DE4219964A1 - Stable aq. polyurethane dispersions for coating textiles etc. - contg readily dispersible oligo:urethane-bis:biurets made from di:isocyanate, poly:ol, ionic chain extender and urea - Google Patents

Abstract

The prodn. of stable aq. polyurethane (PY) dispersions (I) from oligourethane-bis-biurets (II) comprises (A) synthesis of hydrophilically (ionically) modified (II) from polyols, opt. low-mol. wt. diols, ionic chain extenders, isocyanate components (pref. contg. diisocyanates or mixts. thereof with poly- and/or mono-isocyanates) and urea, (B) dispersing the solid (II) in water and (C) chain extension and/or crosslinking to give (I). Stage (A) is carried out continuously in a screw extruder, by introducing all the above components except urea at a first inlet (1) and reacting them in the first section to form a NCO prepolymer, then adding urea via a second inlet (2). The distance L2 between inlets 1 and 2 is between L1/1.6 and L1/3.0, where L1 is the distance from inlet 1 to the discharge point, and the residence time in the extruder (w.r.t. screw length L1) is 2-5 mins.. Pref. the 2-5 mins. residence time is obtd. by varying the screw speed from 200 to 350 (pref. 270-310) r.p.m. or by varying the extruder geometry L/D from 30-50, pref. at least 35 (with L = screw length; D = screw dia.). USE/ADVANTAGE - For the prodn. of crosslinked coatings on substrates, either alone or in combination with other solns. and/or dispersions and/or other addns. of reactive and/or unreactive cpds. (claimed). The process enables the continuous prodn. of hydrophilically modified (II); these modified oligourethanebis-biurets are spontaneously dispersible in water (with suitable additives), to give stable, homogeneous, film-forming dispersions which are useful, e.g. for the prodn. of PU-coated industrial textiles, tarpaulins, clothing, bags etc..

Description

The invention relates to a method for producing stable aqueous polyurethane dispersions from oligourethane bisbiureten, covering the steps

• A) Synthesis of hydrophilic (ionogenic) modified oligoure thanbisbiuret from polyols, optionally low molecular weight laren diols, ionogenic chain extenders, iso- cyanate component, preferably diisocyanates alone or in a mixture with polyisocyanates and / or monofunk ionic isocyanates, and urea,
• B) Dispersing the oligoure present in solid form thanbisbiurets in water and
• C) chain extension and / or crosslinking reactions aqueous polyurethane dispersions.

The invention further relates to the use of the receive NEN aqueous polyurethane dispersions for the production of cross-linked fabrics on a substrate.

Aqueous polyurethane dispersions based on oligourethane bisbiuretes are because of their wide range of applications of great interest.

It is known to have a solid, hydrophilic (mostly ionic) mode to produce a protected NCO group-free oligourethane bisbiuret len, disperse in water and over a polycondensate chain reaction to extend. Such spontaneous solids pergier processes are described in DE-C 25 43 091, DE-A 27 21 985 and NL-A 7 614 550.

According to DE-A 28 48 431, an OH-terminated ionogenic modifi decorated oligourethane in solid state dissolved in water and possibly crosslinked with diisocyanates or formaldehyde.  

The preparation of an aqueous dispersion or solution of Oligourethanes according to the butanone oxime process describes the DE-A 28 27 156. After solidification, the reaction product from ionogenically modified NCO prepolymer and butanone oxime in Water can be dispersed.

According to DE-A 30 27 198, a solidified ionogenic is modified tes NCO prepolymer dispersed in water. The chain extensions It is made with water and / or diamine. This method is a combination of the prepolymer-ionomer mixing process with the solid spontaneous dispersion method.

It is unsatisfactory that the Oligourethane after these ver drive be produced discontinuously. In the DE-A 28 48 431 is also on the possible use of continuously operating reaction screws or tubes referenced, but there are no dispersions, but Solutions obtained due to the lack of the polyol compo not in the polyurethane synthesis recipe to film with dry up good mechanical properties. Besides, is from the examples it can be seen that this is always discontinuous was worked in a low-heated stirred tank.

There is still no known method in which continuous a hydrophilic (ionogenic) modified oligourethane bisbiuret, consisting of polyols, optionally low mo molecular diols, ionogenic chain extenders, iso cyanate component and urea, can be synthesized, which is dispersible in solid form in water and by subsequent chain extension and / or crosslinking craze to implement such aqueous polyurethane dispersions bar, the dried films of which are highly mechanical Show property level.

The invention was therefore based on the object, aqueous poly To produce urethane dispersions, which are used for dispersion used hydrophilically modified oligourethane bis biurete should be maintained continuously.  

This object is achieved in that the Production of this oligourethane bisbiurete continuously a screw extruder, with a special Reaction management is to be observed.

