SE513841C2 - Method for hole or slit forming in one material layer and simultaneously joining this layer with another material layer - Google Patents

Abstract

A method for forming through apertures in the form of holes and/or slots or slits in a web which is intended to form part of absorbent articles, wherein the web is irradiated with at least one focused electromagnetic beam or particle beam from an irradiating source on at least one of its surfaces and in those web regions in which the apertures are to be formed, wherein the properties of the beam and the duration of the irradiation period are selected so that the material will receive in these regions sufficient energy to melt and/or vapourize and/or pyrolyze and/or burn said material, and wherein resultant molten and/or vapourized and/or pyrolyzed and/or combusted material is esssentially removed.

Description

10 15 20 25 30 513 841 2 Openings are often also arranged to form so-called tear instructions, ie lines or curves of openings arranged in a row one after the other, along which lines er / curves the material is intended to be torn apart then large enough and opposite forces are applied to both sides thereof.

In addition, there are a number of other cases well known to those of ordinary skill in the art and applications in which it is necessary or at least desirable to provide openings in web material of the above kind.

As stated above, it is often difficult to find materials that meet all of them the requirements required for use in absorbed articles. It is therefore common to joining or laminating different materials to achieve the combined laminates, which to a greater extent meet these requirements.

Known technology and its problems Known technique for forming openings in web-shaped material of the above kind comprises subjecting the material to conventional processing with e.g. studded rollers during the application of heat, or with different types of punches.

Among modern ways of achieving openings are those that are based on the use of ultrasound or powerful water jets (so-called waterj et technology). One special method for hole formation in plastic films using vacuum coated and perforated rollers are described in, for example, US-A-3 929 135. Common to all of these known methods are that they are of a mechanical nature; during processing always stands the web in direct contact with any highly tangible matter, which transmits it for the formation of openings required the amount of energy.

One of the main problems with prior art is the obvious lack of it fl flexibility that results from the openings being formed precisely through direct contact with matter: To change the size of and / or the interrelationship between the openings that are formed, one must either stop production and replace one studded roller or, in the case of ultrasound, a pattern roller. It's according to 10 15 20 25 30 515 841 3 the laws of nature make it impossible to regulate the speed or temperature of a rotating roller discrete steps; due to the inertia of the mass, the change can only take place continuously between the different steps. This means that during production desires to change the control parameters for the formation of openings according to the prior art had to accept that a large part of the material web, namely the one that has time passes before the control parameters have adopted their new values, will not meet set specifications and thus generally must be discarded. The the inertia of energy-transferring matter is also a problem in that it in itself has a strong limiting effect on the speed of production, by that of matter the inertia limits the speed at which it causes the formation of openings required mechanical energy as well as any heat energy can be supplied the material. The waterjet telmike is also burdened with these disadvantages.

In the case of the formation of openings in web-shaped materials intended for lining absorbent articles, the prior art is generally burdened by an additional disadvantage: the material around the openings is compressed, for example by a pi gg roller or an ultra- sound device pattern roller. Of course, this compression often has one significant negative impact on material properties, eg softness, fl flexibility etc.

Procedures for combined laminating of webs and formation of openings in any of the tracks hardly occur in the prior art. The lamination takes place in a separate step and is carried out conventionally by gluing or ultra- sound welding. It would, of course, be from a production economics point of view desirable to avoid this extra step and still obtain an equally good or better product.

The excitement The main object of the present invention is to provide a method of the kind mentioned at the outset, which is substantially or completely free from the 10 15 20 25 30 515 841 4 associated with the prior art, as well as a structure made by procedure.

These objects and advantages, as well as those other obvious to those skilled in the art, are achieved with a method and a layer structure of the kind initially mentioned, which have the features which appear from the characterizing part of the appended claims 1 and 14.

To use focused electromagnetic rays or particle rays in this way for the formation of openings offers a number of advantages. It is easy to change one the point of attack of the beam (ie the point of the substrate on which the beam is lit) using, for example, a system of mirrors, prisms and / or magnets, as in this context can be called "magnetic mirrors". Mirrors and prisms have one relatively small mass and thus represents little inertia against movement, which means that the point of attack of the beam can be snabbt surface quickly and with very little energy consumption. This, of course, means a considerable gain, relative to the known technology, in terms of fl feasibility when changing control parameters. With a mirror / prism system, you can make the beam move very quickly from that form a pattern of openings to form another. By regulating the mirror / prism system with the help of a computer is obtained a very great freedom when it is important to choose different patterns, which can be obtained immediately after choosing them. Instead of, as in the prior art, stopping the track for fl surface to changing rollers and the like - which of course is in itself a cumbersome procedure - can the control parameters are regulated by means of computer programs and by electronic means control of the mirror or prism system, while production continues undisturbed, because the control parameters take their new care practically instantly. Among known and in this context conceivably useful mirrors systems of the above kind may be mentioned, for example, those described in DE-A1-S 300 822, EP-A1-0 179 275, EP-A2-0 477 458; furthermore, there is a conceivable useful system with so-called cinema forms described in SE 9201056-O. Others conceivable 10 l5 20 25 30 513 841 5 systems, which are in themselves intended for laser engraving, are described in DE-Al- 4 2l2 390 resp DE-C2-3 332 838.

