CA1111067A - Bis ureide of a polyoxyalkylene polyamine as an epoxy additive - Google Patents

Abstract

ABSTRACT OF THE INVENTION
The properties of epoxy resins are improved by the addition of a bis ureide of a polyoxyalkylene polyamine additive. The improved epoxy resin composition comprises a vicinal polyepoxide, an effective amount of a polyamine or a substituted bicylic vicinal anhydride curing agent, and an effective amount of an additive consisting essentially of a bis ureide of a polyoxyalkylene polyamine, said additive having an average molecular weight of at least 4,000.

Description

~ h~ D.75,613-FB

This invention relates to an additive for increasing the adhesive strength of curable epoxy resin compositions, and to epoxy resin composit:ions containing such an additive.
The additive is a bis ureide of a polyoxyalkylene polyamine.
Epoxy resins have a broad range of physical character-istics and, because of this, they have many industrial applications. Epoxy resins have at least one epoxy group and can be converted into a thermoset form having desirable properties. The epoxy groups may be cured by the use of a catalyst or a curing agent, and curing may be accelerated by the addition of small but effective amounts of accelerat-ing agents.
There are many different types of curing agents.
Amines and, more specifically, aliphatic amines are one - 15 commonly employed group of curing agents. Examples include - diethylenetriamine, triethylenetetramine and polyoxyalkylene polyamines, such as polyoxypropylene-diamines and -triamines.
Another class of curing agents comprises the anhy-drides. The most common of these anhydride curing agents are difunctional compounds such as maleic anhydride and phthalic anhydride, and tetrafunctional materials, such as pyromellitic dianhydride.
Epoxy resins which are used for casting, embedding or encapsulating must have the ability to withstand repeated cycles of high and low temperatures without cracking. As the temperature decreases, the stress increases, due to shrinkage, since the lowering of the temperature reduces the ability of the resin to flow and relieve the stress.
; Anhydride-cured resins are most useful in applications requiring high heat deflection. However, anhydride-cured resins are generally brittle and, thus, have a low resistance to thermal shock. Diluents and modifiers do improve the resistance to thermal shock, but these materials adversely affect the heat deflection properties, as shown in May and 35 Tanaka, EPOYY RESINS, New York, 1973, p. 299. Similarly, plasticizers have not been widely used with epoxy resins because most are incompatible with the cured resins.
The physical properties of epoxy resin compositions :

- have been improved by using co-curing agents such as those de-scribed in United States Patent No. 3,549,592. Ureas and sub-stituted ureas have been utilized as epoxy curing agents, co-curing agents and curing accelerators. These urea and substituted urea compounds have been disclosed in United States Patents Nos.
3,294,749; 2,713,569; 3,386,956; 3,386,955; 2,855,372; and 3,639,338.
Compounds having a single terminal ureido group have been disclosed in United States Patents Nos. 2,145,242 and 3,965,072.
`- 10 Our prior Canadian applications Nos. 290,993 and 291,074 disclose that a diureide-terminated polyoxyalkylene material hav-ing a molecular ~eight of 2,000 to 3,000 or an amine-terminated - polyether ureylene having a molecular weight of 4,000 to 4,500 may be employed as an epoxy additive to improve the adhesive strength of amine-cured or anhydride-cured epoxy resin compositions.
The present invention provides a composition useful for increasing the adhesive strength of an amine-cured epoxy resin, or thermal shock resistance of an anhydride-cured epoxy resin.
In particular, the invention provides an additive for curable epoxy resin compositions which comprises a bis ureide of a poly-oxyalkylene polyamine having the formula:

: y Y

C (NH - Z - NH - C ~ X)2 wherein X is hydrogen or a primary amino group; Y is oxygen or sulfur; and Z ~s a polyoxyalkylene group of such a molecular weight that the additive has an average molecular weight of at least 4,000.

Surprisingly, smaller quantities of this additive are ~' required to improve the adhesive strength of amine-cured resins . than are required when the additive of Canadian Application No.
: 290,993 is employed.
The present invention also provides a curable epoxy resin composition which comprises:
(i) a vicinal polyepoxide having an epoxide equivalency of more than 1.8;

- 2a -~3 ' . .

