Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2002-06-24
2004-12-07
Hightower, P. Hampton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S312000, C528S322000, C528S323000, C528S328000, C528S332000, C528S335000, C528S336000, C525S419000, C525S420000, C525S422000, C525S432000, C540S538000, C524S600000, C524S602000, C524S606000, C524S608000
Reexamination Certificate
active
06828413
ABSTRACT:
The invention relates to a process for the preparation of a polyamide comprising at least a step in which a composition that comprises at least (a) a primary aminocarbonamide and (b) an aminocarboxylic acid and/or a lactam is polymerised.
Such a process is for example known from WO-A-9943734, which describes the preparation of a polyamide-6 from a composition containing 6-aminocapronitrile, 6-aminocapronamide, 6-aminocaproic acid, &egr;-caprolactam and water, in the presence of a heterogeneous metal-oxide catalyst at elevated pressure and temperature.
The disadvantage of the process according to WO-A-9943734 is that no high relative viscosities can be obtained, in particular a polyamide-6 with a &eegr;
rel
of more than 2.2. In the context of this application, &eegr;
rel
is understood to be the relative viscosity measured in a 1 wt. % solution of formic acid. Another disadvantage of the process according to WO-A-9943734 is the presence of an amount of aminocapronitrile in the composition. A large amount of water, at least 50 wt. %, is required to hydrolyse and subsequently polymerise this compound. A large amount of water is disadvantageous with respect to obtaining a high &eegr;
rel
in a polymerisation based on a 1-step polycondensation process. Another disadvantage is that several steps (at least 3) are required to obtain the polyamide according to WO-A-9943734. Another disadvantage of the process according to WO-A-9943734 is the need to use a catalyst to obtain a polyamide-6 with a &eegr;
rel
of at least 1.6 and at most 2.2. A polyamide-6 with such a low &eegr;
rel
is of little economic interest; in particular, it is not suitable for the production of fibres, films and moulded parts. Another disadvantage of the process according to WO-A-9943734 is that the polymerisation has to be carried out at elevated pressure, for example at a pressure of 55.10
5
Pa.
The aim of the invention is a process for the preparation of a polyamide that does not show the disadvantages according to the state of the art. In particular the aim of the invention is to prepare a polyamide-6 with a &eegr;
rel
of more than 2.2.
The inventors have now surprisingly found that such a polyamide can be prepared if the composition comprises at least
(a) 10-90 wt. % primary aminocarbonamide;
(b) 10-90 wt. % aminocarboxylic acid and/or lactam;
(c) 0-4 wt. % water;
the amounts being relative to the sum of the compounds (a+b+c).
Preferably the sum of the compounds (a+b+c) is at least 75 wt. % of the total composition, more preferably at least 85 wt. %, and most preferably at least 90 wt. %.
Surprisingly, it was also found that even a small amount of aminonitriles had a major negative influence on the &eegr;
rel
of the polyamide prepared with the process according to the invention. Preferably the composition therefore contains less than 0.1 wt. % aminocarbonitriles, more preferably less than 0.05 wt. %, most preferably less than 0.01 wt. %, the amounts being relative to the total composition. Such an influence was not described in WO-A-9943734.
Preferably the composition according to the invention contains 20-80 wt. %, more preferably 30-70 wt. % of the primary aminocarbonamide.
Preferably the composition according to the invention contains 20-80 wt. %, more preferably 30-70 wt. %, of the aminocarboxylic acid and/or lactam.
Preferably the composition according to the invention contains less than 2 wt. %, more preferably less than 1 wt. % water.
The primary aminocarbonamide present in the composition which is polymerized in the process according to the invention is a compound according to formula (I)
where m=3 to 12, preferably m=4 to 7. A particularly suitable compound is 6-aminocapronamide (m=5).
The aminocarboxylic acid is a compound according to formula (II)
where m=3 to 12, preferably m=4 to 7. A particular suitable aminocarboxylic acid compound is 6-aminocaproic acid (m=5).
