EP1171503A1

EP1171503A1 - Hyperbranched polyesters

Info

Publication number: EP1171503A1
Application number: EP00917103A
Authority: EP
Inventors: Mikael Skrifvars; Jukka Tulisalo; Karri Airola; Jukka Estamo; Pertti Hietakari
Original assignee: Dynea Chemicals Oy
Current assignee: Dynea Chemicals Oy
Priority date: 1999-04-01
Filing date: 2000-04-03
Publication date: 2002-01-16
Also published as: AU3822300A; FI990727A0; WO2000059982A1

Abstract

The invention relates to hyperbranched polyesters, to a process for the manufacture thereof, to their use in unsaturated polyester preparations and to curable resins comprising hyperbranched polyesters. The process for the manufacture of hyperbranched polyesters comprises the following steps: a) reacting a polycarboxylic anhydride with 2 to 4 carboxyl groups, preferably free carboxyl groups, with a polyol with 2 to 10 reactive hydroxyl groups, preferably of equivalent reactivity, in the presence of an amine, the amount of ahnydride being at least 1 mol of anhydride per hydroxyl group of the polyol; and b) reacting the product from step a) with glycidyl (meth)acrylate or allyl glycidyl ether in an amount of at least corresponding to 1 mol of glycidyl (meth)acrylate or allyl glycidyl ether per free carboxylic acid group of the product a); and c) product from the second step b) is further reacted with an unsaturated, aromatic or aliphatic anhydride in an amount sufficient to esterify a part of or all free hydroxyl groups of the product from step b).

Description

Hyperbranched polyesters

The present invention relates to hyperbranched polyesters, to a process for the manufacture thereof, to their use in unsaturated polyester preparations and to curable resins comprising hyperbranched polyesters.

The conventional curable polyester resins generally comprise oligomers and comonomers, and oligomers usually consist of linear molecular chains. The viscosity of the resin increases significantly with increasing chain length of the oligomer. Thus, large amounts of multidimensional comonomers are required for viscosity control of formulas especially for applications, such as spraying, dipping and roll coating. Traditionally used comonomers affect the curing reaction and the propeπies of the final product, Comonomers often have low curing rate, they cause shrinkage of the film during curing, have high costs, limited shelf life and also many of them are volatile and toxic. The legislation in several countries covering environmental protection and occupational safety has tightened during the recent years and set limitations on emissions of volatile organic compounds (NOC), such as styrene, which is a commonly used comonomer in unsaturated polyester resins. Styrene content ranges from 35 % to 50 % in conventional resins. Several methods have been evaluated in order to reduce the amount of styrene in unsaturated polyester resins, and low styrene emission (LSE) resins have been developed with styrene contents below 35 % . LSE resins may contain additives which lower the emissions, or they are suppressed resins, new monomer resins, resins with reduced styrene contents, high solids resins or resins where styrene is totally or paπly replaced with another monomer. The most commonly used method to reduce styrene emissions is to use film forming additives, such as paraffin in the resins.

Oligomers with a highly branched structure and with a spherical shape constitute a family of polymers, which has been increasingly studied during recent years. These oligomers are referred to as hyperbranched polyesters having three-dimensional molecular architecture and possessing starburst topology. These . polymers are also named as dendritic polymers or dendrimers. Hyperbranched polyesters differ significantly from conventional linear oligomers, because the linear oligomer of sufficient molecular weight for polyester resins usually contains an entanglement of flexible molecular chains, usually only with two terminal functional groups on each molecule, while the hyperbranched polyester is a compact spherical molecule with many branches which carry a high number of terminal functional groups on each molecule. These unique features of the hyperbranched polyesters yield interesting and special propeπies which make these compounds very attractive and useful in several applications. The spherical shape yields the compounds favourable and different rheological propeπies, such as lower viscosity, when compared with the conventional linear oligomers. The high number of terminal, functional groups, which can be modified, results in a variety of physical and chemical propeπies. Oligomers with a strongly branched structure can be used in applications, such as catalysts, as carriers for drug substances in pharmaceutical industry, as pharmaceuticals, cosmetics, adhesives, coatings, composites, agricultural chemicals and as multi- functional crosslinking agents.

