Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-03-26
2003-02-25
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S170000, C528S312000, C528S322000, C528S323000, C528S326000, C528S332000, C528S335000, C528S336000, C524S433000, C524S443000, C524S444000, C524S451000, C524S600000, C524S606000
Reexamination Certificate
active
06525166
ABSTRACT:
The invention relates to a polyamide comprising macromolecular chains exhibiting a star configuration, to a process for the manufacture of this polyamide and to the compositions comprising this copolyamide.
Recent years have seen the development of polyamides with a branched structure and of polyamides comprising structures of star type. These polyamides can be used for the manufacture of various articles, such as films, yarns, fibres or moulded articles, which may or may not comprise fillers.
However, P. J. Flory had from 1948 (JACS 70, 2709-18, 1948) studied the synthesis of a star polyamide by polymerization of &egr;-caprolactam with a compound comprising four acidic functional groups, namely tetracarboxypropylcyclohexanone. The results of these studies and the Theological and mechanical properties of these star polyamides were studied and confirmed by T. M. Warakonisky (Chem. Mat. 4-1000-4 1992 and U.S. Pat. No. 4,435,548). Thus, Warakonisky confirmed the decrease in the viscosity of the material in the molten state for similar molecular masses but also showed a significant decrease in the mechanical properties with respect to those of a linear polyamide.
In patent application Ser. No. 2,743,077, the Applicant Company has disclosed a process for the manufacture of a polyamide comprising a mixture of chains of star type and of linear chains. Such a polyamide exhibits a much higher fluidity in a molten medium than that of the linear polyamide with an equivalent molecular mass but, unlike the star polyamides disclosed by Flory and Warakonisky, it exhibits mechanical properties of an equivalent level to that of the linear polyamides with an equivalent molecular mass.
As is disclosed in the abovementioned patent application Ser. No. 2,743,077, this polyamide makes possible the production of moulded articles exhibiting complex shapes over narrow or thin parts. In addition, compositions comprising a high level of bulking or reinforcing fillers are manufactured and can be used in conventional moulding processes.
These advantageous mechanical and Theological properties are obtained in particular when the number-average molecular mass of the polyamide is greater than 15,000 and a concentration by number of linear chains is between 10 and 50%, preferably between 15 and 30%.
The concentration of the linear chain or of a chain of star type can be determined according to a method developed by Farina et al. and presented during the 4th Italian Convention on the Science of the report of this congress.
In short, this method makes it possible to calculate the ratio by mass X
W
of star polymer in the polyamide by determination of the concentration of amine and/or acid end groups. In the case of the presence of a polyfunctional compound (for example, of a polycarboxyl compound), the value X
W
can be defined by the following relationship:
X
W
=([COOH]—[NH
2
])/[COOH]
The polydispersity index D represented by
Mw
_
Mn
_
can be greater than or less than 2, depending on the degree of conversion of the polymer.
According to the process disclosed in patent application Ser. No. 2,743,077, the concentration of star polyamide and thus the fluidity in a molten medium of the polymer is determined, on the one hand, by the polyfunctional monomer/caprolactam ratio and, on the other hand, by the duration of the polymerization process.
As the range of concentration of star polyamide for which the mechanical and rheological properties are optimum for the desired application is relatively narrow, the industrial manufacture of such a polyamide requires procedures for managing and controlling the plant which are very difficult to employ in a reliable way.
In particular, in an industrial process, it is very difficult to exert precise control over the achievement, during the polymerization stage, of a degree of conversion corresponding to the desired ratio by mass X
w
of star structure.
One of the aims of the present invention is, in particular, to provide a novel process for the manufacture of polyamides comprising chains of star structure and linear chains which makes it possible to easily control the concentration of star chains during the polymerization.
To this end, the invention provides a process for the manufacture of a polyamide comprising macromolecular chains of star structure and linear macromolecular chains which consist in polycondensing a mixture of monomers comprising at least:
a) monomers of following general formula (I):
b) monomers of following general formulae (IIa) and (IIb):
c) monomers of following general formula (III):
Z
-
R
3
-
Z
(III)
in which formulae:
R
1
is a linear or cyclic, aromatic or aliphatic, hydrocarbon-comprising radical comprising at least two carbon atoms and which can comprise heteroatoms,
A is a covalent bond or an aliphatic hydrocarbon-comprising radical comprising from 1 to 6 carbon atoms,
Z represents a primary amine radical or a carboxyl group,
R
2
and R
3
, which are identical or different, represent substituted or unsubstituted, aliphatic, cycloaliphatic or aromatic, hydrocarbon-comprising radicals comprising from 2 to 20 carbon atoms, and which can comprise heteroatoms,
Y is a primary amine radical when X represents a carboxyl radical, or
Y is a carboxyl radical when X represents a primary amine radical,
M is an integer between 3 and 8.
The molar concentration of the monomers of formula (I) in the mixture of monomers is between 0.1% and 2% and that of the monomers of formula (III) is between 0.1% and 2%, the remainder to 100% corresponding to the monomers of general formulae (IIa) or (IIb). The polymerization reaction is advantageously carried out until the maximum degree of polymerization is achieved, optionally in the presence of a polycondensation initiator.
Furthermore, according to a preferred characteristic of the invention, the molar ratio of the monomers of formula (I) to the monomers of formula (III) is between 2 and 8. Under these conditions, the process of the invention makes it possible to obtain, reliably and industrially, a polymer comprising a concentration of chains of star type which is optimal for the desired mechanical and rheological properties.
Thus, this concentration by number of chains of star type is advantageously between 50 and 90%, preferably between 70 and 85%.
According to the invention, the monomer of general formula (I) comprises a radical R
1
which can advantageously be a trivalent radical of phenyl or cyclohexanyl type, which may or may not be substituted, tetravalent diaminopolymethylene radicals with a number of methylene groups advantageously of between 2 and 12, such as the radical originating from EDTA (ethylenediaminetetraacetic acid), octovalent cyclohexanonyl or cyclohexadinonyl radicals, or radicals originating from compounds resulting from the reaction of polyols, such as glycerol, sorbitol, mannitol or pentaerythritol, with acrylonitrile.
The preferred radicals R
1
of the invention are the cycloaliphatic radicals, such as the tetravalent cyclohexanonyl radical.
The radical A is preferably a methylene or polymethylene radical, such as the ethylene, propylene or butylene radicals.
According to a preferred embodiment of the invention, the letter m represents an integer greater than 3, advantageously equal to 4, 5 or 6.
According to another characteristic of the invention, the radical R
3
of general formula (III) represents polymethylene radicals which can comprise from 2 to 36 carbon atoms or cycloaliphatic or aromatic radicals.
Mention may be made, by way of example, as compound of formula (III), of succinic acid, adipic acid, terephthalic acid, isophthalic acid, sebacic acid, azelaic acid, dodecanoic acid, fatty acid dimers or di (&bgr;-carboxyethyl)cyclohexanone.
Mention may also be made of diamine compounds, such as hexamethylenediamine, 5-methylpentamethylenediamine, metaxylylenediamine, isophoronediamine or 1,4-diaminocyclohexane.
The monomers of formula (II) are advantageously lactams or amino acids, such as &egr;-caprolactam, lauryllactam and their &o
Di Silvestro Giuseppe
Speroni Franco
Yuan Cuiming
Zhang Haichun
Burns Doane Swecker & Mathis L.L.P.
Hampton-Hightower P.
Nyltech Italia S.r.l.
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