CS262228B1 - A method for recovering solvents which are lost in the processing of unsaturated polyester resins - Google Patents

Abstract

A method of regenerating solvents waste during the processing of unsaturated polyester resins, consisting in adding polymerization inhibitors to the waste solvents at normal temperature, whereby before or after the addition of the inhibitors the solvents are optionally freed from mechanical impurities, then either before or during distillation, high-boiling liquids with a boiling point above 160 °C are added, after which the solvents thus treated are subjected to distillation at a temperature of 40 to 120 °C and the resulting concentrated organic waste is disposed of.

Description

A process for the recovery of solvents which are unsaturated in the treatment of unsaturated polyester resins by adding polymerization inhibitors to the solvents at normal temperature, optionally removing the impurities from the solvents before or after the addition of the inhibitors, then adding high-boilers either before or during distillation. liquids having a boiling point above 160 ° C, after which the treated solvents are distilled at 40 to 120 ° C and the resulting concentrated organic waste is discarded.

The present invention relates to a process for the regeneration of solvents resulting from the processing of unsaturated polyester resins.

In the processing of unsaturated polyester resins into fiberglass or their application as a coating or potting compound, considerable quantities of solvents are used to clean the production equipment. These waste solvents are destroyed by residual liquid polyester resins, peroxides, accelerators, fillers, dyes and dirt from used brushes, cleaning fabrics, etc.

Such contaminated solvents must be treated taking into account current environmental and economic requirements. Disposal, respectively. recovery of this waste is currently most commonly done in the following several ways. The first is that the waste solvents, including polyester resin, etc., are incinerated in special incinerators, using the heat energy obtained. This is an extremely uneconomic method of disposal, and waste containing chlorinated solvents is not suitable for incineration.

Another method is to allow some of the solvents to evaporate from the material in the open air. In doing so, the waste turns into a gel. This gel, already contained in closed containers, is weighed into a solid waste dump, although it still contains a considerable amount of highly flammable and expensive solvents. It is known from the literature that inhibitors are added to the waste, the waste is partially thickened, inhibitors with complicated handling discarded, and the thickened polyester resin obtained is mixed with standard fresh polyester resin and used for processing into less valuable products. Also in this process there is a loss of solvents, in addition it is not possible to process dirty waste in this way, etc. It is also known how the waste is thickened in a vaporizer of special construction with inserted plastic bag into gel state after cooling Remove the evaporator and store it in a solid waste dump. This process is very time consuming and still contains some valuable solvents in the gel.

From the above it is clear that the method of disposal of the above-mentioned waste, respectively. regeneration of the solvents is a very demanding matter. Most of the problems associated with solvent recovery resulting from the processing of unsaturated polyester resins containing accelerators, catalysts, pigments, dyes, resin residues, dirt and mechanical impurities are overcome by the present invention. The invention is based on the first step of adding polymerization inhibitors, in particular hydroquinone, in an amount of 0.01 to 0.1% by weight, to the waste solvents at a temperature of 0 to 30 ° C. based on the weight of the solvents. Possible mechanical impurities can preferably be removed from the solvents by filtration before or after the addition of inhibitors. Organic high-boiling liquids having a boiling point above 160 ° C, selected from the group consisting of aromatic esters, glycol ethers and aromatic hydrocarbons, in quantities of one to two times the weight of the unsaturated polyester resin present or in such a process, are added to the solvents before or during distillation. amount so that the waste containing pigments and dyes remains in liquid form after the solvents have been distilled off. The waste solvents thus treated are subjected to distillation at a temperature of 40 to 120 ° C and the resulting concentrated organic waste is disposed of by known methods.

The advantages of the process of the present invention are both economical and ecological. Regenerative volatile organic solvents used for cleaning up to 98% are recovered from the initial waste treated with the addition of known types of inhibitors and the addition of the high-boiling organic liquid, regardless of whether they are chlorinated solvents such as methylene chloride, ketone, such as acetone, alcoholic such as methanol and ester such as methyl acetate, ethyl acetate, butyl acetate and the like.

The degree of regeneration is essentially determined only by the efficiency of the cooler above the evaporator. Only very coarse impurities need to be removed from the waste stream prior to distillation, which could clog eg a reboiler drain valve, etc. The process of the present invention makes it possible to use solvent-intensive but rinsing and dissolving efficiency rinsing processes. because we regenerate these solvents practically completely.

