DE4113870A1 - DIAMINOCYCLOHEXAN-IMIDAZOLINE AND ITS USE - Google Patents

Abstract

The object of the invention consists of compounds of the general formula (I) in which R<1> is a possibly branched alkyl radical with 1-9, preferably 1-5, C atoms and their use as curing agents for epoxy resins.

Description

The invention relates to novel imidazolyl derivatives, their Use as a curing agent in epoxy resin compositions they contain curable epoxy resin compositions containing them, consisting of an epoxy resin and of the compounds of general formula I and optionally conventional curing and solvents for the production of moldings.

For the production of composites are used today in the Principle applied two methods.

In the wet-on-wet process, the reinforcing mats become Rialien impregnated with the curable mixture and in the Heat in one step until the final thermoset state tet (single-step method).

In the two-stage method, the gain mate becomes and the curable mixture initially so-called Prepregs made, which are then in a time-separated second process step further processed to finished parts become. Here is procedurally again between the use of solvents and solvents to distinguish between free working methods.

The prepregs are usually made in one continuous process in which the reinforcing materials either by impregnating the resin to be used Hardener mixture are passed or the impregnating agent becomes the carrier immediately before his assignment material mixed and by means of a special device knife. The control of a particular carrier material web to be applied impregnating agent quantity  except over the viscosity of the impregnating over downstream squeeze rolls.

In solvent-containing systems is after Imprä fermentation process by supplying heat in the impregnating solution containing solvent evaporates and at the same time Resin system transferred from A to B state. From the with soaked in liquid to highly tacky impregnating agent Reinforcement materials will vary depending on the process conditions and resin system used a slightly sticky to almost dry prepreg. In this process step it is important that on the one hand the solvent of the impregnating mixture is completely withdrawn, but on the other hand, the for the prepreg curing in the second step not agile latent hardener does not start to an ung wanting to reactivate the impregnated reinforcing material prevent it.

For solvent-free systems, depending on the chemical composition of the resin system after the im either also a short heat treatment of the material, or the reinforcing materials become immediate bar after impregnation waiving a geson The heat treatment is laminated on both sides with release liners and fed to a system-adequate intermediate storage. in the This intermediate storage either takes place gradually Licher transition of the resin system in the B-state or the impregnating agent is largely waiving chemical changes solely by physical effects fixed on the carrier materials.

The prepregs obtained in this way can be used as rollers between store and transport before they reach the respective user  according to the case and in component thickness be layered on top of each other. Due to simultaneous printing and temperature action, the prepreg stack becomes a hardened high-strength molding, the still low molar kularen, flowable resins in the high molecular weight C-Zu transition of the duromer.

While in the one-step process long open times and short curing times at low curing temperatures be required in the two-stage process as Another criterion for the longest possible storage stability added to the prepregs. This storage temperatures below room temperature from practice less and less accepted.

Regardless of the Prepregherstellung their curing at the lowest possible temperatures within a short time he Follow, the temperature maximum of the exothermic reaction too at higher layer thicknesses at a low level ver stay and the physical property level of the end products adapted to the requirements of the practice.

These requirements with respect to the curing behavior and Property levels apply in the same way for the in the wet-on-wet process to be processed epoxy resin systems.

For certain applications, only a hardening up to Dimensional stability of the moldings required or even desired, after a possible intermediate storage the final curing in a subsequent temper process takes place at the required temperatures. there But it is important that already in the hardening the  thermal resistance of the material over the cure Temperature rises, otherwise the demolding only after Lowering of the molding temperature is possible.

The curable mixtures based on epoxy resins since Dicyandiamide, which has long been used as a latent hardener, becomes Achieving the desired properties usually with Co-curing agents and / or accelerators combined. Out The literature in this field therefore a variety made known by proposals.

Dicyandiamide is only in a few solvents such as in particular special dimethylformamide or methyl glycol in sufficient Quantities soluble. However, these solvents are toxicological critical and bring both in the production of Prepregs, that is when impregnating the reinforcement materials and transfer to the B state, as well as at the disposal problems with it.

Furthermore, especially with the co-use of bro epoxy resins of the end products increasingly higher thermal resistances demanded by a di cyandiamidhärtung are unreachable. On the other hand can but so far on the use of brominated Epoxidhar for products with reduced flammability be canceled.

