CA1065536A - Curable acrylate compositions having improved thermal properties - Google Patents

Abstract

A B S T R A C T

A polymerizable composition, suitable for use as an adhesive sealant or coating, comprising a urethane-acrylate-capped pre-polymer based on various polymeric or copolymeric compounds, e.g.
polyols or polyamines, in admixture with a compound having male-imide or nadic functionality. The composition provides improved properties, particularly improved resistance to thermal degradati A process for using the composition is also disclosed.

Description

1~65536 BACKG~<OUND OF THE INVENTION
Field of the Invention This invention relates to certain curable acrylate-based (e.g., methacrylate), adhesive, sealant and coating com-poæitions whose thermal properties are improved by addition of a maleimide- or nadic-capped reactive additive.
Prior Art Adhesive and sealant compositions based on acrylate, e.g., methacrylate, monomers polymerizable by free-radical initiation are known in the art. Likewise, anaerobic com-positions are known in the art (see, for example, U.S. Patents

2,895,950, 3,043,820, and 3,218,305). Anaerobic compositions are characterized by their ability to remain liquid in the presence of air, but cure to a strong adhesive bond when air is èxcluded, as by assembling a mated nut and bolt to which the composition has been applied.
Among the most desirable of the anaerobic adhesives are those based on urethane-acrylate monomers, such as are disclosed by Gorman et al. in U.S. patent 3,425,988~ These 20 materials may be regarded as the reaction product of a poly- -isocyanate ~e.g., toluene diisocyanate) with a mono-acrylate having a reactive hydrogen atom in the alcoholic portion thereof (e.g., hydroxypropyl methacrylate).
Various other urethane-acrylate type monomers, having utility beyond anaerobic systems, have been developed recently by Baccei. One of these monomers, described in copending Canadian application serial number 243,813, filed January 20, 1976, comprises a urethane-acrylate-capped polybutadiene polyol or polyamine~ knother related monomer, described in copendin~ Canadian application serial number 247,216, filed on March 5, 1976, comprises a urethane-acrylate-capped ., -- 1 --10~5536 poly(methylene)ether polyol. Still another related monomer, described in copending Canadian application serial number 246,571, filed on February 25, 1976 , comprises a urethane-acrylate-capped vinyl gxafte~ poly(alkylene)ether polyol.
The great advantage of the Gorman et al, and Baccei monomers mentioned above is that they cure to what may be regarded as "structural" strength adhesive bonds. A primary limitation on the usefulness of the Gorman et al. monomers, however, has been the deterioration o~ their cured strength properties during prolonged exposure to elevated temperatures,-e.g., 250~F. or higher. The Baccei monomers provide signi-ficantly improved resistance to thermal degradation but still are not fully satisfactory for all applications.
Malofsky, in copending Canadian application serial number 236,691, filed September 30, 1975, discloses the use of maleimide- a~d nadic-capped additives for use in improving the high temperature performance of ethoxylated bisphenol-A
dimethacrylate as well as alkylene glycol diacrylates having the general formula:
2 1 (CH2)~ ( I ) I O ~ IOC Cl-CH2 R' R" R R' n wherein R represents a radical selected from the group con-sisting of hydrogen, lower alkyl of 1-4 carbon atoms, inclusive, hydroxy alkyl of 1-4 carbon atoms, inclusive, and cH2 o--c--f cH2 R' ~... .

~065536 R' is a radical selected from the group consisting of hydrogen, halogen, and lower alkyl of 1-9 carbon atoms; R" is a radical selected from the group consisting of hydrogen, ---OH and o -O-¦!-f=CH2 R' m is an integer equal to at least 1, e.g., from 1 to 8 or higher, ~or instance, from 1 to 4, inclusive; n is an integer equal to at least 1, for example, 1 to 20 or more; and p i5 0 or 1. Malofsky's teachings, however, do not extend to the urethane-acrylates and do not recogni~e the particular advan-tages to be realized with the latter monomers.
SUMMARY OF THE INVENTION
According to the present invention there is pro-vided an adhesive and sealant compositlon having significantly improved strength at elevated temperatures and improved re-sistance to thermal degradation, as well as generally im-proved room temperature properties. This composition comprises a mixture of (a) a monomer having polymerizable urethane-acrylate functionality;
tb) an additive selected from the group consisting ¢ -R' p - R8-N

N - R ~ _ R8_ O O
wherein R7 and R8 are selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl, alkaryl, heterocyclic; and ~1 C;~ 7 ~1065536 (c) a free radical initiator of free-radical poly-meriza~ion.
In addition there is provided a process for sealing or adhering surfaces which comprises applying to at least one of said surfaces the above polymerizable compositions, then placing said surfaces in an abutting relationship until the composition has cured.
Preferably the monomer having polymerizable urethane-acrylate functionality is a monomer corresponding to either of the following formulas:

(I) (CH2 = C - C - 0 - R *~*Dd*Ii*)zZ
wherein R5 is selected from the class consisting of hydrogen, chlorine and methyl and ethyl radicals; R6 is a divalent organic radical selected from the group consisting of lower alkylene of 1-8 carbon atoms, phenylene and naphthylene; I is a poly-isocyanate radical; D is an aromatic, heterocyclic or cyclo-aliphatic polyol or polyamine radical; Z is a polymeric or copolymeric polyol or polyamine radical; z is an integer corresponding to the valency of Z; d is either 1 or 0; and i is 0 when d is 0, and otherwise is equal to one less than the number of reactive hydrogen atoms of D; and the asterisk (*) represents a urethane or ureide bond; or (II) ~H2C=C-C-0-R -X-a-NH ~ B
wherein n is an integer from 2 to about 6; B is a polyvalent organic radical selected from the group consisting of alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, aralkyl, alkaryl and heterocyclic radicals both substituted and unsubstituted;

X is selected from the group consisting of 0 and R
-N-~'' , R2 is selected from the group consisting o~ hydrogen and lower alkyl of 1 through 7 carbon atoms; and R5 and R6 have the meanings given above.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polymerizable substances useful in the present invention comprise a wide variety of urethane-acrylate~capped monomers or prepolymers. By the latter term is meant poly-merizable substances derived from the reaction of any of a wide variety of polyols or polyamines with polyisocyanates.
As used herein, the term "acrylate" includes the methyl, ethyl and halogen homologues thereof.

