Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-10-24
2003-07-15
Harlan, Robert D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S268000, C524S269000, C524S502000, C524S515000, C525S240000
Reexamination Certificate
active
06593403
ABSTRACT:
The invention relates to a composition for improving the mechanical properties of polyolefins and vinyl polymers, especially polyethylene, polypropylene and also copolymers and mixtures thereof. The plastics may be in the form of virgin material or recycled material. Examples that may be mentioned include polyethylene materials of the kind used in plastics fuel containers (PFCs). The invention relates also to a method of improving the mechanical properties and increasing the molecular weight of the afore-mentioned plastics by chemical modification, to the use of the additive combination according to the invention in improving the mechanical properties of plastics and also to the modified plastics product obtained by the said method.
Although they are employed in many fields of use, technical materials based on polyolefins and vinyl polymers are unable to meet all of the demands that the market requires. An improvement in their properties is desirable, especially as regards their mechanical properties, for example impact strength at low temperatures.
Plastics such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) etc. can, moreover, be damaged by processing and by their use, often for many years, under the influence of thermal stress, oxidation, weathering and light so that the stability of the material is no longer assured and the physical and mechanical properties deteriorate significantly. A consequence of that damage is that the resulting recycled materials cannot be used again for the original application. For example, because of inadequate long-term stability and poor mechanical properties, HDPE recycled from used plastics fuel containers (PFCs) cannot be re-used as the sole material in the production of new PFCs.
EP 702 704 B1 describes the use of an additive combination for stabilising recycled thermo-plastics, by means of which it is possible to improve the mechanical properties of the material. The improvement is, however, not adequate, especially in respect of low temperature impact strength.
The aim of the present invention is accordingly to provide a new additive combination by means of which it is possible to obtain plastics that have, compared with the additives known hitherto, improved mechanical properties, especially improved impact strength. In particular, the addition of such an additive system should also make possible complete and unlimited re-use, for the same application, of HDPE recycled from used plastics fuel containers.
Plastics fuel containers are mass-produced by means of extrusion blow moulding. That type of process, which has short cycle times and many further process parameters, makes high demands of the quality of the HDPE starting material used (thermodynamic properties, Theological properties at high and low shear rates, surface properties in the melt and on cooling of the hollow moulded article, inter alia).
In such a process, used plastics fuel containers (PFCs) are processed for example by comminution, removal of petrol/diesel residues by extraction, for example using solvents. During extraction with solvents (e.g. hexane or other readily volatile alkanes or alkane mixtures), not only are the contaminants (petrol/diesel residues etc.) removed but active stabiliser residues that may be present are also removed. Because of the prior damage that the material has additionally undergone, re-use in demanding applications (for example, in a closed cycle as plastics fuel containers) is virtually impossible.
The use of recycled polyethylene as a constituent of multilayer fuel tanks is described many times in the prior art but, in view of the poorer mechanical properties of the recycled material compared with virgin material, the recycled material is not used in the outer layers of the blow-moulded article. Moreover, the proportion thereof in the product is, at present, max. 45% by weight [
Kunststoffe
82, (1992), 3, 201-206].
The use of mixtures based on commercially available primary and secondary anti-oxidants is merely able to stabilise the material in the processing process and for the duration of its use; an improvement in mechanical properties, however, is not achieved [R. Gächter, H. Müller, “Kunststoff-Additive”, 3rd edition 1989, 26-31+65-74, Carl Hanser Verlag, Munich].
The use of an additive combination comprising at least one multifunctional oxirane in addition to anti-oxidants is described in EP-702 704 B1. The said system can be used for stabilising recycled thermoplastics and modifying the rheology thereof and serves, inter alia, to improve the mechanical properties of the material. However, an improvement in the mechanical properties at low temperatures (<0° C.), especially low temperature impact strength, is not achieved as a result.
It has now been found that that problem can be solved using a composition comprising a material based on polyolefins or vinyl polymers and comprising at least one polymer or oligomer modified by functional groups and comprising a multifunctional epoxide.
It can be advantageous to add at least one anti-oxidant or further processing stabiliser in addition.
The addition of that multifunctional polymeric component results in a further improvement in impact strength, especially in low temperature impact strength at temperatures <0° C., as required for plastics fuel containers (PFCs).
The invention relates to a composition comprising
a) at least one polyolefin or vinyl polymer;
b) at least one di- or poly-functional (co)polymer or (co)oligomer having a glass transition temperature of less than 10° C., wherein the functional group is a carbon-carbon double bond, an epoxy group, an amine group, a carboxylic acid group, a carboxylic acid ester group or a carboxylic anhydride group, an OH group, an SH group or an isocyanate group, and
c) a multifunctional epoxide which is different from the di- or poly-functional (co)polymer or (co)oligomer wherein the functional group is an epoxy group.
The present invention relates also to a composition comprising
a) a recycled material of at least one polyolefin or vinyl polymer;
b) at least one di- or poly-functional (co)polymer or (co)oligomer having a glass transition temperature of less than 10° C., wherein the functional group is a carbon-carbon double bond, an epoxy group, an amine group, a carboxylic acid group, a carboxylic acid ester group or a carboxylic anhydride group, an OH group, an SH group or an isocyanate group.
Preference is given to a composition wherein the polyolefin or vinyl polymer is a recycled material.
In the context of the present invention, recycled material is understood to be a polyolefin or vinyl polymer which has undergone prior damage and which has been collected and taken for reprocessing.
The polyolefin or vinyl polymer which has undergone prior damage is, for example, polyolefin obtained from collections from households, retail businesses (e.g. supermarkets) and in industrial concerns (e.g. stretch films, sacks etc.) and may be, for example, films, bags, bottles and other containers or foamed plastics. However, plastics which have undergone prior damage as a result of use, storage or processing, for example production waste (films etc.) or separately collected scrap materials (agricultural sheeting, vehicle parts etc.), may also be re-used.
Preference is given to recycled polyolefin materials, especially of HDPE, and special preference is given to used vehicle fuel tanks of plastics.
Examples of vinyl polymers are polyvinyl chloride, polystyrene, especially syndiotactic polystyrene and its copolymers (e.g. with acrylonitrile), acrylate polymers, polymethyl methacrylate or polyvinyl acetate.
Preference is given to a composition wherein the vinyl polymer is a polystyrene, polyacrylonitrile or a copolymer thereof.
Examples of polyolefins are:
1. polymers of mono- and di-olefins, for example polypropylene, polyisobutylene, polybutene-1, poly-4-methylpentene-1, polyisoprene or polybutadiene and polymers of cycloolefins such as cyclopentene or norbornene; also, polyethylene (whic
Pfaendner Rudolf
Simon Dirk
Steinert Andreas Konrad
Ciba Specialty Chemicals Corporation
Harlan Robert D.
Stevenson Tyler A.
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