DE1168633B - Process for the production of polyurethane foams - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school KL: C 08 g

Number: File number: Registration date: Display day:

German class: 39 b - 22/04

H 39033 IVc / 39 b March 30, 1960 April 23, 1964

The invention relates to the manufacture of polyurethane foams; it relates in particular to the production of such foams using new catalysts of selected effectiveness to accelerate the reaction between the organic polyisocyanate and the organic polyhydroxyl compound and / or reaction of the polyisocyanate with water with the release of CO ₂ , which serves as a blowing agent during foaming.

The catalysts previously found to be effective in polyurethane foam production were from tert-amine type, mainly used in foam production on an industrial scale N-alkylmorpholines, triethylamine or more recently Triethylenediamine (1,4-diazabicyclo [2,2,2] octane) has been used. Aliphatic sec. Amines are from described by those skilled in the art as being less suitable for use as catalysts in polyurethane production (see "Technical Bulletin HR-26", p. 8, April 1958, published by "The Elastomer Chemicals Department, E.I. DuPont D Nemours & Co. (Inc.) "Wilmington, Delaware).

Surprisingly, it has now been found that imidazoles which are unsubstituted in the 1-position as Catalysts for the production of polyurethane foams can be used advantageously.

The inventive method for the production of polyurethane foams based on optionally resinous polyhydroxyl compounds and organic polyisocyanates in the presence of Amino compounds and optionally organometallic compounds is now characterized in that as Amino compound is a 2-methylimidazole, 2-ethylimidazole or 2,4-dimethylimidazole is used.

The behavior of these imidazoles is surprising since they are the only sec. Containing amino groups Are compounds that have so far been found to be suitable as catalysts in polyurethane foams. In contrast to other sec. Amines do not react with the isocyanates to form ureides and so are not incorporated into the polymer and removed from the system.

The name of the ring members of the imidazole ring was made as follows:

R Process for the production of polyurethane foams

Applicant:

Air Products and Chemicals, Inc., Philadelphia, Pa. (V. St. A.)

Representative:

Dr. W. Schalk, Dipl.-Ing. P. Wirth, Dipl.-Ing. G. E. M. Dannenberg and Dr. V. Schmied-Kowarzik, patent attorneys, Frankfurt / M., Große Eschenheimer Str.

Named as inventor:

Harold A. Green, Elkins Park, Pa. (V. St. A.)

Claimed priority:

V. St. v. America April 8, 1959 (804 884) - -

Polyurethane foam catalysts

Usual - although not equivalent - tert. Amines are:

^ -Diazabicyclo-octane

Ho

CH ₂

CH ₂
HC ₂ ^, CHo

N, N'-dialkylpiperazine and derivatives

N-alk-X

H2C CH ₂

N-ethylmorpholine

HN1

C-N

2 3

5 4

C - CR '
R "

H ₂ C, -CH ₂

"N-llk

^ NC ₂ H ₅ ^ CH ₂

H ₂ C ^.

409 560/468

Triethylamine

N- (CH ₂ H ₅ ),

in contrast, imidazoles are newly used, namely z. B /

2-methylimidazole

H-C-NH

H-C N

In general, alkylimidazoles are less active as a catalyst than tert. Amines. But while the Imidazoles are particularly active in catalyzing the isocyanate-water reaction, they show regarding the reaction of polyhydroxy compounds with polyisocyanates has a lower catalytic activity as tert. Amines. However, this lower activity of the imidazoles does not make them suitable as catalysts unsuitable because, on the contrary, it has been found that in the manufacture of elastic polyurethane foams economically satisfactory results using an alkylimidazole catalyst can be achieved and that even the foams produced match those made using e.g. B. of the more active Ν, Ν'-dialkylpiperazine have been produced as a catalyst, are far superior. To the Evidence of the surprising technical progress were comparative tests between a tert. Amine, namely a Ν, Ν'-dialkylpiperazine, and 2-methylimidazole carried out.

The results are compiled in the table below, from which it can be seen that N, N'-dimethylpiperazine as a catalyst for the production of polyurethane foams in spite of its larger size Effectiveness 2-methylimidazole is inferior. While using 2-methylimidazole produced foam that has desirable properties for flexible polyurethane foams using the piperazine catalyst obtained foams which collapsed, a had irregular structure or had large cells.

