MULTI-TRIP POLYESTER CONTAINERS WITH OXYGEN SCAVENGING MATERIAL

Abstract: A multilayer polyester bottle includes 3 or more polymeric layers, at least the inner and outermost layers being formed of polyester, and one or more intermediate layers comprising an oxygen scavenging material. The total thickness of the polyester layers in the sidewall of the bottle is at least 0.4 mm, and the total thickness of the one or more intermediate layers is at least 0.02 mm, so as to provide a multi-trip polyester bottle. A preform for such a bottle, comprising polyester layers of at least 5 mm and one or more oxygen scavenging layers of at least 0.3 mm, is also described. The bottle may include marker means for indicating when a predetermined period of oxygen scavenging is close to expiry.

Description: MULΗ-TRIP POLYESTER CONTAINERS WITH OXYGEN SCAVENGING MATERIAL This invention relates to polyester containers, and particularly multilayer containers such as bottles for oxygen sensitive products such as beers and fruit juices etc . Oxygen scavenging materials are known, such as those described m WO89/01012, m which a transition metal promotes the oxidation of an oxidisable polymer. O89/01012 gives as an example polyamide materials being oxidised by means of cobalt Siccatol (TM Akzo Chemie) . Multilayer structures are envisaged as potential embodiments . More recently multilayer bottles have been manufactured and sold m the US by Continental PET Technologies Inc. for beer products. These bottles appear to be five layer structures, with layers 1, 3 and 5 being formed from PET, and layers 2 and 4 from a polyamide material known as MXD6 further containing between 300 and 500 ppm cobalt. These bottles may have been made in accordance with the disclosure of W099/38914, filed by Continental PET Technologies Inc. Measurements of the bottles show that the approximate thickness of the layers of these bottles are as follows: Thus the total thickness of the PET layers is 0.27875mm and the oxygen scavenging (MXD6 + CO) layers is 0.015mm. The publicity on recyclymg of these bottles, produced by Continental PET Technologies Inc, makes it clear that these bottles are "single trip" bottles. According to the invention there is provided a polyester bottle comprising a neck portion, a side-wall portion, a shoulder portion interconnecting the neck and side-wall portions, and a base portion, the bottle consisting of three or more polymeric layers, at least the inner and outermost layers being formed of polyester, and one or more intermediate layers comprising an oxygen scavenging material, the total thickness of the polyester layers m the side-wall portion being at least 0.4mm, and the total thickness of the one or more intermediate layers m the side-wall portion being at least 0.02mm, the thickness of the polyester and intermediate layers being so as to provide a multi-trip polyester bottle. Preferably the total thickness of the one or more intermediate layers m the side-wall portion is at least 0.025mm, and the total thickness of the polyester layers m the side-wall portion is at least 0.5mm. Whilst refillable multi-trip bottles are known per-se (as exemplified by EP0247566B) , none of the prior art on bottles with oxygen scavenging materials envisages anything other than single trip bottles. Applicants believe they are the first to appreciate that oxygen scavenging materials can be used to design a multi-trip bottle and to design the bottle accordingly. The oxygen scavenging material conveniently comprises an oxidisable organic polymer and a transition metal m a positive oxidation state. The oxidisable organic polymer is conveniently a polyamide, preferably a polymer containing units of the formula -NH-CH 2 -arylene- CH 2 -NH-CO-alkylene-CO- . The polyester is preferably polyethylene terephthalate . Preferably the bottle has three polymeric layers, an outermost layer of polyester, an innermost layer of polyester, and an intermediate layer comprising an oxidisable organic polymer and a transition metal m a positive oxidation state. The total thickness of the one or more intermediate layers preferably comprises approximately 5% of the total thickness of the side-wall portion. The invention further resides in a preform for a polyester container, the preform comprising a neck portion, a side-wall portion to be drawn, and a closed bottom portion, the preform including three or more polymeric layers, at least the inner and outermost layers being formed of polyester, and one or more intermediate layers comprising an oxygen scavenging polymer, the total thickness of the polyester layers in the side-wall portion being at least 5mm, and the total thickness of the one or more intermediate layers in the side-wall portion being at least 0.3mm, the preform being suitable for the manufacture of a multi-trip polyester container. The total thickness of the one or more intermediate layers in the side-wall portion of the preform is preferably at least 0.35mm, and the total thickness of the polyester layers m the side-wall portion is at least 6mm, preferably at least 7mm. The oxygen scavenging material conveniently comprises an oxidisable organic polymer and a transition metal m a positive oxidation state. The oxidisable organic polymer is conveniently a polyamide preferably a polymer containing units of the formula -NH-CH 2 -arylene- CH 2 -NH-CO-alkylene-CO- The polyester is preferably polyethylene terephthalate . The preform preferably comprises three polymeric layers, an outermost layer of polyester, an innermost layer of polyester and an