WO2011124282A1

WO2011124282A1 - Unsaturated polyester resin or vinyl ester resin compositions

Info

Publication number: WO2011124282A1
Application number: PCT/EP2010/068830
Authority: WO
Inventors: Ronald Ivo Kraeger; Johan Franz Gradus Antonius Jansen
Original assignee: Dsm Ip Assets B.V.
Priority date: 2010-04-08
Filing date: 2010-12-03
Publication date: 2011-10-13

Abstract

The present invention relates to a two-component system comprising a first component and a second component, wherein the first component being a resin composition comprising an unsaturated polyester resin and/or vinyl ester resin, reactive diluent and a ligand according to the following formula (1) wherein each R₁, R₂, R₃ and R₄ are independently selected from hydrogen, C1-C12 alkyl, C3-C8 cycloalkyl, C6-C12 aryl and C5-C12 heteroaryl; X is selected from C=O and -[CR₂]_Z- wherein z is from 1 to 3 and each R is independently selected from hydrogen, hydroxyl, C1-C4 alkoxy and C1-C4 alkyl; each Rx and Ry are independently selected from hydrogen, C1-C8 alkyl, C1-C8-alkyl-O-C1-C8-alkyl, C1-C8-alkyl-O-C6-C10-aryl, C6-C10-aryl, C1-C8-hydroxyalkyl, and (CH₂)nC(O)OR₅ wherein n is from O to 4 and R₅ is hydrogen, C1-C4 alkyl or an amide; Ra is a 2-pyridyl group or an alkylidene-2-pyridyl group; Rb is selected from C1-C24 alkyl, C6-C10 aryl and a group containing a heteroatom; and wherein the resin composition comprises an iron salt or complex; and the second component comprises a peroxide compound.

Description

UNSATURATED POLYESTER RESIN OR VINYL ESTER RESIN COMPOSITIONS

The present invention relates to a two-component system comprising a first component and a second component; the first component being a resin composition comprising an unsaturated polyester resin and/or vinyl ester resin and a reactive diluent and the second component comprising a peroxide compound. The two- component systems according to the invention are suitable for being applied in structural applications. As used herein, suitable for structural applications means that the resin composition upon curing by means of peroxide initiated radical

copolymerization results in structural objects.

As used herein, the term "two-component system" refers to systems where two separate components (A and B) are being spatially separated from each other, for instance in separate cartridges or the like, and is intended to include any system wherein each of such two separate components (A and B) may contain further separate compounds. The components are combined at the time the system is used.

The state of the art unsaturated polyester or vinyl ester resin systems generally are being cured under the influence of peroxides and are pre-accelerated by the presence of metal compounds (especially cobalt salts), tertiary amines and mercaptans. Cobalt naphthenate and cobalt octanoate are the most widely use accelerators. See for instance EP-0761737-A1 , JP-42005092 B,

US-A-4, 329,263, US-A-3,584,076, US-A-3,297,789. An excellent review article of M. Malik et al. in J. M.S. - Rev. Macromol. Chem. Phys., C40(2&3), p.139-165 (2000) gives a good overview of the current status of these resin systems. Curing is addressed in chapter 9. However, for reasons of health protection, in the last years there is a desire to replace these cobalt-based catalysts with safer alternatives for use in peroxide initiated radical copolymerization of unsaturated polyester resins or vinyl ester resins with copolymerizable monomer. Toxicological background can be found in J. Environ. Monit., 2003, 5, 675-680,. Woodhall Stopford et al., Bioaccessability testing of cobalt compounds.

The object of the present invention is to provide a resin composition comprising unsaturated polyester resin and/or vinyl ester resin and reactive diluent that can be efficiently cured by means of peroxide initiated radical copolymerization in the absence of a cobalt compound.

