WO2004017679A2

WO2004017679A2 - Heating sheets with resistor automatically temperature-controlled by positive temperature coefficient (ptc) effect and uses thereof

Info

Publication number: WO2004017679A2
Application number: PCT/FR2003/002498
Authority: WO
Inventors: Henri-Jean Caupin; Alexander Korzhenko; Robert Sharpe Hill
Original assignee: Arkema
Priority date: 2002-08-13
Filing date: 2003-08-08
Publication date: 2004-02-26
Also published as: AU2003274238A1; AU2003274238A8; FR2843674A1; WO2004017679A3

Abstract

The invention concerns a heating sheet comprising at least a conductive polymer layer with resistor automatically temperature-controlled by PTC effect placed between at least two electrically conductive surfaces and its use in building and construction, undersea energy transport, human and animal health care, food industry or process control industry.

Description

HEATED SHEETS WITH RESISTANCE SELF-CONTROLLED BY THE

TEMPERATURE BY PTC EFFECT AND THEIR APPLICATIONS

Field of the invention

The subject of the present invention is heating sheets comprising polymers with resistance which are self-controlled by temperature, their use, as well as the materials for domestic or industrial use which incorporate them and in particular the materials used in the fields of construction and building, energy transport on the seabed, human or animal health, the food industry or the process control industry.

Prior art and technical problem

The known electric heating means suppose the installation of temperature measurement systems to limit the energy contributions as a function of the temperature levels reached in such or such place of the considered set. When the systems in question are heterogeneous, which is most often the case, it is quickly impossible to locate practically the zones where to put the so-called measurement systems intended to give instructions to the electric power supply stations.

Electrical heating cord materials have been known in the industry for a very long time, but they present certain difficulties of installation, of electrical connections, of insertion into floor systems, ceilings, tubes. The heat transfer coefficients are very low, and any failure is very costly to repair.

In the prior art there are numerous documents which describe the implementation of the heating techniques permitted by PTC effect ceramics, and certain plastic polymers in the molten state. The basic principle is that the temperature of any set can be guaranteed without permanent measurement, and this reversibly according to a large number of hot and cold cycles. 5 According to this principle, the devices of the prior art are used for various applications such as:

• instant water heating without the need for storage,

• guarantee of non-condensation of areas or electrical boxes where products must remain dry,

[0 • controlled odor emissions by varying the temperature of the tanks containing said odors,

• anti-fog heaters on mirrors,

• glue guns,

• electric blanket,

15 • heating of food or hot plates or heating tanks for liquids at variable levels in the case of cups drunk gradually with risk of cooling or overheating in the event of lack of PTC performance, 0 • temperature recording by PTC effect, or permanent de-icing of satellite dishes and various external antennas.

In US patent 5,714,096, original compositions or formulations are described such as polypropylene 5 modified by maleic grafts with the use of a solvent and of conductive carbon to modify the temperatures of PTC switc and their implementation for manufacturing conductive pastes for low cost car mirror heaters.

Controlled heating where it is difficult to put and read thermometers has been described in US Patent 6,121,585 with a PTC polymer deposited on a support for an arrangement of heating surfaces intended to keep warm cups of beverages. automobile.

In US patents G.084.206 and 6.373.028 there are described 5 conductive meshes placed on either side of a layer of PTC effect elements. These are integrated in electric blankets comprising multiple layers of different materials. A layer of thermally conductive silicone has regularly distributed holes. The discrete elements of PTC ceramic material are inserted into the holes provided for this purpose. These heating blankets, by their structure composed of multiple layers of different superimposed materials and comprising discrete PTC effect elements which it is necessary to adjust separately in order to be integrated into the heating blanket, are difficult and complicated to manufacture. In addition, their structure does not allow them to design or prepare heating materials with adjustable shapes and powers as needed.

There is therefore a need to have energy supply systems in the form of heating sheets such that their shape and their electrical performance is adaptable to the material to be heated under, on or in which the sheet will be incorporated and which is inexpensive and easier to manufacture than the systems of the prior art.

Summary of the invention

The subject of the invention is heating pads of the type

(A) comprising at least one layer of conductive polymer with resistance self-controlled by temperature by PTC effect placed between at least two electrically conductive surfaces.

According to a first embodiment, the heating sheet of type (ai) consists of a continuous layer of conductive polymer with resistance self-controlled by temperature by PTC effect, placed between two electrically conductive surfaces. According to a second embodiment, the heating sheet of type (a ₂ ) consists of a continuous layer of conductive polymer with resistance self-controlled by temperature by PTC effect placed between two continuous electrically conductive surfaces, in which the assembly formed by the continuous layer of PTC effect conductive polymer and the two electrically conductive continuous surfaces have perforations. According to another embodiment, the heating sheet comprises several contiguous strips formed for each of them of a layer of conductive polymer with PTC effect either continuous and homogeneous or meshed, connected to two electrical conductors located at the ends of said layer.

In the various embodiments of the heating sheets with a continuous, perforated or mesh structure described above, the density of conductive polymer is between 0.01 and 5 Kg / m ² . We prefer for continuous or perforated layers a density of conductive polymer between 1 and 5 Kg / m ² and for the mesh layers a density between 10 and 500 g / m ² .

According to a preferred embodiment, the resulting heating sheets are inserted into an electrically insulating and thermal conductive system in order to be adapted to the intended implementations.

