N,N′-disubstituted N-(2-hydroxyalkyl)-ureas

Details N,N′-disubstituted N-(2-hydroxyalkyl)-ureas N,N′-disubstituted N-(2-hydroxyalkyl)-ureas

1999-08-02

2001-01-23

Niland, Patrick D. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S589000, C524S590000, C528S044000, C528S045000, C528S073000, C528S085000, C544S001000, C544S063000, C544S068000, C560S330000, C560S332000

Reexamination Certificate

active

06177494

ABSTRACT:

BACKGROUND OF THE INVENTION
The present patent application relates to non-crystallizing N,N′-disubstituted N-(2-hydroxyalkyl)-ureas and to the use thereof as hydrolysis protection agents in plastics which contain ester groups.
N,N′-disubstituted N-(2-hydroxyalkyl)-ureas or -thioureas which are used as hydrolysis protection agents for plastics that contain ester groups are disclosed in DE-A 2,106,726. One disadvantage of the ureas or thioureas which are described in this German Patent is their crystallinity, which makes it difficult to admix these ureas in a homogeneous form with plastics containing ester groups and to stabilize such mixtures. These disclosed ureas therefore have to be melted before processing which constitutes an additional operating step. This additional operating step and the crystallinity of these hydrolysis protection agents adversely affect the economics of using the ureas or thioureas described in German Patent 2,106,726 to stabilize plastics which contain ester groups.
Another disadvantage of using the ureas or thioureas described in German Patent 2,106,726 is thermal cleavage due to overheating caused, e.g., by incorrect processing during attempts to liquefy them before they are admixed with the plastics containing ester groups, which liquefaction step is often carried out at considerably increased oven temperatures. Thermal cleavage results in the formation of volatile iso(thio)cyanates which constitute a physiological risk to the processing operator. Over-heating can also occur when these known ureas are used in systems in which curing is conducted at elevated temperatures, e.g., during the processing of thermoplastics using continuous screw devices or during the cure of cast elastomers.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide non-crystallizing ureas.
It is also an object of the present invention to provide hydrolysis protection agents for plastics containing ester groups.
These and other objects which will be apparent to those skilled in the art are accomplished by producing N,N′-disubstituted N-(2-hydroxy-alkyl)-ureas from trimerized hexamethylene diisocyanate and incorporating such ureas into plastics containing ester groups.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
It has now been found that when trimerized hexamethylene diisocyanate is used as a starting material for the production of N,N-disubstituted N-(2-hydroxyalkyl)-ureas, non-crystallizing products are obtained. These non-crystallizing products can be used without problems, optionally as stable solutions in 1,4-butanediol, and impart excellent protection from hydrolysis to plastics containing ester groups.
The present invention therefore relates to non-crystallizing N,N′-disubstituted N-(2-hydroxyalkyl)-ureas represented by general Formula (I)
R′—(—NH—CO—NR
2
—CH
2
—CHR
3
—OH)
n
  (I),
in which
R
1
represents the radical of a trimerized hexamethylene diisocyanate which is diminished by the loss of free NCO groups,
R
2
represents an aliphatic or aromatic hydrocarbon radical having up to 18 carbon atoms, which is optionally substituted by hydroxyl or cyano groups or by one or more halogen atoms,
R
3
represents hydrogen or an alkyl radical having from 1 to 12 carbon atoms, preferably from 1 to 3 carbon atoms, and
n on average, represents a number from 3.0 to 5.0, preferably from 3.2 to 4.5.
The preferred N,N′-disubstituted N-(2-hydroxyalkyl)-ureas of general Formula (I) are those in which
n represents 3.2 to 4.5,
R
2
represents a methyl or hydroxyethyl group,
R
3
represents hydrogen or a methyl group, and
R
1
represents a radical of a trimerized hexamethylene diisocyanate, which is diminished by the loss of free NCO groups, corresponding to the idealized
Formula (II):
