WO2017019679A1

WO2017019679A1 - Epoxy materials and the use thereof

Info

Publication number: WO2017019679A1
Application number: PCT/US2016/044029
Authority: WO
Inventors: Rujul M. MEHTA; Mark W. Brown; Pankaj Gupta; Dwight D. Latham; Kamesh R. VYAKARANAM
Original assignee: Dow Global Technologies Llc
Priority date: 2015-07-30
Filing date: 2016-07-26
Publication date: 2017-02-02

Abstract

Thermoset compositions are disclosed. Such thermosets are the reaction product of an ambient temperature liquid epoxy-terminated prepolymer, a short chain polyalkylene glycol diglycidyl ether, optionally a second epoxy and/or a filler, and a curing agent comprising at least one amine or polyamine. Said reaction product provides a thermoset which has polyurethane like processing and flexibility with good thermal and hydrolytic stability and improved toughness and strength. Such thermosets can be used in applications such as for sealants, adhesives, coatings, gaskets, jointing and castings.

Description

EPOXY MATERIALS AND THE USE THEREOF

FIELD OF THE INVENTION This invention relates to the field of thermosets for applications such as sealants, adhesives, coatings, gaskets, jointing and castings.

BACKGROUND OF THE INVENTION The main types of thermoset polymers include epoxies, polyurethanes, two-part silicones, and vulcanized rubber; each of these thermosets has positive and negative attributes. Epoxies are usually rigid polymers that are formed from the reaction of an epoxy resin and curative agent such as an amine, or polyamine or an anhydride and are preferred for their superior mechanical properties and resistance to high temperature and or chemically aggressive environments. Epoxies generally exhibit limited flexibility and extension.

Polyurethanes are formed from the reaction of a polyol and isocyanate and are preferred for the ease of processing, wide range of mechanical properties spanning from rigid polymers to elastomers that can be obtained depending on the components chosen, and good adhesive properties to a range of substrates. Polyurethanes are generally limited in their thermal and hydrolytic stability.

Two-part cast silicone elastomers and vulcanized rubbers typically have thermal and hydrolytic stabilities that exceed polyurethanes, however; their application is generally limited to softer systems, equal to or less than 80 Shore A, that normally require long cure and demold times, e.g., 15 hours or more. Vulcanized rubbers also require high temperature molding processes that limit their use in field applications, form fitting, or assembly applications without the use of additional primers and adhesives for bonding. Silicones can be cast at ambient temperatures but suffer the same deficiencies as vulcanized rubbers in terms of adhesion and are generally more expensive than urethane systems.

In USP 8,951 ,619 and 9,006,385 we disclosed elastomeric epoxy materials comprising an epoxy-terminated prepolymer and an amine curing agent that demonstrate good thermal and hydrolytic stability.

There therefore remains a need to have thermosets which have polyurethane like processing and flexibility with good thermal and hydrolytic stability and improved toughness and strength. SUMMARY OF THE INVENTION

This invention provides an amine cured epoxy material that combines the processing, mechanical flexibility, and adhesion properties of polyurethanes with the mechanical strength, thermal, and hydrolytic stability typically associated with epoxy materials.

In one embodiment the thermoset comprises the reaction product of (a) from 50 to 95 weight percent of an ambient temperature liquid epoxy-terminated prepolymer formed by reacting a polyoxyaikyleneamine having a molecular weight of from 3,000 to 20,000 with an excess of epoxide, formula

wherein R is the nucleus of an oxyalkylation-susceptible initiator containing 2-12 carbon atoms and 2 to 8 active hydrogen groups, U is an alkyl group containing 1-4 carbon atoms, preferably alkyl group containing 1 or 2 carbon groups, T and V are independently hydrogen, U, or preferably an alkyl group containing one carbon, n is number selected to provide a polyol having a molecular weight of 2,900 to 29,500, and m is an integer of 2 to 8 corresponding to the number of active hydrogen; (b) from 5 to 30 weight percent of a short chain polyalkylene glycol diglycidyl ether of molecular weight between the range of 185 to 790; (c) optionally a second epoxide, which can be the same or different from the first epoxide, preferably having an equivalent weight of 75 grams/equivalent to 210 grams/equivalent, in an amount of 0 to 45 weight percent; (d) optionally a filler in an amount of 0 to 30 parts by weight wherein parts are based on 100 parts of components (a), (b), and (c), if present, preferably if present, one or more of wollastonite, barites, mica, feldspar, talc, silica, crystalline silica, fused silica, fumed silica, glass, metal powders, carbon nanotubes, graphene, calcium carbonate, or glass beads; and (e) a curing agent comprising at least one amine or polyamine having an equivalent weight of less than 200 and having 2 to 5 active hydrogen atoms, wherein weight percent are based on the total weight of components (a), (b), and (c), if present.

In one embodiment of the present invention, the first epoxide disclosed herein above is one or more of the formula

wherein R⁵ is C₆ to Ci_¾ substituted or unsubstituted aromatic, a Ci to C₈ aliphatic, or cycloaliphatic; or heterocyclic polyvalent group and b has an average value of from 1 to 8, preferably the epoxide is one or more of diglycidyl ethers of resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (l,l-bis(4-hydroxylphenyl)-l-phenyl ethane), bisphenol F, bisphenol K, bisphenol S, tetrabromobisphenol A, phenol-formaldehyde novolac resins, alkyl substituted phenol-formaldehyde resins, phenol-hydroxybenzaldehyde resins, cresol- hydroxybenzaldehyde resins, dicyclopentadiene-phenol resins, dicyclopentadiene-substituted phenol resins tetramethylbiphenol, tetramethyl-tetrabromobiphenol,

tetramethyltribromobiphenol, tetrachlorobisphenol A, or combinations thereof.

