METHOD AND A THERMOPLASTIC FILM FOR USE IN A PRINTED PACKAGING OF ABSORBENT HYGIENIC ARTICLES

Abstract

The present disclosure relates to a method for establishing the suitability for printing of a thermoplastic film for use in a packaging of absorbent hygienic articles, said thermoplastic film comprising at least 30% recycled polymer material. The method comprises scanning a sample of said film for Gel Spots, defining an Amount of Gel spots and a Relative Gel Spot Coverage area, and, determining that if the Amount of Gel Spots is less than or equal to a first threshold and the Relative Gel Spot Coverage Area is less than or equal to a second threshold, determining that said thermoplastic film is suitable for printing. The disclosure also relates to a method of forming a package from a thermoplastic film, and to a package comprising a thermoplastic film.

Claims

1. A method for establishing the suitability for printing of a thermoplastic film for use in a packaging of absorbent hygienic articles, said thermoplastic film comprising at least 30% recycled polymer material, the method comprising: Providing a sample of said thermoplastic film, said sample preferably being 10 cm?10 c; Scanning said sample to provide a pixelized image of said sample; Computer analyzing said pixelised image using a thresholding method to transfer the image to a binary image in which each pixel is determined as either dark or light; Defining each group of neighbouring pixels deemed to be dark as a Gel Spot; Defining a Gel Spot Size for each Gel Spot being the circle equivalent diameter to the pixel area of the Gel Spot; Determining an Amount of Gel Spots indicative of the number of Gel Spots in said sample, which have Gel Spot Size greater than or equal to 150 ?m; and Determining a Relative Gel Spot Coverage Area indicative of the relative area of said sample covered by Gel Spots having a Gel Spot Size greater than or equal to 150 ?m, using said circle equivalent diameter; and if said Amount of Gel Spots is less than or equal to a first threshold and said Relative Gel Spot Coverage Area is less than or equal to a second threshold, determining that said thermoplastic film is suitable for printing; and if said Amount of Gel Spots is greater than said first threshold and/or said Relative Gel Spot Coverage Area is greater than said second threshold, determining that said thermoplastic film is not suitable for printing.

2. The method according to claim 1, wherein said first threshold is less than or equal to 450 per 100 cm.sup.2 sample, such as less than or equal to 300 per 100 cm.sup.2 sample.

3. The method according to claim 1, wherein said second threshold is less than or equal to 20%, such as less than or equal to 12%.

4. The method according to claim 1, wherein said film comprises coloured pigments in the film resin.

5. The method according to claim 1, wherein said film has a thickness of between 20 ?m.

6. The method according to claim 1, wherein said film comprises less than 80% recycled polymer material.

7. The method according to claim 1, wherein said film comprises: a. a total sum of phthalates being in the range 0.05 to 250 mg/kg, such as 0.05 to 100 mg/kg or such as 0.05 to 20 mg/kg; and/or b. a total sum of organic tin compounds being in the range 0.0003 to 0.5 mg/kg, such as 0.0003 to 0.1 mg/kg or such as 0.0003 to 0.02 mg/kg; and/or c. a total sum of heavy metals being in the range 0.1 to 100 mg/kg, such as 0.1 to 60 m/kg or 0.1 to 30 mg/kg; and/or d. a total sum of Bisphenol A being in the range 0.05 to 20 mg/kg, such as 0.05 to 10 mg/kg or 0.05 to 5 mg/kg.

8. The method according to claim 1, wherein said method comprises determining a haze of said thermoplastic film, and if said haze is within a haze range, determining that said film is suitable for printing and for a packaging of hygienic absorbent products, and if said haze is outside of said haze range, determining that said film is unsuitable for printing and for a packaging of hygienic absorbent products, wherein said haze range is less than 25%, such as less than 20%, or 4 to 18%, and wherein haze is measured as the percentage of incident light scattered by more than 2.5? through said film.

9. The method according to claim 1, wherein said method comprises: Determining a MD force at 5% elongation in the machine direction of said film, and if said MD force at 5% elongation is within a MD force at 5% elongation range, determining that said film is suitable for printing and for a packaging for hygienic absorbent product, and if said MD force at 5% elongation is outside of said MD force at 5% elongation range, determining that said film is unsuitable for printing and for a packaging for hygienic absorbent products, wherein said MD force at 5% elongation range is greater or equal to 3 N/15 mm, and optionally 4 to 9 N/15 mm.

