TECHNICAL FIELD

The invention relates to a method of bonding, especially structural bonding, of two shaped bodies, especially bodywork elements for motor vehicles, and to the use of one-component thermosetting epoxy resin compositions in such methods.

STATE OF THE ART

One-component thermosetting epoxy resin compositions are frequently used for bonding of metal substrates such as steel sheets when high strengths are required, for example in automobile construction.

In the composite formed from such shaped bodies, these are adhesive-bonded to one another for bonding. This is typically done using adhesives that are applied as adhesive beads to a first shaped body, and then a second shaped body to be bonded is applied to this adhesive bead for bonding of the two shaped bodies.

A further method of bonding shaped bodies such as metal sheets, cast parts and extrusion profiles envisages injecting a liquid adhesive into a closed cavity in order thus to bond the shaped bodies to be bonded to one another. A disadvantage of this method is that it is necessary to create cavities sealed in a fluid-tight manner, which define a space for the liquid adhesive. This can be achieved with seals, for example, or requires elements having very small manufacturing tolerances. The consequence is that such systems are complex and costly to manufacture.

DESCRIPTION OF THE INVENTION

It is therefore an object of the present invention to provide an improved process for bonding, especially structural bonding, of to shaped bodies, which permits less expensive bonding, in a more easily manageable manner, of shaped bodies, for example bodywork elements in motor vehicles.

This object is surprisingly achieved by a method as claimed in claim1.

The method of the invention has the advantage that bonding of two shaped bodies does not require provision of a space sealed fluid-tight for the adhesive; instead, it is possible to use a less expensive open system which is easier to handle and without interspaces sealed fluid-tight. It is thus possible to use, for example, bodywork elements that do not have seals, which is a considerable cost advantage. Moreover, the present invention also permits (adhesive) bonding of shaped bodies with greater manufacturing tolerances because there is no need to provide any spaces sealed fluid-tight for the adhesive. This is also a significant cost advantage over the known systems because this allows the various elements of the system to be manufactured at lower cost and with greater manufacturing tolerances. Moreover, an operation of bonding of the shaped bodies is easier to accomplish since filling of closed spaces with adhesive entails difficulties that can be avoided in this way, especially the displacing of the air in the closed cavity by the adhesive.

Further aspects of the invention are the subject of the further independent claims; preferred executions of the invention are the subject of the dependent claims.

WAYS OF EXECUTING THE INVENTION

The present invention thus relates to a method of bonding, especially structural bonding, of two shaped bodies S1and S2, said method comprising the steps of:a) providing a shaped body S1;b) arranging a shaped body S2with respect to the shaped body S1, forming a cavity (1) between the two shaped bodies S1and S2,c) introducing a one-component thermosetting epoxy resin compositions into the cavity (1),wherein the one-component thermosetting epoxy resin composition is a one-component thermosetting epoxy resin composition comprisingat least one epoxy resin A having an average of more than one epoxy group per molecule;at least one curing agent B for epoxy resins which is activated by elevated temperature;at least one polyester polyol PP obtainable by the reaction ofat least one diol having the structure HO—(CH2)x′—OH where the value of x′=2 to 10, andat least one dicarboxylic acid having the structure HOOC—(CH2)y′—COOH and derivatives of this dicarboxylic acid, where the value of y′=8 to 18.

The proportion of the polyester polyol PP is 1.5% to 20% by weight, based on the total weight of the one-component thermosetting epoxy resin composition.

FIG. 1ashows a cross section of two shaped bodies S1and S2arranged with respect to one another after step b), having a cavity (1) between one another.

The cavity (1) is preferably an open cavity. The term “open” or “open cavity” in this document means “liquid-permeable” or “unsealed”.

It is further advantageous when there is essentially no change in the distance in the cavity (1) between the two shaped bodies after the step b) of arranging a shaped body S2with respect to the shaped body S1. The term “essentially” is preferably understood to mean a change in the distance of less than 30%, less than 20%, especially less than 10%.

It may further be advantageous when there is essentially no change in the distance between the two shaped bodies, 0-100 mm, especially 0-30 mm, alongside the cavity (1), after the step b) of arranging a shaped body S2with respect to the shaped body S1. The word “essentially” here is preferably understood to mean a change in the distance of less than 30%, less than 20%, especially less than 10%.

It may further be advantageous when the distance between the two shaped bodies of 0-100 mm, especially 0-30 mm, alongside the cavity (1) after step b) is 0.5-15 mm, especially 0.5-10 mm, preferably 0.5-5 mm, more preferably 1-3 mm.

It may be further preferable when the one-component thermosetting epoxy resin composition is introduced through at least one introduction opening (2) in at least one of the two shaped bodies. Such an introduction opening (2) can be seen, for example, inFIG. 1bin the shaped body S2. Preferably, the introduction opening (2) is disposed on the side of the shaped body remote from the other shaped body.

Moreover, the at least one introduction opening (2) is preferably directly connected to the cavity (1) via an introduction channel (3a).

However, it may be advantageous when, as shown in cross section ofFIG. 1c, the one-component thermosetting epoxy resin composition is introduced into the cavity (1) through an introduction channel (3b), the introduction channel (3b) being disposed on the surface of at least one of the two shaped bodies that faces the other shaped body.FIG. 1dshows a side view of the two moldings arranged relative to one another.

