CA1077956A - Process for the preparation of polyisocyanates which contain biuret groups - Google Patents
Process for the preparation of polyisocyanates which contain biuret groupsInfo
- Publication number
- CA1077956A CA1077956A CA271,671A CA271671A CA1077956A CA 1077956 A CA1077956 A CA 1077956A CA 271671 A CA271671 A CA 271671A CA 1077956 A CA1077956 A CA 1077956A
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- Canada
- Prior art keywords
- biuret
- diisocyanate
- reaction
- mol
- diamine
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C273/00—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups
- C07C273/18—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of substituted ureas
- C07C273/1809—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of substituted ureas with formation of the N-C(O)-N moiety
- C07C273/1818—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of substituted ureas with formation of the N-C(O)-N moiety from -N=C=O and XNR'R"
- C07C273/1827—X being H
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
- C08G18/72—Polyisocyanates or polyisothiocyanates
- C08G18/77—Polyisocyanates or polyisothiocyanates having heteroatoms in addition to the isocyanate or isothiocyanate nitrogen and oxygen or sulfur
- C08G18/78—Nitrogen
- C08G18/7806—Nitrogen containing -N-C=0 groups
- C08G18/7818—Nitrogen containing -N-C=0 groups containing ureum or ureum derivative groups
- C08G18/7831—Nitrogen containing -N-C=0 groups containing ureum or ureum derivative groups containing biuret groups
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
- C08G18/72—Polyisocyanates or polyisothiocyanates
- C08G18/80—Masked polyisocyanates
- C08G18/8003—Masked polyisocyanates masked with compounds having at least two groups containing active hydrogen
- C08G18/8006—Masked polyisocyanates masked with compounds having at least two groups containing active hydrogen with compounds of C08G18/32
- C08G18/8038—Masked polyisocyanates masked with compounds having at least two groups containing active hydrogen with compounds of C08G18/32 with compounds of C08G18/3225
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Polyurethanes Or Polyureas (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
Abstract of the Disclosure This invention relates to an improved process for the preparation of polyisocyanates which contain biuret groups by the direct reaction of polyamines in vapor form with polyisocyanates.
Description
Mo-1691-F
1~77956 LeA 17,067 PROCESS FOR THE PREPARATION OF POLYISOCYANATES
WHICH CONTAIN BIURET ~ROUPS
Background of the Invention It is already known, for example, to prepare polyisocyanates containing biuret groups from dii~ocyanate~ -and water (US Patent No. 3 201 372); hydrogen sulphide ( British Patent 10436~2); formic acld (US Patent No.
3 392 183 ) or tertiary alcohols (US Patent No.
3 358 010). In these processes, some of the isocyanate groups of the diisocyanates are converted into amino groups which then react with excess diisocyanate to form biuret polyisocyanates via the corre~ponding urea diisocyanates.
These prior art processes have various disadvan~
tages. Firstly, the heterogeneous reaction of diisocyanates with water involves the risk of formation of insoluble poly-ureas which are difficult to remove. Furthermore, the above mentioned process invariably produce gaseous by-products such as carbon dioxide, carbon monoxide, carbon sulphoxide or olefines. Lastly, a particularly serious disadvantage of these prior art processes is that some of the isocyanate groups in the diisocyanate used as starting material are inevitably destroyed by amine formation.
There have, therefore, been several attempts to provide a process for the production of polyisocyanates which contain biuret groups by the direct reaction of polyamine~ with poly-isocyanates, without liberation of volatile by-products or destruction of isocyanate groups by amine formation.
Because of the vigorous reaction of amino groups with iso-cyanate groups, however, considerable practical difficulties were encountered because of the very copious production of LeA 17,067 ' .
1C~77956 insoluble polyureas and crosslinked products. The only methods which met with some measure of success were, therefore, those in which very special starting materials were used. Thus, according tous ~tent ~ 441 588, higher molecular weight diaminopolyethers must be used, as the diamine com-ponent in order to prevent the formation of the above men-tioned difficulty soluble by-products. It is clear that a process requiring the previous complicated preparation of diamino polyethers cannot be regarded as a commercially completely satisfactory solution to the problem. The process according to US Patent 3 824 266 is restricted to the use of diprimary aromatic diamines whose reactivity is reduced by steric or electronic effects and also does not provide a commercially acceptable method of producing polyisocyanates with biuret groups.
The process according to US Patent 3 903 126 also does not provide a commercially accept-able method of producing polyisocyanates with biuret groups by the direct reaction of organic polyisocyanates with sim-ple aliphatic and/or cycloaliphatic polyamines. Thus,according to Example 16 of US Patent 3 903 126 preparation of polyisocyanates with biuret groups from hexamethylene diisocyanate and hexamethylene diamine requires reheating of the reaction mixture to about 180C
for about 12 hours in order to complete the reaction. Such long reheating at a high temperature is not only uneconomical, particularly under large scale production conditions, but also leads to discoloration of the reaction product so that its use in lightfast lacquers is very restricted. Moreover, when Example 16 of US ~atent 3 903 126 LeA 17,067 -2-was repeated, it was found that it was impossible by this method to obtain a biuret polyisocyanate which was both free from monGmeric diisocyanate used as starting material and completely free from insoluble gel-like by-products.
SUMMARY OF THE INVENTION
.
- It has now surprisingly been found that aliphatic diamines containing from 2-12 carbon atoms can be directly reacted with aliphatic diisocyanates containing from 4-12 carbon atoms to yield the corresponding biuret polyisocyanates 10 if the biuret-free diisocyanate used as starting material is first placed into the reaction vessel and the diamine is then introduced in the gaseous form. Under these conditions, the reaction mixture remains a clear solution throughout the introduction of diamine even when hexamethylene diisocyanate 15 is reacted with hexamethylene diamine, and the reaction is completed as soon as all the diamine has been introduced so that no reheating is necessary.
In one aspect the present invention relates to a ~ro- -cess for the preparation of biuret polyisocyanates by reaction of aliphatic diamines containing 2-12 carbon atoms with ali-phatic diisocyanates which are free from biuret groups at a molar ratio of amino groups to isocyanate groups of between about 1:5 to 1:100, characterized in that the diamines are reacted in vapor form with the diisocyanates which have been heated to a temperature of from about 100C to 250C.
Organic polyamines having two aliphatically or cyclo-aliphatically bound primary amino groups are used for the process according to the invention. Examples of such polyamines LeA 17,067 -3-:
107~7956 are dlprimary diamines of the formula R(NH2)2 in which Rrepresents an aliphatic hydrocarbon group with 2 to 12 carbon atoms, a cycloaliphatic hydrocarbon group with 4 to 7 carbon atoms or an araliphatic hydrocarbon group with 8 to 10 carbon atoms e.g. ethylene diamine; propylene-1,2- and -1,3-diamine;
1,4-diaminobutane; 2,2-dimethylpropane-1,3-diamine; 1,6-diaminohexane; 2,5-dimethylhexane-2,5-diamine; 2,2,4-trimethyl-hexane-1,6-diamine; 1,8-diaminooctane; 1,10-diaminodecane;
l,ll-undecanediamine; 1,12-dodecanediamine; 1-methyl-4-~aminoisopropyl)-cyclohexylamine-(l); 3-aminomethyl-3,5,5-trimethyl-cyclohexylamine-(l); 1,2-bis-(aminomethyl)-cyclo-butane; p-xylylenediamine; 1,4-bis-(2-aminoethyl)-benzene;
1,2- and 1,4-diaminocyclohexane; 1,2-, 1,4- and 1,8-diamino-decaline; l-methyl-4-aminoisopropyl-cyclo-hexylamine-(1);
4,4'-diamino-dicyclohexyl; 4,4'-diamino-dicyclohexylmethane;
1~77956 LeA 17,067 PROCESS FOR THE PREPARATION OF POLYISOCYANATES
WHICH CONTAIN BIURET ~ROUPS
Background of the Invention It is already known, for example, to prepare polyisocyanates containing biuret groups from dii~ocyanate~ -and water (US Patent No. 3 201 372); hydrogen sulphide ( British Patent 10436~2); formic acld (US Patent No.
3 392 183 ) or tertiary alcohols (US Patent No.
3 358 010). In these processes, some of the isocyanate groups of the diisocyanates are converted into amino groups which then react with excess diisocyanate to form biuret polyisocyanates via the corre~ponding urea diisocyanates.
These prior art processes have various disadvan~
tages. Firstly, the heterogeneous reaction of diisocyanates with water involves the risk of formation of insoluble poly-ureas which are difficult to remove. Furthermore, the above mentioned process invariably produce gaseous by-products such as carbon dioxide, carbon monoxide, carbon sulphoxide or olefines. Lastly, a particularly serious disadvantage of these prior art processes is that some of the isocyanate groups in the diisocyanate used as starting material are inevitably destroyed by amine formation.
There have, therefore, been several attempts to provide a process for the production of polyisocyanates which contain biuret groups by the direct reaction of polyamine~ with poly-isocyanates, without liberation of volatile by-products or destruction of isocyanate groups by amine formation.
Because of the vigorous reaction of amino groups with iso-cyanate groups, however, considerable practical difficulties were encountered because of the very copious production of LeA 17,067 ' .
1C~77956 insoluble polyureas and crosslinked products. The only methods which met with some measure of success were, therefore, those in which very special starting materials were used. Thus, according tous ~tent ~ 441 588, higher molecular weight diaminopolyethers must be used, as the diamine com-ponent in order to prevent the formation of the above men-tioned difficulty soluble by-products. It is clear that a process requiring the previous complicated preparation of diamino polyethers cannot be regarded as a commercially completely satisfactory solution to the problem. The process according to US Patent 3 824 266 is restricted to the use of diprimary aromatic diamines whose reactivity is reduced by steric or electronic effects and also does not provide a commercially acceptable method of producing polyisocyanates with biuret groups.