10. The method according to claim 1, wherein said method comprises: Determining a CD force at 5% elongation in the cross direction of said film, and if said CD force at 5% elongation is within a CD force at 5% elongation range, determining that said film is suitable for printing and for a packaging for hygienic absorbent product, and if said CD force at 5% elongation is outside of said CD force at 5% elongation range, determining that said film is unsuitable for printing and for a packaging for hygienic absorbent products, wherein said CD force at 5% elongation range is greater or equal to 3 N/15 mm, and optionally 4 to 9 N/15 mm.

11. The method according to claim 1, wherein said method comprises: Determining a CD 2% secant modulus in the cross direction of said film, if said CD 2% secant modulus is within a CD 2% secant modulus range, determining that said film is suitable for printing and for a packaging for hygienic absorbent product, and if said CD 2% secant modulus is outside of said CD 2% secant modulus range, determining that said film is unsuitable for printing and for a packaging for hygienic absorbent products, wherein said CD 2% secant modulus range is from 200 to 600 MPa.

12. The method according to claim 1, wherein said method comprises: Determining a MD 2% secant modulus in the machine direction of said film, and if said MD 2% secant modulus is within a MD 2% secant modulus range, determining that said film is suitable for printing and for a packaging for hygienic absorbent product, and if said MD 2% secant modulus is outside of said MD 2% secant modulus range, determining that said film is unsuitable for printing and for a packaging for hygienic absorbent products, wherein said MD 2% secant modulus range is from 200 to 550 MPa.

13. A method of forming a package for absorbent articles comprising: Providing a thermoplastic film material; Determining said thermoplastic film to be suitable for printing for use in a packaging for hygienic absorbent articles by performing the method according to claim 1; and Forming a package for hygienic absorbent articles comprising said thermoplastic film.

14. The method according to claim 13, comprising Printing at least a portion of said film.

15. The method according to claim 13, wherein said step of forming a package comprises forming a package of said thermoplastic film such that said thermoplastic film forms an outer surface of said package.

16. The method according to claim 13, wherein said package comprises said thermoplastic film as a co-extruded monolayer film.

17. The method according to claim 13, wherein said step of forming a package comprises folding said thermoplastic film to form a pocket or bag.

18. The method according to claim 13, comprising filling said package with absorbent hygienic articles.

19. The method according to claim 18, wherein said absorbent articles is a stack of sanitary articles.

20. The method according to claim 18, wherein said absorbent articles comprise absorbent tissue paper or nonwoven.

21. The method according to claim 1 comprising forming an array of packages of said film, said array comprising at least 1000 packages, such as at least 10 000 packages.

22. A package for an absorbent article made by the method according to claim 13.

23. The package according to claim 22, wherein said thermoplastic film comprises at least 30 to 80% by weight recycled polymers, and said thermoplastic film has a continuous unprinted area (4) of at least 10?10 cm, wherein said thermoplastic film has a Gel Spot Amount being less than or equal to 450 per 100 cm.sup.2 sample and a Gel Spot Relative Coverage Area being less than or equal to 20%, as determined by the method according to any one of claims 1-12.

24. The package according to claim 23, wherein, in said package, said thermoplastic film has a printed area outside of said continuous unprinted area.

25. The package according to claim 23, wherein said thermoplastic film, at least in said unprinted area, is transparent.

26. The package according to claim 22, wherein said thermoplastic film comprises coloured pigment in the film resin.

27. An array of at least 1000 packages according to claim 22, the packages having similar appearance and content.

28. The package according to claim 22 comprising an absorbent hygienic article.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0121] With reference to the appended drawings, below follows a more detailed description of variants of the methods and devices disclosed herein, the variants being cited as examples.

[0122] FIG. 1 is a flow chart schematically illustrating a method for establishing the suitability for printing of a thermoplastic film for use in a packaging of absorbent hygienic articles;

[0123] FIG. 2a is an example of a scanned image from a sample of a thermoplastic film;

[0124] FIG. 2b is a histogram over the distribution of Gel Spot Sizes in FIG. 2a;

[0125] FIG. 3 is a flow chart schematically illustrating a method for forming a packaging of absorbent hygienic articles from a thermoplastic film;

[0126] FIG. 4 illustrates a variant of a packaging comprising absorbent hygienic article;

[0127] FIG. 5 illustrates another variant of a packaging comprising an absorbent hygienic article;

[0128] FIG. 6 illustrates the standardization of the scanned image.

