DE2243392A1 - Rigid cellular polyurethane foams of increased thermal - stability - prepd from aromatic oh-contg polyols and polyisocyanates - Google Patents

Abstract

Polyurethane foam compsn. which is the reaction prod. of (I) an org. polyisocyanate, (II) 10-100., pref. 40-90% wt. cpd. selected from (a) where R is H or 1-3C alkyl, X is H, OH, Cl, Br or 1-12C alkyl, n is 1-2 and m is 0.1 to 4; where R is 1-8C divalent hydrocarbon, -S, -S-S-, and each X is H, Cl, Br or 1-12C alkyl; and (c) reaction prods. of chloromethylated diphenyl ether of structure where n is 0-1, with a phenol of structure where R is H, Cl, Br, cyclohexyl, phenyl or 1-12C alkyl; with 0-90 % wt. polyether of polyester polyol and (III) aldehyde or cpd. capable of releasing HCHO >70 degrees C selected from hexamethylene tetramine, tris(hydroxymethyl)nitromethane and cyclic or linear polymers of HCHO. The reaction is carried out in the presence of a foaming agent.

Description

POLYURETHANE FOAM COMPOSITIONS CONTAINING AROMATIC HYDROXYL GROUPS POLYOLS AND POLYISOCYANATES.

This invention relates to cellular polyurethane compositions, and more particularly hard cellular polyurethane foam masses made from compounds with aromatic compounds Hydroxylgruppqen and polyisocyanates, which are characterized by an improved resistance against thermal degradation.

Polyurethane foams made from aromatic hydroxyl groups Polyols and polyisocyanates have excellent flame retardant properties, especially with regard to their resistance to direct contact with a flame, such as in the "Flame Penetration Test" of the Bureau of Mines in the article by W. R. Andrews, A. D. Cianciolo, E. G. Miller, and L. W. Thompson n J. of Cellular Plasticst page 1Q2 to 108 in the March issue 1968 is described.

However, these foams have poor thermal stability or poor degradation resistance when exposed to heat, such as those found e.g. occurs in insulation for ovens or similar facilities. The thermal resistance can be checked by a test described by J. N. Tilley, H. G. Nadeau, H. E. Reymore, P. H. Waszeciok and A. A. R. Sayigh in J. Cellular Plastics, Volume 4, No. 1 on pages 22-36, in particular page 23.

It has now been found that the thermal resistance of polyurethane foam compositions from a polyol with a plurality of aromatic hydroxyl groups and a polyisocyanate improved by adding an aldehyde or a formaldehyde-releasing compound can be, these additives preferably in an amount of 2 to 50 and particularly preferably in an amount of 5 to 20 parts by weight, based on the Total weight of the polyol and polyisocyanate can be used.

The formaldehyde-releasing compounds used in the formulation Manufacture of the foam added to include formaldehyde itself or those compounds that have formaldehyde at a temperature of about 700 or less hand over. Such compounds are, for example, the cyclic and the linear homopolymers of formaldehyde, such as trioxane and paraformaldehyde, hexamethylenetetramine and tris (hydroxymethyl) nitromethane.

Other aldehydes used in the reaction mixture for the preparation of the Foam can be added. include, for example, aliphatic aldehydes such as Acetaldehyde, propionaldehyde, butyraldehyde and glyoxal; heterocyclic aldehydes, such as furfural, and aromatic aldehydes such as benzaldehyde and hydroxybenzaldehyde.

Since formaldehyde is a gas at room temperature, it is difficult to handle and requires the use of flameproof equipment in the manufacture of the Foams. For this reason, formaldehyde-releasing compounds are preferred or other aldehydes used for the production of the foams. But you can also with good success dissolve formaldehyde in a suitable solvent and this Add the solution to the starting materials for foam production.

The compounds having a plurality of aromatic hydroxyl groups used as polyols in the invention do not contain any groups having an active hydrogen atom other than the aromatic hydroxyl group. These compounds include zeBo those which can be characterized by the following general formula where in this formula R is hydrogen or an alkyl radical having 1 to 3 carbon atoms, X is hydrogen, hydroxyl, chlorine, bromine or an alkyl radical having 1 to 12 carbon atoms, n is an integer from 1 to 2 and m has an average value of about 0.1 to about 4.

Another group of suitable compounds corresponds to the formula in which R is an alkylidene radical with 1 to 8 carbon atoms, and each X is independently hydrogen, an alkyl radical having 1 to 12 carbon atoms, chlorine or bromine.

Other suitable compounds with a variety of aromatic Hydroxyl groups used in the present invention for making polyurethane foam compositions can be used include e.g. B.

the diphenyl ether phenolic resins obtained by reacting a chloromethylated diphenyl ether with a phenol. The chloromethylated diphenyl ethers here correspond to the general formula in which n is an integer from 0 to 1, and the polyol used for the reaction has at least one hydrogen atom in the ortho or para position and corresponds to the general formula in which R is hydrogen, chlorine, bromine, cyclohexyl, phenyl or an alkyl radical having 1 to 12 carbon atoms.

