WO2005097858A1 - Process for preparing aqueous polyurethane dispersions - Google Patents

Process for preparing aqueous polyurethane dispersions Download PDF

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Publication number
WO2005097858A1
WO2005097858A1 PCT/EP2005/050504 EP2005050504W WO2005097858A1 WO 2005097858 A1 WO2005097858 A1 WO 2005097858A1 EP 2005050504 W EP2005050504 W EP 2005050504W WO 2005097858 A1 WO2005097858 A1 WO 2005097858A1
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Prior art keywords
polyurethane
hydroxymethyl
polyols
polyhydroxy
preparing
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PCT/EP2005/050504
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French (fr)
Inventor
Matthias Orschel
Wolfgang Sasse
Lutz Mindach
Klaus-Peter Jonderko
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Degussa Ag
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Publication of WO2005097858A1 publication Critical patent/WO2005097858A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/0838—Manufacture of polymers in the presence of non-reactive compounds
    • C08G18/0842—Manufacture of polymers in the presence of non-reactive compounds in the presence of liquid diluents
    • C08G18/0861—Manufacture of polymers in the presence of non-reactive compounds in the presence of liquid diluents in the presence of a dispersing phase for the polymers or a phase dispersed in the polymers
    • C08G18/0866—Manufacture of polymers in the presence of non-reactive compounds in the presence of liquid diluents in the presence of a dispersing phase for the polymers or a phase dispersed in the polymers the dispersing or dispersed phase being an aqueous medium
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step

Definitions

  • the invention relates to a process for preparing aqueous polyurethane dispersions.
  • the process, or individual steps thereof, is or are carried out in static mixers.
  • Stable aqueous polyurethane dispersions are used for example for one-component, isocyanate- free coating materials, coatings, sealants, adhesives and membranes. Their significance has been increasing continually for years for reasons of ecology (environmental compatibility, workplace safety) and economics. The viscosity and the rheology are independent of the molar mass, which can be adjusted over a wide range. In addition to these advantages these low- solvent or solvent-free products already correspond in terms of their application opportunities largely to their solventborne counterparts.
  • Aqueous polyurethane dispersions are composed of polyurethane polymers or polyurethane- polyurea polymers, which contain not only urethane groups but also urea groups and are obtainable by polyaddition reactions from polyols, polyisocyanates and polyamines.
  • polyurethane prepolymers are prepared which are then dispersed in the aqueous phase and chain-extended with poly ⁇ -mines to build the polyurethane- polyurea polymers.
  • anionic, cationic and nonionic polyurethane dispersions according to the type of hydrophilic group which ensures the stabilization of the polyurethane prepolymer in the aqueous phase. These hydrophilic groups are incorporated into the prepolymer by way of suitable, modified polyols.
  • aqueous polyurethane dispersions The preparation of aqueous polyurethane dispersions has been known for many years and is described in detail in a large number of publications (Houben-Weyl, Methoden der organischen Chemie, Volume E 20, Part I; Ullmann's Encyclopedia of Industrial Chemistry, Release 2003, 7th Edition, Wiley-NCH; Adv. Urethane Sci. Technol. 10 (1987), 121-187; DE 198 12 751; DE 199 57 604; WO 96/40811; US 2002/0028877 etc.). Within the art the Acetone Process, the Prepolymer Mixing Process and the Melt Emulsification Process have acquired the greatest significance. Generally speaking, the dispersions are prepared batchwise in stirred tanks.
  • aqueous polyurethane dispersions can also be prepared by dispersing polyurethane prepolymers having an isocyanate content of ⁇ 12% by mass in static mixers.
  • the viscosities required are set by appropriate temperature adjustment and/or by the use of an auxiliary solvent.
  • a further advantage of the process of the invention is the fact that in the course of ongoing production of the polyurethane dispersions it is still possible to make corrections to the reaction conditions and so to effect fine tuning or else a change of product (adjustment of particle size, for example, through the degree of neutralization or solids content), which in the case of batchwise production is possible only from one batch to the next.
  • the invention provides a process for preparing aqueous polyurethane dispersions which comprises dispersing polyurethane prepolymers having an isocyanate content of ⁇ 12% by mass in water in a static mixer.
  • polyurethane prepolymer it is preferred to use an anionic (a) or cationic (b) hydrophiHcally modified and neutralized polyurethane prepolymer or a polyurethane prepolymer which has been hydrophilically modified by way of nonionic (c) groups. It is also possible to use mixtures of these prepolymers a) to c).
  • the polyurethane prepolymers a) to c) can be prepared by any desired methods. Likewise possible is the preparation of the polyurethane prepolymers a) and b) in a separate static mixer prior to dispersing with the aqueous component. In that case a suitable anionically (a) or cationicaUy (b) modifiable polyurethane prepolymer is reacted with a neutralizing component, prior to dispersing in a static mixer, for partial or complete neutralization, to form the dispersible polyurethane prepolymer, which is said to have been modified.
  • the dispersed polyurethane prepolymer obtained in accordance with the invention is subsequently, if desired, reacted with a chain extender component, likewise in a static mixer or conventionally, by a prior art method, to form the finished polyurethane dispersion.
