WO2002055579A1

WO2002055579A1 - Epoxy resin adduct based on telechelic amino polydiene and its use for reinforcing impact strength of epoxy resin systems

Info

Publication number: WO2002055579A1
Application number: PCT/FR2001/000108
Authority: WO
Inventors: Katell Andromaque; Jean-Jacques Flat; Françoise MECHIN; Jean-Pierre Pascault
Original assignee: Atofina
Priority date: 2001-01-12
Filing date: 2001-01-12
Publication date: 2002-07-18

Abstract

The invention concerns the field of impact-resistant epoxy materials. More particularly, it relates to an epoxy resin adduct obtained by reacting a telechelic conjugated diene amino oligomer free of acrylonitrile with an epoxy resin. The invention also concerns the use of such an adduct for providing epoxy materials with impact strength.

Description

EPOXY ADDUIT BASED ON AMINO TELECHELIC POLYDIENE AND ITS SOUND

APPLICATION IN STRENGTHENING TO SHOCK OF EPOXY NETWORKS

The invention relates to the field of epoxy materials and more particularly to additives having a rubbery character used as impact enhancer for epoxy networks.

According to the invention, by epoxy materials is meant any product of the reaction of an oligomer carrying oxirane or epoxide functions (known as “epoxy resins”) and a hardener. Due to the reactions involved in the crosslinking of these epoxy resins, the end of the reaction results in a crosslinked material corresponding to a more or less dense three-dimensional network depending on the basic characteristics of the resins and hardeners used. As such, the notions of epoxy equivalent weight (or EEW) and functionality of the epoxy resin are critical in order to adjust the density of the network obtained. These epoxy materials are used in various industries. As an indication we can cite the aeronautical industry (airfoil, helicopter blade), the petroleum industry (operating tube, tank, tank), the sports equipment industry (tennis rackets, golf).

Epoxy materials are inherently fragile due to their high network density which guarantees high glass transition temperature (Tg) and therefore high thermomechanical performance. This fragility is essential in many applications both for adhesive applications (reduced peel strength values) and materials (poor impact resistance) and it is essential to find means to improve the impact resistance of these materials without reducing them. thermomechanical performance (high Tg and modulus values). The most commonly used current route consists in dispersing a rubber phase within the fragile epoxy matrix. The invention intends to provide an original way of impact strengthening of epoxy materials by dispersing a new rubber phase. Numerous documents describe the impact reinforcement of epoxy networks by oligomers based on butadiene and acrylonitrile terminated either by carboxylic acid type functions designated by CTBN, as described in

EP 353190 or by amino functions designated by ATBN, as described in DE 3639570.

For this type of additive, butadiene provides the rubbery character while acrylonitrile provides initial miscibility with the epoxy resin before crosslinking.

However, the functional copolymers of butadiene and acrylonitrile (amino- or carboxy-telechelic) have the drawback of having high viscosities and glass transition temperatures the higher the higher their acrylonitrile content. These two characteristics are respectively troublesome both for the implementation of these systems by casting at room temperature but also for the behavior at low temperatures. However, the deletion of the acrylic comonomer has been little considered since it is acrylonitrile which provides the initial miscibility with the epoxy resins.

We have now found a solution which allows the use of an acrylonitrile-free conjugated diene amino telechelic oligomer having a low viscosity and a low glass transition temperature. This oligomer improves the impact resistance of epoxy materials while ensuring satisfactory initial compatibility with the epoxy resin.

The solution found by the Applicant is based on the use as an impact enhancer of an epoxy adduct itself constituting an object of the invention.

The epoxy adduct of the invention is the product of the reaction of a telechelic amino oligomer of conjugated diene and an epoxy resin.

It is preferable to use a molar ratio between the oxirane functions and the amine functions which makes it possible to avoid gelling of the adduct. This synthesis can be carried out in the solvent phase, for example advantageously in toluene, but it will preferably be carried out in bulk.