The process according to US Patent 3 903 126 also does not provide a commercially accept-able method of producing polyisocyanates with biuret groups by the direct reaction of organic polyisocyanates with sim-ple aliphatic and/or cycloaliphatic polyamines. Thus,according to Example 16 of US Patent 3 903 126 preparation of polyisocyanates with biuret groups from hexamethylene diisocyanate and hexamethylene diamine requires reheating of the reaction mixture to about 180C
for about 12 hours in order to complete the reaction. Such long reheating at a high temperature is not only uneconomical, particularly under large scale production conditions, but also leads to discoloration of the reaction product so that its use in lightfast lacquers is very restricted. Moreover, when Example 16 of US ~atent 3 903 126 LeA 17,067 -2-was repeated, it was found that it was impossible by this method to obtain a biuret polyisocyanate which was both free from monGmeric diisocyanate used as starting material and completely free from insoluble gel-like by-products.
SUMMARY OF THE INVENTION
.
- It has now surprisingly been found that aliphatic diamines containing from 2-12 carbon atoms can be directly reacted with aliphatic diisocyanates containing from 4-12 carbon atoms to yield the corresponding biuret polyisocyanates 10 if the biuret-free diisocyanate used as starting material is first placed into the reaction vessel and the diamine is then introduced in the gaseous form. Under these conditions, the reaction mixture remains a clear solution throughout the introduction of diamine even when hexamethylene diisocyanate 15 is reacted with hexamethylene diamine, and the reaction is completed as soon as all the diamine has been introduced so that no reheating is necessary.
In one aspect the present invention relates to a ~ro- -cess for the preparation of biuret polyisocyanates by reaction of aliphatic diamines containing 2-12 carbon atoms with ali-phatic diisocyanates which are free from biuret groups at a molar ratio of amino groups to isocyanate groups of between about 1:5 to 1:100, characterized in that the diamines are reacted in vapor form with the diisocyanates which have been heated to a temperature of from about 100C to 250C.
Organic polyamines having two aliphatically or cyclo-aliphatically bound primary amino groups are used for the process according to the invention. Examples of such polyamines LeA 17,067 -3-:
107~7956 are dlprimary diamines of the formula R(NH2)2 in which Rrepresents an aliphatic hydrocarbon group with 2 to 12 carbon atoms, a cycloaliphatic hydrocarbon group with 4 to 7 carbon atoms or an araliphatic hydrocarbon group with 8 to 10 carbon atoms e.g. ethylene diamine; propylene-1,2- and -1,3-diamine;
1,4-diaminobutane; 2,2-dimethylpropane-1,3-diamine; 1,6-diaminohexane; 2,5-dimethylhexane-2,5-diamine; 2,2,4-trimethyl-hexane-1,6-diamine; 1,8-diaminooctane; 1,10-diaminodecane;
l,ll-undecanediamine; 1,12-dodecanediamine; 1-methyl-4-~aminoisopropyl)-cyclohexylamine-(l); 3-aminomethyl-3,5,5-trimethyl-cyclohexylamine-(l); 1,2-bis-(aminomethyl)-cyclo-butane; p-xylylenediamine; 1,4-bis-(2-aminoethyl)-benzene;
1,2- and 1,4-diaminocyclohexane; 1,2-, 1,4- and 1,8-diamino-decaline; l-methyl-4-aminoisopropyl-cyclo-hexylamine-(1);
4,4'-diamino-dicyclohexyl; 4,4'-diamino-dicyclohexylmethane;
2,2'-(~is-4-amino-cyclohexyl)-propane; 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane; 1,2-bis-(4-aminocyclohexyl)-ethane and 3,3',5,5'-tetramethyl-bis-(4-aminocyclohexyl)-methane and -propane.
Other suitable polyamines for the process according to the invention include bis-(aminoalkyl)-amines preferably having a total of from 4 to 12 carbon atoms, e.g. bis-(2-aminoethyl)-amine, bis(3-aminopropyl)-amine, bis-(4-amino-butyl)-amine, bis-(6-aminohexyl)-amine and isomeric mixtures of dipropylene triamine and dibutylene triamine.
The preferred diamines are tetramethylene diamine, hexamethylenediamine and 1,2-bis-(aminomethyl)-cyclobutane, particularly hexamethylenediamine.
Suitable polysiocyanates for the process according to LeA 17,067 -4-1~779S6 the invention are in particular diisocyanates of the formula Q(NC0)2 in which Q represents an aromatic hydrocarbon group with 6 to 15 carbon atoms; an araliphatic hydrocarbon group with 8 to 10, preferably 8, carbon atoms; an aliphatic hydro-carbon group with 4 to 12 carbon atoms or a cycloaliphatic hydrocarbon groupwit~ 4 to 15 carbon atoms. Examples include tolylene-2,4- and -2,6-diisocyanates and their isomeric mixtures; 4,4'- and 2,4'-diphenylmethane diisocyanate and xylylene diisocyanate. Particularly suitable are the aliphatic and cycloaliphatic diisocyanates such as 1,4-diisocyanatobutane; 1,6-diisocyanatohexane; 2,4,4-trimethyl-hexane-1,6-diisocyanate; l,ll-diisocyanatoundecane; 3-i90-cyanatomethyl-3,5,5-trimethyl-cyclohexylisocyanate-(1);
1,4 -cyclohexane diisocyanate; 4~4l-dicyclohexylmethane diisocyanate and 1,2-bis-(isocyanatomethyl)-cyclobutane.
Hexamethylene diisocyanate is particularly preferred.
Products which are particularly light in color are obtained by the process according to the invention if the diisocyanate used as a starting material is preheated for several hours, suitably about 6 to 10 hours, at about 120 to 195C, preferably about 160 to 180C, andthen distilled.
The process according to the invention is preferably carried out by introducing the diisocyanate into the reaction vessel at an excess of about 5 to 100 and preferably 7 to 25 isocyanate groups to one primary amino group at elevated temperature with vigorous stirring and adding the polyamine in gaseous form, optionally at reduced pressure, and if desired together with a stream of inert gas. In cases where the polyamine has a lower boiling point than the diisocyanate, LeA 17,067 -5-11~77956 the polyamine vapor can be introduced through a simple inlet tube dipping into the diisocyanate. A suitable evaporator for the polyamine is attached to the inlet tube and a vacuum must be applied to keep the reactor at a pressure at which the boiling point of the polyamine is about 10 to 80C below the temperature of the diisocyanate in the reaction vessel because otherwise the polyamine will partly condense in the inlet tube and come into contact with the diisocyanate as a liquid, hence leading to the formation of lC solid polyureas and blockage of ~he inlet tube. If, especially in the case of large reaction batches, the column of liquid above the outlet point of the polyamine vapor is so high that its hydrostatic pressure raises the boiling point of the polyamine to a temperature close to the temperature of the dii~ocyanate, it is preferable to use a hollow stirrer (gasification stirrer) for introducing the polyamine vapor. This stirrer will exert additional suction and ensure uniform distribution of the polyamine vapor in the diisocyanate.
If the boiling point of the polyamine is above that of the diisocyanate, the inlet tube for introducing the poly-amine vapor must be heatable to temperatures above that of the diisocyanate in the vessel. In that case, the inlet tube is preferably heat insulated on the outside to prevent excessive heat exchange with the diisocyanate.
When carrying out the process on a commercial scale, the inlet tube may be replaced not only by a hollow stirrer as already mentioned above, but also by an annular nozzle, which may be one which closes mechanically.
LeA 17,067 -6-There are two methods, for example, by which the rate of introduction of polyamine vapor may be controlled. In the fi~st of these, the total quantity of polyamine is introduced into the evaporator and the rate of distillation i5 controlled by the supply of heat. In the second, the rate of introduction of polyamine into the overheated evaporator is controlled.
It is clear that the process may also be carried out continuously. In that case, a quantity of diisocyanate suitable for the rate of addition of polyamine is introduced into the reactor and an appropriate proportion of the reaction mixture is continuously removed, if desired through - an overflow.
The temperature of the diisocyanate in the reaction vessel is chosen so that the ,~-diisocyanato- or bis- or tris-urea compounds originally formed from the polyamine and diisocyanate rapidly react with addition of isocyanate groups to the urea groups to form biuret compounds in order to avoid precipitation of the difficulty soluble and in most cases high melting urea compounds. It has in practice been found that temperatures above 100C are required for this purpose and temperatures above 120C are preferable.
The upper limit to the temperature range is given by the ;, tendency to discoloration and side reactions and is a maximum of 250C. The preferred temperature range is from about 130C to 200C, particularly from about 140C to 180C.
In a particular embodiment of the process according to the invention by which exceptionally low viscosity biuret polyisocyanates can be prepared, the gaseous polyamine is introduced into the diisocyanate together with a gas - LeA 17,067 -7-1~17795~
which is inert with the reactants and with the end products under the reaction conditions. Nitrogen, for example, is a suitable carrier gas for this purpose. In this embodiment of the process, the volumetric ratio of carrier gas to polyamine vapor is generally between about 2:1 and lO0:1, preferably between about 40:1 and 80:1.
The polyamine vapor can, of course, be obtained not only by evporating a liquid polyamine but also by sublimation of a solid polyamine or simply by passing a vigorous stream of inert gas through a liquid polyamine, a mixture of polyamine vapor and polyamine aerosol being obtained in the last mentioned case.
When the proce~s according to the invention is carried out under the given temperature conditions, the reaction to ~ 15 the biuret polyisocyanate is spontaneous so that virtually no reheating is required once all the polyamine has been added. At the same time, continuous decomposition and re-formation of biuret groups equilibrates the reaction mixture to a complex mixture of mono-, bis- and tris-biurets and higher biurets whose molar distribution finally depends only on the selected isocyanate/amine ratio. Because of these regrouping reactions, a proportion o~ the polyamine, depending on the selected isocyanate excess, is converted into the corresponding polyisocyanate. A biuret polyi~o-cyanate mixture which has been prepared by the processaccording to the invention, for example from hexamethylene diisocyanate and 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, contains, after removal of unreacted excess of hexamethylene-diisocyanate, will contain 3,3'-dimethyl-4,4'diisocyanatodi-LeA 17,067 -8-cyclohexylmethane corresponding to the diamine used as starting material, the quantity depending on the isocyanate/amino ratio.
