Blend

Abstract

A blend comprises a polyester, for example polyethylene terephthalate (PET) and a second component, wherein the second component may be a monomer which is arranged to become polymerised into said polyester, suitably when said blend is melt processed at an elevated temperature, for example in a polyester recycling process. The blend may be used in production of an article, for example a packaging article (eg bottles, jars, trays, cups or films) and / or a film / sheet having increased opacity (and / or reduced light transmission), wherein the opacity can be reduced (and / or transmission increased) subsequent to use of the article to facilitate recycling of the article with a main PET recycle stream.

Description

[0001] Blend

[0002] This invention relates to a blend comprising a thermoplastic polymer. Particularly, although not exclusively, the invention relates to blends for making articles such as packaging materials, films and / or sheets. Preferred embodiments relate to articles (eg containers or films / sheets) which are bright white (eg high L*) and / or are opaque or semi-opaque and / or have high haze. Such articles may be used in household / personal care products which require some opacity. Preferred embodiments aim to facilitate recycling of such articles with a main recycle stream to produce 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 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 TiO2..

[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, 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 (eg bottles or films). 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 articles (eg bottles, jars, trays, cups, films or sheets) 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.

[0008] According to a first aspect of the invention, there is provided a blend comprising a polyester, for example polyethylene terephthalate (PET) and a second component.

[0009] The blend described is suitably arranged to be used in production of an article, for example a packaging article (eg bottles, jars, trays, cups or films) and / or a film / sheet having increased opacity (and / or reduced light transmission), wherein the opacity can be reduced (and / or transmission increased) subsequent to use of the article to facilitate recycling of the article with a main PET recycle stream.

[0010] The blend is suitably arranged to be melt-processed, for example injection moulded or extruded, to produce an article having relatively low transmission and / or high opacity compared to the transmission and / or opacity of the polyester, for example PET, alone. Said blend preferably also has relatively high L*, for example of at least 65 or at least 70, suitably determined as described in Test 2. The second component may be an inorganic pigment or at least act like a pigment, in the blend and / or in an article made from the blend.

[0011] The second component is preferably arranged to react at an elevated temperature which is suitably greater than the minimum melt-processing temperature of the blend (for example, by at least 20°C or at least 30°C), to produce a blend having a higher transmission and / or lower opacity. In addition, the level of visible particles of the second component in the blend, for example as can be observed under an optical microscope (at 50-500x) is suitably less (preferably there are substantially no visible particles of the second component) compared to the level of visible particles before the treatment. Thus, the blend can be used in production of an article, for example a film / sheet and / or a layer of a packaging article having a low transmission; and subsequent to use of the article where low transmission is desirable, the blend and / or article can be treated at an elevated temperature, for example in a polyester recycling process, to produce polyester of higher transmission. The polyester, for example PET, may after treatment at said elevated temperature, have similar transmission and / or L* to virgin polyester, for example PET. Thus, the blend can be recycled as described to produce relatively high quality (i.e., transparent) polyester, for example rPET.

[0012] Said second component is preferably arranged to react with said polyester, for example in an acidolysis reaction. It may be arranged to react during recycling of the blend, for example at an elevated temperature of at least 290°C or 310°C. Said second component is preferably not a polymer. Said second component is preferably not an oligomer. Said second component is preferably not a dimer.

[0013] Said second component is preferably not a dye. Said second component is preferably not an inorganic material, for example pigment. Said second component is preferably not titanium dioxide.

[0014] Said second component may be a monomer which is preferably arranged to become polymerised into said polyester, suitably when said blend is melt processed at an elevated temperature, for example in a polyester recycling process. Said blend is preferably arranged to be melt processed at a first temperature to produce a useful article or component of an article, wherein at the first temperature the second component does not substantially react with the polyester and / or wherein the second component remains as discrete particles dispersed in the polyester. Said blend is preferably arranged to be melt processed at a second temperature, suitably after it has been melt processed at said first temperature and / or when it is in the form of a useful article or component of such an article. Said second temperature is suitably higher than the first temperature and is arranged to cause the second component to become polymerised into said polyester, suitably to allow the blend to be recycled and / or to increase the transmission of the blend.

[0015] Preferably, at said second temperature, said second component is arranged to react with said polyester so a covalent bond is formed between said polyester and said second component.

[0016] Said second component is preferably organic. It may be an organic acid, an organic acid derivative, or a salt derived from an organic acid.

