DE2125908A1 - - Google Patents

Description

Process for the production of microporous fabrics

It is known, water vapor permeable fabrics or Coatings made from solutions of polyurethanes (e.g. dimethylformamide) by coagulation in nonsolvents (e.g. Water) by a number of processes in which the desired microporous structure of the polymers is achieved by adhering to very specific and fixed conditions are to be achieved during coagulation. Failure to comply with the special On the one hand, macropores, i.e. coarse holes that are visible to the naked eye, easily develop in the conditions the film, or the structure becomes unusable, uneven, the surfaces are uneven, or the microporous Structure disappears again in the critical phase of drying with the formation of a non-porous, transparent one clear film.

The use of solutions of polyurethanes or polyurethane ureas in highly polar solvents such as dimethylformamide or dimethylacetamide (possibly using other polymers such as polyvinyl chloride or polyacrylonitrile) for the production of films, coatings on fabrics or as binders for nonwovens with removal of the Solvent by treatment (e.g. immersion) with water, glycerine or other liquids that contain the named

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Miscible with highly polar solvents, but with the polyurethanes are incompatible is already described in German patent specification 888 766. There is already the co-use common solvents (which are non-solvents for the polyurethane), e.g. methylene chloride, acetone or benzene.

In a large number of later industrial property rights, special process steps are specified in order to arrive at the desired microporous structure with more or less improved security. For example, German Patent 1,110,607 proposes for the coagulation of polyether-based polyurethanes to expose hygroscopic polyurethane solutions (e.g. dimethylformamide serves as a solvent) to the action of an atmosphere containing water vapor, possibly in circulation, which has a relative humidity of 15 to 100 % at a temperature * of the dry thermometer from 10 to 38 ° C. As a result of the absorption of the water by the hygroscopic solvent, the polyurethane is precipitated to a greater or lesser extent from the surface, probably with a pre-formation of the microporous structure. When the pregelled films or coatings are placed in water, the hygroscopic solvent is completely removed from the film with coagulation. If the pre-gelation by exposure to the above-mentioned humid atmosphere is omitted, then in most cases transparent, non-permeable films or coarse-pored, inhomogeneous films are obtained.

In the German Offenlegungsschrift 1,444,163 a modified one is used Method indicated in which by adding smaller proportions of nonsolvents (e.g. water) to the polyurethane solution this is brought into a slightly cloudy, dispersion-like form, which - if necessary after heating - after the spreading in flat form directly (i.e. without pre-gelling

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in a humid atmosphere ^ in nonsolvents such as water can be coagulated.

In the German Offenlegungsschrift 1,444,165 another Method indicated, according to which one without yorgelation by direct coagulation in a mixture of nonsolvents and solvents (e.g. dimethylformamide / HgO 10:90 to 95: 5) to receive microporous films.

The procedure according to DOS 1,444,165 requires extended coagulation times, especially for baths with a lot of solvents, because the polyurethane only coagulates slowly. So the capacity of a given production facility becomes strong degraded. In addition, according to this method, microporous structures can only be made with little certainty and apparently only from certain polyurethane compositions.

When working according to DOS 1,444,163 it is difficult to find the right one Amount of nonsolvent to be taken for the preparation of the colloidal dispersions. The process uses raw materials in an unstable state; because the properties of the dispersion change over time and the dependency of temperature and humidity, with the elastomer dispersion in a pasty, no longer smoothly deformable state pass over.

The working method according to DAS 1,110,607 requires an atmosphere with precisely conditioned humidity and a long exposure time in this humid atmosphere. The results are, however, hardly reproducible. Apparently only polyether urethanes can do this are processed. Here, too, there is a relatively low productivity with a low level of security and range of applications achieved.

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According to the proposal of the German Offenlegungsschrift 1.803-021, a dry or moist gas stream acts at a certain flow rate on a surface coated layer of a polyurethane solution until a dense, gelled layer is formed on the surface of the solution due to moisture or evaporation of the solvent . It is then coagulated in water, for example. As will be explained in detail, it is appropriate and desirable that the temperature not-preferably not exceed 5O ⁰ C over 30 ° C.

In the German Auslegeschrift 1,238,206 it is stated that a direct coagulation of elastomers then leads to microporous Structures result when one is in baths which are heated in the vicinity of the boiling point of the bath liquid, e.g. in hot water of 95 ° C, coagulated.

Furthermore, German patent 1,270,276 teaches the polyurethane solutions to be coagulated 10 to 30 % By weight of a quaternary ammonium nitrogen atom containing cationic polyurethane dispersion, up to 7 wt .- # water and possibly up to 2.5 wt .- # anionic, synthetic Add tannins. According to this method, after treating the painted polyurethane solutions with moist Air and subsequent coagulation in water or aqueous solvent mixtures, water vapor permeable polyurethane top layers can be produced much more safely than in the previously described processes. When pretreating with Moist air, however, residence times are necessary in this procedure

a) when adding commercially available tanning agents to the coagulable polyurethane solution using 10 to 30 Wt .- # of cationic polyurethane dispersion not below 10 mins,

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b) in the aftertreatment of the coagulated polyurethane top layers in aqueous neutralized tanning solutions not less than 20 minutes and

c) not be less than 30 minutes without the use of tanning agent.

The invention relates to a process for preparing microporous sheet materials from solutions of polyurethanes in polar organic solvents, which is characterized in that a layer of the polyurethane solution, water vapor can flow up to 190 ⁰ C at a temperature of 101 ° until the content of the layer of organic Solvent has fallen to less than 50 wt .- # and the layer has changed into a solid, mechanically stable, optionally removable, microporous sheet-like structure.

In general, the water vapor is allowed to flow for about 0.1 to 30 minutes over a layer of the polyurethane solution which is located on a support. The solvent is evaporated from the layer and carried away with the flowing water vapor. At the same time, the layer of polyurethane solution absorbs water from the water vapor during this treatment. This process is expediently continued until the polyurethane solution has been removed from the solvent to form a solid sheet which can be detached from the base without mechanical damage. In general, this is the case when the resulting layer contains less than 70 wt. #, Better less than 50 wt. #, Preferably less than 40 wt not more than half, preferably not more than one third, of the solvent.

Compared to known processes for the production of microporous planar structures by coagulating polymer solutions in liquid baths, this process has considerable advantages, which are particularly important for technical implementation.

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1. The state of solution in which the polyurethane is located is not critical. Accordingly, real solutions, colloidal solutions, colloidal dispersions, dispersions, gelled solutions and even partially precipitated solutions of the polyurethanes can be used. All of these gradually different "solution states" are solutions within the meaning of the present invention. Other additives such as nonsolvents and other polymers (polyvinyl chloride, polyamides) or fillers such as silicas or salts do not interfere.

It thus becomes that required in many known processes Step of forming colloidal solutions or dispersions Avoided by careful addition of nonsolvents.

2. The process delivers in a single process step A microporous sheet-like structure from a polyurethane solution. Only very short treatment times are required for this, coagulation baths are avoided. This not only eliminates the laborious washing out of the flat structures, but also the handling and processing of the large amounts of liquid that occur in coagulation baths. When working with coagulation baths there are also other technical difficulties, e.g. so-called wave structures are formed when it is introduced the polyurethane solution in the coagulation bath. Furthermore, solid substances precipitate during coagulation and are in the coagulation bath enrich. These substances can get onto the not yet fully solidified polyurethane surface and this contaminate. These difficulties also disappear.

3. The new process can be applied to a large number of polyurethanes even if these cannot be processed into microporous films by the known processes.

4. The microporous planar structures are obtained practically free of solvents and also contain only a little water. they are practically dry, especially when using steam at a higher temperature.

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5. The fabrics are very smooth and homogeneous Surface without "orange peel effect" or other defects.

6. The microporosity (water vapor permeability) can be influenced to a certain extent by the process variables (temperature, amount of steam, flow rate, solution layer thickness, residence time). The water vapor permeability is usually between Z to about 25 mg / h / cm. However, the method preferably provides water vapor permeability

values (Wdd) between 6 and 18 mg / h / cm, especially between

8 and 15 mg / h / cm.

7. The products of the process according to the invention have particularly high strength. In the technical continuous process of the present invention, both thicker and thinner films can be produced than according to

the methods of the prior art was possible.

In the known processes for producing microporous sheet-like structures by coagulation, it is a cautious one Exposure of the polyurethane solution to a damp atmosphere is prescribed, then the solvent is washed out and only then heated to dryness.

It has hitherto been assumed that a microporous film structure formed in humid air when dried at a high temperature Temperature in the presence of the solvent (mostly dimethylformamide) and water collapses again because the lower boiling water first evaporates during drying and the Solvent, before it is removed itself, the precipitated polyurethane should soften and dissolve again, so that ultimately a non-porous material when the solvent evaporates remains (see OS 1,444,164, column 4 and OS 1,419,147, Column 5/6).

Contrary to this assumption, the effect according to the invention of superheated steam at temperatures of

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101 to 190 ⁰ C provides a particularly rapid and reliably reproducible conversion of the polyurethane solution into a microporous polyurethane without the microporous structure collapsing.

In the method according to the invention, the polyurethane solution can be converted into microporous layers by the action of superheated steam at temperatures of 101 ° to 190 ° C. smoothly and in a short time if the steam is allowed to flow over the layer of the polyurethane solution and for a constant renewal of the steam atmosphere over the layer of polyurethane solution. It is preferred to maintain such conditions that the vapor mixture above the solution does not contain more than 10 mol% of solvent. The solvent is continuously removed in this way, while water vapor is always present.

