WO2011089090A1

WO2011089090A1 - Urethanized polyesters

Info

Publication number: WO2011089090A1
Application number: PCT/EP2011/050522
Authority: WO
Inventors: Heinz-Dietmar Gewiss; Marc Claudius Schrinner; Robert Reyer; Sandra Hackbarth; Christoph Irle; Martin Melchiors
Original assignee: Bayer MaterialScience AG
Current assignee: Covestro Deutschland AG
Priority date: 2010-01-21
Filing date: 2011-01-17
Publication date: 2011-07-28
Anticipated expiration: 2012-07-21
Also published as: EP2348060A1; TW201136964A

Abstract

The invention relates to novel urethanized polyesters, to processes for their preparation and to their use in binder combinations and coating agents.

Description

Urethanized polyesters

In recent years, against the background of increasingly stringent environmental legislation, water-dispersible urethanized polyesters have become more important for a variety of application areas. Today they are used especially as a component of high-quality water- thinnable two-component polyurethane lacquers (2C PUR lacquers).

Despite being broadly accepted in the market for a very wide variety of applications, the currently available urethanized polyesters have disadvantages. Independently of the type of modification, aqueous 2C PUR lacquers currently contain predominantly water-dispersible urethanized polyesters based on phthalic acid (anhydride) or isophthalic acid (anhydride).

Although these normally produce coatings with good resistance to chemical and mechanical stress, even at low temperatures, they exhibit inadequate gloss in many cases.

One object of the present invention was therefore to provide urethanized polyesters whose use in coating agents makes it possible to obtain lacquers with high gloss.

Another object of the present invention was to provide urethanized polyesters whose use in coating agents makes it possible to obtain lacquers having a gloss level at 60° greater than 90, especially greater than 92, according to DIN 67530.

One object of the present invention was therefore to provide urethanized polyesters whose use in coating agents makes it possible to obtain lacquers with good resistance to chemical and mechanical stress and with high gloss.

The above object was achieved by the subjects of the invention.

The present invention provides urethanized polyesters obtainable by a process in which a reaction product is obtained in a first reaction stage from a) 10 to 25 wt.% of an unsubstituted or substituted benzoic acid that can be substituted by 1, 2 or 3 substituents selected from the group comprising F, CI, Br, -OH, -CH₃, -CH₂-CH₃, -O- CH₃ and -0-CH₂-CH₃, b) 15 to 50 wt.% of at least one di- and/or tricarboxylic acid or their anhydrides, c) 20 to 60 wt.% of at least one di- and/or trihydric alcohol and d) 3 to 20 wt.%) of dimethylolpropionic acid and/or dimethylolbutanic acid, the weights of components a) to d) adding up to 100 wt.%,

and the reaction product (A) is reacted in a subsequent reaction stage with at least one organic polyisocyanate (B).

Preferably, the reaction product (A) is obtainable from 11 to 20 wt.% of an unsubstituted or substituted benzoic acid that can be substituted by 1 , 2 or 3 substituents selected from the group comprising F, CI, Br, -OH, -CH₃, -CH₂-CH₃, -0-CH₃ and -0-CH₂-CH₃.

Preferably, the reaction product (A) is obtainable from 25 to 40 wt.% of at least one di- and/or tricarboxylic acid or their anhydrides. Preferably, the reaction product (A) is obtainable from 30 to 50 wt.% of at least one di- and/or trihydric alcohol. Preferably, the reaction product (A) is obtainable from 3 to 15 wt.% of dimethylolpropionic acid.

Preferably, the urethanized polyester has an acid number of 20 to 35 mg KOH/g, as determined according to DIN 3682.

Preferred di- and/or tricarboxylic acids or their anhydrides are those with a molecular weight in the range from 98 g/mol to 600 g/mol.

Preferred di- and/or tricarboxylic acids or their anhydrides are those selected from the group comprising phthalic acid (anhydride), isophthalic acid, terephthalic acid, tetrahydrophthalic acid (anhydride), hexahydrophthalic acid (anhydride), maleic acid (anhydride), succinic acid (anhydride), fumaric acid, adipic acid, sebacic acid, azelaic acid and benzenetricarboxylic acid.