The cavity (1) is preferably a bonding site for the composite of the two shaped bodies, especially an intended structural bonding site. This is therefore preferably configured so as to be able to accommodate a sufficient amount of epoxy resin composition for a structural bond between the two shaped bodies to be assured. For this purpose, in particular, a suitable thickness of the epoxy resin composition introduced and a suitable contact area of the epoxy resin composition introduced with the shaped body S1, or shaped body S2, are advantageous.

Preferably, the cavity (1) is a material recess (4) in at least one of the two shaped bodies.

The shaped bodies S1and S2may be made of the same material or a different material. The shaped bodies are preferably made of metal or other heat-resistant materials, especially metal or heat-resistant plastics, for example polyamides (PA), polyphenylene ethers, e.g. Noryl®, or heat-resistant fiber-reinforced plastics such as carbon fiber-reinforced plastics (CFRP) or glass fiber-reinforced plastics (GFRP). Examples of suitable metals are especially steel, especially electrolytically galvanized steel, hot-dip galvanized steel or oiled steel, Bonazinc-coated steel, and subsequently phosphated steel, and aluminum.

Suitable shaped bodies S1and S2are especially shaped bodies as utilized, for example, in the construction of modes of transport, for example in the automobile industry, or in the manufacture of white goods.

It has been found that, surprisingly, the use of a one-component thermosetting epoxy resin composition as claimed in claim1can provide a self-sealing system. It has been found that, surprisingly, using such an epoxy resin composition that, on cooling, has a sharp transition between an unsolidified state and a solidified state, it is possible to join open systems without the use of sealing elements, for example.

In step b) of arranging the shaped body S2with respect to the shaped body S1, a cavity (1) is formed between the two shaped bodies S1and S2.

The two shaped bodies may be arranged with respect to one another here, for example, in such a way that the two shaped bodies are in direct contact at at least one point or they may be arranged spaced apart from one another. Preferably, in step b), the two shaped bodies S1and S2are prefixed by mechanical joining methodology on one or two sides, especially by rivets, welds, screws or bolts, optionally with the use of spacers. This joining methodology is especially intended to ensure that the two shaped bodies S1and S2arranged with respect to one another remain in the intended position before the introduced epoxy resin composition has solidified and/or hardened.

The epoxy resin composition has one component, meaning that the constituents of the epoxy resin composition, especially at least one epoxy resin A, the at least one hardener B and the at least one polyester polyol PP, are present in one component without occurrence of curing at standard ambient temperature or room temperature. Therefore, the one-component epoxy resin composition is storage-stable. It is therefore salable in this form, whereas, in the case of two-component systems, the mixing of the components is possible only immediately before application.

In this document, the use of the term “independently” in connection with substituents, radicals or groups should be interpreted such that the substituents, radicals or groups having the same designation in the same molecule may occur simultaneously with different meanings.

In this document, a “toughness improver” is understood to mean an addition to an epoxy resin matrix that results in a distinct increase in toughness even in the case of small additions of ≥5% by weight, especially ≥10% by weight, based on the total weight of the epoxy resin compositions and is thus capable of absorbing higher flexural, tensile, impact or shock stress before the matrix cracks or breaks.

The prefix “poly” in substance names such as “polyol”, “polyisocyanate”, “polyether” or “polyamine” in the present document indicates that the respective substance, in a formal sense, contains more than one of the functional groups that occur in its name per molecule.

In the present document, “molecular weight” is understood to mean the molar mass (in grams per mole) of a molecule. “Average molecular weight” is understood to mean the number-average molecular weight Mnof an oligomeric or polymeric mixture of molecules, which is typically determined by means of GPC against polystyrene as standard.

A “primary hydroxyl group” refers to an OH group bonded to a carbon atom having two hydrogens.

In the present document, the term “primary amino group” refers to an NH2group bonded to one organic radical, while the term “secondary amino group” refers to an NH group bonded to two organic radicals which may also together be part of a ring. Accordingly, an amine having one primary amino group is referred to as “primary amine”, one having a secondary amino group correspondingly as “secondary amine”, and one having a tertiary amino group as “tertiary amine”.

In the present document, “room temperature” refers to a temperature of 23° C.

The term “structurally” in relation to the nature of the bonding between shaped bodies is understood in the present document to mean, in particular, a bond using a cured epoxy resin composition having mechanical properties, as referred to hereinafter as preferred mechanical properties, especially in relation to tensile strength, elongation at break and modulus of elasticity.

The epoxy resin A having an average of more than one epoxy group per molecule is preferably an epoxy liquid resin or a solid epoxy resin. The term “solid epoxy resin” is very well known to a person skilled in the art of epoxies and is used in contrast to “liquid epoxy resins”. The glass transition temperature of solid resins is above room temperature, meaning that they can be comminuted at room temperature to give free-flowing powders.

Preferred epoxy resins have the formula (II)



The substituents R′ and R″ here are, independently of each other, either H or CH3.

In solid epoxy resins, the index s has a value of >1.5, especially of 2 to 12.

Such solid epoxy resins are commercially available, for example from Dow or Huntsman or Hexion.

Compounds of the formula (II) having an index s of 1 to 1.5 are referred to as semisolid epoxy resins by the person skilled in the art. For the present invention here, they are likewise considered to be solid resins. However, preferred solid epoxy resins are epoxy resins in the narrower sense, i.e. where the index s has a value of >1.5.

In liquid epoxy resins, the index s has a value of less than 1. Preferably, s has a value of less than 0.2.

