Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-02-09
2003-04-22
Wilson, D. R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S339000, C525S328300, C525S329300
Reexamination Certificate
active
06552132
ABSTRACT:
The invention relates to a process for the hydrogenation of a polymer composed of diene monomer units and nitrile group containing monomer units, as well as to hydrogenated polymer obtained.
Of polymers that contain conjugated diene monomer units and a nitrile group containing monomer unit, such as for instance nitrile butadiene rubber (NBR), the double bonds present in the chain can be hydrogenated, so that for instance the polymers become less sensitive to oxidative degradation, in particular oxidative degradation at elevated temperature. Such hydrogenated polymers are applied, for instance, under the bonnet in cars.
Commercial processes for the preparation of such hydrogenated polymers are very cumbersome and expensive. The polymer containing diene monomer units and nitrile group containing monomer units is for instance dissolved in a suitable solvent and then hydrogenated with hydrogen gas at a high pressure and a high temperature in the presence of a noble metal catalyst. The catalyst and the solvent must subsequently be removed. In addition, when high degrees of hydrogenation are achieved side reactions take place that result in undesirable branching and even gelation.
U.S. Pat. No. 4,452,950 discloses the hydrogenation of polymers containing conjugated diene monomer units and a nitrile group containing monomer unit, in the form of an aqueous dispersion, with the aid of hydrazine. The polymers in themselves are usually already present as an aqueous dispersion in the form of a latex after the polymerization, or can be given the form of an aqueous dispersion. This in itself yields a simplified process for the hydrogenation, but the process also has the drawback that crosslinking takes place in the hydrogenated polymer already during the hydrogenation reaction, but especially also after the hydrogenation reaction, when the hydrogenated polymer is coagulated, separated and dried and also afterwards, during storage. This causes for instance the rheological properties of the hydrogenated polymer to change in an uncontrolled manner, which has an adverse effect on further compounding and processing into moulded articles. It is even possible for the hydrogenated polymer to be entirely unsuitable for further use, because the crosslinking reaction has proceeded to such an extent that the hydrogenated polymer contains gel particles or is even entirely crosslinked.
It is the aim of the invention to provide a process that does not have the above-mentioned drawbacks or has them only to a strongly reduced extent.
Surprisingly, this aim is achieved in that crosslinks formed due to the hydrogenation are broken by adding, before, during or after the hydrogenation, a compound that satisfies formula I or formula II
where
R
1
is a hydrogen atom, an alkyl or cycloalkyl group with 1-30 carbon atoms, or an aromatic group with 6-30 carbon atoms, and
R
2
is an alkyl or cycloalkyl group with 1-30 carbon atoms, or an aromatic group with 6-30 carbon atoms, X is chosen from the group comprising —R
3
, —OR
4
, —SR
4
, —NR
5
R
6
, where R
3
, R
4
and R
5
are a hydrogen atom, an alkyl or cycloalkyl group with 1-30 carbon atoms or an aromatic group with 6-30 carbon atoms and R
6
is an alkyl or cycloalkyl group with 1-30 carbon atoms or an aromatic group with 6-30 carbon atoms
Y is chosen from the group comprising —R
7
, —OR
8
, —SR
8
, —NR
9
R
10
and —N═CR
11
R
12
where R
7
, R
8
, R
9
, R
10
, R
11
and R
12
are a hydrogen atom, an alkyl or cycloalkyl group with 1-30 carbon atoms or an aromatic group with 6-30 carbon atoms, and it being possible for R
3
-R
12
to also contain one or more heteroatoms from the groups 13, 14, 15, 16 or 17 of the Periodic System of the Elements.
The Periodic System of the Elements is understood to be Periodic System according to the IUPAC nomenclature, shown on the inside of the cover of the Handbook of Chemistry and Physics, 67th edition, 1986-1987.
The addition of such a compound causes strong or complete suppression of the crosslinking reaction. Moreover, addition of the compounds according to the invention has the advantage that no ozonolysis needs to be carried out in order to break crosslinked polymer chains.
