Self-regulating heater

Abstract

An electric heater, such as a flat plate electric heater, comprising a semiconductive layer comprising a first electric semiconductive composition having a positive temperature coefficient, the first semiconductive composition comprising polyethylene, polypropylene or a mixture thereof and an electrically conductive filler; a plurality of semiconductive portions located on and protruding from the electric semiconductive layer, wherein the semiconductive portions comprise a second electric semiconductive composition having a positive temperature coefficient, the second semiconductive composition comprising polyethylene, polypropylene or a mixture thereof and an electrically conductive filler; wherein the semiconductive portions are arranged in a regular pattern on the semiconductive layer; and the semiconductive portions are at least twice as thick as the semiconductive layer.

Description

[0001] This invention relates to a self-regulating heater and a method for fabricating such a structure. Specifically, the invention relates to an electric heater comprising a semiconductor layer of an electrosemiconductor composition having a positive temperature coefficient, wherein a plurality of semiconductor portions are located on and protrude from the electrosemiconductor layer. These semiconductor portions act as conductors within the heater, transferring electrical power from a power source to the semiconductor layer. Background of the Invention

[0003] Parallel resistance self-regulating heating cables are known. Such cables typically comprise two conductors extending longitudinally along the cable. Typically, these conductors are embedded within a resistance polymer heating element, which is continuously extruded along the length of the conductor. Therefore, the cable has a parallel resistance configuration, with electricity applied through the two conductors to the heating element connected in parallel between them. The heating element typically has a positive temperature coefficient of resistance. Therefore, as the temperature of the heating element increases, the resistance of the material connecting the conductors increases, thereby reducing the power output. The power output of such heating cables varies with temperature and is referred to as self-regulating or self-limiting.

[0004] Therefore, to avoid overheating and potential damage, they are self-limiting and do not require regulating electronic devices.

[0005] Self-regulation utilizes the conversion of electrical energy into heat by allowing current to pass through a semiconductor medium with a positive temperature coefficient (PTC) characteristic. This raises the temperature of an object above its surroundings until a steady state is reached (self-regulation). Materials with a PTC have resistance that increases with temperature and are the mechanism behind self-regulation. These PTC cables are commonly used for underfloor heating or wrapped around pipes for purposes such as freeze protection. However, the cables do not provide a significant thermal surface area, thus requiring large quantities of cable to provide heating, for example, underfloor heating.

[0006] Therefore, the use of self-regulating flat-plate heaters is also known. WO2014 / 188190 describes an electric heater comprising conductors and heating elements disposed between the conductors, wherein the heating element comprises a conductive material distributed within a first electrically insulating material. The insulating material separates the conductors from the conductive material.

[0007] US7250586 describes a surface heating system for automobile seats, etc., the system comprising a support and a heating layer comprising conductive plastic, characterized in that the heating layer is formed of a flexible film and the support is flexible.

[0008] US4247756 describes a heated floor mat in which two inner conductive layers sandwich a conductor in the middle. The conductor is adhered to the inner layers.

[0009] US7053344 describes a flexible heater for fabrics.

[0010] US2021112631 describes a heating element having at least one thin film of conductive polymer material.

[0011] US5451747 discloses a heating pad with PTC material.

[0012] WO2008 / 133562 describes a heating device comprising two elongated electrodes disposed at a distance and interconnected by a semiconductor heating element based on a polymer material having a positive temperature coefficient (PTC material), wherein the heating element includes an electrode interconnect portion of PTC material having a low resistivity compared to the PTC material in the middle portion.

[0013] EP1275274 describes a device for floor heating that includes a flexible, conductive thermoplastic pad. The device is equipped with at least two electrodes. Current is conducted through the device, causing it to heat up and release heat.

[0014] WO2021 / 188595 describes a blanket comprising a first outer plate, a self-regulating heating element adjacent to the first outer plate, and a second outer plate adjacent to the self-regulating heating element, the second outer plate being joined to the first outer plate, wherein the first outer plate and the second outer plate contain the self-regulating heating element.

[0015] WO2022 / 129251 describes a self-regulating flat plate heater prepared by co-extrusion, wherein a conductor is embedded in a semiconductor composition.

[0016] EP-A-100919 discloses a sheet heater comprising a plurality of electrode covering members, each covering a linear electrode. This arrangement of electrodes and covering members is situated on a sheet-like heating resistance sheet. The sheet may be a PTC sheet.

[0017] Traditional self-regulating heaters rely on metal conductors attached to or embedded in a semiconductor composition. In this invention, these metal conductors (typically wires) are replaced by a portion of the semiconductor material. These portions have higher conductivity than the primary semiconductor material in existing heaters, i.e., the semiconductor layer within the heater.

[0018] Despite being semiconductor, these portions are still sufficient to provide voltage and current to the self-regulating semiconductor composition of the semiconductor layer. Therefore, the semiconductor composition is heated until it reaches a steady state.

[0019] Compared to metallic conductors, the relatively lower conductivity of the semiconductor portion is compensated for by increasing the cross-sectional area. In one embodiment, the polymer used in all semiconductor materials present in the heater can be the same, thus the heater can be fabricated as a single-material structure, facilitating easy recycling. Summary of the Invention

[0020] In one respect, the present invention provides an electric heater, such as a flat plate electric heater, comprising a semiconductor layer, the semiconductor layer comprising a first electric semiconductor composition having a positive temperature coefficient, the first electric semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; A plurality of semiconductor portions located on and protruding from a semiconductor layer, wherein the semiconductor portions include a second electrical semiconductor composition having a positive temperature coefficient, the second electrical semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; The semiconductor portion is arranged in a regular pattern on the semiconductor layer; and The semiconductor portion has a conductivity that is, for example, at least 5 times higher than that of the semiconductor layer. For example, the higher conductivity of the semiconductor portion is provided by the geometry, spacing, thickness and / or content of the conductive filler in the semiconductor portion.

[0021] Preferably, the width of each semiconductor portion (preferably the same semiconductor portion) is 0.05 to 0.5 times the distance between adjacent semiconductor portions. The distance between adjacent semiconductor portions is measured as the distance between the nearest edges of two adjacent semiconductor portions.

[0022] From another perspective, the present invention provides an electric heater, such as a flat plate electric heater, which includes a semiconductor layer, said semiconductor layer including a first electric semiconductor composition having a positive temperature coefficient, the first semiconductor composition including polyethylene, polypropylene or a mixture thereof and conductive filler; A plurality of semiconductor portions located on and protruding from an electrical semiconductor layer, wherein the semiconductor portions include a second electrical semiconductor composition having a positive temperature coefficient, the second semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; The semiconductor portion is arranged in a regular pattern on the semiconductor layer; and The semiconductor portion is at least twice as thick as the semiconductor layer.

[0023] Preferably, the width of each electrical semiconductor portion (preferably the same electrical semiconductor portion) is 0.05 to 0.5 times the distance between adjacent semiconductor portions.

[0024] In another respect, the present invention provides the use of a second semiconductor composition having a positive temperature coefficient as a conductor in a heating device, the second semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and a conductive filler, the heating device comprising a first electrical semiconductor composition, which may be the same as or different from the second composition, having a positive temperature coefficient and comprising polyethylene, polypropylene or a mixture thereof and a conductive filler.

