GB2159147A - (2-aminoethoxy-ethylamino) alkanols as epoxy curing agents - Google Patents

Abstract

Compounds of the formula HOANHCH2CH2OCH2CH2NH2 wherein A is alkylene having 2 to 4 carbon atoms, are provided, for use as curing agents for epoxy resin compositions. The compounds maybe prepared by reacting NH2CH2CH2OCH2CH2NH2 with an alkylene oxide OCH2CHR (e.g. ethylene oxide).

Description

SPECIFICATION 2-[2-Aminoethoxy-2-ethylamino]alkanol as an epoxy curing agent This invention relates to curable epoxy resins. More particularly it relates to 2-[2-aminoethoxy-2-ethyl- amino]alkanols as curative agents.

Epoxy resins constitute a broad class of polymeric materials having a wide range of physical characteristics. The resins are characterized by epoxide groups which are cured by reaction with certain catalysts or curing agents to provide cured epoxy resin compositions with certain desirable properties. Conventional curing agents include such compounds as polyamines, polycarboxylic acids, anhydrides and Lewis acids.

U.S. Patent Nos. 3,420,828 and 4,338,408 describe the synthesis of bis(aminoethyl) ether derivatives such as 2-[2-aminoethoxy- 2-ethylaminolethanol.

The invention relates to an epoxy resin composition which comprises a polyepoxide and a curative agent of the formula: HOANHCH2CH2OCH2CH2NH2, wherein A is an alkyl of 2 to 4 carbon atoms.

The resin when cured is useful for such applications as decorative coatings, encapsulations, adhesives, laminates, potting compounds, etc.

Part A of the two part composition of the present invention comprises an epoxy base resin typically a polyepoxide. Generally, the epoxy base resin is a vicinal polyepoxide containing compound having an average of at least 1.8 reactive 1,2-epoxy groups per molecule. These polyepoxide materials can be monomeric or polymeric, saturated or unsaturated, aliphatic, cycloaliphatic, aromatic, aromatic or heterocyclic, and may be substituted if desired with other substituents besides the epoxy groups, e.g., hydroxyl groups, ether radicals, aromatic halogen atoms and the like.

Preferred polyepoxides are those of glycidyl ethers prepared by epoxidizing the corresponding alkyl ethers or reacting, by known procedures, a molar excess of epichlorohydrin and an aromatic polyhydroxy compound, i.e., isopropylidene bisphenol, novolac, resorcinol, derivatives of aromatic amines, etc. The epoxy derivatives of methylene or isopropylidene bisphenols are especially preferred. The condensation product of epichlorohydrin with bisphenol A is particularly preferred.

A widely used class of polyepoxides which are useful according to the present invention includes the resinous epoxy polyethers obtained by reacting an epihalohydrin, such as epichlorohydrin, and the like, with either a polyhydric phenol or a polyhydric alcohol. Typically the epoxy resins have an average of at least 1.8 reactive, 1,2-epoxy groups per molecule. An illustrative, but by no means exhaustive, listing of suitawble dihydric phenols includes 4,4'-isopropylidene bisphenol, 2,4'-dihydroxydiphenylethylmethane, 3-3'- dihydroxydiphenyldiethylmethane, 3,4'- dihydroxydiphenylmethylpropylmethane, 2,3' dihydroxydiphenylethylphenylmethane, 4,4'-dihydroxydiphenylpropylphenylmethane, 4,4dihydroxydiphenylbutylphenylmethane, 2,2'-dihydroxydiphenylditolylmethane, 4,4'dihydroxydiphenyltolylmethylmethane and the like.Other polyhydric phenols which may also be co-reacted with an ephihalohydrin to provide these epoxy polyethers are such compounds as resorcinol, hydroquinone, substituted hydroquinones, e.g., methylhydroquinone, and the like.

