FR2515659A1 - DURABLE EPOXY THERMOPLASTIC COMPOUND CONTAINING URETHANE, THERMOSETTING COMPOSITION CONTAINING THE SAME, AND METHOD FOR ADHERING TWO SUBSTRATES - Google Patents

Abstract

THE INVENTION RELATES TO A THERMOPLASTIC COMPOUND, WITH EPOXY PENDING, CONTAINING UETHANE. ACCORDING TO THE INVENTION, THIS COMPOUND IS THE PRODUCT OF THE REACTION OF AN EPOXY RESIN CONTAINING MORE THAN ONE AND PREFERENCE TWO HYDROXYL GROUPS AND OF A POLYISOCYANATE, PREFERREDLY A DIISOCYANATE, THE COMPOUND IS FORMED IN THE PRESENCE OF AN AGENT HEAT REACTING EPOXY HARDENER. THE INVENTION APPLIES IN PARTICULAR TO ADHESIVES, SEALING AGENTS OR COATINGS THAT CAN BE HEAT CURED.

Description

The present invention relates to a novel compound which in combination

  with a heat-reactive epoxy curing agent, can be used as an adhesive, sealant or coating composition which, upon application of heat, preferably in an accelerated manner, cross-links to give a joint, a seal or one

thermoset coating.

  Hot melt adhesive compositions or

  Conventional thermofusions are thermo

  junction plastics that are solid at room temperature but become soft and fluid with good wettability of the adherent at high temperatures These adhesives are easy to apply in the molten state between

  adherents, resulting in a strong thermo-

  adhesive plastic during cooling and hardening

ment.

  Thermoplastic adhesives, which are used in the form of solutions, dispersions, or solids,

  usually join simply by physical means.

  Probably the most important means of application

  of thermoplastic adhesives is the process of the thermo-

  melting where the formation of the junction occurs when the melt of the polymer solidifies in position between the adherents The junctions obtained by this process reach their final strength more rapidly than

  obtained with adhesives of the type in solution.

  Obviously, the thermal stability of the thermosetting resin

  plastic determines its possible usefulness as a hot-melt adhesive For the thermoplastic product to be used as a thermofused product, it must have a low melt viscosity, thus allowing the application of

  adhesive to the adherents at acceptable speeds.

  Usually, this means that the polymer must have a low molecular weight. However, many thermoplastics can not be used as hot-melt products because they do not have sufficient cohesive strength at the low molecular weights required for application to a substrate For example, low molecular weight polyolefins, particularly low molecular weight, low density polyethylene, are widely used in hot-melt adhesives for filling corrugated cartons, closing multiwall bags and the like, but do not have a

  sufficient strength to be used in applications

  structural cations such as the manufacture of plywood.

  Furthermore, they do not have sufficient heat resistance to use them to join components that are intermittently exposed to high temperatures.

  such as under the hood of an automobile.

  Indeed, thermoplastic adhesives can not be used when the adhesive, in situ, is re-exposed at high temperatures forcing the adhesive to bend

  thus allowing the junction to break.

  The concept of thermosetting or cross-linking

  adhesion resin is also known from

  Many thermosetting adhesives comprising both condensation polymers and addition polymers are also known and exemplary formaldehyde, phenol formaldehyde and melamine formaldehyde; Epoxy, Unsaturated Polyester and Polyurethane Adhesives More particularly, US Pat. No. 3,723,568 teaches the use of optional polyepoxides and epoxy polymerization catalysts. US Patent No. 4,122,073 teaches a thermosetting resin obtained from polyisocyanates. The crosslinking in these patents is obtained by a reaction with the available sites in the base polymers. US Pat. No. 4,137,364 teaches the crosslinking of an ethylene / vinyl acetate / vinyl alcohol terpolymer. isophthaloyl, bis-caprolactam or vinyl triethoxy silane where the crosslinking is achieved prior to heat activation with additional heat-induced crosslinking after application of the adhesive US Patent No. 4,116,937 teaches another method of

  thermal crosslinking by use of class -

  polyamino bis-maleimide flexible polyimides, which compounds can be extruded in the heat-fused state up to 1500 C and undergo crosslinking at high temperatures located above In the latter two patents, the thermal crosslinking is also obtained by the reactions of The Particular Crosslinking Agent with Available Sites of Basic Polymers US Pat. No. 3,934,056 teaches high tack resin compositions comprising ethylene-vinyl acetate copolymer, chlorinated or chlorosulfonated polyethylene, unsaturated carboxylic acids and the like. An organic peroxide Another thermosetting adhesive is known from U.S. Patent No. 3,945,877. The composition comprises coal tar, ethylene / vinyl acetate copolymer and ethylene / acrylic acid copolymer plus an agent.

  crosslinking agent such as dicumyl peroxide.