  • an auxiliary solvent is added for adjusting the viscosity of the polyurethane prepolymer.
  • Anionically or cationicaUy modifiable (i.e., non-neutralized) or nonionically modified polyurethane prepolymers suitable for the process of the invention are known from the literature (see above) and are prepared by polyaddition reactions of polyols and polyisocyanate components and, if desired, auxiliary solvents and/or catalysts.
  • Polymeric and/or monomeric polyols which have two or more polyisocyanate-reactive hydroxyl groups, such as polyester polyols, polyether polyols, polyhydroxy polycarbonates, polyhydroxy polyacetals, polyhydroxy polyacrylates, polyhydroxy polyesteramides, polyhydroxy polyfhioethers, polyatkylene polyols, polyhydroxy polycaprolactones, vinyl-modified polyether polyols, macromonomeric polyols, techelenes or polyhydroxy epoxy resins or mixtures thereof and/or all low molecular mass polyols such as 1,2-ethanediol, 1,2-propanediol, 1,2-propylene glycol,
  • polyisocyanate-reactive hydroxyl groups such as polyester polyols, polyether polyols, polyhydroxy polycarbonates, polyhydroxy polyacetals, polyhydroxy polyacrylates, polyhydroxy polyesteramides, polyhydroxy polyfhioethers, polyatkylene polyols, polyhydroxy polycaprolactones
  • polyisocyanate components are polyisocyanates, polyisocyanate derivatives or polyisocyanate homologs containing two or more aliphatic, cycloaliphatic or aromatic isocyanate groups.
  • Particularly suitable are the polyisocyanates which are adequately known in polyurethane chemistry, or combinations thereof, such as 1,4-diisocyanatobutane, 1,6-d ⁇ socyanatohexane (HDI), 1,12-diisocyanatododecane, l,4-d ⁇ socy_ ⁇ natocyclohexane, 1- isocyanato-5-isocyanatomethyl-3,3,5-trimethylcyclohexane (IPDI), bis(4-isocyanatocyclo- hexyl)methane (H ⁇ 2 MDI), l,3-bis(l-isocyanato-l-methyl)benzene (XDI), l,3-bis(l-isocyana
  • Compounds which are used that have an anionically, cationicaUy and/or nonionically dispersing action are those containing, for example, carboxylate, sulfonate, phosphonate, sulfonium, ammonium or phosphonium groups or groups which can be converted into the aforementioned groups by salt formation (referred to as anionically or cationicaUy modifiable groups/compounds), and/or polyether groups (referred to as nonionically emulsifiable groups), and which can be incorporated into the prepolymers by means of existing isocyanate-reactive groups, and having two or more polyisocyanate-reactive groups, such as compounds containing OH and/or NH 2 groups, for example.
  • Representatives of these compounds are, for example, 2-hydroxymethyl-3-hydrox propanoic acid, 2-hydroxymethyl-2-methyl-3- hydroxypropanoic acid, 2-hydroxymethyl-2-ethyl-3-hydroxypropanoic acid, 2-hydroxymethyl- 2-propyl-3-hydroxypropanoic acid, citric acid, tartaric acid, alanine, taurine, 2-amino- ethylarninoethanesulfonic acid, polyethylene glycols, polypropylene glycols and polybutylene glycols prepared starting from alcohols, the block copolymers and monomethyl ethers of these polyglycols, and all polymeric polyols modified accordingly.
  • auxiliary solvents are inert solvents which possess no miscibility gap with water over wide ranges, such as N-methylpyrrolidone, n-butyl glycol, di-n-butyl glycol, acetone, methyl ethyl ketone or tetrahydrofuran, for example.
  • the neutralizing component used for anionicaUy modifiable polyurethane prepolymers comprises bases, examples being tertiary amines such as N,N- limethylethanolam_ne, N- methyldiethanolan_ine, triet__anol--r__ine, N,N-dimemyUsopropanol-tmine, N-methyldiiso- propanolamine, t__usopropylamine, N-metih.ylmorpholine, N-ethylmo holine, triethylamine or ammonia, for example, or alkati metal hydroxides such as lithium hydroxide, sodium hydroxide or potassium hydroxide, for example.
  • bases examples being tertiary amines such as N,N- limethylethanolam_ne, N- methyldiethanolan_ine, triet__anol--r__ine, N,N-dimemyUsopropano
  • cationicaUy modifiable polyurethane prepolymers use is made of corresponding acids, such as formic acid, acetic acid, propionic acid, sulfuric acid, dimethyl sulfate or succinic acid, for example.
  • acids such as formic acid, acetic acid, propionic acid, sulfuric acid, dimethyl sulfate or succinic acid, for example.
  • nonionicaUy modified polyurethane prepolymers there is no neutralization step.
  • the chain extender component used comprises polyamines containing two or more polyisocyanate-reactive amino groups.
  • suitable polyamines include adipic dihydrazide, ethylenedi-unine, diethylenetriamine, triethylenetetramine, tettaethylenepent ⁇ tmine,.