intermediate layer comprising an oxidisable organic polymer and a transition metal in a positive oxidation state. The total thickness of the one or more intermediate layers of the preform preferably comprises approximately 5% of the total thickness of the side-wall portion . In addition to polyamides, the oxidisable organic polymer may be selected from a variety of polymers. Examples include ethylenically unsaturated hydrocarbons (for example as described in EP0507207A) , polyolefins such as polypropylene and low density, medium density and high density polyethylene (e.g EP0451762A) , ethylene vinyl copolymers such as EVOH (e.g US5281360), amines (e.g EP0542512), ascorbic acid (e.g WO91/17044), olefm- diene copolymers (e.g EP0713899A) , and aliphatic polyketones (e.g W09813266) . As can be seen from the above, many examples of oxygen scavengers comprising metal promoted oxidisable polymers have previously been proposed, but all for single trip containers. Cobalt neodecanoate and cobalt octoate are now preferred cobalt salts for use in these oxygen scavenging compositions. The invention further resides in a method of providing a multi-trip polyester container comprising the steps of : 1) providing a multi- layer preform comprising three or more polymeric layers, including at least one layer comprising an oxygen scavenging material , ii ) stretch blow moulding the preform to form a blow moulded container body, whereby the container is capable of at least five re-use cycles, each including subjecting the container to a hot caustic wash at a temperature of at least 60°C (140°F) followed by product filling and capping, the container exhibiting substantially no crack failure following the five re-use cycles and dimensional stability to the extent that the maximum volume deviation over the five re-use cycles is a maximum of 1.5%. Refillable containers must be able to withstand these stringent requirements, unlike single trip bottles. The invention further resides in a method of providing a multi-trip polyester container comprising the steps of : l) providing a multi- layer preform comprising three or more polymeric layers, including at least one layer comprising an oxygen scavenging material, 11) stretch blow moulding the preform to form a blow moulded container body, m) filling the container body with product and capping the container, iv) reusing the container by subjecting it to a caustic hot wash at a temperature of at least 60°C (140°F) , followed by further filling and capping, and v) repeating step (iv) to provide at least a five use multi-trip bottle. The invention further resides m a method of providing a multi-trip polyester container comprising the steps of : I) providing a multilayer preform comprising three or more polymeric layers, including at least one layer comprising an oxygen scavenging material , ii) stretch blow-mouldmg the preform to form a multilayer blow moulded container body, the oxidisable organic polymer, the transition metal and the respective amounts thereof being selected such that the layer will scavenge oxygen during a period of oxygen scavenging, the arrangement being such that the wall of the container body has a permeance to oxygen of not more than 0.5 cm 3 / (m 2 atm day), m) filling the container body with product and capping the container, IV) reusing the container by subjecting it to a caustic hot wash at a temperature of at least 60°C (140°) , followed by further filling and capping, and v) repeating step (iv) to provide at least a five use multi-trip container, the period of oxygen scavenging being such that following said five uses of the container the wall of the container body has a permeance to oxygen of still not more than 0.5cm 3 / (m 2 atm day) provided such five uses are completed within an overall total period of 100 weeks. Although such containers are designed to withstand in excess of five trips, and m excess of 100 weeks, it may be necessary to provide some marker means to indicate when the oxygen scavenging properties are nearing exhaustion and the container should no longer be reused. This marker means may be a relatively simple mechanism such as a date or batch code added to the container, or alternatively a more sophisticated mechanism such as an indicator adapted to change its visible appearance following a predetermined a time period after manufacture, or once the bottle has been exposed to a predetermined quantity of oxygen. Conceivably the colour of a marker, or of a layer of the container, conceivably the oxygen scavenging layer, could change under one or both of these conditions. Accordingly there is provided a polyester bottle comprising a neck portion, a side-wall portion, a shoulder portion interconnecting the neck and side-wall portions, and a base portion, the bottle consisting of three or more polymeric layers, at least the inner and outermost layers being formed of polyester, and one or more intermediate layers comprising an oxygen scavenging material such that the layer will scavenge oxygen during a predetermined period of oxygen scavenging, the bottle including marker means adapted to indicate when the predetermined period of oxygen scavenging is close to expiry. In this way bottles can be accepted or rejected for reuse based on their estimated future oxygen barrier performance, regardless of the number of trips they have made or the age of the bottles. This allows the maximum acceptable usage of each bottle, whilst ensuring that certain minimum oxygen barrier capabilities are always met . The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which