In another embodiment of the present invention, the epoxide disclosed herein above is at least one cycloaliphatic first epoxide of the formula

wherein R⁵ is C6 to Cis substituted or unsubstituted aromatic, a d to Cs aliphatic, or cycloaliphatic; or heterocyclic polyvalent group and b has an average value of from 1 to 8.

In another embodiment of the present invention, the first epoxide disclosed herein at least one divinylarene oxide of the following structures:

Structure I

Structure II

Structure III

Structure IV wherein each R¹, R², R³ and R⁴ is individually hydrogen, an alkyl, cycloalkyl, an aryl or an aralkyl group; or a oxidant-resistant group including for example a halogen, a nitro, an isocyanate, or an RO group, wherein R may be an alkyl, aryl or aralkyl;

x is an integer of 0 to 4;

y is an integer greater than or equal to 2 with the proviso that x+y is an integer less than or equal to 6;

z is an integer of 0 to 6 with the proviso that z+y is an integer less than or equal to 8; and Ar is an arene fragment, preferably a 1,3-phenylene group.

In one embodiment of the present invention, the short chain polyalkylene glycol diglycidyl ether disclosed herein above is at least one or more of the formula

wherein R⁶ is H or Ci to C3 aliphatic group and d has an average value from 1 to 12, preferably the short chain polyalkylene glycol diglycidyl ether is poly (propylene glycol) diglycidyl ether having a molecular weight from 185 to 790.

In another embodiment of the present invention, the amine curing agent is at least one curing agent represented by the formula:

wherein R⁷, Q, X, and Y at each occurrence are independently H, d to C14 aliphatic, C3 to C₁₀ cycloaliphatic, or C6 to C14 aromatic or X and Y can link to form a cyclic structure; Z is O, C, S, N, or P; c is 1 to 8; and p is 1 to 3 depending on the valence of Z.

In another embodiment of the present invention, the amine curing agent is represented by the formula

wherein R at each occurrence is independently H or -CH₂CH₂NH₂ and h is 0 to 2 with the proviso that both h's cannot be 0.

In yet another embodiment of the present invention, the thermoset disclosed herein above further comprises (f) an acrylate monomer having an acrylate equivalent weight of 85 grams/equivalent to 160 grams/equivalent, wherein the acrylate monomer component is present in an amount from 1 to 12 part per hundred parts based on the total amount epoxy resin, preferably the acrylate component is hexanediol diacrylate, tripropylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, Methylene glycol diacrylate, 1,4- butanediol diacrylate, dipropylene glycol diacrylate, neopenyl glycol diacrylate, cyclohexane dimethanol diacrylate, pentaerythritol triacrylate, diptenaerythritol pentaacrylate, or combinations thereof.

Another embodiment of the present invention is a multi-layered composite or coating comprising at least one layer comprising the thermoset disclosed herein above, preferably the multilayer coating further comprising one or more layer comprising a paint, a silicone, a polyurethane, an epoxy, a polyolefin, or combinations thereof.

DETAILED DESCRIPTION OF THE INVENTION

The present inventions relates to thermoset materials formed via the reaction of epoxides and amine curatives. Such thermosets are generally suitable for applications where thermosets with high flexibility and good hydrolysis resistance are needed. The thermoset materials of the invention may be used generally in the areas of coatings, sealants, adhesives, gaskets, potting, jointing or casting. The thermoset materials of the present invention may also be used in the automotive industry for engine mounts and suspension bushings. In particular, such thermoset materials are prepared from amine curing of epoxy resins containing an epoxy- terminated prepolymer.

The thermoset resins are synthesized as follows: in a first step, an epoxy-terminated prepolymer (a) is formed and in a second step, the prepolymer formed in the first step is combined with one or more additional epoxide and the mixture is cured by an amine to form the final epoxy-based thermoset. For ease of manufacturing the final product, it is desirable that the prepolymer formed is a liquid at ambient conditions to promote flow especially when filling complex molds. In a further embodiment, it is desirable that both the epoxy-terminated prepolymer and amine curing agent are liquid at ambient temperature. The final thermoset contains "soft" structural segments, provided by the polyether. The epoxy portion, when reacted with suitable short polyfunctional amines, provides "hard" structural elements recurring along the ultimate thermoset polymer network.

The epoxy-based thermoset, not including any filler, will generally display a percent elongation of greater than 5. In further embodiments the epoxy-based thermoset will have an elongation of at least 15, 20 or 25 percent.

In a further embodiment, the presence of the soft and hard segments provide for an epoxy-based thermoset having at least one Tg of less of less than 0°C. The term "Tg" is used to mean the glass transition temperature and is measured via Dynamic Mechanical Thermal Analysis. In a further embodiment, the epoxy-based thermoset will have at least one Tg of less than -15°C, -20°C, -30°C, or less than -40°C. In a further embodiment, the epoxy-based thermoset will have at least one Tg of less than -0°C and at least one Tg of greater than 25 °C.

The epoxy based materials can generally be used in environments where the temperatures are up to about 180°C.

The epoxy-based thermosets of the present invention, without the addition of fillers, generally have a thermal conductivity of less than 0.18 W/m*K, as determined by ASTM C518. In a further embodiment, the thermosets of the present invention have a thermal conductivity of less than 0.16 W/m*K. The thermal conductivity may be further reduced with the addition of hollow spheres, such as glass bubbles.

It was unexpected an epoxy-based thermoset would display the toughness needed for various applications, have good hydrolytic stability, display a good cure profile, and have good insulation properties (low thermal conductivity). For instance, it was unexpected that an epoxy- based thermoset could display tensile strength in excess of 12 MPa, while displaying a maximum elongation of greater than 20%.

