WO1998005696A1

WO1998005696A1 - Aqueous dispersions, their preparation and use as paint binders

Info

Publication number: WO1998005696A1
Application number: PCT/EP1997/003908
Authority: WO
Inventors: Reinhold Hecht; Lutz Hoppe; Erhard Lühmann; Wolfgang Dannhorn
Original assignee: Wolff Walsrode Ag
Priority date: 1996-08-01
Filing date: 1997-07-21
Publication date: 1998-02-12
Also published as: AU3940497A; DE19630905A1

Abstract

Polyurethane urea dispersions are obtained by reacting: (A) 15 to 50 wt %, preferably 20 to 40 wt %, of a linear or weakly branched polyester polyol with a molecular weight from 500 to 6000; (B) 2 to 10 wt %, preferably 3 to 7 wt %, of one or several polyols having a molecular weight < 500; (C) 1 to 10 wt % of at least one mono- and/or difunctional compound, as regards the isocyanate reaction, which in addition contains anionic groups or functional groups which can be converted into anionic groups; (D) 0 to 15 wt % of a hydrophilic, monohydric or dihydric alcohol with ethylene oxide units and a molecular weight from 600 to 3000; (E) 3 to 70 wt %, preferably 40 to 60 wt %, of one or several polyisocyanates, at least 70 wt % of the polyisocyanate component consisting of one or several cycloaliphatic diisocyanates. The resulting product of (A) to (E) is then subjected to a chain-lengthening or cross-linking treatment with (F) 0.5 to 10 wt % of a mixture of one or several diamines with a polyamine with a functionality > 2, at least 20 wt % of component (F) being composed of the polyamine with a functionality > 2. The sum of components (A)-(F) always equals 100 %.

Description

Aqueous dispersions, their production and use as paint binders

The present invention relates to new aqueous dispersions of polyurethane polyureas for the production of ethanol-resistant coatings.

Polyurethane polyureas, which were applied by organic solvent systems, are characterized by outstanding properties, such as. B chemical resistance, abrasion resistance, toughness, tensile strength and elasticity. They are therefore used in a variety of commercial applications, such as. B. as adhesives or coating agents for various substrates such as textiles, plastics, wood. Glass fibers, leather and metals. When drying the coatings, however, problems arise which are caused by the emission of the organic solvents.

An attempt was therefore made to offer the polyurethane-polyurea binder system in the form of aqueous dispersions in solvent-free form or with only a low content of organic solvents.

External emulators can be used to produce stable dispersions of the polyurethane polyurea polymers (cf. US Pat. No. 2,968,575). However, the use of external emulsifiers dramatically deteriorates the water and ethanol resistance of the coatings obtained.

An improvement could, for. B. can be achieved by incorporating groups with an emulsifier function into the polymer chain. These so-called internal emulsifiers are either ionic and / or nonionic in nature. Examples of ionic internal emulsifiers are described in US 3,479,310 and examples of nonionic emulsifiers and the like. a. in the patents US 3 905 929 and US 4 190 566. The use of internal emulsifiers leads to dispersions with improved stabilities and a reduced content of hydrophilic structural components. The resulting

Coatings are characterized by improved water resistance and less loss of mechanical stability in the swollen state. But also these dispersions in no way meet the requirement for a chemical-resistant coating and in particular a coating with good ethanol strength

Coatings with high chemical resistance based on aqueous polyurethane dispersions are obtained if the polymers dispersed in water still have functional groups. As described in EP 0 669 352, these can then be used for crosslinking reactions by adding a suitable co-resin. In practice, such two-component systems can only be formulated with considerable effort and have a limited pot life.

According to DE-OS 3 936 794, polyurethane-polyurea dispersions, which already provide films with improved chemical resistance after physical drying, are based on polycarbonate diols. However, polycarbonate diols are very expensive starting materials, and the coatings are changed or destroyed by ethanol in a test according to DIN 68861, so that they are used alone

Sufficient resistance can not be achieved using these binders

Comparable polyurethane polyurea dispersions based on cheaper starting materials, e.g. Polyester polyols could be produced by incorporating special dimeric fatty acids. Such dispersions are e.g. described in EP 0 643 734. The chemical resistance could only be improved slightly compared to the dispersions based on polycarbonate diol. Another problem is that the dimeric fatty acids can cause embrittlement of the coatings.