The present inventors now, surprisingly, found that efficient curing could be obtained by mixing the two components of a two-component system comprising a first component and a second component, wherein the first component being a resin composition comprising an unsaturated polyester resin and/or vinyl ester resin, reactive diluent and a ligand according to the following formula (1 )

wherein each R-i , R₂, F¾ and R₄ are independently selected from hydrogen, C1-C12 alkyl, C3-C8 cycloalkyl, C6-C12 aryl and C5-C12 heteroaryl;

X is selected from C=0 and -[CR₂]_Z- wherein z is from 1 to 3 and each R is independently selected from hydrogen, hydroxyl, C1-C4 alkoxy and C1-C4 alkyl; each Rx and Ry are independently selected from hydrogen, C1-C8 alkyl, C1-C8-alkyl- O- C1-C8-alkyl, C1-C8-alkyl-O-C6-C10-aryl, C6-C10-aryl, C1-C8-hydroxyalkyl, and (CH₂)nC(0)OR₅ wherein n is from 0 to 4 and R₅ is hydrogen, C1-C4 alkyl or an amide; Ra is a 2-pyridyl group or an alkylidene-2-pyridyl group;

Rb is selected from C1-C24 alkyl, C6-C10 aryl and a group containing a heteroatom; and wherein the resin composition comprises an iron salt or complex

and the second component comprises a peroxide compound.

According to the present invention, compositions with good curing properties can be obtained, i.e. the compositions, obtained by mixing the two components of the two-component system according to the invention, have short gel time, short peak time and/or high peak temperature. In the curing of unsaturated polyester resins or vinyl ester resins, gel time is a very important characteristic of the curing properties. In addition also the time from reaching the gel time to reaching peak temperature, and the level of the peak temperature (higher peak temperature generally results in better curing) are important.

An additional advantage of the present invention is that upon adding the second component, in particular when comprising methyl ethyl ketone peroxide, to a resin composition comprising a vinyl ester resin, foaming of the mixture can be reduced or even prevented. Foaming in vinyl ester resins upon addition of standard methyl ethyl ketone peroxide is decribed in: VezelVersterkt 1 , 1995, 1 1-12. Nabil Boulkertous, Koudhardende Vinylesterharsen.

WO-A-2008/003652 describes the use of iron complexes with bispidon ligands according to formula (1 ) as a drier for air drying auto-oxidative resin composition comprising alkyd resins which comprises unsaturated fatty acid residues. Air drying of auto-oxidative alkyd resins occurs due to reaction of oxygen from the air with the unsaturated fatty acid moieties. This patent publication does not describe the use of such complexes for peroxide initiated radical copolymerization of unsaturated polyester resins and/or vinyl ester resins with copolymerizable monomer. One skilled in the art will appreciate that the mechanism of air drying of auto-oxidative alkyd resins is different than the mechanism of peroxide initiated radical copolymerization of unsaturated polyester resins and/or vinyl ester resins with copolymerizable monomer. Peroxide initiated radical copolymerization of unsaturated polyester resins and/or vinyl ester resins with copolymerizable monomer occurs following decomposition of the peroxide, dosed to the unsaturated polyester resin or vinyl ester resin composition also comprising copolymerizable monomer (also referred to as reactive diluent), by heat or by a redox reaction with an accelerator, thereby generating a reactive radical that initiates radical copolymerization between the resin and the reactive diluent. Oxygen initiates the drying of air drying alkyd resins, whereas oxygen inhibits the curing of unsaturated polyester resin or vinyl ester resin and as such reduces the curing. As such there is no evidence to indicate that siccatives for air drying of auto-oxidative alkyd resins will function as accelerator for peroxide initiated radical copolymerization of resin composition comprising unsaturated polyester resins and/or vinyl ester resins and a copolymerizable monomer. This is further illustrated by the fact that many of the known cobalt alternatives are not able to efficiently dry alkyd resins.

Preferably, Ri and/or R₂ is hydrogen. In a preferred embodiment, R₁ and R₂ are hydrogen.

Preferably, R₃ and R₄ are a 2-pyridyl group.

Preferably, X is selected from C=0 and CH₂. More preferably, X is C=0.