The polyols with several aromatic hydroxyl groups can be used as the only one hydroxyl-containing compound can be used, but they can also be used as a mixture use with other polyether polyols, e.g. with the addition products of one or more alkylene oxides with 2 to 4 carbon atoms, such as ethylene oxide, Propylene oxide or butylene oxide, on glycols, glycerine, 1,2,4-butanetriol, 1,2,6-hexanetriol, Trimethylolpropane, pentaerythritol, sucrose, hexose or sorbitol. Other polyols, the polyols containing aromatic hydroxyl groups as a mixture used are the addition products of the alkylene oxides mentioned with novolak resins, z. B. Novolak polyols having hydroxyl numbers in the range of about 30 to 1200. The polyols can also be mixed with polyesters that contain hydroxyl groups that are mutually exclusive react with organic polyisocyanates. This creates polyester-aromatic-ether-polyurethane compounds. The polyols with aromatic hydroxyl groups can be used in amounts of 10 to 100% by weight, preferably 40 to 90% by weight, based on the total weight of the substances containing the active Provide hydroxyl groups, are used.

Any of those used for polyurethane production can be used as the organic polyisocyanate known polyisocyanates can be used. The polyisocyanate can have two or more Contain isocyanate groups. Mixtures of polyisocyanates are also suitable.

Compounds with terminal ends are also used as organic polyisocyanates Isocyanate groups in consideration, which arise when an excess of polyisocyanates is reacted with polyhydroxy compounds.

Those made from novolak resins and from the blends already mentioned from novolak resins and other polyols and from polymeric isocyanates such as polymethylene polyphenyl isocyanate (PAPI) manufactured polyurethane foams have a higher flame resistance and better self-extinguishing properties than foams that one from non-polymeric isocyanates, e.g. tolylene diisocyanate, or similar isocyanates under similar conditions. Polyurethane foams made from novolak resins and the polymeric polyisocyanates therefore constitute a preferred class of the invention Products.

In the manufacture of polyurethane foams according to the invention can be the ratio of the polyisocyanate compounds to the aromatic hydroxyl groups containing polyols or the mixtures of such polyols with other polyols or other compounds with active hydrogen vary within wide limits. As a rule, however, it is from 0.85 to 2.0, preferably from 1.0 to 1.2, NCO groups per active hydrogen atom in the mixture. To generate gases for expansion the reaction mass, water and excess polyisocyanate can be added. Preferred but the polyurethane foams are made using aliphatic hydrocarbons with boiling points below 1100 C or halogenated aliphatic hydrocarbons with boiling points below 1100 C. Such propellants are e.g. dichlorodifluoromethane, Trichlorofluoromethane, hexane, hexene or pentane.

The polyisocyanates are usually used in an excess amount used against the theoretically required amount to deal with the hydrogen atoms all starting materials and the water in the reaction mixture to react, preferably in an amount of about 1.0 to 1.2 NCO groups for each OH and each active hydrogen atom in the mixture of starting materials.

The polyurethane foams can according to the so-called prepolymer method, a one-shot process or batchwise or any other known Process are produced. The cell-like products are hard to extremely hard Foams and have closed or open cells, but exist in the Stimulate predominantly from closed cells with a low percentage of open or interconnected cells.

In practicing the invention, the novolak resin or a mixture of the novolak resin and one or more other polyols or polyesters with a polyisocyanate in a typical formulation for the manufacture of Polyurethanes implemented. The formulation may and often contain a catalyst it is advantageous to use a variety of catalysts, such as. B. a Amine catalyst and a metal salt of an organic acid. In addition, in a cell size regulating compound and suitable propellants in the formulation to be available.

Suitable catalysts are, for. B. Sodium Acetate; Amine catalysts such as tetramethylenediamine, tetramethylguanidine, tetramethyl-1,1,3,3-butanediamine, Triethylenediamine, triethylamine, dimethylethanolamine, tetramethylethylenediamine and N-.§thylpiperidine; also esters and salts of tin, such as tin (II) oleate and tin (II) octoate and dibutyl tin dilaurate.

Mixtures of two or more such catalysts can also be used use.

The catalysts are usually used in amounts of 0.01 to 5%, based on the total weight of the polyols or those containing hydroxyl groups initially used Connections, used.

The mixture can be used as surface-active agents or emulsifiers the starting materials z. B. Polypropylene glycols with a molecular weight between 2000 to 8000, liquid silicone-glycol copolymers with viscosities from 350 to 3500 Centistokes at 250 C and polysiloxane polyoxyalkylene block copolymers are added.

The formulation of the starting materials can be used as additional additives Compounds for reducing viscosity are added, e.g. B. Tris (2-chloroethyl) phosphate, Dimethylformamide, triethyl phosphate, tributyl phosphate, tricresyl phosphate, dioxane, Acetone and 1,1-dichloroethane.