Carrying EADERSHIP oF method ₁

First, the polyurethane solution is spread in thin layers on substrates such as glass, metal, paper, plastic or rubber with known application devices (slot die, doctor blade devices, roller application devices). The layer thickness of the solution depends on the desired thickness of the microporous surface structure, since approximately h in microporous state, depending on the degree of porosity .The density of the microporous layers between 0 ₉ and the density of the nonporous, solid polymer (to ca _o 1 ' 3) fluctuates, the desired casting thickness of the solution must be adapted to both the concentration of the casting solution and the microporosity. The concentration of the casting solution may vary within wide limits, for example from 5 to 50 ^% _t but is generally between 10 and 40%, preferably between 20 and 35 G © w "- $ £" -The cast thickness of the solutions range from about 0 , 05 Ms 2 nag are generally between 0.2 and 1.5 mm, preferably ₉ O 4 Tbis 1.5 m ** a.

The Poiyurethanlösungen can at temperatures at which they remain pourable, z, B, are applied at 10 to 150 ⁰ C.

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Advantageously, pouring the solutions at about 20 ° to about 6O ⁰ C in degassed form in order to avoid a formation of coarse gas bubbles. The casting bases can be preheated to temperatures up to the maximum of the subsequent steam treatment temperature. Usually one works at 50 ° to 100 ° C.

The steam treatment can for example take place in a "steam room", i.e. a thermally insulated vessel into which overheated water vapor over its entire length through a hole with many holes provided pipe is continuously introduced and the solvent-containing vapor is sucked off or condensed again.

The necessary amount of water vapor depends, among other things, on the thermal insulation of the vapor space, the volume of the Vapor space in relation to the amount of the highly polar solvent introduced by the polyurethane solution and the flow rate of fumes. The amounts of steam required in each case therefore depend, among other things, on the devices used and can easily be determined in preliminary experiments. Experience has shown that this is about 2 to 20 times (preferably 3 to 15 times) the weight of superheated steam in Relation to the given polyurethane solution required.

A particularly suitable polyurethane solvent is dimethylformamide. When used, for example, from about 15 minutes of steam exposure at 110 ° C. in an amount of less than 1 g per minute per g of polyurethane solution, a sufficiently strong film is obtained which contains only small amounts of dimethylformamide. (see figure 3). This film turns out to be microporous after drying. Longer exposure to steam improves microporosity. If the temperature of the steam is increased to 180 ^° C. under otherwise identical conditions, a smooth, completely microporous, practically dimethylformamide-free, almost dry film is obtained after about 8 minutes.

The upper limit of the steam temperature depends, among other things, on the melting or softening or decomposition point of the corresponding polyurethane elastomers and on the boiling point.

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point of the "solvent". In general, the temperature in the vapor space should not exceed about 190 ° C., although in principle, if the polyurethanes are sufficiently stable, the temperatures can be chosen to be even higher. As a rule, however, the maximum steam temperature should remain at least 20 ^° C. below the melting / softening point of the polyurethane. The temperature of the superheated steam is preferably chosen between 101 ° and 150 ⁰ C, particularly 101 ° to 120 ° C.

The exposure time of the (superheated) steam depends, among other things, on the layer thickness of the solution and the amount of steam used and on the temperature in the vapor space, and will generally be shorter, the higher the temperature, the higher the amount of steam used, the higher the flow velocity of the steam mixture and the thinner the layer thickness. Since the equipment conditions (e.g. thermal insulation) are also included, an absolute time limit is difficult, but the exposure time should be between about 1 and 30 minutes and can be determined by simple preliminary tests. Preferably the exposure time to the steam is around 3 to minutes. In the case of a continuous working method, exposure times are usually sufficient up to 15 minutes, e.g. 3 to 8 minutes.

As solvents for the polyurethanes, dimethylformamide and dimethylaeetamide are preferred, since they can be evaporated sufficiently quickly below the specified temperature limits. Other solvents such as dimethyl sulfoxide or N-methylpyrrolidone can only be removed with difficulty at the upper temperature limits and with prolonged exposure due to their higher boiling points and are therefore only of limited use. The use of iron dimethylformamide is particularly preferred.

Used for the technical production of microporous films one preferably continuous © procedures, wherein one

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Pour the solution in the desired width, layer thickness and temperature onto continuously moving substrates, if necessary passes a certain distance through air, leads through the steam treatment room and - if necessary after passing through a post-treatment stage - dries and winds up. Man the solution can be applied directly to a steel belt (preferably with a polished or teflonized surface) or a plastic belt, for example pour it on and guide it through the steam space at a defined belt speed.

The dwell time in the flowing superheated steam depends on the selected working conditions and the size of the apparatus, but is in the order of magnitude already indicated above, at about 1 to 20 minutes, preferably 3 to 8 minutes. The speed of the belt can be varied within wide limits. In the case of very short steam treatment rooms, that is to say only about 2 m long steam treatment rooms, it can be between 0.1 and 2.0 m / min. If the steam treatment section is lengthened to, for example, 10 m, the speed of the belt is between about 0.5 and 10 m / min, preferably about 0.5 to 3 _f 33 m / min or 1.25 to 3.33 m / min adjustable. If the belt is extended further, the speed can be increased accordingly; it is also advantageous to divide the vapor space and pretreat initially at lower temperatures (eg, 101 to 120 ⁰ C) and then to increase the steam temperature (eg 120 to 180 ° C).

Particularly preferred is a continuous process in which there is a regulated temperature difference between the tape base carrying the polyurethane solution layer and the flowing hot steam acting from above. To keeping the tape backing by appropriate heating by any methods, when introduced into the vapor space at temperatures of about 55 ° to 95 ⁰ C, preferably from 70 ° to 85 ° C and the steam temperature in the space over the solution at the same time above 101 ⁰ C. , preferably between 101 ° and 125 ° C. Through this

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ASL

Measure is a-rapid condensation of water on. the cold polyurethane layer avoided with the formation of liquid layers. Such a liquid layer would, for example, due to rapid precipitation, result in a less permeable surface skin. lead, which "greatly impedes the active mass transfer. By maintaining the specified temperature difference, however, when the polyurethane solution layer is introduced into the vapor zone, a barely discernible liquid layer forms on the solution and the vapor exchange takes place in a continuous transition. The gel point of the solution becomes apparent under these conditions reached only at relatively high temperatures in a relatively concentrated solution.

It is only necessary to maintain the temperature gradient at the beginning of the steam treatment, eg on the first third or half of the steam treatment zone; already somewhat solidified polyurethane solution may be in the further course at higher steam temperatures, for example, be up to 150 ⁰ C, treated 110 ° in order to remove the solvent largely.

In other cases it is also possible to remove the microporous layer from the casting belt after about 1 to 8 minutes (depending on steam conditions, etc.) as an already solidified, removable film and to remove any solvent residues in a separate post-treatment stage. As a result of the shortened dwell time, the belt speed can then be increased even further, for example to 5 to 10 m / min. The separate post-treatment stage can in turn consist of an endless belt as a support, but the foils can also be guided through the post-treatment room (drying cabinet) in loops through a system of pulleys attached above or below. This drying cabinet can also be charged with steam in order to prevent the microporous structure from collapsing when the microporous films are dried. In principle, however, it is also possible to pull the already solidified film through liquid aftertreatment baths. These can be water or water / solvent mixtures of any temperature (up to about 1OQ ⁰ C).

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The residual solvent is washed out in the washing baths, according to the usual procedure in coagulation processes. Such a possible combination of procedures does not, however, correspond to the new procedural concept, by means of an essentially single-stage process that is as uniform as possible Process step to get to the end product.

However, it may be desirable to make a change by means of a corresponding liquid aftertreatment stage of the substrate. For example, the elastomer film can be dyed with dyes while it is still swollen. Practically all common dyes are suitable for this, including dyeing in solvents possible.

Another possibility of post-treatment concerns the action of crosslinking agents, for example solutions of formaldehyde and formaldehyde derivatives, for example bis-hydroxymethylurea, melamine methylol ether, in water or organic solvents, which have a crosslinking effect in the subsequent drying process. Furthermore, solutions of polyamines, for example ethylenediamine, undecamethylenediamine or diethylenetriamine, in water or organic solvents can be brought to act on polyurethane films which contain uretdione groups in the molecule and lead to immediate crosslinking.

A preferred procedure uses a combination of the following steps

a) exposure to (superheated) steam until the film solidifies and the film is lifted off the belt,

b) Pressing the film between rollers for removal if possible large amounts of remaining solvent / non-solvent residues, if necessary

c) repeated steam treatment, e.g. with simultaneous suction of the steam on a vacuum filter drum,

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2125308

d) post-treatment such as dyeing, crosslinking, soaking with preparations and stabilizers,

e) if necessary, drying, e.g. in hot air ovens, if necessary in the presence of water vapor.

An example of a continuously operating hot steam treatment line is shown in FIG. 1. The continuously moving casting belt (2) (eg rotating steel belt) runs through a well heat-insulated, optionally heated, cylindrical tube (1) several meters in length. The polyurethane solution is poured on in air outside the vapor space with metering by means of a gear pump through an appropriately wide slot pourer (3) an optionally controlled moisture content of about 40 to 100 %) and then enters the steam treatment room through a small slit (4). In this cylindrical tube (1) a number of hot steam nozzles (5) are installed, which cause a hot steam flow over the polyurethane solution layer. The number, type, position and delivery rate of the hot steam nozzles are adapted to the respective requirements. A heating device (15) is attached to heat the tape base before it enters the steam room. This can use hot air, hot water or a heated metal plate as a heat exchanger, for example. If necessary, the cylindrical tube is subdivided one or more times (6) in order to be able to set the desired steam quantities and temperatures via separate hot steam line nozzles. The superheated steam nozzles are to be charged with the desired amount and temperature of superheated steam through control valves (7) and steam superheater * (8). The microporous film that is formed (or, if substrates are coated - the coated substrate) exits the steam chamber through a slot (9) , B _c dye baths post-treatment baths for crosslinking, preparation

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tion, stabilization), optionally squeezed off (14) and then dried (11). To prevent Steam condensations are preferably the pipe (1), as well as the slots (4), possibly (9) (e.g. electrically) heated (^ 100 ° C).

