Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
U. S. Patent 3,929,749 and Wright et al, Journal of ~ ~-
Applied Polymer Science, 20, 3305-3311 (1976) describe the
reaction of polymers containing amide groups with excess
aqueous alkali hypochlorite in the presence of an inert
solvent at temperatures from O to 15C to form isocyanates.
This process has drawbacks since, because of the presence
of water, it is unavoidable that a portion of the isocyanate
formed is hydrolytically decomposed during the processing
of the reaction mixture. The corresponding amines are
formed by the Hofmann reaction, through the unstable carbamic
acid intermediate. These amines further react with addition-
al isocyanates to form urea compounds, resulting in a -~
further lowing of the theoretical isocyanate yield. Thus,
as shown in Example 15 of U. S. Patent 3,929,744, 5.2%
by weight of isocyanate groups are present when a polymer
containing amide groups is reacted with sodium hypochlorite, ~ `
whereas only 3.25% by weight of isocyanate groups are
measured after isolation of the isocyanate by removal of
water by azeotropic distillation. Further, in the prior
art system, the addition of deemulsifiers to the mixed
; aqueous-organic reaction mixture does not result in rapid
separation of an aqueous phase and an organic isocyanate
containing phase. Therefor, in this procedure, an isocyanate
loss must also be accepted. The long separation times,
which in the most favorable cases are at least several
hours, and sometimes several days, are also a disadvantage
in the processing system.
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DESCRIPTIO~ OF THE INVENTION
The present invention is directed to a process for
the preparation of polyfunctional isocyanates prepared by : :
reacting a N-chloramide derivative of homopolymers or inter-
polymers of acrylamide or methacrylamide with a tertiary amine
having a PKa value of more than 7, in the presence of an inert
solvent, at a temperature between about 20 to about 180C.
The ~chloramide derivatives utilized in the pro-
cess of the invention are formed by chlorination of the
appropriate amide group containing polymers. Suitable amide
group containing polymers are acrylamide or methacrylamide
homopolymers and acrylamide or methacrylamide interpolymers
containing about 5 to 100 mole % acryl- or methacryl-amide,
and free of functional groups which would interfere with ~-
chloramide formation or the N-chloramide-amine reaction. A
group of suitable polymers are disclosed in U. S. Patent
3,929,744. Examples of suitable polymers include polyacryl- i~-
amide, polymethacrylamide, as well as interpolymers or `
acrylamide or methacrylamide with at least one copolymeriz-
able monomer, for example, styrene, methylstyrene, dimethyl-
styrene, p-chlorostyrene, o-chlorostyrene and alkylacrylates,
such as methyl acrylate, methylmethacrylate, ethyl acrylate, ~`.'7.''
ethyl methacrylate, butyl acrylate, hexylacrylate, decyl ~
acrylate, dodecyl acrylate, and the llke, as well as cross- .:
linked products of the aforementioned polymers and in-
terpolymers prepared ~or example by mean6 o~
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known crosslinking techniques, for example, usin~ divinyl
crosslinking agents such as divinyl benzene or divinyl
ether, for example, by employing about 1 to about 10 mole %
of a divinyl crosslinking agent. The molecular weight of
the amide group containing polymers can vary widely.
Preferably, the average molecular weight of the uncrossed
linked polymers is from about 1,000 to about 10,000. Most
preferably, polymers with an average molecular weight from
about 5,000 to, about 10,000 are employed.
Chlorination of amide groups is generally well known.