THE MONOMERS AND PREPOLYM~:RS
The preferred monomers and prepolymers are those disclosed by Gorman et al, and Baccei. These will not be described in more detail.
Preparation of the Gorman et al. monomers involves the reaction of a monofunctionally substituted alkyl or aryl acrylate ester containing an active hydrogen atom on the func-tional substituent. This monofunctional, acrylate-terminated material is reacted with an organic polyisocyanate in suitable proportions so as to convert all of the isocyanate groups to urethane or ureide groups. The mono~unctional alkyl and aryl acrylate esters are preferably the acrylates and methacrylates containing hydroxy or amino functional groups on the non-acrylate portion thereof. Acrylate esters suitable for use have the formula Rl o H2C=C-C-O-R6-X-H
wherein X is selected from the group consisting o~ ~-O - and -N-~.~

`'` 2 ~6~536 R is selected from the group consisting oflhydrogen and lower alkyl of 1 through 7 carbon atoms; R5 is a member selected from the class consisting of hydrogen, chlorine and methyl and ethyl radicals; and R6 is a divalent organic radical selected from the group consisting of lower alkylene of 1 through ~ carbon atoms, phenylene and na,phthylene. Th'ese groups upon proper reaction with a polyisocyanate, yield a sealant monomer of the following general formula:

[H 2 C= C- C-O--R - X- C-NH~B
wherein n is an integer from 2 to about 6; B is a polyvalent organic radical selected from the group consisting of alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, aralkyl, alkaryl and heterocyclic radicals both substituted and unsubstituted; and R5, R6 and X have the meanings given above.
The hydroxy and amine containing materials suitable for use in the preparation of the above monomeric products are exemplified by but not limited to such materials as hydroxy ethyl acrylate, hydroxy ethyl methacrylate, amino ethyl metha-crylate, 3-hydroxy propyl methacrylate, amino propyl metha-crylate, hydroxy hexyl acrylate, t-butylaminoethyl methacrylate, hydroxy octyl methacrylate, and the like.
The polyisocyanates which may be used in preparing these monomers, as well as other monomers and prepolymers of this invention, are discussed below in more detail. For present purposes, the preferred organic polyisocyanates com-prise the higher alkenyl diisocyanates, the cycloalkenyl diisocyanates and the aromatic diisocyanates containing more than 8 carbon atoms and preferably from 15 to 30 carbon atoms, such as, for example, octamethylene diisocyanate, durene diiso-cyanate, and 4,4'-diphenyl diisocyanate.

`'` 1065~3~

¦ The proportions in which the reactants may be combined can ¦be varied somewhat; however, it is generally preEerred to employ ithe reactants in chemically equivalent amounts up to a slight l¦excess, e.g., 1 equivalent excess o the polyisocyanate. As used ilherein the expression "chemically equivalent amount" refers to ,Ithe amount needed to furnish one isocyanate group per hydroxy or ', !
iamine group. ¦

' The reactions may be accomplished in the presence or absence ,of diluents. Preferably diluents which include the hydrccarbons, such as aliphatic, cycloaliphatic and aromatic hydrocarbons, for ,lexample, benzene, toluene, cyclohexane, hexane, heptane and the ; "likelare employed but other diluents~ such as methyl- ïsobut~l ketone, diamyl ketone, isobutyl methacry~ate, and cyclohexyl , . . .
methacrylate can also be beneficially utilized if desired, especially where complete compatibility ~ith the sealant system is desired.
The temperature employed in the reaction may also vary over ~ a wide range. Where the components are combined in approximately ;~ chemical equivalent amounts or with slight excess of the iso-cyanate reactant, useful temperatures may vary from room tempera-ture or below, e.g., 10C. to 15C., up to and including tempera-tures of 100C. to 175C. Where reacting the simpler isocyanates, the components are preferably combined at or near room tempera-,. . .
7- ture, such as temperatures ranging from 20C. to 30C. In the preparation of the high molecular weight isocyanate adducts usin~

,an excess of the isocyanate, the ~eactants may be combined at ,Iroom temperature or preferably heated at temperatures ranging from about 40C. to about 150C. Reactions conducted at about ,90C. to 120C. have been found to proceed quite smoothly.

1 . I

I' .l , , I

6s536 i The other monomers of the presen-t invention rnay be viewed as one-component polymerizable block copolymers (prepolymers) havinc~
rigid and flexible segments. ~h:is is achieved by the chemical Illinking of precursor "prepolymers" which are subsequently "capped"
S ,`,with acrylate, e.g., methacrylate, functionality. Accordingly, in a preferred embodiment, a "flexible" polymeric alkylene ether diol segment of relatively low molecular weight is reacted with a molar excess of a "rigid" diisocyanate such as toluene diisocyanate or methylene diisocyanate (4,4'-diisocyanato diphenylmethane), -thereby forming urethane linkages. Before reacting with the ;diol, the diisocyanate is preferably reacted in excess with , ano~her rigid moiety containinq at least two active hydrogenatoms, such as in hydroxy or amine groùps, ~hereby capping the other rigid moiet~ with -~CO groups. By the term "rigid" segment is meant a segment or segments containing aromatic, heterocyclic or cycloaliphatic rings. If multiple segments are involved, they should he joined by either fusing of the rings or by a minimum number of carbon atoms (e.g., 1-2 if linear, l-about 8 if branched) or hetero atoms such that there is little or no flexing of the segments. By the term "flexible" segment is meant a segment comprising the "Z" radical described herein. Pendent functional groups including aromatic, heterocyclic and cycloaliphatic, among others, may be present in the fle~i~le moiety, and branching may also be incorporated provided that there is no substantial inter-~5 ference with the necessary flexible nature of the segment nordegradation of the cured resin properties disclosed herein.
Illustrative of the polyisocyanates employed in the prepara-` tion of the monomers are, among others, phenyl diisocyanate, toluene diisocyana-te, 4,4'-diphenyl diisocyanate, 4,4'-diphenyl-30 ; ene methane diisocyanate, dianisidine diisocyanate, 1,5-naphthal-,j I
ene diisoc~anate, 4,~'-diphenyl ether diisocyanate, p-phenylene !i . .

