DE1143325B - Process for the one-step production of polyether urethane foams - Google Patents

Description

It is already known that polyurethane foams are produced by a two-stage process can, whereby first a polyether with hydroxyl groups with an organic polyisocyanate or Polyisothiocyanate reacts to form an incompletely converted polymer syrup, the terminal isocyanate or has isothiocyanate groups, and secondly after the prepolymer has ripened Water and further polyisocyanate or polyisothiocyanate is reacted to form a foam which is then hardened.

In "Chemical and Engineering News", December 1, 1958, pp. 48 and 49, processes for the one-step production of polyether foams are proposed, for example by keeping the foam material at 100 to 130 ^° C. for 20 to 25 minutes.

The invention comprises a one-step process for making a polyether urethane foam which is a polyether with terminal hydroxyl groups, an organic compound with at least two isocyanate groups in the molecule and water together in the presence of a thickener, except for a polyalkylene glycol with a molecular weight below 10,000, are reacted, wherein the reaction in the presence of not more than 15 percent by weight, based on polyether and polyisocyanate, lying amount of a high molecular weight film-forming thickener under reaching the viscosity of the reaction mass is close to 15,000 to 30,000 cP.

The terms "polyether" and "isocyanate" used here include the corresponding sulfur analogues, ie polythioethers and isothiocyanates. A high molecular weight film-forming substance is understood to be one which is capable of forming an adhering surface film within 5 to 10 minutes at a temperature of 80 to 100 ^° C.

In the production of foam, a catalyst for the reaction and a surfactant used. When the reagents are mixed, a rapid reaction ensues releasing carbon dioxide which is trapped in the reaction mixture and foaming caused. The generated liquid foam quickly turns into a solid polyurethane foam.

A variety of film-forming agents can be used in the present invention provided they are sufficiently compatible with at least one of the reactants to thicken the reaction mixture. Those that are soluble in one or more of the reagents are particularly suitable. You can go straight to the reaction process for one-step production
of polyurethane foams

Applicant:
Dunlop Rubber Company Limited, London

Representative: Dr. F. Zumstein,

Dipl.-Chem. Dr. rer. nat. E. Assmann

and Dipl.-Chem. Dr. R. Koenigsberger,

Patent Attorneys, Munich 2, Bräuhausstr. 4th

Claimed priority:
Great Britain January 16, 1959 (No. 1608)

Peter Merriman, Birmingham, Warwickshire

(Great Britain),
has been named as the inventor

mixture can be added or incorporated as a premix with one or more other reagents will.

The molecular weight of the film-forming material is not critical. Those connections which having a molecular weight above 5000 have been found to be particularly suitable. The use of resins low molecular weight, i.e. H. below 2000, generally results in an unsatisfactory one Foam, even if the resin is viscous.

Substances suitable as film formers are, for. B. CeDulose ethers, such as benzyl cellulose, ethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropylmethyl cellulose, polymers of compounds which _{contain the grouping CH 2} = C <, z. B. low molecular weight polyethylenes and chlorosulfonated derivatives thereof, polystyrenes, polyvinyl chloride, partially hydrolyzed polyvinyl acetate and copolymers of vinyl chloride or compounds that can react with them, such as copolymers of vinyl chloride with vinyl acetate and vinylidene chloride. Polyalkylene glycol ethers containing OH groups and having a high molecular weight, ie over 10,000, e.g. B. PolyäthylenglykoJe and aryl-substituted, OH group-containing polymers, such as polystyrenes containing two OH groups, are also suitable, although they

30f E0S / 28C

The at least two isocyanate radicals in the molecule are quite reactive with the organic compound Has.

The amount of the high molecular weight film-forming thickeners should not be greater than 15 percent by weight, calculated on the mix. The lower limit, however, is variable and depends on the film-forming type Effectiveness of the compound used as well as its compatibility and the thickening effect. However, the amount of thickener used will generally vary from 0.1 to 10 percent by weight of the reaction mixture.

The increase in viscosity of the reaction mixture at the addition of a certain amount by weight of film-forming thickening agent is generally greater when the molecular weight of the latter is greater than if niedermo ¹ ekulare thickeners are used. Accordingly, a smaller amount by weight of high molecular weight thickener is required than that of low molecular weight in order to achieve the desired viscosity. So if the compatibility of a compound is poor, it can be added in a small amount in a high molecular form, e.g. B. 0.02% hydroxypropyl methyl cellulose ether can be used.

A sufficient amount of film-forming thickener should be added to achieve a To obtain "structural viscosity" of the reaction mixture, which is similar to that in the highly viscous Prepolymers is achieved by the known, above-mentioned two-stage process. The term "structural viscosity" refers to the viscosity of the reaction mixture rather than its resistance to it Understand shear stress. In general, the Newton viscosity increases to about ten fold about 15000 to 3000 ocP when adding the film-forming thickener.

