DE2915094A1 - CONDUCTIVE POLYMER COMPOUNDS - Google Patents

Description

Raychem Corporation / '·. .

300 Constitution Drive ,. Menlo Park, California 94025 (USA)

Conductive polymer compounds

The invention relates to conductive polymer compositions that have a positive Temperature coefficient of their electrical resistance have (PTC), devices that contain such masses and methods for using such masses (according to patent application P 27 46 6o2).

Conductive polymer compositions contain a conductive filler, usually carbon black, dispersed in a polymer. When the polymer is a thermoplastic crystalline polymer and contains an appropriate amount of a suitable conductive filler the masses show PTC behavior, i.e. a sharp increase in de Resistance over a particular temperature range, with the increase beginning around the softening point of the polymer. Such masses have been used, for example, in self-limiting heating strips and are at room temperature has been crosslinked by means of irradiation in order to improve their stability at higher temperatures. Though about PTC behavior reported in conductive polymers in which the polymer is not thermoplastic and crystalline It has been recognized by those skilled in the art that it can be used to achieve a practical Purposes suitable PTC mass is necessary, the conductive;

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gen filler in a thermoplastic crystalline poly! ren to disperse, and that the sharp rise in contradiction at or near the crystalline melting point of the polymer " takes place (see e.g. the article by J. Meyer in "Polymer Engineering and Science" November 1973, _1_3 ',. No. 6, pages' 468.)

Examples of the state of the art relating to PTC compounds] include US Pat. No. 2,978,665, 3,243,753, - 3,412,358, 3,591,526, 3,793,716, 3,823,217 and 3,914,363; GB-PS 1,409,695; "Brit. J. Appl. Phys." Series 2, 2, '567-576 (19 < Carley Read and Stow) and "Kautschuk und Gummi" II WT 13 * 148 (1958, de Meij). The disclosure of the above genanni Prior publications are hereby countered by reference; of the present application. For details of ji For more developments in this area, reference is made to the DT-OS 2,543,314, 2,543,338, 2,543,346, 2,634,999, 2,635,000, ■ 2.634.931, 2.634.932 and 2.655.54 3 as well as the DT-Gbm 7.527.288.

It has now been found that, provided it becomes sufficient A corresponding degree of crosslinking was introduced, the crosslinking of a beige conductive polymer (whether crystalline or amorphous and previously networked or not) has a significant influence on the resistance-temperature behavior of the mass at a Tempei which in relation to the crosslinking temperature (hereinafter hc denoted as T T / una / or at a temperature i

to. the
Draw / temperature at which the polymer is previously crosslinked wc. Such a crosslinking therefore often leads to the fact that the mass exhibits useful PTC behavior at a temperature that _{is related to T c} or that the previously existing useful PTC behavior is improved around T, it has also been found that the relationship between T unc temperature range over which the effect (on the resistance-temperature behavior) is mainly observed, in the case of;: phen polymers at least partially from the arrangement of the I.

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Merketten depends on the time of their networking. For example, if a polymer with a high green strength is tempered at one temperature and then heated (or cooled) to another temperature, both temperatures. 5 temperatures above the melting point, and if immediately- _ ^:. lent is crosslinked to an adequate extent, a PTC effect is observed, which begins at a temperature between the annealing temperature and T. On the other hand, the effect starts near T when the polymer has a low green strength. On crystalline polymers which are crosslinked at temperatures within the melting range and which have preferably been allowed to equilibrate at T before crosslinking; different effects are observed depending on whether T is below or above the peak of the melting range. ·

Therefore, if T is higher than the peak or maximum of crystal melting temperature and the mass sufficiently ^crosslinked: is, it exhibits PTC behavior in zv; ei temperature areas, • wherein the lower bezient to the Kr i stable melting point and higher on T. Still other effects can be observed

crystalline polymers that maintain the peak of the crystal melting range have been networked. It has also been found that the resistance-temperature behavior when a PTC mass is produced by a process that has two cross-linking containing steps at different temperatures, may reflect either or both crosslinking stages.

The invention therefore relates to PTC compounds with physical properties and / or resistance-temperature properties, which were previously not available. For example, the invention enables the production of PTC masses that.

ä) Show PTC behavior that is not related to a thermodynamic transition of the first or second order of the polymer is connected, e.g. the glass point or the crystal melting point, or with chemical instability (where this expression is

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wise the reduction of the stiffness of the network aboveSri: a certain temperature due to the instability of the. Cross-linking points above this temperature, e.g. the labili

• should include disulfide bridges above about 70 ⁰ C);

; 5 or ·! "-

'B) as a useful T, preferably at least 2 times to at least 5O ⁰ C separated from each other, have more; or c) exhibit PTC behavior which is associated with a thermodynamic transition of the polymer (as is known), but with sharper increases in resistance than has previously been achieved with the same polymer and the same conductive filler.

In the description and definition of the invention ^w: to the following terms and abbreviations are used: The term "switching temperature" (usually abbreviated T) b draws a range of temperatures, rapid about a PTC mass e increase in resistance shows. It is defined as the temperature at which the extensions of the essentially straight parts of the curve of the logarithm of the resistance plotted against the temperature (above and below the range) intersect. To be useful for practical purposes, a PTC material must have at least t, which is between about -100 ⁰ C and about 250 ⁰ C and is associated with a temperature range in which the composition has an R value of ... at least 2.5 or an R-. _Q0 value of at least 10 (preferably both), where R- ^ as the ratio of the resistances at the end and at the beginning of a 14 ° C range u R- _O ß as the ratio of the resistances at the end to that at the beginning of a 100 ^c C area is defined. It is further e practical requirement that the resistivity contributes unt semi about 10 C hm χ cm at the beginning of this temperature range. The expression "critical range" denotes a temperature range in which the R ^^ value is at least 2.5 or at least 10 and at the beginning of this the sp is lower than e

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Specific resistance less than about 10 ohm χ cm. is. Tuesday

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T of a PTC compound is said to be useful if the. Curve of their specific resistance <the temperature has a critical range (as defined above) leading to ^; A T between -100 and + 25o ° C leads to: t. The expression "peak" 5 (peak) of the specific resistance ^{-! 11} denotes the maximum • of the specific resistance of the mass when it is heated to --tempe-; temperatures above the usable T.

door, in which the mass peak of their specific ^resistance: stands shows, is called a "peak" or "peak temperature". The ratio of the peak d'js resistivity to the resistivity at the useful temperature T (or at the highest useful T if more than

S S

! a T is present) is called the peak or peak ratio

nis referred to.