[0025] Detailed Description of the Invention

[0026] This invention relates to an electric heater in which conventional metal conductors, such as metal wires, are replaced by semiconductor portions located on and protruding from a semiconductor layer within the heater. The final structure can be made almost entirely from recyclable polymer materials.

[0027] The heater provides heat in a safe, inexpensive, and simple manner. The heater of this invention utilizes the positive temperature coefficient (PTC) principle. To avoid overheating and potential damage to the heater, the generated heat is self-limiting and no regulating electronics are required. As the temperature within the semiconductor layer increases due to the electricity applied to the semiconductor portion, the resistance within the semiconductor layer increases until a steady state is reached and no further heating occurs. Therefore, in one embodiment, the heater of this invention does not include regulating electronics, such as thermal cutoff to prevent overheating.

[0028] The first and second electrical semiconductor compositions do not overheat and do not require overheat protection. The technical solution in this particular invention utilizes the conversion from electrical energy to thermal energy by allowing current to pass through a semiconductor composition with PTC characteristics, which raises the temperature of an object above its surroundings until a steady state (self-regulation) is reached.

[0029] The first and second electrical semiconductor compositions preferably contain polyethylene and conductive fillers (e.g., carbon black). They can be the same or different. The self-regulating thermal phenomenon occurs due to two parallel antagonistic processes: a. Electrons experience electrical losses due to poor conduction through the semiconductor medium, which manifests as thermal radiation.

[0030] b. The thermal expansion of the non-conductive parts of the material leads to a further decrease in conductivity through the separation of conductive filler particles.

[0031] Once these two processes reach equilibrium, a stable high-temperature plateau will be reached.

[0032] Temperature rise in the first electrical semiconductor layer is controlled by a number of factors. These include the distance between the semiconductor portions, the conductivity of the semiconductor portions, the size of the semiconductor portions, the thickness of the semiconductor layer, the amount of conductive filler present in the first electrical semiconductor composition, and the applied voltage.

[0033] The closer semiconductor section increases the temperature at which a stable high-temperature platform can be reached.

[0034] A thicker layer of electrical semiconductors increases the temperature at which a stable high-temperature plateau is reached.

[0035] Increasing the content of conductive filler in any semiconductor composition will raise the temperature at which a stable high-temperature plateau is reached.

[0036] The steady-state high temperature in the preferred semiconductor layer should not exceed 50°C, for example, not exceeding 45°C. The heater should ideally reach a temperature of at least 30°C.

[0037] This gives product designers the freedom to manipulate the generated heat by controlling the size and shape of the object, the location of the semiconductor portion, and the composition of the first semiconductor composition / semiconductor portion in order to achieve a predetermined target temperature.

[0038] It should be understood that the PTC principle also applies to semiconductor components, as these components will also reach a self-regulating stable state. The temperature reached in the semiconductor component depends on several factors and is not necessarily higher than the temperature in the semiconductor layer component.

[0039] Electrical semiconductor composition

[0040] The heater of the present invention includes a first electrically conductive semiconductor composition forming a semiconductor layer structure within the heater. Therefore, the first semiconductor layer comprises or is composed of the first electrically conductive semiconductor composition. The first electrically conductive semiconductor composition includes polyethylene. In a preferred embodiment, the heater of the present invention is essentially a flexible flat plate that can be processed into a desired shape (e.g., cylindrical) as needed.

[0041] Therefore, the heater comprises a first electrosemiconductor composition in a semiconductor layer. The first electrosemiconductor composition comprises polyethylene, polypropylene, or a mixture thereof. It is preferred if the first semiconductor composition contains polyethylene. It is also preferred if the polyethylene is prepared in a high-temperature autoclave or tubular process, such as a homopolymer or copolymer of LDPE.

[0042] Although the term LDPE is an abbreviation for low-density polyethylene, it should be understood to be unrestricted by density range, but rather to include high-density (HP) polyethylene similar to LDPE. The term LDPE only describes and distinguishes the properties of HP polyethylene with typical characteristics, such as the branched structure that differs from polyethylene produced in the presence of olefin polymerization catalysts.

[0043] The term LDPE refers to a low-density homopolymer of ethylene (referred to herein as LDPE homopolymer) or a low-density copolymer of ethylene with one or more comonomers (referred to herein as LDPE copolymer).

[0044] It is preferred if the first electro-semiconductor composition contains an LDPE copolymer. One or more comonomers of the LDPE copolymer are preferably selected from polar comonomers, nonpolar comonomers, or mixtures of polar and nonpolar comonomers. Furthermore, the LDPE homopolymer or LDPE copolymer may optionally be unsaturated.

[0045] As a polar copolymer of LDPE copolymer, a comonomer containing carboxyl and / or ester groups is used as the polar comonomer. More preferably, the polar comonomer of the LDPE copolymer is selected from the group consisting of acrylates, methacrylates, or acetates, or any mixture thereof.

[0046] If present in the LDPE copolymer, the polar comonomer is preferably selected from the group consisting of alkyl acrylates, alkyl methacrylates, or vinyl acetate, or mixtures thereof. Ethylene alkyl acylates or ethylene vinyl acetate are preferred.

[0047] More preferably, the polar comonomer is selected from C1- to C6-alkyl acrylates, C1- to C6-alkyl methacrylates, or vinyl acetate. Even more preferably, the LDPE copolymer is a copolymer of ethylene and C1- to C4-alkyl acrylates, such as methyl acrylate, ethyl acrylate, propyl acrylate, or butyl acrylate, or vinyl acetate, or any mixture thereof. Ethylene methyl acrylate (EMA), ethylene ethyl acrylate (EEA), ethylene butyl acrylate (EBA), or ethylene vinyl acetate (EVA) are preferred.

[0048] As a nonpolar comonomer for LDPE copolymers, a preferred choice is a polyunsaturated comonomer containing only C and H atoms. In a preferred embodiment, the polyunsaturated comonomer consists of a straight-chain carbon chain having at least 8 carbon atoms and at least 4 carbon atoms between non-conjugated double bonds, at least one of which is terminal.

[0049] Preferred diene compounds are 1,7-octadiene, 1,9-decadiene, 1,11-dodecadiene, 1,13-tetradecadiene, or mixtures thereof. Additionally, dienes such as 7-methyl-1,6-octadiene, 9-methyl-1,8-decadiene, or mixtures thereof may be mentioned.

[0050] If the LDPE polymer is a copolymer, it preferably contains 1.0% to 40% by weight, more preferably 5% to 35% by weight, and even more preferably 10% to 30% by weight of one or more comonomers.

[0051] When a polar comonomer is present, the content of the comonomer in the polymer is preferably 5.0 to 30% by weight, for example 7.5 to 20% by weight. Ethylene methyl acrylate (EMA), ethylene ethyl acrylate (EEA), ethylene butyl acrylate (EBA), or ethylene vinyl acetate (EVA) are preferred, especially when 5% to 30% by weight, for example 7.5% to 20% by weight, of the comonomer is present.