A series of hyperbranched (meth)acrylated polyesters with different number of terminal double bonds per molecule has been presented and methods for the manufacture thereof have been disclosed in the patent application WO 96/07688. This publication discloses^' a hyperbranched polyester of a polyol with 3 to 10 reactive hydroxyl groups and an aromatic polycarboxylic anhydride with 2 to 4 carboxyl groups, each hydroxyl group of the polyol forming an ester linkage with one anhydride group of the polycarboxylic anhydride, and fuπher giycidyl (meth)acrylate or allyl giycidyl ether forming ester linkages with the remaining carboxyl groups of the anhydride and free hydroxyl groups. Fuπher, in the hyperbranched polyester, (meth)acrylic anhydride and/or an aliphatic carboxylic anhydride form ester linkages with free hydroxyl groups. The said hyperbranched polyesters can be used as resins which are curable by UN-radiation. The method for the manufacture of said hyperbranched polyesters comprises reacting an aromatic polycarboxylic anhydride with a polyol with 3 to 10 reactive hydroxyl groups in the presence of an activating agent stannous chloride and reacting the obtained product with giycidyl (meth)acrylate or allyl giycidyl ether.

An object of the present invention is to provide an improved, economical and on an industrial scale applicable process for the manufacture of hyperbranched polyesters.

A further object of the invention is to present new hyperbranched polyesters.

A fuπher object of the invention is to provide hyperbranched polyesters which in unsaturated polyester applications require low amounts of mono- or multifunctional comonomer while the resins still retain a low viscosity, a high curing rate, an acceptable degree of curing and the final products manufactured thereof exhibit good mechanical propeπies, and the curing can be performed applying any suitable curing methods.

The objects of the invention are achieved by a method for the manufacture of hyperbranched polyesters, by new hyperbranched polyesters and by resins comprising them, as claimed in the claims.

Characteristics of the method, the polyesters, the resins and the use are stated in the claims.

It has been found that according to the invention new hyperbranched polyesters can be manufactured and an improved method for the manufacture of the hyperbranched polyesters can be provided. Thus, the present invention relates to hyperbranched polyesters of a polyol with 2 to 10 reactive hydroxyl groups, preferably of equivalent reactivity, and a polycarboxylic anhydride with 2 to 4 carboxyl groups, preferably with 3 carboxyl groups, each hydroxyl group of the polyol forming an ester linkage with one anhydride group of the polycarboxylic anhydride, and further giycidyl (meth)acrylate or allyl giycidyl ether forming ester linkage with the remaining carboxyl groups of the anhydride and free hydroxyl groups, and further unsaturated, aromatic or aliphatic anhydride forming ester linkages with free hydroxyl groups. The present invention further relates to a process for the manufacture of said hyperbranched polyester.

The process is a controlled stepwise divergent method with at least two reaction steps and the synthesis staπs at the center of the hyperbranched polyester.

The process comprises the following steps:

First step

a) reacting a polycarboxylic anhydride with 2 to 4 carboxyl groups, preferably free carboxyl groups, with a polyol with 2 to 10 reactive hydroxyl groups, preferably of equivalent reactivity, in the presence of an amine, the amount of anhydride being at least 1 mol of anhydride per hydroxyl group of the polyol,

Second step

b) reacting the product from step a) with giycidyl (meth)acrylate or allyl giycidyl ether in an amount of at least corresponding to 1 mol of giycidyl (meth) aery late or allyl giycidyl ether per free carboxylic acid group of the product of a),

Third step

c) the product from the second step b) is fuπher reacted with an unsaturated, aromatic or aliphatic anhydride in an amount sufficient to esterify a paπ or all free hydroxyl groups of the product from step b).

In the first reaction step, a polycarboxylic anhydride with 2 to 4 carboxyl groups is heated to a temperature of about or below 100 °C, preferably below 80 °C in the presence of a solvent or a mixture of solvents, in the presence of a teπiary aliphatic or aromatic amine, preferably triethylamine as a catalyst and under ineπ gas atmosphere, preferably under nitrogen atmosphere. The polycarboxylic anhydride is preferably an aromatic anhydride, such as trimellitic anhydride or phthalic anhydride. Suitable polyols are polyols having 2 to 10 hydroxyl groups and the hydroxyl groups are preferably of equivalent reactivity , which allows the esterification of each of the hydroxyl groups to proceed equally easily in order to start the building up of the regular molecule. Examples of suitable polyols are pentaeryhtritol, dipentaerythritol, trimethyloyl propane, neopentyl glycol and the like. The amount of added anhydride is at least one mol of anhydride per hydroxyl group of the polyol but preferably the anhydride is added in an excess amount. An excess of 5—50 mol% is suitable. A suitable solvent is dimethylformamide or 1- methyl-2-pyrrolidinone or a mixture thereof. The reaction mixture can be used as such without further purification for the following step of the process.

