MXPA00012629A - Film made of holed plastic material three-dimensionally shaped and related matrix for its realisation - Google Patents

Abstract

The present invention relates to a film made of holed plastic material three-dimensionally shaped, having an upper surface presenting a multiplicity of opening extending in the form of through holes (303) in the direction of a lower surface of the same film;mutually adjacent through holes (303) being separated by segments (301) of film having a profile in the shape of a conic section as a cross section with symmetric sides (304, 305) converging towards the upper surface.

Description

FILM MADE OF PERFORATED PLASTIC MATERIAL TR1DIMENSIONALLY CONFIGURED, AND RELATED MATRIX FOR THE ELABORATION TECHNICAL FIELD The present invention relates to a film made of three-dimensionally shaped perforated plastic material and to a related matrix for its manufacture. A film of this type can be used as a filtration layer in different sectors such as sanitary-hygienic articles, such as feminine sanitary napkins, children's diapers and towels for incontinence protection. It can be used as a filtration layer or film to pack meats that are going to be consumed, allowing a better conservation and a longer duration. This film can also be used in agriculture for tilling with manure and straw or crop protection in the soil or as a protective wrapping for fruit in the plant while it matures, for example grapes. The definitions of some parameters used in the manufacture of perforated plastic material are listed below. The term "liquid penetration time" indicates the time it takes for a known amount of known liquid to pass through a particular filtration layer or film, and therefore determines its ability to be traversed by said liquid. The measurement is carried out following the procedures in accordance with the common Edana 150.3 standard. "Backflow impediment in the coating material" is the parameter that measures the ability of a filtration layer or film to oppose the backflow of a known liquid in the direction of the skin as soon as it penetrates the layer, and the measurement is carried performed following procedures in accordance with the Edana 151.1 common standard. The term "brightness" refers to the relationship between light specularly reflected by a surface, and total reflected light. Therefore, when defining the surface brightness of a film, only the reflected light is taken into account with an angle equal to the angle of incidence, and not reflected light in all other directions.

ANTECEDENTS OF THE TECHNIQUE For many years, after the US patent number 3,929,135 by Procter & Gamble (1974), the efforts have focused mainly to elaborate films of perforated plastic material the most similar to fabrics, with elements of type fiber that define openings that in turn are divided in smaller openings or polygonal forms with said holes to provide the appearance of braided fibers or obtain small roughnesses on the surface of plastic films in order to reduce their gloss.

Figure 1 shows an enlarged schematic view of a portion of a first film made of perforated plastic material 100, known in the prior art. Film 100 is configured as a woven microstructure obtained with segments 101, having a cross section profile with almost vertical side branches 102, and an upper branch 103 with substantially horizontal profile. The number 104 indicates the lower surface of the film 100. The segments 101 are joined to the nodes 105 and delimit holes 106 with the shape of truncated cones in the shape of a pentagonal plane. A film of this type has high values of "penetration" and "hindflow impediment", which negatively influence its functionality, as well as high "brightness", which immediately reveals the nature of the material, that is, plastic. The perforated film of the prior art 100, in order to reduce its surface brightness and / or provide the rough appearance of a fabric, presents on the top of the segments 101 or on other parts of the internal surface of the holes 106, microasperities or microprojections arranged in the manner of a regular checkerboard, as shown by number 107 in Figure 1, which, however, have the disadvantage of retarding the flow of the liquid, offering greater friction during its journey through the truncated cone itself. further, these possible surface projections force the flow to remain deposited around them. The above disadvantages contribute, together with the high level of "backflow impediment" mentioned above, to the unpleasant wet feeling that results when the top filtration layer of a baby diaper or a female incontinence towel or sanitary napkin does not It is able to prevent liquids from coming back and coming in contact with the skin. Figure 2 shows an enlarged schematic view of a second perforated plastic film 200, known in the prior art. Unlike the matrix 100 of Figure 1, the film 200 has segments 201, which have a cross-sectional profile with oblique side branches 202 that terminate at the top surface with a vertex 203. With this conical configuration, the "brightness" It is really reduced. However, the challenge, sometimes excellently achieved, of making such films as similar as possible to fabrics, a feature that takes on particular importance if said films are used for diapers and sanitary napkins, fails to fulfill the main purpose of these films, that is, in the specific case of the hygienic-sanitary sector, allow a rapid absorption of bodily fluids, such as urine or menstrual fluid, from the surface of the skin. These liquids should be flowed in the direction of an absorbent towel and should be prevented from flowing back in the opposite direction, thus avoiding an unpleasant wet feeling for the wearer of diapers or sanitary napkins. Instead of this, especially in the case of the second film 200 of Figure 2, laboratory tests have shown that the presence of rectilinear segments in the cross section profile of the segments 201, which define conical projections, allows to provide said projections with an evident conicity, regular along the entire cross section. This cross section of regular conical shape can, however, compromise the value of "backflow impediment" or "penetration", or even both. If said rectilinear segments are located in the upper part of the truncated cone of the hole or have a slight inclination with respect to the horizontal plane of the upper surface of the film, they define a truncated cone or hole that is excessively closed in the lower part. In this way the value of "penetration" is compromised, and will be very high because the passage area of the terminal part of the truncated cone or bottom of the hole is very small. If said rectilinear segments are located in the lower part of the truncated cone descent or if they are excessively inclined, with respect to the horizontal plane of the upper surface of the film, as shown in figure 2, they define a truncated cone with insufficiently convergent walls. . In this way the modest conicity of the truncated cone will cause a high value of "hindflow impediment", allowing the liquid that has just penetrated to flow back in the opposite direction.

