Packaging

Abstract

A blend comprises a polyester, for example polyethylene terephthalate (PET), and a second polymer, wherein said blend exhibits two glass transition temperatures (Tgs), one being representative of the polyester and a second Tg is representative of said second polymer. Said second polymer is preferably adapted to be transesterified with said polyester. The blend may be used to produce bottles which are bright white (eg high L*) and / or are opaque or semi-opaque and / or have high haze. Preferred embodiments aim to facilitate recycling of such containers with a main recycle stream to product high quality recycled PET (rPET).

Description

[0001] Packaging

[0002] This invention relates to packaging and materials therefor. Preferred embodiments relate to containers, such as PET bottles, which are bright white (eg high L*) and / or are opaque or semiopaque and / or have high haze. Such containers may be used in household / personal care products which require some opacity. Preferred embodiments aim to facilitate recycling of such containers with a main recycle stream to product high quality recycled PET (rPET).

[0003] The plastic packaging industry has long made use of inorganic particles such as titanium dioxide or calcium carbonate in PET to produce packaging with degrees of opacity, light blocking and different colours, particularly whites, pastels and so-called "coloured opaques". More recently, polymers and other organic materials have also been used in PET packaging to produce degrees of opacity, light blocking and whiteness. In these cases, a secondary stretching of the plastic may be necessary to produce the opacity / whiteness. Typically, the polymers and organic materials used are incompatible with PET. By way of example, WO2019117725A1 and W02020106156A1 relate to a single-layer plastic container with light shielding, wherein polymethylpentene and cyclic olefin copolymer respectively are added to a main PET plastic base along with inorganic shielding fillers including TiC>2

[0004] Other plastic containers which address the same problem to protect their contents (e.g. UHT long-life milk) from light radiation are available in different plastic media and with different types of structures, for example: three-layer polyethylene, three-layer PET, two-layer PET or singlelayer PET.

[0005] One problem associated with current approaches is that PET packaging (bottles, jars, trays, cups or films etc.) made with the inclusion of known materials cannot be recycled with a main PET recycle stream of clear uncoloured or tinted packaging to produce clear, high value recycle PET (rPET) for the manufacture of new PET packaging. Incorporation of opaque / white PET packaging into the clear recycle stream in any proportion will impart a degree of haze or whiteness that is undesirable in the rPET if it is to be used in making new packaging (bottles, etc.). This means that, currently, opaque or white PET packaging is destined for low value applications upon recycling, such as strapping, building materials, fibre and insulation.

[0006] It is an object of the present invention to address the above described problems.

[0007] It is an object of preferred embodiments of the present invention to produce packaging articles (eg bottles, jars, trays, cups or films) which are bright white, opaque or semi-opaque and / or have high haze and can be recycled with a main PET recycle stream of clear uncoloured or tinted packaging. According to a first aspect of the invention, there is provided a blend comprising a polyester, for example polyethylene terephthalate (PET), and a second polymer, wherein said blend suitably exhibits two glass transition temperatures (Tgs).

[0008] The blend described is suitably arranged to be used in production of a packaging article (eg bottles, jars, trays, cups or films) having increased opacity, wherein the opacity can be reduced subsequent to use of the packaging article, to facilitate recycling of the packaging article with a main PET recycle stream.

[0009] One Tg is suitably representative of said polyester and a second Tg is representative of said second polymer.

[0010] Unless otherwise stated, glass transition temperature (Tg) may be assessed by DSC and / or as described in ASTM E1356. Unless otherwise stated, Tg referred to herein is the mid-point of the transition region.

[0011] Said polyester may have a Tg of at least 70°C, preferably at least 75°C. The Tg of said polyester may be less than 90°C or less than 85°C.

[0012] Said second polymer may have a Tg of at least 100°C. Said second polymer may have a Tg in the range 100°C to 200°C, for example 100°C to 150°C.

[0013] Said blend suitably exhibits one Tg corresponding to said polyester. Thus, said blend may exhibit one Tg of at least 70°C. Said blend may exhibit one Tg of at least 75°C. Said blend may exhibit one Tg of less than 90°C or less than 85°C.

[0014] Said blend suitably exhibits a second Tg, for example a Tg due, at least in part, to the inclusion of said second polymer in said blend. Said blend suitably exhibits a second Tg of at least 100°C, for example in the range 100°C to 200°C or in the range 100°C to 150°C. The second polymer is suitably incompatible with said polyester which means the polyester and second polymer have a degree of immiscibility which, in turn, means the blend exhibits two Tgs as described.

[0015] The difference in the Tg of the polyester and the second polymer may be at least 10°C, preferably at least 15°C, more preferably at least 20°C. The difference in the Tg of the polyester and the second polymer may be less than 130°C or less than 100°C or less than 75°C. The blend may include one or more additional polymers. For example, it may include a third polymer which may be incompatible with the polyester. If a third polymer is included, it may be substantially compatible with the second polymer which may mean that a blend of the second polymer and third polymer exhibits a single Tg and / or the blend of the first aspect may exhibit a single Tg due to the polyester and a second Tg due to inclusion of the second and / or third polymers.

[0016] Thus, said blend suitably includes a first Tg due to presence of said polyester and a second Tg indicative of inclusion of second and / or third polymers.

[0017] When said blend comprises said polyester and the only polymer in said blend which is incompatible with the polyester is said second polymer, said blend may exhibit one Tg corresponding to said second polymer. Said Tg may be at least 100°C, for example in the range 100°C to 200°C or in the range 100°C to 150°C.

[0018] Said polyester and said second polymer of the first aspect are preferably such that a 1 :1 by weight blend of said polyester and said second polymer exhibit at least two Glass Transition Temperatures (Tgs) as aforesaid when tested as described.

[0019] When said blend is subjected to a heated orientation step, the existence of two Tgs may confirm the incompatibility of polymers in the blend. In this case, preferably, said second polymer has a Tg that is at least 20-30 °C greater than Tg of the polyester.