If, for example, 1,4-diaminocyclohexane is used for biuretizing, e.g. 1,6-diisocyanatohexane, then the reaction mixture will contain 1,4-diisocyanatocyclohexane.
If the biuret polyisocyanate is then freed from excess diisocyanate, the distillate obtained is a diisocyanate mixture which must be used again if the process is carried out on a commercial scale. This necessitates separation of the mixture by distillation because if the mixture were used as such it would require a prolonged starting period, in the ca~e of continuous production, or several batches, in the case of discontinuous production, before a product of constant composition could be obtained. For these reasons, it is preferred to use combinations of diisocyanates and diamines of similar constitution or to carry out biuretization of diisocyanates with amines which are converted into polyisocyanates with a very low vapor pressure. The bis-(aminoalkyl)-amines ~20 already mentioned above, for example, are amines which satisfy this condition ~ince, as a result of the equilibration reaction mentioned above, the most volatile polyisocyanate components to which they could give rise are the triisocyanates with one urea group which corxespond to the polyamine and which are only difficulty volatile, for example, in comparison with hexamethylene diisocyanate.
The biuret polyisocyanates prepared by the process according to the invention, in particular from aliphatic LeA 17,067 -9-.
~77956 starti.ng compounds, are valuable raw materials for the production of high quality lacquers which are weather resistant and stable to light. For use in this field, the reaction mixtures are normally freed from excess diisocyanate in order to obtain a polyisocyanate with a low vapor pressure.
This can be achieved by extraction or by distillation.
Distillation may suitably be carried out with a thin layer evaporator.
~ .
' ,.~
:
LeA 17,067 -10-iO77956 EXAMPLES
Example 1 4620 g (27.5 mol) of 1,6-diisocyanatohexane are introduced at 160C with stirring into a 6-liter four-S necked flask equipped with reflux condenser, contactthermometer and stirrer. A glass tube is mounted on the remaining neck of the flask and arranged to dip about 8 cm below the level of the liquid. At the lower end, the tube is bent sideways in the direction of rotation of the stirrer and drawn out to a tip of about 2 mm in diameter. A ground glass sleeve into which the bridge of a 500 ml distillation apparatus opens is attached to the upper end. The bridge is heated to 200C. The distillation apparatus is charged with 290 g (2.5 mol) of 1,6-diaminohexane heated to 60C, into which a boiling capillary dips. A vacuum of S0 Torr is produced by means of the reflux condenser of the four-necked flask. A gentle stream of nitrogen is passed through ~ the capillary. The distillation flask is then placed into an ; oil bath which is at a temperature of 180C. The diamine begins to distill off at a reaction temperature of from 125C
to 135C. The overheating vapors in the bridge are immediately absorbed by the diisocyanate. The speed of distillation i8 regulated by the depth of immersion of the distillation flask in the oil bath so that the reaction is completed in about 2 hours. The clear reaction mixture is then subjected to thin layer distillation at 175C and 1 Torr. 2150 g of a pale yellow biuret polyisocyanate having an isocyanate content of 22.3~ and a vi~cosity of 12,000 cP at 25C are obtained.
Gel chromatographic analysis indicates approximately the follow-ing composition:
LeA 17,067 -11-0.3 % by weight 1,6-diisocyanatohexane 38.5 % by weight monobiuret 19.5 ~ by weight bis-biuret 12.0 % by weight tris-biuret 57.8 % by weight tetra-biuret 5.0 % by weight penta-biuret 16.9 % by weight unidentified or higher molec-ular weight constituents.
Example 2 Using the same apparatus as in Example 1, 2856 g (17 mol) of 1,6-diisocyanatohexane are placed into a 4-liter flask at 180C and 232 g (2 mol) of 1,6-diaminohexane are distilled into it at 80 Torr over a period of 60 minutes.
The almost completely clear reaction mixture is freed from a small quantity of solid particles by pressure filtration and from excess diisocyanate by thin layer distillation.
A viscous, pale yellow biuret polyisocyanate having an isocyanate content of 20.4% and a viscosity of 73,400 cP at 25C is obtained.
Examrle 3 1288 g (7 2/3 mol) of 1,6-diisocyanatohexane are introduced into a 2-liter reaction flask at 160C and 50 Torr.
The distillation apparatus described in Example 1 is completely immersed in an oil bath which is at a temperature of 220C.
The distillation bridge is also heated to 220C. 38.7 g (1/3 mol) of 1,6-diaminohexane at a temperature of 80C
are introduced dropwise into the distillation flask from a dropping funnel over a period of 30 minutes, the diaminohexane being rapidly gasified on entering the dis~illation flask. Thin layer distillation of the clear LeA 17,067 -12-reaction mixture yields 305 g of a thin liquid consisting of a biuret polyisocyanate having an isocyanate content of 23.8% and a viscosity of 2240 cP at 25C.
Comparison Example I
.
1848 g (11 mol) of 1,6-diisocyanatohexane are introduced into a nitrogen atmosphere at 70C. 116 g tl mol) of 1,6-diaminohexane are added dropwise from a heated dropping ' funnel over a period of about 60 minutes with vigorous ctirring. The pasty reaction mixture obtained is heated to 180C. When ~tirring i9 continued for a further 12 hours at this temperature, the resulting brown reaction mixture still contains considerable proportions of gel-like solids which are difficult to remove by filtration.
Example 4 1512 g (9 mol) of 1,6-diisocyanatohexane are introduced into a 2-liter four-necked flask at 12 mm and heated to mild reflux (approximately 135C). Using the distillation apparatus described in Example 1 (oil bath and bridge heated to 220C), 127.5 g (0.75 mol) of 3-aminomethyl-3,5,5-trimethyl-;20 cyclohexylamine-l ("isophorone diamine") in the form of vapor pass through the inlet tube into the diisocyanate over a period of 50 minutes and immediately react with the diisocyanate to form a clear product. Thin layer distillation yields ` 650 g of a light colored biuret polyisocyanate having an isocyanate content of 23.4% and a viscosity of 18~450 cP at 25C. According to the gas chromatograph, the distillate (990 ` g) contains 0.69~ by weight of 3-isocyanatomethyl-3,5,5-tri-methylcyclohexyl isocyanate-(l).
LeA 17,067 -13-. . . ~ . .
1~77~56 Comparison Example II
1512 g (9 mol) of 1,6-diisocyanatohexane are placed in the reaction vessel at 25C. 127.5 g (0.75 mol) of 3-amino-methyl-3,5,5-trimethyl-cyclohexylamine-(1) are introduced dropwise over a period of 20 minutes. A pasty but easily stirrable reaction mixture is obtained. The polyurea is then heated to cause further reaction. The solid constituents coagulate to a rubbery lump at about 140C so that stirring cannot be continued. The mixture is then heated to 170C
0 for 8 hours without further stirring. By the end of that time, the reaction mixture is to some extent homogeneous.
It changes to a deep yellow in the course of this time.
Example 5 1680 g (10 mol) of 1,6-diisocyanatohexane are intro-duced into a reaction vessel under a light vacuum (600 to 650 Torr) at 160C. 74 g (1 mol) of propylene-1,2-diamine in the form of vapor are then introduced together with a mild stream ; of nitrogen over a period of 90 minutes through a gasification stirrer with stirrer stem heated to 200C. A clear reaction 0 product is obtained and subjected to thin layer distillation.
The yield is 830 g of the pale yellow biuret polyisocyanate having an isocyanate content of 21-7% and a viscosity of 4800 cP at 25C.
Example 6 1512 g (9 mol) of 1,6-diisocyanatohexane are placed in a reaction vessel at 160C and 80 Torr. 43 g (0.377 mol) of 1,4-diaminocyclohexane are then introduced as vapor over a period of 30 minutes as described in Example 3. The LeA 17,067 -14-1077~56 crude product is filtered to remove the very few solid particles contained in it and is then subjected to thin layer distillation. 380 g of a thin liquid, almost colorless, biuret polyisocyanate having an isocyanate content of 24.3 and a viscosity of 2400 cP at 25C are obtained.
Example 7 1512 g (9 mol) of 1,6-diisocyanatohexane are placed in a reaction vessel at 140C and 50 Torr. 158 g (1 mol) of 2,2,4-trimethyl-hexane-1,6-diamine in the form of vapor superheated to 200C are then introduced through a heatable inlet tube with stirring. After treatment in a thin layer evaporator, the clear reaction mixture yields 870 g of a pale yellow biuret polyisocyanate which has an isocyanate content of 21.1~ and a viscosity of 21,700 cP at 25C.
Example 8 1554 g (7 mol) of 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexylisocyanate-(l) are placed in a reaction vessel at 160C and 12mm. 170 g (1 mol) of 3-aminomethyl-3,5,5-trimethylcyclohexylamine-(l) in the form of vapor super-heated to 200C are introduced over a period of 2 hours asdescribed in Example 1. The clear biuret polyisocyanate solution has an isocyanate content of 27.6% and a viscosity of 7300 cP at 25C.
Example 9 :
1512 g (9 mol) of 1,6-diisocyanatohexane are placed in a reaction vessel at 160C and 50 Torr. 61.8g(0.6 mol) of bis-(2-aminoethyl)-amine are introduced in vapor form LeA 17,067 -15-.
:1077956 over a period of 40 minutes in a similar manner to Example 1 After thin layer treatment, the clear reaction mixture yields 620 g of a pale yellow biuret polyisocyanate having an isocyanate content of 28.0% and a viscosity of 10,300 cP at 25C.