11 10t;5536 lidi.isocyanate, 4,4'-dicyclo-hexylmethane dii.socyanate, 1,3- ¦
'ljbis(.isocyancltom~thyl) cyclohexane, cyclohexylene ~iisocyallate, .
¦.tetrachlorophenylene diisocyanate, 2,6-dlethyl-p-phenylenediiso-I cyanate, and 3,5-diethy].~4,4'-dilsocyanatodiphenyl-methane.
S `~Still other polyisoc.yanates that may be used are the higher molecu].ar weight r.igid polyisocyanates obltained by xeactin~
Ipolyamines containing terminal, primary and secondary amine .groups or polyhydric alcohols, for example, the alkane, 'cycloalkane, alkene and cycloalkene polyols such as glycerol, ethylene glycol, bisphenol-A, substituted bisphenol-A, and the like, with an excess o any o~ the above-described isocyanates.
These higher molecular weight urethane or ureide polyisocyanates ` ~ .may be represented by the formula:

~ O
. 1 ' "
[O=C=~I R -N-C~X ~ B
wherein R is an organic radical selected from the group consist-- ing of alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, aralkyl ~` and alkaryl radicals o~ 2 to about Z0 carbon atoms, both sub-I stituted and unsubstituted; and X, B and n are-as previously defined.
As indicated above, the diisocyanate is preferably reacted with anothex rigid segment comprising an aromatic, h~terocyclic or cycloaliphatic compound containing at least two active hydro-. gen atoms, preferably diamines and more preferably diols.
I . Suitable compounds are 2,2-(4,4'-dihydroxydiphenyl)-propane 25 ; (i.e., bispherlol-A), 414'-iso-propylidenedicyclohexanol (i.e., l hydrogenated bisphenol-~), ethoxylated bisphenol-At propoxylated '~bisphenol-A, 2,2-~4,4'-dihydroxydiphenyl)--butane, 3,3-(4,4'-~dihydroxydiphenyl)-pentane,~ ,~ '-(4,4'-dihydroxydiphenyl)-p-,~diisopropylben2ene, 1,3-cyclohexane diol, 1,4-cyclohexane diol, 30 ; 1,4-cyclohexancdimethanol, bicyclic and tricyclic diols such as ji4,8--bis-(hydroxymethyl)-tricyclo [5.2.1.02'6~ decane, 2,2,4,4-:, 1~ . '. I
¦ i 9 --!l .
.

:

tetram~thyl~1,3-cyclobutanedi.ol, hydroquinolle, resorcinol, 2,2 ~ ,4'-dihydroxyd:iphenyl)-sulone, and 4,4'-oxydiphenol, among ¦lothers, as well as halogenated derivatives of the above, such as ltetrabrominated ethoxylated bisphenol-A. These ring compounds ~may also be substituted with either reactive groups or unreactive ~groups such as alkyl groups containing about 1 to 4 carbon atoms.
~This reaction may be carried out at temperatures from room tempera-ture to about 180VC, preferably about 40-120C/ depending upon the specific reactants selected. At the lower temperatures, use of standard catalysts may be desirable. Unreactive diluents may be used, if desired.
l~ The polyisocyanate product thus formed is reacted with a `polymeric compound having at each end of the chain a functional ~ , group containing a reactive hydrogen atom~ preferably in a hydroxyl group.
One of the preferred polymeric compounds is a polybutadiene or copolybutadiene polyol. While either the 1l2- or the 1,4-configuration of butadiene can undergo the reactions involved in this invention, the latter is highly preferred because of the superiority of its cured properties in the formulations of this invention. Thus, the polybutadiene or copolybutadiene used should contain over about 50 percent, preferably at least about - 70 percent, and more preferably at least about 80 percent, of the 1,4-configuration. Techniques for the preparation of such material are known to the art, and a number of suitable materials are com-mercially availabl~.
The 1,4-fraction of the butadiene diols used in the present invention corresponds to the formula HO~C}12 CH CH Cll~a~C, H C~

Il .
., .

11 - 10 ~

~wherein a may vary ~rom 0.65 to about l.O, preferably from ¦about 0.75 to about 0.85; b may vary from 0 to about 0.35, pre- I
,ferably ~rom about 0.25 to about 0.15; n may vary from about l¦5 to about 150, pre~erably from about 10 to about 85; and T
S ~,is hydrogen or an organic radical derived from such compounds las styrene and its simpler derivatives, lower alkyl acrylates and methacrylates, and acrylonitrile, the latter bein~ especially ' preferred. Naturally, T should be selected so as not to substan-tially interfer with the properties imparted by the rest o the-molecule. When b is not zero, the'comonomer residue weight ''percent to which b relates should constitute less than about 40 '- 'percent of the whole copol~mer moiety and preferably less than ' about'3`~0 percent.
Another preferred polymeric compound with which the poly-isocyanate product may be reacted is a poly(methylene)ether or copoly~methylene)ether compound which conforms to'the formula:

HO~ CH:2 ) xO~-CH-O~H
n wherein x is an integer from 1 to about 8, y is an integer from 0 to about 20, z is an integer from 0 to about 10, and n is an integer of about 1 to about 100. Pr'eferably, x is 2 to about 6, y is 1 to about 5, z is 0 to 2, and n is 3 to about 60. More ¦',preferably, x is 4 to about 6, y is 1 to 2, z is 0 to 1, and n is 'i'5 to about 40. R3 and R4 may be hydrogen, lower alkyl radicals ' ,jcontai~ing 1 to about 3 carbon atoms, cycloaliphatic, cycloalkenyl 25 "or aromatic radicals comprising up to about 8 carbon atoms ana ; ~iheterocyclic radicals comprisin~ up'to about 8 carbon~hetero ',atoms. It i5 also highly desirable that the glycol be linear in order to provide a high degree of flexib.ility in the segment. ' ,`Suitable linear polyols would include poly(tetramethylene)ether j glycol and poly(ethylene)ether glycol, among others. Representa- j l!tive branched polyols include poly(l,2-propylene)ether polyol and Ipoly(1,2- or 1,3-butylene)ether glycol. Preparation and properties of polyols of these types are discussed in the literature, e.g., Saunders, J. H., and Frisch, K. C., "Polyurethanes - Chemistry and Technology," Interscience, New York, New York, (1963).
' Still another preferred polymeric compound with which the 1 10 polyisocyanate product may be reacted is a graft polymer derived from poly(alkylene)ether poryol backbones to which have been gra~ted vinyl monomers or poIymers The graft polymers conform to the structural formula:

