DE1239467B - Process for the production of rigid foams based on polyurethane - Google Patents

Description

Process for the production of rigid foams based on polyurethane It is known to produce polyurethanes by reacting organic polyisocyanates with organic To produce polyhydroxyl compounds. According to a special form of implementation the polyaddition is carried out in the presence of blowing agents such as halogenated hydrocarbons, or with formed by the reaction of excess polyisocyanate with water Carbon dioxide carried out; foam-like polyurethanes are obtained, depending on the choice of the polyhydroxyl compounds and the polyisocyanates hard, semi-hard or flexible are. Polyisocyanates are preferred for the production of rigid polyurethane foams with at least two aromatic nuclei and polyhydroxyl compounds with OH equivalent weights from about 100 to 200 used.

It is advantageous to use surface-active materials in the production of foamed polyurethanes Substances such as silicone compounds as foam stabilizers and organometallic compounds, z. B. tin (II) octoate and / or tertiary amines, used as a reaction accelerator.

In the production of such rigid foams, the reaction rate is the polyisocyanates with the polyhydroxyl compound are often too low. The pore structure the finished foam is not even enough, and the products are often too strongly colored.

It has now been found that rigid foams based on polyurethane can be obtained by reacting polyhydroxyl compounds with polyisocyanates of the general formula (I) in which n is 0 to 5 and R is alkyl or cycloalkyl radicals, hydrogen, halogen or a nitrile group, can advantageously be prepared in the presence of customary reaction accelerators, blowing agents and optionally foam stabilizers by using an iron compound-containing polyisocyanate (I).

The rigid polyurethane-based foams produced according to the invention have improved properties compared to those produced by conventional processes, like a more even pore structure and lighter coloring.

According to an advantageous embodiment, are continuous Foams are made by stirring a mixture vigorously at room temperature from reaction accelerator, polyhydroxyl compound, foam stabilizer and blowing agent a polyisocyanate of the type mentioned, which contains an iron compound, is added and foaming in a known manner, for. B. with the usual devices, such as high or Low-pressure foaming systems, under shaping. The procedure can can also be carried out discontinuously.

Suitable iron compounds are those which are found in the polyisocyanate (I) are wholly or partially soluble, e.g. B. iron (II) chloride, iron (II) sulfate, iron (II) nitrate, ferrocene, iron tartrate, iron oxalate or iron benzoate, in particular Iron (III) compounds, such as iron (III) chloride. The iron compounds are too effective mixed with each other; they are used in amounts of 0.001 to 0.5 percent by weight, preferably 0.005 to 0.05 percent by weight, based on the polyisocyanate (I), used and expediently only added to the finished polyisocyanate (I).

Suitable polyhydroxyl compounds are, for example, customary polyethers, such as polymers made from alkylene oxides, their copolymers or addition products to polyols, such as glycol, glycerol, trimethylolpropane or pentaerythritol, or the usual ones Polyesters, such as reaction products of sithylene, propylene, butylene or ethylene glycol with adipic acid, phthalic acid or dimeric acid.

As a blowing agent, for example, low-boiling organic Solvents such as methylene chloride, monofluorotrichloromethane, difluorodichloromethane, Water with an equimolar amount of polyisocyanate, as well as carbon dioxide or nitrogen be used.

Preferred reaction accelerators are, for example, tertiary ones Amines, such as triethylenediamine, triethylamine, trimethylamine or diethylmethylamine, or organometallic compounds such as tin (II) octoate or dibutyltin dilaurate or Mixtures of these compounds in customary amounts of 0.01 to 0.5 percent by weight, based on the total mixture.

The usual silicone compounds are preferably used as foam stabilizers used.

The polyisocyanates of the formula (I) are prepared in a customary manner by first aniline or its nucleus alkylated or halogenated halogen derivatives with aqueous formaldehyde in the presence of acidic catalysts at elevated temperatures converts to polyamines and then the polyamine in the presence of solvents phosgenated.

The polyurethane-based foams produced according to the invention are suitable, for example, as insulating materials for buildings and cooling units or as Packaging means.

The parts and percentages given in the example relate to the Weight.

Example A. Preparation of the polyisocyanate In a container with a stirrer device, 600 parts of chlorobenzene are saturated with phosgene at 60.degree. Then 4500 parts of a solution of 10.5% phenyl base (II) = -472 parts are left in the course of 2.5 hours iz = 0 to 5, and 89.5% chlorobenzene run in.

[II was obtained by reacting aniline with formaldehyde in a molar ratio 2.6: 1.0 in the presence of 25 percent by weight hydrochloric acid, based on aniline 50 to 100 ° C.] The formaldehyde was made up as a 30 to 36% strength aqueous solution. Unreacted aniline and water were distilled off after the condensation had ended.