Example 10 Thin layer treatment of the clear reaction mixture obtained from 1512 g (9 mol) of 1,6-diisocyanatohexane and 984 g (0.75 mol) of di-(1,2-propylene)-triamine (isomeric mixture) in a similar manner to Example 9 yields 680 g of a pale yellow biuret polyisocyanate having an isocyanate content of 20.1% and a viscosity of 23,000 cP at 25C.
Example 11 When 2520 g (15 mol) of 1,6-diisocyanatohexane and 131 g (1 mol) of bis-(3-aminopropyl)-amine are reacted together and freed from excess diisocyanate in a similar manner to Example 9, a pale yellow biuret polyisocyanate having an isocyanate content of 22% and a viscosity of 12,500 cP at 25C is obtained.
In Examples 9, 10, 11, 1,6-diisocyanatohexane obtained as distillate from thin layer distillation contains no other isocyanate component.
Example 12 1740 g (10 mol) of an isomeric mixture of 80% of 2,4- and 20% of 2,6-tolylenediisocyanate are placed in a reaction vessel at 150C and 80 Torr. 158 g (1 mol) of LeA 17,067 -16-:, 18779S~;
2,2,4-trimethylhexane-1,6-diamine are then introduced through a heatable tube as vapor superheated to 220C in a similar manner to Example 7. A clear yellow biuret-molified poly-isocyanate solution having an isocyanate content of 35.7%
and a viscosity of 200 cP at 25C is obtained.
Comparison Example III
The following comparison example is carried out in three variations (a), (b), and (c) to demonstrate that the preparation of biuret polyisocyanates by the procedure described in Example 16 of US Patent 3 903 126 is hardly a commercially usable process since the adverse phenomena known from German Patent No. 1,770,927 are also observed when the method according to this Example is carried out. Considerable difficulties are encountered, particularly when the process is carried out with large batches because large quantities of insoluble polyureas and cross-linked porducts are formed which, although they can be degraded at temperatures of about 200C, promote the formation of unwanted, heavily colored by-products due to the high thermal stresses on the reaction mixture.
Method (a) (corresponding to Example 16 of US Patent 3 903 126 .
14.5 Parts (0.125 mol) of hexamethylenediamine heated to 70C are added over a period of 20 minutes at about 25C
;25 to 168 parts (1 mol) of hexamethylene-1,6-diisocyanate under a nitrogen atmosphere with stirring. The spontaneous precipitation of the pasty, completely insoluble higher LeA 17,067 -17-1C~77~56 molecular weight ~ diisocyanatopolyureas sets in at once.
The polyureas cannot be observed to dissolve evenly.
To achieve biuretization, which proceeds extremely slowly, the reaction mixture must be stirred at 180C for 12 hours, S during which time the solution acquires a reddish yellow tinge. The reaction mixture (yield about 182 parts by weight) contains pulverulent constituents and gel particles and about 20~ by weight of monomeric hexamethylene diisocyanate. It contains a total of 3.5 parts by weight of higher molecular weight constituents which can only be decomposed very slowly at 200C. When attempts are made to fllter this solution, the filter is blocked by the gel particles. After isolation of the solution by centrifuging and removal of monomers by thin layer distillation, a polyisocyanate mixture containing biuret groupe is obtained in the form of a yellow brown product with a red tinge.
The product has an isocyanate content of 17.1~ and a viscosity of 14,300 cP at 25C. It is un3uitable for the production of lightfast, high gloss lacquer films which can be cross-linked by moisture.
MethOd (b?
The procedure is the same as in method (a) but 10 times the quantity of starting materials are used. The time taken for dropwise addition of hexamethylenediamine is 20 ;;
` 25 minutes. The pasty polyureas cannot be seen to dissolve uniformly. The procedure is otherwise the same as under (a~.
' The reddish yellow brown end product cannot be filtered on account of its substantially higher proportion of pulverulent constituents and gel particles (about 45 parts by weight) LeA 17,067 -18-~077956 than in method (a`. In order to obtain a mixture free from gel, l,he reaction mixture must be centrifuged and then freed from gel constituents by decanting. After removal of monomers by thin layer distillation, the reaction product is deep brown in color.
~NCO: 16.9 n25C: >15~,000 cP n75C: 29,800 cP
Method (c) This is carried out in the same way as method (b) but the rate of addition of hexamethylene diamine is slowed down by a factor of 10, i.e. hexamethylenediamine is added dropwise over a period of 200 minutes. The procedure is otherwise the same as in (a) and ~b). This method (c) again requires extremely long reaction times of at least 12 hours.
The same filtration difficulties arise as in method (b).
The end product purified by thin layer distillation is not suitable for theproduction of lightfast, high gloss two-' component lacquers by reaction with hydroxyl polyesters.
n75C = 29,100 cP.
` '.
Example 13 This example describes variations (a) and (b) of theprocess according to the invention, according to which hexamethylenediamine is drawn as superheated vapor (about 190C) into hexamethylenediisocyanate (1008 parts by weight =
6 mol) which is at a temperature of 165C and a vacuum of about 60 Torr through an inlet tube whose upper part (i.e. up to the depth of immersio~ is heated to 190C. The superheated vapor is produced by evaporating 58 parts by weight of hexamethylenediamine (0.5 mol) at about 115 to 120C in LeA 17,067 -19-1~'77956 a small flask (nitrogen capillary). Superheating of the vapors to about l90~C is carried out in a 20 cm long tube which is heated to about 210C. The reaction is carried out in a ground glass beaker to which a vigorously cooled reflux condenser and vacuum attachment are connected.
The heatable inlet tube is immersed to a depth of about 6 cm. No formation of difficulty soluble ~ diisocyanato polyureas can be observed in the reaction vessel during the whole time of addition of hexamethylenediamine vapor, which is completed in about 90 minutes (variation (a) ). The extremely low concentrations of ~,~-diisocyanatoureas and diisocyanatopolyureas formed are converted practically in statu nascendi at the chosen temperature of 165~C to biuret polyisocyanates by equilibration reactions. The completely gel-free reaction mixture can be immediately freed from monomeric hexamethylene diisocyanate by thin layer distillation at 170C and 1 Torr without prior cooling. Yield: 415 parts by weight, % NC~ 21.9, n25oc 11,200 cP, yellow color. In this experiment, the molar ratio of hexamethylenediamine to hexamethylenediisocyanate is 12 : 1.
,;
The product of the process is eminently suitable both for the production of lightfast one-component lacquers which can be cross-linked by moisture and for the production of two-component lacquers with hydroxyl polyesters with elastic, high gloss films being obtained.
Variation (b) is carried out in exactly the same way as described under (a) except that the rate of addition of superheated hexamethylenediamine vapor is slowed down by a factor of about 2 (= 3 hours). When the reaction mixture LeA 17,067 -20-~ ~"
~77956 ' has been worked up, the viscosity of the biuret polyisocyanatemixture at 25C is about 8500 cP. The viscosity of the end products can, therefore, be reduced without any significant damage to the color by reducing the rate of addition of super-heated hexamethylenediamine vapors and doubling the reactiontime.
ExamPle 14 This Example describes two interesting variations of . the process according to which light yellow to colorless biuret polyisocyanates differing widely in their viscosities can be produced even at normal pressure by diluting the superheated hexamethylenediamine vapors with a stream of ~ nitrogen so that from about 40 to 80 parts by volume of ,. nitrogen are introduced for each part by volume of hexamethylene- -:,. 15 diamine va~or introduced into the hexamethylenediisocyanate which is preheated to 158C. The small quantities of hexamethylenediisocyanate vapors escaping from the reflux condenser are condensed in a cooling trap.
. Variation (a) . .
` 20 Molar ratio hexamethylenediisocyanate/hexamethylene-;~ diamine = 18:1.
.~ :
1512 Parts by weight of hexamethylenediisocyanate (9 mol) are heated to 158C and 58 parts by weight (0.5 mol) of superheated hexamethylenediamine vapor are introduced to-.- 25 gether with nitrogen into the reaction vessel from Example 13 through an inlet tube heated to 190C. The nitrogen is introduced into the hexamethylenediamine evaporator which is heated to a temperature of about 115C. The quantity of nitrogen is adjusted by a gas meter so that the volumetric LeA 17,067 -21-1~31779S6 ratio of nitrogen to hexamethylenediamine in the inlet tube for superheated vapor is about 40 : 1. The biuret polyisocyanate solution is ready to be worked up as in Example 13 after only two hours.
The yield is 408 parts by weight, % NCO 21.9, n25C 5800 cP.
15 Parts by weight of hexamethylenediisocyanate are found to be condensed in the cooling trap attached to the reflux condenser.
Variation (b) Molar ratio of hexamethylenediisocyanate to hexa-methylenediamine = 18:1.
The procedure is the same as in Variation (a) of this example except that the volumetric ratio of nitrogen to hexamethylenediamine is adjusted to about 80 : l. ;
A pale yellow solution is obtained after a reaction time of 2 hours and subjected to thin layer distillation.
The yield is 407 parts by wieght, % NCO: 22.3.
The viscosity of this biuret polyisocyanate mixture at 25C is only 4500 cP. The product obtained by diluting the superheated vapor mixture has therefore a lower viscosity by about 22% than the product obtained in Variation (a).
Variation (c) Molar ratio hexametbylenediisocyanate/hexamethylene-diamine = 24:1.
Volumetric ratio nitrogen/hexamethylenediamine = 80:1.
LeA 17,067 -22-The reaction is carried out using 2016 parts by weight of hexamethylenediisocyanate and 58 parts by weight ~0.5 mol) of superheated hexamethylenediamine vapors in a
Other suitable polyamines for the process according to the invention include bis-(aminoalkyl)-amines preferably having a total of from 4 to 12 carbon atoms, e.g. bis-(2-aminoethyl)-amine, bis(3-aminopropyl)-amine, bis-(4-amino-butyl)-amine, bis-(6-aminohexyl)-amine and isomeric mixtures of dipropylene triamine and dibutylene triamine.
The preferred diamines are tetramethylene diamine, hexamethylenediamine and 1,2-bis-(aminomethyl)-cyclobutane, particularly hexamethylenediamine.
