DE102006054678A1 - Aqueous polyurethane dispersion, process for its preparation and its use - Google Patents

Abstract

The invention relates to aqueous Polyurethanandispersyurethans, which is a reaction product of at least one aliphatic polyisocyanate, at least one polyol and at least one dihydroxy-functional carboxylic acid, wherein the polyurethane contains as a further structural component a saturated monocarboxylic acid having 4 to 18 carbon atoms, which has no further functional groups in addition to the acid group. Furthermore, the invention relates to a process for the preparation and use of the polyurethane dispersions as an adhesive, as a binder for paints, as a sealant in building protection and for the sealing of wood surfaces and generally as a coating agent.

Description

The The present invention relates to an aqueous polyurethane dispersion, which contains as a binder a salt of a polyurethane, the a reaction product of at least one aliphatic polyisocyanate, at least one polyol and at least one dihydroxyfunctional carboxylic acid is.

Aqueous polyurethane dispersions are used as adhesives, binders for paints, sealants in Building protection and used for sealing wooden surfaces.

Polyurethane-based adhesives are known, for example, from the international patent application WO 91/09919 and the European patent application EP 0 838 511 A1 known.

she are particularly suitable for the production of household adhesives, the Also called multi-purpose adhesive or all-purpose adhesive. These have the purpose of a variety of household occurring substrates (Paper, cardboard, photos, textiles, leather, felt, bast, cork, foils, Metals, such as aluminum and iron, porcelain, ceramics, glass, wood, various plastics, as well as z. B. polystyrene foams) too stick together. It is expected that on this variety of substrates, which are in their surface structure chemically and physically different, and usually do not undergo any special surface treatment before bonding, sufficient adhesive effect sets.

The Demand for universality represents for An adhesive is a particularly hard selection criterion. It means ultimately that the adhesive molecules to polar we have nonpolar interfaces in the same way high affinity must have. The statement that one certain substance is suitable as an adhesive, therefore, gives the skilled person still no indication, whether they are also used as a household adhesive can be.

Next the demand for universality In the case of household adhesives, there is also a desire to be odorless, solvent-free, physiologically harmless, transparent clear, aqueous formulations to reach. However, these formulations are intended to simultaneously Lead adhesives, their dried films in turn have a certain water resistance feature. About that In addition, these water-based adhesives are also capable of be difficult to bind adhesive substrates such as plastics.

polyurethane dispersions can according to the methods known in the art from difunctional Isocyanates, such as isophorone diisocyanate, meta-tetramethylxylylene diisocyanate or methylene bis (4-isocyanatocyclohexane) getting produced. These diisocyanates are treated with polyols such as Polyether polyols, polyester polyols, polycarbonate polyols, oleochemicals Polyols etc. or mixtures of these polyols according to appropriate drainage with short-chain diisocyanates and dimethylolpropionic acid as further Component using solvents or high boilers such as acetone, methyl ethyl ketone, N-methylpyrollidone-2-one, etc. implemented. After reaching a certain content of isocyanate, the resulting prepolymer neutralized in water. For this purpose, various alkaline compounds such as B. amines, for. As dimethlyethanolamine, alkalis, ammonia solution used. After neutralization, the solvent used is then by distillation recovered from the process or remains when using so-called high boilers in the product, as for example when using N-methylpyrrolidin-2-one of Case is. Another possibility is the preparation of the polyurethane dispersions via so-called polymerization emulsifiers or so-called external emulsifiers. Through these procedures will be however, due to the particle size, not opaque solutions, but just according to the particle size mostly milky white or won beige dispersions. By these methods but no real solutions. This also applies to the hydrosols. This is a name for substances in particularly fine distribution in water as Disperisonsmittel the outer phase available. Often they also become "colloidal Called dispersions ", which means that yourself Hydrosols are already close in particle size real solutions approach or it is very finely divided dispersions. Because of her Fine particles are hydrosols especially for unpigmented, deeply penetrating Primers and solidifiers used as an alternative to real solutions can apply. Advantageously, water replaces the flammable and odoriferous often bothersome perceived solvents. solvent are easily volatile and are therefore of the solvent-containing Products in the living area delivered to the room air. High concentrations of solvents in the air you can in many cases smell, z. B. when painting with solvent-based paints or when cleaning with methylated spirits or benzine. Acting generally solvent narcotic or intoxicating. You can use the central nervous system, Damage liver and kidneys. It can Headache, nausea and tiredness occur. Some solvents are suspected of causing cancer and are harmful to pregnancy in pregnant women Act.