The invention also relates to a single or multi-layer heating structure comprising at least one heating sheet according to the invention.

The invention also relates to the use of a heating mat or structure according to the invention in the fields of construction and building, energy transport in the seabed, human or animal health, industry food or process control industry.

The invention also provides heating materials for household use or for industrial use comprising a heating mat or structure according to the invention, in particular heating systems of the pipe or instantaneous hot plate heat exchanger type.

The invention also provides heating materials for the construction of buildings for floors, walls, ceilings, or under layer of carpet comprising at least one layer or heating structure according to the invention. The invention also provides heating systems comprising at least one heating mat or structure according to the invention.

The invention also relates to the use for the suppression of contamination by pathogenic agents by heating, of at least one heating mat or structure according to the invention.

Within the framework of all the applications cited above, it is also possible to use heating sheets of type (b) comprising at least one layer of conductive polymer with resistance self-controlled by temperature by PTC effect placed between two electrical conductors.

The heating sheet of type (b) more precisely comprises a layer of conductive polymer in the form of a continuous and homogeneous layer or a layer of conductive polymer in the form of a mesh, connected to two electrical conductors situated at the ends of said layer.

According to a preferred embodiment, the conductive polymer forming the layer placed between the two electrical conductors in said heating sheet of type (b) is distributed with a density of between 0.01 and 5 Kg / m ² .

When the conductive polymer forms a continuous layer placed between the two electrical conductors, distribution with a density of between 1 and 5 Kg / m ² is preferred.

When the conductive polymer forms a mesh layer placed between the two electrical conductors, a distribution with a density of between 10 and 500 g / m ² is preferred.

The invention also relates to the use for the suppression of contamination by pathogenic agents by heating a heating sheet of type (b) possibly covered by an electrically insulating and thermally conductive polymer as well as to the use for the suppression contamination by pathogens by heating a single or multi-layer heating structure comprising at least one heating sheet of type (b). Detailed description of the invention

The subject of the invention is a heating sheet of type (a) comprising at least one layer of conductive polymer with resistance self-controlled by temperature by PTC effect placed between at least two electrically conductive surfaces. This layer is adjustable in temperature, power, voltage, heating kinetics and number of stability cycles.

According to a first embodiment, the heating sheet of type (ai) consists of a continuous layer of conductive polymer with resistance self-controlled by temperature by PTC effect, placed between two electrically conductive surfaces. These layers make it possible to generate high powers, for example from 2000 to 100,000 W / m ² with an inertia of a few seconds.

The continuous and homogeneous layer of conductive polymer consists of a block having been melted of PTC material, the compositions of which come from the family of thermoplastics described in patent EP 1,205,514. The electrically conductive surfaces which are also in the form of continuous and homogeneous layers consist of any electrically conductive material or of material allowing the passage of electric conductor, for example plastic plates, the thickness of which varies according to the rigidity. necessary to enclose the molten PTC conductor block.

According to a particular embodiment, the plies with continuous structure of type (a _x ) have current supply conductors spaced apart by the thickness of the PTC thermoplastic material, ie from 0.5 to 2 mm, depending on the evacuation capacities of the energies brought. The network of electrical conductors is preferably integrated in the form of waterproof modules.

According to a second embodiment, the heating sheet of type (a ₂ ) consists of a continuous layer of conductive polymer with resistance self-controlled by temperature by PTC effect placed between two electrically conductive surfaces in which the assembly formed by the layer continuous conductive polymer with PTC effect and the two continuous electrically conductive surfaces have perforations.

According to another embodiment, the heating mat comprises a layer of conductive polymer with resistance self-controlled by temperature by PTC effect placed between 2 electrically conductive surfaces, the surfaces having mesh structures.

According to another embodiment, the heating sheet comprises several contiguous strips formed for each of them of a continuous and homogeneous layer or else a mesh of conductive polymer with PTC effect, connected to two electrical conductors situated at the ends of said layer.

In the case of this sheet made up of several adjoining strips as described above, possibly contiguous, a heating sheet is obtained made up of a network of conductive lines regularly spaced by the continuous or meshed layer of conductive polymer. This network includes lines for supplying the current of variable geometry according to the system studied, for example in the form of a comb, of lines or networks according to the shape of the heated elements. These current lines are then supplied as a function of the powers desired in the various planned applications.

According to another embodiment, the heating sheet consists of a conductive mesh structure: it comprises a layer of conductive polymer which is in the form of a mesh structure and the electrically conductive surfaces are in the form of a network regularly spaced conductive lines distributed over the surface of the mesh.

The meshes consist of any support such as textiles or glass fibers; these supports have meshes of sizes chosen in an appropriate manner according to the intended uses and are impregnated on a regular basis with the thermoplastic PTC substances, the compositions of which come from the family of thermoplastics described in patent EP 1,205,514. The network of conductive lines is made of any electrically conductive material which brings electrical energy to the heating network. It can for example include a metal such as iron, aluminum, copper, nickel, brass and their alloys. The webs with a mesh structure are generally in the form of rolls of adjustable length from 5 to 200 meters or more, and 50 meters in length more conveniently, with variable widths according to the needs of the installations, and conveniently around 1 meter wide in the case of the building. The conductors in the webs with a mesh structure are spaced about 0.05 meters apart, which makes it possible to adjust the powers emitted by making use of variable external connections: space the conductors to reduce the power per m ² , and bring the conductors closer to increase the power per m ² .