In the present invention, the epoxy-terminated prepolymer is formed by the reaction of a polyoxyalkyleneamine with a first epoxide or epoxy resin. The polyoxyalkyleneamine may also be referred to as an amine terminated polyether. Generally the polyoxyalkyleneamine will have an average molecular weight of at least 3,000. Generally the polyoxyalkyleneamine will have an average molecular weight of less than 20,000. In a further embodiment the

polyoxyalkyleneamine will have a molecular weight of at least 3,500. The polyether polyols for producing the polyoxyalkyleneamine are generally obtained by addition of a C₂ to C₈ alkylene oxide to an initiator having a nominal functionality of 2 to 6, that is, having 2 to 6 active hydrogen atoms. In further embodiments, the alkylene oxide will contain 2 to 4 carbon atoms such as ethylene oxide, propylene oxide, butylene oxide and mixtures thereof. When two or more oxides are used, they may be present as random mixtures or as blocks of one or the other polyether. In a preferred embodiment the polyether polyol will be liquid at room temperatures. In a further embodiment the ethylene oxide content of the polyether polyol will be less than 30, less than 25, less than 20 or less than 15 weight percent ethylene oxide. In one embodiment the polyether polyol is a poly(oxypropylene) polyol. Catalysis for polymerization of alkylene oxide to an initiator can be either anionic or cationic. Commonly used catalysts for polymerization of alkylene oxides include KOH, CsOH, boron trifluoride, a double cyanide complex (DMC) catalyst such as zinc hexacyanocobaltate or quaternary phosphazenium compound.

Examples of commonly used initiators include glycerol, trimethylol propane, sucrose, sorbitol, pentaerythritol, ethylene diamine and aminoalcohols, such as, ethanolamine, diethanolamine, and triethanolamine. In a further embodiment the initiator for the polyether contains from 3 to 4 active hydrogen atoms. In a further embodiment, the initiator is a polyhydric initiator.

The polyols will have an equivalent weight of at least about 500 and preferably at least about 750 up to about 1,500 or up to about 2,000. In one embodiment, polyether polyols having a molecular weight of 4,000 and above, based on trihydric initiators are used.

The conversion of the polyether to a polyoxyalkyleneamine can be done by methods known in the art. For example by reductive amination, as described, for example in USP 3,654,370, the contents of which are incorporated by reference.

Polyoxyalkyleneamines may be represented by the general formula

wherein R is the nucleus of an oxyalkylation-susceptible initiator containing 2-12 carbon atoms and 2 to 8 active hydrogen groups, U is an alkyl group containing 1-4 carbon atoms, T and V are independently hydrogen or U, n is number selected to provide a polyol having a molecular weight of as described above and m is an integer of 2 to 8 corresponding to the number of active hydrogen groups originally present in the initiator. In one embodiment, n will have a value of 35 to 100. In a further embodiment R has 2 to 6 or 2 to 4 active hydrogen groups. In another embodiment, the active hydrogen groups are hydroxyl groups. In another embodiment, R is an aliphatic polyhydric initiator. In a further embodiment, R has 3 active hydrogen groups. In further embodiments, n will be less than 90, less than 80, less than 75, or less than 65. In a further embodiment U, T and V are each methyl. Based on the molecular weight of the polyol, the polyoxyalkyleneamine will generally have an amine equivalent weight of from about 900 to about 4,000. In a further embodiment the amine equivalent weight will be less than 3,000. In the practice of this invention, a single molecular weight polyoxyalkyleneamine may be used. Also, mixtures of different polyoxyalkyleneamines, such as mixtures of tri- and higher functional materials and/or different molecular weight or different chemical composition materials, may be used.

Suitable polyoxyalkyleneamines commercially available are, for example;

JEFF AMINE™ D4000 and JEFF AMINE T5000 form Huntsman Corporation.

The first epoxide or epoxy resins used in producing the epoxy terminated prepolymers (a) are compounds containing at least one vicinal epoxy group. The epoxy resin may be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic and may be substituted. The epoxy resin may also be monomeric or polymeric.

In one embodiment, the epoxy resin component is a polyepoxide. Polyepoxide as used herein refers to a compound or mixture of compounds wherein at least one of the compounds contains more than one epoxy moiety. Polyepoxide as used herein also includes advanced or partially advanced epoxy resins, that is, the reaction of a polyepoxide and a chain extender, wherein the resulting epoxy reaction product has, on average, more than one unreacted epoxide unit per molecule. The epoxy resin component may be a solid or liquid at ambient temperature (10°C and above). Generally, a "solid epoxy resin" or "SER" is an epoxy-functional resin that has a Tg generally greater than about 30°C. While the epoxy resin may be a solid, the final epoxy terminated prepolymer will be a liquid at ambient temperature. For ease of handling, in one embodiment the epoxy resin is a liquid at ambient temperatures.

In one embodiment the epoxy resin may be represented by the formula

wherein R⁵ is C₆ to Cis substituted or unsubstituted aromatic, a d to CM, preferably d to Q alphatic, or cycloaliphatic; or heterocyclic polyvalent group and b has an average value of from 1 to 8, preferably from 1 to 4.

Aliphatic poly epoxides may be prepared from the known reaction of epihalohydrins and polyglycols. Examples of aliphatic epoxides include trimethylpropane epoxide and diglycidyl- 1,2-cyclohexane dicarboxylate.

Other epoxies which can be employed herein include, epoxy resins such as, for example, the glycidyl ethers of polyhydric phenols or epoxy resins prepared from an epihalohydrin and a phenol or phenol type compound.

The phenol type compound includes compounds having an average of more than one aromatic hydroxyl group per molecule. Examples of phenol type compounds include dihydroxy phenols, biphenols, bisphenols, halogenated biphenols, halogenated bisphenols, hydrogenated bisphenols, alkylated biphenols, alkylated bisphenols, trisphenols, phenol-aldehyde resins, novolac resins (i.e. the reaction product of phenols and simple aldehydes, preferably formaldehyde), halogenated phenol-aldehyde novolac resins, substituted phenol-aldehyde novolac resins, phenol-hydrocarbon resins, substituted phenol-hydrocarbon resins, phenol- hydroxybenzaldehyde resins, alkylated phenol- hydroxybenzaldehyde resins, hydrocarbon- phenol resins, hydrocarbon- halogenated phenol resins, hydrocarbon-alkylated phenol resins, or combinations thereof.