According to one aspect, the invention relates to a PTC compound that contains
1. a crosslinked polymer and

2. Conductive particles that are within the network structure of the crosslinked polymer are included and one

20 have a particle size of at least 18 ημ,

wherein the composition has a gel fraction of at least 0.6 and having at least a useful T, with the proviso that when the cross-linked polymers containing a crosslinked crystalline polymer or consists of the mass and a useful T _g above the T of the useful mass before the networking

The mass has at least a useful T between 25 and 200 ⁼ the specific resistance of the mass is for many users preferably at least 25 ohm χ cm either at 25 ° C ^{or at a temperature 50 0} C below the useful T (or the n.- t.

most useful T, if there are several of them), depending on which of the two temperatures is the higher, ie if T ₁ . 7 is 5 or lower, the resistivity is preferably at least 25 ohm χ cm, if T is above 75 ° C, d. resistivity preferably at least 25 ohm χ cm

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(T - 50 °). Especially when the mass is used at low voltages, the specific resistance at 25 ° C. can be low, for example 1 ohm χ cm or lower \ ^ although e is preferably at least 3 ohm χ cm, in particular at least 5 χ cm. The critical range of the 'Ma (or at least one of the critical ranges, if the sequence has several useful T's) should preferably have an R ^ Q value of at least 6, where R ₃₀ is the ratio of the specific resistances at the end and at the beginning of a 30 ⁰ C temperature range. According to a further preferred embodiment, the useful T (or each of them) of the mass remains essentially unchanged if the mass is repeatedly subjected to thermal cycles in which the mass moves from a temperature below the useful T to a temperature above the resp , but below the peak temperature and then heated to a temperature below the usable T

will. It is also preferred that the peak ratio is a few 20: 1, in particular at least 100: 1. Next be is Trains t that the useful T is smaller than 150 ⁰ C, which Verh nis the resistors at 200 ⁰ C and in which T is at least 20: and that, if the useful T ratio greater than 150 ⁰ C, that of the · Resistivity at 250 ° C to the corre sponding value at T is at least 20: 1.

The crosslinked polymer can be used in the compositions according to the invention be a mixture of crosslinked polymers and the mass can be further components, such as fillers, flame retardant agents and antioxidants as well as other crosslinked polymers, i.e. no conductive particles included in their network ben, as well as thermoplastic amorphous or crystalline polymers which can be mixed with conductive particles

The invention also relates to a method for producing a PTC compound, which is characterized in that

1. Conductive particles at least 18 microns in size dispersed in a polymer (which also includes a polymer mixture) and

2. the dispersion obtained in step 1 to form a mass with a gel fraction of at least 0.6 crosslinked, which the lei

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capable particles within the nucleus of the crosslinked polymer included contains,

wherein the particles, the polymer and the crosslinking conditions: are such that the crosslinked mass has at least one useful T provided that when the polymer is a
contains crystalline polymer and the mass is a useful one
T before the crosslinking, the crosslinking is carried out at a temperature above 60 ^° C. or is effected in two stages, which are carried out at significantly different temperatures.

If the polymer contains a crystalline polymer, the crosslinking is preferably effected at a temperature above the T of the mass before the crosslinking, in particular under conditions in which the crosslinked mass has a first useful T ₃
■ 15 near the crystalline melting point of the polymer and a second
has a useful T close to the temperature of the crosslinking stage.

According to one embodiment of the method, the crosslinking is effected in two stages, which are substantially different
Temperatures are run. When the polymer is thermoplastic, it is usually preferred to effect the first crosslinking at a lower temperature than the second. Is this
crosslinked polymers an elastomer; o it is generally preferred that the first crosslinking is carried out at a higher temperature than the second.

The invention is explained with reference to the accompanying drawings, in which the figures show the relationship between resistance and temperature of various PTC masses according to the invention, such as
further described in the following examples.

The invention further relates to a device, for example one
A heating strip or a heating band, which has a PTC element and at least one electrode, generally two electrodes, which are connected to a power source, e.g. direct current from a or raeh-

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reren 12 volt batteries or alternating current from a 120 220 volt source, for the purpose of current flow through the PTC element; : the, where the PTC element contains a PTC mass according to obic definition. As discussed in detail in DT-OS 2543.314 '5 in DT-Gbm 7.527.288 / is a problem that shows itself in the operation of PTC devices, the formation of ί called "Heiii.linien", ie the formation of a narrow bands in the PTC material, which has a higher temperature <'■ the PTC material of the environment. In the devices of the invention, the current preferably flows through the PTC element in a manner which substantially prevents the formation of hot lines. Therefore, a preferred device is in the form of a heating strip or strip, which has two parallel electrodes arranged at a distance from one another, which are separated by a distance 1 (e.g. from 0.15 to 1 "cm) and in a core made of the PTC- mass are included, wherein the portion of the core between the electrodes least thick a h having t which is greater than the maximum dimen of the electrodes in the same direction and such daf ratio of L / t is less than 9, preferably less than and insbesondera is less than 5, especially 3 to 4. In another type of preferred device, the PTC mass is in the form of a layer and the electrical connections thereto are such that when the layer is at or near T, the Current mainly flows through the thickness of the layer. Particularly if the polymer in the PTC compound is an elastomer, such layers can be relatively thick, for example more than 0.125 cm The PTC compound is produced by an element consisting of a conductive polymer which does not have a useful T _g at any temperature below a useful T _{g of} the PTC compound. For further details on how hot lines can be prevented, reference is made to the publications mentioned at the outset.

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The invention also relates to a heat-resilient device / which includes a device as defined above which is in thermal contact with a heat-resilient component is composed of an organic polymer which at a • ■ 5 temperature below, preferably not more than 50 ° below the usable T of the PTC mass: (or the lowest usable T, if there are several) resettable

^: · Is.

The invention further relates to heat-recoverable articles which contain a heat-recoverable part, which consists of a; defined above PTC composition and at least two electrodes loading. '' - is connected to an electrical power source to cause current flow through the PTC composition and so heat the object to its reset temperature door · In this Zusanmenhang was particularly useful found that by crosslinking a PTC composition in which the polymer is a thermoplastic crystalline polymer at a temperature above the melting point of the polymer, the tendency of the composition to lose its PTC character on stretching is greatly reduced.

Finally, the invention also relates to a method of steering tion of the electrical current flow through an electrical circuit that contains a PTC element, irr the temperature : 'of the PTC element kept within a critical range or in which the temperature of the PTC element from a value outside this critical range to a value within thereof (or vice versa) is changed, the PTC element containing a PTC mass as defined above. The temperature can be maintained or changed by the self-heating effect of the current flowing through the element or by external ones. Heating or cooling or a combination thereof.

When choosing the conductive filler, the polymer in which it will be dispersed and the crosslinking conditions

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Care should be taken to ensure that a PTC mass m. the desired properties is obtained. However, surrender; for those skilled in the reworking of the invention: With regard to the disclosure and own expertise, no difficulties.

Choice of conductive filler

It has been found that the conductive filler is a part! Chen size of at least 18 πιμ must have a brai to achieve a PTC effect. The PTC behavior becomes more pronounced with increasing particle size. However, this toilet works full effect counteracts the need to incorporate larger amounts by weight of larger-scale fillers in order to achieve the to get the same resistivity. Although this does not imply a serious upper limit for the size of the high-

■ 15 conductive fillers, for example metal particles, which can have sizes up to or even more than 1 μ. If, however, \ is the preferred conductive carbon blacks are used, e; very difficult to obtain satisfactory physical properties ι particles larger than 100 πιμ, because for education!

of the required specific resistance, high proportions of] are necessary. Preferably used according to the invention Carbon blacks have a maximum particle size of 80 ΐημ (average size when a carbon black mixture is used).

It is known that carbon blacks are traditionally characterized by their particle size as well as characterized by the values of their nitrogen absorption and DBP (dibutyl phthalate) absorption, which <Measure of the porosity and the aggregation of the primary parts represent. Regarding details of these characteristics:

and their determination is for example on "Analy:

of Carbon Black "by Schubert, Ford and Lyon in Vol. 8, rope 179 of the "Encyclopedia of Industrial Chemical Analysis" (19ί

John Wiley & Sen, New York, referenced.

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The preferred particle size of the carbon black also depends on the crosslinking temperature (T). With increasing T, the PTC behavior becomes less pronounced, but this can be compensated for by an increase in the particle size of the soot. Preferably, therefore, the particle size should be at least 20 mu if T is above 20 ⁰ C, at least 30 ΐημ for T above 100 ⁰ C and at least 40 ΐημ for T above 150 ⁰ C.