[0017] Said second component may include a carboxylic acid moiety or a moiety which is a derivative of a carboxylic acid moiety.

[0018] Said second component may include 1-5, preferably 1-3, more preferably 1-2, carboxylic acid moieties or moieties which are derivatives of carboxylic acid moieties.

[0019] Said second component may include a sulfo moiety. For example, said second component may include a -SO3 such as a -SOa’ moiety.

[0020] Said second component may include 1-5, preferably 1-3, more preferably 1-2, sulfo moieties for example SO3- moieties. Said second component preferably includes an aromatic moiety. Said second component preferably includes 1-5, preferably 1-3, more preferably 1-2, especially only one, aromatic moiety. An organic acid, an organic acid derivative or a salt derived from an organic acid may be pendent from said aromatic moiety. For example, a carboxylic acid moiety or a moiety which is a derivative of a carboxylic acid moiety may be pendent from said aromatic moiety. Alternatively, or preferably additionally, a sulfo moiety for example which includes a -SOa' moiety may be pendent from said aromatic moiety.

[0021] Said aromatic moiety may include a single aromatic ring or fused aromatic rings. Said aromatic moiety (excluding any pendent functional groups) may include carbon and hydrogen atoms only. For example, the aromatic moiety is preferably not heteroaromatic. Said aromatic moiety is preferably a benzene moiety.

[0022] Said second component preferably includes: at least one moiety which is a carboxylic acid moiety or a moiety which is a derivative of a carboxylic acid moiety (herein “said first functional group”); and at least one sulfo moiety, for example a SOa- moiety (herein “said second functional group”),

[0023] Preferably, said first and second functional groups are bonded to the same aromatic moiety. In this case, preferably, said first and second functional groups are bonded to atoms of the aromatic moiety at positions 1 and 3 relative to one another. Said first and second functional groups may be meta to one another.

[0024] Said second component may include a moiety wherein:

[0025] X includes a moiety -COO- ; and

[0026] Y includes a moiety SO3" wherein suitably the free bond to the C and S atoms respectively indicates a bond which is directly bonded to the benzene ring.

[0027] Y is preferably bonded meta to X.

[0028] X is preferably -COOH. Y is preferably -SO3M, wherein M represents a metal or an ammonium ion, and, preferably, is Na+.

[0029] Said second component may include a moiety: wherein R represents an optional substituent and n is 0 to 4.

[0030] R may be selected from the moieties referred to for X and Y or may represent a bridging atom or group (eg bridging to another aromatic moiety).

[0031] Said second component preferably includes a moiety

[0032] Hydrogen atoms of moiety III may be optionally substituted. Preferably, in moiety III, moiety - CO2- is -COOH and moiety -SOs" is -SOsNa.

[0033] In preferred embodiments, said second component is selected from a sulfoisophthalic acid (e.g., SIPA) and a sulfobenzoic acid (e.g., SSBA). The melting point (eg commencement of melting) of the second component may be greater than 300°C or preferably greater than 325°C. It may be less than 400°C or less than 350°C.

[0034] Said second component may be dispersed, preferably substantially homogenously, in the polyester. Said second component is preferably particulate and is preferably dispersed as discrete particles in the polyester. The particles may be observed under an optical microscope (at 50-500x).

[0035] As used herein, a "dso particle size" is the median diameter, where 50% of the volume is composed of particles larger than the stated dso value, and 50% of the volume is composed of particles smaller than the stated dso value. As used herein, the median particle size is the same as the dso particle size. Particle sizes may be measured using a Beckman Coulter LS230 Laser Diffraction Particle Size Analyzer.

[0036] Said second component preferably consists of particles having a dso of less than 200pm, preferably less than 100pm, more preferably less than 50pm and, especially, 25pm or less. The dso of said particles may be greater than 0.010pm, preferably greater than 0.10pm, more preferably greater than 1.0 pm. dso may be measured as described herein.

[0037] Less than 5 wt%, less than 3 wt% or less than 1 wt% of particles of said second component may have a particle size measured as described herein of more than 100pm. Preferably, at least 99 wt%, more preferably about 100 wt% of particles of said second component have a size of less than 100pm, preferably of less than 50pm.