Particularly preferred di- and/or tricarboxylic acids or their anhydrides are those selected from the group comprising phthalic acid, phthalic anhydride, hexahydrophthalic anhydride, isophthalic acid, maleic anhydride, terephthalic acid, fumaric acid, adipic acid and benzenetricarboxylic acid.

Very particularly preferred di- and/or tricarboxylic acids or their anhydrides are those selected from the group comprising phthalic acid, phthalic anhydride, isophthalic acid and isophthalic anhydride.

Preferred di- and trihydric alcohols are those with a molecular weight range of 62 to 400.

Preferred di- and trihydric alcohols are those selected from the group comprising ethylene glycol, 1 ,2- and 1 ,3-propylene glycol, 1 ,3-, 1 ,4- and 2,3-butanediol, 1,6-hexanediol, 2,5- hexanediol, trimethylhexanediol, diethylene glycol, triethylene glycol, hydrogenated bisphenols, 1 ,4-cyclohexanediol, 1 ,4-cyclohexanedimethanol, neopentyl glycol, 1,4- butanediol, trimethylolpropane, glycerol and trimethylpentanediol.

Particularly preferred di- and trihydric alcohols are those selected from the group comprising ethylene glycol, 1 ,2-propylene glycol, 1,6-hexanediol, 1 ,4-cyclohexanedimethanol, neopentyl glycol, trimethylolpropane and glycerol.

Very particularly preferred di- and trihydric alcohols are those selected from the group comprising neopentyl glycol and trimethylolpropane.

The weight-average molecular weight Mw of the urethanized polyester is preferably in the range between 3500 g/mol and 30,000 g/mol, particularly preferably in the range between 4500 g/mol and 10,000 g/mol and very particularly preferably in the range between 5000 g/mol and 7000 g/mol, as determined according to DIN 55672/1 or DIN 55672/2.

The number-average molecular weight Mn of the urethanized polyester is preferably in the range between 500 and 20,000 g/mol, particularly preferably in the range between 800 and 10,000 g/mol and very particularly preferably in the range between 1000 g/mol and 2000 g/mol, as determined according to DIN 55672/1 or DIN 55672/2.

The hydroxyl number of the urethanized polyester is preferably in the range between 45 and 190 mg KOH/g, particularly preferably in the range between 70 mg KOH/g and 165 mg KOH/g and very particularly preferably in the range between 110 mg KOH/g and 150 mg KOH/g, as determined according to DIN 53240 part 2. Examples of polyisocyanates preferred as component B) are any monomeric diisocyanates and triisocyanates obtainable by phosgenation or by phosgene-free processes, e.g. thermal urethane cleavage. Particularly preferred diisocyanates are those in the molecular weight range from 140 to 400 g/mol which have aliphatically, cycloaliphatically, araliphatically and/or aromatically bonded isocyanate groups, e.g. 1 , 4-diisocyanatobutane, 1,6- diisocyanatohexane (HDI), 2-methyl-l,5-diisocyanatop entane, 1 , 5-diisocyanato-2,2- dimethylpentane, 2,2,4- or 2,4,4-trimethyl-l,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1 ,4-diisocyanatocyclohexane, 2,4- and 2,6-diisocyanato-l-methylcyclohexane, 1,3- a n d 1 , 4-bis(isocyanatomethyl)-cyclohexane, l-isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 4,4'- diisocyanatodicyclohexylmethane, 2,4 '-diisocyanatodicyclohexylmethane, 1 -isocyanato- 1 - methyl-4(3)-isocyanatomethylcyclohexane, bis(isocyanatomethyl)norbornane, 1,3- and 1 ,4- bis(2-isocyanatoprop-2-yl)-benzene (TMXDI), 2,4- and 2,6-diisocyanatotoluene (TDI), 2,4'- and 4,4'-diisocyanatodiphenylmethane (MDI), 1,5-diisocyanatonaphthalene or any mixtures of such diisocyanates.