A variety of carbon blacks are commercially available, but only a small proportion of them are known and known as useful carbon black recommended for use in conductive polymer compounds. the Preferred types of carbon black for the invention are furnace and acetylene blacks, but the less conductive thermal and channel blacks can be used.

Examples of other conductive fillers in addition to RuE are graphite, metal powder, conductive metal salts and oxides and boron or phosphorus doped silicon or germanium.

The selection of the conductive filler is also influenced by the polymer to be used, in particular the compatibility of filler and polymers.

20 Choice of polymer

As already mentioned, the invention is applicable to elastomers and. thermoplastic polymers are useful. The effect that is produced with a compound which already shows pronounced PTC behavior (e.g. a compound based on a crystalline polymer) is relatively small and at most modifies an existing T without removing it, but rather modifies the properties and above T _c and. can even generate a second PTC range with a second T. Although such an effect is very valuable, the invention should be even more useful when the crosslinked polymer is an elastomer, since then a variety of

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Fait of physical properties, coupled with the poss probability that the T of the mass may vary in a predictable manner ζ is present. The crosslinked polymer can be used in the w essentially free of carbon-carbon double bonds e.g. have less than 5 mol% C = C.

: Suitable polymers in which the filler can be dispersed before crosslinking and which can be converted into elasto by crosslinking are rubbers, elastomers, rubbers and thermoplastic elastomers. The terms "elasto mer rubber", "rubber" and "rubber" are used meres a P, which is non-crystalline and has a GIa transition temperature below T and preferably unterhal room temperature (2O ⁰ C) and which rubbery or after Verne elastomeric Has properties. The term "thermoplastic elastomer" is used to designate a material which, even in the non-crosslinked state, still has at least some elastomeric properties in a certain temperature range; such materials generally contain thermoplastic and elastomeric parts. The filler can also be dispersible in a polymer that has been dynamically crosslinked, ie during grinding or any other action of shear forces on the polymer in order to obtain a product which can be subjected to further compounding or molding processes.

It was found that the higher the green strength of the Au gang polymer, the more pronounced the PTC effect is { if other criteria are the same). On the other hand, as already mentioned, it may be desirable to use polymers with a high to temper strength at or near T prior to curing.

Therefore, depending on the circumstances, it may be preferred to be a low green strength polymer or a polymer to be used with a high green strength at 25 ° C. The A print "polymer with high green strength" is the specialist known and denotes a polymer that has a tensile strength

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of at least 10 psi at 20% elongation. Such polymers change their configuration after an equilibration treatment not or only at elevated temperature for the purpose of conversion into the configuration favored at this temperature very slowly when cooling to room temperature. They also have dimensional stability at room temperature in such a way that objects made from it do not distort or flow to any significant extent, even if not interconnected are.

Rubbers suitable for the purposes of the invention include polymers containing carbon atoms in the polymer chain as well as others, e.g. polyisoprene (both natural and synthetic), random ethylene-propylene copolymers, polyisobutylene, random styrene-buladiene copolymer rubbers, styrene-acrylonitrile-butadiene-Terpolynerkautschuke with or without minor amounts of copolymerized cL, ß-unsaturated carboxylic acids, polyacrylate, polyurethane rubbers, random copolymers of vinylidene fluoride and, for example hexafluoropropylene, polychloroprene, chlorinated polyethylene, chlorosulfonated polyethylene, polyethers, weichgemachti ι s polyvinyl chloride containing of more than 21% plasticizers, essentially non-crystalline random copolymers or terpolymers of ethylene with vinyl esters or acids and esters of et, ß-unsaturated acids, as well as silicone gums and basic polymers, e.g. poly (dimethylsiloxane) , poly ( methylphenylsiloxane) and poly (dimethylvinylsiloxane). The silicone rubbers and basic polymers which are particularly useful as starting materials have essentially no green strength. Thermoplastic elastomers that are suitable for the purposes of the invention include graft

30 and block copolymers such as

(i) random copolymers of ethylene and propylene, grafted

with polyethylene or polypropylene side chains,

(ii) Block copolymers of α-olefins, such as polyethylene or polypropylene with ethylene / propylene or ethylene / propylene / diene rubbers, polystyrene with polybutadiene, polystyrene

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with polyisoprene, polystyrene with ethylene-propylene rubberJ poly (vinylcyclohexane) with ethylene-propylene rubber ..- Pol; (oL-methylstyrene) with polysiloxanes, polycarbonates with Pol ¹ ;

\. siloxanes, poly (tetramethylene terephthalate) with poly, (tetra-; 5 methylene oxide) and thermoplastic polyurethane rubbers.

Thermoplastic polymers suitable for use in accordance with de : Invention suitable, can be crystalline or non-crystalline be lin and include:

; (i) polyolefins, such as polyethylene, polypropylene, (ii) thermoplastic copolymers of olefins, v.'ie ethyls propylene, with each other and with other monomers, such as vinyl esters, acids or esters of Ci ₇ ß-unsaturated organic acids,

(iii) halogenated vinyl or vinylidene polymers, such as the j nigen, those of vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and copolymers thereof mi each other or with other halogenated or other

are derived from unsaturated monomers,

(iv) both aliphatic and partially or fully aromatic polyesters, such as poly (hexamethylene adipate) - (sebacat), poly (ethylene terephthalate) and poly (tetra !!! ethylene terephthalate),

(v) polyamides such as nylon-6, nylon-6,6, nylon-6,10 and di Versamide (condensation products from dimerized and trimerized unsaturated fatty acids, in particular Linoleic acid, with polyamines),

(vi) other materials such as polystyrene, polyacrylonitrile, thermoplastic silicone resins, thermoplastic P ether, thermoplastically modified celluloses and polysulfones.

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Choice of networking conditions "■"

Both T and the degree of networking are extraordinary

borrowed important in determining the mass to be bestowed Resistance / temperature properties η. T doesn't just play a major role in determining T, but rather the extent of the PTC behavior exhibited (i.e. increase, gross

; .se), the lower the higher T is, with other criteria are the same. Therefore, a combination of carbon black and poly-

; merem that cutes PTC behavior due to the networking

10 shows crosslinking at room temperature, little or no PTC behavior after crosslinking at, for example, 170 ^° C.

: The inhibiting effect of a rising T can often be through Use of a carbon black with a larger particle size and / or by increasing the extent of the crosslinking counter- " be wrought. It has been found to be essential that the crosslinked polymer have a gel fraction of at least 0.6 Often a higher gel fraction is necessary, e.g. of at least 0.75. For most polymers, the gel fraction should be generally not exceed 0.96, however, polysiloxanes and many unsaturated rubbers, for example, are crosslinked to form higher gel fractions without the physical Properties of the mass are influenced in an undesirable manner.

The cross-linking bridges generated during the cross-linking operation should be stable in the operating range of the PTC compound. Suitable covalent crosslinking bridges are simple covalent bonds and crosslinking bridges that have one or more the connecting structures

-CC-, -CN-, -CO-, -CSC-, -C-SO ₂ -, -Si-, 30 -c-CO-, -C-CO-O-, -CO-NR- and -CO -S- included.

