Source: https://patents.google.com/patent/US6794445B2/en
Timestamp: 2019-04-25 22:12:34
Document Index: 763983765

Matched Legal Cases: ['art 2', 'art 1963', 'art 2', 'art, 1963', 'art 2', 'art, 1963']

US6794445B2 - Aqueous polysiloxane-polyurethane dispersion, its preparation and use in coating compositions - Google Patents
US6794445B2
US6794445B2 US10/413,703 US41370303A US6794445B2 US 6794445 B2 US6794445 B2 US 6794445B2 US 41370303 A US41370303 A US 41370303A US 6794445 B2 US6794445 B2 US 6794445B2
US10/413,703
US20030198819A1 (en
2002-04-17 Priority to DE10216896 priority Critical
2002-04-17 Priority to DE2002116896 priority patent/DE10216896A1/en
2002-04-17 Priority to DE10216896.2 priority
2003-04-15 Assigned to GOLDSCHMIDT AG reassignment GOLDSCHMIDT AG ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HALLACK, MARKUS, REUSMANN, GERHARD
2003-04-15 Application filed by Evonik Goldschmidt GmbH filed Critical Evonik Goldschmidt GmbH
2003-10-23 Publication of US20030198819A1 publication Critical patent/US20030198819A1/en
2004-09-21 Publication of US6794445B2 publication Critical patent/US6794445B2/en
This application claims priority to German Patent Application 102 16 896.2, filed Apr. 17, 2002, herein incorporated by reference.
Modern aqueous binders are capable in many applications of substituting organically dissolved binders. This is so in particular in those segments where aqueous binders may have specific advantages, such as in electrocoating, for example.
It is therefore an object of the invention to provide aqueous binders suitable for high-elasticity coating materials, coatings and sealants, especially for soft feel coating materials, which combine a good soft feel effect with good film mechanical properties and adhesion and also a satisfactory solvent resistance and which, furthermore, contain volatile organic substances to the smallest possible extent, so as to be able to meet exacting requirements with respect to environmental compatibility as well.
In a first embodiment the invention provides aqueous dispersions of polysiloxane-polyurethanes having an acid number of from about 5 to about 100 mg KOH/g polysiloxane-polyurethane solids, a hydroxyl group content of from about 0.25 to about 6.5% by weight, and a urethane group content (calculated as —NH—CO—O—) of from about 2.0 to about 25.0% by weight, based in each case on polysiloxane-polyurethane solids, wherein the polyurethanes are products, where appropriate at least partly neutralized with bases, of the reaction of
The polysiloxane-polyurethane dispersions of the invention generally have solids contents of from about 15 to about 68% by weight, preferably from about 33 to about 60% by weight, and viscosities, determined using a rotational viscometer at 23° C., of from about 10 to about 20,000 mPas, preferably from about 50 to about 5,000 mPas. The pH is situated generally between about 5 and about 10, preferably at from about 6 to about 8, and is determined in accordance with DIN 53 785 following dilution with distilled water to a solids content of 10% by weight. The term “dispersion” moreover, is intended in the context of the present invention to embrace both true aqueous dispersions and also aqueous solutions. The question of whether a particular system is a dispersion or solution is dependent in particular on the amount of saltlike groups present and on the molecular mass of the polymers.
The polysiloxane-polyurethanes present as the disperse phase in the dispersions have in particular, based on solids, a urethane group (—NH—CO—O) content of from about 2.0 to about 25.0% by weight, preferably from about 4.0 to about 19.0% by weight, an acid number of from about 5 to about 100 mg KOH/g, preferably from about 8 to about 40 mg KOH/g, the acid number relating both to free acid groups and to base-neutralized acid groups of the solid, and a hydroxyl group content of from about 0.3 to about 6.5% by weight, preferably from about 0.5 to about 3.5% by weight. The water dilutability of the polysiloxane-polyurethanes can be attributed essentially to the presence therein of the aforementioned anionic groups.