:`~
- (ii) a curing agent comprising a polyamine having at least three reactive amino hydrogen atoms or a substituted bicyclic vicinal anhydride; and (iii) an agent as defined above.
In one preferred embodiment, the additive is a bis (acyl) polyoxypropylene diamine having an average molecular weight of about 4,000.
In another preferred embodiment, the additive is a bis (thio) polyoxypropylene diamine having a molecular weiaht of about 4,000.
It should be noted that the expression "average molec-ular weight" is used because the chain length of the polymeric - portion, e.g., the polyoxyalkylene portion of a polyamine, may vary. Accordingly, that terminology provides a more accurate description of each composition.
The bis ureide compounds are formed by the reaction of urea or a mono-substituted urea (or corresponding thioureas) with a polyoxyalkylene polyamine having a molecular weight such that the bis ureide product has an average molecular weight of at least 4,000. The reactants should be mixed in a molar ratio of 2 to 3; that is, 2 moles of the polyoxyalkylene polyamine to 3 moles of urea or a mono-substituted urea com-pound should be reacted. Generally, the reaction can take place at ambient pressure and at temperatures from 25C to 150c In a preferred embodiment of the invention, the bis ureide additives are formed by reacting urea with polyoxy-alkylene diamines of the formula:
/H2N (IH IH-o)n-72-z wherein X is hydrogen, methyl, or ethyl; Z is alkylene having from 2 to 5 carbon atoms; and n is a number from 15 to 25. A
preferred diamine is polyoxypropylene diamine, wherein X is methyl, _ is a number from 16 to 19 and Z is a 1,2-propylene radical. These polyoxyalkylene polyamines can be prepared i7 . -in accordance with the methods disclosed in U.S. Patents No.
`~ 3,236,895 and 3,654,370.
As previously indicated, urea may he employed as areactant with the polyoxyal]cylene polyamine to produce the bis ureide additive. With urea as a reactant, ammonia is evolved as the terminal primary amino groups of the polyoxy-alkylene polyamine are converted into ureido groups.
Mono-substituted urea compounds can also be used as reactants. For example isoc:yanates of the formula R-N=C=0, wherein R is a monovalent aliphatic or aromatic radical.
Usually, a specific molar ratio of the reactants should be utilized. For example, when urea and a polyoxyalkylene diamine are utilized as the reactants, the molar ratio of urea to polyoxyalkylene diamine should be about 3:2. Generally, it is desirable to utilize a slight excess of the urea or mono-substituted urea compound in order to ensure complete conversion of the amino groups of the polyoxyalkylene compound.
Thus, in the preferred embodiment, with urea and a polyoxypropylene (1,2-propylene) diamine having an average molecular weight of 2,000 as the reactants, one molecule of urea is needed to link two polyoxypropylene diamine molecules, and two other molecules of urea are required to react with the terminal amino groups of the polyoxypropylene diamine.
Alternatively, the bis ureide additive may be prepared in two steps. In the first step, 2 moles of a polyoxyalkyl-ene polyamine are reacted with 1 mole of urea or a mono-substituted urea compound, whereby one molecule of urea links two polyoxyalkylene polyamine molecules. In the second step, the product of the first step is reacted with urea in a molar ratio of 1:2 to form the bis ureide additive of this inven-tion, the terminal amino groups of the product of the first step reacting with urea to form terminal ureido groups.
` In accordance with this invention, an epoxy resin composition having improved adhesive strength or thermal shock resistance may be prepared by admixinq the following ingredients: a polyepoxide, an effective amount of a poly-; amine or anhydride curing agent, and an e~fective amount of an additive as defined above. In addition to the ingredients ' , '' . ~ . ` , '. :

.:

:
- listed above, an accelerator may be mixed with the curable resin composition in order to accelerate the cure.
The polyepoxides which may be used in accordance with this invention are vicinal compositions which can be cured and have an average of at ]east 1.8 reactive 1,2-epoxy groups per molecule. These polyepoxides can be monomeric or poly-meric, saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic, and may have additional substituents other than epoxy groups, e.g. hydroxyl groups, ether groups, or aromatic halogen atoms. Usually such substituents should be unreactive with the amine groups of the polyamine under the conditions employed for curing the resin.
It is preferred to employ glycidyl ethers which are prepared by epoxidizing the corresponding allyl ethers, or by reacting a molar excess of epichlorohydrin and an aromatic polyhydroxy compound, such as isopropylidene bisphenol, a novolak, or resorcinol. In addition, epoxy derivatives of `- methylene or isopropylidene bisphenols are preferred.
One class of polyepoxides which may be used in accord-ance with this invention comprises resinous epoxy polyethers " which may be obtained by reacting an epihalohydrin with a ~; polyhydric phenol or polyhydric alcohol. Suitable dihydric -~ phenols include 4,4'-isopropylidene bisphenol, 2,4'-dihydroxy-diphenylethylmethane, 3,3'-dihydroxydiphenyldiethylmethane, ` 25 3,4'-dihydroxydiphenylmethylpropyl methane, 2,3'-dihydroxy-diphenylethylphenyl methane, 4,4'-dihydroxydiphenylpropyl-phenylmethane, 4,4'-dihydroxydiphenylbutylphenylmethane,

