DE1904936A1 - Epoxy resin compsns. with extended pot life comprising (a) polyepoxy cpds. (b) anhydrides of polybasic carboxylic acids and (c) 0.001-3% (esp. 0.5-1.5% of barbi - Google Patents

Abstract

Epoxy resin compsns. with extended pot life comprising (a) polyepoxy cpds. (b) anhydrides of polybasic carboxylic acids and (c) 0.001-3% (esp. 0.5-1.5% of barbituric acid, thiobarbituric acid, or N-substituted or nitration- or nitrosation products of these, as retarder. Preferred retarder (c) is (thio)barbituric acid, opt. substituted with 1 or 2 alkyl or aryl grps. such as methyl, ethyl, butyl or octyl grps. The new retarders are particularly effective with mixtures of crystallised glycidyl isocyanurate and anhydrides; they may also be used with cycloaliphatic epoxy resins such as the glycidyl ester of hexahydrophthalic acid, or with conventional epoxy resins based on polyhydric phenols (e.g. diphenylolpropane) and epichlorhydrin.

Description

"Retarders for Epoxy Resins" The invention relates to the use certain chemical compounds as additives to extend the service life Mixtures of compounds containing epoxy groups and polybasic anhydrides Carboxylic acids.

Mixtures of compounds containing more than one epoxy group in the molecule and carboxylic acid anhydrides have one of the structure of the epoxy compound and the Carboxylic acid anhydrides and the degree of purity of these compounds and other factors, e.g. the temperature, batch size, etc., dependent service life. It is often desirable to extend the useful life of such mixtures.

It has now been found that the useful life of the mixtures mentioned can be extended in the desired manner> if you add barbituric acid or Thiobarbituric acid or its N-substituted derivatives or its nitration or Nitrosation products used. Barbituric acid is preferably added to the mixtures or their derivatives in an amount of 0.001 to 3 percent by weight, in particular 0.5 to 1.5 percent by weight, based on the epoxy compound, was added.

If alkyl-substituted derivatives of barbituric acid are used, come primarily those that have one or two lower alkyl as substituents or one or two Contain aryl residues. Come as alkyl radicals for example methyl, ethyl, butyl or octyl radicals. These leftovers can also contain other substituents, such as halogen atoms or nitro groups. as Aryl radicals are, for example, phenyl radicals or diphenyl radicals. These too Groups can also contain halogen atoms or nitro groups.

In addition, the thiobarbituric acid itself can successfully act as a retarder be used.

Finally, compounds to be used according to the invention are suitable with a retarding effect the nitration products or nitrosation products of Barbituric acid bZlf. Thiobarbitursures, which are relatively easily available.

The additives according to the invention are in principle suitable for all known ones Compounds containing more than one epoxy group in the molecule and all the usual ones Carboxylic acid anhydrides known as hardeners. The extent of the retarding effect is among other things dependent on the type of epoxy compound. In general, mixtures such epoxy compounds, which have a particularly short service life, more strongly influenced than those that have a longer service life by themselves.

The addition of barbituric acid causes a particularly strong delay or their derivatives in the case of mixtures of glycidyl isocyanurate, in particular of crystallized Glycidyl isocyanurate, and anhydrides of polybasic carboxylic acids, will work well also achieved with so-called cyeloaliphatic epoxy resins. There are some Compounds understood that contain more than one boxidgruppe Mm! Tlolekül, from at least about half of which are included in a cycloaliphatic ring system are. In addition, the term should include the glycidyl esters of polyvalent cycloaliphatic Carboxylic acids, e.g. the diglycidyl esters of hexahydrophthalic acids, fall.

Finally, the addition of barbituric acid or its mentioned Derivatives in known epoxy resins come into question, which are based on polyvalent Phenols, especially diphenylolpropane, and epichlorohydrin are produced.

The anhydrides used in the mixtures to be retarded are polyvalent Carboxylic acids are e.g. hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, Tetrahydrophthalic anhydride, phthalic anhydride, dodecenyl succinic anhydride, Pyromellitic acid dianhydride, methylendomethylene tetrahydrophthalic anhydride, tetrachlorophthalic anhydride, Adipic anhydride, sebacic anhydride and others more.

With the barbituric acid or its derivatives to be used according to the invention the mixtures can optionally be used for a certain period of time extend.

Namely, it is possible to have the retarding effect by adding known accelerator to pick up again.

This has the advantage that, if desired, a delayed Approach can quickly cure a part intended for comparison. Suitable accelerators are for example tris-6dimethylaminomethyll-phenol, dimethylbenzylamine, trimethylbenzylammonium chloride and others more, Example 1: 100 g of triglycidyl isocyanurate (epoxy equivalent 102) and 140 g of hexahydrophthalic anhydride were heated separately to 1200 C and then mixed. The mixture was kept constant at 1200 ° C. and the viscosity curve followed with a rotary viscometer. The time was measured, which to Achieving a viscosity of 1500 cP was necessary. The measurement was carried out after DIN 16 945 (isothermal viscosity curve). From this 10 minutes were subtracted and the value thus obtained is referred to as reactivity.

The reactivity in the batch described above was 22 minutes. 1 g of barbituric acid was added and a reactivity of 100 minutes was then measured.

Example 2: As described in the previous example, the reactivity was of the batch from 100 g of the diglycidyl ester of hexahydrophthalic acid (epoxide equivalent 165) and 85 g of hexahydrophthalic anhydride at 1300 C. The reactivity was 35 minutes.

1 g of barbituric acid was added to the mixture. The reactivity was in this case 70 minutes.

Example 3: A batch of 150 g of an epoxy resin based on of diphenylolpropane (epoxy equivalent 398) and 52 g of hexahydrophthalic acid. The course of the viscosity was followed at 1200 ° C. and 7500 cP was chosen as the measuring point. The reactivity was 70 minutes.

1 g of barbituric acid was added to the batch. In this case it was fraudulent the reactivity 110 minutes.

Example 4: There was a batch of 100 g of a cycloaliphatic Epoxy resin (epoxy equivalent 220) and 63 g hexahydrophthalic anhydride at 1300 C manufactured. The reactivity was 25 minutes.

If 1 g of barbituric acid was added to the batch, the reactivity increased to 50 minutes.

Example 5: A batch of 100 g of an epoxy resin based on of diphenylolpropane (epoxy equivalent 185) and 75 g of hexahydrophthalic anhydride produced and the reactivity 0 determined at 150 C to 300 minutes.

If 1 g of barbituric acid was added to the batch, the reactivity increased to 720 minutes.

Example 6: The approach according to Example 1 was repeated and 1 g each a) N, N'-diphenylbarbituric acid b) 5-nitrobarbituric acid and c) 2-thiobarbituric acid added. The following reactivities of the systems were measured: a) 275 minutes, b) 79 minutes, c) 53 minutes.

Claims (3)

Patent a n p r ü c h e 1) Use of barbituric acid or thiobarbituric acid or their N-substituted derivatives or their nitration or. Nitrosation products as additives to mixtures containing epoxy groups to extend the service life Compounds and anhydrides of multibasic carboxylic acids. 2) Use of compounds according to claim 1 as the service life extending additives in an amount of 0.001 to 3%, based on the epoxy groups containing compounds. 3) Use of such derivatives of barbituric acid or Thiobarbituric acid according to Claim 1 and 2, which have a substituent or contain two alkyl or aryl radicals.