BRIEF DESCRIPTION OF THE INVENTION Therefore, in general, the purpose of the present invention is to provide a film of the type in question with the property of allowing liquids to be rapidly absorbed, preventing their backflow in the opposite direction. These and other objects are achieved by a film made of three-dimensionally shaped perforated plastic material, having an upper surface having a multiplicity of openings extending in the form of through holes in the direction of a lower surface of the same film; the mutually adjacent through holes are separated by segments of said film having a profile with symmetrical sides, converging towards the upper surface, which is characterized in that said profile of the film segments has a conical section as its cross section. Advantageously, this conical section is a semi-ellipse. This profile of the film segments results in a particular three-dimensional configuration of the holes, similar to a funnel, which gives the film according to the invention the property of attracting liquids from the surface and letting them pass quickly only downstream, preventing them from flowing back in the opposite direction. Unlike the known films or strips of three-dimensionally shaped perforated plastic material, described above, the film according to the present invention has a very low value of "backflow impediment", a low value of "penetration", a low value of "brightness", and a small surface area in contact with the user.

The film according to the present invention can be obtained using any technique known in the prior art, wherein any thermoplastic film, for example made of polyethylene and organic and / or inorganic additives or any mixture of polyolefin and organic and / or inorganic additives, it is wrapped in a forming die perforated or extruded directly in the almost molten state, and otherwise, on said die and said film is perforated for example by means of a high pressure jet of cold or hot air or by a high pressure jet of cold or hot water, through the mechanical action of a perforator or any body of mechanical consistency of any material that partially or completely penetrates inside the holes of said matrix causing the film to take the form of said forming matrix. In particular, there is provided a matrix for the production of the film according to the invention made in the form of a coarse mesh of mutually connected elements, with conical cross section, obtained with deposition of metal in successive phases. Other features and advantages of the present invention will be readily apparent from the following detailed description of a preferred embodiment, illustrated only by way of non-limiting description in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1 and 2 show enlarged schematic perspective views of prior art films of plastic materials; Figures 3 and 4 show enlarged schematic perspective views of a portion of a first array mode and a corresponding plastic film according to the present invention; Figure 5 shows a cross-sectional view of a portion of the matrix of Figure 3 and a portion of the film of Figure 4 superimposed on the matrix; Figure 6 shows a schematic representation of the operation of the film of Figure 4; Figure 7 shows an enlarged perspective view of a portion of a second embodiment of the plastic film according to the present invention; Figure 8 shows an enlarged schematic section of a portion of the plastic film according to the present invention struck by light; Figures 9 and 10 show diagrams of the profiles of the "penetration" and, respectively "counterflow impediment" parameters against the passage area for a film according to the present invention.