Preference is thus given to diglycidyl ethers of bisphenol A (DGEBA), of bisphenol F, and of bisphenol A/F. Such liquid resins are available, for example, as Araldite® GY 250, Araldite® PY 304, Araldite® GY 282 (Huntsman) or D.E.R.™ 331 or D.E.R.™ 330 (Dow) or Epikote 828 (Hexion).

Further suitable epoxy resins A are what are called epoxy novolaks. These especially have the following formula:


with R2=


or CH2, R1=H or methyl and z=0 to 7.

More particularly, these are phenol or cresol epoxy novolaks (R2=CH2).

Such epoxy resins are commercially available under the EPN or ECN and Tactix® trade names from Huntsman or from the D.E.N.™ product series from Dow Chemical.

Preferably, the epoxy resin A is a liquid epoxy resin of the formula (II).

In a particularly preferred embodiment, the thermosetting epoxy resin composition contains both at least one liquid epoxy resin of the formula (II) with s<1, especially less than 0.2, and at least one solid epoxy resin of the formula (II) with s>1.5, especially from 2 to 12.

The proportion of the epoxy resin A is preferably 10-60% by weight, especially 30-50% by weight, based on the total weight of the epoxy resin composition.

It is further advantageous when 50-100% by weight, especially 80-100% by weight, of the epoxy resin A is an aforementioned liquid epoxy resin.

It is further advantageous when 0-30% by weight, especially 0-20% by weight, more preferably 5-15% by weight, of the epoxy resin A is an aforementioned solid epoxy resin.

The thermosetting one-component epoxy resin composition further comprises at least one curing agent B for epoxy resins which is activated by elevated temperature. Such latent curing agents are substantially inert at room temperature and are activated by elevated temperature, typically at temperatures of 70° C. or more, which starts the curing reaction. It is possible to use the standard latent curing agents for epoxy resins. The curing agent is preferably a latent nitrogen-containing curing agent for epoxy resins.

Examples of suitable latent curing agents are dicyandiamide, guanamines, guanidines, aminoguanidines and their derivatives; substituted ureas, especially 3-(3-chloro-4-methylphenyl)-1,1-dim ethylurea (chlorotoluron), or phenyldimethylureas, especially p-chlorophenyl-N,N-dimethylurea (monuron), 3-phenyl-1,1-dimethylurea (fenuron) or 3,4-dichlorophenyl-N, N-dimethylurea (diuron), and also imidazoles and amine complexes.

A particularly preferred latent curing agent is dicyandiamide.

The proportion of the curing agent B is preferably 0.5% to 12% by weight, more preferably 1% to 8% by weight, based on the total weight of the epoxy resin composition.

The thermosetting one-component epoxy resin composition further comprises at least one polyester polyol PP obtainable by the reaction ofat least one diol having the structure HO—(CH2)x′—OH where the value of x′=2 to 10, andat least one dicarboxylic acid having the structure HOOC—(CH2)y′—COOH and derivatives of this dicarboxylic acid, where the value of y′=8 to 18.

Derivatives of these dicarboxylic acids are preferably carboxylic esters (especially the methyl and ethyl esters), acid halides (for example acid chlorides) and acid anhydrides.

The melting point is preferably determined with a DSC instrument (DIN 53 765). The sample and an empty reference crucible are heated at a heating rate of 20° C./min. The melting point corresponds to the maximum of the melting peak.

The polyester polyol PP preferably has a softening point of 50 to 110° C., especially 70 to 95° C. The softening point is determined in this document by the ring & ball method according to DIN ISO 4625.

Preferred polyester polyols PP also have a number-average molecular weight of 1500 to 9000, preferably 1500 to 6000, more preferably 2500-5000.

Preferred polyester polyols PP have a hydroxyl number (milliequivalents of KOH per gram of polyester polyol) of about 20 to 50, preferably about 25 to 40.

Moreover, preferred polyesterpolyols have a hydroxy functionality of about 2, especially of 1.9 to 2.1 (average number of hydroxyl groups per polymer chain).

Preferably, the diol usable in the preparation of the polyester polyols PP is selected from the list consisting of ethylene glycol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, octane-1,8-diol and decane-1,10-diol. Mixtures thereof are also possible.

The most preferred are ethylene glycol, butane-1,4-diol and hexane-1,6-diol, especially ethylene glycol and hexane-1,6-diol, particularly hexane-1,6-diol.

Preferably, the dicarboxylic acid usable in the preparation of the polyester polyols PP is selected from the list consisting of decanedioic acid (sebacic acid), undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid and octadecanedioic acid. Derivatives thereof and mixtures thereof are also possible. Preferably, the dicarboxylic acid is selected from the list consisting of decanedioic acid (sebacic acid), undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, and is more preferably dodecanedioic acid.

Preferably, the polyester polyol PP is obtainable by the reaction of just one member from the list of diols described above and just one member of the list of dicarboxylic acids described above.

The proportion of the polyester polyol PP is 1.5% to 20% by weight, based on the total weight of the one-component thermosetting epoxy resin composition. The proportion of polyester polyol PP is preferably 2-15% by weight, 2.5-10% by weight, 3-10% by weight, especially 4-8% by weight, based on the total weight of the one-component thermosetting epoxy resin composition. Such a proportion leads to good spreading characteristics coupled with simultaneously high tensile shear strength values. A proportion of the polyester polyol PP of 2-4.5% by weight, 2.5-4% by weight, based on the total weight of the one-component thermosetting epoxy resin composition, is advantageous for high impact peel strength (I-peel) values, especially at −30° C.