The heating to prevent steam condensation is special Recommended at the entry part of the apparatus, as here the solution layer is still soft and sensitive to inhomogeneous Water exposure is. As soon as the solidification has occurred due to the action of superheated steam, it is in the further apparatus possible exposure to water without affecting the quality of the microporous film.

The removal of the steam or the steam-solvent mixture takes place by suction through pipes (12) of the appropriate cross-section. During the technical implementation the steam is fed to a condensation plant in which at least the majority of dimethylformamide is liquefied will. However, you can also mix the hot steam directly Feed in the distillation columns. The bottom of the cylindrical superheated steam treatment section is expediently also provided with a drain device (13) to Discharge any condensed steam / solvent mixture to be able to.

The results with a continuous superheated steam treatment apparatus as described above are experimental Part reproduced.

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Manufacture of the polyurethane elastomers

For the production of polyurethane solutions for the process according to the invention, a large number of polyurethane elastomers accessible by the most varied of methods are suitable, but all of which contain the typical urethane grouping (see Ulimann, Enzyklopadie der technischen Chemie, 4th edition, volume 14, pp. 338 to 363) , but their tendency to form the microporous structure can vary. It can be, for example, polyurethanes in the narrower sense, which are accessible from higher molecular weight polyhydroxy compounds, dialcohols and diisocyanates by single or multi-stage processes (via NCO pre-adducts). For example, polyesters or polyethers can be reacted with an excess of diisocyanates to form NCO pre-adducts and these can then be reacted with diol compounds such as 1,4-butanediol, N-methyl-diethanolamine, hydroquinone-bis (hydroxyethyl ether), terephthalic acid-bis-hydroxyethyl ester in equivalents or are implemented slightly less than the amount, it being possible to work both in the melt and in solvents. However, the above components can also be converted into elastomers in a grading process and then, for example, dissolved in highly polar solvents.

Particularly suitable, however, are polyurethane ^{hanas as described as "components a w"} in German patent 1,270,276. For their preparation, higher molecular weight, essentially linear polyhydroxy compounds with terminal hydroxyl groups with a molecular weight between 400 and 5000 and optionally other low molecular weight dialcohols, amine alcohols or diamines are used an excess of diisocyanates initially to form a pre-adduct with terminal isocyanate groups and this subsequently with water

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or with bifunctional compounds which contain at least one of their isocyanate-reactive hydrogen atoms bonded to nitrogen atoms. Because of the material compared with diols higher reactivity and reaction velocity of these chain lengthening agents, this reaction is preferably in highly polar, water-soluble solvents, carried out with a boiling point above 100 ⁰ C.

The production of such polyurethane ureas and their solutions is described, for example, in German patents 888,766, 1,123,467, 1,150,517, 1,154,937, the German Auslegeschriften 1,161,007, 1,183,196, 1,186,618, the Belgian Patents 649,619, 646,637, 658,363, 664,346, 666,208, French patents 1,380,082, 1,371,391, 1,383,077 and U.S. Patents 2,929,803, 2,929,804, 3,040,003.

Higher molecular weight, essentially linear polyhydroxyl compounds with terminal hydroxyl groups, which are suitable for the production of elastomeric polyurethanes, are, for example, polyesters, polyester amides, polyethers, polyacetals, polycarbonates or poly-N-alkyl urethanes or mixtures thereof, including those with ester, ether and amide -, urethane, N-Alkylurethangruppen having molecular weights of 400-5000 and melting points of preferably + 60 ° to -50 ° C, conveniently (at 45 ⁰ C. polyhydroxyl compounds having higher melting points can to or at temperatures <
effect products ^

temperatures around or O ⁰ C an excessive hardening of the finished

Particular mention should be made of polyesters made from adipic acid and dialcohols or mixtures of dialcohols, e.g. ethylene glycol, propylene glycol, 1,4-butanediol, 2,2-dimethylpropanediol-1,3 »hexanediol-1,6_or Bishydroxymethylcyclohexane. Preference is given to diols or mixtures of diols having five or more carbon atoms the good hydrolysis resistance of the products made from it

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Polyester. Polyesters obtained by condensation of caprolacetone and diols or 1,6-hexanediol or amines with a narrow molecular weight distribution are also suitable. Particularly good microporous films with excellent surface properties and good water vapor permeability are derived from mixed polyesters, which consist of 90 to 60% by weight Adipic acid and 10 to 40 wt% terephthalic acid and one Diol, preferably ethylene glycol, 1,4-butanediol, neopentyl glycol and / or 1,6-hexanediol have been produced. Further are preferably polyesters or mixed polyesters with molecular weights of about 400 to 1000.

Polyurethane ureas with excellent hydrolysis resistance can also be obtained from polyethers, preferably from polytetramethylene ether diols, which can optionally also be used as mixed polyethers.

Suitable diisocyanates, if appropriate in a mixture, are aliphatic, cycloaliphatic, araliphatic, aromatic diisocyanates or heterocyclic diisocyanates. Particular mention should be made of diisocyanates with a symmetrical structure, e.g. diphenylmethane-4,4'-diisocyanate, diphenyldimethylmethane-4,4'-diisocyanate, 2,2 ^f -6,6'-tetramethyldiphenylmethane diisocyanate, diphenyl-4,4'-diisocyanate, diphenyl ether 4,4 diisocyanate or its alkyl, alkoxyl or halogen-substituted derivatives, also toluylene-2,4- or -2,6-diisocyanates or their technical mixtures, diisopropylphenylene diisocyanate, m-xylylene diisocyanate, p- Xylylene diisocyanate or a, a, a ', a'-tetramethylp-xylylene diisocyanate or their other alkyl or halogen substitution products, dimeric toluene-2,4-diisocyanate, bis (3-m®thyl-4-isocyanatophenyl) urea or naphthylene 1,5-diisocyanate. Aliphatic diisocyanates such as hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1 ^ -Isocyanato -isocyanatomethy ^, 5,5-trime ^w thylcyelohexan or 2,2 ^ · -trimethylhexane-1, G diisocyanate, can

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and produce very little discoloration when exposed to light Products. Cycloaliphatic diisocyanates can be in the form of their pure stereoisomers or in any desired mixing ratios of the stereoisomers can be used.

Diphenylmethane A ^ V diisocyanate, the isomeric Tolylene diisocyanate, p-phenylene diisocyanate and optionally partially - hexamethylene diisocyanate or dicyclohexylmethane-4,4'-diisocyanate used.

The higher molecular weight polyhydroxyl compounds are mixed with the diisocyanates in about a molar ratio of 1: 1.25 to 1: 4.0, optionally in several stages in the melt or in solvents inert to isocyanates, such as tetrahydrofuran, dioxane or chlorobenzene or dimethylformamide, at temperatures of about 20 to 130 ⁰ C, preferably 40 to 100 ⁰ C implemented.

Such reaction times are observed that an essentially linear pre-adduct with terminal NCO groups is obtained, that in the reaction with approximately equivalent amounts of bifunctional chain extenders a substantially linear, In polar solvents soluble elastomeric polyurethane or a polyurethane urea results.

Together with higher molecular weight polyhydroxy compounds, low molecular weight diols (molecular weight preferably below 250), e.g. ethylene glycol, 1,4-butanediol, bis-N, N- (ß-hydroxyethyl) -diethylamine, bis-N, N- (ß-hydroxypropyl) - Diethylamine, N, N ^f -bis-hydroxyethylpiperazine or hydroquinone-bis- (ß-hydroxyethyl ether) can also be used. The amount of low molecular weight diols can, for example, be such that 0.1 to 3 mol OH groups of the low molecular weight diol are present per mole of OH groups of the higher molecular weight polyhydroxyl compound. Diols with tertiary nitrogen increase the colorability, improve the lightfastness and generate attack

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provide for further follow-up treatments, e.g. networking with. strongly alkylating compounds.

The NCO group content of the pre-adducts (calculated on the solvent-free pre-adduct) is of decisive importance for the properties of the polyurethane ureas obtained therefrom. It must be at least 0.75% by weight and should preferably be between about 1.0 and about 7.6% by weight, particularly between about 1.5 and 5.5% by weight, so that the polyurethane ureas are sufficiently high Have melting points, tensile strengths, elongations at break and stress values. In the case of the chain lengthening reaction with water, the NCO content is preferably higher, for example between 3-5 and 7.6% by weight , since some of the NCO groups are first saponified to form amino groups.