Examples of bisphenol A based epoxy resins useful in the present invention include commercially available resins such as D.E.R.™ 300 series and D.E.R. 600 series, commercially available from The Dow Chemical Company. Examples of epoxy novolac resins useful in the present invention include commercially available resins such as D.E.N.™ 400 series, commercially available from The Dow Chemical Company.

In a further embodiment, the epoxy resin compounds may be a resin from an epihalohydrin and resorcinol, catechol, hydroquinone, biphenol, bisphenol A, bisphenol AP (l,l-bis(4-hydroxyphenyl)-l -phenyl ethane), bisphenol F, bisphenol K, bisphenol S, tetrabromobisphenol A, phenol-formaldehyde novolac resins, alkyl substituted phenol- formaldehyde resins, phenol- hydroxybenzaldehyde resins, cresol-hydroxybenzaldehyde resins, dicyclopentadiene-phenol resins, dicyclopentadiene-substituted phenol resins,

tetramethylbiphenol, tetramethyl-tetrabromobiphenol, tetramethyltribromobiphenol, tetrachlorobisphenol A, or combinations thereof.

In another embodiment, the epoxy resin includes those resins produced from an epihalohydrin and an amine. Suitable amines include diaminodiphenylmethane, aminophenol, xylene diamine, anilines, and the like, or combinations thereof.

In another embodiment, include those resins produced from an epihalohydrin and a carboxylic acid. Suitable carboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, tetrahydro- and/or hexahydrophthalic acid, endomethylenetetrahydrophthalic acid, isophthalic acid, methylhexahydrophthalic acid, and the like or combinations thereof.

Other useful epoxide compounds which can be used in the practice of the present invention are cycloaliphatic epoxides. A cycloaliphatic epoxide consists of a saturated carbon ring having an epoxy oxygen bonded to two vicinal atoms in the carbon ring for example as illustrated by the following general formula:

wherein R⁵ and b are as defined above.

The cycloaliphatic epoxide may be a monoepoxide, a diepoxide, a polyepoxide, or a mixture of those. For example, any of the cycloaliphatic epoxide described in USP 3,686,359, incorporated herein by reference, may be used in the present invention. As an illustration, the cycloaliphatic epoxides that may be used in the present invention include, for example, (3,4- epoxycyclohexyl-methyl)-3 ,4-epoxy-cyclohexane carboxylate, bis-(3 ,4-epoxycyclohexyl) adipate, vinylcyclohexene monoxide and mixtures thereof.

Another class of epoxy resins useful in the present invention are based on divinylarene oxide product illustrated generall s I -IV as follows

Structure I

Structure II

In the above Structures I, II, III and IV of the divinylarene dioxide product of the present invention, each R¹, R², R³ and R⁴ individually may be hydrogen, an alkyl, cycloalkyl, an aryl or an aralkyl group; or a oxidant-resistant group including for example a halogen, a nitro, an isocyanate, or an RO group, wherein R may be an alkyl, aryl or aralkyl; x may be an integer of 0 to 4; y may be an integer greater than or equal to 2; x+y may be an integer less than or equal to 6; z may be an integer of 0 to 6; and z+y may be an integer less than or equal to 8; and Ar is an arene fragment including for example, 1,3-phenylene group.

In certain embodiments of the divinylarene dioxide products the alkyl moiety will have from 1 to 36 carbon atoms. In further embodiments the alkyl will have less than 24, or less than 18 carbon atoms. In further embodiments the alkyl will have from 1 to 8 or from 1 to 6 carbon atoms. Similarly the cycloalkyl will contain from 5 to 36 carbon atoms. Generally the cycloalkyl will contain from 5 to 24 carbon atoms.

The aryl moiety present in the divinylarene dioxide will generally contain 12 carbon atoms or less. An aralkyl group will generally contain 6 to 20 carbon atoms. The divinylarene dioxide product produced by the process of the present invention may include for example alkyl-vinyl-arene monoxides depending on the presence of alkylvinylarene in the starting material.

In one embodiment of the present invention, the divinylarene dioxide produced by the process of the present invention may include for example divinylbenzene dioxide,

divinylnaphthalene dioxide, divinylbiphenyl dioxide, divinyldiphenylether dioxide, and mixtures thereof.

Optionally, the epoxy resin may also contain a halogenated or halogen-containing epoxy resin compound. Halogen-containing epoxy resins are compounds containing at least one vicinal epoxy group and at least one halogen. The halogen can be, for example, chlorine or bromine, and is preferably bromine. Examples of halogen-containing epoxy resins useful in the present invention include diglycidyl ether of tetrabromobisphenol A and derivatives thereof. Examples of the epoxy resin useful in the present invention include commercially available resins such as D.E.R. 500 series, commercially available from The Dow Chemical Company.

In general, the epoxy resin has a number average molecular weight of less than 20,000, preferably less than 10,000, and more preferably less than 8,000. Generally, the epoxy resins useful in the present invention have an average molecular weight of from about 200 to about 10,000, preferably from about 200 to about 5,000, and more preferably from about 200 to about 1,000.

The epoxide equivalent weight of the epoxy resins is generally from about 100 to about

8000 and more preferably from about 100 to about 4000. As used herein the terms "epoxide equivalent weight" ("EEW") refers to the average molecular weight of the polyepoxide molecule divided by the average number of oxirane groups present in the molecule. The diepoxides useful in the present invention are the epoxy resins having an epoxy equivalent weight of from about 100 to about 500.

