DE2234747C3 - Flexible surface heating material that can be heated by current passage - Google Patents

Description

-CH-
\

-CH,

35

—SON H ₂ contains and that the crosslinking agent has the general formula

CH,

CH,

40

45

where R is an aliphatic, aromatic or alicyclic compound and π is an integer from 2 to 4.

7. surface heating material according to one of claims 1 to 6, characterized in that the coating (2) can be converted into the crosslinked state by heating.

55

The invention relates to a flexible surface heating material that can be heated through om passage he flexible, heat-resistant support structure and with him attached to this flexible, electrical end coating that contains carbon in addition to a plastic.

Every known flat heating material of this (DT-OS 15 65 316) consists of the electrically conductive one Seal made from a mixture of silicone rubber and plastic. Such mixed carbon tends to : r to coagulation, so · that it is often too uneven The structure of the carbon in the coating occurs as a result, locally non-uniform Heat development is not optimal and can also damage the surface heating material to lead.

The invention is based on the object of using a surface heating material of the type mentioned at the beginning locally more uniform heat generation and improved durability in use

To achieve this object, according to the invention, the coating has a crosslinkable carbon graft polymer of vinyl monomers on the surface of carbon black.

As a result of this measure, the carbon is embedded in a very fine distribution in the coating.In addition, the bond of the carbon to the coating material is improved, since there is also a chemical bond, so that there is improved durability, especially when the surface heating material is subjected to mechanical stresses due to bending or tensile stresses

The support structure is expediently used in the planar heating material according to the invention of fibers, preferably supple and flexible synthetic fibers or synthetic multifilament threads, The support structure is preferably woven by any desired method and, for example 0.10 to 0.15 mm thick. Support structures for surface heating material woven from threads are known (OE-PS 2 19 730), as well as felt-like or flat support layers consisting of a material film (US-PS 33 85 959); in the case of the surface heating material according to OE-PS 219 730, however, in contrast to Invention of conductive silicone rubber as a coating and in the surface heating material according to the US-PS 33 85 959, in contrast to the invention, an organopolysiloxane elastomer Use, so that the above advantages also with these known surface heating materials a coating with a crosslinkable carbon graft polymer cannot be achieved.

In a further development of the invention, the support structure has a porosity or a pore volume of 20 to 65%, preferably from 40 to 60%. A suitable choice of the porosity enables particularly good adhesion the coating applied, for example, as a film or paint, since part of the coating is covered by the Pores penetrate to the other side of the surface heating material. With pore volumes above 65%, the The carbon of the coating falls out more easily, causing a significant change in the resistance of the Surface heating material occurs. If the pore volume is below 20%, the carbon may become detached Coating comes and flat woven layers are difficult to achieve.

In general, the flexible support structure should be thin, but still strong and resistant to bending own. The surface of the support structure should be uniformly uneven in order to ensure uniform application the coating, for example as a paint. The Voiumenporosity is favorably so that cavities from one side of the support structure to go through the other side. Furthermore, the fibers of the support structure should be heat-resistant and have high softening properties. and have decomposition temperatures. In addition, the aim is that the product as possible is free from shrinkage or expansion, which is why the use of high-melting point recommends synthetic fibers and fabrics.

Preferably, in the inventive Flächenheizmaterial the support structure of synthetic Multifflament-fibers is constructed, whose melting point, or their thermal decomposition temperature is above 250 ⁰ C-spun filaments are less suitable, since they are not uniformly thick and have ulizureichende smoothness of the surface and insufficient resistance to stretching . The tensile strength of the structure should be more than 1 0 kgf / cm.

The following is cited as an example for the production of the support structure in the sheet heating material according to the invention: Multifilament threads (75 denier) made of polyester fibers with a strength of 5 g / denier and 110 or 98 threads per 2.54 cm in length are selected - or crosswise woven. The pore volume of this structure is around 50%. An approximately 10% reduction in number of filaments in the transverse direction is selected in consideration of shrinkage by about 10% during processing, although polyester fibers are very suitable, any other heat-resistant fibers can be used, the pore volume is obtained, the thickness and smoothness as long as the required Meet conditions. Then, the support structure prior to use 30 to 60 seconds is subjected to a heat-setting or hot storage at a temperature of 5 to 10 ^0. C below the softening temperature of the fray, to the dimensional stability of the fibers. They are seconds fixed by placing in an oven at 225 ⁰ C for example 45 and cured Further, it may be necessary to the structure prior to the application of the paint provided with grafted carbon in a suitable organic solvent to dive (the same solvent is preferably such that for used the paint ) to remove bubbles inside the structure.

