Abstract A method for sealing at least two multilayer polymeric films each being built up of two or more alternating layers of different thermoplastic component polymers, e.g., polyethylene and polyamide, which includes the steps of applying pressure to at least two of the multilayer films arranged to be sealed together in a sealing area, simultaneously heating the films in the area to a first temperature which is at least equal to the softening point of the polyethylene component, but lower than the softening point of the polyamide component, e.g., about 140* C., and then heating the films in the sealing area to a second temperature which is at least equal to the softening point of the polyamide component, e.g., about 220* C., whereby the layers of the polyamide are fused together to provide a seal between the films. An apparatus for carrying out this method is also disclosed.
The method of claim 1 in which the pressure applied is higher than 100 kg./cm.2 when the films are first heated.
Claim 2
Dependent Claim
33 words
The method of claim 2 in which the pressure applied is from about 300 to about 1,800 kg./cm.2, and preferably from about 500 to about 1,000 kg./cm.2 when the films are first heated.
Claim 3
Dependent Claim
34 words
The method of claim 1 in which the pressure applied to the films at the higher temperatures is not more than about 20 to 30 kg./cm.2 and preferably from about 2 to 8 kg./cm.2.
Claim 4
Dependent Claim
35 words
The method of claim 1 in which there is a gradual transition in the Heating of the films from the first to the second temperature and the heating is carried out in a continuous manner.
Claim 5
Dependent Claim
29 words
The method of claim 1 in which in each film the layers which consist of the highest melting component together have a total thickness of at least 0.005 mm.
Claim 6
Dependent Claim
17 words
The method of claim 1 in which the component polymers of the successive layers are virtually immiscible.
Claim 7
Dependent Claim
19 words
The method of claim 1 in which the layers of each film alternately consist substantially of polyethylene and polyamide.
Claim 8
Dependent Claim
22 words
The method of claim 1 in which the total thickness of each of the films is not more than about 0.100 mm.
Claim 9
Dependent Claim
15 words
The method of claim 1 in which each of the films comprises eight alternate layers.
Claim 10
Dependent Claim
22 words
The method of claim 1 in which one of the outermost films is first covered with metal gauze at the sealing area.
Claim 11
Dependent Claim
26 words
The method of claim 1 in which pressure is applied to the films by a pair of the sealing jaws having contact surfaces that are profiled.