GB2064538A

GB2064538A - Cycloaliphatic Monoisocyanates

Info

Publication number: GB2064538A
Application number: GB8100453A
Authority: GB
Original assignee: WR Grace and Co
Current assignee: WR Grace and Co
Priority date: 1978-11-20
Filing date: 1979-11-19
Publication date: 1981-06-17
Also published as: GB2038855A; FR2441637A1; GB2038855B; FR2441637B1; GB2064538B; DE2946625C2; DE2946625A1

Abstract

A cycloaliphatic monoisocyanate is provided which has the general formula: <IMAGE> wherein R1 to R7 are each independently H, alkyl of 1 to 18 carbon atoms, cycloalkyl of 4 to 8 carbon atoms, aryl of 6 to 14 carbon atoms, alkaryl or aralkyl with the proviso that at least two of R1, R2, R4 and R5 are other than H or methyl, and x is 1 to 7.

Description

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GB 2 064 538 A 1 .DTD:

SPECIFICATION Cycloaiiphatic Monoisocyanates .DTD:

This invention relates to cycloaliphatic monoisocyanates.

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Recently it has been discovered that polyurethane foams contain aromatic amines and that certain aromatic amines may represent a potential health hazzard. Although the theory of formation of 5 the aromatic amines is not clearly understood, it appears that aromatic isocyanates and possibly their reaction products containing urea and urethane linkages are hydrolyzed to produce free aromatic amines which can be leached from the polyurethane foam.

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It has been discovered that at least a stoichiometric amount, sufficient to react with any aromatic amines present, of an amine scavenger which is a hindered cycloaliphatic monoisocyanate of the 10 general formula:

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R3 CO R2 a R4 Rl R5 R6 CC i n77 x wherein R,-R, are each independently H, C,-C,8 alkyl, C4 Cg cycloalkyl, Cs C,4 aryl, alkaryl or aralkyl with the proviso that where R3 is not H, R1, RZ, RQ and R5 can be H and with the further proviso that where R3 is H at least two of R,, R2, RQ and R5 are not H, and x is 1 to 7 (hereafter referred to as 15 "aromatic amine scavengers") when added to urethane prepolymer or the components of a one shot foam system results in polyurethane foams having a low residue of aromatic amines.

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The amount of aromatic amine scavengers added to the system is generally from 0.01 to 15 parts by weight based on the weight of the total reactants used to form the polyurethane other than water. The lower limit is not critical and is determined by the degree of scavenging activity desired. 20 Thus our Application No. 79,39940 provides a method for preparing a polyurethane foam having a reduced aromatic amine content which comprises incorporating into either (i) a urethane-containing prepolymer comprising polyether or polyester units end-capped with an aromatic isocyanate and water, or (ii) an aromatic polyisocyanate, a polyether or polyester, polyol and water, up to 15% by weight based on the weight of (i) or (ii) of a hindered cycloalkphatic monoisocyanate of the general 25 formula given above.

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The cycloaliphatic monoisocyanates of the above formula wherein R, to R7 are each independently H, alkyl of 1 to 1$ carbon atoms, cycloalkyl of 4 to 8 carbon atoms, aryl of 6 to 14 carbon atoms, alkaryl or aralkyl with the proviso that at least two of R, R2, R4 and R5 are other than H or methyl, and x is 1 to 7 are novel and form the subject of the present invention.

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Exemplary hindered aliphatic monoisocyanates of this invention include 2, 6 diethylcyclohexylisocyanate, 2,3,6-triphenylcyclohexylisocyanate, 2,6dipropylcyclohexylisocyanate and 6-methyl-2-ethylcyclohexylisocyanate.

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In one embodiment R3 is other than hydrogen in another embodiment at least two of R,, R2, R4 and R5 are ethyl. x is preferably 3. A specific isocyanate of the present invention is 2,6 diethylcyclohexylisocyanate.

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As used herein, a "hindered" cycloaliphatic monoisocyanate means the aposition contains an alkyl, aryl, cycloalkyl, alkylaryl or arylalkyl substituent and "di- or polyhindered" cycloaliphatic isocyanate means the a and P carbons have a minimum of two substituents.

