DE2635000A1 - SELF-HEATING OBJECTS WITH TISSUE ELECTRODES - Google Patents

Description

DR.-ING. GERALD KLOPSCH 5OOO COLOGNE 1

PATENT ADVERTISER MARSPLATZ 11

July 28, 1976 Kl / En

Rayehern Corporation,

300 Constitution Drive, Menlo Park, California 9 ^ 025 (U.S.A.)

Self-heating objects with fabric electrodes

Heat-restoring objects which are self-heating can be obtained by incorporating at least one flexible, dimensionally deformable fabric electrode into a heat-restoring part which advantageously contains an electrically conductive polymer mass. The electrodes are worked into the T -. Il before it is deformed in its thermally unstable state. As a result of their flexibility, when the heat recoverable member is deformed to its heat unstable state, the electrodes deform and return to the heat stable configuration with it. The polymer mass is chosen so that its ohmic resistance is high enough that, when the electrodes are connected in series to a source of electrical power, the current passing through the mass heats them. The heat generated in this way can be used to provide all or some of the heat required for the recovery of the article, or to use the article as a heating device after recovery. If desired, a polymer composition with a positive temperature coefficient of resistance (PTC) can be selected, which results in the maximum temperature at which the

V 0 9 8 0 9/0 3 1 p

Object itself heated, can be controlled.

The invention relates to heat recoverable articles, in particular self-heating heat-recoverable objects.

Polymeric heat-recoverable articles can e.g. Tube shape as a sealing, insulating or protective cover for elongated objects, e.g. cables and pipes, be used. A tube made of heat-restoring material is slipped over the base and placed on restoring material temperature as it shrinks to a smaller diameter. Because the pipe is compliant and elastic at the reset temperature is, it shrinks and touches the substrate and thereby assumes its shape.

In many cases there is no free or easily accessible end of the elongate article available, so that a heat-recoverable tape-shaped material is wrapped around the substrate and its ends connected. This wrap-around sleeve is heated in position to recover. Examples of such wrapping devices for documents that do not have access to a free end are given in U.S. Patents 3,379,218, 3,555,336 and 3,770,556. The heat-resistant articles described above can suitably be obtained from a wide variety of crosslinked crystalline polymer compositions. Suitable materials and methods for the crosslinking, for example by ionizing radiation, and for the transfer of such articles on the heat-recoverable state are described in U.S. Patent No. 3,086,242. Chemical crosslinking agents such as peroxides can also be used.

In order to make an object made of such a mass heat-recoverable, it is deformed in its dimensions above the crystal melting point (or area) and kept in this deformed state until

709809/0318

the object has cooled below the melting point. 1.-n cooled state, the article can be used as dimensionally unstable
because it shows the so-called "elastic memory" when it is heated up again to above the melting point of the crystal without hindrance, ie it becomes its own
return to original dimensions. In the recovered form the subject matter is often considered to _{Wärmeeinwir-:} kung called dimensionally stable.

The recovery of the heat-recoverable article can suitably be achieved by applying heat to the article using a torch or a heat gun. However, in certain cases, for example when the area where the application of heat is required,
inaccessible or in an area where open
Fire is dangerous or forbidden, as in mines, where j large quantities of flammable gases can be present, I treatment with such agents is undesirable or even impossible. Under these circumstances, conductive poly-mers can be used as a heat-recoverable material in heat-recoverable articles. An object made of a conductive polymer is used as a resistance heater in |

ι wired an electrical conductor circuit and after connection!

with a power source, e.g. eini * 12 to 24 or even ^ 6
Vclt battery or an alternating current source (eg from 115 ■ volts), current flows through the object. As a result, be-; nes Ohm ¹ see resistance it heats up, whereupon this '. Heat can be used in part or in full as the heat required for restoring the object. if
If the temperature is too high, the polymer material is subject to decomposition. Sensitive components that are shielded by the object can also be destroyed
be though the extent of the damage by visual inspection
does not need to be visible.

To avoid high temperatures, thermostats are used
709809/0316

or other control devices are used. However vlr ·: in many cases this makes the purpose of using --er. ReTlsterhit ^ end heat-retractable objects veri'f '·. /. ¹ Z, inderr bulky and expensive components have to be ndet in places that are often inaccessible. It has already been proposed to eliminate these additional components by using a polymer compound which exhibits a positive temperature coefficient of resistance (CpTC). Such masses are referred to as PTC masses.