[0052] When measured at a load of 21.6 kg / 125°C, the required MFR of the polymer is 4.0 g / 10 min or higher, for example at least 6.0 g / 10 min, even more preferably 8.0 g / 10 min to 15 g / 10 min, and most preferably at least 10.0 g / 10 min. An upper limit of 25 g / 10 min is preferred, for example 18 g / 10 min. Using a higher MFR value appears to provide a more uniform layer thickness and allows for higher extrusion yields without altering the ability of polyethylene to be used as a heater via the PTC principle.

[0053] Any LDPE homopolymer or copolymer can have 905 kg / m 3 Up to 935kg / m 3 For example, 910 kg / m 3 Up to 925kg / m 3 The density.

[0054] Polyethylene can be produced by any conventional polymerization method. Preferably, it is LDPE and is produced by free radical polymerization, such as high-pressure free radical polymerization. High-pressure polymerization can occur in a tubular reactor or an autoclave reactor. Preferably, it is a tubular reactor. Typically, the pressure can be in the range of 1200 bar to 3500 bar, and the temperature can be in the range of 150°C to 350°C. Further details regarding high-pressure free radical polymerization are given in WO93 / 08222, which is incorporated herein by reference.

[0055] The first electrical semiconductor composition may contain at least 50% by weight of polyethylene, polypropylene, or mixtures thereof, for example, at least 60% by weight. Any layer containing the first electrical semiconductor composition may be composed of the first electrical semiconductor composition. Therefore, any layer containing the first electrical semiconductor composition may contain at least 50% by weight of polyethylene, polypropylene, or mixtures thereof, for example, at least 60% by weight. Once all other components have been determined, polyethylene, polypropylene, or mixtures thereof will form the balance of the first electrical semiconductor composition.

[0056] conductive filler

[0057] According to the present invention, the first electrical semiconductor composition further comprises a conductive filler, such as carbon black.

[0058] Suitable conductive fillers include graphite, graphene, carbon fiber, carbon nanotubes, metal powder, metal wire, or carbon black. Carbon black is preferred.

[0059] The added conductive filler produces semiconductor properties. Therefore, the amount of conductive filler is sufficient to obtain a semiconductor composition. The amount of conductive filler can vary depending on the desired application and the conductivity of the composition. Preferably, the first electrical semiconductor composition contains 5% to 50% by weight of conductive filler, for example, 15% to 50% by weight. In other preferred embodiments, the amount of conductive filler is 5% to 48% by weight, 10% to 45% by weight, 20% to 45% by weight, 25% to 45% by weight, or 30% to 41% by weight, based on the weight of the first electrical semiconductor composition.

[0060] Therefore, the first composition may contain 5% to 50% by weight of conductive filler, for example, 15% to 50% by weight. In other preferred embodiments, the amount of conductive filler in the first layer is 5% to 48% by weight, 10% to 45% by weight, 20% to 45% by weight, 25% to 45% by weight, or 30% to 41% by weight, based on the weight of the layer.

[0061] Any conductive carbon black can be used. Examples of suitable carbon blacks include furnace black, channel black, gas black, lamp black, thermal black, and acetylene black. Additionally, graphitized furnace blacks (such as those produced by Imerys) and high-structure blacks (such as Ketjenblacks produced by Nouryon) can also be used. Blends can also be used. When using a blend of carbon blacks, the percentage refers to the total amount of carbon black present.

[0062] When measured according to ASTM D3037-93, carbon black can have a 5m... 2 / g to 1500m 2 / g, for example, 10m 2 / g to 300m 2 / g, for example 30m 2 / g to 200m 2 / g nitrogen surface area (BET). In addition, carbon black can possess one or more of the following properties: i) A primary particle size of at least 5 nm, defined as the number-average particle size according to ASTM D3849-95a. ii) When determined according to ASTM D-1510, an iodine adsorption value (IAN) of at least 10 mg / g, for example, from 10 mg / g to 300 mg / g, or from 30 mg / g to 200 mg / g; and / or iii) When measured according to ASTM D 2414, at least 30 cm 3Absorption value of DBP (dibutyl phthalate) per 100g (= oil absorption value), for example, 60cm 3 / 100g to 300cm 3 / 100g, for example, 70cm 3 / 100g to 250cm 3 / 100g, for example, 80cm 3 / 100g to 200cm 3 / 100g, for example, 90cm 3 / 100g to 180cm 3 / 100g.

[0063] In addition, carbon black can possess one or more of the following properties: a) A primary particle size of at least 15 nm, defined as the number-average particle size according to ASTM D3849-95a. b) An iodine value of at least 30 mg / g, according to ASTM D1510; c) An oil absorption value of at least 30 ml / 100 g, as measured according to ASTM D2414.

[0064] Furnace black is preferred. This is the recognized term for a known type of carbon black produced continuously in a furnace reactor. Examples of carbon black, its preparation methods, and reactors can be found in i.a. Cabot's EP-A-0629222, US 4,391,789, US 3,922,335, and US 3,401,020. Examples of commercial furnace black grades can be mentioned in ASTM D1765-98b ia. N351, N293, and N550.

[0065] Other components

[0066] The first semiconductor composition can be crosslinked using a peroxide or silane moisture-curing system. Radiation crosslinking can also be used to avoid the need for a crosslinking agent.

[0067] Preferably, cross-linking is avoided, and the resulting heater is a more recyclable product. The semiconductor composition of the present invention is preferably non-cross-linked.

[0068] antioxidants

[0069] The first semiconductor composition may contain an antioxidant. Among antioxidants that may be mentioned are sterically hindered or semi-sterically hindered phenols, aromatic amines, aliphatic hindered amines, organophosphates, thio compounds, polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, and mixtures thereof.

[0070] More preferably, the antioxidant is selected from the group consisting of 4,4'-bis(1,1'-dimethylbenzyl)diphenylamine, para-oriented styrenated diphenylamine, 4,4'-thiobis(2-tert-butyl-5-methylphenol), polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, 4-(1-methyl-1-phenylethyl)N-[4-(1-methyl-1-phenylethyl)phenyl]aniline or derivatives thereof.

[0071] More preferably, the antioxidant is selected from (but not limited to) 4,4'-bis(1,1'-dimethylbenzyl)diphenylamine, para-oriented styrenediphenylamine, 4,4'-thiobis(2-tert-butyl-5-methylphenol), 2,2'-thiobis(6-tert-butyl-4-methylphenol), distearate thiodipropionate, 2,2'-thiodiethyl-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, or derivatives thereof. Of course, not only one of the antioxidants described above, but any mixture thereof may be used.

[0072] Based on the weight of the semiconductor composition, the amount of antioxidant, optionally a mixture of two or more antioxidants, can be from 0.005% by weight to 2.5% by weight, for example from 0.01% by weight to 2.5% by weight, preferably from 0.01% by weight to 2.0% by weight, more preferably from 0.03% by weight to 2.0% by weight, especially from 0.03% by weight to 1.5% by weight, even more especially from 0.05% by weight to 1.5% by weight, or from 0.1% by weight to 1.5% by weight.

[0073] The first semiconductor composition may contain additional additives. Possible additives include stabilizers, processing aids, flame retardants, acid removers, inorganic fillers, voltage stabilizers, or mixtures thereof.

