DE1936691C3 - Process for making microporous sheeting - Google Patents

Description

30th

The invention relates to a method of making microporous sheeting through Coating of a carrier base or a removable plate that is customary for artificial leather a urea-containing solution of a film-forming synthetic polymer which wholly or mainly of polyurethane dissolved in a water-miscible organic solvent, treatment of the coated carrier material for coagulation of the applied polymer with an aqueous coagulation liquid containing sodium sulphate, Washing out and drying of the web material and, in the case of use of the plate as a base, peeling off the polymer film from the base as a carrierless film.

The microporous web material produced according to the invention has a high water vapor permeability and a uniform microporous structure.

If a layer r, us a solution of a film-forming Polymers (wholly or mainly poly- so urethane) in an organic solvent in Water is immersed, the surface of the layer that is in contact with the water coagulates, quickly and forms a compact or dense structure. The coagulation of the inside of the polyurethane layer however, it is delayed. Therefore, large cavities are easily formed inside, while the surface is so compact or dense that it is difficult to maintain a uniform microporous structure throughout the layer. The sheet material obtained has as a whole has a low gas permeability and is unsatisfactory as a synthetic surface Leather.

In this regard, British patent specification 9 81 642 and Belgian patent specification 6 26 816 describes that if a polyurethane solution is only coagulated in water, a water vapor permeable one Film with a uniform microporous structure, such as that used as a surface layer of a synthetic leather is desired cannot be achieved unless it becomes one of the following additional measures taken:

a) The layer of polymer solution is a humid atmosphere with controlled relative humidity exposed for a certain period of time before immersing the layer in water;

b) The polymer solution is water or another non-solvent for the polymer in carefully added in a coordinated amount, so that the polymer solution is converted to a colloidal dispersion but does not gel;

c) water or another non-solvent for the polymer is added to the polymer solution and mixed so that the mixture gelaragen in one and a liquid portion is separated, and the gel-like part becomes for coating used.

The above-mentioned process a) is described in detail in British Patent 849155. It however, there is a disadvantage that a precisely controlled atmosphere is required and that it takes a long time is required for coagulation of a coating film of appreciable thickness. Furthermore must not only the relative humidity but also the temperature can be controlled and it is used in industrial Do not practice simply to regulate the atmosphere to be homogeneous and evenly microporous Get movies. Furthermore, more than a few hours are required in such an air-conditioned atmosphere needed to moisten and coagulate a layer (0.6 mm) well, e.g. B. a dimethylformamide solution with 20% polyurethane. It is also difficult to determine the correct level of coagulation.

The above-mentioned process b) is described in detail in Belgian patent specification 6 14 056, for example. A film of considerably good microporosity is obtained by this process. However is used in the production of the so-called colloidal dispersion immediately before the actual gelation the colloidal dispersion obtained largely influenced by the concentration and the polymer solution the temperature of the polymer solution used, the proportion of the nonsolvent added to it and by the method of adding the nonsolvent, so it is necessary to have the optimal conditions to be adjusted and controlled very carefully. Therefore it is difficult to get this process into the to implement industrial practice.

The process c) is z. B. in the Belgian patent 6 24 250 communicated. However, the segregation is of the gel complicated, and the regulation and adjustment Getting the right concentration and viscosity of the gel is difficult.

In the case of the above-mentioned processes b) and c), the obtained microporous film tends to be deteriorated Strength.

In NL-OS 67 16 238, which corresponds to the not previously published DT-AS 16 19 270, was already a method of making a sheet or film of high water vapor permeability and described with a microporous structure by applying a water-miscible Solution of a polymer consisting entirely or mainly of polyurethane on a carrier material, Coagulating the coated material

in an aqueous solution of a water-soluble inorganic salt and then washing and drying. In the same NL-OS 67 16 235 a method for the production of a web was already mentioned or a film with higher water vapor permeability and with a microporous structure, by applying a solution containing polyurethane and urea to a carrier material that coated Material coagulated in an aqueous solution of a certain water-soluble inorganic salt and then washed and dried ».