The aim of the present invention was therefore to produce polyurethane-polyurea dispersions which, after physical drying without the addition of crosslinking agents and as the sole binder, provide films with a significantly improved chemical and in particular an improved resistance to ethanol.

The object was surprisingly achieved by providing the dispersions according to the invention described in more detail below, the Particularly outstanding ethanol resistance of the resulting coatings can be attributed to the use of substances known per se in a preferred combination of quantities. The invention relates to polyurethane-polyurea dispersions, built up by polyaddition of:

(A) 15 to 50% by weight, preferably 20 to 40% by weight, of a linear and / or slightly branched polyester polyol with a molecular weight of 500 to 6000,

(B) 2 to 10% by weight, preferably 3 to 7% by weight, of one or more polyols with a molecular weight <500,

(C) 1 to 10% by weight of at least one compound which is mono- and / or difunctional in the sense of the isocyanate reaction and which additionally contains anionic groups or functional groups which can be converted into anionic groups,

(D) 0 to 15% by weight of a hydrophilic monohydric or dihydric alcohol having ethylene oxide units and having a molecular weight in the range from 600 to 3000,

(E) 30 to 70% by weight, preferably 40 to 60% by weight, of one or more polyisocyanates, at least 70% by weight of the polyisocyanate component consisting of one or more cycloaliphatic diisocyanates,

and subsequent chain extension or crosslinking of the resulting product from (A) to (E) with

(F) 0.5 to 10% by weight of a mixture of one or more diamines with a polyamine of functionality> 2, where at least 20% by weight of component (F) consists of the polyamine of functionality> 2.

The percentages of components (A) to (F) add up to 100%. The present invention furthermore relates to the use of the new polyurethane-polyurea dispersions as paint binders for the coating of any substrates

Manufacturing processes for polyurethane-polyurea dispersions are known per se

(e.g. Angewandte Chemie, D Dieterich, 82, 53 (1970))

Linear and / or weakly branched polyester polyols with a molecular weight of 500 to 6000 and in a particularly preferred embodiment from 750 to 3000 are used as component A. These are reaction products of low molecular weight polyols with low molecular weight polycarboxylic acids

Suitable polyols or polyol mixtures for the construction of polyesters containing hydroxyl groups are, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, tylenethylene glycol, neopentyl glycol, 1,4-bis (hydroxymethyl) cyclohexane or dipropylene glycol Polyols which can be used in part to introduce the branches into the polyester molecule are, for example, glycene, tmethylolpropane or pentaerythritol suitable. 1, 6-Hexanediol, neopentylglycol and tmethylolpropane are particularly preferred

The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocratic in nature. Instead of the free polycarboxylic acids, corresponding polycarboxylic acid anhydrides or polycarboxylic acid esters with lower alcohols can also be used. Examples include succinic acid, adipic acid,

Sebacic acid, azelaic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid or dimethyl terephthalate is particularly preferred

Component (A) generally has an average hydroxyl functionality of 2.0, ie 2 OH groups per molecule, through the use or the proportionate When using weakly branched polyester polyols, the average hydroxyl functionality can be increased to a maximum value of 2.5

The low molecular weight polyols mentioned under point (B) with a molecular weight of <500 are ahphatic, cycloaliphatic, aromatic and / or heterocyclic compounds, as have already been mentioned under point (A) for the construction of the polyester polyols. Particularly preferred polyol le are neopentyl glycol and trimethylol propane

The starting component (C) is usually at least one

Hydroxycarboxylic acid and / or aminocarboxylic acid and / or aminosulfonic acid and / or hydroxysulfonic acid. These compounds are incorporated into the prepolymer via the amino and / or hydroxyl groups which are reactive towards isocyanates by neutralizing the carboxyl groups and / or the sulfonic acid groups with organic and / or inorganic bases these compounds have dispersing properties