The vinyl monomers used in the invention can be described by the following general formula :

CH ₂ = C-R '

wherein R and R 'denote a hydrogen atom and various substituents «ie denote an alkyl group. The monomers include those containing functional groups such as acrylic and methacrylic acids, maleic anhydride, acrylamide, and those which have no functional groups such as esters of acrylic and methacrylic acids, maleic anhydride, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate, styrene and derivatives thereof, vinyl ethers and vinyl pyridines. When producing the coating, the procedure can be that vinyl monomers are heated in the presence of carbon black in order to carry out the graft polymerization with the aid of free radical initiators and the polymerization of the vinyl monomers with one another. The vinyl polymers with a relatively short chain length are chemically bonded radially to the surface of the carbon black at active sites. As a result of the polymerization reaction, the chemical surface properties of the carbon black particles are changed because of the large number of vinyl polymer chains bonded to the surface. The particles are better finely dispersible in organic solvents. Varying the vinyl monomers used enables a high degree of different miscibility with the solvent. In addition, the high molecular substance can be made reactive by introducing certain functional groups into the vinyl monomers.

In a further development of the invention, the coating can be crosslinked with the aid of a crosslinking agent, wherein the crosslinking agent is preferably an organic titanium compound, an epoxy compound or a Aziridine compound has the crosslinking agent,

ίο which react with the above-mentioned functional groups, high molecular weight compounds with an epoxy group or organometallic compounds of the general formula Me (OR) _n , wherein R is an alkyl group with 1 - 16 carbon atoms, η a

iS an integer from 2 - 4 and Me a metal atom from one Group means consisting of titanium, zinc, magnesium, lead, Copper, aluminum, cadmium and also contain amino compounds and polyhydric alcohols. By connecting the functional groups introduced into the abovementioned vinyl polymers with the Crosslinking agents such as the high molecular compounds and the above-mentioned organometallic compounds Compounds, the polymerized on the surface of the grafted carbon particles can

nylpolymerisate be crosslinkeda Therefore, the carbon black particles can both physically and chemically be firmly connected. If now current long-term through the associated with the vinyl polymers Carbon black (electrically conductive, high molecular weight

Paint) flows, migration of the carbon black to an electrode can therefore be avoided. It it is desirable to age the material at a temperature above the operating temperature in order to achieve a Obtain film with better electrical stability.

In a further development of the invention, it is preferred that the coating is a polymer with functional groups such as -OH, -COOH, -NH ₂ , = NH, -CONH,

-CH-

CH,

and —SONH2 and that the crosslinking agent the general formula

R -

CH,

CH

2 / π

where R is an aliphatic, aromatic or alicyclic compound and π is an integer from 2 to 4. Such crosslinking agents that have 2 to terminal aziridine rings include:

Ν, Ν'-tetramethylene-bis-ethylene urea, Ν, Ν'-pentamethylene-bis-ethylene urea, Ν, Ν'-hexamethylene-bis-ethylene urea, N.N'-heptamethylene-bis-ethylene urea, Ν, Ν'-octamethylene urea, p-phenylene-bis-ethylene urea, m-phenylene-bis-ethylene urea, m-toluylene-bis-ethylene urea, 1 -Chlor-m-phenylene-bis-ethylene urea, Diphenyl-4,4'-bis-ethylene urea, 3,3'-dimethyl-diphenyl-4,4'-bisethylene urea,

S ^ '- Dimethoxy-diphenyW-bis-ethylene-

urea,

Diphenylmethane-p.p'-bis-ethylene urea,

Tetramethylene-bis-ethylene urethane,

Hexamethylene-bis-ethylene urethane,

Non-methylene-bis-ethylene urethane,

Decamethylene-bis-ethylene urethane,

bis-phenyl-4,4'-bis-ethylene urethane,

p-phenyl-4,4'-bis-ethylene urethane,

p-phenyl ^ / T-bis-ethylene urethane,

p-cyclohexylethylene urethane,

Lysine-bis-ethylene urea,

Tetraaziridinyl-m-xylylenediamine,

Tetraaziridinylmethyl-p-xylylenediamine,

Diaziridinyl-methyl-m-xylylenediamine,

Diphenylmethane-4,4'-tetraaziridinyl

methylenediamine.bis-phenyl ^ / l'-tetraaziridinyl-

methylenediamines.