Through this procedure, the process was carried out and a film was made at the same time high water vapor permeability and microporous structure compared to those described above, Conventional processes a) to c) successfully simplified Improved Process Problems in the mass production of microporous films or webs.

In systems for continuous mass production, this results in a period of a few minutes (different depending on the particular apparatus) between the application of the coating solution on the carrier material and the thawing of the coated material in the coagulation bath. Therefore the applied layer of the solution is exposed to the atmosphere and absorbed during this period Moisture from the air. This moisture absorption has a bad influence on coagulation in the coagulation bath and causes the formation of undesirable macropores in the coagulated Layer. This tendency is particularly noticeable when the relative humidity of the Atmosphere is higher than 45%.

However, it is difficult to control the humidity due to the daily fluctuating weather conditions to regulate and especially to keep it low enough. Furthermore, it is almost impossible to track the period between the coating and the subsequent immersion.

The object of the invention is therefore an improved method for producing one for moisture permeable film or sheet material with micropores, but without macropores, in particular one flexible film or sheet material of high moisture permeability. Such a procedure should be economically advantageous and result in a film or sheet material that, in terms of durability, The appearance and feel of natural leather is not inferior.

The method of the present invention for making microporous sheeting offers the further Advantage of being without the additional steps required by the method of the British patent 9 81 642 are required works.

The method described at the beginning is characterized in that, for coating, a polymer solution with a urea content of up to 40 percent by weight, based on the polymer in the solution, and for coagulation of the polymer, an aqueous coagulation liquid containing 200 to 300 g / l of sodium sulfate and 100 to contains 300 g / l of urea used werdein and the temperature of the coagulation bath is 30 to 55 ⁰ C.

If such a special coagulation bath is used, no macropores will form, even by themselves when the coating solution layer of the atmosphere under any temperature and humidity conditions exposed, and there tougher and softer Film or sheet material with high water vapor permeability and uniform micropores can easy and simple under industrial conditions

S are made.

The coating solution can be an ordinary polyurethane solution in one miscible with water Be a solvent (e.g. dimethylformamide) that contains an appropriate amount of urea

The advantages of the invention are as follows:

1. The polymer solution can be used directly as such and can be easily and uniformly based the carrier material can be applied without difficulty. The coated material can immediately and continuously in a coagulating RegeneratioDsbad, consisting of an aqueous one Solution containing sodium sulfate and urea.

2. When using the coagulation bath with the correct sodium sulfate and urea concentration becomes, the polymer solution quickly assumes a coagulated ^ structure without noticeable Shrinkage and deformation when immersed in the bath and the coagulated material can be continuously washed with water to make the water-miscible organic Solvent to remove the sodium sulfate and urea.

3. After washing in water, just by simply drying, can be slightly tough, softer Film or synthetic leather of high water vapor permeability can be produced.

4. No special device is required in front of the coagulation bath. The implementation is simple and no special exposure to temperature and / or humidity is required. The sodium sulfate and urea are both cheap and readily available.

Any of the known film-forming polyurethanes can be used in the practice of this invention will. Usually, a prepolymer is used to produce such a polyurethane by reaction an organic diisocyanate with a polyalkylene

ether glycol or polyester with terminal hydroxyl groups. The chain of the prepolymer is then with a chain extender that has reactive hydrogen atoms, e.g. B. Diarnin, Diol or Polyo !, extended to make a polyurethane elastomer.

The organic diisocyanate can be an aromatic, an aliphatic or an acyclic diisocyanate or a mixture thereof, e.g. B. toluene-2,4-diisocyanate, Toluylene-2,6-diisocyanate, diphenylmethane

4,4'-diisocyanate, 1,5-naphthylene diisocyanate, hexamethylene diisocyanate or xylylene diisocyanate.

The polyalkylene ether glycol is z. B. polyethylene ether glycol, Polypropylene ether glycol, polytetramethylene ether glycol or polyhexamethylene ether glycol

or a copolymer or a mixture of these. As a polyol or polyalkylene ether, glycerol or Trimethylolpropene can be used.