Examples include representatives of component (C): malic acid, glycolic acid, glycine, taurine, aminocaproic acid and 2-amino-ethylammosulfonic acid. The preferred components (C) include 2,2-bis (hydroxymethyl) alkane monocarboxylic acids with a total of 5 to 8 carbon atoms, ie compounds of the general formula

R

HO C C - C OH

H. I H ', 2nd

COOH

in which R represents an alkyl radical having 1 to 4 carbon atoms. A particularly preferred structural component (C) is 2,2-dimethylolpropionic acid

The starting component (D) is nonionic, hydrophilic polyethylene glycols which have one or two hydroxyl groups it is mono- or dihydric polyether alcohols in the molecular weight range from 600 to 3000, as are obtained in a manner known per se by alkoxylation of mono- or dihydric alcohols as starter molecules, ethylene oxide or mixtures of ethylene oxide with up to 40% by weight as alkylene oxides (based on the total weight of the alkylene oxides) of propylene oxide. The corresponding amino-functional derivatives, known as Jeffamin M or Jeffamin D series (commercial products from Huntsman), are also suitable components (D)

The content of components (C) and / or components (D) must be adjusted so that the dispersibility of the polyurethane polyureas in water is ensured. In a preferred production process, the use of component (D) is completely dispensed with and the hydrophilicity required for the dispersion ensured solely by the use of component (C) The amount of anionic groups incorporated is dimensioned such that a maximum of 100 milliequivalents per 100 g of solid ionic groups are present in the polyurethane polyurea ultimately obtained

The compounds (E) required for the polyaddition reaction are aphatic, cycloahphatic and / or aromatic polyisocyanates

It is essential for the present invention that at least 70% by weight of the polyisocyanate component (E) consists of cycloaliphatic dnsocyanates. In a particularly preferred production process, only cycloaliphatic diisocyanates such as isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate and / or 1 , 4- or 1, 3-cyclohexane diisocyanate used

Examples of other polyisocyanates to be used proportionally (up to 30% by weight) are 1,6-hexamethylene diisocyanate (HDI), tetramethyl endiisocyanate, 2,3,3-Tπ-methylhexamethylene di-isocyanate, 1,4-phenylenedinsocyanate, 2,6- and 2.4 -Toluene dπsocyanat, 1,5 naphthylene diisocyanate, 2,4'- and 4,4'-diphenylmethane diisocyanate It is of course also possible to use those known per se in polyurethane chemistry higher-proportionate polyisocyanates or modified polyisocyanates known per se, for example carbodiimide groups, allophanate groups, isocyanurate groups, urethane groups and / or polyisocyanates having biuret groups.

Components (A) to (E) are placed in a reactor and converted to an NCO-containing prepolymer under anhydrous conditions in a temperature range from 30 to 30 ° C. The ratio of equivalents of isocyanate groups to compounds reactive towards isocyanate groups is 1.1: 1 to 3: 1, preferably 1.5: 1 to 2: 1. When calculating the ratio of equivalents,

Carboxy groups which are introduced into the prepolymer, for example, by using 2,2-dimethylol propionic acid, are not taken into account. The isocyanate polyaddition reaction can take place in the presence of catalysts known in polyurethane chemistry, such as, for example, organo-tin compounds. Furthermore, an organic one can be used before, during or after the prepolymer production

Solvents are used to control viscosity.

Suitable solvents are e.g. As acetone, 2-butanone, tetrahydrofuran, dioxane, dimethylformamide, N-methyl-2-pyrrolidone (NMP), ethyl acetate, alkyl ethers of ethylene and propylene glycol and aromatic hydrocarbons. The use of water-miscible solvents is preferred. Low-boiling solvents, such as. B. acetone used, they can be removed from the resulting polyurethane-polyurea dispersions by distillation, and completely solvent-free dispersions are obtained. Are solvents with higher boiling points than water, such as. B. NMP used, these solvents remain in the polyurethane-polyurea dispersions and accelerate the film formation of the dispersed particles as a coalescence aid.