Ionic crosslinking sites are also suitable, provided

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that the mass at least in the area in the PTC-Verhci is desired, has form instability. It can therefore not

neutralized wise or completely with sodium ions / carboxylated EIa mers in the range up to 100 ⁰ C can be used. However, who for most purposes, the thermally forinstable masses, which te wise or completely neutralized with divalent or polyvalent metal ions, before

It is therefore possible to connect polymer molecules to one another by mutual attachment to a third body, for example by chemical or strong physical bonding a 'the surface of a conductive filler, in particular ^: carbon black. The term "crosslinking" in the context of the invention therefore denotes any means with which bonds between polymer molecules can be formed both directly and through the intermediary of another small or large molecule or a solid body, where η is assumed that such bonds cause the cohesion of the object and a certain degree of dimensional stability over the range of the operating or service temperature of the mass.

In the case of covalent crosslinking, any crosslinking process can be used

; be used, which leads to a product, which the gef has changed PTC properties and in the area of use is dimensionally stable. The crosslinking can therefore be brought about by radiation or by chemical treatment. Suitable chemical crosslinking agents include organic peroxide and other precursor materials useful in application generate free radicals from heat or other activating agents, e.g. metal oxides and amines, or suitable reactive ones Derivatives of amines; Isocyanates and other compounds associated with groups containing active hydrogen with the formation of e.g. ureas, allophanates and can react similarly; Nitroso or oxide compounds such as p-quinone loxine and other difunctional 'chemicals,

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which contain at least one group which attaches to double bonds, such as organosilane hydrides. Also connections, which contain sulfur, which reacts with double bonds to form monosulfide bridges, such as thiurane disulfide, are suitable. In many cases it can also be desired be other materials to increase the crosslinking effect, such as the use of ionizing radiation or other free-radical initiators crosslinking co-agents, ■ including polyunsaturated compounds, however '10 is not limited to admitting.

: Crosslinking by means of irradiation and by means of peroxides is preferred. If ionizing radiation is used, with radiation doses between 5 and 50 mRads the desired te crosslink density achieved without undue compromise in terms of the physical properties of the product. Sofer Peroxides are used, are generally used between 1 and 10 wt .-%, based on the polymer. A part the peroxide can be replaced by coagents. It has also been found that if the crosslinked polymer is a The elastomer is the degree of similarity between T and the crosslinking temperature T of the thermal pretreatment of the Depends on mass before networking. The mass is advantageously kept at the crosslinking temperature for a short time before the crosslinking process. For the majority of the masses it is required time no more than 1/2 minute, for polymers with significant amounts of high molecular weight material (rubbers with high Mooney viscosity and therefore high green strength) longer tempering times preferred. While not wishing to be bound by any particular theory, the brevity of the Annealing period indicate that the annealing serves to give the polymer molecules a relaxation with their characteristic molecular relaxation rate in their preferred configurations at the crosslinking temperature. Therefore, T comes closest to T when the polymer molecules come earlier caused an unstressed configuration at T

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to be taken in front of the network.

; The aforementioned tempering treatment is not related to the tempering of soot-containing compounds, which leads to a reduction in the resistance of the compound, as described, for example, in US Pat. No. 3,861,029. It is assumed that the process described there leads to a "structuring" of the soot dispersion, ie to the formation of preferred routes. Since annealing for the purpose of structuring therefore takes much longer than the above-mentioned relaxation annealing. However, it has been found that it is also advantageous to facilitate the structuring of the carbon black by annealing. When the desired Ve netzungstemperatur above is from about 170 ⁰ C, it is ο expedient to combine the two annealing steps and to keep the Ma in its final shape a sufficient time at T, woit the desired patterning it before Ver networking represents mass takes place . A 10- to 20-minute Te] bodiment at 2OC ⁰ C before crosslinking at this temperature. therefore suitable. The time required for structuring or structuring increases rapidly with decreasing temperature

at
. door / masses, RMC crosslinking temperatures significantly ui terhalb 200 ⁰ C are desired, it may be preferred, wherein: for a short period of time to reduce the resistance to temper mass, optionally at room temperature to cow 'and then the composition before crosslinking for the purpose of relaxation; tion of the polymer molecules at T for a sufficient time. It is understandable that the relaxation times c polymers vary widely with, inter alia, the molecular weight and the temperature. While in some cases masses relax almost instantly at T, in other cases periods of a few minutes are required:

In addition, it is made through the use of softening egg or other viscosity reducers possible to reduce or even increase the Relaxatic tempering to a large extent and in many cases the structure temperature

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to reduce. The optional use of such

Plasticizer is therefore within the scope of the invention. Preference is given to using additives which are polymerized into the polymer : siert or crosslinked with it or in which their viscosity-reducing effect after tempering in another way is neutralized, since such additives would otherwise have a detrimental effect on the resistance stability of the polymer PTC heating devices may have under operating conditions. Softening additives are particularly useful, though Peroxides or other thermally activated crosslinking processes are used, since it is then not possible to use the mass normally to subject the structure to tempering. The used Peroxides or curing agents are often good viscosity reducers for the polymer. Other plasticizers can also

15 can be used advantageously.

The crosslink density has no significant influence on the T of the composition above a certain minimum value, however is the slope of the resistance-temperature curve above of T is a strict function of the crosslink density; the higher the density, the steeper the slope. The optimal extent of the Networking is therefore the one in which the desired slope of resistance / temperature is achieved without an inaccurate Desired compromise in terms of the physical properties of the product is entered.

Especially with polymer masses that are not easily made using ionizing radiation or additives that release free radicals generate crosslinking, such as peroxides, it is advantageous to add crosslinking promoters (or "coagents"). Such Materials are usually unsaturated monomers. Suitable unsaturated monomers (or monomer mixtures) generally contain at least two, and preferably at least three, ethylenic double bonds in each molecule. You should of course preferably be compatible with the polymer and have a low volatility under the processing conditions

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to have. Examples of such monomers are the allyl ester, polycarboxylic acids and other acid components, such as cyanuric acid: for example triallyl cyanuarate and isocyanurate, diallylaconitate , maleate and itaconate and tetraallyl pyromellitate; up to and including

1 1

tris-maleimides, e.g., N, N -ethylene- and N, N -m-phenylene-bis maleimide; Acrylic and methacrylic acid esters of polyhydric alcohols, e.g. dipentaerythritol hexamethacrylate, ethylene] koldimethacrylate, 1,3-butylene glycol dimethacrylate and pentc erythritol tetraethacrylate; Vinyl esters of polyvalent acids e.g., trivinyl cyanurate and citrate; Vinyl and allyl ethers \ ■ polyhydric alcohols, e.g. the tetrallyl and tetraviny.1 ether of pentaerythritol; and bis-acrylamides, e.g., N, N -met len- and N, N -p-phenylene-bis-acrylamide. The amount of for e useful crosslinking required monomers (compared to, except for the nature of the monomers, identical and on mass processed in the same way) depends on the particular monomer and other ingredients, but It = can be determined by a specialist. Quantities in the range from 1 to% by weight of the composition are generally sufficient.

20 Other factors

The compositions according to the invention can contain conventional constituents such as antioxidants, flame retardants, inorganic fillers It has been found that the presence of a non-conductive Fillers (e.g. in amounts of 5 to 35, preferably 10 to 25%, based on the weight of the mass) are often advantageous is. This is particularly the case when the polymer e is polysiloxane and the filler is silica. The property a non-conductive filler reduces the overall coefficient of relaxation of the mass. The improvement in the PTC ratio is therefore in view of Kohler's theory (see example se US-PS 3,243,753), according to which the PTC effect is the difference between the thermal expansion ratios of the body attributed to the filler and the mass, surprisingly *

909844/0748

-—- β »BAD ORIGINAL

copv H

If the crosslinked polymer in the bulk is an elastomer that is made by a rubber with a previously defined green strength is derived, and if the rubber has a tensile strength of 5 to 10 psi 20 $ elongation, have masses zv / square a T value not exceeding 45 ° C, preferably is not more than 35 C below the T value. Such masses can be obtained that the cross-linkable mass sufficiently long at a high temperature before cross-linking is heat treated. The time here can be about a minute. Treatment times of at least two minutes, e.g., 3 to 15 or 3 to 10 minutes, is generally preferred. If the Cross-linking by means of a chemical cross-linking agent occurs, the high temperature should be lower than the crosslinking temperature. Or measures can also be taken to prevent excessive premature cross-linking.