[0074] Preferably, the first electrical semiconductor composition has a strength of less than 20 Ohms when measured at 40°C. The volume resistivity is approximately 12 Ohm. Preferably, the first electro-semiconductor composition has a volume resistivity of less than 12 Ohm when measured at 25°C. Volume resistivity in cm.

[0075] The semiconductor layer can have a thickness of 50 μm to 3000 μm, for example 75 μm to 2000 μm, especially 100 μm to 1000 μm. A thickness of 125 μm to 800 μm is particularly preferred.

[0076] Second floor

[0077] The heater of the present invention can be in the form of a sheet, such as a flat sheet, and therefore comprises multiple layers. In addition to the semiconductor layer comprising the first electrical semiconductor composition, another layer may be present as an insulating layer. A decorative top layer may also be present.

[0078] Therefore, in one embodiment, the electric heater is provided with at least one additional layer above the electric semiconductor layer and / or at least one additional layer below the electric semiconductor layer, preferably an insulating layer, such as a thermal insulating layer.

[0079] As described in detail below, semiconductor portions are disposed on the semiconductor layer. Particularly preferred is that the gaps between the semiconductor portions are filled with an insulating polymer layer, such as a polyethylene-based layer as defined herein, but without conductive filler. Preferably, an LDPE copolymer comprising a polyunsaturated comonomer composed of a linear carbon chain having at least eight carbon atoms and at least four carbon atoms between non-conjugated double bonds, at least one of which is terminal.

[0080] In another embodiment, the gaps between the semiconductor portions are filled with a second layer of the semiconductor composition as defined herein, i.e., a layer having a lower conductivity than the semiconductor portions. The semiconductor composition used to prepare this second layer is conveniently the same as that used to prepare the semiconductor layer.

[0081] The heater of the present invention may have one or more layers to protect the semiconductor composition from damage. For example, an aesthetically pleasing top layer may be a textile, non-woven, or solid board (rubber, plastic, paper, wood, metal, etc.). Alternatively, no top layer may be used.

[0082] Any additional layer can be extrudable, such as a polyolefin layer.

[0083] In a preferred embodiment, the heater has an insulating or heat-reflective layer at its bottom. This insulating layer can be electrically insulating, thermally insulating, or both. This layer increases the heating efficiency of the heater. This layer can include polyolefins, such as polyethylene, especially LDPE, such as LDPE homopolymers or copolymers. Preferably, the insulating layer uses LDPE as the sole polymer component. This layer is preferably a co-extrudeable layer, although lamination of the layer is also an option.

[0084] The heater may be equipped with supports to provide mechanical strength.

[0085] Semiconductor section

[0086] In conventional PTC heaters, there are multiple metal conductors, typically wires. In this invention, these metal conductors are replaced by multiple electrically conductive portions located on and protruding from an electrically conductive layer. These portions have a higher conductivity than the first electrically conductive composition / layer, for example, due to their geometry or due to an increased amount of conductive filler relative to the filler content in the semiconductor layer. Various methods can be devised by those skilled in the art to increase the conductivity of the semiconductor portions.

[0087] In one embodiment, the semiconductor portion has a conductivity that is, for example, at least 5 times higher than that of the electrical semiconductor composition / layer. In another embodiment, the semiconductor portion has a conductivity that is, for example, at least 2 to 20 times higher than that of the electrical semiconductor composition / layer. Conductivity is measured as 1 / resistance and is determined by the ratio between the applied voltage and the generated current (Ohm's Law).

[0088] As used herein, the term "multiple" means at least two, preferably at least four, semiconductor portions. Ideally, the heater of the present invention comprises an even number of semiconductor portions. In use, the semiconductor portions have alternating polarities.

[0089] The semiconductor portion includes a second electrical semiconductor composition comprising polyethylene, polypropylene, or a mixture thereof, and a conductive filler. The first and second electrical semiconductor compositions may be the same or different. The semiconductor portion may be composed of the second electrical semiconductor composition.

[0090] The second electrical semiconductor composition preferably comprises polyethylene. The second electrical semiconductor composition is preferably essentially composed of polyethylene and conductive fillers, i.e., these are the only components other than any standard polymer additives. Furthermore, the semiconductor portion is preferably composed of the second electrical semiconductor composition, and therefore preferably the semiconductor portion consists only of polyethylene and conductive fillers.

[0091] The properties of polyethylene and conductive fillers are as defined above for the first electrical semiconductor composition. It is particularly preferred that the same polyethylene material be used in both the first and second semiconductor compositions, as this facilitates product recycling. Therefore, the polyethylene used in the second electrical semiconductor composition is preferably the polyethylene described above for the first electrical semiconductor composition.

[0092] Alternatively, it may be useful for the semiconductor portion to provide a weaker PTC within the operating temperature range in question. This would make the resistance more "metallic." To reduce the PTC characteristics of the semiconductor portion, the low-density polyethylene typically used in the second electrical semiconductor composition can be replaced with low-pressure polyolefins such as LLDPE, MDPE, HDPE, or PP copolymers. These polymers tend to provide higher conductivity and a weaker PTC than low-density polyethylene.

[0093] In one embodiment, the first and second semiconductor compositions are identical, and the difference in conductivity is achieved through the shape of the semiconductor portions. In another embodiment, the first and second semiconductor compositions are different. In one embodiment, the first and second semiconductor compositions use the same polyethylene, but differ in the content of conductive filler.

[0094] The semiconductor portion should have a higher conductivity than the first semiconductor composition / layer. This can also be calculated based on the geometry at a given temperature and a known VR value. Therefore, changes in conductivity can be achieved by manipulating the geometry of the semiconductor portion or by manipulating the content / property of the conductive filler in the second semiconductor composition.

[0095] The semiconductor portion is preferably at least twice as thick as the semiconductor layer, for example, at least three times thicker. Therefore, typically, the semiconductor layer is in the form of a layer, and the semiconductor portion is located on and protrudes from the semiconductor layer. The semiconductor portion should be at least twice as thick as the semiconductor layer. Thus, if the thickness of the semiconductor layer is 2 mm, then the thickness of the semiconductor portion should be at least 4 mm. Preferably, the semiconductor portion should be 5 times thicker than the semiconductor layer, for example, 5 to 10 times thicker.

[0096] However, the semiconductor portion can be significantly thicker than the semiconductor layer. For example, the semiconductor portion can be 50 or 100 times thicker, or even up to 200 times thicker. Therefore, for a 100-micrometer thin film, the thickness of the semiconductor portion could be 5000 micrometers.

[0097] Furthermore, the thickness of the semiconductor portion does not need to be uniform. Therefore, the above values ​​may apply to the thickest part of the semiconductor portion.

[0098] The semiconductor portion is subjected to the same voltage and current as the semiconductor layer, but due to its higher resistance, heating occurs within the semiconductor layer.

[0099] The difference in conductivity can also be achieved by using more conductive filler than in the semiconductor layer, or by using conductive filler with higher conductivity than the conductive filler used in the semiconductor layer.

[0100] Furthermore, because the conductive path is semiconducting, heat is generated not only in the semiconductor layer but also, to some extent, in the semiconductor portion itself. This contrasts with metallic conductors, which exhibit negligible temperature rise for typical low current densities due to resistive losses. Therefore, this increases the overall heating capacity of the heater.

