A method of providing a laser welded product and a laser welded product

[0001] The present method relates to the provision of a laser welded product in which radiation from the laser reaches an absorbent layer other than the laser welded layer by placing the scattering material between the two absorbent elements.

[0002] This is particularly interesting in layered products in which one of the elements which is laser welded is attached to another absorbent element which could be adversely affected by radiation not absorbed in the laser welded layers.

[0003] One type of product that may be affected are stoma bags, in which it is desirable first to properly provide a bag shell consisting of two layers attached to each other and where the element is then laser welded to one of the layers without affecting the other layers .

[0004] The use of radiation to implement or trigger various processes can be seen, for example, in: GB 1528452,

US 5 702 771, US 6 326 450, US 6 492 019, US 6 248 974, US 6

229 114, WO 02/23962, EP 1331635, EP 0476865, EP 0126787, WO 00/20157, WO 03/007080, and DE 101 58 016, as well as in Russek UA et al. "Laser beam welding of thermoplastics, Proc. SPIE

- the international society for optical engineering: photon processing in microelectronics and photonics II: San Jose, CA,

USA, Jan 27-30 2003, vol. 4977, 2003, pages 458-472, Bachmann F

G: "laser welding of polymers using high-power diode lasers",

-2 Proc. Of SPIE, vol. 4637, 2002, pp. 505-518, and "laserstrahlschweissen von Thermoplasten in

Durchstrahlverf ahren "February 1, 2000, BASF AG, AWETA

THERMOPLASTE, Ludwigshafen, DE. WO 02/00144 discloses methods and articles corresponding to the corresponding preamble parts of the independent claims.

[0005] In a first aspect, the invention relates to a method of welding together the first and second elements by means of transmission radiation in a given direction to the interface between the two elements, the method comprising:

1. providing a first element having, in this direction, a first layer and a second layer attached to each other, the first layer having a first absorption coefficient μa1> 0.4 mm^-1 at a certain wavelength of radiation, and the second layer has a second absorption coefficient μa2> 0.1 mm^-1at this wavelength;

2. providing a second element with, in this direction, a third absorption coefficient μa3 at this wavelength, said third absorption coefficient being smaller than the first and second absorption coefficients;

3. placing the second element in such a way that it abuts against the first layer or is in its vicinity, and so that the radiation enters the second element along this direction before entering the first layer;

-34. providing a third layer with a scattering factor μs> 0.4 mm^-1, at this wavelength, between the first and second layers, in the direction of radiation, and

5. providing radiation along this direction, which radiation:

- penetrates into the second element,

- heats the first layer so that the first layer is welded to the second element; and

- radiation that has passed through the first layer is scattered by the third layer.

[0006] In this context, the first and second layers of the first element may be two individual layers attached to each other, for example by welding (laser or thermal welding, spot welding or the like), gluing, ultrasonic welding or dielectric welding, or they may they shall be made of the same layer of material that is composed in such a way that these two layers are formed.

[0007] During the heating step in which the first layer is welded to the second element, radiation transmitted through the first layer and the second element will be scattered through the third layer both in the direction of the first layer and in other directions facing from the second layer. Thus, the radiation intensity actually reaching the second layer is much lower than the intensity reaching the third layer.

[0008] The direction from which radiation is transferred to the elements is usually at least approximately perpendicular to the general plane of the elements.

However, this is only one way to provide radiation. The actual direction can be at any angle to the elements as long as the order of the elements in the direction of radiation is correct.

[0009] In this context, the dispersion through the third layer may be carried out in any suitable manner, for example by incorporating dispersible powder or fibers into it, or using a surface of the third layer which enables dispersion. This surface may be uneven, for example, sanded.

[0010] Generally, the absorption coefficient of the second element is not important unless it is so high that the radiation overheats the second element or the second element absorbs too much radiation before it reaches the interface between the second element and the first layer.

[0011] On the other hand, μ31 may be larger than 0.6 mm^-1, for example larger than 1.0 mm^-1, preferably larger than 2.0 mm^-1, for example larger than 4.0 mm^-1, to provide the first layer with sufficient absorption and heating.

