IMPROVED DISTILLATION CAPABILITY BY DILUTION WITH A COMPONENT TO BE SEPARATED OFF

Abstract

The invention relates to a method for purifying at least one reaction product of at least one diisocyanate, comprising at least the following steps: (A) providing a mixture A at least containing the at least one reaction product of the at least one diisocyanate and, if applicable, the at least one diisocyanate, (B) adding, if applicable more of, at lease one diisocyanate to mixture A from step (A) in order to obtain a mixture B, and (C) separating off the at least one diisocyanate from mixture B from step (B) by distillation in order to obtain the purified at least one reaction product of the at least one diisocyanate. Furthermore, the present invention comprises the reaction product of at least one diisocyanate which can be obtained by the method according to the invention and the use thereof for producing polyurethane foams, polyurethane hydrogels, polyurethane elastomers, varnishes and bonding adhesives.

Claims

1: A process for purifying at least one reaction product of at least one diisocyanate comprising the steps of: (A) providing a mixture A containing the at least one reaction product of the at least one diisocyanate and optionally, the at least one diisocyanate, (B) adding, optionally additional, at least one diisocyanate to mixture A from step (A) to obtain mixture B, (C) distillatively separating the at least one diisocyanate from mixture B from step (B) to obtain the purified at least one reaction product of the at least one diisocyanate.

2: The process as claimed in claim 1, wherein mixture A is obtained by one selected from the group consisting of trimerization of the at least one diisocyanate, reaction of the at least one diisocyanate with polyols to obtain NCO-terminated prepolymers, urea formation, urethanization, biuretization, allophanatization, carbodiimidization, uretdione formation, uretonimine formation, oxazolidone formation, amide formation, and combinations of these reactions.

3: The process as claimed in claim 1, wherein mixture A contains the at least one diisocyanate in an amount of 0.1% to 90% by weight based on mixture A.

4: The process as claimed in claim 1, wherein mixture B contains the at least one diisocyanate in an amount of 1% to 94% by weight based on the weight of mixture B.

5: The process as claimed in claim 1, wherein step (B) comprises adding the at least one diisocyanate in an amount of 1% to 60% by weight based on mixture A.

6: The process as claimed in claim 1, wherein the purified at least one reaction product of the at least one diisocyanate obtained in step (C) has a content of at least one diisocyanate of 0.001% to 0.5% by weight based on the at least one reaction product.

7: The process as claimed in claim 1, wherein mixture A has a viscosity of 500 to 50 000 mPas, wherein viscosity is determined at 23° C. according to DIN 53019.

8: The process as claimed in claim 1, in that mixture B has a viscosity of 100 to 1400 mPas wherein viscosity is determined at 23° C. according to DIN 53019.

9: The process as claimed in claim 1, wherein the at least one diisocyanate is selected from the group consisting of diisocyanates having aliphatically, cycloaliphatically, araliphatically and aromatically bonded isocyanate groups.

10: The process as claimed in claim 1, wherein the at least one diisocyanate is selected from the group consisting of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), butylene diisocyanate (BDI), pentamethylene diisocyanate (PDI), bisisocyanatocyclohexylmethane (HMDI), 2,2,4-trimethylhexamethylene diisocyanate, bisisocyanatomethylcyclohexane, bisisocyanatomethyltricyclodecane, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate, norbornane diisocyanate, cyclohexane diisocyanate, toluene 2,4-diisocyanate (2,4-TDI), toluene 2,6-diisocyanate (2,6-TDI), 2,2′-methylenediphenyl diisocyanate (2, 2′-MDI), 2,4′-methylenediphenyl diisocyanate (2,4′-MDI), 4,4′-methylenediphenyl diisocyanate (4,4′-MDI), and mixtures thereof.

11: The process as claimed in claim 1, wherein the at least one diisocyanate distillatively separated in step (C) is at least in part used for producing the at least one reaction product present in mixture A.

12: The process as claimed in claim 1, wherein the at least one diisocyanate distillatively separated in step (C) is at least in part employed in step (B).

13: A reaction product of at least one diisocyanate obtained by the process as claimed in claim 1.

14: In a process for producing one selected from the group consisting of polyurethane foams, polyurethane hydrogels, polyurethane elastomers, coatings, and adhesives by reaction of an isocyanate, the improvement comprising including the at least one reaction product as claimed in claim 13.

