WO2002074857A1

WO2002074857A1 - Polyalkylene glycol monoglycidyl ethers

Info

Publication number: WO2002074857A1
Application number: PCT/EP2002/002415
Authority: WO
Inventors: Wolfgang Scherzer; Jörg Volle
Original assignee: Vantico Gmbh & Co. Kg
Priority date: 2001-03-15
Filing date: 2002-03-06
Publication date: 2002-09-26

Abstract

Curable composition comprising: a) an epoxide compound having on average more than one epoxide group in the molecule, b) a polyalkylene glycol monglycidyl ether of the general formula (I), in which R, independently of one another (for n > 1) is a -H or -CH3 radical, and n = 1 to 50, as reactive modifier and c) a curing agent for epoxy resins, and the use of these curable compositions for the coating, hardening and adhesive bonding of metallic or mineral surfaces or for the production of mouldings.

Description

Polyalkylene qlycol monoglycidyl ethers

The invention relates to the use of monoglycidyl ethers based on polyalkylene glycols as reactive modifiers in epoxy resins, and to curable epoxy resin compositions comprising a monoglycidyl ether of this type, and to the use of these curable epoxy resin compositions for the coating, hardening and adhesive bonding of metallic and mineral surfaces and for the production of mouldings. The monoglycidyl ethers used have comparatively low chlorine contents and good elastifying properties, and the curable epoxy resin compositions have in some cases significantly accelerated curing rates on concomitant use of these monoglycidyl ethers.

Curable compositions based on glycidyl compounds and various curing agents, such as, for example, amines, anhydrides, novolaks and catalysts, are widely used in industry for the coating and hardening of metallic and mineral surfaces and for the production of mouldings.

The epoxy resin components used here are essentially epoxy base resins based on difunctional or polyfunctional phenols, such as, for example, bisphenol A, bisphenol F or novolaks. The viscosity of these low-molecular-weight epoxy resins is in many cases too high for processing at room temperature (for example a bisphenol A diglycidyl ether has a viscosity at 25°C of about 10,000 mPa-s).

In addition, the elasticity of the moulded materials produced therefrom is inadequate for certain applications. This problem can be remedied by addition of modifiers in the form of diluents and/or flexibilizers to the epoxy resin.

The modifiers used are predominantly liquid substances whose chemical structure enables their participation in the crosslinking reaction and thus their permanent incorporation into the fully cured epoxy resin.

Suitable for this purpose are compounds containing epoxide groups, in particular mono- and polyglycidyl ethers, for example butyl glycidyl ether, allyl glycidyl ether or phenyl glycidyl ether. An extensive list of reactive modifiers/flexibilizers of this type is given, for example, in "Handbook of Epoxy-Resins" (Lee & Neville), 1967, Chapter 13/7 to 13/18.

The reactive modifiers result in a certain degree of internal plasticization of the epoxy resin moulded material, depending on the type and amount of the added compound, while other, unreactive modifiers merely cause external plasticization with the known disadvantages of this method.

An essential disadvantage of the reactive modifiers used hitherto, such as the mono- functional, aromatic and low-molecular-weight aliphatic glycidyl ethers, is their high volatility and, in particular in the case of high-molecular-weight aliphatic glycidyl ethers, their high chlorine contents.

However, an excessively high chlorine content is evident through a significant impairment of the electrical properties, in particular as a function of the temperature.

The object of the present invention was therefore to eliminate the above-mentioned disadvantages and to provide novel reactive modifiers for curable epoxy resin compositions whose chlorine contents have been reduced compared with the prior art, whose volatility is low, which have elastifying properties, and which furthermore enable comparatively fast curing rates.

This object is achieved by the use of a polyalkylene glycol monoglycidyl ether of the general formula (I)

(I),

in which R, independently of one another (for n > 1), is an -H or -CH₃ radical, and n = 1 to 50, as reactive modifier in curable epoxy resin compositions.

The polyalkylene glycol monoglycidyl ethers can be prepared by reaction of polyalkylene glycols with epichlorohydrin and subsequent treatment with sodium hydroxide solution, with the molar ratio between polyalkylene glycol (diol) and epichlorohydrin (ECH) preferably being 1 :1 and the ratio between OH groups of the diol and ECH being 2:1. An excess of epichlorohydrin results in increased formation of diglycidyl ethers, while a sub-stoichiometric amount of epichlorohydrin results in larger amounts of reactive, unreacted polyalkylene glycols remaining in the product.