As indicated previously, the carbon black should have a minimum particle size based on the T value. However, good results are also obtained when using carbon blacks with a particle size which is preferably above the minimum and below 50 m ^ M ' _? is ", for example, is less than about 42 m / U. This includes the case that the crosslinked polymer is a butyl rubber and / or a halogenated butyl rubber and / or an ethylene-propylene rubber, which is produced by means of a chemical In many areas of application of the PTC compounds, such as self-regulating heating devices, it is important that the PTC compound is chemically stable at the working temperature, which is considerable

can be higher than T and for example in the range s

T _g plus 2o to T ₃ plus 60 lie »Some polymers

9 0 9 8 4 A / 8-7 COPY

ν- '/ _U : BAD ORIGINAL

do not meet these conditions, including in particular poly (epichlorohydrin), which "at a high-lying Temperature, e.g. above 15o C.

The PTC compositions according to the invention are preferred by melt forming, such as injection molding or extrusion of a suitable crosslinkable Mass produced, and this is followed by a cross-linking of the molded product.

The invention is illustrated by the following examples in which the percentages are by weight and the temperatures are degrees Celsius. The examples are summarized in Table 3. Unless otherwise stated, in each example the specified polymer ui. The carbon black is mixed in a 4 inch (10 cm) two roll mixer with the indicated percentages of carbon black, where the mixture is pressed into sheets of β 6 0.03 inch (15 15 χ 0.075 cm). From these plates, 1.5 1 0.03 inch (3.8 2.5 0.075 cm) strips are cut. Electrodes are created by painting 0.25 inch (0.64 cm) wide ribbons of silver paint on opposite ends of the long dimension faces of each strip. Each strip is annealed for 10 minutes at 200 ^C and then placed on a metal plate, which is held at the given temperature (+ 10 ⁰ C) and (wenr the Plattcntemjieratur higher than the room temperature was) was equ..libriert with the plate to to give the polymer time to relax. The strip is then crosslinked while the plate is held at the indicated temperature by exposing it to the indicated radiation dose in megarads from a 6 mA beam of approximately 0.7 MV electrons; the strip thereby to 20 ⁰ C higher at the higher dose, erwä to a somewhat higher tempera usually 10 After cooling, the strip is slowly heated from room temperature up to its peak temperature, its resistors between the electrodes at intervals of 15 ° C measured weather

909844/0749

BATH ORIGINAL

The resistance in the steepest part of the resistance / temperature curve is expressed by the formula.

30 Ln (R _T / R _O ) = CC (TT ₀ )

where R _{T is} the resistance at temperature T and R is the resistance at temperature T _Q at the starting point of this part of the curve and cL is calculated. For a curve with an R "

Ί4 greater than 2.5 and an R ₃₀ greater than 6 is little cc

35 at least about 0.06.

Details of the. Examples "are the types of carbon black used shown in Table 1, details of the polymers used in the examples in Table 2. Details of the examples themselves are shown in Table 3, which also shows the significant resistance / temperature properties of the products.

In Table 3, the polymers and types of carbon black are identified by their numbers in Tables 1 and 2; the trade names of the polymers are also given, along with the particle size of the carbon blacks, the nitrogen and dibutyl phthalate absorption values are given in brackets after the identification number. Comparative examples that are not fall under the invention are marked with a (*).

-22-

Type no.

9-10-11-12-13-14-15-16-17-18-19-20-21-22

Table 1 ASTM
D1976-67
Great size
πιμ N ₂ D
2 / g /
m ^{/ y} cc / Types of soot Nl 15 " 230 Trade name Industry
Great Nl 16 220 Black Pearls 900 17th 112 Black Pearls 880 Nl 18th 200 Shelf 6ύ "0 N166 11-19 142 Black Pearls 700 NIlO 19-21 140 Vulcan 9H SAF-HS N294 22nd 203 Vulcan 9 ' SAF N285 24 100 Vulcan SC SCF 25; 94 - Vulcan 5H 25th 94 Shelf 330 N293 20-25 145 330R shelf 27 85 Vulcan C CF N339 28 92 Elftex 8 30th 1000 Vulcan M N472 30th 254 Ketjen Black EC EC N347 26-30 90 Vulcan XC-72 XCF N440 36 46 Vulcan 3H HAF-HS N550 42 42 Shelf 99 FF N539 42 42 Sterling SO FEF N765 60 30th Sterling SO-I FEF-LS 60 30th Sterling N765 SRF-NS N774 75 27 SRF-S shelf SRF-NS Sterling NS SRF-HM-NS

909844 / Ö748

⁰ OPY H ^ÖAD ORIGINAL

- 35 -

Tabel

Polymers

Type No. Trade name Polymer type Filler type

. 1 Silastic 35U

2 SE 76

3 Silastic 55U

4 Silastic 410

5 Silastic 437

6 Viton B50

7 Nordel 1470

8 epsyn 5508

9 TPR 2000

Nysin

.11 Natsyn 2200 DYNH

Polydimethylsiloxane with a vinyl group content (0.4 %)

vinyl group-free polydimothylsiloxane

Polydimethylsiloxane with a vinyl group content (0.4 %)

Polydimethylsiloxane with a high vinyl content (4 %)

Polydimethylsiloxane with a vinyl group content (0.4 %)

Vinylidene difluoride copolymers res

Ethylene / propylene / diene terpolymer

Ethylene / propylene / diene terpolymer with high green strength

an ethylene / propylene rubber with a content of about 20% polypropylene, which was weakly crosslinked under dynamic conditions, so that a thermoplastic elastomer is present