The invention thus relates to a method for producing setting up stable aqueous polyurethane dispersions Base of oligourethane bisbiuretes, comprising the steps

• A) Synthesis of hydrophilic (ionogenic) modified oligoure thanbisbiuret from polyols, optionally low molecular weight laren diols, ionogenic chain extenders, iso cyanate components, preferably diisocyanates alone or in a mixture with polyisocyanates and / or monofunk ionic isocyanates, and urea,
• B) Dispersing the oligoure present in solid form thanbisbiurets in water and
• C) chain extension and / or crosslinking reactions to aqueous polyurethane dispersions, characterized in that step A is carried out continuously in a screw extruder, with polyols, optionally low molecular weight diols, ionogenic chain extenders and isocyanate component first being fed into a first opening and in a first Reaction route to an NCO prepolymer, then urea is added in a second opening, the second feed opening being at a distance L ₂ between L ₁ / 1.7 and L ₁ / 3.0 from the first feed opening, where L _{1 is} the screw length from the first feed opening to the discharge, and the residence time in the extruder, based on the screw length L ₁ , is 2 to 5 minutes.

The invention further relates to the use of obtained aqueous polyurethane dispersions for production of networked fabrics on a substrate.

For the production of the hydrophilically modified oligourethane bis The following components are suitable for biurets:

• a) as isocyanates organic diisocyanates, for. B. aliphati cal diisocyanates, such as hexamethylene diisocyanate or iso phorone diisocyanate, or aromatic diisocyanates, e.g. B. 4,4'-diphenylmethane diisocyanate, optionally in Ge mix with smaller portions of more functional polyiso cyanates, e.g. B. polymeric diphenylmethane diisocyanate, and / or monofunctional isocyanates, e.g. B. phenyl isocyanate;
• b) as polyols, for example polyester alcohols on the Basis of adipic acid and diols, e.g. B. 1,4-butanediol or 1,6-hexanediol, with a molecular weight of 500 to 5000 g / mol, different diols in one polyester Molecule can be included, or polyether alcohols based on tetrahydrofuran, ethylene oxide or Propylene oxide with a molecular weight of 500 to 5000 g / mol;
• c) as low molecular weight diols, for example ethanediol-1,2 or 1,4-butanediol;
• d) as an ionogenic chain extender, for example 2,2-dimethylolpropionic acid or methyldiethanolamine;
• e) urea.

So far, the continuous synthesis of the necessary io not modified oligourethane bisbiurete on a Schnec ken extruder due to technological reasons for not feasible.

For the process according to the invention, a twin-screw reaction extruder with an L / D ratio, where L is the screw length and D is the screw diameter, of 30 to 50, preferably 35, is usually used in order to guarantee an average residence time of between 2 and 5 minutes The required dwell time of 2 to 5 minutes, based on the screw length L ₁ from the first feed opening to the discharge, is, with a preselected L / D ratio, by suitable selection of the speed of the screws from 200 to 350, preferably 270 to 310 RPM varies. The mass temperature is maintained via separately controllable heating / cooling zones, depending on the raw materials used, between 80 and 250 ° C, preferably between 170 and 230 ° C, so that the complete poly addition reaction takes place and a practical removal of the oligomer at the extruder nozzle is ensured .

Preferably, a co-rotating twin screw extruder, the dosing devices at at least two different points has used. All raw materials are known ter way continuously, for example via heated Do. dosing pumps in liquid or with dosing scales with shaking channel in the solid state, dosed. The components ten a) to d) at the beginning of the reaction screw in the first Opening fed. Components b) to d) can be ge can be metered in together as a solution or mixture.

It is essential to the invention that the urea for converting the NCO prepolymer already formed to the oligourethane bis biuret is not dosed at the beginning of the screw with the other components, but is only metered in in a second opening, the second feed opening being at a distance L from the first feed opening _{2 is located} between L ₁ / 1.7 and L ₁ / 3.0.

The cooled, solid oli discharged from the extruder Gourethanbisbiurete are after appropriate crushing without major shear forces and without an external emulsifier in what dispersed.

Acids or bases are usually used as the dispersing medium to activate the potential ionogenic groups in the oil gourethanbisbiuret through salt formation and chain extensions tion and / or crosslinking agent added.

The oligourethane bisbiurets are surprisingly full ongoing polyaddition reaction in the reaction extrusion that spontaneously disper in water with appropriate additives greedable. The dispersions are homogeneous, stable and film-sized dend.

The aqueous polyurethane dispersions obtained become Production of networked fabrics on a sub strat, such as B. of polyurethane-coated textiles for technical applications, tarpaulins, clothing and bags nerware used. You can mix with others Solutions and / or dispersions and / or other additives  reactive and / or further additions of non-reactive verb applications are processed.

The invention is illustrated by the following examples purifies:

Examples

The synthesis was carried out on a laboratory reaction extruder two snails.