[0038] Said second component preferably has a pKa, measured at STP, of less than 5.0. The pKa may be at least 1 .0 or at least 2.0 or at least 3.0. Preferably the pKa is in the range 3.0 to 5.0. If the pKa is too high, the second component may be too reactive towards the polyester, for example PET. This may mean that the second component reacts with the polyester polymer during the first melt-processing of a blend comprising the polyester and second component to produce an article for example a packaging article. Any such reaction will tend to reduce the ability of the second component to act as a pigment in the blend and, therefore, may not reduce transmission of the polyester to the same extent as a second component which does not react with the polyester to the same extent. However, the second component preferably has some reactivity towards the polyester so that it can react with the polyester and form covalent bonds with it during a subsequent melt-processing of the blend at a higher temperature, for example in a recycling step. Thus, the second component preferably exhibits a balance of properties - not too reactive with the polyester at a first temperature at which the blend may be melt-processed to produce a useful article; but sufficiently reactive with the polyester at a second temperature, higher than the first temperature. The second temperature may represent a temperature at which the blend may be recycled alone or with other polyester having a different identity to that of the polyester of the blend. The differences between the first temperature and second temperature may be at least 10°C, 20°C, 30°C or 40°C.

[0039] Said blend suitably includes less than 2wt%, preferably less than 1wt%, more preferably less than 0.5wt%, more preferably less than 0.1wt%, of particulate material other than said second component. Said blend suitably includes substantially 0wt% of particulate material other than said second component.

[0040] Said blend may be a masterbatch, for example a solid masterbatch, preferably in the form of pellets or granules.

[0041] Said blend (herein the "masterbatch blend”) may include less than 50 wt% of said polyester in combination with said second component.

[0042] Said masterbatch blend may include at least 30wt%, preferably at least 35wt%, more preferably at least 40wt%, of said second component. Said masterbatch blend may include less than 90wt%, preferably less than 80wt% or less than 70wt% of said second component.

[0043] The sum of the wt% of said polyester and said second component in said masterbatch blend may be at least 80 wt%, preferably at least 90 wt%, more preferably at least 95wt%, especially at least 98wt%. The balance may comprise additives selected from antioxidants, process stabilizers, UV additives, compatibilizers, slip agents and chemical or digital markers.

[0044] Said masterbatch blend may include:

[0045] 40 to 80 wt%, preferably 55 to 65wt%, of said polyester;

[0046] 20 to 60 wt%, preferably 35 to 45 wt%, of said second component.

[0047] The polyester in the masterbatch blend may be PET, PBT or a copolymer of the aforesaid.

[0048] As an alternative to the masterbatch blend, said blend may be an article blend which may be a blend used to produce at least part of an article (eg a film / sheet or a packaging article) or the blend may define at least part of an article (eg a film / sheet or a packaging article) itself. A said article (eg a film / sheet or a packaging article) may comprise or consist of said article blend. A packaging article described herein may be, for example, a bottle, jar, tray, cup or film or a preform for a container. 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.

[0049] Said article blend may be formed in a melt-processing apparatus and / or may define at least part of an article, for example a packaging article and / or film / sheet, suitable produced by meltprocessing. Said article may be a preform or a container such as a bottle, which may be made such as by letting down a masterbatch blend, for example as described above, in additional polyester to define the article blend.

[0050] Said article blend may include at least 0.5 wt%, preferably at least 1 .0 wt%, more preferably at least 1 .5 wt% of said second component. Said article blend may include less than 20.0 wt%, preferably less than 10.0 wt%, more preferably less than 6.0 wt%, of said second component.

[0051] Said article blend may include at least 80 wt%, preferably at least 90 wt%, more preferably at least 94 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% of said polyester.

[0052] In said article blend, the sum of the wt% of said polyester (e.g. PET) and said second component is preferably at least 90 wt%, more preferably at least 95 wt%, especially at least 99 wt%.

[0053] In said article blend, a ratio defined as the wt% of polyester (e.g. PET) divided by wt% of said second component may be at least 12 and may be less than 80. It is preferably in the range 10 to 50.

[0054] Said article blend may include:

[0055] 65 to 99 wt%, suitably 80 to 99 wt%, preferably 90 to 99wt%, of polyester;

[0056] 1 to 35 wt%, suitably 1 to 20 wt%, preferably 1 to 10 wt%, of said second component.

[0057] When said blend is an article blend, it may define at least part of an article, for example a packaging article and / or film / sheet, Said an article blend may define a layer of a laminate or of a container (eg a bottle, jar, tray or cup). Such a layer may be in combination with another layer made out of a different material compared to that of said article blend. For example, the other material may be less soluble in water compared to that of said layer made from said article blend.

