Adhesive system for bonding uncured rubber to cured polyurethane

A thermosetting adhesive comprising a bismaleimide compound and an isocyanate-terminated rubber polymer adapted to coreact upon heating is applied to substrate surfaces of a cured polyurethane and an uncured rubber compound. Upon heating, the adhesive crosslinks and the uncured rubber compound is preferably cured simultaneously. The adhesive is particularly useful in the fabrication of compositions by the bonding of cured polyurethane to an uncured rubber compound which becomes cured during the bonding process, such as in the construction of tires containing cured polyurethane reinforcements within uncured rubber carcasses, the retreading of tires containing polyurethane repairs, etc.

FIELD OF THE INVENTION 
The present invention relates to an adhesive system for bonding a cured 
polyurethane to an uncured rubber, and to the resulting composite, where 
the adhesive comprises a bismaleimide and an isocyanate-terminated rubber. 
BACKGROUND OF THE INVENTION 
Heretofore, it was generally known to adhere or glue a cured urethane to a 
cured rubber compound. The use or application of a liquid urethane, that 
is an uncured urethane to a cured or revulcanized rubber was also known. 
However, it is generally not known to adhere an uncured rubber to a cured 
polyurethane. 
U.S. Pat. No. 2,702,773 to Penn relates to bonding a rubber material to a 
transparent polymeric material having active hydrogen containing groups by 
applying a polyisocyanate type compound between the two materials before 
the rubber is vulcanized. 
U.S. Pat. No. 2,837,458 to Coleman relates to bonding rubber to a non-metal 
substrate utilizing an adhesive system containing an organic isocyanate 
and a dithiocarbimic acid. 
U.S. Pat. No. 3,264,249 to Araki et al relates to adhesive compositions 
utilized in medical applications containing mixtures of a compound which 
has a polymerizable double bond and a cyano group joining the carbon atom 
forming the double bond, a diene type polymer, and a polyisocyanate 
compound. 
U.S. Pat. No. 3,264,269 to Rees et al relates to a process for crosslinking 
polymers containing carboxyl groups comprising reacting a diisocyanate 
with said polymer. 
U.S. Pat. No. 3,528,848 to Zoebelein relates to a rubber article containing 
a hydroxylated butadiene polymer having a cured polyurethane lacquer 
coating. 
U.S. Pat. No. 3,595,826 to Conard relates to preparing adhesives by adding 
dichlorobutadiene to acrylonitrile or methacrylonitrile under 
polymerization conditions. 
U.S. Pat. No. 3,645,980 to Baker et al relates to reacting rubber with a 
nitrosophenol or nitrosoamine and reacting the pendant amino or hydroxyl 
group in the resulting product with an isocyanate. 
U.S. Pat. No. 3,648,748 to Lovell relates to a cured rubber tire having 
adhered thereto a laminate of a cured polyurethane composite produced by 
coating the tire with an adhesive, cured polyurethane which is prepared by 
reacting an organic polyisocyanate with a reactive hydrogen-containing 
polymeric material. 
U.S. Pat. No. 3,817,918 to Aufdermarsh relates to an elastomer-polyester 
composition which is adhered together through the utilization of a 
terpolymer of a polyisocyanate, polyhydroxyphenol, and an epoxy resin. 
U.S. Pat. No. 3,832,274 to Owston relates to adhesives made from butadiene, 
an acrylic monomer, methacrylic acid, and the reducing component of a 
Redox polymerization catalyst. 
U.S. Pat. No. 3,832,275 to Matvey et al relates to a composite of a 
vulcanized diene rubber with a low vapor transmission layer having a 
polyurethane outer layer suitable for use in making containers. The low 
vapor transmission layer can be butyl rubber. 
U.S. Pat. No. 3,882,089 to Baker et al relates to the vulcanization of 
rubber utilizing a compound which upon heating is thought to decompose 
into various components including a nitroso compound, a diisocyanate, and 
the like. 
U.S. Pat. No. 3,916,072 to Hausch et al relates to adhesive compounds 
containing aliphatic nitro compounds. 
U.S. Pat. No. 3,917,554 to Inoue et al relates to a nitrile rubber solution 
type adhesive containing a butadiene-acrylonitrile alternating copolymer. 
