MODIFIED HYPERBRANCHED POLYESTER POLYMERS, PROCESSES FOR PREPARING THEM AND USES OF THEM

Abstract: Hyperbranched polyester polyols are modified by esterification with a carboxylic acid and the introduction of acrylate or methacrylate groups. By this consecutive or mixed end-capping the modified hyperbranched polyester polyols can be tailored to obtain either very specific or mixed properties. It is possible to use these modified hyperbranched polyester polyols in new industrial applications, such as inks.

Description: MODIFIED HYPERBRANCHED POLYESTER POLYMERS, PROCESSES FOR PREPARING THEM AND USES OF THEM BACKGROUND OF THE INVENTION Field of the invention The present invention relates to modified hyperbranched polyester polymers, processes for preparation of these modified hyperbranched polymers and the uses of such polymers. Description of related art Hyperbranched polymers can be described as consisting of a core of a polyfunctional molecule, an intermediate, tree structured layer formed by successive branching reactions, and a shell constituted by extending branches carrying functionalities. In the European patent 0 630 389, particular hyperbranched polymers, named dendritic macromolecule by the patentee, are described and also named polyester polyols. These macromolecules are composed of a central initiator molecule having one or more hydroxyl groups, which groups under formation of an initial tree structure are bonded to carboxyl groups of a monomeric chain extender. The dentritic macromolecule can be further extended by a reaction with a chain stopper. In the European patent 0 630 389, the core materials used are polyols, such as trimethylolpropane, ditrimethylopropane and pentaerythritol. The examplified monomeric chain extender is dimethylolpropionic acid. The examplified chain stopper are lauric acid, soybean fatty acid, capric acid, caprylic acid and tall oil fatty acid. In fact, typical macromolecule products bearing hydroxyl groups at its peripheral surface are obtained, by acid catalyzed esterification between pentaerythritol (PETA), the core material, considered to be a chain stopper, and dimethylolpropionic acid (DMPA) which make the shell of the structure. From one mole of PETA and 12 moles of DMPA, a tree-like polydric polyester with 16 external hydroxyl groups is obtained. Such a product is described as a hyperbranched structure from the second generation (two successive esterifications) . The homologue product pertaining to the third generation (approximately molecular weight of 3600 g/mole) bears 32 primary hydroxyl functions. BRIEF SUMMARY OF THE INVENTION It has been discovered that the hyperbranched polyester polymers can be modified and that modified hyperbranched polymers have improved characteristics. The high functionality of hyperbranched polymers allows for chemical and /or physical modifications to achieve certain mechanical, chemical or physical properties. Such polyester polymers can be tailored through consecutive or mixed end-capping to obtain either very specific or mixed properties. Consequently, it is possible to use these modified hyperbranched polymers in new industrial applications. The hydroxyl functions of the hyperbranched polymers are modified via chemical reaction, such as esterification reaction. Reacting with a chemical compound modifies at least a part of the hydroxyl functions of the hyperbranched polymers, in some cases all of the hydroxyl functions. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hyperbranched polyester polyol composed of a central initiator molecule or initiator polymer having two or more hydroxyl groups, which groups under formation of an initial tree structure are bonded to carboxyl groups of a monomeric chain extender holding the hydroxyl groups and the carboxyl groups, which tree structure optionally is extended and further branched from the initiator molecule or initiator polymer by an addition of further molecules of a monomeric chain extender by means of bonding between the hydroxyl groups and the carboxyl groups thereof, wherein the hyperbranched polyester polyol is modified via esterification reaction on at least one hydroxyl group by at least one carboxylic acid and by at least another acid chosen among acrylic acid, methacrylic acid and oligomers thereof. Unmodified hyperbranched polyester polyol are known per se, such as, but without limitation, in European patent application 0 630 389, or international patent application WO 96/07688, or international patent application WO 93/ 17060. By oligomers of acrylic acid and methacrylic acid, we understand products resulting from the consecutive Michael addition of a carboxylic