[0101] The semiconductor sections are arranged in a regular pattern to ensure that heating occurs uniformly within the semiconductor layer. The semiconductor sections must be spaced apart in some way. Therefore, the term "regular pattern" refers to one (or more) themes repeating in a predictable manner.

[0102] In one embodiment, the semiconductor portions are simply arranged in parallel strips on the semiconductor layer. In other embodiments, the semiconductor portions may be arranged in a zigzag pattern, maintaining equal spacing between them. Those skilled in the art can design various arrangements of the semiconductor portions on the semiconductor layer.

[0103] To connect the heater and the semiconductor portion to a power source, a metal connector or conductor (e.g., a wire) may be required to connect the heater to the power source. However, if the heater itself does not have a substantial metal conductor, a wire with a metal conductor is preferred. Therefore, it is conceivable that a metal connector or conductor from the power source, such as the end of a wire, may need to be connected to or embedded within the semiconductor portion to connect the heater to the power source via a cable. Thus, in one embodiment, the electrical connection can be melted into the semiconductor composition (thus eliminating the need for soldering, soldering, etc.).

[0104] However, preferably, the plate does not have linear conductors spanning its length or width. Therefore, in a preferred embodiment, the plate may have electrodes or connectors disposed within the semiconductor portion, thereby allowing connection to a power source. However, the semiconductor portion protruding from the semiconductor layer should not have linear conductors extending along the length or width of the semiconductor portion.

[0105] A core idea is that the metal wire conductors typically embedded in a semiconductor composition are replaced by portions of semiconductor material with a higher conductivity than the semiconductor layer in which they are placed. We can avoid having conductors like wires running through the heater, but it should be understood that connectors or electrodes (which can be metal) may be needed to connect the semiconductor portion to a power source. Such electrodes might be small areas of metal, like a disk.

[0106] This concept is Figure 4a The / b specification provides a clear explanation. Figure 4a In / b, disc-shaped connectors are located at the edge of the protruding semiconductor portion, and these connectors are connected to the power supply via metal wires. However, the metal wires do not extend beyond the length or width of the protruding semiconductor portion. Figure 4a / b indicates that the specific position of the connector can be changed.

[0107] Therefore, from another perspective, the present invention provides an electric heater, such as a flat plate electric heater, which includes a semiconductor layer comprising a first electric semiconductor composition having a positive temperature coefficient, the first semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; A plurality of semiconductor portions located on and protruding from a semiconductor layer, wherein the semiconductor portions include a second electrical semiconductor composition having a positive temperature coefficient, the second electrical semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; The semiconductor portion is arranged in a regular pattern on the semiconductor layer; and The semiconductor portion has a conductivity that is, for example, at least 5 times higher than that of the semiconductor layer. The metal wires are not embedded in or located on a large portion of the length or width of the semiconductor portion.

[0108] "Most" refers to at least 25% of its length or width, such as at least 50% of its length or width, or its entire length or width. Length can be considered as the longer dimension within the semiconductor portion. It should be understood that metal wire conductors typically run parallel to the semiconductor layer longitudinally (or laterally). We aim to avoid such metal wire conductors running longitudinally (or laterally) through the semiconductor layer (typically the entire layer).

[0109] The only possible wire is one that allows a connection from the connector to the power source.

[0110] The conductivity of the semiconductor portion is significantly lower than that of the metal wire. Therefore, to ensure sufficient power transfer through the semiconductor portion to the semiconductive layer, the semiconductor portion can have more than one connection point to the power source. Preferably, if multiple connection points are required, these connection points are evenly spaced to attempt to ensure a uniform temperature and power distribution within the semiconductor portion. The connection points should not be connected by metal wires.

[0111] Connection points (or connectors) are metal electrodes adapted for connection to metal wires from a power source. These metal electrodes / connectors can be placed on or embedded within a semiconductor portion, and are therefore typically at the edge of the semiconductor portion to minimize the amount of semiconductor portion any connection to the power source needs to traverse. These can be made of any conventional metal used for conductors, such as copper or aluminum.

[0112] The geometry and spacing of the semiconductor portions are important. The semiconductor portions can have a thickness (or height) of 0.5 mm to 15 mm, for example, 1.0 mm to 10 mm, meaning the semiconductor portions protrude from the semiconductor layer by, for example, 0.5 mm to 5.0 mm, or, for example, 1.0 mm to 3.0 mm. It is preferable that the thickness of the semiconductor portions is at least twice the thickness of the semiconductor layer, preferably three times the thickness. Thicknesses up to 100 times the thickness of the semiconductor layer are possible.

[0113] The semiconductor portion can have a width of 0.5 mm to 15 mm, for example, 1.0 mm to 10 mm. A minimum of 3.0 mm is preferred. The width of each semiconductor portion is preferably the same. Furthermore, it is preferred if the width of the semiconductor portion is 0.05 to 0.5 times, for example, 0.1 to 0.25 times, the distance between adjacent semiconductor conductor portions. The distance between adjacent semiconductor conductor portions is measured as the nearest distance between the nearest edges of the adjacent portions, see Scheme 1:

[0114] Option 1 – Cross-section of the heater

[0115] Therefore, if the distance between adjacent heaters is 50 mm, then the width of the semiconductor section may be 10 mm (which is 0.2 times the gap).

[0116] The length of the semiconductor portion is determined by the size of the semiconductor layer to which the semiconductor portion will be bonded. The semiconductor portion preferably extends along most of the semiconductor layer, such as the entire semiconductor layer.

[0117] The heater may include at least two separate semiconductor sections, but it may contain more. The semiconductor sections are spaced apart from each other and therefore do not contact each other. The semiconductor sections are preferably substantially parallel to each other. The semiconductor sections should preferably be uniformly spaced to ensure uniform temperature when electricity is applied. Uniform spacing means that the distance between adjacent semiconductor sections is always the same. The semiconductor sections are preferably parallel to each other and arranged linearly. However, theoretically, the semiconductor sections can be curved (e.g., SS-shaped) so that they always remain equidistant from each other. We consider this to be "parallel".

[0118] In one embodiment, the gap between the nearest edges of the semiconductor portions is 20 mm to 150 mm, preferably 30 mm to 90 mm, for example 40 mm to 80 mm.

[0119] Therefore, it is preferable if the heater comprises multiple semiconductor portions that are evenly spaced and substantially parallel to each other, for example, wherein the distance between the conductors is 20 mm to 150 mm.

[0120] The semiconductor portion is in direct contact with the semiconductor layer. Therefore, there should be no layer separating the electrical semiconductor layer from the semiconductor portion (an adhesive could be used). The semiconductor portion can be attached to the outside of the semiconductor layer. This can be achieved if the semiconductor portion is co-extruded with the first electrical semiconductor composition. It can also be achieved by laminating the semiconductor portion onto the first electrical semiconductor composition layer, for example using well-known lamination techniques.

