DE2350765B2 - Process for the production of foils or coated or laminated flexible substrates - Google Patents

Description

The present invention relates to the production of films, textile coatings and laminations Made of polyurethane (urea) powders using the drying and sieving process.

The coating and lamination of flat structures can be carried out using a wide variety of methods Substances and take place according to very different processes. To the state of the art in the textile sector include doctor blade, flattening, spraying and calendering processes. In most cases, for procedural reasons, it is necessary to remove coating or laminating agents that can be applied in the liquid state. Of that exceptions are z. B. calendering processes, as they are common in the rubber industry, the lamination by Flaming of polyurethane foams or the application of polymer powders during heat sealing of flat structures of all kinds. Also known is the squeegee-like application of z. B. polyethylene powders as Back coating of carpets or floor groups in K FZ construction. Of these exceptions Apart from that, the coating and laminating technology is based on technically paintable or sprayable products instructed with an appropriate viscosity range.

The required consistency can be thermoplastic polymers e.g. B. by heating above their melting point also be taught how it happens in the so-called roll melting process A disadvantage However, this technique is that the polymers over a prolonged period of time at elevated temperatures exposed to strong mechanical stress at the same time. Such loads are but not all polymers are grown. In addition, the temperature-resistant precision of the rolls (so-called crowning) of the melt calender, especially with extremely thin application quantities (20

ίο up to 40 g / m ² ) difficult to meet requirements

The method of dissolving polymers in organic solvents and then painting the solutions or to apply syringes is widely used in practice The inherent to these systems Advantages, but also their disadvantages, are known to the person skilled in the art, especially in the case of high-quality products On a polyurethane basis, the solids concentrations of the pourable or sprayable solutions are relative low, so that considerable amounts of solvents are included in the coating or laminating process Need to become. For reasons of ecology and economy, it is also necessary that to collect evaporated solvents or solvent mixtures and after careful rectification to be brought back into the working cycle if possible. Also the necessary work steps for Dissolving, filtering, etc. the pastes are very time-consuming and machine-intensive.

From the possibility of aqueous emulsions or dispersions of polymers for coating and Use of lamination processes is being used to an increasing extent. Is of particular interest in systems of this type their physiological and ecological harmlessness. Their main disadvantage is however, that very few emulsions or dispersions of synthetic polymers are freeze-stable are. In contrast to frozen solutions e.g. B. of polyurethanes in organic solvents Frozen aqueous emulsions or dispersions in most cases no longer after thawing applicable.

In contrast, aqueous suspensions of polymer particles are freeze-stable. From a physical point of view it is unstable dispersions in suspensions. The polymer particles can pass from the suspensions Decanting and then gentle drying can also be obtained as a solid. These solids can be converted back into aqueous suspensions or pastes again at any point in time by you in water, if necessary with the addition of additives such as thickeners, fillers or redispersed inorganic pigments.

A disadvantage of the application of aqueous pastes, however, is that they cause the water to evaporate a considerable amount of energy is required, which is still higher than when applying organic solutions lies.

There is therefore a great deal in the coatings industry

to interest in systems that are processed by dry processes, i.e. without any solvents or dispersants can be.

It has already been stated that in exceptional cases, as in the case of carpet back coatings or in the Heat sealing of textiles, dry powder were applied.

In the documents for Belgian patent 7 70 420 the application of PWR powders after a

modified electrostatic powder spraying process (EPS process). Apart from a very special and complicated machine technology, only powders with very special electrical qualities can be processed, the volume resistance of ^{which should not be below 10 14 ohm · cm}

In the Belgian Patent 6 64 168 is from one Squeegee application spoken in general terms. However, powders according to this Belgian patent specification 6 64 168 fall in a form that can be applied by squeegee only in rough, d. H. allow heavy spreads and the are therefore not universally applicable. There is accordingly a gap ia the technical requirements for the coating and lamination of flat structures, from which the task results, To develop coating processes without the disadvantages described.