The thermosetting epoxy resin composition optionally comprises at least one toughness improver D. The toughness improvers D may be liquid or solid.

More particularly, the toughness improver D is selected from the group consisting of terminally blocked polyurethane polymers D1, liquid rubbers D2 and core-shell polymers D3.

The toughness improver D is preferably a terminally blocked polyurethane polymer D1, preferably a terminally blocked polyurethane prepolymer of the formula (I)



R1here is a p-valent radical of a linear or branched polyurethane prepolymer terminated by isocyanate groups after the removal of the terminal isocyanate groups, and p has a value of 2 to 8.

In addition, R2is independently a substituent selected from the group consisting of



R5, R6, R7and R8here are each independently an alkyl or cycloalkyl or aralkyl or arylalkyl group, or R5together with R6, or R7together with R8, form part of a 4- to 7-membered, optionally substituted ring.

In addition, R9′and R10are each independently an alkyl or aralkyl or arylalkyl group or an alkyloxy or aryloxy or aralkyloxy group, and R11is an alkyl group.

R12, R13and R14are each independently an alkylene group which has 2 to 5 carbon atoms and optionally has double bonds or is substituted, or a phenylene group or a hydrogenated phenylene group.

R15, R16and R17are each independently H or an alkyl group or an aryl group or an aralkyl group, and R18is an aralkyl group or a mono- or polycyclic, substituted or unsubstituted aromatic group that optionally has aromatic hydroxyl groups.

Finally, R4is a radical of an aliphatic, cycloaliphatic, aromatic or araliphatic epoxide containing a primary or secondary hydroxyl group after the removal of the hydroxyl and epoxy groups, and m has a value of 1, 2 or 3.

R18is especially considered to be firstly phenols or polyphenols, especially bisphenols, after removal of a hydroxyl group. Preferred examples of such phenols and bisphenols are especially phenol, cresol, resorcinol, catechol, cardanol (3-pentadecenylphenol (from cashewnutshell oil)), nonylphenol, phenols that have been reacted with styrene or dicyclopentadiene, bisphenol A, bisphenol F and 2,2′-diallylbisphenol A. R18is secondly considered to be especially hydroxybenzyl alcohol and benzyl alcohol after removal of a hydroxyl group.

If R5, R6, R7, R8, R9, R9′, R10, R11, R15, R16or R17is an alkyl group, it is especially a linear or branched C1-C20-alkyl group.

If R5, R6, R7, R8, R9, R9′, R10, R15, R16, R17or R18is an aralkyl group, this moiety is especially a methylene-bonded aromatic group, especially a benzyl group.

If R5, R6, R7, R8, R9, R9′or R10is an alkylaryl group, this is especially a phenylene-bonded C1- to C20-alkyl group, for example tolyl or xylyl.

The R2radicals are preferably the substituents of the formulae



A preferred substituent of the formula


is ε-caprolactam after removal of the NH proton.

Preferred substituents of the formula —O—R18are monophenols or polyphenols, especially bisphenols, after removal of a phenolic hydrogen atom. Particularly preferred examples of such R2radicals are radicals selected from the group consisting of



The Y radical here is a saturated, aromatic or olefinically unsaturated hydrocarbyl radical having 1 to 20 carbon atoms, especially having 1 to 15 carbon atoms. Preferred Y are especially allyl, methyl, nonyl, dodecyl, phenyl, alkyl ether, carboxylic ester or an unsaturated C15-alkyl radical having 1 to 3 double bonds.

Most preferably, R2is —O—R18.

The terminally blocked polyurethane prepolymer of the formula (I) is prepared from the linear or branched polyurethane prepolymer terminated by isocyanate groups with one or more isocyanate-reactive compounds R2H. If two or more such isocyanate-reactive compounds are used, the reaction can be effected sequentially or with a mixture of these compounds.

The reaction is preferably effected in such a way that the one or more isocyanate-reactive compounds R2H are used stoichiometrically or in a stoichiometric excess in order to ensure that all NCO groups have been converted.

The polyurethane prepolymer with isocyanate end groups on which R1is based can be prepared from at least one diisocyanate or triisocyanate and from a polymer QPMhaving terminal amino, thiol or hydroxyl groups and/or from an optionally substituted polyphenol QPP.

Suitable diisocyanates are aliphatic, cycloaliphatic, aromatic or araliphatic diisocyanates, especially commercial products such as methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), toluidine diisocyanate (TODD, isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), 2,5- or 2,6-bis(isocyanatomethyl)bicyclo[2.2.1]heptane, naphthalene 1,5-diisocyanate (NDI), dicyclohexylmethyl diisocyanate (H12MDI), p-phenylene diisocyanate (PPDI), m-tetramethylxylylene diisocyanate (TMXDI), etc. and dimers thereof. Preference is given to HDI, IPDI, MDI or TDI.

Suitable triisocyanates are trimers or biurets of aliphatic, cycloaliphatic, aromatic or araliphatic diisocyanates, especially the isocyanurates and biurets of the diisocyanates described in the previous paragraph. It is of course also possible to use suitable mixtures of di- or triisocyanates.

Especially suitable polymers QPMhaving terminal amino, thiol or hydroxyl groups are polymers QPMhaving two or three terminal amino, thiol or hydroxyl groups.

