DE4316389A1 - Process for the preparation of isocyanate prepolymers by dissolving polyurethane in isocyanates - Google Patents

Abstract

The invention relates to a process for the preparation of isocyanate prepolymers in which polyurethane is dissolved in isocyanate at 120 to 180 DEG C in the presence of a stabilising substance.

Description

The present invention relates to the reuse of polyure thanene for the production of isocyanate prepolymers. For reuse There are several approaches to using polyurethane; some of these include physical, partly chemical preparation processes. By doing Review article entitled "Chemical degradation of polyurethane" by Vincent Gajewski, published in Rubber World, Sept. 1990, page 15 to 18, are as follows for chemical degradation of polyurethane Called reactions:

• - hydrolysis
• - thermolysis
• - oxidation
• - photolysis
• - pyrolysis
• - Solvolysis
• - microbial degradation.

If the processes are evaluated especially with regard to processability of the fission products are as follows for recycling efforts Reactions of particular importance.

• - The hydrolysis (E. Grigat, Kunststoffe, 68, (1978), p. 12) leads to Polyol amine mixtures and CO₂ as a by-product. The mining pro products can be reused very easily.
• - In alcoholysis (G. Bauer in K.J. Thome-Kozminsky (ed.): Recycling international, vol 1, EF-Press, Berlin 1989, p. 415 and F. Simioni, S. Bisello, Cell. Polym. 2 (1983), p. 281) becomes one Implementation, which uses short-chain diols to polyhydroxy alcohols and low molecular weight urethane structure ren leads.

Since recipes developed in both cases (alcoholysis and hydrolysis) can be made by adding fresh polyol and fresh isocyanate lead to new polyurethane foam or similar products other processing methods such as pyrolysis to crack products less interesting.

Another recycling option includes finely powdered polyure than foam in the production of polyurethane in the polyol component add (e.g., as described in U.S. Patent 4,692,470). Here as Basic conditions for the processability a certain grain size of the Polyurethane ground material and a homogeneous distribution of the same in the polyol with at the same time the highest possible content of regrind and low viscosity be guaranteed.  

Hydrolysis, alcoholysis and the incorporation of ground foam into the Polyol components have in common the need to provide them one specifically tailored to their downstream products as polyurethane raw materials tailored recipe.

The object of the present invention is to provide a method for To make available that such precise recipe coordination unnecessary makes and also adherence to certain particle sizes during grinding process not required as a precondition.

Surprisingly, it has now been found that this process conditions can be avoided by using crushed foam, if necessary, coarse pieces or flakes in the isocyanate compo be incorporated. In this way, isocyanate prepolymers can be obtained be used directly as a polyurethane raw material in Allow foam or in the manufacture of non-cellular polyurethanes.

The present invention thus relates to a method for Manufacture of polyurethane prepolymers by dissolving poly urethanes (a), in isocyanates (b), in the presence of stabilizing agents substances (c) and optionally other auxiliaries and additives (d).

Compounds of the following are particularly suitable as isocyanates (b) Formula in question:

Q (NCO) _n ,

in the
n = 2-4, preferably 2, and
Q is an aliphatic hydrocarbon radical with 2-18, preferably 6-10, carbon atoms,
a cycloaliphatic hydrocarbon radical with 4-15, preferably 5-10 C atoms,
an aromatic hydrocarbon residue with 6-15, or
is an araliphatic hydrocarbon radical having 8-15, preferably 8-13, carbon atoms.

Particularly preferred polyisocyanates are hexamethylene diisocyanate, 1.12- Dodecane diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1,4- diisocyanate and any mixtures of these isomers, 1-isocyanato-3,3,5- trimethyl-5-isocyanatomethylcyclohexane, hexahydro-1,3- and / or -1,4- phenylene diisocyanate, perhydro-2,4'- and / or -4,4'-diphenylmethane diiso cyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate as well as any mixtures of these isomers, diphenylmethane-2,4'- and / or -4,4'-diisocyanate, naphthylene-1,5-diisocyanate, triphenylmethane-4,4 ', 4' '- tri isocyanate or polyphenyl-polymethylene polyisocyanates, as described by Aniline-formaldehyde condensation and subsequent phosgenation will hold.

