WO2005014679A1

WO2005014679A1 - Photo-curable urethane-acrylate compounds

Info

Publication number: WO2005014679A1
Application number: PCT/GB2003/003239
Authority: WO
Inventors: Zlatan Batalovic; Branko Dunjic; Srba Tasic; Branislav Bozic; Enis Dzunuzovic; Radomir Saicic; Radomir Matovic
Original assignee: DUGA UK Ltd
Current assignee: DUGA UK Ltd
Priority date: 2003-07-16
Filing date: 2003-07-16
Publication date: 2005-02-17
Anticipated expiration: 2006-01-16
Also published as: AU2003251350A1

Abstract

New UV-polymerisable compounds having the following formula (I); wherein: R is residue of a hyperbranched polyester core moiety of the following general formula (II); wherein: Rl is a core group which is a residue of a multifunctional aliphatic or aromatic polyol; R2 is a residue of an aliphatic or aromatic carboxylic acid having one COOH group and two or more OH groups, wherein n is the hydroxy functionality of the said carboxylic acid and is 2 or more, and m is the functionality of the polyol core group Rl and is at least 2; R3 is a residue of a diisocyanate compound; R4 is a hydrogen atom or methyl group; x is 1 -10, preferably 4 - 8; R5 is an alkylene group; R6 is -OR7, -NR7R8, -SR7 or R9, where R7 and R8 are the same or different and each is independently selected from: (v) an alkyl, acyl, aryl, alkene or alkyne group, (vi) a saturated or unsaturated, optionally aromatic, carbocyclic or heterocyclic group; wherein any of the above groups (i) and (ii) may be optionally substituted; and R9 is selected from any of H, an alkyl, aryl, alkene or alkyne group, a saturated or unsaturated optionally substituted carbocyclic or heterocyclic group, an alkylthio, alkoxycarbonyl, aryloxycarbonyl, carboxy, acyloxy, carbamoyl, cyano, dialkylphosphonato, diarylphosphonato; dialkylphosphinato or diarylphosphinato group; a (being the number of urethane-acrylate chains attached to the central core group R) is from 0 to 10, preferably from 1 to 10, more preferably from 4 to 10; b (being the number of xanthate moieties in the molecule) is from 0 to 10, preferably from 1 to 10, more preferably from 4 to 10; with the proviso that a + b is from 2 to 16, preferably from 10 to 14. UV-polymerisation of the new compounds, which comprise both urethane-acrylate and xanthate moieties, substantially avoids problems of residual photoinitiator or unreacted monomer in the final polymerised products. As such they are especially useful in the production of printing inks and packaging films for foodstuffs. as well as various coatings.

Description

PHOTO-CURABLE URETHANE-ACRYLATE COMPOUNDS

FIELD OF THE INVENTION

This invention relates to photo-curable urethane-acrylate compounds, more particularly to UV-curable compounds comprising urethane and acrylate moieties which are especially useful as film formers, in particular for use in packaging and printing fields.

BACKGROUND OF THE INVENTION AND PRIOR ART

Modern paint industry faces a continual challenge of how to lower the emission of toxic volatile organic compounds (VOC's) from coatings and pigmented films, especially in the field of packaging for foodstuffs. There are also many legislative regulations governing the levels to which VOC's in paints, coatings and packaging is permitted. There is therefore a large investment within the industry into research and development into this issue.

Hitherto there have been many attempts at addressing the problem of toxic emissions of VOC's in paint, pigmenting compounds and packaging, for example the introduction of water-reducible coatings, powder coatings, high-solid paints and radiation-curable coatings. Radiation-curable coatings are probably the most successful of these areas in recent years, owing to their favourable balance of cost versus environmental and health criteria. Indeed, photo-curable coating materials have been in commercial production for around 25 years and are one of the segments of the industry with the highest recent growth.

Conventional coatings based on organic or aqueous solvents are applied onto a substrate where they cure through a combination of natural evaporation of the solvent and chemical reaction within the resulting film. The solvent provides the necessary levelling capability and adequate application viscosity, whilst the chemical reaction results in the polymerised film having the required mechanical properties once cured.

UV-curable coating systems generally utilise an oligomer starting material in combination with a reactive solvent (diluent) and a photoinitiator. The photoinitiator is decomposed by exposure to the UV radiation, yielding free radicals or cations that initiate the polymerisation of the oligomer. Because the reactive diluent itself takes part in the overall polymerisation process, it does not evaporate, and therefore the resulting films are conventionally considered VOC-free.

However, the frequent presence of residual photoinitiator molecules in the resulting film or coating presents a health hazard problem, since they can diffuse into the material (eg. foodstuff) that it is used to coat or surround. There is also the likelihood that there remains residual unpolymerised soluble material in the film. For these reasons UV- curable systems are not currently commercially used for the production of packaging or printable material for foodstuffs and other materials where health and safety concerns are important.

Another undesirable feature of conventional UV-crosslinking systems which are carried out under an air atmosphere is the need to use possibly higher than necessary concentrations of photoinitiator in order to counter the effects of oxygen-induced inhibition of the reacting monomer/oligomer. The presence of oxygen during the UV curing process can have a negative effect on the cure speed as well as on the resulting film properties. Oxygen reacts via a free radical mechanism and by reacting with the photoinitiator, monomer or chain radical forms peroxy radicals. As a result there can be insufficient reactivity remaining to continue the polymerization process, giving uncured (tacky) films. In practice such effects of oxygen inhibition are usually countered by addition of higher than necessary concentrations of photoinitiator to ensure total crosslinking. In a rather different field, the use of hyperbranched polyesters in the manufacture of UV- curable coatings is well known, for example from EP-A-1227076, EP-A-1070748, US-A- 6114489 and US-A-6093777. As compared with conventional polymers which are generally linear with a low number of end groups, hyperbranched polymers are highly branched with a large number of end groups, which can be exploited to determine the physical and chemical properties of the resulting polymer. For example, their melt- and solution-viscosities do not change considerably with any increase in molecular mass, which is of great importance in paints. On the other hand the typically large number of hydroxyl groups in such molecules offers significant possibilities for the tailoring of end properties of the resulting polymerised materials.

h order that they are UV-curable, such hyperbranched polyester molecules typically include an acrylate moiety (so-called "urethane-acrylates"), which are again well documented in the literature, eg. WO-A- 1997/023520, WO-A- 1993/021259, US-A- 2002/0026015, in addition to the other references mentioned above). However the above-discussed photoinitiator component still needs to be used, resulting in the same problems as discussed above.