The polyester which can be used is an organic acid and polycondensate

a glycol. The preferred glycol to be used is a polyalkylene glycol such as ethylene glycol, propylene glycol, Tetramethylene glycol or hexamethylene glycol or a cyclic glycol such as cyclohexanediol,

or an aromatic glycol such as xylylene glycol. the Organic acid can be succinic acid, adipic acid, sebacic acid, or terephthalic acid.

As a chain extender, a diamine, such as. B. Hydrazine, ethylenediamine or methylenediorthochloroaniline, be used.

If desired, a catalyst, e.g. triethylamine, Triethylenediamine, N-Athylnsorpholia, dibutyl tin dilaurate or cobalt naphthenate, used in the manufacture of the polyurethane elastomer will.

In this invention the polyurethane is used as a solution. The solvent for the polymer must be selected from those miscible with water and must be mixed with an aqueous solution of Sodium sulfate and urea can be extracted. Therefore, water-miscible solvents are to be selected. Examples of such solvents are one or a mixture of the following: N.N'-dimethylformamide, Dimethyl sulfoxide, tetrahydrofuran, tetramethylurea, N.N'-dimethylacetamide, dioxane or butyl carbinol. Furthermore, any ketone, which alone is not a good solvent for the polyurethane is, but is easily miscible with the solution, such as. B. acetone and methyl ethyl ketone as diluents can be used insofar as it does not coagulate the polymer.

If desired, a small amount of one or more other film-forming polymers contained in the Solution soluble, such as a vinyl homopolymer, e.g. B. polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, Polyacrylic esters or polyacrylic acid or copolymers of them, the above-mentioned polyurethane solution be added. The amount of such other polymer is preferably 2 to 40 percent by weight, based on the polyurethane.

It is possible to use a coloring substance (e.g. a dye or a pigment), a light stabilizer or a reinforcing substance (e.g. talc, calcium carbonate or finely powdered silica) to the Add polymer solution.

Furthermore, urea is added to the polymer solution in order to reduce the water vapor permeability of the obtained web or film. In the event that a synthetic leather is produced it is important that the water vapor permeability is high. Therefore it is recommended that the Add urea polymer coating solution. The right amount of urea varies depending on the person the chemical structure, the degree of polymerisation and the concentration of the polymer, however is up to 40%, preferably up to 35%, or in particular 15 to 25 percent by weight, based on the polymer in the coating solution. If the amount of urine urine is more than 40%, the solution tends to gel.

When urea is added to the polymer solution, the water vapor permeability of it increases obtained porous film because the latent ability of the polymer solution to coagulate, or its Ability to coagulate quickly is improved, and because after coagulation by washing out the urea remaining in the film creates additional micropores and increases the porosity.

The viscosity of the polymer solution is adjusted so that that it can be conveniently applied to the surface of the substrate. In general a viscosity of about 20,000 to 100,000 centipoise is preferred.

The concentration of the polymer in the polymer solution is in the range from 10 to 40% by weight, preferably from 15 to 35% weight.

The polymer solution (coating solution) is deaerated in the usual manner and on one or both Surfaces of the carrier material applied to the synthetic leather, e.g. B. a woven, knitted or non-woven fabric, a foam pulp, or paper. It is also possible to use the polymer solution Plates made of glass, metal or plastic.

The coating can be carried out in any of the known ways, e.g. B. by squeegee, Roller coating or spraying. Since the polymer solution is homogeneous or uniform, it can can be easily applied to the substrate, and there are no such troubles as in the method described in Belgian patent 6 24 250.

