMS or derivatives thereof toward the external layers and the external surface of the PMMA material, since, thanks to their low molecular weight, they are not excessively hindered in this by the oligomer being polymerized. Examples of possible molecular weights of the PDMS and their derivatives are for example 450, 400, 380, 350, 340, 330, 320, 310, 300, 290, 280, 270, 260, 250.

According to possible forms of embodiment, which can be combined with all the forms of embodiment described here, it may be provided to use a single type of polydimethylsiloxane or a derivative thereof, or a plurality of types of polydimethylsiloxanes (PDMS) or derivatives thereof, for example a mixture of two, three or even more than three polydimethylsiloxanes or derivatives thereof.

The possible plurality of PDMS can also allow a balanced chemical compatibility - incompatibility, in order to obtain perfectly colorless sheets, perfectly transparent and clear.

According to possible forms of embodiment, which can be combined with all the forms of embodiment described here, the one or more anti-scratch additives selected among the PDMS or derivatives thereof are provided incorporated inside the PMMA and present externally, emerging on the external surface of the cast sheet 1 1 of PMMA.

According to possible forms of embodiment, which can be combined with all the forms of embodiment described here, the one or more anti-scratch additives selected among the PDMS or derivatives thereof are not only present externally, emerging on the external surface of the cast sheet 1 1 of PMMA, but also present, for example incorporated, in one or more external layers of the cast sheet 1 1 of PMMA. The external layers can be symmetrical external layers of the cast sheet 1 1 of PMMA, for example in the case of sheets, the external layers are planar symmetrical external layers provided on the two opposite sides or faces of the sheet.

For example, each of the external layers of the cast sheet 1 1 of PMMA in which the one or more anti-scratch additives are incorporated, selected among the PDMS or derivatives thereof, can have a thickness between 0.05 mm and 0.8 mm, in particular between 0.1 mm and 0.5 mm, more in particular between 0.1 mm and 0.3 mm, even more in particular between 0.15 mm and 0.25 mm. Examples of the thickness of the external layer in which the one or more PDMS or derivatives thereof are incorporated are: 0.15 mm, 0.2 mm, 0.25 mm. Examples of the overall thickness of the cast sheet 1 1 of PMMA, for example sheets, can go from 2 mm to 40 mm, for example 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 6 mm, 8 mm, 10 mm, 12 mm, 15 mm, 20 mm, 25 mm, 30 mm, 40 mm. For example, in the case of a 5 mm sheet, the thickness of each of the external layers can be about 0.25 mm.

According to possible forms of embodiment, which can be combined with all the forms of embodiment described here, at least 80% of the one or more anti- scratch additives selected among the PDMS or derivatives thereof present in the PMMA is provided in said external layers of the cast sheet 11 of PMMA and emerging on the external surface. In other words, only 20% or less of the PDMS or derivatives thereof present in the PMMA is contained in the innermost part of the cast sheet 1 1 of PMMA.

According to possible forms of embodiment, which can be combined with all the forms of embodiment described here, the PDMS or derivatives thereof are selected from a group consisting of: polyether polydimethylsiloxane, alkylmethyl trisiloxane and non-ionic polyoxyethylene polydimethylsiloxane.

In possible implementations, the PDMS or derivatives thereof are polyether polydimethylsiloxane and non-ionic polyoxyethylene polydimethylsiloxane. For example it may be provided to use a mixture of polyether polydimethylsiloxane and non-ionic polyoxyethylene polydimethylsiloxane, in particular for example with polyether polydimethylsiloxane from 15% to 25% w/w and non-ionic polyoxyethylene polydimethylsiloxane from 75% to 85% w/w, with the provision that the sum is 100% w/w. An example composition of the mixture can be 20% w/w polyether polydimethylsiloxane and 80% w/w non-ionic polyoxyethylene polydimethylsiloxane.

According to possible forms of embodiment, which can be combined with all the forms of embodiment described here, the PMMA of the sheet 1 1 can also comprise a synergic additive with anti-scratch effect. According to possible forms of embodiment, the synergic additive with anti-scratch effect can be comprised between 0.01% and 0.15% w/w with respect to the weight of the sheet 1 1, in particular between 0.02% and 0.12% w/w, more in particular between 0.04% and 0.1% w/w. In the case of the synergic additive with anti-scratch effect too, it may be provided that it is incorporated to a large extent, that is, for example at least 80%, in the external layers of the sheet 1 1 and emerging on the external surface thereof, as discussed above for the PDMS or derivatives thereof. According to a possible implementation, the synergic additive with anti-scratch effect can be siloxane copolyester.