In yet another field, the use of xanthate salts or esters as photoinitiators in the polymerisation of various monomers is also well known, eg. for the manufacture of linear or star-shaped polymers. See for example EP-A-0467649 and EP-A-0450492. However they have hitherto not been used in the field of UV-initiated polymerisation, because they suffer from the same problems associated with photoinitiators as discussed above.

We have now discovered a new range of polymerisable compounds based on hyperbranched urethane-acrylate oligomers which include one or more xanthate moieties, which are useful for producing polymerised materials for use in a variety of end applications and which obviate or ameloriate at least some of the disadvantages of the currently used prior art materials discussed above. SUMMARY OF THE INVENTION

Accordingly, in a first aspect the invention provides compounds of the following formula ay.

wherein:

R is a residue of a hyperbranched polyester core moiety of the following general formula (II):

wherein: R is a core group which is a residue of a multifunctional aliphatic or aromatic polyol preferably having 2 or more, more preferably 3 or more, even more preferably 4, OH groups; R is a residue of an aliphatic or aromatic carboxylic acid having one COOH group and two or more OH groups, wherein n is the hydroxy functionality of the said carboxylic acid and is 2 or more, and m is the functionality of the polyol core group R¹ and is at least 2;

R³ is a residue of an isocyanate compound selected from any one of the following formulae (1) to (13):

(1) (2)

(3) (4)

(5) (6)

(7) (8)

(9) (10)

(13)

R is a hydrogen atom or methyl group; x is 1 -10, preferably 1-8, more preferably 4-8;

R⁵ is an alkylene group;

R⁶ is -OR⁷, -NR⁷R⁸, -SR⁷ or R⁹, where R⁷ and R⁸ are the same or different and each is independently selected from: (i) an alkyl, acyl, aryl, alkene or alkyne group, (ii) a saturated or unsaturated, optionally aromatic, carbocyclic or heterocyclic group; wherein any of the above groups (i) and (ii) may be optionally substituted; and R⁹ is selected from any of: H, an alkyl, aryl, alkene or alkyne group, a saturated or unsaturated optionally substituted carbocyclic or heterocyclic group, an alkylthio, alkoxycarbonyl, aryloxycarbonyl, carboxy, acyloxy, carbamoyl, cyano, dialkylphosphonato, diarylphosphonato, dialkylphosphinato or diarylphosphinato group; a (being the number of urethane-acrylate chains attached to the central core group R) is from 0 to 10, preferably from 1 to 10, more preferably from 4 to 10; b (being the number of xanthate moieties in the molecule) is from 0 to 10, preferably from 1 to 10, more preferably from 4 to 10; with the proviso that a + b is from 2 to 16, preferably from 4 to 14, more preferably from 10 to 14. In a second aspect the invention provides a method of making compounds of formula (I) according to the first aspect of the invention, comprising the following sequence of steps:

(1) Preparing a hyperbranched polyester compound according to general formula (II) above by reaction of a multifunctional aliphatic or aromatic polyol, preferably having 2 or more, more preferably 3 or more, even more preferably 4, OH groups, with a monofunctional carboxylic acid having one COOH group and two or more OH groups;

(2) Reacting the hyperbranched polyester compound from step (1) with a monohalogen carboxylic acid in an amount and under temperature conditions sufficient to react with a significant proportion, preferably from about 25 to about 50 %, of the OH groups therein;

(3) Reacting the product of step (2) with a compound of the following general formula (III): R-CSS^"M⁺ _(III)

wherein R⁶ is as defined above and M is a metal cation, preferably an alkali metal cation, in an amount corresponding to at least one mole of the compound (III) per halogen atom.

(4) Preparing, in a separate step, an adduct between a diisocyanate compoimd, preferably one with different reactivities of NCO groups, and a hydroxyalkyl acrylate or methacrylate, preferably at a molar ratio of NCO groups of the diisocyanate to OH groups of the hydroxyalkyl (meth)acrylate of about 2:1;

(5) Reacting the product of method step (3) with the adduct of step (4);

(6) Optionally subjecting the product of step (5) to a purification step. In a third aspect the invention further provides a method of preparing an ink, paint, coating or packaging film, comprising polymerising and/or crosslinking and/or curing a composition consisting of or containing at least one compound according to the first aspect of the invention, or at least one compound prepared by the method according to the second aspect of the invention, by irradiation with UV radiation, especially of from about 200 - 400 nm wavelength. Preferred embodiments of this aspect of the invention are described hereinbelow.

In a fourth aspect, the present invention further provides a polymerisable composition comprising a compound according to the first aspect of the invention.

In a fifth aspect, the present invention further provides an ink, paint, coating or packaging film per se, formed by the method according to the third aspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION IN ITS VARIOUS ASPECTS. AND PREFERRED EMBODIMENTS AND EXAMPLES THEREOF

In the above step (1) of the preparative method of the second aspect of the invention, the multifunctional aliphatic or aromatic polyol is preferably an aliphatic or aromatic diol, triol, tetrol or alkoxylated monomer having 2 or more OH groups. Examples of such preferred polyols include: ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, pentanediol, neopentyl glycol, 1,3-propanediol, trimethylolpropane, trimethylolethane, glycerol, erythritol, ditrimethylolpropane, ditrimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, ethoxylated trimethylolethane, propoxylated trimethylolethane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, ethoxylated pentaerythritol and propoxylated pentaerythritol.