  In many of these thermosetting adhesive compositions according to the prior art, the mixture of two, three or four components is necessary in order to obtain a thermoset junction. Thus, the resulting junction depends on the homogeneity of the mixture. many cases, such as epoxy adhesives, two or more components must be mixed just prior to junction preparation This requires application

  fast as the cross-linking reaction starts immediately

  after mixing and is irreversible.

  The subject of the present invention is the production of a composition which can be used as an adhesive, a sealing agent or a coating which is solvent-free. Another object of the present invention is the production of a composition which can be applied in the form of a Another object of the present invention is to produce a novel compound which, in combination with an epoxy curing agent, reacts with the process of producing a thermosetting composition in a minimum time. The present invention further relates to the production of a thermoplastic composition which can be applied in the form of a hot melt and subsequently cured by a heat-cured sealant, adhesive or thermosetting sealant. Initiator triggered thermally to give an adhesive, sealant or thermoset coating at a relatively high temperature Other objects will become better apparent

  upon reading the following description.

  The present invention relates to a thermoplastic, pendant epoxy compound containing urethane, which is the reaction product of an epoxy resin containing more than one and preferably two hydroxyl groups and a

  polyisocyanate, preferably a diisocyanate.

  The compound is preferably formed in the presence of a heat-reactive epoxy curing agent to provide a component material useful as an adhesive, sealant or thermoset coating when heated. Some of the epoxy resins used here as

  reagent to form the new compound are marketed.

  Such materials include certain "Shell" Epon resins, having the general structure:

CH OH CH

  CH 2 -CH-CH 2 C -O CH 2 -CH-CH-CH C H

2- <CHCCH 27 OC 2-C-H

CH 3 CH 3

  N may be from about 1.1 to about 3 to form the novel compound. Another epoxy resin useful as a reagent is a methylolated version of a conventional bis-epi resin sold under the trade name "Apogen-101" by M & T Chemicals. having the idealized structure

HOH 2 C CH OH

0 CH 3-H

CH 2 -CHCH 2 O CH 3 CH 2 CH-H 2

CH 3 -

  In other cases, the hydroxyl-containing reactive epoxy resin can be prepared by reacting a bis-epi resin such as resorcinol diglycidyl ether with a diol as bisphenol A to obtain a hydroxyl-containing epoxy resin: 2 CH 3 v O

  2 CH 2 -CHCH 20 'OCH 2 CHCH 2 + HO OH

1-5 t CCH 3

ICH

  Any diol can be used in the reaction with the bis-epi resin, the only criterion being the final use of the new compound. Thus, aliphatic diols such as diethylene glycol, polyethylene glycol, polypropylene glycol and the like are usable, as well as aromatic polyols. The hydroxyl-containing epoxy resin I is then reacted with its hydroxyl groups with a

  polyisocyanate to form a new thermo compound

  plastic, epoxy pendant, containing urethane, according to the invention, namely:

2515659-

I + R- (NCO) 2

CH O

  CH 2 CHCH 2 CH 2 CH 2 CH 2 CH 2 CHCH 2

CH O

C = O

NH t

R II

t NH l

o R is an organic fragment.

  The reaction between the hydroxyl-containing epoxy resin and the polyisocyanate in the present invention

  is preferably carried out in the presence of a hardening agent.

  latent epoxy to evenly disperse this

  agent throughout the resulting solid reaction product.

  Thus, the reaction is carried out at a lower temperature

  below the decomposition temperature of the latent epoxy curing agent, i.e., at a temperature between 20 and 120 ° C. The reaction is performed in the presence of a catalytic amount, such as 0.01 to 5% These catalysts include, but are not limited to, triphenyl phosphine, sodium dodecyl ether, and the like.

  dibutyltin, stannous octoate and the like.

  In cases where the decomposition temperature of the latent epoxy curing agent is lower than the reaction temperature of the urethane-forming reaction,

  the epoxy curing agent is added to the thermo compound

  epoxy-containing plastic, containing urethane, after cooling to room temperature This can be done by grinding the compound with the curing agent

  of epoxy to obtain a uniform mixture.

  The epoxy curing agent is added to the compound in an amount of from 4 to 50 parts per part of the epoxy resin prior to urethane formation. Well-known heat-activated epoxy curing agents include, but are not limited to dicyandiamide, amine adducts of BF 3,

  4,4'-methylenebis (phenylcyanamide) and the like.

  The epoxy resin to be used for forming the hydroxyl-containing reagent according to the invention comprises the materials having at least and preferably more than one epoxy group such as a group. These compounds may be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic and may be substituted with substituents, such as chlorine, hydroxyl groups, ether radicals and the like.

  can be monomeric or polymeric.