In the second step, the intermediate from the first reaction step is allowed to react with giycidyl (meth)acrylate or allyl giycidyl ether in an amount at least corresponding to one mol of giycidyl (meth)acrylate or allyl giycidyl ether per free carboxylic acid group of the formed polyester, preferably in an excess amount of about 5—20 wt% . Preferred reactant is giycidyl (meth)acrylate. The reaction is carried out in a solvent, such as dimethyl formamide or l-methyl-2-pyrrolidinone or a mixture thereof, in the presence of an inhibitor for radical polymerization. A suitable inhibitor is hydroquinone monomethyl ether. The amine from the previous reaction step, preferably triethylamine acts as a basic catalyst. The reaction temperature is below 100 °C, preferably below 80 °C. The obtained second intermediate reaction mixture can be used without fuπher purification in the following reaction step.

In the third reaction step, the hydroxyl groups of the hyperbranched polyester with terminal double bonds are reacted further by ester formation with an unsaturated, aromatic or aliphatic anhydride, preferably acetic anhydride or (meth)acrylic anhydride, in an amount sufficient to esterify paπ or all of the free hydroxyl groups in order to prepare the hyperbranched polyester molecules with acetyl groups or fuπher end double bonds. The reaction is preferably performed at a temperature below 100 °C, preferably below 80 °C, in the presence of a solvent, such as dimethyl formamide or l-methyl-2-pyrrolidinone or a mixture thereof. Conveniently the solvents used in the previous reaction steps and remaining in the reaction mixture may act as solvents without additional solvents. After the reaction is completed, an inhibitor, preferably benzoquinone is added and the product may optionally be dissolved in an organic solvent which is immiscible with water, such as an aromatic hydrocarbon or a chlorinated hydrocarbon or a mixture thereof, suitably toluene or methylene chloride, for fuπher processing. The product may also be dissolved in styrene in order to obtain a 40—70 % solution of the product in styrene. Styrene is especially favourable as the obtained solution can readily be used in unsaturated polyester resins without removal of the solvent. Other suitable solvents for the same purpose are p-methylstyrene or vinyltoluene. This solution can readily be used for the manufacture of resins and other applications.

Alternatively the third step c) may be omitted if hydroxy functional hyperbranched polyesters are desired. After the reaction is completed in step b), the product may optionally be dissolved in an organic solvent as described above in step c).

The process according to the invention is specially suitable for industrial scale without the drawbacks of the small scale methods according to prior an. New amine catalysts can be used in the process instead of stannous chloride, no isolation of intermediates is required in the process and no distillation of the solvents is needed.

The hyperbranched polyesters obtained with polyols containing two reactive hydroxyl groups, such as neopentyl glycol are new compounds with propeπies especially suitable to serve as reactive blendable comonomers in resins because of their favourable rheological properties.

The hyperbranched polyesters according to the invention, based on a polyol core molecule, a polycarboxylic anhydride as a branching extender and an epoxyacrylate as an end group can be used to improve the mechanical propeπies of high solids unsaturated resins with low conomomer contents while still retaining good mechanical properties of the resin. Thus, styrene content^'s of 30 % by weight or less can be used which is clearly an advantage from an environmental point of view as the styrene emissions will be reduced. The hyperbranched polyesters can also be used in styrene free unsaturated polyester resins, which are based on vinyl ether monomers. The heat distoπion temperature, tensile and flexural strength of cured polyester resins manufactured using hyperbranched polyesters according to the invention are improved when up to 15 % of the hyperbranched polyester or a mixture thereof is added into the high solids unsaturated polyester. The mechanical propeπies of the polyester resins thus obtained can be widely modified and adjusted according to the final use of the resin. The hyperbranched polyesters according to the invention can be used as resins which can be cured by conventional curing systems, such as thermally initiated curing using initiators, such as aliphatic azo compounds or organic peroxides, such as benzoyl peroxide, by a redox reaction initiated curing using organic peroxides, such as methyl ethyl ketone peroxide and metal salts, by photochemically initiated curing using UN-light or by radiation inititated curing by EB-radiation.