[0121] When viewed from above in cross-section, the semiconductor portion can have a rectangular shape. The semiconductor portion can have a rectangular cross-section. However, if the semiconductor portion has a raised edge where it meets the semiconductor layer, this will introduce mechanical stress. Therefore, it is preferable if the edge height of the semiconductor portion gradually decreases, thus achieving a smooth interface between the semiconductor portion and the layer. This is illustrated in scheme 2 or 3:

[0122] Option 2

[0123] Option 3

[0124] Therefore, to avoid mechanical stress on the semiconductor portion, it is preferable that the semiconductor portion is chamfered or beveled at the interface between the semiconductor portion and the electro-semiconductor layer. This results in a smooth interface between these components, and the thickness of the semiconductor portion increases smoothly until the target thickness is reached, for example, as... Figure 2 As shown.

[0125] The semiconductor portion can cover 5%-25% of the surface area of ​​the semiconductor layer.

[0126] The heater of the present invention comprises a plurality of semiconductor portions. The semiconductor portions are formed of a semiconductor composition. It is preferred that the semiconductor portions are all made of the same semiconductor composition to ensure that each individual semiconductor portion behaves identically when electricity is applied. Therefore, the chemical structures of the semiconductor portions are ideally identical, i.e., each semiconductor portion contains the same polymer and the same amount of conductive filler.

[0127] It should be understood that the further a particular part of the semiconductor is from the power source (i.e., the connection point), the greater the voltage drop experienced by the semiconductor part. Typically, power enters the semiconductor part through the connection point, which is typically a metal electrode connection point embedded within or attached to the semiconductor part. This connection point is then connected to the power source.

[0128] In one embodiment, the metal conductor along its entire The length is fused and embedded within the semiconductor portion. This reduces the risk of voltage drop.

[0129] Unlike traditional conductors, in a semiconductor, the further away from a connection point any part of the semiconductor is, the less charge it carries. To ensure uniform heating across the semiconductor layer, adjacent semiconductor parts can be designed such that the distance between adjacent parts decreases as the part of the semiconductor part is further away from its nearest corresponding connection point. Therefore, the semiconductor parts can be arranged in a zigzag pattern, as shown in the following scheme:

[0130] Option 4

[0131] In this setup, the semiconductor portions directly attached to the power supply are spaced apart from adjacent semiconductor portions. Portions farther from the connection point are placed closer together. This means that the power delivered to the semiconductor layer is more evenly distributed.

[0132] In one embodiment, the electric heater is substantially free of metal conductors, such as metal wire conductors, and includes an electric semiconductor layer of a first electric semiconductor composition having a positive temperature coefficient, the first electric semiconductor composition comprising polyethylene, polypropylene, or a mixture thereof, and conductive fillers; A plurality of semiconductor portions located on an electrical semiconductor layer, wherein the semiconductor portions include a second electrical semiconductor composition having a positive temperature coefficient and comprising polyethylene, polypropylene or a mixture thereof and conductive filler; The semiconductor portion is at least three times thicker than the semiconductor layer, and each semiconductor portion has a width of at least 3.0 mm at any point.

[0133] Production

[0134] Heaters can be manufactured using several technologies, including: -Extrusion -Compression molding -laminated.

[0135] Extrusion or lamination is the most convenient method. The heater to be protected can be prepared by co-amylation. In this method, a semiconductive layer can be prepared, for example by extrusion, such as cast film extrusion or blown film extrusion. It can be cooled before co-lamination occurs. The semiconductor portion can also be in the form of an extruded film, which can then be laminated onto the semiconductor layer. The semiconductor portion can also be prepared by extrusion, such as cast film extrusion or blown film extrusion.

[0136] A surface can be heated before co-lamination so that when the co-laminated layers are pressed together, the electro-semiconductor layer adheres to the semiconductor portion.

[0137] Therefore, the desired film or portion can be prepared using cast film or blown film extrusion. In cast film extrusion, a vertically positioned slit die is used to extrude a fine molten film onto a highly polished, high-speed cooling roller. Pressure from an air knife or a vacuum chamber located near the roller pins the melt to the surface of the cooling roller. This results in the fine film being rapidly quenched, which improves its mechanical properties and transparency. The film then passes through a series of further cooling, polishing, and rolling processes, which helps to stretch the film to the correct thickness, then trims its edges and winds it onto a roller for storage.

[0138] In blown film extrusion, molten plastic from the extruder passes through an annular die and emerges in the form of a thin tube. Supplying air into the tube prevents it from collapsing and allows it to be expanded to a larger diameter. Initially, the air bubble consists of molten plastic, but air jets around the outside of the tube (cooling ring) promote cooling, and a freeze line can be identified at a distance from the die exit. Finally, the cooled film passes through folding guides and clamping rollers before being fed into a storage cylinder or, for example, fitted with gusset plates and cut to a certain length.

[0139] A preferred key aspect of this invention is that the claimed heater can be prepared using co-extrusion. Therefore, the heater of this invention is preferably not a typical laminate (where each layer is prepared separately and laminated together, possibly using adhesives). Our product does not require adhesives.

[0140] Therefore, the heater of the present invention can be manufactured continuously.

[0141] Importantly, the semiconductor composition can be co-extruded with the semiconductor portion. The heater of this invention is inexpensive. It is also thin and flexible.

[0142] The semiconductor portion preferably has at least one connection point to allow it to be connected to a power source. Typically, the connection point will be a suitable metal electrode to which a metal conductor from the power source can be easily connected. The semiconductor portion may include multiple such connection points. The connection points should be evenly spaced to ensure uniform heating in the semiconductor layer in contact with the semiconductor portion. These connection points can be attached to or embedded in the semiconductor portion when the polymer is in a molten state.

[0143] In a preferred embodiment of the present invention, the method includes step (a)

[0144] - Provide and melt-blend the first electrical semiconductor composition as defined herein in an extruder. - Provide and melt-mix the second electrical semiconductor composition as defined herein in an extruder (b) Co-extrusion, -A molten mixture of the first electrical semiconductor composition obtained in step (a), -A molten mixture of the second electrical semiconductor composition obtained from step (a), A heater is formed having a semiconductor layer of a first electrical semiconductor composition having a positive temperature coefficient, the first electrical semiconductor composition comprising polyethylene, polypropylene, or a mixture thereof, and conductive filler. Multiple semiconductor portions comprising a second semiconductor composition, the second semiconductor composition being located on and protruding from a first semiconductor layer, wherein the second semiconductor composition has a positive temperature coefficient and comprises polyethylene, polypropylene, or a mixture thereof, and conductive filler; The semiconductor portion is arranged in a regular pattern on the semiconductor layer; and The semiconductor portion has a conductivity that is higher than, for example, at least 5 times higher than, that of the electrically conductive semiconductor layer. This process can be readily adapted to include additional layers above or below the semiconductor layer. In particular, the second layer as defined herein can also be co-extruded above or below the semiconducting layer. Alternatively, the second layer can be laminated above or below the semiconducting layer.

[0145] In one embodiment, crosslinking conditions can then be applied to induce a crosslinking reaction. However, it is preferable not to use a crosslinking reaction.

[0146] Melt mixing refers to mixing at a temperature above the melting point of at least the major polymer component of the mixture, and typically at a temperature at least 10°C to 15°C higher than the melting or softening point of the polymer component.