Fig .1 is a schematic sectional view of a polyester preform m accordance with the present invention, and Fig.2 is a schematic sectional view of a polyester bottle made from the preform of Fig .1 and in accordance with the present invention. Referring to Fig.l, a polyester preform is shown generally at 1 and comprises a neck portion 2, a shoulder portion 3, a side-wall portion 4 and a base portion 5. The preform is formed mostly of polyethylene terephthalate, but is manufactured on a co- injection moulding machine such that there is an intermediate layer 6 of barrier material within the preform. The layer 6 does not extend substantially into the neck portion 2, and is discontinuous m the base portion 5. The intermediate layer 6 divides the side-wall portion 4 into three layers, an outermost layer 7 of PET, the intermediate layer 6, and an innermost layer 8 again of PET. (The innermost layer 8 is "innermost" m the sense that it is towards the inner wall of the preform, as opposed to being towards the middle of the wall . ) The outermost layer 7 of PET has a thickness of approx. 3.325mm, as does the innermost layer 8. The intermediate layer 6 has a thickness of approx. 0.35mm, and is formed of MXD6 polyamide (as sold by Mitsubishi Gas Chemicals of Japan) to which has been added 200 ppm cobalt neodecanoate. The total thickness of the side-wall portion 4 is approx. 7mm. The preform 1 is then transferred to a stretch blow moulding machine and formed into the bottle of Fig.2. The bottle is shown generally at 9 and comprises the neck portion 2 (which is substantially unchanged) , a shoulder portion 3 ' formed from the shoulder portion 3 of the preform, a side-wall portion 4 ' formed from the side-wall portion 4 of the preform, and a base portion 5 ' formed from the base portion 5 of the preform 1. In the side-wall 4' of the blown bottle 9, an outermost PET layer 7' has a thickness of 0.2375mm, as does an innermost layer 8 ' , with an intermediate layer 6 ' having a thickness of 0.025mm. The total thickness of the side-wall portion 4' is 0.5mm. These thicknesses are considerably in excess of those found in prior art multilayer bottles including oxygen scavenging compositions . The bottle 9 is capable of at least 5 trips, each trip consisting of filling and capping, sale of the filled bottle and return of the empty bottle, and a caustic hot wash conventional m the reuse of multi -trip bottles. The intermediate layer 6' scavenges oxygen such that the bottle 9 has excellent oxygen barrier properties for a period m excess of 100 weeks. A marker patch (not shown) is present, for example on the underside of the base 5', to indicate when the 100 week period has been exceeded. In this way bottles nearmg the end of their useful life may be removed from the refilling stream before the oxygen barrier performance is seriously affected.

Claims: CLAIMS ; 1. A polyester bottle comprising a neck portion, a side-wall portion, a shoulder portion interconnecting the neck and side-wall portions, and a base portion, the bottle consisting of 3 or more polymeric layers, at least the inner and outermost layers being formed of polyester, and one or more intermediate layers comprising an oxygen scavenging material the total thickness of the polyester layers m the side-wall portion being at least 0.4mm, and the total thickness of the one or more intermediate layers in the side-wall portion being at least 0.02mm, the thickness of the polyester and intermediate layers being so as to provide a multi-trip polyester bottle. 2. A polyester bottle according to claim 1 characterised m that the total thickness of the one or more intermediate layers m the side-wall portion is at least 0.025mm. 3. A polyester bottle according to claim 1 or claim 2, characterised m that the total thickness of the bottle in the side-wall portion is at least 0.5mm. 4. A polyester bottle according to claim 3, characterised m that the total thickness of the polyester layers in the side-wall portion is at least 0.5mm 5. A polyester bottle according to any of claims 2 to 4, characterised m that the one or more intermediate layers comprise an oxidisable organic polymer and a transition metal in a positive oxidation state. 6. A polyester bottle according to claim 5, characterised in that the oxidisable organic polymer is a polyamide . 7. A polyester bottle according to claim 6, characterised m that the oxidisable organic polymer is a polymer containing units of the formula -NH-CH 2 -arylene- CH 2 -NH-CO-alkylene-CO- . 8. A polyester bottle according to any preceding claim, characterised in that the polyester is polyethylene terephthalate . 9. A polyester bottle according to any preceding claim, characterised m that there are three polymeric layers, an outermost layer of polyester, an innermost layer of polyester and an intermediate layer comprising an oxidisable organic polymer and a transition metal in a positive oxidation state. 10. A polyester bottle according to any preceding claim, characterised m that the total thickness of the one or more intermediate layers comprises approx. 5% of the total thickness of the side-wall portion. 11. A preform for a polyester container, the preform comprising a neck portion, a side-wall portion to be drawn, and a closed bottom portion, the preform including three or more polymeric layers, at least the inner and outermost layers being formed of polyester, and one or more intermediate layers comprising an oxygen scavenging material, the total thickness of the polyester layers in the side-wall portion being at least 5mm, and the total thickness of the one or more intermediate layers m the side-wall portion being at least 0.3mm, the preform being suitable for the manufacture of a multi-trip polyester container . 