The coating can preferably be converted into the crosslinked state by heating. In particular When the coating is composed according to claim 6, the heat treatment can be carried out in a shorter time and also the crosslinking reaction to be completed to a necessary extent so that the Flat support structure made of synthetic fibers is not thermally attacked under the heating conditions.

In the above given by the general formula

gen with the latter polymers very easily be performed.

The polymers to be used according to the invention with such functional groups that with the by the general formula

R -

CH, \

CH,

R -

CH, \

CH ₃

When the compounds are expressed, the aziridine rings can be easily split open when heated. The compounds then react with functional groups such as -OH, -COOH, -NH ₂ , = NH, -CONH,

-CH

-CH,

and -SONH ₂ . Because the by the general formula

CH ₂ \

R—

CH ₂

compounds expressed and used as crosslinking agents and the polymers have the functional groups, such as -OH, -COOH, -NH ₂ , = NH, -CONH,

-CH CH ₂

and -SONH ₂ , are contained together in the electrically conductive polymer mixtures according to the invention, reactions of the first-mentioned compound unexpressed compounds can react,

for example the following mixtures: carbon-graft polymer mixtures having the above-mentioned functional groups produced by graft polymerization of carbon with vinyl monomers, mixtures obtained by mixing the above functional group-containing polymers are produced with carbon powder, and mixtures, produced by the combined use of the grafted carbon-containing polymer mixture will.

The film applied by coating can undergo an aging process to stabilize the electrical properties Properties are subject to. Since prolonged heating, however, there is a risk of impairment of the synthetic fibers that can form the support structure, this treatment is carried out preferably carried out in a shorter time at high temperature. The properties remain the same for long operating times.

The surface heating material according to the invention can be produced, for example, as follows. An electrically conductive, high-molecular coating material of high flexibility, s electrically conductive high molecular material is prepared in a solvent by dissolving an ^e, is applied in a thin layer on the surface of a very pliable and flexible, flat supporting structure, such support structures are, for example, tissue-like structures from different Types of high temperature resistant synthetic fibers such as polyamide and polytetrafluoroethylene fibers. The resulting product is dried, and a thin film of the electrically conductive high molecular weight material is formed on one or both sides of the sheet material. The application of the coating can according to any ^one coating method such as roll coating coating by means of a coating bar (doctor blade), layers Tauchbe or be carried out spray coating The formed on the flat material thin fiin electrically conductive high molecular paint: is then heated to the crosslinking of the elektriscl conductive high-molecular paint and get the electrically conductive surface heating material ic . The surface heating material can be further heated to high temperatures in order to stabilize the electrical properties.

The surface heating material according to the invention is generally provided with flexible electrodes which serve to supply power before use. The flat heating material according to the invention can be tightly covered or completely encased on both sides η 6s of a waterproof, electrically insulating foil, for example made of rubber or a flexible plastic .

material is possible to obtain a flat, plate-like heating element.

The surface heating material according to the invention can be embedded in various materials to a large extent Applications such as the following are used: houses, especially walls, floors and Blankets, furniture such as stools and chairs; Cars and trucks; Rearing cattle, such as pig rearing and Poultry farming; Fisheries such as fish farming in marsh ponds and inland lakes; Agriculture, as for the heating of warm and draw beds; Civil engineering work, such as melting snow or ice from roads, slopes, bridges, etc .; Thermal insulation of water supply pipes, other pipelines, Boiler room cladding etc .; warming garments such as swimwear, coats, jackets, pants; and other personal items, such as gloves. Shoes, slippers, stockings and much more. When in particular the heating layer material is embedded in a diving device or a diving suit, the Working hours underwater, for example when rearing in the ocean or in a lake, are considerable be extended. Therefore, the surface heating material for the future utilization of the oceans and cold areas where snowfall and ice formation are difficult. Flexible sheet heating materials according to the invention can last longer than 2000 hours without difficulty 120 ° C can be used.

