WO1989007123A1

WO1989007123A1 - Epoxy resin compositions

Info

Publication number: WO1989007123A1
Application number: PCT/GB1989/000062
Authority: WO
Inventors: Colin George Tilley; William Robert Ashcroft; David Arthur Cornforth; Christopher Wayne Stephens; Michael Ian Cook
Original assignee: Anchor Chemical Technical Services Limited
Priority date: 1988-01-26
Filing date: 1989-01-24
Publication date: 1989-08-10
Also published as: ES2010108A6; AU2940089A; GB8801661D0; ZA89588B

Abstract

Curable epoxy resin compositions for producing abrasion resistant, flexible coatings comprise an epoxide resin having two or more epoxy groups per molecule, a curing agent which is a polyamine containing at least three amino hydrogen atoms per molecule, or a precursor of such an amine, and a urethane containing co-curable component which is of general formula (I), in which the R1 groups are the same or different and are selected from hydrogen and methyl, the R2 groups are the same or different polyvalent residues, R3 is a polyvalent residue which is or includes a polyether or polythiol residue, UL represents a urethane group, the values of m may be the same or different and are integers of at least 1, and n is zero or an integer.

Description

EPOXY RESIN COMPOSITIONS

The present invention relates to epoxy resin compositions , and particularly to compositions which have good flexibility when cured.

Epoxy resin compositions comprising an epoxide resin (with two or more epoxy groups per molecule) and a separate curing agent containing or capable of providing active amino hydrogen atoms are well known. It is also known to incorporate additional components in the curable composition for providing particular properties in the finally cured composition. Thus, for example, US-A-4 051 195 discloses curable epoxy resins comprising, in addition to the epoxide resin and an aliphatic polyamine curing agent, a polyacrylate or polymethacrylate ester of polyol. This ester has more than one terminal acrylate or methacrylate group and, as disclosed in the patent, is generally produced by substantially complete esterification of an aliphatic polyhydric alcohol with acrylic or methacrylic acid. During the curing operation, the amino groups can react with either the epoxy groups of the epoxide resin or with the terminal double bonds of the ester (by a Michael Addition reaction) to give a co-cured cross-linked system.

The cured compositions disclosed in US-A-4 051 195 are intended primarily for thin film applications and exhibit comparatively low elongations at break (e.g. 2 to 21%).

EA-A-0 231 442 discloses the use of acrylates and methacrylates selected from epoxy (meth)acrylates, polyester (meth) acrylates, polyester/urethane (meth)acrylates, polyether (meth)acrylates and unsaturated polyesters together with polyamines with at least two primary or secondary amino groups for the preparation of hardening agents for amine reactive polymer systems. One such polymer system is an epoxy resin. Not all of the acrylates and methacrylates quoted above would be expected to give cured resins having good flexibility. Furthermore, the polyester/urethane (meth) acrylates which are disclosed in Examples 1 and 3 of EP-A 0 231 442 have molecular weights of ca 650 and 500 respectively would be extremely viscous non-pourable materials (possibly even semi-solid glasses) and difficult to use as a modifier for an epoxy resin system.

The principal modifying agent currently used for obtaining flexible cured epoxides is an alkyl-phenol capped urethane as disclosed in UK-A-1 399 257. However an alkyl-phenol is liberated during curing and can be extracted from the cured system by solvent media.

It is an object of the present invention to obviate or mitigate the above disadvantages and provide a curable epoxy resin composition which, in the cured form, may be used as a relatively thick, flexible, abrasion resistant coating.

According to the present invention there is provided a curable epoxy resin composition comprising an epoxide resin having two or more epoxy groups per molecule, a curing agent which is a polyamine containing at least three amino hydrogen atoms per molecule, or a precursor of such an amine, and a urethane containing co-curable component which is of the general formula

in which the R₁, groups are the same or different and are selected from hydrogen and methyl, the R₂ groups are the same or different polyvalent residues, R₃ is a polyvalent residue which is or includes a polyether or polythiol residue, UL represents a urethane group, the values of m may be the same or different and are integers of at least 1, and n is zero or an integer.

It will be appreciated that the three components defined in the preceeding paragraph will generally be supplied separately to the end user although it should be appreciated that it is possible for the epoxy resin to be admixed with the urethane containing co-curable component and supplied as a mixture to the end user. The invention also provides such a composition.

The invention further provides a method of obtaining a cured epoxide resin by reacting together the three components found in the last but one paragraph.