The chain extenders should have a molecular weight from 18 to about 500, preferably from 32 to 350, and can optionally be used in any desired mixing ratios or in stepwise reactions. In addition to water, for example, ethylenediamine, 1,2- or 1,3-propylenediamine, 1,4-tetramethylenediamine, 1,6-hexamethylenediamine, 2,2 ^ -trimethylhexanediamine-1,6, 1-methylcyclohexane-2,4- diamine, 4,4'-diaminodicyclohexylme than, bis (r ^ -aminopropyl) -methylamine, N, N-bis - ^ - aiainopropyl) -piperazine, araliphatic diamines such as 1,5-tetrahydronaphthalene or aromatic diprimary amines such as 4,4 -Diaminodiphenylmethane, 4 ₉ 4 ^a -Diaminodiphenyiäther, 1-Me thyl-2,4-diaminobenzene or araliphatic diprimeric diamines, such as m-xylylenediamine, p-xylylenediamine, a, a, a ', a ^f -Tetramethyl-pxylylenediaain or 1, 3-bis- (ß-aminoisopropyl) -benzene, also diamines containing sulfonic acid groups, such as 4j4 ^f -diaminostilbene-2,2'-disulfonic acid or 4.4 ^l -diaminodiphenylethane-2.2 ^l -disulfonic acid, hexamethylenediamine-1,6-N -teutylsulphonic acid, 1,6-hexamethyl @ n-3 ° -sulphonic acid or its alkali salts, hydrazide compounds such as carbodihydrazide, adipic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, pimel acidic

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hydrazide, hydracrylic acid dihydrazide, terephthalic acid dihydrazide, Isophthalic acid dihydrazide, ß-semicarbazido-ethane-carbazine ester, ß-aminoethyl-semicarbazide, ß-semicarbazido-propionic acid hydrazide, 4-semicarbazido-benzoic acid hydrazide or also hydrazine hydrate, or Ν, Ν'-diaminopiperazine. These chain extenders can be used individually, in a mixture or together with water. It can also (expediently less than 30 mol%) secondary diamines, preferably with a symmetrical structure, such as piperazine or 2,5-dimethylpiperazine, can be used. The list of chain extenders is naturally incomplete and does not represent a limitation.

If chain extension mixtures are used, the solubility of the polyurethane ureas and the The melting point of the elastomers decreases. Ethylenediamine, m-xylylenediamine, Hydrazine, carbodihydrazide, aliphatic dicarboxylic acid hydrazides, such as glutaric acid dihydrazide, and water are also used. Will If these chain extenders are used together with others, their amount should be at least 50 MoL-96, preferably more than 80 mol% of the total amount.

The implementation of the NCO pre-adducts with the chain extenders preferably takes place in highly polar, water-soluble solvents boiling above 130 ° C. Mention should be made of amide or solvents containing sulfoxide groups with the ability to form strong hydrogen bonds, for example Dimethylformamide, N-methylpyrrolidone, diethylformamide, Dimethylacetamide, formylmorpholine, hexamethylphosphoramide, dimethylacetamide, tetramethylurea or their mixtures. Technically preferred solvents are dimethylformamide and also dimethylacetamide.

These "solvents" can also be "nonsolvents" or

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"Nonsolvent" to be admixed with l . This is understood to mean liquids which do not dissolve the polyurethanes (and preferably also swell only slightly) or which are inert to polyurethanes. The preferred nonsolvent is water. But there are also, for example, hydrocarbons such as benzene, chlorobenzene, aliphatic alcohols such as methanol, ethanol, ethers such as dioxane, tetrahydrofuran, ketones such as butanone-2 and esters such as ethyl acetate.

Other suitable polyurethane elastomers are also those produced by the reaction of bis-chlorocarbonic acid esters and diamines or from bis-carboxylic acid chlorides and diamines (where preferably one of the components is one higher molecular weight compound with a molecular weight of about 400 to 5000). Reaction products may be mentioned by way of example higher molecular weight bis-chloroformic acid ester of polyhydroxyl compounds with diamines and reaction products of higher molecular weight compounds with amino end groups (produced e.g. made of polyhydroxyl compounds, diisocyanates and chain extenders with noticeably excess amounts of NHp-endgroup-containing Chain extenders) and bis-acid chlorides or bischloroformic acid esters. Such connections are e.g. in US * patents 2,929,801, 2,929,802, 2,962,470, 2,957,852. Segmented ones are also suitable Polyester or polyether elastomers, such as those described, for example, in French patents 1,354,553 and 1,359,090 and in Belgian patent 574,385.

In addition, additives can be added to control the coagulation behavior of the polyurethane solutions, e.g. polyvinyl chloride and its mixed polymers, polyacrylonitrile and its mixed polymers, commercially available anionic tanning agents, carboxymethyl cellulose, or polyalkyl (meth) acrylates. These polymers can up to about 50% by weight of the polyurethanes may be included. Emulsifiers

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optical brighteners, antioxidants, special light protection agents like Ν, Ν-dialkylhydrazides, crosslinking substances like Paraformaldehyde, melamine hexamethylolether or other formaldehyde derivatives, Polyisocyanates, quaternizing agents or polyaziridiride derivatives and dyes, expediently insoluble pigments can be added to the solution in the usual form.

The formation of microporosity can also be considerably increased by adding cationic polyurethane dispersions to the polyurethane solution make it easier, but it does so with a deterioration in mechanical strength and light and aging resistance the microporous film in purchase. The amount of cationic polyurethane dispersions should generally not be 35% by weight exceed. It is preferred to take from 0.5 to 20% by weight and especially advantageously 0.5 to 10% by weight. Relate percentages each on solids in the polyurethane solution and the dispersion.

Another influence on the transferability of the polyurethane solutions into microporous layers results from the addition of small amounts of nonsolvents, preferably water, to the polyurethane solutions. The highest possible amount of non-solvent is reached when the polyurethane begins to precipitate. Non-solvents (water) can also be introduced into the system by using the cationic polyurethane dispersion. In this case, too, you can also add nonsolvents. In general, the nonsolvent is not added in pure form, but rather in a mixture with solvent, for example a dimethylformamide / water mixture is used. The total nonsolvent content of the coagulable mixture should generally not exceed 9%. The higher the temperature of the solution, the more water is generally absorbed by the solution.

There is a further influence on the coagulability

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through a thermal pretreatment of the polyurethane mixtures, which may contain non-solvents, for example brief heating z, B. up to 2 hours at 70 to 100 ° C or 2 to 20 hours at 40 to 70 C or by letting such polyurethane mixtures stand for a long time at room temperature, especially if they are Contains lower proportions of non-solvents. The ready-to-use polyurethane mixtures can have viscosities between 1 and 5000 Poise, preferably 10 to 1000 poise.

The solids content of the ready-to-use polyurethane mixtures should be between 5 and 40% by weight, preferably between 10 and 30 % by weight .

The particular advantage of the process, however, is that the elastomer solutions can also be produced without the addition of nonsolvents or coagulation auxiliaries can be used in the same way in a broad chemical variation.

On solid films produced from these polyurethane elastomer solutions by drying the solutions, mechanical Strength values or elastic properties, e.g. after cutting the film into strips or threads, can be determined. Solid foils Polyurethanes that are particularly suitable for the process according to the invention have the following properties:

1. Melting point on the Kofler band at least 180 ⁰ C, preferably above 200 ° C,

2. Tear strength of at least 200 kg / cm, preferably 300 to 800 kg / cm ² ,

3. Elongation at break at least 200 %, preferably 400 to 800 96,

4. Tension forces during the first expansion to 20 %: at least 5.0 kg / cm, preferably 10 to 30 kg / cm; in the expansion

P P

to 100 %% at least 20 kg / cm, preferably 45 to 75 kg / cm, with the first extension to 300 %: at least 60 kg / cm, preferably 80 to 580 kg / cm ,

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5. Molecular weight corresponding to an intrinsic viscosity v> £ of at least 0.6, preferably 0.90 to 1.9

^{c =} concentration in g / 100 ml, C m _r = viscosity of a 1 wt .- # solution of the

Polyurethane in phosphoric acid trisdimethylamide at 25 ⁰ C)

6. Insolubility in slightly polar solvents such as tetrahydrofuran, dioxane or glycol monomethyl ether acetate: solubility in highly polar solvents such as dimethylformamide.

To convert the strength and module information from kg / cm The following relationship applies in g / dtex or mg / dtex:

χ = $. y. 10 ³

where χ is the measure of the tensile strength or the modulus in

Lt "3

kg / cm, y is the measure of the tensile strength or the modulus in

g / dtex, 5 is the measure of density in g / cnr.

If the tensile strength or modulus values y are expressed in mg / dtex, the relationship χ = $ applies. y, where χ and j> have the above meaning *

Solid polyurethane films generally have the following density: Polyester polyurethanes: = approx. 1.2 g / cm ⁵ Polyether polyurethanes: f = approx. 1.0 - 1.05 g / cm ⁵ The density of microporous films is generally between 0.3 and 1.0 g / cm ⁵ .

The mechanical strength values and elastic properties of the microporous fabrics are determined in the same way as the corresponding values for the solid film from the polyurethane elastomer components. Naturally, because of the microporous films, the lower they are, the higher

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is the water vapor permeability of the materials.

The determination of the water vapor permeability takes place according to the method of I UP 15, given in "Das Leder", 1961,

Pp. 86 - 88, which show the water vapor permeability in mg ~

hTcm

supplies (measurement at normal pressure and a relative humidity of 65 % at 20 ⁰ C) or according to a new method which allows much faster determinations and which supplies the so-called permeation coefficient as a measured value, which describes the water vapor permeability through a film of normalized thickness. The measurement or the evaluation of the measurement results is carried out as follows:

A circular film sample with a diameter of 2 cm is loaded with saturated water vapor from one side in an apparatus previously evacuated to 0.1 Torr. The permeiernde by the action of the saturated vapor pressure of 18.7 Torr at 21 ⁰ C water is frozen out in a cold trap and subsequently determined by thawing the cold trap and measure the autogenous vapor pressure in the known measurement volume. The permeation coefficient PK is obtained in g , which

h cm torr

rather the amount of water in grams that is obtained by a

Foil with an area of 1 cm and a thickness of 1 cm at a differential pressure of 1 Torr (dimension: g / h.cm.Torr). The numerical values of the PK value are given below with

Specified multiplied by 10. (For literature see: Lax d'Ans, Springer-Verlag, 1943, p. 1118). The determination of the tensile strength, elongation at break as well as the modules and other elasticity values on the microporous foils is carried out as described for the solid foils.

