CS216489B1 - A method for increasing the activity of ketone peroxide initiators - Google Patents

Abstract

The proposed procedure concerns initiators used for curing unsaturated polyester resins, especially those initiators whose activity has been reduced due to long-term storage. The method consists in treating the initiator solution used by adding hydrogen peroxide in an amount of up to 5 wt. %, based on 100% concentration, and optionally specified organic polar substances in an amount adjusting the miscibility of the initiator solution with water and a water content of not more than 15 wt. %.

Description

(54) A method of increasing the activity of ketone peroxide initiators

The proposed process relates to initiators used for curing unsaturated polyester resins, especially those initiators whose activity has been reduced due to long-term storage. The method consists in treating the initiator solution used with hydrogen peroxide in an amount of up to 5% by weight. %, based on 100% of the concentration, and optionally specified organic polar substances in an amount controlling the miscibility of the initiator solution 8 with water and a water content of not more than 15% by weight; %.

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The invention relates to enhancing the activity of initiators used to cure unsaturated polyester resins. The method is particularly suitable for reactivating initiators whose activity has been reduced due to long-term storage.

Ketone peroxide initiators are commonly used to cure unsaturated polyester resins and compositions based thereon. They can be prepared either from a single ketone, such as methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, etc., or from ketone mixtures, which is more advantageous, especially if necessary to achieve the desired level of initiator activity or consistency, stability, etc. Initiators are a natural phenomenon of the gradual decomposition of the active ingredients, which results in a loss of initiation activity and is often accompanied by turbidity of the initiator system due to the excretion of water in the form of fine droplets or even separation of the aqueous layer. The form of precipitated water is dependent on the solvents used in the preparation of the initiator.

This phenomenon occurs especially in systems with low water miscibility and the excreted water is the cause of a number of resin and composition defects cured by these initiators. Although the loss of reactivity can be partially eliminated by the addition of a larger quantity of freshly prepared initiator, the excluded proportions of water in the initiator with reduced activity must be removed prior to mixing, which is generally quite difficult.

M /

The present invention is directed to a method for enhancing the activity of ketone peroxide initiators used in the form of solutions in organic solvents or plasticizers to cure unsaturated resins or compositions based thereon. The principle of the invention is that hydrogen peroxide is added to the initiator solution in an amount of up to 5% by weight. %, based on 100% of its concentration in the solution, and optionally organic polar substances selected from the group consisting of aliphatic and cycloaliphatic alcohols having a carbon number of 1 to 7, glycols having a carbon number of 2 to 3 and their corresponding diglycols and trlakyl phosphate These polar substances are added in an amount to adjust the miscibility of the initiator solution with water to a water content of not more than 15% by weight. %, preferably up to 7 wt. %, and may contain up to 20 wt. % water and / or denaturing additives such as benzene and toluene. Hydrogen peroxide and optionally said organic polar substances are preferably added immediately prior to application of the initiator solution.

The process according to the invention essentially allows the regeneration of initiators whose initiation activity has fallen below the carrying limit due to storage and achieves their properties which are required of them for curing unsaturated polyester resins. Increasing the miscibility of the initiator solutions with water by the addition of organic polar substances results in a re-dissolution of the possibly eliminated aqueous phase and also permits the use of aqueous hydrogen peroxide solutions without adversely affecting the properties of the cured polyester compositions by the presence of water.

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Hydrogen peroxide may be added in the form of aqueous solutions of various concentrations, at least 10% by weight. %. The optimum temperature of the components is about 20 ° C. Higher temperatures reduce the stability of the initiator system (peroxide decomposition), and at lower temperatures there is a risk of organic ketone peroxides falling out of solution.

Aliphatic and cycloaliphatic alcohols having 8 carbon numbers from 1 to 7, such as methanol, ethanol, isopropanol, n-propanol, butanol, cyclohexanol, methylcyclohexanol and the like, and glycols with carbon numbers, are used as organic polar substances increasing the miscibility of the initiator with water. 2 to 3 and the diglycols derived therefrom, i.e. ethylene glycol, propylene glycol, diethylene glycol and dipropylethylene glycol, or phosphoryl trialkyl esters having a number of carbon atoms in the alkyl groups of 1 to 4, e.g. and water or denaturants in an amount of at most 20 wt. % aalze is applied either individually or in various mixtures and combinations with each other.