The incorporation of the urethane acrylate or (methacrylate) which incorporates a polyether or polythiol residue in the composition provides after curing, a resin which is flexible with good elongation at break, typically at least 50% and possibly in the range 100-200% depending on the particular components of the composition. The cross-linked composition may be used as a comparatively thick coating, e.g. from 100 microns on various substrates or as a sealant. Furthermore, during curing, there is no alkyl phenol liberated and the cured compositions have very good abrasion resistant properties.

The compounds (I) thus have at least two, and preferably more (the exact value depending on the values of m, and n) of terminal acrylate and/or methacrylate residues which can react with the amino groups of the polyamine by means of a Michael Addition reaction. Preferably n is in the range 0 to 4.

Preferably R₁ is hydrogen, i.e. compound (I) is a urethane acrylate. Preferably also R₃ incorporates urethane linkages and preferably the or each R₂ group is an alkyl residue.

The compounds (1) preferably have a molecular weight of from about 1500 to about 10,000.

As indicated above, the compounds (I) contain at least two acrylate or methacrylate residues attached to R₃. The preferred compounds of formula (I) have the structure (II). In this structure the following symbols have the meanings indicated

X = oxygen or sulphur

I, I' and I'' = the same or different polyisocyanate residues (I'' may be a higher functionality polyisocyanate than that illustrated). P = is or includes a polyether or polythiol residue (e.g. a polyalkylene polyol residue, and o, p and q are individually zero or an integer and together total n. Compounds of the formula II may be prepared by initially reacting a polyol or polythiol of the formula (III)

in which R₅ is or includes a polyether or polythiol residue with at least one di- or higher functionality isocyanate which corresponds to at least one of the residues I, I' or I". The -XH groups of compound (III) react with isocyanate groups of the polyisocyanate compound to form the -X-C(O)-N(H)linkages in formula (II) and produce a compound containing free isocyanate groups. This compound can then be reacted with at least one hydroxy ester of acrylic or methacrylic acid. This ester may for example be a mono-ester of acrylic (or methacrylic) acid with a diol (in which case m=2) or a di-ester of the acid with a triol (in which case m=3)

Generally the Est-R₂-O- residues in the compound of formula II (or formula I) will be the same, and the residues I and I' (as well as I" - if present) in formula II will also be the same.

Suitable isocyanates for providing the residues I, I' or I'' are, for example, as follows:

Tolylene-2,4-diisocyanate (and its commercial grade mixtures with tolylene-2,6-diisocyanate), tolylene 2,6-diisocyanate, diphenyl methane 4,4' -diisocyanate, 1,6-hexamethylene diisocyanate, naphthylene-1,5-diisocyanate, m-xylylene diisocyanate, 1-methyl-2,4-diisocyanato cyclohexane, isophorone diisocyanate, 2,4,4-trimethyl-1,6 diisocyanate hexane, dimeric tolylene-2,4-diisocyanate, triρhenylmethane-4,4',4''-triisocyanate, 4,4'- diisocyanato dicyclohexyl methane, trimerisation and polymerisation products of tolylene-2,4-diisocyanate, mixed-trimerisation and mixed-polymerisation products of tolylene-2,4-diisocyanate and 1,6-hexamethylene diisocyanate, mixtures of isomeric diphenyl methane diisocyanates, polyisocyanates containing more than two benzene nuclei each attached through methane groups and diisocyanates of diphenyl methane structure some of whose isocyanate groups are converted into carbodiimide groups and tetramethyl xylylene diisocyanate.

Suitable polyether polyols for providing the residue P are the linear and branched chain polyalkylene ether polyols which may be obtained by alkoxylation of di or polyfunctional alcohols (such as ethylene glycol, trimethylol propane, glycerol or penta-erythritol), or amino modified polyether polyols obtained by alkoxylation of an amine compound bearing at least two active hydrogen atoms (such as monoethylamine, and propylene diamine). The preferred polyols are those in which the alkoxylating agent is ethylene oxide or propylene oxide. Other polyols may be those obtained by polymerisation of a larger cyclic ether ring, such as the polytetramethylene ether glycols.

The P residue may also be provided by a polyether based polyester, for example the polycondensation products of polyether polyols with aromatic or aliphatic (including cycloaliphatic) carboxylic acids, in such stoichiometric proportions as to yield hydroxyl terminal polyester condensates. Suitable polyols are for example the range of polyethylene glycols, the range of polypropylene glycols, and the glycols obtained by alkoxylation of bi or polyfunctional phenols such as ethoxylated bisphenol-A. Suitable carboxylic acids include adipic acid and its homologous range of linear aliphatic dicarboxylic acids, aromatic acids such as the three isomeric phthalic acids, trimellitic acid, pyromellitic acid, and the cycloaliphatic acids such as tetrahydrophthalic acid.