12. A preform according to claim 11, characterised in that the total thickness of the one or more intermediate layers m the side-wall portion is at least 0.35mm. 13 A preform according to claim 11 or claim 12, characterised m that the total thickness of the polyester layers m the side-wall portion is at least 6mm. 14. A preform according to claim 13, characterised in that the total thickness of the preform in the side-wall portion is at least 7mm. 15. A preform according to any of claims 11 to 14, characterised in that the one or more intermediate layers comprise an oxidisable organic polymer and a transition metal in a positive oxidation state. 16. A preform according to claim 15, characterised in that the oxidisable organic polymer is a polyamide. 17. A preform according to claim 16, characterised in that the oxidisable organic polymer is a polymer containing units of the formula -NH-CH -arylene-CH 2 -NH- CO-alkylene-CO- . 18. A preform according to any of claims 11 - 17, characterised in that the polyester is polyethylene terephthalate . 19. A preform according to any of claims 11 - 18, characterised m that there are three polymeric layers, an outermost layer of polyester, an innermost layer of polyester, and an intermediate layer comprising an oxidisable organic polymer and a transition metal in a positive oxidation state. 20. A preform according to any of claims 11 - 19, characterised m that the total thickness of the one or more intermediate layers comprises approx. 5% of the total thickness of the side-wall portion. 21. A method of providing a multi-trip polyester container comprising the steps of : i) providing a multilayer preform comprising three or more polymeric layers, including at least one layer comprising an oxygen scavenging material, 11) stretch blow moulding the preform to form a blow moulded container body, whereby the container is capable of at least five re-use cycles each including subjecting the container to a hot caustic wash at a temperature of at least 60°C (140°F) followed by product filling and capping, the container exhibiting substantially no crack failure following the five re-use cycles and dimensional stability to the extent that the maximum volume deviation over the 5 re-use cycles is a maximum of 1.5%. 22. A method of providing a multi-trip polyester container comprising the steps of: l) providing a multilayer preform comprising three or more polymeric layers, including at least one layer comprising an oxygen scavenging material, ii ) stretch blow moulding the preform to form a multilayer blow moulded container body, m) filling the container body with product and capping the container, iv) re-usmg the container by subjecting it to a caustic hot wash at a temperature of at least 60°C (140°F) , followed by further filling and capping, and v) repeating step (iv) to provide at least a five use multi-trip container. 23. A method according to claim 21 or claim 22, characterised in that the oxygen scavenging material is an oxidisable organic polymer and a transition metal in a positive oxidation state. 24. A method of providing a multi-trip polyester container comprising the steps of: i) providing a multilayer preform comprising three or more polymeric layers, including at least one layer comprising an oxidisable organic polymer and a transition metal in a positive oxidation state, ii) stretch blow moulding the preform to form a multilayer blow moulded container body, the oxidisable organic polymer, the transition metal and the respective amounts thereof being selected such that the layer will scavenge oxygen during a period of oxygen scavenging, the arrangement being such that the wall of the container body has a permeance to oxygen of not more than 0.5cm 3 / (m 2 atm day) , iii) filling the container body with product and capping the container, iv) re-using the container by subjecting it to a caustic hot wash at a temperature of at least 60°C (140°F) , followed by further filling and capping, and v) repeating step (iv) to provide at least a five use multi-trip container, the period of oxygen scavenging being such that following said five uses of the container, the wall of the container body has a permeance to oxygen of still not more than 0.5cm 3 / (m 2 atm day) provided said five uses are completed within an overall total period of 100 weeks . 25. A polyester bottle comprising a neck portion, a side-wall portion, a shoulder portion interconnecting the neck and side-wall portions, and a base portion, the bottle consisting of three or more polymeric layers, at least the inner and outermost layers being formed of polyester and one or more intermediate layers comprising an oxygen scavenging polymer such that the layer will scavenge oxygen during a predetermined period of oxygen scavenging, the bottle including marker means adapted to indicate when the predetermined period of oxygen scavenging is close to expiry. 26. A polyester bottle according to claim 25, characterised in that the oxygen scavenging polymer comprises an oxidisable organic polymer and a transition metal in a positive oxidation state.

Inventors: SERRANO FRANCISCO, SERRANO, FRANCISCO
Applicants: CROWN CORK & SEAL TECH CORP, METAL BOX PLC, SERRANO FRANCISCO, CARNAUDMETALBOX PLC, CROWN CORK & SEAL TECHNOLOGIES CORPORATION, SERRANO, FRANCISCO
Application year: 2000
Main classification: B65D1
IPC codes: B65D1