Preferably, each Rx and Ry are independently selected from C6-C10- aryl and (CH₂)_nC(0)0 R₅ wherein n is from 0 to 4 and R₅ is hydrogen, C1-C4 alkyl or an amide. More preferably, each Rx and Ry are independently selected from C6 aryl and C(0)OR₅ wherein R₅ is C1-C4 alkyl. Even more preferably, each Rx and Ry are independently selected from C(0)OR₅ wherein R₅ is C1-C4 alkyl. In a preferred embodiment, Rx and Ry are the same. Preferably, Rx and Ry are C(0)OCH₃ (i.e. R₅.is methyl).

Preferably, Ra is an alkylidene-2-pyridyl group and more preferably Ra is methylene-2-pyridyl.

Preferably, Rb is selected from a C1-C24 alkyl and a group containing a heteroatom capable of coordinating to a transition metal. More preferably, Rb is a C1-C24 alkyl. Even more preferably, Rb is methyl.

The first component comprises an iron salt or iron complex. More preferably, the first component comprises an iron²⁺ salt or complex or iron³⁺salt or complex. Non-limiting examples of suitable iron salt or complexes are iron carboxylates such iron ethyl hexanoate and iron naphtenate; iron acetoacetates; iron acetyl acetonates: iron halides such as iron chloride . It will be clear that, instead of a single iron salt or complex also a mixture of iron salts and complexes can be used.

Without wishing to be bound by any theory, it is believed that the complex of iron with the ligand according to formula (1 ) accelerates the peroxide initiated radical copolymerization of the resin composition comprising unsaturated polyester resin and/or vinyl ester resin and a reactive diluent.

In a preferred embodiment according to the present invention, the resin composition comprises an iron complex with the ligand according to formula (1 ). In one embodiment, such iron complex is formed in situ by adding, to a resin composition comprising an unsaturated polyester resin and/or a vinyl ester resin and a reactive diluent, the ligand according to formula (1 ) and an iron salt or an iron complex (with a ligand not according to formula (1 )). In another embodiment, an iron complex with the ligand according to formula (1 ) is added to a resin composition comprising an unsaturated polyester resin and/or a vinyl ester resin and a reactive diluent.

The ligands according to formula (1 ) and iron complexes thereof can be prepared according to methods known in the art, as for example described in WO02/48301.

Preferably, the ligand is present in the resin composition in an amount of at least 0.2 μιηοΙ per kilogram of unsaturated polyester resin and/or vinyl ester resin present in the resin composition, more preferably in an amount of at least 0.5 μιηοΙ, even more preferably in an amount of at least 1 μιηοΙ, even more preferably in an amount of at least 5 μιηοΙ and even more preferably in an amount of at least 10 μιηοΙ. Preferably, the ligand is present in the resin composition in an amount of at most 4000 μιηοΙ per kilogram of unsaturated polyester resin and/or vinyl ester resin present in the resin composition, more preferably in an amount of at most 3000 μιηοΙ, even more preferably in an amount of at most 2000 μιηοΙ, even more preferably in an amount of at most 1000 μιηοΙ and even more preferably in an amount of at most 500 μιηοΙ. In a preferred embodiment, the amount of ligand according to formula (1 ) in the resin composition is from 1 to 2000 μιηοΙ per kilogram of unsaturated polyester resin and/or vinyl ester resin present in the resin composition.

Preferably, the iron salt or complex is present in the resin composition in an amount of at least 0.2 μιηοΙ per kilogram of unsaturated polyester resin and/or vinyl ester resin present in the resin composition, more preferably in an amount of at least 0.5 μιηοΙ, even more preferably in an amount of at least 1 μιηοΙ, even more preferably in an amount of at least 5 μιηοΙ and even more preferably in an amount of at least 10 μιηοΙ. Preferably, the iron salt or complex is present in the resin composition in an amount of at most 4000 μιηοΙ per kilogram of unsaturated polyester resin and/or vinyl ester resin present in the resin composition, more preferably in an amount of at most 3000 μιηοΙ, even more preferably in an amount of at most 2000 μιηοΙ, even more preferably in an amount of at most 1000 μιηοΙ and even more preferably in an amount of at most 500 μιηοΙ. In a preferred embodiment, the amount of iron salt or complex according to formula (1 ) in the resin composition is from 1 to 2000 μιηοΙ per kilogram of unsaturated polyester resin and/or vinyl ester resin present in the resin composition.