Other materials which may be used in condensation reactions to form polyesters include the lactones such as caprolactone which effectively contribute both a hydroxylic and a carboxylic group to the polymer.

Suitable polyether thiols for providing the P residue include the liquid prepolymers known as Thiokol (Registered Trade Mark) or polycondensation products of thiodiglycol or condensation products of glycols with thiiranes (episulphides).

Suitable hydroxy acrylate esters (i.e. CH₂=CHR₁-COOR₂OH) which may be reacted with the isocyanate terminal pre-polymer are for example hydroxyethyl acrylate or hydroxypropyl acrylate. A general class of compounds which fall into this description are the B-hydroxy esters derived by reaction of a monoepoxide with acrylic acid. Such monoepoxides may include for example phenyl glycidyl ether, butyl glycidyl ether, allyl glycidyl ether or the epoxides obtained by epoxidation of an olefinic double bond such as for example styrene oxide. Other suitable hydroxy acrylates are prepared by partial esterification of a suitable polyol with acrylic acid and includes such compounds as trimethylol propane diacrylate and pentaerythritol triacrylate. Longer chain hydroxy esters may be prepared by alkoxylation of the above species with for example propylene oxide or ethylene oxide. For example if hydroxy propyl acrylate is reacted with propylene oxide, the resulting polypropylene glycol mono acrylate is a suitable hydroxy ester.

Compounds II may be prepared by condensing a polyol (which provides residue P) with a polyisocyanate under conditions such that one isocyanate group reacts with a hydroxyl group of the polyol, leaving the remaining isocyanate groups free to react in the next stage. In this next stage, the condensation product of the previous stage is reacted with an optionally substituted hydroxy acrylate or methacrylate ester preferably in stoichiometric quantities. This reaction may be conducted at elevated temperatures and the reaction may be uncatalysed or catalysed by materials well known to effect the urethane formation reaction, e.g. tertiary amines, organotin compounds, or organolead compounds.

In general, the viscosity of compounds of formula (II) decreases as the molecular weight of the base polyol or polythiol increases. For preferance the compounds (II) have an approximate molecular weight of 3000-7000, e.g. 4000-5000 and are produced from an oxyalkylated polyol with an approximate molecular weight of 2000-6000, e.g. 3300 to 4300. Such compounds of formula (II) will generally be pourable liquids at ambient temperature. Furthermore, the chemical resistance of the cured epoxides is considerably improved when a higher functionality urethane acrylate is used. Most preferably this functionality is at least 3. It is thus possible to select the appropriate polyols (compound III), isocyanates, and hydroxy acrylate to synthesize products (II) of the desired molecular weight/viscosity and functionality.

One preferred form of compound (II) has a value of p = 1, m = 1 and o and q equal to zero. Such compounds may be prepared from an oxyalkylated (e.g. oxypropylated) triol (e.g. glycerol) with a diisocyanate and 3 moles of a hydroxymonoacrylate to give a product with a total functionality of 3.

Alternatively, a compound (II) of total functionality 4 may be prepared by reacting a linear polyether diol (p = 0) with a diisocyanate (o and q = 0) and reacting the condensation product thus obtained with a monohydroxypolyacrylate ester (e.g. glycerol diacrylate, m = 2) to give a product of the desired functionality.

The curable epoxy resin compositions of the invention will generally be liquid compositions in which conventional epoxy resins and amine curing agents are formulated with the urethane acrylate (or methacrylate) co-component.

The epoxide resins which can be used in accordance with the invention are substances containing more than one epoxide group. The preferred epoxide resins are liquids although it is within the context of the invention to use solid curable resins dissolved in a suitable solvent.

The epoxide resin preferably has an epoxy molar mass (i.e. the mass of resin containing 16g of epoxy oxygen) of from 150 to 3500 and a molecular weight of 300 to 7000. These resins can be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic, optionally substituted for example by chlorine atoms, hydroxyl-, cyano- or ether groups. The glycidyl polyethers of diphenylol propane having an epoxy value of from 0.02 to 0.6 and a molecular weight of from 340 to 7000 are particularly preferred. A typical aliphatic epoxy resin would be for example neopentyl glycol diglycidyl ether. Reactive diluents, for example, styrene oxide, butyl glycidyl ether, glycidyl esters of synthetic, highly branched predominantly tertiary aliphatic monocarboxylic acids, or cycloaliphatic mono epoxides such as 3-vinyl-2,4-dioxaspiro-(5,5)-9,10-epoxy undecane, may optionally be added to the polyepoxides to lower their viscosity.