So far could watery, clear polyurethane dispersions only using organic solvents are prepared after the conversion of the polymer into an alkaline aqueous Medium had to be recovered by thermal separation again. at Use of so-called high boilers remained this disadvantageous in the finished polyurethane dispersions.

It Object of the present invention, particularly finely divided aqueous polyurethane dispersions for disposal to provide, without the use of organic solvents can be produced.

Surprisingly it was found that these Task solved can be saturated by the addition of monofunctional fatty acids in the preparation of the polyurethane dispersions.

object The present application is therefore an aqueous polyurethane dispersion of the type mentioned, which is characterized in that the polyurethane as a further structural component with a saturated monocarboxylic acid Contains 4 to 18 carbon atoms, the except the acid group has no further functional groups.

The Polyurethane dispersion according to the invention can not only be produced without organic solvents, rather, it also has a colloidal polyurethane solution very low viscosity on. This results in a high degree of filling For example, in paint applications allows.

Although it is from the Japanese patent publication JP 46007118 B known to produce polyurethanes with concomitant use of organic carboxylic acids. Here, mono- and dicarboxylic acids having 1 to 18 carbon atoms are used. However, the known compositions also have a foaming catalyst, ie they are used for the production of polyurethane foams. The production of polyurethane foams raises completely different problems than the production of ultrafine aqueous polyurethane dispersions. The cited publication could therefore give no suggestions as to the solution of the above-mentioned technical problem and with regard to the advantages achieved by the present invention.

The Advantages of the present invention are achieved to a particular extent with monocarboxylic acids which Contain 4 to 10 carbon atoms.

Advantageous is the monocarboxylic acid in a proportion of 18 to 26 mol% in the polyurethane. The to be used for the production of the polyurethane dispersion according to the invention Polyisocyanate advantageously has a molecular weight of 168 to 262 daltons and an NCO functionality of 1.8 to 2.2.

suitable Polyisocyanates are the difunctional polyisocyanates such as HDI, MDI.

preferred Polyisocyanate is TMXDI, and particularly preferred is IPDI.

The preferred dihydroxy-functional carboxylic acid is dimethylolpropionic acid.

The Salt of the polyurethane is in the aqueous polyurethane dispersion advantageously in a proportion of 20 to 60 wt .-% based on the Contain total weight of the dispersion, a proportion is preferred from 30 to 40% by weight.

The Invention also relates to a process for the preparation of a polyurethane dispersion according to the invention, which is characterized in that at least one aliphatic Polyisocyanate, at least one polyol, at least one dihydroxyfunktionelle carboxylic acid and a saturated one Monocarboxylic acid be reacted with 4 to 18 carbon atoms to a polyurethane and the resulting product with an aqueous solution of a base to an aqueous Dispersion is processed.

at the process advantageously a) 35 to 45 mol% of polyisocyanate, b) 15 to 19 mol% polyol, c) 20 to 25 mol% dihydroxyfunktionelle carboxylic acid and d) 18 to 26 mol% saturated Monocarboxylic acid implemented together.

Advantageous becomes a monocarboxylic acid with 4 to 10 carbon atoms, more preferably with 8 carbon atoms used.

As the polyisocyanate is advantageously one having a molecular weight of 168 to 262 daltons and an NCO functionality of 1.8 to 2.2, preferably m-tetramethylxylylene diisocyanate and isophorone diisocyanate used in the process. Particularly preferred is IPDI (isophorone diisocyanate).