HO - (R3- ~ R4-~H

Q~
wherein R3 and R4 are alkenyl and/or branched alkenyl radicals havlng 2 to about 10, preferably 3 to about 6, carbon atoms; Q is a vinyl polymeric or copolymeric radical which may be linear or branched alkyl, alkenyl, alkynyl, aromatic, cycloaliphatic or heterocyclic, containing 2 to about 12, preferably 4 to about 10 carbon/hetero atoms, x may range from 0 to about 200, preferably I from about 10 to about 100; y may range from 1 to about 100, preferably from 1 to about 50; and q may range from 1 to about 400, preferably from 1 to about 200. The preferred vinyl radicals, ,i.e., Q, are derived from acrylonitrile, styrene, methyl methacrv-late, vinyl acetate, e-thyl acrylate, vinyl chloride and vinylidene chloride, of which acrylonitrile and styrene are especially pre-ferred. The preferred alkylene ether radicals are derived from ~6~53~i 1,2-propylene oxide, ethylene oxide and tetramethylene oxide.
It will be understood that the term "vinyl" includes pendent unsaturation (e.~., CH2=CH-), polyvinyl derivatives ~e.g., CH3~~tCH2tq), and copolymeric vinyl derivatives (e.g., co-polymers of acrylonitrile and butadiene~.
The above graft poly~er segments and their preparation have been described by Kuryla et al. in Journal of Cellular Plastics,'iPolymer/Polyols, a New Class of Polyurethane Inter-mediates, " March 1966, as well as by Frisch et al., "Advance in Urethane Science and Technology," Vol. 2, page 9 et seq., Technomic Publishing Co., Inc., Westport, Connecticut (1971).
The graft polymer segments are typically prepared by the in situ polymerization of a vinyl monomer in a liquid polyol solution to produce a fine, usually quite stable, dispersion of the polymeric portion in the polyol. The resulting so-called "polymer/polyols" are commercially availlable in the dispersion form from Union Carbide Corp., New York, New York (under the trademark "Niax" polyol), and from BASF - Wyandotte Corp., Wyandotte, Michigan (under the trademark "Pluracol").
In general terms, the procedure for preparation of the polymer/polyol dispersion involves gradually adding one part vinyl monomer to a stirred mixture of 4 parts polyol and about 0.05 part peroxy initiator (e.g., benzoyl peroxide) at a temperature of 80C. or more. Unreacted monomer may sub-sequently be removed by vacuum stripping. Of course, this illustration is not meant to be limiting; appropriate quantities and reaction conditions will vary with the specific materials involved and are within the skill of the art to determine.

, ~,,~ ,, .....

!l ( ~ - . I

!'i It will be observed from the above that the above polymer/
¦¦polyols comprise a mixture o~ two reactive species, namely, the ¦ .
! grafted polyol and the ungrafted polyol, as well as any ungrafted residual vinyl compound (e.g., poly(acrylonitrile)). While the ~'igrafted species can be separated from the dispersion, by well- 1, ,~known solvent techniques, as a solid material, it is not necessary;
ifor purposes of the present invention to do so. In fact, the polymer/polyol dispersion mixture is the preferred reactant since 1~it tends to provide subsequent prepolymer which is both "filled"
(via the solid grafted resin) and "plasticized" (via the polyol).
.; . I
'~If it were desired to separate the grafted polyol, it. ~uld, of coursè,i~be redispersed` in an appropriate soIven~ ~prefera~ly in inert solvent) for subsequent reaction to form ~he prepol~mers of this invention. Thus, it will be understood that the spirit and I5 scope of this invention include use of both the polymer/polyol natural dispersion and a separately prepared dispersion or solu-- tion of the grafted polyol species itself.
The viscosity of the polymer/polyol dispersions useful in this invention covers a broad range, typically from about 500 to about lO,000 cps (measured at 25 using an RTV Brookfield vis-coineter). While viscosity is not considered to be a critical parametex in subsequent preparation of the prepolymer, the lower viscosities are preferred (i.e:, about 500 to about 4,000 cps, measured as above), since they tend to result in prepolymers having correspondingly low viscosities, which is a deinite advantage in certain applications of the prepoly1ner ~e.g., as an ,ladhesive in retaining a bearing on a shaft).
~i ' - `'' ' ' ~

~ ~ 14 ~ I

.

6~536 l, ¦l The vaxious polymeric compounds just described and which j'have functional groups containing an active hydrogen, are reacted ~¦with the polyisocyanate in such proportion that the polyisocya-nate is present in molar excess as to the concentration o~ the ~ active hydrogen-containing groups. In this way a product is assured which has an ~NCO group at each end of the polyol seg-ment. The molar excess o~ polyisocyana~e may vary from about 0~05 to about 6.
This reaction may be carried out at temperatures from about room temperature to about 150C, preferably from about 40C to ~
;about 120C. After addition of the flexible dlol, about 0.1 to 30 hours are required for completion at the preferred temperature range-.~ The reaction may also be catalyzea~ iL desiredr and~
unreactive diluents may be used for viscosity control.
The product of the above reaction is reacted with a molar equivalence t preferably a molar excess, based on -NCO group content, of an acrylate or methacrylate ester containing a hydroxy or amine group on the nonacrylate portion thereo. This results in an adhesive/sealant monomer, or more accurately, prepolymer, capped at both ends with acrylate or methacrylate functionality.
Esters suitable for use in this invention correspond to the formula R O
H2C=C C-O-~ -X-H

wherein X, R5 and R6 are as previously defined.
The suitable hydroxy- or amine-containin~ materials are exemplified by, but not limited to, such materials as hydroxy-i `ethyl acrylate, hydroxyethyl methacrylate, aminoethyl m~ethacry-late, 3~hydroxypropyl methacrylate, aminopropyl methacrylate, hydroxyhexyl acrylate, t-butylaminoethyl methacrylate, hydroxy-. . . .
ioctyl methacrylate, and the monoacrylate or ~onomethacrylate esters OLC bisphenol-A, the fully hydrogena-ted derivative of bls-phenol-A, cyclohexyl diol, and the like.