When using solid crystalline dicyandiamide in liquid epoxy resins without the use of solvents the dicyandiamide either directly in the required Amount dispersed in the epoxy or it is previously a highly filled dicyandiamide / epoxy paste, which at a later time with the main quantity  Epoxy resin and the accelerator to the desired Resin / hardener concentrations is adjusted.

The choice of the accelerator is a compromise between the height of the required curing temperature and the prepeg storage stability. By a strong Be After all, accelerating is not just the curing temperature an epoxy-dicyandiamide mixture on a technical aspired temperature level reduced, but it be there is also the danger that this accelerator already wäh the prepreg storage reacts with the epoxy resin where sustainably limited by the prepreg storage stability becomes.

When using a comparatively weak acceleration niger, however, are to harden the Dicyandia mids very high curing temperatures necessary by the u. a. undesirably high thermal stresses in the final pro be introduced.

When introducing dicyandiamide and accelerator in one Melt of RT solid epoxy resins occur in time compressed form has the same problems as Ver use of a liquid epoxy resin, especially the behavior the accelerator even harder at higher temperatures is mastering. It does not matter if the system serves as a matrix material for fiber composites or as a hot-melt for reactive adhesives or as a powder for Coatings are used.

Object of the present invention was to avoid the disadvantages of the prior art curable mixtures based on epoxy compounds and latent and in the  Epoxy resins soluble or homogeneously distributable curing average, which at relatively low temperature within a short time without high exothermic temperature harden the tips to a dimensionally stable state or to the durome curing final state, one of the requirements of the practice have corresponding thermal resistance, and which in prepregs at room temperature for a sufficient Shelf life.

This task is solved by using a new herd where appropriate, with the concomitant use of latent curing agent.

The invention therefore relates to imidazolyl compounds of the general formula (I)

wherein R¹ is an optionally branched alkyl radical 1-9, preferably 1-5, C atoms.

Another object of the invention are imidazolyl compounds of the general formula II

and the general formula III

in which R ^{1 is} an optionally branched alkyl radical having 1-9, preferably 1-5, C atoms, in which R ² = - (CH ₂ ) _a -, in which a = 2-10, preferably 4-6, in which R ³ =

with b = 0-5 and in which R ⁴ and R ⁵ independently of one another may be H or CH ₃ -.

Another object of the invention are curing agents for glycidyl compounds which can be prepared by Implementation of

• a) 1,2-diaminocyclohexane with
• b) monocarboxylic acids of the general formula V

wherein R ^{1 is} an optionally branched alkyl radical having 1-9 C-atoms, preferably 1-5 C-atoms, to the Imidazo lylverbindungen of the general formula I.

and optionally further reaction of these compounds with diacrylates of the general formula II a

to compounds of general formula II

or with diglycidyl ethers of the general formula III a

to compounds of general formula III

in which R ^{1 is} an optionally branched alkyl radical having 1-9, preferably 1-5 C atoms, in which R ² = - (CH ₂ ) _a -, in which a = 2-10, preferably 4-6, in which R ³ =

with b = 0-5, and wherein R ⁴ and R ^{5 can} independently be H or CH ₃ -.

The products of the invention according to formula III can also use the isolated adducts of 1,2-diamino cyclohexane and glycidyl compounds by reaction with Monocarboxylic acids are produced.

Another object of the invention is the use given by compounds of the general formula I-III if, with the concomitant use of customary amine compounds, auxiliary and additives as curing agents for glycidyl compounds gene.  

Another object of the invention are epoxy resin mold body, which are characterized in that in the first Step the reinforcing or inlay materials with the Binder consisting of

• a) a glycidyl compound averaging more than a glycidyl group per molecule and
• b) Compounds of general formulas I-III and possibly
• c) conventional solvents, fillers, reinforcing or Potting materials, pigments, excipients and given appropriate,
• d) usual nitrogen-containing heterocyclic amine compound fertilize

soaked and in the solid and dimensionally stable state leads, and in second stage at one below the Erwei Chung temperature of the shaped body formed in accordance with step 1 cured temperature.

The imidazolyl compounds of the formula I according to the invention can be prepared by condensation of 1,2-diaminocylo hexane with monocarboxylic acids of the general formula V

R¹-COOH (V)

wherein R ^{1 is} an optionally branched alkyl radical having 1-9 C-atoms, such as the methyl, ethyl, n-propyl, i-propyl, prim, sec, tert-butyl radical, 2-ethylpentyl, 3.3 .5 (3.5.5) -Trimethylpentyl radical is, in the molar ratio of amine to acid of 1: 1 to 3: 1, wherein at Reaktionsstemperatu ren of about 180 ° C in the first stage, the aminoamide and by heating to 180-200 ° C in vacuo in the second stage, the imidazoline is produced.