Suitable compositions contain an organic thermoplastic polymer, in particular a crystalline polymer, the carbon or another finely divided conductor such as a finely divided metal. PTC masses are subject to a relatively small increase in resistance with increasing temperature, until a certain temperature T (which is a temperature

range), sometimes as switching or abnormal temperature designated, is reached. Above T, a further increase in temperature results in a large increase in the Resistance. The rise in resistance can be so sharp that the current drops to a level which corresponds to the temperature of the Mass limited to its T temperature. For crystalline polymers, T is at or just below the crystalline melting point or range.

If a PTC compound is used as part of a self-heating heat-resilient object, it effectively knows the T '- rnper? It-.ir, on dip the npf-pnstand ^ r ■:' *. · ':. - Limit Ir ¹ O. Suitable PTC compounds are in US SN 601.659 of August 4, 1975 and the German patent application P 25 43 346.9. 29 «9. 1975. The types of applications of such heat-recoverable articles proposed above have recently been limited because, in most designs, the heat-recoverable article must be provided with a plurality of electrodes, generally pairs of substantially parallel wires. The object can therefore only be used in

709809/0318

BATH ORIGINAL

its heat unstable state by deformation ir. a-r · direction perpendicular to the direction in which the electrodes are ^:. '. are deformed. This fact has significantly limited the r.Uteilchen design options for self-heating heat-resilient objects.

D'.e S-'findung concerns a heat-resilient flf ^ ör.-stand, which has a heat-recoverable part which contains an electrically resistive material in the at least a flexible cloth electrode and a second "electrode is incorporated, wherein the electrodes are capable of current flow through the material after pre-connecting to a power source with electrical resistance to cause.

The second electrode can be incorporated into the resistance material, can be in contact with the heat-resilient part, for example as a substrate, or can be incorporated into a second part which is adjacent to the heat-resilient part. The second electrode can consist of a. S tires or grids are made of metal, provided that this does not hinder the deformation of the resilient object between its initial, heat-recoverable and heat-recovered state. The second electrode advantageously consists of a flexible fabric electrode that is incorporated into the resistance material.

The heat-recoverable part advantageously has a polymer compound with sufficiently conductive filler, e.g. finely divided carbon black or metal, so that it is able to conduct electrical current at constant voltage, e.g. at 12 to J56 volts from a battery or 115 volts AC. The mass should also have a sufficient Chm ¹ snhen 'resistance so that the V / arm produced is able to bring about the recovery of the heat-recovering part, which can be several millimeters thick. There are many suitable polymers for use in these compositions, in particular

709809/0318

Crosslinked crystalline polymers such as those of US Pat. No. 3,086,242 are particularly useful. An object made from such a polymer can be deformed above the crystal melting point or range (hereinafter referred to as "crystal r-hnri 7_ ^! Dot") and kept in the deformed state until it cools to make the object heat-recoverable do.

The heat-resilient part preferably has at least
a layer of conductive polymer as described above; on.

The layer or layers can either have a constant Watt behavior or a positive temperature coefficient of resistance. Preferably one shows for
PTC material used for a heat-resilient membrane
at least a 6-fold increase in resistance in one; B-rich from J50 ° C above T. A material with con-!

constant watt power has a resistance which rr.with the temperature can increase, but which has no temperature! whose resistance increases so rapidly that it becomes an insulator for most purposes. Within the context! this application is regarded as a material constant wattage a material whose resistivity is not to '<a factor of more than approximately 6 in each temperature-\ ranging from 30 ⁰ C, between 25 ° C and the melting point of the poly; meren or a higher temperature, if the polymer for the purpose! Granting structural stability above the melting point j was crosslinked, increases. Preferably it has a special! fish up V / resistance of at least 1 ohm / cross section unit ■ (I ^ / square) at 25 ° C.