Chlorination of the amide-group-containing homo- and inter- ;~
polymers is preferably carried out by means of chlorine
in an aqueous-mineral acid suspension preferably at tempera-
tures of from about 0 to about 40C. For example, dilute, `~ ;
aqueous hydrochloric acid, sulfuric acid, or phosphoric
acid are suitable as the aqueous, dilute mineral acid. In one
process, one starts out with a neutral, aqueous suspension ~- -
of the amide group containing polymers, and the hydrogen
chloride formed during chlorination as by-product dissolves ~ ;
in the reaction mixture and the chlorination thus takes
place in a dilute aqueous-hydrochloric medium. Preferably,
such a process is started with dilute hydrochloric, or
dilute sulfuric acid-aqueous suspensions of the amide
group containing polymer. Chlorination proceeds exothermically
and is preferably carried out at temperatures from about
0 to about 30C The use of temperatures higher than about
40C is disadvantageous because measurable quantities of
carboxyl groups are formed by hydrolysis at higher temperatures. ;
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Chlorination can be ca,rried out at normal ambient pressure,
as well as at an elevated pressure, The required reaction ',
time declines with inçreasing pressure,` but for economic
reasons, the pre,f,erred pressure'range is between about 1 and
about 6 atm~ abs~ Since chlorination takes place in a '
heterogeneous system, a good mixing of the suspension is
re~uired. The'reaction mixture should be sufficiently ,
dilute so that it can be'stirrred, or mixed in some other
way, without difficulties. The preferred reaction batch '
çoncentr~tion is about 100 to 200 g of amide'group containing ~,
polymer per liter of water or aqueous mineral acid. When - ,
the`above described PXocess conditions are maintained, '"
chlorination is complete after about 1~4 to 2 hours. ; ,
Depending upon the composit;on of the am;de group containing ~,
pQlymers employed~ about 30 to 95% of the amide groups ~ ~
are converted to N-chloramide groups under these conditions. ''
After completion of chlorination reaction, the modified
polymer is the only sol~d substance in the suspension. ', ,
It can be sepa~ated verY easily by filtration or centrifuglng.
Selection of a suitable base is of critical importance ~ ,`
for the success of the process of the`invention. In accordance
~ith the ~nVent~Qn~ tertiary amines with a certain basicity ~'
are employed~ The basicity constant PKa is used as a measure
of the basicity. Tertiary amines suitable for use in the ''- '
pxocess of the'invent~on have to have a minimum basicity '
corresponding to a PKa value of more than 7, Suitable
tertia,ry amines are aliphatic, cycloaliphatic and aromatic
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amines, such as (the pertinent PKa values, in each case
at 25C, are given in parentheses): Trimethylamine (9.80),
triethylamine (10.74), tributylamine (9.89), 2.4.6-
trimethylpyridine (7.45 - 7.63), tri-n-propylamine (10.74),
ethyldimethylamine (10.06), propyldimethylamine (10.16),
isopropyldimethylamine (10.38), methyldimethylamine (10.43),
butyldimethylamine (10.31), 2.3.4.5-tetramethylpyridine
~7.78), and 2.3.4.5.6-pentamethylpyridine (8.75). Preferred
tertiary amines are trimethylamine, triethylamine, tri-n- ~ -
I0 propylamine and tri-n-butylamine. PKa values of various
amines can be found in the conventional chemical handbooks.
In the case of aliphatic tertiary amines, special reference
is made to L. Spialter et al., The Acyclic, Aliphatic Tertiary
Amines, The McMillan Co., New York (1965), and, as to
substituted pyridines, to Klingsberg, Heterocyclic Compounds
Pyridine and Derivatives, part 2, Interscience Publishers,
Inc., New York (1961).
The basicity of the tertiary amine used is of signifi-
cance for the progress of the reaction, i.e. when polymers
with the same N-chloramide content are used, the isocyanate
yield is lower, the lower the pK value of the tertiary
amine.
The tertiary amine is employed in the process of
the invention in quantities of at least about one mole
equivalent per mole of N-chloramide constituent in the polymer. ;The preferred equivalence ratio of N-chloramide constituent
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to tertiary amine is 1 : 1 to 1 : 4. Greater quantities
of tertiary amine can be used without being harmful, but
should be avoided for economic reasons.
. .
