Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-05-11
2001-04-03
Woodward, Ana (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S514000, C525S183000
Reexamination Certificate
active
06211266
ABSTRACT:
The invention relates to thermoplastic molding compositions comprising
A) from 10 to 97.9% by weight of a partly crystalline polyamide,
B) from 0.1 to 50% by weight of a copolyamide composed of
B
1
) from 60 to 90 mol % of units derived from E-caprolactam and
B
2
) from 1 to 50 mol % of units derived from aliphatic dicarboxylic acids and from aliphatic diamines,
C) from 1 to 40% by weight of a copolymer based on styrene or on substituted styrenes and on unsaturated nitriles,
D) from 1 to 50% by weight of a fibrous filler and
E) from 0 to 30% by weight of other additives,
where the percentages by weight of components A) to E) are 100% in total.
In addition, the invention relates to the use of the novel molding compositions for producing fibers, films and moldings, and also to the moldings obtainable in this way, in particular welded moldings or those obtainable by two-component injection molding.
Because of their good mechanical properties, glass-fiber-reinforced polyamides have very wide application, in particular for highly stressed parts in the automotive and electrical industries, and also in mechanical and chemical engineering. A disadvantage of glass-fiber-reinforced polyamides is their high tendency to deform. This presents problems especially when complicated components are being produced which may possibly have to be combined with other components in subsequent steps by welding, screwing or two-component injection molding.
The tendency to deform is also a disadvantage in producing sheet-like or round components, and also components where there are high requirements in relation to dimensional tolerances.
Mixtures of polyamides, styrene copolymers and glass fibers are disclosed in JP-B 55/045 576. U.S. Pat. No. 3,243,478 discloses molding compositions composed of polyamide, styrene copolymers and fillers, and these have good mechanical properties and reduced moisture absorption. DE-A 25 44 252 discloses colored thermoplastic molding compositions which, besides polyamide and glass fibers, may also contain styrene copolymers. The subject matter of DE-A 33 34 561 is reinforced thermoplastic molding compositions which, besides a polyamide based on xylylenediamine (i.e. an amorphous polyamide) comprise other polyamides, and also a styrene copolymer. Molding compositions of this type are particularly good for coating purposes.
The molding compositions known hitherto, however, still have disadvantages with respect to deformation and shrinkage. In addition, the surface of the products is not adequate for the high requirements placed on parts used in applications where they are visible. Dimensionally stable thermoplastic molding compositions are also the subject matter of JP-A 03/009 952, where dimensional stability is improved by using an amorphous polyamide.
It is an object of the present invention to provide fiber-reinforced thermoplastic polyamide molding compositions which have lower shrinkage and deformation, and also an improved surface and reduced moisture absorption. At the same time, the mechanical properties and heat resistance should be retained to a very large extent.
We have found that this object is achieved by means of the molding compositions defined at the outset. Preferred embodiments are given in the subclaims.
Surprisingly, the combination of a partly crystalline polyamide with a copolyamide which is built up essentially from &egr;-caprolactam units gives significantly lower shrinkage and deformation after processing.
The novel thermoplastic molding compositions contain, as component A), from 10 to 97.9% by weight, preferably from 30 to 89.5% by weight and in particular from 30 to 84% by weight, of a partly crystalline thermoplastic polyamide.
The viscosity number of the polyamides of the novel molding compositions, determined in a 0.5% strength by weight solution in 96% strength by weight sulfuric acid at 25° C., in accordance with ISO 307, is generally from 80 to 350 ml/g, preferably from 110 to 240 ml/g.
Preference is given to partly crystalline resins with a molecular weight (weight average) of at least 5000, as described, for example, in U.S. Pat. Nos. 2,071,250, 2,071,251, 2,130,523, 2,130,948, 2,241,322, 2,312,966, 2,512,606 and 3,393,210.