The regeneration of the volatile solvents is carried out at a relatively low temperature, generally up to 120 ° C, on an apparatus which is not very demanding in terms of apparatus, consisting solely of a waste container, a digester equipped with heating, cooling, possibly stirring, cooler and distillate container.

In particular, waste high-boiling esters such as dibutyl phthalate, dimethyl phthalate, methyl benzoate or high-boiling glycols, respectively, can be used as high-boiling organic liquids. glycol ethers such as ethylene glycol, diethylene glycol, trlethylene glycol, etc., or higher boiling aromatic hydrocarbons such as diethylbenzene and the like, or mixtures thereof.

Environmentally, the process of the present invention is advantageous in several respects. The volume of final waste is greatly reduced. If, for example, 10 wt. then at a resin to non-volatile organic solvent ratio of 2: 1, the waste volume is reduced to about 15% by weight. starting amount. It is very important that the concentrated waste remains liquid even after cooling to normal temperature, which facilitates handling. Concentrated waste no longer has the character of a class I combustible, since it no longer contains solvents with a flash point below 21 ° C, such as acetone, ethyl acetate, etc. This gives the concentrated waste the character of waste oils that are normally burned.

The invention is further illustrated by the following examples.

Example 1

The starting waste was about 10 wt. a solution of an unsaturated polyester resin including an initiator and an accelerator in a solvent mixture consisting of acetone, methanol, methyl acetate, ethyl acetate and isobutyl acetate. Up to 122 wt. 0.06 wt. parts of hydroquinone as inhibitor and 4 wt. parts of waste dibutyl phthalate and the resulting solution was homogenized. In the regeneration apparatus with a 100 liter digester content, 87 wt. parts of the solution and the distillation started, the beginning of the distillation being at 57 ° C and the major part leaving at 59 to 62 ° C. After distilling about 30 wt. The remaining 39 wt. parts of the solution. Towards the end of the distillation, the temperature of the distilling vapors was approx

Mp 110 ° C. About 105 wt. parts of distillate and about 17.5 wt. % of the distillation residue, even at 20 ° C, very liquid.

Example 2

The starting waste was 384 wt. parts of a suspension of pigments, dyes and polyester resin in acetone. The proportion of pigments and the like was about 8% by weight. 14% by weight of unsaturated polyester resin. This suspension was previously freed of mechanical impurities by filtration and 0.2 wt. % of hydroquinone as. inhibitor and 15 wt. parts of waste methylbenzoate. 231 wt. parts of the resulting suspension and distillation commenced, the temperature of the distilling vapors rising from 57 to 61 ° C. After distilling about 105 wt. 168 parts by weight of solvent were added. parts of the resulting suspension and continued distillation until a temperature of 65.5 ° C was reached for distillation vapors at which distillation ceased. A total of 155 masses still distilled. parts of distillate. Approximately 124 wt.% Was poured from the distillation apparatus to cool to 50 ° C. parts of the residue, well flowing even at 20 ° C. Thus, the loss was about 3.75% by weight. based on the sum of the input material.

Claims (1)

Process for the recovery of solvents which are unsaturated in the processing of unsaturated polyester resins and containing accelerators, catalysts, pigments, dyes, liquid resin residues and small mechanical impurities, characterized in that firstly polymerization inhibitors, in particular hydroquinone, are added to the waste solvents at 0 to 30 ° C. in an amount of 0.01 to 0.1% by weight, based on the weight of the solvents, wherein before or after the addition of the inhibitors, the solvents are optionally freed of mechanical impurities, preferably by filtration, then organic solvents are added to the solvents during distillation or during the distillation. high boiling liquids having a boiling point above 160 ° C from the group consisting of esters of aromatic acids, glycol ethers and aromatic hydrocarbons, in an amount equivalent to one to two times the weight of the unsaturated polyester resin present or in such an amount, after the solvents have been distilled off, the waste containing pigments and dyes remains in liquid form, after which the waste solvents thus treated are distilled at a temperature of 40 to 120 ° C and the resulting concentrated organic waste is discarded.