Among the polyhydric alcohols which can be coreacted with an epihalohydrin to provide these resinous epoxy polyethers are such compounds as ethylene glycol, propylene glycols, butylene glycols, pentane diols, bis-(4-hydroxycyclohexyl)dimethylmethane, 1 ,4-dimethylolbenzene, glycerol, 1 2,6-hexanetriol, trimethylolpropane, mannitol, sorbitol, erythritol, pentaerythritol, their dimers, trimers and higher polymers, e.g., polyethylene glycols, polypropylene glycols, triglycerol, dipentaerythritol and the like, polyallyl alcohol, polyhydric thioethers, such as 2,2'-,3,3'-tetrahydroxydipropylsulfide and the like, mercapto alcohols such as monothioglycerol, dithioglycerol and the like polyhydric alcohol partial esters, such as monostearin, pentaerythritol monoacetate and the like, and halogenated polyhydric alcohols such as the monochlorohydrins of giycerol, sorbitol, pentaerythritol and the like.

Another class of polymeric polyepoxides which can be amine cured and are in accordance with the present invention includes the epoxy novolac resins obtained by reacting, preferably in the presence of a basic catalyst, e.g., sodium or potassium hydroxide, an epihalohydrin, such as epichlorohydrin, with the resinous condensate of an aldehyde, e.g., formaldehyde, and either a monohydric phenol, e.g., phenol itself, or a polyhydric phenol. Further details concerning the nature and preparation of these epoxy novo lac resins can be obtained in Lee, H. and Neville, K., Handbook of Epoxy Resins, McGraw Hill Book Co., New York, 1967.

It will be appreciated by those skilled in the art that the polyepoxide compositions which are useful according to the practice of the present invention are not limited to those containing the above described polyepoxides, but that these polyepoxides are to be considered merely as being representative of the class of polyepoxides as a whole.

Part B of the two part composition of the present invention comprises a novel curative agent and optionally an accelerator. The epoxy resin curative agent of the present invention is of the formula: HOANHCH2CH2OCH2CH2NH2, wherein A is an alkyl of two, three or four carbon atoms. In the Example is shown a synthesis wherein A is an alkyl of two carbon atoms.

The synthesis of these curative agents is described in U.S. Patent Nos. 3,420,828 and 4,338,408 which are incorporated herein in their entirety by reference.

Generally, the reaction proceeds as follows.

Bis(aminoethyl)ether of the formula H2NCH2CH2OCH2CH2NH2 is reacted with an alkylene oxide of the formula OCH2CHR in accordance with the method of U.S. Patent 3,420,828 wherein R is hydrogen or lower alkyl or mixtures thereof to produce a compound of the formula: HOAN HCH2CH2OCH2CH2N H2, wherein A is an alkyl of from 2 to 4 carbon atoms.

The reaction of this invention should be conducted at an elevated temperature. The alkoxylation is preferably conducted in the temperature range from about 50"C to 1500C. The curative can be separated from the other products by distillation. The starting materials are limited to bis-(aminoethyl)ether, alkylene oxide and mixtures of alkylene oxides. The preparation of the unique compounds of this invention is further illustrated by the Example.

The present invention also relates to a process for forming an epoxy resin comprising contacting a polyepoxide with a curative agent, the improvement consisting of contacting a curative agent of the formula: HOANHCH2CH2OCH2CH2NH2, wherein A is an alkyl of from 2 to 4 carbon atoms. A can be an ethyl, propyl, or butyl alkyl or the process may utilize a mixture thereof. By this process a superior series of epoxy resins is produced which finds use in such applications as decorative coatings, encapsulations, adhesives, laminates, potting compounds, etc. The cured epoxy resin is noted for rapid curing and outstanding properties of flexibility impact strength and adhesion as shown in the Example.

In the process of the present invention, the curative agent and optionally an accelerator are mixed to form a compatible solution. The epoxy base resin is added and the components thoroughly contacted by mixing until a homogeneous mixture is obtained.