A variety of amine derivatives may be utilized as cross-linking or curing agents for the epoxy resin/urethane co-agent blend. These fall into the following sub-groups :

(i) Polyfunctional aliphatic, araliphatic and cycloaliphatic amines containing at least three active hydrogen atoms per molecule, which may consist of linear diamines such as ethylene diamine or hexamethylene diamine, branched chain diamines such as trimethyl hexamethylene diamine, polyfunctional amines such as diethylene triamine or triethylene tetramine, or cyclic diamines, such as diamino-dicyclohexyl methane or m-xylylenediamine or heterocyclic amines such as aminoethyl piperazine. (ii) Condensation products of the above amines with epoxide resins or mono-epoxides in such proportions that an amino-terminal adduct is formed. All of the above amines may be reacted. (iii) Condensation products of the above amines with phenolic bodies and an aldehyde, usually formaldehyde, in such proportions as to give an amino-terminal condensate. All of the above amine types may be used in this sort of condensation reaction, and suitable phenolic bodies include for example phenol, the cresols, 4-t-butyl phenol and nonyl phenol. (iv) Condensation products of the above amine types with mono and difunctional acids, usually long chain fatty acids to yield an amino terminal polyamide. All of the above amine types may be used in this sort of condensation reaction, but the polyalkylene polyamines are especially preferred.

(v) Cyanoethylation products of amines which may be prepared by reaction of any of the above amine types with acrylonitrile.

(vi) Aminoterminal polyethers obtained by reaction of a polyether polyol with acrylonitrile, followed by reduction of the nitrile group, and derivatives of amines of this type.

The curing agent may be a compound which the free amino groups are liberated thermally or by hydration.

All of the above amines or amine condensates may be formulated in conjunction with additives which are well known as components of epoxide resin curing agents and include solvents, diluents such as phthalate esters or hydrocarbon resins, alcohols such as benzyl alcohol, accelerators such as carboxylic acids including for example lactic acid or salicylic acid, phenols or phenolic resins, tertiary amines including for example benzyl dimethylamine or tris dimethylaminomethyl phenol, or metal compounds including for example stannous octoate.

The cross-linked polymer is prepared by blending the appropriate amounts of epoxide resin and urethane acrylic co-agent together with the required amount of cross-linking agent. The proportions of epoxide resin and urethane acrylic co-agent may be varied at will, depending on the degree of elongation and tensile strength desired in the final product. These are blended with the required amount of the amine cross-linking agent. Theoretically, one amino-active hydrogen in the cross-linking agent is provided for each epoxide group and for each acrylic group present in the mixture. Some degree of latitude is however permissible in the amount of curing agent used, and acceptable properties in the cured material may be obtained when the weight of curing agent ranges from about 10% less than that calculated as above to about

10% more than that calculated. If the resultant mixture is viscous it may be de-aerated before cure.

Additional materials may be present in the system dependent upon the particular application envisaged and may include for example fillers and pigments.

The invention will be illustrated by the following non-limiting Examples.

EXAMPLE 1:

Preparation of a trifunctional Polyether With Terminal Carbamic Acid - Acrylic Ester Groups.

500g of a trifunctional propoxylated glycerol with an OH number in the range 39 - 45 mgKOH/g was added, with stirring, to 64g of tolylene-2, 4(2, 6) diisocyanate heated to 85°C. The mixture was maintained at 85oC for 5 hours after which time it had an NCO content of 2.8% by weight.

A mixture of 44g Hydroxyethylacrylate, 1.2g hydroquinone and 0.18g dibutyltindilaurate were added to the isocyanate prepolymer cooled to 60°C. This was followed by further heating at 85°C for 1 hr. At this time no isocyanate was detectable by infra-red spectroscopy. The product has a theoretical equivalent weight of 1657.

EXAMPLE 2:

Preparation of a Difunctional Polyether With Terminal Carbamic Acid - Acrylic Ester Groups.

The procedure was as in Example 1 above except that the isocyanate prepolymer was obtained by reacting 1000g of a linear polypropylene glycol of molecular weight 2000 with 174g of tolylene-2,4(2,6)-diisocyanate. The prepolymer was then capped by further reacting at 85°C with a mixture of 116g hydroxyethylacrylate, 2.6g hydroquinone and 0.4g dibutyltindilaurate. After 2 hrs at 85ºC, no isocyanate was detectable by infra-red spectroscopy.