2,2'-dihydroxydiphenylditolylmethane, and 4,4'-dihydroxy-diphenyltolylmethylmethane. Many other polyhydric phenols, e.g. resorcinol, hydroquinone, and substituted hydroquinones, may be co-reacted with epihalohydrin to provide these epoxy polyethers.
Many polyhydric alcohols can be co-reacted with epi-" halohydrin to provide the epoxy polyethers. Examples include ethylene glycol, propylene glycols, butylene glycols, pentanediols, bis (4-hydroxycyclohexyl) dimethylmeth~ne, 1,4-di-methylolbenzene, glycerol, 1,2,6-hexanetriol, trimethyl-propane, mannitol, sorbitol, erythritol, pentaerythritol, 6~
':
their dimers, trimers and higher polymers, such as poly-ethylene glycols, polypropylene glycols, triglycerol, dipentaerythritol, polyallyl alcohol, polyhydric thioethers, such as 2,2'-, 3,3'-tetrahydroxydipropylsulfide, mercapto alcohols such as monothioglycerol and dithioglycerol, poly-hydric alcohol partial esters such as monostearin, pentaery-thritol, monoacetate, and halogenated polyhydric alcohols such as the monochlorohydrins of glycerol, sorbitol, and pentaerythritol.
Other polyepoxides which may be utilized in accordance with the instant invention i~clude epoxy novolak resins obtained by reacting an epihalohydrin with the resinous con-densate of an aldehyde and a monohydric or polyhydric phenol, in the presence of a basic catalyst, such as sodium or potassium hydroxide. Other information concerning the nature and preparation of these epoxy novolak resins may be obtained from Lee, H. and Neville, K., Handhook of Epoxy Resins, McGraw Hill Book Company, New York, 1967.
It should be understood by those skilled in the art that many polyepoxide compositions may be utilized in accord-ance with the instant invention. Accordingly, the above description of suitable polyepoxides was not intended to be - limiting or exhaustive of all suitable polyepoxides; rather, it was intended to be exemplary of those polyepoxides which may be utilized in accordance with the invention.
Any amine curing agent which is useful in the curing of vicinal epoxides may be used in accordance with one embodiment of the invention. These amine curing agents generally have at least three reactive amino hydrogens.
Alkylene polyamines, oxyalkylene polyamines, and triamino and diamino derivatives of ethylene glycol may be utilized as curing agents, for example, diethylene triamine, triethylene tetramine, polyoxypropylene, and 1,13-diamino-4,7,10-trioxatridecane.
In addition, aromatic amine curing agents and the corresponding cycloaliphatic compounds may be utilized, for example, the alkylene-linked polyphenyl amines, phen~lene diamines and polycyclic or fused aromatic primary amine , , .
.

~ 7-: compounds.
Other curing agents which may be utilized are poly-amine curing agents, such as the condensation products of ;~ polyamines and polycarboxylic acids. An example of such amine compounds is the condensation product of a polyamine and a dimerized fatty acid as prepared in accordance with U.S.
Patent No. 2,379,413.
In accordance with this embodiment of the invention, it is preferred to utilize polyoxyalkylene polyamine compounds as curing agents. These compounds have the formula:
/H2N-(fH-CH2 )n-7r . X
`::
- wherein X is hydrogen, methyl or ethyl; Z is a hydrocarbon radical having 2 to 5 carbon atoms and a valence from 2 to 4;
n is a number from 1 to 15; and r is 2, 3 or 4. Highly preferred are the polyoxypropyl diamines wherein X is methyl, n is a number from 1 to 10, Z is a 1,2-propylene radical and _ is 2. These polyoxyalkylene polyamines may be prepared by the methods disclosed in U.S. Patents No. 3,236,895 and

3,654,370. Greatly preferred is a polyoxypropylene diamine having a molecular weight of about 230.
~` Other curing agents of the polyoxyalkylene polyamine class as depicted in the following formula may be utilized:
Z-/(o-cH2-fH)nNH(cH2)yNH2-/r X
wherein X, Z, _ and r are defined as above and ~ is 2 or 3.
These poly (aminoalkylamino) polyethers are the hydrogenated product of the cyanoalkylated adduct of a polyoxyalkylene polyamine as described above. The cyanoalkylated adducts may be prepared in accordance with the description in U S.
Patent No. 3,666,788. It is preferred to use the hydrogenated cyanoethylated polyoxypropylene triamines.
As previously indicated, an accelerator may be included in the epoxy resin formulation to speed curinq. These accelerators are especially useful when the amine cure takes - place at ambient temperatures. In particular, when an epoxy resin is used as an adhesive in a flammable environment, an elevated temperature cure can be hazardous and, hence, it is desirable to use an accelerator in such circumstances.
Many accelerators have been used. For example, salts of phenol, salicyclic 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. 2,839,480.
A preferred accelerator is disclosed in U.S. Patent No.
3,875,072 and comprises piperazine and an alkanolamine in a weight ratio of 1:8 to 1:1.
The anhydride curing agents which may be utilized in accordance with the instant invention include alkyl-substituted bicyclic vicinal anhydrides, such as the Diels-Alder adduct of maleic anhydride and a substituted cyclo-pentadiene. The preferred anhydride curing agents have the formula:

wherein R is alkyl, preferably having 1 to 4 carbon atoms.
Preferred alkyl groups include methyl, ethyl, propyl, and n-- butyl groups. The most preferred alkyl group is methyl, and the most preferred anhydride is methyl-bicyclo/2,2,17-heptene-2,3-dicarboxylic anhydride.
Typically, anhydride cured epoxy resins are cured at elevated temperatures and, as previously indicated, acceler-ators may be used to speed the cure of the epoxy resin.
Such accelerators are well-known, for example, tertiary amines such as those disclosed in U.S. Patent No. 2,839,480.
It is preferred to use the dialkylamine substituted aromatics and, preferably, the dimethylamino methyl substituted phenols.
In accordance with this invention, it should be under-stood that the amount of the bis ureide additive required ~' ' : `' ~ 7 is empirical and is dependent upon many factors, such as the resin, the curing agent and the accelerator, if one is used.
Generally, the bis ureide additive can be utilized in amounts from 1 to 30 parts by weight, based on 100 parts by weight of the polyepoxide resin constituent and, preferably, from 1 to 10 parts by weight, to increase the adhesive strength of amine-cured compositions, and in amounts of from 1 to 40 parts by weight to improve the thermal shock resistance of anhydride-cured compositions.
Although the amount of bis ureide additive required is empirical, it can be determined by a reasonable amount of routine experimentation. Once an effective amount of the additive has been added to a resin mixture, the epoxy resin composition undergoes a readily visible change. Specifically, the resin becomes opaque and milky white in appearance, and this change becomes more visible during the curing step. As a result of this change, the epoxy resin product has a lustrous white appearance. This optical absorption shift enhances the beauty of cast objects and obviates the need to use white pigments or fillers.
Of course, if too small an amount of the additive is employed, the adhesive strength or thermal shock resistance of the epoxy resin may not be improved. Similarly, if too great an amount of the additive is employed, other properties of the epoxy resin may be undesirably compromised.
The preferred amine-cured epoxy resin compositions comprise polyglycidyl ethers of polyhydric phenols, a poly-oxyalkylene polyamine having a molecular weight from 200 to 500 as curing agent, and an accelerator combination of piper-azine and an alkanolamine in a weight ratio of 1:8 to 1:1.For example, the epoxy resin compositions disclosed in U.S.
Patent No. 3,943,104 may be mixed with the bis ureide in order to improve their adhesive strength.
The cured epoxy resin compositions of the present invention may be prepared in any suitable manner. The curing agent may be mixed with the polyepoxide in amounts according to the equivalent weight of the curing agent employed. The number of equivalents of amine groups or carboxyl groups may .
.

6'7 vary from 0.8 to 1.2 times the number of epoxide equivalents present in ihe curable epoxy resin. It should be understood that a stoichiometric amount is preferred.
When an accelerator is employed, ik may be used in 5 amounts from 1 to 10 parts by weight, based on 100 parts by weight of the resin. Of course, it will be recognized by those in the art that the exact amount of each constituent will vary depending primarily on the intended application of the cured resin. Also, the amount of accelerator employed should be sufficient for the intended purpose of accelerating the cure; but if too much is used, softenin~ of t~le cured resin may result, or other properties may be undesirably compromised.
;~ The bis ureide additive may be incorporated into the uncured resin by mixing. It is preferred that the additive be first mixed with the curing agent and accelerator, if one is used, before adding the polyepoxide resin. After this ! step, all of the constituents can be mixed in accordance with standard methods, and degassed in the presence of a commercial defoamer and minute amounts of a silicone oil. The degassing , prevents voids and bubbles in the cured resin.
~esirable properties of the cured epoxy resin compos-itions, and especially the adhesive strength of the compos-~` itions, have been improved in those resin compositions ` 25 containing polyglycidyl ethers of polyhydric phenols in amounts greater than 50~ by weight of the polyepoxide resin constituent. Preferably, these polyhydric phenols are present in an amount of 80% by weight and even more preferably 100%
by weight.
The preferred amine curing agents are polyamines having an amine equivalent weight of from 20 to 70, for example, - polyoxypropylene diamines having a molecular weight in the range of 200 to 300 and polyoxypropylene polyamines having a molecular weight from 400 to 600.
In accordance with a preferred embodiment of the instant invention, a curable epoxy resin composition comprises:
a diglycidyl ether of a 4,4'-isopropylidene bisphenol; a primary amine-containing curing agent comprises a polyoxy-propylene diamine having a molecular weight from 200 to 250, - an accelerator comprising piperazine and triethanolamine in a weight ratio of 3:7, and an effec-tive amount of a bis ureide of a polyoxyalkylene polyamine having an average molecular weight of at least 4,000, most preferably a bis ureide of a polypropylene diamine having an average molecular weight of approximately 4,000.
A preferred amount of accelerator comprises from 1 to 10 parts by weight per 100 parts by weight of the polyepoxide resin. The accelerator may be a piperazine-alkanolamine accelerator having a weight ratio of 1:8 to 1:1. The preferred amount of the accelerator may be mixed with a polyoxyalkylene diamine curing agent.
Generally, the mixture of epoxy resin, amine curing agent, accelerator, and bis ureide additive is allowed to cure at ambient temperatures of 0 to 45C; however, it may be expeditious to cure the mixture at elevated temperatures up to 135C, if conditions allow elevated temperatures to be employed.
In accordance with another preferred embodiment, polyepoxide resins of the polyglycidyl ether of a polyhydric phenol may be cured by incorporating a stoichiometric amount of a polyoxyalkylene polyamine having a molecular weight of about 230; from 1 to 30 parts by weight, per 100 parts by weight of the polyepoxide resin, of the bis ureide of a poly-oxypropylene diamine having a molecular weight of about 4,000;
and from 1 to 10% by weight, based on the resin, of an accelerator comprising a 30:70 weight percent mixture of piperazine and triethanolamine. This composition may be cured at a room temperature of approximately 25C and will result in a cured polyepoxide resin composition having superior adhesive strength.
In accordance with another preferred embodiment of the invention, a curable epoxy resin composition comprises: a diglycidyl ether of a 4,4'-isopropylidene bisphenol; a curat-; ive amount of an anhydride curing agent comprising methyl- bicyclo/2,2,17heptene 2,3-dicarboxylic anhydride, an accelerator comprising dimethylaminomethyl substituted phenol;