The expression “idealized form of trimerized hexamethylene diisocyanate” refers to the fact that oligomers made up of trimers linked by hexamethylene bridges are also formed during the production of trimerized hexamethylene diisocyanate. Furthermore, the compounds can also contain what are termed asymmetric trimer rings of the following Formula (III)
Production of trimers having an increased proportion of these asymmetric trimer rings is described, for example, in DE-A 1,961,1849.
The non-crystallizing N-alkyl-N-2-hydroxyalkyl-ureas corresponding to Formula (I) according to the invention may be produced by known methods of preparative organic chemistry such as addition of N-substituted 2-hydroxy-alkylamines to trimerized hexamethylene diisocyanate at reaction temperatures of from 20 to 1 00° C., preferably from 20 to 70° C.
This addition reaction may be conducted either in solution or in bulk, but is preferably conducted in solution. Suitable solvents are those which do not have a negative effect on the use of the ureas according to the invention as hydrolysis protection agents in plastics, such as customary plasticizers (e.g., dioctyl phthalate), or organic solvents such as ethanol, isopropanol, dioxane, tetrahydrofuran, chloroform and/or 1 ,4-butanediol.
To remove subsidiary components of the N-substituted 2-hydroxy-alkylamines, which subsidiary components do not react or which only react slowly with isocyanate groups (e.g., N,N-dimethylaminoethanol, N,N-diethylaminoethanol or trimethylamine), the reaction product from the addition reaction, or a solution of the reaction product, can be subjected to a brief vacuum treatment, wherein a gentle flow of nitrogen can be passed through the batch to promote volatilization.
The starting materials, namely the substituted hydroxylamines and the trimerized hexamethylene diisocyanate, are generally used in an equivalent ratio of isocyanate groups to NH groups offrom 1:1 to 1.1:1,preferably from 1:1 to 1.05:1.
As mentioned above, trimerized hexamethylene diisocyanate is used as the isocyanate starting material for the production of ureas of general Formula (I) according to the invention. This isocyanate is obtained by the partial trimerization of hexamethylene diisocyanate and subsequent removal of unreacted monomeric hexamethylene diisocyanate. The production of trimerized hexamethylene diisocyanate is described, for example, in J. Prakt. Chem. 336 (1994) 185-200 and in EP-A 339,396 and EP-A 798,299. These isocyanates are obtainable as commercial products, under trade names such as Desmodur® N 3300 and VP® LS 2025/1, from Bayer AG, Leverkusen.
Suitable reactants for the trimerized hexamethylene diisocyanate include any N-substituted 2-hydroxylalkylamines, preferably 2-hydroxy-ethylamines, such as N-meth-yl-2-hydroxyethylamine, N-methyl-2-hydroxybutylamine, N-isopropyl-2-hydroxy-ethylamine, N-butyl-2-hydroxyhexylamine, or bis(2-hydroxyethyl)-amine.
N-methyl-2-(hydroxyethyl)amine is most preferably used. N-substituted 2-hydroxyl-alkylamines are also described in the above-mentioned German Patent 2,106,726.
The present invention further relates to the use of the non-crystallizing N-alkyl-N-2-hydroxyalkyl-ureas of general Formula (I) to stabilize (as hydrolysis protection agents) any plastics, preferably polyurethanes, which contain ester groups.
In general, from 0.02 to 10% by weight, preferably from 0.1 to 5% by weight, of the hydrolysis protection agent of the present invention is sufficient to stabilize plastics containing ester groups. The hydrolysis protection agents used in the practice of the present invention can either be added to the plastics to be stabilized after the production thereof, or be admixed with the starting materials from which the plastics containing ester groups are produced. The latter type of addition is recommended, particularly for polyurethanes with stabilized ester groups. If the hydrolysis protection agent of the present invention is added during production of a polyurethane, the hydrolysis protection agent can be added either to the polyisocyanate component or to the polyol component.
The expression “polyurethanes which contain ester groups” means any polyurethanes which are produced from hydroxyl compounds containing ester groups, e.g., polyurethane (integrally)

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