Film

Abstract

A transverse direction (TD) shrink film containing an inorganic cavitating agent having an average particle size of greater than 3 microns. The cavitating agent may be calcium carbonate and may have a

Description

The present invention concerns a transverse direction shrink film and a method of making said film. Transverse direction (TD) shrink films are used to closely wrap polymeric film around an article, for example as a label. These films are more oriented in the transverse direction than in the machine direction and so exhibit a greater shrinkage in the transverse direction than in the machine direction when exposed to elevated temperatures. This means that these films can be loosely placed around an article and then exposed to an elevated temperature to cause shrinkage predominantly in one direction, resulting in the film closely wrapping the article. The article that is surrounded by the shrink film is often formed from a different material to the film. Thus, it is important that the two materials can be separated during the recycling process. This is commonly achieved by providing materials with different densities. For example, in the case of polyethylene terephthalate (PET) bottles, polyolefin-based TD shrink films can be easily separated from the PET in the recycling process, after shredding, using a sink-float chamber in which PET flakes sink to the bottom and the polyolefin label flakes float to the surface. The end result is a high purity PET recyclate without any ink contamination from the label. There is increasing interest in switching products in both the dairy and home and personal sectors to transparent PET bottle (from HDPE) so that they can be readily recycled in existing PET recycling facilities. In many applications, the contents of the article need to be hidden by the label. Additionally, in applications such as in the dairy industry, the label needs to protect the contents from the harmful effects of UV light. In both cases, this requires the use of a full body shrink sleeve that is fully opaque, yet still of a density sufficiently below 1 such that, after printing, the label flakes still float in the recycling process. An opaque label can also enhance any print applied thereto. In order to ensure that 99% of the UV region of the electromagnetic spectrum is blocked, without interfering with the near infra-red (NIR) region, a layer of carbon free black can be applied to the label inner surface. However, it is important not to interfere with the NIR region so that the NIR detectors on the recycling lines can see the material of the article through the sleeve, for correct identification and sorting. Thus, the shrink film needs to benefit from a high opacity and whiteness, to either function on its own as an opaque label, or in the case of having a block ink / carbon free black layer on the reverse, to hide the ink layer / carbon free black sufficiently that the label appears white, rather than grey. Opacity and whiteness values of over 75 and 85 respectively are generally accepted as a minimum requirement. These levels are easily obtainable simply by adding a sufficient quantity of a pigment such as titanium dioxide (TiOz) to the film structure. However, since TiO? has a density of approximately 4 g / cm3, the density of the final film very quickly exceeds the ideal target of less than 0.95 g / cm3 for the finished film, where without any TiCh the density is approximately 0.92 g / cm3. At these densities, separation from other materials such as PET cannot be reliably achieved, as the film does not necessarily float on water. Cavitating agents are known in the art to reduce the density of the film, particularly inorganic cavitating agents such as calcium carbonate. The commonly commercially used calcium carbonate is that with average particle sizes of 3 microns or less. These cavitating agents can be used to reduce density to as low as 0.55 g / cm3. However, all other properties of the film must be maintained within workable tolerances, including the shrinkage, tensile properties and coefficient of friction. On a typical sequential stenter line, which comprises both a machine direction (MD) orientation step (typically stretching by 3 to 6x the original dimension) followed by a TD orientation step (typically stretching by 5 to lOx the original dimension), generating cavities is relatively easy due to the high strains involved. The cavities are initiated in the very high strain rate MD orientation step and then elongated and grown in the TD orientation step. This creates cavities that are sufficiently large to reduce the density of the film. However, in order to obtain the necessary TD shrink properties, TD shrink films are not created using standard sequential stenter stretching and instead, a MD orientation step is often not used at all. If there is a MD orientation step, it is used with a very small draw ratio (typically stretching by 