Before the prepolymer is dispersed in water and the chain is extended or crosslinked with component (F), the potential ionic groups present in the prepolymer must be converted into ionic groups by neutralization. For neutralization, especially when using carboxyl group-containing structural components (C), preferably tertiary amines. Such tertiary amines are, for example, triethylamine, tri-n-butylamine,

N-methylmorpholine, N, N-dimethylethanolamine, N-methylpiperidine, N-methylpiperazine and triethanolamine. The use of inorganic bases such as sodium hydroxide or potassium hydroxide as a neutralizing agent is also possible, although less preferred. Mention should also be made of the possibility of using component (C) in neutralized form in the preparation of the prepolymer. Through the

Neutralization of the potential ionic groups, possibly with additional nonionic components (D), ensures that the formation of stable aqueous dispersions is ensured. In general, at least 80%, but preferably 100%, of the potential ionic groups are converted into ionic groups by neutralization. The neutralization reaction usually takes place at

Temperatures below 100 ° C and preferably in the temperature range from 30 to

80 ° C.

The neutralized NCO-containing prepolymers are converted into aqueous dispersions by the methods known in polyurethane chemistry. One possibility is to add the dispersing water, which contains component (F), to the prepolymer. In this process, the organic prepolymer first forms the continuous phase. When water is added, the phase reverses and the water becomes a continuous phase.

In the second possibility of dispersion, the neutralized prepolymer is added to the dispersing water. Component (F) can be initially introduced into the dispersing water or, alternatively, can only be added after the prepolymer has been dispersed.

The dispersing step is preferably carried out in a temperature range from 20 to 40 ° C. The dispersibility of the prepolymers in water can be improved by the additional use of external emulsifiers. Component (F) consists of a mixture of one or more diamines with a polyamine with functionality> 2. The diamines lead to a chain extension of the prepolymers, while the polyamine with the functionality> 2 additionally incorporates crosslinking points in the molecule. Since the reaction of the prepolymer with the components of component (F) takes place in an aqueous medium, the compounds of component (F) are characterized by a far higher reactivity towards isocyanate groups than water. The amount of component (F) to be used depends on the unreacted isocyanate groups of the prepolymer which are still present.

Suitable diamines are, for example, 1,2-diaminoethane, 1,6-diaminohexane, piperazine, 2,5-dimethylpiperazine, l-amino-3-aminomethyl-3,5,5-trimethy! Cyclohexane, 4,4'-diaminodicylo-hexylmethane , 1, 4-diaminocyclohexane and / or 1, 2-propylenediamine. Hydrazine, amino acid hydrazides, bishydrazides and bis-semicarbazides are also suitable as chain extenders.

Examples of polyamines with a functionality of> 2 are diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, polyethyleneimines and melamine.

Polyurethane-polyurea dispersions which have the composition according to the invention and were produced by the processes described are very finely divided, stable in storage and have pH values in the range from 6 to 9. The solids contents are between 20 and 60% by weight, in particular between 25 and 45% by weight. The organic solvent content is at most 15% by weight.

After the physical drying, the polyurethane polyurea dispersions according to the invention provide coatings with very good chemical and in particular very good ethanol resistance.

The new polyurethane polyurea dispersions can be used as paint binders for coating any substrates. These include organic and inorganic materials such as glass, wood, metals, plastics, leather and paper. The polyurethane polyurea dispersions according to the invention can be used as the sole binder. However, there is the possibility of blending with other dispersions, such as polyvinyl acetate, polyethylene, polystyrene, polybutadiene, polyvinyl chloride, polyacrylate and copolymer plastic dispersions. Furthermore, the auxiliaries and additives customary in coating technology, such as pigments, fillers, plasticizers, matting agents, coalescing agents, waxes, defoamers and wetting agents, can be incorporated into the dispersions according to the invention.

The lacquers are applied using the usual methods of lacquer technology, for example by spraying, pouring, dipping or rolling.

The following examples are intended to illustrate the invention without restricting it.