group belonging to an (meth)acrylate compound onto a double bond belonging to another (meth) aery late compound. Examples of oligomers are dimers and trimers of acrylic acid, such as, preferably, dimer of acrylic acid : β-carboxyethyl aery late. The definition of a carboxylic acid does not include acrylic acid, methacrylic acid and oligomers thereof, in the present invention. The modified hyperbranched polyester polyols can have different degrees of modification. Consequently, they contain a variable percentage of free hydroxyl group, a variable percentage of hydroxyl groups which have been acrylated with acrylic acid, methacrylic acid or oligomers thereof, and a variable percentage of hydroxyl groups which have been esterified with carboxylic acid. These percentages have an effect on properties of the obtained product, such as reactivity, rheology. The percentage of free hydroxyl group comprises from 0 to about 99 % based on the initial hydroxyl content of the polyester polyol. The percentage of free hydroxyl group comprises from 0 to about 50 %, and most preferably from 0 to about 35 %. The best results have been obtained from about 0.5 to about 15 % (% based on equivalent). The percentage of hydroxyl groups which have been acrylated with acrylic acid, methacrylic acid or oligomers thereof, comprises from about 20 to about 99 % based on the initial hydroxyl content. The percentage is comprises preferably from about 30 to about 90 %, and most preferably from about 40 to about 85 %. The best results have been obtained from about 45 to about 75 % (% based on equivalent). The percentage of hydroxyl groups that have been esterified with carboxylic acid group(s) comprises from about 5 to about 80 % based on the initial hydroxyl content. The percentage comprises preferably from about 10 to about 70 %, and most preferably from about 15 to about 60 %. The best results have been obtained from about 20 to about 50 % (% based on equivalent). The present invention also relates to a process for preparation of a modified hyperbranched polyester polymer as disclosed above. In view to obtain the appropriate properties as disclosed above, the process can be performed in one or two reaction steps. The process is preferably characterised in that it comprises a first esterification step in which a hyperbranched polyester polyol is reacted with a carboxylic acid and a second acrylation step in which the compound obtained in the first step is reacted with acrylic acid, methacrylic acid or oligomers thereof. The process for the preparation of a modified hyperbranched polyester polyol can also be characterised in that it comprises a first acrylation step in which a polyester polyol is reacted with acrylic acid, methacrylic acid or oligomers thereof, and a second esterification step in which the compound obtained in the first step is reacted with a carboxylic acid. The process for the preparation of a modified hyperbranched polyester polyol can also be characterised in that the polyester polyol is reacted with a carboxylic acid and with acrylic acid, methacrylic acid or oligomers thereof, in one step. The esterification step comprises a reaction with a carboxylic acid. By carboxylic acid, we understand an acid linear or branched, saturated or unsaturated, preferably it is monocarboxylic acid having at least a molecular weight of 60, and most preferably of 88. Examples of saturated carboxylic acid are acetic acid, propionic acid, butyric acid, valeric acid, isobutyric acid, trimethylacetic acid, caproic acid, caprylic acid, heptanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and dimeric and trimeric acids derived from unsaturated fatty acids (such as the product range sold under the trademark PRIPOL by the company UNIQUEMA). Good results have been obtained with propionic acid, lauric acid and stearic acid. The best results have been obtained with lauric acid. Examples of unsaturated carboxylic acids suitable for this purpose are oleic acid, ricinic acid, ricinoleic acid, linoleic acid, linolenic acid, erucic acid, soybean fatty acid, linseed fatty acid, dehydrated castor fatty acid, tall oil fatty acid, tung oil fatty acid, sunflower fatty acid, safflower fatty acid. The esterification step is preferably performed in the presence of a solvent such as an apolar organic solvent like heptane, cyclohexane, toluene, benzene, xylene or mixtures thereof, preferably toluene. The esterification step is preferably performed in the presence of a catalyst, such as p-toluenesulfonic acid, methanesulfonic acid, trifluoromethane sulfonic acid, trifluororacetic acid, sulfuric or phosphoric acid, naphtalene sulfonic acid, Lewis acids such as