  • aU of the mass flows, reaction temperatures, residence times and the individual static mixers are harmonized with one another so as to ensure optimum commixing and reaction times.
  • a non-neutraUzed anionicaUy or cationicaUy modifiable polyurethane prepolymer is pumped from a reservoir continuously into the static mixer.
  • a neutralizing agent is pumped, again continuously, into the static mixer, in which it is mixed with the prepolymer and at the same time neutralizes the anionically or cationicaUy modifiable groups to form hydrophiUc, ionic groups.
  • the resultant modified or neutralized polyurethane prepolymer is subsequently dispersed in a further static mixer in water, which is pumped continuously from a third reservoir again into the second static mixer.
  • the polyurethane dispersion with a free isocyanate group content required for the subsequent chain extension, passes into a third static mixer.
  • the chain extender which if desired may be in the form of an aqueous solution, is metered continuously into the third static mixer. This is where chain extension takes place.
  • the finished, stable polyurethane dispersion can be dispensed directly into reservoirs or processed further or applied.
  • a polyurethane prepolymer which is not hydrophiUcally modified by way of nonionic groups (i.e., a nonionicaUy modified polyurethane prepolymer, as it is caUed)
  • the neutralization step disappears.
  • a non-neutralized, anionically or cationicaUy modifiable polyurethane prepolymer is neutralized and dispersed with a neutra zing agent/water mixture in one step.
  • it is not essential that aU of the steps of the process are carried out continuously in static mixers. It is also not essential whether aU of the steps of the process are carried out in two or more mixers or in only one static mixer.
  • AU that is essential to the invention is the dispersing of the polyurethane prepolymer in a static mixer, said prepolymer having an NCO content of ⁇ 12% by mass prior to dispersing.
  • polyurethane dispersions are prepared which have an NCO content of ⁇ 12% by mass, but preferably ⁇ 5% by mass, very preferably ⁇ 0.5% by mass.
  • a stirred tank is charged with 2400 g of N-methylpyrrolidone, 500 g of dimethylolpropionic acid, 5500 g of Oxyester T 1136 (manufacturer: Degussa) and 135 g of trimethylolpropane and this initial charge is heated to 60°C. Subsequently a solution of 5 g of dibutyltin laurate in
  • the prepolymer thus prepared possesses a viscosity of 7100 mPas at 50°C and an acid number of 21.9 g KOH/g.
  • 300 g of the prepolymer from Example 1 are neutralized in a stirred tank (toothed disk with a peripheral speed of approximately 10 m/s) at 50°C with 10 g of triethylamine (added over the course of 15 s, after-reaction time 15 s) and dispersed by adding 400 g of water (added over the course of 40 s, after-reaction time 15 s).
  • This is foUowedby chain extension with 70 g of a 10% strength solution of ethylenediamine in water.
  • the dispersion obtained has a pH of 8.0, a sohds content of 32.2% (dried at 150°C for 1.5 h) and a viscosity of 33 mPas at 20°C.
  • the prepolymer from Example 1 is pumped from a reservoir at 50°C with a volume flow of 150 gmin into a static mixer (SMX mixer from Sulzer; residence time 0.3 min) and mixed with 5 g/min of triethylamine from a second reservoir.
  • the neutraUzed prepolymer is then dispersed in a further static mixer (SMX mixer from Sulzer; residence time 0.7 min) with a water stream of 200 g/min from a third reservoir, and then subjected to chain extension in a third static mixer (SMXL mixer from Sulzer; residence time 1.2 min) from a fourth reservoir with 35 g/min of a 10% strength solution of ethylenediamine in water.
  • the dispersion obtained has a pH of 8.4, a solids content of 31.7% and a viscosity of 29 mPas at 20°C and is therefore comparable with the conventionally prepared dispersion from Example 2.

Abstract

The invention relates to a process for preparing water-based polyurethane dispersions. The process, or individual steps thereof, is or are carried out in static mixers.

Description

Process for preparing aqueous polyurethane dispersions
The invention relates to a process for preparing aqueous polyurethane dispersions. The process, or individual steps thereof, is or are carried out in static mixers.
Stable aqueous polyurethane dispersions are used for example for one-component, isocyanate- free coating materials, coatings, sealants, adhesives and membranes. Their significance has been increasing continually for years for reasons of ecology (environmental compatibility, workplace safety) and economics. The viscosity and the rheology are independent of the molar mass, which can be adjusted over a wide range. In addition to these advantages these low- solvent or solvent-free products already correspond in terms of their application opportunities largely to their solventborne counterparts.
Aqueous polyurethane dispersions are composed of polyurethane polymers or polyurethane- polyurea polymers, which contain not only urethane groups but also urea groups and are obtainable by polyaddition reactions from polyols, polyisocyanates and polyamines. First, from the polyols and the polyisocyanates, polyurethane prepolymers are prepared which are then dispersed in the aqueous phase and chain-extended with poly∑-mines to build the polyurethane- polyurea polymers. A distinction is made between anionic, cationic and nonionic polyurethane dispersions, according to the type of hydrophilic group which ensures the stabilization of the polyurethane prepolymer in the aqueous phase. These hydrophilic groups are incorporated into the prepolymer by way of suitable, modified polyols.
