WO2008003501A1

WO2008003501A1 - Unsaturated polyester resin compositions

Info

Publication number: WO2008003501A1
Application number: PCT/EP2007/005966
Authority: WO
Inventors: Johan Franz Gradus Antonius Jansen; Ronald Ivo Kraeger
Original assignee: Dsm Ip Assets B.V.
Priority date: 2006-07-06
Filing date: 2007-07-05
Publication date: 2008-01-10

Abstract

The present invention relates to a two-component composition comprising a first component and a second component, wherein the first component being a resin composition comprising an unsaturated polyester resin or vinyl ester resin and a copper compound and a potassium compound; the resin composition being essentially free of cobalt; and the second component comprises a peroxide compound.

Description

UNSATURATED POLYESTER RESIN COMPOSITIONS

The present invention relates to a two-component composition comprising a first component and a second component, wherein the first component being a pre-accelerated resin composition comprising an unsaturated polyester resin or vinyl ester resin composition and the second component comprises a peroxide. The resin compositions show good curing properties in the absence of cobalt. The resin compositions also show slight gel-time drift tendency. The present invention further also relates to objects and structural parts prepared from such two-component compositions. The present invention finally also relates to methods of peroxide curing of unsaturated polyester resin compositions.

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 components. The components are combined at the time the system is used. As meant herein, objects and structural parts are considered to have a thickness of at least 0,5 mm and appropriate mechanical properties. The term "objects and structural parts" as meant herein also includes cured resin compositions as are used in the field of chemical anchoring, construction, roofing, flooring, windmill blades, containers, tanks, pipes, automotive parts, boats, etc.

As meant herein the term gel-time drift (for a specifically selected period of time, for instance 30 or 60 days) reflects the phenomenon, that - when curing is performed at another point of time than at the reference standard moment for curing, for instance 24 hours after preparation of the resin - the gel time observed is different from that at the point of reference. For unsaturated polyester resins, as can generally be cured under the influence of peroxides, gel time represents the time lapsed in the curing phase of the resin to increase in temperature from 25 ⁰C to 35 ⁰C. Normally this corresponds to the time the fluidity (or viscosity) of the resin is still in a range where the resin can be handled easily. In closed mould operations, for instance, this time period is very important to be known. The lower the gel-time drift is, the better predictable the behavior of the resin (and the resulting properties of the cured material) will be.

W. D. Cook et al. in Polym. Int. Vol.50, 2001 , at pages 129-134 describe in an interesting article various aspects of control of gel time and exotherm behavior during cure of unsaturated polyester resins. They also demonstrate how the exotherm behavior during cure of such resins can be followed. Figures 2 and 3 of this article show the gel times in the bottom parts of the exotherms measured. Because these authors focus on the exotherms as a whole, they also introduced some correction of the exotherms for heat loss. As can be seen from the figures, however, such correction for heat loss is not relevant for gel times below 100 minutes.

Gel time drift (hereinafter: "Gtd") can be expressed in a formula as follows:

Gtd = (T25->35°C at y-days " T₂5-35°c after mixing) / T25->35°C after mixing X100%

(formula 1)

In this formula T₂₅^₃₅-C (which also might be represented by T_geι) represents, as mentioned above, the time lapsed in the curing phase of the resin to increase in temperature from 25 °C to 35 °C. The additional reference to "at y days" shows after how many days of preparing the resin the curing is effected. All polyester resins, by their nature, undergo some changes over time from their production till their actual curing. One of the characteristics where such changes become visible is the gel-time drift. The state of the art unsaturated polyester resin systems generally are being cured by means of initiation systems. In general, such unsaturated polyester resin systems are cured under the influence of peroxides and are accelerated (often even pre-accelerated) by the presence of metal compounds, especially cobalt salts, as accelerators. Cobalt naphthenate and cobalt octanoate are the most widely used accelerators. In addition to accelerators, the polyester resins usually also contain inhibitors for ensuring that the resin systems do not gellify prematurely (i.e. that they have a good storage stability). Furthermore, inhibitors are being used to ensure that the resin systems have an appropriate gel time and/or for adjusting the gel-time value of the resin system to an even more suitable value.