The invention is explained in more detail below by means of examples. It shows

F i g. 1 shows a partial view of the surface heating material with its connections to a power source,

2 shows the electrodes and the structure of the heating layer material in a section.

example 1 328 g Soot from an oil-fired oven 72 g Acrylic acid 256 g Butyl acrylate d, j3-azo-bis-isobutyronitrile 30 g (Radical generator) 1000 g Methyl isobutyl ketone

15th

These constituents were placed in a three-necked flask and ^{polymerized for 8 hours at 80 °} C. in a nitrogen atmosphere with agitation or stirring. A polymerized liquid was obtained with a viscosity of 80cP with an output or yield of 97%. Then, a solution of a crosslinking agent was prepared as shown below and added to the polymerized liquid with stirring.

Epoxy resin (crosslinking agent) 76 g

Methyl isobutyl ketone (solvent) 200 g
Polymerized liquid

as stated above 1656 g

Araldit (Shell Chemical Co.) with an epoxy equivalent of 76 was used as the epoxy resin. The same resin was used as a crosslinking agent in all of the following examples.

The mixed solution 2 thus formed was applied onto a fabric-like structure 1 made of polyester fibers (No. 3311 Tetron by Teizin Co.) at a wet pick-up of 115 g / m ² with a dip coating machine at a speed of 3.4 m / min and with hot air at 150 ⁰ C dried. This product was heated for 16 hours at 22O ⁰ C, to complete the cross-linking and the aging treatment.

The resulting surface heating material 3 had a

Sheet resistance of 100 ohms. (Sheet resistance should generally be ^{understood to mean the ohmic resistance per cm 2} with a constant thickness, here 0.12 mm.)

On the other hand, a comparative sample of a sheet heating material was made by applying a mixed one Paint on a structure made of fiberglass. The paint consisted of 328 g of carbon black from an oil heated oven, 328 g of acrylic resin and methyl isobutyl ketone together, with the carbon was neither polymerized nor crosslinked. The suppleness and flexibility of this example The surface heating material 3 obtained were compared with those of the last-mentioned product, as shown in the table 1 can be seen.

The tests were conducted generally according to JIS L-1079 using a Scott flexibility testing machine and an Olsen bending testing machine.

35

40

Table 1

Flexibility testing machine (load 1 kg / 1.5 cm)

Bending testing machine
(Load 1 kg / 13 cm)

Comparative sample ruptured at 28 repetitions

Product according to this example no failure at 1000 W cracked at 8 repetitions
no error at 2000 W

As can be seen from Table 1, the surface heating material according to this example proved to be superior in terms of pliability and flexibility. Then the surface heating material was as in FIG. 1 and 2, cut into suitable pieces, and an electrically conductive silver paint 8 was applied to the areas 4 to which electrodes were to be attached. Wire bands 12 (4 mm wide, 0.2 mm thick, electrical conductivity 5 A) made from 16 coaxial or longitudinally extending wires were then attached by sewing with copper threads 7 in order to form electrodes for the surface heating material.

The electrodes were so flexible that the entire body of the sheet heating material 3 was also very flexible and kept good performance for a long time

The surface heating material obtained in this way was covered with polyvinyl chloride foils on both sides (0.4 mm thick) covered If the distance or length of the electrodes 4 is 420 mm or 900 mm and at

709 611/207

an applied voltage of 100 V and an output of 570 W / m ² current was passed therethrough, to a temperature which was about 3O ⁰ C above room temperature (20 ° C) obtained on the surface of polyvinyl chloride.

Example 2

Soot from an oil-fired oven 220 g Acrylic acid 115 g Acrylonitrile 85 g Azo-bis-isobutyronitrile 20 g Cyclohexanone 680 g

These ingredients were mixed with agitation and heating at 90 ^° C. for 6 hours in the same manner as in Example 1. As a result, a solution of a polymerized substance having a viscosity of 95 cP at an output of 98.5% was obtained.

Then, a crosslinking agent was dissolved in a solvent in the ratio shown below and

added while stirring the above solution of the polymerized substance.