The telechelic amino oligomer of conjugated diene corresponds to the following general formula (reagent 1):

in which :

- R1, R2, R3 and R4, identical or different, are independently selected from the group containing:

linear or branched alkyl radicals having a number of carbon atoms between 1 and 20, preferably between 1 and 4, optionally substituted by one or more substituents selected from the hydroxy, C1 to C6 alkoxy and halogen substituents,

-cycloalkyl radicals having 3 to 12 carbon atoms, optionally substituted by one or more substituents selected from C1 to C6 alkyl, C1 to C6 alkoxy, hydroxy and halogen groups, -alkyl radicals optionally substituted by one or more substituents selected from C1 to C6 alkyl, C1 to C6 alkoxy, hydroxy and halogen groups,

the aryl radicals optionally substituted with one or more substituents selected from C1 to C6 alkyl, C1 to C6 alkoxy, hydroxy and halogen groups, with at least one of the combinations R1-R2 and R3-R4 which may optionally form an aliphatic ring -A is at least one monomer chosen from the group containing: butadiene, isoprene, chloroprene.

The preferred telechelic amino conjugated diene oligomer of the invention is a partially hydrogenated telechelic amino butadiene oligomer such as that obtainable according to US 5,760,157 in the name of the Applicant, hereinafter referred to as PBAT. The PBAT is obtained for example in a two-step process in which a cyanotelechelic oligomer is first prepared in a solvent by priming butadiene with azobisisobutyronitrile (AIBN), the chain ends of which are then hydrogenated in the presence of a Raney cobalt catalyst.

The aminotelechelic oligomer of conjugated diene according to the invention can also be prepared from its teleoxy or hydroxytelechelic carboxy counterparts according to organic chemistry reactions known to those skilled in the art. The nature of the groups between the polydiene skeleton and the amino telecholic functions is not critical for carrying out the invention.

By epoxy resin designated below by E is meant any organic compound having at least two functions of the oxirane type, polymerizable by ring opening. The epoxy resins claimed cover all the usual epoxy resins which are liquid at room temperature or at a higher temperature. These epoxy resins can be monomeric or polymeric on the one hand, aliphatic, cycloaliphatic, heterocyclic or aromatic on the other hand. These resins can be obtained by reacting aromatic glycidic ethers with a molar excess of epichlorohydrin. These resins are described in "Handbook of Epoxy resins" by Lee and Nevill, Me Graw-Hill Book Co, New York (1967). Examples of such epoxy resins include the diglycidyl ether of resorcinol, the diglycidyl ether of bisphenol A, the triglycidyl p-amino phenol, the diglycidyl ether of bromo-bisphenol F, the triglycidyl ether of m-amino phenol , tetraglycidyl methylene dianiline, triglycidyl ether of (trihydroxyphenyl) methane, polyglycidyl ethers of phenol-formaldehyde novolac, novolac orthocresol polyglycidyl ethers and tetra glycidyl ethers of tetraphenyl ethane. Mixtures of at least two of these resins can also be used.

We prefer epoxy resins having at least 1.5 oxirane function per molecule and more preferably still epoxy resins containing between 2 and 4 oxirane functions per molecule. Also preferred are epoxy resins having at least one aromatic ring such as the diglycidyl ethers of bisphenol A.

The adduct of the invention prepared according to the method described later can be diagrammed as follows:

obtained by reacting the compound 1 described above with E in an oxirane / NH ₂ molar ratio greater than 4 and preferably between 6 and 12. E 'is a unit derived from E by opening an oxirane function and contains at minus a terminal oxirane function.

It is well known to those skilled in the art that the preparation of such adducts, depending on the synthesis conditions used, can cause, by the reaction between a terminal epoxide function and a new oligomer, a certain degree of chain elongation of said adduct .

Another object of the invention is the use of the epoxy adduct as an impact enhancer for epoxy networks.

According to one form of the invention, this application is carried out as follows: The epoxy resin and the impact modifier (CTBN or epoxy adduct of PBAT prepared above) are mixed and degassed under vacuum for one hour at 50 ° C.