Constant wattage materials suitable for the purposes of the invention are known. In many cases you can
the polymers used in PTC masses are used in masses of constant wattage by adding a

709809/031 δ

larger proportion of a conductive filler than in PTC-: · '.assen is incorporated. If the T of masses, the PTC character

have, is large enough, these masses can be used as materials of constant wattage. The details, the PTC materials and materials of constant V.'att power, those in heat-recoverable objects according to; of the invention are suitable to characterize are in j US S.N. 6OI.638 and the Dutch patent application; No. 75 / II.392.

The stretchable fabric electrode advantageously contains stranded material
Material of any suitable conductive material. Preferably, the strands are made of a Ma- ^; Material with low specific conductivity, which is j low in price, eg stranded copper wire and preferably 28 to 40 gauge wire strand. Strands from others
Metals including alloys and a \ is zv.ei K r-ipononten · existing metal strands, composite materials from Xete.ll and ° a-Iy. Animal fibers, metal-coated polymer fibers or conductive
Carbon fibers can also be used.

The tissue electrode must be sufficiently flexible Ίί ~ when it is incorporated into the polymer composition, singing in their Acmes- · can be deformed to the same extent 1 ™ as the
Mass if the latter is above the crystal melting point
is heated to make it heat-recoverable, as in
U.S. Patent 3,086,242. ^;

In addition, the electrode should have the resilience of the
heat-restorable part, if this is heated, do not interfere weekly. Such electrodes are advantageously able to change their dimensions by at least 100%, e.g.
in length and width or, if they are tubular, in diameter and / or length, based on the heat-stable state, to change, preferably by at least 300 #. However, any fabric that is compatible with the heat-relieving object is in between

. ' 709809/0316

its initial state the resettable state and ie: n reset state can be deformed for the Z corner suitable for the invention. The suitability of a given: I - '. Aterials can therefore easily be determined for each individual case by simple routine experiments.

Suitable electrode fabrics can be produced by known techniques, e.g. weaving, knitting or lace making. Of these, bobbin lace is preferred because when using this: ¹ technique, electrodes with good compliance or flexibility are obtained. These electrodes can preferably be easily stretched during the deformation process, which makes the polyir.ermass heat-resilient, and furthermore have a minimum; resistance to the recovery of the heat-recoverable part. Advantageously consist tzen umkloppelte ϊ electrodes tubular L', which preferably a [core of thermoplastic material are braided around or geklöppelt. A tubular clapper with a high clapper angle, based on the axis of the tube, for example at an angle greater than approximately 50 and preferably; approximately 75 are particularly beneficial. A suitable braid is obtained using 16 carriers of 4 strands each of tinned copper wire (38 AWG = American wire gauge) at a braiding angle of 75 ° around a cylindrical core which is tubular and made of a conductive or non-conductive thermoplastic Material, and · has an outside diameter of 0.64 cm. Preferably there is; the cylindrical core made of a conductive material which is compatible with the polymer from which the heat-restoring part is made. Usually the braided tube is heated to above the softening point of the thermoplastic core and then flattened, taking care to avoid stretching the braid during this deformation. For some purposes, e.g. when it is desired that the pipe be radially expandable instead of longitudinally expandable, lower conversion

709809/0316

braiding angles can be applied. The braiding properties a radially expanded tube are described in U3-P3 3.253.619.

The 2'finding is now in greater detail on the basis of the Drawings are described, wherein Figure 1 is a perspective view of a braided electrode, Figures 2, 3 and 5 7 through 7 are perspective views of five different embodiments of heat-resilient objects according to the invention and FIG. 4 is a perspective view of a Represent electrode assembly.

In FIG. 1, the braided electrode 10 has a tubular shape Braid 11 which is wrapped over a hollow tubular core 12. In Figure 2, the heat-recoverable Item I3 a plurality of electrodes 10 after the flattening, which are in a layer 14 made of a PTC-Xasse, as described above, are embedded. The electrodes 10 have a common boundary with the PTC layer. Adjacent electrode pairs 10 are connected in series to a current source 15.

In operation, current is passed mass FTC between the electrodes by di ^r j. After sufficient heat has been generated, the object I3 is restored. The PTC layer 14 is deformable in both one and two directions, ie in one direction in order to effect the separation of the electrodes and / or in a direction in order to cause an elongation of the object I3 along the axis of the electrodes to To give heat recovery. An egg

Conventional rigid electrode allows a deformation only i in one direction towards the separation of the electrodes 10. Since the ^[ separation of the electrodes extends the current path and thereby the resistance of the object 13 », the energy output of the object I3 in the expanded state is limited.