1 to 1.5x the original dimension), which is insufficient to initiate cavitation. Thus, the TD shrink sleeve process is almost entirely reliant upon the low strain rate step of theTD orientation to generate cavities, which is very inefficient. It is therefore difficult to create a TD shrink film with good cavitation, particularly the degree of cavitation necessary to have a sufficient impact on the density of the film to compensate for the addition of opacifying agents. Thus, there is a need for a TD shrink film having a sufficiently low density to be recovered during a recycling process when it is part of a packaging material containing other polymers. According to a first aspect of the present invention, there is provided a transverse direction shrink film containing an inorganic cavitating agent having an average particle size of greater than 3 microns. A transverse direction (TD) shrink film is one that is more oriented in the transverse direction than the machine direction. This means that it will undergo more shrinkage in the transverse direction than the machine direction on the application of an elevated temperature. Average particle size in this instance refers to the D50 (i.e. the 50th percentile of the size distribution). It has surprisingly been found that using inorganic cavitating agents having a larger average particle size creates sufficiently large voids in TD shrink films. This is unexpected, as TD shrink films have little to no machine direction orientation, and a very low strain rate transverse direction orientation, which does not easily create the necessary voids. However, the present inventors have found that it was only the larger particles out of the natural size distribution that generated any cavities at all, with larger cavities being generated by larger particles. Thus, the use of an inorganic cavitating agent with a large particle size removes many of the particles that do not generate voids and ensures that the remaining particles contribute to the cavitation of the film, even under the low strain rate TD orientation step. The inorganic cavitating agent may be any suitable cavitating agent known in the art, including calcium carbonate (CaCOs), barium carbonate (BaCOa), aluminium oxide, aluminium sulphate, barium sulphate, magnesium carbonate, silicates such as aluminium silicate (kaolin clay), mica and magnesium silicate (talc), and silicon dioxide, as well as mixtures thereof. The inorganic cavitating agent may be calcium carbonate. The inorganic cavitating agent may have an average particle size of greater than 4 microns. The average particle size may be greater than 4.5 microns, optionally greater than 5 microns. It has been found that the larger the average particle size, the greater the degree of cavitation within the film. Thus, the particle size can be tailored to the degree of cavitation and the density desired. The D90 (i.e. the 90th percentile of the size distribution) of the inorganic cavitating agent may be greater than 10pm, optionally greater than 15 pm. The TD shrink film is polymeric and may be a polyolefin-based TD shrink film. By "polyolefin-based" it is meant that the majority of the film by weight is formed from one or more polyolefin. Optionally, more than 75% of the film by weight is formed from one or more polyolefin. The TD shrink film may be a polypropylene-based TD shrink film, in that the majority of the weight of the film is formed from one or more polypropylene-containing polymers. The TD shrink film may comprise a polypropylene / polyethylene / polybutylene terpolymer and / or a polypropylene / polyethylene copolymer. The TD shrink film may be a monolayer film or a multilayer film. The TD shrink film may comprise a core layer, one or more intermediate layers and / or one or more outer layers. The TD shrink film may comprise a core layer, an intermediate layer on either side thereof and an outer layer on each of the intermediate layers. The outer layers may be printable, sealable, metallised / metallisable and / or barrier layers (either gas or moisture barrier layers). The outer layers may be treated, for example with corona treatment. The outer layers may be printed. The outer layers and / or the intermediate layers are polymeric, may be polyolefinic and may comprise a cyclic olefin copolymer. The film may be sealable to itself, so that it can be sealed to form a tube. The seal may be a heat seal or may be produced by solvent welding. This tube can then be placed around an article and exposed to an elevated temperature to cause the film to shrink and closely surround the article. The film may comprise one or more conventional additives, including antiblocks, slip components (e.g. wax), tack reducing additives (e.g. fumed silica, silica, silicone gum), UV absorbers, dyes, pigments, colorants, fillers, lubricants, cross-linkers, anti-static agents (cationic, anionic and / or non-ionic, e.g. poly-(oxyethylene) sorbitan