EXAMPLE 3:

As Example 1 except the isocyanate prepolymer was obtained from a trifunctional propoxylated glycerol of OH number in the range 54-59 mgKOH/g. EXAMPLE 4 :

As Example 1 except the isocyanate prepolymer was obtained from a trifunctional propoxylated glycerol of OH number in the range 155-165 mgKOH/g.

EXAMPLE 5:

300g of a trifunctional propoxylated glycerol with an OH number in the range 54-59 mgKOH/g were added, with stirring, to 73.2g of (meta) Tetramethyl Xylene Diisocyanate (TMXDI) containing 0.15g of dibutyltindilaurate at 25°C. During the addition the reaction temperature was slowly raised to 50°C where the mixture was maintained for a further 1 hour. At this point the prepolymer mixture had an NCO content of 3.28% by weight.

A mixture of 34g hydroxyethylacrylate and 1.0g hydroquinone were then added to the isocyanate prepolymer at 50ºC. This was followed by further heating to 80°C for 1 hour, after which time no isocyanate was detectable by infrarred spectroscopy.

EXAMPLE 6:

To 469g of an NCO terminated, urethane prepolymer made from a difunctional polypropylene glycol of molecular weight 2000 and Tolylene - 2,4, (2,6) - diisocyanate via the method described in Example 2 were added 1.1g of hydroquinone and 0.16g of dibutyltindilaurate.

The above mixture was heated to 60°C and then 81g of Butoxy-2 hydroxy-propylacrylate were added dropwise over a thirty minute period. After the addition was complete, further heating for 2 hours at 85ºC gave a urethane acrylate in which no free isocyanate was detected by infra-red spectroscopy.

EXAMPLE 7:

This was the same as Example 1 except that the NCO terminated, urethane prepolymer (NCO content = 2.73%) was capped with the appropriate quantity of 2-hydroxypropylacrylate.

EXAMPLE 8:

300g of a difunctional propylene glycol with an OH number in the range 53-58 mgKOH/g were added with stirring, to 74g of (meta) Tetramethyl Xylene Diisocyanate (TMXDI) containing 0.15g of dibutyltindilaurate at 25ºC. During the addition the reaction temperature was gradually raised to 70°C where the mixture was maintained for a further 1 hour. At this point the prepolymer mixture had an NCO content of 2.80% by weight.

A mixture of 51g of Butoxy-2-hydroxy- propylacrylate and 1.0g hydroquinone were then added to the above prepolymer at 50°C. This was followed by further heating to 85ºC, after which time no isocyanate was detectable by infra-red spectroscopy.

EXAMPLE 9:

410g of trifunctional propoxylated glycerol with an OH number in the range 39-45 mgKOH/g were added. with stirring, to 73.2g of (meta) Tetramethyl Xylene Diisocyanate containing 0.15g of dibutyltindilaurate at 25ºC. After the addition the mixture was heated to 50°C for a further 1 hour. At this point the prepolymer had an NCO content of 2.55%.

A mixture of 39.6g of 2-hydroxypropylacrylate and 1.0g of hydroquinone were then added to the prepolymer at 50°C. Further heating at 85°C for 2 hours resulted in a urethane acrylate in which no free NCO was detected by infra-red spectroscopy.

EXAMPLE 10:

427g of a difunctional polytetramethylene ether glycol having an hydroxyl value in the range 107-118 mg KOH/g was added with stirring to a mixture of 224g of dicyclohexylmethane 4,4'- diisocyanate containing 0.2g of dibutyltindilaurate at 80ºC. The reaction mixture was maintained at 80ºC for a further 2 hours after which time the NCO prepolymer had an isocyanate content of 4.9% by weight.

A mixture of 85g hydroxyethylacrylate and 1.5g hydroquinone were added to the above prepolymer cooled to 60ºC. This was followed by further heating to 85°C for 4 hours. At this point no isocyanate was detectable by infra-red spectroscopy.

EXAMPLE 11:

300g of a difunctional liquid polyether thiol having a molecular weight of 850 was added to 120g of 2,4 (2,6) tolylene disocyanate containing 0.5g of dibutyltindilaurate at 75°C. Further heating for 5 hours at this temperature resulted in a thiourethane prepolymer having an NCO content of 8.1% by weight.