In the coagulation bath it is desirable to pour water over the layer at a suitable speed Allow polymer solution to flow to prevent coagulation beneath the outer surface of the layer to proceed evenly as possible so that a microporous structure is formed. to for this purpose it is necessary during the penetration and diffusion of water from the coagulation bath into the layer of polymer solution and the simultaneous solvent transfer from the layer to keep the appropriate speeds in the correct ratio in the coagulation bath. When the rate of coagulation is not higher than the rate of transfer of the solvent, A uniform microporous structure does not form, but sometimes particularly large ones Macropores and numerous macropores are formed just below the surface layer. It was determined, that in the presence of a suitable substance (additive) in the coagulation bath to adjust the penetration rate (or coagulation speed) of the water from the coagulation bath and the exit speed of the solvent from the Layer of polymer solution a satisfactory coagulation can be achieved.

It has been found that the sodium sulfate can regulate the rate of penetration of water. It has been found that the hydrating ability of the salt in aqueous solution is preferred in works in this regard. Of course, the concentration of the salt and the temperature of the bath have one thing Impact.

The other important feature of this invention is the addition of urea to the coagulation bath. It has been found that urea in the coagulation bath reduces the exit velocity of the solvent regulates. The influence of the urea on this exit velocity of the solvent can be related to can be seen with its solubility in this solvent.

The concentration of urea in the coagulation bath can depend on the type and concentration of the inorganic salt present in the coagulation bath vary, but is in the range of 100 to 300 g / l, preferably 150 to 300 g / l. If they are lower is more than 100 g / l, there is apt to be an influence of humidity and the formation of a film with uniform micro-sparse strinlrinr Ir ™ η ei ,,.; ~

become rig. If it is higher than 300 g / 1, the Concentration of the water-miscible solvent (e.g. N.N'-dimethylformamide) near the surface the coating solution become high, and the solubility of the sodium sulfate is markedly reduced, so that the salt crystallizes on the surface, and it is likely that it will die Surface of the porous film damaged by irregularities.

A film with excellent microporous structure is produced by the effects of both sodium sulfate as a means of adjusting the rate of penetration of the water and urea as Means for adjusting the rate of release of the solvent.

The temperature of the Koagulalionsbadcs should be in the range from 30 to 55 C, preferably from 40 to 45 C, lie. If it is lower than 30 ° C, crystals of sodium sulphate can precipitate and the surface the microporous film can be damaged. If it is higher than 55 C, the Coagulation difficult to carry out, and the water vapor permeability of the film obtained is humiliated.

According to the invention, the films obtained always have a uniform microporous structure and no macropores, even if the composition and temperature of the coagulation bath remain the same are set and there is a change in the meteorological conditions.

After coagulation, the film is washed with water to remove the water-miscible organic Solvent to remove the sodium sulfate and the urea remaining in the film, and then the film is dried under normal conditions.

When the polymer solution is applied to one or both surfaces of a sheet or plate made of glass, metal or plastic, the film thereon can be peeled off the carrier sheet or plate. If the polymer solution is applied to one or both surfaces on a material suitable for synthetic leather, ζ. Β. Woven or non-woven material, film, sponge-like material or paper or the like is applied, the microporous film obtained is firmly bound to this carrier material. The material thus obtained is useful as synthetic leather.

The microporous film can have a top coat of an ordinary paint or varnish for Obtain leather without impairing the desired properties or the usefulness of the product.

The invention is explained in detail with reference to the following examples, all of the information from Composition in parts by weight. In these examples the breaking strength, the Elongation at break, water vapor permeability, color fastness and the presence of macropores in the films obtained are defined as follows:

1. Breaking load and elongation at break: These are measured on a sample 2 cm wide and with a clamping length of 5 cm at a take-off speed of 3 cm per minute with an Instron tester measured.

2. Water vapor permeability (abbreviated as WDD in Tables 1, 2, 5, 6 and 7): The weight increase of calcium chloride through a predetermined area of the film sample in an atmosphere of 80% relative humidity and 30 ^° C. was measured, and the water vapor permeability was expressed by the increase in weight (milligrams) per unit time (hour) and per unit area (square centimeter), ie mg / h / cm ² . The higher this value, the higher the water vapor permeability.

3. Fold resistance: This was measured with a Flexi-O-meter (manufactured by Yasuda Precise Machine Manufactory, Ltd., Japan).