The hardener is added at room temperature in stoichiometric quantity by compared to epoxy resin and impact modifier. The mixture is then degassed at room temperature for 15 minutes then it is poured into a mold consisting of two metal plates covered with teflon-coated fabric separated by a teflon frame. The reaction mixtures are then crosslinked for a given time at a given temperature in a thermoregulated enclosure.

Generally, hardeners are used as hardeners of epoxy resins which react at room temperature in the context of so-called “two-component” systems or at temperatures above ambient temperature in the context of so-called “single-component” systems. The choice of crosslinking agent is based on the intended application. By way of examples of such crosslinking agents, there may be mentioned acid anhydrides such as succinic anhydride, tetrahydrophthalic anhydride, nadic anhydride or oligomers carrying anhydride functions such as styrene and anhydride copolymers maleic produced by the Applicant, dicyandiamide and its derivatives, organic dihydrazides such as that of sebacic acid, aliphatic, cycloaliphatic or aromatic polyamines.

Whatever the embodiment of the invention, the level of adduct used can be chosen in order to introduce a weight amount of PBAT of between 1 and 50% by weight relative to the total weight of epoxy + hardener and preferably between 5 and 20% compared to the total epoxy + hardener.

Various other adjuvants can be introduced into the formulation depending on the intended application. Among these adjuvants, mention may be made of non-reactive plasticizers of the phthalate type, rheological agents such as fumed silica, pigments, fillers, reinforcing fibers, catalysts. The following examples illustrate the invention without limiting its scope:

EXAMPLES

Products used Epoxy resin: it is a diglycidic ether of Bisphenol A (DGEBA) having an epoxy weight equivalent (EEW) of 190 g / mol and a viscosity of 4

Pa.s at 33.5 ° C marketed by the company CIBA under the commercial reference

Bakelite 164. Hardener: this is 4,4'-diamino 3,3'-dimethyldicyclohexylmethane having a molar mass of 238 g / mol (or an amino acid equivalent (AEW) of 1 19 g / mol) sold by BASF under the commercial reference

Laromin C260.

PBAT: it is an aminotelechelic oligomer of butadiene synthesized according to US 5,760,157 having a viscosity of 1300 mPa.s at 30 ° C and an equivalent mass of amine of 833 g / mol.

CTBN: it is a carboxy-telechelic copolymer of butadiene and acrylonitrile having an acid functional rate of 0.052 mole of acid per 100 g of CTBN and a Brookfield viscosity of 1500 P at 27 ° C sold by the company BF Goodrich under the commercial reference Hycar 1300 * 8.

Adduct preparation:

100 g of PBAT and 182.5 g of epoxy resin are loaded into a reactor equipped with a stirring anchor, a nitrogen gas inlet and a thermometer, which corresponds to a molar ratio of 8 epoxy functions by NH ₂ function. The initially heterogeneous reaction mixture is brought to 100 ° C. by immersion in a thermoregulated oil bath and the reaction takes place for three hours under an inert nitrogen atmosphere. We thus recover an epoxy adduct of

PBAT (ADD1) which is in the form of a monophasic liquid having an equivalent epoxy mass of 392 g / mol.

Characterization of epoxy materials

Glass transition temperature: they were measured by differential scanning calorimetry. The Tg value was measured during a second temperature sweep with a temperature rise ramp of 10 ° C / min. Young's modulus: Young's moduli were measured during tensile tests according to ISO standard R527.

Charpy shock: the impact resistances were carried out in accordance with ISO standard 179/1 Ae.

Elastic linear fracture mechanics: the fracture toughness values (K _1c ) were measured according to ISO / DIS 13586.2 (1998).

Dispersion of reinforcing particles in the epoxy matrix: the dispersion was analyzed by scanning electron microscopy.

Results obtained:

Prepared formulations:

EPOl is a formulation according to the invention and EP02 / EP03 two against examples. The two formulations EPOl and EP02 contain 10% by weight of functional butadiene oligomers (CTBN and PBAT respectively).