The strength values of the microporous films are naturally lower, the greater the water vapor permeability or the PK value is. Even with the same water

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Water vapor permeability depend on the respective strength properties still crucially on the quality and uniformity of the microporous structure, which by the applied Coagulation method is determined. A particular value of the process according to the invention is that it is uniform Microporous films with a good surface with increased strength compared to other processes, reduced thermoplasticity, improved abrasion properties at high permeabilities can be achieved, while at the same time the process can be shortened in terms of time and its single-stage implementation can be considerably simplified.

The "Heat Distortion Temperature" (HDT) of the polyurethane elastomers is determined according to a method described in Belgian patent specification 73 ^ ·, 194. One is burdened with it a film strip with 1.8 mg / dtex and observes its change in length when the temperature increases in air. With a quick one The polyurethane substance almost completely loses the change in length in the area of the heat disortion temperature Resistance to deformation (under the above load of 1.8 mg / dtex, corresponding to about 1.8 kg / cm). Since under the Process conditions not only dry heat, but simultaneously If steam acts, the HDT is even lower under steam conditions.

The strength factor (FF) of any microporous film represents the ratio of the tear strength of the film to the standard tear strength with the same permeation coefficient

(P ^ value): FF = tear strength of the film ^Λ standard tear strength with the same PK value

The standard tear strength is based on mikroporöse.Filme the substance polyurethane a) of the German laid-open specification 2,025,616 (practically the same as polyurethaneurea a / l of the German patent specification 1,270,276), the different P _R values by adding different amounts of water

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Solution, different "aging" of the solution and exposure to different Moisture levels and gelling temperatures have been set. The course of the curve: tensile strength (in g / dtex) against the logarithm of the PK value for this substance is shown as FF = 1 in FIG.

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Manufacturing instructions for the polyurethane elastomers Polyurethane 1)

300 parts of a polyester of adipic acid and ethylene glycol, molecular weight 665, are mixed with 387 parts of a solution of 190 parts of 4.4 ^f -diphenylmethane diisocyanate and 217 parts of anhydrous dimethylformamide, which has an isocyanate content of 15.6%, between 40 minutes 48 to 56 ⁰ C implemented. According to this, the isocyanate content of the solution (based on solid substance) is 4.5%.

570 parts of the above solution are in a solution of 19.95 parts of carbodihydrazide, which is previously dissolved in 39.9 parts of water, and 948 parts of dimethylformamide entered. A clear, homogeneous solution with a viscosity of 480 poise / 20 ° C. is obtained.

Polyurethane 2)

500 parts of a polyester of adipic acid and ethylene glycol having an average molecular weight of 1019 at 40 ⁰ C with 541 parts of a solution of 240 parts of 4,4-diphenylmethane diisocyanate ^I and 331 parts of dimethylformamide, which, after 30 minutes an isocyanate content of 13.8 % has reacted between 50 and 55 ° C for 30 minutes. According to this, the isocyanate content of the solution, based on the solid substance, is 4.66 %.

Elastomer solution 2a)

450 parts of the above isocyanate solution at 32 ⁰ C in a solution of 16,95 parts of carbodihydrazide which is previously dissolved in 33.85 parts of water and added to 776.5 parts of dimethylformamide. The clear, homogeneous solution has a viscosity of 218 poise / 20 ° C.

Elastomer solution 2b)

479 parts of the above isocyanate solution are added at 32 ^° C. to a solution of 16.95 parts of carbodihydrazide, which is previously dissolved in 33.85 parts of water, and 776.5 parts of dimethylformamide.

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carried. A homogeneous polyurethane solution is obtained with a. Viscosity of 486 poise / 20 ° C.

Polyurethane ^)

300 parts of a polyester of adipic acid and ethylene glycol, molecular weight 2000, are mixed with 234 parts of a solution of 90 parts of 4.4 ^l -diphenylmethane diisocyanate and 196 parts of anhydrous dimethylformamide, which has an isocyanate content of 10.51 % , for 5 hours 50 ° C implemented. According to this, the NCO content of the NCO pre-adduct (based on the solid substance) is 3.00 #.

288 parts of the NCO pre-adduct are dissolved at 35 ° C from 462 parts of dimethylformamide and 6.55 parts of carbodihydrazide, dissolved in 13.1 parts of water, entered. You get one colorless, homogeneous elastomer solution with a viscosity of 420 poise / 20 ° C.

Polyurethane 4)

900 parts of a polytetramethylene ether diol, molecular weight 1000 are mixed with 863 parts of a solution of 350 parts of 4,4'-diphenylmethane diisocyanate and 556 parts of anhydrous dimethylformamide, which after 30 minutes has a titratable isocyanate content of 12.9 % , 30 minutes at 45 to 50 ° C implemented. The isocyanate content of the solution, based on the solid substance, is 2.99 %

790 parts of the above isocyanate solution are converted into a solution of 10.7 parts of hydrazine hydrate and 1385 parts of dimethylformamide at about 30.degree registered. The colorless, homogeneous solution has a viscosity of 792 poise / 20 ° C.

Polyurethane 5)

300 parts of a polyester of adipic acid and 1,4-butanediol, molecular weight 520, are ^{mixed with 458 parts of a solution of 260 parts of 4.4 l} -diphenylmethane diisocyanate and 256 parts of what-

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ser-free dimethylformamide, which has a titratable isocyanate content of 17.0 % , reacted for 35 minutes between 28 and 53 ° C. The isoeyanate content of the solution is, based on the solid substance, 5.31 % »

680 parts of the above isocyanate solution are converted into a solution at 30.degree from 27.9 parts of carbodihydrazide, dissolved in 56 parts of water, and 1123 parts of dimethylformamide entered. The clear, homogeneous solution has a viscosity of 560 poise / 20 ° C.

Polyurethane 6)

100 parts of a polyester of adipic acid and ethylene glycol, molecular weight 2430, and 276 parts of a polyester of adipic acid, 1,4-butanediol, molecular weight 2235, are combined with 273 parts of a solution of 90 parts of 4,4'-diphenylmethane diisocyanate and 223 parts anhydrous dimethylformamide which has an isoeyanate content of 9.65, converted between 45 and 50 ° C for 60 minutes. According to this, the solution has an NCO content (based on solids) of 2.58 %.

580 parts of the above solution are added to a solution of 11.45 parts of carbodihydrazide and 960 parts of dimethylformamide at 70.degree registered. The clear, homogeneous elastomer solution has a viscosity of 540 poise / 20 ° C.

Polyurethane 7)

To 500 parts of a copolyester from adipic acid, hexanediol-1,6 and neopentyl glycol, molecular weight 1610 are at 40 ⁰ C 4,4'-diphenylmethane diisocyanate, 470 parts of a solution of 230 parts and 265 parts of anhydrous dimethylformamide, the titratable Isoeyanat- Has a content of 15.55 % , added. A solution of 27.9 parts of 1,4-butanediol and 66 parts of anhydrous dimethylformamide is then added dropwise over 30 minutes. After a further 90 minutes / 55 ° C, the isoeyanate content of the solution (based on solids) is 2.72 %.

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976 parts of the above solution are turned into a solution at 30 ° C 22.1 parts of carbodihydrazide, which is previously dissolved in 44.2 parts of water, and 1713 parts of dimethylformamide are stirred in. Man receives a clear, homogeneous elastomer solution of 470 poise / 20 ° C.

Polyurethane 8)

To 350 parts of a polyester of adipic acid and 1,4-butanediol, molecular weight 1050, 270 parts of diisocyanate are diphenylmethane at 50 ⁰ C a solution of 168 parts of 4.4 ^l and 149 parts of anhydrous dimethylformamide with an isocyanate content of 17, 8 % added. A solution of 12.1 parts of di- (2-hydroxyethyl ester) terephthalate, dissolved in 90 parts of anhydrous dimethylformamide, is then added dropwise over 30 minutes. After 3 hours the isocyanate content of the NCO pre-adduct (based on solids) is 3 »12 %,

580 parts of the above solution are dissolved at 32 ° C. in a solution of 13.85 parts of carbodihydrazide that was previously dissolved in 27.7 parts of water is dissolved, and entered 942 parts of dimethylformamide. The viscosity of the clear, homogeneous polyurethane solution is 610 poise / 20 ° C.

Polyurethane 9)

500 parts of a mixed polyester of adipic acid, 1,6-hexanediol and neopentyl glycol, molecular weight 895 »are added at 40 ° C. to 764 parts of a solution of 390 parts of 4s, 4'-diphenylmethane diisocyanate and 392 parts of anhydrous dimethylformamide with a titratable isocyanate content 16.8 % added. 50.3 parts of 1,4-butanediol in 11 parts of dimethylformamide are then added dropwise over the course of 30 minutes. After a reaction temperature of 55 ° C., the reaction solution has an isocyanate content of 3.47% (based on solid substance) after 190 minutes.

1000 parts of the above isocyanate solution are converted at 35 ^° C. into a solution of 27.9 parts of carbodihydrazide, previously in 55.8 parts

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Water is dissolved, and 1716 parts of dimethylformamide are entered. The viscosity of the solution is 760 poise / 20 ° C.

Polyurethane 10)

1200 parts of an adipic acid-ethylene glycol / 1,4-butanediol mixed polyester (molar ratio of the glycols 1: 1), molecular weight 2040, are mixed with 105.5 parts of 1,4-butanediol, 611 parts of diphenylmethane-4,4'-diisocyanate and 1034 parts Dimethylformamide is mixed, the temperature is kept at 50 to 55 ^° C. by cooling and, after the exothermic reaction has subsided, the temperature is kept at about 50 to 55 ^° C. by heating for a total of 42 minutes. The NCO pre-adduct solution is slightly cloudy and contains 2.70 % NCO (based on solids).