The prepolymer was cooled to 60°C followed by the addition of 94g of hydroxyethylacrylate and 1.4g of methoxyhydroquinone.

The reaction temperature was raised to 80°C where after 2 hours no isocyanate was detectable by infra-red spectroscopy.

EXAMPLE 12:

500g of an NCO prepolymer was prepared by reacting a difunctional polyether glycol of approximate molecular weight 600 with Diphenylmethane 4,4'-diispcyanate using the method described in previous examples was heated to 60°C.

The NCO prepolymer, having an isocyanate content of 7.0% by weight was the capped with 109g of hydroxyethlacrylate using 0.2g of dibutyltindilaurate as a catalyst and 1.0g of hydroquinone as an inhibitor.

Further heating for 3 hours at 85°C produced a viscous resin that was free of unreacted isocyanate as determined by infra-red spectroscopy.

EXAMPLE 13:

Preparation Of A Flexibilised Epoxide Resin Composition:

70 parts by weight of the product according to Example 1 were mixed with 30 parts by weight of a liquid epoxide resin of Bisphenol A and epichlorohydrin with an epoxide equivalent weight of 190. The mixture was de-gassed and then cured by blending in 20 parts by weight of a phenol-formaldehyde isophoronediamine condensate curing agent with an equivalent weight per active hydrogen of 102 and 1 part by weight of a tertiary amine. The latter acts as a hardening accelerator.

A second blend consisting of 60 parts by weight of the product in Example 1, 40 parts by weight of the above epoxide resin was formulated and cured by blending in 25 parts by weight of the above phenol-formaldehyde polyamine condensate curing agent and 1 part by weight of a tertiary amine accelerator. Both mixes were cast into moulds and allowed to harden for 7 days, the cured materials had the following properties :

70/30 60/40

TENSILE STRENGTH (N/mm²) 8.1 9.1

BREAKING ELONGATION (%) 140 90

EXAMPLE 14:

80 parts by weight of the product according to Example 2 were mixed with 20 parts by weight of the liquid epoxide resin and then hardened by blending in 17 parts by weight of the above phenol-formaldehyde condensate curing agent of equivalent weight per active hydrogen 102 and 5 parts by weight of a tertiary amine accelerator. A second blend consisting of 60 parts by weight of the product in Example 2 and 40 parts by weight of the epoxide resin was formulated and cured by mixing in 26 parts by weight of the above curing agent and 3 parts by weight of the amine accelerator. The cured materials had the following physical properties :

80/20 60/40

TENSILE STRENGTH (N/mm²) 3.3 10.8

BREAKING ELONGATION (%) 201 53

EXAMPLE 15:

80 parts by weight of the product according to Example 3 were mixed with 20 parts by weight of a liquid epoxide resin of equivalent weight 190. The mixture was cured using 17 parts by weight of a phenol-formaldehyde polyamine condensate curing agent and 1 part by weight of a curing accelerator.

A second blend consisting of 60 parts by weight of the product in Example 3 and 40 parts by weight of the above epoxide resin was formulated and cured with 26 parts by weight of the phenol-formaldehyde polyamine condensate and 1 part by weight of the accelerator. After a 7 day cure the materials had the following properties:

80/20 60/40

TENSILE STRENGTH (N/mm²) 6.0 12.0

BREAKING ELONGATION (%) 142 108 EXAMPLE 16 :

80 parts by weight of the product according to Example 1 were mixed with 20 parts by weight of a liquid epoxide resin of equivalent weight 190. The mixture was cured by blending in 18 parts by weight of a cycloaliphatic amine/epoxide resin adduct with an equivalent weight per active hydrogen of 115 and 1 part by weight of a tertiary amine accelerator.

A second blend consisting of 70 parts by weight of the product in Example 1, 30 parts by weight of the above epoxide resin was formulated and cured with 23 parts by weight of the cycloaliphatic amine/epoxide resin adduct. The tertiary amine accelerator was omitted from the formulation. After a 7 day cure at 25°C the test pieces gave the following physical properties.

80/20 70/30

TENSILE STRENGTH (N/mm²) 1.80 3.60

BREAKING ELONGATION (%) 94 50

EXAMPLE 17:

70 parts, by weight of the urethane acrylate prepared in Example 2 were mixed with 30 parts by weight of an epoxide resin and cured by blending in 11 parts by weight of a polyether-diamine curing agent having an equivalent weight per active hydrogen of 57. (Formulation A)

An identical 70/30 blend was also formulated, (B), however this was cured by blending in 11 parts by weight of the polyether-diamine curing agent and 1 part by weight of tertiary amine. After a 7 day cure the following physical properties were determined.

