LU82111A1 - SOLVENT-FREE COATING COMPOSITIONS - Google Patents

Description

L 1 L! $% DESCRIPTIVE MEMORY deposited in support of a

PATENT INVENTION APPLICATION

formed by the so-called Company: LABOFINA S.A.

for

SOLVENT-FREE COATING COMPOSITIONS

Inventors; Messrs Jozef Verborgt, Jozef Braeken and Madame Jolanta Szopinska The present invention relates to coating compositions i free of solvent or of high dry extract, comprising an epoxy resin having more than one epoxy group per molecule, a polyacrylate or polyacrylate compound. methacrylate and an amine-type hardening agent.

Epoxy resins *, in particular polyglycidyl ethers derived from bisphenol A, have many uses in the field of paints and coating compositions, where they are subjected to a curing reaction in the presence of aliphatic or aromatic amines, anhydrides or else polyacid *. However, the use of these compositions based on epoxy resins requires the use of large quantities of solvents to solve the various production and application problems which are due to the viscosity of the epoxy resin itself. In addition, the high prices and the possible shortage of petroleum-based solvents as well as the ecological problems posed by their evaporation, have led researchers to develop coating compositions in aqueous phase or free from solvents. Powder coating compositions are, moreover, a typical example of solvent-free paint. The equipment required to produce and apply the powder coating compositions is however completely different from traditional equipment for preparing or applying solvent-based coating compositions. Accordingly, it is very important for paint manufacturers to find coating compositions free of solvent or of high dry extract which can be prepared and applied with conventional equipment used for solvent-based compositions.

Rather than using volatile petroleum solvents to reduce the viscosity of epoxy resins, it has already been proposed to dilute these resins with non-volatile liquid reactive compounds such as unsaturated polyesters or polyacrylate or polymethacrylate compounds.

The most significant improvement with respect to viscosity was obtained with the compositions described in American patent 4051195, i which comprise an epoxy resin and a polyacrylate or polymethacrylate compound>

However, the implementation period, after addition of the hardening agent, remains very short since it is generally between 2 and 20 minutes. This short period of time is due in particular to the high reactivity of the curing agents used, which are most often aliphatic polyamines. It has moreover been noted that this reactivity is strong not only vis-à-vis the epoxy resins alone, but that it is even stronger vis-à-vis the polyacrylate or polymethacrylate compounds alone. In addition, the use of such curing agents leads, during the solidification reaction, to very high exothermicity peaks ", of the order of 170 to 230 ° C., which can be dangerous when mixing. large quantities of products. Thus, both the very short duration of curing at room temperature, which results in an extremely short duration of use of the composition, and the very high peaks of exothermicity, are factors which seriously limit the use such coating compositions.

The use of cycloaliphatic polyamines is also known as a curing agent for epoxy resins alone, to lengthen their period of use, but the viscosity of these compositions is still too high.

Solvent-free coating compositions must meet a few important criteria, including in particular: - low viscosity of the composition ready for filling, - limited increase in viscosity over time, which requires a fairly long period of stability before reaching the complete gelation of the composition, hence a longer period of time for the easy processing of this composition - a low peak of exothermicity during the curing of the composition, in order to reduce the tensions of the cured resin.

The subject of the present invention is coating compositions which meet these criteria. It relates in particular to coating compositions, free from solvent or with high dry extract, comprising an epoxy resin, a polyacrylate or polymethacrylate and an agent for hardening such that the working period is at least 120 minutes and the peak of exothermicity during this reaction does not exceed 100 ° C. and the viscosity of the composition is less than 2500 centipoise during this period.

The solvent-free or high solids coating composition of the present invention comprising an epoxy resin having more than one 1,2 epoxide group per molecule, a polyacrylate or polymethacrylate compound having more than one acrylate or methacrylate end group and a curing agent is characterized in that the curing agent used is a cycloaliphatic polyamine.

For a composition with a high dry extract, it is necessary to understand compositions which have a solids content of at least 80% by weight, and preferably at least 90% by weight.

The Applicant has found, unexpectedly, that using a cycloaliphatic polyamine as a curing agent for synthetic resins, comprising an epoxy resin and a polyacrylate or polymethacrylate compound, the period between the time when the curing agent in the resin and the time when it gels and therefore also the period of use of the resin.

This implementation period is at least 120 minutes.

It has been found that when a polyacrylate or polymethacrylate compound is added to an epoxy resin in the presence of a cycloaliphatic amine hardener, not only does the resin application period considerably lengthen, but also the peak of exothermicity remains very low throughout the solidification period, this finding is all the more surprising since in those where a polyacrylate or polymethacrylate compound is added to the epoxy resin in the presence of an aliphatic amine hardener, the 1 processing time of the resin, and the peak of exotherm is very high.

The implementation period depends in particular on the evolution of the viscosity of the composition during the curing reaction. Generally a resin will be easily used, provided that the viscosity does not exceed 2,500 centipoises and preferably 1,500 centipoises.

In addition, the Applicant has also found that the use of a

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cycloaliphatic polyamine as curing agent leads to an exothermic peak, during the curing reaction, which is much lower than with other curing agents and which generally does not exceed 100 ° C.