Most commonly, in the state of the art, polymerization initiation of unsaturated polyester resins, etc. by redox reactions involving peroxides, is accelerated or pre-accelerated by a cobalt compound in combination with another accelerator.

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 resin systems. Curing is addressed in chapter 9. For discussion of control of gel time reference can be made to the article of Cook et al. as has been mentioned above. Said article, however, does not present any hint as to the problems of gel-time drift as are being solved according to the present invention.

The phenomenon of gel-time drift, indeed, so far got quite little attention in the literature. Most attention so far has been given in literature to aspects of acceleration of gel time in general, and to improving of pot-life or shelf life of resins. The latter aspects, however, are not necessarily correlated to aspects of gel-time drift, and so, the literature until now gives very little suggestions as to possible solutions for improvement of (i.e. lowering of) gel-time drift. For instance, reference can be made to a paper presented by M. Belford et al., at the Fire Retardant Chemicals Association Spring Conference, March 10-13, 2002 where the gel-time reducing effect of a new antimony pentoxide dispersion (NYACOL APE 3040) has been addressed in fire retardant polyester resins promoted with cobalt.

Accordingly, for the unsaturated polyester resins and vinyl ester resins as are part of the current state of the art there is still need for finding resin systems showing reduced gel-time drift, or in other words, resin systems having only slight gel-time drift when cured with a peroxide. Preferably the mechanical properties of the resin composition after curing with a peroxide are unaffected (or improved) as a result of the changes in the resin composition for achieving the reduced gel-time drift. Moreover, for environmental reasons, the presence of cobalt in the resins is less preferred. The present inventors now, surprisingly, found that two-component compositions with good curing properties could be obtained by providing two- component compositions comprising a first component and a second component, wherein the first component being a resin composition comprising an unsaturated polyester resin or vinyl ester resin and an accelerator comprising a copper compound and a potassium compound, the resin composition being essentially free of cobalt; and wherein the second component comprises a peroxide compound.

Essentially free of cobalt means that the cobalt concentration is lower than 0,01 mmol Co per kg primary resin system, preferably lower than 0,001 mmol Co per kg primary resin system. Most preferably the resin composition is free of cobalt. Preferably, the resin composition is essentially free of vanadium.

Essentially free of vanadium means that the vanadium concentration is lower than 0,001 mmol V per kg primary resin system. Most preferably the resin composition is free of vanadium.

According to the present invention, compositions having good curing properties can be obtained, i.e. the compositions 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 esters, 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. In addition, the compositions according to the present invention can be obtained with reduced gel-time drift tendency

It is known in the prior art that copper can be used as inhibitor for unsaturated polyester resin and vinyl ester resin compositions. US-A-5861466 teaches that a copper salt acts as shelf life stability inhibitor for a vinyl ester resin esterified to a very low epoxy value. Also US2004/0010061 , example 2 teaches that copper naphtenate acts as an inhibitor in styrene-free unsaturated resin compositions formulated with a cobalt carboxylate, vanadium, potassium, zinc or iron compound. US-A-4829106 also teaches that copper salts and potassium salts act as inhibitors for unsaturated polyester resins. US-A-4175064 discloses an accelerator composition for the curing of unsaturated polyester resin composition comprising a cobalt salt and a potassium salt of monocarboxylic acids. This document also teaches that the use of only potassium salt does not result in efficient curing. US-A-5310826 teaches that K-ethylhexanoate acts as an inhibitor for thiol containing unsaturated polyester resin compositions. US-A-4009150 discloses that potassium persulfate can be used as initiator in the polymerization of an ethylenically unsaturated monomer in the presence of an iron or copper chelate. US-A-6329475 discloses that potassium persulfate can be used as initiator in the polymerization of an epoxy vinylester resin in the presence of a copper salt or copper complex and a cobalt or vanadium compound as accelerator. There is, however, no indication at all that a copper compound in combination with a potassium compound can act as accelerator for the peroxide decomposition which is generally used for curing of unsaturated polyester or vinyl ester resin.