DESCRIPTION OF THE ILLUSTRATIVE MODALITY With reference to Figure 3, an embodiment of a matrix 3 is shown for making a film that constitutes the material of the present invention. Said forming matrix can be obtained by nickel electroplating of other metals, such as copper. It is defined by a thick mesh of mutually connected elements according to meshes with a pentagonal plane shape. Each element 30 has a curved cross section having the profile of a conical section, in particular of a semi-ellipse with the lowest diameter per base according to its x-axis and with the largest semi-diameter of said semi-ellipse per height according to its y axis. With reference to figure 4, a film 300 of perforated plastic material obtained with the matrix of figure 3 is shown. Correspondingly, the film 300 according to the present invention has a microstructure formed by segments, generally indicated with the number 310, joined in knots, indicated as 302, and delimiting microholes, indicated in general as 303. Each segment of the film 301 presents, in cross section, a profile in the shape of a semi-ellipse, having as its semi-vertical axis the semi -the largest diameter of the ellipse and as its horizontal axis the smaller diameter of the ellipse itself. In the profile of each film segment, the lateral branches 304, 305 and a vertex 306 are observed. With reference to figure 5, a film 300 formed on a matrix 3 is shown, whose elements 30 are schematically represented in cross section with various layers corresponding to an equal number of phases of the electroplating process. According to a particular metal electroplating technique, an almost vertical growth of the element can be obtained at a certain height, and then have a progressively narrow growth as the metal is deposited, until reaching the top with a very narrow, curved upper surface. In particular, and with reference to Figure 5, this technique consists in making a first deposition to form a support base 4; with the second deposition, the second layer 5 is obtained which provides the matrix with suitable mechanical properties such as strength and tenacity. Finally, with the third deposition, an outer surface layer 6 is obtained to create a surface coating more porous than the other layers, capable of facilitating the release of the film after the perforation phase and capable of providing it with an adequate degree of Surface roughness on the scale of 0.1 to 6.3 μ (preferably between 0.8 and 3.2 μ). The matrix 3 can also be made in more than three phases with intermediate stages having different porosity or with different metals or even in less than three phases for simpler applications, and more economical, even using a single metal. Other construction techniques can be used to obtain said dies, which have elements with curved cross section with the profile of a conical section, although said techniques are more expensive for this purpose, such as machining by electron discharge, gravure or any laser technique , the removal of material by any mechanical machining method such as perforation and engraving or the superposition of concentric tubular sheets previously perforated by any of said techniques. This particular configuration of the matrix elements allows to describe in the matrix three-dimensional openings with a funnel-like shape, shown in Figure 6, instead of a shape similar to a truncated cone, as was the common case in the prior art. Again with reference to figure 6, the funnel shape, unlike the truncated cone shape, allows having a dual conicity, that is to say two truncated cones superimposed, to confer to the hole in the segment defined by the height H1 a mouth D2 wider than D1 and in the segment defined by the height H1 a smaller truncated cone that is of greater height but of less pronounced conicity. The particular shape of the matrix elements, with the cross section in the form of a semi-ellipse with its base equal to the smaller diameter and its height equal to half the larger diameter of said semi-ellipse, gives the film 300 segments or projections with a profile, as shows in figure 5, that it has a wide opening D3 to catch more liquid. In addition, the film 300 has better radiated walls without sharp edges between the segment defined by the height H1 and the segment defined by the height H2, thus facilitating the outflow of liquid being minimally influenced throughout the projection section and, in addition, a smaller truncated cone capable of obstructing the liquid that tries to flow back in the opposite direction, that is, from the lower surface of the film to the upper one. Figure 7 shows a second embodiment of the film, indicated as 400, wherein the arrangement of the film segments, indicated generally as 401, joined at nodes 402 and delimiting holes 403, is of the fan type. The shape of the profile of the segments 401 is identical to that of the segments 301 of Figure 4. This profile of the present invention defines a top (the vertex 304, 406 of the semi-ellipse) that tapers in correspondence with the upper surface of the film, in order to define a wider opening, and a base of such form to define a segment or projection with a truncated higher cone, starting from the lower surface of the film in the direction of the upper surface, for the purpose of offer greater resistance to the fluid that tries to return back up. In addition, the contact surface on top of the film defined