It is true that U.S. Pat. No. 5,442,009 discloses ozone treatment of the hydrogenated and crosslinked polymer, so that chains of the hydrogenated polymer are broken and the effect of the crosslinking reaction is wholly or partly eliminated. After this treatment, however, a second crosslinking reaction occurs. According to U.S. Pat. No. 5,039,737 this second crosslinking reaction can be suppressed by treating the hydrogenated and ozone-treated hydrogenated polymer with hydroxylamine, but this is in itself already cumbersome and the combined treatments to which the hydrogenated polymer is to be subjected thus again become complex and expensive, so that no good alternative is obtained to the existing commercial processes for the hydrogenation of polymers containing conjugated diene monomer units and a nitrile group containing monomer unit. Furthermore, the ozone treatment is cumbersome. The second crosslinking reaction is a different type of reaction from the first crosslinking reaction. There is no indication for the use of hydroxylamine also for suppression of the first crosslinking reaction, the more so since hydroxylamine is used only to react with unstable terminal aldehyde groups to form stable oxime compounds. Moreover, the addition of hydroxylamine in a process for the hydrogenation of said polymers by the action of a copper catalyst as in U.S. Pat. No. 5,039,737, but without an ozonolysis being carried out, does not result in the crosslinks formed being broken and a gel-free, hydrogenated polymer being obtained.
Preferably, compounds are used in which R, is a hydrogen atom.
Examples of compounds that satisfy formula I are primary and secondary amines, hydrbxylamine, derivatives of hydroxylamine and substituted hydrazines, dithiocarbamylsulphenamide compounds, thiuram compounds and dithiocarbamate compounds. Specific examples are methylamine, ethylene diamine, dodecylamine, ethanolamine, cyclohexyldiamine, o-phenylene diamine, 3,4-toluene diamine, 1,8-naphthalene diamine, aniline, methylhydrazine, phenylhydrazine, o-aminophenol, o-aminobenzoic acid, hydroxylamine, N-isopropyl hydroxylamine, O-methylhydroxylamine, O-t-butylhydroxylamine and the sulphur compounds tetramethylthiuram disulphide, N-oxydiethylene dithiocarbamyl-N′-oxydiethylene-sulphenamide. Preferably, use is made of compounds that satisfy formula I where R
3
is an aromatic group with 6-15 carbon atoms, R
4
is a hydrogen atom, or an alkyl group with 1-5 carbon atoms, R
5
is a hydrogen atom, an alkyl group with 1-6 carbon atoms or an aromatic group with 6-10 carbon atoms and R
6
is an alkyl group with 1-6 carbon atoms or an aromatic group with 6-10 carbon atoms, it being possible for R
3
-R
6
to also contain one or more heteroatoms from the groups 13, 14, 15, 16 or 17 of the Periodic System of the Elements. Most preferably, hydroxylamine or orthoaromatic diamines are used.
Examples of compounds that satisfy formula II are imines, azines, hydrazones, semicarbazones, oximes and benzothiazoles. Specific examples are N-phenylbutyl imine, N-isopropylbenzaldehyde imine, acetone azine, benzaldehyde azine, cyclohexanone azine, benzaldehyde hydrazone, benzophenone hydrazone, benzaldehyde oxime, p-nitrobenzaldehyde oxime, o-, p-, and m-chlorobenzaldehydeoxime, cyclohexanone oxime, acetonoxime, 2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazole sulphenamide methyl ethyl ketone oxime, benzophenone oxime.
Preferably, compounds are used that satisfy formula II, where R
7
is an aromatic group that contains 6-10 carbon atoms, R
8
is a hydrogen atom or an alkyl group with 1-6 carbon atoms, R
9
-R
11
are a hydrogen atom, an alkyl group with 1-6 carbon atoms, or an aromatic group with 6-10 carbon atoms, and R
12
an alkyl group with 1-6 carbon atoms or an aromatic group with 6-10 carbon atoms, it being possible for R
7
-R
12
to also contain one or more heteroatoms from the groups 13,
Aagaard Olav M
Belt Johannes W.
Köstermann Mike
Singha Nikhil K
Vermeulen Jacobus A. A.
DSM N.V.
Pillsbury & Winthrop LLP
Wilson D. R.
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