The unsaturated polyester resin or vinyl ester resin as is comprised in the resin compositions according to the present invention, may suitably be selected from the unsaturated polyester resins or vinyl ester resin as are known to the skilled man. Examples of suitable unsaturated polyester or vinyl ester resins to be used as basic resin systems in the resins of the present invention are, subdivided in the categories as classified by Malik et al., cited above.

(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.

(5) Vinyl ester resins: these are resins, which are mostly used because of their because of their hydrolytic resistance and excellent mechanical properties, as well as for their low styrene emission, are having unsaturated sites only in the terminal position, introduced by reaction of epoxy resins (e.g. diglycidyl ether of bisphenol-A, epoxies of the phenol-novolac type, or epoxies based on tetrabromobisphenol-A) with (meth)acrylic acid. Instead of (meth)acrylic acid also (meth)acrylamide may be used.

Besides these classes of resins also so-called dicyclopentadiene (DCPD) resins can be distinguished as unsaturated polyester resins.

As used herein, a vinyl ester resin is a (meth)acrylate functional resin. Besides the vinyl ester resins as described in Malik et al., also the class of vinyl ester urethane resins (also referred to urethane methacylate resins) can be distinguished as vinyl ester resins. Preferably, the vinyl ester used in the present invention is a resin obtained by the esterification of an epoxy resin with (meth)acrylic acid or (meth)acrylamide.

All of these resins, as can suitably used in the context of the present invention, may be modified according to methods known to the skilled man, e.g. for achieving lower acid number, hydroxyl number or anhydride number, or for becoming more flexible due to insertion of flexible units in the backbone, etc. 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 maleic acid with dicyclopentadiene, followed by the resin manufacture as shown above. Of course, also other reactive groups curable by reaction with peroxides may be present in the resins, for instance reactive groups derived from itaconic acid, citraconic acid and allylic groups, etc. Accordingly, the unsaturated polyester resins or vinyl ester resins used in the present invention may contain solvents. The solvents may be inert to the resin system or may be reactive therewith during the curing step. Reactive solvents are particularly preferred. Examples of suitable reactive solvents are styrene, α-methylstyrene, (meth)acrylates, N-vinylpyrrolidone and N-vinylcaprolactam.

The unsaturated polyester resins and vinyl ester resins as are being used in the context of the present invention may be any type of such resins, but preferably are chosen from the group of DCPD-resins, iso-phthalic resins and ortho- phthalic resins and vinyl ester resins. More detailed examples of resins belonging to such groups of resins have been shown in the foregoing part of the specification. More preferably, the resin is an unsaturated polyester resin preferably chosen from the group of DCPD-resins, iso-phthalic resins and ortho-phthalic resins.

The resin composition according to the invention preferably has an acid value in the range of from 0,001 - 300 mg KOH/g of resin composition. As used herein, the acid value of the resin composition is determined titrimetrically according to ISO 2114-2000. Preferably, the molecular weight of the unsaturated polyester resin or vinyl ester resin is in the range of from 500 to 200.000 g/mole. In a preferred embodiment, the resin is an unsaturated polyester resin. As used herein, the molecular weight of the resin is determined using gel permeation chromatography according to ISO 13885-1.

The resin composition according to the present invention generally being free of blowing agents.

The resin composition according to the present invention generally contains less than 5 wt.% water.

In the context of the invention all kinds of copper compounds can be used as copper accelerator compound. According to the invention, the copper accelerator compound present in the resin composition is preferably a copper salt or complex. More preferably, the copper compound is a copper^* compound or a copper^2* compound, more preferably a copper^2* compound. The compound is preferably a copper^* salt or complex or a copper^salt or complex. Even more preferably, the copper compound is a copper^* salt or copper^2* salt, more preferably a copper^2* salt. In view of the solubility of the copper compound in the resin composition, the copper compound is preferably an organo soluble copper compound like for instance copper carboxylates, copper acetoacetates and copper chlorides.. It will be clear that, instead of a single copper compound also a mixture of copper compounds can be used.