According to a particular embodiment and in the case of low powers required for example from 30 to 1500 W / m ² and 15 minutes of inertia, the spacing of current conductors in the meshes of the plies with a mesh structure have dimensions comprised 5 and 50 cm.

The sheets according to the invention can be adapted to all forms of heating materials. In addition, depending on the desired performance, with the plies having a continuous or perforated structure obtained according to the embodiments described above, very reactive systems are obtained which rise to more than 100 ° C. in a few seconds and with powers of more than 100,000 watt / m ² in some cases, depending on the different PTC effect compositions used and placed between the two conductive surfaces.

With the plies with a mesh structure obtained according to the embodiments described above and in particular with the plies made up of adjoining strips, it is possible to manage inputs of powers ranging from 30 to 5000 W / m ² , with higher inertias which are count in minutes, and average temperatures, below 70 ° / 80 ° C, varying the distances between the conductive lines to the current supply and the closer the lines, the higher the power.

The current supplies are made for example with conductors spaced from 0.5 mm to 50 cm depending on the voltages, temperatures and powers desired.

These energy supply systems in PTC effect sheets supported have the advantage of simplifying and diversifying the methods of electrical connection, while remaining reliable even in the event of mechanical damage to surfaces. In these types of tablecloths, the variations in voltage also make it possible to modify the powers supplied and the equilibrium temperatures.

This possibility of heating zones of all dimensions in sheets, in a homogeneous manner, makes it possible to simplify the installation of the heating elements in the most varied industrial and domestic situations. With very different voltages (2.5 to 440 volts), for powers ranging from 30 to 10,000 watts, see from 30 to 100,000 watts per m ² and more, equilibrium temperatures ranging from 0 ° C to 120 or 150 ° C or more, an unlimited range of use of conductive polymer compositions at controlled temperatures is thus defined.

In the various embodiments, the heating coats with a continuous, perforated or mesh structure described above are dosed, according to the desired heating power, with a density of between 0.01 and 5 Kg / m ² , or else of 1 at 5 Kg / m ² , or even from 10 to 500 g / m ² of active substances (conductive polymer with PTC effect) distributed between the continuous surfaces or on the mesh support ensuring the mechanical stability and the operating time.

We prefer for continuous or perforated layers a density of conductive polymer between 1 and 5 Kg / m ² and for the mesh layers a density between 10 and 500 g / m ² .

Depending on the subsequent uses of the heating pads described above, these can be advantageously covered with an electrically insulating but thermally conductive polymer in order to ensure heat transfers while securing the implementation in a conductive medium at more than 42V. This electrically insulating and thermally conductive layer comprises for example aluminum type powders embedded in PMMA type polymer matrices or any other insulating coating system.

The layer of conductive polymer with self-controlled temperature resistance comprises in particular a polymeric composite material made conductive by incorporation of conductive corpuscles of various shapes and origins in a polymer matrix. The application of sufficient voltage leads to heating by the Joule effect. In the absence of a circuit breaker mechanism, the temperature would increase until the material melts or is destroyed. The polymeric PTC composite materials used show an increase in resistance as a function of temperature (PTC effect or "Positive Temperature Coefficient"), so that the intensity stabilizes at an equilibrium temperature.

This PTC effect therefore allows thermal regulation of the current intensity, it has many advantages compared to traditional resistors:

• Regulation of electric heating systems is conventionally obtained by including a thermal circuit breaker in the circuit. In the event of a fault in the latter, the circuit or the safety fuse is blown. The PTC material self-regulates without the need to include a circuit breaker or fuse.

• The PTC heating system presents a lower risk of combustion and short circuit.

• The PTC effect generates electrical energy inputs in moderate temperature zones, which has 2 benefits compared to traditional thermal resistance systems: • The specifications imposed on insulating materials must be less strict;

• The heat can be supplied over a larger area. “The composite material can be transformed by the methods used in the plastics industry (co-extrusion, molding, etc.). It can also be applied as a paint on insulating substrates of any geometry or impregnation baths of the support meshes in the case of a web with a mesh structure.

Several types of composite polymer systems can be used which exhibit the PTC effect.

According to a first type of system, the PTC effect is based on the phenomenon of the expansion of polymer crystals disturbing the network of the conductive charge. The resistance of the composite slowly decreases as the amount of carbon black in a semi-crystalline polymer matrix is increased, to a concentration where the resistance drops. The latter represents a geometric transition called the percolation threshold. It has been found that the maximum of the PTC effect corresponds to a critical concentration which is in the vicinity of the percolation threshold. When the temperature of the material approaches the melting of the matrix, an expansion of the crystalline zone triggers the PTC effect. However, a high energy of the carbon black particles and a low shear modulus of the matrix cause a drop in resistance, known as the NTC (Negative Temperature Coefficient) effect. This first type is described in the following references (CA denotes the Chemical Abstracts): 131: 243891 CA

TI Organic PTC thermistor materials with high transitive temperature AU Yang, Fubiao; Li, Yongqin; Li, Xiaojun CS Department 5, National University of Defense Technology, Changsha, 410073, Peop. Rep. China SO Gongneng Cailiao (1998), 29 (Suppl.), 724-725 CODEN: GOCAEA; ISSN: 1001-9731 PB Gongneng Cailiao Bianjibu

129: 331461 CA

TI Effect of thermal treatment on crystallization and PTC properties of conductive PVDF / CB composite AU Wang, Jikui;

