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
2001-01-25
2002-06-18
Woodward, Ana (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S435000
Reexamination Certificate
active
06407182
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to free-flowing transparent polyamide molding compositions having substantially unimpaired mechanical properties.
2. Discussion of the Background
Transparent copolyamides are generally distinguished over other materials by good low-temperature impact strength and good chemical resistance; in addition, they have high light transparency together with an amorphous structure, which provides good shrinkage behavior. Such materials can be used to produce molded articles having superior properties. However, transparent polyamide compositions have a high melt viscosity, which makes processing them considerably more difficult than other types of molding compositions. For example, thin-walled injection-molded articles can be produced from transparent copolyamides only with difficulty.
Plastics can usually be rendered more free-flowing by lowering the number average molecular weight. However, this generally also results in a significant impairment of the mechanical properties. In the case of polyamides, the impact strength in particular is drastically reduced by lowering the number average molecular weight of the polymer below a critical value.
Another way of improving the flow behavior of plastics is to add so-called flow improvers. Low molecular weight additives are frequently employed for this purpose. In the case of transparent plastics, however, additives of this type frequently result in a loss in transparency or in the formation of deposits in the mold during processing.
CA-A 2,039,136 describes amorphous polyamides having improved flow behavior which are obtained by adding certain types of carbon black to the polyamides. DE-A 3728 334 describes the improvement in the flow of amorphous polyamides by addition of polyolefins grafted with maleic anhydride. A. Siegmann et al. (Polymer, 1985, 26(9), 1325-1330) were able to reduce the melt viscosity of amorphous polyamides by the addition of liquid crystalline polyesters. In all of these cases however, the additives destroy the transparency of the amorphous polyamides.
C.F. Frihart et al. (Plast. Copd. 1990, 13(3), 109-110) were able to reduce the melt viscosity of an amorphous polyamide by adding at least 1% by weight of an additional amorphous polyamide based on a dimeric fatty acid (C
36
-dicarboxylic acid). However, this procedure results in a significant reduction in the modulus of elasticity of the blend.
U.S. Pat. No. 3,442,975 suggests that a polyethyleneimine-PA 6 graft copolymer can be used as flow aid for PA 6. However, this is a crystalline, opaque polyamide, and the mixture of polyethyleneimine-PA 6 graft copolymer with PA 6 is also opaque.
SUMMARY OF THE INVENTION
The object of the present invention is to develop free-flowing transparent polyamide molding compositions which do not have the above-mentioned disadvantages of the prior art, and whose mechanical properties, in particular tensile strength, modulus of elasticity, flexural strength and impact strength, are only slightly impaired compared to the unmodified transparent polyamides. This is achieved by blending the transparent polyamide with a graft copolymer formed from a branched polyamine and polyamide-forming monomers.
DETAILED DESCRIPTION OF THE INVENTION
The molding composition of the present invention comprises the following components:
I) from 50 to 99 parts by weight, preferably from 75 to 98 parts by weight and particularly preferably from 85 to 97 parts by weight, of a transparent polyamide, and
II) from 1 to 50 parts by weight, preferably from 2 to 25 parts by weight and particularly preferably from 3 to 15 parts by weight, of a graft copolymer prepared from the following monomers:
a) from 0.5 to 25% by weight, preferably from 1 to 20% by weight and particularly preferably from 1.5 to 16% by weight, based on the graft copolymer, of a branched polyamine having at least 4, preferably at least 8 and particularly preferably at least 11 nitrogen atoms and having a number average molecular weight Mn of at least 146 g/mol and preferably of at least 500 g/mol, and
b) polyamide-forming monomers selected from lactams, &ohgr;-aminocarboxylic acids and/or equivalent combinations of diamine and dicarboxylic acid, where the sum of the parts by weight of I) and II) is 100.