The in the process is preferred dihydroxy-functional carboxylic acid Dimethylolpropionic.

The The invention also relates to the use of the polyurethane dispersions as an adhesive, as a binder for Paints, as sealants in building protection and sealing of wooden surfaces.

in the Following, the invention will be explained in more detail with reference to embodiments.

Example 1:

• a) batch (based on polytetrahydrofuran 1000 (trade name: u. a. Terathane 1000, supplier DuPont), dimethylolpropionic acid (bis-MPA), caprylic or octanoic acid (trade name: Edenor C 8 98-100, Supplier Cognis) and isophorone diisocyanate (IPDI) (trade name: u. a. Desmodur I, supplier Bayer AG)

For 300 g batch (stage 1), the following weights were used: - 159.35 g of PTHF 1000 correspond to 0.16 mol - 32.74 g Edenor C 8 98-100 correspond to 0.22 mol - 26.20 g of DMPA correspond to 0.19 mol - 81.71 g IPDI correspond to 0.37 mol

• – 238,98 g entm. Wasser (188,98 g theoretisch)
• – 6,02 g 50 %ige NaOH (Überschuß von 10 % bezogen auf 105 g Präpolymer)
• – 121,85 g Präpolymer aus Stufe 1 (105 g theoretisch)

For 366.85 g batch (stage 2) the following weights were used:

• - 238.98 g entm. Water (188.98 g theoretical)
• - 6.02 g of 50% NaOH (excess of 10% based on 105 g prepolymer)
• 121.85 g prepolymer from stage 1 (105 g theoretical)

Method:

Step 1: 1. Submission of PTHF 1000, Edenor C 8 98-100, DMPA and Desmodur I 2. Start of the heating phase at 90 ° C Begin: 0 min Introducing nitrogen Internal temperature = 90.3 ° C 21 min Heating bath set to 95 ° C NCO content = 2.58% 39 min NCO content = 0.89% 61 min 3rd batch was bottled and stored at 110 ° C. 80 min

Level 2:

• 1. Prepare 188.98 g of water and caustic soda
• 2. Start of the heating phase at 85 ° C
• 3. Portionwise addition of the prepolymer from 85 ° C.
• 4. Shortly before the end of the addition of the prepolymer, an additional 50 g entm. Water added
• 5. After the addition was stirred at 85 ° C for 2 hours

Remarks:

The prepolymer was at the filling temperature flowable.

The prepolymer let himself go disperse very well in the lye.

Results:

The The dispersion formed is opaque and homogeneous.

Of the Film is transparent in low layer thickness or slightly cloudy in high layer thickness and stretchy.

Of the pH is 7.85.

The viscosity is 16 mPa · s (Brookfield, spindle 6, 100 rpm, 20 ° C)

Of the Solid content is 22.20%.

The tensile shear strength of beech plywood is 1.14 N / mm ² (speed 50 mm / min).

• b) batch (based on polytetrahydrofuran 1000, Polycarbonate polyol (trade name: Desmophen XP 2501, supplier Bayer AG), dimethylolpropionic acid (Bis-MPA), caprylic acid or octanoic acid and isophorone diisocyanate (IPDI)

For 359.89 g batch (stage 1), the following weights were used: 97.34 g of PTHF 1000 correspond to 0.10 mol - 97.34 g Desmophen XP 2501 correspond to 0.10 mol - 30.73 g Edenor C 8 98-100 correspond to 0.21 mol - 30.73 g of DMPA correspond to 0.23 mol - 103.75 IPDI correspond to 0.47 mol

• – 189,11 g entm. Wasser
• – 5,89 g 50 %ige NaOH (Überschuß von 10 % bezogen auf 105 g Präpolymer)
• – 113,42 g Präpolymer aus Stufe 1 (105 g theoretisch)