While the base solution is being fed in, one is passed at the same time Phosgene stream in the reaction mixture, such that the liquid mixture always with Phosgene is saturated. The temperature is kept at 60 to 65 ° C. After running in the temperature of the solution is increased from 65 to 125 ^ C in the course of 3 hours, a weaker phosgene stream being passed into the mixture. At the end of the phosgenation dissolved phosgene is removed by nitrogen. The chlorobenzene is then distilled off. At the end of the distillation, the pot temperature is around 180 ° C at 0.5 to 1 torr vacuum.

A distillation residue = »MDIIA is obtained in a known manner 1 «(see table); Yield = 595 parts; Key figures: NCO = 30.9%; viscosity = 90cSt / 25 C; Total chlorine: 0.3 () fo; completely soluble in benzene, also in dilute solution; fractions that can be distilled = mixture of diisocyanatodiphenylmethane isomers with over 80 ° / n p, p'-isomers, boiling point l = 180 to 190 ° C; Fe = 0.0010 / o; Na = 0, 001o / o.

B. Dissolving metal compounds in (I) in a stirred tank 200 parts (I), freshly prepared according to A, are submitted in a known manner. 0.06 parts are added over the course of 10 minutes at about 70 ° C. with vigorous stirring FeCl3 = 0.03 added. The mixture is stirred for a further 2 hours.

It works under nitrogen.

Polyisocyanate produced according to A without added metal .......... »MDI / A 1 «with 0.03% FeCI3» MDI / B 1 «with 0.03% AICI3. »MDI / B 2« with 0.03% ZnCIz ........... »MDI / B 3« with 0.03% NaCl ........... »MDI / B4« with 0.03% tin (II) octoate .. »MDI / B 5« C. Manufacture of rigid polyurethane foam Those manufactured in accordance with A and B. Polyisocyanates are made with a reaction product of glycerine with propylene oxide according to the invention to rigid foam under the same conditions by two methods processed.

Method 1: So that the foam forms relatively slowly, are smaller amounts of catalyst than used in process 2.

Application: reaction vessel with agitator. Be in the stirred tank mixed quickly: 100 parts of the polyether, 0.25 parts of triethylenediamine, 1 part Triethylamine, 2 parts of silicone oil, 45 parts of halogenated hydrocarbon propellants and 150 parts of MDI. It will be the time of foam formation and the height of the finished foam measured.

Variant of method 1: Exactly like method 1; one sets, however one: 1 part triethylenediamine and 1 part silicone oil.

The foam is formed in a shorter time.

The following table shows the properties of the Process 1 and 2 produced rigid polyurethane foams and the polyisocyanates (with and without the addition of iron compounds according to the invention) and compared. In the evaluation mean: a) Activity of the MDI: It is with the Stopwatch shows the time from mixing the components to the end of the foam development measured. The approach with the shortest Rk. Time receives grade 1 = very good, the one with the longest the grade 6 = unsatisfactory.

In addition, the height of the foam is measured in centimeters. The approach The lowest layer height receives grade 6, the highest grade 1.

The grade of "activity" results from the combination of time and altitude measurements. b) Pore structure: size and uniformity of the pores. Grades 1 to 6; Grade 1 = very good; Grade 6 = unsatisfactory. c) Color of the finished foam: light brown - desired; Medium brown = undesirable. Method I Method 2 Sample Activity Pore Structure Color Activity Pore Structure Color MDI / A 1-no foam- 5 5 brown MDI / BI 1 1 to 2 light brown 1 MDI / B 2 4 5 brown 4 3 brown MDI / B344-54 brown MDI / B 3 4 4 - 5 4 brown MDI / B 4 - no foam - 5 4 brown MDI / B 5 3 to 4 4 brown 3 3 brown The table shows that a good rigid foam is obtained with the polyisocyanate MDI / B 1. The remaining samples result in rigid foams that are unusable for technical recycling or only of limited use.

Claims (1)

Claim: Process for producing rigid foams based on polyurethane by reacting polyhydroxyl compounds with polyisocyanates of the general formula (I) in which n is 0 to 5 and R is alkyl or cycloalkyl radicals, hydrogen, halogen or a nitrile group, in the presence of customary reaction accelerators, blowing agents and optionally foam stabilizers, it is indicated that polyisocyanates (I) containing an iron compound are used. Documents considered: German Auslegeschrift No. 1,142,233; "Industrial and Engineering Chemistry", 1963, Vol. 55, No. 9, p. 48 until 50.