However, other polyisocyanates also suitable as component B) are any polyisocyanates of uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structure made up of at least two diisocyanates and obtainable by modification of said aliphatic, cycloaliphatic, araliphatic and/or aromatic diisocyanates, e.g. those described as examples in J. Prakt. Chem. 336 (1994) 185 - 200 and EP-A 0 798 299.

Very particularly preferably, component (B) is isophorone diisocyanate.

Preferred urethanized polyesters are those obtainable by a process in which a reaction product (A) is obtained in a first reaction stage from a) 10 to 20 wt.% of an unsubstituted or substituted benzoic acid that can be substituted by 1, 2 or 3 substituents selected from the group comprising F, CI, Br, -OH, -CH₃, -CH₂-CH₃, -O- CH₃ and -0-CH₂-CH₃, b) 25 to 40 wt.% of at least one di- and/or tricarboxylic acid or their anhydrides, c) 30 to 50 wt.% of at least one di- and/or trihydric alcohol and d) 3 to 10 wt.% of dimethylolpropionic acid or dimethylol butanic acid, the weights of components a) to d) adding up to 100 wt.%,

Particularly preferred urethanized polyesters are those obtainable by a process in which a reaction product (A) is obtained in a first reaction stage from a) 10 to 20 wt.% of an unsubstituted benzoic acid, b) 25 to 40 wt.%) of at least one di- and/or tricarboxylic acid selected from the group comprising phthalic acid and isophthalic acid, or their anhydrides, c) 30 to 50 wt.%) of at least one di- and/or trihydric alcohol selected from the group comprising neopentyl glycol and trimethylolpropane, and d) 3 to 10 wt.%) of dimethylolpropionic acid, the weights of components a) to d) adding up to 100 wt.%,

The present invention also provides a process for the preparation of urethanized polyesters wherein, in a first reaction step, components a), b) and c) are reacted for a period preferably of 2 to 40 hours, particularly preferably of 5 to 30 hours, preferably in the presence of an organic solvent or without a solvent, particularly preferably without a solvent, at a temperature preferably in the range between 100°C and 250°C, particularly preferably in the range between 120°C and 220°C. In a second reaction step, the resulting polyester is reacted with component d), preferably in the presence of an organic solvent selected from the group comprising N-methylpyrrolidone, N-ethylpyrrolidone diethylene glycol dimethyl ether, methyl ethyl ketone, methyl isobutyl ketone, acetone, xylene, toluene, butyl acetate and mixtures, particularly preferably in acetone, or without any organic solvent in the presence of a catalyst. The reaction preferably proceeds at a temperature in the range between 50°C and 80°C, for a period of 2 hours to 20 hours.

In a subsequent reaction step, the reaction product (A) is reacted with at least one polyisocyanate (B).

The urethanization already takes place at room temperature (23 °C), but, if desired, can also be carried out at lower or higher temperatures. The reaction can be accelerated by using temperatures of up to 160°C.

However, in the preparation of the urethanized polyesters, it is optionally also possible to accelerate the urethanization reaction by the concomitant use of the conventional catalysts known from polyurethane chemistry, examples being tertiary amines such as triethylamine, pyridine, methylpyridine, benzyldimethylamine, Ν,Ν-endoethylenepiperazine, N- methylpiperidine, pentamethyldiethylenetriamine, Ν,Ν-dimethylaminocyclohexane and Ν,Ν'- dimethylpiperazine, or metal salts such as iron(III) chloride, aluminium tri(ethylacetoacetate), zinc chloride, zinc(II) n-octanoate, zinc(II) 2-ethyl-l-hexanoate, zinc(II) 2-ethylcaproate, zinc(II) stearate, zinc(II) naphthenate, zinc(II) acetylacetonate, tin(II) n-octanoate, tin(II) 2- ethyl-l-hexanoate, tin(II) ethylcaproate, tin(II) laurate, tin(II) palmitate, dibutyltin(IV) oxide, dibutyltin(IV) dichloride, dibutyltin(IV) diacetate, dibutyltin(IV) dimaleate, dibutyltin(IV) dilaurate, dioctyltin(IV) diacetate, bismuth 2-ethyl-l-hexanoate, bismuth octanoate and molybdenum glycolate, or any mixtures of such catalysts.