monooleate), anti-oxidants (e.g. phosphorous acid, tris (2,4-di-tert-butyl phenyl) ester), gloss improvers, prodegradants, additives to improve ink adhesion and / or printability, additives to increase the coefficient of friction (e.g. silicon carbide), additives to increase stiffness (e.g. hydrocarbon resin), and / or additives to increase shrinkage (e.g. hard resin). The core layer may comprise the majority of the thickness of the film. The core layer may comprise more than 60%, optionally more than 70% of the thickness of the film. The inorganic cavitating agent may be located in the core layer of the film. The TD shrink film may comprise between 2 and 15% w / w inorganic cavitating agent, optionally between 4 and 13% w / w inorganic cavitating agent. The film may comprise less than 12% w / w inorganic cavitating agent. The use of larger particle sizes means that less inorganic cavitating agent can be used, as each particle creates a larger cavity or conversely more opacifying agent can be used while still remaining below the density target The TD shrink film may comprise an opacifying agent. The opacifying agent may be any opacifying agent conventionally used, including titanium dioxide, aluminium oxide, aluminium sulphate, barium sulphate, calcium carbonate, magnesium carbonate, silicates (aluminium, magnesium), silicon dioxide and combinations thereof. Titanium dioxide may be used due to its very high refractive index. The opacifying agent may also act as a pigment and can be chosen to give the desired colour, for example white. Opacifying agents may have an average particle diameter in the range 0.01 to 1 pm, which can provide optimal light scattering (depending on their refractive index). Opacifying agents may have a higher density than the polymer of the film. The cavitation created by the inorganic cavitating agent may offset the increase in density caused by the opacifying agent, thereby retaining the desired density of the film overall. The opacifying agent may be in the same layer of the film as the inorganic cavitating agent. This layer may be a core layer of a multilayer film. The inorganic cavitating agent and the resulting cavitation may also contribute to the opacity of the film. A component is considered a cavitating agent if it creates a void and an opacifying agent if it contributes to the opacity of the film. Generally speaking, an opacifying agent does not have a particle size great enough to form cavities. The TD shrink film may have a thickness of between 20 and 100 microns, optionally between 30 and 80 microns. The TD shrink film may have a density of less than 0.95 g / cm3, optionally less than 0.93 g / cm3. This ensures that, even after printing and shrinkage, the shrink film can be separated from other polymeric materials in a sink-float chamber during a recycling process, as the shrink film will float on water. The TD shrink film may be opaque. The TD shrink film may have an opacity of more than 75, optionally more than 80. The opacity may be measured using the contrast ratio method (for example, using a Diffusion Systems Anglia Opacimeter Model 12).This ensures that the film has the desired optical properties, as well as masking any UV blocking layer (such as a layer of carbon free black) that may be present on one side of the film. The film may block more than 99% of the UV region of the electromagnetic spectrum, without interfering with the near infra-red (NIR) region. The TD shrink film may have a whiteness of more than 85. Whiteness can be measured using a spectrophotometer. The TD shrink film may have a shrinkage at 95°C (10 seconds in water) of more than 50% in the transverse direction and less than 10% in the machine direction, optionally more than 60% in the transverse direction and less than 6% in the machine direction. The TD shrink film may have a shrinkage at 80°C (10 seconds in water) of more than 25% in the transverse direction and less than 6% in the machine direction, optionally more than 35% in the transverse direction and less than 4% in the machine direction. The shrink properties of the film can be adjusted depending on the intended application and the desired properties. The degree of orientation in the machine and transverse directions can be used to alter the shrinkage, as the greater the degree of orientation (caused by a higher stretch ratio), the more shrinkage is seen on the application of an elevated temperature. The TD shrink film may have a tensile modulus of more than 600 MPa in the machine direction and more than 800 MPa in the transverse direction, optionally more than 700 MPa in the machine direction and more than 1000 MPa in the transverse direction. According to a second aspect of the present invention, there is provided a label comprising the TD shrink film discussed above. The label may comprise print on at least one side thereof. The label may have been cut from the TD shrink film discussed above. The