Cooking conditions:

The castings are first pre-cooked in a first cycle and then post-cooked in a second cycle. The above formulations were crosslinked under the following conditions:

Average particle diameter

Tg of epoxy materials

Tenacity at break:

Charpy shock

Young's modulus:

Claims

1. Compound of general formula

likely to be obtained by reacting reagent 1 corresponding to the formula

and an epoxy resin (E) having at least two oxirane functions in an oxirane / NH ₂ molar ratio greater than 4 and preferably between 6 and 12, in which

- linear or branched alkyl radicals having a number of carbon atoms between 1 and 20, preferably between 1 and 4, optionally substituted by one or more substituents selected from the hydroxy, C1 to C6 alkoxy and halogen substituents,

- cycloalkyl radicals having 3 to 12 carbon atoms, optionally substituted by one or more substituents selected from C1 to C6 alkyl, C1 to C6 alkoxy, hydroxy and halogen groups, - aryl radicals optionally substituted by one or more substituents selected from C1 to C6 alkyl, C1 to C6 alkoxy, hydroxy and halogen, with at least one of the combinations R1-R2 and R3-R4 possibly forming an aliphatic ring A is a residue of at least one diene monomer chosen from butadiene, isopene and chloroprene,

- E is at least one compound chosen from diglycidyl ether of resorcinol, diglycidyl ether of bisphenol A, triglycidyl p-amino phenol, diglycidyl ether of bromo-bisphenol F, triglycidyl ether of m-amino phenol, tetraglycidyl methylene dianiline, triglycidyl ether of (trihydroxyphenyl) methane, polyglycidyl ethers of phenol-formaldehyde novolac, polyglycidyl ethers of orthocresol novolac and tetraglycidyl ethers of tetraphenyethane,

- E ¹ is a motif derived from E by opening an oxirane function,

- n is between 10 and 200.

2. Compound according to claim 1 characterized in that A is butadiene.

3. Compound according to claim 1 or 2 characterized in that E is the diglycidyl ether of bisphenol A.

4. Compound according to one of the preceding claims, characterized in that n is between 20 and 60.

5. Method for reinforcing impact of epoxy networks consisting of a) homogenization and degassing under vacuum for one hour at a temperature close to 50 ° C. of a mixture containing an epoxy resin and at least one compound according to one of claims 1 to 4, b) adding a hardener to the mixture obtained in a, and degassing at room temperature for 15 minutes, c) crosslinking at a temperature between 20 and 200 ° C of the mixture obtained in b poured into a suitable mold, said reagent representing from 1 to 50% by weight of the total weight of the epoxy resin and the hardener, the hardener being in stochiometry relative to the epoxy resin and to said compound.

6. Method according to claim 5 characterized in that said reactifl represents from 5 to 20% by weight of the total weight of the epoxy resin and the hardener.

7. Method according to claim 5 or 6 characterized in that the epoxy resin is an organic compound having at least two functions of epoxy type, polymerizable by ring opening, it can be monomeric or polymeric on the one hand, aliphatic, cycloaliphatic, heterocyclic or aromatic on the other hand and preferably chosen from the group containing the diglycidyl ether of resorcinol, the diglycidyl ether of bisphenol A, the triglycidyl p-amino phenol, the diglycidyl ether of bromo-bisphenol F, the triglycidyl ether of m- amino phenol, tetraglycidyl methylene dianiline, triglycidyl ether of (trihydroxyphenyl) methane, polyglycidyl ethers of phenol-formaldehyde novolac, polyglycidyl ethers of orthocresol novolac and tetraglycidyl ethers of tetraphenyethane,

8. Method according to claim 7 characterized in that the epoxy resin is the diglycidyl ether of bisphenol A.

9. Method according to one of claims 5 to 8 characterized in that the hardener is chosen from acid anhydrides such as succinic anhydride, tetrahydrophthalic anhydride, nadic anhydride or oligomers carrying anhydride functions such as copolymers of styrene and maleic anhydride, dicyandiamide and its derivatives, organic dihydrazides such as that of sebacic acid, aliphatic, cycloaliphatic or aromatic polyamines.

10. Epoxy networks such as those capable of being obtained by the process according to any one of claims 5 to 9.