[0147] The term "co-extrusion" in this document refers to extruding two or more layers in the same extrusion step. The term "co-extrusion" also refers to the simultaneous formation of all or part of a layer using one or more extrusion heads. For example, triple extrusion can be used to form three layers.

[0148] electric heater

[0149] The heater of the present invention is flexible. It is preferably in the form of a flat plate, although such a plate is flexible and can take the shape of the substrate to which it is applied, or can be formed as a cylinder.

[0150] In operation, an electric current is applied from a power source to the heater to generate heat. Typically, the voltage ranges from 10 to 70 volts, for example, 12 to 30 volts. Therefore, a battery or a power source with a suitable transformer can be used to heat the heater. Providing power to the heater generates heat almost instantaneously. Because the voltage used does not need to be very high, there is no risk of electric shock.

[0151] The heater can be manufactured to any desired size. The width of the heater can be adjusted according to any possible application. The width can be a function of the co-extrusion equipment, and sheets from 5 cm to 5 m can be easily produced.

[0152] As mentioned earlier, the heating power can be controlled by the sheet thickness, the spacing of the semiconductor conductors, the content of conductive filler, and the applied voltage. Moving the semiconductor conductors closer together increases the wattage, thereby increasing the heat generated. The relationship can be expressed as Power = [Voltage]2 / resistance.

[0153] application

[0154] The heater of the present invention can be used in many fields. Therefore, the technology described herein has a wide range of applications.

[0155] We typically provide thermal comfort in winter by heating the entire air in a room or building. In earlier times, our ancestors had a more localized concept of heating: heating people, not places. They used radiant heat sources to heat only specific parts of a room, creating comfortable microclimates. These people used insulated furniture to cope with large temperature differences, such as hooded chairs and folding screens, and they utilized additional personal heat sources to warm specific parts of their bodies. Restoring this ancient method of heating is highly meaningful, especially since modern technology has made it more practical, safe, and efficient.

[0156] Therefore, the heater of the present invention can be used in furniture such as screens, chairs or sofas.

[0157] In one embodiment, the heater of the present invention can be used to heat clothing. Currently available heated clothing has small wires (typically made of fragile carbon fiber) embedded within it. These wires heat up when a low-voltage current passes through them. There are two main types of heated clothing: battery-powered or vehicle-powered (e.g., heated gloves on motorcycles). The heater of the present invention is ideally suited for both applications.

[0158] The heater can also be used in blankets. A major problem with electric blankets currently on the market is the fire risk. These blankets are prone to overheating. This risk is eliminated by using the heater of the present invention. Therefore, in general, the present invention provides a textile comprising the heater of the present invention.

[0159] Radiators are large, fixed, and often unsightly. In many parts of the world, radiators are concealed behind more aesthetically pleasing covers of various designs. These covers can also reduce noise or prevent contact with overheated radiators. However, concealing radiators is inefficient because adding a radiator cover slows the rate at which heat dissipates from the radiator into the room. Heat loss through the building's exterior walls may increase.

[0160] The heater of this invention can replace a radiator, or be used as a heater in walls, under floors, or in ceilings. The heater can even be contained in carpets, rugs, or other floor coverings.

[0161] Unlike traditional passenger cars, electric vehicles generate almost no heat, while the engine heat generated in a traditional passenger car is sufficient to heat the interior. Therefore, electric vehicles require an additional electric heater to heat the interior.

[0162] This heater is powered by the same battery that powers the engine. This can significantly reduce the maximum possible driving range.

[0163] Therefore, it is necessary to heat electric vehicles as efficiently as possible. This invention can be used to heat internal contact surfaces, such as the steering wheel, armrests, door panels, and seats inside a vehicle. More efficient heating is conceivable compared to heating the entire interior volume of the car, especially for short trips.

[0164] The heater of this invention can be used to prevent ice or snow from accumulating on critical surfaces such as solar panels. Therefore, the heater may be useful in de-icing operations. Other surfaces may include rearview mirrors.

[0165] The heater is flexible and can be wrapped around pipes to prevent the liquid inside from freezing. It can also be used to keep fluids heated, such as in swimming pools or liquid containers. Technicians can design numerous applications for these versatile heaters.

[0166] The invention will now be described with reference to the following non-limiting embodiments and accompanying drawings. Attached Figure Description

[0167] Figure 1 The planar heater of the present invention is shown from above and in cross-section. The heater has parallel semiconductor portions located on and protruding from a semiconductor layer. The semiconductor portions are spaced apart, for example, by 8 cm, and the height can be 2 mm to 3 mm or thicker. The semiconductor composition can be formed from EVA or EBA.

[0168] Figure 2 The planar heater of the present invention is shown from above and in cross-section. The heater has parallel semiconductor portions located on and protruding from a semiconductor layer. The semiconductor portions are spaced apart, for example, 8 cm, and their height can be 2 mm to 3 mm. The semiconductor composition can be formed of EVA or EBA. Adjacent edges of the semiconductor portions are beveled to create a smooth gradient increase in height from the semiconductor composition to the semiconductor portions, primarily to reduce mechanical stress.

[0169] Figure 3 The planar heater of the present invention, viewed from above, is shown. The heater has semiconductor portions located on and protruding from a semiconductor layer. The semiconductor composition may be formed of EVA or EBA. The heater is provided with connection points to a voltage source. The portions of the semiconducting portions closest to these respective connection points are spaced far apart from adjacent semiconducting portions, but as the distance from the connection point increases, the adjacent semiconducting portions move closer to each other, thus creating a <>-shaped arrangement. The use of these non-parallel semiconductor portions compensates for the voltage drop that occurs along the semiconductor portions as the distance from the connection point and the power source increases.

[0170] Figure 4a and Figure 4b Shown from above and in cross-section Figure 1 A flat plate heater. The heater has parallel semiconductor portions (2) located on and protruding from the semiconductor layer (1). The semiconductor portions are spaced apart, for example, 8 cm, and the height can be 2 mm to 3 mm or thicker. The semiconductor composition can be formed of EVA or EBA.

[0171] The semiconductor portion includes metal connectors or electrodes (3), which may be in the form of a disc that can be connected to a power source via wires (4). However, the metal wires do not pass through most of the semiconductor portion.

[0172] test: melt flow rate Melt flow rate (MFR) is determined according to ISO 1133 and expressed in g / 10 min. MFR is an indicator of the polymer's flowability and processing properties.

[0173] For polyethylene present in semiconductor compositions, MFR is determined at 125°C. The determination can be performed under a load of 21.6 kg (MFR21).

[0174] Example

[0175] The following materials are used in this article: The semiconductive composition is an EVA1-ethylene vinyl acetate copolymer having 17% by weight of comonomer and 920 kg / m 3 The density, combined with carbon black (38 wt%), and the MFR measured at 125 °C were 7.0 g / 10 min. 21 .

[0176] Example 1 – Semiconductor Layer

[0177] Films were prepared using a 3-layer cast film laboratory production line manufactured by Collin. This line consisted of a 30 mm core extruder and two 25 mm external extruders, each 30 / LD in length. The die width was 300 mm, with flexible die lips ranging from 0.5 mm to 1.2 mm, resulting in a final film width of approximately 250 mm. The cooling roller unit comprised three polished cooling rollers tempered in the range of 15°C to 120°C. The film was wound into a 3-inch core.