[0012] Also μa2 may be greater than 0.4 mm¹, for example larger than 1.0 mm^-1, preferably larger than 2.0 mm^-1, for example larger than 4.0 mm^-1, and, naturally, may be identical to μβ1.

[0013] In this context, the first layer and the second element are adjacent or are adjacent to each other such that when the first layer is heated (as a result of which the volume of the material of the first layer may increase), these two layers will contact and the first layer it will also heat the second element to weld the two materials together.

[0014] Furthermore, the higher the scattering coefficient of the third layer, the more it scatters the radiation emitted from the third layer. Thus, μs can be larger than 0.6 mm^-1, for example larger than 1.0 mm^-1, preferably larger than 2.0 mm^-1, for example larger than 4.0 mm^-1.

[0015] Naturally, to prevent the third layer from moving before laser welding, step 4 may include fixing the third layer to the first layer and / or the second layer. This fastening can be carried out in any suitable manner, for example by means of adhesives, thermal welding or static electricity, or by fixing the third layer in a process in which the first and second layers are attached together.

[0016] In a preferred embodiment, step 5 comprises the use of radiation along the direction and in a predetermined first position or predetermined first arrangement of positions in the overall plane of the first and second layers, the first and second layers being attached to each other in a predetermined second or predefined position the second position system in this plane, with the first position (the first

Positions) and this second position (these second positions) are different. In this situation, preferably, the third layer is in this plane in all of the first positions either as a single piece of material or as a number of different pieces of material.

[0017] Thus, in this embodiment, the first and second elements are laser welded together in a first position (s), which can be made with a continuous weld or spot welds (or a combination thereof), and the first and second layers are attached to each other in a different position (other positions) than those made by laser welding.

Naturally, these positions may be different in the sense that laser welding can be performed independently of this attachment.

[0018] In another embodiment, step 2 includes providing a second element with a predetermined outer contour in the main plane of the first and second layers, and step 6 includes providing radiation along this direction and in the given first contour in this plane, this contour the outer circle circles, in this plane, at least part of the first contour. An example of a product of this type will be a stoma bag, in which the connecting element is to be laser welded to the side of the bag shell and in which the laser welding of the connecting element with the bag shell is in fact done inside (in the plane) the contour of fastening these two layers forming

-7 coat of bag. Thus, in such a way that it is ensured that the welding of the connecting element (second element) to one side (first layer) of the bag, the other side (second layer) is not welded to the first side when the third layer is inside the bag.

[0019] Thus, it is possible to provide a bag coating (heat-sealed or the like) before the actual heat sealing of the connecting element with the bag.

Naturally, it does not depend on whether the joining means work with adhesives or mechanical coupling agents.

[0020] Generally, it is preferred that step 1 includes providing a second layer with at least a given lowest melting point, and wherein step 5 includes providing radiation at a given intensity, so that any radiation transmitted by the second element and heating the second layer does not have of sufficient intensity to heat the second layer to the set lowest temperature.

This may be a limitation of the intensity of radiation transmitted to the first layer (but which may then create problems in laser welding) or require the choice of second layer material or scattering carried out by the third layer.

[0021] Naturally, the same may be true for the third layer in the sense that the third layer may touch or be adjacent to the second layer and thus be heated. Therefore,

Preferably, step 3 also includes providing a third layer with at least a given lowest melting point, and wherein step 5 includes providing radiation at a given intensity, so that any radiation transmitted by the second element and heating the second layer does not have sufficient intensity to heat the second layer is the set lowest temperature. [0022] In one embodiment, step 4 includes providing a third layer with an absorption coefficient of pa, at a given wavelength, where μs> (1/10) * pa.

In this way, the entire functionality of the third layer is scattering and not absorption that would heat the third layer.