by the segments of the film is reduced and, in theory, similar to a point. Therefore, this feature prevents residual liquid deposits between the upper surface of the segment 301, 401 and the surface from which the liquid is absorbed, avoiding the unpleasant sensation of wetting. The liquid just deposited on the upper surface of the film of the present invention flows easily downstream due to the curved top of the segments 301, 401 so that it can slide to one side or the other of said segments. The absence of surface microprojections, generally present in prior art films in order to reduce their gloss and / or provide a fiber-like appearance, facilitates this downward flow. The film according to the present invention has very narrow reflecting surfaces. With reference to Figure 8, the film segment, which has no rectilinear branches in the profile of its cross section and in particular on the upper surface of the film itself, offers surfaces that in theory are only of the point-to-light type incident. This allows low "brightness" values to be obtained without having to subject the film to additional treatment procedures, such as etching. Taking into account a ray of light generated by a known source placed at a known distance reaching the segments with an incidence angle of, for example, 45 °, it can be noted that all the rays reaching the upper surface A, corresponding to the upper surface of the film, almost flat in the segment, are reflected in the direction of the reception lens placed at a known distance. In the case of the film according to the present invention, with the segments having a semi-elliptical cross section, it can be seen that only a minimum portion is reflected in the direction of the receiving lens. Because the film segment has the curved shape of a semi-ellipse, the incident rays are reflected according to the tangent of each point of said curve, so in Figure 8 it can be seen that only the central ray is reflected according to the tangent to the point at the top of the bridge corresponding to the upper surface A of the film. The other rays have a different reflection because they have a different angle of incidence from the point of tangency, for example of tangent B with an angle of incidence of 66 °, so that, being reflected with the same angle, they are not perceived by the receiving lens. A ray with a different angle of incidence, for example of tangent C with an angle of 9 °, being reflected with the same angle 9 °, is also not perceived by the receiving lens. The graphs of Figures 9 and 10 show the relationship that exists between the "counterflow impediment" and the passage area, and between the "penetration" and the passage area respectively, using the film of the present invention. Although the value of "backflow impediment" has an almost regular growth as it increases the area of passage, the value of "penetration" decreases regularly as the area of passage increases until reaching a value of approximately 27%, measured on the basis of the projections or segments of the film. The graph in Figure 9 shows that it is not necessary to increase this value further because the "penetration" value remains almost constant. This is explained because at that value the flow of the liquid through the projections is influenced by its own tension and surface viscosity, while below that value the viscosity and surface tension no longer have influence or in any case its Influence is not enough to decrease the flow noticeably. Considering a value of the passage area equal to approximately 27% for it to be the limit, in which it is not advantageous to proceed for the reasons mentioned above, it can be observed that it corresponds to a value of "penetration" of approximately 1.5 seconds. With reference to the graph of figure 10, to a passage area of 27% corresponds to a value of "counterflow impediment" of around 0.02 g. Therefore, it can be established that for the 27% value for the passage area corresponds the best exchange between the values of "counterflow impediment" and "penetration". The previously reported values are in any case better than those measured in the films of the prior art, and all exchanges between "hindrance impediment" and "penetration" on the scale between 20 and 33% of the passage area are in any case better. This is possible thanks to the particular funnel-like shape of the segments of the film having a cross-section in the shape of a semi-ellipse. This shape hinders the flow back up, opposing the liquid with a longer channel to counterbalance. In the case of prior art films made of perforated plastic material, instead, if the liquid flows past the hole at the base of the film segments, it encounters less resistance each time as it flows upward, so that a Once it has flowed through the film, it is easier for the liquid to move up than down. The advantages of the perforated plastic film of the present invention, produced with matrices having a mesh of elements with curved cross-sectional profile in the form of a semi-ellipse can be summarized as follows: 1.- Counterflow impediment value very low 2.- low penetration value 3.- low brightness value 4.- reduced surface in contact with the user In conclusion, the matrices with the elements defined by the present invention allow to obtain films made of perforated plastic materials with better performance than those that existed in the prior art or in commerce.

