Process for the production of a polypropylene composite

Details Process for the production of a polypropylene composite Process for the production of a polypropylene composite

1992-11-12

1994-04-05

Weston, Caleb

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Composite having voids in a component

4283184, 4283186, 4284111, 156 82, 156242, 156245, 156322, B32B 3126

Patent

active

053003616

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a process for the production of a polypropylene composite which comprises a base layer, a foam layer and a top layer.
The disposal and recycling of plastic parts, preferably in the automotive sector, has become a topical subject. Many concepts have already been developed for the reprocessing and recycling of plastic waste. However, problems are caused in the recycling of composite systems in which the individual components comprise different polymers. In this respect, designs comprising entirely the same basic material are therefore desired.
The uses in question here are primarily those in which shock-absorbing, sound-insulating, heat-insulating or safety objectives must be achieved. The following are some examples from the automotive sector: dashboards, bumpers, headrests, door side panels, armrests, and others.
For these applications, combinations of the following materials have usually been used hitherto: acrylonitrile-butadiene-styrene polymers, polyphenylene oxide blends, polyvinyl chloride, polyurethane, polypropylene, polymethyl methacrylate (ABS, PPO, blends, PVC, PU, PP and PMMA), and a number of other materials, such as textiles or wood fiber molding materials.
Changeover to individual components based on the same material, for example in the case of base (insert)-foam decorative film composite, requires new methods in bonding technology.
It has been found that a strong and durable bond between the base layer and the foam layer can be achieved simply by welding.
The invention also relates to a process for the production of a polypropylene composite comprising at least one solid base layer and a foam layer by bonding the two layers, which comprises softening exclusively the surface of the base layer facing the foam layer by warming and then joining the base layer and the foam layer under a pressure of from 0.1 to 0.4 N/mm.sup.2.
The invention furthermore relates to the composite produced by this process.
The process according to the invention is used primarily for polypropylene composites which comprise at least one solid base layer and a foam layer bonded thereto.
The base layer comprises, for example, a propylene polymer made from
a) from 100 to 50 parts by weight, preferably from 90 to 60 parts by weight, of isotactic polypropylene or copolymers of propylene containing up to 25 parts by weight of ethylene,
b) from 0 to 40 parts by weight, preferably from 10 to 20 parts by weight, of rubber-like, polypropylene-compatible copolymers, and
c) from 0 to 50 parts by weight, preferably from 20 to 40 parts by weight, of reinforcing fillers.
However, the propylene polymer may also be a block copolymer containing from 1 to 40% by weight of copolymerized ethylene.
Preference is given to the use of a homopolymer or copolymer of propylene with a melt flow index MFI 230/5 in accordance with DIN 53 735 of from 5 to 25 g/10 min.
Particularly suitable rubber-like copolymers are amorphous copolymers made from 30-70% by weight of ethylene and 70-30% by weight of propylene, terpolymers made from ethylene, propylene and up to 5% by weight of dienes, preferably ethylidenenorbornene or 1,4-hexadiene, copolymers made from ethylene and from 10 to 45% by weight of vinyl acetate, or block copolymers made from styrene and butadiene or styrene and isoprene which have polystyrene blocks at the two ends of the molecule.
Preferred reinforcing fillers are talc, chalk, sawdust, glass fibers or glass beads; adequate softening of the surface of the base layer must still be possible.
The foam layer likewise comprises a propylene polymer, namely polypropylene or a propylene copolymer.
The foam layer may preferably be produced as a particulate foam from foamed beads or by extrusion. The density is usually between 10 and 100 g/l.
Suitable blowing agents for the foaming are, inter alia, gaseous, such as, for example, fluorinated hydrocarbons, or solid or liquid organic blowing agents having a decomposition or boiling point below the melting point of the polyolefin.
In addition to the blowing agent, conventiona

REFERENCES:
patent: 4826552 (1989-05-01), Breitscheidel et al.
patent: 4854993 (1989-08-01), Celia
patent: 4882002 (1989-11-01), Ando et al.

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