The urethanized polyester is obtained by reacting components (A) and (B) in a ratio preferably in the range between 2: 1 and 5: 1, particularly preferably in the range between 2:1 and 4:1, very particularly preferably in the range between 2.5: 1 and 3.5:1.

Before or during the dispersion step, 25% to 1 10%, preferably 40%> to 1 10%), of the incorporated carboxyl groups are converted to carboxylate groups by the addition of at least one base.

Preferably, the bases are selected from the group comprising ammonia, N-methylmorpholine, triethylamine, dimethylethanolamine, methyldiethanolamine, triethanolamine, morpholine, tripropylamine, ethanolamine, triisopropanolamine, 2-amino-2-methyl-l-propanol and mixtures thereof. Particularly preferred bases are ammonia and dimethylethanolamine.

After the preparation of the urethanized polyester, specific properties can be achieved by also adding small amounts of other organic solvents to the dispersion, examples being ethanol, propanol, butanol, butyl glycol, hexanol, Dowanol PnB, octanol, butyl diglycol, ethyl diglycol, methyl diglycol and methoxypropanol.

Alternative possibilities in the dispersion step are to add the mixture of water and base to the urethanized polyester, to add the water to the mixture of urethanized polyester and base, to add the urethanized polyester to the mixture of water and base or to add the mixture of urethanized polyester and base to the water. If desired, the dispersibility of the urethanized polyesters in water can be improved by the concomitant use of external emulsifiers, e.g. ethoxylated nonylphenol, during dispersion.

The dispersion step is conventionally carried out at 40°C to 120°C.

The present invention also provides an aqueous binder combination containing at least one urethanized polyester according to the invention, as described above.

The aqueous binder combination has a solids content preferably of 30 wt.% to 50 wt.%, particularly preferably of 33 wt.-% to 48 wt.-%.

The proportion of organic solvents in the aqueous binder combination is preferably < 6 wt.%, particularly preferably < 4 wt.% and very particularly preferably < 2 wt.%>.

The viscosity of the aqueous binder combination is preferably from 10 mPa-s to 30,000 mPa-s, particularly preferably from 50 mPa-s to 10,000 mPa-s and very particularly preferably from 500 mPa-s to 8000 mPa-s at 23°C, as determined by means of a Brookfield rotational viscometer.

The pH of the aqueous binder combination is preferably from 5 to 10, particularly preferably from 6 to 9.

Depending on the molecular weight of the urethanized polyester, the content of carboxyl or carboxylate groups, the type of neutralizer used and the types of auxiliary solvent used, if any, the urethanized polyesters are in the form of a solution or a dispersion; in general, however, both dissolved and dispersed fractions are present in the binder combination.

The present invention also provides a coating agent containing at least one aqueous binder combination according to the invention, together with other auxiliary substances and additives.

Preferred auxiliary substances and additives are defoamers, thickeners, flow control agents, pigments and pigment dispersing aids.

The resulting coating agents according to the invention are suitable for all fields in which solvent-containing, solventless other types of aqueous paint and coating systems with an enhanced property profile are used, e.g. the coating of practically all mineral building surfaces such as lime- and/or cement-bonded casts, surfaces containing plaster, fibre cement building materials, and concrete; the lacquering and sealing of wood and ligneous materials such as chipboard, fibreboard and paper; the lacquering and coating of metal surfaces; the coating and lacquering of asphalt- or bitumen-containing road surfaces; and the lacquering and sealing of various plastic surfaces; they are also suitable for the adhesive bonding of various identical or different sheet materials. The coating agents according to the invention can be used in these processes as binders for priming lacquers, filling lacquers and top coat lacquers.