  For the sake of clarity, a large number of polyepoxides and in particular those of the polymeric type are described in terms of the values of the epoxy equivalents. The meaning of this term is described in U.S. Patent No. 2,633,458. The polyepoxides used in the present composition and the present process are those having a

epoxy equivalence of at least 1.0.

  Various examples of polyepoxides that can be used in the composition and the process according to the invention are given in U.S. Patent No. 2,633,458 and

  will understand that the description of this patent pertaining

  examples of the polyepoxides are given only as

  reference in the present description.

  polyethylenically unsaturated monocarboxylic acids of polyethylenically unsaturated monocarboxylic acids such as linseed oil, soybean oil, perilla oil, oiticica oil, nut abrasin oil and dehydrated castor oil;

  methyl linoleate, luteal linoleate, 9,12-

  ethyl octadecadienoate, butyl 9,12,15-octadecatrienoate, butyl oleostearate, abrasive oil fatty acid monoglycerides Ln monoglycerides of soybean oil, sunflower oil, rapeseed oil, hemp seed oil, sardine oil, oil

  cottonseed and the like, in the epoxidized state.

  Another group of epoxy-containing materials which can be used in the composition and process according to the invention comprises the epoxidized esters of unsaturated monohydric alcohols and polycarboxylic acids. For example, di (2,3-epoxybutyl) adipate, di (2,3-epoxybutyl)

  oxalate, di (2,3-epoxyhexyl) succinate, di (3,4-

  epoxybutyl) maleate, di (2,3-epoxyoctyl) pimelate,

  di (2,3-epoxybutyl) phthalate, di (2,3-epoxyoctyl) tetra-

  hydrophthalate, di (4,5-epoxydodecyl) maleate,

  di (2,3-epoxybutyl) tetraphthalate, di (2,3-epoxypentyl) -

  thiodipropionate, di (5,6-epoxytetradecyl) diphenyl-

  dicarboxylate, di (3,4-epoxyheptyl) sulfonyldibutyrate, tri (2,3-epoxybutyl) 1,2,4-butanetricarboxylate,

  di (5,6-epoxypentadecyl) tartrate, di (4,5-epoxytetradecyl) -

  maleate, di (2,3-epoxybutyl) azelate, di (3,4-epoxybutyl) -citrate, di (5,6-epoxyoctyl) cyclohexane-1,2-dicarboxylate,

  di (4,5-epoxyoctadecyl) malonate.

  Another group includes hydrocarbons

  epoxy polyunsaturated unsaturation such as 2,2-bis (2-

  epoxidized cyclohexenyl) propane, epoxidized vinyl cyclohexene

  and the epoxidized cyclopentadiene dimer.

  Another group includes polymers and

  epoxidized copolymers of diolefins such as butadiene.

  Examples include, but are not limited to, butadiene acrylonitrile copolymers (Hycar rubbers),

  butadiene-styrene copolymers and the like.

  Another group includes glycidyl-containing nitrogen compounds such as diglycidyl aniline and

di and triglycidylamine.

  The polyepoxides which are particularly preferred for use in the compositions according to the invention are glycidyl ethers and in particular the glycidyl ethers of polyhydric phenols and polyhydric alcohols. The glycidyl ethers of polyhydric phenols are obtained by reaction of epichlorohydrin with

  polyhydric phenols desired in the presence of an alkali.

  Polyether-A and Polyether-B described in U.S. Patent No. 2,363,458 are good examples of such polyepoxide. Other examples include

  polyglycidyl ether of 1,1,2,2-tetrakis (4-hydroxyphenyl) -

  ethane (epoxy value of 0.45 eq / 100 g) and

  85 C fusion, polyglycidyl ether of 1,1,5,5-tetrakis

  (hydroxyphenyl) pentane (epoxy value of 0.514 eq / 100 g)

and the like, and mixtures thereof.

  Additional examples of epoxy resins usable herein include, but are not limited to, diglycidyl isophthalate, diglycidyl phthalate, o-glycidyl phenyl glycidyl ether, resorcinol diglycidyl ether, phloroglucinol triglycidyl ether, triglycidyl

  methyl phloroglucinol ether, 2,6- (2,3-epoxypropyl) -

  phenyl glycidyl ether, 1- (2,3-epoxy) propoxy-N, N-

  bis (2,3-epoxypropyl) aniline, 2,2-bis-2,3-epoxypropoxy

  propoxy) phenylpropane, the diglycidyl ether of

  bisphenol A, diglycidyl ether of bisphenol-hexafluoro-

  acetone, the diglycidyl ether of 2,2-bis (4-hydroxyphenyl) -

  nonadecane, diglycidyl phenyl ether, triglycidyl 4,4-bis (4hydroxyphenyl) pentanoic acid, diglycidyl ether