[0020] In addition, the refractive index can be used to select the second polymer. Opacity may be enhanced by increasing the absolute value of the difference in the refractive indices of each of the polyester and second polymer. The refractive index may differ by an absolute value of at least 0.02.

[0021] Said polyester and said second polymer of the first aspect are preferably such that, when a 1 :1 , by weight, blend of said polyester and said second polymer is made into a plaque as described in Example 16, the transmission of the plaque through a 3mm region of a plaque is less than 70% (preferably less than 60% or less than 50%) for light with a wavelength of 550nm and / or haze % is greater than 20% when assessed as described in Tests 3 and 2 respectively. The plaque is suitably made by injection moulding on a Boy 22A injection moulding machine with 75mm diameter barrel and 24mm diameter screw, with the program for the machine having barrel temperatures set to achieve a melt temperature of 295°C, a polymer residence time of 90-120 seconds and screw rotation speed during the plasticization part of the injection moulding process between 150-350 rpm. The polyester and said second polymer are preferably such that a blend thereof has a “Robustness Ratio” (R) of less than 1 .15, preferably less than 1.10 wherein:

[0022] R = The transmission (%) through a 3mm region of a test piece B at 550nm

[0023] The transmission (%) through a 3mm region of a test piece A at 550nm wherein: (I) test piece A is made in a process comprising: selection of a blend comprising 88 wt% of said polyester and 12 wt% of the second polymer; and injection moulding the blend at 295°C to produce a standard plague, wherein said injection moulding is suitably undertaken on a Boy 22A injection moulding machine with 75mm diameter barrel and 24mm diameter screw, with the program for the machine having barrel temperatures set to achieve a melt temperature of 295°C, a polymer residence time of 90-120 seconds and screw rotation speed during the plasticization part of the injection moulding process between 150-350 rpm; wherein: (II) test piece B is made as described for test piece A except a temperature of 310°C is used instead of 295°C.

[0024] Said polyester and said second polymer of the first aspect are preferably such that, when a 1 :1 , by weight, blend of said polyester and said second polymer, together with 600ppm titanium metal introduced using a 90% solution of titanium butoxide in n-butanol (the titanium metal suitably acting as a transesterification catalyst) is pelletised, the pellets exhibit a single Glass Transition Temperature (Tg).

[0025] Said second polymer is preferably adapted to be transesterified with said polyester.

[0026] As stated, said blend may, optionally, include a third polymer. The third polymer may have any feature of the second polymer (but is suitably different therefrom). The third polymer may be substantially incompatible with the polyester in said blend. Said third polymer is preferably adapted to be transesterified with said polyester.

[0027] Said second polymer is preferably incompatible (e.g. as illustrated by a blend as described exhibiting two Tgs) with PET and, preferably, is incompatible with PET produced from PTA and MEG, such as Lighter™ C93 PET Copolymer.

[0028] Said second polymer preferably include one or more repeat units which contribute to it being incompatible as aforesaid. In a first example, said second polymer may include a repeat unit which includes no aromatic moiety, for example no cyclic or polycyclic aromatic moiety. Preferably, said second polymer includes a repeat unit which includes no phenyl or naphthalenyl moiety. In said first example, said second polymer may include a repeat unit which includes an ester moiety in combination with a saturated hydrocarbon moiety. In this case, said second polymer may include a lactic acid repeat unit. Said second polymer may be a polylactic acid.

[0029] In a second example, said second polymer may include a repeat unit which contributes to it being incompatible with PET. Said repeat unit may include a cyclic moiety, for example a saturated cyclic moiety. Such a cyclic moiety may be relatively bulky and may contribute to incompatibility of the second polymer and said PET. Said cyclic moiety may comprise carbon and hydrogen atoms only or may be an heterocyclic moiety. Said cyclic moiety may be a four to six-membered cyclic moiety which may be optionally substituted. The cyclic moiety preferably includes only carbon and hydrogen atoms. In said second example, said second polymer may include a repeat unit which includes an ester moiety. Said second polymer may be a copolyester. It may include a repeat unit derived from a diol which incorporates said cyclic moiety. Such a diol may be selected from

[0030] In a preferred embodiment, the co-polyester includes repeat units derived from both I and II.

[0031] The copolymer may be prepared by reaction of diols I and / or II with a dicarboxylic acid (or dicarboxylic acid derivative) with dimethyl terephthalate being a preferred example. Tritan™ copolyester referred to herein is preferred.

[0032] In a third example, said second polymer may be a polycarbonate. A polycarbonate may include a repeat unit which contributes to it being incompatible with said PET. Said repeat unit may include a cyclic, especially a heterocyclic, moiety which is preferably unsaturated. The cyclic moiety which may be a fused ring cyclic moiety may be relatively bulky and may contribute to incompatibility of the second polymer with said PET. In a preferred embodiment, the polycarbonate may incorporate an isosorbide-derived repeat unit and / or may be prepared using an isosorbide monomer.

[0033] When a third polymer is included as described, said third polymer preferably includes one or more repeat units which contribute to it being incompatible as aforesaid. In a first example, said third polymer may include a repeat unit which includes no aromatic moiety, for example no cyclic or polycyclic aromatic moiety. Preferably, said third polymer includes a repeat unit which includes no phenyl or naphthalenyl moiety. In said first example, said third polymer may include a repeat unit which includes an ester moiety in combination with a saturated hydrocarbon moiety. In this case, said third polymer may include a lactic acid repeat unit. Said third polymer may be a polylactic acid.

[0034] In a second example, said third polymer may include a repeat unit which contributes to it being incompatible with PET. Said repeat unit may include a cyclic moiety, for example a saturated cyclic moiety. Such a cyclic moiety may be relatively bulky and may contribute to incompatibility of the third polymer and said PET. Said cyclic moiety may comprise carbon and hydrogen atoms only or may be an heterocyclic moiety. Said cyclic moiety may be a four to six-membered cyclic moiety which may be optionally substituted. The cyclic moiety preferably includes only carbon and hydrogen atoms. In said second example, said third polymer may include a repeat unit which includes an ester moiety. Said third polymer may be a co-polyester. It may include a repeat unit derived from a diol which incorporates said cyclic moiety. Such a diol may be selected from diols of formula I and / or II as described above.