The preparation of aqueous polyurethane dispersions has been known for many years and is described in detail in a large number of publications (Houben-Weyl, Methoden der organischen Chemie, Volume E 20, Part I; Ullmann's Encyclopedia of Industrial Chemistry, Release 2003, 7th Edition, Wiley-NCH; Adv. Urethane Sci. Technol. 10 (1987), 121-187; DE 198 12 751; DE 199 57 604; WO 96/40811; US 2002/0028877 etc.). Within the art the Acetone Process, the Prepolymer Mixing Process and the Melt Emulsification Process have acquired the greatest significance. Generally speaking, the dispersions are prepared batchwise in stirred tanks. In that case the prepolymer is prepared in one tank and where appropriate the neutralization, the dispersing and the chain extension are carried out in the same tank or in a second tank. A disadvantage of these batchwise operations is that for industrial production large stirred tanks with powerful stirrer mechanisms are required in order to apply the high shearing forces that are needed for dispersing and chain extension. A further problem is the reproducible preparation of the dispersions, since because of the complex chemical reactions the properties vary within a certain limits from one batch to the next This problem also occurs during scale- up from laboratory to production. Continuous operations for preparing polyurethane dispersions are known (e.g., GB 14 14930; DE 22 60 870; DE 23 11 635; DE 23 47 299; US 4,742,095; M. Keyvani, Advances in Polymer Technology, 22 (2003), 218-224). AH of these operations require either powerful stirrer units or rotor-stator mixing elements, which entail high capital costs, energy costs and/or operating costs.
The use of static mixers for dispersing and chain extending is known in principle for the preparation of polyisocyanate dispersions in situ (US 5,221,710). The polyurethane prepolymers used for dispersing are adducts having an isocyanate content of at least 12% by mass. To date it has not been possible to carry out continuous dispersion of polyurethane prepolymers having an isocyanate content lower than 12% by mass and preparable by reacting isocyanates with polyols, owing toΛeir high viscosities.
Surprisingly it has now been found that aqueous polyurethane dispersions can also be prepared by dispersing polyurethane prepolymers having an isocyanate content of < 12% by mass in static mixers. The viscosities required are set by appropriate temperature adjustment and/or by the use of an auxiliary solvent.
Surprisingly it has been found that static mixers are very efficient for the continuous preparation of aqueous polyurethane dispersions having < 12% by mass NCO content. One reason for the improved reproducibility and/or compliance with tighter specification limits as compared with conventional preparation in a stirred tank is the short and precisely adjustable residence time in static mixers. _h the course of the preparation of polyurethane dispersions in batch operations, the metering and complete mixing/dispersing of the polyurethane prepolymer in water or of water in the polyurethane prepolymer takes a certain time, normally of the order of several minutes. This time varies within certain limits from one batch to the next and, in comparison with the mixing and residence time in static mixers according to the present process, is very long and is a disadvantage, since in the course of dispersing, the isocyanate groups of the polyurethane prepolymer may react with the water and hence are no longer available for chain extension. As a result there is also variation from one batch to the next in the free isocyanate group content, which makes precise metering of the chain extender component more difficult and also makes it more difficult to adjust the specification. These unwanted side reactions can be reduced to a minimum in static mixers owing to the shorter residence time, since there the volume flows can always be metered and mixed directly in the correct proportion. This is manifested in particular in connection with the use of inexpensive aromatic polyisocyanates which are of high reactivity with water, whose aqueous dispersions are difficult to obtain by batch operations and may require additional process steps (blocking of the isocyanate groups). A further advantage of the process of the invention is the fact that in the course of ongoing production of the polyurethane dispersions it is still possible to make corrections to the reaction conditions and so to effect fine tuning or else a change of product (adjustment of particle size, for example, through the degree of neutralization or solids content), which in the case of batchwise production is possible only from one batch to the next.
The invention provides a process for preparing aqueous polyurethane dispersions which comprises dispersing polyurethane prepolymers having an isocyanate content of < 12% by mass in water in a static mixer.
In the process a polyurethane prepolymer having an isocyanate content of < 12% by mass is dispersed with an aqueous component in a static mixer.
As the polyurethane prepolymer it is preferred to use an anionic (a) or cationic (b) hydrophiHcally modified and neutralized polyurethane prepolymer or a polyurethane prepolymer which has been hydrophilically modified by way of nonionic (c) groups. It is also possible to use mixtures of these prepolymers a) to c).
The polyurethane prepolymers a) to c) can be prepared by any desired methods. Likewise possible is the preparation of the polyurethane prepolymers a) and b) in a separate static mixer prior to dispersing with the aqueous component. In that case a suitable anionically (a) or cationicaUy (b) modifiable polyurethane prepolymer is reacted with a neutralizing component, prior to dispersing in a static mixer, for partial or complete neutralization, to form the dispersible polyurethane prepolymer, which is said to have been modified.