The copper of the copper accelerator compound is preferably present in the resin composition in an amount of at least 0,05 mmol per kg of primary resin system, preferably in an amount of at least 1 mmol per kg of primary resin system. The upper limit of the copper content is not very critical, although for reasons of cost efficiency of course no extremely high concentrations will be applied. Generally the concentration of the copper of the copper containing compound in the primary resin system will be lower than 20 mmol per kg of primary resin system, preferably lower than 5 mmol per kg of primary resin system.

For understanding of the invention, and for proper assessment of the amounts of copper compound to be present in the resin composition, the term "primary resin system" as used herein is understood to mean the total weight of the resin, but excluding any fillers as may be used when applying the resin system for its intended uses. The primary resin system therefore consists of the unsaturated polyester resin or vinyl ester resin, any additives present therein (except for the peroxide component that is to be added shortly before the curing) soluble in the resin, such as accelerators, promoters, inhibitors, low-profile agents, colorants (dyes), thixotropic agents, release agents etc., as well as styrene and/or other solvents as may usually be present therein. The amount of additives soluble in the resin usually may be as from 1 to 25 wt.% of the primary resin system; the amount of styrene and/or other solvent may be as large as up to 50 wt.% of the primary resin system. The primary resin system, however, explicitly does not include compounds not being soluble therein, such as fillers (e.g. glass or carbon fibers), talc, clay, solid pigments (such as, for instance, titanium dioxide (titanium white)), flame retardants, e.g. aluminium oxide hydrates, etc.

The potassium co-accelerator compound is preferably a potassium oxide, hydroxide, carboxylate, carbonate or hydrocarbonate. More preferably, the potassium compound is potassium carboxylate, preferably a potassium C₆-C₂o carboxylate. In another preferred embodiment of the present invention, the potassium carboxylate is in-situ formed by adding potassium hydroxide to the resin composition.

Preferably, the amount of potassium of the potassium co-accelerator compound is from 1 to 150 mmol potassium /kg of primary resin system. More preferably, the amount of potassium of the potassium compound is from 2 to 40 mmol potassium /kg of primary resin system. Preferably, the molar ratio between the copper and the potassium is from 20:1 to 1 :3000, more preferably from 2,5 : 1 to 1 : 40.

In a preferred embodiment, the resin composition further comprises a base. Preferably, the base is an organic base with pK_a > 10. The organic base with pK_a ≥ 10 is preferably a nitrogen containing compound. The nitrogen containing compound is preferably an amine.

The amine preferably has the following formula:

,R₂

R₃ whereby R¹, R² and R³ each individually may represent hydrogen (H), C₁-C₂₀ alkyl, C₆-C₂₀ aryl, C₅-C₂₀ cycloalkyl, C₇-C₂₀ alkylaryl or arylalkyl group that each optionally may contain one or more hetero-atoms (e.g. oxygen, phosphor or sulphur atoms) and/or substituents and a ring may be present between Ri and R₂, R₂ and R₃ and/or R₁ and R₃, which may contain heteroatoms. In a preferred embodiment, R¹, R² and R³ each individually may represent hydrogen (H), C₁-C₂₀ alkyl, C₆-C₂₀ aryl, alkylaryl or arylalkyl group that each optionally may contain one or more hetero-atoms (e.g. oxygen, phosphor or sulphur atoms) and/or substituents. In a more preferred embodiment, R¹, R² and R³ are hydrogen. In another preferred embodiment, R¹, R² and R³ each individually may represent a C₁-C₂₀ alkyl or a C₆-C₂₀ aryl group. In yet another preferred embodiment, at least one of R¹, R² and R³ is an alkyl-O- R⁴ group, whereby R⁴ is hydrogen, a C₁-C₂₀ alkyl group or a ring is present between R⁴ and at least one of the other R groups. In this preferred embodiment, the -O- R⁴ group is preferably in the β-position with respect to the nitrogen atom.