The term “linear” is intended to denote that the compounds contain on average per molecule not more than about 0.5, preferably less than about 0.3, and with particular preference less than about 0.1 branching site, i.e., that the (average) hydroxyl functionality is not more than about 2.5, preferably not more than about 2.3, and with particular preference not more than about 2.1. The term “substantially difunctional” is intended to denote that the compounds contain on average per molecule not more than about 0.1 and preferably no branching sites, i.e., that the average. hydroxyl functionality is not more than about 2.1, and is preferably about 2.0.
The polydimethylsiloxanepolyols are preferably linear polydimethylsiloxanes having terminal hydroxyalkyl functions and an average molecular mass of from 1,500 to 3,000, such as Tegomer® H-Si 2111 and Tegomer® H-Si 2311 (Goldschmidt AG). Likewise suitable are hydroxy(poly-caprolactone)-modified polydimethylsiloxanes, such as Tegomer® H-Si 6440 (Goldschmidt AG).
Particular preference is given to the linear hydroxyalkyl-functional polydimethylsiloxane Tegomer® H-Si 2311.
Corresponding amino-containing polydimethylsiloxanes such as, for example, Tegomer ® A-Si 2322 (Goldschmidt AG) can likewise be reacted in accordance with the synthesis of the invention, but produce less weathering-stable coatings.
Starting component c) comprises at least one hydroxycarboxylic acid and/or aminocarboxylic acid and/or aminosulfonic acid and/or hydroxysulfonic acid of the type specified, for example, in U.S. Pat. No. 3,479,310. Preferred components c) include 2,2-bis(hydroxymethyl)-alkanemonocarboxylic acids having a total of from 5 to 8 carbon atoms, i.e., compounds of the general formula
One example of starting component e) is Tegomer® D3403 (Goldschmidt AG). Starting component f) preferably comprises linear aliphatic diisocyanates of the molecular mass range about 168 to about 1,000, in particular about 168 to about 300, such as hexamethylene diisocyanate, undecane 1,11-diisocyanate or dodecane 1,12-diisocyanate. Likewise suitable as starting component f), though less preferred, are mixtures of such linear aliphatic diisocyanates with other diisocyanates such as isophorone diisocyanate or 2,4-diisocyanatotoluene or else with “paint polyisocyanates” based on hexamethylene diisocyanate, of the type known per se having a maximum molecular mass of about 1,000. However, at least about 50% by weight of starting component f) is composed of linear aliphatic diisocyanates of the type mentioned at the outset.
This convention is generally operated observing an equivalents ratio of isocyanate-reactive groups to isocyanate groups of from about 1.2:1 to about 2.5:1, preferably from about 1.4:1 to about 2.0:1, so as to end up with reaction products having the aforementioned hydroxyl group content. Any carboxyl groups present in the reaction mixture that are intended for conversion into anionic groups are not to be regarded as “isocyanate-reactive” in this context.
In order to carry out the dispersing step it is possible alternatively to add the water/neutralizing agent mixture to the resin, the resin to the water/neutralizing agent mixture, or the resin/neutralizing agent mixture to the water. By “resin” here is meant either the solventlessly prepared polysiloxane-polyurethane or its solution in one of the auxiliary solvents exemplified. The dispersing step is generally accomplished at a temperature within the range from about 20 to about 100° C., preferably from about 40 to about 100° C. The dispersibility of the polysiloxane-polyurethanes in water may be improved if desired by also using external emulsifiers during the dispersing operation. The polysiloxane-polyurethane dispersions of the invention generally have an organic solvent content of less than about 15% and preferably less than about 10% by weight. Following their preparation, it is possible to add further organic solvents to the dispersions of the invention for the purpose of obtaining certain properties, especially alcoholic solvents such as ethanol, n-butanol, n-octanol, butyldiglycol, ethyldiglycol, methyldiglycol or methoxypropanol, for example.