The polymers QPMadvantageously have an equivalent weight of 300-6000, especially of 600-4000, preferably of 700-2200, g/equivalent of NCO-reactive groups.

Suitable polymers QPMare polyols, for example the following commercially available polyols or any mixtures thereof:polyoxyalkylene polyols, also called polyether polyols, which are the polymerization product of ethylene oxide, 1,2-propylene oxide, 1,2- or 2,3-butylene oxide, tetrahydrofuran or mixtures thereof, optionally polymerized with the aid of a starter molecule having two or three active hydrogen atoms, for example water or compounds having two or three OH groups. It is possible to use either polyoxyalkylene polyols having a low degree of unsaturation (measured to ASTM D-2849-69 and reported in milliequivalents of unsaturation per gram of polyol (meq/g)), prepared, for example, with the aid of what are called double metal cyanide complex catalysts (DMC catalysts for short), or polyoxyalkylene polyols having a higher degree of unsaturation, prepared, for example, with the aid of anionic catalysts such as NaOH, KOH or alkali metal alkoxides. Particularly suitable are polyoxypropylenediols and -triols having a degree of unsaturation of less than 0.02 meq/g and having an average molecular weight in the range of 1000-30 000 daltons, polyoxybutylenediols and -triols, polyoxypropylenediols and -triols having an average molecular weight of 400-8000 daltons, and what are called “EO-endcapped” (ethylene oxide-endcapped) polyoxypropylenediols or -triols. The latter are specific polyoxypropylene polyoxyethylene polyols that are obtained, for example, when pure polyoxypropylene polyols, on completion of the polypropoxylation reaction, are alkoxylated with ethylene oxide and hence have primary hydroxyl groups.hydroxy-terminated polybutadiene polyols, for example those that are prepared by polymerization of 1,3-butadiene and allyl alcohol or by oxidation of polybutadiene, and hydrogenation products thereof;styrene-acrylonitrile-grafted polyether polyols as supplied, for example, by BASF under the Lupranol® name;polyhydroxy-terminated acrylonitrile/butadiene copolymers as preparable, for example, from carboxyl-terminated acrylonitrile/butadiene copolymers (commercially available under the Hypox® CTBN name from Emerald Performance Materials) and epoxides or amino alcohols;polyester polyols prepared, for example, from di- to trivalent alcohols, for example ethane-1,2-diol, diethylene glycol, propane-1,2-diol, dipropylene glycol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, neopentyl glycol, glycerol, 1,1,1-trimethylolpropane or mixtures of the aforementioned alcohols with organic dicarboxylic acids or the anhydrides or esters thereof, for example succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid and hexahydrophthalic acid or mixtures of the aforementioned acids, and polyester polyols formed from lactones, for example ε-caprolactone;polycarbonate polyols as obtainable by reaction, for example, of the abovementioned alcohols—used to form the polyester polyols—with dialkyl carbonates, diaryl carbonates or phosgene.

Advantageously, the polymers QPMare difunctional or higher-functionality polyols having OH equivalent weights of 300 to 6000 g/OH equivalent, especially of 600 to 4000 g/OH equivalent, preferably 700-2200 g/OH equivalent. Further advantageously, the polyols are selected from the group consisting of polyethylene glycols, polypropylene glycols, polyethylene glycol-polypropylene glycol block copolymers, polybutylene glycols, hydroxyl-terminated polybutadienes, hydroxyl-terminated butadiene/acrylonitrile copolymers, hydroxyl-terminated synthetic rubbers, hydrogenation products thereof and mixtures of these polyols mentioned.

In addition, polymers QPMused may also be difunctional or higher-functionality amino-terminated polyethylene ethers, polypropylene ethers, as sold, for example, under the Jeffamine® name by Huntsman, polybutylene ethers, polybutadienes, butadiene/acrylonitrile copolymers, as sold, for example, under the Hypro® ATBN name by Emerald Performance Materials, and further amino-terminated synthetic rubbers or mixtures of the components mentioned.

For certain applications, suitable polymers QPMare especially polybutadienes or polyisoprenes having hydroxyl groups or the partially or fully hydrogenated reaction products thereof.

It is additionally possible that the polymers QPMmay also have been chain-extended in the manner known to the person skilled in the art by the reaction of polyamines, polyols and polyisocyanates, especially diamines, diols and diisocyanates.

Using the example of a diisocyanate and a diol, what is formed therefrom, as shown hereinafter, according to the stoichiometry chosen, is a species of the formula (VI) or (VII)


The Y1and Y2radicals are a divalent organic radical and the indices u and v vary according to the stoichiometric ratio from 1 to typically 5.

These species of the formula (VI) or (VII) may then in turn be reacted further. For example, the species of the formula (VI) and a diol having a divalent organic radical Y3can be used to form a chain-extended polyurethane prepolymer of the following formula:



The species of the formula (VII) and a diisocyanate having a divalent organic radical Y4can be used to form a chain-extended polyurethane prepolymer of the following formula:



According to the stoichiometric ratio, the indices x and y vary from 1 to typically 5, and are especially 1 or 2.

In addition, it is also possible to react the species of the formula (VI) with the species of the formula (VII), so as to form a chain-extended polyurethane prepolymer having NCO groups.

For the chain extension, preference is given especially to diols and/or diamines and diisocyanates. It will of course be clear to the person skilled in the art that higher-functionality polyols, for example trimethylolpropane or pentaerythritol, or higher-functionality polyisocyanates, such as isocyanurates of diisocyanates, can also be used for the chain extension.