  tetrachlorobisphenol-A, diglycidyl ether tetra-

  bromobisphenol-A, ie triglycidyl ether of trihydroxy-

  biphenyl, tetraglycidoxy biphenyl, ltetrakis (2,3-

  epoxypropoxy) diphenylmethane, 2,2 ', 4,4'-tetrakis

  (2,3-epoxypropoxy) benzophenone, 3,9-bis L 2- (2,3-epoxy)

  propoxy) phenyl ethyl) -2,4,8,10-tetraoxaspiro 1,5,53 -

  undecane, triglycidoxy-1,1,3-triphenylpropane, tetraglycidoxy tetraphenylethane, polyglycidyl ether of novolac phenolformaldehyde, o-cresol-formaldehyde polyglycidyl ether novolac, butanediol diglycidyl ether, di (2-methyl) glycidyl ether ethylene glycol, polyepichlorohydrin di (2,3-epoxypropyl) ether, polypropylene glycol diglycidyl ether, epoxidized polybutadiene, epoxidized soybean oil, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, the

  polyallyl glycidyl ether, 2,4,6,8,10-pentakis 13- (2,3-

  epoxypropoxy) propyll 2,4,6,8,10-pentamethylcyclopenta

  siloxane, diglycidyl ether of chlorendic diol, diglycidyl ether of dioxanediol, diglycidyl ether of endomethylene cyclohexanediol, diglycidyl ether of hydrogenated bisphenol-A, vinylcyclohexyl dioxide, limonene dioxide, dicyclopentadiene dioxide,

  p-epoxycyclopentenylphenyl glycidyl ether, epoxy-

  dicyclopentenylphenyl glycidyl ether, o-epoxycyclo

  pentenylphenyl glycidyl ether, bis-epoxydicyclopentyl

  ethylene glycol ether, (2,3,4-epoxy) cyclohexyl-

  , 5-spiro (3,4-epoxy) -cyclohexane-m-dioxane, 1,3-bis-3- (2,3-epoxypropoxy) propyl tetramethyldisiloxane, epoxidized polybutadiene, linoleic acid trimeric triglycidyl ester, epoxidized soybean oil, diglycidyl

  ester of linoleic dimer acid, 2,2-bis-4-

  epoxypropyl) cyclohexylpropane, 2,2- (4-1-chloro-2-

  (2,3-epoxypropoxy) propolyl (cyclohexyl) propane, the

  2,2-bis (3,4-epoxycyclohexyl) propane, bis (2,3-epoxy)

  cyclopentyl) ether (liquid isomer), bis (2,3-epoxy-

  cyclopentyl) ether (solid isomer), 1,2-epoxy-6- (2,3-

  epoxypropoxy) hexahydro-4,7-methanoindane, 3,4-epoxycyclohexylmethyl- (3,4-epoxy) cyclohexane carboxylate,

  3,4-epoxy-6-methylcyclohexylmethyl-4-epoxy carboxylate

  6-methylcyclohexane and bis (3,4-epoxy-6-methylcyclohexyl)

  methyl) adipate Tri and tetrafunctional epoxides

  such as triglycidyl isocyanurate and tetraphenylol-

  Ethane epoxy can also be used here.

  The reaction to form hydroxyl groups on the epoxy resin is carried out in the presence of a catalyst at a temperature between 80 and 150 C, preferably between 90 and 125 C. The known catalysts include, without limitation, triphenyl phosphine,

  triisopropylamine and 3- (p-chlorophenyl) -1,1-dimethylurea.

  These catalysts are added to the reaction in amounts of 0.1 to 1.2 parts per 100 parts of the reaction.

epoxy resin.

  The polyisocyanates employed in the present invention to form the novel compound can be aromatic, aliphatic, cycloaliphatic and their

  The diisocyanates are preferred, but

  and tetraisocyanates can also be used

  Examples of diisocyanates are:

  2,4-toluene diisocyanate, the diisocyanate of

  phenylene, xylylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4,4'-biphenylene diisocyanate,

  1,4-tetramethylene diisocyanate and 1,6-hexa

  methylene, 1,4-cyclohexylene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate and methylene diisocyanate dicyclohexylene Diisocyanates wherein each of the isocyanate groups is directly attached to a ring are preferred because usually they react more

easily.

  Other diisocyanates which can be used are the high molecular weight diisocyanates obtained by reaction of polyamines containing terminal groups.

  primary or secondary amine or dihydric alcohols.