The poor results achieved with N, N'-dimethylpiperazine as the catalyst show that despite the greater effectiveness of this catalyst over 2-methylimidazole, the effectiveness alone is not enough to make a catalyst suitable for a particular purpose; this applies especially for use in the manufacture of polyurethane foams, in which many different and to some extent simultaneous reactions take place. In the manufacture of polyurethane foams The catalyst used must therefore not only be effective but also selective in that it can carry out the desired reactions catalyzed; moreover, its effectiveness must be such that the speeds are more definite Reactions are not increased too much. The piperazine catalyst catalyzes urethane formation and the release of gas (bubbling) to foam; in all likelihood it is the release of gas is not properly balanced with the polymerization reaction, so that large and unevenly distributed bubbles are obtained, or foaming and polymerization are so unbalanced that the foam collapses. In contrast, it has 2-methylimidazole for the production of a flexible polyurethane foam with uniform cell structure required selectivity and controlled effectiveness.

attempt

catalyst
Weight percent ¹ )

Polyhydroxyl compound
Parts by weight

Toluylene diisocyanate parts by weight *)

1.04 2-methylimidazole
0.36 N, N-dimethylpiperazine

0.54 N, N-dimethylpiperazine
0.72 N, N-dimethylpiperazine
0.72 N, N-dimethylpiperazine
1.08 N, N-dimethylpiperazine
1.44 N, N-Dimethylpiperazine
3,6 Ν, Ν-dimethylpiperazine

Polypropylene glycol (as in Example 1), Glyce-

polypropoxytriol (hydroxyl number 46)
Polyester made from dimeric oleic acid and glycol

(Hydroxyl number 65, acid number 1.2, viscosity

1800OcP at 25 ⁰ C)
Polyester made from dimeric oleic acid and glycol

(Hydroxyl number 65, acid number 1.2, viscosity

1800OcP at 25 ⁰ C)
Polyester made from dimeric oleic acid and glycol

(Hydroxyl number 65, acid number 1.2, viscosity

1800OcP at 25 ⁰ C)
Unbranched polyester made from dimeric acid and

Ethylene glycol (hydroxyl number 79.3, acid number

1.4, viscosity 1020OcP at 25 ⁰ C)
Unbranched polyester made from dimeric acid and

Ethylene glycol (hydroxyl number 79.3, acid number

1.4, viscosity 10200 cP at 25 ° C)
Unbranched polyester made from dimeric acid and

Ethylene glycol (hydroxyl number 79.3, acid number

1.4, viscosity 1020OcP at 25 ⁰ C)
Unbranched polyester made from dimeric acid and

Ethylene glycol (hydroxyl number 79.3, acid number

1.4, viscosity 10200 cP at 25 ⁰ C)

115
108

108
108

108

108

108

¹ J The percentages of the catalyst relate to the total weight of the reaction mixture including the catalyst. -) As in the examples, a mixture of 80% 2,4- and 20 ° / ₀ 2,6-tolylene diisocyanate was used.

water
Parts by weight ¹ ) 5 Mix
Seconds Rise up
Seconds 6th Ver
search 8.7 Other components
Parts by weight 10 135 Results obtained
(pbotqgraphic images) 1 8.7 3 silicone oil ² ) 12th 173 Good foam with more uniform
Cell structure 2 8.7
8.7 - 12th
12th 150
120 Collapsed 3
4th 8.7 I. 15th 120 I CO ₂ development and large cell structure 5 8.7
8.7 0.4 gelatin 15th
15th 100
80 Slow rise, large cells 6th
7th «, 7 0.4 gelatin
0.4 gelatin 15th - r Unequal structure 8th 0.4 gelatin Together within 45 seconds
please

!) The water used in experiments 5 to 7 contained a small amount of gelatin as a possible surface modifier. ² ) The silicone compound used had been prepared by block polymerization of a polypropylene glycol with dimethyl silicone (as in Example 1).