U.S. Pat. No. 3,991,255 to Blaskiewicz et al relates to the adhesion of 
polyurethane to an EPDM surface by chemically modifying the EPDM by mixing 
it with a halogen donating material. 
U.S. Pat. No. 4,136,219 to Odam et al relates to adhering a urethane paint 
to a vulcanized rubber surface wherein the rubber surface contains a 
halogenated butyl rubber. 
U.S. Pat. No. 4,311,181 to Hausch relates to applying an uncured urethane 
to a cured elastomer substrate utilizing an amine curable polymer or 
prepolymer such as a urethane polymer or prepolymer and a treating agent 
such as N-halohydantoin, a N-haloamide, or a N-haloimide. 
U.S. Pat. No. 4,535,121 to Ozelli relates to an adhesive for flocking 
elastomers containing an isocyanate-terminated polyurethane prepolymer and 
an adhesion promoter which is the reaction product of an aromatic 
diisocyanate with a polyfunctional epoxide. Optionally, nitroso compounds 
can also be utilized. 
U.S. Pat. No. 4,581,425 to Hefner relates to a thermosetting composition 
containing an alkenyl phenyl cyanate and at least one of an aromatic 
polyisocyanate, a polymaleimide, or a polymerizable ethylenically 
unsaturated aromatic monomer. 
Swedish Patent No. 0648593 to Kamensvii relates to coating one surface of a 
cured rubber with an oligodienediisocyanate and remaining rubber surface 
with an aromatic diamine, combining with two surfaces and permitting 
crosslinking to take place. 
Japanese Patent No. 136363 to Mitsubishi relates to a rubber layer, fiber 
layer composite, having therebetween a polyisocyanate and a hydrocarbon 
polymer. 
Japanese Patent No. 0085941 to Ichi-kaku relates to a rubber polyurethane 
laminate containing a polyisocyanate and DMF. 
Patent DL No. 0227388 to Schwarzheide relates to a process for bonding 
rubber to a foam urethane elastomer by coating the rubber with an elastic 
polyurethane sealant composition and pouring a urethane mixture onto the 
incompletely reacted coating. 
Japanese Patent No. 0179251 to Gosei relates to an endless 
ethylene-propylene rubber composite bonded with an intermediate urethane 
segment. 
Japanese Patent No. 0083031 to Beslon relates to a prepreg containing an 
epoxy resin, a reaction product of a liquid butadiene-acrylonitrile 
copolymer, and an epoxy resin, a diaminodiphenylsulphon, and a 
dicyandiamide. 
Japanese Patent 0083032 to Beslon relates to an epoxy prepreg resin 
containing a novolak type epoxy resin, an epoxy resin containing at least 
one N,N-diglycidylamino group; a reaction product of (C-1) a liquid 
butadiene-acrylonitrile copolymer containing carboxyl groups at both ends 
and (C-2) an epoxy resin; 4,4'-diaminodiphenylsulphone; and dicyandiamide 
and a curing accelerator. 
International Publication No. (PCT) 84/00552 pertains to a modified 
thermosetting imide resin mixture useful as a laminating resin where the 
resin mixture consists of a bisimide adapted to coreact upon heating with 
polyisocyanate. 
SUMMARY OF THE INVENTION 
It has now been found that a cured polyurethane elastomer can be 
advantageously adhered to an uncured rubber compound by utilizing a 
thermosetting adhesive comprising an isocyanate terminated rubber polymer 
and a coreactive bismaleimide. Upon heat curing, the adhesive thermosets 
to a crosslinked solid and tenuously adheres to both the cured 
polyurethane substrate and the rubber compound substrate. Preferably, the 
uncured rubber compound cures under heat at the same time the adhesive is 
cured. In practice, the adhesive composition can be applied to either the 
cured polyurethane substrate or the uncured rubber compound substrate, or 
applied to both substrates and then heat cured under pressure while 
joining the respective substrates to provide a strong, thermoset adhesive 
bond securing the substrates together to form a useful composite. Curing 
the uncured rubber compound simultaneously with curing the adhesive 
further strengthens the bond between the adhesive and the cured rubber 
compound. The heat curing step under pressure further provides excellent 
bonding between the polyurethane and rubber substrates while avoiding air 
gaps between the respective substrates as well as within the adhesive 
bond. 