2688 parts of the above solution are in 7 minutes in a hot solution of 50.7 parts of carbodihydrazide in 4150 parts of dimethylformamide stirred in to form a clear, homogeneous elastomer solution with a viscosity of 270 poise / 20 ° C.

Polyurethane 11

300 parts of an adipic acid-ethylene glycol / 1,2-propylene glycol polyester (molar ratio of glycols 60:40) with a molecular weight of 683 are ^{heated to 60 °} C. for 40 minutes with 174.8 parts of diphenylmethane ^^ 'diisocyanate and 119 parts of dimethylformamide the NCO content of the NCO pre-adduct formed is 4.5 % (based on solids content).

In a 70 ° C solution of 16.5 parts of hot-carbodihydrazide in 928 parts of dimethylformamide, 430 parts of the NCO-Voradduktlösung described above are added to form a homogeneous, colorless elastomer solution having 242 poise arises / 20 ⁰ C.

Polyurethane 12)

300 parts of an adipic acid-ethylene glycol / I ^ -propanediol mixed polyester (Molar ratio of diols 6O: 4o), molecular weight 683, with 193 parts of diphenylmethane-4,4'-diisocyanate and

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124 parts dimethylform * -: mid. 37 minutes at 58 to 60 ⁰ C heated (based on solid content) until the NCO content in the formed NCO preadduct is 5.59%.

430 parts of this NCO pre-adduct solution are poured into a 70 ° C. hot tub Solution of 20.6 parts of carbodihydrazide in 940 parts of dimethylformamide entered with the formation of a homogeneous, colorless elastomer solution with a viscosity of 550 poise / 20 ° C.

Polyurethane 13)

500 parts of a polyester of adipic acid and 1,4-butaridiol with a molecular weight of 1500 are reacted with 158 parts of 4,4'-diphenylmethane diisocyanate and 282 parts of anhydrous dimethylformamide for 63 minutes at from 47 to 56.degree. According to this, the isocyanate content of the solution, based on the solid substance, is 3.58 %.

210 parts of the above isocyanate solution are added to a solution of 5.76 parts of carbodihydrazide and 355 parts of dimethylacetamide at about 70 ⁰ C. The clear, homogeneous solution has a viscosity of 485 poise / 20 ° C.

Polyurethane 14)

500 parts of a polyester made from adipic acid and ethylene glycol with an average molecular weight of 655 are mixed with 287 parts of 4,4'-diphenylmethane diisocyanate and 197 parts of dimethylformamide at 32 ° C. After a reaction time of 35 minutes at 42 to 57 ^° C., the isocyanate content of the solution is 3.02 %.

900 parts of the above isocyanate solution are at about 32 ° C in a Solution of 31.4 parts of carbodihydrazide, dissolved in 62 parts of hot water, and 1465 parts of dimethylformamide added. The 30 percent colorless, homogeneous polyurethane solution has a viscosity of 59 poise / 20 ° C. The nJl value of the elastomer is 0.85.

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Polyurethane 15)

100 parts of the 30 percent elastomer solution of the polyurethane 14) are homogenized with 16.7 parts of a 20 percent solution of a copolymer (of 95% polyacrylonitrile and 5 % methyl methacrylate) and dimethylformamide and 11.1 parts of dimethylformamide with vigorous stirring. The solution has a viscosity of approx. 50 poise.

Polyurethane 16)

100 parts of the 30 percent polyurethane solution 14) are with 30 parts of a 5 percent solution of polyvinyl chloride and dimethylformamide are homogenized at about 80 ° C. with thorough stirring.

Polyurethane 17)

170 parts of a mixed polyester of adipic acid, ethylene glycol and 1,4-butanediol with an average molecular weight of 2040 are ^{mixed with 39.6 parts of 4.4 l} -diphenylmethane diisocyanate and 52 parts of anhydrous dimethylformamide at 40 ° to 55 ° for 150 minutes C implemented until the solution has an isocyanate content of 2.45 % .

210 parts of the above are added to a solution of 5.66 parts of carbodihydrazide in 11.3 parts of water and 421 parts of dimethylformamide Stir in NCO pre-adduct solution at 35 ° C. After cooling down is the viscosity of the solution is 561 poise / 20 ° C.

Polyurethane 18)

4000 parts of a mixed polyester of adipic acid, ethylene glycol, 1,4-butanediol (diol ratio 1: 1), with an average molecular weight of 618, are mixed with 2430 parts of 4,4'-diphenylmethane diuocyanate and 1610 parts of anhydrous dimethylformamide between AO to 50 ° C implemented. After 120 minutes the isocyanate content of the solution is 3.33 %.

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7250 parts of the above isocyanate solution are then dissolved with 268.5 parts of carbodihydrazide in 537 parts of hot water and 14804 parts of dimethylformamide were added. A clear, homogeneous polyurethane solution is obtained which has a viscosity of 543 poise owns.

Table 1

Properties of solid films "gulation used polyurethanes

x)

the one for the microporous koa

Poly- Tear- Break- Module Module stay. HDT 'ni value residual elongation 300% 150% elongation (3rd recession

turning curve

300 %)

g / dtex %. mg / dtex % ⁰ C

0.73

0.38

0.73

0.75

0.57

0.76

0.62

0.70

0.75

0.73

0.73

0.92

0.74

0.81

0.53

0.72

0.68 0.75

481

492

557

658

625

356

660

500

559

394

523

461

492

537

437

238

585 489

458 200 292 210 117 660 118 265 271 579 423 578 502 268

115 459

14th

14th

16

18th

18th

20th

12th

16

28

16 14

66 40 41 18 30 140 30 25 21 89 56

20 36 29

14 57

190 187 184 164

161 171

176 178 189

180

179

1.15 0.91

0.93 1.00

1.07

1.03

The value of the viscosity-xji = ηί _in hexamethylphosphoramide is located above for polyurethanes within the limits of 0.7 to 1.5 "All melting points of the polyurethanes (measured on a Kofler bench) are above 220 ⁰ C.

x) Solutions dried in a drying cabinet at 100 C to form a solid film

xx) IiDT Heat Distortion Temperature, see Belgian measurement specification Patent 734,189, where 1.8 mg / dtex is selected as the preload and 2.1 / min as the heating rate.

xxx ) module at 200 %.

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Implementation examples

General, discontinuous procedure for production of microporous layers or foils

To produce microporous films, a polyurethane solution degassed by applying a vacuum is applied to a glass plate or a V ₂ A-BIeCh, area 15 x 25 cm, with a slider, a doctor blade or a slot nozzle, about 1 mm thick. The wet film is then immediately placed with the pad in the steam space, a semi-cylindrical hollow body made of about 2 cm thick elastic polyurethane foam, closed on all sides. The floor space of the interior is approx. 45 x 25 approx and the maximum height approx. 12 cm (volume approx. 11 l). The inner walls are completely coated with water-vapor-impermeable polyurethane film so that the foam walls do not soak up with water and cause drops. One of the two end faces can be opened by means of a lock so that the samples can be inserted into the interior. A silicone hose connected to the water vapor source is inserted into the interior from the other side. As a discharge opening for the steam, an open end of the hose is sufficient here; however, the end of the hose is preferably closed and instead a large number of bores or slots are made along the length of the hose in the steam space. Depending on the design of the outlet openings, different flow conditions for the water vapor can be achieved within the hollow body.

Water vapor of about 0.5 atm is first freed from the water condensed in the lines in a water separator. Then heated to the steam in a steam superheater (passing the steam through an externally temperatures on Tempe to about 600 ⁰ C erhitzfcös Aiuminiumrohi ') MUI leads him in the described reaction, "a space. Pi \> Mlmi »: o <,, ->, cd * t \ no awl-

'■ 2125 9 Π Β

see 5 and 50 1 of steam blown into the half cylinder. The superheated steam escapes at the same time through small openings that are made in the hollow body . The temperature of the steam space, which can be read on a thermometer inserted into the hollow body, is set with the temperature of the steam heated in the steam superheater. The "temperature of the superheated water vapor" is understood to mean the temperature read off by means of a thermometer in the vapor space of the half-cylinder described above the solution layer.

After the steam treatment, the films are peeled off from the underside and removed from the adhering liquid with filter paper freed. For the quantitative determination of the amount of liquid present in the film, the liquid can be extracted from this raw film quantified by removal in vacuo and condensation of the liquid in samples cooled with acetone / dry ice will. The distillates are then examined by gas chromatography, which provides information about the water / dimethylformamide ratio as a function of the time it receives within the film.

Example l)

The solution of the polyurethane 1) is applied by means of a doctor blade in a solution thickness of approx. 1 mm to glass plates and introduced into the steam space described above with the introduction of superheated steam, removed after the specified time and analyzed for the content ^ .n water and dimethylformamide or with regard to the achieved mechanical values and the permeability of the sample examined, the results of his series of tests, which determine the duration of the Hei i / lrkun ^ inifc the changes, in the PoIjuFeiiianXo i: ovr; lLert, v / erclon. in sfi ^ iirea 3 a iiii ?! 3 b: 7lfi * l9 ^ g

', Vl ■■ ", i- ^

From this it can be seen that within the first 5 minutes of the steam treatment at a temperature above 100 C (up to approx. 110 ° C) the dimethylformamide content of the solution film decreases by more than 70% of the original dimethylformamide content (point (A)) of Figures 3a and 3b). As the steam treatment progresses, the solvent content of the film decreases further and after 30 minutes is only about 2 % of the original dimethylformamide content (point (B) in FIGS. 3a and 3b). In contrast to the decrease in solvent, however, the action of water vapor causes a simultaneous absorption of water into the solution film or into the pores of the microporous film that is being formed. After 30 minutes, the water content within the film has increased to approx. 24 % (point (C) in FIGS. 3a and 3b) based on the original solution film. In FIG. 3b, the respective layer composition is shown after certain exposure times to water vapor with regard to the content of the film layer in the components elastomer, dimethylformamide and water vapor.