an acrylonitrile / butadiene rubber with a content of 35% acrylonitrile

cis-1,4-polyisoprene low density polyethylene

Silicon dioxide

Silica, in greater quantity than Silastic 35U

Silicon dioxide

9 8 44/07 4 « QG »* Y" BAD

Table 3

at Polymer black type % ) 25th Irradiate Hardening resistance (Megohms) 0.2 T T Peak 235 0, oil D. R. 100 fO . . . games lungs tempera at peak > 20 ¹ p ¹ O Zen- > 220 0, 048 ^K 14 ^K 30 > 10 CD ! ' dose tur ⁰ C at 25 ° C center temp. > 20 23-45 temp. > 100 0, 058 2.0 4.0 10 -Cn 1. 1. 14 5 35 20th 25th 0.8 0.4 Il - 220 0, 018 2.3 5.2 σ •; 2. Silastic (30/1000 / 5 50 Il 2.0 - > 20 Il - - > 130 0, 065 1.3 2.3 > 10 3. 35U 340) 8th 20th Il 0.01 - > 20 Il 190 - > 100 0, Ü53 2.5 6.1 > 10 I ί 4th 8th 50 Il 0.01 > 20 > 20, Il _ > 250 > 265 0, , 096 2.1 4.5 > 100 I. '{ 5. 15th 30th 25th 10 Il _ _ V Λ /% Il 70 _ ■ · - ^A 0, 091 3.8 13.3 yioo no year
σ j 6th (26-30 / 90 / 20th Il 0.01 > 20 Il 70 > 110 , 028 3.6 13.7 <10 I. I. 7th 124) 50 Il 0.03 > 20 Il > 110 , 081 1.5 2.4 > 100 OO
ο 8. * 7th 25th 20th Il 0.004 Il 130 _ 0, 30.1 9.0 I f to 9. / 22/203/106! 25th 50 Il 0.01 ' > 20 > 170 o _: , 077 > 100 OO Il 70 O, , 134 2.9 8.2 > 1000 £ 10. 12th ■ 10 Il 0.007 ' > 20 Il 70 > 170 0 , 125 6.5 34.4 > 1000 ^, 11. (27/85/103) 35 20th Il 0.02 > 20 Il 70 > 115 0 , 051 5.8 27.5 > 10 ^: ' ο 12. 50 Il 0.1 > 20 Il 25th > 90 0 , 091 2.0 4.3 > 100. £ ¹³ 19th 10 Il 0.002 > 0.2 Il 25th > 280 0 , 132 3.6 11.6 > 100Ö * ° 14. (42/42/109) 20th Il 0.005 > 10 Il 25th > 190 0 , 173 6.4 32.8 > 100p. 15th 40 Il 0.01 > 20 'Il 55 > 90 0 , 014 11.2 90.0 <10 ' 16. 90 Il 0.01 > 20 Il 115 > 75 0 , 057 1.2 1.7 > 10 " 17. * 9. 5 Il 0.001 _ Il 100 _ 0 , 11 2.2 5.1 > 100 18th (25/94/70) 10 Il 0.002 Il 70 0 , 08 4.6 19.9 > 100 " 19th 20th Il 0.007 Il 70 0 , 031 3.1 8.8 10 20th 50 Il 0.2 Il 70 0 , 082 1.6 2.6 > 100 21. 10. 10 Il 0.03 Il 85 0 , 07 3.2 9.4 > 10 22nd (25/94/62) 20th Il 0.1 Il 70 , 051 2.7 7.0 > 10 23 50 Il 0.3 Il 55 2.1 4.3 24. 17th 20th Il 0.01 " oc / nc / λ c icr \ \ cn Il f \ Λ

at
games Polymer carbon black type % Irradiate
lungs
dose Table 3 (Continuation) > 20
> 20 23-45
Il
Il ^T o Spit
Zen-
temp. Ci. ^R 14 ^R 30 8th
3 ^R 100 <0 : ro
cn 26th
27
28. 1. 21. 45
Silastic (60/30/64)
35U 10
20th
50 Hardening
tempera
tur ⁰ C Resistance (Megohms)
at peak
at 25 ° C center temp. 1
> 20
> 20
> 20 23-65
Il
Il
Il 40
40 > 70
> 60 0.046
0.19
0.11 1.9
14.3
4.7 3,
139
19 0
6th
5 > 1000
> 1000 * O
CD 29
30th
31.
32. 20. 40
(60/30/116) 5
10
20th
50 25th
Il
Il 0.05
0.1 > 20 Il
Il 115
100
100
70 250.
> 220
> 130
> 100 0.085
0.150
0.197
0.115 3.3
8.2
15.8
5.0 10,
51,
167
21 1
1 > 100
"> 1000
> 1000
> 100 33. *
34. 11. 25
(20-25 / 145 /
100) 20th
50 Il
• ii
Il
Il 0.0004
0.0004
0.0004
0.006 > 20 Il
Il 100 > 120 0.03
0.07 1.5
2.8 2,
6,
i 7th
0 \. P.
m co
b ■ * - 35.
36. "6. 25
(21/140/114) 20th
50 Il
Il 0.07 '
0.2 C.
> 20 Il
Il 100 > 130 0.033
0.065 1.6
2.5 2
6th 2
6th 37.
38. 8. 30
(24/100/126) 20th
50 Il
Il 0.03
0.3 > 20 Il
Il 70 > 115 0.039
0.087 1.7
3.4 3
10 , 3
, 3 > 1CL ' "O 39.
40 13.30
(28/92/121) 20th
50 M.
M. 0.005
0.04 4. «
> 20
> 20
> 20 Il
Il
Il
It 70 > 140 0.040
0.082 1.8
3.2 3
9 , 2
, 7
, 6
, 4 1 41.
42.
43.
44. 22 42
(75/27/70) 5
10
20th
50 Il
Il 0.005
0.02 > 20 Il
Il 70
55
40
40 > 140
185
> 190
> 100 0.066
0.079
0.097
0.097 2.5
3.0
3.9
3.9 6th
8th
13th
13th , 9
,8th ¹ * t » 45.
46. 15 ^ 20
(30/254/178) 20th
50 Il
Il
Il
Il 0.02
0.03
0.04
0.1. - Il
Il 40 > 85 0.048
0.070 1.9
2.6 3
•. 6th .8 ₍ I'll 47. *
48. * "5.
(11-19 / 142 /
135) 20th
50 Il
! I 0.02
0.3 - - 0.017
0.045 1, '9 1
3 Il
Il 0.0007
0.002

Examples

Polymer black type

Table 3 (continued)

% Irradiation hardening resistance (megohms) conditioning temperature at peak dose door ⁰ C at 25 ° C center temp.

Peak
Zen-
temp. O, 027 ^R 14 , 5 ^R 30 4th ^R 100 - O ₅ , 019 1, , 3 2, , 9 <10 - o _: , 007 1, ,1 1, , 4 <10 - <0
0 1, 1, <10 - 0
0
0 , 01
, 058
, 086 1 , 2
, 3
, 4 <1
1 , 6
,1
, 4 :! S CD O O , 018
, 103
,1 co ro - * ro co 1:
5
10 , 9
, 6
,1 <10
> 10
> 100 1
4th 1
15th
13th > 1CC
> 100

49. * ι · Il 3. 25
(17/112/54) 50 50. * Il
2. SE-76 2. 24
(16/220/110) 50 α
CD
OO 51. *
52. *
53. * Il 1. 30
(15/230/65)
14 August
(30/1000/340) 50
5
20th -P-
O 54. *
55.
56 '. Il 22. 45
(75/27/70) 10
20th
40 so 57. *
58.
59. Il 9. 25
(25/94/70) 5
10
20th 60. * Il 10.
(25/74/62) 20th 61. *
62. * 1.Silastics
35U 15. 15
(30/254/178) 10
20th 63. * 3. Silastics 4. 20
(18/200/122) 12th 64. * 4. 20 12th

25th

0.001 Ο ', 0.0006

Il Il

Il Il Il

Il Il Il

0.02 0.2 23-65

55U (18/200/122)

constant from 25-175 ° C -

0.007 (0.09-23-45
175 ⁰ C)

<0 0

75> 175 0.034 -

In the case of polymer carbon black type games

Table 3 (continued)

Irradiation hardening resistance (Megohms) conditioning temperature at Spit dose door ⁰ C at 25 ° C center temp.

Peak

Zen-

temp.

OIL

Ί4

30th

to
σ
co

65. 4. Silastic 18. 35 18 25 0.0012 (11-145 ° C) -40 410 (42/42/120) 70> 190 0.14 7.5

66.5 Silastic 18. 35 437 (42/42/120)

67, 68, 69, 70. *

71, 72, 73.

74. 75.

5.Silastic 15.437 (30/254/178)

e.Viton B50 15. containing (30/254/178) 2% triallyl containing isocyanurate 2% CaO

6. Viton B50 18th

containing (42/42/120) 2% trimethylolpropane trimethacrylate

76. 5. Silastic

77, 78, 79.