~ - 15 - I

Q6S~3~;
~i Il The reaction may be accomplished in the presence or ~bsence ¦lof diluents. Preerably, diluents which include the hydrocarbons, 1! such as aliphatic, cycloaliphatic and aromatic hydrocarbons, for i} . I
¦jexample, benzene, toluene, cyclohexane, hexane, heptane, and the ,~like, are employed, but other diluents, such as methyl isobutyl ~etone, diamyl ketone, isobutyl methacrylate, and cyclohexyl ~methacrylate can also be beneficially utilized, if desired, ; !
especiaIly where complete compatability with the sealant system is desired.
The temperature employed in the reaction may also vary over ia wide range. Where t~e components are combined in approximately ~chemical equ;valent amounts, useful~tem~eratures may vary ~rom - . - . .... .
room temperature or below, e.g., ro~c to 15C, up to and includ-' ing temperatures of 100C to 180C. Where reacting the simpler isocyanate adducts, the components are preferably combined at or near room temperature, such as temperatures ranging from 2nc to 30 C. At the lower reaction temperatures, use of a catalyst is preferred. When reacting the higher molecular wei~ht isocyanate adducts, higher temperatures are preferred, e.g., about 40C to about 150C.
It will be recognized that the acrylate-terminated adducts o~ this invention can be prepared by processes other than that described above. Thus, for instance, the polyisocyanate compound -~ 'can be reacted with a suitable hydroxyacrylate and this adduct reacted with a suitable polymer having the necessary reactive l! hydrogen.
" These fully-prepared urethane-acrylate monomeric prepolymers of this invention which are prepared from the polyols and poly--amines of Baccei, above described, correspond to ~he formula 5(~ (C1~2=C~C_o_R6*I~D"~ ) Z

~ 16 - ~

t - ~ 3~
~ I r 106 5536 ¦Iwherein R~ and R~ are as previously deined; I is a polyisocya-,~nate radical; D is an aromatic, heterocyc:Lic or cycloaliphatic ¦~polyol or polyamine radical, preferably a diol, and more pre-, ferably a diol of a cycloaliphatic or aromatic compound; Z is a ~I~pol~meric or copolymeric pol~ol or polyamine radical as already l~described; z is an integer correspondiny to the valency of Z; d . is either 1 or 0; and i is O when d is O, and otherwise is equal , to one less than the number of reactive hydro~en atoms of D. As used herein, an asterisk (*) indicates a urethane ~~NH COO~) or ureide (~NH~CO~NH~) bond. -The term "urethane-acrylate," whether used in reference to ~the monomers of either Baccei or Gorman et al., refers to any ..acrylate-terminated ~e.g. t methacrylate-terminated~..polymerizable ., . . . ............................... . . . ......... : , . , ~ species in which any acrylate group (i.e., CH2=C-C-O-R6 in any of the above formulas) is connected to the remainder of the molecule ;by a urethane or ureide bond, and to the functionality o~ such group.
. THE THER~L ADDITIVE

In addition to the monomers and prepol~mers described above, ~he second required material for this invention is an additive which may be described as maleimide- or nadic-capped and which conforms to any of the following structures:

' O

¢ ~-R C ~- RB

~ , o, ~ O ~> ' i ',, . O 'o O
¢~ RB-h'~3 ,, ~, , O , O , ' ' ' 1. ' '"'' ' ~

~ !
6s53~ I

ji The precise nature of R7 and R~ is not critic~l for purposes of this invention and may be any organic radical which does not ! contain any group which will adversely affect the composition for ''purposes disclosed herein. Most commonlyl, R7 and R8 are selected ~rom the group consisting o alkyl, cycloalkyl, aryl, aralkyl alkaryl, any of which may be exceptionally large radicals, e.g., containing up to about 200 carbon atoms or more; preferably they `;will contain from 6 to about 100 carbon atoms~ most preferably, 6 ,to about 50 carbon atoms. R7 and R8 may also contain ether ; linkages as well as sulfur and nitrogen linkages. R7 and R8 may, moreover, contain branching and may be substituted by halogens or ' lower alkyl radicals having 1 ~o abou~ 6 car~on a~oms.
It appears that the benefits of~thls invention are gained primarily through the action of the imide riny unsaturation. It will, therefore, be understood that both R7 and R8 can consist of relatively complicated moieties, provided only that they do not contai~ functionality which interferes with the performance ol the additive for its intended purposes. The useful concentration ran~e for this additive is about 1 to about 80, preferably about 5 to about 35, more preferably about 5 to about 50 percent by weight of the total composition.
The additives of this invention may be prepared by procedures ~described in U. S. Patent 3,562,223. Typical of such additives are those sold under the tradernarks "Keramid" and "M-3" by Rhodia, Inc., New York~ New York, and "HVA-2" by E. I. du Pont de Nemours & Co., Wilmington, Delaware. The preferred additives comprise '! . j ;Ithe bis-maleimide of m-diaminobenzene, the his-maleimides of the various methylene dianilines, and the reaction products of dia-''mines with molar excess of bis-maleimides. The following struc-tures are especially preferl-ed:
,, I
!' ' l , .
.

I, 106S536 o ~ j=o r a H 0=~ a _ O :~
Y~

,, .
Ij .