Epoxy resin (crosslinking agent)
Cyclohexane (solvent)
Solution of the polymerized
Substance see above

65 g 170 g

1220 g

The solution 2 thus formed was applied to a fabric-like structure 1 made of polyamide fibers with a wet pick-up of 140 g / m ² with a dip coating machine at a speed of 1 m / min and dried with hot air at 150 ° C. This product was further ^{heated to 200 °} C. for 30 h in order to complete the crosslinking and the aging treatment. The resulting sheet heating material 3 had a sheet resistance of 50 Ω.

As can be seen from the following Table 2, the suppleness and flexibility of the were found surface heating material 3 obtained in this example as excellent.

Table 2

Flexibility testing machine (load 1 kg / 1.5 cm) Bending testing machine (load 1 kg / 1.5 cm)

Product according to this example no error at 1000 retries no error at 2000 retries

example 3 85 g Soot from an oil-fired furnace 184g Epoxy resin 225 g Vinyl acetate 172 g Cyclohexane Maleic anhydride 196 g Solution of the polymerized 1394 g Azo-bis-isobutyronitrile 32 g 35 Substance as above Octyl alcohol 12g 2 was on egg Cyclohexane 830 g The mixed solution thus formed

These ingredients were heated with agitation under the same conditions as in Example 2 obtained a solution of a polymerized substance with a viscosity of 87 cP at an output of 98.3%.

The next step was a crosslinking agent in a solvent in the one given below Ratio dissolved and added to the above solution with stirring.

Fabric-like structure 1 made of polyester fibers is applied with a dip coating machine under the same conditions as in Example 1, dried and thermally treated in order to obtain the surface heating material 3. The sheet resistance of the sheet heating material 3 was 200 Ω.
As can be seen in the following Table 3, Erwie;

the surface heating material 3 according to this example in terms of suppleness and flexibility as out draws

Table 3

Flexibility testing machine (load 1 kg / 1.5 cm) bending testing machine (Load 1 kg / 13 cm)

Product according to this example no error at 1000 retries no error at 2000 retries

Substance with a viscosity of 93 cP at an output of 98.8%. Then there was a networking medium dissolved in a solvent and in the ratio specified below with tubes of the solution de polymerized substance added.

Example 4 330 g 6o Soot from an oil-fired furnace 137 g Acrylamide 163g Vinyl acetate Azo-bis-isobutyronitrile 35g (Radical generator) 1500g Cyclohexanone

These ingredients were stirred while taking them the same conditions as in Example 2 were heated. A solution of a polymerized one was obtained Tetrapropyl titanate (Crosslinking agent) Cyclohexane (solvent Solution of the polymerized Substance as above

84g 380g

2139 g

The mixed solution 2 thus formed was poured on

[ewebeartige structure 1 made of polyamide fibers with a • "laßaufnahme of 140 g / m ² with a Tauchbeschichungsmaschine at a speed of 1 m / min lufgebracht and with hot air of 150 ⁰ C dried. Further heating was continued for 30 hours at 200 ° C for crosslinking and aging treatment

complete. The sheet resistance of the resulting sheet heating material 3 was 50 Ω.

As can be seen from the following table 4, the surface heating material produced in this example turned out to be excellent in terms of suppleness and flexibility.

Table 4

Flexibility testing machine (load 1 kg / 1.5 cm)

Bending testing machine
(Load 1 kg / 1.5 cm)

Product according to this example no error at 1000 retries no error at 2000 retries

Example 5

Mixture A

Soot from an oil-heated oven 24.0 kg

Acrylic acid 4.4 kg

Butyl acrylate 15.6 kg

Azo-bis-isobutyronitrile 0.64 kg

Cyclohexanone 110.0 kg

Cyclohexanone and the other ingredients were placed in a 2001-capacity reaction vessel equipped with a reflux condenser. The reaction was continued for 5 hours at 90 ^° C. while nitrogen was flowing in at a rate of 10 l / min. At the end of the reaction, a dispersion non-defaulting grafted carbon whose strength was C 18.5 cP at 2O ⁰ and 28.9% solid contained

To 25 kg of the mixed solution obtained, the crosslinking agent solution called Mixture B was added, and the whole mixture was made uniform with a stirrer. The paint had a toughness of 12.5 cP at 20 ^° C. and contained 24.4% solids.