Suitable polysiocyanates for the process according to LeA 17,067 -4-1~779S6 the invention are in particular diisocyanates of the formula Q(NC0)2 in which Q represents an aromatic hydrocarbon group with 6 to 15 carbon atoms; an araliphatic hydrocarbon group with 8 to 10, preferably 8, carbon atoms; an aliphatic hydro-carbon group with 4 to 12 carbon atoms or a cycloaliphatic hydrocarbon groupwit~ 4 to 15 carbon atoms. Examples include tolylene-2,4- and -2,6-diisocyanates and their isomeric mixtures; 4,4'- and 2,4'-diphenylmethane diisocyanate and xylylene diisocyanate. Particularly suitable are the aliphatic and cycloaliphatic diisocyanates such as 1,4-diisocyanatobutane; 1,6-diisocyanatohexane; 2,4,4-trimethyl-hexane-1,6-diisocyanate; l,ll-diisocyanatoundecane; 3-i90-cyanatomethyl-3,5,5-trimethyl-cyclohexylisocyanate-(1);
1,4 -cyclohexane diisocyanate; 4~4l-dicyclohexylmethane diisocyanate and 1,2-bis-(isocyanatomethyl)-cyclobutane.
Hexamethylene diisocyanate is particularly preferred.
Products which are particularly light in color are obtained by the process according to the invention if the diisocyanate used as a starting material is preheated for several hours, suitably about 6 to 10 hours, at about 120 to 195C, preferably about 160 to 180C, andthen distilled.
The process according to the invention is preferably carried out by introducing the diisocyanate into the reaction vessel at an excess of about 5 to 100 and preferably 7 to 25 isocyanate groups to one primary amino group at elevated temperature with vigorous stirring and adding the polyamine in gaseous form, optionally at reduced pressure, and if desired together with a stream of inert gas. In cases where the polyamine has a lower boiling point than the diisocyanate, LeA 17,067 -5-11~77956 the polyamine vapor can be introduced through a simple inlet tube dipping into the diisocyanate. A suitable evaporator for the polyamine is attached to the inlet tube and a vacuum must be applied to keep the reactor at a pressure at which the boiling point of the polyamine is about 10 to 80C below the temperature of the diisocyanate in the reaction vessel because otherwise the polyamine will partly condense in the inlet tube and come into contact with the diisocyanate as a liquid, hence leading to the formation of lC solid polyureas and blockage of ~he inlet tube. If, especially in the case of large reaction batches, the column of liquid above the outlet point of the polyamine vapor is so high that its hydrostatic pressure raises the boiling point of the polyamine to a temperature close to the temperature of the dii~ocyanate, it is preferable to use a hollow stirrer (gasification stirrer) for introducing the polyamine vapor. This stirrer will exert additional suction and ensure uniform distribution of the polyamine vapor in the diisocyanate.
If the boiling point of the polyamine is above that of the diisocyanate, the inlet tube for introducing the poly-amine vapor must be heatable to temperatures above that of the diisocyanate in the vessel. In that case, the inlet tube is preferably heat insulated on the outside to prevent excessive heat exchange with the diisocyanate.
When carrying out the process on a commercial scale, the inlet tube may be replaced not only by a hollow stirrer as already mentioned above, but also by an annular nozzle, which may be one which closes mechanically.
LeA 17,067 -6-There are two methods, for example, by which the rate of introduction of polyamine vapor may be controlled. In the fi~st of these, the total quantity of polyamine is introduced into the evaporator and the rate of distillation i5 controlled by the supply of heat. In the second, the rate of introduction of polyamine into the overheated evaporator is controlled.
It is clear that the process may also be carried out continuously. In that case, a quantity of diisocyanate suitable for the rate of addition of polyamine is introduced into the reactor and an appropriate proportion of the reaction mixture is continuously removed, if desired through - an overflow.
The temperature of the diisocyanate in the reaction vessel is chosen so that the ,~-diisocyanato- or bis- or tris-urea compounds originally formed from the polyamine and diisocyanate rapidly react with addition of isocyanate groups to the urea groups to form biuret compounds in order to avoid precipitation of the difficulty soluble and in most cases high melting urea compounds. It has in practice been found that temperatures above 100C are required for this purpose and temperatures above 120C are preferable.
The upper limit to the temperature range is given by the ;, tendency to discoloration and side reactions and is a maximum of 250C. The preferred temperature range is from about 130C to 200C, particularly from about 140C to 180C.
In a particular embodiment of the process according to the invention by which exceptionally low viscosity biuret polyisocyanates can be prepared, the gaseous polyamine is introduced into the diisocyanate together with a gas - LeA 17,067 -7-1~17795~
which is inert with the reactants and with the end products under the reaction conditions. Nitrogen, for example, is a suitable carrier gas for this purpose. In this embodiment of the process, the volumetric ratio of carrier gas to polyamine vapor is generally between about 2:1 and lO0:1, preferably between about 40:1 and 80:1.
The polyamine vapor can, of course, be obtained not only by evporating a liquid polyamine but also by sublimation of a solid polyamine or simply by passing a vigorous stream of inert gas through a liquid polyamine, a mixture of polyamine vapor and polyamine aerosol being obtained in the last mentioned case.
When the proce~s according to the invention is carried out under the given temperature conditions, the reaction to ~ 15 the biuret polyisocyanate is spontaneous so that virtually no reheating is required once all the polyamine has been added. At the same time, continuous decomposition and re-formation of biuret groups equilibrates the reaction mixture to a complex mixture of mono-, bis- and tris-biurets and higher biurets whose molar distribution finally depends only on the selected isocyanate/amine ratio. Because of these regrouping reactions, a proportion o~ the polyamine, depending on the selected isocyanate excess, is converted into the corresponding polyisocyanate. A biuret polyi~o-cyanate mixture which has been prepared by the processaccording to the invention, for example from hexamethylene diisocyanate and 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, contains, after removal of unreacted excess of hexamethylene-diisocyanate, will contain 3,3'-dimethyl-4,4'diisocyanatodi-LeA 17,067 -8-cyclohexylmethane corresponding to the diamine used as starting material, the quantity depending on the isocyanate/amino ratio.
If, for example, 1,4-diaminocyclohexane is used for biuretizing, e.g. 1,6-diisocyanatohexane, then the reaction mixture will contain 1,4-diisocyanatocyclohexane.
If the biuret polyisocyanate is then freed from excess diisocyanate, the distillate obtained is a diisocyanate mixture which must be used again if the process is carried out on a commercial scale. This necessitates separation of the mixture by distillation because if the mixture were used as such it would require a prolonged starting period, in the ca~e of continuous production, or several batches, in the case of discontinuous production, before a product of constant composition could be obtained. For these reasons, it is preferred to use combinations of diisocyanates and diamines of similar constitution or to carry out biuretization of diisocyanates with amines which are converted into polyisocyanates with a very low vapor pressure. The bis-(aminoalkyl)-amines ~20 already mentioned above, for example, are amines which satisfy this condition ~ince, as a result of the equilibration reaction mentioned above, the most volatile polyisocyanate components to which they could give rise are the triisocyanates with one urea group which corxespond to the polyamine and which are only difficulty volatile, for example, in comparison with hexamethylene diisocyanate.
The biuret polyisocyanates prepared by the process according to the invention, in particular from aliphatic LeA 17,067 -9-.
~77956 starti.ng compounds, are valuable raw materials for the production of high quality lacquers which are weather resistant and stable to light. For use in this field, the reaction mixtures are normally freed from excess diisocyanate in order to obtain a polyisocyanate with a low vapor pressure.
This can be achieved by extraction or by distillation.
Distillation may suitably be carried out with a thin layer evaporator.
~ .
' ,.~
:
LeA 17,067 -10-iO77956 EXAMPLES
Example 1 4620 g (27.5 mol) of 1,6-diisocyanatohexane are introduced at 160C with stirring into a 6-liter four-S necked flask equipped with reflux condenser, contactthermometer and stirrer. A glass tube is mounted on the remaining neck of the flask and arranged to dip about 8 cm below the level of the liquid. At the lower end, the tube is bent sideways in the direction of rotation of the stirrer and drawn out to a tip of about 2 mm in diameter. A ground glass sleeve into which the bridge of a 500 ml distillation apparatus opens is attached to the upper end. The bridge is heated to 200C. The distillation apparatus is charged with 290 g (2.5 mol) of 1,6-diaminohexane heated to 60C, into which a boiling capillary dips. A vacuum of S0 Torr is produced by means of the reflux condenser of the four-necked flask. A gentle stream of nitrogen is passed through ~ the capillary. The distillation flask is then placed into an ; oil bath which is at a temperature of 180C. The diamine begins to distill off at a reaction temperature of from 125C
to 135C. The overheating vapors in the bridge are immediately absorbed by the diisocyanate. The speed of distillation i8 regulated by the depth of immersion of the distillation flask in the oil bath so that the reaction is completed in about 2 hours. The clear reaction mixture is then subjected to thin layer distillation at 175C and 1 Torr. 2150 g of a pale yellow biuret polyisocyanate having an isocyanate content of 22.3~ and a vi~cosity of 12,000 cP at 25C are obtained.
Gel chromatographic analysis indicates approximately the follow-ing composition:
LeA 17,067 -11-0.3 % by weight 1,6-diisocyanatohexane 38.5 % by weight monobiuret 19.5 ~ by weight bis-biuret 12.0 % by weight tris-biuret 57.8 % by weight tetra-biuret 5.0 % by weight penta-biuret 16.9 % by weight unidentified or higher molec-ular weight constituents.
Example 2 Using the same apparatus as in Example 1, 2856 g (17 mol) of 1,6-diisocyanatohexane are placed into a 4-liter flask at 180C and 232 g (2 mol) of 1,6-diaminohexane are distilled into it at 80 Torr over a period of 60 minutes.
The almost completely clear reaction mixture is freed from a small quantity of solid particles by pressure filtration and from excess diisocyanate by thin layer distillation.