Wang, Gengchao; Zhang, Bingyu; Fang, Bin; Zhang, Zhiping CS

Inst. Mater. Sci. Eng., East China Univ. Sci. Technol. ,

Shanghai, 200237, Peop. Rep. China SO Gaofenzi Cailiao Kexue

Yu Gongcheng (1998), 14 (5), 93-95 CODEN: GC KGEI; ISSN: 1000- 7555 PB "Gaofenzi Cailiao Kexue Yu Gongcheng" Bianjibu

125: 277325 CA

TI Influences of crystallization historiés on PTC / NTC effects of PVDF / CB composites AU Zhang, Mingyin; Jia, Wentao;

Chen, Xinfang CS Dep. Materials Science, Jilin Univ., Changchun, 130023, Peop. Rep. China SO J. Appl. Polym. Sci.

(1996), 62 (5), 743-747 CODEN: JAPNAB; ISSN: 0021-8995

104: 121274 CA

TI Heaters IN Shibata, Tsuneo; Nishida, Takeo; Terakado, Masayuki; Nitta, Isao PA Matsushita Electric Industrial Co. , Ltd., Japan SO Jpn. Tokkyo Koho, 5 pp. CODEN: JAXXAD

According to a second type of system, the PTC effect is based on the presence of two immiscible polymers. Among such materials, the PVDF / HDPE systems loaded with carbon black are the best known. The PVDF and HDPE phases are immiscible, so the PTC effect in this case depends very much on the morphology and the distribution of carbon black between these two phases. The carbon black is preferably dispersed in the HDPE phase which becomes the conductive phase. If the PVDF is in good balance compared to the HDPE, the PVDF phase forms a particular structure favorable for the PTC effect. A singular distribution of the conductive PE phase in the PVDF phase is the condition for counteracting the NTC effect which occurs at the melting of HDPE which is less than that of PVDF.

This second type is described in the following references: 131: 287163 CA TI Carbon black-filled immiscible blends of poly (vinylidene fluoride) and high density polyethylenè: the relationship between morphology and positive and negative temperature coefficient effects AU Feng, Jiyun; Chan, Chi-Ming

CS Department of Chemical Engineering Advanced Engineering Materials Facility, The Hong Kong University of Science and Technology, Kowloon, Hong Kong

SO Polym. Eng. Sci. (1999), 39 (7), 1207-1215 CODEN: PYESAZ; ISSN: 0032-3888 PB Society of Plastics Engineers

130: 96227 CA

TI Carbon black-filled immiscible blends of poly (vinylidene fluoride) and high density polyethylenè: electrical properties and morphology AU Feng, Jeng; Chan, Chi-Ming

CS Dep. of Chemical Engineering, Advanced Engineering Materials Facility, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SO Polym. Eng. Sci. (1998), 38 (10), 1649-1657

CODEN: PYESAZ; ISSN: 0032-3888 PB Society of Plastics Engineers

130: 52964 CA

TI Carbon black-filled immiscible blend of poly (vinylidene fluoride) and high-density polyethylenè: electrical properties and morphology

AU Feng, Jiyun; Chan, Chi-Ming CS Department of Chemical Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SO Annu. Tech. Conf. - Soc. Plast. Eng. (1998), 56 ^th (Vol. 2), 2476-2480

CODEN: ACPED4; ISSN: 0272-5223 PB Society of Plastics Engineers and finally patent application WO 9805503

Advantageously, compositions with a PTC effect containing fluorinated polymers can be used, for example those disclosed in application EP-A-1,205,514 (to which it is referred for the description of the polymer blends in question) which describes compositions based on PVDF polymers combined with liquid solvents and compatible diluents or compositions containing polymers PMMA in suspension and mixed well dispersed with suitable conductive particles.

Composite materials will be preferred comprising by weight, the total being 100%: A) 40 to 90% of PVDF homopolymer or copolymer crystallized essentially in beta form,

B) 10 to 60% of a conductive charge,

C) 0 to 40% of a crystalline or semi-crystalline polymer,

D) 0 to 40% of a charge different from C, and such that the beta-shaped crystals are nucleated on the surface of the particles of the conductive charge.

Compound A will be chosen from copolymers of VF2 and VF3 having at least 60 mol% of VF2, the copolymers of

VF2, TFE and HFP having at least 15 mol% of TFE units and advantageously the VF2-TFE-HFP copolymers of respective molar composition 60 to 80/15 to 20/0 to 25.

Compound C will be chosen from a homopolymer PVDF which is not in beta form and the VF2-HFP copolymers containing at least 85% of VF2.

One can also use the compositions comprising, by weight, the total being 100%:

A) 40 to 80% (advantageously 50 to 80%) of PVDF,

B) 10 to 40% of PMMA, C) 10 to 40% of a conductive filler.

The above composition is dissolved in a solvent and then spread on a substrate and the solvent evaporated. The metal terminals for connection to the electrical circuit can be placed at the ends of the coating before or after application.

With regard to PVDF, the copolymers of VDF, TFE and HFP having at least 15% by moles of units are thus designated. TFE and advantageously the VDF-TFE-HFP copolymers of respective molar composition 60 to 80/15 to 20/0 to 25 (the total being 100).