label may act as a sleeve, covering the height of the article. The label may be printed on both sides thereof. The side intended to be closest to the article may be printed with a UV blocking layer, such as carbon free black. The side intended to be furthest from the article may be printed with wording and / or a pattern. The film may be sealed to itself to create a tubular label, which can then be placed around an article before being exposed to an elevated temperature which causes the label to shrink and closely surround the article. The seal may be a heat seal or may be produced by solvent welding. According to a third aspect of the present invention, there is provided an article at least partially surrounded by the TD shrink film or label discussed above. By "at least partially surrounded", it is meant that the TD shrink film extends around the perimeter of the article, covering at least part of the article in a continuous manner. The article may be entirely surrounded by the TD shrink film. Alternatively, the TD shrink film may create a label that surrounds a part of the article, with other parts exposed. For example, the film may create a tubular label that extends around part of the article, or a sleeve that covers the entire height of the article. The article may be a container or other packaging. For example, the article may be a bottle or a jar. The article may comprise a different polymeric material to that in the film. For example, the TD shrink film may be polyolefinic, while the article may be formed from PET or another material. The TD direction of the film may extend around the perimeter of the article (around the circumference of the tubular label). On the application of an elevated temperature, the height of the film does not change but the circumference of the tubular label decreases in order to closely surround the article. Thus, the invention provides a way in which to label or decorate an article, using a shrink film that can then be easily separated from the article in a recycling process. According to a fourth aspect of the present invention, there is provided a method of making an article discussed above, comprising surrounding at least a portion of the article loosely with the TD shrink film or label discussed above and exposing the TD shrink film or label to an elevated temperature, such that it shrinks in the TD direction in order to closely surround at least a portion of the article. The TD shrink film may be sealed to itself in order to form a tube before being placed around the article. The seal may be a heat seal or may be produced by solvent welding. According to a fifth aspect of the present invention, there is provided a method of making a TD shrink film as discussed above comprising including an inorganic cavitating agent having an average particle size of greater than 3 microns in one or more layers of the film and then stretching the film at least 3 times more in the transverse direction than in the machine direction. The film may be stretched by between 3 and 20x its original dimension in the transverse direction, optionally between 5 and lOx. The film may be stretched by less than 3x its original dimension in the machine direction, optionally less than 1.5x. The film may be stretched lx its original dimension, in that the film may not be stretched at all in the machine direction. It has surprisingly been found that even with this low degree of stretching, cavities are still created in the film that can sufficiently reduce the density of the film to compensate for the increase in density caused by any other additives. The film may be produced on a stenter. The stretching may be sequential or simultaneous. Alternatively, the film may be produced using a bubble process. The film may then be printed on at least one side thereof to form a label. The film may also be sealed to itself to form a tubular label. The features of any of the above aspects are equally applicable to any of the other aspects in the present application. The invention will now be more particularly described with reference to the following examples. Example 1 A variety of five-layer films were created, each comprising two layers of cyclic olefin copolymer on each side of a core layer containing the components outlined in the tables below. The outermost layers on both sides also contained 2500ppm silica antiblock. 