SU407927A1 - METHOD OF OBTAINING POLYURETHANE PRE-POLYMER - Google Patents

Description

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This invention relates to the synthesis of polyurethane non-polymers that are cured by air moisture to form protective coatings.

A known method for producing a polyurethane prepolymer by reacting toluylene diisocyanate and transesterified castor oil, followed by treatment with glycol, the ratio of isocyanate groups to alcohol is 1: 1.

To obtain a prepolymer with enhanced resistance to impact and solvents, it has been proposed to carry out the process with a ratio of isocyanate groups of toluene diisocyanate, alcohol groups of transesterified castor oil and glycol alcohol groups equal to 6; 3: 1.

The essence of the proposed invention is that a toluene diisocyanate, e.g. 2,4-toluene diisocyanate, is reacted with a transesterified polyhydric alcohol, castor oil, keeping the ratio of isocyanate and alcohol groups of 2: 1, followed by treatment, for example, diethylene glycol, while keeping the ratio of free isocyanate mops in line alcohol groups 3: 1, preferably at 58-60 ° C, followed by separation of the target product by known methods. You can use castor oil, transesterified with glycerin.

Along with 2,4-toluene diisocyanate, 2,6-toluene diisocyanate or a mixture of arylen diisocyanates can be used as toluene diisocyanate.

Ethylene glycol, triethylene glycol and 1,4butanediol can be used along with diethylene glycol.

Based on the synthesized predolimers, coatings are obtained with an increased drying rate.

Example 1. A 250-ml flask with a ground-in stopper, equipped with a stirrer passed through a mercury valve, with a reflux condenser, nitrogen inlet, a thermometer and a separating funnel protected from air moisture by a calcium chloride tube, is purged with dry nitrogen for 30 minutes. After purging the flask, toluene diisocyanate is fed into it in an amount of 35.3 g and toluene in an amount of 30.0 g. Then, with a continuous supply of nitrogen and stirring, the temperature is raised to 60 ° C. Nitrogen passed through a flask to remove moisture, passes sequentially through columns with sulfuric acid and calcium chloride. Upon reaching the specified temperature, 34.7 g of transesterified glycerin is slowly fed in.

The above ratio of toluene diisocyanate and transesterified CACE VO

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The tbrow oil is normally adjusted depending on the value of the hydroxyl number of the latter.

The adjusted ratio is calculated by the formula

24 g (NCO: OH 2: 1)

where T is the number of grams of toluene diisocyanate per 100 g of preesterified castor oil; g - hydroxyl number of interesterified castor oil in%.

When the temperature of the reaction mass rises above 60-65 ° C (exothermic), the supply of interesterified castor oil is temporarily stopped and the contents of the flask are cooled to 60 ° C. After the supply of pre-esterified castor oil is completed, the temperature is raised to 65 ° C and the reaction mass is maintained at this temperature to an isocyanate number of 18.0–19.3 (in% toluylene diisocyanate), which usually corresponds to the product viscosity –– at 20 ° 80 –JOO ( on funnel VZ-4). Then, in a flask at 58-60 ° C, 3.9 g of diethylene glycol are gradually supplied in separate portions for 4 hours and 45 minutes. At the end of the drying, the exposure is left for 15 minutes. The isocyanate number of the obtained product, determined directly after a 15-minute exposure, is 13.3%; after 17 hours of incubation without stirring, the isocyanate number as a result of the completion of the reaction decreased to

12.5% (theoretically calculated isocyanate number for this product is 12.4%). The resulting product is stable (decrease in the isocyanate number for 6 months, not more than

one%).

Example 2. The process was carried out according to the same scheme as in Example 1. However, diethyl glycol was served at 57-6 ° C for 5 hours, also in separate portions. Psocyanate

the number determined immediately after a 15-minute exposure, 13.2%; the isocyanate number after 17 hours of exposure without stirring due to the completion of the reaction decreased to 12.5% (the calculated isocyanate number

as mentioned, 12.4%); The properties of the obtained polymer when used in non-pigmented coatings are given in the table.

Subject invention

A method of producing a polyurethane prepolymer with terminal isocyanate groups by reacting toluylene diisocyanate and transesterified castor oil with subsequent glycol treatment, characterized in that the process is carried out at a ratio of isocyanate groups to toluene diisocyanococyanate to increase the resistance of the resulting polymers to impact and solvents. interesterified castor oil and glycol alcohol groups equal to 6: 3: 1.