It is possible to use ethylene glycols and propylene glycols, starting from the monomers, i.e. ethylene glycol and propylene glycol, up to polymers having a mean molecular weight of about 3000 (corresponding to a polypropylene glycol of the formula (I), in which the recurrence factor n of a propylene unit is about 50). It is also possible to use mixtures of polyalkylene glycols which are different from one another. Preference is given to polypropylene glycols having a mean molecular weight of from about 230 to 2100 and polyethylene glycols having a mean molecular weight of from about 190 to 1600. This corresponds to polyethylene glycols and polypropylene glycols of the formula (I) in which n = 3 to 35. Particular preference is given to polyethylene glycols and polypropylene glycols of the formula (I) in which n = 6 to 10, such as, for example, polyethylene glycol 400, or polypropylene glycols 400 and 620. Especial preference is given to polypropylene glycols.

The choice of the alkylene glycol with respect to the chain length enables properties such as, for example, elasticity, toxicology or chlorine content, to be adjusted. The chlorine content is comparatively low.

A further essential advantage over the prior art is also the faster incipient curing rate and/or through-curing rate during curing with the corresponding curing agents. A fast curing rate is desired in practice in order to enable coatings to be walked on or overcoated more quickly. A fast curing rate is also desired in adhesive bonds and in the production of mouldings.

The invention therefore relates to a curable composition consisting of a) an epoxide compound having on average more than one epoxide group in the molecule, b) at least one compound of the general formula (I):

in which R, independently of one another (in the case of n > 1), is an -H or -CH₃ radical, and n = 1 to 50, preferably 3 to 35, particularly preferably n = 6 to 10, and c) a curing agent for epoxy resins. The advantageous amount of component b) to be used in the compositions according to the invention can vary within broad limits, depending on the area of application, and is well known to the person skilled in the art. In general, the proportion b) should be not more than 30% by weight, based on the total amount of components a) and b), since otherwise an excessive drop in the mechanical data may occur.

The epoxide compounds a) used concomitantly in accordance with the invention are commercially available products having on average more than one epoxide group per molecule which are derived from polyhydric or polycyclic phenols, in particular bisphenols and novolaks. An extensive list of these diphenols or polyphenols is given in the handbook "Epoxid- Verbindungen und Epoxidharze" [Epoxide Compounds and Epoxy Resins] by A.M. Paquin, Springer Verlag Berlin, 1958, Chapter IV, and Lee & Neville, "Handbook of Epoxy Resins", 1967, Chapter 2. It is also possible to use mixtures of these epoxide compounds. Preferred epoxide compounds a) are glycidyl ethers based on bisphenol A, bisphenol F and novolaks.

The curing agents c) to be used concomitantly in accordance with the invention may contain, for example, amino groups, anhydride groups, phenolic hydroxyl groups and acid groups. However, it is also possible to use catalytic curing agents which cause self-polymerization of the epoxy resins. An extensive list of curing agents of this type is given, for example, in the handbook "Epoxidharze" [Epoxy Resins] by Dr. H. Jahn, Leipzig, 1969, pp. 33-67. The curing agents can be used individually or in combined form. Preference is given to amino group- containing curing agents having at least two reactive hydrogens per molecule. The curing agent c) is employed in the usual advantageous amounts, according to which from 0.5 to 2.0, preferably from 0.75 to 1.25, functional groups of the curing agent c) used are present per epoxide group of components a) and b) in the respective composition.

Depending on the area of application and intended use, component d) used concomitantly in the epoxy resin compositions according to the invention may comprise inorganic and/or organic additives, such as finely divided sands, talc, silica, alumina, metals or metal compounds in the form of turnings and powders, flame-inhibiting substances, fibrous materials, such as, for example, asbestos, thixotropic agents, pigments, flow-control and deaeration agents, solvents, water, dyes, plasticizers, bitumen, mineral oils and the reactive and un- reactive modifiers or flexibilizers known from the prior art, other than those described above. The proportion of these additives is very highly dependent on the respective area of application and can be up to 90% (for example for epoxy resin mortar).

The compositions according to the invention can very generally be employed as casting resins for the production of cured products and can be used in the formulation matched to the respective area of application, for example as adhesives, as matrix resins, as tooling resins or as coating agents or for the production of mouldings.

The invention furthermore relates to a product obtainable by curing a curable composition according to the invention.

Surprisingly, comparatively good adhesion of cured coatings is also achieved so long as these are produced with concomitant use of the polyalkylene glycol monoglycidyl ethers according to the invention.

Analytical methods:

Viscosity: Measured using a Haake RV 20 rotational viscometer in accordance with the manufacturer's instructions. Epoxide value: measured in accordance with DIN 53188. Chlorine content in % (total): measured in accordance with ASTM D 1726/67.

Example 1 (Comparative Example):

A polypropylene glycol diglycidyl ether is obtained from 620 g of polypropylene glycol 620 (1 mol) and 185 g of epichlorohydrin (2 mol) by a generally known process - adduction in the presence of tetrafluoroboric acid and ring closure in the presence of aqueous sodium hydroxide solution.

