Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2001-11-19
2003-02-18
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S375000, C428S391000, C428S412000, C428S480000, C428S483000, C428S903300, C156S272200, C156S275100, C156S297000
Reexamination Certificate
active
06521326
ABSTRACT:
The invention relates to composites with welded regions and composed of moldings formed from thermoplastic molding compositions, and also to laminates made from these composites and to products produced therefrom and to recycled materials obtained therefrom, and also to the use of all of these, in particular in automotive construction.
There are many examples of applications for polyesters. For reinforced polyesters, preference is generally given to pretreated fillers, since these improve the adhesion between polymer matrix and filler and consequently affect many other technical properties.
Particularly preferred surface-treatment agents for the fillers here are epoxysilanized sizes or epoxy compounds (WO-A 94/24201).
If the abovementioned molding compositions are used to form moldings and these moldings are joined together to give composites with formation of welded seams, these welded seams have an ultimate tensile strength which is considerably lower than that of the molding itself if it were identically shaped. The ultimate tensile strength of the welded seams in these composites is generally not more than about 20% of the ultimate tensile strength of the moldings themselves if they were identically shaped, and this has an adverse effect on the ultimate tensile strength of the actual composites formed when compared with that of the moldings if they were identically shaped. This is particularly disadvantageous if composites are to be formed from two or more moldings where it is intended that the welded seams should not have dimensions larger than the moldings from which the composites are formed, as is the case, for example, with welded seams which are to remain invisible.
It is an object of the present invention, therefore, to improve the material properties, in particular the ultimate tensile strength, of the welded regions produced between the individual moldings within the composite.
We have found that this object is achieved by a composite composed of at least one first molding and second molding, where the first molding and the second molding have been immovably bonded to one another via at least one partial region of one surface &agr; of the first molding and of one surface &bgr; of the second molding, via a welded region, and where, based on the first molding, at least 50% by weight of the first molding is composed of a molding composition comprising:
A) from 5 to 99% by weight of a polyester,
B) from 1 to 95% by weight of a fibrous filler pretreated with an aminosilane compound and with an epoxy polymer,
C) from 0 to 30% by weight of an elastomeric polymer, and
D) from 0 to 40% by weight of other additives,
where the total of the percentages by weight of components A) to D) is 100%.
The balance amount of the moulding compound of the first structural part consists either of the components A to D as subsequently defined or consists of at least one polymer homogeneously miscible or compatible with said component A or of another polyester different from component A or of a polycarbonate or of a, poly(styrene-co-acrylonitrile).
The second structural part either has the same composition as the first structural part or consists of a moulding compound containing the components A to D as subsequently defined (fiber-reinforced structural part) in a composition different from the composition of the moulding compound of the first structural part.
In a preferred embodiment, the content of component B in said moulding compound of the second structural part is 0% by weight (fiber-non-reinforced structural part).
Moreover, the moulding compound of the second structural part may contain at least one additional component different from the components A to D, said additional component preferably being homogeneously miscible or compatible with said component A and preferably being another polyester different from component A or a polycarbonate or a poly(styrene-co-acrylonitrile).
The molding compositions according to the invention comprise, as component A), from 5 to 99% by weight, preferably from 20 to 98% by weight and in particular from 25 to 80%, by weight of a preferably thermoplastic polyester.
Use is generally made of polyesters based on aromatic dicarboxylic acids and on an aliphatic or aromatic dihydroxy compound.
A first group of preferred polyesters is that of polyalkylene terephthalates whose alcohol moiety has from 2 to 10 carbon atoms.
Polyalkylene terephthalates of this type are known per se and are described in the literature. Their main chain contains an aromatic ring which derives from the aromatic dicarboxylic acid. There may also be substitution of the aromatic ring, e.g. by halogen, such as chlorine or bromine, or by C
1
-C
4
alkyl, such as methyl, ethyl, iso- or n-propyl, or n-, iso- or tert-butyl.
These polyalkylene terephthalates may be prepared by reacting aromatic dicarboxylic acids, or their esters or other ester-forming derivatives, with aliphatic dihydroxy compounds in a manner known per se.
Preferred dicarboxylic acids are 2,6-naphthalenedicarboxylic acid, terephthalic acid and isophthalic acid, and mixtures of these. Up to 30 mol %, preferably not more than 10 mol %, of the aromatic dicarboxylic acids may be replaced by aliphatic or cycloaliphatic dicarboxylic acids, such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acids and cyclohexanedicarboxylic acids.
Preferred aliphatic dihydroxy compounds are diols having from 2 to 6 carbon atoms, in particular 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexane-diol, 1,4-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethylanol and neopentyl glycol, and mixtures of these.
Particularly preferred polyesters (A) are polyalkylene terephthalates derived from alkanediols having from 2 to 6 carbon atoms. Among these, particular preference is given to polyethylene terephthalate (PET), polypropylene terephthalate and polybutylene terephthalate (PBT), and mixtures of these. Preference is also given to PET and/or PBT which comprise, as other monomer units, up to 1% by weight, preferably up to 0.75% by weight, of 1,6-hexanediol and/or 5-methyl-1,5-pentanediol.
The viscosity number of the polyesters (A) is generally in the range from 50 to 220, preferably from 80 to 160, measured in a 0.5% strength by weight solution in a phenol/o-dichlorobenzene mixture in a weight ratio of 1:1 at 25° C., in accordance with ISO 1628.
Particular preference is given to polyesters whose carboxyl end group content is up to 100 mval/kg of polyester, preferably up to 50 mval/kg of polyester and in particular up to 40 mval/kg of polyester. Polyesters of this type may be prepared, for example, by the process of DE-A 44 01 055. The carboxyl end group content is usually determined by titration methods (e.g. potentiometry).
Particularly preferred molding compositions comprise, as component A), a mixture of polyesters which are different from PBT, for example PET. The proportion e.g. of the PET in the mixture is preferably up to 50% by weight, in particular from 10 to 30% by weight, based on 100% by weight of A).
It is also advantageous to use recycled PET materials (also termed scrap PET) in a mixture with polyalkylene terephthalates, such as PBT.
Recycled materials are generally:
1) those known as post-industrial recycled materials: these are production wastes during polycondensation or during processing, e.g. sprues from injection molding, start-up material from injection molding or extrusion, or edge trims from extruded sheets or films.
2) those known as post-consumer recycled materials: these are plastic items which are collected and treated after utilization by the end consumer. Blow-molded
PET bottles for mineral water, soft drinks and juices are easily the predominant items in terms of quantity.
Both types of recycled material may be used either as ground material or in the form of pellets. In the latter case, the crude recycled materials are isolated and purified and then melted and pelletized using an extruder. This usually facilitates handling and free flow, and metering for further steps in processing.
The recycled m
Fischer Michael
Rau Walter
Welz Martin
BASF - Aktiengesellschaft
Chen Vivian
Keil & Weinkauf
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