A viscous, pale yellow biuret polyisocyanate having an isocyanate content of 20.4% and a viscosity of 73,400 cP at 25C is obtained.
Examrle 3 1288 g (7 2/3 mol) of 1,6-diisocyanatohexane are introduced into a 2-liter reaction flask at 160C and 50 Torr.
The distillation apparatus described in Example 1 is completely immersed in an oil bath which is at a temperature of 220C.
The distillation bridge is also heated to 220C. 38.7 g (1/3 mol) of 1,6-diaminohexane at a temperature of 80C
are introduced dropwise into the distillation flask from a dropping funnel over a period of 30 minutes, the diaminohexane being rapidly gasified on entering the dis~illation flask. Thin layer distillation of the clear LeA 17,067 -12-reaction mixture yields 305 g of a thin liquid consisting of a biuret polyisocyanate having an isocyanate content of 23.8% and a viscosity of 2240 cP at 25C.
Comparison Example I
.
1848 g (11 mol) of 1,6-diisocyanatohexane are introduced into a nitrogen atmosphere at 70C. 116 g tl mol) of 1,6-diaminohexane are added dropwise from a heated dropping ' funnel over a period of about 60 minutes with vigorous ctirring. The pasty reaction mixture obtained is heated to 180C. When ~tirring i9 continued for a further 12 hours at this temperature, the resulting brown reaction mixture still contains considerable proportions of gel-like solids which are difficult to remove by filtration.
Example 4 1512 g (9 mol) of 1,6-diisocyanatohexane are introduced into a 2-liter four-necked flask at 12 mm and heated to mild reflux (approximately 135C). Using the distillation apparatus described in Example 1 (oil bath and bridge heated to 220C), 127.5 g (0.75 mol) of 3-aminomethyl-3,5,5-trimethyl-;20 cyclohexylamine-l ("isophorone diamine") in the form of vapor pass through the inlet tube into the diisocyanate over a period of 50 minutes and immediately react with the diisocyanate to form a clear product. Thin layer distillation yields ` 650 g of a light colored biuret polyisocyanate having an isocyanate content of 23.4% and a viscosity of 18~450 cP at 25C. According to the gas chromatograph, the distillate (990 ` g) contains 0.69~ by weight of 3-isocyanatomethyl-3,5,5-tri-methylcyclohexyl isocyanate-(l).
LeA 17,067 -13-. . . ~ . .
1~77~56 Comparison Example II
1512 g (9 mol) of 1,6-diisocyanatohexane are placed in the reaction vessel at 25C. 127.5 g (0.75 mol) of 3-amino-methyl-3,5,5-trimethyl-cyclohexylamine-(1) are introduced dropwise over a period of 20 minutes. A pasty but easily stirrable reaction mixture is obtained. The polyurea is then heated to cause further reaction. The solid constituents coagulate to a rubbery lump at about 140C so that stirring cannot be continued. The mixture is then heated to 170C
0 for 8 hours without further stirring. By the end of that time, the reaction mixture is to some extent homogeneous.
It changes to a deep yellow in the course of this time.
Example 5 1680 g (10 mol) of 1,6-diisocyanatohexane are intro-duced into a reaction vessel under a light vacuum (600 to 650 Torr) at 160C. 74 g (1 mol) of propylene-1,2-diamine in the form of vapor are then introduced together with a mild stream ; of nitrogen over a period of 90 minutes through a gasification stirrer with stirrer stem heated to 200C. A clear reaction 0 product is obtained and subjected to thin layer distillation.
The yield is 830 g of the pale yellow biuret polyisocyanate having an isocyanate content of 21-7% and a viscosity of 4800 cP at 25C.
Example 6 1512 g (9 mol) of 1,6-diisocyanatohexane are placed in a reaction vessel at 160C and 80 Torr. 43 g (0.377 mol) of 1,4-diaminocyclohexane are then introduced as vapor over a period of 30 minutes as described in Example 3. The LeA 17,067 -14-1077~56 crude product is filtered to remove the very few solid particles contained in it and is then subjected to thin layer distillation. 380 g of a thin liquid, almost colorless, biuret polyisocyanate having an isocyanate content of 24.3 and a viscosity of 2400 cP at 25C are obtained.
Example 7 1512 g (9 mol) of 1,6-diisocyanatohexane are placed in a reaction vessel at 140C and 50 Torr. 158 g (1 mol) of 2,2,4-trimethyl-hexane-1,6-diamine in the form of vapor superheated to 200C are then introduced through a heatable inlet tube with stirring. After treatment in a thin layer evaporator, the clear reaction mixture yields 870 g of a pale yellow biuret polyisocyanate which has an isocyanate content of 21.1~ and a viscosity of 21,700 cP at 25C.
Example 8 1554 g (7 mol) of 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexylisocyanate-(l) are placed in a reaction vessel at 160C and 12mm. 170 g (1 mol) of 3-aminomethyl-3,5,5-trimethylcyclohexylamine-(l) in the form of vapor super-heated to 200C are introduced over a period of 2 hours asdescribed in Example 1. The clear biuret polyisocyanate solution has an isocyanate content of 27.6% and a viscosity of 7300 cP at 25C.
Example 9 :
1512 g (9 mol) of 1,6-diisocyanatohexane are placed in a reaction vessel at 160C and 50 Torr. 61.8g(0.6 mol) of bis-(2-aminoethyl)-amine are introduced in vapor form LeA 17,067 -15-.
:1077956 over a period of 40 minutes in a similar manner to Example 1 After thin layer treatment, the clear reaction mixture yields 620 g of a pale yellow biuret polyisocyanate having an isocyanate content of 28.0% and a viscosity of 10,300 cP at 25C.
Example 10 Thin layer treatment of the clear reaction mixture obtained from 1512 g (9 mol) of 1,6-diisocyanatohexane and 984 g (0.75 mol) of di-(1,2-propylene)-triamine (isomeric mixture) in a similar manner to Example 9 yields 680 g of a pale yellow biuret polyisocyanate having an isocyanate content of 20.1% and a viscosity of 23,000 cP at 25C.
Example 11 When 2520 g (15 mol) of 1,6-diisocyanatohexane and 131 g (1 mol) of bis-(3-aminopropyl)-amine are reacted together and freed from excess diisocyanate in a similar manner to Example 9, a pale yellow biuret polyisocyanate having an isocyanate content of 22% and a viscosity of 12,500 cP at 25C is obtained.
In Examples 9, 10, 11, 1,6-diisocyanatohexane obtained as distillate from thin layer distillation contains no other isocyanate component.
Example 12 1740 g (10 mol) of an isomeric mixture of 80% of 2,4- and 20% of 2,6-tolylenediisocyanate are placed in a reaction vessel at 150C and 80 Torr. 158 g (1 mol) of LeA 17,067 -16-:, 18779S~;
2,2,4-trimethylhexane-1,6-diamine are then introduced through a heatable tube as vapor superheated to 220C in a similar manner to Example 7. A clear yellow biuret-molified poly-isocyanate solution having an isocyanate content of 35.7%
and a viscosity of 200 cP at 25C is obtained.
Comparison Example III
The following comparison example is carried out in three variations (a), (b), and (c) to demonstrate that the preparation of biuret polyisocyanates by the procedure described in Example 16 of US Patent 3 903 126 is hardly a commercially usable process since the adverse phenomena known from German Patent No. 1,770,927 are also observed when the method according to this Example is carried out. Considerable difficulties are encountered, particularly when the process is carried out with large batches because large quantities of insoluble polyureas and cross-linked porducts are formed which, although they can be degraded at temperatures of about 200C, promote the formation of unwanted, heavily colored by-products due to the high thermal stresses on the reaction mixture.
Method (a) (corresponding to Example 16 of US Patent 3 903 126 .
14.5 Parts (0.125 mol) of hexamethylenediamine heated to 70C are added over a period of 20 minutes at about 25C
;25 to 168 parts (1 mol) of hexamethylene-1,6-diisocyanate under a nitrogen atmosphere with stirring. The spontaneous precipitation of the pasty, completely insoluble higher LeA 17,067 -17-1C~77~56 molecular weight ~ diisocyanatopolyureas sets in at once.
The polyureas cannot be observed to dissolve evenly.
To achieve biuretization, which proceeds extremely slowly, the reaction mixture must be stirred at 180C for 12 hours, S during which time the solution acquires a reddish yellow tinge. The reaction mixture (yield about 182 parts by weight) contains pulverulent constituents and gel particles and about 20~ by weight of monomeric hexamethylene diisocyanate. It contains a total of 3.5 parts by weight of higher molecular weight constituents which can only be decomposed very slowly at 200C. When attempts are made to fllter this solution, the filter is blocked by the gel particles. After isolation of the solution by centrifuging and removal of monomers by thin layer distillation, a polyisocyanate mixture containing biuret groupe is obtained in the form of a yellow brown product with a red tinge.
The product has an isocyanate content of 17.1~ and a viscosity of 14,300 cP at 25C. It is un3uitable for the production of lightfast, high gloss lacquer films which can be cross-linked by moisture.
MethOd (b?
The procedure is the same as in method (a) but 10 times the quantity of starting materials are used. The time taken for dropwise addition of hexamethylenediamine is 20 ;;
` 25 minutes. The pasty polyureas cannot be seen to dissolve uniformly. The procedure is otherwise the same as under (a~.
' The reddish yellow brown end product cannot be filtered on account of its substantially higher proportion of pulverulent constituents and gel particles (about 45 parts by weight) LeA 17,067 -18-~077956 than in method (a`. In order to obtain a mixture free from gel, l,he reaction mixture must be centrifuged and then freed from gel constituents by decanting. After removal of monomers by thin layer distillation, the reaction product is deep brown in color.
