RECLOSABLE FASTENERS FOR PLASTICS BAGS AND THE LIKE

FIXATIONS REFERMABLES POUR SACS PLASTIQUES ET ANALOGUES

English Abstract

A reclosable fastener or zipper comprises interengageable male and female
profile members (12, 16), each provided on a base (13, 17). One or both vases
is/are provided with a lateral flange (18, 20, 22, 24). One or more of such
flanges is/are provided with a pair of spaced, shallow convexities (28) with a
layer of sealant material (30) co-extruded into the zone or zones between the
convexities.

French Abstract

Cette invention concerne une fixation refermable ou une fermeture à glissière comprenant des éléments d'emboîtement profilés mâles et femelles interchangeables (12, 16) disposés chacun sur une base (13, 17). Une des ceux bases ou les deux à la fois comportent un rebord latéral (18, 20, 22, 24). Un ou plusieurs de ces rebords présentent une paire de parties faiblement convexes (28) espacées avec une couche de matériau d'étanchéité (30) coextrudé dans la ou les zones situées entre les parties convexes.

Claims

5
CLAIMS:
1. A reclosable fastener comprising interengageable
male and female profile members, each provided on a base, and
with one base being connected to a lateral flange, wherein
said flange is provided with a pair of spaced, shallow
convexities with a layer of sealant material co-extruded into
the zone between the convexities.
2. A reclosable fastener comprising interengageable
male and female profile members, each provided on a base, and
with at least two lateral flanges connected to one base or to
the two bases, wherein one or more of said flanges is provided
with a pair of spaced, shallow convexities with a layer of
sealant co-extruded into the zone or zones between the
convexities.
3. A reclosable fastener according to claim 2, in which
each base is connected to two respective lateral flanges.
4. A reclosable fastener according to any preceding
claim, in which the layer of sealant material is of the order
of 3mm in lateral width.
5. A reclosable fastener according to any preceding
claim, in which the layer of sealant material is of the order
of 0.07mm in thickness.
6. A reclosable fastener according to any preceding
claim, in which the thickness of the layer of sealant material
is of the order of 44% of the combined thickness of the
sealant and flange.
7. A reclosable fastener according to any preceding
claim, in which the convexity which is nearer to the profile
member has a greater lateral width than the convexity which
is further from the profile member.
8. A reclosable fastener according to any preceding
claim, in which the thickness of the flange or flanges is less
outwardly of the outer convexity than inwardly of the inner
convexity.
9. A reclosable fastener according to any preceding

6
claim, in which one said base is connected by a hinge joint
to a lateral flange or flanges.
10. A method of extruding a reclosable fastener which
comprises extruding a male profile member on a base and a
female profile member on a base, with a lateral flange
connected to one base and with a pair of spaced, shallow
convexities proud of the flange, and co-extruding a layer of
sealant material into the zone between the convexities.
11. A method of extruding a reclosable fastener which
comprises extruding a male profile member on a base and a
female profile member on a base, with at least two lateral
flanges connected to one base or to the two bases, and with
a pair of spaced, shallow convexities on one or more of said
flanges, and co-extruding a layer of sealant material into the
zone or zones between the convexities.
12. A method according to claim 10 or 11, in which in
the said co-extrusion process the sealant material does not
fill the zone or zone s to the zone ends.

Description

CA 02452363 2003-12-30
WO 03/003871 PCT/GB02/03044
RECLOSABLE FASTENERS FOR PLASTICS BAGS AND THE LIKE
Field of the invention
This invention relates to a closure strip or zipper for
use as a reclosable fastener for plastics bags, pouches, etc.
It is also concerned with methods of manufacturing such
fasteners. Such zippers comprise male and female profile
elements located on a pair of opposed base members. The base
members are arranged to be bonded to a substrate, such as a
film, in the manufacture of the reclosable bags, pouches, etc.
Each base member and its profiled element are co-extruded.
Such a zipper is usually flanged, i.e. with one or both of the
base members extending laterally out beyond the region of the
male/female closure.
It is known to provide zippers where an adhesive is
provided on the flange or flanges, to aid in the welding of
the flange or flanges to a substrate, i.e. a plastics film or
web .
One of the ongoing objectives in the design of such
z~i.ppers is to reduce the heat required to seal the flanges to
the substrate material. Excessive heat is always a problem
and the lower the sealing temperature the easier it is to
produce an acceptable product.
Another objective is to avoid or at least minimise
leakage of the adhesive material.
Summery of the invention
It is. an object of the present invention to seek to meet
both these objectives.
In accordance with the invention there is provided a
reclosable fastener comprising interengageable male and female
profile member, each provided on a base, and with one base
being connected to a lateral flange, wherein said flange is
provided with a pair of spaced, shallow convexities with a
layer of sealant material co-extruded into the zone between
the convexities.
Also in accordance with the invention there is provided