It has now been found that coatings with certain dry polyurethane powders can be carried out on conventional coating systems using conventional coating and screening processes. In contrast to the Belgian patent 7 70 420, the EPS technology for the application is possible, but not necessary. The present invention differs from Belgian patent specification 6 64 168 in that it is precisely stated according to which special criteria the powder must be selected so that both homogeneous and inhomogeneous, uniform or irregular spreads with weights per unit area of 10 g / m ² up to arbitrary high strengths can be achieved.

It turns out that especially with regard to the surface properties and melting behavior of the Solid particles have to meet high requirements.

The diameter of the particles should be between 5 and 200 μm, preferably between 8 and 150 μm, move. The particles should have a smooth surface and a shape that is as spherical as possible in order to obtain from to ensure good spreadability or pourability from the outset.

Particular importance is to be attached to the melting behavior of the polymers. It turned out to be the best way the addition of an INTRINSIC MELT to identify the products that can be used according to the invention INDEX (1M1) curve.

To determine the time-independent melt index (= »Intrinsic Melt Index«), the Temperature heated plastic melt through a channel (nozzle) with a given ratio of Diameter pressed to length with a certain pressure and the extruded amount as melt index analogous to ASTM D 1238-65 T determined by weighing. The melt index is determined in this way different long preheating times and extrapolated to (= 0, one obtains the intrinsic melt index (it becomes a linear time dependence of the melt index is always assumed). This value is one of the Preheating time-independent constant of the respective substance. The time-independent melt index thus indicates what amount of material under specified test conditions gen would be extruded after a preheating time of 0 minutes if the material could be applied to the To heat the test temperature.

^{A viscometer of the *> r} > type HKV 2000 from Göttfei't in Buchen / Odenwald was used as the testing device for the polymers used in the present application. The nozzle in this device had a length of 15 mm, a diameter of 1.05 mm and a conical inlet connection with an opening angle of 60 °. The pressure on the melt was 177.0 kgf / cm ² .

If one adds the measurement of the time-independent melt index under otherwise identical conditions different temperatures, enters the values obtained in a coordinate system and connects them the points with each other, either straight lines with a characteristic angle of inclination result or but curves.

It has been found that especially those of polyurethane powder are suitable for the purposes of the coating and lamination, whose melting points or melting ranges between 110 and 250 ° C, preferably between 110 ⁰ C and 190 ⁰ C. In addition, the course of 1MI curves should resemble the rising branch of a parabola and in such a manner that the IMI value within a temperature intervals of 5 to 50 ⁰ C, preferably of 10 to 40 ° C, 2 g min per 10 changes to 50 g per 10 minutes as illustrated in the figure. Curves 2 and 3 were recorded on polyurethane powders which can be used according to the invention (products corresponding to Example 1 and 3, respectively), while a powder with a melting behavior according to curve 1 cannot be processed in the method according to the invention.

Polyurethanes or polyurethane ureas suitable for the process according to the invention must also have an ion group content of 1 to 15 milliequivalents per 100 g and a volume resistance of 10 ¹⁰ to 10 ¹⁴ ohm · cm.

The invention therefore relates to a process for the production of foils from polyurethanes or Polyurethane ureas or coated or laminated with polyurethanes or polyurethane ureas flexible substrates by drying powdered polyurethanes or polyurethane ureas applied to a release liner or the flexible substrate, then sintered by the action of heat and / or melts and optionally then calendered, characterized in that as powdery Polyurethanes or polyurethane ureas are used which

a. have a smooth, spherical surface,

b. a mean diameter between 5 and 200 μm,

c. an ion group content of 1 to 15 milliequivalents per 100 g and

d. have a volume ^{resistance of 10 10} to 10 ^H ohm · cm and

e. where the course of the respective IMI curves represent the rising branch of a parabola at temperatures between 110 and 250 ° C, whereby the IMI value changes from 2 g / 10 min. to 50 g / 10 min in a temperature interval of 5 to 50 ° C.