The resins have a lower viscosity than conventional oligomer resins and they can be used with or without comonomers. The resins may also comprise monofunctional or multifunctional comonomers or mixtures thereof, and a suitable amount of co- monomer is 5—20 wt%. As multifunctional comonomers, compounds with reactive double bonds, preferably with 1—6 (meth)acrylate or acrylate groups can be used, and such as trimethyloyl propane tri(meth)acrylate, hexanediol diacrylate, trimethylo- yl propane triallyl ether, pentaerythritol tri/tetraallylether, triallyl cyanurate, trimethyloyl propane triacrylether and pentaerythritol tetraacrylether are suitable. As monofunctional comonomers vinyl aromatic monomers, such as styrene, p-methylstyrene or vinyl toluene are suitable. Also alkyl (meth)acrylates, such as methyl (meth)acrylate may be used. The resins according to the invention can be used in many different fields, such as coating, adhesives, laminates, foils, thin-films and composites.

The following examples illustrate the invention in more detail however they are not intended to be limiting the invention. Preparation and results of analysis of hyperbranched methacrylated polyesters

Example 1

1. Synthesis procedure of Dl

Step 1. Synthesis of intermediate I PEBTCA

PEBTCA

40.0 g (0.294 mol) of pentaerythritol (PE) and 40 ml of triethylamine (TEA) are dissolved in 400 ml of dimethylformamide (DMF). Then 248.0 g (1.29 mol, 10 % excess) of trimellitic anhydride (TMA) is added in poπions within 30 min at a temperature below 55 °C. After the addition the reaction mixture is stirred at 50...55 °C under nitrogen atmosphere for 6 hours and cooled down to room temperature overnight.

The reaction mixture containing the intermediate I PEBTCA is analyzed by HPLC, 1HNMR and acid number titration (TAN). Typical analysis

Composition by high pressure liquid chromatography (HPLC) :

Tetraester 85. ..87 %

Tπester 1.3 %

TMA ÷ acid 10.. . 1 1 %

Titrated acid number (TAN):

213...220 mg KOH/g (217 theoretical)

The reaction mixture is used in the next process step without further purification.

Step 2. Synthesis of intermediate EC Dl-OH

01 -OH D

2.0 g of hydroquinone monomethyl ether (inhibitor) is added into the PEBTCA- reaction mixture from step 1 and the mixture is warmed up to 50... 5 °C Then 0 400.0 ml (2.94 mol. 10 % excess) of giycidyl methacrylate (GMA) is slowly added during 1...2 hours at a temperature below 75 °C. The reaction mixture is fuπher stirred at 70...75 °C for about 10 hours until TAN of the mixture is < 10 ms KOH/g.

The reaction mixmre containing the intermediate D l-OH is analyzed bv GPC. ^lHNMR and acid number titration (TAN) .

The reaction mixture is used in the next step wichout fuπher purification.

Step 3a. Synthesis of final product Dl (60 % solution in styrene)

350.0 g of the reaction mixture containing the intermediate D l-OH from step 2 is warmed up to 50...55 °C. 75 0 ml (0.80 mol) of acetic anhydride (AA) is slowly added during 20 min at 50 ..70 °C. After the addition the mixture is stiπεd at 68...72 °C for 3 hours. Then 550 ml of styrene is added to dissolve the product and the solution is washed with 700 ml of 10 % Na₂C0₃ at 55...60 °C. After separation of the layers another 150 ml of styrene is added and the mixture is washed with 700 ml of water at 55...60 °C. Then 0.25 g of benzoquinone is added and the product is distilled under vacuum below 70 °C / 50 mbar in order to remove resi_dual wa_ter (about 13 ml) and a paπ of styrene (about 550 ml) from the mixture.

Yield is 380 g of about 60 % D l -solution in styrene.

D

The structure of the product is confirmed by ^!HNMR and GPC.