Also in the above method step (1), examples of the monofunctional carboxylic acid having two or more OH groups include: α,α-bis(hydroxymethyl)propionic acid (dimethylol propionic acid), α, -bis(hydroxymethyl)butyric acid, α,α- bis(hydroxymethyl)valeric acid, α,α-bis(hydroxyethyl)propionic acid, and α- phenylcarboxylic acids having at least two hydroxyl groups directly pendent to the phenyl ring (phenolic hydroxyl groups), such as 3,5-dihydroxybenzoic acid.

In the above method step (2), examples of the monohalogen carboxylic acid include: bromoacetic acid, 2-bromopropionic acid, 2-bromobutyric acid, 3-bromopropionic acid, 4-bromobutyric acid, 2-bromohexanoic acid, 2-bromo-3-methylbutyric acid, 2- bromophenylacetic acid, 2-bromotetradecanoic acid, 2-bromo-2-methylpropionic acid, and the same acids as just listed but with chloro and iodo monosubstituents instead of bromme. The temperature conditions in this method step (2) are preferably a temperature of less than about 250°C, more preferably below about 210°C, even more preferably below about 160°C.

In the above method step (3), the compound (III) is preferably an alkali metal salt of alkyl xanthogenate. A particularly preferred example is potassium alkyl xanthogenate. This reaction step is preferably carried out in a solvent, such as ethylacetate, acetone, tetrahydrofuran, ethanol or methylethylketone, at ambient temperature for eg. 24 hours. The obtained intermediate reaction mixture, containing salt from reaction, may be used without further purification.

In the above method step (4), examples of the diisocyanate compound for preparing the adduct include: isophoronediisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, 4,4-diisocyanato-dicyclohexylmethane, toluene-2,4-diisocyante, toluene- 2,6-diisocyante, 1,4-diisocyanate cyclohexane, l,4-diisocyanato-4-methyl-pentane and l,3-bis(2-isocyanatoprop-2-yl)benzene). Examples of the hydroxyalkyl (meth)acrylate component include: 2-hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, polyethyleneglycol monoacrylate, polypropyleneglycol monoacrylate, polyethyleneglycol monomethacrylate, polypropyleneglycol monomethacrylate, 2- hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate). The reaction of this method step is typically, and preferably, carried out in the presence of a catalyst, such as dibutyltindilaurate, at a temperature of below about 60°C, more preferably below about 40°C.

In the above method step (5), the reaction of the product of step (3) with the adduct of step (4) is preferably carried out in a solvent, such as ethylacetate, in the presence of an inhibitor for radical polymerisation, such as hydroquinone, and a suitable catalyst, such as dibutyltindilaurate. The reaction is preferably carried out at a temperature of below about 100°C, more preferably below about 80°C.

The above purification step (6) preferably comprises filtering off the product, extracting the residual salt with water, drying the product with eg. anhydrous magnesium sulphate, filtering off the product again and evaporating the solvent.

After the above purification step (6), additional components such as solvents, other polymerisable binders and conventional additives (eg. pigments, UV stabilisers, flow aids, etc) may be added to the product for preparing a practical UV-polymerisable composition for use in preparing useful polymerised end-products. Examples of this are given in the Examples hereinbelow.

In practical examples of the above preparative method according to the second aspect of the invention, the degree of modification of the OH end groups of the hyperbranched polyester can be important in determining the properties, especially the viscosity, of the ultimate UV-polymerised resins. This degree of modification of the OH end groups of the hyperbranched polyester can be controlled by appropriate selection of the stoichiometric ratios between the hyperbranched polyester core compound starting material (from step 1), and/or the halogenated acid used in step (2), and or the urethane- acrylate adduct used in step (5) in the overall preparative process of the oligomers for polymerisation. For example, one mole of hyperbranched polyester second generation (see Example 1 hereinbelow) has 16 hydroxyl groups, and if 8 moles of urethane acrylic adduct is used, this results in -50% modification of the OH groups. This results in an ultimate resin which has a significantly lower viscosity as compared to that obtained with use of an unmodified hyperbranched polyester. So, by selecting the degree of modification of the OH groups of the hyperbranched polyester it is possible to control the viscosity of the final resin. Practical examples of this are given in the Examples hereinbelow.

Likewise, the degree of xanthate substitution in the subject oligomer compounds of the invention can be controlled by appropriate selection of the stoichiometric ratios between the OH groups of the hyperbranched polyester component and the halogenated carboxylic acid (introducing a halogen atom into the hyperbranched polymer in step (2)), since the halogen atom reacts quantitatively with the xanthate salt introduced in step (3). Again, examples of this are given in the Examples hereinbelow.

Furthermore, the choice of structure of the hydroxyalkyl (meth)acrylate component used in step (4) can also be important in determining the properties, especially the viscosity and reactivity, of the ultimate resins. For instance, the use of long polyalkylene glycol monoacrylate chains to modify the hyperbranched polyester component lowers the viscosity of the resin by covering the highly polar groups (hydroxy or urethane) of the macromolecules, thereby reducing polar intermolecular interactions. For example, the use of Bisomer PEA6 (as in the Examples hereinbelow, which has flexible polyethyleneoxide chains) can give adducts of 558g/mol molecular weight, which considerably reduces the viscosity of the ultimate resin. On the other hand, the use of hydroxyethyl acrylate gives adducts of 338g/mol molecular weight, which is much more rigid and the ultimate resin obtained is of a significantly higher viscosity. Polypropyleneglycol chains are bulkier and less polar than polyethyleneglycol chains, so they result in lower viscosity resins and the cured material is more resistant to polar solvents, particularly water.

The choice between acrylate and methacrylate groups may also be very important. Methacrylate resins have a lower reactivity and need more time for UV crosslinking. They also have an increased sensibility to oxygen inhibition. However, the obtained crosslinked materials feature higher hardness and mechanical strength. Acrylate resins are commonly used for UV curing because the reactivity of the system is the chief parameter (in most cases), which determines their final application.