Mention may also be made of vinylidene fluoride (VDF) copolymers preferably containing at least 60% by weight of VDF, the copolymer being chosen from chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoroethylene (VF3) and tetrafluoroethylene (TFE). Advantageously, the proportion of VDF is at least 75% and preferably at least 85%. Among these comonomers, HFP is preferred.

Advantageously, the PVDF (A) is a mixture of (Al) chosen from homopolymer PVDFs and VDF-HFP copolymers containing at least 85% by weight of HFP and (A2) which are the copolymers of VDF, TFE and the HFP having at least 15 mol% of TFE units and advantageously the VDF-TFE-HFP copolymers of respective molar composition 60 to 80/15 to 20/0 to 25 (the total being 100). The proportions of (A1) and (A2) can be in the ratio (A1) / (A2) between 20/80 and 20/80 by weight. The PVDF can be modified in whole or in part, that is to say that functions are introduced there, the aim is to facilitate the attachment of the paint to the substrate. Advantageously, the modified PVDF is chosen from: PVDF grafted with an unsaturated monomer, the grafting being carried out by irradiation in the absence of oxygen from a mixture, PVDF irradiated in the presence of oxygen (also designated by oxidized PVDF 1) , dehydrofluorinated and then oxidized PVDFs (also designated by oxidized PVDFs 2).

With regard to PMMA, homopolymers of methyl methacrylate and copolymers containing at least 50% by weight of methyl methacrylate are thus designated.

PMMA can contain an acrylic elastomer.

As regards the conductive filler (C), it can be chosen from all powders of electrically conductive materials and advantageously powdered metals, carbon black, graphite and metal oxides.

Advantageously (C) is chosen from carbon black (in preferably pH 2 to 7) and graphite. Advantageously, the graphite (natural or synthetic) is in the form of platelets. Preferably, its particle size is between 5 and 50 μm.

It is also possible to use a composition with PTC effect comprising, by weight, the total being 100%:

A) 40 to 80% of PVDF,

B) 0 to 40% (advantageously 10 to 40%) of an acrylic or styrenic polymer, C) 0 to 40% of an epoxy resin,

D) 0 to 60% of at least one metal oxide,

E) 0 to 25% graphite,

D + E worth at least 10% and advantageously B + C worth at least 10%. (B) can be a mixture of different acrylic and / or styrenic polymers.

Mention may also be made of vinylidene fluoride (VDF) copolymers preferably containing at least 60% by weight of VDF, the copolymer being chosen from chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoroethylene (VF3) and tetrafluoroethylene (TFE).

Advantageously, the proportion of VDF is at least 75% and preferably at least 85%. Among these comonomers we prefer

1 'HFP. Advantageously, the PVDF (A) is chosen from homopolymer PVDFs and VDF-HFP copolymers containing at least

85% by weight of HFP.

The PVDF can be modified in whole or in part, that is to say that functions are introduced therein, the aim is to facilitate the attachment of the composition to a substrate or the attachment of the electrodes to the composition. Advantageously, the modified PVDF is chosen from: PVDF grafted with an unsaturated monomer, the grafting being carried out by irradiation in the absence of oxygen from a mixture, PVDF irradiated in the presence of oxygen (also designated by oxidized PVDF 1) , dehydrofluorinated and then oxidized PVDFs (also known as oxidized PVDFs 2).

As another example of an acrylic polymer (B), mention may be made of block copolymers having at least one block consisting of PMMA within the meaning of the preceding PMMA paragraph, that is to say that this block contains by weight at least 50% of methacrylate. methyl. Among these polymers, mention may be made of triblocks consisting of a poly (butyl acrylate) block between two PMMA blocks. Mention may also be made of the SBM triblocks in which: each block is linked to the other by means of a covalent bond or to an intermediate molecule linked to one of the blocks by a covalent bond and to the other block by a other covalent bond, block M consists of MMA monomers optionally copolymerized with other monomers and comprises at least 50% by weight of methyl methacrylate (MMA), block B is incompatible with PVDF and with block M, block S is incompatible with block B and block M and its Tg or its melting temperature Tf is higher than the Tg of B. As regards the styrene polymers (B) of the composition with PTC effect, mention may be made as d 'example the copolymers with linear or star SBS blocks possibly hydrogenated (they are then designated by S-EB-S). S-B-S triblocks are described in ULLMANN'S encyclopedia of industrial chemistry Vol A 26, pages 655 - 659.

As regards the epoxy resin (C), this means any organic compound having at least two functions of the oxirane type, polymerizable by ring opening. The term "epoxy resins" designates all the usual epoxy resins which are liquid at room temperature (23 ° C.) or at a higher temperature.

As regards the metal oxide (D), mention may be made, for example, of tin and antimony oxides.

As regards graphite (E), advantageously the graphite (natural or synthetic) is in the form of platelets. According to one embodiment, the fact of having latexes with dispersed particles allows their implementation between two conductive surfaces, by soaking, impregnation, drying or extrusion on different continuous supports, or on threads of different natures according to the media. chosen, the desired energy supply densities and the foreseeable mechanical stresses. The supports or the wires can be made of any material whose melting points are in particular greater than 220 ° C. to allow the resistance to heat treatment at 180 ° C. for 30 minutes and for example, either polyester or polyamide 6 or polyamide 6.6.

Once the desired type of performance has been identified, the products with self-controlled temperature resistance (PTC) available can be used according to the following choice parameters:

• Voltage from 9 to 440 v.