Mixture B

Tetrapropyl titanate

Cyclohexanone

0.897 kg
6.36 kg

A portion of the paint mentioned was applied to a glass plate, ^{dried at 150 0} CIh and heated at 225 ° C. for 5 h. The volume resistance was then 0.26 Ω / cm.

The support material originally used was a fabric-like structure with 50% pore volume, cm by weaving multifilament polyester yarns or fibers (75 denier), from 110 threads / 244 in the longitudinal direction and 98 yarns / 2 _T 54cm in the cross direction , was produced. This structure was first passed through a vessel with cyclohexanone as the solvent in order to remove biscuits located between the fibers. The structure was then introduced 5 times into a coating bath at a speed of 1 m / min and then ^{dried for 4 min at a drying temperature of 150 to 160 °} C. The amount of solid substance adhering to the structure was about 9 g / m ² for a single immersion and about 41 g / m ² for five-fold immersion.

The support material structure was dried in an oven at 180 ⁰ C to complete the crosslinking NMtzt h after application of the paint. 2 It was then heated in an oven at 225 ° C for an additional 8 hours for aging. The sheet electrical resistance of the product was 49 Ω and was uniform throughout the structure. The physical properties of the flexible sheet heating material obtained were as follows:

tensile strenght

Tear resistance
(Test procedure
JISK6772)

Bending test (O r s e η)

Flexibility check
(Scott)

26 kg / 3 cm
(longitudinal)
19.5 kg / 3 cm
(in transverse direction)
160 g

Load 1 kg;

no change at

4000 bends

Load 1 kg;

no change at

2000 cycles

The sheet heating material of the present invention showed excellent flexibility in the perpendicular direction to the layer material, so that the conductivity did not change even when bent by up to 180 ° and none Carbon scraped off during the friction resistance test (according to Gak u s h i η).

Example 6

A mixture consisting of 60 g of carbon black of an oil-heated oven, 11 g of acrylic acid, 39 g of butyl acrylate, 16 g of azo-bis-isobutyronitrile and 1100 g of cyclohexanone was 5 as accommodated hours at about 9O ⁰ C in Example 5 for the reaction. A liquid polymer (A) with grafted carbon, in which acrylic acid and butyl acrylate were grafted onto the surface of the carbon black, was obtained. The product contained 28.8% solids with a toughness of 18.5 cP. Then, the following liquid mixture was prepared and mixed with a high speed mixer

Liquid polymer with grafted
Carbon (liquid A)
Diaziridinyl-m-xylylenediamine
Cyclohexanone

Parts

100
6th
4.5

The liquid (B) thus obtained became uniform in an amount of 30 g / m ^{2 of} solid plastic in a similar manner to Example . The surface heating thus obtained was then applied

material 3h heat treated The integrated resistance was 128 ohms at 22O ⁰ C, the physical properties of this Flächenheizmaterials as Dk, following values show excellent Fesügkeit on with good flexibility.

tensile strenght (JIS L-1068)

35.2 kg / 3 cm 14th

Tear resistance (JISK-6772) Bending test (O r s e η)

Flexibility attempt (JIS L-1079; Scott)

1 sheet of drawings

430 g

Load lkg;

no change after

10,000 bends

Loadlkg;

no change at

10,000 cycles

Claims (6)

Patent claims 1. Flexible surface heating material that can be heated by current passage with a flexible, heat-sensitive S constant support structure and with one at this attached flexible, electrically conductive coating, the carbon added to a plastic contains, characterized in that the coating (2) is a crosslinkable carbon ι ο fabric graft polymer made from vinyl monomers the surface of soot 2. Surface heating material according to claim 1, characterized in that the support structure (1) is a Has a porosity of 20 to 65% 3. Flächenheizmaterial according to claim 1 or 2, characterized in that the Stützstruktcir of synthetic multifilament fibers is constructed (1), the melting point or the temperature of the thermal Zerseming is above 250 ⁰ C. 4. surface heating material according to one of claims 1 to 3, characterized in that the Coating (2) mk can be crosslinked with the aid of a crosslinking agent 5. surface heating material according to claim 4, characterized in that the crosslinking agent is a organic titanium compound, an epoxy compound or an aziridine compound 6. Surface heating material according to claim 4 or 5, characterized in that the coating (2) is a polymer with functional groups such as -OH, -COOH, -NH ₂ , = NH, -CONH,