Suitable higher molecular weight polyisocyanates are modification products such simple polyisocyanates, with z. B. isocyanurate, carbodiimide, Allophanate, biuret or uretdione structural units, as per themselves known methods of the prior art from the examples mentioned simple polyisocyanates of the above general Formula can be made. Among the higher molecular weight, modified polyisocyanates are in particular those from  Polyurethane-known prepolymers with terminal isocyanate groups of the molecular weight range 400 to 10,000, preferably 600 up to 8000 and in particular 800 to 5000 of interest. This connection gene are in a conventional manner by implementing over shot amounts of simple polyisocyanates of the exemplary ge named type with organic compounds with at least two against groups reactive via isocyanate groups, in particular organic polyhydroxyl compounds. Suitable such Polyhydroxyl compounds are both simple polyhydric alcohols Molecular weight range 62 to 599, preferably 62 to 200 such as. B. Ethylene glycol, trimethylolpropane, 1,2-propanediol or 1,2-butanediol, ins special but higher molecular weight polyether polyols and / or polyethers polyols of the type known per se from polyurethane chemistry Molecular weights of 600 to 8000, preferably 800 to 4000, the at least two, usually 2 to 8, but preferably 2 to 4 primary and / or have secondary hydroxyl groups. Of course can also be used such NCO prepolymers that for example from low molecular weight polyisocyanates mentioned type and less preferred compounds with over Isocyanate groups reactive groups such. B. Polythioether polyols, hydroxyl-containing polyacetals, polyhydroxypoly carbonates, hydroxyl-containing polyester amides or Copolymers containing hydroxyl groups of olefinically unsaturated Connections have been obtained. To produce the NCO Compounds suitable compounds with isocyanate groups reactive groups, especially hydroxyl groups, are examples as described in U.S. Patent 4,218,543, column 7, line 29 to column 9, line 25 compounds disclosed by way of example. In the manufacture of the NCO These compounds are prepolymers with isocyanate  groups reactive groups with simple polyisocyanates type mentioned above by way of example in compliance with an NCO / OH Equivalent ratio of about 1.5: 1 to 20: 1, preferably 5: 1 to Um brought settlement. The NCO prepolymers generally have one NCO content of 2.5 to 25, preferably 6 to 22% by weight. Out of this already shows that within the scope of the present invention "NCO prepolymers" or under "prepolymers with terminal" Iso cyanate groups "both the reaction products as such and theirs Mixtures with excess amounts of unreacted starting material isocyanates, which are often also referred to as "semi-prepolymers", to ver are standing.

Polyisocyanates particularly preferred for the process according to the invention (b) are the technical polyisocyanates customary in polyurethane chemistry, d. H. Hexamethylene diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanato methyl-cyclohexane (isophorone diisocyanate, abbreviated: IPDI), 4,4'-diiso cyanato-dicyclohexylmethane, 2,4-diisocyanatotoluene, its technical Mixtures with 2,6-diisocyanatotoluene, 4,4'-diisocyanatodiphenylmethane, its mixtures with the corresponding 2,4'- and 2,2'-isomers, Polyiso cyanate mixtures of the diphenylmethane series, as obtained by phosgenation of aniline / formaldehyde condensates in a manner known per se can be obtained, the biuret or isocyanurate groups Modification products of these technical polyisocyanates and in particular NCO prepolymers of the type mentioned based on these technical polyisocyanates on the one hand and the examples mentioned simple polyols and / or polyether polyols and / or polyether polyols on the other hand, as well as any mixtures of such polyisocyanates.  

Suitable as polyurethanes (a) are all cellular polyurethanes, be they Block, molded, hot or cold foams. Of interest to the Processing is mainly the fact that the foam is not fine must be powdered, but quite granular-coarse, even in the form of Flakes can be used. This eliminates cost-causing Grinding treatments and a complex separation of the grain size Seven or layers of wind. The proportion of polyurethane foam can be up to 50%, based on the weight of the total preparation, are preferred however 5-45%.

Suitable stabilizing substances (c) are acylating or alkylating substances, which are known per se and also often used as stabilizers in polyurethane chemistry. Acylating agents are acid chlorides, such as benzoyl chloride, isophthaloyl chloride etc., i.e. compounds of the general formula:

n = 1, 2

Suitable alkylating agents are, for example, methyl iodide, dimethyl sulfate or preferably sulfonic acid alkyl ester of molecular weight range 110 to 250 with 1 to 4 carbon atoms in the alkyl radical. For this include both aliphatic sulfonic acid alkyl esters and methanesulfonic acid methyl ester, n-butanesulfonic acid methyl ester, n-perfluorobutanesulfonic acid methyl ester, n-hexanesulfonic acid ethyl ester as well as aromatic sulfone acidic acid esters such as methyl benzenesulfonate, ethyl ester or n  butyl ester, p-toluenesulfonic acid methyl ester, ethyl ester or n-butyl ester, 1-naphthalenesulfonic acid methyl ester, 3-nitrobenzenesulfonic acid methyl ester or 2-naphthalenesulfonic acid methyl ester. The exemplary ge called aromatic sulfonic acid esters are preferred. Especially before p-toluenesulfonic acid methyl ester is used.