The adhesive composition of the present invention is particularly useful 
for bonding a cured polyurethane elastomeric tire carcass, or a cord or 
reinforcing belt within an uncured rubber tire carcass or a rubber tread 
where superior adhesion of the polyurethane cord or reinforcement is 
critical. Other uses include adhering an uncured rubber tread to a cured 
polyurethane tire carcass or the adhesion of a cured polyurethane tire 
plug to an uncured rubber compound. The adhesive can be further utilized 
in the fabrication of mechanical goods based on rubber/urethane laminates, 
the bonding of polyurethane encapsulated metal components to tires and 
rubber goods, and the like. These and other advantages of this invention 
will become more apparent by referring to the detailed description of the 
invention and the succeeding illustrative examples. 
DETAILED DESCRIPTION OF THE INVENTION 
The urethane substrate or surface which is bonded or adhered to an uncured 
rubber surface can generally be any conventional urethane as well as those 
known to the art and to the literature. For example, the polyurethane can 
be made from a polyether polyol or a polyester polyol which is usually 
reacted with a slight equivalent excess, e.g. from about 0.25 percent to 
about 5 percent by weight, of a polyisocyanate to form a prepolymer having 
terminal isocyanate groups. Generally, any type of polyisocyanate can be 
utilized such as those having the formula R(NCO).sub.n where R is an 
aliphatic, preferably an alkyl group, an aromatic, or an aliphatic 
substituted aromatic such as an alkyl substituted aromatic having from 4 
to 25 carbon atoms, and preferably from 8 to 18 carbon atoms. The number 
of isocyanate groups, that is n, can be 2, 3 or 4, but preferably is 2. 
Examples of specific isocyanates are well known to the art and to the 
literature. Preferred isocyanates include toluene diisocyanate, "MDI," 
that is 4,4'-methylene bis(phenylisocyanate), the various isomers of 
isophorone diisocyanate, and hydrogenated MDI. The polymer can then be 
cured with various curing agents and/or chain extenders such as various 
polyols or polyamines. By way of example, but not intending to be limited 
thereby, examples of specific types of polyurethanes which can be utilized 
are those as set forth in U.S. Pat. Nos. 2,620,516; 2,777,831; 2,843,568; 
2,866,774; 2,900,368; 2,929,800; 2,948,691; 2,948,707; 3,114,735; and the 
like which are hereby fully incorporated by reference. Examples of 
specific types of commercially available polyurethanes include Adiprene 
L-367, a polytetramethylene ether glycol containing approximately 6.4 
percent isocyanate end groups by weight, manufactured by Uniroyal Chemical 
Co.; Adiprene L-42, a polytetramethylene ether glycol containing 
approximately 2.8 percent isocyanate end groups by weight, manufactured by 
Uniroyal Chemical Co.; and Cyanaprene A-7, a polyester-based coating 
polymer with approximately 2.4 percent isocyanate end groups by weight, 
manufactured by American Cyanamid. Blends of various polyurethanes can 
also be utilized. 
Various curing agents or chain extenders can be utilized such as polyol 
type curing agents and preferably amine type curing agents. Specific 
examples of suitable polyol curing agents include the various diols and 
triols containing from 2 to about 8 carbon atoms with from 3 to about 6 
carbon atoms being preferred such as 1,4-butane diol, 1,3-propanediol, 
glycerine, trimethylol propane, and the like. Various polyamine curing 
agents can also be utilized with diamines being preferred. Such amine 
curing agents have from 2 to about 1,000 carbon atoms with specific 
examples including ethylenediamine, the various phenylenediamines, 
amine-terminated polyols, and the like. However, the following curing 
agents are generally preferred: MOCA, that is 4,4'-methylene 
bis(2-chloroaniline); or, desirably a complex of 4,4'-methylene dianiline 
and a salt, or a complex of racemic 2,3-di(4-aminophenyl) butane and a 
salt, as set forth in U.S. Pat. No. 3,755,261 to VanGulick which is hereby 
fully incorporated by reference. The latter two complexes are preferred. 
The methods for preparing the complexes are set forth in U.S. Pat. No. 