In the case of the polyurethane prepolymers in general and in the specific case of the chain-extended polyurethane prepolymers, it should advantageously be ensured that the prepolymers do not have excessively high viscosities, especially when higher-functionality compounds are being used for the chain extension, since this can make it difficult to convert them to the polyurethane prepolymers of the formula (I) or to apply the adhesive.

Preferred polymers QPMare polyols having average molecular weights between 600 and 6000 daltons, selected from the group consisting of polyethylene glycols, polypropylene glycols, polyethylene glycol-polypropylene glycol block polymers, polybutylene glycols, hydroxyl-terminated polybutadienes, hydroxyl-terminated butadiene-acrylonitrile copolymers and mixtures thereof.

Especially preferred polymers QPMare α,ω-dihydroxy polyalkylene glycols having C2-C6-alkylene groups or having mixed C2-C6-alkylene groups, terminated by amino, thiol or, preferably, hydroxyl groups. Particular preference is given to polypropylene glycols or polybutylene glycols. Particular preference is further given to hydroxyl group-terminated polyoxybutylenes.

Especially suitable polyphenols QPPare bis-, tris- and tetraphenols. This is understood to mean not just straight phenols but optionally also substituted phenols. The nature of the substitution may be very varied. More particularly, this is understood to mean substitution directly on the aromatic ring to which the phenolic OH group is bonded. Phenols are additionally understood to mean not just monocyclic aromatics but also polycyclic or fused aromatics or heteroaromatics that have the phenolic OH group directly on the aromatic or heteroaromatic system.

The nature and position of such a substituent affects the reaction with isocyanates necessary for the formation of the polyurethane prepolymer among other properties.

The bis- and trisphenols are particularly suitable. Examples of suitable bisphenols or trisphenols include 1,4-dihydroxybenzene, 1,3-dihydroxybenzene, 1,2-dihydroxybenzene, 1,3-dihydroxytoluene, 3,5-dihydroxybenzoates, 2,2-bis(4-hydroxyphenyl)propane (=bisphenol A), bis(4-hydroxyphenyl)methane (=bisphenol F), bis(4-hydroxyphenyl) sulfone (=bisphenol S), naphthoresorcinol, dihydroxynaphthalene, dihydroxyanthraquinone, dihydroxybiphenyl, 3,3-bis(p-hydroxyphenyl)phthalide, 5,5-bis(4-hydroxyphenyl)hexahydro-4,7-methanoindane, phenolphthalein, fluorescein, 4,4′-[bis(hydroxyphenyl)-1,3-phenylenebis(1-methylethylidene)] (=bisphenol M), 4,4′-[bis(hydroxyphenyl)-1,4-phenylenebis(1-methylethylidene)] (=bisphenol P), 2,2′-diallylbisphenol-A, diphenols and dicresols prepared by reaction of phenols or cresols with diisopropylidenebenzene, phloroglucinol, gallic esters, phenol or cresol novolaks having —OH functionality of 2.0 to 3.5, and all isomers of the aforementioned compounds.

In a first embodiment, the polyurethane prepolymer is prepared from at least one diisocyanate or triisocyanate and from a polymer QPMhaving terminal amino, thiol or hydroxyl groups. The polyurethane prepolymer is prepared in a manner known to the person skilled in the art of polyurethane, especially by using the diisocyanate or triisocyanate in a stoichiometric excess in relation to the amino, thiol or hydroxyl groups of the polymer QPM.

In a second embodiment, the polyurethane prepolymer is prepared from at least one diisocyanate or triisocyanate and from an optionally substituted polyphenol QPP. The polyurethane prepolymer is prepared in a manner known to the person skilled in the art of polyurethane, especially by using the diisocyanate or triisocyanate in a stoichiometric excess in relation to the phenolic groups of the polyphenol QPP.

In a third embodiment, the polyurethane prepolymer is prepared from at least one diisocyanate or triisocyanate and from a polymer QPMhaving terminal amino, thiol or hydroxyl groups and from an optionally substituted polyphenol QPP. There are different options available for preparation of the polyurethane prepolymer from at least one diisocyanate or triisocyanate and from a polymer QPMhaving terminal amino, thiol or hydroxyl groups and/or from an optionally substituted polyphenol QPP.

Particular preference is given to the first embodiment.

The polyurethane polymer having isocyanate end groups preferably has elastic character. It preferably exhibits a glass transition temperature Tg of less than 0° C.

Preferably, the proportions of the following are:

toughness improver D1 10-60% by weight, especially 20-40% by weight;

toughness improver D2 10-30% by weight, especially 20-30% by weight;

toughness improver D3 10-30% by weight, especially 20-30% by weight;

based on the total weight of the epoxy resin composition.

In a preferred embodiment, the one-component thermosetting epoxy resin composition additionally comprises at least one filler F. Preference is given here to mica, talc, kaolin, wollastonite, feldspar, syenite, chlorite, bentonite, montmorillonite, calcium carbonate (precipitated or ground), dolomite, quartz, silicas (fused or precipitated), cristobalite, calcium oxide, aluminum hydroxide, magnesium oxide, hollow ceramic beads, hollow glass beads, hollow organic beads, glass beads, color pigments. Particular preference is given to fillers selected from the group consisting of calcium carbonate, calcium oxide and fumed silicas.