Due to the favorable water / dimethylformamide ratio You can dry them immediately in the foils (e.g. placing them in drying cabinets from 90 to 100 ° C with weak suction of the vapors emitted ^ You can also dry the foils by leaving them in the air, and you get there so to milky-white, microporous films with smooth film surfaces.

As can be seen from Table 2, a white film with good water vapor permeability is obtained after a steam treatment of 5 or 10 minutes between 101 and 110 ^° C. and after drying (Table 2, experiments 1/1 and 1/2 ). As the duration of the action of the superheated water vapor on the solution film progresses, the water vapor permeability of the dried, microporous film is still changed. After a steam treatment of 20 minutes (Table 2, 1/3) one obtains

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Films with good strength and a water vapor permeability of 3 »9 mg / h.cm, which increases to approx. 8.5 mg / h.cm when the steam exposure time is increased, which corresponds approximately to the optimal range of water vapor permeability. The strength factors are well above 1.00, corresponding to a strength that is 11 to 34 % higher with the same water vapor permeability as the comparison film.

Le A 13 612 - A0 -

? 0 9 8 5 1/1 1 2 7

Tabel

Steam treatment Tear breakage of the solution film stiffness extensible. (min) ( ⁰ C) fe / dtex) (<)

module

ioo 150 / R

(mg / dtex)

1/1 VYY 101-110 9.27 - - 10 1/2 10 101-110 0.33 352 85 .. 31 1/3 20th 101-110 0.26 343 110 29 1/4 25th 101-110 0.25 324 95 28 1/5 30th 101-110 305 93

stay PK.10 " ^a water expansion / g \ steam - (^) η.cm.Torr permeability (mg / h. ^{Cm 2} )

Festigice its factor

58 33 34 35

34000 15000 5800 10,000 21000

11.6 7.9 3.9 5.4 8.5

1.20 1.34 1.11 1.15

Cn CO O OO

O
to 2a / l Steam treatment
of the solution film
(min) ( ⁰ C) 101-105 Tear
sturdiness
(f / dfcex) Table 3 module
100
(mg / dt ex). PK.10 " ⁸
G
(h.cm.Torr) Steam
permeability
I mcr / Vi rtm ^ 1 ^w ι 2a / 2 5 101-105 0.22 61 15,000 ν "ig / π» cm y
8.5 2a / 5 10 101-105 0.18 strain
n>. 55 22,000 9.2 ro
—I 2a / 4 15th 115-120 0.18 458 55 11,000 5.8 - <
β 2a / 5 10 115-120 0.12 425 54 8,500 4.7 pc » 2a / 6 15th 150-155 0.12 416 54 11,000 5.8 _ !.
Yy 2a / T 5 150-155 0.15 291 51 12,000 5.4 Ma 2b / l 15th 101-110 0.16 275 57 12,000 5.4 2b / 2 15th 174-186 0.21 587 59 6,600 5.9 15th 0.25 589 70 7,400 B.6 414 415

Counterexample l)

The 26% solution is spread 1 mm thick onto a glass plate. The solution film is immediately ^{dried for 2 hours at 100 °} C. in a drying cabinet. This results in a homogeneous, dense, transparent film that is practically impermeable to water vapor.

Counterexample 2)

The 26% solution is applied 1 mm thick with a doctor blade to a glass plate and then stored ^{in air at 100 ° C. for 15 minutes.} Then the film is 2 hours in a drying oven at 100 ⁰ C dried. In this case too, a transparent film impermeable to water vapor is obtained.

Example 2)

The 26 <£ ige elastomer solution of the polyurethane 2a is applied 1 mm thick to glass plates. The solution films are then exposed to superheated steam in the cylindrical steam space described in Example 1), both the steam temperatures and the steam treatment times being varied. Following drying in a drying cabinet at 100 ^° C., microporous films with good surfaces are always obtained.

It can be seen from Table 3 that the water vapor permeability of the microporous film by steaming the solution film after just 5 minutes of steaming already gives good values. The somewhat low strength values of the 2a series can be explained by the relative low molecular weight of the polyurethane (viscosity lower al rs Ph). With increasing steam treatment temperature die RohfoJi "; in contrast to 2a / l immediately after the steam treatment Irnmor drier. The WaisserdampfdurchlaßRigkej t. the microporous «'!! FoI i on is dei> due to the rising temperature

y η? ia ü ι / η ? ί ^{/ i3} -

Water vapor hardly influenced (Table 3, 2a / l, 4.6). Example 2b)

The elastomer solution of the polyurethane 2b) is applied 1 mm thick to a V ₂ A-BIeCh with a slot nozzle and then exposed to superheated steam at different temperatures. At a steam temperature of 101 to HO ⁰ C, a microporous film with satisfactory water vapor permeability and good strength (2b / l) is obtained. However, you also get a homogeneous, microporous film with a very good surface quality, good water vapor permeability and excellent strength if the temperature of the water vapor is heated above the boiling point of the solvent, for example 174 to 186 ^° C. At this temperature, one obtains directly after the steam treatment dry, microporous films that practically do not have to be subjected to any further drying process (2b / 2).

Example 3)

The 26 # solution of the polyurethane 3 is brushed about 1 mm thick with a doctor blade onto a glass plate (15 × 30 cm) and ^{treated with steam between 101 and 110 °} C. for 15 minutes in the steam space described in Example 1). After drying for 30 minutes at 100 ^° C. in a drying cabinet, a smooth, microporous film with good water vapor permeability and high strength is obtained (Table 3).

Example 4)

The solution film of the polyurethane 4 painted on a glass plate is exposed to ^{superheated steam at 103 to HO 0 C for 15 minutes.} The microporous film then dried shows a smooth, uniform surface and has a good strength factor (Table 3 »4).

Example 5)

The 26 # elastomer solution of the polyurethane 5 is _{applied to a V 2} A sheet metal with a thickness of 1 mm through a slot nozzle. The solution film is then exposed to the steam ^{at 101 to 110 ° C. for 5 minutes.} After drying (30 minutes in the oven at 10O ⁰ C) is obtained a matt finish, equipped with an excellent surface micro-porous film with a good grip, which in a satisfactory water vapor permeability has a good strength (Table 3, 5/1). If the water vapor is allowed to act on the solution film for only 2 minutes longer, a film is obtained with significantly increased water vapor permeability (Table 3, 5/2). "

Example 6)

The 26 <£ ige solution of the polyurethane 6 is spread 1 mm thick on a glass plate. The solution film is then immediately treated in the vapor space described in Example 1 for 15 minutes between 101 to HO ⁰ C with superheated steam and then dried ^{in a drying cabinet at 100 0 C for 1 hour.} A matt, rubber-like, microporous film with very high water vapor permeability and at the same time a good strength factor is obtained (Table 3.6).

Example 7)

After the steam treatment (101 to 110 ° C./15 minutes) of the solution film of the polyurethane 7 applied to a glass plate, the film is ^{dried in a drying cabinet at HO 0} C for 30 minutes. The strength factor of the smooth, very strong microporous film is 1.15 (Table 3.7).

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Example 8)

The elastomer solution of the polyurethane 8 is a doctor blade 1 mm thick on a VGA sheet applied · Immediately thereafter the solution film from 102 to 110 ⁰ C is treated with superheated steam and then half an hour in the oven at 100 ⁰ C dried. A uniform, microporous film is obtained with excellent water vapor permeability and high strength (strength factor 1.5) (Tables 3, 8).

Example 9)

After the steam treatment at 101 to 11O ° C / 15 minutes, and the subsequent 30 minutes drying at 11O ⁰ C is obtained from the solution film a matte, solid, microporous film with a strength factor of 1.19 (Table 3/9).

Example 10-12

The elastomer solutions 10, respectively. 11 and 12 are applied to glass plates in a thickness of about 1 mm and a layer of solution exposed in the steam space described in Example 1 to the steam conditions as shown in Table 3 (including the Measurement results on the microporous films obtained) are listed.

example

The polyurethane solution 13 is brushed onto a glass plate in a layer thickness of approx. 1.3 mm and ^{exposed to flowing steam of 101 to HO 0} C for 15 minutes. An opaque white film is obtained which shows a microporous structure in cross section.

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Example 14

The solution of the polyurethane 14 is applied 0.85 mm thick to a glass plate and then exposed to superheated, flowing steam at 101 to 105 ^{° C. for 15 minutes.} A microporous film with a good surface is obtained.

Example 15

The solution of the polyurethane 15 is 1 mm thick on a glass plate applied and immediately exposed to superheated, flowing steam at about 105 ° C for 15 minutes. It becomes a microporous film good surface and very high water vapor permeability.

Example 16

The polyurethane solution 16 is exposed in a 1 mm thick layer in the usual form to the steam at 101 to 103 ^° C. for 15 minutes with the formation of an opaque white film.

Example 17

The polyurethane solution 17 is applied 1.5 mm thick to a glass plate. Then a dimethylformamide-soaked polyamide 6 fleece (18 g / m ² - 0.8 the polyamide fibers) is placed in the solution film. Then, as usual, superheated steam is allowed to act. A microporous film is obtained with a good, cohesive surface, good water vapor permeability and high strength.