[0035] In a third example, said third polymer may be a polycarbonate. A polycarbonate may include a repeat unit which contributes to it being incompatible with said PET. Said repeat unit may include a cyclic, especially a heterocyclic, moiety which is preferably unsaturated.

[0036] The cyclic moiety which may be a fused ring cyclic moiety may be relatively bulky and may contribute to incompatibility of the third polymer with said PET. In a preferred embodiment, the polycarbonate may incorporate an isosorbide-derived repeat unit and / or may be prepared using an isosorbide monomer.

[0037] Said blend may be a masterbatch, for example a solid masterbatch, preferably in the form of pellets or granules.

[0038] Said blend (herein the “masterbatch blend”) may include less than 20 wt%, preferably less than 10 wt%, of said polyester in combination with said second polymer and optional third polymer as described. The sum of the wt% of said second and third polymers in said masterbatch blend may be at least 80 wt%, preferably at least 90 wt%. The sum is preferably less than 99 wt% or less than 95 wt%. Preferably, said masterbatch blend includes at least 80 wt%, more preferably at least 90 wt%, of said first polymer.

[0039] Said masterbatch blend may include:

[0040] 1 to 20 wt%, preferably 3 to 10 wt%, of said polyester;

[0041] 45 to 99 wt%, preferably 90 to 97 wt%, of said second polymer; and 0 to 45 wt%, preferably 0 to 7 wt%, of said third polymer.

[0042] As an alternative to the masterbatch blend, said blend may be a packaging blend, suitably being a blend used in a packaging material for example for bottles, jars, trays, cups or films). In a preferred embodiment, said is a container preform or a container such as a bottle. Said packaging blend may be formed in a melt-processing apparatus and / or may define at least part of (preferably substantially the entirety of, suitably excluding any closure) a packaging article, for example a preform or a container such as a bottle, which may be made such as by letting down the masterbatch blend in additional polyester to define the packaging blend.

[0043] Said packaging blend may include at least 0.5 wt%, preferably at least 1 .0 wt%, more preferably at least 2.0 wt% of said second polymer. Said packaging blend may include less than 20 wt%, preferably less than 15 wt%, more preferably less than 10 wt%, of said second polymer.

[0044] Said packaging blend may include at least 50 wt%, preferably at least 65 wt%, more preferably at least 80 wt% of a polyester, preferably a single type of polyester which is, preferably, polyethylene terephthalate (PET). Said packaging blend may include less than 99 wt%, preferably less than 96 wt%, of said polyester.

[0045] In said packaging blend, the sum of the wt% of said polyester (e.g. PET), said second polymer and optional third polymer is preferably at least 95 wt%, preferably at least 98 wt%.

[0046] In said packaging blend, a ratio defined as the wt% of polyester (e.g. PET) divided by the sum of the wt% of said second polymer, and optional third polymer, may be at least 5, for example in the range 5 to 25.

[0047] Said blend may be a packaging blend which is in the form of a packaging article (eg a bottle, jar, tray, cup or film). In a preferred embodiment, said packaging article is, for example, a preform or a container such as a bottle. Said preform or container (suitably excluding any closure) may consist essentially of said packaging blend. Said polyester of the first aspect, for example in the masterbatch blend or said packaging blend, is preferably a polyethylene terephthalate which term, in the context of the present specification, may encompass co-polyethylene terephthalates. Co-polyethylene terephthalates of polyethylene terephthalate may contain repeat units from at least 85 mole % (eg at least 92 mole %, or at least at least 97 mole %) terephthalic acid (or a terephthalic acid derivative) and at least 85 mole % (eg at least 92 mole %, or at least at least 97 mole %) of ethylene glycol. In a preferred embodiment, said polyethylene terephthalate has less than 10 mole%, more preferably less than 6mole%, especially less than 2 mole% comonomer substitution. Preferably, said polyethylene terephthalate comprises substantially a homopolymer produced by esterification or transesterification of terephthalic acid or dimethyl terephthalate and ethylene glycol. The monomers may be subjected to polycondensation at high temperatures in vacuum in the presence of a catalyst.

[0048] As used herein the term “IV” refers to the Inherent Viscosity of the polymeric material. It may be determined on a solution of 0.5 g of polymer dissolved in 100 ml of a mixture of phenol (60% by volume) and tetrachloroethane (40% by volume). The IV of the polyester in the blend is preferably greater than 0.5 dL / g, more preferably greater than 0.65 dL / g. it may be less than 0.80 dL / g.

[0049] A container preform as described herein is suitably a test-tube shaped article which may be produced by injection moulding and is suitably arranged to be stretch blow moulded to define a bottle.

[0050] According to a second aspect, there is provided a packaging article which includes said packaging blend according to said first aspect. At least 90 wt%, preferably at least 95 wt%, more preferably at least 99 wt% of a layer of said packaging article may be made up of said packaging blend. Said packaging article preferably includes only one layer. Said packaging article is preferably a monolayer container.

[0051] The packaging article is preferably in the form of a monolayer preform or a container such as a bottle which comprises, preferably consists essentially of, said packaging blend. At least 90 wt%, preferably at least 95 wt%, more preferably at least 99 wt% of said monolayer preform or container may be made up of said packaging blend. For example, said monolayer of said preform or container such as a bottle may include:

[0052] 2 to 20 wt%, preferably 4 to 15 wt%, of said second polymer;

[0053] 0 to 20 wt%, preferably 0 wt%, of said third polymer; and in excess of 80wt% or in excess of 85wt% of a polyester (preferably PET) which is suitably different to said second polymer and optional third polymer.