70/30 (A) 70/30 (B)

TENSILE STRENGTH (N/mm²) 1.5 3.1

BREAKING ELONGATION (%) 95 134

EXAMPLE 18:

80 parts by weight of the urethane acrylate prepared in Example 5 were blended with 20 parts by weight of a liquid epoxide resin having an equivalent weight of 190. The mixture was then cured using 17 parts by weight of a phenol-formaldehyde isophorondiamine condensate and 1 part by weight of a tertiary amine.

A second blend consisting of 60 parts urethane acrylate and 40 parts epoxide resin was formulated and cured with 26 parts of the above curing agent and 1 part tertiary amine.

The following physical properties were recorded:

80/20 60/40

TENSILE STRENGTH (N/mm²) 3.3 11.0

BREAKING ELONGATION (%) 162 69

EXAMPLE 19:

70 parts by weight of the urethane acrylate prepared in Example 2 were blended with 30 parts by weight of a liquid epoxide resin. The system was then cured with 20 parts by weight of an aliphatic polyamine curing agent having an equivalent weight per active hydrogen of 95. After a 7 day cure the following properties were observed.

70/30

TENSILE STRENGTH (N/mm²) 3.2

BREAKING ELONGATION (%) 110

EXAMPLE 20:

80 parts by weight of the urethane acrylate prepared in Example 1 were blended with 20 parts of a lquid epoxide resin. The system was then cured with 11 parts of a cyanoethylated Trimethyl hexamethylene diamine curing agent having an equivalent weight per active hydrogen of 70 and 1 part by weight of tertiary amine.

A second blend consisting of 60 parts of acrylate and 40 parts epoxide resin was formulated and hardened with 17 parts of the cyanoethylated amine and 1 part of tertiary amine.

After 7 days the following properties were observed:

80/20 60/40

TENSILE STRENGTH (N/mm²) 1.76 5.73

BREAKING ELONGATION (%) 172 114 EXAMPLE 21 ;

70 parts of the urethane acrylate prepared in Example 2 were blended with 30 parts of a liquid epoxide resin and hardened with 11 parts of a polyamido-amine curing agent having an equivalent weight per active hydrogen of 50. The test sample gave the following properties:

70/30

TENSILE STRENGTH (N/mm²) 2.1

BREAKING ELONGATION (%) 75

EXAMPLE 22

70 parts by weight of the urethane acrylate prepared in Example 1 was mixed with 30 parts by weight of an epoxide resin of equivalent weight 190. The above formulation was then hardened by blending in 4.5 parts of the aliphatic polyamine, Diethylenetriamine (DETA) and 0.5 parts of a tertiary amine. After a 7 day cure schedule the cured mixture had the following properties:

70/30

TENSILE STRENGTH (N/mm²) 6.3

BREAKING ELONGATION (%) 42 EXAMPLE 23 :

70 parts by weight of the urethane acrylate prepared in Example 1 was mixed with 30 parts by weight of the above epoxide resin and hardened with a mixture of 11 parts by weight of the cycloaliphatic polyamine, Dicyclohexylmethane 4,4'-diamine and 1 part by weight of a tertiary amine. After a 7 day cure schedule at 25oc the cured material had the following physical properties.

70/30

TENSILE STRENGTH (N/mm²) 6.9

BREAKING ELONGATION (%) 114

EXAMPLE 24:

80 parts by weight of the urethane acrylate prepared in Example 19 was mixed with 20 parts by weight of an epoxide resin of equivalent weight 190. The mixture was then hardened by blending in 23 parts by weight of a phenol-formaldehyde isophoronediamine condensate with an equivalent weight per active hydrogen of 102 and 1 part by weight of a tertiary amine. After a 7 day cure schedule at 25°C the cured material had the following physical properties.

80/20

TENSILE STRENGTH (N/mm²) 7.6

BREAKING ELONGATION (%) 97 EXAMPLE 25 :

This example demonstrates the improved abrasion resistance of cured epoxy resins in accordance with the invention as compared to compositions cured without the addition of any flexibiliser and also with a conventional prior art flexibiliser (a nonyl phenol capped urethane). The composition had the formulations shown in the table below which also includes the results of the abrasion tests. All parts are by weight.