[0023] In another aspect, the invention relates to a method of welding together first and second elements by transferring radiation in a given direction to a boundary surface between these two elements, the method comprising:

1. providing a first element having, in a given direction, a first layer and a second layer attached to each other, wherein the first layer has a first absorption coefficient, pal, at a certain wavelength of radiation, and the second layer has a second absorption coefficient pa2> 0.1 mm^-1at this wavelength;

-92. providing a second element with, in this direction, a third absorption coefficient, μa3>, at this wavelength, with μa3> μ31 and μa3> 0.4 mm^-1;

3. placing the second element so that it abuts or is near the first layer and that the radiation penetrates the first layer along this direction before penetrating the second element;

4. providing a third layer having a dissipation factor of μs> 0.4 mm^-1 at this wavelength, between the second element and the second layer in the direction of radiation;

and

5. providing radiation along this direction, which radiation:

- penetrates into the first layer,

- heats the second element so as to heat the first layer to the second element, and

- radiation, which after penetrating the second element is scattered by the third layer.

[0024] In this aspect, the tasks and positions of the first layer and the second element have become interchangeable. There is no need to provide any other differences. The first and second aspects can be selected depending on whether the first and second layers are made of what is desirable from the same material or not made from the same material layer and whether the first layer has an absorption coefficient large enough to allow laser welding or not.

[0025] Then, again, step 4 could include fixing the third layer to the first layer or the second layer.

[0026] Also, step 5 could include providing radiation along this direction and in a given first position or in a given first position arrangement in the overall plane of the first and second layers, the first and second layers being attached to each other in a given second position or a predetermined second position arrangement in this plane, the first position (s) and the second position (s) being different.

[0027] Furthermore, step 1 could include providing a first and a second layer attached to each other along a first predetermined outer contour in the overall plane of the first and second layers, wherein step 2 includes providing a second element having a predefined first contour in that plane, the contour being the outer circle circles the first contour, and in which step 6 includes providing radiation along the direction and in the given second outer contour in this plane.

[0028] Finally, step 1 could include providing a second layer with at least a given lowest melting point wherein step 5 includes providing radiation at a given intensity such that any radiation transmitted by the second element and heating

- the second layer did not have enough strength to heat the second layer to the set lowest temperature.

[0029] A third aspect relates to a laser welded element having, in a given direction,

1. a first element comprising a first layer and a second layer attached to each other, the first layer having a first absorption coefficient, μ31> 0.4 mm^-1 at radiation wavelength, and the second layer has a second absorption coefficient μa2> 0 mm^-1 at this wavelength,

2. a second element with, in this direction, a third absorption coefficient, μa3, at this wavelength, where the third absorption coefficient is smaller than the first and second absorption coefficients, the second element is positioned so that it abuts or is near the first layer and so that the radiation penetrates the second element, along this direction, before penetrating the first layer,

3. a third layer placed between the first and second layers, in the direction of radiation, and having a scattering coefficient, μs> 0.4 mm^-1 and wherein the first layer is welded to the second element, the third layer is attached to one of the first and second layers and is not attached to the second of the first and second elements.

[0030] The laser-welded member may be a stoma bag containing a pouch to which the connecting member is welded.

[0031] The fourth and final aspect of this invention relates to a laser welded element comprising, in a given direction,

1. a first element comprising a first layer and a second layer attached to each other, the first layer having a first absorption coefficient, μδ1, at a certain wavelength of radiation and the second layer having a second absorption coefficient μa2> 0.1 mm^-1 at this wavelength,

2. second element with, in this direction, the third absorption coefficient, μa3> μ31 and μa3> 0.4 mm^-1 at this wavelength, with the second element being positioned so that it rests on or near the first layer and that the radiation penetrates the first layer along this direction before penetrating the second element,

3. a third layer sandwiched between the second element and second layer and having a dissipation factor of μs> 0.4 mm^-1 in the direction of radiation, and in which the first layer is welded to the second element, the third layer is attached to one of the first and second layers, and is not attached to the second of the first and second elements.

[0032] As shown above, the third and fourth aspects can be chosen depending on the absorption coefficient of the first layer and whether it is desirable to have certain common properties (or different properties) in the first and

-13 second layer. As mentioned above, preferably, the third layer has an absorption coefficient of μ3, at this wavelength, where μs> 0.4 mm^-1 and μa <4 mm^-1.

[0033] The present element may be, for example, an ostomy bag in which the gas filter chamber is welded inside the bag shell.