In addition, when using alkylimidazoles together with a more active catalyst, e.g. B. tert. Amines, better ways to Regulation of the properties of the finished foam given, as this increases the speed of the Water diisocyanate (blowing) reaction independent of the polyhydroxyl diisocyanate (addition) reaction can be regulated.

In the case of formulations in which the alkylimidazole is used as a co-catalyst, the can be used in conjunction thus used more active catalyst Tnäthylamin, triethylenediamine or one of the fast acting polyurethane catalysts of the organometallic type, such as. B. dibutyltin dilaurate. on in this way a reduction in the cost of the catalyst is achieved by removing at least part of the more expensive Catalyst, such as. B. triethylenediamine, is replaced by the cheaper alkylimidazole.

The following examples describe the invention.

The foaming occurred immediately; the maximal Foam height was noted after about 2.5 minutes. The flexible foam obtained showed a good one Cell structure, good stability and one only when aging insignificant shrinkage.

In the above approach, a polyether type polyurethane foam was prepared by the one-shot process produced, a way of working that was previously only used with very few of those commonly used in polyurethane formulations suitable catalysts was possible.

Commonly used in polyurethane foam formulations Polyethers used have molecular weights of 2000 or more and are from such that they are recurring

- [O - C - C - O - C - C - O] groups

example 1

The components used in the formulations are the following:

Parts by weight

(1) Polypropylene glycol (molecular weight about 2025) 200

(2) Glycerol polypropoxytriol (molecular weight about 3000, hydroxyl number 56) .. 100

(3) Tolylene diisocyanate (mixture of 80% 2,4- and 20% 2,6-tolylene diisocyanate) 115

(4) Organo-silicone stabilizer (produced by block polymerization of a polypropylene glycol with dimethyl silicone) 1.5

(5) 2-methylimidazole 4.5

(6) water 8.7

The 2-methylimidazole was first dissolved in the water and the solution with the remaining components with the exception of the diisocyanate mixed by stirring for seconds at high speed. Then the diisocyanate was added into the dispersed mixture with stirring for an additional 5 seconds introduced and poured the mixture into a mold.

Y Y

include, where Y is hydrogen atoms or a methyl group.

45

Example 2

The components used in the formulation were:

Weighted parts

(1) polypropylene glycol (molecular weight
around 2025) 200

(2) Glycerol polypropoxytriol (molecular weight about 3000, hydroxyl number 56) .. 100

(3) tolylene diisocyanate (mixture of
80% 2,4- and 20% 2,6-tolylene diisocyanate) 115

(4) organosilicone stabilizer (manufactured
by block polymerization of a polypropylene glycol with dimethyl silicone) .. 2.2

(5) triethylenediamine catalyst 0.6

(6) 2-methylimidazole 1.5

(7) Water 8.7

The two catalysts were dissolved in water and mixed with the other ingredients except for the Mixed diisocyanates; the latter was added after initial vigorous stirring and a further 5 seconds

55

60

7 8

announce long at 875 rev / min. mixed. The A typical formulation of a pliable poly blend was poured into molds, an ester type foamed plastic is the following: Men took place almost immediately, with the maximum foam parts by weight occurring in 60 to 70 seconds. A polyester resin (hydroxyl number 60 to 65,

Foam with a well-developed cell structure and 5 molecular weight about 3000) 100

good stability achieved. Tolylene diisocyanate 28

By using the alkylimidazole as a co-lecithin 5

The catalyst in the above formulation was the 2-methylimidazole 0.7

Amount of triethylenediamine to about half the water 1.5

Amount reduced, which would otherwise be ok with this formulation

would have been needed. A similar reduction A most important use of the polyurethane

the amount of tert. Amine catalyst by replacing catalysts is in continuous production

with alkylimidazole is in typical formulations of uniform polyurethane foams on the

possible with sorbitol polyethers. Conveyor line of the usual foaming devices.