3,755,261. A preferred salt utilized with the 4,4'-methylene dianiline 
compound is sodium chloride or lithium chloride. Due generally to 
availability and costs, the complexes or salts derived from 4,4'-methylene 
dianiline are highly preferred. Another class of amine curing agents which 
can be utilized are the various Versamides, that is the condensation 
products of polyamines and dibasic acids obtained when certain unsaturated 
fatty acids are polymerized, and are manufactured by Henkel Chemical 
Company. 
Equivalent weight of the curing agent utilized with regard to the curable 
prepolymer or polymer, including the amine curing agent, generally ranges 
from about 85 percent to 115 percent with from about 95 to 105 percent 
being preferred. 
The rubber substrate or surface of the present invention is an uncured 
elastomer which is made from various elastomer-forming monomers. One such 
class of monomers are the various conjugated dienes having from 4 to 12 
carbon atoms. Specific examples of diene monomers include butadiene, 
isoprene, pentadiene, hexadiene, heptadiene, octadiene, 
2,3-di-methyl-1,3-butadiene, 2-methyl-1,3-pentadiene, and the like. 
Preferred elastomers are made from monomers of butadiene and/or isoprene. 
Moreover, natural rubber can be utilized. By the term "natural rubber", it 
is meant the elastomeric substance obtained from various trees and plants 
which generally grow in the tropics or desert portions of the world. Such 
material contains a very high content (in excess of 90 percent and often 
in excess of 95 percent) of cis-1,4-polyisoprene. Also included within the 
class of conjugated dienes are the various copolymers and interpolymers 
thereof, e.g., poly(butadiene-isoprene), including various diblock 
copolymers, various triblock copolymers, and the like. 
Another class of useful elastomers are the various copolymers made from 
monomers of conjugated dienes having from 4 to 12 carbon atoms as set 
forth above and vinyl substituted aromatic compounds containing from 8 to 
15 carbon atoms. Examples of specific vinyl substituted aromatic compounds 
include styrene, alphamethylstyrene, 4-t-butylstyrene, vinyl toluene, 
divinyl benzene, isopropenyl benzene, diisopropenyl benzene, and the like, 
with styrene being preferred. Examples of specific copolymers thus include 
poly(styrene-butadiene) (SBR), poly(alpha-methyl-styrene-butadiene), and 
poly(4-t-butylstyrene-butadiene). A preferred copolymer is 
poly(styrene-butadiene). 
Although the following rubber compounds can be utilized, they are not as 
desired as the above elastomers. Thus, butyl rubbers can be utilized which 
are copolymers of isobutylene and a small amount of isoprene. Neoprene, 
that is polychloroprene (2-chloro-1,3-butadiene), can also be utilized. 
Still another class of elastomer rubbers are the nitrile rubbers, that is 
copolymers made from dienes as set forth above having from 4 to 12 carbon 
atoms with acrylonitrile monomers. Usually, the ratio of the two monomers 
in nitrile rubber is similar to the ratio of butadiene to styrene in 
styrene-butadiene rubber. 
Blends of the above said rubbers can also be used. The above elastomers can 
be prepared according to conventional methods known to those skilled in 
the art as well as to the literature. 
While the above description with regard to various polyurethanes and 
uncured elastomers or rubbers has been set forth, it is to be understood 
that this patent is not limited solely thereto in that the invention 
generally pertains to any conventional cured polyurethane and uncured 
rubber substrate as well as to such compounds which are known to the art 
and to the literature. 
In accordance with this invention, the adhesive for adhering the urethane 
substrate to the rubber substrate comprises a thermosetting mixture of a 
bismaleimide compound and an isocyanate-terminated rubber polymer or 
copolymer. The adhesive mixture is adapted to coreact and thermoset upon 
heating to form a solid crosslinked adhesive bond between the cured 
urethane substrate and the uncured rubber substrate. 
The bismaleimide compound can be generally characterized by the following 
formula: 
##STR1## 
where R is an aromatic, an aliphatic, or combinations thereof, or a 
halogen substituent thereof. The aliphatic, especially an alkylene, has 
from 2 to 12 carbon atoms such as ethylene, hexylene, and the like. 