For 308.42 g batch (stage 2) the following weights were used:

• - 189.11 g entm. water
• 5.89 g 50% NaOH (excess of 10% based on 105 g prepolymer)
• 113.42 g prepolymer from stage 1 (105 g theoretical)

Method:

Step 1: 1. Original of PTHF 1000, D. XP 2501, Edenor C 8 98-100, DMPA and D.I. Begin: 0 min 2. Apply to vacuum 13 min 3. Start of the heating phase at 95 ° C 14 min Internal temperature = 95.0 ° C 49 min Internal temperature = 101.0 ° C 55 min Internal temperature = 102.3 ° C 61 min Aerated with nitrogen 69 min Internal temperature = 101.5 ° C NCO content = 1.92% 72 min 3rd batch was bottled and stored at 120 ° C. 77 min

Level 2:

• 1. presentation of entm. Water and caustic soda
• 2. Start of the heating phase at 85 ° C
• 3. Portionwise addition of the prepolymer from 85 ° C.
• 4. After the end of the addition of the prepolymer was at 2 hours 85 ° C stirred
• 5. Cool down to room temperature.

Remarks:

The prepolymer was at the filling temperature flowable.

The prepolymer let himself go disperse very well in the lye.

Results:

The The dispersion formed is opaque and homogeneous.

Of the Film is transparent and flexible.

Of the pH is 7.01.

The viscosity is about 70 mPa · s (Brookfield, spindle 6, 100 rpm, 20 ° C)

Of the Solid content is 36.50%.

• c) Ansatz (Basis Polytetrahydrofuran 1000, fettchemisches Polyesterdiol (Handelsname: Priplast 3192, Lieferant: Fa. Uniquema), Dimethylolpropionsäure (Bis-MPA), Caprylsäure bzw. Octansäure und Isophorondiisocyanat (IPDI)

The tensile shear strength of beech plywood is 3.81 N / mm ² (speed 50 mm / min.)

• c) batch (based on polytetrahydrofuran 1000, fat-chemical polyesterdiol (trade name: Priplast 3192, supplier: Fa. Uniquema), dimethylolpropionic acid (bis-MPA), caprylic acid or octanoic acid and isophorone diisocyanate (IPDI)

For 306.39 g batch (stage 1) the following weights were used: - 89.73 g of PTHF 1000 correspond to 0.10 mol - 89.73 g Priplast 3192 correspond to 0.04 mol - 28.34 g Edenor C 8 98-100 correspond to 0.20 mol - 28.34 g of DMPA correspond to 0.21 mol - 70.25 g IPDI equate to 0.32 mol

• – 188,63 g entm. Wasser
• – 6,37 g 50 %ige NaOH (Überschuß von 10 % bezogen auf 105 g Präpolymer)
• – 106,42 g Präpolymer aus Stufe 1 (105 g theoretisch)

For 301.42 g batch (stage 2) the following weights were used:

• - 188.63 g entm. water
• 6.37 g 50% NaOH (excess of 10% based on 105 g prepolymer)
• 106.42 g prepolymer from stage 1 (105 g theoretical)

Method:

Step 1: 1. Submission of PTHF 1000, Priplast 3192, Edenor C 8 98-100, DMPA and IPDI Begin: 0 min 2. Apply to vacuum 19 min 3. Start of the heating phase at 95 ° C 20 min Internal temperature = 95.0 ° C 49 min Internal temperature = 97.0 ° C 52 min Internal temperature = 99.2 ° C 56 min Internal temperature = 96.4 ° C 70 min Aerated with nitrogen 72 min Internal temperature = 91.2 ° C NCO content = 0.98% 90 min 3rd batch was bottled and stored at 120 ° C. 94 min

Level 2:

• 1. presentation of entm. Water and caustic soda
• 2. Start of the heating phase at 85 ° C
• 3. Portionwise addition of the prepolymer from 85 ° C.
• 4. After the end of the addition of the prepolymer was at 2 hours 85 ° C stirred
• 5. Cool down to room temperature

Remarks:

The prepolymer was at the filling temperature flowable.