In possible forms of embodiment, which can be combined with all the forms of embodiment described here, to make the cast sheets 1 1 of PMMA for example, a mixture of pre-polymer or casting resin (known in jargon as "syrup"), which already contains the anti-scratch compounds described above, that is, the PDMS or derivatives thereof, and possibly also the synergic additive with anti-scratch effect, can be cast in a mold, which can be immersed in water, generally in order to control the exothermicity of the polymerization during solidification. This last operation can provide for example to cast the pre-polymer resin in a mold in water at a temperature that can be 60°C, for example for a thickness of 5 mm. The forming mold can usually consist of sheets of glass separated by a polymer gasket, for example PVC, which defines the thickness of the final sheet. The pre- polymer mixture can be cast in the mold then immersed in the hot water at 60°C, for a thickness of 5 mm, or gradually lower as the thicknesses increase, and polymerization is completed. The mixture can be cast in a vertical or horizontal mold.

Advantageously, the PDMS or derivatives thereof, and possibly also the synergic additive with anti-scratch effect, are selected according to the present description so as to be incompatible with the oligomer being polymerized. The presence of the PDMS or derivatives thereof and possibly also the synergic additive with anti-scratch effect, incompatible with the oligomer being polymerized, causes the material that is polymerized to tend to expel the incompatible compounds, which are therefore obliged to migrate forcedly toward the external surface, that is, they emerge on the surface in great quantities. This migration, as we said, can be promoted by the low molecular weight of the PDMS or derivatives thereof, which therefore are not impeded by the oligomer being polymerized, as discussed above.

The PDMS or derivatives thereof, and possibly also the synergic additive with anti-scratch effect, therefore, suitably selected, can bring the desired surface modifications, to increase the anti-scratch properties of the final PMMA. The PDMS or derivatives thereof, and possibly also the synergic additive with anti- scratch effect, can offer an optimum compromise in terms of surface emergence, since they migrate sufficiently to improve the anti-scratch properties of the surface, but do not have surface tensions and incompatibilities such as to create surface defects in the PMMA. Furthermore, the fact that it is possible to direct all or almost all the quantity of the PDMS or derivatives thereof, and possibly also the synergic additive with anti-scratch effect, toward the surface, allows to optimize the quantity that is used of said compounds, reducing it to the minimum necessary. Consequently, the use of the PDMS or derivatives thereof, and possibly also the synergic additive with anti-scratch effect, does not damage, for example, the clarity and transparency of the final PMMA, which thus has the exceptional optical properties that characterize it, together with the anti-scratch properties that it acquires thanks to the PDMS or derivatives thereof, and possibly also the synergic additive with anti-scratch effect. In particular, Applicant has observed a symmetrical behavior in the migration of the PDMS or derivatives thereof, and possibly also the synergic additive with anti-scratch effect, toward the external surface of the PMMA being polymerized, where they emerge. In this way, the outermost layers and the external surface of the PMMA material, for example in sheets, are affected by and incorporate a large part of said compounds or anti-scratch additives, as we said, for example at least 80%. From experiments carried out, Applicant has verified that the migration of the anti-scratch additives toward the outside is symmetrical with respect to the bulk of the material; in particular, in the sheets there is a symmetrical migration toward the two opposite faces of the sheet of PMMA. It is therefore possible to identify a diagram with a symmetrical increasing gradient of the presence of said compounds from the inside, in particular from the center of the sheet 1 1 toward the external sides.

The cast sheet 1 1 of PMMA therefore has good anti-scratch properties and a lower economic cost compared with similar articles in PMMA with known anti- scratch coatings, since the anti-scratch property is obtained directly in the course of the polymerization and thermoforming using a mold in water, and not in a subsequent coating operation with anti-scratch films or varnishes, thus considerably saving on the work cycle and the double working.

Furthermore, if the cast sheet 11 of PMMA is transparent, its clarity is high and not at all worsened by the use of the anti-scratch compounds as cited, since the quantity thereof is optimized and used efficiently. Applicant has found that, the smaller the quantity of anti-scratch additives used, the smaller is their impact on the optical properties of the PMMA. Since most of the anti-scratch additives are present in the outermost layers of the cast sheet 1 1 of PMMA and emerging on the external surface, that is, in the regions that are subject to scratching, incisions or similar mechanical stresses and in which the presence of the anti- scratch compounds is more needed, the anti-scratch additives are used in the most efficient way possible, preventing an excessive part of them from remaining incorporated in the bulk of the PMMA material.