Alternatively D l can be obtained as a viscous oil according to the following procedure Step 3b. 0

Step 3b. Synthesis of Dl

5

350.0 g of the reaction mixmre containing the intermediate D l-OH from step 2 is

30 warmed up to 50...55 ³C. 75.0 ml (0.80 mol) acetic anhydride (AA) is slowly added during 20 min at 50...70 °C. After the addition, the mixmre is stirred at 68...72 °C for 3 hours. Then, 550 ml of toluene is added to dissolve the product and the solution is washed with 700 ml of 10 % Na-,CO₃ at 55...60 °C. After separation of the layers another 150 ml of toluene is added and the mixmre is washed with 700 ml of water at 55...60 °C. Then 0.25 g of benzoquinone is added and the product is distilled under vacuum below 70 °C / 30 mbar in order to remove residual water (about 10 ml) and toluene (about 700 ml) from the mixmre.

Yield is 250 g of Dl (highly viscous oil).

The structure of the product is confirmed by 1HNMR and GPC.

Preparation of hyperbranched methacrylated polyesters starting from polyols

Example 2

Intermediates II: PGL-OH, DPGL-OH, DDl-OH, TMPA-OH, DTMP-OH and NGL-OH are synthetisized and analyzed in the same way as Dl-OH described in Example 1. No intermediate I is isolated and Steps 1 and 2 are combined. Table 1 summarizes average amounts of staπing materials used in the synthesis of intermediates II.

Table 1

Final products PGL, PMA, DPGL, DPMA, DDl , DD3, TMPA, TMPM, DTMP_, NGL and NMA are synthetisized and analyzed in the same way as Dl described in Example 1 , Step 3. Table 2 summarizes the average amounts of staπing materials used in the synthesis of the earlier mentioned final products.

The chemical structures of obtained hyperbranched polyesters Dl (mw 2378), DTMP (mw 1815), PGL (mw 1465), PMA (mw 1569), DPGL (mw 2248), DPMA (mw 2404), DD3 (mw 3929), DDl (mw 3617), NMA (mw 1329), NGL (mw 1225), TMPM (mw 1209) and TMPA (mw 1131) are presented in the follo- wing.

All the processes described above, can easily be scaled up to larger industrial scales with commercial batch sizes.

Table 2

^ 60 % solution in styrene

001

OTMP

D1

PMA

PGL

Example 3

Testing of mechanical properties

The mechanical propeπies of blends of hyperbranched polyesters and unsamrated polyesters are tested from castings prepared as follows:

Resin mixture preparation

Resin blends are prepared by mixing the unsamrated polyester resin with various amounts of hyperbranched polyesters. The styrene content is 30 % in all blends. The unsamrated polyester is a low molecular weight polyester made from orthophthalic anhydride, maleic anhydride and 1 ,2-propanediol. The amount of hyperbranched polyesters is 5 wt%, 10 wt-% and 15 wt% . The resin blend is cured with 0.4 wt% of promoter (a mixmre of cobalt octoate, dimethyl aniline and methyl hydroquinone) and 1 wt% methyl ethyl ketone peroxide. As a reference, a commercial monomer trimethyloylpropane trimethacrylate is blended with the same polyester in the same way.

Preparation of castings

The casting is prepared at room temperamre using a metal frame. The surface of the frame is Teflon treated in order to prevent sticking of the resin to the metal. The outer size of the frame is 25.5 x 40.5 cm, the inner size is 26 x 21 cm. The thickness of the frame is 4 mm.

The frame is placed on a glass plate covered with Melinex (PET) foil. 400 g of resin is weighed, and air is removed with vacuum. The needed amount of peroxide is then added, and the resin is mixed without causing air-bubble formation.

The resin is poured carefully into the mold, and the mold is then covered with a Melinex film, and a glass plate. A metal plate is put on top as a weight. The casting is left to cure overnight at room temperamre.

The casting is then checked for residual stresses between two Polaroid plastic films, on a light table.

Mechanical testing

Specimens for mechanical testing are cut using a machine saw.

After cuπing the specimens are post-cured at 50 °C for 24 hours. The specimens are placed between two glass plates in an oven. The specimens are cooled slowly to room temperamre (1 h) to decrease residual stresses. The tested samples are then checked between two Polaroid films for residual stresses, and the specimens with least residual stresses are selected. At least five specimens are selected.

The mechanical test is made using an Instron 1175, with a 5 kN load cell. The crosshead speed is 2 mm/min.