4. Presence of macropores: The cut surface of the film became microscopic examined. It also became a folded surface of the film with a razor blade scraped off and this scraped surface examined with a microscope to determine whether macropores (with an average diameter of 10 μm or larger) available.

example 1

105 parts of polyethylene glycol adipate with an average molecular weight of 1050 with terminal - OH groups were dissolved in 200 parts of anhydrous dioxane, and 40 parts of methylene bis (4-phenylisoeyanate) were added. The solution was

Held for 2 hours at 80 ° C in a nitrogen atmosphere and then cooled to 30 ⁰ C. To the solution of the prepolymer with terminal -NCO groups thus obtained, 3.7 parts of ethylene glycol and 0.02 part of triethylenediamine were added together with 100 parts of anhydrous dioxane to obtain a

Carry out chain extension reaction lasting 3 hours. The polymer solution was then cooled and poured into water to remove most of the dioxane. The polymer was isolated and then dried at 80 ° C. under reduced pressure. The polymer was dissolved in N, N'-dimethylformamide to a concentration of 30% by weight. The viscosity of this polymer solution was 45,000 centipoise at 30 ⁰ C.

15% weight of urea based on the polyurethane in the solution was added to the N.N'-dimethylformamide solution of the polyurethane, and the mixture was stirred to prepare a coating solution . This coating solution was applied to the same glass plate 1 mm thick. The coated glass plate was left in an atmosphere of relative humidity of 80% at 20 ° C. for 5 minutes and then immersed for 10 minutes in a 40 ° C. aqueous solution of sodium sulfate and urea of the concentrations shown in Table 1 to form the layer The glass plate with the film thereon was then placed in a hot water bath at 50 ^° C. The film was peeled off the glass plate, washed with hot water for 30 minutes and dried specified.

As a typical example, the film obtained by using a coagulation bath of an aqueous solution containing 250 g / l sodium sulfate and 200 g / l urea had a breaking load of 0.96 kg / mm ² and an elongation at break of 530%.

From the results given in Table 1 is

ίο

to see that a tough, soft, microporous film with high water vapor permeability is obtained can be by coagulation in an aqueous solution with sodium sulfate in a concentration of 200 to 300 g / l and urea in a concentration range of 100 to 300 g / l.

Table 1 Own Sodium sulfate 200 (g / l) 300 330 urine societies material the slide 150 Yes 250 Yes Yes (g / l) macro Yes - Yes - - 50 pores WDD - no - no no (mg / h / cm ² ) macro Yes 7.7 no 7.8 7.4 100 pores no no no WDD 7.4 8.2 macro Yes 7.6 no 7.9 7.3 150 pores no no crystal WDD 7.2 8.2 deposit macro Yes no gen on the 200 pores surface 8.6 7.8 7.7 WDD 6.9 7.4

Urinates "

(g / l)

250

300

350

properties
of slide 150

Sodium sulphate (g / l) 200 250

300 330

Macropores

WDD
Macropores

WDD

Macropores

WDD
Macropores
WDD

yes no no no Crystal deposits on the surface

7.7

7.4 8.1 8.3

no no no no

7.4 crystal deposits on the surface

7.0
Yes

7.6 8.3

Crystal shelf
struggles
on the
surface

7.7 -

yes yes 3.5 3.1

By S

20% weight (based on the polyurethane) of urea was the polyurethane solution prepared according to Example 1 and the mixture was stirred to obtain a coating solution. The coating solution was applied about 1 mm thick on a glass plate. The coated glass plate was then left for 5 minutes in an atmosphere whose temperature and humidity are in Table 2 is listed, and was then for 10 minutes in an aqueous solution (coagulation bath) in Table 2 listed temperature and with a content of 250 g / l sodium sulfate and 200 g / l urea submerged. Then it was placed in a hot water bath at 50 ° C and the film obtained was removed from the

Table 2

380 sodium sulfate crystallized out. and the coagulation bath was unusable.

game 2

Glass plate peeled off. The film was washed with hot water for 30 minutes and air dried The results are shown in Tables 2 and 3. In Table 2, the sign o shows that no macro pores were present in the film, and the number was right: the sign ο gives the water vapor permeability on. Table 3 shows the breaking load and elongation at break of a film obtained by taking di < applied solution layer for a certain period of time in an atmosphere specified in table 3 Temperature and humidity conditions was kept and then in a coagulation bay was coagulated at 45C.