The polyurethane (urea) powders to be used according to the invention can be prepared by reacting NCO prepolymers which contain ionic groups, with primary and / or secondary diamines (with aliphatically bound amino groups) and / or dicarboxylic acid-bis-hydrazides be made in the presence of water. The N H / NCO ratio in the The chain extension reaction is preferably 0.1 to 0.95, particularly preferably 0.25 to 0.85; the The ionic group content of the NCO prepolymers should be such that the products of the process have the desired ion group content of 1 to 15 milliequivalents, preferably 2 to 10 milliequivalents, per 100 ε.

Preference is given to first preparing a solution of both isocyanate groups and ionic groups containing prepolymers in organic solvents, this solution is combined with an aqueous one Solution of the chain extender and finally removes - ideally by distillation - the organic Solvent. In this way, the powders to be used according to the invention are in the form of a obtained sedimenting aqueous dispersions.

A particular advantage of this embodiment is that you do not have to rely on high-speed stirrers, but that the union of the NCO prepolymer with the chain extender by simple low-speed stirring can take place.

In the case of the prepolymers mentioned, which both Have free isocyanate groups as well as ionic groups, it is about the production of compounds known per se from emulsifier-free polyurethane dispersions. Preferably such NCO prepolymers are used, which have an average molecular weight of 300 to 25,000, in particular 800 to 15,000, particularly preferably from 2,000 to 7,000.

The properties of the polyurethane urea powders obtained in this way can be varied within wide limits vary suitable measures in a targeted manner. This is especially true for the hardness and size of the particles.

The first possibility of influencing the property profile lies in the structure of the isocyanate group-containing ionic pre-adduct. This takes place according to known methods (Belgian patents 6 53 223 and 7 30 543) using the starting materials listed in these patents. Besides that there compounds mentioned come as higher molecular weight substances with reactive hydrogen atoms but also compounds containing amino groups, such as those in the French patents 13 61 810 and 13 00 981, the German Auslegeschrift 1122,254 and U.S. Patent 2,888,439 are.

The size of the particles is determined by the content of ionic groups in the pre-adduct, their Hardness mainly due to the chemical nature of those used in the manufacture of the NCO prepolymers Affects polyisocyanates or compounds with reactive hydrogen atoms. You limit yourself in the case of these compounds to those with low molecular weights up to about 500, harder ones are obtained Polyurethanes, if only higher molecular weight up to about 10,000 are used, then softer ones are obtained Products. All mixing ratios are possible between these extremes. As in the pre-adduct formation with relatively large excesses of isocyanate - the molar ratio of the NCO groups to the reactive ones Hydrogen atoms is expediently between 4 and 1.1, preferably between 2 and 1.4 - worked is, the molecular weights of the prepolymers are not very high, is a strict linearity of the Chain structure not necessary. In the production of the powder, however, it is preferred to have a linear structure NCO prepolymers with two terminal, aliphatically bonded isocyanate groups started.

A solution of the prepolymer with an aqueous solution or dispersion of the Chain extender brought to reaction In exceptional cases, the chain extender also, dissolved in an organic solvent, can be added during the dispersion.

According to the invention to use polyurethane powders can be produced basically according to the known methods of Belg. Patent 6 53 7 223 and 30 543 for the production of emulsifier-free poly- ^r> than dispersions.

Suitable chain extenders are, in particular, primary and / or secondary diamines containing aliphatically bonded amino groups and dicarboxylic acid bishydrazides. (In the case of the last-mentioned chain extenders, it can be assumed that it is primarily the amino groups in the 3-position to the carbonyl groups that react with the NCO prepolymer, so that the dicarboxylic acid bis-hydrazides can be regarded, in a first approximation, as difunctional chain extenders. ) Suitable diamines are in particular those with a molecular weight below 250, such as. B.
Ethylenediamine, 1,2-propylenediamine,
N-methylpropylenediamine, butylenediamine,