Examples

1.1. Synthesis of the polyester (according to the invention)

Phthalic anhydride (724 g), isophthalic acid (1039 g), trimethylolpropane (1714 g), neopentyl glycol (521 g) and benzoic acid (745 g) are weighed into a typical esterification apparatus consisting of a flask equipped with reflux condenser, stirrer and dropping funnel, and heated to 140°C under a nitrogen atmosphere. After three hours the temperature is raised to 170°C. Condensation is effected at 220°C until the acid number is < 3 and the hydroxyl number 240 - 270 mg KOH/g. The crude product is purified before the next step and dimethylolpropionic acid (80 g), Desmorapid^® SO (1.5 g) (Sn(II) octanoate) and acetone (808 g) are added, with stirring.

1.2. Synthesis of the aqueous dispersion (according to the invention)

1045 g of the crude polyester product obtained from step 1 are heated to 55°C, reacted with isophorone diisocyanate (305 g) and neutralized with dimethylethanolamine (57.8 g). Finally, the product is dispersed in water (1984 g) and the acetone is distilled off under vacuum.

Solids content: 43.9% The solids content was determined in a drying cabinet and calculated as follows: final weight [g] * 100 / initial weight [g] = wt.% solids

Viscosity (23°C): 2280 mPa-s

The viscosity was determined with a Brookfield rotational viscometer. Acid number: 26.6

The acid number was determined according to DIN 3682. pH: 7.7

The pH was measured according to international standard ISO 976.

2.1. Synthesis of the polyester (according to the invention)

Phthalic anhydride (2056 g), isophthalic acid (3033 g), trimethylolpropane (4506 g), neopentyl glycol (1064 g), benzoic acid (1428 g) and soya oil fatty acid (1636 g) are weighed into a typical esterification apparatus consisting of a flask equipped with reflux condenser, stirrer and dropping funnel, and heated to 140°C under a nitrogen atmosphere. After three hours the temperature is raised to 170°C. Condensation is effected at 220°C until the acid number is < 3 and the hydroxyl number 240 - 270 mg KOH/g. The crude product is purified before the next step and dimethylolpropionic acid (90 g), ethylene glycol (7.5 g), NMP (264.7 g) and Desmorapid^® SO (1.5 g) (Sn(II) octanoate) are added, with stirring.

2.2. Synthesis of the aqueous dispersion (according to the invention)

1584.7 g of the crude polyester product obtained from step 1 are heated to 55°C, reacted with isophorone diisocyanate (262.5 g) and neutralized with dimethylethanolamine (45.7 g). Finally, the product is dispersed in water (1497 g) and the acetone is distilled off under vacuum.

Solids content: 44.7%

The solids content was determined in a drying cabinet and calculated as follows: final weight [g] * 100 / initial weight [g] = wt.% solids

Viscosity (23°C): 2490 mPa-s

The viscosity was determined with a Brookfield rotational viscometer.

Acid number: 26.8 The acid number was determined according to DIN 3682. pH: 7.4

The pH was measured according to international standard ISO 976.

3.1. Synthesis of the polyester (comparison)

Isophthalic acid (759 g), trimethylolpropane (2383 g) and neopentyl glycol (1375 g) are weighed into a typical esterification apparatus consisting of a flask equipped with reflux condenser, stirrer and dropping funnel, and heated to 140°C under a nitrogen atmosphere. After three hours the temperature is raised to 170°C. Condensation is effected at 220°C until the acid number is < 3 and the hydroxyl number 240 - 270 mg KOH/g. The crude product is purified before the next step and trimethylolpropane (12.0 g), dimethylolpropionic acid (90 g), Desmorapid^® SO (1.9 g) (Sn(II) octanoate) and acetone (808 g) are added, with stirring.

3.2. Synthesis of the aqueous dispersion (comparison)

2036.6 g of the crude polyester product obtained from step 1 are heated to 55°C, reacted with isophorone diisocyanate (273.3 g) and neutralized with dimethylethanolamine (53.8 g). Finally, the product is dispersed in water (1833 g) and the acetone is distilled off under vacuum.