BF3, AICI3, SnCl titanates such as tetrabutyl titanates, organotin compounds, preferably p-toluenesulfonic acid. The esterification step preferably takes place at a temperature from about 50 to about 280 °C, preferably from about 100 to about 250 °C depending upon the selected solvent, the reaction conditions and upon pressure. It is also possible to incorporate an alkyl chain by using an alkanoyl halide, such as a compound of general formula R-CO-X, in which X represents an halogen such as Cl, Br, and R represents an alkyl group, preferably having from 4 to 20 carbon atoms. Suitable examples of alkanoyl halide s are lauroyl chloride and hexanoyl chloride. The acrylation step comprises a reaction with acrylic acid, methacrylic acid or oligomers thereof. The acrylation step is performed in the presence of a solvent such as an apolar organic solvent like heptane, cyclohexane, toluene, benzene, xylene or mixtures thereof , and preferably toluene. The acrylation step is preferably performed in the presence of a catalyst, such as p-toluenesulfonic acid, methanesulfonic acid, trifluoromethane sulfonic acid, trifluororacetic acid, sulfuric or phosphoric acid, naphtalene sulfonic acid, Lewis acids such as BF3, AICI3, SnCl titanates such as tetrabutyl titanates, organotin compounds, preferably the same catalyst as used in the esterification step and more preferably p-toluenesulfonic acid. The acrylation step is preferably performed in the presence of a radical polymerisation inhibitor, such as inhibitor described in U.K. patent 2 025 996, and, in particular, methyl ether hydroquinone (MeHQ), or hydroquinone, phenothiazine, di-t-butyl hydroquinone, or a mixture of them, and preferably MeHQ. The acrylation step preferably takes place at a temperature from about 50 to about 200 °C and preferably from about 80 about 150 °C, depending upon the selected solvent, the reaction conditions and upon pressure. Another process for preparing a modified hyperbranched polyester polymer comprises a conversion step of a hyperbranched polyester polyol to an acrylated or methacrylated hyperbranched polyester polyol by reacting a hyperbranched polyester polyol with acrylic anhydride or methacrylic anhydride. Another process for preparing a modified hyperbranched polyester polymer comprises the reaction step of a hyperbranched polyacid with glycidyl acrylate or glycidyl methacrylate in the melt. The reaction preferably takes place at the temperature from about 80 to about 160 °C. The invention also relates to the use of a modified hyperbranched polyester polyol as component in applications such as binders for radiation curing systems such as systems cured with ultra-violet (UV) and infra-red (IR) or electron-beam (EB). The modified hyperbranched polyester polyols of the invention are resins and, as such, can be used to prepare radiation curable inks by addition of pigments and additives. It is particularly useful for flexographic inks, letterpress inks, lithographic inks, gravure inks and jet inks. It is in general used to prepare pigmented formulations for applications that require good wetting of these pigments, excellent flow properties and low yield values (such as described in The Printing Ink Manual, 5 th edition, R.H. Leach and R.J. Pierce, Ed. Blueprint (London), 1993). The modified hyperbranched polyesters polyols of the invention can be formulated with pigments and additives to form an ink. These inks can be used in flexography, gravure, lithography and screen printing, good results have been obtained with flexography. The modified hyperbranched polyester polyols of the invention have an adequate viscosity for grinding, good pigment wetting characteristics, good flow properties after pigment incorporation, appropriate viscosity, low odour after curing. The inks comprising the modified hyperbranched polyester polyols of the invention have an adequate viscosity, a good adhesion, a good UV reactivity, a good EB reactivity, low yield values and good compatibility with acrylated products (monomers, oligomers). The following examples are present to give those skilled in the art a better understanding of the claimed invention. The examples are in no way intended to limit the invention. EXAMPLES Example 1 In a double-wall glass reactor with a capacity of 5 1 and fitted with an agitator, a thermometer, a nitrogen inlet tube, a connection to vacuum and an azeotropic distillation column, 1000 g of polyester polyol (0.57 mol., 1 equivalent OH) sold by Perstorp under the trademark Boltorn H-20, 351 g (1.82 mol., 0.2 equivalent (eq.)) lauric acid, 1.5 % p-toluenesulfonic acid (PTSA), are dissolved in toluene (1174 g, i.e. 40 weight-% on