[0054] Said packaging article may include an identification means to enable a packaging article to be identified as being as described herein and / or being arranged to be treated so the opacity of the composition which makes up the packaging article can be reduced, for example to facilitate recycling of the packaging article with a main PET recycle stream. The identification means may be an identifier (eg code) which is marked on the packaging article, for example so it is not visible to the naked eye or it may comprise an additive, the presence of which can be identified, for example by optical or other means. The identification means may be arranged to be identified by spectroscopic means, for example by near infra-red radiation.

[0055] According to a third aspect of the invention, there is provided a method of producing a packaging article, the method comprising melt-processing a polyester and a second polymer to produce a blend, wherein said blend suitably exhibits two glass transition temperatures (Tgs).

[0056] The method may comprise melt-processing a blend according to said first aspect.

[0057] The packaging article may be as described according to the second aspect.

[0058] The method may comprise:

[0059] (i) selecting a blend according to the first aspect, optionally contacting the blend with one or more other polymers, for example with additional polyester, preferably PET, for example to define a packaging bend according to the first aspect; and melt-processing the blend to produce the packaging article, for example a preform for a container such as a bottle; or

[0060] (ii) selecting a second polymer according to the first aspect (and optionally said third polymer according to the first aspect) and contacting said second polymer (and optional third polymer) with said polyester, for example PET; and melt-processing the second polymer, optional third polymer, and said polyester, for example PET, to produce the packaging article, for example a preform for a container such as a bottle.

[0061] The method may comprise stretch blow-moulding a preform to produce a packaging article in the form of a container such as a bottle.

[0062] The method may comprise associating identification means as described in the first aspect with the packaging article. Said method of the third aspect is preferably a method of increasing the opacity of a container such as a bottle, for example a polyester (e.g. PET) bottle. The method may comprise producing a container which has an increased opacity, for example compared to an otherwise identical container which does not include said second polymer and / or which only includes said polyester (eg PET).

[0063] Advantageously, the blend described can be used to produce a packaging article (eg a bottle, jar, tray, cup or film) having increased opacity and the opacity can be reduced, subsequent to use of the packaging article (eg a bottle, jar, tray, cup or film), to facilitate recycling of the packaging article (eg a bottle, jar, tray, cup or film). Preferably, by reducing opacity, the packaging article may be recycled with a main PET recycle stream and / or recycled to produce clear, high value recycled PET (rPET). In one embodiment, a multiplicity of packaging articles comprising said blend as described, for example bottles, may be selected and processed together to reduce opacity, for example by effecting transesterification. The transesterified material may then be mixed with a main recycle stream (eg comprising virgin PET or other PET) to produce rPET. In another embodiment, packaging articles comprising said blend as described, for example bottles, may be selected and processed with a main recycle stream (eg comprising virgin PET or other PET), for example with a transesterification catalyst, to effect transesterification and to produce clear, high value recycled PET (rPET).

[0064] Preferably, the packaging article, for example container, of the third aspect has a transmission at 400 nm of less than 75%, for example less than 70%, suitably determined as described in Test 3. The packaging article may be arranged such that said second polymer can be transesterified with the polyester (e.g. PET) to produce a material which, if melt processed to produce a further packaging article, for example bottle, having the same wall thickness, would have a transmittance at 400 nm greater (e.g. at least 5% or at least 10% greater) than that of the packaging article (for example container) from which the material was derived.

[0065] The invention extends, in a fourth aspect, to a method of recycling a packaging article, for example a bottle, jar, tray, cup or film, especially a PET bottle, the method comprising selecting a packaging article which includes polyester, a second polymer and optional third polymer as described in any preceding aspect, and treating the packaging article to reduce the level of opacity and / or to effect transesterification of said second polymer with said polyester.

[0066] The method may comprise:

[0067] (i) selecting a packaging article which includes polyester, a second polymer and optional third polymer as described in any preceding aspect, wherein said packaging article has a transmission at 400 nm of less than 75%, less than 70%, less than 60% or less than 50%, for example determined on a cut-section from a wall of the packaging article as described in Test 3; and

[0068] (ii) treating the packaging article to reduce the level of opacity and / or to effect transesterification. After the treatment, a blend may be produced which, when moulded into a plaque having a comparable thickness to the cut section from the wall, has a transmission at 400 nm which is greater than that of the cut section. The difference between the transmission at 400 nm of the cut section and that of the plaque may be at least 10%, at least 20%, at least 30%, or at least 40%.

[0069] The method of treating may comprise use of a transesterification catalyst to facilitate transesterification.

[0070] The method of the fourth aspect may comprise determining if the packaging article includes an identification means (e.g. as described in the first aspect) to confirm the packaging article is as described herein and / or is arranged to be treated (e.g. to effect transesterification) so the opacity of the composition which makes up the packaging article can be reduced. Thus, the method suitably comprises selection of a packaging article which includes an identification means according to the first aspect. The method may comprise selecting a multiplicity (e.g. at least 10 or at least 50) packaging articles which include an identification means according to the first aspect and treating said multiplicity as described in step (ii).

[0071] The method of the fourth aspect may comprise blending the packaging article selected in step (i) or treated as described in step (ii) with additional polyester (e.g. PET). Said additional polyester (e.g. PET) may comprise virgin polyester (e.g. PET) or comprise polyester (e.g. PET) derived from a packaging article (e.g. container) which has a higher light transmission at 400 nm compared to the comparable transmission of the packaging article selected in step (i).

[0072] In the method of the fourth aspect, pellets or granules of recycled PET (rPET) may be produced. The pellets or granules are preferably such that, the light transmission at 400 nm of an injection moulded plaque of the same thickness as the or a packaging article selected in step (i), is greater (e.g. by at least 10% or at least 20%) than the light transmission of said packaging article selected in step (i), for example when assessed as described in Test 3.