Preferably, the molar ratio of iron to ligand is from 0.02 to 20, more preferably from 0.02 to 10, even more preferably from 0.2 to 5, even more preferably from 0.5 to 2 and even more preferably in an equimolar amount.

The composition according to the invention comprises from 30 to 85 wt.% of unsaturated polyester resin and/or vinyl ester resin. As used herein, all amounts in wt.% are given relative to the total weight of the unsaturated polyester resin and vinyl ester resin(s) and reactive diluent, unless otherwise specified. The unsaturated polyester resin or vinyl ester resin as is comprised in the resin composition according to the invention may suitably be selected from the unsaturated polyester resins or vinyl ester resins as are known to the skilled man. Unsaturated polyester and vinyl ester resins are characterised by having carbon-carbon unsaturations which are in conjugation with a carbonyl bond. Examples of suitable unsaturated polyester to be used in the resin composition of the present invention are, subdivided in the categories as classified by M. Malik et al. in J. M.S. - Rev. Macromol. Chem. Phys., C40(2&3), p.139-165 (2000). (1 ) Ortho-resins: these are based on phthalic anhydride, maleic anhydride, or fumaric acid and glycols, such as 1 ,2-propylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, 1 ,3-propylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol or hydrogenated bisphenol-A. Commonly the ones derived from 1 ,2-propylene glycol are used in combination with a reactive diluent such as styrene.

(2) Iso-resins: these are prepared from isophthalic acid, maleic anhydride or fumaric acid, and glycols. These resins may contain higher proportions of reactive diluent than the ortho resins.

(3) Bisphenol-A-fumarates: these are based on ethoxylated bisphenol-A and fumaric acid.

(4) Chlorendics: are resins prepared from chlorine/bromine containing anhydrides or phenols in the preparation of the UP resins.

Besides these classes of resins also so-called dicyclopentadiene (DCPD) resins can be distinguished as unsaturated polyester resins. The class of DCPD-resins is obtained either by modification of any of the above resin types by Diels-Alder reaction with cyclopentadiene, or they are obtained alternatively by first reacting a diacid for example maleic acid with dicyclopentadiene, followed by the usual steps for manufacturing a unsaturated polyester resin, further referred to as a DCPD- maleate resin. Furthermore, unsaturated polyester resins based on itaconic acid as unsaturated dicarboxylic acid can be used.

As used herein, a vinyl ester resin is a (meth)acrylate functional resin. The vinyl ester resin may suitably be selected from the vinyl ester resins as are known to the skilled man. Vinyl ester resins are mostly used because of their hydrolytic resistance and excellent mechanical properties. Vinyl ester resins having unsaturated sites only in the terminal position are for example prepared by reaction of epoxy oligomers or polymers (e.g. diglycidyl ether of bisphenol-A, epoxies of the phenol- novolac type, or epoxies based on tetrabromobisphenol-A) with for example

(meth)acrylic acid. Instead of (meth)acrylic acid also (meth)acrylamide may be used. As used herein, a vinyl ester resin is an oligomer or polymer containing at least one (meth)acrylate functional end group, also known as (meth)acrylate functional resins. This also includes the class of vinyl ester urethane resins (also referred to as urethane (meth)acrylate resins). Preferred vinyl ester resins are methacrylate functional resins including urethane methacrylate resins and resins obtained by reaction of an epoxy oligomer or polymer with methacrylic acid or methacrylamide, preferably with methacrylic acid. Most preferred vinyl ester resins are resins obtained by reaction of an epoxy oligomer or polymer with methacrylic acid.

The unsaturated polyester resin as may be comprised in the resin composition according to the invention preferably has a molecular weight in the range from 500 to 10.000 Dalton, more preferably in the range from 500 to 5000 even more preferably in the range from 750 to 4000. As used herein, the molecular weight of the resin is determined in tetrahydrofurane using gel permeation chromatography according to ISO 13885-1 employing polystyrene standards and appropriate columns designed for the determination of the molecular weights. The unsaturated polyester resin preferably has an acid value in the range from 5 to 80 mg KOH/g resin, more preferably in the range from 10 to 70 mg KOH/g resin. As used herein, the acid value of the resin is determined titrimetrically according to ISO 21 14-2000.