total). This mixture is heated to reflux (about 110 °C) and stirred until all the water is distilled over (= 33 ml). Then, 568 g (8J9 mol., 0.9 eq.) acrylic acid, and 1000 ppm methyl ether hydroquinone (MeHQ) are added and stirring is continued at 110 °C. Oxygen is injected to prevent gelling. When all the water is distilled over (= 131 ml) the mixture is cooled to 60°C and toluene (587 g) added to reach an end concentration of 50 % toluene. This mixture is washed four times with water (20 weight % on total) containing 20 % NaCl, dried via azeotropic distillation to remove all the water and finally filtered. The toluene was distilled and stripped under high vacuum (30 mmHg) to remove all traces of toluene. Properties of the obtained resin are given in Table 1. Viscosity (25 °C, mPa.s, Hόppler) of the resin was measured according to the method described in DIN 53015. Reactivity (m/min) of the resin was the speed of the belt at which a film is dry after passing one time under an UV (ultra-violet) lamp (power 80 W/cm). Examples 2- 10 The procedure according to example 1 was repeated with the difference of charges of lauric acid and acrylic acid. Charges of lauric acid and acrylic acid are given in table 1. Properties of the obtained resins are given in Table 1. Example 11 The procedure according to example 1 was repeated with a charge of lOOOg (0.57 mol., 1 equivalent OH) of polyester polyol sold by Perstorp under the trademark Boltorn H-20, 328 g (4.55 mol, 0.5 eq.) acrylic acid and 337 g (4.55 mol, 0.5 eq.) propionic acid. The obtained resin has a theoretical composition acrylic acid/ propionic acid : 50/50 % (based on equivalent). Example 12 The procedure according to example 1 was repeated with a charge of lOOOg (0.57 mol, 1 equivalent OH) polyester polyol sold by Perstorp under the trademark Boltorn H-20, 328 g (4.55 mol, 0.5 eq.) acrylic acid and 1299 g (4.55 mol, 0.5 eq.) stearic acid. The obtained resin has a theoretical composition acrylic acid/ stearic acid : 50/50 % (based on equivalent). Examples 13-22 The viscosity of the resins obtained according to examples 1 to 10 was adjusted with OTA 480 (trifunctional oligoacrylate available from UCB, S.A.) to match the viscosity of EB 450 (fatty acid modified hexafunctional polyester acrylate available under the trademark EBECRYL from UCB, S.A.), equal to 7500 mPa.s. The pigment wetting was quantified using flow-measurements on a glass plate at a 45° angle (distance in cm after 1 minute). Results are given in table 1 (flow Black paste in cm). Viscosity (25 °C, mPa.s, Brookfield) of the resins with adjusted viscosity was measured according to the method described in ASTM D 2849. The ink was formulated as follows: resin + OTA 480 : 100, carbon black: 20 and Darocure 1173 : 6. The product sold under the trademark Darocure 1173 is available from Ciba. The product sold under the trademark OTA 480 is available from UCB, S.A.. The product carbon black, sold under the trademark Spezialschwarz 250 is available from Degussa. Table 1 Resin resin with adjusted viscosity ink Examples Theoretical Resin Composition Viscosity Reactivity + OTA Viscosity Reactivity Reactivity flow (cm) AA/ Lauric acid/ free (25°C,mPa.s) (m/Min) % (25°C, mPa. s (m/min Ink Black Paste OH % (based Hoppler (m/ijnin) Brookfield (m/min) + 10 % OTA on equivalent) EB450 7500 30 0 7500 30 20 3.8 1 80/20 31516 20 20 7016 25 5.8 2 50/20/30 16211 20 42 7500 15 20 10 (60°C) 3 50/50 8000 <5 0 8000 < 5 10 6 70/20/10 25070 30 18 8000 20 20 4.9 (αo) 16 9500 70/30 14560 15 11.5 8100 15 30 5.4 60/40 9660 10 5.7 7750 15 15 3.1 50/40/10 7630 10 0 7630 5 20 5.9 50/30/20 20240 20 15 8000 10 10 6.6 60/20/20 34340 10 21 8200 15 40 3.1 0 60/30/10 16900 10 12 8600 10 10 6.2 (20 % carbon black) In table 1, AA represents acrylic acid; free OH represents the theoretical percentage (based on equivalent) of non reacted hydroxyl groups; OTA % (in the paragraphs "resin with adjusted viscosity" and "ink") represents the percentage of OTA 480 based on weight. The resins obtained according to examples 1 to 10 and the resin EB 450 were mixed with 6% (on weight) Darocure 1173. The degree of curing under UV of these blends was measured by attenuated total reflectance FTIR (infra red method). The % reacted acrylic unsaturation (% RAU) for a few, clear varnish, formulation was calculated. Results are given in table 2. The change in acrylic absorption at 1410 cm " *** - (in-plane bending) was recorded in multiple internal reflectance (MIR). Variations in film thickness were compensated by normalising the acrylate absorption to a band which remains constant during the curing. An asymmetric CH- stretching vibration at 2924 cm " 1 was