The third aspect of the invention relates to the method of UV- polymerisation/crosslinking/curing of the subject novel compounds for preparing an ink, paint, coating or packaging film. This involves irradiation, under conventionally appropriate conditions, of a composition comprising at least one of the subject new oligomers with UV radiation, especially of from about 200 - 400 nm wavelength.

Depending on the viscosity of the hyperbranched urethane-acrylate oligomer material(s) of the invention, the UV-curable composition comprising it or them may further comprise one or more reactive diluents (preferably copolymerizable compounds having more than one double bond per molecule). Examples of preferred reactive diluents include: hexanediol diacrylate, tripropylene glycol diacrylate, ethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, bisphenol A diacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, tetramethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol diacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tripentaerythritol octaacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol tetramethacrylate, tripentaerythritol octamethacrylate, 1,4-cyclohexane diacrylate, ethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,4- butanediol dimethacrylate bisacrylates and bismethacrylates of polyethylene glycol having a molecular weight of from about 200 to about 1500.

The amount of such reactive diluent(s) added to the reaction mixture is preferably such as to achieve a viscosity of the reactive composition which is from about 0.01 to about 50 Pas. This viscosity may be achieved by adding typically from about 90 to about 10 wt % of reactive diluent(s), as calculated on the weight of the total reaction mixture, preferably from about 30 to about 10 wt %. The actual preferred amount of the reactive diluent(s) will depend on the desired viscosity, coat film thickness, method of application, field of application and the desired mechanical properties of the resulting polymerised material. Examples of this are given hereinbelow.

The reactive composition may in addition comprise conventionally appropriate amounts of any of the following optional adjunct components: solvents, pigments, matting agents, flow control agents, antioxidants, UV stabilisers, adhesion promoters, or other additives used in conventional UV-curing technology.

Not only may the novel oligomers of the present invention be used as the sole UV- reactive constituent binder in UV-polymerisable/curable compositions according to the invention (which is preferred), but they may if desired be used in combination with a second binder based on a similarly structured hyperbranched urethane-acrylate oligomer but without the integral xanthate moiety but which can still be cured without the addition of a photoinitiator. Such a second binder component may for example be a hyperbranched or conventional urethane acrylate or any binder containing unsaturated groups (eg. epoxy acrylate, polyester acrylate, polyether acrylate, unsaturated polyester, etc).

The new oligomers of the present invention may be used to prepare inks, paints, films and coatings for a variety of end uses. These include (but are not limited to): - printing inks for food packaging - UV-curable inks for ink-jet printers - flexographic inks - coatings for optical fibres, - scratch resistant coatings on computer discs, eg. CD's and DVD's, - dental composite resins, - stereolithography, automotive coatings, - wood coatings, - floor coatings, - adhesives.

These end products, ie. an ink, paint, coating or packaging film per se, constitute a fourth aspect of the invention, and examples of these are given in the Examples hereinbelow.

The present invention in its various aspects and its implementation in practice will now be illustrated by way of the following Examples, which should not be construed as limiting the scope of the invention as claimed.

EXAMPLES

In the following Examples the following abbreviations are used:

HBP,G2 Hyperbranched polyester, second generation (M_theor⁼ 1 42 g/mole, 16 OH groups per molecule)

DM Degree of OH group modification

IPDI Isophorone diisocyanate

2-HEA 2-hydroxyethyl acrylate

PEA6 Polyethyleneglycol monoacrylate ( M=336 g/mole) (Bisomer PEA6*)

PPA6 Polypropyleneglycol monoacrylate ( M=590 g/mole) (Bisomer PPA6*)

PPM5S Polypropyleneglycol monomethacrylate (M=376 g/mole) (Bisomer PPM5S*)

DBTDL Dibutyl tin dilaurate (catalyst)

HQ Hydroquinone (inhibitor)

THF Tetrahydrofuran

EtAc Ethyl acetate

2-BrPA 2-bromopropionic acid

KCS₂OC₂H₅ Potassium xanthogenate

X Xanthate

HDDA Hexanediol diacrylate (ex BASF) Irgacure 184 1-hydroxy-cyclohexyl phenyl-ketone (ex Ciba Specialty Chemicals) Fascat 4100 Butylstannoic acid (ex Atofina)

(*trade marks of Laporte Performance Chemicals Limited)

In the above definition of "HBP, G2" the term "hyperbranched polyester, second generation" is explained by the following:

Dendrimers are highly branched structures consisting of a central core from which treelike arms extend three-dimensionally into space, forming a more or less spherical or rod-shaped structure, depending on the type of core used. The number of branches increases systematically from the core of the molecule in a radial direction. Each successive layer of branches is called a generation. Dendrimers are synthhesized with the accurate control of each step by protection/deprotection schemes, to give perfectly branched monodispersed molecules. This is illustrated by the following scheme:

I Generation Dendrimer

III Generation Dendrimer

Hyperbranched macromolecules, on the other hand, are made in a one-pot synthesis and this simplified procedure yields less perfect structures. The fact that they are produced using such simple procedures makes them more cost effective, and therefore more suitable for most commercial applications. Hyperbranched polymers have lower branching efficiency than dendrimers, but possess many of the same properties. The highly branched architecture minimizes chain-chain entanglements and so imparts both high solubility and low melt viscosity to these polymers. Hyperbranched polymers are not monodispersed like dendrimers (all molecules are not the same in size) but their molecular weight distribution is between dendrimer and classical linear polymers. Those do not possess perfect generation like dendrimers, but when the stoichiometric ratio between the molecules of "core" (B₄) and molecules of monomers (AB₂) making a layer (or generation) is the same as in their dendrimer analogues, they have a same name for the generation. This is illustrated by the following scheme:

The above sheme illustrates just one of many possible structures of hyperbranched molecules.

EXAMPLE 1 - Synthesis of HBP_.G2

62.5 g (0.25 mole) of ditrimethylolpropane (DITMP) was poured into a 4-necked reaction flask equipped with a stirrer, a nitrogen inlet, a thermometer and a water-trap. The temperature was raised to 140°C and 402 g (3 mole) of dimethylolpropionic acid (bis- MPA) and 2.32 g of p-toluenesulfonic acid (pTSA) were added. The course of the reaction was followed by acid value tifration. The reaction was continued until an acid value of 8 mg KOH/g was obtained.