An excessive increase in viscosity should be avoided, especially when dealing with bulky objects should be produced, since the heat generated in the exothermic reaction in such a case Scorching or blistering.

Not only is a polyurethane foam produced with an improved pore structure, but the Addition of the film-forming thickener facilitated the process, with very different stirring speeds with a correspondingly increased throughput can be applied to the reaction mixture and the stirring speed from one approach to the next does not have to be changed.

The addition of finely divided filler material to the reaction mixture was also found to be beneficial, e.g. B. the addition of silica, carbon black, cadmium sulfide selenide and bentonite, which cause the formation of a fine-pored Promote structure. Amounts up to 10 percent by weight can be used and allow reducing the amount of film forming agent.

Polyethers are preferred in which all oxygen or sulfur atoms in the molecule with the Carbon atoms are linked by single bonds. Two, three or two are particularly suitable polyalkylene glycol ethers containing four OH groups.

The preferred polyalkylene glycol ethers have lower alkylene groups containing 2, 3 or 4 carbon atoms and have a molecular weight of 500 to 10,000.

The organic compounds with at least two isocyanate radicals in the molecule are preferably organic Diisocyanates, such as. B. aromatic or alicyclic diisocyanates.

In the reaction between the polyether or polythioether and the compound containing isocyanate groups a considerable molar excess, generally 20 to 250%, preferably 50 to 100%, of compounds containing isocyanate radicals, compared to the equimolar proportion used, the is required to react the isocyanate groups with the hydroxyl groups of the polymer. This Excess of isocyanate-containing compound is added to, preferably approximately equimolar

Quantities to react with water. The excess of isocyanate-containing compounds and the water cause foaming of the reaction product, and it is common to use an excessive amount of water admit. The foam is self-curing at the reaction temperature, albeit through curing Application of external heat can be accelerated.

Surfactants that stabilize the

Foam are suitable are, for. B. silicone oils, such as water-soluble copolymers of a polydimethylsiloxane and a lower alkylene oxide.

Suitable catalysts for the reaction are the usual amine catalysts used in the one-step process for producing polyurethane foam, e.g. B. triethylenediamine, N-ethylmorpholine and dimethylbenzylamine. Triethylenediamine is often used together with an organotin compound and / or another tertiary or quaternary amine.
The process according to the invention is illustrated by the following examples. All parts given are parts by weight.

example 1

100 parts of polypropylene glycol with three OH groups in the molecule (molecular weight of about 3000), which had a hydroxyl value of 47, were treated for 6 seconds with a previously prepared mixture of 3 parts of water, 0.7 parts of triethylenediamine and 0.7 parts of a water-soluble, mixed oily copolymer of an alkylene oxide and polydimethylsiloxane. 2 parts of a partially hydrolyzed PoIyvinylacetats were then dissolved at 8O ⁰ C in 38 parts of toluene diisocyanate containing 80% 2,4-isomer and 20% 2,6-isomer. The solution was cooled to room temperature, stirred into the reaction mixture for 6 seconds, and then immediately poured into a paper mold. A rapid reaction followed, producing a liquid foam that did not sink even in the surface layer. A few minutes later, the cured product obtained had a good pore structure which was practically free from voids. Good results have been obtained when stirring speeds of 500 to 3000 revolutions per minute were used.

Comparative tests were carried out in the same way as just described, but "in the absence of any." of the film-forming thickener. When a stirring speed of 800 revolutions per minute was applied, the reaction mixture foamed rapidly. She was poured into a paper mold the top 1.3 cm of the foam gave slightly. The mass hardened after a few minutes a practically open, non-shrinking one

5 6

elastic foam. If a stirring speed should be observed when carrying out further experiments of 2000 revolutions per minute applied using this rule, hardened products were made In addition, the liquid foam of good pore structure significantly collapsed when stirred. The cured product exhibited significant speeds in the range of 500 to 3000 µm. 5 rotations per minute were applied.

Example 2 ^ ' ^e tensile strength of the final product was also

compared to the comparative tests of

100 parts of polypropylene glycol with three OH groups Example 1 obtained hardened foams

(Molecular weight of about 3000) significantly improved with a hy-

The droxyl value of 47 was 6 seconds with an io Example 5
previously prepared mixture of 3 parts of water,