  For example: 2 moles of diisocyanate R 5 (NCO) 2 are reacted with 1 mole of an OH-R 6 -OH diol to form an extended chain diisocyanate, such as

0 O

II He

OCN-R 5-NHCO-R 6-OCHN-R 5-NCO

  o R and R 6 are divalent organic fusgmenias.

  Thus, the alkane and alkene polyols such as 1,5-pentenediol, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, "bisphenol-A" and "substituted bisphenol-A" are usable here for These diols can have molecular weights from about 200 to about 20,000, the high molecular weight range being used when reacting the diisocyanate formed with a low molecular weight epoxy resin. In addition, unsaturated diisocyanates may also be employed. These materials, for example, may be formed from diols such as the hydroxyl terminated homopolymer and copolymer family, which

  are marketed by ARC O under the trade name

  These resins include butadiene homopolymers of the formula: ## STR1 ##

CH: CH HI / CH 2 6

HO (CH CH (C

  H O (CH 2 to CH 2 2 (CH 2-CH) Q-2 (CH 2

  CH = CH 2 n + N is equal to about 50, and diol copolymers of styrene-butadiene and acrylonitrile-butadiene of the formula: HO (CH 2 -CH = CH-CH 2) a (CH-C H 2) b HX n in which X = O for a copolymer X = CN for a copolymer

  of acrylonitrile styrene-butylene

  Butadiene a =, 75 a = 0.85 b =, 25 b = 0.15 n = 54 N = 78-87 One mole of these unsaturated polyols will react with 2 moles of a diisocyanate to form a diisocyanate.

  elongated chain, having unsaturation in its ridge.

  The heating step for curing the pendant epoxy compound containing urethane is usually carried out for 10 seconds to 30 minutes at a temperature of 100 to 300 ° C, preferably 120 to 2000 ° C, sufficient to fully cure. the composition in an adhesive,

  Thermoset and solid sealant or sealant.

  The heating step using a latent epoxy curing agent to cure the compound can be accomplished in several ways. In simple adhesive systems, the composition can be applied by manual means, to a follower, placed in contact with another adherent and the assembled system can be heated in an air oven

  forced until it results in a thermoset junction.

  In addition and preferably, an electric heater

  Magnetic can be used as a faster and more effective means of curing, particularly if the substrates to be joined are plastics. In addition to the formation of high strength junctions, electromagnetic junction techniques help in (a) fast times. hardening of the junction and (b) a

  automation of handling and assembly.

  In the practice of the invention, electromagnetic heating may be employed with the adhesive composition of the present invention to adhere (1) plastic to plastic, (2) plastic to metal and (3) metal For example, a dielectric heater can be used to join (1) and (2) above if the adhesive composition contains

  enough polar groups to heat the composi-

  quickly and allow it to join or stick the adherents Induction heating can also be used to join (1), (2) and (3) Indeed, when at least one of the adherents is an electrically conductive or ferromagnetic metal the heat produced therein is transferred by conductance to the adhesive composition, thereby initiating the curing to form a thermoset adhesive. In the case where the two adherents are made of plastic material, it is necessary to add an energy absorbing material such as an electrically conductive or ferromagnetic material, preferably in the form of fibers or particles (mesh US 10-400) to the adhesive composition. The energy absorbing material is usually added in amounts of between 0.1 and 2 parts by weight.

  weight, for 1 part by weight of the adhesive composition.

  It is also possible to impregnate the plastic adherent at the joint of the junction, particles of the energy absorbing material to use induction heating, but care must be taken that the material

plastic is not deformed.

  The particulate electromagnetic energy absorbing material used in the adhesive composition when induction heating is employed may be one of magnetizable metals including iron, cobalt and nickel or magnetizable alloys or nickel oxides

  and iron and nickel and chromium and iron oxide.

  These metals and alloys have high Curie points

(388-11160C).

  Electrically conductive materials useful herein when induction heating is employed include, but are not limited to, noble metals, copper, aluminum, nickel, zinc as well as lampblack, graphite

and inorganic oxides.

  There are two forms of high-frequency heating that can be used here, whose choice is determined by the material to be adhered. The major distinction comes from the fact that the material is conductive or non-conductive of the electric current. a conductor, such as iron or steel, then we use the induction method If the material is an insulator, such as wood, paper, textiles, synthetic resins, rubber and others, then we can also use a

dielectric heating.

  Most natural and synthetic polymers are non-conductive and therefore suitable for dielectric heating. These polymers can contain a wide variety of dipoles and ions that orient in an electric field and rotate to maintain alignment with the field when The polar groups can be incorporated in the edge of the polymer or can be pendent side groups, additives, chalk extenders, pigments and others. For example, as additives, fillers such as carbon black at a level of 1 % can be used to increase the dielectric response of the adhesive When the polarity of the electric field is reversed millions of times per second, the resulting high frequency of the polar units

  produces heat in the material.