[0073] According to a fifth aspect, there is provided the use of a second polymer (and optional third polymer) as described in any preceding aspect for increasing opacity of polyester (e.g. PET) in a packaging article (eg a bottle, jar, tray, cup or film), wherein the opacity preferably can be reduced (suitably to facilitate recycling of the polyester (e.g. PET)) by a transesterification reaction involving said second polymer (and optional third polymer) Thus, the invention extends to use of said second polymer (and optional third polymer) to increase opacity as aforesaid and improve recyclability of a packaging article (eg a bottle, jar, tray, cup or film).

[0074] The invention extends, in a sixth aspect, to recycled PET (rPET), for example obtained in a method of the fourth aspect and / or comprising a blend comprising polyester and a second polymer as described herein, wherein the blend has been treated to transesterify the second polymer. The rPET may comprise said blend and additional PET which may comprise PET from a source other than said blend and / or may comprise virgin PET.

[0075] Any aspect of any invention described herein may be combined with any other aspect of any invention described herein mutatis mutandis.

[0076] Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0077] Figure 1 is a graph showing bottle wall light transmission for bottles comprising blends as described in Examples 4 to 12;

[0078] Figure 2 shows a DSC analysis of the blends of Examples 13 and 14;

[0079] Figure 3 is a graph of light transmission v. wavelength for plaques of Examples 13, 14 and pure PET-X;

[0080] Figure 4 shows the mean haze of the plaques of Examples 13, 14 and pure PET-X;

[0081] Figure 5 is a graph of light transmission v. wavelength for bottles of Examples 18a, 18b and pure PET-X; and

[0082] Figure 6 includes graphs of light transmission v. wavelength for bottles of Examples 19 to 23.

[0083] The following materials are referred to hereinafter:

[0084] PET-X - refers to a proprietary bottle grade PET (Lighter C93 from Equipolymers, with an Intrinsic Viscosity (IV) of 0.80 + / - 0.02)) Refractive Index 1 .575 n

[0085] Natureworks 4043D (Polylactic acid) - a general purpose polylactic acid grade with an MFR of 6 (210°C 12.16 kg), glass transition temperature 55-60°C and melting point temperature of 145°C. Refractive Index 1 .465 n. Tritan TX1001 (PET Copolyester) -a proprietary amorphous copolyester from Eastman consisting of the diacid terephthalic acid and the diols ethylene glycol, 1 ,4- cyclohexanedimethanol and 2,2,4,4-tetramethyl 1 ,3-cyclobutanediol. The copolyester has a glass transition temperature of 110°C. Refractive Index 1 .54 n.

[0086] Tritan TX2001 (PET Copolyester) -a proprietary amorphous copolyester from Eastman consisting of the diacid terephthalic acid and the diols ethylene glycol, 1 ,4- cyclohexanedimethanol and 2,2,4,4-tetramethyl 1 ,3-cyclobutanediol. The copolyester has a glass transition temperature of 120°C. Refractive Index 1 .54 n.

[0087] Natureworks 4043D / Tritan TX1001 -a 1 :1 mixture by weight of Natureworks 4043D and Tritan TX1001. This can either be a mixture that has been melt blended and pelletized, or simply a physical mixture of pellets of the two polymer resins.

[0088] Verbatim Durabio 3D printer polymer (Isosorbide polycarbonate) - a proprietary polycarbonate from Mitsubishi Chemical that is based on isosorbide and does not contain any Biphenol A (BPA). It has a melting temperature of 235°C.

[0089] In general terms, in preferred embodiments, PET is melt-blended in a twin-screw extruder with a second polymer which may be a polyester or polycarbonate which is relatively incompatible with PET to produce a partially or fully opaque, white compound. This compound can be processed using standard techniques such as injection moulding to make a partially or fully opaque, white article. The degree of opacity / whiteness can be further enhanced by biaxial orientation and stretching of the article, as takes place for example in an injection stretch blow moulding process, typically used to manufacture PET bottles. In preferred embodiments, when desired, the polyester blend and articles made therefrom can be passed through a further processing step wherein the blend is re-melted, for example in a twin-screw extruder, and the polyester blend undergoes a transesterification reaction in the melt phase, preferably with addition of a suitable transesterification catalyst (eg a titanium (IV) alkoxide). In preferred embodiments, transesterification is minimised during melt-processing (eg injection moulding) to produce an article, for example a bottle, thereby to optimise incompatibility between the PET and second polymer and opacity / whiteness resulting therefrom; but transesterification is optimised and / or encouraged during recycling of the PET to produce rPET.

[0090] The following tests are referred to herein:

[0091] Test 1 - L* a* b* colour space assessment of blow-molded bottle and plaques

[0092] For a bottle, a small (60mm x 60mm) square section is first cut from a bottle wall. This section is placed on the holder of a Minolta CM3600A spectrophotometer, with the outer surface of the bottle section towards the instrument aperture. For a plaque, the area of interest is placed on the holder of a Minolta CM3600A spectrophotometer. The Large Area View (LAV) aperture is used, and the colour of the sample is measured in transmission mode using D65 illuminant. L*, a* and b* values are recorded.

[0093] Test 2 - Measurement of haze in to ASTM D1003

[0094] A plaque is placed in the path between the D65 illuminant and the detector of a Minolta CM3600A spectrophotometer and measured over reference white and black backgrounds. These measurements are used by the spectrophotometer to calculate the % haze of the sample, where lower % haze indicates higher clarity compared to the reference measurements, where the reference sample is air (i.e. no plaque).

[0095] Test 3 - Measurement of liqht transmission of blow-molded bottle or plaque

[0096] Light transmission of each bottle is assessed on a cut section from the bottle wall, using a Shimadzu UV Visible Spectrophotometer with an integrating sphere, across the wavelength range 300 - 700nm. Plaques may be assessed in an analogous manner.

[0097] Preforms were manufactured in a Husky GL160 injection moulder, with a two cavity mould installed. PET-X and second polymer(s) were premixed manually and added into a hopper installed above the feed throat of the injection moulder machine. A standard PET injection moulding process was employed to produce preforms.