DETAILED DESCRIPTION

[0129] FIG. 1 is a flow chart schematically illustrating a method for establishing the suitability for printing of a thermoplastic film for use in a packaging of absorbent hygienic articles, the thermoplastic film comprising at least 30% recycled polymer material, the method comprising: [0130] Providing a sample of the thermoplastic film, the sample preferably being 10 cm?10 cm (S100); [0131] Scanning the sample to provide a pixelized image of the sample (S200); [0132] Computer analyzing the pixelised image using a threshold method to transform the image to a binary image wherein each pixel is deemed either light or dark, (S300); [0133] Defining each group of neighbouring pixels deemed to be dark as a Gel Spot (S400); [0134] Defining a Gel Spot Size for each Gel Spot being the circle equivalent diameter to the pixel area of the Gel Spot (S500); [0135] Determining an Amount of Gel Spots indicative of the number of Gel Spots in the sample, which have Gel Spot Size greater than or equal to 150 ?m (S600); and [0136] Determining a Relative Gel Spot Coverage Area indicative of the relative area of the sample covered by Gel Spots having a Gel Spot Size greater than or equal to 150 ?m, using the circle equivalent diameter (S700); and [0137] if the Amount of Gel Spots is less than or equal to a first threshold and the Relative Gel Spot Coverage Area is less than or equal to a second threshold, determining that the thermoplastic film is suitable for printing (S800); and [0138] if the Amount of Gel Spots is greater than the first threshold and/or the Relative Gel Spot Coverage Area is greater than the second threshold, determining that the thermoplastic film is not suitable for printing (S800).

[0139] The method may use a RGB colour model (RGB Red Green Blue) for computer analysing the pixelized image.

[0140] The threshold method to transform the image to a binary image may be a greyscale threshold method.

[0141] In the following, a specific Gel Spot Estimation Method is described. Although in this application, it is disclosed how a more general method may be used, it is to be understood that the disclosure also relates to this specific Gel Spot Estimation Method per se. In particular, the disclosure also relates to a package made from a film displaying an Amount of Gel Spots is less than or equal to 300, for example less than or equal to 400, and a Relative Gel Spot Coverage Area being less than or equal to 12%, for example less than or equal to 20% as determined with the specific Gel Spot Estimation Method. Also the disclosure relates to package comprising a film having an unprinted area, wherein in the unprinted area the film displays an Amount of Gel Spots is less than or equal to 300, for example less than or equal to 400, and a Relative Gel Spot Coverage Area being less than or equal to 12%, for example less than or equal to 20%, as determined by the specific Gel Spot Estimation Method.

Description of the Gel Spot Estimation Method

[0142] A sample area of the film having the size of 100?100 mm is to be scanned.

[0143] To provide a sample of the thermoplastic film (S100), a sample of 110?110 mm is cut from the film. A frame defining the open area 100?100 mm is positioned over the sample to define the area to be scanned.

[0144] To perform the step of scanning the sample to provide a pixelized image of the sample (S200), the frame with the sample is positioned with the film side towards the scanner glass. The sample is to lay flat and relaxed without wrinkles. The scanner is started.

[0145] The scanner used is an Epson Perfection V750 Pro, with the following settings: [0146] Document type: Film (with film side) [0147] Film type: Positive film [0148] Picture type: 24-bit colour [0149] Resolution: 2400 [0150] Correction: off [0151] Configuration: no colour correction

[0152] The sample is scanned three times without moving the sample or frame.

[0153] The scanned images are provided to a computer where they are computer analysed as pixelized images.

[0154] For performing the step of computer analyzing the pixelised image using the RGB spectrum (Red, Green, Blue) (S300), Matlab is used.

[0155] The images are formed in the RGB spectrum.

Initially, an average of the R, G and B channels of all three images is made over every pixel so as to form a combined image.

[0156] A standardization of the light component of the combined image as explained in the above and with reference to FIG. 6 may be performed to account for any brightness variation.

[0157] The standardized image is then transferred to a binary image where each pixel is determined to be either dark or light. All pixels above a constant greyscale threshold are categorised as gel spot pixels. The constant greyscale threshold is a constant value which is applied after the image has been standardized. The constant greyscale threshold may for example be determined by optimising the threshold using a manually counted number of gel spots in a sample as a reference.

The greyscale threshold used in this example method was ?4.05.
Each group of neighbouring gel spot pixels is determined to be a Gel Spot.
To define a Gel Spot Size for each Gel Spot being the circle equivalent diameter to the pixel area of the Gel Spot (S500), and to Determine an Amount of Gel Spots indicative of the number of Gel Spots in the sample, which have Gel Spot Size greater than or equal to 150 ?m (S600), and to determine a Relative Gel Spot Coverage Area indicative of the relative area of the sample covered by Gel Spots having a Gel Spot Size greater than or equal to 150 ?m, using the circle equivalent diameter (S700), Matlab function was used.

