Ketone-aldehyde resins having low water content, high thermal stability and yellowing resistance

Abstract

The invention described herein provides ketone-aldehyde resins, especially cyclohexanone-formaldehyde resins, with low water content and high thermal stability and yellowing resistance, and to a process for preparing them and their use.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention relates to ketone-aldehyde resins, especially cyclohexanone-formaldehyde resins, with low water content and high thermal stability and yellowing resistance, and to a process for preparing them and their use. [0003] 2. Description of the Background [0004] It is known that ketones or mixtures of ketones and aldehydes can be reacted in the presence of basic catalysts or acids to form resinous products. Thus mixtures of cyclohexanone and methylcyclohexanone can be used to prepare resins (Ullmann Vol. 12, p. 551). Cyclohexanone and formaldehyde react to form hard resins which are used in the coatings industry. [0005] Processes for preparing products of this kind are described in, for example, U.S. Pat. No. 2,540,885, U.S. Pat. No. 2,540,886, DD 12433, DE 13 00 256, DE 28 31 613, DD 123481 and DE 12 56 898. [0006] The resins obtained in accordance with the various processes possess softening points, as appar...

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Benefits of technology

[0018] The object on which the present invention was based was to eliminate the aforementioned disadvantages of the commercial products and to find resins which possess a low water content, high thermal stability and yellowing resistance and which are soluble in alcoholic and aromatic solvents. Additionally the nonvolatiles content ought to be high.

Problems solved by technology

Some or all of these additives may remain in the products, and consequently may have adverse effects on properties such as the water resistance of coatings from coating materials manufactured with the products.

According to DD 123481 and DE 12 56 898 it is possible to obtain resins having softening points of up to 160° C. The processes described, however, are costly and inconvenient.

Since the resins to which the invention relates are used, inter alia, in the coatings industry in order to reduce the solvent fraction, such high molecular weights are especially disadvantageous.

The skilled worker is also aware that too high a molecular weight is detrimental to the broad solubility properties of cyclohexanone-formaldehyde resins.

The skilled worker is further aware that resins, in accordance with the process disclosed therein, possess low nonvolatile fractions, as a result of which the thermal stability may be adversely affected and the yields of the process described are low.

The high water content of the standard commercial products prevents their use in high-grade coating materials such as 2-component polyurethane varnishes, for example.

A further disadvantage of the standard commercial products is that solutions of these resins in aromatic solvents such as, say, xylene tend toward clouding owing to the high water content.

These products are unsuitable for applications which use, for example, long-oil alkyd resins.

Furthermore, the resins presently available on the market possess a relatively low temperature stability, and so can be used only to a limited extent, if at all, in baking systems.

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