• Power density from 30 to 15,000 or 100,000 w / m. • Temperatures from + 2 ° C to +150 ° C or more depending on the polymer compositions used.

• Longevity adapted to situations according to the formulas.

• Frequency of hot / cold changes.

• Temperature rise speed. • Regulation mode around the set point.

• Economic limits and surface criteria.

According to another object, the invention relates to single or multi-layer structures for insulation and / or protection, for example from corrosion, comprising the heating layers described above.

By monolayer heating structures is meant the integration of the heating mat with a perforated or mesh structure in a single thickness of insulating material, for example concrete slabs or acrylic floor plates, plasterboard, polymer plates, etc. In this case, the empty spaces formed by the meshes or the perforations allow the complete integration of the heating elements in the insulation and / or corrosion protection structures. By multilayer heating structures means the insertion of the heating mat between different layers of identical or different materials having insulating and / or protective properties, for example corrosion.

The subject of the invention is also the heating materials produced from such heating layers.

In particular, it is possible to use the heating sheets with a continuous structure covered with an electrically insulating but thermally conductive polymer, to produce an instant hot plate exchanger which is lighter and more compact than current systems which limit the installations to sites thereof. dispersed but under strong technical control.

This instantaneous heating plate exchanger is designed according to the known model in aluminum or steel, or any other metal or plastic. The corresponding modules are produced here in PMMA sheets or other plastic binder system loaded with aluminum powder with well distributed particle sizes and already used to make rapid molds for limited series. In doing so, the plates which surround the PTC elements are made electrically insulating, while having very good properties of thermal conductivity desired, with 1 to 5 mm thickness instead of the 20 mm imposed for the moment by the heating elements. at 800 ° C and the problems associated with reducing these temperatures to less than 100 ° C without loss of tightness and without deformation of the metal plates. The elements obtained are much more compact than the models known to date for the same service.

The applications of these heating materials are now specified in all known human and industrial fields with the establishment, on a case-by-case basis, of the most effective PTC-effect polymer compositions. The studied systems of self-limited energy supplies in groundwater can cover the following activities;

• buildings heated in frost-free to + 2 ° C on the ground, or to 15 ° C for a first heating on the ground or on the walls, or the sheets on the ceiling around 40 ° C according to the limits imposed by the stability of the materials , polymers ...).

• Under layers of carpets to dry and avoid the proliferation of mites and ensure immediate contact comfort.

• Domestic uses in gastronomy between 30 and 70/80 ° C and more to improve the tastes of products under controlled cooking, and the temperature maintenance of prepared foods, or even their rapid reheating without other material than a heating plate without thermostat required.

• Contact heating details in the bathrooms.

• Energy transport in the seabed, in water at + 4 ° C from a depth of 500 meters, with the possibility of heating 12 inch tubes% in addition to the precautions of insulating the tubes with insulating elements .

• Defrosting of means of transport by rapid supply of energy at a temperature fixed in advance, and with evolving power; it can be both boat decks and airplane wings and the interiors of cars or commercial vehicles.

• The fields of health, the breeding of all domestic animals as well as for the food industry, with the possibility of heating at any time all surfaces to the desired temperature, from 35 ° C to the pasteurization temperature / 70 ° C during the period deemed optimal after validation tests.

• Industry in general with temperature sensitive products for storage, transport lines, reactors, molds for various materials. • Also, the surfaces under the roots of the plants to allow controlled growth at each optimal determined temperature level. Heat transfers to plants take place much more quickly and economically through root contact than through the air.

According to another object, the invention relates to the PTC materials described for domestic or industrial use in the fields of construction and building, energy transport on the seabed, human or animal health, industry. food or process control industry which includes the devices (layers or heating structures) as described above.

For the construction materials of buildings for industrial or domestic use such as materials for floors, ceiling walls or under layer of carpet for industrial or domestic use, this practical concept of heating sheets is used more particularly to maintain the temperatures at the targeted thresholds: frost-free at + 2 ° C, comfort at 15/25 ° C, drying at 30/40 ° C, heating by low-temperature radiation.

Application transfers are made between the industrial sector and the domestic sector by reducing the size of the zones heated to the usual 10 to 100 m ² in urban or rural housing.

According to another embodiment, the invention relates to heating pipes and in particular heating pipes for the transport of oil or gas in off shore or on shore production which include the heating layers.

The problem of maintaining the temperature of oil flows underwater at more than 500 meters deep is very important, because the water is at 4 ° C due to the pressure, while the fluids are pumpable at more than 50 ° C. It is imperative to maintain minimum temperatures to avoid blocking the circuits. This is achieved with thermal insulation which allow stops limited to a certain number of hours, but without any energy supply to date.

The PTC heating structures described allow the power required to compensate for heat losses of the order of 60 W / m ² to be measured for 12 3/4 inch tubes which offer loss areas of 1 m ² / linear meter. The power required is therefore 480 KW for an 8 km deep-sea tube, which is typical in offshore production. The powers of a few MW on platforms allow this kind of extra power.

In order to be able to heat by controlling the temperature, the sheets are for example inserted into the multilayer corrosion protection of the tubes, between the epoxy layer and the polyolefin layer. The meshes which are possibly empty between two conductors, allow the complete integration of the heating elements in the insulation and corrosion protection structures.

According to another mode of application, the invention relates to the use for the removal by heating of the contamination by pathogenic agents of the heating layers or structures as described above.