Care must be taken in the selection of the inert
organic solvent so that, under the given reaction conditions,
; it will react neither with the N--chloramide group, with the ~
isocyanate group or with the tertiary amine employed. ~ :
Suitable solvents are, for example, methylene chloride,
l.l-dichloroethylene, chloroform, carbon tetrachloride,
trichloroethylene, tetrachloroethylene, pentane, hexane,
~ cyclohexane, heptane, octane, benzene, toluene, ethylbenzene, :.
; chlorobenzene, xylene, dichlorobenzene, d.ethyl ether, ,;
,
tetrahydrofuran, dioxane, acetic methyl ester, acetic -
butyl ester, and propionic methyl ester. Preferred inert
15~ solvents are toluene, xylene, chlorobenzene, acetic
butyl ester, chloroform, tetrachloroethylene, carbon :~
tetrachloride, cyclohexane and dioxane. ~: ~
The preferred concentration of the reaction batch . ~ ` -
is about 100 to about 200 g of polymer with N-chloramide
content per liter of solvent, but lower, as well as higher ~- :
concentrations can also be used.
.
In the process of the invention, the reaction temperatures
can range from about 20 to about 180C. Essentially, the :
reaction temperature depends upon the type of polymer used,
its N-chloramide content, and the basicity of the tertiary
amine. In the case of some starting materials the reaction
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will start spontaneously at room temperature, in some cases
even very vigorously. Generally, the reaction is carried
out at the boiling temperature of the solvent used. The
preferred reaction temperatures are in the range of from
about 65 to about 135C.
The reaction times in the process of the invention
are reasonably short, generally only a few mlnutes. However,
longer reaction times, e.g. a reaction time of an hour,
can also be used without being harmful.
In order to carry out the process of the invention
it is expedient to disperse the polymer containing the N- ;;
chloramide groups in the solvent and then to add the required
minimum quantity of tertiary amine. In some cases, the
reaction starts immediately, in other cases heating to the
desired reaction temperature is necessary. If necessary,
heating is continued for a desired time. After completion
of the reaction, and cooling of the reaction mixture, the ~ ~
reaction mixture is worked up in a conventional manner to ~ `
obtain the product polyisocyanate in a useful form; for
example the hydrochloride of the tertiary amine formed
during the reaction is removed and the polymeric isocyanate ;-<~ -
containing filtrate is concentrated under vaccum.
The filtrate containing the polymeric isocyanate can, `
of course, also be used directly in reactions, e.g. with
compounds containing hydroxyl groups. ~-
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There follows a number of Examples which are to be
considered illustrative rather than limiting. All parts
and percentages are by weight unless otherwise specified.
- All temperatures are degrees Centigrade unless otherwise
specified.
EX~'IPLE 1
10 g of a copolymer of 10 parts methacrylamide, 50
parts methylmethacrylate and 40 parts butylacrylate were
dispersed in 100 g 5% hydrochloric acid. Subsequently,
chlorine was passed through the dispersion for 4 hrs. at
15 to 20C. After stripping of the excess chlorine with
nitrogen, the polymeric N-chloramide was filtered with ;~-
suction, washed with distilled water until neutral and
dried at 35C under a vacuum (30 mbar).
10.2 g of polymeric N-chloramide with an active `~
15~ chlorine content of 3.1% were isolated, i.e. 77% of the amIde~ ~;
- ; groups of the polymer had been converted to chloramide.
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EXA~PLE 2
10 g of a copolymer of 20 parts methacrylamide, 40
parts methylmethacrylate and 40 parts butyl acrylate in 100 ~-
g 5% hydrochloric acid were chlorinated at 20C for 30 ~
,
minutes under a chlorine pressure of 4 bar. The N-chloramide ~ ~
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was isolated as in Example 1. 10.35 g of polymeric N-
chloramide with an active chlorine content of 6.4~ were
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obtained, i.e. 8~/o of the amide groups were chlorinated.