chosen as internal standard and the relative absorbance Ar is defined as (1410) Ar = Λ(2924) where A(1410 ) is the absorbance at 1410 cm " 1 , and A(2924) is the absorbance at 2924 cm " 1 . The relative absorbance is used to calculate the percent reacted acrylate unsaturation (% RAU) according to the following equation Aro - Art %RA U = xl 00 Aro Where Aro is the relative absorbance of the uncured film, and Art is the relative absorbance of the cured film. Table 2 Resin Curing Conditions % RAU m/min 8 20* 95 8 3 x 20 >99 9 10* 98 9 3 x 10 >99 EB450 25* 62 EB450 3 x 25 72 * tack-free These results indicate a very high conversion. These results indicate that, in comparison with a conventional fatty acid modified polyester, the use of modified hyperbranched polyester polyols allows to reach a very low level of unreacted unsaturation. Examples 23-29 To the resin obtained according to examples 2, 4, 5 and 10 was added a yellow pigment sold under the trademark Irgalite yellow BAW 80/20 by Ciba. An ink was obtained. The viscosity of the obtained ink was adjusted with OTA 480 to match the viscosity of EB450, quantities of OTA 480 added are given in table 3. Flow was measured. The results are given in table 3. Table 3 Reference Examples Resin EB 450 2 1 4 4 5 10 OTA % 1 J 0 42 0 25 0 1 I ! ° flow cm 3.6 2.8 ! 3.6 2.5 3.3 3.5 Example 30 The resin obtained according to example 7 was added to EB 450 in an amount defined in table 4 (% based on weight). A yellow pigment sold under the trademark Irgalite yellow BAW 80/20 was added in an amount of 20 % (weight). OTA 480 was added in an amount of 16 % on weight. An ink was obtained. Flow of the ink was measured. Results are given in table 4. Table 4 Flow (cm) % added resin to EB 450 Resin example 0 5 10 20 EB 450 Example 7 5.4 5.7 In order to improve the flow and to lower yield values in final formulated systems, the materials were tried in combustion with EB 450 to see the influence on rheology (cone plate viscometer) Example 31 All resins (obtained according to examples 4, 5, 7, 8, 9 and 11) were tested in a pigment dispersion, based on tree roller mill formulations and diluted in a letdown vehicle (the same type as used in the ink industry). A pigment base was formed as following : - resin 55 - 65 % obtained in examples 1 - 10 - DPGDA 0 - 15 % (depending on the viscosity of the resin) DPGDA represents dipropyleneglycol diacrylate, a product sold by UCB, S.A. - Dispersant 0 or 4 % dispersant sold under the trademark IRR 434 from UCB, S.A. - Pigment 35 % pigment sold under the trademark Irgalite GLO: phtalo blue by CIBA. An ink was formed as following : - pigment base 40 % - EB 40 51.5 % acrylated tetrafunctional oligomer available from UCB, S.A. - Photoinitiator 8 % product available from CIBA under the name Speedcure - Siliconised levelling agent 0.5 % product PA 57 available from Dow Corning. The inks were printed and compared against a reference ink (a commercial ink available from SUN CHEMICAL under the trademark 50 HF 07). The following parameters were evaluated : _ The optical aspect of the printed film, such as gloss, transparency, colour intensity and shade purity was defined as appearance and measured by visual inspection in comparison with the reference (1 is bad, 5 is best) _ Rheology of the inks at very low shear (0J - 1 s " 1 shear rate) (Casson Model described in Emulsions and Emulsion Technology, part III, ed. by Kenneth J. Lissant, Marcel Dekker, Inc. 1984, pp. 66). A good ink should give a glossy, transparent, pure and intense print, no haze and have a low viscosity at low shear and a flat curve. The following results were obtained: Rheology: the viscosity at very low (0.1 s " ) and high (1 s " 1 ) shear rate were compared. Results are given in table 5. 1 ] L Table 5 Reference represents a commercial resin ink sold by SUN CHEMICAL under the trademark 50 HF07. Some trials were also performed using 20 % pigment sold under the trademark Novoperm Gelb P-HG available from Clariant. All the study was done on a cone plate viscometer and Yield value (tau (Pa)) was determined using the Casson Model. All the measurements have been done at a low shear rate between 0 and 5 s " 1 with the HAAKE rheometer (system CV 100 : PK 20-4°). The flow curves tau (shear stress in Pa) as a function of D (shear rate in s " 1 ) has been measured and is described by means of a mathematical model, the Casson Model. Results are given in table 6. Table 6 Resins tau(Pa) at 0.02 Dfe " 1 ) EB 450 188.2 Example 7 27.63 It can be concluded that the radiation curable modified hyperbranched polyester increase the flow of the ink, resulting in a very low yield value, and improve the appearance.