The amount of acylating stabilizer used is 0.1 to 0.5 preferably 0.1 to 0.36 parts by weight of benzoyl chloride, based on the Overall preparation. When using alkylating stabilizers the application rate is 0.0005 to 0.02 parts by weight, preferably 0.001 to 0.01 parts by weight of methyl p-toluenesulfonate, based on the Overall preparation. Regarding the auxiliary and additives (d) include, for example, fillers, dyes and pig ment. More information on the usual auxiliaries and additives is the Technical literature, e.g. the monograph by J.H. Saunders and K.C. Fresh "High Polymers" volume XVI, Polyurethanes, part 2 and 7, publisher Interscience Publishers 1962 and 1964, respectively.

Isocyanates and stabilizers are used to carry out the process substances either together with the polyurethane foam or separately added and heated to 150 ° C in a stirrer. Was the Foam is not presented with the isocyanate from the beginning, so it is now as a powder or in granular form or in the form of flakes at the end admitted. However, the stabilizing substance can also be used entirely In conclusion. The temperature is still 1 h after reaching of the viscosity minimum kept at 150 ° C. The prepoly thus produced mers are immediately usable e.g. B. as a water-curing coating. They can be prepolymerized very well with polyethers and  are above all a very good raw material for polyurethane foams, non-cellular polyurethanes, adhesives and elastomers.

The invention is illustrated by the following examples:

Abbreviations used below:

Raw MDI

4,4'-diisocyanatodiphenylmethane in a mixture with its isomers and higher homologs as obtained by phosgenation of aniline-formaldehyde condensation, NCO content: 30.4%, viscosity η _{25 ° C} : 80 mPa · s

MDI: 4,4'-diisocyanatodiphenylmethane M 65

Mixture of 65% 2,6-tolylene diisocyanate and 35% 2,4-tolylene diiso cyanate, NCO content: 48.3%

T 80

Mixture of 80% 2,6-tolylene diisocyanate and 20% 2,4-tolylene diiso cyanate, NCO content: 48.3%

T 100

100% 2,6-tolylene diisocyanate, NCO content: 48.3%  

Soft polyurethane foam powder

MDI-based polyurethane foam, in the roller mill by means of the shear forces between rollers of different circumferential speeds milled as described in DE-A 42 00 443.

example 1 Foam dissolution in T 65 without stabilizing substance

In an apparatus consisting of a three-necked flask with stirrer and Internal thermometers are presented with 160 g of T 65 and 40 g of polyurethane sprinkle in soft foam powder slowly. After increasing the temperature at 140 ° C a strong increase in viscosity is found, the material becomes a tough porridge. At 150 ° C the reaction mixture becomes thin and is then stirred for a further 1 h at the same temperature. At the Filling is a slight clouding of the otherwise clear substance determine, this cloudiness settles down in a very short time Layer on the bottom of the bottle and the substance is very clear visible. The isocyanate content after the reaction is 32.6% by weight; 2nd Days later it is 31.8% by weight, after 8 days it is 29.1% by weight sunk. After 19 days, the prepolymer was no longer in one flowable, stringy mass transformed.

Example 2 Foam dissolution in M 65 using a stabilizing substance

In an apparatus as in Example 1, 160 g of T 65 and 1.3 ml of one 1 molar solution of methyl p-toluenesulfonate, dissolved in M 65, submitted. After stirring in 40 g of flexible polyurethane foam Reaction carried out as described in Example 1. The reaction  The process is completely analogous, the isocyanate content is 36% by weight. The pre polymer is still thin and clear even after 3 months yellowish liquid.

Example 3 Prepolymer from the product of Example 2

The product from Example 2 (200 g) is mixed with 100 polypropylene glycol (OH- Number 56) prepolymerized. The resulting prepolymer is in the room temperature low viscosity and has an isocyanate content of 22.8 wt .-%. It is also unchanged after 3 months.

Example 4 Foam dissolution in T 80 using a stabilizing substance

In an apparatus as in Example 1, 160 g of T 80 and 1.3 ml of a 1st molar solution of methyl p-toluenesulfonate, dissolved in M 80, submitted and implemented with 40 g flexible polyurethane foam. The resulting prepolymer is a low viscosity, storage stable substance an isocyanate content of 36.2% by weight.

Example 5 Foam dissolution in T 100 using a stabilizing sub punch

In an apparatus as in Example 1, 160 g of T 100 with 40 g of poly urethane soft foam implemented. After the sharp drop in Viscosity becomes 1.3 ml of a 1 molar solution of p-toluenesulfonic acid  methyl ester, dissolved in M 100, added and stirred in. That result de Prepolymer is a thin, storage-stable substance with one Isocyanate content of 36% by weight.

Example 6 Foam dissolution in raw MDI using a stabilizer substance

In an apparatus as in Example 1, 160 g of crude MDI and 1.3 ml a 1 molar solution of methyl p-toluenesulfonate, dissolved in crude MDI submitted and implemented with 40 g flexible polyurethane foam. The resulting prepolymer is a low viscosity, storage stable substance an isocyanate content of 22.5% by weight.