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EXAMPLE 3
10 g of polymeric N-halogen amide with an active
chlorine content of 3.1% prepared by chlorination of a
copolymer of 10 parts methacrylamide, 50 parts methylmethacrylate
and 40 parts butyl acrylate were suspended in 100 ml toluene.
After the addition of 3 g of triethylamine, the mixture
was quickly heated to 100C and left at this temperature
for 30 min. Then, excess triethylamine and 20 ml
toluene were distilled off. After cooling, the precipitated
triethylamine hydrochloride and other undissolved con- `
stituents were removed and the filtrate concentrated under
a vacuum. 9.5 g of resin with an isocyanate content of 3.4%
remained.
EXAMPLE 4
.
Example 3 was repeated, except that instead of toluene,
the same quantities of chlorobenzene, dioxane and acetic
butyl ester were used in each case. The quantities of
polymeric isocyanate that were isolated, as well as their
NCO contents have been compiled in Table 1.
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Table 1
Reaction Medium Quantity by weight of NCO Content
polYmeric isocYanate (~6) .'
chlorobenzene 9.3 g 3.35
dioxane 9.5 g 3.2
acetic butyl ester 9.25 g 3.5
_ g _ : :
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EXAMPLE 5
10 g of polymeric N-halogen amide, prepared by
- chlorination of a copolymer of 20 parts methacrylamide, 40
parts methylmethacrylate and 40 parts butyl acrylate, with
an active chlorine content of 6.4%, in toluene as in ;~
Example 3, was converted to polymeric isocyanate with the
addition of 5 g triethylamine. 9.25 g of a resin with an
NCO content of 4.7% were obtained.
EXAMPLE 6
As described in the preceding examples, additional
polymeric N-chloramides, in toluene, were converted to
polymeric isocyanates with triethylamine.
Table 2 shows the composition of the polymers, the
chlorine content of the polymeric N-halogen amides, as
well as the NCO content of the resulting polymeric
isocyanates.
EXAMPLE 7 ~ -
10 g of polymeric N-halogen amide, prepared by
chlorination of a copolymer of 20 parts acrylamide and 80
parts methylmethacrylate, with an active chlorine content
of 7.7%, in toluene, were converted (as in Example 3) to
a polymeric isocyanate with the addition of 5 g triethylamine.
4.8 g of polyisocyanate with an NCO content of 4.7%
were isolated.
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EXAMPLE 8
10 g of the polymeric N-halogen amide in Example 3
were suspended in 50 ml toluene, and a solution of 3 g
trimethylamine in 50 ml toluene added thereto. The mixture
was quickly heated to reflux temperature (110C). Gaseous
excess trimethylamine escaped during heating up. The
mixture was kept boiling for one hour, then cooled, tri- -
methylamine hydrochloride removed by suction and the filtrate
concentrated under a vacuum. 9.3 g of resin, with an NCO
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; content of 4.5~ were obtained as residue.
EXAMPLE 9
~.
10 g of polymeric, cross-linked N-halogen amide with
an active chlorine content of 17%, prepared by chlorination
of a polymethacrylamide cross-linked with 5% divinyl benzene,
were suspended in 100 ml of toluene and, after addition of
20 g of triethylamine, treated for 30 minutes at 110C.
Cooling was followed by filtering with suction and washing
of the residue with chloroform to remove the triethylamine -
hydrochloride. 7.5 g of a white powder with an NCO content ~ ~;
of 9.8~ remained.
EXAMPLE 10
A mixture of 10 g of polymeric, cross-linked N-halogen
amide of Example 6, 26 g tripropylamine and 100 ml chlorobenzene ;~
was heated for 10 min. to 130C. This was followed by suction ;
filtering, washing with chlorobenzene and drying of the
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residue. 7.7 g of polymeric, cross-linked isocyanate with
an NCO content of 9.6~ were obtained.
WHAT IS CLAIMED IS:
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