Heat distortion temperature

The heat distoπion temperamre (HDT = temperamre of deflection under load) is measured from specimens cut from the castings, size 10 mm x 110 mm.

The specimens are post-cured and checked in the same way as the specimens for the mechanical testing.

The HDT value is measured in a heating bath, which is heated from 20 °C at a rate of 2 C°/min. The specimen is loaded using a constant load. The temperamre at which the specimen bends is registered as the HDT value.

Results of cured resins containing hyperbranched polyesters are provided in the following Tables 3—15. Table 3

Resin with Dl

Table 4

Resin with PGL

l->

Table 5

Resin with PMA

Table 6

Resin with DPGL

Table 7

Resin with DPMA

Table 8

Resin with DDl

Table 9

Resin with DD3

Table 10

Resin with TMPA

Table 11

Resin with TMPM

Table 12

Resin with DTMP

Table 13

Resin with NGL

Table 14

Resin with NMA

Table 15

Reference resin containing trimethyloylpropane trimethacrylate (TMPTMA)

Claims

1. A process for the manufacture of hyperbranched polyesters, characterized in that the process comprises the following steps:

a) reacting a polycarboxylic anhydride with 2 to 4 carboxyl groups, preferably free carboxyl groups, with a polyol with 2 to 10 reactive hydroxyl groups, preferably of equivalent reactivity, in the presence of an amine, the amount of anhydride being at least 1 mol of anhydride per hydroxyl group of the polyol, and

b) reacting the product from step a) with giycidyl (meth) aery late or allyl giycidyl ether in an amount of at least corresponding to 1 mol of giycidyl (meth)acrylate or allyl giycidyl ether per free carboxylic acid group of the product a), and

c) product from the second step b) is further reacted with an unsamrated, aromatic or aliphatic anhydride in an amount sufficient to esterify a paπ of or all free hydroxyl groups of the product from step b).

2. A process according to claim 1, characterized in that the amine is a teπiary aliphatic or aromatic amine, preferably triethylamine.

3. A process according to claim 1 or 2, characterized in that the reaction is carried out in the step a) at a temperamre below 100 °C, preferably below 80 °C in the presence of an organic solvent or mixmre of solvents, the second step b) at a temperamre below 100 °C, preferably below 80 °C in the presence of an organic solvent or mixmre of solvents, and the third step c) at a temperamre below 100 °C, preferably below 80 °C in the presence of an organic solvent or mixmre of solvents.

4. A process according to any one of claims 1—3 , characterized in that the amount of anhydride in step a) and of acrylate in step b) are in excess of the stated amount.

5. A process according to any one of claims 1—4, characterized in that the reaction of step b) is performed in the presence of a basic catalyst and an inhibitor for radical polymerization and in step c) an inhibitor is used.

6. A process according to claim 5, characterized in that the basic catalyst is _the amine used in step a).

7. A process according to claim 5 or 6, characterized in that the inhibitor in step b) is hydroquinone monomethyl ether and in step c) the inhibitor is benzoquinone.

8. A process according to any one of claims 1—7, characterized in that polycarboxylic anhydride is trimellitic anhydride or phthalic anhydride.

9. A process according to any one of claims 1—8, characterized in that the polyol is pentaerythritol, dipentaerythritol, trimethyloylpropane or neopentyl glycol.

10. A process according to any one of claims 1—9, characterized in that the anhydride in step c) is (meth)acrylic anhydride or acetic anhydride.

11. A process according to any one of claims 1—10, characterized in that the product from step a) is allowed to react with giycidyl methacrylate.

12. A process according to any one of claims 1—11 , characterized in that the solvent used in step a) is dimethylformamide or l-methyl-2-pyrrolidinone, in step b) dimethylformamide or l-methyl-2-pyrrolidinone and in step c) dimethylformamide or l-methyl-2-pyrrolidinone, and after the reaction in step c) the product may optionally be dissolved in an aromatic hydrocarbon or a chlorinated hydrocarbon, preferably styrene, p-methylstyrene, vinyltoluene, toluene or methylene chloride.