Examples

example 1

In a 1 liter reaction vessel with an agitation, cooling and heating device, 56.0 g

Desmophen 1200 (weakly branched polyester polyol from Bayer, OH content = approx. 5% by weight), 8.3 g neopentyl glycol, 2.0 g Tπmethylolpropane, 15.0 g polyethylene glycol monomethyl ether with a molecular weight of 750, 5.0 g Weighed dimethylolpropionic acid and 95.9 g 4,4'-diιso-cyanatdιcyclohexylmethane (= Desmo- dur W) at room temperature and dissolved in 78.7 g N-methylpyrrolidone (NMP). Then 0.18 g dibutylzmndilaurate was added and the mixture heated to 65 ° C. and stirred at this temperature for 5 hours. The batch is then cooled to room temperature, 3.7 g of triethylamine being added at about 45 ° C. to neutralize the dimethylolpropionic acid. The prepolymer solution obtained is stirred vigorously at about 25 ° C dispersed in 250 g of water Finally, a mixture of 3.6 g of ethylenediamine and 4.1 g of diethylenetriamine dissolved in 25 g of water is added to the dispersion formed. The dispersion obtained has a solids content of 34.7% by weight. and an NMP content of 14.5% by weight. The pH is 7.6 and the run-out time (measured in the DIM-4 beaker) is 18 s

Example 2

In a 1-1 reaction vessel with Ruhr, cooling and heating device, 81.5 g

Desmophen 1695 (linear polyester polyol from Bayer, OH content = approx. 3.4% by weight), 9.7 g neopenyl glycol, 3.0 g tπmethylolpropane, 11.5 g dimethylol propionic acid and 123.4 g 4.4 '-Diisocyanatdιcyclohexylmethan (= Desmodur W) weighed at room temperature and dissolved in 98.4 g of N-methylpyrrohdon (NMP). Then 0.23 g of dibutylzmndilaurate are added and the mixture is heated to 75 ° C. and stirred for 3 hours at this temperature Approach cooled to room temperature, 8.6 g of triethylamine for neutralization at about 45 ° C. the dimethylolpropionic acid are added. The prepolymer solution obtained is dispersed in 315 g of water with vigorous stirring at about 25 ° C. Finally, a mixture of 4.6 o of ethylenediamine and 5.3 g of diethylenetriamine dissolved in 30 g of water is added to the dispersion formed. The dispersion obtained has a solids content of 34.6% by weight and an NMP content of 14.2% by weight. The pH is 7.7 and the run-out time (measured in a DIN 4 cup) is 20 s .

Example 3

85.4 g of oxyester T 1 136 (linear polyester polyol from Hüls; OH number = 107 mg KOH / g polyester), 13.2 g of neopentyl glycol, 1. Are in a 1 -1 reaction vessel with a stirring, cooling and heating device 1.5 g of dimethylolpropionic acid and 123.4 g of 4,4'-diisocyanate dicyclohexylmethane (= Desmodur W) are weighed in at room temperature and dissolved in 84.5 g of N-methylpyrrolidone (NMP). Then 0.23 g of dibutylzmndilaurate is added and the mixture is adjusted to 75 ° C warmed and stirred for 3 hours at this temperature. The batch is then cooled to room temperature, 8.6 g of triethylamine being added at about 45 ° C. to neutralize the dimethylolpropionic acid. The prepolymer solution obtained is vigorous

Ruhren dispersed in approx. 25 ° C in 335 g water. Finally, a mixture of 4.6 g of ethylenediamine and 5.3 g of diethylenetriamine dissolved in 30 g of water is added to the dispersion formed. The dispersion obtained has a solids content of 34.7% by weight and an NMP content of 12% by weight. The pH is 7.7 and the run-out time (measured in a DIN-4 cup) is 17 s

Example 4 (= comparative example)

In this comparative example, component (B) is not used 100 g Desmophen 1200 (weakly branched polyester polyol from Bayer, OH content = approx. 5% by weight), 10.0 g polyethylene glycol monomethyl ether with a molecular weight of 750 are placed in a 1 -1 reaction vessel with a stirring, cooling and heating device. 10.0 g of dimethylolpropionic acid and 95.9 g of 4,4'-dnsocyanatodicyclohexylethane (= Desmodur W) were weighed in at room temperature and in 92.5 g