Solids content: 46.5%

Viscosity (23°C): 920 mPa-s

The viscosity was determined with a Brookfield rotational viscometer. Acid number: 29.2

The acid number was determined according to DIN 3682. pH: 7.4

The pH was measured according to international standard ISO 976.

4. Preparation of the coating

Example 1 (according to the invention)

Table 1: Formulation of an aqueous 2C PUR varnish

¹ Air Products N.L., additive for improving flow, substrate wetting, defoaming

² Borchers GmbH, Monheim, dispersing additive

³ Borchers GmbH, Monheim, flow control agent and defoamer

⁴ Borchers GmbH, Monheim, thickener

⁵ Tronox Incor., USA, Ti0₂

Example 2 (comparison)

Table 2: Formulation of an aqueous 2C PUR varnish

¹ Air Products N.L., additive for improving flow, substrate wetting, defoaming

² Borchers GmbH, Monheim, dispersing additive

³ Borchers GmbH, Monheim, flow control agent and defoamer

⁴ Borchers GmbH, Monheim, thickener

⁵ Tronox Incor., USA, T1O₂

Technical application data

Table 3: Gloss levels (Clear coat)

Table 4: Gloss levels (Top coat)

Gloss 20°/60°/haze according Gloss 20°/60°/haze according

to DIN 67530 (Table 1) to DIN 67530 (Table 2)

55/85/15 58/72/9

Claims

1. Urethanized polyester with an acid number ranging from 15 to 35 mg KOH/g, obtainable by a process in which a reaction product (A) is obtained in a first reaction stage from a) 10 to 25 wt.% of an unsubstituted or substituted benzoic acid that can be substituted by 1 , 2 or 3 substituents selected from the group comprising F, CI, Br, - CH₃, -CH₂-CH3, -OH, -O-CH3 and -0-CH₂-CH₃, b) 15 to 50 wt.% of at least one di- and/or tricarboxylic acid or their anhydrides, c) 20 to 60 wt.% of at least one di- and/or trihydric alcohol and d) 3 to 20 wt.%) of dimethylolpropionic acid and/or dimethylolbutanic acid, the weights of components a) to d) adding up to 100 wt.%>, and the reaction product (A) is reacted in a subsequent reaction stage with at least one organic polyisocyanate (B).

2. Urethanized polyester according to Claim 1, characterized in that it has an acid number of 20 to 35 mg KOH/g.

3. Urethanized polyester according to Claim 1 , characterized in that the di- and/or tricarboxylic acids or their anhydrides are selected from the group comprising phthalic acid, phthalic anhydride, hexahydrophthalic anhydride, isophthalic acid, maleic anhydride , terephthalic aci d, fumaric aci d, adip ic acid and benzenetricarboxylic acid.

4. Urethanized polyester according to Claim 1, characterized in that the di- and trihydric alcohols are selected from the group comprising ethylene glycol, 1 ,2-propylene g ly c o l , 1 , 6-hexanediol, 1 ,4-cyclohexanedimethanol, neopentyl glycol, trimethylolpropane and glycerol.

5. Urethanized polyester according to one or more of Claims 1 to 4, characterized in that it has a weight-average molecular weight Mw in the range between 3500 g/mol and 30,000 g/mol.

6. Urethanized polyester according to one or more of Claims 1 to 5, characterized in that it has a number-average molecular weight Mn in the range between 500 g/mol and 20,000 g/mol.

7. Urethanized polyester according to one or more of Claims 1 to 6, characterized in that it has a hydroxyl number in the range between 45 mg KOH/g and 190 mg KOH/g.

8. Urethanized polyester according to one or more of Claims 1 to 7, characterized in that it is obtained by reacting components (A) and (B) in a ratio in the range between 2:1 and 5:1.

9. Aqueous binder combination containing at least one urethanized polyester according to one or more of Claims 1 to 8.

10. Aqueous binder combination according to Claim 9, characterized in that it has a solids content of 30 to 50 wt.%.

11. Coating agent containing at least one aqueous binder combination according to Claim 9 or 10, together with other auxiliary substances and additives.