Leave the coating in place with water vapor permeability and the type of pores at the temperature of the coagulation bath temperature

25th
25th
25th
35
25th
35
25th
35

Relative 25 C O 3OX O 35 C O 40 "C 0 45 C 0 55 C 0 60 ( humidity crystal 7.7 8.2 8.3 8.2 6.0 15th (%) deposits 43 on the upper surface O 0 O O O O the same O 8.0 O 8.5 O 8.5 O 8.5 O 6.0 O 27 the same O 7.8 O 8.3 O 8.4 O 8.7 O 6.0 O 2.6 55 the same O 7.8 O 8.5 O 8.8 O 9.1 C. 6.1 O Z7 65 the same O 7.9 O 8.4 O 8.7 O 8.8 O 6.8 O 2.9 75 the same O 8.2 O 8.3 O 8.8 O 8.9 O 6.2 O Z8 75 the same O 8.0 O 8.3 O 8.6 O 8.7 O 6.0 O 2.6 85 the same O 7.8 O 8.0 O 8.8 O 9.0 O 6.1 O Z8 85 the same 7.6 8.1 8.4 8.4 6.1 2.7 93 92

Table 3

temperature Relative Breaking load fracture humidity strain (Cl (%) (kg / mm ² ) (%) 25th 43 1.08 550 25th 55 0.92 570 25th 65 1.10 520 25th 75 0.90 520 35 75 0.88 531 25th 85 0.80 550 35 85 0.86 540 25th 93 0.99 543 35 92 0.92 568

For comparison, the experiment was carried out under exactly the same conditions as mentioned above, except that an aqueous solution (to which no urea had been added) containing 200 g / l of sodium sulfate was used as a coagulation bath and that the applied layer was used in one for 5 minutes Relative humidity atmosphere of 75% at 25 ⁰ C was kept. The obtained film had macropores and a water vapor permeability of 6.9, a breaking load and breaking elongation of 0.95 kg / mm ² and 545%, respectively.

It is also clear from the above results that, according to the method of this invention, a uniformly microporous film without macropores and with high water vapor permeability is obtained by coagulation at 30 to 55 ^° C., ft

even if the applied layer of solution is exposed to an atmosphere with any humidity and temperature conditions. In particular in a coagulation bath of 40 to 45 ^° C., the water vapor permeability of the film obtained is higher.

Example 3

The solution of an ester-polyurethane in a concentration of 35% in Ν, Ν'-dimethylformamide, to which 20% weight of urea (based on the polyurethane) had been added, was applied 1 mm thick to a glass plate. The whole thing was kept for 3 minutes in an atmosphere of 75% humidity at 20 ^° C. and then for 10 minutes in a 40 ° C. warm aqueous solution (coagulation bath) with the inorganic salts, as indicated in Table 4, and 200 g / l The glass plate with the coagulated film thereon was then placed in a hot water bath of 50 ° C., the film peeled off the glass plate, washed with hot water for 30 minutes, and dried at 100 ° C. for 3 minutes. The properties of the films are listed in Table 4.

It is clear from the results in Table 4 that the properties of the films differ depending on the specific inorganic salt which is in the coagulation bath together with the urea. Only with the sodium sulfate used in this invention can a uniform microporous film with high water vapor permeability be produced. If inorganic salts are used, a wedge with macropores and low water vapor permeability is formed.