Preferably, the amount of the base is from 0,05 to 5 % by weight, calculated on the total weight of the primary resin system of the resin composition. More preferably, the amount of the base is from 0,1 to 2 % by weight; even more preferably between 0,25 and 1 % by weight.

These resins all can be cured by means of peroxide curing. The peroxides used for the initiation can be any peroxide known to the skilled man for being used in curing of unsaturated polyester resins. Such peroxides include organic and inorganic peroxides, whether solid or liquid; also hydrogen peroxide may be applied. Examples of suitable peroxides are, for instance, peroxy carbonates (of the formula -OC(O)O-), peroxyesters (of the formula -C(O)OO-), diacylperoxides (of the formula -C(O)OOC(O)-), dialkylperoxides (of the formula -00-), et&- The peroxides can also be oligomeric or polymeric in nature. An extensive series of examples of suitable peroxides can be found, for instance, in US 2002/0091214-A1 , paragraph [0018]. The skilled man can easily obtain information about the peroxides and the precautions to be taken in handling the peroxides in the instructions as given by the peroxide producers.

Preferably, the peroxide is chosen from the group of organic peroxides. Examples of suitable organic peroxides are: tertiary alkyl hydroperoxides (such as, for instance, t-butyl hydroperoxide), other hydroperoxides (such as, for instance, cumene hydroperoxide), the special class of hydroperoxides formed by the group of ketone peroxides (perketones, being an addition product of hydrogen peroxide and a ketone, such as, for instance, methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide and acetylacetone peroxide), peroxyesters or peracids (such as, for instance, t-butyl peresters, benzoyl peroxide, peracetates and perbenzoates, lauryl peroxide, including (di)peroxyesters),-perethers (such as, for instance, peroxy diethyl ether). Often the organic peroxides used as curing agent are tertiary peresters-or tertiary hydroperoxides, i.e. peroxy compounds having tertiary carbon atoms directly united to an -OO-acyl or -OOH group. Clearly also mixtures of these peroxides with other peroxides may be used in the context of the present invention. The peroxides may also be mixed peroxides, i.e. peroxides containing any two of different peroxygen- bearing moieties in one molecule). In case a solid peroxide is being used for the curing, the peroxide is preferably benzoyl peroxide (BPO).

Most preferably, however, the peroxide is a liquid hydroperoxide. The liquid hydroperoxide, of course, also may be a mixture of hydroperoxides. Handling of liquid hydroperoxides when curing the resins for their final use is generally easier: they have better mixing properties and dissolve more quickly in the resin to be cured.

In particular it is preferred that the peroxide is selected from the group of ketone peroxides, a special class of hydroperoxides. The peroxide being most preferred in terms of handling properties and economics is methyl ethyl ketone peroxide (MEK peroxide). In a preferred embodiment of the invention, the resin composition also contains one or more reactive diluents.

Such reactive diluents are especially relevant for reducing the viscosity of the resin in order to improve the resin handling properties, particularly for being used in techniques like vacuum injection, etc. However, the amount of such reactive diluent in the resin composition according to the invention is not critical. Preferably, the reactive diluent is a methacrylate and/or styrene in an amount of at least 5 weight %.

In a further preferred embodiment of the present invention, the resin composition also contains one or more radical inhibitors. More preferably, the resin compositions according to the invention contain one or more radical inhibitors, preferably chosen from the group of phenolic compounds, stable radicals like galvinoxyl and N-oxyl based compounds, catechols and/or phenothiazines.

The amount of radical inhibitor as used in the context of the present invention, may, however, vary within rather wide ranges, and may be chosen as a first indication of the gel time as is desired to be achieved. Preferably, the amount of phenolic inhibitor is from about 0,001 to 35 mmol per kg of primary resin system, and more preferably it amounts to more than 0,01 , most preferably more than 0,1 mmol per kg of primary resin system. 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.