[0034] Recommended embodiments of the invention will be described below with reference to a drawing, in which:

Figure 1 illustrates laser welding of two parts,

Figure 2 illustrates laser welding of two parts having between them an absorbing layer,

Figure 3 illustrates the peel strength achieved during laser welding according to the preferred embodiment,

Figure 4 illustrates a preferred method according to the invention.

[0035] Figure 1 illustrates the transmission laser welding of the transparent part 20 with the absorbing part 30. The laser light penetrates the upper transparent part 20 and is absorbed by the lower absorbing part 30 on the interface 10 between these two parts 20 and 30.

[0036] Preferably, the absorption coefficient of the part 20 is not too high because it would cause the absorption of radiation before it reaches the boundary surface, where this radiation is desired. However, as long as the absorbency of part 20 does not damage this part, it can very well have both some absorbency and the ability to scatter radiation.

[0037] Two lines 11 and 12 are shown. These lines describe the penetration depth - or molten volume - of the radiation in two cases.

[0038] If the absorbing part 30 does not scatter the laser light to any significant degree, the light will penetrate to the depth shown by line 11.

[0039] If the absorbing part 30 also scatters the laser light, the light penetration is reduced, as shown by line 12. Naturally, this effect gradually reduces the depth of penetration with increasing scattering in the material 30. [0040] In these two cases, the same total amount of energy is absorbed, causing more energy to be absorbed near the boundary surface 10, and thus a higher temperature of the boundary surface is obtained when laser light scattering occurs in the material.

[0041] This effect can be used to reduce the amount of absorbent in the material 30. This may be desirable in many applications where the color of the materials and

thirty. It is difficult to find and introduce, for example into polymers, absorbents that would have sufficient absorbency, for example in the infrared zone, but only a small effect on absorption or reflection (color) in the visible area.

[0042] In figure 1, the material 30, which can be homogeneous, has both absorbing and dispersing properties.

However, these effects can be separated. This is shown in figure 2,

-15 which illustrates the transmission laser welding of three parts

20, 30 and 40.

[0043] In this situation, the function of the material 20 is the same, but the main absorption currently takes place in the material 30, and the two lines, 11 and 12, show the depth of penetration (molten volume) of radiation when the material 40 has - or is not large enough scattering coefficient at a given wavelength. The material or part 40 need not have any absorption coefficient at this wavelength.

[0044] Parts 30 and 40 may be joined / secured into one part before welding, or they may be separate parts. The laser light penetrates the transparent part 20 and part of it is absorbed in the absorbing part 30.

[0045] If the lower part 40 does not scatter the laser light, the light penetrates to the depth shown by the line

11. If the lower part 40 also scatters the laser light, then the penetration of this light into 40 is reduced as shown by line 12.

[0046] In these two cases, the same total amount of energy is absorbed, causing more energy to be absorbed, and thus a higher temperature of the boundary surface at the transition surfaces 10, 50 is obtained when the laser light scattering occurs at 40.

[0047] It can be seen that the material 30 in figure 2 can be used to fasten the materials 20 and 40 due to the uniformity in it

-16 intensity distribution - and therefore an even temperature distribution that ensures good welding between material 30 and each of the materials 20 and 40.

[0048] The test in the system shown in Figure 1 was performed, consisting in testing the tensile strength of the welds. [0049] Two types of materials were tested, where the first series of tests was performed on material 20, the transparent material of the example below, and on material 30, the absorbent material of the following example. In Figure 3 these studies are illustrated by a thin line.

[0050] In the second set of materials, the material 20 is again the transparent material of the example below, and the material 30 is the absorbing and dispersing material of the example below, with a final weight concentration of TiO2 of 2%. Figure 3 illustrates this study with a thick line.

Thus, compared to the first set of materials, the material contains some TiO2 with an average particle size of the order

300 nm, which scatter radiation.

[0051] Linear energy (radiation intensity to unit of length - J / mm) was changed to see the effect of differences in scattering on intensity.

[0052] The results of Figure 3 are quite clear in the sense that it can be seen that strong welds are obtained at the energies for the bottom line when the material 30 has a higher dissipation factor. This indicates that scattering increases

- radiation intensity at the boundary surface in such a way as to improve welds at lower energies.