It is therefore possible to use minimum quantities of PDMS or derivatives thereof, and possibly the synergic additive with anti-scratch effect, needed for resistance to scratches and that do not have a negative impact on the optical properties (for example clarity and transparency) of the PMMA: in fact, this guarantees that, thanks to the migration effect due to the incompatibility with the acrylic resin in the course of polymerization, these quantities are localized where they are most required, that is, in the outermost layers of the cast sheet 1 1 of PMMA and emerging onto the external surface.

The emergence of the anti-scratch additives is therefore promoted by the present invention, both in terms of choice of the PDMS or derivatives thereof, incompatible with the casting resin in the course of polymerization, and also advantageously in terms of low molecular weight. The choice of the PDMS or derivatives thereof is particularly advantageous because the phenomenon of migration and emergence is therefore balanced and does not cause problems of final quality because it does not produce surface defects, such as hollows and macro/micro irregularities of the PMMA material, which furthermore would also have a negative influence on the transparency.

It is clear that modifications and/or additions of parts may be made to the heat- insulating device as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of heat-insulating device, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claims

1. Heat- insulating device comprising at least two sheets (1 1) of polymethyl methacrylate comprising one or more anti-scratch additives selected from among polydimethylsiloxanes or derivatives thereof, said two sheets (1 1) being distanced by at least an intermediate support frame (12) to define, between said sheets (1 1), at least a heat-insulating hollow space (13), sealed with respect to the outside by one or more packing elements (15, 16).

2. Device as in claim 1, characterized in that said one or more polydimethylsiloxanes or derivatives thereof are selected from a group consisting of: poly ether polydimethylsiloxane, alkylmethyl trisiloxane, non-ionic polyoxyethylene polydimethylsiloxane.

3. Device as in claim 1 or 2, characterized in that said one or more polydimethylsiloxanes or derivatives thereof are provided between 0.1% and 1% w/w with respect to the weight of each sheet (1 1).

4. Device as in claim 1, 2 or 3, characterized in that said one or more polydimethylsiloxanes or derivatives thereof are selected with a molecular weight less than or equal to 500.

5. Device as in any claim hereinbefore, characterized in that said polymer material has a density less than 1.3 g/cm .

6. Device as in any claim hereinbefore, characterized in that said polymer material has a luminous transmission higher than 85% and a refraction index less than 1.6.

7. Device as in any claim hereinbefore, characterized in that said polymer material is selected from the group of optical polymers.

8. Device as in any claim hereinbefore, characterized in that said polymer material comprises additives to modify mechanical properties of said polymer material.

9. Device as in any claim hereinbefore, characterized in that said sheets (1 1) comprise an external anti-scratch covering layer.

10. Device as in any claim hereinbefore, characterized in that said sheets (1 1) are transparent.

1 1. Device as in any claim hereinbefore, characterized in that said sheets (1 1) at least partly transmit ultraviolet radiation.

12. Device as in any claim hereinbefore, characterized in that said hollow space (13) is filled with a gas with a heat conductivity less than 0.025 W/(m-K).

13. Device as in any claim hereinbefore, characterized in that said one or more packing elements (15, 16) stably connect said sheets (1 1) to said frame (12).

14. Heat-insulating panel comprising a heat-insulating device (10) as in any claim from 1 to 13.

15. Element of a door or window comprising a heat-insulating device (10) as in any claim hereinbefore.

16. Refrigeration apparatus comprising a heat-insulating device (10) as in any claim from 1 to 13.

17. Furnishing element comprising a heat-insulating device (10) as in any claim from 1 to 13.

18. Method to make a heat-insulating device, said method comprising:

- making available at least two polymethyl methacrylate sheets (1 1) comprising one or more anti-scratch additives selected from among polydimethylsiloxanes or derivatives thereof;

- disposing said two sheets (1 1) distanced by at least an intermediate support frame (12) to define, between said sheets (1 1), at least a heat-insulating hollow space (13), sealed with respect to the outside by one or more packing elements (15, 16).

19. Method as in claim 18, characterized in that said one or more polydimethylsiloxanes or derivatives thereof are selected from a group consisting of: polyether polydimethylsiloxane, alkylmethyl trisiloxane, non-ionic poly oxy ethylene polydimethylsiloxane.

20. Method as in claim 18 or 19, characterized in that said one or more polydimethylsiloxanes or derivatives thereof are provided between 0.1% and 1% w/w with respect to the overall weight of each sheet (1 1).

21. Method as in claim 18, 19 or 20, characterized in that said one or more polydimethylsiloxanes or derivatives thereof are selected with a molecular weight less than or equal to 500.