[0058] Said polyester of the first aspect, for example in the blend, masterbatch blend or article 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.

[0059] 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.

[0060] According to a second aspect, there is provided a concentrated formulation for addition to a polyester to reduce the transmission of the polyester and / or an article produced therefrom, for example by melt-processing polyester with the formulation, said concentrated formulation comprising a carrier and a second component as described according to the first aspect.

[0061] Said carrier may be a polyester and said concentrated formulation may be a solid masterbatch. In this case, said concentrated formulation may be a solid masterbatch and / or said concentrated formulation may be a said “masterbatch blend” and may have any feature of the masterbatch blend as described in the first aspect.

[0062] Alternatively, said concentrated formulation may be a liquid formulation comprising a liquid carrier and said second component.

[0063] References to a state of a material herein (e.g. a liquid) refer to the state at standard temperature and pressure (STP). Thus, said liquid formulation is suitably a liquid at STP; and said liquid carrier is suitably a liquid at STP.

[0064] Said concentrated formulation may include at least 10wt%, preferably at least 20wt%, more preferably at least 25wt% liquid carrier. It may include less than 70wt%, preferably less than 60wt%, more preferably less than 50wt%, liquid carrier. Said concentrated formulation may include at least 30wt%, preferably at least 40wt%, more preferably at least 50wt% of said second component. It may include less than 90wt%, preferably less than 80wt%, more preferably less than 75wt% of said second component.

[0065] Said concentrated formulation preferably includes 50 to 70wt% of said second component and 30 to 50wt% of polyester.

[0066] Said liquid carrier is preferably a liquid at 25°C and atmospheric pressure. A liquid carrier is suitably such that it has good solubility in the polyester into which it is to be added. It may comprise an oil (e.g. vegetable or mineral oil) or a glycol. Typical carriers include hydrocarbons, hydrocarbon mixtures, alcohols, esters, polyethers and mixtures of two or more thereof. An compatible organic liquid carrier may be an oil-based vehicle. Examples of such vehicles are the materials sold as Clearslip™ 2, Clearslip™ 3 & Process Aid-1 by ColorMatrix Europe Ltd, of Units 9-11 Unity Grove, Knowsley Business Park, Merseyside, L34 9GT.UK.

[0067] According to a third aspect of the invention, there is provided an article, for example a film / sheet or a packaging article (eg bottle, jar, tray, cup or film), the article including said blend according to said first aspect.

[0068] At least 90 wt%, preferably at least 95 wt%, more preferably at least 99 wt% of a layer of said article may be made up of said blend.

[0069] A part of said article which comprises said blend may exhibit increased opacity (and / or reduced light transmission) compared to an article produced from the polyester alone and, suitably, the opacity can be reduced (and / or transmission increased) subsequent to use of the article, to facilitate recycling of at least the polyester-containing part of the article with a main PET recycle stream.

[0070] A layer of said article may include:

[0071] 65 to 99 wt%, preferably 90 to 99wt%, of polyester;

[0072] 1 to 35 wt%, preferably 1 to 10 wt%, of said second component.

[0073] Said article and / or a polyester-containing part of the article may include an identification means to enable the article (or a part) 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 (and / or transmission increased), for example to facilitate recycling of the article with a main PET recycle stream. The identification means may be an identifier (eg code) which is marked on the 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.

[0074] According to a fourth aspect of the invention, there is provided a method of producing an article, the method comprising melt-processing a polyester and a second component to produce a blend.

[0075] Said method may comprise treating said polyester, for example PET, to reduce the light transmission of the polyester, wherein the method comprises reducing the transmission of the polyester by blending, suitably by melt processing, the polyester with said second component.

[0076] Preferably, the method comprises reducing the light transmission of the polyester by dispersing said second component into the polyester, suitably so discrete particles of said second component are visible (eg using an optical microscope as described herein) in the polyester. The method may further comprise selecting said second component so it can react with the polyester at an elevated temperature (referred to herein as a “second temperature”) suitably so that covalent bonds can be formed between the polyester and said second component at said elevated temperature.

[0077] The method preferably produces a blend described according to the first aspect. The polyester may be as described according to the first aspect. Said second component may be as described according to the first aspect.

[0078] Said method preferably comprises melt processing the polyester and second component at a temperature (herein the “first temperature”) which is less than a temperature at which the second component reacts with the polyester and / or forms covalent bonds with the polyester.