It is also possible to carry out simultaneous partial or complete neutralization and dispersing of a suitable anionically or cationicaUy modifiable polyurethane prepolymer in one step in a single static mixer using a water/neutralizing agent mixture.
The dispersed polyurethane prepolymer obtained in accordance with the invention is subsequently, if desired, reacted with a chain extender component, likewise in a static mixer or conventionally, by a prior art method, to form the finished polyurethane dispersion.
If desired, in the process of the invention an auxiliary solvent is added for adjusting the viscosity of the polyurethane prepolymer.
Anionically or cationicaUy modifiable (i.e., non-neutralized) or nonionically modified polyurethane prepolymers suitable for the process of the invention are known from the literature (see above) and are prepared by polyaddition reactions of polyols and polyisocyanate components and, if desired, auxiliary solvents and/or catalysts. Polymeric and/or monomeric polyols are used which have two or more polyisocyanate-reactive hydroxyl groups, such as polyester polyols, polyether polyols, polyhydroxy polycarbonates, polyhydroxy polyacetals, polyhydroxy polyacrylates, polyhydroxy polyesteramides, polyhydroxy polyfhioethers, polyatkylene polyols, polyhydroxy polycaprolactones, vinyl-modified polyether polyols, macromonomeric polyols, techelenes or polyhydroxy epoxy resins or mixtures thereof and/or all low molecular mass polyols such as 1,2-ethanediol, 1,2-propanediol, 1,2-propylene glycol,
1,3-propanediol, 1,3-propylene glycol, 1,4-butanediol, 1,4-butylene glycol, 1,6-hexanediol, 2-methyl-l,3-propanediol, 2,2-dimethylol-l,3-propanediol, l,4-bis(hydroxymethyl)- cyclohexane, 1,2,3-propanetriol, 2-hydroxymemyl-2-methyl-l,3-propanol, 2-ethyl-2- hydroxymethyl-l,3-propanediol, 2,2-bis(hydroxymethyl)-l,3-propanediol or mixtures thereof. Examples of preferred polyisocyanate components are polyisocyanates, polyisocyanate derivatives or polyisocyanate homologs containing two or more aliphatic, cycloaliphatic or aromatic isocyanate groups. Particularly suitable are the polyisocyanates which are adequately known in polyurethane chemistry, or combinations thereof, such as 1,4-diisocyanatobutane, 1,6-dϋsocyanatohexane (HDI), 1,12-diisocyanatododecane, l,4-dϋsocy_ιnatocyclohexane, 1- isocyanato-5-isocyanatomethyl-3,3,5-trimethylcyclohexane (IPDI), bis(4-isocyanatocyclo- hexyl)methane (Hι2MDI), l,3-bis(l-isocyanato-l-methyl)benzene (XDI), l,3-bis(l-isocyanato- l-methylethyl)benzene (m-TMXDI), 2,4-diisocyanatotoluene (TDI), bis(4-isocyanatophenyl)- methane (MDI), l,6-ά isocyanato-2,2,4(2,4,4)-trimethylhexane (TMDI) and optionally isomers, higher homologs and or technical-grade mixtures of the individual polyisocyanates. In addition it is also possible to use mixtures and derivatives of the abovementioned diisocyanates that contain allophanate, biuret, carbodiimide, isocyanurate, uretdione or urethane groups and if desired blocked polyisocyanates as well, as described in DE 19626 886, for example.
Compounds which are used that have an anionically, cationicaUy and/or nonionically dispersing action are those containing, for example, carboxylate, sulfonate, phosphonate, sulfonium, ammonium or phosphonium groups or groups which can be converted into the aforementioned groups by salt formation (referred to as anionically or cationicaUy modifiable groups/compounds), and/or polyether groups (referred to as nonionically emulsifiable groups), and which can be incorporated into the prepolymers by means of existing isocyanate-reactive groups, and having two or more polyisocyanate-reactive groups, such as compounds containing OH and/or NH2 groups, for example. Representatives of these compounds are, for example, 2-hydroxymethyl-3-hydrox propanoic acid, 2-hydroxymethyl-2-methyl-3- hydroxypropanoic acid, 2-hydroxymethyl-2-ethyl-3-hydroxypropanoic acid, 2-hydroxymethyl- 2-propyl-3-hydroxypropanoic acid, citric acid, tartaric acid, alanine, taurine, 2-amino- ethylarninoethanesulfonic acid, polyethylene glycols, polypropylene glycols and polybutylene glycols prepared starting from alcohols, the block copolymers and monomethyl ethers of these polyglycols, and all polymeric polyols modified accordingly. Preferred auxiliary solvents are inert solvents which possess no miscibility gap with water over wide ranges, such as N-methylpyrrolidone, n-butyl glycol, di-n-butyl glycol, acetone, methyl ethyl ketone or tetrahydrofuran, for example.