According to the invention, the reaction is preferably carried out causes the excess amine and that from the imidazo Linbildung resulting water removed in a vacuum who the.

These imidazolyl compounds prepared in the first stage the general formula I

can in a further step with difunctional Glyci dylverbindungen and / or acrylates are reacted to the Imidazolyl compounds of the general formula II

the general formula III  

in which R ^{1 is} an optionally branched alkyl radical having 1-9, preferably 1-5, C atoms in which R ² = - (CH ₂ ) _a -, in which a = 2-10, preferably 4-6, in which R ³ =

with b = 0-5, and wherein R ⁴ and R ^{5 can} independently be H or CH ₃ .

As glycidyl compounds here are the known alipha tables, cycloaliphatic, aromatic and aralipha table connections, in particular the commercial ones Glycidyl ether can be used as described in the Handbook of Epoxy Resins, Lee & Neville, 1967, Chapter 2.

According to the invention, the glycidyl ethers are preferred Basis of polyhydric phenols such as in particular on Base of 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) with  Epoxy values of 0.2-0.6. In addition, have also the Glycidyl ethers based on bisphenol F and polypropylene glycols proved to be advantageous.

The reaction of the compounds of general formula I with The said diglycidyl ethers are known per se method. According to the invention, it is preferable to proceed in this way ren that the imidazolyl of the general formula I with stoichiometric amounts of diglycidyl ether at 60 to 80 ° C reacted with or without solvent become.

The invention for the preparation of the addition compound concomitantly used acrylate compounds are Ver or Um esterification products of dihydric alcohols and acrylic acids or their esters. These reactions are carried out according to the method belonging to the prior art. As alcohols here can be the straight-chain or branched dihydric aliphatic alcohols such as ethylene glycol, Pro pylene glycol, butanediol, hexanediol, octanediol, decanediol or their isomers are used.

The diacrylates are reacted with the compounds of the formula I. According to the invention, preferably with stoichiometric amounts, based on acrylic double bonds - at about 60-80 ° C for Implementation brought.

The reaction of the glycidyl compounds and / or the acry late with the imidazoline compounds of the general formula I takes place according to the be for the respective reactive groups knew procedures, the ratio of mono-imidazo lylverbindung to the other reactive group preference wise 1: 1.  

The compounds of the formulas I, II, III can be used as a curing agent alone or as a mixture be set, wherein per 100 g of epoxy resin 5-50 g, preferably example 5-40 g, but especially 5-30 g curing agent be used. The quantities depend on the Structure of the respective curing agent and are by a optimally oriented experiments.

It is also possible to use the compounds of the general Use formula I-III in the form of their salts. usable Here are the organic and well-known in this field inorganic salt former. Preference is given to the invention however, the mono- or polyvalent organic carboxylic acids.

The invention co-used as a binder component Epoxy resins are glycidyl esters and ethers with two or more more epoxide groups per molecule (as described in Lee & Neville, Handbook of Epoxy Resins, 1967 Chapter 2) but preferably the glycidyl ethers based on one or polyhydric phenols. According to the invention are preferred Glycidyl ethers of 2,2-bis (4-hydroxyphenyl) -propane (Bisphe nol A) with epoxide values of 0.2-0.6, in particular those at Room temperature liquid compounds with epoxy values in order 0.45 to 0.55. In addition, there are also the glycidyl ethers based on bisphenol F and the novolaks as beneficial proved.

The commercially available halogenated, in particular brominated Epoxy resins based on the phenols listed above are likewise usable, in particular for products which are based on the electronics sector (printed circuit boards) are used should.  

To achieve particularly desired properties can the imidazoline compounds according to the invention also in Mixture with the usual aminic in this field Curing agents are used.

They can be used in combination with dicyandiamide as both Hardening agent act as an accelerator and demzu used in each case desired mixing ratio become. The curing or acceleration Curing behavior is determined by the respective structures and Controlled proportions.

To modify the properties of the final product can in addition to other epoxy resins also modifier or auxiliary be used as phenolic resins, melamine resins, Silicone resins, inorganic and organic fillers such as Quartz flour, titanium dioxide, carbon black, silicon or butadiene chew Tschuk.

To set the desired viscosity can under use viscous resins or diluents but also the usual solvents like Di methylformamide, acetone, methyl ethyl ketone, methyl glycol, Propylene glycol monomethyl ether, short chain alcohols or their mixtures are used.