[0079] The method of the fourth aspect may comprise:

[0080] (i) selecting a blend according to the first aspect, and melt-processing the blend to produce an article, for example a film / sheet or a packaging article, for example a preform for a container such as a bottle; or

[0081] (II) selecting a second component according to the first aspect and contacting said second component with said polyester, for example PET; and melt-processing the second component and said polyester, for example PET, to produce an article, for example a film / sheet or a packaging article, for example a preform for a container such as a bottle. The method may comprise stretch blow-moulding a preform to produce a packaging article in the form of a container such as a bottle.

[0082] The method may comprise associating identification means as described in the third aspect with the article.

[0083] Advantageously, the blend described can be used to produce an article, for example a film / sheet or a packaging article (eg a bottle, jar, tray, cup or film) having increased opacity (and / or reduced transmission) and the opacity can be reduced (and / or transmission increased), subsequent to use of the article to facilitate recycling of the article. Preferably, by reducing opacity (and / or increasing transmission), the article or part thereof 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 articles comprising said blend as described, for example bottles, may be selected and processed together to reduce opacity (and / or increase transmission) as described herein. The processed blend may then be mixed with a main recycle stream (eg comprising other PET) to produce rPET.

[0084] Preferably, the article, for example container, has a transmission at 400 nm of less than 75%, for example less than 70%, suitably determined as described in Test 1. The article may be arranged such that said second component can react with the polyester (e.g. PET) to produce a material which, if melt processed to produce a further article, for example bottle, having the same thickness, would have a transmission at 400 nm greater (e.g. at least 5% or at least 10% greater) than that of the article (for example container) from which the material was derived.

[0085] The invention extends, in a fifth aspect, to a method of recycling an article, for example a film / sheet or a packaging article, the method comprising selecting an article which includes polyester and a second component and treating the article to reduce the level of opacity (and / or increase transmission).

[0086] Said method of recycling may comprise:

[0087] (i) selecting an article or fragment of an article, wherein said article or fragment include polyester and discrete particles of a second component dispersed in the polyester;

[0088] (ii) melt processing the article or said fragments at a temperature (referred to herein as the “second temperature”) at which the second component reacts with the polyester and / or at a temperature such that the transmission of the product of the melt-processing is greater than the transmission of the article or fragment selected in (i).

[0089] The transmissions are suitable assessed in a manner understood by skilled persons in the art. Discrete particles may be observed under an optical microscope (at 50-500x).

[0090] Reaction as described in step (ii) may be confirmed by showing there are fewer (preferably substantially no) discrete particles of the second component in the polyester after step (ii), whereas there were discrete particles of the second component in the polyester of step (i). The product of step (ii) is suitably a recycled polyester.

[0091] The method of the fifth aspect may comprise determining if the article includes an identification means (e.g. as described in the third aspect) to confirm the article is as described herein and / or is arranged to be treated so the opacity of the blend which makes up the packaging article can be reduced (and / or its transmission increased). Thus, the method suitably comprises selection of an article which includes an identification means.

[0092] The method of the fifth aspect may comprise blending the article or fragments thereof 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 other polyester (e.g. PET), for example with relatively high transmission (and / or which does not include significant levels of additives which may be detrimental to the recycle stream) or comprise polyester (e.g. PET) derived from an article (e.g. container) which has a higher light transmission at 400 nm compared to the comparable transmission of the article selected in step (I).

[0093] In the method of the fifth 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 an 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).

[0094] According to a sixth aspect, there is provided the use of a second component as described in any preceding aspect for increasing opacity of polyester (e.g. PET) and / or reducing transmission of a film / sheet or a packaging article (eg a bottle, jar, tray, cup or film), wherein the opacity preferably can be reduced or transmission increased (suitably to facilitate recycling of the polyester (e.g. PET)) by a reaction involving said second component, for example an acidolysis reaction. Thus, the invention extends to use of said second component to increase opacity and / or reduce transmission as aforesaid and improve recyclability of an article.

[0095] The invention extends, in a seventh 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 component as described herein, wherein suitably the blend has been treated to cause the second component to react with the polyester. The rPET may comprise said blend and additional PET which may comprise PET from a source other than said blend.

[0096] Any aspect of any invention described herein may be combined with any other aspect of any invention described herein mutatis mutandis.

[0097] Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0098] Figure 1 is a graph of transmission v wavelength for Examples 4 to 9; and

[0099] Figure 2 is a graph of transmission v wavelength for Examples 6 and 10.