13. A hyperbranched polyester of a polyol comprising two reactive hydroxyl groups, preferably of equivalent reactivity, and a polycarboxylic anhydride with 2 to 4 carboxyl groups, preferably 3 carboxyl groups, each hydroxyl group of the polyol forming an ester-linkage with one anhydride group of the polycarboxylic anhydride and fuπher giycidyl (meth)acrylate or allyl giycidyl ether forming ester- linkages with the remaning carboxyl groups of the anhydride and free hydroxyl groups, and fuπher unsamrated aromatic or aliphatic anhydride forming ester-linkages with free hydroxyl groups.

14. A process for the manufacmre of hyperbranched polyesters, characterized in that the process comprises the following steps:

a) reacting a polycarboxylic anhydride with 2 to 4 carboxyl groups, preferably free carboxyl groups, with a polyol with 2 to 10 reactive hydroxyl groups, preferably of equivalent reactivity, in the presence of an amine, the amount of anhydride being at least 1 mol of anhydride per hydroxyl froup of the polyol, and

b) reacting the product from step a) with giycidyl (meth)acrylate or allyl giycidyl ether in an amount of at least corresponding to 1 mol of giycidyl (meth)acrylate or allyl giycidyl ether per free carboxylic acid group of the product of a).

15. A process according to claim 14, characterized in that the amine is a teπiary aliphatic or aromatic amine, preferably triethylamine.

16. A process according to claim 14 or 15, characterized in that the reaction is carried out in the step a) at a temperamre below 100 °C, preferably below 80 °C in the presence of an organic solvent or mixmre of solvents, and in the second step b) at a temperamre below 100 °C, preferably below 80 °C in the presence of an organic solvent or mixmre of solvents.

17. A process according to any one of claims 14 — 16, characterized in that the amount of anhydride in step a) and of acrylate in step b) are in excess of stated amount.

18. A process according to any one of claims 14—17, characterized in that the reaction of step b) is performed in the presence of a basic catalyst and an inhibitor for radical polymerization.

19. A process according to claim 18, characterized in that the basic catalyst is the amine used in step a).

20. A process according to claim 18 or 19, characterized in that the inhibitor for radical polymerization is hydroquinone monomethyl ether.

21. A process according to any one of claims 14—20, characterized in that polycarboxylic anhydride is trimellitic anhydride or phthalic anhydride.

22. A process according to any one of claims 14 — 21, characterized in that the polyol is pentaerythritol, dipentaerythritol, trimethyloylpropane or neopentyl glycol.

23. A process according to any one of claims 14—22, characterized in that the product from step a) is allowed to react with giycidyl methacrylate.

24. A process according to any one of claims 14 — 23, characterized in that the solvent used in step a) is dimethylformamide or l-methyl-2-pyrrolidinone, in step b) dimethylformamide or l-methyl-2-pyrrolidinone, and after the reaction in step b) the product may optionally be dissolved in an aromatic hydrocarbon or a chlorinated hydrocarbon, preferably styrene, p-methylstyrene, vinyltoluene, toluene or methylene chloride.

25. A hyperbranched polyester of a polyol comprising two reactive hydroxyl groups, preferably of equivalent reactivity, and a polycarboxylic anhydride with 2 to 4 carboxyl groups, preferably 3 carboxyl groups, each hydroxyl group of the polyol forming an ester-linkage with one anhydride group of the polycarboxylic anhydride and fuπher giycidyl (meth)acrylate or allyl giycidyl ether forming ester-linkages with the remaining carboxyl groups of the anhydride and the free hydroxyl groups. όJ.

26. A curable resin, characterized in that it comprises at least one hyperbranched polyester defined in claim 13 or 25.

27. A curable resin, characterized in that it comprises at least one hyperbranched polyester obtainable by a process according to any one of claims 1—12 or 14—24.

28. A curable resin according to claim 26 or 27, characterized in that it fuπher comprises a mono- or multifunctional comonomer, or a mixmre thereof.

29. A curable resin according to any one of claims 26—28, characterized in that the comonomer comprises 1—6 methacrylate or acrylate groups, or it is a vinyl aromatic monomer or a mixmre thereof.

30. A curable resin according to any one of claims 26—29, characterized in that the resin is cured by thermally initiated curing, by redox reaction initiated curing, by photochemically initiated curing or by radiation initiated curing.

31. Use of curable resin according to any one of claims 26—30 for the production of coatings, adhesives, laminates, foils, thin films and reinforced composites.