The product had the following structure:

EXAMPLE 2 - SYNTHESIS OF H2(PEA6)₈

29.3 g (0.13 mole) IPDI, 0.14 g DBTDL and 0.04 g HQ were poured into a 500 ml reactor flask equipped with a mechanical stirrer, a thermometer and a cooler. 44.2 g (0.13 mole) of PEA-6 was added over a 90 minute period while maintaining the temperature below 35°C. The reaction temperature was then allowed to increase from 35°C to 40°C within 30 minutes, and the reaction mixture was stirred at 40°C for 90 minutes. 27.0 g (0.26 mole OH) of the product as specified in Example 1 (HBP,G2) was dissolved in 100 ml THF and added to the reaction mixture. The temperature was increased to 75°C, and the reaction mixture was stirred for about 9 hours. The reaction was followed by FT-IR and stopped when the NCO-peak (2267 cm^"1) had disappeared. The solvent (THF) was then evaporated.

The product had the following structure:

EXAMPLE 3 - ESTERIFICATION OF HBP_.G2 WITH 2-BROMOPROPIONIC ACID - DM =

50%

100.0 g (0.974 mole OH) of the product from Example 1 (HBP,G2) and 74.54 g (0.487 mole) 2-bromopropionic acid were charged in a 4-necked reaction flask equipped with a stirrer, a N₂ inlet, a cooler and a water-trap. The temperature was raised to 175°C over 2 hours and the reaction was continued at this temperature. The course of the reaction was followed by acid value tifration. The reaction was continued until an acid value of 12.5 mg KOH/g was obtained.

The product had the following structure:

EXAMPLE 4 - ESTERIFICATION OF HBP,G2 WITH 2-BROMOPROPIONIC ACID - DM =

25%

100.0 g (0.974 mole OH) of the product from Example 1 (HBP,G2) and 37.3 g (0.243 mole) 2-bromopropionic acid were poured into a 4-necked reaction flask equipped with a stirrer, N inlet, a cooler and a water-trap. The temperature was raised to 175°C over 2 hours and the reaction was continued at this temperature. The course of the reaction was followed by acid value tifration. The reaction was continued until an acid value of 11 mg KOH/g was obtained.

The product had the following structure:

EXAMPLE 5 - SYNTHESIS OF H2(X)₈

10.00 g of the product from Example 3 was dissolved in 25 ml of ethyl acetate in a 250 ml 3-necked flask. 4.70 g (0.029 mole) of KCS₂OC₂H₅ was dissolved in 15 ml of ethyl acetate. While stirring, the solution was added in small portions into the flask. The reaction mixture was stirred at room temperature overnight. The obtained mixture was filtered off, the residual salt was extracted twice with 50 ml of water, then dried with anhydrous MgSO₄ and again filtered. The solvent (ethyl acetate) was then evaporated. Yield was 7.85 g (70.2 %).

The product had the following structure:

EXAMPLE 6 - SYNTHESIS of H2(X)₈(PEA6)₆

10.00 g of the product from Example 3 was dissolved in 25 ml of ethyl acetate in a 250 ml 3-necked flask. 4.70 g (0.029 mole) of KCS₂OC₂H₅ was dissolved in 15 ml of ethyl acetate. While stirring, the solution was added in small portions to the flask. The reaction mixture was stirred at room temperature overnight.

Into a separate flask 4.89 g (0.0220 mole) IPDI, 0.010 g DBTDL and 0.001 g HQ were poured. 7.41 g (0.0220 mole) of PEA-6 was added over a 90 minute period while maintaining the temperature below 35°C. The reaction temperature was then allowed to increase from 35°C to 40°C within 30 minutes, and the reaction mixture was stirred at 40°C for 90 minutes.

These two reaction mixtures were combined and the reaction was continued at 75°C for about 8 hours. The reaction was followed by FT-IR and stopped when the NCO-peak (2267 cm^"1) had disappeared. The obtained mixture was filtered off, the residual salt was extracted twice with 50 ml of water, then dried with anhydrous MgSO and again filtered. The solvent (ethyl acetate) was then evaporated. Yield was 19.7 g (83.9 %).

The product had the following structure:

EXAMPLES 7, 8, 9

The procedure as specified in Example 6 was repeated with different amounts of hydroxy-acrylate monomers. The theoretical composition of the hyperbranched urethane-acrylates of the obtained products is given in Table 1 below. Table 1

The product of Example 7 had the following structure:

The product of Example 8 had the following structure:

The product of Example 9 had the following structure:

EXAMPLE 10 - Synthesis of H2(X)₄(PEA6)ι₀ 10.00 g of the product from Example 4 was dissolved in 25 ml of ethyl acetate in a 250 ml 3-necked flask. 2.93 g (0.018 mole) of KCS₂OC₂H₅ was dissolved in 10 ml of ethyl acetate. While stirring, the solution was added in small portions into the flask. The reaction mixture was stirred at room temperature overnight.

Into a separate flask 10.17 g (0.0458 mole) IPDI, 0.020 g DBTDL and 0.002 g HQ were poured. 15.39 g (0.0458 mole) of PEA6 was added over a 90 minute period while maintaining the temperature below 35°C. The reaction temperature was now allowed to increase from 35°C to 40°C within 30 minutes, and the reaction mixture was stirred at 40°C for 90 minutes.

These two reaction mixtures were combined and reaction was continued at 75°C for about 8 hours. The reaction was followed by FT-IR and stopped when the NCO-peak (2267 cm^"1) had disappeared. The obtained mixture was filtered off, the residual salt was extracted twice with 50 ml of water, then dried with anhydrous MgSO₄ and again filtered. The solvent (ethyl acetate) was then evaporated. Yield was 28.5 g (78.5%).