.
and, an effective amount of a thermal shock resistance improv-ing additive comprising a bis ureide of a polyoxyalkylene polyamine, said additive having a molecular weight of at least

4,000.
In a preferred embodiment, the bis ureide is a bis ureide of a polypropylene diamine having a molecular weight of approximately 4,000. Greatly preferred is an ~L, G~- bis - ureide polyoxypropylene diamine having an average molecular weight of about 4,000.
A preferred ratio of constituents comprises from 1 to ` 10 parts by weight of accelerator; from 80 to 90 parts by weight of anhydride curing agent; and from 1 to 40 parts by ~` weight of the bis ureide additive, wherein all of the above amounts are based on 100 parts by weight of the resin.
Generally, the mixture of epoxy resin, the bis ureide additive, anhydride curing agent, and accelerator is allowed to self-cure at elevated temperatures up to 200C.
In accordance with a greatly preferred embodiment, the epoxy resins of the polyglycidyl ether of polyhydric phenols are cured by mixing them with from 80 to 90 parts by weight of methyl-bicyclo/2,2,17heptene-2,3-dicarboxylic anhydridei from 1 to 40 parts by weight of the thermal shock resistance improving additive consisting essentially of a bis ureide of a polyoxypropylene diamine, said additive having a molecular . 25 weight of about 4,000; and from 1 to 10 parts by weight of a dimethylaminomethyl substituted phenol as accelerator. This composition may be cured at temperatures in the range of 100C to 190C to produce products having superior shock resistance.
In accordance with techniques well-kno~m and under-stood in the art, other additives may be mixed with the poly-epoxide compositions before curing. For example, it may be desirable to add minor amounts of other polyalkylene amine or anhydride co-catalysts, or hardeners, or other accelerator and curing agents as are well-kno~m in the art. In addition, pigments, dyes, fillers, flame-retarding additives and other compounds, natural or synthetic, may be added.
Although it has been stated that the bis ureide of --13- i~AL~ ~6 7 '' this invention has an average molecular weight of at least 4,000, it should be recognized that this average weight does have an upper limit. As should be apparent to those skilled in the art, the viscosity o:E the additive increases with its molecular weight, and the upper limit of the average molecular weight will be a function oX the viscosity. Those skilled in the art will appreciate the undesirability of employing an additive having too high a viscosity.
. .
Solvents for polyepoxides, such as toluene, benzene, xylene, dioxane and ethylene glycol monomethylether, may be utilized, but they are not preferred.
~ The polyepoxide resins may be utilized in any appli-; cation f~r which polyepoxide resin compositions are customarily employed. It should be understood that because of the white lustrous surface of the cured composition, it may be of particular benefit in moulding and casting procedures.
It should be appreciated by those of skill in the art, that the polyepoxide resin compositions of the invention may be utilized as impregnates, surface coatings, pottings, capsulating compositions, laminants, and of particular importance, as adhesives for bonding metallic elements or structures together.
" Surprisingly, smaller amounts of the bis ureide havingan average molecular weight of at least 4,000 are required to improve the adhesive strength or thermal shock resistance of epoxy compositions than are required when a bis ureide having an average molecular weight of 2,000 is utilized as an additive.

~ -14- ~
.

In this Example, a bis ureide polypropylene diamine additive for use in accordance with this invention was pre-pared. The reactants which were utilized in a molar ratio