The prepolymer let himself go disperse very well in the lye.

At the Dispergierprozeß occurred a strong increase in viscosity.

Results:

The The dispersion formed is opaque and homogeneous.

Of the Film is transparent and flexible.

Of the pH is 6.98.

The viscosity is 120 mPa · s (Brookfield, spindle 6, 100 rpm, 20 ° C).

Of the Solid content is 34.94%.

The tensile shear strength of beech plywood is 2.79 N / mm ² (speed 50 mm / min).

Example 2 (Comparative Example)

• a) Durchführung unter Verwendung von organischen Lösungsmitteln Ansatzgröße: 5362,84 g – 1 Mol Polyol (z.B. fettchemisches Polyesterdiol wie Priplast 3192 (CAS-Nummer: 171542-56-6, Lieferant:), Polyetherpolyole wie Polytetrahydrofuran (PTHF 1000), etc.)) und 2 Mol Dimethylolpropionsäure (DMPA) werden vorgelegt. Im Fall von Priplast 3192 würden dies 2003,57 g und von DMPA 268,28 g bedeuten. – Die Mischung wird in 2271,85 g 2-Butanon bzw. Ethylmethylketon (MEK) gelöst, dies entspricht 31,51 Mol. Natürlich können auch andere organische Verbindungen sprich konventionelle Lösungsmittel eingesetzt werden, diese dürfen allerdings nicht mit Isocyanaten reagieren. – Zusatz von 2,27 g Dibutylzinndilaurat als Katalysator, dies entspricht 0,006 Mol. – Die gesamte Mischung wird bei 60 °C homogenisiert. – Wenn die Mischung homogenisiert ist, werden innerhalb von 30 Minuten 638,59 g Isophorondiisocyanat (IPDI), dies entspricht 2,88 Mol, zugegeben. – Nach Beendigung der Zugabe des IPDI wird die Mischung für mindestens 12 Stunden bei 65 °C gerührt. – Nach den 12 Stunden werden dem Ansatz 178,28 g 2-(Dimethylamino)-ethanol, entspricht 2 Mol, zugesetzt und erneut 1 Stunde bei 65 °C gerührt. Das 2-(Dimethylamino)-ethanol dient zur Neutralisation des DMPA. – Anschließend wird zu dem Ansatz portionsweise entmineralisiertes Wasser hinzugegeben, bis der gewünschte Festkörper erreicht ist, z.B. 35 %. Dabei wird aus der Lösung eine Emulsion und schließlich eine Dispersion. – Zum Schluß wird unter vollem Vakuum und 40 °C per thermischen Trennverfahren z.B. mit Hilfe eines Dünnschichtverdampfers das eingesetzte organische Lösungsmittel, in dem Fall MEK, zurückgewonnen.
• b) Durchführung unter Verwendung eines sog. Hochsieders sprich N-Methyl pyrrolidin-2-on (NMP) Ansatzgröße: 5362,84 g – 0,36 Mol bzw. 726,13 g Polycaprolactondiol (Handelsname: Capa 2200, Lieferant: Fa. Solvay) und 0,08 Mol bzw. 241,86 g Polycaprolactondiol (Handelsname: Capa 2302, Lieferant: Fa. Solvay) werden bei 65 °C aufgeschmolzen und vorgelegt. – Zu der Mischung werden 1,28 Mol DMPA sprich 171,61 g hinzugegeben und gelöst – Nach dem Lösen des DMPA werden 4,85 Mol N-Methylpyrrolidin-2-on sprich 481,05 g hinzugegeben und homogenisiert. – Nach Homogenisierung werden 0,04 Mol 4,4'-Butyliden-bis-(6-tert-butyl-m-kresol) sprich 16,09 g (Handelsname: Santowhite BBMC, Lieferant: Flexsys Co) hinzugegeben und homogenisiert. Das Produkt dient als Antioxidationsmittel und erhöht die Temperaturstabilität der Dispersion. – Zusatz von 2,27 g Dibutylzinndilaurat als Katalysator, dies entspricht 0,006 Mol. – Wenn die Mischung homogenisiert ist werden innerhalb von 30 Minuten 3,26 Mol IPDI sprich 723,44 g zugegeben. – Nach Beendigung der Zugabe des IPDI wird die Mischung für mindestens 12 Stunden bei 65 °C gerührt. – Nach den 12 Stunden werden dem Ansatz 1,28 Mol 4-Methylmorpholin (NMM) sprich 129,24 g zugesetzt und erneut 1 Stunde bei 65 °C gerührt. Das NMM dient zur Neutralisation des DMPA. – Anschließend werden zu dem Ansatz 158,70 Mol sprich 2856,77 g entmineralisiertes Wasser portionsweise hinzugegeben und erneut 1 Stunde bei 65 °C gerührt. – Zu Stabilisierung der Dispersion werden 0,41 Mol 25 % ige Ammoniaklösung sprich 14,37 g zugesetzt und homogenisiert.