The focused beam used supplies energy with significantly higher power per surface unit than is the case with known technology, ie the energy supply per time and surface unit is considerably larger. This means that the speed of the track, and hence the production rate can be increased up to about twice or more in relation to prior art.

Because the energy supply is very concentrated in the places where the openings to be formed, very well-defined openings are obtained without undesirable compaction of surrounding materials.

The focused beam may be a beam of charged or uncharged particles or a light beam, which may be coherent or non-coherent, or monochrome or polychrome.

In a preferred embodiment of the present invention, a beam is used of coherent electromagnetic radiation, preferably a laser beam, preferably from a COZ Iases because the wavelength range of rays from a CO 2 laser is such that the efficiency is very high for the conversion of radiant energy into heat in i the material in question (various polymers and cellulose), ie the energy supplied is used very effectively to form openings in the material.

In the process of the present invention, a kan uidum, preferably one gas, is supplied near the focus point on the track and possibly at existing focusing means. Fluidum fl fate serves to remove melted / burned / evaporated material from formed openings in the web, cooling of the openings edges to reduce the protective zone around the openings, and to cold occurring focusing means such as lenses and the like. A common occurring fl uidum is air. If you want a faster processing process, you can 10 15 20 25 30 515 841 6 a gas with a relatively high oxygen content can be used, as this favors the combustion of the web-shaped material at the focus point. Do you want to reduce the risk of the edges of the openings are discolored due to charring, you can instead use an inert gas, such as nitrogen or argon; it may also be appropriate to use an inert gas if the proportion of cellulose in the banana is high.

The through openings can be both liquid and vapor permeable, but are preferably intended to let liquid through.

In one embodiment, the first web-shaped material may be a plastic film or -foil; in another it may be a erd berduk or a layer of nonwoven. The openings may be holes with a diameter of up to 4 mm, preferably 0.3-3 mm, preferably 0.5 -1.5 mm, or slits with a length of up to 10 mm, preferably up to 5 mm. The slits may be straight or more or less curved; they can too cross or break each other.

In the method of the present invention, the first web is at the irradiation in contact with the second web, which comprises materials of one kind similar to the first orbit, and located at that radiation source opposite side of the first trajectory, and the properties of the beam and the length of the irradiation time is chosen so that the material in the first web and / or it second path is supplied with enough energy to in the immediate vicinity of the openings join the paths together. In this way formation is obtained of openings in the first lane at the same time as the first and second lanes laminated with each other. This is, of course, a very technical advance meaning; no separate lamination step is required with the present invention, which of course entails a considerable economic advantage. In addition in relation to the prior art, improved contact between the tracks is achieved, which is favorable for the absorption and transport of liquid through the laminate. 10 15 20 25 30 515 841 7 The present invention is described in more detail below by means of examples and the accompanying drawings, in which Fig. 1 schematically shows an embodiment of the invention, in which formation openings in a first lane while joining it to a second path; and Fig. 2 is a detail enlargement of the circled area in Fig. 1.

In these urer gures, equal reference numerals mean equal objects.

Fig. 1 shows a part of a laser 10 in cross section, which generates a laser beam 20, which is focused by means of a focusing lens 30. The one with the lens 30 the collapsed beam 20 passes further through a nozzle 50 and then out through the same via an opening 60. That of the lens 30 and of the walls of the nozzle 50 limited space is traversed by a shielding gas, which is supplied via a line 40. The beam attacks a first upper web of material 70 at a point and forms thereby an opening 80 in it during simultaneous joining with a second lower material web 90.

As shown in Fig. 2 forms a part of the material which then melts down the hole 80 formed in the web 70, a joint or joint 100 between the webs 70 and 90.