65~36 The additives of this invention tend to improve at least four properties of the cured composition/ the extent and nature of the improvement appearing to depend on the specific monomer or prepolymer involved. These improvements comprise greater resistance to degradation of an adhesi~e bond caused by oxidative effects incurred at elevated temperatures, greater strength of the bond or seal at elevated temperatures, greater strength of the bond or seal at ambient temperature, and often also an improvement of the cure strength obtalned under room temperature curing conditions. The precise nature of the im-provement mechanism is not well understood. Without wishing to be bound by any particular theory, it appears that the addi-tives of this invention tend to copolymerize with the monomers or prepolymers, thereby tending to terminate the molecular "unzipping" effect which appears to characterize thermal deg-radation. The improvement of hot strength is believed due to the increase in glass transition temperature brought about by such copolymerization.
The compositions of this invention cure to a hard, 2Q tough resin via a free-radical mechanism using any of a wide variety of known peroxy initiators. Illustrative of such initiators are the diacyl peroxides such as benzoyl peroxide;
dialkyl peroxides such as di-tert.-butyl peroxide; ketone peroxides such as methylethyl ketone peroxide; and peresters which readily hydrolyze, e.g., tert.-butyl peracetate, tert.
-butyl perbenzoate, di-tert.-butyl diperphthalate, etc. A
particularly useful class of peroxy initiators are the organic hydroperoxides such as cumene hydroperoxide, methylethyl ketone hydroperoxide, tert.-butyl hydroperoxide, etc. Of these, cumene hydroperoxide is especially preferred. The initiators should be used at a concentration of about 0.01 percent to about 10 per-cent by weight of the total 1~65S36 formulation, preferably about 0.1 percent to about 5 percent by weight. Another useful class of initiators comprises carbonyl-containing ultraviolet-activated ree-radical generators, such as acetophenone, benzophenone, and the benzoin ethers. Suitable UV initiators ara disclosed in Canadian Patent 1,009,792. Initiator mixtures may also be used.
The adhesive and sealant orm,ulations of this in-vention may be prepared, if desired, with reactive diluents which are capable of copolymerizing with the instant pre-polymers. Typical of such diluents are the hydroxyalkylacrylates such as hydroxyethyl acrylate, hydroxypropyl acrylate, and the corresponding methacrylate compounds, in-cluding cyclohexyl methacrylate, and tetrahydrofurfuryl methacrylate. Other unsaturated reactive diluents, such as styrene and acrylonitrile, can also be used. When used, the concentration of such diluents should be less than about 60 percent by weight, and preferably about 40 to about 10 percent.
It will also be understood that the curable com-position of this invention can also be formulated as a two-par~ composition. In such a case, the initiator or one of a com~ination of initiators can comprise a second part which is combined with the first, monomeric, part at the point of use.
Thus, the monomer can be applied to one surface to be joined, the initiator can be applied to a second surface, and the two surfaces then joined. Similarly, an accelerator can be applied separately as a second part to one of the surfaces to be joined, e.g., as a primer. Suitable primers are those disclosed in USP 3,625,930,to Toback et al., and particularly those of the thiourea type disclosed in Canadian patent 1,030,695. Such primers are advanta~,eously applied as a spray from dilute solvent solution to either or both surf ac~s to be jo ~
~ - 21 -. . ,.,~ .. . .

1065~36 Ii . I
It may be desirable to accelerate the cure polymerization ~by application of moderate amounts of heat, e.g., 50C to 150C.
At temperatures above about 125C, cure ~Jill typically be complete Iwithin about 10 minutes or less without primer.
~ The compositions of this invention can be formulated into room temperature-curing anaerobic adhesives and sealants. Formu-lations of this type are well described in the art, e.g., USP

3,043,820 to Krieble, among others, utilizing the hydroperoxide I, .
class of initiators. Such anaerobic formulations may also advan-tageously include polymerization accelerators such as organic imides- (e.g., benzoic sulfimide~ and primary~ secondar~ or tertiary ;iam-nes~ and inhibitors or stabilizers~f~t~e ~ulnone-or hydro-quinone families. The accelerators are generally employed in concentrations of less than 10 percent by weight, and the inhibi-tors in concentrations of about 10 to 1,000 parts per million.
Wllen prepared as anaerobic formulations, the compositions of this .
; ~ invention have the advantage of long-term stability and the ability to cure at room temperature upon exclusion of oxygen, as between the mating threads of a nut and bolt or the juxtaposed ~-20 surfaces of a bearing and shaft. The anaerobic cure speed can be .
enhanced by application of moderate heat, e.g., up`to about The following examples provide specific illustrations of various aspects of the present invention and are in no way limita-tions on it.

, EX~PLE 1 il . .
i~ This example illustrates two typical anaerobic adhesive ~formulations utilizing any of the prepolymer resins or mixtures thereof, described in the previous sections.

I, ~ 2~ -1.', ' 65S36I!
~iFormulation (a) Ij - .

¦¦ With good stirring, add 4.6 grams of hydroxypropyl meth- .

!1 acrylate (a co-reactive solvent) to 79 grams of the prepolymer I resin product solution (70-75 percent solids)~ A slurry of 0.38 Igram saccharine in 3.8 grams of triethyleneglycol dimethacrylate ~ is then stirred in. Subsequently, 5.6 grams of acrylic acid l`(aahesion enhancer~ and 2.8 grams of cumene hydroperoxide ~OEI~) .; ,, , are added and stirring is continued for about 1 hour. Minor ` amounts of stabiliæers, accelerators, thickeners, plasticizers, and the like, ~ay be added, as desired, as is known in the art.
, ~arying amounts of a hi~h temperature~additive are added, accora-"ing to the examples belowJ such that the final compositions range ' from 5-75% concentration of the high temperature additive. The ,high temperature additive is vigorously stirred in for a period of 1-24 hours.

Pormulation (b) ; Wlth good stirring, add 23.9 grams of hydroxypropyl meth-acrylate to 70 grams of the prepolymer resinsO Subsequently, 2.9 grams of acrylic acid, 2.7 grams of C~P, and 0.3 gram of tributyl amine are stirred in for about one hour. Minor amounts of stabi-liziers, accelerators, thickeners, plasticizers, and the like, .
may be added, as desired, as is known in the art. Varying amounts I of a high temperature additive are added, according to the examples ,ibelow, such that the final compositions range from S-75% concen-tîation of the high temperature additive. The high temperatureadditive is vigorously stlrred in for a period of 1-24 hours.