Hexamethylenediamine, piperazine,
2-methylpiperazine, dimethylpiperazine,
N, N'-dimethylethylenediamine,
N, N'-diethyl diethylenediamine,
Ν, Ν'-diisopropylethylenediamine,

N.N'-dimethyl-l ^ -propylenediamine,
N, N'-diisopropyl-1,2-propylenediamine,
Ν, Ν'-bis-hydroxyethyl-ethylenediamine,
N-hydroxyethyl-ethylenediamine,

N-hydroxypropyl-ethylenediamine,
N, N'-bis (hydroxypropyl) ethylenediamine,
N, N'-dimethylhexamethylenediamine,
1,3-propylenediamine, y, y'-bisaminopropyl sulfide,
y.y'-bisaminopropyl-methylamine,
N, N-bis- (j> -aminopropyI) -aniline,
NN-Bis- ^ - aminopropylJ-m-toIuidin etc.

Ather diamines are also used as chain extenders and ester diamines as well as those diamines which are used in the hydrogenation of cyanoethylated diols or bifunctional dihydroxy polyesters or dihydroxy polyethers arise.

The diamines can be used in the form of their salts, for example as carbonates or acetates. The salt formation can also only partially, z. B. to improve the solubility can be made. 4ϊ Has a salt formation on the primary amino group result in a reduction in reactivity.

Examples of bishydrazides of low molecular weight dicarboxylic acids are dicarboxylic acid bishydrazides with a molecular weight below 250, such as

Carbonic acid-bis-hydrazide, oxalic acid-l) is-hydrazide, succinic acid-bis-hydrazide,
Adipic acid-bis-hydrazide,
Phthalic acid-bis-hydrazide,
Terephthalic acid-bis-hydrazide,

Tetrahydrophthalic acid-bis-hydrazide, etc.
Bifunctional polyesters with terminal carboxylic acid hydrazide groups can also be used.

Products to be used according to the invention are particularly suitable as solvents in the preparation of the ω water-miscible compounds with a boiling point below 100 "C such as acetone, methyl ethyl ketone, Tetrahydrofuran or ethyl acetate suitable. The use of with water is not Miscible solvents is also possible, if by appropriate stirring for an intensive Mixing of the reactants is ensured. Such solvents are e.g. B. benzene or toluene.

It is also possible to use solvents with a ^{boiling point above 100 °} C. such as the toluene just mentioned or chlorobenzene, dimethylformamide or dimethyl sulfoxide, but their removal from the process products is generally associated with increased expense.

The polyurethane powders to be used according to the invention are preferably prepared in the following manner produced: The ionic NCO prepolymers are made from dihydroxyl compounds of a known type Molecular weight 500-5000, diisocyanates and optionally chain extenders using built up such an excess of diisocyanate that the adduct has 1 to 4% by weight of free NCO groups having. The NCO prepolymer also contains 1-15 Milliequivalents per 100 grams of quaternary nitrogen or Carboxylate or sulfonate groups.

The 30 to 90 wt ° / o solution of the ionic NCO prepolymer in acetone (viscosity at 5O ⁰ C: about 30 to 800OcP) are mixed with aqueous solutions of aliphatic diamines having primary and / or secondary amino groups. The acetone is then distilled off and the polyurethane urea powder is obtained in the form of an aqueous sedimenting dispersion. The process product can be presented in pure form by simple filtration. Although it can be redispersed in water at any later point in time, it is preferred to apply the dry powder by the dry squeegee or sieve method.

You can either with stirring the aqueous solution to the chain extension reaction Add the acetonic or the acetonic to the aqueous solution. The mixing is preferably carried out in suitable equipment carried out continuously by, for example, the two solutions Pumps dosed into a mixing vessel. In the simplest case, the mixing vessel has a stirrer and a Provided overflow, through which the aqueous-acetone dispersion flows into a distillation apparatus Dispersion temperature is between 20 and 60 ° C, preferably between 35 and 55 ° C. The amount of water required for dispersion in which the diamine is dissolved is 0.8 to 3 times that of the ionic NCO prepolymer, preferably 1 to 2 times.