Cycloaliphatic polyamines have at least two aminoaliphatic groups which can react with the epoxy groups of the resin.

Far aminoaliphatic group, one understands an amino group in which the atom of axota is not member of an aromatic cycle nor linked directly to a carbon atom of an aromatic cycle. Generally, the amino group can be linked directly to a carbon of an aliphetic ring or indirectly by a mono or divalent carbon radical.

As examples of suitable cycloaliphatic polyamines, mention may be made of 3,5,5-tr imethyl-3- (aminomethy1) cyclohexylamine, also called isophorone diamine, V, N '»bie- (2-aminoethyl) pipéraKxne , para ** menthane-diamine, 1,3-bis- (aminomethyl) cyclohexane, 1,4-diaminocyclo-hexane, bis- (4-aminocyclohexyl) methane, bis (4-amino-3-methylcyclohexyl ) methane, 2,2, -bis- (4-aminocyclohexyl) propane or their isomers. However, it is preferred to use, for reasons of ease of processing, cycloaliphatic polyamines · liquids such as isophorone diamine in particular.

In order to carry out the curing reaction under suitable conditions, it is advantageous to use the cycloaliphatic diamine in an amount such that there is from 0.5 to 1.2 amine group per epoxy group and per terminal acrylate or methacrylate group.

Although the curing reaction can be carried out completely at room temperature, it can, if desired, be carried out at a higher temperature, between 30 and 180 ° C., optionally in the presence of a catalyst such as triethylamine or acid. salycilique and the like, well known to those skilled in the art.

The epoxy resins used in the present invention are resins which contain more than one 1,2 epoxy group per molecule. They can be saturated or unsaturated, aliphatic, cycloaliphatic or heterocyclic and can be of monomeric or polymeric nature. Preferably, the epoxy resins will contain glycidyl ether or ester groups, they will be liquid rather than solid and will have a weight per epoxide of between 100 and approximately 2000, preferably between 110 and 500. As examples of epoxy resins, may notably cite the glycidyl polyethers of polyhydric phenols which are derived from an epihalohydrin such as for example epichlorohydrin, and from a polyhydric phenol. Examples of such phenols include resorcinol, hydroquinone, bie (4-hydroxyphenyl) - 2,2-propanc or bispfaénoi A, 4,4'-dihydroxybenzophenone, bis (4-hydroxy-phenyl) -l, 1-ethana, bis (4-hydroxyphenyD-1, 1-isobutane, bie (4-hydroxy-phenyl) -2,2-butaae, bis (2-dihydroxynaphtyl) methane, phloroglucinol, and bis (4 -hydroxyphenyl) sulfone Mention may also be made of other polyhydric phenols such as novolak resins containing more substituted phenols or phenol, with parts linked by methylene bridges, as well as halogenated phenolic compounds, for example brominated and chlorinated.

Epoxy resins which consist of polyether glycidyl of polyhydric alcohols can be prepared by reacting a polyhydric alcohol with an epihalohydrin in the presence of an acid catalyst such as boron trifluoride, and subsequently treating the resulting product with an alkaline agent. dehydrohelogenation. Among the polyhydric alcohols which can be used during the preparation of these polyepoxides, mention may be made of glycerine, ethylene glycol, propylene glycol, diethylene glycol, hexanediol, hexanetriol, trimethylolpropane, trimethylolethan pentserythritol and analogues.

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As other epoxy resins, mention may be made of glycid esters of polycarboxylic acids which are derived from an epihalohydrin and a polycarboxylic acid according to the methods described in US Patents 3,893,314 and 3,576,827 introduced here for references. As examples of polycarbo xylic acids, mention may be made of phthalic acid or its anhydride, isophtallq acid / terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic anhydride, adipic acid, dimerized fatty acids, dibasic acids prepared from unsaturated fatty acids and acilic acids and the like. However, the glycidyl polyether of bisphenol A is preferably used.

The polyacrylate or polymethacrylate esters of polyols of the invention are esters which contain more than one terminal acrylate or methacrylate group. These esters are esters of acrylic or methacrylic acids of aliphatic polyhydric alcohols, for example dl and polyacrylates or di and polymethacrylate of alkylline glycols, of alkoxylene glycols, alicyclic glycols and of higher polyols, such as ethylene giycol, triethylene glycol, tetraethylene glycol, tetramé-thylèneglycol, hexanediol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol and the like, or · mixtures of these together or with their analogs partially. λ Examples of these compounds, trimethylolpropane triacrylate may be cited, trimethylolethane triacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, tetramethylene the diméthacrylete, ethylene glycol dimethacrylate, triéthylèneglycoldimétha-methacrylate copolymer, pentaerythritol triacrylate, pentaerythritol tetraacrylate , 1.6 hexanediol diacrylate, 1.6 hexanediol dimethacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaaerylate and the like #. However, 1.6 hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate and pentaerythritol pentaaerylate # will advantageously be used.

It is also possible to use acrylate or methacrylate esters of epoxy resins in which the epoxy resin acts as a polyol.