~NCO: 16.9 n25C: >15~,000 cP n75C: 29,800 cP
Method (c) This is carried out in the same way as method (b) but the rate of addition of hexamethylene diamine is slowed down by a factor of 10, i.e. hexamethylenediamine is added dropwise over a period of 200 minutes. The procedure is otherwise the same as in (a) and ~b). This method (c) again requires extremely long reaction times of at least 12 hours.
The same filtration difficulties arise as in method (b).
The end product purified by thin layer distillation is not suitable for theproduction of lightfast, high gloss two-' component lacquers by reaction with hydroxyl polyesters.
n75C = 29,100 cP.
` '.
Example 13 This example describes variations (a) and (b) of theprocess according to the invention, according to which hexamethylenediamine is drawn as superheated vapor (about 190C) into hexamethylenediisocyanate (1008 parts by weight =
6 mol) which is at a temperature of 165C and a vacuum of about 60 Torr through an inlet tube whose upper part (i.e. up to the depth of immersio~ is heated to 190C. The superheated vapor is produced by evaporating 58 parts by weight of hexamethylenediamine (0.5 mol) at about 115 to 120C in LeA 17,067 -19-1~'77956 a small flask (nitrogen capillary). Superheating of the vapors to about l90~C is carried out in a 20 cm long tube which is heated to about 210C. The reaction is carried out in a ground glass beaker to which a vigorously cooled reflux condenser and vacuum attachment are connected.
The heatable inlet tube is immersed to a depth of about 6 cm. No formation of difficulty soluble ~ diisocyanato polyureas can be observed in the reaction vessel during the whole time of addition of hexamethylenediamine vapor, which is completed in about 90 minutes (variation (a) ). The extremely low concentrations of ~,~-diisocyanatoureas and diisocyanatopolyureas formed are converted practically in statu nascendi at the chosen temperature of 165~C to biuret polyisocyanates by equilibration reactions. The completely gel-free reaction mixture can be immediately freed from monomeric hexamethylene diisocyanate by thin layer distillation at 170C and 1 Torr without prior cooling. Yield: 415 parts by weight, % NC~ 21.9, n25oc 11,200 cP, yellow color. In this experiment, the molar ratio of hexamethylenediamine to hexamethylenediisocyanate is 12 : 1.
,;
The product of the process is eminently suitable both for the production of lightfast one-component lacquers which can be cross-linked by moisture and for the production of two-component lacquers with hydroxyl polyesters with elastic, high gloss films being obtained.
Variation (b) is carried out in exactly the same way as described under (a) except that the rate of addition of superheated hexamethylenediamine vapor is slowed down by a factor of about 2 (= 3 hours). When the reaction mixture LeA 17,067 -20-~ ~"
~77956 ' has been worked up, the viscosity of the biuret polyisocyanatemixture at 25C is about 8500 cP. The viscosity of the end products can, therefore, be reduced without any significant damage to the color by reducing the rate of addition of super-heated hexamethylenediamine vapors and doubling the reactiontime.
ExamPle 14 This Example describes two interesting variations of . the process according to which light yellow to colorless biuret polyisocyanates differing widely in their viscosities can be produced even at normal pressure by diluting the superheated hexamethylenediamine vapors with a stream of ~ nitrogen so that from about 40 to 80 parts by volume of ,. nitrogen are introduced for each part by volume of hexamethylene- -:,. 15 diamine va~or introduced into the hexamethylenediisocyanate which is preheated to 158C. The small quantities of hexamethylenediisocyanate vapors escaping from the reflux condenser are condensed in a cooling trap.
. Variation (a) . .
` 20 Molar ratio hexamethylenediisocyanate/hexamethylene-;~ diamine = 18:1.
.~ :
1512 Parts by weight of hexamethylenediisocyanate (9 mol) are heated to 158C and 58 parts by weight (0.5 mol) of superheated hexamethylenediamine vapor are introduced to-.- 25 gether with nitrogen into the reaction vessel from Example 13 through an inlet tube heated to 190C. The nitrogen is introduced into the hexamethylenediamine evaporator which is heated to a temperature of about 115C. The quantity of nitrogen is adjusted by a gas meter so that the volumetric LeA 17,067 -21-1~31779S6 ratio of nitrogen to hexamethylenediamine in the inlet tube for superheated vapor is about 40 : 1. The biuret polyisocyanate solution is ready to be worked up as in Example 13 after only two hours.
The yield is 408 parts by weight, % NCO 21.9, n25C 5800 cP.
15 Parts by weight of hexamethylenediisocyanate are found to be condensed in the cooling trap attached to the reflux condenser.
Variation (b) Molar ratio of hexamethylenediisocyanate to hexa-methylenediamine = 18:1.
The procedure is the same as in Variation (a) of this example except that the volumetric ratio of nitrogen to hexamethylenediamine is adjusted to about 80 : l. ;
A pale yellow solution is obtained after a reaction time of 2 hours and subjected to thin layer distillation.
The yield is 407 parts by wieght, % NCO: 22.3.
The viscosity of this biuret polyisocyanate mixture at 25C is only 4500 cP. The product obtained by diluting the superheated vapor mixture has therefore a lower viscosity by about 22% than the product obtained in Variation (a).
Variation (c) Molar ratio hexametbylenediisocyanate/hexamethylene-diamine = 24:1.
Volumetric ratio nitrogen/hexamethylenediamine = 80:1.
LeA 17,067 -22-The reaction is carried out using 2016 parts by weight of hexamethylenediisocyanate and 58 parts by weight ~0.5 mol) of superheated hexamethylenediamine vapors in a
3-liter beaker equipped with stirrer and heated inlet tube $ (see Example 13).
The yield after working up and thin layer distillation is 414 parts by weight of yellow biuret polyisocyanate, viscosity 3200 cP at 25C.
~his low viscosity biuret polyisocyanate is very suitable for the production of solvent-free or low solvent one-component and two-component lacquers. The '~ above mentioned variations (a) to (c) of the process may be carried out continuously by freeing the nitrogen leaving the apparatus from small quantities of hexamethylenediisocyanate in a cooling tower and returning it as propellent gas to the hexamethylenediamine evaporator by a gas pressure pump.
., Example 15 This example describes the preparation of an almost colorless biuret polyisocyanate from hexamethylenediisocyanate and hexamethylenediamine used in a molar ratio of 8 : 1 and nitrogen used in a molar ratio to hexamethylene-.~ .
: .
LeA 17,067 -23-~77956 diamine of about 40:], employing exactly the same procedure as described in Example 14, variation (a). A commerical hexamethylenediamine is used which has previously been heated to 180C for B hours to destroy unknown impurities and - 5 catalytically active compounds. HexamethylenediiSocyanate is then purified by distillation. 672 Parts byweight (4 mol) of the distillate and 58 parts by weight of hexamethylene-diamine (0.5 mol) are used. The procedure is otherwise the same as in Example 14, variation (a). The reaction vessel is a 1 liter ground glass beaker.
After thin layer distillation, an almost water-clear biuret polyisocyanate mixture is obtained in a yield of ` 416 partsbyweight, % NCO = 21.5. The product of the process has a viscosity at 25C of 24,800 cP.
Example 16 The procedure is the same as indicated in Example 14 but using the following compounds as diisocyanates and diamines and carrying out the reaction in a 500 cc stirrer flask:
a) Tetramethylenediisocyanate (140 parts by weight ll mol) ) and 11 parts by weight (0.125 mol) of tetramethylene-diamine, molar ratio tetramethylenediisocyanate : tetramethylene-diamine a 8:1.
b) 1,2-Diisocyanatomethyl cyclobutane (166 parts by ~`
weight (1 mol) ) and 14.2 parts by weight of 1,2-bis-amino-methyl cyclobutane (0.125 mol) in a molar ratio of 1,2-diisocyanatomethyl cyclobutane : 1,2-bis-aminomethyl cyclobutane = 8 : 1.
LeA 17,067 -24-~(~7795~;
c) Cycloaliphatic diisocyanates consisting of an isomeric mixture of about 70% by weight of ~ NCO
~.
NCO
and 30% by weight of OCN ~ NCO
(].80 parts by weight = 1 mol) and 15.9 parts by weight (0.125 mol) of a cycloaliphatic diamine consisting of about 70% by weight of CH
L0 and 30% by weight of ; 2 ~ 2 . ~ ,~.
The molar ratio o~ cycloaliphatic diisocyanate isomers to cycloaliphatic diamine isomers used is 8 : 1.
The temperatures employed, the rate of addition iL5 of superheated diamine/nitrogen vapor~ and the reaction ~ LeA 17,067 -25-.
1~779S6 times are exactly the same as in Example 14, variation (a).
Gel-free solutions of biuret polyisocyanates in excess monomeric diisocyanates are obtained in the following yields:
a) 150 parts by weight; isocyanate content of gel-free biuret polyisocyanate solution in monomeric diisocyanate:
: 41.5%
;, b) 179 parts by weight; isocyanate content of gel-free biuret polyisocyanate solution in monomeric diisocyanate:
.0 36.6%.
c) lg5 parts by weight; isocyanate content of gel-free biuret polyisocyanate ~olution in monomeric diisocyanate:
31.5%.
Although the invention has been described in detail for the purpose of illustration, it is to be understood that ~uch detail is solely for that purpose and that variations can be made therein by those skilled in ~he art without de-parting from the spirit and scope of the invention except as it may be limited by the claims.
'.~
; :
: .
.,'~ ' ';
LeA 17,067 -26-
The yield after working up and thin layer distillation is 414 parts by weight of yellow biuret polyisocyanate, viscosity 3200 cP at 25C.
~his low viscosity biuret polyisocyanate is very suitable for the production of solvent-free or low solvent one-component and two-component lacquers. The '~ above mentioned variations (a) to (c) of the process may be carried out continuously by freeing the nitrogen leaving the apparatus from small quantities of hexamethylenediisocyanate in a cooling tower and returning it as propellent gas to the hexamethylenediamine evaporator by a gas pressure pump.
., Example 15 This example describes the preparation of an almost colorless biuret polyisocyanate from hexamethylenediisocyanate and hexamethylenediamine used in a molar ratio of 8 : 1 and nitrogen used in a molar ratio to hexamethylene-.~ .