For continuous mixing with a high throughput, high-speed agitators are preferred or mixers that allow high shear forces to be exerted. Appropriate facilities such as Screw machines, in particular multi-shaft screws. Internal mixers, high pressure or low pressure mixing chambers with countercurrent mixing or ultrasonic dispersers are known to the person skilled in the art. When working in such apparatus, it is preferable to use 70 to 90% solutions and sufficient Flowable prepolymers even worked entirely without solvents.

The properties of the polyurea powders, which are primarily obtained as suspensions, can also be determined the chemical composition of the polyisocyanate pre-adduct also depends on the dispersion conditions targeted influence a The most important factors are: type and amount of chain extenders, the amount of water, Type and amount of the organic solvent, the pH and the reaction temperatures, which of about 0 ° to the boiling point of the organic solvent can be varied, also under pressure can be worked.

The method of mixing the aqueous and organic phases is also essential, d. H. whether these are practically simultaneously, for example in a continuously operating mixing device, takes place or whether the organic is added to the aqueous or aqueous to the organic phase. Be it however, once again emphasizes that useful products can also be obtained with simple means by z. B. while stirring with a normal stirrer the aqueous

ίο phase can flow into the organic. After or during the mixing, the organic solvent is removed by distillation. By filtration the finished powder is obtained from the aqueous polyurethane dispersion formed.

The application of the polyurethane powder takes place according to the usual doctor blade method, i. H. with the help of fixed Squeegee systems such as air, rubber blanket and, above all, roller squeegees as well as with the roll or reverse roll coater.

Surprisingly, polyurethane powders with the properties required according to the invention can be produced Even when dry, loll in a way that is otherwise industrially only applied by painting with pasty approaches is possible.

The powders are so fine and so free-flowing that they can be used without further additives and without additional grinding Pass the finest nozzle of the glass nozzle series to determine the flowability according to the DEGUSSA system.

A further improvement can - if desired -

3 »still by adding small amounts of magnesium stearate, among other things.

usual lubricants. The additional amounts can be between 0.1% and 5%, based on the entire solid.

The flowability of these powders is surprisingly good, even with an adsorptively bound residual moisture content from 0.1 to 5% water. This residual moisture can even be desirable because of these small amounts of water plasticize the plastic and lower the melting point of the process products somewhat.

Both direct and, preferably, reverse coatings can be used according to the process according to the invention produce. In the case of reverse coating, a release liner is preferably used siliconized rubber or, particularly preferably, a steel strip. But of course you can too Usual release papers can be used.

The thickness of the coatings is between 10 g / m ² and a few 100 g / m ² .
If the knife-coated or sieved powder is exposed directly to the action of heat, for example in an IR field, and is then suddenly heated to temperatures above their melting point, they melt together to form homogeneous films. However, if the applied dry powder is heated slowly and only to the melting point, a layer is obtained which is referred to below as a frit and which has a porous, macroporous structure

The coloring or pigmentation of the coating can be done in several ways. The polyurethane powder is preferably used before application powdery colorants or fillers such as carbon black, titanium dioxide, aluminum-bronze, iron or cadium pigments mixed

B e i s ρ i e 1 1

According to example 7 of Belgian patent 8 00 185, a polyurethane powder (spherical particles with a mean diameter of 43 μm; Melting point

145 ° C; Volume resistance: 5 · 10 "ohm · cm; IMI value: curve2in Fig. 1) produced.

The polyurethane powder is knife-coated onto a release paper with an application ^{thickness of 100 g / m 2} and then exposed to a temperature of 140 ° C. in a nozzle channel 12 m long and at a belt speed of 1.5 m. A frit is formed which is viscoplastic, can be separated from the carrier without difficulty and can be handled without any other support.

Example 2

The frit produced according to Example 1 is coated again with the same powder in a second coating process (application thickness: 60 g / m ² ) and then treated in the canal as described in Example 1 at 170 ^{° C.} The result is a homogeneous, transparent film with a total thickness of 160 g / m ² with high tensile strength and elastic properties.