[0100] The following materials are referred to hereinafter:

[0101] PET-X - refers to a proprietary bottle grade PET (Lighter C93 from Equipolymers, with an Intrinsic Viscosity (IV) of 0.80 + / - 0.02)).

[0102] Sodium 5-sulfoisophthalic acid (SI PA), having a melting point in the range 373-375°C and particle sizes of less than 20 microns.

[0103] Sodium 3-Sulfobenzoic acid of the following structure obtained from Tokyo Chemical Industry UK, having a melting point in the range 340-350°C and particle sizes of less than 20 microns

[0104] Titanium dioxide - refers to Chemours Ti-Pure R-104 rutile titanium dioxide pigment powder, with primary particle size of 3-5 microns.

[0105] In general terms, in preferred embodiments, PET is melt-blended in a twin-screw extruder with a white, crystalline, organic material which acts as a pigment. The material is subsequently referred to as “organic pigment”. The organic pigment is an aromatic group-containing metal salt which is relatively incompatible with PET. The organic pigment may be processed with the PET using standard techniques such as injection moulding to make a partially or fully opaque, white article or by extrusion to produce a film. The degree of opacity / whiteness can be further enhanced by biaxial orientation and stretching, as takes place for example in an injection stretch blow moulding process, typically used to manufacture PET bottles. It is believed the organic pigment may act as a cavitation agent during stretching and biaxial orientation of the PET, creating voids in the PET which enhance the whiteness / opacity.

[0106] In preferred embodiments, when desired, the polyester blend and articles, such as containers and films, made therefrom can be passed through a further processing step wherein the blend is re-melted, for example in a twin-screw extruder, such that the organic pigment reacts with the PET, for example in an acidolysis reaction. The reaction may result in the IV of the PET being reduced. Particles of the organic pigment which were visible under an optical microscope (at 50- 500x) prior to the step become substantially invisible and the extrudate produced is highly transparent. Thus, by use of the further processing step, polyester blends and articles can be recycled, either alone or together with a source of transparent polyester (eg transparent polyester bottles) to produce high quality, transparent, recycled polyester.

[0107] The following test is referred to herein:

[0108] Test 1 - Measurement of light transmission of blow-molded bottle

[0109] 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.

[0110] Test 2 - L* a* b* colour space assessment of blow-molded bottle and plagues

[0111] 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. D65 illuminant is used. L* is measured in reflectance over black section of Leneta Form 2A Opacity Chart with LAV mask, in Specular Component Excluded mode.

[0112] Example 1 - General procedure for making preforms Preforms were manufactured in a Husky GL160 injection moulder, with a two cavity mould installed. PET-X and organic pigment 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.

[0113] Example 2 - Alternative procedure for making preforms from pre-compounded material

[0114] Alternatively, PET-X and organic pigment were fed separately, at the required mass dosing rates, by gravimetric feeders into the feedthroat of a Thermo Prism TSE 24 HC twin-screw extruder operating at temperatures typical for PET extrusion. The compound extrudate was cooled on fan conveyors and pelletized. The collected pellets were then crystallized and dried using processes standard for the crystallization and drying of PET, before being used to make preforms on a Husky GL160 injection moulder with a two cavity mould installed. A standard PET injection moulding process was employed to produce the preforms.

[0115] Example 3 - Producing bottles from preforms

[0116] 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.

[0117] Examples 4 to 9 - Production of bottles from compounds

[0118] Following the procedure of Example 1 , preforms were produced by compounding PET-X and a specified organic pigment (Examples 4 to 6) or inorganic pigment (Examples 7 to 9) at a specified let-down-ratio as detailed in the table below.

[0119]

[0120] Bottles were blown from the preforms as described in Example 3 and the light transmission of the bottles was assessed as described in Test 1. Results are provided in Figure 1, with the section thickness of the tested samples through which transmission was measured being provided in the table below.

[0121] The figure shows that addition of the specified pigments to the PET-X reduces the % transmission. The bottles generally appeared opaque compared to a bottle comprising 100% PET-X. Furthermore, incorporation of the organic pigments (Examples 4 to 6) leads to opacity comparable to that achieved using conventional inorganic pigments (Examples 7 to 9).