0.7 parts of triethylenediamine and 0.7 parts of the silicone comparison, 100 parts of a polyglycol oil according to Example 1 were stirred. 1 part partially hydrolysed the acid airgel produced by successive addition of propylene polyvinyl acetate and 5 parts finely divided silica and ethylene oxides to ethylenediamine were made in 38 parts of a mixture 15, 6 seconds with 38 parts toluene diisof of 80% 2,4- and 20 ° / ₀ 2,6-toluene diisocyanate with cyanate, which was used in Example 1, stirred. 80 ^c C dispersed. The solution was cooled to room temperature, a previously prepared mixture of 3 parts of water, stirred for 6 seconds into the reaction mixture of 0.6 parts of the silicone oil according to Example 1 and 3 parts and then immediately in an N-ethylmorpholine was then in poured the polyether-poly paper mold. A rapid reaction followed, the isocyanate mixture was stirred for 6 seconds. The mixture that resulted in the production of a liquid foam was immediately poured into a mold where it had, which even in the surface layer did not slowly foam afterwards and gave rise to an elastic foam. The hardened material of a fairly homogeneous structure obtained a few minutes later hardened. Although product had a good pore structure that practically the liquid foam was quite stable and devoid of large voids. Good results have been achieved with 25 blowholes at stirring speeds of 800 to 2000 using a stirrer speed in the revolutions per minute, the pore size varied considerably from 500 to 3000 revolutions per minute from one batch to another,
obtain. Using the above procedure in Example 3, adding 0.03 part of hydroxypropyl-methyl-cellu-

30 loose ether previously dissolved in 3 parts of water

A cured foam was, as in Example 1, and at the specified stirring speed

described, produced, with the same reactions, however, was the fine structure of the cured

tion substances were used in the same proportions, foam was considerably improved, with the pores now

however, benzyl cellulose was considerably more uniform in place of being partially in the whole form, hydrolyzed polyvinyl acetate is used. 35

4 parts of benzyl cellulose with a viscosity of Example 6
10 cSt were used in 38 parts of toluene diisocyanate

40 ⁰ C dissolved and the solution to room temperature Three mixtures A, B and C were made from the following

cooled down. When adding the solution to the other ingredients prepared with the in the two

Reaction substances a rapid reaction took place, 4 ° play 1, 4 and 5 used were identical:
which is used for the production of a liquid foam

Had a consequence that showed no tendency in the upper parts by weight

to yield surface layer. After a few minutes A. Polypropylene glycol 950

a cured product was obtained, which has a good OH group-containing polystyrene ... 50

Had pore structure that was practically free from voids 45 B. toluene diisocyanate 380

was. When carrying out further experiments under hydrolyzed polyvinyl acetate 10

Using this rule turned out to be condition c. Water 30

of the cured foam as independent of the cellulose ether according to Example 5 0.3

Stirring speed in the range from 500 to 3000 silicone oil according to Example 1 6.5

Revolutions per minute. 50 triethylenediamine 7

Example 4 A was stirred with C for about 5 to 15 seconds,

and then B became instantly in about another 4 bis

A cured foam was stirred in for 7 seconds. The stirring speed was established for example 1 using the same reacting 55 see the limits 500 and 3000 revolutions per substance in the same proportion, but the minute was not essential. A stable, partially hydrolyzed polyvinyl acetate and shaped, liquid foam was obtained which could be poured into 10 parts of polypropylene glycol through 10 parts of a two-large mold from which polystyrene containing OH groups was obtained from the Vis-good moldings. The obtained, 1083OcSt viscosity at 38 ⁰ C is replaced. The two poly 60 cured foam product had an excellent kidneys were comparable at a temperature of 4O ⁰ C pore structure,
mixes. They were allowed to cool to room temperature. Example 7

When the reagents were mixed, a

Liquid foam obtained, with the slight upper limit. A procedure similar to Example 5 was used

surface sinking occurred and no internal collapse was applied, with the exception that it had previously broken up of the cells could be observed. 0.03 part of hydroxypropyl methyl cellulose of dissolved within A few minutes, a cured product was etherified by 0.03 parts of polyethylene glycol mixtures, the obtained with a uniformly good pore structure. Molecular weights in the range of several hundred thousand

to 5000000, dissolved in the 3 parts of water, were replaced.

Similar advantages over the "comparison" were obtained.

Claims (4)

PATENT CLAIMS: 1. A process for the one-step production of polyether urethane foams from a polyether with terminal hydroxyl groups, with the exception of polyalkylene glycols with a molecular weight below 10,000, an organic polyisocyanate and water, characterized in that the reaction takes place in the presence of not more than 15 percent by weight, based on polyether and polyisocyanate , Lying amount of a high molecular weight film-forming thickener takes place with reaching a viscosity of the reaction mass close to 15,000 to 30,000 cP. 2. The method according to claim 1, characterized in that that as a film-forming thickener a cellulose ether, a polymer of compounds that contain a CH = C C group, with a molecular weight above 2000 or a polyalkylene glycol ether with a molecular weight is not used below 10000. 3. The method according to claim 1 or 2, characterized in that a filler particles in one 10 percent by weight reaction mass containing no excess amount is foamed. 4. The method according to claim 1 to 3, characterized in that the film-forming thickener with those constituents of the reaction mass with which it was before the reaction occurs is compatible, is mixed beforehand. Considered publications:
German Auslegeschrift No. 1 022 002;
Belgian Patent No. 568 180;
Doriot, "Polyurethanes". Boston / Mass., 1956.22, para. 3;
Chem. Eng. News, December 1, 1958, pp. 19, 48, 49 309 533,288 1. ■> ';