[0158] The circle equivalent diameter may be calculated as sqrt (4*(Pixel area)/pi). The circle equivalent diameter corresponds to the diameter (?m) the Gel Spot would have if it was in the shape of a circle having the same area as the pixel area of the Gel Spot.

[0159] The image was adjusted by removing small clusters of neighbouring pixels using a Matlab algorithm called bwareopen (image, p, conn), where p=size of clusters to be automatically removed. P was set to 15, and conn to 4. P represents the size of clusters to be automatically removed, and conn the connectivity.

[0160] In addition, an evaluation of the solidity of each group of neighbouring pixels determined to be dark (gel spot pixels) was used to determine which groups are true gel spots.

[0161] The solidity compares the pixel area of a group of gel spot pixels to the area of the smallest possible rectangle that could encase the group of gel spot pixels. The solidity is defined as the (gel spot pixel area)/(the area of the smallest possible rectangle that could encase the group). In this case, the solidity demand was set to 0.3, i.e. a group of neighbouring pixels having a solidity less than 0.3 is deemed not to be a Gel Spot.

[0162] The result from the Matlab computer analysis will be expressed as an Amount of Gel Spots and a Relative Gel Spot Coverage Area.

[0163] In this example, the first threshold applied is 300 per 100 cm.sup.2 sample, and the second threshold applied is 12%. Accordingly, if the Amount of Gel Spots is less than or equal to 300 and the Relative Gel Spot Coverage Area is less than or equal to 12%, it is determined that the thermoplastic film is suitable for printing (S800).

[0164] A film which is deemed suitable for printing may optionally be further evaluated regarding the additional parameters mentioned in the summary section in the above.

[0165] In the following, various parameters measured on three different thermoplastic film samples will be shown. The first sample 01 is a thermoplastic film made by virgin material, hence comprising no recycled polymer material. The virgin material is in this case a polyethylene material, i.e. a fossil-based polymer material. Thus, sample 01 is not a sample as encompassed by the present disclosure, but constitutes a reference for comparison only. Sample 02 is a thermoplastic film comprising 33% recycled polymer material (PCR), with the remainder being of the same virgin material as sample 01. Sample 03 is a thermoplastic film comprising 55% recycled polymer material (PCR), with the remainder being of the same virgin material as sample 01.

[0166] The recycled polymer material in sample 02 and sample 03 comprises an unknown mix of recycled polymer materials. The recycled polymer materials in sample 02 and sample 03 come from the same recycled material sources.

[0167] All three samples 01, 02, 03 are monolayer extruded films.

[0168] All three samples were evaluated using the Gel Count method as described above to determine the Gel Spot Amount and the Relative Gel Spot Area, and a number of additional parameters as indicated in the table were also measured. As seen in the tables below, the Amount of Gel Spots is less than or equal to 300 and the Relative Gel Spot Coverage Area is less than or equal to 12% for all three samples. As indicated in the tables, a number of additional properties of the thermoplastic film materials were also measured.

TABLE-US-00001 MD2% MD2% secant secant Thickness modulus modulus Sample % PCR (um) (MPa) (MPa) 01 0 25 372 464 02 33 25 299 348 03 55 25 320 345

TABLE-US-00002 MD CD Kinetic Kinetic force force (dyn) (dyn) at 5% at 5% Coeff Coeff Rela- elonga- elonga- of of tive tion tion Friction friction Gel Gel Sam- % (N/15 (N/15 (MD) (CD) Haze Spot Spot ple PCR mm) mm) (i/i) (i/i) (%) Amount Area 01 0 6.3 7.8 0.33 0.15 15.5 176 7.59 (0.33) (0.14) 02 33 5.4 5.9 0.15 0.14 10.9 134 6.38 (0.12) (0.12) 03 55 5.7 5.9 0.18 0.14 13 144 7.16 (0.16) (0.12)

[0169] The measured parameters as indicated in the table above may be compared with the desired ranges as set out in the summary section in the above. Accordingly, it is found that both sample 02 with 33% recycled material and sample 03 with 55% recycled material display properties which render the materials suitable for printing and for use as packing materials for hygienic products.