The neutralizing component used for anionicaUy modifiable polyurethane prepolymers comprises bases, examples being tertiary amines such as N,N- limethylethanolam_ne, N- methyldiethanolan_ine, triet__anol--r__ine, N,N-dimemyUsopropanol-tmine, N-methyldiiso- propanolamine, t__usopropylamine, N-metih.ylmorpholine, N-ethylmo holine, triethylamine or ammonia, for example, or alkati metal hydroxides such as lithium hydroxide, sodium hydroxide or potassium hydroxide, for example. For cationicaUy modifiable polyurethane prepolymers use is made of corresponding acids, such as formic acid, acetic acid, propionic acid, sulfuric acid, dimethyl sulfate or succinic acid, for example. In the case of the nonionicaUy modified polyurethane prepolymers there is no neutralization step.
In the final reaction step, in which there is an increase in molar mass in the aqueous medium, the chain extender component used comprises polyamines containing two or more polyisocyanate-reactive amino groups. Examples of suitable polyamines include adipic dihydrazide, ethylenedi-unine, diethylenetriamine, triethylenetetramine, tettaethylenepentεtmine,. pentaethylenehexamine, dipropylenetriamine, hexamethylenediamine, hydrazine, isophoroneώamine, N-(2-armnoethyl)-2--ιminoeth-ιnol, 1,3- and 1,4-phenylenediamine, 4,4'-dipheny_mei__anedi___n_ne, amino-functional polyethylene oxides and/or polypropylene oxides, adducts of salts of 2-acι lamido-2-methylpropane-l-sulfonic acid and elhylenediamine, or any desired combinations or polyamines.
In one preferred exemplary embodiment of the process of the invention aU of the mass flows, reaction temperatures, residence times and the individual static mixers are harmonized with one another so as to ensure optimum commixing and reaction times. A non-neutraUzed anionicaUy or cationicaUy modifiable polyurethane prepolymer is pumped from a reservoir continuously into the static mixer. From a further reservoir a neutralizing agent is pumped, again continuously, into the static mixer, in which it is mixed with the prepolymer and at the same time neutralizes the anionically or cationicaUy modifiable groups to form hydrophiUc, ionic groups. The resultant modified or neutralized polyurethane prepolymer is subsequently dispersed in a further static mixer in water, which is pumped continuously from a third reservoir again into the second static mixer. From the static mixer the polyurethane dispersion, with a free isocyanate group content required for the subsequent chain extension, passes into a third static mixer. Simultaneously, from a fourth reservoir, the chain extender, which if desired may be in the form of an aqueous solution, is metered continuously into the third static mixer. This is where chain extension takes place. The finished, stable polyurethane dispersion can be dispensed directly into reservoirs or processed further or applied. If a polyurethane prepolymer is used which is not hydrophiUcally modified by way of nonionic groups (i.e., a nonionicaUy modified polyurethane prepolymer, as it is caUed), the neutralization step disappears. The same applies to an embodiment in which a non-neutralized, anionically or cationicaUy modifiable polyurethane prepolymer is neutralized and dispersed with a neutra zing agent/water mixture in one step. For the process of the invention it is not essential that aU of the steps of the process are carried out continuously in static mixers. It is also not essential whether aU of the steps of the process are carried out in two or more mixers or in only one static mixer.
AU that is essential to the invention is the dispersing of the polyurethane prepolymer in a static mixer, said prepolymer having an NCO content of < 12% by mass prior to dispersing.
In accordance with the invention polyurethane dispersions are prepared which have an NCO content of < 12% by mass, but preferably < 5% by mass, very preferably < 0.5% by mass.
The examples which foUow serve to illustrate the process of the invention further, without said process being restricted to the examples.
Example 1
Preparation of an anionically modifiable polyurethane prepolymer
A stirred tank is charged with 2400 g of N-methylpyrrolidone, 500 g of dimethylolpropionic acid, 5500 g of Oxyester T 1136 (manufacturer: Degussa) and 135 g of trimethylolpropane and this initial charge is heated to 60°C. Subsequently a solution of 5 g of dibutyltin laurate in
3500 g of isophorone diisocyanate is added over a period of 1 h, after which the mixture is heated to 80°C and reaction is continued until an isocyanate content of 3.8% by mass has been reached. The prepolymer thus prepared possesses a viscosity of 7100 mPas at 50°C and an acid number of 21.9 g KOH/g.
Example 2
Batch preparation of an aqueous polyurethane dispersion
300 g of the prepolymer from Example 1 are neutralized in a stirred tank (toothed disk with a peripheral speed of approximately 10 m/s) at 50°C with 10 g of triethylamine (added over the course of 15 s, after-reaction time 15 s) and dispersed by adding 400 g of water (added over the course of 40 s, after-reaction time 15 s). This is foUowedby chain extension with 70 g of a 10% strength solution of ethylenediamine in water. The dispersion obtained has a pH of 8.0, a sohds content of 32.2% (dried at 150°C for 1.5 h) and a viscosity of 33 mPas at 20°C.