The lactam is a compound according to formula (III)
where m=3 to 12, preferably m=4 to 7. A particular suitable lactam compound is &egr;-caprolactam (m=5).
The composition according to the invention may optionally also contain aminocarboxylic esters, secondary or tertiary aminocarbonamides and oligomers of aminocarboxylic acid compounds. Examples of suitable aminocarboxylic esters are aminocarboxylic esters of which the ester group contains a C
1-14
alkyl group, for example a methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl and tert-butyl group. The aminocarboxylic ester is for example 6-aminocaproic methylester and 6-aminocaproic ethylester. The oligomer is for example the cyclic oligomer of &egr;-caprolactam. Preferably the composition contains at most 25 wt. %, relative to the total composition, more preferably at most 15 wt. %, most preferably at most 5 wt. %, of such compounds.
The process is eminently suitable for the preparation of polyamide-6 (polycapronamide) from a composition of 6-aminocapronamide, 6-aminocaproic acid and/or &egr;-caprolactam. Such a composition can be obtained by mixing the aforementioned individual compounds, which are commercially available. However, a particularly suitable embodiment of the invention is that in which the composition is obtained in the reductive amination of a 5-formylvalerate ester, for example 5-formylmethylvalerate, for example according to the following reaction:
Examples of such a reaction are described in EP-A-729943, EP-A-729944, U.S. Pat. Nos. 4,766,237, 4,730,041, 4,731,445 and 5,068,398. Such a composition typically contains amounts of (a) 6-aminocapronamide and (b) 6-aminocaproic acid and/or &egr;-caprolactam in an a/b ratio=3/1 to 1/3, in particular 2/1 to 1/2. Such ratios are eminently suitable for the execution of the process according to the invention. The mixture, directly obtained via the reductive amination, also contains an amount of water and an alcohol, for example methanol, which can however easily be removed in their entirety or in part, for example through evaporation or distillation. Such a composition (from which the water and the alcohol have been almost completely removed) can then be directly polymerised to obtain polyamide-6. The invention hence also relates to a process for the preparation of polyamide-6 in which the composition is obtained in the reductive amination of a 5-formylvalerate ester performed in the presence of water, preferably 5-formylmethylvalerate.
The 5-formylvalerate ester can for example be obtained from butadiene via (a) a carbonylation and (b) a hydroformylation, for example according to the following reactions:
Examples of reaction step (a) are described in WO-9933779 and WO-9838151. Examples of reaction step (b) are described in WO-9518089 and WO-9733854. The invention hence also relates to a process for the preparation of polyamide-6 in which the composition is obtained from butadiene through successively (a) a carbonylation, (b) a hydroformylation and (c) a reductive amination of the mixtures of intermediates successively obtained.
The polyamide-6 prepared with the aid of the process according to the invention has a &eegr;
rel
of at least 2.2 and a low concentration of cyclic dimer of &egr;-caprolactam.
A particular advantage of the process according to the invention is that no catalyst need to be used, as a result of which the end product (the polyamide) contains no catalyst residues, or the preparation does not comprise a step in which a catalyst must be removed from or deactivated in the reaction mixture or polyamide. Another advantage is that the preparation can be carried out in polymerisation installations that are used on a large technical scale for the polymerisation of &egr;-caprolactam, for example as described in
Kunststoff Handbuch
1, Becker/Braun, Hanser Verlag, 1990, in particular in installations in which the polymerisation is carried out in a VK column (VK=
V
ereinfacht
K
ontinuerlich). In this case the composition according to the invention is supplied to the top of a vertical tube reactor or a series of
Haasen Nicolaas F.
Koning Cornelis E.
Rulkens Rudy
Van Geenen Albert A.
Hampton Hightower P.
Mayer Brown Rowe & Maw LLP
OSM IP Asseta, B.V.
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