[0170] FIGS. 2a and 2b are examples from one scanned image of a sample, which are included to illustrate the distribution of Gel Spots over the thermoplastic film. FIG. 2a is an example of a scanned image of a thermoplastic film, in this case, one of the three images taken for sample 02. Some of the gel spots may be seen as darker spots in the image. FIG. 2b is a histogram showing the distribution of gel spots in the image of FIG. 2a. In this histogram, the Amount of Gel Spots having sizes in the range 150 to 300 ?mare shown in the first staple as seen from the left, the Amount of Gel Spots having sizes in the range 300 to 500 ?m are shown in the second staple, and the Amount of Gel spots having sizes in the range 500 and upwards are shown in the third staple

[0171] As seen from FIG. 2b, in this example histogram the Amount of Gel Spots of Gel spots having sizes between 150 and 300 ?mis about 190, the Amount of Gel Spots of Gel spots having sizes between 300 and 500 ?mis about 10, and the Amount of Gel Spots of Gel spots having sizes greater than 500 ?m are clearly less than 10. Accordingly, the example histogram illustrates an example where the total Amount of Gel Spots is less than 300.

[0172] As indicated in the above example of a specific Gel Spot Count method it is proposed that the first threshold in the general method is set to 300 (the Amount of Gel Spots is less than or equal to 300) and the second threshold to 12% (the Relative Gel Spot Coverage Area is less than or equal to 12%). These thresholds have been found to result in an acceptable print quality upon visual inspection of the thermoplastic films after printing. As such, the methods proposed herein provide an advantage over prior procedures for estimating whether a thermoplastic film will be suitable for printing and for forming a package for hygienic products. Such procedures could for example include manual estimation of the occurrence of Gel Spots by visual inspection of a sample of the film e.g. in a microscope. By comparison, the methods proposed herein provide increased reliability and increases efficiency.

[0173] FIG. 3 is a schematic flow chart of a method for forming a package for absorbent articles comprising: [0174] Providing a thermoplastic film material determined to be suitable for printing for use in a packaging for hygienic absorbent articles in accordance with any of the methods as disclosed herein (S10), and [0175] Forming a package for hygienic absorbent articles comprising the thermoplastic film (S20).

[0176] The method may comprise printing at least a portion of the film, taking advantage of the fact that the film is indeed determined to be suitable for printing.

[0177] The package may be formed by any desired method for forming a package for hygienic absorbent articles comprising the thermoplastic film.

[0178] In particular, the step of forming a package may comprise forming a package of the thermoplastic film such that the thermoplastic film forms an outer surface of the package.

[0179] Optionally, the package comprises the thermoplastic film as a co-extruded monolayer film.

Optionally, the step of forming a package comprises folding the thermoplastic film to form a pocket or bag. Further, the method may comprise filling the package with a single or with a plurality of absorbent hygienic articles. For example, the absorbent articles may be in the form of a stack of sanitary articles.

[0180] FIG. 4 illustrate a package 1 formed from a thermoplastic film 2. The film 2 forms an outside of the package 1, which outside is at least partially provided with a print. The package 1 contains absorbent hygienic articles 3, in this case a stack of absorbent hygienic articles 3.

[0181] The film 2 may be printed using any conventional technique for printing of thermoplastic films for the purpose of forming packagings for absorbent hygiene products. Optionally, the film may be printed by flexoprinting.

[0182] Optionally, and as illustrated in FIG. 4 the film is printed such that the package displays a non-printed area 4 and a printed area 5. When the package 1 includes a non-printed area 4 having as size of at least 10?10 cm, the Amount of Gel Spots and the Relative Gel Spot Coverage Area may be measured in this non-printed area 4 of the package.

[0183] FIG. 5 illustrate another package 1 formed from a thermoplastic film 2. The film 2 is folded to form a pocket-shaped package 1. In this example, the package 1 comprises a single absorbent hygienic article 3. However, it will be understood that package-shaped packages 1 as illustrated in FIG. 4 or pocket-shaped packages 1 as illustrated in FIG. 5 may contain a single or a plurality of absorbent hygienic article 3. Also, a plurality of single-packed absorbent hygienic articles 3 may be packaged in an outer package.

[0184] In other, non-illustrated examples, there may be provided a package comprising absorbent articles such as absorbent tissue paper or nonwoven.

[0185] When the suitability for printing of a thermoplastic film for use in a packaging of absorbent hygienic articles has been established for a formed thermoplastic film, it is envisaged that no further evaluation needs to be made for this thermoplastic film. Accordingly, an array of packages may be formed from the thermoplastic film, e.g. an array comprising at least 1000 packages, such as at least 10 000 packages. Hence, a large number of packages may be formed where the suitability of the film for printing and for use in a packaging of absorbent hygienic articles need not again be verified.

[0186] However, since the use of recycled polymer material will necessarily imply that the properties of the thermoplastic film is altered each time a new source or batch of recycled polymer material is use, the suitability for printing of a thermoplastic film for use in a packaging of absorbent hygienic articles would need to be established for each such new source or batch.