The total water content of the initiator treated according to the invention should not exceed 7% by weight. %. It is always preferred that the miscibility with water is higher (up to a maximum of 15% by weight) than the final water content of the initiation solution. By maintaining these conditions, in addition to increasing the activity of the initiator, some further improvements are achieved, in particular the properties of the cured polyester compositions, for example when applied to unsaturated polyester paints, by increasing adhesion and improving the wettability of the substrates. For the reasons stated above, the amount of hydrogen peroxide used is limited. its minimum necessary concentration. In order to increase the stability of the initiator system during treatment of the initiator for a long time before its application, it is recommended to use one of the known nitrogen-containing stabilizers, such as triethanolamine, piperazine, etc.

Example 1

K 90 wt. parts of a cyclohexanone peroxide-based initiator with water miscibility

4.5 wt. % at 10 to 22 ° C. parts of a mixture of n-propanol, ethanol containing 4 wt. % water and 2 wt. % toluene and 35% hydrogen peroxide in wt. ratio of 1: 1: 1. The mixture is thoroughly mixed and applied as follows:

Ke 100 wt. parts of unsaturated polyester resin containing 35 wt. % styrene is added 1 wt. a part of a cobalt accelerator containing 1 wt. % metal, and 3 wt. parts of the above initiator. The gelation time of the 25 g resin block is reduced by 58% compared to the gelatinization of the resin with the untreated initiator.

Example 2

To the mixed initiator based on cyclohexanone peroxide, methylcyclohexanone peroxide

216,489 and methyl ethyl ketone peroxide, turbid with excreted water and containing in addition 5 wt. % dissolved water, 12 wt. % of a mixture of triethyl phosphate, cyclohexanol and 50% of hydrogen peroxide in a 2: 1: 2 ratio by weight, corresponding to an addition of 2.4 wt. % 100% hydrogen peroxide. This initiates a clarification of the initiator which is applied in an amount of 5 wt. % for curing an unsaturated polyester varnish of the parefinic type comprising a cobalt accelerator (0.03 wt.% metal in bed). The gelation time of the coating film compared to the uncoated primer is reduced by 31%. In addition, the coating is free of defects (bubbles, craters) and its adhesion increases (measured on a solid maple board) from 1.5 MPa to 2.8 MPa.

Example 3

To a cyclohexanone peroxide-based and methylcyclohexanone peroxide-based initiator containing triethyl phosphate and stabilized with piperazine having a water miscibility of 15 wt. %, 5 wt. % 35% hydrogen peroxide. Gelatinization time 25 g of a block composition composed of 100 wt. parts of unsaturated polyester resin, 1 wt. parts of cobalt accelerator (containing 1 wt.% metal) and 3 wt. % of the initiator parts, is reduced from the original value of 581 (when cured with the non-treated initiator) to 377 s (when cured with the initiator modified by the addition of hydrogen peroxide), i.e. by 35%.

Example 4

To a freshly prepared initiator based on cyclohexanone peroxides and methylcyclohexanone peroxides dissolved in dimethyl phthalate, stabilized with triethonolamine and dipicolinic acid, 10 wt. % of a mixture consisting of 50% propylene glycol and 50 wt. % 30% hydrogen peroxide. The gelation time of 25 g of the block of the composition of Example 3 is shortened by 25% compared to the composition containing the initiator.

Claims (3)

SUBJECT OF THE INVENTION A process for increasing the activity of ketone peroxide initiators used in the form of solutions in organic solvents or wetting agents for curing unsaturated polyester resins or non-base compositions thereof, comprising adding to the initiator solution hydrogen peroxide in an amount of up to 5% by weight. %, based on 100% of its concentration in the solution, and optionally organic polar substances from the group comprising aliphatic and cycloaliphatic alcohols having a carbon number of 1 to 7, glycols having a carbon number of 2 to 3 and their corresponding diglycols and trialkyl esters of phosphoric acid % of carbon atoms in alkyl groups 1 to 4, in an amount adjusting the miscibility of the initiator solution and water to a water content of not more than 15 wt. %, preferably up to 7 wt. %. 2. Process according to claim 1, characterized in that the organic polar substances optionally containing up to 20 wt. % water and / or denaturing additives. 3. A process according to claim 1, wherein the hydrogen peroxide and optionally the organic polar substance are preferably added immediately prior to the application of the initiator solution.