5 of 2 to 3, respectively, were JEFFAMINE~D-2000 (made by Jefferson Chemical Company, Austin, Texas) and urea.
- 65 grams (1.08 moles) of urea and 500 grams of JEFFAMINE~D-2000 were heated to 135 C, in a stirred reactor, flushed with nitrogen and stirred under nitrogen for approx-imately 2 hours at 135C. The remainder of the JEFFAMINE
D-2000 (935 grams) was subsequently slowly added over a period of 1.5 hours while ammonia was evolved.
` After approximately 7 hours at 135C, the reaction product was vacuum stripped at 175-180C/2 mm. ~g to produce a viscous residue which had a total amine content of 0.14 meq./g., a primary amine content of 0.05 meq./g. and 1.64% N.
To illustrate the advantage of the bis ureide addit-ives in amine-cured resins, various epoxy formulations employing the diglycidyl ether of 4,4-isopropylidene bisphenol were cured with various known polyamine curing agents. Where indicated a commercial accelerator was utilized. 3 drops of silicone fluid were added to each formulation to prevent the formation of voids and bubbles. After degassing under vacuum, the formulations were cured under the conditions indicated.
In the appropriate Examples, the cured products were sub-jected to the standard American Society for Testing Materials (ASTM) test for peel strength ~ASTM D-903) and the tensile shear strength (ASTM D-1002-64) was measured on adhesive bonds. All substrates were aluminium panels (No.
30 2024-T-3 alloy, 16 gauge), degreased, then etched with chromic acid before bonding. The abbreviations used in the table, pbw, psi and g. stand for parts by weight, pounds per square inch and grams, respectively.
EXA MPLES 2 to 6 : 35 In these Examples, epoxy resins were prepared wherein the diglycidyl ether of a 4,4-isopropylidene bisphenol was cured with a polyoxypropylene diamine curing agent having a molecular weight of 230 to which were added the indicated 'Tr~é~7r~s .

.

f~ i7 amounts of the bis ureide prepared in Example 1. Also added were the indi-cated amo~mts of the accelerator.
The resulting resins were used to bond aluminium to aluminium and :.:
~-` these bonds were subjected to the ASTM test indicated in Table I.

TABLE I
. ExamPles Formulation 2 3 4 5 6 Epoxide, pbw 100 100 100 100 100 ~Eq. 190) Curi~g agent, pbw ) 30 30 30 30 30 Acce2erator, pbw ) 10 10 10 10 10 bis ~reide pbw 2 0 0 2 0 5 bis ~reide, pbw ) 0 2 0 5 0 Tens~le shear, psi ) 9801200 3300 3200 4200 1) Sold by Jefferson Chemical Company, under the name "JEFFAMINE* D-230"

2) A pipera2ine-triethanolamine admixture ~30:70) sold by Jefferson Chem-ical Company, under the name "Accelerator* 398"
` 3) The product of Example 1 : 4) A bis ureide of a polyoxypropylene having an average molecular weight of 2000 and made in accordance with the disclosure in Canadian Application No. 290,993 5) Cure: 7 days, Room Temp.
These Examples illustrate the improved adhesive strength of the epoxy resin formulation as compared to the bis ureide having an average mol-ecular weight of 2,000 and made in accordance with the disclosure of Canad-ian Application No. 290,993. Specifically, a smaller amount of the additive of the present invention is required to improve the adhesive strength of the ` *Trademarks - 15 -~r :
-': :

..
`~ resin than is required if a bis ureide having an average molecular weight of 2,000 were utilized.
EXAMPLES 7 to 10 These Examples illustrate the improved adhesive proper-ties of resins prepared as in Examples 2 to 6 above, except that the ~uring agent was a bis (amino propyl) derivative of JEFFAMINE D-230. This bis ~amino propyl~ derivative is the product of the cyanoethylation of JEFFAMINE D-230.

TABLE II
Examples Formulation 7 8 9 10 Epoxide, pbw (Eq. 190) 100 100 100 100 Curing agent, pbwl) 25 25 25 25 Accelerator, pbw2) 5 5 5 5 Bis ureide pbw3) o 1 2 5 Tensile shear, psi4) 1200 1600 2600 3600 1) A bis (amino propyl) derivative of "JEFF~MI~JE D-230"
2) "Accelerator~398" (see Table I) 3) The product of Example 1 4) Cure: 7 days, Room Temp.
:
EXAMPLES 11 to 14 In these Examples, the resins were prepared as in Examples 2 to 6, except the curing aqent was a polyoxy-propylene d:iamine having an averaqe molecular weight of 400.
- 25 These Examp:Les further demonstrate the surprising improvement in the adhesive properties of the resins prepared in accord-ance with the instant invention. The peel strength of the various resins was tested as indicated in Table III below.
.~
~R ~/e ~7ct r k: S

.
' .

TABLE III
Examples Formulation 11 12 13 14 -~ Epoxide, pbw (Eq. 190) 100100 100 100 Curing agent, pbw1) 50 50 50 50 Accelerator, pbw2) 10 10 10 10 bis ureide pbw3)_ 0 2 5 20 peel strength, pli4) 8.826.127.9 36.1 1) Sold by Je~ferson Chemical Company, under the name "JEFFAMINE D-400"
2) "Accelerator 398" (see Table I) 3) The product of Example 1 4) Cure: 7 days, Room Temp.
-EXAMPLES 15 to 19 The resins of these Examples were prepared in a manner similar to those prepared in Examples 2 to 6, except that the curing agent was a diethylene glycol bis (polyamine). Again, the Examples demonstrate the surprising improvement in the adhesive strength of the epoxy formulations which employed the additive of the present invention.
dern~ s ., ;~ ... , . ~ . . .
.

.