  Dielectric heating is unique in its

  uniformity, speed, specificity and efficiency.

  Most plastic heating processes like

  heating by conduction, by convention or by infra-

  red are surface heating processes, which must establish a temperature in the plastic and subsequently transfer the heat to the mass of the plastic material, by conduction Therefore, the heating of plastics by these methods is a relatively slow process with a temperature As a result, dielectric heating produces heat inside the material and is therefore uniform and fast, eliminating the need for conductive heat transfer.

  In this case, the electric frequency of the electric field

  This magnetic field is produced by a power source of 0.5-1000 k W. The induction heating is similar, but not identical, follow: (a) the magnetic properties replace the dielectric properties; (b) a coil is used to couple the charge rather than electrodes or plates; and (c) induction heaters couple a maximum current to the load Inductive heat production works by the rise and fall of a magnetic field around a conductor with each inversion of an AC power source. practice of this field is usually accomplished

  by a good implementation of a conductive coil.

  When another electrically conductive material is exposed to the field, an induced current may be created. These induced currents may be in the form of statistical or "parasitic" currents which result in the production of heat. Materials which are magnetizable and drivers produce more easily

  heat than materials that are only conductive.

  The heat produced as a result of the magnetic component is the result of hysteresis or work done during the rotation of the magnetizable molecules and as a result of the parasitic current flow Polyolefins and other plastics are neither magnetic nor electrically conductive. Therefore, in themselves, they do not create heat as a result of induction. The use of the electromagnetic induction heating method for the adhesive joining of plastic structures has proved possible by interposing

  selected materials for absorption of electro-

  magnetic in a layer or lining of independent adhesive composition conforming to the surfaces to be joined, the electromagnetic energy passing through the adjacent plastic structures (without these energy absorbing materials) is easily concentrated and absorbed into the adhesive composition by these materials absorbing the energy, thus rapidly beginning the hardening of the

  adhesive composition ern fun thermoset adhesive.

  Electromagnetic energy absorbing materials of various types have been used in the electromagnetic induction heating technique for some time. For example, inorganic oxides and powdered metals have been incorporated in tie layers and subjected to electromagnetic radiation. In each case, the type of the energy source influences the choice of the energy absorbing material When the energy absorbing material is composed of finely divided particles having ferromagnetic properties and these particles are effectively isolated from each other by a non-conductive matrix material containing the particles, the heating effect is substantially confined to that resulting from the effects of hysteresis. Accordingly, the heating is limited to the "Curie" temperature of the ferromagnetic material or to the temperature at which which

  the magnetic properties of this material cease to exist.

  The electromagnetic adhesive composition according to the invention may be in the form of an extruded ribbon, a molded gasket or a cast sheet in liquid form, it may be applied by brush to the surfaces to be joined or it may be spray or use it as

  dip coating for such surfaces.

  The above adhesive composition, when properly used as will be described hereinafter, provides a solvent-free joining system which allows the joining of metal or plastic articles without costly surface pretreatment. Joining or bonding reaction electromagnetically induced, occurs rapidly

  and can adapt to automatic techniques and equipment

manufactured.

  To accomplish the establishment of a concentrated and specifically localized area of heat by induction heating in the context of the junction according to the invention, it has been found that the electromagnetic adhesive compositions described above can be activated and that a junction could be created by an induction heating system operating with an electric frequency of the electromagnetic field of the order of 5 to about 30 megacycles and preferably of the order of 15 to 30 megacycles, this field being produced by a current source from about 1 to about 30 kilowatts

  and preferably of the order of 2 to about 5 kilowatts.

  The electromagnetic field is applied to articles to

  join for a time less than about 2 minutes.

  As has been mentioned up to now, the electromagnetic induction joining system and the improved electromagnetic adhesive compositions according to the invention can be applied to the joining of metals, thermoplastics and thermosets, comprising

  a thermoset material reinforced with fibers.

  It is critical that the urethane-containing pendant epoxy compound of the invention is linear or cyclic, i.e. thermoplastic, prior to use with a latent epoxy curing agent. Thus, the number of groups OH present in the epoxy resin before the reaction with the polyisocyanate may be any number, preferably 2, depending on the functionality of the polyisocyanate to react with it, and the equivalent ratio of -OH to -NCO in the reaction For example, it can be done react a monoepoxide containing two hydroxyl groups obtained from bisphenol and glycidylaldehyde, that is to say

CH-CH 2

HO CH-F -OH

  with an OCN-R-NCO diisocyanate to form a polyurethane:

III + OCN-R-NCO

1 / A

CH-CH 2

* 0 0

  q 5 -CNH-R-NHC-O-Q "CH 4 -O IV o N can be any number according to the ratios of the moles

III and isocyanate.