The vinyl ester resin as may be comprised in the resin composition according to the invention preferably has a molecular weight in the range from 500 to 3000 Dalton, more preferably in the range from 500 to 1500. The vinyl ester resin preferably has an acid value in the range from 0 to 50 mg KOH/g resin.

The amount of reactive diluent in the resin composition according to the invention is usually in the range from 15 to 70 wt.%. The diluent will be applied, for instance, for lowering of the viscosity of the resin composition in order to make handling thereof more easy. For clarity purpose, a reactive diluent is a diluent that is able to copolymerize with the unsaturated polyester resin and the vinyl ester resin. Ethylenically unsaturated compounds can be advantageously used as reactive diluent such as styrene, a-methylstyrene, 4-methylstyrene, (meth)acrylates, N-vinylpyrrolidone and/or N-vinylcaprolactam. Preferably, styrene, dimethyl itaconate and/or

methacrylates are used as reactive diluent.

The resin composition may further comprise a radical inhibitor which retards the peroxide initiated radical copolymerization of the unsaturated polyester resin and/or vinyl ester resin with the reactive diluent. These radical inhibitors are preferably chosen from the group of phenolic compounds, hydroquinones, catechols, stable radicals and/or phenothiazines. The amount of radical inhibitor that can be added may vary within rather wide ranges, and may be chosen as a first indication of the gel time as is desired to be achieved.

Suitable examples of radical inhibitors that can be used in the resin compositions according to the invention are, for instance, 2-methoxyphenol,

4-methoxyphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butylphenol, 2,4,6-trimethyl-phenol, 2,4,6-tris-dimethylaminomethyl phenol,

4,4'-thio-bis(3-methyl-6-t-butylphenol), 4,4'-isopropylidene diphenol,

2,4-di-t-butylphenol, 6,6'-di-t-butyl-2,2'-methylene di-p-cresol, hydroquinone,

2-methylhydroquinone, 2-t-butylhydroquinone, 2,5-di-t-butylhydroquinone,

2,6-di-t-butylhydroquinone, 2,6-dimethylhydroquinone , 2,3,5-trimethylhydroquinone, catechol, 4-t-butylcatechol, 4,6-di-t-butylcatechol, benzoquinone,

2,3,5,6-tetrachloro-1 ,4-benzoquinone, methylbenzoquinone,

2,6-dimethylbenzoquinone, napthoquinone, 1 -oxyl-2,2,6,6-tetramethylpiperidine, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ol (a compound also referred to as TEMPOL), 1-oxyl-2,2,6,6-tetramethylpiperidine-4-one (a compound also referred to as TEMPON), 1-oxyl-2,2,6,6-tetramethyl-4-carboxyl-piperidine (a compound also referred to as 4-carboxy-TEMPO), 1-oxyl-2,2,5,5-tetramethylpyrrolidine,

1-oxyl-2,2,5,5-tetramethyl-3-carboxylpyrrolidine (also called 3-carboxy-PROXYL), galvinoxyl, aluminium-N-nitrosophenyl hydroxylamine, diethylhydroxylamine, phenothiazine and/or derivatives or combinations of any of these compounds.

Advantageously, the amount of radical inhibitor in the resin composition according to the invention (relative to the total amount of unsaturated polyester and vinyl ester resin and reactive diluent present in the resin composition) is in the range of from 0,0001 to 10 % by weight. More preferably, the amount of inhibitor in the resin composition is in the range of from 0,001 to 1 % by weight. The skilled man quite easily can assess, in dependence of the type of inhibitor selected, which amount thereof leads to good results according to the invention.

The second component of the two-component system comprises a peroxide compound. The peroxide is preferably selected from the group of hydroperoxides, peresters, percarbonates and perketones and more preferably selected from a hydroperoxide and perketones. The peroxide being most preferred in terms of handling properties and economics is methyl ethyl ketone peroxide (MEK peroxide). The amount of peroxide can be varied within wide ranges, in general less than 20 wt.%, and preferably less than 10 wt.%.

