Reactive polyolefin hot-melt adhesive for use as a pre-coating that can be reactivated

Abstract

The invention relates to hot-melt adhesive compositions, which have at least one thermoplastic poly-α-olefin that is solid at 25°C and that contains silane groups, at least one thermoplastic poly-α-olefin that is solid at 25°C and that does not contain silane groups, and at least one resin that is tackifying at 25°C, the product of the content of component (a) with respect to the weight and the degree of grafting of component (a) being ≤ 0.06. In comparison to conventional hot-melt adhesive compositions based on poly-α-olefins, the hot-melt adhesive compositions according to the invention are characterized in that the hot-melt adhesive compositions can be reactivated after the processing and cross-linking, i.e., can be put into a liquid or soft state by means of heat and pressure and can be processed well again. At the same time, the hot-melt adhesives according to the invention have the physical processing properties characteristic of reactive polyolefin hot-melt adhesives, such as high initial heat resistance, high final strength and heat stability, and good resistance to environmental influences.

Description

Background technique [0001] For lamination to hot workpieces, mainly dispersion- or solvent-based polyurethane adhesives are used in practice. The binder system has a high molecular weight and provides high green strength after lamination, even at elevated demolding temperatures. Reactive polyurethane hotmelt adhesives have a significantly lower molecular weight than dispersed and dissolved polyurethane adhesives and therefore do not provide green strength, especially at elevated temperatures. This problem is hereinafter referred to as "initial heat resistance" problem. [0002] However, when laminating non-polar substances such as polypropylene or polyethylene with dispersed or dissolved polyurethane adhesives, pretreatment of the substrate is required in the case of polyurethane-based adhesives because polyurethane-based The mixture adheres only insufficiently to non-polar substrates due to its high polarity. Polyolefin hotmelt adhesives (also known as hotmelt adhesives) ...

AI Technical Summary

Problems solved by technology

A problem with these hot melt adhesives, however, is their extremely short open time, which is detrimental to their use as laminating adhesives that do not require reactivation (ie, remelting) during this time.

[0013] These polyolefin hotmelt adhesives are generally suitable for bonding in thin layers, however the problem is that they have a low initial heat resistance immediately after application

This makes the adhesive particularly unsuitable for laminating three-dimensionally shaped components and thermal workpieces

Furthermore, the usual problem with the use of such adhesives is that they have only short reactivation times

[0017] However, a disadvantage of conventional hot melt adhesives is their low strength under hot conditions

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