GB2428629A

GB2428629A - Magnetically detectable bag

Info

Publication number: GB2428629A
Application number: GB0515398A
Authority: GB
Inventors: J Teasdale
Original assignee: B S Teasdale & Son Ltd
Current assignee: B S Teasdale & Son Ltd
Priority date: 2005-07-27
Filing date: 2005-07-27
Publication date: 2007-02-07
Also published as: GB0515398D0; WO2007012898A1

Abstract

A lightweight magnetically detectable bag made out of a film material comprising a layer of a magnetically-detectable material disposed between first and second layers of a plastics material. The first and/or the second layer may be of a non-food colour. The bag is designed to be easily detectable in food products and the like in the event that it enters a food production line, even if it is torn into small pieces by food processing machinery.

Description

DETECTABLE BAG

The present invention relates to detectable materials. In particular the invention relates to detectable materials for use in packaging in the food industry.

The problem of contamination of food by foreign bodies during preparation and handling is well known. Potential contaminants include items of clothing or fragments thereof A number of solutions to the problem have been proposed including visual detection, x- ray detection and magnetic detection.

For reasons of hygiene, clothing is typically made in a light colour (eg white) so that cleanliness of the clothing may be easily monitored. However, fragments of light coloured fabrics mixed with food are not easily detected, making visual detection : .. unreliable. Accordingly, to aid in detection, clothing may be given a non-food colour such as blue so as to be more easily visually detectable. Wa 94/02080 discloses a S...

glove comprising a dye whose colour is modified when the glove is perforated. * S. * S *

Visual detection of fragments is unreliable however, since the foodstuff in preparation is not always visible to an operator. The technique relies on the contaminant being both * .5 * sufficiently large to be easily seen, and located at an exposed surface of the foodstuff. S...

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* 25 US 5,922,482 (DE RICCI) discloses a detectable polymeric protective glove containing a material having conducting and/or magnetic properties which is detectable by a metal- particle detector.

wa 02/07186 discloses a glove produced from a polymeric material that contains an evenly dispersed quantity of electromagnetically detectable particles which may be in powder form. The glove may be produced by mixing the powder with a liquid plastisol to produce a relatively homogeneous mix where the powder or particles represents between 3-6% of the mix.

In addition to the problem of contamination due to fragments of clothing, the problem also exists that fragments of packaging materials such as polythene bags can also be introduced inadvertently into food during preparation.

According to the present invention there is provided a lightweight magnetically detectable bag made out of a film material comprising a layer of a magnetically- detectable material disposed between first and second layers of a plastics material.

The invention has the advantage that fragments of the bag inadvertently introduced into a foodstuff may be detected by a magnetic detector when the foodstuff passes the detector.

Preferably the bag comprises a composite of the magnetically detectable material, the magnetically detectable material being sandwiched between upper and lower layers of the film.

The layer of magnetically-detectable material may comprise a magneticallydetectable powder or the like dispersed within a plastics material. In a preferred embodiment, the * * magneticaljydetectable material comprises a dispersion of iron oxide, preferably synthetic black Fe304, in the plastics material. An example of this material is ECP 226.

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* * The plastics material may be polyethylene, e.g. linear low density polyethylene (LDPE) * 20 or any other material suitable for the manufacture of plastic bags. *..

Preferably at least one of the first and second layers of the plastics material, and most preferably both, is of a non-food colour readily visible to the eye. For example, the * : : layers may be of a blue colour.

The bag may be produced using a cross-head blown film extruder that allows the magnetically detectable material to be introduced in the centre of the resulting composite.

For a better understanding of the present invention, and to show how it may be carried into effect, reference shall now be made by way of example to the accompanying drawings, in which: FIGURE 1 is a cross-sectional schematic of a bag according to the preferred embodiment.

A bag according to the preferred embodiment of the invention comprises a composite of a magnetically-detectable component dispersed in polyethylene material B and a polyethylene material A in the form of an A- B-A sandwich as illustrated schematically in Figure 1. The magnetically detectable polyethylene layer B comprises a dispersion of synthetic black iron oxide, Fe304, in polyethylene.

The bag is formed by introducing the magnetically detectable LDPE compound into the centre of a film during the production process, which employs a cross-head blown film extruder. Preferably, an extruder temperature of 120 to 160 C and a die temperature of 160 to 180 C is employed.

In a currently preferred embodiment, the layer B is formed from a dispersion of synthetic black iron oxide, Fe304, in polyethylene, the dispersion having a melt flow rate of 20g/lomin (190 C/2.l6kg) and a bulk density of 550g/I : * The overall thickness of the resulting composite varies from 50 micron to 100 microns, with the detectable layer being nominally a minimum thickness of 25 microns. *. SS * S S...

* ** Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other *15 moieties, additives, components, integers or steps. $*SS

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

Claims

CLAIMS: 1. A lightweight magnetically detectable bag made out of a film

material comprising a layer of a magnetically-detectable material disposed between first and second layers of a plastics material.
2. A bag as claimed in claim 1, wherein the magnetically-detectable material comprises a dispersion of a magnetically-detectable powder in a plastics material.
3. A bag as claimed in any preceding claim, wherein the plastics material is polyethylene.
4. A bag as claimed in any preceding claim, wherein at least one of the first and second layers is of a non-food colour.

* **
5. A bag as claimed in any preceding claim, wherein both the first and second :.: layers are of a non-food colour. I. SS * U

* *.
6. A bag as claimed in claim 4 or 5, wherein the non-food colour is blue. U..
7. A bag as claimed in claim 5, wherein the first and second layers are of different * colours.
8. A bag as claimed in any preceding claim, wherein film material has a total thickness of 50 to 100 microns.
9. A bag as claimed in claim 8, wherein the layer of magneticallydetectable material has a minimum thickness of 25 microns.
10. A bag as claimed in any preceding claim, wherein the magneticallydetectable material comprises a dispersion of a synthetic black Fe304 in polyethylene.
11. A lightweight magnetically detectable bag substantially as hereinbefore described.