In this particular application of the suppression of contamination by pathogens by heating, it is also possible to use heating sheets of type (b) comprising at least one layer of conductive polymer with resistance self-controlled by temperature by PTC effect placed between two electrical conductors. .

More particularly, these plies of type (b) comprise a layer of conductive polymer in the form of a continuous and homogeneous layer as in the plies of type (ai) described above or else a layer of conductive polymer in the form of a mesh as in the plies described previously and two electrical conductors which are located at the ends of the layers and which supply electrical energy to the system. According to a preferred mode of use, in said heating sheet (b) the conductive polymer forming the layer placed between the two electrical conductors in said heating sheet of type (b) is distributed with a density of between 0.01 and 5 Kg / m ² .

According to another preferred mode of use for the elimination of contamination by pathogenic agents by heating, said heating sheet (b) is covered by an electrically insulating and thermally conductive polymer as described above for sheets of type (a).

The invention also relates to the use for the suppression of contamination by pathogenic agents by heating of a single or multi-layer heating structure comprising at least one heating layer of type (b).

The physical cleaning of technical surfaces is more or less crucial at the micro biological level depending on the destination of these work plans. Whether in the food industry, pharmacy, surgery, various biological laboratories, it is often essential to have clean surfaces which we are also certain to be decontaminated from any external microbial pollution at a time given. This goal is generally presumed to be achieved when surface cleaners are deemed to be antibacterial under the prescribed conditions of use. But it is clear that the surface controls are not done routinely, with each antimicrobial cleaning. The PTC heating option for surfaces allows you to proceed in two stages, the first of which consists in mechanically cleaning the surfaces. Then the second step is that of heating the target surface for the time counted from 1 to 15 minutes to the required temperature and obtaining the desired sanitation.

In a particular mode of application of the removal by heating of contamination by pathogenic agents, the heating layers covered with insulating polymer make it possible to set up instant hot water generation systems which heat the water only when the tap is opened, which are lighter and more compact than current systems and which offer an improved warranty and performance option.

Regarding the various process controls in the industry for the whole temperature range between + 5 ° C and + 150 ° C, it is often very difficult to regulate around the required levels due to the heterogeneity of the systems studied. There are phenomena of surface overheating, for insufficient core temperatures.

In the implementation of delicate food systems, of organic fermentations for example lactic and / or cheese, of maturation of meats, creams, chocolates, glucoses and others, the respect of strict maximum temperatures requires very complex regulation systems .

The installation of heating pads with adjustable shapes and powers as needed makes it possible to simplify the design of these materials. These plies can be adapted in all forms, with the heating conductive surfaces or meshes described above.

In the field of aviation, planes have very sensitive points to outside temperatures at -50 ° C. Current protections are made with constant power inputs, which leads to overheating or too low temperatures. It is therefore desirable to be able to heat at various points in a controlled delocalized manner by integrating, for example, heating layers in the aircraft wings for surface antifreeze protections as well as for maintain the temperature of various evacuation organs and exposed circuits outside the cabin.

This performance is made possible by the uniform and regular heating properties of the sheets of the invention.

The invention will be better understood with regard to the following examples, which are given by way of illustration and not limitation.

Examples

Preparation of heating pads Example la

A roll of 1 meter wide is impregnated by soaking in a suspension of a mixture of PTC polymers (30% of

Graphite, 40% PVDF, 30% PMMA) with a density of

100 g / m ² on a support material either in polyester or in polyamide 6 or in polyamide 6.6 of 1 cm ² (1 cm by 1 cm). Drying is then carried out, then conditioning at 180 ° C. or by continuous printing roller with the following suitable heat treatments. The network of electrical conductors for current control is woven into the mesh with a distribution of 15 cm wide for the polarities of the current. Redistributions are made using a comb of conductors (110 V or 42 V connections).

The conductive meshes give off a power of 100 W / m ² at 12 ° C at 110V and 50 W / m ² at 3 ° C at 42 V.

Example 1b The heating sheets obtained according to example 1a are electrically insulated by application of a PMMA type polymer.

Preparation of monolayer or multilayer structure and applications. Example 2

An electrically insulated heating sheet with 2 mm thick mesh obtained as described in Example 1b is integrated into a thickness of 10 mm of self-leveling cement above the ground concrete and in strips 10 meters long.

The current is connected, giving the indicated temperatures in 20 minutes. The current consumption records show the alternations of power required between day and night, as well as the power changes as a function of temperature during the day.

Example 3

Plates comprising a sheet according to the example la or lb of size 0.5 x 0.5 meters are fixed to the ceilings by adapting to the dimensions of the unit elements of different removable models. The powers are of the order of 100 to 120 W / m ² with about 45 ° C maximum in the case of plaster-type surfaces.

These heating surfaces are suitable for heating houses by radiations under the ceiling or under layers of carpets or in submerged concrete floors.

In the case of floors and carpet mats, the heating layers are immersed in the target environments, with the appropriate temperature thresholds for the required power and the voltage accepted by safety standards.

Example 4

In the case of acrylic floors loaded with glass beads, the heating and conductive layers obtained according to Example 1b are immersed as they are without the need for insulation since the PMMA is waterproof and electrically insulating.

The electrical connections are made from one unrolled strip to the other to allow the installation of homogeneous heating of an area 5 meters wide by 10 meters long. When thermal insulation is installed on the floor, we see that we ultimately keep the same set temperature which is 12 ° C for 110 V.