The product had the following structure:

EXAMPLES 11, 12, 13

The procedure as specified in Example 10 was repeated with different amounts of isophorone diisocyanate and hydroxy acrylate monomers. The theoretical composition of hyperbranched urethane-acrylates of the obtained products is given in Table 2 below. Table 2

The product of Example 11 had the following structure:

The product of Example 12 had the following structure:

The product of Example 13 had the following structure:

COMPARATIVE EXAMPLES

EXAMPLE 14 (SYNTHESIS OF LINEAR POLYESTER)

119.6 g (1.15 mole) of neopentyl glycol (NPG), 146.0 g (1.0 mole) adipic acid and 1.30 g FASCAT 4100 were poured in a 4-necked reaction flask equipped with a stirrer, a N inlet, a cooler and a water-trap. The temperature was raised to 185°C over 2 hours and the reaction was continued at this temperature until an acid value of 4 mg KOH/g was obtained. EXAMPLE 15 (Synthesis of linear urethane-acrylate)

15.0 g (0.0675 mole) IPDI, 0.012 g DBTDL and 0.004 g HQ were charged in a 250 ml reactor flask equipped with a mechanical stirrer, a thermometer and a cooler. 7.83 g (0.0675 mole) of 2-HEA was added over a 90 minute period while maintaining the temperature below 35°C. The reaction temperature was now allowed to increase from 35°C to 40°C within 30 minutes, and the reaction mixture was stirred at 40°C for 90 minutes. 56,0 g (0,0675 mole OH) of linear polyester as specified in Example 14 was dissolved in 20 ml THF and added to the reaction mixture, and it was stirred for 8 hours at 70°C. The reaction was followed by FT-IR and stopped when the NCO-peak (2267 cm^" ^l) had disappeared.

WORKING EXAMPLES

EXAMPLE 16 Coatings formulation

Coating formulations comprising the products obtained in Examples 2 and 6 - 13 were prepared by adding 20 wt% of reactive diluent (HDDA). 4% of Irgacure 184 was added to the coating formulation comprising the oligomer obtained in Example 2. The lacquers obtained were coated on steel panels at a film thickness of 60 μm. The films were cured using a medium pressure halogen UV lamp - 80 W/cm (UVPS) by passing 10 times at a belt speed of 10 rn/min in nitrogen atmosphere. The films were allowed to stand overnight before testing. The properties of the film obtained are given in Table 3 below.

Table 3

The product prepared in Example 2 was mixed with products obtained in Examples 5, 6 and 10 without the addition of photoinitiators. All the compositions contained 20 wt.% of the reactive diluent (HDDA). The compositions of these coating formulations are given in Table 4 below.

Table 4

The complex dynamic viscosity of these diluted resins was determined at 30°C and frequency of 1 Hz, as shown in Table 5 below. Table 5

EXAMPLE 17

Determination of the amount of extractable material from cured films

Mixtures of hyperbranched urethane acrylates containing 20wt% HDDA were coated on glass plates. The films were cured using medium pressure halogen UV lamp (80 W/cm) by passing 10 times at a belt speed of 6 m/min in nitrogen atmosphere. The films were removed from glass plates, held 24 hours at ambient temperature and then extracted with methylene chloride for 6 hours in Soxhlet extractor. After extraction the samples were dried 15 minutes at 70°C and 12 hours in vacuo at ambient temperature. The weight loss due to CH₂C1₂ extraction was thus determined. The results obtained (% of extractables) are given in Table 6 below. Table 6

After 6 hours in boiling methylene chloride (Soxhlet extraction)

EXAMPLE 18

This Example gives a practical description of the mechanism of crosslinking which is important to an understanding of the process of polymerization of the novel oligomers according to the invention.

One of the important characteristics of this process is the living character of the crosslinking reaction. Living free radical polymerisation is a recently developed technique for controlled polymerisation of vinyl monomers. This technique allows the synthesis of a wide range of different materials (block, star, dendritic polymers, etc), which are not attainable via other polymerisation processes or are difficult to prepare. In the present invention the living character is used for the generation of a new portion of free radicals upon irradiation with UV light. The controllable character of this reaction is due to the reversibility of the breaking the C-S bond under UV light. This process is explained by the following mechanism:

R =

Crosslinked material or Block copolymer Star copolymer

R-CH₂

Under UV light, the C-S bond undergoes photolysis giving the macroradical (I), on the one hand, and the dormant radical (II), on the other. The dormant radical cannot initiate the reaction of polymerisation; only the macroradical (I) reacts with monomer (III) (reactive diluent), causing chain growth (crosslinking, in the case of preferred embodiments of the present invention). In the invention the macroradical (I) is exclusively attached to the oligomer, which means that there is no possibility of creating any other polymer chain which is not connected to the oligomer (ie. there is low content of extractable material). The dormant radical can react with the growing macroradical, causing its deactivation. Thus, the obtained material has terminal xanthate groups which may again undergo photolysis under UV light. Since it is a crosslinking reaction, it is not a controlled polymerisation, but the mechanism possesses a living character - the reaction continues upon new UV irradiation until all molecules of the monomers are consumed. That means that by curing, the present invention is able to make an active surface coating with xanthate groups embedded therein. This property can be exploited for various purposes, as already described herein (eg. grafting, sensoring, printing, etc.).

EXAMPLE 19

This Example gives some practical examples of formulations and applications of resins produced accordmg to the present invention.

Urethane-acrylates are the most important binder for coating optical fibres. The chief requirements for a binder in this field are very fast curing (ie. very reactive resins) and good mechanical properties for protection and reinforcement of the glass fibre. Generally, two different coatings are applied: the primary coatmg layer is soft (made of flexible resin with a low Tg and modulus) and applied directly onto the glass fibre, while the secondary coating layer (made of hard resin with a higher Tg and modulus) is coated over the primary layer to protect the fibre during handling. The resins produced according to the present invention are very easy to adjust to fulfil these requirements (the degree and type of modification of the hyperbranched core) and to make them ideal candidates for such applications. At the same time, hydrogen generated during the UV-curing of the coating can diffuse into the core regions of the optical fibres, thereby influencing the transmission characteristics of the fibre. Hydrogen can however also degrade the mechanical characteristics of optical fibres. UK Patent Application No. GB-A-2 204 050 describes the use of xanthate for reducing the generation of H during UV-curing of the coating resins on optical fibres. Hyperbranched urethane-acrylate resins from the present invention which also contain xanthate groups can have the same role in reducing H₂ generation during curing.