Advantageously, the total proportion of the overall filler F is 5-40% by weight, preferably 5-20% by weight, based on the total weight of the epoxy resin composition.

The one-component thermosetting epoxy resin composition may further additionally comprise at least one epoxy group-bearing reactive diluent G. Such reactive diluents are known to those skilled in the art. Preferred examples of epoxy-bearing reactive diluents are:glycidyl ethers of monofunctional, saturated or unsaturated, branched or unbranched, cyclic or open-chain, C4-C30alcohols, e.g. butanol glycidyl ether, hexanol glycidyl ether, 2-ethylhexanol glycidyl ether, allyl glycidyl ether, tetrahydrofurfuryl and furfuryl glycidyl ether, trimethoxysilyl glycidyl ether, and the like;glycidyl ethers of difunctional, saturated or unsaturated, branched or unbranched, cyclic or open-chain, C2-C30alcohols, e.g. ethylene glycol glycidyl ether, butanediol glycidyl ether, hexanediol glycidyl ether, octanediol glycidyl ether, cyclohexanedimethanol diglycidyl ether, neopentyl glycol diglycidyl ether, and the like;glycidyl ethers of tri- or polyfunctional, saturated or unsaturated, branched or unbranched, cyclic or open-chain, alcohols, such as epoxidized castor oil, epoxidized trimethylolpropane, epoxidized pentaerythritol or polyglycidyl ethers of aliphatic polyols, such as sorbitol, glycerol, trimethylolpropane, and the like;glycidyl ethers of phenol compounds and aniline compounds, such as phenyl glycidyl ether, cresyl glycidyl ether, p-tert-butylphenyl glycidyl ether, nonylphenol glycidyl ether, 3-n-pentadecenyl glycidyl ether (from cashew nut shell oil), N,N-diglycidylaniline, and the like;epoxidized amines, such as N,N-diglycidylcyclohexylamine, and the like;epoxidized mono- or dicarboxylic acids, such as glycidyl neodecanoate, glycidyl methacrylate, glycidyl benzoate, diglycidyl phthalate, tetrahydrophthalate and hexahydrophthalate, diglycidyl esters of dimeric fatty acids, and the like;epoxidized di- or trifunctional, low to high molecular weight polyether polyols, such as polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and the like.

Particular preference is given to hexanediol diglycidyl ether, cresyl glycidyl ether, p-tert-butylphenyl glycidyl ether, polypropylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether.

Advantageously, the total proportion of the epoxy-bearing reactive diluent G is 0.1-15% by weight, preferably 0.1-5% by weight, especially preferably 0.1-2% by weight, more preferably 0.2-1% by weight, based on the total weight of the epoxy resin composition.

The one-component thermosetting epoxy resin composition may include further constituents, especially catalysts, stabilizers, especially heat and/or light stabilizers, thixotropic agents, plasticizers, solvents, mineral or organic fillers, blowing agents, dyes and pigments, anticorrosives, surfactants, defoamers and adhesion promoters.

A particularly preferred thermosetting one-component epoxy resin composition comprises:10-60% by weight, especially 30-50% by weight, based on the total weight of the epoxy resin composition, of epoxy resin A having an average of more than one epoxy group per molecule; preferably 50-100% by weight, especially 80-100% by weight, of the epoxy resin A is a liquid epoxy resin and 0-30% by weight, especially 0-20% by weight, more preferably 5-15% by weight, of the epoxy resin A is a solid epoxy resin;1-10% by weight, especially 2-6% by weight, based on the total weight of the epoxy resin composition, of at least one curing agent B for epoxy resins which is activated by elevated temperature;1.5-20% by weight, 2-15% by weight, 2.5-10% by weight, 3-10% by weight, especially 4-8% by weight, based on the total weight of the epoxy resin composition, of at least one polyester polyol PP;at least one toughness improver D selected from the group consisting of terminally blocked polyurethane polymers D1, liquid rubbers D2 and core-shell polymers D3, where the proportions are preferably as follows:

toughness improver D1 10-60% by weight, especially 20-40% by weight;

toughness improver D2 10-30% by weight, especially 20-30% by weight;

toughness improver D3 10-30% by weight, especially 20-30% by weight;

based on the total weight of the epoxy resin composition;preferably 5-40% by weight, preferably 5-20% by weight, based on the total weight of the epoxy resin composition, of a filler F selected from the group consisting of calcium carbonate, calcium oxide and fumed silicas;preferably 0.1-15% by weight, preferably 0.1-5% by weight, especially preferably 0.1-2% by weight, more preferably 0.2-1% by weight, based on the total weight of the epoxy resin composition, of an epoxy-bearing reactive diluent G;

It may further be advantageous when the preferred one-component thermosetting epoxy resin composition consists of the aforementioned constituents to an extent of more than 80% by weight, preferably more than 90% by weight, especially more than 95% by weight, especially preferably more than 98% by weight, most preferably more than 99% by weight, based on the total weight of the epoxy resin composition.

It may further be advantageous when the one-component thermosetting epoxy resin composition has a threshold value for the magnitude of the complex viscosity η* of more than 20′000 Pas, especially more than 40′000 Pas, preferably more than 60′000 Pas, more preferably more than 80′000 Pas, especially preferably more than 100′000 Pas.