Example 7 Dissolving flexible polyurethane foam flakes in T 80

In an apparatus according to Example 1, 160 g of T 80 and 1.32 g of one 1 molar solution of methyl p-toluenesulfonate in T 80 at 150 ° C submitted. 40 g of flexible polyurethane foam are applied within 2 hours Base TDI entered in finger-sized pieces and resolved. After a After stirring for an hour at 150 ° C., the isocyanate content was 36.2% by weight.

Example 8 Dissolving soft polyurethane foam powder in MDI

400 g of MDI are in the form of flakes in an apparatus according to Example 1 and 100 g flexible polyurethane foam powder together with 6.6 g of a 1st  molar solution of methyl p-toluenesulfonate in modified MDI presented and first mixed dry. Then it goes to 150 ° C heated up and waited until liquefaction occurs, then stirring, until everything is resolved The isocyanate content is 24.5% by weight Viscosity 753 mPa · s at 25 ° C.

Example 9 Dissolution of flexible polyurethane foam powder in MDI

As in Example 8, 350 g of MDI in scale form, 180 g are presented Flexible polyurethane foam powder and 6.6 g of a 1 molar solution of p- Toluene sulfonic acid methyl ester in modified MDI. It will continue to ver drive as in Example 8. Isocyanate content: 19.8% by weight, viscosity: 13835 mPa · s at 25 ° C.

Example 10 Dissolve soft polyurethane foam powder in MDI

As in Example 8, 450 g of MDI in scale form, 50 g are presented Flexible polyurethane foam powder and 6.6 g of a 1 molar solution of p- Toluene sulfonic acid methyl ester in modified MDI. It will continue to ver drive as in Example 8. Isocyanate content: 28.4% by weight, viscosity: 112 mPa · s at 25 ° C.

Example 11 Dissolving flexible polyurethane foam powder in T 100

In an apparatus according to Example 1, 700 g of T 100 and 300 g Soft polyurethane foam powder together with 6.6 g of a 1 molar  Solution of p-toluenesulfonic acid methyl ester presented in IPDI and under Stirring heated to 150 ° C. As soon as the viscosity has reached its minimum, is stirred for another hour at 150 ° C. Isocyanate content 29.8% by weight, Viscosity: 1145 mPa · s at 25 ° C.

Example 12 Dissolving flexible polyurethane foam flakes in T 100

In this apparatus according to Example 1, 700 g of T 100 and 6.6 g of 1-molar p-toluenesulfonic acid methyl ester in IPDI and at 150 ° C. heated. Then 300 g of flexible polyurethane foam flakes become successive admitted and dissolved. After dissolving it will be 1 hour stirred. Thereafter, the isocyanate content is 28.0% by weight Viscosity 3043 mPa · s at 25 ° C.

Example 13 Dissolving a thermoplastic polyurethane in M 65

The following are initially introduced in an apparatus according to Example 1: 180 g T 65, 20 g thermoplastic polyurethane and 0.8 g 1 molar Solution of p-toluenesulfonic acid methyl ester in M 65. After dissolving the Granules at 150 ° C at 150 ° C is 1 hour at 150 ° C (after stirred, the isocyanate content of the very thin solution is 42.8 % By weight  

Example 14 Dissolving thermoplastic polyurethane in M 65

80 g of T are initially introduced in an apparatus according to Example 1 65, 20 g thermoplastic polyurethane and 0.8 g 1-molar solution of p- Toluene sulfonic acid methyl ester in Desmodur T 65. After dissolving the Granules are stirred at 150 ° C for 1 hour. The very highly viscous solution has an isocyanate content of 37.4% by weight.

Claims (8)

1. A process for the preparation of isocyanate prepolymers, characterized in that polyurethane is dissolved at 120 to 180 ° C in isocyanate in the presence of a stabilizing substance. 2. The method according to claim 1, characterized in that after the solution has reached its minimum viscosity, 0.3 to 3 hours is stirred at 120 to 180 ° C. 3. The method according to claim 1 or 2, characterized in that lumpy to ground polyurethane foam or granulated thermoplastic polyurethane is used. 4. The method according to any one of claims 1 to 3, characterized records that an acylating agent or Alkylating agent is used. 5. The method according to claim 4, characterized in that benzoyl chloride or p-toluenesulfonic acid methyl ester is used. 6. The method according to claim 5, characterized in that 0.1 to 0.5, preferably 0.1 to 0.35 parts by weight of benzoyl chloride, based on Total preparation, can be used. 7. The method according to claim 5, characterized in that 0.0005 to 0.2, preferably 0.0001 to 0.01 parts by weight of p-toluenesulfonic acid methyl ester, based on the total preparation, are used.   8. The method according to any one of claims 1 to 7, characterized records that polyurethane and isocyanate in a weight ratio nis from 5 to 95 to 45 to 55 can be used.