The following comparative example is intended to illustrate the current state of the art:

• a) Carrying out using organic solvents Batch size: 5362.84 g - 1 mol of polyol (eg oleochemical polyester diol such as Priplast 3192 (CAS number: 171542-56-6, supplier :), polyether polyols such as polytetrahydrofuran (PTHF 1000), etc. )) and 2 moles of dimethylolpropionic acid (DMPA) are presented. In the case of Priplast 3192 this would mean 2003.57 g and of DMPA 268.28 g. - The mixture is dissolved in 2271.85 g of 2-butanone or ethyl methyl ketone (MEK), this corresponds to 31.51 mol. Of course, other organic compounds that is conventional solvents can be used, but they must not react with isocyanates. - Addition of 2.27 g of dibutyltin dilaurate as a catalyst, this corresponds to 0.006 mol. - The entire mixture is homogenized at 60 ° C. - If the mixture is homogenized, 638.59 g of isophorone diisocyanate (IPDI), which corresponds to 2.88 mol, added within 30 minutes. - After completion of the addition of IPDI, the mixture is stirred for at least 12 hours at 65 ° C. After the 12 hours, 178.28 g of 2- (dimethylamino) ethanol, equivalent to 2 mol, are added to the mixture and stirred again at 65 ° C. for 1 hour. The 2- (dimethylamino) ethanol serves to neutralize the DMPA. - Subsequently, to the approach in portions demineralized water is added until the desired solids is reached, for example, 35%. This solution becomes an emulsion and finally a dispersion. - Finally, under full vacuum and 40 ° C by thermal separation process, for example with the aid of a thin-film evaporator, the organic solvent used, in the case of MEK, recovered.
• b) Carrying out using a so-called high boiler, ie N-methylpyrrolidin-2-one (NMP) batch size: 5362.84 g - 0.36 mol or 726.13 g polycaprolactone diol (trade name: Capa 2200, supplier: Solvay ) and 0.08 mol or 241.86 g of polycaprolactone diol (trade name: Capa 2302, supplier: Fa. Solvay) are melted at 65 ° C and submitted. - To the mixture, 1.28 mol DMPA say 171.61 g are added and dissolved - After dissolving the DMPA 4.85 mol of N-methylpyrrolidin-2-one say 481.05 g are added and homogenized. After homogenization, 0.04 mol of 4,4'-butylidenebis (6-tert-butyl-m-cresol), ie 16.09 g (trade name: Santowhite BBMC, supplier: Flexsys Co), are added and homogenized. The product serves as an antioxidant and increases the temperature stability of the dispersion. - Addition of 2.27 g of dibutyltin dilaurate as a catalyst, this corresponds to 0.006 mol. - When the mixture is homogenized, 3.26 moles of IPDI, ie 723.44 g, are added within 30 minutes. - After completion of the addition of IPDI, the mixture is stirred for at least 12 hours at 65 ° C. After the 12 hours, 1.28 mol of 4-methylmorpholine (NMM), ie 129.24 g, are added to the mixture and stirred again at 65 ° C. for 1 hour. The NMM serves to neutralize the DMPA. - Subsequently, to the batch 158.70 moles say 2856.77 g of demineralized water are added in portions and stirred again at 65 ° C for 1 hour. - To stabilize the dispersion 0.41 mol of 25% ammonia solution say 14.37 g are added and homogenized.