-~ TABLE IV
Examples , Formulation 15 16 17 18 19 `, Epoxide, pbw ~ (Eq. 190) 100 100 100 100 100 : Curing agent, pbwl) 30 30 30 30 30 bis ureide, pbw2~ 0 1 2 5 10 peel strength, ` pli3) --- 7.7 10.3 14.2 28.5 1) Diethylene glycol bis (propylamine) - 2) The product of Example 1 - 10 3) Cure: 7 days, Room Temp.
EXAMPLES 20 to 24 In these Examples, epoxy resins were prepared as in ` Examples 2 to 6, except that no accelerator was employed and each resin was cured with triethylenetetramine. As with the .; .
other Examples, the results demonstrate that the adhesive strength of epoxy formulations are improved when the additive - of the present invention is utilized.
TABLE V
Examples 20Formulation 20 21 22 23 24 Epoxide, pbw (Eq. 190) 100 100 100 100 100 Curing agent, pbwl) 12 12 12 12 12 Bis ureide pbw2) 0 1 2 5 10 Tensile shear, `~ psi3) 800 1200 18501600 1400 1) Triethylenetetramine 2) The product of Example 1 3) Cure: 7 days, Room Temp.

.
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: .
- .

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To illustrate the advantage of the bis ureide additives in anhyd-- ride-cured resins, various epoxy formulations employing the diglycidyl ether of 4,4-isopropylidene bisphenol were cured with various known anhydride cur-ing agents. ~here indicated, a commercial accelerator was utilized. 3 drops of silicone fluid were added to each formulation to prevent the forma-tion of voids and bubbles. After degassing under vacuum, the formulations were cured under the conditions indicated. In appropriate Examples, the cured products were subjected to standard American Society for Testing Mate-rials ~ASTM) test for Izod impact strength ~ASTM designation D-256), flex-ural strength and modulus of elasticity in flexure (ASTM designation D-790-66), tensile strength and elongation at break (ASTM designation D-63~-64 T), deflection temperature (ASTM designation D-645-56) and hardness (ASTM desig-nation 2240-64T) and/or hardness Shore D.
EX~MPLES 25 to 29 The following Examples show that resins employing the bis ureide additives are resistant to thermal shock. In addition, these Examples may be compared with those of Canadian Application No. 291,074, in order to show that much smaller amounts of the additive of the present invention are re-quired to improve the thermal shock resistance than are required with the additive disclosed in that patent application.
The resins of these Examples were prepared in accordance with the formulations shown in Table VI below. Approximately 50 gram samples were .` utilized to encapsulate washers (1" o.d., 3/~" i.d., 1/16" thick) supported by a 1/4" ring of filter paper cut from a ~hatham 19 x 19 mm. cellulose ex-traction thimble. The encapsulations were formed in aluminium milk test evaporating dishes (5 cm. dia. x 1 cm. deep). All samples were cured for two hours at 100C, one hour at 130C and three hours at 150C. Ten samples of each formulation were used and the results are shown in Table VII below.

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TABLE VI
Examples -Formulation25 26 27 28 29 Epoxide, pbw tEq. 190) 100 100 100 100 100 Curing agent, pbwl) 85 85 85 85 85 Accelerator, pbw2) 2.5 2.5 2.5 2.5 2.5 Bis ureide3) --- 0.5 loO 2.0 5.0 TABLE VII
Number of samples cracked during cycles4) 1 2 3 4 5 6 7 8 9 10 Example 1; 28 2 1 0 0 0 1 0 0 0 0 .
1) "Nadic Methyl Anhydride" sold by Allied Chemical Corporation, Morristown, N.J. 07960 2) "D~-10" sold by Rohm and Haas, Philadelphia, Pa. 19105 3) Product of Example 1 4) Thermal cycle: Oven at 140C (30 mins.), hath at -20C
(15 mins.), room temperature (15 mins.). Examined for cracking and, if unchanged, recycled to oven.
5) All 10 samples were cracked after cycle 3.
EXAMPLES 30 to 34 In these Examples, the epoxy resins were prepared by using phthalic anhydride as a curing agent and benzyldi-methylamine as the accelerator. Those formulations are sho~n ;~ in Table VIII.
The cured resins were subjected to testing in . . , . :
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accordance with the procedures utilized in Examples 25 to 29. Ten samples of each formulation were used and the test results are shown in Table IX.
These results, when compared to results in the Examples of illustrate that epoxy resins cured in accordance with the instant invention not only provide an improved thermal shock resistance over resins cured with phthalic anhydride, but the resins also have improved thermal shock resis-tance over resins cured in accordance wlth Canadian Application No. 291,074.
TABLE VIII

Examples Formulation ) 30 31 32 33 34 Epoxy resin (Eq. 190), - pbw 100 100 100 100 100 Phthalic anhydride pbw 75 75 75 75 75 Benzyldimethylamine, pbw Bis ureide, pbw ) 0 5 10 20 40 TABLE IX

~umber of samples 3) . cracked during cycles 1 2 3 4 5 6 7 8 9 10 . -- ---- -- _ _ _ _ _ _ Example

6 2 0 0 0 1 0 0 0 0 31 104) _ _ _ _ _ _ 32 5 1 4 ) ~ 34 0 0 0 0 0 0 0 - 1) Cure cycle: 2 hr. at 100C, 1 hr. at 130C, 3 hrs. at 150C

2) Prepared in accordance with Example 1 3) Thermal cycle: oven at 140C ~30 mins.), bath at -20C (15 mins.), room temperature (15 mins.). Examined for cracking and, if unchanged, re-cycled to oven.
4) All 10 samples were cracked after cycle.