  The resulting urethane-containing epoxy thermoplastic material may then be blended with a latent epoxy curing agent, such as a dicyandiamide, and epoxy cured into a thermoset coating, sealant or adhesive,

by heating.

  In addition, a dihydroxyl diepoxide can be used as

0 HOH 2 CH CH 2 OH O

CH 2 -CHCH 20 C OCH 2 CH-CH 2 V

  CH 3 Again, it is reacted with a diisocyanate to form a polyurethane:

V + OCN-R-NCO

0 O

  ## STR2 ##

CH / CH

CH 2 CH 2

  N depends on the ratio of the moles of V and the isocyanate.

  The resulting thermoplastic material (VI) will form

  a thermoset material useful as an adhesive, an agent for

  dryness or coating when heated with an agent

curing latent epoxy.

  An epoxide-terminated polymeric material containing more than two OH groups formed by the reaction of bisphenol-A and epichlorohydrin such as Epon resins, marketed by Shell Chemical Co, i.e.

O CH H 3 OH CH 3 O

  QH 2 -CHCH 2 O-CH 2-CHCH 2 CH 2 CH-CH 2

CH 3 N CH 3 VII

  o N is 2.2, can also be used when reacting a quantity of diisocyanate less than the stoichiometric amount Indeed, in systems containing bifunctional monomers, a high degree of polymerization can not be reached which if the reaction is almost forced to completion The introduction of a trifunctional monomer into the reaction produces a fairly dramatic shift that is best illustrated using a modified form of the Carother equation. A more general factor of fav functionality is introduced, which is defined as the average number of functional groups present per unit of monomer For a system containing No molecules initially and equivalent numbers of E two functional groups A and B, the total number of functional groups is NO fav The number of groups reacted in time to produce N molecules is then 2 (N 0-N) and p = 2 (N 0-N) / NO fav The expression for xn devie then xn = 2 / (2-pfav) but this is only valid when equal numbers of the two

  functional groups are present in the system.

  For a completely bifunctional system such as an equimolar mixture of an epoxy resin containing two hydroxyl groups and a diisocyanate, we have fav = 2 and xn = 20 for p = 0.95 Si, however, we add a trifunctional alcohol and that the mixture is composed of 2 moles of diisocyanate, 1.4 moles of diol and 0.4 moles of triol, fav increases to: fav = (2 x 2 + 1, 4 x 2 + 0.4 x 3) / 3.8 = 2.1 The value of xn is now 200 after

  % conversion, but only a small increase

  at 95.23% so that xn approaches infinity, quite dramatic increase This is a direct result of the incorporation of a trifunctional unit into a linear chain where the unreacted hydroxyl offers This leads to the formation of a very branched structure and the more the number of multifunctional units is important, the more important is the growth in an insoluble three-dimensional network. It is critical that the composition remains thermoplastic and does not reach its gel point prior to its use as a coating. The system has reached its gel point, that is, the system is thermoset. , sealant

or hot melt adhesive.

  The following examples are given to explain the present invention, without in any way limiting the scope unless it is noted Autremo And all

  parts and percentages are by weight.

  The tensile strength properties of the adhesive under shear stress (metal on metal) were determined according to ASTMD 1002-64 in accordance with

  based on a 25.4 mm overlap area.

EXAMPLE 1

  Preparation of the diisocyanate adduct 127.8 g of propylene glycol (molecular weight = 725 g / mol) were added dropwise over a period of 6 hours to a flask containing 61.4 g of diisocyanate The resultant isocyanate and extended chain terminated product will be referred to hereinafter as the diisocyanate A addition product. The reaction mixture is stirred for 4 days at room temperature.

EXAMPLE 2

  A flask containing 100 g of bisphenol A diglycidyl ether, 15 g of bisphenol A and 0.12 g of triphenyl was prepared in 4 equal portions over a period of 30 minutes at a reaction temperature of 120 ° C. Phosphine The reaction was continued at 1200 C for 2.5 hours. The modified reaction product had an epoxide equivalent weight of 292 g / eq based on

on the titration.

  100 g of the modified epoxy reaction product was mixed with 61 g of the diisocyanate adduct A of Example 1 and 6 g of dicyandiamide at room temperature to give a hot melt adhesive with epoxide groups. Reagents The hot melt adhesive was applied between 1000 C cold rolled steel adherents pressed together and placed in an air oven at 180 ° C for 30 minutes. Shearing the shear

resulting was 241 x 105 Pa.