5 The films were oriented using a sequential stenter process. The orientation parameters outlined in the tables below were used, in addition to a TD draw ratio of 9.2, followed by a 1.6% relaxation. MDO draw rollers were set to 70°C throughout. As is conventional, the TDO pre-heat zones had a consecutively lower temperature, starting with that in pre-heat zone 1 and finishing at the stretch zone set-point. One side of the film was then corona treated. The polypropylene co-polymer elastomer in the films was Vistamaxx 3980FL (ExxonMobil Chemical), while the polypropylene / polyethylene / polybutylene terpolymer in the films was Adsyl 6C (Lyondell Basell). The reclaim film was in-house recycled film (APO type manufactured by Innovia Films), including the same components with the exception of the opacifying and voiding agents. Table la Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 PP co-polymer elastomer (%) 25 25 25 25 25 25 25 PP / PE / PB terpolymer (%) 25 25 25 25 25 25 24 Reclaim film (%) 20 20 20 20 20 20 20 60% TiO2 in PP copolymer elastomer 15 15 15 15 15 15 16 70% CaCO3 in PP, D50=3.0pm, D90=10pm 15 15 15 70% CaCO3 in PP, D50=4.5pm, D90=20pm 15 15 70% CaCO3 in PP, D50=7.0pm, D90=25pm 15 15 Orientation Parameters MD Ratio 1.5 1.5 1.5 1.5 1.5 1.5 1.5 MDO Annealing Rolls (°C) 75 75 75 75 75 80 80 TDO Pre-heat zone 1 Temp (°C) 115 115 115 115 115 115 115 TDO Stretch Temp (°C) 87 87 87 87 87 87 87 Table lb Sample 8 Sample 9 Sample 10 Sample 11 Sample 12 Sample 13 PP co-polymer elastomer (%) 25 30 30 30 30 30 PP / PE / PB terpolymer (%) 25 19 15 13 13 13 Reclaim film (%) 20 20 20 20 20 20 60% TiOs in PP copolymer elastomer 12 16 20 22 22 22 70% CaCO3 in PP, D50=3.0pm, D90=10pm 15 70% CaCO3 in PP, D50=4.5pm, D90=20pm 15 15 15 70% CaCO3 in PP, D50=7.0pm, D90=25pm 15 15 Orientation Parameters MD Ratio 1.2 1.2 1.35 1.35 1.35 1.35 MDO Annealing Rolls (°C) 68 68 75 75 75 75 TDO Pre-heat zone 1 Temp (°C) 108 115 115 115 115 115 TDO Stretch Temp (°C) 87 87 87 87 87 87 The properties of the films were then assessed, as outlined in the tables below. Opacity was measured 5 using the contrast ratio method (Diffusion Systems Angla Opacimeter Model 12). Whiteness was measured using an X-Rite Spectrophotometer Ci62 using the CIELab method. Table 2a Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Thickness (pm) 55 58 58 62 62.7 64 61 Density (g / cm3) 0.93 0.928 0.926 0.89 0.873 0.835 0.83 Opacity 76 79 79 81 81 81.4 81 Shrinkage MD (65, 80, 95°C, 10s in water, %) -, -, 5 0, 2, 5 1.5, 2.5, 4 1, 2,5 1, 2.5, 4.5 1, 2, 5 0, 3, 5 Shrinkage TD (65, 80, 95°C, 10s in water, %) -, -, 63 10, 40, 63 10, 38, 61 10, 40, 63 8.5, 38.5, 63 10, 40, 63 9.5, 40, 63 Whiteness (black background) 86 89 88 89 89 Tensile strength MD, TD (N / mm2) 25, 169 24, 154 Elongation MD, TD (%) 288, 29 281, 28 Modulus MD, TD (Mpa) 755, 1340 730, 1270 CoF Treat / treat, untreat / untreat (dynamic) 0.79, 0.23 0.42, 0.39 Gloss (45 degrees) 41 36 Table 2b Sample 8 Sample 9 Sample 10 Sample 11 Sample 12 Sample 13 Thickness (pm) 61.5 58.7 57 58 58.3 60.6 Density (g / cm3) 0.95 0.875 0.905 0.92 0.93 0.88 Opacity 76 78.4 80 82 83 83.4 Shrinkage MD (65, 80, 95°C, 10s in water, %) -, -, 1.0 rd v—1 o' -0.5, -1.5, 1.5 -1, -2, 0.5 -1, -1, 1.5 -1, -1, 1-5 Shrinkage TD (65, 80, 95°C, 10s in water, %) -, -, 67 0, 45, 67 11, 47, 68.5 11, 47, 70 11, 47, 69.5 11, 46, 69.5 Whiteness (black background) 91.5 91.5 Tensile strength MD, TD (N / mm2) 21, 142 19, 129 Elongation MD, TD (%) 273, 35 242, 35 Modulus MD, TD (Mpa) 614,1020 622, 864 CoF Treat / treat, untreat / untreat (dynamic) 0.65, 0.54 0.68, 0.43 Gloss (45 degrees) 37 34 It was found that the samples that were produced with an MD draw ratio of 1.5x (Table la) had a MD 5 shrinkage of 5% at 95°C. Although the other properties were good, this shrinkage is too high for various applications and so the MD draw ratio was reduced for the later samples (Table lb). For Sample 9, the MD draw ratio was reduced to 1.2 and the MD shrinkage reduced to-1 at95°C. The remaining samples were therefore made at a MD draw ratio of 1.35x, which achieved an MD shrinkage of 1.5 %. Comparing the data from Samples 8, 3, 5, 12 and 13 clearly shows the impact of using larger particles of calcium carbonate, as shown in Table 3 below. This data demonstrates a clear reduction in density with increasing average particle size at TiO2 masterbatch concentrations of 15% and 22%. Specifically, the density at 15% TiO2 masterbatch decreased from 0.93 g / cm3 to 0.873 g / cm3 on an increase in average particle size from 3.0 to 4.5 microns, while the density at 22% TiO2 masterbatch decreased from 0.93 g / cm3 to 0.88 g / cm3 on an increase in average particle size from 4.5 to 7 microns. By calculating the theoretical density of each film without cavitation, a theoretical density reduction factor can also be calculated. Table 3 Sample 8 Sample 3 Sample 5 Sample 12 Sample 13 TiO2 Masterbatch Addition % 12 15 15 22 22 CaCOa Masterbatch Addition % 15 15 15 15 15 CaCOa Average Particle size D50 (pm) 3.0 3.0 4.5 4.5 7.0 MD Draw Ratio 1.2 1.5 1.5 1.2 1.2 Density (g / cm3) 0.95 0.93 0.873 0.93 0.88 Density Reduction Factor (Measured Density / Calculated density assuming no cavitation) % 92.3 89.0 83.6 86.0 81.4 There is therefore a clear trend of reducing density with increasing particle size, particularly when the impact of MD draw ratio is taken into account. The original target specification is met by using calcium carbonate with an average particle size of more than 3.0 microns.