[0178] EVA1 is extruded in layers 1 through 3 to form a monolayer. The total film thickness is 125 μm.

[0179] Example 2 – Semiconductor Section

[0180] Thin films were prepared using a 3-layer cast film laboratory production line manufactured by Collin. This line consisted of a 30 mm core extruder and two 25 mm external extruders, each 30 / LD in length. The die width was 300 mm, with flexible die lips ranging from 0.5 mm to 1.2 mm, resulting in a final film width of approximately 250 mm. The cooling roll unit comprised three polished cooling rolls tempered in the range of 15°C to 120°C. The film was wound into a 3-inch core. EVA1 was extruded in layers 1 through 3 to form a monolayer. The total film thickness was 300 μm, but it could be cut to the required dimensions for the semiconductor portion strip.

[0181] Example 3 – Co-lamination

[0182] The semiconductor portion of Example 2 is laminated onto the semiconductor layer of Example 1 by preheating and then thermal lamination.

Claims

1. An electric heater, such as a flat panel electric heater, comprising a semiconductor layer, said semiconductor layer comprising a first electrosemiconductor composition having a positive temperature coefficient, said first semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; A plurality of semiconductor portions located on and protruding from the semiconductor layer, wherein the semiconductor portions include a second electrical semiconductor composition having a positive temperature coefficient, the second electrical semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; The semiconductor portion is arranged in a regular pattern on the semiconductor layer; and The semiconductor portion has a conductivity that is, for example, at least 5 times higher than that of the semiconductor layer. For example, the higher conductivity of the semiconductor portion is provided by the geometry, spacing, thickness, and / or content of the conductive filler in the semiconductor portion.

2. An electric heater, such as a flat panel electric heater, comprising a semiconductor layer, said semiconductor layer comprising a first electrosemiconductor composition having a positive temperature coefficient, said first semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; A plurality of semiconductor portions located on and protruding from the electrical semiconductor layer, wherein the semiconductor portions include a second electrical semiconductor composition having a positive temperature coefficient, the second semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; The semiconductor portion is arranged in a regular pattern on the semiconductor layer; and The semiconductor portion is at least twice as thick as the semiconductor layer.

3. An electric heater, such as a flat plate electric heater, comprising a semiconductor layer of a first electrosemiconductor composition having a positive temperature coefficient, the first electrosemiconductor composition comprising polyethylene, polypropylene, or a mixture thereof, and a conductive filler; A plurality of semiconductor portions located on the electrical semiconductor layer, wherein the semiconductor portions include a second electrical semiconductor composition having a positive temperature coefficient, the second semiconductor composition comprising polyethylene, polypropylene or a mixture thereof and conductive filler; The semiconductor portion has a conductivity that is, for example, at least 5 times higher than that of the electrical semiconductor layer. A power supply suitable for supplying power to at least one connection point on each semiconductor section; The adjacent semiconductor portions are spaced apart from each other, and the distance between adjacent portions of the semiconductor portions decreases as the portion of the semiconductor portion is further away from the nearest corresponding connection point.

4. The electric heater of claim 1, such as a flat plate electric heater, wherein the metal wire is not embedded therein or located thereon along a large portion of the length or width of the semiconductor portion, for example, at least 25% of its length or width, for example, at least 50% of its length or width, for example, its entire length or width.

5. The electric heater of claim 4, wherein the semiconductor portion is provided with a plurality of connection points, such as metal connection points, so that the semiconductor portion can be connected to a power source.

6. The electric heater of claim 5, wherein the connection point is located on the edge of the semiconductor portion.

7. The electric heater according to claim 5 or 6, wherein, The connection point is connected to the power source via a metal wire, preferably, the metal wire does not contact most of the semiconductor portion.

8. The electric heater according to any one of the preceding claims, wherein each semiconductor portion has parallel edges, and the distance between adjacent edges of adjacent semiconductor portions is 20 mm to 150 mm.

9. The electric heater according to any one of the preceding claims, which is substantially free of metal wire conductors.

10. The electric heater according to any one of the preceding claims, wherein, The semiconductor portion has a rectangular cross-section.

11. The electric heater according to any one of the preceding claims, wherein, The semiconductor portion is chamfered or beveled at the interface between the semiconductor portion and the semiconductor layer.

12. The electric heater according to any one of the preceding claims, wherein, The heater is provided with at least one additional layer above the semiconductor layer and / or at least one additional layer below the semiconductor layer, preferably an insulating layer, such as a thermal insulating layer.

13. The electric heater according to any one of the preceding claims, wherein, The polyethylene used in the first and second electrical semiconductor compositions is the same.

14. The electric heater according to any one of the preceding claims, wherein, The first and second electrical semiconductor compositions independently comprise LDPE homopolymers and / or LDPE copolymers, particularly ethylene alkyl acrylate or ethylene vinyl acetate polymers.

15. The electric heater according to any one of the preceding claims, wherein, The conductive filler in the first and / or second electrical semiconductor composition includes carbon black.

16. The electric heater according to any one of the preceding claims, wherein, The first and / or second electrical semiconductor composition comprises 15% to 50% by weight of conductive filler.

17. The electric heater according to any one of the preceding claims, wherein, The heater is manufactured by extrusion, injection molding, compression molding or vacuum forming.

18. The electric heater according to any one of the preceding claims is in sheet form, wherein the thickness of the semiconductor composition layer is 50 μm to 900 μm, for example 125 μm to 800 μm.

19. The electric heater according to any one of the preceding claims, wherein, The width of the semiconductor portion is 1.0 mm to 30 mm, and / or the semiconductor portion covers 5% to 40% by weight of the semiconductor layer.

20. The electric heater according to any one of the preceding claims, wherein, At least one metal electrode, such as at least two metal electrodes, is located on or embedded in each semiconductor portion.

21. A method for preparing a flat-plate electric heater, comprising step (a) - A first electrosemiconductor composition is provided and melt-blended in an extruder, the first electrosemiconductor composition comprising polyethylene, polypropylene, or a mixture thereof, and a conductive filler. - A second electrical semiconductor composition is provided and melt-blended in an extruder. The second electrical semiconductor composition may be the same as or different from the first semiconductor composition. The second electrical semiconductor composition comprises polyethylene, polypropylene, or a mixture thereof, and conductive fillers. (b) Co-extrusion, - A melt mixture of the first electro-semiconductor composition obtained in step (a) to form a layer, and - A molten mixture of the second electro-semiconductor composition obtained in step (a) is used to form an electric heater as claimed in claims 1 to 20.

22. An article comprising a flat electric heater as described in claims 1 to 20, such as a heated textile or vehicle seat.

23. Use of a second semiconductor composition having a positive temperature coefficient as a conductor in a heating device, the second semiconductor composition comprising polyethylene, polypropylene, or a mixture thereof and a conductive filler, the heating device comprising a first electrical semiconductor composition, which may be the same as or different from the second composition, having a positive temperature coefficient and comprising polyethylene, polypropylene, or a mixture thereof and a conductive filler.

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