[0098] Preforms were stretch blow moulded using a Sidel SB01 blow moulding machine into a 1 litre cylindrical bottle. A standard blowing process was utilised. The overall power % of the heating ovens was adjusted to achieve a preform temperature of 115°-120°C as the preform exits the oven and before it enters the blow mould. This is referred to as the blowing temperature.

[0099] Examples 3 to 12 - Production of bottles from compounds

[0100] Following the procedure of Example 1 , preforms were produced by compounding PET-X and a specified second polymeric material at a specified let-down-ratio as detailed in the table below.

[0101] Bottles were blown from the preforms as described in Example 2 and the light transmission of the bottles was assessed as described in Test 3. Results, normalized to a section thickness of 330pm are provided in Figure 1 . In this regard, as the wall thicknesses of the samples are not very different from the nominal thickness of 330 microns, the normalisation involves the measured % transmission being multiplied by the nominal thickness divided by the actual thickness. Figure 1 shows that addition of the specified polymers to the PET-X reduces the % transmission. The bottles generally appeared opaque compared to a bottle comprising 100% PET-X.

[0102] Example 13 - Preparation of blend of PET-X and Tritan TX1001

[0103] A 1 :1 , by weight, blend of PET-X and Tritan TX1001 was compounded in a twin screw extruder and pelletized. An extrudate made from the pellets had a milky, semi-opaque appearance and showed highly viscoelastic behaviour in the molten state. The extrudate was pelletized.

[0104] Example 14 - Preparation of blend of PET-X, Tritan TX1001 and transesterification catalyst

[0105] A 1 :1 , by weight, blend of PET-X and Tritan TX1001 was compounded in a twin screw extruder with addition of 0.427 wt% LDR, at the feedthroat of the twin screw extruder, of a 90% solution of titanium butoxide in n-butanol as a transesterification catalyst (equivalent to addition of 600ppm titanium metal). A clear extrudate was produced and pelletized.

[0106] Example 15 - Comparison of DSC traces for the blends of Examples 13 and 14

[0107] DSC analysis of the blends of Examples 13 and 14 was undertaken and the results are presented in Figure 2. The Example 13 blend shows two glass transitions, indicative of an incompatible physical blend of two polymers. The Example 14 blend shows a single glass transition temperature, with no melting or crystallization peaks, indicating that an amorphous copolyester has been formed.

[0108] Example 16 - Comparison of plagues made from the blends of Examples 13 and 14

[0109] Crystallized and dried pellets of the blend of Example 13 were injection moulded to make stepped plaques having steps of 2mm and 3mm thicknesses. Measurements were made through the 3mm thickness unless otherwise stated. The plaques were found to exhibit a significant degree of opacity.

[0110] Dried pellets of the blend of Example 14 were injection moulded to make 3mm thick stepped plaques. The plaques were found to be comparable in clarity to plaques made from pure PET- X.

[0111] The plaques were assessed as described in Test 1 and data for the plaques is provided in the table below. The values stated are the average of ten measurements.

[0112] Transmission data for Examples 13, 14 and pure PET-X is provided in Figure 3. The mean Haze of the plaques of Examples 13, 14 and pure PET-X, assessed as described in Test 2, is shown in Figure 4.

[0113] Results from Example 15 illustrate that the blend of Example 13 comprises incompatible polymers which are immisible. This immisibiity means that the blends can be used to produce opaque bottles, as illustrated by Examples 9 to 12. However, when the blends include a transesterification catalyst as described for Example 14, the blends become compatible, as illustrated by the blend having a single Tg and the blend exhibiting high transmission when compared as described in Example 16. That is, the plaque comprising the blend of Example 14 has similar L* to pure PET-X and low haze (<10%), whereas a plaque comprising the blend of Example 13 has a sig nficantly lower L* and is substantially opaque, as shown by the measured haze being 98%.

[0114] Example 17 - Preparation of blend of PET-X, Tritan and transesterification catalyst

[0115] The procedure of Example 14 was followed using an equivalent of 400ppm of titanium metal. A clear extrudate was produced using the material.

[0116] Example 18 - Comparison of bottles made with alternative blends of PET-X and Tritan with and without transesterification catalyst and use of blends to make bottles

[0117] Tritan TX2001 , with a glass transition temperature of 120°C, was compounded at 12% LDR in PET-X with the addition of a solution of 90% titanium butoxide in n-butanol at the feedthroat at a level equivalent to addition of 1200ppm titanium metal. A clear copolyester extrudate was produced which was pelletized, crystallized and dried.

[0118] Pellets produced were used to make 1 L bottles (referred to as Example 18a) with a nominal wall thickness of 250 microns. An equivalent process was used to produce a bottle (referred to as Example 18b), but excluding the transesterification catalyst (i.e. excluding titanium butoxide).

[0119] Figure 5 shows that a bottle (Example 18b) made using a blend without the catalyst was white and opaque (low transmission), whereas a bottle (Example 18a) made with the catalyst was substantially clear (high transmission) and / or similar in clarity / colour to a bottle made from pure PET-X. of blends comprising Tritan TX2001 with blends

[0120] Following the procedure described in Example 1 , preforms were made comprising PET-X and either Tritan TX2001 or PEN. Preforms were made using preform injection moulding temperatures of either 295°C or 310°C. The table below describes compositions and conditions used to make preforms.

[0121] The preforms were blown to produce bottles as described in Example 2. The transmission of bottles was then assessed as described in Test 3 and results are presented in Figure 6.

[0122] Referring to Figure 6, the % transmission for Examples 22 and 23 is substantially identical. In contrast the % transmission for Example 20 is disadvantageously higher (i.e. the bottle is less opaque) compared to Examples 22 and 23 which shows that PEN is less incompatible with PET compared to Tritan TX2001 and / or is less robust during injection moulding to produce preforms. For example, the PET / PEN may undergo transesterification during injection moulding, increasing their compatibility and, consequently, increasing transmission and reducing opacity.