Polyalkylene glycol monoglycidyl ethers are prepared analogously to the process from Example 1 by reaction of in each case one mole (2 hydroxyl groups) of the polypropylene glycols and polyethylene glycol listed below with in each case 92.5 g (1 mol) of epichlorohydrin:

Example 2: 620 g of polypropylene glycol 620 Example 3: 400 g of polypropylene glycol 400 Example 4: 400 g of polyethylene glycol 400

Example 5: Araldite GY-E, a commercial, long-chain, aliphatic, monofunctional glycidyl ether from Vantico having an epoxide value of 0.310 - comparative example of a monoglycidyl ether.

The characteristic data of the experiment products obtained are listed in Table 1 below:

Table 1 :

Use examples:

1 ) Curing rate

20 g of the glycidyl ethers from Examples 1 to 5 are homogenized with 80 g of Araldite

GY 260 (bisphenol A diglycidyl ether from Vantico, epoxide equivalent: 185). These formulated epoxy resins are mixed with the curing agent Aradur 43 (a modified aliphatic polyamine, H-active equivalent: 115) in equivalent amounts and cast to give a moulding having a thickness of approximately 6 mm.

The curing rate (Shore D) was measured after 1 , 2 and 3 days at 23°C.

The results are shown in Table 2.

Table 2:

) GE = glycidyl ether; ) EPE = epoxide equivalent value of the composition = grams of glycidyl ether mixture

2) Adhesion to sand-blasted metal sheets

The adhesion of the above-mentioned curable mixtures after curing for 24 hours at 50°C and, for comparison, a curable mixture of GY 260 (185 g) and Aradur 43 (115 g) without concomitant use of a polyalkylene glycol monoglycidyl ether according to the invention is measured. To this end, the curable mixture is applied in a layer thickness of about 0.5 mm to a previously sand-blasted metal sheet and cured for 24 hours at 50°C. The cured film is subsequently removed manually from the sheet. The adhesion is assessed as follows: (-) = Film exhibits absolutely no adhesion, (o) = Film can be removed without difficulty, (Θ) = Film can only be removed with difficulty, (+) = Film can only be removed in pieces, (++) = Film cannot be removed.

The results are shown in Table 3: Table 3:

Note: ^* = very brittle

Discussion of the results:

As can be seen from Table 2, the curable mixtures based on the products used in accordance with the invention (Examples 2 to 4) surprisingly have a faster curing rate than the diglycidyl ether from Example 1 (comparative example) even though they are monofunctional and have higher equivalent weights, i.e. lower epoxide values. Particularly striking is the difference from Example 5 as comparison with a likewise monofunctional glycidyl ether. As can be seen from Table 1 , the chlorine values of the monoglycidyl ethers according to the invention are significantly reduced compared with the comparative example of the diglycidyl ether (Example 1 ).

Table 3 shows that the curable mixtures according to the invention have comparatively better adhesion to the metal sheeting after curing. An improvement in the adhesion compared with the unformulated GY260 and also compared with the other modifiers which are not according to the invention is evident. The improvement in the adhesion properties and the improvement in the curing rate are surprising and could not have been foreseen.

Claims

WHAT IS CLAIMED IS:

1. A curable composition comprising a) an epoxide compound having on average more than one epoxide group in the molecule, b) a polyalkylene glycol monoglycidyl ether of the general formula (I)

(I),

in which R, independently of one another (for n > 1 ) is a -H or -CH₃ radical, and n = 1 to 50, and c) a curing agent for epoxy resins.

2. A composition according to claim 1 , in which n = 3 to 35, preferably n = 6 to 10, for the compound of the general formula (I).

3. A composition according to one of claims 1 and 2, where for the compound of the general formula (I) R is a -CH₃ radical (polypropylene glycol monoglycidyl ether).

4. A composition according to one of claims 1 to 3, characterized in that component a) is derived from a polyhydric or polycyclic phenol.

5. A composition according to claim 4, in which component a) is a glycidyl ether based on bisphenol A, bisphenol F or a novolak.

6. A curable composition according to claim 5, in which component c) is an amine, an anhydride, a phenol or an acid.

7. A curable composition according to claim 6, in which component c) is an amine.

8. A curable composition according to one of claims 1 to 7, characterized in that one or more than one additive which is conventional in epoxy resin technology, selected from inorganic and/or organic additives, such as finely divided sands, talc, silica, alumina, metals or metal compounds in the form of turnings and powders, flame-inhibiting substances, fibrous materials, such as asbestos, thixotropic agents, pigments, flow-control and deaeration agents, solvents, water, dyes, plasticizers, bitumen, mineral oils and diluents or flexibilizers, is present as additional component d).

9. A product obtainable by curing a composition according to one of claims 1 to 8.

10. The use of a curable composition according to one of claims 1 to 8 for the coating, hardening and adhesive bonding of metallic or mineral surfaces or for the production of mouldings.