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~ -22- ~ 67 ~- EXAMPLES 35 to 37 In these Examples hexahydrophthalic anhydride was used as the curing agent with benzyldimethylamine as an accelerator.
Table X presents the formulations of the cured resins. Each o~ the cured resins was subjected to thermal shock resistance testing in accordance with the procedure outlined in Examples 25 to 29. The test results are shown in Table XI below.

TABLE X
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Formulation 35 36 37 Epoxy resin (EEW 190), pbw 100 100 100 --- Hexahydrophthalic anhydride, pbw 78 78 78 Benzyldimethylamine, pbw Bis ureide, pbwl) 0 2 5 - 15 1) Prepared in accordance with Example 1.

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TABLE XI
. . . _ Number of samples 1) -~ cracked during cycles 1 2 3 4 5 6 7 8 9 10 . .
Example 36 6 1 3 - ~

~, ` 1) Thermal cycle: oven at 140C (30 mins.), bath at -20C
(15 mins.), room temperature (15 mins.). Examined for cracking and, if unchanged, recycled to oven.

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Claims (20)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An additive for curable epoxy resin compositions which comprises a bis ureide of a polyoxyalkylene polyamine having the formula:

wherein X is hydrogen or a primary amino group; Y is oxygen or sulfur; and Z is a polyoxyalkylene group of such a molecular weight that the additive has an average molecular weight of at least 4,000.

2. An additive as claimed in claim 1 wherein the polyoxy-alkylene group is a polyoxypropylene group.

3. An additive as claimed in claim 1 or 2 wherein X is a primary amino group and Y is oxygen.

4. An additive as claimed in claim 1 or 2 wherein X is hydrogen and Y is oxygen.

5. An additive as claimed in claim 1 or 2 wherein X is a primary amino group and Y is sulfur.

6. An additive as claimed in claim 1 or 2 wherein X is hydrogen and Y is sulfur.

7. A curable epoxy resin composition which comprises:
(i) a vicinal polyepoxide having an epoxide equivalency of more than 1.8;
(ii) a curing agent comprising a polyamine having at least three reactive amino hydrogen atoms or a substituted bi-cyclic vicinal anhydride; and (iii) an additive which comprises a bis ureide of a polyoxyalkylene polyamine having the formula :

wherein X is hydrogen or a primary amino group; Y is oxygen or sulfur; and Z is a polyoxyalkylene group of such a molecular weight that the additive has an average molecular weight of at least 4,000.

8, A composition as claimed in claim 7 wherein the polyoxy-alkylene group is a polyoxypropylene group.

9. A composition as claimed in claim 7 which comprises a curing accelerator.

10. A composition as claimed in claim 7, 8 or 9 wherein the vicinal polyepoxide comprises a polyglycidyl ether of a poly-hydric alcohol or phenol.

11. A composition as claimed in claim 7, 8 or 9 wherein the curing agent is an alkylene polyamine, an oxyalkylene polyamine, a triamino or diamino derivative of ethylene glycol, an aromatic or cycloaliphatic amine, or a condensation product of a poly-amine and a polycarboxylic acid.

12. A composition as claimed in claim 7, 8 or 9 wherein the curing agent is a compound of the formula:

wherein X is hydrogen, methyl or ethyl; Z is a hydrocarbon radical having 2 to 5 carbon atoms and a valence from 2 to 4, n is a number from 1 to 15, and r is 2, 3 or 4.

13. A composition as claimed in claim 7, 8 or 9 wherein the curing agent is a compound of the formula:

wherein X, Z, n and r have the meanings given in claim 12 and y is 2 or 3.

14. A composition as claimed in claim 9 wherein the acceler-ator comprises piperazine and an alkanolamine in a weight ratio of 1:8 to 1:1.

15. A composition as claimed in claim 14 wherein the curing agent is a compound of the formula:

wherein X is hydrogen, methyl or ethyl; Z is a hydrocarbon radical having 2 to 5 carbon atoms and a valence from 2 to 4, n is a number from 1 to 15, and r is 2, 3 or 4.

16. A composition as claimed in claim 14 wherein the curing agent is a compound of the formula:

wherein X, Z, n and r have the meanings given in claim 12 and y is 2 or 3.

17. A composition as claimed in claim 7, 8 or 9 wherein the curing agent is a compound of the formula:

in which R is alkyl.

18. A composition as claimed in claim 7, 8 or 9 wherein the curing agent is methyl-bicyclo[2,2,1]heptene-2,3-dicarboxylic anhydride.

19. A composition as claimed in claim 9 wherein the acceler-ator is a tertiary amine.

20. A cured epoxy resin composition obtained by curing a curable composition as claimed in claim 7, 8 or 9.