Example Below are a number of examples of experiments performed according to those illustrated embodiments of the present process. In these experiments a COg laser (gas laser) of the brand LASAG, product designation COL 200, which emitted a substantially vertically downward laser beam with a wavelength of 10.6 um against the material to be processed. The material was arranged on the experiments a two-axis movable table, which was regulated with a programmable CNC system by the BOSCH® brand. The laser beam had a diameter before focusing of about 7 mm, a 10 15 20 25 513 841 s beam divergence of about 1.5 mnrad and an approximately Gaussian power distribution over the beam cross ride; in focus, the beam diameter was about 60 μm. Focusing lens focal length was about 38 mm. As shielding gas, air with an excess of 0.1-0.5 bar was used.

The orifice of the gas nozzle had a diameter of about 1.5 mm and was located at processing approx. 1.5 mm above the focal plane, which in turn was up to approx. 3 mm above the surface of the material to be processed.

Table I below presents the results of a number of combined trials drilling holes in surface material and simultaneous joining with another similar materials using the above equipment. The materials used were: B9W = Spunbonded polypropylene with wetting agent, basis weight 20 g / mz (surface material in the experiments) L4-601 = Carded and thermobonded bicomponent material of polyethylene / polyester, basis weight 50 g / mz (spacer material at the experiments) Furthermore, in Table I, the following terms have the following meanings: Pulse response time = time between each laser pulse Average power = the average time value of the power of the emitted laser beam Focus distance = the distance from the focal plane of the collapsed laser beam to the surface of the irradiated material Splitting = distance between holes Other existing concepts should be self-evident.

The speed given in Table I refers to the speed of the movable table in the x-direction. 513 841 md Wo vä om o om: m Wo om šmmšoço fi: H Wo m.o om m; o omm QN Wo ow šomšooèa om EE EE än EEE 62k o EE >> m5 WE >> wox hZ Hoooë fi o oi. E -QE xoæbmwÜ Kšwuâü wEEQQ .Gäwsxom tßüomosm .muåzm 2315 u fi øäwoå .wtoäå> o $ o: øsm fi 515 841 10 Of course, the present invention should not be construed as limited by the above embodiments and examples, but only of the appended patents requirements, within the framework of which there are a number of others conceivable to the person skilled in the art execution forms.

Claims (14)

10 15 20 25 513 am ll Patent claim Method for simultaneously making through openings in the form of holes and / or slits in a first web (70) and joining it with a second web (90), which webs are intended to be included in absorbent articles, characterized in that the first the web (70) is irradiated against one of its surfaces and within the areas of the web in which the apertures are intended to be formed, with at least one focused electromagnetic beam or particle beam from a radiation source, the other web (90) being located on the radiation source opposite side of the first web (70) and with its surface facing the first web in contact with the surface of the first web (70) within the area where irradiation takes place, the properties of the jet (20) and the length of the irradiation time being selected so that the material in the first web the web (70) is supplied with sufficient energy in these areas to melt and / or evaporate and / or pyrolyze and / or burn and in addition the web (90) is supplied with sufficient energy to join the webs and / or the slots (80) in close proximity to the holes, and to thereby substantially remove molten and / or vaporized and / or pyrolyzed and / or combusted material. Method according to claim 1, characterized in that the beam is a laser beam (20). Method according to claim 1 or 2, characterized in that the basis weight of the first web (70) is s-10 g / m 2. Method according to claim 3, characterized in that the basis weight of the first web (70) is 10-50 g / m 2. Method according to one of the preceding claims, characterized in that the openings (80) in the first web are intended to allow liquid to pass through. 10 15 20 25 513 841 12 Method according to one of the preceding claims, characterized in that the first web (70) is intended to be used as a top layer in absorbent articles. Method according to one of the preceding claims, characterized in that the openings (80) are holes with a diameter of up to 4 mm. Method according to Claim 7, characterized in that the holes (80) have a diameter of 0.3-3 mm. Method according to claim 7, characterized in that the holes (80) have a diameter of 0.5-1.5 mm. Method according to one of Claims 1 to 6, characterized in that the openings (80) are slits with a length of up to 10 mm. Method according to Claim 10, characterized in that the slots (80) have a length of up to 5 mm. Method according to one of the preceding claims, characterized in that the first web (70) is a plastic film or foil. Method according to one of Claims 1 to 11, characterized in that the first web (70) is a nonwoven fabric or a layer of nonwoven. Two-layer structure comprising a first web (70) provided with openings in the form of holes and / or slits joined to a second web (90) and intended to be included in an absorbent article, characterized in that it is produced by a method according to any one of the claims 1-13.