The two-component system according to the invention is preferably essentially free of cobalt. Essentially free of cobalt means that the cobalt concentration is lower than 0,1 mmol Co per kg unsaturated polyester resin and vinyl ester resin, preferably lower than 0,01 mmol Co per kg unsaturated polyester resin and vinyl ester resin. Most preferably the two-component composition is free of cobalt. The present invention further relates to the use of a ligand complexed with a transition metal as described above, in peroxide initiated radical

copolymerization of unsaturated polyester resin or vinyl ester resin with reactive diluent as described above, in particular for accelerating the peroxide initiated radical copolymerization of a resin composition comprising an unsaturated polyester resin and/or a vinyl ester resin and reactive diluent. The present invention thus further relates to a process for accelerating the peroxide initiated radical copolymerisation of a resin composition comprising an unsaturated polyester resin and/or a vinyl ester resin and a reactive diluent by preparing a resin composition comprising an unsaturated polyester resin and/or vinyl ester resin, a reactive diluent, a ligand according to formula (1 ) and an iron salt or complex, and by mixing a peroxide to the so obtained resin composition. Furthermore, the present invention relates to a process for pre-accelerating the peroxide initiated radical copolymerisation of a resin composition comprising an unsaturated polyester resin and/or a vinyl ester resin and a reactive diluent by preparing a resin composition comprising an unsaturated polyester resin and/or a vinyl ester resin, a reactive diluent, a ligand according to formula (1 ) and an iron salt or complex.

The present invention further also relates to cured objects or structural parts prepared by mixing the first component with the second component at a temperature in the range of from -20 to +200 °C, preferably in the range of from -20 to +150 °C, and most preferably in the range of from -10 to +80 °C, thereby effecting the peroxide initiated radical copolymerisation of the resin composition.

The present invention further also relates to a process for peroxide initiated radical copolymerisation of the resin composition whereby the radical copolymerisation is performed by mixing the two component of the two-component system as described above. Preferably, the radical copolymerisation is effected essentially free of cobalt. Preferably, the radical copolymerisation is effected at a temperature in the range of from -20 to +200 °C, preferably in the range of from -20 to +150 °C, and most preferably in the range of from -10 to +80 °C.

The invention is now demonstrated by means of a series of examples and comparative examples. All examples are supportive of the scope of claims. The invention, however, is not restricted to the specific embodiments as shown in the examples. Experimental part Dimethyl 2,4-di-(2-pyridyl)-3-methyl-7-(pyridine-2-ylmethyl)-3,7-diaza- bicyclo[3.3.1]nonan-9-one-1 ,5-dicarboxylate (N2Py3o) and the iron (II) complex thereof [Fe(N2Py3o)CI]CI was prepared as followed (following the procedure described in WO0248301 , page 28-34).

Preparation of dimethyl 2,6-di-(2-pyridyl)-1-methyl-piperid-4-one-3,5- dicarboxylate (NPy2)

2-Pyridinecarboxaldehyde (166.3 mmol; 17.81 g) was added drop wise to an ice-bath cooled solution of dimethyl-1 ,3-acetonedicarboxylate (83.1 mmol; 14.48 g) in methanol (60 ml). Next an aqueous solution (40%) of methylamine (83.1 mmol; 6.5 g) was added. The solution was stirred for 15 minutes at 0°C and then left at 19 °C for seven days. At this time crystals were formed that were removed by filtration and washed with cold ethanol. The yield of the title compound was 23.90 g, and it was used for further synthesis without further purification.

