CA1161739A

CA1161739A - Ductile composite material and process for its manufacture

Info

Publication number: CA1161739A
Application number: CA000370027A
Authority: CA
Inventors: Karl Hagen; Karl H. Scholl; Gerhard Kautz; Gerhard Grimm
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1980-02-21
Filing date: 1981-02-04
Publication date: 1984-02-07
Also published as: DE3006447A1

Abstract

DUCTILE COMPOSITE MATERIAL AND
PROCESS FOR ITS MANUFACTURE
Abstract of the Disclosure A laminate of a cold worked thermoplastic inside layer covered with aluminum foil and a process for making the laminate. The laminates are useful for production of deepdrawn parts and intrusion molded parts and as cans, boxes, cups and shells such as condenser shells or shell casings for hunting or practice ammunition.

Description

DUCTILE COMPOSITE MATERIAL AND
PROCESS FOR ITS MANU~ACTURE
Back~round of the Invention 1. Field of the Invention The invention relates to a laminate, with a sandwich-like structure, of a thermoplastic material as inner layer and aluminum foil as cover layers, said composite material having metal-like stability properties.

2. Description of the Prior Art Composite foils of a polyolefin support layer and metal cover layers are known. A process for their manu-facture by combining the layers by means of an adhesion promoting layer is described in German Application 1,779,55~. The composite materials produced in this manner, however, have the drawback that their mechanical properties are primarily determined by the material properties of the center layer of thermoplastic material. That means that a high share of the stability properties of the metallic cover layers of the composite remain unused.
Similar to metals, thermoplastic materials, particularly partially crystalline materials, have the characteristic of cold work hardening, that is, their stability increases when they are wor~ed when cold. Cold working is a method frequently used in metal processing where the material to be worked is subjected to compressive or tensile treatment at temperatures below the crystallite melting point, that is, while "cold". Thus, for instance, in the case of a 6,6-polyamide semi-finished material, the tensile strength increases by a multiple of its original stability if the material i5 subjected to a cross-section reduction by cold rolling. At the same time, the breaking elongation is considerably reduced so that the thermoplastic material obtains ductile properties which correspond with those of selected metallic materials.
Such cold work-hardenecl thermoplastic materials display relaxation effects after transformation, that is, molded parts produced therefrom, such as foils, tend to go back to their original shape in the course of time and particularly when exposed to thermal influences.
A purpose of the invention was to develop a ductile composite material, the mechanical properties of which correspond with aluminum, whereas the other physical properties are determined by the inner plastic layer.
Summary of the Invention This invention relates to a composite material of a thermoplastic material as inner layer and aluminum foils as cover layers wheerein the inner layer is a cold-worked thermoplastic material.
Description of the Preferred Embodiments Useful as thermoplastic materials for the inner layer are partially to highly crystalline plastic materials such as polyolefins, for instance, high and low density polyethylene or polypropylene, polyamides, for instance, polyamide-6, polyamide-6,6 or polyamide-12, and polyether sulfones, polycarbonates, and saturated polyesters.

7~

Preferred are polyamide-6 or polyamide-6,6 which are filled with 5 percent by weight to 40 percent by weight of aluminum needles or aluminum grids. The thickness of the inner layer may vary within wide ranges between 0.5 millimeter and 15 millimeters, preferably between 1 millimeter and 10 milli-meters.
The cover layers consist of aluminum foils which preferably are 0.1 millimeter to 5 millimeters thick.
In one embodiment of the invention, the inner and cover layers are adhered by the use of melt adhesives or adhesion promoting foils. Suited for this purpose are normal plastics such as ethylene/acrylic acid-, ethylene/-vinyl acetate- or hydrogenated butadiene/styrene copolymers.
In accordance with this invention, cold worked thermoplastic materials are used. The cold working of the plastic layer may be carried out in the nor~al manner, for instance, by rolling at temperatures below the crystallite melting point, preferably at room temperature, achieving a reduction in the thickness by 10 to 80 percent, preferably between 30 and 70 percent.
In a preferred process for the manufacture of the laminates of this invention, the inner layer is combined with the cover layers, and, if used, the adhesion promoting foils and the laminate is pressed at a temperature above the softening temperature of the plastic material and adhesion promoting foil at a pressure of 20 bars to 200 bars~
preferably 50 bars to 100 bars for a period of 5 seconds to 60 seconds, preferably 15 seconds to 40 seconds.

17s~9 The plastic foil may be rolled off a coil and the laminate, due to its ductile properties, may also be wound on a coil. The material can be pressed using commonly used machinery, for instance, heatable multi-platen-presses.
The laminates of this invention may be used for the production of deep-drawing parts and intrusion molded parts such as pitchers, cams, beakers, cups and sleeves such as condenser sleeves or cartridge sleeves for ammunition for hunting or target practice.

Example A 4 millimeter thick foil of polyamide-6,6 was cold rolled resulting in a 50 percent recluction of the cross-section. On a multi-platen-press, the cold rolled polyamide-6,6 was pressed together with 0.3 millimeter thick aluminum foil pre-heated to 235C under a pressure of 50 to 100 bars for a period of 30 seconds. A well adhering laminate was obtained.
For comparison purposes, a composite material was produced using a polyamide which had not been cold rolled.
The tensile strength and the breaking elongation according to DIN 53 455 was measured using the composite materials and the raw materials.
The results are presented in the table below.

Tensile Breaking Strength Elongation [N.mm~2] %
Polyamide foil (not cold rolled) 50 200 Polyamide foil (cold rolled) 75 22 Aluminum foil 185 2 20 Laminate (unrolled PA) 58 18 Laminate (cold rolled PA)130 5

Claims

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A laminate of a cold-worked thermoplastic material as inside layer and aluminum foils as cover layers.

2. The laminate of claim 1 wherein the inner layer and the cover layers are combined by adhesion promoting foils.

3. The laminate of claim 1 wherein the thermo-plastic material is a polyolefin or polyamide.

4. The laminate of claim 1 wherein the thermo-plastic material is a polyamide-6 or polyamide-6,6 filled with aluminum needles or grids.

5. A process for the manufacture of the laminate of claim 1 which comprises a) combining the inner layer with the cover layers and b) pressing the material at a tempera-ture above the softening temperature of the thermoplastic material under a pressure of 20 bars to 200 bars for 5 to 60 seconds.

6. A process for the manufacture of the laminate of claim 2 which comprises a) combining the inner layer with the cover layer and the adhesion promoting foils and b) pressing the material at a temperature above the softening temperature of the thermoplastic material and/or the adhesion promoting material under a pressure of 20 bars to 200 bars for 5 to 60 seconds.