Typical UV-curable optical fibre coating compositions of the present invention may comprise from about 20 to about 90 % by weight, preferably from about 50 to about 75 % by weight, of urethane-acrylate oligomer(s) of the present invention, from about 10 to about 90 % by weight, preferably from about 25 to about 40 % by weight of reactive diluent(s), and from 0 to about 10 % by weight, preferably from about 1 to about 5 % by weight of additive(s) (adhesion promoters, stabilisers, etc).

UV-curable ink jet printing is a new area of digital imaging. The main requirements for UV-curable materials in this technology are fast curing, low viscosity, good droplet formation and good cured film properties (such as scratch resistance, adhesion, hardness, flexibility, sharpness of image). The main advantages of UV-curing inks and coatings in this field are: - they emit little or no VOC solvents, - they will not dry during the printing process, but will dry almost instantly when cured ("drop on demand"), - they permit high production rates, - they produce the highest printed gloss available and high quality matt and satin finishes, - they produce chemically durable and abrasion resistant prints, - the curing equipment occupies much less space than conventional thermal drying equipment.

The resins produced according to the present invention can be designed to have a high concentration of unsaturated groups yielding attractive physical properties of the cured films. At the same time, they can have very low shrinkage upon curing (which is a big problem in conventional UV coatings, not just in ink jet printing), owing to their very high molecular weight, giving good adhesion to different substrates.

Typical UV-curable ink jet coating compositions according to the present invention may comprise from about 10 to about 60 % by weight, preferably from about 20 to about 40 % by weight of the urethane-acrylate oligomer(s) of the invention, from about 10 to about 80 % by weight, preferably from about 40 to about 60 % by weight, of reactive diluent(s) (preferably alkoxylated di- or tri- functional monomers), from 0 to about 30% by weight, preferably from about 5 to about 15 % by weight of pigment(s), and from 0 to about 20 % by weight, preferably from about 5 to about 10 % by weight of additive(s). Another application of the resins produced accordmg to the present invention is their use for flexographic inks. The rheology of UV flexographic inks is quite different from other types of inks. Resins for flexographic inks must behave like Newtonian liquids (viscosity remains constant at any shear rate or shear stress). The resins produced according to the present invention can exhibit such Newtonian behaviour (because hyperbranched or star structures minimize chain-chain entanglements, which is responsible for pseudo-plastic behaviour), and are therefore ideal candidates for this application.

At the same time, the wetting of pigments is another critical parameter for this type of coatmg. Resins produced according to the present invention can have a polar shell (arms of polyethylene glycol) and a less polar core (hyperbranched polyester), which makes them good agents for the dispersions of pigments.

Typical UV-curable flexographic ink compositions accordmg to the present invention may comprise from about 10 to about 40 % by weight, preferably from about 15 to about 25 % by weight, of urethane acrylate oligomer(s) of the invention, from about 10 to about 90 % by weight, preferably from about 40 to about 60 % by weight of reactive diluent(s), from 0 to about 30% by weight, preferably from about 10 to about 20 % by weight, of pigment(s), and from 0 to 20 % by weight, preferably 5 to 10 % by weight of additive(s).

The UV-curable oligomers of the present invention may also be used for automotive coatings as an alternative to the conventional two-pack polyurethane/acrylate clearcoats. Furthermore, they can be used as a component of a dual curing coating composition based on polyurethane/acrylate coatings, giving better scratch and abrasion resistance of clearcoats. The resins of this invention comprise some free hydroxyl groups, so they can react with the second component from the two-pack system (ie. the polyisocyanate component). As a result, the obtained films (crosslinked coatings) have a good balance of hardness and flexibility. Conventionally, as discussed in the introduction hereinabove, known UV-curable compositions are generally considered to be VOC-free. However, depending on the required application viscosity, it may be desired or necessary to add to the polymerizable compositions of the present invention one or more solvents in an appropriate amount, thereby increasing the VOC content of the resulting polymer by a modest, but still acceptable, amount. However, this does not significantly detract from the advantages of the invention as already discussed.

Examples of solvents that may be acceptably added in minor amounts on this principle include: ketones, ethers and esters, such as ethyl acetate, n-butyl acetate, methyl ethyl ketone, N-methylpyrrolidone, tetrahydro furan, l-methoxy-2-propanol, methoxy propyl acetate. These solvents may be used as diluents for other binders (eg. conventional acrylic polyols based on hydroxyacrylates and methacrylates, as are well known in the art, eg. Desmophen A365, ex Bayer AG) and crossslinkers.

Typical such dual-curing formulations containing urethane-acrylate resins of the present invention may comprise from about 10 to about 60 % by weight, preferably from about 20 to about 40 % by weight, of the urethane-acrylate oligomer(s) of the invention, from about 10 to about 60 % by weight, preferably from about 20 to about 40 % by weight of conventional acrylic polyol, from about 10 to about 40 % by weight, preferably from about 20 to about 40 % by weight, of reactive diluent(s), from about 5 to about 30 % by weight, preferably from about 10 to about 20 % by weight, of a crosslinker, and from 0 to about 10 % by weight, preferably from about 1 to about 5 % by weight, of additive(s).