The invention is explained in more detail in the following examples. First, a comparative experiment is described and then examples of the Invention given. In the examples and in the comparative experiment, all starting materials are used With the exception of the polyisocyanate mixed at room temperature, then the polyisocyanates admitted and after mixing thoroughly for 8 seconds, the mixture is poured into an open Molded so that the foam can develop freely.

The following formulations of the starting materials were used in the individual experiments used: Comparative experiment: 100 g of triethyl phosphate, 40 g of tris (2-chloroethyl) phosphate 338 g of an aromatic hydroxyl-containing polyol obtained by the reaction of phenol and formaldehyde in the presence of an acidic catalyst and an aromatic hydroxyl functionality of 3.2 and an OH equivalent weight of 106 has 8 g silicone oil (DC 193) (a silicone glycol copolymer in which the glycol derived from ethylene oxide) 170 g of trichloromonofluoromethane 2 g of dimethylethanolamine 0.4 cc of dibutyltin laurate, 462 g of polymethylene polyphenyl isocyanate with an NCO equivalent weight of 135 and an NCO functionality of 2.6.

Example 1 Same formulation as in the comparative experiment, but below Use of: 190 g trichloromonofluoromethane 160 g paraformaldehyde.

Example 2 Same formulation as in the comparative experiment, but below Use of 160 g of benzaldehyde and omission of the triethyl phosphate and tris (2-chloroethyl) phosphate.

Example 3 Same formulation as in the comparative experiment, but below Use of: 40 g triethyl phosphate 80 g symmetrical trioxane 150 g trichloromonofluoromethane.

Example 4 Same formulation as in the comparative experiment, but below Use of: 120 g symmetrical trioxane 150 g trichloromonofluoromethane.

Example 5 Same formulation as in the comparative experiment, but below Addition of 160 g of benzaldehyde.

Example 6 Same formulation as in the comparative experiment, but below Addition of 16 g paraformaldehyde.

The properties of the foam compositions produced are in compiled in the following table: TABLE 1 Comparative Example No.

experiment 1 2 3 4 5 6 density 0.14 0.14 0.15 0.12 0.18 0.16 0.13 kg / cm² Compressive Strength 2.8 1.2 1.7 1.8 0.7 1.1 2.4 kg / cm² Original 0.113 0.114 0.125 0.122 0.108 0.132 0.108 K-factor dimensional stability in 75-80 75-80 75-80 75-80 70 85-90 75-80 of heat ° C Abrasion resistance 1.7 15.7 5.2 2.7 4.9 14.3 2.0 wt% loss Therm. Resistance1 121 74 80 92 103 98 104 Temperature of the cold side in ° C Time for maximum temperature 38 60 60 60 60 60 60 min.

Footnote 1 to Table 1 The thermal resistance is determined according to the Test mentioned at the beginning. A foam sheet with the dimensions 5 x 30 x cm arranged between two horizontal 0.6s5 c .. thick steel plates. A flame of a Meker or Fischer burner is set so that through the controlled supply of natural gas to the burner a temperature of 9270 C, measured with a pyrometer, present when the flame hits the lower steel plate is. The temperature of the foam on the opposite or cold side is continuously over a period of one hour with the help of a thermocouple, the one between the top of the foam board and the bottom of the cold board is arranged, measured. In this test, a foam sample is found to be satisfactory rated if, in the course of 6Q minutes, the cold side of the foam board had a Temperature of 1210 C does not exceed. The device is designed so that the test is automatically interrupted when the temperature of 1210 C in shorter Time than is reached in 60 minutes. For those foam samples that have this Those who pass the test have the better thermal resistance a lower maximum temperature on the cold side for a period of 60 minutes is reached.

From the table it can be seen that in the comparative experiment after 38 minutes the limit temperature of 1210 C for the cold side was exceeded will. In contrast, the foams survive according to all examples of the invention this test and all samples, the temperatures are on the after 60 minutes cold side well below 1210 C.

Claims (7)

Patent claims: f Polyurethane foam compound, which is the reaction product of a reaction mixture which is an aromatic hydroxyl group-containing polyol and an organic one Contains polyisocyanate, characterized in that the reaction mixture also contains contains an aldehyde or a formaldehyde-releasing compound. 2. Foam composition according to claim 1, characterized in that the polyol used has the formula in which R is hydrogen or an alkyl radical having 1 to 3 carbon atoms, X is hydrogen, hydroxyl, chlorine, bromine or an alkyl radical having 1 to 12 carbon atoms, n is an integer from 1 to 2 and m has an average value of 0 , 1 to 4 has. 3. Foam composition according to claim 2, characterized in that X and R are hydrogen. 4. Foam composition according to claim 2, characterized in that polymethylene polyphenylisocyanate was used as the polyisocyanate. 5. Foam composition according to claim 4, characterized in that paraformaldehyde was used as the aldehyde. 6. Foam composition according to claim 4, characterized in that benzaldehyde was used as the aldehyde. 7. foam composition according to claim 4, characterized in that symmetrical trioxane was used as the aldehyde-releasing compound,