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), 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 is in the range of from 0,0001 to 10 % by weight, calculated on the total weight of the primary resin system of the resin composition. More preferably, the amount of radical inhibitor in the resin composition is in the range of from 0,001 to 1 % by weight.

The two-component composition according to the present invention can be applied in all applications as are usual for such types of resins. In particular they can suitably used in closed mould applications, but they also can be applied in open mould applications. For closed mould applications it is especially important that the manufacturer of the closed mould products reliably can use the favorable (i.e. reduced) gel-time drift tendency of the resin compositions according to the invention. End segments where the unsaturated polyester resin or vinyl ester resin compositions according to the present invention can be applied are also marine applications, chemical anchoring, roofing, construction, relining, pipes & tanks, flooring, windmill blades, etc. That is to say, the resin compositions according to the invention can be used in all known uses of unsaturated polyester resins and vinyl ester resins. The present invention further also relates to a process for radically curing a two-component composition according to the invention by effecting the curing essentially free of cobalt, preferably in the absence of cobalt. It has surprisingly been found that the combination of a copper compound and a potassium compound accelerates the radically curing of the unsaturated polyester or vinyl ester with the peroxide. Preferably, the curing is effected at a temperature in the range of from -20 to +200 ⁰C, preferably in the range of from -20 to +100 ⁰C, and most preferably in the range of from -10 to +60 ⁰C (so-called cold curing).

The present invention further also relates to all such objects or structural parts as are being obtained when curing the unsaturated polyester resin or vinyl ester resin compositions according to the invention with a peroxide. These objects and structural parts have excellent mechanical properties. The present invention further also relates to a pre-accelerated resin composition being curable with a peroxide compound as described above.

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 The resins used for curing are commercially available products from DSM Composite Resins B. V., Schaffhausen, Switzerland, and in addition thereto also a resin -hereinafter referred to as Resin A- was specifically prepared on behalf of the inventors for being used in the tests. The peroxides used for curing are commercially available products from Akzo Nobel Inc.

Preparation of Resin A

184,8 g of propylene glycol (PG), 135,8 g of diethylene glycol (DEG), 216,1 g of phthalic anhydride (PAN), 172,8 g of maleic anhydride (MAN), and 0.075 g 2-t-butylhydroquinone were charged in a vessel equipped with a reflux condenser, a temperature measurement device and inert gas inlet. The mixture was heated slowly by usual methods to 205 ⁰C. At 205 ⁰C the mixture was kept under reduced pressure until the acid value reached a value below 16 mg KOH/g resin and the falling ball viscosity at 100 ⁰C was below 50 dPa.s. Then the vacuum was relieved with inert gas, and the mixture was cooled down to 130 ⁰C, and thereafter the solid UP resin so obtained was transferred to a mixture of 355 g of styrene and 0,07 g of mono-t-butyl- hydroquinone and was dissolved at a temperature below 80 ⁰C. The final resin viscosity reached at 23 ^CC was 640 mPa.s, and the Non Volatile Matter content was 64,5 wt.%.

Monitoring of curing

In most of the Examples and Comparative 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_geι or T_25^35X) and peak time (Tpea_k or T_25->pea_k) 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.

For some of the Examples and Comparative Examples also the gel- time drift (Gtd) was calculated. This was done on the basis of the gel times determined at different dates of curing according to formula 1 :

Gtd = (T25->35°C at y-days " T25->35° after mixing) / T25->35°C after mixing X1 OO%

(formula 1) with "y" indicating the number of days after mixing. Examples 1a-b and comparative experiments A-D

Formulations were prepared based on 90 resin, 10 g styrene, 0.24g Cu naphtenate solution (8% Cu) and 1 g K octanoate solution (15% in PEG). Curing was performed at 25 ⁰C using 3 % (relative to the primary resin system) Butanox M-50 and the cure was monitored in the geltimer.

For the comparative experiments formulations were prepared in which the copper resp. the potassium were omitted. The results are shown in table 1.

Table 1

These experiments clearly demonstrate that curing can be obtained by using the combination according to the invention whereas employing only Cu or K no curing was observed within 1200 minutes.