18. (42/42/120)

35

80, 81, 82, 83.

4, Silastic 18. 410 (42/42/120)

20th

20th

25 100 160 200

25 10Q

150

25th

110 0.0011 (11-130 ⁰ C) -40 120> 200 0.10 4.6 16.5

0.0016 0.0025 0.0028 0.0028

0.006

0.0015

0.0012

χ

Λ

-5

15 0.4 -0.02 ^ 0.006

-15 0.02

0.1 25-40
-130
-170
-190

-50
-130
-165

-25

-75

130> 220

145> 220

175> 220

195> 220

130> 170

145 250

175> 250

70> 280

220

0.065 2.8

0.060 2.5

0.04 1.7

0.01 1.2

0.13 Q, 054

6.2 2.1

0.05 2.0

7 6 3.3

1.4

50 5.1 2

4.5 13

> 100> 100

ion> 1 CiQ. , · '

25th 0.0007 2 ,1 -25 85 270 0.046 1.9 4th 77: K) 100 0.0006 5 , 01 -110 160 280 0.073 2.8 9 4O ¹ U · ' CD 150 0.0005 ~ o -150 175 280. 0.051 2.0 4.6 60 - * 200 0.0004 -O ~ 195 205 > 280 0.037 1.7 3 -15 cn
O 25th 0.0008 -2 -25 100 280 0.084 3.3 12.7 > 100 CD 100 0.0003 > 20 , 2 -110 160 > 280 0.096 3.8 3.8 > 100 150 0.0002 > 2 150 190 > 280 ■ 0.094 3.7 '16.7 > 100 200 0.0001 > 0 200 235 > 280 0.069 2.6 8th > 100

Table 3 (continued)

I. O at 4th polymer and .Silastic Soot type % Irradiate Hardening 20th 140 resistance (Megohms) T T Peak 0. cL R. R. D. games 5 437 lungs tempera sh. 185 at peak ¹ p Ό Zen- O ₃ 11 ^K 14 ^K 30 ^K 100 j (33.7 *} dose tur ⁰ C footnote at 25 ° C center temp. -25 100 temp. O ₅ 154. 7.5 29 MOO 84. Silastic 18th 35 18th 25th sh. 185 0.001 > 20 , -120 175 0, 146 8.6 100 > 100 ί 85. 2. 410 (42/42/120) 100 footnote 0.0003 > 20 160 220 > 200 -0. 077 7.7 -80 > 100 86. 150 0.0001 > 20 205 220 > 280 O! 2 ~ 2.9 10 87. 200 0.0001 > 0.2 70-100 130 > 280 0 07 Ί8.0 -500 > 1000Ü j) 88 SE-76 18th 35 40 25th 185 & 0.008 > 1000 100 145 0 046 2.6 8th > 100 89 7th (42/42/120) 100 25th 0.0015 0.5 160 175 220 0 045 1.9 4th > 10 "I. 90 150 0.0009 0.1 225 235 > 280 0 , 23 1.9 ~ 4 > 10, J to 91. 200 0.00002- 40 70 > 280 0 , 15 25th -1000 _ ω 92. Nordel 18th 30th 20th 25th 0.003 yiooo 105 115 -160 0 , 086 7.7 80 > 1000 f " ™ j oo 93. 9 (42/42/120) 100 0.0002 100 -130 130 220 0 , 070 3.3 13th > 1 1 c · ■ · '· O, ⁴ ^ 94. 10 140 0.0001 3 -160 175 220 0 , 089 2.8 6.7 > 1f.O ■. 95. ' 180 0.0001 0.3 -25 150 > 250 0 , 12 3.5 14.3 > 100D 96 Epsyn 18th 48 10 25th 0.00004 > 10 30-100 160 -200 , 09 5.4 35.2 > Κ · 0ύ > 97. 5508 (42/42/120) ti 10 100 0.0001 > 10 ■ 100 130 -200 0 3.5 10 - ¹ JOo 98 8th 45 10 100 0.0002 50 250 ό , 11 see footnote 130 160 , 167 4.5 15th > 10ü 99 8th 45 0.0002 15th -140 150 240 0 10.4 150 MOÜO.i 100. ¹ . . Epsyn 18th 40 0.1 > 1000 > 200 , 085 • · :; ' ^v ^ 5508 (42/42/120) -150 175 3.3 13th > 100 '- ^ 101 Γ> . Eosyn 18th 27 0.065 > 10 > 200 cn f 5508 (42/42/120) 0 O (39.3%) , 15 CO \ -130 160 8th 100 > 1000 ^-ί ^ 102./ 0.09 > 10 > 200 \

Examples

Polymer carbon black type %

Table 3 (continued)

Irradiation hardening resistance (Megohms) treatment tempera- ture at Spit dose door at 25 ⁰ C center temp.

Sharpen-

temp.

di

14th

30th

Ί00

103.
104.

105.
106.

107.

108.

118.
119.

5. Silastic 18. 35s.
(42/42/120) footnote

5.Silastic 18. 45
(42/42/120)

9. TPR 2000 15. 30
(30/254/178)

10. Nysin
, 35-8

H.Natsyn

2200

with 0.05%
Antioxidant

12. DYNH

12. DYNH

15. 30
(30/254/178)

18.. 40
(42/42/120)

15. 20
(30/254/178)

15th
18;

18th
12th
20th

20th

12th
18th

sh.

footnote

200 -0.0007 200 & -0.0007

160 -0.005 160 & -0.005

25 0.005

180 0.001

140
180

25th
100
150
200

150
150

200
200

0.01

0.002

0.001

0.15 0.017 0.010 0.012

0.001. 0.001

0.003 0.009

-10

-0.035 0.007

0.03 • .0.1

> 20> 20

25-45

220> 250 220> 250

175> 250 175> 250

40 -

-170 · 170> 240

25-40 70 145 150 175 235 180 205 250

55 130

145 190

175 220

175 210

170 80 165 22C 160 80 160 215

150 100 170> 170 185 100 195 > 210

0.085 3.3

0.085 3.3

0.092 3.6

0.113 4.9

-0.1 -4

0.09 0.06 0.046

3.5 2.5 1.9

0.065 2.5

0.083 3.2

0.083 3.2

0.054 2.1

13th

13th

16 30

15 6 4

7 8 8 5

> 20> 8> 15

> 100> 100

> 100> 100

> 1000

> 103. · 17. "\ ^.:

> 10C · "60.,:. '

-100 '12

cn O CD

Footnotes in Table 3

The masses containing Norde.L are produced in a Banbury-Mis <. Both the Nordel- and the Epsyn®-haltigei masses are annealed for 5 minutes at 200 ⁰ C, after being irradiated bc. The resistance of the second Nordel-entl trending mass, ixe irradiated at 100 ⁰ C, decreases from 25 to 100 ⁰ C.

Example 97 wicd a few minutes on a hot plate and irradiated shows a very blurred T in the range of 30 100 ⁰ C. Example 98, equilibrated in the longer and is relaxed before the radiation, shows a sharply pronounced at 100 ⁰ C. The resistance of 98 is relatively constant from (up to T, while the doubling of 97 in the 30 ° range of ⁰ to 70 C.