[0122] Example 10 - Recycling

[0123] The compounded material of Example 6 was dried to achieve a moisture content of <50ppm using standard techniques known to those skilled in the art and included in a 3:1 blend of PET- X to the Example 6 material. The compound was then processed on a Thermo Prism 24 HC twin-screw extruder with barrel temperatures set to 315°C and a throughput of 4kg / hr, equating to a residence time of at least 2 minutes. During this extrusion step, it is believed that the sodium 3-sulfobenzoic acid reacts with the PET polyester. In this regard, it is observed that no particles of the sodium 3-sulfobenzoic acid are visible in the extrudate, which is highly transparent. The extruded material is collected by fan-cooled conveyor belts and then the strands are pelletized. The collected pellets are crystallized and then dried.

[0124] The reaction of the sodium 3-sulfobenzoic acid with the polyester reduces the molecular weight of the polymer and hence the intrinsic viscosity. The dried material is then subjected to Solid State Processing (SSP) at 210°C (for PET and similar polyesters) under vacuum, as is routinely performed on recycled polyester materials, to promote reactions that increase the molecular weight of the polyester to a level that is suitable for the production of new articles, as determined from the IV by appropriate testing.

[0125] This material was then processed to make preforms and then bottles as per Examples 1 to 3. The light transmission of these bottles was then assessed as described in Test 1. Results are shown in Figure 2. The figure also includes results for the original compound, Example 6 (referred to as “EG6”), and PET-X. EG10 is the result for the material treated in the present example.

[0126] Example 11 - L* values

[0127] Following the procedure described in Test 2, the L* of compounds detailed in selected examples was assessed and results are provided in the table below.

[0128] The inventors have concluded from the above and other experiments advantageous characteristics of organic pigments 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).

[0129] Advantageous characteristics include the following:

[0130] (i) High melting point: higher than typical target polymer processing temperatures. For PET this means > 300°C. (ii) Presence of at least one aromatic ring with at least one carboxylic acid group on it.

[0131] (iii) Presence of at least one strongly electron-withdrawing group attached to the same aromatic ring as the carboxylic acid group(s).

[0132] (iv) Material is crystalline and forms white or uncoloured crystals.