The curative agent is usually added to the formulation in such an amount that there is one reactive hydrogen atom in the curing component for each epoxy group in the epoxy resin component. These are known as stoichiometric quantities. The stoichiometric quantity can be calculated from the knowledge of the chemical structure and analytical data on the component. Stoichiometry unfortunately is not always calculable. For systems of the present invention, the proper amount of curative is the amount necessary to provide the best desired properties. This amount must be determined experimentally and can be accomplished by routine procedures known in the art. Generally the number of equivalents of reactive curative groups is from about 0.8 to 1.2 times the number of epoxide equivalents present in the curable epoxy resin composition, with from 0.9 to a stoichiometric amount being preferred.The exact amount of constituents in accordance with the above general requirements will depend, as mentioned, primarily on the application for which the cured resin is intended.

For many applications, curing may be accomplished at ambient conditions. For development of optimum achievable properties, however, curing at elevated temperature is necessary. The curing temperature range acceptable in this invention is from about 1200C to about 1800C for about 1 to 3 hours.

Preferably curing is done at about 125"C for 1 to 2 hours.

Optionally, the epoxy resin formulations of the present invention can include an accelerator to speed the amine cure of the epoxy resin. In several applications, an accelerator is beneficial, especially when an epoxy resin is used as an adhesive in flammable environment, thus making prolonged elevated temperature cure inconvenient or even hazardous. Lee, H. and Neville, K., Handbook of Epoxy Resins, pp. 7-14 describes the use of certain amine-containing compounds as epoxy curative agent-accelerators.

Many accelerators are known in the art which can be utilized in accordance with the instant invention.

Examples include salts of phenols; salicylic acids; amine salts of fatty acids such as those disclosed in U.S. Patent No. 2,681,901; and, tertiary amines such as those disclosed in U.S. Patent No. 3,875,072. That accelerator comprises a combination of piperazine and an alkanolamine in a weight ratio of 1:8 to 1:1.

The above amount of accelerator may be admixed with a polyoxyalkylene diamine curative agent in amount of from 10 to 50 parts by weight accelerator to 100 parts by weight of the curing agent.

The following Examples are illustrative of the nature of the instant invention but are not intended to be limitative thereof.

EXAMPLE 1-A Preparation of 2-J2-aminoethoxy-2-ethylaminojethanol A by-product stream from the manufacture of morpholine and 2- (2-aminoethoxy) ethanol, which con tained mostly methoxyethyl morpholine, bis(aminoethyl) ether and aminoethyl morpholine, was reacted as described below with ethylene oxide, and the resulting hydroxyethyl bis(aminoethyl) ether was isolated.

A 16 liter reactor was charged with 7.9 kg. of the by-product stream. this was heated to 80"C. and 0.95 kg. of ethylene oxide were added. The reactants were then digested at 900C for one hour, followed by stripping at 400 Pa vacuum and 125"C. This procedure removed 5.96 kg. of unreacted material. The 2[2aminoethoxy-2-ethylamino]-ethanol was then isolated by passing the mixture through a wiped-film evaporator at 13.3 Pa vacuum and 1800C. Gas chromatographic analysis of by-product stream.

Area percent Water 6.0 Morpholine 1.4 Methoxyethylmorpholine 19.0 Bis(aminoethyl) ether 66.9 Aminoethyl morpholine 4.7 Piperazine/monoethanolamine 1.6 EXAMPLE 1-B Properties of epoxy resin cured with 2[2-aminoethoxy- 2-ethylaminolethanol Formulation: Epoxy resin (EEW 188)1 100 2-[2-2aminoethoxy-2-ethylamino]ethanol 24 Brookfield viscosity, cps. 25"C. 2400 Gel time, mins. (200 g. mass) 23.3 Peak exotherm, "C 184.6 Time to peak temperature, mins. 31.5 Properties of cured 3 mm. casting: 2 Izod impact strength, J/m 74.7 Tensile strength, MPa 64.8 Tensile modulus, MPa 3000 Elongation at break, % 4.1 Flexural strength, MPa 109 Flexural modulus, MPa 3158 HDT, "C, 1.8 MPa/0.45 MPa 60/65 Shore D hardness, 0-10 sec. 90-89 1) Liquid diglycidyl ether of Bishphenol A 2) Cured 2 hours 80"C. 3 hours at 125"C.