Lab tests Some laboratory tests are briefly illustrated to demonstrate the advantages of the film made of perforated plastic material constituting the present invention. The "liquid penetration time" test consists of weighing 5 superimposed absorbent papers ERT: FF3W / S with a load factor of 3.3, by Hollingsworth & Vose Company Ltd., stored for at least 24 hours at a humidity of 65% ± 2 and at a temperature of 20 ° ± 2 ° C. The papers used for this test were subsequently used also for the counterflow impediment test. A square piece of filtration film to be evaluated (in this case the film of the present invention or other similar films) is cut with its side measuring 125 mm and placed on the upper surface of the layer of five recently superimposed absorbent papers (in In this case, the perforated film should have projections or segments oriented towards the absorbent papers and in contact with them). The package thus obtained, which comprises the five absorbent papers and the filtration film, is placed in the base of the so-called "primer" instrument, capable of introducing a known quantity (5 ml) of known liquid and measuring the time it takes that liquid to flow through the filtration film examined. The instrument used for the test is a "list" made by Lenzing AG. The "liquid penetration time" test is immediately followed by the "counterflow impediment in the coating material" test. The value of the weight of the five absorbent papers, previously weighed, multiplies the load factor many times. The result of this product gives the maximum amount of liquid that can be absorbed by said five absorbent papers in order to achieve saturation. Through a "checker", used for the "liquid penetration time" test, an additional quantity of the same liquid is introduced into the package comprising the five absorbent papers and the piece of filtration film, equal to the difference between the result of the aforementioned product and the amount of liquid previously introduced in said test (5 ml). After making this additional introduction, the base contained in the "listador", together with said package of layers of absorbent papers and filtration film, moves towards the instrument of "impediment of backflow" close to the test with the same name, which consists of stratifying a weight 4 kg known on the upper surface of the filtration layer of said package for a known time of 3 minutes for the purpose of uniformly moistening the upper surface of said filtration film. During this time, two absorbent papers ERT.FF3.W / S are weighed by Hollingsworth &; Vose Company Ltd., stored for at least 24 hours at a humidity of 65% ± 2 and at a temperature of 20 ° ± 2 ° C. Once this interval has concluded, the weight is automatically lifted and the two freshly weighted papers are placed on the upper surface of the same filtration film. After the same weight is decreased during a 2 minute interval. After this interval expires, the two papers are weighed again. The difference between this value after the test and that before the test produces the weight of the liquid that has left the filtration layer. The instrument used for the test is a "backflow impediment" manufactured by Lenzing AG. The liquids used for these tests are of two types: simulated urine, prepared in the laboratory by diluting 18 g of sodium chloride in 2 liters of distilled water according to Edana 150.3, with a surface tension of 70 ± 2nM / m and a viscosity of 1.OcPs at 20 ° C; Plasmion solution, produced by Bellon in April 1997 and expiring in April 2000, no. batch 2018-3, with a surface tension of 63 ± 2nM / m and a viscosity of 1.6 cPs at 20 ° C. The brightness tests that followed were done in accordance with ASTM D2447 and C346 standards and were carried out with a micro-brightness reflectometer manufactured by BYK-Gardner GmbH.

Claims (6)

NOVELTY OF THE INVENTION CLAIMS

1. - A film made of three-dimensionally shaped perforated plastic material, having an upper surface having a multiplicity of openings extending in the form of through holes in the direction of a lower surface of the same film; the mutually adjacent through holes are separated by segments of said film having a profile with symmetrical sides converging towards the upper surface, characterized in that said profile of the film segments have a conical section as a cross section.

2. The film made of perforated plastic material according to claim 1, further characterized in that said profile of said film segments have as cross section a semi-ellipse with the minor axis equal to the diameter and lying on the lower surface of the own film and with the vertex, with respect to the largest axis, on the upper surface of the film itself.

3. A matrix for the production of the film according to claims 1 and 2, further characterized in that said matrix is made in the form of a coarse mesh of mutually connected elements, with conical cross section, obtained with the deposition of metal in successive phases.

4. The matrix for the production of the film according to claim 3, further characterized in that each matrix element i 5 is made with three layers, corresponding to an equal number of phases.

5. The matrix for the production of the film according to claim 4, further characterized in that said three layers of matrix element are made of different metals.

6. The matrix for the production of the compliance film 10 with claim 4, further characterized in that said three layers of matrix element are made of the same metal.