Aromatic compounds are preferred such as those having from 6 to 20 carbon 
atoms. Specific examples of aromatic groups, independently, include 
phenylene, biphenyl, and the like, with methylene bis(phenyl) being highly 
preferred. The R group can also be a low molecular weight polymer as 
having a molecular weight up to about 2,000, such as a hydrocarbon 
polymer, for example, polyethylene, or polybutadiene, a nitrogen 
containing polymer such as polyacrylonitrile, or an oxygen or sulfur 
containing polymer. R.sup.1, R.sup.2, R.sup.3 and R.sup.4, independently, 
is an alkyl having from 1 to 6 carbon atoms, a halogen such as fluoro or 
chloro, or hydrogen. When alkyl groups are utilized, they are generally 
straight-chained, that is they are not branched. 
Alkylene-, arylene-bis-maleimides and combinations thereof are particularly 
useful as the crosslinking agent of the present invention. Specific 
bis-maleimides which are useful in the present invention include 
dimethylenedimaleimide, trimethylenedimaleimide, 
tetramethylenedimaleimide, pentamethylenedimaleimide, 
hexamethylenedimaleimide, heptamethylenedimaleimide, 
decamethylenedimaleimide; the bis-maleimides of 
4,4'-methylene-bis(orthochloroaniline), 4,4'-methylenedianiline, 
4,4'-methylene-bis(3-nitroaniline), 4-aminophenylether and 
N,N'-orthophenylenedimaleimide; N,N'-para-phenylenedimaleimide, 
N,N-metaphenylenedimaleimide, N,N'-(oxydi-p-phenylene)bismaleimide, 
N,N'-(methylenedi-p-phenylene)bismaleimide, 
N,N'-(methylenedi-p-phenylene)bis(2-methylmaleimide), 
N,N'-(thiodi-p-phenylene(bismaleimide, 
N,N'-(sulfonyldi-m-phenylene)bismaleimide, polymethylene polyphenylene 
polymaleimides, and the like. The polymaleimides may be used either alone 
or in any combination. Examples of preferred bismaleimides include 
4,4'-methylene-bis(orthochloroaniline), 4,4'-methylenedianiline, 
4-aminophenylether, and N,N'-para-phenylenedimaleimide. 
Bis-maleimides can be synthesized by various methods such as are disclosed 
in U.S. Pat. No. 2,444,536 and the same is incorporated expressly herein 
by reference. Generally, a diluted ether solution of diamine is added to a 
similar diluted ether solution of maleic anhydride which results in a 
maleamic acid. The maleamic acid can be disposed in acetic anhydride and 
converted into the corresponding bis-maleimide in the presence of 
potassium acetate. Bismaleimides typically are prepared by reacting a 
stoichiometric quantity of maleic anhydride relative to amine groups of a 
polyamine in the presence of a suitable solvent. Such polyamines can 
include 1,4-diaminobutane; dodecyl diamine; 1,6-hexane diamine; 
2-methyl-4-ethyl-1,8-diaminooctane; methylene dianiline; diaminodiphenyl 
ether; and anilineformaldehyde condensation products. Preferred solvents 
are N,N-dimethyl-formamide, chloroform and toluene. 
In use, the bismaleimides are often dispersed in an organic aprotic solvent 
with aromatic solvents being preferred. Such solvents do not have high 
boiling points, that is, the boiling points are 150.degree. C. or less and 
preferably 135.degree. C. or less. Aromatic hydrocarbon solvents and 
aliphatic (alkyl desired) substituted aromatic solvents are preferred such 
as those having from 6 to 12 carbon atoms, with from 6 to 9 carbon atoms 
being preferred. Examples of specific aromatic solvents include benzene, 
xylene, toluene, ethylbenzene, indene, anisole, mixtures thereof, and the 
like. Various aliphatic solvents can also be utilized having from about 5 
to about 15 carbon atoms, with the various alkanes having from 6 to 9 
carbon atoms being desired. Typically, the hexanes, heptanes, isooctanes, 
and isononanes, and mixtures thereof are desired. Various ketones having 
from 3 to 10 carbon atoms can also be utilized such as acetone and methyl 
ethyl ketone. Various esters having a total of from 2 to 15 carbon atoms 
can be utilized such as ethylacetate, ethyl butyrate, butyl acetate, and 
the like. Another class of aprotic solvents are the various polyethers, 
that is ethers which have two or more ether linkages therein, having from 
2 to 10 carbon atoms such as ethylene glycol monobutyl ether, ethylene 
glycol monoethyl ether, ethylene glycol monohexyl ether, and the like. The 
amount of solvents utilized is generally from about 10 to about 1,000 
parts by weight solvent for every 100 parts by weight of bismaleimide 
compound and preferably from about 15 to 150 parts by weight solvent per 
100 parts by weight of bismaleimide compound. 