I, . ' , ' 1, ll - 23 - I
ji i 65536 . I

!; EX~MPLE 2 Anaerobic adhesive formulations were prepared according to Example 1 using some o~ the urethan~ methacrylate prepolymers jl ~solutions - 70-75~ in 20-25% triethyleneglycol dimethacrylate) 1~ ' . I .
lldiscussed in earlier sections and designated in Table I. In ~~Table I below, the abbreviated "Genexal Structures" are derived l;as follo~ls: ;
I . !
Description of ~Prepolymers General S-tructure A - A reaction product of two moles of hydroxy-)i propyl methacry].ate (H~) with one mole of il methylene bis-phenylisocyanate (MDI).
'~ B. A mixture of ~a~ a reaction product of two - moles of a.reac~lon ~xoduct- of.HP2~ with.
ii toluene diisocyanate tTDI~ with one mole of . hydrogenated bis-phenol-A tHBPA) and (b) a i reaction pxoduct of x moles of a reaction . of hydroxyethyl methacrylate tHE~) and TDI
with a polypropylene oxide polyol in the : ratio of a/b of approxi~ately 2/1.
C- A reaction product of two moles of a reac-~: tion pxoduct of HPMA, TDI and HBPA with one : ~ .. 25 . mole:of a butadiene/acrylonitrile diol.
-~: D A reaction product of two moles of a reaction product of HPMA, TDI and HBPA with one mole of a poly(tetramethylene)ether diol having a 30 molecular weight of approximately 2000.
: ~ . E .A reaction product of two moles of a reac-' tion product of HP~$~ and PIDI with one mole ~ . of a poly(tetramethylene)ethex diol having : 35 a molecular weight of approximately 650.
. F A reaction product of two moles of a reac-, tion product o~ ~IP~, TDI and HBP~ with one li - mole of a dispersion in a polypropylene oxide 40 : polyol of a polypropylene oxide polvol to : ., which has been graftea a copolymer of styrene , and acrylonitrile. j . , , . . I
'I !
i, . l l! l .

Ii ~ I

!1 ., .
-. ~ -`. . ~.

. r-~

E

. " . '. t~
'. . ~
. ;-- H

: - .
' : ~ ~td1~; td tlJ X

H ~I H H X 1-1 0 ~ (D
, i p ~ h t p~ ¦~
t~ ~ ~ td ~ ~ ¦
i ~ H~ H H r~l tC~ * n O~`)* I`)* tC H ~ .
It td ~d P) ~~ Ph ~j W o @ :~

o l! td tc ~3 ~
' ~ ~r O ~ , I
. I' . ~ ~
1! 25 -1~5S;3~6 Usin~ the above formulations, a number of physical tests were performed. The tensile lap shear test was per-formed according to ASTM D-1002-65. This test involves adhering together over-lapping surfaces o~ two sand blasted steel test strips. The ends of the so-assembled specimens are pulled with a measuring device such as an Instxon Tester, and the tensile shear strength of the bond is measured.
Compressive shear, tested according to military specification MIL-R-46082A(MR), measures the ability of an adhesive to retain a sleeve or bearing on a shaft. The test involves adhering a cylindrical "pin" within the bore of a mating collar. The force required to press the pin from the collar is then measured on an Instron Tester or equivalent.
Example 3 This example demonstrates the dramatic enhancements in ambient and 400F. hot strengths obtained with the adhesive formulations and Kerimid ~ 601~K-601) in the proportion of 82 parts adhesive formulation and 18 parts K-601. These compositions were applied to steel pins and collars, which were then assembled and allowed to cure for 1 hour at 200OF.
They were then allowed to cool to room temperature. Half were tested at ambient temperature and the remaining half were equilibrated at 400F. for 75 minutes and tested at that temperature. The pins were pressed from the collars using an Instron Tester. Table II reports the results in pounds per square inch of compressive shear strength.

~, . ~._.J
.__ ~L~65536 TABLE II
-Compressive Shear Strength, psi.
PrepolymerAmbient Tempercl-ture 400F.

A+K-601 9535 1815 B+K-601 4460 345 C 3625 g95 C+K-601 4720 1710 (1590*) D+K-601 4555 555 E+K-601 4565 895 F+K-601 4510 with 18% m-phenylene dimaleimide instead of K 601.

Room temperature curing enhancement with primers known to the art is demonstrated in Table III. Steel pins and collars were primed prior to bonding with the adhesive.
Curing time was 24 hours at room temperature.
TABLE III
Compressive Shear Strength, psi Prepolymer "Primer T"* "Accelerator 750"*

E+K-601 2470 2120 F+K-601 2950 2905 * Trademark of Loctite Corporation, Newington, Connecticu~

.~

~0~55316 This example demonstrates the excellent retention of adhesive strength when K-601 is added to one of the formulations.
The adhesives were used to bond steel pins and collars (cured 200F, 1 hour). The bonded specimens were heat aged at 450F, cooled to room temperature and tested.
TABLE IV
Compressive Shear Strength, psi Weeks at 450 F
Test PrepolymerCondition 0 1 2 3 4 __ _ _ C , Ambient 3630 1655 950 400 110 C-~18% K-601Ambient 4665 3635 2185 635 390 Additional evidence for the retention of structural strengths at high temperatures by the formulations plus an additive of this invention ~K-601) is provided in the following two ~ables. The adhesive was used to ~ond steel lap shears (Primed with "Accelerator 750" and cured 24 hours at room tem-perature). The adhesive formulation consisted of 75 parts of pr~polymer B (also containing about 15% of a butylene glycol-adipic acid polyester plasticizer) and 25 parts K-601.

