DE2733470A1 - Binary polypropylene moulding compsn. - contg. copolymer of ethylene! and alkyl (meth)acrylate! combining stiffness and cold toughness - Google Patents

Abstract

The compsn. consists of 60-95(wt.)% polypropylene (I) and 5-40% copolymer (II) of 50-90% ethylene and 10-50% 1-8C alkyl (meth)acrylate. (I) has an intrinsic viscosity of 1-9 (in decalin at 130 degrees C) an a density of 0.80-0.92 g./cm3, whilst (II) has a MFI of 0.01-120 (at 190 degrees C and 2.16 kp) and a gel content of 5-100% in the crosslinked state. The compsn. combines good cold toughness with good stiffness. It is suitable for the prodn. of sheets, profiles, panels, hollow mouldings and car body components.

Description

Binary polypropylene molding compound

Polypropylene, especially highly crystalline polypropylene, is one A material valued as a molding compound because it is easy to process, for example and leads to molded parts that have good heat resistance and a have high rigidity.

A known disadvantage of polypropylene, however, is that its toughness (for example the fracture toughness according to DIN 53 443) decreases very sharply with temperatures that below its glass point - i.e. approx. + 40C. In practice this means that at temperatures below + 40C the utility value of molded parts made of polypropylene is severely restricted.

There has therefore been no lack of attempts to test the low temperature toughness of polypropylene molding compounds to improve.

A relatively successful - and meanwhile also practically exercised- The attempt consists in subordinate to the molding compounds in addition to the polypropylene To introduce amounts of certain other linear, thermoplastic polymers. These additional thermoplastic polymers also include in particular Copolymers of higher amounts of ethylene and subordinate amounts of one Alkyl esters of acrylic or methacrylic acid (cf. OE-PS 237 286).

The good properties that an addition of the said thermoplastic Copolymers in polypropylene molding compounds with it, must, however, in turn with a certain disadvantage, namely a clearly noticeable drop in the stiffness values (e.g. in the tensile modulus of elasticity according to DIN 53 457).

Accordingly, it was an object of the present invention to To show polypropylene molding compositions of the type described above, which do not bring only good low-temperature toughness but also good stiffness values.

It has been found that this object can be achieved with polypropylene molding compounds, which are made up of (1) a specific polypropylene and (2) a specific one cross-linked copolymer of ethylene and an alkyl ester of acrylic or methacrylic acid.

The present invention is accordingly a binary one Polypropylene molding compound consisting of or essentially consisting of (1) 60 to 95, preferably 70 to 90, percent by weight (based on the total weight of the components (1) and (2)) one an intrinsic viscosity t2 (measured in decalin at 1300C) from 1 to 9, preferably 2 to 4, and a density (according to DIN 53 479) of 0.80 up to 0.92, preferably 0.88 to 0.91 g / cm3 containing polypropylene and (2) 5 to 40, preferably 10 to 30, percent by weight (based on the total weight of components (1) and (2)) of a crosslinked, in the still uncrosslinked state one Melt index (MFI at 1900C; 2.16 kp) from 0.01 to 120, preferably 0.1 to 20, and in the crosslinked state a gel content of 5 to 100, preferably 15 to 90, % copolymer from (2.1) having 50 to 90, preferably 60 to 80, percent by weight copolymerized ethylene and (2.2) 10 to 50, preferably 20 to 40, percent by weight a polymerized ester of acrylic or methacrylic acid with a C1 bis C8-alkanol, where the sum of the percentages under (1) and (2) and under (2.1) and (2.2) is 100 in each case.

Regarding the material side of the new molding compounds, the following is detailed accept: (1) Polypropylenes with the required characteristics are made of of polymer chemistry known as such and commercially available, so that closer Explanations are superfluous.

(2) For the thermoplastic - i.e. present in the uncrosslinked state - Copolymers of ethylene and an ester component applies accordingly to the Polypropylene (1) Said.

However, it should also be stated that such copolymers the most suitable are those made from 100 parts by weight of ethylene and 30 to 55 parts by weight of the ester component, i.e. about 65 to 77 percent by weight Polymerized ethylene and - in addition to 100% - to about 35 to 23 percent by weight consist of polymerized ester. As has also been shown, there are such Copolymers best suited for the purpose according to the invention, their ester component is n-butyl acrylate.

The crosslinked copolymers to be used according to the invention can in a simple manner from the corresponding, as yet uncrosslinked, thermoplastic copolymers can be obtained by networking them. The networking for its part can be relevant to can be carried out in the usual way, e.g. by means of radical formers or radiation. Instead of more detailed information on this, reference is made to "Kunststoffe", Vol. 60, 1970, Pages 883 - 889. The control or determination of the gel content (= degree of crosslinking) can also be carried out in the relevant customary manner; in particular can the gel content can be reported as the insoluble fraction that occurs after eight hours Extraction with xylene at 1400C from a gritty material sample remains.

(3) If desired, the molding compositions according to the invention can additionally to the components (1) and (2) relevant usual auxiliary zwr. * 2uwatzatorre in the contain usual amounts, e.g. processing aids, stabilizers, coloring agents Fabrics, flame retardant fabrics, etc.

The production of the new molding compounds from their components can be done in relevant usual manner, it goes without saying that one ensures that the components are distributed as homogeneously as possible; - i.e. that one expediently knows about the molten state of the polypropylene and the other component (s) are processed under intensive mixing conditions, for example in a two-screw mixer.

The molding compositions according to the invention can be used for processing Polypropylene molding compounds common processing machines to those for polypropylene known and customary molded parts are processed, e.g. into foils, profiles, Plates, hollow bodies and body parts.

Example A mixture of (1) 75 percent by weight is assumed (based on the total weight of components (1) and (2)) of a gritty, an intrinsic viscosity 09 l (measured in decalin at 130 ° C) of 1.82 and a Density (according to DIN 53 479) of 0.903 g / cm3 containing polypropylene and (2) 25 Weight percent (based on the total weight of components (1) and (2)) one Gritty, crosslinked, in the still uncrosslinked state a melt index (MFI at 1900C; 2.16 kp) of 1.5 and a gel content of 50% in the crosslinked state Copolymer of (2.1) 70 percent by weight polymerized ethylene and (2.2) 30 percent by weight polymerized ester of acrylic acid with n-butanol.

This mixture is homogenized in a kneader at about 2300C.

The result is a molding compound that is tough at low temperatures and relatively stiff Have molded parts manufactured.

Claims (1)

Claim Binary polypropylene molding compound consisting of or in essentially consisting of (1) 60 to 95 percent by weight (based on the total weight of components (1) and (2)) one has an intrinsic viscosity Ir / l (measured in decalin at 13000) from 1 to 9, as well as a density (according to DIN 53 479) from 0.80 to 0.92 g / cm3 containing polypropylene and (2) -5 to 40 percent by weight (based on the total weight of components (1) and (2)) of a crosslinked, in the still uncrosslinked state one Melt index (MFI at 1900C; 2.16 kp) from 0.01 to 120 and in the crosslinked state copolymer from (2.1) 50 to having a gel content of 5 to 100% 90 percent by weight of copolymerized ethylene and (2.2) 10 to 50 percent by weight a polymerized ester of acrylic or methacrylic acid with a Cl bis C8-alkanol, where the sum of the percentages under (1) and (2) and under (2.1) and (2.2) is 100 in each case.