EXAMPLE 20

This Example demonstrates the advantageous property of compounds according to the invention in terms of their greatly reduced (or even eliminated) degree of inhibition by oxygen when UV-crosslinked under an air atmosphere. Coating formulations comprising the products obtained in each of Comparative Example 15 and Examples 2, 6, 7, 12 and 13 were prepared by adding thereto 20 wt % of reactive diluent (HDDA). 4 wt % of photoinitiator (Irgacure 184) was added to the coating formulations comprising the oligomers obtained in Comparative Example 15 and Example 2. The coating formulations were then coated onto steel plates and cured using a medium pressure halogen UV lamp (80 W/cm) by passing each one 10 times thereunder at a belt speed of 10 m min in an air atmosphere. The resulting properties of the obtained films are given in Table 7 below.

Table 7

Finger touch test : - tacking + tack-free (no air inhibition)

Claims

1. A compound of the following formula (I):

(I)

wherein:

wherein: R is a core group which is a residue of a multifunctional aliphatic or aromatic polyol; R² is a residue of an aliphatic or aromatic carboxylic acid having one COOH group and two or more OH groups, wherein n is the hydroxy functionality of the said carboxylic acid and is 2 or more, and m is the functionality of the polyol core group R¹ and is at least 2;

(1) (2)

(3) (4)

(5) (6)

(7) (8)

(9) (10)

(11)

(12)

(13)

R⁴ is a hydrogen atom or methyl group; x is 1 -10;

R⁵ is an alkylene group;

R⁶ is -OR⁷, -NR⁷R⁸, -SR⁷ or R⁹, where R⁷ and R⁸ are the same or different and each is independently selected from: (iii) an alkyl, acyl, aryl, alkene or alkyne group, (iv) a saturated or unsaturated, optionally aromatic, carbocyclic or heterocyclic group; wherein any of the above groups (i) and (ii) may be optionally substituted; and R⁹ is selected from any of: H, an alkyl, aryl, alkene or alkyne group, a saturated or unsaturated optionally substituted carbocyclic or heterocyclic group, an alkylthio, alkoxycarbonyl, aryloxycarbonyl, carboxy, acyloxy, carbamoyl, cyano, dialkylphosphonato, diarylphosphonato, dialkylphosphinato or diarylphosphinato group; a (being the number of urethane-acrylate chains attached to the central core group R) is from 0 to 10, preferably from 1 to 10; b (being the number of xanthate moieties in the molecule) is from 0 to 10, preferably

with the proviso that a + b is from 2 to 16.

2. A compound according to claim 1, wherein in the general formula (I) the core group R¹ is a residue of a multifunctional aliphatic or aromatic polyol having 3 or more OH groups.

3. A compound according to claim 1 or claim 2, wherein in the general formula (I) x is from 1 to 8.

4. A compound according to any one of claims 1 to 3, wherein in the general formula (I) a is from 1 to 10.

5. A compound according to any one of claims 1 to 4, wherein in the general formula (I) b is from 1 to 10.

6. A compound according to any preceding claim, wherein in the general formula (I) a + b is from 4 to 14.

7. A method of making a compound according to any one of claims 1 to 6, comprising: (1) Preparing a hyperbranched polyester compound according to general formula (II) in claim 1 by reaction of a multifunctional aliphatic or aromatic polyol with a monofunctional carboxylic acid having one COOH group and two or more OH groups; (2) Reacting the hyperbranched polyester compound from step (1) with a monohalogen carboxylic acid in an amount and under temperature conditions sufficient to react with from 25 to 50 % of the OH groups therein; (3) Reacting the product of step (2) with a compound of the following general formula (III): R-CSS^_M⁺ _m wherein R⁶ is as defined in general formula (I) and M is a metal cation, in an amount corresponding to at least one mole of the compound (III) per halogen atom; (4) Preparing, in a separate step, an adduct between a diisocyanate compound and a hydroxyalkyl acrylate or methacrylate; (5) Reacting the product of step (3) with the adduct of step (4); (6) Optionally subjecting the product of step (5) to a purification step.

8. A method according to claim 7, wherein in step (1) the multifunctional aliphatic or aromatic polyol is an aliphatic or aromatic diol, triol, tetrol or alkoxylated monomer having 2 or more OH groups.

9. A method according to claim 7 or claim 8, wherein in step (2) the temperature conditions are less than 250 °C.

10. A method according to any one of claims 7 to 9, wherein in step (3) the compound (III) is an alkali metal salt of alkyl xanthogenate.

11. A method according to any one of claims 7 to 10, wherein the adduct prepared in step (4) has a molar ratio of NCO groups of the diisocyanate to OH groups of the hydroxyalkyl (meth)acrylate of approximately 2:1.

12. A method according to any one of claims 7 to 11, wherein in step (5) the reaction is carried out in a solvent in the presence of a radical polymerisation inhibitor and a catalyst.

13. A polymerisable composition including one or more compounds according to any one of claims 1 to 6.

14. A polymerisable composition according to claim 13, comprising from 20 to 90 % by weight of the one or more compounds according to any one of claims 1 to 6, from 10 to 90 % by weight of one or more reactive diluents, and up to 10 % by weight of one or more additives.

15. A polymerisable composition according to claim 13, comprising from 10 to 60 % by weight of the one or more compounds according to any one of claims 1 to 6, from 10 to 80 % by weight of one or more reactive diluents, up to 30% by weight of one or more pigments, and up to 20 % by weight of one or more additives.

16. A polymerisable composition according to claim 13, comprising from 10 to 40 % by weight of the one or more compounds according to any one of claims 1 to 6, from 10 to 90 % by weight of one or more reactive diluents, up to 30 % by weight of one or more pigments, and up to 20 % by weight of one or more additives.

17. A polymerisable composition according to claim 13, comprising from 10 to 60 % by weight of the one or more compounds according to any one of claims 1 to 6, from 10 to 60 % by weight of an acrylic polyol, from 10 to 40 % by weight of one or more reactive diluents, from 5 to 30 % by weight of one or more crosslinking agents, and up to 10% by weight of one or more additives.

18. A method of preparing an ink, paint, coating or packaging film, comprising polymerising and/or crosslinking and/or curing by irradiation with UV radiation a composition according to any one of claims 13 to 17.

19. Ari ink, paint, coatmg or packaging film as prepared by the method of claim 18.