[0123] Example 21 has similar transmission to pure PET-X of Example 19 illustrating that at higher injection moulding temperatures (e.g., 310°C), PET-X and PEN transesterify and become substantially entirely compatible leading to production of bottles which have similar transparency to bottles consisting of PET-X. Thus, if PEN is to be used as a polymer intended to be incompatible with PET, it must be very carefully processed and / or processed at a low injection moulding temperature. Even after such careful processing (e.g., as in Example 20), its ability to opacify PET is significantly less than that for Tritan TX2001 .

[0124] The inventors have concluded from the above and other experiments advantageous characteristics of second polymers which can be blended with polyester, for example PET, to produce blends which can, on the one hand, be used to make opaque bottles; and, on the other hand, can subsequently be treated to substantially eliminate opacity (and / or to cause the blend to have a transmission at or approaching that of pure PET) thereby to allow the blends to be recycled with substantially pure PET obtained from bottles (or from other sources).

[0125] Advantageous characteristics include the following:

[0126] (i) The second polymer is a polyester or polycarbonate polymer or copolymer. (ii) When 50 wt% of a standard PET (e.g., PET-X) and 50 wt% of a selected second polymer are blended and extruded to produce homogenous pellets, the pellets exhibit at least two Glass Transition Temperatures (Tgs) when tested using DSC.

[0127] (iii) When a 1 :1 , by weight, blend of a standard PET and a selected second polymer is used to make a plaque as detailed in Example 16, the transmission of the plaque is less than 70% for light with a wavelength of 550nm and / or the % haze is greater than 20%, when assessed as described in Tests 3 and 2 respectively.

[0128] (iv) The second polymer has, when tested as described, a “Robustness Ratio” (R) of less than 1.10. wherein:

[0129] R = The transmission (%} through a 3mm region of a test piece B at 550nm

[0130] The transmission (%) through a 3mm region of a test piece A at 550nm wherein: test piece A is made in a process comprising: selection of a blend comprising 88 wt% of said polyester and 12 wt% of the second polymer; and injection moulding the blend at 295°C to produce a standard plaque, wherein said injection moulding is suitably undertaken on a Boy 22A injection moulding machine with 75mm diameter barrel and 24mm diameter screw, with the program for the machine having barrel temperatures set to achieve a melt temperature of 295°C, a polymer residence time of 90-120 seconds and screw rotation speed during the plasticization part of the injection moulding process between 150-350 rpm; and wherein: test piece B is made as described for test piece A except a temperature of 310°C is used instead of 295°C.