Preparation of dimethyl 2,4-di-(2-pyridyl)-3-methyl-7-(pyridine-4-ylmethyl) 3,7- diaza-bicvclor3.3.1lnonan-9-one-1 ,5-dicarboxylate (N2Pv2Py'o) (Ra=methylene-4- pyridyl)

To a suspension of NPy2 (32.3 mmol; 12.38 g) in 175 ml of ethanol was added an aqueous (37%) formaldehyde solution (81 mmol; 6.63 g) followed by 4- picolylamine (37.2 mmol; 4.02 g). The yellow suspension was stirred under reflux for 30 minutes, after which the suspension was turned in a clear brown solution. The solvent was removed under reduced pressure and the remaining solid was crystallized from methanol to yield 4 g (25%) of the title compound as a white solid

Preparation of dimethyl 2,4-di-(2-pyridyl)-3-methyl-7-(pyridine-2-ylmethyl) 3,7- diaza-bicvclor3.3.1lnonan-9-one-1 ,5-dicarboxylate (N2Py3o) (Ra=methylene-2- pyridyl)

To a suspension of NPy2 (32.3 mmol; 12.38 g) in 175 ml of ethanol was added an aqueous (37%) formaldehyde solution (81 mmol; 6.63 g) followed by 2- picolylamine (37.2 mmol; 4.02 g). The yellow suspension was stirred under reflux for 30 minutes, after which the suspension was turned in a clear brown solution. The solvent was removed under reduced pressure and the remaining solid was crystallized from ethanol to yield 3.9 g (23%) of the title compound as a white solid.

Preparation of chloro(dimethyl-2,4-di-(2-pyridyl)-3-methyl- 7(pyridine-2-ylmethyl)-3,7-diaza-bicvclor3.3.1lnonan-9-one-1 ,5- dicarboxylatelironnn-chloride hydrate (rFe(N2Pv3o)CHCn

Solution of 0.254 g (2.0 mmol) of FeCI2 in 1.0 ml of methanol was added to a solution of 1.030 g (2.0 mmol) of N2Py3o in 2 ml of methanol. After one day orange-yellow crystals precipitated from the dark brown solution.

The crystals were filtered and after drying dissolved in 1 ,2-propylene glycol to obtain a 1 % solution.

The resins used for curing are commercially available products from DSM Composite Resins B.V., Schaffhausen, Switzerland. The peroxides used for curing are commercially available products from Akzo Nobel Inc. Monitoring of curing

In the Examples presented hereinafter it is mentioned, that curing was monitored by means of standard gel time equipment. This is intended to mean that both the gel time (T_gei or T₂₅->35°c) and peak time (Tp_eak or T₂5- _Peak) were determined by exotherm measurements according to the method of DIN 16945 when curing the resin with the peroxides as indicated in the Examples and Comparative Examples. The equipment used therefore was a Soform gel timer, with a Peakpro software package and National Instruments hardware; the waterbath and thermostat used were respectively Haake W26, and Haake DL30.

Examples 1-3 and comparative experiments A-R

Formulations were prepared based on 50g of Palatal P 5, to which 0.002865 mmol of various ligands as 1 % solution were added and 0.002865 mmol of various transition metals salts/solutions as 1 % solutions (in Comp Ex P-R no transition metal salt or solution was added). After storing the formulations for 3 weeks (allowing for in situ complex formation), the curing of the resins using 2% butanox M50 was monitored with the gel time equipment and the results are shown in table 1. Table 1

As further comparisons, 1 % tetrahydrofuran THF, 1 % dimethylformamide DMF or 1 % ethylacetate was added to formulations containing 0.002865 mmol of either Iron III ethylhexanoate or Iron II naphtenate. In none of these comparative experiments any curing was observed These examples combined with the comparative experiments clearly demonstrate that only with iron salts or complexes in combination with ligands as defined in the claims, a good curing can be obtained. Furthermore the examples clearly show that the complexes can be formed in situ in the resin composition, i.e. by adding the individual components to the resin composition.

Example 4

Example 1 was repeated except that 0.002865 mol preformed

[Fe(N2Py3o)CI]CI as a 1 % solution in propylene glycol was used resulting in a gel time of 4.1 min, a peak time of 12.4 min and a peak temperature of 164 °C

Example 5-12

Formulations were prepared based on 50g of Palatal P 69-02, and different quantities (in gram) of a 1 % solution of [FeCI(N2Py3o]CI in 1 ,2-propylene glycol (1 %) as listed in Table 1. Curing was performed employing 2% Butanox M-50. The cure was monitored using the gel time equipment described above and the results are shown in table 2.

