DE2306893B2 - POLYOLEFINE MOLDING COMPOUNDS - Google Patents

Description

The invention relates to polyolefin molding compositions, consisting from (1) 40 to 60% by weight of a polyethylene and (2) to 60% by weight of a polypropylene, the Polypropylene is a mixture of (2.1) 70 to 90% by weight of a polypropylene, of which (at a weight ratio Polypropylene: toluene of 5:95) less than wt .-% in (under normal conditions) boiling Toluene is soluble, and (2.2) 10 to 30% by weight of a polypropylene of which (at a weight ratio Polypropylene: toluene of 5:95) more than 99% by weight soluble in (under normal conditions) boiling toluene are, - with the provisos, (I) that the sum of the percentages by weight of components (1) and (2) as well as (2.1) and (2.2) each is 100 and (II) that the polypropylenes under (2.1) and (2.2) are approximately equal molecular weight distributions (determined using the gel permeation chromatography method) and (3) customary additives in customary amounts.

The known molding compositions of this type have compared to comparable molding compositions of other types Properties that are particularly advantageous for some areas of application; - but they also have one certain disadvantage, which is that the weld line strength as well as the cold impact strength of Injection molded parts made from these molding compounds still leave something to be desired.

The task of the present invention was "it, To show molding compositions of the type defined at the outset, which do not have the aforementioned disadvantage or which do not are burdened to a significantly lesser extent.

It has been found that the problem posed can be achieved if the molding compositions (1) are polyethylene with a certain density and in particular a certain melt flow index and (2) a polypropylene mixture contain with a certain density and in particular a certain melt flow index; - It is essential that the absolute values of the melt flow indices of the polyethylene and the polypropylene mixture are approximately the same.

The invention accordingly relates to polyolefin molding compositions composed of (1) 40 to 60% by weight of one Polyethylene and (2) 40 to 60% by weight of a polypropylene, the polypropylene being a mixture from (2.1) 70 to 90% by weight of a polypropylene, of which (with a weight ratio of polypropylene: toluene of 5:95) less than 1% by weight in (under normal conditions) is soluble in boiling toluene, and (2.2) 10 bis

30% by weight of a polypropylene, of which (with a weight ratio of polypropylene: toluene of 5:95) more than 99% by weight are soluble in (under normal conditions) boiling toluene, - with the provisos, (I) that the sum of the percentages by weight of components (1) and (2) and (2.1) and (2.2) is 100 in each case and (II) that the polypropylenes under (2.1) and (2.2) have approximately the same molecular weight distributions (determined according to the gel permeation chromatography method) exhibit. The molding compositions according to the invention are characterized in that they contain

(1) polyethylene such as the density of 0.935 to 0.965 g / cm ³ and the melt flow index (according to DIN 53 735, at 230 ⁰ C and 2.16 kg load of between 1 und4g / 10 min and

(2) a polypropylene mixture with a density of 0.895 to 0.910 g / cm ³ and a melt flow index (according to DIN 53 735 at 230 ° C and 2.16 kg load) between 1 and 4 g / 10 min,

with the proviso that the absolute values of the melt flow indices of the polyethylene under (1) and of the polypropylene mixture under (2) are approximately the same.

(In the present context, the expression "approximately the same" always means that none of the corresponding characteristics more than ± 5% of the mean of the two characteristics concerned deviates.)

The individual components of the molding compositions according to the invention are well known as such. Mention should be made only that the polyethylene component (1) in particular after the "Phillips process" but also after the »Ziegler process«, whereby the primary process products - if necessary - can be brought to the desired melt flow index by thermal degradation. Analogous the same applies to the polypropylene components (2), the or their constituents (2.1) and (2.2), after “Ziegler-Natta process” - possibly with a subsequent one thermal degradation - are available.

The production of the molding compositions in question can be carried out in the relevant customary manner with relevant usual devices take place, for. B. with kneaders or extruders. The molding compounds can also be customary auxiliaries or additives are added.

example

Using a commercially available kneader (Melt Temperature: 180 ⁰ C, kneading time 5 minutes) is prepared from the

Components of a polyolefin molding compound made from (1) 50% by weight of a polyethylene and (2) 50% by weight of a polypropylene, the polypropylene being a mixture of (2.1) 75.5% by weight of a polypropylene , of which (with a weight ratio of polypropylene: toluene of 5:95) less than 1 percent by weight is soluble in (under normal conditions) boiling toluene, and (2.2) 24.5% by weight of a polypropylene of which (with a weight ratio of polypropylene : Toluene of 5:95) more than 99 wt .-% are soluble in (under normal conditions) boiling toluene, - with the proviso that the polypropylenes under (2.1) and (2.2) have approximately the same molecular weight distributions (determined by the method of Gel permeation chromatography). According to the invention, the procedure is such that the molding composition contains (1) polyethylene having a density of 0.953 g / cm ³ and a melt flow index (according to DIN 53 735, at 230 ° C. and 2.16 kg load) 2.2 g / 10 min and (2) polypropylene as a mixture of such a density 0.896 g / cm ³ and the melt flow index (according to DIN 53 735 at 230 ⁰ C and 2.16 kg load) 2.2 g / 10 Min.

Injection molded parts (melt temperature during injection molding: approx. 250 ° C) made in the form of boxes (dimensions: 240 120 χ 75 mm; Wall thickness: 1.8 mm). These have good weld line strength as well as good cold impact strength.

Claims (1)

Claim: 1. Polyolefin molding compounds, consisting of (1) 40 to 60% by weight of a polyethylene; and (2) 40 to 60% by weight of a polypropylene, the polypropylene a mixture is composed of (2.1) 70 to 90% by weight of a polypropylene, of which (at a weight ratio Polypropylene: toluene of 5:95) less than 1 percent by weight in (under normal conditions) is soluble in boiling toluene, and (2.2) 10 to 30% by weight of a polypropylene, of which (in a Weight ratio of polypropylene: toluene of 5:95) more than 99% by weight in (under normal conditions) are soluble in boiling toluene, with the provisos, (I) that the sum of the percentages by weight of components (1) and (2) and (2.1) and (2.2) each is 100 and (II) that the polypropylenes under (2.1) and (2.2) the approximately equal molecular weight distributions (determined according to Method of gel permeation chromatography) as well as (3) customary additives in customary Quantities, characterized in that the molding compounds contain (1) polyethylene with a density of 0.935 to 0.965 g / cm ³ and a melt flow index (according to Din 53 735, at 230 ^° C. and 2.16 kg load) between 1 and 4 g / 10 min (2) a propylene mixture of such a density from 0.895 to 0.910 g / cm ³ and the melt flow index (according to DIN 53 735 at 230 ⁰ C and 2.16 kg load) of between 1 and 4 g / 10 min, with the proviso that the absolute values of the melt flow indices of the polyethylene under (1) as well as of the polypropylene mixture under (2) are approximately the same.