Preferably, the one-component thermosetting epoxy resin composition attains more than 50%, especially more than 70%, especially more than 80%, of the rise in viscosity, based on the magnitude of the complex viscosity η* on commencement of the measurement at 150° C. (end of phase 1, start of phase 2), i.e. on commencement of cooling proceeding from 150° C. at a cooling rate of −23° C./min to the threshold for the magnitude of the complex viscosity η* of more than 20′000 Pas, especially more than 40′000 Pas, preferably more than 60′000 Pas, more preferably more than 80′000 Pas, especially preferably more than 100′000 Pas, within 20 seconds, preferably within 10 seconds.

It is further preferable when this is achieved prior to the attainment of cooling of the one-component thermosetting epoxy resin composition to 25° C. This is more preferably achieved 80-280 seconds after the start of the cooling of the one-component thermosetting epoxy resin composition from 150° C. at a cooling rate of −23° C./min.

Preferably, the one-component thermosetting epoxy resin composition reaches a maximum value for the magnitude of the complex viscosity η* of more than 100′000 Pas, especially more than 200′000 Pas, preferably more than 300′000 Pas, more preferably more than 500′000 Pas, preferably prior to the attainment of cooling of the one-component thermosetting epoxy resin composition to 25° C., preferably 80-280 seconds after the start of the cooling of the composition from 150° C. at a cooling rate of −23° C./min.

The aforementioned magnitude of the complex viscosity η* is determined by oscillography as described hereinafter in the examples by means of a rheometer with a heatable plate (MCR 302, Anton Paar) (200 μm gap, measurement plate diameter: 25 mm (plate/plate), deformation 0.01 at 5 Hz, within a temperature range of 150-25° C. (cooling rate −23° C./min)). The aforementioned method composed of three phases corresponds to the method described in the examples under “Measurement of viscosity characteristics”.

Preferably, the one-component thermosetting epoxy resin composition in the cured state has at least one, preferably more than one and more preferably all the mechanical properties listed hereinafter. Impact peel strength (I-peel) and tensile shear strength (TSS) are measured as described below in the examples. Tensile strength and modulus of elasticity are determined to DIN EN ISO 527.

Tensile strength [MPa]>10, >20, especially >25Modulus of elasticity>500, >1000, especially >2000[MPa]I-Peel (23° C.) [N/mm]>20, especially >25I-Peel (−30° C.) [N/mm]>10, especially >15ZSF [MPa]>15, especially >20

Preferably, the one-component thermosetting epoxy resin composition has a viscosity at 23° C. of >5′000 Pas, >10′000 Pas, especially >15′000 Pas, determining the viscosity by oscillography by means of a rheometer with a heatable plate (Anton Paar MCR 302) (1000 μm gap, measurement plate diameter: 25 mm (plate/plate), deformation 0.01 at 5 Hz).

It is further preferable when the one-component thermosetting epoxy resin composition on introduction in step c) is at a temperature of 40-100° C., especially 50-100° C., especially preferably 50-80° C.

Moreover, the one-component thermosetting epoxy resin composition on introduction in step c) is at a temperature of not more than 20° C., not more than 15° C., preferably not more than 10° C., below the melting point of the polyester polyol PP. This is apparent, for example, from table 6. The melting point is preferably determined with a DSC instrument (DIN 53 765). The sample and an empty reference crucible are heated at a heating rate of 20° C./min. The melting point corresponds to the maximum of the melting peak.

It is also advantageous when the one-component thermosetting epoxy resin composition on introduction in step c) has a viscosity of <3′000 Pas, <2′000 Pas, especially <1′000 Pas, determining the viscosity by oscillography by means of a rheometer with a heatable plate (Anton Paar MCR 302) (1000 μm gap, measurement plate diameter: 25 mm (plate/plate), deformation 0.01 at 5 Hz).

It is also preferable when the method additionally comprises the step d) of curing the one-component thermosetting epoxy resin composition, especially at a temperature of at least 100° C., at least 120° C., at least 130° C., especially to a temperature of 140-220° C., especially of 140-200° C., more preferably between 160 and 190° C., for at least 10 min, at least 20 min, especially between 20 and 60 min.

The one-component thermosetting epoxy resin compositions are preferably introduced into the cavity (1) in step c) by means of a pump, by conveying the one-component thermosetting epoxy resin composition from a tank.

A further aspect of the present invention relates to the use of a one-component thermosetting epoxy resin composition as described above as a one-component thermosetting epoxy resin composition for introduction, especially injection, into a cavity (1) between two shaped bodies S1and S2arranged with respect to one another for bonding, especially adhesive bonding, of the two shaped bodies S1and S2to one another. Preferably, the one-component thermosetting epoxy resin composition is one as identified as preferred in the present description.

Yet another aspect of the present invention relates to the use of polyester polyols PP as described above as polyester polyols PP in one-component thermosetting epoxy resin compositions for reducing escape characteristics through lateral openings in cavities on introduction, especially injection, of the one-component thermosetting epoxy resin compositions into cavities having lateral openings. The cavities mentioned are especially above-described open cavities (1). Preferably, the polyester polyols PP, and the one-component thermosetting epoxy resin compositions, are those as identified as preferred in the present description.

The invention is further elucidated hereinafter by examples, but these are not intended to restrict the invention in any way.

LEGEND FOR FIGURES

1cavity2introduction opening3aintroduction channel3bintroduction channel4material recess5base element6transparent outer element7channel8spacer9introduction opening10fixing screws11epoxy resin composition introduced12boundary marker13spread markers