200 _i 101 and 102:

The curable compositions also contain 2,5-dimethyl-2,5-di (t-butylperoxide) hexane (about 4.9% in example 100 and about 4 % in examples 100 and 102) and an antioxidant (about 1 % example 100 and about 0.5% in Examples 101 and 102). In Be game 100 and 102, the masses are ^{cured without irradiation 20 Mir at 185 0} C in a hydraulic press. In example 102 the mass is first hardened in this way and then irradiated at 25 ° C. with a dose of 12 Mrads. The resistance of the sample in Example 100 remains at about 0.1 megohms to about 115 ° C and then begins to increase. The resistance of c sample in Example 101 falls from about 0.065 Megohms at 25 ⁰ C Megohms about 0.033 at 85 ° C and then begins to rise. De resistance of the sample in Example 102 remains at about 0.09 Megohms up to about 110 ⁰ C and then begins to climb

9098U / 0749

BATH ORIGINAL

. 37-

The hardenable composition further contains about 2% 2,5-dimethyl-2 ^- , 5-di (t-butylperoxy) hexyne-3. In Example 103, the composition is cured by heating to 200 ⁰ C. In Example 104, the mass is cured by heating at 200 ⁰ C followed by irradiation at 25 ° C at a dose of 5 Mrads. The effect of the irradiation is to increase the (comparatively low) speed with which the resistance increases at temperatures below T.

The hardenable mass also contains about 2% dicumyl peroxide ^: (40% activity). In Example 105, the composition is cured by heating to 160 ⁰ C. In Example 106, the composition is cured by heating to 160 ⁰ C, and then by irradiation at 25 ⁰ C at a dose of 5 Mrads. The effect of the irradiation is much more pronounced than in Example 104 and is mainly intended to increase the rate at which the resistance increases at temperatures below T, which is very much

is much harder to perceive.

The resistance / temperature curve of this example shows none Trace of resistance peak at 155 ° C which shows when

'irradiated the same mass with 12 megarads at room temperature and which is associated with the melting of the polypropylene

Similar results as in the previous examples are obtained with the following crosslinked polymers: chlorinated polyethylene, polyethylene acrylate, chlorosulfonated polyethylene, plasticized polyvinyl chloride.

In the accompanying drawings, Fig. 1 shows the resistance / temperature properties of those prepared in Examples 67-70 Heating tapes; FIG. 2 shows the resistance / temperature behavior of the tapes from Examples 103 and 104 and FIG. 3 shows

_: -:. ^ - -COPY BAD ORifilWAt

-23IbUb) A

• 32-

the resistance / temperature behavior of the strips from examples 105, 106 and 107.

FIG. 4 shows a band-shaped or strip-shaped heating element according to the invention in cross section. The electrodes 12 are spaced 1 from one another in a core made of PTC compound 14 tet. The heating band is surrounded by an insulating jacket 16. The thickness of the core made of PTC material is t.

Such a band-shaped heating element can be produced in a known manner by making the core of PTC compound in a suitable manner Manner, e.g. by extrusion or overmolding, around the electrodes and then the entire arrangement m the insulating jacket is overmolded.

The curable compositions also contain about 1% of an antioxidant (Agerite Resin D), about 2% peroxide and in Example 1 only about 2% 1 riallyl isocyanurate.

9098U / Ö749

BAD ORIGINAL <ßOFY

ι -

lee

page

CiOPY

Claims (1)

Claims (2) conductive particles, ■ which are included in the network of the cross-linked polymer and have a particle size of at least 18 m / * (according to patent application P 27 46 6o2.) H MOr characterized in that the .lasse a gel fraction of at least o, 6 and at least one useful T ₀ , which is between about 1oo and 25o C, and which is linked to a temperature range in which the mass has an Rw value of at least 2.5 or a R. < ₀₀ value of at least 1o , wherein under Rn ^ - or R ₁ - is the value ^v to be understood urhältnis the resistivity of the mass at the end to the beginning of a 14 ⁰ C or 1oo ° C-- Temparaturbereichs, and in that the polymers of eixem Rubber is derived. which at 25 ° C has a tensile strength of at least 5 psi at 2ofo elongation, and that the mass has a T value not greater than 45 C below the T value. 2) mass according to claim 1, characterized in that it has a T value that is no more than 35 C below s of the T value. 3) mass according to claim 1 or 2, characterized in that the conductive particles have a size of less than 5o m 'i to have. 4) mass according to claim 3, characterized in that the Particle size is less than 42 m, .t <. 5) composition according to claim 3 or 4, characterized in that the polymer is a butyl rubber, a halogenated one 9098U / 07A9 COPY • ο- 11) Composition according to one of claims 6 to 1o, characterized in that the polymer is an elastomer, i & i 12) Composition according to claim 11, characterized in that the polymer is a polysiloxane. 13) mass according to one of claims 6 to 12, characterized in that it continues to be non-conductive Contains particles that are included in the network of the crosslinked polymer. 14) Composition according to one of claims 6 to 13, characterized in that the polymer by covalent attachment points from the group -CG-, -CF-, -C- -CSC-, -C-SO ₂ -, -Si-, - C-CO-, -C-CO-O-, -COKE- and -CO-S- is crosslinked. 15) Method for producing a PTC mass according to a of claims 1 to 14, characterized in that (1) conductive particles with a particle size of at least 18 m, '-ι are dispersed in a polymer and the dispersion is heat-treated, (2) the dispersion obtained in step (1) into a mass with a gel fraction of at least o, 6 is crosslinked, which is the conductive particles within the network of the amorphous polymer included, the particles, the polymer and the crosslinking conditions being such are that the crosslinked mass has at least a useful T. 16) The method according to claim 15, characterized in that ■ d the heat treatment at a high temperature; done for at least a minute. 17) The method according to claim 16, characterized in that d the heat treatment is carried out for at least two minutes. 9Q9844 / 074Ö CX) PY Butyl rubber, an ethylene propylene rubber or is a mixture of two or more such rubbers, which by means of a chemical crosslinking agent are cross-linked. 6) .Mass according to one of claims 1 to 4, characterized in that net that they have a resistivity of at least 25 ohms χ cm at 25 ° C or one temperature of 50 ° C below the usable temperature - depending on which of the two temperatures is higher is - or 50 ° C below the lowest. useful T "if the mass is more than one usable T_ has. 7) A composition according to claim 6, characterized in that it comprises a -Y IU / ert of at least 6, wherein the IU - value than the ^{ra tio} of the resistivities at the end to the resistors at the beginning of 5o ° C Temperatixrbereichs is defined. 8) mass according to claim 6 or 7, characterized in that it aufv / eist more than one useful T. 9) mass according to one of claims 6 to 8, characterized in that the useful T ₃ remains essentially unchanged when the mass is repeatedly thermal. Cycles consisting of heating the mass from a temperature below the useful T to a temperature above but below the peak temperature, followed by cooling to a temperature below the useful T .. 10) Composition according to one of claims 6 to 9, characterized in that the conductive particles are carbon particles with a size of 22 to 80 ie ¹ *. 909844 / 0.7 4fl bad original copy ™ 2915034 18) Method according to claim 16, characterized in that ü; the heat treatment is carried out for 3 to 15 minutes: Cii ^v -: ■ is. · - · 19) The method according to claim 16, characterized by cU The Y / medical treatment 3 to Io Kimrfc cn long-run will. 20) Method according to one of claims 15 to 19, dadurv. characterized in that the dispersion also contains a cross-nucleating agent and that the heat treatment takes place at a temperature so long that a überr; Casual cross-linking is avoided. 21) Method according to one of claims 15 to 2o, characterized characterized in that the crosslinkable dispersion is reshaped by melting. 9098U / 0749 ^COp Y ORIGINAL INSPECTED