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These monoisocyanates can be used not only as amine scavengers in the preparation of polyurethanes, but also in epoxy resins, polyamines and other polymeric compositions.

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The monoisocyanates can be prepared from the corresponding monoamines. Some of these monoamines are known. Those of the formula:

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H 2 a R2 R4 R1 R5 R 1 C I R7 x GB 2 064 538 A 2 wherein Rj, RZ and R4 to R, are each independently H, alkyl, cycloalkyl or alkaryl wherein the alkyl groups contain 2-18 carbon atoms, the cycloalkyl groups contain 4-8 carbon atoms and the alkaryl groups contain 7-14 carbon atoms with the proviso that at least two of R,, R2, R4 and R5 are group members other than H or methyl and with the further proviso that, when only two of R,, RZ, R4 and R5 are alkyl, at least one of the alkyl groups contains at least 4 carbon atoms, and x is 1 to 7 are novel. 5 Examples include 2,6-dibutylcyclohexylamine and 2-butyl, 6- ethylcyclohexylamine.

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There are two general synthetic routes for preparing the dihindered monoamines. The first route is by nitration of the substituted aromatic compound, reduction of the aromatic nitro compound to the aromatic amine and reduction of the aromatic amine. Alternatively, the aromatic amine can be formed and alkylated to give the dihindered aromatic amine.

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The first route includes nitration in the 2-position of an appropriately substituted, for example a 1,3-disubstituted, aromatic compound using nitric acid alone or with sulphuric acid, generally at a temperature of 0 -150 C. See Kobe and Brennecke, Industrial Ft Engineering Chemistry, Vol. 46, No.

4, pages 728-732. Reduction of the nitro compound to the amine using a reduction catalyst such as Raney nickel is then carried out under hydrogen pressures of, say 1-100 atmospheres and temperatures from, say, 0 to 150 C for example in dioxane as solvent. Alternatively, nitrobenzene can be hydrogenated to aniline and the aniline alkylated using the desired olefin or alkyl halide. For example, aniline in the presence of ethylene can be converted to the 2,6- diethylaniline by the Ethyl process using aluminium halide as catalyst at 325 C and 800 psi. Alkylation can also be conducted on ortho-substituted anilines to give mixed alkyl derivatives in the 2,6 position. Reduction from the aromatic nitro to the aromatic amine can be accomplished by standard methods described in Coll. Vol.

I-V Index of Organic Synthesis, p. 21 1. Reduction of the aromatic amine to an aliphatic amine is then accomplished in the presence of a hydrogenation catalyst such as Raney nickel or cobalt or rhodium/AI203 at hydrogen pressures of, say 2-200 atmospheres and a temperature from, say, 0- 250 C (see Coll. Vol I-V Index of Organic Synthesis, pp 208 and 209).

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A specific example of the overall process starts from m-xylene:

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CH 3 @CH3 AN03 fH_s N02 CH3 6 0 CH 3 N02 CH3 06 CH 3 f by proc;ucts H2 dioxane (solvent) 25 C/70 atm.

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NH 2 CH 3 CH j 3 Rh/A1'03.

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H2. 00 C atm.

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NH 2 CH 3 CH 3 S NH 2 CH 3 S CH 3 excess NCO COC12 CH 3_ CH 3 S solvent (i) -20 - -E20 C (ii) 110 -180 C. 1-15 atm.

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3 GB 2 064 538 A 3 The solvent is typically chlorobenzene or dichlorobenzene. The alternative steps in the first route may be written as follows:

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NH 2 NH 2 CH 2=CH2 H 5C2 0 C2 H5 Ni (N catalyst 3250C, 800 psi and the dihindered aromatic amine then reduced.

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A second general route for forming the dihindered aliphatic monoamine is to treat a cyclic ketone (or the cyclic alcohol oxidized to the ketone) with hydroxylamine to form the corresponding oxime which is then reduced either using HZ and catalyst or HZ generating couples (Na-alcohol) for example at 0 to 80 C and 1-5 atmospheres. Typically the oxime is prepared using hydroxylamine hydrochloride and NaZC03 at a temperature of 0 to 50 C and 1-10 atmospheres.