ACRYLATE CAPPED URETHANE - - 60

NONYL PHENOL CAPPED URETHANE - 60 -

EPOXY RESIN EPIKOTE 828 82 33 33

C-12/14 ALKYLGLYCIDYL

ETHER DILUENT 18 7 7

CYCLOALIPHATIC AMINE

HARDNER 47 23 22

ABRASION LOSS AFTER 7

DAY CURE mg/200 CYCLES 18.1 8.1 3.0

The results clearly demonstrate the improved abrasion resistance of the compositions in accordance with the invention as compared to the prior art flexibilised and non-flexibilised compositions.

Claims

1. A curable epoxy resin composition comprising an epoxide resin having two or more epoxy groups per molecule, a curing agent which is a polyamine containing at least three amino hydrogen atoms per molecule, or a precursor of such an amine, and a urethane containing co-curable component which is of the general formula.

2. A composition as claimed in claim 1 wherein the residue R₃ in the compound (I) includes urethane linkages.

3. A composition as claimed in claim 1 or 2 wherein the or each residue R₂ in the compound (I) is an alkyl residue.

4. A composition as claimed in any one of claims 1 to 3 wherein the compound of Formula I has been prepared by reaction of a polyol including polyether or polythiol groups with at least one dior higher functionality isocyanate and reaction of the product with at least one hydroxy ester of acrylic or methacrylic acid.

5. A composition as claimed in claim 4 wherein the polyol has a functionality of at least 3.

6. A composition as claimed in claim 4 or 5 wherein the polyol has been produced by oxyalkylation of polyhydroxy initiator compound.

7. A composition as claimed in claim 6 wherein the polyhydroxy initiator compound is ethylene glycol, trimethylol propane, glycerol or penta-erythritol.

8. A composition as claimed in claim 6 or 7 which is an oxyethylated or oxypropylated product.

9. A composition as claimed in claim 4 wherein the polyol is an amine modified polyether polyol.

10. A composition as claimed in claim 4 wherein the polyol is a polyether based polyester.

11. A composition as claimed in any one of claims 4 to 10 wherein the polyol has a molecular weight of 2000 to 6000.

12. A composition as claimed in any one of claims 4 to 10 wherein the di- or higher functionality isocyanate is selected from tolylene-2,4-diisocyanate (and its mixtures with tolylene-2,6-diisocyanate), tolylene 2,6-diisocyanate, diphenyl methane 4,4' -diisocyanate,1,6-hexamethylene diisocyanate, naphthylene-1,5-diisocyanate, m-xylylene diisocyanate, 1-methyl-2,4-diisocyanato cyclohexane, isophorone diisocyanate, 2,4,4-trimethyl -1,6 diisocyanate hexane, dimeric tolylene -2,4-diisocyanate, triphenylmethane-4,4',4''- tri isocyanate, 4,4'- diisocyanato dicyclohexyl methane, trimerisation and polymerisation products of tolylene-2,4-diisocyanate, mixed-trimerisation and mixed-polymerisation products of tolylene-2,4- diisocyanate and 1,6-hexamethylene diisocyanate, mixtures of isomeric diphenyl methane diisocyanates, polyisocyanates containing more than two benzene nuclei each attached through methane groups and diisocyanates of diphenyl methane structure some of whose isocyanate groups are converted into carbodiimide groups and tetramethyl xylylene diisocyanate.

13. A composition as claimed in any one of claims 4 to 12 wherein the hydroxy acrylate ester is a hydroxyethyl acrylate or a hydroxypropyl acrylate.

14. A composition as claimed in any one of claims 4 to 12 wherein the hydroxy acrylate ester is a β -hydroxy ester derived from reactions of a monoepoxide with acrylic acid.

15. A composition as claimed in any one of claims 1 to 14 wherein the compound (I) has a molecular weight of 3000 to 7000

16. A composition as claimed in any one of claims 1 to 15 wherein the epoxy resin has an epoxy molar mass of from 150 to 3500 and a molecular weight of 300 to 7000.

17. A composition as claimed in any one of claims 1 to 16 wherein the polyamine is an aliphatic araliphatic or cycloaliphatic amine or a condensation product of such an amine.

18. A composition comprising an admixture of a curable epoxy resin and a compound of formula (I) as defined in any one of claims 1 to 15.

19. A method of obtaining a cured epoxy resin composition comprising curing an epoxy resin with a curing agent which is a polyamine containing at least three amino hydrogen atoms per molecule in the presence of a urethane containing co-curable cocomponent as defined in any one of claims 1 to 15.

20. A cured epoxy resin composition obtained by curing a composition as defined in any one of claims 1 to 17.