In the above examples, Preparation 15 is used in this procedure, the reactants described by "one-step" polyether foams. and catalysts continuous in two streams Of course, the use of the alkylimide is divided, mixed and mixed at high speed azoles as a catalyst or co-catalyst are not sprayed through a nozzle onto a conveyor belt, limited to this, but the alkylimidazole can The effectiveness of the alkylimidazole catalyst also the tert. Amine catalyst that has been commonly used at 20 has been used in a number of approaches in machine poryether foam formulations using mixed, flexible "one-step" polyether polymerization of the prepolymer process, urethane foams are shown, of which the following replace in whole or in part. The alkyl imidazole can be typical. The polyol was released at a rate for the production of polyurethane foams speed of 4300 g / min, fed into a mixing head and be used based on the use of poly-25 separate streams of tolylene diisocyanate and the Ester intermediates are based on poly- mixture of catalyst and stabilizer merized fatty acids (dimeric acids), from reac- in water, fed into the same mixing head and tion products of a polyhydric alcohol or continuously sprayed onto a conveyor belt. That polyvalent ether alcohol with a polycarbonate foaming and hardening took place on the runic acid, such as B. diethylene glycol adipate derived. 30 the conveyor belt.

Polypropylene glycol (molecular weight about 2025)

Glycerol polypropoxytriol (molecular weight about 3000, hydroxyl number 56)

Tolylene diisocyanate (mixture of 80% 2,4- and 20% 2,6-tolylene diisocyanate)

Organosilicone stabilizer (produced by block polymerisation of a polypropylene glycol with dimethyl silicone) ...

2-methylimidazole

Triethylenediamine

Appearance; open cells; %

Physical Properties; Cured for 3 hours at 121 ^° C. and normal humidity

Density; g / ccm

Tensile strenght; kg / cm ²

Tear strength: g / cm

Resilience; kg / cm ² with 25% deflection .... Permanent deformation with 50% deflection

% original height

° / o deflection height

71.5 71.5 71.5 28.5 28.5 28.5 36.8 36.8 36.8 0.7
0.5
0.2
100 0.7
0.7
100 0.5
0.7
100 0.0322
1.35
628
0.0203 0.0418
0.95
564
0.0196 0.0327
0.62
473
0.0196 6.7
13.2 10.0
19.4 12.4
24.5

71.5
28.5
36.8

0.7
0.7
0.2
100

0.0420 0.93 410
0.0245

7.8
14.7

Although 2-methylimidazole was used as the catalyst in the above examples, it can be used instead also 2-ethylimidazole or 2,4-dimethylimidazole for Achievement of good polyurethane formulations, but not necessarily all of the properties of those with 2-methylimidazole obtained products are equivalent, can be used.

In common formulations for linear polyether polyurethane foams low density can.

the alkylimidazole catalyst usually in amounts of about 0.7 to 2 percent by weight based on the Polyethers, while polyester foams have about the same proportions of the alkyl imidazole catalyst or in some cases greater amounts up to about 5 to 6 weight percent of the polyester are indicated, depending on the type of used Esters depends. If the alkylimidazole in conjunction with tert. Amine catalysts or active

When organometallic catalysts are used, the total amount of catalyst is usually less than 1 percent by weight of the polyhydroxyl compound, e.g. B. about 0.5 to 0.9 percent by weight, the imidazole catalyst being present in the mixture in the same or in a greater amount is known as the catalyst.

Although in the formulations described above the polymer was driven by the CO ₈ released in the water-isocyanate reaction, the use of alkylimidazole as a catalyst or co-catalyst is of course not restricted to this. The alkylimidazole can be used as the sole or partial catalyst in otherwise known formulations using an additional, inert propellant, such as. B. a volatile haloalkane can be used.

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Claims (2)

Patent claims: 1. Process for the production of polyurethane foams on the basis of optionally resinous polyhydroxyl compounds and organic polyisocyanates in the presence of Amino compounds and optionally organometallic compounds, characterized in that that the amino compound is a 2-methylimidazole, 2-ethylimidazole or 2,4-dimethylimidazole is used. 2. The method according to claim 1, characterized in that a further catalyst, preferably a tertiary amine such as 1,4-diazabicyclooctane is also used will. Considered publications:
German Patent Nos. 960 855, 962 113;
Belgian patent specification No. 545 745. 409 560/468 4.64 ι Bimdesdruckerei Berlin