Examples of suitable amino resins are water-dilutable or water-dispersible melamine-formaldehyde and urea-formaldehyde condensation products, as described, for example, in D. H. Solomon, The Chemistry of Organic Filmformers, p. 235 ff, John Wiley & Sons, Inc., New York, 1967. Alternatively, the melamine resins may be replaced in whole or in part by other crosslinking amino resins, as described, for example, in “Methoden der organischen Chemie” (Houben-Weyl), Vol. 14 Part 2, 4th edition, Georg Thieme Verlag, Stuttgart 1963, p. 319 ff.
Further suitable crosslinker resins include blocked polyisocyanates, based for example on isophorone diisocyanate, hexamethylene diisocyanates, 1,4-dilsocyanatocyclohexane, dicyclohexylmethane diisocyanate, 1,3-diisocyanatobenzene, 1,4-diisocyanatobenzene, 2,4-diisocyanato-1-methylbenzene, 1,3-diisocyanato-2-methylbenzene, 1,3-bisisocyanatomethylbenzene, 2,4-bisisocyanatomethyl-1,5-dimethylbenzene, bis(4-iso-cyanatophenyl)propane, tris-(4-isocyanatophenyt)methane, trimethyl-1,6-diisocyanatohexane or blocked “paint polyisocyanates” such as polyisocyanates containing biuret groups and based on 1,6-diisocyanatohexane, polyisocyanates containing isocyanurate groups and based on 1,6-diisocyanatohexane, or paint polyisocyanates containing urethane groups and based on 2,4- and/or 2,6-diisocyanatotoluene or isophorone diisocyanate on the one hand and low molecular mass polyhydroxyl compounds such as trimethylolpropane, the isomeric propanediols or butanediols or any desired mixtures of such polyhydroxyl compounds on the other, in each case having blocked isocyanatc groups.
Examples of suitable polyisocyanate crosslinkers B) containing free isocyanate groups include organic polyisocyanates having aliphatically, cycloaliphatically, araliphatically and/or aromatically attached free isocyanate groups, which are liquid at room temperature. Such polyisocyanate crosslinkers B) generally have a viscosity, determined using a rotational viscometer at 23° C., of from about 50 to about 10,000 mPas, preferably from about 50 to about 1,500 mPas.
Where necessary, the polyisocyanates may be employed as a blend with small amounts of inert solvents in order to lower the viscosity to a level within the specified ranges. Highly suitable, for example, are “paint polyisocyanates” based on hexamethylene diisocyanate or on 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI) and/or dicyclohexylmethane diisocyanate. By “paint polyisocyanates” based on these diisocyanates are meant the derivatives of these diisocyanates that are known per se and contain biuret, urethane, allophanate, uretdione and/or isocyanurate groups and which following their preparation have been freed in a known way, preferably by distillation, from excess starting diisocyanate down to a residual content of less than about 0.5% by weight. The preferred aliphatic polyisocyanates for use in accordance with the invention include the polyisocyanates which meet the above criteria, contain biuret groups, and are based on hexamethylene diisocyanate, such as may be obtained, for example, by the processes of U.S. Pat. Nos. 3,124,605, 3,903,126, 3,903,127 and 3,976,622, which are composed of mixtures of N,N′,N″-tris-(6-isocyanatohexyl)biuret with minor amounts of its higher homologs, and also the cyclic trimers of hexamethylene diisocyanate which meet the above criteria, as may be obtained in accordance with U.S. Pat. No. 4,324,879, composed essentially of N,N′,N″-tris-(6isocyanatohexyl)isocyanurate as a mixture with minor amounts of its higher homologs.
The aromatic polyisocyanates which are likewise suitable in accordance with the invention but less preferred are, in particular, “paint polyisocyanates” based on 2,4-diisocyanatotoluene or its technical-grade mixtures with 2,6-diisocyanatotoluene or based on 4,4′-diiso-cyanatodiphenylmethane or its mixtures with its isomers and/or higher homologs.
