DE1111380B - Process for the production of foams containing urethane groups - Google Patents

Description

INTERNAT. KL. C 08 g

GERMAN

PATENT OFFICE

F29398IVb / 39b

REGISTRATION DATE: SEPTEMBER 16, 1959

NOTICE
THE REGISTRATION
ANDOUTPUTE
EDITORIAL: JULY 20, 1961

It is known that foams containing urethane groups can be produced by using polyhydroxyl compounds mixed with excess polyisocyanate and water. The water reacts with the polyisocyanate with the formation of urea groups and carbon dioxide, which acts as a propellant for the acts through urethane groups forming a high molecular structure. In the manufacture of urethane groups Having foams by blowing with water are obtained predominantly open-pored Foams.

It is also already known that the reaction of the polyhydroxyl compound with the polyisocyanate, d. H. So the formation of the high molecular structure, in the presence of a decomposing one Propellant, such as ammonium bicarbonate, to make. Even on this from low molecular weight Materials outgoing paths are essentially open-pored foams, which are relatively low strength, high damping and high permanent deformation and an unfavorable Have suspension characteristics.

It has also become known to make foams using an alkali carbonate with water and an organic crosslinking agent. You also get essentially open-cell foams. This statement also applies to the further known method, according to which water is used as a foaming agent together with a nitrogen-containing blowing agent, however, crosslinked without an organic crosslinking agent.

According to the invention, foams containing urethane groups and having closed pores and produce excellent physical properties with great reliability and reproducible as required, if you are in the reaction of a polyhydroxyl compound with a molecular weight over 800 with an excess of polyisocyanate and an organic crosslinking agent with several reactive hydrogen atoms and a molecular weight less than 500 in such an amount that not all existing NCO groups are consumed, a nitrogen-releasing propellant adds as long as the reaction mass is still liquid, the reaction temperature but only then brings to the level required to split off the nitrogen when the crosslinking agent reacts with the reaction product of the polyhydroxyl compound and the polyisocyanate Has.

Examples of blowing agents which split off nitrogen are azo compounds, such as azoisobutyric acid process for the production of
Foams containing urethane groups

Applicant:

Paint factories Bayer Aktiengesellschaft,
Leverkusen-Bayerwerk

Dipl.-Ing. Ulrich Knipp, Leverkusen,

and Dr. Konrad Ellegast, Leichlingen,

have been named as inventors

dinitrile, azohexahydrobenzodinitrile, or nitroso compounds, such as Ν, Ν-dinitrosoterephthalic acid amide, or thiatriazoles, such as tert-butylaminothiatriazole, mentioned.

The polyhydroxyl compounds used are linear or branched polyesters, including those made up of several Acid or alcohol components, polyester amides, polyethers or polythioethers are used. Your molecular weight should generally be between 800 and 3000. Especially when using mixed Polyesters give foams with favorable low and high temperature behavior.

Preferred polyisocyanate components are the tolylene diisocyanates, 1,5-naphthylene diisocyanate and in particular, because of its low melting point, 4,4'-diphenylmethane diisocyanate.

Glycols, amino alcohols, diamines and hydrazines may be mentioned as crosslinking agents.

The polyhydroxyl compound is reacted with an excess of polyisocyanate over the amount calculated on the hydroxyl groups at room temperature or at an elevated temperature. It is possible to already mix in the propellant these components, wherein the reaction temperature must be below the decomposition temperature of the blowing agent, which is generally between 70 and 16O ⁰ C, maintained.

The amount of propellant depends not only on the type of propellant, but also on the desired density of the foam and is generally between 2 and 20%. and especially between 7 and 10%, based on the total amount of the reaction mixture.

You can also already in the reaction product of polyhydroxyl compound and the blowing agent Mix in excess polyisocyanate.

109 648/429

The reaction of the reaction product mentioned with the crosslinking agent also takes place in the liquid phase, a deficiency of crosslinking agent being used so that free NOC groups still remain. The blowing agent can be added together with the crosslinking agent, even dispersed in the crosslinking agent, or even after the reaction of the crosslinking agent, the reaction of the crosslinking agent again having to take place at temperatures such that
no decomposition of the propellant takes place.