20th

Example 3

A powder according to example 11 of Belgian patent 8 00 185 (melting point: 165 ° C., mean Diameter of the spherical particles 61 μΐη; Volume resistance: 10 "ohm · cm; IMI values: curve 3 in FIG. 1) is applied to a steel strip in a thickness of 0.3 mm and melted into a film at a temperature of 175 ° C in the nozzle channel. In a second coating process, the powder is according to jo Example 1 applied with an application thickness of 0.3 mm and then by the action of a Sintered at a temperature of 145 ° C to form a frit that adheres firmly to the prefabricated film. The two layers can no longer be separated mechanically without destruction.

The films formed according to Examples 1 to 3 can be used in a conventional manner by one-sided or two-sided Wet lamination with any carrier material such as cotton fabrics, polyester fabrics, nonwovens etc. can be connected. For example, polyurethane solutions and polyurethane dispersions are suitable for wet lamination or other adhesives are suitable. The lamination can also be based on the principle of Heat sealing is carried out using thermoplastic plastic powders.

Example 4

A porous film produced according to Example 1 is provided with a layer of the polyurethane powder from Example 1 (application ^{thickness 80 g / m 2} ) by knife application and exposed to a temperature of 145 ° C. In the plastic state of the powder, a cotton nettle ( 80 g / m ² ) laminated. After cooling, the laminate is firmly bonded and can withstand more than 1,000,000 Bally flexometer kinks.

Example 5

100 g of polyurethane powder according to Example 1 and 10 g of titanium oxide

are mixed mechanically and applied to a silicone separator using a roller doctor blade. the Layer is subjected to a temperature of 160 ° C. in the channel described in Example 1. It the result is a white, coherent film that has good mechanical stability after cooling having

Example 6

a) 100 g of polyurethane powder as in Example 1 and

5 g of carbon black
are mixed

b) 100 g of polyurethane powder as in Example 1 and

2 g aluminum bronze
are mixed

c) 100 g of polyurethane powder as in Example 1 and

5 g cadmium red pigment
are mixed

The mixtures a, b and c are alternating from solid nozzles, which over the entire width of the The substrate shimmers, applied to a steel band, during the subsequent passage through a squeegee gap calibrated and mixed irregularly at the border zones.

After cooling and separating from the steel sheet, a cohesive, mechanical one is obtained stable film with color effects in the form of inclined colored stripes with smudged Border zones. Due to the influence of the squeegee gap, the same layer thickness is formed everywhere Mixture of components a, b and c is blurred at the boundary zones of the application, so that a locally individual sampling is created as part of a uniform overall aspect.

Example 7

The powder mixtures from Example 6 are applied as described in Example 6, but that applied powder not spread completely flat. The result is a film that, in addition to the color effect, as with the products of Example 6 additionally has irregularities in the surface and with a is comparable to irregular flat embossing.

Example 8
Manufacture of the polyurethane powder

From 950 g of a dehydrated butanediol-adipic acid polyester with an average molecular weight of 2190.166 g 1,6-hexane diisocyanate and 8.8 g of N-methyl diethanolamine a prepolymer is produced in 1 hour at 100.degree. C., which contains 6.7 cm of dimethyl sulfate and a total of 1280 g Acetone is added. A 50% strength prepolymer solution in acetone with an NCO content is obtained of 1.23%.

When mixing 757 parts of this prepolymer with 189 parts of a 1 η aqueous propylenediamine (1,2) solution and 568 g of water form a polyurethane urea suspension. After distilling off of the acetone, filtering, washing and subsequent drying, a polyurethane urea powder is obtained from melting point 168 to 174 ° C

The powder has a mean diameter of the spherical particles of 60 μm and a volume resistance of 10 ¹² ohm-cm.