: .
LeA 17,067 -23-~77956 diamine of about 40:], employing exactly the same procedure as described in Example 14, variation (a). A commerical hexamethylenediamine is used which has previously been heated to 180C for B hours to destroy unknown impurities and - 5 catalytically active compounds. HexamethylenediiSocyanate is then purified by distillation. 672 Parts byweight (4 mol) of the distillate and 58 parts by weight of hexamethylene-diamine (0.5 mol) are used. The procedure is otherwise the same as in Example 14, variation (a). The reaction vessel is a 1 liter ground glass beaker.
After thin layer distillation, an almost water-clear biuret polyisocyanate mixture is obtained in a yield of ` 416 partsbyweight, % NCO = 21.5. The product of the process has a viscosity at 25C of 24,800 cP.
Example 16 The procedure is the same as indicated in Example 14 but using the following compounds as diisocyanates and diamines and carrying out the reaction in a 500 cc stirrer flask:
a) Tetramethylenediisocyanate (140 parts by weight ll mol) ) and 11 parts by weight (0.125 mol) of tetramethylene-diamine, molar ratio tetramethylenediisocyanate : tetramethylene-diamine a 8:1.
b) 1,2-Diisocyanatomethyl cyclobutane (166 parts by ~`
weight (1 mol) ) and 14.2 parts by weight of 1,2-bis-amino-methyl cyclobutane (0.125 mol) in a molar ratio of 1,2-diisocyanatomethyl cyclobutane : 1,2-bis-aminomethyl cyclobutane = 8 : 1.
LeA 17,067 -24-~(~7795~;
c) Cycloaliphatic diisocyanates consisting of an isomeric mixture of about 70% by weight of ~ NCO
~.
NCO
and 30% by weight of OCN ~ NCO
(].80 parts by weight = 1 mol) and 15.9 parts by weight (0.125 mol) of a cycloaliphatic diamine consisting of about 70% by weight of CH
L0 and 30% by weight of ; 2 ~ 2 . ~ ,~.
The molar ratio o~ cycloaliphatic diisocyanate isomers to cycloaliphatic diamine isomers used is 8 : 1.
The temperatures employed, the rate of addition iL5 of superheated diamine/nitrogen vapor~ and the reaction ~ LeA 17,067 -25-.
1~779S6 times are exactly the same as in Example 14, variation (a).
Gel-free solutions of biuret polyisocyanates in excess monomeric diisocyanates are obtained in the following yields:
a) 150 parts by weight; isocyanate content of gel-free biuret polyisocyanate solution in monomeric diisocyanate:
: 41.5%
;, b) 179 parts by weight; isocyanate content of gel-free biuret polyisocyanate solution in monomeric diisocyanate:
.0 36.6%.
c) lg5 parts by weight; isocyanate content of gel-free biuret polyisocyanate ~olution in monomeric diisocyanate:
31.5%.
Although the invention has been described in detail for the purpose of illustration, it is to be understood that ~uch detail is solely for that purpose and that variations can be made therein by those skilled in ~he art without de-parting from the spirit and scope of the invention except as it may be limited by the claims.
'.~
; :
: .
.,'~ ' ';
LeA 17,067 -26-
Claims (7)
1. A process for the preparation of polyisocyanates having biuret groups by the reaction of aliphatic diamines containing from 2 to 12 carbon atoms with aliphatic diisocyanates containing from 4 to 12 carbon atoms which are free from biuret groups at a molar ratio of NH2/NCO between about 1:5 and 1:100, characterized in that the diamines are reacted in vapor form with the diisocyanates which are heated to a temperature of from about 100°C to 250°C.
2. A process according to Claim 1, characterized in that a gaseous mixture comprising a carrier gas which is inert towards the reactants and the diamine in vapor form is introduced into the heated diisocyanates at a volumetric ratio of carrier gas to diamine of between about 2:1 and 100:1.
3. A process according to Claim 1, characterized in that before the biuret-free diisocyanate is used, it is preheated at about 120 to 195°C and is then distilled.
4. The process of Claim 3 wherein the biuret-free diisocyanate is preheated for about 6 to 10 hours at about 160 to 180°C and is then distilled.
5. The process of Claim 1 wherein the diisocyanates are heated to a temperature of from about 130 to 200°C.
6. In a process for the preparation of poly-isocyanates having biuret groups by the reaction of aliphatic diamines containing from 2 to 12 carbon atoms with aliphatic diisocyanates containing 4 to 12 carbon atoms which are free from biuret groups at a molar ratio of NH2/NCO between about 1:5 and 1:100, the improvement comprising reacting the diamines in vapor form with the diisocyanates which are at a temperature of from about 100 to 250°C.
7. A process for the preparation of polyisocyanates having biuret groups by the reaction of hexamethylene diamine with hexamethylene diisocyanate at a molar ratio of NH2/NCO
between about 1:5 and 1:100, characterized in that the hexamethylene diamine is reacted in vapor form with the hexamethylene diisocyanate.
between about 1:5 and 1:100, characterized in that the hexamethylene diamine is reacted in vapor form with the hexamethylene diisocyanate.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2609995A DE2609995C3 (en) | 1976-03-10 | 1976-03-10 | Process for the preparation of polyisocyanates containing biuret groups |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1077956A true CA1077956A (en) | 1980-05-20 |
Family
ID=5972047
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA271,671A Expired CA1077956A (en) | 1976-03-10 | 1977-02-14 | Process for the preparation of polyisocyanates which contain biuret groups |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS52108927A (en) |
| AT (1) | AT346832B (en) |
| AU (1) | AU506589B2 (en) |
| BE (1) | BE852265A (en) |
| BR (1) | BR7701381A (en) |
| CA (1) | CA1077956A (en) |
| CH (1) | CH627739A5 (en) |
| DD (1) | DD130041A5 (en) |
| DE (1) | DE2609995C3 (en) |
| ES (1) | ES456660A1 (en) |
| FR (1) | FR2357589A1 (en) |
| GB (1) | GB1550521A (en) |
| NL (1) | NL7702438A (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2803103A1 (en) * | 1978-01-25 | 1979-07-26 | Bayer Ag | PROCESS FOR THE PREPARATION OF ORGANIC POLYISOCYANATES CONTAINING BIURET AND / OR UREA GROUPS |
| DE3003543A1 (en) * | 1980-01-31 | 1981-08-06 | Bayer Ag, 5090 Leverkusen | METHOD FOR THE PRODUCTION OF MODIFIED POLYISOCYNATES AND THEIR USE AS A BUILD-UP COMPONENT IN THE PRODUCTION OF POLYURETHANE PLASTICS |
| DE3143060A1 (en) * | 1981-10-30 | 1983-05-11 | Chemische Werke Hüls AG, 4370 Marl | Powder coatings based on blocked isophorone diisocyanate adducts |
| IN172016B (en) * | 1986-04-25 | 1993-03-13 | Uop Inc | |
| DE3700209A1 (en) * | 1987-01-07 | 1988-07-21 | Bayer Ag | METHOD FOR PRODUCING POLYISOCYANATES WITH BIURET STRUCTURE |
| DE4439421A1 (en) * | 1994-11-04 | 1996-05-09 | Huels Chemische Werke Ag | New polyamines containing urea groups and processes for their preparation |
| DE19633404A1 (en) * | 1996-08-19 | 1998-02-26 | Basf Ag | Process for the production of polyisocyanates containing biuret groups from (cyclo) aliphatic diisocyanates |
| CN103402978A (en) | 2011-03-03 | 2013-11-20 | 巴斯夫欧洲公司 | Process for preparing polyisocyanates containing biuret groups |
| US8609887B2 (en) | 2011-03-03 | 2013-12-17 | Basf Se | Process for preparing polyisocyanates comprising biuret groups |
-
1976
- 1976-03-10 DE DE2609995A patent/DE2609995C3/en not_active Expired
-
1977
- 1977-02-14 CA CA271,671A patent/CA1077956A/en not_active Expired
- 1977-03-07 NL NL7702438A patent/NL7702438A/en not_active Application Discontinuation
- 1977-03-07 GB GB9418/77A patent/GB1550521A/en not_active Expired
- 1977-03-07 DD DD7700197715A patent/DD130041A5/en unknown
- 1977-03-07 CH CH280277A patent/CH627739A5/en not_active IP Right Cessation
- 1977-03-08 AT AT153977A patent/AT346832B/en not_active IP Right Cessation
- 1977-03-08 BR BR7701381A patent/BR7701381A/en unknown
- 1977-03-09 BE BE175627A patent/BE852265A/en unknown
- 1977-03-09 AU AU23077/77A patent/AU506589B2/en not_active Expired
- 1977-03-09 ES ES456660A patent/ES456660A1/en not_active Expired
- 1977-03-10 JP JP2552177A patent/JPS52108927A/en active Granted
- 1977-03-10 FR FR7707160A patent/FR2357589A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| ES456660A1 (en) | 1978-01-16 |
| FR2357589B1 (en) | 1983-10-07 |
| NL7702438A (en) | 1977-09-13 |
| BE852265A (en) | 1977-09-09 |
| DE2609995A1 (en) | 1977-09-22 |
| AU506589B2 (en) | 1980-01-10 |
| DE2609995C3 (en) | 1979-12-06 |
| FR2357589A1 (en) | 1978-02-03 |
| JPS6229426B2 (en) | 1987-06-25 |
| CH627739A5 (en) | 1982-01-29 |
| GB1550521A (en) | 1979-08-15 |
| JPS52108927A (en) | 1977-09-12 |
| BR7701381A (en) | 1978-05-02 |
| ATA153977A (en) | 1978-04-15 |
| AT346832B (en) | 1978-11-27 |
| AU2307777A (en) | 1978-09-14 |
| DD130041A5 (en) | 1978-03-01 |
| DE2609995B2 (en) | 1978-03-23 |
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