~65536 , TABLE V

Tensile Shear Streng~h, psi Gap 2 mil 20 mil .
Aging Time, Temperature 1 week, 350 F 640 1040 2 wks., " 470 770

4 " " 725 710 6 " " 740 800 10 8 " " 680 760 1 week, 450 F 600 750 2 wks., " 500 590 3 " " 470 680 4 " " 440 650 6 " " 440 610 8 " " 80 710 The "A" formulation with Kerimid was used to adhere 3/8-16 steel nuts and bol~s together. The samples were aged at 400F or 450F for the times shown, but were tested at room temperature. Table VI shows "break/prevail" strength in inch-pounds. "Break" strength is the tor~ue required to cause the first movement between nut and bolt. "Prevail" strength is the torque required to unwind the nut 180 beyond the break point.
TABLE VI
Concentration of K-601, %

Aging Time, Temperature 0 10 50 3 days, 400~ 265~160 245/180 210/150 30 1 week, " 230/135 240/205 125/175 2 wks., " 90/85 135/130 195/230 3 " " 80/70 235/125 125/120 3 wks., 400 F+l wk 450 F 70/90 120/70 120/75 3 " " 5 " " Loose 10/25 20/10 3 " " 7 " " 7/15 35/20 3 " " 9 " " 1/7 5/3 1 ~065536 ¦1 EX~MPLE 7 I! This example demonstrates the excellent therm~l agillg ,properties of another add.itive of this invell~ion (m-phenylene l,dimaleimide ("HV~-2"). The formula-tion used was "B," above.
IIThe adhesive consisted of 75 paxts formu].ation B and 25 ~'parts TIVA-2. The adhesive was used to bond steel lap shears ~which were cured 200F, l hour, then ageci' at 400F or 450F
and tested at room temperature.

TABLE VII
- t 10 . Tensile Shear Strength, psi I'ime 400 F 450 F
l weè~ 2~ 6~0 - , 3 weeks 690 450 4 weeks 830 360

5 weeks 845 140 . - ' '' , EX~PLE 8 , This example illustrates the effect on 400~ hot strengths - .
of increased concentrations of our additive of this invention (m-phenylene dimaleimide). This is illustrated in Table VIII. Steel lap shears were bonded with a "B" formulation containing 0-50% concentrations of the dimaleimide. Initial ,cure was at 200F, I hour, then the samples were equilibrated iat 400F and tested at 400F for tensile shear strength psi).
TABLE VIII

Concentration of }~V~-2, %
0 25 30 35 40 ~5 50 ¦~oo F Strength, 25 395 455 5601585 I960 2~85 pS i .

i - 30 - I
~ I
! I

Claims (23)

WHAT IS CLAIMED IS:

1. A curable composition having improved thermal properties comprising in admixture:
(a) a monomer having polymerizable urethane-acrylate functionality;
(b) an additive selected from the group consisting of wherein R7 and R8 are selected from the group consisting of alkyl, cycloalkyl, aromatic, aralkyl, alkaryl, heterocyclic; and (c) a free radical initiator of free-radical polymerization.

2. A curable composition having improved thermal properties comprising in admixture:
(a) a monomer corresponding to either of the following formulas:

(I) wherein R5 is selected from the class consisting of hydrogen, chlorine and methyl and ethyl radicals; R6 is a divalent organic radical selected from the group consisting of lower alkylene of 1-8 carbon atoms, phenylene and naphthylene; I is a polyisocyanate radical; D is an aromatic, heterocyclic or cycloaliphatic polyol or polyamine radical; Z is a polymeric or copolymeric polyol or polyamine radical; z is an integer corresponding to the valency of Z; d is either 1 or 0; and i is 0 when d is 0, and otherwise is equal to one less than the number of reactive hydrogen atoms of D; and the asterisk (*) represents a urethane or ureide bond;
or (II) wherein n is an integer from 2 to about 6; B is a polyvalent organic radical selected from the group consisting of alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, aralkyl, alkaryl and heterocyclic radicals both substituted and unsubstituted; X is selected from the group consisting of -O- and R2 is selected from the group consisting of hydrogen and lower alkyl of 1 through 7 carbon atoms; and R5 and R6 have the meanings given above;
(b) an additive selected from the group consisting of:
wherein R7 and R8 are selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl, alkaryl, heterocyclic; and (c) a free radical initiator of free-radical polymerization.

3. A composition of Claim 2 wherein Z is derived from a polybutadiene or copolybutadiene polyol or polyamine comprising about 5 to about 150 butadiene units and having at least about 70 percent of the butadiene units in the 1,4-configuration.

4. A composition of Claim 2 wherein Z is derived from a poly(methylene)ether or copoly(methylene)ether polyol.

5. A composition of Claim 2 wherein Z is derived from a poly(alkylene)ether polyol to which has been grafted a vinyl poly-mer or copolymer.

6. A composition of Claim 2 wherein I is toluene diisocy-anate or methylene bis-phenol-isocyanate radical.

7. A composition of Claim 6 wherein D is bisphenol-A or hydrogenated bisphenol-A radical.

8. A composition of Claim 2 wherein R6 is an ethyl or propyl radical.

9. A composition of Claim 2 wherein B is a cycloalkyl, aryl or aralkyl radical.

10. A composition of Claim 2 wherein the additive is

11. A composition of Claim 10 wherein the additive is m-phenylene dimaleimide.

12. A composition of Claim 10 wherein the additive is a bis-maleimide of methylene dianiline or oxy-dianiline.

13. A composition of Claim 10 wherein the additive is a reaction product of methylene dianiline with a molar excess of a bis-maleimide of methylene dianiline.

14. A composition of Claim 2 wherein the free radical initiator is a peroxy or perester compound.

15. A composition of Claim 14 wherein the initiator is a diacyl peroxide.

16. A composition of Claim 14 wherein the initiator is a hydroperoxide and the composition has anaerobic curing prop-erties.

17. A composition of Claim 14 which additionally contains a polymerization accelerator.

18. A composition of Claim 17 wherein the accelerator is an imide or amine.

19. A composition of Claim 2 wherein the free radical initiator is an ultraviolet activated initiator.

20. A composition of Claim 1 which additionally contains an organic solvent.

21. A composition of Claim 20 wherein the solvent is a co-reactive solvent.

22. A process for providing between abutting surfaces, a seal or bond having improved thermal properties comprising applying the composition of Claim 1 to either of such surfaces, placing the surfaces in abutting relationship and allowing the composition to cure.

23. A process for providing between abutting surfaces, a seal or bond having improved thermal properties comprising applying the composition of Claim 16 to either of such surfaces, placing the surfaces in abutting relationship and allowing the composition to cure.