Claims: CLAIMS 1. Modified hyperbranched polyester polyol derived from a hyperbranched polyester polyol comprising a central initiator molecule or initiator polymer having two or more hydroxyl groups, which groups under formation of an initial tree structure are bonded to carboxyl groups of a monomeric chain extender holding hydroxyl groups and carboxyl groups, which tree structure optionally is extended and further branched from the initiator molecule or initiator polymer by an addition of further molecules of a monomeric chain extender by means of bonding between the hydroxyl groups and the carboxyl groups thereof, wherein the hyperbranched polyester polyol is modified via an esterification reaction on at least one hydroxyl group by at least one carboxylic acid and via an acrylation reaction on at least one hydroxyl group by at least another acid chosen among acrylic acid, methacrylic acid and oligomers thereof. 2. Modified hyperbranched polyester polyol according to claim 1 , wherein the carboxylic acid is a monocar boxy lie acid having at least a molecular weight of 60. 3. Modified hyperbranched polyester polyol according to either preceding claim, wherein the carboxylic acid is lauric acid. 4. Modified hyperbranched polyester polyol according to any preceding claim, wherein the percentage of free hydroxyl groups is comprises 0 to about 99 % based on initial hydroxyl content of the hyperbranched polyester polyol. 5. Process for the preparation of a modified hyperbranched polyester polyol according to any preceding claim, characterized in that it comprises a first esterification step in which a hyperbranched polyester polyol is reacted with a carboxylic acid and a second acrylation step in which the compound obtained in the first step is reacted with acrylic acid, methacrylic acid or oligomers thereof. 6. Process for the preparation of a modified hyperbranched polyester polyol according to any of claims 1 to 4, characterized in that it comprises a first acrylation step in which a hyperbranched polyester polyol is reacted with acrylic acid, methacrylic acid or oligomers thereof, and a second esterification step in which the compound obtained in the first step is reacted with a carboxylic acid. 7. Process for the preparation of a modified hyperbranched polyester polyol according to any of claims 1 to 4, characterized in that the polyester polyol is reacted with a carboxylic acid and with acrylic acid, methacrylic acid or oligomers thereof in one step. 8. Process according to claim 5, 6 or 7, wherein the carboxylic acid is a monocarboxylic acid having at least a molecular weight of 60. 9. Process according to claim 8, wherein the carboxylic acid is lauric acid. 10. Use of a hyperbranched polyester polyol according to claim 1 as component in applications such as binders for radiation curing systems, such as systems cured with ultra-violet (UV) and infra-red (IR) or electron-beam (EB). 11. Use of a modified hyperbranched polyester polyol according to claim 1 as a resin in a radiation curable ink by addition of pigments and additives.

Inventors: DE MICHELI PHILIPPE, VANOVERVELT JEAN-CLAUDE, VERSCHUEREN KRIS, DE MICHELI, PHILIPPE, VANOVERVELT, JEAN-CLAUDE, VERSCHUEREN, KRIS
Applicants: MICHELI PHILIPPE DE, UCB SA, VANOVERVELT JEAN CLAUDE, VERSCHUEREN KRIS, DE MICHELI, PHILIPPE, UCB, S.A., VANOVERVELT, JEAN-CLAUDE, VERSCHUEREN, KRIS
Application year: 2000
Main classification: C08G63
IPC codes: C08G63, C08G83