Examples of these are polyamides derived from lactams having from 7 to 13 ring members, such as polycaprolactam, polycaprylolactam and polylaurolactam, and also polyamides obtained by reacting diocarboxylic acids with diamines.
Dicarboxylic acids which may be used are alkanedicarboxylic acids having from 4 to 12 carbon atoms, in particular from 6 to 10 carbon atoms, and aromatic dicarboxylic acids. Mention may be made here merely of adipic acid, azeleic acid, sebacic acid, dodecanedioic acid and terephthalic and/or isophthalic acid.
Particularly suitable diamines are alkanediamines having from 4 to 12 carbon atoms, in particular from 4 to 8 carbon atoms, such as hexamethylenediamine, 1,4-diaminobutane, di(4-aminophenyl)methane, di(4-aminocyclohexyl)methane, 2,2-di(4-aminophenyl)propane or 2,2-di(4-aminocyclohexyl)propane.
Preferred polyamides are polyhexamethyleneadipamide (nylon-6,6), polyhexamethylenesebacamide (nylon-6,10) and polycaprolactam (nylon-6), and also nylon-12, nylon-6,9 and nylon-11.
In addition, mention may be made of polyamides which are obtainable, for example, by condensing 1,4-diaminobutane with adipic acid at elevated temperature (nylon-4,6). Preparation processes for polyamides of this structure are described, for example, in EP-A 38 094, EP-A 38 582 and EP-A 39 524.
Other suitable polyamides are those obtained by copolymerizing two or more of the monomers mentioned above, or mixtures of more than one polyamide, the mixing ratio being as desired. The above copolymers are different from component B).
This includes in particular such partially aromatic copolyamides as nylon-6/6,T and nylon-6,6/6,T, the triamine content of which is less than 0.5% by weight, preferably less than 0.3% by weight (see EP-A 299 444).
The preferred partially aromatic copolyamides with low triamine content may be prepared by the processes described in EP-A 129 195 and 129 196.
The novel molding compositions contain, as component B), from 0.1 to 50% by weight, preferably from 0.5 to 40% by weight and in particular from 1 to 25% by weight, of a copolyamide differing from A) and composed of
B
1
) from 60 to 90 mol %, preferably from 65 to 85 mol % and in particular from 70 to 85 mol %, of units derived from &egr;-caprolactam and
B
2
) from 10 to 40 mol %, preferably from 15 to 35 mol % and in particular from 15 to 30 mol %, of units derived from aliphatic dicarboxylic acids and from aliphatic diamines,
Preferred dicarboxylic acids are alkanedicarboxylic acids having from 6 to 12 carbon atoms, in particular from 6 to 10 carbon atoms, adipic acid being particularly preferred.
Suitable diamines are alkanediamines having from 6 to 12 carbon atoms, in particular from 6 to 8 carbon atoms, hexamethylene-diamine being particularly preferred.
The viscosity number of the copolyamides, among which preference is given to nylon-6/6,6, is generally from 100 to 350 ml/g, preferably from 120 to 330 ml/g, determined in a 0.5% strength by weight solution in 96% strength by weight sulfuric acid at 25° C. in accordance with ISO 307. Processes for preparing copolyamides of this type are known to the person skilled in the art, and further details on this topic are therefore unncessary.
The novel molding compositions contain, as component C), from 1 to 40% by weight, based on the total of components A to E, of at least one copolymer based on styrene or on substituted styrenes and on unsaturated nitriles. Component C is present in preferred novel molding compositions in proportions of from 5 to 35% by weight, in particular from 5 to 15% by weight, based on the total of components A to E.
According to the invention, the copolymers C are built up from
c
1
) from 60 to 95% by weight, preferably from 63 to 85% by weight, of styrene or of substituted styrenes of the formula I or mixtures of these
where R is C
1
-C
8
-alkyl, preferably methyl or ethyl,
Grutke Stefan
Weber Martin
Wolf Peter
BASF - Aktiengesellschaft
Keil & Weinkauf
Woodward Ana
LandOfFree
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