Claims

1. A transverse direction shrink film containing an inorganic cavitating agent having an average particle size of greater than 3 microns.

2. The TD shrink film according to Claim 1, wherein the inorganic cavitating agent is calcium carbonate.

3. The TD shrink film according to Claim 1 or Claim 2, wherein the inorganic cavitating agent has an average particle size of greater than 4 microns, optionally greater than 4.5 microns or greater than 5 microns.

4. The TD shrink film according to any one of Claims 1 to 3, wherein the film is a polyolefin-based TD shrink film, optionally a polypropylene-based TD shrink film.

5. The TD shrink film according to any one of Claims 1 to 4, wherein the film is a multilayer film, which may comprise one or more outer layers and / or one or more intermediate layers.

6. The TD shrink film according to any one of Claims 1 to 5, comprising between 2 and 15% w / w inorganic cavitating agent, optionally between 4 and 13% w / w.

7. The TD shrink film according to any one of Claims 1 to 6, further comprising an opacifying agent, optionally wherein the opacifying agent is titanium dioxide.

8. The TD shrink film according to Claim 7, wherein the opacifying agent is in the same layer of the film as the inorganic cavitating agent, optionally wherein said layer is a core layer of a multilayer film.

9. The TD shrink film according to any one of Claims 1 to 8, wherein the D90 of the inorganic cavitating agent is greater than 10 pm, optionally greater than 15 pm.

10. The TD shrink film according to any one of Claims 1 to 9, wherein the TD shrink film has a thickness of between 20 and 100 microns, optionally between 30 and 80 microns.

11. The TD shrink film according to any one of Claims 1 to 10, wherein the TD shrink film has a density of less than 0.95 g / cm3, optionally less than 0.93 g / cm3.

12. The TD shrink film according to any one of Claims 1 to 11, wherein the TD shrink film has an opacity of more than 75, optionally more than 80.

13. The TD shrink film according to any one of Claims 1 to 12, wherein the TD shrink film has a whiteness of more than 85.

14. The TD shrink film according to any one of Claims 1 to 13, wherein the TD shrink film has a shrinkage at 95°C (10 seconds in water) of more than 50% in the transverse direction and less than 10% in the machine direction, optionally more than 60% in the transverse direction and less than 6% in the machine direction.

15. The TD shrink film according to any one of Claims 1 to 14, wherein the TD shrink film has a tensile modulus of more than 600 MPa in the machine direction and more than 800 MPa in the transverse direction, optionally more than 700 MPa in the machine direction and more than 1000 MPa in the transverse direction.

16. A label comprising the TD shrink film according to any one of Claims 1 to 15 and print on at least one side thereof.

17. An article at least partially surrounded by the TD shrink film or label according to any preceding claim.

18. The article of Claim 17, wherein the article is a container or other packaging comprising a different polymeric material to that in the film.

19. A method of making an article according to Claim 17 or Claim 18, comprising surrounding at least a portion of the article loosely with the TD shrink film according to any one of Claims 1 to 15 or label of Claim 16 and exposing the TD shrink film or label to an elevated temperature, such that it shrinks in the TD direction in order to closely surround at least a portion of the article.

20. A method of making a TD shrink film according to any one of Claims 1 to 15 comprising including an inorganic cavitating agent having an average particle size of greater than 3microns in one or more layers of the film and then stretching the film at least 3x more in the transverse direction than in the machine direction.

21. The method of Claim 20, wherein the film is stretched by between 3 and 20x its original dimension in the transverse direction, optionally between 5 and lOx.

22. The method of Claim 20 or 21, wherein the film is stretched by less than 3x its original dimension in the machine direction, optionally less than 1.5x.

23. The method of any one of Claims 20 to 22, wherein the film is produced on a stenter.Application No: GB2400415.2Claims searched: 1-23Examiner: Tom RingroseDate of search: 27 June 2024Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-13, 15-19 US2004 / 213981 Al (HEWITT J) See examples 4-7, 16, 18, tables, paragraphs [0030], [0033], [0057], claim 1 A 1-23 US5091237 A (HOECHST AG) See examples, claims 1, 7, 10 A 1-23 JP S60135233 A (OJI YUKA GO SEI SHI KK) See examplesCategories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From C08J 0005 / 22 01 / 01 / 2006 B32B 0007 / 028 01 / 01 / 2019 B32B 0027 / 32 01 / 01 / 2006 B65B 0053 / 00 01 / 01 / 2006 C08J 0005 / 18 01 / 01 / 2006 C08L 0023 / 00 01 / 01 / 2006 C08L 0023 / 10 01 / 01 / 2006 C08L 0023 / 12 01 / 01 / 2006