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Example .18

100 parts of the above 30 percent polyurethane solution (14) with a 5 percent solution of a mixed polyamide (from 50 Teil.en caprolactam and 50 parts of a salt from adipic acid and 1,12 -dodecamethylenediamine) and dimethylformamide dissolved at about 80 ° C.

After venting, the solution is applied hot 1 mm thick on a glass plate and then exposed to ^{the superheated steam between 101 to 105 ° C. for 15 minutes.} After drying, the microporous film has a PK value of 450000, corresponding to a water vapor permeability of 11.7 mg / h.cm ² .

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209851/1127

NJ O CO OD

With steam treatment limg
game d. Solution films
min C

Tear resistance
g / dtex

Tabel

Elongation at break %

module

100

mg / dtex

PK.10 " ⁸ g / h. Cm. Torr

Permeable to water vapor-p speed mg / h.cm

3 15 101-110 0.30 557

4 15 103-110 0.25 608 5/1 5 101-110 0.28 254 5/2 7 101-110 0.23 240

6 15 101-110 0.21 539

7 15 101-110 0.29 438

8 15 102-110 0.32 449

9 15 101-110 0.31 273

10 15 101-110 0.30 466

11 5 101-101 not measured

12 15 101

13 15 101-110 0.72 618

14 15 101-105 0.22 322

15 15 105 0.14 260

17 15 101-112 0.41 718

18 15 101-105 not measured

19 11.5 101-105 0.29 361

140

130

27

42

46

110

45

79 83 67 47

82

5,300

12,700 4,100

18,000

110,000 4,500

26,000 3,100

41,000 3,600

110,000 61,000 6,000

535,000 74,000 43,000

250,000

4.2 6.4 2.5 7.6 17.8

3.1 10.4

2.2 11.4

2.5 15.9

4.2

> 25

12.9

11.7

20.1

Strength factor

1.21 1.09 1.11 1.04 1.16 1.15 1.50 1.19 1.48

2.0

2.14 1.77

ΟΙ CD O ■ DO

Example 19)

Numbers in brackets in the following example refer to Figure 1.

In continuous treatment, the polyurethane solution (1) according to manufacturing specification 1 is extracted from a pre-pressure pot using a gear pump with application rates of approximately 11 to 17 g / min through a slot nozzle (3) approximately 15 cm wide and a slot opening from 0.10 to 0, 20 mm poured onto a polished, approx. 20 cm wide, circumferential steel belt (2) with a distance of approx. 300 cm between the drive cylinders of the steel belt. The infused solution is running at a belt speed of 12.5 cm / min initially about 100 cm by air (25 ⁰ C / 6096 RH), then by a semi-cylindrical hollow body (1) of about 110 cm length, 33 cm width and a height of about 18 cm, which is charged with superheated steam. The walls of the hollow cylinder (1) consist of foil-coated, approximately 3 cm thick polyurethane foam. Both ends of the hollow cylinder are each provided with a small slot (4) or (9) for the continuous belt. Drains (13) are installed on the underside of the hollow cylinder to discharge steam and condensed liquid. About 2 to 10 cm above the circumferential steel strip with the applied layer of solution, there are hot steam nozzles (5) at intervals of about 30 cm, which generate even steam fans across the strip at an angle that can be set at any angle to the film surface. Each nozzle consists of a tube with a diameter of approx. 1 cm and has 26 bores, each 1 mm in diameter over a length of 20 cm, which are evenly spaced next to each other. Each superheated steam nozzle is connected to a superheated steam line of around 5 atmospheres. Before it is introduced into the nozzle, the steam is brought to the desired steam temperature by a gas-heated steam preheater and the back pressure in front of the nozzle is measured on a manometer and regulated by a valve. The temperature in the hollow cylinder is measured approximately at the level of the nozzles by 3 thermometers located in the vapor space. The steam space above the revolving casting belt is isolated from the underside of the belt

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54 . 212590 «

To prevent steam penetration.

When passing through the vapor space, the solution layer dries with ongoing cloudiness and formation of a white, microporous layer that hardly smells of solvent and can be continuously removed from the steel belt at the end of the steam cylinder subtracted from. The moisture residues present in the microporous pores of the layer can be squeezed out be squeezed out. However, the microporous, still moist layer is preferably subject to continuous drying in a heated circulating air drying cabinet (approx. 120 to 140 ° C with a residence time of 10 to 15 minutes), into which a weak stream of superheated steam is introduced. Man This gives white, microporous polyurethane layers with good strength. The appropriate quantities, temperatures and directions of flow of the steam from the respective hot steam nozzles (5) are determined empirically.

A particularly favorable setting of the superheated steam nozzles (5) has been shown to allow the steam to exit through the first nozzle (5a) about 2 cm above the entry point of the solution into the steam cylinder with its exit holes horizontally above the solution layer in the direction of the moving belt, the second nozzle (5b) about 10 cm above the belt with stronger steam guidance about at a 30 ° angle in the direction of travel of the belt on the film and the third superheated steam nozzle (5c) about 30 cm in front of the outlet slot (9) about 10 cm above the revolving belt approximately perpendicular to the belt with its steam outlet holes. The temperatures are, for example, approximately 101 to 103 ^° C. for (5a), approximately 103 to 105 ^° C. for (5b) and approximately 108 to 115 ^° C. for (5c). Steam amounts to approx. 30 to 75 g / min through nozzle (5a), 75 to 150 g / min through nozzle (5b) and approx. 50 to 100 g / min of superheated steam through nozzle (5c), which through to approx up to 240 ⁰ C heated preheater is introduced into the steam space. This nozzle arrangement and temperature control can be used to make the still soft

Le A 15 612 - 51 -

2 0 9 a 5 1 M 1 2 7

Solution film initially gently in contact with the flowing steam comes and only in the second half of the steam treatment with increasing solidification of the layer by intensive steam action the solvent is largely removed. The films obtained show excellent strength values at the same time very high water vapor permeability. The hot rub fastness and hot iron fastness are very good. The microporous layers are very kink-resistant (> 500,000 kinks without damage). The films show significantly improved resistance to exposure when compared to films of similar type Composition, but with dispersion and Gerstoff additives according to German Patent 1,270,276.

Example 20)

The continuous apparatus of Example 19 is modified in that the steam treatment chamber is increased cm to a length of 140, that one does not fit the steam nozzles transverse to the direction of belt travel, but on both sides along the tape, (50 bores of 1 mm to 2 cm spacing). The cavity above the belt is reduced to a height of approx. 5 to 15 cm (adjustable). The "steam nozzles" are charged with a mixture of superheated steam and heated air (each produced in steam superheat). The Gießbandunterseite is heated with hot air of approximately 75 to 80 ⁰ C, where the heating of the underside of the belt already is about 10 cm before entering the strip into the vapor space is made. A polyurethane solution 18 (or 17) is applied to the belt with a delivery rate of 18.7 g / min in a width of about 15 cm at a belt speed of 12.5 cm / min. With a steam ₂ O and a temperature from about 120 to 150 g / min H in the vapor space of 101 to '105 ⁰ C, the polyurethane solution on the strip in a microporous, lift-off film is transformed. By appropriately sucking off the dimethylformamide / steam mixture at the end of the belt, a flow of steam (Gemisohes) over the belt is achieved. The residence time in the vapor space is 11.2 minutes. After the tape emerges from the steam space, the is still moist

Le A 13 612 - 52 -

209851 η 127

53 21? 5 9 O Π

Slide lifted off. The moist film still contains 37.7% by weight of the dimethylformamide originally present. 20.2% by weight of the dimethylformamide originally present was replaced by water (the film in this state therefore contains approx. 62.3% by weight of liquid, 65 % of which is dimethylformamide and 35 % H ₂ O). This moist film can be dried by prolonged lying in air at room temperature or in a downstream drying oven with a steam atmosphere at 100 to 103 ⁰ C. In both cases, microporous films with approximately the same water vapor permeability are obtained (film thickness approx. 0.55 mm). The films have completely homogeneous, smooth surfaces, excellent hot rub fastness, ironing fastness and good kink resistance. The light resistance is significantly increased compared to films of the same type with the addition of dispersion and tanning agents according to German federal patent 1,270,276. The handle of the foils is dry and leathery-hard, not rubber-like, softly sticky. The tensile strength is 135 kg / cm with an elongation at break of 400 96 and a water vapor permeability of 6.9 mg / cm · h.

If the polyurethane solution is used instead of the polyurethane solution 18 17, one also obtains homogeneous, smooth »tear-resistant, microporous films of good grip with water vapor permeability of 10 mg / cm .h.

If the underside of the strip is cooled with cold air or cold water, for example, a very high temperature occurs under similar process conditions rapid condensation of water on the polyurethane solution, which leads to the formation of liquid islands on the solution and creates a fairly dense surface skin that allows evaporation of dimethylformamide hindered (blistering in the film) · After drying, films with glossy, water-vapor-impermeable properties are obtained Surface or transparent dense foils. If, on the other hand, the underside of the belt is heated to approximately the same temperature of the steam room, in many cases a transparent, non-porous film obtained.

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ORIGINAL INSj = ¹ ECTED

Claims (1)

212Β9ΠΒ Claim Process for the production of microporous flat structures from solutions of polyurethanes in polar organic solvents, characterized in that one layer of the polyurethane solution Water vapor at a temperature of 101 to 190 ° C is allowed to flow until the content of the layer of organic solvent has dropped to less than 50% by weight and the layer is in. a solid, mechanically stable, optionally removable microporous sheet-like structure has passed over. Le A 13 612 - 54 - 209851/11? 7 GFHQINAL