For the preparation of the prepregs are organic and anorga niche fibers, nonwovens and fabrics based on aramid, Koh or cellulose, metals such as boron, steel, etc., Ke ramik, but especially glass, co-used.  

The preparation of the solvent-containing prepreg ge happens according to the method known per se, in which the Support materials in an impregnating bath with the reactive Soaked resin mixture and after squeezing the over schüssigen amount of resin continuously under energy (usually heat), with simultaneous withdrawal of Lösungsmit be transferred from the A- to the B-state. Depending on ge desired prepreg consistency (tacky to firm) These are then provided on both sides with a release film and rolled up for storage and transport. The Wei Processing is done by cutting and merging the single prepreg layers to a stack, from the through shaping measures with simultaneous heat input highly cross-linked workpiece arises.

The curing agents of the invention may also be used with Success in solventless prepregs based on Epoxy resins and optionally conventional curing agents be used. In this case, the support materials at optionally elevated temperature according to known per se Process impregnated with the binder systems and system adequately stored before they contain as the solvents the systems are further processed.

Other examples of solvent-free systems are wet laminates, fiber-reinforced molded parts produced in situ (RTM), one component hot curing adhesives e.g. B. for the Bonding of body parts in the automotive industry and epoxy resin castings and epoxy resin coatings, which are applied either wet or as a powder.

Preparation of imidazoline compounds example 1

2280 g (20 mol) of 1,2-diaminocyclohexane be submitted and 600 g (10 mol) of acetic acid are added dropwise so that the temperature of the reaction mixture does not exceed 50 ° C. to closing by heating to about 180 ° C by Amid formation freed amount of water (about 180 g) abdestil profiled. The excess amine and that from the imidazoline formation of water are heated by heating to approx. Distilled off 200 ° C at 300 mbar. After about 2 hours at 200 ° C / 300 mbar, the distillation is largely completed.

The present in the bottom reaction product is purified by distillation at 200-230 ° C / 100 mbar. This gives a colorless, semi-solid at RT product with the following characteristics:
AZ: about 400 imidazoline content (according to IR or NMR) <90%.

Example 2

Adduct of imidazoline according to Example 1 and solid epoxide Resin (mean MG 950).

237.5 g of solid medium molecular weight epoxy resin of 950 are dissolved with 237.5 g of methyl ethyl ketone at RT and with a solution of 69 g of imidazoline according to Example 1 in 69 g of methyl ethyl ketone added. It is heated for about 5 hours  Reflux and then checks the Complete speed of the reaction by thin layer chromatography. The Reaction product has a viscosity of about 800 mPa · s / 25 ° C.

Example 3

Adduct of imidazoline according to Example 1 and liquid Epoxy resin (average molecular weight 380).

138 g of imidazoline are dissolved in 200 g of propylene glycol monomethyl dissolved ether, the solution heated to 60 ° C and 190 g liquid epoxy resin (average molecular weight 380) slowly offset. After addition, it is left for 2 hours at 80 ° C. afterreact. After removal of the solvent (up to 150 ° C in vacuo) gives a solid product with an amine number from 174.

Example 4

Addition product of imidazoline according to Example 1 and butane diacrylate.

138 g (1.0 mol) of imidazoline according to Example 1 are dissolved in 100 g Dissolved ethanol and the solution heated to about 40 ° C. at 40-50 ° C then 99.1 g (0.5 mol) of butanediol diacrylate to dripped. The mixture is stirred for 1 hour at about 80 ° C and pulls then the ethanol off. After Dünnschichtchromatiographie are no longer be able to prove the starting raw materials. The Addi tion product has a viscosity of 11.9 Pa · s / 25 ° C.  

Determination of hardening agent influences in connection with brominated resins example 1

100 g of a bro dissolved in 25 g of methyl ethyl ketone (MEK) Epoxy resin (epoxy value approx. 0.18, bromine content approx. 18%) with 10 g of a 50% hardener solution from the reaction product according to the invention and MEK mixed and used for prepreg production. The preparation of the Hardener solution is carried out at RT, with their concentration basically can be chosen arbitrarily.

For preparation of prepregs on a laboratory scale, first an approximately 0.1 m ² glass filament fabric is impregnated with the resin-hardener solution. This is followed by a heat treatment of the thus impregnated reinforcing material of 2 minutes at 120 ° C in a convection oven. During this prepreg process, on the one hand, the solvent is removed from the impregnating agent, and on the other hand, the reaction components are transferred from the A to the B state. This results in almost dry, flexible prepregs, which can be stored for several weeks after cooling at RT until further processing.