The powder is applied to a steel strip at an application thickness of 100 g / m ² and sintered together to form a film by heating to 200 ° C

A second line (60 g / m ² ) of the polyurethane powder from Example 3 is applied to the film. The material is passed through a 1.5 m long IR field at a belt speed of 1.5 m / min

The IR field has a total output of 24 kW over the length and is connected so that one

The surface temperature on the separating support is measured at 200 ° C.

After passing through the IR field, a Cotton knitwear laminated. The lamination is controlled by the gap. The following applies: gap width = Textile thickness + layer thickness - 0.1 mm. The one from Stahlband peeled reverse coating has an excellent level of properties.

Example 9

A spherical polyurethane powder according to Example 3 with a particle diameter of 25 μm, a melting point of 165 ° C. and a volume resistance of 10 "ohm cm is applied to a steel belt with a sieve (application thickness 80 g / m ² ) and then through an IR Field performed as in Example 8. In a second operation, a thin layer (40 g / m ² ) of the polyurethane powder from Example 1. The coating is sintered to a frit and still in the plastic state with a nonwoven fabric Made of polyester / polyamide fibers laminated together to create an excellent composite material.

Example 10, ₅

On a material of cotton poplin the polyurethane powder from Example 1 with about 100 g / m ² abruptly in an IR field (see Example 8) is applied, heated to 180 to 200 ⁰ C and then immediately cooled. This is followed by calendering at a pressure of 7 tons at 110 ° C. A directly coated textile with a smooth surface is obtained.

Example 11

The polyurethane powder from Example 3 is knife-coated onto a steel belt at about 160 g / m ² , sintered as usual, and a cotton mesh fabric is placed on the material, which is still plastic when it cools. The polyurethane powder from Example 1 is then again applied with a knife at approx. 150 g / m ^2. After renewed sintering in the IR field, it is cooled and calendered. A self-supporting, stable film is obtained that can be used, for example, as a conveyor belt.

Example 12

The polyurethane powder from Example 3 is applied to a steel belt and sintered as usual. Im still In its plastic state it becomes under a calibration device consisting of a doctor blade or a Doctor roller with separable surfaces, passed through. The calibration device is around 0.01 to 0.05 mm set lower than the layer thicknesses of steel strip plus sintered powder. The melt is spread and calibrated homogeneously in this way.

Example 13

The polyurethane powder from Example 3 is knife-coated onto a steel belt at room temperature. That Sintering and melting of the powder does not take place through direct heat transfer as in example 1 (nozzle channel) or in Example 8 (IR field), but by indirect heating in such a way that the steel strip primarily is heated by hot air and the heating of the powder through to sintering and melting Heat transfer takes place from the steel belt.

Working methods other than those listed in the examples are also possible, for example can Instead of a nozzle channel, heating channels or units of other designs are used. Likewise is instead of a steel belt as a heat exchanger and hot air as an energy carrier as in Example 13 as well other indirect heating is possible.

1 sheet of drawings

Claims (3)

Patent claims: 1. Process for the production of foils from polyurethanes or polyurethane ureas or of flexible substrates coated or laminated with polyurethanes or polyurethane ureas, by placing powdered polyurethanes or polyurethane ureas dry on a separating support or applying the flexible substrate, then sintering and / or melting and / or under the action of heat possibly subsequently calendered, thereby characterized in that such pulverulent polyurethanes or polyurethane ureas are used be what a. have a smooth, spherical surface, b. a mean diameter between 5 and 200 μm, c. an ion group content of 1 to 15 milli equi vaJenten per 100 g and d. have a volume ^{resistance of 10 10} to 10 ^M ohm · cm and e. where the course of the respective IMI curves represent the rising branch of a parabola at temperatures between 110 and 250 ° C, where the IMI value is in a temperature interval changes from 5 to 50 ° C from 2 g / 10 min. to 50 g / 10 min. 2. The method according to claim 1, characterized in that the flexible substrate is a textile Substrate is. 3. The method according to claim 1 and 2, characterized in that the pulverulent polyurethanes or polyurethane urea an adsorptively bound residual moisture of 0.1 to 5 wt .-% exhibit.