Example 3 Continuous preparation of an aqueous polyurethane dispersion
The prepolymer from Example 1 is pumped from a reservoir at 50°C with a volume flow of 150 gmin into a static mixer (SMX mixer from Sulzer; residence time 0.3 min) and mixed with 5 g/min of triethylamine from a second reservoir. The neutraUzed prepolymer is then dispersed in a further static mixer (SMX mixer from Sulzer; residence time 0.7 min) with a water stream of 200 g/min from a third reservoir, and then subjected to chain extension in a third static mixer (SMXL mixer from Sulzer; residence time 1.2 min) from a fourth reservoir with 35 g/min of a 10% strength solution of ethylenediamine in water. The dispersion obtained has a pH of 8.4, a solids content of 31.7% and a viscosity of 29 mPas at 20°C and is therefore comparable with the conventionally prepared dispersion from Example 2.

Claims

What is claimed is;
1. A process for preparing an aqueous polyurethane dispersion which comprises dispersing polyurethane prepolymers having an isocyanate content of < 12% by mass in water in a static mixer.
2. A process as claimed in claim 1, wherein a) neutralized, anionicaUy modified, b) neutralized, cationicaUy modified and/or c) nonionic dispersible polyurethane prepolymers are used.
3. A process as claimed in claim 2, wherein components a) and/or b) are prepared beforehand by fuHy or partly neutraUzing an anionicaUy or cationicaUy modifiable polyurethane prepolymer with a neutraUzing agent or neutralizing agent mixture in a static mixer.
4. A process as claimed in claim 1, wherein an anionicaUy and/or cationicaUy modifiable polyurethane prepolymer is neutralized and dispersed in a static mixer with a mixture of neutralizing components) and water in one step.
5. A process as claimed in at least one of the preceding claims, wherein a dispersed polyurethane prepolymer containing isocyanate groups is reacted with a chain extender component or with a mixture of chain extender components in a static mixer.
6. A process as claimed in at least one of the preceding claims, wherein an auxiUary solvent is added for adjusting the viscosity of the polyurethane prepolymer.
7. A process as claimed in at least one of the preceding claims, wherein polyols selected from the group consisting of polyester polyols, polyether polyols, polyhydroxy polycarbonates, polyhydroxy polyacetals, polyhydroxy polyacrylates, polyhydroxy polyesteramides, polyhydroxy polyfhioethers, polyalkylene polyols, polyhydroxy polycaprolactones, vinyl- modified polyether polyols, macromonomeric polyols, techelenes or polyhydroxy epoxy resins or mixtures thereof are used as starting compounds for preparing the polyurethane prepolymers.
8. A process as claimed in at least one of the preceding claims, wherein low molecular mass polyols selected from 1,2-ethanediol, 1,2-propanediol, 1,2-propylene glycol, 1,3- propanediol, 1,3-propylene glycol, 1,4-butanediol, 1,4-butylene glycol, 1,6-hexanediol, 2- methyl-l,3-propanediol, 2,2-dimethylol-l,3-propanediol, l,4-bis(hydroxymethyl)- cyclohexane, 1,2,3-propanetriol, 2-hydroxymethyl-2-methyl-l,3-propanol, 2-ethyl-2- hydroxymethyl-l,3-propanediol, 2,2-bis(hydroxymethyl)-l,3-propanediol or mixtures thereof are used as starting compounds for preparing the polyurethane prepolymers.
9. A process as claimed in at least one of the preceding claims, wherein polyisocyanates, polyisocyanate derivatives or polyisocyanate homologs are used as starting compounds for preparing the polyurethane prepolymers.
10. A process as claimed in ateleast one of the preceding claims, wherein polyisocyanate components containing aUophanate, biuret, carbodiimide, isocyanurate, uretdione or urethane groups are used as starting compounds for preparing the polyurethane prepolymers.
ll.A process as claimed in at least one of the preceding claims, wherein blocked polyisocyanates are used as starting compounds for preparing the polyurethane prepolymers.
12. A process as claimed in at least one of the preceding claims, wherein polyisocyanates selected from 1,4-diisocyanatobutane, 1,6-diisocyanatohexane (HDI), 1,12- dϋsocyanatododecane, 1,4-diisocyanatocyclohexane, 1 -isocyanato-5-isocyanatomethyl- 3,3,5-trimethylcyclohexane (TPDI), bis(4-isocyanatocyclohexyl)methane (H]2MDI), 1,3- bis(l-isocyanato-l-methyl)benzene (XDI), l,3-bis(l-isocyanato-l-methylethyl)be__zene (m-TMXDI), 2,4-dϋsocyanatotoluene (TDI), bis(4-isocyanatophenyl)methane (MDI) and l,6-diisocyanato-2,2,4(2,4,4)-trimethylhexane (TMDI) are used as starting compounds for preparing the polyurethane prepolymers.
13. A process as claimed in at least one of the preceding claims, wherein compounds containing carboxylate, sulfonate, phosphonate, sulfonium, ammonium or phosphonium groups or groups which can be converted into the aforementioned groups by salt formation are used for anionic and/or cationic modification.
14. A process as claimed in claim 13, wherein 2-hydroxymethyl-3-hydroxypropanoic acid, 2- hydroxymethyl-2-methyl-3-hydroxyprop_uioic acid, 2-hydroxymethyl-2-ethyl-3- hydroxypropanoic acid, 2-hydroxymethyl-2-propyl-3-hydroxypropanoic acid, citric acid, tartaric acid, alanine, taurine, 2-aminoethylaminoethanesulfonic acid are used.