Raw materials:
MDI
4,4′-diphenylmethane diisocyanate in a purity of 99.5%
Freezing point 37.5 ° C
Polyol
linear polyester based on adipic acid and ethylene glycol
OH number = 40 mgKOH / g
average molar mass = 2800 gmol- ¹
Acid number = 1 mg KOH / g
Water content = 0.07%
Viscosity at 75 ° C = 850 mPas

BD-1.4 butanediol-1.4
DMPS dimethylol propionic acid (2,2-bis (hydroxymethyl) propionic acid
HST urea (carbonic acid diamide)

Extruder regime:
L / D = 35
MDI (liquid), polyol and DMPS or BD-1.4 (for the comparison test) were dosed in the mixture into the first feed opening at the beginning of the screw by means of metering pumps. The urea was added via a weigh feeder with a vibrating chute to the second feed opening for worm location L ₂ = _L1 / 2. The throughput was 11 l · h ^-1 .

The oligourethane bisbiuret obtained after solidification crushed and to 15 wt .-% aqueous dispersions with dispersed in a laboratory stirrer (a-sample). For this purpose, in Example 2 17.72 g of 5% ammonia water with 549.28 g of the  tilled water and in example 3 19.25 g 5% ammo niakwasser with 547.75 g of distilled water each 567 g of basic water mixed. This was followed by 100 g of oligourethane bisbiuret stirred in, with salt bil The dispersion took place.

Table 1 shows the synthesis approaches for Examples 1 to 3 listed.

Example 1 (comparative example)

The Oligourethanbisbiuret was due to the failure hydrophilic-ionic modification not disper in water greedable.

Example 2

The oligourethane bisbiuret spontaneously formed dispersions (a sample) in the basic water. In this oligomer dispersion, 1.5 mol of formaldehyde (as a 37% strength aqueous solution) per mol of biuret end group was slowly added to the chain extension with stirring (b sample). 8.24 ml of the 37% formalin solution (ρ = 1.09 g / cm ³ ) were required for the 667 g of the 15% dispersion. Part of this aqueous polyurethane dispersion mixed with formaldehyde was stirred at 70 ° C. for 12 hours (c-sample). From the finely divided stable aqueous polyurethane dispersions (b and c) obtained in this way and from the a sample, approximately 500 μm thick films were drawn and dried at room temperature.

The films determined:
1. The tensile strength δ _H at maximum force or δ _R when tearing and the corresponding elongation values ε _H or ε _R on film strips of dimensions 10 mm × 100 mm according to DIN 53 455.
2. The water absorption on film discs with a diameter of 50 mm according to DIN 53 495.

Example 3

The procedure was analogous to that of Example 2, with 8.65 ml of the 37% formalin solution (ρ = 1.09 g / cm ³ ) being required for the 667 g of the 15% dispersion. The composition is shown in Table 1.

The results of the test are summarized in Table 2 poses. The mean ones determined by electron microscopy Particle diameters of the dispersions are between 0.1 and 0.5 µm.

Table 2: Test results

Claims (6)

1. Process for the preparation of stable aqueous poly urethane dispersions from oligourethane bisbiuretes to comprehensively the steps

• A) synthesis of hydrophilically (ionically) modified oligourethane bisbiuret from polyols, optionally low molecular weight diols, ionogenic chain extenders, isocyanate component, which preferably contains diisocyanates alone or in a mixture with polyisocyanates and / or monofunctional isocyanates, and urea,
• B) dispersing the solid oligourethane bisbiuret in water and
• C) chain extension and / or crosslinking reactions to give aqueous polyurethane dispersions,

characterized in that step A is carried out continuously in a screw extruder, polyols, optionally low molecular weight diols, ionogenic chain extender and isocyanate component being fed first in a first opening and converted in a first reaction zone to an NCO prepolymer, then in one second opening urea is added, the second feed opening being at a distance L ₂ between L ₁ / 1.7 and L ₁ / 3.0 from the first feed opening, L _{1 being} the screw length from the first feed opening to the discharge, and the residence time in the extruder, bezo gene on the screw length L _1, 2 to 5 minutes. 2. The method according to claim 1, characterized in that the residence time of 2 to 5 minutes by varying the Speed of the screws from 200 to 350, preferably 270 up to 310 rpm.   3. The method according to claim 1, characterized in that the residence time of 2 to 5 minutes by varying the Extruder geometry L / D, where L is the screw length and D mean the screw diameter, from 30 to 50, before preferably 35, is achieved. 4. Use of the aqueous obtained according to claim 1 Polyurethane dispersions for the production of cross-linked Sheets on a substrate. 5. Use of the aqueous polyurethane dispersions according to Claim 4, characterized in that this alone or in a mixture with other solutions and / or Dispersions and / or other additives of reactive and / or other additives of non-reactive compounds be set.