Examples 2a-b

Formulations were prepared based on 100g Palatal P6-01 to which x g Cu napthenate solution (8% Cu) and y g K ethylhexanoate solution in spirits (10% K; commercially available from Heybroek B. V., the Netherlands) were added. Curing was performed with 2 % (relative to the primary resin system) Butanox M50 and the results are shown in the next table 2.

Table 2

These results indicate that various amounts of potassium together with various amounts of copper can be used for curing according to the invention.

Examples 3a-f and comparative experiments E-J

To a mixture of 90 g resin A₁ 10 g styrene and 1 g isophorone diamine was added a copper salt in various amounts and 1g K octanoate in PEG (15%). After stirring for 5 min the formulations were cured with peroxide. The cure was monitored with the gel time equipment and the results are shown in table 3.

Table 3

These examples demonstrate that employing potassium in combination with a copper an efficient curing can take place even at very low copper concentration.

Example 4a-b 4a) To a mixture of 90 g resin A, 10 g styrene, 0,25g copper naphtenate (8%Cu) and 0,5g K octanoate in PEG (15%) was added after stirring for 5 min 3g Butanox M-50. The cure was monitored with the gel time equipment resulting in a gel time of 9.5 min, peak time of 17.8 min and a peak temperature of 179⁰C.

4b) Example 4a was repeated with 0.2 g K octanonate resulting in a gel time of 38.9 min, peak time of 67 min and a peak temperature of 130⁰C. These results indicate that also a low amount of potassium can be used.

Example 5

Formulations were prepared using 9Og resin A, 10 g styrene, 0,25 g Cu naphtenate solution and 1 g K octanoate in PEG. Curing was performed using 3% (relative to the primary resin system) of various peroxides and monitored using the gel timer. The results are shown in table 4.

Table 4

These results indicate that various peroxides can be used. Moreover they indicate that the type of peroxide can be used to tune the curing.

Examples 6a-5k

Formulations were prepared using 100g of various resin systems with 0,008 t-butyl cathechol, 0,24 g Cu naphtenate and 0,17g KOH (50% in water) or 1 g K octanoate (15% in PEG) Curing was performed with 3 % (relative to the primary resin system) Butanox M-50 and the results are shown in table 5. Table 5

These results indicate that various resins can be cured according to the invention. Furthermore these examples illustrate that various K salts can be used as well as that inhibitors can be used to tune the gel time exp 6a vs 1a.

Example 7

4 mm castings were prepared based on 50Og resin A according to the formulations described below (all amounts are in grams) and cured with Butanox M-50. The 4 mm castings were made between hardened borosilicate glass that was separated with a 4mm EPDM U-shaped rim The casting were released and post cured during 24hrs at 60°C and 24hrs at 80⁰C. Mechanical properties of the cured objects were determined according to ISO 527-2. The Heat Distortion Temperature (HDT) was measured according to ISO 75-Ae. Residual styrene contents were measured by gaschromatography using GC-FID (Gas Chromatography with a Flame Ionization Detector), using butylbenzene as an internal. Table 6

These castings results further indicate that the cure system according to the invention can be used for construction purposes.

Example 8

Formulations were prepared based on 18Og resin, 2Og styrene, 0,02g t-butylcatechol, 0.36g KOH solution (50% in water) and 0.48 g Cu naphtenate (8% Cu, in spirits). After stirring for 5 min the formulations were divided in 2 parts of 100g each. The first part was immediately cured 3 g Butanox M-50 whereas the second part was cured after 85 days. The results are shown in table 7.

Table 7

For comparison the gel time drift after 106 days of cobalt based systems, for the Palatal P 69-02 and for the Palatal P 6-01 resins having the same molar amount of transition metal but no potassium, is 94 and 335% respectively.

These results indicate that low drifting systems can be obtained using formulations according to the invention.