[0053] At higher energies, it can be seen during visual inspection of the samples that the welds for the first set of materials break as a result of cracking of these materials, while the welds with the second set of materials break off, indicating that the welds are a weak part and could be made at too high a temperature .

[0054] Also at high linear energies, the material 30, in the first set of materials, is usually discolored or damaged due to the high intensity absorbed by the material.

EXAMPLE [0055] Three types of working samples (49 X 49 X 1 mm^AND3) made by injection technique.

[0056] Transparent sample: low density polyethylene (LDPE, Engage 8401 from DuPont-Dow) or other types of polyethylene or polyethylene / ethylene / vinyl acetate copolymers.

[0057] Absorbing sample: A certain amount of infrared absorbent (PRO-JET 830 NP from Avecia), corresponding to a total final weight concentration of 0.02%, was dissolved in a small amount of mineral oil and mixed with Engage 8401.

[0058] PRO-JET 830 NP has a maximum absorption at 800 nm with a spectrum half width of ~ 110 nm and can be easily mixed with polyethylene. At concentration

-18% by weight 0.02% in polyethylene, absorption coefficient (μ₃) and the scattering factor (μ₃) at 800 nm are, respectively, ~ 0.9 mm^-1 and ~ 0.3 mm^-1.

[0059] Infrared absorbers for laser welding of polymers should be able to mix with polymers and be present in a concentration that provides sufficient absorption and dispersion at the laser welding wavelength.

Commercial laser diodes for laser welding typically have emission wavelengths in the range from 800 nm to 980 nm.

Infrared absorbers with sufficient absorption in this wavelength range can be selected from groups of compounds such as nitroso, cyanine, nigrosine, triphenylmethane, imine and diimine compounds, squaurilium and croconium, and related compounds, quinone, phthalocyanine nickel diolthiolates, and others. Azo, indoaniline and structural formulas of such compounds can be found, for example, in "Infrared Absorbing Dyes" (Topics in applied chemistry), ed.

M. Matsuoka, Plenum Press, New York, 1990. Such dyes can be modified to allow them to be mixed with the polymers to be welded, or they can be made in the form of a pigment, which is then mixed with the polymers. Methods for mixing dyes with polymers include co-precipitation of the dye with the polymers in a solvent or in a high vacuum [see, for example, T. Hiraga et al. "Properties and application of organic dye associates in polymer matrices", Thin Solid Films 273 (1996) 190-194].

Alternatively, dye molecules can be covalently bound to polymer chains [see for example A. Costela et al. "Efficient and highly photostable solid-state dye lasers based on modified dipyrromethene. BF2 complexes incorporated into solid matrices of poly (methyl methacrylate), Appl. Phys. B 76 (2003) 365-369].

[0060] Absorbing and dispersing sample: A masterbatch containing 10% by weight of White was prepared by mixing technique

Pigment 6 (crude TiO2 rutile with 300 nm average crystal size, such as PRETIOX R-200 M from the company

PRECOLOR as) in Engage 8401. Different amounts of masterbatch were mixed with Engage 8401 and some PROJET 830 was dissolved

NP in mineral oil, corresponding to a total final concentration of 0.02% by weight.

[0061] Laser welding experiments were performed using a diode laser with a wavelength of 808 nm, a laser beam with a diameter of 2 mm and various combinations of energy and speed.

[0062] Tensile strength tests of the welded samples were carried out. Figure 3 shows the load at break as a function of the linear energy defined as energy / speed.

[0063] Reflectance measurements for scatter and total transmittance were carried out using an integrated spherical system described, for example, by BC Wilson in 'Optical-Thermal Respons of Laser-20 Irradiated Tissue', ed. AJ Welch and MJC van Gemert,

Plenum Press NY 1995 chapter 8.

[0064] The measurement data were converted into absorption and scattering coefficients using the doubling addition algorithm assuming isotropic scattering and refractive index 1.5 (SA Prahl: "Optical property measurements using the inverse adding-doubling algorithm",

Oregon Medical Laser Center, Portland OR, Jan 1999 <a href="http://omlc.ogi.edu/software/iad/index.html">http://omlc.ogi.edu/software/iad/index.html</a>).