The adhesive of this invention further contains an isocyanate-terminated 
rubber polymer adapted to coreact and crosslink with the bismaleimide 
compound. The isocyanate-terminated rubber polymer is desirably an 
isocyanate terminated, low molecular weight polymer made from diene or 
monoolefin monomers. If the polymer is produced from monoolefin monomers, 
the number of carbon atoms in each unit is from about 2 to about 12 carbon 
atoms with isobutylene being the preferred polymerized monomeric unit. 
When the isocyanate-terminated rubber polymer is made from dienes, any 
diene monomer having from 4 to 10 carbon atoms can be utilized with 
butadiene being the preferred polymerized unit. Copolymers made from two 
or more of the above monomers can also be utilized. By low molecular 
weight, it is meant that the polymer or copolymer has a molecular weight 
from about 600 to about 30,000 and preferably from about 1,000 to about 
10,000. 
The polyisocyanates utilized to endcap or terminate the low molecular 
weight rubber polymer generally have the formula R(NCO).sub.n where n is 
broadly between 1.5 and 4 as an average, and is preferably 2 although 
small amounts of polyisocyanates can be utilized wherein n is 3 or 4. 
Usually the low molecular weight rubber polymer has from 1 to about 4 
isocyanate groups thereon and preferably about 2 such groups. R is 
generally an aliphatic or preferably an alkyl having from 4 to 20 carbon 
atoms, with from 6 to 15 carbon atoms being preferred. Aromatic or 
aliphatic substituted aromatics or desirably alkyl substituted aromatics 
can also be utilized containing a total of from about 6 to about 25 carbon 
atoms, with from about 7 to about 15 carbon atoms being preferred. 
Specific types of suitable diisocyanates which can be utilized include the 
same compounds set forth hereinabove and are fully incorporated by 
reference. Generally, toluene diisocyanate, isophorone, and MDI are 
preferred. 
The isocyanate-terminated rubber polymers generally are liquid and the use 
of solvents for dispersing the polymers is optional. If a solvent is used, 
essentially non-protic solvents are useful such as toluene, various lower 
alkane solvents, or aromatic solvents such as benzene, and similar 
solvents. Solvents can be utilized, if desired, at levels of about 30 to 
300 weight parts solvent for every 100 weight parts of 
isocyanate-terminated rubber polymer. 
The adhesive composition comprises on a weight basis, from about 10 percent 
to about 90 percent, desirably from about 20 percent to about 80 percent, 
and preferably from about 30 percent to about 60 percent bismaleimide 
based on the total weight of the bismaleimide compound and the 
isocyanate-terminated rubber polymer. Hence, the amount of the 
isocyanate-terminated rubber polymer is the difference. 
The adhesive system can be prepared according to any general method by 
mixing the various components together either simultaneously or in any 
order. The adhesive system of the present invention can be added to the 
cured polyurethane substrate, to the uncured rubber substrate, or to both 
substrates, in any conventional manner as by brushing, coating, spraying, 
dipping, and the like. Several coats can be applied. The surface of the 
polyurethane substrate should be generally free of contamination. This can 
be accomplished by rubbing or brushing the surface thereof with a solvent 
such as tetrahydrofuran, acetone, methyl ethyl ketone, and the like. The 
surface of the rubber substrate can also be cleaned in a conventional 
manner such as by solvent wipe, solvent degreasing, and the like. The 
surfaces are allowed to dry thoroughly before and after applying the 
adhesive. The dried substrate surfaces containing the adhesive system of 
the present invention on either the rubber substrate surface, the urethane 
substrate surface, or both, are then brought together in contact with each 
other and subsequently cured. Heat is usually applied to increase the cure 
rate. Inasmuch as the urethanes can revert, or depolymerize, at high 
temperatures, the upper curing temperature range is generally 175.degree. 