The homogeneous reaction mixture can be poured into molds in which it solidifies. The crowd is Can be stored for several days and can be stored either freely or in a form at elevated temperatures be expanded and hardened above the decomposition temperature of the propellant.

The new process offers a high level of processing security. Mixing the propellant into the liquid phase is safe and there is no risk of explosion. There are also advantages from the economic side. The propellant can be mixed in without a roller, so that the expenditure on machinery and energy is reduced. Because the blanks can be poured easily and without loss from the liquid phase, there is a saving in material, since there is no expulsion and waste, as always occurs when parts are inserted from a rolled skin. In addition, the rather complex cutting and deformation of the compacts is saved by the casting process. Last but not least, the closed-cell polyurethane foams obtainable in this way are notable for their extraordinarily high strength, elasticity, very little permanent deformation, low damping and, in particular, their ideal progressive suspension characteristic, which they use as a buffer and spring element in machines for the technical sector - and make vehicle construction suitable. The significance of the new foam bodies can best be seen from the following comparative overview (Brit. Plastics, Vol. XXX [1957], p. 328), in which c represents the quotient of tensile strength in kg / cm ² and density in g / cm ³ (Table 1): ■

45 whereby it slowly freezes. The plastic material becomes 30 to after 4 hours at 150 ° C at the earliest Minutes, a foam with closed pores and the in Table 2 specified physical data arises.

Example 2

To 500 of a linear polyester of adipic acid and ethylene glycol g (OH number 56, acid number <1) for a further 10 is added 90 g of 1,5-naphthylene diisocyanate at 130 ^c C to, cools the reaction mixture after about 10 minutes at 50 to 6O ⁰ C from, are in common with parts of 2,3-butanediol, 37.5 g of azobisisobutyronitrile with thorough stirring to the melt poured into molds between 20 and 40 ° C, and drives the mass after a minimum of one hour at 30 to 50 minutes 150 ⁰ C in closed Compression molds on. The foam has the physical properties given in Table 2:

Table 2

1 2 Tensile strength in kg / cm ²
according to DIN 53504 26th 60 Elongation at break in% after
DIN 53504 310 400 Permanent elongation in ° / o
according to DIN 53504 4th 4.5 Tear strength
in kg / cm
DIN 53507 3 9.8 Volume weight in kg / m ³ .. 147 360 Elasticity according to DIN 53512 77 to 83 77 to 83 Roelig damping
in ° / o at 20 ° C <2 <2

Table 1 kg / cm ² material g / cm ³ Polyurethane foam, open-pore,
foamed with water
Latex foam. . 46.60
11.70
7.25
177.00 Polyvinyl chloride foam
Polyurethane foam, embossed
according to example 1

example 1

55

60

50 g of azoisobutyric acid dinitrile are added to 500 g of an anhydrous linear polyester made from adipic acid and ethylene glycol (OH number 56, acid number <1) and the mixture is stirred thoroughly at 40 to 50 ° C. with a high-speed mixer. Then 150 g of 4,4'-diphenylmethane diisocyanate are added, allowed to react for 60 minutes, then 16.2 g of 1,4-butanediol are added, mixed thoroughly and the mass is poured into molds ^{at 20 ° C.}

© 109 648/429 7.61

Claims (1)

PATENT CLAIM:
Process for the production of foams containing urethane groups based on polyhydroxy compounds and polyisocyanates using nitrogen-containing blowing agents in the absence of water, characterized in that in the known reaction of a polyhydroxyl compound having a molecular weight of more than 800 with an excess of a polyisocyanate and then with an organic crosslinking agent with several reactive hydrogen atoms and a molecular weight below 500 in such an amount that not all of the NCO groups present are consumed, a nitrogen-releasing propellant adds as long as the reaction mass is still liquid, but the reaction temperature only then increases to that for the splitting off of the Nitrogen brings the required height when the crosslinking agent has reacted with the reaction product of polyhydroxyl compound and polyisocyanate. Considered publications:
British Patent No. 794403;
French Patent No. 1108,425;
U.S. Patent No. 2762739.