EXAMPLE 1-C Thermal Shock Properties: Curing with 2-[aminoethoxy-2- ethylaminojethanol Formulation: Epoxy resin (EEW 188) " 100 pbw.

2-[2-aminoethoxy-2-ethylamino]ethanol 24 pbw.

No. of samples cracked during cycle no.

1 2 3 4 5 6 7 8 9 10 Total 0 0 0 0 0 0 0 0 0 0 0 Thermal cycle: oven at 140"C. (30 minutes), bath at -20 C. (15 mins), room temperature (15 mins). Examined for cracking and, if unchanged, recycled ot oven.

Samples were 50 g. encapsulations of a common steel washer (25 mm o.d., 9.5 mm i.d., 1.6 mm thick) supported by a 6 mm ring of filter paper cut from a Whatman 19 x 19 mm cellulose extraction thimble.

The encapsulations were formed in aluminum evaporating dishes (milk test; 5 cm. dia. x 1 cm. deep).

1) Liquid diglycidyl ether of Bisphenol A. epoxy equivalent weight 188 EXAMPLE 2 TABLE 2 - 1 Analysis of products prepared with variable mole ratio of Bis(amino) ethyl ether (BAEE) and Ethylene oxide rEO) Sample 28 29 30 31 32 Mole Ratio, BAEE/EO 1/1 3/1 5/1 7/1 9/1 Total amine, meq/g. 13.3 16.4 17.3 17.5 17.8 Tertiary amine, meq/g. 1.5 0.48 0.66 0.43 0.32 Secondary amine, meq/g. 4.17 3.7 1.5 1.18 1.42 Primary amine, meq/g. 7.63 12.18 15.18 15.89 16.06 Hydroxyl No. 1103 1124 1122 1151 1158 Gas chromatographic Analysic (area /O) Bis(amino ethyl) ether 16.6 48.4 61.7 68.9 72.9 Aminoethylmorpholine - - - - - Unknown 1.0 0.8 - - Unknown 0.9 1.9 2.3 2.4 2.5 Methoxyethylmorpholine - 0.6 1.6 1.6 1.7 Hydroxyethyl BAEE 38.2 37.0 28.5 23.7 20.1 Bis(Hydroxyethyl) 34.3 9.4 4.3 0.6 0.8 BAEE (total) Unknowns 7.3 - - - - Epoxy equivalent weight 47.7 34.96 30.7 29.97 29.6 TABLE 2 - 2 properties of epoxy resin cured with hydroxyethyl BAEE Samples Formulation: E D C B A EPON 8284 100 100 100 100 100 Hydroxyethyl BAEE" Mole Ratio BAEE/EO.