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Alternatively, the same compound can be prepared through 2methylcyclohexanone. 2,6Dimethylcyclohexanone has been prepared in the 6position, methylation at the 6-position and removal of the formyl group. The ketone may then be aminated and phosgenated to give the 2, 6dimethycyclohexylisocyanate.

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Cycloaliphatic amines with a substituent, for example phenyl, in the 1position, such as 1-phenyl- 15 1-cyclohexylamine, can be prepared from 1-phenylcyclohexanol which is available commercially. This can be converted to the corresponding iodide using potassium iodide and polyphosphoric acid. The phenylcyclohexyliodide can then be converted to the amine through the reaction with potassium phthalimide and subsequent hydrolysis with hydrochloric acid to give the amine hydrochloride. The amine hydrochloride can be converted to the amine by use of sodium hydroxide or may be used directly 20 for phosgenation to the corresponding isocyanate:

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OH y KI w polyphosphoric acid f2HCl NaOH COCL2 solvent c=0 + ro CAN 0 solvent The monoamine can be converted into the monisocyanate by phosgenation. The amine may be phosgenated as the free amine, the amine hydrochloride, the amine-carbon dioxide adduct or any other suitable amine salt without or with a solvent such as o-dichlorobenzene, in the presence of excess pfiosgene, either in one or two temperature stages, for example either at 80-180 C or first at minus 20 to plus 20 C and second at 20 C to 200 C at pressures from atmospheric to 50 e.g. 1 to 15, atmospheres.

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The following Example further illustrates the present invention. Unless otherwise noted, all parts and percentages are by weight.

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Example g of known 2,6-diethylcyclohexylamine was dissolved in 230 g of chlorobenzene in an addition funnel. In a separate multiple neck, round bottom flask equipped with stirrer, phosgene and nitrogen inlets and outlets, reflux condenser and thermometer, 200 g of COCL2 was condensed in 230 g of chlorobenzene while maintaining the flask at about -5 C in a bath of acetone cooled with dry ice. The 35 amine solution was added dropwise to the flask over 10 minutes with stirring at 600 rpm while maintaining the reaction temperature at -5 to -3 C. After addition, stirring was continued at 300 rpm GB 2 064 538 A 4 allowing the contents to warm to 130-135 C and excess phosgene was distilled. The reaction was continued for 1 3/4 hrs. with stirring while additional COC12 was passed through the reaction mixture.

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Nitrogen was then sparged through the flask to flush out excess phosgene and hydrogen chloride. The product was freed of chlorobenzene solvent by stripping on a rotary evaporator at 73 C. The residue was distilled under vacuum (0.1 mm Hg) and the fraction boiling between 58-61 C was collected. 5 The yield was 45.6 g (78% theoretical). IR showed a strong NCO absorption. NMR revealed the product to be free of contaminants and to have the desired structure, i.e.

NCO CH3CH2 - CH2CH3 S Elemental analysis found C=70.97, H=10.30, 0=9,33, N=7.95 whereas theoretical is C=72.93, H=10.50, 0=8.84 and N=7.73.

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Claims

Claims .CLME:

1. A cycloaliphatic monoisocyanate of the general formula R3 CO RRR 2 4 R1 RS R6 C R7 x wherein Rt to R7 are each independently H, alkyl of 1 to 18 carbon atoms, cycloalkyl of 4 to 8 carbon atoms, aryl of 6 to 14 carbon atoms, alkaryl or aralkyl with the proviso that at least two of Rt, RZ, R4 and 15 R5 are other than H or methyl, and x is 1 to 7.

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2. A monoisocyanate according to claim 1, wherein R3 is other than H.

3. A monoisocyanate according to claim 1 or claim 2, wherein at least two of Rt, RZ, RQ and R5 are ethyl.

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4. A monoisocyanate according to any one of claims 1 to 3, wherein x is 3.

5. 2,6-diethylcyclohexylisocyanate.

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Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office, Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.

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