[0133] 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 component.2 A blend according to claim 1 , wherein the blend is arranged to be used in production of an article having increased opacity, wherein the opacity can be reduced (and / or transmission increased) subsequent to use of the article to facilitate recycling of the article with a main PET recycle stream.3 A blend according to claim 1 or claim 2, wherein said second component is arranged to react at an elevated temperature to produce a blend having a higher transmission and / or lower opacity than the transmission and / or opacity of the blend prior to the reaction.4 A blend according to any preceding claim, wherein said second component is arranged to react with said polyester in an acidolysis reaction and / or so a covalent bond is formed between said polyester and said second component.5 A blend according to any preceding claim, wherein said second component is not a polymer and / or not an oligomer and / or not a dimer and / or not a dye and / or not an inorganic material.6 A blend according to any preceding claim, wherein said second component is particulate and is dispersed as discrete particles in the polyester.7 A blend according to any preceding claim, wherein said second component consists of particles having a dso of less than 200pm (preferably less than 50pm) and optionally the dso of said particles is greater than 0.010pm (preferably greater than 1.0 pm).8 A blend according to any preceding claim, wherein said second component is a monomer wherein at the first temperature the second component does not substantially react with the polyester and / or wherein the second component is arranged to remain as discrete particles dispersed in the polyester; wherein said blend is arranged to be melt processed at a second temperature, higher than the first temperature, at which temperature the second component is arranged to become polymerised into said polyester, suitably to allow the blend to be recycled and / or to increase the transmission of the blend.9 A blend according to any preceding claim, wherein said second component includes 1-5 carboxylic acid moieties or moieties which are derivatives of carboxylic acid moieties.10 A blend according to any preceding claim, wherein said second component includes 1-5 sulfo moieties for example SO3- moieties.11 A blend according to any preceding claim, wherein said second component includes an aromatic moiety which is preferably a benzene moiety.12 A blend according to any preceding claim, wherein said second component includes: at least one moiety which is a carboxylic acid moiety or a moiety which is a derivative of a carboxylic acid moiety (herein “said first functional group”); and at least one sulfo moiety, for example a SCh" moiety (herein “said second functional group”); wherein said first and second functional groups are bonded to the same aromatic moiety.13 A blend according to any preceding claim, wherein said second component includes a moietywherein:X includes a moiety -COO- ; andY includes a moiety -SOa-; wherein the free bond to the C and S atoms respectively indicates a bond which is directly bonded to the benzene ring.14 A blend according to any preceding claim, wherein the melting point (eg commencement of melting) of the second component is greater than 300°C or preferably greater than 325°C; and / or it is less than 400°C or less than 350°C.15 A blend according to any preceding claim, wherein said second component has a pKa, measured at STP, of less than 5.0; and / or the pKa is at least 1 .0.16 A blend according to any preceding claim, wherein said blend includes less than 2wt% of particulate material other than said second component.17 A blend according to any preceding claim, wherein said blend is a masterbatch, for example a solid masterbatch in the form of pellets or granules.18 A blend according to claim 15, wherein said masterbatch blend includes:40 to 80 wt%, preferably 55 to 65wt%, of said polyester;20 to 60 wt%, preferably 35 to 45 wt%, of said second component.19 A blend according to any of claims 1 to 14, wherein, in an article blend, the sum of the wt% of said polyester (e.g. PET) and said second component is at least 90 wt%; and a ratio defined as the wt% of polyester (e.g. PET) divided by wt% of said second component is at least 12 and less than 80, wherein said article blend includes:80 to 99 wt%, preferably 90 to 99wt%, of polyester;1 to 20 wt%, preferably 1 to 10 wt%, of said second component.20 A blend according to any preceding claim, wherein said polyester is polyethylene terephthalate which has less than 10 mole% (preferably less than 2 mole%) comonomer substitution).21 A blend according to any preceding claim, wherein said polyester is polyethylene terephthalate comprising substantially a homopolymer produced by esterification or transesterification of terephthalic acid or dimethyl terephthalate and ethylene glycol.22 A blend according to any preceding claim, wherein the IV of the polyester in the blend is greater than 0.5 dl_ / g and, optionally, less than 0.80 dL / g.23 A blend according to any preceding claims, in the form of a concentrated formulation for addition to a polyester to reduce the transmission of the polyester and / or an article produced therefrom, said concentrated formulation comprising a carrier and a second component as described in any preceding claim.24 A blend according to claim 23, wherein said concentrated formulation includes at least 10wt%, preferably at least 25wt% liquid carrier; and / or includes less than 70wt%, preferably less than 50wt%, liquid carrier.25 A blend according to claim 23 or claim 24, wherein said concentrated formulation includes at least 30wt%, preferably at least 50wt%, of said second component; and / or includes less than 90wt%, preferably less than 75wt%, of said second component.26 A blend according to any of claims 18 to 20, wherein said concentrated formulation includes 50 to 70wt% of said second component and 30 to 50wt% of polyester.27 An article, for example a film / sheet or a packaging article (eg bottle, jar, tray, cup or film), the article including said blend according to any preceding claim.28 An article according to claim 27, wherein a layer of said article includes:80 to 99 wt%, preferably 90 to 99wt%, of polyester;1 to 35 wt%, preferably 1 to 20 wt%, of said second component.29 A method of producing an article, for example according to claim 27 or claim 28, the method comprising melt-processing a polyester and a second component to produce a blend.30 A method according to claim 29 which comprises reducing the light transmission of the polyester by dispersing said second component into the polyester so discrete particles of said second component are visible in the polyester; and the method further comprising selecting said second component so it can react with the polyester at an elevated temperature (referred to herein as a “second temperature”) so that covalent bonds can be formed between the polyester and said second component at said elevated temperature.31 A method according to claim 29 or claim 30, wherein the method produces a blend according to any of claims 1 to 26.32 A method of recycling an article, for example a film / sheet or a packaging article, the method comprising selecting an article which includes polyester and a second component and treating the article to reduce the level of opacity (and / or increase transmission).33 A method according to claim 32, wherein said method of recycling comprises:(i) selecting an article or fragment of an article, wherein said article or fragment include polyester and discrete particles of a second component dispersed in the polyester;(ii) melt processing the article or said fragments at a temperature (referred to herein as the “second temperature”) at which the second component reacts with the polyester and / or at a temperature such that the transmission of the product of the melt-processing is greater than the transmission of the article or fragment selected in (i).34 A method according to claim 33, the method comprising blending the article or fragments thereof selected in step (i) or treated as described in step (ii) with additional polyester (e.g. PET).35 The use of a second component as described in any of claims 1 to 26 for increasing opacity of polyester (e.g. PET) and / or reducing transmission of a film / sheet or a packaging article(eg a bottle, jar, tray, cup or film), wherein the opacity can be reduced or transmission increased by a reaction involving said second component and polyester.

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