Preferred crosslinker resins are the above-described polyisocyanate crosslinkers containing free isocyanate groups, especially hydrophilicized crosslinkers on this basis. With particular preference, the polyisocyanate component B) comprises those polyisocyanates or polyisocyanate mixtures containing exclusively aliphatically and/or cycloaliphatically attached isocyanate groups with an (average) NCO functionality of between about 2.2 and about 5.0 and a viscosity, determined using a rotational viscometer at 23° C., of from about 50 to about 1,500 mPas.
In the examples below all percentages are by weight. The pH values were determined in accordance with DIN 53 785 following dilution with distilled water to a solids content of 10% by weight.
a) Preparation Examples Example 1 Inventive
A reaction vessel with stirring, cooling, and heating means was charged with 84.0 g of the polyester Oxyester T1136 (hydroxyl content about 3.2%, Degussa AG), 24.0 g of the hydroxyalkyl-modified polydimethylsiloxane Tegomer®H-Si 2311 (Mw=2,500 g/mol, Goldschmidt AG), 16.8 g of 2,2-bis(hydroxymethyl)propionic acid (DMPA) and 54.0 g of N-methylpyrrolidone (NMP) under nitrogen and this initial charge was heated to 60° C. and homogenized.
Then 105.7 g of isophorone diisocyanate (IPDI) and 0.2 g of dibutyltin dilaurate (DBTL) were added and the mixture was stirred at 90° C. until (about 1 h) the theoretical isocyanate content of about 8% had been reached (prepolymer (I)). 12.0 g of 1,4-butanediol were added to this reaction mixture which was then stirred at 90° C. until (about 1 h) the theoretical isocyanate content of about 3.9% had been reached (prepolymer (II)).
Then 27.6 g of trimethylolpropane (TMP) were added and the mixture was stirred at about 120 to about 130° C. until NCO groups were no longer detectable. After the mixture had been cooled to 100° C., 10.1 g of triethylarnine (TEA) and 365.7 g of water were added with stirring.
Preparation was carried out as in Example 1) with the difference that the synthesis took place in accordance with EP-B-0 669 352 (process according to Example 1)) in one step by reacting all the polyol components with the diisocyanate and catalyst until NCO groups were no longer detectable.
This gave an inhomogeneous polysiloxane-polyurethane dispersion 2) in which the polysiloxane Tegomer®H-Si 2311 had not been fully incorporated by reaction.
As a prior art comparative example, the polyester-polyurethane dispersion of Example 1) from EP-B-0 669 352 was chosen.
b) Use Examples Use Example 1 Inventive
50.0 g of the polysiloxane-polyurethane dispersion 1), 3.0 g of silica TS 100 (Degussa AG), 3.0 g of flatting agent Pergopak® M3 (Martinswerk, Bergheim), 0.3 g of TEGO® Wet KL245 (wetting additive, Tego Chemie Service), 0.5 g of TEGO® Foamex 805 (defoamer, Tego Chemie Service), 1.0 g of Acrysol RM8 (thickener, Rohm & Haas) and 42.2 g of distilled water were triturated together.
Then 10.0 g of isocyanate crosslinker Desmodur® N3300 (Bayer AG) were incorporated by emulsification with stirring.
At 23° C. and a relative humidity of about 55%, the paint film was applied to glass or plastic plates, cured at room temperature for 10 minutes and then at 80° C. for one hour. The dry film thickness was 50 μm.
Use Example 2 Comparative
Analogous to Use Example 1), the dispersion chosen being that from Comparative Example 1) instead of the polysiloxane-polyurethane dispersion from Example 1).
Use Example 3 Comparative
In accordance with the prior art, Use Example 1) from EP-B-0 669 352 was tested.
feel Adhesion2
Use Example Dispersion effect1 (cross-cut) Solvent resistance3
1. Value 0 = very good soft feel effect,
2. Cross-cut according to DIN 53230,
3. Exposure carried out for 1 minute with a cotton pad containing
Another factor regarded as being of particular advantage of the polysiloxane-polyurethane dispersion of the invention from Example 1) is the fact that even without the use of flatting agents which influence the tactile properties, such as Pergopak® M3 or Silitin® Z86 (Hoffmann & Söhne KG), for example, it is possible to achieve a pronounced soft feel effect.