These resins are described in particular in US Pat. No. 3,377,406 cited here for reference.

These acrylate or methacrylate polyol esters are mixed with the epoxy resins described above in a weight ratio of approximately 5 to 150 parts of ester per 100 parts of epoxy resin, as described in

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The solvent-free or high solids coating compositions of the present invention can be used in place of solvent-based paints or powder paints. They can be used as an anti-corrosion coating for metals as a mirror back coating, as a primary or finishing coating for concrete, wood or metals, or as a mortar component and for other similar well-known uses of the tradesman.

The following examples are given to better illustrate the present invention, but without limiting its scope.

Example 1

A solvent-free resin was prepared by mixing:

49.0 g diglycidyl ether bisphenol A

29.1 g of 1,6-hexanediol diacrylate 21.9 g of isophorone diamine.

The amounts of each constituent are calculated so as to obtain an amine group per terminal acrylate group and per epoxy group, for a total weight of 100 g.

The viability of the composition was measured just after mixing, it was 80 centipoise.

This viscosity was further measured at various times which are defined with respect to the initial time t ^ which is the time when the components were mixed.

Viscosity at t + 120 minutes: 960 centipoise

Viscosity at t ^ + 180 minutes: 2400 centipoise * The peak of exothermicity during the curing reaction was 36.5 ° C.

For comparison, compositions were prepared with curing agents not in accordance with those of the present invention.

In these compositions, the amounts of the various constituents were calculated to obtain one amine group per terminal acrylate group?

Composition A was prepared by mixing

54) 0 g of diglycidyl ether of bisphenol A

32.2 g of 1.6 hexanediol diacrylate 13.8 g of triethylene tetramine 13 minutes after mixing the constituents, the composition was completely cured and therefore inapplicable. In addition, the exotherm peak during the curing reaction was 145 ° C.

Composition B was prepared by mixing

51.2 g diglycidyl ether bisphenol A

30.5 g of 1.6 hexanediol diacrylate 18.3 g of xylylene diaaine

The initial time is defined by tQ as being the moment when the constituents are mixed, and the viscosity of the composition is measured at the following times; tQ; 85 centipoises tQ + 120 minutes: 3520 centipoises t -f 180 minutes: 8640 centipoises

The peak of exothermicity during the curing reaction was 44 ° C.

If the period during which composition 1 can easily be applied is already longer than with composition A, on the other hand, after 120 minutes, a solvent must be used since the viscosity is too high. Example 2. The following composition, which is free of solvent, was prepared by mixing;

50.0 g diglycidyl ether bisphenol A

29.8 g of 1.6 hexanediol diacrylate 0.2 g of Hodaflow (product sold by Monsanto Cy) 20.0 g of Ti02 22.6 g of isophorone dlamine to>

Immediately after mixing the various constituents, this composition was applied to metal plates. The curing was carried out for 30 minutes in an oven heated to 120 ° C.

The following properties have been determined:

Gloss: 72-84 according to the Lange 60 method

Erichsen according to method D1N 53156:> 7 mm Resistance to reverse impact according to method ÀSTM D 2794:> 100 kg / cm #

Two hours after mixing the constituents, the viscosity was 1020 centipoise. A new application * was then made on other “metal plates. Curing was carried out for 30 minutes in an oven heated to 120 ° C.

The properties obtained were similar to those described above.

Example 3

The following composition was prepared by mixing; 70 g of bisphenol diglycidyl ether A 30 g of 1.6 hexanediol diacrylate 27 g of isophorone diamine

Part of this composition was used to paint a mirror back.

The other part, about 100 g, was used to determine the period during which the composition could be used as well as the peak of exothermicity during the curing reaction.

Implementation period: 210 minutes * r

exotherm: 37 ° C

The mirror is then subjected to a Kesternich test according to the DU 5001t method which consists in subjecting the coating to a humid saturated atmosphere in the presence of sulfur dioxide.

We noticed a slight loss of adhesion on the edges of the

Claims (3)

1. Coating composition free of solvent or of high dry extract comprising an epoxy resin having more than one group 1,2 epoxide per molecule, a polyacrylstt or polymethacrylate compound having more than one terminal group ecrylete had methacrylate and a curing agent characterized in that the curing agent used is a cycloaliphatic polyamine. ίί. 2. Composition according to claim 1, characterized in that the quantity of cycloaliphatic polyamine is such that there is from 0.5 to 1.2 amine group per epoxy group and per terminal acrylate or methacrylate group. 3. Composition according to claims 1 and 2, characterized in that the cycloaliphatic polyamine is chosen from the group comprising 3,5,5-trimethyl-3- (aminomethy1) cyclohexylamine or isophorone diamine, N, N, -bis- ( 2 "amino-ethyDpiperoxin, paramenthanediamine, 1,3-bis- (aminoethyl) cyclohexane, 1,4-diaminocyclohexane, bis- (4-aminocyclohexyl) methane, bis (4-amino- 3-Tsethylcyclohexyl) methane, 2,2'-bis- (4 ~ aminocyclohexyl> propane and their "isomers." A ψ 9