N-methylpyrrolidone (NMP) dissolved 0.18 g of dibutylzmndilaurate are then added and the batch is heated to 65 ° C. and stirred at this temperature for 5 hours. The batch is then cooled to room temperature, 7.5 g of triethylamine being added at about 45 ° C. Neutralization of the dimethylolpropionic acid are added. The prepolymer solution obtained is stirred vigorously at about 25 ° C. in 290 g

Dispersed water Finally, a mixture of 3.6 g of ethylenediamine and 4.1 g of diethylenetriamine dissolved in 25 g of water egg is added to the dispersion formed. The dispersion obtained has a solids content of 35% by weight and an NMP content of 14.5% by weight. The pH is 7.2 and the run-out time (measured in a DIN 4 cup) is 20 s

Example 5 (= comparative example)

These are commercially available polyurethane dispersions

Manufacturers' information based on polyester polyols. The following products were compared with the dispersions according to the invention

NeoRez R-961 and NeoRez R-974 (commercial products from Zeneca) and U 710 and U 910 (commercial products from Alberdingk Boley)

In addition, NeoRez R-985 (commercial product from Zeneca), a polyurethane dispersion based on a polycarbonate diol, was included in the tests Checking the chemical resistance of the dispersions according to the invention and the comparative examples

The chemical resistance was checked on wood (ash). For this purpose, the wooden surface was lightly pre-sanded with sandpaper and the sanding dust wiped off. Using a box squeegee, lifts with a wet film thickness of 120 μm were then drawn onto the wood test surface from the dispersions to be tested. The wet films were then dried at 50 ° C. for 24 hours. The lacquer surfaces were then sanded and the grinding dust removed. A second lift with a thickness of 120 μm was then carried out. It was dried again at 50 ° C for 24 hours.

After cooling to room temperature, approx. 1 x 1 x 1 cm pieces of felt soaked with the test agent were placed on the test areas obtained and covered with a screw cap. After a defined exposure time, the felt pieces were removed and the test area cleaned with a paper towel Chemicals were tested in accordance with DIN 68861

- Ethanol (48 vol% in deionized water, exposure time 1 hour)

- water (deionized water, exposure time 16 hours)

- ammonia (10% by weight solution in water, exposure time 1 hour)

- dibutyl phthalate (exercise duration 16 hours)

- acetone (exposure time 10 s) - coffee (dissolved powder coffee; exposure time 1 hour) The test areas were assessed after storage for 24 hours on the following grading scale

Grade 0 No visible changes

Notel just recognizable changes in gloss or color

Note 2 Slight changes in gloss or color, the structure of the test surface is not changed. Note 3 Strong markings are visible, but the structure of the test surface is largely undamaged. Note 4 Strong markings are visible, the structure of the test surface is changed destroyed

The results of the tests are summarized in the table below. It can be seen that the polyurethane polyurea

Dispersions have significantly better chemical resistance than the commercially available polyester-based polyurethane dispersions. The resistance of the dispersion based on the polycarbonate diol is also exceeded

Table: Results of chemical resistance

Ethanol water ammonia dibutyl acetone coffee phthalate

Ex. L 2 0 1 0 0 0

Ex. 2 0 0 1 0 0 0

Ex. 3 0 0 0 0 0 0

Ex. 4 4 1 1 1 l 0

NeoRez 3 0 0 2 0 1 R-961

NeoRez 4 1 4 3 1 2

R-974

NeoRez 3 0 3 0 0 0 R-985

U 710 3 0 0 3 0 2

U 910 5 0 2 0 0

1

Claims

claims

1 Polyurethane urea dispersions can be obtained by converting

(D) 0 to 15% by weight of a hydrophilic, monohydric or dihydric alcohol having units of ethylene oxide and having a molecular weight of 600

(E) 30 to 70% by weight, preferably 40 to 60% by weight, of one or more polyisocyanates, at least 70% by weight of the polyisocyanate component consisting of one or more cycloaliphatic Dusocyanates,

(F) 0.5 to 10% by weight of a mixture of one or more diamines with a polyamine of functionality> 2, where at least 20% by weight of component (F) consists of the polyamine of functionality> 2, components (A ) - (F) always add up to 100% in total

2. Use of polyurethane urea dispersions according to claim I as paint binders.

3. Coatings made with polyurethane urea dispersions according to claim 1.