Use Example 4 Inventive
Then 6.0 g of amino crosslinker resin Cymel® 327 (American Cyanamid) were added. At 23° C. and a relative humidity of about 55%, the paint film was applied to glass plates, cured at room temperature for 10 minutes and then at 150° C. for 20 minutes. The dry film thickness was 50 μm.
Use Example 5 Comparative
As the state of the art, a baking formulation formulated with amino crosslinker resin and based on a polyester-polyurethane dispersion in accordance with Use Example 14) from EP-B-0 669 352 was chosen.
1. A process for preparing an aqueous polysiloxane-polyurethane dispersion having an acid number of from about 5 to about 100 mg KOH/g polysiloxane-polyurethane solids, a hydroxyl group content of from about 0.25 to about 6.5% by weight, and a urethane group content (calculated as —NH—CO—O—) of from about 2.0 to about 25.0% by weight, based in each case on polysiloxane-polyurethane solids, wherein the polyurethanes are products, where appropriate at least partly neutralized with bases, which comprises
(1) reacting together the following components:
a) a total of from about 3 to about 25% by weight of at least one linear polydimethylsiloxanediol of the molecular mass rage about 1,500 to about 10,000;
iv) hydroxyl-containing linear polyesterpolyols of the molecular mass range about 500 to about 4,000;
iv) alkali metal salts of such acids;
wherein the NCO/OH ratio of each component is from about 1.8:1 to 3.0:1: to form an isocyanate functional prepolymer (I), and
wherein the percentages for components a) to f) added up to 100% by weight of the polyurethane fractions of the polysiloxane-polyurethane solids;
(2) converting the prepolymer (I) into an isocyanate-functional prepolymer (II) by reacting the prepolymer (I) with component d), wherein the NCO/OH ratio is from about 1.2:1 to about 1.6:1, followed by subsequently converting the product obtained by reacting the product with further component b) and/or d), to give the final hydroxyl-containing polysiloxane-polyurethane polymer, and
(3) dispersing the polysiloxane polyurethane polymer by adding the polysiloxane-polyurethane polymer to water in the presence of a neutralizing agent.
2. The process according to claim 1, wherein the components which are reacted are:
from about 5.0 to about 15.0% by weight of component a;
from about 20.0 to about 70.0% by weight of component b;
from about 2.0 to about 7.0% by weight of component c;
from about 0.5 to about 10.0% by weight of component d;
from 0 to about 10.0% by weight of component e; and
from about 7.0 to about 30.0% by weight of component f,
component a is composed of a linear polydimethylsiloxane of molecular mass in the range from about 2,000 to about 4,000;
component b is composed of a linear polyesterdiol of molecular mass about 500 to about 4,000 and/or a linear polycarbonatediol of molecular mass about 750 to about 4,000;
component c is composed of at least about 85% by weight of 2,2-dimethylolpropionic acid and/or 2,2-dimethylolbutyric acid;
component d is composed of at least one low molecular mass diol and/or triol of molecular mass about 90 to about 150; and
component e is composed of at least about 75% by weight of cycloaliphatic diisocyanates of the molecular mass range about 166 to about 300
US10/413,703 2002-04-17 2003-04-15 Aqueous polysiloxane-polyurethane dispersion, its preparation and use in coating compositions Expired - Fee Related US6794445B2 (en)
US20030198819A1 US20030198819A1 (en) 2003-10-23
US6794445B2 true US6794445B2 (en) 2004-09-21
US10/413,703 Expired - Fee Related US6794445B2 (en) 2002-04-17 2003-04-15 Aqueous polysiloxane-polyurethane dispersion, its preparation and use in coating compositions
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