Example 9

To 100 grams of Palatal P 4-01 amounts of different bases have been added as listed in Table below (all amounts are in grams). Reactivity was measured and 2- and 4mm castings were made. The 2mm castings were cured in an open mould with the top side in contact with air. The 4 mm castings were made between hardened borosilicate glass that was separated with a 4mm EPDM U-shaped rim. After 24 hrs at 2O⁰C part of the material was post-cured as indicated in the table.

Mechanical properties of the cured objects were determined according to ISO 527-2. The Heat Distortion Temperature (HDT) was measured according to ISO 75-Ae. Residual styrene and benzaldehyde contents were measured by gaschromatography using GC-FID (Gas Chromatography with a Flame Ionization Detector), using butylbenzene as an internal standard, after extraction of the cured objects in dichloromethane for 48 hrs.

Table 8

These results indicate that good curing characteristics combined with low amounts of residuals can only be obtained when both copper and potassium are present.

Claims

1. Two-component composition comprising a first component and a second component, wherein the first component being a resin composition comprising an unsaturated polyester resin or vinyl ester resin and an accelerator comprising a copper compound and a potassium compound, the resin composition being essentially free of cobalt; and wherein the second component comprises a peroxide compound.

2. Two-component composition according to claim 1 , characterized in that the resin is an unsaturated polyester resin.

3. Two-component composition according to anyone of claims 1-2, characterized in that the copper compound is a copper carboxylate or a copper acetoacetate.

4. Two-component composition according to anyone of claims 1-3, characterized in that the copper is present in an amount of at least 0,05 mmol per kg of primary resin system.

5. Two-component composition according to anyone of claims 1-4, characterized in that the potassium compound is a potassium carboxylate.

6. Two-component composition according to anyone of claims 1-5, characterized in that the potassium is present in an amount of from 1 to 150 mmol/kg of primary resin system.

7. Two-component composition according to anyone of claims 1-6, characterized in that molar ratio between the copper and the potassium is from 20:1 to 1 :3000.

8. Two-component composition according to anyone of claims 1-7, characterized in that the resin composition further comprises a base.

9. Resin composition according to claim 8, characterized in that the base is an organic base with pK_a ≥ 10.

10. Two-component composition according to claim 9, characterized in that the organic base with pK_a ≥ 10 is a nitrogen containing compound, preferably an amine.

11. Two-component composition according to claim 11 , characterized in that the amine is a compound having the following formula: R₂

R₁-N_N R₃ whereby

R¹, R² and R³ each individually may represent hydrogen (H), C₁-C_2O alkyl, C₆-C₂₀ aryl, alkylaryl or arylalkyl group, that each optionally may contain one or more hetero-atoms (e.g. oxygen, phosphor or sulphur atoms) and/or substituents, and a ring may be present between R₁ and R₂, R₂ and R₃ and/or R₁ and R₃, which may contain heteroatoms

12. Two-component composition according to claim 11 , characterized in that R¹,

R² and R³ are hydrogen.

13. Two-component composition according to claim 11 , characterized in that R¹, R² and R³ each individually may represent a C₁-C₂₀ alkyl or a C₆-C₂₀ aryl group.

14. Two-component composition according to claim 11 , characterized in that at least one of R¹, R² and R³ is an alkyl-O- R⁴ group, whereby R⁴ is hydrogen, a C₁-C₂₀ alkyl group or a ring is present between R⁴ and at least one of the other

R groups.

15. Two-component composition according to claim 14, characterized in that the -O- R⁴ group is preferably in the β-position with respect to the nitrogen atom.

16. Two-component composition according to any of claims 1-15, characterized in that the resin composition also contains a radical inhibitor, preferably chosen from the group of phenolic compounds, stable radicals, catechols and/or phenothiazines.

17. Cured structural parts obtained by curing a two-component composition according to any of claims 1-16.

18. Process for radically curing a two-component composition according to anyone of claims 1-11 , characterized in that the curing is effected in the absence of cobalt.

19. Process according to claim 13, characterized in that the peroxide is selected from the group of hydroperoxides, perethers and perketones, and preferably is methylethylketone peroxide.