Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-09-14
2001-11-27
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S514000
Reexamination Certificate
active
06323274
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the addition of polyamides to crystalline polymers pigmented with organic pigments, to a process for the production of crystalline polymers, to injection-molded articles with improved performance properties produced therefrom and to preparations containing polyamides and organic pigments.
Crystalline polymers, such as in particular high-density polyethylene, are widely used for the production of injection-molded articles, such as for example plastic casks, crates, bottles or garden furniture. To this end, the melted polymer is injected into the mold, generally at around 300° C., the mold is then gradually cooled and, finally, the injection molding is removed from the mold. In many cases, it is desirable to produce colored products so that pigments are added to the polymer melts. Phthalocyanines, for example, are used to produce intensive blue and green tones while azo dyes or anthraquinone dyes, for example, are used for red and orange tones. However, a disadvantage in this regard is that, above a critical concentration of around 50 ppm, these organic dyes are capable of interacting with the polymers so that the crystal structure is disturbed. This is reflected in deformation (so-called warpage) of the injection-molded articles, i.e. a surface which, in principle, ought actually to have been flat corresponding to the injection mold develops undulations instead, with the result that, for example, the products are very difficult to stack. Another major disadvantage is that the crystal structure is occasionally disturbed so seriously that cracks and fractures can form in the material on cooling. It will readily be appreciated that, for example, a plastic cask which develops cracks after storage overnight outdoors has no further practical use.
There has been no shortage of attempts in the past to remedy this problem. However, these attempts largely come down to the use of inorganic pigments as opposed to organic pigments. Unfortunately, this seriously restricts the color spectrum. Another possible solution is to allow the injection-molded articles to cool over long periods in the mold. This does not of course help the throughput. German patent application DE-A1 4313090 (BASF) describes a process for avoiding warpage effects in injection-molded articles of HDPE which is characterized by the use of organic pigments which have been subjected to a low-temperature plasma treatment. This process is clearly unsuitable for operation on an industrial scale on account of the large amount of equipment involved. In addition, the crystallinity of the polymer can be reduced by co-condensing corresponding comonomers such as, for example, polypropylene or maleic anhydride [JP-A Hei 06/329811 (Showa Denko KK); U.S. Pat. No. 4,032,600 (Chemplex)]. However, polymers of this type do not necessarily satisfy the requirements involved.
Accordingly, the complex problem addressed by the present invention was to provide additives which would stabilize crystalline polymers pigmented with organic pigments, preferably HDPE pigmented with phthalocyanines, in such a way that warpaging and cold fractures no longer occur.
DESCRIPTION OF THE INVENTION
The present invention relates to the use of polyamides as warpage stabilizers for the production of crystalline polymers pigmented with organic pigments.
It has surprisingly been found that even the addition of small quantities of polyamides to crystalline polymers pigmented with organic pigments clearly reduces warpaging during injection molding and produces a lasting improvement in low-temperature resistance. This effect is of particular relevance when the properties of HDPE pigmented with phthalocyanine pigments or injection-molded articles produced therefrom have to be improved by addition of polyamides based on dimer fatty acid and aromatic diamines.
Polyamides
Polyamides preferably used as stabilizers are condensation products of (a) dicarboxylic acids corresponding to formula (I):
HOOC—X—COOH (I)
in which X is a linear or branched alkylene group containing 4 to 10 carbon atoms or the residue of the dimer fatty acid, with (b) diamines corresponding to formula (II):
H
2
N—Y—NH
2
(II)
in which Y is a linear or branched alkylene group containing 4 to 10 carbon atoms or an optionally C
1-8
-alkyl-, amino- or hydroxy-substituted phenyl radical. Typical examples are polyamides obtained by condensation of adipic acid, 1,12-dodecanedioic acid or dimer fatty acid with hexamethylenediamine, diaminobenzene or triaminobenzene. It has proved to be of particular advantage to use dimer fatty acid as the dicarboxylic acid. Dimer fatty acid is prepared by dimerization of oleic acid and has a total of 36 carbon atoms. In the course of the reaction, an unsaturated cycle is formed in the molecule. The dimer fatty acid may be used as a pure fraction or as the technical mixture which is directly obtained in the dimerization reaction and which still contains branched monomeric carboxylic acids and trimers. In addition, polyamides in the form of condensation products of dimer fatty acid with aromatic diamines, more especially diaminobenzene and triaminobenzene, have proved to be particularly effective stabilizers. The condensation of the two components is accompanied by the formation of a three-dimensional network structure which adapts itself ideally, more particularly to the crystalline structure of the HDPE, and is thus capable of correcting crystallinity defects. Polyamides of the type mentioned are described, for example, in German patent application DE-A1 4408276 (Henkel) to the teaching of which reference is specifically made here. The polyamides are used in quantities of normally 0.01 to 49.9% by weight, preferably 0.1 to 10% by weight and more preferably 1 to 5% by weight, based on the crystalline polymers.
Crystalline Polymers
The problem of warpage and cold cracking affects almost all crystalline olefins when organic pigments are added to them. Accordingly, the present invention also applies, for example, to polyolefins, polyacrylates, polyacrylamides, polyvinyl acetates, polyethylene imines and polyoxymethylenes. However, the greatest technical and economic impact of this problem is on pigmented high-density polyethylene and injection-molded articles produced therefrom because these polymers have particularly high crystallinity and are capable of interacting particularly easily with organic pigments, for example via the central metal atoms in phthalocyanines complexes. As already mentioned, the polyamides to be used in accordance with the invention, particularly those based on dimer fatty acid and aromatic diamines, adapt themselves particularly well to the crystal structure of HDPE in particular, so that improving the properties of high-density polyethylene is not only a central problem addressed by the invention, the proposed solution is also particularly suitable for this purpose.
Organic Pigments
In practice, injection-molded articles based on crystalline polymers, especially HDPE, are only susceptible to warpage and cold cracking when they contain organic pigments. The use of phthalocyanine complexes which can be obtained by reacting metal chlorides with phthalodinitrile and which correspond to formula (III):
where Me is a divalent metal, for example iron, manganese, nickel, cobalt and especially copper, is particularly sensitive. Another group of organic pigments to which the invention applies are azo compounds, especially in the form of azo pigments converted into color lakes. Azo dyes are normally obtained by the action of a diazonium compound on an amine, phenol or on the sulfonic or carboxylic acid group of an amine, phenol or naphthol. Another group of suitable organic pigments are the anthraquinone dyes which correspond to general formula (IV):
where R is hydrogen or hydroxyl. Typical examples where the system of substituents was permutated are anthraquinone, alizarin, quinizarin, chrysazin, hystazarin, purpurin, chrysophanic acid, quinalizarin and flavopurpurin. The pigme
Berti Fabio
Di Fiore Carmine
Rossini Angela
Drach John E.
Henkel Kommanditgesellschaft auf Aktien
Michl Paul R.
Trzaska Steven J.
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