7 0 9809/0318

- Io -

Since layer 14 of article I ^ contains a PTC mass :, heating is limited when the T temperature of the? o-

lymeren in the mass is achieved. The object is there; self-heating and able to advantageously function as a heating device after reset, independently whether the ability to self-heat

is used at the time of resetting the item.

In FIG. 5, the heat-restoring object 50j has two layers of electrodes 10 which are embedded in a layer 14 made of a PTC polymer mass. The electrodes 10 in the upper layer are parallel and in 'another series of the lower layer with which the polymer layer ^by: connected. A layer of electrodes 10 is shown in FIG. 4 prior to incorporation into the heat-recoverable object. Each layer has a distribution electrode 16 at both ends. The distribution electrodes 16 are fabric electrodes _; The and can adhere to the electrodes 10 by having their thermoplastic core set to above the softening point. heats and they are compressed, or by usual; Spot welding or soldering. The distribution ^{electrodes 16 are:} used to distribute the energy to the electrodes 10 of each layer j. The heat-resilient object JO can! extends along and / or perpendicular to the longitudinal axis of the electrodes 10; be deformed.

The heat-resilient objects of FIGS. 2 and 3 can contain a polymer mass with constant wattage instead of a PTC mass.

In FIG. 5, the heat-recoverable article 17 contains a set of electrodes 10 embedded in a layer 18 of a polymer composition with constant wattage, and a second set of electrodes 10 which are embedded in a layer 19 of a PTC polymer composition.

709809/0311

Tn Figure 6 is said to be a heat-recoverable object, which contains three layers of polymer masses. Zv; ei sentences of Electrodes 10 are in two layers 21 and 22 of a foam material constant wattage embedded, the sanrivrich-like include a layer 23 of a PTC polymer material.

In a heat-recoverable object in which only thin films of PTC masses are used, and the Strcm flows in the plane of the film, it has been found that even with moderate energy output the phenomenon of the "hot line" occurs, where only a narrow band of the PTC-S: -hicht functions as a heating device. This problem was addressed in the | already mentioned US application 601,638 discussed. '

The temperature T at which the resistance of a PTC material

rises sharply, is at or below the crystal melting point for crystalline polymers. These polymers, when in a heat recoverable form, are subject to Recovery above its crystalline melting point, and sufficient mobility for effective recovery requires temperatures that are at least 10 ° C above the crystalline melting point. A shift system, such as in Figure 5 or 6, shows a relative resistance between the layer or layers of material con-

constant wattage and the layer of PTC material, so that the layer of constant watt output heats up first when its resistance is higher than the resistance of the -. Layer of PTC mass. The object can be above T be heated by rapidly heating the material of constant watt power before heat conduction increases the temperature of the PTC mass increased to T and thereby interrupts the flow of current.

A more effective method of overcoming the drawbacks of the "hot line" is described in U.S. Application 604,427. The object described there has a structure in which

709809/0316

a relatively low resistance, t! ie table insulated layer of constant W material ^; ; ttleii: tunr. hiss a heating layer of a material constant Ί *: t-power and a layer of PTC composition is arranged as figure "shows wärmerückstelIfähige The object 4 includes a layer 25 of material of constant Vatt-Lois.t mg relatively hoherr.? Resistor, a heat insulating layer 26 of relatively low resistance and a layer 27 of PTC compound of medium initial resistance. The layer 26 may be made of a foamed polymer material so that it has good thermal insulating properties. When current is applied , layer 25 is heated, but layer 27 is thermally cut off by layer 26 and its temperature rise lags behind that of layer 23. Thus layer 25 can be heated to above the crystalline melting point of the heat recoverable part before the energy is thereby cut off that the 'temperature of the PTC mass reaches T. Thermal conductivity effects allow the entire The object is finally heated to above the recovery temperature, ie the crystal melting point by an amount which ensures effective recovery. The layer 25 can also consist of a PTC material, provided that this is a higher one

T has layer 27.
s

Not all layers of a multi-layered heat, resilient object to be heat-resilient, before-j exposed there? at least one layer is heat-restorable and has sufficient "stability" to the to keep other layers in the deformed state, or that the layer has a sufficient restoring force that the forces other layers towards the thermostable configuration. In this case you need the other layers not being heat resilient.