15: A process for producing polyurethane foams, wherein a composition comprising at least one reaction product as claimed in claim 13, water, optionally oligomers produced from at least two low molecular weight diisocyanates, wherein the diisocyanates have a molar mass of 140 bis 278 g/mol, optionally catalysts, optionally salts of weak acids, whose corresponding free acids in water at 25° C. have a pK.sub.a value of ≥3.0 and ≤14.0, optionally surfactants, optionally mono- or polyhdric alcohols or polyols, optionally hydrophilic polyisocyanates, is provided, foamed, and cured.

16: The process as claimed in claim 1, wherein step (B) comprises adding the at least one diisocyanate in an amount of 5% to 50% by weight based on mixture A.

17: The process as claimed in claim 1, wherein step (B) comprises adding the at least one diisocyanate in an amount of 8% to 45% by weight based on mixture A.

18: The process as claimed in claim 1, wherein mixture A has a viscosity of 1000 to 10 000 mPas, wherein viscosity is determined at 23° C. according to DIN 53019.

19: The process as claimed in claim 1, in that mixture B has a viscosity of 150 to 1000 mPas, wherein viscosity is determined at 23° C. according to DIN 53019.

Description

EXAMPLES

[0080] 2960 g of a polyalkylene oxide started from 1,3-propylene glycol having a molar mass of 591 g/mol and an OH number of 190 mg KOH/g and a proportion by weight of ethylene oxide of 87% were added dropwise to a mixture of 1680 g of 1,6-hexamethylene diisocyanate (HDI) and 5.0 g of dibutyl phosphate at 80° C. over 30 min and the resulting mixture was stirred for a further 3.5 h until an NCO content of 9.1% was attained.

[0081] For the individual experiments this mixture was in each case diluted with HDI according to table 1 to obtain the corresponding starting mixtures (SM). The mixture obtained from the abovementioned synthesis (experiments V1, V2 and V3) and the starting mixtures (experiments 4, 5, 6, 7, 8 and 9) were distilled at the temperatures recited in table 1 (VV: pre-evaporator, HV: main evaporator) and in each case at a pressure of 0.7 mbar (a). The obtained distillates/the distillate residues which constitute the respective product were subsequently subjected to determination in each case of the NCO content of the distillate, the HDI content of the distillate, the NCO content of the product, the viscosity of the product, the weight average molecular weight (Mw) of the product, the residual HDI content of the product and the proportion of compounds having a molecular weight below 1000 g/mol by the methods reported below.

[0082] The recited measured values are determined by the following methods:

[0083] Unless otherwise stated all percentages are based on weight.

[0084] Viscosity was determined at 23° C. according to DIN 53019.

[0085] NCO contents were determined by volumetric means according to DIN-EN ISO 11909.

[0086] The weight average molecular weight (Mw), the proportion below 1000 g/mol and the HDI content of the distillate were determined by gel permeation chromatography (GPC) in the solvent THF according to DIN 55672-1.

[0087] The residual HDI content was determined by gas chromatography according to DIN EN ISO 10283.

TABLE-US-00001 TABLE 1 Content of Residual compounds HDI Viscosity Distillation NCO HDI NCO Viscosity HDI with added of starting temperature content of content of content of of Mw of content M < 1000 [% by mixture (VV/HV) distillate distillate product product product of product g/mol Experiment wt.] [mPas] [° C.] [%] [%] [%] [mPas] [%] [%] [%].sup.1 V1 0 1780 130/120 48.9 95 5.0 4330 3280 0.01 5.9 V2 140/130 48.7 99 4.9 4430 3270 0.01 6.1 V3 150/140 48.2 95 4.9 4830 3380 0.02 5.9 4 11 857 130/120 49.5 97 5.0 4340 3250 0.03 6.0 5 140/130 49.2 96 5.0 4390 3260 0.01 6.3 6 150/140 49.0 98 5.0 4380 3260 0.01 6.1 7 43 201 130/120 49.2 100 5.2 4170 3200 0.04 6.5 8 140/130 49.2 100 5.2 4230 3200 0.02 6.5 9 150/140 49.3 100 5.1 4320 3260 0.01 6.2 VComparative .sup.1in the product after distillation

[0088] The inventive experiments and the comparative experiments clearly show that the process according to the invention makes it possible to obtain the distillate in particularly high purity, thus allowing reuse thereof for syntheses. The process according to the invention simultaneously allows the reaction product to be diluted, thus allowing simpler conveying thereof.