Table 4

Inorganic salts concentration Breaking load Elongation at break WDD 9.0 Macropores in the film of the salt 2.4 (g / l) (kg; mnr | (% l 2.5 Sodium sulfate 250 0.96 541 2.7 no Magnesium chloride 250 0.95 531 Z3 Yes Magnesium sulfa * 200 0.92 520 'C air dried.
ι films cir »/ ^ ii-i Ta Yes Calcium chloride 250 1.01 650 Yes Calcium sulfate 250 0.93 530 Yes Example 4 at 105 '
he ΐΐ! ΐΙ * ΐ »η /» Π The properties of the

A Ν, Ν'-dimethylformamide solution of an ester-polyurethane (concentration 35%) with various proportions of urea, as indicated in Table 5, was applied to a glass plate 0.7 mm thick. The coated glass plate was left in an atmosphere of 80% relative humidity at 25 ° C. for 5 minutes and then immersed for 10 minutes in a 45 ° C. aqueous solution (coagulation bath) containing 250 g / l sodium sulfate and 250 g / l urea. the glass plate having thereon the coagulated film was then immersed in a hot water bath at 50 ⁰ C, the film is peeled off from the glass plate, washed with water and 10 minutes gg

For comparison, the test was carried out under the same conditions, except that the coating solution did not contain any urea and the coagulation bath consisted of an aqueous solution containing 250 g / l sodium sulfate. The egg-holding film is mentioned as Control 1 in Table 5. Further, the experiment was carried out under the same conditions as mentioned above, except that the coating solution was 5%

Contained urea and the Koagulationsbatl at an aqueous solution of 250 g / l sodium sulfite <was. The film obtained is noted as control 2'ΐπ Tj belle 5. ' ⁿ '"

Table 5

Proportion of urea Breaking load (%) (kg / mm ² ) 5 0.93 10 0.93 15th 0.95 20th 0.91 25th 0.87 30th 0.92 35 0.85 40 0.86 45 The Pol Control 1 0.93 Control 2 0.93

Elongation at break

547 543 543 529 498 511 496 493

WDD

5.6
7.9
8.8
9.1
9.3
9.6
9.8
10.6

Macropores in the foil

no no no no no no no no

The polyurethane solution gelled and could not be applied. 530 4.2 yes

7.8

It is clear from the above results that with increasing amounts of urea added to the polyurethane solution, the water vapor permeability of the film obtained becomes high.

The controls also clearly show that a uniformly microporous film without macropores cannot be obtained unless a solution is used as a coagulation bath which contains both sodium sulfate and urea.

Example 5

A Ν, Ν'-dimethylformamide solution of an ester polyurethane (Concentration 30%) with 15% weight (based on the polyurethane) urea added, became 0.8 mm thick on the surface of a substrate of 0.8 mm thick and a density of 0.52 applied. This backing material was made of three layers of nonwoven material, which made of nylon 6 fibers of 1.2 denier and polyester fibers of 1.5 denier and 1 part yes

Butadiene / acrylonitrile copolymer had been added. The coated carrier material was for 5 minutes in an atmosphere of different temperatures

doors and humidities as indicated in Table 6, leave and then 10 minutes in a 45 C warm aqueous solution with 250 g / l sodium sulfate and 200 g / l Urea submerged. The carrier material with the coagulated film thereon was then

Washed well in a 50X hot water bath and then air-dried at 110X for 10 minutes. then became an acrylic ester-based leather paint by spraying onto the surface of the polyurethane layer applied and dried and finally a

colorless nitrocellulose varnish for leather on the surface applied. Each of the products was soft and shiny, crazy like natural leather. Handle, had a high water vapor permeability and breaking load, as indicated in Table 6. The evenly

microporous film was firmly anchored to the substrate.

Table 6

the atmosphere
temperature

Relative
humidity

Flexural strength breaking load and elongation at break

Load elongation

(kg / mm ² ) (%)

WDD

Macropores in the film

52

77
85
93
83

Not broken after 200,000 bending cycles

like. like. like. like.