The temperature cycles were tested over periods of 5 days, then 30 and 90 days without significant change in performance. Floor markings are provided to indicate the limits of electrical connections by modules of suitable sizes, for example 50 m ² in a set of 500 m ² or more.

Example 5

For the frost protection of industrial surface, we use netting plies according to example la of 1 meter wide in rolls of 20 to 50 meters with current inputs spaced 10 cm apart with conductive meshes of size 0.5 by 0.5 cm at 2 by 2 cm depending on the required power and a network of integrated conductors in the form of waterproof modules.

The temperatures reached are + 5 ° C minimum and + 28 ° C maximum in less than 30 minutes on the floor, and 45 ° C maximum on ceilings and walls.

In the case of permanent human habitat, presence detections by IR make it possible to trigger localized heaters only when there is a need to heat, and to stop according to selected time delays.

Example 6

To prepare heating tubes used in off-shore and on-shore oil and gas installations, a banner of fixed width is used depending on the power to be transmitted and the diameter of the tubes. This banner is continuously wound around the tube to be treated.

The heating strip is prepared by inserting the heating sheet into the multilayer corrosion protection of the tubes, between the epoxy layer and the polyolefin layer. The thermal balances are established for example at a height of 60 W / m ² at 60 ° C for a 12 inch tube to be immersed under

1500 meters of water in an environment at 4 ° C. The power consumed is 480 KW for an 8 km line which is typical in off-shore installation.

Example 7

When using sensitive surfaces, it is possible to guarantee microbiological cleanliness at all times without the need for immediate prior control.

Heating tests at 70 ° C minimum, and 80 ° C maximum, have shown that conventional germs are eliminated while the control surface has remained contaminated.

This also applies for the guarantee of keeping the water temperature in the hot water reserves without the risk of going below 50 ° C as well as for the instantaneous hot water generation systems with plate exchanger instant heaters.

Claims

1. Heating mat comprising at least one layer of conductive polymer with resistance self-controlled by the temperature by PTC effect placed between at least two electrically conductive surfaces.

2. Heating mat according to claim 1 in which the layer of conductive polymer and the two electrically conductive surfaces are in the form of continuous and homogeneous layers.

3. Heating mat according to claims 1 or 2 in which the assembly formed by the layer of conductive polymer and the two electrically conductive surfaces have perforations.

4. Heating mat comprising several adjacent strips consisting of a layer of conductive polymer, in the form of a continuous and homogeneous layer or in the form of a mesh, connected to two electrical conductors located at the ends of said layer.

5. Heating mat according to claims 1 to 4 in which the conductive polymer forming the layer placed between the two electrical conductors is distributed with a density of between 0.01 and 5 Kg/m ² .

6. Heating mat according to claims 1 to 5 in which the conductive polymer forming the continuous layer placed between the two electrical conductors is distributed with a density of between 1 and 5 Kg/m ² .

7. Heating mat according to claims 1 to 6 in which the conductive polymer forming the mesh layer placed between the two electrical conductors is distributed with a density of between 10 and 500 g/m ² .

8. Heating mat according to any one of the preceding claims covered by an electrically insulating and thermally conductive polymer

9. Single or multi-layer heating structure comprising at least one heating sheet according to one of claims 1 to 8.

10. Heating materials for domestic use or industrial use comprising heating layers or structures according to claims 1 to 9.

11. Heating building construction materials for floors, walls, ceilings, or under carpet layer comprising at least one heating layer or structure according to one of claims 1 to 9.

12. Heating systems comprising at least one heating sheet or structure according to one of claims 1 to 9.

13. Use of a heating sheet or structure according to claims 1 to 9 in the fields of construction and building, energy transport in the seabed, human or animal health, the food industry or the process controls industry.

1. Use for removing contamination by pathogenic agents from at least one heating sheet or structure according to one of Claims 1 to 9 by heating.

15. Use in the fields of construction and building, energy transport in the seabed, human or animal health, the food industry or the process control industry of at least one aquifer heating, said heating sheet comprising at least one layer of conductive polymer with resistance self-controlled by the temperature by PTC effect placed between two electrical conductors.

16. Use, for the removal of contamination by pathogenic agents by heating, of at least one heating mat, said heating mat comprising at least one layer of conductive polymer with resistance self-controlled by the temperature by PTC effect placed between two electrical conductors .

17. Use according to one of claims 15 or 16 of a heating sheet comprising a layer of conductive polymer in the form of a continuous and homogeneous layer, connected to at least two electrical conductors located at the ends of said layer.

18. Use according to one of claims 15 or 16 of a heating sheet comprising a layer of conductive polymer in the form of a mesh, connected to two electrical conductors located at the ends of said layer.

19. Use according to one of claims 15 to 18 in which the conductive polymer forming the layer placed between the two electrical conductors is distributed with a density of between 0.01 and 5 Kg/m ² .

20. Use according to one of claims 15 to 19 in which the conductive polymer forming the continuous layer placed between the two electrical conductors is distributed with a density of between 1 and 5 Kg/m ² .

21. Use according to one of claims 15 to 20 in which the conductive polymer forming the mesh layer placed between the two electrical conductors is distributed with a density of between 10 and 500 g/m ² . 22 Use according to one of claims 15 to 21 in which the sheet is covered by an electrically insulating and thermally conductive polymer.