  The adhesive was used in the same way between

  adhesives composed of glass fibers and polyester.

  The adherents broke before the adhesive junction

  in the shear test of the covering.

EXAMPLE 3

  To a mixture containing 100 g of an epoxy resin containing 357 g / eq of OH, sold by Shell Chemical Co, under the trade name "Epon-1001 F", 6 g of dicyandiamide and 1 g of triphenyl phosphine, was added 71.6 g of the diisocyanate adduct A of Example 1 After heating at 800 ° C. for 1 hour, the adhesive was cooled to room temperature

  and solidified as a reactive hot melt adhesive.

  After application to substrates at 125 ° C. and curing at 160 ° C. for 30 minutes, the adhesive showed a shear strength of 221 × 10 5 Pa at the steel and a substrate break for a polyester.

reinforced with glass fibers.

EXAMPLE 4

  To a mixture containing 100 g of Epon-1001 F, 25 g of an epoxy resin containing 0.2 OH group / mole and marketed by Shelle Chemical Co, under the trade name "Epon 828", 7.5 g of dicyandiamide, 71.6 g of the diisocyanate adduct A of Example 1 was added. After heating at 80 ° C. overnight, the adhesive was applied to substrates at 125 ° C. and cured at 160 ° C. for 30 minutes. minutes The adhesive had a shear strength of 303.3 x 105 Pa over steel and 31.7 x 105 Pa over polyester

reinforced with glass fibers.

EXAMPLE 5

  To 100 g of Epon-828 was added a mixture containing 21 g of bisphenol A and 0.14 g of triphenyl phosphine at 120 ° C. After reaction at 120 ° C. for 3 hours, 100 g of this product containing 100 ml of hydroxyl and epoxy-terminated in 100 g of methylene chloride and then reacted with 61 g of the diisocyanate adduct A of Example 1 in the presence of 0.5 g of dibutyl dilaurate. The reaction was monitored with infrared until no isocyanate could be detected in the reaction mixture.

  added 6 g of dicyandiamide and 2 g of triphenyl phosphine.

  The methylene chloride solvent was removed under vacuum.

  The final heat-set adhesive was applied to substrates at 125 ° C and cured at 160 ° C for 50 minutes. This adhesive had a shear strength of 103.4 x 105 Pa over steel. and 62 x 105 Pa

  vis-à-vis a polyester reinforced with fiberglass.

EXAMPLE 6

  To 100 g of "Epon-1001 F" dissolved in 100 g of methylene chloride was added 48.9 g of diisocyanate adduct A of Example 1 and 0.75 g of dibutyltin dilaurate. The reaction was continued until no trace of isocyanate could be detected in the infrared spectrum

EXAMPLE 7

  To 100 g of the product solution of Example 6,

  40 g of an amine adduct, commercially available, were added.

  The product was cured under the name "Ancamine-870" by Pacific Anchor. After drying under vacuum, the material was cured to a thermoset solid in a high frequency oven.

at 100 amps in 290 seconds.

EXAMPLE 8

  To 100 g of the product solution of Example 6 was added 50 g of Standard-03 iron powder (supplied by EMA Bond) and 40 g of "Ancamine-870". After drying under vacuum, the adhesive final was cured into a thermoset solid by induction heating in an electromagnetic field,

in 75 seconds.

Claims (6)

A thermoplastic, epoxy pendant, urethane-containing epoxy resin, characterized in that it is the reaction product of an epoxy resin containing more than one hydroxyl group and a polyisocyanate. Thermosetting composition, characterized in that it comprises: (a) a heat-reactive epoxy curing agent and (b) a compound according to claim 1.   3. Method for adhering two substrates, characterized in that it consists in coating at least one of said substrates with a composition according to claim 2 and then putting said substrates thus coated in contact and heating said substrates in contact between 100 and 300 C to cause adhesion.   4. Method according to claim 3, characterized in that the heating step is performed by electromagnetic heating. Process according to claim 4, characterized   in that the electromagnetic heating is by induction.   5. Method according to claim 4, characterized in that the electromagnetic heating is by dielectric heating.   7 Curable composition according to the claim   2, characterized in that it is used as sealing agent.   8. Curable composition according to the claim   2, characterized in that it is used as coating.   Curable composition according to claim 2,   characterized in that it is used as an adhesive.   10. A process for reacting an epoxy resin containing more than one hydroxyl group with a polyisocyanate, characterized in that said reaction takes place at a temperature between 20 and 1200 C in the presence of 0.07 to 5% by weight of the reactants a catalyst forming urethane   for a time sufficient to form a thermo compound   plastic, epoxy pendant, containing urethane.