C. or less. Curing generally occurs at temperatures of from about 
125.degree. to about 175.degree. C. and preferably from about 145.degree. 
to about 170.degree. C. Pressure can optionally be utilized with suitable 
pressure ranges being from about 50 to about 10,000 psi and preferably 
from about 100 to about 5,000 psi. Cure of the rubber and the adhesive 
desirably occur in situ. 
The adhesive system of the present invention, as noted above, can be 
utilized in any application wherein it is desirable to bond or adhere a 
cured polyurethane to an uncured rubber, which is cured during the process 
of bonding. A composite or laminate of the rubber, the adhesive, and the 
urethane is thus formed. Specific examples include the adhesion of a cured 
urethane tire core and/or belt to an uncured rubber carcass, and/or tread, 
the adhesion of an uncured rubber tread to a cured polyurethane tire 
carcass, the adhesion of a cured urethane repair plug to an uncured rubber 
substrate, the fabrication of mechanical goods based on rubber/urethane 
laminates of this type, the bonding of polyurethane encapsulated metal 
components to tires and rubber mechanical goods, and the like. The uncured 
rubber substrate is generally and simultaneously cured with the adhesive, 
although it can be cured subsequently. 
The invention will be better understood by reference to the following 
examples wherein parts are by weight and temperatures are in .degree.C., 
unless otherwise indicated.

EXAMPLES 
Urethane-Uncured Rubber Bonding with Bismaleimide/Polybutadiene -NCO 
Prepolymer Adhesive 
Preparation of adhesive cement "E" 
A solution was made of: 
200 g isocyanate-terminated polybutadiene prepolymer XMC-100 (product of 
Arco Chemicals); and 
200 g distilled, desiccated toluene 
About 20.0 grams of the above was mixed vigorously for two minutes, just 
prior to application, with 20.0 grams of a mixture of 200 grams 
bismaleimide XU292 [bis(maleimidophenyl)methane, product of Ciba-Geigy 
Chemical Co.] and 300 grams of distilled, desiccated toluene. The 
resulting mixture was agitated to keep in dispersion as a brush was used 
to apply the adhesive mixture to the polyurethane surface. 
The indicated ingredients were applied to cured polyurethane surfaces as 
specified. Order of application is noted in parenthesis. 
TABLE I 
______________________________________ 
A B C D E 
______________________________________ 
Chemlok 210.sup.a 
(1) (1) (1) (1) None 
(1 coat/dry 2 hrs 
R.T.) 
Chemlok 233.sup.a 
None (2) (2) None None 
(1 coat/dry 1 hr. 
R.T.) 
Chemlok 205.sup.a 
None None (3) (2) None 
(1 coat/dry 1 hr. 
R.T.) 
Adhesive Cement E 
None None None None (1) 
of present invention 
(see previous page) 
(1 coat/dry 20 min 
2 coat/dry 1 hr. 
R.T.) 
NRTie Gum (2) (3) (4) (3) (2) 
(2 layers).sup.b 
Calendered (3) (4) (5) (4) (3) 
cushion stock 
______________________________________ 
Cure Conditions 320.degree. F., 40 min., 5 Tons press. (max) @ 3" ram) 
.sup.a Products of Lord Chemical Corporation used as adhesives for 
elastomer bonding. 
.sup.b Contains natural rubber. 
______________________________________ 
ADHESION TEST RESULTS 
T-Peel Force (pli) 
Sample No. 
24.degree. C. 
100.degree. C. 
Comments 
______________________________________ 
A 1.5, 2.5 1.0 IF 
B 96, 142 2.5 CF/Chunky 
Rubber Tear 
C 46, 40 7.0 -- 
D 5, 5 2.0 Adhesive/Rubber 
Failure 
E 68, 82 11.5 Mixed Chunky 
CF/IR 
______________________________________ 
IF = Interfacial Failure 
CF = Cohesive Failure 
The test results show that the adhesive of the present invention is 
superior to commercial adhesives for bonding cured urethane to in situ 
cured rubber (starting with uncured rubber), by retaining a higher 
strength bond at elevated temperatures, Example "E". 
While in accordance with the Patent Statutes, the best mode and preferred 
embodiment has been set forth, the scope of the invention is not limited 
thereto, but rather by the scope of the attached claims.