The relative amount of epoxy resin employed to make the prepolymer can be varied over wide ranges. Generally the epoxy resin used should be at present in a ratio of at least 3 epoxy groups per amino hydrogen atoms to avoid prepolymer gelling. In further embodiments the ratio of oxirane moieties per amine hydrogen is at least 5, at least 10 and generally up to 20 to 1. In one embodiment, the prepolymer is formed by reacting no less than 4 moles of polyepoxide resin per mole of diamine at temperatures in the range of about 80°C for not less than 1 hour with constant stirring. Exact temperatures and duration depend on the reactivity of the polyepoxide resins being utilized.

The conditions for reaction of the epoxy resin with the polyoxyalkyleneamine are well known in the art. Generally, when using a polyoxyalkyleneamine and epoxy resin which a liquid at ambient temperatures, no solvent is needed. To promote the reaction, the mixture of polyoxyalkyleneamine and epoxy resin is heated to between 70 to 150°C for sufficient time to react the reactive hydrogen atoms available. Optionally the reaction may be carried out in the presence of conventional catalysts that promote the reaction between amines and epoxides. Optionally the reaction may be carried out in the presence of solvents suitable for dissolving the amine and/or epoxy.

In one embodiment, the final epoxy-terminated prepolymer will be a liquid at ambient temperature, that is, generally a liquid at 25 °C and above. In a further embodiment, the epoxy- terminated prepolymer will be a liquid at 20°C and above. In another embodiment the epoxy- terminated prepolymer will be a liquid at 15°C and above. By liquid, it is inferred that the material is pourable or pumpable.

The liquid epoxy-terminated prepolymer (a) is present in the reaction mixture in an amount of equal to or greater than 40 weight percent, preferably equal to or greater than 45 weight percent, and more preferably equal to or greater than 50 weight percent based on the total weight of components (a), (b), and (c), if present. The liquid epoxy-terminated prepolymer (a) is present in the reaction mixture in an amount of equal to or less than 99 weight percent, preferably equal to or less than 95 weight percent, and more preferably equal to or less than 90 weight percent based on the total weight of the components (a), (b), and (c), if present.

In the second step of making the epoxy based thermoset of the present invention, the epoxy prepolymer (a); a short chain polyalkylene glycol diglycidyl ether (b), preferably a short chain polyalkylene glycol diglycidyl ether having a molecular weight from 185 to 790; and optionally a second epoxide (c) such as those disclosed herein above, preferably a liquid epoxy resin having an equivalent weight of 75 grams/equivalent to 210 grams/equivalent, wherein the second epoxide may be the same or different from the first epoxide, are reacted with an amine terminated curing agent. The amine curing agent is a monoamine or a polyamine having an equivalent weight of less than 200 and having 2 to 5 active hydrogen atoms. Generally the amine curing agent will have an equivalent weight of at least 20. The amino equivalent weight means the molecular weight of the curing agent divided by the number of amine active hydrogen atoms. In a further embodiment, the amine or polyamine has from 2 to 4 active hydrogen atoms. In yet another embodiment, the amine curing agent has 4 amino active hydrogen atoms.

The amine curing agent is generally added to provide 0.8 to 1.5 amine equivalents (NH) per epoxy reactive group. In a further embodiment the ratio is from 0.9 to 1.1.

Examples of suitable amine curing agents for use in the present invention include those represented by the following formula:

wherein R⁷, Q, X, and Y at each occurrence are independently H, d toCw aliphatic, C3 to C10 cycloaliphatic, or C6 to C14 aromatic or X and Y can link to form a cyclic structure;

Z is O, C, S, N, or P;

c is 1 to 8;

and

p is 1 to 3 depending on the valence of Z.

In one embodiment Z is oxygen. In a further embodiment Z is oxygen and R⁷ is hydrogen. In another embodiment X and Y are both hydrogen.

Cyclic diamines, as represented by the following formula, may also be used curing agents in the present invention:

Aromatic amine curing agents may also be used such as toluene -2,4-diamine; toluene- 2,6-diamine, isomers of phenylene diamine; aniline; and the like.

In another embodiment the amine curing agent can be the steric and geometric isomers of isophorone diamine, bis(aminomethyl) cyclohexane, methylcyclohexane diamine, or cyclohexane diamine.

Examples of specific amine-terminated curing agents include: monoethanolamine; 1- amino-2-propanol; l-amino-3-propanol; l-amino-2-butanol; 2-amino-l-butanol; isophorone diamine; methylcyclohexane diamine; l,3-bis(aminomethyl) cyclohexane; piperazine;

aminoethylpiperazine; homopiperazine; butylamine; ethylene diamine; hexamethylene diamine; and mixtures thereof. In one embodiment the amine curing agent is an isophorone diamine.

In yet another embodiment the amine curing agent is combination of isophorone diamine and aminoethylpiperazine.

In a further embodiment, amine terminated polyethers having an equivalent weight of less than 200, such as JEFF AMINE D400 from Huntsman Chemical Company. In certain embodiments, the curing may contain a combination of an aliphatic and an aromatic curing agent to have a staged curing process. The combination of amine curing agents allows a first curing step, generally done at 70°C to 80°C whereby the aliphatic amine reacts with the epoxy moiety to form a prepreg, and a second curing step done at temperatures above 80°C for curing with the aromatic amine.

Component (b), a short chain polyalkylene glycol diglycidyl ether, is added with the prepolymer in the second step. Preferred short chain polyalkylene glycol diglycidyl ethers for use in the reaction mixture of the present invention are represented by the following formula:

wherein R⁶ is H or Ci to C3 aliphatic group and d has an average value from 1 to 12.