Table 2

From the examples 4-12 it is clear that preformed [Fe(N2Py3o)CI]CI can be used as an accelerator for curing unsaturated polyester resins. Examples 13-14

Formulations were prepared based on 50g of Atlac 430 and different amounts (in gram) of [Fe(N2Py3o)CI]CI in 1 ,2-propylene glycol (1 %) as listed in Table 3. Curing was performed employing 2% Butanox M50. The cure was monitored using the gel time equipment described above and the results are shown in table 3.

Table 3

From the examples in Table 3 it is clear that [Fe(N2Py3o)CI]CI can be used as an accelerator for curing vinyl ester resins. After the methyl ethyl ketone peroxide was added no foaming was observed. Usually when vinyl ester resins are cured with cobalt and methyl ethyl ketone peroxide, foaming does occur.

Claims

Two-component system comprising a first component and a second component, wherein the first component being a resin composition comprising an unsaturated polyester resin and/or vinyl ester resin, reactive diluent and a ligand according to the following formula (1 )

wherein each R-i , R₂, R3 and R₄ are independently selected from hydrogen, C1-C12 alkyl, C3-C8 cycloalkyl, C6-C12 aryl and C5-C12 heteroaryl;

X is selected from C=0 and -[CR₂]_Z- wherein z is from 1 to 3 and each R is independently selected from hydrogen, hydroxyl, C1-C4 alkoxy and C1-C4 alkyl;

each Rx and Ry are independently selected from hydrogen, C1-C8 alkyl, C1- C8-alkyl-0- C1-C8-alkyl, C1-C8-alkyl-O-C6-C10-aryl, C6-C10-aryl, C1-C8- hydroxyalkyl, and (CH₂)nC(0)OR₅ wherein n is from 0 to 4 and R₅ is hydrogen, C1-C4 alkyl or an amide;

Ra is a 2-pyridyl group or an alkylidene-2-pyridyl group;

Rb is selected from C1-C24 alkyl, C6-C10 aryl and a group containing a heteroatom;

and wherein the resin composition comprises an iron salt or complex;

and the second component comprises a peroxide compound.

Two-component system according to claim 1 , wherein Ra is an alkylidene-2- pyridyl group.

Two-component system according to claim 1 , wherein Ra is methylene-2- pyridyl.

Two-component system according to anyone of the above claims, wherein R₃ and R₄ is a 2-pyridyl group. Two-component system according to anyone of the above claims, wherein R₁ and R₂ is hydrogen.

Two-component system according to anyone of the above claims, wherein X is C=0.

Two-component system according to anyone of the above claims, wherein Rx and Ry are C(0)OCH₃.

Two-component system according to anyone of the above claims, wherein Rb is methyl.

Two-component system according to anyone of the above claims, wherein the resin composition comprises an iron complex with the ligand according to formula (1 ).

Two-component system according to anyone of the above claims, wherein the ligand is present in an amount of from 1 to 2000 μιηοΙ per kilogram of unsaturated polyester resin and/or vinyl ester resin present in the resin composition.

Two-component system according to anyone of the above claims, wherein the molar ratio of iron to ligand is from 0.02 to 20.

Two-component system according to anyone of the above claims, wherein the resin composition comprises styrene, dimethyl itaconate and/or a methacrylate as reactive diluent.

Two-component system according to any of the above claims, wherein that the peroxide is selected from the group of hydroperoxides, peresters, percarbonates and perketones.

Cured objects or structural parts obtained from a two-component system according to any of claims 1-13.

Process for peroxide initiated radical copolymerisation of a resin composition comprising an unsaturated polyester resin and/or vinyl ester resin and a reactive diluent, wherein the radical copolymerisation is performed by mixing the two components from the two-component system according to any one of claims 1-13.

Process for accelerating the peroxide initiated radical copolymerisation of a resin composition comprising an unsaturated polyester resin and/or vinyl ester resin and a reactive diluent by preparing a resin composition comprising an unsaturated polyester resin and/or a vinyl ester resin, a reactive diluent, a ligand according to formula (1 ) and an iron salt or complex, and by mixing a peroxide to the so obtained resin composition.