The prepreg processing to approx. 1 mm thick laminates was carried out in one hour at 150 ° C with a pressure of about 1 bar. The thus cured final product showed no any defects regarding the liability of the individual Prepreg.  

To determine the thermal stability of the matrix material 100 × 10 mm ² large specimens were then removed from the laminates and examined in Torsionsschwingver search according to DIN 53 455. The results of this test are given for different mixing ratios in Table 1.

The other TG values also listed in Table 1 Examples 2-4 were determined analogously to Example 1. When Comparative size was additionally the TG of a currently häu fig used matrix material with dicyandiamide as a hardener and N-methylimidazole as accelerator in the table recorded (mixing ratio: brominated epoxy resin .: Dicyandiamide: N-methylimidazole = 100: 5: 0.8).

Table 1

Thermal resistance of the laminates

Determination of hardening agent influences in connection with BPA-based resins

To determine the curing agent properties depending The nature of the respective structure is reduced to avoid it shearing influences of reinforcing and additional materials the mixtures consisting solely of epoxy resin and Här hardened and tested.

In the examples listed in Table 2, as Epoxy resin a glycidyl ether based on bisphenol A with an epoxy value of 0.53 used.

For the preparation of the test specimens each 100 g of the Epoxy resin with the amount mentioned in Table 2 Här mixed at room temperature and in a Hardened steel tool to 4 mm thick flat moldings. From these moldings are then by sawing or milling Taken from test specimens, in which, in compliance with the test standards listed in Table 2 Property values are determined. In addition to the inventions Curing agents according to the invention was also in the table commercially available phenylimidazoline.

specimen dimensions Bending strength, DIN 53 482 | 80 × 10 × 4 mm³ Deflection, DIN 53 452 80 × 10 × 4 mm³ Impact strength, DIN 53 453 50 × 6 × 4 mm³ Tensile strength, DIN 53 455 Shoulder bar No. 3 Elongation, DIN 53 455 Shoulder bar No. 3 Young's modulus, DIN 53 457 Shoulder bar No. 3 Marten temperature, DIN 53 458 @ Heat Distortion Temperature (HDT), DIN 53 461 120 × 10 × 4 mm³ Glass transition temperature (TG), DIN 53 445 80 × 10 × 1 mm³

Table 2

Properties of the unreinforced molding materials

Claims (6)

1. Compounds of the general formula (I) wherein R ^{1 is} an optionally branched alkyl radical having 1-9 C atoms. 2. imidazolyl compounds of the general formula II and the general formula III in which R ^{1 is} an optionally branched alkyl radical having 1-9 C atoms, in which R ² = - (CH ₂ ) _a -, in which a = 2-10, in which R ³ = with b = 0-5 and in which R ⁴ and R ⁵ independently of one another may be H or CH ₃ -. 3. curing agent for glycidyl compounds, prepared by reaction of

• a) 1,2-diaminocyclohexane with
• b) monocarboxylic acids of the general formula V wherein R ^{1 is} an optionally branched alkyl radical having 1-9 C atoms C atoms, to the Imidazolylverbindun gene of the general formula I. and optionally further reaction of these Verbindun conditions with diacrylates of the general formula II a to compounds of general formula II or with diglycidyl ethers of the general formula III a to compounds of general formula III in which R ^{1 is} an optionally branched alkyl radical having 1-9 C atoms, in which R ² = - (CH ₂ ) _a -, in which a = 2-10, in which R ³ = with b = 0-5 and in which R ⁴ and R ⁵ independently of one another may be H or CH ₃ -.

4. Use of compounds of the general formula I-III, if appropriate, with the co-use of customary Amine compounds, auxiliaries and additives as curing agent for glycidyl compounds. 5. Epoxidharzformkörper, characterized in that in the first stage, the reinforcing or insert materials with the binder consisting of

• a) a glycidyl compound having on average more than one glycidyl group per molecule and
• b) compounds of the general formulas I-III and, where appropriate
• c) conventional solvents, fillers, reinforcing or insert materials, pigments, excipients and optionally
• d) customary nitrogen-containing heterocyclic Aminver compounds

soaked and in the solid and dimensionally stable condition transferred, and second stage at a below the Softening temperature of the formed according to step 1 Forming body temperature to be cured.