<td></td><td>μ (mm^-1)</td><td>μs (mm^-1)</td>

<td>LDPE</td><td> ~0.1</td><td> ~0.1</td>

<td>LDPE + absorber</td><td> 0.9</td><td> 0.3</td>

<td>LDPE + absorber + 0.25% TiO2</td><td> 0.9</td><td> 2.2</td>

<td>LDPE + absorber +0.5% TiO2</td><td> 0.9</td><td> 2.8</td>

<td>LDPE + absorber + 1% TiO2</td><td> 0.9</td><td> 4.8</td>

<td>LDPE + absorber + 2% TiO2</td><td> 0.9</td><td> 11.0</td>

[0065] The table shows the absorption and dispersion coefficients measured on a number of different samples with and without the absorber (PRO-JET 830 NP) and containing different amounts of TiO2.

[0066] Figure 4 shows a preferred embodiment in which the element 42 is at least substantially

21 transparent for a given wavelength, is to be laser welded to the element 44, which absorbs this wavelength, by means of a laser light 50 brought to the interface between the elements 42 and 44 in one or more predetermined positions.

[0067] Element 44 is attached to element 46, which also absorbs at this wavelength, whereby supplying the laser light 50 to the boundary surface may result in sufficient penetration of the laser light into element 44 and affect element 46, thereby heating element 46. Thus, the effect can be obtained that the element 46 is actually laser welded to the element 44, which is not intended.

[0068] The present elements 44 and 46 may be two sides of a bag, such as an ostomy bag, and the element 43 may be a coupling means to be attached to the bag to allow the bag to be attached to the mounting plate or to a person. [0069] Thus, in order to prevent excessive heating of the element 46, a layer was placed between the elements 44 and 46

48. Layer 48 is adapted to scatter radiation at this wavelength so as to prevent (or at least reduce the intensity of) its reaching element 46. [0070] At the same time, the attachment of element 48 to element 44 can be prevented or actually achieved due to the fact that element 44 is heated by radiation and due to the fact that the scattering carried out by element 48 will cause what

- at least partial reflection of radiation back and into element 44, which also facilitates heating in the interface between elements 44 and 48.

[0071] It may be desirable that the element 48 is not attached to any of the elements 44 or 46 and can move freely relative to them, as in a bag, if the elements 44 and 46 are part of the bag.

[0072] Alternatively, it may be desirable for element 48 to be attached to one of these two elements 44 or 46 to prevent it from moving from a position in which it scatters radiation.

[0073] It should be noted that the shape of the element 48 is preferably adapted to any radiation supply system 50 to obtain the desired welding.

[0074] As an alternative to welding the element 42 outside of the element 44 (viewed from the side of the element 46), the element 42 can be placed between the elements 44 and 46, whereby the element 44 will then absorb less radiation at this wavelength or not absorb it not at all, and the absorption of this element will be sufficient to allow welding.

[0075] Next, the element 48 will be placed between the element 42 and the element 46. Again, the element 48 may be attached to one of the elements 42 and 4 or may be free to move with respect to these elements.

[0076] A product with this second structure can be a stoma bag in which the space between the elements 42 and 44 can be used to hold a gas filter for venting the bag.

[0077] Figure 4 shows an embodiment seen from the direction of radiation 50. It can be seen that the element 42, in the plane of the elements, has a contour 42 'completely inside the outer contour 44' of the element 44, where the element 44 can be attached or attached to the element 46. Thus, in the present manner, if the elements 44 and 46 are attached to each other prior to laser welding of the element 42 with the element 44, the elements 44 and 46 will not be laser welded together due to the action of the dispersion element 48.

[0078] In the present embodiment, the elements 42, 44, and 48 are described and shown as thin plate-like elements. Naturally, this is not required. You can also use thicker elements. Furthermore, it is not necessary for the elements 44 and 46 to be attached to each other along the entire perimeter. It is enough if they are attached in given places or points.

COLOPLAST A / S

Proxy:

43P23910PL00

24EP 1 744 870 B1