[0131] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1 A blend comprising a polyester, for example polyethylene terephthalate (PET), and a second polymer, wherein said blend exhibits two glass transition temperatures (Tgs).2 A blend according to claim 1 , wherein said blend is arranged to be used in production of a packaging article having increased opacity, wherein the opacity can be reduced subsequent to use of the packaging article, to facilitate recycling of the packaging article with a main PET recycle stream.3 A blend according to claim 1 or claim 2, wherein said polyester has a Tg of at least 70°C and less than 90°C; and said second polymer has a Tg of at least 100°C, for example 100°C to 150°C.4 A blend according to any preceding claim, wherein said blend exhibits one Tg corresponding to said polyester and a second Tg due, at least in part, to the inclusion of said second polymer in said blend, wherein, preferably, said second polymer is incompatible with said polyester and / or said polyester and second polymer have a degree of immiscibility.5 A blend according to any preceding claim, wherein the difference in the Tg of the polyester and the second polymer is at least 10°C, preferably at least 20°C; and / or said difference in the Tg of the polyester and the second polymer is less than 130°C or less than 75°C.6 A blend according to any preceding claim, wherein said blend optionally includes a third polymer which is incompatible with the polyester; and / or substantially compatible with the second polymer.7 A blend according to any preceding claim, wherein said polyester and said second polymer are such that, when a 1 :1 by weight blend of said polyester and said second polymer is made into a plaque, suitably as described in Example 16, the transmission of the plaque through a 3mm region of the plaque is less than 70% (preferably less than 60% or less than 50%) for light with a wavelength of 550nm and / orthe haze % is greaterthan 20%, suitably when assessed as described in Tests 3 and 2 respectively.8 A blend according to any preceding claim, wherein said polyester and said second polymer are such that, when tested as herein described, a blend thereof has a “Robustness Ratio” (R) of less than 1 .15, preferably less than 1.10 wherein:R = The transmission (%) through a 3mm region of a test piece B at 550nmThe transmission (%) through a 3mm region of a test piece A at 550nm wherein: (I) test piece A is made in a process comprising: selection of a blend comprising 88 wt% of said polyester and 12 wt% of the second polymer; and injection moulding the blend at 295°C to produce a standard plague, wherein said injection moulding is suitably undertaken on a Boy 22A injection moulding machine with 75mm diameter barrel and 24mm diameter screw, with the program for the machine having barrel temperatures set to achieve a melt temperature of 295°C, a polymer residence time of 90-120 seconds and screw rotation speed during the plasticization part of the injection moulding process between 150-350 rpm; and wherein: (II) test piece B is made as described for test piece A except a temperature of 310°C is used instead of 295°C.9 A blend according to any preceding claim, wherein said polyester and said second polymer are such that, when a 1 :1 , by weight, blend of said polyester and said second polymer, together with 600ppm titanium metal introduced using a 90% solution of titanium butoxide in n- butanol (the titanium metal suitably acting as a transesterification catalyst) is pelletised, the pellets exhibit a single Glass Transition Temperature (Tg).10 A blend according to any preceding claim, wherein said second polymer is adapted to be transesterified with said polyester.11 A blend according to any preceding claim, wherein:(i) said second polymer includes a repeat unit which includes no aromatic moiety, for example no cyclic or polycyclic aromatic moiety; wherein, optionally, said second polymer includes a repeat unit which includes an ester moiety in combination with a saturated hydrocarbon moiety; or(ii) said second polymer includes a repeat unit which includes a cyclic moiety, for example a saturated cyclic moiety, wherein, optionally, said cyclic moiety comprises carbon and hydrogen atoms only or is an heterocyclic moiety; or(iii) said second polymer is a polycarbonate.12 A blend according to claim 11 , wherein, when said second polymer is as described in (i), said second polymer includes a lactic acid repeat unit and is, for example, a polylactic acid; and wherein said second polymer is as described in (ii) said cyclic moiety is a four to six-memberedcyclic moiety which is optionally substituted; or said second polymer is a co-polyester including a repeat unit derived from a diol selected fromwherein said second polymer is as described in (iii), said second polymer is a polycarbonate which includes a cyclic, especially a heterocyclic, moiety which is preferably unsaturated.13 A blend according to claim 12, wherein said second polymer is as described in (ii) and is a co-polyester which includes repeat units derived from both I and II.14 A blend according to claim 12, wherein said second polymer is as described in (iii), the polycarbonate incorporates an isosorbide-derived repeat unit and / or is be prepared using an isosorbide monomer.15 A blend according to any preceding claim, wherein said blend is a solid masterbatch.16 A blend according to any preceding claim, wherein said blend includes:1 to 20 wt%, preferably 3 to 10 wt%, of said polyester;45 to 99 wt%, preferably 90 to 97 wt%, of said second polymer; and0 to 45 wt%, preferably 0 to 7 wt%, of a or said third polymer.17 A blend according to any preceding claim, wherein said blend is a packaging blend which includes at least 0.5 wt%, preferably at least 2.0 wt%, of said second polymer; and less than 20 wt%, preferably less than 10 wt%, of said second polymer; and includes at least 50 wt%, preferably at least 80 wt%, of a polyester.18 A blend according to claim 16 or claim 17, wherein, in said packaging blend, the sum of the wt% of said polyester (e.g. PET), said second polymer and an optional third polymer is at least 95 wt%, preferably at least 98 wt%; and / or in said packaging blend, a ratio defined as the wt% of polyester (e.g. PET) divided by the sum of the wt% of said second polymer, and optional third polymer, is at least 5, for example in the range 5 to 25.19 A blend according to any preceding claim, wherein said blend is in the form of a packaging article, for example a preform or a container such as a bottle.20 A packaging article which includes said packaging blend according to any preceding claim.21 A packaging article according to claim 20, wherein said packaging article is in the form of a monolayer preform or a container such as a bottle which comprises, preferably consists essentially of, said packaging blend.22 A packaging article according to claim 21 , wherein said monolayer of said preform or container includes:2 to 20 wt%, preferably 4 to 15 wt%, of said second polymer;0 to 20 wt%, preferably 0 wt%, of a or said third polymer; and in excess of 80wt% or in excess of 85wt% of a polyester (preferably PET).23 A packaging article according to any of claims 20 to 22, wherein said packaging article includes an identification means to enable a packaging article to be identified as being arranged to be treated so the opacity of the composition which makes up the packaging article can be reduced, for example to facilitate recycling of the packaging article with a main PET recycle stream.24 A packaging article according to any of claims 20 to 23, wherein the packaging article, for example container, has a transmission at 400 nm of less than 75%, for example less than 70%, wherein the packaging article is arranged such that said second polymer can be transesterified with the polyester (e.g. PET) to produce a material which, if melt processed to produce a further packaging article, for example bottle, having the same wall thickness, would have a transmittance at 400 nm greater (e.g. at least 5% or at least 10% greater) than that of the packaging article (for example container) from which the material was derived.25 A method of producing a packaging article, for example as described in any of claims 20 to 24, the method comprising melt-processing a polyester and a second polymer to produce a blend, wherein said blend exhibits two glass transition temperatures (Tgs).26 A method according to claim 25, wherein said method is a method of increasing the opacity of a container such as a bottle, for example a polyester (e.g. PET) bottle; and / or said method comprises producing a container which has an increased opacity compared to an otherwise identical container which does not include said second polymer and / or which only includes said polyester (eg PET).27 A method according to claim 25 or claim 26, wherein said blend is used to produce a packaging article having increased opacity, wherein the opacity can be reduced, subsequent to use of the packaging article, to facilitate recycling of the packaging article (e.g. bottle).28 A method according to any of claims 25 to 27, wherein a multiplicity of packaging articles comprising said blend are selected and processed together to reduce opacity, for example by effecting transesterification.29 A method according to ay of claim 25 to 28, wherein said blend is treated to transesterify said second polymer with said polyester.30 A method of recycling a packaging article, for example a container such as a PET bottle, the method comprising selecting a packaging article which includes polyester, a second polymer and optional third polymer as described in any preceding claim, and treating the packaging article to reduce the level of opacity and / or to effect transesterification of said second polymer with said polyester.31 A method according to claim 30, the method comprising:(i) selecting a packaging article which includes polyester, a second polymer and optional third polymer as described in any preceding claim, wherein said packaging article has a transmission at 400 nm of less than 75%, less than 70%, less than 60% or less than 50%, for example determined on a cut-section from a wall of the packaging article as described in Test 3; and(ii) treating the packaging article to reduce the level of opacity and / or to effect transesterification.32 A method according to claim 30 or claim 31 , wherein the method comprises use of a transesterification catalyst to facilitate transesterification.33 A method according to any of claims 30 to 32, wherein the method comprises selection of a packaging article which includes an identification means to enable a packaging article to be identified as being arranged to be treated (eg transesterified) so the opacity of the composition which makes up the packaging article can be reduced, for example to facilitate recycling of the packaging article with a main PET recycle stream. 34 A method according to any of claims 31 to 33, the method comprising blending the packaging article selected in step (i) or treated as described in step (ii) with additional polyester (e.g. PET).35 The use of a second polymer (and optional third polymer) as described in any preceding claim for increasing opacity of polyester (e.g. PET) in a packaging article (e.g. bottle), wherein the opacity can be reduced by a transesterification reaction involving said second polymer (and optional third polymer).

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