15. A process as claimed in at least one of the preceding claims, wherein polyethylene glycols, polypropylene glycols or polybutylene glycols prepared starting from alcohols, block copolymers and monomethyl ethers of these polyglycols, and aU polymeric polyols modified accordingly are used for nonionic modification.
16. A process as claimed in at least one of the preceding claims, wherein adipic dihydrazide, ethylenediamine, diethylenetriamine, triethylenetetramine, tettaethylenepentamine, pentaethylenehexamine, dipropylenetriamine, hexamethylenediamine, hydrazine, isophoronediamine, N-(2-an___noethyl)-2-aminoethanol, 1,3- and 1,4-phenylenediamine, 4,4'-{Upheny_meth- ediamine, ammo-functional polyethylene oxides and or polypropylene oxides, adducts of salts of 2-acrylamido-2-methylpropane-l-sulfonic acid and ethylenediamine, or any desired combinations of polyamines, are used as chain extenders.
17. A process as claimed in at least one of the preceding claims, wherein a polyurethane dispersion having an NCO content of < 12% by mass, but preferably < 5% by mass, more preferably < 0.5% by mass, is prepared.
PCT/EP2005/050504 2004-04-01 2005-02-07 Process for preparing aqueous polyurethane dispersions WO2005097858A1 (en)

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CN105801808A (en) * 2016-01-11 2016-07-27 广东邦固化学科技有限公司 Synthesis and preparation method for strippable waterborne polyurethane used for leather
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CN106496514A (en) * 2016-09-22 2017-03-15 南通万顺化工科技有限公司 A kind of waterborne polyurethane resin
CN107353394A (en) * 2017-08-23 2017-11-17 黄山联固新材料科技有限公司 A kind of coating, polyurethane and preparation method thereof
CN110818881A (en) * 2019-11-22 2020-02-21 万华化学（北京）有限公司 Preparation method of polyurethane ink resin, polyurethane ink resin prepared by preparation method and ink
CN111303753A (en) * 2020-04-08 2020-06-19 万华化学集团股份有限公司 Single-component exposed quick-drying polyurethane waterproof coating and preparation method thereof
CN112724357A (en) * 2014-12-08 2021-04-30 拜耳股份有限公司 Thermoplastic polyurethane, use thereof for producing T-frames for intrauterine systems and T-frames made of said material
CN112778487A (en) * 2019-11-05 2021-05-11 万华化学集团股份有限公司 Aqueous dispersion of polyurethane or polyurethane-urea, preparation method and application thereof
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CN112724357A (en) * 2014-12-08 2021-04-30 拜耳股份有限公司 Thermoplastic polyurethane, use thereof for producing T-frames for intrauterine systems and T-frames made of said material
CN104910343A (en) * 2015-06-26 2015-09-16 四川理工学院 Ionic and nonionic waterborne polyurethane and preparation method thereof
WO2017009161A1 (en) * 2015-07-10 2017-01-19 Covestro Deutschland Ag Process and apparatus for continuous production of aqueous polyurethane dispersions
CN107849208A (en) * 2015-07-10 2018-03-27 科思创德国股份有限公司 Method and apparatus for continuous production aqueous polyurethane dispersion
JP2018519403A (en) * 2015-07-10 2018-07-19 コベストロ、ドイチュラント、アクチエンゲゼルシャフトＣｏｖｅｓｔｒｏ Ｄｅｕｔｓｃｈｌａｎｄ Ａｇ Method and apparatus for continuously producing aqueous polyurethane dispersions
TWI733683B (en) * 2015-07-10 2021-07-21 德商科思創德意志股份有限公司 Process and apparatus for continuous production of aqueous polyurethane dispersions
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CN107849208B (en) * 2015-07-10 2021-02-09 科思创德国股份有限公司 Method and device for the continuous production of aqueous polyurethane dispersions
CN105801808A (en) * 2016-01-11 2016-07-27 广东邦固化学科技有限公司 Synthesis and preparation method for strippable waterborne polyurethane used for leather
CN106496514A (en) * 2016-09-22 2017-03-15 南通万顺化工科技有限公司 A kind of waterborne polyurethane resin
CN107353394A (en) * 2017-08-23 2017-11-17 黄山联固新材料科技有限公司 A kind of coating, polyurethane and preparation method thereof
US11655327B2 (en) 2018-09-20 2023-05-23 3M Innovative Properties Company Polymeric material including a uretdione-containing material and an epoxy component, two-part compositions, and methods
CN112778487A (en) * 2019-11-05 2021-05-11 万华化学集团股份有限公司 Aqueous dispersion of polyurethane or polyurethane-urea, preparation method and application thereof
CN110818881B (en) * 2019-11-22 2021-10-22 万华化学（北京）有限公司 Preparation method of polyurethane ink resin, polyurethane ink resin prepared by preparation method and ink
CN110818881A (en) * 2019-11-22 2020-02-21 万华化学（北京）有限公司 Preparation method of polyurethane ink resin, polyurethane ink resin prepared by preparation method and ink
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