Suitable short chain polyalkylene glycol diglycidyl ethers include diglycidyl ether of poly

(butylene glycol), glycidyl ethers of poly (propylene glycol) or glycidyl ethers of poly (ethylene glycol), preferably the short chain polyalkylene glycol diglycidyl ether is poly (propylene glycol) diglycidyl ether. Preferably, the short chain polyalkylene glycol diglycidyl ether has molecular weight from 185 to 790. More preferably, the short chain polyalkylene glycol diglycidal ether has molecular weight from 350 to 650.

Preferably the ratio of the molecular weight of the polyoxyalkyleneamine to the molecular weight of the polyalkylene glycol diglycidal ether is in the range of 6 to 12, more preferably in the range of 8 to 10.

In one embodiment of the present invention, the short chain polyalkylene glycol diglycidyl ether is poly (propylene glycol) having molecular weight from 185 to 790. In a further embodiment of the present invention, the poly (propylene glycol) has a molecular weight from 350 to 650.

The short chain polyalkylene glycol diglycidyl ether (b) is added in an amount of equal to or greater than 1 weight percent, preferably equal to or greater than 5 weight percent, and more preferably equal to or greater than 10 weight percent based on the total weight of components (a), (b), and (c), if present. The short chain polyalkylene glycol diglycidyl ether (b) is added in an amount of equal to or less than 40 weight percent, preferably equal to or less than 30 weight percent, and more preferably equal to or less than 20 weight percent based on the total weight of components (a), (b), and (c), if present.

The second epoxide (c), if added, is added in an amount of equal to or greater than 1 weight percent, preferably equal to or greater than 5 weight percent, and more preferably equal to or greater than 10 weight percent based on the total weight of components (a), (b), and (c), if present. The second epoxide (c) is added in an amount of equal to or less than 45 weight percent, preferably equal to or less than 35 weight percent, and more preferably equal to or less than 25 weight percent based on the total weight of components (a), (b), and (c), if present.

If desired, one or more other additives which may be used with the thermosets of the present invention include catalysts, flame retarding agents, plasticizers, antioxidants, UV stabilizers, adhesion promoters, dyes, pigments, reinforcing agents, and fillers (d) such as wollastonite, barites, mica, feldspar, talc, silica, crystalline silica, fused silica, fumed silica, glass, metal powders, carbon nanotubes, graphene, calcium carbonate, or glass beads.

The other additive(s), for example a filler (d), if present is added in an amount of equal to or greater than 1 part by weight, preferably equal to or greater than 5 parts by weight, and more preferably equal to or greater than 10 parts by weight wherein parts are based on 100 parts of components (a), (b), and (c), if present. The other additive(s), for example a filler (d), if present is added in an amount of equal to or less than 40 parts by weight, preferably equal to or less than 30 parts by weight, and more preferably equal to or less than 20 parts by weight wherein parts are based on 100 parts of components (a), (b), and (c), if present.

Optionally, one or more acrylate monomer (f) may be added with the prepolymer in the second step. Preferably, the acrylate has an acrylate equivalent weight of 85 grams/equivalent to 160 grams/equivalent. Acrylate equivalent weight may be calculated by dividing the molecular weight of the acrylate component by the number of acrylate moieties present in the acrylate component. For one or more embodiments, the acrylate component is limited exclusively to polyfunctional acrylates, e.g., compounds having two or more vinyl groups.

For one or more embodiments, the polyfunctional acrylate is selected from the group consisting of hexanediol diacrylate, tripropylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, Methylene glycol diacrylate, 1,4-butanediol diacrylate, dipropylene glycol diacrylate, neopenyl glycol diacrylate, cyclohexane dimethanol diacrylate, pentaerythritol triacrylate, diptenaerythritol pentaacrylate and combinations thereof. Acrylate equivalent weight of these polyfunctional acrylates is: 113 grams/equivalent (hexanediol diacrylate), 150 grams/equivalent (tripropylene glycol diacrylate), 107 grams/equivalent (diethylene glycol diacrylate), 99 grams/equivalent (trimethylolpropane triacrylate), 129 grams/equivalent (Methylene glycol diacrylate), 99 grams/equivalent (1,4-butanediol diacrylate), 121 grams/equivalent (dipropylene glycol diacrylate), 106 grams/equivalent (neopenyl glycol diacrylate), 126 grams/equivalent (cyclohexane dimethanol diacrylate), 99 grams/equivalent (pentaerythritol triacrylate), and 105 grams/equivalent (diptenaerythritol pentaacrylate). When present, the acrylate monomer is present in an amount equal to or greater than 0.1 part per hundred (pph), preferably equal to or greater than 1 pph, and more preferably equal to or greater than 5 pph based on the total amount of epoxide in the reaction mixture. When present, the acrylate monomer is present in an amount equal to or less 30 pph, preferably equal to or less than 20 pph, more preferably equal to or less than 15 pph, even more preferably equal to or less than 12 pph based on the total amount of epoxide in the reaction mixture.

In another aspect of the present invention, a process for providing an epoxy based material coating on a surface is provided. The process comprises the steps of

providing a surface to be coated; providing an epoxy terminated prepolymer; providing a short chain polyalkylene glycol diglycidyl ether, optionally providing a second epoxide and/or filler, providing an amine terminated curing agent; bringing the epoxy terminate prepolymer, short chain polyalkylene glycol diglycidyl ether, optional second epoxide and/or filler, and amine terminated curing agent, into contact with said surface and reacting said epoxy terminated prepolymer, short chain polyalkylene glycol diglycidyl ether, optional second epoxide and/or filler, and amine terminated curing agent thereby providing an epoxy based coating.

The epoxy based material can be applied as one or more layers to a surface by known methods in the art, such as spraying, brush coating, extrusion, immersion or flooding or by means of rollers or doctor applicators. The epoxy based material is suitable for formation of coating on essentially any surface, such as metals, plastics, wood, concrete, asphalt or glass. The epoxy based materials of the present invention may be used in conjunction with other layers, such as an anticorrosion layer or adhesion promoting layer. The thermosets of the present invention may also comprise at least one layer of a multi-layered composite or coating. For example, the epoxy based materials may be combined with one or more additional layer of material, such as a paint, a silicone, a polyurethane, an epoxy, a polyolefin, or combinations thereof.