Results:

The The dispersion formed is homogeneously transparent and shows a brownish / bluish color.

Of the Film is thinner Layer thickness transparent.

Of the pH is 8.50.

Of the Solid content is 32.0%.

The tensile shear strength of beech plywood is 7.50 N / mm ² (speed 50 mm / min).

Claims (16)

Aqueous polyurethane dispersion containing as binder a salt of a polyurethane which is a reaction product a) at least one aliphatic polyisocyanate, b) at least one polyol and c) at least one dihydroxy-functional carboxylic acid, characterized in that the polyurethane as a further structural component d) a saturated monocarboxylic acid Contains 4 to 18 carbon atoms, which has no further functional groups except the acid group. Polyurethane dispersion according to claim 1, characterized in that that the Monocarboxylic acid Contains 4 to 10 carbon atoms. Polyurethane dispersion according to claim 1 or 2, characterized characterized in that Monocarboxylic acid in a proportion of 18 to 26 mol% in the polyurethane is. Polyurethane dispersion according to claim 1 to 3, characterized characterized in that Polyisocyanate has a molecular weight of 168 to 262 daltons and a NCO functionality of 1.8 to 2.2. Polyurethane dispersion according to claim 1 to 4, characterized characterized in that Polyisocyanate is isophorone diisocyanate (IPDI). Polyurethane dispersion according to claim 1 to 5, characterized characterized in that dihydroxyfunctional carboxylic acid dimethylolpropionic is. Polyurethane dispersion according to claim 1 to 6, characterized characterized in that they the salt of the polyurethane in a proportion of 20 to 60 wt .-% based on the total weight of the dispersion. Polyurethane dispersion according to claim 1 to 7, characterized characterized in that they the salt of the polyurethane optimally in a proportion of 30 to 40 Wt .-% based on the total weight of the dispersion. Polyurethane dispersion according to claim 1 to 8, characterized characterized in that Dispersion free from volatile Connections and high-boilers is. A process for preparing a polyurethane dispersion according to claim 1 to 9, characterized in that a) at least one aliphatic polyisocyanate, b) at least one polyol, c) at least one dihydroxy-functional carboxylic acid and d) reacting a saturated monocarboxylic acid having 4 to 18 carbon atoms to give a polyurethane and processing the resulting product with an aqueous solution of a base to form an aqueous dispersion. Method according to claim 10, characterized in that that a) 35 to 45 mol% polyisocyanate, b) 15 to 19 mol% polyol, c) 20 to 25 mol% dihydroxy-functional carboxylic acid and d) 18 to 26 mol% saturated Monocarboxylic acid be implemented together. Method according to claim 10 or 11, characterized that one Monocarboxylic acid is used with 4 to 10 carbon atoms. Method according to claim 10 to 12, characterized the existence Polyisocyanate having a molecular weight of 168 to 262 daltons and an NCO functionality from 1.8 to 2.2 is implemented. Method according to claims 10 to 13, characterized that as Polyisocyanate isophorone diisocyanate (IPDI) is implemented. Method according to Claims 8 to 14, characterized that as dihydroxyfunctional carboxylic acid dimethylolpropionic is implemented. Use of the polyurethane dispersions according to claim 1 to 9 as an adhesive, as a binder for paints, as a sealant in building protection and for the sealing of wooden surfaces and generally as a coating agent.