Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1999-10-06
2001-07-03
Woodward, Ana (Department: 1711)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C138S118000, C138S121000, C138S137000, C428S474900
Reexamination Certificate
active
06254949
ABSTRACT:
The invention relates to thermoplastic shaped articles, in particular hollow shaped articles, composed of hard and soft segments, processes for producing them by injection molding, extrusion and extrusion blow molding and the use of molding compositions A and B for producing the shaped articles.
Nowadays, blow molding is very widely used for producing hollow shaped articles. For this process, the tube is extruded into the opened mold and expanded, and the mold is then closed. Portions of the plastic material which extend beyond the required shape are pinched off and, after demolding, are removed as flash, which has to be recycled. The resultant moldings have an encircling pinch-off line, and this is a point of weakness.
Nowadays, 3-dimensional blow molding provides an advanced process for producing moldings of complicated geometry which have no pinch-off line. In contrast to the process described above, protruding portions of the plastic material which must be pinched off and removed as flash arise only at the two ends of the tube or parison. This process also avoids the formation of longitudinal pinch-off lines and is described, for example, in DE-A 37 18 605.
To produce moldings having a combination of materials which alternate in the longitudinal direction, it is advantageous to combine this process with sequential coextrusion. For this, the extrusion die is fed alternately from a number of extruders with different materials during extrusion of the parison, giving a tube having segments of differing construction and material properties. By this means it is possible, for example, to produce in a single operation blow moldings having flexible end zones and a rigid middle section. Until now, parts of this type had to be produced by complicated assembly of many sections.
For coextrusion, good adhesion of the components to one another is necessary. It is therefore advantageous not to switch completely from one component to the other, but just to vary the wall thickness ratio so that in every region of the molding there are layers of both components. The two components are thus mutually connected over a relatively large area and this improves their adhesion.
A further requirement for good adhesion is good compatibility of the components with one another.
Moldings having alternating property combinations are used in automotive construction and mechanical engineering. It is possible, for example, to accommodate within a pipe, a charge-air pipe for a turbodiesel engine for a vehicle, for example, segments for damping and heat expansion. For many applications moreover, the parts must have good heat resistance and good chemical resistance, for example to resist contamination by oil, and therefore both components must have these properties, since the performance of a part composed of a number of components is limited by its weakest component.
EP-B 0 393 409 describes shaped articles composed of a number of sections which are connected via limited areas of contact, the subsections consisting of, respectively, a polyolefin-modified polyamide (a polyamide mixed with a polyolefin functionalized with carboxyl or anhydride groups) and of a polyolefin. The sections are connected by injection-molding or extruding one component onto a hardened subsection composed of the other component. The adhesion of the, per se incompatible, polymers of the subsections of the shaped article is attributable to the compatibilizing effect of the functionalized polyolefin.
EP-A 0 659 534 discloses sequentially extruded coolant pipes having an outer layer of high bursting strength and an inner layer which is inert to coolants and does not swell, the outer layer consisting of a polyamide and the inner or intermediate layer, which is compatible with the outer layer, consisting of polyolefins modified with carboxyl or anhydride groups.
According to EP-A 0 659 535, these coolant pipes may be produced by extrusion blow molding combined with 3D manipulation of the parison.
A disadvantage with these moldings is the use of layers of polyolefin components having comparatively low heat resistance. It is an object of the present invention to provide thermoplastic moldings having alternating hard/soft segments, where the soft segments, besides high flexibility, also have in particular high chemical resistance and heat resistance, and where there is also good adhesion to a hard segment consisting essentially of polyamide. It is a further object of the invention to provide moldings having segments of differing stiffness composed of components connected to one another over a relatively large area, where each of the components has high heat resistance and high heat aging resistance, high long-term service temperature, high chemical resistance, in particular high resistance to oil, fuel and coolants, and high tensile and/or bursting strength.
We have found that this object is achieved by means of shaped articles composed of
a) from 5 to 95% by weight of a molding composition A composed of
a1) from 40 to 100% by weight of at least one thermoplastic polyamide, copolyamide or blends of these as component A1,
a2) from 0 to 60% by weight of fillers and/or reinforcing materials as component A2,
a3) from 0 to 20% by weight of impact modifiers as component A3 and
a4) from 0 to 30% by weight of other additives and processing aids as component A4,
where the total of the amounts of components A1 and, if used, A2 to A4, is 100% by weight,
b) from 5 to 95% by weight of a molding composition B composed of
b1) from 20 to 79.9% by weight of at least one thermoplastic polyamide, copolyamide or blends of these as component B1,
b2) from 20.1 to 80% by weight of at least one crosslinked elastomeric polymer as component B2 and
b3) from 0 to 30% by weight of other additives and processing aids as component B3,
where the total of the amounts of components B1, B2 and, if used, B3 is 100% by weight,
where, in the shaped article, segments of the molding compositions A and B are connected to one another over a relatively large area.
It has been found that when a highly crosslinked elastomeric polymer is used in a mixture with a polyamide, even when there is a high proportion of the elastomeric polymer in the mixture, the continuous phase is formed by the polyamide. The polymer proportion results in a soft component (molding composition B) which also has the properties of the polyamide, in particular high heat resistance, chemical resistance, tensile and bursting strength, and at the same time is compatible with the hard component (molding composition A) composed of polyamide.
Molding Composition A
Molding composition A is built up from
a1) from 40 to 100% by weight of at least one thermoplastic polyamide, copolyamide or blends of these as component A1,
a2) from 0 to 60% by weight of fillers and/or reinforcing materials as component A2,
a3) from 0 to 20% by weight of impact modifiers as component A3 and
a4) from 0 to 30% by weight of other additives and processing aids as component A4,
where the total of the amounts of components A1 and, if used, A2 to A4, is 100% by weight.
The molding compositions A comprise, as component A1, from 40 to 100% by weight, preferably from 70 to 100% by weight, particularly preferably from 85 to 100% by weight, of a thermoplastic polyamide, copolyamide or blends of these.
The polyamides which may be used are known per se. Examples of these are polyhexamethylene adipamide, polyhexamethylene pimelamide, polyhexamethylene suberamide, polyhexamethylene azelamide, polyhexamethylene sebacamide, polyhexamethylene dodecanediamide, polyoctamethylene suberamide, polydodecamethylene dodecanediamide, poly-11-aminoundecanamide and bis-(4-aminocyclohexyl)methanedodecanamide or the products obtained by ring-opening of lactams, eg. polycaprolactam or polylaurolactam. Other suitable polyamides are those based on terephthalic or isophthalic acid as acid component and/or trimethylhexamethylenediamine, bis(4-aminocyclohexyl)methane or 2,2-di(4-aminocyclohexyl)propane as diamine component and polyamide base resins prepared by copolymerizing two o
Gluck Alexander
Gotz Walter
Lohrbächer Volker
Mc Kee Graham Edmund
Völkel Mark
BASF - Aktiengesellschaft
Keil & Weinkauf
Woodward Ana
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