In the embodiment, the electrodes 10 are in one

709809/0318

Layer of a polymer compound embedded. This will be beneficial achieved by arranging the electrodes between two polymer sub-layers, which then rrit each other bonded, e.g., sublayers that have been heated to above their softening point and using have been laminated by lamination rolls.

Although the objects shown are relatively planar, objects of regular or irregular construction can also be used getting produced. E.g. tubular objects with a multiplicity of Ge ^ 'ec ^ le'rCtrs arranged in the pipe: and / or several layers either parallel to the L "n £ \ 3 of the pipe or perpendicular to it. Eir. particularly preferred subject matter is in US patent application 601.3 ^ "+ and in the German patent application P 25 ^ 3 JJ53.9 described. Alternatively, the tubular structure can be around a cylindrical pipe can be arranged and, after installation, used to clean the inside of the pipe, Heat to prevent solids from freezing or salting out.

709809/0316

Claims (20)

Claims 1) JSelf-heating item, indicated by a Part containing a material with electrical resistance and at least one flexible cloth electrode and a second electrode, the electrodes being capable of connection to a source of electrical power To cause current to flow through the material with electrical resistance. 2) Article according to claim 1, characterized in that the electrical resistance material containing part in the heat-recoverable state can be transferred. 3) object according to claims 1, characterized in that the part containing the electrical resistance is heat recoverable is. 4) Object according to claim 1, characterized in that the part containing the electrical resistance material is in the recovered state. 5) Object according to one of claims 1 to 4, characterized in that that the cloth electrode and the second electrode are incorporated into the material with electrical resistance are. 6) Article according to claims 1-5 »characterized by a pair of flexible fabric electrodes, which are in the material are incorporated with electrical resistance. 7) Object according to claim 6, characterized in that the fabric electrode consists of a woven, knitted or ge braided or braided electrode. 709809/0316 8) Object according to claim 7, characterized in that da3 ^! the fabric electrode has a tubular braid.} 9) Object according to claim 7, characterized in that the tubular braiding over a core made of thermoplastic Material is arranged. 10) Object according to claim 9, characterized in that the core is designed as a hollow tube. 11) Object according to claim lo, characterized in that the tubular braiding has a braiding angle relative to the pipe axis of at least 50 °, preferably of at least 75 ° *. 12) Object according to claims 1 to 11, characterized in that each fabric electrode, based on the dimension in the heat-stable state, is variable by more than 100 #, preferably at least 300 fo in its dimension. 13) Object according to one of claims 1 to 32, characterized in that that at least one electrode is made of stranded copper wire. Object according to claim I3, characterized by a One gauge strand of copper wire ranging from 28 to 40. Object according to claims 1 to 1 4, characterized in that that the heat-recoverable part consists of a layer a polymer mass, in the finely divided conductive Filler is incorporated. 16) Article according to claim 15 ,. characterized in that the heat recoverable member includes a layer of constant wattage material. 709809/0318 17) Object according to claim 15 or 16, characterized in that that the heat recoverable part is a layer of a Contains material with a positive temperature coefficient of resistance. 18) object according to claim 15 or l6, characterized in that that the heat recoverable part has a first layer of constant wattage material and a second layer Layer of a material with a positive temperature coefficient of resistance, each layer being Contains at least one cloth electrode which, after connection: with an electrical power source current flow from one! Shift to the other. 19) Object according to claim I5 or 16, characterized marked j. net that the heat-resilient part has a first layer with a positive temperature coefficient of resistance des having between two second layers with koni constant watt power is performed, each layer of which contains at least one fabric electrode, which after connection with a power source current flow from a second to the other arrange second shift. 20) Object according to claim 1 δ, characterized in that a layer of an electrically conductive material of constant wattage is sandwiched between a first one Layer of a material with constant wattage and a second layer of material with positive temperature coefficient of the resistor, both of which contain at least one cloth electrode, the resistance of which is arranged is less than that of the first layer of constant wattage and the second layer of material with positive temperature coefficient. 709809/0318