9/1 (Sample 32) 16 - - - - 7/1 (Sample 31) - 16 - - 5/1 (Sample 30) - - 16 - 3/1 (Sample 29) - - - 18 3/1 (Sample 28) - - - - 26 Brookfield viscosity, cps., 25"C. 600 600 600 750 1400 Gel time, mins, (2009. mass) 25.4 25.8 25.6 23.4 18.5 Peak exothermic temp., "C. 262.0 256.2 254.8 252.5 229.7 Time to peak temperature mins. 30.0 29.0 28.0 26.5 20.5 Properties of cured 3mm Castings:: Izod impact strength, J/m 6.9 10.1 10.1 11.7 12.3 Tensile strength, MPa 63.8 53.1 63.4 60.7 60.7 Tensile modulus, Mpa 2390 2415 2615 2590 2835 Elongation at break, % 7.6 7.4 8 8 6.2 5.0 Flexural strength, MPa 97.9 100.7 101.4 98.6 95.5 Flexural modulus, MPa 2595 2540 2645 2615 2835 HDT, "C., 1.8 MPa/0.45 MPa 93/97.6 94/97.5 89/95 87/91.5 66.5/69 Shore D hardness, 0-10 sec. 77-75 78-75 78-75 76-74 79-75 Adhesive Properties: Tensile shear strength, MPa 23.4 18.6 21.4 22.4 28.3 T-peel strength, N/m 4.0 4.0 3.85 5.1 6.65 1) For analyses, see Table 2-1 2) Cured 2 hours 80"C, 3 hours 125"C.

3) Cured 1 hour at 125"C 4) Shell chem. Co.-diglycidylether of Bisphenol A liquid resin, epoxy equivalent weight 185-190 TABLE 2 - 3 Properties of epoxy resin cured with Hydroxypropyl Bis-(Aminoethyl) ether Formulation: EPON 828 100 Hydroxypropyl BAEE' 34 Properties of Cured 3mm Casting:2 Flexural strength, MPa 110 Flexural modulus, MPa 3100 HDT, "C, 1.8 MPa/0.45 MPa 60/62 Shore D hardness 78-75 1) Analysis:: Total amine 11.4 meq/g Tertiary amine 1.04 meq/g Primary amine 4.73 meq/g Total acetylatables 17.98 meq/g Gas Chromatogram Area % Bis(aminoethyl)ether 2.8 Bis(aminoethyl)ether-1 -propylene 68.5 oxide adduct Bis(aminoethyl)ether-2-propylene 11.2 oxide adduct Unknowns (8 peaks) 17.5 2) Cured 2 hours, 80"C 3 hours 125'C.

Summary of test methods Tensile shear strength, MPa (ASTM Standard Test Method D-1002) T-peel strength, N/m (ASTM Standard Test Method D-1876) Izod impact strength, J/m (ASTM Test D-256) Tensile strength, MPa (ASTM Test D-638) Tensile modulus, MPa (ASTM Test D-638) Elongation of Break, % (ASTM Test D-638) Flexural strength, MPa (ASTM Test D-750) Flexural modulus, MPa (ASTM Test D-790) HDT, 'C, 1.8 MPa/OA5 MPa (ASTM Test D-648) Shore D hardness, 0-10 sec (ASTM Test D-2240) Gel time (Gardco Gel timer; Paul N. Gardner Co.)

Claims (9)

1. An epoxy resin curing agent of the formula: HOANHCH2CH2OCH2CH2NH2, wherein A is alkylene of from 2 to 4 carbon atoms.

2. An epoxy resin composition which comprises: (A) a polyepoxide, and (B) a curing agent fo the formula: HOANHCH2CH2OCH2CH2NH2, wherein a is alkylene of from 2 to 4 carbon atoms.

3. A composition as claimed in Claim 2 which additionally comprises an accelerator.

4. A composition as claimed in Claim 3 wherein the accelerator comprises piperazine and an alkanolamine in a weight ratio of from 1:8 to 1:1.

5. A composition as claimed in any of Claims 2 to 4 wherein the polyepoxide is the condensation product of epichlorohydrin with bisphenol A.

6. A process for forming an epoxy resin which comprises contacting a polyepoxide with a curring agent of the formula: HOANHCH2CH2OCH2CH2NH2, wherein a is alkylene of from 2 to 4 carbon atoms.

7. A curing agent as claimed in Claim 1 and substantially as hereinbefore described with reference to Example 1-A.

8. A composition as claimed in claim 2 and substantially as hereinbefore described with reference to Examples 1 or 2.

9. A process as claimed in Claim 6 and substantially as herein before described with reference to Examples 1 or 2.