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a reclosable fastener comprising interengageable male and
female profile members, each provided on a base, and with at
least two lateral flanges connected to one base or to the two
bases, wherein one or more of said flanges is provided with
a pair of spaced, shallow convexities with a layer of sealant
co-extruded into the zone or zones between the convexities.
Also in accordance with the invention there is provided
a method of extruding a reclosable fastener which comprises
extruding a male profile member on a base and a female profile
member on a base, with a lateral flange connected to one base
and with a pair of spaced, shallow convexities proud of the
flange, and co-extruding a layer of sealant material into the
zone between the convexities.
Also in accordance with the invention there is provided
a method of extruding a reclosable fastener which comprises
extruding a male profile member on a base and a female profile
member on a base, with at least two lateral flanges connected
to one base or to the two bases, and with a pair of spaced,
shallow convexities on one or more of said flanges, and co
extruding a layer of sealant material into the zone or zones
between the convexities.
Preferably, in the co-extrusion process, the sealant
material does not fill the zone or zones right up to the zone
ends. When pressure is applied in the sealing of the zipper
to the film or web, there is therefore space into which the
sealant material can travel, thereby reducing the risk of
leakage.
In a mufti-flanged zipper this zone of infilled sealant
material can be provided on some or all the flanges.
Brief description of the drawings
In order that the invention may be more fully understood,
an embodiment of zipper in accordance with the invention will
now be described by way of example and with reference to the
accompanying drawings, in which:
Fig. 1 is a shadowgraph of the zipper in accordance with

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the invention; and,
Fig. 2 is a schematic illustration giving typical
dimensions for a flange of the zipper shown in Fig. 1.
Description of the preferred embodiment
Referring first to Fig. 1, this shows a zipper comprising
a first profile member 10 having a male element 12 on a base
13 and a second profile member 14 having a female element 16
on a base 17. The profile members 10, 14 can be extruded
polymeric material, such as LDPE. The first profile member
IO 10 has two lateral flanges 18 and 20 extending from the base
13. The second profile member 14 has two lateral flanges 22
and 24. The second profile member 14 is connected to its
flanges 22, 24 not centrally hut at a margin of the base~l7,
thereby to provide a hinged link via a leg,26.
Each of the flanges 18, 20, 22, 24 is provided with a
pair of spaced, shallow convexities 28 formed from the
material of the flange. Between the respective pairs of
convexities 28 are infilled, co-extruded layers 30 of a
sealant material, such as EVA for example. In the co-
extrusion process, the sealant material preferably does not
wholly fill the zones between the convexities 28, but stops
short of the zone ends and is slightly proud of the
convexities. In this way, when heat and pressure is applied
in the process of sealing the flanges to an adjoining
substrate, the sealant material will be squeezed into the
space left available, reducing in thickness to the depth of
the convexities. Thus, leakage of sealant will be reduced or
eliminated.
Fig. 2 shows flange 18 on an enlarged scale and
schematically. The dimensions given in Fig. 2 are in
millimetres. It will be noted that the convexities 28 are not
both the same length; the one nearer the profile of the zipper
is longer. However, they could be of the same length. Also,
the thickness of the outer end 32 of the flange is less than
the thickness of the inner portion 34 of the flange. Again,

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these thicknesses could be the same, depending upon the
extrusion process. The thickness of the sealant layer is
0.070mm. This is about 440 of the overall thickness of the
flange 18 at this zone.
The dimensions are summarised as follows:
Length of sealant layer ....................... 3.OOOmm
Thickness of sealant layer ..................... 0.070mm
Thickness of convexities ....................... 0.070mm
Length of outer end 33 of flange .............. 0.500mm
Thickness of outer end 32 of flange ............ 0.110mm
Thickness of inner end 34 of flange ............ 0.160mm
These dimensions are given by way of example only.
Although in the illustrated embodiment the reclosable
fastener or zipper is shown as having four flanges, the
invention is equally applicable to a zipper having one, two
or three flanges. In the case of a mufti-flanged zipper, one
or more of the two, three or four flanges may be provided with
the two shallow, sealant-constraining convexities.

Representative Drawing