Heat treated profile extruded hook

Abstract

The present invention discloses a method of forming a unitary polymeric protrusion or fastener comprising a strong and flexible thin base and a plurality of spaced apart thin hook members protruding from the unitary base surface, the method Typically involves extruding thermoplastic resin through a die that is machined to form the base layer and spaced ridges, ribs or hook features protruding from above the base layer surface. When die forming spaced ridges or ribs, the cross-sectional shape of the hook member is formed by a template and the initial hook member thickness is formed by cutting the ridge transversely at spaced locations along its length to form the ridge The scattered cutting part. The base layer is then stretched longitudinally (in the ridge direction in the machine direction) to separate the ridge cuts, which are then formed into spaced hook members. These extruded or cut-ribbed hook parts are then heat treated to cause at least a partial thickness shrinkage of at least the hook head portion by 5% to 90%, preferably 30% to 90%.

Description

technical field [0001] This invention relates to molded hook and loop fasteners for use with hooks. Background technique [0002] There are many known methods of forming hook materials for hook and loop fasteners. One of the first manufacturing methods for forming hooks involves weaving monofilament loops onto a fibrous or film substrate or the like, followed by cutting the loops of wire to form the hooks. These monofilament loops are also heated to form head structures such as those disclosed in US Pat. Nos. 4,290,174, 3,138,841 or 4,454,183. Generally, these woven hooks are durable and reusable. However, they are usually expensive and rough to the touch. [0003] For use with disposable garments and the like, it is often desirable to have hooks that are inexpensive and less abrasive. For these applications, the solution is usually to use a continuous extrusion process that simultaneously forms the base layer and the hook element or hook element precursor. See eg US Pa...

AI Technical Summary

Problems solved by technology

However, the limitation of this manufacturing method is that when forming the hook structure, the ribs are very narrow in the direction of extrusion or cutting

Cutting profiled ribs at very tight pitches is difficult in terms of speed for industrial production

In addition, when the cut length intervals are extremely small, it is easy to cause the previous rib cut part to melt due to the heat generated by the cutting operation

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