Transparent polyamides are known (Kunststoffhandbuch [Plastics Handbook] 3/4, Editors G. W. Becker and G. Braun, pp. 803 ff., Carl Hanser Verlag Munich, Vienna, 1998). Transparent polyamides which are suitable for the purposes of the invention are also described, for example, in the following publications: U.S. Pat. No. 2,742,496, CH-B-480 381, CH-B-679 861, DE-A-22 25 938, DE-A-26 42 244, DE-A-27 43 515, DE-A-29 36 759, DE-A-27 32 928, DE-A-43 10 970, EP-A-0 053 876, EP-A-0 271 308, EP-A-0 313 436, EP-A- 0 725 100 and EP-A-0 725 101.
The transparent polyamides used in accordance with the present invention, which can also be in the form of copolyamides, are prepared, for example, from the following monomers:
branched or unbranched aliphatic diamines having 6 to 14 carbon atoms, for example, 1,6-hexamethylenediamine, 2-methyl-1,5-diaminopentane, 2,2,4- or 2,4,4-trimethylhexamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine or 1,12-dodecamethylenediamine;
cycloaliphatic diamines having 6 to 22 carbon atoms, for example, 4,4′-diaminodicyclohexylmethane, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, 4,4′-diaminodicyclohexylpropane, 1,4-diaminocyclohexane, 1,4-bis(aminomethyl)cyclohexane, 2,6-bis(aminomethyl)norbomane or 3-aminomethyl-3,5,5-trimethylcyclohexylamine;
araliphatic diamines having 8 to 22 carbon atoms, for example, m- or p-xylylenediamine or bis(4-aminophenyl)propane;
branched or unbranched aliphatic dicarboxylic acids having 6 to 22 carbon atoms, for example, adipic acid, 2,2,4- or 2,4,4-trimethyladipic acid, azelaic acid, sebacic acid or 1,12-dodecanedioic acid;
cycloaliphatic dicarboxylic acids having 6 to 22 carbon atoms, for example, cyclohexane-1,4-dicarboxylic acid, 4,4′-dicaboxydicyclohexylmethane, 3,3′-dimethyl-4,4′-dicarboxydicyclohexylmethane, 4,4′-dicarboxydicyclohexylpropane and 1,4-bis(carboxymethyl)cyclohexane;
araliphatic dicarboxylic acids having 8 to 22 carbon atoms, for example, 4,4′-diphenylmethanedicarboxylic acid;
aromatic dicarboxylic acids having 8 to 22 carbon atoms, for example isophthalic acid, tributylisophthalic acid, terephthalic acid, 1,4-, 1,5-, 2,6- or 2,7-naphthalenedicarboxylic acid, diphenic acid or 4,4′-oxybis(benzoic acid),
lactams having 6 to 12 carbon atoms or the corresponding aminocarboxylic acids, such as, for example, 6-caprolactam, 6-aminocaproic acid, caprylolactam, &ohgr;-amipocaprylic acid, &ohgr;-aminoundecanoic acid, laurolactam or &ohgr;-aminododecanoic acid.
Examples of transparent polyamides which can be used in accordance with the invention are as follows:
the copolyamide made from terephthalic acid and the isomer mixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamine,
the polyamide made from isophthalic acid and 1,6-hexamethylenediamine,
the copolyamide made from a mixture of terephthalic acid/isophthalic acid and 1,6-hexamethylenediamine,
the copolyamide made from isophthalic acid, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and laurolactam or caprolactam,
the polyamide or copolyamide made from 1,12-dodecanedioic acid, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and, if desired, laurolactam or caprolactam,
the copolyamide made from isophthalic acid, 4,4′-diaminodicyclohexylmethane and laurolactam or caprolactam,
the polyamide made from 1,12-dodecanedioic acid and 4,4′-diaminodicyclohexylmethane,
the copolyamide made from a terephthalic acid/isophthalic acid mixture, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and laurolactam.
The branched polyamine can be, for example, any of the following classes of polyamines:
dendrimers, for example,
((H
2
N—(CH
2
)
3
)
2
N—(CH
2
)
3
)
2
-N(CH
2
)
2
-N((CH
2
)
2
—N((CH
2
)
3
—NH
2
)
Haeger Harald
Hauck Hans-Peter
Maul Juergen
Oenbrink Georg
Richter Ralf
Degussa - AG
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Woodward Ana
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