When used as a coating, the coating provided may have a thickness in the range up to 10 mm, typically in the range of 0.1 to 10 mm. In a further embodiment the coating will have a density of more than 0.5 g/cm³.

The epoxy based material may also be used in cast molding for the production of molded article such as wheels or automotive parts. In production of such materials, the epoxy terminated prepolymer, the short chain polyalkylene glycol diglycidyl ether, optional second epoxide and/or filler, the curing agent, and any additional additives are introduced into a mold, the mold is closed and the reaction mixture is allowed to cure. In such applications, the mold is generally heated to between 80°C and 120°C. The following examples are provided to illustrate the invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated.

EXAMPLES

Example 1 Production of Epoxy Terminated Prepolymer

A 20 gallon stainless steel reactor is charged with 49.6 kg of D.E.R. 383 liquid epoxy resin, a reaction product of epichlorohydrin and bisphenol A, available from The Dow Chemical Company (epoxy equivalent weight = 180.1 g/mol) with agitation followed by addition of 52.3 kg of JEFF AMINE T5000 polyoxyalkyleneamine, a polyoxypropylene triamine with a nominal molar mass of 5000g/mol available from Huntsman Corporation (amine equivalent weight = 952 g/mol). The vessel is degassed, padded with nitrogen and the temperature slowly increased to 125 °C via a heated jacket. The internal temperature is maintained at 120°C and held for three hours. The vessel is then cooled to 80°C, the agitator stopped and the sample discharged. The epoxy terminated prepolymer is found to be a viscous liquid at 25 °C (approximately 90,000 cPs) with a measurable epoxy equivalent weight of 412 g/mol (463 actual).

Examples 2 and 3. Thermoset Polymer Preparation

The epoxy terminated prepolymer prepared in Example 1, additional amount of the D.E.R. 736, which is a polyalkyleneglycol diglycidylether available from The Dow Chemical Company and DE 383 epoxy resin are added to lidded cups suitable for use in a FLACKTEK SPEEDMIXER™ and the sample mixed for 15 seconds at 800 rpm, then mixed at 2350 rpm for 2 minute and then heated in a 50°C oven. Then amine curing agent is added according to the formulations in the Table 1 , the values are in parts by weight. Either isophorone diamine available from Evoniks as Versamid IPDA is used.

Table 1

* C 1 is not an example of the invention After addition of the curing agent, the samples are mixed on a FLACKTEK

SPEEDMIXER for 15 seconds at 800 rpm followed by 2350 rpm for 2 minute. The mixtures are then poured into closed aluminum molds that are preheated to 50°C. The molds are placed back into the oven and allowed to cure for approximately 12 hours at 120°C, demolded, and cooled to room temperature for 24 hours. Tensile properties are then measured according to ASTM D412 and thermal properties are measured via Dynamic Mechanical Thermal Analysis on either TA Instruments ARES G2 or ARES instruments. Frequency of 1 Hz and a heating rate 5°C/min is used to heat the samples from -100°C to 180°C and this cycle is repeated twice. The measured properties of the produced polymers are given in Table 2.

The results show the use of additional epoxide (D.E.R. 383) and polyalkyleneglycol diglycidylether (D.E.R. 736) improves tensile strength and Young's Modulus while preserving thermal properties and incurring only a small loss in elongation at break of the produced thermosets.

Table 2

Examples 4 and 5

The epoxy terminated prepolymer prepared in Example 1, additional amount of the D.E.R. 736 and resorcinol diglycidylether, which is an epoxy resin available from CVC Thermoset Specialties as ERISYS™ RDGE are added to lidded cups suitable for use in a FLACKTEK SPEEDMIXER and the sample mixed for 15 seconds at 800 rpm, then mixed at 2350 rpm for 2 minute and then heated in a 50°C oven. Then l,3-bis(aminomethyl) cyclohexane, an amine curing agent available from Mitsubishi Gas Chemical Company is added according to the formulations shown in the Table 3, the values are in parts by weight. Table 3

After addition of the curing agent, the samples are mixed on a FLACKTEK

SPEEDMIXER for 15 seconds at 800 rpm followed by 2350 rpm for 2 minute. The mixtures are then poured into closed aluminum molds that are preheated to 50°C. The molds are placed back into the oven and allowed to cure for approximately 12 hours at 120°C, demolded and cooled to room temperature for 24 hours. Tensile properties are then measured according to ASTM D412 and thermal properties are measured via Dynamic Mechanical Thermal Analysis on either TA Instruments ARES G2 or ARES instruments. Frequency of 1 Hz and a heating rate 5°C/min is used to heat the samples from -100°C to 180°C and this cycle is repeated twice. The measured properties of the produced polymers are given in Table 4.

Table 4

The results show the use of additional epoxide (resorcinol diglycidylether) and especially polyalkyleneglycol diglycidylether (D.E.R. 736) improves tensile strength and Young's Modulus while preserving thermal properties and incurring only a small loss in elongation at break of the produced thermosets.

Examples 6 to 9 Exotherm Results

The epoxy terminated prepolymer prepared in Example 1, additional amount of the polyalkyleneglycol diglycidylether, D.E.R. 736, D.E.R. 383 epoxy resin, and a diacrylate monomer are added to gallon pails suitable for use in a STATEMIX mixer and the sample mixed for 2 minutes at 1000 rpm and then allowed to cool down. Then amine curative agent(s) are added according to the formulations shown in the Table 5, the values are in parts by weight. Aminoethylpiperazine is available from The Dow Chemical Company and 1 ,6-hexanediol diacrylate and trimethylolpropane triacrylate is available from Sartomer Americas as SR238 and SR351.

