Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2002-01-29
2004-03-30
McKane, Joseph K. (Department: 1626)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S354000
Reexamination Certificate
active
06713596
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the bulk anionic polymerization of lactams with a catalytic system which is very stable at high temperature. This process operates in continuous or batch mode. By polymerizing the lactam in the presence of a polymer an alloy is obtained; it is also possible to work in the presence of fillers such as glass fibres to obtain a composite material. The catalytic system is a mixture of a sufficiently strong base capable of giving a lactamate, and an amide or a bisamide. This catalytic system is dissolved in the lactam, which consists for example of lactam 12. This solution is stable for 24 hours at 160° C. It suffices to heat to between 200 and 350° C., preferably between 230 and 300° C., for polymerization to take place within a few minutes.
PRIOR ART AND TECHNICAL PROBLEM
Patent application BE 1,007,446 A3 published on Jul. 4, 1995 describes the polymerization of caprolactam in the presence of lactamate (sodium or potassium lactamate), of poly(p-phenylene terephthalamide) (PPTA) fibres, and of a product chosen from (i) polyisocyanates blocked with lactams and (ii) acyllactams such as, for example, terephthaloylbiscaprolactam or adipoylbis-caprolactam. These blocked polyisocyanates and these acyllactams are imides or bisimides rather than amides or bisamides.
Chapter 19, pages 255 to 266 of the Book of Abstracts 212 ACS Meeting (1996), published in 1998 by the American Chemical Society, describes the polymerization of caprolactam in the presence of lactamate and N-acyllactams; this is the same process as in the prior art. This means that the two components of the catalytic system are mixed separately with the lactam and placed in contact in the polymerization reactor either in batch mode or in continuous mode. The disadvantage of this process is that the process is required to accurately meter these two flows of the reaction mixture in order to obtain a product with desired properties.
Patent application EP 786,483 describes the polymerization of lactams using a solution of a lactamate and an imide in the lactam, which is poured into the lactam to be polymerized. This catalytic system is unstable, since it consists of lactam 12 which reacts at and above 175° C.
Patent application FR 2,291,231 describes the polymerization of lactams in the presence of a catalytic system consisting (i) of a product chosen from sodium, potassium, alkali metal hydrides and hydroxides, and (ii) of a product chosen from organic isocyanates, ureas, amides and acid chlorides. The example describes only the use of sodium hydride and a promoter, without specifying its name. The extruder is fed with the mixture of lactam, hydride and promoter at 170° C., the extruder being at 250° C. Nothing is written or suggested regarding storage of this solution of unknown composition, and even less so regarding its stability.
Patent FR 1,565,240 describes the polymerization of lactam 12 in toluene using sodium methoxide and an amide such as acetanilide. The reaction takes place in a glass tube heated to 197° C.
BRIEF DESCRIPTION OF THE INVENTION
The Applicant has now developed a novel process for the anionic polymerization of lactams, in which:
(a) (i) a catalyst capable of creating a lactamate and (ii) a regulator chosen from the amides of formula R1—NH—CO—R2, in which R1 can be substituted with a radical R3—CO—NH— or R3—O— and in which R1, R2 and R3 denote an aryl, alkyl or cycloalkyl radical, are dissolved in the molten lactam; the temperature of this reaction mixture being between the melting point of the lactam and 15° C. higher,
(b) the solution from step (a) is introduced into a mixing device and is then heated to a temperature which is sufficient to obtain bulk polymerization of the lactam in no more than 15 minutes.
The inventors have discovered that this solution of step (a) was particularly stable.
According to a second embodiment of the invention, molten lactam not containing the mixture of catalyst and regulator is also introduced into step (b), i.e. the solution from step (a) is a master batch containing more catalyst and regulator than are required to polymerize the lactam in which they are dissolved.
In a third embodiment of the invention, polymerization of the lactam is carried out in the presence of one or more polymers (A) which are introduced either into the solution (a) or into the mixing device in step (b) or into the molten lactam which is added in addition according to the second embodiment of the invention, or according to any combination of these possibilities.
According to a fourth embodiment of the invention, polymerization of the lactam is carried out in the presence of one or more fillers which are introduced either into the solution (a) or into the mixing device in step (b) or into the molten lactam which is added in addition according to the second embodiment of the invention, or according to any combination of these possibilities. The third and fourth embodiments of the invention can also be combined.
According to a second embodiment of the invention, step (b) is replaced with step (b1) in which the solution from step (a) is introduced into a mould and is then heated to a temperature which is sufficient to obtain bulk polymerization of the lactam in no more than 15 minutes, and a polyamide article is thus obtained directly (so-called “RIM” technology). This second embodiment can also be carried out according to several forms as above.
According to a second form of the second embodiment, molten lactam containing neither catalyst nor regulator is added in step (b1) in addition to the solution from step (a) which is a masterbatch, and this molten lactam is optionally mixed in line with that obtained from step (a) before introduction into the mould.
According to a third form of the second embodiment, the polymerization of the lactam is carried out in the presence of one or more polymers (A) which are introduced either into the solution from step (a) or into the mould or into the molten lactam which is added in the second form in addition to that obtained from (a), or alternatively during the in-line mixing in this second form, or a combination of all these possibilities.
According to a fourth form of the second embodiment, the polymerization of the lactam is carried out in the presence of one or more fillers which are introduced either into the solution from step (a) or into the mould or into the molten lactam which is added in the second form in addition to that obtained from (a) or alternatively during the in-line mixing in this second form, or a combination of all these possibilities. The third and fourth forms of the invention can also be combined.
DETAILED DESCRIPTION OF THE INVENTION
As examples of lactams, mention may be made of those containing from 3 to 12 carbon atoms on the main ring and which can be substituted. Mention may be made, for example, of &bgr;,&bgr;-dimethyl-propiolactam, &agr;,&agr;-dimethyl-propiolactam, amylolactam, caprolactam, capryllactam and lauryllactam. The invention is particularly useful for caprolactam and lauryllactam.
The catalyst is a base which is strong enough to create a lactamate. Examples of catalysts which may be mentioned are sodium, potassium, alkali metal hydrides and hydroxides, and alkali metal alkoxides such as sodium methoxide or ethoxide.
As regards the regulator and the radicals R1, R2 and R3, examples of aryl radicals can be phenyl, para-tolyl and alpha-naphthyl. Examples of alkyls can be methyl, ethyl, n-propyl and n-butyl radicals and an example of a cycloalkyl radical is the cyclohexyl radical.
The preferred amides are those in which R1 and R2, which may be identical or different, are phenyl or an alkyl containing not more than 5 carbon atoms, it being possible for R1 to be substituted with R3—O— and R3 being an alkyl containing not more than 5 carbon atoms. Mention may be made, for example, of acetanilide, benzanilide, N-methylacetamide, N-ethylacetamide, N-methylformamide and (4-ethoxyphenyl)acetamide. Other preferred amides are alkylenebisamides such as ethylenebi
Biensan Michel
Faulhammer Heike
Victorien Franck
Vivier Thierry
Atofina
Millen & White et al.
Saeed Kamel
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