0.99

0.99
1.00
0.99
0.98

28

28
29
29
28

6.1

no

6.6 no 6.5 no 6.5 no 6.5 no

Example 6

A solution prepared by adding 25% weight of urea to a Ν, Ν'-dimethylformamide solution of an ester polyurethane (concentration 25%), a solution prepared by adding 20% weight of polyvinyl chloride (based on the polyurethane) and 25% Weight of urea in the above-mentioned polyurethane solution and a solution prepared by adding 7% by weight of polyacrylic acid and 25% by weight of urea in the above-mentioned polyurethane solution was applied 0.5 mm thick to a mixed fabric of polyester and cotton fibers.

19 36 69!

The coated substrate was left in a relative humidity atmosphere for 5 minutes Leave 85% at 25 ° C. for 10 minutes in a 40 ° C. aqueous solution containing 250 g / l sodium sulfate and dipped 200 g / 1 urea. It was then washed with water and kept at 110 ° C for 10 minutes Long air-dried The synthetic leather thus obtained had a structure in which a uniform microporous film was layered and anchored on the carrier material, it had a natural leather look same grip and high water vapor permeability. The characteristics of the product are listed in Table 7.

For comparison, a product is included as control A.

out, which from the above-mentioned polyurethane solution and made using water as a coagulation bath. A product made by using an aqueous solution of 250 g of sodium sulfate as a coagulation bath, B is the control listed, and a product made by using a solution by adding 25% Weight of urea in the above-mentioned polyurethane solution and using the aqueous solution with 250 g / l sodium sulfate as a coagulation bath, is as Control C listed in Table 7. These control samples were made under the same conditions as mentioned above.

Table 7

Also present in the coating solution
plastic

Resistance to bending

None (polyurethane and urea)

Polyvinyl chloride
Polyacrylic acid
Control A
Control B
Control C

WDD

Macropores in
the slide

Not broken at 6.9 no 200000 bending cycleii the same 6.8 no the same 6.8 no the same 1.8 Yes the same 3.5 Yes the same 4.5 Yes Comparative example Attempt 1

Example 1 was repeated with the exception that the urea-containing polyurethane coating mixture according to Example 3 was used. The results obtained are shown in Table 8 below summarized:

Table 8

urea Properties of the film Sodium sulfate (g / l) 200 250 300 (g / l) 150 present present present Macro pores present 4.2 4.2 4.1 50 Moisture 4.1 permeability mg / h / cm ² miss miss miss Macropores present 7.9 8.4 8.1 100 Moisture 7.1 permeability miss miss miss Macro pores present 7.9 8.5 7.9 150 Moisture 7.0 permeability miss miss miss Macro pores present OO *
O, O 8.0 8.1 200 Moisture 6.6 permeable wedge miss miss miss Macropores present 8.5 8.7 7.7 250 Moisture 7.1 permeability miss miss miss Macro pores miss 8.1 8.6 7.9 300 Moisture 5.9 permeability

IO

■ ".UI attempt!

Experiment 1 described above was repeated except that no urea was present in the coagulating liquid was added. The results obtained are shown in Table 9 below:

Table 9

Na ₂ SO ₄ in that Macropores Moisture Coagulation bath permeability (g / l) (mg / h / cm ² ) 150 present 3.9 200 present 4.0 250 present 4.2 300 present 4.4

If one compares the results of experiment 1 (according to the invention) with experiment 2 (comparative experiment), so it is found that when there is no urea in the coagulation liquid or its content is very low is, macropores are formed to a pronounced extent.

Claims (1)

Claim: Process for the production of microporous sheeting by coating a substrate or a removable plate that is customary for artificial leather with a urea-containing solution of a film-forming synthetic polymer which consists entirely or mainly of polyurethane dissolved in a water-miscible organic solvent, treatment of the coated carrier material for coagulating the applied polymer with an aqueous coagulation liquid containing sodium sulfate, washing out and drying the web material and, in the case of using the plate as a base, peeling off the polymer film from the base as a carrierless sheet, characterized in that a polymer solution is used for coating a urea content of up to 40 percent by weight, based on the polymer in the solution, and an aqueous coagulation liquid containing 200 to 300 g / l sodium sulfate and 100 to 300 g / l urea to coagulate the polymer, are used and the temperature of the coagulation bath is 30 ⁰ C to 55 ° C.