After addition of the curing agent, the samples are mixed on the STATEMIX mixer for 2 minutes at 1000 rpm. The mixtures are then poured into an open stainless steel container of 7 inch diameter, such that the height of the resin in the container is approximately 4 inches. A thermometer is held in place such that its sensing junction is approximately at the center of the resin, measuring the core temperature. An additional thermometer is placed outside the container at approximately 2 inch height from the bottom, measuring the wall temperature. Temperatures at these locations are continuously recorded. The maximum temperature recorded and the time interval at which it occurred measured from the time when the mixing of the resin and the curative agent is initiated are given in Table 6.

Table 5

Table 6

The results show the use of additional acrylate monomer (Examples 6 to 8) reduces the maximum exotherm temperature achieved when compared to Example 9 where no acrylate monomer is used. In addition, use of the difunctional acrylate 1,6-hexanediol diacrylate (HDD A) increases the time taken achieve the maximum temperature whereas the use of the trifunctional acrylate reduces the time taken to achieve maximum temperature. In addition, the moldings of Examples 6 to 8 (containing an acrylate monomer) show no surface defects such as wilting and fingering, which are otherwise evident in moldings prepared from Examples 2 and 9 (not containing an acrylate monomer).

Claims

claimed is:

A thermoset comprising the reaction product of

(a) from 50 to 95 weight percent of an ambient temperature liquid epoxy-terminated prepolymer formed by reacting a polyoxyalkyleneamine having a molecular weight of from 3,000 to 20,000 with an excess of a first epoxide, wherein the

polyoxyalkylene

m

wherein R is the nucleus of an oxyalkylation-susceptible initiator containing 2-12 carbon atoms and 2 to 8 active hydrogen groups,

U is an alkyl group containing 1-4 carbon atoms,

T and V are independently hydrogen or U,

n is number selected to provide a polyol having a molecular weight of 2,900 to

29,500,

and

m is an integer of 2 to 8 corresponding to the number of active hydrogen,

(b) from 5 to 30 weight percent of a short chain polyalkylene glycol diglycidyl ether of molecular weight between the range of 185 to 790,

(c) optionally a second epoxide, which can be the same or different from the first epoxide, having an equivalent weight of 75 grams/equivalent to 210 grams/equivalent, in an amount of 0 to 45 weight percent,

(d) optionally a filler in an amount of 0 to 30 parts by weight wherein parts are based on 100 parts of components (a), (b), and (c), if present,

and

(e) a curing agent comprising at least one amine or polyamine having an equivalent weight of less than 200 and having 2 to 5 active hydrogen atoms,

wherein weight percents are based on the total weight of components (a), (b), and (c), if present.

2. The thermoset of Claim 1 wherein U is an alkyl group containing 1 or 2 carbon groups and T and V are independently hydrogen or an alkyl group containing one carbon.

3. The thermoset of Claim 1 wherein the first epoxide is at least one or more of the formula

wherein R⁵ is C6 to Cis substituted or unsubstituted aromatic, a Ci to Cs aliphatic, or cycloaliphatic; or heterocyclic polyvalent group and b has an average value of from 1 to 8.

4. The thermoset of Claim 3 wherein the first epoxide is one or more of diglycidyl ethers of resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (l,l-bis(4- hydroxylphenyl)-l -phenyl ethane), bisphenol F, bisphenol K, bisphenol S, tetrabromobisphenol A, phenol-formaldehyde novolac resins, alkyl substituted phenol-formaldehyde resins, phenol- hydroxybenzaldehyde resins, cresol-hydroxybenzaldehyde resins, dicyclopentadiene -phenol resins, dicyclopentadiene-substituted phenol resins tetramethylbiphenol, tetramethyl- tetrabromobiphenol, tetramethyltribromobiphenol, tetrachlorobisphenol A, or combinations thereof.

5. The thermoset of Claim 3 wherein the first epoxide is at least one cycloaliphatic epoxide of the formula

6. The thermoset of Claim 1 wherein the first epoxide is one or more divinylarene oxide of the following structures:

Structure I

x is an integer of 0 to 4;

z is an integer of 0 to 6 with the proviso that z+y is an integer less than or equal to 8; and Ar is an arene fragment.

7. The thermoset of Claim 1 wherein the short chain polyalkylene glycol diglycidyl ether is at least one or more of the formula

wherein R⁶ is H or Ci to C3 aliphatic group

and d has an average value from 1 to 12.

8. The thermoset of Claim 7 wherein the short chain polyalkylene glycol diglycidyl ether is poly (propylene glycol) diglycidyl ether having a molecular weight from 185 to 790.

9. The thermoset of Claim 1 wherein the filler is one or more of wollastonite, barites, mica, feldspar, talc, silica, crystalline silica, fused silica, fumed silica, glass, metal powders, carbon nanotubes, graphene, calcium carbonate, or glass beads.

10. The thermoset of Claim 1 wherein the amine curing agent is at least one curing agent represented by the formula:

wherein R⁷, Q, X, and Y at each occurrence are independently H, d to Cu aliphatic, C3 to C10 cycloaliphatic, or C₆ to C_M aromatic or X and Y can link to form a cyclic structure;

Z is O, C, S, N, or P;

c is 1 to 8;

and

p is 1 to 3 depending on the valence of Z.

11. The thermoset of Claim 1 wherein the amine curing agent is represented by the formula

wherein R at each occurrence is independently H or -CH₂CH₂NH₂

and

h is 0 to 2 with the proviso that both h's cannot be 0.

12. A multi-layered composite or coating comprising at least one layer comprising the thermoset of Claim 1.

13. The multi-layer composite or coating of Claim 12 further comprising one or more layer comprising a paint, a silicone, a polyurethane, an epoxy, a polyolefin, or combinations thereof.